Profe Cristian Silvestru

Jean-Manuel Raimundo

Professeu Mr Marius Andruh

Mr Philippe Blanchard

Di Mme Niculina Hădade

Maitre Directeur De Thèse

Profess Mr Ion Grosu

Mr Jean Roncali

Di Sis

Andreea Petronela

D Ngers

Small Molecular Donors for Organic Photovoltaics Chapter 5 Electroluminescent Carbon 'Quantum' Dots: a New Concept for Next Generation Optoelectronic Devices

Design, synthesis and supramolecular architectures of new heterocyclic compounds with potential applications in material chemistry and photovoltaic conversion

Andreea Petronela Diac

The optimist sees the glass half full. The pessimist sees the glass half empty. The chemist sees the glass completely full, half in the liquid state, and half in the vapor state.

"You should try to climb very high, if you want to be able to see very far."(C. Brâncuşi)

To my family I would like to offer special thanks to the members of the jury for accepting to participate at the thesis and for the patience to read it.

I am thanking my supervisors: Prof. Dr. Ion Grosu and D. R. Jean Roncali for accepting me as a co-joint PhD student and giving me the opportunity to work in their laboratories.

I am thanking Prof. Dr. Ion Grosu, Professor at ''Babes-Bolyai'' University, for the guidance offered during all these years: Licence, Master and now PhD diplomas, for giving me the opportunity to develop this research work, for guidance, support and encouragement during my formation; in addition he gave me the freedom to grow and develop as scientist.

I am most grateful to D. R. Jean Roncali, Directeur de Recherche at University of Angers, for receiving me in his laboratory in a co-joint thesis and for accepting me to work in his team. I also want to thank him for giving me the opportunity to spend my research stage in Angers and for the help he provided me. Special thanks also for his generous support, helpful discussions and patience for manuscript revision.

I would like to express my special thanks to Dr. Anamaria Terec and Dr. Elena

Bogdan, lecturers at ''Babes-Bolyai'' University, Dr. Niculina Hadade, Associate Professor at ''Babes-Bolyai'' University, and to Dr. Crina Socaci, Dr. Flavia Pop and Dr. Dora Demeter for the guidance and support that they offered me during my PhD; for fruitful discussions, help, support, guidance and collaboration in the lab work. I thank them also for their availability;

for having the office door always open for me.

Thanks also to Dr. Magali Allain from CIMA laboratory in Angers and Dr. Albert Soran and Dr. Richard Attila Varga from Faculty of Chemistry in Cluj-Napoca for X-Ray crystallographic determinations.

I express grateful thanks to Dr. Mihaela Liliana Tintas for the help she provided me during the work for my License and Master diplomas, for her advice, suggestions and support with the work in the lab.

Thanks to Ioana Dobra and Flavia Pop, who were, not only my colleagues but also my friends, for making my stage in Angers, France, a great experience, for being my friends although I was always with my head in the lab. Thank you very much Ioana ("mamii") and Flavia ("fulgusor").

I have had the fortune of working with many helpful colleagues: Ana-Maria Casian, Cosmin Crisan, Nadejda Mate, Mirabela Ligia Golban, Claudia Lar, Monica Rednic, Eszter Lakatos, Lidia Pop, Maria Pascanu, Ana Traistaru, Cristian Rete, Istvan Kocsis, Romina Catana, Ioana Dobra, Ilisca Medrut, Mihaela Liliana Tintas, Adrian Woiczechowski-Pop, Yue

Jiang, Ali Yassin, Djiby Faye, Oksana Toma, Thanhloan Lai, Alexandre Faurie and much others. Thank you all! Special thanks to my friends: Comi, Ana, Nadia, Mira, Claudia for your support and for making the lab work ambience easier and more relaxing and also to Ioana and Flavia (thank you for always being there even I was far away and for all your support and friendship).

My dear family: my mother (Gabriela), my father (Emil), my brother (Daniel), my grandmother (Tereza) and other of my family (Ana, Vasile, Ana-Maria). Thank you for all the support that you offered me during all these years, for your understanding and encouragements. Last but not the least, I have to thank a special person, my lovely Cosmin, for times like these I never find words to express my love for you. I wrote and erased a thousand times, and finally decided not to write a thing.

General Introduction

The research work presented in this thesis is focused on five main fields of interest with reference to synthesis of new: a) heterocyclic cyclopenta [c]pyrans; b) indenopyrone derivatives with fluorescent properties; c) architectures based on cyclopenta [c]pyran unit as potential devices of molecular electronics; d) systems based on N,N'-diphenylhydrazone and triphenylamine as molecular donors for organic photovoltaics and e) electroluminescent carbon 'quantum' dots. The first three subjects and the last were developed at Babes-Bolyai University, Cluj-Napoca, in the research group of Prof. Dr. Ion Grosu, while the subject concerning molecular donors for organic solar cells was developed at Moltech-Anjou, Angers, in the research group of D. R. Jean Roncali.

The first subject presents a study of pseudoazulene derivatives having a cyclopenta [c]pyran unit. The survey comprises the synthesis, structural analysis and reactivity towards electrophilic substitution in order to obtain fluorescent compounds. By following a multi-step strategy which starts from 1,3,4-oxadiazin-6-ones, six new series of cyclopenta [c]pyran derivatives were obtained and investigated using 1D, 2D NMR, UV-Vis/fluorescence spectroscopy, mass spectrometry, cyclic voltammetry and X-Ray diffractometry.

The second subject concerns the investigation of some new indenopyrone derivatives, including separation of regio-and diastereoisomers, study of their fluorescent properties and determination of fluorescence quantum yield.

The third subject describes the synthesis of new architectures based on cyclopenta [c]pyran unit that can be structurally modified by the influence of a chemical or electrochemical stimulus in order to work as potential devices in molecular electronics.

The fourth subject describes the synthesis of new Donor-Acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers. Furthermore, new ADDA and ADADA systems based on triphenylamine as molecular donors for organic solar cells (OSCs) were obtained. The study comprises also a characterization of their electronic properties by UV-Vis absorption spectroscopy, cyclic voltammetry and a preliminary evaluation of their performances in OSCs.

The fifth and last subject outlines the passivation of surface defects on carbon nanoparticles using small organic molecules or polymers in order to obtain photoluminescent carbon nanoparticles dubbed as carbon'quantum'dots. Moreover, the potential of carbon dots to function as energy donors by covalently attaching rhodamine B (RhB) to the free amino group of CDs-PEG1500N and the electroluminescence properties of carbon dots in a LED device were investigated.

Introduction

The cyclopenta [c]pyrans are aromatic compounds consisting of one cyclopentadiene fused at the c-bond of a pyran unit (A1, chart 1). The aromatic character of these derivatives is given by the total number of 10 conjugated π-electrons including the lone pair of the oxygen atom. 1 The parent compound A1 belongs to a large class of heterocyclic compounds, namely pseudoazulenes 2 , which are π-isoelectronic analogues of the non-benzenoid aromatic hydrocarbon azulene. Formally, the cyclopenta [c]pyran moiety results by replacing a vinylene group at C-5-C-6 position of azulene A2 by an oxygen atom (chart 1).

Chart 1

The cyclopenta [c]pyran scaffold appears as the subunit or the core of many natural products called Iridoids. 3 The name "iridoids" given after the first member iridomyrmecin derivative A3 was isolated in 1949 by Pavan 4 from the secretion of ants belonging to the genus Iridomyrmex, species Iridomyrmex humilis. This proved to be an effective insecticide and has antibiotic activity. Furthermore, iridoids are monoterpenes, often found as intermediates in the biosynthesis of alkaloids. Having a partially or fully hydrogenated cyclopenta [c]pyran skeleton, they attracted considerable attention due to their divers and important biological activities. 1,3,5,6,7,8,9 The total synthesis of cyclopentanoid monoterpenes such as the iridoids i,10,11 has been the target of many research works over the last four decades, mainly due to their biological activity and structural interest. Problems like the sensitivity to air, oxygen, acidic or alkaline media make the synthesis of this peculiar 10π system a continuous challenge for chemists. This might be one of the reasons why cyclopenta [c]pyrans were not intensively exploited since their first synthesis in 1963. 12

Literature Data

The biological properties of natural occurring cyclopenta [c]pyrans are of great interest. Strategies involving total or partial synthesis for some of these natural compounds have been developed. 3,9,10,11,12 Over time, different synthetic pathways were followed in order to design aromatic cyclopenta [c]pyrans.

A general, total synthesis is still to be elaborated. However, several strategies starting from cyclopentadienes 13 , fulvenes 14 , oxadiazinones 15 and α-pyrones 16 have been developed for the preparation of parent compound A1 and its derivatives with various substitution patterns.

The parent compound A1 and its 6-tert-butyl derivative were obtained by Seitz et al. 14 using substituted cyclopentadienes as building blocks (scheme 1). Deprotonation of (trimethylsilyl)cyclopentadiene A4 followed by the reaction with bromoacetaldehyde dimethyl-acetal afforded a mixture of tautomers in 55% yield, with A5 as the major component. Its conversion into (dimethylamino)fulvene by hydrolysis, gave A1 in only 5% yield.

Scheme 1

A three-step procedure for the synthesis of 1,4-disubstituted cyclopenta [c]pyrans was described in 1998 by Christl et al. 16 The main steps of this method are (scheme 2): 1)

Diels-Alder reaction with inverse electron demand of cyclopentadiene with 6H-1,3,4oxadiazin-6-ones A6; 2) dehydrogenation with DDQ affording the α-pyrones A7 and A8 in 27-76% yield; 3) reduction of A7 and A8 with DIBAL-H affording the 1,4-disubstituted cyclopenta [c]pyrans A9a-f in yields ranging from 28 to 53%. An exception was reported in the case of A9c, obtained in 9% yield due to the simultaneous reduction of the ester group.

Using AlMe3 instead of DIBAL-H, the isomeric α-pyrones A7/8 (R 1 =R 2 =Ph) were converted into the 3-methyl-1,4-diphenylcyclopenta [c]pyran in 50% yield.

Scheme 2

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Page | 20

A few years later, Christl et al. 17 reported the synthesis of 3-substituted cyclopenta [c]pyrans using α-pyrones as starting materials (scheme 3). The treatment of αpyrone derivative A10 with triethylamine in the presence of different chlorotrialkylsilanes led to ketene acetals A11-A13 in good yields. The enol ester A14 was obtained by treating A10 with triethylamine and benzoyl chloride in 65% yield. However, several analogous experiments with acyl and sulfonyl chlorides failed 17 .

By using the Wittig 17 procedures for the olefination of lactones, two 3-substituted cyclopenta [c]pyrans were prepared. Thus, the reaction of A10 with the respective ylides led to derivatives A16 and A17 (scheme 3) in 29% and 15% yields, respectively. The reduction of A17 by LiAlH4 at low temperatures afforded the primary alcohol A18 (scheme 3), which could not be purified due to decomposition.

Scheme 3

A simple one-pot synthesis was reported for 1,3,4-triphenylcyclopenta [c]pyran A21, which was formed during an attempt to prepare fulvenes from α-dicarbonyl compounds. 17,18 The reaction of cyclopentadiene A19 with sodium methoxide in the presence of A20 gave rise to the red solid A21 in 10% yield (scheme 4) along with large amounts of methyl benzoate and polymeric material. 17 M. D. Banciu, E. E. Castellano, J. Ellena, I. Haiduc, C. Draghici, A. T. Balaban, New J. Chem. 2001, 25, 1472. 18 M. D. Banciu, A. T. Balaban, C. Draghici, I. Haiduc, O. Ivanciuc, Rev. Roum. Chem. 2002, 47, 705.

Scheme 4

Generally, pseudozulenes are rather sensitive compounds compared to azulene. In the series of pseudoazulenes, the stability decreases dramatically going from the nitrogenand sulfur-containing systems to the oxygen analogues. 2,19 It was observed that the stability of these derivatives increases when there is at least one electron-withdrawing substituent in conjugation with the π-electrons of the ring system. The best illustration of this effect is provided by natural products with an electronwithdrawing substituent at position 7 such as a formyl group in most cases and a carboxyl or an ester group in others.

Quantum chemical calculations offered important data related to aromaticity and reactivity of pseuodoazulenes. 2 Although a considerable number of electrophilic substitution reactions are known for pseudoazulenes, 2,20 there are only two papers dealing with these types of substitutions on cyclopenta [c]pyrans. 16,17 The aromatic character of cyclopenta [c]pyrans is not as pronounced as in case of azulenes, 2 however, they participate in electrophilic substitution reactions in mild conditions (scheme 5). The Vilsmeier-Haack formylation of 1,4-disubstituted and 1,3,4trisubstituted cyclopenta [c]pyrans with DMF/POCl3 afforded the corresponding cyclopenta [c]pyran-7-carbaldehydes A23a-e in 61% to 84% yields. The nitro derivatives A24a and A24b were prepared in 56% and 38% yields, respectively, by reacting the appropriate substrates A22 with tetranitromethane in pyridine. Using trifluoroacetic anhydride (TFAA) as electrophile, a notable number of trifluoroacetylated compounds (A25a-g) were obtained in yields ranging from 11% to 42% (scheme 5). 17 The configuration of the two diastereoisomers 2'e and 2''e (R 1 =C6H4-p-Br) was determined by 1 H NMR spectroscopy (figure 1). For the isomer 2'e, the large coupling constant (J4,4a = 14.5 Hz) indicated the trans disposition of H-4 relative to H-4a, while in isomer 2''e the proton H-4 exhibits a more deshielded doublet with a coupling constant (J4,4a = 7.0 Hz) characteristic for the cis configuration.

The electrochemical properties of some compounds have been analyzed by cyclic voltammetry (CV) in methylene chloride as solvent and in presence of tetrabutylammonium hexafluorophosphate (Bu4NPF6) as supporting electrolyte. The CV of all derivatives shows an irreversible oxidation wave with an anodic peak potential Epa decreasing from 1.56V for 2'j to 1.29 V for 2'b (Table 1, Figure 2). A closer examination of the CVs shows that the presence of electron-donating groups as -OCH3, -CH3, C(CH3)3 produces a large negative shift of the anodic peak potential from 1.56 V for derivative 2'j possessing a strong EWG (-NO2) to 1.29 V for compound 2'b having an EDG (-CH3) (table 1). Noteworthy, there are no differences between the stereoisomers regarding the oxidation and reduction processes. The CV recorded in the negative potentials region shows that all compounds (figure 3) present an irreversible reduction wave with a cathodic peak potential varying from -1.25 V for derivative 2'g to -1.08 V for 2'f. In the case of derivative 2'j the cathodic peak potential (Epc) is positively shifted by ca. 100 mV and becomes reversible (figure 3, table 1).

Therefore, the EWG, NO2, allows a better delocalization of negative charges in compound 2'j.

E (V vs SCE) The optoelectronic properties of enol-lactone derivatives 2 were also investigated.

The UV-Vis spectra (figure 4) of 3,4,4a,5-tetrahydrocyclopenta[c]pyran-3-one derivatives 2 performed in dichloromethane showed absorption maxima at around 230 and 290-305 nm (table 2) in case of all derivatives, except for compound 2'j (R = C 6 H 4 -p-NO 2 ). For the latter, a notable red shift (63 nm) to λmax = 361 nm could be observed. This feature could be related to the extended conjugation of the system due to the presence of the NO2 group. The overall analysis of the absorption spectra (figure 4, table 2) revealed some differences between the para-and meta-substituted derivatives and between the diastereoisomers as well. For example, if we compare the brominated meta-substituted derivative 2'i (λmax = 299 nm) with the corresponding para-substituted derivative 2'e (λmax = 302 nm) a slightly shift to higher wavelength could be observed. Furthermore, a small blue shift was observed in case of trans diastereoisomer 2'e (λmax = 302 nm) compared with cis-2''e (λmax = 305 nm).

The photoluminescence properties of compounds 2 have been analyzed in both solution and solid state (for some derivatives). All derivatives 2a-i displayed a blue emission in dichloromethane solution and in solid state, in both cases the excitation wavelength being 370 nm (figure 5, table 2). By excitation at the maximum absorption wavelength, the enol-lactones 2 did not display any emission. It is important to note that compound 2'j fluoresce in dichloromethane with green emission peak at 496 nm and in solid state with yellow emission peak at 533 nm.

Table 2. Absorption and emission data for 3,4,4a,5-tetrahydrocyclopenta [c]pyran-3-one derivatives 2

Cmpd. λ (nm) a εmax (M -1 cm -1 ) λem (nm) b λem (nm) c ФFL (%) In solid state enol-lactones display strong blue fluorescence by irradiation at UV lamp at 365 nm (figure 6). Compared to the diluted CH2Cl2 solutions, the emission spectra in solid state of some compounds (figure 5) showed a better-resolved vibrational fine structure and shifts to longer wavelengths by 24-37 nm. The red shift of the emission observed in the solid state is probably due to the strong intermolecular forces, which drove the molecules to pack at high density and form J-aggregates.

The molecular structure of four enol-lactones (2''c, 2'd, 2'e, 2'h) was confirmed by X-ray diffractometry. Colorless crystals were obtained by slow evaporation from chloroform solution. The results of single crystal X-ray diffraction analysis are presented in Table 3. Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 34 As shown in figure 7, the hydrogen atoms connected to the stereo centers C-7-C-8, The aforementioned compounds crystallize in centrosymmetric space groups, compounds 2''c, 2'd, 2'e in the monoclinic system and compound 2'h in the triclinic system.

In the crystal the molecules of The crystal structure of enol-lactone 2'e is establised by several C-H---π intermolecular interaction, that serve to link the molecules into parallel chains. 28 Important C-H---π interactions (d = 3.082 Å, purple dashed line and 3.018 Å, blue dashed line) could be observed between the molecules disposed in a parallel head-to-head orientation as well as between those in the head-to-tail disposition (d = 3.024 Å, orange dashed line) (figure 8c).

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Page | 37 Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 38 1.3.2. Synthesis of 1,pyrans

The synthesis of 1,4-diaryl-dihydrocyclopenta [c]pyran derivatives 4 and 5 was carried out in good yields by dehydrogenation of the enol-lactone isomeric mixture 2 in presence of DDQ, at reflux in chloroform (scheme 8, in red -the new compounds). 16 After the oxidation was complete a regioisomeric mixture of α-pyrones was identified. Even though pure enol-lactones 2 were employed, both regioisomers 4 and 5 were obtained.

Scheme 8

Similar to enol-lactones, separation and isolation as unique compound of the two regioisomers was not possible by conventional chromatography, but for several members (b, c, d, e, and g) the isomer 4 precipitated in the test tubes during the purification, allowing its isolation.

Purification of α-pyrones on silica gel led to a mixture of isomers 4 and 5, but when neutral aluminum oxide was used for purification by column chromatography, the isomerisation process of 4 to 5 occurred (scheme 9). This isomerisation took place with partial degradation of the product, which explains the low yield (about 25%).

Scheme 9

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Page | 39

The structures of α-pyrone derivatives were investigated by NMR, UV-Vis and fluorescence spectroscopy, mass spectrometry and in some cases by X-Ray diffractometry.

The 1 H NMR spectra of derivatives 4 and 5 exhibit specific signals for the protons of vinylene unit in the range 6.3-7.0 ppm and for the protons of methylene group at position 5 and 7, respectively. The assignment of the signals was based on two-dimensional spectra and the two regioisomers were identified based on the signals of the cyclopenta [c]pyran protons at positions 5, 6 and 7 as illustrated in figure 9 for derivatives 4g and 5g (R 1 = C6H4-m-OCH3). As shown in figure 9, the two regioisomers present a similar pattern in the 1 H NMR spectrum, differences are observed for the upfield chemical shifts of the signals corresponding to the five-membered ring. For isomer 4g, the protons of vinylene group give two signals as doublets of triplets at 6.95 and 6.34 ppm corresponding to H-6 and H-7, respectively and there is also a triplet at 3.50 ppm corresponding to the protons of methylene group. For derivative 5g, the 1 H NMR spectrum reveals more deshielded signals for the protons of methylene group at C-7 at 3.77 ppm and for the vinylene group a doublet of triplets at 6.80 ppm corresponding to the hydrogen atom at position 5 and a shielded doublet of triplets at 6.88 ppm corresponding to proton at position 6.

Dihydrocyclopenta [c]pyrans 4 and 5 are intense yellow solids, behavior illustrated by absorption maxima in the range 366-382 nm in the UV-Vis spectra (figure 10, table 4).

The UV-Vis and fluorescence spectra were recorded in dichloromethane solution at room temperature.

Wavelength Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material

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Page | 41 All compounds exhibit strong absorptions maxima around 366-382 nm in CH2Cl2 solutions, range that may be assigned to π-π * transitions. As it can be observed in figure 10, isomers 4 exhibit only one intense band with two weak shoulders, while isomers 5 exhibit two different intense bands, typical for n-π * and π-π * transitions. Comparing the UV-Vis spectra of the two α-pyrone isomers, a slight shift to higher absorption maxima and to higher values of molecular extinction coefficient could be observed in case of regioisomers 5 (double bond at C-5-C-6 position) (table 4, figure 10), probably due to the conjugation with carbonyl group.

On the other hand, the comparison of UV-Vis spectra of parent 1,4-diphenylcyclopenta [c]pyran 5a (367 nm) with 5b-i revealed a bathochromic shift, especially for the para-substituted-1-aryl derivatives 5b-f (table 4). The most noticeable influence of the substituent appeared in the case of 5c (382 nm) bearing the para-methoxy-phenylene group and it could be explained by the enhancement of electron delocalization in the conjugated system. The influence of electron delocalization effect is more obvious when comparing the values of absorption maxima and molecular extinction coefficient of paramethoxy substituted 5c (382 nm, log ε = 4.27) to those of meta-methoxy derivative 5g (371 nm, log ε = 4.18) in which only the -I effect occurs.

The photoluminescence property of some α-pyrones was also investigated in solution and in solid state (table 5), these derivatives showing good emissions in solid state and very weak emissions in CH2Cl2. The quantum yields calculated relative to quinine sulfate are very low < 0.1% for isomers 4, whereas regioisomers 5 exhibit a better emission and their fluorescence quantum yields are slightly higher than that of derivatives 4 reaching 0.3-0.5 % (table 5). We observed that all pure dihydrocyclopenta [c]pyrans are green emitters by irradiation at 365 nm in solid state. Thus, by excitation at 370 nm both regioisomers display emissions maxima in the range 449-472 nm in solution and 468 -505 nm in solid state, as seen in figure 11, therefore the photoluminescence property is not significantly influenced by the nature and position of substituents.

A slight shift to higher emission maxima and a better-resolved vibrational fine structure could be observed by comparing the fluorescence spectra in solid state to those in solution (figure 11). Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 44 The electrochemical properties of some of the α-pyrone derivatives 4 and 5 were determined by cyclic voltammetry (CV) measurements which were carried out in a threeelectrode cell setup with 0.

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Page | 45 As shown in figure 12, the CV trace of all analyzed compounds shows two irreversible oxidation processes with anodic peak potentials Epa 1 and Epa 2 associated with the formation of unstable radical cations and dications, respectively. In the negative potential region, the CVs show irreversible reduction waves in the range -1.25 ÷ -1.08 V indicative of an unstable anion radical (table 6).

Data comparison of regioisomers 4 and 5 shows that the first anodic peak potential is negatively shifted by ca. 0.15 V in the case of isomers 5 indicating that the oxidation process occurs faster for 4. Furthermore, by comparing the oxidation processes of derivatives 5c and 5g it can be observed that compound 5c bearing a para-methoxy-phenylene unit is oxidized quicker than compound 5g bearing a meta-methoxy group. This feature is probably due to the enhancement of electron delocalization in the conjugated system.

(V) Epa 2 (V) Epc (V) Epa 1 (V) Epa 2 (V) Epc (V)
The single crystal molecular structures of 4b, 4c, 4e and 5f were obtained by X-Ray diffraction using suitable crystals obtained from chloroform or dichloromethane solutions by slow evaporation of the solvent.

Due to the packing effects, the crystal of 4e (figure 13d) contains two different types of molecules with slightly different interatomic distances and torsion angles. Surprisingly, the α-pyrone derivative 4c co-crystallized with one molecule of CH2Cl2, used as solvent (figure 13b). In all cases the dihydrocylopenta [c]

Synthesis of aromatic cyclopenta[c]pyrans

In order to obtain the aromatic cyclopenta [c]pyran derivatives, two synthetic routes, starting from α-pyrones, 16 were taken into consideration:

1. Selective reduction in the presence of DIBAL-H leading to 1,4-disubstituted cyclopenta [c]pyrans.

2. Reaction with trimethylaluminum gave the 1,3,4-trisubstituted cyclopenta [c]pyrans bearing a methyl group in position 3.

The synthesis of 1,4-disubstitued cyclopenta [c]pyran derivatives 6 was carried out in fair yields (12-38%), by selective reduction with DIBAL-H of isomeric mixture of αpyrone derivatives 4 and 5 (scheme 10). The main reason for the recorded low yields is the decomposition of compounds 6 during the purification process by column chromatography on neutral aluminum oxide. This series of aromatic cyclopenta [c]pyrans 6 are deep-red powders that decompose rapidly at room temperature within a few hours, but they can be stored in the freezer for a long period.

a R 1 = C 6 H 5 20% b R 1 = C 6 H 4 -p-CH 3 16% c R 1 = C 6 H 4 -p-OCH 3 14% d R 1 = C 6 H 4 -p-Cl 20% e R 1 = C 6 H 4 -p-Br 38% f R 1 = C 6 H 4 -p-tBu 19% g R 1 = C 6 H 4 -m-OCH 3 23% h R 1 = C 6 H 4 -m-Cl 15% i R 1 = C 6 H 4 -m-Br 12% DIBAL-H / CH 2 Cl 2 -78°C O O Ph R 1 O O Ph R 1 + 4 5 O Ph R 1 6 O Ph R 1 7 CH 3 a R 1 = C 6 H 5 19% c R 1 = C 6 H 4 -p-OCH 3 28% d R 1 = C 6 H 4 -p-Cl 21% e R 1 = C 6 H 4 -p-Br 24% g R 1 = C 6 H 4 -m-OCH 3 27% AlMe 3 / CH 2 Cl 2 40°C Scheme 10
The 1 H NMR spectra of compounds 6 revealed specific signals for the aromatic protons at positions 5, 6 and 7 of the cyclopenta [c]pyran moiety as a doublet of doublets, and a singlet corresponding to the proton of position 3. Thus, the 1 H NMR spectrum of derivative 6e (figure 16) exhibits a set of three doublet of doublets at 6.67, 7.03 and 7.34 ppm corresponding to H-5, H-7 and H-6, respectively and a singlet at 7.68 ppm assigned to H-3. The 1,4-disubstituted cyclopenta [c]pyrans are highly unstable at room temperature.

In order to obtain cyclopenta [c]pyrans with increased stability, the mixture of α-pyrones 4 and 5 was treated with trimethylaluminum leading to products 7 (scheme 10). After purification by column chromatography on neutral aluminum oxide, five 1,3,4trisubstituted cyclopenta [c]pyrans were obtained in good yields, as deep-red amorphous solids slightly more stable than the corresponding 1,4-disubstituted derivatives 6. The structure of all derivatives was confirmed by NMR spectroscopy and mass spectrometry.

The cyclopenta [c]pyran 7d was obtained in 21% yield and its 1 H NMR spectrum is in agreement with the predicted structure (figure 17). Protons H-5 and H-7 give two doublets at 6.17 and 6.93 ppm with coupling constants J5,6 = 2.1 Hz and J6,7 = 4.5 Hz, while for H-6 a doublet of doublets at 7.23 ppm with coupling constants J5, 6 = 2.8 Hz and J6,7 = 4.6 Hz is present. The 13 C NMR spectrum of 7d (figure 17) exhibits distinctive signals for aromatic carbons C-5, C-7 and C-6 at 108.6, 109.4 and 135.7 ppm, respectively. The assignment of the carbon atoms signals was supported by 2D HSQC and HMBC spectra.

Electrophilic substitution reactions

The purpose of this research work was the obtaining of fluorescent aromatic cyclopenta [c]pyrans. Even if derivatives 6 and 7 fulfilled this requirement, their sensitivity to air, acidic or strong alkaline media represents a real drawback for the potential applications. Therefore, we took into consideration to increase the stability of cyclopenta [c]pyran skeleton by introducing electron-withdrawing substituents that would eventually enhance the fluorescence properties. Based on literature data, 2,16 we decided to exploit the aromatic character of cyclopenta [c]pyrans towards electrophilic agents.

Although, the aromatic character of cyclopenta [c]pyrans is not as pronounced as in the case of azulenes 1 , however, they participate to electrophilic substitution reactions in mild conditions. Thus, the obtained derivatives 6 and 7 were subjected to reactions of trifluoroacetylation and formylation.

Theoretical calculations showed that the electron density is higher at positions 5 and 7, and lower at position 6. Molecular orbital calculations predict the highest electron density at position 7 for the pseudoazulene-[c]-series 2 .

Depending on the electrophile, the cyclopenta [c]pyrans behave differently in electrophilic aromatic substitution reactions. Thus, trifluoroacetylation led exclusively to 7monosubstituted derivatives, whilst Vilsmeier-Haack formylation afforded not only the product of monosubstitution as reported in the literature 16 but also the disubstituted products, in some particular conditions.

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Page | 55 1.3.4.1. Trifluoroacetylation The trifluoroacetylation reactions were performed in anhydrous dichloromethane, at room temperature, by reacting the cyclopenta [c]pyrans 6 and 7 with trifluoroacetic anhydride in presence of triethylamine, when monosubstituted products 8 and 9, respectively were obtained (scheme 11).

Scheme 11

As mentioned earlier, the positions susceptible to an electrophilic attack are positions 5 and 7, in which, as stated by theoretical calculations, the electron density is higher 2 . In the case of trifluoroacetylation reaction, only the formation of 7monosubstituted derivative could be observed, while not even traces of the 5monosubstituted product were detected. Formation of 5,7-disubstituted derivatives or of the 5-monosubstituted derivative was not observed even if the temperature was raised to 40°C or when an excess of electrophile was used.

We were able to obtain 13 new trifluoroacetyl-cyclopenta [c]pyrans 8 and 9 in very good yields (63% to 93%) using this procedure and their structures were determined by NMR spectroscopy, mass-spectrometry and, in some cases, by X-ray diffractometry as well. APCI-MS spectrum of trifluroacetyl-cyclopenta [c]pyran 8c revealed that the base peak in the spectrum is at m/z 397.10 for protonated species [M+H] + (Figure 18').

Figure 18'. APCI-MS spectrum of derivative 8c

Trifluoroacetylated derivatives 8 and 9 have higher stability compared to the corresponding cyclopenta [c]pyrans 6 and 7 and are easy to handle at room temperature.

All trifluoroacetylated derivatives 8 and 9 are deep-red or orange solids that exhibit strong orange fluorescence by irradiation at 365 nm with a UV lamp (figure 19).

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Page | 58

Owning two series of cyclopenta [c]pyran derivatives possessing the same chromophore, a trifluoroacetyl group in position 7 and a different substituent at position 3 (H or Me) we next investigated their optical properties in solution by UV-Vis absorption and photoluminescence spectroscopy. Figure 20 shows the absorption spectra of derivatives 8 and 9 measured in CH2Cl2 at room temperature; their photophysical properties are summarized in table 7. All derivatives display three strong absorption bands in the 230-460 nm range, the higher wavelength (around 450 nm) being ascribed to electronic transitions of CF3CO group.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 59 The fluorescence quantum yield of a fluorescent compound is a measure of the capability of molecules to emit the absorbed light energy. The quantum yield of trifluoroacetylated derivatives 8 and 9 was measured using rhodamine 6G (Ф = 0.96) as a standard material. It can be observed (table 7) that compounds 8c and 9c have a higher quantum yield than other compounds probably due to the better charge transfer from the para-methoxy group to the trifluroacetyl group.

The structures of 8a, 8g and 9a (figure 22) were confirmed by X-ray diffraction on monocrystals obtained from CDCl3, by slow evaporation at room temperature. In all three cases the carbon-carbon lengths in the five and six-membered rings (table 8) illustrate that the cyclopenta [c]pyran skeleton has distinctive single and double bonds. At a closer analysis of bond lengths between trifluoroacetyl group and the cyclopenta [c]pyran unit (table 8) there is an indication that the real structures are not in full agreement with the proposed structures, suggesting that the cannonic forms 8'a, 8'g and 9'a have an important contributions to the ground state resonance hybrids (chart 3).

Also, shorter and unequal carbon-fluorine bonds and peculiar values for the carbonoxygen bond length in the six-memberd ring were observed. An interesting feature is the Cmpd.

Bond lengths [Å]

Cmpd.

Bond lengths [Å]

Cmpd. The supramolecular arrangement of the molecules in the lattice is ensured by a number of non-covalent interactions. Intermolecular interactions through strong face-to-

Bond lengths [Å

] 8a C2-C3 1.455(5) 8g C2-C3 1.442(3) 9a C2-C3 1.447(3) C3-C4 1.382(5) C3-C4 1.391(3) C3-C4 1.398(3) C4-C5 1.396(5) C4-C5 1.391(3) C4-C5 1.385(3) C5-C6 1.375(5) C5-C6 1.380(3) C5-C6 1.385(3) C2-C6 1.452(5) C2-C6 1.453(3) C2-C6 1.450(3) C6-C7
face C-H•••π contacts (C-H16•••centroid (C2-C6) = 2.779 Å) and C-H12•••F3 interactions (dH-F = 2.573 Å, angle C-H12-F3 167.29°
) result in a ribbon-like supramolecular association (figure 23) in the case of derivative 8a.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 63 The view of the lattice of compound 8g shows a well-defined molecular arrangement in a tilted head-to-tail disposition, insured by a large number of interactions 30 (figure 24). Thus, notable edge-to-face C-H Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

•••π interactions (C-H17C•••centroid (C11-C16) = 2.990 Å)

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Page | 64

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Page | 66 1.3.4.2. Formylation The mild conditions of Vilsmeier-Haack formylation 31 are suitable for performing electrophilic substitution to aromatic cyclopenta [c]pyrans. The cyclopenta [c]pyrans behave differently when are subjected to formylation compared to the trifluoroacetylation reaction. Therefore, depending on the amount of electrophile reagent and reaction time, monosubstituted and/or disubstituted products can be obtained.

Formylation of cyclopenta [c]pyrans 6 with two equivalents of POCl3 and excess DMF (having the role of both solvent and reagent) at 45°C over 45 min., led to the formation of a mixture of mono-and disubstituted derivatives, which could not be separated due to the very small polarity differences (scheme 12). Despite these drawbacks, using excess of electrophile reagent (7 eq. POCl3) and increasing the reaction time to 20 hours, we managed to obtain only the disubstituted products 12 in very good yields, which could be thus isolated and characterized.

Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 67

The structure of formylated derivatives 12 were analyzed by NMR spectroscopy and mass-spectrometry. For example, the diformylated derivative 12e presents quite a simple 1 H NMR spectrum (figure 26) showing a typical AA'BB' system for the parabromophenylene ring and an overlapped signal at 7.54 ppm assigned to the protons of the 4-phenyl unit. Furthermore, the two singlets at 8.06 and 8.46 ppm were assigned based on two-dimensional spectra to the protons at positions 3 and 6, respectively of the cyclopenta [c]pyran unit. Nevertheless, the two singlets at 9.31 and 9.80 ppm, specific to the formyl groups, confirm without any doubt the structure proposed for 12e. The absorption and photoluminescence properties of 5,7-diformylcyclopenta [c]pyrans 12a-g were studied in CH2Cl2 solution at room temperature.

The optical absorption spectra of compounds 12a-g shown in figure 27 reveal two absorption bands: first absorption band around 293-315 nm is more intense than the second band situated in the 420-428 nm region. The latter can be assigned to an internal charge transfer from the electron donor groups to electron acceptor CHO. 9). All the investigated diformylcyclopenta [c]pyran derivatives are yellow-orange emitters (537-558 nm). Figure 28 displays the normalized spectral data of derivatives 12a-g; the absorption is shown in green and the emission signals are in orange.

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Page | 69 At a first glance, the emission of the diformylated derivatives looks more promissing than that of trifluoroacetylated-cyclopenta [c]pyrans, but the quantum yields calculated relative to rhodamine 123 are again very low (table 9). Single crystal X-Ray diffractometry analysis of derivative 12c revealed a triclinic spatial disposition in centrosymmetric P-1 space group having two molecules per unit. The cyclopenta [c]pyran moiety is not planar (figure 29 The existence of H-bonds between two neighboring molecules found in a head-totail orientation, involving a hydrogen atom of the cyclopenta [c]

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Page | 72

Synthesis of cyclopenta[c]pyrans-based push-pull chromophores

During the last decade, a great attention has been paid to metal-free organic chromophores, due to their facile synthesis and structural versatility, thus allowing one to tune the absorption wavelength, molar extinction coefficient and HOMO-LUMO energy levels. Usually, the structure of a so-called push-pull derivative consists of an electrondonor, a π-linker and an electron-acceptor fragment.

In our continuing interest in the manipulation of the electronic properties of compounds containing cyclopenta [c]pyran moiety, we synthesized three molecular donor (D)-acceptor (A) systems via a Knoevenagel condensation of aldehydes 12 with malonodinitrile in presence of aluminum oxide as base (scheme 13). Derivatives 13 were obtained in good yields ranging from 58 to 91% and their photophysical and electrochemical properties were investigated.

Scheme 13

The structure of all synthesized compounds was confirmed by NMR spectroscopy and mass spectrometry. The 1 H NMR spectrum of derivative 13c (figure 31) reveals four singlets at 7.11, 7.52, 8.06 and 9.28 ppm corresponding to the protons at positions 3, 6, 5 and 7 respectively, an AA'BB' system at 7.18 and 7.72 ppm corresponding to the paramethoxy phenylene ring, the other two signals being assigned to the phenyl unit at position 4. Figure 32 shows the UV-Vis absorption spectra of compounds 13c, f, g in dichloromethane solutions and those of thin film spin-cast on glass from chloroform solutions. The broad maximum wavelength absorption around 450 nm appears to correspond to an intramolecular charge transfer (ICT) between electron-donating and electron-accepting groups, while the absorption band around 360 nm is most likely to be due to π-π* transitions. As generally observed for π-conjugated systems, the spectra of the films present a red shift of λmax and a broadening of the absorption band reflecting intermolecular interactions in the solid state. Further comparison of the solution and solid-state spectra shows that the smallest difference between the two states is observed for compound 13f

and the largest one for compound 13g, suggesting differences in intermolecular interactions (table 10).

The intercept of the tangent to the long wavelength absorption edge regarding the spectra of the films with the horizontal axis gave estimated band gaps (Eg) of 2.22 eV for 13f and 2.09 eV for derivative 13g. These results confirm that, despite limited effects at the molecular level, the nature and position of the substituent on phenylene unit can significantly affect the molecular packing in the solid state. The cyclic voltammograms of derivatives 13c, f, g (figure 33) are similar, showing two irreversible oxidation waves with the first anodic peak potential Epa 1 around 1.60 eV and the second Epa 2 around 1.95 eV. In the negative region, the CV of all compounds exhibits two irreversible reduction waves indicating the formation of unstable anion radicals.

Considering the fact that the open-circuit voltage (Voc) of OPV cells depends on the difference between the LUMO of the acceptor and the HOMO of the donor32 , this high optical gap appears uninteresting and derivatives 13 have not been tested as donors in OPV cells.

Conclusions

In the first chapter of the thesis, a literature survey with respect to pseudoazulenic heterocyclic system consisting of cyclopenta [c]pyran with aromatic skeleton as well as the original results regarding the synthesis of new cyclopenta [c]pyran derivatives were presented.

By following a multi-step strategy which starts from 1,3,4-oxadiazin-6-ones, we synthesized six series of cyclopenta [c]pyrans: 8 new enol-lactone derivatives, 7 new αpyrones, 10 new aromatic cyclopenta [c]pyrans, 13 new trifluoroacetyl derivatives, 5 new diformyl-cyclopenta [c]pyrans and 3 donor-acceptor systems.

The structural analysis of the new compounds was based on complex investigations such as 1D and 2D NMR, UV-Vis/fluorescence spectroscopy, mass spectrometry and X-Ray diffractometry.

Tetra-( 2) and dihydrocyclopenta [c]pyrans (4 and 5) were investigated by photophysical and electrochemical analyses. Both series, enol-lactones ( 2) and α-pyrones It was observed that the aromatic cyclopenta [c]pyrans 6 and 7 do not exhibit fluorescence neither in solution nor in solid-state. However, by introducing electronwithdrawing groups like trifluoroacetyl or formyl, the cyclopenta [c]pyran derivatives 8, 9

and 13 become fluorescent. Furthermore, the electron-withdrawing groups stabilize the cyclopenta [c]pyran unit.

X-Ray diffraction of some derivatives showed strong intra-and intermolecular

interactions such as H-bonding (C-H•••O), C-H•••π, C-X•••X and C-H•••X contacts.
In our attempts to obtain push-pull chromophores with a low band gap, we synthesized three donor-acceptor systems based on cyclopenta [c]pyran but these derivatives proved to be unsuitable for optoelectronic devices due to their high optical gap.

Future work will focus on the study of fluorescence quantum yield in solid state for all series of cyclopenta [c]pyran derivatives. Solvents were dried and distilled under argon using standard procedures prior to use. Chemicals of commercial grade were used without further purification.

Cyclopentadiene was freshly distilled. It can be stored as such in the freezer, but it must be redistilled prior to use.

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 78 A suspension containing 5 mmol of the corresponding oxadiazinone 1 in dry dichloromethane (80 ml) and inert atmosphere was cooled at 0 °C. Then 1.5 mmol TFAA (0.2 ml), 5 mmol TFA (0.38 ml) and 17.5 mmol (1.47 ml) freshly distilled cyclopentadiene were added. Gas evolution was observed and the solution turned from yellow to dark brown. The reaction was monitored by TLC and when the oxadiazinone was consumed, the reaction mixture was neutralized with saturated solution of NaHCO3 to pH 7. The organic phase was washed with water and brine, dried over anhydrous MgSO4 and evaporated to dryness. The obtained residuum was taken up in a mixture of diethyl ether and pentane, when the corresponding diastereoisomeric mixture of enol-lactones precipitated. In some cases both diastereoisomers have been separated by column chromatography on silica gel, but in most cases only a little amount of isomer 2' has been isolated as pure compound. 13 C NMR 150 MHz, CDCl3, δ ppm: 37.5, 42.3, 52.2, 126.8, 127.8, 128.0, 128.2, 128.6, 128.7, 129.0, 129.1, 133.1, 136.2, 139.4, 140.9, 170 Pure isomer obtained by precipitation with diethyl ether, white powder, yield 35%, mp. 143-144°C

Not isolated as unique isomer

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 80

Retention factor Rf = 0.6 (silica, P/EE = 3/2) 75 MHz,CDCl3,δ ppm: 21.35,37.39,42.11,52.12,126.52,127.30,127.74,127.81,128.85,128.87,129.15,130.12,136.12,138.50,138.81,140.85,170.01.

UV/Vis

CH2Cl2, λmax (ε) [nm] =295 (14300).

HRMS (APCI+)

calcd. for C21H19O2 [M+H] + : 303.1380; found: 303.1382. 75 MHz,CDCl3,δ ppm: 37.5,42.2,52.3,55.5,114.0,125.7,126.6,127.8,127.9,128.1,128.9,129.0,136.2,138.6,140.7,159.8,170.2. 100 MHz,CDCl3,δ ppm: 33.4,40.1,48.8,55.5,114.1,124.4,125.8,127.6,128.0,128.1,129.1,129.3,134.1,139.6,140.6,159.9

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Page | 82

Retention factor Rf = 0.6 (silica, P/EE = 3/2) Rf = 0.5 (silica, P/EE = 3/2) 150 MHz,CDCl3,δ ppm: 37.5,42.4,52.1,127.4,128.0,128.1,128.7,128.9,129.0,129.1,131.6,134.4,136.0,139.8,140.1,169.7

Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 83 37.4,42.3,51.9,122.5,127.3,127.9,128.1,128.7,128.9,129.0,131.7,131.9,135.9,139.7,140.2,169.7. 75 MHz,CDCl3,δ ppm: 33.6,40.4,48.7,122.7,126.9,127.3,128.2,128.3,129.3,129.4,132.0,132.1,134.0,139.8,141.5,168.9

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Page | 84 75 MHz,CDCl3,δ ppm: 31.2,34.7,37.4,42.1,51.1,89.6,117.3,125.4,126.3,127.4,127.8,128.8,130.1,136.1,138.8,140.8,151.6,169.9.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 295 (16590)

HRMS (APCI+)

calcd. for C24H25O2 [M+H] + : 345.1849; found: 345.1850 Trituration with a mixture of pentane/ether ethylique = 5/1 led to a ratio of isomers 2'g:2''g = 1.5:1, as a white solid, yield 48%.

Structural properties

Derivative 75 MHz,CDCl3,δ ppm: 37.7,42.4,52.3,55.7,112.1,114.7,119.5,128.0,128.1,128.6,129.1,129.7,133.9,134.5,136.3,139.6,140.8,159.9,170. 75 MHz,CDCl3,δ ppm: 33.4,40.2,48.6,55.5,111.9,114.5,119.2,126.3,127.6,128.1,129.1,129.2,129.7,134.0,134.4,140.5,140.6,159.9, 169.0.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 244 (12500), 299 (23100).

HRMS (APCI+)

calcd. for C21H19O3 Precipitation with diethyl ether gave the trans diastereisomer, as a white solid, yield 46 %.

Structural properties Derivative 2'h

Pure isomer, white solid, yield 46%, mp. 150-151°C

Retention factor Rf = 0.6 (silica, P/EE = 3/2)

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 86

1 H NMR 300 MHz, CDCl3, δ ppm: 2.25 (ddt, J = 17.9, 5.0, 2.6 Hz, 1H, H-5α), 2.57 (dddd, J = 17.9, 7. [START_REF] Diac | Simple and Versatile Molecular Donors for Organic Photovoltaics Prepared by Metal-Free Synthesis[END_REF]2.8,1.6 Hz,1H,3.56 (ddd,J = 14.5,7.4,[START_REF] Diac | Simple and Versatile Molecular Donors for Organic Photovoltaics Prepared by Metal-Free Synthesis[END_REF]9 Hz, 1H, H-4a), 3.67 (d,J = 14.5 Hz,1H,6.26 (dt,J = 5.6,2.6 Hz,1H,6.65 (ddd,J = 5.7,2.5,1.6 Hz,1H,8H,Har),7.61 (s(br), 1H, H-2'). 13 C NMR 75 MHz,CDCl3,δ ppm: 37.7,42.5,52.1,124.9,126.8,127.5,128.2,128.7,129.1,129.2,129.5,130.0,134.8,134.9,136.1,139.5,140.7,169.8.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 243 (8500), 297 (15633).

HRMS (APCI+)

calcd. for C20H16ClO2 [M+H] + : 323.0833; found: 323.0854.

1 1 1 1--- -(3 (3 (3 (3--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -

one one one one

Chemical Formula: C20H15BrO2; Molecular Weight: 367.24

Precipitation with diethyl ether afforded only the trans diastereoisomer, as a white powder, yield 43%.

Structural properties

Derivative 2'i Pure isomer, white solid, yield 43%, mp. 146-147°C

Retention factor Rf = 0.6 (silica, P/EE = 3/2)

1 H NMR 300 MHz, CDCl3, δ ppm: 2.25 (ddt, J = 17.9, 4.9, 2.6 Hz, 1H, H-5α), 2.57 (dddd, J = 17.9, 7.4, 2.8, 1.6 Hz, 1H, H-5β), 3.56 (ddd, J = 14.5, 7.4, 5.0 Hz, 1H, H-4a), 3.67 (d,J = 14.5 Hz,1H,6.26 (dt,J = 5.5,2.6 Hz,1H,6.64 (ddd,J = 5.7,2.5,1.6 Hz,1H,8H,Har),7.76 (s(br), 1H, H-2'). 13 C NMR 75 MHz,CDCl3,δ ppm: 37.4,42.2,51.8,122.6,125.1,127.1,127.9,128.8,128.9,129.3,129.4,130.0,131.4,134.9,135.8,139.1,140.5,169.5.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 237 (9673), 300 (13987).

HRMS (APCI+)

calcd. for C20H16BrO2 [M+H] + : 367.0328; found: 367.0330. 34.2, 37.7, 42.9, 51.8, 124.1, 127.2, 128.4, 129.0, 129.3, 132.4, 135.7, 138.9, 139.2, 142.8, 147.4, 169.4.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 254 (7267), 360 (7433).

HRMS (APCI+)

calcd. for C20H16NO4 [M+H] + : 334.1074; found: 334.1069.

Synthesis of 1,4-diaryl-dihydrocyclopenta[c]pyrans

General procedure:

12 mmol DDQ were added to a solution containing 10 mmol of isomers cis-and trans-2 derivatives in anhydrous chloroform (100 ml) and the solution was refluxed for 1.5 h under inert atmosphere. After being cooled to room temperature the reaction mixture was filtered and the filtrate washed several times with water. The organic phase was dried over anhydrous MgSO4 and the solvent was evaporated in vacuo. The crude product was purified by column chromatography on silica gel affording a mix of regioisomers which could not be separated (except for derivatives c, d, e, and g). It was observed that in presence of aluminum oxide the isomerisation process of 4 to 5 occurred. 75 MHz,CDCl3,δ ppm: 38.1,116.7,117.5,127.2,127.7,128.3,128.6,129.0,130.2,130.6,132.5,134.1,145.7,151.7,158.7,163.3 [START_REF] Adda | ADADA systems based on triphenylamine as molecular donors for organic photovoltaics[END_REF]38.5,120.9,123.2,127.3,127.4,128.2,128.4,129.2,129.5,129.6,133.9,134.0,140.3,150.4,158.9,162.0. 75 MHz,CDCl3,δ ppm: 21.7,38.2,116.3,116.9,127.1,128.2,128.6,129.7,129.8,130.2,130.5,134.2,140.6,145.8,151.9,158.9,163.4.

1,4 1,4 1,4 1,4--- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -one

UV/Vis

CH2Cl2, λmax (log ε) [nm]: 249 (18000), 265 (18300), 369 (22900).

CH2Cl2, λmax (log ε) [nm]: 263 (19133), 372 (19267).

HRMS (APCI+)

calcd. for C21H17O2 13 C NMR 100 MHz,CDCl3,δ ppm: 38.4,55.4,114.2,120.4,122.4,124.9,127.4,128.0,128.4,128.9,129.2,133.5,133.9,150.0,159.0,160.9,162.0. 75 MHz,CDCl3,δ ppm: 38.2,55.7,114.5,115.8,116.0,125.1,128.1,128.6,128.8,130.2,130.6,134.3,145.6,151.9,159.0,161.2,163.5.

UV/Vis

.1171. 1 1 1 1--- -(4 (4 (4 (4--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -

one one one one

Chemical Formula: C20H13ClO2; Molecular Weight: 320.77

Ratio 4d 5d

4 1

Structural properties

Derivative 4d

Derivative 5d

Not isolated as unique isomer, yellow powder, yield 36% 75 MHz,CDCl3,δ ppm: 38.1,116.9,117.7,128.4,128.6,129.3,130.1,130.6,130.9,133.8,136.3,136.7,145.6,150.5,158.6,163.0.

UV/Vis

CH2Cl2, λmax (log ε) [nm]: 263 (19528), 372 (16996).

HRMS (APCI+)

calcd. for C20H14ClO2 [M+H] + : 321.0677; found: 321.0674. 37.9,116.9,117.7,124.5,128.1,128.4,128.5,129.9,130.4,131.1,132.1,133.7,145.5,150.4,158.5,162.9. 75 MHz,CDCl3,δ ppm: 38.1,117.1,117.8,124.7,128.4,128.5,128.6,130.1,130.6,131.3,132.3,133.8,145.7,150.5,158.7,163.1. 34.2,34.9,38.5,101.4,121.0,123.2,125.8,127.2,127.6,128.2,128.3,128.4,128.2,129.6,129.9,133.8,133.9,150.4,153.4,158.8. 75 MHz,CDCl3,δ ppm: 31.2,34.9,38.2,116.0,116.7,125.7,126.7,127.2,127.9,128.2,129.2,129.4,129.9,130.2,133.9,145.5,151.6,153.3,158.6,163.2.

1 1 1 1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -one

UV/Vis

--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -one

UV/Vis

CH2Cl2, λmax (log ε) [nm]: 247 (18500), 266 (17600), 369 (24100).

CH2Cl2, λmax (log ε) [nm]: 247 (18500), 266 (17600), 369 (24100).

HRMS (APCI+)

calcd. for C24H23O2 [M+H] + : 343.1693; found: 343.1689. calcd. for C24H23O2 [M+H] + : 343.1693; found: 343.1691.

1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -one

C NMR

75 MHz,CDCl3,δ ppm: 38.5,55.6,112.5,116.1,120.0,121.5,123.8,127.6,128.3,128.5,129.3,129.9,133.7,133.8,134.4,150.0,158.7,159.9,161.9. 75 MHz,CDCl3,δ ppm: 38.6,56.2,112.9,116.59,117.2,118.1,120.1,128.7,128.9,130.4,130.6,130.9,134.2,134.4,146.1,151.9,159.1,160.5,163.7.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 246 (15100), 267 (12900), 365 (18800).

CH2Cl2, λmax (ε) [nm] = 257 (12667), 368 (12500).

HRMS (APCI+)

calcd. for C21H17O3 [M+H] + : 317.1172; found: 317.1171. calcd. for C21H17O3 [M+H] + : 317.1172; found: 317.1170.

1 1 1 1--- -(3 (3 (3 (3--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -

one one one one

Chemical Formula: C20H13ClO2; Molecular Weight: 320.77

Ratio 4h 5h

4 1

Structural properties

Derivative 4h

Derivative 5h

Not isolated as unique isomer, yellow solid, yield 32% 37.9, 117.3, 118.1, 125.1, 127.0, 128.3, 128.5, 130.0, 130.2, 130.5, 133.7, 134.0, 135.2, 135.3, 145.5, 149.9, 158.4, 162.8.

UV/Vis

CH2Cl2, λmax (ε) [nm] = 255 (16926), 365 (16877).

HRMS (APCI+)

calcd. for C20H14ClO2 [M+H] + : 321.0677; found: 321.0674. 37.7, 117.1, 117.9, 123.0, 125.3, 128.1, 128.3, 129.7, 129.8, 130.2, 130.3, 132.8, 133.5, 134.1, 145.3, 149.6, 158.2, 162.6.

1 1 1 1--- -(3 (3 (3 (3--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -3 3 3 3--- -one

UV/Vis

CH2Cl2, λmax (ε) [nm] = 252 (14133), 368 (13400).

HRMS (APCI+)

calcd. for C20H13BrO2

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Page | 97

Synthesis of 1,4-diaryl-cyclopenta[c]pyrans

General procedure:

A solution containing a mixture of derivatives 4 and 5 (5 mmol) in anhydrous dichloromethane (120 ml) was cooled to -78 °C, and DIBAL-H (17.5 mmol, 17.5 ml solution 1M in hexane) was added for 30 min., when the solution turned red. The reaction mixture was kept at this temperature for additional 90 minutes and the reaction was monitored by TLC. When the reaction was completed, 150 ml 10% solution of sodium and potassium tartrate was added and the reaction mixture was allowed to cool to room temperature. The aqueous phase was extracted twice with dichloromethane (50 ml); the combined organic phases were washed with brine, and then dried over magnesium sulfate. The solvent was removed in vacuum and the red residue was purified by column chromatography on neutral aluminum oxide, activity Brockmann I, in order to obtain the corresponding cyclopenta[c]pyrans 6.

1,4 1,4 1,4 1,4--- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C20H14O; Molecular Weight: 370.32

Structural properties

Derivative 6a

orange solid, yield 20% Retention factor Rf = 0.8 (silica, PE/EE = 3/1)

H (1-C6H5)).
Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 98

13 C NMR 75 MHz,CDCl3,δ ppm: 109.2,110.8,122.1,124.1,127.2,128.2,128.4,128.7,128.72,128.9,130.5,133.5,135.0,135.6,136.0,155.2.

HRMS (APCI+)

calcd. for C20H15O [M+H] + : 271.1117; found: 271.1117.

4 4 4 4--- -phenyl phenyl phenyl phenyl--- -1 1 1 1--- -( ( ( (p p p p--- -tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H16O; Molecular Weight: 284.35

Structural properties

Derivative 6b

Red solid, yield 16%, mp. 172-173°C

Retention factor Rf = 0.8 (silica, PE/EE = 3/1)

1 H NMR 300 MHz, CDCl3, δ ppm: 2.47 (s, 3H, p-CH3), 6.65 (dd, J = 2.6, 0.9 Hz, 1H, H-7), 7.09 (dd, 1H, J = 4.6, 0.9 Hz, H-5), 7.30 (dd, J = 4.6, 2.6 Hz, 1H, H-6), 7. 44-7.71 (m, 5H, 4-C6H5), 7.67 (s, 1H, H-3), 7.38, 7.98 (2 x d, J = 8.0 Hz, 4H, C6H4-p-CH3).

13 C NMR 100 MHz, CDCl3, δ ppm: 21.7, 109. 2, 110.9, 121.8, 124.2, 126.1, 127.3, 128.6, 128.9, 129.0, 129.7, 130.8, 134.7, 135.8, 136.1, 141.1, 155.7.

HRMS (APCI+)

calcd. for C21H17O [M+H] + : 285.1274; found: 285.1282.

1 1 1 1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H16O2; Molecular Weight: 300.35

Structural properties

Derivative 6c

Deep-red solid, yield 14%, mp. 124-126°C

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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Retention factor Rf = 0.6 (silica, PE/EE = 4/1) 13 C NMR 75 MHz, CDCl3, δ ppm: 55. 6, 109.0, 110.8, 114.4, 121.2, 124.1, 126.1, 127.3, 128.2, 128.5, 128.9, 130.6, 134.4, 135.8, 135.9, 155.5, 161.6.

HRMS (APCI+)

calcd. for C21H17O2 [M+H] + : 301.1223; found: 301.1225.

1 1 1 1--- -(4 (4 (4 (4--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C20H13ClO; Molecular Weight: 304.77

Structural properties

Derivative 6d

Deep-red solid, yield 20%, mp. 142-144°C

Retention factor Rf = 0.7 (silica, P/EE = 4/1) 13 C NMR 75 MHz,CDCl3,δ ppm: 109.5,110.4,122.1,124.2,127.2,128.2,128.4,128.8,129.1,130.1,131.9,135.4,135.5,135.9,136.7,153.8.

HRMS (APCI+) calcd. for C20H14ClO

[M+H] + : 305.0728; found: 305.0747.

1 1 1 1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C20H13BrO; Molecular Weight: 349.22

Structural properties

Derivative 6e

Red solid, yield 38%

Retention factor Rf = 0.7 (silica, P/EE = 4/1)

-3, o-H (4-C6H5), m'-H (C6H4-p-Br)), 7.94 (d, J = 9.0 Hz, 2H, o'-H (C6H4-p-Br)).
13 C NMR 75 MHz,CDCl3,δ ppm: 109.8,110.7,122.4,124.5,125.5,127.5,128.5,128.6,129.1,130.6,132.4,132.6,135.7,135.8,136.2,154.2.

MS (APCI+)

m/z = 349.8 [M] + 1 1 1 1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C24H22O; Molecular Weight: 326.43

Structural properties

Derivative 6f

Deep-orange solid, yield 19% , mp. 73-74°C

Retention factor Rf = 0.8 (silica, P/EE = 3/2) 13 C NMR 75 MHz,CDCl3,δ ppm: 29.7,31.2,34.9,109.0,110.8,121.7,124.0,125.8,127.1,128.1,128.4,128.7,128.7,130.6,134.6,135.6,135.9,154.0.

Chemistry and Photovoltaic Conversion ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------

HRMS (APCI+)

calcd. for C24H23O [M+H] + : 327.1743; found: 327.1737.

1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H16O2; Molecular Weight: 300.35

Structural properties

Derivative 6g

Red solid, yield 23% , mp. 81-82°C

Retention factor Rf = 0.6 (silica, P/EE = 3/2) (overlapped peaks, 4H, C6H4-m-OCH3).

13 C NMR 75 MHz, CDCl3, δ ppm: 55. 2, 108.9, 110.5, 113.7, 116.2, 121.1, 121.8, 123.8, 126.9, 127.9, 128.1, 128.5, 129.5, 134.4, 134.7, 135.2, 135.7, 154.7, 159.4.

HRMS (APCI+)

calcd. for C21H17O2 [M+H] + : 301.1223; found: 301.1229.

1 1 1 1--- -(3 (3 (3 (3--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C20H13ClO; Molecular Weight: 304.77

Structural properties

Derivative 6h

Red-orange solid, yield 15%, mp. 128-129°C

Retention factor Rf = 0.7 (silica, P/EE = 4/1)

H-5' (1-C6H4-m-Cl)), 7.72-7.65 (overlapped peaks, 3H, o-H (4-C6H5), H-3), 7.97 (m, 1H, H-6' (C6H4-m-Cl)), 8.05 (s, 1H, H-2' (C6H4-m-Cl)).
13 C NMR 75 MHz, CDCl3, δ ppm: 109. 6, 110.4, 122.4, 124.2, 127.0, 127.3, 128.3, 128.4, 128.7, 128.8, 130.0, 130.5, 134.8, 135.1, 135.3, 135.7, 135.9, 153.3.

1 1 1 1--- -(3 (3 (3 (3--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C20H13BrO; Molecular Weight: 349.22

Structural properties

Derivative 6i

Red-orange solid, yield 12%, mp. 130-131°C

Retention factor Rf = 0.6 (silica, P/EE = 4/1)

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Page | 103

1H, H-2' (C6H4-m-Br)).

13 C NMR 75 MHz,CDCl3,δ ppm: 110.2,111.0,123.0,123.3,124.8,127.8,128.1,128.9,129.0,129.4,130.9 132.2,133.9,135.9,135.9,136.4,136.6,153.7.

Synthesis of 3-methyl-1,4-diaryl-cyclopenta[c]pyrans

General procedure:

To a solution containing a mixture of isomers 4 and 5 (5 mmol) in anhydrous dichloromethane (100 ml), 25 mmol AlMe3 -solution in pentane were added over 20 min. at 0°C. Reaction mixture was stirred for 30 min. at 0 °C, then the temperature was raised to 40°C for 2 hours, and finally it was cooled to -78°C when 10 mL methanol was added. The reaction mass was maintained at -78°C for 30 min., then (100 ml) 10% solution of sodium and potassium tartrate was added and the mixture was allowed to reach the room temperature.

Aqueous phase was extracted twice with dichloromethane (50 ml); the combined organic phases were washed with brine, and dried over magnesium sulfate. The solvent was removed in vacuum and the red residue was purified by column chromatography on neutral aluminum oxide, activity Brockmann I, in order to obtain the corresponding cyclopenta [c]pyrans 7.

3 3 3 3--- -methyl methyl methyl methyl--- -1,4 1,4 1,4 1,4--- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H16O; Molecular Weight: 284.35

Structural properties

Derivative 7a

Deep-red solid, yield 19%, mp. 70-72°C

Retention factor Rf = 0.6 (silica, PE/EE = 4/1)

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 104 13 C NMR 75 MHz,CDCl3,δ ppm: 17.8,110.4,121.4,126.1,127.5,127.7,128.5,128.7,129.9,130.3,132.4,133.0,135.2,137.5,137.8,146.6,158.5.

1 1 1 1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C22H18O2; Molecular Weight: 314.38

Structural properties

Derivative 7c

Deep-orange solid, yield 28%, mp. 13 C NMR 75 MHz,CDCl3,δ ppm: 17.2,55.4,107.9,109.5,114.2,120.4,120.7,126.2,127.5,128.4,129.8,130.4,130.6,134.3,136.4,144.2,155.0,161.4.

HRMS (APCI+)

calcd. for C22H19O2 [M+H] + : 315.1380; found: 315.1384.

1 1 1 1--- -(4 (4 (4 (4--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H15ClO; Molecular Weight: 318.80

Structural properties

Derivative 7d

Dark-red solid, yield 21%, mp. 111-113°C Retention facto r Rf = 0.8 (silica, P/EE = 4/1) 4, 109.2, 120.6, 121.7, 127.6, 128.4, 129.0, 129.7, 129.9, 130.6, 132.1, 135.5, 136.1, 136.5, 144.5, 153.4.

HRMS (APCI+)

calcd. for C21H16ClO [M+H] + : 319.0884; found: 319.0888.

1 1 1 1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C21H15BrO; Molecular Weight: 363.25

Structural properties

Derivative 7e

Deep-red solid, yield 24% Retention factor Rf = 0.6 (silica, P/EE = 4/1)

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Page | 106 7.95 (2 x d, J = 8.4 Hz, 4H, C6H4-p-Br).

13 C NMR 75 MHz,CDCl3,δ ppm: 17.5,108.7,109.5,120.9,121.9,123.7,125.2,127.9,128.7,129.9,130.5,130.9,132.3,132.9,135.9,136.4,144.9.

1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran
Chemical Formula: C22H18O2; Molecular Weight: 314.38

Structural properties

Derivative 7g

Red solid, yield 27%

Retention factor Rf = 0.6 (silica, P/EE = 4/1) Hz, 1H, H-6' (C6H4-m-OCH3)).

13 C NMR 75 MHz,CDCl3,δ ppm: 17.8,56.1,108.8,110.2,114.8,116.8,121.2,121.9,122.4,128.2,129.1,130.4,130.4,131.3,135.6,135.7,136.9,145.1,155.3,160.4.

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Page | 107

Synthesis of trifluoroacetyl-cyclopenta[c]pyrans

General procedure:

To a solution of cyclopenta [c]pyrans 6 or 7 (5 mmol) in anhydrous dichloromethane (100 ml) were added under inert atmosphere, at room temperature, triethylamine (15 mmol, 2.1 ml) and trifluoroacetic anhydride (10 mmol, 1.41 ml). The reaction mixture was stirred at room temperature for 30 minutes. When the cyclopenta [c]pyran was consumed, the organic phase was washed with water and dried over magnesium sulfate. A brownorange residue was obtained after concentration in vacuum; this was purified afterwards on silica gel column chromatography to afford an orange solid, having a strong orange fluorescence by irradiation at 365 nm.

1 1 1 1--- - (1,4 (1,4 (1,4 (1,4-
-- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,2 2,2,2 2,2,2 2,2,2--- -trifluoroethanone

trifluoroethanone trifluoroethanone trifluoroethanone

Chemical Formula: C22H13F3O2; Molecular Weight: 366.33

Structural properties

Derivative 8a

Orange solid, yield 78%, mp. 142-144°C

Retention factor Rf = 0.2 (silica, P/EE = 4/1)

1 H NMR 300 MHz, CDCl3, δ ppm: 6.78 (d, J = 3.9 Hz, 1H, H-5), 7.47-7.74 (overlapped peaks, 10H, H-ar (C6H5)), 8.06 (s, 1H, H-3), 8.16 (dq, J = 3.9, 2.1 Hz, 1H, H-6).

13 C NMR 75 MHz,CDCl3,δ ppm: 111.2,115.9,117.6,120.7,125.3,125.3,128.0,128.6,129.1,129.8,129.0,131.3,133.3,133.5,140.0,141.6,145.9,161.9,172.3.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 237 (4.49), 315 (4.33), 450 (3.92).

HRMS (APCI+)

calcd. for C22H14F3O2 [M+H] + : 367.0940; found: 367.0938.

1 1 1 1--- -(4 (4 (4 (4--- -phenyl phenyl phenyl phenyl--- -1 1 1 1--- -( ( ( (p p p p--- -tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,2 2,2,2 2,2,2 2,2,2--- -trifluoro

trifluoro trifluoro trifluoroethanone ethanone ethanone ethanone

Chemical Formula: C23H15F3O2; Molecular Weight: 380.36

Structural properties

Derivative 8b

Orange solid, yield 69%, mp. 170-171°C

Retention factor Rf = 0.5 (silica, P/EE = 3/2)

1 H NMR 300 MHz, CDCl3, δ ppm: 2.48 (s, 3H, CH3), 6.76 (d, J = 3.9 Hz, 1H, H-5), 7.33 (d,

J = 7.8 Hz, 2H, m'-H (C6H4-p-CH3)), 7.51-7.64 (overlapped peaks, 7H, o'-H (C6H4-p-CH3), H-ar (4- C6H5
)), 8.04 (s, 1H, H-3), 8.16 (dq, J = 3.9, 2.1 Hz, 1H, H-6).

13 C NMR 75 MHz,CDCl3,δ ppm: 22.4,111.6,116.3,116.5,120.1,120.9,125.8,129.2,129.4,129.5,129.7,130.4,131.2,134.0,140.8,142.1,142.4,146.2,162.7.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 245 (4.38), 323 (4.19), 450 (3.79).

HRMS (APCI+)

calcd. for C23H16F3O2 [M+H] + : 381.1097; found: 381.1086. 2 2,2,2 2,2,2 2,2,2

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

----trifluoro trifluoro trifluoro trifluoroethanone ethanone ethanone ethanone

Chemical Formula: C23H15F3O3; Molecular Weight: 396.36

Structural properties

Derivative 8c

Orange solid, yield 93%, mp. 180-181°C

Retention factor Rf = 0.3 (silica, P/EE = 4/1)

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 109 13 C NMR 100 MHz, CDCl3, δ ppm: 55. 5, 111.2, 113.7, 116.1, 119.3, 120.2, 125.3, 125.8, 128.8, 129.1, 129.3, 132.0, 133.6, 140.6, 141.6, 145.5, 162.0, 162.4, 167.9.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 245 (4.42), 333 (4.15), 450 (3.82).

HRMS (APCI+)

calcd. for C23H16F3O3 [M+H] + : 397.1046; found: 397.1049.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,2 2,2,2 2,2,2 2,2,2--- -trifluoroethanone

trifluoroethanone trifluoroethanone trifluoroethanone

Chemical Formula: C22H12ClF3O2; Molecular Weight: 400.78

Structural properties

Derivative 8d

Orange solid, yield 78%, mp. 170-171°C

Retention factor Rf = 0.4 (silica, P/EE = 3/1) 150 MHz,CDCl3,δ ppm: 111.7,115.9,116.8,118.7,120.9,125.6,128.6,128.8,129.3,129.4,131.3,132.1,133.3,137.8,140.4,141.8,146.5,160.7.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 242 (4.45), 318 (4.27), 453 (3.83).

HRMS (APCI+)

calcd. for C22H13ClF3O2 [M+H] + : 401.0551; found: 401.0558. 13 C NMR 75 MHz, CDCl3, δ ppm: 102. 1, 112.2, 116.4, 120.2, 121.4, 126.1, 126.8, 129.3, 129.8, 129.9, 131.9, 131.9, 132.9, 133.8, 141.0, 142.4, 147.1, 161.22.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 242 (4.49), 318 (4.31), 453 (3.85).

HRMS (APCI+)

calcd. for C22H13BrF3O2 [M+H] + : 445.0046; found: 445.0062.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 111

Hz, 1H, H-6).

13 C NMR 100 MHz, CDCl3, δ ppm: 31. 4, 35.2, 111.2, 116.1, 116.4, 119.3, 120.4, 125.2, 125.3, 128.8, 129.1, 129.3, 130.0, 130.7, 133.6, 140.4, 141.6, 145.7, 154.9, 162.2.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 243 (4.45), 323 (4.26), 450 (3.83).

HRMS (APCI+)

calcd. for C26H22F3O2 [M+H] + : 423.1566; found: 423.1584. 13 C NMR 75 MHz, CDCl3, δ ppm: 55.7, 111. 5, 115.2, 116.3, 117.8, 119.8, 121. 0, 122.6, 125.7, 128.9, 129.4, 129.5, 133.6, 134.8, 140.4, 141.8, 146.1, 161.9, 172.4, 172.8.

1 1 1 1--- -(1 (1 (1 (1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 233 (4.55), 315 (4.34), 450 (3.98).

HRMS (APCI+)

calcd. for C23H16F3O3 [M+H] + : 397.1046; found: 397.1051. CDCl3,δ ppm: 111.7,116.0,116.7,118.7,121.1,125.7,128.4,128.8,129.3,129.4,129.5,129.7,131.3,133.3,134.3,135.2,140.2,141.8,146.6,160.1.

1 1 1 1--- -(1 (1 (1 (1--- -(3 (3 (3 (3--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 243 (4.33), 318 (4.20), 450 (3.75).

HRMS (APCI+)

calcd. for C22H13ClF3O2 [M+H] + : 401.0551; found: 401.0558.

1 1 1 1--- -(1 (1 (1 (1--- -(3 (3 (3 (3--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 113 13 C NMR 75 MHz,CDCl3,δ ppm: 111.7,115.8,115.9,119.6,121.1,122.2,125.7,128.8,128.9,129.3,129.4,129.6,132.5,133.3,134.3,135.4,140.2,141.8,146.7,160.0.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 238 (4.40), 313 (4.24), 453 (3.82).

HRMS (APCI+)

calcd. for C22H13BrF3O2 [M+H] + : 445.0046; found: 445.0052. 13 C NMR 75 MHz, CDCl3, δ ppm: 17.9, 110.9, 115.0, 116.0, 119.9, 120. 5, 122.4, 128.2, 128.6, 129.0, 129.7, 130.0, 131.3, 133.97, 134.3, 143.7, 146.4, 152.2, 161.7.

1 1 1 1--- -(3 (3 (3 (3--- -methyl methyl methyl methyl--- -1,4 1,4 1,4 1,4--- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 230 (4.39), 318 (4.23), 458 (3.89).

HRMS (APCI+)

calcd. for C23H16F3O2 [M+H] + : 381.1097; found: 381.1100. 13 C NMR 75 MHz, CDCl3, δ ppm: 17.9, 55. 6, 110.8, 113.6, 114.8, 116.1, 119.8, 119.9, 122.2, 126.0, 128.6, 128.9, 129.7, 132.0, 134.4, 144.2, 145.9, 151.9, 161.7, 162.2.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 238 (4.31), 332 (4.11), 458 (3.81).

HRMS (APCI+)

calcd. for C24H18F3O3 [M+H] + : 411.1203; found: 411.1221. 13 C NMR 100 MHz, CDCl3, δ ppm: 18.0, 77.4, 111.2, 114.8, 119.4, 120.5, 122.6, 126.1, 128.7, 129.1, 129.7, 131.4, 131.5, 132.7, 134.1, 144.0, 147.0, 152.4, 160.4.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 233 (4.34), 322 (4.18), 463 (3.75). 13 C NMR 75 MHz, CDCl3, δ ppm: 18. 4, 90.1, 111.6, 115.2, 116.4, 123.0, 126.6, 129.2, 129.5, 130.1, 131.8, 131.9, 133.1, 134.5, 144.5, 147.4, 152.8, 160.8, 170.8.

1 1 1 1--- -(1 (1 (1 (1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 233 (4.41), 322 (4.25), 463 (3.82).

HRMS (APCI+)

calcd. for C23H15BrF3O2 [M+H] + : 459.0202; found: 459.0206. 13 C NMR 75 MHz, CDCl3, δ ppm: 18. 3, 31.8, 35.6, 111.2, 115.5, 120.5, 122.7, 125.5, 129.0, 129.4, 130.2, 130.5, 134.8, 141.9, 142.1, 144.4, 146.5, 152.4, 155.1, 162.3, 171.8.

)phenyl) )phenyl) )phenyl) )phenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 233 (4.49), 323 (4.30), 458 (3.91).

HRMS (APCI+)

calcd. for C27H24F3O2 [M+H] + : 437.1723; found: 437.1730. 13 C NMR 75 MHz, CDCl3, δ ppm: 18.1, 55. 6, 110.9, 115.2, 115.4, 116.1, 117.5, 119.9, 120.6, 122.6, 122.6, 128.8, 129.1, 129.3, 129.9, 134.4, 135.1, 143.9, 146.5, 152.3, 159.3, 161.6.

1 1 1 1--- -(1 (1 (1 (1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,

Synthesis of diformyl-cyclopenta[c]pyrans

General procedure:

Phosphorus (V) oxychloride (7 mmol, 0.65 ml) was added portion wise at 0°C to a solution of the corresponding cyclopenta [c]pyran derivative 6 (1 mmol) in anhydrous dimethylformamide (10 ml). The reaction mixture was stirred for 10 minutes at room temperature and then heated overnight at 45°C in inert atmosphere. Being cooled to room temperature, 100 ml 0.7M solution of sodium acetate was added, then 2M solution of sodium hydroxide till the pH = 9-10 was reached. The aqueous phase was extracted three times with diethyl ether (80 ml) and then the combined organic phases were washed with water and brine, dried over MgSO4 and concentrated to dryness. The resulted oil was triturated with diethyl ether affording the pure formylated derivatives in good yields.

1,4 1,4 1,4 1,4--- -diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[ diphenylcyclopenta[c c c c]pyran ]pyran ]pyran
]pyran----5,7 5,7 5,7 5,7----dicarbaldehyde dicarbaldehyde dicarbaldehyde dicarbaldehyde Chemical Formula: C22H14O3; Molecular Weight: 326.34

Structural properties

Derivative 12a

Deep-brown solid, yield 75%, mp. 236-237°C

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta [c]pyrans

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Page | 118 13 C NMR 100 MHz, CDCl3, δ ppm: 122. 1, 124.6, 125.3, 126.1, 128.9, 129.4, 129.6, 129.8, 130.3, 132.3, 132.7, 134.3, 140.0, 142.1, 144.1, 161.9, 184.6, 185.9.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 295 (4.55), 420 (3.67).

HRMS (APCI+)

calcd. for C22H15O3 [M+H] + : 327.1016; found: 327.1027.

4 4 4 4--- -phenyl phenyl phenyl phenyl--- -1 1 1 1--- -( ( ( (p p p p--- -tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[ tolyl)cyclopenta[c c c c]pyran ]pyran ]pyran
]pyran----5,7 5,7 5,7 5,7----dicarbaldehyde dicarbaldehyde dicarbaldehyde dicarbaldehyde Chemical Formula: C23H16O3; Molecular Weight: 340.37

Structural properties

Derivative 12b

Ochre solid, yield 42%, mp. 246-247°C 13 C NMR 100 MHz, CDCl3, δ ppm: 21.9; 122.0; 124. 5; 125.4; 126.0; 129.4; 129.5; 129.6; 129.7; 129.9; 130.3; 134.4; 140.0; 141.7; 143.1; 144.0; 162.2; 184.8; 186.0.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 302 (4.55), 423 (3.69).

HRMS (APCI+)

calcd. for C23H17O3 [M+H] + : 341.1172; found: 341.1188.

1 1 1 1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran
]pyran----5,7 5,7 5,7 5,7----dicarbaldehyde dicarbaldehyde dicarbaldehyde dicarbaldehyde Chemical Formula: C23H16O4; Molecular Weight: 356.37

Structural properties

Derivative 12c

Maroon solid, yield 95%, mp. 226-227°C 4; 121.4; 124.5; 124.8; 125.4; 125.9; 129.4; 129.5; 129.7; 132.3; 134.4; 140.2; 141.8; 143.9; 162.0; 163.0; 184.8; 186.0.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 315 (4.42), 427 (3.69).

HRMS (APCI+)

calcd. for C23H17O4 [M+H] + : 357.1121; found: 357.1125.

Structural properties

Derivative 12e

Brick-red solid, yield 83%, mp. 215-216°C 13 C NMR 150 MHz, CDCl3, δ ppm: 121. 5, 124.7, 125.4, 126.2, 127.3, 129.4, 129.6, 129.9, 131.5, 131.8, 132.0, 134.1, 140.4, 144.2, 144.3, 160.9, 184.3, 185.8.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 297 (4.60), 428 (3.65).

HRMS (APCI+)

calcd. for C22H14BrO3 [M+H] + : 405.0121; found: 405.0143.

1 1 1 1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl) butyl) butyl) butyl)phenyl) phenyl) phenyl) phenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran
]pyran----5,7 5,7 5,7 5,7----dicarbaldehyde dicarbaldehyde dicarbaldehyde dicarbaldehyde Chemical Formula: C26H22O3; Molecular Weight: 382.45

Structural properties

Derivative 12f

Brown solid, yield 93%, mp. 216-217°C

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 302 (4.58), 423 (3.69).

HRMS (APCI+)

calcd. for C26H23O3 [M+H] + : 383.1642; found: 383.1644.

1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran
]pyran----5,7 5,7 5,7 5,7----dicarbaldehyde dicarbaldehyde dicarbaldehyde dicarbaldehyde Chemical Formula: C23H16O4; Molecular Weight: 356.37

Structural properties

Derivative 12g

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material

Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 121

Maroon solid, yield 61%, mp. 162-164°C

Synthesis of donor-acceptor systems

General procedure:

Malononitrile (2 mmol, 132 mg) and aluminum oxide (7 mmol, 714 mg) were added to a solution of corresponding diformyl derivatives 12 (1 mmol) in anhydrous dichloromethane (50 ml) and the mixture was stirred overnight at room temperature. The alumina was filtered off and the filtrate evaporated. The crude product was purified by column chromatography on silica gel using diethyl ether as solvent yielding the target compounds. ------------------------------------------------------------------------------------------------------------------------------------ 113.7, 113.9, 114.7, 114.8, 115.3, 119.2, 119.3, 122.3, 123.6, 126.8, 129.4, 129.9, 130.6, 131.7, 132.3, 136.8, 140.6, 145.5, 150.0, 150.1, 163.0, 164.1.

2 2 2 2,2' ,2' ,2' ,2'--- -((1 ((1 ((1 ((1--- -(4 (4 (4 (4--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -5,7 5,7 5,7 5,7--- -diyl) diyl) diyl) diyl)di di di di(meth (meth (meth (methy y y ylyli lyli lyli lylidene))dimalononitrile dene))dimalononitrile dene))dimalononitrile dene))dimalononitrile

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 367 (4.63); 450 (4.38).

HRMS (APCI+)

calcd. for C29H17N4O2 [M+H] + : 453.1346; found: 453.1345.

2,2' 2,2' 2,2' 2,2'--- -((1 ((1 ((1 ((1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -5,7 5,7 5,7 5,7diyl) diyl) diyl) diyl)di(methylyli di(methylyli di(methylyli di(methylylidene))dimalononitrile dene))dimalononitrile dene))dimalononitrile dene))dimalononitrile
Chemical Formula: C32H22N4O; Molecular Weight: 478.54

Structural properties

Derivative 13f Red solid; yield 91%; mp. 270-272°C; Rf = 0.6 (silica gel, diethyl ether). 35.6, 113.6, 113.9, 114.6, 114.8, 119.2, 119.3, 124.2, 126.7, 127.0, 127.4, 129.4, 129.9, 130.1, 130.7, 131.7, 137.0, 140.4, 145.7, 150.0, 150.1, 157.9, 163.1.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 352 (4.62); 446 (4.39).

HRMS (APCI+)

calcd. for C32H23N4O [M+H] + : 479.1866; found: 479.1855.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 123 2,2' 2,2' 2,2' 2,2'--- -((1 ((1 ((1 ((1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -5,7 5,7 5,7 5,7--- -diyl) diyl) diyl) diyl)di(meth di(meth di(meth di(methylylidene))dimalononitrile ylylidene))dimalononitrile ylylidene))dimalononitrile ylylidene))dimalononitrile
Chemical Formula: C29H16N4O2; Molecular Weight: 452.46

Structural properties

Derivative 13g

Red solid; yield 61%; mp. 301-302°C; Rf = 0.5 (silica gel, diethyl ether). 13 C NMR 150 MHz, DMSO-d6, δ ppm: 55.7, 73.6, 75.0, 113.9, 114.1, 114.9, 115.1, 117.8, 118.7, 119.0, 122.7, 123.8, 126.1, 129.4, 129.6, 129.9, 130.5, 131.4, 131.8, 134.8, 141.4, 150.2, 151.0, 159.5, 162.9.

UV-Vis

CH2Cl2, λmax (log ε) [nm]: 348 (4.47); 445 (4.35).

HRMS (APCI+)

calcd. for C29H17N4O2 [M+H] + : 453.1346; found: 453.1338.

Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta[c]pyrans -------------------------------------------------------------------------------------------------------------------------------------

Page | 124 Compounds possessing this motif present multiple pharmacological activities such as antiulcer 34 , antidepressant 35 and antiallergenic 36 ones.

Indenopyrans (e.g. isomers A1 and A2) represent a new class of derivatives used as intermediates for the development of Top I anticancer agents such as indenoisoquinoline products. The indenoisoquinoline's properties were assumed by comparing the cytotoxicity profile of these derivatives to those of other known topoisomerase I inhibitors including camptothecin (A3) and its clinically useful derivatives topotecan (A4) and irinotecan (A5) 37 (chart 1).

Chart 1

pyran-2-ones can be used as perspective building blocks for the preparation of novel trifluoromethylated heterocycles, like indone and carbostyril derivatives.

The important biological functions in nature and the synthetic potential of αpyrones for the construction of a variety of arenes and heteroarenes challenged us to obtain and investigate new indenopyrone derivatives.

Herein we report the synthesis and study of optoelectronic properties of some substituted indenopyran compounds.

Original contributions

For a long time, the Diels-Alder reaction of simple heterosubstituted 1,3-dienes has been considered a standard method for preparing highly functionalized ring systems. 55 Substituted dienes bearing two different heteroatoms are even more appreciated due to their value in natural product synthesis. 56 Taking into account the potential of the diazalactones to participate as dienophile components in inverse-electron demand Diels-Alder reactions, a series of new tetrahydroindeno [1,2-c]pyran derivatives was synthesized. Addition of freshly distilled indene (as diene component) to oxadiazinones 1 (dienophile) occurs under acidic conditions, in presence of TFA and TFAA, leading to the formation of tetrahydroindeno [1,2c]pyran-3-ones as a mixture of regioisomers (scheme 2). As already mentioned in chapter 1, diazalactone derivatives 1 were obtained using a procedure described in literature 28 .

54 S. A.

Scheme 3

In theory, two regioisomers can be formed: isomer 2, which exhibits the benzen ring condenced at C-5a-C-9a and its regioisomer 3 having the benzen ring at C-4b-C-8a. Due to the asymmetric centers found in positions 4 and 4a, each regioisomer can be expressed as a set of diastereoisomers (2'/3' possessing the two hydrogen atoms at positions 4 and 4a in a trans configuration and 2''/3'' having the two hydrogen atoms in a cis configuration, chart 2).

Chart 2.Possible isomers of 3,4,4a,5-tetrahydroindeno [1,2-c]pyran-3-one 2 and 3,4,4a,9tetrahydroindeno [1,2-c]pyran-3-one 3

In most cases regioisomer 2 is preponderantly formed, on occasion the formation of derivative 3 is not even observed (e.g. 3d derivative) and the nature of the substituent influences the ratio between regio-and diastereoisomers (table 1). Conditions:

TFAA 1.5 eq.; TFA 1.55 eq.; indene 6 eq.; 9 days reflux, CCl4

Ratio 2' 2'' 3' 3'' a R = C6H5 1 - - 0.2 b R = C6H4-p-Br 1 1 - 0.25 c R = C6H4-p-t Bu 1 1 0.2 - d R = C6H4-m-OCH3 1.2 1 - -
As the diastereoisomers exhibit very close Rf values, their separation by conventional chromatography was very difficult to accomplish. Nevertheless, successful separation of diastereoisomers 2' and 2'' as individual isomer has been achieved (in a very small amount) for all compounds.

The configuration of the diastereoisomers was assigned by 1 H NMR spectroscopy.

Analyzing the 1 H NMR spectra (figure 1

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Page | 149

With various 1,4-disubstituted indenopyrone derivatives in hand, we next investigated their photophysical properties, the absorption spectra of indeno-derivatives measured in acetonitrile and dichloromethane being shown in figures 2 and 3. Absorption spectra suggest little differences in the electronic band structures for 2a-d in acetonitrile and dichloromethane, respectively. Intense broad absorption bands are present in areas ranging from 275-282 nm and 307-317 nm, respectively, values typical for π -π * and n -π * transitions. A general observation is that, when compared to reference compound 2a, the maximum absorption band of 2b-d is slightly red-shifted due to either electron donating (OCH3, tBu) or electron withdrawing (Br) groups attached at the 1-phenylene ring (table 2).

The influence of the substituent on the electronic spectra determined in acetonitrile generally presents the same trend when recorded in dichloromethane (see fig. 3). However, a slight bathochromic shift could be observed when dichloromethane was used as solvent, in contrast to the hypsochromic shift in the more polar acetonitrile.

The analysis of the absorption spectra (figure 3) revealed some differences between diastereoisomers 2' and 2'', as well as between regioisomers 2''b and 3''b. For example, if we compare the trans isomers 2' with the corresponding cis isomers 2'' a small shift to

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Page | 151

The fluorescence properties of the indeno-pyrone derivatives were also investigated; emission spectral details at various concentrations are given in figure 4 and details about the emission maxima and quantum yield are shown in table 3.

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Page | 152 1) 58 .

ФF = Фref ( )( )( ) (1)
where ФF is the quantum yield of samples, Фref is the quantum yield of 9,10diphenylanthracene, Aref, Sref, nref and Asample, Ssample, nsample are the absorbance at the excited wavelengths, the integrated emission band area and the solvent refractive index of the standard and the sample, respectively.

Remarkably, the fluorescence quantum yield calculated relative to 9,10diphenylanthracene is significantly higher in case of trans isomers 2' as compared to the corresponding cis isomers 2'' (table 4).

58 Shaki, H., Gharanjig, K., Rouhani, S., Khosravi, A., J. Photo. Photobiol A:Chem. 2010, 216, 44.

2'd 2''d

The photoluminescence properties of some dihydroindenopyrones were also investigated in solid state, these derivatives showing emissions maxima in the range of 423-491 nm when excited at 310 nm (figure 5, table 4). Comparing the fluorescence spectra of both diastereoisomers, in solution (acetonitrile) and in solid state (figure 5), an important bathochromic shift of λmax and a broadening of the emission band due to intermolecular interactions could be observed in solid state. Using the same procedure, the enol-lactone isomeric mixture 2'c/3'c was subjected to dehydrogenation and in this case a mixture of regioisomers, namely 6 and 6' was obtained in 17% yield (scheme 4). The 1 H NMR spectrum revealed the formation of fully oxidized derivative 7 in a very small amount, which could not be isolated. After purification by column chromatography on silica gel, the starting enol-lactone derivative 2'c was recovered in 50% yield.

Scheme 4

The structure of the new compounds was determined by NMR spectroscopy and mass spectrometry. The 1 H NMR spectra of α-pyrones 6 and 6' (figure 7) show in the aliphatic region specific signals given by protons at position 9 as a singlet at 4.19 ppm for derivative 6' and at 3.97 ppm for the protons at position 5 in compound 6, respectively. The optoelectronic and photoluminescence properties of the obtained compounds were also investigated, all spectra being recorded in methylene chloride. The UV-Vis absorption spectra (figure 9) show for all three compounds two absorption maxima at around 275 nm and 370 nm, respectively which could be assigned to the π-π* and n-π* transitions. A bathochromic shift (10 nm) in the absorption spectra due to the extended conjugation can be seen in the case of derivative 6' as compared to its regioisomer 6. All derivatives show very weak emission in the range 380-550 nm (figure 9) when excited at 370 nm and the quantum yields calculated relative to 9,10-diphenylanthracene were extremely low (<1%).

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Page | 160

Conclusions

New indenopyrone derivatives have been synthesized and fully analyzed by NMR, UV-Vis and fluorescence spectroscopy, mass spectrometry and X-Ray diffractometry.

Separation of diastereoisomers was possible in a small amount in all cases.

All synthesized derivatives are blue emitters, the indenopyrones having a weaker emission than the corresponding dihydroindenopyrone derivatives.

It was observed that the fluorescence quantum yield calculated relative to 9,10diphenylanthracene is significantly higher for the trans isomers as compared to the corresponding cis isomers.

A Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

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Page | 161

Experimental part

General Remarks

1 H and 13 C NMR spectra were recorded in CDCl3 at room temperature on Bruker

Avance 400 and 600 spectrometer (δ in ppm, J in Hz) at 1 H operating frequencies of 400

MHz (100 MHz for 13 C) and 600 MHz (150 MHz for 13 C), respectively; spectra were referenced using the solvent signal as internal standard.

HRMS in APCI mode ionization were recorded with an LTQ XL ThermoScientific mass spectrometer.

UV-Vis absorption spectra were carried out with a Cecil 9500 spectrophotometer using quartz cuvettes (1 cm).

Fluorescence spectra were taken on a JASCO FP-8300 spectrofluorometer using glass cuvettes (1 cm).

Melting points were measured with a Kleinfeld melting point apparatus and are uncorrected.

Thin layer chromatography was performed on Silica gel 60 chromatographic plates F254 and column chromatography was performed on Silica gel.

Solvents were dried and distilled under argon using standard procedures prior to use. Chemicals of commercial grade were used without further purification. Indene was freshly distilled prior to use.

Chapter 2 -Synthesis and Structural Analysis of new Indenopyrone derivatives -------------------------------------------------------------------------------------------------------------------------------------

Page | 162

Compounds synthesis

Synthesis of dihydroindenopyrone derivatives

General procedure:

5 mmol (0.7 ml) TFAA , 5.25 mmol (0.4 ml) TFA and 30 mmol (3.5 ml) freshly distilled indene were added successively to a suspension containing 5 mmol of the corresponding oxadiazinone 1 in anhydrous tetrachloromethane (80 ml) under inert atmosphere . After the addition, the reaction mixture was refluxed in inert atmosphere while the suspension became a clear yellow solution. The solution changed from yellow to red-brown and the reaction was monitored by TLC. After 5 days at reflux (pH solution changed from 1 to 4), 2.5 mmol (0.35 ml) TFAA and 2.5 mmol (0.2 ml) TFA were added and the reaction was refluxed for 4 more days. After 9 days of reflux (pH 4) the solvent was removed in vacuum and the obtained brown residue was purified on silica gel chromatography column to afford a white or yellow solid.

(4S,4aR) (4S,4aR) (4S,4aR) (4S,4aR)--- -1,4 1,4 1,4 1,4--- -diphenyl diphenyl diphenyl diphenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -

one one one one

Chemical Formula: C24H18O2; Molecular Weight: 338.40

Structural properties

Derivative 2'a

White solid; yield 20%; mp. 151-152°C; Rf = 0.34 (pentane/methyl tert-butyl ether = 8/1).

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

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(4R,4aS) (4R,4aS) (4R,4aS) (4R,4aS)--- -1,4 1,4 1,4 1,4--- -diphenyl diphenyl diphenyl diphenyl--- -4,4a 4,4a 4,4a 4,4a--- -dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(9H) 3(9H) 3(9H) 3(9H)--- -

one one one one

Chemical Formula: C24H18O2; Molecular Weight: 338.40

Structural properties

Derivative 3''a

White solid; mp. 145-147°C; R f = 0.25 (pentane/methyl tert-butyl ether = 8/1). 2; 96.8; 124.8; 125.4; 127.8; 128.0; 128.6; 128.8; 128.9; 129.3; 130.3; 133.8; 134.0; 136.6; 138.2; 142.1; 175.7; 197.0.

(4S,4aR) (4S,4aR) (4S,4aR) (4S,4aR)--- -1 1 1 1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -one

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(4R,4aR) (4R,4aR) (4R,4aR) (4R,4aR)--- -1 1 1 1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -

one one one one

Chemical Formula: C28H26O2; Molecular Weight: 394.50

Structural properties

Derivative 2''c

White solid; yield 45%; mp. 74-76°C; Rf = 0.4 (pentane/methyl tert-butyl ether = 8/1). 4; 32.4; 35.1; 42.0; 48.5; 121.1; 123.0; 125.4; 125.8; 126.7; 128.1; 128.3; 128.4; 129.2; 129.5; 130.0; 134.0; 136.2; 143.4; 146.2; 153.1; 168.9. (acetonitrile) λmax (log ε) [nm]: 278 (3.95), 311 (3.98).

UV-Vis

HRMS (APCI+)

calcd. for C28H27O2 [M+H] + : 395.2006; found: 395.2014.

(4S,4aS) (4S,4aS) (4S,4aS) (4S,4aS)--- -1 1 1 1--- -(4 (4 (4 (4--- -( ( ( (tert tert tert tert--- -butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4,4a 4,4a 4,4a 4,4a--- -dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(9H) 3(9H) 3(9H) 3(9H)--- -

one one one one

Chemical Formula: C28H26O2; Molecular Weight: 394.50

Structural properties

Derivative 3'c

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White solid; yield 45%; Rf = 0.5 (pentane/methyl tert-butyl ether = 8/1), mixture with 2'c in a ratio 10/1. 4; 32.4; 35.1; 42.0; 48.5; 121.1; 123.0; 125.4; 125.8; 126.7; 128.1; 128.3; 128.4; 129.2; 129.5; 130.0; 134.0; 136.2; 143.4; 146.2; 153.1; 168.9.

HRMS (APCI+)

calcd. for C28H27O2 [M+H] + : 395.2006; found: 395.2023. 13 C NMR 150 MHz, CDCl3, δ ppm: 37.0; 44.2; 52.2; 122.8; 123.9; 124.7; 125.4; 127.1; 128.1; 128.7;

(4S,4aR) (4S,4aR) (4S,4aR) (4S,4aR)--- -1 1 1 1--- - (4 (4 (4 (4-
-- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -one
(4R,4aS) (4R,4aS) (4R,4aS) (4R,4aS)--- -1 1 1 1--- -(4 (4 (4 (4--- -bromophenyl) bromophenyl) bromophenyl) bromophenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4,4a 4,4a 4,4a 4,4a--- -dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1 dihydroindeno[2,1--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(9H) 3(9H) 3(9H) 3(9H)--- -one

HRMS (APCI+)

calcd. for C24H18BrO2 [M+H] + : 419.0464; found: 419.0460.

(4S,4aR) (4S,4aR) (4S,4aR) (4S,4aR)--- -1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- -4 4 4 4--- -phenyl phenyl phenyl phenyl--- -4a,5 4a,5 4a,5 4a,5--- -dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2 dihydroindeno[1,2--- -c c c c]pyran ]pyran ]pyran ]pyran--- -3(4H) 3(4H) 3(4H) 3(4H)--- -

one one one one

Chemical Formula: C25H20O3; Molecular Weight: 368.42

Structural properties

Derivative 2'd

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White solid; yield 35%; mp. 144-145°C; Rf = 0.60 (pentane/methyl tert-butyl ether = 5/1). 13 C NMR 150 MHz, CDCl3, δ ppm: 37.0; 44.0; 52.3; 55.5; 113.6; 116.1; 121.2; 123.1; 124.2; 125.2; 127.0; 128.1; 128.5; 129.0; 129.1; 129.8; 143.4; 145.7; 159.8; 169.6. (acetonitrile) λmax (log ε) [nm]: 277 (4.00), 306 (3.97).

UV-Vis

HRMS (APCI+)

calcd. for C25H21O3 [M+H] + : 369.1485; found: 369.1487.

(4S,4aR) (4S,4aR) (4S,4aR) (4S,4aR)--- -1 1 1 1--- -(3 (3 (3 (3--- -methoxyphenyl) methoxyphenyl) methoxyphenyl) methoxyphenyl)--- - 4

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H-2', H-5', o-H (4-C6H5), m-H (4-C6H5)), 7.39 (m, 1H, p-H (4-C6H5)).

13 C NMR 150 MHz, CDCl3, δ ppm: 32. 2, 41.8, 48.3, 55.4, 113.6, 115.8, 120.9, 121.5, 123.0, 125.3, 126.6, 128.0, 128.4, 129.0, 129.3, 129.9, 133.7, 134.0, 135.7, 142.8, 146.1, 159.9, 168.7.

UV-Vis

Synthesis of indenopyrone derivatives

General procedure: DDQ (3.6 mmol, 0.82 g) was added to a solution containing a mixture of isomers 2 and 3 (3 mmol) in anhydrous toluene (80 ml) and the reaction mixture was heated at 80°C in inert atmosphere for 6 days. After being cooled to room temperature the solution was filtered off and the filtrate washed several times with water and brine. The organic phase was dried over MgSO4 and concentrated to dryness. The crude product was purified by column chromatography on silica gel yielding the desired compounds.

1,4 1,4 1,4 1,4--- -diphenylindeno[2,1 diphenylindeno[2,1 diphenylindeno[2,1 diphenylindeno[2,1--- -c] c] c] c
]pyran pyran pyran pyran----3,9 3,9 3,9 3,9----dione dione dione dione Chemical Formula: C24H14O3; Molecular Weight: 350.37

Structural properties

Derivative 4

Yellow solid; yield 15%; mp. 281-282°C; Rf = 0.2 (PE/EE = 7/1). 6; 120.1; 124.5; 125.9; 128.4; 129.4; 129.5; 129.7; 129.8; 129.9; 132.3; 132.6; 132.8; 134.6; 139.0; 139.6; 149.2; 161.6; 162.3; 186.6.

UV-Vis

HRMS (APCI+)

calcd. for C28H25O2 [M+H] + : 393.1849; found: 393.1844.

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Design, Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta[c]pyrans as Potential Logic Gates

Introduction

The design and development of new architectures acting as molecular logic gates is the subject of many publications in the field of nanoscience and represents an area of intense research activity. 61 Due to the increasing demands of miniaturization in informatics technology (IT), chemistry plays a key role through the development of supramolecular systems that can behave similar to semiconductors and could be used for the construction of computers (memories, logical gates) 62 . For the implementation of these functions, molecular and supramolecular systems must be able to respond to some chemical and/or physical stimuli (input: complexations, pH modifications, redox or other chemical reactions, irradiation at different wavelengths, etc.) and generate one or more response signals (output: fluorescence, changes in electrochemical properties etc.).

Specific input signals of basic logic gates can be programmed into single molecules

that generate readable output signals, such as fluorescence 62 or UV-Vis light 63 . Recently, important progress was made in developing molecular logic gates which use the fluorescence property as output, in most cases the fluorescence property being induced by pH modification, complexation with metal ions or by irradiation. 64,65,66,67,68,69,70,71,72,73 The design of such compounds must take into consideration the existence of at least two stable states in the molecular system, the molecule switching from one state to the other must be reversible and should take place under the direct influence of some exterior stimuli (inputs).

The molecules must exhibit very different values of some properties considered output in the two molecular states (for instance, to exhibit fluorescence only in one state when the output is 1 and to exhibit no fluorescence in the other state, when the output is 0). There are four important basic logical gates: YES, NOT, AND and OR and a large number of compounds that can mime these functions are known as far. However, remarkable is the great number of publications which have reported molecules that can mime complex logic gates, such as NOR 74 , INHIBIT 75 , XOR 76 , XNOR 77 . Most of the molecules contain only one output mode. Recent interest is focused on an integrated system involving multiple fluorescent output modes. Some examples of molecular systems with 4 output possibilities were reported. 78,79 Truth tables that define these logic gates are based upon the relations between the input values and the output value of the control property. A notable development during the past few years have reached the AND logic gates and enzyme based molecular systems able to function as logic gates. 63,64 In particular, systems consisting of chemically encoded information as input and fluorescent signal as output has attracted a great deal of attention. An interesting example of AND logical gate is the case of the tetrathiafulvalene(TTF)-antracene dyad A1 (Scheme 1). The fluorescence intensity of a dyad A1 solution has been slightly enhanced by complexation (of the crown ether unit) with Na + (input 1) or by adding fullerene C60 due to the photoinduced intermolecular electronic transfer between C60 and TTF (input 2). When both stimuli (input 1 and input 2) have a simultaneous action, a strong fluorescence has been observed (Figure 1). This behavior mimics an AND logic gate: the system exhibits a strong fluorescence only when both input values are 1, while in the other three cases the compound has only a weak fluorescence (if at least one input value is zero then the output is zero).

Input1 Na + Input2 C60 Output hν ν ν ν 0 0 0 0 1 0 1 0 0 1 1 1

Weak fluorescence Strong fluorescence

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In 1994, A. P. de Silva et at. 81 , 82 reported a small molecule A2 (figure 2) that displays digital OR gate action with a strong fluorescence signal. Derivative A2 is a simple "lumophore-spacer-receptor", but the receptor is significantly non-selective and therefore it can bind to either of two analytes (inputs), Ca 2+ and Mg 2+ . Importantly, the output, luminescence enhancement factor is nearly the same for each analyte (figure 2).

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Original Contributions

The aim of this chapter is to outline the design and synthesis of molecular assemblies based on modified cyclopenta [c]pyran units able to mimic a logic gate. These systems should be structurally modified by the influence of a chemical or electrochemical stimulus in order to work as potential devices for molecular electronics. In this context, photochemistry, which combines light and molecules, might be a good starting point.

Figure 3 outlines the minimum required condition to obtain a logic gate. The molecular system must be reversibly interconverted between at least two stable states by use of an external stimulus. In the two states, these compounds must exhibit different values of at least one property, which is considered to be the answer.

Figure 3

The target compounds contain a cyclopenta [c]pyran unit linked through a spacer to a fragment of terpyridine or phenothiazine that is able to undergo a reversible complexation-decomplexation or a redox reaction, respectively. The controlled competition of luminescence with photoinduced electron transfer (PET) can switch the luminescence "on" or "off" by chemical means in an easy manner. External stimuli, in our case a complexation-decomplextion or a redox process, determine the interconversion of the molecule between at least two stable states. These stimuli will be used as INPUT 1 and

Chapter 3 -Design, Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta [c]

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INPUT 2 (which is 1 when the signal is positive or 0 if the signal is missing). Depending on the combination of the two signals (input 1 and input 2), the molecule exhibits or not fluorescence, which determines the answer = OUTPUT (which is 1 when the molecule exhibits fluorescence and 0 when the fluorescence is absent).

Taking into account the requirements for the design of a logic gate we synthesized two series of derivatives, type 3 (scheme 2) and 5 (scheme 3), one of them containing a terpyridine unit (because of the complexation properties of these units) and another containing a phenothiazine moiety (for its redox properties). Cmpd.

E Yield (%) 3a

H 69 3b COCF3 43

Scheme 2

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Scheme 3

The target compounds were obtained in good yields by a Suzuki cross-coupling reaction involving pinacolyl boronic esters 2 and 4, respectively and several halogenated derivatives 1. Following a procedure previously described in the literature 83 pinacolyl boronic esters 2 and 4 were refluxed overnight in the presence of cesium carbonate and catalytic amounts of tetrakis[triphenylphosphine]palladium with bromo-derivatives 1 to yield the coupled compounds 3 and 5 in good yields (Scheme 2 and 3).

The terpyridine boronic ester 2 was obtained according to literature 84 via a palladium catalysed Miyaura cross-coupling reaction of 4'-(4-bromophenyl)2,2':6',2''terpyridine with bis(neopentylglycolato)diboron.

The other building block used for the synthesis of the target systems is the pinacolyl boronic ester of phenothiazine 4. This derivative was obtained from 3-bromo-10-ethylphenothiazine by a lithiation reaction at low temperature followed by the addition of trimethyl borate as electrophile and in situ transesterification with pinacol. on Cyclopenta [c]

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All structures of the new compounds are unambiguously supported by 1 The optoelectronic properties of the coupling reaction products as well as the component units 6-11 (chart 1) were investigated in CH2Cl2 solution by UV-Vis and fluorescence spectroscopy.

Chart 1

Figure 6 shows the UV-Vis absorption spectra of the molecular systems 3a-b, 5a-c and of each cyclopenta [c]pyran, phenothiazine and terpyridine unit 6-11 in CH2Cl2. on Cyclopenta [c]

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Comparing the electronic properties of molecular systems 3a-b and 5a-c with their building units consisiting of cyclopenta [c]pyrans 6-9, phenothiazine 10 and terpyridine 11, respectively, a different behavior can be observed for each case. Thus, a blue shift of absorption maximum band (ca. 50 nm) was recorded for derivatives 5a-c containing the phenothiazine unit while in case of 3 with a terpyridine fragment, a red shift (ca. 50 nm for 3a and 5 nm for 3b) could be observed..

The photoluminescence properties of all derivatives were also investigated and table 1 summarizes their photophysical data. In all cases, the emission spectra were obtained by excitation at the long-wavelength absorption band maximum (figure 7).

Wavelength [nm]

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Regarding the fluorescence properties, some of compounds have emissions in the blue-green region (3a, 5a) and others in the yellow-orange one (3b, 5b-c, figure 7).

Derivatives 5a-c, containing a phenothiazine unit, exhibit weaker emissions than those with terpyridine structure (3a-b). Furthermore, the emission band maximum is significantly red shifted (ca. 100 nm) for the derivatives bearing an electron-withdrawing group, such as CHO and COCF3.

Next, derivatives 3a-b were tested as potential logic gates. In this context, having molecular systems that contain a guest binding site (terpyridine unit) and a photon interaction site (cyclopenta [c]pyran moiety) as components, a photoinduced electron transfer (PET) mechanism between the two sites can switch the luminescence ''on'' by chemical means, such as complexation reactions. Photoinduced electron transfer is the most popular principle in the design of fluorescent molecular systems. The question that arises is how does PET work? Figure 8 schematically illustrates this mechanism. The fluorophore absorbs the UV light that excites the molecule thus promoting an electron to a higher energy orbital and creating a vacancy in the ground state orbital. The Chapter 3 -Design, Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta [c]

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Page | 192

excited electron is transfered to the receptor that, at its turn, transfere the electron back to the fluorphore completing thus the electronic transfer.

When the receptor binds a guest, it will no longer be able to transfer the excited electron to the fluorophore, disrupting the PET process. The excited electron in the fluorophore will return to its ground state by emitting a photon and thus the fluorescence process occurs. The UV-Vis spectrum of terpyridine-based derivative 3a displays two absorption maxima below 300 nm, assigned to the π-π * electronic transitions in the pyridine rings and an absorption band at 330 nm ascribed to n-π * electronic transitions in the cyclopenta [c]pyran unit (figure 9, black line). The absorption spectrum recorded in acidic conditions reveals a conformational change in the terpyridine unit from trans, trans conformation to the planar cis, cis conformation (maximum band at 418 nm, red line). UV-Vis spectrum of the Fe (II) complex shows the characteristic band of the planar cis, cis conformation and a band at 575 nm assigned to the metal-ligand charge transfer, MLCT (figure 9, green line).

87 E.C. Constable, Chem. Soc. Rev. 2007, 36, 246.

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Wavelength Classical logic gates have two input ports and one output port. The experiment performed on derivative 3a has revealed a logic gate. Thus compound 3a, which operates with H + and Fe 2+ as inputs while employing ultraviolet light as power supply and green light as the output (figure 10) mimics an 'OR' gate. The system's luminescence is switched ''on'' when the terpyridine receptor binds either of two analytes, H + and Fe 2+ .

Chapter 3 -Design, Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta [c] on Cyclopenta [c]

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Conclusions

Two series of molecular systems based on terpyridine and phenothiazine structures have been synthesized and fully characterised by NMR, UV-Vis and fluorescence spectroscopy and mass spectrometry.

Attempts have been made to determine the possibility to use these systems in molecular electronics as potential logic gates.

We demonstrated that compound 3a is able to mimic an ''OR'' gate as it shows important differences in the fluorescence intensity when going from uncomplexed to complexed derivative.

Future work will consist on the analysis of derivatives 5a-c with a focus on their potential as logic gates using this time an electrochemical stimulus as input.

Experimental part

General Remarks

1 H and 13 C NMR spectra were recorded in CDCl3, CD2Cl2, DMSO-d6, acetone-d6 at room temperature on Bruker Avance 300, 400 and 600 spectrometer (δ in ppm, J in Hz) at 1 H operating frequencies of 300 MHz (75 MHz for 13 C), 400 MHz (100 MHz for 13 C) and 600

MHz (150 MHz for 13 C); spectra were referenced using the solvent residual signal as internal standard. The compound's numbering used for NMR assignements was done arbitrary.

HRMS in APCI, positive mode ionization were recorded with an LTQ XL ThermoScientific mass spectrometer.

UV-Vis absorption spectra were carried out on a Cecil 9500 spectrophotometer using quartz cuvettes (1 cm).

Fluorescence spectra were taken on a JASCO FP-8300 spectrofluorometer using glass cuvettes (1 cm).

Melting points were measured with a Kleinfeld melting point apparatus and are uncorrected.

Thin layer chromatography was performed on Silica gel 60 chromatography plates F254 and column chromatography was performed on Silica gel.

Solvents were dried and distilled under argon using standard procedures prior to use. Chemicals of commercial grade were used without further purification.

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Synthesis and characterization of compounds

General procedure:

A mixture of 1,4-disubstituted cyclopenta [c]pyrans 1 (3 mmol), terpyridine or phenothiazine pinacolyl boronic esters 2 or 4 (3.3 mmol) and cesium carbonate (9 mmol, 2.9 g) in dry THF (100 ml) was degassed for 30 minutes under continuous argon current.

Then tetrakis[triphenylphosphine]palladium (10 mol%, 350 mg) was added and the reaction was refluxed for 6 hours. After cooling at room temperature, dichloromethane (50 ml) and water were added and the organic phase separated. The aqueous layer was extracted several times with small amounts of dichloromethane (50 ml) and then the combined organic layers were dried over anhydrous magnesium sulfate. The solvent was evaporated in vacuum and the obtained residuum was purified by chromatography on silica gel.

--- -yl) yl) yl) yl)--- -[1,1' [1,1' [1,1' [1,1'--- -biphenyl] biphenyl] biphenyl]
biphenyl]----4 4 4 4----yl) yl) yl) yl)----2,2':6',2'' 2,2':6',2'' 2,2':6',2'' 2,2':6',2''----terpyridine terpyridine terpyridine terpyridine Chemical Formula: C41H27N3O; Molecular Weight: 577.67

Structural properties

Derivative 3a

Deep-red solid; yield 69%; mp. 224-226°C; Rf = 0.2 (CH2Cl2/CH3OH = 20/1).

1 H NMR 300 MHz, CDCl3, δ ppm: 6.69 (dd, J = 2.8, 0.9 Hz, 1H, H-e), 7.16 (dd, J = 4.7, 0.9 Hz, 1H, Hg), 7.36 (dd, J = 4.7, 2.8 Hz, 1H, H-f), 7.39-7.53 (overlapped peaks, 5H, H-3''', H-5''', H-5,

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Page | 199 2, 110.7, 118.7, 121.4, 123.9, 124.1, 127.2, 127.4, 127.7, 127.9, 128.2, 128.4, 128.8, 129.4, 132.6, 135.1, 135.6, 136.0, 136.9, 138.0, 138.5, 140.6, 141.7, 142.4, 149.2, 149.6, 156.0, 156.2.

UV-Vis

',2''--- -terpyridin] terpyridin] terpyridin] terpyridin]--- -4' 4' 4' 4'--- -yl) yl) yl) yl)--- -[1,1' [1,1' [1,1' [1,1'--- -biphenyl] biphenyl] biphenyl] biphenyl]--- -4 4 4 4--- -yl) yl) yl) yl)--- -4 4 4 4--- -phenylcyclopenta[c]pyran phenylcyclopenta[c]pyran phenylcyclopenta[c]pyran phenylcyclopenta[c]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,2,2 2,2,2 2,2,2 2,2,2--- - trifluoroethanone trifluoroethanone

trifluoroethanone trifluoroethanone

Chemical Formula: C43H26F3N3O2; Molecular Weight: 673.68

Structural properties

Derivative 3b

Orange solid; yield 43%; mp. 265-266°C; Rf = 0.1 (CH2Cl2/CH3OH = 10/0.6).

1 H NMR 400 MHz, CDCl3, δ ppm: 6.80 (d, J = 3.8 Hz, 1H, H-e), 7.38 (t, J = 6.5 Hz, 2H, H-5, H-5''), 7. 3H,2H,8H,o,8.04 (d,J = 8.3 Hz,2H,8.1 (s,1H,, 8.21 (dq, J = 5.9, 2.1 Hz, 1H, H-f), 8.70 (d,J = 8.0 Hz,2H,8.76 (m,2H,8.82 (s,2H,.

13 C NMR 100 MHz,CDCl3,δ ppm: 111.4,116.1,118.9,120.8,121.6,124.0,125.5,126.8,127.8,Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta [c]

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Page | 200 127.9, 128.0, 128.1, 128.8, 129.2, 129.3, 130.7, 132.7, 133.5, 137.1, 138.1, 140.5, 140.8, 141.8, 143.3, 146.1, 149.2, 149.8, 156.1, 156.3, 161.7.

UV-Vis

-phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -1 1 1 1--- -yl)phenyl) yl)phenyl) yl)phenyl) yl)phenyl)--- -10H 10H 10H 10H--- -

phenothiazine phenothiazine phenothiazine phenothiazine

Chemical Formula: C34H25NOS; Molecular Weight: 495.63

Structural properties

Derivative 5a

Deep-red solid; yield 54%; mp. 204-205°C; Rf = 0.4 (P/EE = 4/1).

1 H NMR 600 MHz, CD2Cl2, δ ppm: 1.44 (t, J = 7.00 Hz, 3H, CH3), 3.98 (q, J = 7.00 Hz, 2H, CH2), 6.64

(dd, J = 2.7, 0.9 Hz, 1H, H-5), 6.92-6.95 (overlapped peaks, 2H, H-7', H-9'), 7.00 (d, J = 8.5 Hz, 1H, H-1'), 7.12 (dd, J = 4.6, 0.9 Hz, 1H, H-7), 7.14 (dd, J = 7.3, 0.9 Hz, 1H, H-8'), 7.18 (m,1H,7.30 (dd,J = 4.6,2.7 Hz,1H,7.45 (m,1H,7.48 (m,1H,3H,m,7.72 (d,J = 7.0 Hz,2H,7.74 (s,1H,7.77,8.15 (2 x d,J = 8.4 Hz,4H,o',.

13 C NMR 150 MHz, CD2Cl2, δ ppm: 13. 3, 42.5, 109.5, 111.1, 115.8, 115.9, 122.5, 123.1, 124.2, 124.5, 125.4, 126.1, 126.6, 127.1, 127.7, 127.8, 128.0, 128.7, 129.0, 129.4, 129.9, 132.5, 134.5, 135.4, 136.2, 136.7, 142.6, 145.1, 145.5, 155.4.

UV-Vis

(CH2Cl2) λmax (log ε) [nm]: 248 (4.49), 290 (4.41), 375 (4.19).

HRMS (APCI+)

calcd. for C34H26NOS [M+H] + : 496.1730; found: 496.1750.

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Page | 201 -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran----7 7 7 7----carbaldehyde carbaldehyde carbaldehyde carbaldehyde Chemical Formula: C35H25NO2S; Molecular Weight: 523.64

Structural properties

Derivative 5b

Deep-orange solid; yield 53%; Rf = 0.2 (P/EE = 2/1). 13 C NMR 75 MHz, δ ppm: 12.5,41.1,89.1,102.9,115.4,115.7,122.2,122.5,123.3,123.5,124.0,125.0,125.8,126.1,127.0,127.7,128.4,129.0,130.7,131.3,132.6,133.3,135.6,137.4,141.4,141.5,142.1,143.7,144.3,182.2.

UV-Vis

(CH2Cl2) λmax (log ε) [nm]: 255 (4.52), 305 (4.39), 400 (4.07).

HRMS (APCI+)

calcd. for C35H26NO2S [M+H] + : 524.1679; found: 524.1693.

Chapter 3 -Design, Synthesis and Structural Analysis of some Molecular Architectures based on Cyclopenta [c] -(4 (4 (4 (4----(10 (10 (10 (10----ethyl ethyl 13 C NMR 75 MHz, CD6CO, δ ppm: 13. 4, 18.0, 42.6, 111.3, 115.5, 116.5, 116.7, 120.9, 123.1, 123.6, 124.5, 125.7, 126.4, 127.2, 128.1, 128.6, 129.5, 129.9, 130.7, 131.8, 133.3, 134.9, 135.3, 143.1, 145.0, 145.6, 146.0, 146.6, 146.7, 154.0, 162.3.

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Page | 202 1 1 1 1--- -(1 (1 (1 (1---
ethyl ethyl--- -10H 10H 10H 10H--- -phenothiazin phenothiazin phenothiazin phenothiazin--- -3 3 3 3--- -yl)phenyl) yl)phenyl) yl)phenyl) yl)phenyl)--- -3 3 3 3--- -methyl methyl methyl methyl--- -4 4 4 4--- -phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[ phenylcyclopenta[c c c c]pyran ]pyran ]pyran ]pyran--- -7 7 7 7--- -yl) yl) yl) yl)--- -2,

UV-Vis

(CH2Cl2) λmax (log ε) [nm]: 260 (4.51), 318 (4.39), 425 (4.06).

HRMS (APCI+)

calcd. for C37H27F3NO2S [M+H] + : 606.1709; found: 606.1714.

Small Molecular

Chapter 4

ar Donors for Organic Photo otovoltaics

Introduction

The increasing rate of fossil-fuel consumption, its accompanying greenhouse effect and other negative environmental impacts have resulted in research efforts that focus on renewable energy technologies. Among many options with regard to new energy sources, solar energy is regarded as one of the most attractive because of its abundant supply and inherent inexhaustibility. The photovoltaic conversion of sunlight into electric energy is the optimal way to create a modern society powered by electricity. technologies. 88,89,90,91,92,93,94,95,96 The design of an OPV cell involves the creation of a heterojunction by interfacing an electron donor material with an electron acceptor material. 97 Although soluble conjugated polymers have represented the main class of donor materials for solution-processed bulk heterojunction cells (BHJ), 88,89 in the late years the research activity was focused on the design and synthesis of small molecular donors. 90-93 These efforts were motivated by the advantages of well-defined chemical structures in terms of reproducibility of synthesis, purification and properties combined with reliable analyses of structure-properties relationships. 90-93 In organic materials, due to their low dielectric constant, the absorption of solar photons leads to the formation of coulombically bound electron-hole pairs (excitons) that are dissociated into positive and negative charges by the electrical field at the D-A interface. 98 In a D/A heterojunction this field results essentially from the energy offset between the molecular orbitals of donor and acceptor. Over the past two decades the heterojunction concept has been developed along with two main lines namely planar heterojunctions (PHJs) 97,98,99 initially described by Tang 97 and bulk heterojunctions (BHJs) in which the D-A interface is distributed in the whole volume of the active layer as interpenetrated networks of D and A materials. 100 Two different technologies namely thermal evaporation under high vacuum for PHJs and solution-process for BHJs are used for the fabrication of the two types of cells. These two techniques suggest two different viewpoints on OPV. The relatively expensive fabrication of multilayer cells by successive vacuum depositions seems to imply the production of durable solar modules, while the production of cheap devices using, for example, ink-jet printing on flexible substrates suggests possible applications in shortlifetime products such as packaging. On the other hand, these two technologies imply that besides light harvesting and energy levels, the design of active materials takes also into account physical parameters such as melting and decomposition temperature, solubility and film-forming ability.

Molecular donors have been used in multilayer planar heterojunction cells fabricated by vacuum deposition for a long time, and the field is still very active. 98,99,101 In the past few years, the performances of OPV cells have rapidly increased to reach values of approximately 9.0% for solution-processed single-junction BHJs 102 and about 7.0-8.0% for vacuum deposited PHJs. 103 These high performances result from a multidisciplinary research effort in which advances in device fabrication, replacement of C60 by C70 acceptors, morphological control by additives or solvent annealing are associated with new molecular donors. 96 However, these high performances have been achieved with complex molecules of high molecular weight, prepared by multistep synthesis involving metal-catalyzed coupling reactions and with overall yields sometimes limited to a few percents. In this context, the synthesis of active materials by methods combining high yields, scability, compatibility with industrial processes, low environmental impact and low cost represents a challenging task for chemists interested in OPV. 104 The most efficient polymeric or molecular donor materials known to date are generally obtained by multi-step synthesis involving cross-coupling reactions of aromatic organomettalic reagents containing magnesium, zinc or tin with metal catalysts such as nickel or palladium. 104c In addition to problems of the toxicity and cost of these reagents and catalysts, the remnant traces of metals can lead to deleterious effects on the performances of organic semiconductors. 105 In recent years, several groups have described efficient OPV cells fabricated by vacuum-deposition of small molecular donors. Thus, Furthermore, an even smaller molecule such as compound B (chart1) can still produce a short-circuit current density (Jsc) of almost 7.0 mAcm -2 and a PCE close to 2.0%, although its light harvesting properties are limited. 110

Original Contributions

The goal of this research is to develop new low band gap small molecular donors for solar cells applications with a focus on:

1. The development of new D-A molecules in which a diphenylhydrazone block is connected to a dicyanovinyl acceptor through π-conjugated spacers;

2. The obtaining of ADDA and ADADA systems based on triphenylamine as molecular donors for organic photovoltaics.

In both cases, the evaluation of their potential as donor materials was done in basic bilayer PHJ cells.

Usually, an organic solar cell is composed of five components: a) a support substrate coated with a transparent conductive oxide, ITO; b) a thin layer of poly (3,4ethylenedioxythiophene):poly(styrenesulphonate) (PEDOT:PSS) as hole injection layer; c) an active layer comprising donor materials; d) a layer containing the acceptor material and e) a metal electrode, such as Al, as the cathode (figure 1).

Almost all organic solar cells (OSC) have a planar-layered structure, where the organic light-absorbing layer is sandwiched between two different electrodes. One of the electrodes must be transparent, often indium tin-oxide (ITO), the other electrode is a metal like aluminum.

Figure 1 illustrates the device structures for bilayer heterojunction (a) and bulk heterojunction (b) as well as the fundamental steps occurring in donor-acceptor heterojunction solar cells (c). There are four steps in converting photons to free charge carriers:

1. Light absorption of donor, leads to exciton formation (an electron is promoted from the highest occupied molecular orbital (HOMO) of donor to its lowest unoccupied molecular orbital (LUMO)).

2. Diffusion of the exciton within the active layer to the donor-acceptor interface.

3. Dissociation of exciton from the LUMO of the donor to the LUMO of the acceptor to create free charge carriers that can reach the electrodes.

4. Collection of free charge carriers at the electrodes (holes at the anode and electrons at the cathode).

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Page | 214

Synthesis and characterization of new D-A systems

The first objective of my research work developed during my PhD. stage at the University of Angers (MOLTECH-ANJOU) was to obtain new D-A molecules in which a N,N'diphenylhydrazone donor unit is linked to a dicyanovinyl acceptor group through πconjugated spacers based on: thiophene (1), bithiophene ( 2), thieno [3,4b]thiophene (3), 3,4-ethylenedioxythiophene (EDOT, 4), bis-EDOT ( 5), cyclopentadithiophene ( 6) and dithienopyrrole (7, figure 2). These derivatives combine the advantage of a simple, clean and efficient synthesis with physical properties allowing their implementation into devices using solution and vacuum deposition process.

X-Ray diffraction

Deep-red single crystals of compounds 1, 2, 3 obtained by slow evaporation of chloroform solution were analyzed by X-Ray diffraction. The obtained results are summarized in table 1. As shown in figure 3, for the three compounds the C=N double bond connecting the hydrazone donor unit to the thiophenic spacer presents an E configuration. The three compounds crystallize in centro-symmetric space groups, with one independent molecule in the unit cell, compounds 1 and 3 in the monoclinic system and 2 in the triclinic system. The planarity of the three molecules is evaluated comparing the dihedral angles between the least-square planes of the three fragments: the donor, the πconjugated spacer and the acceptor (Figure 4). The crystal packing of compound 2 reveals the presence of two types of H-bonds: an interaction between the nitrogen atom of the CN group and the hydrogen atom of the vinyl group (N2•••H4 2.72 Å) and the other between the nitrogen atom of the other CN group with the iminic hydrogen (N1•••H13 2.65 Å) (Figure 6).

Optical properties

The UV-Vis absorption spectra of compounds 1-7 recorded in methylene chloride solutions and as thin films spin-cast on glass are shown in figure 8 and the corresponding data are collected in table 2.

The spectra of all compounds present a first absorption band in the near-UV region (350-400 nm) that can be assigned to the π-π * electron transitions followed by a more intense band in the visible region (500-600 nm) assigned to an internal charge transfer (ICT) between the N,N'-diphenylhydrazone donating unit and the dicyanovinyl acceptor moiety. As shown by the data in table 2, the increase of the conjugation length and/or donor strength of the conjugating spacer produces a bathochromic shift of the absorption maximum (λmax) of the ICT band from 507 to 574 nm for 1 and 5, respectively with an increase of the molecular absorption coefficient (ε). The UV-Vis absorption spectra of thinfilms cast on glass from chloroform solutions show in the case of derivatives 1-3, 6 and 7 a bathochromic shift of λmax and a broadening of the absorption band due to intermolecular interactions in the solid state. These phenomena commonly observed for many classes of molecular or polymeric conjugated systems are generally assigned to intermolecular interactions with formation of J-aggregates. In contrast the solid-state spectra of the EDOTcontaining compounds 4 and 5 show narrower absorption bands with a hypsochromic shift of λmax in particular for compound 5 (14 nm) (table 2). This peculiar behaviour that suggests the presence of H-aggregates has been previously observed for other EDOT-containing systems such as hybrid EDOT-thiophene oligomers 116 or push-pull molecules. 117 Although these results provide a further illustration of the major contribution of EDOT units on the formation of H aggregates, a general explanation of this process is still lacking and would require further analyses of structure-properties relationships.

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Page | 223

The intercept of the tangent to the long wavelength absorption edge of the film to the horizontal axis leads to estimated band gap values in the range 1.75-2.00 eV. [a] ELUMO [eV] [b] -3.54 [a] using E 0 ox with an offset of -4.99 eV for SCE vs the vacuum level. 118 [b] determined by EHOMO-ΔE .

ΔE [eV] εmax [M -1 cm -1 ] λmax(f) [nm] Eg [eV] Epa [V] Epc [V] EHOMO [eV]
116 a) M. Turbiez, P. Frère, M. Allain, C. Videlot, J. Ackerman, J.

Electrochemical properties

The electrochemical properties of the compounds were analyzed by cyclic voltammetry (CV) in methylene chloride, in presence of 0.1M tetrabutylammonium hexafluorophosphate as supporting electrolyte. Figure 9 shows the CV recorded at a scan rate of 100 mVs -1 . As expected, according to the UV-Vis absorption data, the anodic peak potentials (Epa) decrease from 1.32 V for compound 1 to 0.79 V for compound 5 (table 2), reflecting the increase donor character of π-conjugated spacers. The CV of derivative 5 containing a bis-EDOT as spacer shows two reversible oxidation waves indicative of stable cation-radical and di-cation. A closer examination of the CVs shows that the oxidation process is not fully reversible, except for compounds 5-7, and a cathodic wave of weak intensity is observed in the reverse scan. This wave, particularly visible in the CV of compound 1 and 3 and hardly discernible in the case of compound 2 can be assigned to the reduction of the product resulted from the coupling of the cation radical, a process frequently observed in the electrochemistry of TPA derivatives. 119 In the negative potential region, the CV of all compounds present an irreversible reduction wave with a cathodic peak potential (Epc) varying from -0.91 V for compound 1 to -1.17 V for compound 5 (Table 2).

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Page | 227 The energy levels of the frontier orbitals have been estimated from the oxidation potentials and the optical data. The energy level of the HOMO orbital of all compounds was determined from the onset of the oxidation process using an offset of -4.99 eV for SCE vs the vacuum level. 118 For all compounds the level of the LUMO is compatible with a photoinduced electron transfer into the LUMO of C60. Figure 10 depicts the energy levels of the compounds with respect to the other components of an organic solar cell.

Evaluation of the photovoltaic properties

The purpose of this work is not to produce champion devices but rather to analyze the effects of subtle structural modifications. In this context, basic PHJs cells appear more appropriate for an analysis of structure-properties relationships. Therefore, the potentialities of these compounds as donor materials for heterojunction solar cells have been evaluated in bilayer PHJ cells of 0.28 cm 2 active area with vacuum-deposited C60 as electron acceptor.

The bi-layer cells were fabricated by deposition of a donor layer onto indium tin oxide (ITO) substrates pre-coated with a 40 nm thick film of spun-cast poly (3,4ethylenedioxythiophene):poly(styrenesulphonate), PEDOT:PSS. The substrates were then introduced in a vacuum chamber, a 30 nm thick layer of C60 fullerene acceptor was deposited by thermal evaporation under a pressure of 4 x 10 -6 mbar and the devices were completed by deposition of a 100 nm layer of aluminium. Each ITO substrate contains two circular cells and each batch typically involves 6-8 cells. After fabrication, the cells were subjected to a 10 min thermal treatment at a temperature of 85 to 160°C.

An interesting specificity of the new donors lies in the fact that their solubility, melting and decomposition temperatures are compatible with both solution-process and vacuum deposition. It was therefore interesting to take advantage of this processing versatility to compare the performances of OPV cells fabricated by the two techniques.

Note that in spite of good solubility, attempts to fabricate PHJ cells from a solution of derivative 3 remained unsuccessful due to inhomogeneity of the spin-cast film. Having little amount of donor materials 6 and 7, the films of these derivatives were obtained only by the spin-coating method.

Using the vacuum-deposition process, the potentialities of compounds 1, 2, 4, 5 as donor materials for heterojunction solar cells have been evaluated in two series of bilayer solar cells. For the first series of devices, ca. 15 nm thin film of the corresponding donor were deposited by thermal evaporation under vacuum while for the second series of

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Page | 230 devices, ca. 20 nm thin film were deposited. In all cases better results were obtained with thinner films (15 nm) and after application of a 10 min. thermal treatment.

Figure 11 shows the current density vs voltage curves for the cells based on compounds 1-3, 6, 7 and the corresponding photovoltaic parameters are listed in Table 3. As shown in table 3, the cells based on a spun-cast films of 1 (entry 1s) gave a shortcircuit current-density (Jsc) of 6.32 mA cm -2 and a power conversion efficiency (PCE) of 2.07%, while the cells based on vacuum deposited donor 1 (entry 1e) show a slight improvement of Jsc from ~6.30 to 6.90 mA cm -2 but a decrease of Voc and FF with as net result a decrease of PCE to ca 1.70%. The results obtained with vacuum-deposited donor 3 reveal a higher of Jsc (8.50 mA cm -2 ), however the maximum PCE is limited to 2.30% due to the decrease of Voc to 0.60 V, in agreement with the higher HOMO level of compound 3.

Comparison of the data for donors 1 and 2 shows that the insertion of a bithienyl bridge produces an increase of PCE to 2.55% for the spin-cast film and 3.22% for the vacuum deposited one. This result is essentially due to a better FF and to an increase of Jsc above 8.0 mA cm -2 . The relatively high value of Voc in spite of the higher HOMO level of compound 2 could be explained by a higher interfacial dipole or to a decrease of charge recombination.

Further work is needed to clarify this point. Comparison of entries 2s and 2e in table 3 shows that the cells made by vacuum deposition present higher Jsc and Voc and hence higher PCE. It is worth noting that the 3.22% PCE is the highest value obtained so far with our standard 0.28 cm 2 bi-layer device. Comparison of the data for donors 6 and 7 with those for 2 reveals that the rigidification of the conjugated system by a covalent bridge produces a decrease of PCE to 0.56% and 1.00% for compounds 6 and 7, respectively. These results are essentially caused by the decrease of the fill factor and short circuit current. By The results obtained with the cells based on donors 4 and 5 show that the replacement of the thiophenes by EDOT units has deleterious consequences for the PV performances (figure 12). Comparison of the data for compounds 1 and 4 reveals a decrease of PCE for both solution-cast and vacuum-deposited donor layers. This results

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Page | 233
essentially from a decrease of Voc associated with the higher HOMO level of compound 4.

On the other hand, by replacing of bithienyl spacer by a bis-EDOT produces an even larger decrease of Jsc with a two-fold decrease of PCE for solution-processed devices while Jsc decreases from 8.40 to 2.17 mA cm -2 and PCE from 3.22 to 0.65% for the cells based on the vacuum-deposited donors layers. Comparison of the results obtained with solution-cast and vacuum deposited donor layers reveals two contrasted behaviours. For compounds 1 and 2, vacuum deposition improves Jsc while the reverse effect is observed for the EDOT-containing donors in particular for compound 5 for which vacuum-deposition leads to a considerable deterioration of the PV performances.

In order to complete these observations, the external quantum efficiency (EQE) spectra of the cells have been recorded under monochromatic irradiation. The spectra of all devices show a first sharp peak at 370-380 nm assigned to the contribution of C60 to the photocurrent. The spectrum of the cell based on vacuum-deposited compound 1 shows a first band at 400 nm followed by a broader band of ca. 50% extending to ca. 600 nm (figure 13). The response of compound 3e is rather similar to that of 1e and both are consistent with the absorption spectra of the donors.

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Page | 235 The spectrum of the cells based on donor 2 shows as expected, an extension of the photo-response with a bathochromic shift of the onset of photo-current to ~650 nm. The EQE spectra of the cells based on solution-cast and vacuum-deposited donor layers are rather similar except for a slight higher intensity for the vacuum-deposited donor (figure 13). The response of compound 6s is rather similar to that of 7s, except the higher intensity observed in the case of donor 7. In both cases, the onset of photo-current about to ~650 nm is consistent with the absorption spectra of donors (figure 13).

As shown in figure 14, the processing technique has a much stronger effect in the case of EDOT-containing donors. For compound 4 the EQE spectra of both types of cells have almost identical shape with a lower photocurrent for the vacuum-deposited donor.

For compound 5, the spectra of the solution-processed and vacuum-deposited donors present as expected, an extension of the photo-response towards longer wavelengths.

However, a marked decrease of EQE is observed in the 500-700 nm region for the vacuumdeposited donor. These EQE spectra agree well with the results obtained under white light illumination and clearly confirm the negative influence of the bis-EDOT spacer on the conversion efficiency of the donor molecule.

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Page | 236 Previous work on hybrid thiophene-EDOT oligomers has shown that the number and position of EDOT units in the conjugated structure exerts a determining influence on the molecular organization and in particular on the formation of J-or H-aggregates. 116,117 In fact, results on OFETs and OPV cells have shown that the spectral signature of H-aggregates is associated with a higher hole-mobility in OFETs but with a dramatic loss of the lightharvesting properties and hence PCE of OPV cells. 116 In this context the results obtained with compounds 4 and 5 provide a further illustration of the problems posed by use of the EDOT building block for the design of OPV materials, even if interesting positive effects have been demonstrated in some cases. 117 Although our results confirm the versatile processability of this class of molecular donors, they also show that depending on the molecular structure, the processing technique can exert a significant influence on the efficiency of the resulting OPV cell. Thus, whereas for compound 1 both methods lead to rather similar results, for compound 2 vacuum deposition leads to a ca 25% increase of PCE due essentially to an increase of Jsc. In contrast, for compounds 4 and 5 vacuum-deposition seems to exalt the deleterious influence of the EDOT unit on molecular packing and hence PV performances.

.Synthesis and characterization of new ADA, ADDA and ADADA systems based on triphenylamine

In the past few years, the compound 8 has served as a reference and starting platform for various modifications of the molecular structure with the double objective of improving the photovoltaic efficiency and deepening the analyses of structure-properties relationships in this class of molecules. 108,113,114,121 The highest PCE reported so far for molecular BHJ cells have been obtained with extended quasi-linear symmetrical molecules of structure A-D-A 95 or D-A-D-A-D. 94 In our continuing interest for the manipulation of the electronic properties of type 8 compounds, we synthesised a series of donor-acceptor systems obtained by introduction of a spacer unit, such as ethynyl between the donor and The reference compound 8 was obtained according to a known procedure described in the literature. 108 Compound 9 was obtained in a multi-step reaction procedure starting from commercially available 4-bromo-diphenylaniline 15 (scheme 2). Firstly, a Sonogashira cross-coupling reaction followed by trimethylsilyl deprotection reaction gave derivative 17 which was further subjected to another metal-catalysed Sonogashira reaction with 5-bromothiophene-2-carbaldehyde 18 yielding derivative 19 in good yield. Finally, a

Knoevenagel condensation of aldehyde 19 with malonidinitrile gave the target compound 9 in 80% yield (scheme 2).

Introduction of a cyanovinyl group between the donor and acceptor units helps to increase the intramolecular charge transfer and reduces also the optical band gap of the molecule. 124 In this context, attempts to synthesise a D-A-A system, such as compound 23 (scheme 4) failed because in the second step, the Vilsmeier-Haack formylation took place at para-position of phenyl ring instead of the free α-position of thiophene unit. Therefore, we obtained an A-D-A system instead of a D-A-A system. The X-ray analysis of compound 14 confirms the proposed structure (figure 16).

Scheme 4

The structure of all compounds was confirmed by NMR and UV-Vis spectroscopy, mass spectrometry, cyclic voltammetry and X-Ray diffraction in case of derivatives 9 and 14.

X-Ray diffraction

Red (9) and orange ( 14) single crystals were obtained from chloroform solution by slow evaporation technique. Both compounds crystallize in centro-symmetric space groups, compound 9 in the monoclinic system and compound 14 in the triclinic system.

As shown in figure 16, for both derivatives, the N atom of triphenylamine unit has a trigonal planar geometry and the π-conjugated backbone adopts a planar geometry. For compound 14, the crystal packing (figure 18) reveals two types of hydrogen bonds between the nitrogen atom of the CN from cyanovinyl group and the hydrogen atom

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Page | 244

Optical properties

The spectroscopic analyses of the molecules were performed in methylene chloride solutions and thin film spun-cast on glass from chloroform solutions (figure 19). The spectrum of all compounds shows a first transition in the 350-400 nm region followed by a main absorption band with a maximum (λmax) at ~500 nm assigned to an internal chargetransfer (ICT). Comparison with compound 8 shows that except for compound 10 for which a small red shift of λmax is observed, all the other compounds presents a small hypsochromic shift of λmax along with an increase of the molecular absorption coefficient (ε). (table 4).

Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 245 Black line: as thin film spin-cast on glass from chloroform solutions.

UV-Vis spectra of the films present a red shift of λmax and a broadening of the absorption band reflecting intermolecular interactions. Further examination of the spectra of solutions and films shows that the smallest difference between the two states is seen for compound 11 and the largest one for compound 13 indicating differences in intermolecular interactions. The intercept of the tangent of the long wavelength absorption edge with the horizontal axis gave estimated band gaps of 2.10 eV for compound 11 and 1.92 eV for compound 13. These results suggest that despite limited effects at the molecular level, the median acceptor group can significantly affect the molecular packing in the solid state.

Electrochemical properties

The electrochemical properties of the final compounds have been analyzed by cyclic voltammetry in methylene chloride solutions in the presence of tetra-n-butyl ammonium hexafluorophosphate (n-Bu4NPF6) as supporting electrolyte. The CV of derivative 9 (figure 20) shows a reversible oxidation process corresponding to the formation of stable cationradical with anodic peak potential Epa at 1.06 V which is positively shifted (ca. 20 mV) compared to reference compound 8.

[nm] εmax [M -1 cm -1 ] λmax f [nm] Eg (eV) Epa1, Epa2 [V] Epc [V] EHOMO (eV) a ELUMO (eV) b EHOMO (eV) c

Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 247 The cyclic voltammogram (CV) of compound 10 shows two reversible one-electron oxidation waves with anodic peak potential Epa 1 and Epa 2 at 0.86 and 1.05 V (figure 20).

Comparison with compound 8 reveals a 190 mV negative shift of Epa 1 which reflects the extension of the conjugated system, in agreement with UV-Vis data. The second oxidation process can be assigned either to the formation of a dication on the extended system or to the formation of a cation-radical on each part of the molecule. In such case, the difference The CV of compound 11 shows a positive shift of Epa to 1.19 V due to the electronwithdrawing effect of the carbonyl group. A similar effect is observed for compound 13

with Epa increasing to 1.21 V.

The CV of compound 12 shows some similarities with that of compound 10, in particular the occurrence of two reversible oxidation steps with Epa 1 and Epa 2 at 1.04 and 1.18 V. Due to the absence of direct conjugation between the two parts of the molecule, these two waves can be unequivocally ascribed to the successive formation of a cationradical on both parts of the system, the Epa 2 -Epa 1 difference reflecting through-space interactions between positive charges.

A specificity of the CV of compound 12 is the presence of a cathodic wave peaking at 0.80 V in the reverse scan. This wave suggests a chemical coupling of the cation-radical to

Chapter 4 -Small Molecular Donors for Organic Photovoltaics

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Page | 248 form a more extended conjugated system. 125 Based on the favorable geometry suggested by the optimized structure of the molecule (see below) and a possible activation of the orthopositions of the phenyl rings, an intramolecular cyclization with formation of a fivemembered ring can be proposed (scheme 5). However, a more detailed electrochemical investigation and/or spectroelectrochemistry analysis are needed to clarify this bahaviour.

Scheme 5. Possible electrochemically induced intramolecular cyclization of compound 12

In the positive potentials region, the CV of compound 14 exhibits two reversible one-electron oxidation waves at Epa 1 = 1.09V and Epa 2 = 1.38V assigned to the formation of stable cation-radical and dication.

In the negative potential region (not shown), the CV of all compounds displays an irreversible reduction process with cathodic peak potential (Epc) in the -1.03V to -1.31V region indicative of unstable anion radical. As expected, the HOMO is essentially distributed over the TPA blocks and the LUMO on the dicyanovinyl acceptor group. The introduction of a median electron-acceptor linking group does not significantly modify the distribution, except for compound 13 for which some LUMO coefficient also appear on the dicyanomethylene group.

The calculated values of the energy levels of the frontier orbitals and HOMO-LUMO gap agree well with experiments and confirm a slight increase of the HOMO for compounds 10 and 12 and a small decrease of HOMO and LUMO for 11 and 13 (table 4).

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Evaluation of the photovoltaic properties

A preliminary evaluation of the new compounds as donor materials for OPV cells has been carried out on bi-layer planar heterojunction of 28 mm 2 active area cells fabricated by spin-casting ca. 20 nm thick films of donor from chloroform solutions containing 5 mg/mL of compound on ITO substrates pre-coated with 40 nm thick films PEDOT:PSS. The substrates were then introduced in a vacuum chamber. A 30 nm thick layer of C60 was deposited by thermal evaporation under a pressure of 2-4 x 10 -6 mbar and the devices were completed by deposition of a 100 nm layer of aluminium. For each experiment, a minimum of 16 OSC (8 devices containing 2 cells of 0.28 cm 2 active area)

were characterized. All devices were thermally treated. A sacrificed cell was first heated for 5 min at 80°C after that the temperature was increased by increments of 10°C until PCE decreased. Then, the other cells were directly heated at the optimized temperature during 5 min. Although the solubility of the compounds was compatible with the fabrication of solution-processed BHJ cells, no attempt in that direction was made at this stage of research. Furthermore, since the purpose of this work is to analyse structure-properties relationships, simple two-layer devices appear as a more convenient tool as they give more reproducible and more reliable results despite an efficiency inferior to that of BHJ cells.

The photovoltaic characteristics of the bi-layer cells based on the six donors are shown in figure 22 and the corresponding data are listed in table 5 using compound 8 as reference. A first examination of the current density vs voltage curves of derivative 9 clearly shows that the introduction of an ethynyl group between the donor and acceptor units exerts a considerable effect on the performances of the cells. Thus, the PCE decresead from 2.50% for reference compound 8 to 1.28% for compound 9. This phenomenon results essentially from the decrease of Jsc from 5.77 mA/cm 2 to 5.52 mA/cm 2 along with a decrease of Voc and FF. The data in table 5 show that the introduction of a median carbonyl or dicyanomethylene acceptor group between the two blocks leads to a net decrease of PCE from 2.50% for 8 to 0.55 and 1.38 % for 11 and 13, respectively. This effect is due in particular to a decrease of the short-circuit current density (Jsc) and before all to low fillfactors FF. A lesser decrease of PCE is observed for 12 which is anyway less efficient that the reference compound 8. On the other hand, a significant improvement of Jsc from 5.77 to 8.41 mA cm -2 is observed for donor 10 which results in slight increase of PCE in spite of a

large decrease of open-circuit voltage (Voc). This reduced voltage is related to the increase of the HOMO level caused by the extension of conjugation in 10.

The results for compound 14 show that introduction of two acceptor groups on both sides of TPA block leads to a slight improvement of Jsc from 5.77 to 6.18 mA cm -2 but to a decrease of Voc and FF with as net result a decrease of PCE to ca. 1.38%.

The external quantum efficiency (EQE) spectra of the cells have been recorded under monochromatic irradiation.

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Page | 254 The external quantum efficiency (EQE) spectra of the cells have been recorded

under monochromatic irradiation. The spectra of all devices exhibit a first peak at 350-380 nm associated mainly with the contribution of the fullerene derivative, followed by a broad band extending from 400 to 700 nm corresponding to the absorption of donors (figure 23). A first evaluation of the potential applications of the compounds as donor materials in simple bi-layer cells has confirmed the determining role of the conjugating bridge on conversion efficiency. The results obtained with EDOT-containing molecules have confirmed the difficulty to predict the effects of this building block on the organization of the material and hence on its electronic properties and photovoltaic performances. On the other hand, the results obtained with donors based on thiophenic spacers and in particular a bithiophene suggest that these materials can represent an interesting trade-off when one considers the balance of the relevant OPV parameters namely, cost, simplicity, cleanness, yield and scalability of the synthesis and conversion efficiency. Furthermore, the possibility to process these materials by both solution process and vacuum deposition appears as an additional interesting characteristic. Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

Conclusions

Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 259 (1.0 g, 4.53 mmol) and sodium acetate in 15 mL dry methanol under argon atmosphere at room temperature. The reaction mixture was stirred overnight at room temperature and then diluted with methylene chloride, washed with water and brine. After removal of solvent the residue is chromatographed on silica gel using methylene chloride as eluent.

Synthesis and characterization of compounds

1 H NMR 300 MHz, CDCl3, δ ppm: 7. 46-7.42 (overlapped peaks, 8H), 7.27-7.20 (overlapped peaks, 14H), 6.74 (d, 2H, J = 3.9 Hz).

13 C NMR 75 MHz,CDCl3,δ ppm: 143.5,141.6,130.6,130.0,126.7,124.8,122.7.

HRMS (MALDI-TOF)

calcd. for C30H24N4S [M] + : 472.1722; found: 472.1718.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 260 (1.0 g, 4.53 mmol) and sodium acetate in 15 mL dry methanol under argon atmosphere at room temperature. The reaction mixture was stirred overnight at room temperature and then diluted with methylene chloride, washed with water and brine. After removal of solvent the residue is chromatographed on silica gel using methylene chloride as eluent.

1 H NMR 300 MHz, CDCl3, δ ppm: 9.85 (s, 1H), 7.61 (d, 1H, J = 3.9 Hz), 7.47-7.42 (overlapped peaks, 5H), 7.27-7.18 (overlapped peaks, 6H), 6.19 (d, 1H, J = 3.9 Hz).

13 C NMR 75 MHz,CDCl3,δ ppm: 183.0,151.8,142.7,141.9,137.1,130.1,128.1,126.1,125.6,122.5.

HRMS (MALDI-TOF)

calcd. for C18H14N2OS [M] + : 306.0827; found: 306.0826.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 261 13 C NMR 75 MHz,CDCl3,δ ppm: 153.8,150.0,142.3,139.1,133.8,130.0,127.3,126.4,125.8,122.5,122.4,114.5,113.5,75.7.

HRMS (MALDI-TOF)

calcd. for C18H14N2OS [M] + : 354.0939; found: 354.0924.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 262 under argon atmosphere. After being cooled to room temperature, the mixture was diluted with methylene chloride and washed with water and brine. After removal of solvent the residue was chromatographed on silica gel using methylene chloride as eluent to give 100 mg of yellow powder.

1 H NMR 300 MHz, CDCl3, δ ppm: 7.46-7.41 (overlapped peaks, 8H), 7.24-7.18 (overlapped peaks, 14H), 7.08 (d,2H,J = 3.6 Hz),6.80 (d,2H, J = 3.9 Hz).

13 C NMR 75 MHz,CDCl3,δ ppm: 143.4,141.0,137.3,130.2,130.0,127.3,124.9,124.0,122.6.

HRMS (FAB)

calcd. for C34H26N4S2 [M] + : 554.1599; found: 554.1601. under argon atmosphere. After being cooled to room temperature, the mixture was diluted with methylene chloride and washed with water and brine. After removal of solvent the residue was chromatographed on silica gel using methylene chloride as eluent to give 100 mg of yellow powder.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion -----------------------------------------------------------------------------------------------------------------------------------------------------------

1 H NMR 300 MHz, CDCl3, δ ppm: 9.85 (s, 1H), 7.67 (d, 1H, J = 3.9 Hz), 7.47-7.42 (overlapped peaks, 4H), 7.28 (d, 1H, J = 3.9 Hz), 7.25-7.18 (overlapped peaks, 8H), 6.83 (d, 1H, J = 3.9 Hz).

13 C NMR 75 MHz,CDCl3,δ ppm: 182.6,147.5,144.0,143.1,141.7,137.6,135.2,130.1,129.3,127.1,126.5,125.2,124.3,122.6.

HRMS (MALDI-TOF)

calcd. for C22H16N2OS2 [M] + : 388.0704; found: 388.0702. (overlapped peaks, 7H).

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

13 C NMR 75 MHz,CDCl3,δ ppm: 150.1,149.8,145.5,143.0,140.5,134.2,133.5,130.1,128.9,127.8,127.3,125.3,124.6,122.5,114.5,113.7,75.7.

HRMS (MALDI)

calcd. for C25H16N4S2 [M] + : 436.0816; found: 436.0804. ----------------------------------------------------------------------------------------------------------------------------------------------------------- Protocol To a solution of 4,4-bis(2-ethylhexyl)-4H-cyclopenta [1,2-b:5,4-b']dithiophene-2,6dicarbaldehyde (12'c) (60 mg, 0.13 mmol) in 30 mL anhydrous THF was added dropwise a solution of N,N'-diphenylhydrazine hydrochloride (11') (14 mg, 0.065 mmol) and sodium acetate (21 mg, 0.26 mmol) in 4 mL dry methanol at room temperature, under argon atmosphere. After that, the mixture was heated at 40°C under inert atmosphere during 20 hours. After being cooled to room temperature, water and methylene chloride were added. The aqueous layer was extracted two times with dichloromethane and then the combined organic extracts were washed with brine and dried over MgSO4. After solvent removal, the crude was chromatographed on silica gel, using a mixture of pentane/diethyl ether = 8/1 as eluent, to give a yellow-orange solid . 75 MHz,CDCl3,δ ppm: 181.7,149.9,149.2,144.7,143.1,137.9,135.8,135.1,130.0,129.5,126.5,125.1,122.6,114.8,54.0,43.3,35.3,34.2,28.6,27.5,22.9,14.2,10.7.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion

HRMS (MALDI-TOF)

calcd. for C39H48N2OS2 [M] + : 624.3208; found: 624.3195.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 266 After solvent removal the crude was purified by column chromatography on silica gel (eluent: pentan/diethyl ether = 9/1) to afford a violet solid. 2, 152.0, 149.9, 149.5, 143.0, 135.3, 135.1, 130.1, 129.5, 129.4, 125.3, 122.6, 121.2, 121.0, 115.5, 114.8, 71.7, 54.1, 43.2, 35.4, 34.1, 28.6, 27.4, 22.9, 14.2, 10.7.

HRMS (MALDI-TOF)

calcd. for C42H48N4S2 [M] + : 672.3320; found: 672.3300.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 267 washed with water and dried over MgSO4. After removal of solvent, the crude was chromatographed on silica gel using as eluent a mixture of diethyl ether/ pentane = 3/2 to afford a orange-brown solid. 75 MHz,CDCl3,δ ppm: 182.9,149.2,145.4,145.1,145.0,143.2,140.3,130.2,130.0,125.1,123.7,122.6,114.6,109.7,51.5,40.5,30.8,28.8,24.1,23.1,14.1,10.8.

HRMS (FAB)

calcd. for C30H31N3OS2 [M] + : 513.1909; found: 513.1895. 13 C NMR 75 MHz,CDCl3,δ ppm: 151.3,150.4,148.3,146.0,143.0,132.4,130.1,129.7,126.8,125.4,122.6,115.7,115.0,114.7,109.3,71.4,51.6,40.5,30.8,28.8,24.1,23.1,14.1,10.8.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

HRMS (FAB)

calcd. for C33H31N5S2 [M] + : 561.2021; found: 561.2015.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 269 75 MHz,CDCl3,δ ppm: 144.4,143.4,139.2,139.0,130.6,130.0,127.6,124.9,122.6,120.0,118.6.

HRMS (FAB)

calcd. for C19H14N2S2 [M] + : 334.0598; found: 334.0588.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

Structural properties

Derivative 8'e

Orange solid; yield 66%; mp. 145-147°C

Protocol

Anhydrous DMF (0.08 mL, 1.08 mmol) and phosphorus oxychloride (0.08 mL, 0.9 mmol) were added to a solution of (E)-1,1-diphenyl-2-(thieno [3,2-b]thiophen-2ylmethylene)hydrazine (9'e) (200 mg, 0.6 mmol) in 10 mL 1,2-dichloroethane. The reaction mixture was heated to 87°C for six hours. After cooling to room temperature, a saturated aqueous solution of sodium acetate and dichloromethane were added and the mixture was stirred for additional two hours. After extraction with CH2Cl2 (3 x 50 mL), the combined organic phases were washed with water and brine, dried over MgSO4 and concentrated. The residue was purified by column chromatography on silica gel (eluent:

CH2Cl2/EP = 2/1) to afford 140 mg orange solid.

1 H NMR 300 MHz, CDCl3, δ ppm: 9.92 (s, 1H), 7.86 (s, 1H), 7. 48-7.43 (overlapped peaks, 4H), 7.28 (s, 1H), 7.25-7.19 (overlapped peaks, 6H), 7.06 (s, 1H).

13 C NMR 75 MHz,CDCl3,δ ppm: 183.2,151.0,146.3,145.0,142.9,138.5,130.1,129.4,129.1,125.5,122.6,118.4.

HRMS (MALDI-TOF)

calcd. for C20H14N2OS2 [M] + : 362.0548; found: 362.0550. 13 C NMR 75 MHz,CDCl3,δ ppm: 153.4,150.8,148.7,142.6,139.3,136.7,130.6,130.2,128.6,125.8,122.6,117.8,114.6,113.8,75.5.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion -----------------------------------------------------------------------------------------------------------------------------------------------------------

HRMS (MALDI-TOF)

calcd. for C23H14N4S22 [M] + : 410.0660; found: 410.0650.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 272 The mixture was quenched with water and extracted with dichloromethane. The combined organic extracts were washed with water, brine and dried over MgSO4.

After solvent removal, the crude was purified by column chromatography on silica gel using a mixture of petroleum ether/dichloromethane = 2/1 as eluent to give 1.26 g of a yellow solid.

1 H NMR 300 MHz, CDCl3, δ ppm: 7. 43-7. 37 (overlapped peaks, 4H), 7.27 (s, 1H), 7.19-7.14 (overlapped peaks, 6H), 6.24 (s, 1H), 4.14 (s(br), 4H).

13 C NMR 75 MHz,CDCl3,δ ppm: 143.6,141.7,140.0,129.9,127.7,124.6,122.5,116.1,99.4,64.9,64.8.

HRMS (MALDI-TOF)

calcd. for C19H16N2O2S [M] + : 336.0932; found: 336.0925.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 273 added and the solution was addionally stirred for 1h. The organic layer was washed twice with water and dried over MgSO4. After removal of solvent the crude was chromatographed on silica gel using dichloromethane as eluent to afford 0.5 g yellow powder.

1 H NMR 300 MHz, CDCl3, δ ppm: 9.87 (s, 1H), 7. 46-7.40 (overlapped peaks, 4H), 7.25-7.16 (overlapped peaks, 7H), 4.31 (m, 2H), 4.20 (m, 2H).

13 C NMR 75 MHz,CDCl3,δ ppm: 179.8,148.4,142.8,138.8,130.1,127.6,125.4,125.2,122.5,116.5,65.5,64.6.

HRMS (MALDI-TOF)

calcd. for C20H16N2O3S [M] + : 364.0882; found: 364.0875. MgSO4. After solvent removal, the crude was purified on silica gel using dichloromethane as eluent to give 0.44 g violet powder.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

1 H NMR 300 MHz, CDCl3, δ ppm: 7.77 (s, 1H), 7. 48-7.42 (overlapped peaks, 4H), 7.28-7.16 (overlapped peaks, 7H), 4.33 (m, 2H), 4.20 (m, 2H).

13 C NMR 75 MHz,CDCl3,δ ppm: 148.8,144.8,142.5,138.4,130.2,130.0,125.9,124.6,122.6,115.7,114.5,111.6,71.1,66.0,64.6.

HRMS (MALDI-TOF)

calcd. for C23H16N4O2S [M] + : 412.0994; found: 412.0987.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion -----------------------------------------------------------------------------------------------------------------------------------------------------------

Protocol

To a solution of aldehyde 10'g (0.35 g, 1.13 mmol) in 100 mL dry THF heated to 66°C

was added dropwise a solution of N,N'-diphenylhydrazine hydrochloride (0.25 g, 1.13 mmol) and sodium acetate (0.18 g, 2.26 mmol) in 8 mL anhydrous methanol. The reaction mixture was refluxed during 24 hours. After being cooled to room temperature, the mixture was quenched with water and dichloromethane. The aqueous layer was extracted twice with CH2Cl2 and the combined organic extracts were dried over MgSO4. After solvent removal, the crude was purified by column chromatography on silica gel, using dichloromethane as eluent to afford 0.27 g of a yellow solid.

1 H NMR 300 MHz, CDCl3, δ ppm: 7. 44-7.37 (overlapped peaks, 4H), 7.32 (s, 1H), 7.20-7.15 (overlapped peaks, 6H), 6.29 (s, 1H), 4.40 (m, 2H), 4.29-4.25(overlapped peaks, 4H), 4.16 (m, 2H).

13 C NMR 75 MHz,CDCl3,δ ppm: 143.7,141.5,139.7,137.6,136.8,129.9,128.1,124.5,122.6,113.6,98.2,65.2,64.8.

HRMS (MALDI-TOF)

calcd. for C25H20N2O4S2 [M] + : 476.0864; found: 476.0859. 1 H NMR 300 MHz, CDCl3, δ ppm: 9. 90 (s, 1H), 7.45-7.39 (overlapped peaks, 4H), 7.28 (s, 1H), 7.22-7.17 (overlapped peaks, 6H), 4.48-4.42 (overlapped peaks, 4H), 4.32(m, 2H), 4.19 (m, 2H).

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

13 C NMR 75 MHz,CDCl3,δ ppm: 179.6,148.1,143.4,140.0,139.5,136.6,130.0,127.2,124.8,122.6,122.1,117.9,115.4,108.7,65.5,65.4,65.0,64.7.

HRMS (MALDI-TOF)

calcd. for C26H20N2O5S2 [M] + : 504.0814; found: 504.0812. 1 H NMR 300 MHz, CDCl3, δ ppm: 7.76 (s, 1H), 7.47-7.41 (overlapped peaks, 4H), 7.24-7.17

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion -----------------------------------------------------------------------------------------------------------------------------------------------------------

(overlaapped peaks, 7H), 4.48 (m, 2H), 4.43-4.38(overlapped peaks, 4H), 4.20 (m, 2H).

13 C NMR 75 MHz,CDCl3,δ ppm: 148.5,144.2,143.1,141.2,139.6,136.2,130.1,126.5,125.2,122.5,120.3,116.2,115.3,111.4,110.7,108.4,68.3,65.9,65.7,64.9,64.7.

HRMS (FAB)

calcd. for C29H20N4O4S2 [M] + : 552.0926; found: 552.0917.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 278

5-((4-(diphenylamino)phenyl)ethynyl)thiophene-2-carbaldehyde

Chemical Formula: C25H17NOS; Molecular Weight: 379.47

Structural properties

Derivative 19

Yellow solid; yield 64% Protocol Bis(triphenylphosphine) palladium dichloride (28 mg, 0.04 mmol), triphenylphosphine (21 mg, 0.08 mmol) and copper iodide (30 mg, 0.15 mmol) were dried under high vacuum for 30 minutes. Then a previously degassed solution of 17 (0.38 g, 1.41 mmol), 5-bromothiophene-2-carbaldehyde (0.25 g, 1.28 mmol) and piperidine (0.87 g, 10.24 mmol) in 20 mL dry toluene was added. The mixture was stirred overnight at 110 °C under argon atmosphere. After being cooled to room temperature, the mixture was filtered through a short pad of Celite and then the Celite was washed several times with dichloromethane. The organic phase was evaporated and the crude product purified by column chromatography on silica gel, using a mixture of petroleum ether/dichloromethane = 1/1 affording 0.3 g yellow solid.

1 H NMR 300 MHz, CDCl3, δ ppm: 9.85 (s, 1H), 7.65 (d, 1H, J = 3.9 Hz), 7.36 (d, 2H, J = 9 Hz), 7.32-7.25 (overlapped peaks, 5H), 7.14-7.07 (overlapped peaks, 6H), 7.00 (d, 2H, J = 9 Hz).

13 C NMR 75 MHz,CDCl3,δ ppm: 182.5,149.1,147.0,143.5,136.3,133.8,132.8,132.0,129.7,125.5,124.2,121.7,114.1,99.0,81.6.

HRMS (MALDI-TOF)

calcd. for C25H17NOS [M] + : 379.1031; found: 379.1023.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 279

2-((5-((4-(diphenylamino)phenyl)ethynyl)thiophen-2-yl)methylene)malononitrile

Chemical Formula: C28H17N3S; Molecular Weight: 427.52

Structural properties

Derivative 9

Red solid; yield 80%; mp. 189-190°C

Protocol

Few drops of triethylamine were added to a mixture of derivative 19 (0.3 g, 0.8 mmol)

and malononitrile (80 mg, 1.18 mmol) in 40 mL CHCl3. After stirring overnight at room temperature under argon atmosphere, the solvent was removed and the residue dissolved in dichloromethane, washed with water and brine and then evaporated.

Purification by column chromatography on silica gel (dichloromethane/petroleum ether = 4 / 1) afforded 270 mg red solid. 13 C NMR 75 MHz, CDCl3, δ ppm: 150.0, 149. 5, 146.8, 138.8, 136.0, 135.2, 133.0, 132.1, 129.7, 125.7, 124.4, 121.3, 114.2, 113.5, 113.4, 102.4, 81.6, 77.4.

HRMS (MALDI-TOF)

calcd. for C28H17N3S [M] + : 427.1143; found: 427.1133. were washed with dichloromethane. The combined organic layers were filtered through a short pad of alumina. The solvent was removed and the residue was chromatographed on silica gel using dichloromethane as eluent to yield 80 mg deep-violet powder. 1, 150.4, 149.8, 146.6, 145.9, 140.5, 136.1, 133.3, 129.8, 127.9, 127.8, 125.8, 125.5, 125.3, 124.7, 123.5, 122.2, 114.7, 113.8, 75.3.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

HRMS (MALDI-TOF)

calcd. for C52H32N6S2 [M] + : 804.2130; found: 804.2125.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 281 4, 150.7, 150.5, 148.9, 146.1, 140.4, 133.8, 132.0, 131.9, 130.1, 127.9, 127.0, 126.6, 125.6, 124.2, 124.0, 122.0, 114.5, 113.7, 77.4, 76.0.

HRMS (MALDI-TOF)

calcd. for C53H32N6OS2 [M] + : 832.2079; found: 832.2081.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

Structural properties

Derivative 12

Red solid; yield 46%; mp. 140-142°C

Protocol A mixture of 10 (100 mg, 0.12 mmol), ethylene glycol (0.06 mL, 1.02 mmol), and ptoluene sulfonic acid (2 mg, 0.012 mmol) in 30 mL of toluene was refluxed for 5 days using a Dean-Stark trap. After solvent removal the residue was dissolved in dichloromethane, washed with water and brine, dried over MgSO4 and concentrated.

Column chromatography on silica gel using dichloromethane as eluent yielded 48 mg red solid. 1, 150.4, 149.8, 146.7, 146.6, 140.5, 137.6, 133.3, 129.8, 127.7, 125.9, 125.4, 124.8, 124.5, 123.5, 122.3, 114.7, 113.8, 109.3, 77.4, 75.4, 65.1.

HRMS (MALDI-TOF)

calcd. for C55H36N6O2S2 [M] + : 876.2341; found: 876.2335. Chromatography on silica gel using dichloromethane as eluent, afforded 120 mg of a dark-red powder. 6, 155.9, 151.2, 150.5, 148.2, 145.5, 140.3, 134.1, 132.8, 130.3, 129.1, 128.0, 127.9, 126.9, 126.2, 125.1, 124.3, 120.8, 155.5, 114.4, 113.6, 77.4, 76.4.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion -----------------------------------------------------------------------------------------------------------------------------------------------------------

HRMS (MALDI-TOF)

calcd. for C56H32N8S2 [M] + : 880.2191; found: 880.2189.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics -------------------------------------------------------------------------------------------------------------------------------------

Page | 284 (overlapped peaks, 4H), 7.23 (d, 1H, J = 3.9 Hz), 7.14-7.05 (overlapped peaks, 10H). 75 MHz,CDCl3,δ ppm: 149.3,148.5,147.3,139.2,135.9,134.2,132.4,129.5,128.3,127.1,126.9,126.6,125.7,125.0,123.7,123.0,122.8,117.4,101.7.

C NMR

HRMS (MALDI-TOF)

calcd. for C29H20N2S2 [M] + : 460.1068; found: 460.1065.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 285 were added at 0°C. The mixture was heated overnight at 87°C under argon atmosphere.

After cooling to room temperature, a saturated aqueous solution of sodium acetate and methylene chloride were added, and the mixture was stirred for an additional hour.

After extraction with dichloromethane, the organic phase was washed with water and brine, dried over MgSO4 and concentrated. After removal of solvent, the crude was chromatographed on silica gel using methylene chloride as eluent to give a yellow solid. CDCl3,δ ppm: 190.6,152.9,148.4,146.9,146.0,139.1,136.7,134.1,132.2,131.5,130.1,128.4,127.5,127.4,126.9,126.6,126.0,125.8,125.6,123.6,122.8,120.7,117.3,102.4.

HRMS (MALDI-TOF)

calcd. for C30H20N2OS2 [M] + : 488.1017; found: 488.1016.

Chapter 4 -Small Molecular Donors for Organic Photovoltaics ------------------------------------------------------------------------------------------------------------------------------------

Structural properties

Derivative 14

Orange powder; yield 73%; mp. 229-231°C

Protocol

Few drops of trietylamine were added to a mixture of derivative 24 (0.18 g, 0.37 mmol)

and malodinitrile (37 mg, 0.55 mmol) in 35 mL chloroform. The reaction mixture was heated to 40°C for five hours, under argon atmosphere. After being cooled to room temperature, the solvent was evaporated and the residue was dissolved in dichloromethane, washed with water, brine and dried over MgSO4. After solvent removal, the crude was chromatographed on silica gel using dichloromethane as eluent affording 145 mg orange powder. 13 C NMR 75 MHz, CDCl3, δ ppm: 207. 1, 158.0, 153.0, 147.9, 145.7, 145.4, 145.1, 139.0, 137.0, 134.0, 133.1, 132.0, 130.7, 130.3, 128.4, 127.6, 127.1, 127.0, 126.6, 126.5, 126.1, 125.2, 123.9, 123.7, 119.6, 105.1, 102.7.

HRMS (MALDI-TOF)

calcd. for C33H20N4S22 [M] + : 536.1129; found: 536.1133.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Introduction

Among optical materials, the strongly fluorescent ones have attracted much attention for their wide range of applications, from display technologies to biology and medicine. A major milestone in the development of fluorescent nanomaterials was the discovery of semiconductor quantum dots (QDs), which are tiny fluorescent particles that have attracted much interest in recent years, especially for their applications in biosensing, biomedical imaging, and others. 128,129 Unfortunately, many QDs are made from toxic compounds and concerns have been raised over potential toxicity and environmental harm. 130 In this regard, photoluminescent carbon nanoparticles dubbed as carbon 'quantum' dots or carbon dots (CDs) are a good alternative to toxic QDs.

Carbon quantum dots have emerged as alternative fluorescent nanoprobes due to their availability, thermal stability and relatively non-cytotoxic nature. ------------------------------------------------------------------------------------------------------------------------------------Page | 298 various organic compounds. 142,143 Alternatives to these frequently used methods are referring to low temperature solution synthesis 144 , or using mesoporous silica as templates in an impregnation 145 and different other physical methods.

Although developments in the synthesis of CDs are reported often 139-145 , the fundamental drawback that limits their application in life sciences is their relatively low quantum yields (QYs). 141,146,147 To date, passivation and doping are popular approaches to enhance the luminescence of CDs. Several organic molecules or polymers have been used to passivate surface defects on the carbon nanoparticles. 148,149,150,151,152 However, the mechanism of surface-grafting to enhance the fluorescence of CDs is still under debate and there is still a significant lack of efficient approaches to enhance the fluorescence of ''bare'' CDs without any surface coverage. It is speculated that quantum effect, emissive traps 153 and mostly radiative recombination of excitons 154 contribute to the photoluminescence (PL) property of CDs.

Furthermore, due to the CDs characteristics to function as either electron acceptor or electron donor 155 , the optoelectronic properties of CDs are strongly dependent on the surface functional groups and morphology 156 . For example, the noncovalent functionalization of these carbon nanomaterials with rhodamine B (RhB) has enabled the development of both dye-semiconductor complexe with enhanced photoelectric conversion efficiency 157 and fluorescent sensors for selective detection of Hg 2+ . 158 On the other hand, covalent conjugation of CDs with organic molecules offers longterm chemical stability in aqueous solution and allows facile and large-scale synthesis. For example, CDs functionalized with fluorescein, rhodamine B or α-naphtyl amine were prepared for increasing the fluorescence properties of the carbonaceous material. 159 Beyond photoluminescent, chemiluminescent and electroluminescent properties of carbon dots have been studied. Zhao et al. observed that the CDs exhibit chemiluminescence in strong alkaline solution due to the radiative recombination process of electrons and holes. 160 Furthermore, carbon dots passivated with 1-hexadecylamine were found to be electroluminescent when sandwiched between a hole layer and an electron transport one. 161 However, most of the light-emitting applications of carbon dots reported so far has been on their use to convert the blue light of a commercial LED into white light. 162,163,164,165 For example, Guo et al. reported ------------------------------------------------------------------------------------------------------------------------------------Page | 300

Original contributions

One objective of this research work is the synthesis and characterization of CDs passivated with small organic molecules such as 1,3-propanediamine (CDs-PD), pphenylenediamine (CDs-PPD), and also polymers like PEG1500N (CDs-PEG1500N).

Another objective is the investigation of electroluminescence properties of CDs in LED devices and, on the other hand, the potential of CDs to function as energy donors by covalently attaching rhodamine B (RhB) to the free amino group of CDs-PEG1500N.

It is well known that the fluorescence quantum yield of carbon nanoparticles is significantly enhanced by their functionalization with oligomers and polymers. 149-153 In this context, the surface defects on the carbon nanoparticles were passivated with both small molecules and oligomers.

The commercially supplied carbon nanoparticles were refluxed in an aqueous nitric acid solution (2.6M) in order to oxidize some of the surface carbons into carboxylic acids.

The resulting nanoparticles were subsequently dialyzed against deionized water and then gravimetrically fractionated for harvesting the smaller nanoparticles. The as-obtained samples still exhibited no detectable photoluminescence. However, upon surface passivation by attaching simple organic species to the acid-treated carbon particles (scheme 1), bright luminescence emissions were observed when irradiated at 365 nm (figure 1).

In this regard, upon being recovered from aqueous solution, the nanoparticles were further refluxed in neat thionyl chloride for the subsequent amidation reaction with small aliphatic diamine derivatives such as 1,3-propandiamine as well as aromatic diamine, pphenylenediamine, and also with oligomeric poly(ethylene glycol)diamine (PEG1500N). After the reaction time elapsed, the mixture was cooled to room temperature, dispersed in deionizated water and centrifuged to 25000g to retain the supernatant. The solution was further dialyzed against deionizated water to remove the free functional moieties and finally the as-prepared samples were fractionated on a gel column (Sephadex TM G-100) to harvest the most fluorescent fraction from each of the samples. The CDs-PD, CDs-PPD and CDs-PEG1500N were obtained as colored aqueous solutions. -----------------------------------------------------------------------------------------------------------------------------------

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The optical absorption spectra of all obtained CDs are shown in figure 2, depicting the typical π-plasmon transitions in the core carbon nanoparticle. The fluorescence spectra also displayed characteristic CDs behavior, in that the emission maxima were progressively red-shifted with the spectral band becoming narrower and reduced in intensity with increasing excitation wavelength (figure 2). Although this behavior is not fully understood, it has been suggested that the presence of defect states near the Fermi level in CDs may explain their excitation-dependent emission behavior. 166 As these defects, which were introduced by chemical oxidation and functionalization, are not equivalent, the result is a mixed range of emission-energy levels generating a broad emission band and excitationdependent band shapes. Other factors such as the presence of particles with different sizes in the sample and the distribution of different emissive sites on each passivated carbon dot have been also associated with this emission behaviour. 149 Nevertheless, the observed emission spectra corresponding to multiple excitation wavelengths covere the entire visible spectral region (figure 2). The photoluminescence quantum yields of the CDs-PD, CDs-PPD and CDs-PEG1500N in aqueous solutions were about 9%, 14% and 10%, respectively (375-425 nm excitation, using the quinine sulphate standard). -----------------------------------------------------------------------------------------------------------------------------------

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The morphology of the passivated CDs-PEG1500N was established using highresolution transmission electron microscopy (HR-TEM) which has revealed a crystalline structure with an average diameter of about 3.5 nm (figure 3). The spectrum for N1s shows two regions: one assigned to C-N bonds (between 400 and 398 eV) and the other to N-H bonds (between 401 and 400.5 eV). The deconvolution of N1s spectrum for all three materials reveals the presence of three types of nitrogen atoms: pyridinic (398.1-399.3 eV), quaternary (401-401.5 eV) and amidic (~ 399.6 eV). The ionization energy from 399.6 eV is a characteristic frequently reported in carbonaceous materials obtained by oxidation with nitric acid and it is assigned to nitrogen species bonded to oxygen.

In conclusion, although the chemical structure can not be exactly determined because the different functionalities present close ionization energies and are difficult to identify, the obtained materials have an ordered structure of graphitic type, and the chemosorption of the amines from CDs-PD and CDs-PEG1500N materials is confirmed by the peaks around 399.6 eV.

In the next step, we investigated the potential of CDs to act as energy donors in FRET by covalently attaching rhodamine B to the free amino group of the passivating polymer in CDs-PEG1500N. -----------------------------------------------Förster resonance energ radiative energy transfer between chromophore, initially in its elect chromophore through non-radiat species (figure 5). The FRET eff between donor emission and ac between two optical species, the placed within the Förster radius The FRET mechanism is cu sensing applications, including bio that dye-CDs nanocomposites c biological media for the real tim both. 171,171,172 In order to improve ------------------------------------------------------------------------energy transfer (FRET) is a mechanism describi r between two light-sensitive molecules (chromophor n its electronic excited state, may transfer energy to radiative dipole-dipole interaction between the FRET efficiency is strongly influenced by the spec n and acceptor absorption, as well as the separati ecies, the most effective transfer being achieved wh r radius (of about 3-5 nm). 167 . FRET diagram with typical time scales indicated nism is currently exploited as photophysical transduce luding biomedical diagnostics. 168,169,170 Reports have de posites can act as efficient FRET-based sensing p e real time monitoring of drug-delivery, two-photon o improve FRET efficiency and analytical performance ence Spectroscopy; Kluwer Academic/Plenum Publishers: New Yor Chem. Commun. 2013, 49, 403. RSC Adv. 2014, 4, 41069. . 2014, 47, 20. Hale, B. McCaughan, J.F. Callan, Chem. Commun. 2013, 49, 8934. . Wang, Y. Wang, D. Zhao, G. Zheng, Adv. Mater. 2013, 25, 6569. ext Generation -------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------Page | 307 efforts are carried out upon the search for new energy donor/acceptor pairs. CDs emitters possess several convenient optical properties over common organic fluorophores that can be usefully exploited in FRET configurations, including broad absorption from UV to visible, excitation dependent emission and strong resistance to photobleaching. 139 The broad absorption and emission spectra of CDs-PEG1500N compared to the narrow excitation spectra of the organic dyes, grants them the potential to function as donor in carbon-dye conjugates. Furthermore, their photoluminescence dependence on the excitation wavelength will increase the spectral overlap between the dye absorption and the carbon dots emission as the excitation wavelength is increasing from 375 to 510 nm. In this context, we subsequently used CDs-PEG1500N as donor in presence of RhB as acceptor, taking into account their good emission spectral overlap with the absorption of RhB, a condition required for high energy transfer efficiency. Figure 6 shows the spectral relationship between the UV-Vis absorption band of RhB and photoluminescence band of CDs-PEG1500N at different excitation wavelengths (as listed). -----------------------------------------------------------------------------------------------------------------------------------

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The covalent linkage of rhodamine B onto the surface of the CDs-PEG1500N has been carried out after several successive reactions, which are depicted in scheme 2. The first three steps regarding the passivation of surface defects on carbon nanoparticles were already described in the first part of this chapter. The final step corresponds to the reaction with RhB isothiocyanate under alkaline anhydrous conditions to the primary amine groups of CDs-PEG1500N.

Scheme 2. Schematic illustration of the surface coupling process of CDs-PEG1500N with RhB

The successful covalent attachement of the RhB was confirmed using FT-IR spectroscopy that indicated that the isothiocyanate moiety was converted into thiourea upon reaction with the terminal primary amine in the CDs-PEG1500N (figure 7). The FT-IR spectrum of the CD-PEG1500N-RhB shows the disaapearing of the absorption band at 2150 cm -1 corresponding to the asymmetric stretching mode in -N=C=S 173 , indicating thus the covalent linkage of RhB to the terminal amine moiety of the CDs-PEG1500N. In addition, the intensity of the band at 1650 cm -1 ascribed to the C=N bond stretch is considerably decreased, while the thiocarbonyl (C=S) band is shifted from 1010 to 1120 cm -1 . This supports the isothiocyanate (N=C=S) conversion to thiourea (N-C(=S)-N), because of the stretching mode of (C=S) being strongly coupled with N-C-N stretching vibrations. 174 We speculate that this hypsochromic shift could take place in our system upon chemical binding of the RhB molecules to CDs-PEG1500N. Indeed, DFT calculations 175 demonstrated that a 2nm shift of the absorption peak could be observed when the angle between the xanthene plane and the phenyl ring will change 4-6 degrees.

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We investigated further the photoluminescence properties of covalently bound RhB molecule to CDs-PEG1500N by steady-state and time-resolved photoluminescence measurements. Figure 9 displays the recorded photoluminescence spectra of CD-PEG1500N-Rh conjugates excited at 375 nm, 405 nm, 420 nm and 450 nm together with the corresponding photoluminescence spectra of RhB and unconjugated CDs-PEG1500N, of identical concentrations with those found in the conjugated system. Note that the intensity of CDs-PEG1500N photoluminescence band decreases along with the increase of photoluminescence band of RhB dye at the selected excitation wavelengths (figure 9). Moreover, the magnitude of spectral variations as quantified by the relative increase of RhB emission intensity (Iconjugated/IRhB) is consistent with the spectral overlapping integrals calculated using Eq.2, when considering the absorption band of RhB dye and the photoluminescence band of CDs-PEG1500N (table 1). This behavior is a clear signature of FRET mechanism, which operates between CDs-PEG1500N as donor and RhB as acceptor. The highest FRET efficiency concluded from the increase of photoluminescence

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Page | 312 band of RhB occurs at 450 nm excitation wavelength, where the overlap between the absorbtion band of RhB dye and the photoluminescence band of CDs-PEG1500N is maximum (figure 6).

Table 1. The overlap integrals calculated from Figure 6.

Excitation wavelength

(nm) J (λ) a (M -1 cm -1 nm 4 ) An alternative method to quantify the efficiency of energy transfer between CDs and Rh molecules in CD-PEG1500N-Rh conjugates is the determination of fluorescence lifetime of both emissive species. As the fluorescence lifetime is the average time that luminescent species spend in its excited state following excitation from the ground energy level, the fluorescence lifetime measurements are sensitive not only to molecular environment, but also mainly to FRET in the case of a donor/acceptor pair. Moreover, fluorescence lifetime measurements can overcome some limitations of steady-state technique, as fluorescence lifetime is independent of sample concentration. In this context, we were interested in characterizing the change in the excited-state lifetime of donor (CDs-PEG1500N) caused by the energy-transfer process, upon conjugation with RhB dye. The decay curves of CDs-PEG1500N and CD-PEG1500N-Rh conjugates recorded when using 405 nm as excitation wavelength are presented in figure 10. In order to minimize the contribution from RhB emission and collect mainly the signal originating from CDs-PEG1500N, the fluorescence signal was filtered over the 417 nm-477 nm wavelength spectral region, using a band-pass filter, as described in the experimental section.

Relative emission of RhB

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 313 Tail fitting operations revealed that the decay curve of CDs-PEG1500N exhibits a long lifetime component of 6.5 ns (66.5%) and a shorter one of 1.8 ns (33.5%, table 2). According to literature data, the 1.8 ns component corresponds to the exciton emission-the intrinsic recombination of initially populated core states, while the long component, here 6.5 ns, is most probably related to the involvement of surface trapped

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Page | 314 states in the carrier recombination process. 176 For the amplitude-averaged fluorescence lifetime of our synthesized CDs-PEG1500N we obtained a value of 4.9 ns, which is in good agreement with similar literature reports. 177,178 The performed measurements on the conjugates reveal that both the exciton emission and surface trapped states of CDs-PEG1500N are affected by the presence of Rh B dye. Specifically, we observed the decrease of lifetime components from 6.5 ns and 1.8 ns to 5.4 ns and 1.3 ns, respectively, as detailed in table 2. Consequently, the average lifetime of CDs-PEG1500N decreased from 4.9 ns to 3.8 ns upon conjugation with Rh B acceptor molecules (see table 2). Shortening of the lifetime of CDs-PEG1500N confirms an efficient energy transfer in our donor-acceptor system, in agreement with the previous results obtained from steady-state fluorescence measurements. Furthermore, we have calculated the FRET efficiency and the rate of energy transfer in our system at 405 nm. Results are listed in table 3, along with the obtained Förster distance and the estimated distance between donor and acceptor. Donor QY 405 43.34 4.9 3.8 0.22 53.7 0.056 0.17 a Calculated using Eq.1; b Calculated using Eq.3; c Calculated using Eq.5; d Calculated using Eq.4;

The Forster separation distance, R0 (the distance at which the energy transfer efficiency is 50%) was calculated as follows:

= 0.211( ( )) /"

(1)

where nD represents the refractive index of the medium (here 1. The carbon dots deposited on top of the PVK polymer formed a thin continuous layer according to the atomic force microscopy (AFM) imaging result (figure 12). In the AFM images, the carbon dots layer (figure 12b) on top of the PVK film (figure 12a), appears to be a relatively even and complete layer, with a kurtosis parameter (Sku) of unity for the ----------------------------------------------------------------------------------------------------------------------------------- The LED device was evaluated by applying a forward bias on the hole-injecting contact (HIL, ITO/PEDOT:PSS). With the external bias, electrons and holes were injected to result in the formation of excitons, from which the positive and negative polarons could radiatively recombine in the carbon dots layer for luminescence emissions.

The electroluminescence from the device was naked eye visible, as white light with a bluish color (figure 13). As it can be observed in figure 13a, the electroluminescence spectrum is broad and covers a wide range of the visible spectral region. On the other hand, the electroluminescence spectra were not sensitive to variations of the applied voltage, 11-15V region (figure 13a). The chromaticity CIE coordinate (0.25, 0.24) for 15V applied biases was calculated from the electroluminescence spectrum (figure 13b).

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

Page | 319 The general overlap between the electroluminescence spectrum and the collection of multiple photoluminescence spectra (obtained with multiple excitation wavelengths) seems to suggest that the recombination zone is within the carbon dots layer, with the PVK layer serving primarily the function of hole-transport (figure 14).

Figure 14. A comparison between the electroluminescence (EL) spectrum from theLED device with the PEGylated carbon dots and the corresponding photoluminescence spectra at the listed excitation wavelengths.

Chapter 5 -Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation

Optoelectronic Devices -------------------------------------------------------------------------------------------------------------------------------------

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In quantum efficiency measurements, the emission signal was maximized by minimizing the distance between the emitting surface and a large area detector (detector active area 100 mm 2 Ophirsilicon photodiode type PD300-3W). The LED device was operated at 15 V (current up to 5 mA), and the recorded power at 440 nm was 130 nW.

Thus, the 'wall-plug efficiency' of the LED device was estimated (as the ratio of the measured power to the input power) to be 1.73 × 10 -6 . The luminescence from the device, operated at 15 V was about 2 × 10 -6 lm [calculated from the total power output measured at room temperature under ambient atmosphere with the following equation: PQ = 683 lm/W ∫(SPQ)λ V(λ) dλ, where PQ is the photometric quantity, SPQ the matching radiometric quantity in W, V(λ) the response of the 'standard' light adapted eye-photopic vision] and a luminance of 0.14 cd/m 2 .

The observed agreement between the electroluminescence and photoluminescence spectra (figure 14) might suggest that the use of more photoluminescent samples of carbon dots should lead to significantly enhanced performance. Among other improvements for future investigations we consider the addition of an electron transport layer in the device and better controlled device fabrication.

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

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Experimental part

General Remarks

The carbon nanopowder sample (<50 nm, purity 99+%), poly(ethylene glycol) bis(3-aminopropyl) terminated (PEG1500N, Mn ~1.500), rhodamine B isothiocyanate (mixed isomers, RhB), poly(9-vinylcarbazole) (PVK), and poly(ethylenedioxythiophene): polystyrene sulphonate (PEDOT:PSS) were purchased from Sigma-Aldrich. Nitric acid (65%), thionyl chloride, and triethylamine (TEA) were acquired from Merck Millipore. Dichloromethane (purchased from Scharlau) and DMF (purchased from Sigma-Aldrich) were dried over calcium hydride and distilled under argon prior to use. Dialysis membrane tubing (cutoff molecular weight 1000) was supplied by Spectrum Laboratories. Water was deionized and purified by being passed through a Milli-Q water purification system.

Measurements

The high resolution transmission electron microscopy (HR-TEM) samples were prepared by placing a drop of dilute carbon dots solution on a holey-carbon grid. The experiments were carried out using a Tecnai TM G 2 F30 S-TWIN transmission electron microscope operating at 300 kV, and the images were analysed with Digital Micrograph software. The TEM specimens were prepared by placing a drop of dilute carbon dots solution on a holey-carbon grid, and the images were analyzed with Digital Micrograph software. The AFM characterization was performed on a Scanning Probe Microscope Ntegra (Nt-MDT), operated in soft-tapping regime of the semicontact mode (tapping mode), and equipped with a standard silicon cantilever with 7.5 N/m nominal spring constant, and 160 kHz resonance frequency and 10 nm nominal tip radius. All data were processed by using first order line flattening algorithm. Infrared absorption measurements were recorded with a Bruker Equinox 55 Fourier transform infrared spectrometer. Each spectrum was measured in attenuated total reflectance (ATR) mode with 60 scans and 2 cm -1 resolution. For FT-IR measurements in ATR mode the films of the donor (i.e. CDs-PEG1500N), the acceptor (i.e. Rh B), and the conjugates (i.e CD-PEG1500N-Rh) were prepared by dropping dispersion onto glass slides and dried at room temperature. The UV-Vis absorption spectra were recorded at room temperature using a Jasco V-670 UV-Vis-NIR spectrophotometer with a band width of 2 nm and 1 nm spectral resolution. The steadystate photoluminescence spectra were collected using a Jasco LP-6500 spectrofluorimeter equipped with xenon lamp as a light source. In all cases, photoluminescence spectra were corrected for the intensity of the excitation lamp and the wavelength dependence of the detection system. Fluorescence lifetime measurements were performed on a PicoQuant

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Device fabrication

The architecture of the device comprised an indium tin oxide (ITO) glass substrate (with the sheet resistance of 20 Ω/□) and cleaned in an ultrasonic bath with extran, water, acetone, isopropanol, followed by 10 minutes of UV-ozone exposure. Subsequently the PEDOT:PSS solution was spin-coated from the water solution at 5.000 rpm for 60 seconds, followed by 15 minutes of thermal treatment at 150°C in air. The PVK solution was spincoated from a solution of 1,2-dichlorobenzene/chloroform mixture at 1.500 rpm for 30 seconds onto the PEDOT:PSS layer, followed by 2 hours of thermal treatment in vacuum at 100°C. The carbon dots layer was deposited from an aqueous solution by spin-coating onto the PVK film at 1.500 rpm for 30 seconds, followed by thermal treatment under vacuum at 80°C for 1 hour. The 100 nm thick aluminum cathode was deposited on top of the carbon dots layer under vacuum (6 x 10 -7 Torr) through a shadow mask that defined a 3 mm x 1.5 mm active area.

Carbon dots synthesis

Synthesis of surface-oxidized carbon nanoparticles

A commercially supplied carbon nanopowder sample (2g) was refluxed in an aqueous nitric acid solution (2.6 M, 160 mL) for 18h. After being cooled to room temperature, the sample was dialyzed against fresh water, followed by centrifuging at 1000g to retain the supernatant, from which surface-oxidized carbon nanoparticles were recovered (about 150 mg).

Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion ------------------------------------------------------------------------------------------------------------------------------------------------------------

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Synthesis of CDs-PD

The surface-oxidized carbon nanoparticles (50 mg) were refluxed in neat SOCl2 (5 mL) for 15h. Upon the removal of excess SOCl2, the sample was mixed with 500 mg of 1,3propandiamine and then heated to 100°C under argon atmosphere for 3 days. The reaction mixture was cooled to room temperature, dispersed in 30 mL water and centrifuged at 14000 rpm for 50 min. to retain the supernatant. As prepared carbon-dots were fractionated on a gel column (Sephadex TM G-100) to harvest the most fluorescent fraction.

Synthesis of CDs-PPD

The surface-oxidized carbon nanoparticles (50 mg) were refluxed in neat SOCl2 (5 mL) for 15h. The excess thionyl chloride was removed and the recovered carbon nanoparticles were dispersed in 1 ml anhydrous DMF. 500 mg p-phenylenediamine was added to the suspension and the reaction mixture was vigorously stirred under argon atmosphere for 3 days at 160°C. After being cooled to room temperature, the mixture was dispersed in 30 mL water via sonication and then centrifuged to 14000 rpm to retain the supernatant. The recovered supernatant was fractionated on a gel column (Sephadex TM G-100) to harvest the most fluorescent fraction of the sample.

Synthesis of CDs-PEG1500N

The carbon soot (1.5 g) was refluxed in 2.6 M aqueous nitric acid for 24 h. The pH of the solution was brought to pH=3 with ammonium bicarbonate before dialysis against fresh water, and then centrifuged at 1000 g to separate heavier particles. The supernatant was retained, evaporated and lyophilized (freeze-dried) to remove water, obtaining 1.28 g of dried particles. A part of the recovered CDs (0.3 g) was refluxed in neat thionyl chloride (60 ml) for 17 h. The excess thionyl chloride was removed on a rotavapor. The recovered CDs was dried overnight in an oven and subsequently added to dry PEG1500N (3 g). The mixture was heated in an oil bath at 110°C under inert atmosphere for 3 days. The reaction mixture was then cooled to room temperature, dispersed in ultrapure water (20 ml), and

Concept for Next Generation Optoelectronic Devices -------------------------------------------------------------------------------------------------------------------------------------

Page | 326 then centrifuged at 25000g for 1 h to retain the supernatant. The supernatant was separated by gel column using Sephadex TM G-100 gel as stationary phase and water as mobile phase.

Synthesis of CD-PEG1500N-Rh

For dye labeling of the CD-PEG1500N we used the isothiocyanate derivative of rhodamine B (RhB). Briefly, after freeze-drying of the material, 100 mg of CDs-PEG1500N were mixed with 6.7 mg RhB, 15 ml dry dichloromethane and 2.5 ml triethylamine. The mixture was stirred under inert atmosphere at room temperature for 24 h. Evaporation of the solvents provided a red solid that was dispersed in 15 ml distilled water and dialyzed against fresh water to remove any free and nonspecifically adsorbed RhB molecules. Dialysis has been performed until no Rh B could be detected in the dialysate by UV-Vis spectroscopy. Freezedrying of the solution lead to CD-PEG1500N-Rh conjugates as a red solid.

PhD Thesis

Andreea Petronela

Design, Synthesis and Supram

Potential Application

Abstract:

The thesis entitled "Design, Synthesis an Architectures of New Heterocyclic Compounds Applications in Material Chemistry and Photovolt structured into five chapters concerning new cyclopenta [c]pyrans; b) indenopyrone derivatives properties; c) potential devices of molecular electro donors for organic photovoltaics and e) electrolu 'quantum' dots.

The first chapter presents a study derivatives having a cyclopenta [c]pyran unit. The su synthesis, structural analysis and reactivity tow substitution in order to obtain fluorescent compound

The second chapter deals with the separa diastereoisomers and the study of fluorescent prope indenopyrone derivatives.

The third chapter describes the sy architectures based on cyclopenta [c]pyran unit that modified by the influence of a chemical or electroch order to work as potential devices in molecular electr

In the fourth chapter, the synthesis and electronic properties of new molecular donors for was described.

The fifth and last chapter outlines the pas defects on carbon nanoparticles using small org polymers in order to obtain photoluminescent car dubbed as carbon'quantum'dots.

Keywords: Cyclopenta

Funding

  from Romanian Government, CNCSIS AT-64/2006, PNCDI II program (UEFISCSU; project: ID_PCCE_2011_2_0069). Thanks also to the French ''Ministère des affaires étrangèrs'' for the Eiffel scholarhip.

Figure 1 .

 1 Figure 1. Fragments of 1 H NMR spectra (300 MHz, CDCl3) of isomer 2'e (top) and isomer 2''e (bottom).

Figure 2 .

 2 Figure 2. Cyclic voltammograms corresponding to the oxidation of enol-lactones 2b, e-j (top) and 2'e vs. 2''e (bottom) in 0.10 M Bu4NPF6/CH2Cl2, Pt electrodes, scan rate 100 mVs -1 .

Figure 3 .

 3 Figure 3. Cyclic voltammograms corresponding to the reduction of enol-lactones 2b, e-j (left) and 2'j (right) in 0.10 M Bu4NPF6/CH2Cl2, Pt electrodes, scan rate 100 mVs -1 .

Figure 4 .

 4 Figure 4. Normalized absorption spectra of trans (top) and cis derivatives 2 (bottom) recorded in CH2Cl2 at room temperature

Figure 6 .

 6 Figure 6. Blue fluorescence of solid 2'e by irradiation at 365 nm

  and C-6-C-7, respectively, in compounds 2'd, 2'e and 2'h are disposed in a trans configuration, while for the derivative 2''c the X-Ray diffraction analysis confirms the cis orientation of the hydrogen atoms H-2-C-2-C-3-H-3.

Figure 7 .

 7 Figure 7. Single crystal molecular structure of compounds 2'd, 2'e, 2'h, 2''c

  2''c are interconnected into 2D sheets by C-H•••π interactions between aromatic -CH and neighboring phenyl group (C-H19•••centroid 2.958 Å, orange dashed line, and C-H13•••centroid 2.854 Å, blue dashed line, figure 8a).

Figure 8a .

 8a Figure 8a. Crystal packing view along a axis of tetrahydrocyclopenta[c]pyran 2''c (only hydrogen atoms involved in interactions are shown); C-H•••π contacts between molecules in a head-to-tail orientation (orange dashed line) and head-to-head (blue dashed line)

Figure 8b .

 8b Figure 8b. Crystal packing view along b axis of tetrahydrocyclopenta[c]pyran 2'd (only hydrogen atoms involved in interactions are shown); C-H•••π contacts between molecules in a head-to-tail orientation (orange dashed line) and head-to-head (purple dashed line)

Figure 8c .

 8c Figure 8c. Crystal packing view along c axis of tetrahydrocyclopenta[c]pyran 2'e (only hydrogen atoms involved in interactions are shown); C-H•••π contacts between molecules in a head-to-tail disposition (orange dashed line) and head-to-head orientation (purple and blue dashed line)

Figure 8d .

 8d Figure 8d. Crystal packing view along a axis of tetrahydrocyclopenta[c]pyran 2'h (only hydrogen atoms involved in interactions are shown); C-H•••π interactions (blue dashed line) and H-bonding (red dashed line)

Figure 9 .

 9 Figure 9. Fragments of 1 H NMR (300 MHz, CDCl3) spectra of derivatives 4g (top) and 5g (bottom)

Figure 10 .

 10 Figure 10. Absorption spectra of dihydrocyclopenta[c]pyrans 4 and 5 in dichloromethane

Figure 11 .

 11 Figure 11. Normalized fluorescence spectra in solution and in solid state (dotted line) of derivatives 4 (top) and 5 (bottom)

  Figure 13. X-Ray structures of derivatives 4b (a), 4c (b), 4e(d) and 5f(c)

Figure 14a .

 14a Figure 14a. Crystal packing view along a axis of dihydrocyclopenta[c]pyran 4b (only hydrogen atoms involved in interactions are shown)

Figure 14b .

 14b Figure 14b. Crystal packing view along c axis of α-pyrone 4c (only hydrogen atoms involved in interactions are shown)

Figure 15 .

 15 Figure 15. MERCURY representation of the lattice view along b axis for compound 5f

Figure 16 .

 16 Figure 16. Fragment of 1 H NMR (CDCl3, 300 MHz) spectrum of derivative 6e

Figure 17 .

 17 Figure 17. Fragments of 1 H NMR (CDCl3, 300 MHz) spectrum (top) and 13 C NMR (CDCl3, 75 MHz) spectrum of derivative 7d (bottom).

The 1 H

 1 NMR spectra (figure 18) of 8 and 9 show typical signals such as a doublet for the aromatic proton H-5 and a more deshielded signal for H-6. The proton at position 6 shows a doublet of quartets due to the additional long range coupling with the fluorine atoms, the influence of the fluorine being also observed in 13 C NMR spectra, where C-6 appears as a quartet. 19 F-NMR spectra show a narrow doublet at -70.26 ppm (JH,F = 2.1 Hz) corresponding to the three fluorine atoms in the molecule.

Figure 18 .

 18 Figure 18. Fragment of 1 H NMR (CDCl3, 300 MHz) spectrum of derivative 8c

Figure 19 .

 19 Figure 19. Orange fluorescence of solid compound 8c by irradiation at 365 nm

Figure 20 .Figure 21 .

 2021 Figure 20. Normalized absorption spectra of derivatives 8 and 9 recorded in CH2Cl2

Figure 22 .

 22 Figure 22. Crystal structures of trifluoroacetyl-cyclopenta[c]pyrans 8a, 8g and 9a

Figure 23 .

 23 Figure 23. Crystal packing view along b axis of trifluoroacetyl-cyclopenta[c]pyran 8a (only hydrogen atoms involved in interactions are shown); C-H•••π contacts (blue dashed line) and C-H•••F interactions (red dashed line)

  between a hydrogen atom belonging to the methoxy group of one molecule and the core of the meta-methoxyphenylene unit belonging to a neighboring molecule can be observed. The fluorine atom of the trifluoroacetyl group forms also strong C-F•••π interactions (C-F2•••centroid = 3.192 Å) with the pyran ring of another molecule. Additionally, the C=O group forms intermolecular hydrogen bonds with the hydrogen of the meta-substituted benzene ring of a neighboring molecule (C-O2•••H14 = 2.675 Å).

Figure 24 .

 24 Figure 24. View of the lattice along c axis (only hydrogen atoms involved in interactions are shown) showing C-H•••π (purple dashed line), C-F•••π (red dashed line) and C-H•••O (blue dashed line) interactions of compound 8g

Figure 25 .

 25 Figure 25. Crystal packing view along b axis (only hydrogen atoms involved in interactions are shown) of compound 9a; C-H•••π contacts (red dashed line), C-H•••F (pink dashed line) and F•••F (green dashed line) interactions `

Figure 26 .

 26 Figure 26. Fragment of 1 H NMR (CDCl3, 600 MHz) spectrum of derivative 12e

Figure 27 .

 27 Figure 27. Normalized absorption spectra of derivatives 12 recorded in CH2Cl2 at room temperature

  and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion

Figure 28 .

 28 Figure 28. Normalized UV-Vis (green) and fluorescence (orange) of derivatives 12

  ); the carbon-carbon bond lengths in the five-membered (C2-C3 1.458 Å, C3-C4 1.373 Å, C4-C5 1.414 Å, C5-C6 1.408 Å) and sixmembered ring (C6-C7 1.430 Å, C7-C8 1.353 Å, C1-C2 1.375 Å) are substantially deviated from the values expected for the structure of 12c, written formally with alternating single and double bonds. The phenyl and phenylene units are almost coplanar with the plane of cyclopenta[c]pyran unit (torsion angles: C18-C7-C6-C5 7.6°; C11-C1-C2-C3 5.7°). The formyl groups have the oxygen atom in an outward orientation, almost coplanar with the plane formed by C5-C6-C7 (torsion angles: C10-C5-C6-C7 10.6°; C9-C3-C2-C1 14.6°).

Figure 29 .

 29 Figure 29. Crystal structure of derivative 12c

  pyran ring of one molecule and the oxygen from the formyl group of the other molecule (C-H8•••O2 2.366 Å) can be observed in the lattice (figure 30). Furthermore, the formyl group of the same molecule forms an H-bond with a hydrogen of the methoxy group (C-H17B•••O2 2.446 Å).

Figure 30 .

 30 Figure 30. Crystal packing view along c axis (only hydrogen atoms involved in interactions are shown) of compound 12c; H-bonds interactions are shown in red and blue dashed line

Figure 31 .

 31 Figure 31. Fragment of 1 H NMR (CDCl3, 600 MHz) spectrum of derivative 13c

Figure 33 .

 33 Figure 33. Cyclic voltammograms of compounds 13c, f, g in 0.10 M Bu4NPF6/CH2Cl2, Pt electrodes, scan rate 100mV s -1

(4 and 5 )

 5 show strong blue fluorescence in solid-state by irradiation at 365 nm and weaker emissions in dichloromethane solutions. A general comparison of fluorescence in solidstate and in solution revealed a slight bathochromic shift of emission maxima, probably due to intermolecular interactions in solid-state.

  C21H18O2; Molecular Weight: 302.37 Trituration with a mixture of pentane/diethyl ether = 8/1 gave a mixture of isomers in a ratio 2'b : 2''b = 1.6 : 1, as a pale yellow solid, yield 65%.

300

  MHz, CDCl3, δ ppm: 3.77 (t, J = 1.8 Hz, 2H, H-7), 3.89 (s, 3H, OCH3), 6.80 (dt, J = 5.7, 2.1 Hz, 1H, H-5), 6.88 (dt, J = 5.7, 2.4 Hz, 1H, H-6), 7.00 (d, J = 8.1 Hz, 1H, H-4' (C6H4-m-OCH3)), 7.33-7.41 (overlapped peaks, 2H, , 4H, m,p-H (C6H5), H-5' (C6H4-m-OCH3)), 7.54 (d, J = 7.2 Hz, 2H, o-H (C6H4-m-OCH3)).

  72 (overlapped peaks, 3H, H-3, m'-H (C6H4-p-Cl)), 8.02 (d, J = 8.7 Hz, 2H, o'-H (C6H4-p-Cl)).

-

  Page | 101 m,p-H (4-C6H5)), 7.61(d, J = 8.4 Hz, 2H, m'-H (C6H4-p-tBu)), 7.69 (s, 1H, H-3), 7.72(d, J = 7.8 Hz, 2H,), 8.03(d, J = 8.4 Hz, 2H,).

  CDCl3, δ ppm: 2.47 (s, 3H, CH3), 3.93 (s, 3H, OCH3), 6.18 (d, J = 1.5 Hz, 1H, H-5), 7.01 (d, J = 3.9 Hz, 1H, H-7), 7.11 (d, J = 8.7 Hz, 2H, m'-H (C6H4-p-OCH3)), 7.22 (dd, J = 4.5, 2.7 Hz, 1H, H-6), 7.44-7.53 (overlapped peaks, 5H, 4-C6H5), 8.09 (d, J = 8.7 Hz, 2H, o'-H (C6H4-p-OCH3)).

  CDCl3, δ ppm: δ 2.45 (s, 3H, CH3), 3.92 (s, 3H, OCH3), 6.15 (d, J = 2.1 Hz, 1H, H-5), 6.98 (d, J = 4.5 Hz, 1H, H-7), 7.09 (dd, J = 8.4, 1.8 Hz, 1H, H-4' (C6H4-m-OCH3)), 7.20 (dd, J = 4.2, 2.7 Hz, 1H, H-6), 7.39-7.51 (overlapped peaks, 6H, H-2' (C6H4-m-OCH3), H-ar (4-C6H5)), 7.61 (t, J = 2.4 Hz, 1H, H-5' (C6H4-m-OCH3)), 7.68 (d, J = 7.5

  dicarbaldehyde dicarbaldehydeChemical Formula: C22H13BrO3; Molecular Weight: 405.24

  solid; yield 58%; mp. 283-285°C; Rf = 0.5 (silica gel, diethyl ether).

Chapter 1 -

 1 Design, Synthesis and Analysis of new Fluorescent Cyclopenta[c]pyrans

  ) of isomers 2'b, 2''b and 3''b significant differences are observed, especially for the hydrogen atom of the stereocenter C-4. For isomer 2'b the large coupling constant (J4,4a = 14.3 Hz) indicates the trans orientation of H-4 relative to H-4a, while the proton H-4 in isomer 2''b exhibits a more deshielded doublet with a moderate coupling constant (J4,4a = 7.1 Hz) characteristic for the cis configuration. On the other hand, the 1 H NMR spectrum confirmed the formation of cis diastereoisomer 3''b (J4,4a = 6.7 Hz).The isomer exhibits characteristic signals for the expected structure. The protons at position 9 give two doublets at 3.75 ppm and 4.12 ppm, respectively with a large coupling constant (J9,9 = 20.6 Hz) characteristic for geminal protons. The proton at position 4 appears as a doublet at 4.87 ppm and the proton at position 4a appears also as a doublet at 4.56 ppm. Noteworthy, in case of isomer 3''b the specific protons of the enol-lactone moiety appear more deshielded than those of isomer 2''b (figure1).

Figure 1 . 1 H

 11 Figure 1. 1 H NMR spectra (600 MHz, CDCl3) of isomers 2'b (top), 2''b (middle) and 3''b (bottom)

regioisomer 2 'Figure 2 .Figure 3 .

 223 Figure 2. Normalized absorption spectra of dihydroindenopyrones 2' (left) and 2'' (right) in acetonitrile (298 K)

DerivativesChapter 2 -

 2 2a-d show good emission, except for cis isomer 3''b, which has a weaker emission, probably due to the smaller conjugation extent and because an intersystem crossing process takes place (an electron is transferred from a singlet energy level into a triplet energy level). The spectral data are normalized, the absorption is shown in red and the emission lines are in blue. Synthesis and Structural Analysis of new Indenopyrone derivatives

Figure 4 .

 4 Figure 4. Normalized UV-Vis (red) and fluorescence (blue) spectra of dihydroindenopyrones 2a-d

Figure 5 . 4 ( 3

 543 Figure 5. Normalized solid state and solution (acetonitrile) fluorescence spectra of some diastereoisomers

Figure 6 .

 6 Figure 6. ORTEP diagram (left) and crystal packing of compound 4 (right) showing C-H•••π interactions (green dashed line), π stacking (red dashed line) and intra-(magenta dashed line) and intermolecular (blue dashed line) H-bonding, respectively.

Figure 7 .

 7 Figure 7. Fragment of 1 H NMR spectrum (CDCl3, 400 MHz) of derivative 6' (top); Fragment of 1 H NMR spectrum (CDCl3, 600 MHz) of derivative 6 (bottom).

Figure 8 .

 8 Figure 8. APCI-MS spectrum of derivative 6'

Figure 9 .

 9 Figure 9. Normalized absorption (left) and fluorescence (right) spectra of α-pyrone derivatives 4, 6 and 6' in dichloromethane

  general comparison of fluorescence spectra in solution and in solid state revealed an important red shift of λmax and a broadening of the emission band due to intermolecular interactions in solid state. X-Ray diffraction of an indenopyrone derivative showed interesting features in the lattice, such as C-H•••π, π•••π and C-H•••O interactions.

  CH2Cl2) λmax (log ε) [nm]: 282 (3.95), 314 (4.01).

  CH2Cl2) λmax (log ε) [nm]: 280(3.98), 308 (4.00).

  White solid; yield 35%; mp. 62-63°C; Rf = 0.4 (pentane/methyl tert-butyl ether = 3/2).

  H and 13 C NMR, UV-Vis, fluorescence and mass spectra. Assignment of the 1 H NMR signals was based on 2D NMR spectra. 1 H NMR spectrum of compound 3b is in agreement with the proposed structure displaying specific signals for the aromatic cyclopenta[c]pyran moiety: a doublet at 6.80 ppm for the proton at position H-d, a singlet at 8.08 ppm for the proton at position H-b and a doublet of quartet at 8.21 ppm for the proton at position H-e. The proton at position H-e appears more deshielded as a doublet of quartet due to the coupling with fluorine atoms from the COCF3 group. For the protons of terpyridine block a singlet at 8.82 ppm corresponding to the protons at positions H-3' and H-5' can be observed, as well as two doublets at 8.76 ppm and 8.70 ppm for protons at positions H-6, H-6'' and H-3, H-3'', respectively and one doublet of doublets at 7.38 ppm for the protons at positions H-5 and H-5''. The other signals appear as overlapped peaks and could not be unequicovally identified.

Figure 4 .

 4 Figure 4. Fragment of 1 H NMR (300 MHz, CDCl3) spectrum of derivative 3b

Figure 5 .

 5 Figure 5. Fragment of 1 H NMR (300MHz, (CD3)2CO spectrum of derivative 5c

Figure 6 .

 6 Figure 6. Normalized absorption spectra of derivatives 3a-b, 5a-c, 6-11 in CH2Cl2 solution

Figure 7 .

 7 Figure 7. Normalized fluorescence spectra of derivatives 3a-b and 5a-c

Figure 8 .

 8 Figure 8. The general view of the principle of PET fluorescence molecular sensor 86

  Various technologies in relation to photovoltaics, such as: crystalline Si, semiconductor-based cells, thin-film solar cells, organic photovoltaic (OPVs) cells and dye-sensitized solar cells (DSSCs) have been developed, all competing for the future solar cell market. Among them, OPVs and DSSCs have been considered as the most promising candidates for next-generation solar cells offering the possibility to develop a low cost and low environmental impact alternative to silicon technology. Furthermore, the lightness, plasticity, processability and versatility of organic materials open the possibility to develop lightweight solar cells on large variety

Figure 1 .Figure 1 '

 11 Figure 1. Device structures of (a) bilayer heterojunction; (b) bulk heterojunction; (c) device working principle from light absorption to charge collection

Figure 1 '

 1 Figure 1'. J-V curves of an organic solar cell under dark and illuminated conditions

Figure 2 . 1 .

 21 Figure 2. Chemical structures of the target D-A molecules

Figure 3 .

 3 Figure 3. Crystallographic structure of compounds 1 (left), 2 (right), 3 (bottom)

Figure 4 . 3 .

 43 Figure 4. Dihedral angles between the planes defined by the three constitutive units of the conjugated system of compounds 1-3.

Figure 5 .

 5 Figure 5. Crystal packing in 1: 2D layer generated by hydrogen bonds (red dashed line) and C-H•••π interactions (cyan dashed line)

Figure 6 . 2 For compound 3 ,

 623 Figure 6. Supramolecular chain generated by hydrogen bonding in the crystal of compound 2

Figure 7 .

 7 Figure 7. Crystal packing of compound 3 showing S•••S interactions (yellow dashed line), hydrogen bonding (red dashed line) and π-π stacking (green dashed line).

Figure 8 .

 8 Figure 8. Normalized UV-Vis absorption spectra of compounds 1-7. Red lines: in CH2Cl2. Black lines: thin films spin-cast on glass from chloroform solutions.

  N. Adams, Acc. Chem. Res. 1969, 2, 175.

Figure 9 .

 9 Figure 9. Cyclic voltammograms corresponding to the oxidation (left) and reduction (right) of compounds 1-7 in 0.10 M Bu4NPF6/CH2Cl2, Pt electrodes, scan rate 100mV s -1 .

Figure 10 .

 10 Figure 10. Electrochemical energy levels of donors 1-7

Figure 11 .

 11 Figure 11. Current-density vs voltage curves for bi-layer photovoltaic cells ITO/PEDOT:PSS/D/C60/Al based on spin-cast (s) and 15 nm vacuum-deposited (e) layers of donors 1, 2, 3, 6 and 7. Empty circles: in the dark; black circles: under AM 1.5 simulated solar light with an incident power light of 90 mW cm -2 .

  obtained for derivatives 6 and 7, an improvement of PCE, Jsc and FF can be observed in the case of derivative 7, but a detailed understanding of the factors that determine this behaviour requires further work.

Figure 12 .

 12 Figure 12. Current density vs voltage curves for a bilayer solar cell (ITO/PEDOT:PSS/D/C60/aluminium. In the dark (open circles) and under simulated solar light with incident power light of 90 mW cm -2 (black circles).

  and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

Figure 13 .

 13 Figure 13. Spectra of external quantum efficiency of bi-layer cells based on donors 1, 2, 3, 6 and 7 under monochromatic irradiation.

Figure 14 .

 14 Figure 14. Spectra of external quantum efficiency of bi-layer cells based on donors 4, and 5 under monochromatic irradiation. (s) Spun-cast donor layer (e) vacuum-deposited donor layer.

  acceptor (compound 9), by extension of the basic structure either by simple dimerization leading to the A-D-D-A compound 10, or by creation of a median acceptor linking group such as carbonyl, dicyanomethylene or cyanovinyl to form A-D-A-D-A structures 11-13 and A-D-A structure 14 (figure15). 121 (a) A. Leliège, D. Demeter, V. Jeux, T. Rousseau, P. Leriche, P. Blanchard, J.Roncali, Chem. Eur. J. 2013, 19, 9948-9960; (b) D. Demeter, V. Jeux, P. Leriche, P. Blanchard, Y. Olivier, J. Cornil, R. Po, J.Roncali, Adv. Funct. Mater. 2013, 23, 4854- 4861; (c) S. Mohamed, D. Demeter, P. Blanchard, J.-A. Laffitte, J.Roncali, Sci. Rep. 2015, 09031.

Figure 15 .

 15 Figure 15. Chemical structures of target compounds

Figure 16 .

 16 Figure 16. X-Ray single crystal structure of compounds 9 (top) and 14 (bottom)

Figure 17 .

 17 Figure 17. Crystal packing of compound 9 showing hydrogen bonding (blue dashed line) and π-π stacking (red dashed line).

  of the vinyl group (N1•••H30 2.675Å, red dashed line) and between nitrogen atom of the CN from dicyanovinyl group and one hydrogen atom of the phenylene ring (N4•••H25 2.699Å, blue dashed line). In the crystal lattice, supramolecular dimmers with head-to-tail disposition sustained by C-H•••π interactions between aromatic -CH and neighbouring phenyl ring [C-H12•••centroid (C12-C17) 2.960Å, C-H17•••centroid (C24-C29) 3.241Å] are observed.

Figure 18 .

 18 Figure 18. Supramolecular chain generated by hydrogen bonding and C-H•••π interactions in the crystal of compound 14

  and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

Figure 19 .

 19 Figure 19. UV-Vis absorption spectra of compounds 9-14. Red line: methylene chloride solutions.

Figure 20 .

 20 Figure 20. Cyclic voltammograms of compounds 9-14 in 0.10 M Bu4NPF6/CH2Cl2, Pt electrodes, scan rate = 100 mV s -1 .

Epa 2 -

 2 Epa 1 would indicates that the second process is influenced by the first positive charge on the other part of the molecule. Further ESR experiments are needed to clarify this point.

  125 (a) R.N. Adams, Acc. Chem. Res. 1969, 2, 175; (b) N. Cocherel, P. Leriche, E. Ripaud, N. Gallego-Planas, P. Frère, J.Roncali, New J. Chem. 2009, 33, 801.

Figure 21 .

 21 Figure 21. Molecular orbital surface of molecules 10-13 (from top to bottom) calculated by DFT/B3LYP/6-31G(d,p) with CH2Cl2 solvent (C-PCM model). Left: optimized geometry, middle HOMO, right: LUMO.

Figure 22 .

 22 Figure 22. Current density vs voltage curves of bilayer cells ITO/PEDOT:PSS/donor/C60/Al. In the dark (open circles) and under AM 1.5 simulated solar light (90 mW cm -2 ) (black/red circles)

Figure 23 .

 23 Figure 23. Spectra of external quantum efficiency of bi-layer cells based on donors 9, 12, 13 and 14 under monochromatic irradiation.

  Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers[START_REF] Ashwell | anti-cancer agent currently in multiple Phase II clinical trials. ARQ 501 activates the cell cycle checkpoint, which results in the selective apoptotic death of cancer cell 47 and is effective against human ovarian cancer and prostate cancer xenografts in mice 48[END_REF][START_REF] Mohamed | Small Molecular Donors for Organic Solar Cells Obtained by Simple and Clean Synthesis Dora Demeter[END_REF][START_REF] Veca | Electroluminescence of carbon 'quantum' dots -From materials to devices[END_REF][START_REF] Diac | Simple and Versatile Molecular Donors for Organic Photovoltaics Prepared by Metal-Free Synthesis[END_REF][START_REF] Adda | ADADA systems based on triphenylamine as molecular donors for organic photovoltaics[END_REF][START_REF] Diac | Covalent conjugation of carbon dots with rhodamine B and assessment of their photophysical properties[END_REF](7) have been synthesized from mono-or di-aldehydes by simple metal-free procedure. Cyclic voltammetry and UV-Vis absorption spectroscopy show that the conjugation extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3, 6, 7 show a broadening and red shift of the absorption bands consistent with the formation of J-aggregates. In contrast the blue shift observed for the EDOTcontaining compounds 4 and 5 suggests the presence of H-aggregates.

  Six molecular donor (D) acceptor (A) systems of structure D-π-A (9), A-D-A-D-A (11-13), A-D-D-A (10) and A-D-A (14) have been synthesized by spatial extension of a reference D-A system with a triphenylamine donor block (8). UV-Vis absorption spectroscopy, cyclic voltammetry and theoretical calculations show that the presence of a median acceptor group has limited effect on the internal charge transfer while direct dimerization leads to an increase of the effective conjugation length. A cursory evaluation of the new compounds as donor material in bilayer solar cells using fullerene C60 as acceptor material shows that the presence of a median acceptor has deleterious effect on conversion efficiency while the simple dimerization of the molecule leads to a substantial improvement of short-circuit current density with a moderate improvement of conversion efficiency. recorded with a Bruker AVANCE III 300 ( 1 H, 300 MHz and 13 C, 75 MHz). Chemical shifts are given in ppm relative to TMS as internal reference and coupling constants (J) in Hz.UV-Vis spectra were recorded with a Perkin Elmer Lambda 19 or 950 spectrometer.Melting points were obtained from a Reichert-Jung Thermovar hot-stage microscope apparatus and are uncorrected. MALDI (Matrix Assisted Laser Desorption/Ionization) -TOF spectra were performed on a BIFLEX III Bruker Daltonics spectrometer using dithranol as matrix.Cyclic voltammetry was performed in dichloromethane solutions purchased from SDS (HPLC grade). Tetrabutylammonium hexafluorophosphate (0.10 M as supporting electrolyte) was purchased from Acros and used without purification. Solutions were deaerated by nitrogen bubbling prior to each experiment. Experiments were carried out in a one-compartment cell equipped with platinum electrodes and saturated calomel reference electrode (SCE) with a Biologic SP-150 potentiostat with positive feedback compensation.Column chromatography purifications were carried out on Merck silica gel Si60 (40-63 μm).Device fabrication and testingIndium-tin oxide coated glass slides of 24mm×25mm×1.1 mm dimensions with a surface resistance of 10 Ω/sq were purchased from Kintec company. Part of the ITO layer was etched away with 37% HCl. The ITO electrodes were then cleaned in ultrasonic bath (successively Deconex (from VWR international GmbH), distilled water (15.3 MΩ cm -1 ), acetone, ethanol and distilled water again for 10 min each and dried in an oven at 100°C. The dried electrodes were then modified by a spun-cast layer of PEDOT:PSS (Clevios P VP. AI 4083 (HC-Starck) filtered through a 0.45 µm membrane just prior use). Spin-casting was achieved at 5000 rpm (r = 10s, t = 60 s), and the electrode was then dried at 130 °C for 15 min. Films of donor materials (ca 20 nm nm) were spun-cast in atmospheric conditions from chloroform solutions containing 5 mg donor/mL. After film deposition the devices were introduced in an argon glovebox (200B, MBraun) equiped with a vacuum chamber and a 30 nm film of Fullerene C60 (99+%) (MER Corporation) and a 100 nm thick aluminium electrode were thermally evaporated on top of the donor film under a pressure of 2-4×10 -6 mbar through a mask defining two cells of 6.0 mm diameter (0.28 cm 2 ) on each ITO electrode.The J vs V curves of the devices were recorded in the dark and under illumination using a Keithley 236 source-measure unit and a home-made acquisition program. The light source was an AM1.5 Solar Constant 575 PV simulator (Steuernagel Lichttecknik, equipped with a metal halogen lamp). For each measurement the incident light intensity (ca 90 mW cm -2 ) was measured by a broad-band power meter (13PEM001, Melles Griot). The devices were illuminated through the ITO electrode side. The efficiency values reported here are not corrected for the possible spectral mismatch of the solar simulator. External quantum efficiency (EQE) was measured using a halogen lamp (Osram) with an Action Spectra Pro 150 monochromator, a lock-in amplifier (Perkin-Elmer 7225) and a S2281 photodiode (Hamamatsu).

  Yellow powder; yield 17%; mp. 268-269°C Protocol To a solution of [2,2'-bithiophene]-5,5'-dicarbaldehyde (12'b) (470 mg, 2.11 mmol) in 120 mL dry THF warmed to 25°C was added a solution of N,N'-diphenylhydrazine hydrochloride (11') (233 mg, 1.05 mmol) and sodium acetate (346 mg, 4.22 mmol) in 30 mL anhydrous methanol. The reaction mixture was stirred during three days at 25°C

  Orange powder; yield 37%; mp. 140-141°C Protocol To a solution of [2,2'-bithiophene]-5,5'-dicarbaldehyde (12'b) (470 mg, 2.11 mmol) in 120 mL dry THF warmed to 25°C was added a solution of N,N'-diphenylhydrazine hydrochloride (11') (233 mg, 1.05 mmol) and sodium acetate (346 mg, 4.22 mmol) in 30 mL anhydrous methanol. The reaction mixture was stirred during three days at 25°C

  powder; yield 62%; mp. 206-208°C Protocol Malonodinitrile (69 mg, 1.04 mmol) and few drops of triethylamine were added to a solution of aldehyde 8'b (200 mg, 0.52 mmol) in 70 mL chloroform and the mixture was heated at 62°C for 15 hours. After cooling at room temperature, the reaction mixture was diluted with methylene chloride, washed with water and brine and dried over anhydrous MgSO4. After solvent removal, the residue was purified by column chromatography (silica gel, eluent: dichloromethane/petroleum ether = 4/1) to give 140 mg of a deep violet powder. 1 H NMR 300 MHz, CDCl3, δ ppm: 7.75 (s, 1H), 7.64 (d, 1H, J = 4.2 Hz), 7.50-7.45 (overlapped peaks, 4H), 7.32 (d, 1H, J = 4.2 Hz), 7.30 (d, 1H, J = 3.9 Hz), 7.28 (m, 1H), 7.25-7.20

  solid; yield 59%; mp. 125-129°C

6

 6 Violet powder; yield 70%; mp.88-89°C Protocol Malonodinitrile (4 mg, 0.048 mmol) and one drop of triethylamine were added to a solution of (E)-6-((2,2-diphenylhydrazono)methyl)-4,4-bis(2-ethylhexyl)-4Hcyclopenta[1,2-b:5,4-b']dithiophene-2-carbaldehyde (8'c) (20 mg, 0.032 mmol) in 6 mL chloroform. The reaction mixture was stirred two hours at room temperature and then two hours at 50°C. After cooling to room temperature, the solution was diluted with methylene chloride, washed with water and brine and dried over magnesium sulphate.

  solid; yield 41%; mp. 151-155°C Protocol A solution of N,N'-diphenylhydrazine hydrochloride (11') (32 mg, 0.14 mmol) and sodium acetate (76 mg, 0.92 mmol) in 6 mL dry methanol was slowly added to a solution of 4-(2-ethylhexyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole-2,6-dicarbaldehyde (12'd) (100 mg, 0.29 mmol) in 40 mL anhydrous THF at room temperature. The reaction mixture was heated at 50°C under argon atmosphere during 20 hours. After returning to room temperature, dichloromethane was added and the organic phase was

  solid; yield 65%; mp. 155-157°C Protocol Three drops of triethylamine were added to a solution of (E)-6-((2,2diphenylhydrazono)methyl)-4-(2-ethylhexyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole-2 carbaldehyde (8'd) (80 mg, 0.16 mmol) and malonitrile (16 mg, 0.25 mmol) in 30 mL chloroform and the resulting solution was stirred overnight at room temperature under argon atmosphere. After removal of solvent, the crude was dissolved in dichloromethane, washed with water and brine, dried over magnesium sulphate and purified by column chromatography on silica gel (eluent: pentane/diethyl ether = 4/1) to afford a deep-violet solid.

  powder; yield 89%; mp. 262-264°CProtocolTo a solution of (E)-5-((2,2-diphenylhydrazono)methyl)thieno[3,2-b]thiophene-2carbaldehyde (8'e) (120 mg, 0.33 mmol) in 30 mL CHCl3, malonodinitrile (50 mg, 0.75 mmol) and few drops of triethylamine were added. The mixture was stirred under argon atmosphere, at room temperature for four hours. After removal of solvent, the residue was solubilized in dichloromethane, washed with water and brine, and dried over magnesium sulphate. The resulting solid was washed with cold ethanol, giving 120 mg of a deep-violet powder. 1 H NMR 300 MHz, CDCl3, δ ppm: 7.81 (d, 2H, J = 8.4 Hz), 7.49-7.44 (overlapped peaks, 4H), 7.30-7.19 (overlapped peaks, 7H), 7.05 (s, 1H).

4

 4 Violet powder; yield 85%; mp. 229-230°CProtocolFew drops of triethylamine were added to a mixture of 8'f (0.46 g, 1.26 mmol) and malononitrile (0.125 g, 1.89 mmol) in 50 mL CHCl3. The reaction mixture was heated to 50°C under argon atmosphere for two hours. The solvent was evaporated and the residue was dissolved in dichloromethane, washed with water and brine and dried over

  Yellow solid; yield 51%; mp. 252-253°C

  Orange solid; yield 65%; mp. 276-277°CProtocolAt 0°C anhydrous DMF (0.06 mL, 0.76 mmol) and phosphorus oxychloride (0.06 mL, 0.65 mmol) were added to a solution of hydrazone derivative 9'g (0.26 g, 0.54 mmol) in 30 mL 1,2-dichloroethane. The mixture was stirred overnight at room temperature under argon atmosphere. A saturated aqueous solution of sodium acetate and dichloromethane were added and the solution was stirred for two addional hours. The aqueous layer was extracted twice with CH2Cl2; the combined organic extracts were washed with water and brine, and then dried over MgSO4. Solvent removal and column chromatography on silica gel (eluent: dichloromethane) gave 0.18 g orange solid.

5

 5 Deep-violet powder; yield 96%; mp. 308-309°CProtocolMalonodinitrile (21 mg, 0.64 mmol) and few drops of triethylamine were added to a solution of aldehyde 8'g (160 mg, 0.32 mmol) in 30 mL chloroform and the mixture was stirred overnight at ambient temperature. After solvent removal the residue was dissolved in dichloromethane, washed with water, brine and dried over MgSO4. The crude was chromatographed on silica gel using dichloromethane as eluent yielding 170 mg a deep violet powder.

  powder; yield 40%; mp. 114-116°C Protocol A solution of copper (II) perchlorate hexahydrate (140 mg, 0.38 mmol) in 5 mL acetonitrile was added dropwise to a solution of 8 (100 mg, 0.25 mmol) in 10 mL acetonitrile. The reaction mixture was stirred for 5 days at room temperature under argon atmosphere. Solid K2CO3 (310 mg, 2.25 mmol) and water (0.6 mL) were added and the solution was further stirred for 30 min. The mixture was filtered and the solids

  solid; yield 45%; mp. 314-315°C Protocol To a mixture of 11 (250 mg, 0.3 mmol) and malononitrile (80 mg, 1.2 mmol) in 30 mL 1,2-dichloroethane cooled to 0 °C, titanium tetrachloride (0.24 ml, 2.2 mmol) and pyridine (0.48 ml, 6 mmol) were slowly added under argon. The solution was refluxed for three days. The reaction mixture was filtered through Celite and the solids were washed several times with dichloromethane. The filtrate was washed with HCl (aq.) and with NaHCO3 (aq.). The organic layer was dried over MgSO4 and concentrated.

Scheme 1 .Figure 1 .

 11 Scheme 1. Schematic representation of the process steps used to synthesise amine-functionalized CDs

Figure 3 .

 3 Figure 3. HR-TEM image of CDs-PEG1500N

Figure 4 .

 4 Figure 4. XPS spectra of (a) oxidized carbon nanoparticles; (b) CDs-PEG1500N and (c) CDs-PD

Figure 5 .

 5 Figure 5. FRET d

  photon imaging, or rformance, substantial

Figure 6 .

 6 Figure 6. Spectral overlap of the normalized RhB absorption and CDs-PEG1500N photoluminescence

Figure 7 .

 7 Figure 7. FT-IR spectra of (a) CDs-PEG1500N; (b) CD-PEG1500N-Rh and (c) RhB

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

Figure 8 .

 8 Figure 8. UV-Vis absorption spectra of CDs-PEG1500N (black spectrum), RhB (red spectrum) and CD-PEG1500N-Rh (blue spectrum) recorded in water

Figure 9 .

 9 Figure 9. Comparison between the photoluminescence spectra of CDs-PEG1500N (black curves), CD-PEG1500N-Rh (blue curves) and RhB (red curves) at indicated excitation wavelengths

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

Figure 10 .

 10 Figure 10. Fluorescence decay curves of CDs-PEG1500N (black curve) and CD-PEG1500N-Rh (blue curve) at 405 nm excitation.

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

Figure 11 .

 11 Figure 11. Carbon quantum dot diode -the architecture of the device with the ITO (anode), PEDOT:PSS (HIL), PVK (HTL), CDs (EL), Al (cathode)

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

-Figure 12 .

 12 Figure 12. AFM images of the (a) HTL -PVK layer (ITO/PEDOT:PSS/PVK) and (b) EL -PEGylated carbon quantum dots layer in the device (the carbon quantum dot layer ontop of PVK is the device without the aluminum electrode).

Figure 13 .

 13 Figure13.(a) Electroluminescence spectra of the device described in Fig.11at 10 V, 11 V, 13 V, and 15 V applied bias and (b) the CIE coordinates of the LED with carbon quantum dots as active layer, operated at 15V and 5 mA. The inset shows a picture of the device at 20 V applied bias.

5. 3 .

 3 ConclusionsThree fluorescent carbon quantum dots materials were obtained by simple passivation of carbon nanoparticles surface with aromatic and aliphatic diamine derivatives, such as p-phenylenediamine, 1,3-propanediamine and oligomeric poly(ethylene glycol)diamine (PEG1500N).Carbon dots functionalized with Rhodamine B (CD-PEG1500N-Rh), were synthesized by covalently attaching Rhodamine B to the free amino group of the passivating polymer in CDs-PEG1500N. The covalent linkage of Rhodamine B to the carbon dots surface led to a nonradiative transfer of energy (FRET) from the CDs to the dye molecule. The efficiency of FRET was quantified by performing steady-state, along with life-time fluorescence measurements of both emissive species. The synthetic accessibility and the transfer efficiency of these conjugates make them reliable candidates for fluorescent materials, which could be later used in sensing and solar cells.The electroluminescence properties of the carbon dots were investigated in multilayer light emitting diodes that use carbon dots as active layer. The devices emitted white light with a slight blue color, visible to the naked eye, suggesting that the carbon dots may potentially serve as a new platform for electroluminescent nanomaterials. Future work will focus on the development of carbon dots with a shorter-chain surface passivation molecule, which would lead to an increased LED efficiency at a lower operating voltage for the corresponding devices.

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

  MicroTime 200 time-resolved confocal fluorescence microscope system based on an inverted microscope (IX 71, Olympus) equipped with a UPLSAPO 60x/NA 1.2 water immersion objective. The excitation beam was provided by 0.55 µW picosecond diode laser head (LDH-D-C-405, Pico-Quant) operating at 405 nm and pulsed at 40 MHz repetition rate. The samples were dropped on microscope cover glasses and analyzed in solution. The signal collected through the objective was spatially and spectrally filtered by a 50 µm pinhole and band-pass filter (FF02-447/60-25, Semrock, NY, USA), before being focused on a PDM Single Photon Avalanche Diode (SPAD) from MPD. The detector signals were processed by the PicoHarp 300 Time-Correlated Single Photon Counting (TCSPC) data acquisition unit, from PicoQuant. Time-resolved fluorescence decay curves were recorded and analyzed using the SymPhoTime software (version 1.6) provided by PicoQuant.

Chapter 5 -

 5 Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices -

  Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers have been synthesized from mono-or di-aldehydes by simple metal-free procedure. Cyclic voltammetry and UV-Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. A first evaluation of the potential of the compounds as donor material in simple bi-layer cells has confirmed the determining role of the conjugating bridge on conversion efficiency. Furthermore, new ADDA and ADADA systems based on triphenylamine as molecular donors for organic solar cells (OSCs) were obtained. UV-Vis absorption spectroscopy, cyclic voltammetry and theoretical calculations show that the presence of a median acceptor group has limited effect on the internal charge transfer while direct dimerization leads to an increase of the effective conjugation length. A cursory evaluation of the new compounds as donor material in bilayer solar cells using fullerene C60 as acceptor material shows that the presence of a median acceptor has deleterious effect on conversion efficiency while the simple dimerization of the molecule leads to a substantial improvement of short-circuit current density with a moderate improvement of conversion efficiency.In the last chapter three fluorescent carbon quantum dots materials were obtained by simple passivation of carbon nanoparticles surface with aromatic and aliphatic diamine derivatives, such as p-phenylenediamine, 1,3-propanediamine and oligomeric poly(ethylene glycol)diamine (PEG1500N). Carbon dots functionalized with Rhodamine B (CD-PEG1500N-Rh) were synthesized by covalently attaching Rhodamine B to the free amino group of the passivating polymer in CDs-PEG1500N. The covalent linkage of Rhodamine B to the carbon dots surface led to a non-radiative transfer of energy (FRET) from the CDs to the dye molecule. The electroluminescence properties of the carbon dots were investigated in a multilayer light emitting diode that use carbon dots as active layer. The device emitted white light with a slight blue color, visible to naked eyes, suggesting that the carbon dots may potentially serve as a new platform for electroluminescent nanomaterials.

  [c]pyrans; Indenopyrone Molecular electronics; Electron-donor; Organic So 'quantum' Dots; Light Emitting Diode (LED).

  La thèse intitulée «Design, S Architectures of New Heterocyclic Applications in Material Chemistry and structurée en cinq chapitres tr cyclopenta[c]pyrannes hétérocyclique; b des propriétés fluorescentes; d) potentie moléculaire; d) donneurs moléculaire organiques et e) carbon'quantum'dots éle Le premier chapitre prése pseudoazulenique ayant une unité cyc porte sur leur synthèse, l'analyse structur des réactions de substitution électrophi ayant des propriétés fluorescentes. Le deuxième chapitre présen diastéréoisomères et l'étude de propriété dérivés d'indenopyrone. Le troisième chapitre décri architectures basées sur l'unité cyclope être modifiés structurellement par l'infl ou électrochimique afin d'élaborer d l'électronique moléculaire. Dans le quatrième chapitre, la des propriétés électroniques des nouvell cellules solaires organiques (OSC) ont Le cinquième et dernier chap défauts de surface des nanoparticules molécules organiques ou des pol nanoparticules de carbone photolumi quantum dots. Mots-clés: Cyclopenta[c]pyrannes; L'électronique moléculaire; Donneur organiques; Carbon «quantum» Dots; and Supramolecular erocyclic Compounds with Potential istry and Photovoltaic Conversion" est pitres traitant de nouveaux: a) yclique; b) dérivés d'indenopyrone avec potentiels dispositifs de l'électronique oléculaires pour les photovoltaïques m'dots électroluminescents. re présente une étude des dérivés unité cyclopenta[c]pyrannique. L'étude se structurale et leur comportement dans électrophile pour obtenir des composés re présente la séparation des régio et propriétés de fluorescence de nouveaux décrit la synthèse des nouvelles té cyclopenta[c]pyrannique, qui peuvent t par l'influence d'un stimulus chimique laborer des potentiels dispositifs de hapitre, la synthèse et la caractérisation es nouvelles molécules donneur pour des C) ont été décrite. rnier chapitre décrit la passivation des particules de carbone avec des petites des polymères pour obtenir des toluminescentse surnommé 'carbon rannes; Indenopyrones; Fluorescence; Donneur d'électrons; Cellules solaires Light Emitting Diode (LED).

Table 1 .

 1 Cyclic voltammetry data for compounds 2b, 2e-j in 0.1 M Bu4NPF6/CH2Cl2, scan rate 100 mV/s, reference SCE

		0.014
											2' i
		0.012									2' h
											2' g
		0.010									2' b 2' f
											2' j
		0.008									2' e
	I (mA)	0.006
		0.004
		0.002
		0.000
		-0.002
		0.0	0.2	0.4	0.6	0.8	1.0	1.2	1.4	1.6	1.8

E (V vs SCE)

Table 3 .

 3 Crystallographic data, details of data collection, and structure refinement parameters for compounds 2

''c, 2'd, 2'e, 2'h

	Cmpd.	2''c	2'd	2'e	2'h
	formula	C21H18O3	C20H15ClO2	C20H15BrO2	C20 H15 Cl O2
	M [g mol -1 ]	318.35	322.77	367.23	322.77
	T [K]	293 (2)	295(2)	297(2)	295(2)
	crystal system	monoclinic	monoclinic	monoclinic	triclinic
	space group	P21/n	C2/c	P2(1) / c	P-1
	a [A]	9.8995(7)	18.3645(16)	13.4298(16)	8.479(2)
	b [A]	7.4959(5)	12.4709(11)	14.5469(18)	8.524(2)

Table 4 .

 4 Absorption maxima of α-pyrone isomers 4 and 5 in

			dichloromethane at room temperature
		4		5
		λ λ λ λmax	log ε	λ λ λ λmax	log ε	λ = λabs5 -λabs4
		[nm]		[nm]		[nm]
	a	-	-	367	4.18	-
	b	-	-	373	4.25	-
	c	-	-	382	4.27	-
	d	-	-	370	4.23	-
	e 368	4.21	372	4.25	4
	f	368	4.26	372	4.29	4
	g 368	4.18	368	4.18	3
	h	-	-	366	4.23	-
	i	-	-	368	4.16	-

Table 5 .

 5 Emission data for α-pyrone derivatives 4 and 5

	4

2 Cl 2 4f -CH 2 Cl 2 4g -CH 2 Cl 2 4e -solid state 4f -solid state 4g -solid state

		1.0			4e -CH
	Emission Intensity [a.u.]	0.4 0.6 0.8
		0.2
		0.0
		400	500	600	700	800
				Wavelength [nm]

Table 6 .

 6 Data of CV in 0.1 M Bu4NPF6, scan rate 100 mV s-1, ref. SCE

	4	5
	Epa 1

Table 7 .

 7 Absorption and photoluminescence data for trifluoroacetylated-derivatives 8 and 9

	8

a Recorded in CH2Cl2 b Determined in CH2Cl2 with rhodamine 6G as reference (Ф = 96 %)

Table 8 .

 8 Bond lengths for derivatives 8a, 8g and 9a

	C-2-C-6 distance of 1.452 (8a), 1.453 (8g), 1450 Å (9a), which is shorter than the
	transannular distances in other azulene compounds (1.47-1.50 Å). 29

29 A.W. Hanson, Acta Cryst. B 1965, 19, 135; H.L. Ammon, M. Sundaralingam, J. Am. Chem. Soc. 1966, 88, 4794; G. Bastiansen, J.L. Derrisen, Acta Chem. Scand. 1966, 29, 1319; H.L. Ammon, P.H. Watts, A.G. Anderson, D.M. Forkey, L.D. Grina, Q. Johnson, Tetrahedron 1970, 26, 5707.

Table 9 .

 9 Absorption and fluorescence data of derivatives 12

		12
	Absorption	Emission	Stokes shift [cm-1]/(nm)	ФFL (%) b
	λmax [nm] a	λmax [nm]

13c Wavelength [nm] 300 400 500 600 700 Absorbance [a.u.] 0.0 0.2 0.4 0.6 0.8 1.0 13f Wavelength [nm] 300 400 500 600 700 Absorbance [a.u.] 0.0 0.2 0.4 0.6 0.8 1.0 13g Wavelength [nm] 300 400 500 600 700 800 Absorbance [a.u.] 0.0 0.2 0.4 0.6 0.8 1.0 Figure 32. UV-Vis absorption spectra of compounds 13c, f, g. Solid

	line: in CH2Cl2. Dashed line: as
	thin film spin-cast on glass from chloroform solutions

Table 10 .

 10 Data

	of UV-Vis absorption spectroscopy and cyclic voltammetry (0.1 M Bu4NPF6/CH2Cl2,
	Pt electrodes, ref SCE) for derivatives 13c

, f, g Cmpd. λmax a [nm] εmax[M -1 cm -1 ] λmax b [nm] Epa 1 , Epa 2 [V] Epc 1 , Epc 2 [V] Eg [eV] 13c

		450	23990	467	1.60, 1.99	-1.02, -1.11	2.19
	13f	446	24865	456	1.62, 1.94	-1.02, -1.11	2.22
	13g	445	22482	502	1.62, 1.94	-0.99, -1.5	2.09

a In CH2Cl2.

b

Thin films spun-cast on glass.

1.5. Experimental part 1.5.1. General Remarks

	1D and 2D NMR spectra were recorded at room temperature using CDCl3 as solvent
	on Bruker Avance 300, 400 or 600 spectrometer (operating at 300, 400 or 600 MHz for
	proton and 75, 100 or 150 MHz for carbon, respectively).
	APCI mass spectra were recorded with an Agilent 6320 ion-trap mass spectrometer
	(Bruker Dalton GmbH, Cluj-Napoca, Romania) equipped with ESI/APCI multisource. HR-MS
	spectra in APCI mode ionization were recorded with an LTQ XL Orbitrap ThermoScientific
	mass spectrometer.
	UV-Vis measurements were performed in CH2Cl2 at room temperature using a Cecil
	Super Aquarius spectrophotometer. Fluorescence measurements were performed in dry
	CH2Cl2 at room temperature using a JASCO FP 8300 spectrofluorometer.
	X-ray structures were performed on a CAD4 Enraf-Nonius diffractometer with
	monochromatic radiation MoKα. For structure solving and refinement the software package
	SHELX-97 was used. The drawings were created with Mercury and Diamond 3.2 program.
	Melting points were measured using a digital Kleinfeld Apotec melting point
	apparatus and values are uncorrected.
	Thin layer chromatography was performed on Silica gel 60 chromatography plates
	F254 and 60 F254 neutral Aluminumoxid. Column chromatography was performed on Silica
	gel or neutral Aluminumoxid.

1.5.2. Compounds synthesis 1.5.2.1. Synthesis of 3,4,4a,5-tetrahydrocyclopenta[c]pyran-3-ones General procedure:

'a).

		174°C
	Retention	Rf = 0.55 (silica, P/EE = 4/1)	Rf = 0.5 (silica, P/EE = 4/1)
	factor
	1 H NMR	400 MHz, CDCl3, δ ppm: 2.25 (ddt, J = 17.8, 5.1, 2.6	400 MHz, CDCl3, δ ppm: 2.28 (ddt,
		Hz, 1H, H-5α), 2.56 (dddd, J = 17.8, 7.9, 2.6, 1.6 Hz,	J = 15.4, 5.4, 2.5 Hz, 1H, H-5α), 2.55
		1H, H-5β), 3.56 (ddd, J = 13.2, 7.9, 5.4, 1H, H-4a),	(dddd, J = 17.9, 8.3, 2.0, 1.5 Hz, 1H,
		3.68 (d, J = 14.5 Hz, 1H, H-4), 6.20 (dt, J = 5.5, 2.6	H-5β), 3.76 (ddd, J = 12.8, 7.7, 5.4
		Hz, 1H, H-7), 6.66 (∼dt, J = 5.5, 1.8 Hz, 1H, H-6),	Hz, 1H, H-4a), 4.20 (d, J = 7.0 Hz, 1H,
		7.29 (d, J = 7.2 Hz, 2H, o'-H), 7.33-7.36	H-4), 6.20 (dt, J = 5.4, 2.5 Hz, 1H, H-
		(overlapped peaks, 2H, p-H, p'-H), 7.40-7.43	7), 6.66 (ddd, J = 5.4, 2.0, 1.5 Hz, 1H,
		(overlapped peaks, 4H, m-H, m'-H), 7.61 (d, J = 7.8	H-6), 7.17-7.69 (m, 10H, H-ar,
		Hz, 2H, o-H).	signals overlapped with the signals
			of isomer 2
	1,4 1,4 1,4 1,4----diphenyl diphenyl diphenyl diphenyl----4a,5 4a,5 4a,5 4a,5----dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[c c c c]pyran ]pyran ]pyran ]pyran----3(4H) 3(4H) 3(4H) 3(4H)----one one one one
	Chemical Formula: C20H16O2; Molecular Weight: 288.34
	Purification by column chromatography on silica gel led to a mixture of isomers in a ratio
	2'a : 2''a = 1 : 1, as a white solid, yield 75%.
		Derivative 2'a	Derivative 2''a
	Structural
	properties
		Pure isomer, white powder, yield 35%, mp. 173-	Not isolated as unique isomer

led to a mixture of isomers 2'd : 2''d =

	Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta[c]pyrans
					, 169.2.
	UV/Vis	CH2Cl2, λmax (ε) [nm] = 275 (14755)	CH2Cl2, λmax (ε) [nm] = 235 (8531),
			297 (14283)
	HRMS	calcd. for C21H19O3 [M+H] + : 319.1329; found:	calcd.	for	C21H19O3	[M+H] + :
	(APCI+)	319.1333.	319.1329; found: 319.1333.
	1 1 1 1----(4 (4 (4 (4----chlorophenyl) chlorophenyl) chlorophenyl) chlorophenyl)----4 4 4 4----phenyl phenyl phenyl phenyl----4a,5 4a,5 4a,5 4a,5----dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[c c c c]pyran ]pyran ]pyran ]pyran----3(4H) 3(4H) 3(4H) 3(4H)----
		one one one one
	Chemical Formula: C20H15ClO2; Molecular Weight: 322.78
	Precipitation with pentane/diethyl ether = 8/1 1 : 1.5, as a
	grey solid, yield 59%.
		Derivative 2'd		Derivative 2''d
	Structural
	properties
		Pure isomer, white solid, yield 9%, mp. 134-	Not isolated as unique isomer
		135°C

'd). 13 C NMR

	1 H NMR	600 MHz, CDCl3, δ ppm: 2.25 (ddt, J = 17.9, 5.1,	300 MHz, CDCl3, δ ppm: 2.28 (ddt, J =
		2.6 Hz, 1H, H-5α), 2.56 (dddd, J = 17.9, 7.8, 2.7,	17.9, 4.8, 2.2 Hz, 1H, H-5α), 2.55
		1.6 Hz, 1H, H-5β), 3.55 (ddd, J = 15.7, 10.4, 6.6 Hz,	(dddd, J = 18.0, 7.9, 2.7, 1.5 Hz, 1H,
		1H, H-4a), 3.67 (d, J = 14.5 Hz, 1H, H-4), 6.23 (dt,	H-5β), 3.55 (ddd, J = 7.2, 5.2, 2.2 Hz,
		J = 5.5, 2.6 Hz, 1H, H-7), 6.61 (∼dt, J = 5.4, 2.4, 1H,	1H, H-4a), 4.66 (d, J = 14.8 Hz, 1H, H-
		H-6), 7.26-7.28 (m, 2H, o-C6H5), 7.34-7.37 (m,	4), 6.23 (dt, J = 5.6, 2.8 Hz, 1H, H-7),
		1H, p-C6H5), 7.40-7.43 (m, 2H, m-C6H5), 7.38,	6.61 (~dt, 1H, H-6), 7.14-7.56
		7.55 (2 x d, 4H, J = 8.4 Hz, C6H4-p-Cl).	(overlapped peaks, 9H, C6H5, C6H4-p-
			Cl, signals overlapped with the
			signals of isomer 2

chromatography on silica gel yielded both distereoisomers in a ratio 2'e : 2''e = 1 : 1, as a white solid. Structural properties Derivative 2'e Derivative 2''e

	Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material
		.
	UV/Vis	CH2Cl2, λmax (ε) [nm] = 228 (12775), 294
		(19365).
	HRMS	calcd. for C20H16ClO2 [M+H] + : 323.0833; found:
	(APCI+)	323.0844.
	1 1 1 1----(4 (4 (4 (4----bromophenyl) bromophenyl) bromophenyl) bromophenyl)----4 4 4 4----phenyl phenyl phenyl phenyl----4a,5 4a,5 4a,5 4a,5----dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[c c c c]pyran ]pyran ]pyran ]pyran----3(4H) 3(4H) 3(4H) 3(4H)----
		one one one one
	Chemical Formula: C20H15BrO2; Molecular Weight: 367.24
	Purification by column Pure isomer, white solid, yield 40%, mp. 139-	Pure isomer, white solid, yield 40%,
		140°C	mp. 191-192°C
	Retention	Rf = 0.6 (silica, P/EE = 3/2)	Rf = 0.4 (silica, P/EE = 3/2)
	factor

led to a mixture of isomers in a ratio 2'f : 2''f= 3 : 1, as a pale yellow solid, yield 67%. Structural properties Derivative 2'c Derivative 2''c

		Chapter 1 -Design, Synthesis and Analysis of new Fluorescent Cyclopenta[c]pyrans
			.
	UV/Vis	CH2Cl2, λmax (ε) [nm] = 241 (11500), 305	CH2Cl2, λmax (ε) [nm] = 232 (14889),
		(20500).	305 (18889).
	HRMS	calcd. for C20H17BrO2 [M+2H] + : 369.0308; found:	calcd. for C20H16BrO2 [M+H] + :
	(APCI+)	369.0308.	367.0328; found: 367.0326.
	1 1 1 1----(4 (4 (4 (4----( ( ( (tert tert tert tert----butyl)phenyl) butyl)phenyl) butyl)phenyl) butyl)phenyl)----4 4 4 4----phenyl phenyl phenyl phenyl----4a,5 4a,5 4a,5 4a,5----dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[ dihydrocyclopenta[c c c c]pyran ]pyran ]pyran ]pyran----
		3(4H) 3(4H) 3(4H) 3(4H)----one one one one
	Chemical Formula: C24H24O2; Molecular Weight: 344.45
	Precipitation with pentane/ether ethylic = 10/1 Pure isomer obtained by precipitation with	Not isolated as unique isomer
		diethyl ether, white solid, yield 15%, mp. 147-
		148°C
	Retention	Rf = 0.7 (silica, P/EE = 3/2)
	factor

2'g Derivative 2''g

	Retention	Rf = 0.7 (silica, P/EE = 3/2)		Rf = 0.5 (silica, P/EE = 3/2)
	factor
	1 H NMR	300 MHz, CDCl3, δ ppm: 2.25 (ddt, J = 17.9, 5.1, 2.6	300 MHz, CDCl3, δ ppm: 2.28 (ddt, J
		Hz, 1H, H-5α), 2.56 (dddd, J = 11.7, 7.5, 4.2, 1.2 Hz,	= 17.9, 5.0, 2.5 Hz, 1H, H-5α), 2.64
		1H, H-5β), 3.54 (ddd, J = 12.1, 8.5, 4.7 Hz, 1H, H-	(dddd, J = 17.7, 8.4, 2.1, 0.6 Hz, 1H,
		4a), 3.68 (d, J = 14.5 Hz, 1H, H-4), 3.85 (s, 3H,	H-5β), 3.74 (dt, J = 7.7, 5.2 Hz, 1H,
		OCH3), 6.20 (dt, J = 5.5, 2.6 Hz, 1H, H-7), 6.67 (dt, J	H-4a), 3.85 (s, 3H, OCH3), 4.20 (d, J
		= 5.7, 2.4 Hz, 1H, H-6), 6.90 (dd, J = 8.2, 1.6 Hz, 1H,	= 6.9 Hz, 1H, H-4), 6.12 (dt, J = 5.5,
		H-4'), 7.14 (s(br), 1H, H-2'), 7.19 (dd, J = 7.8, 1.7	2.6 Hz, 1H, H-7), 6.59 (dt, J = 5.7, 2.4
		Hz, 1H, H-6'), 7.27-7.44 (overlapped peaks, 6H,	Hz, 1H, H-6), 6.92 (dd, J = 7.8, 2.1
		H-ar).	Hz,	1H,	H-4'),	7.15-7.37
			(overlapped peaks, 8H, H-ar).
	13 C NMR
		Pure isomer, white solid, yield 29%, mp. 119-	Pure isomer, white solid, yield 19%,
		120°C		mp. 147-148°C

  one one one

			Ratio	4e	5e
	Chemical Formula: C20H13BrO2; Molecular Weight: 365.22	10	1
		Derivative 4e	Derivative 5e
	Structural
	properties
		Yellow solid, yield 58%, mp. 151-154 °C	Pure isomer, yellow powder, yield 12%,
			mp. 196-198 °C
	Retention factor	Rf = 0.5 (silica, PE/EE = 3/2)	Rf = 0.4 (neutral aluminum oxide, P/EE = 2/1)

1 H NMR 400 MHz, CDCl3, δ ppm: 3.50, (s, J = 2.0 Hz, 2H, H-5), 6.38 (dt, J = 5.8, 2.4 Hz, 1H, H-7), 6.89 (dt, J = 5.8, 2.0 Hz, 1H, H-6), 7.38 (t, J = 7.3 Hz, 1H, p-H (C6H5)), 7.45 (t, J = 7.3 Hz, 2H, m-H (C6H5)), 7.51 (d, J = 7.3 Hz, 2H, o-H (C6H5)), 7.62, 7.68 (2 x d, J = 8.5 Hz, 4H, o′,m′-H (C6H4-p-Br)). 300 MHz, CDCl3, δ ppm: 3.72, (t, J = 2.0 Hz, 2H, H-7), 6.78 (dt, J = 5.6, 1.9 Hz, 1H, H-5), 6.88 (dt, J = 6.0, 1.8 Hz, 1H, H-6), 7.37 (dt, J = 5.4, 2.1 Hz, 1H, p-H (C6H5)), 7.44 (t, J = 7.3 Hz, 2H, m-H (C6H5)), 7.52 (d, J = 6.9 Hz, 2H, o-H (C6H5)), 7.61, 7.75 (2 x d, J = 8.7 Hz, 4H, o′,m′-H (C6H4-p-Br)). 13 C NMR 100 MHz, CDCl3, δ ppm:

  one one one

			Ratio	4f	5f
	Chemical Formula: C24H22O2; Molecular Weight: 342.43		5	1
		Derivative 4f		Derivative 5f
	Structural
	properties
		Pure isomer, yellow solid, yield 52%,	Pure isomer, yellow powder, yield 11%,
		mp. 157-158 °C		mp. 192-193 °C
	Retention	Rf = 0.45 (silica, P/EE = 3/2)	Rf = 0.6 (neutral aluminum oxide, P/EE =
	factor			2/1)

1 H NMR 300 MHz, CDCl3, δ ppm: 3.49 (t, J = 2.1 Hz, 2H, H-5), 6.32 (dt, J = 5.7, 2.1 Hz, 1H, H-7), 6.96 (dt, J = 5.8, 2.0 Hz, 1H, H-6), 7.38 (dt, J = 6.9, 1.8 Hz, 1H, p-H (C6H5)), 7.45 (t, J = 7.8 Hz, 2H, m-H (C6H5)), 7.48-7.54 (m, 4H, o-H (C6H5) + m'-H (C6H4-pt Bu)), 7.76 (d, J = 8.1 Hz, 2H, o'-H (C6H4-pt Bu)). 300 MHz, CDCl3, δ ppm: 3.78 (t, J = 1.8 Hz, 2H, H-7), 6.81 (dt, J = 5.7, 1.8 Hz, 1H, H-5), 6.90 (dt, J = 5.7, 2.4 Hz, 1H, H-6), 7.38 (dt, J = 7.5, 2.4 Hz, 1H, p-H (C6H5)), 7.46 (t, J = 7.2 Hz, 2H, m-H (C6H5)), 7.50-7.59 (m, 4H, o-H (C6H5) + m'-H (C6H4-pt Bu)), 7.87 (d, J = 8.4 Hz, 2H, o'-H (C6H4-pt Bu)). 13 C NMR 75 MHz, CDCl3, δ ppm:

  one one one

			Ratio	4g	5g
	Chemical Formula: C21H16O3; Molecular Weight: 316.35		2	1
		Derivative 4g		Derivative 5g
	Structural
	properties
		Pure isomer, yellow-green solid, yield	Pure isomer, yellow powder, yield 21%,
		48%, mp. 154-155°C		mp. 150-151 °C
	Retention	Rf = 0.4 (silica, P/EE = 3/2)	Rf = 0.25 (neutral aluminum oxide, P/EE =
	factor			2/1)

1 H NMR 300 MHz, CDCl3, δ ppm: 3.50 (t, J = 2.1 Hz, 2H, H-5), 3.88 (s, 3H, OCH3), 6.34 (dt, J = 6.0, 1.8 Hz, 1H, H-7),6.97 (dt, J = 5.7, 2.1 Hz, 1H, H-6), 6.99-7.02 (m, 1H, H-4' (C6H4-m-OCH3)), 7.32-7.35 (m, 1H, H-6' (C6H4-m-OCH3)), 7.38 (s, 1H, H-2' (C6H4m-OCH3)), 7.39 (dt, J = 6.0, 1.8 Hz, 1H, H-5' (C6H4-m-OCH3)), 7.42-7.49 (overlapped peaks, 3H, m,p-H (C6H5)), 7.52 (d, J = 8.7 Hz, 2H, o-H (C6H5)).

  one one one

			Ratio	4i	5i
	Chemical Formula: C20H13BrO2; Molecular Weight: 365.22	1	4
		Derivative 4i		Derivative 5i
	Structural
	properties
		Not isolated as unique isomer	Pure isomer, yellow powder, yield 21%,
				mp. 155-157°C
	Retention	Rf = 0.4 (silica, P/EE = 3/2)	Rf = 0.45 (neutral aluminum oxide, P/EE =
	factor			2/1)

1 H NMR 300 MHz, CDCl3, δ ppm: 3.51 (t, J = 2.0 Hz, 2H, H-5), 6.39 (dt, J = 5.9, 2.3 Hz, 1H, H-7), 6.93 (dt, J = 5.9, 2.0 Hz, 1H, H-6), 7.37-7.54 (overlapped peaks, 8H, o,m,p-H (C6H5), 4′,5′,6′-H (C6H4-m-Br)), 7.81 (s(br), 1H, 2′-H (C6H4-m-Br)). 300 MHz, CDCl3, δ ppm: 3.77 (t, J = 1.8 Hz, 2H, H-7), 6.80 (dt, J = 5.7, 2.1 Hz, 1H, H-5), 6.89 (dt, J = 5.7, 2.4 Hz, 1H, H-6), 7.34-7.41 (overlapped peaks, 2H, p-H (C6H5), H-5' (C6H4-m-Br)), 7.22-7.27 (m, 2H, m-H (C6H5)), 7.51-7.60 (overlapped peaks, 3H, o-H (C6H5), H-6' (C6H4-m-Br)), 7.83 (d, J = 7.8 Hz, 1H, H-4' (C6H4-m-Br)), 8.06 (t, J = 1.8 Hz, 1H, H-2' (C6H4-m-Br)). 13 C NMR 75 MHz, CDCl3, δ ppm:

  Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material

		2 2,2,2 2,2,2 2,2,2----trifluoroethanone trifluoroethanone trifluoroethanone trifluoroethanone
		Chemical Formula: C26H21F3O2; Molecular Weight: 422.44
		Derivative 8f
	Structural
	properties
		Orange solid, yield 83%, mp. 178-179°C
	Retention
	factor	Rf = 0.5 (silica, P/EE = 2/1)

1 H NMR

400 MHz, CDCl3, δ ppm: 1.40 (s, 9H, C(CH3)3), 6.76 (d, J = 3.9 Hz, 1H, H-5), 7.

51-7.64

(overlapped peaks, 9H, H-ar (4-C6H5), C6H4-p-tBu), 8.04 (s, 1H, H-3), 8.16 (dq, J = 3.9, 2.1

  -

	1 H NMR	600 MHz, CDCl3, δ ppm: 3.97 (s, 3H, OCH3), 7.11 (s, 1H, H-3), 7.18 (d, J = 13.3 Hz, 2H, m'-
		H (C6H4-p-OCH3)), 7.45 (m, 2H, o-H (4-C6H5)), 7.52 (s, 1H, H-6), 7.60-7.64 (overlapped
		peaks, 3H, m,p-H (4-C6H5)), 7.72 (d, J = 13.3 Hz, 2H, o'-H (C6H4-p-OCH3)), 8.06 (s, 1H,
		CH(CN)2), 9.28 (s, 1H, CH(CN)2).
	13 C NMR	150 MHz, CDCl3, δ ppm: 56.0,
		Page | 122

Table 1 .

 1 Ratios of regio-and diastereoisomers 2 and 3.

Table 2 .

 2 Absorption details of derivatives 2a-d in acetonitrile and dichloromethane at rt

		acetonitrile		dichloromethane
		λabs (nm)	Concentration	log	λabs (nm)	Concentration	log
			(M)	ε		(M)	ε
	2'a	278; 307	7.3E-05	3.80	280; 309	7.45E-05	3.82
	2'b	280; 310	5.75E-05	3.94	280; 315	6.47E-05	3.83
	2''b	280; 295 (sh); 313	7.81E-05	3.90	282; 295 (sh); 317	7.79E-05	3.92
	3''b	275; 282	7.38E-05	3.98	275; 282	6.85E-05	4.06
	2'c	278; 308	8.92E-05	3.87	282; 294 (sh); 312	6.34E-05	3.97
	2''c	280; 312	7.73E-05	3.74	280; 294 (sh); 314	7.00E-05	3.86
	2'd	276; 307	6.43E-05	3.86	280; 309	6.87E-05	3.87
	2''d	276; 309	7.6E-05	3.68	280; 311	6.98E-05	3.74

Table 4 .

 4 Absorption and emission data for dihydro-indenopyrone derivatives

	Compound	Absorption	Emission	Emission	Stokes shift	Ф c
		λmax [nm] a	λmax [nm] a	λmax [nm] b	[nm]
	2'a	307	382	423	75	7.2 %
	2'b	310	389	445	79	18.1 %
	2''b	313	393	432	80	5.4 %
	3''b	282	392	-	110	0.3 %
	2'c	308	384	-	76	12.6 %
	2''c	312	338; 354; 370	475	58	7.2 %
	2'd	307	386	461	79	10.8 %
	2''d	309	391	491	88	3.6 %

a Recorded in acetonitrile.

b

In solid state.

c

Determined in acetonitrile with 9,10-diphenylanthracene as reference (Ф = 90 %)

59

  one one one

		Chemical Formula: C28H26O2; Molecular Weight: 394.50
		Derivative 2'c
	Structural
	properties
		White solid; yield 45%; mp. 235-236°C; Rf = 0.70 (pentane/methyl tert-butyl ether =
		8/1).
	13 C NMR	150 MHz, CDCl3, δ ppm: 31.4; 35.0; 37.0; 44.1; 52.4; 123.0; 123.7; 125.2; 125.6; 126.9;
		128.0; 128.3; 128.4; 129.0; 129.1; 129.9; 136.0; 136.7; 143.8; 145.6; 153.0; 169.7.
	UV-Vis	(CH2Cl2) λmax (log ε) [nm]: 282 (3.99), 311 (4.06).
		(acetonitrile) λmax (log ε) [nm]: 278 (3.99), 308 (4.03).
	HRMS	calcd. for C28H27O2 [M+H]
	(APCI+)

1 H NMR 600 MHz, CDCl3, δ ppm: 1.38 (s, 9H, C(CH3)3), 2.76 (dd, 1H, J5α, 5β = 16.1 Hz, J5α, 4a = 7.7 Hz, H5α), 2.99 (dd, 1H, J5β, 5α = 16.1 Hz, J5β, 4a = 8.3 Hz, H5β), 3.69 (m from overlapped ddd, 1H, H4a), 3.77 (d, 1H, J4,4a = 14.2 Hz, H4), 7.06 (pseuso t from dd, 1H, J = 7.4 Hz, H-7 or H-8), 7.15-7.19 (overlapped peaks, 2H, H-6 or H-9, H-8 or H-7), 7.23 (d, 1H, J = 7.9 Hz, H-9 or H-6), 7.33 (d, 2H, J = 7.3 Hz, o-H (4-C6H5)), 7.37 (t, 1H, J = 7.4 Hz, p-H (4-C6H5)), 7.44 (m, 2H, m-H (4-C6H5)), 7.47, 7.61 (2 x d, 4H, J = 8.3 Hz, 1-C6H4). + : 395.2006; found: 395.2008. Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

  one one one

		Chemical Formula: C24H17BrO2; Molecular Weight: 417.29
		Derivative 3''b
	Structural
	properties
		White solid; yield 54%; mp. 201-202°C; Rf = 0.3 (pentane/methyl tert-butyl ether =
		8/1).
	1 H NMR	600 MHz, CDCl3, δ ppm: 3.75, 4.12 (2 x d, 2H, J9,9= 20.6 Hz, H-9), 4.56 (d, 1H, J4a,4 = 6.7 Hz,
	UV-Vis	(CH2Cl2) λmax (log ε) [nm]: 275 (4.11), 282 (4.15).

H-4a), 4.87

(d, 1H, J4,4a = 6.7

Hz, H-4), 6.96-7.06 (overlapped peaks, 5H, 4-C6H5), 7.14-7.24 (overlapped peaks, 4H, H-5, H-6, H-7, H-8), 7.56, 7.61 (2 x d, 4H, J = 8.6 Hz, 1-C6H4).

13 C NMR

150 MHz, CDCl3, δ ppm: 36.2; 48.0;

48.6; 119.0; 123.1; 125.0; 125.2; 127.2; 127.8; 127.9; 128.1; 128.6; 128.7; 131.6; 131.9; 133.3; 138.1; 141.7; 143.1; 169.2.

(acetonitrile) λmax (log ε) [nm]: 275 (4.15), 281

(4.16

).

Table 1 .

 1 Absorption and emission data of derivatives 3a

-b, 5a-c Compound Absorption λmax [nm] a Emission λmax [nm] a

				Stokes shift
				[cm -1 ]
	3a	333	390	4389
	3b	455	570	4482
	5a	375	473; 530 (sh)	5525
	5b	400	550	6818
	5c	425	570	5985

a

Recorded in dichloromethane at room temperature.

[nm]

		1.0
					3a
		0.8			3a + Fe 2+ 3a + H +
	Absorbance [a.u.]	0.4 0.6			3a + H + + Fe 2+
		0.2
		0.0
		300	400	500	600	700
	Figure 9. Normalized absorption spectra of derivative 3a recorded under various conditions
			(inputs)

  Würthner et al. have reported cells with PCE of 6.1% based on merocyanine donors. 106 Wong et al. have synthesized donoracceptor molecules based on triphenylamine and fabricated solar cells with a maximum PCE of 6.80% using C70 as acceptor. 107 Recently, a high PCE was achieved with compound A

	(chart 1) when a PCE of 2.53% in a bilayer junction 108 and 4.0% in coevaporated cell 109 was
	obtained.

Chart 1

Table 1 .

 1 Crystallographic data, details of data collection, and structure refinement parameters for compounds 1-3.

	Compound	1	2	3
	formula	C21H14N4S	C51H33Cl3N8S4	C23H14N4S2
	M [g mol -1 ]	354.42	992.44	410.50
	T [K]	293 (2)	293 (2)	293 (2)
	crystal system	monoclinic	triclinic	monoclinic
	space group	P21/n	P-1	C2/c
	a [A]	11.802 (1)	5.4939 (5)	35.046 (7)
	b [A]	8.7604 (8)	14.717 (1)	8.817 (2)
	c [A]	18.7063 (8)	16.805 (1)	13.733 (2)
	α [°]	90	86.677 (7)	90
	β [°]	106.836 (5)	82.864 (7)	101.810 (10)
	γ [°]	90	85.485 (7)	90
	V [A 3 ]	1851.2 (2)	1342.44 (17)	4153.7 (14)
	Z	4	1	8
	ρcalcd [g cm -3 ]	1.272	1.228	1.313
	µ [mm -1 ]	0.186	0.367	0.273
	goodness-of-fit on F 2	1.111	0.976	1.068
	Final R1 / wR2 [I > 2σ (I)] 0.0443 / 0.0874	0.0742 / 0.1940	0.0599 / 0.0849
	R1 / wR2 (all data)	0.0779 / 0.1011	0.1396 / 0.2208	0.1505 / 0.1074

Table 2 .

 2 UV

		-Vis spectroscopy data ((s): ~1 10 -5 M in CH2Cl2); (f): films spin-cast on glass),
	and cyclic voltammetry (in 0.10 M Bu4NPF6/CH2Cl2, scan rate 100 mV s -1 , Pt electrodes, ref.
	SCE).
	Donor	λmax (s) [nm]

Table 3 .

 3 Photovoltaic characteristics of PHJ bi-layer cells ITO/PEDOT:PSS/D/C60/Al under AM 1.5 simulated solar light with an incident power light of 90 mW cm -2 . Data in italics are the average of 6-8 cells, data in bold are the best results for each series.

	Compd	An. Temp [°C]	Jsc [mA cm -2 ]	Voc [V]	FF [%]	PCE [%]
	1s	110	6.40	0.75	33	1.76
	1s	110	6.32	0.79	37	2.07
	1e	110	6.83	0.68	32	1.64
	1e	110	6.87	0.69	32	1.68
	2s	120	7.32	0.74	40	2.41
	2s	120	7.14	0.76	42	2.55
	2e	120	8.73	0.77	40	3.06
	2e	120	8.42	0.80	43	3.22
	3e	140	7.71	0.61	41	2.15
	3e	140	8.53	0.60	40	2.28
	4s	150	5.68	0.66	29	1.28
	4s	150	6.19	0.63	35	1.47
	4e	160	4.78	0.69	29	1.05
	4e	160	5.25	0.69	30	1.20
	5s	160	5.65	0.63	32	1.22
	5s	160	5.30	0.54	41	1.30
	5e	160	2.12	0.66	39	0.63
	5e	160	2.17	0.70	39	0.65
	6e	85	2.92	0.67	22	0.47
	6e	85	3.11	0.64	20	0.56
	7e	130	5.47	0.52	29	0.92
	7e	130	5.88	0.53	28	1.00

Table 4 .

 4 UV-Vis absorption spectroscopy data: ( s : in CH2Cl2; f : thin films spun-cast on glass) and cyclic voltammetry (0.10 M Bu4NPF6/CH2Cl2, scan rate 100 mVs -1 , Pt electrodes, ref SCE) for compounds 8

-14. Donor λmax s

  Using E 0 ox with an offset of -4.99 eV for SCE vs the vacuum level. b Determined by EHOMO-ΔE. c Calculated values Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in

										ELUMO
										(eV) c
	8	502	36300	520	2.00	1.04	-1.10	-5.83 -3.36 -5.23 -2.80
	9	493	44500	508	2.05	1.06	-1.03	-5.90 -3.38	-	-
	10	510	63000	529	1.97 0.86, 1.05 -1.10	-5.74 -3.31 -5.10 -2.83
	11	487	54000	492	2.10	1.19	-1.16	-5.96 -3.42 -5.35 -2.88
	12	501	54000	515	2.12 1.04, 1.18 -1.12	-5.89 -3.42 -5.20 -2.82
	13	489	78000	524	1.92	1.21	-1.31	-6.01 -3.48 -5.45 -2.94
	14	496	50400	512	2.07 1.09, 1.38 -1.26	-5.92 -3.42	-	-

a

Table 5 .

 5 Photovoltaic characteristics of PHJ bi-layer cells ITO/PEDOT:PSS/D/C60/Al under AM 1.5 simulated solar light with an incident power light of 90 mW cm -2 . Data in italics are the average of 6-8 cells, data in bold are the best results for each series.

	Donor	Jsc [mA/cm 2 ]	Voc [V]	FF [%]	PCE [%]
	8	5.77	0.92	52	2.50
	9	4.80	0.73	29	1.16
	9	5.52	0.73	30	1.28
	10	8.04	0.66	41	2.44
	10	8.41	0.63	44	2.62
	11	2.14	0.71	23	0.49
	11	2.66	0.69	28	0.55
	12	4.81	0.97	38	1.96
	12	5.10	0.98	40	2.16
	13	4.55	0.79	32	1.26
	13	4.88	0.79	33	1.38
	14	6.00	0.62	32	1.34
	14	6.18	0.58	34	1.38

2,2'-((5,5'-(((carbonylbis(4,1-phenylene))bis(phenylazanediyl))bis(4,1-phenylene))bis(thiophene-5,2- diyl))bis(methanylylidene))dimalononitrile

		Chemical Formula: C53H32N6OS2; Molecular Weight: 832.99
		Derivative 11
	Structural
	properties
		Deep-red powder; yield 68%; mp. 128-130°C
	1 H NMR	300 MHz, CDCl3, δ ppm: 7.77 (s, 2H), 7.75 (d, 4H, J = 8.7 Hz), 7.70 (d, 2H, J = 4.2 Hz), 7.60
		(d, 4H, J = 8.7 Hz), 7.40-7.35 (overlapped peaks, 6H), 7.21-7.18 (overlapped peaks, 6H),
		7.17 (d, 4H, J = 8.7 Hz), 7.13 (d, 4H, J = 8.7 Hz).
	13 C NMR	75 MHz, CDCl3, δ ppm: 156.

Protocol To a solution of 8 (250 mg, 0.62 mmol) in 50 mL of 1,2-dichloroethane at 0 °C, oxalyl chloride (0.13 mL, 1.49 mmol) and AlCl3 (165 mg, 1.24 mmol) were added. The mixture was stirred 1h at room temp. under argon. Another equivalent of 8 (250 mg, 0.62 mmol) was added and the reaction was stirred at 90 °C for five days. The solution was diluted with dichloromethane, washed with water and brine and dried over MgSO4. Solvent removal and column chromatography on silica gel, using dichloromethane as eluent gave 350 mg of deep-red powder.

(E)-3-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)-2-(thiophen-2-yl)acrylonitrile

		Chemical Formula: C29H20N2S2; Molecular Weight: 460.61
		Derivative 22
	Structural
	properties
		Yellow powder; yield 62%; mp. 153-155°C
	Protocol	To a mixture of 2-(thiophen-2-yl)acetonitrile (0.26 g, 2.11 mmol) and sodium tert-
		butoxide (0.36 g, 3.16 mmol) in 60 mL ethanol was added portionwise 5-(4-
	1 H NMR	300 MHz, CDCl3, δ ppm: 7.53-7.50 (overlapped peaks, 3H), 7.43 (s, 1H), 7.32-7.29

(diphenylamino)phenyl)thiophene-2-carbaldehyde (20) (0.75 g, 2.11 mmol). The reaction mixture was refluxed overnight under argon atmosphere. After being cooled to room temperature, water and dichloromethane were added. The aqueous phase was extracted twice with dichloromethane, and then the combined organic extracts were washed with brine, dried over MgSO4 and concentrated to dryness. The crude was chromatographed on silica gel using as eluent a mixture of dichloromethane and petroleum ether (2 : 1) to afford a yellow powder.

(E)-3-(5-(4-((4-formylphenyl)(phenyl)amino)phenyl)thiophen-2-yl)-2-(thiophen-2-yl)acrylonitrile

		Chemical Formula: C30H20N2OS2; Molecular Weight: 488.62
		Derivative 24
	Structural
	properties
		Yellow powder; yield 59%; mp. 125-135°C
	Protocol	To a solution of derivative 22 (0.4 g, 0.87 mmol) in 40 mL 1,2-dichloroethane,
		anhydrous DMF (0.31 g, 4.18 mmol) and phosphorus oxychloride (0.53 g, 3.48 mmol)

  131,132 Versatile applications of CDs include bioimaging, 133 catalysis, 134 and photoreduction of metals, 135 due to the high electron donor-acceptor ability. Of late, CDs have shown promising applications in bio-sensing136,137 , especially as they exhibit peroxidase like activity.138 At present, CDs can be prepared by diverse methods 139 , including microwave pyrolysis of sucrose 140 , electrochemical oxidation of graphite 141 , thermal decomposition of

	Chapter 5 -Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation
	Optoelectronic Devices
	-

  the obtaining of devices that exhibit different colors depending on carbon dots sizes. 163 More recently, Luck et al. demonstrated that coating a commercial blue emitting LED with carbon dot-agar composite can produce white light

	Chapter 5 -Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation
	Optoelectronic Devices
	-
	emissions. 165

nm Absorbance [a.u.] Wavelength [nm] 400 500 600 700 PL [a.u.] 0 1000 2000 3000 4000 5000 6000 7000 exc. 325 nm exc. 350 nm exc. 375 nm exc. 400 nm exc. 425 nm Figure 2.

  166 J. C. G. Esteves da Silva, H. M. R. Goncalves, TrAC, Trends Anal. Chem. (Pers. Ed.), 2011, 30, 1327. Absorption and normalized photoluminescence spectra (at different excitation wavelengths as listed) of CDs-PD (top), CDs-PPD (middle) and CDs-PEG1500N (bottom) in aqueous solution

	Chapter 5 -Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation
					Optoelectronic Devices
	-
	Absorbance [a.u.]	0.0 0.2 1.0 0.4 0.6 0.8	0.4 0.6 0.8 1.0	CDs-PD 400 exc. 425 CDs-PPD exc. 325 nm exc. 350 nm exc. 375 nm exc. 400 nm Wavelength [nm] 500 600 700 800 exc. 400 nm exc. 425 nm 8000 10000 exc. 325 nm exc. 350 nm exc. 375 nm exc. 400 nm exc. 425 nm exc. 325 nm exc. 350 nm exc. 375 nm Wavelength [nm] 400 500 600 700 PL [a.u.] 0 2000 4000 6000 Normalized Intensity Normalized Intenity
			0.2
			0.0
			200	300	400	500	600	700	800
					Wavelength [nm]

  167 J. R. Lakowicz, Principles of Fluorescence S 168 C. Yu, X. Li, F. Zeng, F. Zheng, S. Wu Chem 169 S.Hu, Q. Zhao, Q. Chang, J. Yang, J. Liu, RSC 170 C. Ding, A. Zhu, Y. Tian, Acc. Chem. Res. 171 C. Fowley, N. Nomikou, A. P. McHale, B. Mc 172 J. Tang, B. Kong, H. Wu, M. Xu, Y. Wang, Y.

	scent Carbon 'Quantum'Dots: a New Concept for Next
	Optoelectronic Devices
	-

Table 2 .

 2 Fluorescence decay parameters of CDs-PEG1500N and CD-PEG1500N-Rh solutions. An are the lifetime and amplitude of the n th component; τavg is the amplitude-weighted average lifetime calculated with:

	Sample	τ τ τ τ1 (ns)	A1 (%)	τ τ τ τ2 (ns)	A2 (%)	τ τ τ τavg (ns)	χ 2
	CDs -PEG1500N	6.5	66.5	1.8	33.5	4.9	1.05
	CD -PEG1500N -Rh	5.4	60.3	1.3	39.7	3.8	0.99
	τn and

Table 3 .

 3 Parameters calculated for CD -PEG1500N -Rh conjugates at 405 nm excitation.

  4, corresponding to PEG),

176 A. R.

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(a) Y.-A. Duan, Y. Geng, H.-B. Li, X.-D. Tang, J.-L. Jin, Z.-M. Su, Org. Electronics 2012, 13, 1213; (b) S. Zeng, L. Yin, C. Ji, X. Jiang, K. Li, Y. Li, Y. Wang, Chem. Commun. 2012, 48, 10627.

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 -------------------------------------------------

Synthesis and Structural Analysis of new

Indenopyrone derivatives

Scheme 2

The TLC monitoring of the reaction and the NMR spectra revealed the formation of several products; therefore, the cycloaddition proceeds neither stereoselectively, nor regioselectively. Analyzing the proposed reaction mechanism (scheme 3), it is obvious that formation of regioisomers can easily occur. A mechanism for the condensation reaction between indene and oxadiazinones was proposed (scheme 3) based on literature reports 57 for the addition of norbornene to oxadiazinone in acidic conditions. Addition of TFA to the reaction mixture leads to protonation of oxadiazinone derivative 1 to the corresponding diazahydroxypyrilium cation, followed by the [4+2]-cycloaddition of indene to give the diaza-adduct. Next, the 4,5-dihydro-2-hydroxypyrilium ion is formed after fast elimination of nitrogen. The dihydro-α-pyrone diastereoisomers are formed after tautomerisation and proton loss. 129.0; 129.1; 130.3; 132.0; 135.6; 136.1; 141.7; 142.3; 145.8; 169.5.

UV-Vis

(CH2Cl2) λmax (log ε) [nm]: 280 (4.02), 315 (3.96).

(acetonitrile) λmax (log ε) [nm]: 278 (4.01), 311 (3.95).

HRMS (APCI+)

calcd. for C24H18BrO2 [M+H] + : 419.0464; found: 419.0466.

one one one

Chemical Formula: C24H17BrO2; Molecular Weight: 417.29

Structural properties

Derivative 2''b

White solid; yield 54%; mp. 199-201°C; Rf = 0.2 (pentane/methyl tert-butyl ether = 8/1).

Theoretical calculations

To better understand the electronic structures, the geometry of derivatives 10-13 was optimized using density functional calculation methods which was conducted according to Becke's three parameter hybrid functional and Lee-Yang-Parr gradient corrected correlation potential (B3LYP) with 6-31G (d,p) 126 atomic basis set in Gaussian 09

program 127 .

The HOMO-LUMO energy gap (∆H-L) was evaluated by B3LYP, while the lowest excitation energy was estimated by using TD-B3LYP level of theory. Both methods were assessed based on the S0 geometries together with the consideration of solvation effect of dichloromethane (CH2Cl2) by the Conductor-Polarizable Continuum Model (C-PCM).

The optimized structures and electronic distributions in the frontier orbitals of the compounds are shown in figure 21. Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices kp 2 describes the relative orientation in space of the transition dipoles of the donor and the acceptor and is taken to be 2/3 assuming rapid orientational averaging of the donor within the lifetime of its excited state, ΦD is the quantum yield of donor fluorescence without acceptor (here 0.17 for 405 nm excitation), J(λ) is the overlap integral between the normalized donor emission and the acceptor extinction coefficient , expressed as follows:

where FD(λ) is the fluorescence intensity of the donor in the absence of acceptor (the integral of the spectrum equals to one), εA(λ) is the wavelength-dependent molar extinction coefficient of the acceptor.

Thus, the separation distance obtained for 405 nm excitation, using Eq. 1, is around 43 Å (see table 3), in good agreement with literature reports showing typical Förster donor -acceptor distance on the order of 10-100 Å.

FRET efficiency at 405 nm excitation was estimated from fluorescence lifetimes using the following equation:

where τD and τDA represent the average fluorescence lifetime of CDs-PEG1500N (4.9 ns) and CD-PEG1500N -Rh (3.8 ns), respectively, at 405 nm excitation, as presented in table 3.

The rate of energy transfer was calculated using the equation:

where τD is the fluorescence emission lifetime in the absence of the acceptor fluorophore, that is the lifetime of CDs-PEG1500N (4.9 ns), R0 is the Förster separation distance, calculated with Eq. 1 and r represents the distance between donor and acceptor, obtained as follows:

(5)

Chapter 5 -Electroluminescent Carbon 'Quantum'Dots: a New Concept for Next Generation Optoelectronic Devices ------------------------------------------------------------------------------------------------------------------------------------

Although the shortening of fluorescence lifetime observed at 405 nm excitation confirms the resonance energy transfer from the CDs-PEG1500N to the acceptor, the energy transfer efficiency calculated at this wavelength using Eq. 3 is only 22%, with a rate of energy transfer of 5.6 × 10 7 s -1 (table 3). One can thus assume that the FRET efficiency is even better at higher wavelengths, i.e. 420 nm and 450 nm, for which the overlapping between the donor and acceptor spectra is more pronounced. Indeed, the steady state fluorescence measurements have suggested the most efficient transfer occurs at 450 nm by the fact that the most significant increase of RhB fluorescence is correlated with the most pronounced decrease of CDs-PEG1500N signal, when compared to reference samples. However, due to the limitations of our time-resolved fluorescence system, we were unable to perform measurements above 405 nm. Furthermore, using Eq. 5 we obtained a donoracceptor distance of approximately 53Å which is in good agreement with the theoretical thickness of PEG layer. 179 All these experiments suggest that the covalent linkage of rhodamine B to the carbon dots surface led to a non-radiative transfer of energy (FRET) from the CDs to the dye molecule. In addition, the synthetic accessibility and the transfer efficiency of these conjugates make them reliable candidates for fluorescent materials to be used later in sensing and solar cells.

The unique excited state redox processes of CDs responsible for the luminescence emissions were further investigated by integration of CDs-PEG1500N into multilayer light emitting diode devices. 180 The LED device of a multilayer structure (ITO/PEDOT:PSS/PVK/carbon dots/Al, figure 11) was constructed by our partners at IMT Bucharest by sequentially spin-coating each layer from orthogonal solvents on top of the ITO substrate, with the Al cathode as the final layer deposited by thermal evaporation method through a shadow mask.

General conclusions

The thesis entitled "Design, Synthesis and Supramolecular Architectures of New Heterocyclic Compounds with Potential Applications in Material Chemistry and Photovoltaic Conversion" is structured into five chapters concerning new: a) heterocyclic cyclopenta [c] The first chapter presents a study of pseudoazulene derivatives having a cyclopenta [c]pyran unit. The survey comprises the synthesis, structural analysis and reactivity towards electrophilic substitution in order to obtain fluorescent compounds. By following a multi-step strategy which starts from 1,3,4-oxadiazin-6-ones, six new series of cyclopenta [c]pyran derivatives were obtained and investigated using 1D, 2D NMR , UV-Vis/fluorescence spectroscopy, mass spectrometry, cyclic voltammetry and X-Ray diffractometry.

The second chapter deals with the investigation of some new indenopyrone derivatives, including separation of regio-and diastereoisomers, study of their fluorescent properties and determination of fluorescence quantum yield.

Two series of molecular systems based on terpyridine and phenothiazine blocks have been synthesized and completely analyzed by NMR, UV-Vis, fluorescence spectroscopy and mass spectrometry. Attempts have been made to determine the application of these systems in molecular electronics as potential logic gates. We obtained a system able to mimic an 'OR' gate. The first chapter presents a study of pseudoazulene derivatives having a cyclopenta [c]pyran unit. The survey comprises the synthesis, structural analysis and reactivity towards electrophilic substitution in order to obtain fluorescent compounds.

LIST OF NEW COMPOUNDS

The second chapter deals with the separation of regio-and diastereoisomers and the study of fluorescent properties of some new indenopyrone derivatives.

The third chapter describes the synthesis of new architectures based on cyclopenta [c]pyran unit that can be structurally modified by the influence of a chemical or electrochemical stimulus in order to work as potential devices in molecular electronics.

In the fourth chapter, the synthesis and characterization of electronic properties of new molecular donors based on N,N'-diphenylhydrazone and triphenylamine blocks for organic solar cells was described.

The fifth chapter outlines the passivation of surface defects on carbon nanoparticles using small organic molecules or polymers in order to obtain photoluminescent carbon nanoparticles dubbed as carbon'quantum'dots.

Keywords:

Cyclopenta [c]pyrans; Indenopyrones; Fluorescence; Molecular electronics; Electron-donor; Organic Solar Cells; Carbon 'quantum' Dots; Light Emitting Diode (LED).