dearest, Mauro; you lightened up fluorescence a bit more dude. Merci également à Marie le grand prof. de français pour les produits qu'elle a fait au cours de M1 stage.

I think I forgot Hella, not really! You will be remembered for long time. All the first translations, hang-outs, fun, and shouting have spiced "Nice" stay. Assia also did her share in translations and joy, merci! Altogether with Diaa, Ilheme, and Najiba, we had a great deal of time and food that I will definitely miss. Dr. Ilheme, despite your early departure from the ICN, the short time was enough to reveal a chemist and person of high standards and a friend for life.

Outside the lab, there are many people who had put up with me in all stages. They are a major highlight in my life. The Janwa; you witnessed it all and are still doing patiently, I will simply quote from your thesis: "Behind each work, there is a secret rider, you were always there", see you soon in Strass. George; an ever-lasting support and a melody for every occasion, laughing is the key of success as you say. Kawsar; the chief of chiefs, for god's sake we need to stop running and making rules; not everyone has your potential. Together, we made the perfect KG group of nice. Ramez; you left your space when you moved. Abed, Tharwat; travelling with you is beyond fun. Habeeb and Hawraa; you added a source of joy with our future chemist, Mariam. Finally Pascal; we will hopefully always meet or run away bro, I am so happy that I have met you.

Back home, the gratitude can go endless and I still have too many experiments to do, so I will cut it short. Thanks for everyone who supported me when I decided to change careers. I am very lucky to have a family that trusts my choices without questioning. You are too many, but I love you all. Mostafa and Iman; you are my residence and comfort. Jinan; you did all what I have to do for years. You, Naim, and your three ugly musketeers are blessings. Suzan and Samah, your craziness makes you so special and we are proud of your success with each day passing, Roy, Iyad, and Karam; you will be one of a kind (chemical) engineers, you know it. Jihan, Souaad, Makram, Fares, David, Osama, Wido…. Silvana; don't get lost in Cuba, I can't live without you all.

Distance did not make some any less of great friends: Rawad, a real brother; we will keep on roaming and reach, we shared all the crazy and wisdom times, all the fun, joy, plans, and determination-I hope you make it to my defense, Bilal, Bahaa; thanks for all and cheers, Naveen, Fadi, George, Anis, Samer, Dani, and the group leader in Dubai, Khodr; here it is man, our chemistry is finally in action, Lamece the royal; I will sum up the 10 pages of jokes you make of me into one line of don't stop because I will miss it, Jihan the one and only; from Lyon to Lebanon, and Marah; a real source of aspiration for many years, I will buy a house in Monaco and you will be invited. If anyone is forgotten, be sure it is for lack of time. I appreciate an equal list of people that I could not name.

Finally, there is nothing better than quoting from the French Nobel Prize winner Jacques Monod: "In science, self-satisfaction is death. Personal self-satisfaction is the death of the scientist. Collective self-satisfaction is the death of the research. It is restlessness, anxiety, dissatisfaction, agony of mind that nourish science." So here it is, a small plan of an unsatisfied scientist who lost his first grant in a war back in 2006, and kept the same target of research till July 2016.

Nice,

July, 2016 • ICT intramolecular charge transfer

• IR infrared

• J spectral overlap in FRET

• kDa kilodalton

• knr sum of non-radiative decay rates

• kr radiative decay rate

• L ligand (tertiary phosphine)

• l the light path length in a sample

• Ld liquid-disordered phase

•

Thesis statement and presentation of the manuscript

The cutting-edge development of technology often takes place at interfaces of supposedly distinct disciplines of science. Research involving interdependent areas of synthetic chemistry, computations, photophysics, biophotonics, and imaging has evolved as a modern mean of analysis to unravel the scientific enigmas. "Fluorescence" is a domain that integrates virtually all the mentioned disciplines and extends to other frontiers of environmental detections, life, medicinal, and pharmaceutical sciences.

"Fluorescence" was observed first by Herschel in 1845 as a phenomenon from quinine solution under sunlight and was further described by Stokes in 1852. A century later, this novelty process was put in the service of science with the invention of "commercial fluorometers" and "fluorescence microscopes". The advances proceeded fast with "confocal microscopy" and more sophisticated Nobel-Prize instruments like the "Zewail's femtosecond (x10 -15 s) spectroscopy". Fluorescence instrumentations are nowadays advanced, not expensive, and easy-to-manipulate.

Eventually, fluorescence techniques have become crucial analytical toolbox for research and industry owing their success to many exquisite characteristics. These techniques are the most sensitive in the field of molecular sensing especially in probing intrinsic biological dynamics.

Their sensitivity has attained the limit of single molecule detection with signal recordings that can be controlled at a distance. They demonstrate high degree of accuracy, non-invasive character in living cells, and ultrahigh spatial and temporal resolutions. Furthermore, fluorescence sensing is extremely versatile providing detections in solid, liquid, gas, and even at the interface of these phases. In addition to instrumentations, the growth in the "design and synthesis of fluorophores" undoubtedly remains the hallmark of progress in fluorescence applications.

An optimal fluorophore is essentially a molecular framework that compiles the required attributes from optical properties such as photostability, brightness, selective excitation and emission to chemical versatility such as tolerance to introduce substituents for bioconjugation and tuning solubility. Such rational design is a challenge by itself. From "organic chemistry" perspectives, this will at least involve a multi-step synthetic route to produce such a smart molecule; hence, adding more challenges of the known limitations of synthesis. Consequently, chemists are highly urged to bring forth new robust, step-and atom-economic routes to synthesize innovative probes and generate libraries of dyes that elucidate structure-property relationships.

In particular, our work has focused on metal-catalyzed reactions such as Buchwald-Hartwig aminations and copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) "click" reactions to create more viable alternatives to otherwise long employed routes. The developed in-house methodologies allowed accessing a fluorene-based library of push-pull dyes as a captivating class of environment-sensitive probes. A push-pull dye consists of a π-scaffold functionalized with an electron donor (D) and acceptor (A). The D-π-A system undergoes a photo-induced intramolecular charge transfer (ICT) state forming a low-energy molecular orbital (MO). Visible light provides sufficient energy to excite the electrons within this new MO, making these compounds generally colored. The ICT also generates dipole moments that augment the sensitivity of these fluorophores in response to polarity and changes of their environments.

The aromatic core (π) plays a key role in the design. Thus, came the choice of the fluorene family in this project. Fluorenes manifest desirable spectroscopic attributes, low cytotoxicity, and appreciable two-photon absorption cross-sections allowing cell imaging with reduced photodamage. Fluorene derivatives are extensively used in biomedical research and material sciences such as optoelectronics.

Two central investigations were explored using our fluorene probes, 1) labeling of oligonucleotides (ODNs), and 2) imaging of lipids in biomembranes.

In fact, despite the complete determination of the 3.5x10 [START_REF] Barthes | Epigénétique et méthylation de l'ADN: Développement d'outils pour la compréhension du mécanisme de méthylation de l'ADN impliquant UHRF[END_REF] base-pair DNA sequences in the human genome project (HGP) in 2001, this explosive acquisition of structural data has paraded very limited information about the complex biological function of DNA. To address these aspects, fluorescence spectroscopy offers an exquisite tool to characterize nucleic acids and to study their interactions, which are fundamentals to understand cellular events such as DNA repair, DNA methylation, and gene silencing. The search of suitable fluorescent markers that can monitor these interactions without affecting the structure and function of the labeled ODN sequences is still at its peak.

Likewise, the heterogeneous lipid distribution in cell membranes is a subject of intense investigations. Three levels of heterogeneity are distinguished. The lateral heterogeneity, described by the lipid raft hypothesis, is under debate till now. Rafts are believed to be behind many processes such as signal transduction and neurodegenerative diseases. Transmembrane lipid asymmetry is the second heterogeneity that is lost in programmed cell death (apoptosis).

Defective apoptosis is the origin of detrimental diseases such as atrophy and cancer. Lastly, the differences between the plasma and intracellular membranes represent the third, least-explored heterogeneity. Thus, designing highly sensitive probes will help to understand the structure and dynamics of biomembranes by sensing different parameters like hydration, viscosity, polarity, and order. This will in turn reflect in understanding the cellular processes and in finding solutions to futile medical problems such as cancer.

In conclusion, the purpose of this thesis was to advance a step in the areas of designing and synthesizing novel fluorescent probes that meet the rigorous and demanding conditions of the above-mentioned biological applications.

The body of the dissertation consists of 5 chapters and a conclusion stating the future perspectives.

• Chapter one is the introduction that states the background of this work.

• Chapter two describes a concise synthetic methodology to prepare a spectrum of aminoaromatics. The methodologies involve selective functionalization of dibromoaromatic scaffolds using air-stable palladium catalytic systems. In particular, rapid mono-and di-aminations were carried out in addition to sequential couplings of different moieties in one-pot. The synthesis was scaled up to prepare the essential probes used in the next chapters. The content of chapter 2 has recently been published online in The Journal of Organic Chemistry.

• Chapter three builds on the developed catalytic conditions of Buchwald-Hartwig amination to explore the effect of the donor part on push-pull molecules. Moreover, it describes various synthetic pathways to study the acceptor part including CuAAC, peptide couplings, and metal-halogen exchange reactions. In effect, we concluded the theoretical and experimental characterization and structure-photophysics relationships of 17 synthesized fluorophores including near-infrared (NIR) probes. The content of chapter 3 has recently been published in Chemistry: A European Journal.

• Chapter four takes the advantage of the rational design and the new "ynone" anchoring point of "chapter three" in bioconjugating the fluorene probes. This chapter describes the synthesis of three probes designed to image membrane lipids. The photophysical characterization of the dyes, their ability to probe large and giant unilamellar vesicles (LUV and GUV) of different lipid compositions, and the imaging of HeLa cells are reported. The optmized dye is the first plasma membrane-specific fluorene-based probe that can be a powerful tool for studying membranes surpassing the features of commonly used probes.

• Chapter five illustrates the synthesis of four emissive nucleobase analogues (phosphoramidites) exploring different linkers and sugars to rationalize the design of a fluorene-based DNA sensor. Then, it covers the journey of site-specific ODN incorporations of the biosensors via solid-phase DNA synthesis, the difficulties encountered, the characterization and the hybridization studies of the labeled ODN sequences, and finally the preliminary application of the optimal biosensor as a mega-Stokes shift donor in a FRET pair. The recorded shift seems exceptional reaching up to 300 nm and very promising to validate the dye in future applications.

• A brief conclusion and future perspectives are stated at the end of the manuscript, followed by the experimental section.

Chapter 1:

Bibliographical Review

I. Luminescence

Luminescence is the process of emission of light quanta upon excitation by any source of external energy such as a chemical reaction (chemiluminescence), thermal energy (thermoluminescence), mechanical action on a solid (mechanoluminescence), light (photoluminescence), etc..

In particular, photoluminescence is defined as an optical property of a substance which absorbs photons and then releases the absorbed energy radiatively from its excited state. [1,2] Chemical functionalities that absorb light in the ultraviolet or visible region are referred as chromophores. Absorption in the visible gives colored compounds.

Depending on the nature of the excited state, photoluminescence is classified into 2 forms, fluorescence and phosphorescence. A molecule or a molecular fragment that has the ability to fluoresce is called a fluorophore. A fluorophore is also commonly termed as a dye in reference to its color property. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]4]

I.1 Fluorescence

Fluorescence can be viewed as a three-stage process. Each stage and its corresponding optical measurements will be discussed in the following sections.

I.1.1 Stage 1: Absorption of light (excitation) I.1.1.1 Light

Light is an electromagnetic radiation described in terms of a "wave-particle duality" concept.

Precisely, light is characterized as a particle (photon) by its energy (E, eV) and as a wave by its wavelength (λ, nm) or wavenumber (, cm -1 ) as shown in eq. 1,

= ℎ = ℎ = 1 Equation 1
where c and h are constant values signifying the speed of light and Planck's constant respectively.

The range of electromagnetic radiations suitable for optical studies and photochemistry is shown in fig. 1 and is characterized by its E and λ. [2,[START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] Figure 1. Range of electromagnetic radiation in optical studies and photochemistry [5] I.1.1.

Absorption

An organic molecule resides in its ground state (S0, singlet by multiplicity) in the absence of external sources of perturbation. In the ground state, two electrons rest in the highest occupied molecular orbital (HOMO) while the lowest unoccupied molecular orbital (LUMO) is free.

Exposing the molecule to a vacuum extreme-ultraviolet radiation (λ < 200 nm) can provide enough energy to ionize it by the expulsion of one of its electrons. However, exposition of the molecule to UV/visible radiation (200-800 nm) induces an electron transition from HOMO to LUMO causing an excited electronic state (S1, singlet by multiplicity). In the excited state, an intersystem crossing to a triplet multiplicity (T1) can take place (fig. 2). [2,4] Figure 2. Light-induced phenomena

I.1.1.3 The Beer-Lambert law

The absorbance (A) measured at any wavelength on a spectrophotometer is proportional to the dye concentration (C, mol/L) and the light path length in a sample (l, cm). The molar absorption coefficient (Ɛ) is the proportionality coefficient in this relation (eq. 2).

= ℰ. .

Equation 2

Many instrumentation and intrinsic factors can cause the fluorophore to absorb light nonlinearly as a deviation from this law. Examples are: inner filter effect, broadband illumination, turbidity of biological samples, and molecular aggregation. The latter is the case of selfassociation that increases the particle size causing more light scattering or shift of its absorption maximum for instance. Aggregation is mainly observed if the fluorophore is concentrated or insoluble. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]

I.1.1.4 Molar absorptivity or absorption coefficient

Molar absorptivity or extinction coefficient (Ɛ) signifies the probability of an electronic transition from the ground to excited state at a given wavelength.

• If Ɛ > 10 5 M -1 .cm -1 , the transition is fully allowed.

• If Ɛ < 10 2 M -1 .cm -1 , the transition is forbidden.

• If 10 2 < Ɛ <10 5 M -1 .cm -1 , the transition is partially allowed.

In general, Ɛ increases as the size of the fluorophore increases. [6]

I.1.1.5 Franck -Condon principle

Since the electronic transitions (ex: S0-S1) take place relatively faster (10 -15 s) than the molecular vibrations (10 -10 -10 -12 s), "an electronic transition is most likely to occur without changes in the positions of the nuclei in the molecular entity and its environment". [7] This principle can be applied to both absorption and fluorescence emission that will be further discussed using the Jablonski diagram (fig. 3). [2]

I.1.2 Stage 2: Excited state and fluorescence lifetime

Fluorescence lifetime (τ) is the average "finite" time a fluorophore stays in the excited state prior to its return to the ground state. Generally, the fluorescence lifetime is in the range of 10 -8 _ 10 -11 s. It depends on all decay forms of the fluorophore as shown in eq. 3,

= 1 ! + !" Equation 3
where kr is the radiative decay rate and knr is the sum of non-radiative decay rates. Fluorescence lifetime spectroscopy (FLS) can provide insights into changes of the microenvironment of the fluorophore. These changes impose direct influence on the non-radiative decay rate by processes like collisional quenching, resonance energy transfer, and vibrational relaxation. This time-resolved measurement involves the irradiation of the sample with a short pulse of light and recording the decay of fluorescence intensity with time. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]8] Figure 3. The Jablonski diagram [START_REF] Barthes | Epigénétique et méthylation de l'ADN: Développement d'outils pour la compréhension du mécanisme de méthylation de l'ADN impliquant UHRF[END_REF]

I.1.3 Stage 3-Fluorescence emission

The Jablonski diagram [START_REF][END_REF] (fig. 3) shows the horizontal lines as the vibrational levels of the electronic states versus energy as the vertical axis. The electronic transition takes place from the lowest vibrational level of the ground state to different vibrational levels of the excited state. The arrows represent the different possible transition processes. An excited molecule undergoes vibrational relaxation (10 -10 -10 -12 s) to the relaxed excited state. Fluorescence may occur if the system returns to S0 emitting a photon (10 -7 -10 -10 s). The molecule might also undergo an intersystem crossing changing its electron spin multiplicity from a singlet (S1) to a triplet state (T1); from which the transition to So emits light as phosphorescence (10 -1 -10 -4 s). [4] According to Kasha's rule, luminescence emission occurs in an appreciable yield only from the lowest vibrational level of the excited state. [11] As a matter of fact, the real archetype of energy transition processes related to light absorption and return to the ground state is much more complex and can involve solvent relaxation, delayed fluorescence, and many non radiative processes and phenomena. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]

I.1.3.1 Steady-state measurement

Steady-state measurements as the major focus of this thesis, are carried out by exposing the sample to a continuous beam of light (fig. 4). The key optical properties that can be characterized are: the "Stokes shift" in homage to the British physicist Stokes and the fluorescence quantum yield. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] Figure 4. Steady-state measurement I. 1.3

.1.1 "Stokes shift"

A fluorophore is mainly identified by its absorption maximum (λabs) and emission maximum (λem). Except for upconversion materials, fluorescence emission is generally shifted to the lower energy side compared to absorption (λem > λabs). This is mainly due to the dissipated part of absorbed energy in nonradiative relaxation. Stokes shift (ΔλSS) is the difference between the band maxima positions of the absorption and emission spectra of the same electronic transition.

ΔλSS can be calculated as shown in eq. 4 and is usually expressed in wavenumber units.

Wavelength l units are also used for convenience. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] Δλ !! = !" -!"# Δλ !! !! = !"# -!" Equation 4

I.1.3.1.2 Fluorescence quantum yield

The quantum yield () is the ratio of the number of photons emitted to the number of photons absorbed (eq. 5). It identifies the efficiency of the fluorescence process versus the other decay pathways of the excited species. [12] = ℎ ℎ = ! ! + !" Equation 5

I. 1.3.1.3 Relative brightness

Relative brightness can be calculated as the product of Ɛ and . Thus, it takes into account both the absorption and the fluorescence efficiency.

II. Fluorophores

Fluorophores constitute a platform of functional dyes and active molecules with marvelous applications in many fields from material to medicinal sciences. [13,[START_REF] Liu | [END_REF] Some examples of the vast diversity of uses are enlisted in the "section III.2" related to fluorene molecules. However, since this work focuses on the design of fluorene push-pull dyes for labeling nucleic acids and imaging biomembrane lipids as target applications, the bibliographical review will be mostly guided towards these dimensions.

The design of novel fluorophores often aims to achieve the maximum number of the following features: [1] • High extinction coefficient: The higher Ɛ implies a more efficient excitation. However, there should be a compromise in designing a dye that is relatively small in size but yet, possesses a high extinction coefficient.

• High quantum yield, and hence higher brightness: This detects the absolute sensitivity of fluorescence detection.

• Optimal excitation wavelengths: Excitation is optimized to obtain the highest brightness at wavelengths close to the absorption maximum. This feature should be chosen based on the application and the availability of the light source.

• Large Stokes shift: It allows to reduce the light-scattering effects and to collect more conveniently the emitted light.

• Optimal emission wavelength: The desired specificity is the narrow and red shifted emission.

• Optimal fluorescence lifetime,

• High photostability,

• Optimal solubility -penetration -reactivity in the used system.

The plethora of dyes is extremely rich and diverse in structures, chemistries, and optical properties. Thousands of fluorophores are well described in literature. Due to this large variety, there is no ultimate universal criterion for classification. Here, we try to distinguish some classes, features, and applications in order to discuss few examples.

Fluorophores can be divided into two main classes based on their origins, namely intrinsic and extrinsic fluorophores. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]

II.1 Intrinsic fluorophores

Intrinsic fluorophores are those that occur naturally with an autofluorescence such as some amino acids (tryptophan and phenylalanine), nicotinamide, flavin, heme, chlorophyll, fluorescent protein (e.g. hemoglobin, green fluorescent protein (GFP)). [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] II.1.1 Fluorescent proteins (GFP) isolated from jellyfish is one example (fig. 5). The folded structure of this fluorophore is encapsulated into a rigid hydrophobic cage increasing its fluorescence efficiency. [15] The encoded GFP and variants were used as extrinsic fluorescent reporters for numerous biological processes (vide infra).

II.1.2 Chlorophyll

Several types of chlorophyll exist. Their main component is the chlorin magnesium ligand (1, fig. 5). Light absorbed by chlorophyll is used to drive photosynthesis, dissipated as heat, or Figure 5. (A) Chlorin magnesium ligand, (B) X-ray structure of GFP and the chemical structure of the embedded fluorophore [15] emitted as fluorescence (1-2%). Despite this small proportion, fluorescence is easy to measure even in full sunlight. It is employed as an indicator of the photosynthetic energy conversion. This fact had resulted in devising special chloprophyll fluorometers that revolutionized the plant and algae research. [16]

II.2 Extrinsic fluorophores

Extrinsic fluorophores are synthetic molecules or modified biochemicals that can be added to a specimen to provide fluorescence or to change its spectral properties. Encoded fluorescent proteins, fluorescent nanocrystals and small-molecule fluorophores are three extrinsic classes. [8,[START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF]

II.2.1 Genetically encoded proteins

These fluorophores are often produced within cells. [START_REF] Heim | [END_REF]19] Advances in this field had led to achieve artificial, endogenous proteins with infrared emissions. The major limitation of these proteins is their relatively large sizes (30-50 kDa) compared to small-molecule fluorophores (0.2-2kDa). Their size restricts their applications as target-injectable probes and may perturb imaging of biological processes. [8] (GFP) is a brilliant example that is used as a gene expression reporter and probe for previously invisible cellular processes (fig. 5). GFP technology was the subject of the 2008 Nobel Prize in chemistry.

II.2.2 Fluorescent nanocrystals

The modern field of fluorescent nanocrystals is developing extremely fast for its prospective applications. Two examples are Quantum dots (Qdots) and upconversion nanocrystals (fig. 6).

Figure 6. Fluorescent nanocrystals

Qdots are photostable nanoparticles with ultrahigh brightness, broad excitation ranges, and narrow emission peaks. [20] To date, the relatively large size of Qdots and the toxicity of their heavy metal constituents limit their applications. [8] Upconverting nanocrystals are unclassical fluorophores that produce anti-Stokes emission.

They are excited at longer wavelength (NIR) and emit light at shorter wavelengths (NIR or visible). Endogenous fluorophores are not excited in this range. Hence, autofluorescence is reduced. [8]

II.2.3 Small-molecule fluorophores

An array of small-molecule fluorophores is described spanning the emission spectrum from blue to NIR. These organic compounds typically contain extended conjugated π-bonds. [8] There exists no benchmark to fairly classify this diverse class. We will categorize them generally into unsubstituted aromatic, classical, and environment-sensitive dyes. This classification mainly depends on their structure dictating their spectroscopic properties and hence, their applications.

II.2.3.1 Unsubstituted aromatic dyes

Nonpolar molecules, such as aromatic hydrocarbons, constitute one part of classical dyes.

They are barely sensitive to polarity so they are rarely used in probing environmental interactions. Their low solubility in common organic solvents and the difficulties of their purifications are other limitations. Unsubstituted aromatics have been used in labeling nucleic acids (Section VI.5.2.2). Further, they are imminent scaffolds for single molecule spectroscopy (SMS) where the main objective is to detect the optical signal of exactly one molecule hidden deep within a condensed phase. In this dimension, the minimum number of functionalities in the design and the higher photostability of unsaturated aromatic dyes are prospective properties.

The 3-D "pseudo-image" of single molecules of pentacene (2) in p-terphenyl (3) is shown as an example (fig. 7(A)). [21,22]

7(B)

). [23] This kind of turn-on processes is very attractive to imaging and read-only memory devices. Moreover, naked pyrene, as well as its derivatives, has found many applications in biological detections since its spectroscopic properties exhibit a ratiometric response due to excimer formation. [24,25] Excimers will be discussed in section III.1.3 in context of fluorene dyes.

Finally, the luminescent polymers of these aromatic families (e.g. polyfluorenes, Section III.1.6) remain superb designs for many uses even in the absence of polar substituents.

The given examples highlight the importance of understanding the properties of aromatic molecules to architect innovative dyes. Fluorene as our major topic and a representative example of this category will be discussed in details in section III.

II.2.3.2 Classical dyes

A second category of classical fluorophores comprises some heteroaryl dyes such as xanthene-based dyes (fluoresceins (5), rhodamines ( 6)), cyanines (7), and BODIPY (8)) that have been employed as fluorescent labels for biomolecules (fig. 8). [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF]26] The spectral sensitivity of these dyes to environmental changes is small. The reason is that their electronic density is delocalized over the whole molecule as a typical feature of these resonant or mesomeric dyes.

Two examples are briefly described here. [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF] • Fluoresceins Fluorescein (5) belongs to the xanthene family with absorption and emission maxima in the visible region (490 nm and 512 nm in water). Fluorescein is quite water-soluble and has appreciable extinction coefficient and high quantum yields. As a result, this family of dyes is one of the most used molecular probes in biolabeling. The drawbacks of these probes are the high rate of photobleaching and the self-quenching problems after bioconjugation. [1,27] O

O R COO - O N COO - N N B N F F R 3 R 3 R 2 R 1 R 2 X N N X R R' n X = S, O, C(CH 3 ) 2 5 6 7 8
Figure 8. Examples of classical dyes

• Cyanines

The group of cyanine dyes ( 7) is a representative family of long-wavelength fluorophores with high extinction coefficient (> 100000 M -1 .cm -1 ) applied in bioconjugations. [28] The basic structure of cyanines is made up of two aryl or heteroaryl groups linked by a polymethine chain with carbon-carbon double bonds. Classical cyanines have some disadvantages like low quantum yield and tendency to aggregate in aqueous media. [26] Advanced derivatives of cyanine have been also reported with improved optical properties for more sophisticated applications. [START_REF] Przhonska | Advanced Fluorescence Reporters in Chemistry and Biology I[END_REF]

II.2.3.3 Environment-sensitive dyes

Environment-sensitive dyes constitute a smart class of fluorophores that can sense biomolecular interactions. Unlike "classical" dyes, they possess the property of polarization of their electronic structures that changes upon optical excitation. This dynamic behavior imposes changes in their fluorescence properties (τ, λem, and ) in response to molecular environment. [1,[START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF] Hence, they are suitable not only to label biological molecules but also to study their interactions (DNA/proteins, biophysical properties of membrane lipids). [START_REF] Loving | [END_REF][31][START_REF] Owen | Methods in Membrane Lipids[END_REF] These dyes might also act as pH and ion chemosensors that respond by changes in their chemical structure by protonation/deprotonation or complexation reactions. [START_REF] Yin | [END_REF] We will focus on their basic sensitivity that is guided by excited state reactions (conformational change, charge, electron and proton transfer, etc.), non-covalent interactions with the surrounding (van der Waals, dipoledipole, etc.), and hydrogen bonding. [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF] Clearly, many different interactions and dynamical processes govern the sensitivity of these dyes. It is hard to identify which factor is dominant in a particular environment. Other factors involve viscosity and rate of solvent relaxation, probeprobe interaction, changes in decay rates, etc. Nevertheless, this complexity rendered these dyes indispensable tools in understanding the dogma of vital biological processes.

Molecular rotors and solvatochromic fluorescent dyes are two classes of environmentsensitive dyes. Solvatochromism will be discussed in details in the next section. In essence, molecular rotors respond to changes in viscosity. The conjugated system of these dyes features high rotational flexibility in non-viscous environments (such as water) that quenches the fluorescence efficiency. On the other hand, viscous media (glycol solvents, biomembranes, biomacromolecules) restrict their rotation mobility increasing dramatically the intensity of their emission. Typical examples of molecular rotors are DCVJ probe (9) and the prodan analogue (10) depicted in fig. 9(A). [34,35] These dyes detect polarity and hydration of their surrounding microenvironments. They have found tremendous applications. [36] II. Solvatofluorochromism can be simply defined as the effect of solvent upon the fluorescence emission of the dye and hence its color. Absorption is generally less sensitive to polarity compared to emission, with few exceptions like molecular rotors. This is because absorption of light is too fast (10 -15 s) relative to the motions of the fluorophore or solvent (10 -9 -10 -12 s) that have the key effect on emission. [31,37] For simplicity, "solvatochromism" term will be used instead of "solvatofluorochromism" in the next sections.

II.3.2 Negative solvatochromism:

Relative to thousands of dyes that exhibit positive solvatochromism, this type is rare.

Negative solvatochromism or hypsochromic shift signifies a displacement in emission band to a shorter wavelength (blue shift) with increasing solvent polarity. A hypsochrmoic shift is observed when the first excited state of the dye is less polar than the ground state. Some examples are shown in fig. 9(B) such as the CI Basic Yellow (11) with delocalized charge and certain merocyanine dyes (12) with polar ground state due to a large contribution from its canonical form. [START_REF] Gordon | Organic Chemistry in Colour[END_REF]

II.3.3 Positive solvatochromism:

The great majority of dyes encounter a change in the emission band to a longer wavelength (red shift) with increasing solvent polarity. This is stated as "bathochromic shift". In the sections that follow, discussions of solvatochromism will refer to this major category of dyes with bathochromic shifts.

Figure 10. The Jablonski diagram illustrating the effect of solvent

To explain the general effect of solvent polarity, the Jablonski diagram (fig. 10) is considered.

In its ground state (S0), the fluorophore (in black) is surrounded by a sphere of solvent molecules (white). The system is promoted to an excited state (S1) upon absorbing a photon of the appropriate energy. The dipole moment of the dye in its excited state (Franck-Condon state) increases dramatically due to an intramolecular charge transfer (ICT). The solvent molecules reorient (or relax) fast to accommodate the now larger dipole of the fluorophore. This solvent relaxation lowers the energy of the excited singlet state resulting in solvent-relaxed state (S1).

Simultaneously, the ground state is destabilized into a transient state (S0) decreasing the gap of energy between the two states. Hence, the emitted photon will be of lower energy and the fluorescence band will be at a longer wavelength. As the polarity of the solvent increases, this effect becomes larger and relaxation increases red-shifting the emission spectra. These effects are guided by the electronic polarizability of the solvent (described by its refractive index n) and the molecular polarizability (which results from reorientation of solvent dipoles as a function of the static dielectric constant, ε). In a similar manner to dipole-dipole interaction, protic solvents can interact with the fluorophore dipole through H-bonding decreasing the energetic band and red-shifting the emission. Water as an example causes a drastic red-shifted emission since it is a strong H-bond donor with a strong dipole. [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF][START_REF] Loving | [END_REF] As described earlier, other interactions might also occur in the excited states as represented in fig. 11 increasing the sensitivity of these dyes. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] Figure 11. Possible interactions that can influence fluorescence emissions Another important property of most environment-sensitive dyes is their poor fluorescence efficiency (quenching effect) in water and polar protic solvents. This is due to the sink of energy via H-bonds and formation of electron traps in bulk water in addition to the increased competition of the non-radiative decays since the energy gap becomes smaller. Manipulating this property has yielded predominant applications. Accordingly, when these dyes are incorporated into proteins or membrane lipids, they are shielded from the bulk water resulting in strong increase in fluorescence intensity (turn-on). [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF] We will distinguish two types of solvatochromic dyes, two-band dyes based on excited-state intramolecular proton transfer ESIPT and single-band dyes based on excited-state charge transfer (CT or ICT). In addition, specific dyes show a special case of twisted internal charge transfer (TICT) that will be exemplified in the case of fluorenone (section III.1.4).

II.3.3.1 Two-band dyes

3-hydroxychromones are particularly interesting ESIPT dyes. The origin of their dual emission is the normal excited state (N*) and the ESIPT tautomer (T*)(fig. 12). [START_REF] Barthes | [END_REF]40] The intramolecular H-bond occurs through a five-membered cycle much weaker than a sixmembered one. As a result, the interactions are easily perturbed sensing any change in the environment (polarity, hydration, electric field, etc.). The response is translated as a change in the relative intensities of the two characteristic emission bands. Hence, these molecules are efficiently used to interrogate the biophysics of membranes, to probe the hydration of the major groove of DNA, and to discriminate the conformational changes of DNA/DNA and DNA/RNA duplexes; to name few investigations. [41][42][43] Figure 12. Dual emission by ESIPT mechanism

II.3.3.2 Single-band dyes

Examples of the most commonly used single-band dyes are depicted in table 1. Their characteristic emission is a single band that responds to changes in the environment polarity by its position and sometimes intensity. Oxazines and phenoxazines (Ex: Nile Red) [44] !"# = 553

!" = 632 = 38 % = 45000 () !!
Red-shifted absorption, emission, high brightness Moderate fluorescence solvatochromism, quenching in water Nitrobenzoxadiazole (NBD) [45] !"# = 456

!" = 541 = . . = 22000 () !!
Red-shifted absorption and emission, small size Weak fluorescence solvatochromism, quenching in water Naphthalene sulfonic acid derivatives (Ex: Dansyl EDA) [46] !"# = 335 UV absorption, very low extinction coefficient, quenching in water Prodan [47] !"# = 361 [48] !"# = 456 Phthalimide derivatives (Ex: 4DMP) [49] !"# = 396

!" = 526 = 49 % = 4600 () !!
!" = 498 = 51 % = 18400 () !!
!" = 604 = 41 % = 12100 () !!
!" = 534 = 12 % = 6500 () !!
Strong sensitivity to polarity, small size and high rigidity UV absorption of this family of dyes, low extinction coefficient, quenching in water, Fluoroprobe [50] !"# = 308 As general trends, these dyes are excited in the violet or UV region. They possess relatively low extinction coefficients compared to classical fluorophores. They show poor quantum yields in polar solvents, particularly in water, which is dramatically increased in apolar media. As a consequence, these dyes are employed for sensing polarity and hydration of the environments.

!" = 695 = 0.1 % = 12000 ()
They are well-established turn-on probes when they are shielded from the bulk water in investigations of proteins and lipid membranes. However, they pose problems in studying the biological processes in which all the steps are exposed to water such peptide-DNA interactions. [START_REF] Morris | Fluorescence-Based Biosensors: From Concepts to Applications[END_REF] Figure 13. Styryl pyridinium electrochromic dye Lastly, electrochromic dyes form a special case of environment-sensitive dyes that operate by the same photophysical (ICT) principle. An external electric field will induce the transition between the electronic states resulting in electrochromic shifts in absorption and emissions.

Commonly, excitation spectra are used to detect the electrochromic effects since emission spectra can also be affected by polarity. Ideally, any solvatochromic dye may operate as an electrochromic one. The efficiency of the dye's response mainly depends on its structural geometry and transition dipole moment. The most commonly used ones are the rod-shaped molecules where the electron donor and acceptor moieties are installed on the two extreme opposite sides. Styryl pyridinium fluorophore (21) is an example of an efficient electrochromic dye that is mainly used in membrane studies (fig. 13). It constitutes a turn-on probe to detect rigid domains of biomembranes. [51] Two areas are still under research in this category of dyes;

that is to synthesize new fluorophores with: a) strong electrochromic responses in emission and b) enhanced fluorescence efficiencies. Despite the diversity of the existing environment sensitive dyes, none of them combines the features of photostability, ultra brightness, red-shifted absorption, and high fluorescence solvatochromism. This critical overview (table 1) urges researchers to find new dyes with enhanced properties. So, comprehensive studies of how to design such fluorophores and the structure-photophysics relationships are still compelling.

II.4 Push-pull dyes

The (ICT) environment-sensitive dyes belong to a broader category of "push-pull" molecules (fig. 14). They consist of a conjugated (usually aromatic, π) system functionalized with an electron-donating and withdrawing group respectively abbreviated as donor (D) and acceptor (A). [52] Figure 14. General architect of push-pull dyes

The D-π-A system undergoes a photo-induced intramolecular charge transfer (ICT) state forming a low-energy molecular orbital (MO). To briefly recall, visible light provides sufficient energy to excite the electrons within this new MO, making these compounds generally colored. [52] The ICT also generates dipole moments that augment the sensitivity of these fluorophores in response to polarity. [31,37] The extent of the ICT character has decisive effects on both the propeties of the molecule. The two extreme forms of the ICT of a fluorene push-pull dye are illustrated in fig. 15. The π-conjugated framework in these compounds is typically made of multiple bonds (olefin or acetylene), aromatics (benzenoids), heteroaromatics (ex: thiophenes), or a combination of these spacers. D-π-A molecules adopt a linear arrangement. However, there are other arrangements of push-pull systems outside the scope of this thesis. Examples are quadrupolar (D-π-A-π-D) and octupolar ((D-π)3-A) systems. In addition to their uses as fluorosensors, push-pull molecules have found fundamental applications in material sciences such as nonlinear optical (NLO) switches, electro-optic, piezochromic materials, and other science fields. [52] Typical electron donors are substituents with positive mesomeric (M) and inductive (I) effects such as OH, NH2, OR and NR2, heterocyclic moieties such as thiophene as well as some metallocenes. Typical electron acceptors featuring negative (M/I) effects involve NO2, CN, CHO and electron deficient heterocyclic compounds such as benzothiazole and imidazole. [52,53] In principle, the ICT degree, the corresponding HOMO-LUMO gap, and hence; the optical properties and response can be tailored by:

(i)
The electronic nature of D and A groups, (ii) Efficient D-A interaction and planarization of the entire system, (iii) Extension, composition, and spatial arrangement of the π -linker, (iv) Reducing the bond-length alternation (BLA). The BLA can be defined as the difference between the average C-C single and multiple bond lengths of the π-system in its two limiting resonance forms (aromatic vs. zwitterionic). [52]

III. Fluorene and its derivatives

As demonstrated, the aromatic core plays a key role in the architecture of efficient fluorophores. Thus, came the choice of the fluorene family as the (π) framework studied in this thesis.

Fluorene or 9H-fluorene is a rigid, planar polycyclic aromatic hydrocarbon with an extended π-electron delocalization (fig. 15). Fluorene forms white crystals that have violet fluorescence from which its name was derived. [54] The benefits of the fluorene core are four-fold:

• First, the fluorene chromophore comprises a methylene group conjugated to two benzene rings (12 π electrons) in high electronic symmetry. This methylene bridge forces the two phenyl rings to be planar increasing their orbital overlap, the rigidity of the system, and the degree of conjugation of electrons. The CH2 bridge greatly compromises the lack of traditional auxochromic heteroatoms (N, O, S, etc..) in facilitating the charge transfer resulting in strong linear and nonlinear interactions upon excitation. [54] • Second, the absence of auxochromes in fluorenes constitutes an advantage over traditional heterocyclic chromophores. Endocyclic heteroatoms in other spacers prompt non-radiative deactivation of the excited states, thus decreasing the quantum yields. [55] Auxochromes also facilitate the forbidden n-π transitions as powerful channels of photodegradation. [2,[START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]56] Correspondingly, the chromophoric systems that include the fluorene nucleus demonstrated relatively high thermal and photochemical stability under both one and multi-photon excitation conditions. [57,58] • Third, the advantage of this family is its high fluorescence efficiency. Indeed, some fluorene derivatives fluoresce with quantum yields that approach "unity". [59][60][61][62] • Fourth, the molecular backbone has two-fold versatile functionality. The acidity of the protons of the methylene group provides a potentially active site for condensation reactions. This position can be used to introduce side groups that can enhance the solubility in organic solvents or water and can tune the electronic properties at the same time. Further, the aromatic hydrogen atoms can be involved in substitution reactions.

Positions 2, 7 and 4, 5 are the most reactive (fig. 15). The possibility of the selective functionalization of fluorenes on the CH2 group or the aromatic rings opens up the gates to synthesis of unique soluble fluorophores with superb properties. This provides access to a broad range of physico-chemical, optical, electrical, and magnetic properties apt for various interesting applications by modulating the electronic abilities of the introduced groups. From structural perspectives, this allows the synthesis of practically important star-like or dendrimer dyes [63,64] and the introduction of desired rigid linkers for covalent labeling of biological species such as DNA or amino acids. [65][START_REF] Fischer | Nanoparticles Based on Π-Conjugated Polymers and Oligomers for Optoelectronic, Imaging, and Sensing Applications: the Illustrative Example of Fluorene-Based Polymers and Oligomers[END_REF][START_REF] Leclerc | [END_REF] This structural robustness and tunable behavior gave us a strong impetus to develop practical fluorene derivatives.

III.1 Particular features of fluorene and its derivatives III.1.1 Two-photon absorption

• Significance

Several modern technologies exploit this process like two-photon fluorescence imaging and photodynamic cancer therapy. [68,69] The seminal work involving two light quanta in one elementary action by Maria Göppert-Mayer in her dissertation in 1931, has established the theoretical framework for two-photon absorption (2PA). 2PA is the near simultaneous absorption of two photons of identical or different frequencies in order to excite a molecule to a higher electronic state. The sum of the energies of the two photons is equal to the energy difference between the initial and final states of the transition. Recalling that energy is inversely proportional to wavelength, the two absorbed photons must have a wavelength about twice that needed for one-photon excitation (fig. 16). For instance, if a fluorophore absorbs UV light (350 nm), it can also be excited by 2PA of NIR (~ 700 nm). [70] A finite instant of time (~10 -15 -10 -18 s) is afforded for a second photon to arrive and complete the excitation into the final electronic state. For this reason, practice of this pioneering work had to wait decades for the invention of the "laser" that provides high intensity radiations to effectuate such transitions.

Since this process depends on simultaneous absorptions, the resulting emission varies with the square of the excitation intensity (quadratic relationship). Thus, 2PA is a nonlinear optical process. Further, water absorbs minimally in the NIR regime; therefore, light can penetrate deeper into thick biological media. In two-photon fluorescence imaging, high spatial resolution is achieved and less phototoxicity is encountered by the biological samples. [71][72][73] Fluorene derivatives have been extensively investigated and employed as dyes with appealing 2PA properties. [59,60,74,75]

III.1.2 Aggregation-Induced Emission Enhancement (AIEE)

When a fluorophore is aggregated in the condensed phase, partial or total fluorescence quenching is often observed. This aggregation-caused quenching (ACQ) is a limitation in practical applications. As opposed to this effect, some distinguished fluorophores such as some fluorene derivatives possess the property of aggregation-induced emission (fig. 17). [76] The AIE property has been applied in recent sensing technologies. [77] Specifically, the aggregation of AIE molecules can be tuned by different parameters (electrostatic interaction, coordination interaction, hydrophobic interaction, steric hindrance, polarity, viscosity) to produce useful turn-on probes. In this context, the fluorene derivatives ( 22) and ( 23) [78] are weakly emissive in solution. Upon aggregation, they show intense emission and change in fluorescence color. [79]

III.1.3 Excimer formation

In fluorescence spectra, excimers are observed as strongly red-shifted bands in concentrated solutions. Excimers can be described as short-lived dimers that are unbound in their ground state but rather tightly bound in their excited state. Since 1970, excimers in fluorene were observed. [80] Successive work has reported this behavior and its applications later, mainly in polyfluorenes, [81] fluorenone (24), and its derivatives [82][83][84] (fig. 18).

N N C C Au Au F F F F F F F F F F

III.1.4 Twisted Intramolecular Charge Transfer (TICT)

TICT is the special case of charge transfer that occurs due to conformational changes (distortion from planarity) in the excited state of the molecules. Literature shows that there is no clear agreement on the need of a real twisting in the molecule to achieve this process. [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] TICT imposes more pronounced solvatochromism and can be controlled to have ratiometric response by switching fluorescence between two possible distinct states of the molecule (TICT vs. excimer emission) changing the solvent (e.g. fluorenone (25), fig. 18). Excimer emission of (25) appeared in apolar solvents. The emission gradually disappeared with increasing the solvent polarity where TICT emission started to appear. This paradigm can be seen as an interesting hypsochromic shift where red-shifted band of excimer is louder in apolar solvents such as toluene than a TICT band. Fluorenone derivatives are reported to participate in several donoracceptor designs inducing TICT emission. [77,83,85]

III.1.5 Profluorescence of fluorene derivatives for turn-on applications

The 9-cycloheptatrienylidene fluorenes (9-CHF, 26) are "profluorescent" derivatives. They possess natural suppressed fluorescence, which is returned upon conversion to emissive species (27) under acidic conditions. 9CHFs can be used as chemosensors for the detection of pH and metal ions (fig. 18). [86,87] The 9-CHF scaffolds also demonstrate that aromatic hydrocarbons can be tailored for sensing techniques without the introduction of any auxochromic heteroatoms.

III.1.6 Polyfluorenes (PF)

PFs can be achieved by different polymerization reactions. [START_REF] Pudzich | Emissive Materials Nanomaterials[END_REF][START_REF] Wallace | Polyfluorenes[END_REF] For instance, fluorene monomers can be directly connected to each others via Pd-or Ni-mediated couplings at the 2 and 7 positions, producing a series of oligofluorenes or polyfluorenes (28) with increasing conjugation lengths (fig. 19). [START_REF] Peterson | [END_REF]91] When the substituents at 9-position of PF (28) are butyl or . Some examples of distinct fluorene derivatives longer chains, the resulting polymers are highly soluble in non polar solvents. [START_REF] Wallace | Polyfluorenes[END_REF] Alkyl chains marginally affect the optical properties of the polymers in dilute solutions since they are far from the conjugation system at positions 2 and 7. However, they induce an aggregation effect in solid states or once concentrated. [92] In addition, the C-9 position is used to incorporate different charged functionalities as pendant groups to render PFs water-soluble and hence, suitable for biological detections. [65,[START_REF] Fischer | Nanoparticles Based on Π-Conjugated Polymers and Oligomers for Optoelectronic, Imaging, and Sensing Applications: the Illustrative Example of Fluorene-Based Polymers and Oligomers[END_REF] PF (29) is a typical example with fluorescence efficiency that ranges from 20 to 40 % in water (fig. 19). [93] Bazan's group has extensively researched this kind of cationic polyfluorenes. [94][95][START_REF] Bazan | Organic Semiconductors in Sensor Applications[END_REF][START_REF] Wang | [END_REF] These PFs have been employed in fluorescence studies and FRET experiments on DNA displaying appreciable variations in properties between single and double stranded DNAs (ssDNA and dsDNA).

Regarding photophysics, polymerization can be viewed as an amplification mechanism to the properties of the parent fluorene family. Increasing the fluorene repeating units extends the π conjugation; thus, narrows the gap between the electronic bands. This, in turn, red shifts the absorption maximum up to 12 repeating units and the emission maxima up to 6 repeating units.

The spectral properties of the polymer reach a constant level after this number of units. PFs generally absorb in the UV region and emit blue light. Their reported fluorescence yield exceeds 50 % both in solutions and solid states. [98] Moreover, color tuning of PFs can span the entire visible spectrum. This is easily achieved by copolymerization with appropriate comonomers such as benzene, naphthalene, thiophene, or benzothiadiazole. Polymers (30) and (31) are two examples (fig. 19). As a final note, polyfluorenes can show a desired ratiometric response (excimer vs. aggregate forms). [81] All the mentioned virtues accompanied by the high thermal and chemical stability made PFs beneficial composites of all dimensions of fluorescence nanotechnology. [99][100][101]

III.2 Array of uses of fluorene and its derivatives

Monomer and polymer derivatives of fluorenes found uses as functional dyes in many fields owing to the success in tailoring their desirable features. [54]

III.2.1 Fluorescence imaging and application related to biology

Fluorenes manifest the needed spectroscopic virtues, low cytotoxicity, and appreciable 2PA cross-sections that allow cell imaging with reduced photodamage. They found important applications in biomedical research and phototherapy, [102][103][104] as well as effective fluorosensors for ions, [105,106] aggregations, [84] proteins, [101] and explosives. [107] Fluorene derivatives are also active ingredients in different medicinal generics like antiviral drugs. [108] Precisely, the applications related to apoptosis and nucleic acids will be discussed in their corresponding sections (V.2.2 and VI.8). With respect to the background of imaging plasma membranes, only a fluorene-quinolizinium cation membrane probe ( 32) is described in literature (fig. 20). [109] Belfield group is pioneering in research related to novel fluorene derivatives, multiphoton imaging, and related applications. [59,68,[110][111][112][113] They have attributed the bright fluorescence of probe (32) to binding with cell membrane proteins. To the best of our knowledge, fluorene dyes have never reported as probes of plasma membrane lipids.

III.2.2 Optical data storage

Optical recording using dyes involves converting excitation energy into thermal energy by non-radiative decay. Essentially, fluorene dyes are coated as recording layers onto discs. [13,114]

III.2.3 Organic Light-Emitting Devices (OLEDs)

OLED is an available technology for emissive flat panel displays. PFs have favorable thermal and photostability as well as enhanced properties of packaging and solubility. They possess efficient emissions of UV or deep blue light making them perfect candidates to blue light emitting diodes. [115,116] III.2.4 Dye-sensitized solar cells (DSSCs)

DSSCs are designed of an efficient dye sensitizer (like fluorenes) anchored to a semiconductor. The light absorbed by the dye photo-induces an electron injection into the conduction band resulting in charge separation that is transported to a charge collector. [117,118]

III.2.5 Non linear optical dyes in telecommunication

In telecommunications, data transmission is most efficient via IR laser radiation.

Consequently, fluorene with high 2PA cross-section can effectively double the energy and convert the IR radiation to visible ones allowing easier detection of the signals. [13]

III.3 Synthesis of aminofluorenes  Conventional routes

To date, the introduction of the nitrogen nucleophile moiety into fluorene scaffolds is not easily accomplished. The described pathways to synthesize aminofluorenes involved long syntheses engaging harsh conditions as nitrations and Ullmann-type couplings. [102,119] For instance, introducing aziridine [120] and dimethyl amine [85] was reported each in five steps. Even incorporating simpler amines such as benzyl amine requires three steps. [121] The synthesis of the (38) is shown in fig. 21. [60] Despite the advanced optical properties of this push-pull dye, catalytic routes could improve its synthetic access.

The synthesis was achieved by conventional methods, namely C9-dimethylation of (33), then regioselective mono-nitration followed by iron-mediated reduction to produce the amino intermediate (36). Nucleophilic substitution afforded the diethyl amine as the donor moiety of the design (37). The acceptor part was installed by a halogen-metal exchange with n-BuLi on adduct (37) followed by treatment with DMF to provide (38) as the push-pull dye.

This approach only permits installing some amine donors; cyclic amines cannot be introduced easily. This limitation prevents the tuning of optical properties; a necessary plan to rationalize the dye designs apt for the challenging applications.

Hence, finding new versatile methodologies to selectively introduce the amine moieties has evolved as a must. In that aspect, we envisioned the palladium-catalyzed C-N coupling reactions as a solution. A robust Buchwald-Hartwig amination can replace the aforementioned classical synthetic pathway by a shorter route.

 Buchwald-Hartwig amination

In 1995, Buchwald and Hartwig simultaneously introduced secondary amines to aryl Bromides (39) using different catalytic Pd systems (fig. 22). [122,123] Several hundred publications have appeared ever since the early work reporting various efficient catalytic systems of varied palladium sources, ligands, bases, and other reaction conditions (inertness, temperature, solvent, and additives). [124][125][126][127] Many mechanisms have been beheld for the Pd catalytic cycle involved in this reaction. Since mechanistic studies is outside the scope of this thesis, a simplified cycle is illustrated in fig. 23 to discuss the general considerations. [128] After the formation of the LnPd(0) catalytic species (n commonly = 2, L = tertiary phosphines), oxidative addition of the aryl halide to LnPd(0) forms a Pd(II) intermediate. Next, coordination of the amine followed by its deprotonation using a base takes place. The electronic and steric properties of the catalyst and the substrate decide the rate of the oxidative addition step. Faster rates are achieved if the chosen catalyst is sterically unhindered and electron-rich. Considering the C-X bond that is broken in this step, the nature of the halide also affects the rate; which follows this general trend (I > Br > Cl > F).

The rate of the amine coordination step depends on both the amine substrate and the catalyst.

The rate increases when the amine is more basic and/or sterically unhindered. Next, the acidity of the coordinated amine determines the rate of deprotonation step.

Reductive elimination depends on the metal/ligand properties. Generally, bulkier and electron poor ligands increase the rate of reductive elimination since this step in the cycle causes the Pd metal to return more electron-rich.

The final step has the biggest impact on the yield of this reaction. If the alkyl group attached to Pd has a β-hydrogen, this hydrogen might be transferred to the metal by forming a double bond on the alkyl group. This competition with the desired reductive elimination step can generate the Ar-H side product decreasing the yield. Considering fluorenes in particular, Pd-catalyzed aminations have been limited to aryl amines (41) [61,83,103,129,130] and few other donors (42) and (43) in specific designs [107,131,132] (fig. 24(A)). A general amination methodology has not been yet reported to diversify the amine donor onto fluorene dyes to the best of our knowledge.

 Selective C-N cross couplings

Pd-catalyzed coupling to one halogen in the presence of another competing halogen atom will be referred to as a "controlled coupling" in this work. In literature, such type of controlled couplings has been limited to a narrow array of substrates based on the halogen or pseudo halogen selectivities (Br/Cl, Br/Otf, or I/Br). [83,133,134] Despite the easy access to simple dihalogenated aromatic scaffolds (e.g. dibromofluorene (44)), controlled couplings on these moieties have seldom been reported especially in the context of synthesizing beneficial materials (fig. 24). [135][136][137][138][139][140] Conventional routes might still be preferred due to the overestimation of the role of glove box in Buchwald-Hartwig C-N couplings. The endless list of costly palladium sources, ligands, and bases also complicates the choice of a suitable system in synthetic chemistry. Hence, one of our main objectives was set to develop robust, air-stable catalytic conditions to diversify the library of dyes and to incorporate challenging amine donors otherwise inaccessible by classical aminations.

IV. Fluorosensing

Fluorescence is the most well-developed, successful, and sensitive technique in all biological sensing technologies (electrochemical, calorimetric, etc..) by virtue of its exquisite features such as: [1]

44

• Ultra-high sensitivity detecting even trace amounts,

• Absolute sensitivity attaining the limit of detection of exactly a single molecule, [21,22] • High temporal resolution establishing precise and fast response,

• Very high spatial resolution allowing efficient cellular imaging,

• Non-destructive and non-invasive character allowing the remote control of interactions in living cells,

• Boost in the domain of "synthetic fluorophores" allowing low dosage and desired selectivity,

• Good repetitiveness of the measurements minimizing false recordings,

• Versatility providing detections in solid, liquid, gas, and even at the interface of these phases. [1] The illuminated cell (fig. 25) presented by Thermo Fisher company as a catalogue to choose a commercial fluorophore obviously demonstrates the strengths of fluorescence techniques.

Nowadays, there exist relatively inexpensive dyes to precisely probe and image most of the important cell organelles, regions, and big part of cellular molecules including H 2 O 2, peroxynitrite, O 2 , Cu + , K + , cysteine, phosphatase, etc… [141] [142] Figure 25. The illuminated cell Fluorophores are used in two distinguished lines of fluorescence applications related to biological detections, labeling and sensing. [1]

IV.1 Fluorescence labeling and detection

Fluorophores used in labeling often belong to the classical dyes that establish fluorescence signals insensitive to environmental conditions. The response "signal" is only proportional to the concentration of the dye. The main role of these 'labels', 'tracers' or 'tags' is solely to detect a particular medium or site. These tools also provide good spatial resolutions for cell imaging.

Fluorescent labels should be photostable with high brightness and should possess optimal conditions of excitation and emission. [1]

IV.2 Fluorescence sensing

This domain comprises the environment-sensitive dyes. A fluorosensor or reporter is defined as a dye that undergoes structural or conformational change in response to specific factors or/and environmental conditions. These changes are reversible and independent of the concentration of the dye. They result in variation of the output signals, particularly the emission parameters. The photostability and brightness remain highly important, but a whole set of parameters could be controlled and optimized to unravel the molecular mechanisms and dynamics of complex biological machineries (nucleic acids, proteins, lipids, etc..). These parameters are summarized in fig. 26 and have been discussed in the previous sections. Herein, FRET and anisotropy will be briefly defined.

IV.2.1 FRET

Förster Resonance Energy Transfer (FRET) [143] is a process occurring between compatible chromophores; namely a donor and an acceptor pair (fig. 27). The donor, initially in its excited state, transfers energy to the acceptor through a non-radiative dipole-dipole coupling resulting in quenching if the acceptor is a quencher, or a new fluorescence emission at wavelength typical for the acceptor if the latter is emissive. [77] The criteria of a FRET platform include:

• Well-separated absorption spectra of the donor and acceptor to ensure independent excitations,

• Well-resolved emission spectra of the donor and acceptor for high accuracy in the measurement of fluorescence intensity ratios,

• Significant spectral overlap "J" between the emission of the donor and the absorption of the acceptor,

• Comparable brightness of the two dyes,

• Appropriate linkers to avoid fluorescence quenching in aqueous media,

• Energy transfer efficiency E inversely proportional to the sixth power of the distance between donor and acceptor as defined in eq. 6,

= ! ! ! ! + ! Equation 6
where R signifies the distance between the donor and acceptor and R0 is the Förster distance at which the fluorescence transfer efficiency is 50 %.

IV.2.2 Anisotropy

The extent of emission polarization of a fluorophore upon excitation is described in terms of the anisotropy (r). The origin of anisotropy is the transition moments that take specific directions within the fluorophore structure. When polarized light is applied to randomly oriented fluorophores, only a fraction of the molecules oriented in a particular way are excited.

Fluorophores having their transition moments along the electric vector of the polarized light correspond to the best orientation for photoexcitation. Depolarized emission can commonly occur due to rotational diffusion that changes the orientation of the transition dipoles during the lifetime of the excited state. In turn, the rotational diffusion depends on the size and the structure of the rotating fluorophore and on the viscosity of the environment. Anisotropy measurements reveal the average angular displacement of the fluorophore that occurs between absorption and emission detecting changes in viscosity of the environment surrounding the fluorophore or its rotational mobility.

Since the time scale of rotational diffusion of biomolecules is in the same range of the decay time of many fluorophores, anisotropy measurement is a good fluorescence technique in biochemistry. For example, anisotropy measurements are used in quantifying proteins denaturation, studying their interactions with other macromolecules, and in probing the internal viscosities of biomembranes and their lipid compositions. This technique is particularly fruitful for studying the interaction and binding of small molecules bearing a fluorophore to larger target molecules (e.g. protein, DNA) since the interaction should result in a large reduction of the mobility of the probe detected by high anisotropy. [1,[START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]144] V. Membrane Lipids Biological membranes are made up of composites of lipids with embedded proteins held by non-covalent interactions. Sugars are bonded to the lipids and proteins of the outer side of the membrane by covalent bonds. The most common arrangement of lipids is a bilayer acting as a barrier for the passage of polar materials. The physical nature of the bilayer membrane will vary depending on its lipid composition and surrounding environment. These physical properties along with the structural specificities of the lipids determine the function of the membrane. As a particular example, cell membranes separate and protect the interior of all cells from the exterior environment. They are also involved in various cellular processes such as transport, adhesions, and signaling. [START_REF] Owen | Methods in Membrane Lipids[END_REF] V.

Classifications of membrane lipids

The lipid structure is amphiphilic with a polar head and lipophilic alkyl chains. A biomembrane can contain up to thousands of lipid molecules that differ by their head groups, their hydrocarbon tails, and the degree of their unsaturation.

In mammalian membranes, lipids can be classified into three groups: glycerophospholipids, sphingolipids, and sterols (fig. 28). [START_REF] Owen | Methods in Membrane Lipids[END_REF] V.1.

Glycerophospholipids

The most common molecule of this series is phosphatidylcholine (46) forming > 50 % of biomembranes. It is composed of a diacylglycerol backone (glycerol esterified with two fatty acids; most commonly one saturated and the other unsaturated) carrying a phosphate group (phosphatidic acid esterified by a choline). Other glycerophospholipids have variations in their structures like saturated instead of unsaturated fatty acids, ethanolamine instead of choline, ether instead of ester linkages. [START_REF] Owen | Methods in Membrane Lipids[END_REF] V.1.

Sphingolipids

Sphingomyelin (SM, 47) is the most abundant molecule of this series. It is a zwitterionic lipid with a head group similar to that of the glycerophospholipids class. However, the other added groups are linked to sphingosine instead of glycerol. SM is interesting for its role in the formation of membrane microdomains "rafts". [START_REF] Owen | Methods in Membrane Lipids[END_REF] V. It is a four-ring steroid structure with a hydroxyl group and a short hydrocarbon chain. [START_REF] Owen | Methods in Membrane Lipids[END_REF] V.2 Heterogeneity of lipid membranes and related fluorophores Lipid molecules are not uniformly distributed in the membrane structure. There is an intrinsic asymmetry between the two monolayers at different levels.

V.2.1 Level One: Lipid raft theory

The lateral heterogeneity of biomembranes is still a controversial area of intense research. In literature, there is more than 4000 scientific papers debating this theory and attempting to track the membrane rafts by different sensing methodologies. To date, the exact nature and functioning of rafts are not entirely figured out. [145] Fluorescence is an acute tool that should definitely help in probing this heterogeneity. This strongly depends on finding new appropriate fluorophores.

In 1997, Simons and Ikonen predicted the presence of lipid and proteins microdomains that are enriched in SM and cholesterol. They postulated that these microdomains play a fundamental role in many membrane and/or cellular processes such as signaling, formation of protein clusters, trafficking, and neurodegenerative diseases. [146] Lipid microdomains originate from the "phase transition" intriguing property of biomembranes. A biomembrane is often just above the melting temperature characteristic of its lipid constituents. At low temperature, the bilayer usually prevails as a highly ordered gel phase.

When the temperature increases above the characteristic melting point of the lipid substituents, the transition into a liquid-crystalline phase takes place where lipid chains are disordered. [147] Since the biomembrane is made up of different lipid molecules with different melting points, the phase transitions are smoothed and the two phases of liquid namely liquid-ordered (Lo) and liquid-disordered (Ld) can coexist. [148] Nowadays, rafts are defined as rigid yet dynamic heterogeneous microdomains that compartmentalize cellular processes and can be stabilized to form larger platforms. [149] Biomembranes can be artificially assembled in model membranes. Giant unilaminar vesicles (GUVs) present the simplest model system of a lipid bilayer used to study the membrane rafts.

GUVs are formed of lipids composing both Lo and Ld phases. Investigations on these model membranes can be summed up to show rafts as liquid-ordered phase Lo consisting of saturated lipids and cholesterol. Lo is surrounded by non-raft Ld domains consisting of unsaturated lipids. [150]  Fluorophores related to raft investigations and model membranes The most commonly used probes are lipophilic fluorophores that partition into Lo and Ld depending on their lipid composition. This complicates their use in cellular membranes, but they are still utilized in artificial models investigations. [151] Figure 29. Imaging GUVs by a pyrene dye that stains Lo and Ld in different colours Environment-sensitive dyes are prospective probes since they can stain by different colors, intensities, or fluorescence lifetimes upon partitioning into the different phases. [151,152] An example of imaging model membranes using a pyrene dye is shown in fig. 29. [153] Their use is still limited in cellular imaging. Hence, the challenge of developing new dyes that can help to elucidate the structure and biophysical properties of biological membranes is still ongoing.

V.2.2 Level two: Transmembrane lipid asymmetry

The transmembrane lipid asymmetry constitutes the second heterogeneity. The outer leaflet Figure 30. Lipid composition in plasma membrane and changes caused by apoptosis of the membrane is normally rich in SM and phosphatidyl choline (PC) whereas the inner leaflet contains phosphatidyl ethanolamine (PE) and phosphatidyl serine (PS). Apoptosis or programmed cell death cause this asymmetry to disappear (fig. 30). [154,155] Defective apoptosis is the origin of detrimental diseases such as atrophy and cancer. Many methods based on all the biomachineries of the cell were developed to detect apoptosis. Among all, two fluorescence assays related to cell membranes will be briefly described here, Annexin V and F2N12S. Once more, the design of smart fluorophores will undoubtedly lead to overcoming the current limitations.

 Annexin V detection assays

In the presence of Ca 2+ , the intrinsic Annexin V fluorescent protein binds specifically to PS. As a result, the membrane outer leaflet in apoptotic cell is stained. On the other hand, Annexin V is not able to penetrate the phospholipid bilayer in healthy cells, so it cannot detect any PS and the healthy cell stays unstained. In a dead cell, the integrity of the plasma membrane is lost, so the PS of the inner leaflet is also stained. If a membrane impermeable DNA label (e.g. propidium iodide) is added, only the dead cell will be double stained. [156,157] This discriminative staining can be detected by fluorescence microscopy or flow cytometry. Developed versions of this assay were reported with high sensitivity able to detect one cell. One disadvantage of this detection is its high dependence on Ca 2+ concentration. [158]  F2N12S detection assay F2N12S is a synthetic 3-hydroxyflavone derivative that exhibits an ESIPT behavior. This results in a dual ratiometric fluorescence emission in response to variations in the lipid compositions of the membrane outer leaflet. The main disadvantage of this probe is the low photostability limiting a continuous fluorescence imaging. [159] Some red-shifted and bright Nile red derivatives are used now to overcome these limitations.

From the broader scope of visualizing the changes of lysosomes and endoplasmic reticulum excellent specificity and sensitivity. [74,119] V.

Level three: heterogeneity among biological membranes

The least explored heterogeneity is the third one. It is represented by the differences in the composition and organization of lipids between the cell membrane and the intracellular membranes. For example, the concentration of cholesterol can reach up to 40 % in plasma membranes while it can be as low as 5% in some organelles like the membrane of the endoplasmic reticulum. [160,161] V.

Fluorescence probing of membrane lipids

The physicochemical properties of biomembranes constitute the basic step to understand their functions. In that aspect, fluorescence microscopy (which provides visual information on the lateral organization) and spectroscopy (which affords data related to molecular interactions, microenvironment, and order) are powerful tools in such analysis. The design of an efficient fluorescent probe will guarantee the successful diagnosis of different parameters (viscosity, polarity, hydration, relaxation, potential measurement) as well as the molecular order and electrostatic potentials at the sites of the probe location. The dye should display strong affinity to the studied site distorting the structure of the membrane. It is usually smaller than the membrane width to detect the steep gradients of parameters across the membrane. [2,[START_REF] Owen | Methods in Membrane Lipids[END_REF]151] V.

Membrane probes

Some parameters that should be addressed while designing a membrane probe are:

• What is the target of the study?

• Does it necessitate insensitive or sensitive dye? With intentiometric or ratiometric response?

• What structure is needed to best fit the biomembrane heterogeneity? Is it charged or not?

In particular, identifying the location and orientation of the probe is indispensable to avoid false conclusions. The simplest assumption is to use polar dyes to study the polar membrane interface, and nonpolar ones for its hydrophobic interior. However, this approach often fails because dyes show heterogeneous distribution in the bilayer. 3-hydroxyflavone and chromone families are neutral and relatively apolar molecules that can be functionalized with suitable chemical moieties to determine their location as precisely as possible. For instance, the introduction of hydrophobic tails decides their affinities and orientation in the membranes, while attaching polar and charged substituents fixes their locations relative to the bilayer. [151] According to the most recent review in 2015, Demchenko classified membrane probes into three main categories (fig. 32). [START_REF] Owen | Methods in Membrane Lipids[END_REF] V.

Dyes partitioning into membranes

This category comprises the probes that do not have similarity in structure to lipids. They are efficient because of their high hydrophobicity that enables their partitioning into the lipid environment without being located in a particular site. Pyrene family is an example of probes that is used to monitor the biophysical dynamics by its excimer formation response. [162] DPH ( 51) is another example used to inquire membrane fluidity by fluorescence anisotropy due to its polarization changes (fig. 32). It has no specific location in the membrane layer. [163] V.

Dyes as phospholipid derivatives

This class includes probes that are analogues to phospholipids or sterols. The fluorophore is usually installed on the polar head or the acyl chain of the phospholipid as in the 3-BODIPY-PC (52). [164] Regarding sterols, it is installed on the oxygen atom or the side chain. The 25-NBDcholesterol (53) is a typical example (fig. 32). [165] O dSQ12S ( 54) is a very recent example of a squaraine dyes rational design with lipophilic and zwitterionic groups (fig. 32). [166] This architecture was able to tune the cell entry allowing selective imaging of the plasma membrane versus the endoplasmic reticulum. The fluorescence enhancement achieved by this dye reached up to 110-fold in biomembranes declaring it as the brightest membrane probe to-date.

VI. Nucleic acids

Nucleic acids, mainly DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are linear biomacromolecules. DNA serves almost passively in storage and transmission of genetic information. The roles of RNA are quite more diverse in regulation of gene expression and protein synthesis. Small noncoding RNA molecules attract interest as potential targets for diagnostics and chemotherapy. [167] This review will be related to DNA with few comments to compare with RNA.

VI.1 Structure of DNA

DNA and RNA are polymers made up of monomeric (deoxy)nucleotides (e.g. 10 3 -10 6 monomeric deoxynucleotides for DNA). A (deoxy)nucleotide is a (deoxy)nucleoside connected to one or more phosphate groups. The (deoxy)nucleoside itself consists of one (deoxy)pentose sugar and one nucleobase. Nucleobases are majorly either purine (adenine (A) and guanine (G))

or pyrimidine bases (thymine (T), cytosine (C), and uracil (U)), (figure 33). [START_REF] Calladine | Understanding DNA[END_REF] Figure 33. Building blocks of nucleic acids In structure, DNA and RNA differ by the sugar and the nucleobases they contain. DNA majorly consists of 2-deoxyribose sugars and A, G, C, and T nucleobases (deoxynucleosides). On the other hand, RNA majorly contains ribose, A, G, C, and U instead of T (nucleosides). [START_REF] Calladine | Understanding DNA[END_REF] The nucleobase is connected to the C-1' atom of the sugar through an N-glycoside bond in βconfiguration; N1 for pyrimidines and N9 for purines. The nucleosides are, in turn, linked to each other through 3´,5´-phosphodiester linkages. [START_REF] Calladine | Understanding DNA[END_REF] An example of the primary structure of an oligodeoxynucleotide (ODN) sequence is presented in fig. 34(A). The sequence is denoted as d(ACT) in the 5'-3' direction.

N N N H N NH 2 NH N N H N O NH 2 N N H NH 2 O NH N H O O NH N H O O (A) (G) (C) (T) (U) O R OH HO BASE ribose: R = OH deoxyribose R = H
• The linear chain folds into a 3-D shape with two topological surfaces: the major and minor grooves. These grooves play essential roles in DNA-ligand and DNA-proteins recognitions.

Three different forms of DNA duplexes exist. They can be distinguished by circular dichroism (CD) spectroscopy. [START_REF] Kypr | [END_REF] They differ in all the structural parameters: termed "B-DNA". Shorter and wider right-handed "A-DNA" form exists under dehydrating conditions whereas left-handed "Z-DNA" form prevails at high salt concentrations and in the presence of polyvalent metal ions. [170]  Quaternary structure Basically, it is the high level organization of DNA into chromosomes. [START_REF] Calladine | Understanding DNA[END_REF] VI.2 DNA synthesis:

Synthesis of DNA can be achieved by using an enzymatic approach, a chemical one, or a combination of both.

Enzymatic DNA synthesis involves the in vitro use of a DNA polymerase and nucleoside triphosphates. While this approach is outside the scope of this work, general comparison to the chemical DNA synthesis is presented in table 2 to demonstrate its limitations precisely with respect to introducing modified nucleobases. [171]

VI.3 The chemistry behind DNA synthesis

Advances in phosphorylation chemistry enabled the facile synthetic access to millions of DNA assays. Chemical synthesis of DNA can produce sequences bearing both natural and chemically-modified nucleobases.

There are four phosphorylation methods successfully engaged in the chemical synthesis of DNA sequences since the beginnings of this domain in 1950s. The phosphodiester ( 61) approach (fig. 35(A)) was more or less abandoned in the 1970s basically for modest yields, numerous possible side reactions, and complications of purification. Here, the other three approaches will be briefly addressed (fig. 35). [172]

VI.3.1 The phosphotriester approach

The defining improvement of this approach compared to the phosphodiester one is the protection of the phosphate in the monomer with 2-cyanoethyl group excluding the side reactions on the free oxygen of the internucleosidic phosphate (62). As a result of the improved selectivity, more efficient coupling agents and catalysts were envisioned. The new chemistry was applied for the first time on solid-support initiating a research era that had led to the full automation of DNA chemical synthesis (fig. 35(B)). [172]

VI.3.2 The phosphite triester and H-phosphoramidite approach

Compared to phosphate (V) reagents, phosphite (III) triesters are faster towards substitution Nowadays, the N,N-diisopropyl-O-cyanoethyl phosphoramidites ( 68) are the standards of the automated solid-support ODN synthesis. [173] The common ways of synthesizing the phosphoramidite monomers are shown in fig. 35(C). They involve:

 Direct nucleophilic substitution of the chlorophosphoramidite (65),

 Weak acid activation of the phosphordiamidite (66) by a weak acid such as 1H-tetrazole (67).

The full solid-support automated synthesis using this method will be discussed in section VI.4.2. The biggest disadvantage of the nucleoside phosphoramidites is their limited stability.

These compounds are air-sensitive and acid-labile. Handling the phosphoramidite of the fluorescent nucleobase analogue remains one of the biggest challenges facing this field. [172,174]

VI.3.3 H-phosphonate approach

The inherent instability of the nucleoside phosphoramidites had led to explore the Hphosphonates class. These compounds are highly stable, economic, and good candidates to achieve efficient couplings. Future advances in the H-phosphonate methods are envisaged to render this approach an optimal replacement to the current phosphoramidite chemistry used in synthesis.

Three successful ways to synthesize the H-phosphonate monomers (70) (71), which in turn condenses with the 5' hydroxyl of the growing sequence. The excess of the activator acyl chloride reacts with the unphosphitylated hydroxyl; hence, saving the capping step used for this purpose in the automated phosphoramidites approach. Finally, the full length ODN is oxidized all at once by iodine establishing the phosphate (V) backbone of the sequence. [172,174]

VI.4 Chemical synthesis of DNA

DNA chemical synthesis can be carried out in solution or on a solid support. [175]

VI.4.1 Solution-phase synthesis

To date, phosphotriester chemistry is the only approach suitable for DNA synthesis in solution. Addition of one or more nucleotides at a time can be performed. Nonetheless, automation has not been yet developed for solution synthesis and laborious purifications are still required after each coupling step. [175]

VI.4.2 Solid-phase DNA synthesis

This well-established methodology is typically achieved on a solid support using an automated instrument. One purification step of the final DNA is needed. The defining advantage of this method is the site-specific introduction of any natural base or nucleobase analogue. The DNA chain is grown stepwise assembling one nucleotide at a time. Therefore, the efficiency depends on every single coupling step. The maximum length of ODNs achieved by this method is around 200 bases. While ODN synthesizers can adapt to all the chemical approaches, phosphoramidite chemistry is the most common strategy because of its high coupling efficiencies although it necessitates the protection of the A (73), G (74), and C (75) nucleobases to avoid critical side reactions (fig. 37). [174] In details, the first nucleoside of the DNA strand is attached to the solid support. Its 5'-OH is protected with a (dimethoxytrityl) DMTr group (fig. 37).

• A) De-blocking (detritylation): The solid is treated with an acid, such as trichloroacetic acid, and washed out. DMTr group is cleaved resulting in a free 5'-OH on the first base.

• B) Base condensation (coupling): The introduced phosphoramidite nucleotide is activated by a weak acid (ex. tetrazole) to remove the iPr2N group and transform into a powerful phosphitylating agent that reacts with the 5'-OH of the first base joining the two bases via a phosphite linkage.

• C) Capping: Some 5'-OH groups remain unbounded. Thus, acetic anhydride and 1methylimidazole are added to block them via acetylation.

• D) Oxidation: The trivalent phosphite linkage is stabilized by oxidation into pentavalent phosphate group using iodine in aqueous basic media.

As a result of the first cycle, one nucleotide residue is added to the ODN strand attached to the solid support. The strand is ready now to enter a second cycle till the programmed sequence is synthesized in full. [174] At the end, treatment with concentrated ammonia solution (rt or 55 °C for 8 h) will cleave the ODN from the solid support and liberate the phosphates from the cyanoethyl groups and the nucleobases from the protecting groups. Milder conditions can be utilized in this postprocessing step if the ODN includes sensitive nucleotide analogues.

Lately, new shorter-step methods are emerging. For example, replacing the DMTr group with an aryloxycarbonyl (carbonate) will shorter the synthesis. That is, both the carbonate protecting with an aqueous mixture of peroxy anions buffered at pH 9.6. [176]

VI.5 Fluorescent labeling of nucleic acids

Fluorescence is the major detection technique in DNA diagnostics, sequencing, and genomics. This environmental-friendly detection technique with exquisite sensitivity has overwhelmed radiography detection. Fluorescence rituals are nowadays practiced in various dimensions such as visualizing nucleic acids within cells by microscopy, [START_REF] Hayashi | Chemical record[END_REF] studying nucleic acid/protein interactions and conformational changes [START_REF] Okamoto | [END_REF]179] , detecting polymerase chain reaction (PCR) products [180] , gel electrophoresis, [181] single nucleotide polymorphism (SNP), [182] etc.. Here, the fluorescent labeling of DNA systems will be briefly discussed. In essence, the reporter fluorophore should be covalently or non-covalently introduced to DNA. It is worth noting that most of these labeling strategies can be also adapted to RNAs.

VI.5.1 Non-covalent or non-specific labeling

Such dyes are not sequence-specific. They are added to visualize DNA as reporters in experimental biology. Numerous dyes already exist.

VI.5.1.1 DNA intercalators

The DNA intercalators mostly share the same general features:

A.

The classical structure of intercalating ligands is planar, aromatic that can fit into the DNA helix without disrupting the H-bonds. These ligands align such that the plane of the rings is parallel to that of the aromatic rings of the nucleobases.

B.

The cationic structure of intercalators, where the rings bear cationic chains or protonated nitrogen atoms, favors electrostatic interactions with the negatively charged phosphate of the DNA structure.

When these dyes intercalate to DNA, their fluorescence efficiencies increase. Examples are ethidium bromide (77) that displays 20-fold increase in fluorescence once bounded and the dimer dyes YOYO (78) and TOTO (79) that are even more sensitive than ethidium bromide (fig. 38). [START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF]

VI.5.1.2 DNA minor-groove binders

The fluorescent probe possesses several aromatic rings connected by single bonds and also contains H-bond donating groups. These features allow the probe to interact with nucleobases exposed into the minor groove. In the bonding state, fluorescence is turned on. The 6diamidino-2-phenylindole (80, DAPI) dye binds to the minor groove mostly at A-T rich regions visualizing the DNA in intracellular imaging. [183] Hoechst stains (81) are also used as binders that exhibit UV excitation and near-blue emission characteristics similar to those of DAPI. [184] The DEAB-TO-3 dye (82) is a recent example that possesses most of the desired attributes for non-covalent labeling of ds-DNA (fig. 38). [185] N

VI.5.2 Covalent labeling

A number of covalent labeling strategies have been developed (fig. 39). [186][187][188][189] Figure 39. Covalent labeling strategies

VI.5.2.1 Strategy A: Fluorophore attached to the sugar-phosphate backbone

The fluorophore is chemically incorporated via a flexible linker (hydrocarbon, poly(ethylene glycol), etc..) to the phosphate group (e.g. 5'-position), to the ribose or to the nucleobase. [171] Some of these markers are commercially available such as the fluorescein derivatives (83).

Other examples are shown in fig. 40 including thiophene (84), BODIPY (85), and pyrene (86) labels. [190][191][192] This type of labeling found huge applications in cellular imaging and DNA sequencing.

However, it has some disadvantages. The flexible linear linker makes it hard to precisely identify

VI.5.2.2 Strategy B: Fluorophore replacing the natural base

This approach can be realized by connecting the fluorophore to the deoxyribose ring or to an anucleosidic moiety.

• Fluorophore connected to deoxyribose (ribose)

The fluorophore connected to deoxyribose can be an aromatic hydrocarbon, a heterocyclic compound, or a natural base mimic. This synthesis is usually demanding since it involves a diastereoselective method for the glycoside bond creation. The attached fluorophore should preferentially be in β-configuration.

The aromatic hydrocarbon nucleobase surrogates do not form Watson-Crick type hydrogen bonds. However, they participate in stacking interactions and can maintain the B-conformation and duplex stability. Many aromatic fluorophores were incorporated by this method.

Naphthalene (87), phenanthrene ( 88) pyrene ( 89), and stylbene (90) derivatives can be excited in the UV region (around 345 nm) outside the range of absorption of the natural nucleobases. [193,194] They exhibit moderate fluorescence efficiencies, which even decrease once they are incorporated into DNA. More extended aromatic systems were also incorporated such asperylene (91) and benzoperylene (92) nucleosides which showed red shifts in absorption and emission and higher quantum yields exceeding 90 % in some cases. Heterocyclic nucleobase substitutes were also successfully introduced to deoxyribose sugar. [186] Some examples are poly- 93), [194] Nile Red (94) [195] and thienylchromone (95) nucleosides. The latter was incorporated into ODNs in our group and was successfully used to study the DNA/protein interactions (fig. 41). [41,43] • Nucleobase fluorescent analogues Nowadays, it is well established that minor chemical modification in the structure of natural nucleobases can change them into highly emissive nucleoside analogues. These fluorophores have the advantage of being comparable in sizes to the natural bases. This helps in maintaining the same type of bonding (Watson-Crick) and hence, not perturbing the DNA conformation.

Pteridines as an example is a frequently used family of fluorescent base analogues in DNA studies. Their QYs can reach up to 30 %. Among this family, DMAP (96) as an adenine analogue and 3-MI (97) as a guanine analogue are two interesting examples. [196] These probes are very sensitive to the environmental and conformational changes (fig. 42).

2-Aminopurine (98, 2-AP) was one of first examples of fluorescent base analogues. 2-AP

became commercially available now. This adenine analogue is red-shifted in absorption to 305

nm. Thus, it can be selectively excited in the presence of natural nucleobases and amino acids.

2AP is widely used since it is highly sensitive to microenvironment. [196] Another method of improving the fluorescence of natural bases is by expanding their conjugated π-systems by adding a vinyl (99) or aromatic group (100) or by fusing an additional aromatic ring (101). [197][198][199] These analogues exhibits high sensitivity to changes in their microenvironments, red-shifted absorptions and emissions, as well as fluorescence efficiency that can reach up to 75 % in aqueous media. 43. [26,200,201]

VI.5.2.3 Strategy C: Chromophore (mainly fluorophore) modifying the natural base

Typically, the fluorophore is linked to the nucleobase through a short spacer. This approach is kind of combination of the previous two methods. The reporter dye will be located outside the DNA helix. The rigidity of the spacer allows controlling the position and orientation of the dye relative to the DNA major or minor grooves. The other advantage is the capacity of preserving the Watson-Crick pairings of bases and hence, the stability and conformation of the DNA helix.

Acetylene moiety is commonly used as a short spacer that preserves the electronic communication between the nucleobase and the chromophore (fig. 44).

The spacer is commonly introduced at the C-5 of the pyrimidines (e.g. 7 of the purines. [42,202] Indeed, 7-deazapurine analogue containing carbon atom instead of nitrogen at position 7 is employed to introduce the spacer at C-7 (e.g. 106 and 107). [203] Position C-8 of purines as in analogue ( 108) is less preferred since it is directly exposed to the phosphate-sugar backbone, so a substituent at this position might lead to destabilize the duplex. [204,205] This approach of labeling was reported in the introduction of fluorenes into ODNs (Section VI.7).

VI.6 Synthetic approaches used in covalent labeling of ODNs

Covalent labeling can be carried out by pre-synthetic or post-synthetic modification of oligonucleotides.

VI.6.1 Pre-synthetic modification

The most common approach is the addition of the fluorophore during solid-phase ODN synthesis using phosphoramidites chemistry. Hence, it requires the synthesis monomers in which the fluorophore is incorporated into a nucleobase, sugar, or an artificial backbone beforehand. The fluorophore should be stable to the conditions of solid-phase synthesis particularly the basic conditions of the deprotection steps. Generally, this method is highly selective and good yielding. It is appropriate to all the three strategies of covalent labeling. The synthesis of the monomer and its stability remain the major burdens.

VI.6.2 Post-synthetic modification

In this case, covalent labeling is performed by attaching a small reactive group into the phosphoramidite building block before the solid-phase synthesis. Afterwards, post-synthetic modification reactions of the active group on the ODN strand with the fluorophore or its precursor are carried out on the solid support or in solution. This approach is suitable to sensitive dyes that do not support the conditions of the DNA synthesizer and to diversityoriented labeling where different fluorophores can be attempted on a single strand. Modification in solution is also appropriate to visualize DNA within cells using developed bioorthogonal ligations. The major limitation is the efficiency of the post-synthetic reaction. It has to be selective, fast, high-yielding, and to tolerate aqueous media and functional moieties of the DNA backbones. [206] Another limitation is the steric hindrance that faces labeling the DNA by the strategy B (that is fluorophore replacing the nucleobase).

Classical post-synthetic ligations involve amine or thiol groups reacting with different moieties such as activated esters, haloacetyls, maleinimides, or disulfides. Modern techniques involve Cu-catalyzed oxidative acetylenic coupling [207] and Pd-catalyzed Sonogashira reactions. [171,208] Regarding bioorthogonal modifications, click chemistry (Cu-catalyzed and Cufree azide-alkyne cycloadditions), [209][210][211][212] Staudinger ligations, and Diels-Alder cycloadditions have been reported. this has led to synthesize competitive machines that produced draft sequence of the human genome. [213,214]

VI.7 Selected sample applications

VI.7.2 Single nucleotide polymorphism (SNP)

SNP is a variation in a single nucleotide at a particular position in the genome that shows an appreciable degree of variation within a population (e.g. >1%). It underlies the biological diversity like the difference in susceptibility to diseases among humans. [215] Hence, SNP detection has been the subject of particular attention for its impact on human health. Two main approaches exist. The first is an enzymatic approach involving DNA ligases, DNA polymerases (e.g TaqMan) or nuclease. The second, involves a complementary synthetic ODN bearing a fluorescent reporter targeting the SNP site (Molecular Beacons, Base-Discriminating Fluorescence -BDF). [202,216] The fluorophore expresses a fluorescence pattern depending on the nucleotides of the SNP site. [182]

VI.8 Fluorene derivatives in the context of DNA applications

To conclude, fig. 45 displays the fluorene derivatives that were described in different investigations of DNA.

Fluorene (109) was found to be a cell-permeable DNA sensitive dye. The combinatorial synthesis reported testing the permeability of 805 different dyes and their sensitivity to DNA.

Fluorene was one out of 8 dyes to show fluorescence sensitivity. [217] The fluorene cationic derivative (110) showed a strong affinity to DNA with high sequence selectivity. The investigation was performed by plasmon resonance and thermal denaturation experiments as well as circular dichroism and UV studies. Fluorene cation demonstrated the ability of selective binding to some sequences and intercalation to others contrary to other cationic species of anthracene. [218] The fluorene molecule was incorporated to a uracil moiety at the C-5 position via an ethynyl linker. Afterwards, the labeled ODNs were prepared via solid-phase synthesis using phosphoramidite chemistry of nucleoside (111). The investigation was extended to incorporate fluorenone moieties into ODNs realizing excimer emissions. Successive publications reported different ODN applications such as hybridization studies, molecular beacons, and SNP detections. [84,219,220] Fluorenes (112) and (113) have been used as small molecule/DNA probes to design FRET pairs validating the efficiency of fluorene family in biosensing. [221][222][223] The push-pull fluorene triphosphate (114) has been introduced into DNA by an enzymatic interaction is visible even by naked eye. [224] Chapter Two

Air-stable palladium catalytic systems for sequential one-pot synthesis of unsymmetrical aminoaromatics

This chapter discusses the methodology we have examined to invest the advances of the palladium catalysis platform in the search of new fluorescent tools. Palladium-catalyzed methodologies have emerged as reliable avenues to generate benign aromatic products. Here, our focus was directed towards five objectives that have not been completely explored in literature: 1) the limitations of introducing aliphatic amines onto fluorene scaffolds to achieve diversity-oriented synthesis (DOS), [225,226] 2) the absence of elaborated reports on selective functionalization of cheap and easily accessible dibromoaromatic scaffolds as starting materials of fluorophores, 3) the increasing demand of finding air-stable catalytic systems that can benefit synthetic chemists and researchers working on the interfaces of science disciplines, 4) the importance of finding new accesses to install different groups (acceptor and donor for example) in one-pot, and 5) the lack of extensive studies related to microwave (MW) enhancement effects on controlled couplings. The screening of various air-stable palladium catalytic systems for selective functionalization of dibromofluorenes is presented in the first part. The scope and the limitations of the proposed methodology (monoamination, diamination, and sequential one-pot couplings) will be discussed in the second part exploring different classes of amines and dibromoaromatics. The described content will appear in The Journal of Organic Chemistry asap.

I. Optimization studies

Our aim was to improvise the Buchwald-Hartwig couplings of aryl amines to bromofluorenes; [61,83,103,129,130] yet to find versatile coupling conditions that work as efficiently upon introducing more challenging aliphatic amines (aziridine and diethyl amine for example).

For that purpose, a stoichiometric mixture of dibromofluorene and N-methylaniline as an acyclic aliphatic-aromatic substrate was chosen. Then, we set out to screen different palladium catalytic conditions. The most successful screening experiments are summarized in the table of fig. 46 displaying the changed parameter of each entry. Their corresponding results are depicted as bar graphs showing the GCMS conversion and the selectivity of mono/di aminated products (115/116) The monodentate ligands (L4-8) mainly led to the diaminofluorene (116) (entries 3-8). The chelating bidentate ligands (XantPhos and BINAP) resulted in the mono-aminated fluorene (115) as the major product (entries 9-10).

The absence of the undesired reduced products with most ligands can be rationalized since dialkylbiaryl Buchwald ligands (L5-8) display some bidentate character like BINAP forming 4coordinate complexes that suppresses the competing β-hydride elimination. [227] The favored diamination with these Buchwald-type ligands could have resulted from their electron-rich density that facilitates the oxidative addition and their bulkiness that accelerates the reductive elimination. [128] Accordingly, the produced mono-aminated fluorene of a catalytic cycle might enter a subsequent catalytic cycle via oxidative addition of its second C-Br bond with relatively fast kinetics preventing its isolation as final product.

On the other hand, the distinct mono-amination using BINAP ligand is remarkable. Although computational studies could provide a mechanistic insight, calculations with BINAP are highly demanding. Many intermediates comprising a very bulky ligand with four flexible phenyl groups in different conformations would be involved. A recent study reported different mechanistic possibilities in the catalytic cycle of BINAP. [228] Among all of them, it has been hypothesized that the hemilabililty of this bisphosphine may switch to a monodentate ligand as a possible route.

Our experimental data suggest that bidentate ligands impose a definite influence on the selectivity of mono-amination contrary to monodentate ones. Other parameters related to BINAP are the steric bulkiness and the turnover-limiting step in the catalytic cycle. It is known that the turn-over limiting step of the arylbromide coupling with amines using bisphosphines is the conversion of the Pd(0) complex to an arylpalladium (II) halide complex. [229,230] This ratedetermining step could have played a role as well in dictating the selectivity. One perspective of this work is to carry out some DFT calculations with our collaborators to probe the mechanism of this reaction in depth.

Cs2CO3 as a representative of carbonate base demonstrated a moderate conversion (entry 11).

t-BuOK and t-BuONa almost gave the same efficient results (Entries 10 vs 12). Pd(dba)2 was mono-selective; however, the reaction did not reach to completion after 18 h (entry 13). The observed slower kinetics is consistent with the more sterically-hindered Pd(dba)L2 species. [231] The cross-coupling did not work at room temperature (entry 15). Dioxane (entry 14) mostly afforded the mono-product, nonetheless the reaction was cleaner in toluene. MW activation gave the shortest reaction time (entries 10 vs 16). The best molar ratio of the [Pd]:ligand was optimized as 1:3 with a loading of 4 mol% (entries 10 vs 17). A lowering to 1 mol% inevitably slowed down the reaction rate. Premixing the catalytic system significantly accelerated the kinetics presuming an efficient activation of Pd(0) complex. It is noteworthy that premixing becomes a prerequisite in the case of BINAP. [232] The mono-amination conditions were established as follows: Pd(OAc)2 (4 mol%), BINAP (12 mol%), NaOtBu (1.1 eq), amine (1.2 eq), toluene MW irradiations for 45 min (entry 16). Doubling the catalytic loading along with excess of amine (entry 18) led to complete diamination.

II. Scope of the selective monoamination reaction

Next, the scope and limitations of the selective mono-amination were examined. The chosen mono-amination conditions were applied to introduce a variety of amines (fig. 48).

The selective mono cross-coupling was efficient on pyrrole (117, 80 %), cyclic secondary amines (119-123, 50-81 %), and primary amines (125-126, 67-82 %). To our delight, the diethylamine was also coupled efficiently (124, 62 %).

Figure 48. Scope and limitation pattern of the selective mono-amination of 44; yields in parenthesis. [a] Under thermal heating conditions; [b] Reaction performed at 1-gram scale; [c] GCMS conversion to the product. Most reactions proceeded to completion in 45 mins under MW irradiation. Piperidine (120) and azetidine (122) were irradiated twice for 45 mins, their isolated yields remained moderate (50-62 %). The reaction was efficiently scaled-up to one gram (124-125). Considering the unprotected piperazine (127), low conversion of starting material was obtained. Surprisingly, no dimerization was observed. This might open up new prospects for conjugation avoiding the additional steps of protection-deprotection of piperazine. The reaction conditions were limited on imidazole (118). Regarding carbamate coupling (128-129), it required higher palladium catalytic loadings, which yielded the debrominated mono-coupled derivative as the major product. Since carbamates present a different reactivity: t-BuOH, NMP, and THF were likewise screened without success. [233,234]

III. Diamination of fluorenes

As discussed previously, minor modification of the catalytic system allows for the preparation of diaminofluorenes (fig. 49). [235] A control reaction by using a large excess of amine (5 eq.) evidenced no inhibition of the process. This does not support the hypothesis that amines might bind as ligands to Pd in this case. [236] A range of diaminofluorenes (116 and 130-133) was prepared in good to excellent yields (61-89 %). The employed conditions revealed to be effective and tolerant towards various model aliphatic and aromatic amines.

IV. Synthesis of unsymmetrical fluorenes

Next, we examined the synthesis of unsymmetrical fluorenes using a one-pot 2-step protocol.

In this case, MW conditions were too harsh and generated inseparable mixtures. On the other side, thermal heating proved to be promising. We targeted two sequential pathways; step. Likewise, it can deliver a vinylaminofluorene as an intermediate of numerous target materials such as push-pull carbaldehydes via oxidative cleavage, polyfluorenes and copolymers via metathesis or Mizoroki-Heck cross-coupling. [237][238][239] The limitations of this type of desymmetrization (fig. 50) are reflective of those of selective mono-amination (e.g. compare products 138 and 118). The choice of amines [240] that worked efficiently for monoamination (fig. 48) would lead to an efficient sequential one-pot C-N/C-N and C-N/Stille couplings. Transmetallation seems easier than incorporation of amine into the Pd complex in the catalytic cycle of the second step. This makes the vinyl moiety more facile to introduce without isolating the intermediate of the first-step. The purification of vinylaminofluorene revealed to be also easier than separation of a mixture of different possible aminofluorenes. This has led to the vinylpyrryl product (137) isolated as the highest yield of this series (76 %).

As a result, the sequential C-N/Stille couplings realized products (134-139, 46-76 %) using the optimized conditions of entry 8 (fig. 50). Specifically, once the mono-aminated product was formed (12-16 h), tributylvinyltin and a subsequent catalytic loading were concomitantly added.

On the other hand, the sequential couplings of two distinct amines had yielded products ( 2. Pd(OAc) 2 (4 mol%), BINAP (12 mol%), NaOtBu (1.1 eq.), amine 2 or tributylvinyltin (1.1 eq.) ,

Toluene, 100 o C, 12-16 h the reaction showed poor yields when it was not followed by a subsequent addition of the catalytic system. The addition of a second stoichiometric amount of the base is mandatory. We chose to concentrate on the double addition to obtain good yields, as many factors can directly deactivate the palladium catalyst outside the glove box and this challenging reaction aims to synthesize useful materials.

Fig. 51 compares the one-pot approach (69 %) to the classical two-step synthesis (75 %) of compound (139). The good yield demonstrates that the developed procedure is cost-and timeefficient in synthesizing interesting products.

V. Scope of the selective conditions on dibromonaphthalene, dibromopyridine, and dibromothiphene

To explore the limits of our methodology on other aromatic families, the optimized conditions of monoamination, diamination, and the sequential cross-couplings of two variant groups were applied to unactivated 2,7-dibromonaphthalenes, 2,5-dibromopyridine, and 2,4dibromothiophenes as models of electron-neutral, electron-deficient, and electron-rich dihalogenated aromatic scaffolds respectively.

The results are illustrated in fig. 52. Regarding the electron-neutral naphthalene moiety, all the optimized catalytic systems worked as adequately as on fluorenes. Aromatic and aliphatic amines were introduced with mono-or di-selectivity as desired furnishing (142-145, 65-83 %).

The sequential synthesis of naphthalenes bearing varied combinations of amines was fruitful and generated compounds (146-147) in appreciable yields (53-64%). The electron-deficient pyridine reacted in higher yields (148-153, 57-94%). ( 152) was prepared as an example of the sequential addition in significant yield (71 %). It is worth noting that 2,5-dibromopyridine underwent monoamination with 0,5 mol% Pd(OAc)2 catalytic system or even with excess amine (5 eq.) in the absence of palladium catalyst. Nevertheless, di-or sequential amination of this heteroaryl compound required the developed catalytic conditions.

The electron-rich 2,4-dibromothiophene appeared as a scope limitation.

Arylaminothiophenes were obtained successfully and were stable to isolate (154-155, 42-54 %). Amination was still selective on such electron-rich aromatic scaffold. Considering saturated cyclic amines (156-158), the mono/di conditions were selective with acceptable conversions (47-72 %). However, these electron-rich products proved to be unstable upon isolation.

VI. Application: a near-IR push-pull sensor

The strength of this method permitted to access in a 3-step simple protocol (fig. 53) the NIR probe (159; λabs = 395 nm and λem = 640 nm in chloroform, fig. 54). This multi-component reaction clearly asserts the versatility of our synthetic approach. The synthesis was concise and

VII. Conclusion

To conclude this chapter, the new methodology is summarized in fig. 55. The selective functionalization of dibromoaromatic scaffolds using air-stable palladium catalytic systems was carried out. This methodology involved rapid mono-and di-selective Buchwald-Hartwig aminations via microwave irradiation. The conditions were optimized to couple sequentially different moieties in one pot. Couplings with a wide scope of amines allowed accessing a new library of symmetrical and unsymmetrical derivatives (37 examples). Using this versatile method, a near-IR push-pull sensor was prepared installing the electron-donating and withdrawing groups through a multi-component reaction. These conditions revealed to be gram-scalable, and adaptable to various groups; hence, promoting facile use in synthetic chemistry. The optimized conditions will be explored more in the DOS-synthesis of a library of Few studies in literature have rationalized the structure-photophysics relationships in the field of chromophores to a certain extent. [113,[241][242][243][244] In the case of 2,7-disubstituted fluorenes, such investigations are still needed. The diverse multi-step syntheses could be a reason. In this chapter, we set to optimize the synthetic routes to diversify the electron-withdrawing group from an aldehyde, ketotriazole or succinyl to methylenemalonitrile, or benzothiadiazole. Then, we have built on our developed Pd-catalyzed methodology to vary the donor from aliphatic or aromatic amines to saturated cyclic amines ranging from aziridine to azepane (fig. 56). First, the synthesis of a library of 16 push-pull fluorene dyes will be described. Among them, several derivatives bear conjugation anchors to follow the effect of further couplings on their spectroscopic properties for biolabeling applications. In the second part of the chapter, we will present the photophysical characterization, the theoretical TD-DFT calculations, and different correlations enclosing structure-property relationships. The main two objectives of this part of the thesis are: 1) to find the optimal D-π-A combination in terms of visible absorption, laser excitation accessibility, brightness, Stokes shift, and prospects for bioconjugation, and 2) to accomplish concise and scalable synthetic accesses to the dyes that will be used in the next chapters.

N.B: The order of the chemical structures still follows the systematic numbering of the thesis, but the discussion will refer to abbreviating the target push-pull dyes as (PP1-16) and the intermediate (161) as (I-6) since this material has already been published. Additional TD-DFT calculations, data, and correlations are provided as supplementary information (SI-XIII) in the experimental part.

I. Synthesis I.1 Variation of the electron-withdrawing group (EWG)

Different EWG with negative mesomeric or/and inductive effects were screened.

Dimethylamine was chosen as the donor. Considering PP1 and other fluorenes in the literature, we noticed that upon converting the formyl EWG into an acetyl moiety, the absorption coefficient decreased and the maximum was blue-shifted from the visible into the UV range. [60,85] These drawbacks limit the utility of such dyes in bioconjugation. Therefore, our major objective was to introduce an EWG bearing an attachment point that retains the vital photophysical properties of the dye once bound as a biosensor. We envisaged the succinyl and propioloyl linkers as being compatible for peptide and click 1,3-dipolar couplings, respectively. Next, we incorporated benzothiadiazole and methylenemalonitrile known to display forceful EW abilities. [62,115] The robust synthesis developed to access the fluorene derivatives PP1-6 is outlined in fig. 57.

The synthesis was achieved by conventional methods, [60,85] namely C9-dimethylation, then regioselective mono-nitration followed by iron-mediated reduction to afford the aminofluorene (36) in 49% yield over three-steps. Reductive amination using NaCNBH3 and paraformaldehyde provided the key adduct (160) with the dimethylamino (D) group in 87% yield. (160) was used to disclose a variety of acceptors in addition to the interesting intermediate I-6 with a vinyl group to describe the effect of this group on the design. Primarily, halogen-metal exchange with n-BuLi on adduct (160) followed by treatment with DMF gave PP1 in 70% yield. Grignard addition of the ethynyl group to PP1 followed by oxidation using MnO2 at 0 °C generated the ethynyl ketone PP2 in an excellent yield (98%). Noticeably, dimerization was observed when this reaction was allowed to proceed at room temperature for longer times. To test the effect of conjugation, PP2 was converted to the keto-triazolyl derivative PP3 in 70% yield with n-hexyl azide under copper-assisted azide-alkyne Huisgen cycloaddition (CuAAC).

Next, the methylenemalonitrile was introduced by Knoevenagel condensation on the formyl of PP1 in the presence of Al2O3 to yield PP4 (85%). [62] Stille coupling of intermediate (160) and tributylvinyltin gave I-6 in very good yield (80%). The target PP5 was obtained by coupling 5bromo-2,1,3-benzothiadiazole to stannyl fluorene generated in situ (82%). Lastly, the succinic linker was obtained by the formation of the Grignard of fluorene (160) at 60 °C and the subsequent addition of succinic anhydride in THF at 0 °C to give compound (167) in 60% yield.

As a preliminary example of peptide functionalization, [245] n-butyl amine was ligated to this compound using DIC and HOBt as activators to form PP6 in 72% yield. Reaction conditions: i) KOH (4 eq.), KI (0.1 eq.), MeI (2.3 eq.), DMSO, rt, overnight, 93%; ii) HNO3, AcOH, rt, 2 h, 73%; iii) Fe (3 eq.), NH4Cl (2 eq.), EtOH(aq.), 80 °C, 4 h, 72%; iv) (CH2O)n (5 eq.), NaCNBH3 (3 eq.), AcOH, rt, overnight, 87%; v) Pd(PPh3)4 (5 mol%), tributylvinyltin (1 eq.), toluene, 80 °C, overnight, 80%; vi) n-BuLi (1.2 eq.), DMF (2 eq.), THF, -78 °C, 3 h, 70%; vii) a. Ethynylmagnesium bromide (1.4 eq.), THF, 0 °C, 2 h, b. MnO2 (15 eq.), DCE, 0 °C, 1 h, 98% (2-steps); viii) n-HexN3 (1.1 eq.), CuI (2 eq.), DIEA (5 eq.), AcOH (1 eq.), DCE, 3 h, 70%; ix) malonitrile (2 eq.), Al2O3 (4 eq.), toluene, overnight, 70 °C, 85%; x) a. Pd(PPh3)4 (10 mol%), Bu3SnSnBu3 (1.3 eq.), toluene, 100 °C, 3 h, b. Pd(PPh3)4 (10 mol%), 5-Bromo-2,1,3-benzothiadiazole (2 eq.), 100 °C, overnight, 82%; xi) Mg (2 eq.), BrCH2CH2Br, succinic anhydride (2 eq.), THF, 60%; xii) DIC (1.1 eq.), HOBt (1.1 eq.), Et3N (1.1 eq.), n-BuNH2 (1.5 eq.), THF, rt, overnight, 72%.

I.2 Variation of the electron-donating group (EDG)

To evaluate the effect of the donor, a concise 2 Subsequently, Buchwald-Hartwig aminations of (169) were carried out using Pd(OAc)2, BINAP, and NaOtBu in toluene, under MW radiation (300 W / 180 °C) for 30 mins; synthesizing PP7-14 in 22-86% range of yields (fig. 58). Generally, the defined route was rapid, efficient, and gram-scalable.

II. Spectroscopic studies II.1 -Acceptor series

Unsymmetrical D-π-A fluorenes differing by their EWGs were characterized by UV and fluorescence in a wide range of solvents. [31] The photophysical properties in selected solvents are summarized in table 3. . Synthetic pathway leading to PP7-14. i) Cl2CHOCH3 (1.5 eq.), ZrCl4 (1.5 eq.), CH2Cl2, 1 h, 0 °C, 77%; ii) Amine (1.2 eq.), t-BuONa (1.2 eq.), Pd(OAc)2 (5 mol%), BINAP (10 mol%), Toluene, MW (300 W/ 180 °C), 30 min. PP7-14 are systematically numbered (170-177) respectively. Table 3. Spectroscopic properties of selected fluorophores with various-EWG and the same dimethylamino donor. Solvent ET(30) [b] Fixed Donor (NMe2) / Varied-Acceptor [a] λ, ΔλSS [c] (nm)

PP1 PP2 PP3 PP4 PP5 PP6 I-6
ε (10 3 .M -1 cm -1 ) [d] 35 Reported values are the averages of two or more independent and reproducible measurements, ±1 nm for wavelengths. [b] Reichardt's parameter was employed to scale the polarity of the solvents. [31] [c] For convenience, Stokes shifts (Δλ = λem-λabs) were expressed in nm rather than in cm -1 . Excitation wavelength used was the absorption maximum. [d] Molar extinction coefficients (ε) in dioxane, relative standard deviations are equal to or less than 5%.

[e] Quantum yields (Φ) were determined using quinine sulfate in 0.1 M HCl solution (λex = 350 nm, Φ = 0.54) [246] or 4'-(dimethylamino)-3-hydroxyflavone in ethanol (Φ = 0.27) [247] as references, relative standard deviations are equal to or less than 15%. [f] Not determined, the compound was insufficiently soluble in water. PP1 [60,85] with dimethylamino (D) and formyl (A) substituents was set as the reference. The Excitation wavelength used was the corresponding absorption maximum.

Presenting benzothiadiazole acceptor, PP5 revealed two distinct absorption maxima around 320 and 450 nm (fig. 60). This dye was only emissive in aprotic and non-polar solvents with mega-Stokes shifts (130-258 nm). This character is quite uncommon for solvatofluorochromic dyes in apolar media; [2,[START_REF] Lakowicz | Principles of Fluorescence Spectroscopy[END_REF] hence, it might open new perspectives in applications in the future.

Among all the considered acceptors, the methylenemalonitrile moiety PP4 presented the most accentuated EW abilities translated in the largest red-shift of both maxima (Figure 59). [248,249] The absorption was located in the blue spectral window (467-501 nm, table 3) (table 1, fig. 60). Reichardt's ET (30) scale was used to evaluate the sensitivity of the dyes to polarity, which followed the order: PP4 > PP3 > PP1≈PP6 (slope comparison in fig. 61). all the tested solvents except for PP4, for which deviation from linearity was observed when protic solvents were included.

perfectly
The emission maximum was proportionally red-shifted along the range of polarity. This quantitative parameter largely accounts for the dielectric constant of the solvent and its H-bond donor ability. [31] The strong positive solvatochromism in the dyes' emission emphasizes the large ICT character of their excited states.

Lippert-Mataga model and Transition dipole moment calculations

The positive solvatochromism was further substantiated using the Lippert-Mataga model. [250,251] The Stokes shifts were plotted as a function of the orientation polarizability in aprotic solvents since this model only takes into account the dipole-dipole interactions.

The linear plots shown were obtained with aprotic solvents according to the Lippert's eq. 7,

! -! = 2 ℎ Δ ( ! -! ) ! ! Equation 7
Where h (= 6.6256 x 10 -27 ergs) is the Planck's constant, c (= 2.9979 x 10 10 cm/s) is the speed of light, and a is the radius of the Onsager's cavity. νA and νF are the wavenumbers (cm -1 ) of the absorption and emission, respectively, Δν is the Stokes shift (cm -1 ), Δf is the Lippert's parameter, and μE and μG are the dipole moments of the excited and ground states, respectively. 62. The differences between the dipole moments of the ground and excited states (µE-µG) were 12.9, 12.6, 13.5, and 14.1 D for PP2, PP6, PP3, and PP4 respectively (SI-XIII). These results confirm the increase of the dipole moments in the excited states.

PP1, PP4, and PP6 were then investigated as representative examples in acetonitrile, chloroform, and toluene by DFT and TDDFT calculations. [START_REF] Frisch | TDDFT calculation: Gaussian[END_REF] The DFT optimization essentially gave the geometry close to planar (fig. 63). Simulations satisfactorily reproduced the entire absorption spectra with slight red shift compared to the experimental values. Calculations showed that the electronic transitions arose from an electron promotion between the HOMO and the LUMO. In the frontier molecular orbitals, the HOMOs were localised at the fluorene and partially on the donor and the LUMOs at the acceptor and the benzene ring attached to it. Thus, the main contribution of the transition (ICT) dipole is in the plane of the molecule along the D-A axis.

To sum up, these fluorophores exhibited important λ-shifts to the red in both their

II.2 -Varied-amine series

Different cyclic amines were characterized using the carbaldehyde as a fixed acceptor. The main data are listed in table 4.

Table 4. Spectroscopic properties of fluorophores with various amines and the same formyl acceptor Solvent ET(30) [a] Varied-Amines / Fixed Acceptor (-CHO) [ PP7 was established as the negative control given its blue-shifted absorption and emission and its extremely low quantum yield (< 1%). Such characteristics were expected due to the weak Normalized intensity, a. u. A common property of solvatochromic dyes with strong ICT character is their low quantum yields in water. The azetidine donor was reported to overcome this limitation and to prevent the quenching of the sensors in aqueous media. [START_REF] Grimm | [END_REF]254] It was proposed that this donor can disfavor the formation of the poorly emissive, twisted internal charge transfer (TICT) states in water.

Unfortunately, applying this strategy on fluorene family was not successful. PP11 bearing the azetidine donor was not emissive in aqueous media. This quenching can not be resulting from the formation of H-aggregates since the absorption maxima of the fluorene derivatives were not blue-shifted in H2O vs. other solvents. [92] An explanation could be that water molecules are acting as an electron-trap for the excited species. [255] PP12 was noticeably emissive contrary to the reported aziridine derivatives of other families like rhodamine. [START_REF] Grimm | [END_REF] Compared to the other members of the series, PP12 was characterized by reduced quantum yields in nonpolar solvents and considerable hypsochromic shifts in absorption and emission (table 4 and fig. 66). It was proposed that the electrondonating ability of this three-membered heterocycle was diminished [256] due to the increased s character of the orbital of nitrogen atom's lone pair and the structurally-and electronicallyenforced pyramidalised nitrogen. [257] This proposal was ascertained with the bent DFT structure of PP12 compared to the coplanar fluorene-piperidine PP9 (fig. 68). The sum of the three C-N-C bond angles (304° versus 333° for trimethylamine) confirms the pyramidalized geometry of the aziridine nitrogen and the planar geometry (348° versus 360° for trigonal geometry) of the piperidine nitrogen. Control analysis of aziridine versus 2-methylaziridine derivative proves that the added methyl has no effect on the geometric parameters (SI). [258,259] The µE-µG of PP12, Interestingly, the strong quenching in water and the important brightness of these dyes in environments of distinct polarities provide the opportunities to develop turn-on sensors upon shielding from water. Aziridine PP12 appeared as the weakest donor among all the considered aliphatic amines. On a side note, aziridine is a popular functional group for cycloadditions in the area of fullerene-fluorophore organic devices. [130,[258][259][260] The straightforward access to PP12 is highly valuable in replacing the long employed classical routes. A conjugation of aziridine should convert this dye into a 5-membered ring adduct that can be detected by a red shift in spectroscopic properties.

determined
The presence of another heteroatom in the donor group was studied with morpholine PP13

and its piperazinyl analogue PP14 comprising a second amine for subsequent peptide coupling.

Compared to PP9 with a similar 6-membered amine ring, the introduction of a nitrogen or oxygen atom blue-shifted the absorption maxima indicating that the negative inductive effect of the second heteroatom had imposed tangible charge redistribution (table 4). The emissions of PP13-14 showed bathochromic shifts with little deviations relative to the maxima of PP9.

Accordingly, with blue-shifted absorptions but yet relatively comparable emission maxima, PP13-14 demonstrated larger Stokes shifts. The molar absorptivities in dioxane were 25.10 3 and 33.10 3 M -1 cm -1 respectively. The quantum yields of these two dyes followed the same trends as the reference compounds PP9 and PP1 and fell nearly in the same range depending on the solvent used. The differences in the dipole moments (µE-µG) of PP15-16 (14.4 and14.9 D) were comparable to that of PP4 (14.1 D) as the highest among all of the studied dyes. The large dipole differences assert the strongest electron-withdrawing ability of the methylenemalonitrile in agreement with DFT calculations. The quantum yields of PP4, PP15, and PP16 strongly correlate with the ET (30) scale confirming the close relationship between the quantum yield and the sensitivity of the CT-type excited states to polarity (figure 71). The decrease of the emission intensity in polar solvents is typical for solvatochromic dyes with strong ICT character. It was advanced that the reduced energy gap between the excited and ground states in polar solvents favored internal conversion and thus non radiative energy release. [261] This linear trend can help to anticipate the emissive behaviour of the dyes with the strongest transition dipole moment in a medium of known polarity.

II.3 Hammett correlation

The correlations of the absorption and emission maxima to the σP Hammett substituent constants were assessed. [START_REF] Frisch | TDDFT calculation: Gaussian[END_REF] This approach could complement the challenging predictions of emission of fluorophores with CT in the excited state by TD-DFT. [START_REF] Silverstein | [END_REF] Thus, four representative molecules were selected: PP1 as a reference, PP4 as the strongest acceptor, PP12 as the weakest donor, and I-6 as a control. In parallel, the linear trend between emission maxima and σP values was noticed exclusively with the dyes presenting large solvatofluorochromism (PP1, PP12, and PP4, fig. 73). Indeed, since the emission occurs through charge-transfer mechanism, this correlation is consistent with the observation that stabilization of the excited states was highly sensitive to polarity. To verify these predictions, the absorption and emission maxima of a reported fluorene dye (diethylamino D and formyl A) were calculated in three solvents (ethanol, acetonitrile, and chloroform). [60,85] The anticipated absorption maxima were in agreement with those recorded experimentally (table 5). The emission maxima were slightly red-shifted (10-20 nm) compared to the experimental values. The error was within the acceptable margin. Hence, this paradigm is an interesting tool to predict spectroscopic properties in the prerequisite design of advanced probes.

III. Conclusion

In

Chapter Four

Fluorene-based membrane probes and cell imaging

Fluorescence imaging has revolutionized the way to observe cellular structures and to understand their functions. [264] In that aspect, small molecule dyes have attracted major attention in advanced applications since their size might be less perturbative than fluorescent proteins and nanoparticles. Further, the chemistry and photophysics of an organic label can be finely tuned. Among organic labels, the turn-on fluorescent probes are extremely attractive for imaging since they ensure simple and convenient use without the need to wash the excess of reagent. In addition, their signal-to-noise ratios are expected to be high. The fluorescent probe should also display high brightness, photostability, and selectivity to the target in order to maximize the imaging resolution. As a matter of fact, the access to organic probes that fulfill all these meticulous requirements is highly challenging from both perspectives of tuning the design and its synthesis. Considering the structure-property relationships and the optimized synthetic routes of chapter 3, we decided on the most prominent properties in terms of visible absorption, laser excitation, accessibility, brightness, Stokes shifts, and positive solvatofluorochromism to access membrane probes. This chapter will present the synthesis of 3 new advanced analogues of PP3 comprising a) a polar deoxyribosyl head (F1), b) a lipophilic long alkyl chain (F2), and c) an amphiphilic anchoring group to fix the dye at the membrane interface and prevent its internalization. Then, we will discuss the spectroscopic characterization of the three dyes, their ability to probe large and giant unilamellar vesicles (LUV and GUV) of different lipid compositions, and the imaging of HeLa cells.

I. Introduction

Considering the characteristics of PP3 dye in particular from chapter 3 (fig. 74), this probe absorbs in the violet (400 nm) and demonstrates an ICT character amongst the highest.

Moreover, PP3 exhibits bright and red-shifted emission (ΔλSS > 100 nm) in aprotic solvents. The largest displacement of its emission is shown in polar solvents where the dye turns almost nonemissive in water. Additionally, the click 1,3-dipolar conjugation of the propioloyl linker adopted in PP3 synthesis confirmed the conservation of the desired optical properties upon conjugation.

This promising ynone group for biolabeling and the turn-on property upon shielding the dye from water render this design of a fluorene dye a good candidate for sensing biomembranes and probing their lipid domains. Regarding this application, there is a strong demand to realize new probes that overcome the drawbacks of the existing environment-sensitive ones such laurdan (180), a lipohilic analogue of prodan (17), and Nile Red ( 14) derivatives (fig. 74). [265][266][267] An effective membrane probe should present the following rigorous properties; it should be excitable in the visible, stain exclusively the plasma membrane with high contrast, distinguish the liquid domains of the membrane by changing its fluorescence color, intensity, or lifetime, show minimal internalization and interference from cell auto-fluorescence, and operate in the visible and NIR spectral window (above 700 nm) open for multi-colour imaging. Searching for probes with the particular attribute of responding specifically to lipid domains can inevitably help in deciphering the lateral heterogeneity of the cell membranes described by the lipid raft hypothesis. [151,268] Lipid rafts are hitherto under debate and are believed to be the origin of fundamental biological processes and diseases.

II. Synthesis

The clickable hydrophobic fluorene core (163) was prepared as described in chapter 3. The synthesis of the azido derivatives (182-184) was carried out by methods reported in literature (detailed in SI-XI). [166,269,270] Next, the clickable ynone ( 163) was converted to the keto-triazolyl derivatives (F1, 80 % yield) with β-azidodeoxyribose, (F2, 75 %) with n-dodecyl azide, and (F3, 61 %) with the azido amphiphilic chain via CuAAC reactions (fig. 75). The optimized click conditions involved CuSO4•5H2O (0.5 eq.), sodium ascorbate (0.7 eq.), DMF/water (3/1), at room temperature for 1-3 h.

III. Photophysical characterization of F1-F3

We first investigated the impact of the triazole substituent on the UV/visible and fluorescence properties in a set of aprotic and protic solvents with large range of E T ( 30) parameter (table 6).

The absorption and emission spectra are shown in fig. 76. [a] as table 3, [b] 20 mM buffer, pH 7.4.

The 3 dyes absorbed strongly in the violet around 400 nm (35.10 3 -38.10 3 M -1 .cm -1 in dioxane).

Their absorption maxima demonstrated little dependence on the polarity change (Δλabs< 20 nm)

displaying almost no solvatochromism. This is an evidence of the absence of ICT character in their ground states contrary to dyes presenting solvent-dependence of their absorption spectra.

An important example of this class of dyes with ICT character in their ground states is the Nile Red (14). However, their emission maxima were red-shifted with large Stokes shifts (e.g. F1:

from 107 nm in toluene to 256 nm in MeOH for Δλss). In sharp contrast to absorption, their emission exhibited high sensitivity to solvent changes. The marked red shift upon the increase in the solvent polarity is in line with the data of the parent compound PP3 (Table 6).

A)

III.1 Hydration study of F1

We next explored the influence of hydration on the emission of dye F1 in mixtures of dioxane and water. LUVs are the simplest models to study biomembranes. Sphingomyelin (SM) and cholesterol (CL) were used to produce liquid ordered membrane phase (Lo); while, liquid disordered membrane phase (Ld) was obtained with the unsaturated phospholipid, dioleoylphosphatidylcholine (DOPC). [151] First, the optimal probe:lipid ratio was determined with F1 by varying the concentration of SM/CL LUVs. saturates at lipid:probe ratio about 500:1. This infers that nearly all the dye molecules were bound to lipids above this ratio. These data also verify the efficient binding of the probe to the lipid membrane, which is about 3 times more favorable than that of the Nile Red derivative probe. [265] It is worth noting that the binding effect on fluorescence was instantaneous; the same spectra were reproduced after the samples were left for 5, 10, 15 min at rt or at 60 °C.

III.2 Photophysical characterization in large unilamellar vesicles of different lipid compositions

Table 7. Investigations in LUVs [a]

[a]Same as table 3; Excitation wavelength used was 390 nm.

Next, the ability of dyes F1-F3 for probing LUVs of different compositions was tested. The emission spectra were recorded (fig. 80). The main spectroscopic properties are given in table 7. The absorption maxima of F1-F3 in different lipid vesicles were around 400 nm. By contrast, their emissions disclosed apparent dependence on the lipid composition and liquid phases of the LUVs. Binding of F1-F3 to lipid vesicles resulted in considerable increase of the fluorescence intensities. Depending on the lipid composition, the quantum yields varied from 57-68, 24-63 and 59-99% for F1, F2, and F3 respectively (table 7). Remarkably, F2 and F3 attested an increase in quantum yields up to three folds in liquid ordered phases (SM/CL and SM/DOPC/CL). In addition, F1-F3 showed a significant shift of their emission to the blue (e.g. from 545 to 487 nm) when lipid phase changed from Lo (SM/CL) to Ld (DOPC). This is consistent with the fact that the Lo phase is less hydrated as a consequence of the higher level of lipid packing as compared to the Ld phase. [151] The differences in the emission (Δλem) between the two extreme states were 23, 68, and 21 nm for F1-F3 respectively. Thus, F2 demonstrates the highest sensitivity that compares favorably to laurdan and Nile red probes with Δλem of 48 and 36 nm, respectively. [153,265] On the other hand, lower sensitivity to phase changes for F1 and F3 are related to the presence of groups that anchor the dye at the interface. The response of the environment-sensitive probes to phase variation is frequently associated with changes in the location and orientation of the fluorophore in membranes. [152] Therefore, the anchor groups in F1 and F3 may limit the freedom of the dye, thus decreasing its sensitivity. Nevertheless, the sensitivity of F1 and F3 to the different phases could be sufficient for imaging applications.

Solvent

III.3 Photodegradation studies

Afterwards, we investigated the time-dependence photodegradation of F1-F3 in their free forms in (fig. 81A), bound to lipid vesicles (DOPC) (fig81B), and in ethanol (SI-XIV) under continuous illumination of the samples. Xylene was chosen as a representative high boiling point apolar solvent mimicking hydrophobic environment. Indeed, photostability of fluorosolvatochromic dyes in apolar media is a major concern since it represents a severe limitation in imaging applications. This is particularly critical in lipid membranes since the commonly used dyes (prodan, laurdan, and Nile red) photobleach rapidly in this apolar environment. [60,153] Prodan (17) and the fluorenecarbaldehyde derivative (162) were used as references (dyes shown in fig. 74).

F1-F3 portrayed different behaviors in xylene and DOPC vesicles (fig. 81). In xylene, the emission intensities were more than 90% for F1 and F3, about 70% for F2 and the aldehyde, and 50% for prodan after 1 h illumination. Once bound to DOPC vesicles, the intensities were more than 90 % for F1, F3, and the aldehyde, but 45% for F2 and prodan after 1 h. First, these results confirm the superior photostability of the fluorene dyes compared to prodan. Noticeably, F1 and F3 demonstrate the highest photostability in both tested conditions. This higher photostability without oxygen depletion indicates that generation of reactive oxygen species, which often accounts for photobleaching of small organic dyes, is limited for fluorene dyes. [264,271] F1 and F3 were more photostable compared to F2 probably because they bear polar groups that could increase the local polarity of the environment in solvent and in lipid bilayer. The lower photostability of F2 parallels its shown higher sensitivity to detect lipid order.

A) Xylene

In polar media like ethanol, the dyes demonstrated the highest photostablility in accordance with the typical increase in the singlet-triplet energy gap which render intersystem crossing less favorable and leads to less free oxygen radical species. [60,153] Their emission intensity remained above 95 % after 1 h.

IV. Imaging

IV.1 Imaging giant unilamellar vesicles (GUV) with F3

The probe to stain membranes and distinguish lipid domains in model LUVs. [265] IV.

Imaging cells with F1-F3

Fluorescence microscopy was next used to examine the staining of cells with the probes F1- observed with laurdan and NR12S probes. [265,272] By contrast, F1 and F2 dyes were distributed differently (fig. 84A-D). The fluorescence intensity image indicates that F1 and F2 penetrate into the cells and mainly stain the cytoplasm (fig. 84B and84D). It should be noted that the fluorescence intensity of F2 in cells was relatively low, which is probably related to very low solubility of this dye in water. Unlike F1 and F3, it probably precipitates before staining the cell membranes. The ratio images further suggest that the intracellular compartments stained in green represent membrane close to the liquid disordered phase as found in endoplasmic reticulum and other membrane-containing organelles (fig. 84A and84C). The magenta color observed well for F1 probe, which matches the liquid ordered phase, corresponds well to the cell plasma membrane staining. The results are in line with those obtained recently with internalizing solvatochromic laurdan and pyrene probes. [153,272,273] Altogether our results support the original design of F3 to obtain the desired probe for staining the plasma membrane without internalization. On the other hand, F1 can stain both cell plasma membranes and cytoplasm showing a clear contrast in their lipid organization.

A) F1 B) F1 C) F2 D) F2 E) F3 F) F3

V. Conclusion:

In conclusion, we have demonstrated the ability of the fluorene family to be a cornerstone of donor in radiative FRET pair application will be also enclosed as a preliminary application. Using Dy681 as the acceptor, the FRET has demonstrated a ratiometric turn-on in NIR region with one of the widest shift to-date (∆λ = 300 nm). This study will be completed in due-time.

I. Fluorene label by anulcleoside approach

Building on the aldehyde (A) extension into a succinyl linker and the optimized peptide coupling (PP6) discussed in chapter 3, our first approach to covalently-label oligonucleotides was to ligate the succinyl moiety of (167) to an anucleosidic moiety "(S)-3-aminopropane-1,2diol" (189, fig. 85-86). This anucleoside linker was developed by the group of Antopolsky [201] in 2001 but pervasively used by Wagenknecht group to synthesize artificial DNAs labeled with various fluorophores ever since. [200,[274][275][276][277] Their reports show insignificant effect of the "anucleoside" group on the duplex stability. Indeed, they have published a list of universal base analogues that supports the hypothesis of the loss of duplex stability mainly originating from removal of the base rather than sugar replacement by anucleosidic units. [278] The "Antopolsky" linker is basically a 1,2-diol fragment with one primary hydroxyl for selective protection with 4,4'-dimethoxytrityl (DMTrCl) reagent and one secondary hydroxyl for phosphitylation. It comprises as well an amine to introduce the dye via a peptide coupling. Thus, this first choice was envisioned to evaluate the preliminary integrity of the push-pull fluorene in ODNs avoiding To study the photophysical properties of the fluorene-anucleoside derivative (190), we performed the peptide coupling of ( 167) and ( 189) using DIC and HOBt as activators (73 %, fig. 86). The emission solvatochromism of this adduct literally spanned the full range of 450-630 nm with increasing the polarity (fig. 87, SI-XV). The quantum yields were 10 % in water, 36 % and 42 % in methanol and ethanol respectively, and 51-82 % in all the tested aprotic solvents displayed. The large solvatofluorochromism of (190) and its emissive character in aqueous media were promising and overcoming the drawback of its UV absorption. So, we proceeded further into synthesizing its phosphoramidite FM1.

Protection of (190) with DMTr group proved to be very difficult. Different reaction conditions were tried (DMF, pyridine, ACN, DBU, Et3N, rt, 60 °C, 130 °C) and none of them was successful. Therefore, we protected the primary OH of aminopropanediol ( 189) before the amide bond formation. The optimized synthesis of FM1 is summarized in fig. 88.

The NH2 group of (189) was protected using CF3COOCH3 (98 %). Next, the DMTr group was selectively introduced to the primary OH group after treatment with DMTrCl in anhydrous pyridine generating (192) in 78 % yield. The amino group was deprotected by methanolic ammonia solution (98 %). [201] The product (193) was coupled afterwards to the succinyl linker of fluorene (167) giving the fluorene anucleosidic mimic (194) in 71 % yield. HBTU was more efficient in this peptide ligation than DIC-HOBT. [245] Product (194) acetonitrile in the presence of Hünig's base (DIEA). [173] Despite the cautions in handling this product, the conversion remained modest and the final product (FM1), which is quite sensitive to oxidation and to hydrolysis, [172] was isolated in 30 % yield after very quick FC purification.

FM1 was obtained as a mixture of two diastereoisomers due to the introduction of a chiral phosphorus atom. The structure of the phosphoramidite was confirmed by 1 H and 31 P NMR spectroscopy, and LCMS.

FM1 was freeze-dried from dry benzene solution and was processed into automated solidphase DNA synthesis using standard protocol with minor modifications (SI-IV). To evaluate the stability of the dye under deprotection conditions, four 15-mer ODNs incorporated by this label (abbreviated as M) in the middle of each sequence were synthesized (table 8): AMA and TMT with "DMTr-on" mode, GMG and CMC with "DMTr-off" mode. The "on" mode signifies that the ODN contains the 5'-DMTr group after ODN synthesis completion on solid phase. The "off" mode means that DMTr is cleaved using the synthesizer by cycling Cl3CCOOH on the solid support for few minutes. The coupling efficiency was monitored by the trityl profile and revealed to be low (30-60 %). This can be attributed to the chosen lengthy linker that might have interfered in the coupling step of the fluorophore to other natural nucleotides during the synthesis.

The ODNs were cleaved from the solid support using concentrated aqueous ammonia solution at rt for 2 h. The ammonia solution was left to stand overnight to deprotect the sequences. The The purified ODNs were characterized by Maldi TOF/TOF, UV-absorption, and fluorescence.

Unfortunately, the mass of the ODNs showed either truncated sequences or a difference of 15 a.m.u. from the expected one (table 8). The 15 mass difference is compatible with the loss of a methyl group either from the amino substituent or fluorene at C-9 position. Despite the mass defect, we will discuss the spectroscopic data of the first batch of ODN labeling for the significant differences from the other labeling strategies that we used later (vide infra).

Table 9. Spectroscopic data of the M-labeled ODNs Samples [a] λabs(nm) λem(nm) ΔλSS(nm) Φ (%) [b] pH [a] 1 μM of ODN in buffer pH 7.0 (10 mM cacodylate, 150 mM NaCl); [b] Quantum yields determined using quinine sulfate in 0.1 M HCl solution (λex = 350 nm, Φ = 0.54) [246] and 7-(dimethylamino)-9,9-dimethyl-9H-fluorene-2-carbaldehyde (λex = 390 nm, Φ = 0.46 ) [85] as references, ±2% mean standard deviation.

TMT
The absorption and emission spectra of the ODNs (table 9, fig. 90) are consistent with the incorporation of the fluorene label into them. The absorption maximum was about 20 nm blue shifted in ODNs in comparison to the value of the free dye 190 (350 vs. 370 nm). This further suggests the donating ability of the amine was decreased supporting the hypothesis that the mass defect is originating from the loss of the methyl from the amine moiety and not from the C-9 position. The alkyl substituents at C-9 position are demonstrated to have minor effect on spectroscopic properties as compared to that of donor groups in push-pull molecules. [52] Given the unexpected mass, the low efficiency of the fluorophore incorporation into ODNs, and the difficulties in the convergent 10-step synthesis of the FM1, we have decided to change the strategy of the labeling to track the chemical group that is not compatible with solid-phase synthesis and that is fragmenting in the process.

II. Fluorene label connected to deoxyribose sugar

Accordingly, the fluorene dye still replaces the natural base but is connected to a deoxyribose moiety instead of the anucleoside linker. The retrosynthesis was based on "click-chemistry" similar to that of the membrane probes (chapter 4). Three fluorene-labeled phosphoramidites (FM2-4) were planned with controlled variation of the fluorene precusor changing the diethyl amine of FM2 to dimethyl amine in FM3 and the dimethyl substituents of the C-9 position into difluoro atoms in FM4 (fig. 91).

II.1 Synthesis of FM2-4

FM2 was prepared by 7-step convergent synthesis starting from 2,7-dibromo-9,9dimethylfluorene ( 44), (fig. 92). Selective C-N coupling on (44) installed the diethyl amine as the donor (57 %), after which metal-halogen exchange reaction with n-BuLi in DMF introduced the formyl (A) group resulting in the push-pull dye (195, 60 %). Grignard addition followed by oxidation gave the clickable synthon (196, 55 %). The optimized CuAAC conditions (chapter 3) with the 3,5-p-ditolyl-2-deoxyribosyl azide established the clicked fluorene-sugar product, FM3 was prepared from the clickable adduct (163, chapter 3) and following the same consecutive steps (iv-viii, 24 % yield over 4 steps) used in the synthesis of phosphoramidite (FM2), (fig. 93). The full synthetic route is described in the experimental part (SI-XII). NMR and HRMS were employed to characterize the diastereomers of each phosphoramidite before administering the ODN synthesis (SI). The results were indisputable; degradation was not taking place under the conventional inert and anhydrous conditions before the solid-phase synthesis. Different DNA oligomers labeled with the X, Y, and Z fluorene dyes were synthesized using respectively FM2, FM3 and FM4 and the "DMTr-off" mode. The coupling profiles on the synthesizer were generally better than those of the anucleosidic moiety FM1. In some cases, the coupling of the artificial base attained 90 % value. Selected sequences were treated and purified (fig. 95 and SI) with the same procedures described before and characterized by Maldi TOF/TOF (table 10). documented. [280] In line with the proposed mechanism, the cleavage starts through a radical process that involves the departure of a proton from the alkyl substituent followed by single electron transfer (SET). It is known, in particular, that the departure of a methyl proton, which is The absorption and fluorescence spectra of the diethylamino fluorene nucleoside (197) were recorded in a set of solvents to be compared to compound (190) and to the dimethylamine donor in (F1), (discussed in chapter 4). Dye (197) has similar spectroscopic features to those of (F1). The major difference imposed by the diethyl amine was the slight red-shift in absorption by 6-20 nm to the visible region (>400 nm) in different solvents in line with an increased inductive effect. The emissions of the two dyes appeared comparable in their maxima with a marginal enhancement in fluorescence efficiency by diethyl amine (table 11, fig. 96).

Table 11. Spectroscopic properties of 197

[a] Same as table 3.

Polar protic solvents quenched fluorescence like in F1 case. The quantum yields of (197) were 2 % in methanol and 8 % in ethanol. In these polar protic solvents, the dye exhibited dramatic red shifts to the NIR region.

Increasing the percentage of methanol to dye (197) dissolved in dioxane solvent shifted the position of the emission band to the red and resulted in increased quenching of the fluorescence (fig. 97).

Solvent εmax [a] 32.10 3 M -1 .cm -1

Water λAbs (nm) 415 DMSO λAbs (nm) λEm (nm) -λEm (nm)

ΔλSS [b] (nm) -ΔλSS (nm)

Φ (%) - Φ (

III.2 pKa determination of (197)

The pH dependence of absorption was studied for the naked dye (197) to calculate its pKa (fig. 98A). Under acidic conditions (pH = 2), the amine is protonated resulting in absorption maximum of 320 nm. As pH increases, the percentage of the neutral form of (197) increases translated in the appearance of a second band at 415 nm. The absorption maximum related to the protonated form completely disappears after pH = 7.

Figure 98. pH dependence of absorption of dye 197

Absorption intensity, a. u. Absorption intensity, a. u.

Wavelength, nm pH

A) B)

pKa of the dye can be extracted at λmax/2 of the plot of absorption intensity as a function of pH.

The experimental pKa of the naked nucleoside was around 5.4 (fig. 98B).

III.3 Photophysical characterization of the X-labeled ODNs

The UV and fluorescence of the synthesized ODNs in their single-and double-stranded forms were recorded in cacodylate buffers. The spectroscopic properties in addition to the melting temperatures of the duplexes are summarized in table 12.

Considering the ss-ODNs, TXT and CXC revealed to be completely non emissive in buffer of pH 7 contrary to GXG sequences (fig. 99). When T or C but not G flanked X, their absorption maxima were blue-shifted (~330 nm) inferring that the flanking bases and the poly-anionic charge DNA had an additional effect on the pKa of the fluorene nucleoside. Each sequence has supposedly a distinct pKa different from the naked nucleoside and from the fluorene in other sequences. Indeed, calculations and experimental studies suggest the presence of regions of increased proton density around DNA that can reach 2 orders of magnitude greater than that of bulk solvent. [281] Accordingly, rising the pH should return the label to its emissive nonprotonated form that absorbs at ~425 nm (fig. 99). We have determined the pH at which each sequence fluoresced the maximum. CXC and TXT were characterized in cacodylate buffer of pH = 8.4, whereas GXG was not protonated and still emissive at pH = 7 suitable for studies at physiological pH. The wavelengthes of the emission were marginally varied (+/-10 nm).

Figure 100. Fluorescence of ss and ds CXC and TXT sequences. Excitation wavelength used was 440 nm.

The characterization of the single-strand and hybridized GXG oligomer at pH=7 was different.

First the ss-GXG was barely emissive (2 %) with more significant red shifts by 10 nm in absorption and 25 nm in emission compared to TXT and CXC (fig. 101 and table 12). To my supreme delight, the dye GXG composition was efficient in base-discriminating the opposite thymidine and cytidine in the duplexes. The fluorescence intensity of the duplex DNA was increased by 6 folds (Φ = 11 %) with a pronounced blue shift in emission from 675 nm in ss-GXG to 640 nm when complemented with CCC sequence. The CTC hybridization resulted in the same shift in emission and 3-fold enhancement in quantum yield (6 %). These characteristics validate that the fluorene design can be useful in detection of target genes and single nucleotide polymorphism (SNP) typing. [182] To conclude, the red emission and the modest fluorescence efficiencies entail that neither the flanking bases in ss DNA nor the different types of hybridization in dsDNA were able to impose a significant hydrophobic environment and that the fluorene nucleoside is likely exposed to hydrophilic media in all cases. However, the change in the fluorescence wavelength and intensity demonstrated a valuable sensitivity of our fluorene dye with high ICT character in particular environment of DNA (e.g. GXG). ICT dyes are usually limited on this detection in hydrophilic media. Therefore, the brightness of this fluorene dye is satisfactory relative to its small size and high ICT character. Furthermore, the GXG sequence offered an easy-detectable change in its emission maximum (> 30 nm) in response to structural changes in DNA. Detection using probe X depends on a change of the fluorescence signal rather than on the thermal stability of duplexes. In this sense, probe X can be compared to the few BDF probes developed by Saito and co-workers for genotyping of SNP. [179,203]

III.4 CD and thermal denaturation studies

The driving forces of double helix formation between complementary strands are the hydrophobicity of the nucleobases, the base-stacking and the complementary hydrogen bonding. [170] Hence, it is important to study the stability of the duplex once an artificial derivative is introduced as a nucleobase surrogate. For that reason, the fluorene conjugate was located in the middle of the sequences to avoid any structural perturbation of the duplex due to end effects. We assessed the influence of the fluorene label on the secondary structure of the duplexes by monitoring the temperature-induced absorbance changes at 260 nm and recording the circular dichroism (CD) spectra (SI-XV). All the tested hybridized DNAs demonstrated the same conformational signature with negative and positive peaks at around 250 and 280 nm respectively, consistent with a B-type helix.

The thermodynamic stability of the ds-DNA was evaluated using the DNA melting temperature (Tm). Tm is defined as the temperature at which half of the DNA strands are in the double-helical state and half are in the random coil states. A larger Tm value infers a higher thermodynamic stability of the duplex. [283] Absorbance of the ds-DNA sample at 260 nm was recorded as a function of temperature. The melting curves were converted into a plot of α versus temperature, where α represents the fraction of single-strands in the duplex state (SI-XV). The melting temperatures were extracted from these curves using the mathematical analysis described in literature. [283] The representative curves of GXG duplexes are depicted in fig. 103.

Thermal denaturation studies showed that the hydrophobic fluorene impose some destabilization to the duplexes compare to the corresponding wild type duplex (table 1, ΔTm= -

III.5 FRET

Many features predict that the push-pull fluorene can meet the requirements of an emissive donor in a radiative Förster Resonance Energy Transfer (FRET) pair with an acceptor dye; compatible absorption with readily available violet laser (405 nm), important extinction coefficient (3.2 x 10 4 M -1 .cm -1 ) relative to its small size, most probable rigid conformation allowing the possibility to control the orientation of the emissive dipole and its distance from the acceptor. [1] In that aspect, the obtained B-conformation of the DNA helix offers an exclusive architecture for this application. The mega-Stokes shifts can be employed to excite acceptors in the red or near-IR such as Dy681 and Dy781 (structures and main properties in the SI). We hypothesize that using the label X as the donor might build a turn on FRET pair where it can act as the light collector and interact with an acceptor as the emitter. FRET should operate at the condition the FRET rate (kT) is superior to the non-radiative rate (knr) of the donor (fig. 104). Important to note, the FRET rate is dependent to the distance separating the donor and the acceptor and thus should be controlled and tuned using the DNA architecture. Upon formation of the duplex between GXG and the complementary sequence labeled by Dy681, an efficient energy transfer was realized with emission maximum at 725 nm. The achieved shift of 300 nm is not reported to-date in literature. We are conducting more studies in the lab to confirm this principle.

As the Dy681 concentration was gradually increased, an increase of the emission band was displayed resulting from the inherent duplex formation (fig. 105). Saturation was reached upon adding more than 1eq. (100 % fig. 104) of Dy681. Comparing the addition of 1 eq. Dy681 to GTG and GXG clearly demonstrate the efficiency of the FRET. In the absence of the donor, the reduced emission of Dy681 in the single and double stranded forms is due to the fact that Dy681 also absorbs at excitation wavelength (about 400nm) albeit less efficiently than the donor X (fig. 106). Comparing the addition of 1 eq. Dy681 to GTG and GXG clearly demonstrates the efficiency of the FRET. In the absence of the donor, the reduced emission of Dy681 in the single and double stranded forms is due to the fact that Dy681 also absorbs at excitation wavelength (about 425 nm) albeit less efficiently than the donor X (fig. 106).

Conclusion and perspectives I. General Conclusion

The goal of this work was to find new fluorene-based push-pull dyes as powerful biosensors.

The rational designing of novel probes that meet the rigorous demands of biological applications Next, we used the Pd-catalyzed methodology to study the effect of varying the electron donating ability on the spectroscopic behavior of the fluorene push-pull design. Introduced donors comprised aliphatic, aromatic, and saturated cyclic amines ranging from aziridine to azepane. To screen the electron withdrawing abilities of the acceptor, various reactions were performed including amongst others: Stille coupling, CuAAC, and peptide coupling that afforded to install the aldehyde, ketotriazole, succinyl, methylenemalonitrile, and benzothiadiazole groups. Among the synthesized dyes, conjugation attachment points were fixed to follow the effect of further couplings on the optical properties for biolabeling purposes. Photophysical

II. Perspectives

Considering the Pd-catalyzed methodology, a complete one-pot synthesis seems promising.

First, the exact role of the second catalytic addition should be understood by screening separately different ligands, bases, and catalytic combinations. Next, the introduction of different coupling moieties with one palladium loading could be attempted to evaluate the results. A Suzuki coupling partner is interesting to advance as well. An asymmetric version of the reaction testing S, R, and rac-BINAP is likewise possible.

Regarding the distinct behavior of BINAP on the monoselectivity of aminations, DFT calculations will provide an insight to comprehend the mechanism. As mentioned, computational studies with BINAP are highly challenging.

With respect to the fluorene library, electrochemical characterization involving cyclic voltametry is now in process on the sideway of the thesis. This is extremely interesting in fluorene case knowing that they are widely used in solar cells and OLEDs.

The synthesized membrane probes can be used in two-photon investigations and fluorescence microscopy. Indeed, fluorenes have large 2P absorption cross-sections at common wavelengths around 800 nm and high photostabilities. The probes can be further taken to biology interfaces with cytotoxicity and invivo applications

The fluorene DNA label is currently studied in FRET applications with dy681 and dy781 leading to 300 and 390 nm shift between the excitation and emission maxima respectively. The related experiments are not finished at the time being for technical limitations of our fluorometer in emission range after 800 nm. Nonetheless, this will be certainly one of the records in FRET applications.

The DNA labeling at this stage should combine the anucleosidic linker (for the higher hydrophobic environment it imposed) with diethyl amine donor (for its compatibility with solidphase synthesis) to test the outcome of a new marker, which is highly prospective.

Postsynthetic labeling by fluorene dyes was already started successfully by CuAAC reaction of PP2 with commercial sequences bearing azido moieties. Three labeled sequences were achieved efficiently in 24 h compared to presynthetic labeling route that spanned a whole thesis. This is simply a marvelous alternative. It avoids the tedious work of DNA synthesis and allows for screening different fluorene dyes in limited time, which in turn will lead to enhanced fluorene biosensors and applications

As side prospective projects, PP2 was also bioconjugated to spermine and amino acids to study their intercalations and DNA/protein interactions. Completing this story is still ongoing.

Last, Fluorenone derivatives were prepared with interesting excimer properties that are currently in the stage of photophysical characterization.

Résumé long

Le développement pointu de la technologie implique souvent les interfaces de disciplines scientifiques prétendues distinctes. La recherche portant sur les domaines interdépendants de la chimie de synthèse, calculs théoriques, photophysique, biophotonique et imagerie a évolué En conclusion, le but de cette thèse était de progresser une étape dans les domaines de la conception et la synthèse de nouvelles sondes fluorescentes qui répondent aux conditions rigoureuses et exigeantes des applications biologiques mentionnées ci-dessus.

Le corps de la thèse se compose de 5 chapitres et une conclusion indiquant les perspectives d'avenir.

• Le premier chapitre est l'introduction qui indique l'arrière-plan de ce travail.

• Le contenu du deuxième chapitre a été publié récemment dans "The Journal of Organic All solvents for absorption and fluorescence experiments were of spectroscopic grade.

Absorption spectra were recorded on a Cary 4 spectrophotometer (Varian) using 1 cm quartz cells. The samples used for spectroscopic measurements contained ≈ 0.1% v/v of the stock solvent. Fluorescence spectra were recorded on FluoroMax 4.0 spectrofluorometer (Jobin Yvon, Horiba). Excitation wavelength was used as mentioned in the corresponding experiments. Stock solutions of the push-pull dyes were prepared using dioxane (< 10 % v/v of DMF was added in case of insoluble dyes). The samples used for spectroscopic measurements contained ≈ 0.1% v/v of the stock solvent.

II. Lipid vesicles

Dioleoylphosphatidylcholine (DOPC) and cholesterol (CL) were purchased from Sigma-Aldrich.

Bovine brain sphingomyelin (SM) was from Avanti Polar Lipids (Alabaster, AL). Large unilamellar vesicles (LUVs) were obtained by the extrusion method as previously described. [287] Briefly, a suspension of multilamellar vesicles was extruded by using a Lipex Biomembranes extruder (Vancouver, Canada). The size of the filters was first 0.2 μm (7 passages) and thereafter 0.1 μm (10 passages). This generates monodisperse LUVs with a mean diameter of 0.11 μm as measured with a Malvern Zetamaster 300 (Malvern, U.K.). LUVs were labeled by adding aliquots (generally 2 μL) of probe stock solutions in dimethyl sulfoxide to 1-mL solutions of vesicles.

Since the probe binding kinetics is very rapid, the fluorescence experiments were performed a few minutes after addition of the aliquot. A 20 mM phosphate buffer, pH 7.4, was used in these experiments. Concentrations of the probes and lipids were generally 0.3 or 0.4 and 100 μM, respectively.

Giant unilamellar vesicles (GUVs) were generated by electroformation in a home-built liquid cell (University of Odense, Denmark), using previously described procedures. [265] A 0.1 mM solution of lipids in chloroform was deposited on the platinum wires of the chamber, and the solvent was evaporated under vacuum for 30 min. The chamber, thermostatted at 55 °C, was filled with a 300 mM sucrose solution, and a 2-V, 10-Hz alternating electric current was applied to this capacitor-like configuration for ca.

VII. Denaturation studies and melting temperatures

Melting curves were recorded by following the temperature-dependence of the absorbance changes of the sample (1 μM concentration of each strand). Absorption spectra were recorded in a Peltier thermostated cell holder on a Cary 4 spectrophotometer (Varian). Wavelength for detection was 260 nm. The pathlength of cell was 1 cm. The temperature range for denaturation measurement was 5 -80 °C. Speed of heating was 0.3 °C/min. Cacodylate buffer pH 7.0 was used (10 mM cacodylate buffer, 150 mM NaCl). The melting curves were converted into a plot of α versus temperature, where α represents the fraction of single-strands in the duplex state. The melting temperatures were extracted from these curves after differentiation as described elsewhere. [283]

VIII. Circular dichroism

Circular dichroism spectra were recorded with 1 μM solution of the canonical dsDNA and labeled dsDNA (fluorene label with variation of its opposite) in the respective cacodylate buffer at 25 °C on a Jasco J-810 spectropolarimeter.

The products will appear in the SI according to the respective order of discussions in chapters 2-5 and not in ascending order of numbers.

IX. Chapter 2 synthetic procedures

, 6H). 13 Br N

Br N were added to a previously-dried reaction tube containing a magnetic bar. The tube was purged with argon for 3 cycles using Schlenk technique. The mixture was dissolved in toluene (0.1 M) and stirred for 15 min at rt under argon. Then, the dibromo aryl reagent (1 eq.) was added and followed by 15 mins further stirred for 15 mins (at rt or 100 °C for better activation). Finally, the amine (liquid or dissolved in toluene) (2.2 eq.) was added, and the reaction mixture was irradiated in the microwave oven at 300 W/ 180 °C for 1 h (or classically heated at 100 °C in an oil bath overnight for thermal activation). The reaction was monitored by TLC and GCMS until complete conversion. The resulting mixture was cooled down to room temperature, diluted by CH2Cl2, and filtered over a pad of Celite ® . The volatiles were removed under reduced pressure, and the residue was purified by silica gel column chromatography to give the desired product. 6-bromo-N,N-dibutylpyridin-2-amine (148): [288] Following GP-A.

Eluent for flash chromatography (CyHex, Rf = 0.21) providing 148 as a yellow solid (98 mg, 0.34 mmol, 88 %). 149): [289] Following GP-A. Eluent for flash chromatography (PE/DCM = gradient up to 9:1, Rf = 0.5) providing 149 as a yellow solid (84 mg, 0.36 mmol, 94 %). This procedure requires the preparation of two reactions in two previously-dried tubes.

First tube: Pd(OAc)2 (3 mg, 0.011 mmol, 4 mol%), t-BuONa (30 mg, 0,32 mmol, 1.1 eq.), and BINAP (21 mg, 0,034 mmol, 12 mol%) were added to a previously-dried reaction tube containing a magnetic bar. The tube was purged with argon for 3 cycles using Schlenk technique.

The mixture was dissolved in 3 mL of toluene (0.1 M) and stirred for 15 min at rt under argon.

Then, dibromofluorene 44 (100 mg, 0,287 mmol, 1.0 eq.) was added followed by 15 min further stirring at 100 °C. Finally, aniline (30 mg, 0,32 mmol, 1.1 eq.) was added, and the reaction mixture was heated at 100 °C in an oil bath. The reaction was monitored by TLC and GCMS until bis-aminated product started to appear (14 h).

Second tube: Pd(OAc)2 (4 mg, 0,017 mmol, 4 mol% relative to 1.5 eq. of 5-bromo-2,1,3benzothiadiazole), t-BuONa (45 mg, 0,47 mmol, 1.1 eq.), and BINAP (32 mg, 0,051 mmol, 12 mol%) were added to a previously-dried reaction tube containing a magnetic bar. The tube was purged with argon for 3 cycles using Schlenk technique. The mixture was dissolved in 4 mL of toluene (0.1 M) and stirred for 15 min at rt under argon. Then, 5-bromo-2,1,3-benzothiadiazole (92 mg, 0,43 mmol, 1.5 eq.) was added followed by 15 min further stirring at 100 °C. Finally, bis(tributyltin) (249 mg, 0,43 mmol, 1.5 eq.) was added, and the reaction mixture was heated at 100 °C in an oil bath for 4 h.

Note: this second reaction tube was prepared around 10 h after the beginning of the first reaction.

Then, another loading of the catalytic system (4 mol% [Pd]/ 12 mol% L/ 1.1 eq. t-BuONa) was re-added to the first reaction tube followed by the content of the second tube (2 eq.). The final mixture was stirred at 100 °C overnight. The reaction was cooled down to room temperature, quenched with NaOH (1N) and stirred for additional 30 min. The organic layer was extracted with DCM (2x) and the combined extracts were washed with water (3x), dried over magnesium sulfate, and evaporated under reduced pressure. The crude product was purified by flash (s, 6H). 13 160 (1.00 g, 3.16 mmol, 1 eq.) was dissolved in dry THF (15 mL). To the resulted clear yellow solution, nBuLi (1.52 mL of 2.5M solution in Hexane, 1.2 eq.) was added dropwise at -78 °C under inert atmosphere. Reaction mixture was stirred for 1h before a yellow precipitate was formed. Then, DMF (0.49 mL, 6.32 mmol, 2 eq.) was added dropwise and the formed solution was stirred for additional 2 h at -78 °C. The reaction was allowed to warm up to room temperature and stirred for 1 h, quenched with 1 M aqueous HCl and extracted with EA (2x). Organic layer was dried over MgSO4 and evaporated in vacuum. The residue was purified by column chromatography. Eluent (EA/CyHex = 1:9, Rf = 0.47) to produce compound PP1 (588 mg, 70 %) as a yellow powder. The mixture was stirred at the same temperature until completion of the reaction monitored by TLC (2h). Then, a saturated solution of aq. NH4Cl (3 mL) was added and the aqueous phase was extracted with EA (3x5 mL). The combined extracts were dried (magnesium sulfate) and evaporated to yield the corresponding propargyl alcohol. The crude propargyl alcohol was batched to the next step without further purification. To a stirred suspension of MnO2 (0.5 g, 15 eq.) in DCE (8 mL), was added dropwise a solution of the residue in DCE (3 mL). The mixture was stirred for 1 h at 0 °C, filtered through a pad of Celite ® , dried over MgSO4, and concentrated in vacuo to yield the pure ketone PP2 (320 mg, 98 %, two steps). Rf = 0.55, solvent (PE/EA = 6:1).

1-azidohexane (S5).

To a solution of sodium azide (1.73 g, 26.6 mmol, 1.1 eq.) in DMSO (53 mL), was added 1-bromohexane (4.00 g, 24.2 mmol, 1 eq.) and the resulting solution was stirred overnight at rt. The conversion was monitored by 13 C-NMR until completion (20 h). The mixture was poured into 100 mL of water and extracted with diethyl ether (2x30 mL). The combined organic layer was dried over MgSO4 and concentrated at reduced pressure to get a yellow liquid, which was further purified by distillation to afford the title product S5 as colorless oil (2.28 g, 74 %). 1 H-NMR (200 MHz, CDCl3, δ): 3.18 (t, 3 J=7.0 Hz, 2H), 1.52 (q, 3 J=7.0 Hz, 2H), 1.36-1.09 (m, 6H), 0.82 (t, 3 J=7.0 Hz, 3H). 13 Then, DIEA (0.18 mL, 1.4 mmol, 5 eq.), CuI (78 mg, 0.41 mmol, 2 eq.), and AcOH (12 μL, 0.1 mmol, 1 eq.) were sequentially added. The reaction mixture was stirred for 3 h at rt, filtered over Once Grignard reagent started to form, the mixture was stirred at room temperature for 1 h.

Then, the resulting solution was transferred dropwise, via a cannula over 30 min, to a solution of succinic anhydride (505 mg, 5.0 mmol, 2 eq.) in dry THF (12 mL) at -10 °C under argon. The reaction mixture was stirred for 2 h at 0 °C, and warmed up gradually to rt, before quenching by aq. HCl (1M) solution. The organic layer was extracted with chloroform (2x), dried over magnesium sulfate, filtered and concentrated under reduced pressure. Hz, 2H, H2') 1.44 (s, 6H, 2CH3). 13

N-butyl-4-(7-(dimethylamino)-9,9-dimethyl-9H-

fluoren-2-yl)-4-oxobutanamide (168/PP6). 167 (50 mg, 0.15 mmol, 1 eq.), DIC (26 μL, 0.16 mmol, 1.1 eq.), HOBt (25 mg, 0.16 mmol, 1.1 eq.), and Et3N (23 μL, 0.16 mmol, 1.1 eq.) were solubilized in 2 mL dry THF and stirred for 30 mins. nBuNH2 (23 μL, 0.22 mmol, 1.5 eq.) was then added and the reaction was stirred overnight. The crude was washed by NaHCO3 (aq.) and extracted with DCM. The organic layer was washed by water, dried with magnesium sulfate, and reduced under pressure. Purification was done by FC eluent ) and clickable anchor/sugar (1.2 eq.) were dissolved in a mixture DMF/water (3/1). CuSO4•5H2O (0.5 eq.) and sodium ascorbate (0.7 eq.) were dissolved in an eppendorf with water and the solution was mixed until the mixture turned yellow/orange. The content of the eppendorf was then transferred into the reaction vial and stirred at room temperature for 1 h. The volatiles were then removed under vacuum and the crude product was purified by gel filtration chromatography.

The azido sugar was prepared with slight modifications from published procedures, and the final product was characterized herein in the text. [166,269,270] To a solution of 5.0 g (37.3 mmol) of 2-deoxy-D-ribose in MeOH (60 mL) was added methanolic hydrogen chloride. The reaction mixture was stirred at room temperature for 25 minutes and neutralized by adding solid sodium bicarbonate (2.0 g). After filtration, the methanol was removed under reduced pressure.

The mixture was re-dissolved in pyridine (30 mL), cooled to 0 °C and p-toluoyl chloride (11 mL, 80 mmol) was added dropwise, and stirred at room temperature overnight. The reaction mixture was diluted with cold water (80 mL) and extracted 3 times with CH2C12. The combined organic layers were washed twice with saturated aqueous solution of NaHCO3, once with 2N HCI solution and once with water, dried on MgSO4, and evaporated.

To the resulting colored sirup (13.0 g) dissolved in acetic acid (20 mL) was slowly added a saturated solution of HC1 in acetic acid at 0 °C and stirred 1 h after the formation of yellowish precipitate (3 h in total). 50 mL of cyclohexane was added and the solid was filtered off, washed Published procedure [166] 1-azido-3-chloropropane (0.602 g, 5.016 mmol, 1 eq) and dodecyl(methyl)amine (1.000 g, 5.016 mmol, 1eq) were dissolved in 15 mL of CH3CN. The solution was then heated at 80°C in a sealed flask (to avoid evaporation) for 6h. The solvent was removed with the help of a rotary evaporator and the crude product was purified by column chromatography with CH2Cl2/MeOH (5 to 10 % of MeOH) as eluent. A yellowish oil was obtained, yield 38%. General procedure (GP-K) of DMtr protection for the synthesis of (S14, S16, and S23). To a stirred solution of the clicked deprotected deoxyrobose sugar (1 eq.) in a mixture of dry DMF (0.25 M) and DIEA (5 eq.) previously cooled down to 0 °C, was added DMTrCl (1.15 eq) under argon. The reaction mixture was stirred at rt overnight and monitored by TLC. A subsequent addition of DIEA (5 eq.) and DMTrCl (1.15 eq.) was re-added if the reaction was not complete.

The volatiles were evaporated and the residue was purified by flash chromatography on silica gel.

General procedure (GP-L) for the synthesis of the final phosphoramidite (FM2-4). To a stirred solution of the DMTr-protected intermediate (1eq., previously dried azeotropically by coevaporation with dry toluene) in DCM (0.1 M) under argon and cooled down at 0 °C, were sequentially added DIEA (5 eq.) and 2-cyanoethyl-N,N-diisopropylchlorophosphoramidite (2 eq). The reaction mixture was stirred at rt for 1-3 h and monitored by TLC until starting material was completely transformed into the diastereomers. The volatiles were removed in vacuo and the residue was purified by fast flash chromatography on silica gel. 13 To the stirred mixture of 7-Bromo-9,9-dimethylfluorenyl-2amine (180 mg, 0.61 mmol, 1 eq.) and paraformaldehyde (125 mg, 6.10 mmol, 10 eq.) in 99 % glacial acetic acid (3 ml) at 0 °C, NaCNBH3 (192 mg, 3.05 mmol, 5 eq.) was added in small portions. The mixture was left to warm up to room temperature and stirred overnight, and then poured into cold water (5 mL). Formed (d, 3 J=8. 5 Hz, 1H, H4), 7.14 (d, 3 J=8.0 Hz, 1H, H5), 6.85 (d, 4 J=1. 5 Hz, 1H, H1), 6.61 (dd, 3 J=8.5 Hz 4 J=1. 5 Hz, 1H, H3), 2.93 (s, 6H, N(CH3)2). 13 2.94 (m, 1H, H2'), 2.66 (m, 1H, H2'). 13

N-(2,3-dihydroxypropyl)-4-(7-(dimethylamino)-

XIII.2 DFT and TDDFT calculations.

All calculations were carried out using the Gaussian03 program. Geometry optimizations of molecules were performed at the B3LYP/6-31+G(d,p) level for all atoms without any symmetry restriction. The first singlet excited states were obtained using time-dependent DFT calculations for isolated molecules starting from optimized geometries at the mPW1PW91/6-31+G(d,p) level of theory. The effects of solvents were taken into account by using the polarisable continuum model (PCM). [START_REF] Frisch | TDDFT calculation: Gaussian[END_REF] DFT optimized geometries, HOMO, LUMO, experimental versus theoretical wavelength val ues, oscillator strengths and x,y,z coordinates. Some compounds are shown here.

XV. Supplementary characterization of chapter 5 XV.1 Photophysical characterization of Dye 190

[a] as table 3.

Solvent [a] Water

!

Abstract: Extensive research focuses on finding straightforward synthesis and prospective probes for biological applications. Push-pull dyes are of particular interest for various uses as biosensors for membranes and nucleic acids. These dyes are highly responsive to changes of their environments. Specifically, push-pull fluorenes exhibit low cytotoxicity and high photostability, but are not yet reported in the two mentioned applications. Furthermore, their synthesis is highly demanding. In this context, our work presents: 1) Step-economic and concise approaches to access challenging aminoaromatics via optimized air-stable Pd catalytic systems involving selective mono/di-amination and sequential one-pot synthesis, 2) Synthesis of a fluorene library varying the acceptor and the donor groups, 3) Structure-photophysics relationships, 4) Synthesis of three advanced dyes and concluding the first plasma membranespecific fluorene probe that can be a powerful tool for studying the structure and biophysical dynamics of membranes. The optimal dye surpasses the features of commonly used probes showing: red-shifted absorption matching the 405 nm diode laser, higher brightness decreasing the dye concentration for staining by ~10-15 folds, high photostability, comparably strong sensitivity to liquid domains of cell membrane, and 5) Synthesis of 4 fluorene-labeled phosphoramidites and their site-specific ODN incorporations evidencing high sensitivity to protic media and pH. Labeled sequences exhibited a far-red emission with modest quantum yields in line with their strong charge transfer character. In DNA duplexes, the dye efficiently base-discriminated opposite cytidine and thymidine. A preliminary application of the DNA fluorescent marker involved testing it as a mega-Stokes shift donor in an emissive FRET pair in combination with Dy681 acceptor. The FRET demonstrated a ratiometric turn-on in NIR region with a shift of 300 nm. Mots clés: fluorène, push-pull colorant, palladium, CuAAC, biocapteurs, membranes, lipides, acides nucléiques

•

  ............................................................................................................................................... • Thesis statement and general presentation ............................................................................................. • a radius of the Onsager's cavity • a.u. arbitrary unit • ACN acetonitrile • ACQ aggregation-caused quenching • Ac acetone • AIEE aggregation-induced emission enhancement • asap as-soon-as-possible • BDF base-discriminating fluorescence • BLA bond length alternation • C concentration • c speed of light • CD circular dichroism • CL cholesterol • cm centimeter • CuAAC copper(I)-catalyzed alkyneazide cycloaddition • D Debye • DAPI 6-diamidino-2-phenylindole • DBU 1,8-diazabicycloundec-7-ene • DCE dichloroethane • DCM dichloromethane • DCPC 2-cyanoethyl-N,N-diisopropylchlorophosphoramidite • DIEA Hünig's base • DMF dimethylformamide • DMSO dimethylsulfoxide • DMTr dimethoxytrityl group • DNA deoxyribonucleic acid • DOPC dioleoylphosphatidylcholine • DOS diversity-oriented synthesis • DSSC dye-sensitized solar cell GFP green fluorescent protein • GUV giant unilamellar vesicle • h Planck's constant • H-bond Hydrogen bonding • HGP human genome project • HOMO highest occupied molecular orbital • I inductive effect

R0 Förster distance where fluorescence transfer efficiency is 50 %•

 50 Lo liquid-ordered phase • LUMO lowest unoccupied molecular orbital • LUV large unilamellar vesicle • M mesomeric effect • MeOH methanol • MO molecular orbital • MW microwave • N* normal excited state • NIR near-infrared • nm nanometer • nM nanomolar • ODN oligonucleotide • OLED organic light-emitting device • PC phosphatidyl choline • PCR polymerase chain reaction • PE phosphatidyl ethanolamine • PE solvent Petroleum ether • PF polyfluorenes • PP push-pull dye • PS phosphatidyl serine • Qdots Quantum dots • r anisotropy • R donor-acceptor distance in FRET • RNA ribonucleic acid • RP HPLC reversed-phase highperformance liquid chromatography • rt room temperature • s second • S singlet multiplicity • SI supplementary information • SM sphingomyelin • SMS single molecule spectroscopy • SNP single nucleotide polymorphism • T triplet multiplicity • T* ESIPT tautomer • THF tetrahydrofuran • TICT twisted internal charge transfer • UV ultraviolet • vs. versus • X Y Z M fluorene ODN labels (FM) • Δf Lippert's parameter • ΔλSS Stokes shift • λ wavelength • λabs absorption maximum • λem emission maximum • μE and μG dipole moments of the excited and ground states • π aromatic core • σP Hammett value • τ fluorescence lifetime • /QY quantum yield

Figure 7 .

 7 Figure 7. (A) SMS of pentacene in p-terphenyl,55 (B) Pyrene-anthracene turn-on process

Figure 9 .

 9 Figure 9. (A) Molecular rotors, (B) Examples of negative solvatochromism

Figure 15 .

 15 Figure 15. The neutral and ICT resonance forms of a fluorene push-pull dye

Figure 16 .

 16 Figure 16. Single-photon versus two-photon absorption

Figure 17

 17 Figure 17. AIEE fluorene derivatives

27 Figure 18

 2718 Figure 18. Some examples of distinct fluorene derivatives

Figure 19 .

 19 Figure 19. Polymers and copolymers of fluorenes

Figure 20 .

 20 Figure 20. (A) The fluorene probe of cell membrane, (B) Fluorescent image of HeLa cells coincubated with the probe

Figure 21 .

 21 Figure 21. Synthesis of the fluorene analogue of prodan

Figure 22 .

 22 Figure 22. Primary developed Buchwald-Hartwig aminations

Figure 23 .

 23 Figure 23. Simplified catalytic cycle for palladium-catalyzed amination

Figure 24 .

 24 Figure 24. Pd-catalyzed synthesis of aminofluorenes

Figure 26 .

 26 Figure 26. Parameters of fluorosensors

Figure 27 .

 27 Figure 27. Schematic illustration of an efficient FRET

Figure 28 .

 28 Figure 28. Lipids in mammalian membranes

Figure 31 .

 31 Figure 31. Fluorene probes employed in imaging lysosome and endoplasmic reticulum

Figure 32 .V. 3 . 1 . 3

 32313 Figure 32. Selective examples of different biomembrane probes

  Figure 34. (A) DNA primary structure, (B) Watson-Crick base pairs, (C) Model of B-DNA

•

  Handedness -right or left • Length of the helix turn • Number of base pairs per turn • Depth of the grooves The most common form shown in fig. 34(C) is the anti-parallel, right-handed double helix

Figure 35 .

 35 Figure 35. Phosphorylation methods employed in ODN synthesis

Figure 36 .

 36 Figure 36. ODN synthesis via H-phosphonate chemistry

Figure 37 .

 37 Figure 37. Solid phase oligonucleotide synthesis via phosphoramidite chemistry

  Since nucleic acids lack adequate intrinsic emission (negligible quantum yields and very short decay times), the design of optimized fluorophores remains the momentum of a successful fluorescence investigation of DNA. A nucleic acid fluorescent probe should meet the spectroscopic demands (high brightness, photostability, selective excitation outside the range of absorption of biomolecules, etc..) and should have the versatility to be incorporated close to the site of the examination without perturbing the natural structure. This in turn, has enriched the library of fluorophores but without achieving the ultimate goal. The urge of finding new candidates increases with the compulsion of developing the DNA nanotechnology and grasping the depth of the fundamental cellular events such as gene silencing, DNA methylation, and DNA repair.

Figure 38 .

 38 Figure 38. Fluorophores for non-covalent labeling

85 Figure 40 .

 8540 Figure 40. Fluorophores attached to the phosphate backbone

Figure 41 .

 41 Figure 41. Fluorophores connected to deoxyribose (R)

Figure 42 . 2 •

 422 Figure 42. Nucleobase fluorescent analogues

104 and 105 )Figure 43 .Figure 44 .

 1054344 Figure 43. Fluorophores connected to anucleosides

  of fluorescent nucleosides VI.7.1 DNA sequencing DNA sequencing is the process of identifying the specific order of nucleotides in a DNA molecule. It is an indispensable tool in all disciplines of biology, diagnostics, medicine and forensic sciences. Fluorescence improved the historical methods using radioactively-labeled ODNs particularly in terms of speed and safety of sequencing. Further, Fluorescent labeling enabled all four bases to be identified in a single lane instead of 4 different lanes. Over the time,

Figure 45 .

 45 Figure 45. Fluorene derivatives employed in DNA investigations

  Monodentate triarylphosphines, such as PPh3 and P(o-Tol)3 were tested with low success (entries 1-2). PPh3 exhibited a poor conversion (5%) whereas P(o-Tol)3 favored diamination (25 %) with dehalogenation side reactions. Reductive dehalogenation was also observed with first generation ligand PCy3 (entry 3). Almost all the other ligands afforded the aminated products(115 and 116) in complete mass balance relative to the amine starting materials (entries 3-10).

  Pd(OAc) 2 (4 mol%) BINAP (12 mol%) amine (1.2 eq.) NaOtBu (1.1 eq.), Toluene, MW, 45 min 115 (86 vs. 76 [a] %)

Figure 49 .

 49 Figure 49. diamination reaction of 44

Figure 50 . 1 .

 501 Figure 50. Sequential couplings of 44; yields in parantheses,[a] GCMS conversion.

Figure 51 .

 51 Figure 51. Sequential one-pot versus classical two-step synthesis of 139

Figure 52 .

 52 Figure 52. Scope and limitations of different dibromoaromatic scaffolds,[a] GCMS conversion to the product.

Figure 54 .

 54 Figure 54. Absorption and emission spectra of 159 in chloroform

Figure 53 .

 53 Figure 53. Construction of push-pull sensor 159

Figure 55 .

 55 Figure 55. Selective functionalization of dibromoaromatics

Figure 56 .

 56 Figure 56. Structure of Prodan and the design of the D-π-A fluorenes in this study.

Figure 57 .

 57 Figure 57. Synthetic pathways leading to PP1-6. Reaction conditions: i) KOH (4 eq.), KI (0.1 eq.), MeI (2.3 eq.), DMSO, rt, overnight, 93%; ii) HNO3, AcOH, rt, 2 h, 73%; iii) Fe (3 eq.), NH4Cl (2 eq.), EtOH(aq.), 80 °C, 4 h, 72%; iv) (CH2O)n (5 eq.), NaCNBH3 (3 eq.), AcOH, rt, overnight, 87%; v) Pd(PPh3)4 (5 mol%), tributylvinyltin (1 eq.), toluene, 80 °C, overnight, 80%; vi) n-BuLi (1.2 eq.), DMF (2 eq.), THF, -78 °C, 3 h, 70%; vii) a. Ethynylmagnesium bromide (1.4 eq.), THF, 0 °C, 2 h, b. MnO2 (15 eq.), DCE, 0 °C, 1 h, 98% (2-steps); viii) n-HexN3 (1.1 eq.), CuI (2 eq.), DIEA (5 eq.), AcOH (1 eq.), DCE, 3 h, 70%; ix) malonitrile (2 eq.), Al2O3 (4 eq.), toluene, overnight, 70 °C, 85%; x) a. Pd(PPh3)4 (10 mol%), Bu3SnSnBu3 (1.3 eq.), toluene, 100 °C, 3 h, b. Pd(PPh3)4 (10 mol%), 5-Bromo-2,1,3-benzothiadiazole (2 eq.), 100 °C, overnight, 82%; xi) Mg (2 eq.), BrCH2CH2Br, succinic anhydride (2 eq.), THF, 60%; xii) DIC (1.1 eq.), HOBt (1.1 eq.), Et3N (1.1 eq.), n-BuNH2 (1.5 eq.), THF, rt, overnight, 72%.

  -step route was planned based on our developed Pd-catalyzed C-N cross-coupling protocol (chapter 2). In a first step, formylation of fluorene (34) at the C-7 position was optimized to obtain the key intermediate (169) with a fixed aldehyde acceptor (fig. 58). Different formylating reagents, Lewis acids (AlCl3, TiCl4, ZrCl4), solvents (THF, CH3CN, CH2Cl2), temperatures, and durations were assessed. Isolation of the different aldehyde regioisomers proved to be a troublesome task. Nevertheless, the desired fluorene-2-carbaldehyde derivative (169) was the exclusive product of the Friedel-Crafts reaction performed with ZrCl4 and Cl2CHOCH3 in CH2Cl2 at 0 °C for 1 h. Diformylation is an inescapable side product if the reaction conditions are not strictly controlled.

169 ,Figure 58

 16958 Figure 58. Synthetic pathway leading to PP7-14. i) Cl2CHOCH3 (1.5 eq.), ZrCl4 (1.5 eq.), CH2Cl2, 1 h, 0 °C, 77%; ii) Amine (1.2 eq.), t-BuONa (1.2 eq.), Pd(OAc)2 (5 mol%), BINAP (10 mol%), Toluene, MW (300 W/ 180 °C), 30 min. PP7-14 are systematically numbered(170-177) respectively.

2 Figure 59 .

 259 Figure 59. Absorbance (dotted line) and emission (solid line) spectra for PP1 (black), PP3 (red), PP4 (blue), PP6 (green) in EtOH (A), DMSO (B), and toluene (C) as representatives of protic, aprotic polar, and aprotic apolar solvents respectively. Excitation wavelength used was the corresponding absorption maximum.

  difference in wavelength (ΔλSS = λem-λabs) was employed to simplify the comparisons as an indication of Stokes shift. In the carbonyl acceptors, the triazolyl PP3 absorbed as strongly as PP1 (38•10 3 M -1 cm -1 in dioxane), whereas PP2 and PP6 showed a two-fold hypochromicity (decrease in absorptivity to around 17•10 3 M -1 cm -1 ). The three carbonyl dyes absorbed in the visible range (370-413 nm in ethanol and displayed particular large Stokes shifts in polar solvents (e.g. 183-226 nm in ethanol). They showed gradually an increased bathochromic shift in their emission maxima when going from the most apolar aprotic solvent to the most polar solvent (

Figure 60 .

 60 Figure 60. Absorption and emission spectra of the selected EWG-varied dyes in dioxane.Excitation wavelength used was the corresponding absorption maximum.

  matching excitations with the argon laser line. The full width at half-maximum height of PP4 is relatively narrow (Δλ1/2∼64 and 82 nm, respectively) illustrating a useful asset for selective excitation. The intermediate I-6 was emissive even in water (13%). Its fluorescence was quenched only in chloroform or upon adding 1% (v/v) of trifluoroacetic acid to 1,2-dichloroethane. The weak EW nature of the vinyl group accounts for the observed blue-shifted absorption and emission.

Figure 61 .

 61 Figure 61. Dependence of the emission on the empirical polarity parameter ET(30) for selected acceptor-varied fluorenes PP1 (violet), PP3 (red), PP6 (blue), and PP4 (green). Correlation factors R 2 are respectively 0.97, 0.98, 0.99 and 0.93. The linear plots shown were obtained withall the tested solvents except for PP4, for which deviation from linearity was observed when protic solvents were included.

Figure 62 .

 62 Figure 62. Lippert-Mataga function plot of PP3. Correlation factors R 2 is 0.93. The plots demonstrated linear relationships. A representative trend is shown for PP3 in fig.

  absorptions and emissions relative to prodan. The absorption of the dyes was negligibly affected by polarity (<10 nm) except for the moderate bathochromic shift of PP4(35 nm). By contrast, all considered dyes showed forceful variations in their colors of emission. The positive solvatofluorochromism confirms the presence of a strong ICT character only at the excited state of these dyes. The modeling and calculations also support this conclusion. By contrast to the peptide-coupled product PP6, the conservation of the desired optical properties for PP3 upon conjugation via CuAAC makes the ynone PP2 a more attractive anchoring point for biolabeling.

Figure 63 .

 63 Figure 63. DFT-TDDFT simulations of PP6. Peptide side chain was shortened to 2 carbons to reduce the calculation time. Representation of the HOMO and LUMO frontier molecular orbitals (Left). Ground state optimized coplanar structure (Right).

  the nitrogen's lone pair as part of the aromatic sextet of pyrrole. The DFT twisted geometry of the pyrrole and fluorene rings could also contribute to this poor donating ability (fig.64).

Figure 64 .

 64 Figure 64. Optimized DFT structure of PP7 Compared to PP1, the 4-to 7-membered amine rings of PP8 and PP10 bathochromically shifted the absorption (10-15 nm, and 20-25 nm in water). The substitution of the methyl group by a longer alkyl chain red-shifted the absorption maxima, in agreement with an increased inductive effect. By contrast the 4-and 6-membered amine rings of PP9 and PP11 resulted in an unexpected hypsochromic shift (5-15 nm) as shown in table 4 and fig. 65-66.

Figure 65 .

 65 Figure 65. Absorbance (dotted line) and emission (solid line) for PP8 (black), PP9 (red), PP12 (green) in EtOH. Excitation wavelength used was the absorption maximum.

Figure 66 .

 66 Figure 66. Absorption and emission spectra of PP8-12 in DMSO. Excitation wavelength used was the absorption maximum.

Figure 67

 67 Figure 67 Absorbance (dotted line) and emission (solid line) for PP9 in toluene (red), chloroform (green), DMSO (black), EtOH (cyan) and H2O (magenta). Since absorption is weakly solvatochromic, one representative spectrum was shown.

  by the Lippert-Mataga model, was the lowest in this series (11.4-13.7 D); thus, attesting its weaker donating ability.

Figure 68 .Figure 69 .

 6869 Figure 68. Ground-state optimised structures of PP9 and PP12 Regarding the series of cyclic amines, PP8-11 showed perfect overlap of the emission dependence on ET(30) inferring marginal effect of the ring size (between 4 and 7 members) on fluorescence properties (fig. 69).

Figure 70 .

 70 Figure 70. Absorbance (dotted line) and emission (solid line) for the optimized push-pull dyes PP15 (black) and PP16 (red) in representative solvents. PP15-16 are systematically numbered 178-179. Excitation wavelength used was the corresponding absorption maximum. Finally, the methylenemalonitrile PP15-16 with piperidine and morpholine groups were respectively synthesized by Knoevenagel condensation on the formyl group of PP9 and PP13 (85 % and 72 % yields respectively) to verify the potential synergic effect of the A and D on the photophysics. Fig. 70 shows their absorption and emissions in selected solvents. The absorptions of PP15-16 appeared in the visible range (440-475 nm, 34-36•10 3 M -1 .cm -1 ) allowing a selective excitation with the blue diode (445 nm) or the argon ion laser line (488 nm). The fluorescence remained in the NIR region (705-713 nm) in polar solvents yielding spectacular mega-Stokes shifts (DMSO and H2O: 240-260 nm, toluene: 105 nm).

Figure 71 .

 71 Figure 71. Dependence of the quantum yield for PP4 (red), PP15 (blue) and PP16 (green) on the empirical polarity parameter ET(30). The linear trends were obtained with all the representative solvents, except chloroform (correlation factors R 2 are respectively 0.965, 0.996, 0.87).

Figure 72 .

 72 Figure 72. Dependence of the respective absorption maxima of PP12, I-6, PP1, and PP4 (in EtOH (blue), acetonitrile (red) and chloroform (green)) on the donor/acceptor Hammett σP value (σP A -σP D ). Correlation factors R 2 are 0.94, 0.89, and 0.91 respectively. Since the D and A substituents in the fluorene derivatives present a mesomeric relationship like in para-disubstituted aromatic derivatives, photophysics of the selected examples were

Figure 73 .

 73 Figure 73. Dependence of the respective emission maxima of PP12, PP1, and PP4 (in EtOH (blue), acetonitrile (red) and chloroform (green)) on the donor/acceptor Hammett σP value (σP A -σP D ). Correlation factors R 2 are 0.88, 0.81, and 0.83 respectively.

  summary, we rationally designed, synthesized, and characterized a library of fluorescent push-pull dyes based on a 2,7-disubstituted fluorene scaffold. These emissive D-π-A derivatives were prepared by straightforward and gram-scalable synthetic pathways. The various electronwithdrawing groups were efficiently introduced on a common and easily accessible synthon via different methodologies including amongst others: Stille coupling, CuAAC, and peptide coupling.The screening of electron-donating groups was chemoselectively carried out via a versatile Buchwald-Hartwig amination on a fluorenyl carbaldehyde intermediate obtained by an optimized formylation reaction. Photophysical studies highlighted the most promising compounds in terms of brightness, mega-Stokes shift, excitation accessibility, and versatility for subsequent conjugation. The propioloyl linker was introduced for conjugation and converted into the ketotriazolyl derivative whilst maintaining the desired optical properties. Such characteristics make the ynone a prospective anchoring point for biolabeling that we build on in the next two chapters. By combining the attractive ED (morpholine, piperidine) and EW (methylenemalonitrile) groups, the synergic effect was tested. These studies led to new pushpull fluorenes with red-shifted absorption and emission. Due to an enhanced intramolecular charger transfer, the dyes were highly solvatofluorochromic over the entire polarity scale and even NIR emissions were observed in protic solvents. DFT calculations confirmed these experimental observations. Correlation of a selected set of D-π-A emitters with Hammett σP values of the considered donor/acceptor pairs provides a complementary tool to anticipate the spectroscopic features desired for specific applications.

Figure 74 .

 74 Figure 74. Common dyes for comparisons

Figure 75 .

 75 Figure75. Synthesis of the membrane probes F1-3 via CuAAC; CuSO4•5H2O (0.5 eq.), sodium ascorbate (0.7 eq.), DMF/water (3/1), rt, 1-3 h

Figure 76 .

 76 Figure 76. . Normalized absorption in toluene as a representative solvent (dotted line) and emission (full line) spectra in different solvents: A) F1, B) F2, and C) F3. Excitation wavelength used was the corresponding absorption maximum.

Figure 77 .

 77 Figure 77. Dioxane-water titration of F1, the numbers signify the increasing percentage of water in dioxne As evidenced in fig. 77, hydration shifts the position of the emission band to the red and results in increased quenching of the fluorescence, which is common in dyes with strong ICT character. In particular, three concentration regions might be distinguished; low polarity medium disturbed by relaxing sole water molecules characterized by blue-shifted emission and brightness, second region with collective effect of water but when it was still not a bulk solvent translated in a collective red shift and decrease in the quantum yield and the third region characterized by quenched emission where the water became a bulk solvent. Hence, The shift from polar aqueous environment to apolar aprotic dioxane results in a turn-on (>25 fold) of the

Figure 78 .

 78 Figure 78. Fluorescence of F1 at different concentration ratios of SM/CL LUVs (phosphate buffer 20 mM, pH 7.4). Excitation wavelength used was 390 nm.

Figure 79 .

 79 Figure 79. Variation of fluorescence intensity of F1 as a function of SM/CL LUVs concentration ratio (in phosphate buffer 20 mM, pH 7.4); the unit concentration of F1 was 0.4 μM.

Figure 81 .

 81 Figure 81. Photodegradation decay curves of F1-3 as a function of time in A) xylene, and B) LUVs (DOPC). Photodegradation was performed at 400 nm with the xenon lamp in the spectrofluorometer (Emission and excitation slits = 8).

  significant shifts in emission of the new probes in Lo and Ld phases open the possibility for ratiometric imaging of lipid order in membranes by recording the emission intensities at two different wavelengths. F3 was used to image GUVs made of DOPC and DOPC/SM/CL since in imaging cells and model membranes, it showed better features compared to the other two dyes(SI-XIV) most probably due to its orientation. The ternary mixture of lipid molecules is a simplified system to model co-existence of lipid domains. F3 was then added to adherent GUVs at concentration of 100 nM and studied without washing by confocal microscopy to evaluate its capability to visualize Ld and Lo phases. The images were processed by collecting the emission of the blue and green regions separated at 500 nm (fig.82A-B). The ratiometric image was obtained by dividing the image of the green channel by the one of the blue channel (fig.82C). F3 distinguishes well the Lo and Ld phases through variations in the green/blue ratio signal (fig.82C). Thus, separated Lo (magenta) and Ld (yellow-green) domains were clearly observed.

Figure 82 .

 82 Figure 82. Confocal fluorescence image of DOPC/SM/CL GUVs stained with F3. Images were obtained by collecting emission of the A) blue channel; B) green channel. C) Ratiometric green/blue imaging of GUVs, the ratios of intensities are displayed by using the color code given on the right scale.

Figure 83 .

 83 Figure 83. Confocal fluorescence image of DOPC GUVs stained with F3. A) Ratiometric green/blue imaging of GUVs, the ratios of intensities are displayed by using the color code given on the right scale. B) Image were obtained by collecting fluorescence intensity recorded for both channels. Control experiment conducted with the DOPC vesicles confirms this interpretation (fig. 83) as the membranes appear in green pseudo-color corresponding to one of the phases observed in the ternary mixture (fig. 82C). F3 stains only the membrane giving bright images with low background fluorescence (fig. 83B). F3 performs comparably to the Nile Red derivative (NR12S)

F3.

  Adherent HeLa cells were incubated with F1-F3 probes at a concentration of 100 nM and imaged after 5-10 min of incubation. F1-F3 presented noticeable differences in their internalization and distribution within cells as evidenced in fig. 84. F3 displayed bright fluorescence exclusively in plasma membranes (colored in magenta, fig. 84E) without internalization of the dye. The ratiometric fluorescence image gave a uniform distribution evidence of the domination of the Lo phase in the cell plasma membranes as it was previously

Figure 84 .

 84 Figure 84. Confocal fluorescence image of HeLa cells stained with F1: A) and B); F2: C) and D); F3: E) and F). Concentration of F1-F3 of 100 nM. Left column: ratiometric green/blue imaging, The ratios of intensities are displayed by using the color code given on the right scale. Right column: imaging obtained by collecting fluorescence intensity recorded for both channels.

  highly sensitive probes that can help in understanding the biophysical behavior of cell membranes by synthesizing three novel probes based on a new design. This work validated the versatility of the introduced ynone linker in biolabeling without compromising the appreciable spectroscopic properties of the core dye. In effect, F3 dye surpasses the features of commonly used laurdan probe for instance. Some of the established improvements compared to laurdan are: red-shifted absorption that matches the 405 nm diode laser, higher brightness, decreasing the used concentration for such staining by ~10-15 folds, high photostability, comparably strong sensitivity to different liquid domains of cell membrane. Moreover, fluorene derivatives present high 2PA cross-section at common wavelengths around 800 nm, which makes them attractive in two-photon excitation microscopy. F3 is the first plasma membrane-specific fluorene-based probe that can be a powerful tool for studying membranes. This chapter outlines the syntheses of four DNA fluorescent markers (FM1-4) comprising push-pull fluorene dyes and their site-specific incorporation into oligonucleotides (ODNs). Indeed, this work is a summary of different study designs that have been carried out in parallel to the previous chapters. Both classical and Pd catalytic routes have been used in establishing the four phosphoramidites that were employed in successive campaigns of solid-phase synthesis of DNAs. Emphasis on synthetic details and degradation studies will be presented to explain the encountered difficulties and argue the compatibility of the alkyl chain of the amino group in DNA labeling by fluorene dyes. In conclusion, the efficient introduction of a stable fluorene amidite into 15-mer ODN sequences has been performed. Spectroscopic characterization (UV, fluorescence, thermal denaturation, CD) of the final labeled ODNs in different contexts of flanking and opposite natural bases will be discussed. The performance of the fluorene dye as a

188 Figure 85 .

 18885 Figure 85. The first phosphoramidite FM1 and its analogue PP6

Figure 87 .

 87 Figure 87. Solvatofluorochromism of 190. Normalized representative absorbance (dotted line) and emission (solid line) spectra in different solvents

193 Figure 88 .

 19388 Figure 88. Synthesis of FM1

  volatiles were removed by lyophilization under vacuum. The AMA and TMT sequences were treated with 50% aqueous acetic acid for 1 hour. Then, the lipophilic DMTr component was extracted with ether. The four crude ODNs were purified by RP-HPLC controlled by UV absorbance monitoring on a photodiode array detector at two wavelengths: 255 and 370 nm, which approximately correspond to the absorption of the DNA natural nucleobases and fluorene, respectively (fig.89).

Figure 89 .

 89 Figure 89. HPLC profile of CMC single strand ODN

Figure 90 .

 90 Figure 90. Absorption and emission spectra of the labeled ODNs. Excitation wavelength used was the corresponding absorption maximum.

Figure 91 .

 91 Figure 91. Retrosynthetic plan of FM2-4

Figure 92 .Figure 93 .

 9293 Figure 92. Synthesis of FM2

Figure 94 .

 94 Figure 94. Synthesis of FM4

Figure 95 .

 95 Figure 95. HPLC profile of CXC single strand ODN (255 nm up -390 nm down) as an example of purity

Figure 96 .

 96 Figure 96. Solvatofluorochromism of 197. Normalized representative absorbance (dotted line) and emission (solid line) spectra in different solvents. Excitation wavelength used was the corresponding absorption maximum.

Figure 99 .

 99 Figure 99. pH dependence of CXC and TXT in buffer (10 mM cacodylate, 150 mM NaCl)

Figure 101 .

 101 Figure 101. Excitation and emission spectra of GXG investigations. Excitation wavelength used was 440 nm.

Figure 102 .

 102 Figure 102. CD results of GXG investigations

Figure 103 .

 103 Figure 103. Melting temperature curves of GXG duplexes (up), GXG-FRET duplexes and control experiments (down) Taken together, CD and thermal denaturation experiments show that the fluorene nucleoside can substitute a natural base opposite in DNA opposite a natural base or an abasic site giving duplexes of B-conformation that are stable to conduct all the spectroscopic studies at 25°C.

Figure 104 .

 104 Figure 104. Simplified energy diagram explaining the turn on FRET between the donor X and the acceptor Dy681. Turn off: in the absence of the acceptor, the knr of the donor rate is dominating the deactivation process. Turn on: In the presence of the acceptor FRET is dominating (kT > knr). Such a preliminary design of FRET pair is to the best of our knowledge original. It should greatly improve the signal-to-noise ratio in in fluorescence detection and imaging, obviates the self-quenching and light scattering, and overcome the drawback of single labeling with mega-Stokes shift dyes that is usually accompanied by poor quantum yields in aqueous media.

Figure 105 .

 105 Figure 105. Fluorescence titration of GXG with Dy681 (λexc =420 nm)

Figure 106 .

 106 Figure 106. Control experiments for energy transfer (λexc= 420 nm)

  urged us to develop efficient synthetic access to conclude a diversity-oriented synthesis of fluorene dyes. The optimized routes allowed us to synthesize fluorophores inaccessible by classical routes or otherwise too demanding to achieve. Structure-photophysics relationships of the library of 2,7-push-pull fluorenes had led in turn to produce biosensors that were successfully employed in respective contexts of imaging cell membranes, labeling ODN sequences, hybridization studies in DNA duplexes, base-discrimination fluorescence, and FRET applications. First, selective functionalization of readily accessible dibromoaromatic scaffolds via air-stable palladium catalytic systems was optimized. The methodologies involved rapid mono-and diselective Buchwald-Hartwig aminations via MW irradiation, and sequential one-pot C-N/Stille or C-N/C-N couplings. The scope of this work comprised synthesis of 37 symmetrical and unsymmetrical aminoaromatic derivatives based on fluorene, naphthalene, pyridine, and thiophene families in addition to a NIR sensor prepared through three-component one-pot reaction.

  characterization, Hammet and Lippert-Mataga correlations, in addition to theoretical TD-DFT calculations enclosed the structure-property relationships and rationalized the ICT character of the push-pull dyes. The most promising compounds in terms of brightness, mega-Stokes shift, excitation accessibility, and versatility for subsequent conjugation were used to design the biosensors used afterwards. Particularly, the propioloyl linker was converted into ketotriazolyl derivatives maintaining the desired optical properties upon bioconjugation. Later, 3 new advanced fluorene dyes were synthesized for membrane studies. The three probes comprised respectively: a) a polar deoxyribosyl head b) a lipophilic long alkyl chain, and c) an amphiphilic anchoring group to fix the dye at the membrane interface and prevent its internalization. Spectroscopic characterization of these fluorophores, their tendency to probe large and giant unilamellar vesicles of different lipid compositions, and imaging of HeLa cells were investigated. This study demonstrated the ability of push-pull fluorenes to be a cornerstone of highly sensitive probes that can help in understanding the biophysical behavior of cell membranes. In effect, the optimal dye surpasses the features of commonly used Laurdan probe. Some of the established improvements are: red-shifted absorption that matches the 405 nm diode laser, higher brightness, decreasing the used concentration for such staining by ~10-15 folds, high photostability, comparably strong sensitivity to different liquid domains of cell membrane. Lastly, we synthesized four fluorene phosphoramidites and incorporated them into oligonucleotides via automated solid-phase synthesis. Detailed spectroscopic studies evidenced a high sensitivity to protic media through a dramatic Stokes shift and to acidity. That observation augured interesting prospects for nucleic acid labeling. The nature of the alkyl chain on the amino group revealed to be crucial for the integrity of the fluorophore once incorporated in ODNs. Labeled sequences exhibited a far-red emission but modest quantum yields considering their large ICT character. In duplexes of different compositions, the dye revealed to efficiently base-discriminate opposite cytidine and thymidine. Once incorporated in DNA, the full separation of the absorption and emission led us to study this dye as a mega-Stokes shift donor (∆λ = 235 nm) in an emissive FRET pair combination with the NIR emitting Dy681. The resulting biosensors display switch-on emission that opens new opportunities for DNA-DNA and DNAprotein interactions.

  comme un moyen moderne d'analyse pour comprendre les énigmes scientifiques. La "Fluorescence" est un domaine qui intègre pratiquement toutes les disciplines mentionnées et étend à d'autres frontières de détections environnementales, de la médicine et des sciences de la vie et pharmaceutiques.La " Fluorescence " a été observée par Herschel en 1845 comme un phénomène de la solution de quinine sous la lumière du soleil et a été décrite plus en détail par Stokes en 1852. Un siècle plus tard, ce processus de nouveauté a été mis en service de la science avec l'invention des «fluorimètres commerciaux» et les "microscopes à fluorescence". Les progrès ont procédé rapidement avec la «microscopie confocale» et des instruments plus sophistiqués ayant obtenus le prix Nobel comme le " spectroscopie de femtoseconde de Zewail (x10 -15 s)". Les instrumentations de fluorescence sont aujourd'hui avancées, pas chers et faciles à manipuler. Les techniques de fluorescence sont devenues des outils analytiques cruciaux pour la recherche et l'industrie grâce à des nombreuses caractéristiques exquises. Ces techniques sont les plus sensibles dans le domaine de la détection moléculaire, en particulier pour l'étude d'interaction dynamique en biologie. Leur sensibilité a atteint la limite de détection d'une seule molécule avec des enregistrements de signaux contrôlés à distance. Ils montrent une précision élevée, un caractère non-invasif dans les cellules vivantes et des résolutions spatiales et temporelles ultrahautes. En outre, la détection de Fluorescence est extrêmement polyvalente, elle est possible à l'état solide, liquide, gaz et même à l'interface de ces phases. En plus d'instrumentations, l´avancement dans "la conception et la synthèse de fluorochromes" reste sans aucun doute la marque de progrès dans les applications de fluorescence. Un fluorophore optimal est essentiellement un cadre moléculaire qui compile les attributs nécessaires à partir des propriétés optiques telles que la photostabilité, la luminosité, l'excitation sélective et l'émission à la polyvalence chimique telles que la tolérance à introduire des substituants pour la bioconjugaison et le réglage de la solubilité. Une telle conception rationnelle est un défi en soi. De la perspective " de la chimie organique ", cela implique au moins une voie de synthèse multi-étapes pour produire une telle molécule intelligente; par conséquent, ajoutant plus de défis des limites connues de la synthèse. Par conséquent, les chimistes sont fortement invités à présenter des nouvelles routes, robustes et présentant une économie d'atomes pour synthétiser des sondes innovantes et générer des bibliothèques de colorants qui élucident les relations structure-propriété. En particulier, notre travail a porté sur les réactions catalysées par des métaux tels que les aminations Buchwald -Hartwig et les réactions de cycloaddition alcyne -azoture catalysée par le cuivre (I) (CuAAC), la chimie "click" pour créer des alternatives plus viables pour des routes d'emploi plus longues. Les méthodologies développées ont permis l'accès à une bibliothèque de colorants push-pull à base de fluorène comme une classe captivante de sondes sensibles à l'environnement. Un colorant push-pull est constitué d'un squelette-π fonctionnalisé avec un donneur d'électrons (D) et un accepteur (A). Le système D-π-A subit un transfert intramoléculaire de charge (TIC) photo-induit formant une orbitale moléculaire (OM) à faible niveau énergétique. La lumière visible fournit suffisamment d'énergie pour exciter les électrons dans cette nouvelle OM, ce qui rend ces composés généralement colorés. Le TIC génère également des moments dipolaires qui augmentent la sensibilité de ces fluorophores en réponse à la polarité et les changements de leur environnement. Le noyau aromatique (π) joue un rôle clé dans la conception. Ainsi, le choix de la famille fluorène est venu dans ce projet. Les Fluorènes manifestent des attributs spectroscopiques souhaitables, de faible cytotoxicité et une absorption à deux photons très appréciable des sections transversales permettant l'imagerie cellulaire avec un photo vieillissement réduit. Les dérivés de fluorène sont largement utilisés dans la recherche biomédicale et les sciences de matériaux tels que l'optoélectronique. Deux applications centrales ont été explorées en utilisant nos sondes fluorène, 1) l'étiquetage des oligonucléotides (ODN), et 2) l'imagerie des lipides dans les membranes biologiques. En fait, malgré la détermination complète des séquences d'ADN de 3.5x10 9 paires de base dans le projet du génome humain (HGP) en 2001, cette acquisition explosive des données structurelles a défilé des informations très limitées sur la fonction biologique complexe de l'ADN. Pour répondre à ces aspects, la spectroscopie de fluorescence offre un outil exquis pour caractériser les acides nucléiques et d'étudier leurs interactions, qui sont fondamentales pour comprendre les événements cellulaires tels que la réparation et la méthylation de l'ADN, et le silençage génique. La recherche de marqueurs fluorescents appropriés qui peuvent surveiller ces interactions sans affecter la structure et la fonction des séquences ODN marqués est encore urgente. De même, la distribution hétérogène des lipides dans les membranes cellulaires est un sujet d'investigations intenses. Trois niveaux d'hétérogénéité existent. L'hétérogénéité latérale, décrite par l'hypothèse de radeaux lipidiques est en débat jusqu'à maintenant. Les radeaux sont soupçonnés d'être derrière de nombreux processus tels que la transduction du signal et les maladies neurodégénératives. L´asymétrie des lipides transmembranaires est la deuxième hétérogénéité qui est perdue dans la mort cellulaire programmée (apoptose). L´apoptose défectueuse est à l'origine de maladies nuisibles tels que l'atrophie et le cancer. Enfin, les différences entre le plasma et les membranes intracellulaires représentent la troisième hétérogénéité moins explorée. Ainsi, la conception de sondes très sensibles aidera à comprendre la structure et la dynamique des membranes biologiques par la détection de différents paramètres tels que l'hydratation, la viscosité, la polarité et l'ordre. Cela va aider à son tour dans la compréhension des processus cellulaires et à trouver des solutions à des problèmes médicaux futiles comme le cancer.

Chemistry" .

 . photophysiques ont mis en évidence les composés les plus prometteurs en termes de luminosité, des déplacements de Stokes, d'accessibilité, d´ excitation et la polyvalence pour la conjugaison ultérieure. L'agent de liaison de propioloyle a été introduit pour la conjugaison et converti en dérivé cétotriazoliyl tout en conservant les propriétés optiques souhaitées. Ces caractéristiques font de l'ynone un point d'ancrage prospectif pour l´étiquetage biologique sur lequel on se base dans les deux chapitres suivants. En combinant les groupes accepteurs ED (morpholine, pipéridine) et donneurs EW (methylenemalonitrile), l'effet synergique a été testé. Ces études ont conduit à de nouvelles fluorènes push-pull avec absorption et émission décalée vers le rouge. En raison d'un transfert de charge intramoléculaire amélioré, les colorants étaient très solvatofluorochromiques sur l'échelle de la polarité entière et même les émissions proches infrarouges ont été observées dans des solvants protiques. Les Calculs DFT ont confirmé ces observations expérimentales. La corrélation d'un ensemble de D-π-A émetteurs dont les valeurs Hammett σP des paires donneur/accepteur considéré fournit un outil complémentaire pour anticiper les caractéristiques spectroscopiques souhaitées pour des applications spécifiques. • Dans le quatrième chapitre, nous avons démontré la capacité de la famille fluorène d´être une pierre de base pour des sondes très sensibles qui peuvent aider à comprendre le comportement biophysique des membranes cellulaires en synthétisant trois nouvelles sondes fluorescentes avec une nouvelle conception. Ce travail a validé la polyvalence d´agent de liaison ynone introduit en étiquetage biologique sans compromettre les propriétés spectroscopiques appréciables du noyau du colorant. En effet, la sonde F3 dépasse les caractéristiques de "Laurdan" couramment utilisé par exemple. Certaines des améliorations établies par rapport à Laurdan sont: une absorption décalée vers le rouge qui correspond au laser diode de 405 nm, une luminosité plus élevée, ce qui diminue la concentration utilisée pour ces marquages de ~ 10-15 fois, une photostabilité élevée, une sensibilité comparativement élevée aux différents domaines liquides de membrane cellulaire. En outre, les dérivés fluorine présente une haute cross-section 2PA aux longueurs d'onde communes autour de 800 nm, ce qui les rend attrayants en microscopie d´excitation à deux photons. F3 est la première sonde à base de fluorène

  2 h. Then, a 50 μL aliquot of the obtained stock solution of GUVs in sucrose (cooled down to room temperature) was added to 200 μL of 300 mM glucose solution to give the final suspension of GUVs used in microscopy experiments. The staining of GUVs was performed by addition of an aliquot of the probe stock solution in DMSO to obtain a 0.1 μM final probe concentration (final DMSO volume <0.25%). Preparation of the double strand solution: 400 μL of a stock solution of 20 mM cacodylate respective buffer solution 80 μL of 1.5 M NaCl solution, 12.5 μL of 64 μM ODN1, 12.5 μL of 64 μM ODN2 and 260 μL of MilliQ® water.

Scheme 1 .

 1 Scheme 1. Synthesis of 2,7-dibromoinated fluorene starting material (44)

Following GP-B, 116 and 130 -133 series of products were prepared on scale ( 0

 1300 Eluent for flash chromatography (PE/Et2O = gradient up to 98:2, Rf = 0.25) providing 116 as a yellow solid (101 mg, 0.25 mmol, 89 %).

2 (

 2 Eluent for flash chromatography (PE/Et2O = gradient up to 98:2, Rf = 0.26) providing 130 as a yellow solid (70 mg, 0.22 mmol, 78 %).1 H-NMR (200 MHz, CDCl3, δ): 7.73(d, 3 J=8.0 Hz, 2H, H4,5), 7.45(d, 4 J=2.0 Hz, 2H, H1,8), 7.39 (dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 2H, H3,6), 7.16 (t, 3 J=2.0 Hz, 4H, NCHpyr), 6.39 (t, 3 J=2.0 Hz, 4H, CHpyr), 1.55 (s, 6H, 2CH3).13 C-NMR (50 MHz, CDCl3, δ): 155.3 (2C, Ca,b), 140.3 (2C, C2,7), 136.3 (2C, Cc,d), 120.9 (2C, C4,5), 120.1 (2C, C3,6), 119.8 (4C, N(CHpyr)), 115.5 (2C, C1,8), 110.5 (4C, CHpyr), 47.4 (C9), 27.3 (2CH3). HRMS (ESI + ): m/z calcd for C23H21N2: 325.1699 [M+H] + ; found 325.1700. 1,1'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyrrolidine (131): Eluent for flash chromatography (PE/EA = gradient up to 98:2, Rf = 0.38) providing 131 as a yellow solid (55 mg, 0.16 mmol, 59 %). 1 H-NMR (200 MHz, TFA-d 1 , δ): 8.02 (d, 3 J=8.5 Hz, 2H, H4,5), 7.88 (d, 4 J=2.0 Hz, 2H, H1,8), 7.58 (dd, 3 J=8.5 Hz, 4 J=2.0 Hz, 2H, H3,6), 4.26 (br t, 3 J=5.0 Hz, 4H, N(CH2)2), 3.79 (br t, 3 J=5.0 Hz, 4H, N(CH2)2), 2.51 (m, 8H, 2N(CH2CH2)2), 1.58 (s, 6H, 2CH3). 13 C-NMR (50 MHz, TFA-d 1 , δ): 159.5 (2C, Ca,b), 142.3 (2C, Cc,d), 141.8 (2C, C2,7), 124.9 (2C, C4,5), 122.2 (2C, C3,6), 117.5 (2C, C1,8), 62.6 (4C, N(CH2)), 50.5 (C9), 27.4 (2CH3), 25.7 (4C, N(CH2CH2)). HRMS (ESI + ): m/z calcd for C23H29N2: 333.2321 [M+H] + ; found 333.2325. Eluent for flash chromatography (PE/EA= gradient up to 9:1, Rf =0.16) providing 132 as a yellow solid (74 mg, 0.20 mmol, 73 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.52 (d, 3 J=8.0 Hz, 2H, H4,5), 6.97 (d, 4 J=2.0 Hz, 2H, H1,8), 6.87 (dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 2H, H3,6), 3.90 (t, 3 J=5.0 Hz, 8H, 2O(CH2)2), 3.21 (t, 3 J=5.0 Hz, 8H, 2N(CH2)2), 1.45 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 154.7 (2C), 150.5 (2C), 132.2 (2C), 119.8 (2C), 114.8 (2C), 110.7 (2C), 67.4C), 50.3 (4C), 47.0, 27.8 (2C). HRMS (ESI + ): m/z calcd for C23H29O2N2: 365.2224 [M+H] Eluent for flash chromatography (PE/EA = gradient up to 98:2, Rf = 0.34) providing 133 as a yellow solid (57 mg, 0.61 mmol, 61 %). 1 H-NMR (500 MHz, TFA-d 1 , 6H). 13 C-NMR (50 MHz, CDCl3, δ): 155.4, 153.6, 152.4, 139.6, 137.5, 135.3, 130.6, 125.7, 120.7, 120.1, 119.1, 115.5, 112.4, 111.1, 51.3 (2C), 46.8, 27.6 (2C), 26.1 (2C), 24.4. HRMS (ESI + ): m/z calcd for C22H26N: 304.2061 [M+H] + ; found 304.2060. Eluent for flash chromatography (PE/EA = gradient up to 95:5, Rf = 0.7) providing 135 as a yellow solid (43 mg, 0.15 mmol, 54 %).

5 Hz, 3 Jcis=11. 0

 530 yellow solid (35 mg, 0.13 mmol, 46 %).1 H-NMR (200 MHz, CDCl3, δ): 7.58 (d, 3 J=8.0 Hz, 1H), 7.51 (d, 3 J=8.0 Hz, 1H), 7.42 (br s, 1H), 7.33 (dd, 3 J=8.0 Hz, 4 J=1.5 Hz, 1H), 6.78 (dd, 3 Jtrans=17.Hz, 1H), 6.47 (d, 4 J=2.0 Hz, 1H), 6.42 (dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 1H), 5.75 (d, 3 Jtrans=17.5 Hz, 1H), 5.20 (d, 3 Jcis=11.0 Hz, 1H), 3.95 (t, 3 J=5.5 Hz, 4H), 2.40 (quint, 3 J=5.5 Hz, 2H), 1.46 (s, 6H). GC-MS (m/z): 275.1 [M] +. . 1-(9,9-dimethyl-7-vinyl-9H-fluoren-2-yl)-1H-pyrrole (137): yellow solid (60 mg, 0.21 mmol, 76 %).

Following

  1.23 (t, 3 J=7.0 Hz, 4H). HRMS (ESI + ): m/z calcd for C18H21N2: 265.1699 [M+H] GP-C. Eluent for flash chromatography (PE/EA = gradient up to 95:5, Rf =0.

  1 H-NMR (200 MHz, CDCl3, δ): 7.18 (t, 3 J=8.0 Hz, 1H, H4), 6.58(d, 3 J=8.0 Hz, 1H, H5), 6.29(d, 3 J=8.0 Hz, 1H, H3), 3.39 (t, 3 J=7.5 Hz, 4H, N(CH2)2), 1.55 (quint, 3 J=7.5 Hz, 4H, N(CH2CH2)2), 1.43-1.25 (m, 4H, (CH3CH2)2), 0.95 (t, 3 J=7.0 Hz, 6H, 2CH3).13 C-NMR (50 MHz, CDCl3, δ): 156.8, 140.4, 139.0, 113.5, 103.7, 48.4 (2C), 29.7 (2C), 20.3 (2C), 14.1 (2C). GC-MS (m/z): 286.1 [M+2] +. .6-bromo-N,N-diethylpyridin-2-amine (

Scheme 3 . 1 , 5 -Following

 315 Scheme 3. 1,5-Pyridine series was prepared on (100 mg scale, 0.39 mmol of S4).

  13 C-NMR(50 MHz, CDCl3, δ): 153.7 (C2, C5), 149.4 (2C-i-Ph), 129.1 (4C-m-Ph), 125.9, 120.0 (C-p-Ph), 119.6 (C-p-Ph), 118.8, 116.4, 42.1 (2CH3). GC-MS (m/z): 294.1 [M+2] +. .

( 3 *

 3 146.5, 138.7, 129.9, 129.1, 125.9, 121.1, 120.1, 119.1, 114.2, 109.4, 46.9, 27.2 (2C). GC-MS (m/z): 289.1 [M+2] +. .7-bromo-N,N,9,9-tetramethyl-9H-fluoren-2-amine (160).To the stirred mixture of 36 (750 mg, 2.60 mmol, 1 eq.) and paraformaldehyde (390 mg, 13.0 mmol, 5 eq.) in glacial acetic acid (10 mL) at 0 °C, NaBH3CN (492 mg,7.80 mmol, 3 eq.) was added in small portions. The mixture was allowed to warm up to room temperature and stirred overnight before being poured into cold water (150 mL). Formed solution was extracted with ethyl acetate 30 mL). Combined organic layer was washed with sat. aq. NaHCO3 solution and dried with magnesium sulfate. Organic solvent was removed under reduced pressure and the obtained residue was purified by crystallization from ethanol to give the product 160 (720 mg, 87 %) as white crystals. Eluent (Tol/DCM = 9:1, Rf = 0.71). 1 H-NMR (200 MHz, CDCl3, δ): 7.56 (d, 3 J=8.0 Hz, 1H), 7.49 (d, 4 J=1.0 Hz, 1H), 7.43-7.37 (m, 2H), 6.76 (s, 1H), 6.74 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H), 3.04 (s, 6H), 1.43 (s, 6H). 13 C-NMR (50 MHz, CDCl3, δ): 155.1, 155.1, 150.6, 138.9, 130.0, 127.6, 125.9, 120.9, 120.1, 118.9, 111.9, 106.8, 47.1, 41.2 (2C), 27.5 (2C). GC-MS (m/z): 265.2 [M+2] +. . N,N,9,9-tetramethyl-7-vinyl-9H-fluoren-2-amine (161/I-6). 160 (100 mg, 0.32 mmol, 1 eq.) and Pd(PPh3)4 (19 mg, 0.016 mmol, 5 mol %) were purged under argon and dissolved in dry toluene (2 mL). Then, tributylvinyltin (107 μL, 0.32 mmol, 1 eq.) was added and the mixture was heated to 80 °C overnight. The crude was quenched by NaOH (1 N) and stirred for additional 30 mins, then extracted with toluene. The organic extract was washed with water (3x), dried by magnesium sulfate, and evaporated under reduced pressure. Residue was purified by column chromatography. Eluent (DCM/CyHex = 1:1, Rf = 0.37) to provide compound I-6 (66 mg, 80 %) as a brown solid. 1 H-NMR (200 MHz, CDCl3, δ): 7.59-7.51 (m, 2H), 7.43 (s, 1H), 7.35 (d, 4 J=2.0 Hz, 1H), 6.86-6.70 (m, 3H), 5.75 (d, 3 Jtrans=20.0 Hz, 1H), 5.20 (d, 3 Jcis=10.0 Hz, 1H), 3.04 (s, 6H), 1.48

  1 H-NMR(200 MHz, CDCl3, δ): 10.03 (s, 1H, CHO), 7.95 (br s, 1H, H1), 7.82 (dd, 3 J=7.5 Hz 4 J=1.0 Hz, 1H, H3), 7.68(d, 3 J=7.5 Hz, 1H, H4), 7.66(d, 3 J=8.0 Hz, 1H, H5), 6.78 (br s, 1H, H8), 6.75 (dd, 3 J=8.0 Hz 4 J=1.0 Hz, 1H, H6), 3.09 (s, 6H, N(CH3)2), 1.54 (s, 6H, 2CH3).13 C-NMR (50 MHz, CDCl3, δ): 192.0 (C=O), 157.1 (Ca), 153.4 (Cb), 151.6 (C7), 146.8 (Cd), 133.7 (C2), 131.2 (C3), 126.1 (Cc), 122.5 (C1), C5), 118.4 (C4), 111.8 (C6), 105.8 (C8), 46.7 (C9), 40.6 (2C, N(CH3)2), 27.3 (2C, 2CH3). GC-MS (m/z): 265 [M +. ]. 1-(7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl)prop-2-yn-1-one (163/PP2). Ethynylmagnesium bromide (3.16 mL, 0.5 M in THF, 1.58 mmol, 1.4 eq.) was added dropwise to a solution of carbaldehyde 162 (300 mg, 1.13 mmol, 1 eq.) in THF (2.5 mL) at 0 °C.

  1 H-NMR (200 MHz, CDCl3, δ): 8.18-8.13 (m, 2H), 7.68-7.61 (m, 2H), 6.76-6.73 (br d, 2H), 3.41 (s, 1H), 3.08 (s, 6H), 1.50 (s, 6H).13 C-NMR (50 MHz, CDCl3, δ): 177.0, 157.4, 153.1, 151.7, 147.0, 133.4, 130.9, 126.1, 123.0, 122.4, 118.2, 111.7, 105.9, 81.0, 80.1, 46.8, 40.7 (2C), 27.3 (2C). HRMS (ESI + ): m/z calcd for C20H20ON: 290.1539 [M+H] + ; found 290.1539.

  To a stirred solution of n-hexyl azide S5 (30 mg, 0.23 mmol, 1.1 eq.) in DCE (1 mL) at 0 °C under argon, was added dropwise a solution of 163 (60 mg, 0.21 mmol, 1 eq.) in DCE (1 mL).

  121.4, 121.3, 119.2, 118.0, 111.7, 106.5, 47.1, 41.1 (2C), 27.7 (2C). HRMS (ESI + ): m/z calcd for C23H22N3S: 372.1529 [M+H] + ; found 372.1532.4-(7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl)-4oxobutanoic acid (167).To a stirred solution of 160 (0.8 g, 2.5 mmol, 1 eq.) in THF (12 mL) under argon, were sequentially added preactivated magnesium turnings (120 mg, 5.0 mmol, 2 eq.) and 3 drops of BrCH2CH2Br. The reaction was initiated by heating to 50 °C.

  The crude was purified by flash chromatography on silica gel eluted with DCM/MeOH (100/0 → 95/5, v/v) to provide the title compound 167 (510 mg, 60 %) as a yellow powder. Rf = 0.43 (DCM/MeOH = 98/2); 1 H NMR (200 MHz, MeOD-d 4 , δ): 7.85 (br s, 1H, H1), 7.76 (dd, 3 J=8.0 Hz 4 J=1.0 Hz, 1H, H3), 7.69 (d, 3 J=8.0 Hz, 1H, H5), 7.60 (d, 3 J=8.0 Hz, 1H, H4), 7.47 (br s, 1H, H8), 7.23 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 3.10 (t, 3 J=6.0 Hz, 2H, H3'), 3.04 (s, 6H, N(CH3)2), 2.45 (t, 3 J=6.0 Hz, 2H, H2') 1.25 (s, 6H, 2CH3). 1 H NMR (200 MHz, DMSO-d 6 , δ): 8.03 (d, 4 J=1.0 Hz, 1H, H1), 7.92 (dd, 3 J=8.0 Hz 4 J=1.0 Hz, 1H, H3), 7.72 (d, 3 J=8.0 Hz, 1H, H5), 7.70 (d, 3 J=8.0 Hz, 1H, H4), 6.91 (d, 4 J=2.0 Hz, 1H, H8), 6.74 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 3.27 (t, 3 J=6.0 Hz, 2H, H3'), 3.00 (s, 6H, N(CH3)2), 2.58 (t, 3 J=6.0

  MeOH = 99:1) to afford compound PP6 (42 mg, 72 %) as a yellow solid. 1 H NMR (200 MHz, CDCl3, δ): 7.98 (s, 1H, H1), 7.95 (dd, 3 J=8.5 Hz 4 J=1.0 Hz, 1H, H3), 7.63 (d, 3 J=8.5 Hz, 1H, H5), 7.59 (d, 3 J=8.0 Hz, 1H, H4), 6.76 (s, 1H, H8), 6.74 (dd, 3 J=8.5 Hz 4 J=2.0 Hz, 1H, H6), 3.41 (t, 3 J=6.5 Hz, 2H, H3'), 3.25 (m, 2H, Hm), 3.06 (s, 6H, N(CH3)2), 2.63 (t, 3 J=6.5 Hz, 2H, H2') 1.48 (s, 6H, 2CH3 ), 1.43-1.25 (m, 4H, Hn,o), 0.91 (t, 3 J=7.0 Hz, 3H, Hp).

169 , 5 .

 1695 Scheme 5. Synthesis of 169 and 170-177 series (on 100 mg scale) of products corresponding to PP7-14 respectively.

  formyl-9,9-dimethyl-9H-fluoren-2yl)piperazine-1-carboxylate (177/PP14). Following GP-E.Yellow solid, Eluent (PE/EA = 8:2, Rf = 0.38), yield=77 % (MW).

0 ( 3 ( 0 ( 0 Hz 4 J=1. 5 9 (

 0300459 1 H-NMR (200 MHz, CDCl3, δ): 10.01 (s, 1H, CHO), 7.91 (br s, 1H, H1), 7.81 (dd, 3 J=7.5 Hz 4 J=1.0 Hz, 1H, H3), 7.71(d, 3 J=7.5 Hz, 1H, H4), 7.07(d, 3 J=8.5 Hz, 1H, H5),6.98(d, 4 J=2.0 Hz, 1H, H8), 6.94 (dd, 3 J=8.5 Hz 4 J=2.0 Hz, 1H, H6), 3.63 (t, 3 J=5.0 Hz, 4H, CH22',6'), 3.26 (t, 3 J=5.0 Hz, 4H, CH23',5'), 1.49 (s, 15H, 5CH3).13 C-NMR (50 MHz, CDCl3, δ): 192.2 (C=O), 156.9 (Ca), 154.8 (COO), 153.9 (Cb), 152.5 (C7), 146.1 (Cd), 134.52(C2), 131.1 (C3), 129.9 (Cc), 122.8 (C1), 122.2 (C5), 119.3 (C4), 115.6 (C6), 110.4 (C8), 80.2 (CMe3), 49.4 (2C, C3',5'), 47.C9), 44.0 (2C, C2',6'), 28.6 (3C, 3CH3Boc), 27.6 (2C, 2CH3). HRMS (ESI + ): m/z calcd for C25H31O3N2: 407.2329 [M+H] + ; found 407.2331.2-((9,9-dimethyl-7-(piperidin-1-yl)-9H-fluoren-2yl)methylene)malononitrile (178/PP15). Following GP-D.Red solid, Eluent (CyHex/EA = 9:1, Rf = 0.28, yield=87 %. 1 H-NMR (200 MHz, CDCl3, δ): 7.98 (d, 4 J=1.5 Hz, 1H, H1), 7.80 (dd, 3 J=8.0 Hz 4 J=1.5 Hz, 1H, H3), 7.73 (s, 1H, CH=C), 7.55 (d, 3 J=8.0 Hz, 2H, H4,5), 6.96 (s, 1H, H8), 6.94 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 3.33 (t, 3 J=5.0 Hz, 4H, H2',6'), 1.72 (m, 6H, H3',4',5'), 1.48 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 159.9 (Cm), 157.4 (Ca), 154.2 (Cb), 153.8 (C7), 147.Cd), 132.1 (C3), 128.3 (C2), 127.8 (Cc), 124.3 (C1), 122.6 (C5), 119.5 (C4), 115.2 (C6), 115.CN), 113.9 (CN), 109.4 (C8), 78.3 (Cn), 50.1 (2C, C2',6'), 47.1 (C9), 27.2 (2C, 2CH3), 25.8 (2C, C3',5'), 24.4 (C4'). HRMS (ESI + ): m/z calcd for C24H24N3: 354.1965 [M+H] + ; found 354.1965. 2-((9,9-dimethyl-7-morpholino-9H-fluoren-2yl)methylene)malononitrile (179/PP16). Following GP-D. Red solid, Eluent (CyHex/EA = 9:1, Rf = 0.3, yield=72 %. 1 H-NMR (200 MHz, CDCl3, δ): 7.99 (br s, 1H, H1), 7.80 (dd, 3 J=8.Hz, 1H, H3), 7.75 (s, 1H, CH=C), 7.68 (d, 3 J=8.0 Hz, 2H, H4,5), 6.96 (s, 1H, H8), 6.94 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 3.90 (t, 3 J=5.0 Hz, 4H, H3',5'), 3.31 (t, 3 J=5.0 Hz, 4H, H2',6'), 1.49 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 159.9 (Cm), 157.3 (Ca), 154.2 (Cb), 153.0 (C7), 146.Cd), 131.9 (C3), 129.0 (C2), 128.6 (Cc), 124.4 (C1), 122.7 (C5), 119.7 (C4), 114.8 (C6), 113.8 (2C, 2CN), 109.1 (C8), 78.9 (Cn), 66.9 (2C, C3',5'), 48.9 (2C, C2',6'), 47.1 (C9), 27.2 (2C, 2CH3). HRMS (ESI + ): m/z calcd for C23H22ON3: 356.1757 [M+H] + ; found 356.1760.

  GP-F) used for the synthesis of (165-167/F1-3): The propioloyl fluorene 163 (1 eq.

  Scheme 6. Synthesis of the "clickable" sugar 182

  , Clarity ® 5u Oligo-RP column 250 x 10 mm Phenomenex ® ). The following gradient system was used: 25 % A -(5min)→ 5 % A / 95 % B -(25 min)→ 100 % B -(10 min) with A= 0.25 CH3CN: 0.75 MilliQ ® water and B= CH3CN. 1 H-NMR (500 MHz, CD3OD-d 4 , δ): 8.71 (s, 1H), 8.33 (s, 1H), 8.31 (dd, 3 J=8.0 4 J=1.5 Hz, 1H), 7.71 (d, 3 J=8.0 Hz, 1H), 7.69 (d, 3 J=8.5 Hz, 1H), 6.87 (d, 4 J=2.0 Hz, 1H), 6.

  36 g, 15 mmol, 1 eq) was dissolved in methyl trifluoroacetate (15 ml, 150 mmol, 10 eq.) by sonication and stirred overnight at rt. The reaction mixture was evaporated and dried by coevaporation with toluene (3*40 mL) to give the title product 191 (2.73 g, 98%) as a colorless oil: 1 H-NMR (200 MHz, CDCl3, δ): 6.82 (br.s, 1H, NH), 3.92 (m, 1H, CHOH), 3.73 (m, 1H, CH a H b OH), 3.62 (m, 1H, CH a H b NH), 3.57 (m, 1H, CH a H b OH), 3.42 (m, 1H, CH a H b NH).

3. 31 ( 192 ( 0 .

 311920 m, 1H, CH a H b NH), 3.25 (dd, 1H, J = 7.5, 9.5 Hz, CH a H b ODMTr), 3.15 (dd, 1H, J = 7.5, 9.9g, 1 eq) was dissolved in 45 mL of 6 M ethanolic ammonia solution and stirred overnight. The crude was evaporated and purified by a column chromatography. Eluent (DCM/MeOH = 99: 1 in the presence of 0.1% Et3N) giving the desired compound 193 as pale yellow oil (0.51 g, 61 %). Note: the product degrades on silica and DMTr is cleaved very quickly. The product can be taken to next step without purification.

  (CH2CH3)2).13 C-NMR (125 MHz, CDCl3, δ): 192.20 (C=O), 157.51 (Ca), 153.39 (Cb), 149.20 (C7), 147.07 (Cd), 133.61 (C2), 131.41 (C3), 125.41 (Cc), 122.63 (C1), 122.53 (C5), 118.29 (C4), 111.08 (C6), 105.28 (C8), 46.78 (C9), 44.87 (2C, N(CH2CH3)2), 27.40 (2CH3), 12.75 (2C, N(CH2CH3)2). GC-MS (m/z): 293.2 [M +. ].

  -1-one(196). Following GP-H on 195 (700 mg, 2.39 mmol) as starting material. Eluent for flash chromatography (CyHex/EA = 9:1, Rf = 0.24) providing the clickable push-pull 196 as a yellow solid (700 mg, 55 %). 1 H-NMR (500 MHz, CDCl3, δ): 8.14 (dd, 3 J=8.0 Hz 4 J=1.5 Hz, 1H, H3), 8.12 (s, 1H, H1), 7.62(d, 3 J=8.5 Hz, 1H, H4), 7.59(d, 3 J=8.0 Hz, 1H, H5), 6.70 (s, 1H, H8), 6.68 (dd, 3 J=8.5 Hz 4 J=2.0 Hz, 1H, H6), 3.45 (q, 3 J=7.0 Hz, 4H, N(CH2CH3)2), 3.40 (s, 1H, C≡CH) 1.49 (s, 6H, 2CH3), 1.23 (t, 3 J=7.0 Hz, 6H, N(CH2CH3)2).13 C-NMR (125 MHz, CDCl3, δ): 177.1 (C=O), 157.7 (Ca), 153.0 (Cb), 149.3 (C7), 147.2 (Cd), 133.3 (C2), 131.1 (C3), 125.3 (Cc), 123.0 (C1), 122.8 (C5), 117.9 (C4), 111.1 (C6), 105.2 (C8), 81.1 (C≡CH), 79.9 (C≡CH), 46.8 (C9), 44.9 (2C, N(CH2CH3)2), 27.4 (2CH3), 12.7 (2C, N(CH2CH3)2). GC-MS (m/z): 317.2 [M] +. . This type of Micheal acceptor compounds is very reactive and cannot be stored for long time. . Following GP-I on 196 (230 mg, 0.73 mmol) as starting material. Eluent for flash chromatography (CyHex/EA = 8:2, Rf = 0.33) providing S13 as a brown solid (390 mg, 73 %). 1 H-NMR (200 MHz, CDCl3, δ): 8.46 (s, 1H, Htriazole), 8.45 (dd, 3 J=8.0 Hz 4 J=1.5 Hz, 1H, H3), 8.39 (d, 3 J=8.0 Hz, 1H, H1), 7.96 (d, 3 J=8.0 Hz, 2H, Hotol), 7.84 (d, 3 J=8.0 Hz, 2H, Hotol), 7.64 (d, 3 J=8.0 Hz, 1H, H4), 7.62 (d, 3 J=8.0 Hz, 1H, H5), 7.28 (d, 3 J=8.0 Hz, 2H, Hmtol), 7.17 (d, 3 J=8.0 Hz, 2H, Hmtol), 6.71 (s, 1H, H8), 6.69 (dd, 3 J=8.0 Hz 4 J=1.5 Hz, 1H, H6), 6.56 (t, 3 J=6.0 Hz, 1H, H1'), 5.82 (m, 1H, H3'), 4.71 (m, 1H, H4'), 4.64 (m, 2H, H5'), 3.46 (q, 3 J=7.0 Hz, 4H, N(CH2CH3)2), 3.28 (m, 1H, H2'a), 2.94 (m, 1H, H2'b), 2.44 (s, 3H, CH3tol), 2.31 (s, 3H, CH3tol), 1.52 (s, 6H, 2CH3), 1.24 (t, 3 J=7.0 Hz, 6H, N(CH2CH3)2).

5 ( 2 (

 52 Following GP-J on S13 (390 mg, 0.55 mmol) as starting material. Eluent for flash chromatography (DCM/Ac = 8:2, Rf = 0.3) providing 197 as a a bright yellow solid (205 mg, 79 %). 1 H-NMR (200 MHz, C5D5N, δ): 9.49 (s, 1H, Htriazole), 8.87 (br s, 1H, H1), 8.83 (br d, 3 J=8.0 Hz, 1H, H3), 7.81 (d, 3 J=8.0 Hz, 2H, H4,5), 6.99 (t, 3 J=6.0 Hz, 1H, H1'), 6.90 (br s, 1H, H8), 6.75 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 5.22 (m, 1H, H3'), 4.62 (m, 1H, H4'), 4.17 (m, 2H, H5'), 3.30 (q, 3 J=7.0 Hz, 4H, N(CH2CH3)2), 3.30-2.20 (m, 2H, H2'), 1.50 (s, 6H, 2CH3), 1.07 (t, 3 J=7.0 Hz, 6H, N(CH2CH3)2). 13 C-NMR (50 MHz, C5D5N, δ): 184.6 (C=O), 157.2 (Ca), 152.2 (Cb), 149.3 (C7), 148.C=CH), 145.5 (Cd), 133.6 (C2), 131.0 (C3), 127.8 (C=CH), 125.3 (Cc), 124.5 (C1), 122.9 (C5), 117.6 (C4), 111.0 (C6), 105.2 (C8), 89.6 (C4'), 89.5 (C1'), 70.6 (C3'), 61.6 (C5'), 46.5 (C9), 44.2C, N(CH2CH3)2), 41.6 (C2'), 26.8 (2C, 2CH3), 12.1 (2C, N(CH2CH3)2). HRMS (ESI + ): m/z calcd for C27H33O4N4: 477.2496 [M+H] + ; found 477.2491. yl)methanone (S14). Following GP-K on 197 (140 mg, 0.29 mmol) as starting material. Eluent for flash chromatography (Tol/Ac = 8:2, in presence of 1% Et3N, Rf = 0.5) providing S14 as a a bright yellow solid (215 mg, 89 %). 1 H-NMR (200 MHz, CD2Cl2, δ): 8.40 (s, 1H, Htriazole), 8.39 (br s, 1H, H1), 8.34 (dd, 3 J=8.0 4 J=2.0 Hz, 1H, H3), 7.61 (2d, 3 J=8.0 Hz, 2H, H4,5), 7.40-7.14 (m, 9H, H-DMTr), 6.79 (d, 3 J=8.0, 4H, H-DMTr), 6.72 (br s, 1H, H8), 6.69 (dd, 3 J=8.0 Hz

4 J=2. 0 1 ( 42 ( 2 ( 200 (

 01422200 Scheme 9. Synthesis of FM3

  with ethyl acetate (3*5 mL). Combined organic layer was washed with saturated aqueous solution of NaHCO3 and dried with magnesium sulfate. Organic solvent was removed under reduced pressure and the obtained residue was purified by flash chromatography on silica gel. Eluent (PE/Et2O = 98:2, Rf = 0.19) to obtain pure dimethylamino product (118 mg, 60 %) as yellow solid. 1 H-NMR (200 MHz, CDCl3, δ): 7.56 (d, 4 J=1.5 Hz, 1H, H8), 7.39 (br d, 3 J=8.0 Hz, 1H, H6), 7.25

1 -( 7 -

 17 C-NMR (50 MHz, CDCl3, δ): 151.3 (C2), 139.7 (t, JFC=5.0 Hz, Cd), 139.2 (m, JFC=5.0 Hz, Ca), 138.6 (m, JFC=5.0 Hz, Cb), 134.9 (C6), 126.9 (C8), 125.9 (t, JFC=5.0 Hz, Cc), 122.9 (t, JFC=243 Hz, C9), 121.5 (C4), 120.3 (C5), 119.6 (C7), 114.7 (C3), 107.4 (C1), 40.5 (2C, N(CH3)2). 19 F-NMR (188 MHz, CDCl3, δ): -109.48. GC-MS (m/z): 323.0 [M] +. . The reactions above were scaled up to prepare more starting materials. 7-(dimethylamino)-9,9-difluoro-9H-fluorene-2-carbaldehyde (S20). Following GP-G on S19 starting material. Yield = 49 %. 1 H-NMR (200 MHz, CDCl3, δ): 9.94 (s, 1H, CHO), 8.01 (d, 4 J=1.5 Hz, 1H, H1), 7.89 (br d, 3 J=8.0 Hz, 1H, H3), 7.48 (d, 3 J=8.0 Hz, 1H, H4), 7.44 (d, 3 J=8.5 Hz, 1H, H5), 6.95 (d, 4 J=2.0 Hz, 1H, H8), 6.72 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 3.06 (s, 6H, N(CH3)2 ). 13 C-NMR (50 MHz, CDCl3, δ): 190.9 (C=O), 152.2 (C7), 147.0 (t, JFC=5.0 Hz, Cd), 140.8 (t, JFC=25.0 Hz, Ca), 138.2 (t, JFC=25.0 Hz, Cb), 135.0 (C3), 134.8 (C2), 125.2 (t, JFC=25.0 Hz, Cc), 124.4 (C1), 122.7 (C5), 122.6 (C9), 119.1 (C4), 114.7 (C6), 107.33 (C8), 40.6 (N(CH3)2). 19 F-NMR (188 MHz, CDCl3, δ): -110.38. HRMS (ESI + ): m/z calcd for C16H14ONF2: 274.1038 [M+H] + ; found 274.1038. HRMS (ESI + ): m/z calcd for C16H14ONF2: 274.1038 [M+H] + ; found 274.1038. ` (dimethylamino)-9,9-difluoro-9H-fluoren-2-yl)prop-2-yn-1-one (203). Following GP-H on S20 as starting material (1.2 g, 4.0 mmol), which was clicked to the azido sugar without purification. This product degrades extremely fast.

  3-triazol-4-yl)methanone (S21).Following GP-I for clicking the substrate and batching directly into deprotection GP-J protocol. Yield=39 % over two steps. 1 H-NMR(200 MHz, C5D5N,

2 (

 2 9.50 (s, 1H, Htriazole), 9.09 (br s, 1H, H1), 8.75 (br d, 3 J=8.0 Hz, 1H, H3), 7.60 (d, 3 J=8.0 Hz, 2H, H4,5), 7.20 (d, 1H, 4 J=2.0 Hz, H8), 6.99 (t, 3 J=6.0 Hz, 1H, H1'), 6.73 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H, H6), 5.23 (m, 1H, H3'), 4.63 (m, 1H, H4'), 4.20 (m, 2H, H5'), 3.20-2.78 (m, 2H, H2'), 2.86 (s, 6H, N(CH3)2), 1.57 (s, 6H, 2CH3). 13 C-NMR (50 MHz, C5D5N, δ): 183.6 (C=O), 152.0 (C7), 148.2 (C=CH), 145.6 (t, JFC=5.0 Hz, Cd), 140.5 (t, JFC=25.0 Hz, Ca), 137.3 (t, JFC=25.0 Hz, Cb), 135.6 and 135.C2), 135.1 (C3), 128.3 (C=CH), 125.7 (C1), 125.6 (m, C9), 125.2 (t, JFC=5.0 Hz, Cc), 122.9 (C5), 118.9 (C4), 114.9 (C6), 107.2 (C8), 89.8 (2C, C1',4'), 70.8 (C3'), 61.9 (C5'), 41.8 (C2'), 39.7 (2C, N(CH3)2). HRMS (ESI + ): m/z calcd for C23H22O4N4F2Na: 479.1501 [M+Na] + ; found 479.1498. yl)methanone (S22). Following GP-K on S12 (150 mg, 0.22 mmol) as starting material. Eluent for flash chromatography (Tol/Ac = 7:3, Rf = 0.25) providing the title compound S22 as a yellow solid (149 mg, 71 %). 1 H-NMR (200 MHz, CD2Cl2, δ): 8.56 (br s, 1H, H1), 8.51 (br d, 3 J=8.0, 1H, H3), 8.46 (s, 1H, Htriazole), 7.51 (2d, 3 J=8.0 Hz, 2H, H4,5), 7.40-7.16 (m, 9H, H-DMTr), 6.01 (d, 4 J=2.0 Hz, 1H, H8), 6.80 (d, 3 J=8.0, 5H, H-DMTr and H6), 6.43 (t, 3 J=6.0 Hz, 1H, H1'), 4.67 (m, 1H, H3'), 4.21 (m, 1H, H4'), 3.73 (s, 6H, (O-CH3)2), 3.29 (m, 2H, H5'), 3.07 (s, 6H, N(CH3)2),

  -3-yl (2-cyanoethyl) diisopropylphosphoramidite (FM4). Following GP-L on S22 (100 mg, 0.09 mmol) as starting material. Eluent for flash chromatography (Tol/Ac = 8:2, Rf = 0.35) providing phosphoramidite FM4 as a yellow solid (105 mg, 88 %).

XV. 2

 2 HPLC profile: GXG (left) and TXT (right) single strand ODN (255 nm up -390 nm down); X-label is FM2. XV.3 Excitation spectra CXC (left) and TXT (right) investigations, X label is FM4. XV.4 Melting temperature curves CXC (left) and TXT (right) duplexes, X label is FM4..

  Key words: fluorene, push-pull dye, palladium, CuAAC, biosensor, membrane, lipids, nucleic acids Résumé: Le développement de nouvelles voies synthétiques permettant l'accès à des sondes à applications biologiques connaît un intérêt accru. Les travaux de cette thèse s'inscrivent dans ce cadre. Ils portent particulièrement sur les colorants « Push-pull » qui se caractérisent par leur sensibilité aux changements de leur environnement, leur faible cytotoxicité et leur photostabilité élevée. En outre, la synthèse de ces fluorènes est très exigeante. Nos travaux ont abouti à : 1) Des approches synthétiques concises pour accéder à des composés aromatiques aminés difficiles à synthétiser, celles-ci via des systèmes Pallado-catalysés optimisés impliquant une amination sélective et une synthèse séquentielle en « one pot », 2) La synthèse d'une bibliothèque vaste de fluorènes avec la diversification des groupements accepteur et donneur. 3) Des relations structure-propriétés photophysiques. 4) La synthèse de trois colorants avancés engendrant la première sonde de fluorènes spécifique aux membranes : un outil puissant pour étudier la structure et les dynamiques biophysiques de ces membranes. Le colorant optimal surpasse les caractéristiques des sondes couramment utilisées montrant: une absorption décalée vers le rouge attenant 405 nm en diode laser, une luminosité plus élevée diminuant la concentration du colorant pour la coloration de ~ 10-15 fois, une haute photo-stabilité, une forte sensibilité aux domaines liquides des membranes des cellules. 5) La Synthèse de 4 phosphoramidites marqués et leurs incorporations dans les oligonucléotides attestant une grande sensibilité aux milieux protiques et au pH. En duplex d'ADN, le colorant est efficace pour la différenciation des bases opposeés. Une application du marqueur d'ADN fluorescent l'a testé comme un donneur pour le déplacement de Stokes dans une paire de FRET émissive en combinaison avec l'accepteur Dy681. Le FRET a démontré une augmentation ratiométrique dans la région proche infrarouge avec un décalage de 300 nm.

Table of Contents

 of • Dedication .................................................................................................................................................................. • Acknowledgments ................................................................................................................................................... • Table of contents ..................................................................................................................................................... • List of abbreviation .

Table 1 .

 1 Environment-sensitive dyes

	Fluorophore family	Representative dye	Example of in MeOH properties	Advantages	Drawbacks

  !!

	Strongest sensitivity to polarity, largest Stokes shifts	UV absorption, low extinction coefficient, quenching in water and other polar solvents

33 34 35 36 37 38

	Br		MeI, KI KOH DMSO, rt 92 %	Br		HNO 3 AcOH, rt 72 %	O 2 N	Br
							Fe, NH 4 Cl	EtOH/H 2 O reflux, 95 %
	N	O	1) nBuLi, THF -78 o C	N	Br	EtI, K 2 CO 3	H 2 N	Br
			2) DMF			DMF, 80 o C
			60 %			75 %

  The formed amide intermediate can produce the arylamine by reductive elimination regenerating the catalyst to

							PdCl 2 (o-tol 3 P) 2
	R 1	39	Br	+	H	N R 2 R 3	or Pd(dba) 2 + o-tol 3 P NaOtBu or LiHMDS toluene, reflux	R 1	40	R 2 N R 3

1.3 Sterols

	They differ widely in structure from the other two groups. Cholesterol (48) is the most

Table 2 . chemical versus enzymatic synthesis of DNA

 2

	Chemical synthesis	Enzymatic synthesis
	Synthesis of short DNA sequences (5-200 bases)	Synthesis of longer sequences
	Allows the facile introduction of natural and	Introduction of modified nucleobases depends
	modified nucleobases	on the tolerance of the DNA polymerase
	Site-specific synthesis	Introduction of modified nucleobases is only predicted to some extent

  in fig.47.

	Entry	Deviation from standard conditions	Screened Ligands
	1	PPh3
	2	P(o-Tol)3
	3	PCy3
	4	P(t-Bu)3
	5	DavePhos	Ligand
	6	BrettPhos	Screening
	7	RuPhos
	8	JohnPhos
	9	XantPhos
	10	-
	11	Cs2CO3	Base
	12	KOtBu	Base
	13	Pd(dba)2	Catalyst
	14	Dioxane	Solvent
	15	rt	Temp
	16	MW (45 min)	Activation
	17	8 mol%	Ligand
	18	Doubled	Loading
		Figure 46. Optimization of the reaction conditions
		100
	GC conversion (%)			Product 116 Product 115
		0
		1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
			Entry
		Figure 47. Results of the optimization study

Br Br 44 Pd(OAc) 2 +(4+mol%) BINAP+(12+mol%) PhMeNH+(1.2+eq.)

NaOt " Bu+(1.1+eq.),+ Toluene,+100+

°C,+18+h

  table 3, fig.59). Compared to PP1 reference, PP3 presented a similar absorption, whereas the emission maximum was red shifted in polar solvents. By contrast, the absorption of PP6 was blue shifted, while the emission showed little change (fig.59). The quantum yields of PP3 and PP6 were in the range of 52 to 86% in all of the tested solvents except in ethanol and water where they were considerably reduced. Altogether, PP3 demonstrated superior absorption and emission properties to those of PP6.

		1,0
							PP2 Em
							PP3 Em
							I6 Em
	Normalized intensity, a. u.	0,5					PP5 Em PP6 Em PP2 Ab PP3 Ab I6 Ab PP5 Ab PP6 Ab
		0,0
		300	400	500	600	700	800
				Wavelength, nm

Table 3 .

 3

	a]

Table 5 .

 5 Prediction study with a Hammett contant-based model

	Solvent	Prediction λabs / λem (nm)	Experimentally λabs / λem (nm)
	CHCl3	401 / 507	399 / 497
	Acetonitrile	395-396 / 541	394 / 518
	EtOH	395 / 576	395 / 554

Table 6 .

 6 Spectroscopic properties of F1-3 and the parent dye PP3 for comparison[a]

	Solvent		PP3	F1	F2	F3
	ET(30)	εmax (10 3 .M -1 .cm -1 )	37.6	38.0	37.1	35.0
	Phosphate Buffer [b] (63.1)	λabs (nm) λem (nm) ΔλSS (nm) Φ (%)	n.d. n.d. n.d. n.d.	390 n.d. n.d. n.d.	401 n.d. n.d. n.d.	n.d. n.d. n.d.
		λabs (nm)	n.d.	395	400
	MeOH	λem (nm)	n.d.	651	647
	(55.4)	ΔλSS (nm)	n.d.	256	247
		Φ (%)	n.d.	1,5	3	2
		λabs (nm)	396	403	400
	EtOH	λem (nm)	622	630	629
	(51.9)	ΔλSS (nm)	226	227	229
		Φ (%)	6	6	8	8
		λabs (nm)	389	395	391
	ACN	λem (nm)	578	586	578
	(45.6)	ΔλSS (nm)	189	191	187
		Φ (%)	77	42	51	61
		λabs (nm)	402	405	402
	DMSO	λem (nm)	582	592	584
	(45.1)	ΔλSS (nm)	180	187	182
		Φ (%)	85	53	75	93
		λabs (nm)	399	403	404
	Chloroform	λem (nm)	532	549	539
	(39.1)	ΔλSS (nm)	133	146	135
		Φ (%)	72	74	56	66
		λabs (nm)	n.d.	393	390
	Ethyl acetate (38.1)	λem (nm) ΔλSS (nm)	n.d. n.d.	550 157	527 137
		Φ (%)	n.d.	72	61	69
		λabs (nm)	391	394	393
	Dioxane	λem (nm)	488	515	502
	(36)	ΔλSS (nm)	97	121	109
		Φ (%)	0.52	82	96	72
		λabs (nm)	394	391	399
	Toluene	λem (nm)	473	498	472
	(33.9)	ΔλSS (nm)	79	107	73
		Φ (%)	0.86	60	85	54

Table 8 .

 8 Theoretical and found masses of the synthesized ODNs

	Abbreviation	Labeled sequence	Theoretical mass	Mass found
	TMT	CGT TTT TMT TTT TGC	4689	4675
	AMA	CGT TTT AMA TTT TGC	4707	2086.5 truncated sequence (CGTTTTA)
	CMC	CGT TTT CMC TTT TGC	4659	4644
	GMG	CGT TTT GMG TTT TGC	4739	4725

Table 10 .

 10 Theoretical and found masses of selected ODN sequences

				SH	SH
	32	80 o C, 6h 96 %	200	94 % BF 3 .O(C 2 H 5 ) 2 , DCM rt, overnight	201
		24 %			19 %
			203			202
	FM4
	204

  , 146.8 mmol, 4 eq.). The resulting reaction mixture was stirred at room temperature overnight before being poured into 200 mL of water. A light yellow precipitate was formed, then filtered out, washed with cold water, and dried under vacuum. The light yellow solid was purified by crystallization from methanol to provide the title compound S2 (2.94 g, 84 %) as white crystals.

	9,9-dimethyl-9H-fluorene (S2): To a stirred solution of 9H-fluorene S1
	(3.00 g, 18.1 mmol, 1 eq.) in DMSO (35 mL) at 60 °C, were sequentially
	added potassium iodide (300 mg, 1.8 mmol, 0.1 eq.), iodomethane (5.76 g,
	40.6 mmol, 2.25 eq.), and very cautiously powdered potassium hydroxide
	(8.30 g

1

H-NMR (200 MHz, CDCl3, δ):

N

  135.8, 130.6 (2C), 126.4, 121.8, 121.7, 121.3, 121.0, 118.6, 116.4, 47.5, 27.1 (2C). HRMS (ESI + ): m/z calcd for C18H16N2Br: 339.0491 [M+H] + ; found 339.0494.

	1-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)azepane
	(119): Eluent for flash chromatography (PE/Et2O = gradient
	up to 98:2, Rf = 0.5) providing 119 as a yellow solid (83 mg,
	0.23 mmol, 81 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.51 (br d,
	3 J=8.0 Hz, 1H, H4'), 7.46 (br s, 1H, H8'), 7.43-7.34 (m, 2H, H5',6'), 6.70 (br s, 1H, H1'), 6.68 (br d,
	3 J=8.0 Hz, 1H, H3'), 3.53 (t, 3 J=6.0 Hz, 4H, CH22,7), 1.84 (br m, 4H, CH23,6), 1.59 (br m, 4H,
	CH24,5), 1.45 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 155.3, 154.9, 149.4, 139.2, 129.9, 129.4,
	125.8, 121.1, 119.7, 118.4, 110.5, 105.1, 49.6 (2C), 47.0, 27.9 (2C), 27.5 (2C), 27.3 (2C). HRMS
	(ESI + ): m/z calcd for C21H25NBr: 370.1165 [M+H] + ; found 370.1166.	Br	N	Ph
	1 H-NMR (200 MHz, CDCl3, δ): 7.49-7.16 (m, 6H),
	7.02-6.86 (m, 5H), 3.29 (s, 3H), 1.34 (s, 6H). 13 C-NMR (50 MHz, CDCl3, δ): 155.5, 154.9, 149.1 1-(7-
	(2C), 138.4, 131.5, 130.1, 129.4 (2C), 126.1, 121.6, 120.8 (3C), 120.6, 119.8, 119.4, 114.4, 47.2,
	40.7, 27.7 (2C). HRMS (ESI + ): m/z calcd for C22H21NBr: 378.0852 [M+H] + ; found 378.0855.
	Thermal heating: (80 mg, 0.21 mmol, 76 %).
	1-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)-1H-pyrrole
	(117): Eluent for flash chromatography (PE/Et2O = gradient up
	to 98:2, Rf = 0.45) providing 117 as a yellow solid (74 mg, 0.22	Br	N
	mmol, 80 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.72 (d, 3 J=8.0 Hz,
	1H), 7.60-7.36 (m, 5H), 7.16 (t, J=2.0 Hz, 2H), 6.40 (t, J=2.0 Hz, 2H), 1.52 (s, 6H). 13 C-NMR (50
	MHz, CDCl3, δ): 155.7, 155.0, 140.6, 137.6, 135.9, 130.4, 126.3, 121.4, 121.1, 121.1, 120.0, 119.7
	(2C), 115.4, 110.6 (2C), 47.7, 27.1 (2C). HRMS (ESI + ): m/z calcd for C19H17NBr: 338.0539 [M+H] + ;
	found 338.0540.
	1-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)-1H-imidazole
	(118): Eluent for flash chromatography (PE/Et2O = gradient
	up to 98:2) providing 2c as a yellow solid (24 mg, 0.07 mmol,	Br		N
	28 %) 1 H-NMR (200 MHz, CDCl3, δ): 7.90 (s, 1H), 7.75 (d,
	3 J=8.0 Hz, 1H), 7.59 (d, 3 J=8.0 Hz, 1H), 7.57 (s, 1H), 7.47 (dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 1H), 7.40-7.32
	(m, 3H), 7.23 (s, 1H), 1.51 (s, 6H). 13 C-NMR (50 MHz, CDCl3, δ): 155.7, 155.3, 137.7, 137.0, 136.9,

bromo-9,9-dimethyl-9H-fluoren-2-yl)piperidine (120): Reaction performed on 1 gram scale (2.84 mmol).

					3
	8'		1'		2	4
	Br	9'		2'	N	5
	7'
	6'	5'	4'	3'	7	6
	Eluent for flash chromatography (PE/EA = gradient up to
	95:5, Rf = 0.6) providing 120 as a yellow solid (625 mg, 1.76
	mmol, 62 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.55 (d, 3 J=8.0 Hz, 1H, H4'), 7.49 (d, 4 J=2.0 Hz, 1H,
	H8'), 7.42 (d, 3 J=8.0 Hz, 1H, H5'), 7.39 (dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 1H, H6'), 7.00 (br s, 1H, H1'), 6.94
	(dd, 3 J=8.0 Hz, 4 J=2.0 Hz, 1H, H3'), 3.23 (t, 3 J=6.0 Hz, 4H, CH22,6), 1.77 (br m, 4H, CH23,5), 1.62 (br
	m, 2H, CH24), 1.45 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 155.3, 154.7, 152.6, 138.7, 130.0,
	129.6, 125.9, 120.7, 120.4, 119.3, 115.5, 110.8, 51.1 (2C), 47.1, 27.3 (2C), 26.0 (2C), 24.4. HRMS
	(ESI + ): m/z calcd for C20H23NBr: 356.1008 [M+H] + ; found 356.1008.
	1-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)pyrrolidine
	(121): Eluent for flash chromatography (PE/Et2O = gradient
	up to 97:3, Rf = 0.32) providing 121 as a yellow solid (79 mg,
	0.23 mmol, 83 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.41 (d, 3 J=8.0
	Hz, 1H, H4'), 7.36 (br d, 4 J=2.0 Hz, 1H, H8'), 7.27 (m, 2H, H5',6'), 6.45 (br s, 1H, H1'), 6.42 (dd,
	3 J=8.0 Hz, 4 J=2.0 Hz, 1H, H3'), 3.24 (t, 3 J=7.0 Hz, 4H, CH22,5), 1.91 (m, 4H, CH23,4), 1.34 (s, 6H,
	2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 155.2, 154.9, 148.2, 139.3, 129.9 (2C), 125.8, 121.1, 119.7,
	118.3, 110.9, 105.5, 48.0 (2C), 47.0, 27.5 (2C), 25.6 (2C). HRMS (ESI + ): m/z calcd for C19H21NBr:
	342.0852 [M+H] + ; found 342.0852.

7-bromo-N-butyl-9,9-dimethyl-9H-fluoren-2-amine (126):

  121.3, 121.1, 120.5, 119.7, 118.0 (2C), 116.9, 112.0, 47.1, 27.2 (2C). HRMS (ESI + ): m/z calcd for C21H19NBr: 364.0695 [M+H] + ; found 364.0698.

				8'			1'		2
		Br		9'			2'	N		3
			7'						4
			6'	5'		4'	3'
	Eluent for flash chromatography (PE/Et2O = gradient up to
	99:1, Rf = 0.11) providing 126 as a yellow solid (64 mg, 0.18
	mol, 67 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.56-7.27 (m, 4H),
	6.71-6.56 (m, 2H), 3.18 (t, 3 J=7.0 Hz, 2H), 1.66 (q, 3 J=7.0 Hz, 2H), 1.52-1.26 (m, 2H), 1.43 (s, 6H),
	0.98 (t, 3 J=7.0 Hz, 2H). 13 C-NMR (50 MHz, CDCl3, δ): 155.3, 154.9, 148.7, 140.0, 139.1, 130.0,
	125.9, 121.2, 119.9, 118.8, 112.0, 106.9, 47.0, 44.2, 31.8, 27.4 (2C), 20.5, 14.1. GC-MS (m/z):
	343.1 [M] +. .	Br	8'	9'	1'	2'	N 2	3	O	4
	7' 6' General Procedure (GP-B): Pd(OAc)2 (8 mol%), t-BuONa (2.2 eq.), and JohnPhos (24 mol%) 5 6 3' 4' 5'
		Br						N
			8'			1'		2		3
				9'			2'
		7'							4
			6'	5'	4'		3'	5
		Br					H N
									Ph

7-bromonaphthalen-2-yl)-1H-pyrrole (143): Following GP-A.

  136.8, 129.2, 129.0, 127.8, 124.7, 124.6, 120.4, 116.1, 104.2, 44.7 (2C), 12.8 (2C). HRMS (ESI + ): m/z calcd for C14H17NBr: 278.0539 [M+H] + ; found 278.0542. Hz, 1H), 6.84(d, 3 J=2.0 Hz, 1H), 7.13 (br s, 1H), 6.37 (t, 3 J=7.0 Hz, 2H), 3.47 (q, 3 J=5.0 Hz,

	1-(Eluent for flash chromatography (PE/Et2O = gradient up to 98:2, Rf	Br	N
	=0.54) providing 143 as a yellow solid (79 mg, 0.29 mmol, 83 %). 1 H-	N
	NMR (200 MHz, CDCl3, δ): 7.87 (br s, 1H), 7.74 (d, 3 J=9.0 Hz, 1H), 7.58
	(d, 3 J=9.0 Hz, 1H), 7.56 (s, 1H), 7.47 (dd, 3 J=8.5 Hz, 4 J=2.0 Hz, 1H), 7.42 (dd, 3 J=8.5 4 J=2. Hz, 1H),
	N 7.10 (t, J=2.0 Hz, 2H), 6.32 (t, J=2.0 Hz, 2H). 13 C-NMR (50 MHz, CDCl3, δ): 139.1, 135.1, 129.8, N
	129.7 (2C), 129.5, 129.0, 121.3, 120.5, 119.5 (2C), 116.3, 111.1 (2C). HRMS (ESI + ): m/z calcd for
	C14H11NBr: 272.0069 [M+H] + ; found 272.0070.
	N 2 ,N 2 ,N 7 ,N 7 -tetraethylnaphthalene-2,7-diamine	(144):
	Following GP-B. Eluent for flash chromatography (PE/EA =
	gradient up to 95:5, Rf =0.29) providing 144 as a yellow solid (62
	mg, 0.23 mmol, 65 %). 1 H-NMR (200 MHz, TFA-d 1 , δ): 8.30 (d,
	H N 3 J=9.0 Hz, 2H, H4,5), 8.20 (s, 2H, H1,8), 7.73 (d, 3 J=9.0 Hz, 2H, H3,6), 3.85 (q, 3 J=6.5 Hz, 8H, 4CH2), O N N Ph 1.23 (t, 3 J=6.5 Hz, 12H, 4CH3). 13 C-NMR (50 MHz, TFA-d 1 , δ): 137.8 (2C), 136.5, 134.9 (2C), 134.8,
	125.3 (2C), 121.5 (2C), 57.4 (4C), 11.3 (4C). HRMS (ESI + ): m/z calcd for C18H27N2: 271.2169
	[M+H] + ; found 271.2170.
	2,7-di(1H-pyrrol-1-yl)naphthalene (145): Following GP-B.
	Eluent for flash chromatography (PE/EA = gradient up to 95:5, Rf
	=0.5) providing 145 as a yellow solid (73 mg, 0.28 mmol, 81
	1 H-NMR (200 MHz, CDCl3, R 1 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.81 (d, 3 J=9.0 Hz, 2H, H4,5), 7.68 Br Br		R 2
	δ): 7.74 (d, 3 J=8.0 Hz, 1H), 7.68 (d, 3 J=8.0 Hz, 1H), 7.52 (s, 1H), (br s, 2H, H1,8), 7.47 (dd, 3 J=9.0 Hz, 4 J=2.0 Hz, 2H, H3,6), 7.15 (t, J=2.0 Hz, 4H, NCHpyr), 6.33 (t, N
	7.45-7.36 (m, 3H), 7.17 (t, J=2.0 Hz, 2H), 6.83 (dd, 3 Jtrans=17.0 Hz, S3 142-147 J=2.0 Hz, 4H, CHpyr). 13 C-NMR (50 MHz, CDCl3, δ): 139.3 (2C), 134.6, 129.6 (2C), 129.4, 119.9
	3 Jcis=11.0 Hz, 1H), 6.40 (t, J=2.0 Hz, 2H), 5.84 (d, 3 Jtrans=17.0 Hz, 1H), 5.30 (d, 3 Jcis=11.0 Hz, 1H), Scheme 2. 2,7-Naphtalene was prepared on (100 mg scale, 0.35 mmol of S3). (2C), 119.6 (4C), 117.0 (2C), 111.0 (4C). GC-MS (m/z): 258.1 [M] +. .
	1.54 (s, 6H). 13 C-NMR (50 MHz, CDCl3, δ): 155.6, 154.1, 140.3, 138.4, 137.2, 136.9, 136.8, 125.9,
	121.0, 120.4, 120.1, 119.9, 119.8 (2C), 115.5, 113.5, 110.5 (2C), 47.0, 27.5 (2C). HRMS (ESI + ): m/z N,N-diethyl-7-(1H-pyrrol-1-yl)naphthalen-2-amine (146):
	calcd for C21H20N: 286.1591 [M+H] + ; found 286.1590. Following GP-C. Eluent for flash chromatography (PE/EA =
	gradient up to 95:5, Rf =0.51) providing 146 as a yellow solid (49		Br	N
	9,9-dimethyl-N-phenyl-7-vinyl-9H-fluoren-2-amine (139): mg, 0.19 mmol, 53 %). 1 H-NMR (200 MHz, CDCl3, δ): 7.70 (d, 3 J=8.5
	Eluent for flash chromatography (PE/DCM = gradient up to 9:1, Hz, 1H), 7.68 (d, 3 J=8.5 Hz, 1H), 7.55 (d, 4 J=2.0 Hz, 1H), 7.26-7.15 (m, 3H), 7.05 (dd, 3 J=8.5 Hz, H N
	Rf = 0.28) providing 139 as a yellow solid (60 mg, 0.19 mmol,	Ph

4 J=2.0

  C-NMR (50 MHz, CDCl3, δ): 155.7, 153.3, 150.7, 140.0, 137.6, 134.9, 128.1, 125.7, 120.9,

	119.9, 118.7, 112.2, 111.7, 106.7, 46.8, 41.1 (2C), 27.7 (2C). HRMS (ESI + ): m/z calcd for C19H22N:
	264.1747 [M+H] + ; found 264.1746.

  C-NMR (50 MHz, CDCl3, δ): 51.3, 31.2, 28.6, 26.2, 22.3, 13.9.

  C-NMR (50 MHz, MeOD-d 4 , δ): 200.1, 176.2, 158.4, 155.3, 145.6, 143.7, 138.4, 137.3, 129.0, 123.7, 123.3, 121.4, 119.5, 114.9, 46.2 (2C), 34.5, 29.8 (2C), 29.0, 27.0. 13 C-NMR (50 MHz, DMSO-d 6 , δ): 197.7, 174.0, 156.5, 152.6, 151.2, 144.5, 133.4, 127.9, 125.7,

	122.0, 121.8, 118.2, 111.6, 106.3, 46.4 (2C), 33.0, 28.0, 27.7, 27.0 (2C). MS (ESI + , MeOH): m/z:
	338,17 [M+H] + .

  13

  1 H-NMR (200 MHz, CDCl3, δ): 10.06 (s, 1H), 7.89 (s, 1H), 7.91-7.81 (m, 3H), 7.84 (d, 4 J=1.5 Hz, 1H), 7.42 (dd, 3 J=8.0 Hz 4 J=2.0 Hz, 1H), 7.17 (t, 3 J=2.0 Hz, 2H), 6.40 (t, 3 J=2.0 Hz, 2H), 1.56 (s, 6H). 13 C-NMR (50 MHz, CDCl3, δ): 192.2, 156.8, 154.4, 145.0, 141.6, 135.5, 135.1, 130.9, 123.1, 122.4, 120.3, 120.1, 119.6 (2C), 115.3, 110.9 (2C), 47.3, 27.1 (2C). HRMS (ESI + ): m/z calcd for C20H18NO: 288.1383 [M+H] + ; found 288.1383.

	7-(azepan-1-yl)-9,9-dimethyl-9H-fluorene-2-carbaldehyde
				3'
	(171/PP8). Following GP-E. Yellow solid, Eluent (PE/EA = 98:2, CDCl3, δ): 9.97 (s, 1H, CHO), 7.87 (d, 4 J=1.5 Hz, 1H, H1), 7.77 (dd, Rf = 0.38), yield=(78 %: MW, 70 %: thermal). 1 H-NMR (500 MHz,	5' 4'	6' 7'	N 1' 2'	6 7	8	5	c d a 9	b	4	1	3 2	O
	3 J=7.5 Hz 4 J=1.5 Hz, 1H, H3), 7.63 (d, 3 J=7.5 Hz, 1H, H4), 7.61 (br d, 3 J=7.0 Hz, 1H, H5), 6.72 (br s,
	1H, H8), 6.71 (dd, 3 J=7.0 Hz 4 J=2.5 Hz, 1H, H6), 3.55 (t, 3 J=6.0 Hz, 4H, CH22',7'), 1.84 (br m, 4H,
	CH23',6'), 1.59 (br m, 4H, CH24',5'), 1.49 (s, 6H, 2CH3). 13 C-NMR (125 MHz, CDCl3, δ): 192.2, 157.5,
	153.4, 150.5, 147.1, 133.6, 131.4, 125.4, 122.6, 122.5, 118.3, 110.9, 105.0, 49.7 (2C), 46.8, 27.8
	(2C), 27.4 (2C), 27.3 (2C). HRMS (ESI + ): m/z calcd for C22H26ON: 320.2009 [M+H] + ; found
	320.2010.
		4'	3'	N 2' 1'	7	8		a 9	b	1	2	O
	Rf = 0.31), yield=64 % (MW). 1 H-NMR (200 MHz, CDCl3, δ): 10.00	5'	6'		6		5	c d		4		3
	(s, 1H, CHO), 7.90 (d, 4 J=1.0 Hz, 1H, H1), 7.80 (dd, 3 J=8.0 Hz 4 J=1.0 Hz, 1H, H3), 7.69 (d, 3 J=8.0 Hz,
	1H, H4), 7.65 (d, 3 J=8.0 Hz, 1H, H5), 6.99 (d, 4 J=2.5 Hz, 1H, H8), 6.93 (dd, 3 J=8.0 Hz 4 J=2.5 Hz, 1H,
	H6), 3.29 (t, 3 J=6.0 Hz, 4H, CH22',6'), 1.73 (br m, 4H, CH23',5'), 1.62 (br m, 2H, CH24'), 1.49 (s, 6H,
	2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 192.3 (C=O), 156.8 (Ca), 153.9 (Cb), 153.4 (C7), 146.5 (Cd),
	134.2 (C2), 131.2 (C3), 128.6 (Cc), 122.7 (C1), 122.1 (C5), 119.0 (C4), 115.4 (C6), 110.1 (C8),
	50.6 (2C, C2',6'), 46.9 (C9), 27.3 (2CH3), 25.9 (2C, C3',5'), 24.4 (C4'). HRMS (ESI + ): m/z calcd for
	C21H24ON: 306.1852 [M+H] + ; found 306.1853.
	9,9-dimethyl-7-(pyrrolidin-1-yl)-9H-fluorene-2-carbaldehyde H8), 6.92 (dd, 3 J=8.0 Hz 4 J=2.5 Hz, 1H, H6), 3.91 (t, 3 J=4.5 Hz, 4H, (CH2)2O), 3.28 (t, 4H, (CH2)2N), O (173/PP10). Following GP-E. Yellow solid, Eluent (PE/EA = 98:2, Rf N 1.50 (s, 6H, 2CH3). 13 C-NMR (50 MHz, CDCl3, δ): 192.2 (C=O), 156.9 (Ca), 153.9 (Cb). 152.6 (C7), = 0.25), yield=22 % (MW). 1 H-NMR (200 MHz, CD2Cl2, δ): 9.94 (s, 146.1 (Cd), 134.5 (C2), 131.1 (C3), 129.7 (Cc), 122.8 (C1), 122.3 (C5), 119.2 (C4), 114.8 (C6), 1H), 7.85 (d, 4 J=1.0 Hz, 1H), 7.77 (dd, 3 J=8.0 Hz 4 J=1.0 Hz, 1H), 7.67-7.61 (m, 2H), 6.60-6.55 (m, 109.6 (C8), 67.0 (2C, (CH2)2O), 49.4 (2C, (CH2)2N), 47.0 (C9), 27.3 (2CH3). HRMS (ESI + ): m/z calcd 2H), 3.38 (t, 3 J=6.0 Hz, 4H), 2.04 (br q, 4H), 1.47 (s, 6H). HRMS (ESI + ): m/z calcd for C20H22ON: 292.1696 [M+H] + ; found 292.1695. Product was obtained with full conversion on GC-MS, but for C20H22O2N: 308.1645 [M+H] + ; found 308.1645.
	was sufficiently unstable during purification.

9,9-dimethyl-7-(piperidin-1-yl)-9H-fluorene-2-carbaldehyde (172/PP9). Following GP-E. Yellow solid, Eluent (PE/EA = 98:2,

  The reaction was then heated to reflux for 12h. The white solid that formed was filtered off and washed several times with ACN and dried. A white powder was obtained, yield 61%.

	1 H NMR (400 MHz, Chloroform-d) δ 3.28 (t, J = 6.8 Hz, 2H), 2.38 (t, J = 7.2
	Hz, 2H), 2.33 -2.24 (m, 2H), 2.17 (s, 3H), 1.71 (p, J = 6.9 Hz, 2H), 1.41 (q, J = 7.5, 7.0 Hz, 2H), 1.20
	(d, J = 7.8 Hz, 18H), 0.86 -0.75 (m, 3H). 13 C NMR (101 MHz, CDCl3) δ 57.9, 54.6, 49.6, 42.2, 31.9,
	29.7, 29.6, 29.6, 29.5, 29.34, 27.51, 27.30, 26.80, 22.68, 14.09. HRMS (ES+) Calc. for C16H35N4
	[M+H] + 283.2856, found 283.2852. Then, the intermediate (500 mg, 1.770 mmol, 1eq) was
	dissolved in ACN (15 mL), and 1,3-propanesultone (1.100 g, 8.851 mmol, 5 eq) was added to the
	mixture. 0.80 (t, J = 6.8 Hz, 2H). 13 C NMR (101 MHz, CDCl3) δ 61.9, 61.4, 59.0, 48.7, 48.1, 47.6, 31.9, 29.6,
	29.5, 29.4, 29.3, 29.2, 26.4, 22.7, 22.3, 22.3, 19.1, 14.1. HRMS (ES+) Calc. for C19H41N4O3S. [M+H] +
	405.2894, found 405.2899.

1 H NMR (400 MHz, Methanol-d 4 ) δ 3.46 -3.36 (m, 4H), 3.31 -3.24 (m, 2H), 2.96 (s, 3H), 2.77 (t, J = 6.7 Hz, 2H), 2.13 -2.00 (m, 2H), 1.97 -1.86 (m, 2H), 1.75 -1.60 (m, 2H), 1.36 -1.13 (m, 18H),

  ).

	Substrates: Fluorene 163 and azidosugar 182 (40 mg, 0.14 mmol, 1 eq.). The crude was purified
	by flash chromatography on silica gel (Eluent DCM/Ac=7/3, Rf=0.40) to provide F1 (50 mg, 80
	%) as bright yellow solid 1 H-NMR (200 MHz, C5D5N, δ): 9.48 (s, 1H, Htriazole), 8.86 (br s, 1H, H1),
	8.82 (br d, 3 J=8.0 Hz, 1H, H3), 7.83 (d, 3 J=8.0 Hz, 1H, H4), 7.81 (d, 3 J=8.5 Hz, 2H, H4,5), 6.99 (t,

3 J=6.

5

Hz, 1H, H1'), 6.90

(d, 4

J=2.0 Hz,1H, H8), 6.77 (dd, 3 J=8.5 Hz 4 J=2.0 Hz, 1H, H6), 5.22 (m, 1H, H3'), 4.62 (m, 1H, H4'), 4.17 (m, 2H, H5'), 3.17-2.85 (m, 2H, H2'), 2.87 (s, 6H, N(CH3)2), 1.50 (s,

  80 (dd, 3 J=8.5 4 J=2.0 Hz, 1H), 4.67 (t, 3 J=6.5 Hz, 2H), 3.54 (m, 2H), 3.45

	(m, 2H), 3.07 (s, 3H), 3.05 (s, 6H), 2.88 (t, 3 J=6.5 Hz, 2H), 2.51 (m, 2H), 2.17 (m, 2H), 1.61 (m, 2H),
	1.50 (s, 6H), 1.33-1.23 (m, 22H), 0.87 (t, 3 J=6.5 Hz, 3H). HRMS (ESI + ): m/z calcd for C39H60O4N5S:
	694.4361 [M+H] + ; found 694.4361.

bis(4-methoxyphenyl)(phenyl)methoxy)-3- (4-(7-(dimethylamino)-9,9-dimethyl-9H-fluoren- 2-yl)-4-oxobutanamido)propan-2-yl (2- cyanoethyl) diisopropylphosphoramidite (188/FM1). Following GP-L on

  ), DIC (114 μL, 0.71 mmol, 1.2 eq.), HBTU (311 mg, 0.72 mmol, 1.2 eq.), and Et3N (252 μL, 1.78 mmol, 3 eq.) were solubilized in 6 mL dry DMF under argon and stirred for 30 mins at 0 °C. Protected sugar 193 (110 mg, 1.19 mmol, 2 eq.) was then added and the reaction was stirred overnight at rt. The crude was washed by NaHCO3 (aq.) and extracted with DCM. The organic layer was washed by water, dried with magnesium sulfate, and reduced under pressure. Purification was done by FC.substrate 194.

	Eluent (DCM/MeOH = 98: 2, Rf = 0.4) to afford compound 194 (312 mg, 71 %) as a yellow solid.
	1 H-NMR (200 MHz, CDCl3, δ): 7.91 (s, 1H), 7.87 (d, 3 J=8.0 Hz, 1H), 7.58 (d, 3 J=8.0 Hz, 1H), 7.54 (d,
	3 J=8.0 Hz, 1H), 7.36 (d, 3 J=8.0 Hz, 1H), 7.34 (s, 1H), 7.27-7.08 (m, 9H), 6.76 (d, 3 J=8.0 Hz, 4H), 3.83
	(m, 1H), 3.71 (s, 6H), 3.51 (m, 1H), 3.42-3.20 (m, 3H), 3.12 (m, 2H), 3.0 (s, 6H), 2.53 (m, 2H), 1.41
	(s, 6H). Yellow solid, Eluent (Tol/Ac = 85:5, Rf = 0.5, 0.58),
	yield=30 %. 1 H-NMR (200 MHz, CDCl3, δ): 7.98 (s,
	1H), 7.84 (d, 3 J=8.0 Hz, 1H), 7.64 (d, 3 J=8.0 Hz, 1H),
	7.60 (d, 3 J=8.0 Hz, 1H), 7.46 (d, 3 J=8.0 Hz, 1H), 7.45 (s, 1H), 7.36-7.21 (m, 9H), 6.86-6.71 (m, 4H),
	4.13-4.02 (m, 2H), 3.78 (s, 6H), 3.69-3.15 (m, 7H), 3.05 (s, 6H), 2.7-2.45 (m, 2H), 1.43 (s, 6H),
	1.26-1.11 (m, 12 H). The higher integration by 3 protons in the DMTr region (7.36-6.71)
	corresponds to initiation of deprotection of the extremely sensitive DMTr in this type of
	compounds. 31 P-NMR (CD3CN, 81 MHz, δ): 149.0, 148.8. MS (ESI + , MeOH): C54H65N4O7P, m/z:
	913,5 [M+H] + .

13

C NMR (50 MHz, CDCl3, δ): 198.6, 173.8, 158.6 (2C), 157.0, 153.0, 151.5, 145.5, 144.8, 138.0, 136.0, 135.9, 130.1 (4C), 129.3, 129.1 (2C), 128.3 (2C), 128.2, 128.0, 125.4 (2C), 122.1, 118.2, 113.3, 111.7, 106.1, 86.3, 70.4, 65.0, 55.3 (2C), 46.9, 42.2, 40.9(2C), 34.1, 30.5, 27.4 (2C). MS (ESI + , MeOH): C45H48N2O6, m/z: 713,2 [M+H] + . (S)-1-(

  C-NMR (50 MHz, CD2Cl2, δ): 183.9, 162.8, 159.0 (2C), 152.5, 148.3, 145.9, 145.1, 141.17, 140.9 (t, JFC=5.0 Hz) 137.6 (t, JFC=25.0 Hz), 136.1, 136.0 (2C), 135.0, 130.4 (2C), 130.3 (2C), 128.4 (2C), 128.3 (2C), 127.8, 127.2, 125.7, 125.5 (t, JFC=5.0 Hz), 123.4, 122.9, 118.9, 115.0, 113.5 (4C), 107.4, 89.5, 87.3, 86.8, 72.0, 64.0, 55.5 (2C), 41.1, 40.7 (2C). HRMS (ESI + ): m/z calcd for C44H40O6N4F2Na: 781.2806 [M+Na] + ; found 781.2808.

Supplementary characterization of chapter 3 XIII.1 Transition Dipole Moment of push-pull dyes (in Debye):

  1 H-NMR (200 MHz, CD2Cl2, δ): 8.57 (s, 1H,), 8.52-8.44 (m, 2H), 7.53-7.48 (m, 2H), 7.40-7.14 (m, 9H), 7.01 (d, Hz, 1H), 6.82-6.78 (m, 5H,)), 6.46 (t, 3 J=6.0 Hz), 4.80-4.72 (m, 1H), 4.37-4.09 (m, 1H), 3.8-3.41 (m, 9H), 3.32-3.27 (m, 2H), 3.07-2,67 (m, 9H), 2.64 and 2.48 (2t, 3 J=6.0 Hz), 1.28-1.10 (m, 12H). 19 F-NMR (188 MHz, CDCl3, δ): -110.73. 31 P-NMR (CD3CN, 81 MHz, δ): 149.1. HRMS (ESI + ): m/z calcd for C53H57O7N6F2NaP: 981.3893 [M+Na] + ; found 981.3887.

	O XIII. Varied-acceptor / fixed donor (NMe2): F F N N N O O DMTrO	N
	PP1	PP2		P O PP3 N	CN	PP4	PP6
	12,9	12.9		13.5		14.1	12.6
			Varied-ring size amine / fixed acceptor (formyl):
	PP8	PP9	PP10	PP11	PP12	PP7	PP13	PP14
	13.3	12.1	13.7	13.3	11.4	13.4	13,1	12,1
	Optimized push-pull dyes (fixed acceptor methylenemalonitrile):
			PP4	PP15			PP16
			14.1	14.4			14.9

4 J=2.0

30)

		HOMO		LUMO
	Solvent	lmax exp	lmax calc.	f: oscillator	Dx	Dy	Dz
		(nm)	(nm)	strentgh
	CH3CN	384	404	0.8266	-3.3174	0.0449	0.0009
	CHCl3	391	402	0.8556	-3.3659	-0.0494	0.0014
	Toluene	387	395	0.8681	-3.3594	-0.0507	0.0001
	PP4 (d=10.34)
		HOMO		LUMO
	Solvent	lmax exp	lmax calc.	f: oscillator	Dx	Dy	Dz
		(nm)	(nm)	strentgh
	CH3CN	488	510	1.0792	-4.2528	-0.1655	-0.0013
	CHCl3	486	505	1.0950	-4.2634	-0.1877	-0.0011
	Toluene	474	497	1.0955	-4.2279	-0.2048	-0.0010

Control compound: contrôle (d=9.37) PP6 (d=10.64)

	PP12 (d=10.35)
		HOMO			LUMO
	E S0-S1	Osc. strength	HOMO			LUMO	Dx ; Dy ; Dz
	(nm)
	491	0.4900						2.8146 0.0414
	(Exp							-0.0109
	488)
	Solvent	lmax exp	lmax calc.	f: oscillator	Dx	Dy	Dz
	Solvent	lmax exp (nm)	lmax calc. (nm)	f: oscillator strentgh	Dx	Dy	Dz
	CH3CN	(nm) 365		(nm) 390		strentgh 0.8240	-3.2485	-0.1510	-0.0308
	CH3CN	351		368		0.8373		-3.1836	0.0535	-0.0569
	CHCl3	368		386		0.8593		-3.3017	-0.1599	-0.0431
	CHCl3 Toluene	352 365		366 381		0.8687 0.8746		-3.2343 -3.3068	0.0547 -0.1636	-0.0543 -0.0459
	Toluene	352		363		0.8844		-3.2481	0.0529	-0.0505
	Contole-aziridine (d=10.35)
	XIV.
		HOMO			LUMO
		HOMO				LUMO
	Solvent	lmax calc.	f: oscillator	Dx	Dy	Dz
			(nm)	strentgh
	CH3CN	371		0.8542		3.2206	-0.2149	-0.0492
	Solvent CHCl3 CH3CN Toluene lmax exp (nm) 369 399 365	lmax calc. (nm) 0.8846 368 0.8995	f: oscillator 3.2684 strentgh 0.83 3.2804	Dx -3.2061 -0.2219 Dy -0.8058 -0.0459 Dz -0.0555 -0.2223 -0.0415
	CHCl3 PP14 (d=10.36) 381		401		0.8211		-3.1968	-0.7700	-0.0675
	Toluene	374		391		0.8601		-3.2292	-0.7963	-0.0518

Supplementary characterization of chapter 4 XIV.1 Photodegradation decay curves of F1-3 as a function of time in ethanol

	HOMO				LUMO
		1,0			F1 F2
					F3
	Fluorescence Intensity, a. u.	0,6 0,8			aldehyde prodan
		-500	0	500	1000 1500 2000 2500 3000 3500 4000
					Time, s

to -5° C), but they duplexes were stable below 30°C (fig.103).

Acknowledgements

First, I would like to express my sincere thankfulness to the "French ministry of education" and the "Doctoral school of Nice-Sophia Antipolis university (ED-SFA)" for offering me this Ph.D grant for three years. I am equally thankful to Pr. Alain Burger for the fruitful leadership of this thesis. In fact, Alain is present and evenly invested in all the work in his lab, especially the

observed for intercalated dyes. [200,[START_REF] Asseline | Proc. Natl. Acad. Sc[END_REF] The emission spectra fit those observed for the free dye in 20-25% methanol in dioxane. Table 12. Spectroscopic data of the X-labeled ODNs Samples [a] Tm (°C) [b] ΔTm (°C) [c] λabs (nm) [d] λem (nm) ΔλSS (nm) Φ (%) [e] pH [a] 1 μM of ODN in buffer pH 7.0 for GXG and 8.4 for TXT and CXC (10 mM cacodylate, 150 mM NaCl); [b] Melting temperature; ±0.5°C; [c] ΔTm corresponds to the difference in Tm with the wild type duplexes TAT-ATA, CAC-GTG and GAG-CTC; [d] Absorption wavelength reflects the ones recorded by excitation spectra (for higher sensitivity at 1 μM) [e] Quantum yields determined using quinine sulfate in 0.1 M HCl solution (λex = 350 nm, F = 0.54) [246] and 7-(dimethylamino)-9,9-dimethyl-9H-fluorene-2-carbaldehyde (λex = 390 nm, Φ = 0.46 ) [85] as references, ±2 % mean standard deviation.

It is also important to compare these X properties to the anucleosidic M-labeled sequences of the first approach despite their mass defects (table 9 vs. 12). The M-labeled sequences absorbed in the UV range (350 nm) and fluoresced in the green region (530-550 nm). Their fluorescence intensities were much higher (10-28 % for M labeled ODNs). This suggests that the flanking bases were able to impose a more significant hydrophobic environment around the fluorene anucleosidic label. This might be favored due to the more flexible nature of anucleosidic linkers.

We then studied the hybridization effects. The GXG 15-mer sequence was hybridized with 6 complementary strands comprising in the position opposite to fluorene dye X: one of the canonical bases at a time, another X dye, or an abasic site (table 12). The CXC and TXT 15-mers were hybridized with three complementary strands including opposite to the fluorene: A or T bases as representatives of purines and pyrimidines, or an abasic site.

When complementary strands were added to TXT and CXC, the emissions were little changed (fig. 100, table 12). The quantum yields of the TXT and CXC ds-DNAs were nearly the same as

Experimental section

I. General methods

All reactions involving water-or air-sensitive material were performed in oven-dried glassware under an argon or nitrogen atmosphere by using Schlenk techniques employing double-line argon-vacuum lines and dry solvents. The synthetic intermediates were coevaporated twice with toluene and dried in vacuo before use in reactions that need anhydrous conditions. All chemical reagents were obtained from commercial sources (Aldrich, Acros, Alfa Aesar) and were used as supplied. Anhydrous solvents and amine reagents were obtained by distillation followed by three cycles of degassing (or recrystallization in case of solid nucleophiles) according to standard procedures. [START_REF] Armarego | Purification of Laboratory Chemicals[END_REF] The reactions were monitored simultaneously by gas chromatography (GC/MS) and by thin-layer chromatography and visualized both by UV radiation (254 & 365 nm) and by spraying with relevant staining agent (KMnO4 or Ninhydrin) followed by a subsequent warming with a heat gun. Column chromatography [START_REF] Still | [END_REF] was performed with flash silica gel (40-63 µm) with the indicated solvent system, using gradients of increasing polarity in most cases. 1 H NMR (200 and 500 MHz), 13 13 C NMR experiments. [286] Chemical shifts (δ) are given in ppm to the nearest 0.01

( 1 H) or 0.1 ppm ( 13 C). The coupling constants (J) are given in Hertz (Hz). The signals are reported as follows: (s=singlet, d=doublet, t=triplet, quint=quintet, sext=sextet m=multiplet, br=broad). Assignments of 1 H and 13 antibiotic solution (penicillin-streptomycin, Gibco-invitrogen) in a humidified incubator with 5% CO2 atmosphere at 37°C. The cell concentration of 5-10*10 4 cells ml -1 was maintained by removal of a portion of the culture and replacement with fresh medium 3 times per week. In fluorescence spectroscopy experiments, CEM-SS cells were also washed twice with HBSS using centrifugation before addition of the probes. To stain the cell suspension with F1-3 probes, an appropriate aliquot of its stock solution in DMSO was added to the lymphocytes (10 6 per mL) in HBSS buffer to obtain a final probe concentration of 100 nM. Spectroscopic measurements were performed under stirring. For the microscopy studies, attached HeLa cells were washed two times by gentle rinsing with HBSS. A freshly prepared solution of F1-3 in HBSS was then added to the cells to a final concentration of 100 nM. Imaging was performed directly without washing step after 5-10 min.

Confocal microscopy images were taken on a Leica TSC SPE-II confocal microscope with HXC PL APO 63x/1.40 OIL CS objective. The excitation light was provided by a 405 nm laser while the fluorescence was detected at two spectral ranges: blue and green separated at 500 nm). The ratiometric images were generated by using special macros under Image J that divides the image of the green channel by the one of the blue channel. For each pixel, a pseudo-color scale is used for coding the ratio, while the intensity is defined by the integral intensity recorded for both channels at the corresponding pixel.

IV. ODN synthesis and purification:

The ODN synthesis was performed on an Expedite 8900 DNA synthesizer (Applied Biosystem) using the "trityl on or off" modes and ultra-mild Pac phosphoramidite chemistry on a 0. 151): [127] Following GP-B. 13 C-NMR (50 MHz, ). 13 with cold dry ether, dried in a vacuum dessicator; yield 8.4 g (58%).

NaN3 (1.17 g, 18.0 mmol) was added to a mixture of α and β-chlorosugar 4 (4.5 g, 11.6 mmol) in dry DMF (150 mL), stirred at RT for 4 h in an inert atmosphere. After completion of the reaction, EtOAc (100 mL) was added to the mixture to form a uniform organic layer. The organic layer was washed with water, brine, and dried (over anhydrous MgSO4). Evaporation under reduced pressure afforded the crude product mixture. The β sugar was eluted as the first fraction. Yield: 2.47 g (55%); Rf= 0.55 (diethyl ether/hexanes=3:7). 1 Dry MeOH (100 mL) followed by potassium carbonate (0.82 g, 15.16 mmol) were added to a dry round-bottom flask loaded with toluoyl -protected (2.18 g, 4.8 mmol). The reaction mixture was stirred under inert atmosphere at RT for 24 h and monitored by TLC. The residue was loaded on a silica gel column, and the desired product was isolated when eluted with 5% MeOH in diethyl ether. Yield: 0.62 g (81%); Rf=0.60 (methanol/diethyl ether=5:95) (2R,3S,5R)-5-azido-2-(hydroxymethyl)tetrahydrofuran-3-ol (182). 1 H NMR (200 MHz, Acetone-d 6 , δ): 5.44 (dd, 3 J = 4.0, 5.5 Hz, 1H, H1), 4.33 (q, 3 J = 5.0 Hz, 1H, H3), 3.89 (q, 3 J = 5.0 Hz, 1H, H4), 3.60 (m, 2H, H5), ), 2.03 (m, 2H, H2). 13 The bromofluorene (1 eq.) was dissolved in dry THF (0.2 M). To the resulted clear yellow solution, nBuLi (2.5M solution in Hexane, 1.2 eq.) was added dropwise at -78 °C under inert atmosphere. Reaction mixture was stirred for 1h before a yellow precipitate was formed. Then, DMF (2-3 eq.) was added dropwise and the formed solution was stirred for additional 2 h at -78 °C. The reaction was allowed to warm up to room temperature and stirred for 1 h, quenched with 1 M aqueous HCl and extracted with EA (2x). Organic layer was dried over MgSO4 and evaporated in vacuum. The residue was purified by column chromatography.

General procedure (GP-H) to synthesize the clickable fluorenes (196 and 203).

Ethynylmagnesium bromide (0.5 M in THF, 1.4 eq.) was added dropwise to a solution of the carbaldehyde (1 eq.) in THF (2.5 mL) at 0 °C. The mixture was stirred at the same temperature until completion of the reaction monitored by TLC (1-2h). Then, a saturated solution of aq.

NH4Cl was added and the aqueous phase was extracted with EA. The combined extracts were dried (magnesium sulfate) and evaporated to yield the corresponding propargyl alcohol. The crude propargyl alcohol was purified by flash chromatography. N.B. It is better to batch to next step without purification.

General procedure (GP-I) of click protocol with β-toluoyl-protected deoxyribose for the synthesis of (S13 and S15). To a stirred solution of S7 (1.1 eq.) in DCE (2.5 M) at 0 °C under argon, was added dropwise a 2.5 M solution of propioloyl fluorene push-pull (1 eq.) in DCE (4 mL). Then, DIEA (5 eq.), CuI (2 eq.), and AcOH (1 eq.) were sequentially added. The reaction mixture was stirred for 3 h at rt, filtered over a pad of Decalite ® , and washed with DCM. The volatiles were reduced in vacuo and the resulting crude was purified by flash chromatography on silica gel.

General procedure (GP-J) of toluoyl deprotection for the synthesis of (165, 197, and S21). The clicked intemediate (1 eq.) is dissolved in Dry MeOH (0.1 M) followed by addition of potassium carbonate (3.2 eq.) and stirring under inert atmosphere at rt for 24 h until completion of the reaction monitored by TLC. The residue was loaded on a silica gel column and purified by chromatography.