Prof. E Tatiana N V Moshkina

Prof. F Pascal Le Poul

Dr Alberto Barsella

Oldřich Pytela

Françoise Filip Bureš

Robin-Le Guen

Sylvain Achelle
email: sylvain.achelle@univ-rennes1.fr

Emiliya V Nosova
email: emilia.nosova@yandex.ru

Galina N Lipunova

Valery N Charushin

] Françoise

Dr S Robin-Le Guen

Achelle

Prof. V N Nosova

Charushin

Prof O Pytela

Prof. F Bureš

Prof E V Nosova

Prof G N Lipunova

Prof. V I N Charushin

Ya

Electron-Withdrawing Substituted Quinazoline Push-Pull Chromophores

Keywords: Synthesis, Electrochemical, Photophysical and Second-Order Nonlinear Optical Properties Synthesis, electrochemical, photophysical quinazoline, push-pull derivatives, intramolecular charge transfer, nonlinear chromophores, fluorescence

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Introduction

Over the last 25 years, there has been a considerable interest in the design of organic push-pull chromophores having electron-donating group (D) linked to an electron-withdrawing one (A) via a π-conjugated bridge (D-π-A structure). [1] In these compounds, intramolecular charge transfer (ICT) occurs and generation of new low-energy molecular orbital induces unique optical and electrochemical properties. [2] These chromophores have found key applications as fluorescent sensors, [3] in optoelectronic, particularly for photovoltaics, [4] organic field effect transistor (OFETs) [5] and in organic light emitting diodes (OLEDs). [6] The generation of a molecular dipole in push-pull chromophores induces also nonlinear optical (NLO) properties such as second order NLO phenomena and two-photon absorption (TPA). The second order NLO properties have found applications as second harmonic generation, used for example to obtain green laser from an infrared source at 1064 nm, [7] second harmonic microscopy [8] and terahertz generation. [9] NLO response is directly related to the ICT and can be easily tuned by varying the D/A couple, [1,10] the π-conjugated spacer [1,2,11] or by branching the chromophore to adopt quadrupolar or octupolar structure. [12] The pyrimidinyl (1,3-diazinyl) fragment has been widely used as electron-deficient part in push-pull structures. [13] The luminescence properties of pyrimidine fluorophores are highly sensible to external stimuli and have been used as sensors of polarity, [14] pH, [14b,c] metal cations [15] and nitrogen explosives. [16] Push-pull pyrimidine derivatives are also well-known for their TPA properties. [17] Some of us have studied the second order NLO properties of pyrimidine chromophores: even if the NLO responses of styrylpyrimidine derivatives remain moderate, [18] extension of the π-conjugated spacer, [19] incorporation of a metal centre between the D/A parts, [20] and reinforcement of the electron-withdrawing character of pyrimidinyl fragment by Ncomplexation or N-methylation [21] induce a significant increase of the second order hyperpolarizability tensor. Akdas-Kilig and coworkers have also described octopolar structures based on bipyrimidinyl electron withdrawing central part. [22] On the contrary, quinazoline (benzopyrimidine) chromophores have been studied only recently. [13a,b,23] Some of these compounds exhibit strong luminescence properties. [24] The quinazolinyl moiety can be considered as stronger electron-withdrawing part than the corresponding pyrimidinyl group due to the possibility of extra electron delocalization into the fused benzene ring. Stronger ICT in quinazoline chromophores is illustrated by red-shifted absorption and emission with regards to their pyrimidine analogues. [13b,24c] To the best of our knowledge, quinazoline chromophores have not been studied for their NLO properties so far, and, therefore, we report herein designed of a series of quinazoline push-pull chromophores 1-3 (Figure 1). In these structures, the electron-withdrawing character of the quinazoline ring is reinforced by cyano and trifluoromethyl substituents. Electrochemical, linear and nonlinear optical properties of these compounds were carefully studied experimentally and theoretically using DFT calculations. The influence of the cyanophenyl-and trifluoromethylphenyl-branches was determined by comparison with already known compound A. [24c] Figure 1. Structures of quinazoline push-pull chromophores 1-3

Results and Discussion

Synthesis of dyes

The synthesis of the 2,4-disubstituted quinazolines 1 and 2 is summarized in Scheme 1. Compounds 8a,b were obtained in three steps following the method similar to reported previously. [25] The condensation of anthranilamide 4 with 4cyanobenzaldehyde (5a) or 4-trifluoromethylbenzaldehyde (5b) and subsequent oxidation with copper(II) chloride led to quinazoline-3H-ones 7a,b. It is worth noting that the use of mild conditions (stirring for 5 h at room temperature) gave Schiff base 6a as condensation product formed by 4-cyanobenzaldehyde 5a.

In the case of 4-trifluoromethylbenzaldehyde 5b and under the same reaction conditions, the cyclization of Schiff base takes place affording 2,3-dihydroquinazolin-4(1H)-one 6b. This fact corresponds to the published results on interaction between anthranilamides and benzaldehydes under various conditions that reports 2,3-dihydroquinazolin-4(1H)-ones as thermodynamic products. [26] 1 H NMR spectroscopy of compound 6a demonstrates signal of N=CH group at δ 8.69 ppm, whereas the spectrum of 6b contains singlet of aliphatic CH atom at δ 5.86 that is in agreement with the proposed structures (see ESI, Figures S1,S2). Slightly different conditions were applied for the synthesis of CF3-derivatives 2, namely, refluxing of bromo-quinazoline 8b with arylboronic acid in the mixture of toluene and EtOH under N2, using Pd(PPh3)4 as a catalyst and saturated solution of Na2CO3 as a base. [24c] The quadruplet signals of CF3 group with J = 272.1-272.9 Hz and carbon atoms (C 3 and C 5 ) of CF3-phenyl fragment with J = 3.9 Hz in the 13 C NMR of target quinazolines 2 were observed. In the mass spectra of quinazolines 1 the peak of molecular ions with 47% (m/z 378 Da for compound 1a) and with 100% (m/z 474 Da and m/z 472 Da for compound 1b,c, respectively) relative intensity were registered.

The synthetic approach to 2-[5-(4diethylaminophenyl)thiophen-2-yl]quinazoline derivative 3a has been earlier developed in 56% yield. [27] It includes the condensation of anthranilamide with (thiophen-2yl)carbaldehyde, chlorodesoxygenation, incorporation of cyanogroup at position 4 of quinazoline core, bromination with NBS and subsequent palladium-catalyzed Suzuki-Miyaura crosscoupling reaction. The new target chromophores 3b,c (Scheme 2) have been obtained using the same method. Purification by column chromatography afforded 4-cyanoquinazoline 3b and 3c in moderate yields. The structures of the compounds 3b,c were confirmed by 1 H and 13 C NMR spectroscopy and mass spectrometry. The peaks of the corresponding molecular ion (m/z 480 and 478 Da, respectively) with 100% relative intensity were observed in their mass spectra.

Electrochemical properties

Electrochemical behavior of compounds 1-3 were studied by cyclic voltammetry in CH2Cl2 containing Bu4NPF6 electrolyte at a scan rate of 0.1 V/s. The working electrode was a glassy carbon disk; Pt wire was used as the counter electrode, and an Ag wire as reference electrode. Ferrocene was used as internal reference for electrochemical measurements. The first oxidation/reduction peak potentials and their differences are listed in Table 1; representative CV diagrams of compounds 1 and 3a are shown in Figure 2.

Table 1. Electrochemical data of compounds 1-3.

Comp.

E1/2 ox1 , V [a] E1/2 red1 , V

[a] ∆E, V [b] EHOMO, eV [c] ELUMO, eV [c] λmax, nm [d] 1a 553 [e] -1.863 [e] 2.78 -5.70 -2.92 445

[a] All potentials are given versus ferrocene.

[b] ∆E = E1/2 ox1 -E1/2 red1 .

[c] EHOMO/LUMO = -(E ox1/red1 + 4.8). [d] Calculated λmax values (λ=1241/∆E).

[e] irreversible peaks Ep.

Compounds 1-3 exhibit an oxidation process with the potential ranging from 0.312 to 0.922 V vs ferrocene and a reduction process from -1.570 to -2.372 V (Table 1), influenced by the particular nature of the substituents. When the donor moiety is NAlk2 (1a, 2a and 3a), the oxidation process is always reversible. The oxidation is irreversible for compounds 1c, 2c and 3c bearing the carbazolyl donor. For these compounds, oxidation leads to the formation of a new electroactive species and an irreversible reduction peak, at lower potential (Ep ≈ -0.5 V) is observed on the reverse scan after the first oxidation. For diphenylamino derivatives 1b and 2b, the formation of a deposit on the working electrode is occurred after the first oxidation step and a fine intense signal is observed attributed to the formation dimerization or polymerization products as described in the literature for carbazole and triphenylamine derivatives. [28] Finally, except the chromophore 2a that exhibits an irreversible reduction signal, a reduction process of compounds 1-3 is reversible.

The HOMO/LUMO and electrochemical gap energies for all compounds were calculated from the potentials values. When employing the carbazol-9-yl donor (1c, 2c and 3c), the oxidation is more difficult than in case of dialkylamino and diphenylamino analogs, while the reduction changes to a lesser extent. In each series, the highest electrochemical band gap is therefore observed for carbazolyl derivatives. The dialkylamino derivatives 1a, 2a and 3a are easier to oxidize but more difficult to reduce than their diphenylamino analogues 1b, 2b and 3b: the gap values are therefore similar for both substituents in each series.

For a given donor substituent, when changing the acceptor from CN to CF3 group, there is a small shift of the Ered values to lower potential values (1 compared to 2), indicating a better acceptor ability of the CN group. This electron-withdrawing effect for both compounds 1b and 2b is confirmed by the measurement of the reduction potential for their unsubstituted analogue A (Ered= -3.34 V).

Finally, when the cyano group is on position 4 of the quinazoline ring (compounds 3), the Ered values are less negative than for compounds 1 and 2 pointing to a more electron-withdrawing ability of this moiety. Compounds 3 are also more easily reduced. This trend supports a stronger ICT for these molecules compared to 1 and 2.

Linear optical properties

The UV/Vis and photoluminesce (PL) spectroscopic data for compounds 1-3 measured in CHCl3 at room temperature are presented in Table 2. The analyses were carried out using low-concentrated solutions of chromophores (0.9-1.7 × 10 -5 M).

As representative examples, normalized spectra of compounds 1 are displayed in Figure 3. Compounds 1 and 2 exhibit charge transfer (CT) absorption band in the UV or purple region with relatively low molar extinction coefficients around 20 mM -1 cm -1 or below. In each series, the most blue-shifted energetic CT absorption bands are observed for the carbazoyl derivatives, whereas the absorption maxima are similar for dialkylamino and diphenylamino chromophores. This is in agreement with the electrochemical band gap values. Compounds 1 and 2 exhibit intense blue-green emission with quantum yield > 0.5. Both compounds 1b and 2b possess red-shifted emission with regards to their unsubstituted analogue A, [24c] indicating a stronger ICT induced by cyanophenyl and trifluoromethylphenyl substituents. Bathochromic shifts of the absorption and emission maxima are observed for cyano derivatives 1 as compared their trifluoromethyl analogues 2, which is in accordance with the electrochemical behaviour. Diphenylamino derivatives 1b and 2b in each series exhibit the most red-shifted emission, as observed in other families of similar push-pull compounds. [14b,19] Compounds 3 are poorly emissive in solution, probably due to twisted intramolecular charge transfer (TICT) excited state. Only carbazole derivative 3c exhibits a moderate photoluminescence quantum yield of 0.10. Positive fluorosolvatochromism associated with a moderate absorption solvatochromism is characteristic of pushpull fluorophores: a bathochromic shift of the emission band is observed when the polarity is increased, which is due to the stabilization of highly polar excited state in polar solvent. [29] Table 3 displays the emission maxima of compounds 1-3 in a series of aprotic solvents of different polarity, evaluated according to the Reichardt polarity scale (ET( 30)). [30] Compounds 1-3 do not exhibit significant absorption solvatochromism (less than 10 nm difference whatever the solvent) was observed without correlation with solvent polarity. Compounds 1 and 2 exhibit the typical behavior of D-π-A derivatives: for each compound, the emission maxima is proportional to ET (30) of the corresponding solvent (Figure S29). Figures 4 and5 (part A) display the normalized spectra and color change in various aprotic solvents upon UV-irradiation of compound 1b. This compound possesses luminescence from blue in n-heptane to orange in MeCN. The slope (m) of the regression line of emission maxima vs ET( 30) is a way to roughly evaluate the ICT. [14c] Compound 1a exhibits the highest m parameter and compounds 1 show higher m value than the corresponding compounds 2 indicating higher ICT into cyano derivatives 1 than into trifluoromethyl analogues. For compounds 3, the fluorosolvatochromism behavior is different as shown on Figure 4 (part B): in solvents with lower polarity (n-heptane, toluene for all compounds as well as 1,4-dioxane and THF in case of 3c) the formation of J-aggregate leading to an emission band in the 550-700 nm range is observed. [31] In higher polarity solvents, compounds 3 exhibit classical positive fluorosolvatochromism. The m parameters were calculated using only the data gained from these solvents. Finally, all compounds are emissive in solid state with emission going from blue for 1c and 2c to red for 3a and 3b (Figure 6). Toluene 33.9 [a] 1,4dioxane 36.0 MeCN 45.6 [a] m [b] Solid state [c] 445 [d] - [e] - [e] 508 528 559 7.74 - [e] [a] ET (30), Reichardt polarity parameter in kcal mol -1

.

[b] Slope of the regression line λmax (nm) vs. ET (30) in nm kcal -1 .

[c] Powder. [d] in cyclohexane (ET(30) = 30.9). [e] not measured.

Second order NLO properties

The second order NLO properties have been studied in chloroform solution by the electric-field induced second harmonic generation (EFISH) method at a non wavelength of 1907 nm. The second harmonic at therefore well clear of the absorption bands of the chromophores. This method provides the NLO response as the 5 in different aprotic solvents.

(part A) and 3c (part B) in heptane, toluene, 1,4-dioxane, CHCl3, and MeCN). Photographs were taken in the dark upon irradiation with (from left to right) in solid te (powder). Photographs were taken in the dark upon irradiation with a

The second order NLO properties have been studied in field induced second ration (EFISH) method at a non-resonant incident wavelength of 1907 nm. The second harmonic at λ = 953 nm is therefore well clear of the absorption bands of the provides the NLO response as the scalar product between the permanent molecule ⃗ in fundamental state and the vector component of described as β//. [32] The results are presented in Table 4. It should be noted that positive µβ that both ground and excited states are polarized in the same direction and that the excited state is more polarized than ground state, in accordance with observation. The NLO responses of compounds moderate mainly due to nonoptimized the higher µβ values for compounds dialkylamino derivatives exhibit the highest diphenylamino derivatives (2a values) and the NLO response of carbazole derivatives is significantly lower, at the detection limit of the us comparison of chromophores 1b analogue A implies that 4 trifluoromethylphenyl electron-withdrawing substituents in C2 position of the quinazoline core significantly enhance the NLO response. Moreover, the cyano substituted compounds significantly higher NLO response than trifluoromethyl substituted chromophores 2 in accordance with higher Hammett constant for cyano group. All these results are in full accordance with the electrochemical and UV increase when absorbance maxima are redshifted and electrochemical gap decreased.

Computational studies

Spatial and electronic properties of all target chromophores 1-3 were investigated at the DFT level by using the Gaussian ® 16 software package. molecules were optimized using the DFT B3LYP/6 method. Energies of the HOMO and the LUMO, their differences, ground-state dipole moments μ and fi (1907 nm) were calculated on the DFT B3LYP/6 level including CHCl3 as a solvent (Table 5).

The calculated HOMO and LUMO energies are within the range of -5.86 to -5. Spatial and electronic properties of all target e investigated at the DFT level by using 16 software package. [START_REF] Frisch | Gaussian 16, Revision A.03[END_REF] The geometries of molecules were optimized using the DFT B3LYP/6-311+G(2df,p) method. Energies of the HOMO and the LUMO, their differences, and first hyperpolarizabilities β (1907 nm) were calculated on the DFT B3LYP/6-311+G(2df,p) as a solvent (Table 5). The calculated HOMO and LUMO energies are within the 3.04 to -2.24 eV, respectively. The ted values are in a good agreement with the electrochemically obtained HOMO and LUMO levels as demonstrated by their correlations (Figures S33-S35 in the ESI). Hence, the used DFT method can be considered as appropriate. In all particular series, the HOMO/LUMO decreases within the ; the differences between chromophores a and donors) are relatively small. Carbazolylsubstituted chromophores showed the largest HOMO-LUMO gaps. Figure 7 shows localization of the HOMO(-1/2) and LUMO(+1/2) as well as Mulliken charges in representative chromophores 1a and 3a that differ in the arrangement of the D/A couple and the π-linker extension. As expected, the HOMO(-1/2) in 1a are mostly spread over the N,N-diethylanilino donor, while the LUMO(+1/2) occupy the quinazoline, 4-cyanophenylene as well as phenylene moieties. The HOMO(-1/2) in 3a is represented by whole 5-(N,Ndiethylanilino)thiophen-2-yl moiety, the LUMO(+1/2) are centrally spread over the quinazoline and thiophene rings. All data calculated at the DFT level by using the Gaussian ® 16 software package and DFT B3LYP/6-311+G(2df,p) method in CHCl3. The first hyperpolarizabilities β(-2ω,ω,ω) were calculated at 1907 nm. The electronic absorption spectra, the longest-wavelength absorption maxima and the corresponding electron transitions were calculated using TD-DFT (nstates = 8) B3LYP/6-311+G(2df,p).

The calculated ground state dipole moments range from 3.84 to 12.89 D and reflect the spatial arrangement of the particular chromophores. In general, the carbazolyl-substituted chromophores in series c showed the lowest dipole moments, whereas the N,N-dialkylamino derivatives in series a possess the largest µ values.

Electronic absorption spectra were calculated using TD-DFT method and CHCl3 as a solvent. All spectra are listed in the ESI (Figures S37-S39), the positions of the longest-wavelength absorption maxima are given in Table 5. In general, the calculated spectra are red-shifted compared to the experimental; however, the calculated and experimental λmax values correlate reasonably (Figure S36). For chromophores 1a-c and 2a-c, the longest-wavelength band appearing between 400 and 500 nm is generated by pure HOMO→LUMO transition. Chromophores 3ac with inversed D-π-A arrangement showed significantly redshifted longest-wavelength band, which may appear as a shoulder (see the full-range experimental absorption spectra in the ESI Figure S29). Whereas this red-shifted band corresponds to the HOMO→LUMO transition, the band localized between 400 and 500 nm is generated by the HOMO→LUMO+1 transition.

The quadratic hyperpolarizability tensors β have been also calculated. A correlation of the experimental and calculated µβ products (Figure S40) confirms the same trends of both quantities. In general, the calculated β values for diphenylamino derivatives 1b and 2b are higher than their respective dialkylamino analogues 1a and 2a. The highest NLO responses have been calculated for chromophores 3a and 3b similarly as proved by the aforementioned EFISH method.

Conclusion

In summary, we have designed and synthesized a series of amino substituted quinazoline push-pull chromophores in which the electron-withdrawing character of the quinazoline core is enhanced by electron-deficient groups, their photophysical and electrochemical properties have been measured. The proposed combination of D and A provided a series of chromophores with wide spectral emission range in both solution and solid state. Compounds with 4-cyanophenyl and 4-trifluoromethylphenyl substituent in C2 position of the quinazoline core exhibited enhanced intramolecular charge transfer with regard to their unsubstituted analogue as shown by their red-shifted absorption and emission spectra as well as their decreased electrochemical gap. These compounds are highly luminescent in chloroform and in the solid state. On the other hand, 4-cyanoquinazolines are poorly emissive in solution but possess red luminescence in the solid state. These compounds exhibit moderate second order NLO response measured by EFISH method. Nevertheless, electron-withdrawing substituents on the quinazoline core induce a significant enhancement of the µβ value. Optimized πconjugated linkers with phenylenevinylene or thienylenevinylene bridges would probably increase the NLO responses.

Experimental Section

General Information

Unless otherwise indicated, all common reagents and solvents were used from commercial suppliers without further purification. Melting points were measured on the instrument Boetius. TLC was and column chromatography was carried out on SiO2. 1 H NMR and 13 C NMR spectra were recorded at room temperature at 300 and 75.3 MHz respectively, on a Bruker AC-300 spectrometer; at 400 and 100 MHz respectively, on a Bruker DRX-400 spectrometer; or at 600 MHz on a Bruker DRX-600 spectrometer ( 1 H NMR spectrum for compound 1c). For compounds 1, 3b,c and 8a mass spectra were recorded on the SHIMADZU GCMS-QP2010 Ultra instrument with electron ionization (EI) of the sample. For compounds 2 and 8b, HRMS spectra were performed at the Centre Régional de Mesures Physiques de l'Ouest" (CRMPO, Université de Rennes1, Rennes, France) using a Bruker MetroTOF-Q II apparatus. Microanalyses (C, H, N) were performed using the Perkin-Elmer 2400 elemental analyzer. The absorption and emission spectra were recorded on Fluoromax-3 spectrophotometer (Jobin-Yvon Horiba). Compounds were excited at their absorption maxima (band or lower energy) to record the emission spectra. All solutions were measured with optical densities below 0.1. Fluorescence quantum yields (± 10%) were determined relative to 9,10-bisphenylethynylanthracene in cyclohexane (ΦF = 1.00). Stocks shifts were calculated considering the lowest energetic absorption band.

The electrochemical studies of the compounds were performed in a with a 3-electrodes cell (WE: Pt, RE: Ag wire, CE: Pt). Ferrocene was added at the end of each experiment to determine redox potential values. The potential of the cell was controlled by a µAUTOLAB Type III potentiostat monitored by a computer. Anhydrous and freshly distilled dichloromethane was used as solvent and degassed with nitrogen. The supporting salt used was NBu4PF6 for electrochemical analysis (>99.9 % Sigma-Aldrich).

Experimental details on EFISH measurements are described elsewhere. [START_REF] Ulrich | [END_REF] Preparation of intermediates 2-Arylquinazoline-4(3H)-ones (7a,b) were synthesized in two steps with isolation of intermediate (Schiff base 6a or dihydroquinazolinone 6b). Starting compound 2-(5-bromothiophen-2-yl)-4-cyanoquinazoline 9 was synthesized as described in our previous work. [27] 2-(4-Cyanobenzylideneamino)benzamide (6a). To a solution of 2aminobenzamide 4 (0.50 g, 3.7 mmol) in ethanol (9 mL) 4cyanobenzaldehyde (0.54 g 3.7 mmol) was added. After stirring for 30 minute the precipitate started to drop out. The reaction mixture was summarily stirred during 5 h, and the precipitate was filtered off and washed with EtOH. Yellow solid, yield 77%, mp 189-191 °C. 1

2-(4-Cyanophenyl)quinazoline-3H-one (7a).

2-(4-Cyanobenzylidenamino)benzamide 6a (0.62 g, 2.5 mmol) was dissolved in ethanol (10 mL), CuCl2 (0.55 g, 4.1 mmol) was added and reaction mixture was refluxed for 2 h. After cooling the formed quinazolinone 6a was filtered off and recrystallized from DMSO. Colorless solid, yield 60%, mp 276-278 °C (mp lit. [35] 280-282 °C) 1 H NMR (400 MHz, DMSO-d6): δ 7.57 (m, 1H), 7.79-7.87 (m, 2H), 8.05 (m, 2H), 8.17

2-(4-Trifluoromethylphenyl)quinazoline-3H-one (7b).

Was synthesized by the same approach as 7a. After cooling of reaction mixture the formed quinazolinone 6b was filtered off and washed with EtOH. Colorless solid, yield 78%, mp 285-287 °C (mp lit. [START_REF] Ulrich | [END_REF] 2-(4-Cyanophenyl)-4-bromoquinazoline (8a). Was obtained similar to described method. 25 To a suspension of 2-(4-cyanophenyl)quinazolin-4(3Н)-one 7a (0.38 g, 1.54 mmol) in toluene (6.8 ml), triethylamine (0.17 ml) and solution of POBr3 (1.75 g, 6.10 mmol) in toluene (3.4 ml) were added. The reaction mixture was stirred at 80 °С for 24 h. After cooling to room temperature the precipitate was filtered off, washed with NaHCO3 solution and dried under reduced pressure. Colorless solid, yield 0.58 g (85%), mp 250-252 °C. 1

2-(4-Trifluoromethylphenyl)-4-bromoquinazoline (8b).

Was synthesized by the same approach as 8a. After cooling to room temperature the product was extracted with CH2Cl2 (50 ml), organic layer was washed with NaHCO3 solution, then concentrated and dried under reduced pressure. 4-Bromoquinazoline 8b was extracted with hexane, solvent was removed under reduced pressure, and the product was used without additional purification. Colorless solid, yield 40%, mp 105-107 °C.

General procedures of Suzuki cross-coupling for the synthesis of quinazolines 1-3.

General procedure I. A solution of bromoquinazoline 8a or 9 (0.8 mmol) in toluene (15 ml) was stirred at room temperature for 5 min, then the corresponding boronic acid or boronic acid pinacol ester (1 mmol), PdCl2(PPh3)2 (15 mg), PPh3 (11 mg), solution of K2CO3 (0.9 g) in water (7.5 ml) and EtOH (8 ml) were added. The mixture was stirred at 85 °C for 7 hours in argon atmosphere in round-bottom pressure flask. After cooling, the target product was filtered off or isolated from the toluene solution.

General procedure II. To the mixture of the 2-(4-trifluorophenyl)-4bromoquinazoline 8b (0.25 mmol) in degassed saturated solution of Na2CO3 (0.5 mL), ethanol (0.5 mL) and toluene (7.5 mL) the appropriate arylboronic acid (0.5 mmol) and Pd(PPh3)4 (0.025 mmol) were added. The solution was heated under reflux for 24 h under nitrogen atmosphere. The reaction mixture was cooled and mixture EtOAc/water (1/1, 10 mL) was added. The organic layer was separated and the aqueous layer was extracted with additional EtOAc (2 × 10 mL). The combined organic extracts were dried over MgSO4 and the solvent was evaporated under reduced pressure.

2-(4-Cyanophenyl)-4-(4-diethylaminophenyl)quinazoline (1a).

Synthesis was accomplished following the general procedure I. The product was purified by column chromatography (SiO2, gradually from hexane/EtOAc (10/1) to hexane/EtOAc (1/1)). Yellow solid, yield 69%, mp 155-157 °C. 1 H NMR (400 MHz, CDCl3): δ 1.27 (t, 6H, J = 7.0 Hz, 2(-CH3)), 3.49 (q, 4H, 2CH2, J = 7.0 Hz), 6.85 (d, 2H, C6H4NEt2, J = 8.2 Hz), 7.58 (t, 1H, CH quinaz, J = 7.6 Hz,), 7.80 (d, 2H, C6H4CN, J = 7.9 Hz), 7.88 (m, 3H), 8.11 (d,1H, CH quinaz, J = 8.3 Hz), 8.32 (d, 1H, CH quinaz, J = 8.3 Hz), 8.83 (d, 2H, C6H4CN, J = 7.9 Hz). 13 121.64, 121.99, 124.23, 125.64, 127.36, 127.78, 129.19, 129.42, 129.70, 130.07, 131.61, 132.41, 133.87, 142.67, 147.17, 150.25, 152.11, 158.31, 167.99 119.10, 120.61, 120.63, 122.05, 123.90, 126.32, 127.05, 127.11, 128.34, 129.27, 129.70, 131.98, 132.53, 134.33, 136.19, 139.96, 140.69, 142.38, 152.18, 158.51, 167.79. MS (m/z, Irel%): 473 [M+H] + (37), 472 [M] + (100), 471 (28), 306 [M-carbazole] + (25), 236 (22), 102 (11), 76 (18). Calcd for C33H20N4 (472): requires C 83.88; H 4.27; N 11.86. Found: C 83.68; H 4.09; N 11.75.

2-(4-Trifluoromethylphenyl)-4-(4-dimethylaminophenyl)quinazoline (2a).

Synthesis was accomplished following the general procedure II. The product was purified by column chromatography (SiO2, petroleum ether/EtOAc, 9/1). Yellow solid, yield 77%, mp 160-162 °C (mp lit. [36] 136-138 °C). 36, 122.71, 123.18, 123.65, 123.68, 125.04, 125.28, 126.94, 127.61, 128.90, 129.01, 129.56, 132.11, 136.07, 139.82, 143.52, 147.42, 148.41, 150.40, 151.89, 157.98 11-8.17 (m, 3H), 8.22 (m, 2H). 13 C NMR (100 MHz, CDCl3): 109.94, 114.34, 120.35, 120.53, 122.88, 123.71, 125.15, 125.33, 126.22, 127.52, 127.65, 128.38, 129.11, 132.03, 133.03, 136.30, 140.80, 141.49, 143.61, 149.08, 151.86, 157.79. MS (m/z, Irel%): 480 [M+2] + (11), 479 [M+1] + (35), 478 [M] + (100), 239 (18), 76 (17). Calcd for C31H18N4S (478): C 77.80; H 3.79; N 11.71. Found: C 77.58; H 3.74; N 11.82.

Scheme 1 .

 1 Scheme 1. Synthesis of compounds 1 and 2. Reagents and conditions: (i) Arylboronic acid or arylboronic acid pinacol ester (for 1c), PdCl2(PPh3)2, PPh3, K2CO3, toluene, EtOH, 85 °C, Argon (for 1); (ii) Arylboronic acid, Pd(PPh3)4, Na2CO3, toluene, EtOH, refluxing, N2 (for 2).

  Scheme 2. Synthesis of 2-(5-(4-aminophenyl)thiophen-2-yl)-4cyanoquinazolines 3a-c. Reagents and conditions: (i) Arylboronic acid (for 3a,b) or arylboronic acid pinacol ester (for 3c), PdCl2(PPh3)2, PPh3, K2CO3, toluene, EtOH, 85 °C, argon.

Figure 2 .

 2 Figure 2. Cyclic voltammograms of chromophores 1a (black), 1b (blue), 1c (green) and 3a (red) in CH2Cl2 solutions with NBu4PF6 (0.1M) as the electrolyte: first oxidation and reduction waves.

Figure 3 .

 3 Figure 3. Normalized absorption (dashed line) and emission spectra (solid lines of compounds 1a (green), 1b (blue) and 1c (red) in CHCl3 solution.

Figure 4 .Figure 6 .

 46 Figure 4. Normalized emission spectra of 1b in different aprotic solvents

  µβ (2ω) at 1907 nm in CHCl3. Molecular concentrations used for the measurements were in the range of10 -3

.

  19 and -3.04 to computed values are in a good agreement with the electrochemically obtained HOMO and LUMO levels demonstrated by their correlations (Figures Hence, the used DFT method can be considered as appropriate. In all particular series, the HOMO/ order of a→b→c; the differences between chromophores b (NAlk2 vs. NPh2 donors) are relatively small. Carbazolyl substituted chromophores showed the largest HOMO scalar product between the permanent dipolar moment of the in fundamental state and the vector component of βThe results are presented in Table4. It β values are obtained indicating that both ground and excited states are polarized in the same d that the excited state is more polarized than ground state, in accordance with fluorosolvatochromic observation. The NLO responses of compounds 1-3 remain nonoptimized π-conjugated linkers with values for compounds 3. In each series, the dialkylamino derivatives exhibit the highest µβ value, followed by and 2b exhibit even similar values) and the NLO response of carbazole derivatives is significantly lower, at the detection limit of the used technique. A 1b and 2b with unsubstituted implies position of the quinazoline core significantly enhance the NLO ver, the cyano substituted compounds 1 exhibit significantly higher NLO response than trifluoromethyl in accordance with higher Hammett . All these results are in full accordance nd UV-Visible data: NLO responses increase when absorbance maxima are redshifted and and AMolecular concentrations used for the to 10 -2 M, µβ ± 10%

Figure 7 .

 7 Figure 7. Localization of frontier molecular orbitals and Mulliken charges in representative chromophores 1a (A) and 3a (B).

  H NMR (400 MHz, DMSO-d6): δ 7.25 (d, 1H, J = 7.8 Hz, CH benzamide), 7.32 (t, 1H, J = 7.4 Hz, CH benzamide), 7.55 (m, 2H, NH, CH benzamide), 7.84 (d, 1H, J = 7.8 Hz, CH benzamide), 7.97 (br. s, 1H, NH), 8.03 (d, 2H, J = 8.1 Hz, C6H4CN), 8.13 (d, 2H, J = 8.1 Hz, C6H4CN), 8.69 (s, 1H, N=CH). Calcd for C15H11N3O (249): C 72.28; H 4.45; N 16.86. Found: C 72.21; Was synthesized by the same approach as 6a. Colorless solid, yield 71%, mp 256-258°C. 1 H NMR (300 MHz, DMSO-d6): δ 5.86 (s, 1H, CH), 6.69 (dd, 1H, J = 8.1 Hz, J = 7.3 Hz, CH), 6.76 (d, 1H, J = 8.1 Hz), 7.26 (m, 2H, CH, NH), 7.61 (dd, 1H, J = 7.3 Hz, J = 1.4 Hz, CH), 7.70 (d, 2H, J = 8.4 Hz, C6H4CF3), 7.77 (d, 2H, J = 8.4 Hz, C6H4CF3), 8.44 (s, 1H, NH).Calcd forC15H11F3N2O (292): C 61.65; H 3.79; N 9.58. Found: C 61.74; H 3.62; N 9.51.

  (br. s, 1H), 8.34 (m, 2H), 12.74 (s, 1H, NH). Calcd forC15H9N3O (247): C 72.87; H 3.67; N 16.99. Found: C 72.68; H 3.54; N 16.89.

  280-282 °C) 1 H NMR (300 MHz, DMSO-d6): δ 7.57 (t, 1H, J = 7.6 Hz, CH quinaz), 7.77 (d, 1H, J = 8.1 Hz, CH quinaz), 7.87 (t, 1H, J = 7.6 Hz, CH quinaz), 7.93 (d, 2H, J = 8.2 Hz, C6H4CF3) 8.17 (d, 1H, J = 8.1 Hz), 8.37 (d, 2H, J = 8.2 Hz, C6H4CF3). Calcd for C15H9F3N2O (290): C 62.07; H 3.13; N 9.65. Found: C 61.98; H 3.02; N 9.46.

  H NMR (400 MHz, DMSO-d6): δ 7.91 (m, 1H), 8.01 (d, 2H, J = 8.2 Hz, C6H4CN), 8.13 (m, 2H,), 8.24 (d, 1H, J = 8.3 Hz, CH quinaz), 8.66 (d, 2H, J = 8.2 Hz, C6H4CN). MS (m/z, Irel %): 311 [M+2] + (23), 309 [M] + (24), 231 (18), 230 [M-Br] + (100), 102 (54), 76 (16), 75 (28), 16 (16). Calcd for C15H8BrN3 (310): C 58.09; H 2.60; N 13.55%. Found: C 58.04; H 2.47; N 13.41.

1 H

 1 NMR (300 MHz, DMSO-d6): δ 7.88-7.97 (m, 3H), 8.16 (d, 2H, J = 3.7 Hz), 8.23 (d, 1H, J = 8.4 Hz, CH quinaz), 8.67 (d, 2H, J = 8.2 Hz, C6H4CF3). HRMS: found [M+H] + 352,9896; requires [M+H] + 352,9896. Calcd for C15H8 79 BrF3N2 (352): C 51.02; H 2.28; N 7.93. Found: C 50.90; H 2.13; N 7.67%.

1 H

 1 C NMR (100 MHz, CDCl3): 12.76 (2C, 2CH3), 44.68 (2C, 2(CH2)), 111.27 (2C, CH), 113.47 (C) , 119.27 (C), 121.96 (C), 123.89 (C), 127.35 (CH), 127.69 (CH), 129.18 (2C, CH), 129.23 (CH), 132.33 (4C, CH), 133.49 (CH), 143.03 (C), 149.64 (C), 152.16 (C), 158.23 (C), 168.21 (C). MS (m/z, Irel %): 379 [M+H] + (14), 378 [M] + (47), 364 (28), 363 [M-CH3] + (100), 335 (16), 230 (13), 181 (11), 102 (13). Calcd for C25H22N4 (378): C 79.34; H 5.86; N 14.80. Found: C, 79.41; H, 5.69; N, 14.55%; Synthesis was accomplished following the general procedure I. The product was purified by column chromatography (SiO2, gradually from hexane/CHCl3 (5/1) to CHCl3).Yellow solid, yield 74%, mp 205-207 °C. NMR (400 MHz, CDCl3): δ 7.13 (t, 2H, NPh2, J = 7.3 Hz), 7.24 (m, 6H), 7.35 (t, 4H, NPh2, J = 7.3 Hz), 7.62 (t, 1H, CH quinaz, J = 7.6 Hz), 7.81 (d, 4H, J = 7.8 Hz), 7.92 (t, 1H, CH quinaz, J = 7.6 Hz,), 8.15 (d, 1H, CH quinaz, J = 8.3 Hz), 8.28 (d, 1H, CH quinaz, J = 8.3 Hz), 8.82 (d, 2H, C6H4CN, J = 7.9 Hz). 13 C NMR (100 MHz, CDCl3): 113.70, 119.16,

  . MS (m/z, Irel%): 475 [M+H] + (37), 474 [M] + (100), 473 (32), 306 [M-NPh2] + (22), 237 (11), 102 (13), 76 (11). Calcd for C33H22N4 (474): C 83.52; H 4.67; N 11.81. Found: C 83.37; H 4.50; N 11.72. 2-(4-Cyanophenyl)-4-(4-(9H-carbazol-9-yl)phenylaminophenyl)quinazoline (1c). Synthesis was accomplished following the general procedure I. After cooling and partially evaporating of reaction mixture the precipitate was filtered off and washed with hexane. Colorless solid, yield 84%, mp 235-237 °C. 1 H NMR (600 MHz, DMSO-d6): δ 7.34 (t, 2H, CH carbazole, J = 7.5 Hz), 7.49 (t, 2H, CH carbazole, J = 7.5 Hz), 7.62 (d, 2H, J = 7.7 Hz), 7.84 (t, 1H, CH quinaz, J = 7.6 Hz), 7.94 (d, 2H, J = 8.2 Hz), 8.05 (d, 2H, J = 8.2 Hz), 7.84 (t, 1H, CH quinaz, J = 7.6 Hz), 8.23 (m, 3H), 8.28 (m, 2H), 8.37 (d, 1H, CH quinaz, J = 8.2 Hz), 8.83 (d, 2H, C6H4CN, J = 8.4 Hz). 13 C NMR (100 MHz, CDCl3): 109.95, 113.99,

  1 H NMR (300 MHz, CDCl3): δ 1.55 (s, 6H, 2CH3), 6.89(d, 2H, C6H4NMe2, J = 8.3 Hz), 7.57 (t, 1H, CH quinaz, J = 7.8 Hz), 7.82(d, 2H, C6H4CF3, J = 8.0 Hz),7.86-7.93 (3H, m), 8.13(d, 1H, CH quinaz, J = 8.4 Hz), 8.29(d, 1H, CH quinaz, J = 8.4 Hz), 8.82(d, 2H, C6H4CF3, J = 8.0 Hz).13 C NMR and JMOD (75 MHz, CDCl3): 40.42 (CH3), 111.94 (CH), 122.05 (C), 124.51 (q, J = 272.9 Hz, CF3), 125.15 (C), 125.46 (q, J = 3.9 Hz, CH), 127.17 (CH), 127.61 (CH), 129.03 (CH), 129.30 (CH), 131.74 (CF3), 132.01 (CH), 133.44 (CH), 142.15 (C), 152.09 (C), 152.26 (C), 158.88 (C), 168.28 (C). HRMS: found [M+H] + 394.1527; requires [M+H] + 394.1526. Calcd for C23H18F3N3 (393): C 70.22; H 4.61; N 10.68. Found: C 70.04; H 4.41; N 10.46. 2-(4-Trifluoromethylphenyl)-4-(4-diphenylaminophenyl)quinazoline (2b). Synthesis was accomplished following the general procedure II. The product was purified by column chromatography (SiO2, petroleum ether/EtOAc, 19/1). Yellow solid, yield 85%, mp 146-148 °C. 1 H NMR (300 MHz, CDCl3): δ 7.13 (t, 2H, NPh2, J = 7.1 Hz), 7.24 (m, 6H), 7.32-7.37 (m, 4H), 7.60 (t, 1H, CH quinaz, J = 7.6 Hz), 7.77 (d, 2H, C6H4CF3, J = 8.2 Hz), 7.81 (d, 2H, C6H4NPh2, J = 8.9 Hz), 7.91 (t, 1H, CH quinaz, J = 7.6 Hz), 8.15 (d, 1H, CH quinaz, J = 8.4 Hz), 8.27 (d, 1H, CH quinaz, J = 8.2 Hz), 8.81 (d, 2H, C6H4CF3, J = 8.2 Hz). 13 C NMR and JMOD (75 MHz, CDCl3): 121.76 (CH), 122.00 (C), 124.19 (CH), 124.51 (q, J = 272.1 Hz, CF3), 125.53 (q, J = 3.9 Hz, CH), 125.64 (CH), 127.34 (CH), 127.50 (CH), 129.04 (CH), 129.44 (CH), 129.70 (CH), 130.35 (C), 131.64 (CH), 131.89 (C), 132.32 (C), 133.75 (CH), 141.89 (C), 147.27 (C), 150.19 (C), 152.22 (C), 158.94 (C), 167.96 (C). HRMS: found [M+H] + 518.1844; requires [M+H] + 518.1839. Calcd for C33H22F3N3 (517): C 76.58; H 4.28; N 8.12. Found: C 76.53; H 4.08; N 8.01. )quinazoline (2c). Synthesis was accomplished following the general procedure II. The product was purified by column chromatography (SiO2, petroleum ether/EtOAc, 9/1) and recrystallization from the mixture of CH2Cl2/heptane three times. Colorless solid, yield 39%, mp 212-214 °C. 1 H NMR (300 MHz, CDCl3): δ 7.35 (t, 2H, CH carbazole, J = 7.6 Hz), 7.48 (t, 2H, CH carbazole, J = 7.6 Hz), 7.61 (d, 2H, J = 8.1 Hz), 7.70 (t, 1H, CH quinaz, J = 7.6 Hz), 7.80-7.88 (m, 4H), 7.99 (t, 1H, CH quinaz, J = 7.6 Hz), 8.16-8.26 (m, 5H), 8.32 (d, 1H, CH quinaz, J = 8.2 Hz), 8.87 (d, 2H, C6H4CF3, J = 8.1 Hz). 13 C NMR and JMOD (75 MHz, CDCl3): 110.00 (CH), 120.56 (CH), 120.63 (CH), 122.06 (C), 123.92 (C), 124.20 (q, J = 272.9 Hz, CF3), 125.65 (q, J = 3.9 Hz, CH), 126.33 (CH), 127.02 (CH), 127.14 (CH), 128.04 (CH), 129.13 (CH), 129.70 (CH), 132.01 (CH), 134.19 (CH), 136.40 (C), 139.90 (C), 140.78 (C), 141.61 (C), 152.27 (C), 159.11 (C), 167.73 (C). HRMS: found [M+H] + 516,1685; requires [M+H] + 516,1682. Calcd for C33H20F3N3 (515): C 76.88; H 3.91; N 8.15. Found: C 76.68; H 3.72; N 8.09. 2-(5-(4-Diphenylaminophenyl)thiophen-2-yl)-4-cyanoquinazoline (3b). Synthesis was accomplished following the general procedure I. The product was purified by column chromatography (SiO2, hexane/EtOAc, 5/1). Orange solid, yield 28%, mp 220-222 °C. 1 H NMR (400 MHz, CDCl3): δ 7.06-7.18 (m, 7H), 7.27-7.33 (m, 6H), 7.60 (d, 2H, J = 8.1 Hz), 7.70 (t, 1H, CH quinaz, J = 7.5 Hz), 7.98 (t, 1H, CH quinaz, J = 7.5 Hz), 8.07 (d, 1H, CH quinaz. J = 8.3 Hz), 8.12 (d, 1H, H-3' thioph, J = 4.0 Hz), 8.19 (d, 1H, CH quinaz, J = 8.2 Hz). 13 C NMR (100 MHz, CDCl3): 114.

  . MS (m/z, Irel%): 482 [M+2] +(11), 481 [M+1] +(36), 480 [M] + (100), 240 (12). Calcd for C31H20N4S (480): C 77.48; H 4.19; N 11.66. Found: C 77.41; H 3.99; N 11.48. 2-(5-(4-(9H-Carbazol-9-yl)phenyl)thiophen-2-yl)-4-cyanoquinazoline (3c). Synthesis was accomplished using the 9H-carbazole-9-(4phenyl)boronic acid pinacol ester as a reagent following the general procedure I. The reaction was carried out for 20 hours. After cooling of reaction mixture the precipitate was filtered off and washed with hexane. Yellow solid, yield 35%, mp 255-257 °C. 1 H NMR (400 MHz, CDCl3): δ 7.32 (t, 2H, CH carbazole, J = 7.4 Hz), 7.42-7.52 (m, 5H), 7.66 (d, 2H, J = 7.8 Hz), 7.75 (t, 1H, CH quinaz, J = 7.6 Hz), 7.96 (d, 2H, J = 8.0 Hz), 8.02 (t, 1H, CH quinaz, J = 7.6 Hz), 8.

Table 2 .

 2 UV-Vis and photoluminescence (PL) data of compounds 1-3 in CHCl3 solution.

	Comp.	λabs, nm	ε, mM -1 cm	-1	λem, nm	ΦF	Stokes shift, cm -1
	1a	408	20.4		496	0.63	4350
	1b	402	20.2		531	0.72	6040
	1c	363sh 340	8.5 11.4		486	0.64	6970
	2a	390	14.5		474	0.76	4540
	2b	396	20.9		517	0.75	5910
	2c	340	12.3		474	0.53	8310
	3a	467sh 403	14.1 28.5		508	> 0.01	1730
	3b	441sh 398	17.4 28.8		494	> 0.01	2430
	3c	365	29.6		469	0.10	6080

Table 3 .

 3 Fluorosolvatochromism of compounds 1-3 and A in various aprotic solvents and in the solid state.

	Comp.	n-hep-
		tane
		30.9 [a]

Table 4 .

 4 µβ values for compounds 1-3 and

	Comp.	µβ, 10 -48 esu	[a]

Table 5 .

 5 DFT calculated data of compounds 1-3

		EHOMO	ELUMO	∆E	µ	λmax	β (-	E
		DFT	DFT	DFT	[D]	TD-DFT	2ω,ω,ω)	HOMO
	Comp.	[eV]	[eV]	[eV]		[nm]	DFT	DFT
							[10 -30	[eV]
							esu]
	1a	-5.52	-2.44	3.08	12.89	462	104	-5.52
	1b	-5.53	-2.54	2.99	10.78	476	139	-5.53
	1c	-5.86	-2.64	3.22	9.04	435	51	-5.86
	2a	-5.50	-2.27	3.22	10.63	441	93	-5.50
	2b	-5.51	-2.24	3.11	8.34	459	125	-5.51
	2c	-5.85	-2.51	3.34	6.54	422	43	-5.85
	3a	-5.19	-2.89	2.30	8.92	638	587	-5.19
	3b	-5.33	-2.97	2.36	5.63	609	551	-5.33
	3c	-5.75	-3.04	2.71	3.84	517	182	-5.75

Acknowledgements

This work was supported by the Russian Foundation for Basic Research (grant numbers 18-03-00112, 19-33-90014).

Entry for the Table of Contents

Chromophores: 4-Сyanoquinazoline, 2-(4-cyanophenyl)quinazoline and 2-(4-trifluorophenyl)quinazoline chromophores bearing 5-(4aminophenyl)thiophen-2-yl or 4-aminophenyl electron-donor (D) units have been synthesized. Data of UV-Vis and emission spectroscopy, cyclic voltammetry, electric field induced second harmonic generation (EFISH) method and quantum-chemical calculations for all compounds have been analyzed.