Photo-crosslinkable emissive molecular materials

Abstract

For applications in the fields of organic electronics and photonics, disclosed are fluorescent charge-transfer compounds emitting in the visible spectral range from blue to red, including a triarylamine moiety, an electron-withdrawing group and at least two photopolymerizable groups. Also disclosed is a method for manufacturing a film-forming and photo-crosslinkable composition including at least one compound of the invention and its use as a precursor of a photocrosslinked emissive layer.

Claims

1. A photopolymerizable emissive compound of general formula (I): ##STR00089## wherein X and Y each independently represent an aryl or heteroaryl; A and B each independently represent a chiral center; L.sub.1 and L.sub.2 each independently represent an alkyl group comprising 1 to 10 carbon atoms, linear or branched, that may be interrupted by one or several atoms —O—, —N— or —S—; said group being optionally substituted with at least one alkyl, alkene, alkyne, oxo, amine, amide, cyano, hydroxyl, carboxy group; T.sub.1 and T.sub.2 each independently represent a photopolymerizable group selected from at least one acryloyl, alkylacryloyl, oxetane, alkyloxetane, styryl, allyl, acrylamide, methacrylamide or cinnamate; Z represents an electron-withdrawing group.

2. A photo-crosslinkable emissive compound of general formula (II-a), (II-b), (II-c) or (II-d) according to claim 1: ##STR00090## ##STR00091##

3. An intermediate compound of general formula: ##STR00092## wherein X and Y each independently represent an aryl or heteroaryl; R represents a —OH or —OTBDMS group; A and Beach independently represent a chiral center; and Z represents an electron-withdrawing group.

4. A composition comprising at least one compound according to claim 1, an initiator and an organic solvent.

5. A kit comprising a first compartment comprising at least one compound according to claim 1, and an organic solvent, and a second compartment comprising the photoinitiator.

6. A method for manufacturing a compound according to claim 1, comprising: (i) synthesizing an intermediate compound of general formula (III-2) comprising an aldehyde group: ##STR00093## wherein A, B, X and Y are defined as in claim 1, obtained by the reaction of the 4-di(4-bromophenyl)aminobenzaldehyde with the compound of formula (III-1): ##STR00094## also noted as ##STR00095## wherein A represents a chiral center; and X represents an aryl or heteroaryl; (ii) a deprotection reaction; (iii) in the case where Z of the compound according to claim 1 is not an aldehyde group, modifying the aldehyde group of the intermediate compound (III-2) into another electron-withdrawing group Z allowing the provision of intermediate compound of formula (III-3bis): ##STR00096## wherein A, B, X and Y are defined as in claim 1, and Z represents an electron-withdrawing group; (iv) and, modifying the compound obtained in (ii) in the case where Z of the compound according to claim 1 is an aldehyde group, or in (iii) in the case where Z of the compound according to claim 1 is not an aldehyde group, allowing for the introduction of spacers L comprising at least one photopolymerizable group T.

7. A method for manufacturing a substrate coated with a thin, amorphous, emissive, photo-crosslinkable and non-doped small molecule-based film, comprising the following steps: a) providing a composition comprising at least one compound of general formula according to claim 1, a solvent and a photoinitiator; b) depositing the composition obtained in a) onto a substrate.

8. A method for manufacturing a photo-crosslinked emissive organic layer or a photo-crosslinked emissive multilayer system comprising the following steps: a′) implementing the method of manufacturing a substrate coated with a photo-crosslinkable emissive film according to claim 7; then b′) the photopolymerization of said film; c′) optionally, repeating steps a′) and b′) resulting in an insoluble emissive multilayer device.

9. A composition comprising at least one compound according to claim 2, an initiator and an organic solvent.

10. A kit comprising a first compartment comprising at least one compound according to claim 2, and an organic solvent, and a second compartment comprising the photoinitiator.

11. A method for manufacturing a substrate coated with a thin, amorphous, emissive, photo-crosslinkable and non-doped small molecule-based film, comprising the following steps: a) providing a composition comprising at least one compound of general formula according to claim 2, a solvent and a photoinitiator; b)depositing the composition obtained in a) onto a substrate.

12. The photopolymerizable emissive compound of general formula (I) according to claim 1, wherein X and Y each independently represent a phenyl group.

13. The photopolymerizable emissive compound of general formula (I) according to claim 1, wherein A and Beach independently represent a —CHMe— group.

14. The photopolymerizable emissive compound of general formula (I) according to claim 1, wherein L.sub.1 and L.sub.2 each independently represent an alkyl group comprising 3 to 10 carbon atoms, linear or branched, that may be interrupted by one or several atoms —O—, —N— or —S—; said group being optionally substituted with at least one alkyl, alkene, alkyne, oxo, amine, amide, cyano, hydroxyl, carboxy group.

15. The photopolymerizable emissive compound of general formula (I) according to claim 1, wherein T.sub.1 and T.sub.2 simultaneously represent an acryloyl group or an alkyloxetane group.

16. The photopolymerizable emissive compound of general formula (I) according to claim 1, wherein Z represents an aldehyde, dicyanovinylidene, cyanovinylidene, benzothiadiazole group or an alkyl ester group comprising at least one photopolymerizable group selected from at least one acryloyl, alkylacryloyl, oxetane, alkyloxetane, styryl, allyl, acrylamide, methacrylamide or cinnamate.

17. The intermediate compound according to claim 3, wherein X and Y each independently represent a phenyl group.

18. The intermediate compound according to claim 3, wherein A and B each independently represent a —CHMe— group.

19. The intermediate compound according to claim 3, wherein Z represents an aldehyde, dicyanovinylidene, cyanovinylidene, benzothiadiazole group or an alkyl ester group comprising at least one photopolymerizable group selected from at least one acryloyl, alkylacryloyl, oxetane, alkyloxetane, styryl, allyl, acrylamide, methacrylamide or cinnamate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 relates to the absorption spectra of compounds II-a, II-b, A, B and C (FIG. 1A) or compounds II-a, II-c and II-d (FIG. 1B) in toluene solution.

(2) FIG. 2 relates to the UV-vis emission spectra of compounds II-a, II-b, A, B and C (FIG. 2A) or compounds II-a, II-c and II-d (FIG. 2B) in toluene solution.

(3) FIG. 3 relates to the absorption spectra of compounds II-a, II-b, A, B and C (FIG. 3A) or compounds II-a, II-c and II-d (FIG. 3B) processed as thin films.

(4) FIG. 4 relates to the emission spectra of compounds II-a, II-b, A, B and C (FIG. 4A) or compounds II-a, II-c and II-d (FIG. 4B) processed as thin films.

(5) FIG. 5 relates to cyclic voltammograms of compounds A, B and C (FIG. 5A) or compounds II-a, II-c and II-d (FIG. 5B), recorded in 10-3 mol.Math.L−1 acetonitrile (support electrolyte: nBu4NPF6 (0.1 mol.Math.L−1); scan rate: 0.1 V.Math.s−1).

(6) FIG. 6 relates to the evolution in infrared absorption spectroscopy of the vibration band at 810 cm−1 (characteristics of photopolymerizable acrylate functions) during the polymerization reaction of compounds II-a.

(7) FIG. 7 relates to the evolution of the maximum absorbance (FIG. 7A) and fluorescence signal intensity (FIG. 7B) of developed organic layers at given irradiation power and irradiation.

(8) FIG. 8 represents the picture in transmission (Abs) and emission (EM) of emissive organic thin films before and after development.

(9) FIG. 9 depicts the profile of organic layers after polymerization at an irradiation power of 450 mW.Math.cm.sup.−2 for 1 min. (FIG. 9A) or at an irradiation power of 30 mW.Math.cm.sup.−2 for 5 min. (FIG. 9B).

(10) FIG. 10 relates to the UV-vis emission spectra of nanoparticles comprising compounds II-a (FIG. 10A) and the UV-vis emission of nanoparticles comprising a mixture of compounds II-a and II-c (FIG. 10B).

(11) FIG. 11 relates to TEM images of photo-crosslinked fluorescent nanoparticles made of photopolymerized compounds II-a (FIG. 11A) or II-c (FIG. 11B).

EXAMPLES

(12) The present invention is further illustrated by the following examples.

A. Material and Methods

Abbreviations

(13) DCC: dicyclohexylcarbodiimide DEAD: diethylazodicarboxylate DIPC: N, N-diisopropylcarbodiimide DMF: dimethylformamide DPTS: dimethylaminopyridinium p-toluenesulfonate DSC: Differential Scanning Calorimetry MeOH: methanol NHE: Normal Hydrogen Electrode RT: room temperature SDS: sodium dodecylsufate TBAF: tetrabutylammonium fluoride TBDMS: tert-butyldimethylsilyl group TBDMSCI: tert-butyldimethylsilyl chloride TEM: Transmission Electronic Microscopy THF: tetrahydrofuran TMS: tetramethylsilane TPO: phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide
Reagents

(14) All chemical reagents and solvents were purchased from commercial sources (Aldrich, Acros, SDS) and used as received. Spectroscopic grade solvents purchased from Aldrich were used for spectroscopic measurements. All air-sensitive reactions were performed under argon using a vacuum line. Analytical TLC was performed on Kieselgel F-254 precoated plates. Visualization was done with UV lamp. Flash chromatography was carried out with silica gel 60 (230-400 mesh) from SDS and 4-bis(4′-tert-butylbiphenyl-4-yl)aminobenzaldehyde was synthesized according to literature procedures (Ishow et al., Chem. Mater. 2008, 20, 6597-6599).

(15) Photopolymerization

(16) Substrate

(17) All polymerization tests were carried out on organic film deposited on glass substrates that were previously cleaned by successive treatments in a wave bath with an alkaline solution (2% Hellmanex), with distilled water and then, absolute ethanol. Each washing step was implemented during 10 min. The glass substrate was then dried under nitrogen flux and stored in an inert atmosphere.

(18) All solutions for depositions implementation were carried out with spectroscopic grade chloroform in order to provide thin layers without micro aggregates.

(19) Physico-Chemical Analysis

(20) Nuclear Magnetic Resonance Spectroscopy (NMR)

(21) .sup.1H NMR and .sup.13C NMR spectra were recorded on Bruker 300 MHz or 400 MHz spectrometers. Chemical shifts δ were reported in ppm relative to TMS and referenced to the residual solvent.

(22) Mass Spectrometry

(23) Low-resolution mass (LR-MS) spectra were obtained by electrospray ion trap mass spectrometry (LC-Esquire, Bruker) in positive-ion mode. High-resolution mass (HR-MS) spectra were obtained either by electrospray ionization coupled with high resolution ion trap orbitrap (LTQ-Orbitrap, ThermoFisher Scientific) or by MALDI-TOF-TOF (Autoflex III de Bruker), both working in ion-positive mode.

(24) UV-Visible Absorption Spectroscopy

(25) Spectroscopic grade solvents have systematically been used for photophysical studies and the fabrication of thin films. UV-visible absorption spectra were recorded using a Varian Model Cary 5E spectrophotometer.

(26) Steady-State Fluorescence Spectroscopy

(27) Corrected emission spectra were obtained using Jobin-Yvon. Inc spectrofluorimeter (Fluorolog 3 equipped with right-angle and front-face configurations for solution and thin films measurements, respectively). Fluorescence quantum yields in solution were determined from fluorescence standard using Coumarine 540 A in ethanol (Φ.sub.f=0.38) or POPOP in cyclohexane (Φ.sub.f=0.38).

(28) Time-Resolved Fluorescence Spectroscopy

(29) Fluorescence intensity decays were measured by the time-correlated single-photon counting method (TCSPC) using the TimeHarp 260 PICO TCSPC module implemented on the FluoTime 300 “EasyTau” fluorescence lifetime spectrometer purchased from Picoquant. Excitation was performed with a picosecond pulsed laser diode at 450±10 nm (FWHM>70 ps) at magic angle. Fluorescence photons were detected at the emission maximum through a monochromator by means of a Hybrid-PMT (PMA Hybrid 40, Picoquant) with an instrument response of 120 ps and connected to a constant-fraction discriminator.

(30) Infrared Absorption Spectroscopy

(31) Potassium bromide monocrystals were used as infrared substrates to investigate the photopolymerization reaction of spin-coated thin films. The spectra were recorded as a function of time under a flow of nitrogen using an infrared Bruker Tensor 27 spectrometer.

(32) Transmission Electron Microscopy (TEM)

(33) Transmission Electron Microscopy imaging was performed using the MO-Jeol 1230 (80 kV) electron microscope. Aqueous solutions of nanoparticles were deposited onto copper grids (300 mesh) coated with carbon thin films and lacey carbon copper grids (300 mesh).

(34) Photoirradiation

(35) Photoirradiation was performed using a continuous Hg—Xe white source lamp (Hamamatsu—LC8) equipped with a bundle of quartz fibers and a collimator. The irradiation was selected by means of a narrow band filter at 365 nm (Semrock, Hg-01-365-25, 12 nm bandwith) with a high transmittance Tav (>93%).

(36) Thermal Analyses

(37) Glass transition temperatures were obtained using differential scanning calorimetry (DSC) (Maia 205 C—Netzsch) in aluminum caps under a nitrogen flow at a scan rate of 30° C..Math.min.sup.−1 over the temperature range from −30° C. to 140° C. after a first heating-cooling cycle to erase the thermal history of the sample.

B. Synthesis of Compounds of Formula (II)

B.1. Synthesis of Compounds of Formula II-a and II-b

(38) The synthesis of compounds of formula II-a to II-f is performed according to the following procedures (see schemes 1, 2 and 3).

(39) ##STR00084## ##STR00085##

(40) ##STR00086##

(41) ##STR00087##

B.1.1. Synthesis of Intermediate Products

Intermediate 1: 1-bromo-4-{1-[(tert-butyldimethylsilyl)oxy]ethyl}benzene

(42) 4-bromo-α-methylbenzyl alcohol (1.7 g, 8.46 mmol, 1 eq.) and dimethylaminopyridine (catalytic amount) were first dissolved in anhydrous dimnethylformnnamide (10 mL). After addition of imidazole (1.73 g, 10.1 mmol, 1.2 eq.), t-butyl-dimethylsilyl chloride (1.51 g, 10.1 mmol, 1.2 eq.) was added. The reaction mixture was stirred at room temperature under argon for 2 days. After dilution with dichloromethane, the organic layer was extracted, washed four times with brine, dried over anhydrous Na.sub.2SO.sub.4, and concentrated under vacuum. The resulting pale yellow oil was purified by silica gel chromatography using petroleum ether:dichloromethane 1:1 as an eluent. Compound 1 was obtained as a colorless oil. (2.16 g, 81%).

(43) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.42 (d, .sup.3J=8.5 Hz, 2H), 7.20 (d, .sup.3J=8.5 Hz, 2H), 4.81 (q, .sup.3J=6.3 Hz, 1H), 1.37 (d, .sup.3J=6.4 Hz, 3H), 0.89 (s, 9H), 0.04 (s, 3H), −0.04 (s, 3H) ppm.

(44) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=146.0, 131.2, 127.0, 120.4, 70.3, 27.2, 25.8, 18.1, −2.9, −4.9 ppm.

Intermediate 2: 4-{1-[(tert-butyldimethylsilyl)oxy]ethyl}phenyl boronic acid

(45) A solution of compound 1 (3.1 g, 9.84 mmol, 1 eq.) in anhydrous tetrahydrofuran (20 mL) was cooled to −80° C. before adding a 1.6 M n-butyllithium solution in hexane (8 mL, 12.8 mmol, 1.3 eq.) dropwise. The resulting mixture was stirred for 1 h at −80° C. and triisopropylborate (9 mL, 39.4 mmol, 4 eq.) was added portionwise over 30 min. The solution was slowly warmed up to room temperature over 3 h and stirred a further hour at room temperature. Excess of n-butyllithium was neutralized with a 1 M HCl solution until pH=3-4. The organic layer was washed twice with brine, dried over anhydrous Na.sub.2SO.sub.4, and concentrated under vacuum. The resulting colorless oil (2.71 g, 97%) was used without further purification.

(46) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=8.19 (d, .sup.3J=8.1 Hz, 2H), 7.47 (d, .sup.3J=7.9 Hz, 2H), 4.95 (q, .sup.3J=6.3 Hz, 1H), 1.46 (d, .sup.3J=6.4 Hz, 3H), 0.93 (s, 9H), 0.08 (s, 3H), 0.00 (s, 3H) ppm.

(47) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=151.7; 135.6; 124.8; 70.9; 27.2; 25.9; 18.3; −4.8 ppm.

Intermediate 3: 4-{bis[4′-{1-[(tert-butyldimethylsilyl)oxy]ethyl}(1,1′-biphenyl)-4-yl]amino}benzaldehyde

(48) 4-di(4-bromophenyl)aminobenzaldehyde (195 mg, 0.46 mmol, 1 eq.), tris-o-tolylphosphine (29 mg, 97 μmol, 21% mol.) and palladium acetate (II) (7 mg, 32 μmol, 7% mol.) were placed in toluene (9 mL) and stirred for 2 min under argon. A solution of boronic acid 2 (326 mg, 1.16 mmol, 2.5 eq.) in deoxygenated methanol (2 mL) was subsequently added, followed by potassium hydroxide (160 mg, 2.8 mmol, 6 eq.) in water (1 mL). The reaction mixture was heated overnight at 70° C. under inert atmosphere. After cooling to room temperature, the extracted organic layer was washed twice with brine, dried over MgSO.sub.4, and concentrated under vacuum. Compound 3 was obtained as a yellow solid after purification by silica gel chromatography using with petroleum ether:dichloromethane 1:4 as an eluent (260 mg, 76%).

(49) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=9.84 (s, 1H), 7.72 (d, .sup.3J=8.7 Hz, 2H), 7.58 (d, .sup.3J=8.6 Hz, 4H), 7.55 (d, .sup.3J=8.2 Hz, 4H), 7.40 (d, .sup.3J=8.2 Hz, 4H), 7.25 (d, .sup.3J=8.3 Hz, 4H), 7.13 (d, .sup.3J=8.8 Hz, 2H), 4.92 (q, 3J=6.5 Hz, 2H), 1.44 (d, 3J=6.3 Hz, 6H), 0.92 (s, 18H), 0.07 (s, 6H), 0.00 (s, 6H) ppm.

(50) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=190.6, 153.3, 146.3, 145.3, 138.7, 137.9, 131.5, 129.5, 128.3, 126.7, 126.4, 125.9, 120.0, 70.7, 27.4, 26.0, 18.4, −4.64 ppm.

(51) HRMS (MALDI-TOF) m/z: (M.sup.+, 100%) calculated for C.sub.47H.sub.59NO.sub.3Si.sub.2 742.4106; found 742.4133.

Intermediate 4: 4-{bis[4′-(1-hydroxyethyl) (1,1′-biphenyl)-4-yl]amino}benzaldehyde

(52) A solution of compound 3 (280 mg, 0.38 mmol, 1 eq.) in anhydrous tetrahydrofuran (10 mL) and tetrabutylammonium fluoride (1 mL, 1 M, 2.6 eq.) was stirred overnight at room temperature under argon. The solution was washed twice with brine, and the organic layer was dried over anhydrous MgSO.sub.4, before solvent removal under vacuum. The crude product was purified by silica gel chromatography using petroleum ether: ethyl acetate 1/1 as an eluent to give compound 4 as a yellow solid (180 mg, 92%).

(53) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=9.84 (s, 1H), 7.73 (d, .sup.3J=8.8 Hz, 2H), 7.60 (d, .sup.3J=3.9 Hz, 4H), 7.57 (d, .sup.3J=4.2 Hz, 4H), 7.46 (d, .sup.3J=8.2 Hz, 4H), 7.27 (d, .sup.3J=8.4 Hz, 4H), 7.15 (d, .sup.3J=8.7 Hz, 2H), 4.97 (q, .sup.3J=6.3 Hz, 2H), 1.55 (d, .sup.3J=6.5 Hz, 6H) ppm.

(54) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=190.5, 153.1, 145.3, 144.9, 139.5, 137.5, 131.4, 129.5, 128.3, 127.0, 126.3, 125.0, 120.1, 70.2, 25.2 ppm.

(55) HRMS (MALDI-TOF) m/z: (M.sup.+, 100%) calculated for C.sub.35H.sub.31NO.sub.3 513.2298; found 513.2293.

Intermediate 5: 4-{bis[4′-(1-hydroxyethyl) (1,1′-biphenyl)-4-yl]amino}-1-(2,2-dicyanovinyl)benzene

(56) To a solution of compound 4 (350 mg, 0.67 mmol, 1 eq.) in anhydrous pyridine (7 mL) and acetic acid (2 mL) were added a catalytic amount of ammonium acetate, followed by malononitrile (185 mg, 2.8 mmol, 4 eq.). The reaction mixture was stirred overnight at room temperature under argon. After addition of a 1 M HCl solution (5 mL), the red solid was filtered off, and washed with a 1 M HCl solution and distilled water. The red solid was dissolved in dichloromethane, and the resulting solution was dried over anhydrous MgSO.sub.4, before solvent removal under vacuum to give compound 5 as a pure red solid (360 mg, 96%).

(57) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.78 (d, .sup.3J=9.0 Hz, 2H), 7.61 (d, .sup.3J=6.0 Hz, 4H), 7.58 (d, .sup.3J=5.5 Hz, 4H), 7.54 (s, 1H), 7.47 (d, .sup.3J=8.2 Hz, 4H), 7.29 (d, .sup.3J=8.5 Hz, 4H), 7.08 (d, .sup.3J=9.0 Hz, 2H), 4.97 (q, .sup.3J=6.4 Hz, 2H), 1.55 (d, .sup.3J=6.5 Hz, 6H) ppm.

(58) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=157.9, 153.2, 145.1, 144.3, 141.8, 139.2, 138.6, 133.1, 128.5, 127.1, 126.8, 126.0, 123.2, 119.1, 75.85, 70.13, 25.24 ppm.

(59) HRMS (MALDI-TOF) m/z: (M.sup.+, 100%) calculated for C.sub.38H.sub.31N.sub.3O.sub.2 561.2411; found 561.2429.

Intermediate 6: 4-(bis(4′-(1-hydroxyethyl)-[1,1′-biphenyl]-4-yl)amino)benzoic acid

(60) To a solution of sodium hydroxyde (6.7 g, 169 mmol, 50 eq.) in ethanol (330 mL) thoroughly deoxgenated are added silver oxyde (3.12 g, 13.5 mmol, 4 eq.) and a deoxygenated solution of compound 3 (2.5 g, 3.37 mmol, 1 eq.) in anhydrous toluene (24 mL). The reaction mixture was stirred under inert atmosphere for 12 h, and further neutralized with a 3 mol.Math.L.sup.−1 HCl aqueous solution, added dropwise. This acidic treatment cleaved the tert-butyldimethylsilyl protective groups to generate the carboxylic acid 13 in one step. After one hour of stirring, the product was extracted with ethylacetate, washed once with distilled water and dried over anhydrous magnesium sulfate. The solution was filtered and dried under vacuum. A white solid with greenish fluorescence and matching compound 13 formed on the flask and was used readily without requiring further purification (1.77 g, 3.34 mmol, 99%).

(61) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.90 (d, J=9.0 Hz, 2H), 7.58 (d, J=8.4 Hz, 4H), 7.54 (d, J=8.7 Hz, 4H), 7.45 (d, J=8.1 Hz, 4H), 7.23 (d, J=8.7 Hz, 4H), 7.10 (d, J=8.9 Hz, 2H), 6.44 (dd, J=17.3, 1.5 Hz, 1H), 6.15 (dd, J=17.3, 10.4 Hz, 1H), 5.85 (dd, J=10.4, 1.5 Hz, 1H), 4.96 (q, J=6.4 Hz, 2H), 4.56-4.51 (m, 2H), 4.51-4.45 (m, 2H), 1.54 (d, J=6.5 Hz, 6H) ppm.

(62) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=166.1, 166.0, 151.9, 145.8, 144.8, 139.6, 136.9, 131.4, 131.1, 128.1, 128.1, 126.9, 125.9, 125.9, 122.1, 120.6, 70.2, 62.4, 62.3, 25.2 ppm.

(63) HR-MS MALDI m/z: [M.sup.+] calculated for C.sub.35H.sub.31NO.sub.4 529.2248; found 529.2224.

Intermediate 7: 2-(acryloyloxy)ethyl 4-(bis(4′-(1-hydroxyethyl)-[1,1′-biphenyl]-4-yl)amino)benzoate

(64) A solution of carboxylic acid derivative 6 (100 mg, 0.19 mmol, 1 eq.), DPTS acidic catalyst (30 mg, 0.1 mmol, 0.5 eq.) and 2-hydroxyethylacrylate (44 μL, 0.28 mmol, 2 eq.) in anhydrous dichloromethane (4 mL) was placed under inert atmosphere and cooled down to 0° C. with an ice bath. The DIPC coupling agent (39 μL, 0.25 mmol, 1.3 eq.) was first diluted in anhydrous dichloromethane (500 μL) and then added dropwise to the reaction mixture. The solution was stirred at room temperature for 12 h before adding saturated sodium chloride solution. The organic layer was extracted, dried over anhydrous sodium sulfate, filtered over a cotton plug, and eventually evaporated to dryness under vacuum. The resulting brown product was purified by silica gel column chromatography using as an eluent a mixture of petroleum ether:ethyl acetate EP/AcOEt 1/1 to yield compound 7 as a white solid, blue-emitting (50 mg, 81.6 μmol, 43%).

(65) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.90 (d, J=9.0 Hz, 2H), 7.58 (d, J=8.4 Hz, 4H), 7.54 (d, J=8.7 Hz, 4H), 7.45 (d, J=8.1 Hz, 4H), 7.23 (d, J=8.7 Hz, 4H), 7.10 (d, J=8.9 Hz, 2H), 6.44 (dd, J=17.3, 1.5 Hz, 1H), 6.15 (dd, J=17.3, 10.4 Hz, 1H), 5.85 (dd, J=10.4, 1.5 Hz, 1H), 4.96 (q, J=6.4 Hz, 2H), 4.56-4.51 (m, 2H), 4.51-4.45 (m, 2H), 1.54 (d, J=6.5 Hz, 6H) ppm.

(66) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=166.1, 166.0, 151.9, 145.8, 144.8, 139.6, 136.9, 131.4, 131.1, 128.1, 128.1, 126.9, 125.9, 125.9, 122.1, 120.6, 70.2, 62.4, 62.3, 25.2 ppm.

(67) HR-MS MALDI m/z: [M]+ calculated for C40H37NO6 627.2615; found 627.2600.

B.1.2. Synthesis of Final Compounds

Compound II-a: Bis(2-(acryloyloxy)ethyl) O,O′-(((4-2(2,2-dicyanovinyl)phenyl)azanediyl)bis([1,1′-biphenyl]-4′,4-diyl))bis(ethane-1,1-diyl)) disuccinate

(68) A solution of 4-(2-(acryloyloxy)ethoxy)-4-oxobutanoic acid (730 mg, 1.30 mmol, 1 eq.), dimethylaminopyridinium p-toluenesulfonate (DPTS) (381 mg, 1.30 mmol, 1 eq.) and compound 5 (1.12 g, 5.2 mmol, 4 eq.) in anhydrous dichloromethane (30 mL) was placed under inert atmosphere and cooled down to 0° C. A solution of dicyclocarbodiimide (DCC) (803 mg, 3.90 mmol, 3 eq.) previously diluted in anhydrous dichloromethane (5 mL) was then added dropwise. The resulting mixture was left under stirring at room temperature for 12 h. After filtration of the solid impurities and concentration of the solution under vacuum, the resulting crude product was dissolved in toluene (˜1-3 mL) and filtered to remove undissolved urea. Purification of the reddish power was performed by silica gel chromatography using petroleum ether/ethyl acetate 6/4 as an eluent to provide compound 8 as a honey-like viscous red compound (790 mg, 0.82 mmol, 63%).

(69) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.78 (d, J=9.0 Hz, 2H), 7.62-7.52 (m, 9H), 7.43 (d, J=8.2 Hz, 4H), 7.28 (d, J=8.2 Hz, 4H), 7.08 (d, J=9.0 Hz, 2H), 6.43 (dd, J=17.3, 1.4 Hz, 2H), 6.13 (dd, J=17.3, 10.4 Hz, 2H), 5.94 (q, J=6.6 Hz, 2H), 5.85 (dd, J=10.4, 1.4 Hz, 2H), 4.39-4.29 (m, 8H), 2.71-2.65 (m, J=4.9 Hz, 8H), 1.58 (d, J=6.8 Hz, 6H) ppm.

(70) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=173.8, 172.1, 171.4, 165.9, 144.4, 140.8, 139.7, 139.6, 138.4, 133.0, 132.9, 131.5, 128.5, 127.9, 127.1, 126.8, 126.7, 123.3, 119.2, 72.5, 71.1, 62.4, 62.2, 29.4, 29.0, 22.2 ppm.

(71) HR-MS (MALDI-TOF) m/z: [M].sup.+ calculated for C.sub.56H.sub.51N.sub.3O.sub.12 957.3467; found 957.3498.

Compound II-c: Bis(2-(acryloyloxy)ethyl) O,O′-((((4-formylphenyl)azanediyl)bis([1,1′-biphenyl]-4′,4-diyl))bis(ethane-1,1-diyl)) disuccinate

(72) A solution of compound 4 (1.42 g, 2.76 mmol, 1 eq.), dimethylaminopyridinium p-toluenesulfonate (DPTS) (811 mg, 2.76 mmol, 1 eq.) and compound 15 (2.39 g, 11 mmol, 4 eq.) in anhydrous dichloromethane (30 mL) was placed under inert atmosphere and cooled down to 0° C. A solution of dicyclocarbodiimide (DCC) (1.7 g, 8.26 mmol, 3 eq.) previously diluted in anhydrous dichloromethane (5 mL) was then added dropwise. The resulting mixture was left under stirring at room temperature for 12 h. After filtration of the solid impurities and concentration of the solution under vacuum, the resulting crude product was dissolved in toluene (˜1-3 mL) and filtered to remove undissolved urea. After concentration of the solution, purification of the white solid was performed by silica gel chromatography using dichloromethane as an eluent to yield the photopolymerizable green emitter II-c as a yellow green amorphous solid (1.6 g, 1.76 mmol, 64%).

(73) .sup.1H NMR (CDCl.sub.3, 300 MHz, δ): 9.84 (s, 1H), 7.73 (d, J=8.8 Hz, 2H), 7.56 (m, 8H), 7.42 (d, J=8.2 Hz, 4H), 7.26 (d, J=8.6 Hz, 4H), 7.14 (d, J=8.7 Hz, 2H), 6.43 (dd, J=17.3, 1.5 Hz, 2H), 6.13 (dd, J=17.3, 10.4 Hz, 1H), 5.94 (q, J=6.6 Hz, 2H), 5.85 (dd, J=10.4, 1.5 Hz, 1H), 4.33 (m, 8H), 2.76-2.62 (m, 8H), 1.58 (d, J=6.5 Hz, 6H) ppm.

(74) .sup.13C NMR (CDCl.sub.3, 75 MHz, δ): 190.4, 172.0, 171.4, 165.8, 153.0, 145.4, 140.5, 139.9, 137.3, 131.4, 131.3, 129.6, 128.3, 127.9, 126.9, 126.6, 126.2, 120.1, 72.5, 62.3, 62.1, 29.3, 28.9, 22.1 ppm.

(75) HR-MS (ESI) m/z: [M].sup.+ calculated for C.sub.53H.sub.51NO.sub.13 910.3433; found 910.3422.

Compound II-d: ((((4-((2-(acryloyloxy)ethoxy)carbonyl)phenyl)azanediyl)bis([1,1′-biphenyl]-4′,4-diyl))bis (ethane-1, 1-diyl))bis(2-(acryloyloxy)ethyl) disuccinate

(76) A solution of compound 7 (440 mg, 0.7 mmol, 1 eq.), dimethylaminopyridinium p-toluenesulfonate (DPTS) (206 mg, 0.7 mmol, 1 eq.) and compound 15 (605 mg, 2.8 mmol, 4 eq.) in anhydrous dichloromethane (10 mL) was placed under inert atmosphere and cooled down to 0° C. A solution of dicyclocarbodiimide (DCC) (433 mg, 2.1 mmol, 3 eq.) previously diluted in anhydrous dichloromethane (2 mL) was then added dropwise. The resulting mixture was left under stirring at room temperature for 12 h. After filtration of the solid impurities and concentration of the solution under vacuum, the resulting crude product was dissolved in toluene (˜1-3 mL) and filtered to remove undissolved urea. After concentration of the solution, purification of the white solid was performed by silica gel chromatography using as an eluent a mixture ethyl acetate/petroleum ether 1/1, and yielded compound II-d as a pale-green amorphous solid (300 mg, 0.32 mmol, 46%).

(77) .sup.1H NMR (CDCl.sub.3, 300 MHz): δ=7.90 (d, J=8.9 Hz, 2H), 7.56 (d, J=8.3 Hz, 4H), 7.53 (d, J=8.7 Hz, 4H), 7.41 (d, J=8.3 Hz, 4H), 7.23 (d, J=8.6 Hz, 4H), 7.10 (d, J=8.9 Hz, 2H), 6.45 (dd, J=17.3, 1.5 Hz, 1H), 6.43 (dd, J=17.3, 1.5 Hz, 2H), 6.15 (dd, J=17.4, 10.3 Hz, 1H), 6.13 (dd, J=17.3, 10.4 Hz, 2H), 5.94 (q, J=6.6 Hz, 2H), 5.86 (dd, J=10.4, 1.8 Hz, 1H), 5.85 (dd, J=10.4, 1.5 Hz, 2H), 4.54-4.52 (m, 2H), 4.50-4.47 (m, 2H), 4.36-4.30 (m, 8H), 2.75-2.62 (m, 8H), 1.58 (d, J=6.6 Hz, 6H) ppm.

(78) .sup.13C NMR (CDCl.sub.3, 75 MHz): δ=172.1, 171.4, 166.0, 166.0, 165.9, 151.9, 145.9, 140.4, 140.0, 136.7, 131.4, 131.4, 131.1, 128.2, 128.1, 127.9, 127.0, 126.6, 125.8, 122.3, 120.7, 72.6, 62.4, 62.3, 62.2, 29.4, 29.0, 22.1 ppm.

(79) HR-MS MALDI m/z: [M].sup.+ calculated for C.sub.58H.sub.57NO.sub.16 1023.3672; found 1023.3661.

C. Studies of Thermal and Photophysical Properties

(80) The thermal and photophysical properties of compounds II-a, II-b, II-c et II-d in solution and processed as thin films have been studied.

(81) Comparative measurements analyses have been performed between compounds II-a up to II-d on one hand, and A, B, C on the other hand:

(82) ##STR00088##

(83) In order to model the polar surroundings and the possible π-π interactions encountered for compounds processed as thin films in multilayer systems, photophysical investigations were performed in toluene.

C.1. Thermal Properties

(84) The use of the compounds of the invention on multilayered electronic or photonic devices requires molecules forming amorphous materials.

(85) Indeed, crystallization or morphologic change of emissive molecules after solution deposition on substrates lead to structural defects that can alter mobility, charge migration and therefore the performances of the final object.

(86) The aim is to show that the compounds of the invention provide amorphous materials, enabling their further use in organic electronics or photonics.

(87) Compounds II-a up to II-d were studied by differential scanning calorimetry between −20° C. and 150° C. in order to determine their glass transition temperature (T.sub.g) and/or melting temperature (T.sub.m).

(88) Amorphous compounds display glass transition temperature but no melting point (the latter characteristic being proper to the crystalline areas of semi-crystalline or crystalline materials).

(89) The thermal results obtained by DSC are listed in Table 1.

(90) TABLE-US-00002 TABLE 1 Phase change temperatures characteristic of the compound of the invention measured by DSC using a 20° C. min.sup.−1 thermal gradient. Compound T.sub.g(° C.) T.sub.m(° C.) II-a 12 not observed II-b 28 not observed II-c 6.4 not observed II-d 1.9 not observed A 41 not observed B 36 not observed C 57 not observed

(91) All studied compounds displayed a glass transition temperature T.sub.g between −20° C. and 150° C. with no melting point over this range of temperatures.

(92) Moreover, these results show that compounds II-a up to II-d display a glass transition temperature lower than those of compounds A, B and C. This difference in T.sub.g mainly stems from the nature of the photopolymerizable groups and the existing spacer (i.e. a bulky flexible chain comprising chiral centers in a racemic ratio), between the triphenylamine core and the photopolymerizable group.

(93) In conclusion, the compounds of the invention possess a specific chemical structure responsible for their amorphous character, which allows for their use in the fabrication of organic layers. In particular, the thermal properties of compounds II-a up to II-d impart with enough mobility the molecular chains linked to the acrylate and oxetane groups to favor photo-crosslinking at room temperature.

C.2. UV-Visible Absorption and Emission Properties of Compounds in the Solid State

(94) The aim is to show that the presence of photopolymerizable groups on triarylamine derivatives does not perturb the photophysical properties (absorption and emission) of these compound; more particularly, when these compounds are structured as thin films.

(95) The UV-vis absorption and emission properties of compounds II-a up to II-d were studied first in toluene solution and secondly as thin films.

C.2.1. In Toluene Solution

(96) Spacer Influence

(97) Compounds II-a and II-b were dissolved in toluene at a concentration equal to 5.Math.10.sup.−5 mol/L.

(98) 5 Compounds II-a and II-b comprise the same dicyanovinylidene electron-withdrawing group and the same spacer but differ from the nature of the photo-crosslinking group (II-a: acrylate; II-b: oxetane).

(99) The results regarding toluene solutions are listed in Table 2 and depicted by FIGS. 1A and 2A.

(100) TABLE-US-00003 TABLE 2 Photophysical properties of compounds II-a, II-b, A, B and C in toluene solution. (~5.10.sup.−5 mol .Math. L.sup.−1). Absorption Absorption band 1 band 2 λ.sub.max(abs)/nm λ.sub.max(abs)/nm Emission Stokes Fluorescence [ε.sub.max/L .Math. [ε.sub.max/L .Math. band.sup.a shift quantum yield.sup.b Compound mol.sup.−1 .Math. cm.sup.−1] mol.sup.−1 .Math. cm.sup.−1] λ.sub.max(em)/nm Δv/cm.sup.−1 Φ.sub.f II-a 450 324 595 5 410 0.29 [30 200] [19 500] II-b 450 324 595 5 410 0.26 [34 000] [21 800] A 445 325 589 5 490 0.31 [34 400] [22 300] B 445 325 589 5 380 0.33 [29 200] [19 000] C 445 325 585 5 380 0.28 [27 700] [19 500] .sup.aExcitation at the absorption maximum. .sup.bMeasured from fluorescence standard using coumarin 540A in ethanol (Φ.sub.f = 0.38).

(101) FIGS. 1A and 2A show the absorption and emission spectra, respectively, of compounds II-a, II-b, A, B and C in toluene solution at a concentration of 5×10.sup.−5 mol.Math.L.sup.−1.

(102) All compounds show similar UV-vis absorption spectra with two absorption bands: i) a first band at around 324 nm corresponding to the π-π* transition related to the biphenylamino unit; ii) a second band at around 445 nm corresponding to charge transfer of the triphenylamino core to the electron-withdrawing unit.

(103) For compounds II-a and II-b, i.e. compounds with strong electron-withdrawing group (dicyanovinylidene) and two polymerizable functions separated from the triphenylamino core by spacers, both absorption and emission spectra display a very slight bathochromic shift (namely towards higher wavelengths) compared to those of compounds A, B, and C.

(104) Such results show that the photophysical properties of compounds II-a and II-b in toluene solution are not influenced by the existing photopolymerizable groups when the latter are separated from the triarylamino core by a spacer. Especially, the presence of a flexible hindered chain comprising a chiral center between the triphenylamino core and the photopolymerizable group allows avoiding the electronic coupling of the photopolymerizable group and the triarylamino core.

(105) Influence of the Electron-Withdrawing Group

(106) Compounds II-a, II-c and II-d were dissolved in toluene at a concentration of 5×10.sup.5 mol.Math.L.sup.1.

(107) All compounds II-a, II-c and II-d comprise two acrylate functions separated from the triarylamino core by identical spacers but present distinct electron-withdrawing groups.

(108) The results obtained in toluene solution are listed in Table 3 and depicted by FIGS. 1B and 2B.

(109) TABLE-US-00004 TABLE 3 Photo-physical properties of compounds II-a, II-c and II-d, in toluene solution (~5.10.sup.−5 mol .Math. L.sup.−1). Absorption Absorption band 1 band 2 λ.sub.max(abs)/nm λ.sub.max(abs)/nm Emission Stokes Fluorescence [ε.sub.max/L .Math. [ε.sub.max/L .Math. band.sup.a shift quantum yield.sup.a Compound mol.sup.−1 .Math. cm.sup.−1] mol.sup.−1 .Math. cm.sup.−1] λ.sub.max(cm)/nm Δv/cm.sup.−1 Φ.sub.f II-a 452 323 585 5 030 0.29 [30 200] [19 500] II-c 370 345 465 5 520 0.37 [25 900] — II-d 346 — 428  5540 0.28 [35 500] .sup.aExcitation at the absorption maximum. .sup.bMeasured from fluorescence standard using coumarin 540A in ethanol as reference (Φ.sub.f = 0.38).

(110) The results show very distinct absorption and emission spectra for compounds II-a, II-c and II-d due to increasing charge transfer for compound II-d to compound II-c and, being maximum for compound II-a. Such discrepancy is more pronounced for emission compared to absorption owing to enhanced dipole moment in the excited state. Various compounds, emitting in distinct spectral ranges (blue, green-blue, red-orange), can be obtained upon mere change of the electron-withdrawing group (Z) without modifying the rest of the molecular backbone. All compounds are strongly emissive with a fluorescence quantum yield Φ.sub.f, largely superior to 0.1. For all compounds, the emission spectra are strongly shifted from the absorption ones, with a large Stokes shift (>5000 cm.sup.1), featuring nuclear reorganization at the excited state. Large Stokes shift value is typical of weak reabsorption of the light emitted by the surrounding molecules and warrants efficient emission in the solid state as thin films, which is a mandatory pre-requisite for the fabrication of performing electroluminescent devices.

C.2.2. As Thin Films

(111) Spacer Influence

(112) Various 130 nm-thick films were fabricated out of neat compounds II-a, II-b, A, B or C following the above mentioned procedure.

(113) The aim is to demonstrate that the photophysical properties of these compounds, be they processed as neat films or dissolved in toluene solution, do not change significantly change.

(114) The results obtained in toluene solution are listed in Table 4 and depicted by FIGS. 3A and 4A.

(115) TABLE-US-00005 TABLE 4 Photo-physical properties of compounds II-a, II-b, A, B and C processed as thin films. Absorption Absorption Emission Stokes band 1 band 2 band.sup.a shift Compound λ.sub.max(abs)/nm λ.sub.max(abs)/nm λ.sub.max(em)/nm Δv/cm.sup.−1 II-a 459 326 635 6 040 II-b 459 326 635 6 040 A 448 326 607 5 850 B 448 326 601 5 680 C 448 326 607 5 850 .sup.aExcitation performed at the absorption maximum.

(116) The results demonstrate the absence of change in the absorption spectra when going from toluene solution to thin films (identical maximum absorption wavelengths for compounds II-a and II-a on one hand and A, B, and C on the other hand; large Stokes shift).

(117) As for the emission spectra, a significant 40 nm bathochromic Stokes shift is however noticed when compounds II-a et II-b are processed as thin films. These results show more polar surroundings within thin films fabricated out of II-a et II-b, enabling better stabilization of the charge transfer excited state of compounds II-a and II-b compared to compounds A, B and C.

(118) In conclusion, these results show that the formation of thin films made out of the compounds of the invention does not alter their photo-physical properties.

(119) Influence of the electron-withdrawing group Various 130 nm-thick films have been fabricated out of neat II-a, II-c, and II-d following the above mentioned procedure.

(120) The results obtained in toluene solution are listed in Table 5 and depicted by FIGS. 3B and 4B.

(121) TABLE-US-00006 TABLE 5 Photo-physical properties of compounds II-a, II-b, II-c processed as thin films. Absorption Absorption Emission Stokes band 1 band 2 band.sup.a shift Compound λ.sub.max(abs)/nm λ.sub.max(abs)/nm λ.sub.max(em)/nm Δv/cm.sup.−1 II-a 458 323 635 6 090 II-c 370 345 496 6 870 II-d 346 — 450 6 680 .sup.aExcitation performed at the absorption maximum.

(122) The results demonstrate that compounds processed as thin films display similar absorption properties as those in toluene solution while their emission signals are clearly shifted to lower energy, with emission centered in the blue, the green and the red regions. These photo-physical characteristics allows envisaging the mixture of three compounds in such carefully calculated ratios that white light emission can be generated.

D. Studies of Electrochemical Properties

(123) The aim is to demonstrate that the compounds of the invention behave more as electron-rather than as hole-transporting materials.

(124) The electrochemical measurements of the redox potentials are performed using cyclic voltametry, using a three-electrode setup. The working electrode and counter electrode are platinum electrodes while the reference electrode is a AgCl/Ag pseudo-reference electrode. Potentials are referred to the standard redox potential of ferricinium/ferrocene couple E.sup.0(Fc.sup.+/Fc) equal to 0.64 V vs ENH. A 0.1 V.Math.s.sup.−1 scan rate was selected with no possibility to make the second oxidation wave reversible at higher scan rate.

D.1. Electrochemical Properties of Compounds A, B and C

(125) Compounds A, B and C comprise no spacer. Conversely, they incorporate electron-withdrawing groups with distinct photopolymerizable functions.

(126) Compounds A, B and C comprise the same chromophore, responsible for the first electrochemical oxidation.

(127) The results obtained from cyclic voltammetry are depicted by FIG. 5A.

(128) Oxidation first regards the triphenylamino core and is characterized by a quasi-reversible wave, centered at a half-wave potential almost identical at 0.60-0.61 V for all compounds A, B and C. Oxidation potentials of the second oxidation wave appear at slightly higher voltage. Yet, this shift is not significant due to the non-complete reversibility of the oxidation process.

(129) These results show that the values of oxidation potential are close to those in literature, hence compounds A, B and C are expected to display higher electron-transporting capability than hole-transporting one.

D.2. Electrochemical Properties of Compounds II-a, II-c and II-d

(130) Compounds II-a, II-c and II-d comprise identical spacers and distinct electron-withdrawing groups. The results obtained from cyclic voltammetry are reported in FIG. 5B.

(131) These experiments evidence two mono-electron oxidation waves corresponding to the successive oxidation of the triphenylamino core into triphenylammonium radical cation and the triphenylammonium cation.

(132) These results show that the electrochemical properties are independent of the photopolymerizable groups in the same as the photophysical properties were, which confirms the absence of π-conjugation between the emissive moieties and photoreactive moieties. Such decoupling accounts for the acrylate photoreactivity observed for compounds A, B and C. The obtained values show that the radiative π-conjugated system wherein the hole-electron pair is supposed to recombine behaves more like an electron carrier rather than a hole carrier. Such characteristics will rule the stacks further fabricated and be essential to ensure efficient charge transport through the emissive layer.

E. Fabrication of Insoluble Emissive Layers

(133) The aim of these experiments is to demonstrate that the compounds of the invention enable the fabrication of insoluble emissive layers upon photopolymerization.

(134) The aim also is to show that the reaction conditions of photopolymerization do not alter the photophysical properties of the compounds constituting the insoluble organic layer after reaction.

E.1. Synthesis of an Insoluble Emissive Organic Layer

(135) Various compositions comprising compounds II-a or II-b (1 wt. %) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator (2 to 5 mol. % relative to compound II-a or II-b) have been prepared in chloroform.

(136) One of these compositions (with compound II-a) was spin-cast on a glass substrate. To such purpose, the photopolymerizable composition was pre-filtered using a PTFE filter (Millex, 0.45 μm), placed on a 1 mL glass syringe. The spin-coating and drying steps were carried out at a rotation speed of 1000 rpm for 60 s and at a spin acceleration of 500 rpm/min. A thin film is obtained.

(137) Then, crosslinking of the film deposited on the substrate was performed through photopolymerization at a 365 nm irradiation wavelength.

(138) Photoconversion

(139) Progress of the photopolymerization of compound II-a was monitored using infrared spectroscopy. The photopolymerizable solution was deposited on a KBr plate and irradiated in situ at 365 nm to initiate the photopolymerization reaction. Infrared spectroscopy monitoring was performed at 810 cm.sup.−1 which corresponds to the out-of-plane C—H bending mode of the photopolymerizable acrylate moiety. The band of the stretching mode of the ester carbonyl groups at 1750 cm.sup.−1 served as an internal reference.

(140) FIG. 6 depicts the evolution of the vibration band resonating ay 810 cm.sup.−1.

(141) In the course of irradiation, the band, characteristic of the polymerizable functions (at 810 cm.sup.−1) significantly decreases. This result shows that the employed reaction conditions enable photopolymerization of compound II-a.

(142) The photoconversion yield of compound II-a after irradiation is about 53%. After development, the percentage of crosslinked monomers compared to non-photocrosslinked ones is about 92%, which corresponds to a high yield of crosslinking of the emissive organic layer.

(143) Photopolymerization Efficiency

(144) In order to perform photopolymerization of the organic film without degrading its emissive properties, the irradiation power and duration were investigated.

(145) The compounds of the invention were dissolved in the presence of a photoinitiator in an organic solvent, spin-cast as thin films on a substrate and further photoplymerized upon irradiation at 365 nm.

(146) The absorption and fluorescence responses of various organic layers were then studied. FIGS. 7A and 7B display the efficiency of the photopolymerization process (in absorption and fluorescence respectively), as a function of the irradiation power and duration.

(147) The size of the circles drawn on each graph represents the absorbance and emission signals of the photopolymerized organic layer compared to those of the organic layer before photopolymerization.

(148) The larger the circle, the higher the absorbance and the fluorescence.

(149) The results show that: for low irradiation power and short irradiation time, absorbance is weak; for high irradiation power and long irradiation time, absorbance is high and fluorescence intensity is weak; for low irradiation power and long irradiation time, both the absorbance and fluorescence intensity are larger.

(150) In conclusion, these experiments show that low-power irradiation for long time conducts to insoluble organic layer while keeping good emissive properties.

E.2. Characterizations of the Insoluble Organic Layer

(151) Thickness of the Insoluble Organic Layer

(152) After removing the non-photopolymerizable compounds by washing with chloroform several times, an insoluble emissive organic layer is obtained with a thickness of around 130 nm (measured using a Dektak Veeco 8 mechanical profilometer).

(153) FIG. 8 represents the picture in transmission (Abs) and emission (EM) of photo-irradiated organic thin layers obtained by spin-coating a solution containing compound II-a, before and after development with organic solvents.

(154) These results show efficient photo-crosslinking in the irradiated areas since matter remains after development. They also prove that the film keeps its emissive properties since the photo-crosslinked areas keep emitting. They evidence that prolonged irradiation leads to superior photo-crosslinking, hence a higher thickness for the photo-crosslinked material and a greater emission (irradiation time increasing clockwise according to 1 min., 3 min., 5 min., 10 min. at a constant 30 mW.Math.cm.sup.−2 power). Prolonged irradiation however leads to more extensive photodegradation since the brightest area after development (top left) also matches the area that emits the less before development by comparison with the rest of the non-irradiated sample. A compromise in terms of energy dose (product of irradiation power with irradiation time) prompts to adopt an energy dose comprised between 0 and 100 J.Math.cm.sup.−2; preferably less than 20 J.Math.cm.sup.−2; preferably less than 10 J.Math.cm.sup.−2; preferably less than 6 J.Math.cm.sup.−2.

(155) Topographic Analyses

(156) The aim is to obtain insoluble emissive organic layers displaying no structural defects.

(157) Any structural defect of the emissive organic later impairs the photophysical properties of the latter. Yet, it is known to the person skilled in the art that photo-crosslinking leads after reaction to shrinking of the organic thin layers. This phenomenon mostly creates cracks or microreliefs within the photopolymerized material; the material can no longer be used in multilayered electronic or photonic devices. Therefore, polymerization conditions strongly influenced the structure of organic layers after polymerization, and thereby their emissive properties.

(158) In order to control the absence of defect within the resulting organic layers and control the efficiency of the polymerization conditions, topographic analyses were performed using a mechanical profilometer and atomic force microscope.

(159) Comparison between two organic layers obtained following distinct polymerization conditions was made using: 1) high irradiation power for a short irradiation time; or 2) low irradiation power for a longer irradiation time.

(160) FIGS. 9A and 9B show the topographic results regarding both organic layers after polymerization.

(161) FIG. 9A clearly shows that polymerization conditions based on high irradiation power (450 mW.Math.cm.sup.−2 for 1 min.) leads to a heterogeneous surface with micro reliefs and defects.

(162) FIG. 9B shows that for milder polymerization conditions based (30 mW.Math.cm.sup.−2 for 5 min.), the surface of the insoluble organic layer surface is homogeneous and displays neither defects, nor micro reliefs.

(163) Optimized irradiation conditions (irradiation power of 3.5 mW.Math.cm.sup.−2 for 30 min.) have been implemented and led to very smooth surfaces after polymerization, with root mean square roughness of 0.7 nm, very close to that of the surface before polymerization.

(164) In conclusion, these results demonstrate that optimized conditions of the photopolymerization of the compounds of the invention enable the fabrication of insoluble emissive organic layers with controlled thickness and devoid of structural defects, after polymerization. The compounds of the invention can be used as precursors of emissive layers for applications in organic electronics and photonics.

F. Fabrication of Photo-Crosslinked Fluorescent Organic Nanoparticles (FONs)

(165) The aim of these experiments is to demonstrate that the compounds of the invention allow providing insoluble photo-crosslinked fluorescent organic nanoparticles.

F.1. Nanoparticule Fabrication

F.1.1. Bulk Fabrication

(166) Monocomponent Nanoparticles

(167) A solution of photopolymerizable compound II-a or II-c (1 mg) and TPO photoinitiator (10 mol. % with respect to the dye concentration) was prepared in THF (1 mL). 50 μL of this solution were quickly added under stirring into Millipore water (2.5 mL) to form bright spots, visible under fluorescence microscope using an oil-immersion objective (magnification 60×, numerical aperture 1.43).

(168) Bicomponent Nanoparticles

(169) Method A.

(170) A mixture of compounds II-a and II-c (1 mg of each) and TPO (10 mol. %) was prepared in THF (1 mL). Nanoprecipitation was performed using the same protocol as that previously described for monocomponent nanoparticles, and yielded nanoparticles (the total amount of II-a and II-c).

(171) Method B. Two distinct solutions of compound II-a or compound II-c (1 mg) containing each TPO (10 mol. %) were prepared in THF (1 mL). Nanoprecipitation was performed using first the solution of compound II-a following the same protocol as that previously described for monocomponent nanoparticles. To the solution of II-a nanoparticles were added 50 μL of solution of compound II-c. In this way, a solution of fluorescent organic nanoparticles II-a and II-c was formed.

F.1.2. Microfluidic Fabrication

(172) A microfluidic setup, made of colinear tubings, an injection needle, and three syringe pumps, could also be used to fabricate photopolymerized FONs.

(173) A first glass syringe (5 mL) was filled with THF solution of one or two fluorescent dyes (0.1% wt.) and the flow was fixed at 10 μL.Math.min.sup.−1. A second plastic syringe (5 mL) was filled with Millipore water and the flow was fixed at 40 μL.Math.min.sup.−1. Finally, a third glass syringe (10 mL) was filled with Fomblin® and the flow was fixed at 100 μL.Math.min.sup.−1.

(174) Both water and THF solution were mixed inside droplets that formed inside the microfluidic setup. Each droplet was separated by perfluorinated oil (Fomblin® type) droplets so that micrometric volumes of nanoprecipitation could be generated. The entire flow of fluids was recuperated and the aqueous layer was separated from the Fomblin® layer after short stirring using a vortex.

F.2. Nanoparticle Photopolymerization

(175) Photopolymerization was performed only with nanoparticles fabricated in bulk solution and incorporated a single component or two components following method A or method B.

(176) Irradiation was used to induce cross-linking either during the nanoprecipitation step or once the nanoparticles have been fabricated. Careful deoxygenation of water before mixing or after forming nanoparticles was carried out using gentle argon bubbling during 2 min. The solution was irradiated for 30 s using a UV lamp equipped (maximum power) with a 365 narrow bandpass filter and a quartz light guide, while maintaining argon bubbling.

F.3. Characterizations

F.3.1. Fluorescence Microscopy

(177) The aim is to study the fluorescent properties of nanoparticles obtained from the compounds of the invention.

(178) For this purpose: first, addition of THF to a drop of non-irradiated solution of nanoparticles (i.e. no-photo-crosslinked nanoparticles) was carried out. This experiment led to the dissolution of nanoparticles into individual molecules featured by a considerable decrease in fluorescence and a loss of the spot-like emission signal; then, THF was added to a solution of irradiated solution of nanoparticles (i.e. photo-crosslinked nanoparticles). In this case, no particular drop of the emission was noted while the spot-like character emission signal remains.

(179) These results show that individual molecules actually emit weakly or less intensively than in the solid state and as nanoparticles, which also provides homogeneous emission throughout the solution.

F.3.2. Photophysical Properties

(180) The aim is to study the influence of the irradiation on the photophysical properties of nanoparticles.

(181) The emission spectra for FONs made of compound II-a were measured before and after irradiation.

(182) The emission spectra for FONs made of compound II-a were found identical whatever the irradiation step order (once the nanoparticles have been generated (post irradiation) or during nanoprecipitation (pre-irradiation).

(183) This results shows that nanoprecipitation (usually on the μs to ms time range) is not influenced by irradiation (FIG. 10A).

(184) After photoirradiation, FONs solution (Nanoparticles (II-a+II-c)) made of co-precipitated compounds II-a (red-emissive) and II-c (green emissive) was compared to a FON solution made of successive precipitation of compound II-a (red-emissive) and compound II-c (green-emissive) (NP II-a+NP II-c).

(185) The results are shown FIG. 10B and Table 6.

(186) TABLE-US-00007 TABLE 6 Emission maximum wavelength of photo-crosslinked FON solutions made of monocomponent dyes (II-a or II-c), bicomponent dyes (coprecipitated NP (II-a + II-c) or successively precipitated NP II-a + NP II-c). NP (II-a + NP II-a + FON NP (II-a) NP (II-c) II-c) NP-II-c (λ.sup.max(em) (nm) 633 500 623 585

(187) The emission spectra of both solutions largely differ: the fluorescent organic nanoparticles (II-a+II-c) solution display emission centered at 623 nm, close to the emission maximum of FONs made exclusively of compound II-a (λ.sub.max(em.)=633 nm), which proves efficient energy transfer from the green emitter to the red emitter (Table 6); on the contrary, successive precipitation of compound II-a and then compound II-c in the same solution yields an emission signal with both green and red components.

(188) These results evidence the possibility of fabricating photo-crosslinked fluorescent nanoparticles with distinct colors by choosing the nanoparticle fabrication method and adjusting the dye composition as a function of the stock solution concentration, the emission spectrum and the quantum yield of each involved species.

F.3.3. Structural Properties

(189) Transmission electron microscopy imaging of photo-crosslinked nanoparticles made of photopolymerized dye II-a (FIG. 11A) or II-c dyes have been recorded (FIG. 11B).

(190) The samples were deposited on TEM copper grids coated with carbon thin films and lacey carbon copper grids respectively.

(191) The mean average size (less than 100 nm or less than 200 nm) depends on the studied compound and the reaction conditions (solvent composition, concentration of the dye stock solution, irradiation time).