Study Of Optical Properties Of Intramolecular Charge-transfer Compounds In Solution And Their Supraparticle Dispersion

Intramolecular charge-transfer compounds(ICICs) have been attracted much interest in recent years because of their possible application in luminous materials, photoconduction materials, nonlinear optical materials, fluoroprobe with electron-donating and electron-accepting structure.With the development of the nano-science and technology, research on organic supracrystals receive much attention because of their unique optical and electronic properties. So studies on ICTCs in mesoscopic field become possible and necessary. It will help seeking for new optical and electronic materials.Despite the extensive application of ICTCs, many questions and difficulties still remain in fundamental research especially for the molecular charge-transfer interaction in solvents and in their supraparticles. These interaction influences the absorption spectra and fluorescent spectra. So it is very important for understanding the photophysical behaviors in photoluminescence and electroluminescence by researching chromophore interaction intra- and inter-molecularly .1. In experiment, some ICTCs have been synthesized , such as: 5-(9-anthryl)-3-(4-nitro phenyl)-1-phenyl-2-pyrazoline, 4,4′-bis-[5(1,3-diphenyl-2-pyrazolinyl)]-benzene, 1,3,5-triphenyl -2-pyrazoline, 4-(N,N-diethylamino)benzaldehyde p-nitrophenylhydrazone, p-nitrobenzaldehyde phenylhydrazone, N,N,N′,N′-tetraphenylbenzidine, 2,3-dihydroquinolin-4(1H)-one, 9-styrylanthr -acene, etc. Then these compounds were dissolved in solvents, and some were prepared into supraparticles by repreciptation.2. The optical properties of 2,3-dihydroquinolin-4(1H)-one in solvents with different concentration and different polarities have been measured by UV-Vis spectra and the fluorescent spectra. It is found that intramolecular charge-transfer from N→Aryl→O exists in the excited state, and there are large dipole moment change between the excited state and the ground state of this compound. 2,3-dihydroquinolin-4(1H)-one compound is one of the strong light-emitting materials.3. 1,3,5-triaryl-2-pyrazoline compounds have conjugated charge-transfer in"Aryl-N-N=C -Aryl"group and nonconjugated charge transfer between the"Aryl-N-N=C -Aryl"chromophore and aryl in 5 position. By studying UV-Vis spectra of 5-(9-Anthryl)-3-(4-nitrophenyl)-1-phenyl-2 -pyrazoline supraparticles, it is found that except for the size-dependence of the optical properties, there is the competition between the nonconjugated charge-transfer and intermolecular charge-transfer interaction, and the later plays the main role in this system. Intermolecular interaction leads to hypsochromically shifte of pyrazoline chromophore, which was not found before. The size-dependence of the optical properties is also found in supraparticles consisting of 4-(N,N-diethylamino)benzaldehyde p-nitrophenylhydrazone and 9-styrylanthracene.4. The UV-Vis spectra and fluorescence spectra of mixed organic supraparticles are researched at the first time in the world. The resulting conclusion are shown that the optical properties of the mixed organic supraparticles are obviously different from that of the mixed solution and they are also different from that of the supraparticles which are formed by the same molecules. Two results are obtained as follows: (1) Charge-transfer is found between the two molecules in 1,3,5-triphenyl-2-pyrazoline and anthracene mixture supraparticles. (2) Intermolecula -r charge-transfer interaction also exists in the mixture supraparticles of p-nitrobenzaldehyde phenylhydrazone and anthracene.