Studies On The Synthesis And Ultraviolet And Fluorescence Properties Of Imidazole-Based Compounds

Organic nonlinear optical (NLO) materials have been the subject of intense research because of their potential applications. Organic two-photon absorption (TPA) materials are being widely focused recently due to their various applicatons including two-photon induced fluorescence microscopy and imaging, three-dime-nsional data storage and fabrication of microstructures, frequency up-converted lasing and optical limiting.Imidazole ring is a non-center symmetrical structure that isπelectron deficient, which may link to strong electron-withdrawing groups and have excellent properties of electronic transmission. Imidazole-based compuonds are excellent organic non-linear optical materials.In this thesis, four series of imidazole-based compuonds have been designed and synthesized, and the structure-property relationships have been investigated. 1. Diketones were synthesized from benzaldehyde, 4-chlorobenz-aldehyde, furfural by benzoin condensation and oxidation. 2-aryl-4, 5-diphenylimidazole, 2-aryl-4, 5-di(4-chlorophenyl)imidazole, 2-aryl-4, 5-di(2-furyl)imidazole were prepared from dicarbonylcompuonds by Debus reaction.2. 2-arylphenanthro[9,10]imidazole compounds were synthesized from phenanthrenequinone, and the structures were obtained by single-crystal X-ray diffraction. The results indicate that the dihedral angle between the imidazole and the attached benzene rings is about 5°.3. A series of structural symmetric and asymmetric biimidazoles were synthesized from diketones and terephthalaldehyde.4. A novel series of imidazole was synthesized by Aldol condensation and Micheal addition.Through the data analysis of UV and fluorescence spectra of compuonds prepared, we probed into the effect of optical performance upon substituents and the conjugation length. The UV maximum absorption wavelength and fluorescence maximum emission wavelength would be a red-shift, if the conjugation length became long or the attached benzene ring with strong electron-withdrawing group.In summary, four series of imidazole-based compounds have been synthesized and characterized, their spectra of UV and fluorescence were obtained and the structure-properties relationships were discussed. The program made an initial exploration for designing and synthezising organic nonlinear optical materials with high thermal stability and excellent properties.