The synthesis and preliminary optical study of 1-alkyl-2,4,5-triphenylimidazole derivatives

A series of 1-alkyl-2,4,5-triphenylimidazole derivatives were synthesized by the alkylation of corresponding 2,4,5-triphenylimidazole derivatives with alkyl bromide using tetra-n-butylammonium bromide as phase-transfer catalyst in the presence of 50% NaOH in butanone in a good yield and five 1-alkyl-2,4,5-triphenylimidazole derivatives containing benzimidazole or benzothiazole fragments in the 4′-position of 2-phenyl ring were prepared by condensation of 1-alkyl-4,5-diphenyl-2-(4-carboxyphenyl)imidazoles with o-benzenediamine or 2-aminothiophenol in PPA under microwave irradiation. These products were identified by 1H NMR, 13C NMR, MS, IR and elemental analysis. At the same time, their UV–visible absorption coefficient (ɛ), maximum absorption wavelengths (λa), fluorescence emission wavelengths (λe), quantum yields (Φ), fluorescence lifetime in solution and solid state were measured. Single crystal of 1-n-butyl-4,5-diphenyl-2-(4-carboxyphenyl)imidazoles was obtained and the structure was determined by X-ray diffraction technique, based on which the relationships between spectral behaviors and molecular structure were discussed. The alkylation method of 2,4,5-triphenylimidazole derivatives and synthetic pathway for 1-alkyl-2,4,5-triphenylimidazole derivatives containing benzimidazole or benzothiazole fragments could provide an attractive and alternative, even a convenient and efficient approach to the preparation of some useful dyes and pigments.