Three novel symmetrical multi-branched 1,3,4-oxadiazole derivatives, 2,5-bis{4-{4-[N,N-di- (4-bromophenyl)amino]styryl}phenyl}-1,3,4-oxadiazole (BrPASPO), 2,5-bis{4-{4-{N,N-di{4-{4-{5-[4- (tert-butyl)phenyl]-1,3,4-oxadiazol-2-yl}styryl}phenyl}amino}styryl}phenyl}-1,3,4-oxadiazole (TPASPO) and 2,5-bis{4-{4-{N,N-bis{4-{3,5-di{5-[4-(tert-butyl)phenyl]-1,3,4-oxadiazol-2-yl}styryl}phenyl}amino}- styryl}phenyl}-1,3,4-oxadiazole (OPASPO) were synthesized through Wittig-Horner and Heck reactions. Their structures were characterized by IR, 1H NMR, MS, and melting points. The maximum absorption peaks in dichloromethane were at 403 nm for BrPASPO, 408 nm for TPASPO and 409 nm for OPASPO, respectively. The maximum emission wavelengths were at 495 nm for BrPASPO, 509 nm for TPASPO, and 506 nm for OPASPO in dichloromethane, respectively. In CH2Cl2 the fluorescence quantum yields were 0.47 for TPASPO and 0.45 for OPASPO. In CH2Cl2 the fluorescence lifetime of 8-branched OPASPO was longer than that of 4-branched TPASPO. The strong intra-molecular charge transfer existed in these sym-metrical 4-branched and 8-branched compounds, which can enhance the ability of fluorescence emission.

Key words: symmetrical oxadiazole derivative, Wittig-Horner reaction, Heck reaction, fluorescence lifetime, solvatochromic effect