H. Mochizuki, T. Hasui, T. Ikeda
Jan 24, 2005
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Journal
Japanese Journal of Applied Physics
Abstract
Three oxadiazole derivatives with an amine and an alkyl tail were designed and synthesized as novel photo- and electro-active materials: 2-(4'-propylbiphenyl-4-yl)-5-(4-N,N-dimethylaminophenyl-4-yl)-1,3,4,-oxadiazole (3-OXD-Me), 2-(4'-heptybiphenyl-4-yl)-5-(4-N,N-dimethylaminophenyl-4-yl)-1,3,4,-oxadiazole (7-OXD-Me), 2-(4'-heptylbiphenyl-4-yl)-5-(4-N,N-diphenylaminophenyl)-1,3,4,-oxadiazole (7-OXD-Ph). It was found that the length of an alkyl tail and the structure of an amine strongly affect the phase structure of the oxadiazole derivatives; 3-OXD-Me showed a crystalline phase, 7-OXD-Me showed a liquid-crystalline (LC; nematic) phase and 7-OXD-Ph exhibited a glassy amorphous state. All the compounds emitted strong blue fluorescence: the maximum wavelengths of emission were 420–436 nm with high quantum yields (0.81–0.91). Furthermore, polarized photoluminescence was observed in 7-OXD-Me in a nematic phase, and the order parameter estimated by the polarized emission was 0.18. These compounds, therefore, are potential multifunctional materials for photo- and electro-active devices.