Preparation of high-efficiency carrier transport material is a key to fabricate more efficient and high performance organic and polymeric light-emitting devices. A series of rod-coil 1,3,4-oxadiazole derivatives with lateral carboxyls, 1,4-bis[5-(4-alkoxyphenyl)-1,3,4-oxadiazol-2-yl]-2,5-di(carboxy)benzenes (7; alkoxy＝OCnH2n＋1; n＝8, 12 and 16) were synthesized by condensation of terephthaloyl chloride (5) with benzohydrazides containing alkoxy chains with different lengths (2). The results show that introduction of two carboxyls whose electron-accepting ability is stronger reduces the electron density of the conjugated segment of 7, and thus leads to the absorption maximum bathochromic-shift compared to 8 (without car-boxyl group). Calculation on the representative compound by the Dmol3 package of MS Modeling 3.0 re-vealed that the decrease of energy levels in 7 was due to the change of the frontier molecular orbital distribu-tion in the central benzene ring because of introduction of two carboxyls. The HOMO and LUMO energy levels of the compounds studied are in the range of －3.62～－3.58 eV and －6.94～－6.90 eV, which showed that they functioned well as electron-transporting materials.

Key words: electrochemical, oxadiazole derivative, band structure