New oxadiazole derivatives as promising electron transport materials:synthesis and characterization of thermal,optical and electrochemical properties

摘要

2,5-bis-(4-biphenyl)-yl-1,3,4-oxadiazole(1a),2,5-bis-(4-(6,8-difluoro)-biphenyl)-yl-1,3,4- oxadiazole(1b)and 2,5-bis-(4-(spiro-fluorenyl)-phenyl)-yl-1,3,4-oxadiazole(1c)were designed, synthesized and characterized.1a-c were easily obtained from Suzuki reactions between 2,5-bis-(4- bromo-phynyl)-[1,3,4]oxadiazole(2)and aromatic boronic acids(3).They were characterized by ~1H-NMR,DSC,TGA,UV-Vis,photoluminescence(PL)spectrometry and CV.The melting temperatures (T m)of 1a-c are 237,208 and 370?C,respectively,much higher than that of 2-tert-butylphenyl-5- biphenyl-1,3,4-oxadiazole(PBD,T m=136 degree).The oxidation potentials of 1a-c are 1.86,1.94 and 1.18 V,and their reduction potentials are-2.31,-2.22 and-2.27 V,respectively,indicating that the introduction of electronegative oxadiazole unit lowers the electron density in molecules and enhances their stabilities.The LUMO/HOMO energy levels of 1a-c are as low as-2.39/-6.56,-2.48/-6.69 and -2.43/-5.88 eV,respectively.The good thermal stabilities and low orbital levels of 1a-c make them promising electron-transporting or hole-blocking materials for organic optoelectronic devices.