Luminescent copoly(aryl ether)s with new electron transporting bis(3-(trifluoromethyl)phenyl)-1,3,4-oxadiazole or bis(3-(trifluoromethyl)phenyl)-4-(4-hexyloxyphenyl)4H-1,2,4-triazole segments

To investigate the effect of trifluoromethyl groups in enhancing electron affinity of aromatic oxadiazole and triazole chromophores, we prepared four new copoly(aryl ether)s (P1-P4) consisting of bis(3-(trifluoromethyl) phenyl)-1,3,4-oxadiazole (ETO) or bis(3-(trifluoromethyl)phenyl)-4-(4-hexyloxyphenyl)-4H-1,2,4-triazole (ETT) segments and hole-transporting segments [2,5-distyrylbenzene (HTB) or bis(styryl)fluorine (HTF)]. Molecular spectra (absorption and photoluminescence) and cyclic voltammetry were used to investigate their optical and electrochemical properties. The emissions of P1-P4 are dominated by the hole-transporting fluorophores with longer emissive wavelengths around 442-453 nm via efficient excitation energy transfer. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of P1-P4, estimated from electrochemical data, are -5.15, -5.18, -5.30, -5.27, -3.39, -3.49, -3.36, and -3.48 eV, respectively. The LUMO levels of ETO and ETT segments are significantly reduced to -3.39similar to-3.36 eV and -3.48similar to-3.49 eV, respectively, as compared with -2.45 eV of P5 containing a 2,5-diphenyl-1,3,4-oxadiazole segment. Moreover, electron and hole affinity can be enhanced simultaneously by introducing isolated hole- and electron-transporting segments in the backbone. (C) 2004 Wiley Periodicals, Inc.