Two novel bipolar Ir(III) complexes based on 9-(4-(pyridin-2-yl)phenyl)-9H-carbazole and N-heterocyclic ligand

Two novel bipolar Ir(III) complexes named (Czppy)2Ir(tfmptz) and (Czppy)2Ir(pptz) were synthesized and characterized, where the Czppy is 9-(4-(pyridin-2-yl)phenyl)-9H-carbazole, tfmptz refers to 2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine and Hpptz represents 2-(1H-tetrazol-5-yl)pyridine, respectively. Their molecular structures were confirmed by 1H NMR and photophysical were investigated. The performances in phosphorescent organic light emitting devices (PhOLEDs) were characterized by a heavy doping concentration of 20 wt% in host as emitting layer. The results suggest that the number of nitrogen atoms in ancillary has no obvious effects on their photophysical properties. Both (Czppy)2Ir(tfmptz) and (Czppy)2Ir(pptz) display the blue-green emission with the peaks at 492, 526 nm. The performances of complexes (Czppy)2Ir(tfmptz) in PhOLEDs superior to that of the (Czppy)2Ir(pptz) due to the poor thermal stability.