Phosphorescent iridium(III) complexes based on 2-phenylimidazo[1,2-a]pyridine-type ligands: Synthesis, photophysical, electrochemical, and electrophosphorescent properties

New iridium(III) cyclometalated complexes based on 2-phenylimidazo[1,2-a]pyridine-type ligands were synthesized and their photophysical, electrochemical and electroluminescent (EL) properties were investigated. The detailed insight into the characters of the emissive excited states was obtained by frontier molecular orbital analysis. These metal complexes exhibit very balanced charge transporting ability for both kinds of charge carriers, which can furnish decent EL performance in the phosphorescent organic light-emitting devices (PHOLEDs) with peak luminance of 15491 cd m^-2 at ca. 13.5 V, external quantum efficiency of 6.81%, luminance efficiency of 34.74 cd A^-1, and power efficiency of 17.54 lm W^-1. These results not only provide a better understanding of the inherent characters of Ir^III phosphors with phenylimidazo[1,2-a]pyridine units, but also valuable information on future molecular design of triplet emitters with unique electronic features for high-performance PHOLEDs.