Novel Cationic 2-Phenylpyridine-based Iridium(III) Complexes Bearing an Ancillary Phosphine Ligand: Synthesis, Photophysics and Crystal Structure

Abstract

Three novel phosphorescent 2-phenylpyridine-based iridium(III) complexes, [(ppy)2Ir(P^N)]PF6 (1), [(dfppy)2Ir(P^N)] PF6 (2), and [(dfmppy)2 Ir(P^N)]PF6 (3), where P^N = 2-[(diphenylphosphino)methyl]pyridine (dppmp), were synthesized and characterized. The absorption, photoluminescence, cyclic voltammetry and thermal stability of the complexes were investigated. The complexes showed bright blue luminescences at wavelengths of 448 ~ 500 nm at room temperature in CHCl3 and revealed that the π-acceptor ability of the phosphorous atom in the ancillary dppmp ligand plays an important role in tuning emission color resulting in a blue-shift emission. The single crystal structure of [(dfmppy)2 Ir(P^N)]PF6 was determined using X-ray crystallography. The iridium metal center adopts a distorted octahedral structure coordinated to two dfmppy and one dppmp ligand, showing cis C-C and trans N-N chelate dispositions. There is a π-π overlap between π electrons delocalized in the difluorophenyl rings.