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, <TEX>$[(ppy)_2Ir(P\^{}N)]PF6\;(1),\;[(dfppy)_2Ir(P\^{}N)]PF_6$</TEX> (2), and <TEX>$[(dfmppy)_2 Ir(P\^{}N)]PF6$</TEX> (3), where <TEX>$P\^{}N$</TEX> = 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 <TEX>$\sim$</TEX> 500 nm at room temperature in <TEX>$CHCl_3$</TEX> and revealed that the <TEX>$\pi$</TEX>-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 <TEX>$[(dfmppy))_2Ir(P\^N)]PF_6$</TEX> 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 <TEX>$\pi-\pi$</TEX> overlap between π electrons delocalized in the difluorophenyl rings.