Synthesis and characterization of blue phosphorescent cyclometalated Ir(III) complexes containing 2-(imidazol-2-yl)pyridine as ancillary ligand

摘要

Four new blue phosphorescent iridium complexes containing 2-(fluoro substituted phenyl)pyridine as the cyclometalated ligands and 2-(imidazol-2-yl)pyridine as an ancillary ligand have been synthesized and characterized. The complexes have the general structure (CN)2Ir(pym), where CN are cyclometalating ligands (e.g., 2-(2,4-difluorophenyl)pyridine (24f2ppyH), 2-(3,4-difluorophenyl)pyridine (34f2ppyH), 2-(3,5-difluorophenyl)pyridine (35f2ppyH), and 2-(3,4,5- trifluorophenyl)pyridine (345f3ppyH)), pym is 2-(imidazol-2-yl) pyridine (pymH). The absorption, emission, and cyclic voltammetry of the complexes were systematically investigated. The (46f2ppy) 2Ir(pym) has been characterized using X-ray crystallography and the electronic ground state calculated using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) consists of a mixture of pym ligand (83.7) and Ir orbitals (12.1), while the lowest occupied molecular orbital (LUMO) is mostly on f2ppy ligands (93.4). By replacing the ancillary ligand pic with pym can finely tune emission of the iridium complexes, showing blue luminescence at a wavelength of 467491 nm at room temperature in CH 2Cl2.