DFT and TD-DFT study on the electronic structures and phosphorescent properties of 6-phenyl-2,2′-bipyridine tridentate iridium(III) complexes and their isomer

We report a theoretical study on three tridentate Ir(III) complexes for organic light-emitting diode (OLED) applications. The geometries, electronic structures, emission properties, and quantum efficiencies of these Ir(III) complexes [((CNN)-N-boolean AND-N-boolean AND)Ir-(III)((CNN)-N-boolean AND-N-boolean AND)](+) (denoted as 1 hereafter), [((CNN)-N-boolean AND-N-boolean AND)Ir-(III)((NCN)-C-boolean AND-N-boolean AND)](+) (2), and [((NCN)-C-boolean AND-N-boolean AND)Ir((III))((NCN)-C-boolean AND-N-boolean AND)](+) (3) were investigated theoretically, where (CNN)-N-boolean AND-N-boolean AND = 6-phenyl-2,2'-bipyridine, (NCN)-C-boolean AND-N-boolean AND = 2,6-pyridyl-benzene. The ground- and excited-state geometries were optimized at the PBE0/LanL2DZ;6-31G* and uPBE0/LanL2DZ;6-31G* level of theory, respectively, within acetonitrile solvent simulated by PCM. The emission bands and singlet-triplet transition properties of 1 and 2 are well reproduced with TD-PBE0//Stuttgart;cc-pVTZ;cc-pVDZ level of theory. The quantum efficiencies of 1 and 2 that were obtained upon metallic character analysis are comparable with the observed efficiencies. The metallic character analysis also revealed that the theoretically designed isomer 3 would highly phosphorescent at 510 nm.