Theoretical study on the electronic structures and phosphorescent properties of five bis-cyclometalated iridium(III) complexes with 2-phenylpyridinato ancillary ligand

A DFT/TDDFT study was performed on five bis-cyclometalated iridium(III) complexes with the same ancillary ligand 2-phenylpyridinato (ppy) and main ligands with different substituted groups (CH(CH3)2, CH3, H, F, and NO2). The geometry structures, electronic structures, absorption, and phosphorescent properties of the five iridium(III) complexes have been investigated. Calculations of ionization potential and electron affinity were used to evaluate the injection abilities of holes and electrons into these complexes. The lowest energy absorption wavelengths are located at 408 nm for 1, 407 nm for 2, 401 nm for 3, 381 nm for 4, and 556 nm for 5, respectively, in good agreement with the HOMO–LUMO energy gaps. The lowest energy emissions of these complexes are localized at 515, 514, 516, 518, and 567 nm at M052X level, respectively. The calculated results indicate that the complex 4 possibly possesses the largest kr value among the five complexes. We hope that this theoretical work can provide constructive information for designing and synthesizing novel phosphorescent materials for use in the organic light-emitting diodes.