Theoretical study on the electronic structures and phosphorescent properties of four Ir(III) complexes with different substituents on the ancillary ligand

The geometry structures, electronic structures, absorption and phosphorescent properties of four Ir(III) complexes [(F²-ppy) ²Ir(pta-X)], where F²-ppy = (2,4-difluoro)phenylpyridine; pta = pyridine-1,2,4-triazole; X = -CF₃; -H; -CH₃; -N(CH₃)₂, are investigated using the density functional method. The results reveal that the electron-accepting group -CF₃ has no obvious effect on absorption and emission properties, while the substitutive group -N(CH₃)₂ with strong electron-donating ability has obvious effect on the emission properties. The mobility of hole and electron were studied computationally based on the Marcus-Hush theory. Calculations of ionisation potential and electron affinity were used to evaluate the injection abilities of holes and electrons into these complexes. We hope that this theoretical work can provide a suitable guide to the future design and synthesis of novel phosphorescent materials for use in the organic light-emitting diodes.