Theoretical studies on the substituent effect on the photophysical properties of two series of heteroleptic Ir(III) complexes

The electronic structures and phosphorescence efficiency for two series of Ir(III) complexes with different substituent groups were theoretically investigated by using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The results reveal that the nature of the different substituents can influence the electron density distributions of frontier molecular orbitals and their energies, resulting in the change of transition character and emission color, while the different number of -(CH2CH2O)-units have an impact on the HOMO and LUMO energy levels of the designed complexes 2a-6a and 2b-6b. It can be speculated that the complexes 1a-4a and 1b-5b are considered to be potential candidates as blue-emitting materials. The assumed complexes 6a and 6b also are the potential candidate as an efficient green-emitting material with high photoluminescent quantum yield. (C) 2015 Elsevier Ltd. All rights reserved.