Theoretical study on the influence of ancillary ligand on the energy and optical properties of heteroleptic phosphorescent Ir(III) complexes

The geometries, energies, and electronic properties of a series of phosphorescent Ir(III) complexes including FIrpic, FIrmpic, FIrpca, and FIrprza have been characterized within density functional theory DFT calculations, which can reproduce and rationalize experimental results. The properties of excited states of the Ir(III) complexes were characterized by the configuration interaction with single-excitation (CIS) method. The ground- and excited-state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. The absorption and phosphorescence wavelengths were computed based on the optimized ground- and excited-state geometries, respectively, by the time-dependent density functional theory (TD-DFT) methods. All the energies have been calculated by B3LYP method. The predictions revealed that the nature of the ancillary ligands can influence the distributions of frontier molecular orbitals and their energies, resulting in impact on the transition character and change in the emission color. In addition, the charge of transport quality has been estimated approximately by the predicted reorganization energy (λ). Our result also indicates that the substituent groups and different auxiliary ligand not only change the character of transition but also affect the rate and balance of charge transfer.