DFT Studies on Second-order Nonlinear Optical Response of Ir(C^N)2(pic) Complexes

Abstract

Density functional theory(DFT) was employed to calculate the geometrical structures, UV-Vis absorption spectra and second-order nonlinear optical(NLO) properties of a family of iridium(III) complexes, which possess of different cyclometallated ligands(C^N) and ancillary ligands[pyridine-2-carboxylate(pic)]. It was found that the modification of the LUMO energy levels was achieved by changing pic ligands and the energy gaps between the HOMO and LUMO were notably increased or decreased. In addition, the degree of conjugation was significantly changed with the substituent groups varied, which led to that the first hyperpolarizability β could be effectively modulated. Through the analysis of time-dependent DFT(TD-DFT) results, we predicted that these studied complexes with π→π* charge transfer was beneficial to the large second-order NLO properties. Therefore, we hope that these studied iridium( III) complexes can be considered as versatile second-order NLO materials.