Predication of second-order optical nonlinearity of [(Bu2tIm)AuX] (X=halogen) using time-dependent density-functional theory combined with sum-over-states method

Abstract

The dipole polarizability and second-order polarizability of recently synthesized (1,3-di-ter-butylimidazol-2-ylidine) gold complexes [(Bu2t Im)AuX] (X=halogen) were investigated by using time-dependent density-functional theory combined with sum-over-states method. We have discovered that these complexes possess remarkably larger molecular second-order polarizability compared with the organometallic and organic complexes. The value of the second-order polarizability increases in the order of F<Cl<Br<I. The analysis of the molecular orbital suggests that the charge transfer from halogen atom to the carbene ligand plays the key role in nonlinear optical response of gold complexes. The gold of these complexes is a bridge of charge transfer, unlike other organometallic complexes, the metal center may be a strong donor or acceptor. These complexes have a possibility to be excellent second-order nonlinear optical materials from the standpoint of transparency, relatively large beta values and relatively small dispersion behaviors.