Theoretical Investigations of Nonlinear Optical Properties of Transition Metal Cluster Anions

摘要

In the framework of density functional theory (DFT), the electronic excitations and nonlinear optical (NLO) properties of six binuelear transition metal cluster anions with the formula of [Ch2M-(μ-Ch)2-M'CN]2-(M = Mo, W; Ch = S, Se; M' = Cu, Ag) have been systemically investigated at both cases of gas phase and DMF solution. The obtained electronic absorption spectra reveal that the element replacements of metals M and ligands Ch have significant influence on the absorptions, especially on the low-lying ones. In addition, the transitions of μ-Ch→M are dominant for the low-lying excitations, whereas the transitions of M'→M as well as Ch→M are mainly responsible for the higher excitations. The calculated molecular first and second hyper- polarizabilities present the remarkable element substitution and solvent effects. The analyses show that the transitions involving μ-Ch→M charge transfer make the critical contributions to the first hyperpolarizability β, and that the charge transfers from the moieties of MCh4 to M'CN as well as those of β-Ch→M and M'→M are responsible for the second hyperpolarizability γ. Moreover, the introduction of solvent leads to the results that the transitions within the moieties of MCh4 and M'CN make larger contributions to the hyperpolafizability, especially to γ.