Equatorial ligand effects on the diradical character dependence of the second hyperpolarizabilities of open-shell singlet transition-metal dinuclear complexes

We investigate the equatorial ligand effects on the diradical character (y) dependence of the longitudinal second hyperpolarizability (γ) of the Re(IV)2F8 transition-metal dinuclear complex with different bond lengths using the spin-unrestricted coupled-cluster method. It is found that the equatorial ligands do not affect the intrinsic y–γ relationship nor the dσ-electron dominant contribution to the maximum γ (γmax) observed in the bare dinuclear analogs but γmax of Re(IV)2F8 is about one order of magnitude larger than that of Re(IV)2.