Large nonlinear optical response of acceptor substituted bis(N-phenyldithiocarbimato)Nickel(II) complexes and the relation to intramolecular charge transfer transitions

The second molecular hyperpolarizability, γ, for bis(N-(4-nitrophenyl)dithiocarbimato)Ni(II) complexes incorporating two p-nitroaniline moieties in a centrosymmetric fashion is found from third harmonic generation measurements to be two orders of magnitude higher than the simple sum of the p-nitroaniline contributions. The molecules with γ values as high as 2×10−33 esu were designed to have efficient “periphery-to-centre” charge transfer transitions demonstrated to be of paramount importance for the nonlinear response by comparison with similar complexes without efficient intramolecular charge transfer transitions.