Crystal structure and third-order nonlinearity of nickel(II) and copper(II) complexes with S-methyl β-N-(4-nitrobenzal)methylenedithiocarbazate

Article abstract of DOI:10.1016/S0277-5387(97)00162-9

Ni^II and Cu^II complexes of general formula ML₂ [HL = S-methyl-β-N-(nitrobenzal)methylenedithiocarbazate] have been synthesized and characterized. The Schiff base acts as a single, negatively charged bidentate ligand forming extensive electron delocalization system. Single crystal X-ray diffraction analysis of the copper(II) complex revealed that the ligand lost a proton from its tautomeric thiol form and coordinates to Cu^II via mercapto sulfur and β-nitrogen atoms. The geometry of the Cu^II ion is square-planar with two equivalent Cu - S and Cu - N bonds. The two nitrobenzal rings and the coordinated moieties are almost in one plane, forming an electronic delocalization system. Third-order response determinations show that the extensive electron delocalization is quite helpful for the complexes exhibit higher second order molecular hyperpolarizability. Crystal structure of the free ligand is also determined for comparison.