Synthesis, structure, and biological activity of bis(benzimidazole)amino thio- and selenoether nickel complexes.

Four new nickel (II) complexes with bis(benzimidazole)thio- and selenoether-based ligands have been synthesized and characterized in the solid state by elemental analysis, IR, magnetic susceptibility and X-ray crystallography, and in solution by FAB+ mass spectrometry, UV-vis spectroscopy and cyclic voltammetry. Single-crystal X-ray diffraction analysis of the compounds revealed octahedral geometries for all nickel centers. Three of the four complexes are dimers with chloride bridges between the two Ni(II) ions. However, in solution all complexes have a monomeric formulation, based on mass spectrometry and osmometry measurements. The complexes were also screened for their cytotoxic activity on human cell lines (HeLa, SK-LU-1 and HEK-293), and compared with a related Cu(II) complex.