Synthesis, crystal structures and cytotoxic activity of mononuclear nickel(II) and dinuclear zinc(II) complexes with ligand derived from S-benzyldithiocarbazate

Ni(L)2 (1) and Zn2(μ-OL)2(L)2 (2), (HL = S-benzyl-β-N-(2-bromobenzylidene) dithiocarbazate), were synthesized and characterized by elemental analysis and X-ray single-crystal diffraction analysis. 1 is a mononuclear neutral nickel(II) complex and the center nickel atom is chelated by donors of N2S2 possessing a distorted tetrahedral configuration, while in 2, the adjacent two complex molecules are linked through two O atoms to form a dimer and the center zinc atom is five-coordinate in a distorted trigonal–bipyramidal geometry. The cytotoxic activity study indicated that 2 showed potent cytotoxic activity against the human liver hepatocellular carcinoma (HepG2) cancer cell lines, with IC50 2.4 ± 0.2 μg·mL− 1, which is slightly weaker than 5-fluoroacil (5-FU) (0.89 ± 0.21 μg·mL− 1) as reference. A gel electrophoresis assay demonstrated the ability of the complex to cleave the pBR322 plasmid DNA.