Synthesis, structure, DNA/BSA interaction and in vitro cytotoxic activity of nickel(II) complexes derived from S-allyldithiocarbazate

Abstract Two nickel(II) complexes with formula NiL 1 and NiL 2 (HL 1  = S-allyl-4-methoxybenzylidene hydrazinecarbodithioate, HL 2  = S-allyl-1-napthylidenehydrazinecarbodithioate) have been synthesized and characterized by elemental analysis, FT-IR, NMR, UV–vis spectroscopy and ESI mass spectrometry. The crystal structure of complex 1 has been determined by single crystal X-ray diffractometry. Both HL 1 and HL 2 ligands are coordinated to the metal in thiolate form. In complexes, squareplanar geometry of the nickel is coordinated with two bidentate ligand units acting through azomethine nitrogen and thiolato sulfur atoms. To explore the potential medicinal value of the complexes with calf thymus DNA and bovine serum albumin (BSA) were studied at normal physiological conditions using fluorescence spectral techniques. The DNA binding constant values of the complexes were found in the range from 5.02 × 10 4 , 3.54 × 10 4 , and the binding affinities are in the following order 1 > 2. In addition, nickel complexes 1 and 2 shows better binding propensity to the bovine serum albumin (BSA) protein, giving a K sv value 5.8 × 10 4 , 4.47 × 10 4 respectively. From the oxidative cleavage of the complexes with pBR322 DNA, it is inferred that the effects of cleavage are dose-dependent. In addition, in vitro cytotoxicity of the complexes assayed against Vero and HeLa cell lines have shown higher cytotoxic activity with the lower IC 50 values indicating their efficiency in killing cancer cells even at various concentrations.