Solution and solid behavior of mono and binuclear zinc(ii) and nickel(ii) complexes with dithiocarbazates: X-ray analysis, mass spectrometry and cytotoxicity against cancer cell lines

Abstract

The current work reports the synthesis and investigation by physical-chemistry and spectroscopic methods of three dithiocarbazates (2-acetylpyridine-S-allyl-dithiocarbazate – HL¹; 2-acetylpyridine-S-p-bromobenzyl-dithiocarbazate – HL²; and 2-acetylpyridine-S-p-nitrobenzyl-dithiocarbazate – HL³) and six novel metal complexes derived from these Schiff-bases. Four crystal structures of the complexes are reported. The single crystal X-ray study showed two binuclear zinc(II) complexes with symmetrical and asymmetrical acetate bridges resulting in different coordination spheres. Another zinc(II) complex and three nickel(II) complexes present dithiocarbazates tridentate with NNS-donor atoms and octahedral geometry to the metal centers. The mass spectrometry data indicated the presence of the molecular ions [M + H]⁺ and characteristic fragments of the compounds. All characterization indicated the same behavior of the compounds as a solid and in solution. The biological activity of the zinc(II) and nickel(II) salts, the free dithiocarbazate ligands and their metal complexes was evaluated by assays with carcinoma mammary MDA-MB-231 cells. The results revealed that the free dithiocarbazates present great in vitro antitumor activity, which is increased after the complexation with zinc, with emphasis on the dimeric complex (1), which had an IC₅₀ of 2.0 μM and exhibits more potential inhibition of tumor cell growth than the nickel(II) complexes.