Comparative Study of Ni(II) Complexes with Dithiocarbazate- and Thiosemicarbazone-Based Ligands: Synthesis, Crystal Structures, and Anticancer Activity

The present work reports a comparative study of thiosemicarbazone (H₂L¹) and dithiocarbazate (H₂L²) ligands and their Ni(II) complexes; [Ni(L¹)(PPh₃)] (<b>1</b>); [Ni(L¹)(Py)] (<b>2</b>); [Ni(L²)(PPh₃)] (<b>3</b>); and [Ni(L²)(Py)] (<b>4</b>). All compounds were characterized by spectroscopy analysis; and the complexes were also characterized by single-crystal X-ray diffraction. The crystal structures of the complexes revealed a distorted square planar geometry with the Ni(II) atoms coordinated to a double-deprotonated and tridentate ligand molecule by the <i>ONS</i> donor system. The coordination sphere is completed by the incorporation of pyridine or triphenylphosphine coligands at the metal center. Biological assays were conducted against the cell lines breast cancer (MCF-7); cisplatin-resistant ovarian cancer (A2780cis); lung cancer (A549); and nontumoral lung (MRC-5). The results show that cytotoxicity was significantly enhanced upon complexation for complexes (<b>2</b>) and (<b>4</b>); whereas it was suppressed for complexes (<b>1</b>) and (<b>3</b>) against the A2780cis and A549 cell lines. Notably; complex (<b>2</b>) exhibited superior cytotoxicity compared to cisplatin against both MCF-7 and A2780cis.