Abstract
Copper(II), nickel(II), palladium(II) and platinum(II) complexes of
ortho-napthaquinone thiosemicarbazone were synthesized and characterized by spectroscopic studies. The in vitro antiproliferative activity of the synthesized compounds against MCF7 human cancer cells were evaluated. The structures of the thiosemicarbazone ligand and the palladium complex were determined by X-ray crystallography.
Copper(II), nickel(II), palladium(II) and platinum(II) complexes of
ortho-naphthaquinone thiosemicarbazone were synthesized and characterized by spectroscopic studies. In both solution (NMR) and solid state (IR, single-crystal X-ray diffraction determination) the free ligand NQTS exists as the thione form. The Pd complex (X-ray) crystallizes as the H-bonded dimer, [Pd(NQTS)Cl]
2
·
2DMSO, where palladium(II) coordinates in a square planar configuration to the monodeprotonated, tridentate thiosemicarbazone ligand. The nickel(II) complex shows 1:2 metal to ligand stoichiometry while the other complexes exhibit 1:1 metal–ligand compositions. In vitro anticancer studies on MCF7 human breast cancer cells reveal that adding a thiosemicarbazone pharmacophore to the parent quinone carbonyl considerably enhances its antiproliferative activity. Among the metal complexes, the nickel compound exhibits the lowest IC
50 value (2.25 μM) suggesting a different mechanism of action involving inhibition of topoisomerase II activity.