Zinc(II) complexes derived from pyridine-2-carbaldehyde thiosemicarbazone and (1E)-1-pyridin-2-ylethan-1-one thiosemicarbazone. Synthesis, crystal structures and antiproliferative activity of zinc(II) complexes

The complexes [ZnCl2(HFoTsc) · H2O], [Zn(FoTsc)2], [ZnCl2(HAcTsc) · H2O] and [Zn(AcTsc)2], where HFoTsc and HAcTsc is pyridine-2-carbaldehyde thiosemicarbazone and (1E)-1-pyridin-2-ylethan-1-one thiosemicarbazone respectively, have been prepared and structurally characterized by means vibrational, and NMR (1H and 13C) spectroscopy. The crystal structures of the complexes [ZnCl2(HFoTsc) · H2O], [Zn(AcTsc)2] and [ZnCl2(HAcTsc) · H2O] have been determined by X-ray crystallography. The metal co-ordination geometry of [ZnCl2(HFoTsc) · H2O] and [ZnCl2(HAcTsc) · H2O] is described as distorted square pyramidal and the two complexes are self-assembled via π → π stacking interactions and intermolecular hydrogen bonds. In these two cases molecular recognition of the hydrogen bonds leads to aggregation and a supramolecular assembly of infinite two-dimensional network. The metal co-ordination geometry of [Zn(AcTsc)2] is described as distorted octahedral configuration in a trans-N(2)-cis-N(1)-cis-S configuration.HFoTsc and HAcTsc and the zinc complexes have been evaluated for antiproliferative activity in vitro against the cells of two human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line) and a mouse fibroblast L-929 cell line. The cytotoxic activity shown by these compounds indicates that coupling of HFoTsc and HAcTsc to Zn(II) metal center result in metallic complexes with important biological properties since they display IC50 values in a μM range similar to or better than that of the antitumor drug cis-platin and are considered as agents with potential antitumor activity candidates for further stages of screening in vitro and/or in vivo.