Tetrakis(thione)platinum(II) complexes: synthesis, spectroscopic characterization, crystal structures, and in vitro cytotoxicity

Abstract

A new series of platinum(II) complexes based on thione ligands with general formula [Pt(thione)4]X2 (X− = Cl−, NO3−) has been synthesized and characterized using CHNS elemental analysis, infrared, 1H and 13C solution-state NMR as well as 13C and 15N solid-state NMR spectroscopy, and X-ray crystallography. The spectroscopic methods confirm the coordination of Pt(II) with thiocarbonyl groups via sulfur of the thione ligands. The X-ray structures showed a distorted square planar geometry for 1, [Pt(MeImt)4]Cl2 (MeImt = N-Methylimidazolidine-2-thione) while the hydrogen bonding interactions in 7, [Pt(iPrImt)4](NO3)2·0.6(H2O) induce a bent see-saw distortion relative to the ideal square planar geometry. The in vitro cytotoxicity studies showed that 2, [Pt(EtImt)4]Cl2 is generally the most effective, a two-fold better cytotoxic agent than cisplatin and carboplatin against MCF7 (human breast cancer).