Synthesis, structure, electrochemistry and cytotoxicity studies of Ru(II) and Pt(II)–N-heterocyclic carbene complexes of CNC-pincer ligand

Synthesis, structure, electrochemistry and theoretical studies of Ru(II) and Pt(II) complexes bearing CNC-pincer carbene ligand [1,1′-[2,6-pyridinylbis(methylene)]bis[3-methylbenzimidazolium)bromide], 1·H2Br2 have been described. The compounds were fully characterized by elemental analysis, NMR, UV–Vis spectroscopy and finally the solid state structure of [Ru(1)2][PF6]2, 2, was confirmed by X-ray diffraction studies. The Pt(II)–NHC complex [Pt(1)Cl][PF6], 3 has been synthesized by silver-carbene transfer method and geometry was optimized theoretically. Cyclic voltammetry studies revealed Ru(II)/Ru(III) reversible oxidation couple at 0.57 V and Pt(II)/Pt(IV) couple at 0.48 V. Anticancer activities of complexes 2 and 3 have been studied upon breast (MCF7), colon (HCT116) and lung (A549) cancer cell lines using MTT assay. IC50 values are compared with cisplatin and carboplatin, among 2 and 3, complex 2 is more potent than complex 3.