Synthesis, crystal structure and biological studies of the highly anticancer active compound trans-dichloridobis(4-methyl-2-N-(2-pyridylmethylene)-aminophenol)ruthenium(II)

A new Ru(II) compound of formula, trans-[RuII(Hpyrimol)2Cl2] (Hpyrimol = 4-methyl-2-N-(2-pyridylmethylene)aminophenol) has been synthesised, starting from Ru(III) chloride and the redox-active ligand Hpyramol. Ligand dehydrogenation takes place to form the coordinated neutral ligand Hpyrimol. This mononuclear compound contains two relatively labile coordinated chloride ligands at trans axial positions. Although the ligand is potentially tridentate and anionic, as found in all previously reported compounds with this ligand so far, the coordination motif of Hpyrimol in the title compound is only bidentate, as a N,N-donor and a non-coordinated neutral phenol group. The neutral phenol groups instead form stable intramolecular hydrogen bonds with the coordinated chloride anions. The compound has been fully structurally characterised by spectroscopy and X-ray diffraction and has also been evaluated for its biological activities. Combined effects of coordinative binding and partial intercalation to DNA are evident from spectroscopic studies. The title compound has also been studied for DNA interaction by using an electrophoretic mobility assay and UV–Vis spectroscopy, and information on the difference of DNA–metal complex interactions guided by metal centres, hydrogen bonds and ligand binding modes was obtained. The in vitro cytotoxic activity makes this compound interesting as a starting point for research on a new class of Ru(II) antitumour compounds.