A ruthenium(II) complex with a methylated polypyridine ligand: synthesis, DNA binding, and antiproliferation activity

A ruthenium polypyridine complex, [Ru(mptpy)(Mmptpy)Cl][PF6]2 (Ru1, mptpy = 4-(4-methylphenyl)-2,2′,6′,2″-mptpyridine, Mmptpy = 2-[4-(4-methylphenyl)-2,2′-bipyridin-6-yl]-1-methylpyridinum), was synthesised and characterised. The structure of the complex was determined by single-crystal X-ray crystallography. The ruthenium(II) core has an octahedral coordination environment. The interactions of the complex with DNA were analysed by UV–Vis and fluorescence spectroscopy, revealing a high binding affinity for double-stranded DNA. DNA photocleavage studies monitored by agarose gel electrophoresis showed that the complex cleaved DNA efficiently, whilst mechanistic studies showed that the complex produced reactive oxygen species including singlet oxygen, superoxide anions, and carbon-based radicals that cleave DNA. The complex also showed notable antiproliferation activity towards cancer cells in methyl thiazolyl tetrazolium assays.