Ruthenium(ii) [3 + 2 + 1] mixed ligand complexes: substituent effect on photolability, photooxidation of bases, photocytotoxicity and photonuclease activity

Abstract

Mixed ligand complexes of ruthenium(II), [Ru(itpy)(bpy)Cl]ClO₄1, [Ru(itpy)(phen)Cl]ClO₄2, [Ru(bitpy)(bpy)Cl]ClO₄3 and [Ru(bitpy)(phen)Cl]ClO₄4 have been synthesized and characterized. Complex 3 has also been characterized crystallographically. These complexes exhibit photolability of the Ru–Cl bond. Upon irradiation at 440 nm in the presence of nucleosides and nucleotides the complexes exchange chloride for the nucleoside or nucleotide. The photolability of the Ru–Cl bond depends on the nature of the substituent in the tridentate tpy ligand. Photolysis of the complexes in the presence of a nucleoside or nucleotide also produces 8-oxoguanine due to the oxidation of guanine by the excited states of the complexes. These four complexes exhibit photonuclease properties and bring about the cleavage of plasmid DNA when irradiated at 440 nm. These complexes have been found to be toxic towards NIH 3T3 cells under photolytic conditions.