Review: Synthesis, characterization, and DNA-binding properties of Ru(II) molecular “light switch” complexes

Abstract

This article presents recent progress in our laboratory on the interactions of Ru(II) polypyridyl complexes with calf thymus DNA (CT-DNA). Mixed polypyridyl Ru(II) complexes [Ru(L)4(AIP)]2+ and [Ru(L)4PyIP]2+, where L is 4-amino pyridine and pyridine (AIP = 2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline; PyIP = 2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), have been synthesized and characterized by elemental analysis, and physicochemical methods such as ESI-MS, UV-Vis, IR, and NMR spectroscopic techniques. Electronic absorption titrations, fluorescence spectroscopy, viscosity measurements, and salt-dependent studies of CT-DNA in the presence of incremental amounts of all four Ru(II) complexes clearly demonstrate that all four complexes bind to DNA by intercalation. The DNA-binding affinities of these complexes follow the order [Ru(4-APy)4(PyIP)]2+ > [Ru(Py)4PyIP]2+ > [Ru(4-APy)4(AIP)]2+ > [Ru(Py)4AIP]2+. Irradiation of pBR 322 DNA with these complexes results in nicking of the plasmid DNA. All four complexes were screened for antimicrobial activity. All complexes also exhibited DNA “light switch” properties. These results suggest that both ancillary ligand and intercalative ligand influence the binding of these complexes to DNA.