EXAFS, DFT, light-induced nucleobase binding, and cytotoxicity of the photoactive complex cis-[Ru(bpy)2(CO)Cl]+

The aqueous photochemistry of cis-[Ru(bpy)2(CO)Cl]+ (1) was investigated at 310 K and under visible light (white) irradiation by NMR and ESI-HR-MS. Complex 1 releases a Cl ligand, coordinates a solvent molecule, and forms the complex cis- [Ru(bpy)2(CO)(H2O)]2+ (2). Also, irradiation experiments were performed in the presence of the nucleobase derivatives 9-ethylguanine (9-EtG) and 9-ethyladenine (9-EtA). Formation of Ru-9-EtG adducts was observed after 3 h irradiation by NMR and HR-MS, while only very small amounts of a Ru-9-EtA adduct could be detected by HR-MS. Solution structural data were obtained by X-ray absorption spectroscopy (XAS) for both 1 and 2. EXAFS gave a Ru-Cl distance of 2.416(7) A for 1 and a Ru-OH2O distance of 2.102(6) A for 2. DFT and TDDFT were employed to study the photophysical and photochemical properties of 1. Calculations show that dissociative metal-centered states can be related to the light-induced release of a Cl ligand and subsequent coordination of a solvent molecule. The compound showed no antiproliferative activity in three human carcinoma cell lines (lung, bladder, pancreas) under the testing conditions, either with or without irradiation with UV light.