Donation and scavenging of nitric oxide (NO) by flipping of the denticity of carboxylate ligand in novel ruthenium complexes: Photolability of the coordinated NO

Novel ruthenium nitrosyl complex [Ru(η1-L1)(PPh3)2(NO)Cl2] (2) (where L1H is 3-chlorobenzoic acid and H is dissociable proton) was synthesized and characterized by spectroscopic and electrochemical studies. Molecular structure of complex 2 was determined by X-ray crystallography. The diamagnetic behaviour of 2 was established by NMR spectral studies and redox property of 2 was investigated. DFT optimization of the structure of 2 provided a linear geometry of {RuII–NO+} moiety. The nitrosyl complex acted as novel nitric oxide (NO) donor upon illumination of light and photoreleased NO was trapped by reduced myoglobin. Amount of photolytically cleaved NO was quantified by Griess reagent. The precursor complex [Ru(η2-L1)(PPh3)2Cl2] (1) was obtained after photorelease of NO and was found to be a potential NO scavenger. Flipping of denticity of carboxylate ligand was observed during NO donation and scavenging. DPPH (2,2-diphenyl-1-picrylhydrazine) radical quenching assay was performed to estimate the amount of generated reactive nitrogen species or/and reactive oxygen species during photolysis of NO.