Photoactive ruthenium nitrosyls derived from quinoline- and pyridine-based ligands: Accelerated photorelease of NO due to quinoline ligation

The ruthenium nitrosyl (PaPy₂Q)Ru(NO)](BF₄)₂, derived from the quinoline-based ligand PaPy₂QH (PaPy₂QH = N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-quinaldine-2-carboxamide; H = dissociable proton) has been synthesized and characterized by X-ray crystallography and spectroscopic techniques. This {Ru–NO}⁶ nitrosyl is soluble in aqueous media and stable under physiological conditions at pH 7. (PaPy₂Q)Ru(NO)]²⁺ releases NO rapidly upon exposure to low-intensity UV light (5 mW/cm²). The NO donor capacity of this nitrosyl (quantum yield = 0.20, λ_irr = 365 nm) is considerably higher than that of analogous nitrosyl derived from a polypyridyl ligand without the quinoline moiety.