A ruthenium nitrosyl that rapidly delivers NO to proteins in aqueous solution upon short exposure to UV light

Two Ru(III) complexes, [Ru(PaPY3)(Cl)](BF4) (2) and [Ru(PaPY3)(NO)](BF4)(2) (3) (PaPY3H = N,N'-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamide), have been synthesized and characterized by spectroscopy and X-ray diffraction. Nitrosyl complex 3 has been prepared by passage of purified NO gas to the hot methanolic solution of the chloro derivative 2. Complex 3 exhibits v(NO) stretching frequency at 1899 cm(-1) indicating a {Ru-NO}(6) configuration. Clean H-1 NMR spectra of 3 in D2O and CD3CN confirm the S = 0 ground state. When an aqueous solution of [Ru(PaPY3)(NO)](BF4)(2) is exposed to low intensity UV light, it rapidly loses NO and forms [Ru(PaPY3)(H2O)](2+). This reaction can be conveniently used to transfer NO to proteins such as myoglobin (Mb) and cytochrome c oxidase. The NO transfer reaction is clean and occurs upon short exposure to light.