Primary and secondary photochemical transformations of biologically active precursor - Nitro-Nitrosyl ruthenium complex

[Display omitted] •Primary photolysis lead to the formation of nitric oxide and paramagnetic ruthenium.•Ruthenium(III) is reduced due to accumulation of nitric oxide.•Secondary photolysis reflect pyridine photocleavage and nitrite bond isomerization. Photolysis of [Ru(II)NOPy2(NO2)2OH] (A) complex was studied under blue light (445 nm) irradiation. The primary photo-process results in the formation of nitric oxide (NO) and a paramagnetic RuIII compound, the latter was detected by EPR technique. The quantum yield (6–11%) of primary photolytic process was determined from the evolution of UV–vis spectra in different solvents (water, ethanol, dimethyl sulfoxide and acetonitrile). The secondary processes compete with the NO-release and lead to a variety of ruthenium forms including new nitrosyl forms. Namely, processes of hydroxyl protonation, pyridine photocleavage and nitro – nitrito bond isomerization take a place. HPLC combined with IR and 15N – NMR spectroscopies clarified the composition of the new forms and their transformations during the photolysis. Supporting EPR and IR DFT calculations confirmed the structure of photoproducts. The oxidation of NO in the secondary processes significantly influences on the total amount of nitric oxide release and reaction routes.