Unprecedented oxidation of aldimine to carboxamido function during reactivity studies on ruthenium complex with acidified nitrite solution: Synthesis of ruthenium nitrosyl complex having {RuNO}6 moiety and photorelease of coordinated NO

Abstract Ruthenium(II) complex namely [Ru(L 1 )(PPh 3 )Cl 2 ] ( 1 ) [where L 1  =  N -(pyridin-2-ylmethylene)quinolin-8-amine] derived from the tridentate ligand containing two pyridine and one imine donors was synthesized. This ruthenium(II) complex was treated with acidified nitrite solution to afford a ruthenium nitrosyl complex [Ru(L 2 )(PPh 3 )(NO)Cl](ClO 4 ) ( 2 ) [where L 2  =  N -(quinolin-8-yl)picolinamide]. These complexes were characterized by elemental analysis, electronic absorption, NMR ( 1 H and 31 P NMR) and IR spectral studies. The molecular structure of 2 was confirmed by X-ray crystallography and the redox property of metal centers was investigated. During nitrosylation of complex 1 , we found out the oxidation of imine functional group to amide functional group in the nitrosyl complex ( 2 ). Here, we also examined probable mechanism of nitric oxide (NO) mediated oxidation of imine to carboxamido group. The resultant nitrosyl complex 2 was found to be photoactive and could deliver NO on demand upon illumination of light.