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(L1)(PPh3)Cl2] (1) [where L1 = 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(L2)(PPh3)(NO)Cl](ClO4) (2) [where L2 = N-(quinolin-8-yl)picolinamide]. These complexes were characterized by elemental analysis, electronic absorption, NMR (1H and 31P 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.