Nitric Oxide Dioxygenase Activity of a Nitrosyl Complex of Cobalt(II) Porphyrinate in the Presence of Hydrogen Peroxide via Putative Peroxynitrite Intermediate

Abstract

The reaction of a cobalt porphyrin complex, [(F 8 TPP)Co], 1 {F 8 TPP = 5,10,15,porphyrinate dianion} in dichloromethane with nitric oxide (NO) led to the nitrosyl complex, [(F 8 TPP)Co(NO)], 2. Spectroscopic studies and structural characterization revealed it as a bent nitrosyl of {CoNO} 8 description. It was stable in the presence of dioxygen. However, it reacts with H 2 O 2 in acetonitrile (or THF) solution at −40 °C (or −80 °C) to result in the corresponding Co(III)-nitrate complex, [(F 8 TPP)Co(NO 3 )], 3. The reaction presumably proceeds via the formation of a Co-peroxynitrite intermediate. X-Band electron paramagnetic resonance and electrospray ionization−mass spectroscopic studies suggest the intermediate formation of the [(porphyrin)Co(III)−O • ] radical, which in turn supports the generation of the corresponding Co(IV)-oxo species during the reaction. This is in accord with the homolytic cleavage of the O−O bond in heme-peroxynitrite proposed in the nitric oxide dioxygenases activity. In addition, the characteristic peroxynitrite-induced phenol ring reaction was also observed.

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

“…and O 2 .− , which may implicate metals as important factors in the physiological formation and transformation of peroxynitrite (Scheme ). While progress has been made to implicate metal ions in the decay of peroxynitrite, a discrete peroxynitrite coordination complex has rarely been observed . Examples of stable peroxynitrite complexes are scarce, and those containing vibrational (i.e., IR spectroscopic) information about the peroxynitrite ligand even more so …”

Molecular Recognition of Imidazole Derivatives by Co(III)-Porphyrins in Phosphate Buffer (pH = 7.4) and Cetylpyridinium Chloride Containing Solutions

“…It is known that cobalt cation in the porphyrin coordination center can have two oxidation states (2 + and 3 + ), and both states can quite easily transform into each other. So, when Co(II)-tetraarylporphyrins are dissolved in electron-donating or non-polar solvents in the presence of organic bases, the Co(II) cation almost instantaneously oxidizes into Co(III), coordinating on itself two additional electron-donating ligands or one ligand and one solvent molecule [49][50][51][52]. The catalyst for this process is molecular oxygen contained in the air.…”

Possible mechanism of antioxidant action of dinitrosyl iron complexes

“…Исходя из этого, мы полагаем, что обнаруженное в работе [16] снижение люцигенин-зависимой хемилюминесценции в тканях животных под действием NO может быть следствием образования ДНКЖ. [24,25]. Аналогичные интермедиаты возникают в реакции между молекулярным кислородом и динитрозильными комплексами железа с синтетическими (не тиольными) лигандами [26].…”