Nitric oxide reduction forming hyponitrite triggered by metal‐containing complexes

Abstract

AbstractNitric oxide reduction yielding N2O is known as a route to detoxify nitric oxide (NO) to relieve nitrosative stress in pathogenic bacteria and fungi. Nitric oxide enzymes are classified into Cu/Fe‐heme NO reductases (NORs) and non‐heme flavindiiron NO reductases (FNORs). In biological system, the mechanism of NO reduction generating N2O was proposed to involve NO coordination to metal centers prior to producing cis/trans‐hyponitrite‐bound intermediate, and the subsequent protonation of hyponitrite‐bound‐Fe/Cu intermediates releases N2O. In this review article, we compile the recently published biomimetic model studies of NO‐to‐[N2O2]2− transformation triggered by the designed transition‐metal complexes. In biomimetic model study, the ON‐NO bond coupling of metal‐nitrosyl complexes yielding [N2O2]2−‐bound species may occur via either the inter/intramolecular radical‐[NO]−‐radical‐[NO]− coupling or metal‐[NO]2− radical coupling with exogenous NO˙. The H‐bonding interaction between hyponitrite and protic solvents promoting/stabilizing the formation of hyponitrite complexes was also demonstrated. In addition, the electronic structure of the designed transition‐metal‐nitrosyl complexes triggering the formation of [N2O2]2−‐bound species and the detailed NO‐to‐[N2O2]2− formation pathways were delineated.