Metal nitrosyl and dinitrosyl complexes as small molecule models for NOD and FNOR

Abstract

The PhD dissertation entitled, “Metal nitrosyl and dinitrosyl complexes as small molecule models for NOD and FNOR” contains five chapters on the topic of mainly the non-heme iron nitrosyls and dinitrosyls and a chromium nitrosyl. The reactivity of these metal nitrosyls with dioxygen (O2) and other reactive oxygen species such as H2O2 have been described in this thesis. Chapter 1 provides a review of recent literature on Fe, Co, Cu, Mn, and Cr nitrosyls, focusing on their reactivity with dioxygen and other reactive oxygen species. The reactivity of the metal nitrosyls with O2 and H2O2 was explored with an aim to understand the mechanism of the nitric oxide dioxygenase (NOD) enzyme, as discussed in chapters 2 to 4. For instance, in chapter 2, the formation of Fe(III)-peroxynitrite intermediate was observed, which decomposes to [FeIV=O] and NO2, leading to the ligand modification. In chapter 3, study of the dioxygen reactivity of two iron-nitrosyls having same ligand framework but different spin-states suggest that the reaction proceeds through different pathways based on M-NO bond strength. In chapter 4, a [CrV=O] intermediate was observed in the reaction of chromium nitrosyl with H2O2. These findings definitely enhance our current understanding of NOD chemistry and make a substantial contribution to the field of metalloenzyme chemistry. In chapter 5, a diiron dinitrosyl complex was synthesized as a model complex of flavodiiron nitric oxide reductase (FNOR). This diiron dinitrosyl complex promotes N–N bond formation leading to transient hyponitrite species through a {Fe(NO)2}9 intermediate to result in the spontaneous release of N2O.