Ligand Control of Dinitrosyl Iron Complexes for Selective Superoxide-Mediated Nitric Oxide Monooxygenation and Superoxide-Dioxygen Interconversion.

Through nitrosylation of [Fe-S] proteins, or the chelatable iron pool, a dinitrosyl iron unit (DNIU) [Fe(NO)] embedded in the form of low-molecular-weight/protein-bound dinitrosyl iron complexes (DNICs) was discovered as a metallocofactor assembled under inflammatory conditions with elevated levels of nitric oxide (NO) and superoxide (O). In an attempt to gain biomimetic insights into the unexplored transformations of the DNIU under inflammation, we investigated the reactivity toward O by a series of DNICs [(NO)Fe(μ-Pyr)Fe(NO)] () and [(NO)Fe(μ-SEt)Fe(NO)] (). During the superoxide-induced conversion of DNIC into DNIC [(K-18-crown-6-ether)(NO)][Fe(μ-Pyr)(μ-O)(Fe(NO))] () and a [Fe(Pyr)(NO)(O)] adduct, stoichiometric NO monooxygenation yielding NO occurs without the transient formation of peroxynitrite-derived OH/NO species.