A thermally stable {FeNO}8 complex: properties and biological reactivity of reduced MNO systems

Abstract

Reduced nitrogen oxide ligands such as NO⁻/HNO or nitroxyl participate in chemistry distinct from nitric oxide (NO). Nitroxyl has been proposed to form at heme centers to generate the Enemark–Feltham designated {FeNO}⁸ system. The synthesis of a thermally stable {FeNO}⁸ species namely, [Co(Cp*)₂][Fe(LN₄)(NO)] (3), housed in a heme-like ligand platform has been achieved by reduction of the corresponding {FeNO}⁷ complex, [Fe(LN₄)(NO)] (1), with decamethylcobaltocene [Co(Cp*)₂] in toluene. This complex readily reacts with metMb, resulting in formation of MbNO via reductive nitrosylation by the coordinated HNO/NO⁻, which can be inhibited with GSH. These results suggest that 3 could serve as a potential HNO therapeutic. Spectroscopic, theoretical, and structural comparisons are made to 1 and the {CoNO}⁸ complex, [Co(LN₄)(NO)] (2), an isoelectronic analogue of 3.