Photolysis of an Archetypal Model Complex. Photooxidation Versus Photoreduction of Azido(porphinato)iron(III)

• Published in: Chemistry : a European journal Vol. 29; no. 54; p. e202301207
• Main Authors: Flesch, Stefan, Vöhringer, Peter
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 26.09.2023
• Subjects: Anions; Chemistry; Cleavage; Infrared spectroscopy; Iron; Irradiation; Photochemicals; Photolysis; Photooxidation; Photoreduction; Room temperature; Thin films; high-valent iron transition metal nitrides photochemistry time-resolved infrared spectroscopy flash-photolysis
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202301207

Azidoporphinatoiron(III) ([1]) is an archetypal model complex for the photochemical generation of nitridoiron(V) complexes via cleavage of dinitrogen. So far, this process has only been studied with continuous irradiation in thin films under cryogenic conditions or in frozen solutions. In addition, the photooxidation from iron(III) to iron(V) competes with photoreduction to iron(II) via cleavage of an azidyl radical. The quantum yields of both pathways remained hitherto undisclosed. Here, we investigated the photolysis of this model complex in room temperature liquid solution using stationary and time-resolved infrared spectroscopy. The two reaction pathways are unambiguously identified in quenching studies and their quantum yields are accurately determined. Nitridoporphinatoiron(V) ([2]) exhibits N-atom-2-electron-transfer reactivity toward tert-butyl isonitrile and forms a carbodiimido species. In the presence of tert-butyl isonitrile, the two products of the photoreduction pathway react to cationic diisonitriloporphinatoiron(III) and azide anions, which in turn combine to reform [1] and the quencher.