Visible light-induced formation of corrole-manganese(V)-oxo complexes: Observation of multiple oxidation pathways

Two manganese(V)-oxo corroles [Mn-v(Cor)O] that differ in their electronic environments were produced by visible light irradiation of highly photo-labile corrole-manganese(IV) bromates. The corrole ligands under study include 5,10,15-tris(pentafluorophenyl)corrole (TPFC), and 5,10,15-triphenylcorrole (TPC). The kinetics of oxygen transfer atom (OAT) reactions with various organic reductants by these photo-generated Mnv(Cor)O were also studied in CH3CN and CH2Cl2 solutions. Mn-v(Cor)O exhibits remarkable solvent and ligand effect on its reactivity and spectral behavior. In the more electron-deficient TPFC system and in the polar solvent CH3CN, Mn-v(Cor)O returned Me corrole in the end of oxidation reactions. However, in the less polar solvent CH2Cl2 or in the less electron-deficient TPC system, Mn-IV product was formed instead of MnIR. Furthermore, with the same substrates and in the same solvent, the order of reactivity of Mn-v(Cor)o was TPC> TPFC, which is inverted from that expected based on the electron-demand of corrole ligands. Our spectral and kinetic results in this study provide compelling evidence in favor of multiple oxidation pathways, where Mn-v(Cor)o may serve as direct two-electron oxidant or undergo a disproportionation reaction to form a manganese(VI)-oxo corrole as the true oxidant. The choice of pathways is strongly dependent on the nature of the solvent and the corrole ligand. (C) 2016 Elsevier Inc All rights reserved.