A series of divalent manganese complexes [MII(HL1–6)Cl2] with the 1,3-bis(2’-Ar-imino)isoindolines (HLn, n = 1–6, Ar = pyridyl, 4-methylpyridyl, imidazolyl, thiazolyl, benzimidazolyl and N-methylbenzimidazolyl, respectively) including the previously reported ligands (HL1–2, 4–6) and complexes ([MII(HL1,5)Cl2]) have been prepared and characterized by electrochemical and spectroscopic methods. In these complexes, it was possible to control the redox potential of the metal center by varying the aryl substituent on the bis-iminoisoindoline moiety, and investigate its effect in a catalase-like reaction, and oxidative bleaching process in buffered aqueous solution. The kinetics of the dismutation of H2O2 into H2O and O2, and the oxidative degradation of morin by H2O2 were investigated in buffered water, where the reactivity of the catalysts in both systems was markedly influenced by the redox and Lewis acidic properties of the metal centers and the concentration of the bicarbonate ions. Both the catalase-like and bleaching activity of the catalysts showed a linear correlation with the MnIII/MnII redox potentials. The E1/2 spans a 561 mV range from 388 mV (Ar = benzymidazolyl) to 948 mV (Ar = 4-methylpyridyl) vs. the SCE. The amount of bicarbonate is a critical issue for the in situ formation of peroxycarbonate as a versatile oxidant, and its participation in the formation of high valent MnIV = O species.
Bystanding F+ Oxidants Enable Selective Reductive Elimination from High-Valent Metal Centers in Catalysis
