Oxidation of 2-aminophenol by iron(III) isoindoline complexes

Series of dichloroiron(III) complexes of 1,3-bis(2'-arylimino)isoindoline, including a new structurally characterized ligand 1,3-bis(5'-methyl-2'-thiazolylimino)isoindoline and its complex, have been used as catalysts for the oxidative coupling of 2-aminophenol (OAPH) to 2-aminophenoxazine-3-one (APX) in DMF solution at ambient temperature. The complexes were suitable as catalyst, and depending on the oxidant used, two different mechanisms can be proposed, namely a metal-based oxidation for dioxygen, and a hydroxyl radical mediated process, including zero-order dependence on the concentration of the substrate, for H2O2. In the former case a mechanism on the basis of kinetic data was proposed assuming ternary complex formation between catalyst, substrate and dioxygen, and a nice correlation was found between the reaction rate and the oxidation potential, E-pa degrees' of the iron center in the precursor complexes. (C) 2014 Elsevier B.V. All rights reserved.