Radical Complexes as functional models for metalloenzymatic catalysis

Significant efforts were directed towards the design and testing of phenol-containing ligands for synthesizing radical-containing transition metal complexes as potential candidates for oxidative catalysis of organic substrates like alcohols, amines and 2-aminophenol with oxygen from air. Functional models for different copper-oxidases, such as Galactose Oxidase (GO), Amine Oxidases (AO) and Phenoxazinone Synthase (PHs) are reported. In most of the cases, an "on-off" mechanism of the radicals without redox participation from the metal centers seems to be operative in the catalysis involving such metal-iminosemiquinone radical complexes.