Oxidative polymerization of pyrrole promoted by four-electron transfer to O₂: Catalysis of O₂-oxidation by μ-oxo dinuclear complexes with macrocyclic ligands

In attempts to provide molecular systems capable of oxidizing aromatic molecules at the expense of O₂ that is reduced predominantly by four electrons to H₂O, μ-oxo dinuclear metalloporhyrins and metallophthalocyanines were employed as catalysts for the O₂-oxidative polymerization of pyrrole. The catalytic behaviors of the complexes depended upon their redox potentials, concentrations and acidity (H₀) of the solutions. The first catalytic system allowing the O₂-oxidative polymerization of pyrrole with more than 1000 turnovers was devised using (μ-oxo)bis[phthalocyaninato)iron(III)] as the homogeneous catalyst.