A manganese(III) corrole complex, 1, has been synthesized and used to study a potential mechanism for oxidation of water to molecular oxygen. Oxidation by t-BuOOH gave the Mn(V)=O complex 2. Addition of hydroxide led to release of oxygen via the Mn(IV) complex 4 and regeneration of complex 1. It could be shown that the oxygen from (18)O-labeled water was incorporated in both the formed molecular oxygen and the peroxy intermediate 4.

Manganificent potential: A dinuclear manganese catalyst contains metal centers that are coordinated by a central phenolate, with adjoining imidazole and carboxylate groups, which are all important functionalities in the natural oxygen‐evolving center. The complex catalyzes the conversion of water to oxygen in the presence of a single‐electron oxidant [Ru(bpy)3]3+ (see picture, bpy=2,2′‐bipyridine, A=acceptor).

A dinuclear ruthenium complex, which acts as a molecular catalyst for water oxidation, has been synthesized and characterized. The electronic and electrochemical properties were studied by UV-vis spectroscopy and cyclic voltammetry. The oxidation potentials of the complex are significantly lowered by introducing a negatively charged carboxylate ligand, in comparison with those of the reported complexes that have neutral ligands. The catalytic activity of the complex toward water oxidation using Ce(NH(4))(2)(NO(3))(6) as a chemical oxidant was investigated by means of an oxygen electrode and mass spectrometry. The turnover number of this catalyst with Ce(IV) as the chemical oxidant was found to be ca. 1700. The mass spectroscopic analysis of the isotopomer distribution in oxygen evolved from (18)O-labeled water indicates that O atoms in the evolved oxygen originate from water.