Tetranuclear manganese(II) complex as a molecular catalyst for the water oxidation reaction

This work investigates a water-soluble tetranuclear Mn(II) coordination complex as an electrocatalyst for the oxygen evolution reaction. Single-crystal X-ray diffraction revealed a cyclic structure containing four equivalent manganese centers connected by bridging carboxylate groups. FTIR spectroscopy supported a bidentate bridging coordination mode, while UV–Vis analysis showed ligand-centered absorption bands at 230 and 284 nm. The electrocatalytic performance was evaluated in phosphate buffer at pH 3, 7, and 9. The complex promoted oxygen evolution throughout the investigated pH range, with the highest activity under acidic conditions. At pH 3, it exhibited an overpotential of 140 mV at a current density of 0.6 mA cm⁻². These results demonstrate the potential of this Mn-based complex as an efficient and low-cost water oxidation catalyst, particularly for acidic water-splitting systems.