A comparison of charge-transfer mechanisms at rotated disk electrode for biomimetic binuclear and tetranuclear oxo-manganese complex in aqueous solution

•Stability of binuclear and tetranuclear oxo-manganese complexes in aqueous solution were studied.•The stability and kinetic behavior are directly related to a μ-oxo bridge.•The kinetic parameters were dependent on the potential applied and rotation rate.•The binuclear and tetranuclear oxo-manganese complexes showed dimerization equilibrium in solution.

Many high-valence multinuclear μ-oxo-bridged manganese complexes have been synthesized to mimic the active site of the natural enzymes. The electrochemical and kinetic parameters were determined for two mimicking complexes ([Mn2IVO2(terpy)2(H2O)2]4+ and [Mn4IVO5(terpy)4(H2O)2]6+) by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode (RDE). Stability and kinetic behavior are directly related to μ-oxo bridges, where the μ-oxo-bridge provides a fast electron transition between metal centers due to stabilization of dx2 − y2 orbitals by the oxygen bond. On the other hand, when the dx2 − y2 orbitals are stabilized by aqua ligands by a coordination bond, a displacement of oxidation potential to more positive potential was observed. A shift of the potential to more negative values with increase in rotation rate was observed, which can be ascribed to a chemical step. The chemical step involves the dimerization process of the binuclear oxo-manganese complex to tetranuclear oxo-manganeses complex.

Graphical abstractThe electrochemical and kinetic parameters were determined for two mimicking complexes ([Mn2IVO2(terpy)2(H2O)2]4+ and [Mn4IVO5(terpy)4(H2O)2]6+) by cyclic voltammetry and linear sweep voltammetry with rotating disk electrode (RDE).Figure optionsDownload full-size imageDownload as PowerPoint slide