Systematic Selection of Metalloporphyrin‐Based Catalysts for Oxygen Reduction by Modulation of the Donor–Acceptor Intermolecular Hardness

Incisive modulation of the intermolecular hardness between metalloporphyrins and O₂ can lead to the identification of promising catalysts for oxygen reduction. The dependency of the electrocatalytic reduction of O₂ by metalloporphyrins on the nature of the central metal yields a volcano‐type curve, which is rationalized to be in accordance with the Sabatier principle by using an approximation of the electrophilicity of the complexes. By using electrochemical and UV/Vis data, the influence of a selection of meso‐substituents on the change in the energy for the π→π* excitation of manganese porphyrins was evaluated allowing one to quantitatively correlate the influence of the various ligands on the electrocatalysis of O₂ reduction by the complexes. A manganese porphyrin was identified that electrocatalyzes the reduction of oxygen at low overpotentials without generating hydrogen peroxide. The activity of the complex became remarkably enhanced upon its pyrolysis at 650 °C.