Spin State Differentiated [3Fe–4S] Cluster Electrocatalyzes Water Oxidation Efficiently

Though there are many synthetic iron–sulfur clusters that have been reported to show catalytic activity mimicking the natural cofactors in metalloenzymes, the influence of the spin state on the catalytic property is seldom touched. Here, a disulfide-bridged triiron(II) complex is shown, namely [Fe₃(Sip)₄][CF₃SO₃]₂ (Fe₃(Sip)₄, HSip = sulfanylpropyliminomethyl-pyridine), can efficiently electrocatalyze water oxidation with a turnover frequency of 932 s⁻¹ and Faraday efficiency of 86%, better than many iron-based catalysts. More importantly, the terminal low-spin (S = 0) iron(II) sites possessing a N4S2 first coordination environment, along with the synergetic catalysis of ligands, play a crucial role in the catalytic process. This research highlights the unconventional applications of iron–sulfur clusters in electrocatalytic water oxidation and underlines a promising avenue for developing innovative catalysts.