Water Oxidation Catalyzed by a Bioinspired Tetranuclear Manganese Complex: Mechanistic Study and Prediction

• Published in: ChemSusChem Vol. 15; no. 15; pp. e202200187 - n/a
• Main Authors: Li, Man, Liao, Rong‐Zhen
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 05.08.2022
• Subjects: density functional calculations; electrocatalysis; manganese; reaction mechanism; water oxidation; Reaction mechanism; tetranuclear manganese cluster; Density Functional Calculations; water oxidation; electrocatalysis
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202200187

Density functional theory calculations were utilized to elucidate the water oxidation mechanism catalyzed by polyanionic tetramanganese complex a [MnIII3MnIVO3(CH3COO)3(A‐α‐SiW9O34)]6−. Theoretical results indicated that catalytic active species 1 (Mn4III,III,IV,IV) was formed after O2 formation in the first turnover. From 1, three sequential proton‐coupled electron transfer (PCET) oxidations led to the MnIV‐oxyl radical 4 (Mn4IV,IV,IV,IV−O⋅). Importantly, 4 had an unusual butterfly‐shaped Mn2O2 core for the two substrate‐coordinated Mn sites, which facilitated O−O bond formation via direct coupling of the oxyl radical and the adjacent MnIV‐coordinated hydroxide to produce the hydroperoxide intermediate Int1 (Mn4III,IV,IV,IV−OOH). This step had an overall energy barrier of 24.9 kcal mol−1. Subsequent PCET oxidation of Int1 to Int2 (Mn4III,IV,IV,IV−O2⋅) enabled the O2 release in a facile process. Furthermore, apart from the Si‐centered complex, computational study suggested that tetramanganese polyoxometalates with Ge, P, and S could also catalyze the water oxidation process, where those bearing P and S likely present higher activities. Float like a butterfly: Density functional theory calculations are employed to investigate the water oxidation mechanism catalyzed by polyanionic tetramanganese complex a ([MnIII3MnIVO3(CH3COO)3(A‐α‐SiW9O34)]6−). Theoretical results suggest the O−O bond formation occurs at MnIV‐oxyl radical (Mn4IV,IV,IV,IV−Ȯ), which possesses an unusual butterfly‐shaped Mn2O2 core, via direct coupling of the oxyl radical and the adjacent MnIV‐coordinated hydroxide. Prediction of catalytic activity for analogous catalysts is conducted computationally.