Working Paper
Authors
- Gustavo Cardenas Autonomous University of Madrid & University of Vienna ,
- Ivan Trentin University of Ulm ,
- Ludwig Schwiedrzik
University of Vienna ,
- David Hernández-Castillo University of Vienna ,
- Grace A. Lowe University of Ulm ,
- Julian Kund University of Ulm ,
- Christine Kranz University of Ulm ,
- Sarah Klingler University of Ulm ,
- Robert Stach University of Ulm ,
- Boris Mizaikoff University of Ulm ,
- Philipp Marquetand University of Vienna & Vienna Research Platform on Accelerating Reaction Discovery, University of Vienna ,
- Juan J. Nogueira Autonomous University of Madrid & IADCHEM, Institute for Advanced Research in Chemistry, Autonomous University of Madrid ,
- Carsten Streb University of Ulm ,
- Leticia González University of Vienna & Vienna Research Platform on Accelerating Reaction Discovery, University of Vienna
Abstract
Despite their technological importance, reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. We combine theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular WOC [Mn4V4O17(OAc)3]3-. Using density functional theory, electrochemistry and IR-spectroscopy, we propose a three-step activation mechanism: one-electron oxidation [Mn3+2Mn4+2]→[Mn3+Mn4+3], acetate-to-water ligand exchange, and another one-electron oxidation [Mn3+Mn4+3]→[Mn4+4]. Analysis of ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn-Teller axis of Mn3+ centers leads to lower activation barriers than attack at Mn4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to formation of the activated species [Mn4V4O17(OAc)2(H2O)(OH)]1-. Computed Redox potentials are in excellent agreement with electrochemical measurements. This interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts.
Content

Supplementary material

Supporting Information - Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst
Supporting Information for
"Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst", including further information on Electrochemistry, Calculation of Ligand Exchange Pathways, and Calculation of Redox Potentials.

Coordinates - Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst
Coordinates for "Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst", including .xyz format coordinates of all optimized intermediates and transition states discussed in the manuscript and SI.