Activation by oxidation and ligand exchange in a molecular manganese vanadium oxide water oxidation catalyst.

Autor: Cárdenas G; Institute of Theoretical Chemistry, University of Vienna Währinger Str. 17 1090 Vienna Austria leticia.gonzalez@univie.ac.at.; Chemistry Department, Universidad Autónoma de Madrid Calle Francisco Tomás y Valiente, 7 28049 Madrid Spain., Trentin I; Institute of Inorganic Chemistry I, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany carsten.streb@uni-ulm.de., Schwiedrzik L; Institute of Theoretical Chemistry, University of Vienna Währinger Str. 17 1090 Vienna Austria leticia.gonzalez@univie.ac.at., Hernández-Castillo D; Institute of Theoretical Chemistry, University of Vienna Währinger Str. 17 1090 Vienna Austria leticia.gonzalez@univie.ac.at., Lowe GA; Institute of Inorganic Chemistry I, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany carsten.streb@uni-ulm.de., Kund J; Institute of Analytical and Bioanalytical Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany., Kranz C; Institute of Analytical and Bioanalytical Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany., Klingler S; Institute of Analytical and Bioanalytical Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany., Stach R; Institute of Analytical and Bioanalytical Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany., Mizaikoff B; Institute of Analytical and Bioanalytical Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany., Marquetand P; Institute of Theoretical Chemistry, University of Vienna Währinger Str. 17 1090 Vienna Austria leticia.gonzalez@univie.ac.at.; IADCHEM, Institute for Advanced Research in Chemistry, Universidad Autónoma de Madrid Madrid Spain., Nogueira JJ; Chemistry Department, Universidad Autónoma de Madrid Calle Francisco Tomás y Valiente, 7 28049 Madrid Spain.; IADCHEM, Institute for Advanced Research in Chemistry, Universidad Autónoma de Madrid Madrid Spain., Streb C; Institute of Inorganic Chemistry I, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany carsten.streb@uni-ulm.de., González L; Institute of Theoretical Chemistry, University of Vienna Währinger Str. 17 1090 Vienna Austria leticia.gonzalez@univie.ac.at.; Vienna Research Platform on Accelerating Reaction Discovery, University of Vienna Währinger Str. 17 1090 Vienna Austria.
Jazyk: angličtina
Zdroj: Chemical science [Chem Sci] 2021 Aug 30; Vol. 12 (39), pp. 12918-12927. Date of Electronic Publication: 2021 Aug 30 (Print Publication: 2021).
DOI: 10.1039/d1sc03239a
Abstrakt: Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn 4 V 4 O 17 (OAc) 3 ] 3- in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn 2 3+ Mn 2 4+ ] to [Mn 3+ Mn 3 4+ ], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn 3+ Mn 3 4+ ] to [Mn 4 4+ ]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn-Teller axis of the Mn 3+ centers leads to significantly lower activation barriers compared with attack at Mn 4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn 4 V 4 O 17 (OAc) 2 (H 2 O)(OH)] - featuring one H 2 O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate 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.
Competing Interests: There are no conflicts to declare.
(This journal is © The Royal Society of Chemistry.)
Databáze: MEDLINE
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