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Mechanisms of Mn(V)-Oxo to Mn(IV)-Oxyl Conversion: From Closed-Cubane Photosystem II to Mn(V) Catalysts and the Role of the Entering Ligands.
Ariafard, Alireza; Longhurst, Matthew; Swiegers, Gerhard F; Stranger, Robert.
Afiliação
  • Ariafard A; Research School of Chemistry, Australian National University, Canberra, Australia.
  • Longhurst M; Intelligent Polymer Research Institute, University of Wollongong, Wollongong, Australia.
  • Swiegers GF; Intelligent Polymer Research Institute, University of Wollongong, Wollongong, Australia.
  • Stranger R; Research School of Chemistry, Australian National University, Canberra, Australia.
Chemistry ; 30(35): e202400396, 2024 Jun 20.
Article em En | MEDLINE | ID: mdl-38659321
ABSTRACT
The low activation barrier for O-O coupling in the closed-cubane Oxygen-Evolving Centre (OEC) of Photosystem II (PSII) requires water coordination with the Mn4 'dangler' ion in the Mn(V)-oxo fragment. This coordination transforms the Mn(V)-oxo complex into a more reactive Mn4(IV)-oxyl species, enhancing O-O coupling. This study explains the mechanism behind the coordination and indicates that in the most stable form of the OEC, the Mn4 fragment adopts a trigonal bipyramidal geometry but needs to transition to a square pyramidal form to be activated for O-O coupling. This transition stabilizes the Mn4 dxy orbital, enabling electron transfer from the oxo ligand to the dxy orbital, converting the oxo ligand into an oxyl species. The role of the water is to coordinate with the square pyramidal structure, reducing the energy gap between the oxo and oxyl forms, thereby lowering the activation energy for O-O coupling. This mechanism applies not only to the OEC system but also to other Mn(V)-based catalysts. For other catalysts, ligands such as OH- stabilize the Mn(IV)-oxyl species better than water, improving catalyst activation for reactions like C-H bond activation. This study is the first to explain the Mn(V)-oxo to Mn(IV)-oxyl conversion, providing a new foundation for Mn-based catalyst design.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE País/Região como assunto: Cuba Idioma: En Revista: Chemistry Assunto da revista: QUIMICA Ano de publicação: 2024 Tipo de documento: Article País de afiliação: Austrália País de publicação: Alemanha
Texto completo
Adicionar na Minha BVS
Imprimir
XML
PubMed Links
Buscar no Google

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE País/Região como assunto: Cuba Idioma: En Revista: Chemistry Assunto da revista: QUIMICA Ano de publicação: 2024 Tipo de documento: Article País de afiliação: Austrália País de publicação: Alemanha