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Published November 18, 2019 | Published + Supplemental Material
Journal Article Open

Redox Tuning via Ligand-Induced Geometric Distortions at a YMn₃O₄ Cubane Model of the Biological Oxygen Evolving Complex

Abstract

The function of proteins involved in electron transfer is dependent on cofactors attaining the necessary reduction potentials. We establish a mode of cluster redox tuning through steric pressure on a synthetic model related to Photosystem II. Resembling the cuboidal [CaMn₃O₄] subsite of the biological oxygen evolving complex (OEC), [Mn4O4] and [YMn₃O₄] complexes featuring ligands of different basicity and chelating properties were characterized by cyclic voltammetry. In the absence of ligand-induced distortions, increasing the basicity of the ligands results in a decrease of cluster reduction potential. Contraction of Y-oxo/Y–Mn distances by 0.1/0.15 Å enforced by a chelating ligand results in an increase of cluster reduction potential even in the presence of strongly basic donors. Related protein-induced changes in Ca-oxo/Ca–Mn distances may have similar effects in tuning the redox potential of the OEC through entatic states and may explain the cation size dependence on the progression of the S-state cycle.

Additional Information

© 2019 American Chemical Society. This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: February 20, 2019; Published: May 16, 2019. This research was supported by the NIH (R01-GM102687B), the Dreyfus Teacher-Scholar Program (T.A.), and Dow Next Generation Educator (instrumentation). The authors declare no competing financial interest.

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Published - acs.inorgchem.9b00510.pdf

Supplemental Material - ic9b00510_si_001.pdf

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August 19, 2023
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