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Coordination Number in High-Spin-Low-Spin Equilibrium in Cluster Models of the S₂ State of the Oxygen Evolving Complex.

ABSTRACT: The S₂ state of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) shows high-spin (HS) and low-spin (LS) EPR signals attributed to distinct structures based on computation. Five-coordinate Mn^III centers are proposed in these species but are absent in available spectroscopic model complexes. Herein, we report the synthesis, crystal structure, electrochemistry, SQUID magnetometry, and EPR spectroscopy of a Mn^IIIMn^IV₃O₄ cuboidal complex featuring five-coordinate Mn^III. This cluster displays a spin ground state of S = 5/2, while conversion to a six-coordinate Mn upon treatment with water results in a spin state change to S = 1/2. These results demonstrate that coordination number, without dramatic changes within the Mn₄O₄ core, has a substantial effect on spectroscopy.

SUBMITTER: Shiau AA

PROVIDER: S-EPMC10575483 | biostudies-literature | 2023 Jul

REPOSITORIES: biostudies-literature

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Coordination Number in High-Spin-Low-Spin Equilibrium in Cluster Models of the S2 State of the Oxygen Evolving Complex.

Shiau Angela A AA Lee Heui Beom HB Oyala Paul H PH Agapie Theodor T

Journal of the American Chemical Society 20230627 27

The S2 state of the Oxygen Evolving Complex (OEC) of Photosystem II (PSII) shows high-spin (HS) and low-spin (LS) EPR signals attributed to distinct structures based on computation. Five-coordinate MnIII centers are proposed in these species but are absent in available spectroscopic model complexes. Herein, we report the synthesis, crystal structure, electrochemistry, SQUID magnetometry, and EPR spectroscopy of a MnIIIMnIV3O4 cubo ...[more]

PMID: 37366634

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