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Orientational Jahn–Teller Isomerism in the Dark‐Stable State of Nature's Water Oxidase
Author(s) -
Drosou Maria,
Zahariou Georgia,
Pantazis Dimitrios A.
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202103425
Subject(s) - chemistry , valence (chemistry) , jahn–teller effect , electron paramagnetic resonance , photochemistry , crystallography , bistability , catalysis , gating , ion , chemical physics , nuclear magnetic resonance , materials science , physics , organic chemistry , physiology , biochemistry , optoelectronics , biology
The tetramanganese–calcium cluster of the oxygen‐evolving complex of photosystem II adopts electronically and magnetically distinct but interconvertible valence isomeric forms in its first light‐driven oxidized catalytic state, S 2 . This bistability is implicated in gating the final catalytic states preceding O−O bond formation, but it is unknown how the biological system enables its emergence and controls its effect. Here we show that the Mn 4 CaO 5 cluster in the resting (dark‐stable) S 1 state adopts orientational Jahn–Teller isomeric forms arising from a directional change in electronic configuration of the “dangler” Mn III ion. The isomers are consistent with available structural data and explain previously unresolved electron paramagnetic resonance spectroscopic observations on the S 1 state. This unique isomerism in the resting state is shown to be the electronic origin of valence isomerism in the S 2 state, establishing a functional role of orientational Jahn–Teller isomerism unprecedented in biological or artificial catalysis.