Fresh Impetus in the Chemistry of Calcium Peroxides

Kornowicz, Arkadiusz; Pietrzak, Tomasz; Korona, Krzesimir; Terlecki, Michał; Justyniak, Iwona; Kubas, Adam; Lewiński, Janusz

doi:10.1021/jacs.4c00906

Cited by 2 publications

References 116 publications

(172 reference statements)

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Closing Kok’s cycle of nature’s water oxidation catalysis

Guo,

He,

Ding

et al. 2024

Nat Commun

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The Mn4CaO5(6) cluster in photosystem II catalyzes water splitting through the Si state cycle (i = 0–4). Molecular O2 is formed and the natural catalyst is reset during the final S3 → (S4) → S0 transition. Only recently experimental breakthroughs have emerged for this transition but without explicit information on the S0-state reconstitution, thus the progression after O2 release remains elusive. In this report, our molecular dynamics simulations combined with density functional calculations suggest a likely missing link for closing the cycle, i.e., restoring the first catalytic state. Specifically, the formation of closed-cubane intermediates with all hexa-coordinate Mn is observed, which would undergo proton release, water dissociation, and ligand transfer to produce the open-cubane structure of the S0 state. Thereby, we theoretically identify the previously unknown structural isomerism in the S0 state that acts as the origin of the proposed structural flexibility prevailing in the cycle, which may be functionally important for nature’s water oxidation catalysis.

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Closing Kok’s cycle of nature’s water oxidation catalysis

Guo,

He,

Ding

et al. 2024

Nat Commun

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Redox-Active Inverse Crowns for Small Molecule Activation

Harder,

Maurer,

Klerner

et al. 2024

Preprint

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The discovery of crown ether host-guest systems initiated the multidisciplinary field of supramolecular chemistry. Whereas cyclic crown ethers selectively bind metal cations in their center, the lesser known inverse crowns are rings of metal cations that efficiently bind anionic entities. In this role, inverse crowns enabled spectacular multiple deprotonation reactions, often with unusual selectivity. Self-assembly of the inverse crown around the multiply charged carbanion during the deprotonation reaction is the driving force for this reactivity. Here, we report on the synthesis of a pre-assembled inverse crown consisting of Na+ cations and a redox-active Mg0 center. We demonstrate its bifunctionality by reducing N2O and subsequent encapsulation of O2ˉ. Calculations reveal that this essentially barrier-free process involves a rare N2O2ˉ dianion, embedded in the inverse crown. The inverse crown can adapt itself for binding larger anions like N2O22ˉ, by extending the ring of metals cations. These redox-active inverse crowns combine the advantages of a strong reducing agent with anion stabilizing properties provided by the ring of metal cations, leading to high reactivity and selectivity.

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Fresh Impetus in the Chemistry of Calcium Peroxides

Cited by 2 publications

References 116 publications

Closing Kok’s cycle of nature’s water oxidation catalysis

Closing Kok’s cycle of nature’s water oxidation catalysis

Redox-Active Inverse Crowns for Small Molecule Activation

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