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Title: CaMn 3 IV O 4 Cubane Models of the Oxygen‐Evolving Complex: Spin Ground States S <9/2 and the Effect of Oxo Protonation
Abstract

We report the single crystal XRD and MicroED structure, magnetic susceptibility, and EPR data of a series of CaMn3IVO4and YMn3IVO4complexes as structural and spectroscopic models of the cuboidal subunit of the oxygen‐evolving complex (OEC). The effect of changes in heterometal identity, cluster geometry, and bridging oxo protonation on the spin‐state structure was investigated. In contrast to previous computational models, we show that the spin ground state of CaMn3IVO4complexes and variants with protonated oxo moieties need not beS=9/2. Desymmetrization of thepseudoC3‐symmetric Ca(Y)Mn3IVO4core leads to a lowerS=5/2 spin ground state. The magnitude of the magnetic exchange coupling is attenuated upon oxo protonation, and anS=3/2 spin ground state is observed in CaMn3IVO3(OH). Our studies complement the observation that the interconversion between the low‐spin and high‐spin forms of the S2state is pH‐dependent, suggesting that the (de)protonation of bridging or terminal oxygen atoms in the OEC may be connected to spin‐state changes.

 
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NSF-PAR ID:
10450161
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Angewandte Chemie International Edition
Volume:
60
Issue:
32
ISSN:
1433-7851
Page Range / eLocation ID:
p. 17671-17679
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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