1. CaMn 3 IV O 4 Cubane Models of the Oxygen-Evolving Complex: Spin Ground States S<9/2 and the Effect of Oxo Protonation.
- Author
-
Lee HB, Shiau AA, Marchiori DA, Oyala PH, Yoo BK, Kaiser JT, Rees DC, Britt RD, and Agapie T
- Subjects
- Biomimetic Materials chemical synthesis, Bridged-Ring Compounds chemical synthesis, Calcium chemistry, Coordination Complexes chemical synthesis, Electron Spin Resonance Spectroscopy, Manganese chemistry, Molecular Structure, Photosystem II Protein Complex chemistry, Yttrium chemistry, Biomimetic Materials chemistry, Bridged-Ring Compounds chemistry, Coordination Complexes chemistry, Protons
- Abstract
We report the single crystal XRD and MicroED structure, magnetic susceptibility, and EPR data of a series of CaMn
3 IV O4 and YMn3 IV O4 complexes 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 CaMn3 IV O4 complexes and variants with protonated oxo moieties need not be S=9/2. Desymmetrization of the pseudo-C3 -symmetric Ca(Y)Mn3 IV O4 core leads to a lower S=5/2 spin ground state. The magnitude of the magnetic exchange coupling is attenuated upon oxo protonation, and an S=3/2 spin ground state is observed in CaMn3 IV O3 (OH). Our studies complement the observation that the interconversion between the low-spin and high-spin forms of the S2 state is pH-dependent, suggesting that the (de)protonation of bridging or terminal oxygen atoms in the OEC may be connected to spin-state changes., (© 2021 Wiley-VCH GmbH.)- Published
- 2021
- Full Text
- View/download PDF