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Calcium Valence-to-Core X-ray Emission Spectroscopy: A Sensitive Probe of Oxo Protonation in Structural Models of the Oxygen-Evolving Complex

Mathe, Zachary and Pantazis, Dimitrios A. and Lee, Heui Beom and Gnewkow, Richard and Van Kuiken, Benjamin E. and Agapie, Theodor and DeBeer, Serena (2019) Calcium Valence-to-Core X-ray Emission Spectroscopy: A Sensitive Probe of Oxo Protonation in Structural Models of the Oxygen-Evolving Complex. Inorganic Chemistry, 58 (23). pp. 16292-16301. ISSN 0020-1669. PMCID PMC6891804. doi:10.1021/acs.inorgchem.9b02866.

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Calcium is an abundant, nontoxic metal that finds many roles in synthetic and biological systems including the oxygen-evolving complex (OEC) of photosystem II. Characterization methods for calcium centers, however, are underdeveloped compared to those available for transition metals. Valence-to-core X-ray emission spectroscopy (VtC XES) selectively probes the electronic structure of an element’s chemical environment, providing insight that complements the geometric information available from other techniques. Here, the utility of calcium VtC XES is established using an in-house dispersive spectrometer in combination with density functional theory. Spectral trends are rationalized within a molecular orbital framework, and Kβ_(2,5) transitions, derived from molecular orbitals with primarily ligand p character, are found to be a promising probe of the calcium coordination environment. In particular, it is shown that calcium VtC XES is sensitive to the electronic structure changes that accompany oxo protonation in Mn₃CaO₄-based molecular mimics of the OEC. Through correlation to calculations, the potential of calcium VtC XES to address unresolved questions regarding the mechanism of biological water oxidation is highlighted.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle
Mathe, Zachary0000-0002-4516-3511
Pantazis, Dimitrios A.0000-0002-2146-9065
Lee, Heui Beom0000-0002-9550-2649
Van Kuiken, Benjamin E.0000-0002-3650-7765
Agapie, Theodor0000-0002-9692-7614
DeBeer, Serena0000-0002-5196-3400
Additional Information:© 2019 American Chemical Society. This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. Received: September 26, 2019; Published: November 19, 2019. The authors acknowledge the Max Planck Society for funding. Z.M. thanks Yvonne Brandenburger and Fabian Strunk for technical expertise with the LabXES spectrometer, as well as Dr. Ragnar Bjornsson and Dr. Vijay Chilkuri for discussions of MO theory. Z.M. acknowledges the Deutscher Akademischer Austauschdienst for M.Sc. scholarship funding. T.A. is grateful to the NIH (Grant R01-GM102687B) for supporting the synthetic model studies. The authors declare no competing financial interest.
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Max Planck SocietyUNSPECIFIED
Deutscher Akademischer Austauschdienst (DAAD)UNSPECIFIED
Issue or Number:23
PubMed Central ID:PMC6891804
Record Number:CaltechAUTHORS:20191120-074543683
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Official Citation:Calcium Valence-to-Core X-ray Emission Spectroscopy: A Sensitive Probe of Oxo Protonation in Structural Models of the Oxygen-Evolving Complex. Zachary Mathe, Dimitrios A. Pantazis, Heui Beom Lee, Richard Gnewkow, Benjamin E. Van Kuiken, Theodor Agapie, and Serena DeBeer. Inorganic Chemistry 2019 58 (23), 16292-16301. DOI: 10.1021/acs.inorgchem.9b02866
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99940
Deposited By: Tony Diaz
Deposited On:20 Nov 2019 19:39
Last Modified:16 Feb 2022 23:13

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