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  Experimental and Computational X-ray Emission Spectroscopy as a Direct Probe of Protonation States in Oxo-Bridged MnIV Dimers Relevant to Redox-Active Metalloproteins

Lasalle-Kaiser, B., Boron III, T. T., Krewald, V., Kern, J., Beckwith, M. A., Delgado-Jaime, M. U., et al. (2013). Experimental and Computational X-ray Emission Spectroscopy as a Direct Probe of Protonation States in Oxo-Bridged MnIV Dimers Relevant to Redox-Active Metalloproteins. Inorganic Chemistry, 52(22), 12915-12922. doi:10.1021/ic400821g.

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Lasalle-Kaiser, Benedikt1, Author
Boron III, Thaddeus T.2, Author
Krewald, Vera3, Author           
Kern, Jan1, 4, Author
Beckwith, Martha. A.3, 5, Author           
Delgado-Jaime, Mario U.3, Author           
Schroeder, Henning1, Author
Alonso-Mori, Roberto4, Author
Nordlund, Dennis4, Author
Weng, Tsu-Chien4, Author
Sokaras, Dimosthenis4, Author
Neese, Frank3, Author           
Bergmann, Uwe4, Author
Yachandra, Vittal K.1, Author
DeBeer, Serena3, 5, Author           
Pecoraro, Vincent L.2, Author
Yano, Junko1, Author
Affiliations:
1 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States, ou_persistent22              
2Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States, ou_persistent22              
3Research Department Neese, Max Planck Institute for Chemical Energy Conversion, Max Planck Society, ou_3023886              
4SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States, ou_persistent22              
5Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States, ou_persistent22              

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 Abstract: The protonation state of oxo bridges in nature is of profound importance for a variety of enzymes, including the Mn4CaO5 cluster of photosystem II and the Mn2O2 cluster in Mn catalase. A set of dinuclear bis-μ-oxo-bridged MnIV complexes in different protonation states was studied by Kβ emission spectroscopy to form the foundation for unraveling the protonation states in the native complex. The valence-to-core regions (valence-to-core XES) of the spectra show significant changes in intensity and peak position upon protonation. DFT calculations were performed to simulate the valence-to-core XES spectra and to assign the spectral features to specific transitions. The Kβ2,5 peaks arise primarily from the ligand 2p to Mn 1s transitions, with a characteristic low energy shoulder appearing upon oxo-bridge protonation. The satellite Kβ″ peak provides a more direct signature of the protonation state change, since the transitions originating from the 2s orbitals of protonated and unprotonated μ-oxo bridges dominate this spectral region. The energies of the Kβ″ features differ by ∼3 eV and thus are well resolved in the experimental spectra. Additionally, our work explores the chemical resolution limits of the method, namely, whether a mixed (μ-O)(μ-OH2) motif can be distinguished from a symmetric (μ-OH)2 one. The results reported here highlight the sensitivity of Kβ valence-to-core XES to single protonation state changes of bridging ligands, and form the basis for further studies of oxo-bridged polymetallic complexes and metalloenzyme active sites. In a complementary paper, the results from X-ray absorption spectroscopy of the same MnIV dimer series are discussed.

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Language(s): eng - English
 Dates: 2013-04-032013-10-252013-11-18
 Publication Status: Published in print
 Pages: 8
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/ic400821g
 Degree: -

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Title: Inorganic Chemistry
  Abbreviation : Inorg. Chem.
Source Genre: Journal
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Publ. Info: Washington, DC : American Chemical Society
Pages: - Volume / Issue: 52 (22) Sequence Number: - Start / End Page: 12915 - 12922 Identifier: ISSN: 0020-1669
CoNE: https://pure.mpg.de/cone/journals/resource/0020-1669