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          Institute: MPI für bioanorganische Chemie     Collection: MPI für bioanorganische Chemie     Display Documents



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ID: 682079.0, MPI für bioanorganische Chemie / MPI für bioanorganische Chemie
Experimental and Computational X-ray Emission Spectroscopy as a Direct Probe of Protonation States in Oxo-Bridged Mn-IV Dimers Relevant to Redox-Active Metalloproteins.
Authors:Lassalle-Kaiser, Benedikt; Boron, Thaddeus T.; Krewald, Vera; Kern, Jan; Beckwith, Martha A.; Delgado-Jaime, Mario Ulises; Schroeder, Henning; Alonso-Mori, Roberto; Nordlund, Dennis; Weng, Tsu-Chien; Sokaras, Dimosthenis; Neese, Frank; Bergmann, Uwe; Yachandra, Vittal K.; DeBeer, Serena; Pecoraro, Vincent L.; Yano, Junko
Language:English
Date of Publication (YYYY-MM-DD):2013
Title of Journal:Inorganic Chemistry
Journal Abbrev.:Inorg. Chem.
Volume:52
Issue / Number:22
Start Page:12915
End Page:12922
Review Status:Peer-review
Audience:Experts Only
Abstract / Description: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-mu-oxo-bridged Mn-IV complexes in different protonation states was studied by K beta 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 K beta(2,5) peaks arise primarily from the ligand 2p to Mn Is transitions, with a characteristic low energy shoulder appearing upon oxo-bridge protonation. The satellite K beta '' peak provides a more direct signature of the protonation state change, since the transitions originating from the 2s orbitals of protonated and unprotonated mu-oxo bridges dominate this spectral region. The energies of the K beta '' features differ by similar to 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 (mu-O)(mu-OH2) motif can be distinguished from a symmetric (mu-OH)(2) one. The results reported here highlight the sensitivity of K beta 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 Mn-IV dimer series are discussed.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für bioanorganische Chemie
External Affiliations:Lassalle-Kaiser, B.; Kern, J.; Schroeder, H.; Yachandra, V.K.; Yano, J.; Univ Calif Berkeley, Lawrence Berkeley Natl Lab, Phys Biosci Div, Berkeley, CA 94720 USA.
Boron, T.T., III; Pecoraro, V.L.; Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA.
Kern, J.; Alonso-Mori, R.; Nordlund, D.; Weng, T.-C.; Sokaras, D.; Bergmann, U.; SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
Beckwith, M.A.; DeBeer, S.; Cornell Univ, Dept Chem & Chem Biol, Ithaca, NY 14853 USA.
Identifiers:ISI:000327225900012 [ID No:1]
ISSN:0020-1669 [ID No:2]
DOI:10.1021/ic400821g
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