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Title: X-ray emission spectroscopy of biomimetic Mn coordination complexes

Abstract

Understanding the function of Mn ions in biological and chemical redox catalysis requires precise knowledge of their electronic structure. X-ray emission spectroscopy (XES) is an emerging technique with a growing application to biological and biomimetic systems. Here, we report an improved, cost-effective spectrometer used to analyze two biomimetic coordination compounds, [Mn IV(OH) 2(Me 2EBC)] 2+ and [Mn IV(O)(OH)(Me 2EBC)] +, the second of which contains a key Mn IV=O structural fragment. Despite having the same formal oxidation state (Mn IV) and tetradentate ligands, XES spectra from these two compounds demonstrate different electronic structures. Experimental measurements and DFT calculations yield different localized spin densities for the two complexes resulting from Mn IV–OH conversion to Mn IV=O. The relevance of the observed spectroscopic changes is discussed for applications in analyzing complex biological systems such as photosystem II. In conclusion, a model of the S 3 intermediate state of photosystem II containing a Mn IV=O fragment is compared to recent time-resolved X-ray diffraction data of the same state.

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1364024
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 8; Journal Issue: 12; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Jensen, Scott C., Davis, Katherine M., and Sullivan,. X-ray emission spectroscopy of biomimetic Mn coordination complexes. United States: N. p., 2017. Web. doi:10.1021/acs.jpclett.7b01209.
Jensen, Scott C., Davis, Katherine M., & Sullivan,. X-ray emission spectroscopy of biomimetic Mn coordination complexes. United States. doi:10.1021/acs.jpclett.7b01209.
Jensen, Scott C., Davis, Katherine M., and Sullivan,. Fri . "X-ray emission spectroscopy of biomimetic Mn coordination complexes". United States. doi:10.1021/acs.jpclett.7b01209. https://www.osti.gov/servlets/purl/1364024.
@article{osti_1364024,
title = {X-ray emission spectroscopy of biomimetic Mn coordination complexes},
author = {Jensen, Scott C. and Davis, Katherine M. and Sullivan,},
abstractNote = {Understanding the function of Mn ions in biological and chemical redox catalysis requires precise knowledge of their electronic structure. X-ray emission spectroscopy (XES) is an emerging technique with a growing application to biological and biomimetic systems. Here, we report an improved, cost-effective spectrometer used to analyze two biomimetic coordination compounds, [MnIV(OH)2(Me2EBC)]2+ and [MnIV(O)(OH)(Me2EBC)]+, the second of which contains a key MnIV=O structural fragment. Despite having the same formal oxidation state (MnIV) and tetradentate ligands, XES spectra from these two compounds demonstrate different electronic structures. Experimental measurements and DFT calculations yield different localized spin densities for the two complexes resulting from MnIV–OH conversion to MnIV=O. The relevance of the observed spectroscopic changes is discussed for applications in analyzing complex biological systems such as photosystem II. In conclusion, a model of the S3 intermediate state of photosystem II containing a MnIV=O fragment is compared to recent time-resolved X-ray diffraction data of the same state.},
doi = {10.1021/acs.jpclett.7b01209},
journal = {Journal of Physical Chemistry Letters},
number = 12,
volume = 8,
place = {United States},
year = {Fri May 19 00:00:00 EDT 2017},
month = {Fri May 19 00:00:00 EDT 2017}
}

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