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Bridging-type changes facilitate successive oxidation steps at about 1 V in two binuclear manganese complexes - implications for photosynthetic water-oxidation

Magnuson, A.; Liebisch, P.; Högblom, Joakim LU ; Anderlund, M. F.; Lomoth, R.; Meyer-Klaucke, W.; Haumann, M. and Dau, H. (2006) In Journal of Inorganic Biochemistry 100(7). p.1234-1243
Abstract
The redox behavior of two synthetic manganese complexes illustrates a mechanistic aspect of importance for light-driven water oxidation in Photosystem 11 (PSII) and design of biomimetic systems (artificial photosynthesis). The coupling between changes in oxidation state and structural changes was investigated for two binuclear manganese complexes (1 and 2), which differ in the set of first sphere ligands to Mn (N3O3 in 1, N2O4 in 2). Both complexes were studied by electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) in three oxidation states which had been previously prepared either electro- or photochemically. The following bridging-type changes are suggested. In 1: Mn-II-(mu-OR)(mu-OCO)(2)-Mn-II double left right... (More)
The redox behavior of two synthetic manganese complexes illustrates a mechanistic aspect of importance for light-driven water oxidation in Photosystem 11 (PSII) and design of biomimetic systems (artificial photosynthesis). The coupling between changes in oxidation state and structural changes was investigated for two binuclear manganese complexes (1 and 2), which differ in the set of first sphere ligands to Mn (N3O3 in 1, N2O4 in 2). Both complexes were studied by electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) in three oxidation states which had been previously prepared either electro- or photochemically. The following bridging-type changes are suggested. In 1: Mn-II-(mu-OR)(mu-OCO)(2)-Mn-II double left right arrow Mn-II-(mu-OR)(mu-OCO)(2)-Mn-III double right arrow Mn-III-(mu-OR)(mu-OCO)-(mu-O)-Mn-IV. In 2: Mn-II-(mu-OR)(mu-OCO)(2)-Mn-III double left right arrow Mn-III-(mu-OR)(mu-OCO)(2)-Mn-III double right arrow Mn-III-(mu-OR)([mu-OCO)(mu-O)-Mn-IV. In both complexes, the first one-electron oxidation proceeds without bridging-type change, but involves a redox-potential increase by 0.5-1 V. The second one-electron oxidation likely is coupled to mu-oxo-bridge (or mu-OH) formation which seems to counteract a further potential increase. In both complexes, mu-O(H) bridge formation is associated with a redox transition proceeding at similar to 1 V, but the mu-O(H) bridge is observed at the Mn-2(III,III) level in I and at the Mn-III,Mn-IV level in 2, demonstrating modulation of the redox behavior by the terminal ligands. It is proposed that also in PSII bridging-type changes facilitate successive oxidation steps at approximately the same potential. (c) 2006 Elsevier Inc. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
absorption spectroscopy, photosynthesis, manganese complex, biomorganic chemistry, EPR, X-ray
in
Journal of Inorganic Biochemistry
volume
100
issue
7
pages
1234 - 1243
publisher
Elsevier
external identifiers
  • wos:000238939200010
  • pmid:16584782
  • scopus:33744509523
ISSN
1873-3344
DOI
10.1016/j.jinorgbio.2006.02.001
language
English
LU publication?
yes
id
fe80922b-423c-48b0-8698-5a641e7948e2 (old id 402170)
date added to LUP
2007-10-09 13:54:59
date last changed
2019-09-17 02:57:53
@article{fe80922b-423c-48b0-8698-5a641e7948e2,
  abstract     = {The redox behavior of two synthetic manganese complexes illustrates a mechanistic aspect of importance for light-driven water oxidation in Photosystem 11 (PSII) and design of biomimetic systems (artificial photosynthesis). The coupling between changes in oxidation state and structural changes was investigated for two binuclear manganese complexes (1 and 2), which differ in the set of first sphere ligands to Mn (N3O3 in 1, N2O4 in 2). Both complexes were studied by electron paramagnetic resonance (EPR) and X-ray absorption spectroscopy (XAS) in three oxidation states which had been previously prepared either electro- or photochemically. The following bridging-type changes are suggested. In 1: Mn-II-(mu-OR)(mu-OCO)(2)-Mn-II double left right arrow Mn-II-(mu-OR)(mu-OCO)(2)-Mn-III double right arrow Mn-III-(mu-OR)(mu-OCO)-(mu-O)-Mn-IV. In 2: Mn-II-(mu-OR)(mu-OCO)(2)-Mn-III double left right arrow Mn-III-(mu-OR)(mu-OCO)(2)-Mn-III double right arrow Mn-III-(mu-OR)([mu-OCO)(mu-O)-Mn-IV. In both complexes, the first one-electron oxidation proceeds without bridging-type change, but involves a redox-potential increase by 0.5-1 V. The second one-electron oxidation likely is coupled to mu-oxo-bridge (or mu-OH) formation which seems to counteract a further potential increase. In both complexes, mu-O(H) bridge formation is associated with a redox transition proceeding at similar to 1 V, but the mu-O(H) bridge is observed at the Mn-2(III,III) level in I and at the Mn-III,Mn-IV level in 2, demonstrating modulation of the redox behavior by the terminal ligands. It is proposed that also in PSII bridging-type changes facilitate successive oxidation steps at approximately the same potential. (c) 2006 Elsevier Inc. All rights reserved.},
  author       = {Magnuson, A. and Liebisch, P. and Högblom, Joakim and Anderlund, M. F. and Lomoth, R. and Meyer-Klaucke, W. and Haumann, M. and Dau, H.},
  issn         = {1873-3344},
  keyword      = {absorption spectroscopy,photosynthesis,manganese complex,biomorganic chemistry,EPR,X-ray},
  language     = {eng},
  number       = {7},
  pages        = {1234--1243},
  publisher    = {Elsevier},
  series       = {Journal of Inorganic Biochemistry},
  title        = {Bridging-type changes facilitate successive oxidation steps at about 1 V in two binuclear manganese complexes - implications for photosynthetic water-oxidation},
  url          = {http://dx.doi.org/10.1016/j.jinorgbio.2006.02.001},
  volume       = {100},
  year         = {2006},
}