TY - JOUR
T1 - Hyperfine coupling to the bridging 17O in the Di-μ-oxo core of a MnIII-MnIV model significant to the core electronic structure of the O2-evolving complex in photosystem II
AU - Usov, Oleg M.
AU - Grigoryants, Vladimir M.
AU - Tagore, Ranitendranath
AU - Brudvig, Gary W.
AU - Scholes, Charles P.
N1 - Copyright:
Copyright 2010 Elsevier B.V., All rights reserved.
PY - 2007/10/3
Y1 - 2007/10/3
N2 - Di-μ-oxo MnIII-MnIV dimers are models for coupled, mixed-valence manganese in the oxygen-evolving centers of green plants. Using a recently reported method of exchanging water oxygen into the di-μ-oxo cross-bridges (Tagore, R.; Chen, H.; Crabtree, R. H.; Brudvig, G. W. J. Am. Chem. Soc. 2006, 128, 9457-9465), we have incorporated 17O into the μ-oxo cross bridges of the MnIII-MnIV bipyridyl dimer for study of oxygen electron-spin hyperfine couplings by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). The ENDOR evidence was for a di-μ-oxo 17O hyperfine coupling of 12.8 ± 1.0 MHz. Narrow and highly resolved EPR features from dimers exchanged with H216O (I = 0) became broadened when the dimer was prepared by exchanging the cross bridging oxygens with H217O (I = 5/2). The EPR broadening due to 17O was quantitatively reproduced by a model where the dimer has two equivalent di-μ-oxo cross-bridging 17Ο, and the 17O hyperfine coupling was highly consistent with that determined by ENDOR. This work explicitly points out evidence for covalent spin transfer to the cross-bridging di-μ-oxo oxygens which provide chemical bonds and antiferromagentic coupling between the mixed-valence manganese centers.
AB - Di-μ-oxo MnIII-MnIV dimers are models for coupled, mixed-valence manganese in the oxygen-evolving centers of green plants. Using a recently reported method of exchanging water oxygen into the di-μ-oxo cross-bridges (Tagore, R.; Chen, H.; Crabtree, R. H.; Brudvig, G. W. J. Am. Chem. Soc. 2006, 128, 9457-9465), we have incorporated 17O into the μ-oxo cross bridges of the MnIII-MnIV bipyridyl dimer for study of oxygen electron-spin hyperfine couplings by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). The ENDOR evidence was for a di-μ-oxo 17O hyperfine coupling of 12.8 ± 1.0 MHz. Narrow and highly resolved EPR features from dimers exchanged with H216O (I = 0) became broadened when the dimer was prepared by exchanging the cross bridging oxygens with H217O (I = 5/2). The EPR broadening due to 17O was quantitatively reproduced by a model where the dimer has two equivalent di-μ-oxo cross-bridging 17Ο, and the 17O hyperfine coupling was highly consistent with that determined by ENDOR. This work explicitly points out evidence for covalent spin transfer to the cross-bridging di-μ-oxo oxygens which provide chemical bonds and antiferromagentic coupling between the mixed-valence manganese centers.
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U2 - 10.1021/ja073179n
DO - 10.1021/ja073179n
M3 - Article
C2 - 17850079
AN - SCOPUS:34848901690
VL - 129
SP - 11886
EP - 11887
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 39
ER -