J. Phys. IV France 7 (1997) C2-603-C2-606
An EXAFS Study of bis(µ-oxo) Bridged Dinuclear Manganese Coordination Compounds as Models for the Manganese Complex of Photosystem IIS. Turconi1, C. P. Horwitz2, Y. Ciringh2, S. T. Weintraub3, J. T. Warden4, J. H. A. Nugent1 and M. C. W. Evans1
1 Department of Biology, University College London, London WC1E 6BT, UK
2 Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213-3890, U.S.A.
3 Department of Biochemistry, The University of Texas Health Science Center, San Antonio, TX 78284, U.S.A.
4 Department of Chemistry, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, U.S.A.
A complex containing four manganese centres is thought to be the catalytic site of photosynthetic water oxidation. The structure and mechanism of action of this complex are largely unknown. Mn-coordination complexes can be used as models for the manganese complex of Photosystem II (PS II). We report here an X-ray Absorption Spectroscopic study of seven different manganese coordination compounds, six of which are binuclear and contain the structural bis (µ-oxo) unit. In all the compounds, manganese is ligatedby 3,3'-17-crown-6-SALPN, providing one crown ether moiety perMn centre. Alkali or alkaline-earth cations were introduced into this crown-ether moiety in binuclear complexes, bringing the cations (Na+ , K+ , Ca2+ and Ba2+) into the vicinity (< 4Å) of the manganese. The results are discussed in terms of their relevance to the PS II manganese complex.
© EDP Sciences 1997