Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure

J. Phys. IV France 7 (1997) C2-603-C2-606
DOI: 10.1051/jp4/1997111

An EXAFS Study of bis(µ-oxo) Bridged Dinuclear Manganese Coordination Compounds as Models for the Manganese Complex of Photosystem II

S. Turconi¹, C. P. Horwitz², Y. Ciringh², S. T. Weintraub³, J. T. Warden⁴, J. H. A. Nugent¹ and M. C. W. Evans<sup>1

1</sup>  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.

Abstract
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