Fe L-Edge X-ray absorption spectroscopy determination of differential orbital covalency of siderophore model compounds: electronic structure contributions to high stability constants

Hocking, Rosalie K., George, Serena DeBeer, Raymond, Kenneth N., Hodgson, Keith O., Hedman, Britt, and Solomon, Edward I. (2010) Fe L-Edge X-ray absorption spectroscopy determination of differential orbital covalency of siderophore model compounds: electronic structure contributions to high stability constants. Journal of the American Chemical Society, 132 (11). pp. 4006-4015.

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Abstract

Most bacteria and fungi produce low-molecular-weight iron chelators called siderophores. Although different siderophore structures have been characterized, the iron-binding moieties often contain catecholate or hydroxamate groups. Siderophores function because of their extraordinarily high stability constants (K-STAB = 10³⁰-10⁴⁹) and selectivity for Fe(III), yet the origin of these high stability constants has been difficult to quantify experimentally. Herein, we utilize Fe L-edge X-ray absorption spectroscopy to determine the differential orbital covalency (i.e., the differences in the mixing of the metal d-orbitals with ligand valence orbitals) of a series of siderophore model compounds. The results enable evaluation of the electronic structure contributions to their high stability constants in terms of sigma- and pi-donor covalent bonding, ionic bonding, and solvent effects. The results indicate substantial differences in the covalent contributions to stability constants of hydroxamate and catecholate complexes and show that increased sigma as well as pi bonding contributes to the high stability constants of catecholate complexes.

Item ID: 28895
Item Type: Article (Research - C1)
ISSN: 1520-5126
Date Deposited: 21 Aug 2013 09:22
FoR Codes: 03 CHEMICAL SCIENCES > 0302 Inorganic Chemistry > 030201 Bioinorganic Chemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970103 Expanding Knowledge in the Chemical Sciences @ 100%
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