title: Ligand K-edge X-ray absorption spectroscopy: a direct probe of ligand-metal covalency.
abstract: Ligand K-edge X-ray absorption spectroscopy (XAS) is a new experimental probe of the covalency of a metal-ligand bond. The intensity of the ligand pre-edge feature is proportional to the mixing of ligand orbitals into the metal d orbitals. The methodology to determine covalencies in one-electron (hole) and many-electron systems is described and demonstrated for a series of metal tetrachlorides [MCl(4)](n)(-), metal tetrathiolates [M(SR)(4)](n)(-), and dimeric iron-sulfur (Fe-S) clusters [Fe(2)S(2)(SR)(4)](2-). It is then applied to blue Cu proteins, the Cu(A) site, hydrogen bonding in Fe-S clusters, and the delocalization behavior in [2Fe-2S] vs [4Fe-4S] clusters. The covalencies determined in these studies provide important electronic structure insight into function.
authors: Department of Chemistry, Stanford University, Stanford, California 94305, USA.
authors: T
authors: T
authors: Glaser
authors: B
authors: B
authors: Hedman
authors: K O
authors: KO
authors: Hodgson
authors: E I
authors: EI
authors: Solomon
mesh_terms: D004577:Electron Probe Microanalysis / Q000379:methods*; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D015394:Molecular Structure
chemical_list: D008024:Ligands; D008670:Metals