Ligand K-edge x-ray adsorption spectroscopic studies of the electronic structure of inorganic model complexes and metalloprotein active sites [Thesis]
- Stanford Univ., CA (United States)
Ligand K-edge X-ray absorption spectroscopy (XAS) has been developed as a technique for the investigation of ligand-metal bonding and has been applied to the study of electronic structure in organic model complexes and metalloprotein active sites. Ligand K-edge XAS has been measured at the chloride K-edge for a series of complexes containing chloride ligands bound to open shell d copper ions. The intensity of the pre-edge feature in these spectra reflects the covalency in the half-occupied d{sub x}2{sub {minus}y}2-derived molecular orbital (HOMO) of the complex. The energy of the pre-edge feature is related to both the charge on the ligand and the HOMO energy. An analysis of the intensity and energy of the pre-edge feature as well as the energy of the rising edge absorption provides quantitative information about the covalency of the ligand-metal interaction, the charge donated by the chloride, and the energy of the copper d-manifold. The results demonstrate that ligand K-edge XAS features can be used to obtain quantitative information about ligand-metal bonding. The results also identify the chemical basis for trends in the XAS data for the complexes: D{sub 4h}CuC1{sub 4}{sup 2{minus}}, D{sub 2d}CuC1{sub 4}{sup 2{minus}}, planar, trans-CuC1{sub 2}(pdmp){sub 2} (pdmp=N-phenyl-3,5-dimethyl- pyrazole), square pyramidal CuCl{sub 5}{sup 3{minus}}, the planar dimer KCuCl{sub 3}, the distorted tetrahedral dimer (Ph{sub 4}P)CuC1{sub 3}, and two dimers with mixed ligation, one containing a bridging chloride, and the other, terminally bound chloride. A geometric distortion from square planar to distorted tetrahedral results in a decrease in the chloride-copper HOMO covalency but an increase in the total charge donation by the chlorides. Thus, while the geometry can maximize the overlap for a highly covalent HOMO, this does not necessarily reflect the overall charge donation. The Cl-Cu(II) bonding interactions are dependent on the nature of the other coordinating ligands.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 10194914
- Report Number(s):
- SLAC-449; SLAC/SSRL-0088; SLAC-R-449; ON: DE95003338; TRN: 94:024086
- Resource Relation:
- Other Information: PBD: Aug 1994
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
LIGANDS
ABSORPTION SPECTROSCOPY
X-RAY SPECTROSCOPY
METALLOPROTEINS
ELECTRONIC STRUCTURE
METALS
CHEMICAL BONDS
CHLORIDES
COPPER COMPLEXES
IRON COMPLEXES
550200
440101
BIOCHEMISTRY
GENERAL DETECTORS OR MONITORS AND RADIOMETRIC INSTRUMENTS