Structure and dynamic behavior of transition-metal ions in aqueous solution: an EXAFS study of electron-exchange reactions

Journal Article · Wed Aug 27 04:00:00 EDT 1980 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00538a033· OSTI ID:5130836

Sham, T K; Hastings, J B; Perlman, M L

The extended x ray absorption fine structure (EXAFS) phenomenon has become a powerful tool for structure determination in the immediate vicinity of an atom of identified Z. In this paper, the power of EXAFS for the study of kinetics and reaction mechanisms in solution are demonstrated. Of particular concern here are the metal-ligand bond distances and the associated Debye-Waller factors of M(H/sub 2/O)/sub 6//sup n+/ complexes in aqueous solution. The metal-oxygen interatomic distances for Cr/sup 3 +/, Cr/sup 2 +/, Mn/sup 2 +/, Fe/sup 2 +/, Fe/sup 3 +/ and Cu/sup 2 +/ obtained by EXAFS are tabulated and compared with reference values of those obtained from solution x-ray scattering experiments and single crystal diffraction work. Although it appears that for these ions in solution the EXAFS r values are slightly smaller than those from diffraction measurements, the differences are within experimental error. With the bond lengths and Debye-Waller information obtained directly from ions in solution the parameters relevant to the kinetics of the electron-exchange reaction can be estimated. For Fe(H/sub 2/)/sub 6//sup 2 +/ and Fe(H/sub 2/O)/sub 6//sup 3 +/, the difference between the Fe to 0 radii of the two ions, r/sup 2/ - r/sup 3/ is the most critical parameter. The relationship connecting the EXAFS parameters and the electron-exchange reaction is shown mathematically. The Debye-Waller factor derived from the EXAFS data also contains important bonding information.

• Research Organization: Brookhaven National Lab., Upton, New York
• OSTI ID: 5130836
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 102:18; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTRA
AQUEOUS SOLUTIONS
BOND LENGTHS
CATIONS
CHARGED PARTICLES
CHROMIUM COMPLEXES
COMPLEXES
COPPER COMPLEXES
DEBYE-WALLER FACTOR
DIMENSIONS
DISPERSIONS
DISTANCE
ELECTRON EXCHANGE
ELECTRON TRANSFER
INTERATOMIC DISTANCES
IONS
IRON COMPLEXES
LENGTH
MANGANESE COMPLEXES
MIXTURES
MOLECULAR STRUCTURE
SOLUTIONS
SPECTRA
SPECTROSCOPY
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY