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X-ray absorption spectroscopy of aqueous aluminum-organic complexes.
MedLine Citation:
PMID:  20443586     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
Aqueous-phase X-ray absorption near-edge structure (XANES) spectra were collected on dissolved Al complexes with organic ligands, including desferrioxamine B, EDTA, acetohydroxamate, malate, oxalate, and salicylate. Spectral interpretations were made using the density functional theory-based modeling package StoBe. The goals of this work were to study the geometric and electronic structural characteristics of these complexes relative to Al(H(2)O)(6)(3+) and to examine the utility of the aqueous Al XANES technique as a tool for probing Al speciation and structure. In the case of EDTA, aqueous Fourier-transform infrared spectroscopy was also used to corroborate the structures of the Al(EDTA)(-) and AlOH(EDTA)(2-) complexes. Synthetic XANES spectra calculated with StoBe reproduced the observed spectral differences between Al(H(2)O)(6)(3+), Al(dfoB)(+), and Al(EDTA)(-). The narrower XANES feature observed for Al(dfoB)(+) relative to Al(H(2)O)(6)(3+) can be attributed to a weaker splitting of the Al 3p-O 2p interactions in the former, while Al(EDTA)(-) exhibits split Al 3p-ligand interactions that likely result from the mixed O/N coordination. In complexes with mixed aqua/organic-oxygen ligation (Al-acetohydroxamate, Al-malate, Al-oxalate, and Al-salicylate), spectra exhibit linear, systematic changes in peak width as a function of H(2)O to organic ligand ratio in the Al coordination sphere. These results highlight the sensitivity of the aqueous Al K-edge XANES spectrum to coordination environment and demonstrate its utility as an experimental probe for future studies of Al speciation in complex solutions.
Authors:
Michael B Hay; Satish C B Myneni
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  114     ISSN:  1520-5215     ISO Abbreviation:  J Phys Chem A     Publication Date:  2010 May 
Date Detail:
Created Date:  2010-05-20     Completed Date:  2010-05-24     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  6138-48     Citation Subset:  -    
Affiliation:
Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey 08544, USA. mbhay@usgs.gov
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