Web Release Date: February 23,
Coordination Studies of Al-EDTA in Aqueous Solution
and
Physical and Chemical Properties Division, National Institute of Standards and Technology, 100 Bureau Drive, Mail Stop 8380, Gaithersburg, Maryland 20889, and Synchrotron Radiation Laboratory, Stanford University, 2575 Sand Hill Road, Palo Alto, California 94025
Received: October 9, 2007
In Final Form: December 9, 2007
Abstract:
The degree of aluminum toxicity is based on its complexation with organic ligands. One of these complexes is AlEDTA- (Al = aluminum, EDTA = ethylenediaminetetraacetate), the structure of which in aqueous solution has been debated on the basis of X-ray absorption and NMR measurements with different interpretations proposing different coordination. In addition, there is a lack of consensus regarding the relationship of crystalline AlEDTA- and its geometry in solution. This debate must be resolved, not merely for scientific interest, but because the use of an incorrect coordination might lead to the wrong interpretation of bioactivity and kinetics data. In this work, we predict the coordination of Al in aqueous AlEDTA- by employing ab initio calculations and Car-Parrinello molecular dynamics simulations. Our results indicate that AlEDTA- favors Al in octahedral coordination in aqueous solution. Furthermore, the predicted crystalline and solution-phase structures of AlEDTA- are similar and agree well with recent X-ray measurements, supporting the strong chelating nature of this metal-organic complex in aqueous solution.
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