| Abstract
| - The geometries and energetics of complexes of Li+, Na+, K+, Be2+, Mg2+, and Ca2+metal cations withdifferent possible uric acid anions (urate) were studied. The complexes were optimized at the B3LYP leveland the 6-311++G(d,p) basis set. Complexes of urate with Mg2+, and Ca2+metal cations were also optimizedat the MP2/6-31+G(d) level. Single point energy calculations were performed at the MP2/6-311++G(d,p)level. The interactions of the metal cations at different nucleophilic sites of various possible urate wereconsidered. It was revealed that metal cations would interact with urate in a bicoordinate manner. In the gasphase, the most preferred position for the interaction of Li+, Na+, and K+ cations is between the N3 and O2sites, while all divalent cations Be2+, Mg2+, and Ca2+ prefer binding between the N7 and O6 sites of thecorresponding urate. The influence of aqueous solvent on the relative stability of different complexes hasbeen examined using the Tomasi's polarized continuum model. The basis set superposition error (BSSE)corrected interaction energy was also computed for complexes. The AIM theory has been applied to analyzethe properties of the bond critical points (electron densities and their Laplacians) involved in the coordinationbetween urate and the metal cations. It was revealed that aqueous solvation would have significant effect onthe relative stability of complexes obtained by the interaction of urate with Mg2+ and Ca2+cations.Consequently, several complexes were found to exist in the water solution. The effect of metal cations ondifferent NH and CO stretching vibrational modes of uric acid has also been discussed.
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