A density functional theoretical study on solvated Al3+-oxalate complexes:structures and thermodynamic properties

Citation
Aja. Aquino et al., A density functional theoretical study on solvated Al3+-oxalate complexes:structures and thermodynamic properties, PHYS CHEM P, 2(13), 2000, pp. 2845-2850
Citations number
29
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
ISSN journal
14639076 → ACNP
Volume
2
Issue
13
Year of publication
2000
Pages
2845 - 2850
Database
ISI
SICI code
1463-9076(2000)2:13<2845:ADFTSO>2.0.ZU;2-#
Abstract
Density functional theory calculations using split-valence polarized basis sets augmented by diffuse s and p functions on the carbon and oxygen atoms were carried out for the complexes of hydrated Al3+ with oxalic acid, and t he oxalate mono- and dianions. Monodentate and bidentate structures with up to three ligands have been computed. The polarized continuum model was use d to study the solvent effect on the structures and stabilities of the comp lexes. Reaction energies for the replacement of water molecules in the alum inum-hexaaquo complex by oxalate ligands have been computed. Based on a det ailed thermodynamical analysis, characteristic differences in the formation of mono- and bidentate structures were found. In the former case the entro py contributions to Delta G are rather small, whereas in the latter case th ey are substantial. Thus, the formation reactions for the monodentate compl exes are energy-driven whereas those for the bidentate complexes are entrop y-driven. In agreement with experiment, the most dominant complex in soluti on is [AlOx(3)](3-). From the complexes with oxalic acid and the partially deprotonated form HOx(-), only the latter should give stable bidentate comp lexes in solution.