Interaction of acetate anion with hydrated Al3+ cation: A theoretical study

Density-functional theory (DFT) methods were used for investigations on the aluminum-hexaaquo complex and on aqueous aluminum-acetate complexes. Solve nt effects were computed by means of the polarized continuum model (PCM). E xtensive basis set studies and comparison of several functionals lead to ef ficient and accurate procedures which were applied to the computation of al uminum-acetate complexes. A variety of structural arrangements such as mono dentate or bidentate with respect to the bonding of the carboxylate group o r cis/trans with respect to the relative position of two acetate molecules were considered, Delta H and Delta G values were calculated for the substit ution reaction of water molecules in the aluminum-hexaaquo complex by aceta te anions, Characteristic differences in Delta S were found depending on th e number of water molecules released per acetate, Overall, we find that mon odentate structures are only slightly preferred over bidentate ones and tha t we expect a relatively complicated system of chemical equilibria without any dominant complex.