Theoretical investigation of dehydration of aquated Al(OH)2+ species in aqueous solution

Abstract

Reaction pathways, solvent effects and energy barriers have been investigated for the dehydration processes of aquated Al(OH)(2)(+) species in aqueous solution by density functional calculations using a supermolecule model. The dehydration processes from Al(H(2)O)(4)(OH)(2)(+) to Al(H(2)O)(2)(OH)(2)(+) involve the water exchange on cis-Al(H(2)O)(4)(OH)(2)(+) and dehydration of the following intermediate pentacoordinate Al(H(2)O)(3)(OH)(2)(+). The calculated results indicate that cis-Al(H(2)O)(4)(OH)(2)(+) exchanges water in a dissociative way with an activation energy of 27.7 kJ mol(-1). Loss of coordinated water from hexacoordinate and pentacoordinate Al(OH)(2)(+) is unfavourable by 22.1 and 6.6 kJ mol(-1), respectively, which supports the presence of the stable hexacoordinate Al(H(2)O)(4)(OH)(2)(+) in aqueous solution. Our results also indicate that both the explicit water molecules and bulk water molecules have great influences on the energy barriers, and they can not be neglected.