THE GEOMETRIES AND PROTON TRANSFER OF HYDRATED DIVALENT LEAD ION CLUSTERS [Pb(H2O)n]2+ (n=1-17)

The low-lying candidates of hydrated divalent lead ion clusters [Pb(H2O)(n)](2+) with up to n = 17 have been extensively studied by using density functional theory (DFT) at B3LYP level. The optimized structures show that for n - 5 - 13 the lowest-energy structures prefer tetra-coordinate with hemi-directed geometries, while the best candidates with n = 14-17 are hexacoordinate with holo-directed geometries, which is just consistent with the experimental observation. Furthermore, the origin of hemi-directed and holo-directed geometries has been revealed. It is found that in the hemi-directed geometries, the lone pair orbital has p character and fewer electrons are transferred from the water molecules to the Pb2+ ion. Contrarily, in the holo-directed geometries, the lone pair orbital has little or no p character and more electrons are transferred to the Pb2+ ion. On the other hand, the proton transfer reactions of the [Pb(H2O)(n)](2+) (n = 2, 4, 8) complexes have been examined, from which the predicted products of these complexes are in good agreement with the experimental observation.