Microsolvation of Sr 2+ , Ba 2+ : Structures, energies, bonding, and nuclear magnetic shieldings

An exhaustive exploration using non–relativistic and four–component relativistic formalisms of the potential energy surfaces for the microsolvation of Sr 2+ , Ba 2+ with up to n  = 6 water molecules is presented in this work. A multitude of well defined local minima stabilized by cation ⋯ water and by water ⋯ water interactions are found. Cation ⋯ water contacts transcend the electrostatic interactions of simplistic ionic bonding. The formal charge causes a chaotropic effect in the structure of the solvent affecting water to water hydrogen bonds and inducing water dissociation and microsolvation of the resulting H + , OH − ions in extreme cases. Relativistic effects are close to 0.7% or smaller in geometries and electronic energies, but they are around 27% for shieldings of Ba 2+ clusters. The nuclei of the central cations are deshielded (around 10% in going from n = 1 to n = 3 ) due to microsolvation.