Microsolvation of Sr2+, Ba2+: 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 Sr2+, Ba2+ with up to n = 6 water molecules is presented in this work. A multitude of well defined local minima stabilized by cation MIDLINE HORIZONTAL ELLIPSIS water and by water MIDLINE HORIZONTAL ELLIPSIS water interactions are found. Cation MIDLINE HORIZONTAL ELLIPSIS 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 Ba2+ clusters. The nuclei of the central cations are deshielded (around 10% in going from n=1 to n=3) due to microsolvation.

Automated summary

In this work, an exhaustive exploration of the potential energy surfaces for the microsolvation of Sr2+ and Ba2+ with up to n=6 water molecules using non-relativistic and four-component relativistic formalisms is presented. The interactions between cation and water, as well as water-water interactions, were found to form stable local minima. The formal charge was shown to have a chaotropic effect on the solvent structure, affecting water-water hydrogen bonds and inducing water dissociation in extreme cases.