Ab Initio and Crystal Structure Analysis of Like-Charged Ion Pairs

A combined approach of crystallographic analyses and ab initio molecular orbital computations provides strong support to the previous theoretical finding of the possible existence of a stable Cl₂²⁻ aggregate in water. Consistent with previous explanations, the stabilization of like-charged ion pairs in aqueous solution was rationalized by the Born model of solvation and the solvent-bridged hydrogen-bonding interactions that offset Coulombic repulsion between the two anions. Analysis of the Cambridge Structural Database revealed correlation patterns in hydrogen-bonding interaction. Further, the ab initio results were compared with those predicted using empirical potential functions and good agreement was obtained.