The influence of water molecule coordination onto the water–aromatic interaction. Strong interactions of water coordinating to a metal ion

Abstract

The interactions between water molecules (non-coordinating and coordinating) and aromatic rings were studied by analyzing data in the Cambridge Structural Database and by quantum chemical calculations. The results show the influence of water coordination to a metal ion; interactions of coordinating water are stronger. The MP2/def2-QZVP interaction energies of non-coordinating water and neutral aqua complexes [ScCl₃(H₂O)₃], [ZnCl₂(H₂O)₄], [CdCl₂(H₂O)₄], and [ZnCl₂(H₂O)₂] with benzene molecule are −3.36, −5.10, −5.43, −6.86, and −5.14 kcal mol⁻¹, respectively. Interactions of charged aqua complexes [ZnCl(H₂O)₅]⁺ and [Zn(H₂O)₆]²⁺ are stronger, −9.69 and −13.96 kcal mol⁻¹, respectively. The calculations also reveal strong long-range interactions: at the distance of 3.0 Å the interaction energies of neutral complexes are in the range of −4.11 to −4.91 kcal mol⁻¹, while interaction energies of charged complexes are −6.37 and −10.76 kcal mol⁻¹.