The Halogen-Bond Nature in Noble Gas-Dihalogen Complexes from Scattering Experiments and Ab Initio Calculations

In order to clarify the nature of the halogen bond (XB), we considered the prototype noble gas-dihalogen molecule (Ng-X₂) systems, focusing on the nature, range, and strength of the interaction. We exploited data gained from molecular beam scattering experiments with the measure of interference effects to obtain a suitable formulation of the interaction potential, with the support of high-level ab initio calculations, and charge displacement analysis. The essential interaction components involved in the Ng-X₂ adducts were characterized, pointing at their critical balance in the definition of the XB. Particular emphasis is devoted to the energy stability of the orientational Ng-X₂ isomers, the barrier for the X₂ hindered rotation, and the influence of the X₂ electronic state. The present integrated study returns reliable force fields for molecular dynamic simulations in Ng-X₂ complexes that can be extended to systems with increasing complexity and whose properties depend on the selective formation of XB.