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–X(2)) 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–X(2) 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–X(2) isomers, the barrier for the X(2) hindered rotation, and the influence of the X(2) electronic state. The present integrated study returns reliable force fields for molecular dynamic simulations in Ng–X(2) complexes that can be extended to systems with increasing complexity and whose properties depend on the selective formation of XB.