The Role of Electronic Distribution and Charge Trasfer in Weak Halogen Bond by Molecular Beam Scattering Experiments and Ab-initio Calculations

The systems studied in this work are gas-phase weakly-buond adducts of the noble gas atoms Ng (He, Ne, Ar) with CCl4 and CF4. Their investigation was motivated by the widespread current interest for the intermolecular halogen bond, a structural motif recognized to play a role in fields ranging from elementary processes to biochemistry. We have performed also high-resolution molecular-beam scattering experiments to measure the absolute scale of the intermolecular potentials for such systems, with high sensitivity. The obtained experimental data can be properly reproduced only including a shifting of the repulsive intermolecular potential walls at shorter distances, and an additional short-range stabilization component. To put these findings ohm a firmer ground, we performed, for selected geometries of the complexes, accurate theoretical calculations aimed to evaluate the intermolecular interaction, and the effects of the complexation on the electron charge density of the constituting moieties.