Halogen–halogen interactions in perhalogenated ethanes: An interacting quantum atoms study

In this paper, intramolecular halogen–halogen interactions in perhalogenated ethanes CX3–CX′3 (X, X′ = F, Cl, Br) were investigated using Bader’s theory of Atoms in Molecules along the potential energy surface defined by the XCCX′ torsion angle. Besides examining the topology of the electron density in terms of critical points, we made use of Pendás’ interacting quantum atoms energy decomposition scheme in order to cast light on the nature of those interactions. Previous conclusions on the important role of the exchange interaction energy in such non-covalent interactions were confirmed, the presence or absence of bond critical points between halogens being rationalized in terms of the competition between primary and secondary exchange channels. Moreover, additional information was inferred from the source function that enables to quantify the role of distant atoms. Finally, we assessed the influence of the chosen computational protocol (basis set and dispersion correction) on the reported energetic decomposition.