Chalcogen and pnicogen bond interactions are studied in the binary XHS:PH2X complexes (X=F, Cl, CCH, COH, CH3, OH, OCH3, and NH2) using quantum chemical calculations. These interactions can be explained in terms of electrostatic effects, considering the chalcogen or pnicogen as a Lewis acid due to the presence of an σ-hole. Almost a perfect linear relationship is found between the interaction energies and the magnitudes of the product of most positive and negative electrostatic potentials. This reveals that both the negative and positive regions of the interacting atoms can be used to predict the strength of the eventual interaction. The nature of chalcogen and pnicogen bond interactions is unveiled by means of the atoms in molecules (AIM) and electron localization function (ELF) analyses.
