Unexplored σ-hole and π-hole interactions in (X2CY)2 complexes (X = F, Cl; Y = O, S)

Abstract

The potentiality of the X2CY molecules (X = F, Cl; Y = O, S) to engage in σ-hole···σ-hole, di-σ-hole, σ-hole···π-hole, and π-hole···π-hole interactions was assessed. In that spirit, potential energy surface (PES) scan was devoted to thoroughly characterize the features of the (X2CY)2 complexes within a series of configurations, including halogen···halogen, halogen···chalcogen, chalcogen···chalcogen, halogen···tetrel, chalcogen···tetrel, and tetrel···tetrel. In most instances, the strength of the inspected interactions declined according to the order: tetrel···tetrel (staggered) > tetrel···tetrel (eclipsed) > chalcogen···tetrel > halogen···tetrel > chalcogen···chalcogen > halogen···chalcogen > halogen···halogen configurations. The strength of the explored complexes within tetrel···tetrel configurations was found to be dominated further by the contributions of the three planar substituents rather than those of the π-hole center. Benchmarking of the binding energies emphasized an approximate similarity between the resulted energetic features that were evaluated at the MP2/aug-cc-pVTZ and CCSD/CBS levels of theory. Quantum theory of atoms in molecules (QTAIM) critically unveiled the closed-shell nature of the halogen-, chalcogen-, and tetrel-bonding interactions within the adopted configurations. Symmetry-adapted perturbation theory-based energy decomposition analysis (SAPT-EDA) demonstrated the domination of the σ-hole interactions by the dispersion forces (Edisp). In addition to the dominant Edisp, preferential contributions of the electrostatic (Eelst) and induction (Eind) forces were detected for the π-hole bonded complexes within all the scouted configurations. The emerging findings from the current work would be a fruitful underpinning for the forthcoming studies in materials science and crystal engineering.