Computational Insight into the Nature and Strength of the -Hole Type Chalcogen???Chalcogen Interactions in the XO₂???CH₃YCH₃ Complexes (X = S, Se, Te; Y = O, S, Se, Te)

In recent years, the non-covalent interactions between chalcogen centers have aroused substantial research interest because of their potential applications in organocatalysis, materials science, drug design, biological systems, crystal engineering, and molecular recognition. However, studies on pi-hole-type chalcogencenter dot center dot center dotchalcogen interactions are scarcely reported in the literature. Herein, the pi-hole-type intermolecular chalcogencenter dot center dot center dotchalcogen interactions in the model complexes formed between XO2 (X = S, Se, Te) and CH3YCH3 (Y = O, S, Se, Te) were systematically studied by using quantum chemical computations. The model complexes are stabilized via one primary Xcenter dot center dot center dotY chalcogen bond (ChB) and the secondary C-Hcenter dot center dot center dotO hydrogen bonds. The binding energies of the studied complexes are in the range of -21.6 similar to-60.4 kJ/mol. The Xcenter dot center dot center dotY distances are significantly smaller than the sum of the van der Waals radii of the corresponding two atoms. The Xcenter dot center dot center dotY ChBs in all the studied complexes except for the SO2center dot center dot center dotCH3OCH3 complex are strong in strength and display a partial covalent character revealed by conducting the quantum theory of atoms in molecules (QTAIM), a non-covalent interaction plot (NCIplot), and natural bond orbital (NBO) analyses. The symmetry-adapted perturbation theory (SAPT) analysis discloses that the Xcenter dot center dot center dotY ChBs are primarily dominated by the electrostatic component.