Unusual chalcogen ••• chalcogen interactions in like ••• like and unlike YQCQY ••• YQCQY complexes (Y = O, S, and Se)

Chalcogen center dot center dot center dot chalcogen interactions were investigated within four types of like center dot center dot center dot like and unlike Y=C=Y center dot center dot center dot Y complexes (where Y = O, S, or Se). A plethora of quantum mechanical calculations, including molecular electrostatic potential (MEP), surface electrostatic potential extrema, point-of-charge (PoC), quantum theory of atoms in molecules (QTAIM), noncovalent interaction (NCI), and symmetry-adapted perturbation theory-based energy decomposition analysis (SAPT-EDA) calculations, were executed. The energetic findings revealed a preferential tendency of the studied chalcogen-bearing molecules to engage in type I, II, III, or IV chalcogenMIDLINE HORIZONTAL ELLIPSISchalcogen interactions. Notably, the selenium-bearing molecules exhibited the most potent ability to favorably participate in all the explored chalcogen center dot center dot center dot chalcogen interactions. Among likeMIDLINE HORIZONTAL ELLIPSISlike complexes, type IV interactions showed the most favorable negative binding energies, whereas type III interactions exhibited the weakest binding energies. Unexpectedly, oxygen-containing complexes within type IV interactions showed an alien pattern of binding energies that decreased along with an increase in the chalcogen atomic size level. QTAIM analysis provided a solo BCP, via chalcogenMIDLINE HORIZONTAL ELLIPSISchalcogen interactions, with no clues as to any secondary ones. SAPT-EDA outlined the domination of the explored interactions by the dispersion forces and indicated the pivotal shares of the electrostatic forces, except type III sigma-hole center dot center dot center dot sigma-hole and di-sigma-hole interactions. These observations demonstrate in better detail all the types of chalcogen center dot center dot center dot Schalcogen interactions, providing persuasive reasons for their more intensive use in versatile fields related to materials science and drug design.