Cooperative effect between the chalcogen (Ch…N) and dihydrogen(H…H) bonds in the series of XHTe…NCH…HY (X=F, Cl, Br, I, H, Y=Li,Na, BeH, MgH) and FHCh…NCH…HNa (Ch=Te, Se, S) triads

Focus on the bonds between molecules instead of bonds between atoms, results in thecreation of large molecules with unusual structures and different physical and chemicalproperties, which are useful for various applications([۱]). Such interactions lead to a tremendousincrease in the variety of crystal architectures and thus properties to be discovered([۲]).There aresome well-known methodologies for evaluating the degree of cooperativity of noncovalentbonds, but herein we emphasize on our proposed methodology that evaluates the origin of thecooperativity of bonds. Cooperative energy of chalcogen and dihydrogen bonds in some ABCtriad systems of the typesXHTe…NCH…HY (X=F, Cl, Br, I, H, Y=Li, Na, BeH, MgH) andFHCh…NCH…HNa (Ch=Te, Se, S) were computed and compared at MP۲/TZVPPD,BP۸۶/TZVPPD, BP۸۶-D۳/TZVPPD, and BP۸۶-D۳/QZVP levels of theory. The cooperativeenergies were evaluated using two different equations/methods, on the basis of interactionenergies versus stabilization energies of the triads and corresponding dyads. In addition, anumber of good to excellent correlations were observed between the interaction, stabilization,and cooperative energies and change in Te…N and H…H bond lengths upon the formation oftriads from the corresponding dyads. All resulting data showed that the strengths of chalcogen(Te…N) and dihydrogen (H…H) bonds increase in the order of H< I < Br < Cl < F, and Be < Mg< Li < Na, respectively. Thus, the shortest Te…N and H…H bond lengths and the largest valuesof interaction, stabilization, and cooperative energies were observed for FHTe…NCH…HNatriad. Then, the resulting data for the above triad were compared with those forFHSe…NCH…HNa and FHS…NCH…HNa triads. The data showed that the interaction,stabilization, and cooperativity energies decrease in the order of Te > Se > S. Also, it was shownthat the more electronegative fluorine atom bonded to chalcogen atom would have nomeaningful effect on the strengths of the Ch…N bond and its cooperativity with the H…H bondin present triad complexes, when F−Ch bond is not along Ch…N bond. Finally, the nature ofboth dihydrogen and chalcogen bonds and the origin of the cooperativity of bonds wereevaluated by NBO and EDA analyses([۳]).