The Degree and Origin of the Cooperativity of the Chalcogen (Ch···N) and Dihydrogen (H···H) Bonds in Some Triad Systems.

The strength and cooperative energy of chalcogen and dihydrogen bonds in some ABC triad systems of the types XHTe…NCH…HY (X = F, Cl, Br, I, H; Y = Li, Na, BeH, MgH) and FHCh…NCH…HNa (Ch = Te, Se, S) were computed and compared at several levels of theory. 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. Then, the comparison of data for the FHTe…NCH…HY, FHSe…NCH…HNa, and FHS…NCH…HNa triads indicated that the interaction, stabilization, and cooperativity energies decrease in the order of Te > Se > S. The data show that in all cases the chalcogen and dihydrogen bonds change the bond dissociation energies (BDEs) and interaction energies (IEs) of each other by the same quantitative value. However, the relative impact of the above bonds on BDEs and IEs of each other depends on the relative strength of these bonds. Finally, the nature of both dihydrogen and chalcogen bonds and the origin of the cooperativity of bonds were evaluated by NBO and energy decomposition analysis (EDA) analyses.