Bond analysis in dihalogen–halide and dihalogen– dimethylchalcogenide systems

The bonding in mixed chalcogen/halogen three- body systems of general formula XI···Y (X = Cl, Br, I; Y = I–, EMe2; E = S, Se, Te) is theoretically examined by using different methodologies, namely: charge-displacement (CD) analysis, which quantifies the electronic flux throughout the whole ad- duct; the energy decomposition analysis combined with natural orbital for chemical valence (EDA-NOCV) method; and zeroth order symmetry adapted perturbation theory (SAPT0), where the latter two methods decompose the contributions of the interaction energy between XI and Y into physically meaningful terms. In the solid state, the distribution of the relative elonga- tions of the two bonds (δXI and δIY) in the three-body systems examined here can be rationalized in terms of only one com- mon equation derived from the bond-valence model. According to CD and EDA-NOCV, the charge transfer between the two fragments does not depend on the exact nature of the atoms involved, but only on the values of δXI and δIY, with a variability of 0.05 e, and on the total charge of the system. On the other hand, using the SAPT0 method and computing the polariza- tion-free value of the charge transfer between the two frag- ments, the results are the same for all of the systems with the same δXI and δIY, irrespectively not only of the nature of the atoms, but also of the total charge of the system (anionic and neutral).