Nghiên cứu vai trò của các tương tác trong việc làm bền các phức giữa CO2 với C2H3X (X = H, F, Cl, Br)

Abstract

The interactions of ethylene and its monohalogen–substituted derivatives with CO₂ were investigated. Interaction energies of 16 stable complexes obtained range from -1.13 to -5.57 kJ.mol^-1 at the CCSD(T)/aug-cc-pVDZ//MP2/aug-cc-pVDZ level. The stability of the C₂H₄∙∙∙ CO₂ complex is determined by the π∙∙∙π interaction which is due to electron density transfer from MO-π(C=C) to MO‑π^*(C=O) dominating the transition from MO-π(C=O) to MO-π^*(C=C). Remarkably, contribution of the π∙∙∙π interaction to strength of complex of CO₂-philic compounds and CO₂ has been revealed for the first time. Substitution of an H atom by a halogen in C₂H₄ makes CO₂∙∙∙C₂H₃X (X = F, Cl, Br) slightly more stable than CO₂∙∙∙C₂H₄, and all the halogenated derivatives have equivalent stability. The strength of CO₂∙∙∙C₂H₃X which is contributed by Lewis acid-base interaction, attractive electrostatic interaction and hydrogen bond, is different from the case of CO₂∙∙∙C₂H₄. The obtained results also show that, upon complexation, a contraction of C-H bond length involved in hydrogen bond and an increase in its stretching frequency are affected by shape of the complex beside predominant dependence on polarity of C-H bond in isolated monomer.