Theoretical Study of Interactions between Halogen-Substituted s-Triazine and Halide Anions.

Theinteractions between halogen-substituted s-trazine(C3H2N3X) and halide anions(Y–) have been investigated at the MP2/aug-cc-pVDZ(aug-cc-pVDZ-PP) level. C3H2N3X caninteract with halide anions to form five types of complexes (C3H2N3X·Y–): astrong σ-type interaction complex, a weak σ-type interactioncomplex, an anion−π interaction complex, a hydrogen-bondingcomplex, and a halogen-bonding complex. The binding energies, structures,and bonding characteristics of these complexes have been discussed.The local details of potential energy surfaces around the bindingsites for some selected complexes have been depicted. The resultsindicate that the binding behavior of F–is quitedifferent from that of Cl–, Br–, and I–. The potential energy surface is separatedinto two parts, the HB-σ–π region and the XB region,by a relatively high energy barrier for complexes C3H2N3Cl·Cl–, C3H2N3Br·Cl–, and C3H2N3I·Cl–. The HB-σ–πregion is characterized by the flat potential energy surface, indicatingthat the binding strength is retained when the anion is held overthe HB-σ–π region. The XB region is characterizedby the steeper potential energy surface, indicating that the bindingstrength is more sensitive to the anion position in this region. Thebinding strength of the HB-σ–π region is strongerthan that of the XB region for C3H2N3Cl·Cl–and C3H2N3Br·Cl–, whereas the binding strengthof the XB region is stronger than that of the HB-σ–πregion for C3H2N3I·Cl–. [ABSTRACT FROM AUTHOR]