Study on the halogen bond and π-π stacking interaction between fluoro substituted iodobenzene and pyrazine

The halogen bonding and π-π stacking interactions between pyrazine (C₄H₄N₂) and fluoro substituted iodobenzene C₆H_5-nF_nI (n = 0, 1, 2, 3, 4, and 5) have been discussed at the M062x-D3/aug-cc-pVTZ level. The calculated interaction energy shows that the halogen bonding interactions are weaker than the corresponding π-π stacking interactions in C₆H_5-nF_nI (n = 0, 1, and 2)-C₄H₄N₂ complexes, while the halogen bonding interactions are stronger than the corresponding π-π stacking interactions in C₆H_5-nF_nI (n = 3, 4, and 5)-C₄H₄N₂ complexes. According to SAPT analysis, it is reveals that the electrostatic energy are the primary source of the attraction for the halogen bonding interactions while the π-π stacking interactions are dominantly dispersion energy. When the halogen bond and π-π stacking interaction coexist, we find out that the formation of π-π stacking will lead to stronger halogen bond interaction and the converse is also true. Graphical abstract.