Type I-IV Halogen⋯Halogen Interactions: A Comparative Theoretical Study in Halobenzene⋯Halobenzene Homodimers

Area of Science:

• Computational chemistry
• Supramolecular chemistry
• Halogen bonding

Background:

• Halogen bonding is crucial in crystal engineering and materials science.
• Existing research primarily focuses on types I-III halogen interactions.
• The energetic contributions of different halogen interaction types require further elucidation.

Purpose of the Study:

• To investigate and compare unexplored type IV halogen⋯halogen interactions with established types I-III.
• To analyze the energetic preferences and trends of halobenzene homodimers.
• To quantify the influence of torsional conformation on interaction energies.

Main Methods:

• Utilized the second-order Møller–Plesset (MP2) method for energetic calculations.
• Designed halobenzene homodimers (Cl, Br, I) to model four interaction types.
• Employed symmetry-adapted perturbation theory-based energy decomposition analysis (SAPT-EDA).

Main Results:

• Type II interactions exhibited the highest binding energies, while type III showed the lowest.
• Binding energies generally decreased with decreasing σ-hole size for types I-III, with an inverse trend for type IV.
• Dispersion forces were found to be the predominant interaction in all studied homodimers.

Conclusions:

• Type IV halogen interactions offer unique energetic profiles, influenced by negative-belt⋯negative-belt contributions.
• The cis configuration of homodimers is energetically superior to the trans configuration.
• The findings provide valuable insights for applications in materials science and crystal engineering.