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

Area of Science:

• Computational chemistry
• Supramolecular chemistry
• Non-covalent interactions

Background:

• Halogen bonding and π-π stacking are crucial non-covalent interactions in molecular recognition.
• Understanding these interactions is key to designing functional materials and pharmaceuticals.
• The interplay between these forces in substituted aromatic systems remains an active area of research.

Purpose of the Study:

• To investigate the nature and relative strengths of halogen bonding and π-π stacking interactions.
• To analyze the influence of fluorine substitution on iodobenzene in these interactions with pyrazine.
• To elucidate the energetic contributions governing these interactions using theoretical methods.

Main Methods:

• Density Functional Theory (DFT) calculations using the M062x-D3/aug-cc-pVTZ level of theory.
• Calculation of interaction energies for pyrazine-fluoroiodobenzene complexes.
• Symmetry Adapted Perturbation Theory (SAPT) analysis to dissect interaction components.

Main Results:

• Halogen bonding is weaker than π-π stacking for less fluorinated iodobenzenes, but stronger for highly fluorinated ones.
• Electrostatic forces dominate halogen bonding, while dispersion forces are key for π-π stacking.
• Coexistence of both interactions enhances the strength of each other.

Conclusions:

• The balance between halogen bonding and π-π stacking is tunable via fluorine substitution.
• Electrostatic and dispersion contributions dictate the preference for one interaction over the other.
• Synergistic effects amplify non-covalent interactions when both halogen bonding and π-π stacking are present.