Curvature and size effects hinder halogen bonds with extended π systems

Area of Science:

• Computational Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Halogen bonding and dispersion forces are key non-covalent interactions.
• Aromatic systems, both planar and curved, are fundamental building blocks in chemistry and materials.
• Understanding interactions with extended aromatic systems is crucial for designing novel materials and molecular assemblies.

Purpose of the Study:

• To investigate the influence of curvature and size on halogen interactions with extended aromatic systems.
• To elucidate the interplay between dispersion forces and halogen bonding in these systems.
• To determine the preferred binding modes (parallel stacking vs. halogen bonding) based on system geometry and halogen size.

Main Methods:

• Computational methods were employed to study dimers formed by dihalogens (Cl2, Br2, I2).
• Interactions were evaluated with planar (coronene, circumcoronene) and curved (corannulene, sumanene, C60) aromatic systems.
• Analysis focused on the energetic contributions of dispersion and halogen bonding.

Main Results:

• Dispersion is the dominant interaction, increasing with halogen size.
• Larger aromatic systems favor parallel stacked structures over halogen-bonded ones.
• Curvature significantly affects binding: concave sides favor parallel dimers, while convex sides can make halogen bonding competitive.

Conclusions:

• Halogen bonding is generally disfavored in large planar and curved aromatic systems.
• Dispersion forces play a critical role, dictating binding modes.
• The convex face of highly curved systems offers conditions where halogen bonding becomes competitive with stacking.