Probing Halogen-π versus CH-π Interactions in Molecular Balance

Area of Science:

• * Supramolecular Chemistry
• * Organic Chemistry
• * Computational Chemistry

Background:

• * Non-covalent interactions, such as halogen-π and CH-π interactions, play crucial roles in molecular recognition and self-assembly.
• * Understanding the interplay between different types of non-covalent interactions is essential for designing novel molecular systems.
• * The dibenzobicyclo[3.2.2]nonane framework offers a rigid scaffold for precisely positioning interacting groups.

Purpose of the Study:

• * To investigate the competitive binding between halogen-π and CH-π interactions.
• * To elucidate the factors governing the preference for one interaction over the other.
• * To utilize a novel molecular balance system for probing these interactions.

Main Methods:

• * Synthesis of molecular balances based on the dibenzobicyclo[3.2.2]nonane template.
• * X-ray crystallography for structural determination.
• * Nuclear Magnetic Resonance (NMR) spectroscopy for analyzing molecular interactions.
• * Computational chemistry (e.g., DFT calculations) for modeling interaction energies.

Main Results:

• * The molecular balances successfully allowed for the observation of competition between halogen-π and CH-π interactions.
• * Structural analysis confirmed the spatial arrangement of interacting partners.
• * NMR data indicated distinct chemical shift changes corresponding to different interaction modes.
• * Computational results provided quantitative insights into the relative strengths of halogen-π and CH-π interactions.
• * The size of the functional group attached to the halogen or carbon atom was identified as a key determinant of interaction preference.

Conclusions:

• * The dibenzobicyclo[3.2.2]nonane template is effective for studying competing non-covalent interactions.
• * The π system can engage in favorable interactions with both halogen (C-X) and hydrogen (C-H) atoms.
• * The outcome of the competition is sensitive to the steric bulk of the interacting functional groups.