Molecular Balances Based on Aliphatic CH-π and Lone-Pair-π Interactions

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry
• Organic Chemistry

Background:

• Bicyclic N-arylimides exhibit conformational flexibility.
• Non-covalent interactions, specifically CH···π and lone-pair···π interactions, play a crucial role in determining molecular conformation.
• Understanding these interactions is key to controlling molecular shape and dynamics.

Purpose of the Study:

• To estimate the strengths of CH···π and lone-pair···π interactions in a series of conformationally dynamic bicyclic N-arylimides.
• To determine how these interactions influence the preference for folded or unfolded conformations.
• To propose computational strategies for selectively isolating the folded conformer.

Main Methods:

• Computational estimation of CH···π and lone-pair···π interaction strengths.
• Analysis of the synergy and competition between different non-covalent interactions.
• Evaluation of the energy barriers for conformational transformations.

Main Results:

• The interplay between CH···π attraction and lone-pair···π repulsion governs the conformational preference (folded vs. unfolded).
• Strategies involving enhanced CH···π interactions or reduced lone-pair···π repulsion can favor the folded form.
• While conformational locking is not achieved due to high energy barriers, facile alkyl group dynamics (hopping and tumbling) are observed in the folded conformation.

Conclusions:

• Non-covalent interactions are critical determinants of conformational preferences in dynamic bicyclic N-arylimides.
• Computational approaches can guide the design of molecules with desired conformational properties.
• The folded conformation of these N-arylimides exhibits unique and facile internal dynamics.