Dipoles affect conformational equilibrium

Area of Science:

• Molecular dynamics and physical chemistry
• Organic chemistry and materials science

Background:

• Electric dipoles play a crucial role in various chemical and physical processes.
• Understanding how molecular dipoles affect structural conformation is essential for materials design and function.

Purpose of the Study:

• To investigate the influence of electric dipoles on the molecular geometry of an aromatic amide.
• To explore the conformational switching of 5-N-amide derivative of anthranilamide (Aaa) in response to varying medium polarity.

Main Methods:

• Utilized nuclear Overhauser effect (NOE) and density-functional theory (DFT) to analyze molecular conformations.
• Employed NMR spectroscopy at low temperatures to observe aggregated conformers.
• Quantified conformational equilibrium dynamics using DFT calculations.

Main Results:

• Aromatic amide (Aaa) exhibits two stable conformations with distinct dipole moments.
• In non-polar solvents, the conformer with a smaller dipole moment predominates.
• Increasing solvent polarity induces the formation of the conformer with a larger dipole moment.
• NMR signal splitting at low temperatures indicates the presence of aggregated conformers.

Conclusions:

• Solvent polarity is a key factor in controlling the conformational equilibrium of molecules with significant electric dipoles.
• The observed conformational switching driven by electric dipoles and medium polarity offers a new paradigm for molecular design.
• This study highlights the interplay between intrinsic molecular properties and the surrounding environment in dictating molecular structure and behavior.