Controlling aromatic helix dimerization in water by tuning charge repulsions.

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Materials Science

Background:

• Aromatic oligoamides are a class of foldamers with potential applications in various fields.
• Achieving controlled self-assembly of foldamers in aqueous media remains a significant challenge.
• Understanding the factors governing foldamer aggregation is crucial for designing functional materials.

Purpose of the Study:

• To design and synthesize water-soluble aromatic oligoamides capable of self-assembly.
• To investigate the influence of charged versus neutral side chains on aggregation behavior in water.
• To characterize the different aggregate structures formed by these foldamers.

Main Methods:

• Synthesis of helically folded aromatic oligoamides with charged and neutral side chains.
• Utilizing Nuclear Magnetic Resonance (NMR) spectroscopy, including 1H DOSY, to study aggregation.
• Employing mass spectrometry and X-ray crystallography (or energy-minimized models) for structural elucidation.

Main Results:

• Water-soluble oligoamides were successfully synthesized, featuring charged side chains.
• Replacing a small number of charged groups with neutral methoxy groups induced the formation of various aggregates (dimers, duplexes, quadruplexes) in water.
• These aggregates did not form in organic solvents, highlighting the role of the aqueous environment.
• The hydrophobic effect was identified as the primary driver for aggregation, modulated by charge presence.

Conclusions:

• The study demonstrates a novel method for controlling aromatic foldamer aggregation in water by fine-tuning charge content.
• The observed aggregation phenomena, driven by hydrophobic effects and charge modulation, provide a new benchmark for foldamer design in aqueous systems.
• These findings open avenues for developing advanced functional materials based on foldamer self-assembly in water.