Polarity-Tolerant Chloride Binding in Foldamer Capsules by Programmed Solvent-Exclusion

Area of Science:

• Supramolecular Chemistry
• Synthetic Organic Chemistry

Background:

• Persistent anion binding is crucial for synthetic receptor design but challenging in polar solvents.
• Nature utilizes solvent exclusion in proteins for effective anion transport in aqueous environments.

Purpose of the Study:

• To design and synthesize a foldameric capsule capable of stable anion binding in high-polarity solvents.
• To investigate the solvent-independent binding affinity and stability of the designed capsule.

Main Methods:

• Utilized sequence-defined foldamer chemistry to create a helical capsule preorganized for anion complexation.
• Employed solid-state and solution-phase studies to confirm capsule stability and solvent exclusion properties.
• Assessed anion binding affinities across varying solvent dielectric constants, comparing with control compounds.

Main Results:

• The foldameric capsule maintained a high, solvent-independent anion affinity (10^5 M^-1) across a 4-fold increase in solvent dielectric constant.
• Control compounds with solvent-exposed binding sites showed significantly reduced anion affinities in polar solvents.
• Dimethyl sulfoxide was found to denature the foldamer, reducing its anion binding affinity.

Conclusions:

• The designed foldameric capsule represents a new prototype for potent anion receptors operating effectively in polar solvents.
• This approach offers potential applications in managing hydrophilic anions in the hydrosphere and biosphere.
• Solvent exclusion is a viable strategy for achieving high anion affinities in challenging polar environments.