From chiral counterions to twisted membranes

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Chirality in amphiphile membranes is typically inherent to the molecular structure.
• Nonchiral amphiphiles can exhibit supramolecular chirality when interacting with chiral counterions.
• Understanding chiral induction mechanisms is key for designing advanced materials.

Purpose of the Study:

• To elucidate the mechanism of chiral induction in nonchiral dicationic membranes by chiral tartrate counterions.
• To demonstrate the first instance of the Pfeiffer effect in a membrane system.
• To explore the application of vibrational circular dichroism in studying membrane chirality.

Main Methods:

• Single-crystal X-ray diffraction to analyze cation conformation.
• (1)H Nuclear Magnetic Resonance (NMR) spectroscopy to confirm ion recognition and conformational lability.
• UV-Vis and Infrared Circular Dichroism (CD) spectroscopy to detect conformational changes and induced chirality.

Main Results:

• Specific anion-cation recognition between tartrate and n-2-n amphiphiles was established.
• Conformationally labile chirality was induced in the nonchiral amphiphilic cations.
• Tartrate ions transitioned from anti to gauche conformations upon binding, inducing chirality in the membrane.

Conclusions:

• The Pfeiffer effect can occur in membrane systems, driven by specific ion recognition.
• Vibrational circular dichroism is a powerful tool for studying chiral conformations in membranes.
• This work provides a framework for designing tunable chiral membrane systems.