Proline-functionalised calix[4]arene: an anion-triggered hydrogelator.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Engineering

Background:

• Calixarenes are macrocyclic compounds with a unique structure.
• Developing stimuli-responsive materials is crucial for advanced applications.
• Anion recognition plays a vital role in chemical sensing and separation.

Purpose of the Study:

• To investigate the hydrogelation behavior of a water-soluble, chiral calix[4]arene.
• To explore the influence of anions and cations on the gelation process.
• To determine the reversibility of the hydrogelation triggered by pH.

Main Methods:

• Synthesis of a water-soluble, chiral calix[4]arene.
• Hydrogel formation studies triggered by various anions.
• Investigation of anion efficacy based on the Hofmeister series.
• Analysis of cation effects on gel properties.
• pH-triggered reversibility studies.

Main Results:

• The chiral calix[4]arene successfully formed hydrogels in the presence of specific anions.
• Gelation efficacy correlated with the Hofmeister series, indicating specific anion interactions.
• Associated cations significantly modified the hydrogel properties.
• Increasing the pH value effectively and reversibly switched off the gelation.

Conclusions:

• Water-soluble chiral calix[4]arenes are effective gelators for anion-responsive hydrogels.
• The Hofmeister series provides a framework for understanding anion-induced gelation.
• Cation choice and pH control offer tunable properties for these hydrogel systems.
• This work presents a versatile platform for developing smart materials for anion sensing or separation.