Multifunctional supramolecular receptors: aqueous ion recognition, HCl sensing and cytotoxic potential

We describe the design, synthesis, and binding behavior of three supramolecular receptors aimed at selective ion-pair recognition in aqueous and organic media. Incorporating squaramide and tertiary amine functionalities, these receptors exhibit strong affinities for anions and ion pairs, especially in the presence of sodium cations. Notably, protonation of the tertiary amine in receptor 1 significantly enhances its water solubility and anion-binding affinity by increasing the acidity of the squaramide protons, thereby strengthening interactions with chloride anions even in competitive, water-rich environments. Receptor 3, modified with a pyrene unit, functions as a fluorescence sensor capable of extracting chloride from aqueous phases into organic solvents, indicating potential applications in molecular sensing and ion transport. Preliminary biological assays reveal that these compounds exhibit cytotoxic activity comparable to cisplatin on specific cell lines, suggesting promise as therapeutic agents. This study highlights the utility of multifunctional receptors in aqueous ion-pair recognition and transport, with implications for both environmental and biomedical applications.