A New Supramolecular Strategy: Control Cation-exchange Selectivity via Anion Receptor

Scientific Achievement

By combining the classic anion receptor calix[4]pyrrole (C4P) and a phenolic ligand, a remarkable enhancement in selectivity was found for Cs+ over Na+, which was confirmed by crystal structures and ab initio molecular dynamics (AIMD), which showed the formation of ion-pair C4P-Cs+–phenolate complexes, while the smaller Na+  ion cannot effectively interact with all four pyrrole rings.

Significance and Impact

This study introduces a new supramolecular strategy of using anion receptors to influence the selectivity of a cation receptor without modifying its structure.

Research Details

• The results of liquid– liquid extraction experiments demonstrate a dramatic enhancement of Cs+ selectivity from alkaline solution when both phenol cation exchanger and C4P are present in a water-immiscible organic solvent.
• This supramolecular concept was structurally validated with crystal structures showing the expected role of C4P as ion-pair receptor.
• DFT and AIMD simulations further support these findings, while showing poor structural organization of the binding site and low affinity for Na+.