Investigating Anion–π Interactions In Ion‐Pair Receptors Based On 3,5‐Dinitrobenzoic Acid

The design, synthesis, and characterization of a series of supramolecular receptors based on electron‐deficient aromatic systems capable of engaging in anion– π interactions are reported. Receptors 1 and 3 combine an electron‐poor aromatic scaffold with a cation‐binding crown ether unit. Binding studies monitored by 1 H NMR titrations in acetonitrile revealed that these receptors exhibit enhanced affinity for bromide anions in the presence of sodium cations, indicating cooperative ion‐pair recognition. Receptor 1 , incorporating both nitro‐substituted aromatic rings and a macrocyclic cation‐binding site, demonstrated the most significant anion– π binding enhancement. In contrast, control receptor 2 , lacking electron‐withdrawing groups, exhibited negligible anion affinity, supporting the role of π ‐acidity in anion binding. Quantum chemical calculations and electrostatic potential maps further confirmed the contribution of anion– π interactions in receptor function. The incorporation of amide functionalities in receptors 3 and 4 improved binding affinity, highlighting the synergistic effect of multiple binding domains. These findings highlight the potential for developing advanced ion‐pair receptors that harness anion– π interactions alongside classical noncovalent binding motifs.