A Synthetic Tetra‐Amide Macrocycle for Anion Recognition at Molecular Level

An engineered tetra‐amide macrocycle is presented, and its conformation and anion recognition properties are investigated. The tetra‐amide macrocycle 1 , containing the m ‐amino benzoic acid, 1,3‐benzenedicarboxylic acid and m ‐xylenedinediamine adopts an envelope‐like conformation in solid‐state, where the m ‐xylenedinediamine ring is perpendicular with the molecular plain. The tetra‐amide macrocycle 1 is able to bind anions such as halides, sulphate and phosphate in DMSO (dimethyl sulphoxide) solution. The stabilities of the fluoride (2.6×10 3 M −1 ) and chloride (5.6×10 2 M −1 ) complexes of 1 in DMSO is higher than that of bromide (66 M −1 ) and iodide (52 M −1 ). SO 4 2− complexes of 1 in DMSO is more stable than the HSO 4 − , NO 3 − and H 2 PO 4 − complexes. Using this information, a quantitative evaluation of the stability of the 1 : 1 complex of 1 , for which overall binding energy in the order −123.98 kcal/mol for SO 4 2− was calculated. The strong binding affinity of the tetra‐amide macrocycle 1 toward the SO 4 2− ion can be explained on the basis of non‐covalant interaction like ion−dipole interaction, hydrogen bonding interaction and size selectivity.