High selectivity for cesium ion by macrocyclic complex based on aromatic amide pyridone hexamer

Abstract

Shape-fixed and persistent aromatic amide hexamer macrocyclic molecules are synthesized via a one-pot method utilizing pyridone diacid and m-phenylenediamine as precursor units, facilitated by intramolecular three-center hydrogen bonds. In ¹H NMR, the significant chemical shift of the macrocyclic amide hydrogen absorption peak indicates the recognition between the macrocyclic system and alkali metal cesium ions. The binding affinity between the cesium ion and the host macromolecule is determined to be 1:1 using the job method, and as 1.00 × 10⁴ M-1 through ¹H NMR titration. X-ray single crystal diffraction confirms that the macrocyclic host is bound to the cesium ion in a ratio of 1:1. The single crystal of pyridone macro ring combined with Cs ion is obtained, which further confirmed that Cs is located in the center of the macro ring cavity, which is very consistent with the theoretical structure prediction.