Ammonium halide selective ion pair recognition and extraction with a chalcogen bonding heteroditopic receptor

Abstract

The first example of a heteroditopic receptor capable of cooperative recognition and extraction of ammonium salt (NH₄X) ion-pairs is described. Consisting of a bidentate 3,5-bis-tellurotriazole chalcogen bond donor binding cleft, the appendage of benzo-15-crown-5 (B15C5) substituents to the tellurium centres facilitates binding of the ammonium cation via a co-facial bis-B15C5 sandwich complex, which serves to switch on chalcogen bonding-mediated anion binding potency. Extensive quantitative ion-pair recognition ¹H NMR titration studies in CD₃CN/CDCl₃ (1 : 1, v/v) solvent media reveal impressive ion-pair binding affinities towards a variety of ammonium halide, nitrate and thiocyanate salts, with the heteroditopic receptor displaying notable ammonium halide salt selectivity. The prodigious solution phase NH₄X recognition also translates to efficient solid–liquid and liquid–liquid extraction capabilities.