Tetradentate halogen bonding macrocyclic anion receptor inspired by the “Texas-sized” molecular box

Inspired by the tetracationic “Texas-sized” molecular box, a neutral analogue containing four iodotriazole halogen bond-promoting subunits (“Ibox”) was synthesized. This new macrocycle was prepared by means of azide–alkyne click chemistry. It was found to recognize Cl⁻, Br⁻ and I⁻ anions (as their tetrabutylammonium salts) in CDCl₃. ¹H NMR spectroscopic titrations revealed a higher affinity for the heavier halide anions and provided support for a preferred 1 : 2 binding stoichiometry.