A hybrid macrocycle containing benzene and pyridine subunits is a better anion receptor than both its homoaromatic congeners

The hybrid tetraamide receptor 3 containing both 2,5-diamidopyridine and 1,3-diamidobenzene anion binding units has been synthesized. NOESY spectroscopy revealed that the new receptor is well preorganized for anion complexation, presumably owing to the macrocyclic topology and the rigidity of the 2,5-diamidopyridine unit. Association constants of 3 with several anions are higher than those determined earlier for its homoaromatic congeners 1 and 2. X-ray crystallographic analysis of the chloride complex of hybrid macrocycle 3 enabled direct comparison of structural aspects of anion recognition by the 2,5-diamidopyridine and 1,3-diamidobenzene moieties.