Anion‐receptor molecules: Macrocyclic and macrobicyclic effects on anion binding by polyammonium receptor molecules

Abstract The stability constants for anion binding by the acyclic hexaamine 1 , its macrocyclic analogue 2 , and the bicyclic compound 3 in their protonated forms are reported. Compound 3 forms stable and selective complexes with halide ions, the stability sequence being I − > Br − > Cl − . Compound 2 forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue 1 and shows a better selectivity pattern. Compound 3 forms stronger complexes with oxalate 2− than 2 and shows a remarkably high binding selectivity between oxalate 2− and malonate 2− . The comparison of the ability of 1–3 to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability and selectivity.