Nonaggregational shape-persistent cyclo[6]aramide and its macrocyclic effect toward binding secondary ammonium salts in moderately polar media.

Simply by introducing steric side chains, the shape-persistent cyclo[6]aramides were found to exhibit nonaggregational behavior and strong association (3 x 10(4) M-1) ability in acetone for binding secondary ammonium salt. The complexation can be switched in an on-and-off fashion using AgPF6 and TBACl, contrasting sharply with their corresponding acyclic pentamer and demonstrating the macrocyclic effect.