Radial Hetero[5]catenanes: Peripheral Isomer Sequences of the Interlocked Macrocycles

A pair of radial [5]catenanes, with either an isomeric cyclic ‐AABB‐ or ‐ABAB‐ type sequence of the interlocked β‐cyclodextrin (β‐CD) and cucurbit[6]uril (CB[6]) units, has been efficiently synthesized. Because of a marked difference in the binding strength and interlocking sequence of the peripheral macrocycles, interesting sequence‐dependent properties, characteristic of mechanically bonded macrocycles, were realized. Variable‐temperature 1 H NMR studies showed that the ‐ABAB‐ isomer has a more independent β‐CD dynamic, whereas the β‐CD motions in the ‐AABB‐ isomer are coupled. Dynamics of the pH‐insensitive β‐CD can also be further modulated upon base‐triggered mobilization of the CB[6]. These unique properties of the mechanical bond expressed in a sequence‐specific fashion and the transmission of the control on the macrocycle dynamics from one interlocked component to another, highlight the potential of similar complex hetero[ n ]catenanes in the design of advanced, multicomponent molecular machines.