Biomimetic Synchronized Motion of Two Interacting Macrocycles in [3]Rotaxane-Based Molecular Shuttles.

Noncovalent interactions between all the neighboring components in biomolecular machines are responsible for their synchronized motion and thus complex functions. This strategy has rarely been used in multicomponent molecular machines. Here, we report four [3]rotaxane-based molecular shuttles. Noncovalent interactions among the three components (two interacting macrocycles and one axle) not only cause a "systems-level" effect on the relative positions of the two macrocycles along the axle, but also result in a synchronized motion of the two macrocycles when adding partial amount of stimuli. Moreover, the intermediate state with one shuttled macrocycle even exist predominantly in the solution during the titration of stimuli, which is theoretically unexpected for the [3]rotaxane with two non-interacting rings. This biomimetic strategy may provide a method for constructing highly complex molecular machines.