Controlling molecular shuttling in a rotaxane with weak ring recognition sites.

We describe a rotaxane molecular shuttle encompassing triazolium and tertiary ammonium units as weak recognition sites for the ring. Such a design, which differs from that of typical controllable rotaxanes, allows the precise tuning of the ring distribution among the two sites - i.e. , the coconformational equilibrium - by changing the solvent polarity or the nature of the counteranions. Shuttling of the ring between the two stations can also be toggled by acid-base stimuli. Such an approach is paradigmatic to obtain rotaxanes that can sense environmental changes and transduce them into a coconformational response and opens avenues for novel applications in sensing and stimuli-responsive materials.