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.