Electrostatic kinetic barriers in the threading/dethreading motion of a rotaxane-like complex.

A new rigid cationic thread, based on the 1,2-bis(bipyridinium)ethane motif, and a 24-crown-8 anionic macrocycle self-assemble into a pseudo-rotaxane complex in aqueous solution. The presence of pH-responsive end groups on the thread, remote from the recognition motif, allows controlling the threading/dethreading rate without perturbing the complex structure or stability. The difference in the rate is attributed to the activation or deactivation of electrostatic barriers on the thread during the sliding process at different pH values.