A fast-moving [2]rotaxane whose stoppers are remote from the copper complex core

[reaction: see text] A new copper-complexed rotaxane is described. It consists of a two-coordination site ring threaded by a sterically non-hindering 2,2'-bipyridine derivative. An electrochemical signal (oxidation or reduction of the copper center, Cu(I) or Cu(II)) induces rearrangement of the system. By using long and flexible linkers between the stoppers and the central complex, ligand exchange is fast, which leads to short response times (on the millisecond time scale and even below).