A copper-complexed rotaxane in motion: pirouetting of the ring on the millisecond timescale.

A new bistable rotaxane, consisting of a 2,2'-bipyridine-containing thread and a ring incorporating both a bidentate chelate and a tridentate fragment, has been prepared; this complex undergoes an electrochemically driven pirouetting motion of the ring around the axis which takes place on the millisecond timescale, i.e. several orders of magnitude faster than the other copper-based machines previously described.