A Chemically and Electrochemically Switchable [2]Catenane Incorporating a Tetrathiafulvalene Unit.

A mechanical switch in a [2]catenane, made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides "inside" the tetracationic cyclophane in the reduced state and "alongside" it in the oxidized species (TTF+ / TTF2+ ). Switching between the reduced (I4+ ) and oxidized state (I5+ (I6+ )) is accompanied by a dramatic color change.