Switchable molecular devices: From rotaxanes to nanoparticles

Rotaxanes have been used as molecular frameworks for the preparation of swi tchable or bistable systems. The properties of a rotaxane that can be switc hed by electrochemical and chemical means are described in detail and used as an example in this discussion. The advantages of the rotaxane framework compared to systems containing the individual active components mixed toget her are considered. A series of practical problems hindering the applicatio n of single-molecule devices in actual circuits are discussed. Finally, som e emerging alternatives to single-molecule devices based on the quickly gro wing field of metal and semiconductor nanoparticles are briefly described.