Photoinduced memory effect in a redox controllable bistable mechanical molecular switch.

Mechanically interlocked molecules (MIMs) in the form of multiand bistable rotaxanes in which the ring component can be switched between different co-conformations in response to external stimuli, constitute an artificial molecular switch. They are of importance when it comes to the development of integrated systems and devices, such as responsive surfaces, molecule-based muscles and actuators, 5] nanovalves for controlled drug delivery, and molecular electronic devices (MEDs). Although the operation of bistable molecular switches is based on classical switching processes between thermodynamically stable states, it has become clear that the fulfillment of useful functions will only become possible if the rates of the mechanical movement between such states can also be controlled. This approach was used recently to implement ratchet-type mechanisms which are essential ingredients for the construction of molecular motors, and is of considerable relevance for the development of sequential logic devices such as flip-flops and memories. For all these purposes, the ability to be able to adjust the shuttling kinetics by modulating the corresponding energy barriers through external stimuli in a convenient, efficient, and reversible manner is a goal which still poses a considerable challenge to chemists. Herein, we discuss the performance of a molecular switch in the form of a bistable [2]rotaxane (Scheme 1), which 1) undergoes relative mechanical movements of its ring and