Electrochemically Controllable Bistable Rotaxanes

An electrochemical stimulus provides a two-fold advantage since it can stimulate molecular actuations through clean redox reactions and also detects simultaneously the resulting molecular movements by sensing the changes in the electromechanical properties of a bistable molecule. CV is often employed to both write and read the electromechanical movements in the redox-active bistable 

It is worth mentioning that movement of the CBPQT4 ring from the benzidine unit to the biphenol unit could also be effected by protonation of the benzidine nitrogen atoms by trifluoroacetic acid, making the unit a much weaker it-electron donor. The recovery stroke of the CBPQT4 ring could be effected by the addition of a stoichiometric amount of pyridine, which deprotonates the protonated benzidine unit. 

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A Redox and Chemically Controllable Bistable Neutral [2]Rotaxane 8.4.3.1 Electrochemical Switching... 

Like rotaxanes, catenanes are mechanically interlocked molecules. However, instead of interlocking one ring shaped macrocycle and a dumbbell shape, catenanes consist of interlocked macrocycles. The number of macrocycles contained in a catenane is indicated by the numeral that precedes it. Catenanes have bistable and multistable forms and a switchable, bistable [2]catenane is commonly exploited in nanotechnology and molecular electronics because its behavior can be controlled by electrochemical processes [89]. Collier et al. was the first to demonstrate the electroactivity of interlocked catenanes [90]. The authors affixed phospholipid counterions to a monolayer of [2]catenanes and then sandwiched this system between two electrodes. This work resulted in a molecular switching device that opened at a positive potential of 2 V and closed at a negative potential of 2 V. 

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