Chemically Controlled Shuttling Processes

No example has so far been reported of a shuttling process controlled by electron transfer chemical reactions. There are, however, very interesting examples of shuttling processes controlled by acid/base reactions. One case is that of the previously discussed compound 13 " (see Figure 14), in which the shuttling of the macrocycle component can be controlled not only electrochemically, but also by protonation/ deprotonation of the benzidine unit [43]. 

Fig. 15. A chemically and electrochemically controllable molecular shuttle 104+. When the dumbbell is in its unperturbed state, the cyclophane exists in an 84 16 ratio (CD3CN, -44 °C) encircling preferentially the comparatively more 7t-electron-rich benzidine site. The cyclophane can be enticed to translate to the biphenol site exclusively either chemically -through protonation of the benzidine nitrogen atoms - or electrochemically - through oxidation of the benzidine unit to its radical cation. Both of these processes are completely reversible, through addition of base, or electrochemical reduction, respectively...

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