Switchable molecular shuttles

Figure 11.38 A [2] rotaxane-based, pH- and redox-switchable molecular shuttle.

Fig. 5 Idealized free energy profiles for a switchable molecular shuttle...

Bissell RA et al (1994) A chemically and electrochemically switchable molecular shuttle. Nature 369 133-137... 

Scheme 2 Switchable molecular shuttle. At equilibrium, the cyclophane preferentially encircles the benzidine unit (84%), but can be shuttled to the biphenol unit by oxidation (top) or protonation (bottom) of benzidine [107]...

Bissell R A, Cordova E, Kaifer A E and Stoddart J F 1994 A chemically and electrochemically switchable molecular shuttle Nature 369 133-7 Wu C G and Bein T 1994 Conducting polyaniline filaments in a mesoporous channel host Science 264 1757-9... 

Example 4, Cadiot-Chodkiewicz active template synthesis of rotaxanes and switchable molecular shuttles with weak intercomponent interactions ... 

Bissell, R. A. Cordova, E. Kaifer, A. E. Stoddart, J. F. A chemically and electrochem-ically switchable molecular shuttle. Nature 1994, 369, 133-137. 

Figure 70 A chemically and electrochemically switchable molecular shuttle.

When one of the two macrocycles carries two different recognition sites, then the opportunity exists to control the dynamic processes in these switchable [2]catenanes in a manner reminiscent of the controllable molecular shuttles (Figure 29) [30-34, 41], In essence, the requirement for being able to switch between state 0 and state 1 in such a [2]catenane is that the symmetric macrocyclic component resides preferentially around one of the two different recognition sites incorporated within the non-... 

Photoisomerizations can often occur by several different mechanisms. Systems that isomerize via a controlled mechanism are potential candidates for molecular machines [184]. Energy in the form of light is absorbed and converted to controlled mechanical force on the molecular scale. Examples of a mono-directional rotor [185, 186], a switchable rotor [187], and a molecular shuttle [188] have been demonstrated. These systems are light-controlled, but there are also examples of systems which control molecular motion based on electro- and/or chemical modulation, such as the threading/imthreading of (pseudo)rotaxanes [189-196]. 

S), then a mechanism for reversible control on the average position of the bead would be accessible. This class of molecules was dubbed switchable or controllable molecular shuttles and they constitute clear examples of bi-stable molecules (Scheme 2). Ideally, one would like to use an easily measurable property to distinguish the two states of the molecule, i.e., to read the molecular state in more digital terms. 

Synthetic methodology for the preparation of switchable rotaxanes has been primarily developed by Stoddart and coworkers [4]. In collaboration with Stoddart, the author s group reported in 1994 a molecular shuttle that exhibited a novel feature dual control. In this rotaxane the average position of the bead could be controlled by both proton- and electron-transfer reactions... 

Altieri, A., Bottari, G., Dehez, F., Leigh, D. A., Wong, J. K. Y. and Zerbetto, F., Remarkable positional discrimination in bistable light- and heat-switchable hydrogen bonded molecular shuttles, Angew. Chem., Int. Ed. Engl, 2003, 42, 2296-2300. 

---