Shuttling motion

Any residual material left in the shuttle is blanketed by a slow flow of dry nitrogen gas to prevent fouling of the shuttle between uses. Pneumatic cylinders, driven from solenoid valves that are controlled by a power- and event-controller, provide the shuttle motion, and position is confirmed by Hall Effect detectors on the pneumatic cyhnders and monitored by the power and event controller. 

Because these approaches can often be equally well applied to the shuttling motion of rotaxanes, the circumrotation of catenanes, and the threading/dethreading of pseudorotaxanes, we do not restrict this discussion to rotation only, but present a small selection of different examples. 

Owing to the size of supramolecules semi-empirical methods are still in use. For instance, semi-empirical PM3 calculations were carried out for metalacryp-tands and metalacryptates and with lead as metal the theoretically predicted favorable cryptand formation was subsequently verified experimentally [123]. In another example, the rate of shuttling motions in rotaxanes was examined with semiempirical AMI calculation by Ghosh et al. [124] who generated different structures with a Monte Carlo procedure and subsequently optimized low-energy conformers. 

Figure 17 Schematic representation of long-range (a) rotation and (b) translation (shuttling) motions of the ring component in rotaxanes.

In cleaning a surface it is very important not only to detach the adhering particles, but also to remove them from the area, i.e., to prevent the possibility of their reattachment. A process of this kind occurs when particles are detached in the dc electric field created by a continuous electrode the detached particles execute a shuttle motion between the substrate and the detaching electrode. 

Additional studies showed that ion pair binding has its own influence on the intercomponent dynamics of rotaxane 20. In polar solvents such as dg-acetone and dg-DMSO, the broad H NMR spectrum revealed dynamic co-conformational behavior between the axle and macrocycle components, most likely pirouetting and shuttling motions. Upon potassium binding, however, only one co-conformation existed in solution, with one of the axle carbonyl groups thought to coordinate to the bound alkali metal, halting the dynamic motion. 

Scheme 30.9 Directional shuttling motion in cationic/ neutral calix[6]arene-based [2]rotaxanes 21bV22...

Fig. 3. The stimuli-triggered reversible shuttling motions in a [2]rotaxane between the ground...

Fig. 5. The photoisomerization-induced shuttling motions in the [3]rotaxane and the corresponding fluorescent intensity changes during the reversible cycles.

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