Recognition systems switch-functionalized

Figure 1 Concept for molecular design of switch-functionalized recognition systems.

Figure 13.8 Schematic operation of a two-station rotaxane as a controllable molecular shuttle, and idealized representation of the potential energy of the system as a function of the position of the ring relative to the axle upon switching off and on station A. The number of dots in each position reflects the relative population of the corresponding coconformation in a statistically significant ensemble. Structures (a) and (c) correspond to equilibrium states, whereas (b) and (d) are metastable states. An alternative approach would be to modify station through an external stimulus in order to make it a stronger recognition site compared to station A.

This purely organic knot synthesis is appealing because in its simplest form it is a one-pot procedure that affords reasonable yields and unique possibilities for the preparation of derivatives in the context of the knots prepared to date. This advantage is at the same time the principal defect of the molecules, as they have yet to show any recognition behavior, and the knot is essentially a closed system. However, the functionalization of the knots makes it possible to use them as scaffolds for pendant groups which have some function, for example, as fluorescent switches. The many other possibilities for these knots have yet to be explored, although the synthetic foundation is laid. 

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