Abstract
The chemistry of molecules displaying novel topologies has experienced an explosive development in the course of the last 25 years. The fast growth of this field originates to a large extend from the new templated synthetic methods which allow to prepare these compounds at a real macroscopic level. Our group, in particular, has proposed a particularly efficient copper(I)-based template synthesis of a large variety of catenanes and rotaxanes at an early stage, participating in the revival of molecular topology. One of the highlights of the field has been the synthesis of the trefoil knot, a particularly challenging target. This object is not only an aesthetically attractive molecule but it also displays interesting properties in relation to coordination chemistry and chirality. A highly promising extension of molecular topology is that of molecular machines. By combining the specific properties of catenanes and rotaxanes, i.e. marked flexibility and propensity to undergo large amplitude motions, and coordination chemistry, it has been possible to elaborate and study a large variety of molecular machines. A representative example is that of an adjustable receptor, based on a [3]rotaxane attached to two mobile porphyrinic plates. This compound and related molecules will lead to "molecular presses" and, eventually, to molecular machines usable in solution to catalyse reactions or change the conformation of given substrates. Another recent molecular machine prototype from our group is a [2]rotaxane which behaves as a molecular shuttle, the gliding motion of the threaded ring being fast and taking place over a relatively large distance. Such sophisticated molecular machine prototypes could lead to transport of matter over long distances or across membranes by proper modifications of the present systems and attachment of receptors on the mobile part of the shuttling machine.
