Our work on molecular nanotopology
Introduction
Manipulating the topology of molecules represents an extremely appealing perspective for chemists. Topology is a powerful way to control precisely the three−dimensional conformational state of molecules and to generate new functions that would be inaccessible otherwise. Chemists have long been attracted to the challenge of synthesising molecules with complex topologies, namely knots (composed of one ring) and links (composed of two rings or more). Although considerable efforts have been invested to enable the synthesis of knotted molecules, they remain extremely difficult to produce and their properties are still unexplored.
Synthesizing molecular knots and links
Conventional approaches to the synthesis of complex knots mostly rely on metal-templation. In our lab, we have developed an innovative strategy that uses the hydrophobic effect to drive the formation of knots and links in water. In this strategy, simple amphiphilic building blocks composed of large planar aromatic moieties spontaneously self-assemble into knots and links in water to minimise the hydrophobic surface area exposed to the environment. This work represents an important milestone because the syntheses are easy to implement, high-yielding and require minimum effort in terms of purification.
These knots and links are excellent receptors and recognise small organic molecules and anions with an exquisite level of selectivity, even in strongly competing solvents like water.
Exploring the properties of knotted molecules
The properties of knotted molecules are mostly unknown. We have used a combination of spectroscopic methods to demonstrate that knotting molecules affects their physical and chemical properties.
We have also discovered that the topology of a molecule can be used to coordinate several switching events in a concerted fashion. This phenomenon is particularly important because the spatial and temporal coordination of switching events, which is commonly observed in biological systems, has been rarely achieved in artificial systems.
It is likely that molecules with complex topologies can be used to perform much more sophisticated tasks.
