CUCURBITURIL - SUPRAMOLECULAR PERSPECTIVES FOR AN OLD LIGAND

This report deals with the preparation and inclusion properties of the synthetic receptor cucurbituril. Although its synthesis dates back to the beginning of the century, complex formation with this ligand has not been studied until quite recently. The most important feature of this macropolycyclic structure is the presence of an internal cavity with a diameter comparable to that of alpha-cyclodextrin. The rigid cavity of cucurbituril constitutes a rather apolar, lipophilic region, but the portals to the interior contain carbonyl groups as binding sites for ions. Bifunctional and amphiphilic substances can be successfully encapsulated. Similar to other cavitands, inclusion may be interpreted in terms of hydrophobic interactions by displacing solvent water molecules upon complexation, and of ion-dipole attractions with the urea moieties. Further profitable uses of cucurbituril as well as the preparation of attractive analogs are currently under research.