Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. Engl. 16/1996)
The cover picture shows the crystal structure of a unique supramolecular architecture consisting of five tris(bispyridine) ligands (shown in different colors) wrapped around five FeII ions (purple) in a double-helical fashion and closed to form a torus around a central chloride ion (green). This circular helicate is an analogue of circular DNA. Its formation also points to the possibility of designing self-assembling systems that generate receptors for specific substrates from a collection of suitable ligands and metal ions. More about the circular helicate and the concept of “virtual combinatorial libraries” is reported by J.-M. Lehn et al. on p. 1838 ff.