Half-clathrochelate Complexes as Versatile Links in Supramolecular Chemistry

Clathrochelate complexes have been widely investigated with different size and shape and used as building blocks for the obtainment of discrete supramolecular architectures. These clathrochelate complexes are very stable and kinetically inert complexes. A new link, described as a 'half-clathrochelate complex' with one boronate ester-cap and one 'open' side can be used as novel structural motifs in supramolecular chemistry. Since the metal ion is not completely encapsulated, these complexes are more labile than standard clathrochelate complexes with two boronate ester caps. The half-clathrochelate complexes are obtained by metal-templated condensation reactions of 2-pyridylaldoximes with boronic acids. For applications in supramolecular chemistry, half-clathrochelate complexes are very intriguing compounds for several reasons: the central metal ion can be varied to obtain diamagnetic or paramagnetic complexes and substituents at the pyridyl group of the oxime ligand can be used to fuse half-clathrochelate complexes into defined supramolecular assemblies such as dinuclear triple-stranded helicates or tetrahedral cages.