Calixarene and resorcinarene ligands in transition metal chemistry

This is an exhaustive review of calixarenes containing transition metals. General preparative routes to calixarene ligands suitable for transition metal complexation are briefly reviewed. The aspects concerning their coordinative properties are organized according to the site and type of donor atom(s) involved in complexation. Emphasis has been placed on synthetic aspects so as to allow the reader to acquire a useful knowledge of the construction of transition metal complexes derived from calixarenes. Structural aspects have been systematically discussed for those complexes which have been characterized by X-ray analysis. Many interesting features of calixarene-derived ligands have been emphasized, e.g. the ability to act as bulky ligands or to behave as a polyoxo surface and the possibility to form novel supramolecular assemblies and to associate a catalytic centre with a potential receptor cavity. It is shown that transition metals are ideal partners for shaping or assembling calixarenes, thus allowing the construction of a number of large molecular systems, leading to various applications, notably liquid crystals, sensors for analytical purposes or molecular filters.