"Size-selectivity" in the template-directed assembly of dinuclear triple-stranded helicates

The self-assembly of supramolecular structures depends on a subtle interplay of a series of different control mechanisms. The geometric as well as electronic complementarity of the molecular building blocks is crucial for the specific formation of defined supramolecular species. In addition, secondary effects, like templating, also have an important function. The templating ability of different cations in the formation of triple-stranded helicate-type complexes from alkyl-bridged di(8-hydroxyquinoline) ligands is investigated by introduction of alkyl chains of different length as ligand spacers. Hereby a "size-selectivity" between the cations and the dinuclear helicate-type complexes [(ligand)(3)M(2)] is observed. Large cations support the formation of big dinuclear complexes, whereas small cations are able to template the formation of small complexes.