Anion-templated synthesis.

In contrast to the well-studied templating properties of cationic and neutral species there are relatively few examples of anion-templated syntheses. This is attributed to some of the intrinsic properties of anions such as their diffuse nature, pH sensitivity, and their relative high solvation free energies. However, the increasing number of anion-templated assemblies reported over the past few years demonstrates that these limitations are not as critical as first thought. This review summarizes the most important results on the use of anions as directing agents for the syntheses of a wide range of inorganic and organic assemblies (such as macrocycles, cages, helicates, rotaxanes, and extended structures). It is hoped that this will stimulate a closer look into this emerging area of supramolecular chemistry.