Abstract

Inclusion compounds may be classified into three main categories: complexes, cavitates, or clathrates. Typical examples for each class of inclusion compounds are the crown complexes, the calix–cavitates, and the hydroquinone clathrates. All of these compounds have in common the ability to incorporate into the cavities of their own molecules, or within their lattices, other molecules of suitable size, spatially to enfold them, that is to hold them, mostly by physical imprisonment.

Materials having the attribute of inclusion have given rise to what is called host–guest chemistry, a typical feature of which is accommodation of a complementary guest species into a concave host framework involving a molecular recognition process such as imaged by the complementarity of a lock and a key. Logically, a new broad area of chemistry grew up on this basis starting in the 1970s. It is called supramolecular chemistry and means the chemistry beyond the molecule. This article surveys the various types of inclusion compounds and their applications.