A simple correlation between the structures of different crystal modifications of a given host-guest complex and their crystallization temperatures

The formation of different crystal modifications of a given host-guest comp lex depending on the crystallization temperature (pseudopolymorphism) is st udied. It is shown that such pseudopolymorphism is a characteristic feature of versatile host compounds. A very important rule for host-guest chemistr y is derived from the results of the X-ray structural investigations of pse udopolymorphs: the higher the crystallization temperature of the modificati on the more closed is the space occupied by guest molecules. On the basis o f the formulated rule a recommendation for the topological control and solu tion of some central problems of supramolecular chemistry is proposed.