Three-dimensional hydrogen-bonded frameworks in organic crystals: a topological study

1551 homomolecular single hydrogen-bonded frameworks in organic crystals have been classified into 148 topological types of three-periodic nets. Different representations of hydrogenbonded frameworks as nets of molecular centroids, edge or ring nets are discussed. To study the influence of hydrogen bonds on the topology of molecular packings, 42 270 molecular crystals without hydrogen bonds have been considered. The topologies of molecular packings are found to be independent of hydrogen bonding. Analysis of 231 homomolecular frameworks composed of crystallographically different molecules shows that molecules not related by symmetry tend to form the same hydrogen-bond pattern. The relations between net topological types, space-group symmetry of crystals, site symmetry and point-group symmetry of molecules are discussed. As a result, a set of rules for the crystal design of molecular frameworks is proposed.