New software for searching the Cambridge Structural Database for solvated and unsolvated crystal structures applied to hydrates

In this paper we describe several new pieces of software that allow the Cambridge Structural Database (CSD) to be searched for solvated and unsolvated crystal structures. One program finds all pairs of solvated and unsolvated crystal structures of the same chemical compound for a given solvent; another program finds all crystal structures that were grown from a particular solvent. In addition, an algorithm was implemented to determine the stereochemistry of a crystal structure from its 3-D atomic coordinates. Results for water as the solvent molecule are presented. It is found that about 25% of all crystal structures grown from water form hydrates. If a chemical compound is soluble in water, it seems almost impossible to predict if it will form a hydrate or not, although presence of both donors and acceptors in the host compound appears to be required. Chiral molecules produce significantly more hydrates, presumably including water to achieve close packing in spite of the lack of inversion centres.