Constructing co-crystals with molecular sense and supramolecular sensibility

Abstract

Themore than 365,000 organic and organometallic small-molecule crystal structures in the Cambridge Structural Database (CSD) are a good source of data for understanding the crystal structures of solvates. It is trivial with the existing search software [1] to find all CSD entries containing a particular solvent, say water, and a survey of the 50most common solvents in the CSD has been published [2]. It might be interesting, however, to know if any of these solvates also exist in an unsolvated form; given a crystal structure of di-isopropylammonium chloride hydrate in the CSD, for example, one could wonder if a crystal structure of di-isopropylammonium chloride itself is present in the database. A computer program was written that for a given solvent molecule finds all pairs of solvated versus unsolvated CSD entries; a list of solvate structures for which no unsolvated form exists in the CSD is also generated. These lists enable us to examine if properties such as the number of hydrogen-bond donors / acceptors or the molecular flexibility influence solvate formation. Results for hydrates will be presented.