Crystal chemistry and solvent effects in polymorphic systems: Sulfathiazole

Sulfathiazole, a compound that forms four known crystal structures, has been examined with a view to understanding its polymorphism. A graph set approach was used to classify the structural differences and similarities of the polymorphs, the results of which indicated packing motifs common to three of the four structures. By combining this analysis with experimental morphological data, it has been possible to examine the origins of the observed solvent dependence of polymorph appearance in this system. In particular, the possible link between the observed hydrogen-bond motifs of each form and the associated processes of nucleation and crystal growth from n-propanol, nitromethane, ethanol, water and ammonia solution, have been considered.