Tuning morphology of sulfadiazine through phase transformation of two novel solvates

Abstract Two new solvates of the widely used antibiotic sulfadiazine were found and fully characterized. The crystal structures of these two solvates were determined. Differences between various sulfadiazine forms were elucidated by analyzing intermolecular interactions, crystal packing modes and molecule conformations. In addition, the phase transformations between solvates and solvent-free form were investigated. The sulfadiazine solvates quickly transformed into solvent-free form in water. The obtained particles were aggregates but with well-defined shape. They maintained the morphology and size of the solvate crystals. The results indicated that solvates can be used as intermediates to regulate the morphology of solvent-free form product through rapid solvent-mediated phase transformation.