An insight into dapsone co-crystals: sulfones as participants in supramolecular interactions

Herein we disclose a new pathway for the design of dapsone co-crystals exploring the formation of N-H center dot center dot center dot O/N interactions using amide and pyridinic derivatives as potential co-formers. Two new co-crystals of dapsone, a sulfonamide antibiotic, with epsilon-caprolactam and 4,4'-bipyridine have been synthesized preferentially by traditional solution techniques, but mechanochemistry has also been addressed. The full structural characterization of these forms is discussed and shows that: (a) in the co-crystal with epsilon-caprolactam the typical N-NH2 center dot center dot center dot O-SO2 interactions of dapsone molecules and the cages formed between them are disrupted by a new N-NH2 center dot center dot center dot O-CONH interaction, in which epsilon-caprolactam molecules further form amide center dot center dot center dot amide R-2(2)(8) synthons and (b) in the co-crystal with 4,4'-bipyridine, the N-NH2 center dot center dot center dot O-SO2 interactions between dapsone molecules are maintained and additional N-NH2 center dot center dot center dot N-pyridine interactions are responsible for the formation of 4,4'-bipyridine channels between dapsone cages. Moreover, the thermal stability of these co-crystals is also discussed, showing that the co-formers leave the structure and hence the reported melting corresponds to the melting of pure dapsone.