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

Abstract

Herein we disclose a new pathway for the design of dapsone co-crystals exploring the formation of N–H⋯O/N interactions using amide and pyridinic derivatives as potential co-formers. Two new co-crystals of dapsone, a sulfonamide antibiotic, with e-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 e-caprolactam the typical NNH2⋯OSO2 interactions of dapsone molecules and the cages formed between them are disrupted by a new NNH2⋯OCONH interaction, in which e-caprolactam molecules further form amide⋯amide R22(8) synthons and (b) in the co-crystal with 4,4′-bipyridine, the NNH2⋯OSO2 interactions between dapsone molecules are maintained and additional NNH2⋯Npyridine 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.