Solvates and a monohydrate of N4-acetylsulfamerazine: Structural, thermochemical, and computational analysis

A monohydrate, and three solvates of a metabolite of an antibacterial agent, sulfamerazine, N4-acetylsulfamerazine (NSMZ), were identified and characterized by nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and single crystal X-ray diffraction. The solvates were obtained with the solvents: acetic acid, methanol, and 1,4-dioxane. All the crystal structures belong to the triclinic, P1¯ space group. Analysis of hydrogen bonding in the crystal structures revealed that the NSMZ molecules form a dimer via a pair of intermolecular N–H⋯N hydrogen bonds. These dimers are interconnected to each other via the solvent molecules forming extended hydrogen bonded networks. The conformations of the NSMZ in the hydrate/solvates are found to be significantly different. Thermal analysis established the stability and confirmed molar ratios of the reported hydrate/solvates, whereas crystal lattice energies and competitive crystallization experiments confirmed the stability of methanol solvate over the hydrate and other solvates.

► N4-acetylsulfamerazine (NSMZ) forms a monohydrate, and three solvates.
► Single crystal X-ray diffraction revealed different hydrogen bonded networks.
► NSMZ molecule adopts different conformations in crystal structures of solvates/hydrate.
► Computational analysis revealed the greater stability of methanol solvate.
► Competitive crystallization experiments are consistent with the computational analysis.