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, P 1 ¯ 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.