Exploring sulfathiourea solvate structures: A combined experimental and computational study on crystal forms, desolvation, and stability

Abstract

Sulfathiourea (STU), a sulfonamide derivative, underwent an extensive solvate screening program, leading to the discovery of the first solvates of this compound. Six solvates were identified, five of which were successfully solved using X-ray powder diffraction data, complemented by electronic structure calculations. Among these, three are monosolvates (with dimethyl sulfoxide, tetrahydrofuran, and dimethyl carbonate). The DMSO solvate exhibits the highest stability of all the solvates, attributed to numerous stabilizing STU···DMSO and DMSO···DMSO interactions. The remaining three solvates are 1,4-dioxane solvates, two of which are polymorphs with hemisolvate stoichiometry. Each of the solvates adopts a unique packing arrangement, with their formation dependent on the starting anhydrate and processing time. Notably, two of the 1,4-dioxane solvates act as intermediates during the formation of the most stable of the three 1,4-dioxane solvates. Pairwise intermolecular energy calculations for all structurally resolved solvates revealed that solvent molecules play a crucial role in stabilizing the lattice energy of these multicomponent solid-state forms. This study, therefore, provides valuable insights into the structural characteristics of STU solvates and their impact on solid-form stability and expands the structural knowledge of sulfonamides.