Solvatomorphs of the Dapsone Structurally Related Molecule 3,3′-Diaminodiphenyl Sulfone with Class 2 Residual Solvents: Insights into Their Crystal Structures, Stability, and Transformations

Three new solvates of 3,3′-diaminodiphenyl sulfone (3APS·ACN_m, 3APS·DX_m, and 3APS·2DX_o) and their solid-state analyses are reported. The two monosolvate compounds (3APS·ACN_m and 3APS·DX_m) may be obtained in the pure form by using different synthetic strategies (e.g., slow evaporation of the solvent, slurry, or adsorption of the solvent), while the disolvate one (3APS·2DX_o) was always obtained in the mixture form with 3APS·DX_m. Interestingly, a previously reported acetonitrile solvate (3APS·ACN_o) was never obtained during the different synthesis attempts. The stability (varying times and temperatures) of the investigated compounds and a preliminary selective adsorption test are also reported. An in silico analysis of the two solvatomorphs with acetonitrile (ACN) and the two different 1,4-dioxane (DX) solvates provides hints to rationalize the results of the solid-state behavior investigation.