Cocrystals and Salts: The Structural Landscape of Multicomponent Solids of Chalcogenadiazoles

To explore the structural landscape of a variety of 1,3,4-chalcogenadiazoles, more than 150 cocrystallization reactions with carboxylic acids as potential coformers were attempted, and the outcome of each was characterized and classified using FTIR. The results from the FTIR screen were subsequently confirmed using single-crystal X-ray diffraction of products (12 were found to be salts, and the remaining 5 were cocrystals). It was noted that the common ΔpKa “rule” did not provide reliable information on salt vs cocrystal formation in these systems, whereas the use of calculated interaction energies for neutral vs salt-based heteromeric dimers identified a noticeable separation between the two, indicating that such calculations can offer a useful predictor for the outcome of cocrystallization reactions.