Synthon hierarchy in theobromine cocrystals with hydroxybenzoic acids as coformers

Pharmaceutical cocrystals, multicomponent solids composed of molecular and/or ionic compounds connected by noncovalent interactions, are objects of interest in crystal engineering. Theobromine, as an active pharmaceutical ingredient, was used for cocrystallization with dihydroxybenzoic acids as crystal coformers. All of these dimethylxanthine derivatives were obtained by slow evaporation from solution and they were structurally-characterized by a single X-ray diffraction method. Solid-state synthesis products through grinding (green chemistry experiments) were confirmed by powder X-ray diffraction measurements. Simultaneous thermal analyses for samples from grinding were performed. The various supramolecular synthons formed by theobromine responsible for the arrangement of molecules in the crystal lattice of its cocrystals were specified. The hydrogen-bonded motifs present in these cocrystals together with theobromine-acid solids deposited in the CSD were summarized. Furthermore, UV-vis spectra measurements were made to check the change in the solubility of theobromine after its cocrystallization.