Two new salts, namely 2,6-diamino-4-chloropyrimidinium 2-carboxy-3-nitrobenzoate, C4H6ClN4
+·C8H4NO6
−, (I), and 2,6-diamino-4-chloropyrimidinium p-toluenesulfonate monohydrate, C4H6ClN4
+·C7H7O3S−·H2O, (II), have been synthesized and characterized by single-crystal X-ray diffraction. In both crystal structures, the N atom in the 1-position of the pyrimidine ring is protonated. In salt (I), the protonated N atom and the amino group of the pyrimidinium cation interact with the carboxylate group of the anion through N—H...O hydrogen bonds to form a heterosynthon with an R
2
2(8) ring motif. In hydrated salt (II), the presence of the water molecule prevents the formation of the familiar R
2
2(8) ring motif. Instead, an expanded ring [i.e.
R
3
2(8)] is formed involving the sulfonate group, the pyrimidinium cation and the water molecule. Both salts form a supramolecular homosynthon [R
2
2(8) ring motif] through N—H...N hydrogen bonds. The molecular structures are further stabilized by π–π stacking, and C=O...π, C—H...O and C—H...Cl interactions.
Understanding the Aqueous Solubility of Anthraquinone Sulfonate Salts: The Quest for High Capacity Electrolytes of Redox Flow Batteries
