Trimesic Acid as a Building Block for Ternary and Quaternary Salts and Salt Cocrystals

High Resolution Image Download MS PowerPoint Slide In the field of cocrystals, the synthon-based design of two-component crystals is well established and the interest is now shifting toward higher order cocrystals as the next challenge. Carboxylic acids form a robust synthon with pyridyl coformers and interact with 2-aminopyrimidines through a pair of strong, charge-assisted hydrogen bonds. In this work we describe the formation of higher order salts and salt cocrystals of trimesic acid using 2,4-diaminopyrimidine (pyrimethamine, trimethoprim) and pyridyl (4,4′-bipyridine, 1,2-di(4-pyridyl)ethylene, 1,3-di(4-pyridyl)propane, 4-phenylpyridine) coformers. We report the single crystal structures of five binary, eight ternary and three quaternary systems with the compositions AB, A 2 B, A 3 B, A 2 BC, A 3 BC, A 2 BC 1.5, ABC 1.5, A 1 2 A 2 B, ABC 1 C, 2 A 2 BC 1 C 2 0.5, and A 1 A 2 BC where A is a 2,4-diaminopyrimidine cation, B is the mono-, di- or trianion of trimesic acid and C is a pyridine. We also show that the ternary and quaternary salts and salt cocrystals can be prepared in bulk quantities by liquid-assisted grinding.