Supramolecular interactions in some organic hydrated 2,4,6-triaminopyrimidinium carboxylate and sulfate salts

Four salts, namely, 2,4,6-triaminopyrimidinium 6-chloronicotinate dihydrate, C 4 H 8 N 5 + ·C 6 H 3 ClNO 2 − ·2H 2 O, (I), 2,4,6-triaminopyrimidinediium pyridine-2,6-dicarboxylate dihydrate, C 4 H 9 N 5 2+ ·C 7 H 3 NO 4 2− ·2H 2 O, (II), 2,4,6-triaminopyrimidinediium sulfate monohydrate, C 4 H 9 N 5 2+ ·SO 4 2− ·H 2 O, (III), and 2,4,6-triaminopyrimidinium 3,5-dinitrobenzoate dihydrate, C 4 H 8 N 5 + ·C 7 H 3 N 2 O 6 − ·2H 2 O, (IV), were synthesized and characterized by X-ray diffraction techniques. Proton transfer from the corresponding acid to the pyrimidine base has occurred in all four crystal structures. Of the four salts, two [(I) and (IV)] exist as monoprotonated bases and two [(II) and (III)] exist as diprotonated bases. In all four crystal structures, the acid interacts with the pyrimidine base through N—H...O hydrogen bonds, generating an R 2 2 (8) ring motif. The sulfate group mimics the role of the carboxylate anions. The water molecules present in compounds (I)–(IV) form water-mediated large ring motifs. The formation of water-mediated interactions in these crystal structures can be used as a model in the study of the hydration of nucleobases. Water molecules play an important role in building supramolecular structures. In addition to these strong hydrogen-bonding interactions, some of the crystal structures are further enriched by aromatic π–π stacking interactions [(I) and (II)].