Supramolecular architectures in cytosinium 6-chloronicotinate monohydrate and 5-bromo-6-methylisocytosinium hydrogen sulfate

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6-chloronicotinate monohydrate, C4H6N3O+center dot C6H3ClNO2-center dot H2O, (I), and 5-bromo-6-methylisocytosinium hydrogen sulfate (or 2-amino-5-bromo-4-oxo-6-methylpyrimidinium hydrogen sulfate), C5H7BrN3O+center dot HSO4-, (II), have been prepared and characterized by single-crystal X-ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt (I), the primary R-2(2)(8) ring motif (supramolecular heterosynthon) is formed via a pair of N-H center dot center dot center dot O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N-H center dot center dot center dot O, N-H center dot center dot center dot N, O-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds, forming R-2(2)(8), R-3(2)(7) and R-5(5)(21) motifs, leading to a hydrogen-bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water-carboxylate O-H center dot center dot center dot O hydrogen bonds and pi-pi interactions between the anions and the cations. In salt (II), the hydrogen sulfate ions are linked via O-H center dot center dot center dot O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N-H center dot center dot center dot O hydrogen bonds and vice versa, generating two R-2(2)(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen-halogen (Br center dot center dot center dot Br) and halogen-oxygen (Br center dot center dot center dot O) interactions.