Hydrogen-bonding patterns in pyrimethaminium pyridine-3-sulfonate

Abstract

In the asymmetric unit of the title salt [systematic name: 2,4-diamino-5-(4-Chlorophenyl)-6-ethyl-pyrimidin-1-ium pyri-dine-3-sulfonate], C12H14N4Cl+·C 5H4NSO3-, there are two independent pyrimethaminium cations and two 3-pyridine sulfonate anions. Each sulfonate group inter-acts with the corresponding protonated pyrimidine ring through two N - H⋯O hydrogen bonds, forming a cyclic hydrogen-bonded bimolecular R 22(8) motif. Even though the primary mode of association is the same, the next higher level of supra-molecular architectures are different due to different hydrogen-bonded networks. In one of the independent molecules in the asymmetric unit, the pyrimethamine cation is paired centrosymmetrically through N - H⋯N hydrogen bonds, generating an R 22(8) ring motif. In the other molecule, the pyrimethamine cation does not form any base pairs; instead it forms hydrogen bonds with the 3-pyridine sulfonate anion. The structure is further stabilized by C - H⋯O, C - H⋯N and π-π stacking [centroid-centroid distance = 3.9465 (13) Å] inter-actions.