Hydrogen-bonding patterns in pyrimethaminium pyridine-3-sulfonate

IN THE ASYMMETRIC UNIT OF THE TITLE SALT [SYSTEMATIC NAME: 2,4-diamino-5-(4-chloro-phen-yl)-6-ethyl-pyrimidin-1-ium pyri-dine-3-sulfonate], C(12)H(14)N(4)Cl(+)·C(5)H(4)NSO(3) (-), 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(2) (2)(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(2) (2)(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.