Supra-molecular inter-actions in 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate.

The crystals of two new salts, 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate, C4H6ClN4+·C7H4ClO3-, (I), and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate, 2C4H6ClN4+·C10H6O6S22-, (II), have been synthesized and characterized by single-crystal X-ray diffraction. In both compounds, the N atom of the pyrimidine group in between the amino substituents is protonated and the pyrimidinium cation forms a pair of N-H⋯O hydrogen bonds with the carboxyl-ate/sulfonate ion, leading to a robust R22(8) motif (supra-molecular heterosynthon). In compound (I), a self-complementary base pairing involving the other pyrimidinium ring nitro-gen atom and one of the amino groups via a pair of N-H⋯N hydrogen bonds [R22(8) homosynthon] is also present. In compound (II), the crystallographic inversion centre coincides with the inversion centre of the naphthalene-1,5-di-sulfonate ion and all the sulfonate O atoms are hydrogen-bond acceptors, generating fused-ring motifs and a quadruple DDAA array. A halogen-bond (Cl⋯Cl) inter-action is present in (I) with a distance and angle of 3.3505 (12) Å and 151.37 (10)°, respectively. In addition, a C-Cl⋯π inter-action and a π-π inter-action in (I) and a π-π inter-action in (II) further stabilize these crystal structures.