Abstract
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.
Highlights
The crystals of two new salts, 2,6-diamino-4-chloropyrimidin-1-ium 5-chlorosalicylate, C4H6ClN4+ÁC7H4ClO3À, (I), and bis(2,6-diamino-4-chloropyrimidin-1ium) naphthalene-1,5-di-sulfonate, 2C4H6ClN4+ÁC10H6O6S22À, (II), have been synthesized and characterized by single-crystal X-ray diffraction
The N atom of the pyrimidine group in between the amino substituents is protonated and the pyrimidinium cation forms a pair of N— HÁ Á ÁO hydrogen bonds with the carboxylate/sulfonate ion, leading to a robust R22(8) motif
The salt of compound (II) crystallizes with one CDAPY (2,6-diamino-4-chloropyrimidinium) cation and half a molecule of NSA anion in the asymmetric unit (Fig. 2), the other half of NSA being generated by an inversion centre
Summary
The study of supramolecular interactions in the crystals of pyrimidinium salts continues to be an active field since the pyrimidine fragment is a component of nucleobases and many drug molecules. The molecules are often self-assembled by hydrogen bonding, halogen bonding, cationÁ Á Á, anionÁ Á Á and – stacking interactions. Among these interactions, halogen bonding is of particular current interest (Cavallo et al, 2016). Symmetry codes: (i) Àx þ 1; Ày; Àz; (ii) Àx þ 12; y À 12; Àz þ 12; (iii) Àx þ 32; y þ 12; Àz þ 12
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