Crystal structure of 2,4-di-amino-6-oxo-3,6-di-hydro-pyrimidin-1-ium p-toluene-sulfonate.

In the title salt, C4H7N4O(+)·C7H7O3S(-), the 2,6-di-amino-4-oxo-1,3-di-hydro-pyrimidin-1-ium cation inter-acts with the sulfonate group of the p-toluene-sulfonate anion via a pair of N-H⋯O hydrogen bonds, forming a hetero-synthon R 2 (2)(8) that mimics the role of a carboxyl-ate. The self-assembled cations form a homo-synthon R 2 (1)(6) motif which is further linked with the sulfonate anion via N-H⋯O hydrogen bonds to generate an R 3 (2)(10) ring motif. The three motifs are fused together and extended as supra-molecular ribbons along the b-axis direction. Adjacent ribbons are further linked via N-H⋯O hydrogen bonds to form an annulus, with an R 4 (4)(20) ring motif, resulting in a tunnel-like arrangement propagating along [010]. There are slipped parallel π-π stacking inter-actions [inter-centroid distance = 3.6539 (7) Å], between the tunnel-like polymer chains, forming slabs parallel to (100).