Crystal structure of 2,4-di­amino-6-oxo-3,6-di­hydro­pyrimidin-1-ium p-toluene­sulfonate

In the title salt, C(4)H(7)N(4)O(+)·C(7)H(7)O(3)S(−), the 2,6-di­amino-4-oxo-1,3-di­hydro­pyrimidin-1-ium cation inter­acts with the sulfonate group of the p-toluene­sulfonate anion via a pair of N—H⋯O hydrogen bonds, forming a hetero-synthon R (2) (2)(8) that mimics the role of a carboxyl­ate. 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 supra­molecular 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 inter­actions [inter-centroid distance = 3.6539 (7) Å], between the tunnel-like polymer chains, forming slabs parallel to (100).