Crystal structure of 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidin-1-ium 3-hy-droxy-pyridine-2-carboxyl-ate.

The asymmetric unit of the title salt, C4H5FN3O(+)·C6H4NO3 (-), contains one 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidin-1-ium (5-fluoro-cytosinium, 5FC) cation and a 3-hy-droxy-picolinate (3HAP) anion. The 4-amino-5-fluoro-2-oxo-2,3-di-hydro-pyrimidine mol-ecule is protonated at one of the pyrimidine N atoms. The typical intra-molecular N-H⋯F and O-H⋯O S(5) and S(6) hydrogen-bond ring motifs are observed in the cations and anions. The protonated N atom and 2-amine group of the 5FC cation inter-act with the 3HPA anion through a pair of nearly parallel N-H⋯O hydrogen bonds, forming a robust R 2 (2)(8) ring motif. The ions are further linked by N-H⋯N, O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, generating R 2 (2)(7), R 3 (3)(12) and R 6 (5)(18) ring motifs, respectively, leading to supra-molecular wave-like sheets parallel to (010). The crystal structure is further stabilized by C-H⋯π inter-actions, generating a three-dimensional architecture.