2-Amino-5-methyl­pyridinium trifluoro­acetate

In the title salt, C₆H₉N₂⁺·C₂F₃O₂⁻, the F atoms of the anion are disordered over two sets of sites, with refined occupancies in a ratio of 0.505 (17):0.495 (17). In the crystal, cations and anions are linked via N—H...O hydrogen bonds, forming R₂²(8) ring motifs. The ionic units are linked into a two-dimensional network parallel to (100) by N—H...O and weak C—H...O hydrogen bonds. The crystal structure is further stabilized by weak C—H...F hydrogen bonds, resulting in a three-dimensional network.

Bis(2,6-diamino-4-chloro­pyrimidin-1-ium) fumarate

In the title salt, 2C₄H₆ClN₄⁺·C₄H₂O₄²⁻, the complete fumarate dianion is generated by crystallographic inversion symmetry. The cation is essentially planar, with a maximum deviation of 0.018 (1) Å. In the anion, the carboxyl­ate group is twisted slightly away from the attached plane, the dihedral angle between the carboxyl­ate and (E)-but-2-ene planes being 12.78 (13)°. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl­ate O atoms of the anion via a pair of N—H...O hydrogen bonds, forming an R₂²(8) ring motif. In addition, another type of R₂²(8) motif is formed by centrosymmetrically related pyrimidinium cations via N—H...N hydrogen bonds. These two combined motifs form a heterotetra­mer. The crystal structure is further stabilized by stong N—H...O, N—H...Cl and weak C—H...O hydrogen bonds, resulting a three-dimensional network.

4,6-Dimeth­oxy-2-(methyl­sulfan­yl)pyrimidine–4-hy­droxy­benzoic acid (1/1)

The base mol­ecule of the title co-crystal, C₇H₁₀N₂O₂S·C₇H₆O₃, is essentially planar, with a maximum deviation of 0.0806 (14) Å for all non-H atoms. The acid mol­ecule is also nearly planar, with a dihedral angle of 8.12 (14)° between the benzene ring and the carb­oxy group. In the crystal, the acid mol­ecules form an inversion dimer through a pair of O—H...O hydrogen bonds with an R₂²(8) ring motif. The pyrimidine mol­ecules are linked on both sides of the dimer into a heterotetra­mer via O—H...N and C—H...O hydrogen bonds with R₂²(8) ring motifs. The heterotetra­mers are further linked by weak C—H...O hydrogen bonds, forming a tape structure along [1-10].