2-Amino-5-methyl­pyridinium 6-oxo-1,6-dihydro­pyridine-2-carboxyl­ate

The anion of the title salt, C₆H₉N₂⁺·C₆H₄NO₃⁻, undergoes an enol-to-keto tautomerism during the crystallization. In the crystal structure, the cation and anion are held together by a relatively short N—H...O hydrogen bond, and the two anions are further connected to each other by a pair of N—H...O hydrogen bonds with an R₂²(8) ring motif, thus forming a centrosymmetric 2 + 2 aggregate. The aggregates are further linked through weak N—H...O and C—H...O hydrogen bonds, resulting a three-dimensional network.

2-Amino-5-methyl­pyridinium 3-chloro­benzoate

The 3-chloro­benzoate anion of the title salt, C₆H₉N₂⁺·C₇H₄ClO₂⁻, is nearly planar with a dihedral angle of 2.44 (13)° between the benzene ring and the carboxyl­ate group. 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 with an R₂²(8) ring motif, forming an approximately planar ion pair with a dihedral angle of 7.92 (5)° between the pyridinium and benzene rings. The ion pairs are further connected via N—H...O and C—H...O hydrogen bonds, forming a two-dimensional network parallel to the bc plane.

2-Amino-5-methyl­pyridinium 2-amino­benzoate

In the 2-amino­benzoate anion of the title salt, C₆H₉N₂⁺·C₇H₆NO₂⁻, an intra­molecular N—H...O hydrogen bond is observed. The dihedral angle between the ring and the CO₂ group is 8.41 (13)°. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl­ate O atoms via a pair of N—H...O hydrogen bonds, forming an R₂²(8) ring motif. The ion pairs are further connected via N—H...O hydrogen bonds, resulting in a donor–donor–acceptor–acceptor (DDAA) array of quadruple hydrogen bonds. The crystal structure also features a weak N—H...O hydrogen bond and a C—H...π inter­action, resulting in a three-dimensional network.

4-Chloro-6-meth­oxy­pyrimidin-2-amine

The title compound, C₅H₆ClN₃O, is essentially planar with a maximum deviation of 0.0256 (11) Å for all non-H atoms. In the crystal, adjacent mol­ecules are linked by a pair of N—H...N hydrogen bonds, forming an inversion dimer with an R₂²(8) ring motif. The dimers are further linked via N—H...O hydrogen bonds into an undulating sheet structure parallel to the bc plane.

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-Chloro-6-meth­oxy­pyrimidin-2-amine–succinic acid (2/1)

The asymmetric unit of the title compound, 2C₅H₆ClN₃O·C₄H₆O₄, consists of one 4-chloro-6-meth­oxy­pyrimidin-2-amine mol­ecule and one half-mol­ecule of succinic acid which lies about an inversion centre. In the crystal, the acid and base mol­ecules are linked through N—H...O and O—H...N hydrogen bonds, forming a tape along [1-10] in which R₂²(8) and R₄²(8) hydrogen-bond motifs are observed. The tapes are further inter­linked through a pair of C—H...O hydrogen bonds into a sheet parallel to (11-2).

2,6-Diamino-4-chloro­pyrimidine–benzoic acid (1/1)

The benzoic acid mol­ecule of the title compound, C₄H₅ClN₄·C₇H₆O₂, is approximately planar, with a dihedral angle of 1.28 (9)° between the carb­oxy group and the benzene ring. In the crystal, two acid and two base mol­ecules are linked through N—H...O and O—H...N hydrogen bonds, forming a centrosymmetric 2 + 2 unit with R₂²(8) and R₄²(8) motifs. These units are further linked through a pair of N—H...N hydrogen bonds into a tape structure along [1-20]. The crystal structure also features weak π–π [centroid–centroid distance = 3.5984 (11) Å] and C—H...π inter­actions.

2,3-Diamino­pyridinium 4-meth­oxy­quinoline-2-carboxyl­ate

In the 4-meth­oxy­quinoline-2-carboxyl­ate anion of the title salt, C₅H₈N₃⁺·C₁₁H₈NO₃⁻, the dihedral angle between the quinoline ring system and the carboxyl­ate group is 16.54 (15)°. In the crystal, the cations and anions are linked via N—H...O and N—H...N hydrogen bonds, forming a centrosymmetric 2 + 2 aggregate with R₂²(9) and R₄²(8) ring motifs. These units are further connected via N—H...O hydrogen bonds into a layer parallel to the bc plane. The crystal structure is also stabilized by weak C—H...O hydrogen bonds and π–π inter­actions between pyridine rings [centroid–centroid distance = 3.5886 (8) Å] and between pyridine and benzene rings [centroid–centroid distance = 3.6328 (8) Å].