2-Amino-5-methyl-pyridinium 3-hy-droxy-pyridine-2-carboxyl-ate.

In the 3-hy-droxy-picolinate anion of the title salt, C6H9N2 (+)·C6H4NO3 (-), an intra-molecular O-H⋯O hydrogen bond with an S(6) graph-set motif is formed, so that the anion is essentially planar, with a dihedral angle of 9.55 (9)° between the pyridine ring and the carboxyl-ate group. In the crystal, the cations and anions are linked via N-H⋯O hydrogen bonds, forming a centrosymmetric 2 + 2 aggregate with R 2 (2)(8) and R 4 (2)(8) ring motifs.

2-Amino-5-methyl-pyridinium 4-methyl-benzoate.

The 4-methyl-benzoate anion of the title salt, C6H9N2(+)·C8H7O2(-), is nearly planar, with a dihedral angle of 6.26 (10)° between the benzene ring and the carboxyl-ate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds with an R2(2)(8) ring motif, forming an approximately planar ion pair with a dihedral angle of 9.

2-Amino-5-methyl-pyridinium 4-chloro-benzoate.

The 4-chloro-benzoate anion of the title salt, C6H9N2(+)·C7H4ClO2(-), is nearly planar with a dihedral angle of 5.14 (16)° between the benzene ring and the carboxyl-ate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds with an R2(2)(8) ring motif.

2-Amino-5-methyl-pyridinium 2-hy-droxy-5-chloro-benzoate.

In the 5-chloro-salicylate anion of the title salt, C6H9N2(+)·C7H4ClO3(-), an intra-molecular O-H⋯O hydrogen bond with an S(6) graph-set motif is observed and the dihedral angle between the benzene ring and the -CO2 group is 1.6 (6)°. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms via a pair of N-H⋯O hydrogen bonds, forming an R2(2)(8) ring motif.

4,6-Dimeth-oxy-2-(methyl-sulfan-yl)pyrimidine-4-hy-droxy-benzoic acid (1/1).

The base mol-ecule 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 mol-ecule is also nearly planar, with a dihedral angle of 8.

Bis(2,6-diamino-4-chloro-pyrimidin-1-ium) fumarate.

In the title salt, 2C4H6ClN4(+)·C4H2O4(2-), the complete fumarate dianion is generated by crystallographic inversion symmetry. The cation is essentially planar, with a maximum deviation of 0.018 (1) Å.

2-Amino-5-methyl-pyridinium trifluoro-acetate.

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).

2-Amino-5-methyl-pyridinium 2-amino-benzoate.

In the 2-amino-benzoate anion of the title salt, C(6)H(9)N(2) (+)·C(7)H(6)NO(2) (-), an intra-molecular N-H⋯O hydrogen bond is observed. The dihedral angle between the ring and the CO(2) group is 8.41 (13)°.

2-Amino-5-methyl-pyridinium 3-chloro-benzoate.

The 3-chloro-benzoate anion of the title salt, C(6)H(9)N(2) (+)·C(7)H(4)ClO(2) (-), is nearly planar with a dihedral angle of 2.44 (13)° between the benzene ring and the carboxyl-ate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxyl-ate O atoms of the anion via a pair of N-H⋯O hydrogen bonds with an R(2) (2)(8) ring motif, forming an approximately planar ion pair with a dihedral angle of 7.

2-Amino-5-methyl-pyridinium 6-oxo-1,6-dihydro-pyridine-2-carboxyl-ate.

The anion of the title salt, C(6)H(9)N(2) (+)·C(6)H(4)NO(3) (-), 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 R(2) (2)(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.

Ethyl 6-(4-meth-oxy-phen-yl)-2-oxo-4-phenyl-cyclo-hex-3-ene-carboxyl-ate.

The asymmetric unit of the title compound, C(22)H(22)O(4), consists of two independent mol-ecules (A and B). The cyclo-hexene rings adopt slightly distorted sofa conformations in both mol-ecules. The dihedral angles between the benzene rings are 74.

(2E)-3-(2-Fluoro-phen-yl)-1-(4-fluoro-phen-yl)prop-2-en-1-one.

In the title compouund, C(15)H(10)F(2)O, the mol-ecule exists in an E conformation with respect to the C=C bond [1.3382 (16) Å]. The dihedral angle between the fluoro-substituted benzene rings is 6.