2-Amino-5-chloro­pyridinium 6-oxo-1,6-dihydro­pyridine-2-carboxyl­ate 0.85-hydrate

In the title salt, C5H6ClN2 +·C6H4NO3 −·0.85H2O, the pyridin­ium ring is planar, with a maximum deviation of 0.010 (2) Å. In the crystal structure, the cations, anions and water mol­ecules are linked via N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network

2-Amino-5-methyl­pyridinium nicotinate

In the title compound, C6H9N2 +·C6H4NO2 −, the 2-amino-5-methyl­pyridinium cation is essentially planar, with a maximum deviation of 0.023 (2) Å. In the crystal, the cations and anions are linked via strong N—H⋯O hydrogen bonds, forming a two dimensional network parallel to (100). In addition, π⋯π inter­actions involving the pyridinium and pyridine rings, with centroid–centroid distances of 3.6383 (8) Å, are observed

2-Amino-5-methyl­pyridinium 2-carb­oxy­acetate

In the title mol­ecular salt, C6H9N2 +·C3H3O4 −, the cation is essentially planar, with a maximum deviation of 0.010 (3) Å. In the anion, an intra­molecular O—H⋯O hydrogen bond generates an S(6) ring and results in a folded conformation. In the crystal, the protonated NH group 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 R 2 2(8) ring motif. Weak inter­molecular C—H⋯O inter­actions help to further stabilize the crystal structure

2-Amino-5-chloro­pyridinium (Z)-3-carb­oxy­prop-2-enoate 0.25-hydrate

In the title hydrated salt, C5H6ClN2 +·C4H3O4 −·0.25H2O, the water O atom lies on a twofold axis with 0.25 occupancy. The 2-amino-5-chloro­pyridinium cation is almost planar, with a maximum deviation of 0.015 (3) Å. In the hydrogen malate anion, an intra­molecular O—H⋯O hydrogen bond generates an S(7) ring and results in a folded conformation. 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 R 2 2(8) ring motif. The ion pairs are further connected via O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, forming layers parallel to the ab plane which stack down the c axis

2-Amino-3-ammonio­pyridinium dichloride

The asymmetric unit of the title compound, C5H9N3 2+·2Cl−, contains two diprotonated 2,3-diamino­pyridine cations and four chloride anions. In the crystal structure, the anions and cations are connected by inter­molecular N—H⋯Cl and C—H⋯Cl hydrogen bonds, forming a three-dimensional network. The crystal structure is further stabilized by π–π inter­actions between pyridinium rings [centroid–centroid distance = 3.695 (1) Å]

5,6-Di-2-thienyl-2,3-dihydro­pyrazine

In the title compound, C12H10N2S2, which was synthesized by the reaction of 2,2′-thenil and ethyl­enediamine, the dihedral angle between the two thio­phene rings is 66.33 (9)°. In the crystal structure, inter­molecular C—H⋯N hydrogen bonds link the mol­ecules into infinite chains along the b axis and weak C—H⋯π inter­actions may further stabilize the structure

3,4-Diaminopyridinium 2-carboxy-4,6-dinitrophenolate

In the title salt, C5H8N3 +·C7H3N2O7 −, the pyridine N atom of the 3,4-diamino­pyridine mol­ecule is protonated. The 3,5-dinitro­salicylate anion shows whole-mol­ecule disorder over two orientations with a refined occupancy ratio of 0.875 (4): 0.125 (4). In the crystal, the cations and anions are connected by inter­molecular N—H⋯O and C—H⋯O hydrogen bonds, forming a three-dimensional network

4-Meth­oxy­quinolinium-2-carboxyl­ate dihydrate

The title hydrated quinoline derivative, C11H9NO3·2H2O, crystallizes as a zwitterion in which the quinoline N atom is protonated. The quinoline ring is essentially planar, with a maximum deviation of 0.017 (2) Å. An intra­molecular N—H⋯O hydrogen bond between the protonated N atom and the O atom of the carboxyl­ate group in the zwitterion forms an S(5) ring motif. In the crystal, the zwitterions are connected into inversion dimers via pairs of N—H⋯O and C—H⋯O hydrogen bonds with R 2 2(4) and R 1 2(6) motifs. The water mol­ecules are connected via O—H⋯O hydrogen bonds, forming supra­molecular chains along the c axis. Furthermore, the chains and the dimers are connected via O—H⋯O hydrogen bonds, forming ladder-like supra­molecular ribbons along the c axis

2-Amino-5-chloro­pyridinium trifluoro­acetate

The asymmetric unit of the title salt, C5H6ClN2 +·C2F3O2 −, contains two independent 2-amino-5-chloro­pyridinium cations and two independent trifluoro­acetate anions. The F atoms of both anions are disordered over two sets of positions, with occupancy ratios of 0.672 (12):0.328 (12) and 0.587 (15):0.413 (15). In the crystal, the cations and anions are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001)

2-Amino-5-methyl­pyridinium 4-hydroxy­benzoate

In the title salt, C6H9N2 +·C7H5O3 −, the carboxyl­ate mean plane of the 4-hydroxy­benzoate anion is twisted by 13.07 (4)° from the attached ring. In the crystal structure, the ions are linked into a two-dimensional network by N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds. Within this network, the N—H⋯O hydrogen bonds generate R 2 2(8) ring motifs. In addition, π–π inter­actions involving the pyridinium rings, with a centroid–centroid distance of 3.7599 (4) Å, are observed