2,3-Diaminopyridinium sorbate–sorbic acid (1/1)

In the title molecular salt–adduct, C5H8N3 +·C6H7O2 −·C6H8O2, the 2,3-diaminopyridinium cation is essentially planar, with a maximum deviation of 0.013 (2) Å, and is protanated at its pyridine N atom. The sorbate anion and sorbic acid molecules exist in extended conformations. In the crystal, the protonated N atom and one of the two amino-group H atoms are hydrogen bonded to the sorbate anion through a pair of N—H⋯O hydrogen bonds, forming an R 1 2(6) ring motif. The carboxyl groups of the sorbic acid molecules and the carboxylate groups of the sorbate anions are connected via O—H⋯O hydrogen bonds. Furthermore, the ion pairs and neutral molecules are connected via intermolecular N—H⋯O hydrogen bonds, forming sheets lying parallel to (100).

In the title molecular salt-adduct, C 5 H 8 N 3 + ÁC 6 H 7 O 2 À ÁC 6 H 8 O 2 , the 2,3-diaminopyridinium cation is essentially planar, with a maximum deviation of 0.013 (2) Å , and is protanated at its pyridine N atom. The sorbate anion and sorbic acid molecules exist in extended conformations. In the crystal, the protonated N atom and one of the two amino-group H atoms are hydrogen bonded to the sorbate anion through a pair of N-HÁ Á ÁO hydrogen bonds, forming an R 1 2 (6) ring motif. The carboxyl groups of the sorbic acid molecules and the carboxylate groups of the sorbate anions are connected via O-HÁ Á ÁO hydrogen bonds. Furthermore, the ion pairs and neutral molecules are connected via intermolecular N-HÁ Á ÁO hydrogen bonds, forming sheets lying parallel to (100).
In the crystal, (Fig. 2), the protonated N1 atom and the 2-amino group N atom (N2) is hydrogen-bonded to the carboxylate oxygen atoms (O1A and O2A) via a pair of N-H···O hydrogen bonds forming a ring motif R 1 2 (6) (Bernstein et al., 1995). The carboxyl groups of the sorbic acid molecules and the carboxylate groups of the sorbate anions are connected via O-H···O hydrogen bonds. Furthermore, the ion pairs and neutral molecules are connected via N-H···O hydrogen bonds (see Table 1 for symmetry codes) forming two-dimensional networks parallel to (100).

Experimental
A hot methanol solution (20 ml) of 2,3-diaminopyridine (59 mg, Aldrich) and sorbic acid (56 mg, Merck) were mixed and warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and brown plates of the title compound appeared after a few days.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.