4-Aminopyridinium 2-hydroxybenzoate

In the salicylate anion of the title salt, C5H7N2 +·C7H5O3 −, an intramolecular O—H⋯O hydrogen bond generating an S(6) ring motif is observed. In the crystal structure, the cations and anions are linked into a two-dimensional network parallel to the ab plane by N—H⋯O and C—H⋯O hydrogen bonds. The network contains R 2 2(7) and R 1 2(4) ring motifs. Weak π–π interactions between the benzene and pyridinium rings [centroid–centroid distance = 3.688 (1) Å] are also observed.

In the salicylate anion of the title salt, C 5 H 7 N 2 + ÁC 7 H 5 O 3 À , an intramolecular O-HÁ Á ÁO hydrogen bond generating an S(6) ring motif is observed. In the crystal structure, the cations and anions are linked into a two-dimensional network parallel to the ab plane by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds. The network contains R 2 2 (7) and R 1 2 (4) ring motifs. Weakinteractions between the benzene and pyridinium rings [centroid-centroid distance = 3.688 (1) Å ] are also observed.
Salicylic acid (SA) is a common component in liquid scintillation systems. Salts of salicylic acid are good candidates for dry solid scintillators. Knowledge of these structural data is important to the development of a fundamental understanding of its scintillating properties, and more generally a predictive capability for tailoring materials to achieve desired scintillation properties. The present study has been carried out in order to study the hydrogen bonding patterns present in the crystal structure of 4-aminopyridinium salicylate, (I).
The bond lengths (Allen et al., 1987) and angles are within normal ranges.

Experimental
A hot methanol solution (20 ml) of 4-aminopyridine (0.04705 g, Aldrich) and salicylic acid (0.0691 g, Merck) was warmed for 30 min over a water bath. The solution was cooled slowly and kept at room temperature. After a few days, colourless crystals were obtained. were refined using a riding model, with U iso (H) = 1.2 U eq (C). Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Dashed line indicates the intramolecular hydrogen bond.

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.