2-Amino-5-methylpyridinium 2-hydroxy-5-chlorobenzoate

In the 5-chlorosalicylate anion of the title salt, C6H9N2 +·C7H4ClO3 −, an intramolecular 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 carboxylate O atoms via a pair of N—H⋯O hydrogen bonds, forming an R 2 2(8) ring motif. The crystal structure also features N—H⋯O and weak C—H⋯O interactions, resulting in a layer parallel to (10-1).

In the 5-chlorosalicylate anion of the title salt, C 6 H 9 N 2 + Á-C 7 H 4 ClO 3 À , an intramolecular O-HÁ Á ÁO hydrogen bond with an S(6) graph-set motif is observed and the dihedral angle between the benzene ring and the -CO 2 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 carboxylate O atoms via a pair of N-HÁ Á ÁO hydrogen bonds, forming an R 2 2 (8) ring motif. The crystal structure also features N-HÁ Á ÁO and weak C-HÁ Á ÁO interactions, resulting in a layer parallel to (101).

Related literature
For details of non-covalent interactions, see: Desiraju (2007); Aakeroy & Seddon (1993). For background to the chemistry of substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For related structures, see: Nahringbauer & Kvick (1977); Raza et al. (2010); Thanigaimani et al. (2012a,b). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bondlength data, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 stacking and electrostatic interactions, etc., have attracted intense interest in recent years because of their fascinating structural diversity and potential applications for functional materials (Desiraju, 2007). Especially, the application of intermolecular hydrogen bonds is a well known and efficient tool in the field of organic crystal design owing to its strength and directional properties (Aakeroy & Seddon, 1993). Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997;Katritzky et al., 1996). The are often involved in hydrogen-bond interactions. In order to study potential hydrogen bonding interactions, as part of our ongoing studies on pyridine derivatives (Thanigaimani et al., 2012a,b), the crystal structure determination of the title compound (I) was carried out.

Experimental
Hot methanol solutions (20 ml) of 2-amino5-methylpyridine (54 mg, Aldrich) and 5-chlorosalicylic acid (43 mg, Aldrich) 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 crystals of the title compound (I) appeared after a few days.

Refinement
O-and N-bound H atoms were located in a difference Fourier maps. Atoms H1O3, H1N1 and H2N2 were refined freely, while atom H1N2 was refined with a bond length restraint N-H = 0.85 (1) Å [refined distance: O3-H1O3 = 0.92 (7)  1.5U eq (methyl C). A rotating group model was used for the methyl group.

Figure 1
The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids.

Figure 2
The crystal packing of the title compound. The H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.  (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 > σ(F 2 ) is used only for calculating R-factors(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.