2,3-Diaminopyridinium 3-chlorobenzoate–3-chlorobenzoic acid (1/1)

The asymmetric unit of the title compound, C5H8N3 +·C7H4ClO2 −·C7H5ClO2, contains an ion pair and a 3-chlorobenzoic acid molecule. In the cation, the pyridine N atom is protonated. In the crystal, the components are connected via N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, thereby forming sheets lying parallel to (100).

The asymmetric unit of the title compound, C 5 H 8 N 3 + Á-C 7 H 4 ClO 2 À ÁC 7 H 5 ClO 2 , contains an ion pair and a 3-chlorobenzoic acid molecule. In the cation, the pyridine N atom is protonated. In the crystal, the components are connected via N-HÁ Á ÁO, O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, thereby forming sheets lying parallel to (100).
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 Comment 2-Aminopyridine is one of the most frequently used synthons in supramolecular chemistry based on hydrogen bonds (Bis & Zaworotko, 2005;Bis et al., 2006). In the crystals of such compounds, weak intermolecular interactions involving halide ions, halogen-halide interactions, as well as π···π stacking effects, are found to play an important role in the organization of the structural units (Desiraju, 2001;Haddad & Willett, 2001;Willett et al., 2003). In order to study some interesting hydrogen bonding interactions, the synthesis and structure of the title compound, (I), is presented here.
In the crystal of (I), (Fig. 2), the ion-pairs and the neutral acid molecules are connected via N-H···O, O-H···N and C-H···O hydrogen bonds forming two-dimensional networks parallel to (1 0 0)-plane.

Experimental
Hot methanol solutions (20 ml) of 2,3-diaminopyridine (27 mg, Aldrich) and 3-chlorobenzoic acid (39 mg, Merck) were mixed and warmed over a heated magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature. Brown plates of (I) appeared from the mother liquor 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.