2,3-Diaminopyridinium 3-carboxy-4-hydroxybenzenesulfonate monohydrate

In the title hydrated molecular salt, C5H8N3 +·C7H5O6S−·H2O, the ion pairs and water molecules are connected by N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, thereby forming a three-dimensional network. There is an intramolecular O—H⋯O hydrogen bond in the 3-carboxy-4-hydroxybenzenesulfonate anion, which generates an S(6) ring motif.


Related literature
For background to 5-sulfosalicylic acid and related compounds, see: Marzotto et al. (2001); Onoda et al. (2001); Baskar Raj et al. (2003). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used in 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 Comment 5-sulfosalicylic acid, (5-SSA), has been known for a long time to possess anti-inflammatory activity. When it forms complexes with metals, its biological activity is greatly enhanced (Marzotto et al., 2001). Hydrogen-bonding patterns involving sulfonate groups in biological systems and metal complexes are of current interest (Onoda et al., 2001). Such interactions can be utilized for designing supramolecular architectures (Baskar Raj et al., 2003). With the aim of gaining more insight into hydrogen-bonding interactions involving 5-SSA and pyridine derivatives, we report here the molecular and supramolecular structure of the title compound.
In the crystal (Fig. 2), the ion-pairs and water molecules are connected via N-H···O, O-H···O and C-H···O hydrogen bonds (Table 1), forming a three-dimensional network.

Experimental
Hot methanol solutions (20 ml) of 2,3-diaminopyridine (52 mg, Aldrich) and 5-sulfosalicylic acid (54. 5 mg, Merck) were mixed and warmed over a heating magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature. Brown plates of the title compound appeared from the mother liquor after a few days.

Refinement
All hydrogen atoms were located from a difference Fourier maps and refined freely [N-H = 0.86 (3)

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.