2-Amino-3-ammoniopyridinium dichloride

The asymmetric unit of the title compound, C5H9N3 2+·2Cl−, contains two diprotonated 2,3-diaminopyridine cations and four chloride anions. In the crystal structure, the anions and cations are connected by intermolecular N—H⋯Cl and C—H⋯Cl hydrogen bonds, forming a three-dimensional network. The crystal structure is further stabilized by π–π interactions between pyridinium rings [centroid–centroid distance = 3.695 (1) Å].

Its molecular and crystal structure is presented here.

Experimental
To a hot methanol solution (20 ml) of 2,3-diaminopyridine (27 mg, Aldrich) was added a few drops of hydrochloric acid.
The solution was warmed over a water bath for a few minutes. The resulting solution was allowed to cool slowly to room temperature. Crystals of the title compound appeared from the mother liquor after a few days.

Refinement
All the H atoms were located in a difference Fourier map and allowed to refine freely  Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen atoms are shown as spheres of arbitrary radius. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq