2-Amino­pyridin-1-ium triiodide

The asymmetric unit of the title compound, C₅H₇N₂^+.I₃⁻, consists of one 2-amino­pyridin-1-ium cation (apyH⁺) and one triiodide anion, both located in general postions. The apyH⁺ cation is planar within the experimental uncertainties. The short N—C distance [1.328 (5) Å] of the exocyclic NH₂ group is typical for the imino-form of protonated 2-amino­pyridines. Consequently, the bond lengths within the six-membered ring vary significantly. The geometric parameters of the triiodide anion are in the typical range, with bond lengths of 2.8966 (3) and 2.9389 (3) Å and a bond angle of 176.02 (1)°. In the crystal, N—H ... I hydrogen bonds connect adjacent ions into screwed chains along the b-axis direction. These chains are twisted pairwise into rectangular rods. The pyridinium moieties of neighbouring rods are arranged parallel to each other with a plane-to-plane distance of 3.423 (5) Å.