2-(2H-Tetrazol-5-yl)pyridinium perchlorate monohydrate

In the cation of the title compound, C6H6N5 +·ClO4 −·H2O, the pyridinium and tetrazole rings are essentially coplanar, making a dihedral angle of 1.2 (2)°. In the crystal, intermolecular N—H⋯O and O—H⋯O hydrogen bonds link the cations, anions and water molecules into a ribbon-like structure along the c axis. Adjacent ribbons are linked via π–π stacking interactions between the tetrazole rings, with a centroid–centroid distance of 3.484 (2) Å.

In the cation of the title compound, C 6 H 6 N 5 + ÁClO 4 À ÁH 2 O, the pyridinium and tetrazole rings are essentially coplanar, making a dihedral angle of 1.2 (2) . In the crystal, intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the cations, anions and water molecules into a ribbon-like structure along the c axis. Adjacent ribbons are linked via stacking interactions between the tetrazole rings, with a centroid-centroid distance of 3.484 (2) Å .
J. Dai and W.-N. Zheng

Comment
In the past few years, more and more people have focused on the chemistry of tetrazole derivatives because of their multiple coordination modes as ligands to metal ions and for the construction of novel metal-organic frameworks (Zhao et al., 2008;. As an extension of these work on the structure and properties (Fu et al., 2007;, we report here the crystal structure of the title compound 2-(2H-tetrazol-5-yl)pyridinium perchlorate monohydrate.
In the title compound ( Fig.1), the pyridine N atom is protonated. The pyridinium and tetrazole rings are essentially coplanar, with the dihedral angle between them being 1.2 (2)°. The geometric parameters of the tetrazole rings are comparable to those in related structures (Zhao et al., 2008;Fu et al., 2009).
The crystal packing is stabilized by N-H···O and O-H···O hydrogen bonds. These hydrogen bonds link the ionic units and water molecules to form a ribbon like structure parallel to the c axis (Table 1 and Fig.2).

Experimental
Picolinonitrile (30 mmol), NaN 3 (45 mmol), NH 4 Cl (33 mmol) and DMF (50 ml) were added in a flask under nitrogen atmosphere and the mixture was stirred at 110°C for 20 h. The resulting solution was then poured into ice-water (100 ml), and a white solid was obtained after adding HCl (6 M) till pH = 6. The precipitate was filtered and washed with distilled water.
Colourless block-shaped crystals suitable for X-ray analysis were obtained from the crude product by slow evaporation of a water-HClO 4 (50:1 v/v) solution.

Refinement
All H atoms attached to C and N atoms were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic), N-H = 0.86 Å (pyridine N) and N-H = 0.90 Å (tetrazole N) with U iso (H) =1.2U eq (C,N). H atoms of the water molecule were located in difference Fourier maps and freely refined. In the last stage of the refinement they were treated as riding on the O atom, with U ĩso (H) = 1.5U eq (O). Fig. 1. The asymmetric unit of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.