5-[1-(Carboxymethyl)pyridinium-4-yl]-1,2,3,4-tetrazol-1-ide

In the title compound, C8H7N5O2, the tetrazole and pyridine rings are twisted from each other by a dihedral angle of 17.97 (1)°. The zwitterionic molecules are connected by O—H⋯N hydrogen bonds into a chain parallel to [20]. Further C—H⋯O and C—H⋯N hydrogen bonds link the chains, building up a three-dimensional network.

In the title compound, C 8 H 7 N 5 O 2 , the tetrazole and pyridine rings are twisted from each other by a dihedral angle of 17.97 (1) . The zwitterionic molecules are connected by O-HÁ Á ÁN hydrogen bonds into a chain parallel to [201]. Further C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds link the chains, building up a three-dimensional network.

Comment
In the past few years, there was increasing interest in the chemistry of tetrazole derivatives owing their multiple coordination modes as ligands to metal ions and for the construction of novel metal-organic frameworks (Dai & Fu 2008;Fu et al., 2009;Wen, 2008). We report here the crystal structure of the title compound, 5-(1-(carboxymethyl)pyridinium-4-yl)tetrazol-1-ide.
In the title compound (Fig.1), a carboxymethanide group was connected to the pyridine N atom, thus indicating a positive charge in the pyridine N atom. And the tetrazole ring was showing a negative charge to make the charge balance. The tetrazole and pyridine rings are twisted from each other by a dihedral angle of 17.97 (1)°. The geometric parameters of the tetrazole rings are comparable to those in related molecules (Fu et al., 2009).
In the crystal structure, the zwitterionic molecules are connected by the O-H···N hydrogen bonds, with the O···N distance of 2.646 (2)Å. This H-bonds link the zwitterionic units into a one-dimentional chain parallel to the [2 0 -1] direction (Table   1 and Fig.2). Futhermore, C-H···O and C-H···N link the chain building up a three dimensionnal network (Table 1, Fig. 2).

Refinement
All H atoms attached to C and atoms were fixed geometrically and treated as riding on their parent atoms with C-H = 0.93 Å (aromatic), 0.97 Å (methylene) and O-H = 0.82 Å with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (O).
In the absence of significant anomalous scattering, the absolute configuration could not be reliably determined and then the Friedel pairs were merged and any references to the Flack parameter were removed. Fig. 1

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.