4-(1H-Tetrazol-5-yl)-1H-indole

There are two molecules with similar configurations in the asymmetric unit of the title compound, C9H7N5, which are linked by intermolecular N—H⋯N hydrogen bonds into chains with graph-set motif C 2 2(8) along the b axis. The indole core has the expected planar geometry in the two molecules, with a maximum deviation of 0.008 (8) Å from the least-squares plane defined by the nine constituent atoms, and the dihedral angles between the indole and tetrazole rings are similar [42.4 (2) and 42.7 (2)°].

There are two molecules with similar configurations in the asymmetric unit of the title compound, C 9 H 7 N 5 , which are linked by intermolecular N-HÁ Á ÁN hydrogen bonds into chains with graph-set motif C 2 2 (8) along the b axis. The indole core has the expected planar geometry in the two molecules, with a maximum deviation of 0.008 (8) Å from the leastsquares plane defined by the nine constituent atoms, and the dihedral angles between the indole and tetrazole rings are similar [42.4 (2) and 42.7 (2) ].
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BX2301). Indole and its derivatives always possess good physiological activity, which are widely used as medicine, pesticide and organic chemical intermediates (Takatoshi & Makoto, 1994). Meanwhile, tetrazole is not only of good anticancer activities but also a kind of excellent ligands, it can coordinate all kinds of metal ions to form the complexes with significant optical activity (Itoh et al., 1995). In recent decades, there are some reports on the compounds which are synthesized by the combination of the tetrazole and indole rings, and the property study reveals that these compounds always perform unique pharmacological activities (Semenov, 2002).We report here the compound structure of 4-(1-H-tetrazol-5-yl)-1H-indole, (I).
As far as we know, there are no reports on the indole connecting the tetrazole on the C atom. In the title compound C 9 H 7 N 5 , (I) there two molecules in the asymmetric unit which are linked by one intra and intermolecular N-H···N hydrogen bond with set graph-motif C 2 2 (8) along b axis (Bernstein et al., 1995), Fig. 2. The indole core has the expected planar geometry. In both molecules of the symmetric unit the dihedral angles between the indole and tetrazole rings are very close similar 42.4 (2) and 42.7 (2)° so, the two crystallographically independent molecules have almost the same extended conformations and similar bond lengths and angles.

Experimental
All chemicals used (reagent grade) were commercially available. 5-Cyanoindole is synthesized following the methods described by Frederick (Frederick, 1949). To the stirring DMF solution of NaN 3 and Triethylamine, 5-Cyanoindole was added.
Then the whole mixture was heated to 120°C, 1 h later, the solution was cooled to room temperature, and DMF was distilled in vacuum. With some follow-up treatment, the crude product was recrystallized in methanol and seven days later, yellow prism crystal was obtained.

Refinement
In general, H atoms bound to carbon were placed in geometrical positions and refined using a riding model, with C-H = 0.93 and Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the the atom-numbering scheme.