2,3,4,9-Tetrahydro-1H-carbazole

In the title compound, C12H13N, two methylene C atoms of the cyclohexene ring are disordered over two sites with occupancies of 0.591 (10) and 0.409 (10); both disorder components adopt half-chair conformations. The crystal structure is stabilized by intermolecular N—H⋯π and C—H⋯π interactions.

In the title compound, C 12 H 13 N, two methylene C atoms of the cyclohexene ring are disordered over two sites with occupancies of 0.591 (10) and 0.409 (10); both disorder components adopt half-chair conformations. The crystal structure is stabilized by intermolecular N-HÁ Á Á and C-HÁ Á Á interactions.

Comment
Carbazole derivatives exhibit good charge transfer and hole transporting properties, which are being explored for a multitude of optoelectronic and photocatalytic applications, including organic light emitting diodes (OLEDs) (Mi et al., 2003). In carbazole derivatives, the preliminary study shows that the presence of oxygenated substituents increases their biological activity (Hewlins et al., 1984). The 2,3-disubstituted indoles have been used as bidentate synthons for the synthesis of various medicinally important carbazole alkaloids (Mohanakrishnan & Srinivasan, 1995a,b). Intercalation between the base pairs in DNA has been implicated for their anticancer activity. It was conceived that the benzo[b] carbazoles as isosteric analogs of pyrido[4,3-b]carbazoles, with oxygenated D-ring could mimic the anti-cancer activity of ellipticine. So it was of interest to study the anticancer activity of D-ring oxygenated benzo[b]carbazoles as it is believed that these molecules could form a stable intercalation complex with DNA (Kansal & Potier, 1986). Tetrahydrocarbazole derivatives are present in the framework of indole-type alkaloids of biological interest (Phillipson & Zenk, 1980;Saxton, 1983;Abraham, 1975).
We report here the crystal structure of the title compound ( Fig. 1).

Experimental
A mixture of cyclohexanone (0.12 mol) and glacial acetic acid (40 ml) was heated and then redistilled phenylhydrazine (0.1 mol) was added dropwise for 30 min. The mixture was refluxed on a water bath for a further period of 30 min. The reaction mixture was poured into ice-cold water with continuous stirring and brown-coloured solid separated out. It was filtered, washed repeatedly with water and recrystallized from methanol in the presence of a little decolorized carbon to give the title compound. Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a methanol solution.

Refinement
Atoms C10 and C11 of the cyclohexene ring are disordered over two positions (C10A/C10B and C11A/C11B) with refined occupancies of 0.591 (10) and 0.409 (10). The corresponding bond distances involving the disordered atoms were restrained to be equal. H atoms were positioned geometrically (C-H = 0.93Å and N-H = 0.86%A) and were treated as riding on their parent atoms, with U iso (H)=1.2U eq (C,N). In the absence of significant anomalous dispersion effects, Friedel pairs were merged before the final refinement.

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