Crystal structure of 5-[2-(9H-carbazol-9-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione

The molecular and crystal structure of an unusual oxadiazolethione derivative is reported. The crystal structure is stabilized by N–H⋯O, N–H⋯S, C–H⋯N and C–H⋯S hydrogen bonds together with C–H⋯π(ring) and π–π contacts.


Chemical context
Carbazole derivatives have been shown to have several industrial applications including use in optoelectronic devices (Fitilis et al., 2007;Peng et al., 2011), dye-sensitized solar cells (Li et al., 2010) and photochromic dyes (Billah et al., 2008). Moreover, fused heterocycles with carbazole scaffolds are noted for their biological activities. They are found in drugs such as tubingensin A and B and have been shown to have both antiviral and cytotoxic activities (TePaske et al., 1989). The anti-inflammatory agents caprofen and etodolaca and the antipyretic agent nincazole (Ghoneim et al., 2006) are also carbazole based. The biological activity of so many carbazolebased heterocycles encouraged us to synthesize the title compound and its molecular crystal structure is reported here.

Structural commentary
In the title compound C 16 H 13 N 3 OS, (I), the oxadiazolethione ring binds to the carbazole ring system through a C2-C3-C4-N3 ethylene chain with the ring systems inclined at an angle of ISSN 2056-9890 40.71 (6) , Fig. 1. The carbazole ring system is almost planar with the outer C5-C10 and C11-C16 benzene rings subtending angles of 0.38 (13) and 0.64 (13) , respectively, to the central N3/C5/C10/C11/C16 ring. Bond lengths and angles in both ring systems are normal and similar to those found in the numerous other carbazole structures (see, for example, Kimura et al., 1985) and those of the few known oxadiazolethione derivatives with alkane chains at C5 (Khan et al. 2014;Zheng et al. 2006).

Refinement
Crystal data, data collection and structure refinement details are summarized in

Figure 4
Chains of molecules of (I) along the ac diagonal. Centroid-centroid contacts are drawn as green dotted lines.

5-[2-(9H-carbazol-9-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione
Crystal data 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.