5-(3,6-Dibromo-9H-carbazol-9-yl)pentanenitrile

In the title compound, C17H14Br2N2, the carbazole skeleton is nearly planar [maximum deviation = 0.055 (2) Å]. In the crystal, aromatic π–π stacking is observed between parallel carbazole ring systems of adjacent molecules, the shortest centroid–centroid distance between benzene rings being 3.4769 (11) Å.

In the title compound, C 17 H 14 Br 2 N 2 , the carbazole skeleton is nearly planar [maximum deviation = 0.055 (2) Å ]. In the crystal, aromaticstacking is observed between parallel carbazole ring systems of adjacent molecules, the shortest centroid-centroid distance between benzene rings being 3.4769 (11) Å .

Comment
Tetrahydrocarbazole systems are present in the framework of a number of indole-type alkaloids of biological interest (Saxton, 1983). The structures of tricyclic, tetracyclic and pentacyclic ring systems with dithiolane and other substituents of the tetrahydrocarbazole core, have been reported previously (Patır et al., 1997;Hökelek & Patır, 1999). Substituted carbazole based monomers exhibit good electroactive and photoactive properties which make them the most promising candidates for hole transporting mobility of charge carriers (Cloutet et al., 1999) and photoluminescence efficiencies (Wei et al., 2006).
Carbazole based heterocyclic polymer systems can be chemically or electrochemically polymerized to yield materials with interesting properties with a number of applications, such as electroluminescent (Tirapattur et al., 2003), photoactive devices (Taoudi et al., 2001), sensors and rechargable batteries (Saraswathi et al., 1999) and electrochromic displays (Sarac et al., 2000). The title compound, (I), may be considered as a synthetic precursor of tetracyclic indole alkaloids of biological interests. The present study was undertaken to ascertain its crystal structure.
The title compound consists of a carbazole skeleton with a pentanenitrile group (Fig. 1), where the bond lengths and angles are within normal ranges, and generally agree with those in the previously reported compounds. In all structures atom N9 is substituted.

Experimental
For the preparation of the title compound, (I), sodium hydride (1.16 g, 30.76 mmol) was added to a solution of 3,6-dibromocarbazole (5.00 g, 15.38 mmol) in dry tetrahydrofuran (200 ml) in several portions, and stirred at 353 K for 2 h under argon atmosphere. Then, chlorovaleronitrile (3.46 ml, 30.76 mmol) was added and stirred at 373 K for 6 d. The reaction mixture was cooled in an ice bath, and hydrochloric acid (10%, 200 ml) was added. After the extraction with chloroform (300 ml), the organic layer was dried over anhydrous magnesium sulfate and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography using silica gel and chloroform, and the product was recrystallized from diethyl ether (yield 4.50 g, 80.12%; m.p. 327 K).
supplementary materials sup-2 Refinement H atoms were positioned geometrically with C-H = 0.95 and 0.99 Å for aromatic and methylene H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title molecule with the atom-numbering scheme. The displacement ellipsoids are drawn at the 50% probability level. 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 > σ(F 2 ) is used only for calculating Rfactors(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.