7,9-Dimethyl-5-phenylsulfonyl-5H-benzo[b]carbazole

In the title compound, C24H19NO2S, the mean plane of the benzo[b]carbazole ring system makes a dihedral angle of 79.26 (5)° with the phenyl ring. The S atom is in a distorted tetrahedral configuration. The crystal structure exhibits weak C—H⋯O and C—H⋯π interactions.


Comment
Carbazole and its derivatives have become quite attractive compounds owing to their applications in pharmacy and molecular electronics. It has been reported that carbazole derivatives possess various biological activities, such as antitumor (Itoigawa et al., 2000), antioxidative (Tachibana et al., 2001), anti-inflammatory and antimutagenic (Ramsewak et al., 1999).
Carbazole derivatives also exhibit electroactivity and luminescence properties and are considered to be potential candidates for electronic such as colour displays, organic semiconductor lasers and solar cells (Friend et al., 1999). These compounds are thermally and photochemically stable, which makes them useful materials for technological applications. For instance, the carbazole ring is easily funtionalized and covalently linked to other molecules (Diaz et al., 2002). This enables its use as a convenient building block for the design and synthesis of molecular glasses, which are widely studied as components of electroactive and photoactive materials (Zhang et al., 2004).
Against this background, and in order to obtain detailed information on molecular conformations in the solid state, X-ray studies of the title compounds (I) have been carried out. X-Ray analysis confirms the molecular structure and atom connectivity for (I), as illustrated in Fig. 1. The benzocarbazole ring is planar, with bond distances and angles comparable to those reported similiar structures (Hökelek et al., 1998;Hosomi et al., 2000). The mean planes of the benzo(b)carbazole and phenyl rings form a dihedral angle of 79.26 (5)°. The N1-S1-C1 plane is almost orthogonal to carbazole ring [dihedral angle 87.20 (7)°] and phenyl ring [dihedral angle 88.44 (7)°]. The best plane of pyrrole ring N1/C7/C12/C13/C22 subtends a dihedral angle of 28.11 (11)° with sulfonyl group.
The average S-O, S-C, and S-N distances are 1.418, 1.760 and 1.664 Å, respectively, in (I); these are comparable as observed in similiar structures (Chakkaravarthi et al., 2007;Sankaranarayanan et al., 2000). The N-C bond lengths, namely N1-C7 and N1-C22 [1.430 (2) & 1.434 (2) Å in (I)] deviate slightly from the normal mean value reported in the literature (Allen et al., 1987). This indicates that the substitution of the phenylsulfonyl group at atom N1 results in an lengthening of the C-N bond lengths. This may be due to the electron-withdrawing character of the phenylsulfonyl group (Govindasamy et al., 1998). The S atom exhibits significant deviation from that of a regular tetrahedron, with the largest deviations being seen for the O-S-O [O1-S1-O2 119.66 (7)°] and O-S-N angles [O1-S-N1 106.78 (7)°]. The widening of the angles may be due to repulsive interactions between the two short S=O bonds, similar to what is observed in related structures (Chakkaravarthi et al., 2008;Rodriguez et al., 1995).

Refinement
H atoms were positioned geometrically and refined using riding model with C-H = 0.93 Å and U iso (H) = 1.2Ueq(C) for aromatic H atoms and C-H = 0.96 Å and U iso (H) = 1.5Ueq(C) for methyl H atoms. Fig. 1. The molecular structure of (I), with atom labeling scheme. Displacement ellipsoids are drawn at 50% probability level. H atoms are presented as a small spheres of arbitrary radius. Intramolecular H-bonds are shown as dashed lines.