2-(4,5-Dimethoxy-2-nitrophenyl)-4-methoxy-3-methyl-9-phenylsulfonyl-9H-carbazole

In the title compound, C28H24N2O7S, the carbazole system is essentially planar, with a maximum deviation of 0.0644 (19) Å for the C atom connected to the 4,5-dimethoxy-2-nitrophenyl group. The dihedral angle between the carbazole moiety and the dimethoxy-substituted nitrophenyl ring is 58.55 (7)°. The sulfonyl group forms two intramolecular C—H⋯O bonds with the adjacent carbazole system, forming two cyclic S(6) motifs. In the crystal, molecules are linked along the a axis in bands consisting of cyclic R 3 3(15) motifs through two further C—H⋯O hydrogen bonds.


Comment
Carbazole and its derivative have become quite attractive compounds owing to their applications in pharmacy and molecular electronics. It has been reported that carbazole derivatives exhibit various biological activities such as antitumor (Itoigawa et al., 2000), anti-inflammatory and antimutagenic (Ramsewak et al., 1999). Carbazole derivatives also exhibit electroactivity and luminenscence and are considered to be potential candidates for electronic applications such as colour displays, organic semiconductors, laser and solar cells (Friend et al., 1999;Zhang et al., 2004).
The title compound, C 28 H 24 N 2 O 7 S, comprises a carbazole ring system which is attached to a phenylsulfonyl ring, a dimethoxy substituted nitrophenyl ring, a methoxy group and a methyl group. The carbazole ring system is essentially planar with maximum deviation of 0.0644 (19) Å for the carbon atom (C10). The methyl group carbon atom (C26) deviates from the adjacent carbazole ring by -0.172 (7) Å. The carbazole ring system is almost orthogonal to phenyl ring (C19-C24) attached to sulfonyl group with dihedral angle of 87.51 (10)°. The dihedral angle between the carbazole ring and the dimethoxy substituted nitrophenyl ring (C13-C18) is 58.55 (7)°.

Refinement
The positions of hydrogen atoms were localized from the difference electron density maps and their distances were geometrically constrained. The hydrogen atoms bound to the C atoms are treated as riding atoms, with d(C-H)=0.93 and Uiso(H) = 1.2Ueq(C) for aromatic, d(C-H)=0.96 and Uiso(H) =1.5Ueq(C) for methyl groups. The rotation angles for methyl groups were optimized by least squares. In the absence of significant anomalous dispersion effects, an absolute structure was not determined and 1749 Friedel pairs were merged.

Figure 1
The molecular structure of the title compound with the atom numbering scheme, displacement ellipsoids are drawn at 30% probability level. H atoms are present as small spheres of arbitary radius. The intramolecular C-H···O hydrogen bonds, which are generate S(6) ring motifs, shown as a dashed lines (see Table 1 for details).  The packing arrangement of the title compound viewed down b axis. The dashed lines indicate C-H···O intermolecular interactions, which results in R 3 3 (15) ring motifs. The hydrogen atoms not involved in the hydrogen bonding and phenylsulfonyl group have been excluded for clarity. Symmetry codes: (i). -1/2 + x,-y,z (ii). 1 + x,y,z.

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. 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 R-factors(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.