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

In the title compound, C28H22N2O8S, the carbazole ring system is roughly planar, with a maximum deviation of 0.084 (3) Å for the C atom connected to the 4,5-dimethoxy-2-nitrophenyl ring. The dihedral angle between the carbazole system and the dimethoxy-substituted nitrophenyl ring is 57.05 (10)°. The aldehyde C atom deviates by 0.164 (5) Å from its attached carbazole ring system. The molecular structure is stabilized by C—H⋯O interactions which generate two S(6) and one S(7) ring motif. In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming R 3 3(15) ring motifs, which are further crosslinked by R 3 2(19) ring motifs, resulting in (002) layers. The crystal packing also features C—H⋯π interactions.

In the title compound, C 28 H 22 N 2 O 8 S, the carbazole ring system is roughly planar, with a maximum deviation of 0.084 (3) Å for the C atom connected to the 4,5-dimethoxy-2nitrophenyl ring. The dihedral angle between the carbazole system and the dimethoxy-substituted nitrophenyl ring is 57.05 (10) . The aldehyde C atom deviates by 0.164 (5) Å from its attached carbazole ring system. The molecular structure is stabilized by C-HÁ Á ÁO interactions which generate two S(6) and one S(7) ring motif. In the crystal, molecules are linked by C-HÁ Á ÁO hydrogen bonds, forming R 3 3 (15) ring motifs, which are further crosslinked by R 3 2 (19) ring motifs, resulting in (002) layers. The crystal packing also features C-HÁ Á Á interactions. For the Thorpe-Ingold effect, see: Bassindale (1984). For standard bond lengths, see: Allen et al. (1987). For graph-set notation: Bernstein et al. (1995).

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 22 N 2 O 8 S, comprises a carbazole ring system which is attached to a phenylsulfonyl ring, a dimethoxy substituted nitrophenyl ring, a methoxy group and a aldehyde group. The carbazole ring system is essentially planar with maximum deviation of 0.084 (3)Å for the carbon (C10) atom connected to 4,5-dimethoxy-2-nitrophenyl ring. The aldehyde group carbon (C26) atom and methoxy group oxygen (O5) atom are deviate from the adjacent carbazole ring by -0.164 (5)Å and -0.017 (2)Å, respectively. The carbazole ring system is almost orthogonal to phenyl ring (C19-C24) attached to sulfonyl group with dihedral angle of 88.31 (13)°. The dihedral angle between the carbazole ring and the dimethoxy substituted nitrophenyl ring (C13-C18) is 57.05 (10)°.

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 and aldehyde group, 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 1310 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 non-classical C-H···O hydrogen bonds, which are generate S(6) and S(7) ring motifs, shown as a dashed lines.  The packing arrangement of the title compound viewed down b axis. The dashed lines indicate C-H···O intermolecular interactions, which are results in R 3 3 (15) and R 3 2 (19) 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, 1-y, z; (ii) -1+x, y, z; (iii).

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