Crystal structure of 2-(2,4-dichlorophenyl)-4-hydroxy-9-phenylsulfonyl-9H-carbazole-3-carbaldehyde

The hydroxy group in this carbazole derivative is involved in an intramolecular O—H⋯O hydrogen bond, which generates an S(6) graph-set motif. In the crystal, pairs of C—H⋯Cl hydrogen bonds link molecules into inversion dimers with an R 2 2(26) motif. Weak C—H⋯O interactions further link these dimers into ribbons propagating in [100].

In the title compound, C 25 H 15 Cl 2 NO 4 S, the dichlorophenyl ring is twisted by 68.69 (11) from the mean plane of the carbazole ring system [r.m.s. deviation = 0.084 (2) ]. The hydroxy group is involved in an intramolecular O-HÁ Á ÁO hydrogen bond, which generates an S(6) graph-set motif. In the crystal, pairs of C-HÁ Á ÁCl hydrogen bonds link molecules into inversion dimers with an R 2 2 (26) motif. Weak C-HÁ Á ÁO interactions further link these dimers into ribbons propagating in [100].

Chemical context
In continuation of our studies of carbazole derivatives, which are found to possess various biological activities, such as antioxidative (Tachibana et al., 2001), anti-inflammatory and antimutagenic (Ramsewak et al., 1999), antibiotic, antifungal and cytotoxic (Chakraborty et al., 1965(Chakraborty et al., , 1978, we report herein on the synthesis and crystal structure of the title compound (I) (Fig. 1).

Structural commentary
The geometric parameters of (I) agree well with those reported for related structures [Chakkaravarthi et al. 2008[Chakkaravarthi et al. , 2009]. The C1-C6 phenyl ring makes a dihedral angle of 79.76 (11) with the carbazole ring system (C7-C18/N1). The dichlorophenyl ring (C21-C25) is twisted by 68.69 (11) from the mean plane of the carbazole ring system and inclined at an angle of 32.22 (13) to the phenyl ring.

Refinement
Crystal data, data collection and structure refinement details are summarized in  The molecular structure of (I) showing the atomic labelling scheme and 50% probability displacement ellipsoids.

Figure 2
A portion of the crystal packing of (I) showing the hydrogen-bonded (dashed lines) ribbon [symmetry codes: (i) 1-x, 2-y, 1-z; (ii) 1 + x, y, z]. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx þ 1; Ày þ 2; Àz þ 1; (ii) x þ 1; y; z. were positioned geometrically and refined using a riding model, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C). The components of the anisotropic displacement parameters in the direction of the bond between O4 and C19 were restrained to be equal within an effective standard deviation of 0.001 using the DELU command in SHELXL97 (Sheldrick, 2008 Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008). 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. 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 > 2sigma(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq C1