Crystal structure of (E)-N-[(2-chloro-6-methoxyquinolin-3-yl)methylidene]-9-ethyl-9H-carbazol-3-amine

In the title compound, C25H20ClN3O, the dihedral between the carbazole and quinoline ring systems is 50.2 (1)°. The crystal packing features C—H⋯π and π—π interactions, which generate a three-dimensional network.


Chemical context
It has been reported that carbazole derivatives possess various biological activities, such as antitumor (Itoigawa et al., 2000), anti-oxidative (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 devices 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 (Díaz 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). Quinoline derivatives are known to possess a variety of biological properties such as antimalarial and antiviral activity (Cunico et al., 2006;Hartline et al., 2005). Against this background, and in order to obtain detailed information on its molecular conformation in the solid state, the crystal structure of the title compound has been determined. ISSN 2056-9890 2. Structural commentary Fig. 1. shows a displacement ellipsoid plot of (I), with the atom-numbering scheme. The C N bond of the central imine group adopts an E conformation. The mean planes through the essentially planar carbazole [N1/C1-C12; maximum deviation = 0.052 (2) Å for atom C12] and quinoline [N3/C16-C24; maximum deviation = 0.050 (2) Å for atom C16] ring systems form a dihedral angle of 50.2 (1) . The sum of the bond angles around N1 (360.05 ) of the pyrrole ring is in accordance with sp 2 hybridization. Atom Cl1 deviates from the plane of the attached quinoline ring system by 0.100 (1) Å . The geometric parameters of the title molecule agree well with those reported for similar structures (Murugavel et al., 2009;Archana et al., 2011).

Figure 1
Molecular structure of the title compound showing displacement ellipsoids at the 30% probability level. H atoms are drawn as a small spheres of arbitrary radii.

Synthesis and crystallization
A 25 ml round-bottom flask was charged with dimedone (1 mmol), 2-chloro-6-methoxyquinoline-3-carbaldehyde (1 mmol) 9-ethyl-9H-carbazol-3-amine (1 mmol) and sulfated SnO 2 -fly ash catalyst (50 mg) in water (15 ml) and was refluxed at 353 K for 5-10 minutes. The completion of the reaction was monitored by TLC (ethyl acetate and hexane as an eluent 20%). After completion, the reaction mixture was cooled to ambient temperature. Then dichloromethane (20 ml) was added and the organic layer filtered, dried on anhydrous Na 2 SO 4 and the solvent removed using a rotary evaporator. The crude product was purified by column chromatography on silica gel (200 mesh) with hexane and ethyl acetate (4:1) as eluent to afford the title compound in good yield (10%). Red blocks suitable for X-ray diffraction analysis were obtained by recrystallization from dichloromethane solution at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were positioned geometrically and constrained to ride on their parent atom with C-H = 0.93-0.97 Å and with U iso (H)=1.5U eq for methyl H atoms and 1.2U eq (C) for other H atoms.

Computing details
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia (1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.24 e Å −3 Δρ min = −0.14 e Å −3 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.