2-[(1Z)-(9-Ethyl-9H-carbazol-3-yl)methyleneamino]-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile–benzene (2/1)

In the title compound, 2C24H21N3S·C6H6, the two independent Schiff base molecules (A and B) in the asymmetric unit differ in the orientation of the tetrahydrobenzothiophene ring system with respect to the carbazole ring system by 180° rotation about the C—C bond in the C—C=N—C linkage. The two molecules also differ in the orientation of the ethyl groups [C—N—C—C torsion angle of 90.7 (3)° in molecule A, and −79.4 (3)° in molecule B]. In molecule B, two methylene C atoms of the cyclohexene ring are disordered over two sites with occupancies of 0.58 (1) and 0.42 (1). The cyclohexene rings in both molecules adopt half-chair conformations. The dihedral angle between the thiophene ring and the carbazole ring system is 8.07 (9)° in molecule A [3.10 (9)° in molecule B]. In the crystal structure, the independent molecules are linked into dimers by intermolecular C—H⋯N hydrogen bonds. In addition, C—H⋯π interactions are observed.

In the title compound, 2C 24 H 21 N 3 SÁC 6 H 6 , the two independent Schiff base molecules (A and B) in the asymmetric unit differ in the orientation of the tetrahydrobenzothiophene ring system with respect to the carbazole ring system by 180 rotation about the C-C bond in the C-C N-C linkage. The two molecules also differ in the orientation of the ethyl groups [C-N-C-C torsion angle of 90.7 (3) in molecule A, and À79.4 (3) in molecule B]. In molecule B, two methylene C atoms of the cyclohexene ring are disordered over two sites with occupancies of 0.58 (1) and 0.42 (1). The cyclohexene rings in both molecules adopt half-chair conformations. The dihedral angle between the thiophene ring and the carbazole ring system is 8.07 (9) in molecule A [3.10 (9) in molecule B]. In the crystal structure, the independent molecules are linked into dimers by intermolecular C-HÁ Á ÁN hydrogen bonds. In addition, C-HÁ Á Á interactions are observed.
In the crystal structure ( Fig. 2), the benzene solvent molecule is not involved in intermolecular hydrogen bonding. The Schiff base molecules are linked into dimers by pairs of intermolecular C22A-H22A···N3B hydrogen bonds (Table 1). The crystal structure is further stabilized by weak intermolecular C-H···π interactions (Table 1).

Experimental
A mixture of carbazolealdehyde (0.50 g, 0.0022 mol) and 2-amino-3-cyanobenzothiophene (0.38 g, 0.0022 mol) in methanol (15 ml) was refluxed for 5 h with stirring to give a light yellow precipitate. It was then filtered and washed with methanol to give the pure Schiff base. Good quality single crystals were recrystallized from a mixture of benzene, chloroform and methanol (4:4:2). (Yield 78 %, M.p. 468 K).
supplementary materials sup-2 Refinement Atoms C18B and C19B are both disordered over two positions with occupancies of 0.58 (1) and 0.42 (1). In both disorder components, the C-C distances involving the disordered atoms were restrained to be equal. In the benzene solvent molecule, the C-C distances were restrained to 1.384 (3) Å. The U ij components of atom C18X and all C atoms of the benzene solvent molecule were restrained to an approximate isotropic behaviour. H atoms were placed in their calculated positions [C-H = 0.93-97 Å] and refined using a riding model with U iso = 1.2 or 1.5 U eq (C). Fig. 1. The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 20 % probability level. For clarity, the benzene solvent molecule is not shown. 2-[(1Z)-(9-Ethyl-9H-carbazol-3-yl)methyleneamino]-4,5,6,7-tetrahydro-1-benzothiophene-3carbonitrile-benzene (2/1)

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.