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

Hoong-Kun Fun; Jia Hao Goh; Abdullah M Asiri; Salman A Khan; Khalid A Khan

doi:10.1107/S1600536810014947

. 2010 Apr 28;66(Pt 5):o1200–o1201. doi: 10.1107/S1600536810014947

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

Hoong-Kun Fun ^a,^*,^‡, Jia Hao Goh ^a,^§, Abdullah M Asiri ^b,^¶, Salman A Khan ^b, Khalid A Khan ^b

PMCID: PMC2979233 PMID: 21579233

Abstract

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.

Related literature

For biological and other applications of Schiff base compounds, see: Abu-Hussen (2006 ▶); Elerman et al. (2002 ▶); Panneerselvam et al. (2005 ▶); Walsh et al. (1996 ▶). For ring puckering parameters, see: Cremer & Pople (1975 ▶). For a related structure, see: Elerman & Elmali (1998 ▶).

Experimental

Crystal data

2C₂₄H₂₁N₃S·C₆H₆
M _r = 845.10
Triclinic,
a = 11.4816 (1) Å
b = 13.7322 (2) Å
c = 14.8358 (2) Å
α = 81.841 (1)°
β = 77.083 (1)°
γ = 83.864 (1)°
V = 2250.00 (5) Å³
Z = 2
Mo Kα radiation
μ = 0.16 mm⁻¹
T = 293 K
0.45 × 0.15 × 0.07 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.931, T _max = 0.989
48693 measured reflections
13169 independent reflections
6227 reflections with I > 2σ(I)
R _int = 0.048

Refinement

R[F ² > 2σ(F ²)] = 0.070
wR(F ²) = 0.167
S = 1.01
13169 reflections
580 parameters
63 restraints
H-atom parameters constrained
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810014947/ci5065sup1.cif

e-66-o1200-sup1.cif^{(39.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810014947/ci5065Isup2.hkl

e-66-o1200-Isup2.hkl^{(643.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1, Cg2 and Cg3 are the centroids of the C1B–C6B, C7A–C12A and C14A–C16A/C21A/S1A rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C22A—H22A⋯N3Bⁱ	0.97	2.59	3.487 (3)	155
C11A—H11A⋯Cg1ⁱⁱ	0.93	2.65	3.499 (3)	153
C11B—H11B⋯Cg2ⁱ	0.93	2.82	3.725 (3)	166
C27—H27A⋯Cg3ⁱⁱⁱ	0.93	2.71	3.625 (6)	169

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

HKF and JHG thank Universiti Sains Malaysia (USM) for the Research University Golden Goose grant (No. 1001/PFIZIK/811012). JHG also thanks USM for the award of a USM fellowship. The authors thank the Department of Chemistry, King Abdulaziz University, for providing research facilities.

supplementary crystallographic information

Comment

Schiff bases are an important class of compounds in medicinal and pharmaceutical field. They show biological applications including anti-bacterial (Abu-Hussen, 2006), anti-fungal (Panneerselvam et al., 2005) and anti-tumor (Walsh et al., 1996) activities. In the field of coordination chemistry, they are used extensively as ligands due to intramolecular hydrogen bonds between O and N atoms, which is applicable for the formation of metal complexes. Schiff bases are also used in the field of photochromism and thermochromism in the solid state (Elerman et al., 2002). In this paper, we report the crystal structure of the title Schiff base compound.

The asymmetric unit of the title compound (Fig. 1) consists of two crystallographically independent Schiff base molecules and a benzene solvent molecule. The two independent main molecules differ in the orientation of the tetrahydrobenzothiophene ring system with respect to the 9H-carbazole ring system by 180° rotation about the C9—C13 bond. The conformation of the ethyl group (C22/C23) also differs in both molecules, with C1A—N1A—C22A—C23A torsion angle of 90.7 (3)° in molecule A, indicating (+)-anti-clinal conformation, whereas C1B—N1B—C22B—C23B torsion angle of -79.4 (3)° in molecule B, indicating (-)-syn-clinal conformation.

In molecule A, the cyclohexene ring (C16A-C21A) adopts a half-chair conformation, with puckering parameters of Q = 0.433 (3) Å, θ = 49.1 (4)° and φ = 145.4 (5)° (Cremer & Pople, 1975). In both the major and minor conformers of molecule B, the cyclohexene rings adopt half-chair conformations; the puckering parameters: Q = 0.508 (7) Å, θ = 50.0 (6)° and φ = 155.0 (7)° for the major conformer and Q = 0.467 (9) Å, θ = 130.4 (7)°, and φ = 330.0 (10)° for the minor conformer. The dihedral angle between the thiophene ring and the carbazole ring system is 8.07 (9)° in molecule A and 3.10 (9)° in molecule B. The bond lengths and angles are comparable to a related 4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile structure (Elerman & Elmali, 1998).

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).