N-[(E)-Thio­phen-2-yl­methyl­idene]-1,3-benzothia­zol-2-amine

Irvin N Booysen; Muhammed B Ismail; Matthew P Akerman

doi:10.1107/S1600536812030498

. 2012 Jul 18;68(Pt 8):o2489. doi: 10.1107/S1600536812030498

N-[(E)-Thiophen-2-ylmethylidene]-1,3-benzothiazol-2-amine

Irvin N Booysen ^a, Muhammed B Ismail ^a, Matthew P Akerman ^a,^*

PMCID: PMC3414944 PMID: 22904931

Abstract

In the title thiophene-derived Schiff base compound, C₁₂H₈N₂S₂, the thiophene ring is slighty rotated from the benzothiazole group mean plane, giving a dihedral angle of 12.87 (6)°. The largest displacement of an atom in the molecule from the nine-atom mean plane defined by the non-H atoms of the benzothiazole ring system is 0.572 (1) Å, exhibited by the C atom at the 3-position of the thiophene ring. In the crystal, weak C—H⋯S hydrogen bonds involving the thiophene group S atom and the 4-position thiophene C—H group of a symmetry-related molecule lead to an infinite one-dimensional chain colinear with the c axis. The structure is further stabilized by π–π interactions; the distance between the thiazole ring centroid and the centroid of an adjacent benzene ring is 3.686 (1) Å. The crystal studied was an inversion twin with the ratio of components 0.73 (3):0.27 (3).

Related literature

For the synthesis and crystal structure of 2-aminobenzothiazole, see: Ding et al. (2009 ▶). For crystal structures containing 2-aminobenzothiazole derivatives, see: Garcia-Hernandez et al. (2006 ▶). For inhibitory properties against human cancer cell lines and general antitumor properties of benzothiazole derivatives, see: Racane et al. (2001 ▶); O’Brien et al. (2003 ▶). For antibacterial, antifungal, antitumor and antiviral activites of benzthiazoles, see: Yadav & Malipatil (2011 ▶); Singh & Seghal (1988 ▶); Pattan et al. (2005 ▶).

Experimental

Crystal data

C₁₂H₈N₂S₂
M _r = 244.32
Monoclinic,
a = 10.7244 (5) Å
b = 4.6021 (2) Å
c = 11.1280 (5) Å
β = 100.367 (2)°
V = 540.25 (4) Å³
Z = 2
Mo Kα radiation
μ = 0.46 mm⁻¹
T = 100 K
0.45 × 0.20 × 0.12 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2010 ▶) T _min = 0.625, T _max = 0.749
14476 measured reflections
7768 independent reflections
7126 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.033
wR(F ²) = 0.085
S = 1.04
7768 reflections
145 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 0.62 e Å⁻³
Δρ_min = −0.36 e Å⁻³
Absolute structure: Flack (1983 ▶), 2974 Friedel pairs
Flack parameter: 0.27 (3)

Data collection: APEX2 (Bruker, 2010 ▶); cell refinement: SAINT (Bruker, 2010 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: WinGX (Farrugia, 1999 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812030498/lh5495sup1.cif

e-68-o2489-sup1.cif^{(19.8KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812030498/lh5495Isup2.hkl

e-68-o2489-Isup2.hkl^{(372.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812030498/lh5495Isup3.cml

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C11—H11⋯S2ⁱ	0.95	2.92	3.517 (1)	122 (1)

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Symmetry code: (i) Inline graphic .

Acknowledgments

We are grateful to the University of KwaZulu-Natal and the National Research Foundation of South Africa for funding.

supplementary crystallographic information

Comment

Benzothiazoles are naturally occurring molecules which consist of a 5-membered 1,3-thiazole ring fused to a benzene ring. Their derivatives are abundantly distributed in nature and have been shown to have very interesting pharmacological activity, particularly antibacterial, antifungal, antitumor and antiviral properties (Yadav & Malipatil, 2011; Singh & Seghal, 1988; Pattan et al., 2005). The heterocyclic scaffold is readily substituted at the 2-position of the thiazole ring, allowing for derivatization.

The thiophene ring of the title compound (I) is not in the same plane as the 1,3-benzothiazole moiety, with a dihedral angle of 13.6 (1)° relative to the benzthiazole ring. This out-of-plane rotation of the thiophene results in the carbon atom in the 3-position of the thiophene ring (C10) sitting 0.572 (1) Å from the 9-atom mean plane defined by all non-hydrogen atoms of the benzthiazole ring system. The C8—N2 bond distance of 1.290 (1) Å and the C7—N2—C8 bond angle of 118.12 (7)° emphasize the sp² hybridization of the imino nitrogen atom (refer to Figure 1 for the atom numbering scheme). An (E)-configuration about the imine bond is observed for this Schiff base moiety.

The structure exhibits both hydrogen bonding and π···π interactions. The distance between the centroid of the benzene ring and the centroid of the thiazole ring of an adjacent molecule is 3.686 (1) Å. In addition to the π···π interactions there are non-classical hydrogen bonds between the thiophene sulfur atom, S2, and the thiophene hydrogen atom H11 of an adjacent molecule. This hydrogen bond links the molecules into infinite, one-dimensional hydrogen-bonded chains, which are co-linear with the c-axis. The adjacent, hydrogen-bonded molecules are not both in the same plane, the 24-atom mean planes of two adjacent molecules make an angle of 75.9 (1)° to each other. Although the hydrogen bonds are not likely very strong as they are only marginally shorter than the sum of the van der Waals radii (0.066 Å), these intermolecular interactions can stabilize the lattice.

Experimental

A mixture of 2-aminobenzothiazole (1.27 g; 8.45 mmol) and thiophene-2-carbaldehyde (0.92 ml; 10.2 mmol) in methanol (50 ml) was heated to reflux for 24 h. The resulting orange solution was allowed to cool to room temperature and concentrated by rotary evaporation under reduced pressure. Dry toluene (45 ml) was added to the solution and heated to reflux with a Dean and Stark apparatus for an additional 24 h. Upon cooling the title compound was isolated as brown, needle-shaped crystals.