2-(1H-Benzoimidazol-2-yl)-6-ethoxy­phenol

Chin Sing Yeap; Hadi Kargar; Reza Kia; Arezoo Jamshidvand; Hoong-Kun Fun

doi:10.1107/S1600536809008071

. 2009 Mar 14;65(Pt 4):o745–o746. doi: 10.1107/S1600536809008071

2-(1H-Benzoimidazol-2-yl)-6-ethoxyphenol

Chin Sing Yeap ^a, Hadi Kargar ^b,^‡, Reza Kia ^a, Arezoo Jamshidvand ^b, Hoong-Kun Fun ^a,^*

PMCID: PMC2969036 PMID: 21582478

Abstract

The title Schiff base compound, C₁₅H₁₄N₂O₂, consists of two crystallographically independent molecules, A and B. Molecule A is almost planar, whereas molecule B is slightly twisted, the dihedral angles between the benzimidazole group and the benzene rings being 2.65 (12) and 13.17 (15)°, respectively. The methyl group of molecule B is disordered over two positions, with a refined site-occupancy ratio of 0.581 (7):0.419 (7). In each molecule, intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. In the crystal structure, both types of molecules are linked via intermolecular bifurcated N—H⋯O hydrogen bonds into one-dimensional extended chains along [010] and form R ₁ ²(5) ring motifs. The crystal structure is further stabilized by intermolecular C—H⋯π and π–π interactions [centroid–centroid distances = 3.4758 (16)–3.596 (2) Å].

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For benzimidazole chemistry, reaction mechanisms and bioactivity, see, for example: Latif et al. (1983 ▶); Craigo et al. (1999 ▶); Gudmundsson et al. (2000 ▶); Trivedi et al.(2006 ▶); Kim et al. (1996 ▶); Ramla et al. (2006 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₁₅H₁₄N₂O₂
M _r = 254.28
Monoclinic,
a = 22.5305 (4) Å
b = 12.0113 (2) Å
c = 21.4241 (3) Å
β = 120.449 (1)°
V = 4998.17 (14) Å³
Z = 16
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.38 × 0.23 × 0.18 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.966, T _max = 0.984
49947 measured reflections
5171 independent reflections
4238 reflections with I > 2σ(I)
R _int = 0.043

Refinement

R[F ² > 2σ(F ²)] = 0.067
wR(F ²) = 0.151
S = 1.19
5171 reflections
372 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.57 e Å⁻³
Δρ_min = −0.48 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); 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/S1600536809008071/lh2781sup1.cif

e-65-0o745-sup1.cif^{(28KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809008071/lh2781Isup2.hkl

e-65-0o745-Isup2.hkl^{(253.3KB, hkl)}

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
O1A—H1OA⋯N1A	0.91 (4)	1.67 (4)	2.557 (4)	164 (4)
N2A—H1NA⋯O1B	0.81 (4)	2.14 (4)	2.865 (3)	149 (3)
N2A—H1NA⋯O2B	0.81 (4)	2.57 (4)	3.199 (3)	136 (3)
O1B—H1OB⋯N1B	0.97 (4)	1.67 (4)	2.567 (3)	151 (3)
N2B—H1NB⋯O1Aⁱ	0.94 (4)	1.95 (4)	2.877 (3)	167 (4)
N2B—H1NB⋯O2Aⁱ	0.94 (4)	2.55 (4)	3.136 (3)	121 (3)
C4A—H4AA⋯Cg1ⁱⁱ	0.93	2.80	3.590 (4)	143
C14B—H14C⋯Cg2ⁱⁱⁱ	0.97	2.84	3.721 (5)	152
C15B—H15D⋯Cg3^iv	0.96	2.76	3.715 (8)	176

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) . Cg1, Cg2 and Cg3 are the centroids of the C8B–C13B, C1B–C6B and N1A–C1A–C6A–N2A–C7A rings, respectively.

Acknowledgments

HKF and RK thank the Malaysian Government and Universiti Sains Malaysia for the Science Fund grant No. 305/PFIZIK/613312. RK thanks Universiti Sains Malaysia for a post-doctoral research fellowship. YCS thanks Universiti Sains Malaysia for a studentship award. HK and AJ thank PNU for financial support. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

supplementary crystallographic information

Comment

Benzimidazoles are used widely in biological applications and as pharmaceutical agents (Craigo et al., 1999; Gudmundsson et al., 2000; Trivedi et al., 2006). They are also used as topoisomerase I inhibitors (Kim et al., 1996) and for antitumor activity (Ramla et al., 2006). Due to these important applications, many synthetic routes towards benzimidazoles have been developed. They can, for example, be synthesized by the reaction of phenolic aldehydes with o-phenylenediamine (Latif et al.,, 1983). Based on this route the title compound was synthesized and its crystal structure is reported here.

The asymmetric unit of the title compound, Fig. 1, consists of two crystallographically independent molecules, A and B with a slightly different conformations due to a disordered group. Intramolecular O—H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). The two molecules A and B are linked together by a bifurcated hydrogen bond involving the two oxygen atoms of the hydroxy and ethoxy groups with a R₁²(5) ring motif. The molecule A is almost planar wheares the molecule B is slightly twisted with the dihedral angles between the benzimidazole and the phenyl rings being 2.65 (12) and 13.17 (15) °, respectively. The methyl group of molecule B is disordered over two positions with a refined site-occupancy ratio of 0.581 (7):0.419 (7). The crystal structure is further stabilized by intermolecular C—H···π [Cg1, Cg2 and Cg3 are the centroids of the C8B–C13B, C1B–C6B and N1A/C1A/C6A/N2A/C7A rings] (Table 1) and π-π interactions [Cg1···Cg4ⁱⁱⁱ = 3.596 (2) and Cg3···Cg5ⁱⁱⁱ = 3.4758 (16) Å; (iii) -x, y, 1/2 - z ; Cg4 and Cg5 are the centroids of the N1B/C1B/C6B/N2B/C7B and C8A–C13A rings]. In the crystal structure, molecules are linked together into 1-D extended chains along the [0 1 0] direction (Fig. 2).

Experimental

An ethanolic solution (50 ml) of 3-ethoxy-salicylaldehyde (2 mmol, 332 mg) was added to 1,2-phenylenediamine (1 mmol, 217 mg). The mixture was refluxed for 2 h, and cooled to room temperature. The resulting colourless powder was filtered, washed with cooled ethanol and dried in vacuo. Single crystals suitable for X-ray diffraction were obtained from an methanol solution at room temperature.