(E)-2-[(2,4,6-Tri­meth­oxy­benzyl­idene)amino]­phenol

Narissara Kaewmanee; Suchada Chantrapromma; Nawong Boonnak; Ching Kheng Quah; Hoong-Kun Fun

doi:10.1107/S1600536813032996

. 2013 Dec 14;70(Pt 1):o62–o63. doi: 10.1107/S1600536813032996

(E)-2-[(2,4,6-Trimethoxybenzylidene)amino]phenol¹

Narissara Kaewmanee ^a, Suchada Chantrapromma ^b,^*,^‡, Nawong Boonnak ^c, Ching Kheng Quah ^d, Hoong-Kun Fun ^d,^e,^§

PMCID: PMC3914096 PMID: 24527001

Abstract

There are two independent molecules in the asymmetric unit of the title compound, C₁₆H₁₇NO₄, with similar conformations but some differences in their bond angles. Each molecule adopts a trans configuration with respect to the methylidene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one molecule and 83.53 (7)° in the other. All methoxy groups are approximately coplanar with the attached benzene rings, with C_methyl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent molecules are linked together by O—H⋯N and O—H⋯O hydrogen bonds and a π–π interaction [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H⋯O interactions and another π–π interaction [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.

Related literature

For organic bond-length data, see: Allen et al. (1987 ▶). For related literature on hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For background to and application of aza-stilbene, see: Cheng et al. (2010 ▶); da Silva et al. (2011 ▶); Fujita et al. (2012 ▶); Lu et al. (2012 ▶); Tamizh et al. (2012 ▶). For related structures, see: Kaewmanee et al. (2013 ▶); Sun et al. (2011 ▶). graphic file with name e-70-00o62-scheme1.jpg

Experimental

Crystal data

C₁₆H₁₇NO₄
M _r = 287.31
Triclinic,
a = 7.3819 (6) Å
b = 11.7036 (9) Å
c = 16.4373 (13) Å
α = 89.469 (2)°
β = 85.616 (2)°
γ = 80.456 (2)°
V = 1396.34 (19) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 100 K
0.49 × 0.16 × 0.16 mm

Data collection

Bruker SMART APEX2 CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.954, T _max = 0.985
29313 measured reflections
8129 independent reflections
5872 reflections with I > 2σ(I)
R _int = 0.048

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.148
S = 1.02
8129 reflections
393 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.41 e Å⁻³
Δρ_min = −0.32 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, PLATON (Spek, 2009 ▶), Mercury (Macrae et al., 2006 ▶) and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536813032996/is5324sup1.cif

e-70-00o62-sup1.cif^{(38KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813032996/is5324Isup2.hkl

e-70-00o62-Isup2.hkl^{(397.6KB, hkl)}

Click here for additional data file.^{(5.8KB, cml)}

Supporting information file. DOI: 10.1107/S1600536813032996/is5324Isup3.cml

Additional supporting information: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4A—H1O4⋯O3B	0.88 (2)	2.53 (2)	2.9924 (15)	114.0 (17)
O4A—H1O4⋯N1B	0.88 (2)	1.96 (2)	2.7897 (15)	158 (2)
O4B—H2O4⋯N1A	0.88 (2)	2.00 (2)	2.8013 (16)	151 (2)
O4B—H2O4⋯N1B	0.88 (2)	2.35 (2)	2.7891 (16)	111.1 (18)
C13B—H13B⋯O3A ⁱ	0.95	2.59	3.4639 (19)	154
C15B—H15D⋯O4A ⁱⁱ	0.98	2.43	3.3847 (18)	164

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

Acknowledgments

NK thanks the Center of Excellence for Innovation in Chemistry (PERCH–CIC), Commission on Higher Education, Ministry of Education, and the Graduate School, Prince of Songkla University, for financial support. The authors extend their appreciation to the Malaysian Government and Universiti Sains Malaysia for APEX DE2012 grant No.1002/PFIZIK/910323, and the Deanship of Scientific Research and the Research Center, College of Pharmacy, King Saud University.

supplementary crystallographic information

1. Comment

Aza-stilbenes are a special group of compounds in the Schiff base family which can be synthesized by the reaction of aldehyde with aniline. Aza-stilbenes have been shown to possess potent biological properties such as antibacterial (Tamizh et al., 2012), antioxidant (Cheng et al., 2010; Lu et al., 2012), antifungal (da Silva et al., 2011) and antiproliferative (Fujita et al., 2012) activities. The interesting biological activities of aza-stilbenes have led us to synthesize the title compound (I) and study its antibacterial and antioxidant activities. Our antibacterial assay have shown that (I) possesses moderate to weak antibacterial activity against B. subtilis, S. aureus, P. aeruginosa, S. typhi and S.sonnei with the MIC values in the range of 37.5 to 150 µg/ml. In addition (I) also shows interesting antioxidant activity by DPPH assay with the IC₅₀ value of 0.080 ± 0.0004 µg/ml. We report here the crystal structure of the title compound.

There are two independent molecules, A and B in the asymmetric unit of the title compound, with similar conformations but some differences in bond angles (Fig. 1). The molecular structure exists in a trans configuration with respect to the methylidene C7═N1 double bond [1.2868 (13) and 1.2823 (19) Å for molecules A and B, respectively] and with the torsion angle C8—N1—C7—C1 = -175.58 (13)° for molecule A [177.48 (13)° for molecule B]. The molecule is twisted with the dihedral angle between the two substituted benzene rings being 80.52 (7)° in molecule A and 83.53 (7)° in molecule B. In both molecules, the three methoxy groups are co-planar with their bound benzene rings with the C14—O1—C2—C3 = -3.2 (2)°, C15—O2—C4—C3 = -6.7 (2)° and C16—O3—C6—C5 = -1.5 (2)° in molecule A, and the corresponding values are 5.07 (19), 1.86 (19) and -1.7 (2)° in molecule B. In each molecule, an intramolecular O—H···N hydrogen bond (Fig. 1 and Table 1) generates an S(5) ring motif (Bernstein et al., 1995). The bond distances are in normal ranges (Allen et al., 1987) and are comparable with the related structures (Kaewmanee et al., 2013; Sun et al., 2011).

In the crystal structure, the molecules are linked into dimers by O—H···N and O—H···O hydrogen bonds (Table 1) which form two R²₁(6) ring motifs and an R²₂(10) ring motif (Fig. 2). These dimers are further linked by C—H···O interactions (Table1) into chains along the b direction which arranged into sheets parallel to the ab plane (Fig. 3). There are π–π interactions with Cg1···Cg3 and Cg1···Cg3^iv distances of 3.6030 (9) and 3.9452 (9) Å, respectively (Fig. 2) [symmetry code: (iv) = -1 + x, y, z]; Cg1 and Cg3 are the centroids of C1A–C6A and C1B–C6B rings, respectively.]

2. Experimental

The title compound (I) was prepared by mixing 1:1 molar ratio solutions of 2-aminophenol (2.5 mmol, 0.25 g) in toluene (20 ml) and 2,4,6-trimethoxybenzaldehyde (2.5 mmol, 0.50 g) in toluene (20 ml). The reaction mixture was refluxed for around 4 h, yielding white solids , which was collected by filtration, washed with cold ethanol and dried in air. Colorless block-shaped single crystals suitable for X-ray structure determination were recrystalized from methanol by slow evaporation of the solvent at room temperature after several days (m.p. 450–452 K).