Crystal structure of (E)-2-hydroxy-4′-methoxyazastilbene

The title compound has an E conformation with respect to the azomethine C=N bond and the aromatic rings are inclined to one another by 3.29 (4)°. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming zigzag chains along [10-1].

The title azastilbene derivative, C 14 H 13 NO 2 {systematic name: (E)-2-[(4methoxybenzylidene)amino]phenol}, is a product of the condensation reaction between 4-methoxybenzaldehyde and 2-aminophenol. The molecule adopts an E conformation with respect to the azomethine C N bond and is almost planar, the dihedral angle between the two substituted benzene rings being 3.29 (4) . The methoxy group is coplanar with the benzene ring to which it is attached, the C methyl -O-C-C torsion angle being À1.14 (12) . There is an intramolecular O-HÁ Á ÁN hydrogen bond generating an S(5) ring motif. In the crystal, molecules are linked via C-HÁ Á ÁO hydrogen bonds, forming zigzag chains along [101]. The chains are linked via C-HÁ Á Á interactions, forming a threedimensional structure.

Chemical context
Azastilbenes have been reported to possess various biological activities 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) including lipoxygenase inhibitor (Aslam et al., 2012b) activities. Pd II and Ru III complexes of azastilbenes have been synthesized and some have shown potent antibacterial activity (Briel et al., 1998;Prabhakaran et al., 2008;Puthilibai et al., 2009). The interesting biological activities of azastilbenes have attracted us to synthesis a series of azastilbenes, including the title compound, and to study their antibacterial and antioxidant activities (Kaewmanee et al., 2013(Kaewmanee et al., , 2014. The antibacterial assay for the title compound indicated that it 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 mg/ml. In addition, it also shows interesting antioxidant activity by DPPH assay with the IC 50 value of 0.080AE0.0004 mg/ml. Herein, we report on the synthesis, spectroscopic and crystallographic characterization of the title compound.

Synthesis and crystallization
A solution of 4-methoxybenzaldehyde (2.5 mmol, 0.37 g) in water (20 ml) and 2-aminophenol (2.5 mmol, 0.25 g) in water (20 ml) were mixed and stirred at room temperature for around 8 h until a white precipitate appeared. The resulting white solid was filtered, washed several times with cold ethanol and then dried in vacuo overnight to yield the desired azastilbene (430 mg, 76% yield). Colourless block-shaped crystals, suitable for X-ray structure analysis, were obtained by recrystallization from methanol by slow evaporation at room temperature after several days (m.p. 388-390 K).
UV The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 60% probability level. The intramolecular O-HÁ Á ÁN hydrogen bond is shown as a dashed line (see Table 1).

Figure 2
A view along the b axis of the crystal packing of the title compound. The C-HÁ Á ÁO hydrogen bonds are shown as dashed lines (see Table 1 for details).

Figure 3
A view of the C-HÁ Á Á interactions (dashed lines) in the crystal of the title compound (see Table 1 for details; ring centroids are shown as coloured spheres). Table 1 Hydrogen-bond geometry (Å , ).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The OH H atom was located in a difference Fourier map and freely refined. The C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms: C-H = 0.93-0.96 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms. Crystal structure of (E)-2-hydroxy-4′-methoxyazastilbene Suchada Chantrapromma, Narissara Kaewmanee, Nawong Boonnak, Kan Chantrapromma,

Special details
Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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.