Crystal structure of (E)-2-hy-droxy-4'-meth-oxy-aza-stilbene.

The title aza-stilbene derivative, C14H13NO2 {systematic name: (E)-2-[(4-meth-oxy-benzyl-idene)amino]-phenol}, is a product of the condensation reaction between 4-meth-oxy-benzaldehyde and 2-amino-phenol. The mol-ecule 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 meth-oxy group is coplanar with the benzene ring to which it is attached, the Cmeth-yl-O-C-C torsion angle being -1.14 (12)°. There is an intra-molecular O-H⋯N hydrogen bond generating an S(5) ring motif. In the crystal, mol-ecules are linked via C-H⋯O hydrogen bonds, forming zigzag chains along [10-1]. The chains are linked via C-H⋯π inter-actions, forming a three-dimensional structure.

Chemical context

Aza­stilbenes have been reported to possess various biological activities such as anti­bacterial (Tamizh et al., 2012 ▸), anti-oxidant (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. PdII and RuIII 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 anti-oxidant activities (Kaewmanee et al., 2013 ▸, 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 µg/ml. In addition, it also shows inter­esting anti­oxidant activity by DPPH assay with the IC50 value of 0.080±0.0004 µg/ml. Herein, we report on the synthesis, spectroscopic and crystallographic characterization of the title compound.

Structural commentary

The title aza­stilbene compound (Fig. 1 ▸) has an E conformation about the azomethine C7=N1 double bond [1.2825 (10) Å], the C8—N1—C7—C1 torsion angle being −178.67 (8)°. The mol­ecule is almost planar with a dihedral angle of 3.29 (4)° between the two substituted benzene rings. The meth­oxy group is co-planar with the benzene ring to which it is attached, the C14—O1—C4—C5 torsion angle being −1.14 (12)°. There is an intra­molecular O—H⋯N hydrogen bond (Fig. 1 ▸ and Table 1 ▸) that generates an S(5) ring motif. The bond lengths are comparable with those found for some closely related structures (Habibi et al., 2013 ▸; Aslam et al., 2012a ▸; Kaewmanee et al., 2013 ▸, 2014 ▸; Sun et al., 2011 ▸).

Figure 1

The mol­ecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 60% probability level. The intramolecular O—H⋯N hydrogen bond is shown as a dashed line (see Table 1 ▸).

Table 1

Hydrogen-bond geometry (, )

Cg1 and Cg2 are the centroids of rings C1C6 and C8C13, respectively.

DHA	DH	HA	D A	DHA
O2H1O2N1	0.774(18)	2.078(17)	2.6315(11)	128.7(17)
C14H14BO2i	0.96	2.71	3.2876(12)	119
C2H2A Cg2ii	0.93	2.93	3.5662(9)	127
C13H13A Cg1iii	0.93	2.76	3.4671(9)	134

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

Supra­molecular features

In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming zigzag chains along [10] (Fig. 2 ▸ and Table 1 ▸). The chains are linked via C—H⋯π inter­actions (Fig. 3 ▸ and Table 1 ▸), forming a three-dimensional structure.

Figure 2

A view along the b axis of the crystal packing of the title compound. The C—H⋯O hydrogen bonds are shown as dashed lines (see Table 1 ▸ for details).

Figure 3

A view of the C—H⋯π inter­actions (dashed lines) in the crystal of the title compound (see Table 1 ▸ for details; ring centroids are shown as coloured spheres).

Database survey

A search of the Cambridge Structural Database (CSD, Version 5.36; Groom & Allen, 2014 ▸) for aza­stilbenes gave over 2800 hits. A search for 2-(benzyl­idene­amino)­phenols gave 78 hits, and for 2-[(4-meth­oxy­benzyl­idene)amino]­phenols there were five hits. In the compound that most closely resembles the title compound, namely 5-{[(2-hy­droxy­phen­yl)imino]­meth­yl}-2-meth­oxy­phenol (Habibi et al., 2013 ▸), the two aromatic rings are inclined to one another by ca 16.9°.

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–Vis (CH3OH) λmax (log∊): 275 (1.93), 340 (0.61) nm; FT–IR (KBr) ν: 3337, 1595, 1510, 1248, 1027 cm−1.; 1H NMR (300 MHz, DMSO-d 6) δ, p.p.m.: 8.87 (s, 1H), 8.61 (s, 1H), 7.98 (d, J = 8.7 Hz, 2H), 7.18 (dd, J = 7.5, 1.2 Hz, 1H), 7.06 (d, J = 8.7 Hz, 2H), 7.03 (td, J = 7.5, 1.2 Hz, 1H), 6.83 (td, J = 7.5, 1.2 Hz, 1H), 6.09 (dd, J = 7.5, 1.2 Hz, 1H), 3.84 (s, –OCH3). The UV–Vis spectroscopic data showed absorption bands of an aza­stilbene (275 and 340 nm) while the FT–IR spectrum exhibited the stretching vibrations of O—H (3337 cm−1), C=N (1595 cm−1), C=C (1510 cm−1), C—N (1248 cm−1) and C—O (1027 cm−1). The successful synthesis was also supported by the 1H NMR spectroscopic data, which showed the characteristic signals of an olefinic proton at 8.61 (s, 1H) and para-substituted aromatic protons at 7.98 (d, J = 8.7 Hz, 2H) and 7.06 (d, J = 8.7 Hz, 2H), respectively. Moreover the 1H NMR spectrum also showed typical signals of ortho-substituted aromatic protons at 7.18 (dd, J = 7.5, 1.2 Hz, 1H), 7.03 (td, J = 7.5, 1.2 Hz, 1H), 6.83 (td, J = 7.5, 1.2 Hz, 1H) and 6.09 (dd, J = 7.5, 1.2 Hz, 1H) and a meth­oxy proton at 3.84 (s, –OCH3).

The anti­bacterial activity investigation of the title compound against Gram-positive bacteria, which are B. subtilis, S. aureus, MRSA and E. faecalis, and Gram-negative bacteria, which are P. aeruginosa, S. sonnei and S. typhi, showed moderate, mild or no inhibition. The most inter­esting anti­bacterial activity showed moderate activity against P. aeruginosa with an MIC value of 37.5 µg/ml.

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.

Table 2

Experimental details

Crystal data
Chemical formula	C14H13NO2
M r	227.25
Crystal system, space group	Monoclinic, P c
Temperature (K)	100
a, b, c ()	8.0357(3), 5.5554(2), 12.8733(5)
()	101.312(1)
V (3)	563.52(4)
Z	2
Radiation type	Mo K
(mm1)	0.09
Crystal size (mm)	0.55 0.48 0.41
Data collection
Diffractometer	Bruker APEXII D8 Venture
Absorption correction	Multi-scan (SADABS; Bruker, 2009 ▸)
T min, T max	0.953, 0.964
No. of measured, independent and observed [I > 2(I)] reflections	26314, 3449, 3414
R int	0.023
(sin /)max (1)	0.715
Refinement
R[F 2 > 2(F 2)], wR(F 2), S	0.037, 0.100, 1.09
No. of reflections	3449
No. of parameters	160
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
max, min (e 3)	0.37, 0.28

Computer programs: APEX2 and SAINT (Bruker, 2009 ▸), SHELXS97, SHELXL97 and SHELXTL (Sheldrick, 2008 ▸), Mercury (Macrae et al., 2008 ▸), PLATON (Spek, 2009 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S2056989015008348/su5124sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015008348/su5124Isup2.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989015008348/su5124Isup3.cml

CCDC reference: 1062128

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

C14H13NO2	Dx = 1.339 Mg m−3
Mr = 227.25	Melting point = 388–390 K
Monoclinic, Pc	Mo Kα radiation, λ = 0.71073 Å
a = 8.0357 (3) Å	Cell parameters from 3449 reflections
b = 5.5554 (2) Å	θ = 2.6–30.5°
c = 12.8733 (5) Å	µ = 0.09 mm−1
β = 101.312 (1)°	T = 100 K
V = 563.52 (4) Å3	Block, colorless
Z = 2	0.55 × 0.48 × 0.41 mm
F(000) = 240

Bruker APEXII D8 Venture diffractometer	3414 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.023
Absorption correction: multi-scan (SADABS; Bruker, 2009)	θmax = 30.5°, θmin = 2.6°
Tmin = 0.953, Tmax = 0.964	h = −11→11
26314 measured reflections	k = −7→7
3449 independent reflections	l = −18→18

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.037	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.100	w = 1/[σ2(Fo2) + (0.0786P)2 + 0.0298P] where P = (Fo2 + 2Fc2)/3
S = 1.09	(Δ/σ)max < 0.001
3449 reflections	Δρmax = 0.37 e Å−3
160 parameters	Δρmin = −0.28 e Å−3
2 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.054 (8)

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

	x	y	z	Uiso*/Ueq
O1	0.29289 (8)	0.08802 (12)	0.07528 (5)	0.01815 (14)
O2	0.92146 (10)	0.70962 (12)	0.58775 (6)	0.02323 (15)
H1O2	0.859 (2)	0.653 (3)	0.5407 (15)	0.028 (3)*
N1	0.72131 (9)	0.33548 (14)	0.53665 (5)	0.01630 (16)
C1	0.54115 (10)	0.13926 (16)	0.38967 (6)	0.01455 (16)
C2	0.55623 (10)	0.31817 (15)	0.31478 (7)	0.01598 (16)
H2A	0.6239	0.4524	0.3353	0.019*
C3	0.47132 (10)	0.29620 (15)	0.21094 (7)	0.01586 (16)
H3A	0.4826	0.4149	0.1618	0.019*
C4	0.36790 (10)	0.09459 (15)	0.17945 (6)	0.01416 (16)
C5	0.35026 (11)	−0.08418 (16)	0.25290 (6)	0.01607 (17)
H5A	0.2812	−0.2171	0.2326	0.019*
C6	0.43785 (11)	−0.05985 (16)	0.35704 (6)	0.01649 (16)
H6A	0.4273	−0.1791	0.4061	0.020*
C7	0.63122 (10)	0.15284 (17)	0.49969 (6)	0.01611 (17)
H7A	0.6229	0.0242	0.5446	0.019*
C8	0.81013 (9)	0.34278 (15)	0.64262 (6)	0.01427 (16)
C9	0.91560 (10)	0.54613 (15)	0.66557 (6)	0.01633 (16)
C10	1.01507 (11)	0.57944 (17)	0.76609 (7)	0.01860 (17)
H10A	1.0854	0.7133	0.7803	0.022*
C11	1.00837 (11)	0.41075 (16)	0.84506 (7)	0.01799 (17)
H11A	1.0752	0.4309	0.9122	0.022*
C12	0.90092 (10)	0.21016 (17)	0.82364 (6)	0.01711 (16)
H12A	0.8951	0.0994	0.8770	0.021*
C13	0.80332 (10)	0.17641 (15)	0.72308 (6)	0.01595 (16)
H13A	0.7331	0.0424	0.7092	0.019*
C14	0.19195 (12)	−0.11830 (17)	0.03898 (7)	0.02058 (18)
H14A	0.1551	−0.1096	−0.0365	0.031*
H14B	0.0948	−0.1225	0.0720	0.031*
H14C	0.2582	−0.2615	0.0570	0.031*

	U11	U22	U33	U12	U13	U23
O1	0.0188 (3)	0.0212 (3)	0.0130 (3)	−0.0025 (2)	−0.0003 (2)	−0.0004 (2)
O2	0.0342 (3)	0.0193 (3)	0.0161 (3)	−0.0091 (3)	0.0045 (2)	0.0009 (2)
N1	0.0173 (3)	0.0180 (4)	0.0132 (3)	−0.0009 (2)	0.0019 (3)	−0.0010 (2)
C1	0.0157 (4)	0.0152 (3)	0.0125 (3)	−0.0003 (3)	0.0023 (3)	−0.0016 (3)
C2	0.0172 (4)	0.0142 (3)	0.0162 (4)	−0.0019 (3)	0.0024 (3)	−0.0010 (3)
C3	0.0170 (3)	0.0146 (3)	0.0155 (3)	−0.0005 (3)	0.0021 (3)	0.0013 (3)
C4	0.0133 (3)	0.0159 (4)	0.0132 (4)	0.0003 (3)	0.0026 (3)	−0.0010 (2)
C5	0.0177 (3)	0.0163 (4)	0.0142 (4)	−0.0031 (3)	0.0030 (3)	−0.0013 (3)
C6	0.0208 (4)	0.0158 (3)	0.0131 (3)	−0.0027 (3)	0.0039 (3)	−0.0002 (3)
C7	0.0176 (4)	0.0178 (4)	0.0131 (3)	−0.0008 (3)	0.0032 (3)	−0.0013 (3)
C8	0.0148 (3)	0.0150 (3)	0.0131 (3)	−0.0002 (3)	0.0029 (3)	−0.0014 (3)
C9	0.0183 (4)	0.0166 (3)	0.0148 (3)	−0.0022 (3)	0.0050 (3)	−0.0013 (3)
C10	0.0188 (4)	0.0196 (4)	0.0174 (3)	−0.0040 (3)	0.0036 (3)	−0.0042 (3)
C11	0.0172 (3)	0.0220 (4)	0.0141 (3)	−0.0008 (3)	0.0013 (3)	−0.0030 (3)
C12	0.0179 (4)	0.0184 (4)	0.0147 (4)	−0.0001 (3)	0.0025 (3)	0.0006 (3)
C13	0.0172 (3)	0.0162 (4)	0.0141 (4)	−0.0016 (3)	0.0023 (3)	−0.0005 (3)
C14	0.0194 (4)	0.0224 (4)	0.0178 (4)	−0.0031 (3)	−0.0015 (3)	−0.0028 (3)

O1—C4	1.3586 (9)	C6—H6A	0.9300
O1—C14	1.4287 (10)	C7—H7A	0.9300
O2—C9	1.3599 (11)	C8—C13	1.3973 (11)
O2—H1O2	0.772 (19)	C8—C9	1.4084 (11)
N1—C7	1.2825 (10)	C9—C10	1.3935 (11)
N1—C8	1.4107 (10)	C10—C11	1.3915 (13)
C1—C6	1.3972 (11)	C10—H10A	0.9300
C1—C2	1.4065 (11)	C11—C12	1.4035 (12)
C1—C7	1.4605 (10)	C11—H11A	0.9300
C2—C3	1.3818 (11)	C12—C13	1.3884 (11)
C2—H2A	0.9300	C12—H12A	0.9300
C3—C4	1.4062 (11)	C13—H13A	0.9300
C3—H3A	0.9300	C14—H14A	0.9600
C4—C5	1.3975 (11)	C14—H14B	0.9600
C5—C6	1.3932 (11)	C14—H14C	0.9600
C5—H5A	0.9300
C4—O1—C14	117.25 (7)	C13—C8—C9	118.98 (7)
C9—O2—H1O2	101.3 (12)	C13—C8—N1	127.73 (7)
C7—N1—C8	121.55 (7)	C9—C8—N1	113.29 (7)
C6—C1—C2	118.64 (7)	O2—C9—C10	119.93 (8)
C6—C1—C7	118.99 (7)	O2—C9—C8	119.18 (7)
C2—C1—C7	122.36 (7)	C10—C9—C8	120.88 (7)
C3—C2—C1	120.54 (7)	C11—C10—C9	119.45 (8)
C3—C2—H2A	119.7	C11—C10—H10A	120.3
C1—C2—H2A	119.7	C9—C10—H10A	120.3
C2—C3—C4	120.07 (8)	C10—C11—C12	120.11 (8)
C2—C3—H3A	120.0	C10—C11—H11A	119.9
C4—C3—H3A	120.0	C12—C11—H11A	119.9
O1—C4—C5	124.37 (7)	C13—C12—C11	120.24 (8)
O1—C4—C3	115.38 (7)	C13—C12—H12A	119.9
C5—C4—C3	120.24 (7)	C11—C12—H12A	119.9
C6—C5—C4	118.88 (7)	C12—C13—C8	120.31 (8)
C6—C5—H5A	120.6	C12—C13—H13A	119.8
C4—C5—H5A	120.6	C8—C13—H13A	119.8
C5—C6—C1	121.63 (8)	O1—C14—H14A	109.5
C5—C6—H6A	119.2	O1—C14—H14B	109.5
C1—C6—H6A	119.2	H14A—C14—H14B	109.5
N1—C7—C1	122.48 (7)	O1—C14—H14C	109.5
N1—C7—H7A	118.8	H14A—C14—H14C	109.5
C1—C7—H7A	118.8	H14B—C14—H14C	109.5
C6—C1—C2—C3	−0.41 (12)	C2—C1—C7—N1	4.45 (12)
C7—C1—C2—C3	178.77 (7)	C7—N1—C8—C13	−6.46 (13)
C1—C2—C3—C4	0.40 (12)	C7—N1—C8—C9	173.81 (7)
C14—O1—C4—C5	−1.14 (12)	C13—C8—C9—O2	−179.42 (8)
C14—O1—C4—C3	177.64 (7)	N1—C8—C9—O2	0.34 (11)
C2—C3—C4—O1	−178.73 (7)	C13—C8—C9—C10	1.49 (12)
C2—C3—C4—C5	0.10 (12)	N1—C8—C9—C10	−178.75 (7)
O1—C4—C5—C6	178.14 (7)	O2—C9—C10—C11	−179.85 (8)
C3—C4—C5—C6	−0.58 (12)	C8—C9—C10—C11	−0.77 (13)
C4—C5—C6—C1	0.57 (13)	C9—C10—C11—C12	−0.61 (14)
C2—C1—C6—C5	−0.09 (13)	C10—C11—C12—C13	1.27 (13)
C7—C1—C6—C5	−179.29 (7)	C11—C12—C13—C8	−0.54 (13)
C8—N1—C7—C1	−178.67 (8)	C9—C8—C13—C12	−0.82 (12)
C6—C1—C7—N1	−176.38 (8)	N1—C8—C13—C12	179.45 (7)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···N1	0.774 (18)	2.078 (17)	2.6315 (11)	128.7 (17)
C14—H14B···O2i	0.96	2.71	3.2876 (12)	119
C2—H2A···Cg2ii	0.93	2.93	3.5662 (9)	127
C13—H13A···Cg1iii	0.93	2.76	3.4671 (9)	134