(E)-4-Bromo-2-[(2-hydr­oxy-5-methyl­phenyl)­iminometh­yl]phenol

The mol­ecule of the title compound, C₁₄H₁₂BrNO₂, crystallizes in a zwitterionic form, with a strong intra­molecular N—H...O hydrogen bond. The dihedral angle between the aromatic rings is 9.3 (3)°. Inter­molecular O—H...O hydrogen bonds generate C(8) chains running parallel to the [100] direction.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.043
• wR factor = 0.084
• Data-to-parameter ratio = 15.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.80 mm
PLAT341_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          8

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           26.00
           From the CIF: _reflns_number_total               2549
           Count of symmetry unique reflns         1515
           Completeness (_total/calc)            168.25%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1034
           Fraction of Friedel pairs measured     0.683
           Are heavy atom types Z>Si present        yes

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Schiff bases have been extensively used as ligands in the field of coordination chemistry (Calligaris et al., 1972). There are two characteristic properties of Schiff bases, viz. photochromism and thermochromism (Cohen et al., 1964). These properties result from proton transfer from the hydroxyl O atom to the imine N atom (Hadjoudis et al., 1987). Schiff bases display two possible tautomeric forms, namely the phenol-imine and keto-amine forms. In the solid state, the keto-amine tautomer has been found in naphthaldimine (Hökelek et al., 2000). Nevertheless, in the solid state, it has been established that there is keto-amine tautomerism in naphthaldimine, while the phenol-imine form exists in salicylaldimine Schiff bases (Dey et al., 2001). Our investigations show that compound (I) exists in a zwitterionic form.

An ORTEP-3 (Farrugia, 1997) plot of the molecule of (I) is shown in Fig.1. The C1—C7, C7═N1 and N1—C8 bond lengths are 1.406 (6), 1.289 (6) and 1.409 (6) Å, respectively (Table 1), and agree with the corresponding distances in (Z)-6-[(2-fluorophenyliminio)methylene]-2,3-dihydroxyphenolate [1.419 (3), 1.295 (2) and 1.412 (2) Å; Petek et al., 2006]. In the zwitterionic form, the molecule of the title compound is nearly planar, with a dihedral angle between the aromatic rings of 9.3 (3)°.

Fig.1 also shows a strong intramolecular hydrogen bond (N1—H1···O1) can be described as an S(6) motif (Bernstein et al., 1995). Atom O2 in the reference molecule at (x, y, z) acts as a hydrogen-bond donor, via H2, to O1 in the molecule at (1/2 + x, 3/2 - y, 1 - z), so forming a C(8) chain running parallel to the [100] direction (Fig.2).

Related literature

Schiff base compounds can be classified by their photochromic and thermochromic characteristics (Cohen et al., 1964; Hadjoudis et al., 1987). For ring motif details, see: Bernstein et al. (1995). For related literature, see: Calligaris et al. (1972); Dey et al. (2001); Hökelek et al. (2000); Petek et al. (2006).

S2. Experimental

A solution of 5-bromosalicylaldehyde (0.05 g, 0.25 mmol) in ethanol (20 ml) was added to a solution of 2-hydroxy-5-nitroaniline (0.038 g 0.25 mmol) in ethanol (20 ml). The reaction mixture was stirred for 1 h under reflux. Single crystals of the title compound suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield 71%; m.p. 456–459 K).

S3. Refinement

Atom H1 was located in a difference map and refined freely. The remaining H atoms were placed in calculated positions and constrained to ride on their parents atoms, with C—H = 0.93–0.96 Å and U_iso(H) = kU_eq(parent atom), where k = 1.5 for methyl and hydroxyl H atoms, and 1.2 for other H atoms.

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level.
	Fig. 2. View of the crystal packing of (I). Hydrogen bonds are drawn as dashed lines. H atoms not involved in the interactions have been omitted for clarity.

(E)-4-Bromo-2-[(2-hydroxy-5-methylphenyl)iminomethyl]phenol

Crystal data

C14H12BrNO2	F(000) = 616
Mr = 306.16	Dx = 1.548 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P2ac 2ab	Cell parameters from 5730 reflections
a = 8.2763 (8) Å	θ = 2.2–29.5°
b = 8.4451 (9) Å	µ = 3.12 mm^−1
c = 18.795 (2) Å	T = 296 K
V = 1313.7 (2) Å^3	Prism, brown
Z = 4	0.80 × 0.37 × 0.13 mm

Data collection

Stoe IPDS II diffractometer	2549 independent reflections
Radiation source: fine-focus sealed tube	1541 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.073
Detector resolution: 6.67 pixels mm^-1	θmax = 26.0°, θmin = 2.2°
rotation method scans	h = −10→10
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −10→6
Tmin = 0.289, Tmax = 0.680	l = −23→23
6028 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.043	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.084	w = 1/[σ^2(Fo^2) + (0.0287P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.91	(Δ/σ)max = 0.001
2549 reflections	Δρmax = 0.31 e Å^−3
167 parameters	Δρmin = −0.30 e Å^−3
0 restraints	Absolute structure: Flack (1983); 1052 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.010 (15)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.5123 (5)	0.4814 (6)	0.6768 (3)	0.0472 (11)
C2	0.4416 (5)	0.6051 (8)	0.6358 (2)	0.0529 (15)
C3	0.2843 (5)	0.6545 (7)	0.6554 (3)	0.0558 (15)
H3	0.2355	0.7366	0.6304	0.067*
C4	0.2033 (6)	0.5854 (7)	0.7097 (3)	0.0551 (16)
H4	0.0991	0.6185	0.7207	0.066*
C5	0.2749 (6)	0.4652 (7)	0.7491 (2)	0.0509 (14)
C6	0.4245 (6)	0.4155 (7)	0.7336 (2)	0.0558 (16)
H6	0.4712	0.3359	0.7609	0.067*
C7	0.6666 (6)	0.4226 (6)	0.6601 (2)	0.0526 (13)
H7	0.7082	0.3397	0.6870	0.063*
C8	0.9084 (5)	0.4353 (7)	0.5857 (2)	0.0450 (13)
C9	0.9898 (6)	0.3034 (7)	0.6103 (2)	0.0498 (13)
H9	0.9424	0.2399	0.6449	0.060*
C10	1.1407 (7)	0.2646 (7)	0.5841 (3)	0.0591 (14)
C11	1.2065 (6)	0.3619 (10)	0.5315 (3)	0.0684 (17)
H11	1.3066	0.3364	0.5121	0.082*
C12	1.1267 (6)	0.4950 (8)	0.5073 (2)	0.0607 (15)
H12	1.1738	0.5589	0.4727	0.073*
C13	0.9777 (6)	0.5331 (7)	0.5346 (2)	0.0497 (13)
C14	1.2316 (7)	0.1219 (9)	0.6121 (3)	0.086 (2)
H14A	1.2118	0.1107	0.6622	0.129*
H14B	1.3453	0.1361	0.6041	0.129*
H14C	1.1954	0.0285	0.5878	0.129*
N1	0.7527 (5)	0.4790 (6)	0.6088 (2)	0.0493 (12)
H1	0.703 (6)	0.544 (7)	0.585 (2)	0.059*
O1	0.5191 (4)	0.6667 (5)	0.58287 (17)	0.0631 (12)
O2	0.8903 (4)	0.6614 (5)	0.51439 (17)	0.0657 (11)
H2	0.9404	0.7111	0.4841	0.098*
Br1	0.15523 (6)	0.36922 (9)	0.82415 (3)	0.0725 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.045 (2)	0.043 (3)	0.053 (2)	0.004 (2)	0.001 (3)	0.009 (3)
C2	0.058 (3)	0.049 (5)	0.052 (3)	−0.008 (3)	−0.014 (2)	0.001 (3)
C3	0.059 (3)	0.036 (4)	0.072 (3)	0.009 (3)	−0.016 (2)	0.003 (3)
C4	0.047 (3)	0.057 (5)	0.061 (3)	0.005 (3)	−0.004 (2)	−0.008 (3)
C5	0.054 (3)	0.048 (4)	0.051 (3)	0.002 (3)	−0.001 (2)	0.001 (3)
C6	0.054 (3)	0.053 (5)	0.060 (3)	0.005 (3)	0.000 (2)	0.014 (3)
C7	0.059 (3)	0.051 (3)	0.047 (3)	0.000 (3)	−0.001 (2)	0.020 (2)
C8	0.050 (3)	0.042 (4)	0.043 (2)	−0.004 (2)	−0.002 (2)	0.006 (2)
C9	0.058 (3)	0.044 (4)	0.048 (3)	−0.003 (3)	0.009 (2)	0.008 (2)
C10	0.068 (3)	0.040 (4)	0.069 (3)	−0.003 (3)	0.009 (3)	−0.006 (3)
C11	0.071 (3)	0.067 (5)	0.067 (3)	0.000 (4)	0.028 (3)	−0.019 (4)
C12	0.075 (4)	0.055 (4)	0.052 (3)	−0.014 (3)	0.010 (3)	0.004 (3)
C13	0.059 (3)	0.039 (4)	0.051 (3)	−0.006 (3)	−0.001 (2)	0.004 (3)
C14	0.085 (4)	0.056 (5)	0.117 (5)	0.022 (4)	0.025 (3)	0.016 (5)
N1	0.047 (2)	0.046 (3)	0.054 (3)	0.004 (2)	−0.0036 (19)	0.013 (2)
O1	0.064 (2)	0.056 (3)	0.069 (2)	0.003 (2)	−0.0036 (17)	0.031 (2)
O2	0.073 (2)	0.058 (3)	0.0655 (19)	0.003 (2)	0.0138 (17)	0.030 (2)
Br1	0.0639 (3)	0.0783 (5)	0.0753 (3)	−0.0022 (4)	0.0147 (3)	0.0103 (4)

Geometric parameters (Å, º)

C1—C6	1.406 (6)	C8—N1	1.409 (6)
C1—C7	1.406 (6)	C9—C10	1.382 (7)
C1—C2	1.424 (7)	C9—H9	0.93
C2—O1	1.293 (6)	C10—C11	1.397 (8)
C2—C3	1.415 (7)	C10—C14	1.515 (8)
C3—C4	1.354 (7)	C11—C12	1.380 (9)
C3—H3	0.93	C11—H11	0.93
C4—C5	1.389 (7)	C12—C13	1.373 (7)
C4—H4	0.93	C12—H12	0.93
C5—C6	1.340 (6)	C13—O2	1.357 (6)
C5—Br1	1.905 (5)	C14—H14A	0.96
C6—H6	0.93	C14—H14B	0.96
C7—N1	1.289 (6)	C14—H14C	0.96
C7—H7	0.93	N1—H1	0.82 (5)
C8—C9	1.381 (7)	O2—H2	0.82
C8—C13	1.390 (7)
C6—C1—C7	119.9 (5)	C8—C9—H9	119.6
C6—C1—C2	119.3 (4)	C10—C9—H9	119.6
C7—C1—C2	120.8 (4)	C9—C10—C11	117.7 (5)
O1—C2—C3	122.5 (5)	C9—C10—C14	121.0 (5)
O1—C2—C1	120.5 (4)	C11—C10—C14	121.4 (5)
C3—C2—C1	117.0 (5)	C12—C11—C10	121.7 (5)
C4—C3—C2	121.6 (5)	C12—C11—H11	119.1
C4—C3—H3	119.2	C10—C11—H11	119.1
C2—C3—H3	119.2	C13—C12—C11	119.8 (5)
C3—C4—C5	120.4 (5)	C13—C12—H12	120.1
C3—C4—H4	119.8	C11—C12—H12	120.1
C5—C4—H4	119.8	O2—C13—C12	124.1 (5)
C6—C5—C4	120.5 (5)	O2—C13—C8	116.6 (4)
C6—C5—Br1	120.5 (4)	C12—C13—C8	119.3 (5)
C4—C5—Br1	118.9 (4)	C10—C14—H14A	109.5
C5—C6—C1	121.2 (5)	C10—C14—H14B	109.5
C5—C6—H6	119.4	H14A—C14—H14B	109.5
C1—C6—H6	119.4	C10—C14—H14C	109.5
N1—C7—C1	122.6 (5)	H14A—C14—H14C	109.5
N1—C7—H7	118.7	H14B—C14—H14C	109.5
C1—C7—H7	118.7	C7—N1—C8	129.7 (5)
C9—C8—C13	120.6 (5)	C7—N1—H1	112 (3)
C9—C8—N1	123.6 (5)	C8—N1—H1	118 (3)
C13—C8—N1	115.8 (5)	C13—O2—H2	109.5
C8—C9—C10	120.9 (5)
C6—C1—C2—O1	−179.4 (5)	N1—C8—C9—C10	178.3 (5)
C7—C1—C2—O1	−0.7 (8)	C8—C9—C10—C11	−0.9 (8)
C6—C1—C2—C3	0.0 (8)	C8—C9—C10—C14	178.7 (5)
C7—C1—C2—C3	178.6 (5)	C9—C10—C11—C12	1.8 (9)
O1—C2—C3—C4	178.0 (5)	C14—C10—C11—C12	−177.8 (6)
C1—C2—C3—C4	−1.3 (8)	C10—C11—C12—C13	−1.0 (9)
C2—C3—C4—C5	1.5 (8)	C11—C12—C13—O2	179.8 (5)
C3—C4—C5—C6	−0.4 (8)	C11—C12—C13—C8	−0.7 (8)
C3—C4—C5—Br1	−179.2 (4)	C9—C8—C13—O2	−178.9 (4)
C4—C5—C6—C1	−0.9 (8)	N1—C8—C13—O2	1.9 (6)
Br1—C5—C6—C1	177.8 (4)	C9—C8—C13—C12	1.6 (7)
C7—C1—C6—C5	−177.5 (5)	N1—C8—C13—C12	−177.6 (5)
C2—C1—C6—C5	1.1 (8)	C1—C7—N1—C8	179.4 (5)
C6—C1—C7—N1	−179.6 (5)	C9—C8—N1—C7	9.0 (8)
C2—C1—C7—N1	1.7 (8)	C13—C8—N1—C7	−171.8 (5)
C13—C8—C9—C10	−0.8 (7)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1^i	0.82	1.75	2.566 (5)	171
N1—H1···O1	0.82 (5)	1.84 (5)	2.547 (6)	144 (5)

Symmetry code: (i) x+1/2, −y+3/2, −z+1.