2-Hydr­oxy-5-(2-hydr­oxy-3-methoxy­benzyl­ideneamino)benzoic acid

The title compound, C₁₅H₁₃NO₅, was obtained by the condensation of o-vanillin with 5-amino­salicylic acid. The mol­ecule is nonplanar with a dihedral angle of 13.2 (2)° between the two aromatic rings. The carboxyl and meth­oxy groups are almost coplanar with the attached rings. The mol­ecular structure is stabilized by O—H...N and O—H...O hydrogen bonds. Inter­molecular O—H...O hydrogen bonds link the mol­ecules into a chain along the c axis, and adjacent chains are crosslinked by C—H...O hydrogen bonds and π–π stacking inter­actions involving the two benzene rings [centroid–centroid distance = 3.685 (3) Å].

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.056
• wR factor = 0.170
• Data-to-parameter ratio = 12.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT026_ALERT_3_C Ratio Observed / Unique Reflections too Low ....         45 Perc.
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          6

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

   1 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
   0 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 intensively investigated recently owing to their strong coordination capability (Yamada, 1999) and diverse biological activities, such as antibacterial, antitumor activities etc (Yang et al., 2000).

The title compound has a non-planar molecular structure (Fig. 1). The dihedral angle between the two aromatic rings is 13.2 (2)°. The O3—C9—C10—C11 [-5.3 (7)°], O4—C9—C10—C15 [-3.6 (6)°] and C8—O2—C4—C5 [12.8 (6)°] torsion angles indicate that the carboxyl and methoxy groups are almost coplanar with the attached rings. Intramolecular O—H···N1 and O—H···O hydrogen bonds are observed in the molecular structure, similar to those reported in a related structure (Bourque et al., 2005).

In the crystal structure, intermolecular O4—H4···O1(x,3/2 - y,1/2 + z) hydrogen bonds link the molecules into a chain along the c axis (Fig. 2). The adjacent chains are cross-linked by C—H···O hydrogen bonds (Table 1) and π-π stacking interactions involving the two benzene rings, with a centroid···centroid distance of 3.685 (3) Å.

Related literature

For general background, see: Yamada (1999); Yang et al. (2000). For a related structure, see: Bourque et al. (2005).

S2. Experimental

To an ethanol (10 ml) solution of 5-aminosalicylic acid (1.5305 g, 10 mmol) was added an ethanol (5 ml) solution of o-vanillin (1.5212 g, 10 mmol). The mixture was heated under reflux for 2 h to ensure completion, at which point a yellow precipitate was collected by suction filtration and washed with ethanol and Et₂O. Crystals of the title compound suitable for X-ray analysis were grown from an ethanol solution after about two weeks.

S3. Refinement

All H atoms were placed in geometrically idealized positions (O—H = 0.82 Å and C—H = 0.93–0.96 Å) and treated as riding on their parent atoms, with U_iso(H) = 1.5U_eq(C_methyl, O) or 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen bonds are shown as dashed lines.
	Fig. 2. View of O—H···O hydrogen-bonded (dashed lines) chains in the title compound.

2-Hydroxy-5-(2-hydroxy-3-methoxybenzylideneamino)benzoic acid

Crystal data

C15H13NO5	F(000) = 600
Mr = 287.26	Dx = 1.443 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 741 reflections
a = 8.1049 (9) Å	θ = 2.6–20.0°
b = 14.084 (2) Å	µ = 0.11 mm^−1
c = 12.1998 (17) Å	T = 298 K
β = 108.264 (2)°	Block, red
V = 1322.5 (3) Å^3	0.49 × 0.45 × 0.12 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2332 independent reflections
Radiation source: fine-focus sealed tube	1041 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.069
φ and ω scans	θmax = 25.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.948, Tmax = 0.987	k = −13→16
6151 measured reflections	l = −11→14

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.170	H-atom parameters constrained
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0562P)^2 + 0.7223P] where P = (Fo^2 + 2Fc^2)/3
2332 reflections	(Δ/σ)max = 0.001
190 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

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
N1	0.7167 (4)	0.4976 (2)	0.5754 (2)	0.0374 (9)
O1	0.8177 (4)	0.54458 (19)	0.4044 (2)	0.0471 (8)
H1	0.7885	0.5505	0.4626	0.071*
O2	0.8971 (4)	0.5021 (2)	0.2205 (2)	0.0581 (9)
O3	0.6394 (4)	0.78059 (19)	0.9247 (3)	0.0633 (10)
O4	0.7650 (4)	0.80386 (19)	0.7888 (2)	0.0608 (9)
H4	0.7795	0.8569	0.8178	0.091*
O5	0.5298 (4)	0.6170 (2)	0.9536 (2)	0.0583 (9)
H5	0.5517	0.6735	0.9667	0.087*
C1	0.7309 (5)	0.4100 (3)	0.5451 (3)	0.0436 (11)
H1A	0.7054	0.3618	0.5893	0.052*
C2	0.7826 (5)	0.3842 (3)	0.4492 (3)	0.0393 (10)
C3	0.8223 (5)	0.4552 (3)	0.3802 (3)	0.0365 (10)
C4	0.8684 (5)	0.4269 (3)	0.2827 (3)	0.0424 (11)
C5	0.8794 (6)	0.3335 (3)	0.2583 (4)	0.0525 (12)
H5A	0.9107	0.3159	0.1941	0.063*
C6	0.8440 (6)	0.2633 (3)	0.3295 (4)	0.0594 (14)
H6	0.8547	0.1994	0.3133	0.071*
C7	0.7944 (6)	0.2882 (3)	0.4215 (4)	0.0545 (13)
H7	0.7677	0.2412	0.4669	0.065*
C8	0.9075 (6)	0.4835 (3)	0.1078 (3)	0.0697 (15)
H8A	0.9274	0.5420	0.0734	0.105*
H8B	0.8005	0.4558	0.0609	0.105*
H8C	1.0015	0.4405	0.1133	0.105*
C9	0.6839 (6)	0.7504 (3)	0.8431 (4)	0.0448 (11)
C10	0.6492 (5)	0.6533 (3)	0.8013 (3)	0.0352 (10)
C11	0.5761 (5)	0.5903 (3)	0.8611 (3)	0.0403 (11)
C12	0.5489 (5)	0.4966 (3)	0.8259 (3)	0.0467 (11)
H12	0.4997	0.4547	0.8658	0.056*
C13	0.5934 (5)	0.4648 (3)	0.7332 (3)	0.0412 (11)
H13	0.5760	0.4015	0.7111	0.049*
C14	0.6654 (5)	0.5275 (3)	0.6713 (3)	0.0342 (10)
C15	0.6903 (5)	0.6201 (3)	0.7050 (3)	0.0376 (10)
H15	0.7355	0.6622	0.6630	0.045*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.039 (2)	0.039 (2)	0.0338 (18)	0.0012 (17)	0.0120 (16)	−0.0096 (16)
O1	0.064 (2)	0.0417 (19)	0.0417 (17)	0.0020 (15)	0.0258 (15)	−0.0024 (14)
O2	0.075 (2)	0.063 (2)	0.0466 (18)	0.0013 (17)	0.0340 (17)	−0.0001 (16)
O3	0.095 (3)	0.047 (2)	0.065 (2)	0.0026 (17)	0.050 (2)	−0.0042 (16)
O4	0.093 (3)	0.0392 (18)	0.070 (2)	−0.0052 (17)	0.0539 (19)	−0.0074 (16)
O5	0.078 (2)	0.058 (2)	0.0528 (19)	−0.0047 (17)	0.0402 (18)	−0.0057 (15)
C1	0.052 (3)	0.042 (3)	0.039 (2)	−0.002 (2)	0.017 (2)	0.002 (2)
C2	0.047 (3)	0.038 (3)	0.035 (2)	0.003 (2)	0.015 (2)	−0.003 (2)
C3	0.031 (3)	0.038 (3)	0.038 (2)	0.006 (2)	0.0071 (19)	−0.005 (2)
C4	0.040 (3)	0.045 (3)	0.042 (2)	0.003 (2)	0.013 (2)	−0.005 (2)
C5	0.054 (3)	0.061 (3)	0.043 (3)	0.009 (3)	0.016 (2)	−0.012 (2)
C6	0.074 (4)	0.044 (3)	0.058 (3)	0.009 (3)	0.018 (3)	−0.012 (3)
C7	0.070 (4)	0.044 (3)	0.050 (3)	−0.002 (2)	0.020 (3)	−0.003 (2)
C8	0.076 (4)	0.099 (4)	0.041 (3)	0.014 (3)	0.029 (3)	0.009 (3)
C9	0.057 (3)	0.041 (3)	0.044 (3)	0.008 (2)	0.027 (2)	0.003 (2)
C10	0.038 (3)	0.038 (2)	0.032 (2)	0.003 (2)	0.0139 (19)	0.0016 (19)
C11	0.044 (3)	0.047 (3)	0.034 (2)	0.006 (2)	0.018 (2)	0.004 (2)
C12	0.051 (3)	0.049 (3)	0.045 (3)	−0.008 (2)	0.023 (2)	0.005 (2)
C13	0.046 (3)	0.041 (3)	0.039 (2)	−0.008 (2)	0.017 (2)	−0.002 (2)
C14	0.033 (3)	0.038 (3)	0.033 (2)	0.0008 (19)	0.0118 (19)	0.0009 (19)
C15	0.035 (3)	0.041 (3)	0.038 (2)	0.003 (2)	0.0116 (19)	0.009 (2)

Geometric parameters (Å, º)

N1—C1	1.304 (4)	C5—H5A	0.93
N1—C14	1.423 (4)	C6—C7	1.351 (5)
O1—C3	1.297 (4)	C6—H6	0.93
O1—H1	0.82	C7—H7	0.93
O2—C4	1.364 (5)	C8—H8A	0.96
O2—C8	1.428 (4)	C8—H8B	0.96
O3—C9	1.236 (4)	C8—H8C	0.96
O4—C9	1.308 (5)	C9—C10	1.455 (5)
O4—H4	0.82	C10—C11	1.394 (5)
O5—C11	1.349 (4)	C10—C15	1.398 (5)
O5—H5	0.82	C11—C12	1.384 (5)
C1—C2	1.408 (5)	C12—C13	1.365 (5)
C1—H1A	0.93	C12—H12	0.93
C2—C7	1.405 (5)	C13—C14	1.402 (5)
C2—C3	1.408 (5)	C13—H13	0.93
C3—C4	1.411 (5)	C14—C15	1.363 (5)
C4—C5	1.358 (5)	C15—H15	0.93
C5—C6	1.404 (6)
C1—N1—C14	126.0 (3)	O2—C8—H8B	109.5
C3—O1—H1	109.5	H8A—C8—H8B	109.5
C4—O2—C8	117.8 (3)	O2—C8—H8C	109.5
C9—O4—H4	109.5	H8A—C8—H8C	109.5
C11—O5—H5	109.5	H8B—C8—H8C	109.5
N1—C1—C2	123.8 (4)	O3—C9—O4	122.0 (4)
N1—C1—H1A	118.1	O3—C9—C10	122.2 (4)
C2—C1—H1A	118.1	O4—C9—C10	115.9 (4)
C7—C2—C3	119.6 (4)	C11—C10—C15	118.6 (4)
C7—C2—C1	120.6 (4)	C11—C10—C9	118.8 (4)
C3—C2—C1	119.8 (4)	C15—C10—C9	122.5 (4)
O1—C3—C2	121.7 (3)	O5—C11—C12	117.8 (4)
O1—C3—C4	120.0 (4)	O5—C11—C10	122.4 (4)
C2—C3—C4	118.3 (4)	C12—C11—C10	119.8 (4)
C5—C4—O2	126.6 (4)	C13—C12—C11	120.8 (4)
C5—C4—C3	120.7 (4)	C13—C12—H12	119.6
O2—C4—C3	112.7 (4)	C11—C12—H12	119.6
C4—C5—C6	120.5 (4)	C12—C13—C14	120.1 (4)
C4—C5—H5A	119.8	C12—C13—H13	119.9
C6—C5—H5A	119.8	C14—C13—H13	119.9
C7—C6—C5	120.1 (4)	C15—C14—C13	119.2 (4)
C7—C6—H6	119.9	C15—C14—N1	118.5 (3)
C5—C6—H6	119.9	C13—C14—N1	122.3 (4)
C6—C7—C2	120.7 (4)	C14—C15—C10	121.4 (4)
C6—C7—H7	119.7	C14—C15—H15	119.3
C2—C7—H7	119.7	C10—C15—H15	119.3
O2—C8—H8A	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.82	1.81	2.555 (4)	150
O5—H5···O3	0.82	1.81	2.533 (4)	147
O4—H4···O1^i	0.82	1.71	2.520 (4)	168
C12—H12···O5^ii	0.93	2.50	3.358 (5)	153

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