(E)-3-[(2-Hydroxy-3-methoxybenzylidene)amino]benzoic acid

In the title compound, C15H13NO4, the dihedral angle between the substituted benzene rings is 9.9 (8)°. Part of the molecule (the salicylaldimine segment) is disordered over two sets of sites, with a refined site-occupancy ratio of 0.550 (14):0.450 (14). Intramolecular O—H⋯N hydrogen bonds form S(6) ring motifs. In the crystal, pairs of O—H⋯O hydrogen bonds link molecules into centrosymmetric dimers with R 2 2(8) ring motifs. The crystal packing also features C—H⋯π interactions.

In the title compound, C 15 H 13 NO 4 , the dihedral angle between the substituted benzene rings is 9.9 (8) . Part of the molecule (the salicylaldimine segment) is disordered over two sets of sites, with a refined site-occupancy ratio of 0.550 (14):0.450 (14). Intramolecular O-HÁ Á ÁN hydrogen bonds form S(6) ring motifs. In the crystal, pairs of O-HÁ Á ÁO hydrogen bonds link molecules into centrosymmetric dimers with R 2 2 (8) ring motifs. The crystal packing also features C-HÁ Á Á interactions.
Cg1 and Cg2 are the centroids of the C9-C14 and C9A-C14A rings, respectively. The asymmetric unit of the title compound, Fig. 1, comprises a potentially bidentate N,O-donor Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within the normal ranges.

Experimental
The title compound was synthesized by adding 3-methoxyosalicylaldehyde (2 mmol) to a solution of 3-carboxyaniline (2 mmol) in ethanol (30 ml). The mixture was refluxed with stirring for half an hour. The resultant solution was filtered.
Pale yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
The O-bound hydrogen atoms were positioned by a rotating O-H group model and constrained to the parent atoms with U iso (H) = 1.5 U eq (O). The rest of the hydrogen atoms were positioned geometrically with C-H = 0.93-0.97 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was applied to the methyl group. Since the crystal was very small and not optimal for diffraction the Data/Parameter ratio was not good. The similarity restraints (SIMU, DELU, and SAME) were applied to model the disorder.  The ORTEP plot of the title compound, showing 40% probability displacement ellipsoids and the atomic numbering. The major component of the disordered part was used. The dashed line shows the intramolecular H-bonding.

Figure 2
The packing diagram of the title compound viewed down the c-axis showing linking of dimers with R 2 2 (8) ring motifs. Only the hydrogen atoms involved the H-bonding and the major component are shown.

sup-3
Acta Cryst. (2012). E68, o1067  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.59 e Å −3 Δρ min = −0.28 e Å −3 Special details 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.  (7) 0.080 (7) −0.014 (7) 0.027 (6) 0.007 (6)  0.067 (9) 0.069 (7) 0.099 (11) −0.017 (7) 0.035 (7) 0.039 (7)  C8A-C9A-C10A-O3A −13 (7)