(E)-3-[(3-Ethoxy-2-hydroxybenzylidene)amino]benzoic acid

In the title compound, C16H15NO4, a potential bidentate N,O-donor Schiff base ligand, the benzene rings are inclined to one another by 4.24 (12)°. The molecule has an E conformation about the C=N bond. An intramolecular O—H⋯N hydrogen bond makes an S(6) ring motif. In the crystal, pairs of O—H⋯O hydrogen bonds link the molecules, forming inversion dimers with R 2 2(8) ring motifs. These dimers are further connected by C—H⋯O interactions, forming a sheet in (104). There is also a C—H⋯π interaction present involving neighbouring molecules.

In the title compound, C 16 H 15 NO 4 , a potential bidentate N,Odonor Schiff base ligand, the benzene rings are inclined to one another by 4.24 (12) . The molecule has an E conformation about the C N bond. An intramolecular O-HÁ Á ÁN hydrogen bond makes an S(6) ring motif. In the crystal, pairs of O-HÁ Á ÁO hydrogen bonds link the molecules, forming inversion dimers with R 2 2 (8) ring motifs. These dimers are further connected by C-HÁ Á ÁO interactions, forming a sheet in (104). There is also a C-HÁ Á Á interaction present involving neighbouring molecules.
The molecular structure of the title compound is illustrated in Fig. 1. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The intramolecular O3-H3A···N1 hydrogen bond (Table 1) makes an S(6) ring motif (Bernstein et al., 1995). The dihedral angle between the benzene rings is 4.24 (12)°. The molecule has an E conformation about the C8═N1 bond.
In the crystal, pairs of O-H···O hydrogen bonds (Table 1) link molecules to form inversion dimers with an R 2 2 (8) ring motif. These dimers are connected further by C-H···O interactions along the b axis direction, forming a sheet (Fig. 2).
There is also a C-H···π interaction present involving neighbouring molecules (Table 1).

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

Refinement
The O-bound hydrogen atoms were located in a difference Fourier map and constrained to ride on the parent atoms with U iso (H) = 1.5 U eq (O). The rest of the hydrogen atoms were included in calculated positions and treated as riding atoms: C -H = 0.93, 0.96 and 0.97 Å for CH, CH 3 and CH 2 H atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for CH 3 H atoms, and = 1.2 for other H atoms. A rotating group model was applied to the methyl group.

Computing details
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009   The crystal packing of the title compound, viewed along the c-axis, showing the inversion dimers, with an R 2 2 (8) ring motif, which are further connected through C-H···O interactions along the b-axis direction -see Table 1 for details. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.20 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.