N′-[(1E)-(2-Hydroxynaphthalen-1-yl)methylidene]-2-methoxybenzohydrazide

There are three independent molecules in the asymmetric unit of the title compound, C19H16N2O3, in which the dihedral angles between the naphthalene ring system and the benzene ring are 7.52 (16), 18.15 (18), and 13.9 (2)°. All the molecules exist in the trans configuration with respect to the methylidene units. In each molecule there is one O—H⋯N and one N—H⋯O intramolecular hydrogen bond. In the crystal, two of the molecules are linked via a bifurcated N—H⋯(O,O) hydrogen bond. All three molecules are further linked via C—H⋯O interactions.

There are three independent molecules in the asymmetric unit of the title compound, C 19 H 16 N 2 O 3 , in which the dihedral angles between the naphthalene ring system and the benzene ring are 7.52 (16), 18.15 (18), and 13.9 (2) . All the molecules exist in the trans configuration with respect to the methylidene units. In each molecule there is one O-HÁ Á ÁN and one N-HÁ Á ÁO intramolecular hydrogen bond. In the crystal, two of the molecules are linked via a bifurcated N-HÁ Á Á(O,O) hydrogen bond. All three molecules are further linked via C-HÁ Á ÁO interactions. H atoms treated by a mixture of independent and constrained refinement Á max = 0.13 e Å À3 Á min = À0.15 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). (ii) Àx þ 2; Ày þ 1; Àz þ 1; (iii) Àx þ 1; Ày þ 1; Àz þ 1.
In the asymmetric unit of the title compound there are three (A, B and C) independent molecules (Fig. 1). The bond distances and angles are comparable to those observed in similar compounds (Li, 2011b,c). The dihedral angles between the naphthalene and the benzene rings in the three molecules are 7.52 (16), 18.15 (18), and 13.9 (2)°, for molecules A, B and C, respectively. All the molecules exist in the trans configuration with respect to the methylidene units. In each molecule there is an O-H···N and a N-H···O intramolecular hydrogen bond (Table 1).
In the crystal the A and C molecules are linked by a bifurcated hydrogen bond involving the NH group of molecule A [N2-H2···O8] ( Table 1). All three molecules are further linked to one another via C-H···O interactions (Table 1).

Experimental
A mixture of 2-methoxybenzhydrazide (0.166 g, 1 mmol) and 2-hydroxy-1-naphthaldehyde (0.172 g, 1 mmol) in 30 ml of ethanol containing few drops of acetic acid was refluxed for about 1 h. On cooling to room temperature, a solid precipitate was formed. The solid was filtered and then recrystallized from methanol. Colourless crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of a solution of the title compound in methanol.

Refinement
The NH H-atoms were located from a difference Fourier map and were freely refined. The OH and C-bound H-atoms were positioned geometrically and refined using a riding model: O-H = 0.82 Å, C-H = 0.93 and 0.96 Å, for CH and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (O,C), where k = 1.5 for OH and CH 3 H-atoms, and k = 1.2 for all other H-atoms.

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 supplementary materials sup-3 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.