2,4-Dihydroxy-N′-(2-hydroxy-4-methoxybenzylidene)benzohydrazide

In the title compound, C15H14N2O5, the dihedral angle between the two benzene rings is 4.3 (3)° and the molecule adopts an E configuration with respect to the C=N bond. Intramolecular O—H⋯N and N—H⋯O hydrogen bonds are observed. In the crystal structure, the molecules are linked through intermolecular N—H⋯O and O—H⋯O hydrogen bonds to form layers parallel to the ac plane.

In the title compound, C 15 H 14 N 2 O 5 , the dihedral angle between the two benzene rings is 4.3 (3) and the molecule adopts an E configuration with respect to the C N bond. Intramolecular O-HÁ Á ÁN and N-HÁ Á ÁO hydrogen bonds are observed. In the crystal structure, the molecules are linked through intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds to form layers parallel to the ac plane.

Comment
Hydrazone compounds have been widely investigated for their biological properties (Patil et al., 2010;Cukurovali et al., 2006). Furthermore, the crystal structures of hydrazone compounds have also attracted much attention in recent years (Mohd Lair et al., 2009;Lin & Sang, 2009;Suleiman Gwaram et al., 2010). In the present work, the title new hydrazone compound is reported.
In the molecule of the title compound ( Fig. 1), the dihedral angle between the two benzene rings is 4.3 (3)°. The molecule adopts an E configuration with respect to the C═N bond. There are intramolecular O-H···N and N-H···O hydrogen bonds (Table 1) in the molecule. All the bond lengths are within normal ranges (Allen et al., 1987) and are comparable with those observed in related structures (Li & Ban, 2009;Lo & Ng, 2009;Ning & Xu, 2009;Zhu et al., 2009).
In the crystal structure, molecules are linked through intermolecular N-H···O and O-H···O hydrogen bonds (Table 1) to form layers parallel to the ac plane (Fig. 2).

Experimental
A mixture of 2-hydroxy-4-methoxybenzaldehyde (0.152 g, 1 mmol) and 2,4-dihydroxybenzohydrazide (0.168 g, 1 mmol) in methanol (50 ml) was stirred at room temperature for 1 h. The mixture was filtered to remove impurities, and then left at room temperature. After a few days, single crystals of the title compound, suitable for X-ray diffraction, were formed.

Refinement
Atom H2 was located in a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å.
Other H atoms were positioned geometrically and refined using the riding-model approximation, with C-H = 0.93 or 0.96 Å, O-H = 0.82 Å and U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (methyl C and O). The ratio of observed to unique reflections is low (34%), and the value of R int is greater (0.127) probably due to the poor diffraction quality of the crystal. Fig. 1. The molecular structure of the title compound with atom labels and 30% probability displacement ellipsoids for non-H atoms. Intramolecular hydrogen bonds are shown as dashed lines.

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 > σ(F 2 ) is used only for calculating Rfactors(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.