N′-(2,5-Dihydroxybenzylidene)-2-hydroxy-3-methylbenzohydrazide

In the title compound, C15H14N2O4, the dihedral angle between the two benzene rings is 4.1 (2)°. The molecule adopts an E configuration with respect to the C=N bond. There are intramolecular O—H⋯N and O—H⋯O hydrogen bonds in the molecule. In the crystal structure, molecules are linked through intermolecular N—H⋯O and O—H⋯O hydrogen bonds, forming chains running along the c axis.

In the title compound, C 15 H 14 N 2 O 4 , the dihedral angle between the two benzene rings is 4.1 (2) . The molecule adopts an E configuration with respect to the C N bond. There are intramolecular O-HÁ Á ÁN and O-HÁ Á ÁO hydrogen bonds in the molecule. In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, forming chains running along the c axis.

Comment
Hydrazone compounds have been widely investigated for their biological properties (Patil et al., 2010;Cukurovali et al., 2006). Furthermore, the crystal structures of the hydrazone compounds have also attracted much attention in recent years (Mohd Lair et al., 2009;Lin & Sang, 2009;Suleiman Gwaram et al., 2010). As a continuation of our work on the structural characterization of such compounds (Han & Zhao, 2010a,b), the title new hydrazone compound is reported.
In the title compound, Fig. 1, the dihedral angle between the two benzene rings is 4.1 (2)°. The molecule adopts an E configuration with respect to the C═N bond. There are intramolecular O-H···N and O-H···O hydrogen bonds in the molecule (Table 1). All the bond lengths are within normal ranges (Allen et al., 1987), and are comparable with those in the similar compounds (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 chains running along the c axis (Fig. 2).

Experimental
A mixture of 2,5-dihydroxybenzaldehyde (0.138 g, 1 mmol) and 2-hydroxy-3-methylbenzohydrazide (0.166 g, 1 mmol) in 50 ml methanol 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
Amino H atom was located from a difference Fourier map and refined isotropically, with 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). Fig. 1. The molecular structure of the title compounds 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.