2-Hydroxy-N′-(2-hydroxy-4-methoxybenzylidene)-3-methylbenzohydrazide monohydrate

In the title compound, C16H16N2O4·H2O, the dihedral angle between the two benzene rings is 12.4 (2)° and 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 hydrazone molecule, which both generate S(6) rings. In the crystal structure, molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds, forming layers parallel to the ab plane. The crystal studied was a non-merohedral twin with a domain ratio of 0.887 (3):0.113 (3).

In the title compound, C 16 H 16 N 2 O 4 ÁH 2 O, the dihedral angle between the two benzene rings is 12.4 (2) and 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 hydrazone molecule, which both generate S(6) rings. In the crystal structure, molecules are linked by N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds, forming layers parallel to the ab plane. The crystal studied was a non-merohedral twin with a domain ratio of 0.887 (3):0.113 (3).
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 ab plane ( Fig. 2).

Experimental
A mixture of 4-methoxysalicylaldehyde (0.152 g, 1 mmol) and 2-hydroxy-3-methylbenzohydrazide (0.166 g, 1 mmol) in 50 ml me thanol 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, colourless blocks of (I) were formed.

Refinement
The crystal turned out to be a non-merohedral twin (twin law: -1 0 0/0 -1 0/ 0.331 0 1) with a fractional contribution of the minor component of 0.113 (3). Amino H and water H atoms were located from a difference Fourier map and refined isotropically, with N-H, O-H, and H···H distances restrained to 0.90 (1), 0.85 (1), and 1.37 (2) Å, respectively. 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 (I) with 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 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 > 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.