(E)-N′-(3,4-Dimethoxybenzylidene)-2,4-dihydroxybenzohydrazide methanol solvate

The title compound, C16H16N2O5·CH3OH, was obtained from a condensation reaction of 3,4-dimethoxybenzaldehyde and 2,4-dihydroxybenzohydrazide. The non-H atoms of the Schiff base molecule are approximately coplanar (r.m.s. deviation = 0.043 Å) and the dihedral angle between the two benzene rings is 1.6 (1)°. The molecule adopts an E configuration with respect to the C=N double bond. An intramolecular O—H⋯O hydrogen bond is observed. The Schiff base and methanol molecules are linked into a two-dimensional network parallel to (10) by intermolecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds.


Comment
Hydrazones and Schiff bases have been attracted much attention for their excellent biological properties, especially for their potential pharmacological and antitumor properties (Kucukguzel et al., 2006;Khattab et al., 2005;Karthikeyan et al., 2006;Okabe et al., 1993). Recently, a large number of hydrazone derivatives have been prepared and structurally characterized (Shan et al., 2008;Fun et al., 2008;Ma et al., 2008;Diao et al., 2008a,b;Ejsmont et al., 2008). As part of the ongoing study, we report herein the crystal structure of the title compound.
The molecular structure of the title compound is shown in Fig. 1 Table 1).
Experimental 3,4-Dimethoxybenzaldehyde (1.0 mmol, 166.2 mg) was dissolved in methanol (50 ml), then 2,4-dihydroxybenzohydrazide (1.0 mmol, 168.2 mg) was added slowly into the solution, and the mixture was kept at reflux with continuous stirring for 1 h. After the solution had cooled to room temperature colourless crystallites appeared. The crystallites were filtered and washed with methanol for three times. Recrystallization from an absolute methanol yielded block-shaped single crystals of the title compound.

Refinement
Atom H1A was located from a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1) Å. Other H atoms were placed in calculated positions with C-H = 0.93-0.96 Å and O-H = 0.82 Å, and refined in riding mode with U iso (H) = 1.2U eq (C) and 1.5U eq (O and C methyl ). A rotating group model was used for methyl and hydroxyl groups.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.