N′-[(E)-2-Hydroxy-5-methoxybenzylidene]pyridine-4-carbohydrazide

In the title compound, C14H13N3O3, the dihedral angle between the pyridine and benzene rings is 15.17 (18)°. The torsion angle of the –C=N—N—C– system between two aromatic rings is −167.1 (3)°. Intramolecular O—H⋯N hydrogen bonding generates S(6) rings. In the crystal structure, neighbouring molecules are linked together along the c axis by weak intermolecular C—H⋯O and N—H⋯O hydrogen bonds, generating R 1 2(6) ring motifs.

In the title compound, C 14 H 13 N 3 O 3 , the dihedral angle between the pyridine and benzene rings is 15.17 (18) . The torsion angle of the -C N-N-C-system between two aromatic rings is À167.1 (3) . Intramolecular O-HÁ Á ÁN hydrogen bonding generates S(6) rings. In the crystal structure, neighbouring molecules are linked together along the c axis by weak intermolecular C-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, generating R 1 2 (6) ring motifs.

Comment
In the search for new biologically active compounds, isoniazid (isonicotinylhydrazine) derivatives have been found to possess potential tuberculostatic activity (Janin, 2007;Maccari et al., 2005). Here, we present the crystal structure of the title compound, (I).

Experimental
The isoniazid derivative was prepared following procedure reported by Lourenco et al., (2008). 5-methoxysalicylaldehyde (1.0 mmol) was added to isoniazid (1.0 mmol) in ethanol. After stirring for 3 h at reflux condition, the resulting mixture was concentrated at room temperature. The residue was purified by washing with cold ethanol and diethyl ether to give the pure derivative. Colourless single crystals suitable for X-ray analysis were obtained by re-crystallization from methanol.

Refinement
In the absence of significant anomalous dispersion effects, Freidel pairs were merged. The calculation of the Flack (1983) parameter was suppressed by the MERG 4 command in SHELXL97 (Sheldrick, 2008), as the lack of anomalous scatterers did not allow the determination of the absolute configuration from the X-ray measurements. The H atoms of the O-H and N-H groups were found from a difference Fourier map and refined freely [O1-H1 = 0.96 (4) and N2-H2 = 0.88 (4) Å]. The remaining H atoms were placed in idealized positions and allowed to ride on their parent atoms, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and U iso (H) = 1.5U eq (C) for methyl H and U iso (H) = 1.2U eq (C) for aromatic H. Fig. 1

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted Rfactors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.