3-Hydroxy-N′-(2-methoxybenzylidene)-2-naphthohydrazide

In the title Schiff base compound, C19H16N2O3, the dihedral angle between the mean planes of the benzene ring and the naphthyl ring system is 0.8 (2)°. The mean plane of the hydrazide group forms dihedral angles of 2.0 (2) and 2.2 (2)°, respectively, with the mean planes of the benzene ring and the naphthyl ring system. A strong intramolecular N—H⋯O hydrogen bond is present. In the crystal, intermolecular O—H⋯O hydrogen bonds form chains along the c axis and help to provide stability in the crystal packing.

In the title Schiff base compound, C 19 H 16 N 2 O 3 , the dihedral angle between the mean planes of the benzene ring and the naphthyl ring system is 0.8 (2) . The mean plane of the hydrazide group forms dihedral angles of 2.0 (2) and 2.2 (2) , respectively, with the mean planes of the benzene ring and the naphthyl ring system. A strong intramolecular N-HÁ Á ÁO hydrogen bond is present. In the crystal, intermolecular O-HÁ Á ÁO hydrogen bonds form chains along the c axis and help to provide stability in the crystal packing.

Experimental
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: JJ2010).

3-Hydroxy
Schiff base compounds, important to the pharmaceutical and medicinal fields (Dao et al., 2000;Sriram et al., 2006;Karthikeyan et al., 2006), have been used as versatile ligands in a variety of coordination chemistry applications (Ali et al., 2008;Kargar et al., 2009;Yeap et al., 2009). A number of contributions to these areas have been recently reported Nadeem et al., 2009;Eltayeb et al., 2008). With our continued interest in the structural chararcterization of these compounds (Hao, 2009a,b) the title compound, C 19 H 16 N 2 O 3 , (I), is reported.
In the title compound,(I), the mean plane of the hydrazide group, O2/C9/N2/N1/C8, forms dihedral angles of 2.0 (2) and 2.2 (2)°, with the mean planes of the benzene (C1-C6) and naphthyl rings (C10-C19), respectively ( Fig. 1). The dihedral angle between the mean planes of the benzene and naphthyl rings is 0.9 (2)°, indicating the planarity of the molecule. All the bond lengths and angles are within normal values (Allen et al., 1987). Crystal packing is enhanced by strong intramolecular N-H···O and intermolecular O-H···O hydrogen bonds (Table 1), forming infinite one-dimensional chains running along the c axis of the unit cell (Fig. 2).
Experimental 2-Methoxybenzaldehyde (0.1 mmol, 13.6 mg) and 3-hydroxy-2-naphthohydrazide (0.1 mmol) were refluxed in a 30 ml methanol solution for 30 min to give a clear colorless solution. Colorless block-shaped single crystals of the compound were formed by slow evaporation of the solvent over several days at room temperature.

Refinement
H2 was located from a difference Fourier map and refined isotropically, with the N-H distance restrained to 0.90 (1)Å, and with U iso restrained to 0.08Å 2 . Other H atoms were constrained to ideal geometries, with d(C-H) = 0.93-0.96 Å, d(O-H) = 0.82 Å, and with U iso (H) = 1.2U eq (C) and 1.5U eq (O3 and C7). Fig. 1. The molecular structure of the title compound with 30% probability ellipsoids. A strong intramolecular N-H···O hydrogen bond is shown as a dashed line.

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 > 2σ(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.