1-[(2-Anilinoethyl)iminiomethyl]-2-naphtholate

The title Schiff base compound, C19H18N2O, was prepared by the reaction of equimolar quantities of 2-hydroxy-1-naphthaldehyde with N-phenylethane-1,2-diamine in a methanol solution. The molecule adopts a zwitterionic conformation with the naphthyl OH group deprotonated and the imine N atom protonated. An intramolecular N—H⋯O hydrogen bond forms between them. The dihedral angle between the benzene ring and the naphthyl system is 86.9 (2)°. In the crystal structure, molecules are linked through intermolecular N—H⋯O hydrogen bonds, forming chains running along the b axis.

The title Schiff base compound, C 19 H 18 N 2 O, was prepared by the reaction of equimolar quantities of 2-hydroxy-1-naphthaldehyde with N-phenylethane-1,2-diamine in a methanol solution. The molecule adopts a zwitterionic conformation with the naphthyl OH group deprotonated and the imine N atom protonated. An intramolecular N-HÁ Á ÁO hydrogen bond forms between them. The dihedral angle between the benzene ring and the naphthyl system is 86.9 (2) . In the crystal structure, molecules are linked through intermolecular N-HÁ Á ÁO hydrogen bonds, forming chains running along the b axis.

Experimental
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2625).
In (I), the H atom of the phenol group is transferred to the imine N atom, forming an intramolecular N-H···O hydrogen bond ( Table 1). The dihedral angle between the benzene ring and the naphthyl ring is 86.9 (2)°. All the bond lengths are within normal values (Allen et al., 1987). In the crystal structure of the compound, molecules are linked through intermolecular N-H···O hydrogen bonds (Table 1), forming chains running along the b axis ( Fig. 2).
Experimental 2-Hydroxy-1-naphthylaldehyde (0.1 mmol, 17.2 mg) and N-phenylethane-1,2-diamine (0.1 mmol, 13.6 mg) were refluxed in a 30 ml methanol solution for 30 min to give a clear orange solution. Yellow block-shaped single crystals of the compound were formed by slow evaporation of the solvent over several days at room temperature.

Refinement
In the absence of significant anomalous dispersion effects, 1421 Freidel pairs were merged. H1 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 .

Figures
Fig . 1. The molecular structure of (I) with 30% probability ellipsoids. The 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 > 2sigma(F 2 ) is used only for calculat-supplementary materials sup-3 ing R-factors(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.