Crystal structure of 1-[(Z)-2-phenylhydrazin-1-ylidene]naphthalen-2(1H)-one

In the title compound, C16H12N2O, the dihedral angle between the planes of the benzene ring and naphthalenone ring system is 1.89 (8)°; an intramolecular N—H⋯O hydrogen bond occurs between the imino group and the carbonyl group. In the crystal, molecules are linked by weak C—H⋯π interactions into supramolecular chains propagating along the [01-1] direction.

Cg1 and Cg3 are the centroids of the C1-C6 and C12-C17 rings, respectively. Supporting information for this paper is available from the IUCr electronic archives (Reference: XU5845).

S1. Comment
The azo dyes are by far the most important class, accounting for over 50% of all commercial dyes, and having been studied more than other class (Lee et al., 2004;Oueslati et al., 2004). Azo dyes contain at least one azo group (-N=N-) but can contain two (diazo), three(triazo), or, more rarely, four (tetrakisazo) or more (polyazo) azo groups. The azo group is attached to two groups, of which at least one, but more usually both are aromatic. They exist in the Trans form in which the band angle is 120°, the nitrogen atoms are sp 2 hybridized. Almost without exception, azo dyes are made by diazotization of primary aromatic amine followed by coupling of the resultant diazonium salt with an electronrichnucleophile. We report here in the crystal structure of the title compound, obtained through the diazotization of aniline followed by a coupling reaction with2-naphthol.
The molecular structure of (I) and the atom-numbering scheme are shown in Figure 1. Two aromatic rings A (C1-C6) and B (C7-C16) show a little deviation from planarity with a dihedral angle of 1.56°. Intramolecular hydrogen bonds are formed between the phenol hydroxyl groups and the nearest N atom in the aminobenze groups (Table 1).

S2. Experimental
Treatment of aniline (0.02 mol) in 6 ml of 12M HCl and NaNO 2 (0.0214 mol) in 8 ml of H 2 O for 30 min. To the obtained solution, was added dropwise a solution of naphthalen-2-ol, and the resulting brown precipitates were filtrated and washed with water, and dried in a desiccator for several days. Single crystals were obtained by slow evaporation from a pentane solution.

S3. Refinement
The imino-H atom was located in a difference Fourier map and refined freely with U iso (H) = 1.2U eq (N). Other H atoms were placed in geometrically idealized positions and refined as riding, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title molecule with the atom-numbering scheme. Ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.20 e Å −3 Δρ min = −0.20 e Å −3 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 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 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.