4-[(3-Hydroxyanilino)(phenyl)methylidene]-3-methyl-1-phenyl-1H-pyrazol-5(4H)-one

In the title compound, C23H19N3O2, the dihedral angles formed by the pyrazolone ring with the three benzene rings are 30.91 (6), 60.96 (4) and 57.01 (4)°. The ligand is in the enamine–keto form and its structure is stabilized by an intramolecular N—H⋯O hydrogen bond. In the crystal, O—H⋯N hydrogen bonds link molecules into chains parallel to [01-1].

In the title compound, C 23 H 19 N 3 O 2 , the dihedral angles formed by the pyrazolone ring with the three benzene rings are 30.91 (6), 60.96 (4) and 57.01 (4) . The ligand is in the enamine-keto form and its structure is stabilized by an intramolecular N-HÁ Á ÁO hydrogen bond. In the crystal, O-HÁ Á ÁN hydrogen bonds link molecules into chains parallel to [011].
The reaction of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with primary amines affords Schiff bases that can function as N-and O-donor tridentates ligands, (Wang et al., 2002;Ramasamy et al., 2010;Thakar et al., 2010;Xu et al., 2006;Zhu et al., 2005;Wang et al., 2003). In order to expand this field, a novel Schiff base has been synthesized and its crystal structure is reported herein for the first time. The compound (I) was prepared from the reaction of 1-phenyl-3-methyl-4benzoyl-5-pyrazolone (H1PMBP) and 3-aminophenol. The asymmetric unit of structure (I), and the atomic numbering used, are illustrated in Fig.1.
A strong intramolecular N1-H1N···O2 hydrogen bond (Table 1) is observed, leading to an enamine-keto tautomeric form. This case is similar to that found by Xu et al. (2006)  forming chains parallel to the [0 1 -1] direction. Part of the chain structure is shown in Fig.2.

Experimental
All reagents were obtained from commercial sources and used without further purification. H1PMBP was synthesized according to the method proposed by Jensen (Jensen,1959). Ethanol solution of 139 mg (0.1 mol) of H1PMBP and 54.5 mg (0.1 mol) of m-aminophenol were refluxed together for 24 h over a steam bath. The excess solvent was removed by evaporation. The title compound separated out as a yellow powder, which was collected, dried in air and dissolved afterwards in a hot mixture ethanol/water (9.5/0.5). A bright yellow single crystals, suitable for X-ray analysis, were obtained by slow cooling of a warmed ethanol solution for one night. The product is stable in air, and soluble in acetone and ethanol. Elemental analysis: calculated C 74.78, H 5.18, N 11.37%; found C 74.34, H 5.20, N 11.33%.

Refinement
The H atoms, except for the H-atoms of the OH and NH groups which were located from Fourier difference maps, were positioned geometrically and refined using a riding model, with C-H = 0.95-0.99 Å and with U iso (H) = 1.2 (1.5 for methyl groups) times U eq (C).

Figure 1
The asymmetric unit of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii. Hydrogen bond is shown as dashed line.

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 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.