3-Methyl-1-phenyl-4-[(phenyl)(2-phenylhydrazin-1-yl)methylidene]-1H-pyrazol-5(4H)-one

The title compound, C23H20N4O, is a heterocyclic phenylhydrazone Schiff base with a pyrazole moiety. In the crystal, a variety of interactions occur, including N—H⋯π and π–π stacking between the phenyl ring of the phenylhydrazinyl group and its symmetry-generated equivalent [centroid–centroid distance = 3.6512 (7) Å].

The title compound, C 23 H 20 N 4 O, is a heterocyclic phenylhydrazone Schiff base with a pyrazole moiety. In the crystal, a variety of interactions occur, including N-HÁ Á Á andstacking between the phenyl ring of the phenylhydrazinyl group and its symmetry-generated equivalent [centroidcentroid distance = 3.6512 (7) Å ].
In the crystal structure π stacking occurs between the phenyls of adjacent phenylhydazone groups with a centroid to centroid distance of 3.6512 (7) Å and slippage of 0.922 Å (Fig. 2). The dihedral angles formed by the least square planes between the phenyl of the phenylhydrazone group with the pyrazole and the C21-C26 aromatic ring are 85.29 (6)° and 77.88 (6)° repectively. The phenyl on the pyrazole group is slight twisted out of the pyrazole plane by 12.84 (4)°. The packing of the title compound is shown in Figure 3.

Experimental
A mixture of phenylhydrazine and 4-benzoyl-3-methyl-1-phenyl-2-pyrazoline-5-one (ratio 1:1) in methanol was refluxed for 5 h. The mixture was poured into cold distilled water to precipitate the yellow titled compound (yield: 92%; m.p: 190-192°C), which was isolated by filtration and recrystalized from methanol. Single crystals of the titled compound suitable for X-ray diffraction was obtained from methanol by slow evaporation at room temperature.

Refinement
The carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms and C-H 0.98 Å for the methyl group) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U~eq~(C). The H atoms of the methyl group were allowed to rotate with a fixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2008), with U(H) set to 1.5 U~eq~(C)). The nitrogen-bound H atoms were located on a difference Fourier map and refined freely with isotropic parameters.

Figure 1
The molecular structure of the title compound, with atom labels and anistropic displacement ellipsoids (drawn at 50% probability level).

Figure 2
Inter and intra molecular contacts as well as the short ring interaction between C31-C36 and C31 i -C36 i (blue dashed line). Symmetry operators: i -x + 1, -y, -z + 2.

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.