3-[5-(2,4-Dichlorophenyl)-1-phenyl-4,5-dihydro-1H-pyrazol-3-yl]-4-hydroxy-2H-chromen-2-one

In the title compound, C24H16Cl2N2O3, the chromene ring system is almost planar, with a maximum deviation of 0.042 (1) Å. It makes dihedral angles of 3.72 (6), 73.37 (5) and 12.00 (5)° with the dihydropyrazole, benzene and phenyl rings, respectively. An intramolecular O—H⋯N hydrogen bond forms an S(6) ring motif. In the crystal, molecules are linked via C—H⋯O interactions, forming an infinite chain along the a axis. The crystal packing is further stabilized by a π–π stacking interaction [centroid–centroid distance = 3.5471 (7) Å] and a Cl⋯Cl short contact [Cl⋯Cl = 3.214 (1) Å].


Comment
In our earlier work we have reported the crystal structure of chalcone (Asad et al., 2010). In continuation of our work, we reported here the crystal structure of pyrazoline (title compound) which was afforded by the condensation of chalcone with phenylhydrazine. A large number of pyrazoline derivatives showed a broad range of biological properties such as antibacterial (Siddiqui et al., 2008), antiviral (Goodell et al., 2006), antiparasitic (Bernstein et al., 1947), anti-inflammatory (Mohammad et al., 2008), antidepressant (Chimenti et al., 2004) and anticancer (Hollis et al., 1984) activities.
In the crystal structure, the molecules are linked via C14-H14···O2 i (Table 1) to form infinite chains along the a axis.
The crystal packing is further stabilized by π-π stacking interactions with Cg-Cg distance of 3.5471 (7)

Experimental
The compound, 3-[(E)-3-(2,4-dichlorophenyl)prop-2-enoyl]-4-hydroxy-2H-chromen-2-one (2.76 mmol, 1.00 g) was dissolved in acetic acid (20 ml) and phenylhydrazine (2.76 mmol, 0.30 g) was added to it. The reaction mixture was refluxed on a heating mantle for 2 h. After the reaction was over, the reaction mixture was cooled to room temperature and poured into ice cold water. The yellow-colour solid formed was filtered, washed with water, dried and recrystallized from chloroform-methanol (80:20 v/v) to get the pure title compound in 62.5% yield.

Refinement
H1O3 was located in a difference Fourier map and freely refined. The remaining H atoms were positioned geometrically and refined using a riding model (C-H = 0.97 Å for methylene, 0.98 Å for methine and 0.93 Å for the rest of H atoms) with U iso (H) = 1.2U eq (C). The highest residual electron density peak is located 0.78 Å from atom Cl2.
Figures Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen atoms are shown as spheres of arbitrary radius.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 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.