1-(4-Chlorophenyl)-3-phenyl-1H-pyrazol-5(4H)-one

In the crystal of the title compound, C15H11ClN2O, the molecules are linked by C—H⋯O and weak C—H⋯π interactions. The chlorophenyl and phenyl rings are twisted with respect to the central pyrazolone ring, making dihedral angles of 18.23 (8) and 8.35 (8)°, respectively. The N—N and C=O bond lengths are comparable to those reported for pyrazolone compounds.

In the crystal of the title compound, C 15 H 11 ClN 2 O, the molecules are linked by C-HÁ Á ÁO and weak C-HÁ Á Á interactions. The chlorophenyl and phenyl rings are twisted with respect to the central pyrazolone ring, making dihedral angles of 18.23 (8) and 8.35 (8) , respectively. The N-N and C O bond lengths are comparable to those reported for pyrazolone compounds.

Comment
Pyrazolones and their derivatives constitute a group of organic compounds that have been extensively studied due to their diverse properties and applications. For example, many more applications have been devised for this group of molecules in the pharmaceutical field. Moreover, they have been applied to the solvent extraction of metal ions (Bose et al., 2005), for analytical purposes (Ito et al., 2001), in the preparation of azo colorants (Whitaker, 1995), as ligands in complexes with catalytic activity (Bao et al., 2006) and in the synthesis of rare earth metal complexes with interesting photophysical properties (Shi et al., 2005). Also, it is important in understanding the behaviour of these compounds with respect to the mechanisms of pharmacological activities (Li et al., 2000). In order to expand this field, the novel title compound (I) has been synthesized, and its crystal structure is reported herein for the first time.
The asymmetric unit of the title compound is built up from a central pyrazolone ring substituted in 1,3 by a 4-chlorophenyl and a phenyl rings (Fig. 1). The chlorophenyl and phenyl rings are slightly twisted with respect to the central pyrazolone ring making dihedral angles of 18.23 (8)° and 8.35 (8)° respectively, thus indicating a high degree of conjugation and electron delocalization.The N(1)-N(2) and C(7)=O(1) distances are comparable, within experimental errors, with related pyrazolones reported in the literature ( Table 2).
The cohesion of the crystal is assured by weak C-H···O and C-H···π interactions (Table 1).

Experimental
All reagents were obtained from commercial sources and used without further purification. 1-(4-chlorophenyl)-3-phenyl-1H-pyrazol-5(4H)-one was synthesized according to the method proposed by Jensen (1959 golden single crystals of CPP were grown from ethanol by slow evaporation over a period of several weeks.