3-(4-Methoxyphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde

Four independent molecules comprise the asymmetric unit of the title compound, C17H14N2O2. The central pyrazoline ring is flanked by an N-bound benzene ring and a C-bound methoxy-substituted benzene ring. The greatest difference between the independent molecules is found in the relative orientations of the benzene rings with the range of dihedral angles being 23.59 (6)–42.55 (6)°. In the crystal, extensive C—H⋯O interactions link molecules into layers parallel to (02) and these are linked by C—H⋯π contacts.

Four independent molecules comprise the asymmetric unit of the title compound, C 17 H 14 N 2 O 2 . The central pyrazoline ring is flanked by an N-bound benzene ring and a C-bound methoxysubstituted benzene ring. The greatest difference between the independent molecules is found in the relative orientations of the benzene rings with the range of dihedral angles being 23.59 (6)-42.55 (6) . In the crystal, extensive C-HÁ Á ÁO interactions link molecules into layers parallel to (021) and these are linked by C-HÁ Á Á contacts.  Table 1 Hydrogen-bond geometry (Å , ).

Comment
Pyrazolines and their derivatives have been found to possess a broad spectrum of biological activity such as anti-bacterial, anti-depressant, anti-convulsant, anti-hypertensive, anti-oxidant, and anti-tumour properties (Kaushik et al., 2010;Krishnamurthy et al., 2004). Recent reports shows the potential anti-viral activity of this class of compounds against flavivirus and HIV (Ali et al., 2007). In continuation of structural studies in this area (Prasath et al., 2011), the title compound, (I), was investigated.
Four independent molecules comprise the crystallographic asymmetric unit of (I), Fig. 1. Each molecule comprises a central five-membered pyrazoline ring with a benzene ring attached at the N1-atom and a methoxy-substituted benzene ring at the C3-atom. Differences in the molecules relate primarily to the relative orientations of the various substituents, in particular for the N-bound benzene ring. Thus, the dihedral angles formed between the pyrazoline ring and the N-bound benzene ring are 13.36 (7), 2.54 (7), 15.29 (7) and 1.27 (7)°, respectively, for the independent molecules with the O1, O3, O5 and O7 atoms, respectively. The variation in the dihedral angles formed between the pyrazoline ring and the methoxybenzene ring range from 30.75 (7)° (O1-molecule) to 33.46 (7)° (O7-molecule), i.e. display relatively small differences.
The dihedral angles formed between the benzene rings within each molecule range from 23.59 (6)° (O1-molecule) to 42.55 (6)° (O5-molecule). Supramolecular layers in the (0 2 1) plane are formed in the crystal structure via C-H···O interactions, Fig. 3 and Table   1. Layers comprise rows of pairs of molecules whereby the aldehyde-O atoms face each other and are connected C-H···O interactions, with the methoxybenzene rings directed to the periphery allowing them to self-associate and thereby propagate the layer. The closest interactions between the layers are of the type C-H···π, Table 1
The resulting mixture was further stirred at 333 K for 6 h and cooled to room temperature. The crude product was poured into crushed ice which resulted in the deposition of a white precipitate. The resultant solid was filtered, dried and purified by column chromatography using chloroform. Recrystallization was by slow evaporation of a chloroform solution of (I) which yielded colourless prisms. M.pt. 403-405 K. Yield: 76%.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H 0.95 to 0.98 Å, U iso (H) = 1.2 to 1.5U eq (C)] and were included in the refinement in the riding model approximation.  Fig. 1. The molecular structures of the four independent molecules comprising the asymmetric unit of (I) showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level. Fig. 2. Overlay diagram of the four independent molecules comprising the asymmetric unit of (I). The independent molecule with the O1, O3, O5 (inverted molecule) and O7 atom are illustrated in red, blue, green and black, respectively.    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 Rfactors(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.