3,5-Bis(4-bromophenyl)-1-phenyl-4,5-dihydro-1H-pyrazole

In the title compound, C21H16Br2N2, the central pyrazole ring adopts an flattened envelope conformation, with the stereogenic C atom in the flap position. The deviations from planarity for this ring are relatively minor (r.m.s. deviation = 0.045 Å) and the dihedral angles formed with the N- and Cimine-bound benzene rings are 7.73 (13) and 11.00 (13)°, respectively. By contrast, the benzene ring bound at the chiral C atom is almost orthogonal to the rest of the molecule; the dihedral angle formed between this ring and the pyrazole ring is 79.53 (13)°. In the crystal, the packing is stabilized by C—H⋯N and C—H⋯Br interactions.

In the title compound, C 21 H 16 Br 2 N 2 , the central pyrazole ring adopts an flattened envelope conformation, with the stereogenic C atom in the flap position. The deviations from planarity for this ring are relatively minor (r.m.s. deviation = 0.045 Å ) and the dihedral angles formed with the N-and C imine -bound benzene rings are 7.73 (13) and 11.00 (13) , respectively. By contrast, the benzene ring bound at the chiral C atom is almost orthogonal to the rest of the molecule; the dihedral angle formed between this ring and the pyrazole ring is 79.53 (13) . In the crystal, the packing is stabilized by C-HÁ Á ÁN and C-HÁ Á ÁBr interactions.  (2007). For the structure of the parent compound, 1,3,5triphenyl-2-pyrazoline, see: Foces-Foces et al. (2001). For conformational analysis, see: Cremer & Pople (1975 Table 1 Hydrogen-bond geometry (Å , ).

Comment
Derivatives of pyrazoline possess a range of pharmacological activities, having, for example, anti-tumour, anti-microbial, and anti-tubercular activities (Hes et al., 1978;Amir et al., 2008). Further, some of these compounds also have anti-inflammatory, anti-diabetic, anaesthetic, analgesic and DPPH scavenging properties (Sarojini et al., 2010). In continuation of previous structural studies of pyrazoline derivatives (Fun et al., 2010, Yathirajan et al., 2007, the title compound, (I), was synthesised and its crystal structure determined.
The structure analysis of (I) shows the C1 centre to have an S configuration, Fig. 1. The conformation of the central pyrazole ring is an envelope on the C1 atom as defined by the ring-puckering parameters of q 2 = 0.101 (3) Å and φ 2 = 251.7 (14) ° (Cremer & Pople, 1975). That being stated, the maximum deviations from the five atoms of the ring are 0.052 (2) and -0.064 (3) Å for the N2 and C1 atoms, respectively; the r.m.s. deviation = 0.0450 Å. The N2-and C3-bound benzene rings are approximately co-planar with the central ring as seen in the dihedral angles formed between their respective least-squares planes and that through the pyrazole ring of 7.73 (13) and 11.00 (13) °; the dihedral angle between these benzene rings is 4.32 (12) °. By contrast, the C1-bound benzene ring is almost orthogonal to the remaining molecule with a dihedral angle of 79.53 (13) ° formed between it and the pyrazole ring. To a first approximation, the overall conformation in (I) resembles that in the analogous 1,3,5-triphenyl-2-pyrazoline "parent" compound although the deviations from planarity are slightly greater in the literature structure (Foces-Foces et al., 2001). Further, the N1-N2 [1.369 (3) Å] and N1═C3 [1.291 (3) Å] bond distances in (I) are comparable to the equivalent distances in 1,3,5-triphenyl-2-pyrazoline of 1.387 (5) and 1.285 (7) Å, respectively.
The molecules are consolidated into a 3-D network by C-H···N and C-H···Br contacts, Fig. 2 and Table 1.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.95 to 1.00 Å) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2 to 1.5U eq (C). Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.