3,5-Dimethyl-1-(4-nitrophenyl)-1H-pyrazole

In the title pyrazole derivative, C11H11N3O2, the benzene ring is twisted [dihedral angle = 31.38 (12)°] with respect to the pyrazole ring (r.m.s. deviation = 0.009 Å). The nitro group is effectively coplanar with the benzene ring to which it is attached [O—N—C—C torsion angle = −6.5 (3)°]. Supramolecular chains along the b axis are formed owing to π–π interactions [3.8653 (2) Å] between translationally related molecules involving both the five- and six-membered rings.

In the title pyrazole derivative, C 11 H 11 N 3 O 2 , the benzene ring is twisted [dihedral angle = 31.38 (12) ] with respect to the pyrazole ring (r.m.s. deviation = 0.009 Å ). The nitro group is effectively coplanar with the benzene ring to which it is attached [O-N-C-C torsion angle = À6.5 (3) ]. Supramolecular chains along the b axis are formed owing tointeractions [3.8653 (2) Å ] between translationally related molecules involving both the five-and six-membered rings.

Comment
Pyrazoles are key structures in numerous compounds of therapeutic importance (Sil et al., 2005, Haddad et al., 2004. Compounds containing this ring system are known to display diverse pharmacological activities, for example as antimalarial agents (Bekhit et al., 2012), anti-inflammatory agents (Bekhit et al., 2010), and against cardiovascular disease (Higashi et al., 2006). A general route to pyrazole derivatives involves reaction of an arylhydrazine, ArNHNH 2 , with a βdicarbonyl compound, R′COCH 2 COY. In connection with recent structural studies Baddeley et al., 2012), we now wish to report the structure of the title compound, (I), prepared from 4-O 2 NC 6 H 4 NHNH 2 and MeCOCH 2 COMe.
In (I), Fig. 1, the pyrazole ring is planar with a r.m.s. deviation for the fitted atoms of 0.009 Å. The benzene ring is twisted out of this plane forming a dihedral angle of 31.38 (12)°. The nitro group is effectively co-planar with the benzene ring to which it is connected as seen in the value of the O1-N3-C9-C8 torsion angle of -6.5 (3)°.
The most prominent intermolecular interactions in the crystal structure of (I) are of the type π-π. These form between translationally related molecules along the b axis, involving both the five-and six-membered rings, and therefore, the ring centroid separations are 3.8653 (2)

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.95-0.98 Å) and refined as riding with U iso (H) = 1.2-1.5U eq (C). In the absence of significant anomalous scattering effects, 515 Friedel pairs were averaged in the final refinement.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.