3-(4-Aminophenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide

In the molecule of title pyrazoline derivative, C17H18N4OS, the pyrazole ring adopts an envelope conformation with the flap atom, which bears the methoxyphenyl substituent, displaced by 0.0750 (12) Å from the plane through the other ring atoms. The two substituted benzene rings make a dihedral angle of 70.59 (6)°. The methoxy group is twisted slightly with respect to the attached benzene ring [Cmethyl—O—C—C torsion angle = −8.84 (15)°]. An intramolecular N—H⋯N hydrogen bond occurs. In the crystal, the pyrazoline molecules are linked by N—H⋯O and N—H⋯S hydrogen bonds into zigzag layers parallel to the bc plane and stacked along the a axis by π–π interactions with centroid–centroid distances of 3.4690 (7) and 3.5792 (7) Å. C—H⋯π interactions are also present.


Comment
Pyrazolines are five-membered heterocyclic compounds having three carbon atoms and two adjacent nitrogen atoms within the pyrazoline ring. Numerous pyrazolines have been found to possess considerable biological activities with several prominent effects, such as antimicrobial (Sakthinathan et al., 2012), antiamoebic (Husain et al., 2008), antiinflammatory (Shoman et al., 2009), analgesic (Khode et al., 2009) and anticancer (Lv et al., 2011;Shaharyar et al., 2010) activities, as well as optical properties (Gong et al., 2010). Owing to these interesting properties of pyrazolines and our on-going research on fluorescence and biologically active compounds, the title pyrazoline derivative (I) was synthesized by cyclization of the chalcone derivative with thiosemicarbazide. Herein the crystal structure of (I) is reported.

Experimental
The title compound was synthesized by dissolving (E)-1-(4-aminophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (0.25 g, 1.0 mmol) in a solution of KOH (0.11 g, 2.0 mmol) in ethanol (20 ml). An excess thiosemicarbazide (0.18 g, 2.0 mmol) in ethanol (20 ml) was then added, and the reaction mixture was vigorously stirred and refluxed for 4 h. The brown solid of the title compound obtained after cooling was filtered off under vacuum. Brown block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystallized from C 2 H 5 OH by slow evaporation of the solvent at room temperature after several days. M. p. 479-480 K.

Refinement
Amino and thioamide H atoms were located in a difference Fourier map and refined isotropically. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.95 Å for aromatic, 1.00 Å for CH, 0.99 Å for CH 2 and 0.98 for CH 3 atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl group.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Intramolecular N-H···N hydrogen bond is shown as a dashed line.  Crystal packing of the title compound viewed along the c axis. Hydrogen bonds are shown as dashed lines.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.