3-Ethyl-6-[3-(4-fluorophenyl)-1H-pyrazol-4-yl]-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole

In the title compound, C14H11FN6S, the 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole ring system is essentially planar [maximum deviation = 0.022 (3) Å] and is inclined at dihedral angles of 15.00 (18) and 52.82 (16)° with respect to the pyrazole and phenyl rings. In the crystal, molecules are linked into two-dimensional networks parallel to (100) via intermolecular N—H⋯N and weak C—H⋯N hydrogen bonds. The crystal packing is further consolidated by weak π–π stacking interactions, with a centroid–centroid distance of 3.590 (2) Å. The crystal studied was an inversion twin with a 0.37 (13):0.63 (13) domain ratio.


Comment
The recent literature is enriched with progressive findings about the synthesis and pharmacological activity of fused heterocycles. Heterocycles bearing a triazole or 1,3,4-thiadiazole moiety are reported to show biological properties such as antibacterial (Farghaly, 2004), anti aggregatory agent (Czarnocka et al., 1991), anti-inflammatory (Unangst et al., 1992) and anticancer (Dhanya et al., 2009) activities. In addition, the N-bridged heterocycles derived from 1,2,4-triazoles have applications in the field of medicine, agriculture and industry (Farghaly et al., 2006). 1,3,4-Thiadiazoles exhibit broad spectrum of biological activities, possibly due to the presence of toxophoric N-C-S moiety (Omar & Aboulwafa, 1986). Keeping in view of the biological importance, the title compound was synthesized to study its crystal structure.

Refinement
H1N2 was located in a difference Fourier map and allowed to refined freely. The remaining H atoms were positioned geometrically and refined using a riding model with C-H = 0.93-0.97 Å and U iso (H) = 1.2 or 1.5 U eq (C). A rotating-group model was applied for the methyl group. The crystal studied was an inversion twin with a 0.37 (13) : 0.63 (13) domain ratio.
The reported Flack parameter was obtained by TWIN/BASF procedure in SHELXL (Sheldrick, 2008). Fig. 1. The molecular structure of the title compound showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.