4-Amino-3-(4-pyridyl)-1,2,4-triazole-5(4H)-thione

In the title molecule, C7H7N5S, the pyridyl and triazole rings form a dihedral angle of 20.07 (6)°. Intermolecular N—H⋯N hydrogen bonds link the molecules into chains extended in the direction [10]. Further stability is provided by π⋯π stacking interactions, indicated by short distances between the centroids of triazole rings [3.480 (5) Å] and pyridyl rings [3.574 (5) Å] of neighbouring molecules.

In the title molecule, C 7 H 7 N 5 S, the pyridyl and triazole rings form a dihedral angle of 20.07 (6) . Intermolecular N-HÁ Á ÁN hydrogen bonds link the molecules into chains extended in the direction [101]. Further stability is provided by Á Á Á stacking interactions, indicated by short distances between the centroids of triazole rings [3.480 (5) Å ] and pyridyl rings [3.574 (5) Å ] of neighbouring molecules.
In (I) (Fig. 1), the molecule exists as a thione tautomer. All bond lengths and angles are normal and comparable with those found in related compounds (Kajdan et al., 2000). The dihedral angle between the pyridinyl and triazole rings is 20.07 (6)°.

Experimental
Potassium hydroxide (8.4 g, 0.15 mol) in 100 ml of absolute ethanol was added to isonicotinohydrazide (13.7 g, 0.10 mol) under ice bath. The mixture was stirred until the solution became clear, and carbon disulfide (9.04 ml, 0.15 mol) was added.
The solution was reacted for 12 h at room temperature and 100 ml dried ethyl ether were added to form a precipitate, which was filtered and washed with ethyl ether several times. The precipitate was mixed with hydrazine hydrate (8.0 g, 160 mmol) and 10 ml water. The solution was refluxed for 2 h until the colour of the solution became clear green. After cooling to room temperature, 100 ml ice water was added and neutralized with 3M hydrochloric acid to form the precipitate, which was isolated by filtration and purified by recrystallization from ethanol to give pure 3-pyridinyl-4-amino-5--mercapto-1,2,4-triazole.
Crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of an Dimethylformamide solution.

Refinement
The hydrogen atoms were geometrically positioned (C-H 0.93 Å, N-H 0.86-0.90 Å) and were included in the refinement in the riding model approximation, with U iso (H)=1.2-1.5Ueq of the parent atom. Fig. 1. The molecular structure of (I) showing the atomic numbering and 30% probability displacement ellipsoids.

Figures
supplementary materials sup-2 4-Amino-3-(4-pyridyl)-1,2,4-triazole-5(4H)-thione 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.