3-Ethyl-4-[(E)-2-methylbenzylideneamino]-1H-1,2,4-triazole-5(4H)-thione

Crystals of the title compound, C12H14N4S, were obtained from a condensation reaction of 4-amino-3-ethyl-1H-1,2,4-triazole-5(4H)-thione and 2-methylbenzaldehyde. In the molecular structure, there is a short N=C double bond [1.255 (2) Å], and the benzene and triazole rings are located on opposite sites of this double bond. The two rings are approximately parallel to each other, the dihedral angle being 1.75 (11)°. A partially overlapped arrangement is observed between the nearly parallel triazole and benzene rings of adjacent molecules; the perpendicular distance of the centroid of the triazole ring from the benzene ring is 3.482 Å, indicating the existence of π–π stacking in the crystal structure.

Crystals of the title compound, C 12 H 14 N 4 S, were obtained from a condensation reaction of 4-amino-3-ethyl-1H-1,2,4triazole-5(4H)-thione and 2-methylbenzaldehyde. In the molecular structure, there is a short N C double bond [1.255 (2) Å ], and the benzene and triazole rings are located on opposite sites of this double bond. The two rings are approximately parallel to each other, the dihedral angle being 1.75 (11) . A partially overlapped arrangement is observed between the nearly parallel triazole and benzene rings of adjacent molecules; the perpendicular distance of the centroid of the triazole ring from the benzene ring is 3.482 Å , indicating the existence ofstacking in the crystal structure.

Comment
Since some hydrazone derivatives have shown to be potential DNA damaging and mutagenic agents (Okabe et al., 1993), a series of new hydrazone derivatives have been prepared in our laboratory (Shan et al., 2003). As part of the ongoing investigation, the title compound has recently been prepared and its crystal structure is reported here.
The molecule displays a nearly coplanar structure except for methyl H atoms, the maximum atomic deviation for non-H atom is 0.1457 (18) Å (N4), and the atomic deviations for ehtyl C3 and C4 atoms are 0.011 (2) and 0.037 (2) Å, respectively.
A partially overlapped arrangement is observed between the nearly parallel triazole ring and benzene ring of the adjacent molecule [dihedral angle 1.75 (11)°] (Fig. 2), the perpendicular distance of the centroid of the N3-triazole ring on the C6 ii -benzene ring is 3.482 Å and the perpendicular distance of the centroid of the C6 ii -benzene ring on the N3-triazole ring is 3.504 Å [symmetry code: (ii) 1 + x, y, z], these are significantly shorter than the van der Waals thickness of the aromatic ring (3.7 Å; Cotton & Wilkinson, 1972) and suggest the existence of π-π stacking in the crystal structure.
Experimental 4-Amino-3-ethyl-1H-1,2,4-triazole-5(4H)-thione (0.29 g, 2 mmol) was dissolved in ethanol (25 ml), then acetic acid (1 ml) was added slowly to the ethanol solution with stirring. The solution was heated at 333 K for several minutes until the solution cleared. 2-Methylbenzaldehyde (0.24 g, 2 mmol) was then dropped slowly into the solution, and the mixture was refluxed for 5 h. After the solution had cooled to room temperature yellow powder crystals appeared. The powder crystals were separated and washed with water three times. Single crystals of the title compound were obtained by recrystallization from an absolute ethanol solution.

Refinement
H atom bonded to N atom was located in a difference Fourier map and refined as riding in its as-found relative position with U iso (H) = 1.5U eq (N). Methyl H atoms were placed in calculated positions with C-H = 0.96 Å and the torsion angles supplementary materials sup-2 were refined to fit the electron density, U iso (H) = 1.5U eq (C). Other H atoms were placed in calculated positions with C-H = 0.93 (aromatic) and 0.97 Å (methylene), and refined in riding mode with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound with 40% probability displacement ellipsoids for non-H atoms. Dashed line indicates hydrogen bonding.  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 Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S 0.70986 (7