Crystal structure of 4-amino-3-(thiophen-3-ylmethyl)-1H-1,2,4-triazole-5(4H)-thione

The synthesis and crystal structure of a new thiophene monomer containing an additional 1,2,4-triazole ring are reported. The compound has a V-shaped conformation with the thiophene ring disordered over two positions by a rotation of approximately 180°.

In the title compound, C 7 H 8 N 4 S 2 , the thiophene ring shows rotational disorder over two orientations in a 0.6957 (15):0.3043 (15) ratio. The plane of the 1,2,4triazole ring makes a dihedral angle of 75.02 (17) with the major-disorder component of the thiophene ring. In the crystal, two types of inversion dimers, described by the graph-set motifs R 2 2 (8) and R 2 2 (10), are formed by N-HÁ Á ÁS interactions. Chains of molecules running in the [101] direction are linked by weaker N-HÁ Á ÁN interactions. The thiophene ring is involved inand C-HÁ Á Á interactions.

Chemical context
Recently, the synthesis, characterization and antifungal activities, together with crystal structure determinations, of thiophene-based heterocyclic chalcones have been investigated (Ming et al., 2017). Thiophene-containing -diketonate complexes of copper(II) have been studied and their deposits obtained by electropolymerization have been characterized (Oyarce et al., 2017). Combinations of the thiophene ring with other heterocyclic rings have also been investigated, such as a -keto-enol group embedded with thiophene and pyridine moieties giving interesting applications in the field of solidphase extraction (Radi et al., 2016).
As part of our ongoing studies of new polythiophenes and their properties Vu et al., 2016;Vu Quoc et al., 2017), we have synthesized a new thiophene monomer containing an additional 1,2,4-triazole ring. The polymer obtained from 4-amino-3-(thiophen-3-ylmethyl)-1H-1,2,4triazole-5(4H)-thione using FeCl 3 as oxidant was further characterized by IR and NMR spectroscopy, and TGA and is soluble in most common organic solvents, such as DMF and DMSO. We present here the synthesis and crystal structure of the title compound, 3.

Supramolecular features
The crystal packing of the title compound is shown in Fig. 2. The 1H-1,2,4-triazole-5(4H)-thione ring possesses an NH 2 group, which, in principle, can act as a donor or acceptor for hydrogen bonding, an NH group, which can act as a donor, and an N atom and C S group, which can only act as acceptors. Two types of inversion dimers are formed ( Fig. 3 and Table 1). The first one, described as graph-set motif R 2 2 (8), involves hydrogen bonds between the NH and C S groups, whereas in the second one, the NH 2 group interacts with the C S grouping, resulting in a ring structure of graph-set R 2 2 (10). The second H atom of the NH 2 group interacts with the N atom of a neighbouring 1H-1,2,4-triazole-5(4H)-thione ring, resulting in chains of graph-set C(5) in the [101] direction ( Fig. 3 Table 1 Hydrogen-bond geometry (Å , ).

Figure 1
A view of the asymmetric unit of the title compound, showing the atomlabelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as small circles of arbitrary radii. The minor component of the disordered thiophene rings is shown in pale yellow.

Figure 2
Crystal packing of the title compound shown in projection down the a axis.
The packing was further investigated by an analysis of the Hirshfeld surface and two-dimensional fingerprint plots using CrystalExplorer (

Figure 4
Part of the crystal packing of the title compound, showing thestacking interactions between the thiophene (yellow) and 1,2,4-triazole (blue) rings (only the major component of the disordered thiophene ring is shown).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Both thiophene rings are disordered over two orientations by a rotation of approximately 180 around the C5-C3 bond. The final occupancy factors are 0.6957 (15) and 0.3043 (15). For the disordered thiophene ring, bond lengths and angles were restrained to the target mean values observed in 3-CH 2 -thiophene fragments in the CSD (Groom et al., 2016) and the same anisotropic displacement parameters were used for equivalent atoms. The H atoms attached to atoms N1 and N4 were found in a difference density Fourier map and refined freely. The other H atoms were placed at calculated positions and refined in riding mode, with C-H distances of 0.95 (aromatic) and 0.99 Å (CH 2 ), and isotropic displacement parameters equal to 1.2U eq of the parent atoms. In the final cycles of refinement, two reflections showing very poor agreement were omitted as outliers.   program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

4-Amino-3-(thiophen-3-ylmethyl)-1H-1,2,4-triazole-5(4H)-thione
Crystal data Special details 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.