Crystal structure, Hirshfeld surface analysis and computational studies of 5-[(prop-2-en-1-yl)sulfanyl]-1-[2-(trifluoromethyl)phenyl]-1H-tetrazole

The title compound was synthesized from 2-(trifluoromethyl)aniline by a multi-step reaction and is constructed from a pair of aromatic rings [2-(trifluoromethyl)phenyl and tetrazole], which are turned by 76.8 (1)° relative to each other because of significant steric hindrance of the trifluoromethyl group at the ortho position of the benzene ring·In the crystal, very weak C—H⋯N and C—H⋯F hydrogen bonds and aromatic π–π stacking interactions link the molecules into a three-dimensional network.


Chemical context
Tetrazoles are a well-known class of aromatic five-membered heterocycles, which have been investigated since the end of the 19th century. Their biological properties, including antiviral, anticancer, anti-tuberculosis, antifungal and antioxidant activities have been shown by numerous studies (see, for example, Ostrovskii et al., 2017). They also are increasingly regarded as efficient and selective inhibitors of enzymes governing the metabolic processes in the human body (Pegklidou et al., 2010;Al-Hourani et al., 2012;Aggarwal et al., 2016).

Supramolecular features
As shown in Fig. 2 and listed in Table 1, the crystal structure of (I) features several weak intermolecular interactions. The hydrogen atoms of the (prop-2-en-1-yl)sulfanyl group are involved in C-HÁ Á ÁN bonding with the tetrazole ring of an adjacent molecule; these bonds link independent molecules into layers (Fig. 3). The layers are interconnected by C-HÁ Á ÁF contacts into a three-dimensional network (Fig. 4).

Hirshfeld surface analysis and computational study
To further analyse the intermolecular interactions between the molecules of (I), Hirshfeld surface analysis through the mapping of the normalized contact distance (d norm ) as well as calculation of the interaction energies were performed using CrystalExplorer (Turner et al., 2017;Spackman & Jayatilaka, 2009). The most prominent interactions among the allyl group H atoms and tetrazole N atoms as well as among allylic H atoms and F atoms of neighbouring molecules can be seen in the Hirshfeld surface plot as the red areas (Fig. 5a). Fingerprint plots were produced to show the intermolecular surface bond distances with the regions highlighted for C-HÁ Á ÁF The hydrogen-bonding of molecules in (I). Hydrogen bonds are shown as dashed lines. The symmetry codes are as in Table 1. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) x þ 1; y; z; (ii) Àx þ 1; Ày þ 1; z À 1 2 ; (iii) Àx þ 1; Ày þ 1; z þ 1 2 ; (iv) Àx þ 3 2 ; y þ 1 2 ; z þ 1 2 .

Figure 3
A C-HÁ Á ÁN-bonded layer in the structure of compound (I).

Figure 1
The molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level.

Figure 4
A view along the a axis of the crystal packing of the title compound.
( Fig. 5b) and C-HÁ Á ÁN (Fig. 5c) interactions. The contribution to the surface area for HÁ Á ÁH contacts is 19.8%. The interaction energies in (I) were calculated using a dispersion-corrected CE-B3LYP/6-31G(d,p) quantum level of theory, as available in CrystalExplorer. The total intermolecular energy is the sum of energies of four main components, viz. electrostatic, polarization, dispersion and exchange-repulsion factors of 1.057, 0.740, 0.871 and 0.618, respectively (Mackenzie et al., 2017). The total calculated energy of the intermolecular interactions of (I) is À115.9 kJ mol À . From Table 2, one can see the highest energy value (-36.2 kJ mol À ) covers C-HÁ Á ÁN and C-HÁ Á ÁF interactions with the neighbouring molecule generated by the symmetry code Àx + 1, Ày + 1, z À 1 2 . The interactions between the neighbouring 2-(trifluoromethyl)phenyl rings stacked along [100] cover À25.7 kJ mol À1 and are mainly dispersive in nature.  Slyvka, 2015), the tetrazole moieties are bonded to the metal ions through two heterocyclic nitrogen atoms and the allylic C C bond in the chelate-bridging mode. Slyvka et al., 2018) (VI), the organic molecule is coordinated to the copper atom by the allylic C C bond and the only tetrazole nitrogen atom. As a result of the presence of back-donation from an occupied 3d metal orbital to a low-lying empty * orbital of the olefin, in all these compounds the double bond of the (prop-2-en-1yl)sulfanyl group is slightly elongated to 1.35-1.38 Å , in comparison with noncoordinated olefin bond value. The other S-substituted 1-phenyl-1H-tetrazole-5-thiol structures in the Cambridge Structural Database have different alkyl substituents, such as 2-naphthyl (TICRAY; Alves et al., 1996), 1,7,7trimethylbicyclo[2.2.1]hept-2-yl (GIJRAU; Bodrov et al., 2013) and benzoyl (BAZVAA; Kim et al., 2003).
After complete precipitation of the triethylammonium dithiocarbamate salt, the solution was filtered. The solid was washed with anhydrous ether and air-dried for about 10 min. The salt was then dissolved in about 7.5 ml of chloroform, treated with 1.4 ml of triethylamine and cooled to 273 K. To this solution was added ethyl chloroformate (1.02 ml, 0.01 mol) dropwise over a 15 min period under intensive stirring. The resulting solution was stirred at 273 K for 10 min and allowed to warm to room temperature over 1 h. The chloroform solution was washed with 3 M HCI and twice with water and dried over Na 2 SO 4 . The chloroform was evaporated and the 1-isothiocyanato-2-(trifluoromethyl)benzene was distilled in vacuo.
The obtained isothiocyanate (1.016 g, 5.0 mmol) was mixed with water (10 ml) and NaN 3 (0.71 g, 0.011 mol) and refluxed under intensive stirring until the suspension disappeared. The solution was cooled to room temperature and washed with TBME. The water fraction was separated and acidified with 3 M HCl (Caution! During the acidification beware of toxic HN 3 gas). The sediment of 1-[2-(trifluoromethyl)phenyl]-1Htetrazole-5-thiol was separated by filtration and used for alkylation without further purification.
1-[2-(Trifluoromethyl)phenyl]-1H-tetrazole-5-thiol (0.985g, 0.004 mol) was dissolved in a solution of KOH (0.22 g, 0.004 mol) in ethanol (10 ml). To the solution allyl bromide (0.43 ml, 0.005 mole) was added and the mixture was heated at 323 K for 1 h. The solvent was removed in vacuo and to the residue was added water (5 ml) and dichloromethane (10 ml). The dichloromethane was separated and removed to give the title compound. Colourless blocks of (I) were obtained by recrystallization from an ethanol solution, m.p. 336 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. H atoms were positioned geometrically and refined using riding model, with C-H = 0.95 or 0.99 Å and U iso (H) = 1.2U eq (C).

Funding information
EG gratefully acknowledges financial support from the Slovenian Research Agency (ARRS).