Crystal structure analysis of [5-(4-methoxyphenyl)-2-methyl-2H-1,2,3-triazol-4-yl](thiophen-2-yl)methanone

The molecular conformation is stabilized via intramolecular C—H⋯O and C—H⋯N contacts. The supramolecular structure is mainly governed by C—H⋯N hydrogen-bonded centrosymmetric dimers, C—H⋯O and C—H⋯S hydrogen bonds and S⋯π stacking interactions, which together lead to the formation of a layered crystal packing.


Chemical context
Compounds containing the 1,2,3-triazole scaffold are considered to be an important class of five-membered N-heterocycles (having two carbon and three nitrogen atoms) because of their unique structural and chemical properties (Kolb & Sharpless, 2003;Freitas et al., 2014). In the last few decades, significant attention has been paid to this kind of structural units owing to their versatile applications in the fields of materials science and medicinal chemistry (Zhou & Wang, 2012;Venugopala et al., 2016). In addition, 1,2,3-triazoles have also been found to be quite relevant in objective-oriented synthesis (Billing & Nilsson, 2005), bioconjugation (Speers et al., 2003) and combinatorial chemistry (Lö ber et al., 2003). The geometrical shapes and interaction functions of natural heterocycles and amides can be very similar to those of 1,2,3triazoles (Thibault et al., 2006).
In general, the 1,2,3-triazole nucleus is the most fundamental heterocyclic component found in various pharmacologically active agents (Agalave et al., 2011). In particular, potential pharmaceuticals based on the 1,2,3-triazole ring include anti-HIV (Giffin et al., 2008), anticancer (Singh et al., 2012), anti-tubercular (Patpi et al., 2012), antimicrobial (Demaray et al., 2008) and antifungal (Lass-Floerl et al., 2011) agents. This is due to the fact that the 1,2,3-triazole structural unit is stable against metabolic degradation as well as oxidation and reduction in acidic and basic conditions (Ferreira et al., 2010). Importantly, this special class of structural unit is capable of forming hydrogen-bonding interactions (the N atom acts as an acceptor) as well asstacking and other intermolecular interactions with biological targets to improve ISSN 2056-9890 their solubility (Lauria et al., 2014). Hence, it is of extreme importance to explore and understand the supramolecular structure of compounds in which the structural motif is based on 1,2,3-triazole. Keeping in mind the above-mentioned features, we report here the crystal structure and packing analysis of the title compound [5-(4-methoxyphenyl)-2methyl-2H-1,2,3-triazol-4-yl](thiophen-2-yl)methanone (1).

Structural commentary
The single-crystal X-ray diffraction study shows that compound 1 crystallizes in the monoclinic space group P2 1 /n with one molecule (Z 0 = 1) in the asymmetric unit (Fig. 1). In the molecular structure, the N-methylated triazol ring is substituted at the two carbon atoms C7 and C8 by a paramethoxy phenyl and a methanone-thienyl ring, respectively, resulting in four conformationally flexible parts in the molecule around the C8-C9, C9-C10, C1-C7 and C4-O1 single bonds (see Fig. 1). The conformation of the molecule in the crystal is stabilized via intramolecular C2-H2Á Á ÁO2 [C2Á Á ÁO2 = 2.961 (2) Å ] and C11-H11Á Á ÁN1 [C11Á Á ÁN1 = 2.950 (2) Å ] contacts ( Fig. 1; Table 1). For this reason, the thienyl and triazole rings are nearly coplanar, with an angle of 13.63 (10) between their mean planes, while the phenyl ring is tilted out from the mean planes of the thienyl and triazole rings by 38.84 (9) and 34.04 (10) , respectively. It is also important to mention here that the methoxy group attached to C4 is in the same plane as the phenyl ring.

Figure 2
Crystal packing of 1 showing the formation of molecular sheets via two types of centrosymmetric C-HÁ Á ÁN dimers (shaded in light yellow and green), forming ribbons connected through C-HÁ Á ÁO and SÁ Á ÁC() interactions.

Figure 1
The asymmetric unit of compound 1 highlighting the intramolecular C-HÁ Á ÁO and C-HÁ Á ÁN contacts. Displacement ellipsoids are drawn at the 50% probability level.

Analysis of molecular electrostatic potential and Hirshfeld fingerprint plots
A deeper insight into intermolecular interactions can be obtained from molecular electrostatic potential (MESP), and two-dimensional fingerprint plots (McKinnon et al., 2007) mapped on the Hirshfeld surface (Spackman & Jayatilaka, 2009). All the plots were computed using the programme CrystalExplorer 17.5 (Turner et al., 2017). The MESP plot of compound 1 (Fig. 4) shows that the centres of both the triazole and thiophene five-membered rings have nearly neutral ESP values (0.000 and À0.002 a.u., respectively), while the benzene ring is highly electronegative (À0.028 a.u.) compared to the two heterocyclic rings. This electrostatic complementarity among the rings leads to favourable stacking interactions in the crystal packing as a result of a layered supramolecular architecture. Intermolecular hydrogen-bond donors and acceptors appear as blue (positive ESP) and red (negative ESP) regions, respectively, on the surface (Fig. 4). The two-dimensional fingerprint plots and the contributions of individual interatomic contacts toward the overall crystal packing are shown in Fig. 5. It is observed that several directional hydrogen-bonding contacts such as NÁ Á ÁH (7.7%), OÁ Á ÁH (11.0%), SÁ Á ÁH (6.3%) along with CÁ Á ÁH (18.5%), HÁ Á ÁH (41.6%) and other interatomic contacts stabilize the crystal packing of compound 1.

Synthesis and crystallization
The title compound was synthesized according to the procedure described elsewhere (Girish et al., 2014). Single crystals of the pure compound were grown by slow evaporation of a toluene solution at room temperature (297-301 K).

Refinement
Crystal data, data collection and structure refinement details are given in Table 2. Hydrogen atoms were positioned geometrically and refined as riding: C-H = 0.98 Å with U iso (H) =1.5U eq (C) for the methyl group and C-H = 0.95Å with U iso (H) = 1.2U eq (C) for the aromatic C atoms.  Two-dimensional full fingerprint plots and decomposed fingerprint plots over the Hirshfeld surface for various intermolecular atom-atom contacts in compound 1. The numbers in red indicate the percentage contributions of each contact.

5-(4-Methoxyphenyl)-2-methyl-2H-1,2,3-triazol-4-yl](thiophen-2-yl)methanone
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.