Crystal structure of 1-anilino-5-methyl-1H-1,2,3-triazole-4-carboxylic acid monohydrate

The water molecule connects the molecules in the crystal packing. The crystal structure exhibits N—H⋯O, O—H⋯O and O—H⋯N interactions, resulting in the formation of a three-dimensional framework.


Chemical context
Triazoles are a class of compounds that have aroused chemical interest because of their wide range of applications, including their biological relevance and the development of new materials. Triazoles have potent antifungal activity, being an important class of drugs (Peyton et al., 2015). Their antitubercular (Zhang et al., 2017), anticancer (Teixeira et al., 2019), antimicrobial (Yadav et al., 2018) and antiviral (Jordã o et al., 2009) activities have also been evaluated. This class of compounds has also aroused interest in materials chemistry, mainly in the development of systems with uptake capacity for both CO 2 and H 2 (Mukherjee et al., 2019).

Structural commentary
The title molecule (Fig. 1) is formed by planar aniline and triazolic rings, which subtend a dihedral angle of 87.41 (5) . Atoms O1 and O2 are located 0.237 (2) and 0.208 (2) Å , respectively, outside the plane of the triazole ring. The methyl group exhibits occupational disorder of the hydrogen atoms. ISSN 2056-9890

Hirshfeld surface analysis
For an unequivocal description of the supramolecular system, Hirshfeld Surface (HS) analysis was performed. The isosur-face was plotted for the weight function equal to 0.5. The red areas in Fig. 4 correspond to short contacts between atoms inside and outside the surface atom, d i and d e . There are three spots on the surface, and in the corresponding fingerprint plot (FPP; Fig. 5), they are represented as sharp spikes. Chemically, they correspond to classical hydrogen bonds. Two of these involve interactions between the carboxyl group and the water molecule while the third is the interaction between N-triazole and the water molecule. These hydrogen bonds are the shortest contacts, assigned in the FPP as OÁ Á ÁH and NÁ Á ÁH. The NÁ Á ÁH interaction contributes 15.8% to the HS, while the OÁ Á ÁH interaction corresponds to 18.1%. The majority of the interactions are HÁ Á ÁH, being equal to 36.0%.

Figure 2
A partial packing diagram showing the hydrogen-bond network along the a axis and the R 4 4 (12) (green) and R 4 4 (14) (yellow) motifs. All hydrogen atoms bonded to carbon are omitted for clarity.

Figure 3
Views along the c axis showing the layers consolidated by the hydrogenbond network: (a) a C 2 2 (7) chain along the b-axis direction and (b) a C 2 2 (9) chain along [110]. All hydrogen atoms bonded to carbon are omitted for clarity.

Figure 1
The molecular structure of the title compound with anisotropic atomic displacement ellipsoids shown at the 50% probability level.
values are affected by the hydrogen bonds in the crystal packing. In addition, in studies of halogenated phenyl derivatives, differences in C-HÁ Á Á interactions were shown to result in changes in the crystal packing (Jordã o et al., 2012).

Synthesis and crystallization
The title compound was synthesized by the alkaline hydrolysis of 5-methyl-1-(phenylamino)-1H-[1,2,3]-triazole-4-carboxylic acid ethyl ester (Jordã o et al., 2009), 1. 3.6 mmol of 1 were dissolved in 30.0 ml of a sodium hydroxide solution (0.1 mol L À1 ) (NaOH, VETEC). This mixture was refluxed at 373 K for about 48 h. The product was neutralized using dilute hydrochloric acid (HCl, VETEC), filtered and dried in vacuo. The title compound was dissolved in methanol and kept at room temperature. After a few days, colourless block-shaped crystals, suitable for X-ray analysis, were obtained by slow evaporation (yield 83%). Hirshfeld surface mapped with d norm .

Figure 5
The fingerprint plots for the title compound. IR spectrum of the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were located in a difference-Fourier map and freely refined except for hydrogen atoms bound to C10 which are disordered (occupancy 0.5) and were refined using a riding model with C-H = 0.96 Å and U iso (H) = 1.5U eq (C).

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.