2-{[5-(Pyridin-4-yl)-4-p-tolyl-4H-1,2,4-triazol-3-yl]methyl}acrylic acid hemihydrate

The asymmetric unit of the title compound, 2C18H16N4O2·H2O, consists of two organic molecules and one solvent molecule. The symmetry-independent organic molecules have slightly different conformations: the 1,2,4-triazole ring forms dihedral angles of 84.61 (4), 89.68 (5) and 22.38 (6)°, respectively, with the 2-propenecarbocylic, p-tolyl and 4-pyridyl groups in one independent molecule, and 71.35 (4), 82.13 (5) and 24.82 (6)°, respectively, in the second. In the crystal, molecules ralated by the 21 screw axes are assembled via O—H⋯N and O—H⋯O hydrogen bonds into infinite chains and these are linked by further O—H⋯N hydrogen bonds into undulating sheets parallel to the bc plane. Adjacent sheets are connected by weak C—H⋯O interactions, forming a three-dimensional structure.

The structure investigation of the title compound with potential antibacterial activity has been undertaken to determine its spatial structure and to facilitate the interpretation of 1 H-, 13 C-NMR and MS data.
The X-ray analysis showed that the crystal structure is a hemihydrate. The asymmetric part of the unit cell contains two symmetry-independent molecules, denoted A and B, of the compound (I) (solute) and one molecule of water (solvent) ( Fig. 1). The independent molecules of (I) differ to a rather moderate extent in conformation. The weighted r.m.s. deviation for the superposition of the non-H atoms in both molecules is 0.674 Å (Spek, 2009). The differences concern the angular arrangement of the system of 1,2,4-triazole, towards three substituents, i.e. the 2-propenecarbocylic, p-tolyl The interatomic distances C7═C8 take the values of 1.325 (2) in the molecule A and 1.317 (2) Å in the molecule B and confirm the presence of the double bond between these atoms.
In the crystal lattice, the symmetry-independent molecules A and B of (I) are connected with hydrogen bonds forming chains made separately from molecules A and B. Molecules A are joined to one another through the O11A-H11A···N22A i hydrogen bonds while molecules B through the O11B-H11B···O25 and O25-H25B···N22B ii hydrogen bonds. The latter are connected via water molecules (Table 1 crystal weak hydrogen bonds C6A-H6A2···O10B iii , C24A-H24A···O10B iv , C24B-H24B···O10A iii are observed. They connect the adjacent sheets into three-dimensional structure.

Refinement
The positions of the carboxyl groups and water H atoms were obtained from a difference Fourier map and were refined freely. The remaining H atoms were positioned geometrically and were refined within the riding model approximation: 2U eq (C) or 1.5U eq (C) for methyl H. The methyl groups were refined as rigid groups which were allowed to rotate. The difference density of 0.80 e / Å has no physical meaning and is rather due to the crystal quality.

Figure 1
The independent molecules of (I) and water showing the atomic labelling scheme. Non-H atoms are drawn as 30% probability displacement ellipsoids and H atoms are drawn as spheres of an arbitrary radius.  The hydrogen bonding in the title structure. For symmetry codes, see Table 1. H atoms not involved in hydrogen-bonding have been omitted for clarity.

Figure 3
The hydrogen-bonded undulating sheet in (I).  Special details Experimental. none Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. 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 > 2σ(F 2 ) is used only for calculating R-factors(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.