Nicotinaldehyde [2,8-bis(trifluoromethyl)quinolin-4-yl]hydrazone monohydrate

In the title compound, C17H10F6N4·H2O, the pyridine ring is not coplanar with the quinoline ring system; the dihedral angle between the two planes is 21.3 (1)°. One of the trifluoromethyl group is disordered over two orientations with occupancies of 0.70 (1) and 0.30 (1). The water molecule is disordered over two positions with occupancies of 0.76 (1) and 0.24 (1). In the crystal, the water molecule is linked to the main molecule via N—H⋯O and C—H⋯O hydrogen bonds, and inversion-related pairs are linked via O—H⋯N hydrogen bonds. In addition, a weak π–π interaction is observed between the pyridine ring and the pyridine ring of the quinoline unit, with a centroid–centroid distance of 3.650 (2) Å.

In the title compound, C 17 H 10 F 6 N 4 ÁH 2 O, the pyridine ring is not coplanar with the quinoline ring system; the dihedral angle between the two planes is 21.3 (1) . One of the trifluoromethyl group is disordered over two orientations with occupancies of 0.70 (1) and 0.30 (1). The water molecule is disordered over two positions with occupancies of 0.76 (1) and 0.24 (1). In the crystal, the water molecule is linked to the main molecule via N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, and inversionrelated pairs are linked via O-HÁ Á ÁN hydrogen bonds. In addition, a weakinteraction is observed between the pyridine ring and the pyridine ring of the quinoline unit, with a centroid-centroid distance of 3.650 (2) Å .   Table 1 Hydrogen-bond geometry (Å , ).   (Mao et al. 2009;Bermudez et al. 2004;Jayaprakash et al. 2006). Quinoline is an essential structural unit found in mefloquin and recently developed antimycobacterial drugs (Andries et al. 2005). Thus, quinoline derivatives are good lead molecules to further develop drug candidates against mycobacterium tuberculosis and as antibacterial agents. On the basis of these observations we have synthesized few quinoline derivatives, in which a hydrazone group has been attached at the 4th position of the mefloquin ring system, expecting that these newly designed molecules would exhibit some antibacterial activity. The crystal structures of the mefloquine base and its salt complexes have been reported (Skörska et al. 2005). Earlier, we reported the crystal structure of 3,4-dimethoxybenzaldehyde [2,8-bis(trifluoromethyl)quinolin-4-yl]hydrazone (Al-eryani et al., 2010). We report here the crystal structure of the title compound.

Related literature
The asymmetric unit of the title compound contains one nicotinaldehyde [2,8-bis(trifluoromethyl)quinolin-4yl]hydrazone molecule and one water molecule (Fig. 1). The dihedral angle [21.3 (1)°] between the quinoline ring system and the pyridine ring indicates that these two systems are non coplanar.

Experimental
A mixture of [2,8-bis(trifluoromethyl)quinolin-4-yl]hydrazine (10 mmol) and nicotinaldehyde (10 mmol) in glacial acetic acid (50 ml) was heated at reflux for 3 h. The reaction mixture was concentrated under reduced pressure, cooled, and the obtained solid hydrazone was filtered, washed with water and cold ethanol. The crude product was purified by column chromatography. Single crystals suitable for X-ray analysis were obtained by slow evaporation of an methanol-water solution at room temperature.

Refinement
One of the trifluoromethyl group is disordered over two orientations with occupancies of 0.702 (8) and 0.298 (8). The C-F distances involving disordered F atoms were restrained to be equal and U ij parameters of these atoms were restrained to an approximate isotropic behaviour. The water molecule is disordered over two positions with occupancies of 0.758 (13) and 0.242 (13); the H atoms of the major disorder component were located in a difference map and refined with O-H and H···H distances of 0.84 (2) and 1.35 (2) Å, respectively. Due to disorder of the oxygen atom in water molecule, all H atoms could not be located. The N-bound H atom was located in a difference map and refined freely. The remaining H atoms were positioned at calculated positions [C-H = 0.93 Å] and refined using a riding model with U iso (H) = 1.2U 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.
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 > 2sigma(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.  (5) 169 (3) O1W-H1W···N4 i 0.83 (5) 2.06 (6) 2.855 (5) 163 (7) C9-H9···O1W 0.93 2.42 3.331 (5) 167 Symmetry codes: (i) −x+1, −y+1, −z.