Crystal structure of (E)-N′-(3-fluoro-2-hydroxybenzylidene)isonicotinohydrazide

The title isonicotinohydrazide derivative is planar, with an r.m.s. deviation for the fitted non-H atoms of 0.062 Å, and an intramolecular O—H⋯N hydrogen bond with an S(6) ring motif. In the crystal, molecules are linked by N—H⋯N and C—H⋯N hydrogen bonds forming chains propagating along the a-axis direction.


Chemical context
Hydrazone-based chelators of metal ions are interesting compounds that receive a significant amount of interest (Bendová et al., 2010;Jansová et al., 2014;Hrušková et al., 2016). We have recently published the structures of two derivatives of the prototypical chelator from this class, salicyl aldehyde isonicotinoyl hydrazide (SIH), which were synthesized as potential sensors for metal ions (Chainok et al., 2016). The structures reported have fluorine and methyl substitution in position 5 on the benzene ring. Herein, we report the crystal structure of a further analogue in this series bearing a fluorine substituent in position 3 of the benzene ring, which was synthesized in order to investigate the effect of the distance between the reporting fluorine atom and the metal chelating unit.

Synthesis and crystallization
Isonicotinic acid hydrazide (301 mg, 2.19 mmol) and 3fluorosalicylaldehyde (338 mg, 2.69 mmol) were suspended in a 1:1 mixture of water and ethanol (6 ml). The reaction mixture was stirred at 363 K for 24 h and formation of a precipitate was observed. The reaction mixture was allowed to cool to room temperature and then filtered. The isolated solid was washed with water to give the product as a white solid (510 mg, 1.97 mmol, 90%). Colourless rod-like crystals, suitable for X-ray diffraction analysis, were grown by slow evaporation of a solution in methanol of the title compound

Figure 2
A view of the hydrogen-bonded chains, formed in the crystal structure of the title compound via bifurcated-acceptor N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds (dashed lines; Table 1).

Figure 3
Part of the crystal structure of the title compound, showing the formation of the layers, parallel to the ab plane, formed via C-HÁ Á ÁO hydrogen bonds, and theinteractions (dashed lines).

Figure 1
The molecular structure of the title compound, with the atom labelling and 50% probability displacement ellipsoids. The intramolecular hydrogen bond is shown as a dashed line (see Table 1).
atoms were placed at calculated positions and refined using a riding-model approximation: N-H = 0.86 Å , O-H = 0.82 Å and C-H = 0.93 Å with U iso (H) = 1.5U eq (O) and 1.2U eq (N,C) for other H atoms.

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.