4-Fluoro-N-(4-hydroxybenzylidene)aniline

In the title compound, C13H10FNO, the benzene ring planes are inclined at an angle of 50.52 (8)°. A characteristic of aromatic Schiff bases with N-aryl substituents is that the terminal phenyl rings are twisted relative to the plane of the HC=N link between them. In this case, the HC=N unit makes dihedral angles of 10.6 (2) and 40.5 (2)° with the hydroxybenzene and flurobenzene rings, respectively. In the crystal, O—H⋯N and C—H⋯F hydrogen bonds lead to the formation of chains along the c- and b-axis directions, respectively. C—H⋯π contacts link molecules along a and these contacts combine to generate a three-dimensional network with molecules stacked along the b-axis direction.

In the title compound, C 13 H 10 FNO, the benzene ring planes are inclined at an angle of 50.52 (8) . A characteristic of aromatic Schiff bases with N-aryl substituents is that the terminal phenyl rings are twisted relative to the plane of the HC N link between them. In this case, the HC N unit makes dihedral angles of 10.6 (2) and 40.5 (2) with the hydroxybenzene and flurobenzene rings, respectively. In the crystal, O-HÁ Á ÁN and C-HÁ Á ÁF hydrogen bonds lead to the formation of chains along the c-and b-axis directions, respectively. C-HÁ Á Á contacts link molecules along a and these contacts combine to generate a three-dimensional network with molecules stacked along the b-axis direction.

S1. Comment
Schiff base compounds have been used as fine chemicals and pharmaceutical substrates (Akkurt et al., 2013). They are important ligands in coordination chemistry due to their ease of preparation and ability to be modified both electronically and sterically (Li et al., 2008 andZhang, 2010). As a part of our study into the co-ordination behaviour of ligands having a 4-hydroxy substituent on the benzylidene fragment, X-ray structural analysis of the title compound was carried out, and the results are reported herein. confirm a degree of electron delocalization between the benzene rings, and the molecule can be regarded as a partially delocalized π-electron system. All other bond lengths are within the expected ranges (Allen et al., 1987).
In the crystal, the molecules are linked by O1-H1···N1 hydrogen bonds to form infinite one-dimensional zigzag chains with graph set notation C(8) (Bernstein et al.,, 1995)

S2. Experimental
4-Fluoro-4-hydroxybenzylideneaniline was prepared by mixing equimolar amounts of 4-hydroxy benzaldehyde and 4fluoro aniline in ethanol (40 ml). The reaction mixture was refluxed for about 6 h and the resulting solution was slowly evaporated at room temperature. After three days single crystals of the title compound, suitable for X-ray structure analysis were obtained.

S3. Refinement
All the H atoms were positioned geometrically and treated as riding atoms: E-H = 0.93, 0.96, 0.97 and 0.82 Å for CH, CH 3 , CH 2 and OH H atoms, respectively, with U iso (H) = k × U eq (C,O), where k = 1.5 for CH 3 and OH H atoms and = 1.2 for other H atoms. The best crystal investigated was still of poor quality and very weakly diffracting, with no usable data obtained above θ = 23.5 °. Nonetheless the structure solved readily and refined to give acceptable uncertainties on the metrical data. Because of the very weak data, the final data/parameter ratio is considerably less than an ideal value.  The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.      Overall packing for the compound (I).  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.13 e Å −3 Δρ min = −0.12 e Å −3

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.