(E)-2-[(3-Fluorophenyl)iminomethyl]-4-(trifluoromethoxy)phenol

The title compound, C14H9F4NO2, is a Schiff base which adopts the phenol–imine tautomeric form in the solid state. The H atom is located on the hydroxy O atom rather than on the N atom. This H atom is involved in a strong intramolecular O—H⋯N hydrogen bond. The molecule is almost planar, the angle between the benzene rings being 2.14 (13)°.


Comment
Schiff bases have been extensively used as ligands in the field of coordination chemistry (Calligaris et al., 1972). Schiff base compounds can be classified by their photochromic and thermochromic characteristics (Cohen et al., 1964). These properties result from proton transfer from the hydroxyl O atom to the imine N atom (Hadjoudis et al., 1987). There are two types of intramolecular hydrogen bonds in Schiff bases, which may be stabilized either in keto-amine (N-H···O hydrogen bond) (Şahin et al., 2005) or phenol-imine (N···H-O hydrogen bond) tautomeric forms (Hadjoudis et al., 1987). The present X-ray investigation shows that the title compound is a Schiff base and exists in the phenol-imine form in the solid-state.

Refinement
The H atom bonded to O1 was refined freely. All other H atoms were placed in calculated positions and constrained to ride on their parent atoms, with C-H = 0.93 Å and U iso (H) = 1.2 U eq (C). The CF 3 group showed rotational disorder. For atoms F1A, F2A and F3A the site occupancy factor is 0.288 (17) and for F1B, F2B and F3B the site occupancy factor is 0.712 (17).
The disorder was refined using the restraint commands DFIX, ISOR and SIMU. Fig. 1. The molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.

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 supplementary materials sup-3 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. ( Fig. 1