(E)-1-(4-Methylphenyl)ethanone [8-(trifluoromethyl)quinolin-4-yl]hydrazone

In the title compound, C19H16F3N3, the dihedral angle between the naphthalene and quinoline ring systems is 14.58 (8)°. The hydrazone C—N—N=C—C chain is in an extended conformation and its mean plane is nearly coplanar with the quinoline plane [dihedral angle = 3.45 (9)°]. The bond angles within the phenyl ring show the almost additive influence of the two para substituents. In the crystal, weak π–π [centroid–centroid distances = 3.779 (2) and 3.718 (1) Å] and C—H⋯F directional interactions join the molecules into centrosymmetric dimers, which are further connected into infinite zigzag chains propagating along a.

In the title compound, C 19 H 16 F 3 N 3 , the dihedral angle between the naphthalene and quinoline ring systems is 14.58 (8) . The hydrazone C-N-N C-C chain is in an extended conformation and its mean plane is nearly coplanar with the quinoline plane [dihedral angle = 3.45 (9) ]. The bond angles within the phenyl ring show the almost additive influence of the two para substituents. In the crystal, weak -[centroid-centroid distances = 3.779 (2) and 3.718 (1) Å ] and C-HÁ Á ÁF directional interactions join the molecules into centrosymmetric dimers, which are further connected into infinite zigzag chains propagating along a.

Comment
Hydrazones constitute a class of compounds of general formula R 1 R 2 C═ N-NR 3 R 4 . Serbutoviez et al. (1995) have shown that some diaryl hydrazone derivatives show efficient second-order nonlinear activity. They connected the tendency to crystallize in Λ-shaped pairs with the possibility of the application for the frequency conversion but not for electrooptics.
Here we present the structure of (E)-1-(4-methylphenyl)ethanone [8-(trifluoromethyl) The overall conformation of the molecules of I can be described by the values of dihedral angles between the three planar fragments: the quinoline ring system (hereinafter A will denote pyridine ring, B -trifluoromethylphenyl ring, planar within 0.0076 (14) Å), the central extended C-N-N═ C-C chain (maximum deviation from the least-squares plane of 0.0158 (12) Å), and the phenyl ring (C, maximum deviation 0.021 (2) Å). While the first two fragments are almost coplanar, dihedral angle between the planes is only 3.45 (9)°, this fragment is significantly, by 14.5 (1)°, twisted with respect to the phenyl ring plane. Such conformation is rather typical; for 186 fragments found in 155 similar compunds (Ar 1 -N-N═C-Ar 2 ) found in the Cambridge Structual Database [CSD, Conquest 5.31; Allen, 2002] the Ar 1 plane is close to coplanarity with the central chain (mean value 5.9 (3)°, maximum 18.7°), while it is more twisted with respect to Ar 2 plane (mean 17 (2)°, 33 examples of angles larger than 30°). The bond length pattern within the chain reflects the more single/double character of certain bonds. The bond angles within the phenyl ring are influenced by the presence of substituents; as expected for p-substitution, the influences are almost additive. The sum of values given by Domenicano (1988) or found in the CSD for mono-substituted phenyl rings are very close to the actual values in (I).
In the crystal the molecules are connected into dimers by π-π interactions: centroid-to-centroid distance between rings A and B (2-x,-y,-z) is 3.779 (2)Å with an offset of 22.1°, which gives the interplanar distance of 3.509Å (mean value).
Distance between centroids of rings B and B(2-x,-y,-z) is 3.718 (1) Å, with interplanar distance of 3.516Å resulting in an offset of 19.0°. These dimers, in which there are additional C-H···F (Table 1) contacts (Fig. 2), are further connected into zig-zag chains (Λ-shaped) along a direction. It might be noted, that the N-H hydrogen atom is so hidden by the neighboring C6-H6 and C14 methyl hydrogen atoms that it can not be involved in any intermolecular interactions.

Experimental
A solution of 4-hydrazino-8-(trifluoromethyl)quinoline (2.2 g, 10 mmole) and 4-methyl-acetophenone (10.2 mmole ) in 10 ml of ethanol was refluxed for 24 hrs under nitrogen atmosphere and in absence of light. The reaction mass was then cooled and the solid separated was collected by filtration and recrystallized from ethanol. M.P.: 449-451 K. Hydrogen atoms were located geometrically (C(methyl)-H 0.93 Å, C(ar)-H 0.96 Å, N-H 0.86 Å) and refined as a riding model; the U iso values of H atoms were set at 1.2 (1.5 for methyl groups) times U eq of their carrier atom. Fig. 1. Anisotropic ellipsoid representation of the compound I together with atom labelling scheme. The ellipsoids are drawn at 50% probability level, hydrogen atoms are depicted as spheres with 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 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 > σ(F 2 ) is used only for calculating Rfactors(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.