4-Phenyl-2,6-bis(4-tolyl)pyridine

The title molecule, C25H21N, situated on the crystallographic twofold axis has a symmetry point group 2. The interplanar angles between the central pyridyl ring and the phenyl and the methylphenyl rings are 32.8 (2) and 23.7 (2)°, respectively. In the crystal packing, the central pyridyl rings of adjacent molecules are involved in π–π interactions, forming one-dimensional arrays along the c axis with centroid–centroid distances of 3.714 (1) Å.


Comment
The Kröhnke type pyridines with different substituents as well as their syntheses have been widely studied. The reason is a prominent functionalization of the Kröhnke type pyridines as building blocks in both organic and inorganic supramolecular chemistry (Cave & Raston, 2001;Kröhnke, 1976). In this article, the synthesis and the crystal structure of a new Kröhnke type pyridine compound, 4-phenyl-2,6-bis-(4-tolyl)-pyridine, is presented.

Experimental
The mixture of benzaldehyde (1.06 g, 10 mmol), 4-methylacetophenone (2.68 g, 20 mmol) and NaOH (0.80 g, 20 mmol) in water (20 ml) and 95% ethanol (20 ml) was stirred for 3 h at room temperature, then the solution of ammonium acetate (7.70 g, 100 mmol) in 95% ethanol (60 ml) was added, and further refluxed at 343 K for 8 h. The resulting solution was cooled, solvent reduced to 20 ml to give a white precipitate which was collected by filtration and washed with ethanol.

Refinement
All the hydrogens were observable in the difference electron density map. However, they were placed into the idealized positions and refined using a riding atom formalism. C-H aryl =0.93Å, C-H methyl =0.96 Å. U iso (H aryl )=1.2U eq (C aryl ); Fig. 1. The title molecule with displacement ellipsoids drawn at the 30% probability level. The H atoms are shown as spheres of arbitrary radii. The atoms labelled by "A" are related to their counterparts by the rotation by 180° about the crystallographic two-fold axis.

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.