1,4-Dimethoxy-2,5-bis{2-[4-(trifluoromethyl)phenyl]ethynyl}benzene

The asymmetric unit of the title compound, C26H16F6O2, contains one half of the molecule situated on an inversion centre. In the rod-like molecule, the two terminal benzene rings form a dihedral angle of 71.9 (1)° with the central benzene ring. The trifluoromethyl group is rotationally disordered over two orientations in a 0.53 (1):0.47 (1) ratio. The crystal packing exhibits no classical intermolecular interactions.

The asymmetric unit of the title compound, C 26 H 16 F 6 O 2 , contains one half of the molecule situated on an inversion centre. In the rod-like molecule, the two terminal benzene rings form a dihedral angle of 71.9 (1) with the central benzene ring. The trifluoromethyl group is rotationally disordered over two orientations in a 0.53 (1):0.47 (1) ratio. The crystal packing exhibits no classical intermolecular interactions.

Comment
Recently, the synthesis and applications of new aryleneethynylene derivatives were reported (Dirk et al., 2001;Miljanić et al., 2005;Morin et al., 2007). To make our own contribution in this field of material science, herewith we report the synthesis and crystal structure of the title compound, (I), which can be used as luminescent material.
In (I) (Fig. 1), all bond lengths and angles are normal and correspond to those reported for 1,4-bis(p-tolylethynyl)benzene (Filatov & Petrukhina, 2005). The asymmetric unit of (I) contains a half of the rod-like molecule. The centroid of the central benzene ring is situated on an inversion centre. The central benzene ring and C2-C7 ring form a dihedral angle of 71.9 (1)°.
The crystal packing exhibits no classical intermolecular interactions.
Experimental 1,4-Dimethoxy-2,5-diethynylbenzene (93 mg, 0.5 mmol), Pd(PPh 3 ) 2 Cl 2 (17.5 mg)and CuI (9.5 mg) were added to triethylamine (3 ml) and tetrahydrofuran (9 ml)in a Schlenk flask under N 2 atmosphere. The mixture was stirred at room temperature overnight. Then the solution was cooled to room temperature and the solvent was removed in vacuum. CH 2 Cl 2 (15 ml) was added and the suspension was filtered. The filtrate was washed with HCl (1 mol l -1 ), ammonium chloride solution and water.
Then organic phase was dried with MgSO 4 and concentrated. The crude product was purified by column chromatography on silica gel to afford the title compound (185.3 mg, 78%). Crystals suitable for X-ray structure analysis were obtained by slowly evaporating dichloromethane solution of the title compound at room temperature.

Figures
Fig . 1. The molecular structure of (I) showing the atom-numbering scheme and 50% probabilty displacement ellipsoids. Unlabelled atoms are related with the labelled ones by symmetry operation (-x, 2 -y, 2 -z). For the disordered F atoms, only major parts are shown.