(E,E,E)-1,6-Bis(4-chlorophenyl)hexa-1,3,5-triene

The title molecule, C18H14Cl2, lies about an inversion centre. The hexatriene chain is planar with a maximum deviation of 0.0001 (17) Å. The torsion angle of the single bond between the chain and the benzene ring is −168.49 (17)°. In the crystal, the shortest intermolecular distance between the Cl atoms is 4.0785 (11) Å.

The title molecule, C 18 H 14 Cl 2 , lies about an inversion centre. The hexatriene chain is planar with a maximum deviation of 0.0001 (17) Å . The torsion angle of the single bond between the chain and the benzene ring is À168.49 (17) . In the crystal, the shortest intermolecular distance between the Cl atoms is 4.0785 (11) Å .

Comment
The luminescence properties of the linear all-trans-diphenyl polyenes Ph-(CH=CH) n -Ph (DPH) have been the subject of numerous investigations (Sonoda et al.(2003)). The emission properties of DPH and its derivatives in solution have been extensively studied because of its unique fluorescence behavior (Alford & Palmer,1986). DPH is known to exhibit dual fluorescence from S 1 and S 2 at thermal equilibrium. The crystal structure of (E,E,E)-1,6-bis(2,4-dichlorophenyl)hexa-1,3,5-triene has been studied (Sonoda et al.2003). In the crystal structure of the related compound, E,E,E-1,6-bis(pchlorophenyl)-1,3,5-hexatriene, the benzene rings are π···π stacked with unit translation along the b-axis with a centroid to centroid distance of 4.0785 (11)Å, a perpendicular distance between the planes of 3.4728 (8)Å and a slippage of 2.139Å.

Experimental
The compound was prepared and purified as described previously (Spangler et al.1989). Crystals suitable for the X-ray diffraction study was obtained free evaporation of an solvent chloroform from a highly diluted solution in the dark at room temperature.

Refinement
H atoms attached to C atoms were placed in geometrically idealized positions with Csp 2 = 0.930 Å,and constrained to ride on their parent atoms, with U iso (H) = 1.2 Ueq .

Computing details
Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SUPERFLIP (Palatinus & Chapuis, 2007); program(s) used to refine structure: OLEX2 (Dolomanov et al., 2009) and SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009  The structure of the title compound in 30% probability ellipsoids. H atoms are shown as small spheres of arbitrary radii. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.17 e Å −3 Δρ min = −0.21 e Å −3 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.