(Z,E,Z)-1,6-Di-1-naphthylhexa-1,3,5-triene

The title compound, C26H20, lies about an inversion centre. The naphthalene unit and the hexatriene chain are each approximately planar (maximum deviations of 0.0143 and 0.0042 Å, respectively), and are inclined to one another at a dihedral angle of 49.20 (4)°. The dihedral angle between the two naphthalene ring systems of neighboring molecules is 85.71 (4)°.

The title compound, C 26 H 20 , lies about an inversion centre. The naphthalene unit and the hexatriene chain are each approximately planar (maximum deviations of 0.0143 and 0.0042 Å , respectively), and are inclined to one another at a dihedral angle of 49.20 (4) . The dihedral angle between the two naphthalene ring systems of neighboring molecules is 85.71 (4) .
In the present compound, the averaged value of the C-C single bond length in the hexatriene chain is 1.457 Å, that of the C=C double bond length is 1.341 Å, and the resulting bond-length alternation (δr, the difference between the single and double bond lengths) is 0.116 Å. The title compound lies about an inversion centre.
The naphthalene ring and the hexatriene chain are approximately planar, with the maximum deviations of 0.0143 and 0.0042 Å from the least-squares planes, respectively (Fig. 1). The dihedral angle between the ring and the chain is 49.20 (4)°.
Thus, the steric hindrance between C9-H and C13-H is minimized by the twisting around the C10-C11 single bond.
C-C-C internal bond angles in the hexatriene chain are all somewhat wider than 120°, which also minimizes the steric hindrance.
The structure of (I) can be compared with those of (Z,E,Z)-1,6-diphenylhexa-1,3,5-triene 4,4'-dicarboxylic acid dialkyl esters (Sonoda et al., 2005). In the case of the dimethyl ester, for example, δr is 0.111 Å and other geometrical parameters for the triene chain including C-C-C bond angles are all comparable with the values in (I). Also in this compound, the benzene ring and the triene chain are nearly planar for conjugation. The torsion angle of the single bond between the ring and the chain is 41.0 (2)°, significantly smaller than the C9-C10-C11-C12 angle in (I). This is probably due to the additional steric hindrance between C2-H and C11-H in (I).
For another related structure of (Z)-1,2-di(1-naphthyl)ethylene, the twisting not only around the naphthalene-ethylene single bond but also around the C=C double bond minimize the large steric hindrance between the two hydrogen atoms at the 2-position of the naphthalene ring (Aldoshin et al., 1984). Different from the high planarity of the hexatriene unit in (I), the C-C═C-C torsion angle in this compound is 14.6°. While, the torsion angle of 44.1° about the naphthalene-ethylene single bond is similar to or even slightly smaller than the corresponding angle in (I).
In the crystal structure of (I), there are some C-H···π contacts (Fig. 2). The dihedral angle between the two naphthalene rings of the neighboring molecules is 85.71 (4)°.

Refinement
All non-hydrogen atoms were refined anisotropically and hydrogen atoms were located by geometric considerations and refined as riding on their carrier atoms [ C-H = 0.94 Å, U eq = 1.2 U iso (C) ]. Fig. 1. A view of the molecular structure and the atom-numbering scheme of (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The title compound lies about an inversion centre [(*) -x, -y, -z]. 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.