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

Yoriko Sonoda; Masaru Yoshida; Midori Goto

doi:10.1107/S1600536809000592

. 2009 Jan 14;65(Pt 2):o294. doi: 10.1107/S1600536809000592

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

Yoriko Sonoda ^a,^*, Masaru Yoshida ^a, Midori Goto ^b

PMCID: PMC2968162 PMID: 21581904

Abstract

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)°.

Related literature

For the potential use of α,ω-diarylpolyenes as non-linear optical materials, see: Geskin et al. (2003 ▶); Rumi et al. (2000 ▶). For a study of the relationship between the crystal structure and the photophysical properties of 1,6-diarylhexa-1,3,5-trienes, see: Sonoda et al. (2006 ▶); Sonoda, Goto et al. (2007 ▶). For related structures, see: Aldoshin et al. (1984 ▶); Sonoda et al. (2005 ▶); Sonoda, Tsuzuki et al. (2007 ▶).

Experimental

Crystal data

C₂₆H₂₀
M _r = 332.42
Monoclinic,
a = 5.0071 (8) Å
b = 11.0709 (17) Å
c = 16.110 (3) Å
β = 96.535 (3)°
V = 887.2 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 203 (2) K
0.30 × 0.10 × 0.05 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.910, T _max = 0.997
5367 measured reflections
2023 independent reflections
1366 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.043
wR(F ²) = 0.114
S = 1.01
2023 reflections
118 parameters
H-atom parameters constrained
Δρ_max = 0.16 e Å⁻³
Δρ_min = −0.16 e Å⁻³

Data collection: SMART (Bruker, 2001 ▶); cell refinement: SAINT (Bruker, 2001 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809000592/at2699sup1.cif

e-65-0o294-sup1.cif^{(15KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809000592/at2699Isup2.hkl

e-65-0o294-Isup2.hkl^{(99.5KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

α,ω-Diarylpolyenes are known as fluorescent molecules in solution, and are also attractive because of their potential use as non-linear optical materials (Rumi et al., 2000; Geskin et al., 2003). During an ongoing study on the relationship between the crystal structure and the photophysical properties of 1,6-diarylhexa-1,3,5-trienes (Sonoda et al., 2006; Sonoda, Goto et al., 2007), we obtained the title compound (I), whose structure we report here.

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)°.

Experimental

Compound (I) was synthesized by the Wittig reaction of 1-naphthaldehyde and (E)-but-2-ene-1,4-bis(triphenylphosphonium chloride). The reaction gave a mixture of Z,E,Z and E,E,E isomers (predominantly Z,E,Z), from which the Z,E,Z isomer (I) was crystallized from dichloromethane by slow evaporation at room temperature in the dark. ¹H NMR (CDCl₃, 300 MHz): δ 7.95–7.99 (2H, m, arom.), 7.80–7.90 (4H, m, arom.), 7.43–7.55 (8H, m, arom.), 6.95 (2H, d, J = 11.1 Hz, triene), 6.72 (2H, dd, J = 7.7, 3.0 Hz, triene), 6.47 (2H, ddd, J = 11.0, 7.8, 3.2 Hz, triene).