1,4-Bis[(3,5-dimethoxy­phen­yl)ethyn­yl]benzene

Katsuhiko Ono; Koki Nakagawa; Masaaki Tomura

doi:10.1107/S160053680900155X

. 2009 Jan 17;65(Pt 2):o346. doi: 10.1107/S160053680900155X

1,4-Bis[(3,5-dimethoxyphenyl)ethynyl]benzene

Katsuhiko Ono ^a,^*, Koki Nakagawa ^a, Masaaki Tomura ^b

PMCID: PMC2968219 PMID: 21581947

Abstract

The title compound, C₂₆H₂₂O₄, is a derivative of 1,4-bis(phenylethynyl)benzene substituted by four methoxy groups on the terminal benzene rings. The molecule is almost planar with an r.m.s. deviation of 0.266 Å. The dihedral angles between the two terminal benzene rings and the central benzene ring are 7.96 (6) and 13.32 (7)°. In the crystal structure, molecules aggregate via C—H⋯O interactions, forming molecular tapes along the a axis, which aggregate to form a herring-bone structure.

Related literature

For the crystal structure of 1,4-bis[(2,6-dimethoxyphenyl)ethynyl]benzene, see: Ono et al. (2008 ▶). For related sructures, including a 1,4-bis(phenylethynyl)benzene system, see: Watt et al. (2004 ▶); Li et al. (1998 ▶); Filatov & Petrukhina (2005 ▶).

Experimental

Crystal data

C₂₆H₂₂O₄
M _r = 398.44
Monoclinic,
a = 8.8980 (5) Å
b = 19.4610 (8) Å
c = 12.2820 (5) Å
β = 100.607 (1)°
V = 2090.46 (17) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 173 (1) K
0.30 × 0.25 × 0.15 mm

Data collection

Rigaku Mercury CCD diffractometer
Absorption correction: none
15238 measured reflections
4638 independent reflections
3914 reflections with I > 2σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.048
wR(F ²) = 0.140
S = 1.11
4638 reflections
271 parameters
H-atom parameters constrained
Δρ_max = 0.26 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Data collection: CrystalClear (Rigaku, 2001 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SIR2002 (Burla et al., 2003 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: PLATON (Spek, 2003 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680900155X/ci2753sup1.cif

e-65-0o346-sup1.cif^{(21KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053680900155X/ci2753Isup2.hkl

e-65-0o346-Isup2.hkl^{(222.6KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C11—H11⋯O4ⁱ	0.95	2.42	3.3511 (17)	167
C14—H14⋯O2ⁱⁱ	0.95	2.37	3.2758 (16)	160

Open in a new tab

Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was supported by a Grant-in-Aid for Scientific Research (grant No. 19550034) from the Ministry of Education, Culture, Sports, Science and Technology, Japan. The authors thank the Instrument Center of the Institute for Molecular Science for the X-ray structure analysis.

supplementary crystallographic information

Comment

The synthetic research of ethynylated aromatic compounds has attracted considerable attention because of interests in their molecular structures, optical properties, and molecular electronics. Among these ethynylated aromatic compounds, 1,4-bis(phenylethynyl)benzene derivatives have been extensively studied. These compounds have stiff, linear molecular structures and are used as building blocks in the applications. Recently, we found that 1,4-bis[(2,6-dimethoxyphenyl)ethynyl]benzene, (II), formed a zigzag molecular network in the crystal (Ono et al., 2008). The crystal structure is different from those of 1,4-bis(phenylethynyl)benzene derivatives (Watt et al., 2004; Li et al., 1998; Filatov & Petrukhina, 2005). With regard to this, we investigated the molecular and crystal structure of the title compound, (I), which is a regioisomer of (II). The substitution effect of four methoxy groups at the terminal benzene rings was studied.

The molecular structure of (I) is shown in Fig. 1. The molecule is almost planar with an r.m.s deviation of 0.266 Å. The dihedral angles between the terminal benzene rings and the central benzene ring are 7.96 (6)° (C1–C6) and 13.32 (7)° (C17–C22). The methoxy groups are coplanar with the attached benzene rings.

The crystal structure is characterized by a molecular tape along the a axis formed by C—H···O interactions (Table 1 and Fig. 2). The molecular tapes aggregate to form a herring-bone-type structure, as shown in Fig.3. The crystal structure of (I) is different from that of (II). The crystal structures of (I) and (II) indicate that the methoxy groups at terminal benzene rings play an important role in the crystal packing.

Experimental

The title compound (I) was prepared as follows: Tetrakis(triphenylphosphine)palladium(0) [Pd(PPh₃)₄] (52 mg, 0.045 mmol) was added to a mixture of 1-ethynyl-3,5-dimethoxybenzene (0.39 g, 2.4 mmol), 1,4-diiodobenzene (0.39 g, 1.2 mmol) and copper(I) iodide (5 mg, 0.03 mmol) in dry triethylamine (7 ml) under nitrogen. The reaction mixture was stirred for 18 h at 353 K. After removal of the solvent, dichloromethane (20 ml) and aqueous disodium ethylenediaminetetraacetate (Na₂edta) solution (5%, 20 ml) were added. The organic layer was separated and washed with water (20 ml). The organic solution was dried over Na₂SO₄and concentrated. The residue was chromatographed on silica gel (CH₂Cl₂) to afford the title compound (0.23 g, 49%) as a yellow powder. Yellow crystals of the compound, suitable for X-ray analysis were grown from an ethanol solution.