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Acta Crystallogr Sect E Struct Rep Online. 2010 April 1; 66(Pt 4): o837–o838.
Published online 2010 March 13. doi:  10.1107/S1600536810005258
PMCID: PMC2983920



The centrosymmetric title compound, C18H28I2O2, crystallized in the monoclinic space group P21/c with the alkyl chains having extended all-trans conformations, similar to those in the centrosymmetric bromo analogue [Li et al. (2008 [triangle]). Acta Cryst. E64, o1930] that crystallized in the triclinic space group P An external file that holds a picture, illustration, etc.
Object name is e-66-0o837-efi1.jpg. The difference between the two structures lies in the orientation of the two alkyl chains with respect to the C(aromatic)—O bond. In the title compound, the O—Calk­yl—Calk­yl—Calk­yl torsion angle is 55.8 (5)°, while in the bromo analogue this angle is −179.1 (2)°. In the title compound, the C-atoms of the alkyl chain are almost coplanar [maximum deviation of 0.052 (5) Å] and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue, these two mean planes are almost coplanar, making a dihedral angle of 4.1 (2)°. Another difference between the crystal structures of the two compounds is that in the title compound there are no halide(...)halide inter­actions. Instead, symmetry-related mol­ecules are linked via C—H(...)π contacts, forming a two-dimensional network.

Related literature

For use of the title compound in the synthesis of conjugated polymers, see: Van Heyningen et al. (2003 [triangle]); Mayor & Didschies (2003 [triangle]). For the various syntheses of the title compound, see: Castanet et al. (2002 [triangle]); Van Heyningen et al. (2003 [triangle]); Mayor & Didschies (2003 [triangle]); Plater et al. (2004 [triangle]). For the synthesis and crystal structure of the bromo analogue, see: Maruyama & Kawanishi (2002 [triangle]); Li et al. (2008 [triangle]). For bond distances, see Allen et al. (1987 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0o837-scheme1.jpg


Crystal data

  • C18H28I2O2
  • M r = 530.20
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0o837-efi2.jpg
  • a = 9.4481 (9) Å
  • b = 7.8455 (6) Å
  • c = 13.457 (2) Å
  • β = 92.148 (12)°
  • V = 996.80 (16) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 3.16 mm−1
  • T = 173 K
  • 0.32 × 0.11 × 0.06 mm

Data collection

  • STOE IPDS diffractometer
  • Absorption correction: multi-scan MULscanABS in PLATON (Spek, 2009 [triangle]) T min = 0.952, T max = 1.042
  • 7660 measured reflections
  • 1962 independent reflections
  • 1216 reflections with I > 2σ(I)
  • R int = 0.058


  • R[F 2 > 2σ(F 2)] = 0.029
  • wR(F 2) = 0.055
  • S = 0.79
  • 1962 reflections
  • 101 parameters
  • H-atom parameters constrained
  • Δρmax = 0.81 e Å−3
  • Δρmin = −1.31 e Å−3

Data collection: EXPOSE in IPDS-I (Stoe & Cie, 2000 [triangle]); cell refinement: CELL in IPDS-I; data reduction: INTEGRATE in IPDS-I; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: Mercury (Macrae et al., 2006 [triangle]); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 [triangle]).

Table 1
C—H(...)π inter­actions (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810005258/lx2134sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810005258/lx2134Isup2.hkl

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

supplementary crystallographic information


The title compound has been used as a building block for the elaboration of organic–electronic materials, for example as a monomer for the synthesis of conjugated polymers (Van Heyningen et al., 2003; Mayor & Didschies, 2003). Our interest in this compound lies in the possibility of using it as a spacer-unit in linked materials for the creation of structured, discotic mesophases. The synthesis of the title compound has been reported by various groups (Van Heyningen et al., 2003; Mayor & Didschies, 2003; Plater et al., 2004). Here it was synthesized by iodination of 1,4-bis(hexyloxy)benzene (Castanet et al., 2002). The crystal structure of the bromo-analogue, synthesized by (Maruyama & Kawanishi, 2002), has been described by (Li et al., 2008).

The molecular structure of the title compound is illustrated in Fig. 1. Bond lengths are normal (Allen et al., 1987) and similar to those in the bromo-analogue (Li et al., 2008). The molecule possesses Ci symmetry with the inversion center situated at the center of the aromatic ring. The alkyl chains adopt a fully extended all-trans conformation. The C-atoms of the alkyl chain are almost coplanar (max. deviation of 0.052 (5) Å) and this mean plane is inclined to the benzene ring by 50.3 (3)°. In the bromo-analogue the alkyl chains also adopt a fully extended all-trans conformation. The alkyl C-atoms are also coplanar [max. deviation of 0.034 (4) Å] but here lie almost in the same plane as the aromatic ring, with a dihedral angle of 4.1 (2)°.

The different comformations of the two compounds are illustrated in Fig. 2. It can be seen that the alkyl chains are orientated differently with respect to the C(aromatic)—O bonds. The O1—C1'—C2'—C3' torsion angle is 55.8 (5)° in the title compound (Fig. 2b), while in the bromo-analogue this same angle is -179.1 (2)° (Fig. 2a). In the crystal structure of the title compound there are no halide···halide interactions, in contrast to the Br···Br interactions [3.410 (3) Å] observed in the bromo-analogue. However, symmetry related molecules are linked by C—H···π interactions leading to the formation of a two-dimensional network (Table 1 and Fig. 3; Cg is the centroid of the C1–C3/C1i–C3i benzene ring).


The title compound was synthesized by iodination of 1,4-bis(hexyloxy)benzene (Castanet et al., 2002). To a solution of 1,4-bis(hexyloxy)benzene (0.75 mmol) and N-iodosuccinimide (2.40 mmol) in dry acetonitrile (5.0 ml) was added trifluoroacetic acid (1.50 mmol) at RT. The mixture was heated and stirred at 363 K for 2 h. The reaction mixture was then cooled to RT and concentrated. Diethyl ether (30 ml) was added and the heterogeneous mixture was filtered to remove the white precipitate of succinimide that had formed. The organic layer was then washed with 10% NaHSO3 (aq) (3 × 30 ml) and dried over MgSO4. The crude product was purified by column chromatography [silica gel, Petroleum ether : CH2Cl2 (5:1)] and recrystallisation in methanol. Single crystals of the title compound were grown by slow evaporation of a concentrated solution in CH2Cl2 at RT. 1H NMR, 400 MHz (CDCl3) δ 7.17 (s, 2H, H3,3i), 3.93 (t, J = 6.6 Hz, 4H, H1'), 1.80 (quint, J = 6.6 Hz, 4H, H2'), 1.50 (m, 4H, H3'), 1.35 (m, 8H, H4',5'), 0.91 (t, J = 7.0 Hz, H6'); 13C NMR, 100 MHz (CDCl3) δ 152.8 (C2,2i), 122.7 (C3,3i), 86.3 (C1,1i), 70.3 (C1'), 31.4 (C5'), 29.1 (C2'), 25.7 (C3'), 22.6 (C4'), 14.0 (C6'); MS (EI): [M]+ = 529.95. The same numbering scheme has been used for the crystal structure.


The H-atoms could all be located in difference electron-density maps. In the final cycles of refinement they were included in calculated positions and treated as riding atoms: C—H = 0.98 - 0.99 Å, with Uiso(H) = k × Ueq(parent C-atom), where k = 1.2 for H-aromatic and H-methylene, and 1.5 for H-methyl.


Fig. 1.
A view of the molecular structure of the title compound, with displacement ellipoids drawn at the 50% probabilty level. Atoms labelled i are related to the other atoms by the symmetry operation -x+1, -y+1, -z.
Fig. 2.
A view of the different molecular conformations in (a) the bromo-analogue (Li et al., 2008), and (b) the title compound. The H-atoms have been omitted for clarity.
Fig. 3.
A view along the a-axis of the crystal packing in the title compound. The C—H···π interactions are illustrated by the H···C contacts [H4'2···C-atoms of the benzene ...

Crystal data

C18H28I2O2F(000) = 516
Mr = 530.20Dx = 1.767 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 7553 reflections
a = 9.4481 (9) Åθ = 0.9–26.3°
b = 7.8455 (6) ŵ = 3.16 mm1
c = 13.457 (2) ÅT = 173 K
β = 92.148 (12)°Rod, colorless
V = 996.80 (16) Å30.32 × 0.11 × 0.06 mm
Z = 2

Data collection

STOE IPDS diffractometer1962 independent reflections
Radiation source: fine-focus sealed tube1216 reflections with I > 2σ(I)
graphiteRint = 0.058
[var phi] rotation scansθmax = 26.1°, θmin = 2.6°
Absorption correction: multi-scan MULscanABS in PLATON (Spek, 2009)h = −11→11
Tmin = 0.952, Tmax = 1.042k = −9→9
7660 measured reflectionsl = −16→16


Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.029Hydrogen site location: difference Fourier map
wR(F2) = 0.055H-atom parameters constrained
S = 0.79w = 1/[σ2(Fo2) + (0.0227P)2] where P = (Fo2 + 2Fc2)/3
1962 reflections(Δ/σ)max < 0.001
101 parametersΔρmax = 0.81 e Å3
0 restraintsΔρmin = −1.31 e Å3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

I10.82998 (3)0.69287 (4)0.01561 (3)0.0307 (1)
O10.7295 (3)0.3497 (4)0.0975 (2)0.0276 (10)
C10.6122 (4)0.4192 (6)0.0508 (3)0.0215 (14)
C1'0.7158 (4)0.1961 (7)0.1533 (3)0.0279 (16)
C20.6307 (4)0.5768 (6)0.0054 (3)0.0214 (16)
C2'0.8638 (5)0.1475 (6)0.1902 (4)0.0286 (16)
C30.5180 (4)0.6593 (6)−0.0459 (3)0.0170 (14)
C3'0.9402 (4)0.2857 (6)0.2498 (3)0.0242 (16)
C4'1.0897 (5)0.2350 (6)0.2818 (3)0.0261 (16)
C5'1.1699 (5)0.3737 (6)0.3398 (4)0.0332 (17)
C6'1.3227 (5)0.3225 (8)0.3657 (4)0.0373 (16)

Atomic displacement parameters (Å2)

I10.0231 (1)0.0311 (2)0.0374 (2)−0.0054 (2)−0.0051 (1)0.0055 (2)
O10.0202 (14)0.026 (2)0.0358 (19)−0.0003 (12)−0.0093 (13)0.0145 (15)
C10.019 (2)0.021 (3)0.024 (2)0.0025 (18)−0.0054 (18)−0.001 (2)
C1'0.028 (2)0.021 (3)0.034 (3)−0.003 (2)−0.0063 (19)0.007 (3)
C20.021 (2)0.023 (3)0.020 (3)−0.0020 (18)−0.0013 (17)−0.003 (2)
C2'0.029 (2)0.025 (3)0.031 (3)0.001 (2)−0.008 (2)0.005 (2)
C30.0108 (19)0.022 (3)0.018 (2)−0.0001 (18)−0.0003 (16)−0.001 (2)
C3'0.022 (2)0.023 (3)0.027 (3)0.002 (2)−0.0054 (18)0.004 (2)
C4'0.028 (2)0.026 (3)0.024 (3)0.0020 (18)−0.004 (2)0.006 (2)
C5'0.031 (3)0.025 (3)0.043 (3)−0.001 (2)−0.007 (2)0.008 (2)
C6'0.027 (2)0.039 (3)0.045 (3)−0.006 (3)−0.010 (2)0.002 (3)

Geometric parameters (Å, °)

I1—C22.091 (4)C2'—H2'10.9900
O1—C11.367 (5)C2'—H2'20.9900
O1—C1'1.428 (6)C3—H30.9500
C1—C21.393 (6)C3'—H3'10.9900
C1—C3i1.375 (6)C3'—H3'20.9900
C1'—C2'1.515 (6)C4'—H4'10.9900
C2—C31.405 (6)C4'—H4'20.9900
C2'—C3'1.515 (7)C5'—H5'10.9900
C3'—C4'1.514 (6)C5'—H5'20.9900
C4'—C5'1.524 (7)C6'—H6'10.9800
C5'—C6'1.526 (7)C6'—H6'20.9800
I1···O13.073 (3)H2'1···H4'12.4800
I1···C6'ii3.736 (5)H2'2···H4'22.5400
O1···I13.073 (3)H3'1···O12.4900
C6'···I1vi3.736 (5)H4'1···H2'12.4800
C1—O1—C1'119.4 (3)C2—C3—H3121.00
O1—C1—C2116.3 (3)C1i—C3—H3121.00
O1—C1—C3i123.5 (4)C2'—C3'—H3'1109.00
C2—C1—C3i120.2 (4)C2'—C3'—H3'2109.00
O1—C1'—C2'106.5 (3)C4'—C3'—H3'1109.00
I1—C2—C1119.0 (3)C4'—C3'—H3'2109.00
I1—C2—C3119.7 (3)H3'1—C3'—H3'2108.00
C1—C2—C3121.3 (4)C3'—C4'—H4'1109.00
C1'—C2'—C3'114.1 (4)C3'—C4'—H4'2109.00
C1i—C3—C2118.5 (4)C5'—C4'—H4'1109.00
C2'—C3'—C4'112.5 (4)C5'—C4'—H4'2109.00
C3'—C4'—C5'113.5 (4)H4'1—C4'—H4'2108.00
C4'—C5'—C6'112.1 (4)C4'—C5'—H5'1109.00
C1'—O1—C1—C2174.3 (4)C2—C1—C3i—C2i−0.2 (6)
C1'—O1—C1—C3i−6.7 (6)O1—C1'—C2'—C3'55.8 (5)
C1—O1—C1'—C2'176.8 (4)I1—C2—C3—C1i−179.5 (3)
O1—C1—C2—I1−1.5 (5)C1—C2—C3—C1i−0.2 (6)
O1—C1—C2—C3179.2 (4)C1'—C2'—C3'—C4'−177.7 (4)
C3i—C1—C2—I1179.5 (3)C2'—C3'—C4'—C5'178.6 (4)
C3i—C1—C2—C30.2 (6)C3'—C4'—C5'—C6'−176.7 (4)
O1—C1—C3i—C2i−179.1 (4)

Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x+5/2, y+1/2, −z+1/2; (iii) −x+3/2, y+1/2, −z+1/2; (iv) −x+2, −y+1, −z; (v) x−1/2, −y+1/2, z−1/2; (vi) −x+5/2, y−1/2, −z+1/2; (vii) −x+3/2, y−1/2, −z+1/2; (viii) x+1/2, −y+1/2, z+1/2.

Table 1 C—H···π interactions (Å, °)

Cg1 is the centroid of the C1–C3/C1i–C3i ring.

C4'—H4'2···Cgii0.992.743.595 (5)145.0

Symmetry codes: (i) -x+1, -y+1, -z; (ii) -x+3/2, y-1/2, -z+1/2.


Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LX2134).


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