Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109001991/gd3269sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109001991/gd3269Isup2.hkl |
CCDC reference: 728206
Reagents and solvents were purchased from Aldrich and used without further purification unless otherwise specified. The reported melting points are not corrected.
Compound (I) was obtained in four consecutive steps. First, 2-(2-ethoxyethoxy)ethyl-4-methylbenzenesulfonate was prepared from 2-(2-ethoxyethoxy)ethanol (Aldrich) following a reported procedure (Lenz et al., 1991). Secondly, the treatment of the tosylate with LiBr yielded the bromide (II), which was then attached to the biphenyl unit to afford the ester (III). Finally, the hydrolysis of (III) in a basic medium afforded the acid (I).
For the preparation of 1-(2-ethoxyethoxy)-2-bromoethane, (II), LiBr (10.4 g, 0.12 mol) and 2-(2-ethoxyethoxy)ethyl-4-methylbenzenesulfonate (Lenz et al., 1991) (34.4 g, 0.12 mol) in dry acetone (220 ml) were heated under reflux for 24 h under a nitrogen atmosphere. The mixture was allowed to cool to room temperature and the suspended solid was filtered off. The acetone was removed from the filtrate under reduced pressure. The remainig oil was dissolved in CH2Cl2 (300 ml), washed with water (2 × 150 ml) and dried (Na2SO4), and the solvent was removed under reduced pressure to afford an oil (yield 21.4 g, 91%). 1H NMR (CDCl3): δH 3.78 (t, 2H, J = 6.4 Hz), 3.74 (t, 2H, J = 6.4 Hz), 3.66 (t, 2H, J = 6.4 Hz), 3.48 (c, 2H, J = 7.06 Hz), 3.45 (t, 2H, J = 7.2 Hz), 1.18 (t, 3H, J = 7.06 Hz).
For the preparation of methyl 4'-[2-(2-ethoxyethoxy)ethoxy]-4-biphenylcarboxylate, (III), methyl 4,4'-hydroxybiphenylcarboxylate (7.5 g, 32.8 mmol) and K2CO3 (10.9 g,79 mmol) were dissolved in dimethylformamide (24 ml) and heated at 373 K for an hour. A solution of (II) (10.9 g, 79 mmol) in dimethylformamide (4 ml) was then added slowly. The reaction mixture was heated under reflux for 3 d and then poured into water (150 ml), and the solid product was isolated by filtration, dried under vacuum and then recrystallized from cyclohexane to yield the methyl ester as a yellow solid (yield 9.5 g, 84%; m.p. 368 K. 1H NMR (CDCl3): δH 8.05 (d, 2H, J = 8.40 Hz), 7.59 (d, 2H, J = 8.40 Hz), 7.53 (d, 2H, J = 8.77 Hz), 6.98 (d, 2H, J = 8.78 Hz), 4.17 (t, 2H, J = 5.01 Hz), 3.91 (s, 3H, J = 5.01 Hz), 3.87 (t, 2H, J = 5.01 Hz), 3.73 (t, 2H, J = 4.95 Hz), 3.62 (t, 2H, J = 4.95 Hz), 3.52 (c, 2H, J = 7.05 Hz), 1.20 (t, 3H, J = 7.06 Hz).
For the preparation (I), a mixture containing water (2.5 ml), methanol (47.5 ml), KOH (3.3 g, 60 mol) and the methyl ester (III) (7 g, 20.3 mmol) was heated under reflux for 24 h. The solvent was then removed under reduced pressure. The residue was treated with10 N HCl (15 ml) and ethyl ether (100 ml). The solid was filtered off and recrystallized from benzene, yielding the acid (I) as a white solid (yield 7.6 g, 70%; m.p. 458 K. 1H NMR (CDCl3): δH 8.12 (d, 2H2,4, J = 7.05), 7.62 (d, 2H1,5, J = 7.06 Hz), 7.54 (d, 2H8,12, J = 7.25 Hz), 6.99 (d, 2H9,11, J = 7.25 Hz), 4.18 (t, 2H14, J = 3.63 Hz), 3.88 (t, 2H15, J = 3.63 Hz), 3.73 (t, 2H17, J = 3.62 Hz), 3.62 (t, 2H18, J = 3.63 Hz), 3.54 (c, 2H20, J = 6.87 Hz), 1.21 (t, 3H21, J = 6.87 Hz). 13C NMR (CDCl3): δ = 170.2 (C22), 156.9 (C10), 142.0 (C6), 131.1 (C2,4), 129.5 (C3), 128.9 (C8,12), 128.5 (C7), 128.2 (C1,5), 115.5 (C9,11), 70.6 (C17), 70.3 (C18), 70.1 (C15), 69.8 (C14), 67.7 (C20), 15.4 (C21). Analysis calculated for C19H22O5 (330.4): C 69.07, H 6.71%; found: C 68.90, H 6.63%.
Small plates of colourless single crystals suitable for X-ray analysis were obtained by slow diffusion of ethyl ether into a dichloromethane solution of (I) at room temperature.
Atoms in the unbound –OC2H4OC2H4OEt group exhibit an increasing vibrational behaviour when traversing the tail from the phenyl-bound O atom [Ueq(O) = 0.0570 (4) Å2] towards the Et end [Ueq(C) = 0.1313 (15) Å2]. This is a feature found in many reported structures with similarly unbound end groups, as inspection of the CSD confirms (see, for instance, entries FAZFIW, LENLUL, LIXCEA, OKARUN, VIRXAV and VUMTUS [please also give original references for each refcode], all of them corresponding to reasonably well refined structures with R < 0.075 and no apparent disorder). H atoms were placed at calculated positions [C—H = 0.93 Å (aromatic), 0.96 Å (methyl) and 0.97 Å (ethyl), and O—H = 0.82 Å] and allowed to ride; in addition, methyl groups were allowed to rotate. Displacement parameters were taken as Uiso(H) = xUeq(carrier), where x = 1.5 (methyl H atoms) or x = 1.2 (all other H atoms).
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).
C19H22O5 | F(000) = 704 |
Mr = 330.37 | Dx = 1.291 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 1583 reflections |
a = 25.430 (7) Å | θ = 2.4–22.9° |
b = 7.769 (2) Å | µ = 0.09 mm−1 |
c = 8.656 (2) Å | T = 294 K |
β = 96.187 (5)° | Plates, colourless |
V = 1700.3 (8) Å3 | 0.60 × 0.50 × 0.10 mm |
Z = 4 |
Bruker SMART CCD area-detector diffractometer | 3634 independent reflections |
Radiation source: fine-focus sealed tube | 2230 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.026 |
phi and ω scans | θmax = 27.0°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS in SAINT-NT; Bruker, 2002) | h = −31→31 |
Tmin = 0.95, Tmax = 0.99 | k = −9→6 |
9420 measured reflections | l = −11→11 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.063 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.191 | H-atom parameters constrained |
S = 0.99 | w = 1/[σ2(Fo2) + (0.1098P)2] where P = (Fo2 + 2Fc2)/3 |
3634 reflections | (Δ/σ)max < 0.001 |
219 parameters | Δρmax = 0.23 e Å−3 |
0 restraints | Δρmin = −0.14 e Å−3 |
C19H22O5 | V = 1700.3 (8) Å3 |
Mr = 330.37 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 25.430 (7) Å | µ = 0.09 mm−1 |
b = 7.769 (2) Å | T = 294 K |
c = 8.656 (2) Å | 0.60 × 0.50 × 0.10 mm |
β = 96.187 (5)° |
Bruker SMART CCD area-detector diffractometer | 3634 independent reflections |
Absorption correction: multi-scan (SADABS in SAINT-NT; Bruker, 2002) | 2230 reflections with I > 2σ(I) |
Tmin = 0.95, Tmax = 0.99 | Rint = 0.026 |
9420 measured reflections |
R[F2 > 2σ(F2)] = 0.063 | 0 restraints |
wR(F2) = 0.191 | H-atom parameters constrained |
S = 0.99 | Δρmax = 0.23 e Å−3 |
3634 reflections | Δρmin = −0.14 e Å−3 |
219 parameters |
Experimental. 1HNMR and 13C NMR spectra were recorded on a Bruker ARX300 spectrometer at 25 °C. |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.15576 (9) | 0.6058 (3) | 0.6032 (3) | 0.0555 (6) | |
H1 | 0.1860 | 0.6742 | 0.6146 | 0.067* | |
C2 | 0.12236 (9) | 0.6057 (3) | 0.7180 (3) | 0.0568 (6) | |
H2 | 0.1307 | 0.6724 | 0.8065 | 0.068* | |
C3 | 0.07696 (8) | 0.5086 (3) | 0.7045 (2) | 0.0465 (5) | |
C4 | 0.06513 (9) | 0.4117 (3) | 0.5711 (2) | 0.0537 (6) | |
H4 | 0.0341 | 0.3473 | 0.5584 | 0.064* | |
C5 | 0.09869 (9) | 0.4100 (3) | 0.4580 (3) | 0.0532 (6) | |
H5 | 0.0902 | 0.3427 | 0.3700 | 0.064* | |
C6 | 0.14520 (8) | 0.5058 (2) | 0.4704 (2) | 0.0435 (5) | |
C7 | 0.18191 (8) | 0.5016 (2) | 0.3475 (2) | 0.0435 (5) | |
C8 | 0.16623 (9) | 0.4356 (3) | 0.2012 (3) | 0.0530 (6) | |
H8 | 0.1318 | 0.3950 | 0.1799 | 0.064* | |
C9 | 0.19938 (9) | 0.4275 (3) | 0.0863 (3) | 0.0542 (6) | |
H9 | 0.1873 | 0.3814 | −0.0102 | 0.065* | |
C10 | 0.25055 (8) | 0.4876 (3) | 0.1139 (2) | 0.0461 (5) | |
C11 | 0.26716 (9) | 0.5581 (3) | 0.2584 (2) | 0.0521 (6) | |
H11 | 0.3013 | 0.6012 | 0.2781 | 0.063* | |
C12 | 0.23362 (8) | 0.5648 (3) | 0.3721 (2) | 0.0486 (5) | |
H12 | 0.2456 | 0.6125 | 0.4680 | 0.058* | |
O13 | 0.28714 (6) | 0.4826 (2) | 0.00990 (16) | 0.0570 (4) | |
C14 | 0.27139 (10) | 0.4136 (3) | −0.1402 (3) | 0.0620 (6) | |
H14A | 0.2450 | 0.4875 | −0.1957 | 0.074* | |
H14B | 0.2559 | 0.3004 | −0.1307 | 0.074* | |
C15 | 0.31857 (10) | 0.4010 (3) | −0.2273 (3) | 0.0647 (7) | |
H15A | 0.3472 | 0.3456 | −0.1627 | 0.078* | |
H15B | 0.3101 | 0.3308 | −0.3193 | 0.078* | |
O16 | 0.33485 (6) | 0.56469 (19) | −0.27114 (18) | 0.0604 (5) | |
C17 | 0.37864 (10) | 0.5582 (4) | −0.3559 (3) | 0.0697 (7) | |
H17A | 0.3712 | 0.4799 | −0.4428 | 0.084* | |
H17B | 0.4089 | 0.5138 | −0.2901 | 0.084* | |
C18 | 0.39175 (11) | 0.7302 (4) | −0.4150 (3) | 0.0718 (7) | |
H18A | 0.4166 | 0.7181 | −0.4918 | 0.086* | |
H18B | 0.3600 | 0.7844 | −0.4647 | 0.086* | |
O19 | 0.41392 (7) | 0.8332 (2) | −0.2923 (2) | 0.0780 (6) | |
C20 | 0.43138 (15) | 0.9941 (5) | −0.3457 (4) | 0.1064 (11) | |
H20A | 0.4014 | 1.0582 | −0.3946 | 0.128* | |
H20B | 0.4558 | 0.9751 | −0.4226 | 0.128* | |
C21 | 0.45739 (17) | 1.0931 (5) | −0.2167 (6) | 0.1313 (15) | |
H21A | 0.4316 | 1.1301 | −0.1505 | 0.197* | |
H21B | 0.4743 | 1.1918 | −0.2561 | 0.197* | |
H21C | 0.4834 | 1.0226 | −0.1583 | 0.197* | |
C22 | 0.04230 (8) | 0.5066 (3) | 0.8313 (2) | 0.0487 (5) | |
O23 | 0.05595 (7) | 0.5912 (2) | 0.95267 (18) | 0.0711 (5) | |
O24 | 0.00103 (6) | 0.4157 (2) | 0.81277 (19) | 0.0704 (5) | |
H24 | −0.0180 | 0.4142 | 0.8834 | 0.084* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0581 (14) | 0.0547 (13) | 0.0545 (13) | −0.0142 (10) | 0.0106 (11) | −0.0051 (11) |
C2 | 0.0647 (15) | 0.0585 (14) | 0.0481 (12) | −0.0127 (11) | 0.0111 (11) | −0.0114 (11) |
C3 | 0.0461 (12) | 0.0448 (12) | 0.0484 (12) | 0.0039 (10) | 0.0049 (10) | 0.0036 (10) |
C4 | 0.0460 (12) | 0.0644 (15) | 0.0508 (13) | −0.0080 (10) | 0.0053 (10) | −0.0050 (11) |
C5 | 0.0521 (13) | 0.0594 (14) | 0.0482 (12) | −0.0077 (10) | 0.0053 (10) | −0.0095 (11) |
C6 | 0.0485 (12) | 0.0371 (11) | 0.0444 (11) | 0.0012 (9) | 0.0028 (10) | 0.0039 (9) |
C7 | 0.0469 (12) | 0.0390 (11) | 0.0441 (11) | 0.0010 (9) | 0.0025 (9) | 0.0024 (9) |
C8 | 0.0462 (12) | 0.0623 (14) | 0.0506 (12) | −0.0101 (10) | 0.0059 (10) | −0.0044 (11) |
C9 | 0.0570 (14) | 0.0608 (14) | 0.0449 (12) | −0.0111 (11) | 0.0069 (10) | −0.0082 (11) |
C10 | 0.0515 (13) | 0.0411 (11) | 0.0468 (12) | −0.0003 (9) | 0.0111 (10) | 0.0019 (10) |
C11 | 0.0480 (12) | 0.0554 (13) | 0.0526 (13) | −0.0097 (10) | 0.0039 (10) | −0.0002 (11) |
C12 | 0.0499 (12) | 0.0504 (12) | 0.0454 (11) | −0.0055 (10) | 0.0042 (10) | −0.0045 (10) |
O13 | 0.0575 (10) | 0.0665 (10) | 0.0489 (9) | −0.0096 (7) | 0.0145 (7) | −0.0072 (7) |
C14 | 0.0706 (16) | 0.0620 (15) | 0.0554 (13) | −0.0147 (12) | 0.0162 (12) | −0.0140 (12) |
C15 | 0.0732 (17) | 0.0622 (15) | 0.0622 (14) | −0.0063 (12) | 0.0225 (13) | −0.0125 (12) |
O16 | 0.0661 (11) | 0.0584 (10) | 0.0605 (9) | −0.0005 (8) | 0.0233 (8) | −0.0039 (8) |
C17 | 0.0705 (17) | 0.0801 (18) | 0.0630 (15) | 0.0056 (13) | 0.0278 (13) | −0.0026 (14) |
C18 | 0.0771 (18) | 0.0852 (19) | 0.0559 (14) | 0.0026 (14) | 0.0201 (13) | 0.0041 (14) |
O19 | 0.0857 (13) | 0.0820 (13) | 0.0679 (11) | −0.0156 (10) | 0.0151 (10) | 0.0085 (10) |
C20 | 0.107 (3) | 0.100 (3) | 0.110 (3) | −0.025 (2) | 0.004 (2) | 0.028 (2) |
C21 | 0.108 (3) | 0.105 (3) | 0.181 (4) | −0.024 (2) | 0.015 (3) | 0.007 (3) |
C22 | 0.0460 (12) | 0.0528 (13) | 0.0472 (12) | 0.0025 (10) | 0.0048 (10) | 0.0022 (11) |
O23 | 0.0705 (11) | 0.0887 (13) | 0.0564 (10) | −0.0138 (9) | 0.0170 (8) | −0.0174 (9) |
O24 | 0.0558 (10) | 0.0975 (14) | 0.0609 (10) | −0.0161 (9) | 0.0203 (8) | −0.0078 (9) |
C1—C2 | 1.376 (3) | C14—C15 | 1.487 (3) |
C1—C6 | 1.390 (3) | C14—H14A | 0.9700 |
C1—H1 | 0.9300 | C14—H14B | 0.9700 |
C2—C3 | 1.373 (3) | C15—O16 | 1.402 (3) |
C2—H2 | 0.9300 | C15—H15A | 0.9700 |
C3—C4 | 1.384 (3) | C15—H15B | 0.9700 |
C3—C22 | 1.480 (3) | O16—C17 | 1.399 (3) |
C4—C5 | 1.367 (3) | C17—C18 | 1.481 (4) |
C4—H4 | 0.9300 | C17—H17A | 0.9700 |
C5—C6 | 1.392 (3) | C17—H17B | 0.9700 |
C5—H5 | 0.9300 | C18—O19 | 1.399 (3) |
C6—C7 | 1.490 (3) | C18—H18A | 0.9700 |
C7—C8 | 1.384 (3) | C18—H18B | 0.9700 |
C7—C12 | 1.398 (3) | O19—C20 | 1.420 (3) |
C8—C9 | 1.373 (3) | C20—C21 | 1.455 (5) |
C8—H8 | 0.9300 | C20—H20A | 0.9700 |
C9—C10 | 1.379 (3) | C20—H20B | 0.9700 |
C9—H9 | 0.9300 | C21—H21A | 0.9600 |
C10—O13 | 1.363 (2) | C21—H21B | 0.9600 |
C10—C11 | 1.389 (3) | C21—H21C | 0.9600 |
C11—C12 | 1.371 (3) | C22—O24 | 1.261 (3) |
C11—H11 | 0.9300 | C22—O23 | 1.256 (2) |
C12—H12 | 0.9300 | O24—H24 | 0.8201 |
O13—C14 | 1.423 (3) | ||
C2—C1—C6 | 121.2 (2) | O13—C14—H14B | 109.9 |
C2—C1—H1 | 119.4 | C15—C14—H14B | 109.9 |
C6—C1—H1 | 119.4 | H14A—C14—H14B | 108.3 |
C3—C2—C1 | 121.2 (2) | O16—C15—C14 | 110.8 (2) |
C3—C2—H2 | 119.4 | O16—C15—H15A | 109.5 |
C1—C2—H2 | 119.4 | C14—C15—H15A | 109.5 |
C2—C3—C4 | 118.4 (2) | O16—C15—H15B | 109.5 |
C2—C3—C22 | 120.3 (2) | C14—C15—H15B | 109.5 |
C4—C3—C22 | 121.32 (19) | H15A—C15—H15B | 108.1 |
C5—C4—C3 | 120.4 (2) | C15—O16—C17 | 112.60 (18) |
C5—C4—H4 | 119.8 | O16—C17—C18 | 111.7 (2) |
C3—C4—H4 | 119.8 | O16—C17—H17A | 109.3 |
C4—C5—C6 | 122.0 (2) | C18—C17—H17A | 109.3 |
C4—C5—H5 | 119.0 | O16—C17—H17B | 109.3 |
C6—C5—H5 | 119.0 | C18—C17—H17B | 109.3 |
C5—C6—C1 | 116.7 (2) | H17A—C17—H17B | 107.9 |
C5—C6—C7 | 121.75 (19) | O19—C18—C17 | 109.9 (2) |
C1—C6—C7 | 121.51 (19) | O19—C18—H18A | 109.7 |
C8—C7—C12 | 116.3 (2) | C17—C18—H18A | 109.7 |
C8—C7—C6 | 121.35 (19) | O19—C18—H18B | 109.7 |
C12—C7—C6 | 122.35 (19) | C17—C18—H18B | 109.7 |
C9—C8—C7 | 122.7 (2) | H18A—C18—H18B | 108.2 |
C9—C8—H8 | 118.6 | C18—O19—C20 | 111.8 (2) |
C7—C8—H8 | 118.6 | O19—C20—C21 | 110.3 (3) |
C8—C9—C10 | 120.1 (2) | O19—C20—H20A | 109.6 |
C8—C9—H9 | 120.0 | C21—C20—H20A | 109.6 |
C10—C9—H9 | 120.0 | O19—C20—H20B | 109.6 |
O13—C10—C9 | 125.11 (19) | C21—C20—H20B | 109.6 |
O13—C10—C11 | 116.28 (19) | H20A—C20—H20B | 108.1 |
C9—C10—C11 | 118.6 (2) | C20—C21—H21A | 109.5 |
C12—C11—C10 | 120.6 (2) | C20—C21—H21B | 109.5 |
C12—C11—H11 | 119.7 | H21A—C21—H21B | 109.5 |
C10—C11—H11 | 119.7 | C20—C21—H21C | 109.5 |
C11—C12—C7 | 121.6 (2) | H21A—C21—H21C | 109.5 |
C11—C12—H12 | 119.2 | H21B—C21—H21C | 109.5 |
C7—C12—H12 | 119.2 | O24—C22—O23 | 123.4 (2) |
C10—O13—C14 | 117.94 (16) | O24—C22—C3 | 117.73 (19) |
O13—C14—C15 | 108.9 (2) | O23—C22—C3 | 118.8 (2) |
O13—C14—H14A | 109.9 | C22—O24—H24 | 117.6 |
C15—C14—H14A | 109.9 | ||
C6—C1—C2—C3 | −1.0 (4) | O13—C10—C11—C12 | −178.34 (19) |
C1—C2—C3—C4 | −0.7 (3) | C9—C10—C11—C12 | 1.2 (3) |
C1—C2—C3—C22 | 178.3 (2) | C10—C11—C12—C7 | 0.0 (3) |
C2—C3—C4—C5 | 1.6 (3) | C8—C7—C12—C11 | −1.3 (3) |
C22—C3—C4—C5 | −177.4 (2) | C6—C7—C12—C11 | 179.17 (19) |
C3—C4—C5—C6 | −0.9 (3) | C9—C10—O13—C14 | 1.4 (3) |
C4—C5—C6—C1 | −0.8 (3) | C11—C10—O13—C14 | −179.1 (2) |
C4—C5—C6—C7 | 179.3 (2) | C10—O13—C14—C15 | −173.27 (19) |
C2—C1—C6—C5 | 1.7 (3) | O13—C14—C15—O16 | −72.1 (3) |
C2—C1—C6—C7 | −178.3 (2) | C14—C15—O16—C17 | −178.9 (2) |
C5—C6—C7—C8 | 15.1 (3) | C15—O16—C17—C18 | 174.1 (2) |
C1—C6—C7—C8 | −164.9 (2) | O16—C17—C18—O19 | 72.2 (3) |
C5—C6—C7—C12 | −165.4 (2) | C17—C18—O19—C20 | 174.8 (2) |
C1—C6—C7—C12 | 14.6 (3) | C18—O19—C20—C21 | −176.2 (3) |
C12—C7—C8—C9 | 1.6 (3) | C2—C3—C22—O24 | 179.8 (2) |
C6—C7—C8—C9 | −178.9 (2) | C4—C3—C22—O24 | −1.2 (3) |
C7—C8—C9—C10 | −0.4 (3) | C2—C3—C22—O23 | −1.9 (3) |
C8—C9—C10—O13 | 178.5 (2) | C4—C3—C22—O23 | 177.0 (2) |
C8—C9—C10—C11 | −1.0 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O24—H24···O23i | 0.82 | 1.80 | 2.619 (2) | 176 |
C18—H18B···O13ii | 0.97 | 2.58 | 3.478 (3) | 154 |
C1—H1···Cg2iii | 0.93 | 2.83 | 2.83 | 138 |
C14—H14B···Cg2iv | 0.97 | 2.74 | 2.74 | 149 |
Symmetry codes: (i) −x, −y+1, −z+2; (ii) x, −y+3/2, z−1/2; (iii) x, −y+3/2, z+1/2; (iv) x, −y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C19H22O5 |
Mr | 330.37 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 294 |
a, b, c (Å) | 25.430 (7), 7.769 (2), 8.656 (2) |
β (°) | 96.187 (5) |
V (Å3) | 1700.3 (8) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.60 × 0.50 × 0.10 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS in SAINT-NT; Bruker, 2002) |
Tmin, Tmax | 0.95, 0.99 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 9420, 3634, 2230 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.639 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.063, 0.191, 0.99 |
No. of reflections | 3634 |
No. of parameters | 219 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.23, −0.14 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).
D—H···A | D—H | H···A | D···A | D—H···A |
O24—H24···O23i | 0.82 | 1.80 | 2.619 (2) | 176 |
C18—H18B···O13ii | 0.97 | 2.58 | 3.478 (3) | 154 |
C1—H1···Cg2iii | 0.93 | 2.83 | 2.83 | 138. |
C14—H14B···Cg2iv | 0.97 | 2.74 | 2.74 | 149 |
Symmetry codes: (i) −x, −y+1, −z+2; (ii) x, −y+3/2, z−1/2; (iii) x, −y+3/2, z+1/2; (iv) x, −y+1/2, z−1/2. |
The smectic C (SmC) mesophase is one of the oldest and best studied types of liquid crystals (LCs), from both the experimental and the theoretical point of view (Goodby, 1998). Most of these studies were conducted with the aim of understanding at the molecular level the structural features distinctive of the SmC mesophase: a lamellar arrangement of elongated molecules, tilted on average by an angle θ from the normal to the lamellae. Several techniques have been used in order to asses specific aspects of the intermolecular organization in a wide variety of SmC materials, and different theoretical approaches have been followed in order to either describe the phase transitions between the SmC, SmA and nematic (N) phases (Guillon, 1998; Huang, 1998) or suggest suitable models for the tilted lamellar organization, either in compounds with dipolar moments non-collinear with the main molecular axis or in compounds without any dipolar moment but containing molecular fragments with different lateral areas, giving rise to different packing requirements. In spite of the long time devoted to their study, interest in SmC LCs is still alive (Sanchez Ferrer & Finkelmann, 2008; Vadnais et al., 2008), owing to the applications they exhibit, for example, in electro-optic devices, such as surface stabilized ferroelectric liquid crystal displays (Shinkawa et al., 2008; Wang & Bos, 2004).
As part of a systematic (Montani et al., 2009) with calamitic (i.e. rod-shaped) mesogens of three-block molecular architecture (biphenyl, aliphatic chains, oxyethylenic chains), the LC behaviour of EtOC2H4OC2H4O biphenyloic acid, C19H22O5, (I), has been studied. This compound can be a priori considered as a calamitic mesogen consisting of dimeric units made up by hydrogen-bonding association of the carboxylic acid groups. In such a case, the central core would have five rings, and there would be two terminal oxyethylene chains, a molecular geometry suitable for smectic mesophases. As shown by polarized optical microscopy and powder X-ray diffraction (Montani et al., 2009), (I) did exhibit a SmC mesophase from 458 to 463 K, with an interlamellar distance of 30.8 Å. This value cannot be simply explained in terms of tilted extended molecules; indeed, the PM3-estimated (Stewart, 1988) molecular length for a fully extended dimer of (I) is 45 Å, significantly longer than the interlamellar distance. Even if a tilt of ca 45° could account for this difference, this value looks unacceptable, as the extreme tilt angles already found in SmC phases are 38°. A gauche conformation for the oxyethylene chains of the dimeric unit thus seems a more realistic explanation; indeed, this hypothesis finds two additional a priori supports: (i) the PM3-calculated molecular length for this conformation (35 Å) is much closer to the experimental interlamellar distance, and (ii) a search of the Cambridge Structural Database (CSD; Allen, 2002) for compounds with oxyethylene chains whose conformation is not determined by specific interactions (like cation complexation) showed anti conformations in less 25% of cases.
As a key step in validating this hypothesis, we have succeeded in crystallizing and solving the crystalline structure of (I), shown in Fig. 1. The figure also depicts the head-to-head hydrogen-bonding interaction between the centrosymmetrically related carboxyl groups (Table 1); this rather strong interaction leads to the formation of the expected extended dimeric units, with a span of ca 34 Å between the outermost methyl groups. The interatomic bond distances and angles are unexceptional, save perhaps for an apparent shortening in bond lengths while traversing the chain towards the Et end, ascribable to libration and tied to the increasing vibration of the tail (see Experimental). The main conformational aspects of the molecules are to be found in the few torsion angles differing significantly (by more than 5°) from 0 or 180°, viz. C5—C6—C7—C8 = 15.1 (3)°, O13—C14—C15—O16 = -72.1 (3)° and O16—C17—C18—O19= 72.2 (3)°. The first angle accounts for the slight rotation of the two phenyl rings, while the remaining two represent a twofold bending of the dimer's linear `spine' defined by the O13···O13i [symmetry code: (i) -x, -y + 1, -z + 2] vector, 23.688 (1) Å in length. This line, representative of the molecular direction, makes angles of 46.0 (1), 89.3 (1) and 37.8 (1)° with the a, b and c crystallographic axes, respectively; thus, the dimeric axes are almost contained by the (010) plane and nearly aligned to the crystallographic [103] direction.
The rather small rotation between phenyl rings in the monomers as well as the restraints imposed by symmetry on the related counterpart completing the dimer force the four aromatic rings plus their carboxylate ends to stay within a rather well defined plane (the mean deviation for the 30 atoms is 0.12 Å); the terminal tails in the dimers protrude outwards in an `anti' fashion and their least-squares lines subtend to the plane normal an angle of ca 120°. The dimers are organized in pairs, with their axes approximately parallel to each other but rotated around this axis by about 65 (1)°, as measured by the dihedral angle between the latter least-squares planes (see Fig. 1). There is no π stacking in the structure (no coplanarity, the minimum centre-to-centre distance is 4.80 Å). The ethyleneoxide chains of both components of each pair mutually interdigitate (the minimum O···C distance is approximately 3.4 Å), being nearly perpendicular to the mean molecular planes, as a consequence of the gauche conformations exhibited around the C14—C15 and C17—C18 bonds (all other torsion angles corresponding to trans conformations). Fig. 2 shows two packing views along the b and c axes: the way in which the dimers align, as well as the broad two-dimensional structure their association through weak C—H···O and C—H···π interactions (Table 1) gives rise to, can be clearly appreciated, with the hydrophobic methyl groups bunching at heights of x ≈ 0.50 and the hydrophilic carboxylates in the vicinity of x ≈ 0.00. Thus, the results presented here support our original hypothesis for the molecular description of the SmC phase of (I) and fully validate the geometric estimations made: in the crystalline phase the compound exhibits a gauche conformation for the oxyethylene chains, with a total molecular length of 34 Å, in excellent agreement with that predicted by PM3 calculations. Moreover, a lamellar organization is still present in the crystalline phase, also showing strong microsegregation between the aromatic parts and the oxyethylene chains, probably as a consequence of their differences both in polarity and in packing requirements. Microsegregation is widely recognized as a driving force for lamellar structures (Tschierske, 1998, 2001). The interlamellar distance measured by powder X-ray diffraction in the SmC phase of (I) is close to thatfound in the crystalline phase, which can be taken as the crystallographic a parameter [30.8 versus 25.430 (7) Å]. The difference can arise from several factors:
(i) The crystallographic structure has been solved at room temperature, and if an extrapolation of the molecular length to 460 K (corresponding to the SmC phase) is made, an additional 1.7 Å is obtained when only the dependence on temperature of the methylene volume (Guillon et al., 1986) is taken into account. For the whole molecule, this could be estimated as 2–3 Å.
(ii) In addition, the tilt angle can vary, as stated above, from its crystallographic value (ca 43°) to ca 28° (acceptable for SmC phases).
(iii) Finally, some conformational disorder at the oxyethylene chains may appear, increasing the effective molecular length. As stated above, the oxyethylene chains point towards a direction nearly orthogonal to the mean molecular plane. The effective molecular length in the direction of the C3···C10 axis is ca 32–33 Å.
This study is an additional proof of the usefulness of single-crystal analysis for providing key information in the interpretation of LC structures at the molecular level.