Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113002485/uk3060sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113002485/uk3060IIsup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270113002485/uk3060IIIsup3.hkl | |
Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270113002485/uk3060IIsup4.cml | |
Chemical Markup Language (CML) file https://doi.org/10.1107/S0108270113002485/uk3060IIIsup5.cml |
CCDC references: 925783; 925784
All chemical precursors were purchased from Aldrich and used without further purification. Differential scanning calorimetry (DSC) was performed with a Shimadzu DSC-50 apparatus. Elemental analysis was carried out at Servicio a Terceros of INQUIMAE on a Carlo Erba CHNS-O EA1108 analyser. 1H NMR spectra were measured on a Bruker AM500 spectrometer, using CDCl3 as solvent and its residual peaks as internal references (7.26 p.p.m. for 1H).
Both (II) and (III) were synthesized in two steps from catechol (benzene-1,2-diol). The first step consisted of a Williamson's etherification of both hydroxy groups by reacting catechol with the appropriate bromoalkane, following published procedures (Boden et al., 1993). The second step was an aromatic electrophilic substitution in the activated para positions relative to the alkoxy chains.
For the preparation of 1,2-dibromo-4,5-bis(decyloxy)benzene, (II), 1,2-bis(decyloxy)benzene (1.282 g) was dissolved in cold CH2Cl2 (16 ml), placed in a two-necked flask equipped with an NaHSO3 bubbler with pressure compensation and immersed in an ice bath. Bromine (0.35 ml dissolved in 5 ml CH2Cl2) was added dropwise and the mixture was allowed to warm to room temperature. The progress of the reaction was monitored by thin-layer chromatography (TLC) (CH2Cl2–cyclohexane 1:3 v/v). When the reaction was complete, it was stopped by the addition of aqueous NaHSO3. The aqueous phase was discarded and the organic phase was washed successively with water, aqueous NaHSO3 and water, and then dried with anhydrous Na2SO4, filtered and evaporated to dryness in a rotary evaporator. The solid was recrystallized from ethanol (yield 1.56 g, 87%). Spectroscopic analysis: 1H NMR (Frequency?, CD3Cl, δ, p.p.m.): 7.058 (s, 2H), 3.94 (t, 4H), 1.78 (q, 4H), 1.44 (q, 4H), 1.34–1.27 (m, 24H), 0.88 (t, 6H). Single crystals were obtained by slow cooling (2 K per day) of a concentrated ethanol solution of (II).
For the preparation of 1,2-dibromo-4,5-bis(hexadecyloxy)benzene, (III), the synthetic procedure was identical to that followed for the preparation of (II), using 1,2-bis(hexadecyloxy)benzene (2.009 g dissolved in 25 ml CH2Cl2) instead of 1,2-bis(decyloxy)benzene and 0.40 ml Br2 instead of 0.35 ml (yield 1.88 g, 73%). Analysis, found (calculated for C38H68Br2O2) (%): C 63.6 (63.68), H 9.6 (9.56). Spectroscopic analysis: 1H NMR (Frequency?, CD3Cl, δ, p.p.m.): 7.06 (s, 2H), 3.94 (t, 4H), 1.78 (q, 4H), 1.44 (q, 4H), 1.34–1,27 (m, 48H) 0.88 (t, 6H). Single crystals were obtained by slow cooling of and solvent evaporation from a concentrated solution of (III) in chloroform.
Compound (III) posed no problems, either in the data collection or in the model refinement. In contrast, (II) showed disorder in the hydrophilic region, for which a low-temperature data set was needed to resolve the problem. In this way, a reasonable model could be refined, even when neglecting some (impossible to model) disorder effects. This was evident in some important reflection outliers, as well as some significant Δρ peaks, e.g. 1.67 e Å-3 at 2.04 Å from Br1.
All the H atoms in (III), and most of those in (II), were seen in difference maps, but they were subsequently placed in geometrically idealized positions and allowed to ride on their parent atoms, with aromatic C—H = 0.93 Å, methylene C—H = 0.97 Å and methyl C—H = 0.96 Å, and with Uiso(H) = 1.2, 1.2 and 1.5Ueq(C), respectively.
For both compounds, data collection: CrysAlis PRO (Oxford Diffraction, 2009); cell refinement: CrysAlis PRO (Oxford Diffraction, 2009); data reduction: CrysAlis PRO (Oxford Diffraction, 2009); 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: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).
C26H44Br2O2 | F(000) = 2288 |
Mr = 548.43 | Dx = 1.358 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.7107 Å |
Hall symbol: -C 2yc | Cell parameters from 11243 reflections |
a = 67.0788 (15) Å | θ = 2.1–25.8° |
b = 4.4717 (1) Å | µ = 3.04 mm−1 |
c = 18.2399 (4) Å | T = 150 K |
β = 101.216 (2)° | Plate, colourless |
V = 5366.7 (2) Å3 | 0.56 × 0.27 × 0.07 mm |
Z = 8 |
Oxford Gemini S Ultra CCD area-detector diffractometer | 5387 independent reflections |
Radiation source: fine-focus sealed tube | 4981 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.068 |
ω scans, thick slices | θmax = 26.2°, θmin = 1.9° |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | h = −82→82 |
Tmin = 0.42, Tmax = 0.78 | k = −4→5 |
28792 measured reflections | l = −22→22 |
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)] = 0.069 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.184 | H-atom parameters constrained |
S = 1.21 | w = 1/[σ2(Fo2) + (0.0236P)2 + 122.7172P] where P = (Fo2 + 2Fc2)/3 |
5387 reflections | (Δ/σ)max < 0.001 |
271 parameters | Δρmax = 1.67 e Å−3 |
0 restraints | Δρmin = −0.95 e Å−3 |
C26H44Br2O2 | V = 5366.7 (2) Å3 |
Mr = 548.43 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 67.0788 (15) Å | µ = 3.04 mm−1 |
b = 4.4717 (1) Å | T = 150 K |
c = 18.2399 (4) Å | 0.56 × 0.27 × 0.07 mm |
β = 101.216 (2)° |
Oxford Gemini S Ultra CCD area-detector diffractometer | 5387 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | 4981 reflections with I > 2σ(I) |
Tmin = 0.42, Tmax = 0.78 | Rint = 0.068 |
28792 measured reflections |
R[F2 > 2σ(F2)] = 0.069 | 0 restraints |
wR(F2) = 0.184 | H-atom parameters constrained |
S = 1.21 | w = 1/[σ2(Fo2) + (0.0236P)2 + 122.7172P] where P = (Fo2 + 2Fc2)/3 |
5387 reflections | Δρmax = 1.67 e Å−3 |
271 parameters | Δρmin = −0.95 e Å−3 |
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 | ||
Br1 | 0.225869 (11) | 0.04646 (19) | 0.45773 (4) | 0.0389 (2) | |
Br2 | 0.249896 (11) | 0.45935 (19) | 0.34532 (4) | 0.0366 (2) | |
O1 | 0.17000 (7) | −0.1276 (11) | 0.2145 (3) | 0.0297 (10) | |
O2 | 0.18712 (7) | 0.2238 (10) | 0.1327 (2) | 0.0276 (10) | |
C1 | 0.21452 (10) | 0.1098 (16) | 0.3549 (3) | 0.0268 (14) | |
C2 | 0.22418 (8) | 0.2811 (14) | 0.3103 (3) | 0.0220 (12) | |
C3 | 0.21497 (10) | 0.3305 (15) | 0.2353 (4) | 0.0287 (14) | |
H3 | 0.2212 | 0.4568 | 0.2059 | 0.034* | |
C4 | 0.19705 (9) | 0.1950 (15) | 0.2051 (3) | 0.0244 (13) | |
C5 | 0.18738 (9) | 0.0024 (15) | 0.2497 (4) | 0.0268 (14) | |
C6 | 0.19618 (9) | −0.0303 (15) | 0.3267 (4) | 0.0265 (14) | |
H6 | 0.1897 | −0.1443 | 0.3578 | 0.032* | |
C7 | 0.15963 (10) | −0.3154 (15) | 0.2613 (4) | 0.0300 (14) | |
H7A | 0.1542 | −0.1931 | 0.2968 | 0.036* | |
H7B | 0.1691 | −0.4591 | 0.2888 | 0.036* | |
C8 | 0.14293 (10) | −0.4722 (15) | 0.2110 (4) | 0.0271 (13) | |
H8A | 0.1372 | −0.6189 | 0.2401 | 0.033* | |
H8B | 0.1486 | −0.5802 | 0.1738 | 0.033* | |
C9 | 0.12568 (10) | −0.2721 (15) | 0.1703 (4) | 0.0279 (14) | |
H9A | 0.1213 | −0.1412 | 0.2065 | 0.034* | |
H9B | 0.1309 | −0.1473 | 0.1348 | 0.034* | |
C10 | 0.10730 (10) | −0.4473 (17) | 0.1288 (4) | 0.0317 (15) | |
H10A | 0.1117 | −0.5768 | 0.0924 | 0.038* | |
H10B | 0.1022 | −0.5737 | 0.1644 | 0.038* | |
C11 | 0.09000 (10) | −0.2517 (16) | 0.0889 (4) | 0.0302 (14) | |
H11A | 0.0950 | −0.1239 | 0.0536 | 0.036* | |
H11B | 0.0854 | −0.1240 | 0.1253 | 0.036* | |
C12 | 0.07198 (11) | −0.4314 (17) | 0.0473 (5) | 0.0373 (17) | |
H12A | 0.0764 | −0.5476 | 0.0084 | 0.045* | |
H12B | 0.0677 | −0.5705 | 0.0819 | 0.045* | |
C13 | 0.05388 (11) | −0.2398 (17) | 0.0119 (4) | 0.0341 (15) | |
H13A | 0.0490 | −0.1321 | 0.0511 | 0.041* | |
H13B | 0.0584 | −0.0933 | −0.0206 | 0.041* | |
C14 | 0.03652 (11) | −0.4177 (19) | −0.0328 (5) | 0.0409 (18) | |
H14A | 0.0318 | −0.5605 | 0.0000 | 0.049* | |
H14B | 0.0415 | −0.5296 | −0.0711 | 0.049* | |
C15 | 0.01860 (12) | −0.223 (2) | −0.0699 (5) | 0.049 (2) | |
H15A | 0.0133 | −0.1163 | −0.0314 | 0.059* | |
H15B | 0.0234 | −0.0765 | −0.1016 | 0.059* | |
C16 | 0.00144 (13) | −0.403 (3) | −0.1167 (6) | 0.067 (3) | |
H16A | −0.0093 | −0.2705 | −0.1387 | 0.101* | |
H16B | −0.0036 | −0.5456 | −0.0855 | 0.101* | |
H16C | 0.0065 | −0.5067 | −0.1556 | 0.101* | |
C17 | 0.19550 (10) | 0.4289 (15) | 0.0888 (4) | 0.0280 (14) | |
H17A | 0.2090 | 0.3645 | 0.0836 | 0.034* | |
H17B | 0.1966 | 0.6247 | 0.1121 | 0.034* | |
C18 | 0.18131 (11) | 0.4434 (18) | 0.0114 (4) | 0.0367 (16) | |
H18A | 0.1875 | 0.5674 | −0.0217 | 0.044* | |
H18B | 0.1796 | 0.2440 | −0.0099 | 0.044* | |
C19 | 0.16053 (11) | 0.5708 (18) | 0.0163 (4) | 0.0341 (16) | |
H19A | 0.1536 | 0.4312 | 0.0435 | 0.041* | |
H19B | 0.1624 | 0.7562 | 0.0445 | 0.041* | |
C20 | 0.14738 (11) | 0.6299 (18) | −0.0591 (4) | 0.0343 (16) | |
H20A | 0.1456 | 0.4440 | −0.0870 | 0.041* | |
H20B | 0.1544 | 0.7682 | −0.0862 | 0.041* | |
C21 | 0.12653 (12) | 0.758 (2) | −0.0558 (4) | 0.0394 (18) | |
H21A | 0.1283 | 0.9427 | −0.0272 | 0.047* | |
H21B | 0.1193 | 0.6185 | −0.0297 | 0.047* | |
C22 | 0.11359 (12) | 0.822 (2) | −0.1328 (4) | 0.0416 (18) | |
H22A | 0.1120 | 0.6397 | −0.1620 | 0.050* | |
H22B | 0.1205 | 0.9672 | −0.1585 | 0.050* | |
C23 | 0.09249 (12) | 0.944 (2) | −0.1275 (4) | 0.045 (2) | |
H23A | 0.0941 | 1.1203 | −0.0960 | 0.055* | |
H23B | 0.0853 | 0.7944 | −0.1041 | 0.055* | |
C24 | 0.07956 (12) | 1.026 (2) | −0.2054 (4) | 0.047 (2) | |
H24A | 0.0864 | 1.1828 | −0.2278 | 0.057* | |
H24B | 0.0785 | 0.8521 | −0.2379 | 0.057* | |
C25 | 0.05857 (14) | 1.129 (3) | −0.2000 (5) | 0.075 (4) | |
H25A | 0.0596 | 1.3030 | −0.1677 | 0.090* | |
H25B | 0.0518 | 0.9723 | −0.1776 | 0.090* | |
C26 | 0.04596 (15) | 1.209 (3) | −0.2762 (6) | 0.076 (4) | |
H26A | 0.0327 | 1.2735 | −0.2705 | 0.114* | |
H26B | 0.0447 | 1.0358 | −0.3081 | 0.114* | |
H26C | 0.0525 | 1.3664 | −0.2982 | 0.114* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.0387 (4) | 0.0495 (5) | 0.0265 (4) | −0.0037 (3) | 0.0012 (3) | 0.0035 (3) |
Br2 | 0.0304 (4) | 0.0450 (4) | 0.0334 (4) | −0.0083 (3) | 0.0035 (3) | −0.0020 (3) |
O1 | 0.029 (2) | 0.033 (3) | 0.026 (2) | −0.006 (2) | 0.0024 (18) | −0.001 (2) |
O2 | 0.034 (2) | 0.023 (2) | 0.025 (2) | −0.0042 (19) | 0.0049 (18) | 0.0005 (19) |
C1 | 0.035 (3) | 0.029 (3) | 0.014 (3) | 0.010 (3) | −0.001 (2) | 0.003 (3) |
C2 | 0.014 (3) | 0.025 (3) | 0.027 (3) | −0.004 (2) | 0.004 (2) | −0.008 (3) |
C3 | 0.035 (3) | 0.025 (3) | 0.028 (3) | 0.002 (3) | 0.014 (3) | 0.003 (3) |
C4 | 0.028 (3) | 0.023 (3) | 0.021 (3) | 0.005 (3) | 0.004 (2) | 0.000 (3) |
C5 | 0.017 (3) | 0.026 (3) | 0.040 (4) | −0.003 (2) | 0.011 (3) | −0.001 (3) |
C6 | 0.022 (3) | 0.024 (3) | 0.035 (4) | 0.003 (3) | 0.009 (3) | 0.008 (3) |
C7 | 0.036 (3) | 0.023 (3) | 0.033 (3) | −0.001 (3) | 0.013 (3) | 0.009 (3) |
C8 | 0.036 (3) | 0.021 (3) | 0.026 (3) | 0.000 (3) | 0.009 (3) | 0.001 (3) |
C9 | 0.031 (3) | 0.022 (3) | 0.035 (3) | −0.004 (3) | 0.015 (3) | −0.004 (3) |
C10 | 0.034 (3) | 0.033 (4) | 0.031 (3) | 0.000 (3) | 0.011 (3) | 0.006 (3) |
C11 | 0.035 (3) | 0.027 (3) | 0.029 (3) | −0.002 (3) | 0.008 (3) | −0.001 (3) |
C12 | 0.034 (4) | 0.028 (4) | 0.049 (4) | −0.004 (3) | 0.006 (3) | −0.001 (3) |
C13 | 0.039 (4) | 0.032 (4) | 0.030 (3) | 0.000 (3) | 0.004 (3) | −0.006 (3) |
C14 | 0.039 (4) | 0.036 (4) | 0.047 (4) | −0.001 (3) | 0.007 (3) | −0.003 (4) |
C15 | 0.037 (4) | 0.043 (5) | 0.065 (6) | −0.001 (4) | 0.005 (4) | −0.003 (4) |
C16 | 0.038 (5) | 0.068 (7) | 0.085 (8) | −0.004 (5) | −0.013 (5) | 0.006 (6) |
C17 | 0.037 (3) | 0.021 (3) | 0.029 (3) | 0.001 (3) | 0.016 (3) | 0.011 (3) |
C18 | 0.039 (4) | 0.035 (4) | 0.035 (4) | 0.001 (3) | 0.006 (3) | 0.001 (3) |
C19 | 0.045 (4) | 0.039 (4) | 0.017 (3) | 0.001 (3) | 0.005 (3) | −0.003 (3) |
C20 | 0.041 (4) | 0.042 (4) | 0.020 (3) | 0.005 (3) | 0.005 (3) | 0.003 (3) |
C21 | 0.049 (4) | 0.056 (5) | 0.016 (3) | 0.006 (4) | 0.011 (3) | 0.005 (3) |
C22 | 0.045 (4) | 0.051 (5) | 0.028 (4) | 0.003 (4) | 0.005 (3) | 0.006 (4) |
C23 | 0.044 (4) | 0.064 (6) | 0.030 (4) | 0.007 (4) | 0.012 (3) | 0.008 (4) |
C24 | 0.041 (4) | 0.069 (6) | 0.031 (4) | 0.007 (4) | 0.005 (3) | −0.001 (4) |
C25 | 0.048 (5) | 0.129 (11) | 0.046 (5) | 0.028 (6) | 0.006 (4) | 0.022 (7) |
C26 | 0.050 (5) | 0.125 (11) | 0.051 (6) | 0.024 (7) | 0.002 (4) | 0.018 (7) |
Br1—C1 | 1.903 (6) | C14—H14B | 0.9700 |
Br2—C2 | 1.895 (6) | C15—C16 | 1.523 (12) |
O1—C5 | 1.348 (8) | C15—H15A | 0.9700 |
O1—C7 | 1.465 (8) | C15—H15B | 0.9700 |
O2—C4 | 1.365 (7) | C16—H16A | 0.9600 |
O2—C17 | 1.405 (7) | C16—H16B | 0.9600 |
C1—C2 | 1.369 (9) | C16—H16C | 0.9600 |
C1—C6 | 1.387 (9) | C17—C18 | 1.543 (10) |
C2—C3 | 1.406 (9) | C17—H17A | 0.9700 |
C3—C4 | 1.363 (9) | C17—H17B | 0.9700 |
C3—H3 | 0.9300 | C18—C19 | 1.525 (10) |
C4—C5 | 1.425 (9) | C18—H18A | 0.9700 |
C5—C6 | 1.421 (9) | C18—H18B | 0.9700 |
C6—H6 | 0.9300 | C19—C20 | 1.506 (9) |
C7—C8 | 1.479 (9) | C19—H19A | 0.9700 |
C7—H7A | 0.9700 | C19—H19B | 0.9700 |
C7—H7B | 0.9700 | C20—C21 | 1.524 (10) |
C8—C9 | 1.535 (9) | C20—H20A | 0.9700 |
C8—H8A | 0.9700 | C20—H20B | 0.9700 |
C8—H8B | 0.9700 | C21—C22 | 1.528 (9) |
C9—C10 | 1.531 (9) | C21—H21A | 0.9700 |
C9—H9A | 0.9700 | C21—H21B | 0.9700 |
C9—H9B | 0.9700 | C22—C23 | 1.536 (11) |
C10—C11 | 1.521 (9) | C22—H22A | 0.9700 |
C10—H10A | 0.9700 | C22—H22B | 0.9700 |
C10—H10B | 0.9700 | C23—C24 | 1.558 (10) |
C11—C12 | 1.525 (9) | C23—H23A | 0.9700 |
C11—H11A | 0.9700 | C23—H23B | 0.9700 |
C11—H11B | 0.9700 | C24—C25 | 1.504 (12) |
C12—C13 | 1.522 (10) | C24—H24A | 0.9700 |
C12—H12A | 0.9700 | C24—H24B | 0.9700 |
C12—H12B | 0.9700 | C25—C26 | 1.522 (12) |
C13—C14 | 1.511 (10) | C25—H25A | 0.9700 |
C13—H13A | 0.9700 | C25—H25B | 0.9700 |
C13—H13B | 0.9700 | C26—H26A | 0.9600 |
C14—C15 | 1.530 (11) | C26—H26B | 0.9600 |
C14—H14A | 0.9700 | C26—H26C | 0.9600 |
C5—O1—C7 | 115.7 (5) | C14—C15—H15A | 109.0 |
C4—O2—C17 | 116.1 (5) | C16—C15—H15B | 109.0 |
C2—C1—C6 | 121.3 (6) | C14—C15—H15B | 109.0 |
C2—C1—Br1 | 121.6 (5) | H15A—C15—H15B | 107.8 |
C6—C1—Br1 | 117.0 (5) | C15—C16—H16A | 109.5 |
C1—C2—C3 | 119.8 (6) | C15—C16—H16B | 109.5 |
C1—C2—Br2 | 122.7 (5) | H16A—C16—H16B | 109.5 |
C3—C2—Br2 | 117.5 (5) | C15—C16—H16C | 109.5 |
C4—C3—C2 | 120.6 (6) | H16A—C16—H16C | 109.5 |
C4—C3—H3 | 119.7 | H16B—C16—H16C | 109.5 |
C2—C3—H3 | 119.7 | O2—C17—C18 | 107.8 (6) |
C3—C4—O2 | 125.1 (6) | O2—C17—H17A | 110.2 |
C3—C4—C5 | 120.1 (6) | C18—C17—H17A | 110.2 |
O2—C4—C5 | 114.8 (6) | O2—C17—H17B | 110.2 |
O1—C5—C6 | 125.5 (6) | C18—C17—H17B | 110.2 |
O1—C5—C4 | 115.9 (6) | H17A—C17—H17B | 108.5 |
C6—C5—C4 | 118.6 (6) | C19—C18—C17 | 111.7 (6) |
C1—C6—C5 | 119.2 (6) | C19—C18—H18A | 109.3 |
C1—C6—H6 | 120.4 | C17—C18—H18A | 109.3 |
C5—C6—H6 | 120.4 | C19—C18—H18B | 109.3 |
O1—C7—C8 | 107.4 (5) | C17—C18—H18B | 109.3 |
O1—C7—H7A | 110.2 | H18A—C18—H18B | 107.9 |
C8—C7—H7A | 110.2 | C20—C19—C18 | 113.0 (6) |
O1—C7—H7B | 110.2 | C20—C19—H19A | 109.0 |
C8—C7—H7B | 110.2 | C18—C19—H19A | 109.0 |
H7A—C7—H7B | 108.5 | C20—C19—H19B | 109.0 |
C7—C8—C9 | 115.6 (6) | C18—C19—H19B | 109.0 |
C7—C8—H8A | 108.4 | H19A—C19—H19B | 107.8 |
C9—C8—H8A | 108.4 | C19—C20—C21 | 114.1 (6) |
C7—C8—H8B | 108.4 | C19—C20—H20A | 108.7 |
C9—C8—H8B | 108.4 | C21—C20—H20A | 108.7 |
H8A—C8—H8B | 107.4 | C19—C20—H20B | 108.7 |
C10—C9—C8 | 113.5 (6) | C21—C20—H20B | 108.7 |
C10—C9—H9A | 108.9 | H20A—C20—H20B | 107.6 |
C8—C9—H9A | 108.9 | C20—C21—C22 | 113.3 (6) |
C10—C9—H9B | 108.9 | C20—C21—H21A | 108.9 |
C8—C9—H9B | 108.9 | C22—C21—H21A | 108.9 |
H9A—C9—H9B | 107.7 | C20—C21—H21B | 108.9 |
C11—C10—C9 | 114.1 (6) | C22—C21—H21B | 108.9 |
C11—C10—H10A | 108.7 | H21A—C21—H21B | 107.7 |
C9—C10—H10A | 108.7 | C21—C22—C23 | 112.0 (6) |
C11—C10—H10B | 108.7 | C21—C22—H22A | 109.2 |
C9—C10—H10B | 108.7 | C23—C22—H22A | 109.2 |
H10A—C10—H10B | 107.6 | C21—C22—H22B | 109.2 |
C10—C11—C12 | 113.1 (6) | C23—C22—H22B | 109.2 |
C10—C11—H11A | 109.0 | H22A—C22—H22B | 107.9 |
C12—C11—H11A | 109.0 | C22—C23—C24 | 112.5 (6) |
C10—C11—H11B | 109.0 | C22—C23—H23A | 109.1 |
C12—C11—H11B | 109.0 | C24—C23—H23A | 109.1 |
H11A—C11—H11B | 107.8 | C22—C23—H23B | 109.1 |
C13—C12—C11 | 113.8 (6) | C24—C23—H23B | 109.1 |
C13—C12—H12A | 108.8 | H23A—C23—H23B | 107.8 |
C11—C12—H12A | 108.8 | C25—C24—C23 | 112.0 (7) |
C13—C12—H12B | 108.8 | C25—C24—H24A | 109.2 |
C11—C12—H12B | 108.8 | C23—C24—H24A | 109.2 |
H12A—C12—H12B | 107.7 | C25—C24—H24B | 109.2 |
C14—C13—C12 | 113.6 (6) | C23—C24—H24B | 109.2 |
C14—C13—H13A | 108.9 | H24A—C24—H24B | 107.9 |
C12—C13—H13A | 108.9 | C24—C25—C26 | 111.9 (8) |
C14—C13—H13B | 108.9 | C24—C25—H25A | 109.2 |
C12—C13—H13B | 108.9 | C26—C25—H25A | 109.2 |
H13A—C13—H13B | 107.7 | C24—C25—H25B | 109.2 |
C13—C14—C15 | 113.4 (7) | C26—C25—H25B | 109.2 |
C13—C14—H14A | 108.9 | H25A—C25—H25B | 107.9 |
C15—C14—H14A | 108.9 | C25—C26—H26A | 109.5 |
C13—C14—H14B | 108.9 | C25—C26—H26B | 109.5 |
C15—C14—H14B | 108.9 | H26A—C26—H26B | 109.5 |
H14A—C14—H14B | 107.7 | C25—C26—H26C | 109.5 |
C16—C15—C14 | 113.0 (8) | H26A—C26—H26C | 109.5 |
C16—C15—H15A | 109.0 | H26B—C26—H26C | 109.5 |
C6—C1—C2—C3 | 3.4 (10) | C4—C5—C6—C1 | −4.1 (9) |
Br1—C1—C2—C3 | −177.9 (5) | C5—O1—C7—C8 | −171.5 (5) |
C6—C1—C2—Br2 | −176.7 (5) | O1—C7—C8—C9 | −66.3 (7) |
Br1—C1—C2—Br2 | 2.0 (8) | O2—C17—C18—C19 | 65.0 (8) |
C1—C2—C3—C4 | −3.9 (10) | C7—C8—C9—C10 | −171.0 (6) |
Br2—C2—C3—C4 | 176.1 (5) | C8—C9—C10—C11 | 179.4 (6) |
C2—C3—C4—O2 | −178.7 (6) | C9—C10—C11—C12 | 179.4 (6) |
C2—C3—C4—C5 | 0.4 (10) | C10—C11—C12—C13 | 175.6 (6) |
C17—O2—C4—C3 | −5.4 (9) | C11—C12—C13—C14 | 176.9 (7) |
C17—O2—C4—C5 | 175.5 (6) | C12—C13—C14—C15 | −178.5 (7) |
C7—O1—C5—C6 | 0.4 (9) | C13—C14—C15—C16 | 178.2 (8) |
C7—O1—C5—C4 | −177.5 (6) | C4—O2—C17—C18 | −176.2 (5) |
C3—C4—C5—O1 | −178.3 (6) | C17—C18—C19—C20 | 171.6 (6) |
O2—C4—C5—O1 | 0.8 (8) | C18—C19—C20—C21 | −179.8 (7) |
C3—C4—C5—C6 | 3.6 (9) | C19—C20—C21—C22 | 178.9 (7) |
O2—C4—C5—C6 | −177.2 (6) | C20—C21—C22—C23 | 178.5 (7) |
C2—C1—C6—C5 | 0.7 (10) | C21—C22—C23—C24 | 177.0 (8) |
Br1—C1—C6—C5 | −178.1 (5) | C22—C23—C24—C25 | 177.0 (9) |
O1—C5—C6—C1 | 178.0 (6) | C23—C24—C25—C26 | −179.9 (10) |
C38H68Br2O2 | F(000) = 1528 |
Mr = 716.72 | Dx = 1.231 Mg m−3 |
Monoclinic, Cc | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: C -2yc | Cell parameters from 8379 reflections |
a = 50.158 (5) Å | θ = 3.6–29.0° |
b = 8.360 (3) Å | µ = 2.13 mm−1 |
c = 9.248 (3) Å | T = 294 K |
β = 94.136 (5)° | Plate, colourless |
V = 3868 (2) Å3 | 0.58 × 0.32 × 0.10 mm |
Z = 4 |
Oxford Gemini S Ultra CCD area-detector diffractometer | 6905 independent reflections |
Radiation source: fine-focus sealed tube | 4926 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.024 |
ω scans, thick slices | θmax = 27.0°, θmin = 3.6° |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | h = −55→63 |
Tmin = 0.45, Tmax = 0.82 | k = −10→10 |
16641 measured reflections | l = −11→11 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.024 | H-atom parameters constrained |
wR(F2) = 0.053 | w = 1/[σ2(Fo2) + (0.0318P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.84 | (Δ/σ)max = 0.001 |
6905 reflections | Δρmax = 0.26 e Å−3 |
379 parameters | Δρmin = −0.18 e Å−3 |
2 restraints | Absolute structure: Flack (1983), with how many Friedel pairs? |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.087 (5) |
C38H68Br2O2 | V = 3868 (2) Å3 |
Mr = 716.72 | Z = 4 |
Monoclinic, Cc | Mo Kα radiation |
a = 50.158 (5) Å | µ = 2.13 mm−1 |
b = 8.360 (3) Å | T = 294 K |
c = 9.248 (3) Å | 0.58 × 0.32 × 0.10 mm |
β = 94.136 (5)° |
Oxford Gemini S Ultra CCD area-detector diffractometer | 6905 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | 4926 reflections with I > 2σ(I) |
Tmin = 0.45, Tmax = 0.82 | Rint = 0.024 |
16641 measured reflections |
R[F2 > 2σ(F2)] = 0.024 | H-atom parameters constrained |
wR(F2) = 0.053 | Δρmax = 0.26 e Å−3 |
S = 0.84 | Δρmin = −0.18 e Å−3 |
6905 reflections | Absolute structure: Flack (1983), with how many Friedel pairs? |
379 parameters | Absolute structure parameter: 0.087 (5) |
2 restraints |
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 | ||
Br1 | 0.265200 (6) | 0.10931 (4) | 0.61498 (3) | 0.08034 (10) | |
Br2 | 0.233107 (6) | 0.31448 (4) | 0.34048 (2) | 0.07120 (9) | |
O1 | 0.18247 (3) | 0.24640 (17) | 0.90673 (14) | 0.0424 (3) | |
O2 | 0.15942 (3) | 0.4158 (2) | 0.70339 (15) | 0.0475 (4) | |
C1 | 0.23212 (4) | 0.2101 (3) | 0.6346 (2) | 0.0460 (5) | |
C2 | 0.21907 (4) | 0.2945 (3) | 0.5242 (2) | 0.0437 (5) | |
C3 | 0.19459 (4) | 0.3661 (3) | 0.5428 (2) | 0.0423 (5) | |
H3 | 0.1859 | 0.4242 | 0.4678 | 0.051* | |
C4 | 0.18326 (4) | 0.3503 (2) | 0.6741 (2) | 0.0363 (5) | |
C5 | 0.19608 (4) | 0.2611 (2) | 0.7859 (2) | 0.0359 (5) | |
C6 | 0.22054 (4) | 0.1931 (3) | 0.7672 (2) | 0.0411 (5) | |
H6 | 0.2294 | 0.1359 | 0.8424 | 0.049* | |
C7 | 0.19065 (4) | 0.1218 (3) | 1.0097 (2) | 0.0447 (5) | |
H7A | 0.2063 | 0.1552 | 1.0697 | 0.054* | |
H7B | 0.1949 | 0.0245 | 0.9592 | 0.054* | |
C8 | 0.16749 (4) | 0.0940 (3) | 1.1017 (2) | 0.0439 (5) | |
H8A | 0.1633 | 0.1932 | 1.1494 | 0.053* | |
H8B | 0.1727 | 0.0162 | 1.1763 | 0.053* | |
C9 | 0.14270 (4) | 0.0343 (3) | 1.0145 (2) | 0.0449 (5) | |
H9A | 0.1475 | −0.0583 | 0.9589 | 0.054* | |
H9B | 0.1367 | 0.1169 | 0.9462 | 0.054* | |
C10 | 0.11952 (4) | −0.0115 (3) | 1.1042 (2) | 0.0458 (5) | |
H11A | 0.1251 | −0.0986 | 1.1687 | 0.055* | |
H11B | 0.1152 | 0.0791 | 1.1637 | 0.055* | |
C11 | 0.09473 (5) | −0.0619 (3) | 1.0130 (2) | 0.0494 (6) | |
H10A | 0.0992 | −0.1534 | 0.9549 | 0.059* | |
H10B | 0.0896 | 0.0246 | 0.9467 | 0.059* | |
C12 | 0.07085 (4) | −0.1052 (3) | 1.0966 (2) | 0.0489 (6) | |
H12A | 0.0758 | −0.1930 | 1.1616 | 0.059* | |
H12B | 0.0664 | −0.0143 | 1.1554 | 0.059* | |
C13 | 0.04641 (5) | −0.1527 (3) | 1.0012 (3) | 0.0513 (6) | |
H13A | 0.0510 | −0.2439 | 0.9430 | 0.062* | |
H13B | 0.0417 | −0.0651 | 0.9354 | 0.062* | |
C14 | 0.02199 (5) | −0.1954 (3) | 1.0813 (2) | 0.0507 (6) | |
H14A | 0.0265 | −0.2841 | 1.1462 | 0.061* | |
H14B | 0.0174 | −0.1048 | 1.1403 | 0.061* | |
C15 | −0.00213 (5) | −0.2403 (3) | 0.9834 (2) | 0.0542 (6) | |
H15A | 0.0026 | −0.3307 | 0.9245 | 0.065* | |
H15B | −0.0064 | −0.1516 | 0.9183 | 0.065* | |
C16 | −0.02704 (5) | −0.2835 (3) | 1.0589 (2) | 0.0541 (6) | |
H16A | −0.0230 | −0.3736 | 1.1228 | 0.065* | |
H16B | −0.0317 | −0.1938 | 1.1186 | 0.065* | |
C17 | −0.05075 (5) | −0.3254 (3) | 0.9581 (3) | 0.0568 (7) | |
H17A | −0.0460 | −0.4148 | 0.8983 | 0.068* | |
H17B | −0.0548 | −0.2352 | 0.8943 | 0.068* | |
C18 | −0.07597 (5) | −0.3694 (3) | 1.0318 (3) | 0.0567 (6) | |
H18A | −0.0721 | −0.4603 | 1.0949 | 0.068* | |
H18B | −0.0808 | −0.2804 | 1.0919 | 0.068* | |
C19 | −0.09948 (5) | −0.4099 (3) | 0.9274 (3) | 0.0599 (7) | |
H19A | −0.0946 | −0.4989 | 0.8675 | 0.072* | |
H19B | −0.1032 | −0.3190 | 0.8640 | 0.072* | |
C20 | −0.12493 (5) | −0.4535 (3) | 0.9980 (3) | 0.0606 (7) | |
H20A | −0.1213 | −0.5444 | 1.0615 | 0.073* | |
H20B | −0.1299 | −0.3645 | 1.0576 | 0.073* | |
C21 | −0.14827 (5) | −0.4942 (4) | 0.8926 (3) | 0.0752 (8) | |
H21A | −0.1433 | −0.5831 | 0.8329 | 0.090* | |
H21B | −0.1520 | −0.4032 | 0.8292 | 0.090* | |
C22 | −0.17372 (6) | −0.5381 (5) | 0.9634 (4) | 0.0953 (10) | |
H22A | −0.1876 | −0.5615 | 0.8897 | 0.143* | |
H22B | −0.1791 | −0.4500 | 1.0214 | 0.143* | |
H22C | −0.1705 | −0.6304 | 1.0239 | 0.143* | |
C23 | 0.14154 (4) | 0.4670 (3) | 0.5843 (2) | 0.0419 (5) | |
H23A | 0.1381 | 0.3803 | 0.5158 | 0.050* | |
H23B | 0.1491 | 0.5562 | 0.5341 | 0.050* | |
C24 | 0.11629 (4) | 0.5164 (3) | 0.6499 (2) | 0.0442 (5) | |
H24A | 0.1202 | 0.6058 | 0.7148 | 0.053* | |
H24B | 0.1102 | 0.4284 | 0.7074 | 0.053* | |
C25 | 0.09390 (4) | 0.5642 (3) | 0.5396 (2) | 0.0451 (5) | |
H25A | 0.0998 | 0.6536 | 0.4831 | 0.054* | |
H25B | 0.0900 | 0.4755 | 0.4738 | 0.054* | |
C26 | 0.06862 (4) | 0.6109 (3) | 0.6091 (2) | 0.0482 (6) | |
H26A | 0.0726 | 0.7009 | 0.6732 | 0.058* | |
H26B | 0.0633 | 0.5223 | 0.6683 | 0.058* | |
C27 | 0.04518 (5) | 0.6556 (3) | 0.5041 (2) | 0.0495 (6) | |
H27A | 0.0503 | 0.7454 | 0.4457 | 0.059* | |
H27B | 0.0411 | 0.5662 | 0.4394 | 0.059* | |
C28 | 0.02041 (4) | 0.6994 (3) | 0.5790 (2) | 0.0495 (6) | |
H28A | 0.0246 | 0.7888 | 0.6434 | 0.059* | |
H28B | 0.0156 | 0.6096 | 0.6384 | 0.059* | |
C29 | −0.00362 (5) | 0.7435 (3) | 0.4789 (2) | 0.0518 (6) | |
H29A | −0.0080 | 0.6546 | 0.4142 | 0.062* | |
H29B | 0.0009 | 0.8342 | 0.4201 | 0.062* | |
C30 | −0.02816 (4) | 0.7856 (3) | 0.5588 (2) | 0.0522 (6) | |
H30A | −0.0325 | 0.6951 | 0.6186 | 0.063* | |
H30B | −0.0237 | 0.8748 | 0.6231 | 0.063* | |
C31 | −0.05271 (5) | 0.8290 (3) | 0.4630 (3) | 0.0535 (6) | |
H31A | −0.0574 | 0.7397 | 0.3991 | 0.064* | |
H31B | −0.0486 | 0.9196 | 0.4031 | 0.064* | |
C32 | −0.07674 (4) | 0.8709 (3) | 0.5480 (2) | 0.0545 (6) | |
H32A | −0.0806 | 0.7807 | 0.6091 | 0.065* | |
H32B | −0.0720 | 0.9607 | 0.6110 | 0.065* | |
C33 | −0.10175 (5) | 0.9127 (3) | 0.4554 (2) | 0.0542 (6) | |
H33A | −0.1066 | 0.8231 | 0.3923 | 0.065* | |
H33B | −0.0980 | 1.0033 | 0.3946 | 0.065* | |
C34 | −0.12536 (5) | 0.9535 (3) | 0.5426 (3) | 0.0562 (6) | |
H34A | −0.1289 | 0.8629 | 0.6039 | 0.067* | |
H34B | −0.1205 | 1.0431 | 0.6057 | 0.067* | |
C35 | −0.15089 (5) | 0.9956 (3) | 0.4526 (3) | 0.0573 (7) | |
H35A | −0.1560 | 0.9055 | 0.3907 | 0.069* | |
H35B | −0.1474 | 1.0855 | 0.3904 | 0.069* | |
C36 | −0.17411 (5) | 1.0383 (4) | 0.5426 (3) | 0.0585 (7) | |
H36A | −0.1771 | 0.9498 | 0.6072 | 0.070* | |
H36B | −0.1691 | 1.1305 | 0.6021 | 0.070* | |
C37 | −0.19989 (5) | 1.0751 (4) | 0.4554 (3) | 0.0706 (9) | |
H37A | −0.2055 | 0.9813 | 0.3994 | 0.085* | |
H37B | −0.1968 | 1.1606 | 0.3878 | 0.085* | |
C38 | −0.22209 (6) | 1.1239 (4) | 0.5483 (3) | 0.0829 (9) | |
H38A | −0.2381 | 1.1441 | 0.4875 | 0.124* | |
H38B | −0.2170 | 1.2193 | 0.6011 | 0.124* | |
H38C | −0.2253 | 1.0395 | 0.6152 | 0.124* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Br1 | 0.03922 (15) | 0.1009 (2) | 0.1034 (2) | 0.02751 (17) | 0.02233 (13) | 0.0018 (2) |
Br2 | 0.05548 (17) | 0.1022 (2) | 0.05902 (13) | 0.00078 (17) | 0.02555 (11) | −0.00573 (16) |
O1 | 0.0394 (9) | 0.0432 (8) | 0.0460 (8) | 0.0086 (7) | 0.0122 (6) | 0.0078 (7) |
O2 | 0.0338 (9) | 0.0651 (11) | 0.0443 (8) | 0.0207 (8) | 0.0067 (6) | 0.0098 (7) |
C1 | 0.0251 (11) | 0.0487 (15) | 0.0649 (14) | 0.0019 (10) | 0.0069 (10) | −0.0076 (11) |
C2 | 0.0369 (12) | 0.0472 (14) | 0.0488 (12) | −0.0037 (11) | 0.0144 (10) | −0.0078 (10) |
C3 | 0.0329 (13) | 0.0474 (15) | 0.0468 (12) | 0.0016 (10) | 0.0046 (9) | 0.0010 (10) |
C4 | 0.0234 (11) | 0.0374 (13) | 0.0480 (12) | 0.0027 (9) | 0.0029 (8) | −0.0030 (9) |
C5 | 0.0263 (11) | 0.0344 (11) | 0.0470 (12) | −0.0037 (9) | 0.0038 (9) | −0.0028 (9) |
C6 | 0.0225 (11) | 0.0460 (14) | 0.0543 (12) | 0.0021 (10) | −0.0007 (9) | −0.0010 (10) |
C7 | 0.0286 (12) | 0.0523 (15) | 0.0523 (13) | 0.0059 (11) | −0.0037 (10) | 0.0133 (11) |
C8 | 0.0394 (12) | 0.0516 (14) | 0.0397 (11) | 0.0025 (11) | −0.0042 (9) | 0.0122 (10) |
C9 | 0.0354 (13) | 0.0558 (14) | 0.0432 (12) | −0.0045 (11) | 0.0016 (9) | 0.0021 (10) |
C10 | 0.0399 (13) | 0.0567 (15) | 0.0409 (11) | −0.0069 (11) | 0.0032 (9) | 0.0032 (10) |
C11 | 0.0399 (14) | 0.0607 (16) | 0.0483 (13) | −0.0076 (11) | 0.0071 (10) | 0.0016 (10) |
C12 | 0.0372 (13) | 0.0618 (15) | 0.0481 (12) | −0.0042 (12) | 0.0051 (10) | 0.0010 (11) |
C13 | 0.0393 (15) | 0.0642 (16) | 0.0512 (13) | −0.0077 (12) | 0.0079 (10) | −0.0020 (11) |
C14 | 0.0363 (13) | 0.0621 (16) | 0.0538 (13) | −0.0066 (12) | 0.0037 (10) | 0.0015 (12) |
C15 | 0.0424 (15) | 0.0686 (18) | 0.0522 (13) | −0.0082 (12) | 0.0084 (11) | 0.0003 (11) |
C16 | 0.0382 (14) | 0.0708 (18) | 0.0534 (13) | −0.0072 (12) | 0.0045 (10) | 0.0008 (12) |
C17 | 0.0389 (15) | 0.0754 (18) | 0.0573 (14) | −0.0093 (13) | 0.0110 (11) | 0.0054 (12) |
C18 | 0.0370 (14) | 0.0742 (18) | 0.0594 (14) | −0.0102 (12) | 0.0074 (10) | 0.0035 (12) |
C19 | 0.0399 (14) | 0.082 (2) | 0.0582 (15) | −0.0121 (14) | 0.0093 (11) | 0.0050 (13) |
C20 | 0.0395 (14) | 0.0783 (18) | 0.0646 (15) | −0.0063 (13) | 0.0087 (11) | 0.0055 (13) |
C21 | 0.0376 (15) | 0.105 (3) | 0.0832 (19) | −0.0136 (16) | 0.0081 (13) | 0.0021 (16) |
C22 | 0.0400 (18) | 0.129 (3) | 0.118 (3) | −0.0182 (19) | 0.0089 (16) | 0.008 (2) |
C23 | 0.0280 (12) | 0.0506 (14) | 0.0474 (12) | 0.0052 (10) | 0.0050 (9) | 0.0082 (10) |
C24 | 0.0329 (12) | 0.0549 (15) | 0.0453 (12) | 0.0069 (11) | 0.0068 (9) | 0.0058 (10) |
C25 | 0.0312 (12) | 0.0568 (15) | 0.0482 (12) | 0.0095 (11) | 0.0081 (9) | 0.0039 (10) |
C26 | 0.0313 (12) | 0.0657 (16) | 0.0478 (12) | 0.0115 (12) | 0.0041 (9) | 0.0027 (11) |
C27 | 0.0341 (13) | 0.0648 (16) | 0.0502 (13) | 0.0098 (12) | 0.0061 (10) | 0.0013 (11) |
C28 | 0.0314 (12) | 0.0655 (17) | 0.0515 (12) | 0.0112 (11) | 0.0028 (9) | −0.0006 (11) |
C29 | 0.0343 (13) | 0.0702 (17) | 0.0514 (13) | 0.0092 (12) | 0.0062 (10) | −0.0001 (11) |
C30 | 0.0301 (12) | 0.0715 (18) | 0.0548 (13) | 0.0124 (11) | 0.0027 (9) | 0.0017 (12) |
C31 | 0.0357 (14) | 0.0724 (18) | 0.0528 (13) | 0.0109 (12) | 0.0063 (11) | 0.0027 (12) |
C32 | 0.0297 (12) | 0.0799 (18) | 0.0535 (13) | 0.0136 (12) | 0.0010 (10) | 0.0025 (11) |
C33 | 0.0378 (13) | 0.0763 (19) | 0.0488 (13) | 0.0083 (12) | 0.0043 (10) | 0.0019 (12) |
C34 | 0.0290 (13) | 0.0838 (18) | 0.0557 (14) | 0.0123 (13) | 0.0026 (10) | 0.0023 (12) |
C35 | 0.0388 (14) | 0.083 (2) | 0.0503 (13) | 0.0137 (13) | 0.0056 (10) | 0.0026 (13) |
C36 | 0.0384 (14) | 0.0829 (19) | 0.0542 (14) | 0.0110 (13) | 0.0026 (11) | −0.0015 (13) |
C37 | 0.0430 (17) | 0.101 (3) | 0.0682 (18) | 0.0147 (16) | 0.0033 (13) | 0.0016 (16) |
C38 | 0.0439 (17) | 0.112 (3) | 0.092 (2) | 0.0294 (17) | 0.0051 (14) | −0.0060 (19) |
Br1—C1 | 1.881 (2) | C20—H20B | 0.9700 |
Br2—C2 | 1.893 (2) | C21—C22 | 1.521 (4) |
O1—C5 | 1.357 (2) | C21—H21A | 0.9700 |
O1—C7 | 1.451 (3) | C21—H21B | 0.9700 |
O2—C4 | 1.360 (2) | C22—H22A | 0.9600 |
O2—C23 | 1.435 (3) | C22—H22B | 0.9600 |
C1—C2 | 1.369 (3) | C22—H22C | 0.9600 |
C1—C6 | 1.401 (3) | C23—C24 | 1.501 (3) |
C2—C3 | 1.388 (3) | C23—H23A | 0.9700 |
C3—C4 | 1.383 (3) | C23—H23B | 0.9700 |
C3—H3 | 0.9300 | C24—C25 | 1.515 (3) |
C4—C5 | 1.393 (3) | C24—H24A | 0.9700 |
C5—C6 | 1.374 (3) | C24—H24B | 0.9700 |
C6—H6 | 0.9300 | C25—C26 | 1.514 (3) |
C7—C8 | 1.506 (3) | C25—H25A | 0.9700 |
C7—H7A | 0.9700 | C25—H25B | 0.9700 |
C7—H7B | 0.9700 | C26—C27 | 1.516 (3) |
C8—C9 | 1.517 (3) | C26—H26A | 0.9700 |
C8—H8A | 0.9700 | C26—H26B | 0.9700 |
C8—H8B | 0.9700 | C27—C28 | 1.510 (3) |
C9—C10 | 1.525 (3) | C27—H27A | 0.9700 |
C9—H9A | 0.9700 | C27—H27B | 0.9700 |
C9—H9B | 0.9700 | C28—C29 | 1.511 (3) |
C10—C11 | 1.512 (3) | C28—H28A | 0.9700 |
C10—H11A | 0.9700 | C28—H28B | 0.9700 |
C10—H11B | 0.9700 | C29—C30 | 1.522 (3) |
C11—C12 | 1.515 (3) | C29—H29A | 0.9700 |
C11—H10A | 0.9700 | C29—H29B | 0.9700 |
C11—H10B | 0.9700 | C30—C31 | 1.508 (3) |
C12—C13 | 1.511 (3) | C30—H30A | 0.9700 |
C12—H12A | 0.9700 | C30—H30B | 0.9700 |
C12—H12B | 0.9700 | C31—C32 | 1.526 (3) |
C13—C14 | 1.519 (3) | C31—H31A | 0.9700 |
C13—H13A | 0.9700 | C31—H31B | 0.9700 |
C13—H13B | 0.9700 | C32—C33 | 1.508 (3) |
C14—C15 | 1.506 (3) | C32—H32A | 0.9700 |
C14—H14A | 0.9700 | C32—H32B | 0.9700 |
C14—H14B | 0.9700 | C33—C34 | 1.519 (3) |
C15—C16 | 1.518 (3) | C33—H33A | 0.9700 |
C15—H15A | 0.9700 | C33—H33B | 0.9700 |
C15—H15B | 0.9700 | C34—C35 | 1.518 (3) |
C16—C17 | 1.499 (3) | C34—H34A | 0.9700 |
C16—H16A | 0.9700 | C34—H34B | 0.9700 |
C16—H16B | 0.9700 | C35—C36 | 1.522 (3) |
C17—C18 | 1.524 (3) | C35—H35A | 0.9700 |
C17—H17A | 0.9700 | C35—H35B | 0.9700 |
C17—H17B | 0.9700 | C36—C37 | 1.505 (3) |
C18—C19 | 1.508 (3) | C36—H36A | 0.9700 |
C18—H18A | 0.9700 | C36—H36B | 0.9700 |
C18—H18B | 0.9700 | C37—C38 | 1.511 (4) |
C19—C20 | 1.519 (3) | C37—H37A | 0.9700 |
C19—H19A | 0.9700 | C37—H37B | 0.9700 |
C19—H19B | 0.9700 | C38—H38A | 0.9600 |
C20—C21 | 1.507 (3) | C38—H38B | 0.9600 |
C20—H20A | 0.9700 | C38—H38C | 0.9600 |
C5—O1—C7 | 118.08 (16) | C22—C21—H21A | 108.7 |
C4—O2—C23 | 118.49 (15) | C20—C21—H21B | 108.7 |
C2—C1—C6 | 119.92 (19) | C22—C21—H21B | 108.7 |
C2—C1—Br1 | 122.46 (16) | H21A—C21—H21B | 107.6 |
C6—C1—Br1 | 117.60 (17) | C21—C22—H22A | 109.5 |
C1—C2—C3 | 120.64 (19) | C21—C22—H22B | 109.5 |
C1—C2—Br2 | 121.74 (16) | H22A—C22—H22B | 109.5 |
C3—C2—Br2 | 117.60 (17) | C21—C22—H22C | 109.5 |
C4—C3—C2 | 119.4 (2) | H22A—C22—H22C | 109.5 |
C4—C3—H3 | 120.3 | H22B—C22—H22C | 109.5 |
C2—C3—H3 | 120.3 | O2—C23—C24 | 105.69 (16) |
O2—C4—C3 | 123.98 (19) | O2—C23—H23A | 110.6 |
O2—C4—C5 | 115.67 (17) | C24—C23—H23A | 110.6 |
C3—C4—C5 | 120.34 (19) | O2—C23—H23B | 110.6 |
O1—C5—C6 | 124.96 (19) | C24—C23—H23B | 110.6 |
O1—C5—C4 | 115.26 (18) | H23A—C23—H23B | 108.7 |
C6—C5—C4 | 119.76 (19) | C23—C24—C25 | 113.97 (17) |
C5—C6—C1 | 119.89 (19) | C23—C24—H24A | 108.8 |
C5—C6—H6 | 120.1 | C25—C24—H24A | 108.8 |
C1—C6—H6 | 120.1 | C23—C24—H24B | 108.8 |
O1—C7—C8 | 106.76 (17) | C25—C24—H24B | 108.8 |
O1—C7—H7A | 110.4 | H24A—C24—H24B | 107.7 |
C8—C7—H7A | 110.4 | C26—C25—C24 | 112.64 (17) |
O1—C7—H7B | 110.4 | C26—C25—H25A | 109.1 |
C8—C7—H7B | 110.4 | C24—C25—H25A | 109.1 |
H7A—C7—H7B | 108.6 | C26—C25—H25B | 109.1 |
C7—C8—C9 | 112.76 (18) | C24—C25—H25B | 109.1 |
C7—C8—H8A | 109.0 | H25A—C25—H25B | 107.8 |
C9—C8—H8A | 109.0 | C25—C26—C27 | 115.21 (17) |
C7—C8—H8B | 109.0 | C25—C26—H26A | 108.5 |
C9—C8—H8B | 109.0 | C27—C26—H26A | 108.5 |
H8A—C8—H8B | 107.8 | C25—C26—H26B | 108.5 |
C8—C9—C10 | 114.92 (17) | C27—C26—H26B | 108.5 |
C8—C9—H9A | 108.5 | H26A—C26—H26B | 107.5 |
C10—C9—H9A | 108.5 | C28—C27—C26 | 113.06 (18) |
C8—C9—H9B | 108.5 | C28—C27—H27A | 109.0 |
C10—C9—H9B | 108.5 | C26—C27—H27A | 109.0 |
H9A—C9—H9B | 107.5 | C28—C27—H27B | 109.0 |
C11—C10—C9 | 113.27 (16) | C26—C27—H27B | 109.0 |
C11—C10—H11A | 108.9 | H27A—C27—H27B | 107.8 |
C9—C10—H11A | 108.9 | C27—C28—C29 | 115.14 (18) |
C11—C10—H11B | 108.9 | C27—C28—H28A | 108.5 |
C9—C10—H11B | 108.9 | C29—C28—H28A | 108.5 |
H11A—C10—H11B | 107.7 | C27—C28—H28B | 108.5 |
C10—C11—C12 | 115.50 (18) | C29—C28—H28B | 108.5 |
C10—C11—H10A | 108.4 | H28A—C28—H28B | 107.5 |
C12—C11—H10A | 108.4 | C28—C29—C30 | 113.36 (18) |
C10—C11—H10B | 108.4 | C28—C29—H29A | 108.9 |
C12—C11—H10B | 108.4 | C30—C29—H29A | 108.9 |
H10A—C11—H10B | 107.5 | C28—C29—H29B | 108.9 |
C13—C12—C11 | 113.76 (18) | C30—C29—H29B | 108.9 |
C13—C12—H12A | 108.8 | H29A—C29—H29B | 107.7 |
C11—C12—H12A | 108.8 | C31—C30—C29 | 115.16 (18) |
C13—C12—H12B | 108.8 | C31—C30—H30A | 108.5 |
C11—C12—H12B | 108.8 | C29—C30—H30A | 108.5 |
H12A—C12—H12B | 107.7 | C31—C30—H30B | 108.5 |
C12—C13—C14 | 115.21 (19) | C29—C30—H30B | 108.5 |
C12—C13—H13A | 108.5 | H30A—C30—H30B | 107.5 |
C14—C13—H13A | 108.5 | C30—C31—C32 | 113.24 (19) |
C12—C13—H13B | 108.5 | C30—C31—H31A | 108.9 |
C14—C13—H13B | 108.5 | C32—C31—H31A | 108.9 |
H13A—C13—H13B | 107.5 | C30—C31—H31B | 108.9 |
C15—C14—C13 | 113.97 (19) | C32—C31—H31B | 108.9 |
C15—C14—H14A | 108.8 | H31A—C31—H31B | 107.7 |
C13—C14—H14A | 108.8 | C33—C32—C31 | 114.63 (19) |
C15—C14—H14B | 108.8 | C33—C32—H32A | 108.6 |
C13—C14—H14B | 108.8 | C31—C32—H32A | 108.6 |
H14A—C14—H14B | 107.7 | C33—C32—H32B | 108.6 |
C14—C15—C16 | 115.77 (19) | C31—C32—H32B | 108.6 |
C14—C15—H15A | 108.3 | H32A—C32—H32B | 107.6 |
C16—C15—H15A | 108.3 | C32—C33—C34 | 113.54 (18) |
C14—C15—H15B | 108.3 | C32—C33—H33A | 108.9 |
C16—C15—H15B | 108.3 | C34—C33—H33A | 108.9 |
H15A—C15—H15B | 107.4 | C32—C33—H33B | 108.9 |
C17—C16—C15 | 114.32 (19) | C34—C33—H33B | 108.9 |
C17—C16—H16A | 108.7 | H33A—C33—H33B | 107.7 |
C15—C16—H16A | 108.7 | C35—C34—C33 | 114.82 (19) |
C17—C16—H16B | 108.7 | C35—C34—H34A | 108.6 |
C15—C16—H16B | 108.7 | C33—C34—H34A | 108.6 |
H16A—C16—H16B | 107.6 | C35—C34—H34B | 108.6 |
C16—C17—C18 | 115.2 (2) | C33—C34—H34B | 108.6 |
C16—C17—H17A | 108.5 | H34A—C34—H34B | 107.5 |
C18—C17—H17A | 108.5 | C34—C35—C36 | 113.76 (19) |
C16—C17—H17B | 108.5 | C34—C35—H35A | 108.8 |
C18—C17—H17B | 108.5 | C36—C35—H35A | 108.8 |
H17A—C17—H17B | 107.5 | C34—C35—H35B | 108.8 |
C19—C18—C17 | 113.8 (2) | C36—C35—H35B | 108.8 |
C19—C18—H18A | 108.8 | H35A—C35—H35B | 107.7 |
C17—C18—H18A | 108.8 | C37—C36—C35 | 114.6 (2) |
C19—C18—H18B | 108.8 | C37—C36—H36A | 108.6 |
C17—C18—H18B | 108.8 | C35—C36—H36A | 108.6 |
H18A—C18—H18B | 107.7 | C37—C36—H36B | 108.6 |
C18—C19—C20 | 114.9 (2) | C35—C36—H36B | 108.6 |
C18—C19—H19A | 108.5 | H36A—C36—H36B | 107.6 |
C20—C19—H19A | 108.5 | C36—C37—C38 | 113.0 (2) |
C18—C19—H19B | 108.5 | C36—C37—H37A | 109.0 |
C20—C19—H19B | 108.5 | C38—C37—H37A | 109.0 |
H19A—C19—H19B | 107.5 | C36—C37—H37B | 109.0 |
C21—C20—C19 | 114.5 (2) | C38—C37—H37B | 109.0 |
C21—C20—H20A | 108.6 | H37A—C37—H37B | 107.8 |
C19—C20—H20A | 108.6 | C37—C38—H38A | 109.5 |
C21—C20—H20B | 108.6 | C37—C38—H38B | 109.5 |
C19—C20—H20B | 108.6 | H38A—C38—H38B | 109.5 |
H20A—C20—H20B | 107.6 | C37—C38—H38C | 109.5 |
C20—C21—C22 | 114.4 (2) | H38A—C38—H38C | 109.5 |
C20—C21—H21A | 108.7 | H38B—C38—H38C | 109.5 |
C6—C1—C2—C3 | 1.1 (3) | C10—C11—C12—C13 | 179.2 (2) |
Br1—C1—C2—C3 | 179.52 (16) | C11—C12—C13—C14 | −179.4 (2) |
C6—C1—C2—Br2 | −177.56 (16) | C12—C13—C14—C15 | 179.3 (2) |
Br1—C1—C2—Br2 | 0.9 (3) | C13—C14—C15—C16 | −179.8 (2) |
C1—C2—C3—C4 | −0.6 (3) | C14—C15—C16—C17 | 179.2 (2) |
Br2—C2—C3—C4 | 178.09 (16) | C15—C16—C17—C18 | 179.9 (2) |
C23—O2—C4—C3 | 17.4 (3) | C16—C17—C18—C19 | 179.6 (2) |
C23—O2—C4—C5 | −161.66 (19) | C17—C18—C19—C20 | −179.8 (2) |
C2—C3—C4—O2 | 179.9 (2) | C18—C19—C20—C21 | −179.9 (2) |
C2—C3—C4—C5 | −1.0 (3) | C19—C20—C21—C22 | 179.9 (3) |
C7—O1—C5—C6 | −15.4 (3) | C4—O2—C23—C24 | 174.14 (18) |
C7—O1—C5—C4 | 163.21 (19) | O2—C23—C24—C25 | −175.97 (19) |
O2—C4—C5—O1 | 2.6 (3) | C23—C24—C25—C26 | 179.1 (2) |
C3—C4—C5—O1 | −176.50 (18) | C24—C25—C26—C27 | −178.4 (2) |
O2—C4—C5—C6 | −178.69 (19) | C25—C26—C27—C28 | 179.4 (2) |
C3—C4—C5—C6 | 2.2 (3) | C26—C27—C28—C29 | −179.5 (2) |
O1—C5—C6—C1 | 176.85 (19) | C27—C28—C29—C30 | 179.6 (2) |
C4—C5—C6—C1 | −1.7 (3) | C28—C29—C30—C31 | −179.5 (2) |
C2—C1—C6—C5 | 0.1 (3) | C29—C30—C31—C32 | −179.7 (2) |
Br1—C1—C6—C5 | −178.44 (16) | C30—C31—C32—C33 | −179.2 (2) |
C5—O1—C7—C8 | −160.79 (18) | C31—C32—C33—C34 | 179.9 (2) |
O1—C7—C8—C9 | 62.6 (3) | C32—C33—C34—C35 | −179.8 (2) |
C7—C8—C9—C10 | 174.3 (2) | C33—C34—C35—C36 | −179.2 (2) |
C8—C9—C10—C11 | 176.9 (2) | C34—C35—C36—C37 | −178.0 (3) |
C9—C10—C11—C12 | −178.7 (2) | C35—C36—C37—C38 | −177.4 (3) |
Experimental details
(II) | (III) | |
Crystal data | ||
Chemical formula | C26H44Br2O2 | C38H68Br2O2 |
Mr | 548.43 | 716.72 |
Crystal system, space group | Monoclinic, C2/c | Monoclinic, Cc |
Temperature (K) | 150 | 294 |
a, b, c (Å) | 67.0788 (15), 4.4717 (1), 18.2399 (4) | 50.158 (5), 8.360 (3), 9.248 (3) |
β (°) | 101.216 (2) | 94.136 (5) |
V (Å3) | 5366.7 (2) | 3868 (2) |
Z | 8 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 3.04 | 2.13 |
Crystal size (mm) | 0.56 × 0.27 × 0.07 | 0.58 × 0.32 × 0.10 |
Data collection | ||
Diffractometer | Oxford Gemini S Ultra CCD area-detector diffractometer | Oxford Gemini S Ultra CCD area-detector diffractometer |
Absorption correction | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) | Multi-scan (CrysAlis PRO; Oxford Diffraction, 2009) |
Tmin, Tmax | 0.42, 0.78 | 0.45, 0.82 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 28792, 5387, 4981 | 16641, 6905, 4926 |
Rint | 0.068 | 0.024 |
(sin θ/λ)max (Å−1) | 0.620 | 0.639 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.069, 0.184, 1.21 | 0.024, 0.053, 0.84 |
No. of reflections | 5387 | 6905 |
No. of parameters | 271 | 379 |
No. of restraints | 0 | 2 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
w = 1/[σ2(Fo2) + (0.0236P)2 + 122.7172P] where P = (Fo2 + 2Fc2)/3 | w = 1/[σ2(Fo2) + (0.0318P)2] where P = (Fo2 + 2Fc2)/3 | |
Δρmax, Δρmin (e Å−3) | 1.67, −0.95 | 0.26, −0.18 |
Absolute structure | ? | Flack (1983), with how many Friedel pairs? |
Absolute structure parameter | ? | 0.087 (5) |
Computer programs: CrysAlis PRO (Oxford Diffraction, 2009), SHELXS97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).
The mean interaliphatic distance is 3.80Å. |
C—X···(X—C)' | X···X' | (C—X)···X' | X···(X—C)' | Interaction type |
C1—Br1···(Br1-C1)i | 3.7722 (15) | 118.6 (2) | 118.6 (2) | I |
C1—Br1···(Br2-C2)i | 3.6437 (10) | 171.5 (2) | 122.1 (2) | II |
C1—Br1···(Br2-C2)ii | 3.8704 (11) | 73.0 (2) | 91.0 (2) | I |
Symmetry codes: (i) -x + 1/2, -y + 1/2, -z + 1; (ii) x, y - 1, z. |
Cg1 is the centre of the C1–C6 ring. The mean interaliphatic distance is 3.90 Å. |
C—X···Cg | C···X | X···Cg | C···Cg | C—X···Cg |
C2—Br2···Cg1i | 1.893 | 3.976 (3) | 4.941 | 109.1 |
Symmetry code: (i) x, -y + 1, z - 1/2. |
The design of advanced materials exhibiting selected crystalline structures based on specific intermolecular interactions is nowadays one of the main conceptual tools in materials science. Knowledge of the strength and directionality of noncovalent interactions (hydrogen bonds, π–π stacking, halogen bonds etc.) allows for such design, and hundreds of successful examples can be found in growing research fields like crystal engineering (Desiraju, 2003) or supramolecular chemistry (Steed & Atwood, 2009; Bruce, 2012). In most cases, the structure is governed by one prevalent interaction (and was designed on this basis). The predictability of the crystalline structure a given compound will adopt, on the basis of the intermolecular interactions it can exhibit, is high in such cases, but diminishes when the number of competing interactions rises. One way to explore the relative influence of different interactions, keeping a few constant and allowing for a smooth variation of just one or two, is to work with different members of an homologous series.
In a study of the structure of dihalogenodimethoxybenzene compounds (Cukiernik et al., 2008), we found that the structure of 1,2-dibromo-4,5-dimethoxybenzene, (I) (Scheme 1), results from a combination of π–π, dipolar and halogen-bonding interactions. In this work, we report the crystal structures of two heavier homologues of this series, namely 1,2-dibromo-4,5-bis(decyloxy)benzene, (II), and 1,2-dibromo-4,5-bis(hexadecyloxy)benzene, (III) (Scheme 1), and analyse the relative influence halogen bonding, π–π stacking and van der Waals interactions have on the structures and, consequently, on some physical properties of these compounds.
Fig. 1 presents molecular views of both (II) and (III), where their striking `jellyfish-like' geometry (which defines their packing characteristics in some way) is apparent. The bond lengths and angles are featureless, and a distinguishing fact is the `straight' character of the terminal aliphatic chains, as disclosed by the extremely narrow span of the C—C—C—C torsion angles, viz. 171.0 (6)–179.9 (10)° in (II) and 174.13 (11)–179.9 (2)° in (III).
According to their geometric disposition, C—X···X—C interactions (X = halogen) have historically been divided into types I and II (see Scheme 2). [For further details on the subject, see Desiraju & Parthasarathy (1989, and references therein)]. In the case of (II), molecules interact weakly via C—Br···(Br—C) contacts of types I and II, some of them at the upper limit for stabilizing Br···Br distances {due to cumulative experimental evidence, there is an increasing tendency to accept small (though not negligible) stabilization effects arising from rather long Br···Br contacts [up to 10% longer than twice the Br van der Waals radius, ~3.7 Å; see, for example, Jones & Kuś (2007, 2011) and Al-Far & Ali (2007)]}, and details of these are presented in Table 1.
The first and second entries, corresponding respectively to type I and type II contacts (Fig. 2a, labelled A), define dimeric units arranged in a head-to-head fashion (Fig. 2a, labelled B). In turn, as a consequence of a third C—Br···(Br—C) type-I contact (Table 1, entry 3) in conjunction with van der Waals interactions between aliphatic chains, these dimeric units are held together as one-dimensional strands parallel to b. van der Waals interactions between parallel aliphatic chains also link the dimeric units along c, defining broad planar arrays parallel to (100), \sim a/2 wide along a (Is this Fig. 2a, the part labelled C?).
Fig. 2(b) gives a simplified view of the way in which both kinds of Br···Br' interactions build up.
The case of compound (III) is similar in general terms, viz. leading van der Waals interactions between aliphatic chains result in broad planar arrays parallel to (100), but the results are realised in quite different ways. To begin with, the head-to-head contacts joining antiparallel units in (II) are replaced by noticebly weaker C—Br···π contacts (Table 2) between parallel groups in (III), as shown in Fig. 3(a) (labelled A). These halogen···π interactions, presented in detail in Fig. 4, define columnar arrays along c (Fig. 3b, labelled B), which in turn interleave their long aliphatic chains, linking them into broad planar arrays parallel to (100), ~a/2 wide along a (Fig. 3, labelled C).
These results are of significance for interpreting some physical properties of these compounds, namely their melting point (m.p.). Indeed, the trend of the m.p. along the whole homologous series, according to literature data (Sauer & Wegner, 1988; Kalashnikova et al., 2003; Wohrle & Schmidt, 1988; Hanack et al., 1990), is shown in Fig. 5. In order to be able to discuss this trend in terms of the crystalline structures solved here, we measured the m.p. of the structurally characterized compounds directly by differential scanning calorimetry (DSC) on single crystals from the same crop used for structure elucidation. Single crystals of (II) melted at 316.5 K (ΔH = 66 kJ mol-1), and single crystals of (III) melted at 332.5 K (ΔH = 86 kJ mol-1), very close to the previously reported values for powder samples. This agreement validates the use of the present structural information for the interpretation of the m.p. trend along the whole series.
This kind of behaviour [an initial decrease in m.p. for increasing chain length (n), up to a certain n value, then a progressive increase in m.p. for further increase in n, up to a limiting value] is frequently found in homologous series with polar components (aliphatic alcohols, aliphatic carboxylic acids etc.; Lutton, 1967; Weast, 1986) and is often interpreted in terms of a diblock molecular architecture, in which both molecular blocks (here denoted 1 and 2) exhibit different packing requirements. For a homologous series, one of the molecular blocks (e.g. 2) is the aliphatic chain; in such a case, the usual argument takes the form that, for short aliphatic chains, the packing is governed by the 1 block; a progressive increase in chain length progressively disturbs this packing, facilitating the melting process. For long-chain homologues, the packing of the aliphatic chains is the main driving force for the crystalline structure; in those cases, the 1 block acts as a disturbing agent for the packing, this effect being stronger (lower m.p.) as chain length decreases. These kinds of arguments are found in the fields of physical organic chemistry, polymers and liquid crystals (Platé Shibaev, 1974; Weber et al., 1990; Ibn-Elhaj et al., 1992). However, even if accepted and often based on powder X-ray diffraction evidence, they are not always supported by single-crystal crystallographic evidence.
In the present case, the structures of (I), (II) and (III) provide direct experimental structural support for this interpretation. Indeed, the crystalline structure of (I) is essentially built up by π–π and halogen-bond interactions, while the prevalent interactions driving the structures of (II) and (III) are van der Waals interactions between the aliphatic chains. In the case of (II), halogen C—Br···(Br—C) contacts are still present and contribute to the global structure. In the case of (III), van der Waals interactions between the aliphatic chains are almost exclusive, weaker C—Br···(ring centroid) interactions being the only additional interactions detected.
Further possible steps for providing additional evidence for the homologous series under study could be to crystallize and solve the structure of the n = 2 homologue, as well as to find the `transition point', i.e. the n value for which the head-to-head arrangement found in (II) is replaced by the `tail-contact' arrangement found in (III). Further work on the subject is in progress.