The title crown ether, C28H40O8, crystallizes in an orthorhombic cell with the full molecule generated from crystallographic inversion symmetry. The ring consists of 30 atoms which could potentially influence the size of the ring cavity and the conformational flexibility. Unusual C-O-C-C and O-C-C-O torsion-angle geometries, deviating by as much as 30° from their ideal values, have been observed.
Supporting information
CCDC reference: 145549
The dimeric compound was formed as a side product in the synthesis of the
monomer 1,3-xylyl-15-crown-4 reported by Gray et al. (1976, 1977).
Isolation and purification from the oligomeric fraction, followed by repeated
crystallization of the crude product from ethanol, produced crystals suitable
for an X-ray experiment.
All hydrogen atoms were constrained to ride on their parent carbon atom with
Uiso(H) = 1.2Ueq(C); C—H distances refined to 0.95 or 0.99 Å for aromatic CH and CH2 groups, respectively.
Data collection: Locally modified CAD4-Version 5 Software (Enraf-Nonius, 1989); cell refinement: SET4 (de Boer & Duisenberg, 1984); data reduction: HELENA (Spek, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: PLATON.
Crystal data top
C28H40O8 | F(000) = 1088 |
Mr = 504.60 | Dx = 1.294 Mg m−3 |
Orthorhombic, Pccn | Mo Kα (Zr filtered) radiation, λ = 0.71073 Å |
Hall symbol: -P 2ab 2ac | Cell parameters from 25 reflections |
a = 16.9096 (17) Å | θ = 14.0–17.9° |
b = 18.351 (2) Å | µ = 0.09 mm−1 |
c = 8.350 (2) Å | T = 100 K |
V = 2591.0 (8) Å3 | Block, colourless |
Z = 4 | 0.58 × 0.45 × 0.42 mm |
Data collection top
Enraf Nonius CAD-4F diffractometer | Rint = 0.028 |
Radiation source: rotating anode | θmax = 27.5°, θmin = 1.6° |
Graphite monochromator | h = 0→21 |
ω/2θ scans | k = −23→23 |
5946 measured reflections | l = 0→10 |
2976 independent reflections | 2 standard reflections every 60 min |
2337 reflections with I > 2σ(I) | intensity decay: 3.5% |
Refinement top
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)] = 0.043 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.109 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0469P)2 + 1.2483P] where P = (Fo2 + 2Fc2)/3 |
2976 reflections | (Δ/σ)max = 0.001 |
163 parameters | Δρmax = 0.56 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
Crystal data top
C28H40O8 | V = 2591.0 (8) Å3 |
Mr = 504.60 | Z = 4 |
Orthorhombic, Pccn | Mo Kα (Zr filtered) radiation |
a = 16.9096 (17) Å | µ = 0.09 mm−1 |
b = 18.351 (2) Å | T = 100 K |
c = 8.350 (2) Å | 0.58 × 0.45 × 0.42 mm |
Data collection top
Enraf Nonius CAD-4F diffractometer | Rint = 0.028 |
5946 measured reflections | 2 standard reflections every 60 min |
2976 independent reflections | intensity decay: 3.5% |
2337 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.109 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.56 e Å−3 |
2976 reflections | Δρmin = −0.22 e Å−3 |
163 parameters | |
Special details top
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. |
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) top | x | y | z | Uiso*/Ueq | |
O1 | −0.03830 (6) | 0.09811 (7) | 0.61773 (13) | 0.0269 (3) | |
O2 | 0.08263 (6) | 0.15216 (5) | 0.28697 (12) | 0.0192 (2) | |
O3 | 0.15828 (6) | 0.12745 (6) | −0.01500 (13) | 0.0223 (2) | |
O4 | 0.18470 (6) | 0.02467 (6) | −0.26293 (12) | 0.0210 (2) | |
C1 | −0.11489 (8) | 0.06066 (8) | 1.01751 (17) | 0.0176 (3) | |
H1 | −0.1009 | 0.0108 | 1.0284 | 0.021* | |
C2 | −0.16272 (8) | 0.09322 (8) | 1.13273 (17) | 0.0183 (3) | |
C3 | −0.18354 (9) | 0.16589 (8) | 1.11454 (19) | 0.0219 (3) | |
H3 | −0.2166 | 0.1886 | 1.1918 | 0.026* | |
C4 | −0.15638 (9) | 0.20573 (8) | 0.98418 (19) | 0.0233 (3) | |
H4 | −0.1704 | 0.2556 | 0.9735 | 0.028* | |
C5 | −0.10900 (8) | 0.17296 (8) | 0.86989 (18) | 0.0205 (3) | |
H5 | −0.0912 | 0.2001 | 0.7800 | 0.025* | |
C6 | −0.08736 (8) | 0.10007 (8) | 0.88669 (17) | 0.0180 (3) | |
C7 | −0.03018 (9) | 0.06551 (9) | 0.77082 (18) | 0.0232 (3) | |
H7A | 0.0246 | 0.0721 | 0.8100 | 0.028* | |
H7B | −0.0409 | 0.0126 | 0.7631 | 0.028* | |
C8 | 0.03278 (8) | 0.10001 (8) | 0.52810 (17) | 0.0197 (3) | |
H8A | 0.0501 | 0.0501 | 0.4999 | 0.024* | |
H8B | 0.0754 | 0.1242 | 0.5897 | 0.024* | |
C9 | 0.01299 (9) | 0.14305 (9) | 0.37931 (18) | 0.0209 (3) | |
H9A | −0.0275 | 0.1169 | 0.3158 | 0.025* | |
H9B | −0.0087 | 0.1913 | 0.4095 | 0.025* | |
C10 | 0.06613 (9) | 0.19243 (8) | 0.14525 (17) | 0.0208 (3) | |
H10A | 0.0479 | 0.2420 | 0.1739 | 0.025* | |
H10B | 0.0235 | 0.1681 | 0.0840 | 0.025* | |
C11 | 0.13910 (9) | 0.19735 (8) | 0.04474 (18) | 0.0213 (3) | |
H11A | 0.1301 | 0.2313 | −0.0455 | 0.026* | |
H11B | 0.1835 | 0.2163 | 0.1099 | 0.026* | |
C12 | 0.22508 (9) | 0.12963 (9) | −0.11801 (19) | 0.0241 (3) | |
H12A | 0.2701 | 0.1529 | −0.0622 | 0.029* | |
H12B | 0.2126 | 0.1588 | −0.2145 | 0.029* | |
C13 | 0.24675 (9) | 0.05381 (8) | −0.16576 (18) | 0.0215 (3) | |
H13A | 0.2970 | 0.0542 | −0.2266 | 0.026* | |
H13B | 0.2540 | 0.0232 | −0.0692 | 0.026* | |
C14 | −0.19017 (9) | 0.05190 (8) | 1.27946 (18) | 0.0211 (3) | |
H14A | −0.1579 | 0.0673 | 1.3725 | 0.025* | |
H14B | −0.2458 | 0.0651 | 1.3021 | 0.025* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0193 (5) | 0.0425 (7) | 0.0188 (5) | 0.0038 (5) | 0.0031 (4) | 0.0065 (5) |
O2 | 0.0172 (5) | 0.0227 (5) | 0.0176 (5) | 0.0016 (4) | 0.0003 (4) | 0.0035 (4) |
O3 | 0.0230 (5) | 0.0198 (5) | 0.0242 (5) | −0.0023 (4) | 0.0065 (4) | 0.0011 (4) |
O4 | 0.0206 (5) | 0.0236 (5) | 0.0189 (5) | −0.0015 (4) | −0.0019 (4) | 0.0035 (4) |
C1 | 0.0160 (6) | 0.0177 (7) | 0.0192 (7) | −0.0012 (5) | −0.0018 (5) | 0.0011 (6) |
C2 | 0.0152 (6) | 0.0231 (7) | 0.0167 (7) | −0.0030 (5) | −0.0015 (5) | −0.0002 (6) |
C3 | 0.0212 (7) | 0.0229 (8) | 0.0215 (7) | 0.0028 (6) | 0.0008 (6) | −0.0039 (6) |
C4 | 0.0238 (7) | 0.0189 (7) | 0.0271 (8) | 0.0010 (6) | −0.0019 (6) | 0.0013 (6) |
C5 | 0.0185 (7) | 0.0215 (7) | 0.0214 (7) | −0.0037 (6) | −0.0017 (6) | 0.0043 (6) |
C6 | 0.0146 (6) | 0.0227 (7) | 0.0167 (7) | −0.0013 (5) | −0.0024 (5) | −0.0006 (6) |
C7 | 0.0237 (7) | 0.0269 (8) | 0.0191 (7) | 0.0033 (6) | 0.0044 (6) | 0.0030 (6) |
C8 | 0.0177 (7) | 0.0218 (7) | 0.0195 (7) | 0.0001 (5) | 0.0036 (6) | 0.0010 (6) |
C9 | 0.0172 (7) | 0.0247 (8) | 0.0208 (7) | 0.0006 (6) | 0.0006 (6) | −0.0002 (6) |
C10 | 0.0214 (7) | 0.0205 (7) | 0.0204 (7) | 0.0026 (6) | −0.0030 (6) | 0.0032 (6) |
C11 | 0.0244 (7) | 0.0194 (7) | 0.0201 (7) | −0.0018 (6) | −0.0009 (6) | 0.0043 (6) |
C12 | 0.0224 (7) | 0.0255 (8) | 0.0245 (8) | −0.0056 (6) | 0.0059 (6) | 0.0024 (6) |
C13 | 0.0187 (6) | 0.0251 (7) | 0.0208 (7) | −0.0033 (6) | 0.0001 (6) | 0.0015 (6) |
C14 | 0.0211 (7) | 0.0235 (7) | 0.0187 (7) | −0.0015 (6) | 0.0020 (6) | −0.0003 (6) |
Geometric parameters (Å, º) top
O1—C8 | 1.4163 (17) | C7—H7A | 0.9900 |
O1—C7 | 1.4180 (18) | C7—H7B | 0.9900 |
O2—C9 | 1.4175 (17) | C8—C9 | 1.510 (2) |
O2—C10 | 1.4228 (17) | C8—H8A | 0.9900 |
O3—C11 | 1.4140 (18) | C8—H8B | 0.9900 |
O3—C12 | 1.4203 (17) | C9—H9A | 0.9900 |
O4—C14i | 1.4149 (18) | C9—H9B | 0.9900 |
O4—C13 | 1.4302 (18) | C10—C11 | 1.495 (2) |
C1—C6 | 1.390 (2) | C10—H10A | 0.9900 |
C1—C2 | 1.392 (2) | C10—H10B | 0.9900 |
C1—H1 | 0.9500 | C11—H11A | 0.9900 |
C2—C3 | 1.388 (2) | C11—H11B | 0.9900 |
C2—C14 | 1.514 (2) | C12—C13 | 1.493 (2) |
C3—C4 | 1.389 (2) | C12—H12A | 0.9900 |
C3—H3 | 0.9500 | C12—H12B | 0.9900 |
C4—C5 | 1.384 (2) | C13—H13A | 0.9900 |
C4—H4 | 0.9500 | C13—H13B | 0.9900 |
C5—C6 | 1.394 (2) | C14—O4i | 1.4150 (18) |
C5—H5 | 0.9500 | C14—H14A | 0.9900 |
C6—C7 | 1.508 (2) | C14—H14B | 0.9900 |
| | | |
C8—O1—C7 | 113.87 (11) | O2—C9—H9A | 109.9 |
C9—O2—C10 | 110.54 (11) | C8—C9—H9A | 109.9 |
C11—O3—C12 | 111.74 (11) | O2—C9—H9B | 109.9 |
C14i—O4—C13 | 112.25 (11) | C8—C9—H9B | 109.9 |
C6—C1—C2 | 120.96 (13) | H9A—C9—H9B | 108.3 |
C6—C1—H1 | 119.5 | O2—C10—C11 | 109.67 (11) |
C2—C1—H1 | 119.5 | O2—C10—H10A | 109.7 |
C3—C2—C1 | 118.97 (13) | C11—C10—H10A | 109.7 |
C3—C2—C14 | 119.48 (13) | O2—C10—H10B | 109.7 |
C1—C2—C14 | 121.52 (13) | C11—C10—H10B | 109.7 |
C2—C3—C4 | 120.51 (14) | H10A—C10—H10B | 108.2 |
C2—C3—H3 | 119.7 | O3—C11—C10 | 109.43 (12) |
C4—C3—H3 | 119.7 | O3—C11—H11A | 109.8 |
C5—C4—C3 | 120.21 (14) | C10—C11—H11A | 109.8 |
C5—C4—H4 | 119.9 | O3—C11—H11B | 109.8 |
C3—C4—H4 | 119.9 | C10—C11—H11B | 109.8 |
C4—C5—C6 | 119.98 (14) | H11A—C11—H11B | 108.2 |
C4—C5—H5 | 120.0 | O3—C12—C13 | 109.31 (12) |
C6—C5—H5 | 120.0 | O3—C12—H12A | 109.8 |
C1—C6—C5 | 119.37 (13) | C13—C12—H12A | 109.8 |
C1—C6—C7 | 120.01 (13) | O3—C12—H12B | 109.8 |
C5—C6—C7 | 120.49 (13) | C13—C12—H12B | 109.8 |
O1—C7—C6 | 109.81 (12) | H12A—C12—H12B | 108.3 |
O1—C7—H7A | 109.7 | O4—C13—C12 | 108.65 (13) |
C6—C7—H7A | 109.7 | O4—C13—H13A | 110.0 |
O1—C7—H7B | 109.7 | C12—C13—H13A | 110.0 |
C6—C7—H7B | 109.7 | O4—C13—H13B | 110.0 |
H7A—C7—H7B | 108.2 | C12—C13—H13B | 110.0 |
O1—C8—C9 | 105.05 (11) | H13A—C13—H13B | 108.3 |
O1—C8—H8A | 110.7 | O4i—C14—C2 | 113.47 (12) |
C9—C8—H8A | 110.7 | O4i—C14—H14A | 108.9 |
O1—C8—H8B | 110.7 | C2—C14—H14A | 108.9 |
C9—C8—H8B | 110.7 | O4i—C14—H14B | 108.9 |
H8A—C8—H8B | 108.8 | C2—C14—H14B | 108.9 |
O2—C9—C8 | 108.98 (11) | H14A—C14—H14B | 107.7 |
| | | |
C6—C1—C2—C3 | 0.7 (2) | C7—O1—C8—C9 | −174.42 (12) |
C6—C1—C2—C14 | −177.28 (13) | C10—O2—C9—C8 | 179.85 (12) |
C1—C2—C3—C4 | −0.6 (2) | O1—C8—C9—O2 | 175.94 (11) |
C14—C2—C3—C4 | 177.38 (14) | C9—O2—C10—C11 | −176.43 (12) |
C2—C3—C4—C5 | 0.8 (2) | C12—O3—C11—C10 | 177.09 (12) |
C3—C4—C5—C6 | −1.0 (2) | O2—C10—C11—O3 | 67.86 (15) |
C2—C1—C6—C5 | −0.9 (2) | C11—O3—C12—C13 | 175.10 (12) |
C2—C1—C6—C7 | 174.90 (13) | C14i—O4—C13—C12 | −164.85 (12) |
C4—C5—C6—C1 | 1.1 (2) | O3—C12—C13—O4 | 66.53 (15) |
C4—C5—C6—C7 | −174.74 (13) | C13—O4—C14i—C2i | 76.52 (15) |
C8—O1—C7—C6 | 148.79 (13) | C3—C2—C14—O4i | 163.19 (13) |
C1—C6—C7—O1 | 152.98 (13) | C1—C2—C14—O4i | −18.83 (19) |
C5—C6—C7—O1 | −31.26 (19) | | |
Symmetry code: (i) −x, −y, −z+1. |
Experimental details
Crystal data |
Chemical formula | C28H40O8 |
Mr | 504.60 |
Crystal system, space group | Orthorhombic, Pccn |
Temperature (K) | 100 |
a, b, c (Å) | 16.9096 (17), 18.351 (2), 8.350 (2) |
V (Å3) | 2591.0 (8) |
Z | 4 |
Radiation type | Mo Kα (Zr filtered) |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.58 × 0.45 × 0.42 |
|
Data collection |
Diffractometer | Enraf Nonius CAD-4F diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5946, 2976, 2337 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.649 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.109, 1.03 |
No. of reflections | 2976 |
No. of parameters | 163 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.56, −0.22 |
Selected geometric parameters (Å, º) topO1—C8 | 1.4163 (17) | O3—C11 | 1.4140 (18) |
O1—C7 | 1.4180 (18) | O3—C12 | 1.4203 (17) |
O2—C9 | 1.4175 (17) | O4—C14i | 1.4149 (18) |
O2—C10 | 1.4228 (17) | O4—C13 | 1.4302 (18) |
| | | |
C8—O1—C7 | 113.87 (11) | C11—O3—C12 | 111.74 (11) |
C9—O2—C10 | 110.54 (11) | C14i—O4—C13 | 112.25 (11) |
| | | |
C8—O1—C7—C6 | 148.79 (13) | O2—C10—C11—O3 | 67.86 (15) |
C7—O1—C8—C9 | −174.42 (12) | C11—O3—C12—C13 | 175.10 (12) |
C10—O2—C9—C8 | 179.85 (12) | C14i—O4—C13—C12 | −164.85 (12) |
O1—C8—C9—O2 | 175.94 (11) | O3—C12—C13—O4 | 66.53 (15) |
C9—O2—C10—C11 | −176.43 (12) | C13—O4—C14i—C2i | 76.52 (15) |
C12—O3—C11—C10 | 177.09 (12) | | |
Symmetry code: (i) −x, −y, −z+1. |
Macrocyclic compounds such as crown ethers can show selectivity, via the oxygen atoms, in complexing with a diverse range of neutral, polar and cationic substrates. The ligand properties can also be modified by altering the number of oxygen atoms, replacing oxygen with other heteroatoms or changing the length of aliphatic chains and/or aromatic groups between the oxygen atoms.
The crown ether molecule, (I), (Figure 1) crystallizes in an orthorhombic unit cell, with the full molecule generated by an inversion operation. Selected geometric parameters are presented in Table 1. Bond distances and bond angles are within normal ranges; Csp3—O between 1.4149 (18)–1.4302 (18) Å and C—O—C angles from 110.54 (11) to 113.87 (11)°, these values being comparable with other crown ether complexes based on benzo-annelated systems such as dibenzo-30-crown-10 (Bush & Truter, 1972). \sch
Torsion angle analysis around C—O and aliphatic C—C bonds within the crown ring, can provide an insight into the puckering of the ligand. In general the C—O—C—C torsion angles are expected to lie close to 180° (trans) whereas the O—C—C—O torsion angles tend to cluster around 60° (gauche). In this molecule, two C—O—C—C torsion angles possess unusual geometries; C8—O1—C7—C6 deviates significantly from the ideal trans value, 148.79 (13)°, and C13—O4—C14—C2 is gauche, 76.52 (15)°, whilst all other C—O—C—C values group around ±180°. Two O—C—C—O torsion angles adopt their expected gauche-type geometries while the third (belonging to O2—C9—C8—O1) is trans, 175.94 (11)°. Smaller rings such as dibenzo-26-crown-8 also display unusual torsion angle measurements (Buchanan et al., 1997).
The absence of interannular contacts, illustrated by non-bonding distances between O1···C8i of 3.835 (2) and C1···O3i of 3.529 (2) Å, [symmetry code: (i) -x, -y, 1 - z], results in a small central ring cavity. There seems to be no correlation between the number of atoms in the ring and the size of the cavity, other 30 atom crown species show appreciably larger central cavities (Anelli et al., 1988). Overall the crown ether is flat, the largest deviation from the mean plane, of the 30 ring atoms, being 0.890 (2) Å, with slight puckering at the xylyl moiety. The packing efficiency of the compound was anaylsed, using the CALC VOID option in PLATON (Spek, 1999). The packing index (Kitajgorodskij, 1973) of this crown is 71%, which is comparable to the value obtained for dibenzo-30-crown-10 (Bush & Truter, 1972), 68%, and 30-crown-10 (Bheda et al., 1994) of 67%.
The crown ether ring has rearranged on complexation with a diphenyl magnesium substrate (Markies et al., 1994), leading to a change in the torsion angle descriptors and hence the ring conformation. Only three of the four oxygen atoms ligate to the magnesium ions; presumably either steric interactions between diphenyl groups on the magnesium and the 1,3-xylyl units, or a relatively long O1···O2 distance of 3.577 (2) Å, prevents full participation. It would be interesting to see if higher coordination numbers could be achieved with other cationic species such as K+ or Na+ (Mercer & Truter, 1973; Owen & Truter, 1979).