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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

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010000250X/fg1578sup1.cif
Contains datablocks I, s316a

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S010827010000250X/fg1578Isup2.hkl
Contains datablock I

CCDC reference: 145549

Comment top

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).

Experimental top

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.

Refinement top

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.

Computing details top

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.

Figures top
[Figure 1] Fig. 1. Displacement ellipsoids plot (50% probability) of the ligand with atom labels. Symmetry operation to generate equivalent atoms: -x, -y, 1 - z.
(I) top
Crystal data top
C28H40O8F(000) = 1088
Mr = 504.60Dx = 1.294 Mg m3
Orthorhombic, PccnMo Kα (Zr filtered) radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2acCell parameters from 25 reflections
a = 16.9096 (17) Åθ = 14.0–17.9°
b = 18.351 (2) ŵ = 0.09 mm1
c = 8.350 (2) ÅT = 100 K
V = 2591.0 (8) Å3Block, colourless
Z = 40.58 × 0.45 × 0.42 mm
Data collection top
Enraf Nonius CAD-4F
diffractometer
Rint = 0.028
Radiation source: rotating anodeθmax = 27.5°, θmin = 1.6°
Graphite monochromatorh = 021
ω/2θ scansk = 2323
5946 measured reflectionsl = 010
2976 independent reflections2 standard reflections every 60 min
2337 reflections with I > 2σ(I) intensity decay: 3.5%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.043Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.109H-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 parametersΔρmax = 0.56 e Å3
0 restraintsΔρmin = 0.22 e Å3
Crystal data top
C28H40O8V = 2591.0 (8) Å3
Mr = 504.60Z = 4
Orthorhombic, PccnMo Kα (Zr filtered) radiation
a = 16.9096 (17) ŵ = 0.09 mm1
b = 18.351 (2) ÅT = 100 K
c = 8.350 (2) Å0.58 × 0.45 × 0.42 mm
Data collection top
Enraf Nonius CAD-4F
diffractometer
Rint = 0.028
5946 measured reflections2 standard reflections every 60 min
2976 independent reflections intensity decay: 3.5%
2337 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0430 restraints
wR(F2) = 0.109H-atom parameters constrained
S = 1.03Δρmax = 0.56 e Å3
2976 reflectionsΔρmin = 0.22 e Å3
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
xyzUiso*/Ueq
O10.03830 (6)0.09811 (7)0.61773 (13)0.0269 (3)
O20.08263 (6)0.15216 (5)0.28697 (12)0.0192 (2)
O30.15828 (6)0.12745 (6)0.01500 (13)0.0223 (2)
O40.18470 (6)0.02467 (6)0.26293 (12)0.0210 (2)
C10.11489 (8)0.06066 (8)1.01751 (17)0.0176 (3)
H10.10090.01081.02840.021*
C20.16272 (8)0.09322 (8)1.13273 (17)0.0183 (3)
C30.18354 (9)0.16589 (8)1.11454 (19)0.0219 (3)
H30.21660.18861.19180.026*
C40.15638 (9)0.20573 (8)0.98418 (19)0.0233 (3)
H40.17040.25560.97350.028*
C50.10900 (8)0.17296 (8)0.86989 (18)0.0205 (3)
H50.09120.20010.78000.025*
C60.08736 (8)0.10007 (8)0.88669 (17)0.0180 (3)
C70.03018 (9)0.06551 (9)0.77082 (18)0.0232 (3)
H7A0.02460.07210.81000.028*
H7B0.04090.01260.76310.028*
C80.03278 (8)0.10001 (8)0.52810 (17)0.0197 (3)
H8A0.05010.05010.49990.024*
H8B0.07540.12420.58970.024*
C90.01299 (9)0.14305 (9)0.37931 (18)0.0209 (3)
H9A0.02750.11690.31580.025*
H9B0.00870.19130.40950.025*
C100.06613 (9)0.19243 (8)0.14525 (17)0.0208 (3)
H10A0.04790.24200.17390.025*
H10B0.02350.16810.08400.025*
C110.13910 (9)0.19735 (8)0.04474 (18)0.0213 (3)
H11A0.13010.23130.04550.026*
H11B0.18350.21630.10990.026*
C120.22508 (9)0.12963 (9)0.11801 (19)0.0241 (3)
H12A0.27010.15290.06220.029*
H12B0.21260.15880.21450.029*
C130.24675 (9)0.05381 (8)0.16576 (18)0.0215 (3)
H13A0.29700.05420.22660.026*
H13B0.25400.02320.06920.026*
C140.19017 (9)0.05190 (8)1.27946 (18)0.0211 (3)
H14A0.15790.06731.37250.025*
H14B0.24580.06511.30210.025*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0193 (5)0.0425 (7)0.0188 (5)0.0038 (5)0.0031 (4)0.0065 (5)
O20.0172 (5)0.0227 (5)0.0176 (5)0.0016 (4)0.0003 (4)0.0035 (4)
O30.0230 (5)0.0198 (5)0.0242 (5)0.0023 (4)0.0065 (4)0.0011 (4)
O40.0206 (5)0.0236 (5)0.0189 (5)0.0015 (4)0.0019 (4)0.0035 (4)
C10.0160 (6)0.0177 (7)0.0192 (7)0.0012 (5)0.0018 (5)0.0011 (6)
C20.0152 (6)0.0231 (7)0.0167 (7)0.0030 (5)0.0015 (5)0.0002 (6)
C30.0212 (7)0.0229 (8)0.0215 (7)0.0028 (6)0.0008 (6)0.0039 (6)
C40.0238 (7)0.0189 (7)0.0271 (8)0.0010 (6)0.0019 (6)0.0013 (6)
C50.0185 (7)0.0215 (7)0.0214 (7)0.0037 (6)0.0017 (6)0.0043 (6)
C60.0146 (6)0.0227 (7)0.0167 (7)0.0013 (5)0.0024 (5)0.0006 (6)
C70.0237 (7)0.0269 (8)0.0191 (7)0.0033 (6)0.0044 (6)0.0030 (6)
C80.0177 (7)0.0218 (7)0.0195 (7)0.0001 (5)0.0036 (6)0.0010 (6)
C90.0172 (7)0.0247 (8)0.0208 (7)0.0006 (6)0.0006 (6)0.0002 (6)
C100.0214 (7)0.0205 (7)0.0204 (7)0.0026 (6)0.0030 (6)0.0032 (6)
C110.0244 (7)0.0194 (7)0.0201 (7)0.0018 (6)0.0009 (6)0.0043 (6)
C120.0224 (7)0.0255 (8)0.0245 (8)0.0056 (6)0.0059 (6)0.0024 (6)
C130.0187 (6)0.0251 (7)0.0208 (7)0.0033 (6)0.0001 (6)0.0015 (6)
C140.0211 (7)0.0235 (7)0.0187 (7)0.0015 (6)0.0020 (6)0.0003 (6)
Geometric parameters (Å, º) top
O1—C81.4163 (17)C7—H7A0.9900
O1—C71.4180 (18)C7—H7B0.9900
O2—C91.4175 (17)C8—C91.510 (2)
O2—C101.4228 (17)C8—H8A0.9900
O3—C111.4140 (18)C8—H8B0.9900
O3—C121.4203 (17)C9—H9A0.9900
O4—C14i1.4149 (18)C9—H9B0.9900
O4—C131.4302 (18)C10—C111.495 (2)
C1—C61.390 (2)C10—H10A0.9900
C1—C21.392 (2)C10—H10B0.9900
C1—H10.9500C11—H11A0.9900
C2—C31.388 (2)C11—H11B0.9900
C2—C141.514 (2)C12—C131.493 (2)
C3—C41.389 (2)C12—H12A0.9900
C3—H30.9500C12—H12B0.9900
C4—C51.384 (2)C13—H13A0.9900
C4—H40.9500C13—H13B0.9900
C5—C61.394 (2)C14—O4i1.4150 (18)
C5—H50.9500C14—H14A0.9900
C6—C71.508 (2)C14—H14B0.9900
C8—O1—C7113.87 (11)O2—C9—H9A109.9
C9—O2—C10110.54 (11)C8—C9—H9A109.9
C11—O3—C12111.74 (11)O2—C9—H9B109.9
C14i—O4—C13112.25 (11)C8—C9—H9B109.9
C6—C1—C2120.96 (13)H9A—C9—H9B108.3
C6—C1—H1119.5O2—C10—C11109.67 (11)
C2—C1—H1119.5O2—C10—H10A109.7
C3—C2—C1118.97 (13)C11—C10—H10A109.7
C3—C2—C14119.48 (13)O2—C10—H10B109.7
C1—C2—C14121.52 (13)C11—C10—H10B109.7
C2—C3—C4120.51 (14)H10A—C10—H10B108.2
C2—C3—H3119.7O3—C11—C10109.43 (12)
C4—C3—H3119.7O3—C11—H11A109.8
C5—C4—C3120.21 (14)C10—C11—H11A109.8
C5—C4—H4119.9O3—C11—H11B109.8
C3—C4—H4119.9C10—C11—H11B109.8
C4—C5—C6119.98 (14)H11A—C11—H11B108.2
C4—C5—H5120.0O3—C12—C13109.31 (12)
C6—C5—H5120.0O3—C12—H12A109.8
C1—C6—C5119.37 (13)C13—C12—H12A109.8
C1—C6—C7120.01 (13)O3—C12—H12B109.8
C5—C6—C7120.49 (13)C13—C12—H12B109.8
O1—C7—C6109.81 (12)H12A—C12—H12B108.3
O1—C7—H7A109.7O4—C13—C12108.65 (13)
C6—C7—H7A109.7O4—C13—H13A110.0
O1—C7—H7B109.7C12—C13—H13A110.0
C6—C7—H7B109.7O4—C13—H13B110.0
H7A—C7—H7B108.2C12—C13—H13B110.0
O1—C8—C9105.05 (11)H13A—C13—H13B108.3
O1—C8—H8A110.7O4i—C14—C2113.47 (12)
C9—C8—H8A110.7O4i—C14—H14A108.9
O1—C8—H8B110.7C2—C14—H14A108.9
C9—C8—H8B110.7O4i—C14—H14B108.9
H8A—C8—H8B108.8C2—C14—H14B108.9
O2—C9—C8108.98 (11)H14A—C14—H14B107.7
C6—C1—C2—C30.7 (2)C7—O1—C8—C9174.42 (12)
C6—C1—C2—C14177.28 (13)C10—O2—C9—C8179.85 (12)
C1—C2—C3—C40.6 (2)O1—C8—C9—O2175.94 (11)
C14—C2—C3—C4177.38 (14)C9—O2—C10—C11176.43 (12)
C2—C3—C4—C50.8 (2)C12—O3—C11—C10177.09 (12)
C3—C4—C5—C61.0 (2)O2—C10—C11—O367.86 (15)
C2—C1—C6—C50.9 (2)C11—O3—C12—C13175.10 (12)
C2—C1—C6—C7174.90 (13)C14i—O4—C13—C12164.85 (12)
C4—C5—C6—C11.1 (2)O3—C12—C13—O466.53 (15)
C4—C5—C6—C7174.74 (13)C13—O4—C14i—C2i76.52 (15)
C8—O1—C7—C6148.79 (13)C3—C2—C14—O4i163.19 (13)
C1—C6—C7—O1152.98 (13)C1—C2—C14—O4i18.83 (19)
C5—C6—C7—O131.26 (19)
Symmetry code: (i) x, y, z+1.

Experimental details

Crystal data
Chemical formulaC28H40O8
Mr504.60
Crystal system, space groupOrthorhombic, Pccn
Temperature (K)100
a, b, c (Å)16.9096 (17), 18.351 (2), 8.350 (2)
V3)2591.0 (8)
Z4
Radiation typeMo Kα (Zr filtered)
µ (mm1)0.09
Crystal size (mm)0.58 × 0.45 × 0.42
Data collection
DiffractometerEnraf Nonius CAD-4F
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
5946, 2976, 2337
Rint0.028
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.109, 1.03
No. of reflections2976
No. of parameters163
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.56, 0.22

Computer programs: Locally modified CAD4-Version 5 Software (Enraf-Nonius, 1989), SET4 (de Boer & Duisenberg, 1984), HELENA (Spek, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 1999), PLATON.

Selected geometric parameters (Å, º) top
O1—C81.4163 (17)O3—C111.4140 (18)
O1—C71.4180 (18)O3—C121.4203 (17)
O2—C91.4175 (17)O4—C14i1.4149 (18)
O2—C101.4228 (17)O4—C131.4302 (18)
C8—O1—C7113.87 (11)C11—O3—C12111.74 (11)
C9—O2—C10110.54 (11)C14i—O4—C13112.25 (11)
C8—O1—C7—C6148.79 (13)O2—C10—C11—O367.86 (15)
C7—O1—C8—C9174.42 (12)C11—O3—C12—C13175.10 (12)
C10—O2—C9—C8179.85 (12)C14i—O4—C13—C12164.85 (12)
O1—C8—C9—O2175.94 (11)O3—C12—C13—O466.53 (15)
C9—O2—C10—C11176.43 (12)C13—O4—C14i—C2i76.52 (15)
C12—O3—C11—C10177.09 (12)
Symmetry code: (i) x, y, z+1.
 

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