Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802016975/bt6172sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536802016975/bt6172Isup2.hkl |
CCDC reference: 198973
The title compound was prepared from bromo-2,5-dimethoxybenzene using a synthesis developed by Fleming & Mah (1975) and refined by Olofson and co-workers (Fitzgerald et al., 1992). Their method is a one-step synthesis using 2,2,6,6-tetramethylpiperidine in refluxing tetrahydrofuran and provides moderate yields.
H atoms were located in the difference Fourier maps, then positioned geometrically and allowed to ride on their respective parent atoms. [Is this added text acceptable?]
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Fig. 1. Displacement ellipsoid plot shown at the 50% probability level, viewed perpendicular to the mean plane [symmetry code: (i) 2 − x, −y, 1 − z]. |
C18H18O4 | F(000) = 316 |
Mr = 298.32 | Dx = 1.342 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 11.1715 (9) Å | Cell parameters from 2419 reflections |
b = 5.9994 (5) Å | θ = 3.1–27.4° |
c = 11.7159 (10) Å | µ = 0.09 mm−1 |
β = 109.961 (2)° | T = 298 K |
V = 738.05 (11) Å3 | Plate, clear pale yellow |
Z = 2 | 0.41 × 0.27 × 0.11 mm |
Bruker SMART APEX diffractometer | 1159 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.043 |
Graphite monochromator | θmax = 27.5°, θmin = 2.2° |
ω scans | h = −14→14 |
6951 measured reflections | k = −7→7 |
1696 independent reflections | l = −15→15 |
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)] = 0.053 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.140 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0745P)2] where P = (Fo2 + 2Fc2)/3 |
1696 reflections | (Δ/σ)max < 0.001 |
100 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.33 e Å−3 |
C18H18O4 | V = 738.05 (11) Å3 |
Mr = 298.32 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 11.1715 (9) Å | µ = 0.09 mm−1 |
b = 5.9994 (5) Å | T = 298 K |
c = 11.7159 (10) Å | 0.41 × 0.27 × 0.11 mm |
β = 109.961 (2)° |
Bruker SMART APEX diffractometer | 1159 reflections with I > 2σ(I) |
6951 measured reflections | Rint = 0.043 |
1696 independent reflections |
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.140 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.20 e Å−3 |
1696 reflections | Δρmin = −0.33 e Å−3 |
100 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.93841 (14) | −0.0031 (2) | 0.58475 (13) | 0.0388 (4) | |
H1A | 0.8971 | −0.0051 | 0.6415 | 0.047* | |
C2 | 0.90694 (13) | 0.1619 (2) | 0.49551 (13) | 0.0371 (4) | |
C3 | 0.81446 (15) | 0.3322 (2) | 0.48978 (14) | 0.0424 (4) | |
O3 | 0.75942 (12) | 0.31463 (18) | 0.57774 (11) | 0.0567 (4) | |
C3' | 0.6846 (2) | 0.4977 (4) | 0.5903 (2) | 0.0732 (6) | |
H3'A | 0.6511 | 0.4672 | 0.6540 | 0.110* | |
H3'B | 0.6155 | 0.5204 | 0.5154 | 0.110* | |
H3'C | 0.7364 | 0.6294 | 0.6100 | 0.110* | |
C4 | 0.78783 (15) | 0.4906 (3) | 0.40273 (15) | 0.0485 (4) | |
H4A | 0.7272 | 0.5990 | 0.3994 | 0.058* | |
C5 | 0.85135 (16) | 0.4937 (3) | 0.31609 (15) | 0.0477 (4) | |
H5A | 0.8320 | 0.6045 | 0.2571 | 0.057* | |
C6 | 0.93910 (15) | 0.3381 (2) | 0.31856 (13) | 0.0415 (4) | |
O6 | 1.00633 (11) | 0.32670 (18) | 0.24022 (10) | 0.0551 (4) | |
C6' | 0.9926 (2) | 0.5070 (3) | 0.15832 (18) | 0.0722 (6) | |
H6'A | 1.0438 | 0.4802 | 0.1086 | 0.108* | |
H6'B | 1.0197 | 0.6425 | 0.2033 | 0.108* | |
H6'C | 0.9048 | 0.5203 | 0.1077 | 0.108* | |
C7 | 0.97036 (14) | 0.1643 (2) | 0.40879 (13) | 0.0369 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0413 (8) | 0.0408 (8) | 0.0347 (8) | −0.0050 (7) | 0.0135 (6) | −0.0012 (6) |
C2 | 0.0368 (8) | 0.0358 (8) | 0.0354 (8) | −0.0044 (6) | 0.0079 (6) | −0.0018 (6) |
C3 | 0.0399 (8) | 0.0430 (9) | 0.0418 (9) | −0.0025 (7) | 0.0106 (7) | −0.0049 (7) |
O3 | 0.0601 (8) | 0.0581 (8) | 0.0593 (8) | 0.0124 (6) | 0.0302 (6) | 0.0023 (6) |
C3' | 0.0627 (13) | 0.0778 (14) | 0.0891 (15) | 0.0194 (10) | 0.0387 (11) | −0.0018 (11) |
C4 | 0.0454 (9) | 0.0423 (9) | 0.0515 (10) | 0.0081 (7) | 0.0083 (8) | 0.0007 (8) |
C5 | 0.0524 (10) | 0.0401 (9) | 0.0430 (9) | 0.0014 (7) | 0.0067 (7) | 0.0087 (7) |
C6 | 0.0442 (9) | 0.0418 (9) | 0.0344 (8) | −0.0064 (7) | 0.0079 (7) | 0.0029 (7) |
O6 | 0.0641 (8) | 0.0575 (8) | 0.0474 (7) | 0.0045 (6) | 0.0236 (6) | 0.0171 (5) |
C6' | 0.0966 (16) | 0.0706 (12) | 0.0534 (11) | 0.0009 (11) | 0.0307 (11) | 0.0245 (10) |
C7 | 0.0376 (8) | 0.0360 (8) | 0.0324 (7) | −0.0062 (6) | 0.0060 (6) | −0.0012 (6) |
C1—C7i | 1.388 (2) | C4—C5 | 1.423 (2) |
C1—C2 | 1.395 (2) | C5—C6 | 1.347 (2) |
C2—C7 | 1.423 (2) | C6—O6 | 1.3717 (19) |
C2—C3 | 1.438 (2) | C6—C7 | 1.440 (2) |
C3—C4 | 1.351 (2) | O6—C6' | 1.4191 (19) |
C3—O3 | 1.3725 (19) | C7—C1i | 1.388 (2) |
O3—C3' | 1.418 (2) | ||
C7i—C1—C2 | 121.85 (13) | C6—C5—C4 | 120.80 (14) |
C1—C2—C7 | 118.87 (13) | C5—C6—O6 | 125.51 (14) |
C1—C2—C3 | 122.17 (14) | C5—C6—C7 | 120.65 (14) |
C7—C2—C3 | 118.95 (13) | O6—C6—C7 | 113.84 (13) |
C4—C3—O3 | 125.55 (14) | C6—O6—C6' | 117.18 (14) |
C4—C3—C2 | 120.31 (15) | C1i—C7—C2 | 119.27 (13) |
O3—C3—C2 | 114.15 (13) | C1i—C7—C6 | 122.27 (14) |
C3—O3—C3' | 116.71 (14) | C2—C7—C6 | 118.44 (13) |
C3—C4—C5 | 120.85 (14) |
Symmetry code: (i) −x+2, −y, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C18H18O4 |
Mr | 298.32 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 298 |
a, b, c (Å) | 11.1715 (9), 5.9994 (5), 11.7159 (10) |
β (°) | 109.961 (2) |
V (Å3) | 738.05 (11) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.41 × 0.27 × 0.11 |
Data collection | |
Diffractometer | Bruker SMART APEX diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6951, 1696, 1159 |
Rint | 0.043 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.053, 0.140, 1.01 |
No. of reflections | 1696 |
No. of parameters | 100 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.33 |
Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SAINT, SHELXTL (Bruker, 1997), SHELXTL.
There has been considerable ongoing research involving the electrochemistry of compounds incorporating multiple quinones. Some of these compounds are anthracene derivatives (Jozefiak et al., 1989), while others are based on triptycene architecture (Doerner et al., 1998; Jozefiak et al., 1989; Quast & Fuchsbauer, 1986; Russel & Suleman, 1981). 1,4,5,8-Tetramethoxyanthracene (1,4,5,8-TMA), (I), has been used as an intermediate in the syntheses of some of these compounds. During research involving the synthesis of molecules that can undergo photoinduced electron transfer, 1,4,5,8-TMA was used as a synthetic intermediate.
The structure of (I) consists of individual molecules having no unusually short intermolecular contacts. The packing is in columns parallel to the b axis. Each molecule is planar, as shown in Fig. 1, with an average deviation from the least-squares plane through all non-H atoms of 0.064 Å, and a maximum of 0.164 Å by the methyl atom C3'. The molecule is slightly distorted, since aromatic-ring angles deviate from 120°, ranging from 118.44 (13)° at C2—C7—C6 to 122.27 (14)° at C1—C7—C6. Perhaps the most interesting feature of this structure is the tilt of the bond angles at the methoxy groups. Both methoxy groups bend toward each other down the length of the molecule, with facing MeO-ϕ angles of 113.85 (13) and 114.16 (13)°. These distortions presumably originate from packing effects in the solid state.