research communications
2] benzene hemisolvate
of 4′-bromo-2′,5′-dimethoxy-2,5-dioxo-[1,1′-biphenyl]-3,4-dicarbonitrile [BrHBQ(CN)aDepartment of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL, 35487, USA
*Correspondence e-mail: swoski@ua.edu
In the crystal of the title compound, C16H9BrN2O4·0.5C6H6, the molecules stack in a centrosymmetric in a 2:1 stoichiometry with co-crystallized benzene solvent molecules and interact via various weak interactions. This induces a geometry different from that predicted by theory, and is unique among the hemibiquinones heretofore reported.
Keywords: hemibiquinone; molecular rectifier; crystal structure.
CCDC reference: 1470649
1. Chemical context
A new class of molecules, dubbed hemibiquinones (HBQs), has been developed and reported as potential molecular rectifiers. Biphenyl derivatives have garnered great attention to themselves as conductors of electricity (Venkataraman et al., 2006). Thus, control over the molecular equilibrium geometry, and therefore the overlap of the π orbitals, allows for control over the governing electrical characteristics. The efficiency of conduction through a given molecule is dependent on the torsion angle between adjacent electrophores.
The title hemibiquinone (HBQ) molecule, 4′-bromo-2′,5′-dimethoxy-2,5-dioxo-[1,1′-biphenyl]-3,4-dicarbonitrile 1 (Fig. 1), has been isolated as a molecule that will self-assemble on a gold surface as a potential unimolecular rectifier. HBQ 1 is predicted to act as a molecular diode due to the linking of the electron-rich 4′-bromo-2′,5′-dimethoxybenzene donor with an electron-poor 3,4-dicarbonitrile quinone acceptor. This follows the scheme outlined by Aviram & Ranter (1974), where an electron-rich donor and an electron-poor acceptor are covalently bonded through an isolating saturated bridge. In HBQs, the predicted dihedral twist away from coplanarity of the two rings would decrease orbital overlap and allow for partial isolation of the donor and acceptor moieties. We have developed a selective synthesis for this hemibiquinone derivative that is scalable to gram quantities.
2. Structural commentary
As in the other reported HBQ molecules (Meany et al., 2015), we seek to use and compare the inter-ring torsion angles in the crystals as a guide against gas-phase calculated values. However, crystallized benzene solvent molecules in the prevent us from drawing direct conclusions about the geometry. Packing effects distort the biphenyl molecule out of plane in the opposite direction as the hydroquinone starting material [BrHBQH2(CN)2], Fig. 2. The C—C biphenyl bond [1.482 (2) Å] in 1 is comparable to that in the hydroquinone [1.481 (2) Å]. In this molecule, the C5—C4—C7—C8 torsion is 125.3 (2)°, compared to the hydroquinone torsion angle of −126.50°, (Meany, 2015). DFT (B3LYP-DGDZVP) calculations performed on the target molecule in the gas phase predict an angle of −39.71°. This significant discrepancy is due to packing interactions in the solid phase, especially from benzene. Finally, the quinone ring is slightly buckled, likely due to supramolecular packing effects.
As in other structures, the methoxy groups are aligned nearly in-plane with the benzene ring, C2—C3—O2—C13 being bent out of plane by 2.9 (3)° and C5—C6—O1—C14 bent out of plane by −7.0 (3)°. The methoxy group bond angle C3—O2—C13 is measured at 117.4 (1)°, and C6—O1—C14 is measured at 117.3 (1)°. The methyl portions of each of these groups point away from the sterically restricting groups ortho to these positions, typical for this class.
Continuing the trend from the hydroquinone, the C9—C10 bond in 1 [1.346 (2) Å] is shorter than than the corresponding hydroquinone C9—C10 bond [1.408 (2) Å] and the C1—C6 bond [1.334 (6) Å] of BrHBQBr (Meany, 2015). The stronger polarization of 1 due to the dicyanoquinone relative to the starting materials weakens the bond through repulsive effects. The Br1—C1 bond is slightly longer in 1 [1.893 (2) Å] compared to the same bond in the hydroquinone precursor [1.885 (1) Å], but is still shorter than that of the starting material BrHBQBr [1.898 (4) Å; Meany, 2015]. The calculated (B3LYP-DGDZVP) of BrHBQH2(CN)2 is only 6.17 D, compared to a of 7.78 D for compound 1.
3. Supramolecular features
The molecule packs in P with two HBQ molecules and one solvent molecule, the latter completed by a crystallographic inversion centre. The molecules align antiparallel to one another in the primarily along the c crystallographic axis. The quinone rings are mostly parallel to the ac plane and sandwich, in a 2:1 ratio, a benzene solvent molecule. The plane of the dimethoxybenzene ring aligns with the diagonal of the ab plane.
Analysis of the short contacts shows an off-center donor–acceptor-type π–π interaction between benzene and the HBQ molecule. Fig3. 3 and 4 show the great extent of π-overlap between benzene and HBQ 1. It is readily apparent that the benzene ring, rather than being centered between the quinone rings exactly, is actually slightly off-center. Instead, the electron density of the benzene is centered over the slightly electropositive C9—C10 bond.
Each HBQ molecule interacts with a total of three benzene molecules by short contacts. As mentioned above, one molecule of benzene is sandwiched between two quinone rings. Additionally, the 3-substituted nitrile group accepts a C—H⋯N hydrogen bond from a solvent molecule (H⋯N = 2.81 Å, C—H⋯N = 147°). The third benzene molecule exhibits short contacts to the 4′-bromine atom on the opposite end of the molecule, where H17 and H18 link to Br1 almost symmetrically (H17⋯Br1 = 3.05 Å, C17—H17⋯Br1 = 127°; H18⋯Br1 = 3.04 Å, C18—H178⋯Br1 = 128°). Since the benzene molecule π-stacks parallel to the the benzene molecule is oriented in the same direction relative to the dimethoxybenzene ring. Although, in previous HBQ crystals the 4 and 4′ groups show evidence of intermolecular halogen bonding, due to the excess electron density around the aryl bromine atoms and the nitrile groups, an attractive interaction is not possible, rather a slightly repulsive interaction is favored. Instead, the protons on C17 and C18 bifurcate to Br1 as an acceptor, forming slightly asymmetric hydrogen bonds between the dimethoxybenzene ring and the benzene solvent molecule. As discussed above, the quinone carbonyl groups are deflected from perfect planarity. In previous structures, methoxy oxygen atoms tended to deflect the carbonyl groups through repulsive effects. However, this structure contains some attractive intermolecular hydrogen bonding character, including the C14—H14B⋯O4 contact, which is a moderate interaction at 2.57 Å and a bond angle of 157°. A second weaker interaction occurs between the C5—H5 dimethoxybenzene grouping and O4 (2.64 Å and 134°). Projection of the O4 carbonyl atom to a neighboring quinoid proton H12 is also evident at a bond length of 2.65 Å and a C12—H12⋯O4 angle of 147°. There is a fourth and weakest interaction with O4, viz. C16≡N1⋯O4 with an N1⋯O4 bond length of 3.159 (2) Å and a bond angle of 129.91 (1)°. Two contacts are made with O3: a C2—H2⋯O3 (2.65 Å and 142°) bond and weak π-contacts [C10⋯O3 and C11⋯O3 = 3.251 (2) and 3.187 (2) Å, respectively]. Additionally, there is a short contact between C10 and C8, at 3.486 (3) Å. The N2 nitrile atom possibly accepts a very weak interaction from the methoxy C13 and H13A pair (2.82 Å and 97°). There is a long C13⋯N2 [(3.101 (3) Å] interaction as well. Even longer than those interactions, H13 also has a weak H⋯π interaction with the dimethoxybenzene ring on an adjacent molecule (H⋯π = 2.88 Å). The packing is shown in Fig. 5.
4. Synthesis and crystallization
4′-Bromo-2,5-dihydroxy-2′,5′-dimethoxy-[1,1′-biphenyl]-3,4-dicarbonitrile (0.126 g, 0.337 mmol) was suspended in a mixture of 100 mL of H2O and 100 mL of benzene. FeCl3 (0.340 g, 2.09 mmol) was added in one portion. The resulting mixture was capped and stirred overnight. The resulting phases were separated, and the organic phase was washed with water and dried over anhydrous Na2SO4. Evaporation of the solvent produced a crude product. The pure product was precipitated from a chloroform solution by addition of hexane, yielding 0.0460 g (36.7%). Black, block-shaped crystals of 1 were grown from chloroform solution with residual benzene at 296 K. 1H NMR (360 MHz, CDCl3) δ = 7.22 (s, 1H, ArH), 7.12 (s, 1H, ArH), 6.71 (s, 1H, ArH), 3.87 (s, 3H, OCH3), 3.76 (s, 3H, OCH3).
5. Refinement
H atoms attached to carbon atoms were positioned geometrically and constrained to ride on their parent atoms, with C—H-bond distances of 0.95 Å for aromatic C—H, 1.00, 0.99 and 0.98 Å for aliphatic CH3, 0.88 Å. Methyl H atoms were allowed to rotate but not to tip to best fit the experimental electron density. Uiso(H) values were set to a multiple of Ueq(C) with 1.5 for CH3. Crystal data, data collection and structure details are summarized in Table 1.
Supporting information
CCDC reference: 1470649
https://doi.org/10.1107/S2056989016005120/hb7567sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016005120/hb7567Isup2.hkl
Data collection: APEX2 (Bruker, 2012); cell
SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015b) SHELXLE (Hübschle et al., 2011); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).C16H9BrN2O4·0.5C6H6 | Z = 2 |
Mr = 412.22 | F(000) = 414 |
Triclinic, P1 | Dx = 1.603 Mg m−3 |
a = 8.0427 (17) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 10.343 (2) Å | Cell parameters from 5182 reflections |
c = 11.007 (2) Å | θ = 2.9–27.4° |
α = 104.469 (2)° | µ = 2.43 mm−1 |
β = 95.120 (2)° | T = 173 K |
γ = 102.851 (2)° | Block, black |
V = 854.1 (3) Å3 | 0.21 × 0.11 × 0.06 mm |
Bruker AXS SMART APEXII CCD diffractometer | 3382 reflections with I > 2σ(I) |
Radiation source: sealed X-ray tube | Rint = 0.022 |
phi and ω scans | θmax = 27.6°, θmin = 2.9° |
Absorption correction: multi-scan (SADABS; Bruker, 2001) | h = −10→10 |
Tmin = 0.600, Tmax = 0.746 | k = −13→13 |
11856 measured reflections | l = −14→14 |
3957 independent reflections |
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)] = 0.028 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.068 | H-atom parameters constrained |
S = 1.06 | w = 1/[σ2(Fo2) + (0.0307P)2 + 0.3076P] where P = (Fo2 + 2Fc2)/3 |
3957 reflections | (Δ/σ)max < 0.001 |
237 parameters | Δρmax = 0.40 e Å−3 |
0 restraints | Δρmin = −0.35 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.1145 (2) | −0.15670 (19) | −0.05223 (15) | 0.0248 (4) | |
C2 | 0.2309 (2) | −0.02953 (19) | −0.02559 (16) | 0.0249 (4) | |
H2 | 0.2677 | 0.0071 | −0.0925 | 0.030* | |
C3 | 0.2939 (2) | 0.04468 (18) | 0.10043 (16) | 0.0240 (4) | |
C4 | 0.2382 (2) | −0.01088 (18) | 0.19817 (15) | 0.0216 (3) | |
C5 | 0.1153 (2) | −0.13776 (18) | 0.16872 (15) | 0.0219 (3) | |
H5 | 0.0746 | −0.1731 | 0.2353 | 0.026* | |
C6 | 0.0521 (2) | −0.21285 (18) | 0.04302 (16) | 0.0235 (4) | |
C7 | 0.3088 (2) | 0.06338 (17) | 0.33278 (15) | 0.0207 (3) | |
C8 | 0.5003 (2) | 0.10333 (17) | 0.36973 (15) | 0.0207 (3) | |
C9 | 0.5736 (2) | 0.19577 (17) | 0.50147 (15) | 0.0207 (3) | |
C10 | 0.4713 (2) | 0.21563 (17) | 0.59112 (15) | 0.0212 (3) | |
C11 | 0.2798 (2) | 0.15131 (17) | 0.55889 (16) | 0.0215 (3) | |
C12 | 0.2090 (2) | 0.08304 (18) | 0.42447 (16) | 0.0224 (3) | |
H12 | 0.0872 | 0.0513 | 0.4011 | 0.027* | |
C13 | 0.4568 (3) | 0.2362 (2) | 0.04085 (19) | 0.0327 (4) | |
H13A | 0.5171 | 0.1797 | −0.0155 | 0.049* | |
H13B | 0.5338 | 0.3282 | 0.0801 | 0.049* | |
H13C | 0.3540 | 0.2445 | −0.0084 | 0.049* | |
C14 | −0.1132 (3) | −0.4035 (2) | 0.10228 (19) | 0.0356 (4) | |
H14A | −0.1932 | −0.4943 | 0.0630 | 0.053* | |
H14B | −0.1695 | −0.3463 | 0.1616 | 0.053* | |
H14C | −0.0097 | −0.4148 | 0.1483 | 0.053* | |
C15 | 0.5379 (2) | 0.29235 (19) | 0.72153 (16) | 0.0260 (4) | |
C16 | 0.7587 (2) | 0.24907 (19) | 0.52856 (16) | 0.0257 (4) | |
C17 | 0.3212 (2) | 0.45790 (19) | 0.48189 (19) | 0.0298 (4) | |
H17 | 0.1988 | 0.4292 | 0.4699 | 0.036* | |
C18 | 0.4079 (3) | 0.43078 (19) | 0.37931 (18) | 0.0301 (4) | |
H18 | 0.3454 | 0.3836 | 0.2969 | 0.036* | |
C19 | 0.5876 (3) | 0.4731 (2) | 0.39738 (18) | 0.0306 (4) | |
H19 | 0.6478 | 0.4547 | 0.3271 | 0.037* | |
N1 | 0.9050 (2) | 0.2909 (2) | 0.55007 (17) | 0.0393 (4) | |
N2 | 0.5915 (2) | 0.35262 (19) | 0.82435 (15) | 0.0399 (4) | |
O1 | −0.06536 (16) | −0.33788 (13) | 0.00550 (12) | 0.0311 (3) | |
O2 | 0.40645 (18) | 0.17220 (13) | 0.13801 (12) | 0.0327 (3) | |
O3 | 0.59685 (17) | 0.05565 (14) | 0.30356 (12) | 0.0308 (3) | |
O4 | 0.19158 (16) | 0.15713 (14) | 0.64297 (12) | 0.0303 (3) | |
Br1 | 0.04198 (3) | −0.26003 (2) | −0.22428 (2) | 0.03965 (8) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0214 (8) | 0.0332 (10) | 0.0170 (8) | 0.0076 (7) | 0.0021 (6) | 0.0015 (7) |
C2 | 0.0256 (9) | 0.0318 (10) | 0.0200 (8) | 0.0081 (8) | 0.0074 (7) | 0.0098 (7) |
C3 | 0.0254 (9) | 0.0231 (9) | 0.0231 (8) | 0.0045 (7) | 0.0069 (7) | 0.0062 (7) |
C4 | 0.0235 (8) | 0.0217 (9) | 0.0190 (8) | 0.0055 (7) | 0.0057 (6) | 0.0042 (6) |
C5 | 0.0225 (8) | 0.0242 (9) | 0.0194 (8) | 0.0058 (7) | 0.0062 (6) | 0.0059 (7) |
C6 | 0.0180 (8) | 0.0256 (9) | 0.0248 (8) | 0.0044 (7) | 0.0040 (6) | 0.0035 (7) |
C7 | 0.0242 (8) | 0.0165 (8) | 0.0211 (8) | 0.0021 (7) | 0.0053 (6) | 0.0065 (6) |
C8 | 0.0230 (8) | 0.0193 (8) | 0.0212 (8) | 0.0033 (7) | 0.0081 (6) | 0.0085 (6) |
C9 | 0.0208 (8) | 0.0199 (8) | 0.0229 (8) | 0.0041 (7) | 0.0039 (6) | 0.0093 (7) |
C10 | 0.0239 (8) | 0.0208 (9) | 0.0195 (8) | 0.0034 (7) | 0.0048 (6) | 0.0080 (6) |
C11 | 0.0223 (8) | 0.0208 (8) | 0.0220 (8) | 0.0048 (7) | 0.0068 (6) | 0.0065 (6) |
C12 | 0.0205 (8) | 0.0226 (9) | 0.0218 (8) | 0.0015 (7) | 0.0047 (6) | 0.0051 (7) |
C13 | 0.0354 (10) | 0.0330 (10) | 0.0332 (10) | 0.0033 (9) | 0.0115 (8) | 0.0182 (8) |
C14 | 0.0371 (11) | 0.0271 (10) | 0.0350 (10) | −0.0038 (9) | 0.0107 (8) | 0.0037 (8) |
C15 | 0.0250 (9) | 0.0292 (10) | 0.0240 (9) | 0.0031 (8) | 0.0054 (7) | 0.0108 (7) |
C16 | 0.0256 (9) | 0.0307 (10) | 0.0227 (8) | 0.0059 (8) | 0.0056 (7) | 0.0114 (7) |
C17 | 0.0237 (9) | 0.0242 (9) | 0.0399 (10) | 0.0022 (8) | 0.0026 (8) | 0.0105 (8) |
C18 | 0.0329 (10) | 0.0237 (9) | 0.0293 (9) | 0.0030 (8) | −0.0015 (8) | 0.0053 (7) |
C19 | 0.0329 (10) | 0.0282 (10) | 0.0322 (10) | 0.0088 (8) | 0.0098 (8) | 0.0083 (8) |
N1 | 0.0243 (9) | 0.0536 (12) | 0.0407 (10) | 0.0062 (8) | 0.0046 (7) | 0.0181 (9) |
N2 | 0.0457 (10) | 0.0428 (10) | 0.0235 (8) | −0.0013 (8) | 0.0018 (7) | 0.0077 (7) |
O1 | 0.0283 (7) | 0.0286 (7) | 0.0267 (6) | −0.0046 (6) | 0.0027 (5) | 0.0013 (5) |
O2 | 0.0445 (8) | 0.0254 (7) | 0.0232 (6) | −0.0044 (6) | 0.0095 (6) | 0.0078 (5) |
O3 | 0.0284 (7) | 0.0338 (7) | 0.0307 (7) | 0.0086 (6) | 0.0142 (5) | 0.0058 (6) |
O4 | 0.0271 (7) | 0.0380 (8) | 0.0241 (6) | 0.0055 (6) | 0.0113 (5) | 0.0054 (5) |
Br1 | 0.03537 (12) | 0.05225 (15) | 0.01873 (10) | −0.00172 (9) | 0.00001 (7) | 0.00002 (8) |
C1—C2 | 1.379 (3) | C11—O4 | 1.213 (2) |
C1—C6 | 1.399 (2) | C11—C12 | 1.470 (2) |
C1—Br1 | 1.8928 (17) | C12—H12 | 0.9500 |
C2—C3 | 1.393 (2) | C13—O2 | 1.434 (2) |
C2—H2 | 0.9500 | C13—H13A | 0.9800 |
C3—O2 | 1.364 (2) | C13—H13B | 0.9800 |
C3—C4 | 1.403 (2) | C13—H13C | 0.9800 |
C4—C5 | 1.399 (2) | C14—O1 | 1.436 (2) |
C4—C7 | 1.482 (2) | C14—H14A | 0.9800 |
C5—C6 | 1.392 (2) | C14—H14B | 0.9800 |
C5—H5 | 0.9500 | C14—H14C | 0.9800 |
C6—O1 | 1.362 (2) | C15—N2 | 1.138 (2) |
C7—C12 | 1.349 (2) | C16—N1 | 1.141 (2) |
C7—C8 | 1.493 (2) | C17—C18 | 1.382 (3) |
C8—O3 | 1.212 (2) | C17—C19i | 1.390 (3) |
C8—C9 | 1.506 (2) | C17—H17 | 0.9500 |
C9—C10 | 1.346 (2) | C18—C19 | 1.394 (3) |
C9—C16 | 1.443 (2) | C18—H18 | 0.9500 |
C10—C15 | 1.443 (2) | C19—C17i | 1.390 (3) |
C10—C11 | 1.506 (2) | C19—H19 | 0.9500 |
C2—C1—C6 | 122.44 (15) | O4—C11—C10 | 119.64 (15) |
C2—C1—Br1 | 118.35 (13) | C12—C11—C10 | 117.32 (14) |
C6—C1—Br1 | 119.19 (13) | C7—C12—C11 | 123.04 (15) |
C1—C2—C3 | 119.35 (15) | C7—C12—H12 | 118.5 |
C1—C2—H2 | 120.3 | C11—C12—H12 | 118.5 |
C3—C2—H2 | 120.3 | O2—C13—H13A | 109.5 |
O2—C3—C2 | 124.46 (15) | O2—C13—H13B | 109.5 |
O2—C3—C4 | 115.94 (15) | H13A—C13—H13B | 109.5 |
C2—C3—C4 | 119.59 (16) | O2—C13—H13C | 109.5 |
C5—C4—C3 | 119.93 (15) | H13A—C13—H13C | 109.5 |
C5—C4—C7 | 119.47 (14) | H13B—C13—H13C | 109.5 |
C3—C4—C7 | 120.60 (15) | O1—C14—H14A | 109.5 |
C6—C5—C4 | 120.83 (15) | O1—C14—H14B | 109.5 |
C6—C5—H5 | 119.6 | H14A—C14—H14B | 109.5 |
C4—C5—H5 | 119.6 | O1—C14—H14C | 109.5 |
O1—C6—C5 | 124.89 (15) | H14A—C14—H14C | 109.5 |
O1—C6—C1 | 117.32 (15) | H14B—C14—H14C | 109.5 |
C5—C6—C1 | 117.79 (16) | N2—C15—C10 | 179.5 (2) |
C12—C7—C4 | 123.16 (15) | N1—C16—C9 | 179.8 (2) |
C12—C7—C8 | 118.87 (15) | C18—C17—C19i | 120.29 (17) |
C4—C7—C8 | 117.58 (14) | C18—C17—H17 | 119.9 |
O3—C8—C7 | 123.21 (15) | C19i—C17—H17 | 119.9 |
O3—C8—C9 | 118.80 (15) | C17—C18—C19 | 119.66 (17) |
C7—C8—C9 | 117.66 (14) | C17—C18—H18 | 120.2 |
C10—C9—C16 | 122.54 (15) | C19—C18—H18 | 120.2 |
C10—C9—C8 | 120.68 (15) | C17i—C19—C18 | 120.05 (18) |
C16—C9—C8 | 116.49 (14) | C17i—C19—H19 | 120.0 |
C9—C10—C15 | 122.68 (15) | C18—C19—H19 | 120.0 |
C9—C10—C11 | 120.23 (15) | C6—O1—C14 | 117.33 (14) |
C15—C10—C11 | 117.03 (14) | C3—O2—C13 | 117.42 (14) |
O4—C11—C12 | 123.04 (16) | ||
C6—C1—C2—C3 | 2.2 (3) | C4—C7—C8—C9 | 171.61 (14) |
Br1—C1—C2—C3 | −176.22 (13) | O3—C8—C9—C10 | −158.87 (16) |
C1—C2—C3—O2 | −178.67 (17) | C7—C8—C9—C10 | 14.8 (2) |
C1—C2—C3—C4 | 0.0 (3) | O3—C8—C9—C16 | 15.1 (2) |
O2—C3—C4—C5 | 176.45 (16) | C7—C8—C9—C16 | −171.25 (14) |
C2—C3—C4—C5 | −2.3 (3) | C16—C9—C10—C15 | 0.3 (3) |
O2—C3—C4—C7 | −3.8 (2) | C8—C9—C10—C15 | 173.92 (15) |
C2—C3—C4—C7 | 177.44 (16) | C16—C9—C10—C11 | −176.80 (15) |
C3—C4—C5—C6 | 2.5 (3) | C8—C9—C10—C11 | −3.2 (2) |
C7—C4—C5—C6 | −177.20 (15) | C9—C10—C11—O4 | 171.98 (16) |
C4—C5—C6—O1 | 178.97 (16) | C15—C10—C11—O4 | −5.3 (2) |
C4—C5—C6—C1 | −0.4 (3) | C9—C10—C11—C12 | −7.8 (2) |
C2—C1—C6—O1 | 178.57 (16) | C15—C10—C11—C12 | 174.96 (15) |
Br1—C1—C6—O1 | −3.0 (2) | C4—C7—C12—C11 | 177.18 (15) |
C2—C1—C6—C5 | −2.0 (3) | C8—C7—C12—C11 | 4.5 (2) |
Br1—C1—C6—C5 | 176.44 (12) | O4—C11—C12—C7 | −172.59 (17) |
C5—C4—C7—C12 | −47.4 (2) | C10—C11—C12—C7 | 7.1 (2) |
C3—C4—C7—C12 | 132.83 (18) | C19i—C17—C18—C19 | 0.0 (3) |
C5—C4—C7—C8 | 125.34 (17) | C17—C18—C19—C17i | 0.0 (3) |
C3—C4—C7—C8 | −54.4 (2) | C5—C6—O1—C14 | −7.0 (3) |
C12—C7—C8—O3 | 158.02 (17) | C1—C6—O1—C14 | 172.39 (16) |
C4—C7—C8—O3 | −15.1 (2) | C2—C3—O2—C13 | 2.9 (3) |
C12—C7—C8—C9 | −15.3 (2) | C4—C3—O2—C13 | −175.80 (16) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Acknowledgements
This research was supported by the National Science Foundation (CHE-08–48206). JEM is grateful to the Department of Education's Graduate Assistance in Areas of National Need (GAANN) Program for fellowship support. We appreciate the assistance of Professor David Dixon and Dr Edward Garner in performing DFT calculations.
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