research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

ISSN: 2056-9890

Crystal structure of 4′-bromo-2′,5′-dimeth­­oxy-2,5-dioxo-[1,1′-biphen­yl]-3,4-dicarbo­nitrile [BrHBQ(CN)2] benzene hemisolvate


aDepartment of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL, 35487, USA
*Correspondence e-mail:

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 25 February 2016; accepted 25 March 2016; online 31 March 2016)

In the crystal of the title compound, C16H9BrN2O4·0.5C6H6, the mol­ecules stack in a centrosymmetric unit cell 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.

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[Venkataraman, L., Klare, J. E., Nuckolls, C., Hybertsen, M. S. & Steigerwald, M. L. (2006). Nature, 442, 904-907.]). 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.

[Scheme 1]

The title hemibi­quinone (HBQ) mol­ecule, 4′-bromo-2′,5′-dimeth­oxy-2,5-dioxo-[1,1′-biphen­yl]-3,4-dicarbo­nitrile 1 (Fig. 1[link]), 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[Aviram, A. & Ratner, M. A. (1974). Chem. Phys. Lett. 29, 277-283.]), 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.

[Figure 1]
Figure 1
The mol­ecular structure of HBQ 1 showing the atom-numbering scheme. Ellipsoids are displayed at the 50% probability level. Hydrogen atoms are displayed as calculated.

2. Structural commentary

As in the other reported HBQ mol­ecules (Meany et al., 2015[Meany, J. E., Kelley, S. P., Metzger, R. M., Rogers, R. D. & Woski, S. A. (2015). Acta Cryst. E71, 1454-1456.]), 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 crystal structure 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[link]. 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—C4C7—C8 torsion is 125.3 (2)°, compared to the hydro­quinone torsion angle of −126.50°, (Meany, 2015[Meany, J. E., Kelley, S. P., Metzger, R. M., Rogers, R. D. & Woski, S. A. (2015). Acta Cryst. E71, 1454-1456.]). 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.

[Figure 2]
Figure 2
Mol­ecular overlay of 1 (blue) with the reduced precursor hydro­quinone (BrHBQH2(CN)2, red). Viewed along the plane of the di­meth­oxy­benzene ring and the C—C biphenyl bond (left), and parallel to the plane of the di­meth­oxy­benzene ring (right). The overlay is meant to show the divergent geometry between the precursor and the title mol­ecule, based on the different solid-state inter­actions.

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[Meany, J. E., Kelley, S. P., Metzger, R. M., Rogers, R. D. & Woski, S. A. (2015). Acta Cryst. E71, 1454-1456.]). 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[Meany, J. E., Kelley, S. P., Metzger, R. M., Rogers, R. D. & Woski, S. A. (2015). Acta Cryst. E71, 1454-1456.]]. The calculated dipole moment (B3LYP-DGDZVP) of BrHBQH2(CN)2 is only 6.17 D, compared to a dipole moment of 7.78 D for compound 1.

3. Supra­molecular features

The mol­ecule packs in space group P[\overline{1}] 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 unit cell, 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 ππ inter­action between benzene and the HBQ mol­ecule. Fig3. 3[link] and 4[link] 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.

[Figure 3]
Figure 3
Packing diagram showing the off-center ππ short contacts of 1 with the inter­calated solvent benzene. Weak hydrogen bonds from O2 project closely to the benzene protons.
[Figure 4]
Figure 4
Packing diagram showing the off-center ππ short contacts of 1 with the inter­calated solvent benzene as the asymmetric unit to only one HBQ. Weak hydrogen bonds from O2 project close to the benzene protons.

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 quinones, 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[link].

[Figure 5]
Figure 5
Packing diagram showing the b directional π-stacks and the weak c directional halogen bonds. Viewed along the a axis.

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 refinement details are summarized in Table 1[link].

Table 1
Experimental details

Crystal data
Chemical formula C16H9BrN2O4·0.5C6H6
Mr 412.22
Crystal system, space group Triclinic, P[\overline{1}]
Temperature (K) 173
a, b, c (Å) 8.0427 (17), 10.343 (2), 11.007 (2)
α, β, γ (°) 104.469 (2), 95.120 (2), 102.851 (2)
V3) 854.1 (3)
Z 2
Radiation type Mo Kα
μ (mm−1) 2.43
Crystal size (mm) 0.21 × 0.11 × 0.06
Data collection
Diffractometer Bruker AXS SMART APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2001[Bruker (2001). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.600, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections 11856, 3957, 3382
Rint 0.022
(sin θ/λ)max−1) 0.653
R[F2 > 2σ(F2)], wR(F2), S 0.028, 0.068, 1.06
No. of reflections 3957
No. of parameters 237
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.40, −0.35
Computer programs: APEX2 and SAINT (Bruker, 2012[Bruker (2012). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014/7 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]) SHELXLE (Hübschle et al., 2011[Hübschle, C. B., Sheldrick, G. M. & Dittrich, B. (2011). J. Appl. Cryst. 44, 1281-1284.]), Mercury (Macrae et al., 2006[Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453-457.]) and SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Supporting information

Computing details top

Data collection: APEX2 (Bruker, 2012); cell refinement: 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).

4'-Bromo-2',5'-dimethoxy-2,5-dioxo-[1,1'-biphenyl]-3,4-dicarbonitrile benzene hemisolvate top
Crystal data top
C16H9BrN2O4·0.5C6H6Z = 2
Mr = 412.22F(000) = 414
Triclinic, P1Dx = 1.603 Mg m3
a = 8.0427 (17) ÅMo Kα radiation, λ = 0.71073 Å
b = 10.343 (2) ÅCell parameters from 5182 reflections
c = 11.007 (2) Åθ = 2.9–27.4°
α = 104.469 (2)°µ = 2.43 mm1
β = 95.120 (2)°T = 173 K
γ = 102.851 (2)°Block, black
V = 854.1 (3) Å30.21 × 0.11 × 0.06 mm
Data collection top
3382 reflections with I > 2σ(I)
Radiation source: sealed X-ray tubeRint = 0.022
phi and ω scansθmax = 27.6°, θmin = 2.9°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 1010
Tmin = 0.600, Tmax = 0.746k = 1313
11856 measured reflectionsl = 1414
3957 independent reflections
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)] = 0.028Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.068H-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 parametersΔρmax = 0.40 e Å3
0 restraintsΔρmin = 0.35 e Å3
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
C10.1145 (2)0.15670 (19)0.05223 (15)0.0248 (4)
C20.2309 (2)0.02953 (19)0.02559 (16)0.0249 (4)
C30.2939 (2)0.04468 (18)0.10043 (16)0.0240 (4)
C40.2382 (2)0.01088 (18)0.19817 (15)0.0216 (3)
C50.1153 (2)0.13776 (18)0.16872 (15)0.0219 (3)
C60.0521 (2)0.21285 (18)0.04302 (16)0.0235 (4)
C70.3088 (2)0.06338 (17)0.33278 (15)0.0207 (3)
C80.5003 (2)0.10333 (17)0.36973 (15)0.0207 (3)
C90.5736 (2)0.19577 (17)0.50147 (15)0.0207 (3)
C100.4713 (2)0.21563 (17)0.59112 (15)0.0212 (3)
C110.2798 (2)0.15131 (17)0.55889 (16)0.0215 (3)
C120.2090 (2)0.08304 (18)0.42447 (16)0.0224 (3)
C130.4568 (3)0.2362 (2)0.04085 (19)0.0327 (4)
C140.1132 (3)0.4035 (2)0.10228 (19)0.0356 (4)
C150.5379 (2)0.29235 (19)0.72153 (16)0.0260 (4)
C160.7587 (2)0.24907 (19)0.52856 (16)0.0257 (4)
C170.3212 (2)0.45790 (19)0.48189 (19)0.0298 (4)
C180.4079 (3)0.43078 (19)0.37931 (18)0.0301 (4)
C190.5876 (3)0.4731 (2)0.39738 (18)0.0306 (4)
N10.9050 (2)0.2909 (2)0.55007 (17)0.0393 (4)
N20.5915 (2)0.35262 (19)0.82435 (15)0.0399 (4)
O10.06536 (16)0.33788 (13)0.00550 (12)0.0311 (3)
O20.40645 (18)0.17220 (13)0.13801 (12)0.0327 (3)
O30.59685 (17)0.05565 (14)0.30356 (12)0.0308 (3)
O40.19158 (16)0.15713 (14)0.64297 (12)0.0303 (3)
Br10.04198 (3)0.26003 (2)0.22428 (2)0.03965 (8)
Atomic displacement parameters (Å2) top
C10.0214 (8)0.0332 (10)0.0170 (8)0.0076 (7)0.0021 (6)0.0015 (7)
C20.0256 (9)0.0318 (10)0.0200 (8)0.0081 (8)0.0074 (7)0.0098 (7)
C30.0254 (9)0.0231 (9)0.0231 (8)0.0045 (7)0.0069 (7)0.0062 (7)
C40.0235 (8)0.0217 (9)0.0190 (8)0.0055 (7)0.0057 (6)0.0042 (6)
C50.0225 (8)0.0242 (9)0.0194 (8)0.0058 (7)0.0062 (6)0.0059 (7)
C60.0180 (8)0.0256 (9)0.0248 (8)0.0044 (7)0.0040 (6)0.0035 (7)
C70.0242 (8)0.0165 (8)0.0211 (8)0.0021 (7)0.0053 (6)0.0065 (6)
C80.0230 (8)0.0193 (8)0.0212 (8)0.0033 (7)0.0081 (6)0.0085 (6)
C90.0208 (8)0.0199 (8)0.0229 (8)0.0041 (7)0.0039 (6)0.0093 (7)
C100.0239 (8)0.0208 (9)0.0195 (8)0.0034 (7)0.0048 (6)0.0080 (6)
C110.0223 (8)0.0208 (8)0.0220 (8)0.0048 (7)0.0068 (6)0.0065 (6)
C120.0205 (8)0.0226 (9)0.0218 (8)0.0015 (7)0.0047 (6)0.0051 (7)
C130.0354 (10)0.0330 (10)0.0332 (10)0.0033 (9)0.0115 (8)0.0182 (8)
C140.0371 (11)0.0271 (10)0.0350 (10)0.0038 (9)0.0107 (8)0.0037 (8)
C150.0250 (9)0.0292 (10)0.0240 (9)0.0031 (8)0.0054 (7)0.0108 (7)
C160.0256 (9)0.0307 (10)0.0227 (8)0.0059 (8)0.0056 (7)0.0114 (7)
C170.0237 (9)0.0242 (9)0.0399 (10)0.0022 (8)0.0026 (8)0.0105 (8)
C180.0329 (10)0.0237 (9)0.0293 (9)0.0030 (8)0.0015 (8)0.0053 (7)
C190.0329 (10)0.0282 (10)0.0322 (10)0.0088 (8)0.0098 (8)0.0083 (8)
N10.0243 (9)0.0536 (12)0.0407 (10)0.0062 (8)0.0046 (7)0.0181 (9)
N20.0457 (10)0.0428 (10)0.0235 (8)0.0013 (8)0.0018 (7)0.0077 (7)
O10.0283 (7)0.0286 (7)0.0267 (6)0.0046 (6)0.0027 (5)0.0013 (5)
O20.0445 (8)0.0254 (7)0.0232 (6)0.0044 (6)0.0095 (6)0.0078 (5)
O30.0284 (7)0.0338 (7)0.0307 (7)0.0086 (6)0.0142 (5)0.0058 (6)
O40.0271 (7)0.0380 (8)0.0241 (6)0.0055 (6)0.0113 (5)0.0054 (5)
Br10.03537 (12)0.05225 (15)0.01873 (10)0.00172 (9)0.00001 (7)0.00002 (8)
Geometric parameters (Å, º) top
C1—C21.379 (3)C11—O41.213 (2)
C1—C61.399 (2)C11—C121.470 (2)
C1—Br11.8928 (17)C12—H120.9500
C2—C31.393 (2)C13—O21.434 (2)
C3—O21.364 (2)C13—H13B0.9800
C3—C41.403 (2)C13—H13C0.9800
C4—C51.399 (2)C14—O11.436 (2)
C4—C71.482 (2)C14—H14A0.9800
C5—C61.392 (2)C14—H14B0.9800
C6—O11.362 (2)C15—N21.138 (2)
C7—C121.349 (2)C16—N11.141 (2)
C7—C81.493 (2)C17—C181.382 (3)
C8—O31.212 (2)C17—C19i1.390 (3)
C8—C91.506 (2)C17—H170.9500
C9—C101.346 (2)C18—C191.394 (3)
C9—C161.443 (2)C18—H180.9500
C10—C151.443 (2)C19—C17i1.390 (3)
C10—C111.506 (2)C19—H190.9500
C2—C1—C6122.44 (15)O4—C11—C10119.64 (15)
C2—C1—Br1118.35 (13)C12—C11—C10117.32 (14)
C6—C1—Br1119.19 (13)C7—C12—C11123.04 (15)
C1—C2—C3119.35 (15)C7—C12—H12118.5
O2—C3—C2124.46 (15)O2—C13—H13B109.5
O2—C3—C4115.94 (15)H13A—C13—H13B109.5
C2—C3—C4119.59 (16)O2—C13—H13C109.5
C5—C4—C3119.93 (15)H13A—C13—H13C109.5
C5—C4—C7119.47 (14)H13B—C13—H13C109.5
C3—C4—C7120.60 (15)O1—C14—H14A109.5
C6—C5—C4120.83 (15)O1—C14—H14B109.5
O1—C6—C5124.89 (15)H14A—C14—H14C109.5
O1—C6—C1117.32 (15)H14B—C14—H14C109.5
C5—C6—C1117.79 (16)N2—C15—C10179.5 (2)
C12—C7—C4123.16 (15)N1—C16—C9179.8 (2)
C12—C7—C8118.87 (15)C18—C17—C19i120.29 (17)
C4—C7—C8117.58 (14)C18—C17—H17119.9
O3—C8—C7123.21 (15)C19i—C17—H17119.9
O3—C8—C9118.80 (15)C17—C18—C19119.66 (17)
C7—C8—C9117.66 (14)C17—C18—H18120.2
C10—C9—C16122.54 (15)C19—C18—H18120.2
C10—C9—C8120.68 (15)C17i—C19—C18120.05 (18)
C16—C9—C8116.49 (14)C17i—C19—H19120.0
C9—C10—C15122.68 (15)C18—C19—H19120.0
C9—C10—C11120.23 (15)C6—O1—C14117.33 (14)
C15—C10—C11117.03 (14)C3—O2—C13117.42 (14)
O4—C11—C12123.04 (16)
C6—C1—C2—C32.2 (3)C4—C7—C8—C9171.61 (14)
Br1—C1—C2—C3176.22 (13)O3—C8—C9—C10158.87 (16)
C1—C2—C3—O2178.67 (17)C7—C8—C9—C1014.8 (2)
C1—C2—C3—C40.0 (3)O3—C8—C9—C1615.1 (2)
O2—C3—C4—C5176.45 (16)C7—C8—C9—C16171.25 (14)
C2—C3—C4—C52.3 (3)C16—C9—C10—C150.3 (3)
O2—C3—C4—C73.8 (2)C8—C9—C10—C15173.92 (15)
C2—C3—C4—C7177.44 (16)C16—C9—C10—C11176.80 (15)
C3—C4—C5—C62.5 (3)C8—C9—C10—C113.2 (2)
C7—C4—C5—C6177.20 (15)C9—C10—C11—O4171.98 (16)
C4—C5—C6—O1178.97 (16)C15—C10—C11—O45.3 (2)
C4—C5—C6—C10.4 (3)C9—C10—C11—C127.8 (2)
C2—C1—C6—O1178.57 (16)C15—C10—C11—C12174.96 (15)
Br1—C1—C6—O13.0 (2)C4—C7—C12—C11177.18 (15)
C2—C1—C6—C52.0 (3)C8—C7—C12—C114.5 (2)
Br1—C1—C6—C5176.44 (12)O4—C11—C12—C7172.59 (17)
C5—C4—C7—C1247.4 (2)C10—C11—C12—C77.1 (2)
C3—C4—C7—C12132.83 (18)C19i—C17—C18—C190.0 (3)
C5—C4—C7—C8125.34 (17)C17—C18—C19—C17i0.0 (3)
C3—C4—C7—C854.4 (2)C5—C6—O1—C147.0 (3)
C12—C7—C8—O3158.02 (17)C1—C6—O1—C14172.39 (16)
C4—C7—C8—O315.1 (2)C2—C3—O2—C132.9 (3)
C12—C7—C8—C915.3 (2)C4—C3—O2—C13175.80 (16)
Symmetry code: (i) x+1, y+1, z+1.


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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