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

Meany, J.E.; Gerlach, D.L.; Papish, E.T.; Woski, S.A.

doi:10.1107/S2056989016005120

research communications

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ISSN: 2056-9890

Volume 72| Part 4| April 2016| Pages 600-603

https://doi.org/10.1107/S2056989016005120

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

Joseph E. Meany,^a Deidra L. Gerlach,^a Elizabeth T. Papish ^a and Stephen A. Woski ^a ^*

^aDepartment of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, AL, 35487, USA
^*Correspondence e-mail: swoski@ua.edu

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.

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.

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 ), 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. 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.

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). 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 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 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.

Figure 3
Packing diagram showing the off-center π–π short contacts of 1 with the intercalated solvent benzene. Weak hydrogen bonds from O2 project closely to the benzene protons.

Figure 4
Packing diagram showing the off-center π–π 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.

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. U_iso(H) values were set to a multiple of U_eq(C) with 1.5 for CH₃. Crystal data, data collection and structure refinement details are summarized in Table 1.

Table 1
Experimental details

Crystal data
Chemical formula	C₁₆H₉BrN₂O₄·0.5C₆H₆
M_r	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)
V (Å³)	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 )
T_min, T_max	0.600, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	11856, 3957, 3382
R_int	0.022
(sin θ/λ)_max (Å⁻¹)	0.653

Refinement
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
Δρ_max, Δρ_min (e Å⁻³)	0.40, −0.35
Computer programs: APEX2 and SAINT (Bruker, 2012 ), SHELXT (Sheldrick, 2015a ), SHELXL2014/7 (Sheldrick, 2015b ) SHELXLE (Hübschle et al., 2011 ), Mercury (Macrae et al., 2006 ) and SHELXTL (Sheldrick, 2008 ).

Supporting information

CCDC reference: 1470649

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989016005120/hb7567sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016005120/hb7567Isup2.hkl

checkCIF report

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

C₁₆H₉BrN₂O₄·0.5C₆H₆	Z = 2
M_r = 412.22	F(000) = 414
Triclinic, P1	D_x = 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

Data collection top

Bruker AXS SMART APEXII CCD diffractometer	3382 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube	R_int = 0.022
phi and ω scans	θ_max = 27.6°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −10→10
T_min = 0.600, T_max = 0.746	k = −13→13
11856 measured reflections	l = −14→14
3957 independent reflections

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.068	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0307P)² + 0.3076P] where P = (F_o² + 2F_c²)/3
3957 reflections	(Δ/σ)_max < 0.001
237 parameters	Δρ_max = 0.40 e Å⁻³
0 restraints	Δρ_min = −0.35 e Å⁻³

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

	x	y	z	U_iso*/U_eq
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)

Atomic displacement parameters (Å²) top

	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)

Geometric parameters (Å, º) top

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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