Crystal structure of 4-bromo­cinnamic anhydride

In the crystal, mol­ecules of the title compound [systematic name: (E)-3-(4-bromo­phen­yl)prop-2-enoyl (E)-3-(4-bromo­phen­yl)prop-2-enoate], C₁₈H₁₂Br₂O₃, reside across twofold axes passing through the central O atom of the C(O)—O—C(O) linkage [Z′ = ½]. The mol­ecule framework adopts an E configuration across the C=C bonds and a gauche conformation across the anhydride bridge, with a O—C—O—C torsion angle of 31.70 (11)°. The three-dimensional supra­molecular structure is governed by the inter­play of C—H⋯O hydrogen bonds and slipped stacking inter­actions involving carbon­yl/C₆H₄Br and anti­parallel C₆H₄Br/C₆H₄Br pairs. Hirshfeld surface and fingerprint plot analyses reveal major contributions from Br⋯H/H⋯Br and O⋯H/H⋯O contacts. The largest inter­action energies (up to −48.9 kJ mol⁻¹) are associated with stacking of the mol­ecules, which highlight the dispersion-dominated stabilization. The comparable energetics of hydrogen-bonded pairs (−37.9 kJ mol⁻¹) is a result of as many as four synergetic geometrically favorable C—H⋯O inter­actions. The study represents the first structural characterization of a p-halogenated cinnamic anhydride and these findings could be applicable to crystal design with cinnamic derivatives.

1. Chemical context

Cinnamic anhydride derivatives, R—CH=CH—C(O)—O—C(O)—CH=CH—R′, where R and R′ denote aromatic substituents, represent a versatile class of compounds applicable to organic synthesis, medicinal chemistry, and materials science (Raja et al., 2017). Their electrophilic carbonyl groups render them reactive toward nucleophiles such as alcohols, amines and enolates, enabling the selective introduction of carbonyl functionalities into diverse mol­ecular frameworks (Lin et al., 2021; Robinson et al., 2013). Noteworthy applications include esterification of xylans using ionic liquids to produce hemicellulose derivatives (Yang et al., 2017), the efficient one-pot synthesis of thio­esters with sodium thio­sulfate penta­hydrate (Liao & Liang, 2018), and C—H activation strategies such as rhodium(I)-catalyzed alkenylation of 2-pyridones (Zhao et al., 2019). Furthermore, their potential as selective acetyl­cholinesterase inhibitors has underscored their relevance in medicinal and neuropharmacological research (Giessel et al., 2019).

Within this family, halogen-substituted cinnamic anhydrides are of particular inter­est because the electronic effects of halogen substituents can influence both the mol­ecular reactivity and crystal packing (Raja et al., 2017). For example, crystal engineering with cinnanic acid derivatives attracts significant attention in the view of solid-state [2 + 2] cyclo­additions (Liu et al., 2025). Despite this relevance, the crystal structures of p-halocinnamic anhydrides have not previously been reported. The presence of a halogen atom offers the possibility of halogen bonding and other directional inter­molecular inter­actions. Herein, we describe the first single-crystal X-ray diffraction study of such a species, namely the title compound p-bromo­cinnamic anhydride (I), providing detailed insights into its mol­ecular geometry and supra­molecular features in the solid state.

2. Structural commentary

The title compound crystallizes in monoclinic space group C2/c, with the unique portion of the structure comprising half a mol­ecule (Z′ = ½) lying about a crystallographic twofold rotation axis passing through the central anhydride O1 atom (Fig. 1).

Figure 1 The mol­ecular structure of (I), showing the atom labeling and displacement ellipsoids drawn at the 50% probability level. [Symmetry code: (v) −x + 1, y, −z + .]

The mol­ecule adopts a E-configuration about each C=C double bond and displays a gauche conformation across the O—C—O—C anhydride bridge. The dihedral angle between the two C=C—C(O) planes is 55.36 (3)°. This conformation differs from the syn–tt–tt arrangement predicted to be the most stable in the gas phase for cinnamic anhydride and 3-chloro­cinnamic anhydride relatives at the B3LYP/6-311++g(d,p) level of theory (Mary et al., 2014a,b).

Each half of the mol­ecule, comprising a 4-bromo­phen­yl–vin­yl–carboxyl fragment, is nearly planar, with dihedral angle of 4.66 (6)° between the 4-bromo­phenyl ring and the C=C—C(O) plane. This value is slightly smaller than the corresponding torsion angle of 8.85° observed in crystalline 4-bromo­cinnamic acid (Yates & Sparkes, 2013).

3. Supra­molecular features

In the crystal, mol­ecules of (I) are linked into hydrogen-bonded chains running down the c-axis direction (Fig. 2), in which the inversion-related 4-bromo­phen­yl—vin­yl—carboxyl fragments [symmetry code: (i) −x + 1, −y, −z + 1] are linked by two pairs of reciprocal C2—H⋯O2ⁱ and C5—H⋯O2ⁱ hydrogen bonds (Table 1). These multiple inter­actions are geometrically favorable, as it is reflected by nearly straight angles at the hydrogen atoms [168.0 (17) and 171.6 (16)°]. The C2⋯O2ⁱ separation of 3.4574 (18) Å perfectly agrees with the mean value for such hydrogen bonds from statistical analysis of cinnamate esters (3.47 Å; Pálinkó, 1999). A second type of packing-defining force is associated with two kinds of stacking inter­actions. The first motif arises from anti­parallel alignment of the inversion-related C₆H₄—C=C—C=O fragments, which yields double carbon­yl/ring inter­actions with notably short O2⋯Cg1^vi and O2⋯plane distances of 3.4770 (13) Å and 3.3876 (14) Å, respectively [Cg1 is the ring centroid; symmetry code: (vi) −x + 1, −y + 1, −z + 1] (Fig. 2). In combination with the above hydrogen bonding, these inter­actions assemble the mol­ecules into the layers parallel to the bc plane.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯O2^i	0.95 (2)	2.51 (2)	3.4574 (18)	171.6 (16)
C5—H5⋯O2^i	0.95 (2)	2.59 (2)	3.5219 (18)	168.0 (17)
C6—H6⋯Br1^ii	0.96 (2)	3.20 (2)	3.9492 (14)	136.0 (15)
C8—H8⋯Br1^iii	0.94 (2)	3.20 (2)	4.1064 (15)	161.0 (15)
C9—H9⋯Br1^iv	0.971 (19)	3.095 (18)	3.8551 (14)	136.3 (13)
Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Figure 2 (a) Supra­molecular chain down the c-axis direction, sustained by multiple C—H⋯O hydrogen bonding; (b) double carbon­yl–π stacking inter­actions supporting columns along b-axis direction. O⋯π contacts and hydrogen bonds are indicated in red and blue, respectively. [Symmetry codes: (i) −x + 1, −y, −z + 1; (v) −x + 1, y, −z + ; (vi) −x + 1, −y + 1, −z + 1.]

This pattern bears a close resemblance to the one in methyl 4-bromo­cinnamate (Leiserowitz & Schmidt, 1965). The present structure inherits not only its local hydrogen-bonding motif with multiple reciprocal inter­actions, but also stacking of hydrogen-bonded dimers leading to similar columns. In fact, (I) may be best related to methyl 4-bromo­cinnamate when considering the anhydride linkage C1—O1—C1ⁱⁱ [symmetry code: (ii) −x + 1, y, −z + ] as a kind of bridge between pairs of 4-bromo­cinnamate ‘tectons' that formally condition connection of the columns in a second dimension. This is illustrative of a general principle of crystal engineering and it may suggest certain and still unexplored potential of anhydrides for crystal design.

The second type of stacking is found between the layers (Fig. 3), in the form of slipped-anti­parallel dimers of Br—C₆H₄ fragments [symmetry code: (vii) −x + , −y + , −z + 1], with two bromine atoms located approximately above the corresponding ring centroids [Br1⋯Cg1^vii = 4.0521 (6) Å; Br1⋯plane = 3.6963 (12) Å]. However, this stack is associated with relatively large slippage of 24.19 (2)°, defined as the angle subtended by the Br1⋯Cg1^vii axis to the ring normal. The lack of the essential overlap is also reflected by the large inter­centroid distance of 4.375 (2) Å.

Figure 3 Projection of the structure in the ac-plane showing mutual inter­actions of C6H4Br groups and C—H⋯Br contacts between successive hydrogen- and O⋯π bonded layers (which are orthogonal to the drawing plane and are indicated by blue strips). [Symmetry codes: (i) −x + 1, −y, −z + 1; (ii) −x + , y − , −z + ; (v) −x + 1, y, −z + ; (vii) −x + , −z + , −z + 1.]

The bromine atoms also engage in a set of distal contacts, e.g. Br1⋯Br1^viii = 3.7166 (2) Å [symmetry code: (viii) −x + , y + , −z + ]. These separations slightly exceed the sum of the van der Waals radii for bromine (3.70 Å; Bondi, 1964), suggesting a weakness of the present halogen⋯halogen contacts. As well, there are three types of H⋯Br contacts (Table 1), the shortest of which is H9⋯Br1^iv = 3.095 (18) Å [symmetry code: (iv) x, −y + 2, z + ]. They are reflective of very weak hydrogen bonding or dispersion forces.

4. Hirshfeld surface analysis

The Hirshfeld surface (HS) of compound (I), mapped over the normalized contact distance (d_norm) (Fig. 4), highlights the contributions of carbonyl-based hydrogen bonding and C⋯C contacts associated with π–π inter­actions to the consolidation of the crystal structure (Spackman & Jayatilaka, 2008). Two sets of four intense red spots on the HS correspond to reciprocal C=O⋯H—C inter­actions, involving carbonyl oxygen atoms and two types of hydrogen donors: vinyl hydrogen (H⋯O = 2.51 Å) and aromatic ortho-hydrogen (H⋯O = 2.59 Å)]. Weaker red spots are associated with mutual C⋯C contacts, one set between the aromatic ortho-carbon and vinyl carbon (3.35 Å) along the b-axis, and the other between an ortho-carbon and a carbonyl carbon (3.38 Å) across adjacent mol­ecular b-axis columns.

Figure 4 Hirshfeld surface of the mol­ecule of (I) mapped over dnorm.

The two-dimensional fingerprint plots (Fig. 5) further qu­antify the contributions of specific inter­actions to the HS (McKinnon et al., 2007; Spackman & McKinnon, 2002). The largest contribution arises from Br⋯H/H⋯Br contacts (24.5%), mainly involving ortho-positioned aromatic hydrogens. These appear as wing-like features in the fingerprint plot (Fig. 4b), with characteristic tips at d_e/d_i ≃ 1.9/1.1 Å, indicative of directional inter­actions. Therefore, in spite of relatively large distances, the fingerprint plots allow attribution of the contacts to very weak C—H⋯Br hydrogen bonding.

Figure 5 Two-dimensional fingerprint plots showing all inter­actions and delineated into the principal contributions of different types of the contacts (including also reciprocal contacts).

O⋯H/H⋯O contacts (19.2%), corresponding to the above C=O⋯H—C inter­actions, produce the sharpest spikes at d_e/d_i ≃ 1.4/1.0 Å (Fig. 5d). C⋯C contacts (6.2%) reflect slipped stacking between vinyl and aromatic fragments. Perceptible contributions also include C⋯O/O⋯C (3.9%) and C⋯Br/Br⋯C (3.2%), which are consistent with the observed O⋯π (d_e/d_i ≃ 1.9/1.6 Å) and Br⋯π contacts. A smaller percentage arise from Br⋯Br (2.3%) contacts, corresponding to weak halogen⋯halogen inter­actions at distances approaching the sum of the van der Waals radii (3.70 Å; Bondi, 1964).

5. Inter­action energy calculations

Pairwise inter­action energies were calculated using the CE-B3LYP model implemented in CrystalExplorer (Mackenzie et al., 2017; Turner et al., 2015) to assess the energetic contributions stabilizing the supra­molecular architecture of (I) (Fig. 6). The total inter­action energy (E_tot) is expressed as the sum of electrostatic (E_ele), polarization (E_pol), dispersion (E_dis) and exchange-repulsion (E_rep) terms.

Figure 6 Principal pathways of pairwise inter­molecular inter­actions, identified with a cut-off limit of 12.0 kJ mol^−1. Partial energetic contributions, symmetry operations, and geometric related parameters are summarized in Table 2.

Considering inter­actions with |E_tot| ≥ 12.0 kJ mol⁻¹, five symmetry-independent paths were identified in the closest environment of the title mol­ecule (Table 2). The strongest inter­action [E_tot = −48.9 kJ mol⁻¹; R = 5.70 Å] occurs between translation-related mol­ecules along the b-axis, where C⋯C contacts between p-bromo­phenyl rings and vinyl groups dominate (pair A⋯B, Fig. 6). This inter­action is dispersion-driven (E_dis = −58.9 kJ mol⁻¹) and its significant energy originates in a relatively large inter­action area.

Table 2
Calculated inter­action energies (kJ mol⁻¹)

R is the distance between centroids of the inter­acting mol­ecules. Inter­action energies were calculated employing the CE-B3LYP/6–31G(d,p) functional/basis set combination. The scale factors used to determine E_tot: k_ele = 1.057, k_pol = 0.740, k_dis = 0.871, and k_rep = 0.618 (Mackenzie et al., 2017).

Path	Symmetry relation	Type	R (Å)	Eele	Epol	Edis	Erep	Etot
A⋯B	x, y + 1, z	C⋯C; dispersion	5.70	−17.2	−5.8	−58.9	40.4	−48.9
A⋯C	-x + 1, −y, −z + 1	C—H⋯O; HB	10.48	−32.2	−7.7	−16.5	26.2	−37.9
A⋯D	-x + 1, −y + 1, −z + 1	O⋯π; dispersion	7.15	−0.7	−3.2	−56.8	32.4	−31.1
A⋯E	-x + , −y + , −z + 1	Br⋯π stacking	12.71	6.8	−0.4	−28.9	0.0	−18.3
A⋯F	x, −y + 2, z +	Br⋯H	7.59	−7.0	−1.1	−17.1	15.5	−13.5

Second notable inter­action energy (E_tot = −37.9 kJ mol⁻¹; R = 10.48 Å) is supported by C—H⋯O bonding of inversion-related mol­ecules (−x + 1, −y, −z + 1; pair A⋯C) and it is characterized by prevalence of the electrostatic component (E_ele = −32.2 kJ mol⁻¹). These relatively large values agree with the formation of multiple hydrogen bonds, which act in synergy. Accordingly, a comparable C—H⋯O-bonded dimer of acrylic acid, which retains only two out of four present directional bonds, revealed a lower by half inter­action energy of −19.9 kJ mol⁻¹ (Czernek et al., 2023). Another significant pair (A⋯D) between inversion-related mol­ecules (−x + 1, −y + 1, −z + 1) yields E_tot = −31.1 kJ mol⁻¹ (R = 7.15 Å), dominated by dispersion (E_dis = −56.8 kJ mol⁻¹) and arising from C=O⋯π contacts.

Two further moderate in strength inter­actions are the pair A⋯E [E_tot = −18.3 kJ mol⁻¹; R = 12.71 Å], attributed to slipped anti­parallel stacking generating Br⋯π contacts, and pair A⋯F [E_tot = −13.5 kJ mol⁻¹; R = 7.15 Å], associated with Br⋯H contacts. Both are governed primarily by dispersion, but in the latter case the E_ele component is also perceptible, being the third electrostatic contributor among the entire hierarchy of inter­action energies.

6. Database survey

A search of the Cambridge Structural Database (CSD, July 2025 release; Groom et al., 2016) for cinnamic anhydride derivatives revealed no closely related crystal structures, indicating an absence of this subclass in the structural record. In contrast, numerous entries exist for cinnamic acid precursors, particularly for trans-cinnamic acid itself (for the most recent redetermination, see Howard et al., 2009), as well as for para-halogenated analogues such as 4-fluoro­cinnamic (Jenkins et al., 2006), 4-chloro­cinnamic (Hsieh et al., 2005), and 4-bromo­cinnamic (Schmidt, 1964) acids. In addition, a recent study provided 21 examples of 4-halophenyl 4-halocinnamate esters (Liu et al., 2025). The most comparable methyl 4-bromo­cinnamate (Refcode: MEBCIN; Leiserowitz & Schmidt, 1965) is mentioned above.

The absence of structurally characterized cinnamic anhydrides in the CSD may reflect intrinsic crystallization challenges associated with this subclass, including increased conformational flexibility (Mary et al., 2014a,b), which can hinder efficient packing, and a higher propensity for hydrolysis under ambient conditions, both of which may favor amorphous or poorly crystalline forms (Raja et al., 2017).

In this context, the present study reports the first single-crystal X-ray diffraction analysis of a p-halogenated cinnamic anhydride, providing detailed insights into its conformation, mol­ecular symmetry, and supra­molecular organization. This work establishes a useful reference point for future studies on the solid-state behavior and reactivity of cinnamic anhydride derivatives.

7. Synthesis and crystallization

4-Bromo­cinnamic acid was obtained from a commercial supplier and used without further purification. The title compound (I) was synthesized via a one-pot condensation reaction using N,N′-di­cyclo­hexyl­carbodi­imide (DCC) as coupling agent (Albert et al., 2017). 4-Bromo­cinnamic acid (200 mg, 0.881 mmol) was dissolved in chloro­form (8 ml) and DCC (0.881 mmol) was added. The reaction mixture was refluxed for 24 h, during which time a white precipitate of di­cyclo­hexyl­urea formed, which was removed by filtration after cooling. The filtrate was concentrated under reduced pressure and the crude product was washed with cold methanol and dried affording 4-bromo­cinnamic anhydride as a colorless solid (185 mg, 95%). M.p. = 470.5–470.8 K. FT-IR (ATR, cm⁻¹): 3272 (Ar CH), 2924 and 2856 (vinyl CH), 1707 (C=O), 1644 (vinyl C=C), 1599 (Ar C C), 1485 and 1447 (ring skeletal vibrations), 1367 (C—O—C), 1226 (C—O), 1069 (C—H bending), 986 (vinyl CH wag), 813 (aromatic CH bending), 618 (C—Br), 515 (C—Br stretching/ring deformation) and 488 (C—O—C bending and ring torsion).

Single crystals suitable for X-ray diffraction were obtained by slow evaporation of a dilute solution of the compound in the mixed solvents of ethyl acetate/di­chloro­methane (1:10, v/v) stored at 278 K. Colorless crystals formed over the period of 7 d.

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. All hydrogen atoms were located and then freely refined with isotropic displacement parameters, which results in C—H = 0.94 (2)–0.971 (19) Å. One outlier (200) was omitted in the last cycles of refinement.

Table 3
Experimental details

Crystal data
Chemical formula	C18H12Br2O3
Mr	436.10
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	150
a, b, c (Å)	20.6900 (5), 5.7029 (1), 13.5534 (3)
β (°)	93.392 (1)
V (Å^3)	1596.40 (6)
Z	4
Radiation type	Mo Kα
μ (mm^−1)	5.09
Crystal size (mm)	0.38 × 0.22 × 0.21
Data collection
Diffractometer	Bruker D8 Venture κ-geometry diffractometer 208039-01
Absorption correction	Multi-scan (SADABS; Krause et al., 2015)
Tmin, Tmax	0.505, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	20264, 1784, 1702
Rint	0.028
(sin θ/λ)max (Å^−1)	0.649
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.017, 0.045, 1.09
No. of reflections	1784
No. of parameters	129
H-atom treatment	All H-atom parameters refined
Δρmax, Δρmin (e Å^−3)	0.27, −0.33
Computer programs: APEX5 and SAINT (Bruker, 2018), SHELXS97 (Sheldrick, 2008), SHELXL2019/3 (Sheldrick, 2015) and DIAMOND (Brandenburg, 1999).

Supporting information

Computing details

(E)-3-(4-Bromophenyl)prop-2-enoyl (E)-3-(4-bromophenyl)prop-2-enoate

Crystal data

C18H12Br2O3	F(000) = 856
Mr = 436.10	Dx = 1.814 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 20.6900 (5) Å	Cell parameters from 9867 reflections
b = 5.7029 (1) Å	θ = 3.0–27.5°
c = 13.5534 (3) Å	µ = 5.09 mm^−1
β = 93.392 (1)°	T = 150 K
V = 1596.40 (6) Å^3	Prism, colourless
Z = 4	0.38 × 0.22 × 0.21 mm

Data collection

Bruker D8 Venture κ-geometry diffractometer 208039-01	1784 independent reflections
Radiation source: micro-focus X-ray source	1702 reflections with I > 2σ(I)
Detector resolution: 52.0833 pixels mm^-1	Rint = 0.028
ω–scans	θmax = 27.5°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −26→26
Tmin = 0.505, Tmax = 0.746	k = −7→7
20264 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.017	Hydrogen site location: difference Fourier map
wR(F^2) = 0.045	All H-atom parameters refined
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0202P)^2 + 1.5368P] where P = (Fo^2 + 2Fc^2)/3
1784 reflections	(Δ/σ)max = 0.002
129 parameters	Δρmax = 0.27 e Å^−3
0 restraints	Δρmin = −0.33 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.72429 (2)	1.05887 (3)	0.32640 (2)	0.02833 (7)
O2	0.47808 (6)	−0.05003 (19)	0.64920 (8)	0.0292 (2)
O1	0.500000	0.2596 (2)	0.750000	0.0256 (3)
C1	0.50364 (7)	0.1372 (3)	0.66208 (10)	0.0214 (3)
C2	0.53902 (7)	0.2660 (2)	0.58928 (10)	0.0219 (3)
C3	0.57054 (7)	0.4669 (3)	0.60876 (10)	0.0217 (3)
C4	0.60848 (7)	0.5984 (2)	0.53989 (10)	0.0204 (3)
C5	0.61593 (7)	0.5260 (3)	0.44231 (11)	0.0230 (3)
C6	0.65139 (7)	0.6601 (3)	0.37961 (11)	0.0240 (3)
C7	0.67923 (7)	0.8681 (3)	0.41427 (10)	0.0215 (3)
C8	0.67399 (8)	0.9422 (3)	0.51050 (12)	0.0250 (3)
C9	0.63846 (7)	0.8065 (3)	0.57250 (10)	0.0236 (3)
H2	0.5376 (9)	0.194 (3)	0.5257 (14)	0.030 (4)*
H3	0.5691 (9)	0.534 (3)	0.6727 (15)	0.027 (5)*
H5	0.5967 (10)	0.385 (4)	0.4184 (14)	0.034 (5)*
H6	0.6569 (10)	0.609 (4)	0.3128 (15)	0.033 (5)*
H8	0.6933 (10)	1.082 (3)	0.5347 (15)	0.031 (5)*
H9	0.6335 (9)	0.858 (3)	0.6399 (14)	0.028 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.02947 (10)	0.02528 (10)	0.03090 (10)	−0.00097 (6)	0.00744 (6)	0.00371 (6)
O2	0.0363 (6)	0.0248 (6)	0.0267 (5)	−0.0059 (4)	0.0044 (5)	−0.0049 (4)
O1	0.0436 (9)	0.0166 (7)	0.0171 (6)	0.000	0.0066 (6)	0.000
C1	0.0242 (7)	0.0212 (7)	0.0188 (6)	0.0041 (6)	0.0017 (5)	−0.0016 (5)
C2	0.0254 (7)	0.0222 (7)	0.0182 (6)	0.0039 (5)	0.0024 (5)	−0.0014 (5)
C3	0.0263 (7)	0.0217 (7)	0.0171 (6)	0.0050 (5)	0.0010 (5)	0.0006 (5)
C4	0.0223 (6)	0.0187 (6)	0.0201 (6)	0.0044 (5)	−0.0001 (5)	0.0008 (5)
C5	0.0267 (7)	0.0199 (7)	0.0226 (7)	0.0004 (6)	0.0018 (5)	−0.0031 (5)
C6	0.0262 (7)	0.0238 (7)	0.0224 (7)	0.0026 (6)	0.0039 (5)	−0.0028 (6)
C7	0.0194 (6)	0.0201 (6)	0.0251 (7)	0.0039 (5)	0.0022 (5)	0.0039 (5)
C8	0.0271 (7)	0.0199 (7)	0.0277 (7)	0.0003 (6)	−0.0024 (6)	−0.0017 (6)
C9	0.0285 (7)	0.0220 (7)	0.0200 (7)	0.0029 (6)	−0.0011 (5)	−0.0023 (5)

Geometric parameters (Å, º)

Br1—C7	1.8981 (14)	C4—C5	1.403 (2)
O2—C1	1.2000 (19)	C5—C6	1.385 (2)
O1—C1^i	1.3869 (15)	C5—H5	0.95 (2)
O1—C1	1.3869 (15)	C6—C7	1.388 (2)
C1—C2	1.461 (2)	C6—H6	0.96 (2)
C2—C3	1.337 (2)	C7—C8	1.381 (2)
C2—H2	0.95 (2)	C8—C9	1.385 (2)
C3—C4	1.462 (2)	C8—H8	0.94 (2)
C3—H3	0.95 (2)	C9—H9	0.971 (19)
C4—C9	1.399 (2)
C1^i—O1—C1	119.57 (16)	C6—C5—H5	119.1 (12)
O2—C1—O1	121.80 (13)	C4—C5—H5	120.4 (12)
O2—C1—C2	125.68 (13)	C5—C6—C7	119.23 (13)
O1—C1—C2	112.48 (12)	C5—C6—H6	120.5 (12)
C3—C2—C1	123.73 (13)	C7—C6—H6	120.2 (12)
C3—C2—H2	122.5 (11)	C8—C7—C6	121.79 (13)
C1—C2—H2	113.8 (11)	C8—C7—Br1	119.07 (11)
C2—C3—C4	125.98 (13)	C6—C7—Br1	119.14 (11)
C2—C3—H3	118.9 (11)	C7—C8—C9	118.43 (14)
C4—C3—H3	115.1 (11)	C7—C8—H8	122.2 (12)
C9—C4—C5	118.43 (13)	C9—C8—H8	119.4 (12)
C9—C4—C3	118.58 (13)	C8—C9—C4	121.58 (13)
C5—C4—C3	122.99 (13)	C8—C9—H9	119.5 (11)
C6—C5—C4	120.51 (14)	C4—C9—H9	118.9 (11)
C1^i—O1—C1—O2	31.70 (11)	C4—C5—C6—C7	−0.4 (2)
C1^i—O1—C1—C2	−150.51 (13)	C5—C6—C7—C8	1.7 (2)
O2—C1—C2—C3	−175.29 (15)	C5—C6—C7—Br1	−177.02 (11)
O1—C1—C2—C3	7.02 (19)	C6—C7—C8—C9	−1.7 (2)
C1—C2—C3—C4	177.73 (13)	Br1—C7—C8—C9	177.08 (11)
C2—C3—C4—C9	179.97 (14)	C7—C8—C9—C4	0.3 (2)
C2—C3—C4—C5	0.3 (2)	C5—C4—C9—C8	1.0 (2)
C9—C4—C5—C6	−1.0 (2)	C3—C4—C9—C8	−178.64 (13)
C3—C4—C5—C6	178.68 (13)

Symmetry code: (i) −x+1, y, −z+3/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···O2^ii	0.95 (2)	2.51 (2)	3.4574 (18)	171.6 (16)
C5—H5···O2^ii	0.95 (2)	2.59 (2)	3.5219 (18)	168.0 (17)
C6—H6···Br1^iii	0.96 (2)	3.20 (2)	3.9492 (14)	136.0 (15)
C8—H8···Br1^iv	0.94 (2)	3.20 (2)	4.1064 (15)	161.0 (15)
C9—H9···Br1^v	0.971 (19)	3.095 (18)	3.8551 (14)	136.3 (13)

Symmetry codes: (ii) −x+1, −y, −z+1; (iii) −x+3/2, y−1/2, −z+1/2; (iv) −x+3/2, −y+5/2, −z+1; (v) x, −y+2, z+1/2.