Crystal structure and Hirshfeld surface analysis of a conformationally unsymmetrical bis­chalcone: (1E,4E)-1,5-bis­(4-bromo­phen­yl)penta-1,4-dien-3-one

Arif Tawfeeq, N.; Kwong, H.C.; Mohamed Tahir, M.I.; Ravoof, T.B.S.A.

doi:10.1107/S2056989019006480

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ISSN: 2056-9890

Volume 75| Part 6| June 2019| Pages 774-779

https://doi.org/10.1107/S2056989019006480

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Crystal structure and Hirshfeld surface analysis of a conformationally unsymmetrical bischalcone: (1E,4E)-1,5-bis(4-bromophenyl)penta-1,4-dien-3-one

Nabeel Arif Tawfeeq,^a,^b Huey Chong Kwong,^a Mohamed Ibrahim Mohamed Tahir ^a ^* and Thahira B. S. A. Ravoof ^a

^aDepartment of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia, and ^bDepartment of Chemistry, College of Education for Women, University of Anbar, Iraq
^*Correspondence e-mail: ibra@upm.edu.my

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 25 April 2019; accepted 7 May 2019; online 10 May 2019)

In the title bischalcone, C₁₇H₁₂Br₂O, the olefinic double bonds are almost coplanar with their attached 4-bromophenyl rings [torsion angles = −10.2 (4) and −6.2 (4)°], while the carbonyl double bond is in an s-trans conformation with with respect to one of the C=C bonds and an s-cis conformation with respect to the other [C=C—C=O = 160.7 (3) and −15.2 (4)°, respectively]. The dihedral angle between the 4-bromophenyl rings is 51.56 (2)°. In the crystal, molecules are linked into a zigzag chain propagating along [001] by weak C—H⋯π interactions. The conformations of related bischalcones are surveyed and a Hirshfeld surface analysis is used to investigate and quantify the intermolecular contacts.

Keywords: crystal structure; bischalcone; pentadienone bridge; C—H⋯π interactions; Hirshfeld surface analysis.

CCDC reference: 1914420

1. Chemical context

Dibenzalacetone, or bischalcone, [(1E,4E)-1,5-diphenylpenta-1,4-dien-3-one] was first prepared by the base-catalyzed Aldol condensation of benzaldehyde and acetone (Conard & Morris, 1932 ): it results in a highly conjugated system involving the α,β-unsaturated pentadienone (–C=C—(C=O)—C=C—) moiety. Bischalcones have a number of uses including anti-inflammatory (Mahapatra et al., 2017 ) and anti-oxidant (Pandey & Syed, 2009 ) agents. Different bischalcones consist of two benzene rings substituted with different types of functional groups (electron donor or acceptor) bonded to the ends of the central α,β-unsaturated ketone which provides good configuration for the transfer of intramolecular charge (Fun et al., 2011 ). In a continuation of our ongoing studies on the non-linear optical properties of various chalcone derivatives (Sim et al., 2017 ; Kwong et al., 2018 ), we report herein the synthesis, structure determination and Hirshfeld surface analysis of the title compound (I).

2. Structural commentary

The asymmetric unit of (I) consists of a single molecule, consisting of two 4-bromophenyl rings connected by a penta-1,4-dien-3-one bridge (Fig. 1). The bond lengths and angles of the central chain are consistent with those in related structures (Butcher et al., 2007a ; Ruanwas et al., 2011 ). The overall conformation of (I) can be described by the the torsion angles between the olefinic double bonds and 4-bromophenyl rings [τ1 (C1—C6—C7—C8); τ4 (C13—C12—C11—C10)] and the carbonyl double bond [τ2 (C7—C8—C9—O1); τ3 (C11—C10—C9—O1)] (Fig. 2). The 4-bromophenyl rings in (I) are close to coplanar with their attached olefinic double bonds [τ₁ = −10.2 (4)°; τ₄ = −6.2 (4)°] but the conformations of the olefinic double bonds are very different: one is in s-trans [τ₂ = 160.7 (3)°] conformation and in s-cis [τ₃ = −15.2 (4)°] conformation with the central C=O double bond. These torsions result in an overall twisted shape for (I) with the dihedral angle between the 4-bromophenyl ring being 51.56 (2)°.

Figure 1
The molecular structure of the title compound showing 50% displacement ellipsoids.

Figure 2
General chemical diagram showing torsion angles, τ₁, τ₂, τ₃ and τ₄ in the title compound.

3. Supramolecular features

No classical hydrogen bonding is possible in (I) and in the crystal, molecules are linked by C—H⋯π interactions (Table 1): the first of these results in a phenyl–phenyl T-shaped geometry via C1—H1A⋯Cg1ⁱ (Fig. 3a). The C14—H14A⋯Cg2ⁱⁱ (Fig. 3b) interactions lead to a zigzag chain along the c-axis direction.

Table 1
Hydrogen-bond geometry (Å, °)

Cg1 and Cg2 are the centroids of the C1–C16 and C12–C17 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1A⋯Cg1ⁱ	0.93	2.86	3.539 (3)	131
C14—H14A⋯Cg2ⁱⁱ	0.93	2.74	3.428 (3)	131
Symmetry codes: (i) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (ii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Figure 3
A partial packing diagram of the title compound, with (a) C1—H1A⋯π and (b) C14—H14A⋯π interactions (dotted lines). Hydrogen atoms not involved in these interactions have been omitted for clarity.

4. Database survey

A survey of the Cambridge Structural Database (CSD, version 5.40, last update February 2019; (Groom et al., 2016 )) using (1E,4E)-1,5-diphenylpenta-1,4-dien-3-one as the main skeleton revealed the presence of 27 structures containing a similar bischalcone moiety to the title compound but with different substituents on the terminal phenyl rings. The different substituents (R₁ and R₂) together with the torsion angles of the penta-4,4-dien-3-one connecting bridge are compiled in Table 2. For the conformationally symmetrical compounds (i.e. both C=C—C=O bonds are either s-cis or s-trans), the olefinic double bonds are close to coplanar with their attached phenyl rings as indicated by their τ₁ and τ₄ torsion angles, which fall in the range of 0.0–17.8°, except for the compounds AMEXUN and HUDLEY, which have somewhat larger τ₁ and τ₄ values of 22.5–27.4°. The olefinic double bonds for the symmetrical compounds are mostly in s-cis conformations with the carbonyl double bond (τ₂/τ₃ torsion angles of 0.1–21.9°). However, both the olefinic double bonds of compounds GOLGOD and GOLGOD02 are in s-trans conformations with the carbonyl double bond (τ₂/τ₃ = 152.2–153.4°). Furthermore, it may be noted that the symmetrical conformation at the penta-4,4-dien-3-one connection bridge is not affected by the different substituents at the R₁ and R₂ positions in EDUSEE, SAFZOO and XOHVUN. Most of the unsymmetrical compounds (one C=C—C=O bond s-cis and one s-trans) have τ₁ and τ₄ values of 0.5–17.2°, which indicates that the olefinic double bonds are close to coplanar to their attached phenyl ring. The outliers are MESXEQ and WIHBUL, which have τ₁ and τ₄ values of 18.2–51.8° and 21.4–51.8°, respectively. The torsion angles τ₂ and τ₃ for the unsymmetrical compounds, including (I), are in the ranges 160.2–178.7° and 0.5–23.7°, respectively, which indicate s-trans and s-cis conformations between the olefinic double bonds and the carbonyl double bond.

Table 2
Torsion angles τ₁, τ₂, τ₃ and τ₄ (°)

Compound	R₁	R₂	τ₁	τ₂	τ₃	τ₄
Symmetrical
AMEXUN (Mark et al., 2016 )	4-(benzyloxy)-3-methoxyphenyl	4-(benzyloxy)-3-methoxyphenyl	27.4	19.3	20.4	22.5
COGNOD01 (Rawal et al., 2016 )	4-(diethylamino)phenyl	4-(diethylamino)phenyl	1.2, 4.0	11.0, 4.2	1.3, 2.9	0.7, 1.6
DUMWIS (Fun et al., 2010 )	2,4,5-trimethoxyphenyl	2,4,5-trimethoxyphenyl	11.6, 0.4, 11.8	0.7, 4.0, 5.5	3.0, 8.2, 6.0	9.8, 2.9, 3.7
EDUSEE (Rawal et al., 2016)	4-(diethylamino)phenyl	4-benzonitrile	15.6, 5.9	0.1, 6.4	8.1, 7.7	3.7, 3.2
GOLGOD (Shan et al., 1999 )	4-methoxyphenyl	4-methoxyphenyl	3.2	153.4	152.9	2.7
GOLGOD02 (Harrison et al., 2006 )	4-methoxyphenyl	4-methoxyphenyl	2.4	152.2	152.2	2.4
HIDMIQ (Zhou et al., 1999 )	2-methoxyphenyl	2-methoxyphenyl	0.2	1.4	1.2	8.8
HUDLEY (Feng et al., 2009 )	2,4-dimethylpheny	2,4-dimethylpheny	26.1	3.1	1.1	24.6
KOFCEO (Arshad et al., 2008 )	4-methylphenyl	4-methylphenyl	16.6	4.0	13	180
LEJNOE (Butcher et al., 2006 )	4-chlorophenyl	4-chlorophenyl	17.8	9.8	9.8	17.8
LESGAT (Park et al., 2013 )	2-(trifluoromethyl)phenyl	2-(trifluoromethyl)phenyl	0.5	0.3	2.9	13.7
SAFZOQ (Samshuddin et al., 2012 )	3-nitropheny	phenyl	6.1	11.3	21.9	10.4
SIMTUE (Nizam Mohideen et al., 2007 )	2-chlorophenyl	2-chlorophenyl	8.8	3.4	0.9	0.5
UPAWEO (Huang et al., 2011 )	2,6-difluorophenyl	2,6-difluorophenyl	2.3	4.4	0.8	178
UPAWEO01 (Schwarzer & Weber, 2014a )	2,6-difluorophenyl	2,6-difluorophenyl	2.3	4.4	0.8	0.5
WACXON (Hubig et al., 1992 )	o-tolyl	o-tolyl	10.3	1.1	2.8	1.5
XOHVOH (Schwarzer & Weber, 2014b )	pentafluorophenyl	pentafluorophenyl	3.0, 7.9	1.0, 5.7	1.6, 3.4	5.7, 2.3
XOHVUN (Schwarzer & Weber, 2014b)	pentafluorophenyl	phenyl	5.6	2.4	3.3	7.8

Unsymmetrical
(I)	4-bromophenyl	4-bromophenyl	10.2	160.7	15.2	6.2
IFAQAJ (Kapdi et al., 2013 )	3,5-dimethoxyphenyl	3,5-dimethoxyphenyl	5.4	173.1	0.6	3.2
LEJNOE01 (Maluleka & Mphahlele, 2017 )	4-chlorophenyl	4-chlorophenyl	11.2	160.2	13.6	6.6
MESXEQ (Dravida et al., 2018 )	2,6-dichlorophenyl	2,6-dichlorophenyl	46.8, 48.7, 51.8	175.3, 4.3, 178.7	7.5, 4.3, 15.5	32.7, 48.7, 51.8
QAJNOG (Ruanwas et al., 2011)	2,4,6-trimethoxyphenyl	2,4,6-trimethoxyphenyl	6.6, 0.5	176.8, 169.4	1.2, 0.5	3.7, 11.8
WIHBUL (Butcher et al., 2007a)	4-fluorophenyl	4-fluorophenyl	18.2, 18.7	169.0, 166.3	10.4, 8.8	21.8, 21.4
XIFTOW (Butcher et al., 2007b )	3,4-dimethoxyphenyl	3,4-dimethoxyphenyl	1.6, 1.6	162.8, 170.8	23.3, 23.7	3.1, 20.3
ZAPKIN (Chantrapromma et al., 2016 )	4-ethoxyphenyl	4-ethoxyphenyl	17.2	168.4	17.1	13.8
Multiple sets of torsion angles are stated for compounds COGNOD01, DUMWIS, EDUSEE, XOHVOH, MESXEQ, QAJNOG, WIHBUL and XIFTOW because there is more than one independent molecule in their asymmetric units. A third molecule with full molecule disorder in compound WIHBUL was excluded from this table.

5. Hirshfeld surface analysis

The Hirshfeld surfaces mapped with normalized contact distance d_norm and the two-dimensional fingerprint plots for (I) were generated using CrystalExplorer17.5 (Turner et al., 2017 ). The darkest red spots on the Hirshfeld surface mapped with d_norm (Fig. 4a) correspond to the C14—H14A⋯Cg2ⁱⁱ interaction. Even through the C1—H1A⋯Cg1ⁱ interaction is not visible in the d_norm surface mapping, this interaction can be seen as a unique pattern of a red `circle' on the shape-index surface mapping (Fig. 4b). Besides the C—H⋯π interactions, the d_norm surface mapping indicated a short contact between atom O1 and C5 with a distance of 0.06 Å shorter than the sum of the van der Waals radii of O and C atoms (3.22 Å; Fig. 5a). Together with this short contact, another weak C7—H7A⋯O1 interaction was also revealed as light spots on the d_norm surface (Fig. 5b).

Figure 4
The Hirshfeld surface mapped with (a) d_norm and (b) shape-index for the title compound showing the C—H⋯π interactions.

Figure 5
The Hirshfeld surface mapped with d_norm showing (a) the C5⋯O1 short contact and (b) the weak C7—H7A⋯O1 interaction.

As illustrated in Fig. 6, the corresponding fingerprint plots for (I) are shown with characteristic pseudo-symmetric wings in the d_e and d_i diagonal axes. The H⋯C/C⋯H contacts are the most populated contacts and contribute 34.1% to the total intermolecular contacts, followed by H⋯H (22.1%), H⋯Br/Br⋯H (20.4%) and H⋯O/O⋯H (9.2%) contacts (Fig. 6). As the C—H⋯π bonds are the main interaction in the crystal, the most populated H⋯C/C⋯H contacts appear as two symmetrical narrow wings at diagonal axes d_e + d_i ≃ 2.7 Å (Fig. 6b). The H⋯H contacts appear in the central region of the fingerprint plots with d_e = d_i = 2.4 Å (Fig. 6c). With the presence of relatively larger bromine atoms in the structure, the H⋯Br/Br⋯H contacts appear as symmetrical broad wing at diagonal axes of d_e + d_i ≃ 3.0 Å (Fig. 6d). Two symmetric spikes in the fingerprint plots with a short spike at d_e + d_i ≃ 2.7 Å represent the H⋯O/O⋯H contacts (Fig. 6e), indicating the presence of the weak C7—H7A⋯O1 interaction. The percentage contributions for other contacts are less than 15% in the Hirshfeld surface mapping.

Figure 6
The two-dimensional fingerprint plots of the title compound for different intermolecular contacts and their percentage contributions to the Hirshfeld surface. d_e and d_i are the distances from the Hirshfeld surface to the nearest atom interior and exterior, respectively, to the surface.

6. Synthesis and crystallization

A mixture of 4-bromobenzaldehyde (4.9 g, 12.5 mmol) and acetone (0.363 g, 6.25 mmol) dissolved in absolute ethanol (30 ml) was slowly added to an aqueous solution of potassium hydroxide (4.0 g in 20 ml water). The mixture was vigorously stirred at room temperature for two h and then 20 ml chilled water was added. The resulting yellow precipitate was recovered by vacuum filtration and washed with cold water (100 ml). The crude product was recrystallized from absolute ethanol solution as yellow blocks.

(1E,4E)-1,5-Bis(4-bromophenyl)penta-1,4-dien-3-one; pure yellow solid (4.6 g, 88.6%), m.p. 484 K; IR ν_max 594, 687, 813, 979, 1066, 1181, 1320, 1398, 1480, 1581, 1643 cm⁻¹, UV–Vis λ_max. 227 and 317 nm, ¹H NMR: δ_H (500MHz, CDCl₃) 7.02 (2H, H-1), 7.45 (4H, H-2), 7.54 (4H, H-3), 7.67 (2H, H-4); ¹³C NMR: δ_C (125MHz, CDCl₃) 124.62, 125.69, 129.25, 131.74, 133.29, 141.83, 188.22; HRMS (ES): MH⁺, found: 392 C₁₇H₁₂Br₂O⁺ requires: 391.92.

7. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. C-bound H atoms were positioned geometrically (C–H = 0.93 Å) and refined using a riding model with U_iso(H) = 1.5U_eq(C).

Table 3
Experimental details

Crystal data
Chemical formula	C₁₇H₁₂Br₂O
M_r	392.09
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	17.5920 (2), 14.0777 (3), 5.7956 (1)
β (°)	98.742 (1)
V (Å³)	1418.63 (4)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	7.17
Crystal size (mm)	0.12 × 0.06 × 0.03

Data collection
Diffractometer	Agilent SuperNova Dual diffractometer with an Atlas detector
Absorption correction	Multi-scan (CrysAlis PRO; Agilent, 2014 )
T_min, T_max	0.64, 0.79
No. of measured, independent and observed [I > 2σ(I)] reflections	17456, 2524, 2372
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.597

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.022, 0.056, 1.15
No. of reflections	2524
No. of parameters	181
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.42, −0.40
Computer programs: CrysAlis PRO (Agilent, 2014), SHELXS97 (Sheldrick, 2008 ), SHELXL2013 (Sheldrick, 2015 ), Mercury (Macrae et al., 2006 ) and PLATON (Spek, 2009 ).

Supporting information

CCDC reference: 1914420

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989019006480/hb7821sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019006480/hb7821Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989019006480/hb7821Isup3.cml

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2015); molecular graphics: SHELXL2013 (Sheldrick, 2015) and Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2015) and PLATON (Spek, 2009).

(1E,4E)-1,5-Bis(4-bromophenyl)penta-1,4-dien-3-one top

Crystal data top

C₁₇H₁₂Br₂O	F(000) = 768
M_r = 392.09	D_x = 1.836 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
a = 17.5920 (2) Å	Cell parameters from 11112 reflections
b = 14.0777 (3) Å	θ = 4–76°
c = 5.7956 (1) Å	µ = 7.17 mm⁻¹
β = 98.742 (1)°	T = 100 K
V = 1418.63 (4) Å³	Block, yellow
Z = 4	0.12 × 0.06 × 0.03 mm

Data collection top

Agilent SuperNova Dual diffractometer with an Atlas detector	2372 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.031
ω scans	θ_max = 67.1°, θ_min = 4.0°
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2014)	h = −21→18
T_min = 0.64, T_max = 0.79	k = −16→16
17456 measured reflections	l = −6→6
2524 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.022	H-atom parameters constrained
wR(F²) = 0.056	w = 1/[σ²(F_o²) + (0.0179P)² + 1.9865P] where P = (F_o² + 2F_c²)/3
S = 1.15	(Δ/σ)_max = 0.003
2524 reflections	Δρ_max = 0.42 e Å⁻³
181 parameters	Δρ_min = −0.40 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
Br1	0.14690 (2)	0.38377 (2)	−0.19437 (5)	0.02381 (9)
Br2	1.00765 (2)	0.35118 (2)	0.21721 (5)	0.02140 (9)
O1	0.58973 (11)	0.35870 (14)	0.9112 (3)	0.0230 (4)
C1	0.33281 (15)	0.33927 (19)	0.3232 (4)	0.0190 (5)
H1A	0.341393	0.310601	0.469408	0.023*
C2	0.25910 (14)	0.34239 (19)	0.2021 (4)	0.0193 (5)
H2A	0.218193	0.316997	0.266165	0.023*
C3	0.24703 (14)	0.38441 (19)	−0.0186 (4)	0.0192 (5)
C4	0.30666 (15)	0.42466 (18)	−0.1141 (4)	0.0193 (5)
H4A	0.297492	0.453469	−0.260084	0.023*
C5	0.38031 (14)	0.42161 (18)	0.0103 (4)	0.0187 (5)
H5A	0.420665	0.448675	−0.053317	0.022*
C6	0.39517 (14)	0.37826 (18)	0.2313 (4)	0.0176 (5)
C7	0.47449 (15)	0.37678 (18)	0.3537 (4)	0.0187 (5)
H7A	0.512770	0.395031	0.268379	0.022*
C8	0.49705 (15)	0.35175 (18)	0.5758 (4)	0.0188 (5)
H8A	0.460021	0.328563	0.659851	0.023*
C9	0.57702 (15)	0.35856 (18)	0.6962 (4)	0.0194 (5)
C10	0.64033 (14)	0.36427 (18)	0.5544 (4)	0.0186 (5)
H10A	0.630488	0.349029	0.396510	0.022*
C11	0.71104 (14)	0.39078 (18)	0.6484 (4)	0.0169 (5)
H11A	0.717134	0.413278	0.800928	0.020*
C12	0.78029 (14)	0.38804 (18)	0.5353 (4)	0.0165 (5)
C13	0.77978 (14)	0.34717 (18)	0.3144 (4)	0.0166 (5)
H13A	0.733445	0.327076	0.229449	0.020*
C14	0.84699 (14)	0.33627 (18)	0.2209 (4)	0.0174 (5)
H14A	0.846014	0.308769	0.074547	0.021*
C15	0.91600 (14)	0.36684 (18)	0.3479 (4)	0.0180 (5)
C16	0.91859 (14)	0.40921 (18)	0.5654 (4)	0.0180 (5)
H16A	0.964994	0.430278	0.647991	0.022*
C17	0.85050 (14)	0.41952 (19)	0.6572 (4)	0.0171 (5)
H17A	0.851669	0.447926	0.802583	0.021*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.01735 (14)	0.02515 (16)	0.02724 (15)	0.00374 (11)	−0.00210 (10)	0.00155 (11)
Br2	0.01568 (14)	0.02560 (16)	0.02334 (15)	−0.00101 (10)	0.00433 (10)	−0.00280 (11)
O1	0.0235 (9)	0.0274 (11)	0.0181 (9)	−0.0039 (8)	0.0034 (7)	0.0004 (7)
C1	0.0212 (13)	0.0189 (13)	0.0173 (12)	0.0008 (10)	0.0041 (10)	−0.0004 (10)
C2	0.0175 (12)	0.0185 (13)	0.0225 (13)	−0.0010 (10)	0.0054 (10)	0.0002 (10)
C3	0.0182 (12)	0.0179 (13)	0.0209 (12)	0.0038 (10)	0.0009 (10)	−0.0009 (10)
C4	0.0252 (13)	0.0153 (13)	0.0174 (12)	0.0039 (11)	0.0040 (10)	−0.0002 (10)
C5	0.0203 (12)	0.0163 (13)	0.0208 (12)	−0.0001 (10)	0.0074 (10)	−0.0009 (10)
C6	0.0200 (13)	0.0141 (12)	0.0192 (12)	0.0006 (10)	0.0048 (10)	−0.0035 (10)
C7	0.0183 (12)	0.0165 (13)	0.0225 (12)	−0.0013 (10)	0.0067 (10)	−0.0013 (10)
C8	0.0183 (12)	0.0169 (13)	0.0220 (13)	−0.0023 (10)	0.0054 (10)	−0.0026 (10)
C9	0.0218 (13)	0.0157 (13)	0.0213 (13)	0.0002 (10)	0.0050 (10)	−0.0005 (10)
C10	0.0194 (13)	0.0193 (14)	0.0168 (12)	0.0009 (10)	0.0022 (10)	−0.0008 (10)
C11	0.0190 (12)	0.0144 (13)	0.0171 (11)	0.0020 (10)	0.0022 (9)	0.0001 (9)
C12	0.0170 (12)	0.0147 (12)	0.0175 (12)	0.0007 (10)	0.0014 (9)	0.0031 (10)
C13	0.0151 (12)	0.0175 (13)	0.0157 (11)	−0.0007 (10)	−0.0022 (9)	0.0009 (9)
C14	0.0201 (12)	0.0166 (13)	0.0147 (11)	0.0000 (10)	0.0005 (10)	−0.0002 (10)
C15	0.0177 (12)	0.0179 (13)	0.0187 (12)	0.0021 (10)	0.0034 (10)	0.0034 (10)
C16	0.0166 (12)	0.0188 (13)	0.0172 (12)	−0.0013 (10)	−0.0019 (9)	0.0005 (10)
C17	0.0195 (12)	0.0173 (13)	0.0137 (11)	−0.0015 (10)	−0.0007 (9)	0.0003 (10)

Geometric parameters (Å, º) top

Br1—C3	1.896 (3)	C8—H8A	0.9300
Br2—C15	1.895 (2)	C9—C10	1.484 (4)
O1—C9	1.232 (3)	C10—C11	1.333 (4)
C1—C2	1.378 (4)	C10—H10A	0.9300
C1—C6	1.402 (4)	C11—C12	1.469 (3)
C1—H1A	0.9300	C11—H11A	0.9300
C2—C3	1.396 (4)	C12—C17	1.399 (3)
C2—H2A	0.9300	C12—C13	1.402 (3)
C3—C4	1.380 (4)	C13—C14	1.382 (4)
C4—C5	1.384 (4)	C13—H13A	0.9300
C4—H4A	0.9300	C14—C15	1.389 (4)
C5—C6	1.407 (4)	C14—H14A	0.9300
C5—H5A	0.9300	C15—C16	1.389 (4)
C6—C7	1.466 (4)	C16—C17	1.390 (4)
C7—C8	1.336 (4)	C16—H16A	0.9300
C7—H7A	0.9300	C17—H17A	0.9300
C8—C9	1.475 (4)

C2—C1—C6	121.6 (2)	C8—C9—C10	118.9 (2)
C2—C1—H1A	119.2	C11—C10—C9	121.4 (2)
C6—C1—H1A	119.2	C11—C10—H10A	119.3
C1—C2—C3	118.7 (2)	C9—C10—H10A	119.3
C1—C2—H2A	120.6	C10—C11—C12	126.6 (2)
C3—C2—H2A	120.6	C10—C11—H11A	116.7
C4—C3—C2	121.5 (2)	C12—C11—H11A	116.7
C4—C3—Br1	119.17 (19)	C17—C12—C13	118.3 (2)
C2—C3—Br1	119.33 (19)	C17—C12—C11	119.7 (2)
C3—C4—C5	119.1 (2)	C13—C12—C11	121.8 (2)
C3—C4—H4A	120.4	C14—C13—C12	121.1 (2)
C5—C4—H4A	120.4	C14—C13—H13A	119.5
C4—C5—C6	121.2 (2)	C12—C13—H13A	119.5
C4—C5—H5A	119.4	C13—C14—C15	119.3 (2)
C6—C5—H5A	119.4	C13—C14—H14A	120.4
C1—C6—C5	117.9 (2)	C15—C14—H14A	120.4
C1—C6—C7	123.6 (2)	C16—C15—C14	121.3 (2)
C5—C6—C7	118.5 (2)	C16—C15—Br2	119.99 (19)
C8—C7—C6	126.3 (2)	C14—C15—Br2	118.71 (19)
C8—C7—H7A	116.9	C15—C16—C17	118.7 (2)
C6—C7—H7A	116.9	C15—C16—H16A	120.6
C7—C8—C9	124.1 (2)	C17—C16—H16A	120.6
C7—C8—H8A	117.9	C16—C17—C12	121.3 (2)
C9—C8—H8A	117.9	C16—C17—H17A	119.3
O1—C9—C8	119.5 (2)	C12—C17—H17A	119.3
O1—C9—C10	121.6 (2)

C6—C1—C2—C3	0.9 (4)	O1—C9—C10—C11	−15.2 (4)
C1—C2—C3—C4	−1.7 (4)	C8—C9—C10—C11	165.4 (2)
C1—C2—C3—Br1	176.9 (2)	C9—C10—C11—C12	171.9 (2)
C2—C3—C4—C5	1.2 (4)	C10—C11—C12—C17	179.3 (3)
Br1—C3—C4—C5	−177.34 (19)	C10—C11—C12—C13	−6.2 (4)
C3—C4—C5—C6	0.0 (4)	C17—C12—C13—C14	1.4 (4)
C2—C1—C6—C5	0.3 (4)	C11—C12—C13—C14	−173.2 (2)
C2—C1—C6—C7	179.9 (2)	C12—C13—C14—C15	−0.3 (4)
C4—C5—C6—C1	−0.8 (4)	C13—C14—C15—C16	−0.8 (4)
C4—C5—C6—C7	179.6 (2)	C13—C14—C15—Br2	179.91 (19)
C1—C6—C7—C8	−10.2 (4)	C14—C15—C16—C17	0.9 (4)
C5—C6—C7—C8	169.4 (3)	Br2—C15—C16—C17	−179.82 (19)
C6—C7—C8—C9	−175.0 (2)	C15—C16—C17—C12	0.1 (4)
C7—C8—C9—O1	160.7 (3)	C13—C12—C17—C16	−1.3 (4)
C7—C8—C9—C10	−19.8 (4)	C11—C12—C17—C16	173.4 (2)

Hydrogen-bond geometry (Å, º) top

Cg1 and Cg2 are the centroids of the C1–C16 and C12–C17 rings, respectively.

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1A···Cg1ⁱ	0.93	2.86	3.539 (3)	131
C14—H14A···Cg2ⁱⁱ	0.93	2.74	3.428 (3)	131

Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) x, −y+1/2, z−1/2.

Torsion angles τ1, τ2, τ3 and τ4 (°) top

Compound	R₁	R₂	τ₁	τ₂	τ₃	τ₄
Symmetrical
AMEXUN (Mark et al., 2016)	4-(benzyloxy)-3-methoxyphenyl	4-(benzyloxy)-3-methoxyphenyl	27.4	19.3	20.4	22.5
COGNOD01 (Rawal et al., 2016)	4-(diethylamino)phenyl	4-(diethylamino)phenyl	1.2, 4.0	11.0, 4.2	1.3, 2.9	0.7, 1.6
DUMWIS (Fun et al., 2010)	2,4,5-trimethoxyphenyl	2,4,5-trimethoxyphenyl	11.6, 0.4, 11.8	0.7, 4.0, 5.5	3.0, 8.2, 6.0	9.8, 2.9, 3.7
EDUSEE (Rawal et al., 2016)	4-(diethylamino)phenyl	4-benzonitrile	15.6, 5.9	0.1, 6.4	8.1, 7.7	3.7, 3.2
GOLGOD (Shan et al., 1999)	4-methoxyphenyl	4-methoxyphenyl	3.2	153.4	152.9	2.7
GOLGOD02 (Harrison et al., 2006)	4-methoxyphenyl	4-methoxyphenyl	2.4	152.2	152.2	2.4
HIDMIQ (Zhou et al., 1999)	2-methoxyphenyl	2-methoxyphenyl	0.2	1.4	1.2	8.8
HUDLEY (Feng et al., 2009)	2,4-dimethylpheny	2,4-dimethylpheny	26.1	3.1	1.1	24.6
KOFCEO (Arshad et al., 2008)	4-methylphenyl	4-methylphenyl	16.6	4.0	13	180
LEJNOE (Butcher et al., 2006)	4-chlorophenyl	4-chlorophenyl	17.8	9.8	9.8	17.8
LESGAT (Park et al., 2013)	2-(trifluoromethyl)phenyl	2-(trifluoromethyl)phenyl	0.5	0.3	2.9	13.7
SAFZOQ (Samshuddin et al., 2012)	3-nitropheny	phenyl	6.1	11.3	21.9	10.4
SIMTUE (Nizam Mohideen et al., 2007)	2-chlorophenyl	2-chlorophenyl	8.8	3.4	0.9	0.5
UPAWEO (Huang et al., 2011)	2,6-difluorophenyl	2,6-difluorophenyl	2.3	4.4	0.8	178
UPAWEO01 (Schwarzer & Weber, 2014a)	2,6-difluorophenyl	2,6-difluorophenyl	2.3	4.4	0.8	0.5
WACXON (Hubig et al., 1992)	o-tolyl	o-tolyl	10.3	1.1	2.8	1.5
XOHVOH (Schwarzer & Weber, 2014b)	pentafluorophenyl	pentafluorophenyl	3.0, 7.9	1.0, 5.7	1.6, 3.4	5.7, 2.3
XOHVUN (Schwarzer & Weber, 2014b)	pentafluorophenyl	phenyl	5.6	2.4	3.3	7.8

Unsymmetrical
(I)	4-bromophenyl	4-bromophenyl	10.2	160.7	15.2	6.2
IFAQAJ (Kapdi et al., 2013)	3,5-dimethoxyphenyl	3,5-dimethoxyphenyl	5.4	173.1	0.6	3.2
LEJNOE01 (Maluleka & Mphahlele, 2017)	4-chlorophenyl	4-chlorophenyl	11.2	160.2	13.6	6.6
MESXEQ (Dravida et al., 2018)	2,6-dichlorophenyl	2,6-dichlorophenyl	46.8, 48.7, 51.8	175.3, 4.3, 178.7	7.5, 4.3, 15.5	32.7, 48.7, 51.8
QAJNOG (Ruanwas et al., 2011)	2,4,6-trimethoxyphenyl	2,4,6-trimethoxyphenyl	6.6, 0.5	176.8, 169.4	1.2, 0.5	3.7, 11.8
WIHBUL (Butcher et al., 2007a)	4-fluorophenyl	4-fluorophenyl	18.2, 18.7	169.0, 166.3	10.4, 8.8	21.8, 21.4
XIFTOW (Butcher et al., 2007b)	3,4-dimethoxyphenyl	3,4-dimethoxyphenyl	1.6, 1.6	162.8, 170.8	23.3, 23.7	3.1, 20.3
ZAPKIN (Chantrapromma et al., 2016)	4-ethoxyphenyl	4-ethoxyphenyl	17.2	168.4	17.1	13.8

Multiple sets of torsion angles are stated for compounds COGNOD01, DUMWIS, EDUSEE, XOHVOH, MESXEQ, QAJNOG, WIHBUL and XIFTOW because there is more than one independent molecule in their asymmetric units. A third molecule with full molecule disorder in compound WIHBUL was excluded from this table.

Acknowledgements

We thank the Universiti Putra Malaysia for the use of their facilities and the University of Anbar, Ministry of Higher Education, in Iraq for a scholarship (NAT).

Funding information

This research was funded by the UPM under the Research University Grant Scheme (RUGS No. 05–01-11–1234RU).

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