Synthesis, crystal structure, Hirshfeld surface analysis, density function theory calculations and photophysical properties of methyl 4′-[(4-bromobenzo­yl)­oxy]biphenyl-4-carboxyl­ate: a compound with bromine⋯oxygen contacts

Anilkumar, H.; Selvanandan, S.; Omkariah, M.A.; Harish Kumar, M.; Srinivasa, T.S.; Palakshamurthy, B.S.

doi:10.1107/S2056989025001604

research communications

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ISSN: 2056-9890

Volume 81| Part 3| March 2025| Pages 264-270

https://doi.org/10.1107/S2056989025001604

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Synthesis, crystal structure, Hirshfeld surface analysis, density function theory calculations and photophysical properties of methyl 4′-[(4-bromobenzoyl)oxy]biphenyl-4-carboxylate: a compound with bromine⋯oxygen contacts

Hanumaiah Anilkumar,^a Selvaraj Selvanandan,^b Metikurke Amruthesh Omkariah,^c Mahadevaiah Harish Kumar,^d Hosapalya Thimmaiah Srinivasa ^e and Bandrehalli Siddagangaiah Palakshamurthy ^f ^*

^aDepartment of Physics, Government First Grade College, Chikkballapur, Karnataka-562101, India, ^bDepartment of Physics, ACS College of Engineering, Bangalore, Karnataka-560074, India, ^cDepartment of Physics, Government First Grade College, Kadur, Karnataka-577548, India, ^dDepartment of Physics, Government Engineering College, Ramanagara, 562159, Karnataka, India, ^eRaman Research Institute, C. V. Raman, Avenue, Sadashivanagar, Bangalore, Karnataka, India, and ^fDepartment of PG Studies and Research in Physics, Albert Einstein Block, UCS, Tumkur University, Tumkur, Karnataka-572103, India
^*Correspondence e-mail: palaksha.bspm@gmail.com

Edited by M. Weil, Vienna University of Technology, Austria (Received 13 January 2025; accepted 21 February 2025; online 28 February 2025)

In the molecular title compound, C₂₁H₁₅BrO₄, the dihedral angles between the aromatic bromo-benzene ring and the immediate neighbors (first and second aromatic ring of the biphenyl moiety) are 56.57 (2) and 50.91 (4)°. The dihedral angle between the aromatic rings of the biphenyl fragment is 5.78 (4)°. The torsion angles across the ester groups associated with bromo-benzene and methyl moieties are 178.0 (1) and 176.86 (2)°, respectively, revealing an anti-periplanar conformation in both cases. In the crystal, the packing of the molecules is stabilized by Br⋯O contacts running infinitely along [001]. In addition, the crystal packing is consolidated by various C—H⋯π interactions. Hirshfeld surface analysis revealed that the most important contributions to the crystal packing arise from H⋯H (27.1%), C⋯H/H⋯C (39.3%), O⋯H/H⋯O (15.4%) and Br⋯H/H⋯Br (10.6%) contacts. The net interaction energies for the title compound were computed as E_ele = −41.9 kJ mol⁻¹, E_pol = −11 kJ mol⁻¹, E_dis = −209.7 kJ mol⁻¹ and E_rep = 108.9 kJ mol⁻¹, with a total interaction energy E_tot of −167.9 kJ mol⁻¹. The ground-state dipole moment (μ_g) is calculated as 1.2936 debye and the energy gap between HOMO and LUMO orbitals is 4.5203 eV as calculated with density functional theory using the B3LYP/6–31 G level basis set. The electronic absorption and fluorescence spectra of the compound were recorded and studied in different solvents by varying polarity. These results were used to elucidate the solvatochromic properties, and spectral deviations were studied by the linear solvation energy relationship. Lippert, Bakhshiev, and Bilot–Kawski–Chamma–Viallet equations were used to estimate the ground and excited-state dipole moments (μ_e). The excited dipole moment is found to be higher than the ground state dipole moment, which indicates that π-electrons are more distributed in polar excited molecules.

Keywords: crystal structure; physical properties; Hirshfeld surface; density function theory; biphenyl-4-carboxylate and solvatochromic.

CCDC reference: 2384236

1. Chemical context

Molecules derived from biphenyl are found to exhibit liquid-crystal properties because of their linearity, high symmetry and thermal stability (Ranganathan & Ramesh, 2006 ; Imai et al., 2001 ). The thermotropic liquid crystalline phases containing biphenyl moieties have an ability to form ordered structures so that they have been widely studied in recent decades (Bagheri et al., 2004 ). The methylene entity that is directly attached to biphenyl mesogens undergoes self-polycondensation, revealing smectic (Sm) A and B phases (Nakata & Watanabe, 1994 ). The absence of alkyl chains/highly polar groups at the ends in the molecular structures of liquid crystals induces non-liquid crystal properties (Harish Kumar et al., 2024b ). Rigid cores such as cyclic π- or heterocyclic π-systems are responsible for electro-optical phenomena. For example, biphenyl-4-carboxylate derivatives are found to exhibit liquid-crystal properties, which play an important role in electro-optical phenomena caused by weak electric fields (Mikulko et al., 2006 ). It is well known that molecules derived from conjugated biphenyl-4-carboxylate exhibit optical non-linearity, especially when they have donor and acceptor substituents at each end of the molecular systems. This originates from an efficient intramolecular charge transfer through a highly polarizable π-electron system. The electro-optical response depends on the structure, sample thickness, birefringence, light absorption, scattering and other factors. Therefore, the results of electro-optical measurements are in most cases arbitrary and, consequently, the absolute values of neither linear nor higher order electro-optical coefficients can be determined (Dardas et al., 2009 ). However, the knowledge of linear and non-linear electro-optical coefficients are required to study the material response to an applied electric field. In this scenario it is necessary to look at the dipole moment, which has an influence on the refractive index or polarization changes at high electric field. Keeping this in mind, we made an attempt to synthesize corresponding phases and report here on the crystal structure analysis, solvatochromism response and dipole moment of the title compound, C₂₁H₁₅BrO₄, (I).

2. Structural commentary

The molecular structure of (I) is shown in Fig. 1. The dihedral angles between the bromobenzene and the aromatic rings (C8–C13) and (C14–C19) of the biphenyl moiety are 56.57 (2) and 50.91 (4)°, respectively, whereas the dihedral angle between the two aromatic rings of the biphenyl moiety is 5.78 (4)°. The torsion angles involving the biphenyl moiety and the attached ester groups are 178.0 (3)° (C1—C7—O2—C8) and 176.9 (4)° (C17—C20—O4—C21), respectively, making the conformation anti-periplanar in both cases.

Figure 1
The molecular structure of (I)

, showing displacement ellipsoids at the 50% probability level.

3. Supramolecular features

The crystal packing is stabilized by a halogen–oxygen (Br⋯O) interaction C—Br1⋯O3—C with a Br⋯O distance of 3.105 (2) Å, forming infinite chains running parallel to [001] (Fig. 2). The packing is further consolidated by six C—H⋯π interactions between aromatic CH groups and the centroids (Cg) of adjacent aromatic rings (Table 1), as illustrated in Fig. 3.

Table 1
Hydrogen-bond geometry (Å, °)

Cg1, Cg2 and Cg3 are the centroids of the aromatic rings C1–C6, C8–C13 and C14–C19, respectively

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯Cg1ⁱ	0.93	2.82	3.526 (4)	133
C6—H6⋯Cg1ⁱⁱ	0.93	2.83	3.523 (4)	133
C10—H10⋯Cg2ⁱⁱⁱ	0.93	2.83	3.523 (4)	132
C13—H13⋯Cg2^iv	0.93	2.87	3.552 (4)	131
C16—H16⋯Cg3ⁱⁱⁱ	0.93	2.92	3.566 (4)	128
C19—H19⋯Cg3^iv	0.93	2.99	3.623 (4)	127
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y-{\script{1\over 2}}, z]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{3\over 2}}, z]$ ; (iii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z]$ ; (iv) $[x-{\script{1\over 2}}, -y+{\script{3\over 2}}, z]$ .

Figure 2
The molecular packing of (I)

. Dashed lines indicate Br⋯O interactions.

Figure 3
The molecular packing of (I)

. Dashed lines indicate C—H⋯Cg interactions.

4. Database survey

A search of the Cambridge Structural Database (CSD, version 5.42, update of November 2020; Groom et al., 2016 ) for molecules containing the biphenyl carboxylate fragment resulted in more than thirty matches, with molecular features similar to (I) for compounds with refcodes DEZYUF (Ardeleanu et al., 2018 ), DOJLIB (Lin et al., 2024 ), FIRYEN (Royal & Baudoin, 2019 ) and VUCFEI (Harish Kumar et al., 2024a ). In these compounds, the dihedral angle between the aromatic rings of the biphenyl moieties are in the range of 33.07 (3) to 38.14 (5)°. They have simple substituent groups at one end of the biphenyl moiety. Compounds with refcodes COFMET (Cai et al., 2024 ), ASUJAB (Lustig et al., 2016 ), CUXCAC (Das et al., 2021 ) all have substituents in the biphenyl fragments, with dihedral angles between the aromatic rings of the biphenyl moiety in the range 44.04 (3) to 51.06 (2)°. It is quite characteristic that the dihedral angle between unsubstituted biphenyl rings are around 30 to 45° due to steric hindrance between ortho-hydrogen atoms of each ring. The small value of 5.78 (4)° for the dihedral angle found in the title compound is due to the presence of bulky groups at each end of the molecule and the interactions resulting from halogen⋯oxygen contacts at one end of the biphenyl moiety.

5. Hirshfeld surface analysis

Hirshfeld surface analysis was carried out using CrystalExplorer (Spackman et al., 2021 ) to quantify the various intermolecular interaction present in (I). Fig. 4 illustrates the Hirshfeld surface mapped with d_norm where red spots near the oxygen atom of the surface correspond to the short contacts in the molecule. The Br⋯O contact associated with electrophilic region of the Hirshfeld surface is shown in Fig. 5. The two-dimensional fingerprint plots (Fig. 6) reveal that the major contributions to the crystal packing are from H⋯H/H⋯H (27.1%), C⋯H/H⋯C (39.3%), O⋯H/H⋯O (15.4%) and Br⋯H/H⋯Br (10.6%) contacts.

Figure 4
Hirshfeld surface of (I)

mapped with d_norm.

Figure 5
Hirshfeld surface of (I)

mapped with d_norm. The dashed lines indicate Br⋯O interactions running parallel [001].

Figure 6
Two-dimensional fingerprint plots for (I)

Energy framework calculations were performed using the basis set B3LYP /6-31G(d.p). The net interaction energies for the title compound are E_ele = −41.9 kJ mol⁻¹, E_pol = −11 kJ mol⁻¹, E_dis = −209.7 kJ mol⁻¹ and E_rep = 108.9 kJ mol⁻¹, with a total interaction energy E_tot of −167.9 kJ mol⁻¹, which shows that E_dis is the major interaction. The energy framework showing the electrostatic (coulomb) potential force, the dispersion force and the total energy diagram are shown in Fig. 7.

Figure 7
Energy frameworks calculated for (I)

, viewed along [100], showing (a) Coulomb potential force, (b) dispersion force and (c) total energy diagrams. The cylindrical radii are proportional to the relative strength of the corresponding energies (adjusted to a cutoff value of 5 kJ mol⁻¹).

6. Density functional theory (DFT) calculations

DFT calculations were carried out using Gaussian-09W (Frisch et al., 2009 ), with Gaussian View 5.0 used to generate the optimized structure of (I). The optimized parameters of the title compound were obtained using the B3LYP/6-311G (d,p) basis set. The dipole moment of the molecule in the gaseous phase was computed to be 1.2936 debye, and is illustrated in Fig. 8. Furthermore, the frontier molecular orbitals HOMO and LUMO of (I) were computed, with energies of HOMO and LUMO of – 6.2450 and −1.7246 eV, respectively (the energy gap ΔE is 4.5203 eV; Fig. 9). The molecular electrostatic potential (MEP) surface of the optimized structure is shown in Fig. 10. The nucleophilic and electrophilic reactive sites of (I) are represented by red and blue regions on the MEP surface. For (I), the red area covers the oxygen atoms of the ester functionality, revealing the sensitivity towards nucleophilic attack. The pale blue area around the aromatic rings indicates weak electrophilic sites.

Figure 8
The direction of the dipole moment of (I)

in the gaseous phase indicated by the arrow.

Figure 9
HOMO and LUMO of (I)

with the energy band gap E_g.

Figure 10
MEP surface plots of (I)

; regions of attractive potential appear in red and those of repulsive potential appear in blue.

7. Photophysical properties

The photophysical properties of (I) were estimated by the solvatochromism method (Reichardt & Welton, 2011 ). The absorption spectra in different polar liquids were recorded, and intensity maxima observed between 285 and 288 nm (Fig. 11). Since the solvent polarity is susceptible to longer wavelength absorption, the samples were excited at longer wavelength to get emission spectra for calculation of the photophysical parameters. The ground state and experimental excited dipole moments were derived according to Lippert (1957 ), Bakhshiev (1964 ) and Bilot–Kawski–Chamma–Viallet (Bilot & Kawski, 1963 ; Chamma & Viallet, 1970 ) polarity functions, as detailed in equations (1)–(3). Among these, Bakhshiev and Bilot–Kawski–Chamma–Viallet equations give good results with reduced errors in the calculation. Fig. 12 shows $[{\buildrel {-} \over \nu}_{a} {\bar{\nu}}-{\buildrel{-} \over\nu} _{f}]$ versus $[ F_{1}(\varepsilon ,n)]$ , $[{\buildrel {-} \over \nu}_{a}-{\buildrel{-} \over\nu }_{f}]$ versus $[ F_{2}(\varepsilon ,n)]$ and ( $[ {{\buildrel {-} \over \nu}_{a}+{\buildrel{-} \over\nu} _{f}}]$ )/2 versus $[ F_{3}(\varepsilon ,n)]$ , resulting in linear graphs with slopes m₁, m₂ and m₃, respectively.

$[{\buildrel {-} \over \nu}_{a}-{\buildrel{-} \over\nu} _{f}=m_{1}F_{1}+ constant, \eqno(1)]$

$[{\buildrel {-} \over \nu}_{a}-{\buildrel{-} \over\nu} _{f}=m_{2}F_{2}+ constant, \eqno(2)]$

$[{{{\buildrel {-} \over \nu}_{a}+{\buildrel{-} \over\nu} _{f}}\over{2}}= m_{3}F_{3}+ constant. \eqno(3)]$

The expressions for the Lippert polarity [ $[ F_{1}(\varepsilon, n)]$ ] , Bakhshiev polarity [ $[ F_{2}(\varepsilon, n)]$ ] and Bilot–Kawski–Chamma–Viallet [ $[ F_{3}(\varepsilon, n)]$ ] polarity functions are given by equations (4)– (6):

$[F_{1}(\varepsilon, n)=\left[ {{\varepsilon -1 }\over{2\varepsilon+1 }}-{{{n^{2}-1}}\over{2n^{2}+1}}\right], \eqno(4)]$

$[F_{2}(\varepsilon, n)={{2n^{2}+1}\over{n^{2}+2}}\left[ {{\varepsilon -1 }\over{\varepsilon+2 }}-{{{n^{2}-1}}\over{n^{2}+2}}\right], \eqno(5)]$

$[F_{3}(\varepsilon, n)= \left[ {{2n^{2}+1}\over{2(n^{2}+2)}}\left( {{\varepsilon -1 }\over{\varepsilon+2 }}-{{{n^{2}-1}}\over{n^{2}+2}}\right)+{{3(n^{4}-1)}\over{2(n^{2}+2)^{2}}}\right], \eqno(6)]$

where $[ {\buildrel {-} \over \nu}_{a}]$ and $[ {\buildrel {-} \over \nu}_{f}]$ are the absorption and fluorescence maxima wavenumbers in cm⁻¹, respectively; is the refractive index and $[ \varepsilon]$ is the permittivity. The slopes , , are connected with ground and exited state dipole moments through equations (7)– (9):

$[m_{1}={{2(\mu _{e}-\mu _{g})^{2}}\over{hca^{3}_{0}}}, \eqno(7)]$

$[m_{2}={{2(\mu _{e}-\mu _{g})^{2}}\over{hca^{3}_{0}}}, \eqno(8)]$

$[m_{3}={{2(\mu ^{2}_{e}-\mu ^{2}_{g})}\over{hca^{3}_{0}}}, \eqno(9)]$

where μ_e and μ_g are the excited and ground state dipole moments of the solute molecule (h and c are Planck's constant and velocity of light in a vacuum, respectively); a₀ is the Onsager cavity radius of the title compound as determined by Suppans's equation a₀ = (3M/4πδN)^1/3 where δ is the density of the solute molecule, M is molecular weight and N is Avagadro's number.

$[\mu _{g}={{\left\vert m_{3}-m_{2} \right\vert}\over{2}} \left({{hca^{3}_{0}}\over{2m_{2}}}\right)^{1/2}, \eqno(10)]$

$[\mu _{e}={{\left\vert m_{3}+m_{2} \right\vert}\over{2}} \left({{hca^{3}_{0}}\over{2m_{2}}}\right)^{1/2}, \eqno(11)]$

$[{{\mu_e}\over{\mu_g}}={{\left\vert m_3+m_2 \right\vert}\over{\left\vert m_3-m_2 \right\vert}}. \eqno(12)]$

The solvent polarity function values $[ F_{1}(\varepsilon, n)]$ , $[ F_{2}(\varepsilon, n)]$ , and $[ F_{3}(\varepsilon, n)]$ of various solvents on the band shift data of the title compound is summarized in Table 2. The slopes and intercepts of the fitted lines are given in Table 3 with good correlation coefficients obtained in all cases. The ground state and excited state dipole moments were estimated by the above equations under assumption that the symmetry of (I) remains unchanged upon electronic transition. The ground and excited dipole moments are found to be parallel according to equations (8) and (9). This part of the study demonstrates that the title compound is more polar in the excited state than in the ground state for all the solvents. The ratio of the dipole moments can be determined by Stokes shifts in different solvents as functions of ɛ and n. The calculated values for (I) are collated in Table 4.

Table 2
Solvatochromic data for (I) (cm⁻¹) with calculated values of F₁, F₂ and F₃

Solvent	$[ {\buildrel {-} \over \nu}_{a}]$	$[ {\buildrel {-} \over \nu}_{f}]$	$[ {\buildrel {-} \over \nu}_{a}]$ − $[ {\buildrel {-} \over \nu}_{f}]$	( $[ {\buildrel {-} \over \nu}_{a}]$ + $[ {\buildrel {-} \over \nu}_{f}]$ )/2	F₁(ɛ, n)	F₂(ɛ, n)	F₁(ɛ, n)
Hexane	35018.66	25278.69	9739.96	30148.68	0.0010	0.0018	0.2540
Methyl formate	34931.50	26829.07	8102.43	30880.29	0.2421	0.6091	0.5383
Benzene	34580.37	28213.51	6366.85	31396.94	0.0045	0.0099	0.3430
THF	34872.48	27029.94	7842.53	30951.21	0.2095	0.5490	0.5511
CCl4	34665.78	25457.60	9208.18	30061.69	0.1434	0.3632	0.4936
Ethyl acetate	35018.66	26970.89	8047.76	30994.78	0.1996	0.4890	0.4979
Acetone	30659.54	28696.87	1962.67	29678.21	0.2841	0.7902	0.6395
Methanol	34872.48	30151.35	4721.12	32511.92	0.3083	0.8545	0.6514
Ethanol	34872.48	24628.11	10244.37	29750.30	0.2888	0.8129	0.6523
Dimethyl formamide	34665.782	25972.67	8693.10	30319.229	0.2757	0.8368	0.7077

Table 3
Statistical treatment of the correlations of solvent spectroscopic shifts of the title compound

Method	Slope	Intercept	Correlation coefficient	Number of data
Lippert correlation	8054	6928	0.97	5
Bakhshiev correlation	2820	6398	0.97	5
Bilot–Kawaski–Chamma–Viallet correlation	8626	24622	0.82	5

Table 4
Ground and excited states dipole moments of (I) (in debye^a)

Molecule	Radius a (Å)	μ_g^b (D)	μ_g^c (D)	μ_e^d (D)	(μ_e/μ_g)^e (D)
(I)	4.6	1.2936	5.37	10.59	1.97
Notes: (a) 1 debye = 3.33564×10⁻³⁰ cm = 10–18 esu cm; (b) the theoretical ground state dipole moment was obtained from Gaussian 09; (c) the experimental ground-state dipole moment was calculated according to equation (10); (d) the experimental excited dipole moment was calculated according to equation (11); (e) the ratio of excited state and ground state dipole moments was calculated using equation (12).

Figure 11
The absorption spectra of (I)

recorded in different solvents.

Figure 12
The variation of Stokes shift according to the (a) Lippert, (b) Bakshiev and (c) Bilot– Kawski–Chamma–Viallet functions in different solvents.

8. Synthesis and crystallization

4-Bromobenzoic acid (1 equiv.) was reacted with methyl 4′-hydroxy-[1,1′-biphenyl]-4-carboxylate (1 equiv.) in dry chloroform in the presence of dicyclohexylcarbodiimide (1.2 equiv.) and a catalytic quantity of dimethyl aminopyrimidine at room temperature for about 12 h. After completion of the reaction, the mixture was poured into water and extracted into chloroform. The organic solvent was washed with water (10 ml), dilute acetic acid (10 ml) and dried over sodium sulfate. The crude final product was recrystallized from chloroform at room temperature.

9. Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 5. The structure was refined as a two-component inversion twin. All H atoms were positioned with idealized geometry and refined using a riding model with C—H = 0.93–0.96 Å and U_iso(H) = 1.2–1.5U_eq(C).

Table 5
Experimental details

Crystal data
Chemical formula	C₂₁H₁₅BrO₄
M_r	411.24
Crystal system, space group	Orthorhombic, Pna2₁
Temperature (K)	300
a, b, c (Å)	5.9754 (8), 7.2962 (9), 39.537 (5)
V (Å³)	1723.7 (4)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	2.41
Crystal size (mm)	0.28 × 0.24 × 0.21

Data collection
Diffractometer	Bruker SMART APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.152, 0.601
No. of measured, independent and observed [I > 2σ(I)] reflections	41401, 5204, 4189
R_int	0.039
(sin θ/λ)_max (Å⁻¹)	0.715

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.072, 1.05
No. of reflections	5204
No. of parameters	236
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.46
Absolute structure	Refined as an inversion twin
Absolute structure parameter	0.060 (11)
Computer programs: APEX2 and SAINT (Bruker, 2017 ), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ), Mercury (Macrae et al., 2020 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2384236

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989025001604/wm5751sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989025001604/wm5751Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989025001604/wm5751Isup3.cml

checkCIF report

Computing details top

Methyl 4'-[(4-bromobenzoyl)oxy]biphenyl-4-carboxylate top

Crystal data top

C₂₁H₁₅BrO₄	D_x = 1.585 Mg m⁻³
M_r = 411.24	Melting point: 460 K
Orthorhombic, Pna2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 4189 reflections
a = 5.9754 (8) Å	θ = 2.8–30.0°
b = 7.2962 (9) Å	µ = 2.41 mm⁻¹
c = 39.537 (5) Å	T = 300 K
V = 1723.7 (4) Å³	Prism, colourless
Z = 4	0.28 × 0.24 × 0.21 mm
F(000) = 832

Data collection top

Bruker SMART APEXII CCD diffractometer	5204 independent reflections
Radiation source: fine-focus sealed tube	4189 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.039
Detector resolution: 1.02 pixels mm^-1	θ_max = 30.6°, θ_min = 2.8°
φ and Ω scans	h = −8→8
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −10→10
T_min = 0.152, T_max = 0.601	l = −55→56
41401 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.035	H-atom parameters constrained
wR(F²) = 0.072	w = 1/[σ²(F_o²) + (0.0182P)² + 0.6795P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max < 0.001
5204 reflections	Δρ_max = 0.27 e Å⁻³
236 parameters	Δρ_min = −0.46 e Å⁻³
1 restraint	Absolute structure: Refined as an inversion twin
0.12 constraints	Absolute structure parameter: 0.060 (11)
Primary atom site location: structure-invariant direct methods

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.

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Br1	1.33516 (7)	0.54905 (5)	0.28015 (2)	0.05786 (12)
O2	0.9870 (4)	0.5141 (3)	0.44334 (6)	0.0385 (5)
O1	0.6870 (4)	0.3799 (4)	0.41979 (7)	0.0572 (7)
C21	0.1186 (9)	0.5432 (8)	0.71793 (12)	0.0705 (15)
H21A	−0.031918	0.589171	0.717313	0.106*
H21B	0.117386	0.417942	0.725346	0.106*
H21C	0.205866	0.615516	0.733346	0.106*
O4	0.2160 (5)	0.5539 (4)	0.68434 (7)	0.0606 (8)
C20	0.4255 (7)	0.4952 (5)	0.68076 (10)	0.0447 (8)
C17	0.5027 (6)	0.5032 (5)	0.64515 (8)	0.0364 (7)
C18	0.7117 (6)	0.4322 (5)	0.63731 (9)	0.0414 (8)
H18	0.801659	0.385070	0.654425	0.050*
C19	0.7869 (5)	0.4308 (5)	0.60442 (9)	0.0390 (7)
H19	0.927359	0.382180	0.599737	0.047*
C14	0.6585 (5)	0.5002 (4)	0.57790 (8)	0.0304 (6)
C11	0.7408 (5)	0.5000 (4)	0.54250 (8)	0.0296 (6)
C12	0.9405 (6)	0.4156 (5)	0.53322 (8)	0.0375 (7)
H12	1.024510	0.356560	0.549743	0.045*
C13	1.0183 (6)	0.4166 (5)	0.50024 (8)	0.0384 (7)
H13	1.152969	0.359944	0.494794	0.046*
C8	0.8942 (5)	0.5024 (4)	0.47567 (8)	0.0327 (6)
C7	0.8675 (6)	0.4483 (4)	0.41677 (8)	0.0355 (7)
C1	0.9865 (6)	0.4774 (4)	0.38438 (8)	0.0327 (6)
C6	0.8794 (6)	0.4209 (5)	0.35476 (9)	0.0370 (8)
H6	0.738063	0.367892	0.355958	0.044*
C5	0.9820 (6)	0.4433 (5)	0.32362 (8)	0.0424 (8)
H5	0.910596	0.406027	0.303881	0.051*
C4	1.1928 (6)	0.5221 (5)	0.32236 (8)	0.0394 (7)
C10	0.6189 (6)	0.5857 (5)	0.51662 (8)	0.0384 (7)
H10	0.483925	0.642600	0.521791	0.046*
C9	0.6957 (6)	0.5876 (5)	0.48333 (9)	0.0400 (8)
H9	0.613348	0.645774	0.466508	0.048*
C16	0.3731 (5)	0.5741 (5)	0.61941 (9)	0.0370 (7)
H16	0.233589	0.623998	0.624316	0.044*
C15	0.4492 (5)	0.5716 (5)	0.58628 (8)	0.0368 (7)
H15	0.358554	0.618626	0.569238	0.044*
C2	1.1985 (5)	0.5553 (4)	0.38240 (8)	0.0365 (7)
H2	1.272007	0.591248	0.402036	0.044*
C3	1.3003 (6)	0.5793 (5)	0.35129 (9)	0.0389 (7)
H3	1.440710	0.633865	0.349921	0.047*
O3	0.5380 (5)	0.4447 (5)	0.70399 (7)	0.0732 (10)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0637 (2)	0.0753 (2)	0.03460 (15)	−0.00193 (19)	0.0122 (2)	0.0024 (2)
O2	0.0385 (12)	0.0495 (13)	0.0275 (10)	−0.0062 (10)	0.0031 (9)	−0.0048 (9)
O1	0.0510 (15)	0.0747 (18)	0.0459 (15)	−0.0271 (14)	0.0108 (12)	−0.0129 (14)
C21	0.069 (3)	0.101 (4)	0.041 (3)	0.004 (3)	0.015 (2)	0.003 (2)
O4	0.0532 (16)	0.092 (2)	0.0369 (15)	0.0124 (15)	0.0089 (12)	0.0039 (14)
C20	0.050 (2)	0.052 (2)	0.0323 (16)	−0.0042 (16)	0.0003 (15)	−0.0007 (14)
C17	0.0399 (16)	0.0391 (17)	0.0302 (14)	−0.0033 (13)	−0.0020 (13)	−0.0003 (13)
C18	0.0397 (17)	0.050 (2)	0.0351 (16)	0.0046 (15)	−0.0046 (13)	0.0008 (15)
C19	0.0328 (16)	0.050 (2)	0.0348 (16)	0.0074 (14)	−0.0039 (12)	0.0010 (14)
C14	0.0328 (13)	0.0256 (13)	0.0329 (15)	−0.0002 (12)	−0.0010 (12)	−0.0009 (11)
C11	0.0330 (14)	0.0247 (12)	0.0311 (14)	−0.0015 (11)	−0.0005 (12)	−0.0010 (11)
C12	0.0387 (16)	0.0393 (18)	0.0344 (16)	0.0076 (14)	−0.0010 (13)	0.0016 (13)
C13	0.0341 (16)	0.0447 (18)	0.0365 (17)	0.0087 (14)	0.0033 (13)	−0.0019 (13)
C8	0.0333 (15)	0.0322 (15)	0.0327 (15)	−0.0050 (12)	0.0044 (12)	−0.0031 (12)
C7	0.0390 (17)	0.0326 (15)	0.0350 (16)	−0.0014 (13)	0.0023 (13)	−0.0030 (13)
C1	0.0381 (15)	0.0279 (14)	0.0322 (15)	0.0001 (12)	−0.0005 (12)	−0.0015 (12)
C6	0.0348 (16)	0.0366 (16)	0.039 (2)	−0.0028 (12)	−0.0020 (14)	−0.0031 (14)
C5	0.0446 (18)	0.0495 (19)	0.0329 (17)	−0.0003 (15)	−0.0052 (14)	−0.0044 (14)
C4	0.0452 (19)	0.0421 (17)	0.0308 (16)	0.0024 (14)	0.0037 (13)	0.0025 (13)
C10	0.0381 (16)	0.0432 (18)	0.0339 (16)	0.0130 (14)	0.0028 (13)	0.0005 (13)
C9	0.0434 (19)	0.0443 (19)	0.0323 (15)	0.0120 (15)	−0.0019 (13)	0.0055 (13)
C16	0.0296 (16)	0.0448 (19)	0.0367 (16)	0.0039 (13)	0.0019 (12)	0.0009 (14)
C15	0.0353 (15)	0.0430 (18)	0.0322 (15)	0.0051 (14)	−0.0030 (12)	0.0058 (13)
C2	0.0357 (16)	0.0411 (17)	0.0327 (15)	−0.0014 (13)	−0.0026 (12)	−0.0019 (13)
C3	0.0340 (16)	0.0447 (18)	0.0379 (17)	−0.0030 (13)	0.0047 (13)	0.0006 (14)
O3	0.0623 (19)	0.125 (3)	0.0323 (14)	0.0227 (19)	−0.0003 (13)	0.0077 (16)

Geometric parameters (Å, º) top

Br1—C4	1.884 (3)	C12—C13	1.384 (4)
O2—O2	0.000 (4)	C12—H12	0.9300
O2—C7	1.358 (4)	C13—C8	1.373 (5)
O2—C8	1.396 (4)	C13—H13	0.9300
O1—C7	1.195 (4)	C8—C9	1.373 (5)
C21—O4	1.452 (5)	C7—C1	1.480 (4)
C21—H21A	0.9600	C1—C2	1.390 (4)
C21—H21B	0.9600	C1—C6	1.397 (5)
C21—H21C	0.9600	C6—C5	1.385 (5)
O4—C20	1.331 (5)	C6—H6	0.9300
C20—O3	1.196 (5)	C5—C4	1.386 (5)
C20—C17	1.483 (5)	C5—H5	0.9300
C17—C16	1.379 (5)	C4—C3	1.376 (5)
C17—C18	1.387 (5)	C10—C9	1.394 (5)
C18—C19	1.376 (5)	C10—H10	0.9300
C18—H18	0.9300	C9—H9	0.9300
C19—C14	1.394 (4)	C16—C15	1.387 (4)
C19—H19	0.9300	C16—H16	0.9300
C14—C15	1.395 (4)	C15—H15	0.9300
C14—C11	1.484 (4)	C2—C3	1.384 (5)
C11—C12	1.392 (5)	C2—H2	0.9300
C11—C10	1.403 (4)	C3—H3	0.9300

C7—O2—C8	118.6 (3)	C9—C8—O2	121.2 (3)
O4—C21—H21A	109.5	C13—C8—O2	117.4 (3)
O4—C21—H21B	109.5	O1—C7—O2	123.0 (3)
H21A—C21—H21B	109.5	O1—C7—C1	125.5 (3)
O4—C21—H21C	109.5	O2—C7—C1	111.5 (3)
H21A—C21—H21C	109.5	C2—C1—C6	119.4 (3)
H21B—C21—H21C	109.5	C2—C1—C7	123.0 (3)
C20—O4—C21	117.2 (3)	C6—C1—C7	117.6 (3)
O3—C20—O4	123.1 (4)	C5—C6—C1	120.5 (3)
O3—C20—C17	124.5 (4)	C5—C6—H6	119.7
O4—C20—C17	112.4 (3)	C1—C6—H6	119.7
C16—C17—C18	118.7 (3)	C6—C5—C4	118.9 (3)
C16—C17—C20	122.7 (3)	C6—C5—H5	120.6
C18—C17—C20	118.5 (3)	C4—C5—H5	120.6
C19—C18—C17	120.5 (3)	C3—C4—C5	121.4 (3)
C19—C18—H18	119.7	C3—C4—Br1	119.6 (3)
C17—C18—H18	119.7	C5—C4—Br1	119.1 (3)
C18—C19—C14	121.9 (3)	C9—C10—C11	121.5 (3)
C18—C19—H19	119.0	C9—C10—H10	119.3
C14—C19—H19	119.1	C11—C10—H10	119.3
C19—C14—C15	116.8 (3)	C8—C9—C10	119.2 (3)
C19—C14—C11	121.8 (3)	C8—C9—H9	120.4
C15—C14—C11	121.4 (3)	C10—C9—H9	120.4
C12—C11—C10	116.7 (3)	C17—C16—C15	120.5 (3)
C12—C11—C14	122.2 (3)	C17—C16—H16	119.7
C10—C11—C14	121.1 (3)	C15—C16—H16	119.7
C13—C12—C11	122.3 (3)	C16—C15—C14	121.6 (3)
C13—C12—H12	118.9	C16—C15—H15	119.2
C11—C12—H12	118.9	C14—C15—H15	119.2
C8—C13—C12	119.2 (3)	C3—C2—C1	120.2 (3)
C8—C13—H13	120.4	C3—C2—H2	119.9
C12—C13—H13	120.4	C1—C2—H2	119.9
C9—C8—C13	121.1 (3)	C4—C3—C2	119.7 (3)
C9—C8—O2	121.2 (3)	C4—C3—H3	120.2
C13—C8—O2	117.4 (3)	C2—C3—H3	120.2

C21—O4—C20—O3	−4.2 (6)	O2—C7—C1—C2	2.7 (4)
C21—O4—C20—C17	176.9 (4)	O1—C7—C1—C6	0.2 (5)
O3—C20—C17—C16	−175.4 (4)	O2—C7—C1—C6	−178.2 (3)
O4—C20—C17—C16	3.5 (5)	O2—C7—C1—C6	−178.2 (3)
O3—C20—C17—C18	6.2 (6)	C2—C1—C6—C5	−0.5 (5)
O4—C20—C17—C18	−174.8 (3)	C7—C1—C6—C5	−179.7 (3)
C16—C17—C18—C19	−0.7 (5)	C1—C6—C5—C4	0.2 (5)
C20—C17—C18—C19	177.7 (3)	C6—C5—C4—C3	−0.5 (5)
C17—C18—C19—C14	0.2 (5)	C6—C5—C4—Br1	178.9 (3)
C18—C19—C14—C11	179.5 (3)	C12—C11—C10—C9	−0.6 (5)
C19—C14—C11—C12	6.1 (5)	C14—C11—C10—C9	179.5 (3)
C15—C14—C11—C12	−174.4 (3)	C13—C8—C9—C10	−0.3 (5)
C19—C14—C11—C10	−174.0 (3)	O2—C8—C9—C10	−174.5 (3)
C15—C14—C11—C10	5.5 (5)	O2—C8—C9—C10	−174.5 (3)
C10—C11—C12—C13	0.6 (5)	C11—C10—C9—C8	0.5 (5)
C14—C11—C12—C13	−179.5 (3)	C18—C17—C16—C15	1.0 (5)
C11—C12—C13—C8	−0.5 (5)	C20—C17—C16—C15	−177.3 (3)
C12—C13—C8—C9	0.3 (5)	C17—C16—C15—C14	−0.8 (5)
C12—C13—C8—O2	174.7 (3)	C19—C14—C15—C16	0.3 (5)
C12—C13—C8—O2	174.7 (3)	C11—C14—C15—C16	−179.2 (3)
C7—O2—C8—C9	−60.4 (4)	C6—C1—C2—C3	1.1 (5)
C7—O2—C8—C13	125.3 (3)	C7—C1—C2—C3	−179.8 (3)
C8—O2—C7—O1	−0.5 (5)	C5—C4—C3—C2	1.1 (5)
C8—O2—C7—C1	178.0 (3)	Br1—C4—C3—C2	−178.3 (3)
O1—C7—C1—C2	−178.9 (3)	C1—C2—C3—C4	−1.4 (5)
O2—C7—C1—C2	2.7 (4)

Hydrogen-bond geometry (Å, º) top

Cg1, Cg2 and Cg3 are the centroids of the aromatic rings C1–C6, C8–C13 and C14–C19, respectively

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···Cg1ⁱ	0.93	2.82	3.526 (4)	133
C6—H6···Cg1ⁱⁱ	0.93	2.83	3.523 (4)	133
C10—H10···Cg2ⁱⁱⁱ	0.93	2.83	3.523 (4)	132
C13—H13···Cg2^iv	0.93	2.87	3.552 (4)	131
C16—H16···Cg3ⁱⁱⁱ	0.93	2.92	3.566 (4)	128
C19—H19···Cg3^iv	0.93	2.99	3.623 (4)	127

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

Salvatochomic data of (I) with calculated values of F1, F2 and F3 top

Solvent	ã~ (cm^-1)	\v_f (cm^-1)	\v_a - \v_f (cm^-1)	(\v_a - \v_f)/2 (cm^-1)	F₁	F₂	F₃
Hexane	35018.66	25278.69	9739.96	30148.68	0.0010	0.0018	0.2540
Methyl formate	34931.50	26829.07	8102.43	30880.29	0.2421	0.6091	0.5383
Benzene	34580.37	28213.51	6366.85	31396.94	0.0045	0.0099	0.3430
THF	34872.48	27029.94	7842.53	30951.21	0.2095	0.5490	0.5511
CCl4	34665.78	25457.60	9208.18	30061.69	0.1434	0.3632	0.4936
Ethyl acetate	35018.66	26970.89	8047.76	30994.78	0.1996	0.4890	0.4979
Acetone	30659.54	28696.87	1962.67	29678.21	0.2841	0.7902	0.6395
Methanol	34872.48	30151.35	4721.12	32511.92	0.3083	0.8545	0.6514
Ethanol	34872.48	24628.11	10244.37	29750.30	0.2888	0.8129	0.6523
Dimethyl formamide	34665.782	25972.67	8693.10	30319.229	0.2757	0.8368	0.7077

Statistical treatment of the correlations of solvent spectroscopic shifts of the title compound top

Method	Slope	Intercept	Correlation coefficient	Number of data
Lippert correlation	8054	6928	0.97	5
Bakhshiev correlation	2820	6398	0.97	5
Bilot–Kawaski–Chamma–Viallet correlation	8626	24622	0.82	5

Ground and excited states dipole moments of (I) (in Debye) top

Molecule	(Å)	(D)	(D)	(D)
(I)	4.6	1.2936	5.37	10.59	1.97

Notes: (a) 1 Debye = 3.33564×10^–30 cm = 10-18 esu cm; (b) the theoretical ground state dipole moment was obtained from Gaussian 09; (c) the experimental ground-state dipole moment was calculated according to equation (10); (d) the experimental excited dipole moment was calculated according to equation 11); (e) the ratio of excited state and ground state dipole moments was calculated using equation (12).

Acknowledgements

The authors thank the Vision Group on Science and Technology, Government of Karnataka, for the award of a major project under the CISEE scheme (reference No. VGST/ CISEE/GRD-319/2014–15) to carry out this work at the Department of PG Studies and Research in Physics, UCS, Tumkur University.

Funding information

Funding for this research was provided by: Vision Group on Science and Technology, Government of Karnataka (grant No. VGST/ CISEE/GRD-319/2014–15 to Palakshamurthy B. S).

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