Crystal structure of 4,4′-bis­(4-bromo­phen­yl)-1,1′,3,3′-tetra­thia­fulvalene

Rigin, S.; Fonari, M.

doi:10.1107/S2056989019009952

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ISSN: 2056-9890

Volume 75| Part 8| August 2019| Pages 1195-1198

https://doi.org/10.1107/S2056989019009952

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Crystal structure of 4,4′-bis(4-bromophenyl)-1,1′,3,3′-tetrathiafulvalene

Sergei Rigin ^a ^* and Marina Fonari ^a

^aDepartment of Chemistry, New Mexico Highlands University, Las Vegas, New Mexico, 87701, USA
^*Correspondence e-mail: rigindale@gmail.com

Edited by E. V. Boldyreva, Russian Academy of Sciences, Russia (Received 15 April 2019; accepted 11 July 2019; online 16 July 2019)

The molecule of the title compound, C₁₈H₁₀Br₂S₄, has a C-shape, with C_s molecular symmetry. The dihedral angle between the planes of the dithiol and phenyl rings is 8.35 (9)°. In the crystal, molecules form helical chains along [001], the shortest interactions being π⋯S contacts within the helices. The intermolecular interactions were investigated by Hirshfeld surface analysis. Density functional theory (DFT) was used to calculate HOMO–LUMO energy levels of the title compound and its trans isomer.

Keywords: crystal structure; tetrathiafulvalene; derivative; weak interactions; Hirshfeld surface analysis; DFT calculations.

CCDC reference: 1940080

1. Chemical context

So far significant progress has been achieved in improving the performance of organic field-effect transistors (OFETs) using such materials as oligoacenes, oligothiophenes and polythiophenes (Mas-Torrent & Rovira, 2011 ; Pfattner, et al., 2016 ). Numerous derivatives of the sulfur heterocycle 2,2′-bis(1,3-dithiolylidene), known as tetrathiafulvalene (TTF), have been noted as components of OFETs (Fourmigué & Batail, 2004 ; Bendikov et al., 2004 ). High charge mobilities have been reported for thiophene-fused TTF and dibenzo-TTF in single-crystal OFETs obtained from solutions, as well as in tetra(octadecylthio)-TTF films (Mas-Torrent et al., 2004a ,b ). A comparatively high mobility was reported for biphenyl-substituted TTF (Noda et al., 2005 , 2007 ). Correlations between mobilities and herring-bone crystal structures have been investigated (Pfattner, et al., 2016; Mas-Torrent & Rovira, 2011), including for phenyl-substituted oligothiophenes (Noda et al., 2007). Among the numerous reported halogenated tetrathiafulvalenes (Fourmigué & Batail, 2004), only a few have been crystallographically characterized. The synthesis and characterization of two halogen TTF derivatives, 4,4′-bis(4-chlorophenyl)tetrathiafulvalene and 4,4′-bis(4-bromophenyl)tetrathiafulvalene have been reported, but only the crystal structure of the chloro-substituted compound has been documented (Madhu & Das, 2008 ), which shows short Cl⋯Cl contacts. Herein, we report the crystal structure, the Hirshfeld surface analysis and the molecular orbital analysis of the title compound, 4,4′-bis(4-bromophenyl)-1,1′,3,3′-tetrathiafulvalene (BBP-TTF).

2. Structural commentary

The molecular structure of the title compound is illustrated in Fig. 1. The molecule has a C-shape with C_s molecular symmetry and resides on the mirror plane passing through the central C1=C1(x, −y + 3/2, z) bond [1.343 (7) Å]. The C—S distances in the TTF moiety are in the range 1.729 (4)–1.778 (4) Å and correspond to reported values (CSD version 5.40, last update November 2018; Groom et al., 2016 ). The dihedral angle between the dithiol and phenyl rings is 8.35 (9)°.

Figure 1
A view of the molecular structure of the title compound with the atom labelling. Displacement ellipsoids are drawn at the 50% probability level. Suffix a corresponds to the symmetry operation x, −y + $[{3\over 2}]$ , z.

3. Supramolecular features

In the crystal (Fig. 2), no significant intermolecular interactions were found. Molecules related by the twofold screw axis form helices along the c-axis direction. The dihedral angle between the mean planes of the adjacent molecules in the helix is 36.59 (3)° and the helical pitch is 6.1991 (5) Å. The shortest interactions within the chain, as indicated by Mercury (Macrae et al., 2006 ), are the S⋯π contacts C3⋯S2(1 − x, y, z − $[1\over2]$ ) = 3.458 (4) and C2⋯S2(1 − x, y, z − $[1\over2]$ ) = 3.465 (4) Å, followed by the C2—H2⋯C4(1 − x, y, $[1\over2]$ + z) [2.72, 3.467 (5) Å] short contacts that are in agreement with the Hirshfeld (1977 ) surface analysis.

Figure 2
The crystal packing of the title compound.

4. Hirshfeld surface analysis

CrystalExplorer17.5 (Wolff et al., 2012 , Mackenzie et al., 2017 ) was used to generate the molecular Hirshfeld surface. The total d_norm surface of the title compound is shown in Fig. 3 where the red spots correspond to the most significant interactions in the crystal. In the studied molecule, they include only weak C—H⋯π interactions at distances that are slightly higher than the sum of van der Waals radii.

Figure 3
Hirshfeld surface mapped over d_norm for the title compound in the range −0.1138 to 1.1257 a.u.

5. Frontier molecular orbital calculations

The highest occupied molecular orbital (HOMO) acts as an electron donor and the lowest unoccupied molecular orbital (LUMO) acts as an electron acceptor. A small HOMO–LUMO energy gap indicates a highly polarizable molecule and high chemical reactivity. Molecular orbital energy levels for the title compound were calculated with Gaussian 16W software (Frisch et al., 2016 ) using density functional theory (DFT) at the B3LYP/6-311+G(d,p) level of theory. The frontier orbitals of the title compound and its trans-isomer are shown in Figs. 4 and 5, respectively. The energy gap determines chemical hardness, chemical potential, electronegativity and the electrophilicity index. The orbital energy values for the title compound, its trans-isomer and unsubstituted TTF are summarized in Table 1. The conformation energy difference between the cis- and trans isomers is 1.6331 kJ mol⁻¹. For both isomers the energy gap is large; hence both molecules are considered to be hard materials and would be difficult to polarize. As seen from Table 1, the bromophenyl substituents reduce the HOMO–LUMO energy gap and therefore the unsubstituted TTF molecule would be even more difficult to polarize.

Table 1
Calculated frontier molecular orbital energies (eV) for the title compound, its trans isomer and unsubstituted TTF and the conformational energy differences (kJ mol⁻¹) between the cis and trans isomers

	cis isomer	trans isomer	TTF
E(HOMO)	−5.0559	−5.0186	−4.8488
E(LUMO)	−1.8283	−1.8049	−1.1252
E(HOMO-1)	−6.3966	−6.3941	−6.6303
E(LUMO+1)	−1.6457	−1.6515	−0.7140
ΔE(HOMO–LUMO)	3.2275	3.2137	3.7236
ΔE(HOMO-1–LUMO+1)	4.7508	4.7427	5.9163

Chemical hardness (η)	1.6138	1.6068	1.8618
Chemical potential (μ)	3.4421	3.4118	2.9870
Electronegativity (χ)	−3.4421	−3.4118	−2.9870
Electrophilicity index (ω)	3.6709	3.6221	2.3961

ΔE(cis–trans)	1.6331

Figure 4
Molecular orbital energy levels of the title compound (cis isomer).

Figure 5
Molecular orbital energy levels of the trans isomer of the title compound.

6. Database survey

A search of the Cambridge Structural Database (CSD version 5.40, last update November 2018, Groom et al., 2016) for substituted TTF-phenyl derivatives related to the title compound yielded six structures. They include: bis(4,4′-diphenyltetrathiafulvalenium)bis(pentafluorophenyl)gold(I) (CAKTAJ; Cerrada et al., 1998 ), 4,5′-diphenyltetrathiafulvalene (DPTFUL; Escande & Lapasset, 1979 , and DPTFUL01; Noda et al., 2007), 4,4′-bis(4-chlorophenyl)-1,1′,3,3′-tetrathiafulvalene (GOBVUP; Madhu & Das, 2008), 4,5′-bis(p-tolyl)tetrathiafulvalene (MOPJOR; Noda et al., 2007), 4,5′-bis(4-ethylphenyl)tetrathiafulvalene (MOPJUX; Noda et al., 2007), and 4,5′-bis(4-(trifluoromethyl)phenyl)tetrathiafulvalene (MOPKEI; Noda et al., 2007). Contrary to the title compound, they all exhibit inversion or pseudo-inversion symmetry with a trans-arrangement of the phenyl substituents about the central C=C bond. The C=C bond lengths vary from 1.339 Å (MOPJUX) to 1.353 Å (DPTFUL); the value observed for the title compound falls within this limit. All of the above molecules are almost planar, with tilt angles between the dithiol and phenyl rings varying from 5.39 to 10.18° for the two independent molecules in DPTFUL01 to 28.28° in GOBVUP and 30.29° in MOPKEI; the greatest twisting was observed for halogen-substituted derivatives.

7. Crystallization

The single crystals of the title compound were obtained in attempt to co-crystallize it with tetracyanoquinodimethane (TCNQ) in a 1:1 molar ratio. A saturated solution of 4,4′-bis(4-bromophenyl)-1,1′,3,3′-tetrathiafulvalene (2 mg, Aldrich) in chloroform was mixed with a saturated solution of TCNQ (1 mg, Aldrich) in acetonitrile and left at room temperature. Red prismatic crystals suitable for the X-ray diffraction analysis were obtained after a week of slow evaporation.

8. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen atoms were positioned geometrically and refined using a riding model: C—H = 0.93 Å with U_iso(H) = 1.2U_eq(C).

Table 2
Experimental details

Crystal data
Chemical formula	C₁₈H₁₀Br₂S₄
M_r	514.32
Crystal system, space group	Orthorhombic, Abm2
Temperature (K)	90
a, b, c (Å)	7.5981 (6), 37.411 (3), 6.1991 (5)
V (Å³)	1762.1 (2)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	5.07
Crystal size (mm)	0.17 × 0.11 × 0.05

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2016 )
T_min, T_max	0.625, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections	34235, 1580, 1530
R_int	0.066
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.017, 0.041, 1.09
No. of reflections	1580
No. of parameters	109
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.29, −0.29
Absolute structure	Flack x determined using 663 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	0.014 (5)
Computer programs: APEX2 and SAINT (Bruker, 2016), SHELXT (Sheldrick, 2015a ), SHELXL2018 (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 1940080

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989019009952/eb2019sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989019009952/eb2019Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989019009952/eb2019Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

4,4'-Bis(4-bromophenyl)-1,1',3,3'-tetrathiafulvalene top

Crystal data top

C₁₈H₁₀Br₂S₄	D_x = 1.939 Mg m⁻³
M_r = 514.32	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Abm2	Cell parameters from 9390 reflections
a = 7.5981 (6) Å	θ = 2.2–28.4°
b = 37.411 (3) Å	µ = 5.07 mm⁻¹
c = 6.1991 (5) Å	T = 90 K
V = 1762.1 (2) Å³	Prism, red
Z = 4	0.17 × 0.11 × 0.05 mm
F(000) = 1008

Data collection top

Bruker APEXII CCD diffractometer	1530 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.066
Absorption correction: multi-scan (SADABS; Bruker, 2016)	θ_max = 25.0°, θ_min = 1.1°
T_min = 0.625, T_max = 0.747	h = −9→9
34235 measured reflections	k = −44→44
1580 independent reflections	l = −7→7

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.017	w = 1/[σ²(F_o²) + (0.0126P)² + 2.1911P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.041	(Δ/σ)_max = 0.003
S = 1.09	Δρ_max = 0.29 e Å⁻³
1580 reflections	Δρ_min = −0.29 e Å⁻³
109 parameters	Absolute structure: Flack x determined using 663 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
1 restraint	Absolute structure parameter: 0.014 (5)
Primary atom site location: dual

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	0.79020 (5)	0.53149 (2)	0.04905 (9)	0.02338 (12)
S1	0.84814 (9)	0.70527 (2)	0.54322 (17)	0.01212 (17)
S2	0.64506 (12)	0.70791 (2)	0.95068 (14)	0.01322 (19)
C1	0.7514 (4)	0.73205 (10)	0.7447 (6)	0.0120 (7)
C2	0.6459 (5)	0.66817 (10)	0.8081 (6)	0.0122 (8)
H2	0.583254	0.648059	0.861560	0.015*
C3	0.7350 (5)	0.66579 (9)	0.6225 (6)	0.0117 (8)
C4	0.7515 (4)	0.63362 (9)	0.4874 (6)	0.0125 (8)
C5	0.6886 (4)	0.60030 (9)	0.5600 (9)	0.0159 (7)
H5	0.637106	0.598599	0.699223	0.019*
C6	0.7004 (5)	0.56997 (10)	0.4326 (7)	0.0182 (8)
H6	0.658485	0.547656	0.484660	0.022*
C7	0.7737 (5)	0.57250 (10)	0.2289 (7)	0.0148 (8)
C8	0.8384 (4)	0.60494 (10)	0.1519 (6)	0.0133 (7)
H8	0.890749	0.606365	0.012995	0.016*
C9	0.8253 (4)	0.63529 (10)	0.2817 (6)	0.0129 (8)
H9	0.867405	0.657541	0.228922	0.015*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0322 (2)	0.01276 (17)	0.02519 (19)	−0.00010 (14)	0.0039 (2)	−0.0046 (2)
S1	0.0126 (4)	0.0117 (4)	0.0120 (4)	−0.0005 (3)	0.0032 (5)	0.0006 (5)
S2	0.0148 (4)	0.0149 (4)	0.0100 (4)	0.0001 (4)	0.0030 (4)	0.0018 (4)
C1	0.0071 (15)	0.0181 (17)	0.0109 (16)	0.0014 (14)	0.0010 (12)	0.0008 (15)
C2	0.0111 (17)	0.0111 (19)	0.0145 (18)	−0.0007 (13)	−0.0011 (14)	0.0022 (14)
C3	0.0089 (17)	0.0126 (19)	0.0134 (18)	0.0024 (13)	−0.0025 (12)	0.0042 (13)
C4	0.0074 (15)	0.0130 (18)	0.017 (2)	0.0019 (12)	−0.0022 (12)	0.0010 (13)
C5	0.0136 (15)	0.0191 (17)	0.0149 (16)	0.0002 (12)	0.0022 (19)	0.002 (2)
C6	0.022 (2)	0.0124 (19)	0.020 (2)	0.0007 (15)	0.0009 (16)	0.0067 (17)
C7	0.0141 (18)	0.0119 (19)	0.0186 (19)	0.0014 (14)	−0.0036 (16)	−0.0017 (16)
C8	0.0121 (18)	0.0160 (19)	0.0117 (17)	−0.0007 (14)	0.0003 (15)	0.0017 (15)
C9	0.0115 (17)	0.0127 (19)	0.0144 (18)	0.0007 (14)	−0.0014 (14)	0.0029 (15)

Geometric parameters (Å, º) top

Br1—C7	1.901 (4)	C4—C9	1.394 (5)
S1—C1	1.762 (4)	C5—H5	0.9500
S1—C3	1.778 (4)	C5—C6	1.385 (6)
S2—C1	1.760 (4)	C6—H6	0.9500
S2—C2	1.729 (4)	C6—C7	1.384 (6)
C1—C1ⁱ	1.343 (7)	C7—C8	1.394 (5)
C2—H2	0.9500	C8—H8	0.9500
C2—C3	1.338 (5)	C8—C9	1.396 (6)
C3—C4	1.472 (5)	C9—H9	0.9500
C4—C5	1.409 (5)

C1—S1—C3	94.28 (17)	C6—C5—C4	121.4 (4)
C2—S2—C1	93.94 (18)	C6—C5—H5	119.3
S2—C1—S1	114.5 (2)	C5—C6—H6	120.3
C1ⁱ—C1—S1	124.66 (13)	C7—C6—C5	119.4 (4)
C1ⁱ—C1—S2	120.87 (12)	C7—C6—H6	120.3
S2—C2—H2	120.1	C6—C7—Br1	120.5 (3)
C3—C2—S2	119.9 (3)	C6—C7—C8	120.9 (4)
C3—C2—H2	120.1	C8—C7—Br1	118.6 (3)
C2—C3—S1	115.3 (3)	C7—C8—H8	120.5
C2—C3—C4	125.9 (3)	C7—C8—C9	119.1 (3)
C4—C3—S1	118.7 (2)	C9—C8—H8	120.5
C5—C4—C3	120.9 (3)	C4—C9—C8	121.3 (3)
C9—C4—C3	121.2 (3)	C4—C9—H9	119.3
C9—C4—C5	117.9 (4)	C8—C9—H9	119.3
C4—C5—H5	119.3

Symmetry code: (i) x, −y+3/2, z.

Calculated frontier molecular orbital energies (eV) for the title compound, its trans isomer and unsubstituted TTF and the conformational energy differences (kJ mol^-1) between the cis and trans isomers top

	cis isomer	trans isomer	TTF
E(HOMO)	-5.0559	-5.0186	-4.8488
E(LUMO)	-1.8283	-1.8049	-1.1252
E(HOMO-1)	-6.3966	-6.3941	-6.6303
E(LUMO+1)	-1.6457	-1.6515	-0.7140
ΔE(HOMO–LUMO)	3.2275	3.2137	3.7236
ΔE(HOMO-1–LUMO+1)	4.7508	4.7427	5.9163

Chemical hardness (η)	1.6138	1.6068	1.8618
Chemical potential (µ)	3.4421	3.4118	2.9870
Electronegativity (χ)	-3.4421	-3.4118	-2.9870
Electrophilicity index (ω)	3.6709	3.6221	2.3961

ΔE(cis–trans)	1.6331

Funding information

Funding for this research was provided by: NSF DMR 1523611 (PREM).

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