The molecule of the title compound 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.
Keywords: crystal structure, tetrathiafulvalene, derivative, weak interactions, Hirshfeld surface analysis, DFT calculations
Abstract
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.
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).
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 + 
, z.
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 − 
) = 3.458 (4) and C2⋯S2(1 − x, y, z − ) = 3.465 (4) Å, followed by the C2—H2⋯C4(1 − x, y, + 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.
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.
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.
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.
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 |
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.
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.
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, A b m2 |
| 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[F 2 > 2σ(F 2)], wR(F 2), 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 |
| Δρmax, Δρmin (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) |
Supplementary Material
Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989019009952/eb2019sup1.cif
Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989019009952/eb2019Isup2.hkl
Supporting information file. DOI: 10.1107/S2056989019009952/eb2019Isup3.cml
CCDC reference: 1940080
Additional supporting information: crystallographic information; 3D view; checkCIF report
supplementary crystallographic information
Crystal data
| C18H10Br2S4 | Dx = 1.939 Mg m−3 |
| Mr = 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
| Bruker APEXII CCD diffractometer | 1530 reflections with I > 2σ(I) |
| φ and ω scans | Rint = 0.066 |
| Absorption correction: multi-scan (SADABS; Bruker, 2016) | θmax = 25.0°, θmin = 1.1° |
| Tmin = 0.625, Tmax = 0.747 | h = −9→9 |
| 34235 measured reflections | k = −44→44 |
| 1580 independent reflections | l = −7→7 |
Refinement
| 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(Fo2) + (0.0126P)2 + 2.1911P] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.041 | (Δ/σ)max = 0.003 |
| S = 1.09 | Δρmax = 0.29 e Å−3 |
| 1580 reflections | Δρmin = −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
| 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)
| x | y | z | Uiso*/Ueq | ||
| 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)
| 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)
| 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.
Funding Statement
This work was funded by National Science Foundation grant DMR 1523611 (PREM).
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989019009952/eb2019sup1.cif
Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989019009952/eb2019Isup2.hkl
Supporting information file. DOI: 10.1107/S2056989019009952/eb2019Isup3.cml
CCDC reference: 1940080
Additional supporting information: crystallographic information; 3D view; checkCIF report