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TRANSCRIPT
Supporting Information
Meeting the Challenging Electronic Structure of
Thiophene-Based Heterophenoquinones
Francesco Tampieri, Letizia Colella, Ali Maghsoumi, Javier Martí-Rujas, Emilio Parisini,
Matteo Tommasini, Chiara Bertarelli, Antonio Barbon
I. Synthesis of QDTT S2
II. UV-visible characterization S3
III. Hyperfine coupling constants calculations for the monomer of QBT S4
IV. DFT calculations of vibrational properties S5
V. X-ray data collection S7
VI. 1H-NMR spectra of QBT S12
VII. EPR spectrum of QBT in chloroform S13
S2
I - Synthesis of QDTT
Unless otherwise specified, all reagents, catalysts, spectroscopic grade and reagent grade solvents
were commercial (Sigma Aldrich). All reactions of air- water-sensitive reagents and intermediates
were carried out in dried glassware and argon atmosphere. Solvents were previously dried by
conventional methods and stored under argon. Air- and water-sensitive solutions were transferred
with hypodermic syringes or via cannula.
4,4’-(Dithieno[3,2-b:2’,3’-d]thiophene-2,6-diyl)bis(2,6-di-tert-butylphenol) (ADTT)
Pd(PPh3)4 (82 mg, 0.0706 mmol), tris[3,5-di-tert-butylphenol-4-(trimethylsilyloxy)phenyl]boroxine
(644.5 mg, 0.706 mmol) and Na2CO3 (673 mg, 6.35 mmol) aq solution (1 M) were added to a solution
of 2,6-dibromodithieno[3,2-b:2`,3`-d]thiophene (250 mg, 0.706 mmol) in previously degassed DME
(2:1 with respect to water). The reaction was refluxed overnight, and then it was extracted with ethyl
acetate. The organic fractions were combined, dried over Na2SO4, filtered, and then the solvent was
removed under reduced pressure. The raw product was purified using flash chromatography (silica
gel, 95:5 hexane: ethyl acetate) to afford 175 mg (41% yield) of ADTT as a yellow crystalline solid.
1H-NMR (400 MHz, CDCl3, ppm): δ 7.454 (s, 4H; Ph-H), 7.355 (s, 2H; Dithienoth-H3,H5), 5.305 (s, 2H;
-OH), 1.505 (s, 36H; t-Bu); MS (ESI): m/z calcd for C36H44O2S3+H+: 605 [M+H+], found: 604.6 (M+).
4,4’-(dithieno[3,2-b:2’,3’-d]thiophene-2,6-di-yl)bis(2,6-di-tert-butylcyclohexa-2,5-dienone) (QDTT)
To a solution of ADTT (100 mg, 0.165 mmol) in CH2Cl2 (70 mL), K3Fe(CN)6 (543 mg, 1.65 mmol) and a
0.4 M aq. solution of KOH (925.8 mg, 16.5 mmol) were added. The resulting mixture was stirred until
the starting material was completely reacted (≈ 30 min). The reaction mixture was extracted with
methylene chloride and washed with water and the organic solvent was removed under reduced
pressure, giving the desired product in quantitative yield as a green solid.
1H-NMR (600 MHz, (CD3)2CO, ppm): δ 8.08 (s, 2H; Th1-H), 7.68 (s, 2H; Ph-H), 7.33 (s, 2H; Ph-H),
1.364 (s, 36H; t-Bu); MS (ESI): m/z calcd for C36H42O2S3+H+: 603 [M+H+], found: 603.6 (M+).
S3
II - UV-visible characterization
250 300 350 400 450 500
ADTT
ABTA
bso
rba
nce
(a
.u.)
Wavelength (nm)
Figure S1. Normalized UV-Vis absorption spectra in chloroform of the aromatic precursors: ADTT
(red line), ABT (green line).
500 550 600 650 700 750 800 850 900
QDTT
QBT
Wavelength (nm)
Ab
so
rba
nce
(a
.u.)
Figure S2. Normalized UV-Vis absorption spectra of quinones in chloroform: QDTT (red line), QBT
(green line).
S4
III - Hyperfine coupling constants calculations for the monomer of QBT
DFT calculations of the hyperfine coupling constants (hfccs) for the half molecule of QBT. The
calculations are done with Gaussian09 using the functional B3LYP and 6-311g** as basis set.
The dihedral angle between the thiophenic ring and the phenyl one is varied from 0° (coplanar rings)
and 90° (perpendicular).
Table S1. hfccs of QBT half molecule, end-capped with a methyl group, varying the dihedral angle
between the thiophenic and phenyl rings
Proton aiso /G
0° 15° 30° 45° 60° 75° 90°
ph2 1.87 1.92 1.98 2.06 2.18 2.34 2.43
ph1 1.81 1.86 1.93 2.04 2.19 2.35 2.43
th2 0.83 0.83 0.74 0.61 0.49 0.44 0.45
th1 -3.94 -3.89 -3.37 -2.62 -1.75 -0.87 -0.41
ph1
ph2
th1 th2
S5
IV - DFT calculations of vibrational properties
Figure S3. Normal modes assigned to features 1 and 2 in the IR spectra of QBT and QDTT (from
DFT calculations on displaced geometries, see Figure 4 and the main text for details on the geometry
displacement procedure). The reported wavenumbers have not been scaled by the 0.98 factor. Red
arrows represent displacement vectors; CC bonds are represented as green (blue) lines of different
thickness according to their relative stretching (shrinking).
Figure S4. Representation of the ECC normal modes of QBT in the optimized and displaced
geometries (see Figure 5a and the main text for details on the geometry displacement procedure).
S6
The reported wavenumbers have not been scaled by the 0.98 factor. Red arrows represent
displacement vectors; CC bonds are represented as green (blue) lines of different thickness according
to their relative stretching (shrinking).
Figure S5. Representation of the ECC normal modes of QDTT in the optimized and displaced
geometries (see Figure 5b and the main text for details on the geometry displacement procedure).
The reported wavenumbers have not been scaled by the 0.98 factor. Red arrows represent
displacement vectors; CC bonds are represented as green (blue) lines of different thickness according
to their relative stretching (shrinking).
S7
V - X-ray data collection
Single crystal data collection of QBT was done at 100 K using synchrotron radiation (𝜆 = 0.77489 Å)
at the BL-13-Xaloc Beamline at Alba-CELLS Synchrotron, Barcelona) under the Proposal Number
2013100590.
Single crystal data collection of QDTT was done at 100 K using a Bruker X8 Prospector APEX-II/CCD
diffractometer equipped with a microfocusing mirror (Cu-Kα radiation, 𝜆 = 1.54178 Å).
The structures were determined using direct methods and refined (based on F2 using all
independent data) by full-matrix least-square methods (SHELXTL 97). All non-hydrogen atoms were
located from different Fourier maps and refined with isotropic displacement parameters.
Further detailed crystallographic information is provided in Table S2.
Table S2. Crystallographic data for QBT and QDTT.
Compound QBT QDTT
Empirical formula
Formula weight
Crystal temperature (K)
Crystal system
Space group
Z
a (Å)
b (Å)
c (Å)
a (deg)
(deg)
(deg)
V (Å3)
Dc (Mg.cm-3)
(mm-1)
F (000)
Rint
Rf/ wRf
All data Rf/ wRf
C19 H23Cl3 O1S1
405.78
100(2)
Monoclinic
P21/n
4
5.8890(12)
18.621(4)
18.648(4)
90.00
92.70(3)
90.00
2042.65(7)
1.320
0.554
848
0.0928
0.0478/ 0.1384
0.0499/ 0.1420
C18H21O1S1.50
301.44
100(2)
Tetragonal
P42212
8
23.474(2)
23.474(2)
6.1972(8)
90.00
90.00
90.00
3414.7(7)
1.173
2.200
1288
0.0310
0.0639/0.1750
0.0758/0.1805
S8
Structural description of QBT.
Dark green crystals of size 0.07 x 0.06 x 0.04 mm were obtained by slow evaporation from a
chloroform-d solution. The asymmetric unit of the crystal contains one QBT and one chloroform-d
molecule.
The packing arrangement shows no π-π interactions. Stabilizing Cmethyl-H···Cl and C-H···O contacts
(2.9 Å and 2.03 Å, respectively) are formed between the solvent molecule and the QBT.
Figure S6. Crystal packing of QBT viewed along the crystallographic a-axis.
S9
Figure S7. Pictures showing the contacts between QBT and chloroform molecules viewed along the
crystallographic a-axis.
Table S3. Bond lengths and angles QBT.
Bond distance (Å)
1 C11 O2 1.244(3)
2 C4 C5 1.402(3)
3 C5 S1 1.748(2)
4 S1 C6 1.743(2)
5 C6 C6 1.391(3)
6 C8 C7 1.366(3)
7 C11 C8 1.484(3)
8 C11 C3 1.475(3)
9 C3 C100 1.362(3)
10 C100 C4 1.435(3)
11 C5 C17 1.419(3)
12 C17 C16 1.376(3)
13 C16 C6 1.417(3)
14 C9 C8 1.524(3)
S10
Table S4. Torsion Angles in QBT.
Torsion angles (˚)
1 C7 C4 C5 C17 -177.3(2)
2 C100 C4 C5 S1 175.8(1)
Table S5. Angles in QBT.
Angles (˚)
1 C5 C4 C7 121.2(2)
2 C17 C5 C4 128.7(2)
Structural description of QDTT.
Dark green crystals were obtained by slow evaporation from a toluene-d8 solution. The asymmetric
unit of QDTT contains only half of the molecule, while the other half is generated through an
inversion center. The packing arrangement of the molecules in the crystal show no π-π interactions
involving any portion of the long conjugated aromatic system. Large empty cavities (135 Å3) are
present in the crystal (Figure S8). This is also confirmed by the low crystal density compared to QBT.
Lattice stability is largely or almost uniquely provided by van der Waals contacts that are formed
between the t-butyl moieties.
Figure S8. Crystal packing of QDTT viewed along the crystallographic c-axis.
S11
Table S6. Bond lengths of QDTT.
Bond distance (Å)
1 O1 C8 1.24(1)
2 C8 C9 1.49(1)
3 C9 C10 1.35(1)
4 C10 C5 1.42(1)
5 C5 C6 1.45(1)
6 C6 C7 1.35(1)
7 C5 C4 1.39(1)
8 C4 S1 1.77(1)
9 S1 C1 1.733(9)
10 C1 C1 1.35(1)
11 C1 C2 1.41(1)
12 C2 C3 1.36(1)
13 C3 C4 1.43(1)
14 C2 S2 1.76(?)
Table S7. Torsion Angles QDTT.
Torsion angle (˚)
1 C10 C5 C4 C3 179.7(9)
2 C6 C5 C4 S1 -172.4(7)
Table S8. Angles QDTT.
Angles (˚)
1 C6 C5 C4 120.1(8)
2 C3 C4 C5 129.6(9)
3 C10 C5 C4 121.3(9)
S12
VI - 1H-NMR spectra of QBT
The spectrum at room temperature (298 K) is consistent with a thermal activation of the rotational
motion about the thiophene-thiophene bond leading to an interconversion between the cis and trans
isomers: according to standard models for exchange processes, the protons of the two conformers are
expected to become equivalent, and their chemical shift to be the averaged value of those at low
temperature. This is also our experimental finding. The presence of narrow linewidths indicates that
the fast motion régime has been reached, that is 𝜏𝛿𝜔 ≪ 1, for the motion; in the expression 𝛿𝜔 is the
difference in frequency of the two merging signals and 𝜏 is the correlation time of the motion.
With increasing of the temperature we observe a broadening of the lines assigned to phenyl protons.
This evidence is consistent with the rotation of the phenyl rings.
8.2 8.1 8.0 7.9 7.8 7.7 7.6 7.5 7.4 7.3
**
**
*
*
*
298 K 600 MHz
Chemical shift (ppm)
313 K 600 MHz
*
Figure S9. 1H-NMR (600 MHz) spectra of sample QBT in deuterated acetone at different
temperatures in the aromatic region. The blue asterisks refer to proton th1 and th2 and the red
asterisks to protons ph1 and ph2.
S13
VII - EPR spectra of QBT in chloroform
The spectrum at room temperature of QBT is shown in Figure S10. The total concentration of QBT is
rather high (1 mM) and the line-width of the observed biradical state is larger than that shown for the
toluene solution in Figure 2 of the main text.
The spectrum has been simulated as sum of two species (see figure S10, red trace) as the best fit
simulation (see Figure S10, grey trace) gave a clear poor reproduction of the spectrum.
Table S9. Hyperfine coupling constant (a) for the proton interaction for QBT in chloroform solution
at room temperature as determined from the simulation of the EPR spectrum in Figure S10 (red
trace) and the relative attribution (see main text).
a (G) Multiplicity Attribution
Species 1
3.78
1.30
0.41
1
2
1
Hth1
Hph
Hth2
Species 2
3.82
1.34
2.12
1
2
1
Hth1
Hph
Hth2
3390 3395
Magnetic field (G)
Figure S10. Cw-EPR spectrum of a 1 mM solution of QBT in deuterated chloroform. In red the
simulation obtained as a 1:1 sum of two species that are interpreted as the two cis/trans conformers.
The simulation parameters are reported in Table S9. In grey the simulation by using a single species.
S14
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