Donor/acceptor-substituted anthradithiophene materials: Synthesis, optical and electrochemical properties

Article abstract of DOI:10.1016/j.tet.2011.06.098

The synthesis and characterization of two new anthradithiophene (ADT) derivatives bearing electron donating (triphenylamine) or accepting (5-formylthiophen-2-yl unit) moieties have been performed to assess their potential as materials for organic photovoltaics. Optical spectroscopy was used to evaluate the effect of electron rich/poor substituents on the visible absorption spectrum and on the stability towards photo-oxidation. The results are interpreted with the assistance of quantum-chemical calculations and cyclic voltammetry experiments.

Full text of DOI:10.1016/j.tet.2011.06.098

Tetrahedron 67 (2011) 7156e7161
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Donor/acceptor-substituted anthradithiophene materials: synthesis, optical
and electrochemical properties
a
a
b
a
a
ˇ
Jean-Yves Balandier , Florence Quist , Noham Sebaihi , Claude Niebel , Benoît Tylleman ,
b
b
b
b
b
ꢀ
Pol Boudard , Saïd Bouzakraoui , Vincent Lemaur , Jerome Cornil , Roberto Lazzaroni ,
Yves Henri Geerts a, Sara Stas a
,
*
a
ꢁ
ꢀ
ꢀ
Laboratoire Chimie des Polymeres, Universite Libre de Bruxelles (ULB), Faculte des Sciences, CP 206/1 Boulevard du Triomphe, 1050 Bruxelles, Belgium
Service de Chimie des Materiaux Nouveaux, Universite de Mons (UMONS), Place du Parc 20, 7000 Mons, Belgium
b
ꢀ
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 May 2011
Received in revised form 22 June 2011
Accepted 27 June 2011
Available online 2 July 2011
The synthesis and characterization of two new anthradithiophene (ADT) derivatives bearing electron
donating (triphenylamine) or accepting (5-formylthiophen-2-yl unit) moieties have been performed to
assess their potential as materials for organic photovoltaics. Optical spectroscopy was used to evaluate
the effect of electron rich/poor substituents on the visible absorption spectrum and on the stability
towards photo-oxidation. The results are interpreted with the assistance of quantum-chemical calcula-
tions and cyclic voltammetry experiments.
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Anthradithiophene
Donor/acceptor systems
Cyclic voltammetry
Stability studies
Organic electronics
1. Introduction
the influence of the substitution of the ADT skeleton by electron
withdrawing or donating groups on its stability towards photo-
Over the past 10 years, many studies have been reported in the
literature on several organic semiconductors, such as acenes, oli-
gothiophenes, and their use in various electronic devices (field-
effect transistors, light-emitting diodes, photovoltaic cells and
sensors).1 Currently, fused (hetero)acenes represent one of the
most studied categories of organic semiconductors. Recent publi-
cations described the functionalization of pentacene or anthradi-
thiophene cores by several groups, such as trialkylsilylethynyl or
thiophenyl groups to lead to soluble semiconductors.2 Additionally,
it has been demonstrated that the presence of such substituents
enhances the stability of these derivatives towards photo-
oxidation, especially in solution.2aec,3 With this synthetic strategy,
it has been possible to reach extended fused linear (hetero)
acenes.2,4 Chemical reactions involving these compounds were also
rendered feasible and were engaged in oligomerization and/or
polymerization processes.5 For example, we have recently reported
the synthesis of dimers of anthrathiophene and anthradithiophene
derivatives.6 However, the stability improvements provided by
these substituents still remain limited. Therefore, we investigated
induced degradation. We describe the synthesis and the charac-
terization of new anthradithiophene (ADT) derivatives bearing
triphenylamine as electron donor (DADT) and 5-formylthiophen-2-
yl group as electron acceptor (AADT) moieties. Octyl chains were
attached on positions 2 and 8 of the ADT skeleton in order to fulfil
solubility requirements and to prevent side reactions, which could
occur by the metallation of those positions using n-BuLi.6 The
spectroscopic and electrochemical properties of these semi-
conductors were evaluated and supported by quantum-chemical
calculations.
2. Results and discussion
DADT and AADT were prepared as presented in Scheme 1.
Synthesis of the key intermediate 2,8-dioctylanthradithiophene-
5,11-dione 1 was achieved in three steps with an overall yield of
63%, starting from commercial thiophene-2,3-dicarboxaldehyde.
Protection of the aldehyde functions of the latter was carried out in
quantitative yield by reaction with ethylene glycol, in the presence
of p-toluenesulfonic acid monohydrate.4f 5-Octylthiophene-2,3-
dicarboxaldehyde (3) was then obtained in 75% yield by metal-
lation of the protected compound 2 using n-BuLi, followed by re-
action of the organolithium intermediate with 1-iodooctane and
* Corresponding author. Fax: þ32 2 650 5410; e-mail address: Sara.Stas@vub.ac.be
(S. Stas).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.06.098

J.-Y. Balandier et al. / Tetrahedron 67 (2011) 7156e7161
7157
Scheme 1. Synthesis of ADT derivatives 4, 5, AADT and DADT. Reagents and conditions: (i) ethylene glycol/p-TSA/toluene/reflux/16 h/quant.; (ii) (1) n-BuLi/THF/ꢀ80 ꢁC, (2) 1-
iodooctane/ꢀ80 ꢁC to rt/16 h, (3) HCl (3 M)/reflux/1 h/75%; (iii) KOH (5%)/cyclohexane-1,4-dione/ethanol/84%; (iv) (1) 4-bromo-N,N-diphenylaniline/n-BuLi/THF/ꢀ80 ꢁC, (2)
SnCl2/HCl (6 M)/rt/80%; (v) (1) LiAlH4/THF/reflux/30 min, (2) HCl (6 M)/reflux/3 h/62%; (vi) (1) thiophene/n-BuLi/THF/ꢀ80 ꢁC, (2) SnCl2/HCl (6 M)/rt/86%; (vii) (1) n-BuLi/THF/
ꢀ30 ꢁC, (2) DMF/ꢀ80 ꢁC to rt/66%.
then by deprotection of the aldehyde functions using 3 M HClaq
solution. Compound 1 was produced in 84% yield by reaction of
dialdehyde 3 with cyclohexane-1,4-dione in presence of 5% KOHaq
solution. DADT and derivative 5 were achieved with yields of, re-
spectively, 80% and 86%, by reaction of the diquinone 1 with the
corresponding lithium intermediates of 4-bromo-N,N-diphenyla-
niline (for DADT) and thiophene (for 5) followed by reduction/de-
oxygenation using SnCl2 in 6 M HClaq solution. Metallation of the
thienyl units, on positions 5,11 of the ADT 5 backbone using n-BuLi,
followed by reaction of the corresponding dilithiated species with
DMF, afforded AADT in good yield (66%). Finally, in order to com-
pare the effect of electron donating or withdrawing groups on the
stability towards photo-oxidation of the ADT core, the synthesis of
2,8-dioctylanthradithiophene 4 was performed. This control com-
pound was prepared in 62% yield by reduction of the diquinone 1
using LiAlH4. Note that all ADT derivatives were produced as
a mixture of isomers since their synthesis were made starting from
a mixture of syn/anti isomers of 2,8-dioctylanthradithiophene-5,11-
dione 1.
Except ADT 4, other compounds possess reasonable solubilities
(up to 10ꢀ2 M) in several common organic solvents, such as chlo-
roform, dichloromethane, tetrahydrofuran, toluene, o-di-
chlorobenzene and nitrobenzene; and were characterized by NMR
and UV/vis spectroscopies, mass spectrometry and cyclic voltam-
metry (See Supplementary data).
Optical measurements were carried out in chloroform solutions
of the compounds and were compared to theoretical simulations.
To do so, geometry optimizations have been performed at the
density functional theory (DFT) level, using the B3LYP functional7
and the 6-31G(d,p) basis set. The octyl chains in 2,8 positions of
the ADT skeleton were replaced by methyl chains in the geometry
optimizations to reduce the computational costs and since they do
not contribute to the description of the frontier electronic levels
and hence the first absorption peaks. The pendant thiophene and
triphenylamine (TPA) units are found to be almost perpendicular to
the conjugated core in the optimized geometry, i.e., 89ꢁ and 79ꢁ for
the pendant thiophene and TPA units, respectively. The vertical
transition energies to the lowest excited states of the isolated
compounds were computed from the optimized geometries with
the time-dependent density functional theory (TD-DFT) formal-
ism,8 using the same functional and basis set. Gaussian 03 package
was used for all calculations.9
Compounds 5, AADT and DADT present spectral profiles similar
to that of the control ADT 4, showing an intense band in the range
of 300e315 nm and three additional peaks located at lower ener-
gies (Table 1, Fig. 1). Since the calculations yield a single optically-
coupled excited state in this energy range, the latter are assigned
to vibronic satellites (Fig. SI24). Bathochromic shifts of the ab-
sorption maxima of, respectively, 22 nm (0.11 eV) and 27 nm
(0.14 eV) are observed going from 4 to DADT and from 4 to 5. These
observed red shifts are due to the substitution of the ADT 4 skeleton
Table 1
Experimental optical data and calculated vertical transition energies (DEvertical) to
the lowest excited state as well as calculated HOMO and LUMO values of 4, 5, AADT
and DADT in the gas phase
Product
Experimental
Theory
H (eV)
a
labs
lem
Egb
DEvertical
L (eV)
[nm (eV)]
[nm (eV)]
530 (2.34)
[eV]
[nm (eV)]
DADT
312 (3.99)
440 (2.82)
472 (2.63)
505 (2.46)
310 (4.00)
455 (2.73)
483 (2.57)
516 (2.41)
310 (4.00)
446 (2.78)
475 (2.61)
510 (2.43)
304 (4.08)
424 (2.93)
452 (2.75)
483 (2.57)
2.40
2.31
2.40
2.54
510 (2.43)
ꢀ4.56
ꢀ5.07
ꢀ4.72
ꢀ4.69
ꢀ1.80
AADT
577 (2.15)
528 (2.35)
493 (2.52)
524 (2.37)
517 (2.40)
490 (2.53)
ꢀ2.38
ꢀ2.02
ꢀ1.86
5
4
a
lexcitation
¼
labs of the lower energy band.
Optical band gaps determined from the intersection between normalized ab-
sorption and emission spectra.
b

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J.-Y. Balandier et al. / Tetrahedron 67 (2011) 7156e7161
emission spectra of all ADT derivatives. The band gap value de-
creases from 2.54 eV for 4 to 2.40 eV for 5 and DADT and to 2.31 eV
for AADT.
The stability of 4, 5, AADT and DADT towards photo-oxidation
was investigated by monitoring the absorbance decay of 10ꢀ5
M
chloroform solutions stored in the dark at room temperature, under
ambient atmosphere and exposed to 10 cm of 8W UV/vis lamps
(l1¼244 nm and l2¼366 nm) (Fig. 3 and SI1e4).
1,2
1,0
4
5
AADT
0,8
DADT
Fig. 1. UV/vis spectra of 4, 5, AADT and DADT in CHCl3 (10ꢀ5 M).
0,6
0,4
0,2
0,0
on its 5,11 positions by triphenylamine (DADT) and thiophenyl (5)
units. AADT presents also a slightly red-shifted absorption maxima
of 6 nm (0.02 eV) compared to its synthetic precursor 5. The cal-
culated transition energies follow the same behaviour going from 4
to 5 (27 nm (0.13 eV)), from 4 to DADT (20 nm (0.10 eV)) and from 5
to AADT (7 nm (0.03 eV)). The good agreement between the ex-
perimental measurements and the calculated data points to the
relevance of combining DFT and TDFT methods to characterize the
optical properties of ADT derivatives since this allows: (i) explain-
ing the relative shifts between the energy of the first excited state of
each derivative and; (ii) rationalizing the nature of the low energy
peaks and therefore ruling out any extrinsic effects in the experi-
mental measurements. This also demonstrates that this method-
ology can prove useful to design new ADT derivatives prior to their
synthesis.
0
10
20
30
40
50
60
70
80
90
100
time (s)
Fig. 3. Evolution of the lower energy band absorptions of 4 (483 nm), 5 (510 nm),
AADT (516 nm) and DADT (505 nm) (10ꢀ5 M) in CHCl3, under UV/vis lamps exposure
l1¼244 nm and l2¼366 nm) and at room temperature under ambient atmosphere.
(
Taking into account an absorbance decay of 50% of the lower
energy bands of all ADT compounds, the stability order observed is
as follows: AADT (58 s)>5 (40 s)>DADT (35 s)>4 (25 s). ADT de-
rivatives substituted on the central ring of the ADTcore are known to
be more stable towards photo-degradation than those without any
‘protecting’ groups.2aec,3 The same tendency is observed in our case
since the stability of compounds 5, AADT and DADT is higher than
that of the control ADT 4. It can also be noticed that compounds
bearing electron donating groups DADT and 5 possess similar sta-
bilities (Fig. 3). Product bearing electron-withdrawing groups
(AADT) has a higher stability than products with donor groups on
their ADT backbone (DADT and 5). It was previously demonstrated
that the photo-induced degradation of fused linear (hetero)acenes is
due to the formation of endoperoxide bridge across the most re-
active central ring.3 The reaction involved in the degradation process
can be compared to a DielseAlder cycloaddition where the diene is
the central ring of the (hetero)acenes and the dienophile is the O2
singlet formed upon UV/vis irradiation. Therefore, the reactivity of
the central ring with the latter can be (i) increased with donor
groups and (ii) decreased with acceptor groups on it. With this in
mind, ADT bearing electron-withdrawing groups (AADT) is less re-
active to oxygen than 5 and DADT, which are substituted with
electron donating groups and this is likely responsible for the higher
stability towards photo-oxidation of AADT. The higher stability of
AADT can be rationalized from the calculated energy of the HOMO
levels among the four ADT molecules (Table 1) since AADT possesses
the deepest HOMO level (ꢀ5.07 eV). It can also be noted that DADT
presents a higher stability than the control ADT 4, although theo-
retical calculation shows that it has a less stable HOMO level
(ꢀ4.56 eV) than that of compound 4 (with a deeper HOMO level at
ꢀ4.69 eV). In this case, the steric hindrance afforded by the triphe-
nylamine groups substituted on positions 5,11 of the ADT core is
responsible of the higher stability of DADT than that of ADT 4.
All ADT derivatives show fluorescence in solution (Fig. 2). Sub-
stitution of the ADT core by thiophenyl and triphenylamine groups
leads to a red shift of the emission maximum, which is in agree-
ment with the observations made in the UV/vis spectra. Bath-
ochromic shifts of 35 nm (0.17 eV) and of 37 nm (0.18 eV) are
measured from 4 to 5 and from 4 to DADT, respectively. In addition,
a displacement of 49 nm (0.20 eV) to the lower energies is noted
from 5 to AADT. The optical band gaps, listed in Table 1, were es-
timated from the intersection of the normalized absorption and
1,1
1,0
0,9
4
0,8
5
AADT
0,7
DADT
0,6
0,5
0,4
0,3
0,2
0,1
0,0
450 475 500 525 550 575 600 625 650 675 700 725 750
Wavelength (nm)
Fig. 2. Emission spectra of
(
4
(
lexcitation¼483 nm),
5
(
lexcitation¼510 nm), AADT
lexcitation¼516 nm) and DADT (lexcitation¼505 nm) in CHCl3 (10ꢀ5 M).

J.-Y. Balandier et al. / Tetrahedron 67 (2011) 7156e7161
7159
Table 2
Furthermore, several isosbestic points were observed in 4, 5, AADT
and DADT UV/vis spectra (Figs. SI1e4). This indicates the co-
existence in solution of two species: the starting derivatives and
their corresponding oxidized species. Throughout all these experi-
ments, it was also found that freshly prepared solutions of all
products stored in the dark remain stable for at least 24 h. As
a consequence, this observation shows that the light irradiation acts
as the agent responsible for the ADTs degradation.
The stability of spin-coated thin films of soluble ADT derivatives
5, AADT and DADT towards photo-induced degradation was also
assessed by following the same experimental procedure described
above (Fig. 4 and SI5e8). As expected, the stability order in the thin
film state is identical to the one observed in solution
(AADT>5>DADT), however the degradation rates are different.
Indeed, in solution, ADT 5 and DADT possess similar stabilities
whereas in the solid state the first one (5) is much more stable. For
50% of absorbance decay of the lower energy bands of 5 and DADT,
their stability is about 240 s and 90 s, respectively. It also can be
noticed that the ADT bearing aldehyde functions (AADT) is ex-
tremely stable compared to products substituted with electron
donating groups (5 and DADT) since under irradiation for 360 s the
absorbance decay of AADT is only about ꢀ4% (Abs360 of 5¼ꢀ70%
and Abs360 of DADT¼ꢀ80%). Moreover, after irradiation during 5 h,
the absorbance of AADT decreases only with 25% (Fig. SI7).
Oxidative potential values E¼(EpcþEpa)/2 in V (vs Fcþ/Fc couple) of compounds 5,
AADT and DADT in CH2Cl2 solution containing 0.1 M of TBAPF6 at scan rate of
100 mV sꢀ1 and their estimated HOMO energy levels (eV)
Product
Eox1 (V)
HOMOa (eV)
DADT
AADT
5
0.16
0.44
0.31
ꢀ4.96
ꢀ5.24
ꢀ5.11
a
HOMO energy levels are estimated from the first oxidation potential waves
according to HOMO¼ꢀ(4.8þEox1).10
3. Conclusion
Two new derivatives of 2,8-alkylated anthradithiophenes bear-
ing electron donating (triphenylamine) and withdrawing (5-
formylthiophen-2-yl) groups were prepared, isolated and charac-
terized. These new fused heteroacene derivatives exhibit reason-
able stabilities in solution without light exposure. It has also been
proven by optical experiments that the ADT skeleton is much more
resistant towards photo-oxidation when the latter is substituted on
positions 5,11 by electron acceptor units.
4. Experimental section
The electrochemical properties of soluble ADT derivatives (5,
AADT and DADT) were studied using cyclic voltammetry (Figs.
SI25e27) and are collected in Table 2. Oxidation processes were
measured in dichloromethane versus the Fcþ/Fc couple. All mea-
surements were also performed under light exclusion in degassed
solutions of the products to avoid the presence in solution of their
photo-oxidized corresponding species. Both compounds 5 and
AADT present single quasi-reversible oxidations at Eox1 5¼0.31 V
and Eox1 AADT¼0.44 V, respectively. These waves are ascribed to the
oxidation of 5 and AADT into their corresponding radical-cation
species. The oxidative process of AADT appears positively shifted
compared to that of ADT 5 due to the presence of electron-
withdrawing aldehyde functions, which render AADT more diffi-
cult to oxidize than 5. DADT exhibits multiple oxidative waves (Eox1
4.1. Materials and methods
All chemicals and solvents were purchased from Acros, Aldrich
and Alfa Aeser and were used without further purification unless
otherwise stated. THF was dried by conventional method (Na/
benzophenone distillation under argon) and collected with glass
syringes. TLC: SiO2 Silica gel 60F254 on aluminium sheet (Merck).
Column chromatography: Silica gel 60 (particle size
0.063e0.200 mm, Merck). 1H NMR (300 MHz) and 13C NMR
(75 MHz) were recorded on Bruker Advance 300 spectrometer.
Chemical shifts are given in parts per million and coupling con-
stants J in Hertz. The residual signal of the solvent was taken as
internal reference standard. EI-HRMS and MALDI-ToF measure-
ments were made on a Waters AutoSpec 6 and on a Waters QToF
Premier apparatus, respectively. Absorption spectra were recorded
in CHCl3 on an Agilent 8453 spectrophotometer. Emission spectra
were measured on an Aminco Bowman series 2 luminescence
spectrophotometer. The thin films were prepared by spin coating
¼0.16 V, Eox2 DADT¼0.44 V and Eox3 DADT¼0.78 V) with the first
DADT
quasi-reversible one shifted to negative potentials, which is caused
by the substitution of the ADT backbone with electron rich tri-
phenylamine groups. These electrochemical measurements also
confirm the stability observed in the photo-oxidation studies since
200 m
L of toluene solutions of the compounds (10 mg mLꢀ1) on
E
ox1 AADT>Eox1 5>Eox1 DADT.
glass cover slides (20ꢂ20 mm) and using the following rotating
sequence: 150 rpm (10 s), 750 rpm (10 s) and 1500 rpm (30 s).
Melting points were observed by microscopy using a Mettler FP 82
hot stage. Cyclic Voltammetry experiments were performed with
a Princeton Applied research Parstat 2273 potentiostat equipped
with Electrochemistry Powersuite 2.58 software. Measurements
were carried out at room temperature in a three-electrode single-
compartment cell (5 mL), at a scan rate of 100 mV sꢀ1. Concentra-
tions of 10ꢀ3 M in CH2Cl2 solutions containing TBAPF6 (0.1 M) as
supporting electrolyte were prepared. Before each measurement,
solutions were degassed for 10 min by nitrogen bubbling. A plati-
num disc (ؼ1.6 mm, ALS Japan) was used as a working electrode. A
platinum wire (ؼ0.5 mm, ALS Japan) was employed as counter
electrode and an Ag/AgCl/NaCl(satd) electrode (ALS Japan) was
used as reference. The Ag/AgCl electrode was checked against the
ferrocenium/ferrocene (Fcþ/Fc) before and after each experiment.
All potentials are reported versus Fcþ/Fc couple.
1,2
1,0
0,8
0,6
0,4
0,2
0,0
5
AADT
DADT
0
50
100
150
200
250
300
350
400
time (s)
4.2. Synthetic procedures
Fig. 4. Evolution of the lower energy band absorptions of 5 (516 nm), AADT (543 nm)
4.2.1. 2,8-Dioctylanthradithiophene-5,11-dione (syn/anti isomers)
(1). To a mixture of 5-octylthiophene-2,3-dicarboxaldehyde (3)
and DADT (510 nm) thin films, under UV/vis lamps exposure
l2¼366 nm) and at room temperature under ambient atmosphere.
(
l1¼244 nm and

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J.-Y. Balandier et al. / Tetrahedron 67 (2011) 7156e7161
(3.60 g, 14.3 mmol) and 1,4-cyclohexanedione (0.80 g, 7.1 mmol), in
180 mL of absolute ethanol, was slowly added 3 mL of 5% solution of
potassium hydroxide. The medium was then stirred until the total
consumption of starting materials (reaction monitored by TLC
(CH2Cl2), 30 min). The yellow precipitate formed was isolated by
filtration, washed with ethanol, methanol and dried. The product
was solubilized in hot toluene and purified by column chroma-
tography to afford a pale yellow solid of syn/anti isomers mixture of
2,8-dioctylanthradithiophene-5,11-dione 1 (3.24 g, 5.95 mmol).
added dropwise 4.42 mL of n-BuLi (commercial solution 2.5 M from
Acros, 11.04 mmol) and the mixture was stirred for 10e15 min.
Then 1 (1.00 g, 1.84 mmol) was added in one portion. After 10 min,
the cooling bath was removed and the mixture was stirred until the
complete dissolution of the diquinone (w30 min). Finally, the re-
action was protected from the light and a solution of SnCl2 (8. 00 g)
in HClaq 6 M (20 mL) was slowly added. The reaction was stirred
(still protected from the light) for additional 20 min and then the
mixture was poured into 350 mL of methanol. The precipitate
formed was then isolated by filtration, washed with HCl 6 M, H2O,
MeOH and dried. The desired product 5 was obtained (1.08 g,
1.59 mmol) as a red solid. Yield 86%. 1H NMR (300 MHz, CDCl3,
Yield 84%. 1H NMR (300 MHz, CDCl3, 25 ꢁC) : 8.79 (s, 2H, HADT),
d
8.66 (s, 2H, HADT), 7.27 (s, 2H, H3, H9), 3.01 (t, J¼7.6 Hz, 4H, Ha), 1.80
(m, 4H, Hb), 1.38 (s, 20H, Hceg), 0.93 (t, J¼6.4 Hz, 6H, Hh). 13C NMR
(75 MHz, CDCl3, 25 ꢁC)
d: 183.4, 154.0, 144.7, 144.6, 144.3, 144.2,
25 ꢁC)
d
: 8.21 (s, 2H, HADT), 8.09 (s, 2H, HADT), 7.70 (dd, J¼5.1, 1.2 Hz,
130.6, 130.5, 129.09, 129.07, 122.3, 121.9, 32.0, 31.3, 31.1, 29.4, 29.33,
29.29, 22.8, 14.3. Rf¼0.80 (toluene). C34H41O2S2: MALDI-HRMS:
(MHþ): calcd: 545.2548; found: 545.2550. Mp: 226e229 ꢁC.
2H, Hthio), 7.39 (dd, J¼5.2, 3.4 Hz, 2H, Hthio), 7.28 (dd, J¼3.4, 1.2 Hz,
2H, Hthio), 6.93 (s, 2H, H3, H9), 2.85 (t, J¼7.3 Hz, 4H, Ha), 1.72 (m, 4H,
Hb),1.26 (m, 20H, Hceg), 0.87 (t, J¼6.7 Hz, 6H, Hh). 13C NMR (75 MHz,
CDCl3, 25 ꢁC)
d: 150.0, 149.9, 140.14, 140.08, 139.95, 139.8, 138.9,
4.2.2. 2,3-Bis(1,3-dioxolan-2-yl)thiophene (2). It was synthesized
138.8, 129.9, 129.83, 129.75, 129.7, 129.5, 129.4, 129.0, 128.9, 128.6,
127.5, 127.48, 127.45, 127.42, 127.1, 127.03, 126.97, 119.9, 119.0, 118.9,
118.7, 118.6, 32.0, 31.53, 30.48, 29.5, 29.34, 29.25, 22.8, 14.2. Rf¼0.40
(petroleum ether/dichloromethane 95/5 v/v). C42H46S4: MALDI-
according to procedure previously described.4f
4.2.3. 5-Octylthiophene-2,3-dicarboxaldehyde (3). To a solution of
2,3-bis(1,3-dioxolan-2-yl)thiophene (2) (4.67 g, 20.5 mmol) in
40 mL of dry THF, at ꢀ80 ꢁC under argon, was added dropwise n-
BuLi (2.5 M solution in hexane, 9.84 mL, 24.6 mmol) and the mix-
ture was stirred at ꢀ80 ꢁC for 10 min. Then 4.44 mL of 1-iodooctane
(5.91 g, 24.6 mmol) was added in one portion at ꢀ80 ꢁC and after
20 min stirring at ꢀ80 ꢁC, the cold bath was removed and the
medium was stirred for 16 h. The medium was diluted by addition
of diethyl ether and washed twice with water. Organic layer was
dried over MgSO4, and solvents were removed under vacuum. Fil-
tration on silica gel (petroleum ether/ethyl acetate 2/1 v/v, Rf¼0.60)
ꢃ
HRMS: (Mþ ): calcd: 678.2482; found: 678.2510. Mp: 182e186 ꢁC.
4.2.6. 2,8-Dioctyl-5,11-bis(5-formylthiophen-2-yl)anthradithiophene
(syn/anti isomers) (AADT). To a solution of compound 5 (0.50 g,
0.74 mmol) in 20 mL of dry THF cooled to ꢀ30 ꢁC under argon, was
added dropwise 0.65 mL of n-BuLi (commercial solution 2.5 M from
Acros,1.62 mmol) and the mixture was stirred for 10e15 min. Then,
the mixture was cooled to ꢀ80 ꢁC and anhydrous DMF (0.15 g,
0.16 mL, 2.00 mmol) was added in one portion. After 10 min, the
cooling bath was removed and the mixture was stirred for 10 min at
room temperature. The reaction was then quenched by addition of
30 mL of water and the mixture was poured into 300 mL of
methanol. The precipitate formed was then isolated by filtration,
dried and purified by column chromatography on silica gel (CH2Cl2)
to afford pure desired dialdehyde derivative AADT (0.36 g,
0.49 mmol) as a red solid. Yield 66%. 1H NMR (300 MHz, CDCl3,
afforded 2,3-bis(1,3-dioxolan-2-yl)-5-octylthiophene as
a pale
yellow liquid, which was diluted in 40 mL of THF. HCl (40 mL, 3 M)
was added and the medium was then refluxed for 1 h. After cooling
to room temperature, the mixture was extracted twice with diethyl
ether. The combined organic layers were washed successively with
a KOHaq solution (1 M), water, dried over MgSO4 and the solvent
was removed. Purification by column chromatography on silica gel
(petroleum ether/ethyl acetate 2/1 v/v, Rf¼0.86) gave 5-
octylthiophene-2,3-dicarboxaldehyde (3) (3.89 g, 15.4 mmol) as
25 ꢁC)
d
: 10.13 (s, 2H, CHO), 8.12 (s, 2H, HADT), 8.08 (d, J¼3.7 Hz, 2H,
H
thio), 8.00 (s, 2H, HADT), 7.39 (d, J¼3.7 Hz, 2H, Hthio), 6.92 (s, 2H, H3,
H9), 2.84 (t, J¼7.3 Hz, 4H, Ha), 1.81e1.65 (m, 4H, Hb), 1.29 (m, 20H,
yellow liquid. Yield 75%. 1H NMR (300 MHz, CDCl3, 25 ꢁC)
d: 10.39
H
ceg), 0.87 (t, J¼6.6 Hz, 6H, Hh). 13C NMR (75 MHz, CDCl3, 25 ꢁC)
d:
(s, 1H, CHO), 10.33 (s, 1H, CHO), 7.32 (s, 1H, H4), 2.87 (t, J¼7.6 Hz, 2H,
183.1, 151.03, 150.99, 150.6, 150.4, 150.2, 145.44, 145.40, 145.35,
140.6, 139.7, 139.6, 136.9, 131.53, 131.47, 131.4, 128.6, 128.5, 128.4,
128.0, 127.9, 127.6, 126.6, 119.7, 118.3, 118.2, 118.1, 118.0, 32.0, 31.5,
30.4, 29.5, 29.33, 29.25, 22.8, 14.2. Rf¼0.82 (dichloromethane).
Ha), 1.72 (m, 2H, Hb), 1.32 (m, 10H, Hceg), 0.88 (t, J¼6.7 Hz, 3H, Hh).
13C NMR (75 MHz, CDCl3, 25 ꢁC)
d: 185.0, 182.4, 156.5, 145.2, 144.1,
127.0, 31.9, 31.3, 30.7, 29.33, 29.26, 29.1, 22.8, 14.2. Rf¼0.86 (petro-
ꢃ
ꢃ
leum ether/ethyl acetate 2/1 v/v). C14H20O2S: EI-HRMS: (Mþ ):
C42H46O2S4: MALDI-HRMS: (Mþ ): calcd: 734.2381; found:
calcd: 252.1184; found: 252.1185.
734.2408. Mp: 267e273 ꢁC.
4.2.4. 2,8-Dioctylanthradithiophene (syn/anti isomers) (4). Under
argon, LiAlH4 (0.28 g, 7.44 mmol) was slowly added to a suspension
of 2,8-dioctylanthradithiophene-5,11-dione 1 (1.01 g, 1.86 mmol) in
70 mL of dry THF, at room temperature. The mixture was heated at
reflux for 30 min and then was cooled to room temperature. HClaq
6 M was slowly added and the mixture was refluxed for 3 h. After
cooling to room temperature, the residue was filtered and the
isolated solid was washed successively with water, petroleum ether
and diethyl ether. After drying, the solid residue was treated again
with LiAlH4 (0.28 g, 7.44 mmol) using the same procedure. 2,8-
Dioctylanthradithiophene (0.60 g, 1.16 mmol) 4 was obtained as
an orange solid. Yield 62%. The solubility of the compound is too
4.2.7. 2,8-Dioctyl-5,11-bis(4-(diphenylamino)phenyl)an-
thradithiophene (syn/anti isomers) (DADT). To a solution of 4-
bromo-N,N-diphenylaniline (2.17 g, 6.69 mmol) in 50 mL of dry
THF cooled to ꢀ80 ꢁC under argon, was added dropwise 2.68 mL of
n-BuLi (commercial solution 2.5 M from Acros, 6.70 mmol) and the
mixture was stirred for 10e15 min. Then 1 (0.91 g, 1.67 mmol) was
added in one portion. After 10 min, the cooling bath was removed
and the mixture was stirred until the complete dissolution of the
diquinone (w1 h). Finally, the reaction was protected from the light
and a solution of SnCl2 (7.00 g) in 6 M HClaq (17 mL) was slowly
added. The reaction was stirred (still protected from the light) for
additional 30 min and then the mixture was poured in 250 mL of
methanol. The precipitate formed was then isolated by filtration,
washed with HCl 6 M, H2O, MeOH, petroleum ether and dried. The
desired product DADT was obtained (1.34 g, 1.34 mmol) as a red
ꢃ
low for NMR measurements. C34H42S2: MALDI-HRMS: (Mþ ): calcd:
514.2728; found: 514.2737. Mp >300 ꢁC.
4.2.5. 2,8-Dioctyl-5,11-bis(thiophen-2-yl)anthradithiophene
(syn/
solid. Yield 80%. 1H NMR (300 MHz, CDCl3, 25 ꢁC)
d: 8.18 (s, 2H,
anti isomers) (5). To a solution of thiophene (0.93 g, 0.89 mL,
H
H
ADT), 8.06 (s, 2H, HADT), 7.41e7.32 (m, 24H, HTPA), 7.11 (m, 4H,
11.04 mmol) in 50 mL of dry THF cooled to ꢀ80 ꢁC under argon, was
TPA), 6.97 (s, 2H, H3, H9), 2.88 (t, J¼7.3 Hz, 4H, Ha), 1.75 (m, 4H, Hb),

J.-Y. Balandier et al. / Tetrahedron 67 (2011) 7156e7161
7161
1.48e1.18 (m, 20H, Hceg), 0.88 (t, J¼6.4 Hz, 6H, Hh). 13C NMR
Q.; Chi, X.; Shengxiong, X.; Zeis, R.; Lefenfeld, M.; Siegrist, T.; Steigerwald, M. L.;
Nuckolls, C. J. Am. Chem. Soc. 2006, 128, 1340.
3. Ono, K.; Totani, H.; Hiei, T.; Yoshino, A.; Saito, K.; Eguchi, K.; Tomura, M.;
(75 MHz, CDCl3, 25 ꢁC)
d: 149.3, 149.2, 148.0, 147.4, 147.3, 147.2,
139.6, 139.5, 138.0, 137.9, 136.5, 135.4, 133.5, 133.3, 133.1, 132.5,
129.6, 128.3, 128.1, 127.9, 127.7, 125.11, 125.05, 124.99, 123.3, 123.1,
123.03, 122.99, 120.1, 119.4, 119.3, 119.1, 119.0, 32.0, 31.6, 30.6, 29.5,
Nishida, J. I.; Yamashita, Y. Tetrahedron 2007, 63, 9699.
4. For representative examples see: (a) Kim, C.; Huang, P. Y.; Jhuang, J. W.; Chen,
M. C.; Ho, J. C.; Hu, T. S.; Yan, J. Y.; Chen, L. H.; Lee, G. H.; Facchetti, A.; Marks, T. J.
Org. Electron. 2010, 11, 1363; (b) Yamamoto, T.; Takimiya, K. J. Am. Chem. Soc.
2007, 129, 2224; (c) Chen, M. C.; Kim, C.; Chen, S. Y.; Chiang, Y. J.; Chung, M. C.;
Facchetti, A.; Marks, T. J. J. Mater. Chem. 2008, 18, 1029; (d) Valiyev, F.; Hu, W. S.;
Chen, H. Y.; Kuo, M. Y.; Chao, I.; Tao, Y. T. Chem. Mater. 2007, 19, 3018; (e) Odom,
S. A.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2003, 5, 4245; (f) Laquindanum, J. G.;
Katz, H. E.; Lovinger, A. J. J. Am. Chem. Soc. 1998, 120, 664; (g) Palayangola, S. S.;
Mondal, R.; Shah, B. K.; Neckers, D. C. J. Org. Chem. 2007, 72, 6584; (h) Tang, M.
L.; Reichardt, A. D.; Wei, P.; Bao, Z. J. Am. Chem. Soc. 2009, 131, 5264; (i) Payne,
M. M.; Odom, S. A.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2004, 6, 3325; (j)
Purushothaman, B.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2010, 12, 2060; (k)
Kaur, I.; Jazdzyk, M.; Stein, N. N.; Prusevich, P.; Miller, G. P. J. Am. Chem. Soc.
2010, 132, 1261.
5. (a) Okamoto, T.; Jiang, Y.; Qu, F.; Mayer, A. C.; Parmer, J. E.; McGehee, M. D.; Bao,
Z. Macromolecules 2008, 41, 6977; (b) Jiang, Y.; Okamoto, T.; Becerril, H. A.;
Hong, S.; Tang, M. L.; Mayer, A. C.; Parmer, J. E.; McGehee, M. D.; Bao, Z. Mac-
romolecules 2010, 43, 6361; (c) Ito, K.; Suzuki, T.; Sakamoto, Y.; Kubota, D.;
Inoue, Y.; Sato, F.; Tokito, S. Angew. Chem., Int. Ed. 2003, 42, 1159; (d) Merlo, J. A.;
Newman, C. R.; Gerlach, C. P.; Kelley, T. W.; Muyres, D. V.; Fritz, S. E.; Toney, M.
F.; Frisbie, C. D. J. Am. Chem. Soc. 2005, 127, 3997; (e) Laquindanum, J. G.; Katz,
H. E.; Lovinger, A. J.; Dodabalapur, A. Adv. Mater. 1997, 9, 36; (f) Li, C. X.; Sir-
ringhaus, H.; Garnier, F.; Holmes, A. B.; Moratti, S. C.; Feeder, N.; Clegg, W.; Teat,
S. J.; Friend, R. H. J. Am. Chem. Soc. 1998, 120, 2206; (g) Lehnherr, D.; McDonald,
R.; Fergusson, M. J.; Tykwinski, R. R. Tetrahedron 2008, 64, 11449; (h) Lehnherr,
D.; Tykwinski, R. R. Org. Lett. 2007, 9, 4583; (i) Lehnherr, D.; Gao, J.; Hegmann,
F. A.; Tykwinski, R. R. J. Org. Chem. 2009, 74, 5017.
ꢃ
29.4, 29.3, 22.8, 14.3. C70H68N2S2: MALDI-HRMS: (Mþ ): calcd:
1000.4824; found: 1000.4852. Mp: 240e244 ꢁC.
Acknowledgements
The authors would like to thank Pascal Gerbaux (UMONS) for MS
measurements. The collaboration between Brussels and Mons is
ꢀ
supported by Region Wallonne (Mirage project), jointly with the
European Commission (FEDERdSmartfilm RF project) and the Bel-
gian Federal Office of Science Policy (PAI 6/27). Research in Mons is
also supported by the OPTI2MAT Excellence Program and by FNRS-
FRFC. B.T. and N.S. are FRIA research fellows. J.C. is a senior research
fellow of the Belgian National Fund for Scientific Research (FNRS).
Supplementary data
Cyclic voltammograms, optical studies, NMR, mass and theo-
ritical spectra are shown in Supplementary data. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.tet.2011.06.098.
6. Balandier, J. Y.; Quist, F.; Stas, S.; Tylleman, B.; Ragoen, C.; Mayence, A.; Bou-
zakraoui, S.; Cornil, J.; Geerts, Y. H. Org. Lett. 2011, 13, 548.
7. (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648; (b) Lee, C.; Yang, W.; Parr, R. G.
Phys. Rev. B 1988, 37, 785.
8. (a) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. J. Chem. Phys. 1998, 109, 8218;
(b) Bauernschmitt, R.; Ahlrichs, R. Chem. Phys. Lett. 1996, 256, 454; (c) Casida,
M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R. J. Chem. Phys. 1998, 108, 4439.
9. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Montgomery, J. A. J.; Vreven, T.; Kudin, K. N.; Burant, J. C.;
Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.;
Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.;
Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken,
V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin,
A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth,
G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels,
A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox,
D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A.
Gaussian 03, Revision B.03; Gaussian: Wallingford, CT, 2004.
References and notes
1. (a) For example: Mas-Torrent, M.; Rovira, C. Chem. Soc. Rev. 2008, 37, 827; (b)
Allard, S.; Forstern, M.; Souharce, B.; Thiem, H.; Scherf, U. Angew. Chem., Int. Ed.
2008, 47, 4070; (c) Facchetti, A. Mater. Today 2007, 10, 28; (d) Coakley, K. M.;
McGehee, M. D. Chem. Mater. 2004, 16, 4533; (e) Chen, C. T. Chem. Mater. 2004,
ꢀ
16, 4389; (f) Murphy, A. R.; Frechet, J. M. J. Chem. Rev. 2007, 107, 1066; (g) An-
thony, J. E. Chem. Rev. 2006, 106, 5028; (h) See, K. C.; Becknell, A.; Miragliotta, J.;
Katz, H. E. Adv. Mater. 2007, 19, 3322; (i) Huang, J.; Miragliotta, J.; Becknell, A.;
Katz, H. E. J. Am. Chem. Soc. 2007, 129, 9366; (j) Marinelli, F.; Dell’Aquila, A.;
Torsi, L.; Tey, J.; Suranna, G. P.; Mastrorilli, P.; Romanazzi, G.; Nobile, C. F.;
Mhaisalkar, S. G.; Cioffi, N.; Palmisano, F. Sens. Actuators, B 2009, 140, 445.
2. (a) Payne, M. M.; Delcamp, J. H.; Parkin, S. R.; Anthony, J. E. Org. Lett. 2004, 6,
1609; (b) Anthony, J. E.; Brooks, J. S.; Eaton, D. L.; Parkin, S. R. J. Am. Chem. Soc.
2001, 123, 9482; (c) Wang, J.; Liu, K.; Liu, Y. Y.; Song, C. L.; Shi, Z. F.; Peng, J. B.;
Zhang, H. L.; Cao, X. P. Org. Lett. 2009, 11, 2563; (d) Lloyd, M. T.; Mayer, A. C.;
Subramanian, S.; Mourey, D. A.; Herman, D. J.; Bapat, A. V.; Anthony, J. E.;
Malliaras, G. G. J. Am. Chem. Soc. 2007, 129, 9144; (e) Gorodetsky, A. A.; Cox, M.;
Tremblay, N. J.; Kymissis, I.; Nuckolls, C. Chem. Mater. 2009, 21, 4090; (f) Miao,
10. Chi, C.; Wegner, G. Macromol. Rapid Commun. 2005, 26, 1532.