Synthesis of a Thiophene Analogue of Isoindigo by C–H Activation/Oxidative Cyclization and Application of Its Copolymeric Materials to Organic Transistors

Article abstract of DOI:10.1002/ejoc.201701663

A novel method for the synthesis of a thiophene analogue of isoindigo (TIIG) is described. The reaction involves a palladium-catalyzed C–H activation/oxidative cyclization sequence. This new methodology has potential for diversifying the isoindigo family. The thin-film transistors (TFTs) prepared from a TIIG-based copolymer (PIDTT-TIIG) with indacenodithieno[3,2-b]thiophene (IDTT) exhibit unipolar charge-transport properties with hole mobilities of 0.17 cm² V^–1 s^–1.

Full text of DOI:10.1002/ejoc.201701663

A Journal of
Accepted Article
Title: Synthesis of a Thiophene Analogue of Isoindigo via C-
H Activation/Oxidative Cyclization and Application of Its
Copolymeric Materials to Organic Transistors
Authors: Hua-Chun Wang, Jingwei Tao, Wei-Yun Bai, Zi-Yi Xie,
Xiancheng Ren, Hongxiang Li, and Yun-Xiang Xu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
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to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201701663
Link to VoR: http://dx.doi.org/10.1002/ejoc.201701663
Supported by

European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
Synthesis of a Thiophene Analogue of Isoindigo via C-H
Activation/Oxidative Cyclization and Application of Its
Copolymeric Materials to Organic Transistors
Hua-Chun Wang, [a] Jingwei Tao,†[b] Wei-Yun Bai , Zi-Yi Xie , Hongxiang Li,* Xiancheng Ren,
†
[a]
[a]
[b]
[a]
and Yun-Xiang Xu*[a] [b]
for optoelectronic materials.[9] For example, Ding et al. reported
Abstract: A novel synthetic method of a thiophene analogue of
isoindigo (TIIG) is described. The reaction is implemented through
palladium-catalyzed C-H activation/oxidative cyclization process. This
new methodology has potential for the expansion of isoindigo family.
The thin film transistors (TFTs) of TIIG-based copolymer (PIDTT-TIIG)
with indacenodithieno[3,2-b]thiophene (IDTT) exhibited unipolar
palladium-catalyzed dehydrohalogenative coupling reaction,
using this methodology to synthesize a pentacyclic lactam
building block as acceptor in OSCs.[9a]
After thinking over new potential synthetic strategy of
isoindigo derivatives, it was envisioned that C-H/C-H activation
could be a useful tool for their synthesis. Since isoindigo molecule
could be considered as π backbone locked by lactam units from
the retrosynthetic analysis view, one alternative way to construct
the isoindigo structure could begin from construction of amide
bond, and then fusion of the π units. This approach could combine
the advantages of readiness of building up amide bonds[9a, 10] and
recently developed aryl C-H/C-H bond activation strategy.[11]
2
−1 −1
charge transport properties with hole mobilities of 0.17 cm V s .
Introduction
Isoindigo as
a structural isomer of indigo has attracted
considerable attention in organic solar cells (OSCs) and organic
field-effect transistors (OFETs) since Reynolds and co-workers
first incorporated isoindigo into small molecule semiconductors as
electron-donating materials in 2010.[1] The unique structure of
isoindigo is derived from the lactam rings which provide good
solubility and strong electron-withdrawing capability.[2] In terms of
excellent properties of isoindigo building block, plenty of isoindigo
derivatives have been already reported, such as a thiophene
Herein, as
a proof-of-concept, 6-(5-oxothieno[3,2-b]pyrrol-6-
ylidene)thieno[3,2-b]pyrrol-5-one (TIIG), an useful derivative of
isoindigo family, could be prepared from palladium-catalyzed
oxidative coupling of C-H/C-H bond (Scheme 1). Relative to
traditional synthetic route of TIIG, which usually starts from the
reaction of N-alkylthiophen-3-amine with oxalyl chloride,
subsequently treated with Lawesson's reagent (Scheme 1),[3a] the
overall yield is comparable. However, the new method showed
vast potential structural tunability. Based on TIIG, two low-
bandgap polymers were prepared, which exhibit decent charge
transport properties.
analogue
of
isoindigo,[3]
thiophene-fused
isoindigo,[4]
benzothienoisoindigo,[5] thieno[3,2-b]thiophene isoindigo[6] and
thieno[3,2-b][1]benzothiophene isoindigo,[7] resulting in high
power conversion efficiencies (PCEs) for OSCs or high charge
carrier mobilities for OFETs. However, the syntheses of these
isoindigo derivatives usually need tedious work. And the synthetic
method of isoindigo derivatives is relatively unitary. To further
expand the isoindigo family, it is necessary to develop new
synthetic approaches.
Over the past years, substantial efforts have been paid to
develop transition metal-catalyzed synthetic methodology which
involve the directly aryl C–H functionalization and C–C bond
formation by intramolecular cyclization process.[8] To reduce the
cost of materials that are used for OFETs and OSCs, the new
strategy has been applied to the synthesis of polycyclic module
[
a]
H.-C. Wang, W.-Y. Bai, Prof. X. Ren, Prof. Y.-X. Xu
College of Polymer Science & Engineering, State Key Laboratory of
Polymer Materials Engineering, Sichuan University
Chengdu 610065 (China)
Scheme 1. Different routes for the synthesis of TIIG.
E-mail: yxxu@scu.edu.cn
J. Tao, Prof. H. Li, Prof. Y.-X. Xu
Results and Discussion
[
b]
Key Laboratory of Synthetic and Self-Assembly, Chemistry for
Organic Functional Molecules, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences
Shanghai 200032 (China)
E-mail: lhx@mail.sioc.ac.cn
These authors contributed equally to this work.
The detailed synthetic route was shown in Scheme 1. First
the condensation between N-hexylthiophen-3-amine[12] and
fumaric dichloride gave the intermediate TVTDA-H. Further
cyclization using palladium-catalyzed C–H activation generated
the product TIIG-H. The cyclization reaction was first attempted
†
[
]
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/chem. 2017XXXXX.
2
under conditions of Pd(OAc) (2 equiv.) as oxidant and AcOH
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European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
Table 1. Optimization of the cyclization reaction conditions[a]
.
o
Yield[b] (%)
Entry
Pd (equiv.)
Oxidant (equiv.)
Solvent
Time (h)
T ( C)
1
2
3
4
5
6
7
8
9
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
2
2
2
2
2
2
2
(2)
(2)
(2)
(2)
(2)
(2)
(2)
-
AcOH
PhCl
3
110
110
110
80
35
17
24
48
27
21
24
10
6
-
8
-
dioxane
DCE
4
-
24
12
12
17
24
24
24
24
24
24
24
-
toluene
DMF
110
150
70
-
-
DMSO
DCE
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
Pd(OAc)
2
2
2
2
2
2
2
(0.2)
(0.2)
(0.2)
(0.2)
(0.2)
(0.2)
(0.2)
AgOAc (4)
80
Ag
PhI(OAc)
Na
2
O (4)
(4)
(4)
(4)
(4)
(4)
DCE
80
10
11
12
13
14
2
DCE
80
trace
6
2
S
2
O
8
DCE
80
K
2
S
2
O
8
DCE
80
5
Cu(OAc)
2
DCE
80
16
27
Ag CO
2
3
DCE
80
[
a] General reaction conditions: TVTDA-H (0.11 mmol), Pd (0.2 equiv.), oxidant (4 equiv.), solvent (10 mL). [b] Yield of isolated products.
(
acetic acid) as solvent. After the mixture was stirred at 110 °C for
h under argon (Table 1, Entry 1), the target TIIG-H was afforded
established, it is valuable to further explore their usage in
3
in 35% yield. Subsequently, examining the different solvents such
as chlorobenzene (PhCl), 1,4-dioxane, 1,2-dichloroethane (DCE),
toluene, N,N-dimethylformamide (DMF) and dimethyl sulfoxide
(
DMSO) under similar conditions, DCE was found to be the best
solvent, and the yield was improved to 48% (Table 1, Entry 2-7).
Considering the cost of palladium catalyst, further studies were
carried out by introducing the oxidant (4 equiv.) using a catalytic
amount of Pd(OAc)
screening of several oxidants such as AgOAc, Ag
Na , K , Cu(OAc) and Ag CO revealed that Ag
2
(0.2 equiv.) and DCE as the solvent. The
O, PhI(OAc)
CO
3
2
2
,
2
S
2
O
8
2
S
2
O
8
2
2
3
2
showed slightly better oxidation efficiency, getting the desired
product in 27% yield (Table 1, Entry 8-14). Under this condition,
the effect of additives was tested and proved to be not positive
(
Table S1, Entry 1-5). Besides, the replacement of Pd(OAc)
PdCl , PdCl (CH CN) and PdCl (PhCN) did not improve the
yield (Table S1, Entry 6-8).
After the new synthetic strategy of TIIG-H unit was
2
by
2
2
3
2
2
2
Scheme 2. Synthetic route of PaIDT-TIIG and PIDTT-TIIG.
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European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
optoelectronic materials. It is reported that TIIG based semi-
crystalline materials presented high hole mobilities.[3b, c, 13] We
wondered if it is possible to use this unit to make high mobility
ladder-type materials, which is less explored but still very
important.[14] Ladder-type structure IDTT and unsymmetrical
skeleton aIDT were chosen as donor units. The synthetic route of
PaIDT-TIIG and PIDTT-TIIG was depicted in Scheme 2. TIIG was
prepared under optimized reaction conditions with 22% yield,
which was subsequently brominated to afford the monomer TIIG-
diBr in 62% yield. Finally, copolymerization between TIIG–diBr
aIDT-diTin or IDTT-diTin via Stille coupling reaction gave the
product PaIDT-TIIG or PIDTT-TIIG. The resulting polymers can be
readily dissolved in chlorinated solvents, such as chloroform and
dichlorobenzene (DCB).
diffraction (XRD) were used to investigate the morphological and
structural features of both films (Figure S5). AFM images
indicated that thin films of PIDTT-TIIG presents more smooth
surfaces than those of PaIDT-TIIG, which may be indicate the
latter one has local aggregation. XRD patterns underscore the
amorphous structure of both polymers, which is compatible with
phenomenon observed in their DSC curves.
The number average molecular weights (Mn) were 18.8 and
24.7 kDa with polydispersity indexes (PDI) of 2.17 and 2.75 for
PaIDT-TIIG and PIDTT-TIIG, respectively. Thermal analysis of
PaIDT-TIIG and PIDTT-TIIG are estimated by thermogravimetric
analysis (TGA) and differential scanning calorimetry (DSC) at a
temperature ramp rate of 10 °C/min under nitrogen, and the
results are depicted in Figure S2 and S3. Both polymers exhibit
d
good thermal stability with thermal decomposition temperature (T )
higher than 410 °C. The DSC curves of two polymers show no
obvious thermal transitions up to 300 °C, which is consistent with
their amorphous character.
The normalized UV-vis absorption spectra of both polymers
in solution and in thin film are displayed in Figure S1 and the
relevant data are summarized in Table S1. They possess similarly
broad absorption bands with absorption maximum shifted towards
the near-infrared region of the spectrum. The absorption peak of
PaIDT-TIIG and PIDTT-TIIG are located at 799 and 814 nm in
Figure 1. The transfer and output curves of a, b) PaIDT-TIIG thin film
transistors; c, d) PIDTT-TIIG thin film transistors.
3
CHCl and DCB solution, respectively. In the solid states, the
Table 2. Bottom-gate/top-contacted TFTs devices characteristics for
absorption peak are blue-shifted to 782 and 807 nm, respectively,
which indicates that both polymers may be twisted slightly in the
solid state. Cyclic voltammetry (CV) measurement (Figure S4)
was used to study the electrochemical behavior of these two
polymers. The HOMO and LUMO energy levels for PaIDT-TIIG
and PIDTT-TIIG are -4.97 and -3.59, and -4.98 and -3.75 eV,
respectively. The calculated electrochemical band gaps are
consistent with their optical band gaps.
polymers PaIDT-TIIG and PIDTT-TIIG.
2
-1 -1
Polymer
μ
h
(cm V s )
V
th (V)
Ion/Ioff
3.7×10-3 (2.5×10-3)
3
4
6
PaIDT-TIIG
PIDTT-TIIG
-10.10 ~ -23.46
-5.46 ~ -9.68
10 -10
5
0.17 (0.14)
10 -10
The charge carriers transport properties of PaIDT-TIIG and
PIDTT-TIIG was explored by thin-film transistors (TFTs) with
bottom-gate/top-contacted structure. PaIDT-TIIG and PIDTT-TIIG
thin films were spin-coated from chloroform and chlorbenzene
solutions, respectively. The field effect mobility (μ) was extracted
from the saturation regime, and the mobility was calculated by
Conclusions
linear fitting of (IDS)1/2 versus V
G
curves. Figure 1 shows the
In conclusion, we have developed a novel method to obtain
transfer and output curves of PaIDT-TIIG and PIDTT-TIIG thin film
transistors, and the device performance of PaIDT-TIIG and
PIDTT-TIIG thin films is summarized in Table 2. Both PaIDT-TIIG
and PIDTT-TIIG exhibit typical p-type TFT characteristics with
well-defined linear and saturation regimes, and the maximum hole
a
thiophene analogue of isoindigo by palladium-catalyzed
oxidative C-H/C-H cross-coupling. And two ladder-type donor
based polymers were also made based on this monomer and
showed moderate charge transport properties. We expect more
isoindigo derivatives could be developed by this new C-H/C-H
activation strategy. And by applying organic synthetic
methodologies to preparation of optoelectronic materials, a series
of new materials could be found and explored in the future.
mobility (μ
h
) are 3.7×10-3 cm2 V−1 s−1 and 0.17 cm2 V−1 s−1,
respectively. In order to elucidate the difference of the device
performance, atomic force microscopy (AFM) and X-ray
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European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
G T
source current, μ is the mobility, and V and V are the gate voltage and
Experimental Section
threshold voltage, respectively.
Materials and Measurements: All reactions and operations were carried
out under argon (Ar) atmosphere with the use of standard Schlenk
techniques. All chemicals, unless otherwise specified, were purchased
from Adamas and used as received. Toluene and dichloromethane were
purified by distillation with calcium hydride. N-hexylthiophen-3-amine, N-
General procedure for the cyclization reaction: A mixture of TVTDA-H
0.11 mmol), Pd catalyst, oxidant and additive in solvent (10 mL) was
refluxed for 3-48 hours under Ar. After cooling to room temperature, the
reaction mixture was filtered over celite, extracted with CH Cl . The
combined organic phase was washed with brine and then dried over
anhydrous Na SO . After removal of the solvent, the crude product was
purified through a silica gel column with a mixture of petroleum/CH Cl
2:3) as eluent to give a purple solid TIIG-H.
(
2
2
(
2-ethylhexyl)thiophen-3-amines, aIDT-diTin and IDTT-diTin were
2
4
synthesized according to previously reported procedures.[12, 15]
The H and 13C NMR spectra were collected on a Bruker ASCEND 400
spectrometer operating at 400 MHz in deuterated chloroform solution
with TMS as reference, respectively. UV-Vis spectra were measured
using a Shimadzu UV-1750 spectrophotometer. Cyclic voltammetry (CV)
of polymer film was conducted using a CHI 600E Electrochemical
Analyzer with a standard three-electrode system consisting of ITO
working electrode, Ag/AgCl reference electrode and Pt wire counter
electrode, calibrated against ferrocene, in acetonitrile with 0.1 M
2
2
1
(
1
4
1
4
Synthesis of N ,N -dihexyl-N ,N -di(thiophen-3-yl)fumaramide
TVTDA-H): To a solution of fumaric acid (1.15 g, 9.93 mmol) in dry
CH Cl (40 mL) were added oxalyl chloride (5.08 mL, 59.6 mmol) and 3
(
2
2
drops of DMF. The mixture was stirred at room temperature overnight.
The solvent was removed under vacuum to obtain fumaric dichloride,
which was used in next step without purification. To the solution of
fumaric dichloride in dry CH
N-hexylthiophen-3-amine (4.01 g, 21.9 mmol) and Et
CH Cl (30 mL) at 0 °C. The mixture was stirred at room temperature
overnight. Then, the mixture was poured into water and extracted with
4
CH Cl three times. The organic layer was dried over anhydrous Na SO .
2
Cl
2
(20 mL) was slowly added a solution of
-1
Bu
were calculated from the equations: ELUMO = – (Ered – EFc + 4.8) eV and
HOMO = – (Eox –EFc + 4.8) eV, where Ered and Eox are taken from the
onset of reduction and oxidation, respectively, and EFc is the half-wave
4 6
NPF at a scan rate of 100 mV s . HOMO and LUMO energy levels
3
N (2 mL) in dry
2
2
E
2
2
2
potential of ferrocene. The number-average molecular weights (M
PaIDT-TIIG and PIDTT-TIIG were measured with gel-permeation
n
) of
After removal of the solvent, the crude product was purified through a
silica gel column with a mixture of petroleum/EtOAc (4:1) as eluent to
chromatography (GPC) in CHCl
3
and high temperature (150 °C) GPC in
1
give a white solid (2.59 g, 58%). mp 136 °C (DSC). H NMR (400 MHz,
1
,2,4-trichlorobenzene using polystyrene as standard, respectively. The
Chloroform-d): δ 7.35 (dd, J = 5.1, 3.1 Hz, 2H), 7.03 (dd, J = 3.2, 1.4 Hz,
H), 6.90 (s, 2H), 6.88 (dd, J = 5.1, 1.4 Hz, 2H), 3.71 – 3.60 (t, 4H), 1.50
m, 4H), 1.31 – 1.17 (m, 12H), 0.89 – 0.78 (t, 6H). 13C NMR (101 MHz,
thermogravimetric analysis (TGA) was carried out on a NETZSCH
TG209 F1 Thermo Gravimetric Analyzer and the differential scanning
calorimetry (DSC) experiments were carried out on a TA Q200
instrument. Both the TGA and DSC was performed under purified
nitrogen gas flow with a temperature ramp rate of 10 °C/min. The Fourier
transform infrared spectroscope (FTIR) were measured at room
temperature using Thermo Scientific Nicolet iS50 FTIR with a resolution
2
(
Chloroform-d): δ 164.4, 139.9, 131.8, 126.5, 126.1, 121.3, 49.5, 31.4,
-1
2
7.7, 26.4, 22.5, 14.0. FTIR (KBr, cm ): 3098, 2951, 2927, 2853, 1624,
+
1
526, 1466, 1437, 1394, 970. HRMS (ESI, m/z): [M+Na] , calcd. for
24 34 2 2 2
C H N O S , 469.1954; found, 469.1955
1
4
1
4
Synthesis of N ,N -bis(2-ethylhexyl)-N ,N -di(thiophen-3-
of 4 cm−1. The wavenumber range was from 500 cm−1 to 4000 cm−1
.
yl)fumaramide (TVTDA): To a solution of fumaric acid (895 mg, 7.71
Devices Fabrication and Measurement of TFTs: TFTs with bottom-
gate/top-contact configuration were prepared to characterize the
electrical performance of the polymers. A heavily n-doped Si wafer with a
2 2
mmol) in dry CH Cl (50 mL) were added oxalyl chloride (4.14 mL, 48.6
mmol) and 3 drops of DMF. The mixture was stirred at room temperature
overnight. The solvent was removed under vacuum to obtain fumaric
dichloride, which was used in next step without purification. To the
2 i
thermally grown SiO (300 nm, C
= 10 nF cm−2) was utilized as the
substrate and gate dielectric layer. Cleaning of Si wafers and
solution of fumaric dichloride in dry CH
solution of N-(2-ethylhexyl) thiophen-3-amine (3.40 g, 14.6 mmol) and
Et N (2 mL) in dry CH Cl (30 mL) at 0 °C. The mixture was stirred at
room temperature overnight. Then, the mixture was poured into water
and extracted with CH Cl three times. The organic layer was dried over
anhydrous Na SO . After removal of the solvent, the crude product was
purified through a silica gel column with a mixture of petroleum/EtOAc
2 2
Cl (20 mL) was slowly added a
modification of trimethoxy(octadecyl)-silane (OTMS) as self-assembled
2
monolayer (SAM) on SiO surface were carried out according to
3
2
2
previously reported method.[16] The polymers (PaIDT-TIIG and PIDTT-
TIIG) were dissolved in chloroform (3 mg mL−1) and chlorbenzene (5 mg
mL−1), respectively. And the thin films were deposited through spin-
coating the solutions with a spin rate of 3000 rpm min−1 for 30 s under
ambient conditions. Thereafter, Au contacts (30 nm) were thermally
evaporated onto the polymer films to form source and drain electrodes
with a channel length (L) of 31 μm and a width (W) of 273 μm using a
shadow mask. The electrical performance of TFTs was characterized in a
glove box using a Keithley 4200 semiconductor parametric analyzer. The
field-effect mobility was calculated in the saturation regime using the
2
2
2
4
1
(
3:1) as eluent to give a white solid (1.83 g, 47%). mp 132 °C (DSC). H
NMR (400 MHz, Chloroform-d): δ 7.35 (dd, J = 5.1, 3.1 Hz, 2H), 7.03 (dd,
J = 3.2, 1.4 Hz, 2H), 6.94 (s, 2H), 6.88 (dd, J = 5.1, 1.4 Hz, 2H), 3.63 (m,
H), 1.50 (m, 2H), 1.34 – 1.10 (m, 16H), 0.81 (m, 12H). 13C NMR (101
4
MHz, Chloroform-d): δ 164.9, 140.2, 132.0, 126.4, 126.0, 121.1, 52.7,
-1
3
7.6, 30.3, 28.5, 23.6, 23.0, 14.0, 10.4. FTIR (KBr, cm ): 3098, 2956,
i G T
following equation: IDS = (μWC/2L)(V − V
)2, where IDS is the drain-to-
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European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
2
928, 2872, 1623, 1525, 1459, 1430, 1400, 972. HRMS (ESI, m/z):
Polymerization of PaIDT-TIIG: aIDT-diTin (151 mg, 0.17 mmol) and
TIIG-diBr (105 mg, 0.16 mmol) were charged in a 25 mL three-neck flask
under argon. After adding toluene (5 mL), the mixture was degassed by
+
[M+Na] , calcd. for C28
42 2 2 2
H N O S , 525.2580; found, 525.2578.
Synthesis of (E)-4,4'-dihexyl-[6,6'-bithieno[3,2-b]pyrrolylidene]-
,5'(4H,4'H)-dione (TIIG-H): A mixture of TVTDA-H (53 mg, 0.119 mmol)
and Pd(OAc) (53 mg, 0.237 mmol) in 1,2-dichloroethane (10 mL) was
refluxed for 24 hours under Ar. After cooling to room temperature, the
reaction mixture was filtered over celite, extracted with CH Cl . The
combined organic phase was washed with brine and then dried over
anhydrous Na SO . After removal of the solvent, the crude product was
purified through a silica gel column with a mixture of petroleum/CH Cl
2:3) as eluent to give a purple solid (25 mg, 48%). mp 123 °C (DSC). H
NMR (400 MHz, Chloroform-d): δ 7.54 (d, J = 5.2 Hz, 2H), 6.82 (d, J =
5
three freeze/pump/thew cycles to remove O
2 2 3
. Then Pd (dba) (7.3 mg, 5
2
mol%) and P(o-tol) (19.5 mg, 0.064 mmol) were added. The mixture was
3
degassed once more. Then the mixture was heated at 120 °C for 72
hours. After cooling to room temperature, the mixture was poured into
methanol. The precipitate was collected and washed by Soxhlet
extraction with acetone, hexane, dichloromethane and chloroform
sequentially. The polymer was recovered as a solid from the chloroform
fraction by precipitation from methanol. The solid was dried under
2
2
2
4
2
2
1
(
n
vacuum, affording dark green solid (147 mg, 86%). M =18.8 kDa, PDI=
-
1
5
0
1
3
.2 Hz, 2H), 3.81 (t, J = 7.3 Hz, 4H), 1.73 (4H), 1.42 – 1.23 (m, 12H),
2.17. FTIR (KBr, cm ): 3435, 2952, 2921, 2853, 1676, 1506, 1458, 1437,
1397, 1317, 1219, 1121, 1106, 792.
.92 – 0.83 (t, 6H). 13C NMR (101 MHz, Chloroform-d): δ 171.0, 151.2,
-
1
34.3, 121.1, 111.2, 41.8, 31.4, 28.5, 26.6, 22.5, 14.0. FTIR (KBr, cm ):
Polymerization of PIDTT-TIIG: IDTT-diTin (150 mg, 0.15 mmol) and
TIIG-diBr (93 mg, 0.14 mmol) were charged in a 25 mL three-neck flask
under argon. After adding toluene (5 mL), the mixture was degassed by
098, 2957, 2926, 2855, 1674, 1507, 1485, 1377, 1341,1309, 1107, 713.
+
HRMS (ESI, m/z): [M+Na] , calcd. for C24
30 2 2 2
H N O S , 465.1641; found,
465.1619.
three freeze/pump/thew cycles to remove O
2 2 3
. Then Pd (dba) (6.5 mg, 5
Synthesis of (E)-4,4'-bis(2-ethylhexyl)-[6,6'-bithieno[3,2-
mol%) and P(o-tol) (17.3 mg, 0.057 mmol) were added. The mixture was
3
b]pyrrolylidene]-5,5'(4H,4'H)-dione (TIIG): A mixture of TVTDA-H (66
degassed once more. Then the mixture was heated at 120 °C for 72
hours. After cooling to room temperature, the mixture was poured into
methanol. The precipitate was collected and washed by Soxhlet
extraction with acetone, hexane, dichloromethane and chloroform
sequentially. Then left solid in the filter paper was collected and dried
2
mg, 0.131 mmol) and Pd(OAc) (59 mg, 0.263 mmol) in 1,2-
dichloroethane (10 mL) was refluxed for 24 hours under Ar. After cooling
to room temperature, the reaction mixture was filtered over celite,
extracted with CH
brine and then dried over anhydrous Na
solvent, the crude product was purified through a silica gel column with a
2
Cl
2
. The combined organic phase was washed with
-
1
2
SO . After removal of the
4
n
(121 mg, 56%). M =24.7 kDa, PDI=2.75. FTIR (KBr, cm ): 3442, 2953,
2923, 2854, 1678, 1637, 1508, 1459, 1400, 1364, 1306, 1121, 1108,
800.
mixture of petroleum/CH
2
Cl
2
(2:1) as eluent to give a purple solid (15 mg,
1
2
=
=
2%). mp 123 °C (DSC). H NMR (400 MHz, Chloroform-d): δ 7.35 (dd, J
5.1, 3.1 Hz, 2H), 7.03 (dd, J = 3.2, 1.4 Hz, 2H), 6.94 (s, 2H), 6.88 (dd, J
5.1, 1.4 Hz, 2H), 3.63 (m, 4H), 1.50 (m, 2H), 1.34 – 1.10 (m, 16H), 0.81
m, 12H). 13C NMR (101 MHz, Chloroform-d): δ 164.9, 140.2, 132.0,
Acknowledgements
(
126.4, 126.0, 121.1, 52.7, 37.6, 30.3, 28.5, 23.6, 23.0, 14.0, 10.4. FTIR
-
1
Y.-X. X. thanks the financial support from the National Natural
Science Foundation of China (51403135), State Key Laboratory
of Polymer Materials Engineering (Grant No. sklpme2014-3-16)
and Key Laboratory of Synthetic and Self-Assembly Chemistry for
Organic Functional Molecules (Grant No. K2016-7).
(
KBr, cm ): 3111, 2959, 2924, 2860, 1668, 1502, 1486, 1379, 1338,
+
1
309, 1107, 721. HRMS (ESI, m/z): [M+Na] , calcd. for C28
42 2 2 2
H N O S ,
5
25.2580; found, 525.2578.
Synthesis of (E)-2,2'-dibromo-4,4'-bis(2-ethylhexyl)-[6,6'-
bithieno[3,2-b]pyrrolylidene]-5,5'(4H,4'H)-dione (TIIG-diBr): To a
solution of TIIG (33 mg, 0.066 mmol) in chloroform (5 mL) was added N-
bromosuccinimide (25 mg, 0.139 mmol) under Ar, and the reaction
mixture was stirred for 24 h at room temperature. Then, the mixture was
Keywords: thiophene analogue of isoindigo • Pd catalyst • C–H
activation • hole mobility • organic transistors
[
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European Journal of Organic Chemistry
10.1002/ejoc.201701663
FULL PAPER
FULL PAPER
†
[a]
†[b]
C-H/C-H activation/oxidative
Hua-Chun Wang,
Jingwei Tao,
[a]
[
a]
cyclization: The cyclization reaction
has been developed by palladium-
catalyzed oxidative coupling of C-H/C-
H bond, and a thiophene analogue of
isoindigo (TIIG) was obtained with
moderate yields. Its copolymer
Wei-Yun Bai , Zi-Yi Xie , Hongxiang
Li,*[b] Xiancheng Ren,[a] and Yun-Xiang
Xu*[a [b]
Page No. – Page No.
Synthesis of a Thiophene Analogue
of Isoindigo via C-H
Activation/Oxidative Cyclization and
Application of Its Copolymeric
Materials to Organic Transistors
(
PIDTT-TIIG) with
indacenodithieno[3,2-b]thiophene
IDTT) exhibited unipolar charge
transport in thin film transistors with
(
2
−1 −1
hole mobilities of 0.17 cm V s .
This article is protected by copyright. All rights reserved.