Synthesis, structures, and properties of fused thiophenes for organic field-effect transistors

Article abstract of DOI:10.1002/chem.200902755

A series of fused thiophenes composed of fused a-oligothiophene units as building blocks, end-capped with either styrene or l-pentyl-4-vinylbenzene groups, has been synthesized through Stille coupling reactions. The compounds have been fully characterized by means of ¹H NMR spectrometry, high-resolution mass spectrometry, and elemental analysis. The molecules present a trans-trans configuration between their double bonds, which has been verified and confirmed by Fourier-transform infrared spectroscopy and single-crystal X-ray diffraction analysis. The X-ray crystal structures showed π- π overlap and sulfur-sulfur interactions between the adjacent molecules. The decomposition temperatures were all found to be above 300 °C, indicating that compounds of this series possess excellent thermal stability. The fact that no phase transition occurs at low temperature indicates that they should be well-suited for application in devices. Moreover, they possess low HOMO energy levels, based on cyclic voltammetry measurements, and suitable energy gaps, as determined from their thin-film UV/Vis spectra. Thinfilm X-ray diffraction analysis and atomic force microscopy revealed high crystallinity on supporting substrates. In addition, as the substrate temperature has a significant influence on the morphology and the degree of crystallinity, the device performance could be optimized by varying the substrate temperature. These materials were found to exhibit optimal field-effect performance, with a mobility of 0.17 Cm₂V^-1S^-1 and an on/off ratio of 10⁵, at a substrate temperature of 70°C.

Full text of DOI:10.1002/chem.200902755

FULL PAPER
DOI: 10.1002/chem.200902755
Synthesis, Structures, and Properties of Fused Thiophenes for
Organic Field-Effect Transistors
Ying Liu,[a, b] Chong-an Di,[a] Chunyan Du,[a, b] Yunqi Liu,*[a] Kun Lu,[a, b]
Wenfeng Qiu,[a] and Gui Yu[a]
Abstract: A series of fused thiophenes
p overlap and sulfur–sulfur interactions
between the adjacent molecules. The
decomposition temperatures were all
found to be above 3008C, indicating
that compounds of this series possess
excellent thermal stability. The fact
that no phase transition occurs at low
temperature indicates that they should
be well-suited for application in devi-
ces. Moreover, they possess low
HOMO energy levels, based on cyclic
voltammetry measurements, and suita-
composed of fused a-oligothiophene
units as building blocks, end-capped
with either styrene or 1-pentyl-4-vinyl-
benzene groups, has been synthesized
through Stille coupling reactions. The
compounds have been fully character-
ble energy gaps, as determined from
their thin-film UV/Vis spectra. Thin-
film X-ray diffraction analysis and
atomic force microscopy revealed high
crystallinity on supporting substrates.
In addition, as the substrate tempera-
ture has a significant influence on the
morphology and the degree of crystal-
linity, the device performance could be
optimized by varying the substrate
temperature. These materials were
found to exhibit optimal field-effect
1
ized by means of H NMR spectrome-
try, high-resolution mass spectrometry,
and elemental analysis. The molecules
present a trans–trans configuration be-
tween their double bonds, which has
been verified and confirmed by Fouri-
er-transform infrared spectroscopy and
single-crystal X-ray diffraction analysis.
The X-ray crystal structures showed p–
Keywords: device performance
organic field-effect transistors
·
·
performance, with
a
mobility of
0.17 cm2 Vꢀ1 sꢀ1 and an on/off ratio of
semiconductors · sulfur heterocycles
105, at a substrate temperature of 708C.
Introduction
cene have shown superior field-effect performance and mo-
bilities in excess of 1 cm2 Vꢀ1 sꢀ1.[2] Thiophene-based materi-
als have been considered as promising candidates for organ-
ic semiconductors and are proposed to have good OFET
performance due to various intra- and intermolecular inter-
actions, including weak hydrogen bonding, p–p stacking,
and sulfur–sulfur interactions.[3] Oligothiophenes consisting
of a-linked thiophene units (a-oligothiophenes, a-nT) and
derivatives thereof have been widely used in OFETs.[3c,4]
However, these oligomers can easily twist from planarity,
thus decreasing conjugation through torsion about single
bonds, which may potentially affect the band gap in the
solid state.[5] An effective approach to resolving this problem
is to combine the stability of the thiophene ring with the
planarity of linear acenes to produce thienoacenes.[3a,b,6]
Fused thiophenes can be regarded as fused a-oligothio-
phenes and their derivatives. Linearly condensed thiophenes
give the most extended p-conjugation and the highest pla-
narity. In addition, efficient intermolecular S···S interactions
in the fused thiophenes may contribute to carrier transport.
Therefore, the exploration of organic semiconductors based
on fused thiophenes would appear to be highly promising.
In recent years, organic field-effect transistors (OFETs), the
critical components of future organic electronics, have at-
tracted a lot of interest as a low-cost alternative to conven-
tional silicon transistors for electronic applications.[1] The
design and synthesis of novel materials to improve the key
OFET performance, including carrier mobility, on/off ratio,
and threshold voltage, are major challenges in organic semi-
conductor research. Organic semiconductors such as penta-
[a] Y. Liu, Dr. C.-a. Di, C. Du, Prof. Y. Liu, K. Lu, Dr. W. Qiu,
Prof. G. Yu
CAS Key Laboratory of Organic Solids
Beijing National Laboratory for Molecular Sciences
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (China)
Fax : (+86)10-6255-9373
E-mail: liuyq@iccas.ac.cn
[b] Y. Liu, C. Du, K. Lu
Graduate School of the Chinese Academy of Sciences
Beijing 100039 (China)
Chem. Eur. J. 2010, 16, 2231 – 2239
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2231

In our research aimed at finding superior semiconductors,
we have focused our attention on fused thiophenes and
have successfully synthesized a series of high-performance
organic semiconductors.[7] Fused a-oligothiophenes based on
thienoACHTUNGTRENNUNG[3,2-b]thiophene (TT) and dithieno[3,2-b:2’,3’-d]thio-
phene (DTT) represent versatile and effective molecular
scaffolds in the design of organic semiconductors. However,
semiconductors containing thieno
ACHTUNGTNER[NUNG 3,2-b]thieno[2’,3’:4,5]-
thieno[2,3-d]thiophene (TTA) have scarcely been stud-
ACHTUNGTRENNUNG
ied.[7c,8] A series of new organic semiconductors has been
synthesized, which have fused a-oligothiophene units as the
building blocks, end-capped with either styrene or 1-pentyl-
4-vinylbenzene groups. Double bonds in the backbones of
these materials facilitate p-electron delocalization and
extend the effective conjugation length of the system.[9] Sev-
eral research groups have developed semiconductors with
high performance by selecting conjugated vinylene-based
compounds.[10] In the current work, some organic semicon-
ductors have been designed and synthesized by varying the
degree of fusion in a series of fused thiophenes. The prod-
ucts may represent a new family of candidate materials for
use in OFETs. These semiconductors display good polycrys-
talline film-forming properties, and the molecules are orient-
ed in an orderly manner with a p–p stacking direction paral-
lel to the substrate. Their properties ensure that OFETs
based on these materials will exhibit high device perfor-
mance, which has been verified by device fabrication and
measurement. An identical approach has been followed to
synthesize six target compounds by Stille coupling reac-
tions.[11] The building blocks were synthesized in a specific
manner by oxidative couplings. Scheme 1 shows the chemi-
cal structures of the fused thiophenes end-capped with sty-
rene (2a, 3a, and 4a) and 1-pentyl-4-vinylbenzene (2b, 3b,
and 4b), and the synthetic route used to obtain them. The
products have been characterized by high-resolution mass
spectrometry, 1H NMR spectrometry, Fourier-transform in-
frared spectroscopy, and elemental analysis. Their photo-
electronic properties have been probed by UV/Vis spectro-
photometry, fluorescence spectroscopy, and cyclic voltam-
metry.
Scheme 1. Synthetic routes to 2a–4a and 2b–4b.
AHCTUNGTREG(NNNU styryl)stannane (1a) was prepared by the reaction of phe-
nylacetylene with tributyltin hydride (Bu3SnH) catalyzed by
azobis(isobutyronitrile) (AIBN).[15] Similarly, reaction of 4-
pentylphenylacetylene with Bu3SnH in the presence of
AIBN gave (E)-b-tributyl[2-(4-pentylphenyl)vinyl]stannane
(1b). The subsequent [PdACHTUNGTRNENUG(PPh3)2Cl2]-catalyzed Stille cou-
plings of the appropriate stannyl and bromo compounds
used to synthesize the six fused thiophenes are shown in
Scheme 1. Palladium-catalyzed Stille coupling of 2 with 1a
by refluxing for 12 h in toluene solution afforded 2a in 70%
yield. Likewise, Stille coupling of 2 with the corresponding
1b afforded 2b in 73% yield. 3a and 3b were synthesized
through an analogous procedure in 65 and 70% yield, re-
spectively. 4a and 4b derived from TTA were prepared by
Stille couplings of 4 with the corresponding compounds 1a
and 1b in 70 and 63% yield, respectively. One of the great-
est challenges was the purification of the compounds be-
cause homo-couplings of the stannyl and bromo compounds
occurred as side reactions in all of the syntheses. After the
obtained materials had been purified by multiple Soxhlet
extraction using methanol and acetone, they were further
purified by threefold gradient sublimation under vacuum.
They were all obtained as yellow solids and were found to
be slightly soluble in THF, chloroform, toluene, and chloro-
benzene. Their chemical structures were determined by EI-
MS or MALDI-TOF MS, 1H NMR spectrometry, Fourier-
transform infrared (FTIR) spectroscopy, and elemental anal-
yses. Single-crystal X-ray structure determinations of two of
the target compounds confirmed the proposed structures.
Results and Discussion
Synthesis: The key building blocks were synthesized by an
approach involving a combination of cross-coupling reac-
tions and oxidative couplings. TT was obtained in 52% yield
in six steps starting from 3-bromothiophene and was con-
verted into 2,5-dibromo-thienoACTHNUGRTNEUNG[3,2-b]thiophene 2 by treat-
ment with two equivalents of N-bromosuccinimide (NBS) in
CHCl3.[12] DTT was obtained in 25% yield in two steps from
2,3-dibromothiophene.[13] The synthetic route used to pre-
ACTHNUTRGNEUNG
pare TTA[14] started from 3-bromothieno[3,2-b]thiophene.[12]
The same methodology was implemented for the synthesis
of 2,6-dibromodithieno[3,2-b;2’,3’-d]thiophene 3[13b] and 2,6-
dibromothieno
ACHTUNGTRENNUNG[3,2-b]thieno[2’,3’:4,5]thienoAHCTUNGTRNEN[UGN 2,3-d]thiophene
4[7c] using two equivalents of NBS in CHCl3. (E)-b-Tributyl-
2232
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2231 – 2239

Organic Field-Effect Transistors
FULL PAPER
None of the compounds could be characterized by 13C NMR
spectroscopic analysis due to their poor solubility.
Thermal properties: The thermal properties of the new
fused thiophenes were evaluated by thermal gravimetric
analysis (TGA) and differential scanning calorimetry
(DSC). The onset of decomposition temperatures, 2a
(3178C), 2b (3458C), 3a (3438C), 3b (3598C), 4a (3508C),
and 4b (3898C), increase with the extent of thiophene ring
fusion and on adding the alkyl-substituted groups. There is
no doubt that extension of the conjugation of the fused a-
oligothiophenes and attachment of the the alkyl-substituted
groups improved the thermal stability.[16] The DSC traces of
2a and 4a did not show any obvious endothermic peaks be-
tween 0 and 2858C in either the heating or cooling cycles,
but those of 2b, 3a, and 3b displayed single endothermic
peaks at 1448C, 2888C, and 2218C, respectively. The DSC
trace of 4b showed two endothermic melting peaks at
2168C and 2658C. The former was strong with high enthal-
py, while the latter was relatively weak with low enthalpy.
As identified by polarized optical micrography, some solid–
solid phase transitions of 4b occurred at both endothermic
peaks, although an isotropic phase was not observed before
the decomposition temperature. The fact that the onset de-
composition temperatures of all of the fused thiophenes are
above 3008C shows that they have excellent thermal stabili-
ty, and the absence of any phase transitions at low tempera-
tures indicates that this series of compounds should be well-
suited for application in devices.
Figure 1. Front and side views of the molecular structures of a) 3a and
b) 4a with 50% probability ellipsoids.
Molecular and single-crystal structures: The effect of molec-
ular conformation and packing property in single crystals on
charge-carrier transport is one of the fundamental issues for
organic semiconducting materials. Single crystals of 3a were
obtained by slow evaporation of the volatiles from a solu-
tion in methanol/toluene (2:1), while those of 4a were ob-
tained by slow sublimation in a temperature-gradient fur-
nace. Unfortunately, no single crystals of the compounds 2a,
2b, 3b, and 4b could be obtained. X-ray diffraction studies
were performed on the crystals of 3a and 4a to determine
their solid-state structures. Figure 1 shows that the molecu-
lar structure of 3a has a twisted geometry, with the central
DTT core not lying in the same plane with a torsion angle
of 1308 along its long axis. The angle by which the benzene
rings in 3a are displaced from the plane of the long axis is
9.868. In contrast, the molecular backbone of the TTA core
in 4a is almost flat, and the angle by which the benzene
rings are displaced from the mean plane is 7.558. As expect-
ed, the geometric structures of 3a and 4a display a trans–
trans configuration between their double bonds, which may
increase the mobility of the charge carriers.[17] We assumed
that the other compounds 2a, 2b, 3b, and 4b would have a
similar trans–trans molecular configuration, confirmation of
which was provided by the results of a subsequent FTIR
spectroscopy study. The unit cells of the derivatives are
shown in Figure 2. Each unit cell contains two layers along
the c-axis direction, such that one half of the c-axis length,
Figure 2. Stereographic views of unit cells of molecules a) 3a and b) 4a
(hydrogen atoms have been omitted for clarity).
21.14 and 22.90 ꢁ for 3a and 4a, respectively, corresponds
to the width of each layer. In Figure 3, it can be seen that
the molecules are packed to form a sheet-like array, in
which short S···S contacts are observed. The intermolecular
short S···S contact in the bc plane of the sheet-like array of
3a has a distance of 3.44 ꢁ, while that in the ac plane of 4a
has a distance of 3.42 ꢁ. Intermolecular S···S contacts in-
crease the effective dimensionality of the electronic struc-
ture and are beneficial to charge transport. The molecular
sheets are piled up and form a columnar stacking with an in-
terplanar separation of 2.23 ꢁ (3a) in the b-axis direction
and 2.20 ꢁ (4a) in the a-axis direction. The interaction be-
tween the stacks is reinforced by the close intermolecular
S···S contacts. Such packing is similar to that of other fused
thiophenes.[3a,18] Both molecules display a nearly flat, sym-
metric molecular geometry, which facilitates tight molecular
packing. The molecules pack in a herringbone geometry,
similar to those of pentacene[19] and most fused thio-
phenes,[20] and the tilt angle between the two molecular
planes is 37.138 in 3a and 43.088 in 4a.
It was important to identify the configurations of the
other four compounds (2a, 2b, 3b, and 4b), because isomer-
Chem. Eur. J. 2010, 16, 2231 – 2239
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2233

Y. Liu et al.
Figure 4. FT-IR spectra of 2a, 2b, 3a, 3b, 4a, and 4b.
tra, the former are blue-shifted because the molecules adopt
a herringbone packing motif that leads to H aggrega-
tion.[23,24] This is usually related to excitonic coupling be-
tween adjacent molecules in a closely packed structure. We
conclude that there are strong interactions between neigh-
boring molecules in the film. The optical band gaps Eg
(2.53 eV (2a), 2.52 eV (2b), 2.40 eV (3a), 2.58 eV (3b),
2.37 eV (4a), and 2.41 eV (4b)) were determined by extrap-
olating the long-wavelength absorption edges, lonset (Eg =
1240/lonset eV), of their vacuum-deposited thin-film spectra.
Figure 3. Stacking patterns in the crystals: a) 3a: view along the a axis;
b) 4a: view along the b axis. For clarity, only one sheet-like array of mol-
ecules (0.5 < c <1.0) is depicted. Intermolecular S···S interactions are in-
dicated with dotted lines.
ization about double bonds often occurs during thermal
evaporation and deposition processes. The six compounds
were purified by gradient sublimation under vacuum. There-
fore, it was necessary to verify that all of the molecules re-
tained the same trans configuration. This was confirmed by
FTIR spectroscopy (see Figure 4). The FTIR spectra of each
of the six molecules featured a strong absorption band at
ꢁ946 cmꢀ1, which corresponds to an out-of-plane bending
[17,21]
ꢀ
vibration of a trans-vinylene C H bond.
No bands due
ꢀ1
ꢀ
to cis-vinylene C H bonds in the region ꢁ882–862 cm
were observed in the spectra. It was thus established that all
of the compounds exhibit trans–trans conjugation, which is
favorable for ordering in the solid state. This was important
and gratifying as even a small percentage of cis-isomers may
prevent good organization in thin films and hence decrease
the mobility of charge carriers. From Figure 4, it can be seen
that the monosubstituted phenyl ring (2a, 3a, and 4a) gives
rise to a characteristic absorption band at ꢁ698 cmꢀ1, while
no band due to the 1,4-disubstituted phenyl ring (2b, 3b,
and 4b) is observed in this region.[22]
Optical and electrochemical properties: The UV/Vis absorp-
tion spectra of the compounds in dilute THF solution and of
vacuum-deposited thin films on quartz substrates are shown
in Figure 5. In solution, the compounds show redshifts of
their absorption peaks with increasing degree of fusion of
the a-oligothiophene units. For the compounds sharing the
same building block (2a and 2b, 3a and 3b, 4a and 4b), the
absorption spectra in solution of the 1-pentyl-4-vinylben-
zene-substituted compounds exhibit a small redshift and a
similar peak shape to the spectra of the styrene-substituted
compounds. On comparing the solid-state and solution spec-
Figure 5. Normalized UV/Vis absorption spectra in THF solution (sol.)
and in the solid state (film).
2234
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2231 – 2239

Organic Field-Effect Transistors
FULL PAPER
In order to understand the charge-transport properties, to
assess the ionization potentials (hole-injecting ability), and
to verify the electrochemical stability of the compounds,
cyclic voltammetry (CV) measurements were performed.
We used a conventional three-electrode cell with Pt working
electrodes, a platinum wire counter electrode, and an Ag/
AgCl reference electrode in THF solution at room tempera-
ture. Compounds 2a–4a underwent an irreversible oxidation
process between 1.13 and 1.16 V, while the oxidations of
2b–4b were partially reversible and appeared at 0.95 V
versus Ag/AgCl. No reduction potentials of the six com-
pounds below zero voltage could be observed, as shown in
Figure 6. The ionization potentials (EHOMO; HOMO: highest
Studies on thin films: Thin films (of thickness about 50 nm)
of the materials on n-octadecyltrichlorosilane (OTS)-modi-
fied SiO2/Si substrates at different substrate temperatures
were investigated by means of thin-film X-ray diffraction
(XRD) analysis and atomic force microscopy (AFM).
Figure 7 shows the X-ray diffraction patterns of the six films
at different substrate temperatures (Tsub), which indicate
that they show their best mobilities at 708C (for 2a, 3a, and
3b) and 1008C (for 2b, 4a, and 4b). All of the XRD pat-
terns exhibit strong and sharp diffraction peaks with multi-
ple orders of reflection, which is indicative of a preferred
orientation of the molecules in the films with high crystallin-
ity on the substrates. Compared to the pentyl-substituted
2b–4b, compounds 2a–4a exhibit stronger and sharper pri-
mary peaks, indicating that these molecules are perfectly
oriented in the crystal grains. The first strong reflection
peak in the XRD pattern of a film of 3a at 2q ꢁ4.118 corre-
sponds to a d-spacing of 21.4 ꢁ (see Figure 7c), which is co-
incident with the length of the molecule (21.1 ꢁ) deter-
mined by single-crystal XRD experiments. This suggests
that the molecules of 3a are arranged with their long axes
almost perpendicular to the substrate, with the p–p stacking
direction parallel to the substrate, in which case the charge
carriers would transport easily with high mobilities.[27] The
molecules of 4a pack in the same manner as those of 3a.
The first strong reflection peak in the XRD pattern of a
film of 4a at 2q ꢁ 3.828 corresponds to a d-spacing of
23.1 ꢁ, coincident with the length of the molecule (22.9 ꢁ).
The diffraction peaks of 3a and 4a correspond well with
those observed by powder
occupied molecular orbital) of p-conjugated systems can be
onset
ox
estimated by using the equation EHOMO =ꢀ
(4.40 + E
)
eV.[25]
E
onset
is the onset potential for oxidation. The values of
ox
onset
E
for 2a, 2b, 3a, 3b, 4a and 4b of 1.03, 0.73, 0.99, 0.82,
ox
0.96, and 0.74 V, corresponding to estimated EHOMO levels of
ꢀ5.43, ꢀ5.13, ꢀ5.39, ꢀ5.22, ꢀ5.36, and ꢀ5.14 eV, respective-
ly, are indicative of good electrochemical stability. It is
worthy of note that these HOMO levels match the work
function of gold metal (ꢀ5.2 eV), so that hole injection from
a gold source electrode in a p-type OFET can be expected
to be efficient. All of the studied compounds have lower-
lying HOMO energy levels and larger band gaps than penta-
cene (EHOMO =ꢀ4.60 eV, Eg =2.21 eV), suggesting that they
should show better stabilities towards oxygen under ambient
conditions.[26]
XRD, revealing that the mole-
cules in the films pack in the
same manner as in the crystal-
line state. This orientation is
known to be favorable for ach-
ieving high mobility since the
stacking structure increases the
intermolecular p-overlap[28] and
the stacking direction is also
consistent with the direction of
current flow.[29] We assume that
2a adopts a similar thin-film
structure because the monolay-
er thickness of films (19.5 ꢁ)
determined by thin-film XRD
measurements is coincident
with the length of the molecule
(19.5 ꢁ) calculated by Chem-
Draw 3D and optimized by Ma-
terial Studio 3.0. However, the
tilt angles of films of 2b–4b de-
posited from the vapor phase
are not easily deduced from the
X-ray diffractograms because of
the absence of the first reflec-
Figure 6. Cyclic voltammograms measured at a scan rate of 100 mVsꢀ1 in 0.1m Bu4NPF6 in THF. a) 2a, b) 2b,
c) 3a, d) 3b, e) 4a, f) 4b.
tion peak. Figure 8 shows
atomic
force
microscopy
Chem. Eur. J. 2010, 16, 2231 – 2239
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2235

Y. Liu et al.
cently, better performance of
2b, with a mobility of up to
0.15 cm2 Vꢀ1 sꢀ1, has been ob-
tained at
T
sub =608C.[30] Al-
though the introduction of alkyl
chains at the longitudinal ends
of semiconducting molecules
has previously proved to be a
promising approach for improv-
ing OFET characteristics,[31] in
our case, the n-pentyl groups
had no beneficial effect on per-
formance. The styrene end-
capped fused thiophenes (3a,
4a) exhibited superior device
performance compared to the
corresponding 1-pentyl-4-vinyl-
benzene end-capped fused thio-
phenes (3b, 4b) under the same
device fabrication conditions.
For example, the best OFET of
3a exhibited a mFET more than
ten times higher than that of 3b
(0.17 versus 0.013 cm2 Vꢀ1 sꢀ1),
while the mFET of 4a was four
Figure 7. Thin-film X-ray diffractograms of a) 2a (Tsub =708C), b) 2b (Tsub =1008C), c) 3a (Tsub =708C), d) 3b
(Tsub =708C), e) 4a (Tsub =1008C), and f) 4b (Tsub =1008C).
(AFM) images of thin films deposited on SiO2/Si substrates.
The AFM images of 2a–4a all show plate-like grains con-
sisting of flat terraces. In particular, the thin film of 3a was
seen to consist of large plate-like and interconnected poly-
crystalline grains of several microns on the substrate at
708C, which should facilitate carrier transport and thus
result in superior transport properties. For the alkyl-substi-
tuted compounds 2b–4b, the AFM image of 3b reveals a
mixture of rod-like and plate-like grains. The grain sizes of
2b and 4b are smaller and inter-grain connection is less ex-
tensive than that in 3b. This trend in the morphologies is
Figure 8. 2ꢂ2 mm2 AFM images at different substrate temperatures:
a) 2a (Tsub =708C), b) 2b (Tsub =1008C), c) 3a (Tsub =708C), d) 3b
(Tsub =708C), e) 4a (Tsub =1008C), and f) 4b (Tsub =1008C).
consistent with the fluctuation trends in the mFET values,
those of 2a–4a being higher than those of the alkyl-substi-
tuted 2b–4b (the mFET values are in the order: 2a ꢁ 2b, 3a
> 3b, 4a > 4b).
OFET device performance: Devices were fabricated by
vacuum deposition on OTS-treated SiO2/Si substrates at var-
ious temperatures. Their performances were measured in a
top-contact configuration (drain and source electrodes de-
posited above the semiconductor) with Au electrodes. The
performances were measured in air and the results are
shown in Table 1. Typical field-effect transistor output and
transfer characteristics using 3a as the active semiconductor
are presented in Figure 9. All of the OFET devices exhibit-
ed p-type operation.
times that of 4b (0.06 versus 0.014 cm2 Vꢀ1 sꢀ1), which may
be attributed to the more effective p-conjugation and closer
p–p overlap in the former. As is well known, the morpholo-
gies of thin films dramatically influence device performan-
ces. This is consistent with the aforementioned thin-film
XRD and AFM images, which indicate superior film mor-
phology and molecular order in the non-alkyl-substituted
compounds compared to the alkyl-substituted compounds.
Devices fabricated from 3a at Tsub =708C showed a best
hole mobility of 0.17 cm2 Vꢀ1 sꢀ1 and an on/off ratio of 105 in
a saturation regime. It is accepted that the charge carrier
transport in OFETs is dominated by highly ordered thin
films with large interconnected polycrystalline grains. At
It was observed that the OFET performance of each com-
pound depended on the temperature of the substrate. When
2b was deposited at a substrate temperature of 1008C, the
resultant device showed a mobility of 0.04 cm2 Vꢀ1 sꢀ1. Re-
T
sub =708C, all diffraction peaks became stronger and sharp-
2236
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2231 – 2239

Organic Field-Effect Transistors
FULL PAPER
Table 1. Field-effect transistor characteristics: the carrier mobility mFET
on/off current ratio Ion/off, and threshold voltage VT of materials deposited
,
a lowering of the charge transport, as manifested in a de-
crease in mobility to 0.07 cm2 Vꢀ1 sꢀ1.
at different substrate temperatures Tsub
.
Material
Tsub [8C]
mFET [cm2 Vꢀ1 sꢀ1
]
Ion/off
VT [V]
2a
20
70
100
20
70
100
20
70
100
20
70
100
20
70
100
120
150
20
70
100
120
0.03
0.04
0.04
0.013
0.018
0.04
0.08
0.17
105
ꢀ21.0
ꢀ11.0
ꢀ11.5
ꢀ1.6
ꢀ9.1
+0.8
ꢀ6.1
ꢀ10.1
ꢀ9.7
ꢀ1.1
ꢀ6.4
ꢀ4.2
ꢀ9.5
ꢀ10.0
ꢀ8.7
ꢀ15.4
ꢀ20.2
+1.0
ꢀ17.8
ꢀ3.5
+5
Conclusions
105
105
In conclusion, we have synthesized a new series of oligomers
based on thieno[3,2-b]thiophene, dithieno[3,2-b:2’,3’-d]thio-
phene, and thieno[3,2-b]thieno[2’,3’:4,5]thieno[2,3-d]thio-
phene, end-capped with either styrene or 1-pentyl-4-vinyl-
benzene groups, by means of Stille coupling reactions. Their
chemical structures, which feature a trans–trans configura-
tion between the double bonds, have been determined by
Fourier-transform infrared spectroscopy and single-crystal
X-ray diffraction analysis. Investigation of their physico-
chemical properties has indicated that they are more stable
than pentacene. They have been used as p-type semiconduc-
tors for organic field-effect transistors, which showed a high
mobility of 0.17 cm2 Vꢀ1 sꢀ1 and a large on/off ratio of 105.
2b
3a
3b
4a
4ꢂ106
3ꢂ104
106
105
105
0.07
105
6.2ꢂ10ꢀ3
0.013
9.4ꢂ10ꢀ3
0.02
105
2ꢂ104
104
104
0.03
0.06
0.02
0.017
0.01
0.017
0.014
0.008
104
105
104
104
4b
105
105
104
104
Experimental Section
General: Chemicals were purchased from Aldrich or Alfa Aesar and
were used as received. Solvents and other common reagents were ob-
tained from the Beijing Chemical Plant. 1H NMR (300 MHz) and
1H NMR (400 MHz) spectra were obtained on Bruker DMX-300 and
DMX-400 NMR spectrometers, respectively, using tetramethylsilane as
an internal standard. Mass spectra were determined on a Micromass
GCT-MS spectrometer. Elemental analyses were performed with a Carlo
Erba model 1160 elemental analyzer. TGA measurements were carried
out on a TA SDT 2960 instrument under a dry nitrogen flow, heating
from room temperature (RT) to 5508C at a rate of 108Cminꢀ1. DSC
analyses were performed on a TA DSC 2010 instrument under a dry N2
flow, heating from RT to 3008C at a rate of 108C minꢀ1. Electronic ab-
sorption spectra were measured on a Jasco V570 UV/Vis spectrophotom-
eter. Emission spectra were recorded on a Hitachi F-4500 fluorescence
spectrometer. FT-IR spectra were determined using
a Perkin-Elmer
Tensor 27 spectrometer with samples in KBr pellets. Cyclic voltammetric
measurements were carried out at RT in a conventional three-electrode
cell using Pt button working electrodes of diameter 2 mm, a platinum
wire counter electrode, and an Ag/AgCl reference electrode, with a
0.1 molLꢀ1 solution of tetrabutylammonium hexafluorophosphate
(Bu4NPF6) in tetrahydrofuran (THF) as the electrolyte, using a comput-
er-controlled CHI660C instrument. Thin-film X-ray diffraction measure-
ments were made in the reflection mode at RT using a 2 kW Rigaku X-
ray diffraction system. The films were also imaged in air using a Digital
Instruments Nanoscope III atomic force microscope operated in tapping
mode.
Figure 9. a) Output and b) transfer characteristics of OFET devices based
on 3a at Tsub =708C at different gate voltages.
X-ray diffraction measurements: X-ray crystal structure determinations
were carried out in reflection mode using a Rigaku MM-007 X-ray dif-
fraction system (MoKa radiation, l=0.71073 ꢁ). The data were collected
at 113 K, and the structure was solved by direct methods using SHELXS-
97 and refined by using the SHELXL-97 program. Colorless prismatic
crystals of 3a were obtained by slow evaporation of the volatiles from a
solution in methanol/toluene (2:1). Crystallographic data for 3a: crystal
size: 0.14ꢂ0.12ꢂ0.08 mm3; monoclinic; P21/n; Z=4; a=7.3557(18), b=
er, and, at the same time, the AFM images revealed that the
grain size increased and the intergrain connection was im-
proved, indicative of improved ordering in the films. Both
AFM and thin-film XRD showed that the films of 3a depos-
ited at Tsub =708C had the best film morphology and molec-
ular ordering, consistent with the highest mFET obtained
under these conditions. When the substrate temperature was
increased to 1008C, the molecules of 3a formed larger as-
semblies on the substrate and simultaneously some bounda-
ries between the grains were formed, which probably led to
6.0295(14), c=42.272(8) ꢁ; V=1872.7(7) ꢁ3; 1calcd =1.421 gcmꢀ3
; final
R=0.0789, wR=0.1896; GoF=1.093 with I>2.00s(I). Yellow platelet
crystals of 4a were obtained by slow sublimation in a temperature-gradi-
ent furnace. Crystallographic data for 4a: crystal size: 0.12ꢂ0.10ꢂ
0.02 mm3; monoclinic; P21/c; Z=4; a=5.8990(18), b=7.401(2), c=
45.799(13) ꢁ; V=1998.9(10) ꢁ3; 1calcd =1.517 gcmꢀ3
;
final R=0.0697,
wR=0.1391; GoF=0.985 with I>2.00s(I). CCDC-711682 (3a) and
Chem. Eur. J. 2010, 16, 2231 – 2239
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2237

Y. Liu et al.
711683 (4a) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(t, 2H, J(H,H)=18.8 Hz), 7.40 (s, 2H), 7.36–7.31 (t, 4H, J(H,H)=
15.0 Hz), 7.25–7.21 (t, 2H, J(H,H)=14.0 Hz), 7.04–6.98 ppm (d, 2H,
J(H,H)=16.0 Hz); MS (EI): m/z (%): 400 (100) [M+]; elemental analysis
calcd (%) for C24H16S3: C 71.96, H 4.03, S 24.01; found: C 71.80, H 4.11,
S 13.70.
Device fabrication: OFET devices were made by subliming the molecules
(film thickness: 50 nm) onto OTS-modified SiO2/Si substrates, followed
by Au deposition through a shadow mask to define the source and drain
electrodes. Prior to the deposition, OTS was deposited by placing the
SiO2 substrates in a vacuum oven saturated with OTS vapor for 3 h. The
performances were measured in a top-contact configuration (drain and
source electrodes deposited above the semiconductor). Gold source and
drain contacts (50 nm) were deposited onto the organic layer through a
shadow mask. The channel length (L) and width (W) were 3000 and
50 mm, respectively. The OFET characteristics of the devices were deter-
mined at room temperature in air by using a Hewlett–Packard 4140B
semiconductor parameter analyzer. The mobilities in the saturation
regime were determined using Equation (1):
2,6-Bis[2-(4-pentylphenyl)vinyl]dithieno[3,2-b:2’,3’-d]thiophene (3b): 3b
was prepared according to the procedure described for 2b by Stille cou-
pling of 2,6-dibromodithieno[3,2-b:2’,3’-d]thiophene with (E)-b-tributyl[2-
(4-pentylphenyl)vinyl]stannane in 70% yield (1.89 g). 1H NMR
(300 MHz, [D8]THF, 278C, TMS): d=7.46–7.43 (d, 4H, J(H,H)=9.0 Hz),
7.39–7.34 (d, 2H, J(H,H)=15.0 Hz), 7.35 (s, 2H), 7.18–7.15 (d, 4H,
J(H,H)=9.0 Hz), 6.99–6.94 (d, 2H, J(H,H)=15.0 Hz), 2.63–2.58 (t, 4H,
J(H,H)=7.5 Hz), 1.65–1.58 (m, 4H), 1.36–1.29 (m, 8H), 0.93–0.88 ppm
(t, 6H, J(H,H)=7.5 Hz); MS (MALDI-TOF): m/z: calcd for C32H36S3:
540.8; found: 540.9; elemental analysis calcd (%) for C34H36S3: C 75.50,
H 6.71, S 17.79; found: C 75.43, H 6.83, S 17.33.
2,6-Distyrylthieno[3,2-b]thieno[2’,3’:4,5]thieno[2,3-d]thiophene (4a): 4a
was prepared according to the procedure described for 2a by Stille cou-
pling of 2,6-dibromothieno[3,2-b]thieno[2’,3’:4,5]thieno[2,3-d]thiophene
with (E)-b-tributyl(styryl)stannane. 4a was isolated as a yellow solid
(1.60 g, 70%). HRMS (MALDI): m/z: calcd for C26H16S4: 456.0135;
found: 456.0138; elemental analysis calcd (%) for C26H16S4: C 68.38, H
3.53, S 28.09; found: C 68.33, H 3.51, S 27.89.
2
ð1Þ
IDS ¼ ðmFETWCi=2LÞðVGꢀVTÞ
where IDS is the drain-source current in the saturated regime, mFET is the
field-effect mobility, W is the channel width, L is the channel length, Ci is
the capacitance of the SiO2 dielectric layer, VG is the gate voltage, and
VT is the threshold voltage.
2,6-Bis[2-(4-pentylphenyl)vinyl]thieno[3,2-b]thieno[2’,3’:4,5]thieno[2,3-
d]thiophene (4b): 4b was prepared according to the procedure described
for 2b by Stille coupling of 2,6-dibromothieno[3,2-b]thieno[2’,3’:4,5]-
thieno[2,3-d]thiophene with (E)-b-tributyl[2-(4-pentylphenyl)vinyl]stan-
2,5-Distyrylthieno[3,2-b]thiophene
(2a):
Phenylacetylene
(2.24 g,
20.0 mmol), Bu3SnH (5.8 g, 20.0 mmol), AIBN (0.20 g), and dry toluene
(100 mL) were placed in a three-necked flask equipped with a condenser.
The mixture was heated at 908C under a nitrogen atmosphere for 12 h
and then cooled to room temperature. The yellow solution of (E)-b-tribu-
tyl(styryl)stannane thus obtained was used directly for the next step with-
out further purification. (E)-b-Tributyl(styryl)stannane, 2,5-dibromothie-
no[3,2-b]thiophene (1.49 g, 5 mmol), and [Pd(PPh3)2Cl2] (3 mol%) were
mixed in dry toluene (150 mL). Nitrogen was bubbled through the mix-
ture for 15 min and then it was refluxed under a nitrogen atmosphere for
3 days. Thereafter, the mixture was cooled to room temperature and an-
hydrous methanol (100 mL) was added. The precipitate formed was col-
lected by filtration and washed with dilute acid (5% HCl), water, metha-
nol, and finally three times with acetone to remove the starting material
as well as the monosubstituted by-product. The material was further puri-
fied by three sublimations to afford 2a as a bright-yellow solid (1.2 g,
70%). 1H NMR (400 MHz, [D8]THF, 278C, TMS): d=7.52–7.51 (d, 4H,
J(H,H)=7.6 Hz), 7.41–7.37 (d, 2H, J(H,H)=16.0 Hz), 7.33–7.31 (t, 4H,
J(H,H)=14.0 Hz), 7.30 (s, 2H), 7.23–7.19 (t, 2H, J(H,H)=15.0 Hz),
6.98–6.94 ppm (d, 2H, J(H,H)=16.0 Hz); MS (EI): m/z (%): 344 (100)
[M+]; elemental analysis calcd (%) for C22H16S2: C 76.70, H 4.68, S
18.62; found: C 76.54, H 4.64, S 18.63.
nane. 4b was isolated as
a
yellow solid (1.88 g, 63%). 1H NMR
(300 MHz, [D8]THF, 578C, TMS): d=7.43–7.40 (d, 4H, J(H,H)=9.0 Hz),
7.33–7.28 (d, 2H, J(H,H)=15.0 Hz), 7.36 (s, 2H), 7.17–7.14 (d, 4H,
J(H,H)=9.0 Hz), 7.00–6.95 (d, 2H, J(H,H)=15.0 Hz), 2.64–2.59 (t, 4H,
J(H,H)=7.5 Hz), 1.72–1.62 (m, 4H), 1.37–1.29 (m, 8H), 0.92–0.88 ppm
(t, 6H, J(H,H)=6.0 Hz); MS (MALDI-TOF): m/z: calcd for C32H36S4:
596.9; found: 596.8; elemental analysis calcd (%) for C32H36S4: C 72.43,
H 6.08, S 21.49; found: C 72.54, H 6.15, S 21.24.
Acknowledgements
The present research was financially supported by the National Natural
Science Foundation of China (20825208, 60736004, 60671047, 50673093,
20721061), the National Major State Basic Research Development Pro-
gram (2006CB806203, 2006CB932103, 2009CB623603), the National
High-Tech Research and Development Program of China
(2008AA03Z101), and the Chinese Academy of Sciences.
2,5-Bis[2-(4-pentylphenyl)vinyl]thieno[3,2-b]thiophene (2b): 4-Pentyl-
phenylacetylene (6.88 g, 40.0 mmol), Bu3SnH (11.6 g, 40.0 mmol), AIBN
(0.20 g), and dry toluene (100 mL) were placed in a three-necked flask
equipped with a condenser. The mixture was heated to 908C under a ni-
trogen atmosphere for 12 h and then cooled to room temperature. The
yellow solution of (E)-b-tributyl[2-(4-pentylphenyl)vinyl]stannane thus
obtained was used directly for the next step without further purification.
2b was prepared according to the procedure described for 2a by Stille
coupling of 2,5-dibromothieno[3,2-b]thiophene with (E)-b-tributyl[2-(4-
pentylphenyl)vinyl]stannane in the presence of [Pd(PPh3)2Cl2] (3 mol%)
and was isolated as a yellow solid (1.77 g, 73%). 1H NMR (300 MHz,
[D8]THF, 578C, TMS): d=7.44–7.41 (d, 4H, J(H,H)=9.0 Hz), 7.36–7.31
(d, 2H, J(H,H)=15.0 Hz), 7.26 (s, 2H), 7.17–7.14 (d, 4H, J(H,H)=
9.0 Hz), 6.95–6.90 (d, 2H, J(H,H)=15.0 Hz), 2.63–2.58 (t, 4H, J(H,H)=
7.5 Hz), 1.68–1.60 (m, 4H), 1.50–1.29 (m, 8H), 0.93–0.88 ppm (t, 6H,
J(H,H)=7.5 Hz); MS (MALDI-TOF): m/z: calcd for C32H36S2: 484.8;
found: 484.9; elemental analysis calcd (%) for C32H36S2: C 79.29, H 7.49,
S 13.23; found: C 78.91, H 7.44, S 13.44.
[1] a) H. E. A. Huitema, G. H. Gelinck, J. B. P. H. van der Putten, K. E.
Kuijk, C. M. Hart, E. Cantatore, P. T. Herwig, A. J. J. M. van Bree-
men, D. M. de Leeuw, Nature 2001, 414, 599; b) P. Mach, S. J. Rodri-
guez, R. Nortrup, P. Wiltzius, J. A. Rogers, Appl. Phys. Lett. 2001,
78, 3592–3594; c) U. Mitschke, P. Bꢃuerle, J. Mater. Chem. 2000, 10,
1471–1507; d) B. Crone, A. Dodabalapur, A. Gelperin, L. Torsi,
H. E. Katz, A. J. Lovinger, Z. Bao, Appl. Phys. Lett. 2001, 78, 2229–
2231; e) M. Mushrush, A. Facchetti, M. Lefenfeld, H. E. Katz, T. J.
Marks, J. Am. Chem. Soc. 2003, 125, 9414–9423.
[2] a) H. E. Katz, Chem. Mater. 2004, 16, 4748–4756; b) H. Klauk, M.
Halik, U. Zschieschang, G. Schmid, W. Radlik, W. Weber, J. Appl.
Phys. 2002, 92, 5259–5263; c) T. W. Kelley, L. D. Boardman, T. D.
Dunbar, D. V. Muyres, M. J. Pellerite, T. P. Smith, J. Phys. Chem. B
2003, 107, 5877–5881; d) C. D. Sheraw, L. Zhou, J. R. Huang, D. J.
Gundlach, T. N. Jackson, M. G. Kane, I. G. Hill, M. S. Hammond, J.
Campi, B. K. Greening, J. Francl, J. West, Appl. Phys. Lett. 2002, 80,
1088–1090; e) Y.-Y. Lin, D. J. Gundlach, S. F. Nelson, T. N. Jackson,
IEEE Electron Device Lett. 1997, 18, 606–608.
2,5-Distyryldithieno[3,2-b:2’,3’-d]thiophene (3a): 3a was prepared ac-
cording to the procedure described for 2a by Stille coupling of 2,6-dibro-
modithieno[3,2-b:2’,3’-d]thiophene with (E)-b-tributyl(styryl)stannane. 3a
was isolated as
a
yellow solid (1.3 g, 65%). 1H NMR (300 MHz,
[3] a) X.-C. Li, H. Sirringhaus, F. Garnier, A. B. Holmes, S. C. Moratti,
N. Feeder, W. Clegg, S. J. Teat, R. H. Friend, J. Am. Chem. Soc.
[D8]THF, 578C, TMS): d=7.56–7.54 (d, 4H, J(H,H)=7.9 Hz), 7.47–7.41
2238
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 2231 – 2239

Organic Field-Effect Transistors
FULL PAPER
1998, 120, 2206–2207; b) M. He, F. Zhang, J. Org. Chem. 2007, 72,
442–451; c) H. K. Tian, J. W. Shi, B. He, N. H. Hu, S. Q. Dong,
D. H. Yan, J. P. Zhang, Y. H. Geng, F. S. Wang, Adv. Funct. Mater.
2007, 17, 1940–1951; d) E. A. Marseglia, F. Grepioni, E. Tedesco, D.
Braga, Mol. Cryst. Liq. Cryst. 2000, 348, 137–151.
[14] a) Y. Mazaki, K. Kobayashi, Tetrahedron Lett. 1989, 30, 3315–3318;
b) N. Sato, Y. Mazaki, K. Kobayashi, T. Kobayashi, J. Chem. Soc.
Perkin Trans. 2 1992, 765–770; c) H. Lumbroso, J. M. Catel, G. Le
Coustumer, C. G. Andrieu, J. Mol. Struct. 1999, 513, 201–218.
[15] C. Rim, D. Y. Son, Org. Lett. 2003, 5, 3443–3445.
[16] J. H. Gao, L. Q. Li, Q. Meng, R. J. Li, H. Jiang, H. X. Li, W. P. Hu,
J. Mater. Chem. 2007, 17, 1421–1426.
[17] N. Drolet, J. F. Morin, N. Leclerc, S. Wakim, Y. Tao, L. Mario, Adv.
Funct. Mater. 2005, 15, 1671–1682.
[18] a) Y. Mazaki, K. Kobayashi, J. Chem. Soc. Perkin Trans. 2 1992,
761–764; b) J. J. Morrison, M. M. Murray, X. C. Li, A. B. Holmes,
S. C. Morratti, R. H. Friend, H. Sirringhaus, Synth. Met. 1999, 102,
987–988; c) J. E. Anthony, Chem. Rev. 2006, 106, 5028–5048.
[19] a) S. T. Bromley, M. Mas-Torrent, P. Hadley, C. Rovira, J. Am.
Chem. Soc. 2004, 126, 6544–6545; b) J. Cornil, J. Ph. Calbert, J. L.
Bredas, J. Am. Chem. Soc. 2001, 123, 1250–1251; c) S. E. Fritz, S. M.
Martin, C. D. Frisbie, M. D. Ward, M. F. Toney, J. Am. Chem. Soc.
2004, 126, 4084–4085.
[4] a) H. K. Tian, J. W. Shi, D. H. Yan, L. X. Wang, Y. H. Geng, F. S.
Wang, Adv. Mater. 2006, 18, 2149–2152; b) H. E. Katz, J. G. Laquin-
danum, A. J. Lovinger, Chem. Mater. 1998, 10, 633–638; c) M.-H.
Yoon, A. Facchetti, C. E. Stern, T. J. Marks, J. Am. Chem. Soc. 2006,
128, 5792; d) B. S. Ong, Y. Wu, P. Liu, S. Gardner, Adv. Mater. 2005,
17, 1141–1144; e) X. Cai, C. P. Gerlach, C. D. Frisbie, J. Phys.
Chem. C 2007, 111, 452–456.
[5] a) X. N. Zhang, M. Kçhler, A. J. Matzger, Macromolecules 2004, 37,
6306–6315; b) H. E. Katz, Z. Bao, S. L. Gilat, Acc. Chem. Res. 2001,
34, 359–369; c) N. DiCꢄsare, M. BelletÞte, A. Donat-Bouillud, M.
Leclerc, G. Durocher, Macromolecules 1998, 31, 6289–6296.
[6] X. N. Zhang, A. J. Matzger, J. Org. Chem. 2003, 68, 9813–9815.
[7] a) Y. M. Sun, Y. Q. Ma, Y. Q. Liu, Y. Y. Lin, Z. Y. Wang, Y. Wang,
C.-a. Di, K. Xiao, X. M. Chen, W. F. Qiu, B. Zhang, G. Yu, W. P. Hu,
D. B. Zhu, Adv. Funct. Mater. 2006, 16, 426–432; b) K. Xiao, Y. Liu,
T. Qi, W. Zhang, F. Wang, J. Gao, W. Qiu, Y. Ma, G. Cui, S. Chen,
X. Zhan, G. Yu, J. Qin, W. Hu, D. Zhu, J. Am. Chem. Soc. 2005,
127, 13281–13286; c) Y. Liu, Y. Wang, W. Wu, Y. Liu, H. Xi, L.
Wang, W. Qiu, K. Lu, C. Du, G. Yu, Adv. Funct. Mater. 2009, 19,
772–778.
[8] H. H. Fong, V. A. Pozdin, A. Amassian, G. G. Malliaras, D.-M. Smil-
gies, M. He, S. Gasper, F. Zhang, M. Sorensen, J. Am. Chem. Soc.
2008, 130, 13202–13203.
[9] a) G. Distefano, M. D. Colle, D. Jones, M. Zambianchi, L. Favaretto,
A. Modelli, J. Phys. Chem. 1993, 97, 3504–3509; b) E. Orti, P. M. Vi-
ruela, J. Sanchez-Marin, F. Tomas, J. Phys. Chem. 1995, 99, 4955–
4963; c) J. Roncali, Chem. Rev. 1997, 97, 173–205.
[10] a) H. Meng, F. Sun, M. B. Goldfinger, F. Gao, D. J. Londono, W. J.
Marshal, G. S. Blackman, K. D. Dobbs, D. E. Keys, J. Am. Chem.
Soc. 2006, 128, 9304–9305; b) H. Klauk, U. Zschieschang, R. T.
Weitz, H. Meng, F. Sun, G. Nunes, D. E. Keys, C. R. Fincher, Z.
Xiang, Adv. Mater. 2007, 19, 3882–3887; c) F. Cicoira, C. Santato, A.
Dadvand, C. Harnagea, A. Pignolet, P. Bellutti, Z. Xiang, F. Rosei,
H. Meng, D. F. Perepichka, J. Mater. Chem. 2008, 18, 158–161; d) C.
Videlot-Ackermann, J. Ackermann, H. Brisset, K. Kawamura, N.
Yoshimoto, P. Raynal, A. El Kassmi, F. Fages, J. Am. Chem. Soc.
2005, 127, 16346–16347.
[20] a) L. San Miguel, W. W. Porter III, A. J. Matzger, Org. Lett. 2007, 9,
ˇ
1005–1008; b) X. N. Zhang, A. P. Cotꢄ, A. J. Matzger, J. Am. Chem.
Soc. 2005, 127, 10502–10503.
[21] S. Son, A. Dodabalapur, A. J. Lovinger, M. E. Galvin, Science 1995,
269, 376–378.
[22] Y. K. Jhon, J. J. Semler, J. Genzer, Macromolecules 2008, 41, 6719–
6727.
[23] X. N. Zhang, J. P. Johnson, J. W. Kampf, A. J. Matzger, Chem. Mater.
2006, 18, 3470–3476.
[24] a) T. Kono, D. Kumaki, J.-i. Nishida, T. Sakanoue, M. Kakita, H.
Tada, S. Tokito, Y. Yamashita, Chem. Mater. 2007, 19, 1218–1220;
b) S. Tirapattur, M. BelletÞte, N. Drolet, M. Leclerc, G. Durocher,
Chem. Phys. Lett. 2003, 370, 799–804; c) J. H. Park, D. S. Chung,
J. W. Park, T. Ahn, H. Kong, Y. K. Jung, J. Lee, M. H. Yi, C. E.
Park, S. K. Kwon, D. D. Shim, Org. Lett. 2007, 9, 2573–2576.
[25] a) X. Gao, W. Wu, Y. Liu, S. Jiao, W. Qiu, G. Yu, L. Wang, D. Zhu,
J. Mater. Chem. 2007, 17, 736–743; b) J. L. Brꢄdas, R. Silbey, D. S.
Boudreaux, R. R. Chance, J. Am. Chem. Soc. 1983, 105, 6555–6559.
[26] H. Meng, M. Bendikov, G. Mitchell, R. Helgeson, F. Wudl, Z. Bao,
T. Siegrist, C. Kloc, C.-H. Chen, Adv. Mater. 2003, 15, 1090–1093.
[27] L. San Miguel, W. W. Porter III, A. J. Matzger, Org. Lett. 2007, 9,
1005–1008.
[28] M. DeLongchamp, S. Sambasivan, D. A. Fischer, E. K. Lin, P.
Chang, A. R. Murphy, J. M. J. Frꢄchet, V. Subramanian, Adv. Mater.
2005, 17, 2340–2344.
[11] a) L. San Miguel, A. J. Matzger, Macromolecules 2007, 40, 9233–
9237; b) P. Espinet, A. M. Echavarren, Angew. Chem. 2004, 116,
4808–4839; Angew. Chem. Int. Ed. 2004, 43, 4704–4734; c) X. J.
Zhang, Y. Qu, L. J. Bu, H. K. Tian, J. P. Zhang, L. X. Wang, Y. H.
Geng, F. S. Wang, Chem. Eur. J. 2007, 13, 6238–6248.
[12] a) S.-H. Jung, H. K. Kim, S.-H. Kim, Y. H. Kim, S. C. Jeoung, D.
Kim, Macromolecules 2000, 33, 9277–9288; b) L. S. Fuller, B. Iddon,
K. A. Smith, J. Chem. Soc. Perkin Trans. 1 1997, 3465–3470.
[13] a) F. Allared, J. Hellberg, T. Remonen, Tetrahedron Lett. 2002, 43,
1553–1554; b) J. Frey, A. D. Bond, A. B. Holmes, Chem. Commun.
2002, 2424–2425.
[29] F. Valiyev, W.-S. Hu, H.-Y. Chen, M.-Y. Kuo, I. Chao, Y.-T. Tao,
Chem. Mater. 2007, 19, 3018–3026.
[30] P. Liu, Y. Wu, H. L. Pan, Y. N. Li, S. Gardner, B. S. Ong, S. P. Zhu,
Chem. Mater. 2009, 21, 2727–2732.
[31] a) M. Halik, H. Klauk, U. Zschieschang, G. Schmid, S. Ponomaren-
ko, S. Kirchmeyer, W. Weber, Adv. Mater. 2003, 15, 917–922; b) H.
Meng, F. Sun, M. B. Goldfinger, G. D. Jaycox, Z. Li, W. J. Marshall,
G. S. Blakman, J. Am. Chem. Soc. 2005, 127, 2406–2407.
Received: October 6, 2009
Published online: January 11, 2010
Chem. Eur. J. 2010, 16, 2231 – 2239
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2239