Small asymmetric anthracene-thiophene compounds as organic thin-film transistors

Article abstract of DOI:10.1016/j.tet.2013.07.041

Anthracene and thiophene compounds are promising materials for OTFTs. We report here, the synthesis, as well as the physical, thermal, and optoelectronic properties of alkyl-substituted asymmetric anthracene-thiophene compounds connected by a bridged triple bond. The target molecules were synthesized using 2-bromoanthracene as the starting material, and the proceeding reactions included alkylation, bromination, and the Sonogashira coupling reaction. The synthesized compounds were both thermally and electrochemically stable. Among the synthesized compounds, HTEA (7a) and DTEA (7b) showed mobility and on/off ratio values of 1.3×10^-1 cm²/V s, 2.6×10 ⁶ and 2.0×10^-2 cm²/V s, 1.0×10 ⁶, respectively.

Full text of DOI:10.1016/j.tet.2013.07.041

Tetrahedron 69 (2013) 8191e8198
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Small asymmetric anthraceneethiophene compounds as organic
thin-film transistors
Baji Shaik a, Ji Hee Park a, Tae Kyu An b, Young Ri Noh a, Soon Byung Yoon a,
,
a,
*
Chan Eon Park b, Young Jin Yoon a, Yun-Hi Kim a , Sang-Gyeong Lee
*
a Department of Chemistry, Research Institute of Natural Science (RINS), Graduate School for Molecular Materials and Nanochemistry,
Gyeongsang National University, Jinju 660-701, Republic of Korea
b Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Anthracene and thiophene compounds are promising materials for OTFTs. We report here, the synthesis,
as well as the physical, thermal, and optoelectronic properties of alkyl-substituted asymmetric an-
thraceneethiophene compounds connected by a bridged triple bond. The target molecules were syn-
thesized using 2-bromoanthracene as the starting material, and the proceeding reactions included
alkylation, bromination, and the Sonogashira coupling reaction. The synthesized compounds were both
thermally and electrochemically stable. Among the synthesized compounds, HTEA (7a) and DTEA (7b)
showed mobility and on/off ratio values of 1.3ꢀ10ꢁ1 cm2/V s, 2.6ꢀ106 and 2.0ꢀ10ꢁ2 cm2/V s, 1.0ꢀ106,
respectively.
Received 11 February 2013
Received in revised form 11 July 2013
Accepted 11 July 2013
Available online 18 July 2013
Keywords:
Organic thin-film transistors
Sonogashira coupling
Asymmetric anthracene derivatives
Solution processing
Ó 2013 Elsevier Ltd. All rights reserved.
P-type charge carrier mobility
1. Introduction
In the last few years, anthracene and thiophene compounds
have been mostly synthesized for OTFTs. Most of the research has
Organic semiconductors came to light in the late 1940s. How-
ever, they still need to develop a lot compared to traditional in-
organic semiconductors. With the first demonstration of organic
semiconductors in the OLED field, OTFTs made a huge impact; this
lead to dramatic improvement in this research field. Organic
semiconductors have many advantages over traditional inorganic
semiconductors.1e7 Due to their ease of synthesis and low cost they
have become of great interest in a short time. In recent years or-
ganic thin-film transistor research has become one of the major
research areas. OTFTs have several applications in active matrix
displays, RIF tags, and smart cards, etc.8,9
The conjugation property of organic compounds is the key factor
behind their semiconductor properties. During the last few years
several organic compounds have been synthesized and used in
OTFTs. Among them, thiophene, fluorene, anthracene, pentacene,
carbazole, pyrene, naphthalene, and many other compounds and
their derivatives have played a major role.10e20 Charge mobility is an
important aspect in terms of OTFTs. Charge mobility depends on
several factors such as the nature of the substance, process of device
manufacturing, annealing process, and molecular packing. Among
these, molecular packing is one of the most important parameters.
been done on polymers or symmetrical monomers or oligomers.
Very few asymmetric compounds have been synthesized for the
purpose of OTFTs;21 in contrast, more asymmetric molecules have
been synthesized in other fields like pharmaceuticals. In the past,
we synthesized asymmetric anthracene- and thiophene-based
compounds connected by a double bond, and we found that they
have the potential to be developed as OTFTs.22
In this paper we report the synthesis of asymmetric anthrace-
neethiophene compounds connected by a triple bond. The thermal,
physical, chemical, optical, and mobility properties have been ex-
tensively studied. We introduced alkyl chains to increase the sol-
ubility. In addition to the solubility, the end group alkyl chains have
one more advantage in that they increase the molecular ordering,
which enhances the charge mobility. The synthesized compounds
HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b) are shown in
Fig. 1. These compounds can be expected to give OTFT characters,
even though the compounds are small and asymmetric.
2. Results and discussion
2.1. Optical properties
The optical properties of the synthesized compounds were in-
vestigated by using UVevisible absorption and photoluminescence
* Corresponding authors. Tel.: þ82 55 772 1487; fax: þ82 55 772 1489; e-mail
address: leesang@gnu.ac.kr (S.-G. Lee).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.041

8192
B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
R
S
S
R'
S
HBTEA (13a): R' = C6H13
DBTEA (13b): R' = C12H25
HTEA (7a): R = C6H13
DTEA (7b): R = C12H25
Fig. 1. Structure of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b).
(PL) spectra in a dilute CHCl3 solution as well as on thin films. Figs. 2
and 3 represent the UV spectra and PL spectra, respectively, of the
compounds. The films were made by dip-coating the materials on
quartz in a chloroform solution at room temperature. The UVevis
absorption spectra of the four small molecules in thin films were
red-shifted relative to those in solution. These phenomena can be
explained by J-aggregation of the molecules,23 which correlates
with the particular molecular packing structure.24 Intermolecular
interactions between adjacent molecules in a solid state can be
characterized by UVevisible spectroscopy. Based on the shift in the
peak position, we can guess that the molecular packing structure in
a film state of molecules. The red-shift in the UV absorption spectra
can be interpreted as molecules stacked in a head-to-tail arrange-
ment.25 Therefore, the four synthesized molecules HTEA (7a), DTEA
(7b), HBTEA (13a), and DBTEA (13b) were well arranged head-to-
tail. These phenomena indicate that the small synthesized mole-
cules can transfer electrons from one molecule to another easily.
UVevisible absorption and PL emission spectral data are tabulated
in Table 1. The HTEA (7a) and HBTEA (13a) films show a red-shift of
6 and 51 nm, respectively, in the UV region compared to the
compounds in the dilute chloroform solution. This red-shift effect is
as result of the formation of an aggregation or excimer in the thin
HTEA(solution)
HTEA(film)
HBTEA(solution)
HBTEA(film)
DTEA(solution)
DTEA(film)
1.0
0.8
0.6
0.4
0.2
0.0
DBTEA(solution)
DBTEA(film)
400
450
500
550
600
650
700
750
Wavelength (nm)
Fig. 3. Photoluminescence spectra of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA
(13b) in a dilute CHCl3 solution and thin film.
Table 1
UVevisible and PL spectra of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b)
film due to
pep stacking or intermolecular interaction caused by
*
a
b
Compound
labs/nm
lem/nm
their planar structure leads to J-aggregations.26
Solution
Film
Solution
Film
HTEA (7a)
DTEA (7b)
HBTEA (13a)
DBTEA (13b)
359, 391, 412
359, 378, 399
361, 376, 398
352, 382, 404
394, 418
398, 422
383, 449
385, 436
430
431
460
461
508
504
535
545
HTEA(solution)
HTEA(film)
1.0
0.8
0.6
0.4
0.2
0.0
a
HBTEA(solution)
HBTEA(film)
DTEA(solution)
DTEA(film)
DBTEA(solution)
DBTEA(film)
Measured in a dilute CHCl3 solution and thin-film state.
Excited at the absorption maxima.
b
absorption value at 545 nm while DTEA (7b) has the lowest ab-
sorption value at 504 nm. HBTEA (13a) and DBTEA (13b) have
greater lem values than HTEA (7a) and DTEA (7b) both in the so-
lution state and film state due to an increase in conjugation as
a result of the introduction of one more thiophene ring.
400
500
2.2. Thermal properties
Wavelength (nm)
The thermal properties data of HTEA (7a), DTEA (7b), HBTEA
(13a), and DBTEA (13b) revealed that all compounds were ther-
mally stable. The TGA graphs of the four compounds are shown in
Fig. 4. The decomposition temperatures with 5% weight loss for
HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b) were ob-
served at 398 ꢂC, 389 ꢂC, 363 ꢂC, and 410 ꢂC, respectively. Among all
the compounds DBTEA (13b) was the most thermally stable, while
DTEA (7b) was the least thermally stable. The DSC graphs of the
four compounds are shown in Fig. 5. The upper curve represents the
first cooling while the lower curve represents the first heating. The
endothermic melting point temperatures of HTEA (7a), DTEA (7b),
HBTEA (13a), and DBTEA (13b) were observed at 128 ꢂC, 103 ꢂC,
195 ꢂC, and 191 ꢂC, respectively. The exothermic crystallization
temperatures of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA
Fig. 2. UVevisible absorption spectra of HTEA (7a), DTEA (7b), HBTEA (13a), and
DBTEA (13b) in a dilute CHCl3 solution and thin film.
When compared to HTEA (7a) and DTEA (7b), the HBTEA (13a)
and DBTEA (13b) films show a 12e30 nm high wavelength in the
UV absorption spectrum due to an increase in conjugation attrib-
uted to the presence of one more thiophene ring. While in solution
of HTEA (7a) has greater absorption value at 412 nm compared to
the others due to the well-arranged structure of the hexyl side
chain compared to the dodecyl side chain.
Based on their emission spectra, all the films show a clear, dis-
tinct red-shift of approximately 75e85 nm compared to the solu-
tion state. Among the four compounds DBTEA (13b) has a greater

B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
8193
(13b) were observed at 122 ꢂC, 63 ꢂC, 190 ꢂC, and 190 ꢂC, re-
spectively. HBTEA (13a) and DBTEA (13b) have the highest crys-
tallization temperature of 190 ꢂC, while DTEA (7b) exhibited the
lowest crystallization temperature of 63 ꢂC. HTEA (7a) displays
a high melting temperature and crystallization temperature com-
pared to DTEA (7b); in a similar way, this trend was also observed
in HBTEA (13a) and DBTEA (13b). Compounds containing the short
alkyl side chain (hexyl) exhibited both a high melting temperature
and crystallization temperature compared to compounds contain-
ing the long alkyl side chain (dodecyl). These data illustrate that all
the compounds have a well-crystalline structure and can be used
for making thin-film transistors.
HBTEA (13a), and DBTEA (13b), respectively. HBTEA (13a) has the
least oxidation potential compared to the others; this is due to the
presence of the two thiophene rings, causing an increase in electron
density in the compound, leading to it easily undergoing oxidation.
DTEA (7b) was electrochemically more stable than the others and
has a high onset oxidation potential, Eox
.
DBTEA
DTEA
HBTEA
HTEA
HTEA(Td= 398oC)
HBTEA(Td= 363oC)
100
90
DTEA(Td= 389oC)
DBTEA(Td= 410oC)
80
70
60
50
40
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
E(V) vs Ag/AgCl (eV)
Fig. 6. Cyclic voltammogram of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b)
(working electrode: glassy carbon, reference electrode: Ag/AgCl in KCl (satd), counter
electrode: Pt wire, electrolyte: 0.1 M TBAP in methylene chloride, purge time: 60 s,
scan rate: 50 mV/s).
0
100
200
300
400
500
o
600
700
Temperature( C)
Fig. 4. TGA thermogram of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b).
Table 2
Electrochemical properties of HTEA (7a), DTEA (7b), HBTEA (13a), and DBTEA (13b)
Compound
Oxidation Eonset (V)
HOMO (eV)
LUMO (eV)
Eg (eV)
DBTEA (1st haeting)
DBTEA (1st cooling)
HTEA (7a)
DTEA (7b)
HBTEA (13a)
DBTEA (13b)
1.11
1.17
1.05
1.16
ꢁ5.55
ꢁ5.61
ꢁ5.49
ꢁ5.60
ꢁ2.72
ꢁ2.78
ꢁ2.92
ꢁ2.79
2.73
2.85
2.66
2.71
Tc= 190o
C
HOMOeLUMO gap measured according to the onset of UV absorption (¼1240/lonset
eV). HOMO (eV) measured according to the onset of oxidation (HOMO¼4.44þEonset
ferrocene¼4.84ꢁEonset (oxidation of ferrocene)¼4.84ꢁ0.40¼4.44).
;
Tm= 191o
200
C
50
100
150
250
Temperature(oC)
Temperature(oC)
These results suggest that these compounds have good elec-
trochemical stability. The HOMO (LUMO) energy levels of HTEA
(7a), DTEA (7b), HBTEA (13a), and DBTEA (13b) were ꢁ5.55
(ꢁ2.72), ꢁ5.61 (ꢁ2.78), ꢁ5.49 (ꢁ2.92), and ꢁ5.60 (ꢁ2.79) eV, re-
spectively. The LUMO energy level was calculated from the HOMO
and Eg values. It was clearly observed that the HOMOeLUMO en-
ergy gap was less in both HBTEA (13a) and DBTEA (13b) than HTEA
(7a) and DTEA (7b); this is due to the increase in conjugation
length, which lowers the HOMOeLUMO energy gap in both HBTEA
(13a) and DBTEA (13b).
HTEA (1st haeting)
HTEA (1st cooling)
DTEA (1st haeting)
DTEA (1st cooling)
Tc= 122o
C
Tc= 63oC
Tm=103oC
Tm= 128o
140
C
50
100
150
200
250
60
80
100
120
160
180
Temperature(oC)
Temperature(oC)
Fig. 5. Differential scanning calorimetry (DSC) thermogram of HTEA (7a), DTEA (7b),
HBTEA (13a), and DBTEA (13b).
2.4. XRD analysis
In order to determine the crystallinity and molecular packing
XRD analysis was performed on the thin films of HTEA (7a) and
DTEA (7b). The XRD patterns of both films are shown in Fig. 7. Both
HTEA (7a) and DTEA (7b) displayed diffractions through XRD
2.3. Electrochemical properties
Cyclic voltammetry (CV) measurements of the synthesized
compounds were taken in order to determine the electrochemical
stability, HOMO, and LUMO energy levels. CV graphs of the four
compounds are shown in Fig. 6. The CV of HTEA (7a), DTEA (7b),
analysis confirming their crystalline strucꢂture. HTEA (7a) showed
ꢀ
its first strong reflection peak at 2
q
¼2.76 , with d-spacing 32.1 A
and the others are its second, third, and fourth orders, respectively.
HBTEA (13a), and DBTEA (13b) was measured in a 1.0ꢀ10ꢁ3
M
DTEA (7b) showed its first diffraction peak at 2
q
¼2.06ꢂ with d-
ꢀ
CHCl3 solution containing 0.1 M Bu4NClO4. The onset oxidation
potential is summarized in Table 2. The onset oxidation potential
Eox values were 1.11, 1.17, 1.05, and 1.16 V for HTEA (7a), DTEA (7b),
spacing 42.8 A. From the XRD data, the pep stacking ratio of the
molecules in the in-plane phase showed that HTEA (7a) is excep-
tionally higher than DTEA (7b). The more diffraction peaks in HTEA

8194
B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
(7a) compared to DTEA (7b) confirmed that, HTEA (7a) has more
crystalline structure than DTEA (7b). And also, HTEA (7a) has well-
ordered molecular crystals to compare with DTEA (7b). As a result
of this, HTEA (7a) has higher charge mobility than the DTEA (7b).
(a)
(b)
10
10
10
10
10
10
10
10
10
10
0.0035
0.0030
0.0025
0.0020
0.0015
0.0010
0.0005
0.0000
-0.0005
2.5x10
0V
-20V
-40V
-60V
-80V
2.0x10
1.5x10
1.0x10
5.0x10
(a)
(b)
0.0
-5.0x10
0
-20
-40
(V)
-60
-80
-80
-60
-40
V
-20
(V)
0
20
V
D
G
Fig. 8. (a) Drain current (ID) versus gate voltage (VG) characteristics of HTEA (7a). (b)
Drain current (ID) versus drain-source voltage (VD) characteristics of the HTEA (7a)
OTFT at different gate voltages (VG).
Fig. 7. XRD patterns of HTEA (7a) and DTEA (7b) [(a) in-plane (b) out-of-plane].
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
1.5x10-6
(a)
(b)
-80V
-60V
-40V
-20V
0V
0.0020
0.0015
0.0010
0.0005
0.0000
1.0x10-6
2.5. OTFT characterization
Top-contact OTFTs were made by depositing the drain and
source electrodes above HTEA (7a) and DTEA (7b). The HTEA (7a)
and DTEA (7b) layers were spin-coated from 0.7 to 0.5 wt % chlo-
roform solutions, respectively. The mobility, oneoff ratio, and
threshold voltage of the films of HTEA (7a) and DTEA (7b) are
tabulated in Table 3. The voltageecurrent graphs are represented in
Figs. 8 and 9. Figs. 8a and 9a show plots of the drain current (ID)
versus gate voltage (VG), and Figs. 8b and 9b show plots of the drain
current (ID) versus drain-source voltage (VD) for HTEA (7a) and
DTEA (7b)-based OTFTs. From the graphs it was clearly evident that
when the gate voltage decreased to below zero, there was a sudden
increase in drain current flow, indicating P-type OTFTs. The current
increases linearly with drain voltage, at low drain voltages. When
the drain voltage reaches to the gate voltage, the voltage drop at the
drain contact falls to zero, and the conducting channel is pinched
off, this is known as saturated regime. At this stage current becomes
independent of the drain voltage. In the saturated regime,
VDꢃ(VGꢁVT). Field-effect mobility was calculated in the saturation
5.0x10-7
0.0
-5.0x10-7
-80
-60
-40
-20
(V)
0
20
0
-10
-20
-30
-40
-50
-60
V
G
V
(V)
D
Fig. 9. (a) Drain current (ID) versus gate voltage (VG) characteristics of DTEA (7b). (b)
Drain current (ID) versus drain-source voltage (VD) characteristics of DTEA (7b) OTFT at
different gate voltages (VG).
3. Conclusions
In conclusion, we synthesized asymmetric HTEA (7a), DTEA (7b),
HBTEA (13a), and DBTEA (13b) by using the Sonogashira coupling
reactionand otherreactions, andexamined theiroptical,thermal, and
electrochemical properties. Examination of their thermal properties
revealed that the four materials have good thermal stability. In-
vestigation of their optical and electrochemical properties revealed
that DTEA (7b) and DBTEA (13b) had higher oxidation potentials due
totheirhigherHOMOenergylevels [ꢁ5.61 eV forDTEA(7b), ꢁ5.60eV
for DBTEA (13b)]. HTEA(7a)and DTEA (7b) showed good solubility in
toluene and chlorobenzene, and were also soluble in chloroform after
heating. HBTEA (13a) and DBTEA (13b) showed good solubility in
toluene and chlorobenzene under hot conditions, but were sparingly
soluble in chloroform under both cold and hot conditions. The greater
solubility of HTEA (7a) and DTEA (7b) enabled OTFTs to be made.
Devices using HTEA (7a) and DTEA (7b) thin films were prepared by
spin-coating, andexhibitedamobilityof1.3ꢀ10ꢁ1 cm2/Vswithanon/
off current ratio of up to 2.6ꢀ106 and a threshold voltage of ꢁ1.43 V,
[HTEA (7a)]; a mobility of 2.0ꢀ10ꢁ2 cm2/V s, on/off ratio of 1.0ꢀ106
and threshold voltage of ꢁ5 V [DTEA(7b)]. These results suggest that
the presence of a short alkyl side chain leads to a well-ordered mo-
lecular arrangement and shows good mobility. We hope this research
willenhancethedevelopmentofmoreasymmetriccompoundsinthe
field of OTFTs as well as in the field of organic semiconductors.
regime using the equation ID¼(W/2L)
m
Ci (VGꢁVT)2. Where ID is the
source-drain current, VD is the source-drain voltage, VG is the gate
voltage, VT is the threshold voltage, and Ci is the capacitance per
unit area of SiO2 layer. The HTEA (7a)-based OTFT showed a higher
performance in terms of both mobility (1.3ꢀ10ꢁ1 cm2/V s) and on/
off ratio (2.6ꢀ106), due to HTEA (7a) having a more crystalline
structure than DTEA (7b). XRD data confirmed the more crystalline
structure of HTEA (7a) compared to DTEA (7b). In addition, the
short alkyl side chain in HTEA (7a) favored the well-ordering of
molecules. This crystalline structure and the well-ordered molec-
ular arrangement in HTEA (7a) lead to easy charge transport. As
a result, HTEA (7a) exhibited high mobility compared to DTEA (7b).
DTEA (7b) exhibited a mobility of 2.0ꢀ10ꢁ2 cm2/V s and an on/off
ratio of 1.0ꢀ106. The greater solubility of HTEA (7a) and DTEA (7b)
enabled the production of OTFTs. On the other hand, the low sol-
ubility of HBTEA (13a) and DBTEA (13b) disfavored the making of
OTFTs.
Table 3
TFT properties of HTEA (7a) and DTEA (7b)
4. Experimental section
4.1. General methods
Mobility (cm2/V s)
On/off ratio
Threshold voltage (V)
HTEA (7a)a
DTEA (7b)b
1.3ꢀ10ꢁ1
2.6ꢀ106
ꢁ1.43
ꢁ5
2.0ꢀ10ꢁ2
1.0ꢀ106
a
4.1.1. Materials. All the reagents and chemicals were purchased
from SigmaeAldrich Co. The solvents such as tetrahydrofuran
Top-contact, OTS, spin-coating (chloroform 0.7 wt %, 4000 rpm, 60 s).
Top-contact, OTS, spin-coating (chloroform 0.5 wt %, 2000 rpm, 60 s).
b

B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
8195
(THF), diethyl ether, toluene, and acetonitrile were used after dis-
tillation in the presence of sodium/benzophenone or calcium hy-
dride under nitrogen gas. Chromatography was performed on silica
gel (70e230 mesh, Merck) using gravity flow.
silicon as gate with a thickness of 300 nm, thermally grown on
SiO2 dielectric layer. The octadecyltrichlorosilane monolayer
was treated in toluene solution for about 2 h. Solutions of the
organic semiconductors were spin-coated at 4000 rpm from
0.7 wt %, 4000 rpm from 0.7 wt % chloroform solutions to get
HTEA and DTEA thin films, respectively. Gold source and drain
electrodes were evaporated on top of organic layers (100 nm).
4.1.2. Spectroscopic measurements. 1H and 13C NMR spectra were
recorded on 300 MHz and 75 MHz spectrometers, respectively. The
chemical shift values were reported in
d
units (ppm) relative to an
The channel length and width were 100 mm and of 2000 mm,
internal standard (TMS). Mattson genesis series FTIR spectropho-
tometer was used for IR analysis. Mass spectra analysis was carried
on a JMS-700, JEOL. UVevisible absorption and photoluminescence
(PL) spectra were obtained by using PerkineElmer LAMBDA-900
UV/VIS/NIR spectrophotometer and an LS-50B luminescence
spectrophotometer, respectively. The XRD data was obtained from
mode X-ray diffraction (1D XRD) spectroscopy at the 5 A beam line
in the Pohang Accelerator Laboratory.
respectively. The electrical measurements of the OTFETs were
obtained in an air with the help of KEITHLEY 2400 and 236
source/measure units. Field-effect mobilities were measured in
the saturation regime, by using the slope of the source-drain
graph.
4.2. Synthesis
4.1.3. Electrochemical measurements. Cyclic voltammogram mea-
surements were carried out on an epsilon E3 at room temperature
in a tetrabutylammonium perchlorite (0.1 M solution) in acetoni-
trile under nitrogen atmosphere at a scan rate of 50 mV/s. A Pt wire
and Ag/AgCl electrodes were served as the counter and reference
The asymmetric HTEA (7a), DTEA (7b), HBTEA (13a), and
DBTEA (13b) were synthesized according to Schemes 1 and 2.
Compounds 6 and 8 were synthesized according to literature
procedure and the spectral data were coincided with literature
data.27,28
R
R
S
i)
S
ii)
S
Br
3a : R = C6H13
3b : R = C12H25
2a : R = C6H13
2b : R = C12H25
1
R
S
R
S
X
iii) or iv)
v) or vi)
5a : R = C6H13
5b : R = C12H25
4a : R = C6H13
, X = SiMe3
4b : R = C12H25, X = CMe2OH
R
S
vii)
5a or 5b
Br
6
HTEA (7a) : R = C6H13
DTEA (7b) : R = C12H25
Scheme 1. Synthesis of HTEA (7a) and DTEA (7b). Reagents and conditions. (i) n-BuLi, 1-bromohexane; (ii) NBS, AcOH, chloroform; (iii) ethynyltrimethylsilane, Pd(pph3)2Cl2, CuI, i-
Pr2NH, reflux; (iv) 2-methyl-3-butyn-2-ol, Pd(pph3)2Cl2, CuI, Et3N, reflux; (v) Bu4NF, THF; (vi) KOH, i-PrOH, reflux; (vii) Pd (dppf)2Cl2, CuI, toluene, i-Pr2NH.
electrodes, respectively. Melting points were measured with the
electrothermal Mode 1307 digital analyzer and were uncorrected.
Differential scanning calorimetry (DSC) measurements were car-
ried out under nitrogen by using a TA instruments 2100 differential
scanning calorimeter, by heating from 30 ꢂC to 300 ꢂC at a rate of
10 ꢂC/min. Thermogravimetric analysis (TGA) was obtained under
nitrogen by using a TA instruments 2050 thermogravimetric ana-
lyzer, by heating at a 10 ꢂC/min heating rate from 30 ꢂC to 700 ꢂC.
4.2.1. 2-Hexylthiophene (2a). To a solution of thiophene (5.0 g,
60 mmol) in THF (50 mL) was added dropwise n-BuLi (40.6 mL,
65mmol,1.6M in hexane) at ꢁ78ꢂC. The reaction mixturewas stirred
for 1 h at ꢁ78 ꢂC under nitrogen. To the reaction mixture added
slowly 1-bromohexane (10.7 g, 65 mmol), and elevated to room
temperature and stirred for 12 h. The reaction was quenched with
waterand product was extracted with diethyl ether. The organic layer
was washed with water, brine, and dried over MgSO4, and then
evaporated under reduced pressure. The residuewas purified by flash
column chromatography on silica gel with hexane as eluent to give 2a
as colorless liquid. Yield: 8.3 g (82%); IR (KBr): 3071 cmꢁ1 (sp2 CeH),
4.1.4. Device fabrication and characterization of field-effect tran-
sistors. Top-contact OTFETs were fabricated on highly n-doped

8196
B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
i)
ii)
S
Br
S
R'
S
R'
S
S
S
10a : R' = C6H13
9a : R' = C6H13
8
10b : R' = C12H25
9b : R' = C12H25
iii)
S
R'
iv)
S
R'
HO
S
S
12a : R' = C6H13
11a : R' = C6H13
12b : R' = C12H25
11b : R' = C12H25
S
R'
S
v)
12a or 12b
Br
6
HBTEA (13a) : R' = C6H13
DBTEA (13b) : R' = C12H25
Scheme 2. Synthesis of HBTEA (13a) and DBTEA (13b). Reagents and conditions. (i) n-BuLi, 1-bromohexane; (ii) NBS, AcOH, chloroform; (iii) 2-methyl-3-butyn-2-ol, Pd(pph3)2Cl2,
CuI, Et3N, reflux; (iv) KOH, i-PrOH, reflux; (v) Pd (dppf)2Cl2, CuI, toluene, i-Pr2NH.
2921e2854 cmꢁ1 (sp3 CeH), 1470 cmꢁ1 (C]C); 1H NMR (300 MHz,
CDCl3, ppm):
Yield: 98%; IR (KBr): 3065 cmꢁ1 (sp2 CeH), 2956e2858 cmꢁ1 (sp3
CeH), 1525e1433 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
d
7.08 (d, 1H, J¼4.8 Hz), 6.88 (dd, 1H, J¼4.8 Hz), 6.69 (d,
1H, J¼3.3 Hz), 2.81 (t, 2H, J¼7.7 Hz), 1.68e1.61 (m, 2H), 1.34e1.26
d
6.87e6.86 (d, 1H, J¼3.6 Hz), 6.56e6.55 (d, 1H, J¼3.6 Hz),
(m, 6H), 1.02e0.98 (t, 3H, J¼1.8 Hz); EIMS m/z (%): 168 (100, Mþ).
2.80e2.75 (t, 2H, J¼7.6 Hz), 1.72e1.62 (m, 2H), 1.35e1.31 (m, 18H),
0.95e0.91 (t, 3H, J¼6.6 Hz); 13C NMR (75 MHz, CDCl3, ppm):
4.2.2. 2-Dodecylthiophene (2b). Compound 2b was synthesized by
the same procedure for synthesis of 2a. Colorless liquid. Yield: 81%;
IR (KBr): 3106e3038 cmꢁ1 (sp2 CeH), 2923e2856 cmꢁ1 (sp3 CeH),
d 147.63, 129.36, 124.32, 108.59, 31.99, 31.51, 29.70, 29.60, 22.76,
14.18 Hz; EIMS m/z (%): 330 (100, Mþ).
1475 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
d
7.20e7.18 (dd,
4.2.5. [(5-Hexylthiophen-2-yl)ethynyl]trimethylsilane (4a). To a dea-
erated solution of 3a (34.6 g, 140 mmol) in i-Pr2NH (300 mL) were
added Pd(pph3)2Cl2 (2.25 g, 0.28 mmol) and CuI (1.6 g, 8.4 mmol) at
room temperature. And then ethynyltrimethylsilane (19.4 mL,
140 mmol) was added dropwise to the reaction mixture and stirred
at 90 ꢂC for 12 h, and then allowed to reach at room temperature.
The reaction mixture was filtered and solvent was removed by
evaporation under reduced pressure and the residue performed
flash column chromatography on silica gel with hexane as eluent to
give 4a as light brown liquid. Yield: 21.0 g (58%); IR (KBr):
2958e2927 cmꢁ1 (sp2 CeH), 2853 cmꢁ1 (sp3 CeH), 2098 cmꢁ1
(C^C), 1504e1465 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
1H, J¼1.2 Hz), 7.03e7.00 (dd, 1H, J¼3.3 Hz), 6.89e6.88 (dd, 1H,
J¼0.9 Hz), 2.96e2.91 (t, 2H, J¼7.3 Hz), 1.85e1.75 (m, 2H), 1.41 (m,
18H), 1.05e1.00 (t, 3H, J¼6.6 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d
145.85, 126.65, 122.74, 32.10, 30.06, 29.83, 29.55, 22.86, 14.25 Hz;
EIMS m/z (%): 252 (100, Mþ).
4.2.3. 2-Bromo-5-hexylthiophene (3a). Compound 2a (30 g,
178 mmol) was dissolved in chloroform/acetic acid (100 mL/
100 mL, v/v) and added NBS (34.9 g, 198 mmol) at room temper-
ature. The reaction mixture was stirred for 2 h and quenched with
water (100 mL). The product was extracted with CH2Cl2 and
washed with water, brine, and dried over MgSO4, and then evap-
orated under reduced pressure. The residue was purified by flash
column chromatography on silica gel with hexane as eluent to give
3a as colorless liquid. Yield: 39 g (90%); IR (KBr): 3068 cmꢁ1 (sp2
CeH), 2951e2852 cmꢁ1 (sp3 CeH), 1521e1436 cmꢁ1 (C]C); 1H
d
7.01e6.99 (d, 1H, J¼3.3 Hz), 6.64e6.62 (d, 1H, J¼3.6 Hz), 2.77e2.72
(t, 2H, J¼7.2 Hz), 1.67e1.62 (m, 2H), 1.34e1.31 (m, 6H), 1.13e0.92 (t,
3H, J¼1.8 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d 147.94, 131.94,
123.95, 119.93, 96.77, 75.98, 65.71, 31.95, 31.57, 31.36, 29.67, 29.39,
22.72, 14.15 Hz; EIMS m/z (%): 264 (100, Mþ).
NMR (300 MHz, CDCl3, ppm):
d
6.86e6.85 (d, 1H, J¼3.6 Hz),
6.55e6.54 (d, 1H, J¼3.6 Hz), 2.78e2.73 (t, 2H, J¼7.2 Hz), 1.67e1.62
4.2.6. 4-(5-Dodecylthiophen-2-yl)-2-methylbut-3-yn-2-ol (4b). To
a deaerated solution of 3b (3.93 g, 12 mmol) in Et3N (40 mL) were
added Pd(pph3)2Cl2(60 mg, 0.072 mmol) and CuI (8 mg, 0.04 mmol)
at room temperature. And then 2-methyl-3-butyn-2-ol (1.172 mL
18 mmol) was added to reaction mixture and stirred at 90 ꢂC for
12 h, and then allowed to reach at room temperature. The reaction
mixture was filtered and the solvent was removed under reduced
(m, 2H), 1.35e1.32 (m, 6H), 1.12e0.91 (t, 3H, J¼1.8 Hz); 13C NMR
(75 MHz, CDCl3, ppm): d 147.66, 129.37, 124.33, 108.55, 31.53, 31.43,
30.34, 28.66, 22.57, 14.08 Hz; EIMS m/z (%): 246 (100, Mþ).
4.2.4. 2-Bromo-5-dodecylthiophene (3b). Compound 3b was syn-
thesized by the same procedure for synthesis of 3a. Colorless liquid.

B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
8197
pressure and the residue performed flash column chromatography
on silica gel with hexane/EtOAc (4:1, v/v) as eluent to give 4b as
light brown liquid. Yield: 2.97 g (73%); IR (KBr): 3652 cmꢁ1 (OeH),
3071 cmꢁ1 (sp2 CeH), 2952e2844 cmꢁ1 (sp3 CeH), 2094 cmꢁ1
(C^C), 1498 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
synthesis of 7a. Yellow colored solid. Yield: 47%; mp: 105 ꢂC; IR
(KBr): 2953e2918 cmꢁ1 (sp2 CeH), 2847 cmꢁ1 (sp3 CeH),
2102 cmꢁ1 (C^C), 1495 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3,
ppm):
d 8.40 (s, 2H), 8.20 (s, 1H), 8.04e7.96 (m, 3H), 7.53e7.48 (m,
3H), 7.18e7.17 (d, 1H, J¼3.6 Hz), 6.73e6.72 (d, 1H, J¼3.6 Hz),
2.86e2.81 (t, 2H, J¼7.6 Hz), 1.76e1.66 (m, 2H), 1.28 (m, 18H),
0.92e0.88 (t, 3H, J¼6.6 Hz); EIMS m/z (%): 452 (100, Mþ). Anal.
Calcd for C32H36S: C, 84.90; H, 8.02; S, 7.08. Found: C, 84.62; H, 8.09,
S, 7.10.
d
7.00e6.99 (d, 1H, J¼3.3 Hz), 6.62e6.61 (d, 1H, J¼3.6 Hz),
2.78e2.73 (t, 2H, J¼7.5 Hz), 2.64 (s, 1H), 1.61 (m, 6H), 1.28 (m, 20H),
0.93e1.88 (t, 3H, J¼6.6 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d
147.94, 131.94, 123.95, 119.93, 96.77, 75.98, 65.71, 31.95, 31.57,
31.36, 29.67, 29.39, 22.72, 14.15 Hz; HRMS: calcd for C21H34OS:
334.2330, found: 334.2331.
4.2.11. 5-Hexyl-2,20-bithiophene (9a). Compound 9a was synthe-
sized by the same procedure for synthesis of 2a. Light green colored
liquid. Yield: 75%; IR (KBr): 3078 cmꢁ1 (sp2 CeH), 2953e2853 cmꢁ1
(sp3 CeH), 1475e1428 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3,
4.2.7. 2-Ethynyl-5-hexylthiophene (5a). To a solution of 4a (21.35 g,
81 mmol) in THF (200 mL) was added Bu4NF (1.0 M hexane, 28 mL,
28 mmol) at room temperature. The reaction mixture was stirred
for 12 h. The reaction mixture was filtered, and the solvent was
removed under reduced pressure and the residue performed flash
column chromatography on silica gel with hexane as eluent to give
5a as colorless oil. Yield: 10.0 g (64%); IR (KBr): 3288 cmꢁ1 (sp
CeH), 3065 cmꢁ1 (sp2 CeH), 2953e2856 cmꢁ1 (sp3 CeH),
2095 cmꢁ1 (C^C), 1523e1435 cmꢁ1 (C]C); 1H NMR (300 MHz,
ppm):
d 7.24e7.19 (m, 2H), 7.09e6.78 (m, 2H), 6.77e6.76 (d, 1H,
J¼2.7 Hz), 2.91e2.86 (t, 2H, J¼7.3 Hz), 1.81e1.74 (m, 2H), 1.49e1.41
(m, 6H),1.05e1.00 (t, 3H, J¼6.7 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d
145.39, 138.10,134.89, 127.76, 124.80, 123.75, 123.46, 123.04, 31.74,
30.28, 28.93, 22.76, 14.26 Hz; EIMS m/z (%): 250 (100, Mþ).
4.2.12. 5-Dodecyl-2,20-bithiophene (9b). Compound 9b was syn-
thesized by the same procedure for synthesis of 2a. Light green
colored liquid. Yield: 78%; IR (KBr): 3081 cmꢁ1 (sp2 CeH),
2956e2851 cmꢁ1 (sp3 CeH), 1478e1431 cmꢁ1 (C]C); 1H NMR
CDCl3, ppm):
d
7.13e7.12 (d, 1H, J¼3.6 Hz), 6.67e6.66 (d, 1H,
J¼3.6 Hz), 3.31 (s, 1H), 2.83e2.80 (t, 2H, J¼7.6 Hz), 1.71e1.64 (m,
2H), 1.36e1.33 (m, 6H), 0.96e0.91 (t, 3H, J¼6.7 Hz); 13C NMR
(75 MHz, CDCl3, ppm):
d
148.56, 133.09, 123.97, 119.26, 80.42, 31.56,
(300 MHz, CDCl3, ppm): d 7.23e7.19 (m, 2H), 7.09e7.05 (m, 2H),
31.54, 30.17, 28.75, 22.61; EIMS m/z (%): 192 (100, Mþ).
6.77e6.76 (d, 1H, J¼3 Hz), 2.90e2.85 (t, 2H, J¼7.5 Hz), 1.83e1.74 (m,
2H), 1.39 (m, 18H), 1.04e1.00 (t, 3H, J¼6.6 Hz); 13C NMR (75 MHz,
4.2.8. 2-Dodecyl-5-ethynylthiophene (5b). To a solution of KOH
(1.49 g, 27 mmol) and isopropyl alcohol (10 mL), 4b (2.97 g,
9 mmol) in isopropyl alcohol (20 mL) was added dropwise with
stirring for 30 min at 50 ꢂC. And then the temperature of the re-
action mixture increased to 80 ꢂC and stirred for 12 h. After the
completion of reaction, water was added for quenching, and
extracted with ether. The solvent was removed under reduced
pressure and the residue performed flash column chromatography
on silica gel with n-hexane/EtOAc (4:1, v/v) as eluent to give 5b as
light brown color liquid. Yield: 1.63 g (65%); IR (KBr): 3283 cmꢁ1 (sp
CeH), 3063 cmꢁ1 (sp2 CeH), 2951e2858 cmꢁ1 (sp3 CeH),
2093 cmꢁ1 (C^C), 1523e1438 cmꢁ1 (C]C); 1H NMR (300 MHz,
CDCl3, ppm): d 145.34, 138.10, 134.89, 127.73, 124.77, 123.70, 123.41,
122.99, 32.13, 31.78, 29.86, 29.58, 22.90,14.32 Hz; EIMS m/z (%): 334
(100, Mþ).
4.2.13. 5-Bromo-50-hexyl-2,20-bithiophene (10a). Compound 10a
was synthesized by the same procedure for synthesis of 3a. Light
green colored liquid. Yield: 93%; IR (KBr): 3067 cmꢁ1 (sp2 CeH),
2955e2848 cmꢁ1 (sp3 CeH), 1515e1424 cmꢁ1 (C]C); 1H
NMR (300 MHz, CDCl3, ppm):
d 6.97e6.94 (m, 2H), 6.86e6.85
(d, 1H, J¼3.6 Hz), 6.70e6.69 (d, 1H, J¼3.3 Hz), 2.84e2.79 (t,
2H, J¼7.6 Hz), 1.73e1.66 (m, 2H), 1.41e1.35 (m, 6H), 0.95e0.92
(t, 3H, J¼3.4 Hz); 13C NMR (75 MHz, CDCl3, ppm):
CDCl3, ppm):
d
7.12e7.10 (d, 1H, J¼3.6 Hz) 6.65e6.64 (d, 1H,
d 145.93, 139.53, 133.76, 130.50, 124.81, 123.70, 123.01,
J¼3.6 Hz), 3.30 (s, 1H), 2.81e2.76 (t, 2H, J¼7.5 Hz), 1.69e1.65 (m,
110.15, 31.60, 30.20, 28.83, 22.65, 14.17 Hz; EIMS m/z (%): 328
2H), 1.33e1.28 (m, 18H), 0.93e0.88 (t, 3H, J¼6.7 Hz); 13C NMR
(100, Mþ).
(75 MHz, CDCl3, ppm): d 148.60, 133.10, 123.95, 119.19, 80.38, 31.95,
31.56, 31.38, 30.15, 29.66, 29.56, 29.38, 29.04, 22.72, 14.15 Hz; EIMS
4.2.14. 5-Bromo-50-dodecyl-2,20-bithiophene (10b). Compound 10b
was synthesized by the same procedure for synthesis of 3a. Light
green colored liquid. Yield: 93%; IR (KBr): 3069 cmꢁ1 (sp2 CeH),
2953e2844 cmꢁ1 (sp3 CeH), 1518e1421 cmꢁ1 (C]C); 1H NMR
m/z (%): 276 (100, Mþ).
4.2.9. 2-(Anthracen-2-ylethynyl)-5-hexylthiophene (7a). To a solu-
tion of 6 (2.0 g, 7 mmol) in toluene and i-Pr2NH (15 mL) were added
Pd(dppf)2Cl2 (0.3 g, 0.37 mmol) and CuI (0.14 g, 0.73 mmol) at room
temperature. And then 5a (1.54 g, 67.3 mmol) in toluene (15 mL) and
i-Pr2NH (15 mL) were added dropwise to the reaction mixture. The
reaction mixture was stirred for 12 h at 90 ꢂC and then allowed to
reach at room temperature. The reaction mixture was filtered and
the solvent was removed under reduced pressure and the residue
performed flash column chromatography on silica gel with hexane
as eluent to give 7a as yellow solid. Yield: 1.28 g (48%); mp: 128 ꢂC; IR
(KBr): 2956 cmꢁ1 (sp2 CeH), 2848 cmꢁ1 (sp3 CeH), 2096 cmꢁ1
(300 MHz, CDCl3, ppm):
d
6.98e6.95 (t, 2H, J¼4.0 Hz), 6.87e6.86 (d,
1H, J¼3.9 Hz), 6.71e6.70 (d, 1H, J¼3.6 Hz), 2.85e2.80 (t, 2H,
J¼7.6 Hz), 1.78e1.68 (m, 2H), 1.39e1.34 (m, 18H), 0.99e0.95 (t, 3H,
J¼6.6 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d 145.88, 139.58, 133.82,
130.50, 124.82, 123.67, 122.96, 110.17, 32.09, 31.70, 30.26, 29.85,
29.82, 29.73, 29.54, 29.53, 29.25, 22.86, 14.30 Hz; EIMS m/z (%): 413
(100, Mþ).
4.2.15. 4-(50-Hexyl-2,20-bithiophen-5-yl)-2-methylbut-3-yn-2-ol
(11a). Compound 11a was synthesized by the same procedure
for synthesis of 4b. Light brown colored solid. Yield: 82%; mp:
165 ꢂC; IR (KBr): 3654 cmꢁ1 (OeH), 3075 cmꢁ1 (sp2 CeH),
2951e2842 cmꢁ1 (sp3 CeH), 2098 cmꢁ1 (C^C), 1496 cmꢁ1 (C]C);
(C^C), 1465 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
d 8.40 (s,
2H), 8.20 (s, 1H), 8.03e7.96 (m, 3H), 7.51e7.48 (m, 3H), 7.19e7.18 (d,
1H, J¼3.6 Hz), 6.73e6.72 (d, 1H, J¼3.6 Hz), 2.86e2.81 (t, 2H,
J¼7.5 Hz), 1.76e1.66 (m, 2H), 1.38e1.34 (m, 6H), 0.95e0.90 (t, 3H,
J¼6.7 Hz); EIMS m/z (%): 368 (100, Mþ). Anal. Calcd for C26H24S: C,
84.74; H, 6.56; S, 8.70. Found: C, 84.71; H, 6.47, S, 8.76.
1H NMR (300 MHz, CDCl3, ppm):
d
7.07e7.06 (d, 1H, J¼3.6 Hz),
6.99e6.98 (d, 1H, J¼3.3 Hz), 6.95e6.93 (d, 1H, J¼3.9 Hz), 6.69e6.68
(d, 1H, J¼3.6 Hz), 2.82e2.77 (t, 2H, J¼7.5 Hz), 2.19 (s, 1H), 1.71e1.66
(m, 2H), 1.63 (s, 6H), 1.37e1.32 (m, 6H), 0.93e0.89 (t, 3H, J¼6.7 Hz);
4.2.10. 2-(Anthracen-2-ylethynyl)-5-dodecylthiophene
13C NMR (75 MHz, CDCl3, ppm):
d 146.18, 139.37, 134.03, 132.84,
(7b). Compound 7b was synthesized by the same procedure for
124.88, 123.90, 122.51, 120.48, 98.14, 65.85, 31.56, 31.33, 30.18,

8198
B. Shaik et al. / Tetrahedron 69 (2013) 8191e8198
28.75, 22.58, 14.10 Hz; HRMS: calcd for C19H24OS2: 332.1269,
found: 332.1267.
CDCl3, ppm): d 8.41 (s, 2H), 8.22 (s, 1H), 8.04e7.97 (m, 3H),
7.53e7.49 (m, 3H), 7.24e7.23 (d, 1H, J¼3.9 Hz), 7.05e7.02 (dd, 2H,
J¼3.6, 3.9 Hz), 6.72e6.71 (d, 1H, J¼3.6 Hz), 2.85e2.79 (t, 2H,
J¼7.6 Hz), 1.75e1.65 (m, 2H), 1.28 (m, 18H), 0.92e0.87 (t, 3H,
J¼6.7 Hz); EIMS m/z (%): 534 (100, Mþ). Anal. Calcd for C36H38S2: C,
80.85; H, 7.16; S, 11.99. Found: C, 80.81; H, 7.11, S, 11.92.
4.2.16. 4-(50-Dodecyl-2,20-bithiophen-5-yl)-2-methylbut-3-yn-2-ol
(11b). Compound 11b was synthesized by the same procedure for
synthesis of 4b. Light brown colored solid. Yield: 73%; mp: 189 ꢂC;
IR (KBr): 3652 cmꢁ1 (OeH), 3079 cmꢁ1 (sp2 CeH),
2956e2848 cmꢁ1 (sp3 CeH), 2094 cmꢁ1 (C^C), 1496 cmꢁ1 (C]C);
Acknowledgements
1H NMR (300 MHz, CDCl3, ppm):
d
7.07e7.06 (d, 1H, J¼3.6 Hz),
6.99e6.98 (d, 1H, J¼3.6 Hz), 6.95e6.93 (d, 1H, J¼3.6 Hz), 6.69e6.68
(d, 1H, J¼3.6 Hz), 2.82e2.77 (t, 2H, J¼7.5 Hz), 2.09 (s, 1H), 1.73e1.63
(m, 6H), 1.40e1.28 (m, 18H), 0.92e0.88 (t, 3H, J¼6.6 Hz); 13C NMR
This research was supported by the Basic Science Research
Program through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(Grant Number: 2010-0023775).
(75 MHz, CDCl3, ppm):
d 146.20, 139.38, 134.02, 132.85, 124.89,
123.90, 122.51,120.44, 98.09, 65.84, 31.95, 31.33, 29.66, 29.57, 29.38,
22.72, 14.17; HRMS: calcd for
416.2205.
C25H36OS2: 416.2208, found:
Supplementary data
HRMS and elemental analysis data are included. Supplementary
data associated with this article can be found in the online version,
at http://dx.doi.org/10.1016/j.tet.2013.07.041.
4.2.17. 5-Ethynyl-50-hexyl-2,20-bithiophene (12a). Compound 12a
was synthesized by the same procedure for synthesis of 5b. Brown
colored liquid. Yield: 84%; IR (KBr): 3281 cmꢁ1 (sp CeH), 3065 cmꢁ1
(sp2 CeH), 2948e2860 cmꢁ1 (sp3 CeH), 2091 cmꢁ1 (C^C),
1525e1441 cmꢁ1 (C]C); 1H NMR (300 MHz, CDCl3, ppm):
References and notes
d
7.18e7.17 (d, 1H, J¼3.6 Hz), 7.02e7.01 (d, 1H, J¼3.6 Hz), 6.97e6.95
1. Lim, E.; Jung, B.-J.; Shim, H.-K. J. Polym. Sci., Part A: Polym. Chem. 2005, 44, 243.
2. Lee, J.; Cho, H. J.; Cho, N. S.; Hwang, D.-H.; Kang, J.-M.; Lim, E.; Lee, J.-I.; Shim,
H.-K. J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 2943.
3. Yang, R.; Tian, R.; Hou, Q.; Zhang, Y.; Li, Y.; Yang, W.; Zhang, C.; Cao, Y. J. Polym.
Sci., Part A: Polym. Chem. 2005, 43, 823.
4. Katz, H. E.; Bao, Z.; Gilat, S. L. Acc. Chem. Res. 2001, 34, 359.
5. Horowitz, G. Adv. Mater. 1998, 10, 365.
6. Brabec, C. J.; Sariciftci, N. S.; Hummelen, J. C. Adv. Funct. Mater. 2001, 11, 15.
7. Lee, J.; Jung, B. J.; Lee, S. K.; Lee, J. I.; Cho, H. J.; Shim, H. K. J. Polym. Sci., Part A:
Polym. Chem. 2005, 43, 1845.
8. Linrun, F.; Xiaoli, X.; Xiaojun, G. ECS Trans. 2011, 37, 105.
9. Fujisaki, Y.; Nakajima, Y.; Takei, T.; Fukagawa, H. IEEE Trans. Electron Devices
2012, 59, 3442.
10. Orgiu, E.; Masillamani, A.; Vogel, J.-O.; Treossi, E.; Kiersnowski, A.; Kastler, M.;
Pisula, W.; Doetz, F.; Palermo, V.; Samori, P. Chem. Commun. 2012, 1562.
11. Youn, J.; Huang, P.; Huang, Y.; Chen, M.; Lin, Y.-J.; Huang, H.; Ortiz, R. P.; Stern,
C.; Chung, M.-C.; Feng, C.-Y. Adv. Funct. Mater. 2012, 22, 48.
12. Sunhee, P.; Jaemin, L.; Jung, M. K.; Hyun, S. L.; Jongsun, L.; Seung, H. C.; Jun, Y. L.;
Changjin, L. Mol. Cryst. Liq. Cryst. 2009, 504, 52.
(d, 1H, J¼3.96 Hz), 6.71e6.70 (d, 1H, J¼3.6 Hz), 3.41 (s, 1H),
2.84e2.79 (t, 2H, J¼7.5 Hz), 1.75e1.65 (m, 2H), 1.41e1.30 (m, 6H),
0.96e0.91 (t, 3H, J¼6.6 Hz); 13C NMR (75 MHz, CDCl3, ppm):
d
146.40, 139.88, 133.91, 133.86, 124.93, 124.14, 122.42, 119.81, 81.95,
31.59, 30.21, 28.79, 22.62, 14.13 Hz; EIMS m/z (%): 274 (100, Mþ).
4.2.18. 5-Dodecyl-50-ethynyl-2,20-bithiophene
(12b). Compound
12b was synthesized by the same procedure for synthesis of 5b.
Brown colored liquid. Yield: 66%; IR (KBr): 3286 cmꢁ1 (sp CeH),
3069 cmꢁ1 (sp2 CeH), 2954e2847 cmꢁ1 (sp3 CeH), 2096 cmꢁ1
(C^C), 1496 cmꢁ1 (C]C), 789 cmꢁ1 (sp2 CeH); 1H NMR (300 MHz,
CDCl3, ppm):
d
7.17e7.16 (d, 1H, J¼3.8 Hz), 7.01e7.00 (d, 1H,
J¼3.6 Hz), 6.96e6.94 (d, 1H, J¼3.8 Hz), 6.70e6.69 (d, 1H, J¼3.6 Hz),
3.40 (s, 1H), 2.82e2.77 (t, 2H, J¼7.5 Hz), 1.71e1.54 (m, 2H),
1.34e1.27 (m, 18H), 0.92e0.87 (t, 3H, J¼7.5 Hz); 13C NMR (75 MHz,
13. Ong, B. S.; Wu, Y.; Li, Y.; Liu, P.; Pan, H. Chem.dEur. J. 2008, 14, 4766.
14. Kong, H.; Chung, D. S.; Kang, I.-N.; Lim, E.; Jung, Y. K.; Park, J.-H.; Park, C. E.;
Shim, H.-K. Bull. Korean Chem. Soc. 2007, 28, 1945.
CDCl3, ppm):
d 146.4, 139.8, 133.9, 133.8, 124.9, 124.1, 122.4, 119.7,
15. Inoue, Y.; Tokito, S.; Ito, K.; Suzuki, T. J. Appl. Phys. 2004, 95, 5795.
16. Meng, H.; Sun, F.; Goldfinger, M. B.; Gao, F.; Londono, D. J.; Marshal, W. J.;
Blackman, G. S.; Dobbs, K. D.; Keys, D. E. J. Am. Chem. Soc. 2006, 128, 9304.
17. He, Z.; Xiao, K.; Durant, W.; Hensley, D. K.; Anthony, J. E.; Hong, K.; Kilbey, S. M.;
Chen, J.; Li, D. Adv. Funct. Mater. 2011, 21, 3617.
18. Yuan, G.-C.; Lu, Z.; Xu, Z.; Gong, C.; Qun-Liang Song, Q.-L.; Zhao, S.-L.; Zhang,
F.-J.; Xua, N.; Gan, Y.; Yang, H.-B.; Li, C.-M. Org. Electron. 2009, 10, 1388.
19. Kwon, J.; Hong, J.-P.; Lee, W.; Noh, S.; Lee, C.; Lee, S.; Hong, J.-I. Org. Electron.
2010, 11, 1103.
82.9, 81.9, 31.9, 31.6, 30.1, 29.6, 29.5, 29.3, 29.0, 22.7, 14.1 Hz; HRMS:
calcd for C22H30S2: 358.1789, found: 358.1786.
4.2.19. 5-(Anthracen-2-ylethynyl)-50-hexyl-2,20-bithiophene
(13a). Compound 13a was synthesized by the same procedure for
synthesis of 7a. Yellow colored solid. Yield: 52%; mp: 195 ꢂC; IR
(KBr): 2919e2953 cmꢁ1 (sp2 CeH), 2850 cmꢁ1 (sp3 CeH),
2098 cmꢁ1 (C^C), 1604e1517 cmꢁ1 (C]C); 1H NMR (300 MHz,
20. Tszydel, I.; Kucinska, M.; Marszalek, T.; Rybakiewicz, R.; Nosal, A.; Jung, J.;
Gazicki-Lipman, M.; Pitsalidis, C.; Gravalidis, C. Adv. Funct. Mater. 2012, 22,
3840.
CDCl3, ppm):
d 8.41 (s, 2H), 8.22 (s, 1H), 8.03e7.97 (m, 3H),
7.52e7.49 (m, 3H), 7.24e7.23 (d, 1H, J¼3.6 Hz), 7.05e7.03 (dd, 2H,
J¼3.6 Hz, J¼3.9 Hz), 6.72e6.71 (d, 1H, J¼3.6 Hz), 2.85e2.80 (t, 2H,
J¼7.6 Hz), 1.73e1.66 (m, 2H), 1.36e1.27 (m, 6H), 0.92e0.90 (t, 3H,
J¼3.1 Hz); EIMS m/z (%): 450 (100, Mþ). Anal. Calcd for C30H26S2: C,
79.95; H, 5.82; S, 14.23. Found: C, 79.79; H, 5.73, S, 14.24.
21. Kim, S.-O.; An, T. K.; Chen, J.; Kang, I. I.; Kang, S. H.; Chung, D. S.; Park, C. E.; Kim,
Y.-H.; Kwon, S.-K. Adv. Funct. Mater. 2011, 21, 1616.
22. Hwang, M. J.; Park, J. H.; Jeong, E. B.; Kang, I. L.; Lee, D. H.; Park, C. E.; Singh, O.
M.; Choi, H. J.; Kim, Y.-H.; Yoon, Y. J. Bull. Korean Chem. Soc. 2012, 33, 3810.
23. Menzel, H.; Weichart, B.; Schmidt, A.; Paul, S.; Knoll, W.; Stumpe, J.; Fischer, T.
Langmuir 1994, 10, 1926.
24. (a) Spano, F. C. Annu. Rev. Phys. Chem. 2006, 57, 217; (b) Meinardi, F.; Cerminara,
M.; Sassella, A.; Bonifacio, R.; Tubino, R. Phys. Rev. Lett. 2003, 91, 247401.
25. Spano, F. C. Acc. Chem. Res. 2010, 43, 429.
4 . 2 . 2 0 . 5 - ( A n t h r a c e n - 2 - y l e t h y n y l ) - 5 0- d o d e c y l - 2 , 2 0-
bithiophene (13b). Compound 13b was synthesized by the same
procedure for synthesis of 7a. Light brown colored solid. Yield: 45%;
mp: 191 ꢂC; IR (KBr): 2928e2959 cmꢁ1 (sp2 CeH), 2864 cmꢁ1 (sp3
CeH), 2095 cmꢁ1 (C^C), 1495 cmꢁ1 (C]C); 1H NMR (300 MHz,
26. Drolet, N.; Morin, J.-F.; Leclerc, N.; Wakim, S.; Tao, Y.; Leclerc, M. Adv. Funct.
Mater. 2005, 15, 1671.
27. Coleman, R. S.; Mortensen, M. A. Tetrahedron Lett. 2003, 44, 1215.
28. Tao, X.-C.; Zhou, W.; Zhang, Y.-P.; Dai, C.-Y.; Shen, D.; Huang, M. Chin. J. Chem.
2006, 24, 939.