Synthesis and liquid crystal properties of a novel family of oligothiophene derivatives

Article abstract of DOI:10.1016/j.tet.2004.04.029

In order to develop novel oligothiophene-based liquid crystals capable of hydrogen bonding, new terthiophene derivatives containing an alkylamide group, N,N′-dialkyl-5,5″-dichloro-2,2′:5′,2″- terthiophene-4,4″-dicarboxamide (DNC_nDCl3T, n=8, 18)

Full text of DOI:10.1016/j.tet.2004.04.029

Tetrahedron 60 (2004) 5259–5264
Synthesis and liquid crystal properties of a novel family of
oligothiophene derivatives
a
a
a
a
a
Ping Liu,a Yamin Zhang, Guiju Feng, Jianhua Hu, Xiaoping Zhou, Qizhong Zhao,
,
*
Yunhua Xu,b Zhen Tonga and Wenji Dengb
aPolymer Structure and Modification, Research Institute of Materials Science, South China University of Technology,
Guangzhou 510640, China
bDepartment of Applied Physics, South China University of Technology, Guangzhou 510640, China
Received 10 September 2003; revised 29 March 2004; accepted 5 April 2004
Abstract—In order to develop novel oligothiophene-based liquid0 crystals capable of 00hydrogen bonding, new terthiophene derivatives
containing an alkylamide group, N,N0-dialkyl-5,500-dichloro-2,20:5 ,200-terthiophene-4,4 -dicarboxamide (DNCnDCl3T, n¼8, 18), N,N0-
dialkyl-5,500-dibromo-2,20:50,200-terthiophene-4,400-dicarboxamide (DNCnDBr3T, n¼5, 8, 16, 18), or N,N0-dialkyl-5,500-diiodo-2,20:50,200-
terthiophene-4,400-dica-rboxamide (DNCnDI3T, n¼8, 18), were designed and synthesized, and their thermal behaviour was examined. It was
found that DNC18DCl3T, DNC18DI3T and DNCnDBr3T (n¼8, 16, 18) form a smectic A phase and that the alkyl chain length greatly affects
liquid crystal phase formation. The absence of liquid crystallinity in the corresponding ester derivatives suggests that intermolecular
hydrogen bonding also plays a role in the formation of a liquid crystal phases in the DNCnDBr3T system.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
appeared.17–20 It has been reported that terthiophenes
substituted with long alkyl or alkanoyl groups at the
terminal a- and a00-positions, for example, 5-alkyloxy-
carbony0l0-500-alkyl-2,20:50,200-terthiophenes and 5,500-dialkyl-
2,20:50,2 -terthiophenes exhibit a smectic liquid crystalline
phase. Both 5-substituted and 5000-disubstituted quarter-
thiophenes have also been reported to exhibit smectic and
nematic liquid crystalline phases. However, examples of
oligothiophene-based liquid crystals are still scarce.
Oligothiophenes with well defined structures have recently
received a great deal of attention not only as model
compounds for conducting polythiophenes, but also as a
new class of functional p-electron systems. A variety of
oligothiophenes have been synthesized1 and their molecular
and crystal structures,2,3 self ordering,4,5 electrochemical,6,7
photophysical,8,9 optical,10,11 and electrical properties,12,13
have all been studied. In addition, their potential application
in field-effect transistors,14 photovoltaic devices,15 and
organic electroluminescent devices16 has been investigated.
This paper reports on the synthesis of new compounds
containing a0 terthiophene moiety, N,N0-dialkyl-5,500-
dichloro-2,2 :50,200-terthiophene-4,400-dicarboxamide
(DNCnDCl3T, n¼8, 18), N,N0-dialkyl-5,500-dibromo-
2,20:50,200-terthiophene-4,400-dicarboxamide (DNCnDBr3T,
n¼5, 8, 16, 18), or N,N0-dialkyl-5,500-diiodo-2,20:50,200-
terthiophene-4,400-dicarboxamide (DNCnDI3T, n¼8, 18)
(Scheme 1), and their liquid crystal properties. The
relationship between molecular structure and liquid crystal-
line behaviour is discussed.
Oligothiophenes are crystalline compounds because of their
planar molecular structures and both vacuum-evaporated
and spin-coated films of oligothiophenes have been reported
to be polycrystalline. Since the properties and functionality
of a material are greatly affected by its morphology, it is of
both fundamental and technological interest to exert control
over the morphology of oligothiophenes in the design of
novel functional organic materials.
Recently, several reports regarding the liquid crystalline
properties of oligothiophene derivatives have
2. Results and discussion
Novel families of oligothiophene derivatives containing an
alkylamide group at the b- and b0-position of 2,20:50,200-
terthiophene, DNCnDCl3T (n¼8, 18), DNCnDBr3T (n¼5,
8, 16, 18) and DNCnDI3T (n¼8, 18), were synthesized
according to the procedures shown in the Scheme 2. All
Keywords: Oligothiophene derivatives; Liquid crystal; Intermolecular
hydrogen bonding.
*
Corresponding author. Tel.: þ86-20-87111686;
e-mail address: mcpliu@scut.edu.cn
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.04.029

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P. Liu et al. / Tetrahedron 60 (2004) 5259–5264
Scheme 1.
Scheme 2.
compounds were characterized by IR and 1H NMR
spectroscopy, mass spectrometry, and elemental analysis.
The effects of the alkyl chain length in the alkylamido group
on liquid crystalline behaviour were investigated. Like
DNC18DBr3T, DNC16DBr3T was found to form a SmA
phase. In addition, DNC16DBr3T exhibited crystal
DSC and polarized light microscopy performed on DNC18-
DCl3T, DNCnDBr3T (n¼8, 16, 18) and DNC18DI3T
revealed that these compounds, containing two alkylamide
groups at the b- and b0-position of 3T, formed a smectic A
(SmA) phase. Figure 1 shows the polarizing micrograph of
the DNC18DCl3T, DNC18DBr3T and DNC18DI3T SmA
phase formed from the isotropic liquid in the cooling
process. A focal-conic fan texture typical of a SmA phase
was clearly observed.
The formation of a SmA phase by DNC18DCl3T, DNC18-
DBr3T and DNC18DI3T was also evidenced by DSC.
Figure 2 shows the DSC curves for DNC18DBr3T. When the
crystalline sample of DNC18DBr3T was heated, an
endothermic peak was observed at 110 8C to give a smectic
A phase. Upon further heating, the onset of the transition
from a SmA phase into the isotropic liquid was observed at
121 8C. When the isotropic liquid was cooled, the onset of
the transition into a SmA phase was observed at approxi-
mately 123 8C. The SmA phase crystallized at 107 8C. The
trace was reproducible.
Figure 1. Photomicrograph of the texture of the SmA phase of DNC18-
DCl3T, DNC18DBr3T and DNC18DI3T obtained on cooling the melt. (a):
DNC18DCl3T; (b): DNC18DBr3T; (c): DNC18DI3T (magnification£200).

P. Liu et al. / Tetrahedron 60 (2004) 5259–5264
5261
that the alkylamide groups in the b- and b0-position of 3T
play an important role in the formation of liquid crystal
phases in the DNCnDBr3T system. Table 1 summarizes the
transition temperatures of DNC18DCl3T, DNCnDBr3T
(n¼8, 16, 18) and DNC18DI3T, together with the enthalpy
changes (DH) associated with the phase transitions.
It is suggested that intermolecular hydrogen bonding
between the amido groups is involved in liquid crystal
phase formation. The presence of intermolecular hydrogen
bonding was evidence by infrared (IR) absorption spec-
troscopy. Figure 3 shows the IR absorption spectra of
DNC18DBr3T in its crystalline and liquid crystalline phases
in the wavelength region of the N–H stretching vibration
mode. The crystalline sample showed only a broad
absorption at around 3300 cm21, which is attributable to
the stretching vibration of hydrogen-bonded N–H groups.
The liquid crystalline sample showed both the hydrogen
bonded absorption band and a sharp absorption peak at
3419 cm21 that is attributable to the free N–H groups. The
spectrum of the isotropic liquid was almost identical to that
of the liquid crystal. The changes in the IR absorption
spectra between the crystal and the liquid crystal phases
during both heating and cooling were reproducible. This
indicates that the molecules in the SmA phase only partly
forms intermolecular hydrogen bonds, whereas in the
crystal phase all the molecules are fixed tightly by the
intermolecular hydrogen bonding. Partial intermolecular
hydrogen bonding interactions may play a role in the
formation of liquid crystal phases in the DNCnDBr3T
system.
Figure 2. DSC curves for DNC18DBr3T.
polymorphism, showing two different crystal forms. In
contrast, with DNC8DBr3T, the formation of a liquid
crystalline phase did not occur on heating. However, a SmA
phase appeared on cooling in the temperature range from
about 126–109 8C, as observed by polarized light
microscopy.
It is noteworthy that DNC8DCl3T DNC5DBr3T, and
DNC8DI3T did not form liquid crystal phase, and showed
only the phase transition between the crystal and the
isotropic liquid, as revealed by DSC and polarized light
microscopy. The absence of a liquid crystalline phase for
DNC8DCl3T, DNC5DBr3T and DNC8DI3T is thought to be
because there are strong hydrogen bonding interactions in
these molecules, and they thus favor direct crystallization
from the isotropic liquid.
In order to gain information on the importance of the amide
group in the formation of liquid crystal phases, the thermal
behavior of the corresponding ester compounds, DOCn-
DBr3T (n¼5, 8, 16, 18) were examined. It was found that
DOCnDBr3T (n¼5, 8, 16, 18) did not exhibit a liquid
crystalline phase, showing only melting and crystallization
behavior upon heating and cooling. These results indicate
Table 1. Transition temperatures and enthalpy changes of DNC18DCl3T,
DNCnDBr3T (n¼8, 16, 18) and DNC18DI3T
Compound
Transition temperature (8C); enthalpy change (in
parentheses) (kJ mol21
)
DNC18DCl3Ta
DNC8DBr3Tb
DNC16DBr3Tc
DNC18DBr3Ta
DNC18DI3Ta
K
K
K
K
K
114(43)
109(—)
110(46)
107(56)
130(62)
SmA
SmA
SmA
SmA
SmA
121(3.3)
126(—)
127(3.6)
123(3.7)
143(4.3)
I
I
I
I
I
K: crystal, SA: smectic A liquid crystal, I: isotropic liquid.
a
Transition temperatures and enthalpy changes were determined by DSC
upon cooling.
Transition temperatures and enthalpy changes were determined by
polarized light microscopy.
Transition temperatures and enthalpy changes were determined by DSC
upon heating.
b
c
Figure 3. Infrared absorption spectra of DNC18DBr3T; (a) crystal at
100 8C; (b) SmA phase at 120 8C formed on heating the crystal.

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P. Liu et al. / Tetrahedron 60 (2004) 5259–5264
3. Conclusion
pressure to give DNC8DCl3T. The product was purified by
silica gel column chromatography using chloroform as the
eluent (yield 62% based on 5,500-dichloro-2,20:50,200-terthio-
A novel family of terthiophene derivatives containing an
alkylamide group, DNCnDCl3T, (n¼8, 18), DNCnDBr3T,
(n¼5, 8, 16, 18) or DNCnDI3T, (n¼8, 18), were designed
and synthesized. DNC18DCl3T, DNCnDBr3T, (n¼8, 16,
18) and DNC18DI3T, were found to form a SmA phase,
thereby constituting a new class of oligothiophene-based
liquid crystals. It was shown that the alkyl chain length
greatly affected liquid crystal phase formation. The absence
of liquid crystallinity for DOCnDBr3T and changes in the IR
spectra suggest that the alkylamide group is involved in
liquid crystal phase formation in the DNCnDBr3T.
00
1
phene-4,4 -dicarboxylic acid). H NMR (400 MHz, THF-
d8): d (ppm)¼7.34 (s, 2H, ArH), 7.30 (t, 2H, NH), 7.29 (s,
2H, ArH), 3.36 (dt, 4H, octyl a-CH2), 1.60 (tt, 4H, octyl
b-CH2), 1.47–1.22 (m, 20H, octyl CH2), 0.88 (t, 6H, CH3).
IR (KBr, cm21): 3301 (nN–H), 2956, 2922, 2855 (nC–H),
1623 (nCvO). MS(EI): m/z 628 (Mþ). Elemental analysis:
found C 57.49, H 6.40, N 4.38%. Calcd for C30H40N2S3-
O2Cl2 C 57.40, H 6.42, N 4.47%.
The DNC18DCl3T was synthesized using analogous pro-
cedures with stearylamine (yield 55%). 1H NMR (400 MHz,
THF-d8): d (ppm)¼7.33 (s, 2H, ArH), 7.32 (t, 2H, NH), 7.26
(s, 2H, ArH), 3.39 (dt, 4H, stearyl a-CH2), 1.61 (tt, 4H,
stearyl b-CH2), 1.45–1.23 (m, 60H, stearyl CH2), 0.88 (t,
6H, CH3). IR (KBr, cm21): 3311 (nN–H), 2958, 2919, 2847
(nC–H), 1618 (nCvO). MS(EI): m/z 908 (Mþ). Elemental
analysis: found C 66.03, H 9.01, N 3.15%. Calcd for
C50H80N2S3O2Cl2 C 66.12, H 8.88, N 3.08%.
4. Experimental
4.1. Synthesis
2-Bromothiophene,2,5-dibromothiophene,[1,3-bis-(di-
phenyphosphino) propane] nickel(II) chloride (NiCl2-
(dppp), magnesium, diisopropylamine, butyllithium
(hexane solution), thionyl chloride, triethylamine, mono-
alkylamines (CnH2nþ1NH2, n¼5, 8, 16, 18), and 1-iodo-
alkanes (CnH2nþ1I, n¼5, 8, 16, 18) were commercially
available and used without further purification. 2,20:50,200-
Terthiophene (3T) was prepared by the Grignard coupling
reaction of 2,5-dibromothiophene with 2-bromo-
magnesiumthiophene in ether at refluxing. Synthetic
procedures are illustrated in the Scheme 2.
4.1.2. Synthesis of N,N0-dialkyl-5,500-dibromo-2,20:50,200-
terthiophene-4,400-dicarboxamide (DNCnDBr3T, n55, 8,
16, 18). 5,500-Dibromo-2,20:50,200-terthiophene (DBr3T) was
prepared by the reaction of 3T (3.5 g, 14.1 mmol) with
N-bromosuccinimide (5.0 g, 28.2 mmol) in chloroform
(200 mL) at room temperature for 5 h and purified by silica
gel column chromatography using chloroform as eluent,
followed by recrystallization from a benzene/hexane
mixture (1:2 v/v).
4.1.1. Synthesis of N,N0-dialkyl-5,500-dichloro-2,20:50,200-
terthiophene-4,400-dicarboxamide (DNCnDCl3T, n58,
18). 5,500-Dichloro-2,20:50,200-terthiophene (DCl3T) was
prepared by the reaction of 3T (3.0 g, 12.1 mmol) with
N-chlorosuccinimide (3.2 g, 24.2 mmol) in chloroform
(200 mL) at room temperature for 5 h and purified by silica
gel column chromatography using chloroform as eluent,
followed by recrystallization from a benzene/hexane
mixture (1:2 v/v).
DBr3T (2.8 g, 6.89 mmol), was added to a THF solution
(50 mL) of LDA (27.44 mmol) at 278 8C and the solution
was stirred for 1 h. Excess dry ice was added to the
solution and the resulting mixture was stirred for 2 h. The
solution was allowed to warm to room temperature and
aqueous hydrochloric acid was added. After stirring for 5 h,
the resulting solid was 00collected and wa0s0hed with hot
acetonitrile to give 5,5 -dibromo-2,20:50,2 -terthiophene-
4,400-dicarboxylic acid (yield 65% based on DBr3T).
A hexane solution of butyllithium was added to a THF
solution of diisopropylamine at 278 8C under a nitrogen
atmosphere to give lithium diisopropylamine (LDA).
DCl3T (3.0 g, 9.46 mmol), was added to a THF solution
(50 mL) of LDA (37.84 mmol) at 278 8C and the solution
was stirred for 1 h. Excess dry ice was added to the
solution and the resulting mixture was stirred for 2 h. The
solution was allowed to warm to room temperature
and aqueous hydrochloric acid was added. After stirring
for 5 h, the resulting solid was 00collected and washed
with hot acetonitrile to give 5,5 -dichloro-2,20:50,200-ter-
thiophene-4,400-dicarboxylic acid (yield 65% based on
DCl3T).
A dichloromethane solution (100 mL) of 5,500-dibromo-
2,20:50,200-terthiophene-4,400-dicarboxylic acid (1.0 g,
2.0 mmol) and SOCl2 (0.48 g, 4.0 mmol) was heated at
reflux for 8 h. After the solvent was removed under reduced
pressure, the resulting solid was added to a THF solution
(100 mL) of amylamine (0.35 g, 4.0 mmol) in the presence
of triethylamine (2.3 mL) at 0 8C and the solution was
stirred for 5 h at 0 8C. The solvent was removed under
reduced pressure to give DNC5DBr3T. The product was
purified by silica gel column chromatography us0i0ng chloro-
form as the eluent (yield 71% based on 5,5 -dibromo-
2,20:50,200-terthiophene-4,400-dicarboxylic acid). 1H NMR
(600 MHz, THF-d8): d (ppm)¼7.35 (s, 2H, ArH), 7.32 (t,
2H, NH), 7.28 (s, 2H, ArH), 3.36 (dt, 4H, pentyl a-CH2),
1.60 (tt, 4H, pentyl b-CH2), 1.45–1.33 (m, 8H, pentyl CH2),
0.88 (t, 6H, CH3). IR (KBr, cm21): 3388 (nN–H), 2958,
2927, 2859 (nC–H), 1625 (nCvO). MS(EI): m/z 632 (Mþ).
Elemental analysis: found C 45.65, H 4.44, N 4.47%. Calcd
for C24H28N2S3O2Br2 C 45.58, H 4.46, N 4.43%.
A dichloromethane solution (100 mL) of 5,500-dichloro-
2,20:50,200-terthiophene-4,400-dicarboxylic acid (1.0 g,
2.47 mmol) and SOCl2 (0.59 g, 4.94 mmol) was heated at
reflux for 8 h. After the solvent was removed under reduced
pressure, the resulting solid was added to a THF solution
(100 mL) of octylamine (0.64 g, 4.94 mmol) in the presence
of triethylamine (2.5 mL) at 0 8C and the solution stirred for
5 h at 0 8C. The solvent was removed under reduced
The DNC8DBr3T, DNC16DBr3T and DNC18DBr3T were

P. Liu et al. / Tetrahedron 60 (2004) 5259–5264
5263
synthesized using analogous procedures with octylamine,
1-hexadecylamine, or stearylamine (yields 55–63%).
(tt, 4H, octyl b-CH2), 1.47–1.24(m, 20H, octyl CH2), 0.88
(t, 6H, CH3). IR (KBr, cm21): 3303 (nN–H), 2957, 2922,
2854 (nC – H), 1624 (nCvO). MS(EI): m/z 810 (Mþ).
Elemental analysis: found C 44.18, H 5.05, N 3.43%.
Calcd for C30H40N2S3O2I2 C 44.45, H 4.97, N 3.46%.
DNC8DBr3T: 1H NMR (600 MHz, THF-d8): d (ppm)¼7.36
(s, 2H, ArH), 7.31 (t, 2H, NH), 7.28 (s, 2H, ArH), 3.38 (dt,
4H, octyl a-CH2), 1.61 (tt, 4H, octyl b-CH2), 1.46–1.23 (m,
20H, octyl CH2), 0.88 (t, 6H, CH3). IR (KBr, cm21): 3302
(nN–H), 2958, 2923, 2853 (nC–H), 1625 (nCvO). MS(EI):
m/z 716 (Mþ). Elemental analysis: found C 50.38, H 5.60, N
3.96%. Calcd for C30H40N2S3O2Br2 C 50.28, H 5.63, N 3.91%.
The DNC18DI3T was synthesized using analogous pro-
cedures with stearylamine (yield 72%). 1H NMR (400 MHz,
THF-d8): d (ppm)¼7.32 (s, 2H, ArH), 7.30 (t, 2H, NH), 7.27
(s, 2H, ArH), 3.36 (dt, 4H, stearyl a-CH2), 1.60 (tt, 4H,
stearyl b-CH2), 1.43–1.21 (m, 60H, stearyl CH2), 0.88 (t,
6H, CH3). IR (KBr, cm21): 3313 (nN–H), 2957, 2916, 2850
(nC–H), 1617 (nCvO). MS(EI): m/z 1091 (Mþ). Elemental
analysis: found C 54.98, H 7.45, N 2.54%. Calcd for
C50H80N2S3O2I2 C 55.04, H 7.39, N 2.57%.
DNC16DBr3T: 1H NMR (600 MHz, THF-d8):
d
(ppm)¼7.35 (s, 2H, ArH), 7.32 (t, 2H, NH), 7.29 (s, 2H,
ArH), 3.34 (dt, 4H, cetyl a-CH2), 1.58 (tt, 4H, cetyl b-CH2),
1.48–1.15 (m, 52H, cetyl CH2), 0.88 (t, 6H, CH3). IR (KBr,
cm21): 3328 (nN–H), 2948, 2921, 2850 (nC–H), 1619
(nCvO). MS(EI): m/z 941 (Mþ). Elemental analysis: found
C 58.74, H 7.64, N 3.01%. Calcd for C46H72N2S3O2Br2 C
58.71, H 7.71, N 2.98%.
4.1.4. Synthesis of 4,400-bis-(alkyloxycarbonyl)-5,500-
dibromo-2,20:50,200-terthiophene (DOCnDBr3T, n55, 8,
16, 18). 5,500-Dibromo-2,20:50,200-terthiophene-4,400-di-
carboxylic acid (0.5 g, 1.0 mmol) was reacted with
1-iodopentane (0.40 g, 2.0 mmol) in the presence of
potassium carbonate (0.20 g, 1.5 mmol) in hexamethyl-
phosphorotriamide (20 mL) at room temperature for 24 h
under a nitrogen atmosphere. The resulting solid was
collected to give DOC5DBr3T. The product was purified
by silica gel column chromatography using chloroform as
DNC18DBr3T: 1H NMR (600 MHz, THF-d8):
d
(ppm)¼7.35 (s, 2H, ArH), 7.31 (t, 2H, NH), 7.28 (s, 2H,
ArH), 3.38 (dt, 4H, stearyl a-CH2), 1.60 (tt, 4H, stearyl
b-CH2), 1.45–1.22 (m, 60H, stearyl CH2), 0.88 (t, 6H,
CH3). IR (KBr, cm21): 3312 (nN–H), 2956, 2918, 2849
(nC–H), 1619 (nCvO). MS(EI): m/z 997 (Mþ). Elemental
analysis: found C 60.36, H 8.00, N 2.79%. Calcd for
C50H80N2S3O2Br2 C 60.22, H 8.09, N 2.81%.
1
the eluent (yield 91%). H NMR (400 MHz, THF-d8): d
(ppm)¼7.45 (s, 2H, ArH), 7.40 (s, 2H, ArH), 4.29 (t, 4H,
pentyl a-CH2), 1.64–1.27 (m, 12H, pentyl CH2), 0.93 (t,
6H, CH3). IR (KBr, cm21): 2953, 2935, 2862 (nC–H), 1683
(nCvO). MS (EI): m/z 634 (Mþ). Elemental analysis: found
C 45.44, H 4.00%. Calcd for C24H26S3O4Br2 C 45.43, H
4.13%.
4.1.3. Synthesis of N,N0-dialkyl-5,500-diiodo-2,20:50,200-
terthiophene-4,400-dicarboxamide (DNCnDI3T, n58,
18). 5,500-Diiodo-2,20:50,200-terthiophene (DI3T) was pre-
pared by the reaction of 3T (3.0 g, 12.1 mmol) with
N-iodosuccinimide (5.4 g, 24.2 mmol) in chloroform
(200 mL) at room temperature for 5 h and purified by silica
gel column chromatography using chloroform as eluent,
followed by recrystallization from a benzene/hexane
mixture (1:2 v/v).
The DOC8DBr3T, DOC16DBr3T and DOC18DBr3T were
synthesized using analogous procedures with 1-iodooctane,
1-iodohexadecane, or 1-iodooctadcane (yields 91–93%).
DOC8DBr3T: 1H NMR (400 MHz, THF-d8): d (ppm)¼7.45
(s, 2H, ArH), 7.40 (s, 2H, ArH), 4.28 (t, 4H, octyl a-CH2),
1.59–1.13 (m, 24H, octyl CH2), 0.89 (t, 6H, CH3). IR (KBr,
cm21): 2958, 2924, 2852 (nC–H), 1707 (nCvO). MS(EI): m/z
718 (Mþ). Elemental analysis: found C 50.19, H 5.32%.
Calcd for C30H38S3O4Br2 C 50.14, H 5.33%.
DI3T (2.8 g, 5.60 mmol), was added to a THF solution
(50 mL) of LDA (22.4 mmol) at 278 8C and the solution
was stirred for 1 h. Excess dry ice was added to the
solution and the resulting mixture was stirred for 2 h. The
solution was allowed to warm to room temperature and
aqueous hydrochloric acid was added. After stirring for 5 h,
the resulting solid w0a0 s collected and washed with hot
acetonitrile to give 5,5 -diiodo-2,20:50,200-terthiophene-4,400-
dicarboxylic acid (yield 75% based on DI3T).
DOC16DBr3T: 1H NMR (400 MHz, THF-d8):
d
(ppm)¼7.45 (s, 2H, ArH), 7.39 (s, 2H, ArH), 4.20 (t, 4H,
cetyl a-CH2), 1.55–1.05 (m, 56H, cetyl CH2), 0.86 (t, 6H,
CH3). IR (KBr, cm21): 2955, 2917, 2848 (nC–H), 1688
(nCvO). MS (EI): m/z 943 (Mþ). Elemental analysis: found C
58.82, H 7.47%. Calcd for C46H70S3O4Br2 C 58.59, H, 7.48%.
A dichl0o0 romethane solution (100 mL) of 5,500-diiodo-
2,20:50,2 -terthiophene-4,400-dicarboxylic acid (1.0 g,
1.7 mmol) and SOCl2 (0.40 g, 3.4 mmol) was heated at
reflux for 8 h. After the solvent was removed under reduced
pressure, the resulting solid was added to a THF solution
(100 mL) of octylamine (0.43 g, 3.4 mmol) in the presence
of triethylamine (2.5 mL) at 0 8C and the solution was
stirred for 5 h at 0 8C. The solvent was removed under
reduced pressure to give DNC8DI3T. The product was
purified by silica gel column chromatography using chloro-
form as the eluent (yield 75% based on 5,500-diiodo-
2,20:50,200-terthiophene-4,400-dicarboxylic acid). 1H NMR
(400 MHz, THF-d8): d (ppm)¼7.37 (s, 2H, ArH), 7.33 (t,
2H, NH), 7.27 (s, 2H, ArH), 3.38 (dt, 4H, octyl a-CH2), 1.62
DOC18DBr3T: 1H NMR (400 MHz, THF-d8):
d
(ppm)¼7.45 (s, 2H, ArH), 7.39 (s, 2H, ArH), 4.28 (t, 4H,
stearyl a-CH2), 1.57–0.99 (m, 64H, stearyl CH2), 0.88 (t,
6H, CH3). IR (KBr, cm21): 2956, 2918, 2849 (nC–H), 1689
(nCvO). MS(EI): m/z 999 (Mþ). Elemental analysis: found
C 60.82, H 8.06%. Calcd for C50H78S3O4Br2 C 60.11, H
7.87%.
4.2. Characterization
Differential scanning calorimetry (DSC) was performed

5264
P. Liu et al. / Tetrahedron 60 (2004) 5259–5264
¨
6. Bauerle, P.; Segelbacher, U.; Maier, A.; Mehring, M. J. Am.
using a SSC/5200(SEIKO I&E) calorimeter. Polarizing
microscopy was carried out with an OPTI-PHOT X2
(Nikon) microscope, fitted with a TH-600PM hot stage
(Linkam) and crossed polarizers.
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Acknowledgements
This work was supported by Ministry of Education of the
People’s Republic of China (Research Funds for Chinese
Scholars Returning from Abroad), the Ministry of Science
and Technology of the People’s Republic of China
(National Key Program for Basic Research, 2001-
CCA03500). We also thank the Natural Science Foundation
of South China University of Technology for financial
support.
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