Synthesis and characterization of new planar butterfly-shaped fused oligothiophenes

Article abstract of DOI:10.1016/j.tet.2011.11.061

A simple oxidative cyclization reaction was used to construct new seven-ring-fused butterfly-shaped oligothiophene backbone: dibenzothieno[1,2-b: 4,3-b′:6,7-b″:9,8-b″′]tetrathiophene. The new materials show high stability and strong solid state fluorescen

Full text of DOI:10.1016/j.tet.2011.11.061

Tetrahedron 68 (2012) 1192e1197
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of new planar butterfly-shaped fused
oligothiophenes
*
Jing Wang, Huan Xu, Bin Li, Xiao-Ping Cao, Hao-Li Zhang
State Key Laboratory of Applied Organic Chemistry (SKLAOC), College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2011
Received in revised form 9 November 2011
Accepted 22 November 2011
Available online 27 November 2011
A simple oxidative cyclization reaction was used to construct new seven-ring-fused butterfly-shaped
oligothiophene backbone: dibenzothieno[1,2-b:4,3-b0:6,7-b00:9,8-b000]tetrathiophene. The new materials
show high stability and strong solid state fluorescence. X-ray crystallography results reveal that they
exist in 2-D stacked structures in their crystals.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Oligothiophene
Organic semiconductor
Fused-ring systems
Air-stable
1. Introduction
design and synthesis of a new seven-ring-fused dibenzothieno[1,2-
b:4,3-b0:6,7-b00:9,8-b000]tetrathiophene backbone, which can be
Owing to the growing interests in the field of organic semi-
conductors (OSCs), conjugated oligomers and fused aromatics have
attracted intense attentions for their potential applications in or-
ganic field-effect transistors (OFETs) and organic light emitting
diodes (OLEDs). Among these materials, linear acenes and oligo-
thiophenes are the two most studied classes of OSCs to date.1e4
Linear acenes, such as pentacene5,6 are common benchmarks in
the field of organic electronics with very high mobility. But pen-
tacene and other higher acenes generally suffer from low envi-
ronmental stability and poor solubility in common organic
solvents, which limits their practical applications.7,8 At the same
time, fused thiophene oligomers seem to enjoy an increased sta-
bility in comparison with linearly linked structures, together with
a more efficient conjugation.9e12 Bis(dithienobenzene) represents
one of the earliest reports of an air-stable organic semiconductor,
which exhibited reasonable thin-film mobility (0.04 cm2 Vꢀ1 sꢀ1).13
Despite some work already invested in synthesis and device studies
of fused thienothiophene and benzothiophene derivatives, the
design of new OSCs continues to be an important area of materials
research.
functionalized by different alkyl substituents in a simple way
(Scheme 1). The molecules can be described as a symmetric ‘butter-
fly’ shape.
OH
B OH
OH
Na+
OH
BuLi
B(OMe)3
NaOH
R
R
R
B
R
S
S
S
OH
3
2
4
R
I
I
S
S
FeCl3
Pd(PPh3)4
MeNO2
I
I
S
4
S
S
S
5
R
R
6
R
S
R
S
S
S
1a R = C2H5
1b R = C6H13
In our search for superior semiconductors for OFETs, we focused
our attention on fused thiophenes. In this paper, we report the
1c
R = C12H25
S
R
R
1
* Corresponding author. Tel./fax: þ86 931 8912365; e-mail address: Hao-
Scheme 1. Synthesis of compounds 1aec.
li.zhang@lzu.edu.cn (H.-L. Zhang).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.11.061

J. Wang et al. / Tetrahedron 68 (2012) 1192e1197
1193
employed to confirm the structure and purity of all new
compounds.
2.2. Optical properties
UVevis and fluorescence spectra of compounds 1aec are
shown in Fig. 1, and the optical data are collected in Table 1. The
solution-based absorption and emission measurements were car-
ried out at very low concentrations (<10ꢀ5 M) in DCM. All com-
pounds showed similar absorption pattern with the peaks at 225,
305, 356 and 377 nm (Table 1). This result indicated that the dif-
ferent length of n-alkyl groups had little influence on the molec-
ular
p
-system, which is as expected.18 As shown in Fig. 2, the
photophysical properties of drop-cast films of compounds 1aec
were also measured and were compared with that in solution. The
thin-film absorptions were red shifted and broadened compared
to those recorded in solution, apparently due to the increased
electronic interactions in the film.19
Fig. 1. Normalized UVevis absorption (solid lines) and photoluminescence (dashed
lines) spectra of 1aec recorded in DCM.
All three compounds show strong blue photoluminance (PL) in
solution, but emit yellow light in the solid state (Fig. 3). The nor-
malized PL spectra of compounds 1aec in thin-film are shown in
Fig. 2. The PL spectra of the three compounds were virtually
identical, consisting of a maximum emission at 409 nm in solution
and 516 nm in thin-film, indicated that the different n-alkyl groups
had little influence on the excited-state energies of the parent
backbone. Emission maxima (lmax) and fluorescence quantum
yields (FF) are presented in Table 1. All three compounds show very
small Stoke’s shift (5e25 nm) in solution and much larger Stoke’s
shift (131 nm) in thin-film. In thin-film state, the fluorescence of
compounds 1aec is comparably weak (absolute FFz2.5%).
The photo-stabilities of compounds 1aec were investigated by
monitoring the reduction in the absorbance at lmax in an air-
saturated 1.0ꢁ10ꢀ4 M toluene solution under ambient light at
27 ꢂC (Fig. 4). There was comparatively little change (less than 15%)
in the absorption of compounds 1aec even after 8 days of ambient
light illumination. The new materials are substantially more stable
than pentacene, which is known to deteriorated in a few min-
utes.8,20 The observed stability order is: 1a>1c>1b. By using the
density functional theory (DFT) calculation, the HOMO energies for
1aec are found at ꢀ5.14, ꢀ5.09 and ꢀ5.07 eV (vs vacuum) (Table 1),
which are lower than that of pentacene.21 The band gap estimated
from lowest-energy absorption edges of their solid state absorption
onset was found to be 3.01, 3.02 and 2.94 eV for 1aec, respectively.
The relatively low HOMO level and larger band gap of 1 may be the
2. Results and discussion
2.1. Synthesis
The synthesis of compounds 1aec was presented in Scheme 1.
Compounds 4a and 4c were synthesized by a similar process to that
reported for compound 4b.14 The starting compounds, tetraiodo-
thiophene (5) was prepared according to literature methods.15 The
2,3,4,5-tetra(5-alkylthiophen-2-yl)thiophene (6) was obtained by
Suzuki cross-coupling reaction between tetraiodothiophene (5)
and trihydroxyboronate salt (4). The FeCl3 oxidative cyclization
protocol was then utilized to construct the dibenzothieno[1,2-
b:4,3-b0:6,7-b00:9,8-b000]tetrathiophene skeleton via thienylethienyl
carbonecarbon bond formation.16,17 The oxidative cyclization re-
action using ferric chloride, which is an effective way to construct
polycyclic aromatic hydrocarbons, was accomplished within
30 min under a mild condition to afford 1a, 1b and 1c in 60%, 50%
and 45% yields, respectively.
Compounds 1aec are pale yellow solids, which are readily dis-
solved in common organic solvents, such as CHCl3, CH2Cl2, THF and
toluene. So they were purified conveniently by flash column
chromatography rather than vacuum sublimation usually used for
the purification of insoluble organic semiconductors. 1H and 13C
NMR spectra and MS associated with elemental analysis were
Table 1
Optical absorption wavelength (
l), fluorescence emission wavelength (E), band gap (Eg), fluorescence quantum yields (FF), half-life time, decomposition temperatures and DFT-
MO theoretical calculation for compounds 1aec
Compound
l
(nm)
Eem (nm)
Eem (nm)
Eg (eV)a
Eg (eV)a
FF
FF
Half-life
time (day)
Dec
Theoretical calculationc
temp (ꢂC)b
Soln
Film
Soln
Film
Soln
Film
Soln
Film
ELUMO (eV)
EHOMO (eV)
1a
223
308
363
385
227
310
363
385
223
306
365
386
227
303
355
375
225
305
356
377
225
305
356
377
390
409
516
516
516
3.22
3.22
3.22
3.01
3.02
2.94
5.9
4.5
3.3
2.9
2.8
2.1
52.7
35.0
51.0
255
415
320
ꢀ1.44
ꢀ5.14
ꢀ5.09
ꢀ5.07
1b
390
409
ꢀ1.39
ꢀ1.37
1c
390
409
a
Optical HOMOeLUMO gaps determined from the onset of lowest-energy visible absorption band. The onset is defined as the intersection between the baseline and
a tangent line that touches the point of inflection.
b
The decomposition point is listed as the temperature at which 10% of the mass is lost as determined by a TGA experiment (10 ꢂC minꢀ1) run at atmospheric pressure and
under nitrogen.
c
HOMO and LUMO levels and energy gap were obtained by DFT calculation at B3LYP/6-31G (d) level using Gaussian 03 package.

1194
J. Wang et al. / Tetrahedron 68 (2012) 1192e1197
Fig. 2. Thin-film UVevis absorption (solid lines) and photoluminescence (dashed
lines) spectra of 1aec.
Fig. 4. Photo-stability of 1aec monitored through decrease in their absorption in
toluene solution upon exposure to ambient light and air at 27 ꢂC.
Fig. 3. Solid fluorescence of compounds 1aec.
reason that they are more stable than pentacene. The theoretical
calculation results indicate that the lengthening of n-alkyl chains
results in an increase of the HOMO, LUMO energies.
the crystals. X-ray analyses display that the size of substituents has
an effect on molecular solid-state packing.
Compound 1a is slightly twisty. As shown in Fig. 6a, the fourth
and fifth thiophene rings and ethyl moieties lie on either side of the
five-ring-fused p-system plane, which contains the first to the third
2.3. Thermal properties
The thermal properties of compounds 1aec were investigated
by thermogravimetric analysis (TGA) (Table 1). The new materials
show very high decomposition temperatures. The observed ther-
mal stability order is: 1b>1c>1a (Fig. 5). The TGA results demon-
strated that the new conjugated backbone is thermally stable. The
stronger pep interactions between stacks of 1b as evidenced by X-
ray (Fig. 6) may be the reason for it high stability. Such a remarkable
stability is particularly important for application of these com-
pounds in OTFTs, where the stability of organic semiconductors is
still a major limitation.
2.4. X-ray single crystal analysis
Single crystals of compounds 1a and 1b, which were success-
fully obtained by slow evaporation of solution in a chloroform/
ethanol mixture, have been analyzed by X-ray diffraction to eluci-
date its molecular structure and packing characteristics. Com-
pounds 1a and 1b crystallize in triclinic crystal system with Pꢀ1
space group and all form a slipped face-to-face
p
-stacking motif in
Fig. 5. TGA plots of 1aec with a heating rate of 10 ꢂC minꢀ1 under N2.

J. Wang et al. / Tetrahedron 68 (2012) 1192e1197
1195
other molecule, which has ethyl group below the five-ring-fused p-
system plane form the unit of molecular packing in the crystal. The
ꢀ
interplanar distance is 3.527 A. The short distances of S/S are
ꢀ
ꢀ
3.722 A and 3.747 A, respectively.
While the seven fused rings, compound 1b forms planar struc-
ture. There are two n-hexyl groups at amorphous state, and the exact
structures of two n-hexyl groups were not defined. One molecule,
which has n-hexyl group above the five-ring-fused
and the other molecule, which has n-hexyl group below the five-
ring-fused -system plane form the unit of molecular packing in
p-system plane,
p
ꢀ
the crystal. The interplanar distance is 3.514 A and the shortest
distance of S/S is 4.078 A. Both interplanar distances of 1a and 1b
are lower than the sum of van der Waals radii of sulfur (3.68 A),
ꢀ
22
ꢀ
indicating strong pep interactions between stacks (Fig. 6).
3. Conclusion
A series of new planar seven-ring-fused oligothiophenes de-
rivatives were successfully synthesized by four steps reactions. The
new molecule can be described as a butterfly-like shape. These
molecules exhibit high photo and thermal stability, along with
strong solid state fluorescence making them good candidates for
applications in organic optoelectronics.
4. Experimental section
4.1. General materials and methods
All chemicals and solvents were obtained from commercial
suppliers and used without further purification unless otherwise
noted. 1H NMR spectra were recorded on a Bruker 400 MHz spec-
trometer and calibrated to the residual protonated solvent at
d
0.00 ppm for deuterated chloroform (CDCl3). 13C NMR experi-
ments were carried out in CDCl3 and calibrated at
d 77.00. UVevis
absorption spectra were recorded using a T6 UVevis spectrometer.
IR spectra were obtained as KBr discs on a Bruker V70 FT-IR spec-
trometer. Elemental analyses were obtained at the UBC Microana-
lytical facility. Fluorescence measurements were made using an
LS55 fluorescence spectrometer. Thermogravimetric analysis (TGA)
was carried out on a PerkineElmer TGA7. A heating rate of
10 ꢂC minꢀ1 under flowing N2 was used with runs being conducted
from room temperature to high temperature.
4.2. Synthesis of compounds
4.2.1. Synthesis of 4aec. The synthesis of compound 4a serves as
an illustrative example. Compound 4c was synthesized in a similar
manner. Compound 4b was synthesized by literature method.14
4.2.1.1. Sodium(5-ethylthiophen-2-yl)trihydroxyborate (4a). 2-
Ethylthiophene (1.40 g, 12.50 mmol) was dissolved in dry THF
(20 mL) and the solution was stirred at ꢀ78 ꢂC under argon. n-BuLi
(6 mL, 15.00 mmol, 2.5 M solution in hexane) was added dropwise
to the solution over a period of 30 min, after which the reaction
mixture was allowed to warm to room temperature and stirred for
a further 1.5 h. The mixture was then slowly added over a period of
1 h to a solution of trimethylborate (2.58 g, 25.00 mmol) in dry THF
(15 mL), which had been pre-cooled to ꢀ78 ꢂC. The resulting
mixture was allowed to slowly warm to room temperature and left
stirring overnight. Dilute hydrochloric acid (5 mL, 2 M) was added
and the mixture was extracted with diethyl ether (3ꢁ10 mL). The
combined organic layers were dried, filtered, and the solvent was
removed under vacuum. The residue was dissolved in a minimum
amount of warm toluene under stirring and the solution allowed
cooling to room temperature. Saturated NaOH solution was added
dropwise until no further precipitate formed. The mixture was
Fig. 6. (a) X-ray crystal structure of compound 1a. (b) X-ray crystal structure of
compound 1b. (Yellow spheres depict S atoms and gray spheres C. Alkyl groups have
been omitted.)
thiophene rings and two phenyl rings. The dihedral angles between
the five-ring-fused
phene rings are 10.6ꢂ and 7.5ꢂ, respectively. One molecule, which
has ethyl group above the five-ring-fused -system plane, and the
p-system plane of the fourth and fifth thio-
p

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J. Wang et al. / Tetrahedron 68 (2012) 1192e1197
allowed to stir for 30 min. The precipitate obtained was filtered off,
washed with toluene and petroleum ether and dried under vacuum
to give the compound as a white amorphous solid, which was used
for next step without further purification. Mp >300 ꢂC 1H NMR
(APCI) 1084. Found: 1085 [MþHþ.]. Calcd for C68H108S5: C, 75.21; H,
10.02; S, 14.77. Found: C, 75.22; H, 9.99; S, 14.79.
4.2.3. Synthesis of 1aec. The synthesis of compound 1a serves as
an illustrative example. Compounds 1b and c were synthesized in
a similar manner.
(400 MHz, D2O)
(q, J¼7.6 Hz, 2H), 1.32 (t, J¼7.6 Hz, 3H). IR (KBr): 3414, 2958, 1443,
1229, 936, 530 cmꢀ1
d: 6.78 (d, J¼3.6 Hz, 1H), 6.65 (d, J¼3.6 Hz, 1H), 2.75
.
4.2.3.1. 2,5,9,12-Tetraethyldibenzothieno[1,2-b:4,3-b0:6,7-b00:9,8-
b000]tetrathiophene (1a). Toavigorouslystirredsolutionofcompound
6a (105 mg, 0.20 mmol) in dichloromethane (20 mL) was added
dropwise a solution of FeCl3 (195 mg,1.20 mmol) in MeNO2 (3 mL) at
4.2.1.2. Sodium(5-dodecylthiophen-2-yl) trihydroxyborate (4c).
Compound 4c was prepared from 2c (3.15 g, 12.50 mmol) and get
a white amorphous solid, which was used for next step without
further purification. Mp >300 ꢂC 1H NMR (400 MHz, D2O)
d
: 6.76 (d,
0
ꢂC. Anhydrous MeOH was added after 30 min and stirred for an-
J¼3.6 Hz,1H), 6.40 (d, J¼3.6 Hz,1H), 2.70 (t, J¼7.6 Hz, 2H), 1.56e1.63
other 60 min. The mixture was washed with brine, 2 M aqueous
NaOH and NH4Cl solution, respectively, and dried over Na2SO4. The
solution was then filtered, the solvents removed and the residue
purified by column chromatography, using hexane as the eluent to
give the desired product as a yellow solid (62 mg, 60% yield). Mp
(m, 2H), 1.20e1.32 (m, 18H), 0.84 (t, J¼6.8 Hz, 3H). IR (KBr): 3371,
2920, 1465, 1441, 1237, 931, 524 cmꢀ1
.
4.2.2. Synthesis of 6aec. The synthesis of compound 6a serves as
an illustrative example. Compounds 6b and 6c were synthesized in
a similar manner.
180e182 ꢂC 1H NMR (400 MHz, CDCl3)
d: 7.45 (s, 2H), 7.36 (s, 2H), 3.12
(q, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H), 3.04 (q, J¼7.6 Hz, 4H), 1.52 (t, J¼7.6 Hz,
6H), 1.46 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 6H). 13C NMR (100 MHz, CDCl3)
d:
4.2.2.1. 2,3,4,5-Tetra(5-ethylthiophen-2-yl)thiophene (6a). The
aryl trihydroxyboronate salt 4a (2.45 g, 12.50 mmol), aryl halide 5
(735 mg,1.25 mmol), Pd(PPh3)4 (58 mg, 0.05 mmol) and a saturated
aqueous solution of NaHCO3 (1.05 g, 12.50 mmol) were placed in
a flame flask under argon. Freshly distilled and de-gassed THF
(25 mL) was added and the mixture was heated and stirred at reflux
for 48 h. After cooling to room temperature the mixture was poured
into a saturated solution of NH4Cl, and extracted with ethyl acetate
(3ꢁ10 mL). The combined organic layers were washed with satu-
rated brine and dried over Na2SO4. The solution was then filtered,
the solvents removed and the residue purified by column chro-
matography, using hexane as the eluent to yield a yellow oil
148.08, 145.72, 134.05, 133.65, 130.14, 130.04, 128.57, 126.72, 118.73,
117.95, 24.23, 23.76, 15.72, 15.65. IR (KBr): 3435, 2955, 2856, 1460,
1370, 718, 500 cmꢀ1. MS (EI): m/z¼520. Calcd for C28H24S5: C, 64.57;
H, 4.64; S, 30.79. Found: C, 64.65; H, 4.67; S, 30.68.
4.2.3.2. 2,5,9,12-Tetrahexyldibenzothieno[1,2-b:4,3-b0:6,7-b00:9,8-
b000]tetrathiophene (1b). Compound 1b was prepared from com-
pound 6b (150 mg, 0.20 mmol) and purified by column chroma-
tography, using hexane as the eluent to yield a yellow solid (74 mg,
50% yield). Mp 79e80 ꢂC 1H NMR (400 MHz, CDCl3)
d: 7.46 (s, 2H),
7.38 (s, 2H), 3.09 (t, J¼7.6 Hz, 4H), 3.01 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H),
1.90 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H), 1.83 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H),
1.36e1.54 (m, 24H), 0.91 (t, J¼6.8 Hz, 12H). 13C NMR (100 MHz,
(197 mg, 30% yield). 1H NMR (400 MHz, CDCl3)
d
: 6.88 (d, J¼3.6 Hz,
2H), 6.68 (d, J¼3.6 Hz, 2H), 6.62 (t, 1J¼4.8 Hz, 2J¼3.6 Hz, 4H), 2.79 (q,
1J¼7.6 Hz, 2J¼4.8 Hz, 4H), 2.74 (q, 1J¼7.6 Hz, 2J¼4.8 Hz, 4H), 1.25 (t,
CDCl3) d: 146.71, 144.34, 134.04, 133.64, 130.24, 130.16, 128.57,
126.76, 119.49, 118.69, 31.66, 31.61, 31.42, 31.37, 30.92, 30.46, 28.94,
28.83, 22.64, 22.59, 14.12, 14.10. IR (KBr): 3432, 2952, 2852, 1461,
1375, 730, 505 cmꢀ1. LRMS (APCI) 744. Found: 745 [MþHþ.]. Calcd for
C44H56S5: C, 70.91; H, 7.57; S, 21.52. Found: C, 70.95; H, 7.57; S, 21.48.
J¼7.6 Hz, 12H). 13C NMR (100 MHz, CDCl3)
d: 149.12, 148.34, 133.24,
133.09, 132.81, 132.23, 128.86, 125.81, 123.25, 122.93, 23.47, 23.37,
15.98,15.65. MS (EI): m/z¼524. Calcd for C28H28S5: C, 64.08; H, 5.38;
S, 30.54. Found: C, 64.15; H, 5.30; S, 30.55.
4.2.3.3. 2,5,9,12-Tetradodecyldibenzothieno[1,2-b:4,3-b0:6,7-
b00:9,8-b000]tetrathiophene (1c). Compound 1c was prepared from
compound 6c (217 mg, 0.20 mmol) and purified by column chroma-
tography, using hexane as the eluent to yield a yellow solid (97 mg,
4.2.2.2. 2,3,4,5-Tetra(5-hexylthiophen-2-yl)thiophene
(6b). Compound 6b was prepared by coupling of compound 4b
(3.15 g, 12.50 mmol) with 5 (735 mg, 1.25 mmol) and purified by
column chromatography, using hexane as the eluent to yield
45%yield). Mp42e44 ꢂC 1H NMR (400 MHz, CDCl3)
d: 7.44 (s, 2H), 7.36
a yellow oil (374 mg, 40% yield). 1H NMR (400 MHz, CDCl3)
d: 6.88
(s, 2H), 3.07 (t, J¼7.6 Hz, 4H), 2.99 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H), 1.89 (t,
(d, J¼3.6 Hz, 2H), 6.66 (d, J¼3.6 Hz, 2H), 6.59 (t, 1J¼4.0 Hz, 2J¼3.6 Hz,
1J¼7.6 Hz, 2J¼7.2 Hz, 4H), 1.82 (t, 1J¼7.6 Hz, 2J¼7.2 Hz, 4H), 1.36e1.54
4H), 2.68e2.75 (m, 8H), 1.60 (t, 1J¼7.2 Hz, 2J¼6.8 Hz, 8H), 1.25e1.34
(m, 72H), 0.87 (t, J¼7.2 Hz,12H). 13C NMR (100 MHz, CDCl3)
d: 146.66,
(m, 24H), 0.88 (t, J¼6.8 Hz, 12H). 13C NMR (100 MHz, CDCl3)
d
:
144.29, 134.01, 133.60, 130.21, 130.12, 128.54, 126.72, 119.46, 118.65,
31.93,31.44,31.39,30.90, 30.45,29.68,29.66,29.56,29.47, 29.41, 29.37,
29.28, 29.16, 22.69, 14.12. IR (KBr): 3437, 2953, 2852, 1465, 1377, 721,
506 cmꢀ1. LRMS (APCI) 1080. Found: 1081 [MþHþ.]. Calcd for
C68H104S5: C, 75.49; H, 9.69; S,14.82. Found: C, 75.53; H, 9.65; S,14.82.
147.45, 146.84, 133.33, 133.18, 132.74, 132.24, 128.80, 125.69, 123.83,
123.70, 31.58, 31.55, 31.53, 31.41, 30.07, 30.06, 28.75, 28.49, 22.60,
22.55, 14.09, 14.06. LRMS (APCI) 748. Found: 749 [MþHþ.]. Calcd for
C44H60S5: C, 70.53; H, 8.07; S, 21.40. Found: C, 70.60; H, 8.05; S,
21.35.
4.3. Crystal data for compounds 1a and 1b23
4.2.2.3. 2,3,4,5-Tetra(5-dodecylthiophen-2-yl)thiophene
(6c). Compound 6c was prepared by coupling of compound 4c
(4.20 g, 12.50 mmol) with 5 (735 mg, 1.25 mmol) and purified by
column chromatography, using hexane as the eluent to yield
a yellow solid (474 mg, 35% yield). Mp 42e44 ꢂC.1H NMR (400 MHz,
Single crystal X-ray diffraction measurements were made on
a Bruker X8 APEX diffractometer with graphite monochromated
ꢀ
Mo K
a
radiation (
l
¼0.71073 A) at 296(2) K.
CDCl3)
d
: 6.88 (d, J¼3.6 Hz, 2H), 6.66 (d, J¼3.6 Hz, 2H), 6.59 (t,
4.3.1. Compound 1a. CCDC reference number 751387. C28H24S5,
1J¼4.0 Hz, 2J¼3.6 Hz, 4H), 2.67e2.75 (m, 8H), 1.60 (t, 1J¼6.8 Hz,
M¼520.77, triclinic, space group: Pꢀ1, a¼10.7535(4) A,
ꢀ
2J¼6.4 Hz, 8H), 1.26e1.35 (m, 72H), 0.88 (t, J¼6.8 Hz, 12H). 13C NMR
a
g
¼64.898(2)ꢂꢂ, b¼11.2604(4) A,
b
¼69.859(2)ꢂ, c¼11.9865(5) A,
ꢀ
3
ꢀ
ꢀ
3
(100 MHz, CDCl3)
d
: 147.46, 146.84, 133.33, 133.17, 132.73, 132.22,
¼85.849(2) , V¼1229.33(8) A , Z¼2, Dx¼1.407 Mg/m .
128.80, 125.67, 123.82, 123.69, 31.93, 31.66, 31.46, 30.07, 29.73,
29.68, 29.65, 29.57, 29.39, 29.36, 29.14, 28.86, 22.70, 14.13. LRMS
4.3.2. Compound 1b. CCDC reference number 751388. C44H56S5,
ꢀ
M¼745.19, triclinic, space group: Pꢀ1, a¼10.1471(4) A, ¼104.485
a

J. Wang et al. / Tetrahedron 68 (2012) 1192e1197
1197
ꢂ
ꢂ
¼98.156(2)ꢂ,
ꢀ
ꢀ
g
7. Meng, H.; Bendikov, M.; Mitchello, G.; Helgeson, R.; Wudl, F.; Bao, Z.; Siegrist, T.;
Kloc, C. H. Adv. Mater. 2003, 15, 1090.
8. Coppo, P.; Yeates, S. G. Adv. Mater. 2005, 17, 3001.
9. Imamura, K.; Hirayama, D.; Yoshimura, H.; Takimiya, K.; Aso, Y.; Otsubo, T.
Tetrahedron Lett. 1999, 40, 2789.
10. Lee, K.; Sotzing, G. A. Macromolecules 2001, 34, 5746.
11. Lee, K.; Yavuz, M. S.; Sotzing, G. A. Macromolecules 2006, 39, 3118.
12. Nielsen, C. B.; Fraser, J. M.; Schroeder, B. C.; Junping, D.; White, A. J. P.; Zhang,
W.; McCulloch, I. Org. Lett. 2011, 13, 2414.
(2) , b¼11.6413(4) A,
b
¼96.393(2) , c¼18.6557(7) A,
3
3
ꢀ
V¼2087.15 (13) A , Z¼2, Dx¼1.186 Mg/m .
Acknowledgements
This work is supported by National Natural Science Foundation
of China (NSFC. 21073079, J1010067), the Fundamental Research
Funds for the Central Universities, National Basic Research Program
of China (973 Program) No. 2012CB933100 and 111 Project.
13. Laquindanum, J. G.; Katz, H. E.; Lovinger, A. J.; Dodabalapur, A. Adv. Mater. 1997,
9, 36.
14. Cammidge, A. N.; Goddard, V. H. M.; Gopee, H.; Harrison, N. L.; Hughes, D. L.;
Schubert, C. J.; Sutton, B. M.; Watts, G. L.; Whitehead, A. J. Org. Lett. 2006, 8,
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Supplementary data
1H and 13C spectra for all the new compounds. Supplementary
data related to this article can be found online at doi:10.1016/
j.tet.2011.11.061.
17. Pei, J.; Zhang, W.; Mao, J.; Zhou, X. Tetrahedron Lett. 2006, 47, 1551.
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€
Pisula, W.; Mullen, K. Adv. Mater. 2009, 21, 213.
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Tykwinski, R. R.; Parkin, S. R.; Anthony, J. E. J. Appl. Phys. 2005, 98, 33701.
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References and notes
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23. All crystallographic data have been deposited at the Cambridge Crystallo-
graphic Data Centre. Copies of the data can be obtained free of charge on ap-
plication to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK.
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