Macromolecules
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(λ = 1.542 Å, scan rate: 0.6 s/step). The electrochemical cyclic
voltammetry was recorded on CH Instruments CHI 614 A with
carbon, platinum (Pt), and Ag/Ag+ as working, counter, and reference
electrode, respectively. The solvent is acetonitrile, ferrocene is used as
internal standard, and tetrabutylammonium hexafluorophosphate is
the electrolyte (scan rate 100 mV/s).
0.018 mol) and Ni(dppp)Cl2 (0.048 g, 0.09 mmol) in 25 mL of dry
ether, and the reaction was stirred overnight at room temperature.
After completing the reaction, the solution was then purged into cold
water and extracted twice with 50 mL of ether. The combined organic
phase was washed with water, dried over anhydrous MgSO4, filtered,
and concentrated. Purification was carried out via silica column
chromatography, using hexane as eluent. After concentration, the light
blue solid (2.6 g) 2,2′-bithiophene was obtained (0.015 mol, yield
Synthesis of Monomers and Polymers. Synthesis of 2-
Hexylthiophene (1).17 One equivalent (52 mL) of n-butyllithium
(1.6 M in hexane) was added dropwisely into a solution of thiophene
(7 g, 0.08 mol) in 50 mL of dry THF at −78 °C under a N2
atmosphere and kept stirring for 1 h. Then 1-bromohexane (15.1 g,
0.09 mol) was added in one portion, and the solution was warm to
room temperature. After 12 h, the solution was purged into cold water
and extracted with 50 mL of ether. The combined organic phase was
washed with water, dried over anhydrous MgSO4, filtered, and
concentrated. Distillation under vacuum gave 10.8 g of compound 1
1
85%). H NMR (δ, CDCl3): 7.23 (dd, 1H), 7.19 (dd, 1H), 7.03 (m,
1H).
Synthesis of 5,5′-Dibromo-2,2′-bithiophene (6). N-Bromosuccini-
mide (NBS) (4.49 g, 0.025 mol) was slowly added to a solution of
2,2′-bithiophene (2 g, 0.012 mol) in 30 mL of acetic acid at room
temperature. After the precipitate was formed, the solution was kept
stirring for 3 h. Then the reaction was purged into cold water, and a
large amount of solid was formed. The crude product was collected by
filtration and washed with water until neutral. Finally, the residue was
purified via silica column chromatography, using hexane as eluent to
1
(0.064 mol, yield 80%) as a colorless oil. H NMR (δ, CDCl3): 7.10
(m, 1H), 6.90 (m, 1H), 6.77 (m, 1H), 2.82 (t, 2H), 1.67 (m, 2H), 1.34
(m, 6H), 0.89 (t, 3H).
1
give a white solid (3.5 g) title compound (0.011 mol, yield 90%). H
Synthesis of 2-Hexyl-5-tributylstannylthiophene (2).18 Compound
1 (5 g, 0.03 mol) was dissolved in 30 mL of dry THF in a rounded-
bottom flask under a N2 atmosphere. 18.5 mL of n-butyllithium (1.6 M
in hexane) was added dropwisely at −78 °C. After stirring for 1 h,
tributyltin chloride (9.66 g, 0.03 mol) was added in one portion. Then
the reaction was warm to room temperature and stirred overnight.
Finally, the solution was purged into cold water. The organic phase
was separated, and the aqueous layer was twice extracted with 50 mL
of ether. The organic layers were collected and dried over anhydrous
MgSO4. After removing the solvent, the crude product was purified by
passing Al2O3 column and hexane was used as eluent. A colorless oil
(12.62 g) 5-tributylstannyl-2 hexylthiophene was obtained (0.027 mol,
yield 92%). 1H NMR (δ, CDCl3): 7.98 (d, 1H), 6.90 (d, 1H), 2.85 (t,
2H), 1.72 (m, 2H), 1.34 (m, 12H), 1.28 (m, 6H), 1.08 (m, 6H), 0.92
(m, 12H).
NMR (δ, CDCl3): 6.97 (d, 1H), 6.86 (d, 1H).
Synthesis of 5′-Bromo-2,2′-bithiophene-5-carbaldehyde (7). To a
solution of compound 6 (2 g, 6 mmol) in 20 mL of dry THF, 3.8 mL
of n-butyllithium (1.6 M in hexane) was slowly added at −78 °C under
a N2 atmosphere. One hour later, DMF (0.45 g, 6 mmol) was added in
one portion and warmed to room temperature. After 2 h, the solution
was purged into cold water and kept stirring for 1 h. The organic phase
was separated, and the aqueous layer was extracted with 50 mL of
ether twice. The organic layers were collected and dried over
anhydrous MgSO4. After the solvent was removed, the crude product
was purified by passing through SiO2 column, using CH2Cl2:hexane
(2:1) as eluent. A light yellow solid (1.13 g) 5′-bromo-2,2′-
bithiophene-5-carbaldehyde was obtained20 (4 mmol, yield 67%). H
1
NMR (δ, CDCl3): 9.82 (s, 1H), 7.63 (d, 1H), 7.22 (d, 1H), 7.18 (d,
1H), 7.01 (d, 1H).
Synthesis of 3-Hexylthiophene (3). To a solution of Mg (2.98 g,
0.12 mol) in 50 mL of dry ether, 1-bromohexane (10.12 g, 0.06 mol)
was slowly added at 0 °C under N2 gas, and then the solution was
heated to reflux for 2 h. Prepared Grignard reagent was purged into an
one-necked flask containing 3-bromothiophene (5 g, 0.03 mol) and
Ni(dppp)Cl2 (0.083 g, 0.2 mmol) in 50 mL of dry ether, and the
reaction was stirred overnight at room temperature. After completing
the reaction cycle, the solution was purged into cold water and twice
extracted with 50 mL of ether. The combined organic phase was
washed with water, dried over anhydrous MgSO4, filtered, and
concentrated. The purification step was carried out via silica column
chromatography, using hexane as eluent. After concentration, the
colorless oil (4.39 g) 3-hexylthiophene was obtained (0.026 mol, yield
87%). 1H NMR (δ, CDCl3): 7.21 (m, 1H), 6.90 (m, 2H), 2.61 (t, 2H),
1.61 (m, 2H), 1.29 (m, 6H), 0.87 (t, 3H). 13C NMR (δ, CDCl3):
143.2; 128.2; 125.0; 119.7; 31.7; 30.6; 30.3; 29.0; 22.6; 14.1.
Synthesis of 5-Tributylstannyl-3-hexylthiophene (4).19 Com-
pound 3 (3 g, 0.017 mol) was dissolved in 25 mL of dry THF in a
rounded-bottom flask under a N2 atmosphere. 11.1 mL of n-
butyllithium (1.6 M in hexane) was added dropwisely at −78 °C.
After the solution was stirred for 1 h, tributyltin chloride (5.8 g, 0.017
mol) was added in one portion. Then the reaction was warm to room
temperature and stirred overnight. Finally, the solution was purged
into cold water. The organic phase was separated, and the aqueous
layer was extracted with 50 mL of ether twice. The organic layers were
collected and dried over anhydrous MgSO4. After the solvent was
removed, the crude product was purified by passing through Al2O3
column, using hexane as eluent. A colorless oil (7.54 g) of 5-
tributylstannyl-3-hexylthiophene was obtained (0.016 mol, yield 97%).
1H NMR (δ, CDCl3): 7.20 (s, 1H), 6.90 (s, 1H), 2.97 (t, 2H), 1.61
(m, 8H), 1.36 (m, 12H), 1.03 (m, 6H), 0.91 (m, 12H).
Synthesis of 5″-Hexyl-2,2′:5′,2″-terthiophene-5-carbaldehyde
(8).21 To a solution of compound 2 (2 g, 4.3 mmol) and compound
7 (1 g, 3.6 mmol) in 25 mL of dry THF, Pd(PPh3)2Cl2 (0.12 g, 0.18
mmol) was added as catalyst under a N2 atmosphere, and the solution
was heated to reflux overnight. After removal of the solvent, the
mixture was directly purified by column chromatography (SiO2), using
CH2Cl2:hexane (2:1) as a mobile phase. 0.94 g of title compound was
obtained as a yellow solid (2.6 mmol, yield 71%). 1H NMR (δ,
CDCl3): 9.84 (s, 1H), 7.63 (d, 1H), 7.15 (d, 1H), 7.07 (d, 1H), 7.01
(d, 1H), 6.68 (d, 1H), 2.77 (t, 2H), 1.65 (m, 2H), 1.33 (m, 6H), 0.89
(t, 3H). 13C NMR (δ, CDCl3): 182.40, 147.07, 146.72, 141.32, 133.73,
133.71, 128.78, 126.78, 126.89, 125.04, 124.023, 123.82, 123.79, 31.52,
30.19, 29.7, 28.7, 22.5, 14.06.
Synthesis of 2,5-Dibromothiophene-3-carbaldehyde (9). Thio-
phene-3-carbaldehyde (3 g, 0.027 mol) was dissolved in 30 mL of
DMF in an one-necked flask, and the NBS (9.99 g, 0.056 mol) was
then slowly added to the solution. After stirring overnight, the solution
was purged into cold water and extracted twice with 50 mL of ether.
The combined organic phase was then dried over anhydrous MgSO4,
filtered, and concentrated. The crude product was purified via silica
column chromatography, using CH2Cl2:hexane (1:1) as mobile phase
to get 3.68 g of title compound22 (0.014 mol, yield 51%). 1H NMR (δ,
CDCl3): 9.78 (s, 1H), 7.33 (s, 1H). 13C NMR (δ, CDCl3): 189.14,
139.35, 128.69, 124.20, 113.41.
Synthesis of 5,5″-Dihexyl-2,2′:5′,2″-terthiophene-3-carbaldehyde
(10). To a solution of compound 9 (1 g, 3.7 mmol) and compound 2
(3.72 g, 8.1 mmol) in 25 mL of dry THF, Pd(PPh3)2Cl2 (0.29 g, 0.4
mmol) was added as catalyst under a N2 atmosphere, and the solution
was heated to reflux overnight. After removal of the solvent, the
mixture was directly purified by column chromatography (SiO2), using
CH2Cl2:hexane (1:1) as mobile phase. 0.86 g of title compound was
obtained as a yellow liquid (1.9 mmol, yield 52%). 1H NMR (δ,
CDCl3): 10.06 (s, 1H), 7.43 (s, 1H), 7.09 (d, 1H), 6.99 (d, 1H), 6.80
(d, 1H), 6.68 (d, 1H), 2.81 (m, 4H), 1.67 (m, 4H), 1.33 (m, 12H),
0.89 (m, 6H). 13C NMR (δ, CDCl3): 185.20, 150.00, 146.82, 146.29,
137.03, 136.62, 132.96, 129.57, 128.88, 125.34, 124.88, 124.46, 121.35,
Synthesis of 2,2′-Bithiophene (5). To a solution of Mg (0.89 g,
0.036 mol) in 25 mL of dry ether, 2-bromothiophene (3 g, 0.018 mol)
was slowly added at 0 °C under N2 gas protection, and then the
solution was heated to reflux for 2 h. Prepared Grignard reagent was
purged into an one necked-flask contained 2-bromothiophene (3 g,
C
dx.doi.org/10.1021/ma4007945 | Macromolecules XXXX, XXX, XXX−XXX