Supporting information for
Donor-Acceptor (Donor) Polymers with Differently Conjugated Side Groups at the Acceptor Units
for Photovoltaics
Hongmei Qin, Lisheng Li, Tianxiang Liang, Xiaobin Peng,* Junbiao Peng and Yong Cao
Contents:
1. Synthesis of the monomers
2. Synthesis of the polymers
3. Density functional theory calculations of the polymers
4. AFM height images
5. References
1
S
N
N
Br
H2 N
Br Zn
S
Mg
S
AcOH
S
NH2
Br
S
C6H13
S
Br
Br CuBr
THF
O
S
ClOCCOCl O
2
1
O
S
O
Br2
S
O
Br
S
3
C8H17
S SnBu3
O
C8H17
S
S
O
Br
C8H17
Pd(PPh3)2Cl2
14
S
15
4
Br
O
NBS
O
S
C8H17
C8H17
C8H17
S SnBu3
C8H17
S
S
Br
O
C8H17
O
S
S SnBu3
O
O
Pd(PPh3)2Cl2
C8H17
C8H17
O
S
S
S
Br
O
C8H17
C8H17
S
Br
6
13
5
C8H17
C6H13
+
S
C8H17
S
AcOH
S
2
3
N
+
5
N
N
N
Br
S
Br
S
S
Br
C8H17
C6H13
S
AcOH
2
C6H13
S
S
O
C6H13
S
LiBr
Br
S
S
C8H17
9
7
S
S
C8H17
S
AcOH
2
+
4
S
N
S
Br
S
C8H17
S
S
N
C8H17
C8H17
C8H17
Br
AcOH
2
S
+
6
N
N
S
8
Br
S
10
OC8H17
OC8H17
n-BuLi
THF
Sn
Sn
SnMe3Cl
OC8H17
11
OC8H17
12
Scheme S1. Synthesis of the acceptor monomers and the donor monomer
1. Synthesis of monomers:
2
Br
1.1. 4,7-Bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (1)
Compound 1 was synthesized according to a previously reported method.1
1
H NMR (CDCl3, 400 MHz, δ(ppm)): 7.81 (d, 2H), 7.79(s, 2H), 7.16 (d, 2H).
1.2. 3,6-Bis(5-bromothiophen-2-yl)benzene-1,2-diamine (2)
4,7-Bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (0.458g, 1.0 mmol), zinc powder
(0.845 g, 13 mmol), and acetic acid (20 mL) were mixed and heated at 60 ℃ for 1 hour.
The mixture was then cooled down and filtered in a 100 mL flask. After removal of the
volatile solvent, the white solid (0.35g), compound 2, was obtained and used without
further purification. 1H NMR (CDCl3, 400 MHz, δ(ppm)): 7.07 (d, 2H), 6.95 (d, 2H),
6.85 (s, 2H).
1.3. 1,2-Bis(5-hexylthiophen-2-yl)ethane-1,2-dione (3)
A Grignard reagent was prepared by the dropwised addition of 2-bromo-5-hexylthiophene (152 mmol) to a stirred suspension of iodine-activated magnesium (4.0 g, 165
mmol) in THF (100 mL). In a separate flask, LiBr (25.5 g, 293 mmol) in THF (110 mL)
was added to a stirred suspension of CuBr (21.1 g, 146 mmol) in THF (110mL) to form a
pale green suspension. This mixture was then cooled to 0 °C and then the Grignard
reagent was slowly added to the LiBr/CuBr suspension. Oxalyl chloride (7.77 g, 61.0
mmol) was then added slowly via syringe to maintain a temperature below 0 °C. The
mixture was stirred at 0 °C for 60 min, allowed to warm to room temperature and
quenched with saturated aqueous NH4Cl. The organic layer was separated and the
aqueous layer extracted repeatedly with ethyl acetate. The combined organic layers were
dried with anhydrous Na2SO4, concentrated by rotary evaporation, and separated on a
silica column using petroleum ether as the eluent to give us the first band as the desired
3
product.. 1H NMR (CDCl3, 400 MHz, δ(ppm)): 7.86 (d, 2H), 6.88 (d, 2H), 2.86 (t, 4 H),
1.74 (m, 4 H), 1.32 (m, 12 H), 0.89 (t, 6 H).
1.4. 1,2-Bis(4'-octyl-[2,2'-bithiophen]-5-yl)ethane-1,2-dione (4)
1,2-Bis(4-bromothienyl)ethane-1,2-dione (3 mmol), 3.65 g of tributyl(4-octylthiophen2-yl)stannane (7.5 mmol) and 74 mg of Pd(PPh3)2Cl2 were added to a round bottom flask
purged with N2 gas. 30 ml of THF, degassed with N2 prior to use, were injected into it.
The reaction was stirred under reflux for 12 hours. The cooled mixture was extracted
with dichloromethane and deionized water. The organic layer was collected, dried over
anhydrous MgSO4 and concentrated, and purified by column chromatography with
petroleum ether /dichloromethane (V:V=2:1) as the eluent to yield 4 (90 % yield). 1H
NMR (CDCl3, 400 MHz, δ(ppm)): 8.05 (d, 2H), 7.26 (s, 2H), 7.23 (d, 2H), 6.99 (s, 2H),
2.82 (t, 4 H), 1.69 (m, 4 H), 1.38 (m, 20 H), 0.90 (t, 6 H).
1.5. 1,2-Bis(4-(4-octylthiophen-2-yl)phenyl)ethane-1,2-dione (5)
Same procedure as for compound 4 was used to synthesize 5.
1
H NMR (CDCl3, 400
MHz, δ(ppm)):7.98 (d, 4H), 7.71(d, 4H), 7.31 (s, 2H), 7.00 (s, 2H), 2.62 (t, 4H), 1.65(m,
4H), 1.28 (m, 20H), 0.89 (t, 6H).
1.6. 1,2-Bis(4-(3,4'-dioctyl-[2,2'-bithiophen]-5-yl)phenyl)ethane-1,2-dione (6)
Same procedure as for compound 4 was used to synthesize 6. 1H NMR (CDCl3, 400
MHz, δ(ppm)): 7.99 (d, 4H), 7.69(d, 4H), 7.31 (s, 2H), 7.01 (s, 2H), 6.93 (s, 2H), 2.77 (t,
4H), 2.61 (t, 4H), 1.62(m, 8H), 1.40 (m, 40H), 0.89 (m, 12H).
1.7. 5,8-Bis(5-bromothiophen-2-yl)-2,3-bis(5-hexylthiophen-2-yl)quinoxaline (7)
3,6-Bis(5-bromothiophen-2-yl)benzene-1,2-diamine (0.43 g, 1.0 mmol), 1,2-bis(5hexylthiophen-2-yl)ethane-1,2-dione (1 mmol), and acetic acid (10 mL) were mixed and
4
heated at 60 ℃ for 10 hour under a N2 atmosphere. After cooling, water was added. The
organic layer was separated and the aqueous layer extracted repeatedly with chloroform.
The combined organic layers were dried with anhydrous Na2SO4, concentrated by rotary
evaporation.
Finally, the crude compound was purified by column chromatography
(silica gel, eluent: petroleum ether/dichloromethane (V:V=2:1)) to give 7 as red solid.
Yield: 0.79 g (80%). 1H NMR (CDCl3, 400 MHz, δ(ppm)): 7.81 (s, 2H), 7.55 (d, 2H),
7.19 (d, 2H), 7.08 (d, 2H), 6.89 (d, 2H), 2.61 (t, 4H), 1.65 (m, 4H), 1.33 (m, 12H), 0.89
(m, 6H).
1.8. 5,8-Bis(5-bromothiophen-2-yl)-2,3-bis(4'-octyl-[2,2'-bithiophen]-5-yl)quinoxaline
(8)
Same procedure as for compound 7 was used to synthesize 8. 1H NMR (CDCl3, 400
MHz, δ(ppm)): 7.91 (s, 2H), 7.57 (d, 2H), 7.54 (d, 2H), 7.20 (s, 2H), 7.14 (d, 2H), 7.10
(d, 2H),6.90 (s, 2H), 2.63 (t, 4H), 1.62 (m, 4H), 1.40 (m, 20H), 0.85 (m, 6H).
1.9. 5,8-bis(5-bromothiophen-2-yl)-2,3-bis(4-(4-octylthiophen-2-yl)phenyl)quinoxaline
(9)
Same procedure as for compound 7 was used to synthesize 9. Yield: 0.79 g (80%). 1H
NMR (CDCl3, 400 MHz, δ(ppm)): 8.00 (s, 2H), 7.74(d, 4H), 7.63 (d, 4H), 7.53 (d, 2H),
7.25 (s, 2H), 7.11 (d, 2H), 6.92 (s, 2H), 2.62 (t, 4H), 1.63 (m, 4H), 1.31 (m, 20H), 0.89
(m, 6H).
1.10.
5,8-Bis(5-bromothiophen-2-yl)-2,3-bis(4-(3,4'-dioctyl-[2,2'-bithiophen]-5-
yl)phenyl)-quinoxaline (10)
Same procedure as for compound 7 was used to synthesize 10. 1H NMR (CDCl3, 400
MHz, δ(ppm)): 8.09 (s, 2H), 7.78 (d, 4H), 7.67 (d, 4H), 7.58 (d, 2H), 7.26 (s, 2H), 7.11
5
(d, 2H),7.02 (s, 2H), 6.93 (s, 2H), 2.80 (t, 4H), 2.64 (t, 4H), 1.65 (m, 8H), 1.40 (m, 40H),
0.92 (m, 12H).
1.11. 4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene (11)
Compound 11 was synthesized according to a previously reported method.2
1
H NMR (CDCl3, 400 MHz, δ(ppm)): 7.47 (d, 2H), 7.36 (d, 2H), 4.28 (t, 4H), 2.62 (t,
4H), 1.91(m, 4H), 1.57 (m, 4H), 1.38 (m, 16H), 0.90 (m, 6H).
1.12. (4,8-Bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane)
(12)
Compound 11 (2.68 g, 6 mmol) and 100 mL of THF were added into a flask under an
inert atmosphere. The solution was cooled down to -78 °C by a liquid nitrogen-acetone
bath, and 5.3 mL of n-butyllithium (13.2 mmol, 2.5 M in n-hexane) was added
dropwised. After being stirred at -78 °C for 1 h, a great deal of white solid precipitate
appeared in the flask. The reaction mixture was allowed to warm to room temperature
and left to stir for 30 min. Then, the solution was refluxed for 90 min. It was then cooled
to -78 °C and 14 mmol of trimethyltin chloride (14 mL, 1 M in n-hexane) was added in
one portion, and the reactant turned to clear rapidly. The cooling bath was removed, and
the reactant was stirred at ambient temperature for 12 h. Then, it was poured into 200 mL
of cool water and extracted by ether three times. The organic layer was washed by water
two times and then dried by anhydrous MgSO4. After removing solvent under vacuum,
the residue was recrystallized by ethyl alcohol two times. 4.03 g of compound 12 (4.56
mmol, yield 76%) was obtained as colorless needle crystal. 1H NMR (CDCl3, 400 MHz,
δ(ppm)): 7.53 (s, 2H), 4.32 (t, 4H), 2.62 (t, 4H), 1.92 (m, 4H), 1.57 (m, 4H), 1.38 (m,
16H), 0.91 (m, 6H), 0.47 (s, 18H).
6
1.13. 1,2-Bis(4-(5-bromo-4-octylthiophen-2-yl)phenyl)ethane-1,2-dione (13)
Compound 5 (1.20 g, 2mmol) was dissolved in 20 mL THF and cooled to 0 ºC. To the
cold solution, N-bromosuccinimide (0.82g, 4.6 mmol) was added and the mixture was
stirred at 0 °C for 30 min. Then the reaction mixture was allowed to warm to room
temperature and left to stir for 12 h. After quenched with saturated aqueous water, the
organic layer was separated and the aqueous layer extracted repeatedly with ethyl acetate.
The combined organic layers were dried with anhydrous Na2SO4, concentrated by rotary
evaporation. Purification by recrystallization (THF) gave 1.25 g (82%) of compound 13
as yellow needles.1H NMR (CDCl3, 400 MHz, δ(ppm)): 7.99 (d, 4H), 7.63(d, 4H), 7.16
(s, 2H), 2.58 (t, 4H), 1.62(m, 4H), 1.34 (m, 20H), 0.89 (m, 6H).
1.14. 1,2-Di(thiophen-2-yl)ethane-1,2-dione (14)
Same procedure as for compound 3 was used to synthesize 14. 1H NMR (CDCl3, 400
MHz, δ(ppm)): 8.16 (d, 2H), 7.85 (d, 2H), 7.21 (t, 2H).
1.15. 1,2-Bis(5-bromothiophen-2-yl)ethane-1,2-dione (15)
1,2-Di(thiophen-2-yl)ethane-1,2-dione
(400
mg,
1.98
mmol)
and
sodium
hydrogencarbonate (672 mg, 8.0mmol) were dissolved in 2 mL chloroform and cooled to
0 ºC. To the cold solution bromine (1.28 g, 8.0 mmol) was added dropwised and the
reaction mixture was heated to 80 ºC for 4 hours. The reaction mixture was allowed to
cool to room temperature and poured on top of a silica column. Purification by flash
chromatography
(petrol
ether)
and
subsequent
recrystallization
(dichloromethane/methanol) gave 421 mg (56%) of 15 as yellow needles. 1H NMR
(CDCl3, 400 MHz, δ(ppm)): 7.90 (d, 2H), 7.19 (d, 2H).
7
2. Synthesis of the polymers
2.1.
Poly[(4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene)-co-alt-(2,3-bis(4-(4-
octylthiophen-2-yl)phenyl)-5,8-di(thiophen-2-yl)quinoxaline)] (PBDT-PTQ)
5,8-bis(5-bromothiophen-2-yl)-2,3-bis(4-(4-octylthiophen-2-yl)phenyl)quinoxaline
(0.25
mmol)
and
(4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene-2,6-
diyl)bis(trimethylstannane) (0.25 mmol) were dissolved in dry toluene (10 mL) under a
argon atmosphere. After the solution was deoxygenated, Pd (PPh3)4 (5mg) was added
under an argon atmosphere, and then the reaction mixture was bubbled with Ar for 30
min and stirred at refluxing for 48 h under argon. Then the mixture was cooled down to
room temperature and poured into 200 mL methanol. The polymer was precipitated and
then collected by filtration. After drying in the vacuum drying oven, the polymer was
dissolved in toluene and purified by silica-gel chromatography with toluene eluent. The
polymer was reprecipitated using methanol and then dried to give PBDT-PTQ as a dark
green solid (yield: 76%). Mn = 10.1 k; polydispersity = 1.1. 1H NMR (CDCl3, 400 MHz,
δ(ppm)): 8.2-7.3 (br, 6H), 7.2-6.0 (br, 14H), 4.5-3.6 (br, 4H), 13.2-7.2 (br, 4H), 2.1-0.7
(br, 60H).
2.2.
Poly[(4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene)-co-alt-(2,3-bis(5-
hexylthiophen-2-yl)-5,8-di(thiophen-2-yl)quinoxaline)] (PBDT-TQ)
The polymerization procedure for monomer 12 (0.25 mmol) and monomer 7 (0.25
mmol) is the same as that of PBDT-PTQ. PBDT-TQ was obtained as a dark red solid
(yield 70%). Mn = 12.3 k; polydispersity = 1.1. 1H NMR (CDCl3, 400 MHz, δ(ppm)):8.27.3 (br, 6H), 7.2-6.0 (br, 6H), 4.5-3.6 (br, 4H), 13.2-7.2 (br, 4H), 2.1-0.7 (br, 52H).
8
2.3.
Poly[(4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene)-co-alt-(2,3-bis(4'-octyl-
[2,2'-bithiophen]-5-yl)-5,8-di(thiophen-2-yl)quinoxaline)] ( PBDT-TTQ)
The polymerization procedure for monomer 12 (0.25 mmol) and monomer 8 (0.25
mmol) is the same as that of PBDT-PTQ. PBDT-TTQ was obtained as a dark red solid
(yield 73%). Mn = 22.7 k; polydispersity = 1.1. 1H NMR (CDCl3, 400 MHz, δ(ppm)):
8.3-7.3 (br, 6H), 7.2-6.0 (br, 10H), 4.5-3.6 (br, 4H), 13.2-7.2 (br, 4H), 2.1-0.7 (br, 60H).
2.4.
Poly[(4,8-bis(octyloxy)benzo[1,2-b:4,5-b']dithiophene)-co-alt-(2,3-bis(4-(3,4'-
dioctyl-[2,2'-bithiophen]-5-yl)phenyl)-5,8-di(thiophen-2-yl)quinoxaline)] (PBDT-PTTQ)
The polymerization procedure for monomer 12 (0.25 mmol) and monomer 10 (0.25
mmol) is the same as that of PBDT-PTQ. PBDT-PTTQ was obtained as a dark red solid
(yield 68%). Mn = 71.3 k; polydispersity = 1.2. 1H NMR (CDCl3, 400 MHz, δ(ppm)):8.27.3 (br, 10H), 7.2-6.0 (br, 12H), 4.5-3.6 (br, 4H), 13.2-7.2 (br, 8H), 2.1-0.7 (br, 90H).
9
3. Density functional theory calculations of the polymers
Figure S1. The optimum geometries of the monomers of the four polymers obtained
from density functional theory calculations (a) BDT-TQ, (b) BDT-TTQ, (c) BDT-PTQ
and (d) BDT-PTTQ.
10
Figure S2. The HOMO electron-state-density distribution of the monomers of the four
polymers obtained from density functional theory calculations: (a) BDT-TQ, (b) BDTTTQ, (c) BDT-PTQ and (d) BDT-PTTQ.
11
Figure S3. The LUMO electron-state-density distribution of the monomers of the four
polymers obtained from density functional theory calculations: (a) BDT-TQ, (b) BDTTTQ, (c) BDT-PTQ and (d) BDT-PTTQ.
12
4. AFM height images
FIGURE S4. Tapping mode AFM height images of the polymer:PC70BM films (a)
PBDT-PTQ, (b) PBDT-PTTQ, (c) PBDT-TQ, and (d) PBDT-TTQ. The dimension of the
AFM images is 4×4 μm and the height is 10 nm.
5. REFERENCES:
1. Lee, P.I.; Hsu , S. L.C.; Lee, J. F. Sol. Energy Mater. Sol. Cells, 2011, 95, 17561761.
2. Hou, J.; Park, M.H.; Zhang, S.; Yao, Y.; Chen, L.M.; Li , J.H.; Yang, Y.
Macromolecules, 2008, 41, 6012-6018.
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