Supporting Information
DONOR-ACCEPTOR SEMICONDUCTING POLYMERS CONTAINING PYROMELLITIC DIIMIDE
UNITS
Ruvini S. Kularatne, Prakash Sista, Harsha D. Magurudeniya, Jing Hao, Hien Q. Nguyen, Michael C.
Biewer, Mihaela C. Stefan*
Synthesis of the Monomers and Polymers
The synthesis of the two donor monomers 1,4-diethynyl-2,5-bis(octyloxy)benzene, 2,7diethynyl-9,9-dioctyl-9H-fluorene have been synthesized according to the previously reported
procedures.26
Scheme 1. Synthesis of 3,6-dibromo-N,N’-dodecylpyromelliticdiimide
Synthesis of 1,4-dibromo-2,3,5,6-tetramethylbenzene (1)
1,2,4,5-Tetramethylbenzene (15 g, 0.1112 mol) and iodine (0.6 g, 2.4×10 -3 mol) in
dichloromethane (50 mL) were added to a three neck flask equipped with a refluxing condenser
and a dropping funnel. A solution of bromine (14.4 mL, 0.28 mol) in dichloromethane (20 mL)
was added slowly through the dropping funnel in dark. After the addition the reaction was
stirred overnight and then it was quenched in 5 M NaOH (200 mL) to consume the excess
bromine. The organic phase was extracted with dichloromethane (100 mL ×2), washed with
deionized water (100 mL×3), and dried over anhydrous MgSO4. The solution was concentrated
under vacuum to obtain white needle like crystals. (32.40 g, 99% yield). 1H NMR (270 MHz,
CDCl3): H 2.48 (s, 12H). 13C NMR (270 MHz, CDCl3): c 22.3, 128.1, 135.0.
Synthesis of 3,6-dibromobenzene-1,2,4,5-tetracarboxylic acid (2)
1,4-Dibromo-2,3,5,6-tetramethylbenzene (10 .0 g, 0.0342 mol) was dissolved in pyridine (230
mL) and deionized water (100 mL). The reaction mixture was stirred at 120° C and KMnO 4 (48
1
g, 0.303 mol) was added to the reaction mixture in small portions over an hour and it was
refluxed for two days. The reaction mixture was filtered to separate the brown precipitate
(MnO2) and it was washed several times with hot water. The filtrate was concentrated and the
pyridine was removed under vacuum. To the resulting white solid, NaOH (20 g) was added and
the mixture was dissolved in water (100 mL) and it was refluxed. When the compound was
dissolved, KMnO4 (48 g, 0.303 mol) was added in small portions and the reaction mixture was
stirred at 90 °C for one day. The excess of KMnO4 was destroyed by the cautious addition of
ethanol (25 mL). The reaction mixture was filtered to remove the MnO2 and the filtrate was
acidified with 5M HCl (300 mL). The solvent was removed under vacuum and acetone (100 mL)
was added to the residual solid and was stirred at room temperature for one day. The mixture
was filtered to separate NaCl and the filtrate was concentrated in vacuum to obtain a white
solid. (9. 78 g, 70%). 13C NMR (270 MHz, DMSO-D6): c 115.2. 137.3, 166.0.
Synthesis of 3,6-dibromopyromellitic dianhydride (3)
3,6-Dibromobenzene-1,2,4,5-tetracarboxylic acid (2.0 g, 0.0050 mol) was added to a three neck
flask under a nitrogen atmosphere. Acetic acid (10 mL, 0.175 mol) and acetic anhydride (2.86
mL, 0.300 mol) were added and the reaction mixture was refluxed for 1 hour. At this time a
white precipitate was formed and another portion of acetic anhydride (0.92 mL, 0.009 mol) was
added and the reaction mixture was refluxed two more hours. The white precipitate was
filtered and was washed several times with acetic acid and was dried under vacuum to obtained
white needle like crystals. (1.18 g, 63%). IR (KBr): 1700 cm-1 and 1657 cm-1 (C=O anhydride),
1213 cm-1 and 915 cm-1 (-CO-O-CO-).
Synthesis of 3,6-dibromo-N,N’-dodecylpyromelliticdiimide (4)
3,6-Dibromopyromellitic dianhydride (1.18 g, 3.31 mmol) was dissolved in dry THF (125 mL)
under a nitrogen atmosphere. When the compound was completely dissolved dodecyl amine
(2.16 mL, 9.39 mmol) was added to the reaction, at which time a white precipitate was formed
and the reaction mixture was stirred for 12 hours at room temperature. The solvent was
evaporated in vacuum to obtain a white solid which was dissolved in acetic anhydride (50 mL).
Sodium acetate (1.027 g, 12.52 mmol) was added to the reaction mixture and was stirred at 100
°C for one hour. The reaction mixture was poured into deionized water (300 mL) and the
organic phase was extracted with chloroform (150 mL), washed with water (3×100 mL) and
brine (3×100 mL), and dried over anhydrous MgSO4. The organic phase was concentrated in
vacuum to obtain an orange solid, which was further purified by column chromatography using
methylene chloride as the eluent to obtain a white solid (1.30 g, 55%). 1H NMR (270 MHz,
CDCl3): H 2.48 (s, 12H). 13C NMR (270 MHz, CDCl3): c 22.3, 128.1, 135.0.
2
Scheme 2. Synthesis of 3,3'-didodecyl-5,5'-diethynyl-2,2'-bithiophene.
Synthesis of 2-bromo-3-dodecylthiophene (5)
3-Dodecylthiophene (10.0 g, 0.0396 mol) was dissolved in THF (200 mL). At 0 °C Nbromosuccinimide (6.91 g, 0.0388 mol) was added to the reaction mixture gradually over one
hour. The reaction mixture was stirred for two hours at 0 °C, and was quenched in deionized
water. The organic phase was extracted into hexanes (100 mL), washed with water (100 mL× 5),
and dried over anhydrous MgSO4. The organic phase was concentrated under vacuum to obtain
brown oil, which was further purified by column chromatography using hexane as the eluent to
obtain colorless oil. (7.86 g, 60%). 1H NMR (270 MHz, CDCl3H 0.85 (t, 3H), 1.26 (q, 20H), 1.54
(q, 2H), 2.55 (t, 2H), 6.79 (d, 1H), 7.18 (d, 1H).
Synthesis of 3,3'-didodecyl-2,2'-bithiophene (6)
Magnesium turnings (0.218 g, 0.009 mol) were added to a three-neck round bottomed flask
and dried under vacuum for 2 hrs. The vacuum was cancelled with nitrogen followed by the
addition of 2-bromo-3-dodecylthiophene (2.0 g, 0.0060 mol) and anhydrous ether (60 mL). The
reaction was initiated by heating the flask and by adding several drops of 1,2-dibromoethane.
After 30 minutes the reaction mixture turned to a grey color indicating the formation of 2magnesiobromo-3-dodecylthiophene (flask A). In another round bottom flask [1,3bis(diphenylphosphino)propane]dichloronickel(II) (0.1626 g, 0.0003 mol), 2-bromo-3dodecylthiophene (2.0 g, 0.0060 mol), and anhydrous diethyl ether (60 mL) were added under a
nitrogen atmosphere (flask B). The 2-magnesiobromo-3-dodecylthiophene from flask A was
cannulated to the flask B. The reaction mixture was stirred overnight at 40 °C. The reaction
mixture was extracted with ethyl acetate (100 mL) and the organic phase was washed with
water (100 mL× 3), brine (100 mL× 3), dried over anhydrous magnesium sulfate, filtered and
concentrated to obtain a brown oil which was further purified by column chromatography
3
(eluent hexane) to obtain a clear oil of 3,3'-didodecyl-2,2'-bithiophene (2.10 g, 0.0041 mol,
70%) 1HNMR (CDCl3, 270 MHz): H 0.92 (t, 6H), 1.26 (m, 40H), 1.57 (m, 4H), 2.52 (t, 4H), 6.99 (d,
2H), 7.28(d, 2H).
Synthesis of 5,5'-dibromo-3,3'-didodecyl-2,2'-bithiophene (7)
3,3'-Didodecyl-2,2'-bithiophene (1.40g, 0.00278 mol) was dissolved in a mixture of chloroform
(50 mL) and acetic acid (50mL). At 0 °C N-bromosuccinimide (1.04 g, 0.00587 mol) was added
slowly to the reaction mixture over a period of an hour, and was stirred at room temperature
for two hours. At this time the reaction was quenched in deionized water (100 mL), the organic
phase was extracted with diethyl ether (100 mL), washed with water (100 mL× 3), dried over
anhydrous magnesium sulfate and was concentrated in vacuum to obtain a yellow oil. (1.52 g,
86%). 1HNMR (CDCl3, 270 MHz): H 0.86 (t, 6H), 1.21 (m, 40H), 1.57 (m, 4H), 2.41 (t, 4H), 6.83 (s,
2H).
Synthesis of (3,3'-didodecyl-2,2'-bithiophene-5,5'-diyl)bis(ethyne-2,1-diyl)bis(trimethylsilane) (8)
5,5'-Dibromo-3,3'-didodecyl-2,2'-bithiophene (1.58 g, 0.0024 mol), copper iodide (15 mg), and
bistriphenylphosphine dichloropalladium(II) (150 mg) were dissolved in triethylamine ( 10 mL)
under a nitrogen atmosphere. When the reactants were dissolved completely
ethynyltrimethylsilane (0.738 mL, 0.00528 mol) was added to the reaction mixture and the
reaction was stirred at 80 °C for two hours. The reaction mixture was quenched in 2N HCl (150
mL). The organic phase was extracted with diethyl ether (150 mL), washed with water ((100
mL× 3), brine (100 mL× 3), and was dried over anhydrous magnesium sulfate. The organic phase
was concentrated in vacuum to obtain a black oil, which was further purified by column
chromatography using hexane as the eluent to obtain light brown oil. (1.3 g, 78%). 1HNMR
(CDCl3, 270 MHz): H 0.25 (s, 18H), 0.88 (t, 6H), 1.22 (m, 40H), 1.57 (m, 4H), 2.43 (t, 4H), 7.09 (s,
2H).
Synthesis of 3,3'-didodecyl-5,5'-diethynyl-2,2'-bithiophene (9)
(3,3'-Didodecyl-2,2'-bithiophene-5,5'-diyl)bis(ethyne-2,1-diyl)bis(trimethylsilane)
(1.3
g,
0.00187 mol) was diluted with methylene chloride (25 mL) to which a solution of potassium
hydroxide (0.519 g, 0.0092 mol) dissolved in methanol(25 mL) was added. The reaction was
stirred at room temperature for 3 hours at which time the reaction was quenched in water. The
organic phase was extracted with diethyl ether (150 mL× 3), washed with water (100 mL× 3),
brine (100 mL× 3), and was dried over anhydrous magnesium sulfate. The organic phase was
concentrated in vacuum to obtain a light brown oil. (1.23 g, 95%). 1HNMR (CDCl3, 270 MHz): H
0.89 (t, 6H), 1.24 (m, 40H), 1.51 (m, 4H), 2.46 (t, 4H), 3.36 (s, 2H), 7.14 (s, 2H).
4
a
a
H2O
CDCl3
7
6
5
4
 ppm
3
2
TMS
1
0
Figure 1. 1H NMR spectrum of 1,4-dibromo-2,3,5,6-tetramethylbenzene
5
DMSO-d 6
c
a
b
a
b
c
200 180 160 140 120 100 80
 ppm
60
40
20
0
Figure 2. 13C NMR spectrum of 3,6-dibromobenzene-1,2,4,5-tetracarboxylic acid
6
100
%Transmittance
90
80
70
60
50
4000
3500
3000
2500
2000
1500
-1
Wavenumber (cm )
1000
Figure 3. IR spectrum of 3,6-dibromopyromellitic acid
7
100
90
% Transmittance
80
70
60
50
40
3500
3000
2500
2000
1500
-1
Wavenumber (cm )
1000
500
Figure 4. IR spectrum of 3,6-dibromopyromellitic dianhydride
8
H2O
CDCl3
TMS
a
b
b
a
8
7
6
5
4
 ppm
3
2
1
0
Figure 5. 1H NMR spectrum of 3,6-dibromo-N,N’-dodecylpyromellitc dianhydride
9
CDCl3
c
b
a
d
e
e
TMS
a
b
d
c
160
140
120
100
80
 ppm
60
40
20
0
Figure 6. 13C NMR spectrum of 3,6-dibromo-N,N’-dodecylpyromellitc diimide
10
c
d
b
a
CDCl3
d
a
b
c
TMS
8
7
6
5
4
3
 ppm
2
1
0
Figure 7. 1H NMR spectrum of 2-bromo-3-dodecylthiophene (5)
11
c
d
b
d
a
a b
c
8
7
6
5
4
 ppm
3
2
1
0
Figure 8 . 1H NMR spectrum of 3,3'-didodecyl-2,2'-bithiophene (6)
12
Alkyl chain
b
CDCl3
a
a
b
8
7
6
5
4
 ppm
3
2
1
0
Figure 9. 1H NMR spectrum of 5,5'-dibromo-3,3'-didodecyl-2,2'-bithiophene (7)
13
b
b
c
a
Alkyl chain
TMS
a
c
8
7
6
5
4
 ppm
3
2
1
0
Figure 10. 1H NMR spectrum of (3,3'-didodecyl-2,2'-bithiophene-5,5'-diyl)bis(ethyne-2,1diyl)bis(trimethylsilane) (8)
14
Alkyl chain
b
a
b
a
c
CDCl3
c
8
7
6
5
4
 ppm
3
2
1
0
Figure 11. 1H NMR spectrum of 3,3'-didodecyl-5,5'-diethynyl-2,2'-bithiophene (9)
15
d
CDCl3
TMS
c
a
b
a
7.8
7.6
b
7.4
7.2
 ppm
d
9
8
7
6
5
4
 ppm
7.0
c
3
2
1
0
Figure 12. 1H NMR spectrum of poly{N,N’-dodecylpyromelliticdiimide-alt-1,4-diethynyl-2,5bis(octyloxy)benzene} (P1)
16
CDCl3
TMS
e
b
c
a
d
bc
a
8.0
7.8
7.6
7.4
7.2
7.0
6.8
6.6
 ppm
e
9
8
7
6
5
4
 ppm
d
3
2
1
0
Figure 13. 1H NMR spectrum of poly{N,N’-dodecylpyromelliticdiimide-alt-2,7-diethynyl-9,9dioctyl-9H-fluorene} (P2)
17
TMS
c
d
CDCl3
b
a
c
a
8
d
b
7
6
5
4
 ppm
3
2
1
0
Figure 14. 1H NMR spectrum of poly{N,N’-dodecylpyromelliticdiimide-alt-3,3'-didodecyl-5,5'diethynyl-2,2'-bithiophene} (P3)
Polymer P1
0.00 mg/mL of PCBM
0.01 mg/mLof PCBM
0.03 mg/mLof PCBM
0.05 mg/mLof PCBM
0.07 mg/mLof PCBM
15
Polymer P2
0.00 mg/mL of PCBM
0.01 mg/mLof PCBM
0.03 mg/mLof PCBM
0.05 mg/mLof PCBM
0.07 mg/mLof PCBM
400
300
5
Intensity (a.u.)
Intensity (a.u.)
Intensity (a.u.)
10
Polymer P3
0.00 mg/mL of PCBM
0.01 mg/mLof PCBM
0.03 mg/mLof PCBM
0.05 mg/mLof PCBM
0.07 mg/mLof PCBM
15
10
200
5
100
0
550
600
650
Wavelength (nm)
(a)
700
0
0
500
550
600
Wavelenght (nm)
(b)
650
700
450
500
550
600
Wavelength (nm)
650
(c)
Figure 15 Fluorescence spectra of the (a) poly{N,N’-dodecylpyromelliticdiimide-alt-1,4diethynyl-2,5-bis(octyloxy)benzene} (P1), (b) poly{N,N’-dodecylpyromelliticdiimide-alt-2,7diethynyl-9,9-dioctyl-9H-fluorene} (P2), (c) poly{N,N’-dodecylpyromelliticdiimide-alt-3,3'didodecyl-5,5'-diethynyl-2,2'-bithiophene} (P3) with varying concentrations of PCBM.
18
P6
0.3
0.1
0.0
-4
Current ( Amp X 10 )
-4
-4
Current ( Amp X 10 )
0.2
0.0
-0.1
-0.2
-0.3
-0.2
-0.4
-0.6
0.0
-0.1
-0.2
-0.8
-0.4
-2.5
P8
0.2
0.4
0.1
Current ( Amp X 10 )
P7
0.6
0.2
-1.0
-2.0
-1.5
-1.0
-0.5 0.0
Voltage (V)
0.5
1.0
1.5
-2.5
2.0
-2.0
(a)
-1.5
-1.0
-0.5 0.0
Voltage (V)
0.5
1.0
1.5
-0.3
-2.5
2.0
-2.0
(b)
-1.5
-1.0 -0.5 0.0
Voltage (V)
0.5
1.0
1.5
2.0
(c)
Figure 16. Cyclic voltammograms of (a) poly{N,N’-dodecylpyromelliticdiimide-alt-1,4-diethynyl2,5-bis(octyloxy)benzene} (P1), (b) poly{N,N’-dodecylpyromelliticdiimide-alt-2,7-diethynyl-9,9dioctyl-9H-fluorene} (P2), (c) poly{N,N’-dodecylpyromelliticdiimide-alt-3,3'-didodecyl-5,5'diethynyl-2,2'-bithiophene} (P3).
100
100
P6
100
P8
90
90
80
70
60
Weight Percent %
90
weight percent %
Weight Percent %
P7
80
70
80
70
60
50
60
50
40
40
100
200
300
0
Temperature C
(a)
400
500
100
200
300
0
Temperature C
(b)
400
500
100
200
300
0
Temperature C
400
500
(c)
Figure 17. TGA spectra of the (a) poly{N,N’-dodecylpyromelliticdiimide-alt-1,4-diethynyl-2,5bis(octyloxy)benzene} (P1), (b) poly{N,N’-dodecylpyromelliticdiimide-alt-2,7-diethynyl-9,9dioctyl-9H-fluorene} (P2), (c) poly{N,N’-dodecylpyromelliticdiimide-alt-3,3'-didodecyl-5,5'diethynyl-2,2'-bithiophene} (P3)
19
5000
30.0 A
0
15.9 A
o
30.65 A
1000
3000
2000
4.5 A
0
1000
Intensity (a.u)
5000
Intensity (a.u.)
Intensity (a.u.)
1200
6000
4000
4000
3000
4.0 A
o
10
20
2
(a)
30
800
600
2000
400
1000
200
0
0
0
40
0
1400
7000
3.88 A
0
0
10
20
2
30
40
0
10
20
30
40
2
(b)
(c)
Figure 18. XRD of the (a) poly{N,N’-dodecylpyromelliticdiimide-alt-1,4-diethynyl-2,5bis(octyloxy)benzene} (P1), (b) poly{N,N’-dodecylpyromelliticdiimide-alt-2,7-diethynyl-9,9dioctyl-9H-fluorene} (P2), (c) poly{N,N’-dodecylpyromelliticdiimide-alt-3,3'-didodecyl-5,5'diethynyl-2,2'-bithiophene} (P3)
20