the small-molecule blend films of TPAKP-3:PC71BM at various
weight ratios (1 : 1, 1 : 2, 1 : 3, and 1 : 4) by fabricating the hole-
and electron-only devices. The electron and hole mobilities were
determined precisely by fitting the plots of the dark current versus
voltage (J–V) curves for single-carrier devices to the SCLC
model. The dark current is given by:
stored below room temperature (11.2 g, 68%). 1H NMR
(300 MHz, CDCl3), d (ppm): 7.43 (d, J ¼ 8.7 Hz, 4H), 7.31
(t, J ¼ 7.8 Hz, 2H), 7.11–7.01 (m, 3H), 6.91 (d, J ¼ 8.7 Hz, 4H).
4,40,400-Tribromotriphenylamine (4b). This compound was
prepared by the same procedure as that described for compound
4a with 1 and 3.3 molar equivalents of TPA and NBS,
respectively, to yield a white solid (yield ¼ 90%). 1H NMR
(300 MHz, CDCl3), d (ppm): 7.36 (d, J ¼ 8.3 Hz, 6H), 6.92 (d, J ¼
8.3 Hz, 6H).
J ¼ 9303r mV2/8L3
where 303r is the permittivity of the polymer, m is the carrier
mobility, and L is the device thickness.
N-Phenyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-N-[4-
(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl] aniline (5a).
n-BuLi (2.5 M in hexane, 10.9 mL, 27.3 mmol) was added
dropwise (using a syringe) to a solution of 4a (5.00 g, 12.4 mmol)
Synthesis
2,5-Bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4c] pyrrole-
1,4(2H,5H)-dione(2). In an oven-dried two-necked 250 mL
round-bottom flask, a mixture of 3,6-dithiophen-2-yl-2,5-dihy-
dro-pyrrolo[3,4-c]pyrrole-1,4-dione (1, 5.00 g, 16.90 mmol) and
anhydrous K2CO3 (7.60 g, 54.90 mmol) were dissolved in
anhydrous N,N-dimethylformamide (DMF, 120 mL) and was
heated at 120 ꢂC under N2 for 1 h. 3-(Bromomethyl)heptane
(9.80 g, 50.7 mmol) was then added dropwise, followed by a small
amount of 18-crown-6. The reaction mixture was further stirred
ꢂ
in anhydrous THF (80 mL) at ꢀ78 C under N2 and then the
mixture was stirred at ꢀ78 ꢂC for 2 h. 2-Isopropoxy-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane (6.32 mL, 31.0 mmol) was
added in one portion to the mixture, which was then warmed to
room temperature and stirred overnight. The solvent was evap-
orated under vacuum; the crude product was dissolved in
CH2Cl2 (50 mL) and washed with water (3 ꢁ 50 mL). The
organic phase was dried (MgSO4) and the solvent was evapo-
rated under vacuum. The residue was purified chromatographi-
cally (SiO2, hexane–EtOAc, 20 : 1) to afford a white solid
(3.63 g, 59%). 1H NMR (300 MHz, DMSO-d6), d (ppm): 7.56 (d,
J ¼ 8.7 Hz, 4H), 7.34 (t, J ¼ 7.8 Hz, 2H), 7.12 (t, J ¼ 7.5 Hz, 1H),
7.04 (d, J ¼ 7.8 Hz, 2H), 6.95 (d, J ¼ 8.4 Hz, 4H), 1.26 (s, 24H).
ꢂ
at 150 C overnight, before being cooled to room temperature
and poured into distilled water (400 mL). After stirring the
resulting suspension at room temperature for 1 h, the solid was
collected by vacuum filtration, washed with several portions of
distilled water and methanol, and then dried under vacuum. The
crude product was purified chromatographically (SiO2; hexane–
1
EtOAc, 4 : 1) to yield a dark red solid (6.65 g, 75%). H NMR
Tris[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)
phenyl-
(300 MHz, CDCl3), d (ppm): 8.89 (dd, J ¼ 3.9 Hz, 1.2 Hz, 2H),
7.63 (dd, J ¼ 4.8 Hz, 0.9 Hz, 2H), 7.27 (dd, J ¼ 6.3 Hz, 3.9 Hz,
2H), 4.04–3.96 (m, 4H), 1.87–1.83 (m, 2H), 1.38–1.24 (m, 16H),
0.87 (t, J ¼ 7.2 Hz, 12H).
amine (5b). This compound was prepared in the same procedure
as that described for 5a using 1 : 3.3 : 3.5 molar equivalents of 4b,
n-BuLi and 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxabor-
1
olane, respectively, as a white solid (yield ¼ 62%). H NMR
(300 MHz, CDCl3), d (ppm): 7.66 (d, J ¼ 8.7 Hz, 6H), 7.07 (d, J ¼
3-(5-Bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)-6-(thiophen-2-
yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (3). N-Bromosuccini-
mide (NBS, 1.70 g, 9.52 mmol) was added in portions to a solu-
tion of 2 (5 g, 9.52 mmol) in CHCl3 (100 mL) in a two-necked
flask at 5 ꢂC. The mixture was warmed to room temperature and
stirred overnight. CH2Cl2 was added and then the solution was
washed with brine. The organic phase was dried (MgSO4) and
the solvent was evaporated under reduced pressure. The crude
product was purified chromatographically (SiO2;hexane–EtOAc,
8.4 Hz, 6H), 1.34 (s, 36H).
6,60-(5,50-(4,40-(Phenylazanediyl)bis(4,1-phenylene))bis(thio-
phene-5,2-diyl))bis(5-(2-ethylhexyl)-2-(octan-3-yl)-3-(thiophen-2-
yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione)
(TPAKP-2).
A
mixture of compound 5a (0.5 g, 1.00 mmol), compound 3 (1.39 g,
2.3 mmol), and 2 M K2CO3 (360 mg, 2.6 mmol) were dissolved in
30 mL of toluene and ethanol (3 : 1)followed by Pd(PPh3)4
(45 mg, 0.04 mmol) and degassed for 10 min. The resulting
mixture was then stirred under reflux for 36 h. The solvent was
evaporated under vacuum and the residue was partitioned
between CH2Cl2 and water; the organic phase was washed with
brine and dried (MgSO4) and then the solvent was evaporated
under vacuum. The residue was purified chromatographically
(SiO2; CH2Cl2) and the product was washed with MeOH and
hexane to yield a black solid (0.71 g, 55%). 1H NMR (300 MHz,
CDCl3), d (ppm): 9.00 (d, J ¼ 4.2 Hz, 2H), 8.87 (d, J ¼ 3.9 Hz,
2H), 7.62–7.56 (m, 5H), 7.40 (d, J ¼ 4.2 Hz, 2H), 7.36–7.31
(m, 2H), 7.28–7.25 (m, 3H), 7.20–7.13 (m, 7H), 4.04 (m, 8H), 1.92
(m, 6H), 1.41–1.23 (m, 30H), 0.93–0.83 (m, 24H). 13C NMR
(75 MHz, CDCl3): d 162.1, 161.8, 149.9, 148.0, 146.7, 140.7,
139.8, 137.5, 135.2, 130.5, 130.1, 129.9, 128.6, 128.2, 127.8, 127.3,
125.7, 124.7, 124.1, 124.0, 108.4, 108.0, 46.2, 39.4, 39.3, 30.5,
30.4, 29.5, 28.7, 28.5, 25.0, 23.9, 23.7, 23.3, 14.3, 14.2, 10.8, 10.7.
1
1 : 1) to yield a red solid (3.30 g, 58%). H NMR (300 MHz,
1
CDCl3), d (ppm): H NMR (300 MHz, CDCl3), d (ppm): 8.90
(dd, J ¼ 3.9 Hz, 1.2 Hz, 1H), 8.63 (d, 4.2 Hz, 1H) 7.64 (dd, J ¼ 5.1
Hz, 1.2 Hz, 1H), 7.29–7.22 (m, 2H), 4.03–3.92 (m, 4H), 1.84
(m, 2H), 1.38–1.23 (m, 16H), 0.91–0.85 (m, 12H).
4,40-Dibromotriphenylamine (4a). NBS (15.2 g, 81.5 mmol) was
added in portions to a solution of TPA (1ꢂ0.0 g, 40.8 mmol) in
DMF (120 mL) in a two-necked flask at 0 C. The mixture was
warmed to room temperature, stirred for an additional 12 h, and
then poured into excess water and extracted with CH2Cl2. The
combined extracts were washed with brine and dried (MgSO4)
and then the solvent was evaporated under reduced pressure. The
residue was purified chromatographically (SiO2; hexane–
CH2Cl2, 5 : 1) to yield as colorless oil, which solidified when
This journal is ª The Royal Society of Chemistry 2012
J. Mater. Chem., 2012, 22, 7945–7953 | 7947