Yunqi Liu et al.
COMMUNICATION
exhibit a relatively low mobility of 10ꢀ4 cm2 Vꢀ1 sꢀ1 with Ion/
Ioff of 105 and a mobility of 5ꢁ10ꢀ3 cm2 Vꢀ1 sꢀ1 with Ion/Ioff of
107, respectively. Thus, the mobility of DO-BIPO-DI is 2–3
orders of magnitude higher compared to those of OHD-
BIPO-DI and OHD-BIPO-DI. This could be explained by
a stronger molecular interaction and a better molecular ori-
entation of DO-BIPO-DI in the solid state (see AFM
images in Figure 5). X-ray diffraction (XRD) data provide
evidence of a better molecular orientation of the compound
DO-BIPO-DI (Figure 6).
In summary, we developed a new family of asymmetric ar-
ylenediimides, namely dialkyl-14H-benzoACTHNUGTRENNU[G 4,5]isoquinoCAHTUNGTRNE[NUGN 2,3-
a]perimidin-14-one-3,4,10,11-tetracarboxylic diimides. These
compounds can be readily synthesized and structurally
modified by appending different groups to the N atoms of
imides. The thermal properties and electronic performance
under an N2 atmosphere. Subsequently, the solvent was evaporated and
the residue was purified by column chromatography on silica gel using
a mixture of dichloromethane/ethyl acetate (5:1 v/v) as an eluent. Finally,
the product was recrystallized from ethanol/chloroform (3:1 v/v) to give
a purple solid (910 mg, 50% yield). M.p. 270–2738C; 1H NMR (CDCl3,
400 MHz): d=0.87 (m, 6H), 1.28–1.43 (m, 20H), 1.75 (m, 4H), 4.20 (m,
4H), 7.65 (d, J=8.3 Hz, 1H), 8.63 (d, J=8.3 Hz, 2H), 8.80–8.83 (m, 3H),
9.05 (d, J=8.3 Hz, 1H), 9.12 ppm (d, J=8.3 Hz, 1H); 13C NMR (CDCl3,
75 MHz): d=14.90, 23.38, 27.86, 27.97, 28.93, 29.79, 29.85, 29.91, 29.98,
32.43, 41.40, 41.50, 115.14, 119.89, 120.38, 122.90, 122.97, 124.45, 124.79,
125.58, 126.23, 126.28, 126.49, 126.62, 127.64, 127.79, 129.19, 129.34,
131.64, 132.50, 136.47, 143.16, 158.48, 160.73, 160.82, 160.90, 161.03 ppm;
MS (MALDI-TOF) m/z [M+] calcd. for C42H42N4O5: 682.3; found, 682.3;
elemental analysis (%) calcd for C42H42N4O5: C 73.88, H 6.2, N 8.21;
found: C 74.14, H 6.02, N 8.17.
Synthesis of OHD-BIPO-DI
OHD-BIPO-DI was synthesized according to the procedure described
for DO-BIPO-DI using 5 (1 g, 2.94 mmol), 8 (1.45 g, 2.94 mmol), and 1-
butanol (80 mL). The crude product was purified by column chromatog-
raphy on silica gel using a mixture of dichloromethane/ethyl acetate (5:1
v/v) as an eluent to afford OHD-BIPO-DI as a yellow solid (800 mg,
34% yield). M.p. 241–2448C; 1H NMR (CDCl3, 400 MHz): d=0.86 (m,
9H), 1.28–1.45 (m, 34H), 1.75 (m, 2H), 1.99 (m, 1H), 4.17 (m, 4H), 7.62
(d, J=8.0 Hz, 1H), 8.59 (m, 2H), 8.75–8.80 (m, 3H), 9.03 (d, J=10.4 Hz,
1H), 9.14 ppm (d, J=10.4 Hz, 1H); 13C NMR (CDCl3, 75 MHz): d=
14.13, 22.68, 26.44, 26.45, 27.23, 28.03, 29.29, 29.34, 29.39, 29.61, 29.75,
30.07, 31.70, 31.88, 31.91, 36.73, 40.61, 45.04, 115.90, 118.46, 118.55,
118.99, 121.35, 125.26, 125.85, 126.53, 126.58, 126.95, 127.68, 128.47,
129.33, 130.78, 131.02, 132.90, 133.43, 137.63, 142.70, 146.90, 161.06,
162.84, 162.93, 162.99, 163.23 ppm; MS (MALDI-TOF) m/z [M+] calcd.
for C50H58N4O5: 794.4; found, 794.4; elemental analysis (%) calcd for
C50H58N4O5: C 75.54, H 7.35, N 7.05; found: C 75.82, H 7.25, N 6.99.
Figure 5. Atomic force microscopy (AFM) images of the compounds on
OTS-treated SiO2. (a) DO-BIPO-DI, (b) OHD-BIPO-DI, and (c) DHD-
BIPO-DI.
Synthesis of DHD-BIPO-DI
DHD-BIPO-DI was synthesized according to the procedure described
for BIPO-DI using 6 (1 g, 2.22 mmol), 8 (1.1 g, 2.22 mmol), and 1-butanol
(80 mL). The crude product was purified by column chromatography on
silica gel using a mixture of dichloromethane/ethyl acetate (5:1 v/v) as an
eluent to yield DHD-BIPO-DI as a yellow solid (710 mg, 35% yield).
M.p. 140–1438C; 1H NMR (CDCl3, 400 MHz): d=0.84 (m, 12H), 1.24–
1.40 (m, 48H), 2.00 (m, 2H), 4.12 (m, 2H), 7.63 (d, J=8.0 Hz, 1H), 8.59
(m, 2H), 8.77–8.81 (m, 3H), 9.03 (d, J=10.4 Hz, 1H), 9.14 ppm (d, J=
10.4 Hz, 1H); 13C NMR (CDCl3, 75 MHz): d=14.30, 22.69, 26.44, 26.47,
26.54, 27.44, 29.34, 29.58, 29.61, 29.71, 29.74, 29.78, 30.02, 30.07, 31.71,
31.91, 36.66, 116.03, 118.54, 118.80, 119.09, 126.04, 126.74, 127.03, 127.96,
128.69, 130.99, 131.16, 133.07, 142.91, 161.21, 163.13, 163.16, 163.49,
163.78 ppm; MS (MALDI-TOF) m/z [M+] calcd. for C58H74N4O5: 906.6;
found, 906.5; elemental analysis (%) calcd for C58H74N4O5: C 76.79, H
8.22, N 6.18; found: C 77.02, H 8.13, N 6.07. .
Figure 6. XRD data of the compounds on OTS-treated SiO2.
Fabrication of OFET Devices
OFET devices with a bottom-gate/bottom-contact configuration were
fabricated on a highly n-doped silicon wafer with a thermally oxidized
300 nm-thick SiO2 as a gate dielectric layer. Source and drain electrodes
made of gold were pre-prepared on the SiO2/Si substrates. The channel
length and width are 0.04 and 1.4 mm, respectively. Before the deposition
of organic semiconductors, OTS treatment was performed on the SiO2
gate dielectrics under vacuum to form an OTS self-assembled monolayer.
Organic thin films were then deposited onto the OTS-modified SiO2 sur-
face under vacuum. AFM measurements were carried out using a Nano-
scope V instrument. XRD of thin films was performed in the reflection
mode at 40 kV and 200 mA with CuKa radiation using a 2 kW Rigaku X-
ray diffractometer. The electrical characteristics of the OFET devices
were recorded at room temperature inside a glove box filled with nitro-
gen gas by using a Keithley 4200 SCS semiconductor parameter analyzer.
The mobility of the devices was calculated in the saturation regime using
the following equation:
could be tuned through the incorporation of alkyl groups.
Imide groups were found to be effective to tune energy
levels and give rise to an n-type performance. The DO-
BIPO-DI-based OFET devices show a good field-effect per-
formance with an electron mobility of 0.05 cm2 Vꢀ1 sꢀ1 and
a large current on/off ratio of 108.
Experimental Section
Synthesis of DO-BIPO-DI
Compounds 5 (1 g, 2.94 mmol) and 7 (1.1 g, 2.94 mmol) were dissolved in
1-butanol (80 mL). The reaction mixture was heated for 12 h at 1508C
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