Synthesis and Electro-Optical Properties of Carbazole-Substituted Pyrene Derivatives
Jeong et al.
development of blue emitting materials, especially, are still
demanded.20–25 In particular, dual-purpose blue emitters
intended to serve blue emitting as well as charge trans-
porting properties are becoming important, because they
can make it possible to simplify the layered structures of
OLED devices.26ꢁ27
Recently, we have been interested in applying pyrene
molecules with carbazole substituents as a key dual-
purpose material for blue emission and charge transport
in OLEDs. Thus, we have synthesized two derivatives of
the pyrenes, and studied their use in OLEDs. We report
the synthesis of 9H-carbazol-9-ylpyrene (MCzP) and 1,6-
di(9H-carbazol-9-yl)pyrene (DCzP) whose structures are
based on the pyrenes substituted with asymmetric mono-
carbazole and symmetric di-carbazole moieties, respec-
tively, and discuss their photophysical and electro-optical
properties.
8.31 (d, J = 8.0 Hz, 2H), 8.21 (d, J = 9.2 Hz, 2H), 7.69
(d, J = 9.2 Hz, 2H), 7.35 (t, 3H), 7.05 (m, 4H).
2.3. Synthesis of 1,6-di(9H-carbazol-9-yl)pyrene
(DCzP)
In the first step, 1,6-dibromopyrene (DBP) was synthesized
as follows. Bromine (11.53 ml, 225 mmol) was added drop
wise in the solution of pyrene (10.00 g, 49.4 mmol) in
carbon tetrachloride (100 mL). The resulting solution was
reacted for 12 h at room temperature. Extracted materials
after the reaction were recrystallized in the toluene to give
rise to DBP.28ꢁ29
In the second step, DBP (2.00 g, 5.56 mmol), 9H-
carbazole (2.45 mg, 13.9 mmol), potassium carbon-
ate (2.30 g, 16.64 mmol) and copper powder (0.11 g,
1.73 mmol) were added in a three-neck flask and slowly
stirred in nitrobenzene (30 mL). The resulting solution was
ꢁ
refluxed for 30 h at 180 C. The mixture was allowed to
2. EXPERIMENTAL DETAILS
cool to room temperature, and was extracted with ethyl
acetate and DI water, then dried over Na2SO4 and con-
centrated. The residue was purified by silica gel chro-
matography using 2:1 EtOAc/hexane as an eluent, yielding
compound DCzP as a white solid.
2.1. Materials
Thin layer chromatography (TLC) analyses were carried
out on a pre-coated 0.2 mm HPTLC silica gel 60 plate
(Merck, Darmstadt). Flash column chromatography was
performed with silica gel (Merck silica gel 60, 70–
230 mesh). 1-Bromopyrene, 9H-carbazole, potassium car-
DCzP: Yield: 27%, 1H-NMR (CDCl3, 400 MHz) ꢅ
(ppm); 8.36 (d, J = 8.0 Hz, 2H), 8.28 (m, 4H), 8.15
(d, J = 8.0 Hz, 2H), 8.06 (d, J = 9.2 Hz, 2H), 7.69
(d, J = 9.2 Hz, 2H), 7.35 (m, 8H), 7.05 (m, 4H).
Delivered by Publishing Technology to: Chinese University of Hong Kong
bonate, sodium sulfate, copper powder, pyrene, bromine,
IP: 206.214.2.197 On: Tue, 15 Dec 2015 14:31:25
toluene, were all purchased from Aldrich Chemical Co.
Copyright: American Scientific Publishers
4, 4ꢀ, 4ꢀꢀ- Tris(N-(2-naphthyl)-N-phenyl-amino)-tripheny-
lamine (2-TNATA) and 2,9-dimethyl-4,7-diphenyl-1,10-
phenanthroline (BCP) were obtained from Doosan
Electro-Materials Co., Ltd. (Korea). Tris (8-hydroxy-
quinolinato) aluminum (Alq3ꢂ and bis(naphthylphenyl-
amino)biphenyl (ꢃ-NPD) were purchased from SFC Co.,
Ltd. (Korea). All organic compounds for fabrication of
OLEDs were sublimation grade and used without further
purification. The glass substrate with patterned indium-tin
oxide (ITO, 20 ꢄ/ꢀ) for OLED devices was purchased
from SUNIC Co. (Korea).
2.4. Fabrication of OLED Devices
OLED devices with two different structures were fab-
ricated on an ITO coated glass. Under a pressure of
1×10−6 torr, all organic compounds such as 2-TNATA
used as hole injection layer (HIL), ꢃ-NPD used as hole
transport layer (HTL), DCzP used as emission layer
(EML), BCP used as hole blocking layer (HBL), and Alq3
used as electron transport layer (ETL) were deposited by
thermal deposition at a rate of 1–2 Å/sec. Finally, 1.0 nm
of LiF layer as an EIL and 120 nm of Al film as a cath-
ode were vapor-deposited under the same pressure to yield
OLED devices with the configurations of ITO (150 nm)/ꢃ-
NPD (30 nm)/DCzP (40 nm)/LiF (1 nm)/Al (150 nm)
(D1) and ITO (150 nm)/2-TNATA (15 nm)/ꢃ-NPD
(20 nm)/DCzP (40 nm)/BCP (15 nm)/Alq3 (10 nm)/LiF
(1 nm)/Al (120 nm) (D2). The devices were sealed with
a glass cap to protect from the air. The active area of the
OLED was 2.0×2.0 mm2.
2.2. Synthesis of 9H-carbazol-9-ylpyrene (MCzP)
1-Bromopyrene (2.00 g, 7.11 mmol), 9H-carbazole
(1.78 g, 10.67 mmol), potassium carbonate (2.94 g,
21.27 mmol) and copper powder (0.14 g, 2.20 mmol)
were added in a three-neck flask and slowly stirred in
nitrobenzene (30 mL). The resulting solution was refluxed
for 24 h at 180 ꢁC. The mixture was allowed to cool
to room temperature and extracted with ethyl acetate and
DI water, then dried over Na2SO4 and concentrated. The
residue was purified by silica gel chromatography using
2:1 EtOAc/hexane as an eluent, yielding compound MCzP
as a white solid.
2.5. Measurements
1H NMR spectra of materials in CDCl3 were recorded
on a 400 MHz Bruker AM-400 spectrometer. Thermal
properties of the synthesized compounds were obtained
from TG/DTA SDT Q600 analyzer (TA Instrument). Mass
spectral data were obtained from the Korea Basic Science
MCzP: Yield: 38%, 1H-NMR (DMSO, 400 MHz) ꢅ
(ppm); 8.59 (d, J = 8.0 Hz, 2H), 8.45 (d, J = 8.0 Hz, 2H),
4352
J. Nanosci. Nanotechnol. 11, 4351–4356, 2011