Synthesis of asymmetric anthracene derivatives and their application for blue organic light-emitting diodes

Article abstract of DOI:10.1002/bkcs.10640

Aryl-substituted asymmetric anthracene blue host materials, 10-naphthalene-2-yl-9-phenyl-2-triphenylsilylanthracene (6) and 9-(4-(tert-butyl)phenyl)-10-(2-methyl-5-(naphthalen-1-yl)phenyl)anthracene (7) were synthesized and characterized. Asymmetric anthr

Full text of DOI:10.1002/bkcs.10640

Article
DOI: 10.1002/bkcs.10640
BULLETIN OF THE
I.-S. Choi et al.
KOREAN CHEMICAL SOCIETY
Synthesis of Asymmetric Anthracene Derivatives and Their Application
for Blue Organic Light-emitting Diodes
†,
In-Su Choi,† Myoung-Hoon Jeong,† Seon Hee Lee,‡ Myung Hwan Park,‡, and Yongseog Chung
*
*
†Department of Chemistry, Chungbuk National University, Chungbuk 28644, Republic of Korea.
*E-mail: yschung@chungbuk.ac.kr
‡Department of Chemistry Education, Chungbuk National University, Chungbuk 28644, Republic of Korea.
*E-mail: mhpark98@chungbuk.ac.kr
Received September 24, 2015, Accepted October 8, 2015, Published online January 22, 2016
Aryl-substituted asymmetric anthracene blue host materials, 10-naphthalene-2-yl-9-phenyl-2-
triphenylsilylanthracene (6) and 9-(4-(tert-butyl)phenyl)-10-(2-methyl-5-(naphthalen-1-yl)phenyl)anthra-
cene (7) were synthesized and characterized. Asymmetric anthracene derivatives 6 and 7 possessed high
thermal stabilities that are suitable as emitting layer materials for blue organic light-emitting device. The elec-
troluminescence emission maximum of BD-142-doped (7 wt %) two devices exhibited at 464 nm (for 6)
and 472 nm (for 7), respectively. All devices showed good performances as blue host materials. The 7-based
device especially displayed higher device performances in terms of brightness (Lmax = 37 090 cd/m2), lumi-
nous current density (7.26 cd/A), and external quantum efficiencies (5.80%) than those of 6-based device.
Keywords: Anthracene, OLED, Blue-emitter, Host material, Electroluminescence
Introduction
naphthalene-2-yl-9-phenyl-2-triphenylsilylanthracene
(6)
and 9-(4-(tert-butyl)phenyl)-10-(2-methyl-5-(naphthalen-1-
yl)phenyl)anthracene (7) to provide improved thermal stabil-
ity and excellent electronic/optical properties. Additionally,
we aimed to introduce bulky aryl groups into the anthracene
moieties to effectively reduce intramolecular π–π stacking
as well as minimize concentration quenching, which can result
in bright blue EL emission. Details of synthesis, characteriza-
tion of asymmetric anthracene compounds (6 and 7), and their
luminescence properties as blue host materials for OLEDs are
described.
Organic light-emitting diodes (OLEDs) have a number of
attentions because of their high luminance, fast response time,
broad viewing angle, and full-color realization.1,2 In order to
achieve full-color images, OLEDs require highly stable, effi-
cient, and extremely pure red, green, and blue emission.
OLED materials with high performances forred and green col-
ors developed to date,3,4 further enhancement for blue-
emitting materials is still required.5 The development of novel
blue host materials with outstanding electroluminescence
(EL) properties is very difficult owing to their inherent large
band gap. A variety of blue host materials such as distyrylar-
ylene6 and anthracene derivatives7–14 have been recently
developed. Among them, anthracene-based materials are
shown to be one of the most effective blue host materials
because of their remarkable photophysical and electrolumi-
nescent properties.15–19 Despite their excellent electronic
and optical properties, these organic fluorescent π-conjugated
materials have some problems about device failure and ther-
mal stability. To prevent such problems and improve thermal
stabilities, silicon-cored (triphenylsilane)20 or asymmetric
anthracene derivatives21,22 containing bulky aryl groups were
recently reported. For example, nonplanar anthracene com-
pounds with bulkyaryl substituent at the 10-position exhibited
highthermal stability andoutstanding ELpropertyasbluehost
materials.22 Accordingly, the anthracene derivatives with the
bulky substituent at the 9,10-position can lead to hindering
close packing of the molecular structure and achieving highly
efficient EL properties. In this regard, we prepared new blue-
emitting asymmetric anthracene derivatives such as 10-
Experimental Section
General Considerations. All chemicals were purchased
from Aldrich (St. Louis, MO, USA) and were used without
any further purification. All solvents such as toluene, diethyl
ether, and n-hexane were dried by distillation from sodium
diphenylketyl under dinitrogen and were stored over 3 Å acti-
vated molecular sieves.23 Spectrophotometric grade CH2Cl2
was used as received. 3-(4-Bromophenyl)phthalide,24 2-(10-
(4-(tert-butyl)phenyl)anthracen-9-yl)-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane,20 and 1-(3-iodo-4-methylphenyl)naph-
thalene22 were analogously prepared according to the reported
procedures. All reactions were carried out under a nitrogen
atmosphere. Deuterated solvents from Cambridge Isotope
Laboratories were used after drying over activated molecular
sieves (5 Å). NMR spectra were recorded at ambient temper-
ature on Bruker Avance 400 spectrometer (400.13 MHz for
1H and 100.62 MHz for 13C; Billerica, MA, USA) or Bruker
DPX-300 NMR spectrometer (300.13 MHz for 1H and
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Wiley Online Library
136

Article
BULLETIN OF THE
ISSN (Print) 0253-2964 | (Online) 1229-5949
KOREAN CHEMICAL SOCIETY
75.47 MHz for 13C) using standard parameters. Chemical
shifts are given in ppm, and are referenced against
external Me4Si (1H and 13C). The thermal properties of com-
pound were investigated by TA Instrument TGA2940 system
and TA Instrument DSC2910 system (New Castle. Delaware,
1:7 v/v) afforded 3 as a yellowish green solid (6.1 g, 33.8%).
1H NMR (CDCl3, 300.13 MHz): δ 8.41 (s, 1H), 8.22 (d,
J = 1.8 Hz, 1H), 8.06 (s, 1H), 8.03 (s, 1H), 8.02–7.99 (m,
1H), 7.90–7.88 (m, 2H), 7.66 (d, J = 8.8 Hz, 1H),
7.61–7.57 (m, 2H), 7.54–7.46 (m, 3H), 7.37–7.35 (m, 1H),
7.35–7.31 (m, 1H). 13C NMR (CDCl3, 75.47 MHz): δ
137.41, 135.63, 133.30, 132.78, 132.04, 131.91, 130.49,
130.09, 129.88, 129.20, 128.80, 128.59, 128.30, 128.05,
127.88, 126.96, 126.54, 126.36, 125.79, 125.72, 119.47.
Synthesis of 10-naphthalene-2-yl-2-triphenylsilylan-
thracene (4). A hexane solution of n-BuLi (10.8 mL,
17.3 mmol, 1.6 M solution in hexane) was slowly added to
a solution of 3 (5.5 g, 14.5 mmol) in THF (75 mL) at
ꢀ
USA) under a nitrogen atmosphere at a heating rate of 10 C/
min. UV/Vis absorption and PL spectra were recorded on a
Beckman PU 650 (San Francisco, CA, USA) and a Jasco
FP-750 (Todyo, Japan), respectively, in CHCl3 solvent with
a 1-cm quartz cuvette at ambient temperature. Cyclic voltam-
metry (CV) measurements were performed using an AUTO-
LAB/PGSTAT12 system (Artisan Technology Group,
Champaign, IL, USA). Electroluminescent spectra were
measured at Dongjin Semichem Co. Ltd. (Seoul, Republic
of Korea).
ꢀ
−78 C. After stirring for 30 min, a solution of triphenylsilyl
chloride (4.3 g, 14.5 mmol) in THF (15 mL) was added to the
reaction mixture and stirred for 30 min. The solution was
slowly allowed to warm to room temperature. The complete-
ness of the reaction was checked by TLC. After the reaction
was quenched with water, the aqueous layer was extracted
with ethyl acetate (30 mL). The combined organic portions
were dried over MgSO4 and concentrated under reduced pres-
sure. Purification by column chromatography (eluent:
CH2Cl2/n-hexane, 1:3 v/v) afforded 4 as a yellowish green
solid (6.7 g, 69.9%). 1H NMR (CDCl3, 300.13 MHz): δ
8.49 (d, J = 17.6 Hz, 1H), 8.33–8.28 (m, 1H), 8.04–7.87
(m, 5H), 7.69–7.62 (m, 8H), 7.58–7.55 (m, 4H), 7.50–7.33
(m, 11H). 13C NMR (CDCl3, 75.47 MHz): δ 138.90,
136.44, 135.40, 134.20, 134.05, 133.35, 132.72, 131.43,
131.13, 130.94, 130.79, 130.50, 130.24, 130.12, 129.67,
129.44, 128.56, 128.03, 127.94, 127.92, 127.84, 127.40,
126.82, 126.64, 126.37, 126.16, 125.74, 125.14.
Synthesis of 2-(3-bromobenzyl)benzoic acid (1). 3-(4-
Bromophenyl)phthalide (10.5 g, 36.5 mmol), iodine (6.3 g,
24.8 mmol) and red phosphorus (5.7 g, 184.0 mmol) were
dissolved in propionic acid (60 mL) and a distilled water
ꢀ
(1.5 mL) was added. After stirring for 20 min at 100 C,
the solution was cooled to room temperature. The resulting
solution was extracted with CHCl3. The combined organic
portions were dried over MgSO4 and the solvent was removed
under reduced pressure. A yellow solid 1 was obtained (8.8 g,
83.2%) without further purification. 1H NMR (CDCl3,
300.13 MHz): δ 8.10 (dd, J = 7.8 Hz, 1.2 Hz, 1H), 7.51
(td, J = 7.6 Hz, 1.4 Hz, 1H), 7.37 (d, J = 7.7 Hz, 1H), 7.33
(d, J = 1.4 Hz, 1H), 7.31 (s, 1H), 7.23 (d, J = 7.7 Hz, 1H),
7.16–7.09 (m, 2H), 4.42 (s, 2H).
Synthesis of 3-bromo-9,10-dihydro-9-oxoanthracene
(2). 1 (8.8 g, 30.3 mmol) was slowly added to concentrated
ꢀ
H2SO4 at 0 C. After stirring for 1 h, the reaction was slowly
Synthesis of 9-bromo-10-naphthalene-2-yl-2-triphenyl-
silylanthracene (5). A solution of 4 (6.2 g, 11.0 mmol) in
N,N-dimethylformamide (DMF; 620 mL) was slowly
added to a solution of N-bromosuccinimide (NBS; 2.1 g,
12.1 mmol) in DMF (70 mL). The completeness of the reac-
tion was checked by TLC. After the reaction was quenched
with water, the resulting solid was collected by filtration and
successively dissolved in CH2Cl2. The combined organic por-
tions were dried over MgSO4 and concentrated under reduced
pressure. Purification by column chromatography (eluent:
CH2Cl2/n-hexane, 1:3 v/v) afforded 5 as a yellow solid
allowed to warm to room temperature and stirred for 1 h. After
quenching with water, the resulting solid was collected by fil-
tration and successively washed with hot ethanol. A light gray
solid 2 was obtained (6.9 g, 82.9%). 1H NMR (CDCl3,
300.13 MHz): δ 8.34 (d, J = 7.9 Hz, 1H), 8.21 (d,
J = 8.4 Hz, 1H), 7.63 (s, 1H), 7.61–7.57 (m, 2H), 7.48 (d,
J = 8.0 Hz, 1H), 7.46 (d, J = 7.8 Hz, 1H), 4.32 (s, 2H). 13C
NMR (CDCl3, 75.47 MHz): δ 183.43, 142.03, 139.76,
133.02, 131.66, 131.28, 130.84, 130.55, 129.34, 128.42,
127.97, 127.60, 127.25, 31.94.
1
Synthesis of 2-bromo-10-(naphthalene-2-yl)anthracene
(3). A hexane solution of n-BuLi (34.9 mL, 55.8 mmol,
1.6 M solution in hexane) was slowly added to a solution of
2-bromonaphthalene (11.6 g, 55.8 mmol) in THF (390 mL)
(4.7 g, 67.3%). H NMR (CDCl3, 300.13 MHz): δ 8.91 (s,
1H), 8.61 (d, J = 8.9 Hz, 1H), 8.04–7.97 (m, 3H),
7.90–7.86 (m, 2H), 7.67–7.64 (m, 7H), 7.59–7.55 (m, 4H),
7.46–7.37 (m, 11H). 13C NMR (CDCl3, 75.47 MHz): δ
138.14, 137.37, 136.45, 135.69, 133.78, 133.64, 133.25,
132.79, 133.78, 133.64, 133.25, 132.79, 131.70, 131.41,
130.97, 130.36, 130.11, 129.77, 129.43, 129.17, 127.98,
127.39, 126.92, 126.55, 126.36, 126.19, 125.91, 123.73.
Synthesis of 10-naphthalene-2-yl-9-phenyl-2-triphenyl-
silylanthracene (6). Phenylboronic acid (0.90 g,
8.03 mmol), 5 (4.69 g, 7.30 mmol), Pd(PPh3)4 (0.17 g,
0.15 mmol), and K2CO3 (6.05 g, 43.80 mmol) were dis-
solved in toluene (80 mL) and a distilled water (20 mL)
was added. After the solution was heated at reflux overnight,
ꢀ
at −78 C. After stirring for 1 h, a solution of 2 (12.6 g,
46.5 mmol) in THF (230 mL) was added to the reaction mix-
ture and stirred for 30 min. Thesolutionwas slowly allowed to
warm to room temperature. The completeness of the reaction
was checked by TLC. After the reaction was quenched with
6 M aqueous solution of HCl (90 mL), the organic layer
was separated, and the aqueous layer was extracted with ethyl
acetate (150 mL). The combined organic portions were dried
over MgSO4 and concentrated under reduced pressure. Purifi-
cation by column chromatography (eluent: CH2Cl2/n-hexane,
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
137

Synthesis of Asymmetric Anthracene Derivatives and
Their Application for Blue OLEDs
BULLETIN OF THE
Article
KOREAN CHEMICAL SOCIETY
it was cooled to ambient temperature. After the reaction was
quenched with water, the aqueous layer was extracted with
CH2Cl2 (30 mL). The combined organic portions were dried
over MgSO4 and concentrated under reduced pressure. Purifi-
cation by column chromatography (eluent: CH2Cl2/n-hexane,
1:9 v/v) afforded 6 asayellow solid (2.94 g, 63.1%). 1HNMR
(CDCl3, 300.13 MHz): δ 8.05 (d, J = 8.4 Hz, 1H), 8.02–7.98
(m, 3H), 7.92–7.89(m, 1H), 7.77–7.70(m, 3H), 7.63–7.56(m,
3H), 7.51–7.47 (m, 7H), 7.42–7.39 (m, 3H), 7.38–7.36 (m,
2H), 7.35–7.34 (m, 2H), 7.34–7.33 (m, 2H), 7.31–7.28 (m,
6H), 7.26 (s, 1H). 13C NMR (CDCl3, 75.47 MHz): δ
138.33, 137.98, 137.87, 136.59, 136.42, 136.23, 133.97,
133.38, 132.74, 131.05, 130.97, 130.64, 130.36, 130.22,
130.14, 129.89, 129.53, 129.45, 129.21, 128.17, 128.05,
127.93, 127.87, 127.79, 127.26, 127.21, 126.96, 126.39,
126.17, 125.72, 125.38, 124.97.
Synthesis of 9-(4-(tert-butyl)phenyl)-10-(2-methyl-5-
(naphthalen-1-yl)phenyl)anthracene (7). 2-(10-(4-(tert-
Butyl)phenyl)anthracen-9-yl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2.50 g, 5.72 mmol), 1-(3-iodo-4-methylphe-
nyl)naphthalene (1.97 g, 5.72 mmol), Pd(PPh3)4 (0.33 g,
0.29 mmol), and K2CO3 (3.16 g, 22.90 mmol) were dis-
solved in toluene (80 mL) and a distilled water (30 mL)
was added. After the solution was heated at reflux overnight,
it was cooled to ambient temperature. After the reaction was
quenched with water, the aqueous layer was extracted with
CH2Cl2 (80 mL). The combined organic portions were dried
over MgSO4 and concentrated under reduced pressure. Purifi-
cation by column chromatography (eluent: CH2Cl2/n-hexane,
1:10 v/v) afforded 7 as a white solid (1.70 g, 56%). 1H NMR
(CDCl3, 400.13 MHz): δ 8.17 (d, J = 3.75 Hz, 1H), 7.90 (d,
J = 3.75 Hz, 1H), 7.84 (d, J = 4.0 Hz, 2H), 7.77 (d,
J = 4.0 Hz, 2H), 7.58–7.64 (m, 4H), 7.52 (d, J = 3.5 Hz,
1H), 7.49–7.52 (m, 2H), 7.43–7.48 (m, 3H), 7.33–7.40 (m,
5H), 2.05 (s, 3H), 1.48 (s, 9H). 13C NMR (CDCl3,
100.62 MHz): δ 150.24, 139.92, 138.54, 138.30, 137.31,
137.05, 135.93, 135.83, 133.88, 133.02, 131.65, 131.02,
130.94, 130.13, 129.97, 129.70, 129.52, 128.30, 127.54,
127.38, 127.12, 126.56, 126.05, 125.67, 125.38, 125.22,
125.17, 124.88, 34.75, 31.55, 29.70, 19.67.
(2), was prepared from ring opening reaction of 3-(4-bromo-
phenyl)phthalide in the presence of red phosphorus and
iodine, followed by ring cyclization in high yield (83%). 2-
Bromo-10-(naphthalene-2-yl)anthracene (3) was produced
by the reaction of lithium salts of 2-bromonaphthalene, fol-
lowed by acidification in good yield. The compound 3 can
be readily converted into the corresponding lithium salt in
THF, which subsequently reacted with triphenylsilyl chloride
to afford 4 in 70% yields. After the compound 5 was synthe-
sized by bromination of 4 using NBS in DMF, the final
compound 6 was obtained by the Pd-catalyzed Suzuki
coupling reaction of 5 with phenylboronic acid in the
presence of a catalytic amount of Pd(PPh3)4 and excess
K2CO3 as a yellow solid (63%). The novel compound 7 was
also prepared from Pd-catalyzed Suzuki coupling reaction
of 2-(10-(4-(tert-butyl)phenyl)anthracen-9-yl)-4,4,5,5-tetra-
methyl-1,3,2-dioxaborolane with 1-(3-iodo-4-methylphenyl)
naphthalene according to a published procedure.22 The
1
formation of all compounds 1–7 was confirmed by H and
13C NMR spectroscopy (Figure S1–S13, Supporting
information).
Thermal Properties. The thermal properties of 6 and 7 were
investigated by thermogravimetric analysis (TGA) and differ-
ential scanning calorimetry (DSC) under N2 atmosphere.
Thermal stability was compared on the basis of Td5, which
represents 5% weight loss of compounds with increasing tem-
perature. The compound 6 and 7 exhibited Td5 values of
ꢀ
350and320 C, respectively, indicatingexcellent thermal sta-
bility. Additionally, the morphological stability of 6 and 7 was
ꢀ
monitored by DSC, which was performed from 0 to 450 C at
ꢀ
a heating rate of 10 C/min. The glass transiꢀtion temperature
(Tg) of 6 and 7 was obtained at 253 and 221 C, respectively.
Alsoꢀ, the melting temperature of 6 and 7 occurred at 331 and
299 C, respectively (Figure S14). The results of the second
scan were recorded to eliminate differences from the sample
history. Theseresultsclearlyshowthatthebulkytriphenylsilyl
group on the C2 position of anthracene moiety of the com-
pound 6 leads to enhanced thermal stability compared with
7. Additionally, high Tg of 6 and 7 can enhance operational
device lifetime for OLEDs using two asymmetric anthracene
compounds.25,26
Cyclic Voltammetry. CV measurements were carried out
with a three-electrode cell configuration consisting of plati-
num working and counter electrodes and an Ag/AgNO3
(0.1 M in MeCN) reference electrode at room temperature.
The solvent was MeCN and tetra-n-butylammonium hexa-
fluorophosphate (0.1 M) was used as the supporting electro-
lyte. The oxidation potentials were recorded at a scan rate of
50 mV/s and reported with reference to the ferrocene/ferroce-
nium (Fc/Fc+) redox couple.
Photophysical and Electrochemical Properties. The photo-
physical properties of anthracene-based compounds 6 and
7 were investigated by UV–Vis absorption and photolumines-
cence (PL) spectroscopy (Figure 1 and Table 1). The absorp-
tion spectra of 6 and 7 in dilute CH2Cl2 exhibited
the characteristic π–π* vibronic transition patterns (λabs
=
364, 383, and 404 nm for 6 and λabs = 356, 375, and
396 nmfor7)oftheisolated anthracenegroup. Theabsorption
maximum wavelengths (λabs) of 6 are slightly red-shifted
by 8 nm in comparison with those of compound 7. The emis-
sion maximum (λem) of 6 and 7 was 431 and 434 nm, respec-
tively. The PL spectra of two compounds were similar to
previously reported asymmetric anthracene derivatives,20,22
assignable to the lowest π–π* transition of anthracene
moieties.
Results and Discussion
Synthesis and Characterization. The synthetic procedures
toward anthracene derivatives 6 and 7 are shown in Scheme 1.
A new compound, 3-bromo-9,10-dihydro-9-oxoanthracene
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
138

Synthesis of Asymmetric Anthracene Derivatives and
Their Application for Blue OLEDs
BULLETIN OF THE
Article
KOREAN CHEMICAL SOCIETY
O
O
Li
O
2
CO2H
/ THF
1.
2. H3O+
Br
P, I2
H2SO4
H2O, EtCO2H
Br
Br
Br
3
1
1. n-BuLi
THF
2. Ph3SiCl
B(OH)2
NBS
DMF
Pd(PPh3)4, K2CO3
toluene/H2O
Si
Si
Si
Br
5
4
6
I
O
B
O
Pd(PPh3)4, K2CO3
toluene/H2O
7
Scheme 1. Synthetic routes for asymmetric anthracene derivatives 6 and 7.
Figure 1. UV–Vis absorption and PL spectra of 6 (a) and 7 (b) in CH2Cl2 solution.
Theelectrochemical properties of 6and7wereexamined by
CVmeasurements. Fromthefirstoxidationonsetpotential, the
HOMO energy levels of 6 and 7 were estimated to be −5.56
and −5.51 eV, respectively. The LUMO energy levels of
6 and 7 were also calculated as −2.64 and −2.49 eV,
respectively. The anthracene-based compounds 6 and 7 have
wide optical band gaps (Eg) of ca. 2.9–3.1 eV.
Electroluminescent Properties. The anthracene-based com-
pounds 6 and 7 were investigated as blue host materials in
blue-emitting OLEDs with BD-142 fluorescent dopant.
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
139

Synthesis of Asymmetric Anthracene Derivatives and
Their Application for Blue OLEDs
BULLETIN OF THE
Article
KOREAN CHEMICAL SOCIETY
Because of the similar HOMO energy levels of 6, 7, and 4,4’-
bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) (ca.
5.4 eV), NPB was used as the hole-transporting layer
(HTL) material.
showninFigure 3, twodevices emitted theexpectedbluelight.
Figure 3 shows the EL spectra of 6 or 7 based devices with a
7 wt % ratio of BD-142 at 20 mA/cm2. The EL emission max-
imum of two devices exhibits one peak at 464 (for 6) and
472 (for 7) nm, respectively.
The CIE color coordinates appeared at (0.143, 0.167) for
6 and (0.135, 0.175) for 7. The detailed EL characteristics
of the fabricated devices were summarized in Table 2. Accord-
ing to the current density–voltage–luminance (I–V–L) curves
(Figure 4), two devices showed good performance as blue host
materials. In particular, 7-based device exhibited a turn-on
voltage of 3.0 V, a maximum brightness (Lmax) of
37 090 cd/m2 at 11.0 V, and a maximum external efficiency
(ηext) of 5.80% (7.26 cd/A). These results indicate that
6 and 7 properly function as a blue emitting layer.
As shown in Figure 2, the OLEDs were constructed with the
following configuration: ITO/HI-406 (65 nm)/NPB (20 nm)/
6 or 7 (35 nm, BD-142 (7 wt %))/Bebq2 (20 nm)/LiF (1 nm)/
Al device, where ITO is the anode; HI-406 (purchased from
Idemitsu Kosan Co. Tokyo, Japan) is served as the hole-
injection layer (HIL); NPB is the HTL; the newly purified
anthracene derivatives 6 or 7 (host) and BD-142 (purchased
from Idemitsu Kosan Co.) (dopant) are served as the EML;
bis(10-hydroxy-benzo[h]-quinolinato)beryllium (Bebq2) is
the electron-transporting layer (ETL); a thin LiF serves as
an electron-injection layer at the Al cathode interface. As
Table 1. Photophysical and electrochemical properties of 6 and 7.
Compound
λ
abs (nm)a
λ
em (nm)a
Eg (eV)b
Eox (V)c
HOMO (eV)d
LUMO (eV)e
6
7
364, 383, 404
356, 375, 396
431
434
2.92
3.02
0.76
0.71
−5.56
−5.51
−2.64
−2.49
a
In CH2Cl2.
b
Estimated from the absorption edge.
c
d
e
The oxidation onset potential vs. an Fc/Fc+ couple.
Calculated from the Eox
Estimated from the HOMO and band-gap (Eg) energies.
.
Figure 2. Energy diagrams of devices using 6 or 7 with BD-142 (7 wt
%) as an emitter.
Figure 3. EL spectra of the devices using 6 and 7 with BD-142 (7 wt
%) at 20 mA/cm2.
Table 2. EL performances of BD-142 (7 wt %)-doped blue OLEDs.
Compound
Von (V)a
V (V)b
η
ext (%)c
η
lum (cd/A)d
η
pw (lm/W)e
Lmax (cd/m2)f
CIE (x, y)
6
7
3.00
3.00
4.56
5.20
4.83
5.80
6.15
7.26
4.23
4.38
19 680
37 090
(0.143, 0.167)
(0.135, 0.175)
a
Turn-on voltage.
b
Recorded at 20 mA/cm2.
c
d
e
f
Maximum external quantum efficiency.
Maximum luminous current density.
Maximum power efficiency.
Maximum luminance at 11 V.
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
140

Synthesis of Asymmetric Anthracene Derivatives and
Their Application for Blue OLEDs
BULLETIN OF THE
Article
KOREAN CHEMICAL SOCIETY
Figure 4. The I–V–L curves of the (a) 6- and (b) 7-based device.
7. H. Park, J. Lee, I. Kang, H. Y. Chu, J.-I. Lee, S.-K. Kwon,
Y.-H. Kim, J. Mater. Chem. 2012, 22, 2695.
Conclusion
8. I. Cho, S. H. Kim, J. H. Kim, S. Park, S. Y. Park, J. Mater. Chem.
2012, 22, 123.
In summary, anthracene-based new blue host materials 6 and
7 were synthesized and characterized. The anthracene deriva-
tives possessed high thermal stabilities that are appropriate as
novel host materials for blue OLEDs. All devices showed
good performances as blue host materials. The 7-based device
especially displays higher device performances with respect to
brightness, luminous current density, and external quantum
efficiencies than those of 6-based device. Relevant further
studies using various anthracene derivatives to enhance the
performance of devices are in progress.
9. J.-K. Bin, J.-I. Hong, Org. Electron. 2011, 12, 802.
10. K. H. Lee, J. N. You, S. Kang, J. Y. Lee, H. J. Kwon, Y. K. Kim,
S. S. Yoon, Thin Solid Films 2010, 518, 6253.
11. C.-J. Zheng, W.-M. Zhao, Z.-Q. Wang, D. Huang, J. Ye,
X.-M. Ou, X.-H. Zhang, C.-S. Lee, S.-T. Lee, J. Mater. Chem.
2010, 20, 1560.
12. S.-K. Kim, B. Yang, Y. Ma, J.-H. Lee, J.-W. Park, J. Mater.
Chem. 2008, 18, 3376.
13. J.-Y. Park, S. Y. Jung, J. Y. Lee, Y. G. Baek, Thin Solid Films
2008, 516, 2917.
Acknowledgments. This work was supported by the Basic
Science Research Program (NRF-2013R1A1A2061792 for
M. H. Park and No. 2010-0023904 for Y. Chung) through
the National Research Foundation of Korea (NRF) funded
by the Ministry of Education. Y. Chung thanks the support
from the research grant of Chungbuk National University
in 2013.
14. P.-I. Shih, C.-Y. Chuang, C.-H. Chien, E. W.-G. Diau, C.-F. Shu,
Adv. Funct. Mater. 2007, 17, 3141.
15. Y. Zhang, S.-L. Lai,Q.-X. Tong, M.-F. Lo, T.-W. Ng, M.-Y. Chan,
Z.-C. Wen, J. He, K.-S. Jeff, X.-L. Tang, W.-M. Liu, C.-C. Ko,
P.-F. Wang, C.-S. Lee, Chem. Mater. 2012, 24, 61.
16. A.
Thangthong,
D.
Meunmart,
N.
Prachumrak,
S. Jungsuttiwong, T. Keawin, T. Sudyoadsuk, V. Promarak,
Chem. Commun. 2011, 47, 7122.
17. Y. Sun, L. Duan, D. Zhang, J. Qiao, G. Dong, L. Wang, Y. Qiu,
Adv. Funct. Mater. 2011, 21, 1881.
SupportingInformation. Additionalsupportinginformation
is available in the online version of this article.
18. I. -S. Choi, S. H. Kim, H. -C. Ahn, Y. Kim, Y. Chung, Bull.
Korean Chem. Soc. 2013, 34, 2211.
References
19. J.-K. Park, K.-H. Lee, S. Kang, J.-Y. Lee, J.-S. Park, J.-H. Seo,
Y.-K. Kim, S.-S. Yoon, Org. Electron. 2010, 11, 905.
20. Y.-Y. Lyu, J. Kwak, O. Kwon, S.-H. Lee, D. Kim, C. Lee,
K. Char, Adv. Mater. 2008, 20, 2720.
21. R. Kim, S. Lee, K.-H. Kim, Y.-J. Lee, S.-K. Kwon, J.-J. Kim,
Y.-H. Kim, Chem. Commun. 2013, 49, 4664.
1. C. W. Tang, S. A. Van Slyke, Appl. Phys. Lett. 1987, 51, 913.
2. J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks,
K. Mackay, R. H. Friend, P. L. Burns, A. B. Holmes, Nature
1990, 347, 539.
22. K.-R. Wee, W.-S. Han, J.-E. Kim, A.-L. Kim, S. Kwon,
S. O. Kang, J. Mater. Chem. 2011, 21, 1115.
3. J. Li, T. Zhang, Y. Liang, R. Yang, Adv. Funct. Mater. 2013,
23, 619.
23. W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory
Chemicals, 6th ed., Elsevier, Amsterdam, Netherlands, 2009.
24. L.-L. Huang, M.-H. Xu, G.-Q. Lin, J. Am. Chem. Soc. 2007,
128, 5624.
25. Y. H. Kim, H. C. Jeong, S. H. Kim, K. Yang, S. K. Kwon, Adv.
Funct. Mater. 2005, 15, 1799.
4. S.-J. Lee, J.-S. Park, M. Song, I. A. Shin, Y.-I. Kim, J. W. Lee,
J.-W. Kang, Y.-S. Gal, S. Kang, J. Y. Lee, S.-H. Jung, H.-S. Kim,
M.-Y. Chae, S.-H. Jin, Adv. Funct. Mater. 2009, 19, 2205.
5. R. Seifert, I. Rabelo de Moraes, S. Scholz, M. C. Gather,
B. Lüssem, K. Leo, Org. Electron. 2013, 14, 115.
6. N.-C. Seong, Y.-M. Jeon, T.-H. Lim, J.-W. Kim, C.-W. Lee,
E.-J. Lee, J.-G. Jang, H.-J. Jang, J.-Y. Lee, M.-S. Gong, Synth.
Met. 2007, 157, 421.
26. M.-H. Ho, Y.-S. Wu, S.-W. Wen, T.-M. Chen, C.-H. Chen, Appl.
Phys. Lett. 2007, 91, 083515.
Bull. Korean Chem. Soc. 2016, Vol. 37, 136–141
© 2016 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.bkcs.wiley-vch.de
141