Organic electroluminescence devices based on anthracene sulfide derivatives

Article abstract of DOI:10.1016/j.tetlet.2010.09.089

A series of anthracene derivatives are synthesized and fabricated as light-emitting materials in OLED devices. The incorporation of the chalcogen atoms, either oxygen or sulfur, in between the anthracene moiety and the alkyl or aryl substituents affected drastically the photo- and electroluminescence properties of the materials, especially the HOMO-LUMO band gap and the emitting color of the devices. The new anthracene sulfide derivatives represent a new design for further modification of other light-emitting doped materials.

Full text of DOI:10.1016/j.tetlet.2010.09.089

Tetrahedron Letters 51 (2010) 6392–6395
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Organic electroluminescence devices based on anthracene sulfide derivatives
a
b
c
a
Chakkrapan Nerungsi , Piangkhwan Wanitchang , Somboon Sahasithiwat , Karoon Sadorn ,
b
a,d,
⇑
Teerakiat Kerdcharoen , Tienthong Thongpanchang
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
Department of Physics, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
National Metal and Materials Technology Center, National Science and Technology Development Agency, Thailand Science Park, Phathumthani 12120, Thailand
National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Thailand Science Park, Phathumthani 12120, Thailand
a
b
c
d
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of anthracene derivatives are synthesized and fabricated as light-emitting materials in OLED
devices. The incorporation of the chalcogen atoms, either oxygen or sulfur, in between the anthracene
moiety and the alkyl or aryl substituents affected drastically the photo- and electroluminescence prop-
erties of the materials, especially the HOMO–LUMO band gap and the emitting color of the devices.
The new anthracene sulfide derivatives represent a new design for further modification of other light-
emitting doped materials.
Received 10 April 2010
Revised 25 August 2010
Accepted 20 September 2010
Available online 29 September 2010
Ó 2010 Elsevier Ltd. All rights reserved.
1
. Introduction
Small organic molecules that exhibit red, green or blue colors
The UV absorption and fluorescence spectra of the anthracene
derivatives were recorded in chloroform, Figure 1. All the absorp-
1
2
3
tion spectra exhibited similar characteristic vibrational patterns
4
a
have been widely investigated for the development of electronic de-
vices such as organic light-emitting diodes (OLEDs). Among the blue
emitters, anthracene derivatives demonstrate high-performance
with excellent photoluminescence and electroluminescence prop-
of the anthracene group in the region of 340–420 nm. The bath-
ochromic shift (5 nm) of the sulfide derivative ADS in comparison
to that of the ether derivative ADO indicated that the decrease in
the HOMO–LUMO band gap (Fig. 2) was due to an electron delocal-
4
5
erties. Interestingly, recent reports indicated that introduction of
ization effect from the heavier chalcogen atom. Alkyl substituents
heteroatoms, especially chalcogens, onto the anthracene core could
change its molecular characteristics and electronic properties. In
this Letter, anthracene sulfides, [9,10-bis(1-dodecylthio)anthracene
with different chain lengths did not affect substantially the elec-
tronic properties of the anthracene as was evident from the indis-
tinguishable spectra of ADS and APrS. In contrast, the aryl
substituents, both phenyl (of APS) and naphthyl (of ANS), caused
a red shift, possibly due to the participation of the conjugated sys-
tem between the aryl substituents and the anthracene ring. The
fluorescence spectra of anthracene derivatives show blue emission
with a maximum peak at 442–476 nm. Similar to the absorption
spectra, bathochromic shifts in the emission spectra were also ob-
served upon changing the substituents.
5
(
ADS), 9,10-bis(1-propylthio)anthracene (APrS), 9,10-bis(phenyl-
thio)anthracene (APS), and 9,10-bis(2-naphthylthio)anthracene
ANS)] and an ether, [9,10-bis(1-dodecyloxy)anthracene (ADO)]
(
were prepared and their properties as light emitting materials in
OLED devices were investigated. ADO and ADS were designed to
demonstrate the influence of the chalcogen atoms while ADS, APrS,
APS, and ANS would highlight the effect of the type of alkyl or aryl
side chains as well as the effect of chain length.
The relative fluorescence quantum yields (
f
U ) of the anthracene
As shown in Scheme 1, 9,10-bis(1-dodecyloxy)anthracene (ADO)
derivatives in dilute CHCl solution were measured using harmane
3
9
was prepared by the reduction of 9,10-anthraquinone (1) with
(U
f
ꢀ0.83) and harmine (
U
f
ꢀ0.45) as calibration standards. All
6
Na
2
2
S O
4
, followed by Williamson ether synthesis in the presence
the anthracene sulfide derivatives gave fluorescence quantum
of KOH and 1-bromododecane (34% overall yield). For the synthesis
yields of 0.006–0.048 whereas the ether derivative (ADO) gave a
of anthracene sulfide derivatives, treatment of anthraquinone 1
high fluorescence quantum yield of 0.46 (Table 1). The lower U
f
with Zn, K
2
CO3, and acetic anhydride in THF provided 9,10-diacet-
of the other anthracene sulfide derivatives might be attributed to
quenching from the sulfide substituents, that is, the sulfur lone pair
of electrons participated in the photo-induced electron transfer to
oxyanthracene (2) in 87% yield. The acid-mediated substitution
reaction of anthracene 2 with dodecane, propane, benzene, and 2-
naphthalene thiols gave disulfide derivatives; ADS, APrS, APS, and
ANS in 81%, 71%, 36%, and 17% yields, respectively.7
1
0
the excited state of the anthracene.
,8
The effect of a sulfur atom on the photo- and electrochemical
properties of the anthracene core could be substantiated by
comparison of the UV and fluorescence spectra as well as the
HOMO–LUMO band gap between ANS and the non-sulfur
⇑
Corresponding author. Tel./fax: +66 2 201 5139.
E-mail address: tettp@mahidol.ac.th (T. Thongpanchang).
0
040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.089

C. Nerungsi et al. / Tetrahedron Letters 51 (2010) 6392–6395
6393
O
O
O
1
) Na2S2O4, TBAB
H2O, CH2Cl2
2
) KOH, 1-bromododecane
O
1
ADO (34%)
OAc
SR
Zn, K2CO3
RSH
Ac2O, THF, rt.
p-TsOH
Toluene, reflux
OAc
(87%)
SR
2
R = dodecyl, propyl, phenyl, naphthyl
S
S
S
S
ADS (81%)
APrS (71%)
S
S
S
S
APS (36%)
ANS (17%)
Scheme 1. Syntheses of anthracene derivatives.
ADO ADS APrS APS ANS
1
.0
-1.50
ADO
ADS
APrS
APS
ANS
-2.07
LUMO
-
2.00
-2.30
-2.37
0.8
-2.57
-2.63
-
2.50
-
-
-
3.00
3.50
4.00
0
.6
2
.94
2.88
2.88
2.81
2.75 band gap
HOMO
0.4
-
4.50
0.2
-
5.00
-
5.01
-
5.18
-
-
5.50
6.00
-5.25
-
5.38
-5.38
0.0
350
400
450
500
550
600
decreasing band gap
Wavelength (nm)
Figure 2. The energy levels of the HOMO–LUMO orbitals of the anthracene
derivatives.
Figure 1. UV (—) and fluorescence spectra (4) of the anthracene derivatives.
derivative, 9,10-bis(2-naphthyl)anthracene (ADN).4a ANS showed a
red shift of 42 nm in the UV spectrum, (from 377 nm in ADN to
S
S
4
3
19 nm in ANS), corresponding to a decrease in the band gap from
.01 to 2.75 eV. The HOMO and LUMO energy levels of ANS (ꢁ5.38
and ꢁ2.63 eV, respectively) were higher than those of ADN (ꢁ5.88
and ꢁ2.87 eV, respectively). In addition, a red shift of 49 nm in the
fluorescence spectrum of ANS (kem at 476 nm) compared to ADN
(kem at 427 nm) was also observed. These results demonstrate
the participation of the sulfur atom in the anthracene conjugated
system, resulting in a drastic change in the electronic properties
of the anthracene ring.
ADN
ANS

6
394
C. Nerungsi et al. / Tetrahedron Letters 51 (2010) 6392–6395
Table 1
Physical data of anthracene derivatives and electroluminescence performances of their devices
a
b
c
d
e
f
g
g
g
CIE (x, y)g
Compound
k
max, abs
k
max, em
T
m
U
f
HOMO /LUMO (eV)
Nurn-on
I
eff, max (cd/A)
B
max at voltage
EL kmax (nm)
(nm)
(nm)
(°C)
voltageg (V)
cd/m2)
(
(V)
ADO
ADS
APrS
APS
407
412
412
417
419
442
460
461
463
476
50
69
109
213
239
0.46
ꢁ5.01/ꢁ2.07
ꢁ5.25/ꢁ2.37
ꢁ5.18/ꢁ2.30
ꢁ5.38/ꢁ2.57
ꢁ5.38/ꢁ2.63
6.6
6.9
8.8
7.8
8.6
0.08
0.09
0.08
0.11
0.03
214
319
203
290
132
11.5
10.5
13.5
11.0
11.0
450
465
465
465
470
0.17, 0.14
0.16, 0.16
0.17, 0.17
0.17, 0.18
0.20, 0.22
0.048
0.023
0.038
0.006
ANS
a
b
c
d
e
f
Maximum absorption wavelength in CHCl
Maximum emission wavelength in CHCl
Obtained from differential scanning calorimetry (DSC) measurements.
Fluorescence quantum yield in CHCl
HOMO level was determined from the onset of the first oxidation wave in the cyclic voltammogram.
3
.
3
.
3
.
LUMO level was calculated from the difference between the HOMO level and the optical band gap estimated from the onset of the lowest-energy visible absorption edge.
Obtained from the electroluminescence devices.
g
The electroluminescence properties of ADO, ADS, APrS, APS,
and ANS were investigated. All the synthetic materials were sub-
jected to device fabrication in simple doped device structures
ADO
ADS
APrS
APS
ANS
(
p
Fig. 3). Due to the low melting temperatures and potentially close
-stack solid state packing of ADO, ADS, and APrS,5
,11
poly(N-
100
vinylcarbazole) (PVK) was used as a host material matrix in all
the electroluminescence (EL) devices to improve the film-forming
properties in the emitting layer, which was fabricated by a spin
1
2
coating process. Thus the OLED devices prepared in this work
have the following structure: indium tin oxide (ITO) (anode)|3,4-
polyethylene-dioxythiophene:polystyrene sulfonate (PEDOT:PSS)
1
0
(
1
35 nm) (hole transporting layer)|PVK:anthracene derivatives
wt % (68 nm) (emitting layer)|Ca (10 nm) (cathode)|Al (100 nm)
(
protective layer).
The current density–voltage and the luminance–voltage charac-
1
0
2
4
6
8
10
12
14
teristics of the OLED devices are shown in Figures 3 and 4. The
maximum EL brightness of ADO, ADS, APrS, APS, and ANS reached
Voltage (V)
2
2
14, 319, 203, 290, and 132 cd/m , respectively. Figure 5 shows the
Figure 4. The luminance versus voltage plots of the anthracene derivative doped
plots of current efficiency versus current density of the devices.
The ADO-based device exhibited a maximum current efficiency
in the same range as those of the sulfur analogs ADS, APrS, and
APS (see Table 1). The maximum current efficiency of ANS was
lowest at 0.03 cd/A.
devices.
blue light with a peak at 440 nm, from the luminescence of PVK,
corresponding to the CIE coordinates of (0.25, 0.20). In the pres-
ence of the doped material, the EL kmax of the device is red shifted
Fig. 6): ADO 450 nm, CIE (0.17, 0.14), ADS 465 nm, CIE (0.16, 0.16),
APrS 465 nm, CIE (0.17, 0.17), APS 465 nm, (0.17, 0.18) and ANS
70 nm, CIE (0.20, 0.22), indicating energy transfer from PVK to
The EL kmax values of all the doped devices are in the region of
4
50–470 nm, with the observed red shift in the devices doped with
(
sulfur-containing materials. The non-doped device emitted purple-
4
6
5
4
3
2
1
00
00
00
00
00
00
0
0
.12
ADO
ADS
APrS
APS
ANS
ADO
ADS
APrS
APS
ANS
0.10
0.08
0
0
0
0
.06
.04
.02
.00
Ca (10 nm)/Al (100 nm)
PVK:anthracene 1 wt%
PEDOT:PSS
ITO coated glass
0
2
4
6
8
10
12
14
0
100
200
300
400
500
Voltage (V)
Current density(mA/cm2)
Figure 3. The current density versus voltage plots of the anthracene derivative
Figure 5. Current efficiency versus current density of anthracene derivative based
doped devices.
devices.

C. Nerungsi et al. / Tetrahedron Letters 51 (2010) 6392–6395
6395
to yield 9,10-bis(1-dodecylthio)anthracene (ADS) (1.18 g, 81%
yield).
Acknowledgments
Financial support from the National Synchrotron Research Cen-
ter (Grant 2-2549/PS01) for T.T. and scholarship support from the
Royal Golden Jubilee (RGJ) program, the Development and Promo-
tion of Science and Technology Talents (DPST) and the Center for
Innovation in Chemistry: Postgraduate Education and Research
Program in Chemistry (PERCH-CIC) for C.N., P.W., and K.S. are
gratefully acknowledged.
Supplementary data
Supplementary data (the synthesis, H and 13C NMR spectra and
cyclic voltammograms (CV) of compounds ADO, ADS, APrS, APS
and ANS) associated with this article can be found, in the online
version, at doi:10.1016/j.tetlet.2010.09.089.
1
Figure 6. The Commission Internationale de L’Eclairage (CIE) chromaticity coordi-
nates of the doped devices.
References and notes
1
2
3
.
.
.
For some selected examples, see: (a) Yeh, H.-C.; Chan, L.-H.; Wu, W.-C.; Chen,
C.-T. J. Mater. Chem. 2004, 14, 1293; (b) Chen, C. H.; Tang, C. W.; Shi, J.; Klubek,
K. P. Thin Solid Films 2000, 363, 327; (c) Thomas, K. R. J.; Lin, J. T.; Tao, Y.-T.;
Chuen, C.-H. Adv. Mater. 2002, 14, 822; (d) Ma, C.-Q.; Liang, Z.; Wang, X.-S.;
Zhang, B.-W.; Cao, Y.; Wang, L.-D.; Qiu, Y. Synth. Met. 2003, 138, 537.
For selected examples, see: (a) Lee, M.-T.; Yen, C.-K.; Yang, W.-P.; Chen, H.-H.;
Liao, C.-H.; Tsai, C.-H.; Chen, C. H. Org. Lett. 2004, 6, 1241; (b) Yu, M.-X.; Duan,
J.-P.; Lin, C.-H.; Cheng, C.-H.; Tao, Y.-T. Chem. Mater. 2002, 14, 3958; (c) Chen, C.
H.; Tang, C. W. Appl. Phys. Lett. 2001, 79, 3711; (d) Tao, Y. T.; Balasubramaniam,
E.; Danel, A.; Jarosz, B.; Tomasik, P. Appl. Phys. Lett. 2000, 77, 1575.
For some selected examples, see: (a) Mitsumori, T.; Bendikov, M.; Dautel, O.;
Wudl, F.; Shioya, T.; Sato, H.; Sato, Y. J. Am. Chem. Soc. 2004, 126, 16793; (b) Wu,
Y. Z.; Zheng, X. Y.; Zhu, W. Q.; Sun, R. G.; Jiang, X. Y.; Zhang, Z. L.; Xu, S. H. Appl.
Phys. Lett. 2003, 83, 5077; (c) Lee, M.-T.; Liao, C.-H.; Tsai, C.-H.; Chen, C. H. Adv.
Mater. 2005, 17, 2493.
the anthracene derivatives. Moreover, the results showed that the
length of the alkyl side chain has only a small effect on the lumi-
nescence properties of the molecules, while the effect of the aryl
side chain was more drastic.
In conclusion, incorporation of chalcogen atoms, especially sul-
fur, onto the anthracene core drastically changes the photo and
electronic properties of the molecules. This work has demonstrated
the potential application of this new class of sulfur-containing
materials for OLED devices. Further research on the design of more
efficient sulfur-containing dopants as well as the device fabrication
technique is required to improve the EL efficiency and these stud-
ies are currently in progress.
4. (a) Tao, S.; Xu, S.; Zhang, X. Chem. Phys. Lett. 2006, 429, 622; (b) Zhang, Z.; Tang,
H.; Wang, H.; Liang, X.; Lui, J.; Qiu, Y.; Shi, G. Thin Solid Films 2007, 515, 3893;
(
c) Shen, W.-J.; Dodda, R.; Wu, C.-C.; Wu, F.-I.; Lui, T.-H.; Chen, H.-H.; Chen, C.
2
. Typical procedure for the synthesis of anthracene bissulfide
H.; Shu, C.-F. Chem. Mater. 2004, 16, 930; (d) Danel, K.; Huang, T.-H.; Lin, J. T.;
Tao, Y.-T.; Chuen, C.-H. Chem. Mater. 2002, 14, 3860; (e) Gebeyehu, D.; Walzer,
K.; He, G.; Pfeiffer, M.; Leo, K.; Brandt, J.; Gerhard, A.; Stößel, P.; Vestweber, H.
Synth. Met. 2005, 148, 205.
Kobayashi, K.; Masu, H.; Shuto, A.; Yamaguchi, K. Chem. Mater. 2005, 17, 6666.
Kraus, G. A.; Man, T. O. Synth. Commun. 1986, 16, 1037.
Sadorn, K.; Sinananwanich, W.; Areephong, J.; Wongma, C.; Nerungsi, C.;
Pakawatchai, C.; Thongpanchang, T. Tetrahedron Lett. 2008, 49, 4519.
Charoonniyomporn, P.; Thongpanchang, T.; Witayakarn, S.; Thebtaranonth, Y.;
Phillips, K. E. S.; Katz, T. J. Tetrahedron Lett. 2004, 45, 457.
derivatives
2
.1. 9,10-Bis(1-dodecylthio)anthracene (ADS)
5
6
7
.
.
.
A mixture of 9,10-diacetoxyanthracene (0.74 g, 2.51 mmol) and
-dodecanethiol (6.03 g, 25.1 mmol) was refluxed in toluene
1
8.
(
2
20.0 mL) in the presence of p-toluenesulfonic acid (4.78 g,
5.1 mmol) for 6 h. The reaction was cooled to room temperature
and quenched with sat. NaHCO (20 mL) and then extracted with
EtOAc (3 ꢂ 30 mL). The combined organic extract was washed with
O, dried over Na SO and evaporated to dryness. The crude prod-
uct was purified by crystallization from a solution of CH Cl /MeOH
9. Pardo, A.; Reyman, D.; Poyato, J. M. L.; Medina, F. J. Lumin. 1992, 51, 269.
0. Beecroft, R. A.; Davidson, R. S.; Goodwin, D.; Pratt, J. E. Tetrahedron 1984, 40,
487.
1
3
4
1
1. Sasaki, H.; Wakayama, Y.; Chikyow, T.; Barrena, E.; Dosch, H.; Kobayashi, K.
Appl. Phys. Lett. 2006, 88, 081907.
2. Zhang, Y.; Hu, Y.; Chen, J.; Zhou, Q.; Ma, D. J. Phys. D: Appl. Phys. 2003, 36, 2006.
H
2
2
4
1
2
2