Synthesis and characterization of 9,10-substituted anthracene derivatives as blue light-emitting and hole-transporting materials for electroluminescent devices

Article abstract of DOI:10.1016/j.tet.2011.12.083

New 9,10-substituted anthracene derivatives were designed and synthesized for application as blue-emitting and hole-transporting materials in electroluminescent devices. They were characterized by H NMR, C NMR, FTIR, UV-vis, PL spectroscopy, and mass spectrometry. The theoretical calculation of three-dimensional structure and the energy densities of HOMO and LUMO states, as well as optical properties of these new obtained materials, supported the claim that they had non-coplanar structures. Their optical, thermal, and electrochemical properties could be tuned by varying the peripheral substituents. All of them were electrochemically and thermally stable molecules. Materials having electron donating triphenylamine as peripheral substituents showed promising potential as both blue light-emitting materials and hole-transporting materials for electroluminescent devices. Efficient blue and Alq3-based green OLEDs with maximum luminance efficiencies and CIE coordinates of 1.65 cd/A and (0.15, 0.16) and 6.25 cd/A and (0.26, 0.49) were achieved, respectively.

Full text of DOI:10.1016/j.tet.2011.12.083

Tetrahedron 68 (2012) 1853e1861
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and characterization of 9,10-substituted anthracene derivatives as blue
light-emitting and hole-transporting materials for electroluminescent devices
A-monrat Thangthong, Duangratchaneekorn Meunmart, Narid Prachumrak, Siriporn Jungsuttiwong,
*
Tinnagon Keawin, Taweesak Sudyoadsuk, Vinich Promarak
Center for Organic Electronic and Alternative Energy, Department of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University,
Warinchumrap, Ubon Ratchathani 34190, Thailand
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 October 2011
Received in revised form 21 December 2011
Accepted 29 December 2011
Available online 3 January 2012
New 9,10-substituted anthracene derivatives were designed and synthesized for application as blue-
emitting and hole-transporting materials in electroluminescent devices. They were characterized by H
NMR, C NMR, FTIR, UVevis, PL spectroscopy, and mass spectrometry. The theoretical calculation of three-
dimensional structure and the energy densities of HOMO and LUMO states, as well as optical properties
of these new obtained materials, supported the claim that they had non-coplanar structures. Their op-
tical, thermal, and electrochemical properties could be tuned by varying the peripheral substituents. All
of them were electrochemically and thermally stable molecules. Materials having electron donating
triphenylamine as peripheral substituents showed promising potential as both blue light-emitting ma-
terials and hole-transporting materials for electroluminescent devices. Efficient blue and Alq3-based
green OLEDs with maximum luminance efficiencies and CIE coordinates of 1.65 cd/A and (0.15, 0.16)
and 6.25 cd/A and (0.26, 0.49) were achieved, respectively.
Keywords:
Anthracene
Blue light-emitting material
Hole-transporting material
Triphenylamine
Organic light-emitting diode
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
has received considerable interest. Anthracene derivatives have
been extensively used as fluorescent chromophores in the con-
The use of
p
-conjugated organic compounds as electrolumi-
struction of chemosensors for many applications.13 In-
corporation of anthracene and its 9,10-substituted derivatives
into polymer main-chains14 or linked as pendent groups15 con-
tributes to solve the problem of preparation of films with good
optical quality or to suppress excimer formation. A number of
polymeric and molecular 9,10-substituted anthracenes have also
been developed and studied as blue light-emitting materials for
OLED devices.6,15,16 However, new classes of anthracene based-
blue light-emitters with improvements in terms of efficiency
and color purity remain to be explored. In this work, the
designed 9,10-substituted anthracenes incorporating different
characteristic aromatic rings such as fluorene, thiophene, and
nescent materials in organic light-emitting diodes (OLEDs) was
originally introduced by van Slyke over two decades ago.1 Since
then, the development of new p-conjugated compounds especially
small molecules with superior physical, optical, thermal, and
electrochemical properties has become one of the most reviving
research areas.2e4 OLEDs for flat-panel displays are showing great
promise, and a related application for a flexible flat-panel display is
progressing.5 Full-color displays are required for red, green, and
blue light-emitting materials. Although many fluorescent blue
emitters have been reported, such as anthracene derivatives,6
phenylene derivatives,7 pyrene derivatives,8 fluorene derivatives,9
carbazole derivaties,10 triarylamine derivatives,11 and phosphores-
cent iridium complexes,12 there is still a clear need for further
improvements in terms of efficiency and color purity compared to
red and green emitters.
triphenylamine as
and characterized (Fig. 1). The introduction of planar thiophene
would allow a long -conjugation system to be achieved, while
p-conjugation substituents were synthesized
p
integration of the bulky triphenylamine could suppress aggre-
gation of the planar anthracene ring, as well as increase the
hole-transporting capability and thermal stability.17 Fluorene
also has a number of advantages, including its capability to emit
in the blue part of the visible spectrum, chemical and photo-
chemical stability.9,18 The physical and photophysical properties
of these compounds were investigated with the aim of
Due to its unique chemical and electron-rich structure, low
electronic band gap and strong blue fluorescence, anthracene
* Corresponding author. Tel.: þ6 645 353 401x4510; fax: þ6 645 288 379; e-mail
addresses: pvinich@ubu.ac.th, pvinich@gmail.com (V. Promarak).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.12.083

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A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
Fig. 1. Chemical structures of 9,10-substituted anthracenes 1e4.
Scheme 1. Synthetic route to 1e4. Reagents and conditions: (i) 50% NaOH, n-Bu4NBr,
C6H13Br, DMSO, rt; (ii) Pd(PPh3)4, 2 M Na2CO3, THF, reflux; (iii) NBS, THF, rt; (iv) NiCl2,
Zn, PPh3, DMAc, bpy, 90 ꢀC.
understanding the structureeproperty relationships and de-
veloping novel molecular -conjugated materials. Investigations
p
on OLED device fabrication and characterization are also
demonstrated.
2.2. Quantum calculation and optical properties
To understand the electronic properties and the geometries of
1e4, quantum chemical calculations were performed using the
TDDFT/B3LYP/6-31G (d,p) method.21 The optimized structures of
these compounds revealed that all molecules adopted non-co-
planar conformations. Particularly, the planar anthracene unit was
twisted nearly perpendicular to the adjacent thiophene, fluorene,
and triphenylamine moieties because of a steric repulsion between
anthracene peri-hydrogen atoms (1,8 and 4,5 positions) and hy-
drogen atoms of those aromatic rings. Such structural characteris-
tics can influence some of their electronic and physical properties
such as a suppression of the conjugation. As demonstrated in Fig. 2
2. Results and discussion
2.1. Synthesis
The molecular structures of the target anthracenes bearing
fluorene, thiophene, bithiophene, and triphenylamine as 9,10-
substituents are shown in Fig. 1. As illustrated in Scheme 1, we
began the synthesis with alkylation of 2-iodofluorene 519 at C-9
position of the fluorene ring with dihexyl chains followed by
palladium-catalyzed Suzuki cross-coupling of the resultant in
excess amounts with 9-bromoanthracene-10-boronic acid to give
6 in a fair yield of 52%. Target anthracene 1 bearing fluorene and
thiophene rings as 9,10-substituents was formed by Suzuki cross-
coupling of 6 with 2-thiopheneboronic acid in 76% yield as light
yellow solids. To form the more extended
cule of 2, a two-step synthesis was carried out by regioselective
bromination at -position of thiophene ring of 1 with NBS in THF
p-conjugation mole-
a
followed by reductive nickel-catalyzed dimerization reaction of
the obtained 7 with the catalytic system of NiCl2, zinc powder,
PPh3, and bipyridine (bpy) in DMAc at 90 ꢀC. Anthracene 2, a di-
mer of 1, was obtained as a greenish solid in an overall yield of
60%. In the target anthracenes 3 and 4, a substituent group with
a
hole-transporting property was introduced. Compound 3
bearing fluorene and triphenylamine as substituents was ob-
tained as a light yellow solid in a good yield of 79% by Suzuki
cross-coupling of readily formed
6 with N,N-diphenyl-N-4-
aminophenylboronic acid.20 Target anthracene 4, a dimer of 3,
was successfully synthesized by carrying out double Suzuki
cross-coupling of ready dialkylated 2,7-diiodofluorene 819
with 9-bromoanthracene-10-boronic acid (2.11 equiv) followed
by coupling of the obtained
9
with N,N-diphenyl-N-4-
aminophenylboronic acid, and gained as a deep yellow solid in
75% yield. All newly synthesized compounds were fully charac-
terized by standard spectroscopic methods. They had good sol-
ubility in most organic solvents at room temperature, resulting
from the presence of n-hexyl groups at the C-9 of fluorene ring.
As a result, no crystallization thin film should be obtained from
a solution casting.
Fig. 2. The HOMO (bottom) and LUMO (top) orbitals of 2 and 4.

A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
1855
(also see Supplementary data), in the highest occupied molecular
orbitals (HOMO) of 1 and 2, -electrons are located on the an-
thracene and thiophene moieties, while in the HOMO orbitals of 3
and 4, -electrons are delocalized over anthracene and donor tri-
phenylamine segments. The participation of the fluorene ring in the
-conjugation system was diminished in all cases. In the lowest
unoccupied molecular orbitals (LUMO) of all compounds, electrons
located only on anthracene rings. The HOMOeLUMO energy gaps
(Eg calcd) were calculated and presented in Table 1. These calcu-
lated values slightly deviated from those obtained from the ex-
perimental results (w0.01e0.18 eV). There are factors responsible
for the errors because the orbital energy difference between HOMO
and LUMO is still an approximate estimation of the transition en-
ergy, since the transition energy also contains significant contri-
butions from some two-electron integrals. The real situation is that
an accurate description of the lowest singlet excited state requires
a linear combination of a number of excited configurations.
were nearly identical, despite somewhat different molecular sizes,
indicating they had comparable -conjugation length. This can be
explained by an out of plane twisting of the fluorene unit from
p
p
p
adjacent anthracene rings as mentioned earlier (Fig. 2) limiting the
delocalization of
amine units only. In contrast, the Eg of 1 is noticeably higher than
that of its corresponding dimer 2 indicating remarkably longer
conjugation length in 2. This is due to less a hindered thiophene
ring in the molecules allowing extended -electron delocalization
p-electrons on the anthracene and triphenyl-
p
p-
p
over the anthracene and bithiophene moieties.
These compounds in solution fluoresced ranging from bright
blue to blue-green colors with featureless photoluminescence (PL)
spectra (Fig. 3), which is similar to what was observed for most 9,10-
diphenylanthracenes.6 The solution PL spectrum of the dimer 2 red-
shifted with respect to that of 1, whereas the PL spectra of 3 and
dimer 4 were duplicate. These results were in agreement to what
was observed from the theoretical and UVevis experiments. These
Table 1
Physical and photophysical data of 1e4
lem (nm) lem (nm) Stokes shiftc (nm) FF
Tg/Tc/Tm/T5d (ꢀC) Egf (eV) Eg calcdg (eV) E1/2h (V)
Eonseth (V) HOMO/LUMOi (eV)
a
a
b
d
e
Compd labs (nm)
1
2
3
4
359, 378, 398 439
439
483
458
466
41
72
85
85
0.12 d/115/209/330
0.04 d/d/326/370
0.73 79/d/d/397
2.96
2.87
2.90
3.11
3.05
2.93
2.90
1.20, 1.45 1.12
ꢁ5.56/ꢁ2.60
ꢁ5.52/ꢁ2.65
ꢁ5.32/ꢁ2.42
ꢁ5.32/ꢁ2.43
363, 383, 402 474
359, 380, 399 484
360, 380, 400 485
1.15, 1.40 1.08
0.95, 1.21 0.88
0.96, 1.25 0.88
0.77 155/225/338/424 2.89
a
b
c
Measured in a dilute CH2Cl2 solution.
Measured on a vapor deposition thin film and excited at 390 nm.
Stokes shift calculated from the difference between lmax of the absorption and emission spectra.
d
e
f
Determined in CH2Cl2 solutions (A<0.1) at room temperature using quinine sulfate solution in 0.01 M H2SO4
(
FF¼0.54) as a standard.23
Obtained from DSC on the second heating cycle and TGA measurements under N2 at a heating rate of 10 ꢀC/min.
Estimated from the onset of the absorption spectra (Eg¼1240/lonset).
g
h
Obtained from quantum chemical calculation using TDDFT/ B3LYP/6-31G (d,p).
Measured using a three-electrode system fitted with a glassy carbon working electrode, a platinum rod counter electrode, and SCE reference electrode in degassed CH2Cl2
containing 0.1 M n-Bu4NPF6 as a supporting electrolyte at a scan rate of 50 mV/s.
i
Calculated using the empirical equation: HOMO¼ꢁ(4.44þEonset) and LUMO¼HOMOþEg.
Photophysical properties of 1e4 were investigated in dilute
CH2Cl2 solution and thin film obtained by thermal evaporation on
quartz substrate. The pertinent data are presented Figs. 3 and 4, and
summarized in Table 1. Their UVevis spectra showed two absorp-
tion bands, which were assigned in terms of the strong absorption
*
band in the region of 250e310 nm corresponding to the pep local
electron transition of the individual aromatic units, and the less
intense three absorption bands in the region of 350e400 nm at-
materials showed a slight Stokes shift (41e85 nm) suggesting less
energy loss during the relaxation process and efficient fluorescence.
The thin film PL emission spectrum of 1, shown in Fig. 4, was similar
to its solution PL spectrum in terms of line shape, emission lmax and
full width at a half-maximum, thus indicating or less, if any, solid
state packing occurred in this case due to its bulky molecular
structure. However, the thin film PL spectrum of 2 exhibited
a bathochromic shift caused by solid state packing, thus indicating
greater planarity between the anthracene and bithiophene units
tributed to the characteristic
pep electron transition of the an-
*
thracene. Their HOMOeLUMO energy gaps (Eg) were estimated
from the onset of the absorption spectra to be 2.96, 2.87, 2.90, and
2.89 eV, respectively. The Egs of 3 and its corresponding dimer 4
1.0
1
2
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0.6
0.4
0.2
0.0
3
4
0.8
0.6
0.4
0.2
0.0
1
2
3
4
400
450
500
550
600
300
400
500
600
Wavelength (nm)
Wavelength (nm)
Fig. 4. PL spectra of 1e4 measured as thin film obtained by vapor deposition on quartz
Fig. 3. UVevis absorption and PL spectra of 1e4 measured in dilute CH2Cl2 solution.
substrate.

1856
A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
and better
p
-electron delocalization in the conjugated system. In the
diphenylaminophenyl)-1,3,4-oxadiazol-5-yl]-9,9-bis-n-hexyl-
fluorene.24 Steric hindrance of an adjacent anthracene ring might
play a key role in preventing such electrochemical reactions in both
molecules. CV curves of 1 and 2 showed two irreversible oxidation
processes. Duplicate CV curves of each compound were noticed
under multiple scans demonstrating stable molecules (see
Supplementary data). In the case of 1, the first oxidation wave cor-
responds to the removal of electrons from the terminal thiophene
ring to form the radical cation. No oxidationpeak at a lower potential
due to a dimerization coupling of such species was detected, unlike
cases of 3 and 4 having bulky structures, their thin film PL spectra
exhibited a hypsochromic shift of about 19e26 nm compared to
their corresponding solution spectra. This result may also be at-
tributed to the aforementioned solid state packing force, which
prohibits the electron-vibration coupling between the triphenyl-
amine substituent and the anthracene photoactive unit.
Fluorescence quantum yields (FF) of 1e4 measured in dilute
solution using quinine sulfate solution in 0.01 M H2SO4
(FF¼0.54)
as a standard were 0.12, 0.04, 0.73 and 0.77, respectively. The results
indicated that direct attachment of the thiophene ring to the lu-
minous anthracene moiety in compound 1 lowered the FF (0.12)
and the value was rather reduced in compound 2 (FF¼0.04) having
two thiophene rings. The decrease in FF value with the increase in
the thiophene units is usually observed in most of the thiophene
oligomers as the molecule becoming more planar and likely to
what was observed in most cases of a-unsubstituted short oligo-
thiophenes.25 In our case, this electrochemical dimerization cou-
pling could be prevented by a steric hindrance of the nearby
anthracene moiety. Moreover, under these CV experiment condi-
tions, no distinct reduction process was observed in all cases. The
HOMO and LUMO energy levels of 1e4 were calculated from the
oxidation onset potentials (Eonset) and energy gaps (Eg) and the re-
sults are summarized in Table 1. The HOMO levels of these materials
ranged from ꢁ5.56 to ꢁ5.32 eV matching well with the work func-
tions of the gold (Au) or indium tin oxide (ITO) electrodes and fa-
voring the injection and transport of holes.
fluorescence quenching by intermolecular
pep
stacking.22 In
contrast, replacing the thiophene ring with electron donating tri-
phenylamine in compound 3 significantly increased the FF (0.73)
and the value was slightly higher in the dimer 4 (FF¼0.77).
The thermal properties of 1e4 were investigated by the ther-
mogravimetric analysis (TGA) and differential scanning calorimetry
(DSC), and the results are shown in Fig. 5 and summarized in Table 1.
These results suggest that all compounds were thermally stable
materials with 5% weight loss temperatures (T5d) well over 330 ꢀC.
During the first heating DSC scan of crystalline samples 1 and 2, only
endothermic melting peaks (Tm) at 209 and 328 ꢀC were detected,
respectively. In their DSC second heating scan, the thermogram of 1
showed broad exothermic peaks due to the crystallization (Tc) at
115 ꢀC followed by the melting peak, while the second heating
thermogram of dimer 2 was the same as the first cycle. Compounds 3
and 4 bearing triphenylamine as a substituent exhibited different
thermal behavior. The asymmetric nature of this group may play an
additional role to the molecular packing. The DSC thermogram (first
scan) of 3 only revealed an endothermic peak at 155 ꢀC due to
melting of the crystalline sample, while under a second heating
cycle, only endothermic baseline shift owing to glass transition (Tg)
at 79 ꢀC was detected with no crystallization and melting peaks at
higher temperature being observed. The thermogram (second scan)
of 4 displays Tg at 155 ꢀC and Tc around 225 ꢀC to give the same
crystals as obtained by crystallization from solution, which then
melted at 338 ꢀC. The abilityof 3 and 4 toform a molecular glass with
the possibility to prepare thin films from these materials both by
evaporation and by solution casting is highly desirable for applica-
tions in electroluminescent devices (Fig 6).
2.3. Electrochemical and thermal properties
Electrochemical behaviors of all compounds were investigated
by cyclic voltammetry (CV), and the resulting data are shown in
Fig. 5 and summarized in Table 1. The experiment was carried out in
degassed CH2Cl2 containing 0.1 M n-Bu4NPF6 as a supporting elec-
trolyte under argon atmosphere. Compound 3 and its corresponding
dimer 4 were found to exhibit two quasi-reversible oxidation pro-
cesses at 0.95 and 1.21 V, and 0.96 and 1.26 V, respectively. The first
oxidation wave was assigned to the removal of electrons from the
peripheral triphenylamines resulting in radical cations, while the
second was attributed to the formation of an anthracene radical
cation. The onset oxidation potentials (Eonset) of 3 and 4 estimated
from the first anodic oxidation wave were at the same value of
0.88 V, which is very close to the data reported for most triphenyl-
amine derivatives (0.90 V). Their multiple CV scans revealed iden-
tical CV curves with no additional peak at a lower potential on the
cathodic scan (Epc) being observed (see Supplementary data). This
indicates that no oxidative coupling, or a weak oxidative coupling if
any at the p-phenyl rings of the peripheral triphenylamine, led to
electro-polymerization and electrochemically stable molecules.
Usually, this type of electrochemical coupling reaction is detected in
most triphenylamine derivatives with an unsubstituted at p-posi-
tion of the phenyl ring as in case of 2,7-bis[2-(4-
Fig. 6. DSC (second heating) and TAG thermograms of 1e4 measured under N2 at
Fig. 5. CV curves of 1e4 measured in CH2Cl2 at a scan rate of 50 mV/s.
heating rate of 10 ꢀC/min.

A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
1857
2.0
2.4. Electroluminescence properties
Device I
Device II
Device III
Device IV
In order to investigate the electroluminescence properties of
1e4, OLED devices were fabricated with the following device
structure: indium tin oxide (ITO)/PEDOT:PSS/EML(50 nm)/
BCP(40 nm)/LiF(0.5 nm):Al(150 nm), where these materials were
used as the emitting layer (EML). Conductive polymer poly(3,4-
1.6
1.2
0.8
0.4
0.0
ethylenedioxythiophene):poly(4-styrenesulfonate)
(PEDOT:PSS)
as hole injection layer and 2,9-dimethyl-4,7-diphenyl-1,10-
phenanthroline (BCP) as hole-blocking layer were also used to
enable high-performance devices. The voltageeluminance and
voltageecurrent density (JeVeL) characteristics of the devices are
shown in Figs. 7 and 8, and their electrical parameters are sum-
marized in Table 2. The results revealed that 3 and 4, owing to the
electron donating triphenylamine in the molecules had the best
EML properties among these four materials. Device IV having 4 as
EML showed the best performance with a high maximum bright-
ness of 4586 cd/m2 at 8.8 V, a low turn-on voltage of 4.6 V, a max-
imum luminous efficiency of 1.65 cd/A and a maximum external
quantum efficiency of 0.34%. A slightly lower device performance
was observed from device III displaying maximum brightness of
2621 cd/m2 at 8.6 V, turn-on voltage of 4.4 V, a maximum luminous
efficiency of 1.28 cd/A and a maximum external quantum efficiency
of 0.26%. Devices I and II exhibited poorer device performance. The
trend in device luminous efficiencies matches very well with the
observed decrease in PL quantum efficiencies in going from 4 to 3 to
1 to 2 (Table 1). Fluorescence quantum yields (FF) of both 3 and 4
were significantly higher than those of 1 and 2. The efficiency of an
OLED depends both on the balance of electrons and holes and the
FF of the emitter.26 Analysis of band energy diagrams of all devices
also revealed that the HOMO levels of all compounds
(5.32e5.56 eV) lied between those of PEDOT:PSS (5.00 eV) and BCP
(6.50 eV) (see Supplementary data). However, there is a barrier
around 0.32 eV for holes to migrate from the PEDOT:PSS/EML in-
terface in devices III and IV, while such energy barrier
(0.52e0.56 eV) is wider in devices I and II. This suggests that a mi-
gration of the hole from the PEDOT:PSS to EML layer is more ef-
fective in devices III and IV resulting the charge efficiently
recombining in the emitting layer and better device performance.
Fig. 9 showed the normalized electroluminescence (EL) spectra of
all diodes. In device III and IV, the EL emission was very similar to
their corresponding PL emission with emission lmax of 457 and
465 nm, respectively. However, we observed a spectral shift in the
EL spectra for compounds 1 and 2. The EL spectrum of device I (1 as
EML) displayed an emission peak at 440 nm corresponding PL
emission of compound 1 and shoulder emission owing to exciplex
0
100
200
300
400
500
600
2
Current density (Am/cm )
Fig. 8. Variation in luminance efficiency with current density of OLED devices with
1e4 as EML.
species at the longer wavelength, while EL spectrum of device II (2
as EML) presented a totally red-shifted emission peak (498 nm)
from the exciplex species. However, stable emission was obtained
from the all diodes with the EL spectra not changing much over the
entire drive voltages (see Supplementary data).
As the HOMO levels of both 3 and 4, having a hole-transporting
moiety in the molecules, matching well with the work function of
ITO (4.8 eV), these compounds may potentially serve as hole-
transporting materials (HTM). To test this hypothesis, double-
layer green OLED devices with the structure of ITO/PEDOT:PSS/
HTL(40 nm)/Alq3(50 nm)/LiF(0.5 nm):Al(150 nm) were fabricated,
where these materials were used as hole-transporting layers (HTL)
and tris-(8-hydroxyquinoline)aluminum (Alq3) as the green light-
emitting (EML) and electron-transporting layers (ETL). The refer-
ence device with the same structure based on commonly used
commercial HTM, N,N0-diphenyl-N,N0-bis(1-naphthyl)-(1,10-bi-
phenyl)-4,40-diamine (NPB), as HTL was made for comparison.
When comparing of HOMO and LUMO levels of layers for the
devices, it was found that the HOMO levels of compounds 3 and 4
(5.32 eV) lay between those of PEDOT:PSS (5.00 eV) and Alq3
(5.80 eV), while the LUMO level of Alq3 (3.00 eV) lay between those
of 3 and 4 (2.43e2.43 eV) and LiF:Al (4.20 eV) (see Supplementary
data). There is a barrier of around 0.32 eV for holes to migrate from
the HTL layer to Alq3 layer, while that for electron to transport from
the Alq3 to the HTL layer is about 0.57 eV. According to this band
diagram and device configuration, both compounds can transport
a hole injected from ITO/PEDOT:PSS to the Alq3 emitting layer.
Under applied voltage, all devices emitted a bright green lumi-
nescence with EL spectra (lmax 507e515 nm) matching with the PL
spectrum of Alq3 and also other reported EL spectra of Alq3 devices
(Fig. 10).27 No emission at the longer wavelength owing to exciplex
species formed at the interface of HTL and ETL materials, which is
often occurred in the devices fabricated from HTL with planar
molecular structure, was detected.28 In our case, the formation
exciplex species could be prevented by the bulky nature of both the
anthracene core and triphenylamine at the peripheral of the mol-
ecules. From these results and in view of the fact that barrier for
electron-migration at the Alq3/HTL interface (0.57 eV) is nearly
twice higher than those for hole-migration at the HTL/Alq3 in-
terface (0.32 eV), thus these compounds act only as HTM and Alq3
would act preferably as an electron blocker more than as a hole
blocker and charge recombination thus confined to Alq3 layer.
The voltageeluminance and voltageecurrent density (JeVeL)
characteristics of the devices are shown in Figs. 11 and 12, and their
electrical parameters are summarized in Table 2. These results
clearly demonstrate the hole-transporting ability of 3 and 4 with
superior device performance (maximum brightness and efficiency)
4
10
600
Device I
Device II
Device III
Device IV
500
400
300
200
100
0
3
2
1
10
10
10
0
2
4
6
8
10
Applied Voltage (V)
Fig. 7. JeVeL characteristics of OLED devices with 1e4 as EML.

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A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
Table 2
Device characteristics of OLEDs with 1e4 and NBP as either EML or HTL
a
b
c
d
Device
Structure
Von
lem
Lmax
Vmax
Je
237
479
436
512
891
hf
EQEg
CIEh
I
II
ITO/PEDOT:PSS/1/BCP/LiF:Al
ITO/PEDOT:PSS/2/BCP/LiF:Al
ITO/PEDOT:PSS/3/BCP/LiF:Al
ITO/PEDOT:PSS/4/BCP/LiF:Al
ITO/PEDOT:PSS/3/Alq3/LiF:Al
ITO/PEDOT:PSS/4/Alq3/LiF:Al
ITO/PEDOT:PSS/NPB/Alq3/LiF:Al
5.7
4.7
4.4
4.6
3.8
4.0
3.4
440
498
457
465
515
509
515
504
1427
2621
9.0
9.4
8.6
0.48
0.37
1.28
1.65
4.13
6.25
4.45
0.10
0.03
0.26
0.34
0.20
0.30
0.22
0.15, 0.13
0.22, 0.44
0.14, 0.13
0.15, 0.16
0.27, 0.52
0.26, 0.49
0.25, 0.47
III
IV
V
VI
VII
4586
8.8
18,035
32,270
30,044
10.6
11.4
11.0
894
1362
a
Turn-on voltage (V) at luminance of 10 cd/m2.
Emission maximum.
b
c
Maximum luminance (cd/m2) at the applied voltage (V).
Voltage (V) at maximum luminance.
Current density (mA/cm2).
d
e
f
Luminance efficiency (cd/A).
External quantum efficiency (%).
CIE coordinates (x,y).
g
h
5
10
1600
1400
1200
1000
800
600
400
200
0
Device V
Device VI
Device VII
4
10
3
10
2
10
0
2
4
6
8
10
12
Applied Voltage (V)
Fig. 11. JeVeL characteristics of green OLED devices with 3, 4, and NPB as HTL.
7
Fig. 9. EL spectra of OLED devices with 1e4 as EML.
Device V
6
5
4
3
2
1
0
Device VI
Device VII
0
200
400
600
800
1000
1200
2
Current density (Am/cm )
Fig. 12. Variation in luminance efficiency with current density of green OLED devices
with 3, 4, and NPB as HTL.
Fig. 10. EL spectra of green OLED devices with 3, 4, and NPB as HTL.
6.25 cd/A and a maximum external quantum efficiency of 0.30%. A
slightly lower device performance was observed from compound 3-
based device (device VI) showing a maximum brightness of
18,035 cd/m2 at 10.6 V, turn-on voltage of 3.8 V, a maximum lu-
minous efficiency of 4.13 cd/A and a maximum external quantum
efficiency of 0.20%.
comparable to the NPB-based device (device VII). Device VI, having
compound 4 as HTL, exhibited the best performance with a high
maximum brightness of 32,270 cd/m2 for green OLED at 11.4 V,
a low turn-on voltage of 4 V, a maximum luminous efficiency of

A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
1859
3. Conclusions
an analytical material and supporting electrolyte tetrabutyl am-
monium hexafluorophosphate (n-Bu4NPF6) were 10ꢁ3 M and 0.1 M,
respectively. High resolution mass spectrometry (HRMS) analysis
was performed by Mass Spectrometry Unit, Mahidol University,
Thailand.
The ground state geometries were fully optimized using density
functional theory (DFT) at the B3LYP/6-31G (d,p) level, as imple-
mented in Gaussian 03. TDDFT/B3LYP calculation of lowest excita-
tion energies was performed at the optimized geometries of the
ground states.21
In conclusion, we have successfully synthesized four new 9,10-
substituted anthracenes with the combined characteristics of
light-emitting and hole-transporting materials. These materials
showed blue emission with high emission quantum efficiency over
70% in the solution and strong luminance in solid state. All of them
were electrochemically and thermally stable with degradation
temperature well above 330 ꢀC. Most importantly, two of these
materials, having the electron donating triphenylamine as a pe-
ripheral substituent, showed promising potential as both blue
light-emitting materials and hole-transporting materials for Alq3-
based OELD devices. Their ability as HTL for green OLEDs was
comparable to a common hole-transporter NPB. Blue OLEDs with
a maximum luminance efficiency of 1.65 cd/A, and green OLEDs
with maximum luminance efficiency of 6.25 cd/A were achieved.
4.2. Fabrication and characterization of OLEDs
OLED devices using 1e4 as EL with configuration of ITO/
PEDOT:PSS/EML(50 nm)/BCP(40 nm)/LiF(0.5 nm):Al(150 nm) and
double-layer green OLED devices using 3, 4, and NPB as HTL with
configuration ITO/PEDOT:PSS/HTL(40 nm)/Alq3(50 nm)/LiF(0.5 n-
m):Al(150 nm) were fabricated and characterized as followed. The
patterned indium tin oxide (ITO) glass substrate with a sheet re-
4. Experimental
sistance 14 U/ (purchased from Kintec Company) was thoroughly
4.1. General procedure
cleaned by successive ultrasonic treatment in detergent, deionized
water, isopropanol, and acetone, and then dried at 60 ꢀC in a vac-
uum oven. A 50 nm thick PEDOT:PSS hole injection layer was spin-
coated on top of ITO from a 0.75 wt % dispersion in water at a spin
speed of 3000 rpm for 20 s and dried at 200 ꢀC for 15 min under
vacuum. Thin films of each organic EML or HTL were deposited on
top of PEDOT:PSS layer by evaporation from resistively heated
alumina crucibles at evaporation rate of 0.5e1.0 nm/s in vacuum
evaporator deposition (ES280, ANS Technology) under a base
pressure of w10ꢁ5 mbar. The film thickness was monitored and
recorded by quartz oscillator thickness meter (TM-350, MAXTEK). A
40 nm thick hole-blocking layer of BCP or a 50 nm thick green-
emitting layer of Alq3 was then deposited on the organic EML or
HTL, respectively, without breaking the vacuum chamber. The
chamber was vented with dry air to load the cathode materials and
pumped back; a 0.5 nm thick LiF and a 150 nm thick aluminum
layers were then subsequently deposited through a shadow mask
on the top of EML/HTL film without breaking vacuum to form an
active diode areas of 4 mm2. The measurement of device efficiency
was performed according to M.E. Thomson’s protocol and the de-
vice external quantum efficiencies were calculated using procedure
reported previously.29 Current densityevoltageeluminescence
(JeVeL) characteristics were measured simultaneous by the use of
a Keithley 2400 source meter and a Newport 1835C power meter
equipped with a Newport 818-UV/CM calibrated silicon photodi-
ode. The EL spectra were acquired by an Ocean Optics USB4000
multichannel spectrometer. All the measurements were performed
under ambient atmosphere at room temperature.
All reagents were purchased from Aldrich, Acros or Fluka and
used without further purification. All solvents were supplied by
Thai companies and used without further distillation. Tetrahydro-
furan (THF) was refluxed with sodium and benzophenone, and
freshly distilled prior to use. Dichloromethane for cyclic voltam-
metry (CV) measurements was washed with concd H2SO4 and
distilled twice from calcium hydride.
1H and 13C nuclear magnetic resonance (NMR) spectra were
€
recorded on a Bruker AVANCE 300 MHz spectrometer with tetra-
methylsilane as the internal reference using CDCl3 as solvent in all
cases. High resolution mass spectrometry (HRMS) was performed
by Mass Spectrometry Unit at Chulabhorn Research Institute (CRI).
Infrared (IR) spectra were measured on a PerkineElmer FTIR
spectroscopy spectrum RXI spectrometer as potassium bromide
(KBr) disc. Ultravioletevisible (UVevis) spectra were recorded as
a diluted solution in spectroscopic grade dichloromethane on
a PerkineElmer UV Lambda 25 spectrometer. Photoluminescence
spectra and the fluorescence quantum yields (FF) were recorded
with a PerkineElmer LS 50B Luminescence Spectrometer as a dilute
solution in spectroscopic grade dichloromethane and thin film
obtained by thermal deposition. The fluorescence quantum yields
(FF) were determined by comparison with a fluorescence standard
of known fluorescence quantum yield value according to the fol-
lowing equation23
:
!
ꢀ
ꢁ
Slopex
SlopeST
hx
h2ST
Fx
¼
FST
(1)
where the subscripts x refer to the unknown samples and ST refers
4.3. Synthesis and characterization
to the standard quinine sulfate solution in 0.01 M H2SO4, whose
fluorescence quantum yield is known to be 0.54.
cence quantum yield, slope is the slope from the plot of integrated
fluorescence intensity versus absorbance, and is the refractive
index of the solvent. The refractive indexes of the solvents were
taken as 1.424 and 1.333 for CH2Cl2 and 0.01 M H2SO4, respectively
(see Supplementary data).
Differential scanning calorimetry (DSC) analysis and thermog-
ravimetry analysis (TGA) were performed on a METTLER DSC823e
thermal analyzer and a Rigaku TG-DTA 8120 thermal analyzer, re-
spectively, with heating rate of 10 ꢀC/min under nitrogen atmo-
sphere. Cyclic voltammetry (CV) measurements were carried out
on an Autolab Potentiostat PGSTAT 12 with a three-electrode sys-
tem (platinum counter electrode, glassy carbon working electrode,
and Ag/Agþ reference electrode) at scan rate of 50 mV/s in
dichloromethane under argon atmosphere. The concentrations of
F
is the fluores-
4.3.1. 9-Bromo-10-(9,9-dihexylfluoren-2-yl)anthracene (6). A mix-
ture of 2-iodo-9,9-bis-n-hexylfluorene (1.28 g, 2.79 mmol), 9-
bromoanthracen-10-boronic acid (0.84 g, 2.79 mmol), Pd(PPh3)4
(0.065 g, 0.12 mmol) and 2 M Na2CO3 (8 ml) aqueous solution in
THF (12 ml) was degassed with N2 for 5 min. The reaction mixture
was stirred at reflux under N2 for 18 h. After being cooled to room
temperature, water (50 ml) was added and extracted with CH2Cl2
(50 mlꢂ2). The combined organic phase was washed with water
(50 ml), brine solution (50 ml), dried over anhydrous Na2SO4, fil-
tered, and the solvents were removed to dryness. Purification by
column chromatography over silica gel eluting with a mixture of
CH2Cl2 and hexane (1:4) followed by recrystallization from a mix-
ture of CH2Cl2 and methanol afforded the 9-bromo-10-(9,9-
dihexylfluoren-2-yl) anthracene 6 (0.66 g, 52%) as a light yellow
solid, mp 158 ꢀC; nmax (KBr) 2928, 1462, 1438, 1344, 1260, 1020,
h

1860
A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
890 cmꢁ1
;
dH (300 MHz, CDCl3) 0.76e0.88 (10H, m),1.09e1.14 (12H,
anthracen-9-yl)-2,20-bithiophene 2 (0.35 g, 63%) as a greenish solid,
mp >250 ꢀC; nmax (KBr) 2922, 1557, 1447, 1369, 1270, 1018, 824,
m), 1.95e2.01 (4H, m), 7.34e7.40 (7H, m), 7.59 (2H, t, J¼8.8 Hz), 7.72
(2H, d, J¼9.0 Hz), 7.81 (1H, dd, J¼3.3, 2.7 Hz), 7.89 (1H, d, J¼7.5 Hz),
8.62 (2H, d, J¼8.7 Hz); dC (75 Hz, CDCl3) 13.99, 22.47, 23.85, 29.60,
31.52, 40.37, 55.26, 119.62, 119.83, 122.92, 124.87, 125.46, 125.91,
126.54, 126.92, 127.32, 127.44, 129.73, 130.30, 131.20, 136.90, 140.81,
and 150.95; HRMS (ESI): [MHþ] found 589.3042. C39H42Br requires
589.2432.
764 cmꢁ1
; dH (300 MHz, CDCl3) 0.78e0.82 (20H, m), 1.12e1.18 (24H,
m), 2.03 (8H, t, J¼8.1 Hz), 7.22 (2H, d, J¼3.3 Hz), 7.36e7.55 (20H, m),
7.80e7.87 (6H, m), 7.95 (2H, d, J¼8.1 Hz), 8.12 (4H, d, J¼9.0 Hz); dC
(75 Hz, CDCl3) 14.01, 22.50, 23.89, 29.65, 31.54, 40.44, 55.28, 119.65,
119.82, 122.93, 123.88, 125.18, 125.78, 126.02, 126.69, 127.13, 127.27,
128.04, 129.75, 130.04, 130.49, 131.60, 137.33, 138.50, 138.73, 139.48,
140.73, 140.92, 150.91, 150.99; HRMS (ESI): [MHþ] found 1183.6210.
C86H87S2 requires 1183.6244.
4.3.2. 9-(9,9-Dihexylfluoren-2-yl)-10-thiophen-2-yl-anthracene
(1). A mixture of 6 (0.67 g, 1.14 mmol), 2-thiopheneboronic acid
(0.16 g, 1.25 mmol), Pd(PPh3)4 (0.025 g, 0.023 mmol), and 2 M
Na2CO3 aqueous solution (6 ml) in THF (10 ml) was degassed with
N2 for 5 min. The reaction mixture was stirred at reflux under N2 for
20 h. After being cooled to room temperature, water (50 ml) was
added and extracted with CH2Cl2 (50 mlꢂ2). The combined organic
phase was washed with water (50 ml), brine solution (50 ml), dried
over anhydrous Na2SO4, filtered, and the solvents were removed to
dryness. Purification by column chromatography over silica gel
eluting with a mixture of CH2Cl2 and hexane (1:4) followed by re-
crystallization from a mixture of CH2Cl2 and methanol afforded the
9-(9,9-dihexylfluoren-2-yl)-10-thiophen-2-yl-anthracene 1 (0.51 g,
76%) as a light yellow solid, mp 186 ꢀC; nmax (KBr) 2930, 1458, 1440,
4.3.5. 9-(9,9-Dihexylfluoren-2-yl)-10-(4-diphenylaminophenyl)an-
thracene (3). A mixture of 6 (0.52 g, 0.88 mmol), N,N-diphenyl-N-4-
aminophenylboronic acid (0.28 g, 0.97 mmol), Pd(PPh3)4 (0.021 g,
0.017 mmol), and 2 M Na2CO3 aqueous solution (6 ml) in THF (10 ml)
was degassed with N2 for 5 min. The reaction mixture was stirred at
reflux under N2. After being cooled to room temperature, water
(50 ml) was added and extracted with CH2Cl2 (50 mlꢂ2). The com-
bined organic phase was washed with water (50 ml), brine solution
(50 ml), dried over anhydrous Na2SO4, filtered, and the solvents were
removed to dryness. Purification by column chromatography over
silica gel eluting with a mixture of CH2Cl2 and hexane (1:4) followed
by recrystallization from a mixture of CH2Cl2 and methanol afforded
the 9-(9,9-dihexylfluoren-2-yl)-10-(4-diphenylaminophenyl) an-
thracene 3 (0.52 g, 79%) as a light yellow solid, mp 146 ꢀC; nmax (KBr)
1380, 1224, 1028, 824 cmꢁ1
; dH (300 MHz, CDCl3) 0.78e0.82 (10H,
m), 1.12e1.18 (12H, m), 2.03 (4H, t, J¼9.0 Hz), 7.34e7.47 (11H, m),
7.66 (1H, d, J¼4.8 Hz), 7.79 (2H, d, J¼8.7 Hz), 7.84 (1H, d, J¼7.8 Hz),
7.92e7.98 (3H, m); dC (75 Hz, CDCl3) 14.03, 22.51, 23.89, 29.66, 31.55,
40.45, 55.27, 119.64, 119.82, 122.92, 125.10, 125.57, 126.03, 126.73,
126.91, 127.03, 127.20, 127.26, 128.66, 129.50, 129.75, 131.65, 137.40,
139.17, 139.31, 140.87, 141.05, 150.91, 151.02; HRMS (ESI): [MHþ]
found 593.3186. C43H45S requires 593.3197.
2929, 1590, 1494, 1380, 1273, 1019, 823, 746 cmꢁ1
; dH (300 MHz,
CDCl3) 0.75e0.80 (10H, m), 1.09e1.16 (12H, m), 1.98e2.03 (4H, m),
7.07e7.12 (2H, t, J¼7.0 Hz), 7.26e7.46 (21H, m), 7.77e7.95 (6H, m); dC
(75 Hz, CDCl3) 14.02, 22.51, 23.89, 31.55, 40.47, 55.26, 119.61, 119.78,
122.91, 123.10, 123.13, 124.71, 124.97, 126.16, 126.88, 127.10, 127.19,
129.40, 129.89, 130.10, 130.15, 132.14, 132.69, 136.92, 137.70, 140.54,
141.00, 147.17, 147.84, 150.86, 150.98; HRMS (ESI): [MHþ] found
754.4386. C57H56N requires 754.4407.
4.3.3. 2-Bromo-5-(10-(9,9-dihexylfluoren-2-yl)anthracen-9-yl)thio-
phene (7). To a solution of 1 (0.60 g, 1.01 mmol) in tetrahydrofuran
(15 ml) was added NBS (0.18 g, 1.01 mmol) in small portions. While
adding NBS, the reaction was monitored by TLC. Soon after the
starting material was consumed, water was added and the mixture
was extracted with CH2Cl2 (50 mlꢂ2). The combined organic phase
was washed with water (50 ml), a dilute NaHCO3 aqueous solution
(50 ml), brine solution (50 ml), dried over anhydrous Na2SO4, fil-
tered, and the solvents were removed to dryness. Purification by
recrystallization of a mixture of CH2Cl2 and methanol gave the 2-
bromo-5-(10-(9,9-dihexylfluoren-2-yl)anthracen-9-yl)thiophene 7
(0.64 g, 95%) as a light yellow solid, mp 191 ꢀC; nmax (KBr) 2926,1469,
4.3.6. 2,7-Bis(9-bromoanthracene-10-yl)-9,9-dihexylfluorene (9). A
mixture of 2,7-diiodo-9,9-bis-n-hexylfluorene (1.11 g, 1.90 mmol), 9-
bromoanthracen-10-boronic acid (1.20 g, 3.99 mmol), Pd(PPh3)4
(0.11 g, 0.10 mmol), and 2 M Na2CO3 (10 ml) aqueous solution in THF
(15 ml) was degassed with N2 for 5 min. The reaction mixture was
stirred at reflux under N2 for 20 h. After being cooled to room
temperature, water (50 ml) was added and extracted with CH2Cl2
(50 mlꢂ2). The combined organic phase was washed with water
(50 ml), brine solution (50 ml), dried over anhydrous Na2SO4, fil-
tered, and the solvents were removed to dryness. Purification by
column chromatography over silica gel eluting with a mixture of
CH2Cl2 and hexane (1:4) followed by recrystallization from a mixture
of CH2Cl2 and methanol afforded the 2,7-bis(9-bromoanthracene-
10-yl)-9,9-dihexylfluorene 9 (0.90 g, 56%) as a light yellow solid, mp
1433, 1334, 1261, 1020, 878 cmꢁ1
; dH (300 MHz, CDCl3) 0.74e0.92
(10H, m), 1.08e1.15 (12H, m), 1.97e2.05 (4H, m), 6.99 (1H, d,
J¼3.9 Hz), 7.29e7.47 (10H, m), 7.75 (2H, d, J¼8.7 Hz), 7.81e7.84 (1H,
m), and 7.92e7.97 (3H, m); dC (75 Hz, CDCl3) 14.00, 22.49, 23.87,
29.63, 31.53, 40.42, 55.26, 112.83, 119.65, 119.82, 122.92, 125.17,
125.91, 126.37, 126.91, 127.13, 127.30, 128.87, 129.67, 129.94, 130.14,
131.56, 134.10, 137.16, 139.81, 140.76, 140.87, 141.18, 150.91, 150.96;
HRMS (ESI): [MHþ] found 671.5429. C43H44BrS requires 671.2349.
188 ꢀC; nmax (KBr) 2927, 1460, 1440, 1340, 1261, 1020, 893 cmꢁ1
; dH
(300 MHz, CDCl3) 0.8 (6H, t, J¼6.9 Hz), 0.94 (4H, m), 1.14e1.27 (12H,
m), 2.04 (4H, t, J¼7.8 Hz), 7.40e7.48 (8H, m), 7.65 (4H, t, J¼8.4 Hz),
7.79 (4H, d, J¼9.0 Hz), 8.04 (2H, d, J¼8.1 Hz), 8.66 (4H, d, J¼9.0 Hz); dC
(75 Hz, CDCl3) 14.02, 22.40, 24.06, 29.55, 31.57, 40.34, 55.51, 119.86,
122.70, 125.56, 126.04, 126.97, 127.40, 127.95, 130.01, 130.34, 131.21,
137.32, 138.229, 140.53,151.21; HRMS (ESI): [MHþ] found 843.8920.
C53H49Br2 requires 843.2193.
4.3.4. 5,50-Bis(10-(9,9-dihexylfluoren-2-yl)anthracen-9-yl)-2,20-bi-
thiophene (2). A mixture of 7 (0.65 g, 0.96 mmol), NiCl2 (0.75 g,
5.78 mmol), Zn powder (0.11 g,1.73 mmol), PPh3 (0.15 g, 0.57 mmol),
and bipyridine (bpy) (0.06 g, 0.38 mmol) in DMAc (10 ml) was
degassed with N2 for 10 min. The reaction mixture was stirred at
reflux under N2 for 24 h. After being cooled to room temperature,
water (50 ml) was added and extracted with CH2Cl2 (50 mlꢂ2). The
combined organic phase was washed with water (50 ml), brine so-
lution (50 ml), dried over anhydrous Na2SO4, filtered, and the sol-
vents were removed to dryness. Purification by column
chromatography over silica gel eluting with a mixture of CH2Cl2 and
hexane (1:5) followed by recrystallization from a mixture of CH2Cl2
and methanol afforded the 5,50-bis(10-(9,9-dihexylfluoren-2-yl)
4.3.7. 2,7-Bis(9-(4-diphenylaminophenyl) anthracene-10-yl)-9,9-
dihexylfluorene (4). A mixture of
9 (0.51 g, 0.60 mmol), N,N-
diphenyl-N-4-aminophenylboronic acid (0.37 g, 1.27 mmol),
Pd(PPh3)4 (0.01 g, 0.01 mmol), and 2 M Na2CO3 aqueous solution
(6 ml) in THF (10 ml) was degassed with N2 for 5 min. The reaction
mixture was stirred at reflux under N2. After being cooled to room
temperature, water (50 ml) was added and extracted with CH2Cl2
(50 mlꢂ2). The combined organic phase was washed with water
(50 ml), brine solution (50 ml), dried overanhydrous Na2SO4, filtered,

A.-monrat Thangthong et al. / Tetrahedron 68 (2012) 1853e1861
1861
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and the solvents were removed to dryness. Purification by column
chromatography over silica gel eluting with a mixture of CH2Cl2 and
hexane (1:6) followed by recrystallization from a mixture of CH2Cl2
and methanol afforded the 2,7-bis(9-(4-diphenylaminophenyl)an-
thracene-10-yl)-9,9-dihexylfluorene 4 (0.45 g, 75%) as a deep yellow
solid, mp >250 ꢀC; nmax (KBr) 2922,1590,1491,1384,1273,1019, 823,
764 cmꢁ1
;
dH (300 MHz, CDCl3) 0.82 (6H, t, J¼6.9 Hz), 0.91 (4H, br s),
1.17e1.28 (12H, m), 2.06 (4H, t, J¼7.8 Hz), 7.12 (4H, t, J¼6.9 Hz),
7.31e7.48(32H, m), 7.55e7.56 (4H, m), 7.85 (4H, d, J¼8.7 Hz), 7.90 (4H,
d, J¼8.4 Hz), 8.07 (2H, d, J¼8.1 Hz); dC (75 Hz, CDCl3) 14.05, 22.48,
24.10, 29.65, 31.62, 40.51, 55.50,119.77,123.12,124.73,125.02,126.28,
127.07, 127.16, 129.41, 130.14, 130.20, 132.16, 132.70, 137.00, 137.55,
137.96, 140.43, 147.20, 147.85, 151.18; HRMS (ESI): [MHþ] found
1173.6070. C89H77N2 requires 1173.6081.
ꢀ
10. (a) Romero, D. B.; Schaer, M.; Leclerc, M.; Ades, D.; Siove, A.; Zuppiroli, L. Synth.
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Acknowledgements
This work was financially supported by the Thailand Research
Fund (RMU5080052). We acknowledge the scholarship support
from Center of Excellence for Innovation in Chemistry (PERCH-CIC),
Ubon Ratchathani University, and the Strategic Scholarships for
Frontier Research Network for Research Groups (CHE-RES-RG50)
from the Office of the Higher Education Commission, Thailand.
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Supplementary data
H NMR and C NMR spectra, and more results for theoretical
calculation, quantum yield, CV curve, band energy diagram of OLED
devices, and EL spectra. Supplementary data related to this article
can be found online at doi:10.1016/j.tet.2011.12.083.
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