Synthesis and properties of new luminescent hole transporting materials of triarylamine with dehydroabietic acid methyl ester moieties

Article abstract of DOI:10.1016/j.tet.2013.07.071

A series of triarylamines based on dehydroabietic acid methyl ester moieties (6a-h) were synthesized for possible application as hole transporting materials for organic electroluminescent devices. The target compounds were characterized by elemental analysis, FT-IR, NMR, and mass spectrometry. Their optical, electrochemical, and thermal properties were investigated using UV-vis, PL spectroscopy, cyclic voltammetry (CV), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), respectively. CV measurements show that the compounds present suitable HOMO values (in a range of -4.63 to -5.11 eV) for hole injection, which is confirmed by theoretical calculations. All compounds were thermally stable. Organic light-emitting diode devices having 6f, 6g, and 6h as a hole transporting layer showed better performance of maximum brightness, turn-on voltage, and maximum luminous efficiency than a comparable device NPB. These compounds could be excellent candidates for applications in OLED devices.

Full text of DOI:10.1016/j.tet.2013.07.071

Tetrahedron 69 (2013) 8405e8411
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and properties of new luminescent hole transporting
materials of triarylamine with dehydroabietic acid methyl ester
moieties
,
b,
c
,
,
b,
c
,
,b,c,d,
d, Zhanqian Song a
Hong Gao a
d, Jie Song e, Xinwen Zhang f, Shibin Shang a
*
a Institute of Chemical Industry of Forestry Products, CAF, Nanjing 210042, PR China
b Key Lab. of Biomass Energy and Material, Jiangsu Province, Nanjing 210042, PR China
c National Engineering Lab. for Biomass Chemical Utilization, Nanjing 210042, PR China
d Key and Lab. on Forest Chemical Engineering, SFA, Nanjing 210042, PR China
e Department of Chemistry and Biochemistry, University of Michigan-Flint, 303E Kearsley Street, Flint, MI 48502, USA
f Key Laboratory for Organic Electronics & Information Displays, Institute of Advanced Materials, Nanjing University of Posts and Telecommunications,
Nanjing 210036, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of triarylamines based on dehydroabietic acid methyl ester moieties (6aeh) were synthesized for
possible application as hole transporting materials for organic electroluminescent devices. The target
compounds were characterized by elemental analysis, FT-IR, NMR, and mass spectrometry. Their optical,
electrochemical, and thermal properties were investigated using UVevis, PL spectroscopy, cyclic vol-
tammetry (CV), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC),
respectively. CV measurements show that the compounds present suitable HOMO values (in a range of
ꢀ4.63 to ꢀ5.11 eV) for hole injection, which is confirmed by theoretical calculations. All compounds were
thermally stable. Organic light-emitting diode devices having 6f, 6g, and 6h as a hole transporting layer
showed better performance of maximum brightness, turn-on voltage, and maximum luminous efficiency
than a comparable device NPB. These compounds could be excellent candidates for applications in OLED
devices.
Received 13 March 2013
Received in revised form 10 July 2013
Accepted 18 July 2013
Available online 27 July 2013
Keywords:
Triarylamine
Dehydroabietic acid methyl ester
Synthesis
Luminescent
Hole transporting
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
material (HTM) should display excellent solubility, high thermal
stability, good film-forming ability, and proper HOMO energy value
Molecular organic semiconductors have been of great interest
due to their applications in organic light-emitting diodes (OLEDs),
especially for next generation flat-panel displays.1 Layered device
consisting of charge-transporting and light-emitting layers can
achieve higher charge injection efficiency and better charge bal-
ance than those of single-layer devices using emitting materials
alone.2
In general, the hole transporting layer in layered OLEDs facili-
tates hole injection from the anode into the organic layer and
transports the injected holes to the emitting layer. The hole trans-
porting layer (HTL) can also prevent electrons from escaping the
emitting layer to the anode.3 They could improve the luminance
efficiency and working life of the device by increasing the efficiency
of injection and formation of exciton. The ideal hole transporting
for efficient hole injection and high mobility.4
So far, triarylamine derivatives, such as N,N0-bis-(naphthyl)-
N,N0-bis-phenyl-1,10-biphenyl-4,40-diamine(NPB)5 and N,N0-bis(3-
methylphenyl)-N,N0-bis-phenyl-benzidine (TPD),6 have been the
most widely used hole transporting materials because of their high
hole mobilities.7e10 However, TPD films prepared by sublimation
tend to crystallize over time, even at ambient temperature. Nu-
merous efforts have been devoted to synthesizing new HTM with
better thermal and morphological stability. There is strong interest
in the development of amorphous molecular materials for these
applications.11e15 How to improve the thermal stability and keep
the hole transporting is the aim of this study. Previous studies
showed that the introduction of the backbone of dehydroabietic
acid could improve the thermal stability.16 In this paper, a new
group of eight hole transporting materials were synthesized by
combining methyl 13-aminodehydrodeisopropylabietate with aryl
halides through the cross-coupling reaction (Scheme 2). Theoreti-
cal calculations were carried out to provide more insights into the
* Corresponding author. Tel./fax: þ86 25 85482468; e-mail addresses: songzq@
hotmail.com, gaoh2188@hotmail.com (Z. Song).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.071

8406
H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
Br
Br
NH2
NO2
COOCH3
COOCH3
COOCH3
COOCH3
1
2
3
4
Scheme 1. The structures of the intermediates 1e4.
R2
N
6a R1=H, R2 = OCH3
6b R1=H, R2=
Br
6c R1=H, R2 = CH3
6d R1, R2=H
R1
6e R1, R2 = OCH3
6g R1, R2 = CH3
6h R1=H, R2=
COOCH3
R2
NH2
Br
H
6a-6e, 6g-6h
N
Br
R1
R1
Br
5a R1=H
5b R1=OCH3
COOCH3
N
COOCH3
4
R1
5
Regents and conditions:
R1=H
COOCH3
Pd(OAc)2, P(t-Bu)2, NaOt-Bu,
o-xylene, 130°C
f
6
Scheme 2. The synthetic routes of triarylamines 6aeh.
electronic structure of compounds obtained. Optical, electro-
chemical, thermal, and hole transporting properties of synthesized
compounds were studied as well.
orbital features might provide important clues toward un-
derstanding the distinct photophysical properties of the synthe-
sized compounds.27
Calculated HOMO, LUMO energies, and HOMOeLUMO energy
gaps (Eg cal) are listed in Table 1. It can be seen from Table 1 that the
electron-donating power of the substituent increases to strengthen
the nitrogen electron density, the HOMO value gradually increases
from ꢀ4.87 eV for 6d to ꢀ4.72 eV for 6a and ꢀ4.53 eV for 6e, same
tendency occurs among 6d, 6c, and 6g. In addition, lower Eg of 6f
(3.84 eV), 6b (4.01 eV), and 6h (4.13 eV) than other compounds is
ascribed to the extended conjugation system could decrease the
energy gap between the HOMO and LUMO.28 It also indicates that
the conjugated length in the compounds could be increased by the
introduction of naphthalene and biphenyl units. Sample maps of
HOMO and LUMO of 6a and 6f are listed in Fig. 1, while other
compounds can be seen in Supplemental data. It shows that
2. Results and discussion
2.1. Synthesis
The starting material, dehydroabietic acid, was obtained from
commercial product of disproportionated rosin and purified by re-
peated crystallization by the ethanolamine salt.17 The intermediates,
i.e., methyl dehydroabietate 1,18 methyl 12-bromodehydroabietate
2,19 methyl 12-bromo-13-nitro-deisopropyldehydroabietate 3,20,21
and methyl 13-aminodeisopropyldehydroabietate 422e24 were
prepared according to procedures described in references, and their
structures were described in Scheme 1.
The intermediates, diarylamines (5a and 5b) were synthesized
by palladium catalyzed cross-coupling reactions of aryl halides
with compound 4,25 and triarylamines compounds 6aeh were
synthesized by the same conditions with diarylamine 5a or 5b. The
synthetic routes were described in Scheme 2.
HOMOs have
p-electrons delocalized over the three benzene/aryl
rings and N atom, while in LUMOs,
benzene/naphthene/bipenyl rings.
p-electrons are localized on the
2.3. Physical properties
2.2. Quantum-chemical calculations
2.3.1. Optical properties. UVevis absorption and photolumin
escence spectra of compounds 6aeh in methanol are shown in
Fig. 2 and related data are summarized in Table 1. As shown in the
UVevis spectra, the absorption spectra of compounds 6a, 6c, 6e,
and 6g are similar and their absorption maxima show slight red-
shifts with changing the substituents on the benzene rings, com-
pared to 6d. Large differences exist among the absorption spectra of
To understand the electronic properties of 6aef, quantum-
chemical calculations were performed at the B3LYP/6-31G* level
using the Gaussian 09 program.26 Since electronic excitation from
the highest occupied molecular orbitals (HOMO) to lowest un-
occupied molecular orbitals (LUMO) produces the excited state, the

H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
8407
Table 1
Physical and photophysical data of 6aeh
labs (nm)a
lem (nm)b
Ffa
sF1/
s
F2 (ns)a
Tm/T5d (ꢁC)c
Eg cal (eV)d
HOMO/LUMO (eV)d
Eg exp (eV)e
E
(V)f
HOMO/LUMO (eV)g
ox
Compd
onset
6a
6b
6c
6d
6e
6f
240, 298
240, 318
240, 292
240, 291
240, 298
219, 286
240, 294
240, 318
376
419
369
366
389
452
372
418
15.81
74.13
87.96
80.90
36.01
33.90
34.55
52.95
2.27/7.54
0.71/2.70
2.03/8.06
1.88/8.87
4.41/5.80
2.97/16.86
4.91/6.84
2.66/2.66
122.8/311.1
d/461.4
173.7/350.6
147.5/307.8
d/360.4
117.3/378.1
151.1/289.6
d/426.6
4.44
4.01
4.54
4.59
4.28
3.84
4.50
4.13
ꢀ4.72/ꢀ0.28
ꢀ4.95/ꢀ0.94
ꢀ4.80/ꢀ0.26
ꢀ4.87/ꢀ0.28
ꢀ4.53/ꢀ0.25
ꢀ4.91/ꢀ1.07
ꢀ4.73/ꢀ0.23
ꢀ4.85/ꢀ0.72
3.33
3.20
3.38
3.40
3.23
3.07
3.35
3.22
0.29
0.82
0.45
0.52
0.19
0.67
0.36
0.47
ꢀ4.73/ꢀ1.40
ꢀ5.26/ꢀ2.06
ꢀ4.89/ꢀ1.51
ꢀ4.96/ꢀ1.56
ꢀ4.63/ꢀ1.40
ꢀ5.11/ꢀ2.04
ꢀ4.80/ꢀ1.45
ꢀ4.91/ꢀ1.69
6g
6h
a
Measured in a dilute methanol solution (1.0ꢂ10ꢀ5 mol/l) at room temperature.
b
c
d
e
f
Measured in methanol solutions (1.0ꢂ10ꢀ6 mol/l) at room temperature.
Obtained from DSC on the first heating cycle and TGA measurements under N2 at a heating rate of 10 ꢁC/min.
Obtained from quantum-chemical calculation using B3LYP/6-31G (d,p).
Estimated from the onset of the absorption spectra (Eg exp¼1240/lonset).
Measured using a three electrode system fitted with a glassy carbon working electrode, a platinum rod counter electrode, and Ag/Agþ reference electrode in degassed
CH2Cl2 containing 0.1 M Bu4NClO4 as a supporting electrolyte at a scan rate of 100 mV/s.
g
ox
Calculated using the empirical equation: HOMO¼ꢀ(E
þ4.44) and LUMO¼HOMOþEg exp
.
onset
Fig. 1. HOMO and LUMO orbitals of 6a and 6f.
compounds 6f, 6b, and 6h, which may be due to the presence of the
naphthalene and biphenyl moieties attached to N atom. As a result,
compound 6f with naphthalene moiety shows a broad
transition band with maximum at 286 nm. Compounds 6b and 6h
pep*
with biphenyl moieties show broad
a maximum at 318 nm.
pep* transition bands with
As shown in Table 1, emission peaks of 6aeh in methanol are at
366e452 nm, corresponding to blue light emission. Similar to the
UVevis absorption, compounds with electron-donating sub-
stituents on aromatic rings, such as OCH3 (6a, 6e), and CH3 (6c, 6g)
show slight red-shift fluorescence emission and increased fluo-
rescence intensity over 6d (without substituent on aromatic ring),
which is due to electron-donating substituents on aromatic rings
producing pep conjugations. However, the introduction of natha-
phene (6f) and biphenyl (6b and 6h) moieties causes a large red-
shift of fluorescence emission spectra, which is rising from the
extension of the conjugated length. Their maximum emission
Fig. 2. UVevis absorption and PL spectra of 6aeh in methanol.

8408
H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
peaks even shift to a longer wavelength of the blue light region,
which are 452 nm, 419 nm, and 418 nm for 6f, 6b, and 6h, re-
spectively. Therefore, substituents of electron-donating and ex-
tended conjugation system have
a great influence on the
fluorescence properties of molecules.
In additional, the fluorescence quantum yields ranges from
15.81% to 87.96%. Larger values are found for 6d (80.9%), and 6c
(87.96%). The fluorescence lifetime is found in the range between
2.66 ns and 16.86 ns. The compound 6f has the highest value
(16.86 ns). The fluorescence quantum yields and lifetimes are not
directly affected by the substituents and conjugated system.
2.3.2. Electrochemical properties. Cyclic voltammetry (CV) was
employed to investigate electrochemical properties of the com-
pounds. Additionally, the HOMO and LUMO energy levels were
estimated from CV measurement results.29 CV was carried out on
a Chi660D electrochemistry workstation with a three-electrode cell
in chloroform in the presence of tetrabutylammonium perchlorate
(Bu4NClO4, 0.10 M) as the supporting electrolyte with a scanning
rate of 100 mV/s at room temperature (Fig. 3) and the results are
listed in Table 1. Glassy carbon and platinum wire are used as
working and counter electrodes, respectively, and an Ag/Agþ elec-
trode is used as the reference electrode. All solutions have been
deaerated with N2 gas prior to the experiments.
Fig. 4. The relationship between Eg
and Eg
.
exp
cal
2.3.3. Thermal properties. For OLED applications, thermal stability
of organic materials is crucial for device stability and lifetime.
Thermal instability of the amorphous organic layer may result in
degradation of organic devices due to morphological changes. The
thermal properties of 6aeh were investigated by thermogravi-
metric analysis (TGA) and differential scanning calorimetry (DSC).
The results are summarized in Table 1 (also see Supplementary
data). TGA shows that all compounds are stable in nitrogen with
temperature at 5% weight loss (T5d) well over 300 ꢁC, except
compound 6g (T5d¼289.6 ꢁC); moreover, compounds 6b and 6h
have T5d greater than 400 ꢁC. It is important to keep thermal deg-
radation temperatures above 300 ꢁC in order to be well above op-
erating temperatures of relevant devices and so that compounds
can be applied using vacuum deposition techniques. A higher
thermal degradation temperature means there is a wider temper-
ature range in which the compounds could be used. During the first
heating DSC scan of samples 6aeh, compounds 6a, 6c, 6d, 6f, and
6g exhibited endothermic melting peaks (Tm) at 122.8, 173.7, 147.5,
117.3, and 115.1 ꢁC, respectively, while compounds 6b, 6e, and 6h
had no observed melting peaks.
2.4. Hole transporting properties
To investigate the hole transporting properties of 6aeh, OLEDs
(devices 6aeh) were fabricated using these compounds as hole
transporting layers (HTL) with the device configuration of ITO/tri-
arylamine (50 nm)/Alq3 (50 nm)/LiF (0.8 nm)/Al (80 nm). Tris(8-
hydroxyquinolinato) aluminum (Alq3) served as the emitting
layer (EML) as well as the electron-transporting layer while LiF/Al
was used as a bilayer cathode. A control device was fabricated using
NPB as the HTL in the same device architecture. The luminan-
ceevoltage (LeV), current densityevoltage (JeV), and luminance
Fig. 3. CV curves of 6aeh measured in CH2Cl2/n-Bu4NPF6 at a scanning rate of 100 mV/s.
Ox
The onset oxidation potentials (E
) are obtained by the tan-
onset
gent method from the thresholds of oxidation potentials. The
HOMO and LUMO energy levels of 6aeh are calculated from the
Ox
oxidation onset potentials (E
) and energy gaps (Eg exp). These
onset
results are summarized in Table 1. HOMO levels of eight com-
pounds ranging from ꢀ5.26 to ꢀ4.63 eV are higher than the widely
used HTM NPB (ꢀ5.40 eV). The higher HOMO energy means that
a smaller energy barrier exists between the interface of ITO and the
synthesized materials and results in higher hole injection efficiency
and lower joule heat.30
HOMO energies from experimental and theoretical studies are in
good agreement but LUMO energies are quite different. Neither
experimental (using empirical method) nor theoretical studies
could give the exact values of HOMO or LUMO energies. Instead the
relative value of their differences, Eg cal and Eg exp are more impor-
tant. Though there are some differences in their absolute values, the
perfect linear relationship is observed between them (R2¼0.956), as
shown in Fig. 4. It implies that both Eg cal and Eg exp could demon-
strate the trend of HOMOeLUMO gaps and, as a result, is used to
efficiencyecurrent density (heJ) characteristics of the devices are
shown in Figs. 5e7, and their electrical parameters are summarized
in Table 2.
The turn-on voltage at 1 cd/m2 for devices 6a and 6deh is in the
range of 2.6e3.9 V and the operating voltage at 100 cd/m2 is in the
range of 3.5e5.6 V. This indicates good performance for these de-
vices. Devices having 6a, 6deh as HTL show good performance with
a high maximum brightness of 8914, 7063, 6518, 14,602, 16,141, and
12,554 cd/m2 at 9.0 V, respectively, a low turn-on voltage of 3.0, 3.9,
3.0, 3.2, 2.7, and 2.6 V and a maximum luminance efficiency of 2.4,
3.2, 2.1, 2.7, 2.1, and 2.1 cd/A. However, the device 6b shows lower
performance in terms of maximum brightness (1422 cd/m2), turn-
on voltage (3.7 V), and maximum luminance efficiency (1.8 cd/A).
The device 6c shows higher luminance efficiency (2.7 cd/A), but
lower brightness (236 cd/m2) and higher turn-on voltage (4.8 V). A
comparable device performance is observed from device NPB,
evaluate pep* transitions and luminous properties in this work.

H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
8409
Table 2
Device characteristics of OLEDs with 6aeh and NPB as HTL
a
b
c
Device
Structure
Von
V100
Lmax
Jd
601
132
8.4
316
450
h
e/V
6a
6b
6c
6d
6e
6f
6g
6h
NPB
ITO/6a/Alq3/LiF/Al
ITO/6b/Alq3/LiF/Al
ITO/6c/Alq3/LiF/Al
ITO/6d/Alq3/LiF/Al
ITO/6e/Alq3/LiF/Al
ITO/6f/Alq3/LiF/Al
ITO/6g/Alq3/LiF/Al
ITO/6h/Alq3/LiF/Al
ITO/NPB/Alq3/LiF/Al
3.0
3.7
4.8
3.9
3.0
3.2
2.7
2.6
3.5
4.8
6.0
7.8
5.6
4.8
4.7
3.8
3.5
4.8
8914
1422
236
7063
6518
14,602
16,141
12,554
9467
2.4/5.2
1.8/6.2
2.7/8.2
3.2/6.7
2.1/5.7
2.7/6.7
2.1/6.2
2.1/4.7
2.0/6.9
638
1095
1226
572
a
Turn-on voltage (V) at luminance of 1 cd/m2.
Voltage (V) at luminance of 100 cd/m2.
Maximum luminance (cd/m2).
b
c
d
e
Current density (mA/cm2) at maximum luminance.
Luminance efficiency (cd/A).
Fig. 5. LeV characteristics of OLED devices.
performance with a high maximum brightness of 14,602 cd/m2,
a lower turn-on voltage of 3.2 V, and a maximum luminance effi-
ciency of 2.7 cd/A.
In order to explain the different efficiencies of the OLED devices,
analysis of band energy diagrams of all devices revealed that the
HOMO levels of all HTM materials (ꢀ4.63 to 5.26 eV) lay between
those of ITO (ꢀ4.80 eV) and Alq3 (ꢀ5.7 eV). The injection barrier for
holes to migrate from the HTL to EML (Alq3) is 0.97 eV (6a), 0.44 eV
(6b), 0.81 eV (6c), 0.74 eV (6d), 1.07 eV (6e), 0.59 eV (6f), 0.90 eV
(6g), and 0.79 eV (6h), respectively. Energy barriers of 6f, 6d, and 6c
are narrower. It suggests that a migration of holes from the HTL to
EML layer are more effective in devices 6f, 6d, and 6c compared to
devices 6a, 6e, 6g, and 6h, which is due to the charges efficiently
recombining in the emitting layer and higher luminance efficiency.
As to the device 6b, it shows lower performance in spite of its
narrowest energy barrier. This may be the effect of electron-
withdrawing bromine on biphenyl and the fluoro group with
electron withdrawing ability reducing the electron density of ni-
trogen. Therefore, 6b becomes more difficult to be oxidized and
thus shows the lowest-lying HOMO energy level of ꢀ5.26 eV.
Fig. 6. JeV characteristics of OLED devices.
3. Conclusion
In summary, eight luminescent hole transporting materials
(6aeh) containing triarylamine and dehydroabietic acid methyl
ester moieties have been synthesized and characterized. The pho-
toluminescence spectra of these compounds exhibit a maximum
between 366 and 452 nm in methanol, corresponding to blue light
region. The HOMO values of molecules are ꢀ4.63 to ꢀ5.11 eV, which
are in favor of the hole-injection. The synthesized materials 6aeh
show stable thermal properties. OLED devices having 6f, 6g, and 6h
as HTL demonstrate better performance of maximum brightness,
lower turn-on voltage, and higher maximum luminous efficiency
than a control device NPB. Among them, 6f gives the most prom-
ising and balanced performance. These results imply that the hole
transporting materials containing triarylamine with dehydroabietic
acid methyl ester moieties could be a great candidate for the ap-
plication in OLEDs.
Fig. 7.
heJ characteristics of OLED devices.
4. Experimental
4.1. General procedure
which with a maximum brightness of 9467 cd/m2, a turn-on volt-
age of 3.5 V, and a maximum luminance efficiency of 2.0 cd/A. OLED
devices having 6f, 6g, and 6h as HTL demonstrate better perfor-
mance of maximum brightness, lower turn-on voltage, and higher
maximum luminance efficiency than a control device NPB. Among
them, device 6f, having compound 6f as HTL, exhibits the best
Reagents and solvents were commercially available and used as
received. UVevis absorption spectra were recorded with a Shi-
madzu UV-2450 spectrophotometer. Fluorescence spectra were
collected with a PE LS50-B spectrophotometer at room tempera-
ture. The fluorescence absolute quantum yields (Ff) and the

8410
H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
fluorescence lifetime (
s
F) were measured by Fluoromax-4 fluores-
6.84e6.86 (2H, d, J¼1.1, AreH), 6.87e6.91 (3H, m, AreH), 6.97e6.99
(2H, m, AreH), 7.14e7.15 (1H, d, J¼8.65, AreH), 7.18e7.21 (2H, m,
cence spectrometer (Horiba Jobin Yvon Inc., France). TGA and DSC
of the synthesized compounds were determined by 409PC ther-
mogravimetric analyzer and a Diamond DSC thermal analyzer.
Cyclic voltammetry (CV) were carried out on a Chi660D electro-
chemistry workstation.
AreH); 13C NMR (DMSO-d6, 125 MHz)
d: 16.2, 17.94, 20.92, 24.63,
29.23, 36.13, 36.33, 37.59, 44.77, 46.85, 51.76, 55.15, 114.90 (2C),
120.76, 121.12, 121.43 (2C), 122.61, 125.08, 127.05 (2C), 129.07 (2C),
135.31, 139.96, 143.48, 144.73, 147.85, 155.72, 177.92 (C]O); m/z
(ESI) 470.3 [MþH]þ.
4.4.2. Methyl 13-[N,N-(p-bromobiphenyl)-phenyl]aminodeisopropyld
4.2. Fabrication of OLEDs
ehydroabietate 6b. Yellow solid, mp¼150.2 ꢁC; Anal. Calcd for
C
31H35NO3: C, 72.72%; H, 6.10%; N, 2.36%. Found: C, 73.04%; H,
5.99%; N 2.16%. IR (Smart iTR) nmax/cmꢀ1: 2934, 1724, 1594, 1486,
1257; 1H NMR (DMSO-d6, 500 MHz)
d: 1.16 (3H, s, CH3), 1.20 (3H, s,
CH3), 1.25e1.39 (2H, m, 2ꢂ CH), 1.59e1.75 (5H, m, 2ꢂ CH2 and CH),
2.04e2.06 (1H, d, J¼11.0, CH), 2.27e2.29 (1H, d, J¼13.5, CH),
2.62e2.75 (2H, m, CH2), 3.60 (3H, s, COOCH3), 6.73 (1H, s, AreH),
6.82e6.83 (1H, d, J¼7.0, AreH), 6.97e7.04 (4H, d, J¼7.5, AreH),
7.20e7.22 (1H, d, J¼8.5, AreH), 7.27e7.31 (2H, d, J¼7.85, AreH),
7.35e7.38 (1H, t, J¼7.0, AreH), 7.40e7.48 (2H, t, J¼7.8, AreH),
The devices have the structure of ITO/triarylamine
(50 nm)/Alq3 (50 nm)/LiF (0.8 nm)/Al (80 nm). In the devices, triar-
ylamine was used as the hole transport layer, and tris(8-
hydroxyquinolinato) aluminum (Alq3) served as the emitting layer
(EML) as well as the electron-transport layer while LiF/Al was used as
a bilayer cathode. The device was fabricated using an indium tin oxide
7.53e7.57 (2H, d, J¼2.9, AreH), 7.58e7.66 (4H, d, J¼7.5, AreH); 13
C
NMR (DMSO-d6, 125 MHz) d: 16.25, 17.97, 20.92, 24.67, 29.21, 36.16,
36.48, 37.59, 44.74, 46.90, 51.83, 122.35, 122.85, 123.74, 123.96,
124.37, 125.44, 126.06, 126.54, 126.81, 127.47, 127.79, 128.07, 128.67,
128.75, 128.82, 128.99, 129.48, 131.75, 131.86, 133.60, 135.71, 139.61,
144.73, 147.11, 177.97 (C]O); m/z (ESI) 513.3 [MþHꢀBr]þ.
coated glass substrate with a sheet resistance of 10
U per square. The
substrate was cleaned in ultrasonic baths of detergent, alcohol, and
acetone, de-ionized water in turn, and then dried at 120 ꢁC in a vac-
uum oven for more than 1 h.
4.4.3. Methyl 13-[N,N-(4-methylphenyl)-phenyl]aminodeisopropylde
hydroabietate 6c. White crystal, mp¼173.7 ꢁC; Anal. Calcd for
C
31H33NO2: C, 82.08%; H, 7.78%; N, 3.09%. Found: C, 82.11%; H,
The respective organic layers and the cathode layer were de-
posited at 5ꢂ10ꢀ4 Pa. The deposition rates of organic layer, LiF, and
Al were 0.1e0.2 nm/s, 0.02e0.04 nm/s, and 0.3e0.5 nm/s, re-
spectively. The film thickness was monitored by a quartz oscillator
thickness meter. The emission area of the device was 12 mm2, and
only the luminance in the forward direction was measured. The
Electroluminescence characteristics of the devices were measured
using a Keithley 2602 source-measure unit. All of the devices were
characterized without encapsulation and all of the measurements
were carried out at room temperature under ambient conditions.
7.53%; N, 3.02%. IR (Smart iTR) nmax/cmꢀ1: 2938, 1723, 1593, 1496,
1250; 1H NMR (DMSO-d6, 500 MHz)
d: 1.15 (3H, s, CH3), 1.20 (3H, s,
CH3), 1.24e1.35 (2H, m, 2ꢂ CH), 1.56e1.76 (5H, m, 2ꢂ CH2 and CH),
2.01e2.04 (1H, d, J¼12.15, CH), 2.25 (3H, s, AreCH3), 2.29e2.33 (1H,
d, J¼20.5, 2H), 2.64e2.70 (2H, m, CH2), 3.60 (3H, s, COOCH3), 6.62
(1H, s, AreH), 6.73e6.74 (1H, d, J¼8.05, AreH), 6.87e6.90 (4H, d,
J¼7.5, AreH), 6.92e6.95 (1H, t, J¼7.6, AreH), 7.08e7.10 (2H, d,
J¼11.0, AreH), 7.15e7.17 (1H, d, J¼8.6, AreH), 7.21e7.24 (2H, t,
J¼7.65, AreH); 13C NMR (DMSO-d6, 125 MHz)
d: 16.22, 17.95, 20.32,
20.92, 24.66, 29.21, 36.14, 36.38, 37.59, 44.76, 46.87, 51.87, 121.42,
121.81, 122.51 (2C), 123.32, 124.30 (2C), 125.20, 129.20 (2C), 129.95
(2C), 132.07, 135.43, 143.91, 144.54, 144.73, 47.58, 177.96 (C]O); m/z
(ESI) 454.5 [MþH]þ.
4.3. General procedure for synthesis 6aeh
A mixture of 0.4 mmol diarylamine (5a or 5b), 0.44 mmol aryl
bromide, and 0.48 mmol sodium tert-butoxide was transferred to
dry 1 mL o-xylene in a flask under nitrogen atmosphere and
0.04 mmol tri-tert-butylphosphine and 0.01 mmol palladium ace-
tate were then added. The solution was stirred at 130 ꢁC until the
complete consumption of diarylamine as determined by TLC. The
reaction mixture was then cooled to room temperature, dissolved
in diethyl ether (5 mL), and then washed with brine. The organic
phase was dried over anhydrous magnesium sulfate, filtered, and
concentrated under reduced pressure. The residue was purified by
silica column chromatography using mixtures of petroleum ether/
ethyl acetate (9/1 to 12/1) as eluent.
4.4.4. Methyl 13-(N,N-bis-phenyl) aminodeisopropyldehydroabietate
6d. Brown powder, mp¼147.5 ꢁC; Anal. Calcd for C30H33NO2: C,
81.97%; H, 7.57%; N, 3.19%. Found: C, 82.11%; H, 7.43%; N, 3.07%. IR
(Smart iTR) nmax/cmꢀ1: 2940, 1724, 1590, 1491, 1255; 1H NMR
(DMSO-d6, 500 MHz) d: 1.15 (3H, s, CH3), 1.20 (3H, s, CH3), 1.24e1.36
(2H, m, 2ꢂ CH), 1.57e1.77 (5H, m, 2ꢂ CH2 and CH), 2.02e2.05 (1H,
dd, J¼2.05 and 12.45, CH), 2.27e2.29 (1H, d, J¼13.1, CH), 2.65e2.71
(2H, m, CH2), 3.60 (3H, s, COOCH3), 6.67 (1H, s, AreH), 6.76e6.78
(1H, dd, J¼2.3 and 8.5, AreH), 6.94e6.95 (4H, d, J¼7.6, AreH),
7.00e7.02 (2H, t, J¼9.65, AreH), 7.18e7.20 (1H, d, J¼8.6, AreH),
7.24e7.29 (4H, t, J¼7.5, AreH); 13C NMR (DMSO-d6, 125 MHz)
d:
16.20, 17.94, 20.89, 24.62, 29.18, 36.12, 36.41, 37.57, 44.72, 46.86,
51.77, 121.96, 122.35 (2C), 123.23 (4C), 123.95, 125.28, 129.29 (4C),
135.54, 143.70, 144.33,144.36, 147.33, 177.91 (C]O); m/z (ESI) 440.2
[MþH]þ.
4.4. Characterization of 6aeh
4.4.1. Methyl 13-[N,N-(4-methoxyphenyl)-phenyl]aminodeisopropyl
dehydroabietate 6a. White crystal, mp¼122.8 ꢁC; Anal. Calcd for
C
31H35NO3: C, 79.28%; H, 7.51%; N, 2.98%. Found: C, 79.74%; H,
4.4.5. Methyl 13-[N,N-bis(4-methoxyphenyl)]aminodeisopropyldehy
8.01%; N, 3.00%. IR (Smart iTR) nmax/cmꢀ1: 2936, 1722, 1593, 1597,
droabietate 6e. White crystal, mp¼160.2 ꢁC; Anal. Calcd for
1242; 1H NMR (DMSO-d6, 500 MHz)
d: 1.14 (3H, s, CH3), 1.19 (3H, s,
C32H37NO4: C, 76.92%; H, 7.46%; N, 2.80%. Found: C, 76.39%; H,
CH3), 1.23e1.34 (2H, m, 2ꢂ CH), 1.56e1.77 (5H, m, 2ꢂ CH2 and CH),
2.01e2.04 (1H, dd, J¼2.15 and 12.5, CH), 2.25e2.28 (1H, d, J¼13.3,
CH), 2.63e2.71 (2H, m, CH2), 3.60 (3H, s, COOCH3), 3.73 (3H, s,
OCH3), 6.61 (1H, s, AreH), 6.71e6.73 (1H, dd, J¼2.45 and 8.5, CH),
7.69%; N, 2.50%. IR (Smart iTR) nmax/cmꢀ1: 2940, 1724, 1606, 1502,
1241; 1H NMR (CDCl3, 500 MHz)
: 1.19 (3H, s, CH3), 1.26 (3H, s,
d
CH3), 1.33e1.50 (1H, m, 2ꢂ CH), 1.62e1.81 (5H, m, 2ꢂ CH2 and CH),
2.18e2.25 (2H, d, J¼13.1, 2ꢂ CH), 2.71e2.75 (2H, m, CH2), 3.65 (3H,

H. Gao et al. / Tetrahedron 69 (2013) 8405e8411
8411
s, COOCH3), 3.77 (6H, s, 2ꢂ OCH3), 6.59 (1H, s, AreH), 6.69e6.71
(1H, d, J¼7.4, AreH), 6.78e6.80 (4H, d, J¼8.85, AreH), 7.00e7.01
(4H, d, J¼7.6, AreH), 7.01e7.03 (1H, d, J¼8.5, AreH); 13C NMR
125.40, 126.03, 126.61, 126.77, 127.33, 127.44, 128.79 (2C), 128.84,
129.41 (2C), 133.58, 135.68, 139.59, 144.12, 144.71, 146.81, 147.09,
177.93 (C]O); m/z (ESI) 516.4 [MþH]þ.
(DMSO-d6,125 MHz) d: 16.19,17.95, 20.98, 24.65, 29.32, 36.15, 36.21,
37.63, 44.85, 46.85, 51.75, 55.13 (2C), 114.72 (4C), 118.59, 120.16,
124.82, 125.83 (4C), 134.98, 140.61 (2C), 141.94, 145.59, 155.14 (2C),
177.94 (C]O); m/z (ESI) 500.8 [MþH]þ.
Acknowledgements
We are grateful for financial support from the National Natural
Science Foundation of China (31170539) and the Presidential
Foundation of the Chinese Academy of Forestry (CAFINT2009C02).
4.4.6. Methyl 13-[N,N-(a-naphthalene)-phenyl]aminodeisopropyldeh
ydroabietate 6f. Light yellow crystal, mp¼117.3 ꢁC; Anal. Calcd for
C
34H35NO2: C, 83.40%; H, 7.20%; N, 2.86%. Found: C, 82.93%; H,
Supplementary data
7.27%; N, 2.71%. IR (Smart iTR) nmax/cmꢀ1: 2939, 1723, 1592, 1495,
1383, 1250; 1H NMR (DMSO-d6, 500 MHz)
d: 1.11 (3H, s, CH3), 1.17
More results on quantum-chemical calculation, and DSC/TGA
thermograms. Supplementary data related to this article can be
found at http://dx.doi.org/10.1016/j.tet.2013.07.071.
(3H, s, CH3),1.18e1.29 (2H, m, 2ꢂ CH),1.56e1.71 (5H, m, 2ꢂ CH2 and
CH), 1.99e2.02 (1H, d, J¼12.5, CH), 2.21e2.23 (1H, d, J¼13.0, CH),
2.58e2.63 (2H, m, CH2), 3.58 (3H, s, COOCH3), 6.63 (1H, s, AreH),
6.72e6.73 (1H, d, J¼8.5, AreH), 6.80e6.81 (2H, d, J¼8.0, AreH),
6.83e6.86 (1H, t, J¼7.5, AreH), 7.10e7.11 (1H, d, J¼8.5, Naph-
thaleneeH), 7.13e7.16 (2H, t, J¼8.15, AreH), 7.29e7.31 (1H, d, J¼7.0,
AreH), 7.38e7.41 (1H, t, J¼7.4, NaphthaleneeH), 7.48e7.52 (2H, d,
J¼7.5, NaphthaleneeH), 7.85e7.91 (2H, t, J¼5.05, NaphthaleneeH),
7.96e8.00 (1H, d, J¼11.0, NaphthaleneeH); 13C NMR (DMSO-d6,
References and notes
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dehydroabietate 6g. Colorless crystal, mp¼151.1 ꢁC; Anal. Calcd for
C
32H37NO2: C, 82.19%; H, 7.97%; N, 3.00%. Found: C, 81.93%; H,
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d
: 1.14 (3H, s, CH3), 1.19 (3H, s, CH3),
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1.32e1.39 (2H, m, CH2), 1.58e1.74 (5H, m, 2ꢂ CH2 and CH),
2.00e2.03 (1H, dd, J¼2.05 and 12.45, CH), 2.24 (6H, s, 2ꢂ AreCH3),
2.28e2.30 (1H, d, J¼10.0, CH), 2.62e2.68 (2H, m, CH2), 3.60 (3H, s,
CO2CH3), 6.58 (1H, s, AreH), 6.68e6.70 (1H, dd J¼2.4 and 8.5,
AreH), 6.83e6.85 (4H, d, J¼8.4, AreH), 7.05e7.07 (4H, d, J¼8.15,
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Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.;
Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.;
Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
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125 MHz) d: 16.19, 18.01, 20.16, 21.11, 24.77, 29.50, 36.14, 36.19,
37.74, 45.05, 46.88, 51.74, 120.72, 122.52, 123.63 (4C), 125.02, 129.79
(4C), 131.45 (2C), 135.24, 143.32, 144.80 (2C), 144.99, 177.93; m/z
(ESI) 468.0 [MþH]þ.
4.4.8. Methyl 13-[N,N-biphenyl-phenyl]aminodeisopropyldehydroab
ietate 6h. Yellow crystal, mp¼157.0 ꢁC; Anal. Calcd for C36H37NO32
:
C, 83.85%; H, 7.23%; N, 2.72%. Found: C, 83.45%; H, 7.66%; N, 2.76%.
IR (Smart iTR) nmax/cmꢀ1: 2932, 1722, 1593, 1479, 1248; 1H NMR
(DMSO-d6, 500 MHz) d: 1.16 (3H, s, CH3), 1.20 (3H, s, CH3), 1.25e1.37
(2H, m, 2ꢂ CH), 1.57e1.78 (5H, m, 2ꢂ CH2 and CH), 2.03e2.05 (1H,
d, J¼10.2, CH), 2.28e2.30 (1H, d, J¼11.55, CH), 2.67e2.73 (2H, m,
CH2), 3.60 (3H, s, COOCH3), 6.73 (1H, s, AreH), 6.82e6.84 (1H, dd,
J¼8.35, and 1.75, AreH), 6.98e7.02 (3H, t, J¼8.85, AreH), 7.02e7.04
(1H, d, J¼8.7, AreH), 7.21e7.23 (1H, d, J¼8.6, AreH), 7.27e7.29 (1H,
d, J¼7.4, AreH), 7.30e7.31 (1H, d, J¼7.05, AreH), 7.40e7.48 (3H, t,
J¼7.75, AreH), 7.55e7.56 (2H, d, AreH), 7.60e7.61 (2H, d, J¼7.55,
AreH), 7.65e7.66 (1H, d, J¼7.6, AreH); 13C NMR (DMSO-d6,
€
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125 MHz)d: 16.22, 17.95, 20.89, 24.63, 29.18, 36.13, 36.46, 37.57,
44.72, 46.87, 51.79, 122.32, 122.77, 122.82 (2C), 123.71, 124.34,
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