Conjugated asymmetric donor-substituted 1,3,5-triazines: New host materials for blue phosphorescent organic light-emitting diodes

Article abstract of DOI:10.1002/chem.201101118

Conjugated asymmetric donor-substituted 1,3,5-triazines (ADTs) have been synthesized by nucleophilic substitution of organolithium catalyzed by [Pd(PPh₃)₄]. Theoretical and experimental investigations show that ADTs possess high solubility and thermostability, high fluorescent quantum yield (35 %), low HOMO (-6.0 eV) and LUMO (-2.8 eV), and high triplet energy (E_T, 3.0 eV) according to the different substitution pattern of triazine. The application as host materials for blue PHOLEDs yielded a maximum current efficiency of 20.9 cd A^-1, a maximum external quantum efficiency of 9.8 %, and a brightness of 9671 cd m^-2 at 5.4 V, making ADTs good candidates for optoelectronic devices.

Full text of DOI:10.1002/chem.201101118

FULL PAPER
DOI: 10.1002/chem.201101118
Conjugated Asymmetric Donor-Substituted 1,3,5-Triazines: New Host
Materials for Blue Phosphorescent Organic Light-Emitting Diodes
Zhong-Fu An,[a] Run-Feng Chen,*[a] Jun Yin,[a] Guo-Hua Xie,[b] Hui-Fang Shi,[a]
Taiju Tsuboi,[c] and Wei Huang*[a]
Abstract:
donor-substituted
(ADTs) have been synthesized by nu-
cleophilic substitution of organolithium
catalyzed by [PdACHTUNGTRENNUNG(PPh3)4]. Theoretical
and experimental investigations show
that ADTs possess high solubility and
thermostability, high fluorescent quan-
tum yield (35%), low HOMO
Conjugated
asymmetric
1,3,5-triazines
(ꢀ6.0 eV) and LUMO (ꢀ2.8 eV), and
high triplet energy (ET, 3.0 eV) accord-
ing to the different substitution pattern
of triazine. The application as host ma-
terials for blue PHOLEDs yielded a
maximum
current
efficiency
of
20.9 cdAꢀ1, a maximum external quan-
tum efficiency of 9.8%, and a bright-
ness of 9671 cdmꢀ2 at 5.4 V, making
ADTs good candidates for optoelec-
tronic devices.
Keywords: asymmetric
tures · conjugation · donor–acceptor
systems organic light-emitting
diodes · lithium · phosphorescence
architec-
·
Introduction
(di-2-pyridylamino) phenyl)-1,3,5-triazine were synthesized
and used as blue-emitting materials.[15] 2,4,6-Tris(diaryl-
The fascination of donor-acceptor (D–A, or p–n) architec-
tures[1] has been widely recognized in the design of organic
optoelectronic materials for organic light emitting diodes
(OLED),[2] organic photovoltaics (OPV),[3] sensors,[4] organic
field-effect transistor (OFET),[5] non-linear optics (NLO),
magnetic materials,[6] and many more.[7] Plenty of organic
donors have been developed for this design of functional
materials due to the electron-rich feature of the p-conjugat-
ed systems.[8] However, organic acceptors are quite few.
Among the limited members of acceptors such as perylene
diimides,[9] pyridines,[10] pyrimidines,[11] 1,3,4-oxadiazoles,[12]
1,2,4-triazoles,[13] and benzothiadiazoles,[14] triazines have rel-
atively high electron affinity and good thermal stability,
which are very attractive for the D–A system design. The
2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine and 2,4,6-tris(p-
amino)-1,3,5-triazines[16] and bitriazines derivatives[17] were
ACHTUNGTRENNUNG
reported as electron-transport host materials for OLEDs.
2,4,6-Tris(carbazole)-1,3,5-triazine (TCzT) was found to be a
highly efficient bipolar host material for phosphorescent
OLEDs (PHOLEDs).[18] Star-shaped 1,3,5-triazines with
cyanoACTHNURTGNEUvGN inylene 4-nitrophenyls arms were used for OPV with
a power conversion efficiency of up to 3.82%.[19] In addition,
the NLO properties of triazine derivatives based on 2,4,6-
tris(benzyloxy)-1,3,5-triazine were also published.[20] These
reported triazine derivatives with D–A architectures are
mostly the octupolar symmetrical molecules. It is well
known that asymmetric architectures could increase the
number of the conformers and amount of energy for the
crystallization, which favor the stability of amorphous film
for high-performance devices.[21] Strohriegl et al. reported a
series of asymmetric triazine derivatives with a flexible link-
ꢀ
age (C O bond) between the triazine core and the donor
moiety for blue PHOLEDs,[22] and high glass transition tem-
perature (up to 1708C) and triplet energy (up to 2.96 eV) of
the material were also observed. In addition, asymmetric tri-
azines with donors connected directly to the triazine core
(acceptor) can benefit both from the D–A architectures and
from the fine turning of the energy levels of the materials.[23]
However, there are limited studies on the conjugated asym-
metric triazine derivatives for organic electronics, especially
in the field of blue PHOLEDs. These considerations moti-
vated us to design and investigate the conjugated asymmet-
ric donor-substituted triazine derivatives, although it is diffi-
cult to prepare them.
[a] Z.-F. An, Dr. R.-F. Chen, J. Yin, H.-F. Shi, Prof. W. Huang
Key Laboratory for Organic Electronics
& Information Displays (KLOEID)
and Institute of Advanced Materials (IAM)
Nanjing University of Posts and Telecommunications (NUPT)
9 Wenyuan Road, Nanjing 210046 (P.R. China)
Fax : (+86)25-8586-6999
E-mail: wei-huang@njupt.edu.cn
iamrfchen@njupt.edu.cn
[b] G.-H. Xie
State Key Laboratory on Integrated Optoelectronics
College of Electronic Science and Engineering
Jilin University, 2699 Qianjin Street
Changchun 130012 (P.R. China)
[c] Prof. T. Tsuboi
In this manuscript, a series of conjugated asymmetric
donor-substituted 1,3,5-triazines (ADTs) were successfully
synthesized through catalytic nucleophilic substitution of or-
ganolithium with an innovative synthetic strategy
Faculty of Engineering, Kyoto Sangyo University
Kamigamo, Kyoto 603-8555 (Japan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101118.
Chem. Eur. J. 2011, 17, 10871 – 10878
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
10871

Table 1. Optical and thermal properties of the ADTs.
UVlmax [nm]
(Scheme 1).
The
prepared
ADTs have good solubility due
to the asymmetric structures
and high thermostability for TCzT[16]
PLlmax [nm]
Tm
[8C]
Td
[8C]
fF
film
CHCl3
film
Eopt
CHCl3
film
–
289, 333
3.4
–
392, (425)
452
439
379, 398
454
417, 441, 464
373, 393
452
266
268
>300
246
286
–
–
ThDCzT
278, 324
278, 326
278, 311, 323
277, 323
270, 322
278, 307, 320
279, 328
282, 326
292, 314, 327
278, 331
278, 329
3.32
3.41
3.64
3.22
3.37
3.70
452
452
461
480
474
447
439
445
450
365
369
422
0.061
0.096
0.351
0.076
0.041
0.348
device fabrications. The differ-
PhDCzT
ent photophysical properties of
NPhDCzT
the D–A type ADTs were ob-
DThCzT
DPhCzT
DNPhCzT
served because of the different
substitution pattern of the
donors. ADTs can not only be
good host materials for blue
PHOLEDs with a high triplet
280, 310, 322
290
Results and Discussion
energy up to 3.0 eV, but also blue-light-emitting materials
with the quantum efficiency up to 35% in solid film
(Table 1). These properties indicate that the ADTs have
great potential for organic electronics, especially for blue
PHOLEDs. To the best of our knowledge, this is the first
conjugated asymmetric donor-substituted 1,3,5-triazines for
blue PHOLEDs.
The structures and synthetic routes of ADTs are shown in
Scheme 1. The ADTs were synthesized through nucleophilic
substitution of the cyanuric chloride in two steps with high
yields. In the first step, the mono- and diaryl (Ph, Th, and
NPh)-substituted triazines were prepared by using
a
Grignard reaction and nucleophilic substitution, according
Scheme 1. Synthesis of the asymmetric donor-substituted 1,3,5-triazines (ADTs).
10872
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Chem. Eur. J. 2011, 17, 10871 – 10878

Conjugated Asymmetric Donor-Substituted 1,3,5-Triazines
FULL PAPER
to the different reactivity of chlorine of cyanuric chloride at
different temperatures.[24] In the second step (see Scheme 1),
the catalyzed nucleophilic substitution of the cyanuric chlor-
ine with lithium carbazole results in the desired compounds.
signed to p–p* transition of the conjugated backbone. The
optical energy band gaps (Eopt) of ADTs determined from
the onset of UV/Vis spectra in solid film range from 3.22 to
3.70 eV with the corresponding order: DNPhCzT>
NPhDCzT>PhDCzTꢁTCzT>DPhCzT>ThDCzT>
Without the [PdACHTUNGTRENNUNG(PPh3)4] catalyst, the yield is very low
(around 25%). Another synthetic route with inversed syn-
thesis sequence, that is, carbazole substitution followed by
Grignard reaction, turns out to be unsuccessful, due to the
DThCzT. The ADTs exhibit blue emissions in chloroform
and their PL peaks range from 447 to 480 nm according to
the different substitution pattern of the 1,3,5-triazine. The
absent PL data of TCzT in chloroform is due to its poor sol-
ubility in organic solutions. In the solid state, the PL spectra
of ADTs are blueshifted up to 63 nm in comparison with
that in solution, probably due to the better stabilizing effects
of the solvent on the base state (S0) than the excited state
(S1) of the D–A structure of ADTs.[26] The strongest PL
peaks of ThDCzT, PhDCzT, DThCzT, and DPhCzT in solid
film are significantly redshifted with low photoluminescent
efficiency (<10%) in comparison with that of NPhDCzT
and DNPhCzT. The low quantum efficiency is probably due
to the intermolecular aggregation because of the planar ar-
chitectures as revealed by the DFT-optimized structures.
The high quantum efficiency (approx. 35%) of NPhDCzT
and DNPhCzT in film suggests they have a good potential
as blue OLED emitters, which maybe attribute to non-
planar architectures of NPhDCzT and DNPhCzT.
ꢀ
poor reactivity of the dichorotriazine towards Grignard C C
coupling as illustrated in Scheme S1 in the Supporting Infor-
mation. This successful and efficient synthetic route with the
innovative Pd catalyzed nucleophilic substitution method
makes the preparation of various donor-substituted carba-
zole-based 1,3,5-triazines feasible, which will greatly pro-
mote the research of the triazine-based materials.
The ADTs have good solubility in chloroform and chloro-
benzene, which greatly improves the processability and ap-
plications of the triazine-based materials. The starting tem-
perature of thermal decomposition (Td) of the compounds is
between 3658C and 4508C (see Table 1), and a high content
of carbazoles results in a higher Td. Their melting points
(Tm) are all above 2458C and no glass transition tempera-
ture was observed by differential scanning calorimetry
(DSC). The thermal properties of ADTs are quite good for
optoelectronic devices.
The normalized UV/Vis absorption and photoluminescent
(PL) spectra of ADTs in both CHCl3 solution and thin solid
film were shown in Figure 1 and summarized in Table 1.
Two absorption bands around 275 and 320 nm were ob-
served for all the six ADTs both in solution and film, in
which the band around 275 nm can be associated with n–p*
transition,[8a,25] and the other bands around 320 nm are as-
From the HOMOs and LUMOs of ADTs shown in
Figure 2, the LUMO has high distribution density on tri-
AHCTUNGTREGaNNUN zine core because it is an acceptor, whereas the HOMOs
are dominated by the carbazole substituent because it is a
strong donor. This D–A architecture of ADTs can lead to
separated electron density distribution between the HOMO
and LUMO, which is very obvious in ThDCzT, PhDCzT,
DThCzT, and DPhCzT. This separation provides the materi-
al with a charge–transfer (C–T) state as observed in PL
spectra, efficient hole- and electron-transporting properties,
and the prevention of reverse energy-transfer, which enables
the related ADTs to have excellent potential as host materi-
als.[27]
Electrochemical properties of ADTs were further investi-
gated by cyclic voltammetry (CV). All the compounds un-
derwent quasi-reversible redox behavior. From the onset po-
tential of electrochemical reduction and oxidation, the
LUMO, HOMO, and the energy gap (Eg) were calculated
and listed in Table 2. Since the HOMOs of ADTs are domi-
nated by carbazole (see Table 2), their energy levels of
Table 2. Experimental and theoretical HOMO, LUMO and triplet-state
energy [eV] of ADTs.
From CV
From calculation
exptlET
HOMO LUMO Eg
HOMO LUMO Eg
calcdET
TCzT
ThDCzT
PhDCzT
ꢀ6.0[a]
ꢀ6.04
ꢀ6.06
ꢀ2.6[a]
ꢀ2.82
ꢀ2.80
ꢀ2.22
ꢀ2.88
ꢀ2.81
ꢀ1.98
–
ꢀ5.80
ꢀ1.39
ꢀ1.96
ꢀ1.82
ꢀ1.11
ꢀ2.04
ꢀ1.91
ꢀ0.80
4.41 3.09
2.81[a]
2.94
2.94
3.00
2.65
2.96
2.97
3.22 ꢀ5.79
3.26 ꢀ5.80
3.77 ꢀ5.64
3.16 ꢀ5.79
3.22 ꢀ5.78
3.93 ꢀ5.51
3.83 2.62
3.98 3.14
4.53 3.09
3.75 2.61
3.87 3.10
4.70 3.10
NPhDCzT ꢀ5.99
DThCzT
DPhCzT
ꢀ6.04
ꢀ6.03
DNPhCzT ꢀ5.91
Figure 1. Normalized optical absorption and photoluminescent spectra of
ADTs a) in dilute chloroform solution and b) in solid film.
[a] Measured by ultraviolet photoelectron spectroscopy, see ref. [16].
Chem. Eur. J. 2011, 17, 10871 – 10878
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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10873

W. Huang, R.-F. Chen et al.
TCzT>PhDCzT>DPhCzT>ThDCzT>DThCzT.
This
order also exists for Eg, because the HOMOs of ADTs are
almost identical. The CV-measured frontier orbitals are well
predicted by the DFT calculations with good coordination
as listed in Table 2. The lower LUMOs of ADTs suggest
properties such as good electron ejection and transportation
of the material, which is very crucial for organic optoelec-
tronic devices.
Phosphorescent spectra of ADTs were measured at 77 K
with 5 ms delay as shown in Figure S1 in the Supporting In-
formation. The triplet-state energy (exptlET) listed in Table 2
was obtained by taking the highest energy peak of phos-
phorescent spectra as the transition energy of T1!S0. Small
systemic errors (<0.3 eV) between DFT calculations and
experimental measurements on evaluating triplet-state (T1)
energy was observed with good coordination. With the ex-
ception of DThCzT (2.65 eV), ADTs show a higher exptlET
(2.94–3.00 eV) than TCzT (2.81 eV), which is very good as
host materials for blue PHOLEDs.[28]
To further investigate the potential of ADTs for optoelec-
tronic devices, ADTs and TCzT (used for comparison) were
chosen to act as host materials for blue PHOLEDs. Iridi-
umACTHNUTRGNEUNG
(III) [bis(4,6-difluorophenyl)-pyridinato-N,C2’] picolinate
(FIrpic), with two emission peaks (a typical emission peak
around 472 nm and a shoulder at 500 nm) and the ET of
2.62 eV,[29] was used as guest material because it is one of
the most efficient and popular blue phosphorescent dyes for
OLED. The ADTs hosted PHOLEDs were fabricated with
the device configuration: ITO/MoOx (2 nm)/m-MTDATA:
MoOx (15 wt.%, 30 nm)/m-MTDATA (10 nm)/IrACHTUNGTRENNUNG(ppz)3
(10 nm)/ADTs or TCzT:FIrpic (10 wt.%, 10 nm)/BPhen
(40 nm)/LiF (1 nm)/Al. The electroluminescence (EL) spec-
tra were shown in Figure 3 and the correlative properties
were summarized in Table 3. The EL spectra of ADTs
hosted devices resemble the PL spectrum of FIrpic[29] and
are more stable than that of TCzT with the increasing cur-
rent density, which indicates that PhDCzT, NPhDCzT, and
DNPhCzT are good host materials for blue PHOLEDs.[30] In
addition, lower turn-on voltages (below 2.8 V) and higher
maximum external quantum efficiencies (EQE) of up to 9.8,
9.0, and 9.3% (see Table 3) were also observed. Excitedly,
these three devices have high brightness (9671, 7771, and
4566 cdmꢀ2, respectively) at a low voltage of 5.4 V (see
Figure 4). PhDCzT, NPhDCzT, and DNPhCzT-based devices
show maximum current efficiency of 20.9, 17.4, and
18.3 cdAꢀ1 and maximum power efficiency of 21.0, 17.1, and
Figure 2. The computed spatial distributions of HOMOs and LUMOs of
ADTs.
Table 3. Electroluminescent properties of ADTs as host materials for
blue PHOLED.
HOMO are similar with little variation (<0.1 eV), whereas
for LUMOs, a significant difference was observed. This in-
dependent modification of HOMO and LUMO of ADTs
with various substituents can greatly facilitate the molecular
design of the desired materials. In comparison with TCzT,
the substitution of diphenylamine leads to an increased
LUMO, whereas the other substituents result in a decreased
LUMO in the following order: DNPhCzT>NPhDCzT>
Device
hmax
[cdAꢀ1
hmax
[lmWꢀ1
Vturn-on
[V]
B
EQEmax
[%]
[a]
[b]
[c]
]
]
[cdmꢀ2
]
TCzT
PhDCzT
NPhDCzT 17.4
DNPhCzT 18.3
10.4
20.9
9.3
2.85
<2.8
<2.8
<2.8
1263
9671
7771
4566
5.2
9.8
9.0
9.3
20.0
17.1
17.9
[a] Maximum current efficiency. [b] Maximum power efficiency. [c] Lumi-
nance at 5.4 V.
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Conjugated Asymmetric Donor-Substituted 1,3,5-Triazines
FULL PAPER
~
&
*
Figure 3. Normalized electroluminescence spectra of a) PhDCzT, b) NPhDCzT, c) DNPhCzT, and d) TCzT-based devices. Key: =10; =20; =30;
ꢀ2
!
=40; 3 =50 mAcm
.
stability for device fabrications. The typical D–A com-
pounds of ThDCzT, PhDCzT, DThCzT, and DPhCzT with
separated electron density distribution of frontier orbitals
show low LUMO (ꢀ2.80 to ꢀ2.88 eV) and high ET (2.65–
2.96 eV) as revealed by both theoretical and experimental
investigations, indicating they are very good host materials
for blue PHOLEDs. The devices show that the conjugated
asymmetrical ADTs have lower turn-on voltage, higher effi-
ciencies, and higher brightness and stability than the sym-
metrical TCzT as host materials for FIrpic. The conjugated
ADTs are very interesting optoelectronic materials and
their photophysical properties can be effectively modified
by asymmetric donor substitution.
Figure 4. Current
efficiency–voltage–luminance
characteristics
of
~
!
&
*
PhDCzT ( ), NPhDCzT ( ), DNPhCzT ( ), and TCzT-based ( ) devi-
ces.
17.9 LmWꢀ1, respectively. The symmetric TCzT-based
device shows lower EQE of 5.2% and efficiencies of
10.4 cdAꢀ1 and 9.3 LmWꢀ1 under the same device structure
(see Table 3), which suggests that conjugated asymmetrical
ADTs are better host materials for blue PHOLEDs.
Experimental Section
Materials: All manipulations involving air-sensitive reagents were per-
formed in an atmosphere of dry N2. Tetrahydrofuran (THF) and toluene
were dried and purified by routine procedures. All reagents, unless other-
wise specified, were purchased from Aldrich, Acros, or Alfa Aesar, and
used without further treatments.
Measurements: NMR spectra were collected on a Bruker Ultra Shield
Plus 400 MHz instruments with CDCl3 and [D]DMSO as the solvent and
tetramethylsilane (TMS) as the internal standard. GC-MS experiments
were carried out using a Shimadzu GCMS-QP2010. MALDI-TOF-MS
was determined on a Buker Daltonics flex Analysis. Elemental analyses
were performed on Elementar Vario MICRO elemental analyzer. Mass
spectrometric data were obtained on a LCT Premier XE (Waters) mass
spectrometry and an ESI-TOF HRMS spectrometry. Thermogravimetric
analyses (TGA) were conducted on a DTG-60 Shimadzu thermal analyst
Conclusion
In summary, a novel series of conjugated asymmetric donor-
substituted 1,3,5-triazines (ADTs) have been synthesized ac-
cording to an innovative synthetic strategy that will greatly
promote the research of the triazine-based D–A molecules.
The prepared ADTs have good solubility and high thermo-
Chem. Eur. J. 2011, 17, 10871 – 10878
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10875

W. Huang, R.-F. Chen et al.
system under a heating rate of 108Cminꢀ1 and a nitrogen flow rate of
50 cm3minꢀ1. Differential scanning calorimetry (DSC) was run on a Pyris
1 DSC (Perkin Elmer Co.) thermal analyst system under a heating rate
of 208Cminꢀ1 and an argon flow rate of 50 cm3 minꢀ1. Ultraviolet/visible
(UV/Vis) spectra were recorded on an UV-3600 SHIMADZU UV/Vis-
NIR spectrophotometer and fluorescence spectra were obtained using a
2-Chloro-4,6-di(thiophen-2-yl)-1,3,5-triazine: Following the above proce-
dure 1, 2.9 g (65% yield) of yellow solid was obtained from 2-bromothio-
phene (3.89 g, 23.9 mmol), magnesium turnings (0.61 g, 24.9 mmol), and
2,4,6-trichloro-1,3,5-triazine (2.0 g, 10.8 mmol) at 358C for 12 h. GC-MS
(CH2Cl2): m/z: 279. 1H NMR (CDCl3, 400 MHz): d=8.26 (d, 2H), 7.69
(d, 2H), 7.22 ppm (t, 2H).
RF-5301PC spectrofluorophotometer with
a xenon lamp as a light
2,4-Dichloro-6-phenyl-1,3,5-triazine: Following the above standard proce-
dure 1, 1.16 g (47% yield) of white solid was obtained from bromoben-
zene (1.36 mL, 13.0 mmol), magnesium turnings (0.34 g, 14.0 mmol),
2,4,6-trichloro-1,3,5-triazine (2.0 g, 10.8 mmol) at 08C for 4 h. GC-MS
(CH2Cl2): m/z: 225.
source. The concentrations of the compound solutions (in CHCl3) were
adjusted to about 0.01 mgmLꢀ1 or less. The thin solid films were pre-
pared by casting solution of the compounds on quartz substrates. The
phosphorescence spectra of the compounds (in CHCl3) were measured
using an Edinburgh LFS920 fluorescence spectrophotometer at 77 K,
with a 5 ms delay time after the excitation (l=337 nm) with a microsec-
ond flash lamp. The highest occupied molecular orbital (HOMO), the
lowest unoccupied molecular orbital (LUMO), and the energy gap be-
tween them (Eg) were measured by cyclic voltammetry (CV). The CV
measurements were performed at room temperature on a CHI660E
system in a typical three-electrode cell with a working electrode (glass
carbon), a reference electrode (Ag/Ag+, referenced against ferrocene/fer-
rocenium (FOC)), and a counter electrode (Pt wire) in an acetonitrile so-
lution of Bu4NPF6 (0.10m) at a sweeping rate of 100 mVsꢀ1. The HOMO/
LUMO energy levels of the material are estimated based on the refer-
ence energy level of ferrocene (4.8 eV below the vacuum): HOMO/
2-Chloro-4,6-diphenyl-1,3,5-triazine: Following the above standard proce-
dure 1, 2.18 g (50% yield) of white solid was obtained from bromoben-
zene (8.7 g, 55.4 mmol), magnesium turnings (1.38 g, 57.5 mmol), 2,4,6-tri-
chloro-1,3,5-triazine (3.0 g, 16.2 mmol) at 358C for 12 h. GC-MS
(CH2Cl2): m/z: 267; 1H NMR (CDCl3, 400 MHz): d=8.59 (d, 4H), 7.61
(t, 2H), 7.52 ppm (t, 4H); 13C NMR (CDCl3, 100 MHz): d=173.36,
172.17, 134.35, 133.56, 129.40, 128.82 ppm.
Synthesis of monomer 4,6-dichloro-2-(N,N-diphenyl)-1,3,5-triazine: Pro-
cedure 2: Diphenylamine (2.02 g, 12.0 mmol) was placed in a 50 mL
round-bottom flask equipped with a stir. Dry THF (20 mL) was injected
with a syringe into the flask under nitrogen atmosphere. Then the solu-
tion was cooled in an icy bath and stirred for ten minutes. Then, 1.6m n-
butyllithium/hexane solution (8.1 mL, 13.0 mmol) was added slowly into
the solution. The mixture was stirred for another 30 min at room temper-
ature, and its color became yellow. Then, the yellow solution was slowly
dropped into a stirred solution of 2,4,6-trichloro-1,3,5-triazine (2.0 g,
10.8 mmol) in dry THF (20 mL) at 08C for 30 min. After stirring for 4 h
at 08C, the mixture was poured into water and extracted with CH2Cl2.
The layers were separated, and the organic layers were collected and
dried over sodium sulfate. The solvent was removed by rotary evapora-
tion, and the residue was purified by flash column chromatography to
give a yellow solid (3.0 g, 87% yield). GC-MS (CH2Cl2): m/z: 315.
LUMO=ꢀ
G
ꢀ(ꢀ0.017)]ꢀ4.8 eV, in which the value of 0.017 V is for
N
FOC versus Ag/Ag+ and Eonset is the onset potential of the oxidation or
the reduction.
Computational methods: Theoretical calculations were performed on
Gaussian 03 program with the Beckeꢁs three-parameter exchange func-
tional along with the Lee Yang Parrꢁs correlation functional (B3LYP)
using 6–31G (d) basis sets. The ground and lowest triplet-state geometries
were fully optimized and these optimized stationary points were further
characterized by harmonic vibration frequency analysis to ensure that
real local minima had been found. The properties of the designed model
compounds in Table S1, such as highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO) energy,
energy gap (Eg), and triplet-state energy (3Eg) were derived from the
computed results according to literature publications.[7d,26,31]
6-Chloro-2,4-di(N,N-diphenyl)-1,3,5-triazine: Following the standard pro-
cedure 2, 0.87 g (74% yield) of yellow solid was obtained from diphenyl-
amine (0.96 g, 5.67 mmol), 1.6m n-butyllithium/hexane solution (3.7 mL,
5.96 mmol), and 2,4,6-trichloro-1,3,5-triazine (0.5 g, 2.71 mmol) at 358C
for 12 h. GC-MS (CH2Cl2): m/z: 448; 1H NMR (CDCl3, 400 MHz): d=
7.25 (t, 8H), 7.17–7.11 ppm (m, 12H). 13C NMR (CDCl3, 100 MHz): d=
169.90, 165.61, 142.63, 128.77, 127.47, 126.15 ppm.
Device fabrication and measurement: In a general procedure, ITO-
coated glass substrates were etched, patterned, and washed with deter-
gent, deionized water, acetone, and ethanol in turn. Organic layers were
deposited by high-vacuum (ꢁ4ꢂ10ꢀ4 Pa) thermal evaporation with a
rate of 0.1–0.2 nmsꢀ1. To reduce the ohmic loss, a layer heavily p-doped
with MoOx (because of the low doping efficiencies of transition-metal-
oxide-based acceptors in amorphous organic matrixes) was directly de-
posited onto the ITO substrate for each sample. The layer thickness and
the deposition rate were monitored in situ by an oscillating quartz thick-
ness monitor. The devices without encapsulation were measured immedi-
ately after fabrication under ambient atmosphere at room temperature.
Electroluminescent (EL) spectra of the devices were measured by a
PR650 spectroscan spectrometer. The luminance–voltage and current–
voltage characteristics were measured simultaneously with a programma-
ble Keithley 2400 voltage–current source.
Synthesis of 9,9’-[6-(thiophen-2-yl)-1,3,5-triazine-2,4-diyl]bis(9H-carba-
zole) (ThDCzT): Procedure 3: 9H-carbazole (0.5 g, 3.0 mmol) was placed
in a 50 mL round-bottom flask equipped with a stir. Dry THF (5 mL)
was injected with a syringe into the flask under nitrogen atmosphere.
Then the solution was cooled in an icy bath and stirred for ten minutes,
and 1.6m n-butyllithium/hexane solution (1.94 mL, 3.1 mmol) was added
into slowly. The mixture was stirred for another 30 min at room tempera-
ture to form yellow slurry. A mixture of 2,4-dichloro-6-(thiophen-2-yl)-
1,3,5-triazine (0.3 g, 1.3 mmol) and [PdACHTNUTRGEN(UNG PPh3)4] (160 mg, 0.13 mmol) in
THF (5 mL) were slowly dropped into the slurry of the prepared lithium
carbazole. A large amount of solid product was precipitated. The mixture
was heated at 808C overnight. The precipitation was filtered and washed
with water and acetone several times. The solid was first dried in air and
then recrystallizations from chlorbenzene to give a solid (0.46 g, 72%).
1H NMR (CDCl3, 400 MHz): d=9.04 (d, 4H), 8.42 (s, 1H), 8.10 (d, 4H),
7.75 (s, 1H), 7.54 (t, 4H), 7.44 (t, 4H), 7.34 ppm (d, 1H); 13C NMR
(CDCl3, 100 MHz): d=168.56, 164.40, 141.85, 138.91, 132.52, 131.80,
128.74, 126.99, 126.60, 123.40, 119.68, 117.72 ppm; MALDI-TOF: m/z
calcd for C31H19N5S: 493.58 [M+H]+; found: 494.379; elemental analysis
calcd (%) for C31H19N5S: C 75.43, H 3.88, N 14.19, S 6.50; found: C
75.46, H 3.81, N 13.94.
Synthesis of monomer 2,4-dichloro-6-(thiophen-2-yl)-1,3,5-triazine: Pro-
cedure 1: A solution of 2-bromothiophene (2.12 g, 13.0 mmol) in dry
THF (15 mL) was added slowly to a stirred mixture of magnesium turn-
ings (0.34 g, 14.0 mmol) in dry THF (5 mL) containing a catalytic amount
of iodine under nitrogen to obtain the Grignard reagent. The Grignard
reagent solution was dropped slowly into a stirred solution of 2,4,6-tri-
chloro-1,3,5-triazine (2.0 g, 10.8 mmol) in dry THF (20 mL) at 08C. After
stirring for 4 h, the mixture was poured into water and extracted with
CH2Cl2. The layers were separated, and the organic layers were collected
and dried over sodium sulfate. The solvent was removed by rotary evapo-
ration, and the residue was purified by flash column chromatography to
9-[4,6-Di(thiophen-2-yl)-1,3,5-triazin-2-yl]-9H-carbazole (DThCzT): Fol-
lowing procedure 3, 0.22 g (50% yield) of target product was obtained
from 9H-carbazole (0.22 g, 1.3 mmol), 1.6m n-butyllithium/hexane solu-
tion (0.87 mL, 1.3 mmol), 2-chloro-4,6-di(thiophen-2-yl)-1,3,5-triazine
give
a yellow solid (0.9 g, 36% yield). GC-MS (CH2Cl2) m/z: 231.
1H NMR (CDCl3, 400 MHz): d=8.27 (d, 1H), 7.78 (d, 1H), 7.23 ppm (t,
1H); 13C NMR (CDCl3, 100 MHz): d=129.29, 135.09, 136.17, 137.97,
170.19, 171.61 ppm.
(0.3 g, 1.1 mmol) and [PdACTHNUTRGNEUNG(PPh3)4] (140 mg, 0.11 mmol) at 808C for 12 h.
1H NMR (CDCl3, 400 MHz): 9.17 (d, 2H); 8.37 (d, 2H); 8.08 (d, 2H);
7.71 (d, 2H); 7.61 (t, 2H); 7.45 (t, 2H); 7.30 ppm (t, 2H); 13C NMR
10876
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Chem. Eur. J. 2011, 17, 10871 – 10878

Conjugated Asymmetric Donor-Substituted 1,3,5-Triazines
FULL PAPER
(CDCl3, 100 MHz): d=118.23, 119.54, 123.38, 126.76, 127.03, 128.56,
131.73, 132.30, 139.06, 141.76, 164.37, 168.15 ppm; HRMS (EI): m/z calcd
for C23H14N4S2: 411.0738 [M+H]+; found: 411.0739.
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9,9’-(6-Phenyl-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (PhDCzT): Fol-
lowing procedure 3, 0.38 g (58% yield) of target product was obtained
from 9H-carbazole (0.51 g, 3.1 mmol), 1.6m n-butyllithium/hexane solu-
tion (2.1 mL, 3.2 mmol), 2,4-dichloro-6-phenyl-1,3,5-triazine (0.3 g,
1.3 mmol) and [PdACHTUNGTRENNUNG
(PPh3)4] (170 mg) at 808C for 12 h. 1H NMR (CDCl3,
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400 MHz): d=9.05 (d, 4H), 8.76 (d, 2H), 8.11 (d, 4H), 7.69 (d, 2H),
7.57–7.44 ppm (m, 9H). 13C NMR (CDCl3, 100 MHz): d=173.08, 164.78,
138.95, 136.20, 132.93, 129.23, 129.00, 127.02, 126.58, 123.38, 119.73,
117.56 ppm; MALDI-TOF: m/z calcd for C33H21N5: 487.55 [M+H]+;
found: 488.388; elemental analysis calcd (%) for C33H21N5: C 81.29, H
4.34, N 14.36; found: C 80.92, H 4.39, N 14.39.
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9-(4,6-Diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (DPhCzT): Following
procedure 3, 0.2 g target product (65% yield) was obtained from 9H-car-
bazole (0.15 g, 0.90 mmol), 1.6m n-butyllithium/hexane solution (0.56 mL,
0.90 mmol), 2-chloro-4,6-diphenyl-1,3,5-triazine (0.2 g, 0.75 mmol) and
[PdACHTUNGTRENNUNG
(PPh3)4] (93 mg) at 808C for 12 h. 1H NMR (CDCl3, 400 MHz): d=
9.17 (d, 2H); 8.78 (t, 4H); 8.10 (d, 2H); 7.66–7.60 (m, 8H); 7.45 ppm (t,
2H); 13C NMR (CDCl3, 100 MHz): d=172.51, 165.26, 139.17, 136.31,
132.73, 129.16, 128.84, 127.03, 126.69, 123.31, 119.69, 117.74 ppm;
MALDI-TOF: m/z calcd for C27H18N4: 398.46 [M+H]+; found: 399.391;
elemental analysis calcd (%) for C27H18N4: C 81.39, H 4.55, N 14.06;
found: C 81.43, H 4.78, N 13.77.
4,6-Di(9H-carbazol-9-yl)-N,N-diphenyl-1,3,5-triazin-2-amine
(NPhDCzT): Following procedure 3, 0.20 g (78% yield) of target product
was obtained from 9H-carbazole (0.23 g, 1.39 mmol), 1.6m n-butyllithi-
um/hexane solution (0.91 mL, 1.45 mmol), 4,6-dichloro-2-(N,N-diphenyl)-
1,3,5-triazine (0.2 g, 0.63 mmol) and [PdACHTNUTRGEN(UNG PPh3)4] (93 mg) at 808C for 12 h.
1H NMR (CDCl3, 400 MHz): d=8.56 (d, 4H), 8.00 (d, 4H), 7.62–7.54 (m,
8H), 7.45 (t, 2H), 7.33 (t, 4H), 7.26 ppm (t, 4H); 13C NMR (CDCl3,
100 MHz): d=167.01, 164.33, 143.18, 139.00, 129.62, 128.53, 127.12,
126.52, 126.28, 122.84, 119.34, 117.98 ppm; MALDI-TOF: m/z calcd for
C39H26N6, 578.66 [M+H]+; found 579.531; elemental analysis calcd (%)
for C39H26N6: C 80.95, H 4.53, N 14.52; found: C 80.65, H 4.58, N 14.41.
6-(9H-Carbazol-9-yl)-N2,N2,N4,N4-tetraphenyl-1,3,5-triazine-2,4-diamine
(DNPhCzT): Following procedure 3, 0.48 g (75% yield) of target product
was obtained from 9H-carbazole (0.22 g, 1.32 mmol), 1.6m n-butyllithi-
um/hexane solution (0.91 mL, 1.45 mmol), 6-chloro-2,4-di(N,N-diphenyl)-
1,3,5-triazine (0.5 g, 1.11 mmol) and [PdACHTNUTRGEN(UNG PPh3)4] (93 mg, 0.074 mmol) at
808C for 12 h. 1H NMR ([D]DMSO, 400 MHz): d=8.00 (d, 2H, J=
7.6 Hz), 7.74 (d, 2H, J=8.4 Hz), 7.68–6.94 (m, 22H), 6.88 ppm (d, 2H,
J=1.6 Hz). 13C NMR (CDCl3, 100 MHz): d=166.49, 164.02, 143.39,
139.09, 128.99, 128.22, 128.00, 127.51, 126.09, 122.28, 118.83, 118.52 ppm;
MALDI-TOF: m/z calcd for C39H28N6: 580.68 [M+H]+; found 581.583;
elemental analysis calcd (%) for C39H28N6: C 80.67, H 4.86, N 14.47;
found: C 80.54, H 4.88, N 14.44.
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Acknowledgements
We thank the National Basic Research Program of China
(2009CB930601), National Natural Science Foundation of China
(20804020, 20905038, 60976019 and 20974046), Scientific Research Foun-
dation of Nanjing University of Posts and Telecommunications
(NY210017), and the Program for Postgraduates Research Innovations in
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Received: April 12, 2011
Published online: September 2, 2011
10878
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 10871 – 10878