An excited state managing molecular design platform of blue thermally activated delayed fluorescence emitters by π-linker engineering

Article abstract of DOI:10.1039/c9tc05550a

A molecular design platform of blue thermally activated delayed fluorescence (TADF) emitters to boost the external quantum efficiency and efficiency roll-off of blue TADF organic light-emitting diodes (OLEDs) was developed. A molecular structure hiring one or two excited state controlling subunits in the π-linker between a donor and an acceptor was employed. The subunit in the π-linker was a phenyl unit to precisely control the performances of TADF devices. It was described that the phenyl subunit simultaneously improved the external quantum efficiency and efficiency roll-off of TADF OLEDs. A high external quantum efficiency of 28.5% was demonstrated using the material design having two phenyl sub units.

Full text of DOI:10.1039/c9tc05550a

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Materials Chemistry C
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An excited state managing molecular design
platform of blue thermally activated delayed
Cite this:DOI: 10.1039/c9tc05550a
fluorescence emitters by p-linker engineering†
Kyung Hyung Lee,‡a Soon Ok Jeon, ‡*b Yeon Sook Chung,b Masaki Numata,c
b
Hasup Lee,b Eun Kyung Lee,
Hyeonho Choi
Eun Suk Kwon,b Myungsun Sim,b
b
a
and Jun Yeob Lee
*
A molecular design platform of blue thermally activated delayed fluorescence (TADF) emitters to boost the
external quantum efficiency and efficiency roll-off of blue TADF organic light-emitting diodes (OLEDs) was
developed. A molecular structure hiring one or two excited state controlling subunits in the p-linker between
a donor and an acceptor was employed. The subunit in the p-linker was a phenyl unit to precisely control
the performances of TADF devices. It was described that the phenyl subunit simultaneously improved
the external quantum efficiency and efficiency roll-off of TADF OLEDs. A high external quantum
efficiency of 28.5% was demonstrated using the material design having two phenyl sub units.
Received 10th October 2019,
Accepted 11th December 2019
DOI: 10.1039/c9tc05550a
rsc.li/materials-c
p-linker is to control the orbital overlap for radiative transition,
it can also affect the RISC by strengthening or weakening the CT
Introduction
Since the first demonstration of close to 20% external quantum properties of TADF emitters. For instance, the introduction of a
efficiency (EQE) using a thermally activated delayed fluores- methyl group or a CN group into the p-linker controlled the
cence (TADF) emitter, the progress of the TADF device char- emission energy and RISC properties of TADF emitters.23,24
acteristics has been surprisingly remarkable. The EQE of
Herein, we describe a molecular design platform of blue
TADF organic light-emitting diodes (OLEDs) was even further TADF emitters for high EQE and improved efficiency roll-off.
enhanced from 20% to close to 30% in the red device and even A p-linker engineering approach through phenyl subunits was
over 30% in the green and blue devices by developing several employed to reduce the singlet–triplet energy gap (DEST) for an
material design platforms of TADF emitters.1–17
efficient RISC process. It was demonstrated that the molecular
The most popular material design platform of TADF emitters design platform adopting phenyl subunits in the p-linker facilitated
is the donor-p linker-acceptor structure. The donor and acceptor the RISC process and enhanced the EQE of TADF OLEDs. Moreover,
parts in the TADF structure mainly govern the charge transfer the supplementary reduction of the efficiency roll-off was proven by
(CT) characteristics related with the singlet and triplet energies, p-linker engineering. A high EQE of 28.5% was demonstrated using
and the p-linker part dominates the orbital overlap for efficient a TADF material with two phenyl subunits in the p-linker.
light emission. In many research studies, donor and acceptor
engineering was the main approach to manage the TADF
performances of TADF emitters because the key process of
reverse intersystem crossing (RISC) was mostly determined by
Results and discussion
the donor and the acceptor.18 A p-linker engineering has been A p-linker modifying approach was adopted to establish
a minor part in the TADF material design.19 However, the a molecular design platform of highly efficient blue TADF
importance of the p-linker has been described in several pub- emitters. The motivation for p-linker engineering is that the
lications in recent years.20–22 Although the main role of the aromatic linker can control the excited state of TADF emitters
by electronic communication and spatial management of the
a School of Chemical Engineering, Sungkyunkwan University 2066, Seobu-ro,
molecular structure. One or two phenyl subunits were intro-
duced into the phenyl linker at the ortho position to the donor
substitution position to manage the excited state through the
donor geometry control. We selected CTrz as a standard blue
TADF material because of its promising property reported in
previous work.25
Jangan-gu, Suwon, Gyeonggi, 16419, Korea. E-mail: leej17@skku.edu
b Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd,
130 Samsung-ro, Suwon-si, Gyeonggi-do 16678, Korea. E-mail: so.jeon@samsung.com
c Samsung R&D Institute Japan, 2-7 Sugasawa-cho, Tsurumu-ku, Yokohama, Japan
† Electronic supplementary information (ESI) available. See DOI: 10.1039/c9tc05550a
‡ Kyung Hyung Lee and Soon Ok Jeon contributed equally.
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Synthesis
excited state (T1). kB is the Boltzmann constant and T is the
temperature, which is set to 298 K. DEST denotes the energy
difference between the S1 and T1 states, and lS represents the
reorganization energy which can be formulated as:
For the construction of 1PCTrz and 2PCTrz containing a phenyl
substituted phenyl linker, an N-carbazolylcarbazole donor and a
fluorophenyl modified diphenyltriazine group with one or two phenyl
units were coupled by the SNAr reaction as shown in Scheme 1. The
fluoro intermediates were synthesized using a palladium catalyzed
cross coupling procedure described in the ESI.† 26
All three final products were purified by flash-column chro-
matography followed by sublimation to ensure 499.5% purity.
The chemical structures were fully confirmed by the respective
1H and 13C NMR spectra and mass data. Their thermal proper-
ties were examined by thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC) (see Fig. S1, ESI†). The
decomposition temperature (Td, corresponding to 5% weight
loss) of 1PCTrz and 2PCTrz was similar to that of CTrz. Although
the molecular weight was increased due to the attachment of one
or two phenyl units, the temperature was not increased due to
the twisted donor structure by attaching the phenyl subunits to
the ortho positions of the phenyl linker. In the DSC measure-
ments, both CTrz and 1PCTrz exhibit a distinct glass-transition
temperature (Tg) of 150 and 158 1C, respectively.
lS = ES1(T1 geometry) ꢀ ES1(S1 geometry)
All the DFT and TD-DFT computations were performed using
the Gaussian 09 package,32 and the SOC calculations were
performed using the ADF package.33 The HONTO (Highest
Occupied Natural Transition Orbital) and the LUNTO (Lowest
Unoccupied Natural Transition Orbital) of S1 and T1 states were
calculated by NANCY.34,35 Also, we calculated the overlap
between the HONTO and the LUNTO to describe CT (Charge-
transfer) and LE (Local-excitation) characters for S1 and T1
states. The overlap between the HONTO and the LUNTO (Fs)
was defined as
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Ð
rHðrÞrLðrÞdr
ðrHðrÞ þ rLðrÞÞdr
FS ¼
ÂÐ
Ã
1
2
where rH(r) and rL(r) are the electronic densities of the HONTO
and the LUNTO.
Calculations
The calculation results are summarized in Table S1 (ESI†) to
forecast the photophysical characteristics of the three emitters.
The lS of the TADF emitters was decreased with the help of the
phenyl subunits because they can restrict the molecular motion
by steric hindrance. This can easily be predicted by the excited
state geometry of the three emitters in S1 and T1 states in Fig. 1.
The geometrical change in the S1 and T1 states was minimized
in the 2PCTrz emitter, which reduced the lS. The increase of the
number of phenyl sub-units intensified the CT characters in
both S1 and T1 states (Fig. 2). Although the three TADF emitters
showed a small overlap value in the CT dominant S1 state, the
strengthened CT character of 1PCTrz and 2PCTrz in the S1 state
The molecular geometries in the ground (S0) state were opti-
mized using the B3LYP27 functional and the 6-31G(d,p) basis
set. The excited-state geometries and energies were derived by
time-dependent density functional theory (TD-DFT) at the
MPW1B9528/6-31G(d,p) level of theory. The reverse intersystem
crossing (RISC) rate, kRISC, was computed by the Fermi Golden
rule29 and Marcus theory:30,31
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ꢀ
ꢁ
2
2p
ꢀh
1
ðDEST þ lSÞ
4lSkBT
2
kRISC
¼
jhS1jHSOjT1ij
exp ꢀ
4pkBTlS
where |hS1|HSO|T1i| is the Spin–Orbit Coupling (SOC) matrix decreased the DEST. The large overlap value in the T1 state of
element between the singlet excited state (S1) and the triplet CTrz showed that the LE character is dominant in the T1 state
Scheme 1 Synthetic route to TADF materials.
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Fig. 1 Optimized geometry of the TADF emitters in the ground and excited states.
of CTrz. The dominant LE character in the T1 state of CTrz potential of the p-linker engineering method using phenyl
improves the SOC matrix element value.29
subunits as a platform to improve the TADF characteristics of
The kRISC values estimated from the calculated material the emitters was confirmed.
parameters such as lS, the SOC matrix element, and DEST were
The HOMO and LUMO levels of the TADF emitters were
gradually increased by adding the phenyl subunits. The SOC characterized by analyzing the ionization potential and electron
matrix element of CTrz is larger than those of two other emitters, affinity from the oxidation and reduction potentials of cyclic
but the reduction of DEST and lS was mostly responsible for voltammetry measurements in Fig. S2 (ESI†). The estimated
the large kRISC in 1PCTrz and 2PCTrz emitters. Therefore, the HOMO/LUMO levels of the CTrz, 1PCTrz, and 2PCTrz TADF
Fig. 2 HONTO (blue)/LUNTO(red) for the S1 and T1 states of TADF emitters.
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emitters were ꢀ5.55/ꢀ2.55, ꢀ5.49/ꢀ2.51, and ꢀ5.50/ꢀ2.45 eV,
respectively. The addition of a phenyl subunit had little
effect on the energy levels although a slight HOMO level shift
by the isolated donor unit was observed in the 1PCTrz and
2PCTrz emitters.
Photophysical properties
The photophysical characterization results of the TADF emitters
are shown in Fig. 3. The singlet energy/triplet energy/DEST values
of the CTrz, 1PCTrz, and 2PCTrz emitters were 3.13/2.89/0.24 eV,
3.06/2.90/0.16 eV and 2.97/2.86/0.11 eV, respectively, from the
onset energy of the fluorescence and phosphorescence spectra.
A gradual decrease of the singlet energy and DEST was noticed
in the photoluminescence (PL) measurement of the emitters.
As the fluorescence emission originated from CT emission as
confirmed in the broad emission spectrum, the strong CT character
of 1PCTrz and 2PCTrz stabilized the singlet energy. However, the
triplet energy decrease was not as large as that of the singlet energy
because the origin of phosphorescence is mixed emission of CT
and local triplet emission. Although the CT character was strength-
ened by the phenyl subunits, the local triplet energy would be
increased by the twisted structure disrupting the conjugation of the
backbone structure, which resulted in a small change of the triplet
energy. The simultaneous CT triplet energy reduction and local
triplet energy increase hybridized the CT and local triplet excited
states, resulting in the hybridized triplet excited states. This result
was in agreement with the HONTO and LUNTO calculation results.
The DEST was governed by the singlet energy as the triplet energy
was similar to those of the three emitters. Therefore, the phenyl
subunit was effective to reduce the DEST. In the ultraviolet-visible
(UV-Vis) absorption, the main absorption in the backbone
structure was similarly discerned and CT absorption below
400 nm was noted in the TADF emitters. The photophysical data
are summarized in Table 1.
The dynamics of the TADF emission were analyzed using the
transient PL characterization of the emitters doped in the
DPEPO host. The prompt decay and delayed decay of the PL
emission are presented in Fig. 4. The excited state lifetime for
the prompt emission was relatively short in CTrz (11.6 ns)
compared to those of 1PCTrz (16.1 ns) and 2PCTrz (29.3 ns).
As the number of the phenyl subunits increased, the HOMO–
LUMO overlap was reduced, which delayed the prompt emis-
sion process. However, the delayed fluorescence process was
accelerated by the phenyl subunits. The delayed fluorescence
lifetimes of CTrz, 1PCTrz, and 2PCTrz were 80.4, 55.8, and
31.4 ms, respectively. The strong CT character narrowing the gap
Fig. 3 UV-Vis and PL spectra of CTrz (a), 1PCTrz (b) and 2PCTrz (c) TADF
emitters.
between the singlet and triplet excited states facilitated the CTrz to 87% of 1PCTrz and 90% of 2PCTrz. The phenyl
RISC process of the 1PCTrz and 2PCTrz TADF emitters. The subunits assisted the radiative transition of the TADF emitters
RISC rate constants (kRISC) were increased from 2.74 ꢁ 104 of along with the RISC process of the triplet excitons. The
CTrz to 3.97 ꢁ 104 of 1PCTrz and 7.27 ꢁ 104 of 2PCTrz (Table 2). increased PLQY of the two TADF emitters built on the phenyl
The PL quantum yield (PLQY) of the three TADF materials subunit platform is due to the reduction of the non-radiative
was measured by doping the emitter in the DPEPO host at an transition as can be estimated from the non-radiative rate
emitter content of 10 wt%. It was carried out to correlate the constants (knr) of 0.16 ꢁ 109
s
ꢀ1, 0.11 ꢁ 109 sꢀ1 and 0.06 ꢁ
PLQY with the device performances of the TADF emitters by 109 sꢀ1 in CTrz, 1PCTrz and 2PCTrz, respectively.36 The phenyl
doping them into the DPEPO host at 10 wt% doping concen- subunit seems to rigidify the backbone structure by applying large
tration. The PLQY under nitrogen was increased from 84% of steric hindrance to the carbazolylcarbazole donor. In spite of the
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Table 1 Summarized photophysical properties of CTRz, 1PCTRz and
2PCTrz TADF emitters
Table 2 Summarized PLQY and transient PL characteristics of CTrz,
1PCTrz and 2PCTrz TADF emitters
a
b
b
Singlet Triplet
Ftotal
(%)
Fprompt FTADF tp
td
kISC
kRISC
HOMOa LUMOa HOMO–LUMO energyb energyb DEST
(%)
(%)
(ns) (ms) (107 sꢀ1
)
(104 sꢀ1
)
(eV)
(eV)
gap (eV)
(eV)
(eV)
(eV)
CTrz
1PCTrz 87
2PCTrz 90
84
35
36
37
49
51
53
11.6 80.4 5.62
16.1 55.8 3.99
29.3 31.4 2.17
2.74
3.97
7.27
CTrz
ꢀ5.55
ꢀ2.55
ꢀ2.51
ꢀ2.46
3.00
2.98
3.04
3.13
3.06
2.97
2.89
2.90
2.86
0.24
0.16
0.11
1PCTrz ꢀ5.49
2PCTrz ꢀ5.50
a
b
10 wt% doped film in DPEPO. Calculated according to the method
a
b
Measured from cyclic voltammetry scanning. Calculated from the reported in ref. 37.
fluorescent and phosphorescent spectrum onset point.
HOMO gap between the DPEPO and TADF emitters, the
large distortion of the donor hampering the oscillator strength of reduction of the hole transport properties by the subunits would
the emitter by the isolated HOMO and LUMO, the suppressed non- be the main factor for the low J in 1PCTrz and 2PCTrz. In the
radiative process positively influenced the PLQY of the emitters. case of L, the relative trend was the same as the J at low voltage,
This is well correlated with the small reorganization energy of but the order of L disagreed with that of J at high voltage. This is
1PCTrz and 2PCTrz as summarized in Table S1 (ESI†).
due to external quantum efficiency (EQE) change according to L.
The EQE data of the TADF devices were plotted against
current density in Fig. 7. The Lambertian distribution of light
Device performances
The TADF performances of the three emitters were evaluated in emission was assumed in the EQE measurement. The max-
vacuum evaporated TADF devices by dispersing the TADF imum EQE of the device was in the order of 2PCTrz (28.5%) 4
materials in the DPEPO host at a doping concentration of 1PCTrz (26.7%) 4 CTrz (24.8%). The maximum EQE was
20%. A high doping concentration was used to open a hole governed by the number of subunit in the phenyl linker. The
transport channel in the DPEPO host because the DPEPO is an increase of the number of subunits enhanced the maximum
electron transport type host with poor hole injection and EQE of the TADF devices.
transport properties. The device structure is shown in Fig. 5.
Considering the PLQY of the TADF emitters, the EQE of the
The voltage sweep method was used to collect the current TADF devices was rather high. Therefore, the horizontal dipole
density ( J) and luminance (L) data of TADF devices. The J and orientation of the emitters was measured by angle dependent
L plots of the TADF devices are presented in Fig. 6. The phenyl PL analysis. The experimental results are presented in Fig. 8.
subunit in the p-linker affected the J of the TADF devices, The horizontal dipole orientation of the doped film was mea-
resulting in low J values in 1PCTrz and 2PCTrz emitters. The sured to correlate the device performances with the horizontal
reduction of J in the two devices can be interpreted by the effect dipole orientation. The three doped emitters in the DPEPO
of the phenyl subunit which twisted the carbazolylcarbazole matrix exhibited a horizontal dipole orientation ratio over 85%,
donor from the phenyl linker. The carbazolylcarbazole donor suggesting that the three TADF emitters are similarly aligned
was almost perpendicular to the phenyl linker, which hindered along the substrate irrespective of the phenyl subunits. The
the carrier transport by a weak intermolecular orbital overlap anisotropic orientation of the dipole contributed to the high
for carrier hopping. The small twisting of the donor unit was EQE of the three emitters. The EQE roll-off judged by the J value
advantageous for carrier hopping in the CTrz emitter. As the at which the EQE of the device is half of the maximum EQE
holes are mainly carried by the TADF emitters due to the large followed the same order (2PCTrz (9.4 mA cmꢀ2) 4 1PCTrz
Fig. 4 The prompt decay (a) and delayed decay of (b) CTrz, 1PCTrz, 2PCTrz emitters doped in the DPEPO host at 10 wt% doping concentration and IRF
(Instrument Response Function).
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Fig. 5 Energy diagram of the TADF devices and chemical structure of the materials.
Fig. 6 The J and L plots of CTrz, 1PCTrz and 2PCTrz TADF devices.
Fig. 7 The EQE data against current density of CTrz, 1PCTrz and 2PCTrz
TADF devices.
(2.6 mA cmꢀ2) 4 CTrz (1.5 mA cmꢀ2)) as the maximum EQE.
The addition of the phenyl subunits improved the EQE roll-off
Fig. 8 The angle-dependent p-polarized PL intensity data of DPE-
characteristics of the TADF devices. As the EQE drop at high L is PO:CTrz (a), DPEPO:1PCTrz (b) and DPEPO:2PCTrz (c).
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Experimental
Chemicals were purchased from Sigma-Aldrich Co., Tokyo
Chemical Industry Co., and Wako Pure Chemical Industries
Ltd, and used without further purification. 1H NMR and
13C NMR spectra were recorded on a Bruker ASCEND 500 at
500 MHz using CD2Cl2 as the solvent. The MALDI-TOF mass
spectra were recorded using a Bruker Ultraflex III TOF/TOF
200 spectrometer. The Ultraviolet-Visible (UV-Vis) spectra were
obtained by means of a Varian model UV-Vis-NIR spectro-
photometer 5000 and the fluorescence spectra were measured
using a HITACHI F7000 spectrometer for the solution states.
The UV-Vis absorption and solution photoluminescence (PL)
emission spectra of the materials were obtained from dilute
toluene solution (1 ꢁ 10ꢀ5 M), while the triplet energy values of
the TADF materials were obtained from the photoluminescence
spectra at 77 K using liquid nitrogen. The energy levels were
measured by using cyclic voltammetry (CV). Each material
was dissolved in anhydrous dichloromethane with 0.1 M tetra-
butylammonium hexafluorophosphate as an electrolyte to
measure the oxidation from which the HOMO energy level
was estimated. Glassy carbon was used as the working elec-
trode, a platinum wire was used as the counter electrode, and a
saturated Ag/AgCl was used as the reference electrode. Ferro-
cene was used as the standard reference. All solutions were
purged with nitrogen for 10 minutes before each experiment.
The LUMO levels of each material were estimated from the
difference between the HOMO energy level and the optical
band gap which were estimated from the absorption edge of
the UV-Vis spectra.
Fig. 9 The EL spectra of CTrz, 1PCTrz and 2PCTrz TADF devices.
triggered by the long excited state lifetime of triplet excitons,
the reduced delayed fluorescence lifetime of the 1PCTrz and
2PCTrz emitters upgraded the EQE roll-off performances. The
new blue TADF emitters with the phenyl subunit in the p-linker
simultaneously improved the efficiency roll-off due to the
facilitated RISC process and the suppressed non-radiative loss
mechanism.
The light-emission spectra of the TADF devices in Fig. 9
show the emission spectra of CTrz, 1PCTrz and 2PCTrz TADF
devices. The peak wavelengths of the CTrz, 1PCTrz, and 2PCTrz
devices were 482, 482, and 488 nm, respectively. The corres-
ponding color coordinates of the CTrz, 1PCTrz, and 2PCTrz
devices were (0.17,0.28), (0.17,0.30), and (0.18, 0.35), respec-
tively. The strong CT character of the 2PCTrz by the twisted
donor unit caused the bathochromic shift of the emission
spectrum. The device data of the TADF devices are summarized
in Table 3.
Synthesis
General procedure for SNAr reaction: synthesis of 9-(4-(4,6-
diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-3,90-bicarbazole (CTrz) as
a
representative. To a solution of 2-(4-fluorophenyl)-4,6-
diphenyl-1,3,5-triazine (1.95 g, 5.96 mmol) in N,N-dimethyl-
formamide (DMF, 20 mL) 9H-3,90-bicarbazole (2.2 g, 6.62 mmol)
Conclusions
A molecular design platform to boost the external quantum and cesium carbonate (4.31 g, 13.24 mmol) were added at room
efficiency and efficiency roll-off of the blue TADF emitters was temperature. The reaction mixture was stirred at 160 1C for
developed by hiring one or two excited state controlling sub- 12 hours. After allowing it to cool to room temperature, the
units in the p-linker between a donor and an acceptor. The reaction mixture was diluted with MeOH (200 mL) and filtered.
phenyl subunit in the p-linker simultaneously improved the The reaction mixture was carefully washed with water/MeOH
external quantum efficiency and efficiency roll-off of the TADF (100/100 mL). The resulting brown solid was collected by filtration.
OLEDs due to the facilitated RISC process and the suppressed The crude product was purified by column chromatography using
non-radiative loss mechanism. A high external quantum effi- dichloromethane/n-hexane (1/3) as the eluent. The yellow solid
ciency of 28.5% was achieved using the material design having was obtained and then the product was recrystallized from toluene
two phenyl subunits in the blue emitters, opening a pathway to and finally dried under vacuum to give 9-(4-(4,6-diphenyl-1,3,5-
get access to the ideal device performances of blue TADF OLEDs. triazin-2-yl)phenyl)-9H-3,90-bicarbazole (CTrz) as a yellow crystal in
Table 3 Summarized device performances of the CTrz, 1PCTrz and 2PCTrz devices
External quantum efficiency (%)
Power efficiency (lm Wꢀ1
)
Current efficiency (cd Aꢀ1
)
Color coordinates
[1000 cd mꢀ2
]
[Max]
[1000 cd mꢀ2
]
[Max]
[1000 cd mꢀ2
]
[Max]
x
y
CTrz
1PCTrz
2PCTrz
8.6
11.7
19.4
24.8
26.7
28.5
7.8
10.2
20.7
45.4
50.2
57.1
16.6
23.5
42.8
50.6
55.9
64.4
0.165
0.171
0.182
0.282
0.302
0.348
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3.24 g (77%) yield. 1H NMR (500 MHz, CD2Cl2): d (ppm) 9.10
The material was thermally evaporated and then encapsu-
(d, 2H), 8.85 (d, 4H), 8.34 (s, 1H), 8.20 (d, 2H), 8.19 (d, 1H), 7.94 lated with a glass lid in a nitrogen-filled glove box to protect the
(d, 2H), 7.79 (d, 1H), 7.66 (m, 8H), 7.55 (t, 1H), 7.44 (m, 4H), 7.35 device from moisture and oxygen. Electrical characterization of
(t, 1H), 7.30 (m, 2H); 13C NMR (75.5 MHz, CD2Cl2): 172.4, 171.49, the devices was performed using a Keithley 2400 source meter
142.36, 141.74, 140.14, 136.70, 133.3, 131.29, 130.84,129.5, 129.31, and optical characterization was carried out using a CS 2000
127.42, 127.35, 126.47, 126.41, 123.63, 121.34, 121.21, 120.75, spectroradiometer.
120.21, 119.99, 111.68, 110.88, 110.35; MALDI-TOF/MS: 639.34
[(M + H)+]. Anal. calcd for C45H29N5: C, 84.48; H, 4.57; N, 10.95.
Conflicts of interest
Found: C, 84.4; H, 4.6; N, 11.0.
9-(5-(4,6-Diphenyl-1,3,5-triazin-2-yl)-[1,10-biphenyl]-2-yl)-9H-3,90-
There are no conflicts to declare.
bicarbazole (1PCTrz). By following the same procedure as that
used for the synthesis of CTrz, using 2-(6-fluoro-[1,10-biphenyl]-3-
yl)-4,6-diphenyl-1,3,5-triazine (6.78 g, 16.85 mmol) as an acceptor Acknowledgements
and 9H-3,90-bicarbazole (7.00 g, 21.06 mmol) as a donor 1PCTrz
This material is based upon work supported in the part by the
(9.30 g, 62%) was synthesized. 1H NMR (500 MHz, CD2Cl2):
Samsung Advanced Institute of Technology (SAIT).
d (ppm) 9.14 (d, 1H), 9.04 (dd, 1H), 8.84 (m, 4H), 8.22 (d, 1H),
8.18 (dd, 2H), 8.06 (d, 1H), 7.88 (d, 1H), 7.65 (m, 6H), 7.41
(m, 7H), 7.30 (m, 7H), 7.17 (m, 3H); 13C-NMR (75.5 MHz,
CD2Cl2): d 170.91, 170.99, 141.79, 141.64, 141.22, 139.94,
References
138.51, 138.35, 136.95, 136.08, 132.78, 132.30, 129.99, 129.72,
129.40, 128.98, 128.75, 128.32, 128.05, 127.63, 126.53, 125.82,
125.24, 124.29, 123.00, 122.93, 120.40, 120.24, 120.13, 119.57,
119.16, 111.31, 110.43, 109.78; MALDI-TOF/MS: 715.37
[(M + H)+]. Anal. calcd for C51H33N5: C, 85.57; H, 4.65; N, 9.78.
Found: C, 85.6; H, 4.6; N, 9.8.
9-(50-(4,6-Diphenyl-1,3,5-triazin-2-yl)-[1,10:30,100-terphenyl]-20-
yl)-9H-3,90-bicarbazole (2PCTrz). By following the same proce-
dure as that used for the synthesis of CTrz, using 2-(20-fluoro-
[1,10:30,100-terphenyl]-50-yl)-4,6-diphenyl-1,3,5-triazine (2.60 g,
5.41 mmol) as an acceptor and 9H-3,90-bicarbazole (2.00 g,
6.02 mmol) as a donor 2PCTrz (4.00 g, 84%) was synthesized.
1H NMR (500 MHz, CD2Cl2): d (ppm) 9.07 (s, 2H), 8.83 (dd, 4H),
8.16 (d, 2H), 8.04 (d, 1H), 7.91 (d, 1H), 7.65 (m, 2H), 7.61
(m, 4H), 7.41 (t, 2H), 7.33 (m, 5H), 7.29 (m, 6H), 7.13 (m, 8H);
13C NMR (75.5 MHz, CD2Cl2): 172.6, 143.8, 142.4, 139.3, 136.6,
133.4, 131.7, 129.7, 129.4, 128.7, 128.1, 126.4, 125.6, 123.6,
120.7, 120.5, 120.1, 112.1, 111.2, 110.4; MALDI-TOF/MS:
791.40 [(M + H)+]. Anal. calcd for C57H37N5: C, 86.45; H, 4.71;
N, 8.84. Found: C, 86.2; H, 4.7; N, 8.8.
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