Efficient pyrene-imidazole derivatives for organic light-emitting diodes

Article abstract of DOI:10.1039/c5ra25424h

Two light emitting materials, 9-phenyl-10-(4-(1,2,2-triphenylvinyl)phenyl)-9H-pyreno[4,5-d]imidazole (PyTPEI) and 9-phenyl-10-(4'-(1,2,2-triphenylvinyl)-[1,1'-biphenyl]-4-yl)-9H-pyreno[4,5-d]imidazolepyreneimidazole (PyPTPEI), containing pyrene, imidazole

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Efficient Pyrene-Imidazole Derivatives for Organic Light-emitting
Diodes
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a
a
b
a
a
Yulong Liu, Qing Bai, Jinyu Li, Shitong Zhang, Chen Zhang, Fang Lu, Bing Yang, and Ping Lu*
DOI: 10.1039/x0xx00000x
Two light emitting materials, 9-phenyl-10-(4-(1,2,2-triphenylvinyl)phenyl)-9H-pyreno[4,5-d]imidazole (PyTPEI) and 9-
phenyl-10-(4'-(1,2,2-triphenylvinyl)-[1,1'-biphenyl]-4-yl)-9H-pyreno[4,5-d]imidazolepyreneimidazole (PyPTPEI), containing
pyrene, imidazole and tetraphenylethene units are synthesized with high yields. Both of them exhibit good thermal
stability with decomposition temperature of 458 °C and 474 °C, respectively. The fluorescent quantum efficiency in
amorphous film are as high as 70% for PyTPEI and 63% for PyPTPEI, respectively. In particular, PyPTPEI shows the blue-
shifted emission due to the more twisted conformation and reduced intermolecular interaction as compared with PyTPEI.
The maximum current efficiency and maximum brightness of non-doped OLED device using PyTPEI as active layer reaches
www.rsc.org/
2
2
8
.73 cd/A and 27419 cd/m , which is better than that of PyPTPEI (7.68 cd/A and 19419 cd/m ).
8
newly resulted luminogens with high solid-state efficiencies.
Introduction
The development of pyrene chemistry is highly position-
dependent. The electrophilic substitution of pyrene is known
Over the past decades, organic light-emitting diodes (OLEDs)
have been one of the mostly developed field due to their
potential applications in large-area, high-resolution flat panel
9
-11
to take place preferentially at the 1, 3, 6, and 8-positions.
Thus, 1-substituted pyrenes and 1, 3, 6, 8-tetrasubstituted
pyrenes can be easily accessible by direct electrophilic
substitution of pyrene which has already generated abundant
1
displays and full-color lighting sources. Creation of the
luminogens with high solid-state efficiency is very important to
2
facilitate the applications in OLEDs. Pyrene represents one of
1
2
luminogens. The 4, 5, 9, and 10-positions of the pyrene ring
are very favorable to extend the aromatic system. Fortunately,
these positions can be reached through the oxidation of
the mostly investigated small organic molecule which is best
known for its high photoluminescence efficiency, good thermal
3
stability, and promising carrier mobility. However, pyrene π-
pyrene using a mixture of ruthenium (III) chloride (RuCl
3
) and
sodium periodate (NaIO ) in heterogeneous system, which
4
system suffers heavily from the aggregation-caused-quenching
selectively provides pyrene-4, 5-dione and pyrene-4, 5, 9, 10-
tetraone, depending on the reaction temperature and the
(ACQ) effect originating from the strong π-π interaction of
pyrene, which would limit its solid-state emission to some
4
extent. So far, some chemical modifications have been
1
3
amount of oxidant used. On the other hand, 1, 3-imidazole is
a commonly used five-mumbered-ring functional group for
efficient light emitting materials in virtue of its amphoteric
introduced with the aim of inhibiting molecular aggregation
5
including the attachment of branched alkyl, blending with
2
6
,7
characteristics originated from the two different kinds of sp
transparent polymers, etc. These processes, however, are
often accompanied by severe side effects. For example, the
steric effects of bulky alicyclics can twist the conformations of
the chromophoric units and jeopardize the electronic
1
4
hybridnitrogen atoms. Based on these consideration, in this
work, a facile and one-pot straightforward methodology is
used to prepare a novel polycyclic skeleton using pyrene and
1
4a,15
5
imidazole as the key units.
Tetraphenylethylene (TPE) is
conjugation in the luminophores. And non-conjugated
introduced by Pd-catalyzed Suzuki cross-coupling reaction. It is
hoped that TPE will work with the pyrene-imidazole unit
synergistically and cooperatively, and their melts at the
molecular level will afford adducts with the combined
advantages of the two components, that is, both AIE-activity
and good carrier injection and transport property. Through the
judicious structural design, we have succeeded in creating new
pyrene-based luminogens as well as displaying good
performance in OLEDs. Especially, device based on PyTPEI
exhibited green emission with external quantum efficiency and
polymers can dilute the luminophore density and subsequently
obstruct the charge transport in electroluminescence (EL)
7
devices. Alternative strategy is of great interest.
In recent year, the attachment of aggregation-induced
emission (AIE) group, such as tetraphenylethylene (TPE), into
the ACQ units has proved to be a promising way to provide the
a
State Key Laboratory of Supramolecular Structure and Materials, Jilin University,
Street No.2699, Changchun, 130012, China.E-mail: lup@jlu.edu.cn.
-1
b
Pharmacy Department, Changchun Medical College, China.
Electronic Supplementary Information (ESI) available: See
current efficiency up to 3.46% and 8.73 cd A , respectively,
which indicates great potential application in optoelectronic
†
DOI: 10.1039/x0xx00000x
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Fig. 1 DSC and TGA thermograms of PyTPEI and PyPTPEI under nitrogen at a
–
1
.
heating rate of 10 °C min
resulting from the additional phenyl ring between pyrene-
imidazole and TPE. The rigid pyrene-imidazole moiety was
responsible for their high thermostability. In addition, the
exothermic peak was at 243 °C for PyTPEI and 235 °C for
PyPTPEI during the thermal scanning indicating the crystalline
†
state. (Fig. 1 and Fig. S9, ESI ). The good thermal stability is
very important for their applications in OLEDs.
Photophysical Properties
The absorption spectra and PL emission spectra of TPE and
intermediate 1 were measured in Fig. 2A and Fig. 2B. As can be
seen from Fig. 2A, TPE show absorption at 315 nm
corresponding to its π–π* transitions. However, intermediate 1
exhibits complex absorption profiles, owing to multiple
localized π–π* transitions, which originated from the
combination of pyrene and imidazole segment. Thus the
absorption profiles of PyTPEI and PyPTPEI are similar to that of
intermediate 1 which are dominated by multiple localized π-π*
Scheme 1 Synthetic routes to PyTPEI and PyPTPEI.
Field.
Results and discussion
Synthesis and Characterization
The synthesis process for PyTPEI and PyPTPEI were shown in transitions originating from pyrene, imidazole and the TPE
Scheme 1. The synthetic formulation strategy is based on the chromophores. The observed peak in the longer-wavelength
1
heterocyclization of imidazole and pyrene, whereby pyrene-4, region of 386 nm with vibrational fine structure is attributed to
6
5-tetraone and 4-bromobenzaldehyde were applied as the pyrene-imidazole-localized π-π* electronic excitation (Fig. 2C).
starting materials to afford compound 1.
1
5(a)
Compounds 2a The absorption spectra for each compound in amorphous film
and 2b could be obtained through the boronation of (2- were very similar to that of solution, except that the
bromoethene-1,1,2-triyl)tribenzene
and
(2-(4- absorption edges were both red-shifted about 5 nm (Fig. 2D).
1
7
bromophenyl)ethene-1,1,2-triyl)tribenzene,
respectively.
The optical energy gaps for PyTPEI and PyPTPEI were thus
And then, the targeted products were achieved by the Pd- calculated to be 2.90 and 2.88 eV (Table 1), respectively. Both
catalyzed Suzuki cross-coupling reaction with high yields. The of them showed AIE-activity, that is, they were non-emissive in
1
compounds were thoroughly characterized by NMR ( H and C) THF but exhibited intense emission in their aggregate state (Fig.
13
†
spectroscopy, mass spectrometry and elemental analysis. The S10 and Fig. S11, ESI ). Interestingly, PyTPEI showed a green
analytical data of PyTPEI and PyPTPEI were consistent well emission peaking at 488 nm, whereas PyPTPEI displayed blue-
with their proposed structure.
shifted emission peaking at 473 nm in film although it
possessed one more phenyl ring. This might be derived from
the reduced intermolecular interactions in PyPTPEI because
the newly formed biphenyl unit between pyrene-imidazole
and TPE could rotate freely and increase the steric hindrance
in solid state. The quantum efficiencies in films measured by
integral sphere were as high as 70% for PyTPEI and 63% for
PyPTPEI, respectively. However PLQY of intermediate 1 in film
was only 9.6% with considerable bathochromic-shift (69nm) of
emission compared to that of intermediate 1 in dilute solution
Thermal Properties
The thermal stability of PyTPEI and PyPTPEI was characterized
by thermal gravimetric analysis (TGA) and differential scanning
calorimetry (DSC) under a nitrogen atmosphere. As shown in
Fig. 1, PyTPEI and PyPTPEI exhibited excellent thermal stability
with decomposition temperature (5% weight loss) at 458 °C
and 474 °C, respectively. In DSC heating cycles, no Tg was
detected for PyTPEI due to its rigid polycyclic skeleton, and Tm
appeared at 315 °C. While T and T for PyPTPEI were at 162 °C
g
m
(
Fig. 2B). In addition, the emission spectra of intermediate 1
and 283 °C respectively, which was much lower than PyTPEI
demonstrating a more flexible molecular feature in PyPTPEI
became broad and structureless, which is typical for excimer
2
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Fig. 3 (A) Molecular structure of PyTPEI in one unit cell. (B) Top view. (C)
Molecular arrangement along a axis, side view.
Fig. 2 Normalized absorption and emission spectra of intermediate 1, TPE, PyTPEI
-
5
and PyPTPEI in 2-methyltetrahydrofuran (A, B, C 10 M) and in film (B, D
thickness: 30 nm).
Fig. 4 The HOMOs and LUMOs for PyTPEI and PyPTPEI obtained at the B3LYP/6-
Table 1. Optical and electrochemical properties of PyTPEI and PyPTPEI.
3
1G level.
a,b
abs (nm)
a,b
PL (nm)
c
d
e
Compound
PyTPEI
λ
λ
Φ
f
E
g
E
g
solu/film
solu/film
433/488
[eV]
2.90
[eV]
2.99
interaction between N-3 atom of imiazole and hydrogen atom
on phenyl ring attaching to the N-1 atom of imidazole in
adjacent molecule along b axis with a distance of 2.97 Å (Fig.
290,350,386/
0.70
0.63
2
95,353,388
290,348,386/
96,354,390
†
PyPTPEI
436/473
2.88
2.92
S12, ESI ). The abundant intermolecular interactions helped to
2
lock the molecular rotations of TPE in the solid state and
suppress the non-radiative pathway of consuming the exciton
a
b
Measured in 2-methyltetrahydrofuran. Measured in solid thin film on
c
quartz plates. Determined in evaporated film by the measurement in energy to further increase the photoluminescence efficiency.
d
integrating sphere system. Optical energy bandgap (E
opt
g
) estimated from
Theoretical Calculations
e
tion edge in solution. Electrochemical bandgap determined
the absor
p
To evaluate their frontier molecular orbitals and energy
bandgaps, density functional theory (DFT) calculations were
Obviously, aggregation in intermediate 1 red- performed with a B3LYP/6–31G(d,p) basis set using the
from cyclic voltammetry.
4
,14a
emission.
shifts emission and decreases emission efficiency dramatically Gaussian 03W program (Fig. 4). The distribution of the lowest
with notorious ACQ effect. In consequence, attaching TPE units unoccupied molecular orbitals (LUMOs) and the highest
to a pyrene-imidazole as ornaments endows the resultant occupied molecular orbitals (HOMOs) were very similar for
products with typical AIE activity and efficient solid-state PyTPEI and PyPTPEI. The HOMOs of the two objective
photoluminescence.
compounds were mainly delocalized over the pyrene-
imidazole segment, while their LUMOs were mainly located on
imidazole and TPE groups. In addition, the calculated bandgaps
of the compounds were nearly same which is consistent with
their comparison of experimental bandgap based on optical
energy bandgap and electrochemical bandgap.
X-ray Molecular Structure and Crystal Packing
The single crystal of PyTPEI was obtained by the solvent
evaporation method in dichloromethane. As depicted in Fig. 3,
the crystal belonged to triclinic space group P-1. The whole
molecule formed an anti-parallel arrangement, pyrene-
imidazole and TPE units alternately stacked together based on
Electrochemical Properties
1
8
head-to-tail intermolecular interactions. There was no The electrochemical properties of these compounds were
overlap between the adjacent pyrene unit which suggested examined by cyclic voltammetry (CV). Both of them underwent
that the generally obseved excimer formation via π-π stackings irreversible oxidation and reduction process in dry
in pyrene π-system could be avoided and accordingly dichloromethane and DMF using (Bu N)PF as electrolytes
4
6
eliminated the ACQ effect. It is found that there were four C- under N atmosphere. According to the onset potentials, the
2
H•••π (I, II, III, IV) interactions between hydrogen atom on HOMO levels of PyTPEI and PyPTPEI were calculated to be -
phenyl rings of TPE and the π clouds of pyrene in adjacent 5.30 and -5.36 eV, while the LUMO levels of PyTPEI and
molecules with distances of 2.73-2.99 Å, and one C-H•••N (V) PyPTPEI were calculated to be -2.31 eV and -2.44 eV,
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2
10
0
10
-2
10
PyTPE hole-only
PyTPEI
PyPTPEI
PyTPE electron-only
PyPTPE hole-only
PyPTPE electron-only
-4
10
-3.0
-2.5
-2.0
0.0
0.5
1.0
1.5
7
8
5.0x10
1.0x10
+
Potential (V vs. Ag/Ag )
Electric field intensity (V/cm)
Fig. 5 Cyclic voltammogram of PyTPEI and PyPTPEI in CH
Cl
2 2
(oxidation) and DMF
(
reduction), measured with 0.1 M (Bu
-
4
N)PF
6
as supporting electrolyte at a scan
Fig. 7 The electron and hole current density versus electric field intensity curves
1
.
rate of 100 mV s
of the single carrier devices based on PyTPEI and PyPTPEI.
Fig. 8 AFM images (5 µm × 5 µm) of evaporated films on the quartz plate before
Fig. 6 (A) Electroluminescence (EL) spectra for PyTPEI and PyPTPEI measured at 9
V. (B) Current density-voltage-brightness (J-V-L) characteristics. (C) Current
efficiency versus brightness curves. (D) Current efficiency and power efficiency
versus current density curves.
and after annealing at 120 °C for 1 h under ambient atmosphere.
coordinate of (0.209, 0.401) for PyTPEI and (0.202, 0.336) for
PyPTPEI, respectively, where the initial band of EL spectra in
PyPTPEI was blue-shifted about 20 nm compared with PyTPEI
respectively, by comparison to ferrocene (Fig. 5). The HOMO-
LUMO energy gaps obtained from CV measurement concided
well with the optical energy gaps got from UV-vis
measurements (Table 1).
(
Fig. 6A). The electroluminescent spectra were in consistent
with the emission profiles of their amorphous films.
Fig. 6B plots the current density–luminescence–voltage (J–
L–V) curves of both devices. The turn-on voltages (Von) of
devices were both at 2.8 V suggesting that the dissipation of
Electroluminescence Properties
Owing to their high solid-state efficiencies and good thermal energy associated with carrier injection or transportation is
stability, non-doped OLEDs based on PyTPEI and PyPTPEI were quite low. The LE curves (Fig. 6D) showed a relatively stable
fabricated with a typical configuration of ITO/PEDOT: PSS (40 light output, even when the current density approached 300
-2
nm)/NPB (50 nm)/EML (20 nm)/TPBi (40 nm)/LiF (0.5 nm)/Al mA cm , their EL spectrum did not change in operating
120 nm), where TPBi was used as electron-transport layer and conditions. The PyTPEI-based device had the highest LE and
(
-1
NPB was used as the hole-transport layer. The device external quantum efficiency (EQE) of 8.73 cd A and 3.46%,
-2
performance was summarized in Table 2. Both devices gave respectively, yielding a maximum luminance of 27419 cd m at
green electroluminescence (EL) peaking at 500 nm with 8.3 V. As compared, the device using PyPTPEI as the active
Commission Internationale de L’E’ clairage (CIE) chromaticity layer showed moderate performance with a ηc.max of 7.68 cd A
4
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Table 2. Electroluminescence properties of the devices.
quantum calculations and OLEDs are performed. Both of them
show high thermal stability. The attachment of TPE group to
pyrene-imidazole endows PyTPEI and PyPTPEI with AIE-activity
and high efficiencies in solid state. A blue-shifted fluorescence
Device
V
on
CE (cd
A )
EQEb
(%)
Brightness
(cd m )
EL c
(nm)
CIE
d
(x,y)
a
-1
b
-2
b
(V)
PyTPEI
2.8
2.8
8.73
7.68
3.46
3.35
27419
19419
500
500
(0.209, of PyPTPEI in the solid state is observed due to the reduced
.401) intermolecular interactions. In OLEDs, PyTPEI shows a better
(0.202, device performance with the maximum current efficiency of
0
PyPTPEI
−
1
−2
0
.336) 8.73 cd A . Even when the brightness reached 10000 cd m ,
the device still exhibits a very low efficiency roll-off. These
a
−2 b
Driving voltage at 1 cd m . Maximum value of current efficiency (CE), external
c
molecules provides a design strategy to prevent the
quantum efficiency (EQE) and brightness.
Peak wavelength of
d
−2
aggregation-induced fluorescence quenching of pyrene
system and facilitates their applications in OLEDs.
π
electroluminescence (EL) spectra. CIE coordinates measured at 1000 cd m .
-1
-2
an EQE of 3.35% and a maximum luminance of 19419 cd m .
,
To further investigate the merits towards fusion of pyrene,
imidazole and TPE subunits at molecular level and better
understand the effect of 1, 3-imidazole on the energy levels
and the carrier injection and transport property in devices, the
hole-only device with the configuration of ITO/PEDOT-PSS (40
nm)/NPB (10 nm)/EML (70 nm)/NPB (20 nm)/Al (120 nm) and
the electron-only device with the configuration of ITO/TPBi (20
nm)/EML (70 nm)/TPBi (10 nm)/LiF (1 nm)/Al (120 nm) for
PyTPE and PyPTPEI were fabricated. The results (Fig. 7)
indicated that both PyTPEI and PyPTPEI showed high carrier
injection and transport ability which confirmed that 1,3-
imidazole can act as a bipolar type building block. Their hole
current values of PyTPEI and PyPTPEI were very similar and
both higher than their corresponding electron current values.
Furthermore, electron current values of PyTPEI was much
higher than PyPTPEI, indicating that more carriers could be
transported to the emitting layer of PyTPEI in OLED, which is
crucial to obtain higher efficiency in PyTPEI than PyPTPEI
owing to the dual-injection/transportation procedure of OLEDs.
The devices based on PyTPEI and PyPTPEI will stably
assemble during the device fabrication process. The
amorphous films of PyTPEI and PyPTPEI were obtained
through vacuum deposition method as proved by X-ray
diffracꢀon (Fig. S15, ESI†). Morphology of these films were
investigated by atomic force microscopy (AFM). The images
are given in Fig. 8. The PyTPEI film exhibits a quite smooth
surface morphology with a roughness of 1.40 nm. After
Experimental Section
All of the reagents and solvents used for the syntheses were
purchased from Aldrich or Acros and were used as received. All
of the reactions were performed under
a dry-nitrogen
1
atmosphere. The H NMR spectra were recorded on an
AVANCZ 500 spectrometers at 298 K by utilizing deuterated
dimethyl sulfoxide (DMSO) as solvents and tetramethylsilane
1
3
(
TMS) as a standard. The C-NMR spectra were recorded on
an AVANCZ 500 spectrometers at 298 K by utilizing deuterated
trichloromethane as solvents and tetramethylsilane (TMS) as a
standard. The final compounds were characterized by Flash EA
1
112, CHNS-O elemental analysis instrument. The MALDI-TOF
mass spectra were recorded using an AXIMA-CFRTM plus
instrument. Diffraction data were collected on a Rigaku RAXIS-
PRID diffractometer using the ω-scan mode with graphite-
monochromator Mo•Kα radiation. UV-vis absorption spectra
were recorded on UV-3100 spectrophotometer. Fluorescence
measurements were carried out with RF-5301PC. The film PL
efficiencies were measured on
a Gliden Fluorescence
Systemusing an integrating sphere, with a 366.8 nm Edinburgh
Instruments Ltd light emitting diode as the excitation source.
Instrument model (FLS920). Thermal gravimetric analysis (TGA)
was measured on a Perkin-Elmer thermal analysis system from
3
0 °C to 900 °C at a heating rate of 10 K/min under nitrogen
flow rate of 80 ml/min. Differential scanning calorimetry (DSC)
was performed on a NETZSCH (DSC-204) unit from 30 °C to
o
annealing at 120 C for 1 h under ambient atmosphere, the
4
00 °C at a heating rate of 10 K/min under nitrogen
film morphology became more smooth with a roughness of
atmosphere. The electrochemical properties (oxidation and
reduction potentials) were carried out via cyclic voltammetry
0.74 nm. In the case of PyPTPEI, it also shows a fairly smooth
surface morphology with a roughness of 0.97 nm. After
o
annealing at 120 C for 1 h under ambient atmosphere, the
(
CV) measurements by using a standard one-compartment,
three-electrode electrochemical cell given by a BAS 100B/W
film morphology is basically unchanged. Both of them provide
a homogeneous morphology of amorphous evaporated film
indicating the possibility to keep uniform films throughout the
device fabrication process.
electrochemical
analyzer.
(TBAPF6) in
Tetrabutylammoniumhexafluorophosphate
anhydrous dimethyl formamide (DMF) or anhydrous
dichloromethane (0.1 M) were used as the electrolyte for
negative or positive scan. The ground-state geometries were
optimized at the B3LYP/6-31G(d, p) level, which is a common
method to provide molecular geometries. The HOMO/LUMO
Conclusions
In summary, we have designed and synthesized two efficient distributions are calculated on the basis of optimized ground-
light emitting materials, PyTPEI and PyPTPEI, and determined state.
their difference and relationship upon their molecular
Device Fabrication: The EL devices were fabricated by
-6
structure. A comparative study of these two compounds vacuum deposition of the materials at 10 Torr onto ITO glass
-1
through spectroscopic, electrochemical, crystallographic, with a sheet resistance of 25 Ω square . All of the organic
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layers were deposited at a rate of 1.0 Å s . The cathode was MHz, CDCl
Journal Name
-1
13
3
, 25°C): δ C NMR (126 MHz, CDCl ) δ 143.72,
3
-1
deposited with LiF (0.5 nm) at a deposition rate of 0.1 Å s and 143.69, 143.66, 143.3, 141.3, 140.4, 137.8, 132.2, 131.9, 131.7,
then capping with Al metal (120 nm) through thermal 131.4, 131.34, 130.26, 130.0, 129.7, 129.2, 128.0, 127.8,
-1
evaporation at a rate of 4.0 Å s . The electroluminescent (EL) 127.71, 127.65, 127.57, 126.58, 126.56, 126.52, 126.47, 126.1,
spectra and Commission Internationale De L’Eclairage (CIE) 125.3, 124.6, 124.3, 123.6, 122.9, 118.0. Elemental analysis:
36 2
coordination of these devices were measured by a PR650 calculated for C55H N : C, 91.13; H, 5.01; N, 3.86; found: C,
spectroscan spectrometer. The luminance-current and density- 91.27; H, 5.14; N, 3.59.
voltage characteristics were recorded simultaneously with the
measurement of the EL spectra by combining the
Acknowledgements
spectrometer with a Keithley model 2400 programmable
voltage-current source. All measurements were carried out at
room temperature under ambient conditions.
This work was supported by the Ministry of Science and
Technology of China (2013CB834801), and the National
Science Foundation of China (21374038 and 91233113).
Synthesis of compound 1: A mixture of aniline (2.3 ml, 25.0
mmol), pyrene-4,5-dione (1.2 g, 5.0 mmol), 4-
bromobenzaldehyde (1.2 g, 6.0 mmol), ammonium acetate
(1.5 g, 20.0 mmol), and acetic acid (15 ml) was refluxed under Notes and references
nitrogen in an oil bath. After 2 h, the mixture was cooled and
filtered. The solid product was washed with an acetic
acid/water mixture (1:1, 50 mL). And then, it was separated by
1
(a) C. W. Tang, S. A. VanSlyke, Appl. Phys. Lett., 1987, 51
9
923; (c) T. P. I. Saragi, T. Spehr, A. Siebert, T. F. Lieker, J.
Salbeck, Chem. Rev., 2007, 107, 1011; (d) C. D. Müller, A.
Falcou, N. Reckefuss, M. Rojahn, V. Wiederhirn, P. Rudati, H.
Frohne, O. Nuyken, H. Becker, K. Meerholz, Nature, 2003,
421, 829; (e) J. U. Park, M. Hardy, S. J. Kang, K. Barton, K.
Adair, D. K. Mukhopadhyay, C. Y. Lee, M. S. Strano, A. G.
Alleyne, J. G. Georgiadis, P. M. Ferreira, J. A. Rogers, Nat.
,
13; (b) S. R. Forrest, M. E. Thompson, Chem. Rev., 2007, 107
,
+
1
chromatography. Yield: 86.0%. MS: 472.5 (M (H )). H NMR
500 MHz, DMSO-d , 25°C): δ 8.95 (d, J = 7.0 Hz, 1H), 8.33 (d, J
7.4 Hz, 1H), 8.27-8.17 (m, 4H), 7.86-7.72 (m, 6H), 7.63-7.58
m, 4H), 7.32 (d, J = 7.9 Hz, 1H).
Synthesis of PyTPEI:
triphenylvinyl)-1,3,2-dioxaborolane (2a) (0.92 g, 2.4 mmol), 10-
4-bromophenyl)-9-phenyl-9H-pyreno[4,5-d]imidazole (1) (0.95
g, 2.0 mmol), dry toluene (24 mL), and 16 mL aqueous of K CO
solution (2.0 mol L ) were placed in a round-bottom flask.
Pd(PPh (0.14 g, 0.12 mmol) was then added and the mixture
(
6
=
(
4,4,5,5-tetramethyl-2-(1,2,2-
Mater., 2007,
(a) D. A. Pardo, G. E. Jabbour, N. Peyghambarian, Adv. Mater.,
000, 12, 1249; (b) S. R. Forrest, Nature, 2004, 428, 911.
(a) T. M. Figueira-Duarte, K. Müllen, Chem. Rev., 2011, 111
260; (b) S. Bailey, D. Visontai, C. J. Lambert, M. R. Lambert,
H. Frampton, D. Frampton, J. Chem. Phys., 2014, 140, 054708;
c) S. Q. Zhang, X. L. Qiao, Y. Chen, Y. Y. Wang, R. M. Edkins, Z.
6, 782.
2
3
(
2
2
3
,
-1
7
3 4
)
(
was vigorously stirred at 90 °C for 48h. After cooling to room
temperature, the resulting mixture was extracted with
dichloromethane followed by purification by column
Q. Liu, H. X. Li, Q. Fang, Org. Lett., 2014, 16, 342.
(a) K.-C. Wu, P.-J. Ku, C.-S. Lin, H.-T. Shih, F.-I. Wu, M.-J.
Huang, J.-J. Lin, I.-C. Chen, C.-H. Cheng, Adv. Funct. Mater.,
4
+
chromatography on silica gel. Yield: 80%. MS: 649.2 (M (H )).
1
2
008, 18
Venkatakrishnan, D.-F. Huang, T. J. Chow, Org. Lett., 2007,
215; (c) T. Oyamada, H. Uchiuzou, S. Akiyama, Y. Oku, N.
Shimoji, K. Matsushige, H. Sasabe, C. Adachi, J. Appl. Phys.,
, 67; (b) J. N. Moorthy, P. Natarajan, P.
H NMR (500 MHz, DMSO-d
6
, 25°C): δ 8.91 (d, J = 7.6 Hz, 1H),
9,
5
8
7
9
1
1
1
.31 (d, J = 7.3 Hz, 1H), 8.25-8.17 (m, 4H), 7.78-7.71 (m, 6H),
.41 (d, J = 8.5 Hz, 2H), 7.30 (d, J = 8.3 Hz, 1H), 7.18-7.12 (m,
3
2
3
005, 98, 074506; (d) I. B. Berlman, J. Phys. Chem., 1970, 74,
085.
1
3
H), 7.02-6.94 (m, 8H). C NMR (125 MHz, CDCl , 25°C): δ
43.5, 143.4, 143.3, 132.2, 131.7, 131.4, 131.33, 131.29, 130.1,
29.2, 128.8, 128.0, 127.8, 127.69, 127.67, 127.5, 126.59,
5
6
(a) C.-L. Chiang, S.-M. Tseng, C.-T. Chen, C.-P. Hsu, C.-F. Shu,
Adv. Funct. Mater., 2008, 18, 248; (b) J.-S. Yang, J.-L. Yan,
Chem. Commun., 2008, 1501; (c) J. Wang, Y. F. Zhao, C. D.
Dou, H. Sun, P. Xu, K. Q. Ye, J. Y. Zhang, S. M. Jiang, F. Li, Y.
Wang, J. Phys. Chem. B, 2007, 111, 5082; (d) J. N. Moorthy, P.
Natarajan, P. Venkatakrishnan, D.-F. Huang, T. J. Chow, Org.
26.56, 126.42, 125.3, 124.4
，
124.3，123.6，122.9，117.97.
Elemental analysis: calculated for C49
H
32
N
2
: C, 90.71; H, 4.97; N,
4.32; found: C, 90.87; H, 4.74; N, 4.39.
Synthesis of PyPTPEI:
4,4,5,5-tetramethyl-2-(4-(1,2,2-
Lett., 2007, 9, 5215.
triphenylvinyl)phenyl)-1,3,2-dioxaborolane (2b) (1.10 g, 2.4
mmol), 10-(4-bromophenyl)-9-phenyl-9H-pyreno[4,5-
d]imidazole (1) (0.95 g, 2.0 mmol), dry toluene (24 ml), and 16
(a) C. Fan, S. Wang, J. W. Hong, G. C. Bazan, K. W. Plaxco, A.
J. Heeger, Proc. Natl. Acad. Sci. USA, 2003, 100, 6297; (b) B. S.
Gaylord, S. Wang, A. J. Heeger, G. C. Bazan, J. Am. Chem. Soc.,
2
001, 123, 6417.
-
1
mL aqueous of K
2
CO
3
solution (2.0 mol L ) were placed in a
(0.14 g, 0.12 mmol) was then
7
8
S. Hecht, J. M. J. Fréchet, Angew. Chem. Int. Ed., 2001, 40, 74.
round-bottom flask. Pd(PPh )
3 4
(a) Y. N. Hong, J. W. Y. Lam, B. Z. Tang, Chem. Soc. Rev., 2011,
40, 5361; (b) Y. N. Hong, J. W. Y. Lam, B. Z. Tang, Chem.
Commun., 2009, 4332; (c) X. F. Ji, P. Wang, H. Wang, F. H.
Huang, Chinese J. Polym. Sci., 2015, 33, 890; (d) Y. Liu, X.
Feng, J. B. Shi, J. G. Zhi, B. Tong, Y. P. Dong, Chinese J. Polym.
Sci., 2012, 30, 443.
added and the mixture was vigorously stirred at 90 °C for 48h.
After cooling to room temperature, the resulting mixture was
extracted with dichloromethane followed by purification by
column chromatography on silica gel. Yield: 85%. MS: 726.0 (M
+
1
(
H )), H NMR (500 MHz, DMSO-d
6
, 25°C): δ 8.96 (d, J = 7.6 Hz,
9
1
(a) H. Vollmann, H. Becker, M. Corell, H. Streeck, Liebigs Ann.,
1937, 531, 1; (b) L. Altschuler, E. Berliner, J. Am. Chem. Soc.,
1H), 8.32 (d, J = 7.2 Hz, 1H), 8.23 (t, J = 8.6 Hz, 1H), 8.21-8.16
1
966, 88, 5837.
0 (a) M. J. S. Dewar, R. D. Dennington, J. Am. Chem. Soc., 1989,
11, 3804; (b) R. A. Hites, Calculated Molecular Properties of
(
m, 3H), 7.85-7.80 (m, 2H), 7.76 (dt, J = 7.9, 6.8 Hz, 4H), 7.68
dd, J = 21.5, 8.5 Hz, 4H), 7.53 (d, J = 8.3 Hz, 2H), 7.31 (d, J = 7.8
(
1
1
Hz, 1H), 7.20-7.08 (m, 9H), 7.07-6.96 (m, 8H). C NMR (125
3
Polycyclic Aromatic Hydrocarbons, Elsevier, New York, 1987.
6
| J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5RA25424H
Highly efficient green OLED based on AIE-active pyrene-imidazole derivative PyTPEI achieves the
highest LE of 8.73 cd/A with low efficiency roll-off.