Zigzag molecules from pyrene-modified carbazole oligomers: Synthesis, characterization, and application in OLEDs

Article abstract of DOI:10.1021/jo702075r

(Chemical Equation Presented) A series of monodisperse, pyrene-modified oligocarbazoles were synthesized and fully characterized. Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag molecular backbone and stable, size-independent absorption, and emission were observed from these oligomers in solutions because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with four different architectures (types 1-4) based on these oligomers were fabricated and investigated. Pyrene-modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport). Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3 presented an external quantum efficiency of 0.69% and a maximum brightness of 1782 cd/m² at 13.5 V, which indicated these oligomers were promising optoelectric materials.

Full text of DOI:10.1021/jo702075r

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers:
Synthesis, Characterization, and Application in OLEDs
Zujin Zhao,† Xinjun Xu,‡ Hongbo Wang,† Ping Lu,*,† Gui Yu,‡ and Yunqi Liu*,‡
Department of Chemistry, Zhejiang UniVersity, Hangzhou 310027, People’s Republic of China, and
Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences,
Beijing 100080, People’s Republic of China
pinglu@zju.edu.cn
ReceiVed September 21, 2007
A series of monodisperse, pyrene-modified oligocarbazoles were synthesized and fully characterized.
Carbazoles were linked by ethynylene through the 3- and 6-positions, forming a zigzag molecular backbone
and stable, size-independent absorption, and emission were observed from these oligomers in solutions
because their conjugation length was confined. Oligomers with pyrene exhibited much higher fluorescence
quantum yields than those of oligomers without it. Different positions of pyrene in the oligocarbazole
main chain resulted in a remarkable change in absorption and emission spectra. Moreover, devices with
four different architectures (types 1-4) based on these oligomers were fabricated and investigated. Pyrene-
modified carbazole oligomers exhibited bifunctional properties (light-emitting and hole-transport).
Moreover, these devices showed moderate performances; for example,the device based on Cz3PyCz3
presented an external quantum efficiency of 0.69% and a maximum brightness of 1782 cd/m2 at 13.5 V,
which indicated these oligomers were promising optoelectric materials.
1. Introduction
analogous polydisperse polymers. Significant developments in
modern synthetic chemistry, especially the chemistry of carbon-
carbon bond formation (through Kumada, Stille, Yamamoto,
Suzuki, Heck, and Sonogashira couplings, etc.),6 have allowed
the precise control on the orientation of functional groups in
oligomers and thus the resulting optimized physical properties.
Depending on these advanced synthetic techniques, different
conjugated building blocks (thiophene, pyrrole, phenylene, and
fluorene moieties, etc.) have been developed and utilized.
Carbazole and its derivatives have been widely used as a
functional building block in the fabrication of the organic
photoconductors, nonlinear optical materials, and photorefractive
Conjugated oligomers are subjected to important investiga-
tions from both academic and industrial laboratories1 due to
their promising applications, such as organic light-emitting
diodes (OLEDs),2 solar cells,3 field-effect transistors (FETs),4
and models5 to understand the fundamental properties of their
* Corresponding author. Tel: + 86-571-879- 52543.
† Zhejiang University.
‡ Chinese Academy of Sciences.
(1) Skotheim, T. A., L. Elsenbaumer, R., Reynolds, J. R., Eds. Handbook
of Conducting Polymers, 2nd ed.; Marcel Dekker: New York, 1998.
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10.1021/jo702075r CCC: $40.75 © 2008 American Chemical Society
Published on Web 12/21/2007
594
J. Org. Chem. 2008, 73, 594-602

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers
materials7 due to their specific optical and electrochemical
properties. In the field of OLED technology, carbazole deriva-
tives are usually used as promising blue light-emitting materials.8
Interestingly, white light is also achieved from carbazole dimers
or oligomers serving as a single-emitting-component layer in
device.9 Meanwhile, a great many of carbazole homopolymers
or oligomers as well as carbazole-containing polymers or small
molecules, such as widely used PVK (polyvinylcarbazole) and
CBP (N,N′-dicarbazolyl-4, 4′-biphenyl), are of excellent hole-
transport ability, due to the electron-donating capabilities.10
Furthermore, carbazole derivatives are of high triplet energy
and capable of using host materials in highly efficient blue,
green, or red electrophosphorescence devices11 due to efficient
energy transfer from these hosts to doped triplet emitters.
Recently, many reports have discussed their applications in light-
emitting dendrimers with carbazole-based dendrons incorporated
at antennal positions for efficient energy harvest and transfer.12
In particular, carbazole-based dendrons can also be used to
construct phosphorescent dendrimers,13 in which high triplet
energy of carbazole is transferred to the core affording an
excellent efficiency of device and avoiding phase separation in
some doped systems. On the other hand, chemically, the
carbazole moiety can be easily modified at its 3-, 6-, or
9-positions and covalently linked to other molecular moieties,14
while its 2- and 7-positions are comparably stable. Nevertheless,
there are also reports on carbazole oligomers linked together
through their 2- and 7-positions.6,15 These compounds can be
used as models to investigate structure-property relationship
of corresponding polymers or adopted as optoelectronic materi-
als. Besides these remarkable advantages, it is also recognized
that the thermal stability or glass-state durability of organic
compounds can be greatly improved by introducing carbazoles
into the core structures.16 Thus, structural modification of
carbazole for improved optoelectronic performance of materials,
such as hole-transport/emitting/electron-transport (three-in-one)
for simplified OLED architecture, is feasible, challengeable, and
valuable.17
Here, we wish to report the synthesis and characterization of
a series of well-defined, monodisperse, ethynylene-linked oli-
gocarbazoles. Two considerations were taken into our mind
using the oligocarbazole as the main chain. First, from a
synthetic point of view, well-defined and highly pure chro-
mophores could be obtained, which would offer improved
stability and comparable optical and electronic properties and
facilitate systematic investigation of structure-property relation-
ship. Second, oligocarbazoles linked through the 3,6-positions
had defined efficient conjugation length and thus could prevent
undesirable optical defects arising from dispersed molecular size.
Moreover, comparing with single or double bond linked
carbazole oligomers or polymers, triple bond linked ones are
not abundantly reported. On the other hand, pyrene was selected
and introduced to oligocarbazole because it is rigid and highly
fluorescent and its derivatives have been wildly used as
optoelectronic materials.18 After investigation of these oligomers
in different types of devices, our preliminary results indicated
that these pyrene-functionalized, ethynylene-linked oligocarba-
zoles could be used as both light-emitting and hole-transporting
materials in efficient OLEDs.
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2. Results and Discussion
2.1. Synthesis. A Pd/Cu-catalyzed Sonogashira coupling
reaction was used to build ethynylene-linked molecules. Detailed
experimental conditions for oligomer formation were similar
to the published method.19 1-Ethynylpyrene and 1,8-diethy-
nylpyrene were prepared according to the reference.20 The
synthetic approach to necessary intermediates 1-14 is outlined
in Scheme 1. Alkylation of 3-iodo-9H-carbazole afforded
9-heptyl-3-iodo-9H-carbazole (1) in 94% yield. Pd/Cu-catalyzed
coupling of 1 and 3-methyl-1-butyn-3-ol provided 2, and
subsequent treatment of 2 with base generated 3 in 79% total
yield. Similar procedures were performed from 3,6-diiodo-9H-
carbazole to obtain 9-heptyl-3,6-diiodo-9H-carbazole (4) and
3,6-diethynyl-9-heptyl-9H-carbazole (6) in 91% and 54% yields,
respectively. Treatment of 3 with 3 equiv of 4 in the presence
of CuI/Pd(PPh3)2Cl2/Ph3P/NEt3 afforded intermediate (7) in 72%
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X.; Wang, F. AdV. Funct. Mater. 2006, 16, 575. (b) Kwon, T.-H.; Kim, M.
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Y.-T.; Ko, C.-W. J. Am. Chem. Soc. 2001, 123, 9404. (c) Thomas, K. R.
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J. Org. Chem, Vol. 73, No. 2, 2008 595

Zhao, Z.
SCHEME 1a
a Key: (a) n-C7H15Br, KOH, tetrabutylammonium hydrogen sulfate, acetone, rt; (b) 3-methyl-1-butyn-3-ol, CuI, Pd(PPh3)2Cl2, Ph3P, NEt3, N2, reflux; (c)
KOH, 2-propanol, reflux.
SCHEME 2a
a Key: (d) CuI, Pd(PPh3)2Cl2, Ph3P, NEt3, N2, reflux.
yield after separation by column chromatography. Compound
7 was then converted to 9 in 75% yield after cross-coupling
and subsequent deprotection. Similarly, 13 was obtained from
11 in 63% yield. Compounds 10, 11, and 14 were synthesized
in 67%, 70%, and 62% yields, respectively.
Final construction to target molecules is illustrated in Scheme
2. PyCz3 and PyCz4 were obtained in 55% and 46% yields,
respectively. Coupling 6 with 2 equiv of 11 led to the pyrene-
anchored PyCz3Py in 58% yield. PyCz5Py, Cz5, and Cz7 were
synthesized by similar procedures in 45%, 61%, and 51% yields,
respectively. Treatment of 1,8-diethynylpyrene with 2 equiv of
10 afforded Cz3PyCz3 in 39% yield. The structures of the final
1
oligomers were verified by H and 13C NMR spectroscopy,
MALDI-TOF MS measurement, and element analysis. More-
over, due to the presence of the flexible n-heptyl substituents,
all of these synthesized compounds were soluble in common
organic solvents, such as CH2Cl2 and THF.
2.2. Optical Properties. The UV-vis absorption and PL
properties of these synthesized oligomers in dilute solutions and
in the solid state are presented in Table 1. Absorption spectra
of these compounds were complex with multiple overlapping
broad bands. Some representative spectra are shown in Figure
596 J. Org. Chem., Vol. 73, No. 2, 2008

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers
TABLE 1. Optical, Thermal, and Electrochemical Properties of Oligomers
absa (nm)
em (nm)
THF
compd
PyCz3
PyCz4
PyCz3Py
PyCz5Py
Cz3PyCz3
Cz5
THF film cyclohexane
film
Φb
Egc (eV) E°x d (V)
E°x d (V)
HOMO/LUMOe(eV) Tg/TmTdf (°C)
onset
p
405
405
405
405
443
363
364
415
415
417
417
462
367
369
411 (436)
411 (436)
411 (436)
450
460 (487)
401
446
446
446
449
469
(384) 405
(381) 405
467
468
469
472
513
456
467
0.92
0.89
0.88
0.82
0.83
0.38
0.32
2.89
2.89
2.86
2.85
2.64
3.19
3.18
0.89
0.80
0.95
0.86
0.94
0.77
0.78
1.12, 1.84
1.02, 1.76
1.04, 1.76
0.97, 1.72
1.17, 1.99
1.00, 1.77
0.96, 1.69
-5.29/-2.40
-5.28/-2.39
-5.35/-2.49
-5.27/-2.42
-5.34/-2.70
-5.17/-1.98
-5.18/-2.00
94/NA/446
104/NA/458
101/190/466
125/NA/476
165/NA/468
119/180/449
138/209/454
Cz7
400
a First absorption peak. b Measured in THF solutions using DPA as a standard. c Determined from UV-vis absorption spectra d E°xonset ) onset oxidation
potential; E°xp ) oxidation peak potential; potentials vs Ag/AgCl, working electrode Pt, 0.1 M Bu4NPF6-CH2Cl2, scan rate 100 mV/s. e HOMO ) E°x
onset
+ 4.4 eV; LUMO ) HOMO - Eg eV. f Measured by DSC and TGA analysis in N2 at a heating rate of 10 °C/min; NA, not observed.
FIGURE 1. UV-vis absorption spectra of some compounds in THF (a) and in thin neat film (b).
FIGURE 2. PL emission spectra of some compounds in THF (a) and in thin neat films (b).
1. Cz5 and Cz7 exhibited the same maximum absorption peaks
at about 363 nm in THF solutions. Pyrene-end-capped oligomers
PyCz3, PyCz4, PyCz3Py, and PyCz5Py exhibited the same
maximum absorption peaks at 405 nm due to their same efficient
conjugation length, while pyrene-centered oligomer Cz3PyCz3
exhibited a maximum absorption peak at 443 nm, which was
red-shifted by 38 nm with respect to those of oligomers with
pyrene at their ends. The π-π* energy gaps (Eg, Table 1) of
these oligomers were calculated from the UV-vis absorption
threshold. It was obvious that the Eg’s of oligomers could be
greatly reduced by introduction of pyrene at the center of
oligomer backbone. In the case of solid states, absorption spectra
of these oligomers were slightly red-shifted compared to those
FIGURE 3. PL emission spectra of PyCz3Py and PyCz5Py in
cyclohexane.
in solutions, which was ascribed to the enhanced intermolecular
interaction.
Figure 2 displays the PL emission spectra of these oligomers
excited at 350 nm. These oligomers showed a blue to green PL
emission with the maximum emission peaks varying from 405
to 469 nm in THF solutions. Large Stokes’ shifts, about 40 nm
in THF, were observed for these oligomers, except Cz3PyCz3,
indicating that the ground-state conformations (more twisted)
of these oligomers were different from those in excited states
(more coplanar structure).6 Moreover, PL emission spectra of
PyCz3, PyCz4, and PyCz3Py were solvent dependent. With
the increment of the solvent polarity (from cyclohexane to THF),
large red shifts (35 nm) were observed (Table 1). It suggested
that the excited states of these pyrene-modified oligocarbazoles
possessed more polar character, and polar environments ef-
ficiently enhanced the intramolecular charge transfer from
J. Org. Chem, Vol. 73, No. 2, 2008 597

Zhao, Z.
FIGURE 4. Molecule modeling of PyCz5Py in cyclohexane solution: front view (left) and side view (right).
carbazole donor to pyrene acceptor. Interestingly, PyCz5Py
exhibited a broad, featureless, and red-shifted emission (450
nm) in cyclohexane solution (Figure 3) with respect to that of
PyCz3Py, although both oligomers had an identical efficient
conjugation length.21 In fact, this red-shifted emission was quite
similar to the excimer emission of pyrene (about 450 nm).22
With regard to the self-assembling of macrocycles composed
of ethynylene-linked carbazoles23 in poor solvent such as
cyclohexane, we inferred that this red shift arose from the
intramolecular π-π stacking of two pyrenes at both ends of
PyCz5Py. The main chain length of PyCz5Py was theoretically
and practically suitable for two pyrenes to be parallel and close
enough to form the excimer. Figure 4 displays the molecular
modeling of PyCz5Py in cyclohexane solution. However, in
FIGURE 5. TGA and DCS (inset) thermograms of Cz7 and PyCz5Py
in N2 at a heating rate of 10 °C/min.
THF solution, emission of PyCz5Py resembled to those
emission characteristics of PyCz3, PyCz4, and PyCz3Py with
intramolecular charge-transfer character. Concerning PL emis-
sions of all oligomers in the solid state, the shapes of emission
spectra were similar to those in THF solutions, respectively,
but with bathochromical shifts in the maximum emission
wavelengths. As seen from Table 1, it seemed that incorporation
of pyrene could reduce this bathochromical shift to some extent.
For example, emission of Cz5 in the solid state red-shifted by
51 nm in comparison with that in THF solution, while emission
of PyCz4 in the solid state showed only 22 nm red shift.
In general, the carbazole oligomers or polymers were of low
fluorescence quantum yields and were not suitable as OLED
emitters. By introduction of pyrene, quantum yields of oligomers
were significantly increased. For instance, quantum yields of
Cz5 and Cz7 were 0.38 and 0.32 in THF solutions, respectively,
while pyrene-modified oligomers exhibited much higher quan-
tum yields measured between 0.82 and 0.92. The reason might
be that excitons could be well confined in the low-band gap,
highly chromophoric segment (pyrene). In the case of oligomers
without pyrene, some energy loss might happen during the
process of exciton migration.24 Moreover, slightly decrement
of quantum yields with the increment of the molecular size was
FIGURE 6. Cyclic voltammograms of Cz7 and PyCz5Py (0.5 mM)
in 0.1 M Bu4NPF6-CH2Cl2, scan rate 100 mV/s.
observed (PyCz3 vs PyCz4, PyCz3Py vs PyCz5Py), which
might be due to the faster nonradiative energy decay in the larger
molecules.
2.3. Thermal Stabilities. Thermal stabilities of these oligo-
mers were examined by differential scanning calorimetry (DSC)
and thermogravimetric analysis (TGA) in N2 at a heating rate
of 10 °C/min, and the results are listed in Table 1. Figure 5
shows the TGA and DSC thermgrams of Cz7 and PyCz5Py as
an example. All of these oligomers exhibited high glass-
transition temperatures (Tg’s) in the range of 94-165 °C. The
Tg’s of some oligomers appear to be relatively higher than those
of widely used hole-transport materials, such as 1,4-bis(1-
naphthylphenylamino)diphenyl (R-NPD, Tg ) 100 °C), 4,4′-
bis(4-(N-(1-naphthyl)-N-phenylamino)phenyl)biphenyl (NPB, Tg
) 96 °C), and 1,4-bis(phenyl-m-tolylamino)diphenyl (TPD, Tg
(21) (a) Zhao, Z.; Xu, X.; Wang, F.; Yu, G.; Lu, P.; Liu, Y.; Zhu, D.
Synth. Met. 2006, 156, 209. (b) Wang, Z.; Shao, H.; Ye, J.; Tang, L.; Lu,
P. J. Phys. Chem. B 2005, 109, 19627.
(22) Nandy, R.; Subramoni, M.; Varghese, B.; Sankararaman, S. J. Org.
Chem. 2007, 72, 938.
(23) (a) Zhang, W.; Moore, J. S. J. Am. Chem. Soc. 2004, 126, 12796.
(b) Balakrishnan, K.; Datar, A.; Zhang, W.; Yang, X.; Naddo, T.; Huang,
J.; Zuo, J.; Yen, M.; Moore, J. S.; Zang, L. J. Am. Chem. Soc. 2006, 128,
6576. (c) Zhao, T.; Liu, Z.; Song, Y.; Xu, W.; Zhang, D.; Zhu, D. J. Org.
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2004, 16, 2165.
598 J. Org. Chem., Vol. 73, No. 2, 2008

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers
FIGURE 7. EL spectra: (a) type 3 devices based on Cz5 and Cz7; (b) type 2 devices based on PyCz5Py and Cz3PyCz3; (c) type 1-4 devices
based on PyCz4.
2.4. Cyclic Voltammetric Studies. The electronic properties
of these compounds were investigated by cyclic voltammetry
at room temperature and the results are listed in the Table 1.
Figure 6 shows cyclic voltammograms (CVs) of Cz7 and
PyCz5Py as an example. All of these oligomers displayed two
irreversible oxidation peaks (first peak, 0.96-1.17 V; second
peak, 1.72-1.99 V), which might be due to the formation of
cation and dication radical, respectively. The highest occupied
molecular orbital (HOMO) and lowest unoccupied molecular
orbital (LUMO) energy levels of Cz5 (-5.17, -1.98 eV) and
Cz7 (-5.18, -2.00 eV) were very close to those of tercarbazole
(-5.2, -1.6 eV)15 or the related homopolymer (-5.1, -2.0
eV).26 It suggested that HOMO levels of Cz5 and Cz7 were
close to the HOMO level of PEDOT:PSS (-5.2 eV), indicating
a good hole injection contact. Moreover, their LUMO levels
represented a small barrier for electron injection from a
commonly used cathode such as barium, which has a work
function of -2.2 eV.26 Adjusting the structure by inserting
FIGURE 8. Energy alignments in type 1-4 devices based on PyCz4.
pyrene into the main chain improved the electronic communica-
tion between carbazole and pyrene. Thus, HOMO and LUMO
energy levels of pyrene-modified compounds were apparently
raised compared to those of Cz5 and Cz7. Furthermore, the
HOMO and LUMO energy levels of these oligomers were
) 60 °C).17c,25 Moreover, Cz3PyCz3 exhibited much higher
Tg (165 °C) than those of others. The Tg enhancement of
Cz3PyCz3 might be due to its center position of pyrene at
oligomer backbone. Melting points of PyCz3Py (190 °C), Cz5
comparable to those of widely used hole transporting materials
(180 °C), and Cz7 (209 °C) were detected, while those of others
(NPB: HOMO, -5.2 eV; LUMO, -2.2 eV),25 and therefore,
were not observed. The thermal stabilities of compounds were
these compounds might be used for hole-transporting materials
further determined by TGA measurement. High decomposition
in OLEDs.
temperatures (Td’s, corresponding to a 5% weight loss), in the
2.5. Electroluminescent Properties. First, hole-transport
range of 446-476 °C, were observed from these oligomers.
abilities of oligomers (Cz5 and Cz7) were investigated in
All of these results indicated that these synthesized oligomers
OLEDs with a configuration of type 3 (ITO/PEDOT:PSS (30
were of high morphological and thermal stabilities, which was
a critical issue for device stability and lifetime.
nm)/Cz5 or Cz7(50 nm)/Alq3(45 nm)/Al(100 nm)), in which
(26) Dijken, A.; Bastiaansen, J. J. A. M.; Kiggen, N. M. M.; Langeveld,
B. M. W.; Rothe, C.; Monkman, A.; Bach, I.; Sto¨ssel, P.; Brunner, K. J.
Am. Chem. Soc. 2004, 126, 7718.
(25) Li, J.; Liu, D.; Lee, C.-S.; Kwong, H.-L.; Lee, S. Chem. Mater.
2005, 17, 1208.
J. Org. Chem, Vol. 73, No. 2, 2008 599

Zhao, Z.
TABLE 2. Summary of Devicea Performances
compd
device
EL (nm)
fwhm (nm)
onset voltage (V)
h
max,ext(%)
hmax,L(cd/A)
Lmax(cd/m2, V)
Cz5
Cz7
Cz3PyCz3
PyCz5Py
PyCz4
type 3
type 3
type 2
type 2
type 1
type 2
type 3
type 4
520
520
516
468
468
468
524
504
92
93
86
68
66
70
123
126
5.6
8.4
4.6
4.7
NA
4.1
3.4
3.7
0.70
0.23
0.69
0.39
NA
0.59
0.40
0.65
1.89
0.63
1.87
0.56
NA
0.87
1.08
1.64
2138, 13
326, 16.5
1782, 13.5
667, 11
0.49, 4.6
987, 10
1891, 8.5
1628, 13
a Devices: type 1, ITO/PEDOT/PSS (30 nm):oligomer (50 nm)/Al (100 nm); type 2, ITO/PEDOT:PSS (30 nm)/oligomer (50 nm)/TPBI (20 nm)/Al (100
nm); type 3, ITO/PEDOT:PSS (30 nm)/oligomer (50 nm)/Alq3 (45 nm)/Al (100 nm); type 4, ITO/PEDOT:PSS (30 nm)/oligomer (50 nm)/BCP (15 nm)/Alq3
(45 nm)/Al (100 nm). J-V-L characteristics and efficiency spectra of OLEDs are given in the Supporting Information.
PEDOT:PSS was used as a hole-injection layer and Alq3 was
used as an emitting layer as well as electron-transporting and
hole-blocking layer. Both devices showed identical EL peaks
at 520 nm (Figure 7a), originated from Alq3, indicating that
both Cz5 and Cz7 served as hole-transporting materials only
and did not function as emitter. The device based on Cz5
exhibited a maximum brightness of 2138 cd/m2 at 13 V and a
maximum external quantum efficiency of 0.70% as well as an
onset voltage of 5.6 V. The good performances of device
indicated that carbazole oligomers could be the promising
candidate for hole-transporting materials, which was attributed
to its electron-rich nature of carbazole and its relatively high-
energy levels.
nm)/PyCz4(50 nm)/Alq3(45 nm)/Al(100 nm), and type 4 (ITO/
PEDOT:PSS(30 nm)/PyCz4(50 nm)/BCP(15 nm)/Alq3(45 nm)/
Al(100 nm). Their energy levels are displayed in Figure 8. 2,9-
Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was used as
a hole-blocking layer. Figure 7c shows the EL spectra of PyCz4
in four devices. The single-layer device (type 1) exhibited an
emission peak at 468 nm. The performance of this device was
rather poor because of the unbalance of holes and electrons.
There was a quite small barrier of 0.08 eV for holes transporting
from ITO/PEDOT:PSS to PyCz4, which facilitated hole trans-
port, while there was a large barrier of 1.81 eV between PyCz4
and Al which almost forbid electron transport from Al to PyCz4.
The double-layer device (type 2) exhibited identical emission
spectra but improved performances with respect to those of the
type 1 device, which should be attributed to the introduction of
electron-transporting as well as hole-blocking layer (TPBI). The
identical blue emission (468 nm) coming from PyCz4 in both
type 1 and type 2 devices suggested that PyCz4 could serve as
a blue-light emitter in OLEDs. The type 3 device showed a
red-shifted EL emission with a peak at 524 nm coming from
Alq3, and no emission from PyCz4 was observed. It indicated
that PyCz4 functioned as hole-transporting material here, and
charge recombination took place at the Alq3 layer. Interestingly,
the type 4 device with an additional hole-blocking layer (BCP)
between PyCz4 and Alq3 presented the emission at 504 nm.
This emission should be the combination of the emissions from
PyCz4 and Alq3. Furthermore, devices with an electron-
transporting layer exhibited better performances than those
without it, such as low turn-on voltages (3.4-4.1 V), high
external efficiency (0.40-0.65%), and maximum brightness
(987 cd/m2 at 10 V-1891 cd/m2 at 8.5 V). Table 2 summarizes
the performances of all devices.
Second, in order to investigate the influence of pyrene
modification on ethynylene-linked oligocarbazole, type 2 (ITO/
PEDOT:PSS(30 nm)/PyCz5Py or Cz3PyCz3(50 nm)/TPBI(20
nm)/Al (100 nm)) was fabricated, in which 1,3,5-tris(N-
phenylbenzimidazol-2-yl)benzene (TPBI) was adopted as an
electron-transporting and hole-blocking layer and the oligomer
with similar molecular length, PyCz5Py or Cz3PyCz3, was used
as emitting as well as hole-transporting layer. Figure 7b shows
the EL spectra of both devices. Pyrene-end-capped oligomer,
PyCz5Py, showed blue EL emission with a peak at 468 nm,
while pyrene-centered oligomer, Cz3PyCz3, exhibited green
emission with a peak at 516 nm. Such a color tuning was
consistent with those of PL emission in solutions and in solid
states due to the different positions of pyrene at oligomer
backbone. Moreover, EL spectra of pyrene-modified carbazoles
were quite similar to their PL spectra in thin neat films, which
indicated that both PL and EL emissions originated from the
same radiative-decay process of singlet excitons.27 Furthermore,
devices based on Cz3PyCz3 exhibited better performances than
those of device based on PyCz5Py, such as a maximum
brightness of 1782 cd/m2 at 13.5 V, a high maximum external
quantum efficiency of 0.69%, luminence efficiency of 1.87 cd/
A, and so on. This was attributed to the lower LUMO energy
level of Cz3PyCz3 (-2.70 eV) than that of PyCz5Py, which
was beneficial for electron transfer from TPBI layer to emitting
layer. Charge recombination mainly took place and was confined
in the low-band gap segment pyrene, while attached carbazoles
mainly transport holes only because of short conjugation length.
Finally, the bifunctional property (light-emitting property and
hole-transport ability) of PyCz4 was revealed. Four types of
devices with different architecture were comparatively fabri-
cated. They were type 1 (ITO/PEDOT:PSS(30 nm)/PyCz4(50
nm)/Al(100 nm)), type 2 (ITO/PEDOT:PSS(30 nm)/PyCz4(50
nm)/TPBI(20 nm)/Al(100 nm), type 3 (ITO/PEDOT:PSS(30
3. Conclusions
In conclusion, a series of pyrene-modified, ethynylene-linked
oligocarbazoles were synthesized by a stepwise route involving
a Sonogashira coupling reaction. Ethynylene linkages at the 3-
and 6-positions of carbazoles resulted in a zigzag shape of
molecular backbones. This kind of structure defined conjugation
length of molecules and suppressed red shifts in absorption and
emission spectra of oligomers in solutions when oligomer’s size
elongated through carbazole accumulation. Furthermore, intro-
duction of pyrene unit(s) into different positions of oligomers
tuned molecules’ emission wavelength effectively. Meanwhile,
the fluorescence quantum efficiency was improved significantly.
OLEDs with different architectures based on these oligomers
were fabricated and investigated. The results indicated that Cz5
and Cz7 without pyrene could be used as hole-transporting
materials only, while pyrene-modified oligomers were of both
(27) Shih, P.-I.; Tseng, Y.-H.; Wu, F.-I.; Dixit, A. K.; Shu, C.-F. AdV.
Funct. Mater. 2006, 16, 1582.
600 J. Org. Chem., Vol. 73, No. 2, 2008

Zigzag Molecules from Pyrene-Modified Carbazole Oligomers
109.1, 109.2, 111.2, 114.0, 114.5, 114.7, 119.5, 120.8, 121.8, 122.8,
123.1, 124.1, 124.2, 125.2, 126.2, 129.5, 129.6, 129.8, 130.1, 134.4,
140.0, 140.2, 140.4, 140.5, 141.0; MS (MALDI-TOF) (m/z) 965.8
(M+).
light-emitting properties and hole-transport abilities. Incorpora-
tion of low-band gap fluorophore into homopolymer should be
a good way to generate bifuncitonal or multifunctional opto-
electronic materials.
9-Heptyl-3-iodo-6-(pyren-1-ylethynyl)-9H-carbazole (11): 70%
1
yield; H NMR (CDCl3) δ 0.86 (t, 3H, J ) 7.0 Hz), 1.21-1.31
Experimental Section
(m, 8H), 1.80-1.82 (m, 2H), 4.19 (t, 2H, J ) 7.0 Hz), 7.14 (d,
1H, J ) 8.5 Hz), 7.36 (d, 1H, J ) 8.0 Hz), 7.70 (dd, 1H, J1 ) 8.5
Hz, J2 ) 1.5 Hz), 7.80 (dd, 1H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 7.99-
8.06 (m, 3H), 8.11 (d, 1H, J ) 8.0 Hz), 8.16-8.22 (m, 4H), 8.35
(s, 1H), 8.41 (s, 1H), 8.72 (d, 1H, J ) 8.5 Hz); 13C NMR (CDCl3)
δ 14.3, 22.8, 27.4, 29.1, 29.3, 31.9, 43.5, 82.2, 87.5, 96.7, 109.2,
111.2, 114.3, 118.7, 121.9, 124.4, 124.6, 124.8, 125.2, 125.6, 125.7,
126.0, 126.4, 127.5, 128.1, 128.4, 129.6, 129.7, 130.2, 131.1, 131.4,
131.5, 131.9, 134.5, 140.1, 140.3; MS (MALDI-TOF) (m/z) 615.2
(M+).
Compounds 3, 4 and 6 were prepared following a method similar
to that of ref 28.
3-Ethynyl-9-heptyl-9H-carbazole (3): 1H NMR (CDCl3) δ 0.86
(t, 3 H, J ) 7.0 Hz), 1.23-1.27 (m, 4 H), 1.30-1.38 (m, 4 H),
1.83-1.88 (m, 2 H), 3.06 (s, 1 H), 4.28 (t, 2 H, J ) 7.5 Hz), 7.23-
7.26 (m, 1 H), 7.33 (d, 1 H, J ) 8.5 Hz), 7.40 (d, 1 H, J ) 8.5
Hz), 7.46-7.49 (m, 1 H), 7.59 (dd, 1 H, J1 ) 8.5 Hz, J2 ) 1.5
Hz), 8.07 (d, 1 H, J ) 8.0 Hz), 8.25 (s, 1 H); 13C NMR (CDCl3)
δ 14.2, 22.7, 27.4, 29.1, 31.9, 43.4, 75.2, 85.3, 108.8, 109.1, 112.0,
119.5, 120. 7, 122.5, 122.9, 124.8, 126.3, 129.8, 140.5, 141.0; MS
(EI) (m/z) 289 (M+).
9-Heptyl-3-((9-heptyl-6-(pyren-1-ylethynyl)-9H-carbazol-3-yl-
)ethynyl)-6-iodo-9H-carbazole (14): 62% yield; 1H NMR (CDCl3)
δ 0.85-0.89 (m, 6H), 1.24-1.37 (m, 16H), 1.82-1.85 (m, 2H),
1.88-1.90 (m, 2H), 4.23 (t, 2H, J ) 7.5 Hz), 4.30 (t, 2H, J ) 7.5
Hz), 7.17 (d, 1H, J ) 9.0 Hz), 7.35-7.44 (m, 3H), 7.69-7.72 (m,
3H), 7.84 (dd, 1H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 8.01-8.09 (m, 3H),
8.15 (d, 1H, J ) 7.5 Hz), 8.19-8.27 (m, 5H), 8.38 (d, 1H, J ) 1.0
Hz), 8.40 (d, 1H, J ) 1.5 Hz), 8.46 (d, 1H, J ) 1.5 Hz), 8.77 (d,
1H, J ) 7.5 Hz); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3,
31.9, 32.0, 43.5, 43.6, 81.9, 87.4, 89.1, 89.2, 96.9, 109.2, 109.3,
111.2, 114.3, 114.7, 118.8, 121.8, 122.8, 122.9, 124.2, 124.3, 124.5,
124.7, 124.8, 125.2, 125.7, 125.7, 126.0, 126.4, 127.6, 128.2, 128.4,
129.6, 129.7, 129.9, 130.0, 130.1, 131.2, 131.4, 131.6, 132.0, 134.4,
140.0, 140.2, 140.5, 140.8; MS (MALDI-TOF) (m/z) 902.5 (M+).
9-Heptyl-3-((9-heptyl-6-((9-heptyl-9H-carbazol-3-yl)ethynyl)-
9H-carbazol-3-yl)ethynyl)-6-(pyren-1-ylethynyl)-9H-carbazole
(PyCz3): 55% yield; 1H NMR (CDCl3) δ 0.84-0.89 (m, 9H),
1.25-1.27 (m, 12H), 1.35-1.36 (m, 12H), 1.85-1.91 (m, 6H),
4.26-4.31 (m, 6H), 7.22-7.25 (m, 1H), 7.36-7.49 (m, 7H), 7.68-
7.74 (m, 4H), 7.83 (dd, 1H, J1 ) 8.5 Hz, J2 ) 1.0 Hz), 7.99-8.26
(m, 9H), 8.34-8.35 (m, 3H), 8.40 (s, 1H), 8.47 (s, 1H), 8.77 (d,
1H, J ) 9.5 Hz); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3,
32.0, 43.5, 43.6, 87.4, 88.9, 89.1, 89.3, 96.9, 109.0, 109.1, 109.2,
109.3, 114.0, 114.3, 114.6, 114.7, 114.9, 118.8, 119.5, 120. 8, 122.8,
122.9, 123.0, 123.1, 124.1, 124.2, 124.3, 124.5, 124.7, 124.8, 125.6,
125.7, 126.1, 126.6, 126.4, 127.6, 128.1, 128.4, 129.5, 129.7, 129.9,
130.0, 131.2, 131.5, 131.6, 132.0, 140.2, 140.5, 140.8, 141.0; MS
(MALDI-TOF) (m/z) 1063.9 (M+). Anal. Calcd for C79H73N3: C,
89.14; H, 6.91; N, 3.95. Found: C, 89.11; H, 6.98; N, 3.92.
9-Heptyl-3-((9-heptyl-6-((9-heptyl-6-((9-heptyl-9H-carbazol-
3-yl)ethynyl)-9H-carbazol-3-yl)ethynyl)-9H-carbazol-3-yl)ethy-
nyl)-6-(pyren-1-ylethynyl)-9H-carbazole (PyCz4): 46% yield; 1H
NMR (CDCl3) δ 0.83-0.88 (m, 12H), 1.24-1.30 (m, 16H), 1.35
(m, 16H), 1.80-1.88 (m, 8H), 4.21 (t, 2H, J ) 7.5 Hz), 4.25-
4.29 (m, 6H), 7.21-7.24 (m, 1H), 7.31-7.46 (m, 9H), 7.65-7.74
(m, 6H), 7.82 (dd, 1H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.97-8.24 (m,
10H), 8.32-8.35 (m, 4H), 8.40 (s, 1H), 8.46 (s, 1H), 8.76 (d, 1H,
J ) 9.0 Hz); MS (MALDI) (m/z) 14.3, 22.8, 27.5, 29.2, 29.3, 31.9,
32.0, 43.4, 43.6, 87.4, 88.9, 89.1, 89.2, 89.3, 89.4, 96.9, 108.9,
109.1, 109.2, 109.3, 114.0, 114.3, 114.6, 114.7, 114.9, 118.8, 119.4,
120.8, 122.8, 123.0, 123.1, 124.1, 124.2, 124.3, 124.5, 124.7, 124.8,
125.6, 125.7, 126.0, 126.2, 126.4, 127.5, 128.1, 128.4, 129.4, 129.7,
129.8, 129.9, 130.0, 131.1, 131.4, 131.6, 132.0, 140.1, 140.4, 140.5,
140. 8, 141.0; MS (MALDI-TOF) (m/z) 1351.0 (M+). Anal. Calcd
for C100H94N4: C, 88.85; H, 7.01; N, 4.14. Found: C, 88.90; H,
7.07; N, 4.21.
9-Heptyl-3,6-diiodo-9H-carbazole (4): 1H NMR (CDCl3) δ 0.85
(t, 3 H, J ) 7.0 Hz), 1.22-1.31 (m, 8 H), 1.79-1.82 (m, 2 H),
4.20 (t, 2 H, J ) 7.0 Hz), 7.16 (d, 2 H, J ) 9.0 Hz), 7.70 (dd, 2 H,
J1 ) 8.5 Hz, J2 ) 1.5 Hz), 8.32 (d, 2 H, J ) 1.0 Hz); 13C NMR
(CDCl3) δ 14.3, 22.8, 27.4, 29.1, 29.2, 31.9, 43.5, 81.9, 111.1, 124.2,
129.5, 134.7, 139.7; MS (ESI) (m/z) 517.8 (M+).
3,6-Diethynyl-9-heptyl-9H-carbazole (6): 1H NMR (CDCl3) δ
0.85 (t, 3 H, J ) 7.5 Hz), 1.21-1.26 (m, 4 H), 1.31-1.34 (m, 4
H), 1.80-1.86 (m, 2 H), 3.07 (s, 2 H), 4.25 (t, 2 H, J ) 7.5 Hz),
7.32 (d, 2 H, J ) 8.5 Hz), 7.60 (dd, 2 H, J1 ) 8.0 Hz, J2 ) 2.0
Hz), 8.21 (d, 2 H, J ) 1.5 Hz); 13C NMR (CDCl3) δ 14.3, 22.8,
27.4, 29.2, 31.9, 43. 6, 75.7, 85.0, 109.2, 112.9, 122.5, 125.0, 130.4,
140.9; MS (EI) (m/z) 313 (M+).
General Procedure for the Synthesis of Compounds 7, 10,
11, 14, PyCz3, PyCz4, PyCz3Py, PyCz5Py, Cz3PyCz3, Cz5, and
Cz7. These compounds were obtained following an essentially
similar procedure. An illustrative example is provided for 7.
9-Heptyl-3-((9-heptyl-9H-carbazol-3-yl)ethynyl)-6-iodo-9H-
carbazole (7). Compound 3 (289 mg, 1 mmol), compound 4 (1551
mg, 3 mmol), cuprous iodide (10 mg, 0.05 mmol), dichlorobis-
(triphenylphosphine)palladium(II) (3.5 mg, 0.005 mmol), triph-
enylphosphine (5 mg, 0.02 mmol), and dry triethylamine (100 mL)
were placed in a 150 mL round bottle flask equipped with a Teflon-
covered magnetic stir bar. After the solution was purged with
nitrogen for 30 min, it was refluxed under nitrogen for 4 h. The
reaction mixture was filtered, and the filtrate was evaporated under
reduced pressure. The residue was purified through column
chromatography (silica gel, hexane/methylene chloride as eluent).
In this way, 448 mg (72% yield) of 7 was obtained: 1H NMR
(CDCl3) δ 0.85-0.88 (m, 6H), 1.25-1.29 (m, 8H), 1.33-1.39 (m,
8H), 1.84-1.90 (m, 4H), 4.26 (t, 2H, J ) 7.0 Hz), 4.30 (t, 2H, J
) 7.0 Hz), 7.19 (d, 1H, J ) 8.5 Hz), 7.25-7.28 (m, 1H), 7.36-
7.42 (m, 3H), 7.47-7.51 (m, 1H), 7.67-7.73 (m, 3H), 8.11 (d,
1H, J ) 7.5 Hz), 8.26 (s, 1H), 8.33 (s, 1H), 8.40 (d, 1H, J ) 1.5
Hz); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3, 31.9, 32.0,
43.5, 43.6, 81.9, 88.6, 89.4, 109.0, 109.2, 111.2, 113.9, 114.8, 119.5,
120.8, 121.8, 122.8, 123.1, 124.1, 125.3, 126.3, 129.4, 129.6, 130.1,
134.4, 140.0, 140.2, 141.1; MS (MALDI-TOF) (m/z) 678.6 (M+).
9-Heptyl-3-((9-heptyl-6-((9-heptyl-9H-carbazol-3-yl)ethynyl)-
9H-carbazol-3-yl)ethynyl)-6-iodo-9H-carbazole (10): 67% yield;
1H NMR (CDCl3) δ 0.84-0.89 (m, 9H), 1.25-1.28 (m, 12H),
1.32-1.40 (m, 12H), 1.82-1.89 (m, 6H), 4.23 (t, 2H, J ) 7.5 Hz),
4.27-4.30 (m, 4H), 7.17 (d, 1H, J ) 8.5 Hz), 7.26-7.27 (m, 1H),
7.34-7.41 (m, 5H), 7.47-7.50 (m, 1H), 7.68-7.71 (m, 5H), 8.12
(d, 1H, J ) 7.5 Hz), 8.26 (s, 1H), 8.33 (s, 2H), 8.35 (s, 1H), 8.40
(d, 1H, J ) 0.5 Hz); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2,
29.3, 31.9, 32.0, 43.4, 43.5, 43.6, 81.9, 88.9, 89.0, 89.3, 109.0,
6,6′-(9-Heptyl-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)bis-
(9-heptyl-3-(pyren-1-ylethynyl)-9H-carbazole) (PyCz3Py): 58%
yield; 1H NMR (CDCl3) δ 0.85-0.88 (m, 9H), 1.25-1.28 (m, 12H),
1.33-1.37 (m, 12H), 1.86-1.88 (m, 6H), 4.23-4.27 (m, 6H),
7.35-7.40 (m, 6H), 7.70-7.74 (m, 4H), 7.81 (dd, 2H, J1 ) 8.5
Hz, J2 ) 1.0 Hz), 7.93-8.01 (m, 6H), 8.06 (d, 2H, J ) 8.0 Hz),
8.12 (d, 2H, J ) 7.5 Hz), 8.16-8.20 (m, 6H), 8.35 (s, 2H), 8.39
(28) (a) Beginn, C.; Grazulevicius, J. V.; Strohriegl, P. Macromol. Chem.
Phys. 1994, 195, 2353. (b) Grigalevicius, S.; Grazulevicius, J. V.; Gaidelis,
V.; Jankauskas, V. Polymer 2002, 43, 2603.
J. Org. Chem, Vol. 73, No. 2, 2008 601

Zhao, Z.
(s, 2H), 8.45 (s, 2H), 8.72 (d, 2H, J ) 9.5 Hz); 13C NMR (CDCl3)
δ 14.1, 22.6, 27.3, 29.0, 29.1, 31.8, 43.4, 87.2, 89.0, 89.1, 96.7,
109.0, 109.1, 114.1, 114.4, 114.6, 118.6, 122.6, 122.7, 124.0, 124.1,
124.3, 124.4, 124.6, 125.4, 125.5, 125.8, 126.1, 127.3, 127.8, 128.1,
129.4, 129.6, 129.7, 130.9, 131.2, 131.3, 131.7, 140.3, 140.5; MS
(MALDI-TOF) (m/z) 1287.6 (M+). Anal. Calcd for C97H81N3: C,
90.40; H, 6.34; N, 3.26. Found: C, 90.42; H, 6.31; N, 3.22.
6,6′-(9-Heptyl-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)bis-
(9-heptyl-3-((9-heptyl-6-(pyren-1-ylethynyl)-9H-carbazol-3-yl)-
ethynyl)-9H-carbazole) (PyCz5Py): 45% yield; 1H NMR (CDCl3)
δ 0.84-0.88 (m, 15H), 1.22-1.25 (m, 20H), 1.28-1.32 (m, 20H),
1.79-1.90 (m, 10H), 4.13 (t, 4H, J ) 7.5 Hz), 4.19 (t, 4H, J ) 7.5
Hz), 4.28 (t, 2H, J ) 7.0 Hz), 7.26-7.30 (m, 6H), 7.35-7.39 (m,
4H), 7.65-7.23 (m, 8H), 7.80 (dd, 2H, J1 ) 8.5 Hz, J2 ) 1.5 Hz),
7.96-7.98 (m, 4H), 8.02 (d, 2H, J ) 9.0 Hz), 8.07 (d, 2H, J ) 8.0
Hz), 8.14 (d, 2H, J ) 7.5 Hz), 8.18-8.22 (m, 6H), 8.31 (m, 6H),
8.38 (s, 2H), 8.40 (s, 2H), 8.74 (d, 2H, J ) 8.0 Hz); 13C NMR
(CDCl3) δ 14.3, 22.8, 27.4, 27.5, 29.2, 29.3, 32.0, 43.4, 43.5, 87.4,
89.2, 89.3, 97.0, 109.1, 109.2, 114.2, 114.6, 114.7, 114.8, 118.8,
122.7, 122.8, 122.9, 124.1, 124.2, 124.5, 124.6, 124.8, 125.5, 125.7,
126.0, 126.3, 127.5, 128.0, 128.3, 129.6, 129.7, 129.8, 129.9, 131.0,
131.4, 131.5, 131.9, 140.3, 140.4, 140.7; MS (MALDI-TOF) (m/
z) 1863.1 (M+). Anal. Calcd for C139H123N5: C, 89.59; H, 6.65; N,
3.76. Found: C, 89.60; H, 6.61; N, 3.77.
129.9, 140.1, 140.4, 140.5, 141.0; MS (MALDI-TOF) (m/z) 1988.4
(M+). Anal. Calcd for C145H149N7: C, 87.52; H, 7.55; N, 4.93.
Found: C, 87.47; H, 7.59; N, 4.99.
General Procedure for the Synthesis of the Compounds (9
and 13). Both compounds were obtained following an essentially
similar procedure. An illustrative example is provided for 9.
3-Ethynyl-9-heptyl-6-((9-heptyl-9H-carbazol-3-yl)ethynyl)-
9H-carbazole (9). Compound 7 (678 mg, 1 mmol), 3-methyl-1-
butyn-3-ol (126 mg, 1.5 mmol), cuprous iodide (10 mg, 0.05 mmol),
dichlorobis(triphenylphosphine)palladium(II) (3.5 mg, 0.005 mmol),
triphenylphosphine (5 mg, 0.02 mmol), and dry triethylamine (100
mL) were placed in a 150 mL round bottle flask equipped with a
Teflon-covered magnetic stir bar. After the solution was purged
with nitrogen for 30 min, it was refluxed under nitrogen for 8 h.
The reaction mixture was filtered, and the filtrate was evaporated
under reduced pressure. The residue was purified by column
chromatography (silica gel, hexane/methylene chloride as eluent)
to get 8. Then 8, 500 mg of KOH, and 100 mL of 2-propanol were
placed in a 150 mL round-bottom flask equipped with a Teflon-
covered magnetic stir bar. After the solution was purged with
nitrogen for 30 min, it was refluxed under nitrogen for 4 h. The
solvent was then removed, and the crude product was purified by
column chromatography (silica gel, hexane/methylene chloride as
eluent) to afford 9 (576 mg, 75% total yield): 1H NMR (CDCl3) δ
0.85-0.88 (m, 6H), 1.23-1.28 (m, 8H), 1.33-1.38 (m, 8H), 1.84-
1.89 (m, 4H), 3.08 (s, 1H), 4.25-4.30 (m, 4H), 7.24-7.27 (m,
1H), 7.32 (d, 1H, J ) 8.5 Hz), 7.35-7.41 (m, 3H), 7.46-7.50 (m,
1H), 7.60 (dd, 1H, J1 ) 8.5 Hz, J2 ) 1.0 Hz), 7.67-7.70 (m, 2H),
8.11 (d, 1H, J ) 7.5 Hz), 8.25 (d, 1H, J ) 1.5 Hz), 8.29 (d, 1H,
J ) 1.5 Hz), 8.33 (d, 1H, J ) 2.0 Hz); 13C NMR (CDCl3) δ 14.3,
22.8, 27.5, 29.2, 29.3, 31.9, 32.0, 43.5, 43.6, 75.6, 85.2, 88.7, 89.4,
109.0, 109.1, 109.2, 112.7, 114.0, 114.9, 119.5, 120.8, 122.7, 122.8,
123.1, 124.1, 125.1, 126.3, 129.5, 130.0, 130.2, 140.2, 140.5, 140.9,
141.1; MS (MALDI-TOF) (m/z) 576.5 (M+).
1,8-Bis((9-heptyl-6-((9-heptyl-6-((9-heptyl-9H-carbazol-3-yl)-
ethynyl)-9H-carbazol-3-yl)ethynyl)-9H-carbazol-3-yl)ethynyl)-
1
pyrene (Cz3PyCz3): 39% yield; H NMR (CDCl3) δ 0.82-0.88
(m, 18H), 1.21-1.35(m, 48H), 1.78-1.88 (m, 12H), 4.14 (t, 4H, J
) 7.0 Hz), 4.21-4.27 (m, 8H), 7.21-7.24 (m, 2H), 7.25-7.30
(m, 4H), 7.31-7.40 (m, 10H), 7.64-7.68 (m, 8H), 7.85 (dd, 2H,
J1 ) 8.5 Hz, J2 ) 1.0 Hz), 8.02 (s, 2H), 8.08-8.12 (m, 4H), 8.24-
8.29 (m, 8H), 8.34 (d, 2H, J ) 1.0 Hz), 8.44 (d, 2H, J ) 1.5 Hz),
8.9 (s, 2H); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3, 29.8,
31.3, 31.5, 31.9, 43.4, 43.5, 87.5, 88.9, 89.2, 89.3, 89.4, 97.5, 108.9,
109.1, 109.3, 114.0, 114.2, 114.6, 114.7, 114.8, 117.4, 119.4, 119.5,
120.8, 122.8, 122.9, 123.1, 124.0, 124.1, 124.2, 124.5, 124.6, 125.0,
125.2, 125.8, 126.2, 126.7, 126.8, 127.0, 127.1, 127.9, 128.2, 129.4,
129.5, 129.7, 129.8, 129.9, 130.0, 131.3, 132.0, 140.1, 140.4, 140.8,
141.0. MS (MALDI-TOF) (m/z) 1925.4 (M+). Anal. Calcd for
3-Ethynyl-9-heptyl-6-(pyren-1-ylethynyl)-9H-carbazole (13):
1
63% total yield; H NMR (CDCl3) δ 0.86 (t, 3H, J ) 7.0 Hz),
1.23-1.28 (m, 4H), 1.31-1.37 (m, 4H), 1.83-1.89 (m, 2H), 3.10
(s, 1H), 4.27 (t, 2H, J ) 7.5 Hz), 7.34 (d, 1H, J ) 8.5 Hz), 7.41
(d, 1H, J ) 8.5 Hz), 7.62 (dd, 1H, J 1) 8.5 Hz, J2 ) 1.5 Hz), 7.82
(dd, 1H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 8.00-8.09 (m, 3H), 8.13 (d,
1H, J ) 8.0 Hz), 8.18-8.24 (m, 4H), 8.30 (d, 1H, J ) 1.0 Hz),
8.42 (d, 1H, J ) 1.5 Hz), 8.75 (d, 1H, J ) 9.0 Hz); 13C NMR
(CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3, 31.9, 43.6, 75.7, 85.1, 87.4,
96.7, 109.2, 109.4, 113.0, 114.5, 118.7, 122.7, 122.8, 124.5, 124.7,
124.8, 125.1, 125.7, 125.8, 126.0, 126.4, 127.6, 128.2, 128.4, 129.7,
130.1, 130.4, 131.2, 131.4, 131.6, 132.0, 140.8, 140.9; MS
(MALDI-TOF) (m/z) 513.4 (M+).
C
142H136N6: C, 88.52; H, 7.11; N, 4.36. Found: C, 88.60; H, 7.05;
N, 4.43.
6,6′-(9-Heptyl-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)bis-
(9-heptyl-3-((9-heptyl-9H-carbazol-3-yl)ethynyl)-9H-carba-
zole) (Cz5): 61% yield; 1H NMR (CDCl3) δ 0.84-0.88 (m, 15H),
1.24-1.28 (m, 20H), 1.34-1.36 (m, 20H), 1.83-1.89 (m, 10H),
4.23-4.29 (m, 10H), 7.22-7.25 (m, 2H), 7.34-7.39 (m, 10H),
7.45-7.48 (m, 2H), 7.67-7.72 (m, 8H), 8.10 (d, 2H, J ) 7.5 Hz),
8.34-8.35 (m, 8H); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2,
29.3, 32.0, 43.4, 43.6, 88.9, 89.1, 89.3, 108.9, 109.1, 109.2, 114.0,
114.6, 114.7, 119.4, 120.8, 122.7, 122.8, 123.1, 124.0, 124.2, 129.4,
129.8, 129.9, 140.1, 140.4, 140.5, 141.0; MS (MALDI-TOF) (m/
z) 1414.0 (M+). Anal. Calcd for C103H107N5: C, 87.43; H, 7.62; N,
4.95. Found: C, 87.47; H, 7.65; N, 4.90.
Acknowledgment. P.L. thanks the National Natural Science
Foundation of China (20374045, 20674070) and the Natural
Science Foundation of Zhejiang Province (R404109) for support.
We thank Prof. Chuande Wu for his assistance in drawing the
molecular models depicted in Figure 4. This work was partially
supported by the Major State Basic Research Development
Program and the Chinese Academy of Sciences.
6,6′-(9-Heptyl-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)bis-
(9-heptyl-3-((9-heptyl-6-((9-heptyl-9H-carbazol-3-yl)ethynyl)-
1
9H-carbazol-3-yl)ethynyl)-9H-carbazole) (Cz7): 51% yield; H
NMR (CDCl3) δ 0.86-0.90 (m, 21 H), 1.27 (m, 28H), 1.36 (m,
28H), 1.85-1.91 (m, 14H), 4.24-4.28 (m, 12H), 4.31-4.34 (m,
2H), 7.24-7.27 (m, 2H), 7.35-7.42 (m, 14H), 7.47-7.50 (m, 2H),
7.69-7.75 (m, 12H), 8.12 (d, 2H, J ) 8.0 Hz), 8.34-8.39 (m,
12H); 13C NMR (CDCl3) δ 14.3, 22.8, 27.5, 29.2, 29.3, 32.0, 43.4,
43.5, 88.9, 89.2, 89.3, 108.9, 109.1, 109.2, 114.0, 114.6, 114.7,
119.4, 120.8, 122.8, 122.9, 123.1, 124.0, 124.2, 126.2, 129.7, 129.8,
Supporting Information Available: General information,
OLED fabrication and measurement, NMR and mass spectra of
new compounds, and J-V-L characteristics and efficiency spectra
of OLEDs. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO702075R
602 J. Org. Chem., Vol. 73, No. 2, 2008