Solution-processable stiff dendrimers: Synthesis, photophysics, film morphology, and electroluminescence

Article abstract of DOI:10.1021/jo802237c

(Figure Presented) A series of solution-processable conjugated dendrimers (T1-T5) consisting of a pyrene core, fluorene/carbazole dendrons, and acetylene linkages have been successfully synthesized and fully characterized. The effects of generation on the

Full text of DOI:10.1021/jo802237c

Solution-Processable Stiff Dendrimers: Synthesis, Photophysics, Film
Morphology, and Electroluminescence
Zujin Zhao,† Juo-Hao Li,‡ Xiaopeng Chen,† Xiaoming Wang,† Ping Lu,*,† and
Yang Yang*,‡
Department of Chemistry, Zhejiang UniVersity, Hangzhou 310027, People’s Republic of China, and
Department of Materials Science and Engineering, UniVersity of California, Los Angeles, California 90095
pinglu@zju.edu.cn; yangy@ucla.edu
ReceiVed October 9, 2008
A series of solution-processable conjugated dendrimers (T1-T5) consisting of a pyrene core, fluorene/
carbazole dendrons, and acetylene linkages have been successfully synthesized and fully characterized.
The effects of generation on the photoluminescence (PL) and electroluminescence (EL) of dendrimers
are investigated. Photon harvest and energy transfer are observed in these dendritic systems. Efficient
electroluminescent single layer dendrimer devices are achieved through control of dendrimer generation
and optimization of spin-coating speed. A T3-based device exhibits yellow EL (CIE: 0.49, 0.50) with a
maximum brightness of 5590 cd/m2 at 16 V, a high current efficiency of 2.67 cd/A at 8.6 V, and a best
external quantum efficiency of 0.86%.
1. Introduction
vacuum, developed by Tang and VanSlyke,2 while fluorescent
polymers, discovered at Cambridge,3 may be deposited directly
from solution by simple processes such as spin-coating and ink-
jet printing.4 Besides small molecules and polymers, a new class
of materials, light-emitting dendrimers, is becoming prominent
in OLEDs recently.5 Dendrimers are hyperbranched macromol-
ecules combining the merits of well-defined structures and
superior chemical purity possessed by small molecules and
In the field of organic light-emitting diodes (OLEDs), great
effort has been made on developing new materials as well as
optimizing device architectures to realize full-color, flat-panel
displays with improved efficiency and lifetime.1 Two classes
of materials, small molecules and conjugated polymers, have
received the most attention in the past two decades. Small
organic molecules with well-defined structures and excellent
purity are generally processed by thermal evaporation under high
(2) Tang, C. W.; van Slyke, S. A. Appl. Phys. Lett. 1987, 51, 913.
(3) Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks, R. N.;
Mackay, K.; Friend, R. H.; Burn, P. L.; Holmes, A. B. Nature 1990, 347, 539.
(4) (a) Yang, Y.; Chang, S. C.; Bharathan, J.; Liu, J. J. Mater. Sci.: Mater.
Electron. 2000, 11, 89. (b) de Gans, B. J.; Schubert, U. S. Macromol. Rapid
Commun. 2003, 24, 659.
† Zhejiang University.
‡ University of California.
(1) (a) D’Andrade, B. W.; Forrest, S. R. AdV. Mater. 2004, 16, 1585. (b)
Chen, C.-T. Chem, Mater. 2004, 16, 4389. (c) Shih, P.-I.; Tseng, Y.-H.; Wu,
F.-I.; Dixit, A. K.; Shu, C.-F. AdV. Funct. Mater. 2006, 16, 1582.
10.1021/jo802237c CCC: $40.75
Published on Web 11/19/2008
2009 American Chemical Society
J. Org. Chem. 2009, 74, 383–395 383

Zhao et al.
simple solution-processing advantage of polymers.6 The well-
designed and controlled molecular synthesis of dendrimers can
offer desired properties, such as formation of high-quality
amorphous film by the simple spin-coating method,7 emission
enhancement via energy transfer from peripheries to the emitting
core,8 suppression of aggregates and fluorescence quenching
by encapsulating the emitting segment,9 and tunable charge
transport ability through generation control.10 Moreover, the
ability to easily tune the size, topology, molecular weight, and
consequently the properties of the dendrimers has led to their
widespread use in a variety of applications from material to
biology science.11
So far, a great many of dendrimers have been synthesized
and studied, such as dendrimers with stilbene dendronds,6,9a,c,d,12
and dendrimers with poly(benzyl ether) dendronds.5e,f,13 For
acetylene-linked dendrimers, Moore14 reported the first fluo-
rescent dendrimers consisting of a 9,10-(diphenylacetylenyl)an-
thracene chromophore and triphenylamine-containing dendrons.
The performances of LEDs utilizing them as emitting-layers
are relatively poor. Later, Jin15 reported dendrimers with the
same core but with 1,3,4-oxadiazole-containing dendrons.
However, no significant improvement in the EL efficiency is
observed. The poor EL properties of these materials are ascribed
to the acetylene linkages, which allow the dendrimers to adopt
a more planar structure. The enhancement in planarity will
induce stronger intermolecular interactions between chro-
mophores, resulting in nonradiative decay of excitons. Therefore,
dendrimers with acetylene linkages are considered as unpromis-
ing light-emitting materials5c and only a few reports are available
in the literature. Nevertheless, in our opinion, although π-π
stacking between aromatic chromophores can result in lumi-
nescence quenching accompanied by a red-shift in emission, it
can lead to higher charge transport. In this regard, if we can
have a good control on the degree of intermolecular interactions
to balance the negative and positive factors, the acetylene-linked
dendrimers may emit strong EL with high efficiency.
In this paper, we report the synthesis and characterization of
a new series of acetylene-linked dendrimers inspired from
Moore’s models.16 Polycyclic aromatic pyrene is chosen as a
chromophoric core of stiff dendrimers because of its excellent
PL efficiency,17 high carrier mobility, and wide use of its
derivatives as active layers in field effect transistors (FETs)18
and OLEDs.19 Moreover, it allows researchers to study the
generation effect on the aggregation of dendrimers20 because
pyrenes are prone to excimer formation in concentrated solutions
and in solid states.21 On the basis of our previous work,22 strong
blue fluorescent carbazole/fluorene combinations are chosen as
dendrons. This is because carbazole possesses good hole
transport ability and can be easily modified at its 3-, 6-, and
9-positions.23 Meantime, efficient energy harvest and transfer
are observed in carbazole-based dendrons,24 and the singlet and
triplet energy of carbazole can be transferred to the core,
affording a high EL efficiency.25 Fluorene is a blue chromophore
that can also be utilized to construct dendrimers with desired
characteristics and usage.26 Here, the bis(n-heptyl)-substituted
fluorenes embedded in the dendrons can extend the dendrimer
(5) (a) Howard, W. E. Sci. Am. 2004, 290, 64. (b) Holder, E.; Langeveld,
B. M. W.; Schubert, U. S. AdV. Mater. 2005, 17, 1109. (c) Burn, P. L.; Lo,
S.-C.; Samuel, I. D. W. AdV. Mater. 2007, 19, 1675. (d) Anthopoulos, T. D.;
Frampton, M. J.; Namdas, E. B.; Burn, P. L.; Samuel, I. D. W. AdV. Mater.
2004, 16, 557. (e) Furuta, P.; Brooks, J.; Thompson, M. E.; Fre´chet, J. M. J.
J. Am. Chem. Soc. 2003, 125, 13165. (f) Freeman, A. W.; Koene, S. C.;
Malenfant, P. R. L.; Thompson, M. E.; Fre´chet, J. M. J. J. Am. Chem. Soc.
2000, 122, 12385. (g) Kwon, T. W.; Alam, M. M.; Jenekhe, S. A. Chem, Mater.
2004, 16, 4657. (h) Choi, D. H.; Han, K.; Chang, I.-H.; Zhang, X.-H.; Ahn,
K.-H.; Lee, Y. K.; Jang, J. Synth. Met. 2007, 157, 332. (i) Bolink, H. J.; Barea,
E.; Costa, R. D.; Coronado, E.; Sudhakar, S.; Zhen, C.; Sellinger, A. Org.
Electron. 2008, 9, 155.
(6) (a) Lupton, J. M.; Samuel, I. D. W.; Beavington, R.; Burn, P. L.; Ba¨ssler,
H. AdV. Mater. 2001, 13, 258. (b) Frampton, M. J.; Beavington, R.; Samuel,
I. D. W.; Burn, P. L. Synth. Met. 2001, 121, 1671. (c) Ma, D.; Hu, Y.; Zhang,
Y.; Wang, L.; Jing, X.; Wang, F.; Lupton, J. M.; Samuel, I. D. W.; Lo, S.-C.;
Burn, P. L. Synth. Met. 2003, 137, 1125. (d) Pillow, J. N. G.; Halim, M.; Lupton,
J. M.; Burn, P. L.; Samuel, I. D. W. Macromolecules 1999, 32, 5985.
(7) (a) Lai, W.-Y.; Zhu, R.; Fan, Q.-L.; Hou, L.-T.; Cao, Y.; Huang, W.
Macromolecules 2006, 39, 3707. (b) Sun, Y.; Xiao, K.; Liu, Y.; Wang, J.; Pei,
J.; Yu, G.; Zhu, D. AdV. Funct. Mater. 2005, 15, 818.
(8) (a) Chen, C.-H.; Lin, J. T.; Yeh, M.-C. P. Org. Lett. 2006, 8, 2233. (b)
Goodson, T. Acc. Chem. Res. 2005, 38, 99. (c) Goodson, T. Annu. ReV. Phys.
Chem. 2005, 56, 581. (d) Kawa, M.; Takahagi, T. Chem. Mater. 2004, 16, 2282.
(e) Zhu, L.; Tong, X.; Li, M.; Wang, E. J. Phys. Chem. B 2001, 105, 2461. (f)
Wang, J.-L.; Yan, J.; Tang, Z.-M.; Xiao, Q.; Ma, Y.; Pei, J. J. Am. Chem. Soc.
2008, 130, 9952.
(9) (a) Halim, M.; Pillow, J. N. G.; Burn, P. L.; Samuel, I. D. W. AdV. Mater.
1999, 11, 371. (b) Pa˙lsson, L.-O.; Beavington, R.; Frampton, M. J.; Lupton,
J. M.; Magennis, S. W.; Markham, J. P. J.; Pillow, J. N. G.; Burn, P. L.; Samuel,
I. D. W. Macromolecules 2002, 35, 7891. (c) Markham, J. P. J.; Lo, S.-C.;
Magennis, S. W.; Burn, P. L.; Samuel, I. D. W. Appl. Phys. Lett. 2002, 80,
2645. (d) Kwok, C. C.; Wong, M. S. Macromolecules 2001, 34, 6821.
(10) (a) Burn, P. L.; Halim, M.; Pillow, J. N. G.; Samuel, I. D. W. SPIE
1999, 3797, 66. (b) Lupton, J. M.; Samuel, I. D. W.; Beavington, R.; Burn,
P. L.; Ba¨ssler, H. AdV. Mater. 2001, 13, 258. (c) Lupton, J. M.; Samuel, I. D. W.;
Beavington, R.; Frampton, M. J.; Burn, P. L.; Ba¨ssler, H. Phys. ReV. B 2001,
63, 155206.
(16) Devadoss, C.; Bharathi, P.; Moore, J. S. J. Am. Chem. Soc. 1996, 118,
9635.
(17) Bevilacqua, P. C.; Kierzek, R.; Johnson, K. A.; Turner, D. H. Science
1992, 258, 1355.
(18) (a) Moggia, F.; Videlot-Ackermann, C.; Ackermann, J.; Raynal, P.;
Brisset, H.; Fages, F. J. Mater. Chem. 2006, 16, 2380. (b) Zhang, H.; Wang, Y.;
Shao, K.; Liu, Y.; Chen, S.; Qiu, W.; Sun, X.; Qi, T.; Ma, Y.; Yu, G.; Su, Z.;
Zhu, D. Chem. Commun. 2006, 755.
(19) (a) Tao, S.; Peng, Z.; Zhang, X.; Wang, P.; Lee, C.-S.; Lee, S.-T. AdV.
Funct. Mater. 2005, 15, 1716. (b) Tang, C.; Liu, F.; Xia, Y.-J.; Wei, A.; Li,
S.-B.; Fan, Q.-L.; Huang, W. J. Mater. Chem. 2006, 16, 4074. (c) Cirpan, A.;
Rathnayake, H. P.; Lahti, P. M.; Karasz, F. E. J. Mater. Chem. 2007, 17, 3030.
(d) Zhao, Z.; Zhang, P.; Wang, F.; Wang, Z.; Lu, P.; Tian, W. Chem. Phys.
Lett. 2006, 423, 293. (e) Zhao, Z.; Li, J.-H.; Lu, P.; Yang, Y. AdV. Funct. Mater.
2007, 17, 2203. (f) Zhao, Z.; Xu, X.; Jiang, Z.; Lu, P.; Yu, G.; Liu, Y. J. Org.
Chem. 2007, 72, 8345. (g) Hancock, J. M.; Gifford, A. P.; Tonzola, C. J.; Jenekhe,
S. A. J. Phys. Chem. C 2007, 111, 6875.
(20) Bernhardt, S.; Kastler, M.; Enkelmann, V.; Baumgarten, M.; Mu¨llen,
K. Chem. Eur. J. 2006, 12, 6117.
(21) (a) Venkataramana, G.; Sankararaman, S. Org. Lett. 2006, 8, 2739. (b)
Nandy, R.; Subramoni, M.; Varghese, B.; Sankararaman, S. J. Org. Chem. 2007,
72, 938.
(11) (a) Newkome, G. R.; Moorefield, C. N.; Vo¨gtle, F. Dendrimers and
Dendrons, Wiley-VCH: Weinheim, Germany, 2001. (b) Fre´chet, J. M. J.;
Tomalia, D. A., Eds. Dendrimers and Other Dendritic Polymers; Wiley-VCH:
Chichester, UK, 2001. (c) Tomalia, D. A.; Fre´chet, J. M. J. Prog. Polym. Sci.
2005, 30, 217. (d) Majoral, J.-P. New J. Chem. 2007, 31, 1039.
(12) Garc´ıa-Mart´ınez, J. C.; D´ıez-Barra, E.; Rodr´ıguez-Lo´pez, J. Curr. Org.
Synth. 2008, 5, 267.
(13) (a) Hecht, S.; Fre´chet, J. M. J. Angew. Chem., Int. Ed. 2001, 40, 74. (b)
Freeman, A. W.; Fre´chet, J. M. J.; Koene, S. C.; Thompson, M. E. Polym. Prepr.
(Am. Chem. Soc. DiV. Polym. Chem.) 1999, 40, 1246. (c) Koene, S. C.; Freeman,
A. W.; Killeen, K. A.; Fre´chet, J. M. J.; Thompson, M. E. Polym. Mater. Sci.
Eng. 1999, 80, 238.
(22) (a) Zhao, Z.; Xu, X.; Chen, X.; Wang, X.; Lu, P.; Yu, G.; Liu, Y.
Tetrahedron 2008, 64, 2658. (b) Zhao, Z.; Li, J.-H.; Chen, X.; Lu, P.; Yang, Y.
Org. Lett. 2008, 10, 3041.
(23) (a) Zhu, Z.; Moore, J. S. J. Org. Chem. 2000, 65, 116. (b) Zhu, Z.;
Moore, J. S. Macromolecules 2000, 33, 801.
(24) (a) Loiseau, F.; Campagna, S.; Hameurlaine, A.; Dehaen, W. J. Am.
Chem. Soc. 2005, 127, 11352. (b) Wong, K.-T.; Lin, Y.-H.; Wu, H.-H.; Fungo,
F. Org. Lett. 2007, 9, 4531.
(25) (a) Ding, J.; Gao, J.; Cheng, Y.; Xie, Z.; Wang, L.; Ma, D.; Jing, X.;
Wang, F. AdV. Funct. Mater. 2006, 16, 575. (b) Kwon, T.-H.; Kim, M. K.; Kwon,
J.; Shin, D.-Y.; Park, S. J.; Lee, C.-L.; Kim, J.-J.; Hong, J.-I. Chem. Mater.
2007, 19, 3673.
(14) Wang, P. W.; Liu, Y. J.; Decadoss, C.; Bharathi, P.; Moore, J. S. AdV.
Mater. 1996, 8, 237.
(15) Cha, S. W.; Choi, S.-H.; Kim, K.; Jin, J.-I. J. Mater. Chem. 2003, 13,
1900.
(26) (a) Sun, M.; Li, J.; Li, B.; Fu, Y.; Bo, Z. Macromolecules 2005, 38,
2651. (b) Wang, S.; Gaylord, B. S.; Bazan, G. C. AdV. Mater. 2004, 16, 2127.
(c) Mongin, O.; Krishna, T. R.; Werts, M. H. V.; Caminade, A.-M.; Majoral,
J.-P.; Blanchard-Desce, M. Chem. Commun. 2006, 915.
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Solution-Processable Stiff Dendrimers
SCHEME 1a
a Conditions and reagents: (a) Pd(PPh3)2Cl2, PPh3, CuI, Et3N, N2, reflux. (b) KOH, 2-propanol, reflux. (c) KI, KIO3, acetic acid, 80 °C. (d) Pd(PPh3)4,
PPh3, CuI, i-Pr2NH, N2, reflux. (e) n-Bu4NF, THF, rt.
J. Org. Chem. Vol. 74, No. 1, 2009 385

Zhao et al.
SCHEME 2a
a Conditions and reagents: (a) Pd(PPh3)2Cl2, PPh3, CuI, Et3N, N2, reflux. (f) Pd(PPh3)4, PPh3, CuI, i-Pr2NH/benzene (1/1, v/v), N2, reflux.
386 J. Org. Chem. Vol. 74, No. 1, 2009

Solution-Processable Stiff Dendrimers
TABLE 1. Optical, Electrochemical, and Thermal Properties of Dendrimers T1-T5
CH2Cl2
film
λabs (nm)
0.58 397, 478, 506
0.65 378, 402, 478, 532, 568
507
b
c
ox
Eg
λem (nm) (eV)
E
HOMO/LUMO
(eV)
Tg/Td
(°C)
onset
λabs (nm) (ε × 105)a
T1 395 (2.4), 474 (0.9), 501 (1.0)
T2 381 (3.8), 401 (4.0), 476 (0.9),
503 (1.0)
λem (nm)
523 (560)
Φ
(V)
531, 572
2.35
2.35
1.58
1.52
-5.98/-3.62
-5.92/-3.56
154/436
128/431
525 (553)
T3 374 (9.1), 390 (9.0), 475 (0.9),
501 (1.0)
T4 383 (14.9), 401 (14.1), 475 (0.9), (414) (440) 523 (560) 0.46 382, 479, 503
523 (559)
0.48 368, 478, 503
558
562
530
2.35
2.35
2.35
1.49
1.46
1.36
-5.89/-3.53
-5.86/-3.51
-5.76/-3.41
174/442
160/439
161/425
501 (1.0)
T5 376 (20.1), 390 (19.9), 476 (0.9), (405) 522 (558)
0.42 370, 476, 504
501 (1.0)
a Mole absorption coefficient (ε): M-1 cm-1, within an error of (0.1 × 105 M-1 cm-1
.
b Energy band gap determined from UV-vis absorption
c
spectra. Eox
) onset oxidation potential; potentials vs Ag/AgCl, working electrode Pt, 0.1 M Bu4NPF6-CH2Cl2, scan rate 100 mV/s.
onset
molecules, and afford a good solubility and better film-forming
property. On the basis of the synthesized dendrimers, the effects
of generations on the PL and EL of dendrimers are demon-
strated. Moreover, the influence of spin-coating speed on the
performances of dendrimer LED is investigated.
exhibit an X shape with a calculated length of about 5 and 7
nm, respectively. T3, T4, and T5 show a dense “pancake-like”
shape with a calculated diameter of about 9, 11, and 14 nm,
respectively. Because T5 possesses many arms at its periphery,
its dendrons are distorted in order to avoid the involved steric
crowdedness. The whole molecule thus is “thick” in the
periphery and “thin” in the center, which hampers the pyrene
ring from another molecule to get close to form excimer. Since
molecules with smaller dendrons are more planar and “smooth”,
efficient isolation of one pyrene ring from the others is relatively
difficult.
2.3. Optical Properties. The absorption spectra of the
dendrimers in CH2Cl2 and in thin neat films are illustrated in
Figure 2, and the relevant data are listed in Table 1. All the
dendrimers show two prominent absorption bands with maxima
at about 500 and 390 nm, respectively. Since 1,3,6,8-tetrak-
is(phenylethynyl)pyrene absorbs strongly at 475 nm with a weak
band in the range of 350-400 nm,21a,29 the first absorption band
should be ascribed to π-π* transitions of the core (pyrene ring
with a certain extension). The molar absorption coefficient (ε)
is insensitive to the generation number, probably because the
peripheral fluorene/carbazole dendrons do not efficiently con-
jugated to the core through 3,6,9-carbazole linkages.30 The
second band is assigned to the absorption of fluorene/carbazole
dendrons, and the molar absorption coefficient (ε) increases with
the generation number. As T2 possesses a larger conjugation
system than T1, it exhibits a slightly red-shifted (2 nm)
absorption maximum and larger ε. Similarly, the second
absorption band of T4 is red-shifted by 11 nm as fluorene units
accumulate in the dendrons in comparison with that of T3. Solid
state absorption spectra of the dendrimers are similar to those
in solutions but for a slight shift to longer wavelength. Since
the dendrons of T1-T5 absorb at lower wavelength than the
pyrene core, they may serve as antennas for energy injection
and transfer as well as spacers between chromophores to
suppress aggregates or excimer formation.
2. Results and Discussion
2.1. Synthesis. Schemes 1 and 2 illustrate the synthetic routes
of intermediates and final dendrimers. A Pd/Cu-catalyzed
Sonogashira coupling reaction is used as a key reaction to
construct these acetylene-linked denrimers. Compounds 1-5,27
6 and 7,28 and 1,3,6,8-tetraethynylpyrene (19)29 are prepared
according to references’ methods. Coupling of 19 with an excess
amount of 3 and 5 gives T1 and T2, respectively, in moderate
yields. T3 and T4 can be synthesized either by coupling of 19
with an excess amount of dendron 17 and 18, or by coupling
of intermediate 21 with an excess amount of 3 and 5,
respectively. The former reacts much more efficiently than the
later. It is encouraged to use a large excess amount of 3, 5, 17,
or 18 to react with all the terminal acetylenes in 19 and 21
completely. The structures of the dendrimers are verified by 1H
and 13C NMR spectroscopies, MALDI-TOF MS measurement,
and element analysis, except for T5, whose mass spectrum is
not obtained. All the dendrimers are highly soluble in common
organic solvents, such as CH2Cl2, CHCl3, THF, and toluene,
and can form a large thin film by spin-coating their solutions.
The thermal stability of the dendrimers is examined by
differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA) in N2 at a heating rate of 20 deg/min, and the
results are listed in Table 1. All the denrimers exhibit high glass
transition temperatures (Tg). T3 exhibits the highest value of
174 °C, while T2 shows the lowest value of 128 °C. A moderate
value of 161 °C is observed in T5 with the largest size,
indicating that there is no correlation between the dendrimer
size and the Tg value. All the dendrimers enjoy high thermal
stability, with decomposition temperatures (Td, corresponding
to a 5% weight loss) in the range of 425-442 °C. Such high Tg
and Td values of the dendrimers are advantages for OLED
applications, which help to enhance device stability and lifetime.
2.2. Visualization and Simulation. Structures of dendrimer
T1-T5 are optimized by the MM+ method in the Gaussian 03
program. Figure 1 displays the molecular models. T1 and T2
The PL spectra of the dendrimers in dilute CH2Cl2 solutions
(∼1 × 10-6 M) and in thin neat films are displayed in Figure
3. The wavelength of excitation light is 380 nm. In solutions,
these dendrimers exhibit a strong generation-independent emis-
sion peak at ∼522 nm with a narrow full width at half-emission
maximum (fwhm) of ∼25 nm, which is attributed to the
(30) (a) Loiseau, F.; Campagna, S.; Hameurlaine, A.; Dehaen, W. J. Am.
Chem. Soc. 2005, 127, 11352. (b) Xu, T.; Lu, R.; Liu, X.; Zheng, X.; Qiu, X.;
Zhao, Y. Org. Lett. 2007, 9, 797. (c) Brunner, K.; Dijken, A.; Bo¨rner, H.;
Bastiaansen, J. J. A. M.; Kiggen, K. M. M.; Langeveld, B. M. W. J. Am. Chem.
Soc. 2004, 126, 6035. (d) Li, Y.; Ding, J.; Day, M.; Tao, Y.; Lu, J.; D’iorio, M.
Chem. Mater. 2004, 16, 2165.
(27) Zhao, Z.; Xu, X.; Xu, L.; Yu, G.; Lu, P.; Liu, Y. Synth. Met. 2007,
157, 414.
(28) Zhang, Q.; Chen, J.; Cheng, Y.; Wang, L.; Ma, D.; Jing, X.; Wang, F.
J. Mater. Chem. 2004, 14, 895.
(29) Venkataramana, G.; Sankararaman, S. Eur. J. Org. Chem. 2005, 4162.
J. Org. Chem. Vol. 74, No. 1, 2009 387

Zhao et al.
FIGURE 1. Molecular models of T1-T5 optimized by the MM+ method in the Gaussian 03 program.
emission from the core.29 The emission changes little with
different excitation wavelength. When the dendrimers are
excited in the absorption range of the dendrons at 350-390
nm, the emission spectra are dominated by strong emission from
the core with weak dendron emission at 400-450 nm.22a When
the solutions are excited in the absorption range of the core at
450-500 nm, only weak emission is recorded. The observation
of strong core emission upon excitation of fluorene/carbazole
dendrons suggests the occurrence of efficient intramolecular
singlet energy transfer.16 One noticeable thing is that dendrimer
T4 exhibits the strongest dendron emission among the den-
drimers, which might be due to its incomplete energy transfer
in longer conjugated arms.
In thin films, T1 and T2 emit at 531 and 532 nm with
shoulder peaks at 572 and 568 nm, respectively, which are red-
shifted from those in the solutions by ∼8 nm. On the contrary,
T3 and T4 exhibit a much broader and strongly red-shifted
emission at ∼560 nm. A possible reason for this difference is
that dendrimers T3 and T4 are more stretched and “pancake-
like” structures, and thus are prone to close, face-to-face stacking
that leads to the aggregates and/or excimer formation of pyrene
rings. T5 shows only one emission peak at 530 nm and the
excimer formation between pyrene rings seems to be suppressed
by its large, stiff, and twisted dendrons.
All the dendrimers are highly fluorescent in both solutions
and solid states. The PL quantum yields of the dendrimers are
388 J. Org. Chem. Vol. 74, No. 1, 2009

Solution-Processable Stiff Dendrimers
FIGURE 2. Absorption spectra of dendrimers in dilute CH2Cl2 solutions (a) and in thin neat films (b).
FIGURE 3. PL spectra of dendrimers in dilute CH2Cl2 solutions (a) and in thin neat films (b).
measured in degassed cyclohexane solutions by using 9,10-
bis(phenylethynyl)anthracene (Φ ) 1.0 in cyclohexane)31 as a
standard. As show in Table 1, the quantum yields of the
dendrimers are much higher than that of 1,3,6,8-tetrakis(phe-
nylethynyl)pyrene (0.18).29 On the other hand, the quantum yield
declines with generation increases seen from T1 (0.58), T3
(0.48), and T5 (0.42). This is possibly due to incomplete energy
transfer, particularly in stiff T5, even though its largest dendrons
have the best photon-harvesting ability. The energy transfer
efficiency may decrease as generation increases because some
of the arms are far away from the core.16 T2 exhibits a highest
quantum yield of 0.65, which may be due to its better
conjugation system in which excited energy can be transferred
to the core efficiently.
2.4. Film Morphology. The impact of generation on the film
morphology of dendrimers is investigated. The films are
prepared by spin-coating p-xylene solutions of dendrimers (2
wt %) on SiO2/Si substrate at a spin speed of 2000 rpm. To
obtain uniform thin films, the films are prepared by spin-coating
once, because during every secondary spin-coating, some of the
dendrimer molecules will be redissolved by the added solution,
which produces locally higher concentrations (near the inter-
face). The film morphology is investigated by atomic force
microscopy (AFM) at a tapping mode. Generally, all the films
are amorphous with a fairly smooth surface, suggesting that
these dendrimers possess good film-forming ability. Figure 4
compares the film morphology of T3 and T5. The surface of
the T5 film appears to be rougher than that of the T3 film, which
should be attributed to T5’s large, rigid, and twisted dendrons.
The obvious difference in film morphology arising from different
generations may, in most cases, have influence on their device
performances.
2.5. Electrochemical Property. The electrochemical prop-
erty of dendrimers was investigated by cyclic voltammetry
carried out in 0.1 M Bu4NPF6-CH2Cl2 at a scan rate of 100
mV/s. The cyclic voltammograms are shown in Figure 5, and
the relative data of energy levels are listed in Table 1. There is
one poorly resolved reversible oxidation peak observed for each
dendrimer. On the basis of roughly evaluated onset oxidation
potentials, the highest occupied molecular orbital (HOMO)
energy levels of dendrimers are estimated in the range of -5.98
to -5.76 eV (HOMO ) Eox
+ 4.4 eV). The lowest
onset
unoccupied molecular orbital (LUMO) energy levels are ranged
from -3.62 to -3.41 eV, calculated from the HOMO energy
level and energy band gap (Eg) determined from the UV-vis
absorption threshold (LUMO ) HOMO - Eg eV). The obtained
data seem to suggest that dendrimers with higher generation
possess higher energy levels.
2.6. Electroluminescence. 2.6.1. Generation Effect. The
generation effect on the EL property of the dendrimers is
investigated in single-layer devices with a configuration of ITO
(120 nm)/PEDOT (25 nm)/dendrimer/Cs2CO3 (1 nm)/Al (100
nm). The details of device fabrication can be found elsewhere.32
The dendrimer films are fabricated by a spin-coating speed
ranging from 800 to 3500 rpm from p-xylene solutions
containing 4 wt % T1, 4 wt % T2, 2.5 wt % T3, 2 wt % T4,
and 2 wt % T5, respectively. Figure 6 displays the EL spectra
of dendrimers. The EL spectra of the dendrimers are broader
than but resemble their PL spectra in thin neat films, revealing
that both PL and EL originate from the same radiative-decay
process of singlet excitons.33 T1 and T2 show greenish yellow
EL at 576 and 572 nm with Commission Internationale
d’Eclairage (CIE) chromaticity coordinates of (0.48, 0.51) and
(32) Huang, J.; Li, G.; Wu, E.; Xu, Q.; Yang, Y. AdV. Mater. 2006, 18, 114.
(33) Shih, P.-I.; Tseng, Y.-H.; Wu, F.-I.; Dixit, A. K.; Shu, C.-F. AdV. Funct.
Mater. 2006, 16, 1582.
(31) Berlman, I. B. Handbook of Fluorescence Spectra of Aromatic Mol-
ecules; Academic Press: New York, 1971.
J. Org. Chem. Vol. 74, No. 1, 2009 389

Zhao et al.
FIGURE 4. AFM images of T3 film (up) and T5 film (down).
intermolecular interaction. Interestingly, we find that a certain
extent of intermolecular interaction can improve the device
efficiency. Figure 7 shows the current density-voltage-luminance
(J-V-L) characteristics and current efficiency curves of a T3-
based device as an example (for device performances of other
dendrimers, please refer to the Supporting Information). When
the dendrimer films are prepared under comparable spin-coating
speeds, a T3-based device exhibits best performance charac-
teristics. For example, at a speed of 1500 rpm, a T3-based device
exhibits a maximum brightness of 5590 cd/m2 at 16 V with a
high current efficiency of 2.67 cd/A at 8.6 V. Moreover, Figure
8 compares the external quantum efficiency curves of the most
efficient devices based on T1-T5. A T3-based device shows
the highest external quantum efficiency with a peak value of
0.86%. While the peak values of T1-, T2-, T4-, and T5-based
devices are only 0.09%, 0.23%, 0.57%, and 0.49%, respectively.
Such findings are in contrast to the general belief that a
dendrimer with a higher generation can improve the device
performances.5g,9a,10b The best performance of T3 indicates the
distinctive effect of intermolecular interaction is offset by the
constructive one. As mentioned before, strong intermolecular
π-π interaction between dendrimer molecules is undesirable
because it results in decreased efficiency and red-shifted
emission. On the other hand, such strong interaction can lead
to better hole transport between dendrons, as well as carrier
transport through a hopping pathway between pyrene rings. Thus
red-shifted emission with high efficiency is observed. Although
the further increase in generation as well as dendron size hinders
close intramolecular π-π stacking, it has, however, lowered
carrier-transporting efficiency. The inferior performance but
blue-shifted emission of T5 with respect to that of T3 is a good
indicator.
FIGURE 5. Cyclic voltammograms of dendrimers T1-T5 in 0.1 M
Bu4NPF6-CH2Cl2, scan rate 100 mV/s.
(0.47, 0.52), respectively. T3 and T4 show yellow EL (CIE:
0.49, 0.50 for T3, and 0.51, 0.49 for T4) at 560 nm. On the
other hand, T5 exhibits a narrow yellowish green (CIE: 0.39,
0.59) EL at 530 nm with a weak emission at ∼560 nm, which
is comparable to its PL in both solutions and solid states. Since
materials with repeating fluorene units have been reported to
undergo a process of alignment in an electric field and small-
sized molecules with high mobility are prone to form ag-
gregates,34 the broader and redder EL of T1 and T2 may be
due to further aggregation of their molecules, which results in
close stacking of pyrene rings and formation of excimers upon
electric excitation. Thus, dendrons with two or more generations
seem to be required to achieve efficient isolation of the core of
this kind of dendrimers in the electronic field.
Generally, aggregation and/or excimer formation will quench
the PL and EL efficiencies due to excited energy loss through
2.6.2. Effect of Spin Speed. Since spin-coating has become
one of the most commonly used techniques for thin polymer
film preparation, the relationships between fabrication conditions
(spin speed, solvent, concentration, etc.) and electronic and
(34) (a) Weinfurtner, K.-H.; Fujikawa, H.; Tokito, S.; Taga, Y. Appl. Phys.
Lett. 2000, 76, 2502. (b) Bradley, D. D. C.; Grell, M.; Long, X.; Mellor, H.;
Grice, A. Proc. SPIE 1998, 3145, 254.
390 J. Org. Chem. Vol. 74, No. 1, 2009

Solution-Processable Stiff Dendrimers
FIGURE 6. EL spectra of dendrimer devices with a configuration of ITO/PEDOT/T1-T5/Cs2CO3/Al.
photonic properties of polymer films as well as device perfor-
mances have been extensively studied.35,36 Generally, low spin
speed results in thick films and thermodynamically favorable
aggregation of molecules because a low rate of solvent evapora-
tion encourages strong intermolecular interaction. On the
contrary, high spin speed gives thin films and the molecules
may be locked in an unfavorable conformation caused by solvent
molecules and the centrifugal force.32 In the case of these
dendrimers, the EL spectra and device efficiency are dependent
on film microstructure and thickness controlled by spin speed.
The EL spectra of T1, T2, and T4 become narrow gradually as
spin speed increases. The EL spectra of T3 and T5 also change
with spin speed but lack correlation. The current density and
brightness of devices increase as spin speed increases, particu-
larly those of devices fabricated with large-sized dendrimers.
The current efficiency is also dependent on the spin speed, and
a higher efficiency can be achieved by optimization of the spin
speed. Although the change in spin speed seems to be a subtle
modulation in the fabrication condition, it does affect the
performances of the dendrimer-based LEDs, thus offering an
opportunity to further enhance their device efficiency by further
engineering control.
3. Conclusions
In this work, the successfully convergent synthesis and
detailed characterization of a series of solution-processable stiff
dendrimers consisting of a pyrene core, carbazole/fluorene
dendrons, and acetylene linkages are described. These dendrim-
ers show good thermal stability, strong fluorescence, efficient
photon-harvesting, and excellent film-forming properties. Al-
though the acetylene-linked dendrimers are generally considered
as unpromising materials for OLEDs, we found that they can
show high EL efficiency in single-layer devices by proper
structural and engineering controls. A good control on the degree
of intermolecular interaction through generation modulation is
important in order to maximize carrier transport but minimize
(35) (a) Blatchford, J. W.; Jessen, S. W.; Lin, L.-B.; Gustafson, T. L.; Fu,
D.-K.; Wang, H.-L.; Swager, T. M.; MacDiarmid, A. G.; Epstein, A. J. Phys.
ReV. B 1996, 79, 3299. (b) Cao, Y.; Parker, I. D.; Yu, C.; Zhang, C.; Heeger,
A. J. Nature 1999, 397, 414. (c) Diaz-Garcia, M. A.; Hide, F.; Schwartz, B. J.;
Andersson, M. R.; Pei, Q.; Heeger, A. J. Synth. Met. 1997, 84, 455.
(36) (a) Shi, Y.; Liu, J.; Yang, Y. J. Appl. Phys. 2000, 87, 4254. (b) Shi, Y.;
Liu, J.; Yang, Y. Macromol. Symp. 2000, 154, 187. (c) Liu, J.; Shi, Y.; Ma, L.;
Yang, Y. J. Appl. Phys. 2000, 88, 605.
J. Org. Chem. Vol. 74, No. 1, 2009 391

Zhao et al.
FIGURE 7. J-V-L characteristics and current efficiency curves of T3-based devices with a configuration of ITO/PEDOT/T3/Cs2CO3/Al.
Hz), 7.46 (dd, 2 H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 7.72 (d, 2 H, J )
8.5 Hz), 8.15 (d, 2 H, J ) 1.0 Hz) ppm; 13C NMR (CDCl3) δ 31.9,
65.9, 82.9, 92.8, 109.9, 115.0, 121.7, 123.1, 124.3, 128.7, 130.3,
133.5, 136.1, 140.6 ppm; MALDI-TOF-MS (m/z) calcd for
C28H24BrNO2 (M+) 485.1, found 485.0.
9-(4-Bromophenyl)-3,6-diethynyl-9H-carbazole (9). A mixture
of 8 (1 g, 2 mmol), potassium hydroxide (2 g, 35 mmol), and 150
mL of 2-propanol was placed in a 250 mL round bottle flask
equipped with a Teflon covered magnetic stir bar. After the resulting
mixture was refluxed for 3 h under N2, it was cooled to room
temperature. The solution was poured into water and extracted by
CH2Cl2. After washing by water and drying by MgSO4, the solvent
was then removed and the residue was purified through column
chromatography (silica gel, hexane/dichloromethane as eluent). In
this way, 0.64 g (86% yield) of brown, oil-like 9 was obtained. 1H
NMR (CDCl3) δ 3.10 (s, 2 H), 7.28 (d, 2 H, J ) 8.5 Hz), 7.41 (d,
2 H, J ) 8.5 Hz), 7.55 (dd, 2 H, J ) 8.5 Hz, J ) 1.5 Hz), 7.75 (d,
2 H, J ) 9.0 Hz), 8.25 (d, 2 H, J ) 0.5 Hz) ppm; 13C NMR (CDCl3)
δ 76.2, 84.6, 110.1, 114.4, 122.0, 123.1, 125.0, 128.9, 130.8, 133.6,
136.0, 141.1 ppm; MALDI-TOF-MS (m/z) calcd for C22H12BrN
(M+) 369.0, found 370.9.
FIGURE 8. External quantum efficiency curves of the most efficient
devices based on T1-T5.
excimer formation. Fabrication conditions, such as spin speed,
have significant influence on EL performances. With an
optimization of spin speed, the T3-based LED exhibits yellow
EL (CIE: 0.49, 0.50) with a maximum brightness of 5590 cd/
m2 at 16 V, a high current efficiency of 2.67 cd/A at 8.6 V, and
a best external quantum efficiency of 0.86%.
4,4′-(9-(4-((Trimethylsilyl)ethynyl)phenyl)-9H-carbazole-3,6-
diyl)bis(2-methylbut-3-yn-2-ol) (10). 8 (2 g, 4 mmol), ethynylt-
rimethylsilane (0.6 g, 6 mmol), cuprous iodide (20 mg, 0.1 mmol),
Pd(Ph3P)4 (11.5 mg, 0.01 mmol), PPh3 (10.5 mg, 0.04 mmol), and
dry diisopropylamine (150 mL) were placed in a 250 mL round
bottle flask. After the solution was purged with nitrogen for half
an hour, it was refluxed under nitrogen for 12 h. The reaction
mixture was evaporated under reduced pressure, and then the residue
was purified through column chromatography (silica gel, hexane/
dichloromethane/ethyl acetate as eluent) to afford yellow, oil-like
4. Experimental Section
4,4′-(9-(4-Bromophenyl)-9H-carbazole-3,6-diyl)bis(2-methyl-
but-3-yn-2-ol) (8). 7 (2.9 g, 5 mmol), 3-methyl-1-butyn-3-ol (1 g,
12 mmol), cuprous iodide (20 mg, 0.1 mmol), Pd(PPh3)2Cl2 (7 mg,
0.01 mmol), PPh3 (10 mg, 0.04 mmol), and dry triethylamine (150
mL) were placed in a 250 mL round bottle flask equipped with a
Teflon covered magnetic stir bar. After the solution was purged
with nitrogen for half an hour, it was refluxed under nitrogen for
12 h. The reaction mixture was evaporated under reduced pressure,
and then the residue was purified through column chromatography
(silica gel, hexane/dichloromethane/ethyl acetate as eluent) to afford
a brown solid 8 (1.9 g, 78% yield). 1H NMR (CDCl3) δ 1.67 (s, 12
H), 2.20 (br, 2 H), 7.24 (d, 2 H, J ) 8.5 Hz), 7.37 (d, 2 H, J ) 8.5
1
10 (1.8 g, 90% yield). H NMR (CDCl3) δ 0.30 (s, 9 H), 1.68 (s,
12 H), 2.35 (br, 2 H), 7.22 (d, 2 H, J ) 8.5 Hz), 7.39 (dd, 2 H, J1
) 8.5 Hz, J2 ) 2.0 Hz), 7.43 (d, 2 H, J ) 8.5 Hz), 7.67 (d, 2 H,
J ) 8.0 Hz), 8.12 (s, 2 H) ppm; 13C NMR (CDCl3) δ 0.2, 31.9,
66.0, 83.0, 92.8, 96.1, 104.2, 110.0, 115.0, 123.0, 123.2, 124.3,
126.8, 130.3, 133.8, 137.0, 140.6 ppm; MALDI-TOF-MS (m/z)
calcd for C33H33NO2Si (M+) 503.2, found 503.7.
392 J. Org. Chem. Vol. 74, No. 1, 2009

Solution-Processable Stiff Dendrimers
4,4′-(9-(4-Ethynylphenyl)-9H-carbazole-3,6-diyl)bis(2-meth-
ylbut-3-yn-2-ol) (11). 10 (5 g, 10 mmol) was dissolved in 150 mL
of THF containing 12 mmol of tetrabutyl ammonium fluoride
(TBAF). The reaction mixture was stirred at room temperature under
nitrogen overnight, then it was poured into water and extracted by
CH2Cl2. After washing by water and drying by MgSO4, the solvent
was removed under reduced pressure and the residue was purified
through column chromatography (silica gel, hexane/dichloromethane/
ethyl acetate as eluent) to afford a white solid (4 g, 95% total yield).
1H NMR (CDCl3) δ 1.67 (s, 12 H), 2.22 (br, 2 H), 3.20 (s, 1 H),
7.27 (d, 2 H, J ) 9.0 Hz), 7.44-7.47 (m, 4 H), 7.71 (d, 2 H, J )
8.5 Hz), 8.15 (d, 2 H, J ) 1.0 Hz) ppm; 13C NMR (CDCl3) δ 31.9,
66.0, 78.8, 82.9, 83.0, 92.8, 110.0, 115.0, 121.9, 123.2, 124.4, 126.9,
130.3, 134.0, 137.4, 140.6 ppm; MALDI-TOF-MS (m/z) calcd for
C30H25NO2 (M+) 431.2, found 431.3.
(m, 16 H), 1.47 (s, 36 H), 2.02-2.04 (m, 16 H), 7.40 (d, 4 H, J )
9.0 Hz), 7.49 (dd, 6 H, J1 ) 9.0 Hz, J2 ) 2.0 Hz), 7.56-7.61 (m,
22 H), 7.67 (dd, 2 H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 7.71 (d, 8 H, J )
8.0 Hz), 7.77-7.79 (m, 6 H), 8.15 (d, 4 H, J ) 2.0 Hz), 8.38 (d,
2 H, J ) 1.0 Hz) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 24.0, 29.3,
30.3, 32.1, 32.3, 35.0, 40.7, 40.8, 55.6, 89.5, 89.6, 90.9, 91.0, 91.1,
91.5, 109.5, 110.2, 115.8, 116.6, 120.2, 120.3, 122.0, 122.2, 122.4,
122.6, 123.4, 123.8, 124.0, 124.4, 126.1, 126.2, 126.3, 126.7, 128.9,
130.4, 130.9, 131.0, 131.1, 133.2, 133.6, 136.2, 138.3, 139.1, 140.8,
140.9, 141.1, 141.2, 143.5, 151.4, 151.4 ppm; MALDI-TOF-MS
(m/z) calcd for C190H210BrN3 (M+) 2612.6, found 2613.1.
9,9′-(4,4′-(7,7′-(9-(4-Ethynylphenyl)-9H-carbazole-3,6-diyl)bis-
(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))bis(ethyne-
2,1-diyl)bis(4,1-phenylene))bis(3,6-di-tert-butyl-9H-carbazole) (15).
13 (3.7 g, 2 mmol), 3-methyl-1-butyn-3-ol (0.2 g, 2.4 mmol),
cuprous iodide (20 mg, 0.1 mmol), Pd(Ph3P)4 (11.5 mg, 0.01 mmol),
Ph3P (10.5 mg, 0.04 mmol), and dry diisopropylamine (150 mL)
were placed in a 250 mL round bottle flask equipped with a Teflon
covered magnetic stir bar. After the solution was purged with
nitrogen for half an hour, it was refluxed under nitrogen for 12 h.
The reaction mixture was evaporated under reduced pressure and
the residue was purified through column chromatography (silica
gel, hexane/ethyl acetate as eluent) to afford a pale yellow solid.
Then the obtained solid, potassium hydroxide (1 g, 17 mmol), and
150 mL of 2-propanol were placed in a 250 mL round bottle flask.
After the resulting mixture was refluxed for 3 h under N2, it was
cooled to room temperature. The solution was then poured into
water and extracted by CH2Cl2. After washing by water and drying
by MgSO4, the solvent was removed and the residue was purified
through column chromatography (silica gel, hexane/dichloromethane
as eluent). In this way, 2.3 g (65% total yield) of 15 (a pale yellow
solid) was obtained. 1H NMR (CDCl3) δ 0.67 (br, 8 H), 0.82 (t, 12
H, J ) 7.5 Hz), 1.09 (br, 24 H), 1.17-1.21 (m, 8 H), 1.47 (s, 36
H), 2.02-2.05 (m, 8 H), 3.21 (s, 1 H), 7.40 (d, 6 H, J ) 9.0 Hz),
7.48 (dd, 4 H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.56-7.61 (m, 14 H),
7.67 (dd, 2 H, J1 ) 8.5 Hz, J2 ) 1.5 Hz), 7.71 (dd, 4 H, J1 ) 8.0
Hz, J2 ) 2.5 Hz), 7.76-7.78 (m, 6 H), 8.15 (d, 4 H, J ) 1.5 Hz),
8.39 (s, 2 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.6, 24.0, 29.3,
30.3, 32.1, 32.3, 35.0, 40.7, 55.5, 78.8, 82.9, 89.4, 89.6, 90.9, 91.5,
109.5, 110.3, 115.8, 116.5, 120.2, 120.3, 121.9, 122.0, 122.6, 123.5,
123.8, 124.0, 124.4, 126.2, 126.3, 126.7, 127.1, 130.4, 130.9, 131.1,
133.2, 134.1, 137.4, 138.3, 139.1, 140.7, 140.8, 141.2, 143.4, 151.4
ppm; MALDI-TOF-MS (m/z) calcd for C134H139N3 (M+) 1790.1,
found 1791.2.
4,4′-(9-(4-((9,9-Diheptyl-7-iodo-9H-fluoren-2-yl)ethynyl)phe-
nyl)-9H-carbazole-3,6-diyl)bis(2-methylbut-3-yn-2-ol) (12). 11
(4.3 g, 10 mmol), 9,9-diheptyl-2,7-diiodo-9H-fluorene (2) (18.5 g,
30 mmol), cuprous iodide (100 mg, 0.5 mmol), Pd(PPh3)2Cl2 (35
mg, 0.05 mmol), PPh3 (50 mg, 0.2 mmol), and dry triethylamine
300 mL were placed in a 500 mL round bottle flask equipped with
a Teflon covered magnetic stir bar. After the solution was purged
with nitrogen for half an hour, 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/dichloromethane/ethyl acetate
1
as eluent) to afford white solid 12 (7.3 g, 80% yield). H NMR
(CDCl3) δ 0.62 (br, 4 H), 0.81 (t, 6 H, J ) 7.5 Hz), 1.07 (br, 12
H), 1.16-1.21 (m, 4 H), 1.68 (s, 12 H), 1.93-1.98 (m, 4 H), 2.31
(br, 2 H), 7.30 (d, 2 H, J ) 8.5), 7.42-7.49 (m, 5 H), 7.53-7.56
(m, 2 H), 7.64-7.68 (m, 3 H), 7.77 (d, 2 H, J ) 8.5 Hz), 8.16 (s,
2 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 23.9, 29.2, 30.1, 31.9,
32.0, 40.5, 55.7, 66.0, 83.0, 89.0, 91.9, 92.8, 93.5, 110.1, 115.0,
120.1, 121.9, 122.0, 123.2, 124.4, 126.2, 127.0, 130.3, 131.1, 132.4,
133.4, 136.3, 136.8, 140.2, 140.7, 140.9, 150.5, 153.6 ppm;
MALDI-TOF-MS (m/z) calcd for C57H60INO2 (M+) 917.4, found
917.6.
9,9′-(4,4′-(7,7′-(9-(4-Bromophenyl)-9H-carbazole-3,6-diyl)bis-
(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))bis(ethyne-
2,1-diyl)bis(4,1-phenylene))bis(3,6-di-tert-butyl-9H-carbazole) (13).
3 (2.2 g, 2.5 mmol), 9 (0.37 g, 1 mmol), cuprous iodide (10 mg,
0.05 mmol), Pd(PPh3)2Cl2 (3.5 mg, 0.005 mmol), PPh3 (5 mg, 0.02
mmol), and dry triethylamine (150 mL) were placed in a 250 mL
round bottle flask equipped with a Teflon covered magnetic stir
bar. After the solution was purged with nitrogen for half an hour,
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/dichloromethane as eluent) to afford pale yellow solid 13
(1.5 g, 82% yield). 1H NMR (CDCl3) δ 0.68 (br, 8 H), 0.82 (t, 12
H, J ) 7.5 Hz), 1.09 (br, 24 H), 1.18-1.22 (m, 8 H), 1.47 (s, 36
H), 2.02-2.05 (m, 8 H), 7.34 (d, 2 H, J ) 8.0 Hz), 7.40 (d, 4 H,
J ) 9.5 Hz), 7.44 (d, 2 H, J ) 8.0 Hz), 7.48 (dd, 4 H, J1 ) 8.5 Hz,
J2 ) 1.5 Hz), 7.56-7.60 (m, 12 H), 7.65 (d, 2 H, J ) 9.0 Hz),
7.69-7.71 (m, 4 H), 7.74-7.78 (m, 6 H), 8.15 (d, 4 H, J ) 1.5
Hz), 8.38 (s, 2 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 24.1, 29.3,
30.3, 32.1, 32.2, 35.0, 40.7, 55.5, 89.4, 89.6, 90.9, 91.5, 109.5,
110.2, 115.8, 116.5, 120.2, 120.3, 121.9, 122.0, 122.6, 123.4, 123.8,
124.0, 124.4, 126.2, 126.3, 126.6, 128.9, 130.4, 130.9, 131.1, 133.2,
133.6, 136.2, 138.3, 139.1, 140.7, 140.8, 141.2, 143.4, 151.4 ppm;
MALDI-TOF-MS (m/z) calcd for C132H138BrN3 (M+) 1844.0, found
1844.8.
9,9′-(4,4′-(7,7′-(7,7′-(9-(4-Ethynylphenyl)-9H-carbazole-3,6-
diyl)bis(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))-
bis(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))bis-
(ethyne-2,1-diyl)bis(4,1-phenylene))bis(3,6-di-tert-butyl-9H-
carbazole) (16). The procedure was analogous to that described
1
for 15 (47% yield, a pale yellow solid). H NMR (CDCl3) δ 0.64
(br, 16 H), 0.82 (t, 24 H, J ) 7.5 Hz), 1.08 (br, 48 H), 1.18-1.22
(m, 16 H), 1.47 (s, 36 H), 2.02-2.04 (m, 16 H), 3.22 (s, 1 H), 7.41
(d, 6 H, J ) 8.5 Hz), 7.49 (dd, 4 H, J1 ) 9.0 Hz, J2 ) 2.0 Hz),
7.56-7.61 (m, 22 H), 7.67 (dd, 2 H, J1 ) 8.5 Hz, J2 ) 1.0 Hz),
7.71 (d, 8 H, J ) 8.0 Hz), 7.77-7.79 (m, 6 H), 8.15 (d, 4 H, J )
1.5 Hz), 8.39 (s, 2 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 24.0,
29.3, 30.3, 32.1, 32.3, 35.0, 40.7, 40.8, 55.5, 78.8, 82.9, 89.5, 89.6,
90.9, 91.0, 91.1, 91.5, 109.5, 110.3, 115.8, 116.5, 120.2, 120.3,
120.3, 122.00, 122.1, 122.2, 122.3, 122.6, 123.5, 123.8, 124.0,
124.4, 126.1, 126.2, 126.3, 126.7, 127.1, 130.4, 130.9, 131.0, 131.1,
133.2, 134.1, 137.5, 138.3, 139.1, 140.7, 140.8, 140.9, 141.1, 141.2,
143.4, 151.4 ppm; MALDI-TOF-MS (m/z) calcd for C192H211N3
(M+) 2558.7, found 2559.3.
9,9′-(4,4′-(7,7′-(7,7′-(9-(4-Bromophenyl)-9H-carbazole-3,6-
diyl)bis(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))-
bis(ethyne-2,1-diyl)bis(9,9-diheptyl-9H-fluorene-7,2-diyl))bis-
(ethyne-2,1-diyl)bis(4,1-phenylene))bis(3,6-di-tert-butyl-9H-
carbazole) (14). The procedure was analogous to that described
9,9′-(4,4′-(7,7′-(9-(4-((9,9-Diheptyl-7-iodo-9H-fluoren-2-yl)ethy-
nyl)phenyl)-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)bis(9,9-dihep-
tyl-9H-fluorene-7,2-diyl))bis(ethyne-2,1-diyl)bis(4,1-phenylene))bis(3,6-
di-tert-butyl-9H-carbazole) (17). The procedure was analogous to
1
1
for 13 (78% yield, a pale green solid). H NMR (CDCl3) δ 0.65
that described for 12 (73% yield, a pale yellow solid). H NMR
(br, 16 H), 0.82 (t, 24 H, J ) 7.5 Hz), 1.08 (br, 48 H), 1.18-1.22
(CDCl3) δ 0.67 (br, 12 H), 0.81-0.84 (m, 18 H), 1.08-1.10 (m,
J. Org. Chem. Vol. 74, No. 1, 2009 393

Zhao et al.
36 H), 1.18-1.22 (m, 12 H), 1.47 (s, 36 H), 1.95-2.06 (m, 12 H),
7.40 (d, 4 H, J ) 9.0 Hz), 7.44 (d, 2 H, J ) 8.5 Hz), 7.49 (dd, 4
H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.55-7.62 (m, 18 H), 7.68-7.69
(m, 4 H), 7.72 (dd, 4 H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.78 (d, 4 H,
J ) 6.0 Hz), 7.83 (d, 2 H, J ) 8.5 Hz), 8.15 (d, 4 H, J ) 2.0 Hz),
8.40 (d, 2 H, J ) 1.5 Hz) ppm; 13C NMR (CDCl3) δ 14.3, 22.8,
24.0, 29.3, 30.3, 32.1, 32.3, 35.0, 40.7, 55.5, 78.8, 82.9, 89.4, 89.6,
90.9, 91.5, 109.5, 110.3, 115.8, 116.5, 120.2, 120.3, 121.9, 122.0,
122.6, 123.5, 123.8, 124.0, 124.4, 126.2, 126.3, 126.7, 127.1, 130.4,
130.9, 131.1, 133.2, 134.2, 137.4, 138.3, 139.2, 140.7, 140.8, 141.2,
143.4, 151.4 ppm; MALDI-TOF-MS (m/z) calcd for C161H174IN3
(M+) 2276.3, found 2150.0 (M+ - I). Anal. Calcd for C161H174IN3:
C, 84.89; H, 7.70; N, 1.84. Found: C, 84.91; H, 7.74; N, 1.82.
9,9′-(4,4′-(7,7′-(7,7′-(9-(4-((9,9-Diheptyl-7-iodo-9H-fluoren-2-
yl)ethynyl)phenyl)-9H-carbazole-3,6-diyl)bis(ethyne-2,1-diyl)-
bis(9,9-diheptyl-9H-fluorene-7,2-diyl))bis(ethyne-2,1-diyl)bis(9,9-
diheptyl-9H-fluorene-7,2-diyl))bis(ethyne-2,1-diyl)bis(4,1-
phenylene))bis(3,6-di-tert-butyl-9H-carbazole) (18). The procedure
was analogous to that described for 12 (67% yield, a pale yellow
solid). 1H NMR (CDCl3) δ 0.65 (br, 20 H), 0.80-0.84 (m, 32 H),
1.08 (br, 58 H), 1.18-1.21 (m, 20 H), 1.47 (s, 36 H), 1.95-2.04
(m, 20 H), 7.40 (d, 4 H, J ) 8.5 Hz), 7.45 (d, 2 H, J ) 8.5 Hz),
7.49 (dd, 4 H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.55-7.62 (m, 26 H),
7.68-7.72 (m, 12 H), 7.78 (d, 4 H, J ) 8.5 Hz), 7.83 (d, 2 H, J )
8.0 Hz), 8.15 (d, 4 H, J ) 1.5 Hz), 8.40 (s, 2 H) ppm; 13C NMR
(CDCl3) δ 14.3, 22.8, 24.0, 29.2, 29.3, 30.2, 30.3, 32.0, 32.1, 32.2,
35.0, 40.5, 40.7, 40.8, 55.5, 55.7, 89.0, 89.5, 89.6, 90.9, 91.0, 91.2,
91.4, 92.0, 93.6, 109.6, 110.4, 115.7, 116.5, 120.1, 120.3, 121.9,
122.0, 122.1, 122.3, 122.6, 123.3, 123.5, 123.8, 124.0, 124.4, 126.1,
126.2, 126.6, 127.1, 130.4, 130.9, 131.0, 131.1, 131.2, 132.4, 133.2,
133.5, 136.3, 136.8, 138.3, 139.1, 140.2, 140.7, 140.8, 140.9, 141.0,
141.1, 143.4, 150.6, 151.4, 153.7 ppm; MALDI-TOF-MS (m/z)
calcd for C219H246IN3 (M+) 3044.8, found 2919.7 (M+ - I). Anal.
Calcd for C219H246IN3: C, 86.32; H, 8.14; N, 1.38. Found: C, 86.12;
H, 8.34; N, 1.29.
calcd for C228H198N4 (M+) 2291.6, found 2294.3. Anal. Calcd for
C
228H198N4: C, 91.46; H, 6.67; N, 1.87. Found: C, 91.50; H, 6.68;
N, 1.90.
1,3,6,8-Tetrakis((7-((4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phe-
nyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)pyrene (T1).
The procedure was analogous to that described for 12 (79% yield,
an orange-red solid). 1H NMR (CDCl3) δ 0.73 (br, 16 H), 0.83 (t,
24 H, J ) 7.5 Hz), 1.13 (br, 48 H), 1.20-1.25 (m, 16 H), 1.48 (s,
72 H), 2.10-2.11 (m, 16 H), 7.41 (d, 8 H, J ) 8.5 Hz), 7.49 (dd,
8 H, J1 ) 8.5 Hz, J2 ) 2.0 Hz), 7.58-7.62 (m, 16 H), 7.74-7.80
(m, 24 H), 8.15 (d, 8 H, J ) 1.5 Hz), 8.60 (s, 2 H), 8.92 (s, 4 H)
ppm; 13C NMR (CDCl3) δ 14.3, 22.9, 24.1, 29.3, 30.3, 32.1, 32.3,
35.0, 40.7, 55.7, 88.6, 89.6, 91.4, 97.6, 116.6, 119.5, 120.4, 120.5,
122.0, 122.6, 123.9, 124.0, 124.6, 126.3, 126.7, 127.3, 131.2, 131.4,
132.1, 133.3, 138.4, 139.2, 141.1, 141.4, 143.5, 151.5, 151.7 ppm;
MALDI-TOF-MS (m/z) calcd for C244H262N4 (M+) 3248.1, found
3247.9. Anal. Calcd for C244H262N4: C, 90.15; H, 8.12; N, 1.72.
Found: C, 90.34; H, 8.19; N, 1.44.
1,3,6,8-Tetrakis((7-((7-((4-(3,6-di-tert-butyl-9H-carbazol-9-
yl)phenyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)-9,9-di-
heptyl-9H-fluoren-2-yl)ethynyl)pyrene (T2). The procedure was
analogous to that described for 12 (74% yield, an orange-red solid).
1H NMR (CDCl3) δ 0.66-0.71 (m, 32 H), 0.81-0.84 (m, 48 H),
1.09-1.12 (m, 96 H), 1.19-1.23 (m, 32 H), 1.48 (s, 72 H),
2.04-2.10 (m, 32 H), 7.41 (d, 8 H, J ) 9.0 Hz), 7.49 (dd, 8 H, J1
) 8.5 Hz, J2 ) 2.5 Hz), 7.57-7.64 (m, 32 H), 7.71-7.73 (m, 12
H), 7.76-7.82 (m, 20 H), 8.15 (d, 8 H, J ) 2.0 Hz), 8.60 (s, 2 H),
8.93 (s, 4 H) ppm; 13C NMR (CDCl3) δ 14.3, 14.3, 22.9, 24.0,
29.3, 30.3, 32.1, 32.3, 35.0, 40.7, 40.8, 55.6, 55.7, 88.5, 89.5, 91.1,
91.2, 91.4, 97.6, 109.5, 116.6, 119.5, 120.3, 120.4, 122.0, 122.1,
122.3, 122.5, 123.8, 124.0, 126.3, 126.7, 131.0, 131.1, 131.3, 132.1,
133.2, 138.3, 139.1, 140.9, 141.0, 141.1, 141.5, 143.5, 151.4, 151.5,
151.6 ppm; MALDI-TOF-MS (m/z) calcd for C360H406N4 (M+)
4785.2, found 4785.3. Anal. Calcd for C360H406N4: C, 90.29; H,
8.54; N, 1.17. Found: C, 90.17; H, 8.71; N, 1.09.
1,3,6,8-Tetrakis((7-((4-(3,6-bis((7-((4-(3,6-di-tert-butyl-9H-car-
bazol-9-yl)phenyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)-
9H-carbazol-9-yl)phenyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-
yl)ethynyl)pyrene (T3). The procedure was analogous to that
described for 12 (65% yield, an orange-red solid). 1H NMR (CDCl3)
δ 0.68 (br, 48 H), 0.81-0.85 (m, 72 H), 1.01-1.23 (m, 192 H),
1.47 (s, 144 H), 2.04 (br, 48 H), 7.40 (d, 16 H, J ) 8.5 Hz),
7.48-7.50 (m, 20 H), 7.57-7.60 (m, 48 H), 7.63-7.65 (m, 20 H),
7.69-7.74 (m, 24 H), 7.76-7.88 (m, 40 H), 8.15 (d, 16 H, J ) 8.5
Hz), 8.41 (s, 8 H), 8.63 (s, 2 H), 8.95 (s, 4 H) ppm; 13C NMR
(CDCl3) δ 14.3, 14.4, 22.9, 24.1, 29.3, 30.3, 32.1, 32.2, 35.0, 40.7,
55.6, 55.7, 89.4, 89.6, 90.9, 91.5, 115.7, 116.5, 120.2, 120.3, 120.5,
120.5, 121.9, 122.0, 122.6, 123.5, 123.8, 124.0, 126.2, 126.3, 126.4,
126.7, 127.1, 130.4, 130.9, 131.1, 131.3, 131.4, 133.2, 133.5, 139.1,
140.7, 140.8, 141.2, 143.4, 151.4, 151.4 ppm; MALDI-TOF-MS
(m/z) calcd for C668H702N12 (M+) 8892, found 8897. Anal. Calcd
for C668H702N12: C, 90.16; H, 7.95; N, 1.89. Found: C, 90.15; H,
7.99; N, 1.89.
1,3,6,8-Tetrakis((7-((4-(3,6-bis((7-((7-((4-(3,6-di-tert-butyl-9H-
carbazol-9-yl)phenyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethy-
nyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)-9H-carbazol-9-yl)phe-
nyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)pyrene (T4).
The procedure was analogous to that described for 12 (60% yield,
an orange-red solid). 1H NMR (CDCl3) δ 0.65 (br, 80 H), 0.80-0.84
(m, 120 H), 1.09-1.20 (m, 320 H), 1.47 (s, 144 H), 2.03 (br, 80
H), 7.40 (d, 16 H, J ) 8.5 Hz), 7.48-7.50 (m, 20 H), 7.57-7.76
(m, 100 H), 7.70-7.72 (m, 40 H), 7.77-7.86 (m, 40 H), 8.15 (d,
16 H, J ) 1.5 Hz), 8.41 (s, 8 H), 8.63 (s, 2 H), 8.95 (s, 4 H) ppm;
13C NMR (CDCl3) δ 14.3, 22.9, 24.0, 29.3, 30.3, 32.1, 32.3, 35.0,
40.7, 40.8, 55.5, 55.7, 89.5, 89.6, 90.9, 91.0, 91.1, 91.4, 115.8,
116.6, 120.3, 120.3, 120.5, 121.9, 122.0, 122.1, 122.3, 122. 6, 123.5,
123.8,124.0, 126.6, 127.1, 130.4, 130.9, 131.0, 131.1, 131.3, 133.2,
133.5, 138.3, 139.1, 140.7, 140.8, 140.9, 141.1, 143.4, 151.4 ppm;
MALDI-TOF-MS (m/z) calcd for C900H990N12 (M+) 11966, found
4,4′,4′′,4′′′,4′′′′,4′′′′′-(9,9′,9′′-(4,4′,4′′-(7,7′,7′′-(8-((7-((4-(3,6-
Bis(3-hydroxy-3-methylbut-1-ynyl)-9H-carbazol-9-yl)phenyl)-
ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)pyrene-1,3,6-triyl)
tris(ethyne-2,1-diyl)tris(9,9-diheptyl-9H-fluorene-7,2-
diyl))tris(ethyne-2,1-diyl)tris(4,1-phenylene))tris(9H-carbazole-
9,6,3-triyl))hexakis(2-methylbut-3-yn-2-ol) (20). The procedure
was analogous to that described for 12 (58% yield, an orange-red
solid). 1H NMR (CDCl3) δ 0.74 (br, 16 H), 0.83 (t, 24 H, J ) 7.5
Hz), 1.13 (br, 48 H), 1.20-1.25 (m, 16 H), 1.69 (s, 48 H), 2.11
(br, 24 H), 7.34 (d, 8 H, J ) 8.5 Hz), 7.49 (dd, 8 H, J1 ) 8.0 Hz,
J2 ) 2.0 Hz), 7.54 (d, 8 H, J ) 8.5 Hz), 7.60-7.62 (m, 8 H),
7.74-7.82 (m, 24 H), 8.18 (d, 8 H, J ) 1.0 Hz), 8.57 (s, 2 H),
8.89 (s, 4 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.9, 24.1, 29.3,
30.3, 31.9, 32.1, 40.7, 55.7, 66.0, 83.0, 88.6, 89.2, 92.0, 92.8, 97.6,
110.1, 115.1, 119.4, 120.5, 120.5, 122.0, 122.3, 123.3, 124.4, 124.6,
126.3, 127.0, 127.2, 130.3, 131.3, 131.4, 132.0, 133.4, 134.3, 136.9,
140.7, 141.2, 141.3, 151.5, 151.6 ppm; MALDI-TOF-MS (m/z)
calcd for C252H246N4O8 (M+) 3455.9, found 3458.8. Anal. Calcd
for C252H246N4O8: C, 87.51; H, 7.17; N, 1.62. Found: C, 87.46; H,
7.19; N, 1.51.
1,3,6,8-Tetrakis((7-((4-(3,6-diethynyl-9H-carbazol-9-yl)phe-
nyl)ethynyl)-9,9-diheptyl-9H-fluoren-2-yl)ethynyl)pyrene (21).
The procedure was analogous to that described for 9 (71% yield,
an orange-red solid). 1H NMR (CDCl3) δ 0.72 (br, 16 H), 0.83 (t,
24 H, J ) 7.5 Hz), 1.13 (br, 48 H), 1.20-1.23 (m, 16 H), 2.10-2.11
(m, 16 H), 3.11 (s, 8 H), 7.37 (d, 8 H, J ) 8.5 Hz), 7.55-7.63 (m,
24 H), 7.75-7.83 (m, 24 H), 8.27 (d, 8 H, J ) 1.0 Hz), 8.60 (s, 2
H), 8.92 (s, 4 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 24.1, 29.3,
30.3, 32.1, 40.7, 55.7, 76.2, 84.2, 88.6, 89.1, 92.1, 97.5, 110.2,
114.4, 119.4, 120.4, 120.5, 121.9, 122.2, 123.1, 123.4, 124.5, 125.0,
126.3, 127.1, 127.2, 130.8, 131.2, 131.3, 132.0, 133.5, 134.2, 136.7,
141.0, 141.2, 141.3, 151.5, 151.6 ppm; MALDI-TOF-MS (m/z)
394 J. Org. Chem. Vol. 74, No. 1, 2009

Solution-Processable Stiff Dendrimers
11979. Anal. Calcd for C900H990N12: C, 90.26; H, 8.33; N, 1.40.
Found: C, 90.21; H, 8.34; N, 1.40.
126.7, 127.1, 128.7, 128.8, 130.4, 131.0, 131.1, 132.2, 132.3, 132.4,
133.2, 133.5, 138.3, 139.2, 140.7, 140. 9, 141.2, 143.2, 143.5, 151.4
ppm. Anal. Calcd for C1516H1582N28: C, 90.16; H, 7.90; N, 1.94.
Found: C, 90.26; H, 7.89; N, 1.93.
1,3,6,8-Tetrakis((7-((4-(3,6-bis((7-((4-(3,6-bis((7-((4-(3,6-di-
tert-butyl-9H-carbazol-9-yl)phenyl)ethynyl)-9,9-diheptyl-9H-
fluoren-2-yl)ethynyl)-9H-carbazol-9-yl)phenyl)ethynyl)-9,9-di-
heptyl-9H-fluoren-2-yl)ethynyl)-9H-carbazol-9-yl)phenyl)ethynyl)-
9,9-diheptyl-9H-fluoren-2-yl)ethynyl)pyrene (T5). The procedure
was analogous to that described for 12 (41% yield, an orange-red
solid) except for changes in catalyst (Pd(Ph3P)4) and solvent (i-
Acknowledgment. P.L. thanks the National Natural Science
Foundation of China (20674070) and the Natural Science
Foundation of Zhejiang Province (R404109).
1
Supporting Information Available: General information,
NMR and mass spectra of new compounds, TGA charts of
dendrimers, and J-V-L characteristics and current efficiency
curves of devices. This material is available free of charge via
the Internet at http://pubs.acs.org.
Pr2NH/benzene (1/1, v/v)). H NMR (CDCl3) δ 0.68 (br, 112 H),
0.81-0.85 (m, 168 H), 1.10-1.26 (m, 448 H), 1.47 (s, 288 H),
2.05 (br, 112 H), 7.39-7.49 (m, 96 H), 7.57-7.86 (m, 296 H),
8.14 (s, 32 H), 8.40 (s, 16H), 8.42 (s, 8 H), 8.63 (s, 2 H), 8.95 (s,
4 H) ppm; 13C NMR (CDCl3) δ 14.3, 22.8, 24.1, 29.3, 30.3, 32.1,
32.3, 35.0, 40.7, 55.6, 89.4, 89.6, 91.0, 91.5, 109.5, 110.4, 115.8,
116.6, 120.3, 121.9, 122.0, 122.7, 123.5, 123.8, 124.0, 126.2, 126.3,
JO802237C
J. Org. Chem. Vol. 74, No. 1, 2009 395