Synthesis and functional properties of star-burst dendrimers that contain carbazole as peripheral edges and triazine as a central core

Article abstract of DOI:10.1071/CH07038

With the aim of combining the electron and hole-transporting moieties into one molecule and to continue our investigation into the structure?property correlations of dendrimers, two novel star-burst dendrimers 1 and 2 constructed with carbazoles as the peripheral hole-transporting moieties and one triazine moiety as an electron-transporting central core, have been synthesized. The convergent synthetic approach uses palladium-catalyzed Suzuki cross-coupling as a key reaction. Their functional properties have also been investigated. CSIRO 2007.

Full text of DOI:10.1071/CH07038

Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2007, 60, 603–607
Synthesis and Functional Properties of Star-Burst Dendrimers
that Contain Carbazole as Peripheral Edges and Triazine
as a Central Core
A
B,D
and Man Shing WongC
Mo Jun Xiong, Zhong Hui Li,
A
West China School of Pharmacy, Sichuan University, Chengdu 610041, Sichuan Province, China.
Department of Chemistry, Sichuan College of Education, Chengdu 610041, Sichuan Province, China.
Department of Chemistry, Hong Kong Baptist University, Hong Kong SAR, China.
B
C
D
Corresponding author. Email: zhonghli@sohu.com
With the aim of combining the electron and hole-transporting moieties into one molecule and to continue our investigation
into the structure–property correlations of dendrimers, two novel star-burst dendrimers 1 and 2 constructed with carbazoles
as the peripheral hole-transporting moieties and one triazine moiety as an electron-transporting central core, have been
synthesized. The convergent synthetic approach uses palladium-catalyzed Suzuki cross-coupling as a key reaction. Their
functional properties have also been investigated.
Manuscript received: 4 February 2007.
Final version: 1 May 2007.
Introduction
G1-Br into the corresponding diiodide 3 was also carried out in
42% yield using I2/HIO4 under reflux.[
11]
The chemoselective
Since the first reports on dendrimers were published in 1985,[1,2]
research interests in this field have increased exponentially
because of their unique functional properties and potential
palladium-catalyzed Suzuki cross-coupling of two equivalents
of G1-B(OH)2 with one equivalent of the diiodide 3 afforded
dendronized bromide G2-Br in a high isolated yield of 91%.
Transformation of the bromide G2-Br into the corresponding
boronic acid G2-B(OH)2 was easily carried out in a yield of
51% by the same procedure as the preparation of G1-B(OH)2.
[
3]
applications in such fields as light harvesting, light power
limiting, electroluminescence,[ medicine, and so on. Tri-
4]
[5]
azines have higher electron affinity (EA) values than 1,3,4-
oxadiazoles (PBD) and 1,2,4-triazoles,[6] so they have been
The 2,4,6-tri(p-bromo)phenyl-1,3,5-triazine (4) was prepared
explored as building blocks for electron-transporting materials
according to the literature method.[
12]
Triplet-Suzuki cross-
[
7]
(ETMs) for organic light-emitting diodes (OLEDs). Further-
coupling between the tribromide 4 and an excess of boronic
acid G1-B(OH)2 or G2-B(OH)2 using Pd(OAc)2:2P(o-tolyl)3 as
a catalyst afforded the desired star-burst dendrimers 1 and 2,
respectively, in excellent or moderate yield.
more, carbazoles have high ionization potentials (IPs) and good
hole-transporting abilities, they have thus been used to construct
[8]
functional materials for applications in photoconductors,
photocopiers, and laser printers,[ as well as in OLEDs as
9]
hole-transportingmaterials(HTMs).[10] Withtheaimofcombin-
The thermal properties of these star-burst dendrimers were
examined by differential scanning calorimetry (DSC) and ther-
mogravimetric analysis (TGA) (Table 1). The decomposition
temperatures (Tdec) of the newly synthesized dendrimers 1 and 2
ingtheelectronandhole-transportingmoietiesintoonemolecule
and to continue our investigation into the structure–property cor-
relations of dendrimers,[
4d,e,11]
we report here the synthesis and
◦
are ∼600 C, which indicates that all the new dendrimers have a
functional properties of novel star-burst dendrimers constructed
with carbazoles as the peripheral hole-transporting moieties
and one triazine moiety as an electron-transporting central core.
veryhighthermalstability.Theglasstransitiontemperatures(Tg)
◦
of the newly synthesized dendrimers are 201 and 274 C, respec-
tively, and increase as the generation increases. On the other
hand, the DSC analyses further confirmed that all the dendrimers
form an extremely stable amorphous glass because neither melt-
ing transitions nor crystallization transitions were detected after
their glass transition temperatures.
In view of the electronic absorption spectra obtained in
chloroform, the absorption bands of the first generation den-
drimer 1 peaked at 344, 293, and 242 nm, while the absorption
bands of the second generation dendrimer 2 peaked at 312, 294,
and 243 nm, and its absorption maxima was remarkably blue-
shifted (ꢀ32 nm) as compared to the first generation dendrimer
1.This may be a result of the generation increase, which leads to a
poorer co-planarity of the resulting molecule. Furthermore, their
Results and Discussion
The strategy for the preparation of carbazole and triazine-based
dendrimers 1 and 2 is outlined in Scheme 1. The chemo-
selective Ullmann condensation of carbazole with 1-bromo-
4
1
7
-iodobenzene in the presence of metallic copper afforded
-bromo-4-carbazolyl-benzene (G1-Br) in an isolated yield of
1%. Transformation of the bromide G1-Br into correspond-
[
11]
ing boronic acid G1-B(OH)2 was then easily carried out in a
yield of 87% by lithium–bromide exchange at low temperature,
followed by reaction with trimethyl borate at room temperature
andsubsequentlyacid hydrolysis.Transformationofthebromide
©
CSIRO 2007
10.1071/CH07038
0004-9425/07/080603

6
04
M. J. Xiong, Z. H. Li, and M. S. Wong
I
Br
(
b)
NH
N
Br
N
B(OH)2
(a), 71%
87%
G1-Br
G1-B(OH)2
(c)
42%
N
I
G1-B(OH)2
d), 91%
(
b)
N
Br
2
G -B(OH)
N
Br
2
(
5
1%
I
3
G1
N
G2-Br
Br
N
N
N
G1-B(OH)2
(d), 98%
d), 47%
G2-B(OH)2
G1
G1
(
e)
N
N
1
Br
CN
6
7%
N
(
G2
Br
Br
4
N
N
N
G2
G2
2
◦
Scheme 1. Synthetic route to the new dendrimers. Reagents and conditions: (a) Cu, K2CO3, triglyme, N2, 180–200 C,
n
◦
◦
+
overnight; (b) (i) Bu Li, tetrahydrofuran, −78 C, 1 h; (ii) B(OCH3)3, −78 C to room temp., 2 h; (iii) H ; (c) I2, HIO4,
◦
◦
AcOH–H2SO4, CHCl3, 80 C, 3–4 h; (d) 5 mol-% Pd(OAc)2:2P(o-tolyl)3, 2 M K2CO3, toluene–methanol, N2, 75 C, overnight;
◦
(
e) CF3SO3H, dry CHCl3, 0 C to room temp., 24 h.
molar absorptivities increase with a generation increase (Fig. 1
the dendrimers are 3.1 and 5.6 ns, respectively, which are several
times greater than the linear analogues and in the nanosecond
timescale (Table 1), which indicates that emission mainly comes
from the singlet excited states and may possess partial property
of the triplet excited states.
em
and Table 1). Surprisingly, the emission maxima (λ
484 nm)
max
of the second-generation dendrimer 2 is remarkably red-shifted
em
max
(
ꢀ27 nm) as compared to the first generation dendrimer 1 (λ
4
57 nm) (Fig. 1 and Table 1). Upon excitation either at 290 nm,
∗
attributed to the n→π transition of the carbazole moiety, or at
To probe the redox properties of these star-burst dendrimers,
cyclic voltammetry performed in a three-electrode cell set-up
with 0.1 M Bu4NPF4 as a supporting electrolyte in CH2Cl2 was
carried out. The results are tabulated in Fig. 2 and Table 1.
The electrochemical behaviours of the dendrimer 1 exhibit one
reversible three-electrons anodic redox couple (E1/2 0.50 eV),
which corresponds to removal of electrons from the peripheral
carbazole moieties of the dendrons, and another irreversible one-
electron cathodic redox couple (E1/2 −1.80 eV) that corresponds
to injection of electrons to the triazine core to form radical tri-
cations and a single anion, respectively. On the other hand, the
second generation of dendrimer 2, except for exhibiting one
irreversible hexyl-electrons anodic redox couple (E1/2 0.47 eV),
which corresponds to removal of electrons from the peripheral
carbazole moieties of the dendrons, and another irreversible one-
electron cathodic redox couple (E1/2 −1.81 eV) that corresponds
∗
3
50 nm, which corresponds to the π→π transition of the con-
jugated π-system, the emission spectra obtained are identical.
This suggests that the energy or excitation can efficiently trans-
fer from the peripheral carbazole moiety to the central triazine
core. The energy transfer efficiencies (ETEs) of these dendritic
wedges are 64 and 75%, respectively, for 1 and 2 as estimated
by comparing the difference in intensity at the absorption max-
imum of the dendritic wedges of the absorption spectrum and
the fluorescence excitation spectrum.[ The fluorescence quan-
tum yields (ΦPL) measured in chloroform using quinine sulfate
monohydrate as a standard are 0.65 and 0.40, respectively, and
decrease as the generation increases. This indicates that the flu-
orescence of these dendrimers is weakened as the number of
generations increase, which leads to a poorer co-planarity of the
resulting molecule. Furthermore, the fluorescence lifetimes of
11]

Star-Burst Dendrimers
605
Table 1. Summary of physical measurements of dendrimers 1 and 2
A
λem [nm] ΦA,C
B
A,D
[ns] ETEA,E [%] HOMO [eV] E1/2F [eV] EgG [eV] TgH [ C] Tdec [ C]
◦ ◦
F
I
Dendrimer
λabs [nm]
τ
5
−1
−1
(
ε × 10 [M cm ])
1
344 (0.89)
457
484
0.65
0.40
3.07
64
75
−5.30
−5.27
0.50
−1.80
3.19
3.17
201
274
595
602
2
2
93 (1.17)
42 (1.34)
2
312 (1.60)
5.59
0.47
1.29
−1.81
2
2
94 (1.68)
43 (1.82)
A
Measured in CHCl3.
B
C
D
E
F
Excited at the absorption maxima.
Using quinine sulfate monohydrate (Φ313 0.48) as a standard.
Using nitrogen laser as excitation source.
ETE is determined by comparing the absorption maximium of the dendritic wedges of the absorption and fluorescence excitation spectra.
+
E1/2 versus Fc /Fc estimated by CV method using a platinum disk electrode as a working electrode, platinum wire as a counter electrode, and a SCE as a
+
reference electrode with an agar salt bridge connecting to the oligomer solution. All the potentials were calibrated with ferrocene, E1/2 (Fc/Fc ) = 0.45V
versus SCE.
G
Estimated from the edge of electronic absorption spectra.
Determined by differential scanning calorimeter from re-melt after cooling with a heating rate of 10 C min under N2.
H
I
◦
−1
◦
−1
Determined by thermal gravimetric analyzer with a heating rate of 10 C min under N2.
decrease with the generation increase, which indicates that a
better delocalization of electrons was carried out with the gener-
ation increase. The reduction potentials of these new dendrimers
are essentially unaffected by the generations of dendrimers as
the reduction occurs only at the central core. In general, with
an incorporation of triarylamine-based dendritic end-caps, the
HOMO energy level of the dendrimers increases to ∼5.30 eV
2
1
1
0
0
0
.0
.6
.2
.8
.4
.0
1
2
1.0
0.8
0.6
0.4
0.2
0.0
(
relative to the vacuum level) as estimated by the electrochem-
ical method. Such a high HOMO energy level greatly reduces
the energy barrier for the hole injection from ITO (φ = 5.0 eV)
to the emissive dendrimers. As a result, the dendrimers 1 and 2
[13,14]
can also be used as hole transport/injection materials.
2
50 300 350 400 450 500 550 600 650 700
Wavelength [nm]
Conclusions
Fig. 1. Absorption spectrum and emission spectrum of new dendrimers 1
and 2, measured in chloroform.
We have presented a facile approach for the synthesis of two
novel star-burst dendrimers constructed by carbazole as the
peripheral hole-transporting moiety and one triazine moiety
as an electron-transporting central core by palladium-catalyzed
Suzuki cross-coupling as a key reaction. We believe that this
approach will be applicable for the construction of other struc-
turally uniform and well-defined π-conjugated functional den-
dronized compounds. All of the dendrimers were characterized
1
2
8
4
0
1
2
1
13
Ϫ4
Ϫ8
by a combination of H NMR, C NMR, and matrix-assisted
laser desorption ionization time-of-flight (MALDI-TOF) mass
spectroscopy.[ These dendrimers exhibit very high thermal
andelectrochemicalstabilities.ThedetailsoftheOLEDs’perfor-
mance using these materials as hole transfer and emitting layers,
or as host materials for electrophosphorescent applications, will
be reported in the future.
15]
Ϫ12
Ϫ16
Ϫ20
Ϫ24
400 600 800 1000 1200 1400 1600 1800 2000
Potential [mV]
Experimental
General Procedures and Requirements
Fig. 2. Cyclic voltammograms of the dendrimers 1 and 2, measured in
CH2Cl2 (SCE as a reference electrode).
All the solvents were dried by standard methods wherever
needed. H NMR spectra were recorded using either a JEOL
1
to injection of electrons to the triazine core to form radical hexyl-
cations and a single-anion, respectively, still exhibits one other
irreversiblethree-electronanodicredoxcouple(E1/2 ≈ 1.29 eV),
which corresponds to removal of electrons from the interior
carbazole moieties to form radical tri-cations. Furthermore,
the first oxidation potentials of these new dendrimers slightly
JHM-EX270 FT NMR spectrometer or a Varian INOVA-400 FT
NMR spectrometer and are referenced to the residual CHCl3
at 7.24 ppm or dimethyl sulfoxide (DMSO) at 2.5 ppm. 13
C
NMR spectra were recorded using a Varian INOVA-400 FT
NMR spectrometer and were referenced to CDCl3 (77 ppm)
or (D6)DMSO (39.5 ppm). Mass spectrometry measurements

6
06
M. J. Xiong, Z. H. Li, and M. S. Wong
were carried out using fast atom bombardment (FAB) on
an API ASTAR Pulsar I Hybrid Mass Spectrometer. High-
resolution mass spectrometry was carried using MALDI-TOF
mass spectrometry. Thermal stabilities were determined by ther-
mal gravimetric analysis (PE-TGA6) with a heating rate of
(3 × 50 mL). The combined organic layer was dried over anhy-
drous Na2SO4 and evaporated to dryness.The crude product was
then purified by precipitating with petroleum spirits to afford the
desiredboronicacidasawhitesolid(3.73 g, 87%). δH (400 MHz,
(D6)DMSO) 8.27 (s, 2H), 8.25 (d, J 8.0, 2H), 7.59 (d, J 8.4, 2H),
7.41–7.46 (m, 4H), 7.27–7.31 (m, 2H). δC (100 MHz, CDCl3)
139.9, 138.5, 136.0, 126.3, 125.4, 122.8, 120.6, 120.1, 109.7.
◦ −1
1
0 C min under N2. The glass transitions and melting tran-
sitions were extracted from the second run DSC traces, which
were determined using a differential scanning calorimeter (PE
◦
−1
Pyris Diamond DSC) with a heating rate of 10 C min under
N2. Fluorescence spectra were recorded using a PTI Lumines-
cence Spectrophotometer, and the fluorescence quantum yield
in chloroform was determined by dilution method using qui-
nine sulfate monohydrate (Φ313 0.48) as a standard. The ETE
was determined by comparing the absorption maximium of the
dendritic wedges of the absorption and fluorescence excitation
spectra. The first ionization potential (Ip) was estimated by the
ꢀ ꢀ
-(3 ,6 -Diiodocarbazolyl)-1-bromobenzene 3
4
A mixture of 4-carbazolyl-1-bromobenzene 1 (1.75 g,
5.45 mmol), acetic acid (20 mL), water (2 mL), concentrated sul-
furic acid (2 mL), iodine (1.52 g, 6 mmol), iodic acid (2.05 g),
◦
and carbon tetrachloride (5 mL) was heated at 80 C for 6 h with
good magnetic stirring. After the product slurry was cooled
to room temperature, it was poured into water and extracted
with dichloromethane (3 × 50 mL). The combined dark purple
organic layer was decolorized with sodium sulfite, washed with
water, dried over anhydrous Na2SO4, filtered, and evaporated
to dryness. Purification of the crude product by silica-gel chro-
matography using petroleum spirits as eluent afforded the title
compound as a light-yellow solid in 42% yield. δH (400 MHz,
CDCl3)8.37(d, J1.6, 8H), 7.72(dd, J8.4, 2H), 7.65(d, J8.6, 2H),
7.35 (d, J 8.8, 2H), 7.09 (d, J 8.4, 2H). δC (100 MHz, CDCl3)
+
E1/2 versus Fc /Fc value, which was determined by a cyclic
voltammetric method (Voltammetric Analyzer CV-50W) using
a platinum disk electrode as a working electrode, platinum wire
as a counter electrode, and a SCE as a reference electrode with
an agar salt bridge connecting to the dendrimer solution dis-
solved in CH2Cl2 and using 0.1 M of Bu4NPF6 as a supporting
−
1
electrolyte with a scan rate of 100 mV s . The potential was
+
calibrated with ferrocene (E1/2 (Fc/Fc ) 0.43V versus SCE) as
1
8
39.8, 135.7, 135.0, 133.4, 129.4, 128.5, 124.5, 121.7, 111.7,
3.2. m/z (FAB) 575.2 (M + 1).
an external standard.
+
Synthetic Procedures and Physical Data for All
New Compounds
ꢀ
ꢀ
ꢀ
ꢀ
4-[3 ,6 -Di(4 -carbazolylbenzen-1 -yl)carbazolyl]-
-bromobenzene, G2-Br
1
4
-Carbazolyl-1-bromobenzene, G1-Br
A mixture of G1-B(OH)2 (495 mg, 1.72 mmol), compound
(449 mg, 0.78 mmol), palladium(ii) acetate (18 mg), tri-
o-tolylphosphine (48 mg), toluene (30 mL), methanol (15 mL),
and 2 M K2CO3 (4 mL) was stirred under an atmosphere of
A mixture of 1-bromo-4-iodobenzene (5.66 g, 20 mmol), car-
bazole (3.68 g, 22 mmol), copper bronze (1.28 g, 20 mmol), and
potassium carbonate (3.43 g, 25 mmol) in 20 mL of triglyme was
3
◦
stirred under inert atmosphere at 180–200 C for 24 h.After cool-
◦
nitrogen at 50 C overnight. After cooling to room tempera-
ing to room temperature, the solution was poured into cool water
and extracted with dichloromethane (3 × 50 mL). The combined
organic solution was washed with water, dried over anhydrous
sodium sulfate, filtered, and evaporated to dryness. The crude
product was purified by short silica-gel column chromatography
using petroleum ether as eluent to afford the desired product as a
white solid (4.29 g, 71% yield) and 1,4-bis(carbazolyl)benzene
as a white solid (1.41 g, 28%).
ture, the reaction mixture was poured into a large amount of
cool water and extracted with dichloromethane (3 × 50 mL).The
combined organic layers were dried over anhydrous Na2SO4
and evaporated to dryness. The crude product was then puri-
fied by silica gel column chromatography with petroleum
spirits/dichloromethane (2/1, v/v) as eluent to afford a yellow
solid with an isolated yield of 91% (571 mg). δH (400 MHz,
CDCl3) 8.53 (d, J 1.2, 2H), 8.16 (d, J 7.6, 4H), 7.95 (d, J 8.8, 4H),
.78–7.81 (m, 4H), 7.67 (d, J 8.8, 4H), 7.55 (d, J 8.8, 4H), 7.50 (d,
J 8.4, 4H), 7.41–7.45 (m, 4H), 7.28–7.32 (m, 4H). δC (100 MHz,
CDCl3) 140.9, 140.8, 140.7, 136.5, 136.4, 133.3, 133.1, 128.6,
127.4, 126.0, 125.9, 124.2, 123.4, 121.3, 120.3, 119.9, 119.1,
δH for G1-Br (400 MHz, CDCl3) 8.13 (d, J 8.00, 2H), 7.71–
7
7
.73 (m, 2H), 7.40–7.45 (m, 2H), 7.35–7.39 (m, 4H), 7.27–7.31
(
m, 2H). δC (100 MHz, CDCl3) 140.6, 136.8, 133.1, 128.7,
1
26.1, 123.5, 120.9, 120.4, 120.2, 109.5. m/z (FAB) 323.3
+
(
M + 1).
+
1
10.3, 109.9. m/z (FAB) 804.9 (M ).
δH for 1,4-bis(carbazolyl)benzene (400 MHz, CDCl3) 8.18
d, J 7.6, 2H), 7.81 (s, 4H), 7.56 (d, J 8.4, 4H), 7.47 (t, J 7.2, 4H),
(
ꢀ
ꢀ
ꢀ
ꢀ
7
1
.33 (t, J 7.8, 4H). δC (100 MHz, CDCl3) 140.7, 136.6, 128.3,
26.1, 123.5, 120.4, 120.3, 109.7. m/z (FAB) 408.5 (M ).
4-[3 ,6 -Di(4 -carbazolylbenzene-1 -yl)carbazolyl]
phenylboronic Acid, G2-B(OH)2
+
The synthetic procedure for G1-B(OH)2 was followed using
4
-Carbazolyl-1-bromophenylboronic Acid G1-B(OH)2
G2-Br (1.21 g, 1.5 mmol), n-butyllithium (1.5 mL, 2.25 mmol),
and trimethyl borate (0.27 mL, 2.25 mmol). The crude product
was then purified by silica gel column chromatography with
dichloromethane/ethylacetateasagradienteluenttoaffordayel-
low solid with an isolated yield of 51% (595 mg). δH (400 MHz,
(D6)DMSO) 8.95 (s, 2H), 8.32 (s, 2H), 8.27 (d, J 8.0, 4H), 8.15
(d, J 8.4, 6H), 7.96 (d, J 8.8, 2H), 7.78 (d, J 8.4, 4H), 7.73 (d,
J 8.0, 2H), 7.61 (d, J 8.0, 2H), 7.30–7.49 (m, 20H). δC (100 MHz,
CDCl3) 141.5, 141.0, 140.9, 140.6, 136.4, 136.2, 132.5, 128.6,
127.4, 125.9, 123.8, 123.4, 120.3, 119.9, 120.3, 119.9, 118.9,
116.8, 110.6, 109.9.
A 100 mL two-necked flask that contained G1-Br (4.83 g,
5 mmol) in 40 mL of dry tetrahydrofuran equipped with a
1
◦
magnetic stirrer was placed in a −78 C acetone–dry ice bath.
Under a nitrogen atmosphere, 1.5 M of n-butyllithium (11.3 mL,
1
8 mmol) was added dropwise while maintaining good stirring.
After stirring for 1 h, trimethyl borate (2.1 mL, 18 mmol) was
added. After stirring for another 2 h, water was first added to the
reaction mixture and then HCl (6 M) was added in a dropwise
fashion until an acidic solution was obtained. The reaction mix-
ture was poured into water and extracted with dichloromethane

Star-Burst Dendrimers
607
2
,4,6-Tri(p-bromophenyl)-1,3,5-triazine 4
[3] (a) A. Adronov, J. M. J. Fréchet, Chem. Commun. 2000, 1701.
The synthetic procedure in the literature[12] was followed.
doi:10.1039/B005993P
(
b) A. Adronov, S. L. Gilat, J. M. J. Fréchet, K. Ohta,
F. V. R. Neuwahl, G. R. Heming, J. Am. Chem. Soc. 2000, 122, 1175.
doi:10.1021/JA993272E
4] (a) P.-W. Wang, Y.-J. Liu, C. Devadoss, P. Bharathi, J. S. Moore, Adv.
Mater. 1996, 8, 237. doi:10.1002/ADMA.19960080311
(b) X. T. Tao, Y. D. Zhang, T. Wada, H. Sasabe, H. Suzuki,
T. Watanabe, S. Miyata, Adv. Mater. 1998, 10, 226. doi:10.1002/
2
1
,4,6-Tri(p-(4-carbazolyl-1-phenyl)phenyl)-
,3,5-triazine 1
[
To a mixture of compound 4 (164 mg, 0.30 mmol),
G1-B(OH)2 (388 mg, 1.35 mmol), palladium(ii) acetate (15 mg,
mol-%), and tri-o-tolylphosphine (41 mg, 10 mol-%) in a
00 mL round-bottom flask were added toluene (20 mL),
methanol(10 mL), anda 2 M aqueoussolutionofK2CO3 (3 mL).
The reaction mixture was stirred under an atmosphere of nitro-
5
1
(
(
(
SICI)1521-4095(199802)10:3<226::AID-ADMA226>3.0.CO;2-E
c) K. Katsuma, Y. Shirota, Adv. Mater. 1998, 10, 223. doi:10.1002/
SICI)1521-4095(199802)10:3<223::AID-ADMA223>3.0.CO;2-Q
◦
(d) C. C. Kwok, M. S. Wong, Macromolecules 2001, 34, 6821.
doi:10.1021/MA010749+
gen at 75 C for overnight. After cooling to room temperature,
the reaction mixture was poured into cool water and extracted
with dichloromethane (3 × 50 mL). The combined organic lay-
ers were dried over anhydrous Na2SO4, filtered, and evaporated
to dryness.The crude product was then purified by silica-gel col-
umn chromatography using petroleum spirits/dichloromethane
2/1, v/v) as eluent to afford a white solid (305 mg, 98% yield).
δH (400 MHz, CDCl3) 8.97 (d, J 8.8, 6H), 8.16 (d, J 7.6, 6H),
.96 (t, J 7.6, 12H), 7.72 (d, J 8.4, 6H), 7.51 (d, J 8.4, 6H), 7.44
t, J 7.6, 6H), 7.31 (t, J 7.0, 6H). δC (100 MHz, CDCl3) 171.4,
(
e) C. C. Kwok, M. S. Wong, Chem. Mater. 2002, 14, 3158.
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(
1
1
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(
1
(
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ꢀ ꢀ ꢀ
,4,6-Tri(p-(4-(3,6 -di(4 -carbazolylbenzen-1 -yl)
2
carbazolyl-1-phenyl)phenyl))-1,3,5-triazine 2
(
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The synthetic procedure of 1 was followed using com-
pound 4 (71 mg, 0.13 mmol), G2-B(OH)2 (400 mg, 0.52 mmol),
palladium(ii) acetate (6 mg), tri-o-tolylphosphine (16 mg), 2 M
K2CO3 (2 mL), toluene (20 mL), and methanol (10 mL). The
crude product was then purified by silica-gel column chromato-
graphy with dichloromethane/ethyl acetate (2/1, v/v) as eluent
to afford a yellow solid with an isolated yield of 47% (150 mg).
δH (400 MHz, CDCl3) 8.99 (d, J 8.4, 6H), 8.56 (s, 6H), 8.16 (d, J
[
[
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12H), 7.68(t, J7.2, 20H), 7.51(d, J8.0, 12H), 7.44(t, J7.2, 12H),
7.30 (t, J 7.8, 12H). δC (100 MHz, CDCl3) 171.2, 144.0, 140.9,
140.8, 139.4, 137.3, 136.3, 135.5, 132.9, 129.7, 129.0, 128.7,
128.5, 128.2, 127.4, 127.2, 125.9, 125.7, 124.3, 123.4, 120.3,
119.9, 119.0, 110.5, 109.8. Calc. for C183H114N12: 2480.9354.
1
(
8, 6194. doi:10.1021/CM062111O
d) N. D. McClenaghan, R. Passalacqua, F. Loiseau, S. Campagna,
B. Verheyde, A. Hameurlaine, W. Dehaen, J. Am. Chem. Soc. 2003,
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e) T. H. Xu, R. Lu, X. P. Qiu, X. L. Liu, P. C. Xue,
1
(
Found: 2480.9244.
C. H. Tan, C. Y. Bao, Y. Y. Zhao, Eur. J. Org. Chem. 2006, 4014.
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Acknowledgment
We are grateful to the Hong Kong Research Grants Council (HKBU
[11] Z. H. Li, M. S. Wong, Org. Lett. 2006, 8, 1499. doi:10.1021/
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12] J. Pang,Y. Tao, S. Freiberg, X.-P.Yang, M. D’Iorio, S. Wang, J. Mater.
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2
018/05P) for financial support of this work.
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