Facile synthesis of a new class of aggregation-induced emission materials derived from triphenylethylene

Article abstract of DOI:10.1039/c0jm00229a

A series of new aggregation-induced emission compounds with strong blue light-emitting properties derived from triphenylethylene were facilely synthesized by a Wittig-Horner reaction of bis(4-bromophenyl)methanone with diethyl 4-bromobenzylphosphonate, fo

Full text of DOI:10.1039/c0jm00229a

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Facile synthesis of a new class of aggregation-induced emission materials
derived from triphenylethylene
a
a
Bingjia Xu, Zhenguo Chi, Zhiyong Yang,a Jingbo Chen,b Shaozhi Deng,b Haiyin Li,a Xiaofang Li,a
*
b
a
Yi Zhang, Ningsheng Xu and Jiarui Xu
a
*
Received 31st January 2010, Accepted 18th March 2010
First published as an Advance Article on the web 15th April 2010
DOI: 10.1039/c0jm00229a
A series of new aggregation-induced emission compounds with strong blue light-emitting properties
derived from triphenylethylene were facilely synthesized by a Wittig–Horner reaction of bis(4-
bromophenyl)methanone with diethyl 4-bromobenzylphosphonate, followed by a Suzuki reaction with
arylboronic acids. Their maximum fluorescence emission wavelengths were 452–462 nm. The glass
transition temperatures ranged from 70–145 ꢀC, and the decomposition temperatures were 360–508 ꢀC.
The unoptimized device fabricated with benzofuranyl substituted compound as emitter turned on at ꢁ6
V, and the maximum luminance was ꢁ1500 cd mꢂ2
.
be the same in McMurry coupling reaction, otherwise there are
various products with self- or crossed reaction.
Introduction
Most p-conjugated organic molecules have a very high lumines-
cence efficiency in dilute solutions, but they exhibit relatively
weak or no emissions when fabricated into thin films. This is
because intra- and intermolecular interactions, such as p–p
interactions, quench the emission process.1 It is difficult to obtain
highly emissive materials in the solid state and also to make
optoelectronic devices because the organic emissive materials in
the devices are normally used as thin solid films, in which
aggregation is inherently accompanied with film formation.2 It is
thus highly desirable to develop electroluminescent materials that
can emit intense light in the solid state, which is expected to
overcome the aggregation quenching problem. Indeed, a few rare
examples, including silole derivatives, 1,1,2,2-tetraphenylethene
(TPE) derivatives and 1-cyano-trans-1,2-bis-(4-methylbiphenyl)-
ethylene (CN-MBE), have been recently found to show significant
enhancement in their light emission upon aggregation or in the
solid state.3 This intriguing phenomenon was named aggregation-
induced emission (AIE) by Tang et al.3a or aggregation-induced
emission enhancement (AIEE) by Park et al.3b Since then, AIE
materials have been found to be promising emitters for the
fabrication of highly efficient electroluminescent devices and
stimuli-responsive materials for use in multifunctional switches.4
However, discoveries of AIE materials are quite limited, and most
of them are silole-based compounds, which are complicated and
difficult to prepare. The double bonds of TPE derivatives were
synthesized by McMurry reaction with TiCl3 (or TiCl4) under
THF reflux for 20 h.3h However, the double bonds of triphenyl-
ethylene derivatives are introduced by Wittig–Horner reaction
which is milder and shorter time in relation to the McMurry
reaction; moreover, it is well-known that the two reactants must
Recently, a series of triphenylethylene carbazole derivatives
with strong blue light emission, high glass transition temperature
(Tg), and AIE effect were developed in our laboratory.5 The
twisted configuration of the three phenyl rings in triphenyl-
ethylene, due to the bulky carbazole group substituents, is
considered as one of the possible reasons for the AIE effect.
Here, we report a new class of triphenylethylene derivatives
with strong blue light emission and AIE effect. The derivatives
were easily prepared by a two-step reaction, including the Wit-
tig–Horner and Suzuki reactions. The photophysical, thermal,
AIE, electrochemical, and device properties were preliminarily
evaluated.
Results and discussion
Synthesis
Our strategy for the synthesis of this new series of triphenyl-
ethylene derivatives is outlined in Scheme 1. The key precursor,
4,40,400-(ethene-1,1,2-triyl)tris(bromobenzene)(VP3-Br3),
was
synthesized with a 87% yield from bis(4-bromophenyl)metha-
none with diethyl 4-bromobenzylphosphonate through the
aPCFM Lab and DSAPM Lab, OFCM Institute, State Key Laboratory of
Optoelectronic Materials and Technologies, School of Chemistry and
Chemical Engineering, Sun Yat-sen University, Guangzhou, 510275,
China. E-mail: chizhg@mail.sysu.edu.cn; xjr@mail.sysu.edu.cn; Fax:
+86 20 84112222; Tel: +86 20 84111081
bSchool of Physics and Physic Engineering, Sun Yat-sen University,
Guangzhou, 510275, China
Scheme 1 Synthetic routes to the desired compounds.
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Wittig–Horner reaction. Cross-coupling of the VP3-Br3 with the
corresponding arylboronic acids under Pd-catalyzed Suzuki
conditions afforded the products VP3-B3, VP3-T3, VP3-N3, VP3-
(TB)3, VP3-(BFu)3, VP3-(Bt)3, and VP3-(TA)3 in acceptable
yields from 42% to 74%. All compounds were characterized with
proton nuclear magnetic resonance (1H NMR), carbon nuclear
magnetic resonance (13C NMR), high-resolution mass spectros-
copy (MS), and Fourier transform infrared spectroscopy
(FTIR).
and 249 ꢀC, respectively. However, as can be seen, the fused ring
substituted derivatives, VP3-N3, VP3-(BFu)3, VP3-(Bt)3, and
VP3-(TA)3, have no crystallization and melting peaks but only
glass transition peaks. This indicates that the presence of the
fused ring units in these compounds effectively suppressed the
crystallinity and resulted in very little crystal formation when it
was cooled from the melting state. As such, it is expected to yield
better electroluminescent properties.
It is interesting to notice that VP3-B3 and VP3-(TB)3 have cold
crystallization peaks at 123 and 212 ꢀC, respectively, while VP3-
T3 showed no such peak. This indicates that the crystallization of
compound VP3-T3 occurred at a very fast speed, and there
existed no amorphous glassy phase after 10 ꢀC minꢂ1 cooling
from its melt. This is why there is no glass transition peak in its
heating DSC curve. To try to obtain an amorphous glassy phase,
the VP3-T3 melt was quenched by liquid nitrogen. As expected, in
theꢀfirst heating run, there existed a clear glass transition peak at
76 C. However, in the second heating run, the glass transition
peak could not be observed (Fig. 2). It is very interesting that
there are two small cold crystallization peaks at 115 ꢀC and
Thermal properties
The thermal properties of these compounds were investigated by
differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA) and are summarized in Table 1. The DSC curves
for the samples recorded during the second heating runs at a scan
rate of 10 ꢀC minꢂ1 are shown in Fig. 1 (first heating–cooling run:
ꢀ
the compounds were heated to 300 C and then cooled to room
temperature both at 10 ꢀC minꢂ1 rates). It can be seen that all the
compounds, with the exception of VP3-T3, exhibited a glass
transition peak. The Tg values of the compounds ranged from
ꢀ
167 C, respectively. But, the endothermic enthalpy of melting
ꢀ
peak is obviously larger than the sum of exothermic enthalpy of
70–145 C. The Tg of the compound VP3-(TA)3 was the highest
ꢀ
(145 C) due to the bulky thianthrenyl group. All the Tg values
were much higher than that of 1-methyl-1,2,3,4,5-pentaphe-
ꢀ
nylsilole (MPPS, 54 C) and 1,1,2,3,4,5-hexaphenylsilole (HPS,
65 ꢀC), the two typical AIE-active compounds reported.6
The DSC curves of the phenyl substituted derivatives, VP3-B3,
VP3-T3, and VP3-(TB)3, show strong melting peaks at 198, 227
Table 1 Thermal properties of the compounds
Tg/ꢀC
Tm/ꢀC
Td/ꢀC
VP3-B3
VP3-T3
VP3-(TB)3
VP3-N3
VP3-(BFu)3
VP3-(Bt)3
VP3-(TA)3
70
76a
119
95
124
134
145
198
227
249
N/A
N/A
N/A
N/A
361
376
376
427
495
508
494
a
Obtained from heating DSC curve of the sample prepared by quenching
from its melt.
Fig. 2 DSC heating curves for VP3-T3 samples obtained: (1) melt
quenched by liquid nitrogen; (2) after first heating run, the melt was
cooled to room temperature at 10 ꢀC minꢂ1
.
Fig. 1 DSC curves for the compounds at a scan rate of 10 ꢀC minꢂ1
(second heating scan).
Fig. 3 TGA curves of the compounds.
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the two cold crystallization peaks. This result also indicates that
the speed of crystallization of VP3-T3 was very fast and there
were large quantity of crystals formed even though the liquid
nitrogen was used to freeze its melt.
units that hindered the intermolecular interaction that tended to
decrease the planarity of the molecules. This suggested that the
substitution of the fused rings did not bring great changes to the
conjugation of the molecular structure.
The decomposition temperature (Td) here is defined as the
temperature at which 5% weight loss occurs during heating in
nitrogen. As shown by the TGA curves presented in Fig. 3, the
compounds were highly stable since they started to decompose at
361–508 ꢀC. The Td values of the compounds were also much
higher than those of the ꢀreported AIE-active compounds MPPS
The quantum yields (FFL) of the compounds in THF with
9,10-diphenylanthracene as the standard (FFL ¼ 90%) ranged
from 0.6 to 1.6%. However, the FFL determined in cyclohexane
was in a range of 17.4 to 35.5%. 15- and 33-fold increases in FFL
when compared to those of THF solutions and cyclohexane
solutions, respectively.
(309 C) and HPS (351 C).10 The fused ring substituted deriv-
ꢀ
atives displayed good thermal stability with Td over 427 ꢀC. The
amounts of carbonized residues (char yield) of VP3-(BFu)3, VP3-
(Bt)3, and VP3-(TA)3 were 22, 38, and 49%, respectively, at
900 ꢀC in nitrogen. These are much higher than those of the non-
heteroatom containing compounds: VP3-B3, VP3-T3, VP3-(TB)3,
and VP3-N3. The high char yields of these compounds can be
ascribed to their heterocyclic units.
AIE properties
Almost no PL signal could be detected from a dilute solution of
the compounds in tetrahydrofuran (THF). The corresponding
emission spectra of compound VP3-T3 in aqueous THF with
different water/THF ratios are shown in Fig. 4. The emission
from the THF solution of VP3-T3 was so weak that almost no PL
signal was recorded. However, a dramatic enhancement in
luminescence was observed for the ꢁ70 : 30 (v/v) water/THF
mixture. While the PL intensity in THF was only 20, it was
boosted to 895 in 90 : 10 (v/v) water/THF. Similar effects were
Optical properties
The optical properties of the compounds in tetrahydrofuran
(THF) solution and in TLC thin film were investigated by UV-vis
and photoluminescence (PL) spectroscopy. As shown in Table 2,
the UV maximum absorption wavelengths of the compounds
were in the range of 330–345 nm. Clearly, the fused ring units had
only a little influence on the maximum absorption wavelength.
The maximum absorption wavelengths of VP3-N3 and VP3-
(TA)3 were 331 and 330 nm, respectively. These were especially
shorter than those of the three phenyl substituted derivatives:
VP3-B3, VP3-T3, and VP3-(TB)3.
The PL spectra of the compounds showed maxima at 454–
467 nm in THF solution and at 452–462 nm in solid thin film. As
such, it exhibited blue light emission. In the case of a solid thin
film, the maximum emission peaks of the phenyl-substituted
derivatives were slightly red-shifted (1–5 nm) compared to the
case of the solution. It indicates that the intermolecular inter-
action of the derivatives increased the planarity of the molecules
in the solid state, which resulted in red-shifts of the PL spectra.
On the other hand, the maximum emission peaks of the fused
ring-substituted derivative films were slightly blue-shifted (3–
6 nm) compared with their respective solutions. The blue-shifts
could be attributed to the steric effects of the bulk fused ring
Fig. 4 PL spectra of VP3-T3 in water/THF mixtures. The inset depicts
the changes in PL peak intensity.
Table 2 Optical properties of the compounds
em
max
l
/nm
FFL (%)
abs
max
l
/nm
a
b
c
d
e
VP3-B3
VP3-T3
VP3-(TB)3
VP3-N3
VP3-(BFu)3
VP3-(Bt)3
VP3-(TA)3
338
342
342
331
345
340
330
454
454
459
455
467
462
457
456
459
460
452
462
456
453
0.6
0.9
1.6
1.1
1.0
1.4
1.0
17.4
21.2
24.8
17.9
33.5
35.5
17.8
a
b
In THF. In THF. TLC thin film. Fluorescence quantum yields
c
d
Fig. 5 The emission images of VP3-T3 in pure THF (a), H2O 90% (b),
and TLC thin film (c) under UV light (365 nm) illumination at room
temperature.
e
measured in THF solution. Fluorescence quantum yields measured in
cyclohexane solution using 9,10-diphenylanthracene as standard.
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observed for the other compounds. The emission images of VP3-
T3 in pure THF, 90 : 10 (v/v) water/THF, and TLC solid thin film
under UV light (365 nm) illumination at room temperature are
shown in Fig. 5. As can be clearly seen, the THF solution of VP3-
T3 showed a rather weak fluorescence. However, the compound
in high water fractions of water/THF mixture or in solid thin film
exhibited very strong fluorescence.
The absorption spectra of VP3-T3 in the water/THF mixtures
are shown in Fig. 6. The spectral profile was virtually unchanged
when up to ꢁ30% water was added to the THF solution. When
the water fraction was further increased, the whole spectrum
started to rise. The increase in the absorbance in the whole
spectral region was due to light scattering of the nano-aggre-
gates, which effectively decreased the light transmission through
the mixtures.7 The abrupt broad change in the shape of the
absorbance from 70% water fraction agreed well with the sudden
jump in the PL intensity and the quantum yield shown in Fig. 4
and Table 3. These results confirm that the VP3-T3 molecules
started to markedly aggregate when >60% of the poor solvent
(water) was added to the THF solution.
Fig. 7 Effect of temperature on the PL relative peak intensity of the
compounds and DPA in THF.
volume fraction of water in the water/THF mixture was
increased to 90%, the FFL of VP3-T3 rose to 23%, which was
about 25-fold higher than that in THF. However, to the same
water fraction, the FFL of VP3-B3 was only six-fold higher than
that in the THF solution. The above results indicate that the
compound molecules started to aggregate markedly when the
volume fraction of water reached 60%. Since water is a non-
solvent of these compounds, the molecules must have aggregated
in the water/THF mixtures with higher contents of water. This
proves that the emissions were induced by aggregation of the
derivatives.
In order to have a quantitative estimation of the AIE process,
the photoluminescent quantum yields (FFL) were calculated for
the derivatives in mixtures of water and THF in various
proportions using 9,10-diphenylanthracene (DPA) as the stan-
dard. As can be seen from Table 3, the FFL values of the THF
solutions were very low and almost unchanged when water was
added up to 60% (v/v), but it started to increase swiftly upon
addition of 70% (v/v) water. However, the extent of the increase
was not the same for each compound. For example, when the
The effect of temperature on the PL relative peak intensity of
the compounds in dilute THF solutions (10ꢂ5 mol Lꢂ1) is shown
in Fig. 7. It can be seen that the relative peak intensity of DPA
remained almost unchanged with the temperature increased from
77 K. In contrast, all of the new compounds had dramatic
decreases near the melting point of THF (Tm z 165 K).
However, the extent of the decrease was not the same for each
compound. The PL peak intensities of VP3-B3, VP3-T3, VP3-
(TB)3, VP3-N3, VP3-(BFu)3, VP3-(Bt)3, and VP3-(TA)3 near the
Tm were about 159-, 112-, 51-, 153-, 34-, 19-, and 64-fold higher
than those at room temperature, respectively. The extent of the
decrease seems closely related to the size of substituent because it
is well known that a large substituent rotates with more difficulty
than a small substituent due to steric effects. Furthermore, the
AIE effects of frozen compound molecules in the solid are similar
to the effects of aggregation in liquid because of the restriction on
the rotation of groups. Among the three substituents, phenyl,
tolylene, and p-tert-butylphenyl, the phenyl group was the
smallest and the p-tert-butylphenyl group was the biggest, which
results in the following decreasing order of PL peak intensities:
VP3-B3 (159-fold), VP3-T3 (112-fold), VP3-(TB)3 (51-fold). In
addition, among the fused ring substituents, the naphthyl group
was the smallest, and thus the extent of the decrease in VP3-N3
was the highest.
Fig. 6 UV absorption spectra of VP3-T3 in water/THF mixtures with
different volume fractions of water.
Table 3 PL quantum yields (FFL) of the compounds in mixtures of
water and THF in various proportions
H2O (%)
0
10
30
50
60
70
80
90
VP3-B3
VP3-T3
VP3-(TB)3
VP3-N3
VP3-(BFu)3
VP3-(Bt)3
VP3-(TA)3
0.6
0.9
1.6
1.0
1.0
1.4
1.1
0.6
0.9
1.5
1.0
1.1
1.4
1.0
0.6
0.9
1.7
1.1
1.2
1.6
1.0
0.6
0.9
1.7
1.3
1.3
1.8
1.0
0.7
0.9
31
1.4
1.4
2.3
2.2
1.1
22
35
2.7
5.1
2.5
5.3
0.8
17
12
1.9
3.8
2.0
2.4
3.8
23
23
11
19
22
9.3
Electrochemical properties and electronic structure of the
derivatives
It is well known that the highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO),
which are connected to the redox potentials, are two important
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Fig. 9 The energy level diagram of ITO/NPB/VP3-(BFu)3/Alq3/LiF/Al.
(The energy levels except VP3-(BFu)3 were from literature.9)
Fig. 8 CV curve of VP3-T3 in CH2Cl2.
Table 4 Energy levels of the molecular orbitals and band gaps of the
compounds
HOMO/eV
LUMO/eV
DEg/eV
VP3-B3
VP3-T3
VP3-(TB)3
VP3-N3
VP3-(BFu)3
VP3-(Bt)3
VP3-(TA)3
5.58
5.53
5.57
5.65
5.61
5.66
5.54
2.36
2.33
2.37
2.40
2.47
2.46
2.25
3.22
3.20
3.20
3.25
3.14
3.20
3.29
parameters for electroluminescence materials. This is on account
of their relationship with the hole-/electron-injecting ability in
organic light emitting diodes (OLEDs). In order to measure the
HOMO levels of the synthesized compounds, cyclic voltammetry
(CV) analyses were carried out. As an example, the CV curve of
VP3-T3 is shown in Fig. 8. The HOMO energy levels were
obtained using the oxidation potential. The energy band gaps
(DEg) of the compounds were estimated from the onset wave-
length of their UV absorptions. The LUMO energy levels were
obtained by using the HOMO energy and the energy band gap
(DEg ¼ HOMO ꢂ LUMO). The HOMO, LUMO, and DEg
values are listed in Table 4. The DEg values of the compounds
were found to be in the range of 3.14–3.29 eV. Compounds VP3-
(BFu)3 and VP3-(TA)3 exhibited the narrowest energy band gap
and the widest energy band gap, respectively. The HOMO values
ranged from 5.53 to 5.66 eV. Compound VP3-T3 had the lowest
HOMO level and VP3-(Bt)3 had the highest HOMO level. The
LUMO values ranged from 2.25 to 2.47 eV. VP3-(TA)3 possessed
the lowest LUMO level and VP3-(BFu)3 possessed the highest
LUMO level.
Fig. 10 Current–voltage–luminance characteristics of the device (inset:
the image was taken at 10 V voltage).
transporting layer. LiF was used between the electron-trans-
porting layer and cathode Al to enhance electron injection, and
indium-tin oxide (ITO) coated glass was used as the substrate
and anode. The energy level diagram of the device is shown in
Fig. 9.
The current–voltage–luminance characteristics of the unopti-
mized device without packaging are presented in Fig. 10. The
turn-on voltage, which is defined as the voltage when the lumi-
nance is 1 cd mꢂ2, was 6.0 V, and a luminance of ꢁ1500 cd mꢂ2
was obtained at 17 V.
Device fabrication and electroluminescence properties
The strong blue light emission and high thermal stability of the
compounds prompted us to use them to construct electrolumi-
nescence devices. As an example, a multilayer electrolumines-
cence device, ITO/NPB/VP3-(BFu)3/Alq3/LiF/Al, was fabricated
using
vapor
deposition
processes.
4,40-Bis(1-naph-
thylphenylamino)biphenyl (NPB) was used as the hole-trans-
porting layer, and VP3-(BFu)3 as the emitting layer,
8-hydroxyquinoline aluminium (Alq3) as the electron-
Fig. 11 Electroluminescence spectrum of the device.
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The electroluminescence (EL) spectrum of VP3-(BFu)3 was
shown in Fig. 11. Comparison of the EL spectrum with PL
emission spectrum of the compound on TLC plate showed that
the profiles of the EL band and the PL band were similar with
about 12 nm red-shift for the EL peak (474 nm) compared with
that of the PL peak (462 nm).
concentrations of all samples were adjusted to 10 mM after
adding Ultra-pure water.
Cyclic voltammetry (CV) measurement was carried out on
a Shanghai Chenhua electrochemical workstations CHI660C in
a three-electrode cell with a Pt disk working electrode, a Ag/AgCl
reference electrode, and a glassy carbon counter electrode. All
CV measurements were performed under an inert argon atmo-
sphere with supporting electrolyte of 0.1 M tetrabutylammonium
perchlorate (n-Bu4NClO4) in dichloromethane at a scan rate of
100 mV sꢂ1 using ferrocene (Fc) as standard. The HOMO energy
levels were obtained using the onset oxidation potential from the
CV curves. The lowest unoccupied molecular orbital/highest
occupied molecular orbital (LUMO/HOMO) energy gaps, DEg,
for the compounds were estimated from the onset absorption
wavelength of UV-vis absorption spectra.
Extended investigation and further optimization on the elec-
troluminescence devices based on the new series AIE compounds
are being carried out in our laboratory and will be reported in
due course.
Conclusions
We have developed a new class of AIE compounds, composed of
triphenylethylene derivatives. The compounds exhibit a strongly
enhanced emission in the aggregated state. The derivatives are all
blue light emitters, and their maximum fluorescence emission
wavelengths are 452–462 nm. The glass transition temperature
range is from 70 to 145 ꢀC, and the decomposition temperatures
Synthesis of VP3-Br3
A solution of bis(4-bromophenyl)methanone (5.00 g, 14.7 mmol)
and diethyl 4-bromobenzylphosphonate (4.50 g, 14.7 mmol) in
anhydrous THF (200 mL) was stirred under an argon atmo-
sphere at room temperature. And then potassium tert-butyloxide
(1.97 g, 17.6 mmol) was added and the mixture was stirred for
2 h. The reaction mixture was concentrated and purified by silica
gel column chromatography using n-hexane as eluent. And
ꢀ
(5% weight loss) are in the range of 360–508 C, both of which
are higher than those of the silole derivatives ever reported in the
literature. The compounds were used to construct electrolumi-
nescence devices. One such device containing VP3-(BFu)3
exhibits a turn-on voltage of 6.0 V and a luminance of
ꢁ1500 cd mꢂ2. It gave a considerable performance without
further optimization of the device configurations.
1
a white powder was obtained with the yield of 87% (6.30 g). H
NMR (300 MHz, CDCl3) d (ppm): 7.42 (t, 4H), 7.25 (d, 2H), 7.10
(d, 2H), 7.00 (d, 2H), 6.85 (d, 2H), 6.83 (s, 1H); 13C NMR
(75 MHz, CDCl3) d (ppm): 141.72, 141.26, 138.48, 135.81,
132.30, 132.20, 131.57, 131.54, 131.19, 129.38, 128.20, 127.95,
122.28, 121.35; FTIR (KBr) n (cmꢂ1): 3022 (Ar and ]C–H
stretching), 1610, 1587, 1484, 822, 652; MS (EI), m/z: 492 ([M ꢂ
H]+, calcd for C20H13Br3, 493); Anal. Calc. for C20H13Br3: C
48.72, H 2.66, Br 48.62; found: C 48.70, H 2.68, Br 48.59%.
Experimental
All reagents and chemicals purchased from Alfa Aesar were used
as received. Tetrahydrofuran (THF) was distilled from sodium/
benzophenone. Ultra-pure water was used in the experiments.
All other solvents were purchased as analytical grade from
Guangzhou Dongzheng Company and used without further
purification. 1H NMR and 13C NMR were measured on
a Mercury-Plus 300 spectrometer with chemical shifts reported as
ppm (in CDCl3, TMS as internal standard). Mass spectra were
measured with Thermo spectrometers (MAT95XP-HRMS).
Elemental analysis was done with an Elementar Vario EL
Elemental Analyzer. Fluorescence spectra were determined with
a Shimadzu RF-5301PC spectrometer and the slit widths were
1.5 nm for excitation and 3 nm for emission except VP3-(TB)3
(excitation: 1.5 nm, emission: 1.5 nm). The fluorescence spectra
at low temperature were done with an Edinburgh Instruments
Ltd spectrometer (FLSP920). The Differential scanning calo-
rimetry (DSC) curves were obtained with a NETZSCH thermal
analyzer (DSC 204) at a heating rate of 10 ꢀC minꢂ1 under a N2
atmosphere. Thermogravimetric analyses (TGA) were per-
formed with a TA thermal analyzer (Q50) under a N2 atmo-
sphere with a heating rate of 20 ꢀC minꢂ1. The fluorescence
quantum yields (FFL) of all the compounds in THF or THF/
water mixture were evaluated using 9,10-diphenylanthracene as
the reference.8
General procedure for the synthesis of compounds VP3-B3, VP3-
T3, VP3-N3, VP3-(TB)3, VP3-(BFu)3, VP3-(Bt)3 and VP3-(TA)3
VP3-Br3 (0.30, 0.6 mmol) and the corresponding boric acid
(2.8 mmol) were dissolved in toluene (30 mL), and then 2 M
aqueous K2CO3 solution (1.5 mL) and 5 drops of Aliquat336
were added. The mixture was stirred for 45 min under an argon
atmosphere at room temperature. Then the Pd(Pph3)4 catalyst
(catalytic amount) was added and the reaction mixture was
stirred at 85 ꢀC for 16 h. After cooling to room temperature, the
product was concentrated and purified by silica gel column
chromatography using dichloromethane/n-hexane (v/v ¼ 1/3).
Yields of products: VP3-B3 53%; VP3-T3 56%; VP3-N3 64%; VP3-
(TB)3 71%; VP3-(BFu)3 42%; VP3-(Bt)3 62%; VP3-(TA)3 74%.
1
VP3-B3. H NMR (300 MHz, CDCl3) d: 7.71–7.53 (m, 10H),
7.50–7.28 (m, 15H), 7.18 (d, 2H), 7.09 (s, 1H); 13C NMR
(75 MHz, CDCl3) d (ppm): 142.54, 142.03, 140.83, 140.78,
140.71, 140.55, 140.35, 139.54, 136.59, 131.10, 130.24, 129.02,
128.94, 128.29, 128.05, 127.58, 127.45, 127.20, 127.04, 126.86;
FTIR (KBr) n (cmꢂ1): 3029 (Ar and ]C–H stretching), 1594,
1487, 1447, 845, 762,694; MS (EI), m/z: 484 ([M]+, calcd for
C38H28, 484); Anal. Calc. for C38H28: C 94.18, H 5.82; found: C
94.09, H 5.86%.
The THF–water mixtures with different water fractions were
prepared by adding Ultra-pure water slowly into the THF
solution of samples under ultrasound at room temperature. For
example, a 70% water fraction mixture was prepared by adding
7 mL Ultra-pure water into 3 mL of an appropriate concentra-
tion THF solution of sample in a 10 mL volumetric flask. The
4140 | J. Mater. Chem., 2010, 20, 4135–4141
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1
VP3-T3. H NMR (300 MHz, CDCl3) d: 7.62–7.41(m, 12H),
138.86, 137.04, 136.54, 136.47, 136.41, 136.12, 136.06, 135.71,
135.59, 135.29, 135.18, 135.13, 130.40, 130.24, 129.72, 129.40,
129.07, 128.67, 128.50, 127.95, 127.77, 127.51, 127.29; FTIR
(KBr) n (cmꢂ1): 3050(Ar and ]C–H stretching), 1605, 1574,
1507, 1439, 1384, 1108, 842, 747; MS (EI), m/z: 899 ([M]+, calcd
for C56H34S6, 899); Anal. Calc. for C56H34S6: C 74.79, H 3.81, S
21.39; found: C 74.74, H 3.86, S 21.33%.
7.41–7.25 (m, 6H), 7.25–7.22 (d, 2H), 7.19–7.11 (q, 4H), 7.03 (s,
1H), 2.39 (d, 6H), 2.36 (s, 3H); 13C NMR (75 MHz, CDCl3)
d (ppm): 142.32, 141.96, 140.42, 140.22, 139.44, 139.26, 137.97,
137.93, 137.86, 137.32, 137.19, 136.35, 131.06, 130.19, 129.72,
129.65, 128.23, 127.91, 127.32, 127.01, 126.87, 126.61, 21.54;
FTIR (KBr) n (cmꢂ1): 3029 (Ar and ]C–H stretching), 2921,
2856, 1620, 1500, 1447, 1396, 810; MS (EI), m/z: 526 ([M]+, calcd
for C41H34, 526); Anal. Calc. for C41H34: C 93.49, H 6.51; found:
C 93.44, H 6.58%.
Acknowledgements
The authors gratefully acknowledge the financial support from
the National Natural Science Foundation of China (Grant
numbers: 50773096, 50473020), the Start-up Fund for Recruiting
Professionals from ‘‘985 Project’’ of SYSU, the Science and
Technology Planning Project of Guangdong Province, China
(Grant numbers: 2007A010500001-2, 2008B090500196),
Construction Project for University-Industry cooperation plat-
form for Flat Panel Display from The Commission of Economy
and Informatization of Guangdong Province (Grant numbers:
20081203), and the Open Research Fund of State Key Labora-
tory of Optoelectronic Materials and Technologies.
1
VP3-N3. H NMR (300 MHz, CDCl3) d: 8.03–7.98 (q, 2H),
7.95–7.81 (m, 7H), 7.63–7.37 (m, 20H), 7.37–7.25 (q, 4H), 7.24 (s,
1H); 13C NMR (75 MHz, CDCl3) d (ppm): 142.37, 140.32,
140.20, 140.04, 139.49, 136.62, 134.01, 131.75, 131.66, 130.80,
130.57, 130.29, 130.01, 129.78, 128.53, 128.38, 127.94, 127.86,
127.71, 127.22, 127.14, 126.26, 126.15, 126.00, 125.61; FTIR
(KBr) n (cmꢂ1): 3036 (Ar and ]C–H stretching), 1589, 1500,
1447, 845, 800, 775; MS (EI), m/z: 634 ([M]+, calcd for C50H34,
634); Anal. Calc. for C50H34: C 94.60, H 5.40; found: C 94.57, H
5.44%.
VP3-(TB)3. 1H NMR (300 MHz, CDCl3) d: 7.61 (d, 4H), 7.55
(d, 4H), 7.50–7.30 (m, 14H), 7.12 (d, 2H), 7.05 (s, 1H), 1.37 (t,
18H), 1.34 (d, 9H); 13C NMR (75 MHz, CDCl3) d (ppm): 150.58,
150.50, 150.40, 142.27, 141.96, 140.34, 140.10, 139.34, 139.29,
137.97, 137.88, 137.82, 136.36, 131.02, 130.18, 128.18, 127.92,
127.37, 126.97, 126.82, 126.65, 125.96, 125.88, 34.93, 31.75;
FTIR (KBr) n (cmꢂ1): 3029 (Ar and ]C–H stretching), 2961,
2866, 1607, 1497, 1459, 1260, 1113, 822; MS (EI), m/z: 652([M]+,
calcd for C50H52, 652); Anal. Calc. for C50H52: C 91.97, H 8.03;
found: C 91.91, H 8.08%.
Notes and references
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S. K. Kwon, S. D. Jung and S. Y. Park, J. Am. Chem. Soc., 2002,
124, 14410; (c) J. W. Chen, C. C. W. Law, J. W. Y. Lam,
Y. P. Dong, S. M. F. Lo, I. D. Williams, D. B. Zhu and
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H. X. Shao, J. C. Ye, L. Tang and P. Lu, J. Phys. Chem. B, 2005,
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1
VP3-(BFu)3. H NMR (300 MHz, CDCl3) d: 8.08–7.88 (m,
9H); 7.88–7.70 (m, 4H); 7.68–7.53 (m, 8H), 7.53–7.29 (m, 12H),
7.21 (s, 1H); 13C NMR (75 MHz, CDCl3) d (ppm): 156.32, 153.57,
143.03, 142.41, 139.98, 137.06, 135.88, 135.02, 131.05, 130.21,
129.32, 128.86, 128.64, 128.50,128.26, 127.45, 126.92, 126.76,
125.56, 125.28, 125.18, 124.39, 123.48, 123.00, 120.90, 119.97,
119.83; FTIR (KBr) n (cmꢂ1): 3029 (Ar and ]C–H stretching),
1585, 1515, 1450, 1392, 1191, 840, 750; MS (EI), m/z: 754 ([M]+,
calcd for C56H34O3, 754); Anal. Calc. for C56H34O3: C 89.10, H
4.54; found: C 89.12, H 4.51%.
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VP3-(Bt)3. 1H NMR (300 MHz, CDCl3) d: 8.21–8.09 (m, 6H);
7.86–7.74 (m, 7H), 7.64–7.56 (m, 6H), 7.56–7.37(m,12H), 7.28 (d,
2H), 7.21 (s, 1H); 13C NMR (75 MHz, CDCl3) d (ppm): 142.91,
142.37, 140.13, 140.06, 139.75, 139.25, 138.83, 138.68, 138.59,
137.20, 136.89, 136.76, 136.48, 135.96, 131.14, 130.32, 128.99,
128.62, 128.44, 128.29, 128.17, 127.05, 125.36, 124.60, 122.86,
121.95, 120.77, 120.66; FTIR (KBr) n (cmꢂ1): 3057 (Ar and ]C–
H stretching), 1602, 1580, 1510, 1454, 1439, 1382, 795, 745; MS
(EI), m/z: 803 ([M]+, calcd for C56H34S3, 803); Anal. Calc. for
C56H34S3: C 83.75, H 4.27, S 11.98; found: C 83.77, H 4.25, S
12.01%.
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VP3-(TA)3. 1H NMR (300 MHz, CDCl3) d: 7.60 (d, 2H), 7.38–
7.26 (m, 14H), 7.24–7.13 (m, 6H), 7.13–7.03 (q, 2H); 13C NMR
(75 MHz, CDCl3) d (ppm): 142.40, 142.29, 139.85, 139.72,
This journal is ª The Royal Society of Chemistry 2010
J. Mater. Chem., 2010, 20, 4135–4141 | 4141