A multi-sensing fluorescent compound derived from cyanoacrylic acid

Article abstract of DOI:10.1039/b910718e

A new cyanoacrylic acid derivative of carbazole-triphenylethylene as a fluorescent probe has been synthesized and characterized. The derivative exhibits not only aggregation-induced effect (AIE) properties, but also interesting fluorescence multi-responses to solvents, water, ethanol and metal ions due to its chemical structure. Responses of the compound solution in DMF to water can be explained in terms of H-bond, multimer and AIE effects. In addition, the derivative was found to be highly sensitive to potassium ions. It is suggested that the compound has potential applications in chemosensors.

Full text of DOI:10.1039/b910718e

View Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/materials | Journal of Materials Chemistry
A multi-sensing fluorescent compound derived from cyanoacrylic acid
a
Xiqi Zhang, Zhiyong Yang, Zhenguo Chi,
a
ab
Meina Chen,a Bingjia Xu,a Chengcheng Wang,a Siwei Liu,a
*
a
Yi Zhang and Jiarui Xu
a
*
Received 1st June 2009, Accepted 8th October 2009
First published as an Advance Article on the web 9th November 2009
DOI: 10.1039/b910718e
A new cyanoacrylic acid derivative of carbazole-triphenylethylene as a fluorescent probe has been
synthesized and characterized. The derivative exhibits not only aggregation-induced effect (AIE)
properties, but also interesting fluorescence multi-responses to solvents, water, ethanol and metal ions
due to its chemical structure. Responses of the compound solution in DMF to water can be explained
in terms of H-bond, multimer and AIE effects. In addition, the derivative was found to be highly
sensitive to potassium ions. It is suggested that the compound has potential applications in
chemosensors.
Responses to water and ethanol
Introduction
The Cz2P4CA in dimethylformamide (DMF) showed interesting
Fluorescent chemosensors are of great value to pharmaceutics,
physiology, chemistry and environmental sciences due to their
selectivity and sensitivity for some chemical materials, which is
a fundamental goal for chemists.1 Very recently, aggregation-
induced emission (AIE) materials were used as fluorescent
chemosensors to detect DNA and proteins.2 AIE materials were
first reported by Tang et al. in 2001,3 which are contrary to
common fluorescent materials and are weakly fluorescent in
solution; however, they exhibit strong fluorescence upon aggre-
gation. Considering the introduction of the AIE effect to
fluorescent chemosensors, we synthesized an interesting
cyanoacrylic acid derivative that exhibits not only AIE
properties but also multi-sensing properties to many chemicals.
response sensitivities when water was added. Photoluminescence
(PL) emission wavelength and intensity of the solutions with
different water fractions (VH O%) are shown in Fig. 1(a). As
2
V
H O% increased, the change of PL emission wavelength
2
exhibited a 4-step process: first, a blue shift (VH O% < 2%), then
2
a red shift (VH O% ¼ 2–40%), followed by another blue shift
2
(VH O% ¼ 40–50%), and finally another red shift (VH O% > 50%).
2
2
A corresponding change in wavelength was also observed for PL
emission intensity: first enhanced (VH O% < 8%), then reduced
2
(VH O% ¼ 8–40%) again enhanced (VH O% ¼ 40–50%), and at
2
2
last reduced (VH O% > 50%).
2
To investigate whether the carboxyl group is a major
contributor to the above responses in Step 1 and 2, similar
experiments were done by using Cz2P4CE. As shown in Fig. 1(b),
with an increase of water fraction, the fluorescence emission
wavelength and intensity of Cz2P4CE exhibits a large difference
in comparison to Cz2P4CA. The fluorescence emission intensity
of Cz2P4CE in solution was very weak until the water fraction
increased to more than 25%. In the 25–50% water fraction
region, fluorescence emission intensity increased sharply by
Results and discussion
Synthesis
This new cyanoacrylic acid derivative Cz2P4CA (3-(40-(2,2-bis(4-
(9H-carbazole-9-yl)phenyl)vinyl)biphenyl-4-yl)-2-cyano acrylic
acid) was prepared by a Pd-catalyzed Suzuki coupling reaction of
an intermediate compound 9,90-(4,40-(2-(4- bromophenyl)ethene-
1,1-diyl)bis(4,1-phenylene))bis(9H-carbazole) (2)4 with 4-formyl
phenylboronic acid followed by Knoevenagel condensation with
cyanoacetic acid. As a reference compound, Cz2P4CE (3-(40-(2,2-
bis(4-(9H-carbazol-9-yl)phenyl) vinyl) biphenyl- 4-yl)-2-cyano-
acrylate), with an ethyl carboxylic group instead of a carboxylic
group in Cz2P4CA, was also synthesized. The chemical structure
and the synthetic routes to the two cyanoacrylic acid derivatives
are depicted in Scheme 1.
about 250-fold, reflecting
a notable AIE effect. Photo-
luminescence photos of Cz2P4CA and Cz2P4CE solutions in
DMF with varying water fractions under 365 nm UV irradiation
are shown in Fig. 2.
A schematic graph proposed for the 4-step changes is shown
in Fig. 3. In Step I, as it is known, DMF is an extremely good
H-bond acceptor and its electron donor capacity is even higher
than that of water. In other words, the H-bond between
Cz2P4CA and DMF is more stable. As the VH O% increased, the
2
strength of the H-bond between Cz2P4CA and DMF would
decrease because of competition with water, thus resulting in an
increase of the energy level of excitation and the occurrence of
a blue shift with enhanced intensity. This is typical intra-
molecular charge transfer (ICT) fluorescent probe character:
more stable H-bond complexes were formed to lower the energy
level upon excitation, which resulted in a red shift with reduced
intensity when returning to ground state.5 The effect in this step
aKey Laboratory for Polymeric Composite and Functional Materials of
Ministry of Education, Materials Science Institute, 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
bKey Laboratory of Designed Synthesis and Application of Polymer
Material, School of Chemistry and Chemical Engineering, Sun Yat-sen
University, Guangzhou, 510275, China
292 | J. Mater. Chem., 2010, 20, 292–298
This journal is ª The Royal Society of Chemistry 2010

View Online
Scheme 1 Synthetic routes of Cz2P4CA and Cz2P4CE.
Fig. 2 Photoluminescence of Cz2P4CA (a) and Cz2P4CE (b) in DMF
solutions with water fractions under UV irradiation (excited at 365 nm).
may be called the H-bond effect. Obviously, it was difficult to
find traces of H-bond interactions associated with Cz2P4CE.
In Step II, with an increase of water fraction, the solubility of
Cz2P4CA in mixed solvents decreased and led to an increase of
Cz2P4CA concentration in DMF, and resulted in the formation
of dimers or multimers of Cz2P4CA. The formation of dimers or
multimers is the possible reason for the red shift with reduced intensity.
Fig. 1 PL wavelength and intensity of (a) Cz2P4CA and (b) Cz2P4CE
(50mM) in DMF with varying amounts of water (% fraction of volume).
This journal is ª The Royal Society of Chemistry 2010
J. Mater. Chem., 2010, 20, 292–298 | 293

View Online
Fig. 3 Schematic graph for the 4-step changes in PL wavelength and intensity during water addition.
From Fig. 1(a), we see that when the water fraction was
increased from 2%, the wavelength has a red shift. Yet, PL
intensity did not decrease until the water fraction was more than
8%. It was suggested that the change in wavelength was more
sensitive than that of intensity. Further evidence was obtained
from the excitation spectrum (Fig. 4a): when the water fraction
was at or below 4%, there was no 450 nm peak; as the water
fraction reached 6%, the 450 nm peak likely reflected dimer
formation appeared in the excitation spectrum. The peaks
appeared at ꢀ475 nm probably reflected multimer formation in
high water fraction (24% and 36%). In comparison, there are no
new peaks appeared in the excitation spectra of Cz2P4CE as the
increase of water fraction. 1H NMR spectra of the two
compounds in CDCl3 with varying concentrations (c ¼ 5, 0.5 and
0.05 mM) were carried out to prove the existence of molecular
association of carboxylic acid. As the concentration increased,
suspension was indeed composed of amorphous particles, which
was also observed for several AIE compounds in THF–water
mixtures.6 The wide angle X-ray diffraction patterns of the two
kinds of particles also showed to be different in some diffraction
bands as well as in crystallinity (Fig. 6), and need further detailed
identification.
1
fine H-NMR structures of Cz2P4CE could be still observed.
However, the 5 mM solution of Cz2P4CA did not present a fine
1H-NMR spectrum (Fig. 5). These different 1H-NMR behaviors
are thought to be related to the different chemical structures of
the compounds, because the carboxylic group in Cz2P4CA can
form intermolecular hydrogen bonds. Therefore, it is possible
that the intermolecular interactions promote molecular asso-
ciation through intermolecular hydrogen bonding to form mul-
timers. It is well known that the existence of multimer (a mixture
of dimer, trimer, tetramer,., etc.) will often result in the
disappearance of the fine structures of NMR spectra. The effect
of this step may be called the multimer effect.
In Step III, a blue shift with enhanced intensity of PL emission
was the consequence of AIE effect. In this region of water frac-
tion, Cz2P4CA would aggregate into suspension as crystal
particles, which led to a blue shift of PL emission at 470–490 nm.
The suspension was unstable and would form precipitates after
several minutes.
In comparison to Step III, the suspension formed in Step IV is
transparent and remained stable for months. This formation of
a suspension caused a red shift and a reduction in intensity. The
Fig. 4 Excitation spectrum changes of (a) Cz2P4CA and (b) Cz2P4CE
(50 mM) in DMF with varying amounts of H2O (% fraction of volume).
294 | J. Mater. Chem., 2010, 20, 292–298
This journal is ª The Royal Society of Chemistry 2010

View Online
Fig. 7 Fluorescence emission wavelength and intensity of Cz2P4CA (50
mM) in DMF with different ethanol fraction.
Solvent effects
To study the solvent effects on Cz2P4CA, the fluorescence spectra
of the compound in six common solvents at the same concen-
tration (10ꢁ5mol Lꢁ1, 50mM) were measured (Fig. 8). As shown in
Table 1, there are complicated interactions between Cz2P4CA
and different solvents. The maximum emission wavelength shifts
from 489 nm (in DMSO and DMF) to 547 nm (in CH2Cl2)
without following the variation of polarity of the solvents. On
the other hand, the fluorescence quantum yield was highest in the
dioxane (Dio) solution (0.11), and as high as ꢀ40 times in the
acetic acid (HAc) solution (0.0027). The emission wavelengths of
the solutions in DMF, DMSO, THF, HAc and CH2Cl2 shifted to
red as increasing the concentration. For example, the emission
wavelength of 0.5 mM DMF solution was 489 nm and increased
to 523 nm for the 50 mM DMF solution, showing a 34 nm red-
shift, the largest wavelength shift among the five solvents.
However, for the case of dioxane solution, the wavelength did
not change with the concentration.
Fig. 5 1H NMR spectra of CDCl3 solutions of Cz2P4CA and Cz2P4CE
at different concentrations.
The Cz2P4CA compound in DMF solution can also exhibit
a response to ethanol, but is quite different from that for water
(Fig. 7). By increasing ethanol fraction (Vethanol%), the fluores-
cence emission wavelength of Cz2P4CA exhibited a blue shift
(Vethanol% < 8%) and then a red shift (Vethanol% > 8%), while the
fluorescence intensity was enhanced the entire time under
experimental conditions.
Concentration effect
Fig. 9 shows the relationship between fluorescence emission and
concentration of Cz2P4CA in DMF solution. While fluorescence
intensity enhanced sharply by ꢀ10 times as the concentration
Fig. 6 WXRD patterns of the crystal and amorphous particles of
Cz2P4CA obtained from the Step III (a) and Step IV (b).
Fig. 8 Fluorescence emission spectra of Cz2P4CA (50 mM) in different
solvents.
This journal is ª The Royal Society of Chemistry 2010
J. Mater. Chem., 2010, 20, 292–298 | 295

View Online
Table 1 Fluorescence properties of Cz2P4CA in different solvents
Responses to metal ions
Responses of Cz2P4CA to various metal ions (M) were also
investigated. Here, the ions are provided from their acetates
(M(OAc)x, where x ¼ 1 for monovalent metal ion, and 2 for
divalent metal ion). As shown in Fig. 10(a), a blue shift was
observed upon addition of Cu2+, Ni2+, Co2+, Mn2+ and K+, while
a red shift of about 21 nm on addition of Zn2+. Among these
metal ions, the response for Zn2+ is an exceptional case probably
due to its d10 atomic orbital configuration. From Fig. 10(a), it can
be seen that the compound is particularly sensitive to K+ with
large slope. The Cz2P4CA and Cz2P4CE also showed remarkably
different responses for metal ion K+: there was a blue shift of
43 nm for Cz2P4CA while only a blue shift of 4 nm for Cz2P4CE
when adding 10 equivalent K+ (Fig. 10(b)).
solvent
DMF DMSO THF
Dio
HAc
CH2Cl2
a
b
em
max
l
(nm)
489
523
489
504
495
525
506
506
544
549
547
555
c
FFL
0.017
0.027
0.053 0.11
0.0027 0.066
a
0.5 mM. b 50 mM. c Fluorescence quantum yields, using 9,10-diphenyl-
anthracene as standard.
increased from 0.001 to 0.1 mM, there was a large red shift of
ꢀ 50 nm of the maximum emission wavelength (from 472 nm to
526 nm). It was clear that the compound had a sensitive
response to its concentration in the solution in this region. The
maximum emission wavelength had a slight red shift, and
intensity decreased after enhancing slowly to the maximum of
ꢀ0.6 mM.
As shown in Fig. 10(a), fluorescence quenching was observed
for Cz2P4CA upon addition of the above metal ions. The
following equation has often been used to describe the static
The cyanoacrylic acid moiety must play an important role in
these phenomena due to the carboxyl group being capable of
forming hydrogen bonds (H-bonds) with solvent molecules.
These H-bonds between Cz2P4CA and solvent molecules
change the energy level of the ground and excited states of the
Cz2P4CA molecule quite similarly to those of typical ICT
fluorescent probes.5b Meanwhile, the AIE moiety of the
Cz2P4CA molecule plays a unique role in these energy level
changes. Therefore, there are variations in both fluorescence
maximum emission wavelength and fluorescence intensity of
the spectra of Cz2P4CA in different solvents and concent-
rations.
7
quenching mechanism with good linearity:
log[(I0ꢁI)/I] ¼ log Ka + nlogC
where log is the common logarithm, C is the concentration of
metal ion in the mixture system, I0 is the PL intensity of the
Cz2P4CA in DMF solution without metal ion, I is the PL
intensity of the system while the concentration of metal ion is C,
Ka is the association constant and n is the association ratio.
As seen in Fig. 11, a good linearity between log[(I0ꢁI)/I]
and the logC was constructed (linear correlation coefficient
Fig. 10 PL wavelength changes of (a) Cz2P4CA (50 mM) in DMF with
increasing concentrations of metal ions (M(OAc)x); and (b) Cz2P4CA and
Cz2P4CE (50 mM) in DMF upon adding KOAc.
Fig. 9 (a) PL emission spectra and (b) PL peak wavelength and intensity
with varying concentration of Cz2P4CA in DMF solution.
296 | J. Mater. Chem., 2010, 20, 292–298
This journal is ª The Royal Society of Chemistry 2010

View Online
1H-NMR was measured on a Mercury-Plus 300 spectrometer
with chemical shifts reported as ppm (in CDCl3 or DMSO-d6,
TMS as internal standard). Mass spectra were measured on
a Thermo MAT95XP-HRMS spectrometer or a Thermo DSQ-
MS spectrometer. Elemental analyses were performed with an
Elementar Vario EL Elemental Analyzer. Fluorescence spectra
were determined on Shimadzu RF-5301PC spectrometer and the
slit width was 3 nm for both excitation and emission. The
fluorescent compounds and the metal ions of acetate were all
dissolved in DMF in proper proportion.
Synthesis of 1
To a stirred carbazole (25.0 g, 0.149 mol) in anhydrous DMF
(200 mL), t-BuOK (20.0 g, 0.178 mol) was added and heated to
60 ꢃC, followed by the addition of bis(4-fluorophenyl) metha-
none (14.8 g, 0.0678 mol). The reaction mixture was then heated
to 110 ꢃC for 12 h. The resulting mixture was poured into water
(500 mL) and filtered. Washed with water for 3 times and dis-
solved in CH2Cl2, dried over Na2SO4. The crude product was
recrystallized with acetone to give 1 (32.0 g, 92% yield). 1H NMR
(300 MHz, CDCl3) dppm: 7.36 (t, 4 H), 7.48 (t, 4 H), 7.58 (d, 4
H), 7.82 (d, 4 H), 8.19 (d, 8 H). MS (EI) calcd for C52H36N2, 512;
found, 512. Anal. Calc. for C52H36N2: C 86.69, H 4.72, N 5.46;
Found: C 86.75, H 4.81, N 5.39.
Fig. 11 Plot of log[(I0ꢁI)/I] vs. logC for different metal ions added into
Cz2P4CA (50 mM) in DMF.
Table 2 Data of Ka, n and R2 of different metal ions for Cz2P4CA
Ion
Ka/Mꢁ1
N
R2
Zn2+
Cu2+
Ni2+
Co2+
Mn2+
K+
51
148
117
224
123
1.82 ꢂ 104
0.51
0.66
0.51
0.56
0.49
0.90
0.995
0.998
0.987
0.998
0.996
0.997
Synthesis of 2
To a stirred solution of 1 (10.4 g, 0.0203 mol) and diethyl
(4-bromophenyl) methylphosphonate (6.20 g, 0.0203 mol) in
anhydrous THF (200 mL) at room temperature, t-BuOK (2.20 g,
0.0200 mol) was added under Ar gas. After stirred for 12 h at
room temperature, the resulting mixture was poured into ethanol
(400 mL) and filtered, washed with ethanol for 3 times and dried
to give 2 (12.6 g, 95% yield). 1H NMR (300 MHz, CDCl3) dppm:
7.05 (d, 2H), 7.11 (s, 1H), 7.27–7.57 (m, 16H), 7.58–7.71 (m, 6H),
8.10–8.24 (m, 4H) MS (EI) calcd. for C44H29N2Br 666, found
666. Anal. Calc. for C44H29N2Br: C 79.40, H 4.39, Br 12.00,
N 4.21; Found: C 79.31, H 4.42, Br 11.95, N 4.18.
R2: 0.995–0.998, see Table 2). According to the above equation,
the association ratio (n) of Zn2+, Cu2+, Ni2+, Co2+ and Mn2+ with
Cz2P4CA was obtained from 0.49 to 0.66 and thus the stoichio-
metric ratio between Cz2P4CA and these metal ions was 1 : 2.
However, for K+ n was 0.9, giving a 1 : 1 stoichiometric ratio
between Cz2P4CA and K+. The association constant, Ka, for K+
was 1.82 ꢂ 104 Mꢁ1, the highest amongst all the metal ions
studied here.
Conclusions
A fluorescent compound Cz2P4CA with AIE effect and inter-
esting fluorescence responses to water, ethanol and metal ions
has been synthesized and characterized. The special response of
the compound solution in DMF to water can be explained in
terms of H-bond, multimer and AIE effects. It was found that the
compound exhibits high sensitivity to K+ and a different
response to Zn2+. It is suggested that Cz2P4CA may be a pro-
mising fluorescent probe or chemosensor to investigate the
interactions between fluorescent molecules and various media.
Synthesis of 3
2 (3.30 g, 4.96 ꢂ 10ꢁ3 mol) and 4-formylphenylboronic acid
(0.750 g, 5.00 ꢂ 10ꢁ3 mol) were dissolved in the mixture of
toluene (20.0 mL), TBAB (1.00 g) and 2M potassium carbonate
aqueous solution (5 mL). The mixture was stirred at room
temperature for 0.5 h under Ar gas followed adding tetrak-
is(triphenylphosphine)palladium (0.0100 g, 8.70 ꢂ 10ꢁ6 mol) and
then heated to 90 ꢃC for 24 h. After that the mixture was poured
into water and extracted three times with ethyl acetate. The
organic layer was dried over anhydrous sodium sulfate. After
removing the solvent under reduced pressure, the residue was
loaded onto silica gel column with n-hexane–CH2Cl2 (1 : 1, v/v)
Experimental
Materials and Measurements
1
All reagents and chemicals were purchased from Alfa-Aesar
company and used as received. Analytical grade DMF was
purified by distillation under an inert nitrogen atmosphere.
Ultra-pure water was used in the experiments. All other solvents
as analytical grade were purchased from Guangzhou Dongzheng
Company and used without further purification.
as eluent to give 3 (1.90 g, 55% yield). H NMR (300 MHz,
CDCl3) dppm: 7.24 (s, 1H), 7.26–7.37 (m, 6H), 7.42–7.79
(m, 20H), 7.95 (d, 2H), 8.13–8.22 (m, 4H), 10.05 (s, 1H) MS
(EI) calcd. for C51H34N2O 690, found 690. Anal. Calc.
for C51H34N2O: C 88.67, H 4.96, N 4.06; Found: C 88.61, H 4.92,
N 4.03.
This journal is ª The Royal Society of Chemistry 2010
J. Mater. Chem., 2010, 20, 292–298 | 297

View Online
Synthesis of Cz2P4CA
Professionals from ‘‘985 Project’’ of SYSU, the Science and
Technology Planning Project of Guangdong Province, China
(Grant numbers: 2007A010500001-2, 2008B090500196), and
Construction Project for University-Industry cooperation plat-
form for Flat Panel Display from Department of Information
Industry of Guangdong Province (Grant numbers: 20081203).
3 (0.330 g, 4.78 ꢂ 10ꢁ4 mol), cyanoacetic acid (0.0800 g, 9.41 ꢂ
10ꢁ4 mol), and piperidine (20 drops) were added to 100 mL
acetonitrile. The mixture was refluxed for 20 h. Then the solvent
was removed and the residue was purified by column chroma-
tography with CH2Cl2–CH3OH (10 : 1, v/v) as eluent to give 4
1
(0.330 g, 91% yield). H NMR (300 MHz, DMSO-d6) dppm:
7.26–7.35 (m, 4H), 7.40–7.91 (m, 22H), 7.92–8.03 (m, 4H), 8.21–
8.31 (m, 4H); MS (FAB) calc. for C54H35N3O2 758, found 758;
Anal. Calc. for C54H35N3O2: C 85.58, H 4.65, N 5.54. Found: C
85.62, H 4.41, N 5.67.
Notes and references
1 (a) V. Amendola, L. Fabbrizzi, M. Licchelli, C. Mangano,
P. Pallavicini, L. Parodi and A. Poggi, Coord. Chem. Rev., 1999, 190;
(b) A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson,
A. J. M. Huxley, C. P. McCoy, J. T. Rademacher and T. E. Rice,
Chem. Rev., 1997, 97, 1515.
Synthesis of Cz2P4CE
2 (a) H. Tong, Y. Hong, Y. Dong, M. Haubler, J. W. Y. Lam, Z. Li,
Z. Guo and B. Tang, Chem. Commun., 2006, 3705; (b) Y. Dong,
J. W. Y. Lam, A. Qin, Z. Li, J. Liu, J. Sun, Y. Dong and B. Tang,
Chem. Phys. Lett., 2007, 446, 124; (c) H. Tong, Y. Hong, Y. Dong,
3 (0.100 g, 1.45 ꢂ 10ꢁ4 mol), ethyl cyanoacetate (0.0400 g, 3.54 ꢂ
10ꢁ4 mol), and piperidine (10 drops) were added to 40.0 mL
acetonitrile. The mixture was refluxed for 20 h. Then the solvent
was removed and the residue was purified by column chroma-
tography with n-hexane–CH2Cl2 (1 : 2, v/v) as eluent to give 5
€
M. Haussler, Z. Li, J. W. Y. Lam, Y. Dong, H. H. Y. Sun,
I. Williams and B. Tang, J. Phys. Chem. B, 2007, 111, 11817; (d)
M. Wang, D. Zhang, G. Zhang, Y. Tang, S. Wang and D. Zhu,
Anal. Chem., 2008, 80, 6443.
1
(0.100 g, 88% yield). H NMR (300 MHz, CDCl3) dppm: 1.42
3 J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu, H. S. Kwok,
X. Zhan, Y. Liu, D. Zhu and B. Tang, Chem. Commun., 2001, 1740.
4 (a) Z. Yang, T. Yu, M. N. Chen, X. Q. Zhang, C. Wang, B. Xu,
X. Zhou, S. Liu, Y. Zhang, Z. Chi and J. Xu, Acta Polym. Sin.,
2009, 6, 62; (b) Z. Yang, Z. Chi, T. Yu, X. Zhang, M. Chen, B. Xu,
S. Liu, Y. Zhang and J. Xu, J. Mater. Chem., 2009, 19, 5541.
5 (a) Y. Sun, C. Zhong, R. Gong and E. Fu, Org. Biomol. Chem., 2008, 6,
3044; (b) S. Mahanta, R. B. Singh, S. Kar and N. Guchhait,
J. Photochem. Photobiol., A, 2008, 194, 318.
(t, 3H), 4.41 (d, 2H), 7.23 (s, 1H), 7.27–7.37 (m, 6H), 7.41–7.79
(m, 20H), 8.08 (d, 2H), 8.17 (d, 4H), 8.27 (s, 1H) MS (EI) calcd.
for C56H39N3O2 786, found 786. Anal. Calc. for C56H39N3O2: C
85.58, H 5.00, N 5.35; found C 85.61, H 4.98, N 5.31.
Acknowledgements
€
6 H. Tong, Y. Dong, M. Haußler, J. W. Y. Lam, H. Sung, I. Williams,
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
J. Sun and B. Tang, Chem. Commun., 2006, 1133.
7 X. Feng, C. Bai, Z. Lin, N. Wang and C. Wang, Chin. J. Anal. Chem.,
1998, 26, 154.
298 | J. Mater. Chem., 2010, 20, 292–298
This journal is ª The Royal Society of Chemistry 2010