Comparison of responsive behaviors of two cinnamic acid derivatives containing carbazolyl triphenylethylene

Article abstract of DOI:10.1007/s10895-010-0697-y

Two cinnamic acid derivatives (CPA and CPC) containing carbazolyl triphenylethylene moiety have been synthesized and characterized. The two derivatives possessed aggregation-induced emission property. They exhibited different and interesting responsive be

Full text of DOI:10.1007/s10895-010-0697-y

J Fluoresc (2011) 21:133–140
DOI 10.1007/s10895-010-0697-y
ORIGINAL PAPER
Comparison of Responsive Behaviors of Two Cinnamic Acid
Derivatives Containing Carbazolyl Triphenylethylene
Xi-qi Zhang & Zhen-guo Chi & Bing-jia Xu & Hai-yin Li &
Wei Zhou & Xiao-fang Li & Yi Zhang & Si-wei Liu &
Jia-rui Xu
Received: 8 April 2010 /Accepted: 22 June 2010 /Published online: 1 July 2010
#
Springer Science+Business Media, LLC 2010
Abstract Two cinnamic acid derivatives (CPA and
CPC) containing carbazolyl triphenylethylene moiety
have been synthesized and characterized. The two
derivatives possessed aggregation-induced emission prop-
erty. They exhibited different and interesting responsive
behaviors to solvents, water and metal ions. Considering
the structural differences between the two derivatives
resulting in different interactions between their molecules
and the various media was proposed as a possible
explanation for these observations. The intermolecular
interactions of CPC were much stronger than those of
CPA, which promoted molecular association through
intermolecular hydrogen bonding to form multimers. It
was found that CPC and CPA exhibited high sensitivity
to K+ and Mn2+, respectively. It is suggested that the
derivatives have potential technological applications in
chemosensor fields.
Introduction
Fluorescent chemosensors are receiving increasing attention
due to their potential applications in analytical chemistry,
the life sciences, medical analysis, and environmental
monitoring [1–7]. As a new class of fluorescent materials,
aggregation-induced emission (AIE) materials that are
highly luminescent in their aggregation states have attracted
much interest owing to their unique properties [8]. Tang et
al. have very recently employed a hexaphenylsilole deriv-
ative to detect DNA and proteins by making use of the AIE
phenomenon [9, 10].
Recently, a series of compounds containing triphenyl-
ethylene moiety with AIE properties and favorable thermal
stabilities have been developed in our laboratory [11, 12].
In order to improve the responsibility of the compounds to
better use as a chemosensor, we introduced the cinnamic
acid unit to the compounds and obtained cinnamic acid
derivatives. In our previous study, we have found that a
cinnamic acid derivative, CPC, exhibited interesting fluo-
rescence multi-responses to solvents, water and metal ions
[13]. In this paper, we will further report the different
responsive behaviors resulting from their special chemical
structures between CPC and the other derivative, CPA.
.
Keywords Cinnamic acid derivative Responsive
.
.
.
behavior Chemosensor Carbazolyl triphenylethylene
Aggregation-induced emission
Electronic supplementary material The online version of this article
(doi:10.1007/s10895-010-0697-y) contains supplementary material,
which is available to authorized users.
Experimental
Materials and methods
:
:
:
:
:
X.-q. Zhang Z.-g. Chi (*) B.-j. Xu H.-y. Li W. Zhou
:
:
:
X.-f. Li Y. Zhang S.-w. Liu J.-r. Xu (*)
PCFM Lab, DSAPM Lab, FCM 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
e-mail: xjr@mail.sysu.edu.cn
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 were analytical grade and purchased

134
J Fluoresc (2011) 21:133–140
from Guangzhou Dongzheng Company and used without
further purification. Intermediates 1 and 2 were synthesized
according to our previous procedure [11–13].
7.41–7.78 (m, 24H), 7.98 (d, 1H), 8.25 (q, 4H); 13C NMR
(125 MHz, DMSO-d6) δ ppm: 167.47, 143.27, 140.95,
140.82, 140.41, 140.02, 139.94, 138.82, 137.70, 136.34,
133.38, 131.64, 130.09, 129.87, 128.78, 128.63, 128.50,
127.36, 126.76, 126.51, 126.26, 122.77, 120.50, 120.10,
119.10, 109.65; IR (KBr) v: 3044, 1682, 1623, 1599, 1513,
1477, 1451, 1421, 1361, 1334, 1315, 1229, 1170, 835, 816,
748, 723 cm−1; MS (FAB) calcd. for C53H36N2O2 733,
found 733; Anal. Calc. for C53H36N2O2: C 86.86, H 4.95,
N 3.82. Found: C 86.81, H 4.92, N 3.79.
1H-NMR was measured on a Mercury-Plus 300 spec-
trometer and 13C-NMR spectra were recorded on a Varian
INOVA500NB 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. UV-Vis spectra were
obtained using a Shimadzu UV-Vis-NIR Spectrophotometer
UV-3150. Fluorescence spectra were determined on a
Shimadzu RF-5301PC spectrometer with a slit width of
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 the compound CPC
3 (0.33 g, 0.48 mmol), cyanoacetic acid (0.08 g, 0.94 mmol),
and piperidine (20 drops) were added to 100 mL acetonitrile.
The mixture was refluxed for 20 h. The solvent was then
removed and the residue was purified by column chromatog-
raphy with CH2Cl2/CH3OH (10:1, v/v) as eluent to give CPC
(0.33 g, 91% yield).1H NMR (300 MHz, DMSO-d6) δppm:
7.26–7.35 (m, 4H), 7.40–7.91 (m, 22H), 7.92–8.03 (m, 4H),
8.21–8.31 (m, 4H); 13C NMR (125 MHz, DMSO-d6) δppm:
163.19, 148.02, 141.67, 140.95, 140.56, 140.02, 139.94,
138.79, 137.39, 136.63, 136.36, 132.00, 131.64, 130.18,
130.12, 128.65, 128.47, 127.39, 126.81, 126.52, 126.42,
126.27, 122.78, 120.51, 120.11, 118.64, 109.66; IR (KBr) v:
3424, 3049, 2217, 1624, 1597, 1513, 1478, 1451, 1391,
1363, 1334, 1314, 1228, 1191, 1171, 835, 817, 750,
723 cm−1; 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.
Synthesis of compound 3
2 (3.3 g, 5 mmol) and 4-formylphenylboronic acid (0.75 g,
5 mmol) were dissolved in the mixture of toluene (20 mL),
TBAB (1 g) and 2 M potassium carbonate aqueous solution
(5 mL). The mixture was stirred at room temperature for
0.5 h under Ar gas, followed by addition of tetrakis
(triphenylphosphine)palladium (0.01 g) and then heated to
90 °C for 24 h. After this, 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 a silica gel column with n-hexane/ CH2Cl2
1
(1:1, v/v) as eluent to give 3 (1.9 g, 55% yield). H NMR
(300 MHz, CDCl3) δppm: 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 88.63, H 4.91, N 4.10.
Results and discussion
Synthesis
The two cinnamic acid derivatives were prepared according to
the synthesis route shown in Scheme 1. CPC was synthesized
according to our previous procedure [13]. The new com-
pound, CPA, was prepared with 3 and ethyl 2-(diethoxyphos-
phoryl)acetate by Wittig-Horner reaction. From Scheme 1, we
can see that CPA has a similar chemical structure to CPC,
except that the H in CPA is replaced by a cyano group in
CPC. Both structures include the dicarbazol-triphenylehtylene
moiety, which provides the unique AIE feature [11].
Synthesis of the compound CPA
To a stirred solution of 3 (0.45 g, 0.65 mmol)and ethyl 2-
(diethoxyphosphoryl) acetate (0.16 g, 0.71 mmol) in
anhydrous THF (10 mL) at room temperature, t-BuOK
(0.24 g, 2.14 mmol) was added under Ar gas. After stirred
for 12 h at room temperature, the resulting mixture was
acidified by 5 mL concentrated HCl and poured into 50 mL
water. And then, the mixture was extracted three times with
methylene chloride. The organic layer was dried over
anhydrous sodium sulfate. After removing the solvent
under reduced pressure, the residue was loaded onto a
silica gel column with CH2Cl2 /methanol (20:1, v/v) as
Responses to solvents
To study the responses of CPA and CPC to solvents, the
UV and photoluminescence (PL) spectra (Fig. 1S, 2S, in the
Supplementary Information) of the compounds were mea-
sured in five common solvents at the same concentration
(10−5 M), as summarized in Table 1. Table 1 shows that the
1
eluent to give 0.25 g yellow solid CPA (52% yield). H
NMR (300 MHz, DMSO-d6) δ ppm: 7.24–7.35 (m, 6H),

J Fluoresc (2011) 21:133–140
135
Scheme 1 Synthetic routes of
CPC and CPA
Br
N
H
N
O
Br
O
P(O)(OC2H5)2
N
N
F
F
t-BuOK, DMF
N
t-BuOK, THF
1
2
B(OH)2
Toluene, H2O,TBAB
K2CO3, Pd(PPh3)4
O
NC
COOH
O
NC COOH
N
N
N
N
CH3CN , piperidine
CPC
3
(1)
(2)
(C2H5O)2(O)P
COOCH2CH3
HCl, H2O
t-BuOK, THF
COOH
N
N
CPA
optical properties of both CPA and CPC did not monoton-
ically change with increasing solvent polarity (polarity order:
methylene chloride (MC) < tetrahydrofuran (THF) < dioxane
(DX) < N,N-dimethyl formamide (DMF) < dimethyl
sulfoxide (DMSO)) due to the existence of H-bond
interactions between the compounds and the solvents, except
MC. The maximum emission wavelengths for CPA and
CPC shifted from 463 nm (in DX) to 486 nm (in MC) and
from 474 nm (in DMF) to 547 nm (in MC), respectively. The
carboxylic acid moiety must play an important role in these
phenomena due to the carboxyl groups being capable of
forming hydrogen bonds (H-bonds) with solvent molecules.
Although the solvent responses were quite different, both of
the compounds exhibited the strongest emission in DX and
the most red-shifted emission in MC. It is known that MC
cannot form hydrogen bonds with carboxylic acids, thus, it is
possible that the carboxylic acid moieties form molecular
associations through intermolecular hydrogen bonding inter-
actions and may be responsible for the red-shift in emission
wavelength.
Responses to water
CPA and CPC showed interesting responsive sensitivities
when water was added into their solutions in DMF (Fig. 3S,
in the Supplementary Information). PL emission wave-
lengths and fluorescence images of the solutions with
different water fractions (VH2O%) are shown in Figs. 1 and
2, respectively. As VH2O% increased, the changes in PL
emission wavelength exhibited a 3-step (redshift-blueshift-
Table 1 Optical properties of
CPA/CPC in different solvents
lambasx(nm)
lemmax(nm)
lemxax(nm)
a
PL(a.u.)
CPA
ΦFL
CPA
CPC
CPA
CPC
CPC
CPA
CPC
CPA
CPC
MC
343
342
340
344
344
373
367
370
361
364
486
466
463
478
471
547
495
506
474
489
90
78
292
297
954
44
377
376
377
377
378
397
382
398
383
383
2.1
1.6
2.9
2.1
3.1
6.6
5.3
11
THF
DX
164
125
136
a Quantum yields (ΦFL) were cal-
culated on the basis of 9,10-
diphenylanthracene as standard
DMF
DMSO
1.1
2.7
133

136
J Fluoresc (2011) 21:133–140
488
540
530
520
510
500
490
480
470
association). To experimentally verify the existence of
molecular associations with carboxylic acid, absorption,
emission and excitation spectra of CPA and CPC were
recorded at a wide range of concentrations in DMF
solutions.
484
480
476
472
468
464
When investigating concentration responses on the
fluorescence emission of CPA and CPC in DMF solutions,
a remarkable modification in the fluorescence spectra was
observed as the concentration increased (Fig. 3 and Fig. 4S,
5S in the Supplementary Information), while the wave-
length of UV absorption (Fig. 6S, in the Supplementary
Information) changed very little. As the concentration of
CPC increased from 0.001 mM to 0.1 mM, there was larger
red shift (~50 nm, from 472 nm to 526 nm) in the maxima
emission wavelength than that of CPA (~13 nm, from
468 nm to 481 nm). It is clear that both compounds gave a
sensitive response to concentration in this concentration
range and that CPC is more sensitive than CPA. The
emission wavelength showed almost no change for CPA
when the concentration was higher than 0.1 mM. However,
for CPC, the wavelength gradually increased with concen-
CPA
CPC
0
20
40
60
80
100
V(H2O)/%
Fig. 1 PL emission wavelength of CPA and CPC (50 μM) in DMF
with different H2O fractions
redshift) or a 4-step (blueshift-redshift-blueshift-redshift)
process for CPA and CPC, respectively. The fluorescent
responsive behaviors of CPA and CPC, with rich color
changes in DMF and water mixtures, were probably caused
by the synergistic interaction between the compound
molecules and the media, such as the H-bond effect, the
effect of molecular associations with carboxylic acids and
the AIE effect. These results suggest that the compounds
are potential materials for use as probes to detect
intermolecular interactions.
484
200
480
150
476
Responses to concentrations
100
It is well known that two carboxylic groups can be
connected by hydrogen bonds to form dimers, trimers and
so on, up to multimers (commonly called a molecular
472
50
Wavelength
PL intensity
468
0
0.0
0.2
0.4
0.6
0.8
1.0
CPA / mM
300
530
520
510
500
490
480
470
250
200
150
100
50
Wavelength
PL intensity
0
0.0
0.2
0.4
0.6
0.8
1.0
CPC / mM
Fig. 2 Photographs of CPA (top) and CPC (bottom) (50 μM) in
Fig. 3 PL emission spectra of CPA (top) and CPC (bottom) in DMF
DMF with different H2O fractions
at different concentrations

J Fluoresc (2011) 21:133–140
137
250
200
150
100
50
tration over the entire concentration range. From the
excitation spectra (Fig. 4), it can be clearly seen that new
peaks appeared around 450–500 nm when the concentra-
tion of CPC was increased above 0.06 mM. However, no
new peaks appeared for CPA. These results imply that the
cyano group or the cyanoacrylic acid moiety in CPC plays
an important role.
It is well known that the emission wavelength of a
fluorescent molecule is independent of excitation wave-
length. Thus, it can be used for component qualitative
analysis according to the emission spectra obtained at
different excitation wavelengths. Figure 5 shows the
excitation spectra and fluorescence emission spectra of
CPA and CPC in DMF solution excited at different
wavelengths. The 0.1 mM solutions were excited by
398 nm, 410 nm and 435 nm and the 0.08 mM solutions
were excited by 402 nm, 410 nm and 435 nm, respectively.
CPA
emission
exicitation
0.1mM
ex:398(em:480)
ex:410(em:480)
ex:435(em:480)
0.08mM
ex:402(em:480)
ex:410(em:480)
ex:435(em:480)
0
300
400
500
600
700
Wavelength / nm
exicitation
emission
CPC
200
150
100
50
0.1mM
ex:410(em:520)
ex:398(em:517)
ex:435(em:528)
CPA / mM
240
0.001
0.005
0.01
0.08mM
ex:402(em:498)
ex:410(em:497)
ex:435(em:518)
0.02
0.04
0.06
0.08
0.1
0.2
0.4
0.6
180
120
60
0
300
400
500
600
700
Wavelength / nm
0.8
1.0
Fig. 5 PL excitation and emission spectra of CPA and CPC in DMF
(c=0.1 mM and 0.08 mM) by different excited wavelengths
0
300
350
400
450
Wavelength / nm
Although the CPA solutions were excited by different
wavelengths, the maximum emission wavelengths were the
same, 480 nm, which indicated that a single fluorescent-
emitting component was present at concentrations of either
0.1 mM or 0.08 mM. It can be also seen that the shapes of
the two excitation spectra were identical. However, for
CPC solutions, the maximum emission wavelengths
obtained under different excited wavelengths were different.
For 0.1 mM solution, under excitation at 398 nm, 410 nm and
435 nm, the maximum emission wavelengths obtained were
517 nm, 520 nm and 528 nm. For 0.08 mM solutions, under
excitation at 402 nm, 410 nm and 435 nm, they were 498 nm,
497 nm and 518 nm, respectively. On the other hand, the
shapes of the two excitation spectra were different. It can be
seen that new weak peaks at ~480 nm appeared in the
excitation spectrum of the 0.1 mM solution. The results
indicate that the fluorescent-emitting component was not
unique and it was thought that there existed various molecular
associations of carboxylic acids (dimers, trimers,…, multi-
mers or mixtures) in the solution.
CPC / mM
0.0001
0.001
0.005
0.01
0.02
0.04
0.05
0.08
0.1
300
200
100
0
0.2
0.4
0.6
0.8
1
250
300
350
400
450
500
550
Wavelength / nm
Fig. 4 Excitation spectra of CPA and CPC in DMF at different
concentrations

138
J Fluoresc (2011) 21:133–140
CDCl3
CPA
5mM
0.5mM
0.05mM
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
Fig. 8 Photographs of CPA (top) and CPC (bottom) (50 μM) in
DMF with 0.5 mM metal ions
CPC
CDCl3
5mM
0.5mM
0.05mM
1.5
K+
CPA
Zn2+
1.0
Cu2+
Ni2+
0.5
Co2+
0.0
Mn2+
-0.5
-1.0
-1.5
-2.0
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0
Fig. 6 1H-NMR of CPA and CPC in CDCl3 at different concentrations
1
Figure 6 shows the H-NMR spectra of the compounds
in CDCl3 at different concentrations (c=5, 0.5 and
0.05 mM). As the concentration increased, fine H-NMR
-5.5
-5.0
-4.5
logC
-4.0
-3.5
-3.0
1
structures of CPA could still be observed. However, the
5 mM solution of CPC did not present a fine H-NMR
0.6
0.3
1
Zn2+
Cu2+
Ni2+
CPC
Co2+
20
10
0.0
Mn2+
K+
Zn2+
Cu2+
Mn2+
K+
Co2+
Ni2+
0
-10
-20
-30
-40
-0.3
-0.6
-0.9
CPA
CPC
-5.5
-5.0
-4.5
logC
-4.0
-3.5
Fig. 7 PL wavelength changes of CPA and CPC in DMF (50 μM)
with metal ions 0.5 mM
Fig. 9 Plot of log½ðI0 ꢀ IÞ=Iꢁ vs logC for different metal ions added
into CPA and CPC (50 μM) in DMF

J Fluoresc (2011) 21:133–140
139
Table 2 The parameters of CPA/CPC with different metal ions
obtained from the fluorescent static quenching mechanism
among these metal ions, the responsive behavior of CPC
for Zn2+ is an exceptional case, probably due to its atomic
orbital configuration. It can be seen clearly that CPC and
CPA are particularly sensitive to K+ and Mn2+, respectively.
It is very clear that simple modification of the substituent
groups of the cinnamic acid derivatives containing carba-
zolyl triphenylethylene can dramatically influence their
response behaviors. Figure 8 shows photographs of the
solution of CPA-metal ion or CPC-metal ion under
irradiation at 365 nm.
As shown in Fig. 8S (in the Supplementary Information),
fluorescence quenching was observed for CPA and CPC
upon addition of the above metal ions. The following
equation has often been used to describe the static
quenching mechanism, with good linearity [14]:
Ion
Ka(M−1
)
n
R2
CPA
CPC
CPA
CPC
CPA
CPC
Zn2+
Cu2+
Ni2+
Co2+
Mn2+
K+
5.39×102
2.97×104
4.21×103
9.90×103
1.47×105
9.22×102
51
0.82
0.98
0.90
0.87
1.21
0.84
0.51
0.66
0.51
0.56
0.49
0.90
0.952
0.988
0.996
0.991
0.996
0.958
0.995
0.998
0.987
0.998
0.996
0.997
148
117
224
123
1.82×104
1
spectrum. These different H-NMR behaviors are thought
to be related to the different chemical structures of the
compounds in solution. It is well known that the
introduction of a cyano group can significantly increase
intermolecular interactions because of its high polarity and
ability of form hydrogen bonds. Therefore, it is possible
that the intermolecular interactions of CPC are much
stronger than those of CPA, which promotes molecular
association through intermolecular hydrogen bonding to
form multimers.
log½ðI0 ꢀ IÞ=Iꢁ ¼ log Ka þ n log C
Where log is the common logarithm, C is the concentration
of metal ion in the mixture system, I0 is the PL intensity of
the CPC 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. 9, a good linearity between log½ðI0 ꢀ IÞ=Iꢁ
and the logarithm of the concentration of metal ion (C)
(linear correlation coefficient R2: 0.995–0.998 for CPC, and
0.952–0.996 for CPA, respectively) was constructed. The
parameters were listed in Table 2. According to the above
equation, the association ratio (n) of Zn2+, Cu2+, Ni2+, Co2+
and Mn2+ with CPC was obtained from 0.49 to 0.66 and
thus the stoichiometric ratio between CPC and these metal
ions was 1:2. However, for K+ n was 0.9, giving a 1:1
stoichiometric ratio between CPC and K+. The association
constant, Ka, for K+ was 1.82×104 M−1, the highest amongst
Responses to metal ions
We also investigated the response behaviors of CPA and
CPC towards various metal ions in acetate form. As shown
in Figs. 7 and 7S (in the Supplementary Information), a
blue shift with CPA was observed upon addition of Zn2+,
Cu2+, Ni2+, Co2+, Mn2+ and K+. However, for CPC, a red
shift of about 21 nm occurred on addition of Zn2+. Clearly,
Fig. 10 Calculated spatial dis-
tributions of LUMO and HOMO
of CPA and CPC

140
J Fluoresc (2011) 21:133–140
Acknowledgements The authors gratefully acknowledge the finan-
cial 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), Construction Project for
University-Industry cooperation platform 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 Laboratory of Optoelectronic Materials and Technologies.
all the metal ions studied here. In contrast, for CPA, n was in
the range 0.82–1.21, thus the stoichiometric ratio between
CPA and these metal ions was 1:1. Ka for Mn2+ was the
highest amongst the metal ions.
Molecular energy levels of the compounds
To better understand the structure-property relationships
of the two derivatives, it would be very helpful to study
their molecular energy levels and electronic structures.
The lowest unoccupied molecular orbital/highest occu-
pied molecular orbital (LUMO/HOMO) energy gaps
(ΔEg)for CPA and CPC were estimated from the onset
absorption wavelengths of UV absorption spectra and
were 2.98 eV and 2.75 eV, respectively. The HOMO
energy levels of the two derivatives were obtained using
the onset oxidation potentials from cyclic voltammetry
(CV) curves and the HOMO values of CPA and CPC
were 5.59 eV and 5.52 eV, respectively. Thus, the LUMO
energy levels of CPA and CPC were 2.61 eV and 2.77 eV,
respectively. From the energy levels, it could be seen that
CPC exhibited lower band gap and higher LUMO than
CPA, which might result in essential differences in
responsive behaviors to solvents, water and metal ions
between the two derivatives. To gain insight as to why the
two derivatives exhibited the differences in energy levels,
we obtained their HOMOs and LUMOs based on B3LYP/
6-31G(d) calculations [15] (Fig. 10). The calculation
results showed that the majority of the electron distribu-
tion of the HOMO was located on the carbazolyl
triphenylethylene moiety, and the LUMO distribution
resided on the cinnamic acid moiety. The electron
distribution of the HOMOs of the two compounds were
very similar to each other. However, due to the effect of
cyano group (CN), the electron of the LUMO of CPC
distributed much more concentrated on the cinnamic acid
moiety. From Fig. 10, we could also see that there existed
antibonding repulsion between p-orbitals in CN and C =
C, which caused CPC to be high LUMO energy level.
References
1. Amendola V, Fabbrizzi L, Licchelli M, Mangano C, Pallavicini P,
Parodi L, Poggi A (1999) Molecular events switched by transition
metals. Coord Chem Rev 190–192:649–669
2. De Silva AP, Gunaratne HQN, Gunnlaugsson T, Huxley AJM, McCoy
CP, Rademacher JT, Rice TE (1997) Signaling recognition events with
fluorescent sensors and switches. Chem Rev 97:1515–1566
3. Wiegmann TB, Welling LW, Beatty DM, Howard DE, Vamos S,
Morris JA (1993) Simultaneous imaging of intracellular [Ca2+
]
and pH in single MDCK and glomerular epithelial cells. J Physiol
265:C1184–C1190
4. Salvador JM, Inesi G, Rigaud JL, Mata AM (1998) Ca2+ transport
by reconstituted synaptosomal ATPase is associated with H+
countertransport and net charge displacement. J Biol Chem
273:18230–18234
5. Vo-Dinh T, Viallet P, Ramirez L, Pal A, Vigo J (1994) Detection
of cadmium ion using the fluorescence probe Indo-1. Anal Chim
Acta 295:67–72
6. Hirshfeld KM, Toptygin D, Grandhige G, Packard BZ, Brand L
(1998) A nanosecond fluorescence study of the simultaneous
influx of Ca2+ and Cd2+ into liposomes. Biophys Chem 71:63–72
7. Yuasa J, Fukuzumi S (2006) An Off-On fluorescence sensor for
metal ions in stepwise complex formation of 2, 3, 5, 6-tetrakis(2-
pyridyl)pyrazine with metal ions. J Am Chem Soc 128:15976–15977
8. Liu JZ, Lam JWY, Tang BZ (2009) Aggregation-induced emission
of silole molecules and polymers: fundamental and applications. J
Inorg Organomet Polym 19:249–285
9. Dong Y, Lam JWY, Qin A, Li Z, Liu J, Sun J, Dong Y, Tang B
(2007) Endowing hexaphenylsilole with chemical sensory and
biological probing properties by attaching amino pendants to the
silolyl core. Chem Phys Lett 446:124–127
10. Wang M, Zhang D, Zhang G, Tang Y, Wang S, Zhu D (2008)
Fluorescence turn-on detection of DNA and label-free fluores-
cence nuclease assay based on the aggregation-induced emission
of silole. Anal Chem 80:6443–6448
11. Yang Z, Chi Z, Yu T, Zhang X, Chen M, Xu B, Liu S, Zhang Y,
Xu J (2009) Triphenylethylene carbazole derivatives as a new
class of AIE materials with strong blue light emission and high
glass transition temperature. J Mater Chem 19:5541–5546
12. Xu B, Chi Z, Yang Z, Chen J, Deng S, Li H, Li X, Zhang Y, Xu
N, Xu J (2010) Facile synthesis of a new class of aggregation-
induced emission materials derived from triphenylethylene. J
Mater Chem. doi:10.1039/C0JM00229A
13. Zhang X, Yang Z, Chi Z, Chen M, Xu B, Wang C, Liu S, Zhang
Y, Xu J (2010) A multi-sensing fluorescent compound derived
from cyanoacrylic acid. J Mater Chem 20:292–298
14. Feng X, Bai C, Lin Z, Wang N, Wang C (1998) The interaction
between acridine orange and bovine serum albumin. Chin J Anal
Chem 26:154–157
Conclusions
Two fluorescent compounds, CPA and CPC, were synthe-
sized, possessing AIE effects and interesting fluorescence
responses to solvents, water, and metal ions. The response
behaviors of the compounds are different due to the
difference of their chemical structures. It was found that
CPC exhibits high sensitivity to K+ and a different
response to Zn2+. It is therefore clear that simple modifi-
cation of the substituent group of the cinnamic acid
derivatives containing carbazolyl triphenylethylene can
dramatically influence their response behaviors.
15. Frisch MJ, Trucks GW, Schlegel HB et al (2004) Gaussian 03.
Revision D.01. Gaussian, Inc, Wallingford