A new piezochromic fluorescence and aggregation-induced emission compound containing tetraphenylethylene and triphenylamine moieties with morphology-alterable property

Article abstract of DOI:10.1007/s10895-011-0990-4

A novel piezochromic fluorescent (PCF) compound with aggregation-induced emission (AIE) effect and morphology-alterable emission property was developed. The amorphous and crystalline aggregates were obtained, and their spectroscopic properties and morphol

Full text of DOI:10.1007/s10895-011-0990-4

J Fluoresc (2012) 22:565–572
DOI 10.1007/s10895-011-0990-4
ORIGINAL PAPER
A New Piezochromic Fluorescence and Aggregation-Induced
Emission Compound Containing Tetraphenylethylene
and Triphenylamine Moieties with Morphology-alterable
Property
Xie Zhou & Hai-yin Li & Zhen-guo Chi & Bing-jia Xu &
Xi-qi Zhang & Yi Zhang & Si-wei Liu & Jia-rui Xu
Received: 18 August 2011 /Accepted: 19 September 2011 /Published online: 1 October 2011
#
Springer Science+Business Media, LLC 2011
Abstract A novel piezochromic fluorescent (PCF) com-
pound with aggregation-induced emission (AIE) effect and
morphology-alterable emission property was developed.
The amorphous and crystalline aggregates were obtained,
and their spectroscopic properties and morphological
structures were reversibly and repeatedly exhibited upon
pressing (fuming) or annealing. The piezochromic
fluorescent nature was generated through crystalline-
amorphous phase transformation. It was proposed that
AIE compounds existing a twisted propeller-shaped
conformation will exhibit PCF activity. The common
relationship betweeen AIE and PCF established will
guide researchers in identifying and synthesizing more
piezochromic fluorescent materials.
Introduction
The modification or alteration of molecular chemical
structures is the most common approach for controlling
fluorescence properties. However, for the dynamic control
of solid state fluorescence with high efficiency, reversibil-
ity, and reproducibility, effective materials are quite limited
because most chemical reactions in the solid state involve
insufficient conversion and irreversible reactions, or result
in loss of fluorescence capability [1, 2]. To overcome this
problem, a very attractive approach is to control the solid
fluorescence properties dynamically by altering the mode of
solid state molecular stacking without changing the
chemical structure of the constituting molecules. If the
fluorescent color change of a material is based on a
pressure-dependent mode of molecular stacking, it is called
piezochromic fluorescent material. Many piezochromic
materials based on the change of absorption characteristics
under pressure have been reported [3–5]. As fluorescence
can be detected with high sensitivity, materials exhibiting
piezochromic fluorescence have a wide variety of applica-
tions such as optical recording and strain- or pressure-
sensing systems. However, piezochromic fluorescent mate-
rials are exceedingly rare [6–10]. Recently, a lot of
fluorescent compounds with AIE effect have been synthe-
sized in our laboratory, and it has been very interesting to
find that some of the AIE compounds are piezochromic
fluorescent materials [11–15]. AIE materials are an impor-
tant class of anti-aggregation-caused-quenching materials
first reported by Tang in 2001 [16] and have attracted
considerable research attention because of their potential
.
Keywords Piezochromic fluorescence Morphology-alterable
.
.
.
emission Phase transformation Tetraphenylethylene
Aggregation-induced emission
X. Zhou
School of Pharmaceutical Sciences, Sun Yat-sen University,
Guangzhou 510275, China
:
:
:
:
:
H.-y. Li Z.-g. Chi (*) B.-j. Xu X.-q. Zhang Y. Zhang
:
S.-w. Liu J.-r. Xu (*)
PCFM Lab, DSAPM Lab, KLGHEI of Environment and Energy
Chemistry, 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

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J Fluoresc (2012) 22:565–572
application in various fields such as organic light-emitting
devices and chemosensors [17–27]. To the best of our
knowledge, except our laboratory, there are only two
research groups reported their studies on piezochromic
fluorescent material with AIE effect [28, 29]. In this article,
we present a new PCF-AIE compound (TPA-TPE) as an
example. It is found that the piezochromic fluorescent
nature is generated through crystalline-amorphous phase
transformation. It was proposed that AIE compounds
existing a twisted propeller-shaped conformation will
exhibit PCF activity.
Synthesis of Br-TPE
A 2.2 M solution of n-butyllithium in hexane (20.0 mmol,
9.1 mL) was added to a solution of diphenylmethane
(3.36 g, 20.0 mmol) in anhydrous tetrahydrofuran (50 mL)
at 0 °C under an argon atmosphere. After stirring for 1 h at
that temperature, the bis(4-bromophenyl)methanone
(5.44 g, 16.0 mmol) was added and the reaction mixture
was stirred for 10 h allowing the temperature to rise
gradually to room temperature. Then the reaction was
quenched with an aqueous solution of ammonium chloride
and the mixture was extracted with dichloromethane. The
organic layer was evaporated after drying with anhydrous
sodium sulfate and the resulting crude alcohol was
dissolved in toluene (80 mL). The p-toluenesulphonic acid
(0.68 g, 3.6 mmol) was added, and the mixture was
refluxed overnight and cooled to room temperature. The
mixture was evaporated and the crude product was
purified by silica gel column chromatography using n-
Experimental
Materials and Methods
Diphenylmethane, 4,4′-dibromobenzophenone, n-butyllithium
in hexane (2.2 M), tetrakis(triphenylphosphine) palladium(0),
tetrabutyl ammonium bromide (TBAB), and p-toluenesul-
phonic acid purchased from Alfa Aesar were used as received.
hexane as eluent to yield a light yellow powder
1
(5.70 g, 73%). H NMR (300 MHz, CDCl ) δ(ppm):
3
4
-(diphenylamino)phenylboronic acid was obtained from
6.82–6.90 (m, 4H), 6.95–7.05 (s, 4H), 7.06–7.16 (s, 6H),
7.18–7.27 (m, 4H); C NMR (75 MHz, CDCl3) δ(ppm):
1
3
Zhenjiang Haitong Chemical Industry Co., Ltd. (China). All
other reagents and solvents were purchased as analytical grade
from Guangzhou Dongzheng Company (China) and used
without further purification.
120.93, 127.10, 128.10, 131.30, 133.20, 138.55, 142.38,
−
1
143.40; FT-IR (K.Br) υ (cm ): 3053, 3021, 2354, 1590,
1480, 1434, 1382, 1065, 1007, 826, 761, 696, 482;
1
+
Proton and carbon nuclear magnetic resonance ( H-NMR
HRMS (EI), m/z: 490([M] , calcd for C H Br , 490);
2
6
18
2
1
3
and C-NMR) spectra were measured on a Mercury-Plus
00 spectrometer [CDCl , tetramethylsilane (TMS) as the
Anal. calcd for C H Br : C 63.70, H 3.70; found:
26 18 2
C 63.65, H 3.72.
3
3
internal standard]. High resolution mass spectra (HRMS)
were measured on a Thermo MAT95XP-HRMS spectrome-
ter. Elemental analyses (EA) were performed with an
Elementar Vario EL elemental analyzer. Photoluminescence
spectra (PL) were measured on a Shimadzu RF-5301pc
spectrometer with a slit width of 1.5 nm for both excitation
and emission. UV-vis absorption spectra (UV) were
recorded on a Hitachi UV-vis spectrophotometer (U-
Synthesis of TPA-TPE
Br-TPE (0.245 g, 0.5 mmol) and 4-(diphenylamino)
phenylboronic acid (0.289 g, 1.0 mmol) in toluene
(15 mL), 2 M aqueous K CO solution (1.5 mL) and 5
2
3
drops of TBAB were added. The mixture was stirred for
40 min under an argon atmosphere at room temperature.
Then the Pd(PPh ) catalyst (catalytic amount) was added
3
900). Differential scanning calorimetry (DSC) curves
were obtained with a NETZSCH thermal analyzer (DSC
04 F1) at a heating rate of 10 °C/min under N2
3
4
and the reaction mixture was stirred at 80 °C for 16 h.
After cooling to room temperature, the product was
concentrated and purified by silica gel column chroma-
tography with CH Cl : n-hexane (v: v, 1: 4) to afford
2
atmosphere. Pressed samples were prepared by pressing
the crystalline samples obtained from dichloromethane/n-
hexane solution (1:4, v/v) in an an IR pellet press at
2
2
1
white powder (0.340 g, yield 83%). H NMR (300 MHz,
1
,500 psi for 1 min. Annealing experiments were done on
CDCl ) δ(ppm): 6.98–7.17 (m, 29H), 7.21–7.30 (m, 9H),
3
1
3
a hot-stage with automatic temperature control system.
The water-DMF mixtures with different water fractions
were prepared by slowly adding distilled water into the
DMF solution of samples under ultrasound at room
temperature. For example, a 70% water fraction mixture
was prepared in a volumetric flask by adding 7 mL
distilled water into 3 mL DMF solution of the sample. The
concentrations of all samples were adjusted to 10 μM after
adding distilled water.
7.30–7.36 (d, 4H), 7.42–7.49 (d, 4H);
C NMR
(75 MHz, CDCl ) δ(ppm): 123.15, 124.25, 124.60,
3
125.95, 126.65, 127.60, 127.95, 129.40, 131.60,
132.05, 138.45, 140.40, 141.30, 142.65, 144.05,
−
1
147.80; FT-IR (KBr) υ (cm ): 3033, 2361, 1590, 1486,
1318, 1279, 813, 748, 696, 508; HRMS (EI), m/z: 818
+
([M] , calcd for C H N , 818); Anal. calcd for
6
2
46
2
C H N : C 90.92, H 5.66, N 3.42; found: C 90.89, H
6
2
46
2
5.63, N 3.47.

J Fluoresc (2012) 22:565–572
567
Results and Discussion
differential scanning calorimetry (DSC) curves of the
samples: (a) obtained from dichloromethane; (b) obtained
from dichloromethane/n-hexane; (c) melt quenched to room
temperature; (d) crystalline sample was fumed with
dichloromethane for 12 h; (e) crystalline sample was
pressed at 1,500 psi for 1 min; (f) fumed sample was
annealed at 180 °C for 5 min; (g) pressed sample was
annealed at 180 °C for 5 min.
Synthesis
The synthetic route for the desired compound TPA-TPE is
illustrated in Scheme 1. Suzuki coupling of 4,4′-(2,2-
diphenylethene-1,1-diyl)bis(bromobenzene) (Br-TPE) with
4
-(diphenylamino)phenylboronic acid provided the target
compound with 83% yield. The synthesis of Br-TPE started
with diphenylmethane and used two steps. The hydroxy
intermediate was not purified further and could be used
directly in the next step. After the dehydration reaction of
hydroxy intermediate in the presence of p-toluenesulphonic
acid, the bromide intermediate Br-TPE was obtained. The
molecular structures of the target compound and interme-
The crystalline and amorphous nature of the samples
was verified by their WAXD, where that of the former
exhibited many sharp reflection peaks (Fig. 2, Curve b),
and that of the latter gave only a weak, broad, and diffused
peak (Fig. 3, Curve a). The amorphous aggregate was
yellowish green in appearance, with a strong green
emission at 497 nm (Fig. 4, Curve a), whereas the
crystalline aggregate was white, with a strong blue emission
at 450 nm (Fig. 3, Curve b). The DSC heating curve of the
amorphous sample showed a cold-crystallization peak
around 134 °C, except for a melting peak at around 190 °C
(Fig. 4, Curve a). The sizes of the two peaks were very close,
which means the sample is amorphous. The crystal
corresponding to the melting peak was completely generated
through cold-crystallization. However, the crystalline sample
only showed a sharp melting peak at ~200 °C, with no cold-
crystallization peak (Fig. 5, Curve b). If the amorphous
sample is annealed at 180 °C for 5 min, it will revert to the
crystalline state.
1
diate were confirmed by nuclear magnetic resonance ( H-
1
3
NMR, C-NMR), Fourier transform infrared spectroscopy,
elementary analysis, and high resolution mass spectrometry.
Morphology-Alterable and PCF Properties
To investigate morphology-alterable emission and piezo-
chromic fluorescent properties, we carried out a series of
experiments as schematically illustrated in Fig. 1.
When the solutions of the compound in different
solvents were evaporated to dryness with a vacuum
evaporator, two different aggregates were obtained: amor-
phous aggregate from dichloromethane and crystalline
aggregate from dichloromethane/n-hexane mixed solvent
When the crystalline aggregate samples were treated in
three different conditions, namely, (1) heated to the melted
state then quenched by liquid nitrogen to room temperature,
(2) fumed with dichloromethane for 12 h, and (3) pressed
for 1 min by 1,500 psi, they all reverted to the amorphous
(
1:4, v/v).
Figures 2, 3 and 4 show wide-angle X-ray diffracto-
grams (WAXD), photoluminescence (PL) spectra and
Scheme 1 Synthetic route of
Br
Br
the compound
) n-BuLi,THF, 0 o
C
H C
3
SO H
3
1
HO
CH
2
O
Toluene, reflux
2)
Br
Br
Br
Br
Br-TPE
N
N
B(OH)
2
TPA-TPE
Pd(PPh ) , K CO (2M, aq.)
TBAB, Toluene, 80 C, 16h
3
4
2
3
o
N

5
68
J Fluoresc (2012) 22:565–572
Fig. 1 A schematic representation of treatment procedures. The pictures in each group were taken at room temperature under (left) natural and
right) UV lights
(
states. These results were also confirmed by WAXD, which
only generated diffused peaks (Fig. 3, curves c, d, and e). The
PL spectra of the obtained samples red-shifted to ~500 nm,
which were very close to the amorphous sample obtained
from the dichloromethane solution. The result obtained from
treatment (3) indicates that the compound has significant
piezochromic property.
compounds such as typical triphenylethylene, tetraphenyl-
ethylene, silole, and cyano distyrylbenzene derivatives have
one common structural feature: multiple phenyl peripheries
are linked to an olefinic core via rotatable C-C single bonds to
form AIE moiety. The steric effect causes the AIE moieties or
the molecules to take a twisted propeller-shaped conforma-
tion, making it difficult for them to assume a dense packing
structure. Thus, the crystals have low lattice energy and are
easily crashed by external pressure. This “crash” may be
The piezochromic behavior of the compound may be
attributed to its twisted structure (Fig. 5). Reported AIE
1.2
1.0
0.8
0.6
0.4
0.2
0.0
g
f
b
e
g
d
c
d
c
b
a
e
a
f
0
10
20
30
40
50
350
400
450
500
550
600
650
700
2θ / deg.
Wavelength / nm
Fig. 2 WAXD patterns of the TPA-TPE samples obtained under
Fig. 3 PL spectra of the TPA-TPE samples obtained under different
different conditions
conditions

J Fluoresc (2012) 22:565–572
569
Fuming time (s)
0
3
6
9
1
4
0
0
0
20
20
g
f
120
e
630
9
1
1500
00
200
6
0
d
c
2
3
400
600
b
a
0
4
00
500
600
60
120
180
240
300
360
Wavelength / nm
o
Temperature / C
Fig. 6 PL spectra of the crystalline sample under fuming with
dichloromethane
Fig. 4 DSC heating curves of the TPA-TPE samples obtained under
different conditions
crystallization peak at around 157 °C and a melting peak at
around 197 °C. The melting peak temperatures of the fumed
and pressed samples were the same. However, the former
exhibited a 27 °C higher cold-crystallization temperature than
the pressed sample.
The amorphous samples obtained by fuming and
pressing treatments, which can be reverted to the crystalline
state by annealing at 180 °C for 5 min, exhibited good
morphological reversibility. However, the amorphous sam-
ple obtained by melt quenching cannot be reverted to its
crystalline state by the annealing method and has no cold-
crystallization and melting transition peaks in heating DSC
curve (Fig.4 Curve c). The reversible behavior of the
amorphous sample can be achieved by dissolving it in
dichloromethane/n-hexane mixed solvent (1:4, v/v) and
then evaporating the solution to dryness with a vacuum
evaporator.
triggered by planarization of molecular conformation under
external pressure (“pressing flat”) and should result in the
generation of piezochromic fluorescent behavior. According
to the hypothesis, we try pressing or grinding more than 30
AIE compounds synthesized in our laboratory, and as
expected, almost all the compounds exhibit piezochromic
fluorescent effect. We believe that the common relationship
betweeen AIE and PCF will guide researchers in identifying
and synthesizing more piezochromic fluorescent materials.
The DSC heating curves of the three treated samples
exhibited results which were considerably different from
one another (Fig. 4, curves c, d, and e). The quenched
sample exhibited only a glass transition at ~134 °C and no
cold-crystallization peak; the fumed sample showed a cold-
crystallizaion peak at around 184 °C followed by a melting
peak at 197 °C; and the pressed sample showed a cold-
Fig. 5 The lowest-energy con-
former optimized using the
MM2 force field for TPA-TPE

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J Fluoresc (2012) 22:565–572
Figures 6 and 7 show the relationship of the PL spectra
of the compound with dichloromethane fuming time. The
PL peak intensity of the crystalline sample dramatically
decreased within 420 s. Following this, the curve slowed
down. The wavelength exhibited significant red-shifts from
4
50 to 493 nm. From 0 to 900 s, the wavelength quickly
red-shifted with an increase in fuming time, and then it
became flat. As the compound is AIE active, the permeation
of a good solvent during fuming can loosen the packing of the
molecules, leading to the increase in intramolecular rotations,
the increase in non-emissive decay of excited state energy, and
the decrease in the PL intensity.
a
b
c
d
To verify whether the chemical structure of TPA-TPE
1
changed after heating, fuming, and pressing, H-NMR
experiments in CDCl were conducted. Figure 8 shows
that the H-NMR spectra are the same, which indicates
6.4
6.8
7.2
7.6
8.0
3
1
Chemical shift (ppm)
that the chemical structure did not change. This further
implies that the different spectroscopic properties of TPA-TPE
were caused by physical processes. In other words, the
piezochromic fluorescent nature was generated through
crystalline-amorphous phase transformation.
1
Fig. 8 H NMR of the TPA-TPE samples (in CDCl
3
) a obtained from
dichloromethane; b melt quenched to room temperature; c crystalline
sample was fumed with dichloromethane for 12 h; and d crystalline
sample was pressed at 1,500 psi for 1 min
intensity (a.u.) in pure DMF is only 3.6. However, in water/
DMF mixture with 30% water fraction, the PL intensity is
elevated to 186.9, which is about 52 times higher than that
of the pure DMF solution. This increase in fluorescence
intensity is attributed to an AIE effect caused by the
formation of molecular aggregates, in which the restriction
in intramolecular rotations leads to increased fluorescent
emission. Emission images of TPA-TPE in pure DMF and
30% and 90% water fraction mixtures under 365 nm UV
illumination are shown in Fig. 1(inset). The compounds in
30% and 90% water fractions of water/DMF mixtures
AIE Properties
To confirm whether a compound is AIE active, fluorescent
behaviors are usually studied with a poor solvent added into
a good one. The compound is insoluble in water, so
increasing water fraction in the mixed solvent can change
its existing form from a solution or well-dispersed state in
pure DMF to aggregated particles in mixtures with high
water content. The PL spectra of 10 μM TPA-TPE in water/
DMF mixtures with different water contents are shown in
Fig. 9. The figure shows that if the water fraction is less
than 30%, the PL intensity is very weak. However, a
dramatic enhancement in luminescence is observed for a
water/DMF mixture with 30% water fraction. The PL
200
Water Fraction
2
25
150
100
0
1
2
3
4
5
7
%
0%
0%
0%
0%
0%
0%
5
0
5
4
4
4
00
90
80
70
1
1
60
20
150
75
0
0
0
20
40
60
80 100
Water fraction / v%
Peak intensity
Wavelength
90%
8
0
0
4
460
4
00
500
600
450
Wavelength / nm
0
-
500
0
500
1000
1500
2000
2500
3000
Fig. 9 PL spectra of the dilute solutions of TPA-TPE in water/DMF
mixtures with different water fractions (10 μM; excitation: 365 nm).
The inset depicts changes in PL peak intensity (up) and emission
images of TPA-TPE in pure DMF, and 30% and 90% water fraction
mixtures under 365 nm UV illumination (10 μM) (down)
Time / s
Fig. 7 PL peak intensity and wavelength versus fuming time with
dichloromethane

J Fluoresc (2012) 22:565–572
571
6
7
. Sagara Y, Kato T (2009) Mechanically induced luminescence
changes in molecular assemblies. Nat Chem 1:605–610
. Kunzelman J, Kinami M, Crenshaw BR, Protasiewicz JD, Weder
C (2008) Oligo(p-phenylene vinylene)s as a “new” class of
piezochromic fluorophores. Adv Mater 20:119–122
. Sagara Y, Mutai T, Yoshikawa I, Araki K (2007) Material design
for piezochromic luminescence: hydrogen-bond-directed assemblies
of a pyrene derivative. J Am Chem Soc 129:1520–1521
exhibit strong green emission. However, in pure DMF, the
emission is very weak and virtually invisible. Thus, the
compound has strong AIE activity. In other words, TPA-
TPE has both aggregation-induced emission and piezochro-
mic fluorescence characteristics and it has been called PAIE
material in our laboratory.
8
9
. Mutai T, Satou H, Araki K (2005) Reproducible on–off switching
of solid-state luminescence by controlling molecular packing
through heat-mode interconversion. Nat Mater 4:685–687
Conclusions
1
0. Mizukami S, Hojou H, Sugaya K, Koyama E, Tokuhisa H, Sasaki
T, Kanesato M (2005) Fluorescence color modulation by
intramolecular and intermolecular π-π interactions in a helical
zinc(II) complex. Chem Mater 17:50–56
A novel piezochromic compound with aggregation-induced
emission effect and morphology-alterable emission property
was developed. The amorphous and crystalline aggregates can
be obtained by evaporation of different solutions. The
emission properties of the novel piezochromic compound
can reversibly and repeatedly switch the fluorescence upon
pressing (fuming) or annealing due to crystalline-amorphous
phase transformation. These excellent properties make the
compound a promising candidate for stimuli-responsive,
smart, and luminescent materials for information recording
and light emitting device applications. It was proposed that
AIE compounds existing a twisted propeller-shaped confor-
mation will exhibit piezochromic fluorescent activity. The
common structure-property relationship established will guide
researchers in identifying and synthesizing more piezochromic
fluorescent materials.
1
1. Li HY, Zhang XQ, Chi ZG, Xu BJ, Zhou W, Liu SW, Zhang Y,
Xu JR (2011) New thermally stable piezofluorochromic
aggregation-induced emission compounds. Org Lett 13:556–559
2. Zhang XQ, Chi ZG, Zhang JY, Li HY, Xu BJ, Li XF, Liu SW,
Zhang Y, Xu JR (2011) Piezofluorochromic properties and
mechanism of an aggregation-induced emission enhancement
compound containing N-hexyl-phenothiazine and anthracene
moieties. J Phys Chem B 115:7606–7611
3. Zhang XQ, Chi ZG, Li HY, Xu BJ, Li XF, Zhou W, Liu SW,
Zhang Y, Xu JR (2011) Piezofluorochromism of an aggregation-
induced emission compound derived from tetraphenylethylene.
Chem Asian J 6:808–811
4. Li HY, Chi ZG, Xu BJ, Zhang XQ, Li XF, Liu SW, Zhang Y, Xu
JR (2011) Aggregation-induced emission enhancement com-
pounds containing triphenylamine-anthrylenevinylene and tetra-
phenylethene moieties. J Mater Chem 21:3760–3767
5. Xu BJ, Chi ZG, Zhang JY, Zhang XQ, Li HY, Li XF, Liu SW,
Zhang Y, Xu JR (2011) Piezofluorochromic and aggregation-
induced-emission compounds containing triphenylethylene and
tetraphenylethylene moieties. Chem Asian J 6:1470–1478
6. Luo JD, Xie ZL, Lam JWY, Cheng L, Chen HY, Qiu CF, Kwok
HS, Zhan XW, Liu YQ, Zhu DB, Tang BZ (2001) Aggregation-
induced emission of 1-methyl-1,2,3,4,5- pentaphenylsilole. Chem
Commun 1740–1741
7. Zhang XQ, Yang ZY, Chi ZG, Chen MN, Xu BJ, Wang CC, Liu SW,
Zhang Y, Xu JR (2010) A multi-sensing fluorescent compound
derived from cyanoacrylic acid. J Mater Chem 20:292–298
8. Yang ZY, Chi ZG, Yu T, Zhang XQ, Chen MN, Xu BJ, Liu SW,
Zhang Y, Xu JR (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
9. Hong YN, Lam JWY, Tang BZ (2009) Aggregation-induced
emission: phenomenon, mechanism and applications. Chem
Commun 29:4332–4353
0. Zhao YS, Fu HB, Peng AD, Ma Y, Xiao DB, Yao JN (2008) Low-
dimensional nanomaterials based on small organic molecules:
preparation and optoelectronic properties. Adv Mater 20:2859–2876
1. Zhang XQ, Chi ZG, Xu BJ, Li HY, Yang ZY, Li XF, Liu SW,
Zhang Y, Xu JR (2011) Synthesis of blue light emitting bis
(triphenylethylene) derivatives: a case of aggregation-induced
emission enhancement. Dyes Pigments 89:56–62
22. Xu BJ, Chi ZG, Yang ZY, Chen JB, Deng SZ, Li HY, Li XF, Zhang Y,
Xu NS, Xu JR (2010) Facile synthesis of a new class of aggregation-
induced emission materials derived from triphenylethylene. J Mater
Chem 20:4135–4141
23. Li HY, Chi ZG, Xu BJ, Zhang XQ, Yang ZY, Li XF, Liu SW,
Zhang Y, Xu JR (2010) New aggregation-induced emission
enhancement materials combined triarylamine and dicarbazolyl
triphenylethylene moieties. J Mater Chem 20:6103–6110
24. Li XF, Chi ZG, Xu BJ, Li HY, Zhang XQ, Zhou W, Zhang Y, Liu SW,
Xu JR (2011) Synthesis and characterization of triphenylethylene
1
1
1
1
1
Acknowledgement The authors gratefully acknowledge the finan-
cial support from the National Natural Science Foundation of China
(
51173210, 51073177), Construction Project for University-Industry
cooperation platform for Flat Panel Display from The Commission of
Economy and Informatization of Guangdong, the Fundamental
Research Funds for the Central Universities and Natural Science
Foundation of Guangdong (S2011020001190).
1
1
References
1
2
2
1
2
. Irie M, Fukaminato T, Sasaki T, Tamai N, Kawai T (2002)
Organic chemistry: a digital fluorescent molecular photoswitch.
Nature 420:759–760
. Papaefstathiou GS, Zhong Z, Geng L, MacGillivray LR (2004)
Coordination-driven self-assembly directs a single-crystal-to-single-
crystal transformation that exhibits photocontrolled fluorescence. J
Am Chem Soc 126:9158–9159
3
. Mizuguchi J, Tanifuji N, Kobayashi K (2003) Electronic and
structural characterization of a piezochromic indigoid: 11-(3′-
oxodihydrobenzothiophen- 2′-ylidene)cyclopenta[1,2-b:4,3-b′]
dibenzothiophene. J Phys Chem B 107:12635–12638
4
. Yamamoto T, Muramatsu Y, Lee BL, Kokubo H, Sasaki S, Hasegawa
M, Yagi T, Kubota K (2003) Preparation of new main-chain
type polyanthraquinones. Chemical reactivity, packing Structure,
piezochromism, conductivity, and liquid crystalline and photonic
properties of the polymers. Chem Mater 15:4384–4393
5
. Gentili PL, Nocchetti M, Miliani C, Favaro G (2004) Unexpected
chromogenic properties of 1,3,3-trimethylspiro(indoline-2,3′-[3H]
naphtho [2,1-b][1,4]oxazine) in the solid phase: photochromism,
piezochromism and acidichromism. New J Chem 28:379–386

5
72
J Fluoresc (2012) 22:565–572
derivatives with aggregation-induced emission characteristics.
J Fluoresc 21:1969–1977
27. Yang ZY, Chi ZG, Xu BJ, Li HY, Zhang XQ, Li XF, Liu SW,
Zhang Y, Xu JR (2010) High-Tg carbazole derivatives as a new
class of aggregation-induced emission enhancement materials. J
Mater Chem 20:7352–7359
28. Yoon SJ, Chung JW, Gierschner J, Kim KS, Choi MG, Kim D,
Park SY (2010) Multistimuli two-color luminescence switching
via different slip-stacking of highly fluorescent molecular sheets. J
Am Chem Soc 132:13675–13683
2
2
5. Zhang XQ, Chi ZG, Xu BJ, Li HY, Zhou W, Li XF, Zhang Y, Liu
SW, Xu JR (2011) Comparison of responsive behaviors of two
cinnamic acid derivatives containing carbazolyl triphenylethylene.
J Fluoresc 21:133–140
6. Xu BJ, Chi ZG, Li XF, Li HY, Zhou W, Zhang XQ, Wang CC,
Zhang Y, Liu SW, Xu JR (2011) Synthesis and properties of
diphenylcarbazole triphenylethylene derivatives with aggregation-
induced emission, blue light emission and high thermal stability. J
Fluoresc 21:433–441
29. Dou CD, Han L, Zhao SS, Zhang HY, Wang Y (2011) Multi-
stimuli-responsive fluorescence switching of a donor-acceptor π-
conjugated compound. J Phys Chem Lett 2:666–670