Reversible multistimuli-response fluorescent switch based on tetraphenylethene-spiropyran molecules

Article abstract of DOI:10.1002/chem.201405426

Two tetraphenylethene (TPE)-functionalized spiropyran (SP) molecules with very similar structure were designed and synthesized. The two molecules exhibit aggregation-induced emission (AIE) properties, as well as multistimuli-responsive color-changing prop

Full text of DOI:10.1002/chem.201405426

DOI: 10.1002/chem.201405426
Full Paper
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Photochromism
Reversible Multistimuli-Response Fluorescent Switch Based on
Tetraphenylethene–Spiropyran Molecules
Qingkai Qi, Jingyu Qian, Suqian Ma, Bin Xu,* Sean Xiao-An Zhang, and Wenjing Tian*[a]
Abstract: Two tetraphenylethene (TPE)-functionalized spiro-
pyran (SP) molecules with very similar structure were de-
signed and synthesized. The two molecules exhibit aggrega-
tion-induced emission (AIE) properties, as well as multistimu-
li-responsive color-changing properties, such as photo-
chromism and acidchromism. The investigation of their dif-
ferent photochromic and acidchromic characteristics and
dual-response fluorescent switch during isomerization indi-
cated that the different link position between TPE and SP
will significantly affect the extended p-conjugated system,
resulting in completely different photochromic and acid-
chromic properties.
Introduction
emission organogels by blending tetraphenylethene gel with
spiropyran gel.[14] Based on the photoisomerization of spiropy-
ran, the emission of the organogels can be switched by alter-
nating UV/Vis illumination. Thus, it is envisaged that the com-
bination of SP with TPE by a covalent bond may directly im-
prove their performances and expand their application fields.
Herein, we designed and synthesized two new molecules
(TPE-SP1 and TPE-SP2) by covalently linking TPE with spiropy-
ran by using carbon–carbon double bonds (Scheme 1). The
two molecules exhibit AIE properties and obvious photochro-
mic and acidchromic properties. The investigation of the pho-
tochromism of the two compounds indicated that although
they have very similar molecular structure, their photochromic
characteristics are different. In addition, the modulation of the
two emission colors, switch of TPE-SP1 and the emission on–
off switch of TPE-SP2, can be realized in the solid state upon
acid/base treatment. To the best of our knowledge, the solid
fluorescence switch of spiropyran systems triggered by acid/
base has rarely reported. The related origin of the different lu-
minescent changes under external stimuli was then investigat-
ed by combining experimental analyses with theoretical calcu-
lations. The results indicated that TPE-MC1 with much larger p-
conjugation length between the TPE moiety and merocyanine
(MC) moiety will give a red emission, whereas TPE-MC2 will
have completely quenched emission due to poor conjugation
and the intramolecular energy and electron-transfer quench-
ing.
Spiropyrans and their derivatives are well known as molecular
switches, which show distinctive absorption characteristics
during structural isomerization between the ring-closed form
(CF) and ring-open form (OF) upon external stimulus.[1] Up to
now, various stimuli, such as UV/Vis light,[1,2] acid/base,[3]
heat,[4] electricity,[5] and mechanoforce[6] all have been reported
to accelerate this CF–OF transformation. Due to their excellent
stimuli-response properties, spiropyrans have been widely
studied for use in data storage,[7] chemical sensors,[8] smart ma-
terials,[9] and biological imaging[10] etc. However, the weak
emission of spiropyran in the aggregation state limited some
of the above applications. Thus the development of highly
emissive organic luminescent materials with multistimuli-re-
sponse color-changing properties is of important significance
to gain multifunctional sensor materials to further widen the
field of applications. Twisted p-conjugated molecules, such as
TPE and its derivatives, have become a research hotspot in
recent years due to their aggregation-induced emission (AIE)
properties,[11] which have conquered the drawbacks from the
notorious quenching effect caused by aggregation of the tradi-
tional dyes with a planer conformation and realized their wide
applications in organic light emitting devices (OLED)[12] and
bio-labels.[13] Therefore, the combination of spiropyran with
TPE is envisioned to realize a new type of multiresponsive lu-
minescent material. Zhang et al. reported multicolored tunable
[a] Dr. Q. Qi, J. Qian, S. Ma, Dr. B. Xu, Prof. S. X.-A. Zhang, Prof. W. Tian
College of Chemistry Jilin University
State Key Lab of Supramolecular Structure and Materials
Changchun, Jilin University
Results and Discussion
Design and synthesis
130012 (P.R. China)
Fax: (+86)0431-8519-3421
E-mail: wjtian@jlu.edu.cn
TPE-SP1 and TPE-SP2 were synthesized by a series of chemical
reactions according to Scheme 1. The detailed synthetic proce-
dure and characterizations are described in the Experimental
Section and Supporting Information.
xubin@jlu.edu.cn
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405426.
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this AIE phenomenon has al-
ready been thoroughly re-
searched and the increased fluo-
rescent intensity attributed to
the formation of molecular ag-
gregates, in which the intramo-
lecular free rotation has been
blocked.[15]
Photochromic properties in the
solution state
Similar to the reported spiropy-
ran molecular switches, the CF–
OF isomerization of both two
molecules can be triggered by
UV light. Herein, the isomeriza-
tions of TPE-SP1 and TPE-SP2 in
Scheme 1. Synthetic route to TPE-SP1 and TPE-SP2.
dichloromethane and phenylcar-
binol solution were investigated
respectively. As can be seen
Aggregation-induced emission properties
from the UV/Vis absorption of TPE-SP1 and TPE-SP2 in
Figure 2, the two compounds can undergo reversible photoiso-
merization between their unconjugated CF isomer and conju-
gated OF isomer under the irradiation of a 254 nm hand-held
ultraviolet lamp. The absorption peak at 366 nm for CF of TPE-
SP1 gradually decreased and a new absorption peak at 528 nm
assigned to the OF appeared and increased with exposure du-
ration (Figure 2a). For contrast, TPE-SP2 has a gradually de-
creased CF absorption peak at about 350 nm and a new gener-
ated and increased OF absorption peak at about 476 nm
under continuous UV irradiation
The AIE properties of TPE-SP1 and TPE-SP2 were investigated
in their THF/water solution, and both the two compounds
show obvious AIE properties as shown in Figure 1. When the
water fraction (fw) is lower than 70%, the PL curve is almost
flat lines parallel to the abscissa, which indicated that there is
no emission in pure THF solution. However, both cyan emis-
sions with peaks at 482 nm for TPE-SP1 and 483 nm for TPE-
SP2 turn on when large amounts (>70%) of water, a poor sol-
vent, was added into their THF solution. The mechanism for
(Figure 2b). The OF absorption
peak of TPE-SP1 (528 nm) has an
obvious redshift compared with
that of TPE-SP2 (476 nm), which
confirmed that the OF of TPE-
SP1 has a better p-conjugation
than that of TPE-SP2. Interesting-
ly, TPE-SP1 more easily trans-
forms from CF to OF, because
TPE-SP1 can achieve the maxi-
mum ring-open ratio after 7 min
UV irradiation, whereas TPE-SP2
needs nearly 30 min. Thus, the
different link position between
TPE and SP will lead to the dif-
ferent photochromic behaviors
and capacity. The reason may be
that the better p-conjugation
between TPE and MC in TPE-
MC1 improves the stability of
the MC moiety by dispersing the
positive charge of the nitrogen
Figure 1. a,c) Fluorescent images of TPE-SP1 and TPE-SP2, respectively, in different water fraction (fw) mixtures
under 365 nm UV illumination. b,d) Fluorescence spectra of TPE-SP1 and TPE-SP2 (10À5 m), respectively, in THF/
H2O mixtures with different fw values. Insets: plot of I/I0 versus water fraction, in which I and I0 represent the fluo-
rescence intensities in a THF/water mixture with a specific fw and in pure THF.
cation of indoline and makes
photochromism easier.[16] In con-
trast to the absorption change
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creased emission of CF at
490 nm and gradually increased
new emission of the OF at
615 nm with time in the dark
(Figure 3c and d). This reverse
process with an obvious fluores-
cent switch can be realized
many times under alternating
visible-light on–off irradiation.
However, TPE-SP2 is not sensi-
tive to light when dissolved in
phenylcarbinol, and it cannot
transform to CF when exposed
to visible light. Besides, even
under the continuous irradiation
of 254 nm UV light for 10 min,
TPE-SP2 cannot increase the
ratio of the OF (Figure S2, Sup-
porting Information).
Figure 2. Time-dependent UV/Vis absorption spectra of a) TPE-SP1 and b) TPE-SP2 (10À5 m) in dichloromethane re-
corded under 254 nm hand-held ultraviolet lamp irradiation.
in response to UV light, the PL spectra during the whole pro-
Photophysical properties in solution and aggregation state
cess in dichloromethane were less obvious because of the
weak emission of the TPE unit in good solvent as it can dissi-
pate the energy of excited molecules by free rotation.[17]
To investigate the PL change during this process, phenylcar-
binol was selected as another solvent due to its high viscosity
that can be used to restrict the intramolecular rotations of the
TPE unit to a certain degree and then result in the enhanced
emission in their solution. It appears that the two compounds
can partially convert into OF once dissolved in phenylcarbinol
because the OF is highly stabi-
Due to the introduction of a high-emissive TPE moiety, the
powders of the two compounds have high quantum yields
(FTPE-SP1 =58%, FTPE>SP2 =83%). As shown in Figure 4, the red-
shifted emissions of TPE-SP1 (473, 484 nm) compared to TPE-
SP2 (460, 475 nm) in their THF solutions and powders indicat-
ed that TPE-SP1 has a better extended p-conjugation, which
was further confirmed by the corresponding absorption spec-
tra in dichloromethane solution (Figure 2) and diffused reflec-
lized in alcohols by the strong
H-bonding interaction with sol-
vent molecules.[4] Additionally,
TPE-SP1 in phenylcarbinol was
supersensitive to light because
the OF TPE-SP1 can easily iso-
merize to the CF upon visible-
light (>500 nm) irradiation and
then CF reverts to OF when left
immediately in the dark (Fig-
ure 3a). The corresponding ab-
sorption spectra of TPE-SP1 in
phenylcarbinol shows significant
absorbance changes at two dis-
tinct wavelengths with time in
darkness (Figure 3b). Fluores-
cence excitation spectra of TPE-
SP1 in phenylcarbinol are shown
in Figure S1 (Supporting Infor-
mation), and the best excitation
wavelength for CF and OF is
about 380 and 540 nm, which
were then selected as the excit-
ing light. The PL spectra show
the CF–OF isomerization accom-
Figure 3. a) Visible and fluorescent pictures taken under visible light and 365 nm UV light. Time-dependent UV (b)
panied with the gradually de- and corresponding PL spectra (c,d) of TPE-SP1 (10À5 m) in phenylcarbinol with time in the dark.
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tion of the phenolate fragment of the OF. Indeed, the new ab-
sorption spectra (in Figure S3, Supporting Information) of cor-
responding protonated OF (POF) shows the band at 620 and
580 nm, respectively. Fascinatingly, the emissions for both POF
of TPE-SP1 and TPE-SP2 also show totally different changing
trends in Figure 5b and d, which is similar to the fluorescence
change on the TLC plate. In fact, the POF emission of TPE-SP1
has a red emission at about 630 nm with 3.4% quantum yield,
whereas TPE-SP2 merely has totally quenched emission (quan-
tum yield <0.01%). The reversible fluorescent switch can be
realized by fuming the POF of the two dyes with triethylamine
(TEA) and then the emission color can switch back to bright
cyan.
Figure 4. PL spectra of TPE-SP1 and TPE-SP2 in solution and the solid state.
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: TPE-SP1 in THF; : TPE-SP1 in powder; : TPE-SP2 in THF; : TPE-SP2 in
powder.
Mechanism research
tance absorption spectra of their powders (Figure S3, Support-
ing Information).
The different fluorescence change trend for the two molecules
under the same stimuli was then investigated by the experi-
mental research and theoretical calculation. The mechanism
for fluorescence quenching is proposed to be the photoin-
duced activation of the intramolecular energy and electron-
transfer process within a fluorophore–photochrome dyad that
Acidchromic properties in the aggregation state
As the isomerization of spiropyrans can also be triggered by
acid, the acid-stimuli responsive
solid emissions of the two mole-
cules were investigated. Letters
“JLU” and “SSM”, abbreviations
of Jilin University and supermo-
lecular structure and materials,
were written on the TLC plate
with TPE-SP1 and TPE-SP2 as flu-
orescent dyes, respectively (Fig-
ure 5a and c). Interestingly, the
two dye molecules written on
the TLC plate have totally differ-
ent emission change. The PL
spectra of TPE-SP1 show that
the emission intensity at 482 nm
decreased at first and then
a new emission at about 630 nm
appears and increased gradually,
while the emission intensity at
480 nm for TPE-SP2 decreased
all the time. With the solvent
evaporation, acidic silica gel in
the TLC plate can trigger the
two molecules to open the spiro
ring and isomerize to the OF,
and then an emission change
from cyan to red occurs on the
TLC plate for TPE-SP1 during this
transformation, whereas TPE-SP2
merely shows cyan emission
quenching as time goes by. The
exposure of the powders of TPE-
Figure 5. a,c) Time-dependent fluorescent pictures and corresponding PL spectra of TPE-SP1 and TPE-SP2, respec-
tively, on the TLC plate. b,d) Fluorescent pictures and corresponding PL spectra of initial, HCl fumed and then TEA
fumed powders of TPE-SP1 and TPE-SP2, respectively. Insets of b,d): reversible switching of the emission of TPE-
SP1 and TPE-SP2 to vapors of
concentrated hydrochloric acid
can also result in the protona- SP1 and TPE-SP2 by the HCl/TEA fuming cycle.
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MC1, TPE-MC2 will only have
a completely quenched emission
due to the combination effect of
the energy and electron-transfer
processes.
Conclusions
The reversible and different
dual-response
fluorescent
switches triggered by UV/Vis and
acid/base have been realized
during the CF–OF transformation
of both TPE-SP1 and TPE-SP2.
The comparisons of two OF/POF
molecules indicate the different
link position between TPE and
SP will result in the different p-
conjugated system that will fi-
nally lead to totally different
photochromic and acidchromic
properties. This reversible and
different multistimuli-response
fluorescence switch for the two
molecules may have potential
applications in the fluorescent
sensors in the future.
Figure 6. a) UV/Vis absorption spectra of SP, MC, and MCH, and emission spectra of TPE. b) Energy diagrams and
the pictorial representations of HOMO and LUMO orbitals of TPE, MC, MCH, and SP in their ground state calculat-
Experimental Section
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ed by using B3LYP/6-31G** by Gaussian 09. : SP; : MC; : MCH; : TPE.
Materials
THF, toluene, and ethanol were
distilled in the presence of sodium benzophenoneketyl, calcium
hydride, and magnesium, respectively, then stored under nitrogen
can encourage the transformation of the photochrome from
one state to another.[18] The energy-transfer process is support-
ed by a wide range of spectral
overlaps between the absorption
spectra of MC/MCH and the
emission band of TPE (Figure 6a).
Besides, the calculated much
lower LUMO energy level of MC/
MCH than that of TPE indicates
that the intramolecular electron-
transfer pathway from TPE to
MC/MCH may also occur in this
system (Figure 6b).
Although the energy and elec-
tron transfer may also exist for
TPE-SP1 according to the signifi-
cantly decreased fluorescence
quantum yield during the ring-
opening process, the better con-
jugation of the OF/POF structure
seems to be critical to keep the
red emission. As shown in
Figure 7, due to lack of effective
conjugation length as in TPE- Figure 7. Possible origin for two different modes of fluorescent switches.
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immediately prior to use. DMF and Dimethylacetamide (DMAc)
were distilled under vacuum from phosphorus pentoxide. 2,3,3-Tri-
methylindolenine and 5-bromosalicylaldehyde were purchased
from Energy Chemical. Benzophenone and 4-bromobenzophenone
were purchased from Alfa Aesar. Diphenylmethane, n-butyllithium
(nBuLi), p-toluenesulfonic acid (PTSA), iodomethane, and all the
other chemicals were purchased from Aladdin and used as re-
ceived without further purification. 4-Bromo-2-hydroxybenalde-
hyde, N-methyl-2,3,3-trimethylindolenine iodide, tetraphenyle-
thene, and 1,3,3-trimethylindolinobenzopyrylospiran (SP) were syn-
thesized according to previous literature reports.[11h,19–21]
1-(4-Formyl)-l,2,2-triphenylethylene (3)
1H NMR (500 MHz, CDCl3, TMS): d=9.90 (s, 1H), 7.61 (d, J=8.2 Hz,
2H), 7.19 (d, J=8.2 Hz, 2H), 7.13–7.10 (m, 9H), 7.05–6.99 ppm (m,
6H). LC-HRMS (ESI): m/z: calcd: 361.1587; found: 361.1582 [M+H]+.
Synthesis of 1-(4-vinylphenyl)-l,2,2-triphenylethylene (4)
4-(1,2,2-Triphenylvinyl)benzaldehyde (3) (3.6 g, 10 mmol) and meth-
yltriphenylphosphonium bromide (4.3 g, 12 mmol) were dissolved
in THF (15 mL) and THF (25 mL) solution containing potassium tert-
butoxide (1.68 g, 15 mmol) was slowly added dropwise at 08C
under a N2 atmosphere. The reaction went on for 10 h. Then the
reaction mixture was quenched with the addition of a saturated
aqueous solution of sodium chloride (10 mL). The organic layer
was extracted with dichloromethane (3ꢁ50 mL), and the combined
organic layer was dried over anhydrous MgSO4. The solvent was re-
moved in a rotary evaporator and the crude product was purified
using column chromatography (petroleum ether/CH2Cl2, 4:1 v/v) to
Instruments
1H NMR spectra were recorded on a 500 MHz Bruker Avance, by
using CDCl3 as the solvent and tetramethylsilane (TMS) as an inter-
nal standard (d=0.00 ppm). 13C NMR spectra were recorded on
a 125 MHz Bruker Avance, using CDCl3 as a solvent and CDCl3 as
an internal standard (d=77.00 ppm). LC-HRMS was obtained by
Agilent 1290-microTOF Q II. Element analyses were performed on
a FlashEA1112 spectrometer. GCMS were recorded on a Thermo
Fisher ITQ1100. UV/Vis spectra were measured on a Shimadzu UV-
2550 spectrophotometer. Fluorescence spectra were recorded by
Shimadzu RF-5301 PC spectrometer and Maya2000Pro optical fiber
spectrophotometer. Solid PL efficiencies were measured by using
an integrating sphere (C-701, Labsphere), with 365 and 470 nm
Ocean Optics LLS-LED as the excitation source, and the light was
introduced into the integrating sphere through optical fiber. The
fluorescence microscopy images were obtained on an Olympus
BX51 fluorescence microscope. The ground state geometries were
fully optimized by the DFT method with the Becke three-parameter
hybrid exchange and the Lee–Yang–Parr correlation functional
(B3LYP) and 6-31G** basis set by using the Gaussian 03 software
package.
1
yield compound 4 (3.4 g, 67%) as a white solid. H NMR (500 MHz,
CDCl3, TMS): d=7.14 (d, J=7.9 Hz, 2H), 7.12–7.07 (m, 9H), 7.06–
7.00 (m, 6H), 6.98 (d, J=7.8 Hz, 2H), 6.61 (dd, J=17.6, 11.0 Hz, 1H),
5.66 (d, J=17.6 Hz, 1H), 5.18 ppm (d, J=10.9 Hz, 1H); MS (EI): m/z:
calcd for C28H22: 358.17; found: 358.76.
Synthesis of TPE-SP1
1-(4-Vinylphenyl)-l,2,2-triphenylethylene (4) (1 mmol, 0.36 g), 1,3,3-
trimethylindolino-7’-bromobenzopyrylospiran (1a) (1 mmol, 0.35 g),
K3PO4 (3 mmol, 0.65 g), and Pd(OAc)2 as the catalyst (200 mg) were
dissolved in dry DMAc (5 mL). The reaction mixture was heated to
110 8C in an oil bath and stirred for 24 h under a N2 atmosphere.
After being cooled to room temperature, the reaction mixture was
poured into water and filtered to get the precipitated solid. The
product was then purified by flash column chromatography (petro-
leum ether/ethyl acetate, 50:1 v/v) to give TPE-SP1 as a yellow
solid (0.25 g, 39%). 1H NMR (500 MHz, CDCl3, TMS): d=7.22–6.81
(m, 28H), 6.54 (d, J=7.7 Hz, 1H), 5.68 (d, J=10.2 Hz, 1H), 2.74 (s,
3H), 1.33 (s, 3H), 1.18 ppm (s, 3H); 13C NMR (125 MHz, CDCl3, TMS):
d=154.67, 148.21, 143.71, 143.68, 143.62, 143.24, 141.07, 140.56,
139.04, 136.78, 135.17, 131.66, 131.37, 131.32, 131.30, 129.13,
128.66, 127.88, 127.74, 127.65, 127.59, 126.79, 126.49, 126.45,
126.39, 125.82, 121.47, 119.23, 119.12, 118.99, 118.40, 112.05,
106.80, 104.30, 51.73, 28.94, 25.84, 20.16 ppm; LC-HRMS (ESI): m/z:
calcd: 634.3104; found: 634.3084 [M+H]+; elemental analysis calcd
(%) for C47H39NO: C 89.06, H 6.20, N 2.21, O 2.52; found: C 89.02, H
6.20, N 2.18, O 2.60.
Synthesis and characterizations
Tetraphenylethene–spiropyran (TPE-SP1 and TPE-SP2) was prepared
according to the synthetic routes shown in Scheme 1. Compound
1a and 1b were synthesized according to the literature method.[21]
Compounds 2 and 3 were synthesized according to the literature
method.[22–24]
1,3,3-Trimethylindolino-7’-bromobenzopyrylospiran (1a)
1H NMR (500 MHz, CDCl3, TMS): d=7.18 (t, J=7.6 Hz, 1H), 7.07 (d,
J=7.2 Hz, 1H), 6.95 (dd, J=8.0, 1.8 Hz, 1H), 6.92–6.89 (m, 2H), 6.85
(t, J=7.4 Hz, 1H), 6.81 (d, J=10.3 Hz, 1H), 6.53 (d, J=7.7 Hz, 1H),
5.71 (d, J=10.3 Hz, 1H), 2.72 (s, 3H), 1.30 (s, 3H), 1.16 ppm (s, 3H);
MS (EI): m/z: calcd for C19H18BrNO: 355.06; found: 354.95.
Synthesis of TPE-SP2
1-(4-Vinylphenyl)-l,2,2-triphenylethylene (4) (1 mmol, 0.36 g), 1,3,3-
trimethylindolino-6’-bromobenzopyrylospiran
(1b)
(1 mmol,
1,3,3-Trimethylindolino-6’-bromobenzopyrylospiran (1b)
0.35 g), K3PO4 (3 mmol, 0.65 g), and Pd(OAc)2 as the catalyst
(200 mg) were dissolved in dry DMAc (5 mL). The reaction mixture
was heated to 1108C in an oil bath and stirred for 24 h under N2
atmosphere. After being cooled to room temperature, the reaction
mixture was poured into water and filtered to give the precipitated
solid. The product was then purified by flash column chromatogra-
phy (petroleum ether/ethyl acetate, 50:1 v/v) to give TPE-SP2 as
a pale-yellow solid (0.22 g, 34%). 1H NMR (500 MHz, CDCl3, TMS):
d=7.24–6.77 (m, 27H), 6.69 (d, J=8.4 Hz, 1H), 6.53 (d, J=7.7 Hz,
1H), 5.71 (d, J=10.2 Hz, 1H), 2.73 (s, 3H), 1.31 (s, 3H), 1.17 ppm (s,
3H); 13C NMR (125 MHz, CDCl3, TMS): d=154.27, 148.15, 143.77,
143.70, 142.73, 140.94, 140.63, 136.71, 135.62, 131.67, 131.40,
1H NMR (500 MHz, CDCl3, TMS): d=7.22–7.12 (m, 3H), 7.07 (d, J=
7.2 Hz, 1H), 6.85 (t, J=7.4 Hz, 1H), 6.78 (d, J=10.2 Hz, 1H), 6.60 (d,
J=9.3 Hz, 1H), 6.53 (d, J=7.7 Hz, 1H), 5.72 (d, J=10.3 Hz, 1H),
2.71 (s, 3H), 1.29 (s, 3H), 1.16 ppm (s, 3H); MS (EI): m/z: calcd for
C19H18BrNO: 355.06; found: 354.96.
1-(4-Bromophenyl)-1,2,2-triphenylethene (2)
1H NMR (500 MHz, CDCl3, TMS): d=7.22 (d, J=8.5 Hz, 2H), 7.15–
7.08 (m, 9H), 7.05–6.99 (m, 6H), 6.90 ppm (d, J=8.5 Hz, 2H); MS
(EI): m/z: calcd for C26H19Br: 410.07; found: 410.35.
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Sample preparation for AIE measurements
AIE performance of TPE-SP1 or TPE-SP2: Stock THF solution of TPE-
SP1 or TPE-SP2 with a concentration of 1ꢁ10À4 m was prepared.
The stock solution (1 mL) was added to 10 mL volumetric flasks.
After an appropriate amount of THF was added, water was added
dropwise under vigorous stirring to prepare 1ꢁ10À5 m solutions
with different water fractions (0–90 vol%). The PL spectra measure-
ments of the resulting solutions were then performed immediately.
Acknowledgements
This work was supported by the 973 Program (No.
2013CB834702), the Natural Science Foundation of China (No.
21204027, 21221063), program for Chang Jiang Scholars and
Innovative Research Team in University (No. IRT101713018),
and Graduate Innovation Fund of Jilin University (No.
2014013).
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Keywords: acidchromism · aggregation induced emission ·
fluorescent switch · isomerization · photochromism
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Published online on && &&, 0000
Chem. Eur. J. 2014, 20, 1 – 8
www.chemeurj.org
7
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ

Full Paper
FULL PAPER
&
Photochromism
Q. Qi, J. Qian, S. Ma, B. Xu,*
S. X.-A. Zhang, W. Tian*
&& – &&
Reversible Multistimuli-Response
Fluorescent Switch Based on
Tetraphenylethene–Spiropyran
Molecules
Unlocking emission: Two tetraphenyle-
thene (TPE)-functionalized spiropyran
(SP) molecules were designed and syn-
thesized that exhibit not only aggrega-
tion-induced emission properties but
also multistimuli-responsive properties,
such as photochromism and acidchrom-
ism. The reversible and different dual-re-
sponse fluorescent switches triggered
by UV/Vis and acid/base have been real-
ized during the ring-closed (CF) to ring-
open (OF) transformation (see scheme).
&
&
Chem. Eur. J. 2014, 20, 1 – 8
www.chemeurj.org
8
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!