Influence of cyano groups on the properties of piezofluorochromic aggregation-induced emission enhancement compounds derived from tetraphenylvinyl-capped ethane

Article abstract of DOI:10.1039/c4tc02165g

Three tetraphenylvinyl-capped ethane derivatives with 0, 1, and 2 cyano groups at the ethane moiety, namely, biTPE, biTPE-CN, and TPE-CN, respectively, were synthesized and characterized via photoluminescence, ultraviolet-visible absorption, wide-angle X-

Full text of DOI:10.1039/c4tc02165g

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DOI: 10.1039/C4TC02165G
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Materials Chemistry C
ARTICLE
Influence of cyano groups on the properties of
piezofluorochromic aggregation-induced emission
enhancement compounds derived from
tetraphenylvinyl-capped ethane†
Cite this: DOI: 10.1039/x0xx00000x
Qingyun Lu,‡ Xiaofang Li,‡ Jun Li, Zhiyong Yang,* Bingjia Xu, Zhenguo Chi,* Jiarui Xu
and Yi Zhang*
Three tetraphenylvinyl-capped ethane derivatives, with 0, 1, and 2 cyano groups at the ethane
moiety, namely, biTPE, biTPE-CN, and TPE-CN, respectively, were synthesized and
characterized via photoluminescence, ultraviolet-visible absorption, wide-angle X-ray diffraction,
fluorescence lifetime, and other techniques. Results indicate that the compounds possess
piezofluorochromic properties and exhibit aggregation-induced emission enhancement. The
distinct piezofluorochromic properties of all three compounds were reversible upon grinding and
fuming. Introduction of cyano groups to the molecular structures of the derivatives significantly
enhanced their piezofluorochromic activity. The relationship between structure and property was
studied in detail. The results obtained will be of great help in understanding the
piezofluorochromic mechanism and designing new piezofluorochromic materials.
Received 00th September 2014,
Accepted 00th September 2014
DOI: 10.1039/x0xx00000x
www.rsc.org/
However, considering the effects of aggregation-induced
quenching occurring in most luminogenic materials, the
Introduction
Stimuli-responsive fluorescent materials are a class of “smart”
materials with fluorescent colors or intensities that can change in
response to external stimuli, such as pressure, pH value, viscosity,
temperature, light, biomolecules, metal ions, and so on. These
materials have drawn considerable attention because of their
promising potential applications in optical recording, fluorescent
switches, and security inks.1–13 Newly developed piezofluorochromic
materials that show remarkable color and emission changes in the
solid state as a result of external pressure or mechanical grinding,
also called mechanofluorochromic materials, have been widely
investigated over the last few years.14–36 Reversible
piezofluorochromic behavior can generally be achieved by
converting the molecular packing mode in the solid state.37
availability of piezofluorochromic materials based on changes
in physical molecular packing mode is quite limited. In 2001,
aggregation-induced emission (AIE) was reported by Tang’s
group.38 The following year, Park’s group reported AIE-
enhanced (AIEE) materials, which are similar to AIE
materials.39 Since then, AIE materials have attracted
considerable research attention because of their potential
applications in various fields, such as organic light-emitting
devices and chemosensors.40–42 Besides their fluorescent
emission enhancement properties, AIE materials possess
mechanical force stimulus–response properties. In 2005, Tang’s
group reported that several AIE compounds possess bright–
dark switching properties between their crystalline and
amorphous states.43 This unusual crystallization-induced
emission enhancement effect allows the emission of these
materials to be repeatedly switched between dark and bright
states by fuming–heating or heating–cooling. In 2010, Park’s
PCFM Lab, GD HPPC Lab, KLGHEI of Environment and Energy Chemistry,
State Key Laboratory of Optoelectronic Material and Technologies, School
of Chemistry and Chemical Engineering, Sun Yet-sen University, Guangzhou
510275, China. Fax: +86-20-84112222; Tel: +86-20-84112712; E-mail:
group reported the piezofluorochromism of
a
cyano-
Zhiyong
Yang,
yangzhy29@mail.sysu.edu.cn;
Zhenguo
Chi,
distyrylbenzene derivative that is also an AIE compound.44
However, the relationship between the molecular structures of
the AIE compound and its piezofluorochromic nature was not
clearly understood then. Almost within the same year, our
group synthesized and reported several new piezofluorochromic
chizhg@mail.sysu.edu.cn; Yi Zhang, ceszy@mail.sysu.edu.cn
†Electronic Supplementary Information (ESI) available: Table S1-S3; Figure
S1 and S2; See DOI: 10.1039/x0xx00000x
‡
Theses authors contributed equally to the preparation of this work.
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compounds with AIE natures. We further proposed that different numbers of cyano groups were synthesized, and their
piezofluorochromism is a common property of most AIE AIE and piezofluorochromic properties were characterized.
compounds
and
denoted
these
compounds
as Piezofluorochromic activity can be signDifOicI:a1n0t.1ly03V9eie/nwCh4AaTrntCicc0lee2dO16nl5binGye
piezofluorochromic AIE (PAIE) materials.45–50 The discovery of introduction of cyano groups to the molecular structures of the
PAIE as a common property allows new opportunities for derivatives. Structure-property relationships were studied in
designing and synthesizing other piezofluorochromic materials. detail using emission and absorption spectra, wide-angle X-ray
Recently, some studies on the relationship between molecular diffraction, fluorescence lifetime decay, and other techniques.
structure and piezofluorochromism have been reported by The results obtained will help guide piezofluorochromic
Yang’s group.51-54
mechanism studies and enable the development of other
In this study, tetraphenylvinyl-capped ethane derivatives, piezofluorochromic materials in the near future.
with 0, 1, and 2 cyano groups at the ethane moiety with
Scheme 1. Synthetic routes for biTPE, biTPE‐CN and TPE‐CN.
Three tetraphenylvinyl-capped ethane derivatives possessing 0,
1, and 2 cyano groups, namely, biTPE, biTPE-CN, and TPE-CN,
Results and Discussion
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respectively, were successfully synthesized according to the routes biTPE and biTPE-CN are nearly non-emissive whereas TPE-CN
shown in Scheme 1. The chemical structures of all compounds were exhibits a weak orange emission in dilute THF solution. However,
characterized via nuclear magnetic resonance, mass spectrometry, all three compounds are highly emissive in their solid VfoierwmAsrt.icSleimOnillinaer
DOI: 10.1039/C4TC02165G
and elemental analysis.
to observations from the UV-vis spectra, the maximum emission
The optical properties of the derivatives were investigated using wavelengths of the compounds in THF solution and as solid powders
their UV-vis and photoluminescence (PL) spectra in tetrahydrofuran red-shift as the number of cyano groups increases. The emission
(THF) solution and in the solid state (Table 1). As shown in Fig. 1, color of biTPE-CN is green, that of biTPE is blue, and that of TPE-
the UV-vis spectra of the compounds in dilute THF solution exhibit CN is reddish-orange. To gain a better understanding of the optical
two absorption bands corresponding to the absorption of TPE units properties of the three compounds, we calculated their energy levels
and π-π* transitions of the conjugated π-electron system in the and energy gaps (ΔEg) by cyclic voltammetry analysis and UV-vis
molecules. With increasing number of cyano groups, the maximum absorption spectroscopy (Table 1 and Fig. S2). The ΔEg values of
absorption wavelength of the corresponding compound, which is biTPE, biTPE-CN, and TPE-CN exhibit a decreasing tendency,
related to the π-π* transition of the conjugated π-electron system, which supports the hypothesis that introducing cyano groups can
shows red-shifts from 368 nm to 405 nm. This shift indicates that reduce the electron transition energy between the ground state and
introduction of cyano groups to the molecules can reduce the the excited state. Therefore, we successfully demonstrate a simple
electron transition energy from the ground state to the excited state. molecular design strategy to tune the PL color of TPE-capped
The PL spectra of the compounds both in dilute THF solution and as ethane derivatives by introduction of cyano groups.
solid powders are shown in Fig. S1 (†ESI). Upon excitation, both
Table 1. Optical and electronic properties of the compounds
Compound
biTPE
λabs a (nm)
301, 368
301, 383
303, 405
λem b (nm)
474
λem c (nm)
457
EHOMO (eV)
5.46
ELUMO (eV)
2.51
ΔEg (eV)
2.95
biTPE‐CN
503
491
5.63
2.85
2.78
TPE‐CN
575
517
5.74
3.22
2.52
a, b In THF; c Solid powder.
derivatives presented evident AIE or AIEE characteristics. The PL
signals of the compounds in a dilute THF solution were relatively
weak and remained nearly unchanged at low fw (fw ≤60%). This
phenomenon may be attributed to intramolecular rotations of the
compounds, which serve as relaxation channels for the excited state.
However, the PL intensity of the compounds began to increase
rapidly at fw >60% because of aggregation of the molecules. As fw
increases from 80% to 90%, the PL spectra exhibit decreasing
intensities with red-shifted emission (Fig. 2 and Table 2); these
results can be interpreted in terms of ratio changes of the two
existing forms of the compounds, namely, their amorphous and
crystalline phases.
Table 2. The maximum emission wavelength of the compounds with the
water fractions of 80 % and 90 %
Fig. 1 UV−vis absorpꢀon spectra of biTPE, biTPE‐CN, and TPE‐CN in THF
solution, concentration: 10 μM.
Water
λ
em (biTPE)(nm)
λem (biTPE‐CN) (nm)
λem (TPE‐CN) (nm)
fraction
As discussed above, all three compounds exhibit weak emission in
dilute solution but strong fluorescence as solids, which reveals their
80 %
458
477
483
500
514
570
n
ature as AIE molecules. To investigate the AIE activity of the
90 %
compounds, their PL behaviors were studied in dilute mixtures of
water/THF with different water fractions (fw, the volume percentage
of water in the mixtures), and the corresponding emission spectra are
shown in Fig. 2. The PL behaviors of all of the compounds in
water/THF remained nearly constant with increasing fw, and the
The morphology of aggregated TPE-CN in water/THF mixtures
with fw of 80% and 90% was observed by scanning electron
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microscopy (SEM). The SEM images in Fig. 3 evidently show two
completely different aggregated forms: crystals and amorphous
aggregates. TPE-CN tends to aggregate in the form of rod-shaped
crystals with a diameter about 100 nm at fw = 80% and aggregate as
irregular spheres or ellipsoids at fw = 90%. Evidently, the aggregated
forms of the compounds are distinct in different water solutions.
View Article Online
DOI: 10.1039/C4TC02165G
Fig. 3 SEM images of TPE‐CN in water/THF mixtures with water fractions of
80 % (left) and 90 % (right).
Fig. 4 Calculated spatial electron distributions of LUMOs and HOMOs, and
the optimized conformation structures of the compounds.
To obtain further insights into the photophysical properties of the
three compounds at the molecular level, quantum mechanical
computations were carried out using a Gaussian 03 program. The
HOMOs and LUMOs of these compounds were obtained according
to the density functional method at the B3LYP/6-31G level after
optimizing their structures to the lowest energy spatial
conformations, as shown in Fig. 4. The HOMOs of the three
compounds show similar dispersed electron cloud distributions over
the entire molecules. However, variations in the electron cloud
distributions of their LUMOs lead to different photophysical
properties. After introduction of cyano groups to biTPE-CN and
TPE-CN, most of the electron clouds of the TPE moieties transferred
to the cyano groups at their LUMOs because of the strong electron-
withdrawing ability of the cyano group. This observation indicates
that photoinduced intramolecular charge transfers occur in the
excited states of these two compounds. Thus, among the derivatives,
TPE-CN, which possesses two cyano groups, emits the strongest
fluorescence in THF solution. Moreover, the three compounds adopt
a twisted spatial conformation at their optimized lowest energy states;
this conformation disfavors close molecular packing in the solid
state and leads to efficient fluorescence in this state. Dihedral angles
between phenyl groups A and A’ in the three derivatives increase
with increasing number of cyano groups, whereas dihedral angles
between phenyl rings in TPE units (A-B, A-C, and A-D) are
maintained, as demonstrated in Table S1. Introduction of cyano
groups exerts little influence on the conformations of the TPE
moieties but can evidently enhance the degree of molecular
distortions because of steric hindrance effects. These increases in
molecular distortion can cause the compounds to adopt different
Fig. 2 PL spectra of biTPE, biTPE‐CN, and TPE‐CN in water/THF mixtures with
different water fractions. The insets depict changes in PL peak intensity and
emission images of the compounds in mixtures with different water fraction
under 365 nm UV illumination.
4 | J. Name., 2014, 00, 1‐10
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molecular packing modes in the solid state and may affect their 50 nm, respectively, in their fluorescent emission spectra. The results
macroscopic properties. of our previous quantum mechanical computations indicated that
As the three compounds adopt a twisted spatial conformation in cyano groups can enhance the distortion degree of the molecules
View Article Online
DOI: 10.1039/C4TC02165G
their optimized structures, assembly of the molecules into dense and because of steric hindrance. Therefore, we can infer that the
closely packed structures is difficult. The crystals are easily piezofluorochromic properties of the compounds are related to their
destroyed by external pressure because of weak intermolecular distortion degrees; here, molecules with higher degrees of distortion
interactions. This destruction may be triggered by slip deformation display more evident piezofluorochromic properties under the
under external pressure. Destruction of crystalline structures may stimulus of external pressure. Thus, the piezofluorochromic property
lead to molecular conformation planarization and ultimately result in of
a
compound can be significantly improved simply by introducing
red-shifting in the PL spectrum.37 As such, the three compounds
must exhibit piezofluorochromic characteristics.
a cyano group to its molecular structure.
Pristine or original samples of the three compounds were prepared
by adding copious amounts of n-hexane to their dichloromethane
solutions. Images of these compounds obtained at room temperature
under natural and UV lights and with different sample treatments,
including grinding, fuming, and regrinding, are shown in Fig. 5. As
expected, the AIE compounds exhibit evident piezofluorochromic
properties. The color and the emission of pristine samples showed
bathochromic shifts after grinding. In addition, pristine states could
be recovered by fuming the ground samples with n-hexane vapor,
which suggests that the piezofluorochromic properties of the
compounds are finely reversible. These reversible switches of both
color and emission demonstrate that the compounds are promising
materials for optical recording and pressure-sensing applications.
Fig. 5 Images of biTPE, biTPE‐CN, and TPE‐CN samples (A) taken under
natural light and (B) 365 nm UV light with different processes: Original,
original sample; Ground, ground sample; Fumed, fumed sample which
obtained by fuming the ground sample in n‐hexane vapor for 5 min; Re‐
ground, ground sample of the above fumed sample.
Fig. 6 Normalized PL spectra of biTPE, biTPE‐CN, and TPE‐CN samples. The
insets depict changes on the maximum emission wavelength of the
compounds.
The detailed PL spectra of the compounds after grinding and
fuming are shown in Fig. 6. After grinding, the pristine samples of
biTPE, biTPE-CN, and TPE-CN exhibited red-shifts of 19, 24, and
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with blue-shifts in PL emission. The most obvious
original sample
grinding
fuming
biTPE
piezofluorochromic characteristics of TPE-CN are attributed to
View Article Online
maximum changes in degree of crystallineDOstIr:u1c0t.u10re39o/Crd4eTrC0in216th5iGs
regrinding
sample after grinding compared with the two other samples.
original sample
grinding
fuming
regrinding
0
0
0
10
20
30
40
50
2θ / deg
biTPE
original sample
grinding
fuming
biTPE-CN
grinding
0
5
10
15
20
25
30
35
Time / ns
original sample
grinding
fuming
regrinding
10
20
30
40
50
2θ / deg
biTPE-CN
TPE-CN
original sample
grinding
fuming
regrinding
0
5
10
15
20
25
30
35
Time / ns
original sample
grinding
fuming
regrinding
10
20
30
40
50
TPE-CN
2θ / deg
Fig. 7 WAXD curves of biTPE, biTPE‐CN, and TPE‐CN samples with different
treatments.
To study the mechanism of piezofluorochromism, wide-angle X-
ray diffraction (WAXD) measurements were carried out on the
samples. The WAXD curves of the three compounds obtained after
grinding and fuming are shown in Fig. 7. We can clearly observe
that all of the WAXD curves of the pristine samples display sharp
diffraction peaks. These diffraction peaks decrease in either number
or intensity after grinding and are particularly notable on TPE-CN,
which contains the largest number of cyano groups. Thus, we can
conclude that the original samples exhibit relatively high degrees of
order in their crystalline structures. The structural orders of the
0
5
10
15
20
25
30
35
Time / ns
Fig. 8 Time‐resolved emission decay curves of biTPE, biTPE‐CN and TPE‐CN
samples.
The time-resolved emission decay behaviors of the compounds
were further studied after grinding and fuming to understand the
mechanism of piezofluorochromism. Time-resolved fluorescence
curves (Fig. 8) and lifetime data (Table 3) feature two lifetimes (τ1
and τ2), and the weighted mean lifetimes (<τ>) of the original
samples increase with increasing number of cyano groups. In
comparison with the pristine samples, the <τ> values of the ground
samples are prolonged for approximately 0.2 ns, which indicates that
samples were destroyed to
a certain degree after grinding, leading to
red-shifts in their PL spectra. Either the number or intensity of
diffraction peaks can be recovered by fuming the ground samples
with n-hexane vapor; such recovery presents a reversible process
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changes in fluorescent color are accompanied by significant changes twisted conformations. As the molecular structures of the
in the fluorescent lifetime of the samples. The <τ> of fumed ground compounds are similar, the crystal C1 of TPE-CN may also be
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samples is fairly difficult to return to original values, which is assumed to adopt J-aggregated packing.
DOI: 10.1039/C4TC02165G
probably due to interactions between the solvent and samples.
Table 3. Solid state fluorescence lifetime data of biTPE, biTPE‐CN and TPE‐
CN samples
Compound
biTPE
Sample
original
τ1 (ns)
0.59
0.60
0.68
0.69
0.72
0.68
0.75
0.75
1.14
1.12
1.31
1.47
A1
τ2 (ns)
1.32
1.44
1.39
1.54
1.62
1.68
1.92
1.76
2.64
2.70
2.77
2.91
A2
<τ> (ns)
0.70
0.90
0.91
1.00
1.09
1.36
1.35
1.37
2.26
2.43
2.37
2.58
85 %
64 %
67 %
64 %
58 %
32 %
49 %
38 %
26 %
17 %
28 %
23 %
15 %
36 %
33 %
36 %
42 %
68 %
51 %
62 %
74 %
83 %
72 %
77 %
grinding
fuming
regrinding
original
grinding
fuming
Fig. 9 Normalized PL spectra of the different crystals. The insets depict the
fluorescence microscope images of the crystals.
biTPE‐CN
regrinding
original
grinding
fuming
TPE‐CN
regrinding
The relationship between the molecular aggregation state and
luminescence properties of the compounds can be determined
directly and definitively by single crystals, which present a highly
ordered molecular packing structure. The single crystals of biTPE
and biTPE-CN were grown in toluene and acetone, respectively.
Two types of TPE-CN crystals showing different fluorescent
emissions were also obtained in a mixture of dichloromethane and n-
hexane (C1, green; C2, orange). The normalized PL spectra of biTPE,
biTPE-CN, and TPE-CN crystals are shown in Fig. 9. The emission
peaks of single crystals of biTPE and biTPE-CN and crystal C1 of
TPE-CN are identical to those of their pristine samples, which
indicates that the corresponding pristine samples adopt molecular
packing modes similar to those of the crystals in the present work.
The PL emission wavelength of the TPE-CN C2 crystal is identical to
that of its ground sample, which suggests that the two TPE-CN
samples present similar molecular packing modes.
Fig. 10 Molecular packing of biTPE and biTPE‐CN in their single crystal
structures.
Conclusions
Three tetraphenylvinyl-capped ethane derivatives with 0, 1, and 2
cyano groups at the ethane moiety, namely, biTPE, biTPE-CN, and
TPE-CN, respectively, were designed and successfully synthesized
to better understand the influence of cyano groups on photophysical
properties. These compounds exhibited strong AIE activities and
significant cyano number-dependent piezofluorochromic properties.
Spectroscopic properties and morphological structures were
reversibly and repeatedly achieved upon grinding or fuming. These
excellent properties indicate that the compounds are promising
The crystalline structures of biTPE and biTPE-CN were
determined by single-crystal XRD analysis. X-ray crystallographic
intensity data were collected and are shown in in Tables S2 and S3.
As shown in Fig. 10, biTPE and biTPE-CN are packed in a head-to-
head fashion to form J-aggregates. The π-π interactions in the biTPE
and biTPE-CN crystals are relatively weak because of their highly
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stimuli-responsive luminescent materials with potential applications
in recording, pressure-sensing, and light-emitting.
resolved emission decay behaviors were measured on an
Edinburgh Instruments spectrometer (FLSP920). Ground
View Article Online
Piezofluorochromic activity was considerably enhanced by
introduction of cyano groups to the molecular structures of the
compound. We proposed that the twisted conformations of these
compounds are a key factor influencing their piezofluorochromic
activity. Structure–property relationships were studied in detail, and
samples were prepared by grinding, usinDgOaI: 1m0.o1r0t3a9r/Ca4nTdC0p2e1s6t5leG.
The method of solvent vapor fuming treatment is filling the
ground sample on a grooved glass, which was then placed it in
a large beaker saturated with n-hexane vapor for 5 min at the
temperature of 70 °C. The water/THF mixtures with different
water fractions were prepared by slowly adding distilled water
into the THF solution of samples under ultrasound at room
temperature. Scanning electron microscopy (SEM) images were
obtained from a Hitachi S4800 microscope operated at 15 kV.
Fluorescence microscopy images were taken on a Zeiss
the results obtained can help researchers obtain
a better
understanding of the piezofluorochromic mechanism and develop
other piezofluorochromic materials in the near future.
Experimental
Axio Observer A1
crystallographic intensity data were collected by using a Bruker
Smart 1000 CCD diffractometer equipped with
fluorescence
microscope.
X-ray
General information
a
4-Methylphenylboronic acid, bromotriphenylethylen, 4-
graphitemonochromated enhance (Mo) X-ray source. CCDC
1026011 and 1026015 contain the supplementary
crystallographic data for this paper
formylphenylboronic acid,
n-bromosuccinimide, benzoyl
peroxide, potassium tert-butoxide (t-BuOK), tetrakis(triphenyl
phosphine) palladium(0), cyanotrimethylsilane, tetrabutyl-
ammonium fluoride (1 M) THF solution, 4-bromophenyl-
Synthesis
acetonitrile,
iodine,
bis(pinacolato)diboron,
tetrabutyl-
TPE-E: TPE-CH2Br (5.00 g, 11.8 mmol) and triethyl phosphate
(10 mL) were added into a 100 mL round-bottom flask. Then
the mixture was stirred and refluxed for 24 h at 150 °C. After
cooling to room temperature, the reaction mixture was purified
ammonium hydroxide (TBAOH), methyl trioctyl ammonium
chloride, [1,1'-Bis(diphenylphosphino)ferrocene] dichloro-
palladium(II), and tetrabutylammonium perchlorate (electro-
chemical grade) were purchased from Alfa Aesar and used as
received. Ultra-pure water was used in all of the experiments.
All other reagents and solvents were purchased as analytical
reagent-grade chemicals from Guangzhou Dongzheng
Company (China) and used without further purification.
Intermediates TPE-CH355, TPE-CHO45, TPE-CH2Br56, BCN-
Br57, and BCN-BO58 were synthesized according to literature
methods.
Proton and carbon-13 nuclear magnetic resonance spectra
(1H NMR and 13C NMR) were measured on a Mercury-Plus
300 spectrometer [CDCl3 as solvent and tetramethylsilane
(TMS) as internal standard]. Mass spectra (MS) were
performed on a Thermo DSQ MS spectrometer. Elemental
analyses (EA) were performed with an Elementar Vario EL
elemental analyzer. Ultraviolet−visible (UV−vis) absorption
by silica gel column chromatography (acetone/
v/v) to afford a white powder (4.20 g, 74 % yield). H NMR
(300 MHz, CDCl3) (ppm) : 7.04-7.11 (m, 10H), 6.95-7.04 (m,
9H), 3.86-4.01 (m, 4H), 3.07 (d, 2H), 1.22 (t, 6H); 13C NMR
(75 MHz, CDCl3) (ppm) : 143.90, 143.77, 143.72, 142.62,
n-hexane, 1/5,
1
δ
δ
141.17, 140.67, 131.68, 131.48, 129.76, 129.64, 129.44, 129.35,
127.83, 126.64, 126.58, 62.58, 62.50, 34.85, 33.03, 31.36,
16.86, 16.79; MS(EI), m/z: 482 ([M]+, calcd for C31H31O3P,
482).
TPE-CH2CN: A solution of TPE-CH2Br (3.44g, 8.08 mmol) in
acetonitrile (40 mL) was stirred at room temperature. Then
trimethyl cyanide (1.60 g, 16.2 mmol) and tetrabutylammonium
fluoride (16.2 mL, 16.2 mmol) in THF were added and stirred
for 12 h under argon atmosphere. The reaction mixture was
spectra
were
determined
on
a
Hitachi
U-3900
purified by silica gel column chromatography (ethyl acetate/
hexane, 1/4, v/v) to afford a white powder (1.89 g, 63 % yield).
1H NMR (300 MHz, CDCl3)
(ppm) : 7.07-7.14 (m, 9H), 6.98-
7.07 (m, 10H), 3.66 (s, 2H); 13C NMR (75 MHz, CDCl3)
n-
spectrophotometer. Photoluminescence (PL) spectra were
measured on a Shimadzu RF-5301PC spectrometer with a slit
width of 3.0 nm for both excitation and emission. Cyclic
voltammetry (CV) measurement was carried out on a Shanghai
Chenhua electrochemical workstation CHI660C in a three-electrode
cell with a glassy carbon disk counter electrode, an Ag/AgCl
δ
δ
(ppm) : 143.88, 143.58, 143.52, 141.80, 140.11, 132.19, 131.42,
127.95, 127.86, 127.47, 126.81, 126.78, 118.02, 23.70; MS(EI),
m/z: 371 ([M]+, calcd for C28H21N, 371).
biTPE: A solution of TPE-E (0.50 g, 1.04 mmol) and TPE-
CHO (0.31 g, 0.87 mmol) in THF (20 mL) was stirred at room
reference electrode, and
a Pt working electrode. All CV
measurements were performed under an inert argon atmosphere with
supporting electrolyte of 0.1M tetrabutyl ammonium perchlorate (n-
Bu4NClO4) in dichloromethane at scan rate of 100 mV/s using
ferrocene as standard. The energy gaps ΔEg for the compounds were
estimated from the absorption edges of UV-visible absorption
spectra. Wide-angle X-ray diffraction (WAXD) measurements
were carried out by using a Rigaku X-ray diffractometer
temperature. Then t-BuOK (0.50 g, 4.46 mmol) was added and
the mixture was stirred for 12 h. After the solvent was removed
under reduced pressure, the residue was recrystallized with
THF/ethanol to afford a white powder (0.56 g, 93 % yield). 1H
NMR (300 MHz, CDCl3)
18H), 7.01-7.07 (m, 12H), 6.98 (d, 4H), 6.91 (s, 2H); 13C NMR
(75 MHz, CDCl3) (ppm) : 143.90, 143.80, 143.27, 141.26,
δ (ppm) : 7.19 (d, 4H), 7.07-7.14 (m,
(D/max-2200) with an X-ray source of Cu Kα(
λ
= 0.15406 nm)
δ
at 40 kV and 30 mA, at a scan rate of 4° (2
θ) per 1 min. Time-
140.79, 135.60, 131.85, 131.58, 131.52, 128.34, 127.92, 127.85,
8 | J. Name., 2014, 00, 1‐10
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ARTICLE
126.67, 125.92; MS(EI), m/z: 688 ([M]+, calcd for C54H40, 688);
Anal. calcd for C54H40: C 94.15, H 5.85; found: C 94.18, H 5.82.
10.
11.
S. Hirata, T. Watanabe, Adv. Mater., 2006, 18, 2725-2729.
Z. Ning, Z. Chen, Q. Zhang, Y. Yan, S. Qian, Y. Cao and H. Tian,
Adv. Funct. Mater., 2007, 17, 3799-3807.
View Article Online
12.
13.
M. Kinami, B. R. Crenshaw and C. Weder, Chem. Mater., 2006,
18, 946-955.
DOI: 10.1039/C4TC02165G
biTPE-CN: A solution of TPE-CH2CN(0.50 g, 1.35 mmol) and
TPE-CHO (0.49 g, 13.5 mmol) in ethanol (20 mL) was stirred
at room temperature. Then tetrabutylammonium hydroxide
solution (0.8 M, 5 drops) was added and the mixture was heated
B. R. Crenshaw, M. Burnworth, D. Khariwala, A. Hiltner, P. T.
Mather, R. Simha and C. Weder, Macromolecules, 2007, 40, 2400-
2408.
X. Zhang, Z. Chi, Y. Zhang, S. Liu and Jiarui Xu, J. Mater. Chem.
C, 2013, 1, 3376-3390.
J. Kunzelman, M. Kinami, B. R. Crenshaw, J. D. Protasiewicz and
C. Weder, Adv. Mater., 2008, 20, 119-122.
C. Dou, D. Chen, J. Iqbal, Y. Yuan, H. Zhang and Y. Wang,
Langmuir, 2011, 27, 6323-6329.
14.
15.
16.
to reflux for 2 h. A light green solid precipitated from the
1
system (0.81 g, 84 % yield). H NMR (300 MHz, CDCl3)
δ
(ppm): 7.60 (d, 2H); 7.38 (s, 1H ), 7.34 (d, 2H), 7.06-7.17 (m,
22H), 7.00-7.06 (m, 12H); 13C NMR (75 MHz, CDCl3)
(ppm):
δ
146.49, 144.96, 143.58, 143.55, 143.52, 143.46, 143.45, 143.34,
142.47, 142.10, 141.36, 141.30, 140.22, 140.09, 132.66, 132.14,
132.10, 132.02, 131.90, 131.48, 128.87, 128.04, 127.88, 126.87,
125.31, 118.29, 110.61; MS(EI), m/z : 713 ([M]+, calcd for
C55H39N, 713); Anal. calcd for C55H39N: C 92.53, H 5.51, N
1.96; found: C 92.50, H 5.53, N 1.99.
17.
18.
A. Pucci and G. Ruggeri, J. Mater. Chem., 2011, 21, 8282-8291.
A. Pucci, R. Bizzarri and G. Ruggeri, Soft Matter, 2011, 7, 3689-
3700.
A. Pucci, M. Bertoldo and S. Bronco, Macromol. Rapid Commun.,
2005, 26 (13), 1043-1048.
M. Kinami, B. R. Crenshaw and C. Weder, Chem. Mater., 2006,
18 , 946-955.
B. R. Crenshaw, M. Burnworth, D. Khariwala, A. Hiltner, P. T.
Mather, R. Simha and C. Weder, Macromolecules, 2007, 40, 2400-
2408.
Y. Ooyama and Y. Harima, J. Mater. Chem., 2011, 21, 8372-8380.
Y. Ooyama, G. Ito, H. Fukuoka, T. Nagano, Y. Kagawa, I. Imae, K.
Komaguchi and Y. Harima, Tetrahedron, 2010, 66, 7268-7271.
Y. Sagara and T. Kato, Angew. Chem. Int. Ed., 2008, 47, 5175-
5178.
M. Teng, X. Jia, X. Chen, Z. Ma and Y. Wei, Chem. Commun.,
2011, 47, 6078-6080.
X. Sun, X. Zhang, X. Li, S. Liu and G. Zhang, J. Mater. Chem.,
2012, 22, 17332-17339.
N. D. Nguyen, G. Q. Zhang, J. W. Lu, A. E. Sherman and C. L.
Fraser, J. Mater. Chem., 2011, 21, 8409-8415.
G. Zhang, J. Lu, M. Sabat and C. L. Fraser, J. Am. Chem. Soc.,
2010, 132, 2160-2162.
G. Zhang, J. Lu and C. L. Fraser, Inorg. Chem., 2010, 49, 10747-
10749.
J. Liang, F. Hu, X. Lv, Z. Chen, Z. Chen, J. Yin, G. A. Yu and S. H.
Liu, Dyes and Pigments, 2012, 95, 485-490.
V. N. Kozhevnikov, B. Donnio and D. W. Bruce, Angew. Chem, Int.
Ed., 2008, 47, 6286-6289.
T. Abe, T. Itakura, N. Ikeda and K. Shinozaki, Dalton Trans., 2009,
711-715.
J. Ni, X. Zhang, Y. H. Wu, L. Y. Zhang and Z. N. Chen, Chem. Eur.
J., 2011, 17, 1171-1183.
W. E. Lee, C. L. Lee, T. Sakaguchi, M. Fujiki and G. Kwak, Chem.
Commun., 2011, 47, 3526-3528.
M. Sase, S. Yamaguchi, Y. Sagara, I. Yoshikawa, T. Mutai and K.
Araki, J. Mater. Chem., 2011, 21, 8347-8354.
Y. Sagara, S. Yamane, T. Mutai, K. Araki and T. Kato, Adv. Funct.
Mater., 2009, 19, 1869-1875.
Z. Chi, X. Zhang, B. Xu, X. Zhou, C. Ma, Y. Zhang, S. Liu and J.
Xu, Chem. Soc. Rev., 2012, 41, 3878-3896.
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. Z. Tang, Chem. Commun.,
2001, 1740-1741.
B. K. An, S. K. Kwon, S. D. Jung and S. Y. Park, J. Am. Chem.
Soc., 2002, 124, 14410-14415.
Y. Hong, J. W. Y. Lam and B. Z. Tang, Chem. Soc. Rev., 2011, 40,
5361-5388.
X. Zhang, Z. Yang, Z. Chi, M. Chen, B. Xu, C. Wang, S. Liu, Y.
Zhang and J. Xu, J. Mater. Chem., 2010, 20, 292-298.
X. Zhang, Z. Chi, H. Li, B. Xu, X. Li, S. Liu, Y. Zhang and J. Xu, J.
Mater. Chem., 2011, 21, 1788-1796.
Y. Q. Dong, J. W. Y. Lam, Z. Li, A. J. Qin, H. Tong, Y. P. Dong,
X. D. Feng and B. Z. Tang, J. Inorg. Organomet. Polym. Mater. ,
2005, 15, 287-291.
S. J. Yoon, J. W. Chung, J. Gierschner, K. S. Kim, M. G. Choi, D.
Kim and S. Y. Park, J. Am. Chem. Soc., 2010, 132, 13675-13683.
X. Zhang, Z. Chi, H. Li, B. Xu, X. Li, W. Zhou, S. Liu, Y. Zhang
and J. Xu, Chem.-Asian J., 2011, 6, 808-811.
19.
20.
21.
TPE-CN: A solution of BCN-BO (0.50 g, 1.04 mmol) and
bromotriphenylethylene (0.77 g, 2.29 mmol) in 1, 4-dioxane
(25 mL) was stirred at room temperature. 2 M potassium
carbonate aqueous solution (2 mL) and aliquat 336 (10 drops)
were added and the mixture was stirred for 0.5 h under an argon
atmosphere. Then the Pd(PPh3)4 catalyst (catalytic amount) was
added and the reaction mixture was stirred at 90 °C for 16 h.
After cooling to room temperature, the reaction mixture was
purified by silica gel column chromatography (dichloromethane
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
/n-hexane, 1/3, v/v) to afford a light yellow powder (0.40 g,
1
52 % yield). H NMR (300 MHz, CDCl3)
4H), 7.08-7.18 (m, 22H), 6.99-7.08 (m, 12H); 13C NMR (75
MHz, CDCl3) (ppm) : 147.73, 143.29, 143.15, 143.04, 139.67,
δ (ppm) : 7.55 (d,
δ
132.22, 131.47, 130.16, 128.19, 127.90, 127.27, 127.03, 124.34,
116.98; MS(EI), m/z: 738 ([M]+, calcd for C56H38N2, 738); Anal.
calcd for C56H38N2: C 91.03, H 5.18, N 3.79; found: C 91.00, H
5.20, N 3.81.
Acknowledgements
The authors gratefully acknowledge the financial support from
the NSF of China (51173210, 51473185), the Fundamental
Research Funds for the Central Universities and NSF of
Guangdong (S2011020001190).
Notes and references
1.
2.
3.
C. E. Olson, M. J. R. Previte and J. T. Fourkas, Nat. Mater., 2002, 1,
225-228.
M. Irie, T. Fukaminato, T. Sasaki, N. Tamai and T. Kawai, Nature,
2002, 420, 759-760.
A. Kishimura, T. Yamashita, K. Yamaguchi and T. Aida, Nat.
Mater., 2005, 4, 546-549.
39.
40.
41.
42.
43.
4.
5.
T. Mutai, H. Satou and K. Araki, Nat. Mater., 2005, 4, 685-687.
S. J. Toal, K. A. Jones, D. Magde and W. C. Trogler, J. Am. Chem.
Soc., 2005, 127, 11661-11665.
6.
7.
8.
9.
S. J. Park, S. G. Kuang, M. Fryd, J. G. Saven and S. J. Park, J. Am.
Chem. Soc., 2010, 132, 9931-9933.
S. Srinivasan, P. A. Babu, S. Mahesh and A. Ajayaghosh, J. Am.
Chem. Soc., 2009, 131, 15122-15123.
S. J. Lim, B. K. An, S. D. Jung, M. A. Chung and S. Y. Park,
Angew. Chem. Int. Ed., 2004, 43, 6346-6350.
C. Löwe and C. Weder, Adv. Mater., 2002, 14, 1625-1629.
44.
45.
This journal is © The Royal Society of Chemistry 2014
J. Name., 2014, 00, 1‐10 | 9

Journal of Materials Chemistry C
Page 10 of 11
Journal Name
ARTICLE
46.
47.
48.
49.
50.
H. Li, X. Zhang, Z. Chi, B. Xu, W. Zhou, S. Liu, Y. Zhang and J.
Xu, Org. Lett., 2011, 13, 556-559.
H. Li, Z. Chi, B. Xu, X. Zhang, X. Li, S. Liu, Y. Zhang and J. Xu, J.
Mater. Chem., 2011, 21, 3760-3767.
B. Xu, Z. Chi, X. Zhang, H. Li, C. Chen, S. Liu, Y. Zhang and J.
Xu, Chem. Commun., 2011, 47, 11080-11082.
X. Zhang, Z. Chi, B. Xu, C. Chen, X. Zhou, Y. Zhang, S. Liu and J.
Xu, J. Mater. Chem., 2012, 22, 18505-18513.
View Article Online
DOI: 10.1039/C4TC02165G
B. Xu, M. Xie, J. He, B. Xu, Z. Chi, W. Tian, L. Jiang, F. Zhao, S.
Liu, Y. Zhang, Z. Xu and J. Xu, Chem. Commun., 2013, 49, 273-
275.
51.
52.
53.
54.
55.
56.
57.
58.
W. Liu, Y. Wang, M. Sun, D. Zhang, M. Zheng and W. Yang,
Chem. Commun., 2013, 49, 6042-6044.
L. Bu, M. Sun, D. Zhang, W. Liu, Y. Wang, M. Zheng, S. Xue and
W. Yang, J. Mater. Chem. C, 2013, 1, 2028-2035.
Y. Wang, W. Liu, L. Bu, J. Li, M. Zheng, D. Zhang, M. Sun, Y.
Tao, S. Xue and W. Yang, J. Mater. Chem. C, 2013, 1, 856-862
M. Zheng, D. Zhang, M. Sun, Y. Li, T. Liu, S. Xue and W. Yang, J.
Mater. Chem. C, 2014, 2, 1913-1920.
M. Banerjee, S. J. Emond, S. V. Lindeman and R. Rathore, J. Org.
Chem., 2007, 72, 8054-8061.
L. Tang, J. K. Jin, A. Qin, Y. W. Zhang, Y. Mao, J. Mei, J. Z. Sun
and B. Z. Tang, Chem Commun., 2009, 4974-4976.
H. C. Yeh, W. C. Wu, Y. S. Wen, D. C. Dai, J. K. Wang and C. T.
Chen, J. Org. Chem., 2004, 69, 6455-6462.
T. Lee, C. A. Landis, B. M. Dhar, B. J. Jung, J. Sun, A. Sarjeant, H.
J. Lee and H. E. Katz, J. Am. Chem. Soc., 2009, 131, 1692-1705.
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Journal of Materials Chemistry C
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DOI: 10.1039/C4TC02165G
Table of Contents
Three tetraphenylvinyl-capped ethane derivatives containing different cyano group number exhibited strong AIE
activities and significant cyano number-dependent piezofluorochromic properties.