Triphenylethylene-based fluorophores: Facile preparation and full-color emission in both solution and solid states

Article abstract of DOI:10.1016/j.dyepig.2016.04.014

A series of triphenylethylene-based luminophoric molecules were efficiently synthesized. The substituent effect of the fluorophores on their photophysical properties was then investigated. Consequently, it was found that longer conjugated system and larger molecular dipole of the donor-π-acceptor fluorophores could result in bathochromic shifts of UV-vis absorption and emission bands, so do the Stokes shifts. Especially, full-color fluorescent emissions in both solution and solid states could be achieved by changing conjugation length and substituents with different electron-donating or accepting abilities in the triphenylethylene skeleton. The density functional theory calculations further demonstrated that with the increase of the electron-donating or accepting abilities of the substituents, the energy gaps of the fluorophores gradually decreased, which elucidated the substituent effect of the organic fluorophores on their photophysical properties.

Full text of DOI:10.1016/j.dyepig.2016.04.014

Dyes and Pigments 132 (2016) 282e290
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Triphenylethylene-based fluorophores: Facile preparation and full-
color emission in both solution and solid states
Wei Wen, Zi-Fa Shi, Xiao-Ping Cao*, Nian-Sheng Xu
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of triphenylethylene-based luminophoric molecules were efficiently synthesized. The substit-
uent effect of the fluorophores on their photophysical properties was then investigated. Consequently, it
was found that longer conjugated system and larger molecular dipole of the donorepeacceptor fluo-
rophores could result in bathochromic shifts of UVevis absorption and emission bands, so do the Stokes
shifts. Especially, full-color fluorescent emissions in both solution and solid states could be achieved by
changing conjugation length and substituents with different electron-donating or accepting abilities in
the triphenylethylene skeleton. The density functional theory calculations further demonstrated that
with the increase of the electron-donating or accepting abilities of the substituents, the energy gaps of
the fluorophores gradually decreased, which elucidated the substituent effect of the organic fluorophores
on their photophysical properties.
Received 1 February 2016
Accepted 6 April 2016
Available online 7 April 2016
Keywords:
Fluorescence
Full-color emission
Materials science
Solid-state luminescence
Triphenylethylene
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
twisted structure, and is relatively easily prepared. It can be
transformed into its derivatives with donorepeacceptor (DepeA)
Considerable interest about luminescent materials has been
attracted to organic lighting-emitting diodes (OLEDs) because of
their vast application in display and lighting in recent years [1e3].
However, many organic fluorophores with multiple aromatic rings
suffer from the notorious aggregation-caused quenching (ACQ)
effect in solid states [4e6]. In 2001, Tang's group discovered a novel
and unusual phenomenon, termed aggregation-induced emission
(AIE), which is an anti-ACQ effect [7]: Many molecules are weak or
non-luminescent in the solution state but become highly emissive
when in the aggregated states. It has technological implications to
modulate solid-state optical properties of fluorophores due to their
real world applications, which are commonly used as solid films in
photonic and electronic devices [8e11]. Notably, motivated by the
commercial potentials of full-color displays [12,13] and white-
lighting emission [14e16], it has a urgent need to realize multicolor
emission with molecular mixtures of similar chemical structures.
However, a limited number of fluorophores was found to show
admirable color-tunable AIE behaviors in the solid state. Most of the
AIE-active molecules reported emit blue and green lights [17e20].
Triphenylethylene is also an AIE-type molecule [21e25]. It has a
system due to the asymmetric nature of its structure, which could
modulate emission to longer wavelength more easily. Remarkably,
the DepeA type molecules usually exhibit distinctive fluorescence
properties owing to their intramolecular charge transfer (ICT)
transitions, which endows them with tuned electronic states under
various environments [26e29].
In this work, we designed and synthesized a series of triphe-
nylethylene skeleton derivatives. Their max emission peaks could
be tuned in full-color range both in solution and solid states by
conjugation extension and introduction of the DepeA structure,
from 383 nm to 643 nm in THF solution and from 458 nm to 687 nm
in solid, respectively.
2. Results and discussion
2.1. Synthesis
Herein, we report a series of fluorophores 3aec, 4aec, 5aec, and
7aee based on a triphenylethylene skeleton consisting of various
combinations of different substituent (Scheme 1). In the design of
these compounds, we take the following factors into account. (i) As
an AIE-type molecule, triphenylethylene can make its derivatives
exhibit AIE properties [21e25]. (ii) Conjugation length extension
* Corresponding author.
E-mail address: caoxpinglzu@163.com (X.-P. Cao).
can generate a significant bathochromic shift of fluorescent
http://dx.doi.org/10.1016/j.dyepig.2016.04.014
0143-7208/© 2016 Elsevier Ltd. All rights reserved.

W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
283
Scheme 1. Synthesis and structures of fluorophores 3aec, 4aec, 5aec, and 7aee.
emission [30]. (iii) Both electronic and steric effects of a cyano
group affect the emission process of an AIE fluorophore [31e33].
(iv) The DepeA system is an attractive electronic structure for
organic light-emitting materials because the photophysical and
redox properties can be fine-tuned by the judicious combination of
a donor and an acceptor [34e36]. By the combination of the con-
jugative effect, strong intramolecular pushepull electronic effect,
and twisted structure, these fluorophores show fluorescence and
large Stokes shifts in both solution and solid states.
By combining all the considerations above, the triphenyl-
ethylene derivatives 3aec [37,38] were prepared through a Horner-
Wadsworth-Emmons (HWE) olefination reaction from commercial
substituted benzophenones 1aec and phosphite ester 2 [39] in
70e80% yields in the presence of potassium tert-butoxide at 25 ꢀC.
The methoxyl (eOCH3) and dimethylamino [eN(CH3)2] groups
were employed as the electron donor (D) groups, because they had
the different strength of the electron-donating ability which could
be reflected from the molecular dipole moments (Table 1) and the
substrates could be obtained directly from the commercial re-
agents. At the same time, a cyano (eCN) group was introduced as an
electron acceptor (A) group in order to facilitate subsequent func-
tional group transformation. Then, reduction of the eCN groups in
compounds 3aec by DIBAL-H afforded the aldehydes 4aec
[11,40,41] in 90e95% yields (another type fluorophores). With the
5aec were obtained in 70e80% yields by the HWE olefination re-
action of aldehydes 4aec with phosphite ester 2 under the same
conditions as described above. On the other hand, in order to make
the conjugated system more twisted for increasing AIE effect of the
molecules, compounds 7aec were synthesized in 80e88% yields
through the Knoevenagel condensation of aldehydes 4aec with
phenylacetonitrile 6a. Another two compounds 7d and 7e were
also synthesized from aldehydes 4a and 4b with p-nitro-
benzeneacetonitrile 6b in 90e94% yields for the increasing of
molecular polarity by the introduction of nitro (eNO2) group. The
chemical structures of the new compounds were all characterized
by 1H and 13C NMR, and high resolution mass spectra (see
supporting information).
2.2. Photophysical properties
With all the synthetic compounds in hand, UVevis absorption
spectra was first investigated in diluted THF solution (Table 1 and
Fig. S1). The spectra of the fluorophores 3a, 4a, 5a, and 7a show a
single absorption band corresponding to a
pep* transition with
lmax at 321 nm (3a), 333 nm (4a), 366 nm (5a), and 366 nm (7a),
respectively. The introduction of electron-donating (D) groups in
the benzene ring of triphenylethylene skeleton produces the
emergence of a new transition from 350 nm (3b) to 436 nm (7c)
assigned to an intramolecular charge transfer (ICT) between the
aldehydes 4aec in hand, on one hand, the p-extended derivatives

284
W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
Table 1
Photophysical properties of fluorophores 3aec, 4aec, 5aec, and 7aee in solution and powder.
Samples Band gap (eV)c Band gap (eV)d Dipole moment (D)d Solutiona
Solidb
labs (nm)a lem (nm) Stokes shift (nm) Ff (%)e
t
(ns)f labs (nm)g lem (nm) Stokes shift (nm) Ff (%)e (ns)f
t
3a
3b
3c
4a
4b
4c
5a
5b
5c
7a
7b
7c
7d
7e
3.46
2.97
2.77
3.31
3.08
2.65
3.01
2.88
2.58
2.96
2.79
2.43
2.75
2.48
3.94
3.71
3.33
3.77
3.51
3.16
3.25
3.07
2.75
3.22
3.09
2.77
2.95
2.68
5.8
8.2
9.4
4.1
6.1
7.4
6.6
9.1
10.8
4.4
7.0
7.8
8.5
11.6
321
291, 350 395
267, 364 412
333
292, 356 396
271, 407 401
366
298, 379 467
328, 415 481
390
69
45
48
50
40
4.6 31.0 343
467
485
550
458
525
578
482
524
592
499
519
636
619
687
124
97
38.2 2.5
10.7 eh
0.6 eh
4.5 6.9
5.6 7.1
388
415
135
111
150
133
87
129
155
160
109
187
206
237
383
3.9 25.4 347
5.5 0.5
6.6 6.7
5.9 7.0
16.6 0.5
3.0 1.9
4.2 1.0
4.5 1.0
2.8 0.5
5.3 0.3
4.6 eh
4.5 1.4
375
445
395
395
437
339
410
449
413
450
1.2 eh
e
0.4 eh
456
90
88
66
102
122
180
171
222
36.0 1.5
43.0 1.1
9.1 0.4
34.4 1.5
26.5 0.3
5.3 1.0
46.1 11.7
1.4 2.4
366
468
290, 388 510
324, 436 616
313, 381 552
421
643
a
Measured in THF (10
Measured using powder.
Calculated from UVevis absorption.
Calculated from DFT calculations [B3LYP/6-31G(d) level] by Gaussian 09 program.
Absolute fluorescence quantum yield determined with a calibrated integrating sphere system.
Averaged fluorescence lifetimes.
Measured using thin film prepared from CH2Cl2 solution.
Fluorescence lifetimes were too short to detected
m
M).
b
c
d
e
f
g
h
electron donor of the molecules and the electron acceptor groups.
Comparison of the UVevis absorption spectra of fluorophores 3bec
and 4bec showed that the replacement of the eCN group by the
eCHO group induces a bathochromic shift of the
pep* transition
(3b: 291 nm, 4b: 292 nm, 3c: 267 nm, 4c: 271 nm) and ICT bands
(3b: 350 nm, 4b: 356 nm, 3c: 364 nm, 4c: 407 nm). For the fluo-
rophores 5b, 5c, 7b, and 7c, the bathochromic shifts for ICT bands
(5b: 379 nm, 7b: 388 nm, 5c: 415 nm, 7c: 436 nm) were observed
with the transfer of eCN group from benzene to olefin, while the
hypsochromic shift for the
pep* transition (5b: 298 nm, 7b:
290 nm, 5c: 328 nm, 7c: 324 nm). Compared to fluorophores 7a and
7b, the ICT bands of fluorophores 7d and 7e were observed at
longer wavelengths (7d: 381 nm, 7e: 421 nm) when the stronger
electron accepting eNO2 groups were introduced.
For all the synthetic fluorophores, as UVevis absorption tuned
from 321 nm (3a) to 436 nm (7c) by the extension of conjugation
length with additional phenylethylene unit and incorporation of
electron-donating (D) and electron-accepting (A) groups, the
maximum emission of the selected fluorophores range from
383 nm (4a) to 643 nm (7e) with the absolute fluorescence quan-
tum yields (FQYs) around 2.8e16.6% in THF solution. It can be
attributed to the intramolecular rotation of benzene rings in dilute
solutions and the non-radiant energy consumption resulting in low
Fig. 1. Fluorescent emission spectra of fluorophores 3aec, 4aec, 5aec, and 7aee in
tetrahydrofuran at 10 M.
m
compared with 3a (390 nm) and 4a (383 nm), respectively. How-
ever, the maximum emission of 4c (401 nm) exhibited significantly
hypsochromic shift compared to 3c (412 nm) when the stronger
electron-donating ability group eN(CH3)2 was introduced in the
benzene rings of the triphenylethylene skeleton. But for the two
quantum yields (most
Фf < 10%). Then fluorescence lifetimes of the
fluorophores were measured. The fluorescence decay of fluo-
rophore 5c obeyed mono-exponential function with fluorescence
lifetime of 1.0 ns. The other fluorophores obeyed bi-exponential or
tri-exponential function with averaged fluorescence lifetimes
around 0.3e31.0 ns (Fig. S5 and Table S1). They all fell into the
nanosecond region. And the solution emission color ranging from
blue to red covered the whole visible region (Fig. 1). Accordingly,
the band gap energy became narrower with additional conjugation
units or introducing electron-donating (D) and electron-accepting
(A) groups (Table 1). The fluorophores of DepeA substituted
pattern exhibited the larger bathochromic emission and smaller
band gap energy.
Then the substituent and the regioisomeric effects on the pho-
tophysical properties of the fluorophores were investigated. The
maximum emission of 3b (395 nm) and 4b (396 nm) with two
eOCH3 groups exhibited 5 nm and 13 nm bathochromic shifts
types of longer
p-conjugated molecules (5aec and 7aec), the
maximum emission of 7a (468 nm), 7b (510 nm), and 7c (616 nm)
exhibited 12 nm, 43 nm, and 135 nm bathochromic shifts compared
with 5a (456 nm), 5b (467 nm), and 5c (481 nm) when eCN groups
transformed from the benzene groups to the olefins, respectively
(Table 1 and Fig. S2). Compared to fluorophores 7aeb, when the
stronger electron-accepting ability groups eNO2 were introduced,
fluorophores 7d (552 nm) and 7e (643 nm) exhibited more
significantly bathochromic shifts. It is very interesting that fluo-
rophores 7aee exhibited large Stokes shifts (102e222 nm). Espe-
cially, fluorophores 7c (180 nm), 7d (171 nm), and 7e (222 nm)
showed larger Stokes shifts, which will be vital to their real world
applications [42,43]. Thus, the enhancement of the molecular

W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
285
dipole of the De
p
eA fluorophores resulted in the bathochromic
exponential function with averaged fluorescence lifetimes around
0.3e11.7 ns, but the fluorescence lifetimes of fluorophores 3bec
and 4bec were too short to be detected (Table 1, Fig. S6, and
Table S2). As shown in Fig. 2(b), the fluorescence photos of the
selected fluorophores 3a, 4a, 5aec, and 7aee in powder under
365 nm irradiation unambiguously demonstrated their panchro-
matic properties. In addition, all the fluorophores 3aec, 4aec,
5aec, and 7aee (except 3b and 5a) exhibited the large Stokes shifts
of more than 100 nm in the solid state as well (Table 1 and Fig. S4).
Especially for fluorophore 7e, the Stokes shift is even up to 237 nm,
which could effectively avoid imaging interference of absorption
bands to the emission bands.
shift of the UVevis absorption, so do the fluorescent emission.
The photophysical properties of the fluorophores in the solid
state were also further investigated. All these fluorophores showed
broad solid-state absorption in the UVevisible region ranged from
339 nm (7a) to 450 nm (7e) (Table 1 and Fig. S3). As shown in
Fig. 2(a), the emissions of fluorophores 3aec, 4aec, 5aec, and 7aee
covered the whole visible region in the solid state and had further
bathochromic shifts compared with those in solution. The
maximum emission ranged from 458 nm (4a) to 687 nm (7e).
As most of these AIE molecules, the non-planar structure of the
triphenylethylene skeleton was effective to avoid the intermolec-
ular
pep stacking in solid states, and subsequently prevent the
fluorescence quenching of the fluorophores. Consequently, by
2.3. Analysis of structure-property relation
changing the substituents with different electron-donating or
electron-accepting abilities in the skeleton,
a
series of
To confirm the molecular structures of these species and un-
derstand the above emission features of these fluorophores, X-ray
single crystal analysis has been conducted for compounds 3a, 3c,
and 7b. The crystals suitable for X-ray analysis were obtained from
petroleum ether and CH2Cl2 [44]. The crystal structures of com-
pounds 3a and 3c were shown in Fig. 3. It was found that the tri-
phenylethylene skeleton displayed a twisted framework as the
dihedral angles between three benzene rings and the central
ethylene moiety are 6.7ꢀ, 69.9ꢀ, 26.7ꢀ (3a) and 40.7ꢀ, 60.8ꢀ, 13.9ꢀ
(3c), respectively (Fig. S7 and Fig. S8). These non-planar structure
could restrain the intermolecular face-to-face packing. The 3a
triphenylethylene-based fluorophores with full-color fluorescent
emissions in the solid state could be obtained with the absolute
fluorescence quantum yields (FQYs) around 0.4e46.1%. As shown in
Table 1, among the synthesized fluorophores, the emission in-
tensity of these compounds was dependent on the introduced
electron-donating (D) or electron-accepting (A) groups. For the
same conjugation structure, when the donor groups [eOCH3 and
eN(CH3)2] were attached to the benzene rings of the triphenyl-
ethylene skeleton, the FQYs were decreased. Even, the FQYs of
fluorophores with the substitution of eN(CH3)2 in solid state were
decreased much more (3c: 0.6%, 4c: 0.4%, 5c: 9.1%, 7c: 5.3%). We
speculated that it might be owing to the lone electron pairs of the
nitrogen atoms [in eN(CH3)2] partially quenched the fluorescence
of the four fluorophores. While the eCHO group as an acceptor
group connected to triphenylethylene, the FQYs of fluorophores
4aec were below 10% and lower than those in solutions. Compared
to fluorophores 4aec, the emission intensity of fluorophores 5aec
which submitted by eCN group was obviously enhanced in solid
state. However, the FQYs of the fluorophores with eNO2 group as
acceptor were dependent on the introduced donor group, such as
fluorophores 7d and 7e. The fluorescence decay of fluorophore 4a
obeyed mono-exponential function with fluorescence lifetime of
0.5 ns. The other fluorophores obeyed bi-exponential or tri-
molecules are arranged in a loose manner, and pep intermolecular
interactions are hampered, owing to steric hindrance imposed by
one of the benzene rings without CN-substituted, which can
effectively minimize the quenching of fluorescence caused by solid
aggregation to give a 38.2% absolute fluorescence quantum yield in
the solid state [Fig. 3(a,b)]. However, compared with compound 3a,
the 3c molecules appeared closer arrangement in crystal packing,
where the distance between the carbon atom of benzene connected
with eN(CH3)2 group and the plane of the benzene ring with CN-
substituted in adjacent molecule is 3.47 Å [Fig. 3(c,d)]. This allowed
a certain degree of overlap of conjugated system between adjacent
molecules, and then resulted in a certain pep stacking interactions,
which led to fluorescence quenching. So compound 3c gave only a
0.6% absolute fluorescence quantum yield in the solid state.
The crystal structure of compound 7b was shown in Fig. 4. The
triphenylethylene framework is distorted as the dihedral angles
between three benzene rings and the central ethylene moiety are
36.8ꢀ, 66.3ꢀ, and 20.1ꢀ, respectively (Fig. S9). It was noted that two
hydrogen atoms (in eOCH3) interact with eCN group (neighboring
molecule) and one of the benzene rings of the triphenylethylene
Fig. 2. (a) Fluorescent emission spectra of fluorophores 3aec, 4aec, 5aec, and 7aee in
powder. (b) Photographs of the powder of selected fluorophores 3a, 4a, 5aec, and
7aee under 365 nm UV light.
Fig. 3. Single crystal structures of compounds 3a (a,b) and 3c (c,d) from the packing
view.

286
W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
density of the HOMOs are mainly distributed on the substituted
tristyl moieties. Compared with compounds 3a and 4a, the HOMOs
of compounds 3c and 4c with the strong electron-donating
eN(CH3)2 group showed upshift more seriously than their
LUMOs, respectively. Therefore, the energy gaps of compounds 3c
(3.33 eV) and 4c (3.16 eV) were smaller than that of compounds 3a
(3.94 eV) and 4a (3.77 eV), which well explained that the absorp-
tion and emission bands of compounds 3c and 4c were longer than
those of compounds 3a and 4a. Fluorophores 5aec and 7aec have
similar results compared with fluorophores 3aec and 4aec, but the
HOMOs of compounds 7d and 7e with the strong electron-
accepting eNO2 group moved to downshift, while their LUMOs
showed downshift more seriously. Hence, the energy gaps of
compounds 7d (2.95 eV) and 7e (2.68 eV) were smaller than that of
compounds 7a (3.22 eV) and 7b (3.09 eV), which well explained
that the absorption and emission bands of compounds 7d and 7e
were longer than those of compounds 7a and 7b. Thus, the
panchromatic emissive properties of the triphenylethylene-based
fluorophores could be theoretically explained.
Fig. 4. Single crystal structure of compound 7b from the (a) b axis view and (b)
packing view.
framework (neighboring molecule) to form one OCH2eH,,,N
hydrogen bond (2.73 Å) and one OCH2eH,,,p bond (2.82 Å),
3. Conclusions
respectively. Then a network is formed in the crystal as shown in
Fig. 4(a), the oxygen atom (in eOCH3) interacts with one hydrogen
atom of the benzene ring of the triphenylethylene framework
(neighboring molecule) to form one CeH,,,O hydrogen bond
(2.70 Å). The molecules arranged in two layers with two opposite
directions [Fig. 4(b)]. The two layers were induced by two CH,,,C
interactions with distances 2.87 Å and 2.78 Å, respectively. It is the
OCH2eH,,,N hydrogen bond that fix the double bonds, and pre-
vent the free twisting motions around the double bonds. Assisted
by the strong supramolecular interactions, the molecule becomes
In summary, we have obtained a series of triphenylethylene-
based fluorophores exhibiting fluorescent emission in the region
ranging from blue to red in both solution and solid states. By
changing the conjugation length and the substituents on the tri-
phenylethylene skeleton, the fluorescent emission wavelength
could cover the entire visible spectral region with maxima wave-
lengths ranging from 390 nm to 643 nm in solution and
458 nme687 nm in solid state. Some structure-property relation-
ships were rationalized by a combination of X-ray crystallographic
analysis and DFT calculations. It showed that with the increase of
the electron-donating abilities or electron-accepting abilities of the
substituents, the energy gaps of the fluorophores gradually
decreased, which theoretically elucidated the substituent effect of
the fluorophores on their photophysical properties. Comparing to
other reported fluorophores, the synthetic triphenylethylene-based
fluorophores mentioned above enjoy the advantages of facile syn-
thesis and tunable full-color fluorescent emission, which would
provide more opportunity for their real world applications.
more rigid. The twisted structure of compound 7b prevents
pep
stacking interactions along the long molecular axis by the bulky
eCN and phenyl substituents. Thus the strong supramolecular in-
teractions induce tight packing and rigid molecules, without par-
allel stacking, making compound 7b show strong fluorescence with
26.5% absolute fluorescence quantum yield in the solid state.
To gain insight into the influence of the p-conjugted system in
the ground state and electronic effect of substituents on the aro-
matic rings of the skeleton, density functional theory (DFT) calcu-
lations [B3LYP/6-31G(d) level] of fluorophores 3aec, 4aec, 5aec,
and 7aee were further carried out by Gaussian 09 program, and the
optimized geometries and HOMO/LUMO plots of the fluorophores
are illustrated in Fig. 5. All of the molecules adopt twisted non-
planar conformations at the terminal aromatic rings, which is
favorable for active intramolecular rotations of the aromatic rings
in solution. Obviously, the electron density of the LUMOs are mainly
localized over the electron-accepting moieties, but the electron
4. Experimental section
4.1. General information
All reactions that required anhydrous conditions were carried
out by standard procedures under argon atmosphere. Commer-
cially available reagents 1aec and 6aeb were used as received. The
Fig. 5. Calculated molecular orbitals and energy levels of fluorophores 3aec, 4aec, 5aec, and 7aee.

W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
287
solvents were dried by distillation over appropriate drying re-
agents. Petroleum ether used had a boiling range of 60e90 ꢀC.
Reactions were monitored by TLC on silica gel GF 254 plates. Col-
umn chromatography was performed through silica gel
(200e300 mesh). 1H and 13C NMR spectra were recorded on a
Bruker AM 400 MHz spectrometer, as were the DEPT 135 experi-
(petroleum ether/ethyl acetate 3:1). m.p.: 156e157 ꢀC. 1H NMR
(400 MHz, CDCl3, 25 ꢀC, TMS):
AreH), 7.25 (d, J ¼ 9.6 Hz, 2H; AreH), 7.11 (d, J ¼ 8.8 Hz, 2H; AreH),
7.03 (d, J ¼ 8.8 Hz, 2H; AreH), 6.69 (s, 1H; CH), 6.67 (d, J ¼ 8.0 Hz,
4H; AreH), 3.00 (s, 6H; NCH3), 2.99 (s, 6H; NCH3). MS (ESI-TOF): m/z
368.2 ([M þ H]þ, calcd for C25H26N3 368.2). The data were identical
with those in the reference. [38].
d
(ppm) 7.37 (d, J ¼ 8.4 Hz, 2H;
ments. Chemical shift values (d)are given in ppm and coupling
constants (J) in Hz. Residual solvent signals in the 1H and 13C NMR
spectra were used as an internal reference (CDCl3: dH ¼ 7.26,
dC ¼ 77.0 ppm). Multiplicity was indicated as follows: s (singlet),
d (doublet), m (multiplet). Melting points were determined by use
of a microscope apparatus and are uncorrected. Mass spectra were
obtained using electrospray ionization (ESI), as indicated, on a
Thermo Orbitrap Elite mass spectrometer. Single crystal X-ray
diffraction measurements were made on a Bruker X8 APEX
4.3. The preparation and characterization data of fluorophores
4aec
4.3.1. 4-(2,2-Diphenylethenyl)benzaldehyde (4a)
A solution of DIBAL-H (7.3 mL,1.5 M in toluene, 10.95 mmol) was
added dropwise to a stirred solution of compound 3a (1.55 g,
5.52 mmol) in anhydrous toluene (50 mL) at 0 ꢀC under argon at-
mosphere. The reaction mixture was stirred at 0 ꢀC for 5 h and
quenched by CH3OH (20 mL). Then the aqueous solution of satu-
rated seignette salt (20 mL) was added into the resulting mixture
and the stirring continuously at 25 ꢀC for 2 h until the solution was
divided into two layers. The organic layer was dried over anhydrous
MgSO4, and concentrated under reduced pressure. Flash column
chromatography of the residue through silica gel afforded com-
pound 4a as a white amorphous solid (1.49 g, 95%). Rf ¼ 0.38 (pe-
troleum ether/ethyl acetate 15:1). m.p.: 97e99 ꢀC. 1H NMR
diffractometer working with graphite monochromated Mo Ka ra-
diation. UVevis absorptions were carried out on a UV-Cary100
spectrophotometer. The fluorescence spectra and the absolute
fluorescence quantum yields were measured from the solution and
powder form using the Edinburgh Instruments (FLS920). Phosphite
ester 2 was synthesized as previously reported [39].
4.2. The preparation and characterization data of fluorophores
3aec
(400 MHz, CDCl3, 25 ꢀC, TMS):
d (ppm) 9.91 (s, 1H; CHO), 7.65 (d,
4.2.1. 4-(2,2-Diphenylethenyl)benzonitrile (3a)
J ¼ 8.4 Hz, 2H; AreH), 7.37e7.35 (m, 8H; AreH), 7.21e7.19 (m, 2H;
AreH), 7.17 (d, J ¼ 8.4 Hz, 2H; AreH), 7.01 (s, 1H; CH). MS (ESI-TOF):
m/z 285.1 ([M þ H]þ, calcd for C21H17O 285.1). The data were
identical with those in the reference. [25].
Potassium tert-butoxide (1.18 g, 10.54 mmol) was added to a
solution of benzophenone 1a (956 mg, 5.25 mmol) and phosphite
ester 2 (1.97 g, 7.79 mmol) in anhydrous THF (100 mL) at 0 ꢀC under
argon atmosphere, then the reaction mixture was stirred at 25 ꢀC
for 5 h. A color change from colorless to yellow was observed. Upon
completion of the reaction, the solvent was concentrated under
reduced pressure. The resulting residue was diluted with water
(20 mL) and then extracted with ethyl acetate (3 ꢁ 20 mL). The
combined organic layers were dried over anhydrous MgSO4, and
concentrated under reduced pressure. Flash column chromatog-
raphy of the residue through silica gel afforded compound 3a as a
white amorphous solid (1.18 g, 80%). Rf ¼ 0.35 (petroleum ether/
ethyl acetate 15:1). m.p.: 110e111 ꢀC. 1H NMR (400 MHz, CDCl3,
4.3.2. 4-[2,2-Bis(4-methoxy-phenyl)ethenyl]benzaldehyde (4b)
The preparation procedure was the same as that used for com-
pound 4a. Starting with compound 3b (1.87 g, 5.48 mmol), DIBAL-H
(7.3 mL, 1.5 M in toluene, 10.95 mmol), compound 4b was obtained
as a green amorphous solid (1.74 g, 92%). Rf ¼ 0.50 (petroleum
ether/ethyl acetate 4:1). m.p.: 116e118 ꢀC. 1H NMR (400 MHz,
CDCl3, 25 ꢀC, TMS):
d
(ppm) 9.89 (s,1H; CHO), 7.64 (d, J ¼ 8.4 Hz, 2H;
AreH), 7.28 (d, J ¼ 8.8 Hz, 2H; AreH), 7.17 (d, J ¼ 8.4 Hz, 2H; AreH),
7.10 (d, J ¼ 8.8 Hz, 2H; AreH), 6.87 (d, J ¼ 8.4 Hz, 4H; AreH), 6.86 (s,
1H; CH), 3.84 (s, 3H; OCH3), 3.83 (s, 3H; OCH3). MS (ESI-TOF): m/z
345.1 ([M þ H]þ, calcd for C23H21O3 345.1). The data were identical
with those in the reference. [41].
25 ꢀC, TMS):
d
(ppm) 7.40 (d, J ¼ 8.4 Hz, 2H; AreH), 7.37e7.34 (m,
8H; AreH), 7.18e7.16 (m, 2H; AreH), 7.09 (d, J ¼ 8.0 Hz, 2H; AreH),
6.95 (s, 1H; CH). MS (ESI-TOF): m/z 282.1 ([M þ H]þ, calcd for
C
21H16N 282.1). The data were identical with those in the reference.
[37].
4.3.3. 4-[2,2-Bis(4-dimethylamino-phenyl)ethenyl]benzaldehyde
(4c)
4.2.2. 4-[2,2-Bis(4-methoxy-phenyl)ethenyl]benzonitrile (3b)
The preparation procedure was the same as that used for com-
pound 4a. Starting with compound 3c (2.02 g, 5.50 mmol), DIBAL-H
(7.3 mL, 1.5 M in toluene, 10.95 mmol), compound 4c was obtained
as a yellow amorphous solid (1.84 g, 90%). Rf ¼ 0.65 (petroleum
ether/ethyl acetate 3:1). m.p.: 178e179 ꢀC. 1H NMR (400 MHz,
The preparation procedure was the same as that used for com-
pound 3a. Starting with bis(4-methoxyphenyl)methanone 1b
(1.27 g, 5.25 mmol), phosphite ester 2 (1.97 g, 7.79 mmol) and
potassium tert-butoxide (1.18 g, 10.54 mmol), compound 3b was
obtained as a white amorphous solid (1.38 g, 77%). Rf ¼ 0.50 (pe-
troleum ether/ethyl acetate 4:1). m.p.: 112e113 ꢀC. 1H NMR
CDCl3, 25 ꢀC, TMS):
d
(ppm) 9.87 (s,1H; CHO), 7.62 (d, J ¼ 8.0 Hz, 2H;
AreH), 7.27 (d, J ¼ 8.0 Hz, 2H; AreH), 7.19 (d, J ¼ 8.4 Hz, 2H; AreH),
7.06 (d, J ¼ 8.8 Hz, 2H; AreH), 6.76 (s, 1H; CH), 6.68 (d, J ¼ 8.4 Hz,
2H; AreH), 6.67 (d, J ¼ 8.4 Hz, 2H; AreH), 3.00 (s, 6H; NCH3), 2.99
(s, 6H; NCH3). MS (ESI-TOF): m/z 371.2 ([M þ H]þ, calcd for
(400 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 7.37 (d, J ¼ 8.0 Hz, 2H;
AreH), 7.25 (d, J ¼ 9.0 Hz, 2H; AreH), 7.08 (d, J ¼ 8.4 Hz, 2H; AreH),
7.06 (d, J ¼ 8.4 Hz, 2H; AreH), 6.86 (d, J ¼ 8.0 Hz, 2H; AreH), 6.85 (d,
J ¼ 9.0 Hz, 2H; AreH), 6.79 (s, 1H; CH), 3.82 (s, 3H; OCH3), 3.80 (s,
3H; OCH3). MS (ESI-TOF): m/z 341.1 ([M]þ, calcd for C23H19NO2
341.1). The data were identical with those in the reference. [38].
C
25H27N2O 371.2). The data were identical with those in the refer-
ence. [40].
4.4. The preparation and characterization data of fluorophores
5aec
4.2.3. 4-[2,2-Bis(4-dimethylamino-phenyl)ethenyl]benzonitrile (3c)
The preparation procedure was the same as that used for com-
pound 3a. Starting with 4,40-bis(dimethylamino)benzophenone 1c
(1.41 g, 5.26 mmol), phosphite ester 2 (1.97 g, 7.79 mmol) and po-
tassium tert-butoxide (1.18 g, 10.54 mmol), compound 3c was ob-
tained as a yellow amorphous solid (1.35 g, 70%). Rf ¼ 0.55
4.4.1. (E)-4-[4-(2,2-Diphenylvinyl)styryl]benzonitrile (5a)
The preparation procedure was the same as that used for com-
pound 3a. Starting with aldehyde 4a (148 mg, 0.52 mmol), phos-
phite ester 2 (197 mg, 0.78 mmol), compound 5a was obtained as a

288
W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
green amorphous solid (159 mg, 80%). Rf ¼ 0.73 (petroleum ether/
ethyl acetate 4:1). m.p.: 153e155 ꢀC. 1H NMR (400 MHz, CDCl3,
resulting residue was diluted with water (10 mL) and then
extracted with ethyl acetate (3 ꢁ 10 mL). The combined organic
layers were dried over anhydrous MgSO4, and concentrated under
reduced pressure. Flash column chromatography of the residue
through silica gel afforded 7a as a greenish yellow amorphous solid
(179 mg, 88%). Rf ¼ 0.38 (petroleum ether/ethyl acetate 20:1). m.p.:
25 ꢀC, TMS):
d
(ppm) 7.61 (d, J ¼ 8.0 Hz, 2H; AreH), 7.53 (d,
J ¼ 8.4 Hz, 2H; AreH), 7.37e7.30 (m, 10H; AreH), 7.25e7.23 (m, 2H;
AreH), 7.12 (d, J ¼ 16.6 Hz, 1H; CH), 7.04 (d, J ¼ 8.4 Hz, 2H; AreH),
7.01 (d, J ¼ 16.6 Hz, 1H; CH), 6.98 (s, 1H; CH). 13C NMR (100 MHz,
CDCl3, 25 ꢀC, TMS):
d
(ppm) 143.3 (C), 143.2 (C), 141.8 (C), 140.3 (C),
135e137 ꢀC. 1H NMR (400 MHz, CDCl3, 25 ꢀC, TMS):
d (ppm) 7.70 (d,
137.9 (C), 134.6 (C), 132.4 (CH), 131.9 (CH), 130.3 (CH), 130.0 (CH),
128.7 (CH), 128.2 (CH), 127.7 (CH), 127.6 (CH), 127.5 (CH), 126.7 (CH),
126.5 (CH), 126.4 (CH), 119.0 (C), 110.4 (C), one AreCH resonance
was not resolved. HRMS (ESI-TOF): m/z 383.1664 ([M]þ, calcd for
J ¼ 8.4 Hz, 2H; AreH), 7.65 (d, J ¼ 7.2 Hz, 2H; AreH), 7.46e7.32 (m,
12H; AreH, CH), 7.24e7.22 (m, 2H; AreH), 7.11 (d, J ¼ 8.4 Hz, 2H;
AreH), 7.00 (s, 1H; CH). 13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 144.6 (C),143.0 (C), 141.7 (CH), 140.0 (C),139.9 (C),134.7 (C),
C
29H21N 383.1669).
131.9 (C), 130.2 (CH), 130.0 (CH), 129.1 (CH), 129.0 (CH), 128.8 (CH),
128.3 (CH), 127.91 (CH), 127.87 (CH), 127.7 (CH), 127.1 (CH), 125.9
(CH), 118.2 (C), 110.6 (C), one AreCH resonance was not resolved.
4.4.2. (E)-4-{4-[2,2-Bis(4-methoxy-phenyl)vinyl]styryl}benzonitrile
(5b)
HRMS (ESI-TOF): m/z 384.1743 ([M þ H]þ, calcd for C29H22
N
The preparation procedure was the same as that used for com-
pound 3a. Starting with compound 4b (179 mg, 0.52 mmol),
phosphite ester 2 (197 mg, 0.78 mmol), compound 5b was obtained
as a greenish yellow amorphous solid (179 mg, 78%). Rf ¼ 0.54
(petroleum ether/ethyl acetate 3:1). m.p.: 189e190 ꢀC. 1H NMR
384.1747).
4.5.2. (Z)-2-Phenyl-3-{4-[2,2-bis(4-methoxy-phenyl)vinyl]phenyl}
acrylonitrile (7b)
The preparation procedure was the same as that used for com-
pound 7a. Starting with aldehyde 4b (182 mg, 0.53 mmol), phe-
nylacetonitrile 6a (64 mg, 0.55 mmol) and sodium methoxide
solution in anhydrous CH3OH (0.05 mL, 1 M in CH3OH), compound
7b was obtained as a yellow amorphous solid (200 mg, 85%).
Rf ¼ 0.50 (petroleum ether/ethyl acetate 4:1). m.p.: 145e147 ꢀC. 1H
(400 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 7.61 (d, J ¼ 8.4 Hz, 2H;
AreH), 7.53 (d, J ¼ 8.4 Hz, 2H; AreH), 7.30 (d, J ¼ 8.4 Hz, 2H; AreH),
7.27 (d, J ¼ 8.8 Hz, 2H; AreH), 7.14 (d, J ¼ 8.8 Hz, 2H; AreH), 7.08 (d,
J ¼ 17.0 Hz, 1H; CH), 7.05 (d, J ¼ 8.0 Hz, 2H; AreH), 7.01 (d,
J ¼ 17.0 Hz, 1H; CH), 6.89 (d, J ¼ 8.8 Hz, 2H; AreH), 6.86 (d,
J ¼ 8.8 Hz, 2H; AreH), 6.83 (s, 1H; CH), 3.85 (s, 3H; OCH3), 3.83 (s,
NMR (400 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 7.70 (d, J ¼ 8.0 Hz, 2H;
3H; OCH3). 13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 159.4
AreH), 7.65 (d, J ¼ 7.2 Hz, 2H; AreH), 7.45e7.36 (m, 4H; AreH, CH),
7.28 (d, J ¼ 8.4 Hz, 2H; AreH), 7.14 (d, J ¼ 7.2 Hz, 2H; AreH), 7.12 (d,
J ¼ 6.8 Hz, 2H; AreH), 6.90 (d, J ¼ 8.8 Hz, 2H; AreH), 6.87 (d,
J ¼ 8.8 Hz, 2H; AreH), 6.85 (s, 1H; CH), 3.86 (s, 3H; OCH3), 3.83 (s,
(C), 159.1 (C), 142.6 (C), 141.9 (C), 138.5 (C), 136.1 (C), 134.1 (C), 132.6
(C), 132.4 (CH), 132.1 (CH), 131.6 (CH), 129.8 (CH), 128.9 (CH), 126.7
(CH), 126.6 (CH), 126.1 (CH), 125.5 (CH), 119.0 (C), 114.1 (CH), 113.6
(CH), 110.3 (C), 55.3 (CH3), 55.2 (CH3). HRMS (ESI-TOF): m/z
443.1873 ([M]þ, calcd for C31H25NO2 443.1879).
3H; OCH3). 13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d (ppm) 159.6
(C), 159.3 (C), 143.9 (C), 141.8 (CH), 140.5 (C), 135.9 (C), 134.7 (C),
132.2 (C), 131.5 (CH), 131.4 (C), 129.8 (CH), 129.1 (CH), 129.01 (CH),
128.99 (CH), 128.9 (CH), 125.8 (CH), 125.1 (CH), 118.2 (C), 114.2 (CH),
113.6 (CH), 110.1 (C), 55.3 (CH3), 55.2 (CH3). HRMS (ESI-TOF): m/z
443.1874 ([M]þ, calcd for C31H25NO2 443.1879).
4.4.3. (E)-4-{4-[2,2-Bis(4-dimethylamino-phenyl)vinyl]styryl}
benzonitrile (5c)
The preparation procedure was the same as that used for com-
pound 3a. Starting with compound 4c (192 mg, 0.52 mmol),
phosphite ester 2 (197 mg, 0.78 mmol), compound 5c was obtained
as an orange amorphous solid (171 mg, 70%). Rf ¼ 0.56 (petroleum
ether/ethyl acetate 3:1). m.p.: 152e153 ꢀC. 1H NMR (400 MHz,
4.5.3. (Z)-2-Phenyl-3-{4-[2,2-bis(4-dimethylamino-phenyl)vinyl]
phenyl}acrylonitrile (7c)
The preparation procedure was the same as that used for com-
pound 7a. Starting with aldehyde 4c (196 mg, 0.53 mmol), phe-
nylacetonitrile 6a (64 mg, 0.55 mmol) and sodium methoxide
solution in CH3OH (0.05 mL, 1 M in CH3OH), compound 7c was
obtained as a red amorphous solid (199 mg, 80%). Rf ¼ 0.55 (pe-
troleum ether/ethyl acetate 3:1). m.p.: 171e173 ꢀC. 1H NMR
CDCl3, 25 ꢀC, TMS):
d
(ppm) 7.60 (d, J ¼ 8.4 Hz, 2H; AreH), 7.53 (d,
J ¼ 8.4 Hz, 2H; AreH), 7.29 (d, J ¼ 8.4 Hz, 2H; AreH), 7.26 (d,
J ¼ 8.8 Hz, 2H; AreH), 7.12 (d, J ¼ 16.2 Hz,1H; CH), 7.10 (d, J ¼ 8.4 Hz,
2H; AreH), 7.08 (d, J ¼ 8.0 Hz, 2H; AreH), 6.99 (d, J ¼ 16.2 Hz, 1H;
CH), 6.75 (s, 1H; CH), 6.70 (d, J ¼ 7.2 Hz, 2H; AreH), 6.68 (d,
J ¼ 7.6 Hz, 2H; AreH), 3.00 (s, 6H; NCH3), 2.98 ppm (s, 6H; NCH3).
(400 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 7.70 (d, J ¼ 8.4 Hz, 2H;
13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 150.1 (C), 149.8 (C),
AreH), 7.64 (d, J ¼ 7.2 Hz, 2H; AreH), 7.45e7.35 (m, 4H; AreH, CH),
7.27 (d, J ¼ 8.8 Hz, 2H; AreH), 7.15 (d, J ¼ 8.4 Hz, 2H; AreH), 7.09 (d,
J ¼ 8.8 Hz, 2H; AreH), 6.76 (s, 1H; CH), 6.70 (d, J ¼ 8.8 Hz, 2H;
AreH), 6.68 (d, J ¼ 8.8 Hz, 2H; AreH), 3.02 (s, 6H; NCH3), 2.99 (s,
143.7 (C), 142.1 (C), 139.5 (C), 133.4 (C), 132.4 (CH), 132.3 (CH), 131.4
(CH), 129.6 (CH), 128.8 (CH), 126.6 (CH), 126.5 (CH), 125.6 (CH),
123.2 (CH), 119.1 (C), 112.3 (CH), 111.9 (CH), 110.1 (C), 40.5 (CH3), two
AreC and one CH3 resonances were not resolved. HRMS (ESI-TOF):
m/z 470.2583 ([M þ H]þ, calcd for C33H32N3 470.2589).
6H; NCH3). 13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d (ppm) 150.3
(C), 149.9 (C), 145.3 (C), 142.1 (CH), 141.6 (C), 134.9 (C), 131.8 (C),
131.3 (CH), 130.7 (C), 129.6 (CH), 129.1 (CH), 129.0 (CH), 128.8 (CH),
127.8 (C), 125.8 (CH), 122.7 (CH), 118.5 (C), 112.2 (CH), 111.8 (CH),
109.3 (C), 40.42 (CH3), 40.38 (CH3), one AreCH resonance was not
resolved. HRMS (ESI-TOF): m/z 470.2586 ([M þ H]þ, calcd for
4.5. The preparation and characterization data of fluorophores
7aee
4.5.1. (Z)-2-Phenyl-3-[4-(2,2-diphenylvinyl)phenyl]acrylonitrile
(7a)
C33H32N3 470.2589).
A freshly prepared sodium methoxide solution in anhydrous
CH3OH (0.05 mL, 1 M in CH3OH) was added dropwise to a solution
of aldehyde 4a (150 mg, 0.53 mmol) and phenylacetonitrile 6a
(64 mg, 0.55 mmol) in EtOH (100 mL) at 25 ꢀC. Then the reaction
mixture was stirred for 5 h at the same temperature. A color change
from colorless to yellow was observed. Upon completion of the
reaction, the solvent was concentrated under reduced pressure. The
4.5.4. (Z)-2-(4-Nitrophenyl)-3-[4-(2,2-diphenylvinyl)phenyl]
acrylonitrile (7d)
The preparation procedure was the same as that used for com-
pound 7a. Starting with aldehyde 4a (150 mg, 0.53 mmol), p-
nitrobenzeneacetonitrile 6b (89 mg, 0.55 mmol) and sodium
methoxide solution in CH3OH (0.05 mL, 1 M in CH3OH), compound
7d was obtained as a red amorphous solid (213 mg, 94%). Rf ¼ 0.75

W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
289
(petroleum ether/ethyl acetate 3:1). m.p.: 153e154 ꢀC. 1H NMR
(400 MHz, CDCl3, 25 ꢀC, TMS):
stacked conjugated molecules. synthesis, structure, and spectral character-
ization of alkyl bithiazole oligomers. J Am Chem Soc 2003;125:5040e50.
[10] Davis R, Rath NP, Das S. Thermally reversible fluorescent polymorphs of
alkoxy-cyano-substituted diphenylbutadienes: role of crystal packing in solid
state fluorescence. Chem Commun 2004:74e5.
d
(ppm) 8.29 (d, J ¼ 9.2 Hz, 2H;
AreH), 7.81 (d, J ¼ 9.2 Hz, 2H; AreH), 7.74 (d, J ¼ 8.4 Hz, 2H; AreH),
7.55 (s, 1H; CH), 7.39e7.34 (m, 8H; AreH), 7.23e7.21 (m, 2H; AreH),
7.14 (d, J ¼ 8.4 Hz, 2H; AreH), 7.00 (s, 1H; CH). 13C NMR (100 MHz,
[11] Wilson JN, Smith MD, Enkelmann V, Bunz UHF. Cruciform [p]-systems: effect
of aggregation on emission. Chem Commun 2004:1700e1.
CDCl3, 25 ꢀC, TMS):
d (ppm) 147.8 (C),145.5 (C),144.9 (CH),142.8 (C),
[12] Kim E, Park SB. Chemistry as a prism: a review of light-emitting materials
having tunable emission wavelengths. Chem Asian J 2009;4:1646e58.
[13] Shimizu M, Hiyama T. Organic fluorophores exhibiting highly efficient pho-
toluminescence in the solid state. Chem Asian J 2010;5:1516e31.
[14] Farinola GM, Ragni R. Electroluminescent materials for white organic light
emitting diodes. Chem Soc Rev 2011;40:3467e82.
[15] Su H-C, Chen H-F, Fang F-C, Liu C-C, Wu C-C, Wong K-T, et al. Solid-state white
light-emitting electrochemical cells using iridium-based cationic transition
metal complexes. J Am Chem Soc 2008;130:3413e9.
141.3 (C), 140.8 (C), 139.8 (C), 131.0 (C), 130.20 (CH), 130.16 (CH),
129.6 (CH),128.9 (CH),128.3 (CH),128.1 (CH),128.0 (CH),127.8 (CH),
126.8 (CH), 126.6 (CH), 124.4 (CH), 117.4 (C), 108.2 (C). HRMS (ESI-
TOF): m/z 428.1514 ([M]þ, calcd for C29H20N2O2 428.1520).
4.5.5. (Z)-2-(4-Nitrophenyl)-3-{4-[2,2-bis(4-methoxy-phenyl)
vinyl]phenyl} acrylonitrile (7e)
[16] Praveen VK, Ranjith C, Armaroli N. White-light-emitting supramolecular gels.
Angew Chem Int Ed 2014;53:365e8.
The preparation procedure was the same as that used for com-
pound 7a. Starting with aldehyde 4b (182 mg, 0.53 mmol), p-
nitrobenzeneacetonitrile 6b (89 mg, 0.55 mmol) and sodium
methoxide solution in CH3OH (0.05 mL, 1 M in CH3OH), compound
7e was obtained as a red amorphous solid (233 mg, 90%). Rf ¼ 0.58
(petroleum ether/ethyl acetate 4:1). m.p.: 77e79 ꢀC. 1H NMR
[17] An B-K, Kwon S-K, Jung S-D, Park SY. Enhanced emission and its switching in
fluorescent organic nanoparticles. J Am Chem Soc 2002;124:14410e5.
[18] Chen J, Law CCW, Lam JWY, Dong Y, Lo SMF, Williams ID, et al. Synthesis, light
emission, nanoaggregation, and restricted intramolecular rotation of 1,1-
substituted 2,3,4,5-tetraphenylsiloles. Chem Mater 2003;15:1535e46.
[19] Xie Z, Yang B, Xie W, Liu L, Shen F, Wang H, et al. A class of nonplanar con-
jugated compounds with aggregation-induced emission: structural and op-
tical properties of 2,5-diphenyl-1,4-distyrylbenzene derivatives with all cis
double bonds. J Phys Chem B 2006;110:20993e1000.
[20] Zeng Q, Li Z, Dong Y, Ca Di, Qin A, Hong Y, et al. Fluorescence enhancements of
benzene-cored luminophors by restricted intramolecular rotations: AIE and
AIEE effects. Chem Commun 2007:70e2.
[21] Yang Z, Chi Z, Yu T, Zhang X, Chen M, Xu B, et al. Triphenylethylene carbazole
derivatives as a new class of AIE materials with strong blue light emission and
high glass transition temperature. J Mater Chem 2009;19:5541e6.
[22] Zhang X, Yang Z, Chi Z, Chen M, Xu B, Wang C, et al. A multi-sensing fluo-
rescent compound derived from cyanoacrylic acid. J Mater Chem 2010;20:
292e8.
(400 MHz, CDCl3, 25 ꢀC, TMS):
d
(ppm) 8.29 (d, J ¼ 9.2 Hz, 2H;
AreH), 7.81 (d, J ¼ 8.8 Hz, 2H; AreH), 7.74 (d, J ¼ 8.4 Hz, 2H; AreH),
7.55 (s, 1H; CH), 7.28 (d, J ¼ 8.8 Hz, 2H; AreH), 7.15 (d, J ¼ 7.2 Hz, 2H;
AreH), 7.13 (d, J ¼ 8.8 Hz, 2H; AreH), 6.89 (d, J ¼ 8.8 Hz, 2H; AreH),
6.87 (d, J ¼ 8.8 Hz, 2H; AreH), 6.85 (s, 1H; CH), 3.86 (s, 3H; OCH3),
3.83 (s, 3H; OCH3). 13C NMR (100 MHz, CDCl3, 25 ꢀC, TMS):
d (ppm)
159.7 (C), 159.4 (C), 147.7 (C), 145.0 (CH), 144.9 (C), 141.9 (C), 140.9
(C), 135.8 (C), 132.1 (C), 131.5 (CH), 130.5 (C), 130.0 (CH), 129.7 (CH),
129.1 (CH), 126.5 (CH), 124.8 (CH), 124.3 (CH), 117.5 (C), 114.2 (CH),
113.7 (CH), 107.7 (C), 55.3 (CH3), 55.2 (CH3). HRMS (ESI-TOF): m/z
488.1725 ([M]þ, calcd for C31H24N2O4 488.1730).
[23] Yang Z, Chi Z, Xu B, Li H, Zhang X, Li X, et al. High-Tg carbazole derivatives as a
new class of aggregation-induced emission enhancement materials. J Mater
Chem 2010;20:7352e9.
[24] Zhang X, Chi Z, Li H, Xu B, Li X, Liu S, et al. Synthesis and properties of novel
aggregation-induced emission compounds with combined tetraphenyl-
ethylene and dicarbazolyl triphenylethylene moieties. J Mater Chem 2011;21:
1788e96.
Acknowledgments
[25] Zhang X, Chi Z, Xu B, Chen C, Zhou X, Zhang Y, et al. End-group effects of
piezofluorochromic aggregation-induced enhanced emission compounds
containing distyrylanthracene. J Mater Chem 2012;22:18505e13.
[26] Sun X, Liu Y, Xu X, Yang C, Yu G, Chen S, et al. Novel electroactive and pho-
toactive molecular materials based on conjugated donor-acceptor structures
for optoelectronic device applications. J Phys Chem B 2005;109:10786e92.
[27] Kim FS, Guo X, Watson MD, Jenekhe SA. High-mobility ambipolar transistors
and high-gain Inverters from a donoreacceptor copolymer semiconductor.
Adv Mater 2010;22:478e82.
[28] Shen XY, Yuan WZ, Liu Y, Zhao Q, Lu P, Ma Y, et al. Fumaronitrile-based flu-
orogen: red to near-infrared fluorescence, aggregation-induced emission,
solvatochromism, and twisted intramolecular charge transfer. J Phys Chem C
2012;116:10541e7.
The authors are grateful to the National Natural Science Foun-
dation of China (Grant Nos. 21572085, 21272098, 21572086, and
21190034), the Program for Changjiang Scholars and Innovative
Research Team in University (PCSIRT: IRT_15R28), and the 111
Project for financial support. We gratefully acknowledge Yong-
Liang Shao in Lanzhou University for X-ray crystallographic
analyses.
Appendix A. Supplementary data
[29] Shen XY, Wang YJ, Zhao E, Yuan WZ, Liu Y, Lu P, et al. Effects of substitution
with donoreacceptor groups on the properties of tetraphenylethene trimer:
aggregation-induced emission, solvatochromism, and mechanochromism.
J Phys Chem C 2013;117:7334e47.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2016.04.014.
[30] Mishra A, Behera RK, Behera PK, Mishra BK, Behera GB. Cyanines during the
1990s: a review. Chem Rev 2000;100:1973e2012.
References
[31] Li Y, Li F, Zhang H, Xie Z, Xie W, Xu H, et al. Tight intermolecular packing
through supramolecular interactions in crystals of cyano substituted
oligo(para-phenylene vinylene): a key factor for aggregation-induced emis-
sion. Chem Commun 2007:231e3.
[1] Friend RH, Gymer RW, Holmes AB, Burroughes JH, Marks RN, Taliani C, et al.
Electroluminescence in conjugated polymers. Nature 1999;397:121e8.
[2] D'Andrade BW, Forrest SR. White organic light-emitting devices for solid-state
lighting. Adv Mater 2004;16:1585e95.
[32] Yeh H-C, Wu W-C, Wen Y-S, Dai D-C, Wang J-K, Chen C-T. Derivative of a,b-
dicyanostilbene: convenient precursor for the synthesis of diphenylmalei-
mide compounds, EꢂZ isomerization, crystal structure, and solid-state fluo-
rescence. J Org Chem 2004;69:6455e62.
[3] Huang J, Sun N, Dong Y, Tang R, Lu P, Cai P, et al. Similar or totally different:
the control of conjugation degree through minor structural modifications, and
deep-blue aggregation-induced emission luminogens for non-doped OLEDs.
Adv Funct Mater 2013;23:2329e37.
[4] Thomas SW, Joly GD, Swager TM. Chemical sensors based on amplifying
fluorescent conjugated polymers. Chem Rev 2007;107:1339e86.
[5] Yuan WZ, Lu P, Chen S, Lam JWY, Wang Z, Liu Y, et al. Changing the behavior of
chromophores from aggregation-caused quenching to aggregation-induced
emission: development of highly efficient light emitters in the solid state.
Adv Mater 2010;22:2159e63.
[6] Hong Y, Lam JWY, Tang BZ. Aggregation-induced emission. Chem Soc Rev
2011;40:5361e88.
[7] Luo J, Xie Z, Lam JWY, Cheng L, Chen H, Qiu C, et al. Aggregation-induced
emission of 1-methyl-1,2,3,4,5-pentaphenylsilole. Chem Commun 2001:
1740e1.
[33] Palayangoda SS, Cai X, Adhikari RM, Neckers DC. Carbazole-based donor-
acceptor compounds: highly fluorescent organic nanoparticles. Org Lett
2008;10:281e4.
[34] Gompper R, Wagner H-U. Donor-acceptor-substituted cyclic
p-electron sys-
temsꢂprobes for theories and building blocks for new materials. Angew Chem
Int Ed 1988;27:1437e55.
[35] Ajayaghosh A. Donor-acceptor type low band gap polymers: polysquaraines
and related systems. Chem Soc Rev 2003;32:181e91.
[36] Meier H. Conjugated oligomers with terminal donor-acceptor substitution.
Angew Chem Int Ed 2005;44:2482e506.
ꢀ
ꢀ
[37] Pericas MA, Castellnou D, Rodríguez I, Riera A, Sola L. Tail-tied ligands: an
immobilized analogue of (R)-2-piperidino-1,1,2-triphenylethanol with intact
high catalytic activity and enantioselectivity. Adv Synth Catal 2003;345:
1305e13.
[8] Strohriegl P, Grazulevicius JV. Charge-transporting molecular glasses. Adv
Mater 2002;14:1439e52.
[9] Koren AB, Curtis MD, Francis AH, Kampf JW. Intermolecular interactions in p-
[38] Allen RE, Schumann EL, Day WC, Van Campen MG. Amidines of certain

290
W. Wen et al. / Dyes and Pigments 132 (2016) 282e290
substituted triphenylethylenes. J Am Chem Soc 1958;80:591e8.
[42] Escobedo JO, Rusin O, Lim S, Strongin RM. NIR dyes for bioimaging applica-
tions. Curr Opin Chem Biol 2010;14:64e70.
[43] Nienhaus K, Ulrich Nienhaus G. Fluorescent proteins for live-cell imaging with
super-resolution. Chem Soc Rev 2014;43:1088e106.
[39] Nishizawa T, Lim HK, Tajima K, Hashimoto K. Highly uniaxial orientation in
oligo(p-phenylenevinylene) films induced during wet-coating process. J Am
Chem Soc 2009;131:2464e5.
[40] Tang K, Liang M, Liu Y, Sun Z, Xue S. 2D-
p
-A type organic dyes based on N,N-
[44] CCDC 1426808 (3a), 1446547 (3c), 1426810 (7b). contain the supplementary
crystallographic data for this paper. These data are provided free of charge by
The Cambridge Crystallographic Data Centre.
dimethylaryl amine and rhodamine-3-acetic acid for dye-sensitized solar
cells. Chin J Chem 2011;29:89e96.
[41] Yoshimasa M, Toru K, Toshimitsu H, Hydrazone derivative and electropho-
tographic photoreceptor therefrom. Patent (1992), JP 04004260 A 19920108.