Aggregation-Induced Emission of Hexaphenyl-1,3-butadiene

Article abstract of DOI:10.1002/cjoc.201500116

A new type of AIE molecules based on hexaphenyl-1,3-butadienes was reported with respect to the synthesis and characterization. This material exhibited different maximum emission wavelength and enhanced emission intensity at different aggregate state (amo

Full text of DOI:10.1002/cjoc.201500116

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DOI: 10.1002/cjoc.201500116
Aggregation-Induced Emission of Hexaphenyl-1,3-butadiene
a
a
,a
a
b
Yahui Zhang, Lingwei Kong, Jianbing Shi,* Bin Tong, Junge Zhi,
b
,a
Xiao Feng, and Yuping Dong*
a
School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
b
School of Chemistry, Beijing Institute of Technology, Beijing 100081, China
A new type of AIE molecules based on hexaphenyl-1,3-butadienes was reported with respect to the synthesis
and characterization. This material exhibited different maximum emission wavelength and enhanced emission in-
tensity at different aggregate state (amorphous and crystalline state).
Keywords aggregation-induced emission, hexaphenyl-1,3-butadienes, aggregate state, phase transition
Introduction
applications.
In our previous report, aryl-substituted 1,3-butadiene
The development of organic luminescent materials is
of significance due to their important applications in
fluorescent sensors and light-emitting diode fabrica-
derivatives proved excellent candidates for AIE chro-
mophores with simple synthesis and outstanding mech-
[8]
anochromic behavior. If two hydrogen atoms in the
[1]
tion. In recent years, some luminogenic materials
were found emitting more efficiently in the form of film
than in solution and have received considerable interest.
As one of the typical examples, the emission of silole
molecules was first demonstrated to be stronger in the
aggregate state than that in the solution state by Tang
positions 2 and 3 in tetra-aryl substituted 1,3-butadiene
derivatives can be substituted by aryl groups, we specu-
lated the target substances should enhance the AIE
properties and deepen the understanding of the AIE
mechanism. In this report, three hexaphenyl-1,3-buta-
diene (HPB) derivatives without and with the different
alkyl groups were synthesized by a one-step reaction
[2]
et al. in 2001. A concept of aggregation-induced
emission (AIE) was coined accordingly for the unusual
phenomenon in the aggregate state. Such a novel effect
has enabled the AIE luminogens to find potential
high-tech applications in sensors and opto-electrical
[9]
under mild conditions according to the reference as
shown in Scheme 1. All compounds were purified and
characterized by standard spectroscopic techniques in-
cluding NMR, MS and elemental analysis, see supple-
mentary information.
[
3]
devices over the past years.
Most AIE molecules share some common features
such as propeller-like structures with some rotors. Both
experimental results and theoretical calculations have
indicated that the AIE mechanism of those AIE lumino-
gens is to block the radiationless relaxation channel and
open the radiative decay pathway because the rotations
of the rotors are restricted due to the involved physical
constraint in the aggregate state. So the compounds
with a more twisted configuration can efficiently pre-
vent parallel orientation of conjugated chromophores
and strengthen the restricted intramolecular rotation
Scheme 1 Synthetic routes of HPB-C
x
B(OH)2
R
Pd(OAc)2
+
Ag CO
2
3
[4]
R
R
R = H
HPB-C0
HPB-C2
C H
2
5
(
RIR) effect. Under the guidance of the mechanism un-
C5H11 HPB-C5
derstanding, researchers have designed and synthesized
a large variety of AIE molecules, including hydrocarbon
system, heteroatom system, organometallic system,
Results and Discussion
[
5]
[6]
[7]
and so on. The exploitation and design of new AIE
molecules remain a promising direction in this exciting
area given their fundamental importance and practical
Three compounds are soluble in common organic
solvents such as dichloromethane and tetrahydrofuran
(THF) but insoluble in water. Therefore, AIE features of
*
E-mail: bing@bit.edu.cn; chdongyp@bit.edu.cn; Tel.: 0086-10-68917390; Fax: 0086-10-68917390
Received February 6, 2015; accepted May 20, 2015; published online June 2, 2015.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201500116 or from the author.
Chin. J. Chem. 2015, 33, 701—704
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Zhang et al.
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HPB-C
x
were studied by measuring the change in their
of HPB-C
0
was successfully obtained. We attempted
fluorescence intensity in THF-water mixtures as plotted
in Figure S1 (see SI). The correlation between the net
2 5
other solvents and/or methods for HPB-C and HPB-C
but failed. This is probably due to the existence of alkyl
groups resulting to different stereoisomers such as Z-Z,
Z-E and E-E isomers, which are unfavorable for the
highly ordered alignment of molecules. Crystal of
change in the maximum PL intensities of HPB-C
the water fraction (f ) is shown in Figure 1. The fluo-
rescence intensities of their THF solution with an f
x
and
w
w
lower than 60% were negligibly small. This is due to the
non-radiative decay caused by the free intramolecular
rotation of the σ bonds between phenyl and alkenyl. The
HPB-C
crystal X-ray crystallography (SXRD) analysis. As
shown in Figure 2A, HPB-C adopts a highly twisted
0
with high quality was used for the single-
0
emission began to drastically increase once the f
reached 70%, at which point, the aggregates started to
form because the transmittance of HPB-C distinctly
decreased at high water contents (≥70%). This indi-
cated that the molecules of HPB-C have clustered into
larger size of the aggregates, as shown in Figure S2 (SI),
and the free rotations were restricted. With an f of 90%,
the PL intensities of HPB-C , HPB-C and HPB-C
w
conformation, which had a helical structure for the
backbone of the butadiene. In addition, there are large
torsion angles between the ethylenic group and the
phenyl group of 47.10°, 44.77°, 33.91°, 61.77°, 38.33°
x
x
and 64.26° for θ
any phenyl groups in HPB-C
tate in solvents and thus consume the exciton energies
and make HPB-C non-emissive in solutions. Upon ag-
1
－θ
6
, respectively. This indicated that
0
molecule can freely ro-
w
0
2
5
0
were increased by ~14, 12 and 17 fold, respectively. The
dynamic light scattering (DLS) confirmed the aggregate
gregation, these intramolecular rotations are highly re-
stricted and boost the emissive efficiency. Moreover, the
dihedral angles between the adjacent phenyl rings are
56.35°, 69.88°, 63.91°, 82.85°, 17.22° and 86.86° for
formation, and their particle diameter sizes of HPB-C
HPB-C and HPB-C were 330, 303 and 234 nm, re-
spectively, when f reached 70% (Figure S3 in SI). Evi-
dently, the enhanced emission intensity of HPB-C is
spectacularly boosted by the aggregation. In other words,
HPB-C is AIE active. Moreover, alkyl chains show
0
,
2
5
w
θ
AB, θBC, θCD, θDE, θEF and θFA, respectively. And the
x
crystal packing of the adjacent HPB-C molecules is
0
mainly edge-to-face interactions such as aromatic CH…
π interactions and hardly formed π-π interactions. Their
distances are found to be 2.923 Å and 3.323 Å as shown
in Figure 2C. The interactions of the aromatic CH…π in
turn stabilize the twisted conformation of the molecules,
which is in favor of hindering the rotation of the single
bond between phenyl rings and ethylenic group and
minimizes the possibility of forming excimers in the
crystal. These results demonstrate that the formation of
aggregates imposes physical restraints on the intra-
molecular rotations, and thus blocks the radiationless
relaxation channel and opens the radiative decay path-
way.
x
little effect on the AIE performance although increased
times of fluorescence intensity have slightly different
values.
1
6
2
8
4
0
HPB-C0
HPB-C2
HPB-C5
1
x
Thermal stability of the HPB-C was evaluated by
thermo gravimetric analysis (TGA) under nitrogen. As
shown in Figure S4 (SI), the decomposition tempera-
d
tures (T ) of these three compounds range from 268 to
288 ℃, demonstrating that all compounds are thermally
stable. A good thermal stability is required for future
device applications. Moreover, the melting points of
these three compounds are 204.4, 183.0 and 116.0 ℃,
respectively, far lower than T
melted samples using liquid nitrogen to obtain the
amorphous state because we found that HPB-C tends
d
. So we quenched the
0
20
40
60
80
100
Water fraction/vol%
0
Figure 1 Correlation between the net change in PL intensity
to crystallize. It is interesting to note the difference be-
tween the crystal and amorphous states although both of
them belong to the aggregated state. Powder X-ray dif-
fraction (PXRD) was performed to track the phase state.
[
(
[
(I−I )/I ] of HPB-C , HPB-C and HPB-C at 490 nm without
0 0 0 2 5
I ) and with different water fractions in the THF/water mixtures.
0
−
5
HPB-C ]＝7×10 mol/L; Excitation wavelength: 360 nm.
x
As shown in Figure 3A, the PXRD pattern of HPB-C
0
The crystal structure of the chromophores is the di-
in single crystal (HPB-C -1) showed multiple peaks
0
rect evidence we can utilize to know the arrangement of
the AIE molecules in the solid state, which is helpful for
the understanding of the AIE mechanism. Single crys-
while almost no peak was observed for amorphous state
(HPB-C -2). Correspondingly, the maximum emission
0
wavelength of HPB-C in amorphous state (red in Fig-
0
tals of HPB-C
lization in a CH
x
were grown through their slow crystal-
Cl solvent. But only the single crystal
ure 3B) is shifted to 493 nm from 471 nm in single
crystal. In the above discussion about the aggregate
2
2
702
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Chin. J. Chem. 2015, 33, 701—704

Aggregation-Induced Emission of Hexaphenyl-1,3-butadiene
0
Figure 2 (A) ORTEP drawing of single-crystal structure of HPB-C (deletion of the hydrogen atom for clarity); (B) packing structure of
0 0
HPB-C single crystal and (C) intermolecular interactions of HPB-C .
formation of HPB-C
non-solvent, its maximum emission wavelengths are
about 480, 486 and 488 nm when the f s reach 70%,
0% and 90%, respectively. So the aggregate state in the
0
in mixture solution by addition of
(A)
HPB-C -1
0
HPB-C -2
w
0
HPB-C -3
8
0
mixture solution consists of amorphous state or a mix-
ture of amorphous and crystalline states, that is, loose
alignment is formed when the molecules of HPB-C are
0
forced to rapidly aggregate. It is straightforward to un-
derstand because the formation of the aggregates was
too fast to regularly arrange when a large amount of
water was added into the THF solution. But amorphous
HPB-C
methane vapour. The sharp diffraction peaks in its
PXRD pattern (HPB-C -3 in Figure 3A) appear again,
that is, the crystalline state can be recovered. In addition,
the maximum emission wavelength also returned to 471
nm (blue in Figure 3B). What is more interesting, the
emission intensity of HPB-C is gradually enhanced
0
with the extended exposure time of fumigation, as
shown in Figure S5. To better understand the unique PL
0
can re-crystallize by fuming with dichloro-
0
10
20
30
o
θ /( )
40
50
2
HPB-C -1
(B)
0
1
0
.0
.8
HPB-C -2
0
HPB-C -3
0
0
behaviors of HPB-C in crystalline and amorphous
states, we studied their UV-Vis absorption spectra by the
assistance of integrating sphere. In order to compare the
difference, the spectra are normalized and shown in
Figure S6. The small red-shift was observed for amor-
phous states, which is consistent with the above PL re-
sults. Additionally, the quantum yield (Φ) is an impor-
tant parameter for a chromophore, and the emission ef-
ficiency can be quantitatively evaluated accordingly.
0.6
0
0
0
.4
.2
.0
4
00
450
500
550
600
The absolute PL quantum yields of HPB-C
amorphous and crystalline states were determined by
using an integrating sphere. The Φ values of HPB-C in
0
in both
Wavelength/nm
0
Figure 3 (A) PXRD patterns and (B) normalized PL spectra of
crystalline and amorphous states were 3.53% and 2.42%,
respectively. These result indicated that the more com-
pact aggregates, the more efficient emission. On the
other hand, these results demonstrated that the AIE
mechanism is mainly due to RIR. We also investigated
the reversibility between amorphous and crystalline
state, as shown in Figure S7 where the reproducibility
maintains well after four melting-freezing-fuming cy-
the HPB-C at different states. 1－single crystal; 2－amorphous;
0
3－crystal obtained from amorphous state by CH Cl vapor fum-
2
2
ing. The excitation wavelength is at 360 nm.
change reversibly between 471 and 494 nm with almost
no deterioration, indicating the excellent reversibility of
its aggregate state. Compared with photoluminescence
properties of HPB-C
0
, the AIE characteristics are ob-
, too (Figure 1). The
cles. Their maximum emission wavelengths (λmax
)
served in HPB-C and HPB-C
2
5
Chin. J. Chem. 2015, 33, 701—704
© 2015 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Zhang et al.
COMMUNICATION
fluorescence intensities of the two compounds in amor-
phous state, however, persistently decrease with the in-
creasing of fumigation time in the dichloromethane va-
por until 190 s and then almost unchangeable (Figure S5
in SI). We speculated that the formation of the regular
aggregation induced by dichloromethane vapor is very
slow or difficult due to the steric hindrance induced by
alkyl group.
Chen, D. Y.; Shi, J. B.; Wu, Y. M.; Tong, B.; Zhi, J. G.; Dong, Y. P.
Sci. China Chem. 2013, 56, 1239; (h) Yuan, Y. Y.; Kwok, R. T. K.;
Zhang, R. Y.; Tang, B. Z.; Liu, B. Chem. Commun. 2014, 50, 11465;
(i) Shi, J. B.; Wu, Y. M.; Tong, B.; Zhi, J. G.; Dong, Y. P. Sens.
Actuators B-Chem. 2014, 197, 334; (j) Chen, L.; Jiang, Y. B.; Nie,
H.; Lu, P.; Sung, H. H. Y.; Williams, I. D.; Kwok, H. S.; Huang, F.;
Qin, A. J.; Zhao, Z. J.; Tang, B. Z. Adv. Funct. Mater. 2014, 24, 3621;
(k) Jung, S. H.; Kwon, K.-Y.; Jung, J. H. Chem. Commun. 2015, 51,
952; (l) Guo, Y.; Tong, X.; Ji, L.; Wang, Z.; Wang, H.; Hu, J.; Pei, R.
Chem. Commun. 2015, 51, 596; (m) Geng, J.; Liao, L. D.; Qin, W.;
Tang, B. Z.; Thakor, N.; Liu, B. J. Nanosci. Nanotechnol. 2015, 15,
Conclusions
1
864.
[
4] (a) Chen, J. W.; Law, C. C. W.; Lam, J. W. Y.; Dong, Y. P.; Lo, S. M.
In summary, we successfully synthesized and char-
acterized a new series of AIE-active dyes of hexaphe-
nyl-1,3-butadienes. The RIR process is the predominant
mechanism for the AIE effects. The results imply that
this is an effective molecular strategy to design new AIE
materials. It is also anticipated that more amazing AIE
chromophores based on HPB can be designed with the
introduction of diversified functional groups, which
may help us realize a better understanding of AIE phe-
nomenon, mechanism, and application.
F.; Williams, I. D.; Zhu, D. B.; Tang, B. Z. Chem. Mater. 2003, 15,
1
535; (b) Tong, H.; Dong, Y.; Hong, Y.; Haussler, M.; Lam, J. W. Y.;
Sung, H. H. Y.; Yu, X.; Sun, J.; Williams, I. D.; Kwok, H. S.; Tang,
B. Z. J. Phys. Chem. C 2007, 111, 2287; (c) Zeng, Q.; Li, Z.; Dong,
Y.; Di, C. A.; Qin, A.; Hong, Y.; Ji, L.; Zhu, Z.; Jim, C. K. W.; Yu, G.;
Li, Q.; Li, Z.; Liu, Y.; Qin, J.; Tang, B. Z. Chem. Commun. 2007, 70;
(
d) Shi, J. Q.; Chang, N.; Li, C. H.; Mei, J.; Deng, C. M.; Luo, X. L.;
Liu, Z. P.; Bo, Z. S.; Dong, Y. Q.; Tang, B. Z. Chem. Commun. 2012,
8, 10675.
4
[
5] (a) Tong, H.; Dong, Y. Q.; Haussler, M.; Lam, J. W. Y.; Sung, H. H.
Y.; Williams, I. D.; Sun, J. Z.; Tang, B. Z. Chem. Commun. 2006,
1133; (b) Luo, X. L.; Li, J. N.; Li, C. H.; Heng, L. P.; Dong, Y. Q.;
Liu, Z. P.; Bo, Z. S.; Tang, B. Z. Adv. Mater. 2011, 23, 3261; (c)
Zhang, Z. Y.; Xu, B.; Su, J. H.; Shen, L. P.; Xie, Y. S.; Tian, H.
Angew. Chem., Int. Ed. 2011, 50, 11654; (d) Li, Y. X.; Chen, Z.; Cui,
Y.; Xia, G. M.; Yang, X. F. J. Phys. Chem. C 2012, 116, 6401; (e)
Yang, L. J.; Ye, J. W.; Xu, L. F.; Yang, X. Y.; Gong, W. T.; Lin, Y.;
Ning, G. L. RSC Adv. 2012, 2, 11529; (f) Li, C.; Luo, X.; Zhao, W.;
Huang, Z.; Liu, Z.; Tong, B.; Dong, Y. Sci. China Chem. 2013, 56,
Acknowledgement
This work was financially supported by the National
Natural Science Foundation of China (Grant Nos.
2
1474009, 51328302, 51073026, 51061160500), the
National Basic Research Program of China (973 Pro-
gram; Grant No. 2013CB834704) and Basic Research
Foundation of Beijing Institute of Technology (Grant
No. 20130942007).
1
173; (g) Dong, Y. F.; Wang, W. L.; Cewen, C. W.; Shi, J. B.; Tong,
B.; Feng, X.; Zhi, J. G.; Dong, Y. P. Tetrahedron Lett. 2014, 55, 1496;
h) Zhang, G.-F.; Aldred, M. P.; Chen, Z.-Q.; Chen, T.; Meng, X.;
(
Zhu, M.-Q. RSC Adv. 2015, 5, 1079.
[
6] (a) Li, Z.; Dong, Y. Q.; Lam, J. W. Y.; Sun, J. X.; Qin, A. J.;
Haeussler, M.; Dong, Y. P.; Sung, H. H. Y.; Williams, I. D.; Kwok, H.
S.; Tang, B. Z. Adv. Funct. Mater. 2009, 19, 905; (b) Shiraishi, K.;
Kashiwabara, T.; Sanji, T.; Tanaka, M. New J. Chem. 2009, 33, 1680;
(c) Feng, X.; Tong, B.; Shen, J.; Shi, J.; Han, T.; Chen, L.; Zhi, J.; Lu,
P.; Ma, Y.; Dong, Y. J. Phys. Chem. B 2010, 114, 16731; (d)
Bandrowsky, T. L.; Carroll, J. B.; Braddock-Wilking, J.
Organometallics 2011, 30, 3559; (e) Han, T.; Feng, X.; Tong, B.; Shi,
J.; Chen, L.; Zhi, J.; Dong, Y. Chem. Commun. 2012, 48, 416; (f)
Dong, Y. J.; Xu, B.; Zhang, J. B.; Tan, X.; Wang, L. J.; Chen, J. L.;
Lv, H. G.; Wen, S. P.; Li, B.; Ye, L.; Zou, B.; Tian, W. J. Angew.
Chem., Int. Ed. 2012, 51, 10782; (g) Ma, S.; Zhang, J.; Chen, J.;
Wang, L.; Xu, B.; Tian, W. Chin. J. Chem. 2013, 31, 1418; (h)
Yoshii, R.; Nagai, A.; Tanaka, K.; Chujo, Y. Chem. Eur. J. 2013, 19,
4506; (i) Wang, Z.; Fang, Y.; Sun, J.; Qin, A.; Tang, B. Z. Sci. China
Chem. 2013, 56, 1187; (j) Wang, X.; Wu, Y.; Liu, Q.; Li, Z.; Yan, H.;
Ji, C.; Duan, J.; Liu, Z. Chem. Commun. 2015, 51, 784.
References
[
1] (a) Zhou, Y.; He, Q. G.; Yang, Y.; Zhong, H. Z.; He, C.; Sang, G. Y.;
Liu, W.; Yang, C. H.; Bai, F. L.; Li, Y. F. Adv. Funct. Mater. 2008, 18,
3
299; (b) Bunz, U. H. F. Chem. Rev. 2000, 100, 1605; (c) Duarte, A.;
Pu, K. Y.; Liu, B.; Bazan, G. C. Chem. Mater. 2011, 23, 501; (d) Wan,
W.; Du, H. L.; Wang, J.; Le, Y. P.; Jiang, H. Z.; Chen, H.; Zhu, S. Z.;
Hao, J. Dyes Pigm. 2013, 96, 642; (e) Rochat, S.; Swager, T. M. ACS
Appl. Mater. Interfaces 2013, 5, 4488; (f) Chen, D. C.; Zhou, H.; Li,
X. C.; Liu, M.; Ye, H.; Su, S. J.; Cao, Y. Org. Electron. 2014, 15,
1197; (g) Li, K.; Liu, B. Chem. Soc. Rev. 2014, 43, 6570; (h) Feng, G.
X.; Liu, J.; Zhang, R. Y.; Liu, B. Chem. Commun. 2014, 50, 9497.
2] (a) Luo, J. D.; Xie, Z. L.; Lam, J. W. Y.; Cheng, L.; Chen, H. Y.; Qiu,
C. F.; Kwok, H. S.; Zhan, X. W.; Liu, Y. Q.; Zhu, D. B.; Tang, B. Z.
Chem. Commun. 2001, 1740; (b) Hong, Y.; Lam, J. W. Y.; Tang, B. Z.
Chem. Commun. 2009, 4332; (c) Hong, Y.; Lam, J. W. Y.; Tang, B. Z.
Chem. Soc. Rev. 2011, 40, 5361; (d) Mei, J.; Hong, Y.; Lam, J. W. Y.;
Qin, A.; Tang, Y.; Tang, B. Z. Adv. Mater. 2014, 26, 5429.
3] (a) Hong, Y.; Xiong, H.; Lam, J. W. Y.; Haeussler, M.; Liu, J.; Yu, Y.;
Zhong, Y.; Sung, H. H. Y.; Williams, I. D.; Wong, K. S.; Tang, B. Z.
Chem. Eur. J. 2010, 16, 1232; (b) Xu, Y. H.; Chen, L.; Guo, Z. Q.;
Nagai, A.; Jiang, D. L. J. Am. Chem. Soc. 2011, 133, 17622; (c) Luo,
J.; Wang, X.; Wang, X.; Su, W. Chin. J. Chem. 2012, 30, 2488; (d)
Zhang, X.; Zhang, X.; Yang, B.; Wang, S.; Liu, M.; Zhang, Y.; Tao,
L.; Wei, Y. RSC Adv. 2013, 3, 9633; (e) He, B. R.; Ye, S. H.; Guo, Y.
J.; Chen, B.; Xu, X. F.; Qiu, H. Y.; Zhao, Z. J. Sci. China Chem.
[
[
[7] (a) Luo, Z. T.; Yuan, X.; Yu, Y.; Zhang, Q. B.; Leong, D. T.; Lee, J.
Y.; Xie, J. P. J. Am. Chem. Soc. 2012, 134, 16662; (b) Liang, J. H.;
Chen, Z.; Yin, J.; Yu, G. A.; Liu, S. H. Chem. Commun. 2013, 49,
3567; (c) Chen, Z.; Zhang, J.; Song, M.; Yin, J.; Yu, G.-A.; Liu, S. H.
Chem. Commun. 2015, 51, 326.
[8] (a) Zhang, Y.; Han, T.; Gu, S.; Zhou, T.; Zhao, C.; Guo, Y.; Feng, X.;
Tong, B.; Bing, J.; Shi, J.; Zhi, J.; Dong, Y. Chem. Eur. J. 2014, 20,
8856; (b) Han, T.; Zhang, Y.; Feng, X.; Lin, Z.; Tong, B.; Shi, J.; Zhi,
J.; Dong, Y. Chem. Commun. 2013, 49, 7049.
2
013, 56, 1221; (f) Shi, J. B.; Wu, Y. M.; Sun, S.; Tong, B.; Zhi, J. G.;
[9] Satoh, T.; Ogino, S.; Miura, M.; Aromitra, M. Angew. Chem., Int. Ed.
2004, 43, 5063.
Dong, Y. P. J. Polym. Sci. Part A-Polym. Chem. 2013, 51, 229; (g)
(Pan, B.; Qin, X.)
704
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Chin. J. Chem. 2015, 33, 701—704