Red fluorescent luminogen from pyrrole derivatives with aggregation-enhanced emission for cell membrane imaging

Article abstract of DOI:10.1039/c5cc02054a

A dye emitted red fluorescence with aggregation-enhanced emission properties was reported here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines during bio-imaging. This journal is

Full text of DOI:10.1039/c5cc02054a

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DOI: 10.1039/C5CC02054A
A graphical and textual abstract
Red fluorescent luminogen from pyrrole derivatives with
aggregation-enhanced emission for cell membrane imaging
Guogang Liu, Didi Chen, Lingwei Kong, Jianbing Shi, Bin Tong, Junge Zhi, Xiao Feng and
Yuping Dong
A dye emitted red fluorescence with aggregation-enhanced emission properties was reported
here. It can be utilized to specifically recognize the cell membrane of MCF-7 and 293T cell lines
during the bio-imaging.

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DOI: 10.1039/C5CC02054A
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Red fluorescent luminogen from pyrrole derivatives
with aggregation-enhanced emission for cell membrane
imaging
Cite this: DOI: 10.1039/x0xx00000x
Guogang Liu,a Didi Chen,a Lingwei Kong,a Jianbing Shi,*a Bin Tong,a Junge Zhi,b
Xiao Feng,b and Yuping Dong*a
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
www.rsc.org/
fluorescence becomes lower. In our previous work, carboxylic salt of
aryl-substituted pyrrole derivatives can be used for “turn-on” probe
for sensitively and selectively detecting aluminium ions based on the
AIE mechanism.8b, 8c But those pyrrole derivatives mainly emit in
the blue areas, which is unfavorable for the bio-imaging. In this
manuscript, therefore, we report a new compound 5 with an
extended π-conjugation structure, as shown in Scheme 1. And it is
also a typical D-π-A structure, which has a pyrrolyl group as the
electron donor, methyl benzoate as an electron acceptor, and
A dye emitted red fluorescence with aggregation-enhanced
emission properties was reported here. It can be utilized to
specifically recognize the cell membrane of MCF-7 and 293T
cell lines during the bio-imaging.
It is well known that the fluorescent intensity of many organic dyes
weakens when their solution concentrations are increased or when
they are aggregated in experimental condition, which is due to the
formation of such detrimental species as excimers and exciplexes.1
This phenomenon is commonly called aggregation-caused quenching
(ACQ). This ACQ effect was particularly obvious in the applications
of the fluorophores as biosensors or cell imaging agent because of
their planar and rigid backbones which tend to aggregate in their
aqueous practical environment.2 A photo-physical phenomenon
associated with fluorogen aggregation is aggregation-induced
emission (AIE), which is opposite to the ACQ phenomenon.3 In the
AIE process, weakly fluorescent chromophores are induced to emit
efficiently by the aggregation formation. A number of organic
molecules with propeller-shaped structures have been found to show
pronounced AIE effect, such as siloles,4 tetraphenylethene,5
distyrylanthracene,6 cyano-substituted diarylethylene,7 and aryl-
substituted pyrrole derivatives.8 The discovery of AIE molecules
offers a straightforward solution to overcome the ACQ problem.
Moreover, there are increasing evidences indicating that AIE dyes
have highly potential in biosensor or bioimaging,9 which have some
advantages such as higher sensitivity,10 larger signal-to-noise ratio
with minimized background fluorescence,11 and so on. Yet, most
AIE fluorogens used for light-up probe or imaging agent are limited
to those with either blue or green emission.9a, 12 As a result, it is
highly desirable to develop AIE dyes with long wavelength emission
phenylethynyl as
a π-conjugation bridge, respectively. This
compound shows the red photoluminescence with the aggregation-
enhanced emission (AEE) characteristics that emitted weakly in the
solution but strongly in the aggregation. Furthermore, this AEE dye
can be applied in the cell imaging, specifically for the membrane of
MCF-7 and 293T cell lines.
Scheme 1. Synthesis route of target compound 5
. (i) CuCl/TMEDA/O2, 50oC; (ii)
methyl 4‐aminobenzoate, reflux; (iii) ICl/NaHCO3, r.t.; (iv) methyl 4‐
ethynylbenzoate/PdCl2(PPh3)2/CuI/PPh3, 65oC.
The compound 5 was prepared by the synthetic route as shown in
for cell imaging because deployment of such dyes can reduce the Scheme 1. The oxidative coupling reaction of 1-bromo-4-
photo-limiting interference.13
One effective strategy to seek long wavelength emissive
fluorophores is to combine electron rich units with deficient ones so
2 and methyl 4-aminobenzoate in the moderate yield (56%).
as to form a donor (D) – acceptor (A) structure.14 Their fluorescent
intensity in strong D-A system, however, is dependent on the
ethynylbenzene (1) gave 1,4-di(4-bromophenyl)-butadiyne (2) in
89% yield. The pyrrole derivative (3) was synthesized by reaction of
Iodination of compound 3 using ICl afforded di-iodinated the pyrrole
derivative 4 in good yield (83%). The Sonogashira cross-coupling
reaction of compound 4 with methyl 4-ethynylbenzoate gave the
polarity of the environments, for example, lower fluorescent
intensity in high polar media.15 Another efficient method to get long
wavelength emissive fluorophores is to increase the degree of π-
conjugation, which the environmental dependence for their
target product
5
in 28% yield. All compounds were fully
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characterized by spectroscopic methods, see the electronic Moreover, the Φ values of 5 in the aggregate by the addition of
supplementary information (ESI) for details.
water (fw = 99%) or hexane (fH = 99%) were 5.71% and 4.29%,
respectively. The result is in good agreDeOmIe: n10t.1w03i9th/C5tCheC0a2b0o54vAe
View Article Online
We first studied the absorption and photoluminescence (PL)
spectra of 5 in some solvents with different polarities (dielectric
constant (ε)). As shown in Fig. S1a, the absorption bands from 275
to 400 nm are attributed to π–π* transitions of the conjugated
aromatic segments, whereas those at longer wavelength from 400 to
600 nm are due to the intramolecular charge transfer between the
donor and acceptor. It can be found that the longer absorption peak
is located at 455 nm in hexane while others are located between 465
and 470 nm in the rest of seven solvents. Moreover, the emission in
hexane shows the strongest intensity in these eight solvents and the
shortest in emissive maximum located at 577 nm, as shown in Fig.
S1b, which is blue-shifted 10 nm or more than others. Except for
hexane, there are no obvious changes in the absorption or emission
maximum although those solvents are big differences in ε. In D-A
system, the absorption or emission is more or less dependent of
solvent polarity. But for the pyrrole derivative 5, it is insensitive to
the environmental polarity based on the above fluorescence and
absorption results of different solvent response. This represents an
advantage for some applications such as bio-imaging because there
is different polarity in the different organelle of cell.
discussion. That is, it is a typical AEE dye with a satisfactory
emission efficiency in solid state compared with other reported red
emission dyes.16
8000
8
6
4
2
0
10
8
13 nm
10 nm
(a)
(b)
fH (vol%)
8000
6000
4000
2000
0
fW (vol%)
0
6
0
I
I
10
20
30
40
50
60
70
80
90
99
6000
4000
2000
0
I
I
10
20
30
40
50
60
70
80
90
99
I
I
4
2
0
0
20
40
60
80 100
0
20
40
60
80 100
Water Fraction (vol%)
Hexane Fraction (vol%)
550
600
650
700
750
550
600
650
700
750
Wavelength (nm)
Wavelength (nm)
Fig. 1 PL spectra of
different water or hexane fraction. [
Insert: Correlation between the net increase in PL intensity [(I‐I0)/I0] of
water or hexane fraction
5
in the (a) THF‐water and (b) THF‐hexane mixtures with
] = 10 μM; Excitation wavelength: 470 nm.
and
5
5
.
To gain a better understanding of this optical property at the
molecular level, density functional theory calculations were carried
Many fluorescent dyes aggregate when dispersed in aqueous out using a suite of Gaussian 09 program. The nonlocal density
media or bound to biological media in large quantities. Compared to functional of B3LYP with 6-31G (d) basis sets was used for the
traditional ACQ dyes, AIE dyes can emit efficiently by the computation. Fig.
2 shows the optimized structures, orbital
aggregation formation. Dye 5 is soluble in common solvents such as distributions of the highest occupied molecular orbital (HOMO) and
DCM, THF and AN but insoluble in water. Dilute solutions of 5 in lowest unoccupied molecular orbital (LUMO) of 5. The
THF are weakly emissive. Addition of non-solvent water into its conformation of 5 in the monomolecular state is flexible and twisted
THF solution can quickly enhance the emission when the water according to the optimized structure (Fig. 2a), which is difficult to
fraction exceeds 60% because of aggregation formation, as shown in pack in a highly ordered fashion. Actually, we attempted a variety of
Fig. 1a. The fluorescent intensity of dye 5 is increased by methods to grow single crystals of 5 but all failed. This seems to be a
approximately 7 fold when the water fraction reached 80% along hint that the emission enhancement was not attributed to the J-
with a slight 10 nm red-shift from 593 nm to 603 nm. Its emission aggregation during the aggregation formation. For a D-A system, the
decreased slightly when the water fraction exceeded 80%, see the process of twisted intramolecular charge transfer (TICT) often
inset of Fig. 1a. The track of the transmittance of different water occurred. But TICT is very sensitive to the change of environment,
fraction showed that the nanoparticles were formed when fw became particularly the polarity variation. For example, 1,4-bis[1-cyano-2-
higher than 60%, which transmittance is obvious reduced as shown (4-(diphenylamino)phenyl)vinyl]benzene is composed of two pairs
in Fig. S2a (see ESI). The dynamic light scattering (DLS) further of D-A units and exhibited a marked solvatochromic effect in
confirmed the aggregation formation, and its particle diameter sizes solution with its emission red-shifting from green (λem = 510 nm) in
were 108.5 and 65.2 nm at the water fraction 80% and 99%, hexane to red (λem = 667 nm) in DMF.17 But for this pyrrole
respectively, as shown in Figs. S3a and S3b in ESI. If non-solvent derivative 5, it is insensitive to the solvent polarity in solution as the
hexane, a nonpolar solvent, is used, the enhanced intensity of 5 above-mentioned discussion, which can be inferred that the weaker
reached 9-fold when fH reached 99% along with an obvious blue- emission of 5 in solution is not predominately controlled by TICT.
shift from 593 to 580 nm (Fig. 1b). The transmittance of them is The calculated result of LUMO demonstrated that the electron
almost the same (Fig. S2b in ESI) but DLS results indicated that density is mainly centered on the pyrrole core and 1,2,5-position
nanoparticles were also formed and their sizes are approximately substituted groups (Fig. 2c), and no obvious charge separation was
15.6 nm (Fig. S3c in ESI), which have no effect on the transmittance. observed between the donor and acceptor units. These results can
Evidently, the enhanced emission of 5 is induced by the aggregation presumably exclude the possibility that the emission enhancement in
formation, or in other words, 5 is AEE–active. Additionally, the the aggregation state is originated from the inhibition of the TICT
quantum yield (Φ) is the important parameter for a fluorophore, and process. From the above discussion on optical properties and
the emission efficiency can be quantitatively evaluated accordingly. theoretical calculation, it can be concluded that the restriction of
The absolute PL quantum yields of 5 in both solution and solid states intramolecular rotation or motion is the major factor for the AEE
were determined by using an integrating sphere. The Φ values of 5 phenomena observed in the twisted conformation of 5. Based on the
in THF solution and solid state were 0.88% and 5.44%, respectively. DFT calculations, compared to its HOMO, there are greatly
2 | J. Name., 2012, 00, 1‐3
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extended the conjugation degree in the LUMO because the exhibits low cytotoxicity. Even the concentration reached 25 μM, the
electronic clouds evenly distributed on the pyrrolyl core, 1-postion cell viability remained above 90% after 24 h, which confirmed the
methyl benzoate, 2,5-position 4-{2-[(4-methoxycarbonyl)phenyl] good biocompatibility of dye 5. Simultaneously,VietwheArtidclaetOanlionef
ethynyl}phenyl, and 3,4-postion ethynyl groups, which are very big apoptosis of MCF-7 and 293T cells furtherDsOhoI:w10.l1i0tt3le9/iCn5fCluCe0n2c0e54oAn
conjugated systems and thus led to the red emission. Moreover, it is cell viability. As shown in Fig. S7, there are no obvious early
noteworthy noting that there is a good electron delocalization in the apoptosis and death in MCF-7 cells or 293T cells for 6 h and 24 h
ethynyl groups whether HOMO or LUMO, which indicates that incubation with 10 μM of dye 5. Therefore, this AEE dye is expected
triple bond may serve as a good π–bridge for the charge motion in to be a promising candidate for cellular membrane imaging with
D-π-A system.
some such advantages as AEE characteristic, intense red emission,
and excellent biocompatibility.
Fig. 2 (a) The optimized structure of 5 and (b) its molecular orbital amplitude plot
of HOMO and (c) that of LUMO calculated using B3LYP/6‐31G basis set with G09
program.
Fig. 3 CLSM images of living MCF‐7 (a‐c) and 293T (d‐f) cells treated with 10 μM
solution of dye
cellular membrane staining dye DiO (10 nM) for 15 min at 37 oC. (a) and (d) are
excited at 543 nm with a filter of 555‐700 nm; (b) and (e) are excited at 488 nm
with a filter of 500‐535 nm; (c) and (f) are their merged pictures with bright field
image.
5
for 10 min at 37 oC. The cells were pre‐stained with commercial
Due to its red emission, dye 5 is therefore used as a fluorescent
probe for live cell imaging. Human breast cancer cells (MCF-7 cells)
and human embryonic kidney cells (293T cells) were chosen as the
model cell-lines for the fluorescence imaging study by confocal laser
scanning microscopy (CLSM). As shown in Fig. 3, intense red
fluorescence could be observed on the cell membrane of MCF-7 and
293T cells after incubating for 10 min with 10 μM of dye 5,
respectively, upon excitation at 543 nm with red fluorescence signals
collected 555-700 nm. There are almost no uptake inside the cells
such as cytoplasm and other organelles. Even the incubation time is
increased to 120 min, it is still targeting on the cell membranes, as
shown in Fig. S4 (ESI). It is indicated that this dye can be specific
staining for cell membranes. This selectivity for cell membranes is
presumably originated from the interaction between methyl benzoate
groups and phospholipids which are a major component of cell
membranes. In addition, dye 5 shows the similar photostability in
comparison with DiO after a continuous irradiation for 60 min, as
shown in Fig. S5 (ESI). The signal loss of dye 5 and DiO is about
57% and 53%, respectively. After irradiation for 120 min, the
residue signals are about 27% and 10% for dye 5 and DiO,
respectively, which indicates that photostability of dye 5 is superior
to that of DiO during the long time irradiation. To probe the
cytotoxicity of 5, the viabilities of these two cell lines were
In conclusion, we designed and synthesized a new red fluorescent
dye with the AEE feature. The fluorophore has a D-π-A structure but
is insensitive to the environmental polarity, which allows us to take
advantage of the stability to stain the living cells. More importantly,
the triple bond used for π-bridge can extend the conjugation and
coplanarity, which is beneficial for red emission. This red dye is
specifically targeted for the imaging of cellular membrane with
excellent biocompatibility. Our results thus provide a general
molecular design principle to develop red fluorescent probes for the
cellular imaging.
This work was financially supported by the National Natural
Scientific Foundation of China (Grant Nos. 21474009, 51328302,
51073026, 51061160500), the National Basic Research Program of
China (973 Program; Grant No. 2013CB834704) and Basic Research
Foundation of Beijing Institute of Technology (Grant No.
20130942007).
Notes and references
evaluated
by
the
3-(4,5-dimethylthiazol-2-yl)-5-(3-
a
School of Materials Science and Engineering, Beijing Institute of
carboxymethoxyphenyl)-2-(4-sulfophenyl) -2H-tetrazolium (MTS)
assay. We probed the influence at concentrations of 5, 10, 25, 50 and
100 μM following 6 and 24 hours of the incubation. As shown in Fig.
S6 in the ESI, the results of cytotoxicity testing indicate that dye 5
Technology, Beijing 100081, China
E-mail: bing@bit.edu.cn; chdongyp@bit.edu.cn
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Shi, B. Tong, Y. F. Dong, J. W. Y. Lam, Y. P. Dong and B. Z. Tang, J. Mater.
Chem. C, 2013, 1, 7534.
School of Chemistry, Beijing Institute of Technology, Beijing 100081,
China
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Electronic Supplementary Information (ESI) available: Experimental
DOI: 10.1039/C5CC02054A
9 (a) D. Ding, K. Li, B. Liu and B. Z. Tang, Acc. Chem. Res., 2013, 46, 2441;
section, the absorption and fluorescence spectra of
5
in the different
in the
(b) Z. G. Song, Y. N. Hong, R. T. K. Kwok, J. W. Y. Lam, B. Liu and B. Z.
Tang, J. Mater. Chem. B, 2014, 2, 1717; (c) L. Y. Wang, L. L. Yang and D.
R. Cao, Curr. Org. Chem., 2014, 18, 1028.
solvents, transmittance and dynamic light scattering results of
5
mixtures of THF-water or THF-hexane with different fraction,
biocompatibility evaluations. See DOI: 10.1039/c000000x/
10 (a) Z. Zhu, L. Xu, H. Li, X. Zhou, J. Qin and C. Yang, Chem. Commun.,
2014, 50, 7060; (b) Y. Guo, X. Tong, L. Ji, Z. Wang, H. Wang, J. Hu and R.
Pei, Chem. Commun., 2015, 51, 596.
1 (a) Y. N. Teo and E. T. Kool, Bioconjugate Chem., 2009, 20, 2371; (b) D. J.
Stewart, M. J. Dalton, R. N. Swiger, T. M. Cooper, J. E. Haley and L.-S. Tan,
J. Phys. Chem. A, 2013, 117, 3909.
11 (a) E. Zhao, H. Deng, S. Chen, Y. Hong, C. W. T. Leung, J. W. Y. Lam
and B. Z. Tang, Chem. Commun., 2014, 50, 14451; (b) F. Hu, Y. Y. Huang,
G. X. Zhang, R. Zhao, H. Yang and D. Q. Zhang, Anal. Chem., 2014, 86,
7987.
2 (a) I. B. Kim, J. N. Wilson and U. H. F. Bunz, Chem. Commun., 2005, 1273;
(b) I. B. Kim, H. Shin, A. J. Garcia and U. H. F. Bunz, Bioconjugate Chem.,
2007, 18, 815; (c) C. Xue, F. Cai and H. Liu, Chem.-Eur. J., 2008, 14, 1648.
12 X. Wang, J. Hu, G. Zhang and S. Liu, J. Am. Chem. Soc., 2014, 136, 9890.
3 (a) J. D. Luo, Z. L. Xie, J. W. Y. Lam, L. Cheng, H. Y. Chen, C. F. Qiu, H.
S. Kwok, X. W. Zhan, Y. Q. Liu, D. B. Zhu and B. Z. Tang, Chem. Commun.,
2001, 1740; (b) Y. Hong, J. W. Y. Lam and B. Z. Tang, Chem. Commun.,
2009, 4332; (c) Y. Hong, J. W. Y. Lam and B. Z. Tang, Chem. Soc. Rev.,
2011, 40, 5361; (d) J. Mei, Y. Hong, J. W. Y. Lam, A. Qin, Y. Tang and B. Z.
Tang, Adv. Mater., 2014, 26, 5429.
13 (a) J. V. Frangioni, Curr. Opin. Chem. Biol., 2003, 7, 626; (b) S. A.
Hilderbrand and R. Weissleder, Curr. Opin. Chem. Biol., 2010, 14, 71; (c) M.
A. Pysz, S. S. Gambhir and J. K. Willmann, Clin. Radiol., 2010, 65, 500.
14 (a) K. R. J. Thomas, J. T. Lin, M. Velusamy, Y.-T. Tao and C.-H. Chuen,
Adv. Funct. Mater., 2004, 14, 83; (b) X. B. Du and Z. Y. Wang, Chem.
Commun., 2011, 47, 4276.
4 (a) J. W. Chen, C. C. W. Law, J. W. Y. Lam, Y. P. Dong, S. M. F. Lo, I. D.
Williams, D. B. Zhu and B. Z. Tang, Chem. Mater., 2003, 15, 1535; (b) L. R.
Xu, Y. Li, S. H. Li, R. R. Hu, A. J. Qin, B. Z. Tang and B. Su, Analyst, 2014,
139, 2332; (c) L. Chen, Y. B. Jiang, H. Nie, P. Lu, H. H. Y. Sung, I. D.
Williams, H. S. Kwok, F. Huang, A. J. Qin, Z. J. Zhao and B. Z. Tang, Adv.
Funct. Mater., 2014, 24, 3621; (d) B. Chen, H. Nie, P. Lu, J. Zhou, A. J. Qin,
H. Y. Qiu, Z. J. Zhao and B. Z. Tang, Chem. Commun., 2014, 50, 4500.
15 G. L. Gibson, T. M. McCormick and D. S. Seferos, J. Am. Chem. Soc.,
2012, 134, 539.
16 (a) R. Yoshii, A. Hirose, K. Tanaka and Y. Chujo, J. Am. Chem. Soc.,
2014, 136, 18131; (b) Z. Tao and Y. Qian, Chin. J. Org. Chem., 2014, 34,
2354; (c) K. Namba, A. Osawa, A. Nakayama, A. Mera, F. Tano, Y. Chuman,
E. Sakuda, T. Taketsugu, K. Sakaguchi, N. Kitamura and K. Tanino, Chem.
Sci., 2015, 6, 1083.
5 (a) Y. Q. Dong, J. W. Y. Lam, A. J. Qin, J. Z. Liu, Z. Li and B. Z. Tang,
Appl. Phys. Lett., 2007, 91, 011111; (b) Q. Chen, D. Q. Zhang, G. X. Zhang,
X. Y. Yang, Y. Feng, Q. H. Fan and D. B. Zhu, Adv. Funct. Mater., 2010, 20,
3244; (c) Z. J. Zhao, C. M. Deng, S. M. Chen, J. W. Y. Lam, W. Qin, P. Lu,
Z. M. Wang, H. S. Kwok, Y. G. Ma, H. Y. Qiu and B. Z. Tang, Chem.
Commun., 2011, 47, 8847; (d) X. B. Du, J. Qi, Z. Q. Zhang, D. G. Ma and Z.
Y. Wang, Chem. Mater., 2012, 24, 2178; (e) Y. F. Dong, W. L. Wang, C. W.
Zhong, J. B. Shi, B. Tong, X. Feng, J. G. Zhi and Y. P. Dong, Tetrahedron
17 H.-H. Fang, Q.-D. Chen, J. Yang, H. Xia, B.-R. Gao, J. Feng, Y.-G. Ma
and H.-B. Sun, J. Phys. Chem. C, 2010, 114, 11958.
Lett., 2014, 55, 1496; (f) Y. Zhang, D. Li, Y. Li and J. Yu, Chem. Sci., 2014,
5, 2710.
6 (a) J. T. He, B. Xu, F. P. Chen, H. J. Xia, K. P. Li, L. Ye and W. J. Tian, J.
Phys. Chem. C, 2009, 113, 9892; (b) H. Y. Li, Z. G. Chi, B. J. Xu, X. Q.
Zhang, X. F. Li, S. W. Liu, Y. Zhang and J. R. Xu, J. Mater. Chem., 2011, 21,
3760; (c) B. Xu, J. B. Zhang, S. Q. Ma, J. L. Chen, Y. J. Dong and W. J. Tian,
Prog. Chem., 2013, 25, 1079; (d) L. Y. Bu, M. X. Sun, D. T. Zhang, W. Liu,
Y. L. Wang, M. Zheng, S. F. Xue and W. J. Yang, J. Mater. Chem. C, 2013,
1, 2028; (e) X. Li, K. Ma, H. G. Lu, B. Xu, Z. L. Wang, Y. Zhang, Y. J. Gao,
L. L. Yan and W. J. Tian, Anal. Bioanal. Chem., 2014, 406, 851.
7 (a) Y. P. Li, F. Li, H. Y. Zhang, Z. Q. Xie, W. J. Xie, H. Xu, B. Li, F. Z.
Shen, L. Ye, M. Hanif, D. G. Ma and Y. G. Ma, Chem. Commun., 2007, 231;
(b) B. Wang, Y. C. Wang, J. L. Hua, Y. H. Jiang, J. H. Huang, S. X. Qian and
H. Tian, Chem.-Eur. J., 2011, 17, 2647; (c) H. T. Zhou, W. Huang, L. Ding,
S. Y. Cai, X. Li, B. Li and J. H. Su, Tetrahedron, 2014, 70, 7050.
8 (a) X. Feng, B. Tong, J. Shen, J. Shi, T. Han, L. Chen, J. Zhi, P. Lu, Y. Ma
and Y. Dong, J. Phys. Chem. B, 2010, 114, 16731; (b) T. Han, X. Feng, B.
Tong, J. Shi, L. Chen, J. Zhi and Y. Dong, Chem. Commun., 2012, 48, 416;
(c) X. Y. Shi, H. Wang, T. Y. Han, X. Feng, B. Tong, J. B. Shi, J. G. Zhi and
Y. P. Dong, J. Mater. Chem., 2012, 22, 19296; (d) T. Y. Han, X. Feng, J. B.
4 | J. Name., 2012, 00, 1‐3
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