Rh-Catalyzed Formal [3+2] Cyclization for the Synthesis of 5-Aryl-2-(quinolin-2-yl)oxazoles and Its Applications in Metal Ions Probes

Article abstract of DOI:10.1002/cjoc.202000454

A facile and efficient strategy for the synthesis of 5-aryl-2-(quinolin-2-yl)oxazoles via rhodium-catalyzed formal [3+2] cyclization of 4-aryl-1-tosyl-1H-1,2,3-triazoles with quinoline-2-carbaldehydes has been described. The protocol employs mild conditions and offers good yields of diverse 2,5-aryloxazole derivatives with a broad reaction scope. It is amenable to gram-scale synthesis and easily transformation. Moreover, this 5-aryl-2-(quinolin-2-yl)oxazole skeleton is indeed a new fluorophore and its applications in metal ions probes are also investigated and showed fluorescent responses to mercury ion.

Full text of DOI:10.1002/cjoc.202000454

Chinese Journal
of Chemistry
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Accepted Article
Title: Rh-catalyzed formal [3+2] cyclization for synthesis of 5-aryl-2-(quinolin-2-
yl)oxazoles and its applications in metal ions probes
Authors: Tongtong Zhou, Xinwei He,* Youpeng Zuo, Yuhao Wu, Wangcheng Hu,
Shiwen Zhang, Jiahui Duan and Yongjia Shang*
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Chinese Journal
of Chemistry
2-(Quinolin-2-yl)oxazoles, Cyclization, Metal ions probes, N-Sulfonyl-
1,2,3-triazoles
Concise Report
CJC
中
国 化 学 - An International Journal
Rh-catalyzed formal [3+2] cyclization for synthesis of 5-aryl-2-(quinolin-2-
yl)oxazoles and its applications in metal ions probes
Tongtong Zhou, Xinwei He,* Youpeng Zuo, Yuhao Wu, Wangcheng Hu, Shiwen Zhang, Jiahui Duan and Yongjia Shang*
Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials (State Key Laboratory Cultivation Base),
College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241002, P.R. China
Cite this paper: Chin. J. Chem. 2019, 37, XXX—XXX. DOI: 10.1002/cjoc.201900XXX
Summary of main observation and conclusion A facile and efficient strategy for the synthesis of 5-aryl-2-(quinolin-2-yl)oxazoles via rhodium-catalyzed
formal [3+2] cyclization of 4-aryl-1-tosyl-1H-1,2,3-triazoles with quinoline-2-carbaldehydes has been described. The protocol employs mild conditons and
offers good yields of diverse 2,5-aryloxazole derivatives with a broad reaction scope. It is amenable to gram-scale synthesis and easily transformation.
Moreover, this 5-aryl-2-(quinolin-2-yl)oxazole skeleton is indeed a new fluorophore and its applications in metal ions probes are also investigated and
showed fluorescent responses to mercury ion.
cycloadditions. For instance, Fokin and co-workers exploited the
reactivity of Rh-AVC to achieve imidazoles in good to excellent
Background and Originality Content
In the last few decades, the design and synthesis of functional
mole-cules that could sense specific ions has attracted intense
interest in diverse research fields.1 Oxazoles, quinolines and their
derivatives are well recognized for their important role designing
novel drug moieties for medicinal applications.2,3 As a consequence,
the combination of these two structural features within a single
framework giving novel quinolone-oxazoles has potential for
biological and pharmacological activities.4 In addition, the extend π
structure of these compound also has potential fluorescence
properties to expedite their applications in material science as
ligands and chemosensors. To date, only one method has been
reported for the synthesis of 2-(quinolin-2-yl)oxazoles based on the
cross-dehydrogenative coupling of quinoline N-oxides with 1,3-
azoles (Scheme 1a).5 However, this strategy still possesses some
limitations, including excess metal catalyst, additive/base, and high
temperature, and the substrate scope is also relatively limited.
Therefore, the development of simple, efficient, and
environmentally benign strategies for the formation of 2-(quinolin-
2-yl)oxazoles is quite appealing.
yields with N-sulfonyl 1,2,3-triazoles and nitriles.13 Very recently,
they reported that Rh-AVC reacted with aldehydes to give 3-
sulfonyl-4-oxazolines through an intramolecular cyclization.14
Inspired by our previous reports and in line with our long-standing
interesting in diazo chemistry,15 we herein report our new results
on the synthesis of 5-aryl-2-(quinolin-2-yl)oxazoles in good yields
via Rh-catalyzed formal [3+2] cyclization from 4-aryl-1-tosyl-1H-
1,2,3-triazoles and quinoline-2-carbaldehydes under mild
conditions (Scheme 1b).
Scheme 1 Synthetic strategies for 2-(quinolin-2-yl)oxazoles
work
previous
N
(a)
equiv.)
equiv.)
Cu(OAc)2 (2.0
N
O
PivOH
(1.0
H
+
+
N
pyridine (1.0 equiv.)
O
H
N
O
Ar
Ar
150 oC,
o
-xylene,
work
this
(b)
Ar
N
N
N
Rh
mol%)
h
-N2
TsH
,
2(OAc)4 (5
R
N
Ts
DCM, 110 o 24
C,
X
OHC
X
O
Ar
R
=
CH)
N,
(X
N-Sulfonyl-1,2,3-triazoles have recently emerged as structural
motifs that are studied for synthesizing a variety of biologically
active heterocycles,6 including pyrrole,7 tetrahydropyridines,8
imidazoles,9 pyrroloindoline10 and others.11 In these
transformations, the highly reactive rhodium azavinyl carbenes
(Rh-AVC), derived from Rh(II)-catalyzed denitrogenation of N-
sulfonyl-1,2,3-triazoles has been successfully employed as a [1C],
[2C], or aza-[3C]-synthon in various [3+n] cycloaddition reactions.12
In particularly, a wide range of unsaturated chemical bonds,
including aldehyde, nitrile, have been well explored in the [3 + 2]
Results and Discussion
We commenced our investigation using 4-phenyl-1-tosyl-1H-
1,2,3-triazole (1a), quinoline-2-carbaldehyde (2a) as the model
substrates to identify the reaction conditions for this formal [3+2]
cyclization.
Preliminary
examination
identified
DCM
(dichloromethane) as the solvent choice in the presence of
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Rh2(oct)4 as catalyst, affording the target product 3a in 39% yield
(Table 1, entries 1-7). No reaction occurred in the absence of
transition metal catalyst (Table 1, entry 8). To our delight, increasing
the catalyst loading to 5 mol% resulted in a significantly higher yield
(75%, Table 1, entry 9). However, the desired product 3a was
isolated in 28% yield in DCE as solvent with the same catalyst
loading (Table 1, entry 3). Subsequently, changing the catalyst to
other metal catalysts and rhodium catalysts did not improve the
efficiency (Table 1, entries 11-16). In addition, the effects of the
temperature and reaction time were also investigated. It was found
that neither increasing nor decreasing the reaction
temperature/time could improve the yield (Table 1, entries 17-20).
Taken together, 5 mol% Rh2(oct)4 as catalyst, DCM as solvent at
110 °C for 24 h were selected as the optimized reaction conditions
(Table 1, entry 9).
respectively) changing the p-tosyl group to (4-fluorophenyl)sulfonyl,
(4-methoxyphenyl)sulfonyl, and (2,4,6-triisopropylphenyl)sulfonyl
groups of the substrate 1,2,3-triazoles. Similarly, the substrates 1
with electron-donating group (e.g., Me, Et, OMe) on the para-
position of aryl group were well suitable for this reaction, affording
the corresponding products 3b, 3c, and 3d in 65%, 62%, and 76%
yields, respectively. While the same position was replaced by
moderate electron-withdrawing groups (e.g., F, Br), the reactivity
of the process was hampered and the yield was lightly reduced (3e,
3f). These results indicated that electronic effect of the
substituents on the phenyl ring had a certain effect on the Rh-
carbene intermediate derived from 1,2,3-triazoles in the presence
of Rh-catalyst. Though the electron-withdrawing group (e.g. F, Br)
could improve the activity of Rh-carbene intermediate, which also
was easily decomposed in the reaction conditions to decrease the
yield of the desired product. To our surprise, trifluoromethyl as
strong electron-withdrawing substituent afforded the desired
product 3g in 76% yield. Similarly, the yield of compound 3l was
decreased to 49% when the Rh-carbene intermediate bearing with
two CF3 groups for its higher reactivity and easily decomposed. The
reaction also effectively for meta- and ortho-substituted 1,2,3-
triazoles on the aryl group, generating the corresponding products
3h-3k in 71%-82% yields. In addition, 1,2,3-triazoles bearing with
ditrifluoromethyl group at the meta-position of phenyl ring was
also compatible. Noteworthy was the ability to incorporate an
extend π structure into the product (3m), providing potential
applications in photochemical properties and chemosensors.
The optimized reaction conditions were then challenged with a
diversity of substituted quinoline-2-carbaldehydes to probe its
scope, by taking 1a as the reaction partner. Satisfactorily,
substituents including electron-rich (e.g., Me) groups and electron-
deficient (e.g., F, Cl, and Br) groups at the 6-, 7-, and 8-positons of
the quinolyl rings were well-tolerated. The corresponding products
3n-3r were obtained in 66%-78% yields. In addition to quinoline-2-
Table 1 Optimization of the reaction conditions.a
N
N
N
catalyst mol%)
(4
N
Ts
+
solvent, 110 o 24 h
C,
N
O
OHC
N
Ph
Ph
3a
1a
2a
Entry
1
Catalyst
Solvent
DCM
Yield/%
39
Rh2(oct)4
2
3
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
/
toluene
DCE
24
14 (28c)
30
4
PhCl
5
MeNO2
CHCl3
THF
trace
trace
trace
nr
6
7
8
9c
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
Rh2(oct)4
Rh2(oct)4
CuI
75
10d
11c
12c
13c
14c
15c
16c
17c,e
18c,f
19c,g
20c,h
54
carbaldehydes,
2-naphthaldehydes
and
benzofuran-2-
17
carbaldehyde were examined. The desired products 3s, 3t, and 3u
were successfully obtained in 71%, 64%, and 70% yields,
respectively. Unfortunately, when other heteroaromatic aldehydes,
such as benzo[b]thiophene-2-carbaldehyde, 1-methyl-1H-indole-2-
carbaldehyde, benzo[d]thiazole-2-carbaldehyde, and quinoxaline-
2-carbaldehyde were employed, the reaction system became
sluggish and the corresponding products 3v-3y were hardly
observed, which trouble the [3+2] cyclization process.
[Cp*RhCl2]2
nd
[(PPh)3P]3RhCl
Co2(CO)8
45
32
Ni(acac)2
Rh2(OAc)4
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
Rh2(oct)4
50
27
17
29
56
75
a
Reaction conditions: 4-phenyl-1-tosyl-1H-1,2,3-triazole 1a (0.2 mmol),
quinoline-2-carbaldehyde 2a (0.2 mmol), catalyst (4 mol%), and solvent (2
mL) under argon atmosphere at 110 °C for 24 h. c The catalyst loading was
5 mol%. d The catalyst loading was 6 mol%. e 90 °C. f 120 °C. g For 12 h. h For
30 h.
With the optimized conditions established, the substrate scope
of this formal [3+2] cyclization was evaluated as shown in Table 2.
The yield of 3a was relatively moderate (48%, 30%, and 28%,
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Running title
Chin. J. Chem.
Table 2 Substrate scope.a,b
molecules, which has potential applications in material science as
ligands and chemosensors.
Scheme 2 Further studies
N
N
N
O
Rh
mol%)
2(oct)4 (5
R
N
Ts
+
DCM, 110 o 24 h
C,
X
OHC
X
=
Ar
Ar
1
R
3
2
CH)
N,
(X
Gram-scale
(a)
synthesis
N
N
O
N
N
mol
Rh
%)
2(oct)4 (5
+
Ts
DCM, 110 o 24 h
N
N
O
C,
OHC
N
Ph
N
Ph
Br
mmol)
R
Br
mmol)
1a
(5
2f
75%, 48%c
(5
=
3r
60%)
g,
(1.05
3a: R
H,
=
3b: R Me, 65%
Further transformation
N
(b)
X-ray of 3a
2018443)
=
3c: R Et, 62%
(CCDC
=
3d: R OMe, 76%
N
N
N
O
O
N
R
O
N
O
N
N
Br
3r
Me
R
p-Tol
=
3e: R
54%
=
R
Me, 75%
F,
3h:
Cl
mol%)
=
=
3i: R Cl, 76%
=
R
3j:
Pd(PPh3)2 2 (4
3f: R Br, 59%
=
4
(92% yield)
CuI mol%),
(4
Et N
Br, 71%
N
N
O
R
CF3 76%
,
3
3g:
Ar, 100 o 24 h
N
C,
N
N
F
O
N
F3C
O
N
3f
O
Br
N
5
p-Tol
(93% yield)
3k, 82%
3l, 49%
N
F3C
N
N
O
O
N
R
On the basis of the previously described experimental finding
=
=
=
3n: R Me, 78%
3m, 70%
and the literature precedence,14,16 a proposed mechanism is
illustrated in Scheme 3. Initially, 1,2,3-triazoles 1 reacted with Rh-
catalyst extruding nitrogen and generated Rh(II)-azavinyl carbine
species A. Subsequently, interaction of the carbene center with the
carbonyl group of substrate 2 formed the intermediate ylide B,
which underwent cyclization, leading to the intermediate C. Finally,
removal of the p-toluenesulfonic acid (detected by GC-MS)
followed by affording the desired 2,5-aryloxazoles 3.
iPr
3o: R
66%
Br, 71%
F,
R
3p:
N
O
N
O
N
N
3r, 69%
Br
Cl
67%
3q,
N
N
O
O
O
Scheme 3 Proposed mechanism
R
=
3s: R
71%
3u, 70%
H,
N
N
=
3t: R Br, 64%
N
Ts
unsuccessful examples
Ar
1
N
N
N2
RhII
X
O
S
O
H
N
N
O
3v
O
O
3w
N
S
[Rh]
Ar
-tol
p
N
Ar
Ts
N
C
N
N
N
A
O
O
S
3y
3x
p-tolSO2H
X
X
OHC
N
2
a
O
Reaction conditions: 4-aryl-1-tosyl-1H-1,2,3-triazoles
1 (0.2 mmol),
NTs
X
O
aromatic aldehydes 2 (0.2 mmol), and Rh2(OAc)4 (5 mol%) in DCM (2 mL)
under argon atmosphere at 110 °C for 24 h. Isolated yields. (4-
Ar
-
Ar
3
[Rh ]
B
b
c
Fluorophenyl)sulfonyl was used instead of p-tosyl group.
We previously reported a novel ferrocenyl-isoxazoles as a
multiple signal probe for highly selective recognition of Cu2+ ions.17
This class of compounds have rarely been reported in the field of
molecular sensing and might have a potential significance for the
application of the π extent isoxazole derivatives in molecular
recognition. During the preparation of 5-aryl-2-(quinolin-2-
yl)oxazoles, we found that these compound were strongly emissive
under UV light and this skeleton was indeed a new fluorophore.
Therefore, we selectively investigated the photophysical properties
of compounds 3a, 3d, 3g, 3m, 3s, 3u, 4 and 5 (see the ESI). These
To demenstrate the efficiency and utility of this strategy, a
gram-scale synthesis was performed by using 4-phenyl-1-tosyl-1H-
1,2,3-triazole (1a, 5 mmol) and 8-bromoquinoline-2-carbaldehyde
(2f, 5 mmol) as substrates under the standard conditions (Scheme
2a). Gratifyingly, the desired product 3r was afforded in 60% yield
(1.05 g). In addition, the halo-substituted product 3r and 3f were
used for late-stage transformation, affording the Sonogashira
coupling products 4 and 5 in 92% and 93% yields, respectively
(Scheme 2b). This fantastic outcome indicates that this method is a
prospectively powerful tool for late-stage modification of π extend
Chin. J. Chem. 2019, 37, XXX－XXX
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First author et al.
Report
compounds have good fluorescence properties in mixed methanol
under 365 nm irradiation with a hand-held UV lamp (Figure 1).
compound 3a and the response towards K+, Na+, Ni2+, Mg2+, Ca2+,
Pb2+ and Hg2+metal ions were investigated (Figure 2b). To our
delight, dramatic fluorescence quenching of compound 3a was
observed upon the addition of Hg2+ ion to the solution and a new
emission peak appeared at 594 nm. By contrast, a gradually
decreased fluorescent intensity was observed when gradually
addition of other metal ions including Na+, K+, Mg2+, Ca2+, Pb2+, and
Ni2+. These results indicated that compound 3a showed highly
selective sensing toward Hg2+ ion over the other metal ions
investigated.
Figure 1 The fluorescence colours of 2-(quinolin-2-yl)oxazoles in MeOH
(2.5 ×10-5 M) under UV irradiation (365 nm).
We next studied the impact of the different substituents on the
absorbance and fluorescent properties of the selected 2,5-
aryloxazoles (Table 3). 2-(quinolin-2-yl)oxazole 3a absorbs light at
348 nm (ε = 2.08 × 104). When 2-quinolinyl changed to 2-
naphthalenyl and 2-benzofuranyl, we found that the maximum
absorption wavelength of compounds 3s (λmax = 323 nm, ε = 3.12 ×
104) and 3u (λmax = 336 nm, ε = 2.27 × 104) had a light blue shift. On
the other hand, the presence of electron-donating (3d) and π
extend groups (3m) on the phenyl ring showed a light red shift of
the maximum absorption wavelength. Also the emission spectra of
these selective compounds were evaluated (see ESI, Figure S2).
Similarly, the compounds 3d and 3m showed intense emission
spectra (492 nm and 476 nm) with an excellent Stokes shifts (136
nm and 117 nm).
Figure 2 (a) absorption spectra of compound 3a (c = 2.5 × 10-5 M) in
MeOH-H2O (v/v = 1:1) upon addition of several cations. (b) fluorescence
emission spectra of 3a (c = 2.5 × 10-5 M) in MeOH-H2O (v/v = 1:1) upon
addition of several cations.
Conclusions
In summary, the synthesis of novel 5-aryl-2-(quinolin-2-
yl)oxazole derivatives as a new chemosensor in metal ion
recognition has been achieved via Rh-catalyzed formal [3+2]
cyclization of 4-aryl-1-tosyl-1H-1,2,3-triazoles with quinoline-2-
carbaldehydes. This highly efficient protocol constructs two new
carbon-heteroatom bonds and one new five-membered ring
Table 3 Photophysical properties of the selected compounds in MeOH
(2.5 ×10-5 M).
Compound
λabsa/nm
ε(M−1cm-1)
λemb/nm
Stokes shift (nm)
87
through
sequential
denitrogenation/1,3-dipolar
3a
348
20840
435
cycloaddition/elimination process. This process does not require
additive/base in the presence lower catalyst loadings under mild
conditions, thus, this protocol is complementary to the inherent
shortcomings of the existing cross-dehydrogenative coupling of
quinoline N-oxides with 1,3-azoles. In addition, this work not only
3d
3g
3m
3s
3u
4
356
343
359
323
336
290
383
3520
23640
19560
31200
22760
29560
3360
492, 594
415
136, 211
72
476
117
provided
a simple and efficient one-pot reaction for the
399
76
construction of multifunctional oxazole derivatives that are not
easy accessible by other approaches but also demonstrated their
application in metal ion probes.
392
56
482
192
5
459, 594
76, 211
a Absorption maxima. b Fluorescent emission maxima.
Experimental
General procedure for the synthesis of 2,5-aryloxazoles 3.
A mixture of 4-aryl-1-sulfonyl-1H-1,2,3-triazoles 1 (0.2 mmol),
quinoline-2-carbaldehydes 2 (0.2 mmol) or 2-naphthaldehydes (0.2
mmol) or benzofuran-2-carbaldehyde (0.2 mmol), and Rh2(oct)4
(0.01 mmol) in DCM (2 mL) was heated to 110 °C in an oil bath for
24 h. After the reaction was complete (as determined using TLC),
the reaction mixture was cooled to room temperature, extracted
with CH2Cl2 (3 × 10 mL), and washed with brine. The organic layers
were combined, dried over Na2SO4, filtered, and then evaporated
under vacuum. The residue was purified using flash column
chromatography with a silica gel (200-300 mesh), using ethyl
acetate and petroleum ether (1:10, v/v) as the elution solvent to
Subsequently, the metal-recognition properties of receptor 3a
as ligand (L) were evaluated by UV-Vis spectroscopy (Figure 2a). A
very strong high-energy (HE) absorption peak at 348 nm (ε = 2.26 ×
104) and a weak low-energy (LE) waveless peak at 287nm can be
observed for compound 3a in MeOH (c = 2.5 ×10-5 M). To our
delight, we found that a red shift of the HE absorption wavelength
to 353 nm and no LE absorption wavelength can be observed upon
the addition of 2.5 ×10-5 M Hg2+ cations to the solution of
compound 3a, compared to other metal ions which increased
either HE absorption peak or LE absorption peak at 294 nm and 349
nm to 362 nm. On the other hand, the fluorescence character of
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Chin. J. Chem. 2019, 37, XXX－XXX
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Running title
Chin. J. Chem.
give desired products 3.
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General procedure for the synthesis of compounds 4 and 5. A
mixture of 2-(8-bromoquinolin-2-yl)-5-phenyloxazole 3r (0.2 mmol)
or 5-(4-bromophenyl)-2-(quinolin-2-yl)oxazole 3f (0.2 mmol), 1-
ethynyl-4-methylbenzene (0.2 mmol), Pd(PPh3)2Cl2 (4 mol%), and
CuI (4 mol%) in triethylamine (2 mL) was stirred under argon
atmosphere at 100 ºC in an oil bath for 24 h. After the reaction was
complete (as determined using TLC), the reaction mixture was
cooled to room temperature, extracted with CH2Cl2 (3 × 10 mL), and
washed with brine. The organic layers were combined, dried over
Na2SO4, filtered, and then evaporated under vacuum. The residue
was purified using flash column chromatography with a silica gel
(200-300 mesh), using ethyl acetate and petroleum ether (1:12, v/v)
as the elution solvent to give the Sonogashira products 4 or 5.
Ukaji, Y. Development of
a one-pot synthetic method for
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2018xxxxx.
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Acknowledgement
phenylnaphtho[1,3]selenazoles
under
transition-metal-free
The work was partially supported by the National Natural
Science Foundation of China (No. 21772001), the Anhui Provincial
Natural Science Foundation (No. 1808085MB41), and Cultivation
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Running title
Chin. J. Chem.
H insertion or Wolff rearrangement of 5-aryl-1H-pyrazoles and diazo
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Zhang, Z.; He, X.; Shang, Y.; Yu, Z.; Wang, S.; Wu, F. Ferrocenyl-
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a novel electrochemical, colorimetric and
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(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2019
Manuscript revised: XXXX, 2019
Manuscript accepted: XXXX, 2019
Accepted manuscript online: XXXX, 2019
Version of record online: XXXX, 2019
(a) Jiang, M.; Ding, X.; Yu, X.; Deng, W.-P. Synthesis of 2,5-epoxy-1,4-
benzoxazepines via rhodium(II)-catalyzed reaction of 1-tosyl-1,2,3-
triazoles and salicylaldehydes. Tetrahedron 2016, 72, 176-183; (b) Li,
Chin. J. Chem. 2019, 37, XXX－XXX
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
This article is protected by copyright. All rights reserved.

Entry for the Table of Contents
Page No.
Rh-catalyzed formal [3+2] cyclization for
synthesis of 5-aryl-2-(quinolin-2-yl)oxazoles and
its applications in metal ions probes
N
N
O
N
Rh
mol%)
2(OAc)4 (5
R
N
Ts
+
110 o 24 h
DCM,
C,
X
OHC
(X
X
Ar
Ar
R
=
CH, O)
N,
fluorescence
Hg2+
non-fluorescence
mild conditions
tolerance
&
functional
good
groups
& easily transformation
gram-scale
synthesis
in ions
probe
fluorescence
&
applications
good
properties
Tongtong Zhou, Xinwei He,* Youpeng Zuo,
Yuhao Wu, Wangcheng Hu, Shiwen Zhang, Jiahui
Duan and Yongjia Shang*
fluorescence
quenched
a Department, Institution, Address 1
E-mail:
c Department, Institution, Address 3
E-mail:
b Department, Institution, Address 2
E-mail:
Chin. J. Chem. 2018, template© 2018 SIOC, CAS, Shanghai,
&
WILEY-VCH Verlag GmbH
&
Co. KGaA,
Weinheim
This article is protected by copyright. All rights reserved.