Highly sensitive fluorescent sensor targeting CuCl2based on thiophene attached anthracene compound (TA)

Article abstract of DOI:10.1016/j.tetlet.2017.01.071

A novel thiophene attached anthracene (TA) based fluorescent compound was designed and synthesized. The TA showed a high quantum yield (Qy?=?0.34) in regard to fluorescence. We applied this TA compound to detect specific metal compound and found that it could identify CuCl₂from other metals through dramatic fluorescence change at λ_max?=?460?nm. It showed strong quenching fluorescence property with CuCl₂while with other metal compounds it exhibited strong blue fluorescence emission. UV/Vis absorption spectroscopy clearly demonstrated that the quenching property of TA at λ_max?=?460?nm was due to overlapping of the fluorescence peak of TA at λ_max?=?460?nm and the absorption band of CuCl₂(from 190?nm to 525?nm). Binding constant (K′), which was 0.0895?mM^?2, indicated a complexation ratio between TA and CuCl₂as 1:2 and this interaction induced quenching property.

Full text of DOI:10.1016/j.tetlet.2017.01.071

Accepted Manuscript
Highly sensitive fluorescent sensor targeting CuCl2 based on thiophene attached
anthracene compound (TA)
Thuy Van Thi Nguyen, Young Jun Seo
PII:
S0040-4039(17)30102-8
DOI:
http://dx.doi.org/10.1016/j.tetlet.2017.01.071
TETL 48574
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
5 December 2016
16 January 2017
23 January 2017
Please cite this article as: Van Thi Nguyen, T., Jun Seo, Y., Highly sensitive fluorescent sensor targeting CuCl2
based on thiophene attached anthracene compound (TA), Tetrahedron Letters (2017), doi: http://dx.doi.org/10.1016/
j.tetlet.2017.01.071
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Tetrahedron Letters
Highly sensitive fluorescent sensor targeting CuCl2 based on thiophene attached
anthracene compound (TA)
Thuy Van Thi Nguyena, Young Jun Seoa,b,
aDepartment of Bioactive Material Sciences, Chonbuk National University, South Korea
b Department of Chemistry, Chonbuk National University, South Korea
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A novel thiophene attached anthracene (TA) based fluorescent compound was designed and
synthesized. The TA showed a high quantum yield (Qy=0.34) in regard to fluorescence. We
applied this TA compound to detect specific metal compound and found that it could identify
CuCl2 from other metals through dramatic fluorescence change at λmax = 460 nm. It showed
strong quenching fluorescence property with CuCl2 while with other metal compounds it
exhibited strong blue fluorescence emission. UV/Vis absorption spectroscopy clearly
demonstrated that the quenching property of TA at λmax = 460 nm was due to overlapping of the
fluorescence peak of TA at λmax = 460 nm and the absorption band of CuCl2 (from 190 nm to
525 nm). Binding constant (K’), which was 0.0895 mM-2, indicated a complexation ratio
between TA and CuCl2 as 1:2 and this interaction induced quenching property.
Available online
Keywords:
Fluorophore
Thiophene attached anthracene
Sensor
CuCl2
Binding constant
2016 Elsevier Ltd. All rights reserved.
Development of novel types of photochromic compound is
exceedingly important due to the possibility of their diverse
applications especially for sensing of metal,1 small molecule,2
macromolecule3 and biomolecule.4 Fluorescent molecules are
particularly sensitive to the changes in environment5 and thus
they could be used for diverse diagnostics, molecular imaging,
and biophysics areas.6 Thus, our goal is to develop novel
fluorescent compound which is very sensitive to a specific
material. Anthracene is a unique fluorescence material that has
high fluorescence quantum yield, and can form dimerized
structure under light illumination.7 Thiophene is also a unique
heterocyclic aromatic compound that can be used in thiophene-
based oligopolymers to utilize the high electrical transfer
property.8 Our strategy to develop a photochromic compound
involved combination of two units of anthracene and thiophene
to generate a material with novel photophysical property. Based
on this concept we designed and synthesized a thiophene
attached anthracene compound (TA). Herein, we report a
particular photophysical property of thiophene-based anthracene
(TA) which has remarkable sensitivity to a specific metal, CuCl2.
TA AgNO3 CaCl2 CdCl2 CoCl2 CuCl2 KCl MgCl2 NiCl2 ZnCl2
Scheme 1. Structure of thiophene attached anthracene (TA) and its photo
sensing ability to the specific metal.
synthesized from 5-bromo-2-thiophenecarboxaldehyde (1) via
reduction using sodium borohydride (NaBH4). Next, we coupled
it with anthracene-9,10-diboronic acid bis(pinacol) ester (3) to
produce thiophene attached anthracene compound (TA) using
Suzuki coupling condition (Scheme 2).
First, to obtain thiophene attached anthracene compound at
two symmetric positions, a two-step reaction was performed. In
the first step, (5-bromothien-2-yl) methanol (2) compound was
———
 Corresponding author. Department of Chemistry, Chonbuk National University, Jeonju 561-756, South Korea. Fax: +82-63-270-3408; Tel.: +82-63-
270-3417; e-mail: yseo@jbnu.ac.kr

2
(a)
(c)
TA
TA
TA-AgNO3
TA-CaCl2
TA-CdCl2
TA-CoCl2
TA-CuCl2
TA-KCl
TA-MgCl2
TA-NiCl2
TA-ZnCl2
400
300
200
100
0
TA-AgNO3
TA-CaCl2
TA-CdCl2
TA-CoCl2
TA-CuCl2
TA-KCl
TA-MgCl2
TA-NiCl2
TA-ZnCl2
0.6
0.4
0.2
0.0
300
400
500
600
700
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450
500
550
600
Wavelength(nm)
Scheme 2. Design and synthesis of thiophene attached anthracene
Wavelength(nm)
fluorescence compounds. Reagents and conditions: i. NaBH4, MeOH, rt, 2hr,
63% yield; ii. Pd(PPh3)4, K2CO3, 1,4-dioxane-H2O, reflux, 90˚C, 2hr, 62%
yield.
(b)
To check the basic photo physical property of our TA
compound, we measured the UV/Vis spectra and chose the
excitation wavelength at λmax=374 nm. Emission wavelength was
obtained at λmax=460 nm using the excitation wavelength,
λmax=374 nm (Fig. 1). To note, the TA exhibited a high quantum
yield Qy=0.34 in MeOH, which was strong enough for diverse
applications (see supplementary information).
Figure 2. (a) Fluorescence spectra, (b) Photo image, and (c) UV/Vis
spectra of TA compound with different metals in DMSO. All samples were
prepared in DMSO at 25ºC in a concentration of 3 µM of TA and 30 mM of
each metal. We used λmax=374 nm wavelength for the excitation.
100
0.08
TA
TA
80
60
40
20
0
0.06
0.04
0.02
0.00
To further clarify the quenching property of TA we changed
the solvent from DMSO, the polar aprotic solvent to water, which
is a polar protic solvent and measured the UV/Vis absorption
spectra (Fig. S10A). Interestingly, the absorption wavelength of
CuCl2 changed to the range from (190 nm – 520 nm) to (190 nm
– 310 nm), which did not overlap with the wavelength of
fluorescence of TA at λmax=460 nm and no quenching property
could be observed (Fig. S10B). This result strongly suggested
that the quenching of TA by CuCl2 originated from overlapping
of the fluorescence wavelength of TA and the absorption
wavelength of CuCl2.
200
250
300
350
400
450
400
450
500
550
600
Wavelength(nm)
Wavelength(nm)
Figure 1. UV/Vis absorption spectra and fluorescence spectra of TA
compound. All samples were prepared at a concentration of 1 µM of TA in
MeOH. We used λmax=374 nm wavelength for the excitation.
Next, we focused on studying the interaction between CuCl2
and TA compound. For this purpose, fluorescence titrations of
TA (3 µM) with various concentrations of CuCl2 in DMSO were
performed (Fig. S11). As shown in Fig 3, the fluorescence
emission intensity at 460 nm decreased gradually upon the
addition of from 1mM CuCl2 and complete quenching could be
observed at 30 mM of CuCl2. To determine interaction ratio and
binding constant (K) of this complex, the Benesi–Hildebrand
double reciprocal method was employed using the following two
equations (see supporting information for detail information): 9
We examined the potential of TA as a metal sensor by
screening several different metal compounds, such as ZnCl2,
AgNO3, CaCl2, CdCl2, CoCl2, CuCl2, KCl, MgCl2, and NiCl2
in DMSO solvent. Noticeably, as shown in Fig.2a, fluorescence
spectra exhibited selective discrimination property toward the
above-mentioned metals. All the metals, viz. ZnCl2, AgNO3,
CaCl2, CdCl2, CoCl2, KCl, and MgCl2 exhibited high
fluorescence signal at the λmax= 440 nm except NiCl2, which
exhibited a small redshifted emission at λmax = 465 nm.
Furthermore, with addition of the TA compound to a solution
contain 50mM of CuCl2, a dramatic quenching property could be
realized which can be used to identify CuCl2 from other metals.
The photo in Fig. 2b clearly shows the quenching property for
CuCl2, while all other metals exhibited a moderate fluorescence
(Fig. 2b).
We calculated both the equations and obtained two
corresponding graphs at high concentration of CuCl2 range from
3 mM to 30 mM. Equation (1) did not produce a linear fit line to
calculate binding constant value (Fig. S12). Thus, any possibility
of binding between CuCl2 and TA in the ratio 1:1 was excluded.
However, following equation (2), we could obtain a linear fit line
with 1:2 complexions. From this result, we confirm that CuCl2
molecule tend to bind with S and O atoms on each side. As
shown in figure 4, the intercept and slope of the fitted straight
line gave the binding constant, K’ = 0.0895 mM-2. This result
also indicated that interaction ratio between TA and CuCl2 was
1:2. Therefore, it can be inferred that two CuCl2 molecules and
one TA molecule formed complex through S and O atoms at both
symmetric sides of the TA molecule and exhibited a complete
quenching.
To understand the origin of this fluorescence signal change,
UV/Vis absorption spectra of each metal were measured (Fig. 2c).
The UV absorption spectra indicated that the absorption
wavelengths of the metals except CuCl2 did not overlap with the
emission wavelength of TA. The absorption wavelength of
CuCl2 completely overlapped with the fluorescence wavelength
of TA broadly covering the absorption wavelength from 190 nm
to 520 nm. From these results, we assume that the fluorescence
quenching of TA by CuCl2 may be originated from the excited
electron of TA transfer to the absorption of CuCl2.

wavelength shifted without overlapping with the fluorescence
wavelength of TA. Thus, no fluorescence quenching could be
observed. Binding constant (K’), which is 0.0895 mM-2, clearly
indicated that the complexation ratio between TA and CuCl2 was
1:2 and further support the quenching property of TA with CuCl2.
We believe that this TA fluorescence compound maybe used in
the application to sense CuCl2.
=
=
+
+
(1)
(2)
Acknowledgments
TA
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0
TA-CuCl2 1mM
TA-CuCl2 2mM
TA-CuCl2 3mM
TA-CuCl2 4mM
TA-CuCl2 5mM
TA-CuCl2 6mM
TA-CuCl2 7mM
TA-CuCl2 8mM
TA-CuCl2 9mM
TA-CuCl2 10mM
TA-CuCl2 15mM
TA-CuCl2 20mM
TA-CuCl2 25mM
TA-CuCl2 30mM
This work was carried out with the support of "Cooperative
Research Program for Agriculture Science & Technology
Development (Project No. PJ01227701)", Rural Development
Administration, Republic of Korea. Thuy Van Thi Nguyen was
supported by the BK21 PLUS program from the Department of
Bioactive Material Science.
Supplementary Data
400
450
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600
Electronic Supplementary Information (ESI) available: The sample
preparation details, synthetic procedure, quantum yield, UV absorption,
and fluorescence spectra, are available online.
Wavelength(nm)
Figure 3. UV/Vis spectra and Fluorescence spectra of TA compound in
DMSO with the present of CuCl2 at the different concentrations. All samples
were prepared at 25ºC at a concentration of 3 µM of TA. We used λmax=374
nm wavelength for excitation.
References
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2.
3.
4.
Huang, Y.; Li, F.; Ye, C.; Qin, M.; Ran, W.; Song, Y. Scientific
Reports. 2015, 5, 9724.
Qin, M.; Huang, Y.; Li, F.; Song, Y. J. Mater. Chem. C. 2015, 3,
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Dutta, P.; Saikia, D.; Adhikary, N. C.; Sarma, N. S. ACS Appl.
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(a) Ying, Z.; Tao, Y.; Shuzhang, X.; Fuyou, L.; Chunyan, L.; Xia,
G.; Junchen, W.; Mengxiao, Y.; Chunhui, H. J Am Chem Soc.
2008, 130, 15750; (b) Kim, E. S.; Lorenzo, B.; Igor, L. M. Angew.
Chem. Int. Ed. 2006, 45, 4562. (c) Kim, I.S.; Seo, Y.J.
Tetrahedron Letters. 2014, 55, 1461; (d) Kim, I.S.; Seo, Y.J.
Bioorganic & Medicinal Chemistry Letters. 2014, 24, 1589; (e)
Lee, D.G.; Kim, I.S.; Park, J.W.; Seo, Y.J. Chem. Commun. 2014,
50, 7273; (f) Joo, H. N.; Seo, Y. J. Chem. Commun. 2015, 51,
2939.
7
TA:CuCl2=1:2
Y' = 2.70 + 31.43 * X'
6
5
4
3
2
K'= 0.0859 mM-1
R'=0.999
5.
6.
(a) Phillips, J. A.; Liu, H.; Meghan, B.; Dogonghue, O.; Xiong,
X.; Wang, R.; You, M.; Sefah, K.; Tan, W. Bioconjugate Chem.
2011, 22, 282; (b) Stojanovic, M. N.; De Prada, P.; Landry, D. W.
J Am Chem Soc. 2001, 123, 4928; (c) Nachtigall, O.; Lomoth, R.;
Dahlstrand, C.; Lundstedt, A.; Gogoll, A.; Webb, M. J.;
Grennberg, H. Eur J Org Chem. 2014, 5, 966; (d) Jiang, Y.; Fang,
X.; Bai, C. Anal Chem. 2004, 76, 5230.
(a) Ozaki, H.; Nishihira, A.; Wakabayashi, M. Bioorg Med Chem
Lett. 2006, 16, 4381; (b) Ferapontova, E. E.; Olsen, E. M.;
Gothelf, K. V. J Am Chem Soc. 2008, 130, 4256; (c) Yamamoto,
R.; Kumar, P. K. R. Genes Cells, 2000, 5, 389.
0.00
0.02
0.04
0.06
0.08
0.10
0.12
1/[CuCl2]2 (mM)-2
Figure 4. Plot of 1/(Fo−F) vs. 1/[CuCl2]2 to determine the binding
constant and the stoichiometry for CuCl2 binding to TA in DMSO. The
concentration of CuCl2 is ranging from 3 mM to 30 mM. The samples were
measured at 374 nm.
7.
8.
Draper, R. E.; Adam, J. D. Chem. Commun. 2016, 52, 8196.
Yin, X.; Guo, F.; Lalancette, A. R.; Frieder Jakle.
Macromolecules. 2016, 49, 537.
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298, 201. (b)Pradipta. P. Photochemistry and photobiology A
Chem. 2010, 212, 43.
From all the above-mentioned results, we suggest that the TA
compound can be used as a novel fluorescence material to sense
specific metal, such as CuCl2.
Novel thiophene-attached anthracene fluorescent
compound (TA) was designed and developed.
TA compound showed highly selective
fluorescence quenching property to the CuCl2.
Binding constant (K’= 0.0895 mM-2) clearly
indicated that the complexation ratio between TA
and CuCl2 was 1:2.
In conclusion, a thiophene attached anthracene compound (TA)
was developed as a novel fluorescence material to sense specific
metal. TA exhibited fluorescence emission at λmax=460 nm using
370 nm excitation and showed a high quantum yield Qy=0.34.
We applied this TA compound to detect selective metal
compounds. In this regard, the TA was able to identify CuCl2
from other metals through dramatic fluorescence quenching
property. Furthermore, we demonstrated that this dramatic
fluorescence quenching property originated from overlap
between fluorescence wavelength of TA and absorption
wavelength of CuCl2. This hypothesis was further supported by
using water, a polar protic solvent in which the absorption

4
Graphical Abstract
We designed and synthesized a novel thiophene attached
anthracene (TA) based fluorescent compound and applied for
sensing CuCl2.
Leave this area blank for abstract info.
Highly sensitive fluorescent sensor targeting
CuCl2 based on thiophene attached anthracene
compound (TA)
Thuy Van Thi Nguyenb, Young Jun Seoa, b,
*
TA
400
300
200
100
0
TA-CuCl2 1mM
TA-CuCl2 2mM
TA-CuCl2 3mM
TA-CuCl2 4mM
TA-CuCl2 5mM
TA-CuCl2 6mM
TA-CuCl2 7mM
TA-CuCl2 8mM
TA-CuCl2 9mM
TA-CuCl2 10mM
TA-CuCl2 15mM
TA-CuCl2 20mM
TA-CuCl2 25mM
TA-CuCl2 30mM
400
450
500
550
600
Wavelength(nm)