Polymer-based fluorescence sensor incorporating thiazole moiety for direct and visual detection of Hg2+ and Ag+

Article abstract of DOI:10.1016/j.tet.2015.01.052

A thiazole-based conjugated polymer was synthesized by the polymerization reaction of 4,7-dibromo-2-methylbenzo[d]thiazole with 1,4-diethynyl-2,5-bis(octyloxy)benzene via Pd-catalyzed Sonogashira coupling reaction. The conjugated polymer emits bright green fluorescence and exhibits 'turn-off' fluorescent quenching responses towards both Hg²⁺ and Ag⁺ over other cations, such as Li⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Zn²⁺, Cd²⁺, Co²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Al³⁺ and Fe³⁺. More importantly, the color change of this polymer solution could be clearly observed by the naked eyes upon the addition of Hg²⁺ (green to colorless) and Ag+ (green to yellow), indicating that this thiazole-based conjugated polymer material could be used as a colorimetric sensor for directly visual detection of Hg²⁺ and Ag⁺.

Full text of DOI:10.1016/j.tet.2015.01.052

Accepted Manuscript
Polymer-based Fluorescence Sensor incorporating Thiazole Moiety for Direct and
2+
+
Visual Detection of Hg and Ag
Fei Li, Fandian Meng, Yuxiang Wang, Chengjian Zhu, Yixiang Cheng
PII:
S0040-4020(15)00107-6
10.1016/j.tet.2015.01.052
TET 26375
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 20 November 2014
Revised Date: 11 January 2015
Accepted Date: 23 January 2015
Please cite this article as: Li F, Meng F, Wang Y, Zhu C, Cheng Y, Polymer-based Fluorescence Sensor
2+
+
incorporating Thiazole Moiety for Direct and Visual Detection of Hg and Ag , Tetrahedron (2015), doi:
0.1016/j.tet.2015.01.052.
1
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ACCEPTED MANUSCRIPT
Graphical Abstract:
Polymer-based sensor incorporating thiazole ligand moiety exhibited “turn-off” fluorescence
2
+
+
response on both Hg and Ag . The color change of this polymer solution could be clearly
2
+
+
observed by the naked eyes upon the addition of Hg (green to colorless) and Ag (green to
yellow).
1

ACCEPTED MANUSCRIPT
Polymer-based Fluorescence Sensor incorporating Thiazole Moiety
2+
+
for Direct and Visual Detection of Hg and Ag
Fei Li, Fandian Meng, Yuxiang Wang, Chengjian Zhu*, Yixiang Cheng*
Key Lab of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering,
Nanjing University, Nanjing 210093, China
E-mail: yxcheng@nju.edu.cn; cjzhu@nju.edu.cn
ABSTRACT: A thiazole-based conjugated polymer was synthesized by the polymerization
reaction of 4,7-dibromo-2-methylbenzo[d]thiazole with 1,4-diethynyl-2,5-bis(octyloxy)benzene
via Pd-catalyzed Sonogashira coupling reaction. The conjugated polymer emits bright green
2
+
+
fluorescence and exhibits “turn-off” fluorescent quenching responses towards both Hg and Ag
+
+
2+
2+
2+
2+
2+
2+
2+
2+
2+
3+
over other cations, such as Li , K , Ca , Mg , Ba , Zn , Cd , Co , Ni , Pb , Cu , Al and
3+
Fe . More importantly, the color change of this polymer solution could be clearly observed by the
2
+
naked eyes upon the addition of Hg (green to colorless) and Ag+ (green to yellow), indicating
that this thiazole-based conjugated polymer material could be used as a colormetric sensor for
2
+
+
directly visual detection of Hg and Ag .
Keywords: Fluorescence sensor; Conjugated polymer; Hg and Ag ; Benzo[d]thiazole
2
+
+
1
. Introduction
In the past decades, conjugated polymers have attracted much attention on organic light–
emitting diodes, molecular sensors and solar cells since these polymer-based materials with
tunable optical and electronic properties can be greatly improved by careful combination of
[
1]
designed monomers at well-defined molecular level. Conjugated polymers as fluorescent
sensors have been widely utilized as popular probes for chemical, biological, and medical
applications. Polymer-based fluorescent chemosensors for direct recognition of various
metal ions have several advantages over small molecule sensors, such as enhancements
associated with electronic interaction between receptors and analytes within the
[
2]
π-electronic polymer backbone. The high selectivity and sensitivity of conjugated
polymers on various metal ions originates from the sensory signal amplification due to
energy migration along the polymer backbone upon light excitations.
Recently, the research on the polymer-based fluorescence sensor for metal ions detection
[
3]
+
2+
is emerging as an area of current interest. Among them, Ag and Hg as heavy metal
ions have attracted considerable research interest, because researchers are interested in
detecting these two ions due to their poisonous pollutants for health and environment. It is
well known that mercury, one of the most toxic heavy metal elements, can lead to the
dysfunction of cells and consequently cause a wide range of diseases even at a low
concentration, such as digestive, nephrogenic and especially neurological disorders on
[
4]
+
account of its high affinity for thiol groups of proteins and enzymes. Meanwhile, Ag
also plays an essential role in imaging industry, electronic and photographic product.
+
Although its toxicity is surpassed only by mercury, Ag has been also ranked as the highest
2

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[
5]
+
2+
toxicity class. Many fluorescence sensors for Ag or Hg detection have been reported.
But most of them are based on small molecules, and the polymer-based fluorescence
[
6]
chemosensors are very few. Therefore, the development of highly selective and sensitive
+
2+
polymer-based chemosensors for directly visual recognition of Ag and Hg is still greatly
attractive.
There have been some reports on thiazole-based derivatives as fluorescence sensors for
the detection of transition metals, but very few thiazole-based conjugated polymers were
2
+
+ [7]
used as fluorescence sensors for directly visual detection of Hg and Ag . In this paper,
we designed and synthesized conjugated polymer incorporating thiazole moiety in the
polymer main chain backbone via Sonogashira reaction. This thiazole-based polymer can exhibit
2
+
+
“
turn-off’ fluorescence response behavior only towards Hg and Ag . Interestingly, upon the
2
+
+
addition of Hg and Ag , the color of polymer solution could be clearly observed from bright
2
+
+
green to pale green by the naked eyes for direct detection of Hg and Ag at a low concentration
under a commercially available UV lamp.
2
. Results and discussion
The synthesis procedures of the thiazole-based polymer are outlined in Scheme 1. Monomers
4
,7-dibromo-2-methylbenzo[d]thiazole (M-1) and 1,4-diethynyl-2,5-bis(octyloxy)benzene (M-2)
[8,3c]
were synthesized according to the reported literatures.
The thiazole-based polymer could be
synthesized by the polymerization of M-1 with M-2 via the Pd-catalyzed halogenoalkane-alkyne
Sonogashira reaction. The polymer could be further purified by washing with MeOH and collected
as brown solids. The thiazole-based polymer could be dissolved in common organic solvents
(
THF, toluene, CH Cl , CHCl ) due to the flexible n-octyl substituents. GPC result of polymer
2 2 3
shows moderate molecular weights. TGA of polymer was carried out under a N atmosphere at a
2
heating rate of 10 ºC/min. TGA result shows that the degradayion temperature (T ) of 5% weight
d
loss of the polymer is 276 ºC, indicating that this polymer can provide desirable thermal property
for practical applications as fluorescence sensor (Figure S16).
Scheme 1. Synthesis of polymer.
The UV-vis absorption spectra of polymer sensor toward various anions were conducted in
-5
THF (1×10 mol/L) at room temperature. As shown in Figure 1a, the polymer sensor exhibits an
absorption maxima at 439 nm, which is attributed to a π-π* transition of conjugated polymer
[4c]
2+
backbone. Upon the addition of Hg , the intensities of absorption peak at 439 shows obvious
decrease with blue shift as high as 17 nm. But no changes were observed for the absorption
2
+
spectrum of the polymer sensor beyond 10 equiv of Hg . The UV-vis absorption response
2
+
behavior of the polymer on Hg can be regarded as the reduction of the π-conjugated system
2
+ [4c, 7b, 7c, 9]
induced by the coordination of thiazole ligand moiety of polymer sensor with the Hg .
In addition, the strongest absorbance peak at 439 nm shows an obvious decrease upon the
3

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+
increasing concentration of Ag , meanwhile, a new absorption peak centered at 508 nm turns on a
gradual increase with two clear isosbestic point at 359 nm and 459nm, indicating an unusual
+
[9]
interaction between thiazole ligand moiety of the polymer sensor with Ag .
But no changes
+
could be observed for the absorption spectrum of the polymer sensor beyond 10 equiv of Ag .
Furthermore, as is evident from Figure 2, almost no the absorption response behaviors of the
2
+
+
polymer sensor were observed for other metal ions. Only Hg and Ag can lead to a prominent
absorption change in absorption spectra of the polymer sensor, which may be attributed to the
[4h]
poor coordination ability of the polymer sensor with other metal ions. More interestingly, the
color changes of polymer solution could be clearly observed from green to colorless and pale
2
+
+
yellow by the naked eyes upon addition of Hg and Ag , respectively (inset, Figure 2),
demonstrating that the polymer sensor could be effectively used as a colorimetric chemosensor for
2+
+
Hg and Ag detection with high selectivity and sensitivity.
-
5
Figure 1. (a) UV–vis spectral changes of the polymer (1×10 mol/L in THF) upon the addition of increasing
2+
-5
amounts of Hg . (b) UV–vis spectral changes of the polymer (1×10 mol/L in THF) upon the addition of
+
-5
increasing amounts of Ag . (c) Absorbance at 439 nm of the polymer sensor solution (1×10 mol/L in THF) as a
2+
-5
function of Hg concentration. (d) Absorbance at 508 nm of the polymer sensor solution (1×10 mol/L in THF) as
+
a function of Ag concentration.
4

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-
5
Figure 2. UV–vis spectral changes of the polymer (1×10 mol/L in THF) upon 5 equiv. of various metal
ions. Inset: the solution color of the polymer before and after the addition of various metal ions.
The fluorescence responses of the polymer sensor toward various ions were carried out in THF
-5
(
1×10 mol/L corresponding to benzo[d]thiazole moiety) by using the excitation wavelength at
3
81 nm. The polymer sensor emits strong fluorescence at 474 nm as shown in Figure 3. But
2
+
obvious fluorescence quenching could be observed upon the addition of Hg , which could be
attributed to the reduction of the π-conjugated system induced by the coordination of thiazole
2
+
2+
moiety of polymer sensor with Hg . Hg leads to about 90% fluorescence quenching for the
polymer at a concentration of 3:1 molar ratio. It can be also found that the fluorescent intensity of
2
+
the polymer shows a gradual decrease with the concentration mole ratio of Hg from 0 to 3.0
(
Figure 4a), and bright green fluorescence of solution almost disappears (Figure 4a inset). A curve
2+
-5
7
11
equation in the range of Hg concentrations from 0 to 3.0 × 10 mol/L is F = 1.15×10 -3.52×10
2
+
[Hg ], R= -0.99563, N= 11(Figure S1). According to the equation and the standard deviation of
2
+
the blank, the fluorescence detection limit of the polymer solution for Hg was determined to be
-7
as low as 5.1 × 10 mol/L. Herein, we further performed the fluorescence response behaviors of
+
2+
the polymer on Ag under the same condition as Hg ion determination. Meanwhile, fluorescence
+
quenching effect could be observed upon the addition of Ag , which could be attributed to
+
+
coordination interaction between thiazole moiety and Ag . Ag leads to about 71.4% fluorescence
quenching for the polymer sensor at a concentration of 1:1 molar ratio, and bright green solution
turns on pale green (Figure 4b inset). It can be also found that the fluorescent intensity of the
+
polymer shows a gradual decrease with the concentration mole ratio of Ag from 0 to 1.0. A curve
+
-5
-5
equation in the range of Ag concentrations from 0.2×10 to 1.0×10 mol/L is F =
7
12
+
1
.32×10 -1.07×10 [Ag ], R= -0.9791, N= 9 (Figure S2). According to the equation and the
+
standard deviation of the blank, the fluorescence detection limit of the polymer sensor for Ag
-7
could reach as low as 1.68×10 mol/L.
5

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-
5
Figure 3. Fluorescence spectra changes of the polymer (1×10 mol/L in THF) upon the addition of 5
equiv. various metal ions. Inset: visible fluorescence of the polymer before and after the addition of
various metal ions under a 365 nm UV lamp.
In a set of comparable experiments, we investigated the fluorescence response behaviors of the
2
+
+
polymer sensor on other metal ions under the same conditions as Hg and Ag ion determination.
As is evident from Figure 3, almost no obvious fluorescence changes could be observed upon the
+
+
2+
2+
2+
2+
2+
2+
2+
2+
2+
3+
3+
addition of Li , K , Ca , Mg , Ba , Zn , Cd , Co , Ni , Pb , Cu , Al and Fe , indicating
2
+
+
that the resulting polymer sensor possesses remarkable recognition ability for Hg and Ag . In
this paper, we further investigated the utility of the polymer as an ion-selective fluorescence
2
+
+
-5
2+
sensor for Hg and Ag . Herein, we subjected the polymer (1×10 mol/L) to a mixture of Hg
-4
-4
(
2×10 mol/L) and each of the metal ions (2×10 mol/L). The deviations from other metal ions’
interference are less than 5% in the coexisted metal ions experiment (Figure S3). Meanwhile, we
-
5
+
-5
subjected the polymer (1×10 mol/L) to a mixture of Ag (5×10 mol/L) and each of the metal
-5
ions (5×10 mol/L) as shown in Figure S4. The deviations from other metal ions’ interference are
2
+
less than 5% in the coexisted metal experiment, especially for Hg . The unique selectivity and
2
+
+
high sensitivity recognition of the polymer sensor only for Hg and Ag can be attributed to
2
+
several factors, such as the structural rigidity of the thiazole unit, the matched radius of the Hg
+
2+
+ [9, 4c,
and Ag ion, its soft acid property, and the binding ability of thiazole unit with Hg and Ag .
4
h]
6

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-5
Figure 4. (a) Fluorescence spectra changes of the polymer (1×10 mol/L in THF) upon the addition of increasing
2+
2+
amounts of Hg . Inset: visible fluorescence of the polymer before (left) and after (right) the addition of Hg
-
5
under a 365 nm UV lamp. (b) Fluorescence spectra changes of the polymer (1×10 mol/L in THF) upon the
+
addition of increasing amounts of Ag . Inset: visible fluorescence of the polymer before (right) and after (left) the
+
2+
addition of Ag under a 365 nm UV lamp. (c) Plot of PL quenching efficiencies (I/I0) versus Hg concentration,
2+
where I is the fluorescent intensity of the polymer sensor with the addition of Hg , and I is the fluorescent
0
+
intensity of the polymer sensor. (d) Plot of PL quenching efficiencies (I/I ) versus Ag concentration.
0
2
+
The stoichiometry for Hg with polymer could be determined on the basis of the
2
+ n
Benesi-Hildebrand expression: 1/(F - F ) = 1/{K(Fmin – F )[Hg ] } + 1/(F – F ), where F and F
0
0
min
0
[10]
0
2
+
are the fluorescent intensities in the absence and presence of Hg , respectively. Herein, Fmin is
2
+
the minimum fluorescent intensity in the presence of Hg , and K is the associated constant.
2
+ n
Plotting the 1/(F - F ) quantity against [Hg ] (n = 1) by using the fluorescent intensity for
0
polymer (λem = 474 nm) gave an excellent linear curve, indicating that there is a 1:1 binding mode
2+
between polymer and Hg . In addition, the associated constants calculated from the slope and
4
-1
+
intercept of the line is 2.81 × 10 M (Figure S5). As for Ag , plotting the 1/(F - F ) quantity
0
+
n
against [Ag ] (n = 2) by using the fluorescent intensity for polymer (λ = 474 nm) gave an
em
+
excellent linear curve, indicating that there is a 1:2 binding mode between polymer and Ag . In
1
0
addition, the associated constants calculated from the slope and intercept of the line is 3.71×10
-2
+
2+
M (Figure S6). A possible mechanism for polymer Ag and Hg detection can be attributed to
2
+
+
coordination interaction between S or N atoms of thiazole ligand moiety and Hg / Ag . In order
1
to further investigate the mechanism of recognition process, H NMR titration of the polymer
2
+
+
sensor on Hg and Ag was carried out, as shown in the ESI, Figure S14 and Figure S15. It could
1
be clearly observed that the H NMR signal of the methyl group of thiazole moiety was shifted to
2
+
+
downfield region upon addition of Hg /Ag , indicating the electron density change of H in methyl
7

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2+
+
group due to the coordination interaction between Hg or Ag and S or N atoms of thiazole
ligand.
3
. Conclusions
The benzo[d]thiazole-based polymer sensor could exhibit the most pronounced fluorescence
2
+
+
response behaviors towards only Hg and Ag due to thiazole ligand moiety in the polymer main
2
+
+
chain as the metal binding site. More importantly, Hg and Ag can lead to the color changes
from green to colorless and yellow, respectively, which could be clearly observed by naked eyes.
The results also demonstrate that this thiazole-based conjugated polymer can be used as a highly
2
+
+
selective and sensitive fluorescence sensor for direct and visual detection of Hg and Ag .
4
4
. Experimental section
.1. General methods and materials
All of the solvents and reagents were commercially available and of analytical reagent grade. THF,
DMF, and Et N were purified by distillation. NMR spectra were collected on a Bruker
3
4
00/500/600 spectrometer and are reported in parts per million (ppm) relative to TMS as an
internal standard. Fluorescence spectra were recorded on a Fluoromax-4 Spectrofluorometer.
Ultraviolet-visible (UV-vis) spectra were obtained using a Perkin-Elmer Lambda 35
spectrophotometer. Elemental analysis was performed on an Elementar Vario MICRO analyzer.
Thermogravimetric analysis (TGA) was performed on a Perkin–Elmer Pyris-1 instrument under a
N atmosphere. Molecular weights were determined by gel-permeation chromatography (GPC)
2
with a Waters 244 HPLC pump; THF was used as the solvent relative to polystyrene standards.
-2
The solvent of cation solution was water. The concentration of cation solution was 10 mol/L, and
the volume of the polymer solution was 3 mL.
4
.2 Synthesis of Polymer sensor
A mixture of M-1 (120.4 mg, 0.39 mmol), M-2 (150 mg, 0.39 mmol), Pd(PPh ) (45.3 mg, 0.04
3
4
mmol) and CuI (7.5 mg, 0.04 mmol) was dissolved in 16 mL DMF and 8 mL Et N. The solution
3
was stirred at 70 ºC for 2 d under N atmosphere and cooled to room temperature, and then filtered
2
through a short silica gel column. After the solvent was removed, the mixture was dissolved in 2
mL CH Cl , and then added into 50 mL CH OH to precipitate conjugated polymer. The polymer
2
2
3
was filtered and washed with methanol several times. The thiazole-based polymer was dried in
1
vacuum to give brown solids in 70% yield. H NMR (400 MHz, CDCl ): 7.84 (s, 1H), 7.52 (m,
3
1
1
1
2
H), 7.19 (m, 1H), 7.04 (m, 1H), 4.08 (m, 4H), 2.93 (m, 3H), 1.93 (s, 4H), 1.37 (m, 8H), 1.27 (m,
1
3
2H), 0.88 (s, 6H); C NMR (150 MHz, CDCl ): 153.87, 153.75, 153.03, 138.93, 130.87, 130.03,
3
29.78, 129.31, 127.41, 117.53, 117.29, 116.48, 92.55, 59.78, 69.49, 69.58, 31.90, 29.74, 29.58,
9.49, 29.35, 29.18, 26.25, 26.07, 22.72, 20.53, 17.81, 14.15; GPC: M =15850, M =10950,
w
n
PDI=1.45; Anal. Calcd for C H NO S: C, 77.38; H, 7.83; N, 2.65, found C, 77.24; H, 7.65; N,
3
4
41
2
2
.68.
Acknowledgements
8

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We gratefully acknowledge the National Natural Science Foundation of China (21174061,
5
1173078, 21172106, and 21474048), and open project of Beijing National Laboratory for
Molecular Sciences.
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Supporting Information
Polymer-Based Fluorescence Sensor incorporating Thiazole Moiety
2+
+
for Direct and Visual Detection of Hg and Ag
Fei Li, Fandian Meng, Yuxiang Wang, Chengjian Zhu and Yixiang Cheng*
Key Lab of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical
Engineering, Nanjing University, Nanjing 210093, China
E-mail: yxcheng@nju.edu.cn
Contents:
1
. Synthesis procedures of monomers and polymer, and experimental
section.
. Fluorescence responsive behaviors of polymer sensor on various
2
metal ions.
1
3
. H NMR spectra of compounds and TGA curve of polymer sensor.
1
. Synthesis procedures of monomers and polymer, and experimental
section.
1

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Scheme. S1. Synthesis procedures monomers and polymer. (TMSA: Trimethyl silyl
acetylene;HMDO: Hexamethyldisiloxane)
Synthesis of N-(2,5-dibromophenyl)acetamide (2)
A mixture of compound 1 (11.24 g, 40 mmol) and iron powder (22.00 g, 400 mmol)
in AcOH (20 mL) was stirred at 70 ºC for overnight. The mixture was washed with
water and extracted with ethyl acetate after cooling to room temperature. The
collected organic layers were dried over anhydrous Na SO . The solvent was removed
2
4
under reduced pressure to afford 2,5-dibromoaniline. Acetyl chloride (3.32 g, 42.4
mmol) was slowly added to a solution of the foregoing 2,5-dibromoaniline in pyridine
(80 mL), and the resulting mixture was heated under reflux for 1 h. The reaction
mixture was poured into ice water (200 mL) after cooling to room temperature. The
precipitate was collected by filtration and recrystallized from MeOH (20 mL) to give
1
the pure product 2 as a white solid (11.20 g, 96% yield). H NMR (500 MHz, CDCl ):
3
8
.57 (br s, 1H), 7.57 (br s, 1H), 7.37 (d, J=8.5 Hz, 1H), 7.10 (d, J=8.5 Hz, 1H), 2.24 (s,
3
H).
2

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Synthesis of 4,7-dibromo-2-methylbenzo[d]thiazole (M-1)
A solution of compound 2 (2.93 g, 10 mmol) and hexamethyldisiloxane (HMDO)
(2.92 g, 18 mmol) in toluene (50 mL) was added to phosphorus pentasulfide (0.72 g,
3
.25 mmol) at 60 ºC, and the mixture was heated under reflux for 5 h. The crude
product was purified by flash chromatography on silica gel by using ethyl acetate as
eluent to obtain a mixture. And then the solution of the above mixture and sodium
hydroxide (3.2 g, 80 mmol) in water-EtOH (40 mL-2 mL) was added dropwise to the
potassium ferricyanide (13.17 g, 40 mmol) in water (20 mL). The mixed solution was
stirred at 95 ºC for 2 min and cooled in an ice bath to produce the precipitate.
Subsequently, the precipitate was filtered, washed with water, and concentrated in
vacuo. The crude product was purified by column chromatography (petroleum
ether/ethyl acetate =20/1, v/v) to obtain the product M-1 as pale yellow powders (2.13
1
g, 70% yield). H NMR (400 MHz, CDCl ): 7.55 (d, J = 9.5 Hz, 1H), 7.36 (d, J = 9.5
3
Hz, 1H), 2.88 (s, 3H).
2
. Fluorescence responsive behaviors of polymer sensor on various
metal ions.
3

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Figure S1. Calibration curve was obtained from the plot of fluorescence intensity
2
+
with the added Hg from 1:0-1:20.0 molar ratios.
Figure S2. Calibration curve was obtained from the plot of fluorescence intensity
+
with the added Ag from 1:0-1:7.0 molar ratios.
4

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-5
-1
Figure S3. Metal specificity: the concentration of the polymer is 1.0 × 10 mol·L ,
2
+
-4
-1
Hg and other metal ion are used at a concentration of 2.0 × 10 mol·L , respectively.
+
+
2+
2+
2+
2+
2+
2+
2+
2+
2+
3+
Mix: the mixture of Li , K , Ca , Mg , Ba , Zn , Cd , Co , Ni , Pb , Cu , Al
3
+
-4
-1
and Fe (each 2.0 × 10 mol·L ).
-5
-1
Figure S4. Metal specificity: the concentration of the polymer is 1.0 × 10 mol·L ,
+
-5
-1
Ag and other metal ion are used at a concentration of 5.0 × 10 mol·L , respectively.
+
+
2+
2+
2+
2+
2+
2+
2+
2+
2+
3+
Mix: the mixture of Li , K , Ca , Mg , Ba , Zn , Cd , Co , Ni , Pb , Cu , Al
3
+
-5
-1
and Fe (each 5.0 × 10 mol·L ).
5

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2
+
Figure S5. Benesi-Hildebrand plot for Hg -bound polymer.
+
Figure S6. Benesi-Hildebrand plot for Ag -bound polymer.
Figure S7. The solution color of the polymer before and after the addition of various
metal ions
6

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1
3
. H NMR spectra of compounds and TGA curve of polymer sensor.
1
Figure S8. H NMR of 1 (CDCl , 500 MHz)
3
1
Figure S9. H NMR of 2 (CDCl , 500 MHz)
3
7

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1
Figure S10. H NMR of M-1 (CDCl , 400 MHz)
3
1
Figure S11. H NMR of M-2 (CDCl , 300 MHz)
3
8

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1
Figure S12. H NMR of polymer sensor (CDCl , 400 MHz)
3
1
3
Figure S13. C NMR of polymer sensor (CDCl , 150 MHz)
3
9

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1
2+
Figure S14. H NMR titration of the polymer sensor (CDCl ) with Hg (0, 0.5, 1, 2
3
6
e.q.,d -DMSO)
1
+
Figure S15. H NMR titration of the polymer sensor (CDCl ) with Ag (0, 0.5, 1, 2
3
6
e.q.,d -DMSO)
1
0

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Figure S16. TGA curve of polymer sensor
1
1