A series of selective and sensitive fluorescent sensors based on a thiophen-2-yl-benzothiazole unit for Hg2+

Article abstract of DOI:10.1039/c5nj02259b

Different types of fluorescent probes for Hg²⁺ based on the 5-thiophen-2-yl-benzothiazole derivatives (TBT, 2-thiophen-2-yl-benzothiazole; CTBT, 9-(5-benzothiazol-2-yl-thiophen-2-yl)-9H-carbazole; DTBT, 2-(5-acenaphthen-5-yl-thiophen-2-yl)-benzothiazole; and NTBT, 6-(5-benzothiazol-2-yl-thiophen-2-yl)-2-hexyl-benzo[de]isoquinoline-1,3-dione) were realized by changing the subsituents. Multisignaling changes were observed through UV-vis absorption and fluorescence spectra upon addition of Hg²⁺. The addition of Hg²⁺ on TBT induced a remarkable OFF/ON-type fluorescence signaling behavior. With the introduction of electron-donating carbazole, the detection behavior of CTBT was just the reverse of what TBT displayed, while a ratiometric fluorescent probe based on DTBT for Hg²⁺ was prepared by introducing the weak electron-drawing group acenaphthene. Moreover, the dichloromethane solution of CTBT and DTBT showed a distinct color change from colorless to yellow with the addition of Hg²⁺, which indicated that these two probes would facilitate the naked-eye detection of Hg²⁺. However, both UV-vis absorption and fluorescence spectra of NTBT with strong electron-withdrawing substituents showed no obvious change upon addition of Hg²⁺. It would be concluded that the electronic properties of the molecule was one of the vital factors in designing chemosensor molecules.

Full text of DOI:10.1039/c5nj02259b

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ARTICLE
A series of selective and sensitive fluorescent sensor based on
2+
thiophen-2-yl-benzothiazole unit for Hg
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a
a
b
Qunbo Mei,* RuqiangTian, Yujie Shi, Qingfang Hua, Chen Chen, Bihai Tong, *
DOI: 10.1039/x0xx00000x
2+
Different types of fluorescent probes for Hg based on the 5-thiophen-2-yl-benzothiazole
www.rsc.org/
derivatives (TBT, 2-thiophen-2-yl-benzothiazole; CTBT, 9-(5-benzothiazol-2-yl-thiophen-2-yl)-9H-
carbazole; DTBT, 2-(5acenaphten-5-yl-thiophen-2-yl) -benzothiazole; NTBT, 6-(5-benzothiazol-2-
yl-thiophen-2-yl) -2-hexyl-benzo[de]isoquinoline-1, 3-dione) were realized by changing the
subsituents. Multisignaling changes were observed through UV-vis absorption and fluorescent
2
+
2+
spectra upon addition of Hg .The addition of Hg on TBT induced a remarkable OFF/ON- type
fluorescent signaling behavior. With the introduction of electron-donating carbazole, the
detection behavior of CTBT was just the reverse of what TBT displayed. While a ratiometric
2
+
fluorescent probe based on DTBT for Hg was prepared by introducing the weak electron-
drawing group acenaphtene. Moreover, the dichloromethane solution of CTBT and DTBT showed
2
+
distinct color change from colorless to yellow with the addition of Hg , which indicated that
2
+
these two probes would facilitate naked-eye detection of Hg . However, both UV-vis absorption
and fluorescence spectra of NTBT with strong electron-withdrawing substituent showed no
2
+
obvious change upon addition of Hg . It would be concluded that the electronic property of the
molecule was one of vital factors in designing chemosensor molecules.
have been developed based on small molecular. However, most
Introduction
2
+
of the reported Hg
probes have some shortcomings,
In the past few years, the field of probing the presence and particularly in terms of sensitivity, selectivity, interference from
concentration of heavy and transitionꢀmetal ions has attracted a other metal ions, the turnꢀoff response, and low solubility in
4
significant amount of attention due to emerging environmental aqueous solution. As a result, considerable efforts have been
1
2+
and human health problems. Particularly, mercury is one of the committed to design new and practical chemosensors for Hg
most harmful metal ions which can cause considerable damage detection.
to human beings even at low concentrations owing to
Some specific chemosensors based on organic molecular
bioaccumulation, long residence, and permanent deterioration systems/materials have been developed for the detection of
2
2+
5
6
in the central nervous and endocrine system. Because of the Hg in recent years, including azoꢀderivatives, rhodamine,
7
8
high toxicity and serious effects on human health and benzothiazole,
fluorescein,
etc.
As
fluorophores,
environment resulting from mercury contamination, the benzothiazole moiety is one of the most useful scaffolds for the
2
+
detection of Hg has been attracting a significant amount of construction of fluorogenic chemosensors for varieties of
9
attention. Applying fluorescent sensors to detect heavy metal important chemical species. However, as far as we know, only
ions are favored over other common analytical methods a few ratiometric fluorescent sensors with benzothiazole moiety
because of their advantages such as high sensitivity, good for metal ions have been found in the literature until now.
3
selectivity, quick response, and local observation. So far, a Therefore, the development of a new series of ratiometric
2
+
number of fluorescent and colorimetric Hg chemosensors fluorescent sensors that can selectively and sensitively detect
2
+
10
Hg is a highly challenging task.
thinking, some thiophenꢀ2ꢀylꢀbenzothiazole derivatives (TBT
CTBT
substituents. Upon addition of Hg
benzothiazole derivatives (TBT CTBT
dichloromethane solution, different types of fluorescent probes
Based on the above
,
,
DTBT, and NTBT) were designed by changing the
2
+
to thiophenꢀ2ꢀylꢀ
,
, DTBT, and NTBT) in
2
+
for Hg were received. The new series of probes showed a
selective, sensitive, and reversible color and fluorescence
change response to the Hg . Herein, a new method about how
2
+
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to design fluorescent probe was achieved by changing the
electronic property of the molecule by introducing different
substituents.
TBT
0
.7
(
a)
CTBT
DTBT
NTBT
0
.6
.5
.4
.3
.2
.1
0.0
0
Results and discussion
0
The synthetic route for some thiophenꢀ2ꢀylꢀbenzothiazole
derivatives(TBT, CTBT, DTBT, and NTBT) is shown in Scheme 1.
These compounds based on thiophenꢀ2ꢀylꢀbenzothiazole unit were
synthesized by introducing different substituents from electronꢀ
donating group to electronꢀwithdrawing group. The structure of
thiophenꢀ2ꢀylꢀbenzothiazole derivatives (TBT, CTBT, DTBT, and
NTBT) and all immediate were identified by NMR spectroscopy and
mass spectrometry (MS).
0
0
0
2
50
300
350
400
450
500
Wavelength nm
TBT
1
0
0
0
0
0
.0 (b)
CTBT
DTBT
NTBT
.8
.6
.4
.2
.0
400
500
600
Wavelength nm
-5
Figure 1. Spectra of compounds TBT, CTBT, DTBT, and NTBT (c=2×10 M) in
dichloromethane solution. (a) UV-vis spectra. (b) Fluoresescence spectra:
TBT (λex=340 nm) CTBT (λex=385 nm) DTBT (λex=380 nm) and NTBT (λex=390
nm)
Scheme 1. Synthetic route for TBT, CTBT, DTBT, and NTBT
For a better understanding of the optical properties of TBT,
CTBT, DTBT, and NTBT, theoretical calculations were performed
using the Gaussian 03 package at the B3LYP level. The calculation
results revealed that both the highest occupied molecular orbital
The absorption spectra of compounds TBT, CTBT, DTBT, and
NTBT measured in dichloromethane solution were shown in Figure
11
1(a). All of the compounds displayed intense absorption bands
below 350 nm, which were assigned to the high energy band π→π*
transition. The bands at about 350ꢀ450 nm were assigned to the low
energy band n→π* transitions. Comparatively, the more redꢀshift in
the absorption spectra of CTBT, DTBT, and NTBT than of TBT
can be accounted for by considering the increased conjugation.
The fluorescent intensity measurement for these compounds
TBT, CTBT, DTBT, and NTBT was carried out in
dichloromethane solutions (Figure1(b)). TBT upon excitation at 340
nm showed a fluorescent band around 435 nm. Similarly, CTBT and
DTBT upon excitation at 385 and 380 nm have emitted fluorescent
band at 453 and 468 nm with Stoke’s shift of 68 and 88 nm,
respectively. However, NTBT showed a fluorescent emission peak
at 507 nm, which redꢀshifted approximately 70 nm compared with
TBT.
(
HOMO) and lowest unoccupied molecular orbital (LUMO) of TBT
and DTBT were mainly distributed over the whole conjugated
backbone. As shown in Table S1, the HOMO of CTBT primarily
resided on the carbazole part and the LUMO primarily resided on the
benzothiazole and thiophene part. However, the HOMO distribution
of NTBT resides primarily on the benzothiazole and thiophene part,
and LUMO were located primarily on the naphthalimide part. In
TBT, CTBT, DTBT, and NTBT, the sulfur atom contributed to the
LUMO orbital. Hence, the interaction of the sulfur atom and
2
+
nitrogen atom with Hg can change the orbital energy level,
realizing the optical detection. The absorption spectra was in
agreement with the result obtained from the theoretical calculations
1
2
(
Figure S1).
For an excellent chemosensor, high selectivity is a matter of
necessity. Herein, the selective coordination studies of TBT, CTBT,
DTBT, and NTBT by absorption spectroscopy were then extended
+
2+
2+
3+
2+
3+
2+
+
to different metal ions (Ag , Cd , Co , Cr , Cu , Fe , Hg , K ,
2
+
+
2+
2+
2+
Mg , Na , Ni , Pb , Zn ) in dichloromethane solution. As shown
2
+
in Figure 2(a), only the addition of Hg resulted in prominent
2
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absorption change, whereas very weak variations of absorption
spectra of TBT was observed upon addition of an excess of the other
metal ions. Therefore, TBT displayed high selectivity in sensing
n+
DTBT+M
(c)
2
.5
.0
2
+
Hg . The absorption response of CTBT to various cations and its
2
2
+
selectivity for Hg are illustrated in Figure 2(b). Uponsome metal
+
+
2+
ions of alkaline and alkalineꢀearth metals (K , Na , Mg ) transitionꢀ
1.5
1.0
0.5
+
2+
2+
2+
2+
metal ions (Ag , Cd , Co , Ni , Pb ), a much weaker response
2+
was given compared to Hg at the same concentration. When with
3
+
2+
3+
2+
Cr , Cu , Fe , Zn , a slightly response of CTBT was observed.
2
+
Thus CTBT was more sensitively to detect Hg than other metal
ions mentioned above. The DTBT behavior in the presence of 2
equiv of different metal ions indicated that only Hg promoted a
notable response in its absorption spectra (Figure 2 (c)). By addition
2
+
0.0BlankAg+ Cd2+Co2+Cr3+Cu2+Fe3+ K+ Mg2+ Na+ Ni2+Pb2+Zn2+Hg2+
3+
2+
3+
of transition metal ions (Cr , Cu , Fe ), although a weak new peak
at 448 nm of DTBT was observed, the typical absorption of DTBT
showed slight change in UVꢀvis spectra (Figure S4). However, the
absorption of NTBT were almost alike upon addition of different
metal ions, there was only a little enhanced at 402 nm by adding
n+
NTBT+M
(d)
1
.0
.8
.6
.4
.2
0
0
0
0
0
2
+
Hg . In conclusion, TBT, CTBT and DTBT can serve as highly
2
+
selective chemosensor for Hg .
a)
n+
TBT+M
(
.0
2
1.5
.0BlankAg+ Cd2+Co2+Cr3+Cu2+Fe3+
K+ Mg2+ Na+ Ni2+Pb2+Zn2+Hg2+
-
5
1.0
Figure 2. Absorption response of TBT, CTBT, DTBT and NTBT (c=2×10 M) in
the presence of various metal cations in dichloromethane solution. Bars
represent the ratio of absorbance intensity. (a) TBT: 4 equiv, A360 nm/A325 nm
b) CTBT: 2 equiv, A464 nm/A364 nm. (c) DTBT: 2 equiv, A448 nm/A368 nm. (d) NTBT:
2 equiv, A402 nm/A392 nm
.
0
.5
(
1
.
0
.0BlankAg+ Cd2+Co2+Cr3+Cu2+Fe3+ K+ Mg2+ Na+ Ni2+ Pb2+Zn2+Hg2+
The absorption spectrum of TBT in dichloromethane was
shown in Figure 3(a). The TBT displayed intense absorption band in
the ultraviolet region of 325 nm. The addition of increasing amounts
of Hg to the solution of TBT promoted a gradual decrease of
n+
CTBT+M
(b)
2+
3
.5
.0
.5
.0
.5
.0
.5
absorption band centered at 325nm with the concomitant increase in
a new lowꢀenergy band centered at 360nm. The isosbestic points at
3
2
3
38nm clearly indicated the presence of a unique complex in
2
equilibrium with the free ligand. The new absorption band red
shifted about 35 nm, which induced only a little change of solution
color (inset of Figure 3(a)). The Job’s plot for TBT and metal
1
1
2+
revealed complex stoichiometry between TBT and Hg in
0
dichloromethane. From the Job’s plot, a maximum absence intensity
2
+
was showed when the molecular fraction of Hg was close to 0.66,
0
.0BlankAg+ Cd2+Co2+Cr3+Cu2+Fe3+ K+ Mg2+ Na+ Ni2+Pb2+Zn2+Hg2+
2+
which indicated the 1:2 complex formation between TBT and Hg
ꢀ5
with a total concentration of 2.0×10 M.
The fluorescent behavior of TBT in the presence of the 2 equiv
2
+
2+
Hg was examined (Figure 3(b)). Upon gradual addition of Hg to
TBT in dichloromethane solution, a gradual enhancement in the
fluorescent intensity was observed at 435 nm and the fluorescent
band red shifted to 469 nm gradually. It could be assigned to
2
+
complexation reaction between TBT and Hg . Hence, TBT can be
2
+
used as “turnꢀon” luminescent molecular probe to Hg (inset of
13
Figure 3(b)). According to the literature, the detection limit was
also estimated from the titration results and was 3.16 ꢁM (Figure
S6).
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1
1
1
.4
.2
.0
.8
2+
Hg . The strong decrease of the fluorescence can be explained
0
2+
0
.6 0.4 (a)
in terms of the complexation reaction between CTBT and Hg .
0
.4
.2
.0
1
3
0
According to the literature, the detection limit was also
estimated from the titration results and was 5.89 ꢁM (Figure
S7).
0
0
.0 0.2 0.4 0.6 0.8 1.0
2
+
2+
[
Hg ]/[TBT+Hg ]
0.3
(
a1)
0.7
.6
.5
.4
.3
.2
0.1
.0
1
.4
.2
1.0
.8
0
.2
1
(
a)
0
0
0.1
CTBT
CTBT
+
0.6
0.4
0
Hg2+
(
a2)
0.2
0
0.0
0.0
0.0 0.2 0.4 0.6 0.8 1.0
2
50
300
350
400
450
500
(
a1)
[
Hg ]/[CTBT+Hg ]
2+
2+
Wavelength nm
0
(a2)
0
9
00
00
00
00
00
00
00
00
00
(b)
8
7
0
2
50
300
350
400
450
500
6
Wavelength nm
5
4
8
00
00
00
00
3
7
(
b)
2
6
1
5
0
4
00
500
Wavelength nm
600
400
300
200
-5
Figure 3. Changes in the spectra of TBT (c=2×10 M) in dichloromethane
2
+
solution with various amounts of Hg (0-2 equiv). (a) UV-vis absorption
2
+
spectra, Inset: (a1) Job’s plot of TBT and Hg ; (a2) Solution color change
100
2
+
upon addition of Hg . (b)Luminescent spectra, (λex=340 nm). Inset:
2
+
0
fluorescent color change upon addition of Hg .
400
450
500
550
The absorption spectral response of CTBT in dichloromethane
solution was shown in Figure 4(a). Upon addition of Hg , the
Wavelength nm
2
+
absorbance of CTBT at 288 nm and 364 nm progressively decreased
while a new band at 464 nm appeared and its absorbance increased Figure 4. Changes in the spectra of CTBT (c=2×10 M) in dichloromethane
gradually, which corresponding to a maximum absorptionred shifted solution with various amounts of Hg (0-2 equiv). (a) UV-vis absorption
-
5
2
+
2
+
1
00 nm and induced an evident change of solution color from spectra, Inset: (a1) Job’s plot of CTBT and Hg ; (a2) Solution color change
2+
colorless to yellow. This result indicated that CTBT can serve as a upon addition of Hg . (b) Luminescent spectra, (λex=370 nm). Inset:
2+
2+
sensitive nakedꢀeye indicator for Hg (inset of Figure 4(a)). fluorescent color change upon addition of Hg .
2
+
Moreover, the isosbestic points at 252 nm and 411 nm clearly
The Hg titration experiment revealed several intriguing
indicated the presence of a unique complex in equilibrium with the features of DTBT. The DTBT exhibited a maximum absorption at
free ligand. A Job’s plot indicated that CTBT formed a 1:1 complex 368 nm, which gradually shifted to long wavelength with the
2
+
2+
2+
with Hg in dichloromethane solution.
The fluorescent behavior of CTBT in the presence of the caught by the S atom of DTBT. The solution color changed from
sequential addition of Hg (Figure 5(a)), illustrating that Hg was
2
+
2+
Hg was also investigated by photoluminescent technique. The colorless to yellow in the presence of 2 equiv of Hg (inset of Figure
luminescence spectra of CTBT in the absence and presence of 5(a)), which could be observed by naked eye. A clear isosbestic
2
+
Hg was shown in Figure 4(b), CTBT in dichloromethane point at 405 nm indicated the coexistence of the free DTBT and the
2
+
solution showed an intense fluorescent band at 453nm and its Hg ꢀDTBT complex. From the Job’s plot analysis, a 1:1 binding
fluorescent color was blue. A strong decrease of the fluorescent complex was further confirmed (inset of Figure 5(a)).
2
+
intensity was observed upon addition of Hg . After addition of
1
It was well known that fluorescent spectroscopy was more
2
+
equiv of Hg , the fluorescence at 453 nm of CTBT was sensitive toward small changes that affect the electronic properties of
quenched obviously and only very weak luminescence was the molecular probe. Hence, the binding ability of DTBT with Hg
2
+
observed. Hence, CTBT shows obviously colorimetric sensing ion was also investigated by fluorescent spectroscopy (Figure 5(b)).
2
+
2+
of Hg and can be used as a “turn off” luminescent probe to Upon addition of Hg , the intensity of the fluorescent band at 468
nm decreased and a new band at 567 nm appeared, which red shifted
4
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about 100 nm. After addition of approximately 1 equiv of Hg , the to excitation wavelength at 390 nm and was monitored after each
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2
+
2
+
fluorescence of DTBT at 468 nm was completely quenched. A clear stepwise addition of Hg to the dichloromethane solution of NTBT.
isosbestic point at 525 nm indicated DTBT could be used as a As shown in Figure 6(b), a gradual enhancement in the fluorescence
fluorescent ratiometric chemosensor. As a result, an obvious change intensity was observed at 507 nm, upon increasing the concentration
2
+
in fluorescent color from blue to yellow was observed (inset of 6 equiv of Hg that could not be assigned to complexation reaction
2
+
Figure 5(b)). By the changes in the fluorimetric response of DTBT between NTBT and Hg . While there was no obvious change of the
in the presence of varying concentrations of Hg , the stoichiometry solution color in the absence and presence of Hg (inset of Figure
2
+
2+
of the complex system was also determined to be 1:1. It indicated the 6(b)). Hence, NTBT can not be used as a molecular fluorescence
2
+
2+
formation of 1:1complex between DTBT and Hg , which was in probe to Hg from the selective optical response experiments and
agreement with the result obtained from the UVꢀvis absorption the spectra titration experiments.
spectra. The DTBT showed better optical behavior, ratiometric
0.65
fluorescent sensor, and also nakedꢀeye sensitive in the detection of
0
.60 (a)
2
+
Hg . The corresponding detection limit was determined to be 3.98
0.55
.50
.45
.40
.35
.30
.25
0.20
.15
.10
.05
2
+
0
ꢁM. Importantly, there was a liner absorption response to Hg
NTBT NTBT
0
concentration ranging from 6 to 26 µM (Figure S8), indicating that
+
Hg2+
0
probe DTBT may be potentially useful for the quantitative
0
2
+ 14
determination of Hg .
0
0
1.0
0.8
0.6
0.4
0.2
0.0
1
.0
.8
.6
0.4
.2
0.0
0
(
a)
0
0
0
0
DTBT DTBT
+
Hg2+
0.00
0
300
400
500
Wavelength nm
0
.0 0.2 20+.4 0.6 2+ 0.8 1.0
[Hg ]/[DTBT+Hg ]
(a1)
(a2)
700
6
50
00
50
00
50
00
50
300
50
00
50
00
6
(b)
5
5
4
4
2
50
300
350
400
450
500
3
Wavelength nm
2
2
1000
1
(
b)
1
800
50
0
500
600
Wavelength nm
600
-5
Figure 6. Changes in the spectra of NTBT(c=2×10 M) in dichloromethane
2
+
400
solution with various amounts of Hg (0-6 equiv).(a) UV-vis absorption
2+
spectra, Inset: solution color change upon addition of Hg . (b) Luminescent
2
+
200
spectra, (λex=390nm). Inset: fluorescent color change upon addition of Hg .
2
+
The chemosensor TBT sensed Hg
through remarkable
enhancement of fluorescence, which acted as a fluorescent OFF/ON
probe. The detecting limiting for Hg was calculated to be 3.16 µM,
0
400
500
600
700
2
+
Wavelength nm
indicating that TBT was potentially useful for the quantitative
2
+
2+
determination of Hg concentration. When upon addition of Hg on
Figure 5. Changes in the spectra of DTBT(c=2×10 M) in dichloromethane CTBT with the electronꢀdonating group induced
solution with various amounts of Hg (0-2 equiv).(a) UV-vis absorption pronouncedON/OFFꢀtypefluorescent signaling behavior. While a
-
5
a
2
+
2
+
2+
spectra, Inset: (a1) Job’s plot of DTBT and Hg ; (a2) Solution color change ratiometric fluorescent probe based on DTBT for Hg was
2
+
upon addition of Hg . (b) Luminescent spectra, (λex=380 nm). Inset: developed by replacing the carbazoly with acenaphtenꢀ5ꢀyl, which
2
+
fluorescent color change upon addition of Hg .
was a weak electronꢀdrawing group. Moreover, CTBT and DTBT
Figure 6 showed the titration profiles of NTBT during Hg . allowed determination of Hg with a detection limit of 5.89 µM and
When Hg was added to solution of NTBT, the absorption of 3.98 µM. The dichloromethane solution of CTBT and DTBT
NTBT at 340 nm decreased, while band at 392 nm increased showed distinct color change from colorless to yellow with the
gradually and exhibited a small redꢀshift from 392 to 402 nm (Figure addition of Hg , which indicated that the two probes would serve as
2
+
2+
2
+
2+
2+
6
(a)). In the fluorescence titration experiment, NTBT was subjected a sensitive nakedꢀeye indicator for Hg . However, both UVꢀvis and
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fluorescence spectra of NTBT with strong electronꢀwithdrawing the mercury ion and the S atom, the possible binding mechanism
2
+
2+
substituent showed no obvious change upon addition of Hg . The was Hg coordinated with the sulfur atom of the thiophene ring and
detection effects and the types of probes for metal ions were related the sulfur atom of the thiazole ring(Figure 7(b)).
1
to the electronic property of the molecule.
As shown in the H NMR spectra of DTBT, upon addition of 1
1
5
2+
2+
According to Pearson’s hardꢀsoft acidꢀbase theory, Hg was equiv. of Hg , it resulted in a considerable downfield shift of
soft acid that can interact preferentially with sulfur or nitrogen atom thiophene protons. These data confirmed the conclusion that DTBT
1
6
2+
used as soft base. Hence, we deduced that the significant variations was involved in the coordination with Hg . DTBT formed a 1:1
2
+
in the photophysical properties of TBT, CTBT and DTBT were complex with Hg from the mentionedꢀabove Job’s plot. From
induced by coordination of Hg to the lone pair electrons on the Figure S11 can be seen, when added to the system about 90%
sulfur atom or nitrogen atom of the thiophene and benzothiazole volume of water, the fluorescence intensity was hardly changed but
unit. In order to demonstrate the complexation mode of Hg with the maximum emission peak was red shifted. DTBT has no the
TBT, CTBT, DTBT, and NTBT, H NMR titration experiments in effect of aggregation induced emission enhancement. The effect of
2+
2+
1
CDCl3 was performed. The active protons were assigned and this phenomenon was similar with the addition of mercury ions in
displayed in Figure 7. Apparently, the signals of TBT, CTBT and the system (Figure 4(b)). So DTBT had no the weak bonding effect
DTBT for these active protons shifted to downfield in certain between the mercury ion and the sulfur atom of the thiazole ring
1
7
2+
degree. According to the literature, when the mercury ion was when the Hg was added. Accordingly, the possible binding
2+
coordinated with the N atom of aromatic heterocyclic compounds, mechanism of DTBT with Hg was proposed as in Figure 7(c)
the fluorescence emission may be red shift. So the red shift of the according to literature, which Hg coordinated with the sulfur
fluorescence spectra of TBT when upon gradual addition of Hg
was due to the coordination between the mercury ion and the N
atom, the possible binding mechanism was Hg coordinated with showed that there was little change of the spectrum, which indicated
1
7
2+
2
+
atom of the thiophene ring and the N atom of the thiazole ring.
1
However, the H NMR titration experiment in CDCl of NTBT
3
2
+
2+
the sulfur atom of the thiophene ring and the N atom of the thiazole that there was not formed complexbetween NTBT and Hg . In
ring. From Figure S9 can be seen, with the increase of the conclusion, different electronic cloud distribution which caused by
proportion of water in the system, the luminescence intensity of the different substituents would result in different binding
TBT was gradually increased. TBT had a very good effect of mechanism. At present, it was still difficult to determine the accurate
aggregation induced emission enhancement. The effect of this sensing mechanism. However, according to the absorption and
2
+
1
phenomenon was similar with the addition of mercury ions in the fluorescent spectral response to Hg and the complicated H NMR
2
+
system (Figure 3(b)). The result showed that the binding mechanism spectra of TBT, CTBT, DTBT, and NTBT after adding Hg , we
2
+
of TBT with Hg may be coordination between the mercury ion and tentatively attributed the sensing mechanism to the complexation of
2
+
2+
the sulfur atom of the thiazole ring. When the Hg was added, the TBT, CTBT, and DTBT with Hg .While the compound NTBT and
2
+
weak bonding effect can change the distance between TBT molecule Hg was not formed complex.
and close to each other, then the fluorescence was gradually
enhanced. All the analysis mentionedꢀabove formed a 1:2 (TBTꢀ
2
+
2+
Hg ) binding model which suggested that Hg was bound to the
sulfur atom of the thiophene ring and N, S atom of the benzothiazole
2
+
ring. As result, the possible binding mechanism of TBT with Hg
was schematically depicted in Figure 7(a).
While CTBT with electronꢀdonating substituent formed a 1:1
2
+
1
complex with Hg , we also carried out H NMR experiments so as
2
+
to further seek the detailed information on the complexation of Hg
with CTBT in CDCl . As shown in Figure 7(b), upon addition of 1.0
equiv. Hg could lead to a significant downshift of the H , H , and
3
2
+
a
b
H . These data confirmed the conclusion that both the sulfur atom of
c
the thiophene ring and the sulfur atom or the nitrogen atom of the
(
a)
benzothiazole ring of CTBT were involved in the coordination with
2
+
Hg . From Figure S10 can be seen, when added to the system about
0% volume of water, the fluorescence intensity was hardly
6
changed. When more water was added, the fluorescence intensity
decreased rapidly. CTBT had no the effect of aggregation induced
emission enhancement. The effect of this phenomenon was similar
with the addition of mercury ions in the system (Figure 4(b)). So
CTBT had no the weak bonding effect between the mercury ion and
2
+
the sulfur atom of the thiazole ring when the Hg was added.
1
8
According to relevant literature, when the mercury ion was
coordinated with the S atom, the fluorescence emission may be
weakened. So the cause of fluorescence quenching of CTBT when
2
+
upon gradual addition of Hg was due to the coordination between
(b)
6
| J. Name., 2013, 00, 1-3
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DOI: 10.1039/C5NJ02259B
Experimental section
Generaldetails
All manipulations involving airꢀsensitive reagent were
performed in an atmosphere of dry N atmosphere. All reagents
2
and solvents were obtained from aladdin. Silica column
chromatography was performed using silica gel (200ꢀ300mesh).
Thoretical calculation measurements
The structure optimization of model compound of TBT, CTBT,
DTBT, and NTBT were performed with the Gaussian 03 package
using B3LYP density function theory (DFT). The 6ꢀ31G (d) basis set
was used to treat all atoms. The contours of the HOMO and LUMO
orbitals were plotted. On the basis of groundꢀstate optimization, the
timeꢀdependent density functional theory approach was applied to
predict their absorption properties.
(
c)
Instruments and reagents
1
13
H NMR and C NMR spectra were recorded with a Varian
Spectrometer at 400 MHz. Mass spectrometric data were obtained
with a Shimadzu GCMSꢀQP 2010 Plus spectrometry. UVꢀvis
absorption spectra were measured on an UVꢀ3600 Shimadzu UVꢀvis
spectrophotometer. Fluorescent experiments at room temperature
were measured on an Edinburgh Instruments Xeꢀ920 spectrometer.
Spectrophotometric and spectrofluorimetric titrations were peformed
in the spectrofluorimetic cell with 2 mL of the solution of
compounds TBT, CTBT, DTBT, and NTBT by adding from 3 to
(
d)
Figure 7. The possible binding mechanism of compound TBT, CTBT, DTBT,
2
+
and NTBT with Hg . (a) TBT (b) CTBT (c) DTBT (d) NTBT.
Conclusions
In conclusion, we have demonstrated a series of selective and 150 µL of the mercury perchlorate with the calibrated micropipet.
2+
sensitive fluorescent Hg chemosensors based on the thiophenꢀ2ꢀylꢀ Absorption and fluorescence spectra were recorded after every single
benzothiazole derivatives. By changing the subsituents (from addition and corrected on the dilution coefficient. Fluorescence
electronꢀdonating group to electronꢀwithdrawing group), different spectra were corrected on the changes of absorption at the excitation
types of fluorescent probes were received. The probe based on TBT wavelength.
2
+
for Hg emerged remarkable enhancement of fluorescence. With the
introduction of electronꢀdonating carbazole, the detection behavior
of CTBT was just the reverse of what TBT displayed. And a
ratiometric fluorescent probe based on DTBT for Hg was prepared
by introducing the weak electronꢀdrawing group
Synthesis
19
2
-thiophen-2-yl-benzothiazole (TBT): Thiopheneꢀ2ꢀcarbaldehyde
2
+
(
0.56 g, 5 mmol), and 2ꢀaminoꢀbenzenethiol (0.75 g, 6 mmol) were
o
dissolved in DMF (5 mL). The mixture was stirred at 120 C for 24
h. The mixture was poured into water. After removal of the solvent,
the crude product was purified by column chromatography (silica
gel, 50:1 petroleum ether/ethyl acetate). Further recrystallization of
the products by petroleum ether to obtain the desired compound as
white powder in 31.8% (0.34 g) yield. m.p. 95 C. H NMR (400
MHz, CDCl ) δ (ppm): 8.03 (d,1H, J = 8.1 Hz), 7.85 (d, 1H, J = 7.9
Hz), 7.66 (d, 1H, J = 3.7 Hz), 7.52ꢀ7.46 (m, 2H), 7.37 (t, 1H, J = 7.6
acenaphteneintothiophenꢀ2ꢀylꢀbenzothiazole unit. However, both
UVꢀvis absorption and fluorescent spectra of NTBT with strong
electronꢀwithdrawing substituent showed no obvious change upon
2
+
addition of Hg . Moreover, the dichloromethane solution of CTBT
and DTBT were changed from colorless to yellow. It indicated that
CTBT and DTBT can serve as highly selective and sensitive nakedꢀ
o
1
3
2
+
2+
eye chemodosimeter for Hg . The interaction between Hg and the
sulfur atom and nitrogen atom of the thiophenꢀ2ꢀylꢀbenzothiazole
derivatives was responsible for the significant variations in optical
signals. These results demonstrated the excellent sensing ability of
13
3
Hz), 7.14 (dd, 1H, J = 4.9, 3.8 Hz). C NMR (100 MHz, CDCl ) δ
(
ppm) =120.7, 122.0, 122.8, 124.1, 126.7, 129.0, 130.1, 135.0,
ꢀ1
1
3
1
37.9, 154.55, 161.9. GC MS (m/z=217). IR υ (cm ): 3402, 3105,
061, 2929, 2860, 1590, 1537, 1484, 1424, 1309, 1214, 1126, 1073,
046, 915, 854, 827, 757, 696. HRMS (ESI) calcd for C11
2+
the thiophenꢀ2ꢀylꢀbenzothiazole derivatives for Hg . This also
supplied a view of designing fluorescent probe. It was concluded
that the electronic property of the molecule was one of vital factors
in designing chemosensor molecules. The detection effects and the
type of probes for metal ions were related to the electronic property
of the molecule. Future work will focus on how to realize the
excellent sensing performance of the thiophenꢀ2ꢀylꢀbenzothiazole
derivatives in water solution by modifying the chemical structure of
these sensors.
H
7
NS
2
[
M+H]+: 218.0093; found: 218.0102.
20
9
-thiophen-2-yl-9H-carbazole: 9Hꢀcarbazole (0.50 g, 3 mmol), 2ꢀ
bromoꢀthiophene (0.73 g, 4.5 mmol), CuI (0.045 g, 0.24 mmol), KI
0.75 g, 4.5 mmol), K CO (2.49 g, 9.0 mmol), Lꢀproline (0.035 g,
.31mmol) were mixed in DMF (15 mL), and the mixture was
(
0
2
3
o
heated at 145 C for 48 h. The reaction mixture was cooled and
poured into cold water. The mixture was extracted with
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COMMUNICATION
Journal Name
dichloromethane (DCM). The organic layer was washed with water (d, 1H,
J
= 6.9 Hz) 7.13 (d, 1H,
J
= 7.3 Hz) 3.44ꢀ3.39 (m, 2H) 3.36ꢀ
1
3
and dried over anhydrous Na SO . The solvent was removed under 3.31 (m, 2H). C NMR (100 MHz, CDCl ) δ (ppm) = 29.9, 30.6,
2
4
3
reduced pressure, and the residue was purified by column 116.8, 120.1, 120.2, 121.8, 129.1, 130.9, 140.3, 146.0, 146.3. GC
chromatography (silica gel, petroleum ether) 0.50 g of 9ꢀthiophenꢀ2ꢀ MS (m/z=232).
21
ylꢀ9Hꢀcarbazole was obtained as white powder (yield 67.3%). m.p. 4, 4, 5, 5-tetramethyl-2-thiophen-2-yl-[1, 3, 2]dioxaborolane: nꢀ
o
1
4
5ꢀ47 C. H NMR (400 MHz, CDCl
3
) δ (ppm): 8.12 (d, 2H,
J = 7.8 Butyllithium (32 mL of a 1.6 M solution in hexane,51.2 mmol) was
Hz), 7.48ꢀ7.42 (m, 4H), 7.39 (dd, 1H,
J
= 5.5, 1.4 Hz), 7.34ꢀ7.29 (m, slowly added to a solution of thiophene (4.2 g, 50 mmol) in THF (30
13
o
2H), 7.22ꢀ7.18 (m, 2H). C NMR (100 MHz, CDCl
3
) δ (ppm) = mL) at ꢀ78 C, and stirred for 2 h. 2ꢀIsopropoxyꢀ4, 4, 5, 5ꢀ
1
10.2, 120.2, 120.6, 123.5, 124.3, 124.8, 126.2, 126.3, 138.8, 142.0. tetramethylꢀ1, 3, 2, dioxaborolane (10.8 mL, 52 mmol) was then
ꢀ
1
o
GC MS (m/z=249). IR υ (cm ): 3439, 3061, 1608, 1546, 1484, 1458, promptly injected into the solution. After stirring for 1 h at ꢀ78 C,
1
7
5
327, 1239, 1152, 845, 748, 696. Anal. Calcd for C16H11NS: C, the reaction mixture was allowed to stand overnight at room
7.07; H, 4.45; N, 5.62. Found: C, 76.28; H, 4.39; N, 5.65. temperature under a nitrogen atmosphere. The mixture was poured
-carbazol-9-yl-thiophene-carbaldehyde
To a threeꢀnecked round into iceꢀwater and extracted with dichloromethane. After drying over
:
bottom flask were added (0.80 g, 3.2 mmol) of 9ꢀthiophenꢀ2ꢀylꢀ9Hꢀ magnesium sulfate, the extract was concentrated, and purified by
carbazole, 1.24 mL (16 mmol) of anhydrous DMF and 10 mL of flash silica gel column chromatography (petroleum ether), to give a
o
o
1
anhydrous chloroform. The solution was cooled to 0 C, and 0.37 mL colorless crystal (7.14 g, 68%). m.p.64 C. H NMR (400 MHz,
of POCl (4 mmol) was added dropwise with stirring. The solution CDCl ) δ (ppm): 7.65 (dd, 2H, = 7.2, 4.0 Hz), 7.20 (dd,1H, = 4.6,
) δ (ppm) = 24.8,
3
3
J
J
13
was then warmed to room temperature followed by refluxing for 4 h, 3.6 Hz), 1.35 (s, 12H). C NMR (100 MHz, CDCl
3
then poured into ice water. The water layer was extracted with 84.1, 128.2, 132.4, 137.2. GC MS (m/z=210).
dichloromethane (3×50 mL), and then dried over MgSO
evaporation of the solvent, the crude product was purified by column mmol) and 4, 4, 5, 5ꢀtetramethylꢀ2ꢀ thiophenꢀ2ꢀylꢀ[1, 3,
chromatography (silica gel, 20:1 petroleum ether/ethyl acetate) to 2]dioxaborolane (2.81 g, 13 mmol), and Pd(PPh (897 mg, 6
generate a yellow solid (0.35 g, 39%). m.p. 102ꢀ104 C. H NMR mol%) were dissolved in toluene (15 mL), followed by the addition
400 MHz, CDCl ) δ (ppm): 9.96 (s, 1H), 8.12 (d, 2H, = 7.7 Hz), of aqueous potassium carbonate (2.0 M, 5 mL), with the reaction
.89 (d,1H, = 4.0 Hz), 7.68 (d, 2H, = 8.2 Hz), 7.48 (t, 2H,
Hz), 7.36 (dd, 3H,
4
:
. After 2-acenaphthen-5-yl-thiophene 5ꢀBromoꢀacenaphthene (3.10 g, 13
3 4
)
o
1
(
3
J
o
7
J
J
J
= 7.7 mixture vigorously stirred at 90 C for 24 h under a nitrogen
= 10.6, 5.7 Hz). C NMR (100 MHz, CDCl ) δ atmosphere. After cooling, the reaction solution was extracted with
ppm) = 110.3, 120.5, 121.7, 123.7, 124.3, 126.7, 136.1, 139.7, toluene and subsequently washed with water. The organic phase was
1
3
J
3
(
ꢀ
1
1
2
7
5
9
40.5, 148.6, 182.9. GC MS (m/z=277). IR υ (cm ): 3414, 3043, dried over magnesium sulfate. Further purification was performed
920, 2804, 1674 (C=O), 1597, 1544, 1469, 1333, 1224, 1046, 802, using flash silica gel column chromatography(petroleum ether) to
41, 713, 666. Anal. Calcd for C17H11NOS: C, 73.62; H, 4.00; N, generate a yellow oil (2.71 g, 86.3%). H NMR (400 MHz, CDCl
1
3
) δ
= 7.1 Hz), 7.52ꢀ7.46
= 8.4 Hz), 7.36ꢀ7.29 (m, 3H), 7.20ꢀ7.17 (m,
.05. Found: C, 72.83; H, 4.27; N, 4.85.
(ppm): 8.00 (d, 1H,
5ꢀ (m, 1H), 7.39 (d,2H,
J = 8.4 Hz), 7.57 (d, 1H, J
-(5-benzothiazol-2-yl-thiophen-2-yl)-9H-carbazole (CTBT)
:
J
1
3
3
Carbazolꢀ9ꢀylꢀthiopheneꢀcarbaldehyde (0.55 g, 2 mmol), and 2ꢀ 1H), 3.46ꢀ3.41 (m, 4H). C NMR (100 MHz, CDCl ) δ (ppm) =
aminoꢀbenzenethiol (0.30 g, 2.4 mmol) were dissolved in DMF (5 30.6, 31.0, 119.8, 122.3, 123.6, 124.3, 124.5, 125.8, 127.3, 127.7,
o
mL). The mixture was stirred at 120 C for 24 h. The mixture was 127.7, 127.8, 130.7, 139.8, 141.7, 143.8, 146.1. GC MS (m/z=236).
ꢀ
1
poured into water. After removal of the solvent, the crude product IR υ (cm ): 3432, 3061, 2930, 2856, 1604, 1455, 1418, 1362, 852,
was purified by column chromatography (silica gel, 4:1 petroleum 779, 732. Anal. Calcd for C16H12S: C, 81.31; H, 5.12. Found: C,
ether/dichloromethane). Further recrystallization of the products was 77.73; H, 7.20.
by petroleum ether into ethyl acetate to obtain the desired compound 5-acenaphthen-5-yl-thiophene-2-carbaldehyde
:
To a threeꢀnecked
o
as yellowꢀcolored powder in 42% (0.32 g) yield. m.p. 178ꢀ180 C. round bottom flask were added (1.89 g, 8 mmol) of 2ꢀacenaphthenꢀ
1
H NMR (400 MHz, CDCl
d, 1H, = 8.2 Hz), 7.89 (d, 1H,
.57ꢀ7.54 (d, 2H), 7.52ꢀ7.33 (m, 6H), 7.25 (d, 1H,
3
) δ (ppm) 8.13 (d, 2H,
J = 7.6 Hz), 8.05 5ꢀylꢀthiophene, 1.24 mL (16 mmol) of anhydrous DMF and 10 mL
o
(
7
J
J
= 7.5 Hz), 7.73 (d,1H,
J
= 4.0 Hz), of anhydrous chloroform. The solution was cooled to 0 C, and 0.74
13
J
= 4.1 Hz).
C
3
mL of POCl (8 mmol) was added dropwise with stirring. The
3
NMR (100 MHz, CDCl ) δ (ppm) = 110.4, 120.3, 121.2, 121.6, solution was then warmed to room temperature followed by
1
1
1
23.1, 123.9, 124.7, 125.5, 126.5, 126.6, 127.6, 134.6, 134.6, 141.2, refluxing for 4 h, then poured into ice water. The water layer was
ꢀ
1
42.4, 153.7, 161.0. GC MS (m/z=382). IR υ (cm ): 3422, 1604, extracted with dichloromethane (3×50 mL), and then dried over
557, 1493, 1447, 1308, 1223, 1057, 898, 806, 759, 713. HRMS MgSO . After evaporation of the solvent, the crude product was
[M+H]+: 383.0697; found: 383.0692. purified by column chromatography (silica gel, 8:1 petroleum
In the absence of light, a solution of 3.60 g ether/ethyl acetate) to generate a yellow solid (1.5 g, 71.1%). m.p.
4
(
14 2 2
ESI) calcd for C23H N S
5-bromo-acenaphthene:
o
1
(
20.2 mmol) Nꢀbromosuccinimide (NBS) in 10mL of anhydrous 64ꢀ65 C. H NMR (400 MHz, CDCl
3
) δ (ppm): 9.95 (s, 1H), 8.12
= 8.4 Hz), 7.68 (d, 1H, = 7.2
= 15.6, 6.0 Hz), 7.40 (t, 2H, = 6.6 Hz), 3.44ꢀ
reaction mixture was stirred for 4 h at room temperature. It was then 3.43 (m, 4H). C NMR (100 MHz, CDCl ) δ (ppm) = 30.2, 30.5,
o
DMF was added dropwise at 0 C to a solution of 3.10 g (20 mmol) (d, 1H,
of acenaphthene in 10 mL of anhydrous DMF within 30 min. The Hz), 7.58 (dd, 2H,
J
= 3.8 Hz), 7.93 (d, 1H,
J
J
J
J
13
3
poured into iceꢀwater to generate yellow power, then washed with 119.2, 120.1, 120.2, 126.6, 127.5, 129.1, 129.1, 129.9, 1367.0,
water and ethanol, the yellow powder turned into white crystal (3.21 139.6, 142.8, 146.6, 148.4, 152.8, 182.9. GC MS (m/z=264). IR υ
o
1
ꢀ1
g, 77.5%). m.p. 46ꢀ49 C. H NMR (400 MHz, CDCl
3
) δ (ppm): 7.78 (cm ): 3440, 2912, 2829, 1660 (C=O), 1594, 1447, 1428, 1362,
(
d, 1H, = 8.4 Hz) 7.66(d, 1H, = 7.3 Hz) 7.58ꢀ7.53 (m, 1H) 7.33
J
J
8
| J. Name., 2013, 00, 1-3
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Journal Name COMMUNICATION
233, 1047, 815, 788. Anal. Calcd for C17H12OS: C, 77.24; H, Specialized Research Fund for the Doctoral Program of Higher
View Article Online
DOI: 10.1039/C5NJ02259B
1
4.58. Found: C, 73.74; H, 4.33.
Education (SRFDP) (20113223110005), Jiangsu Planned Projects
2-(5-acenaphten-5-yl-thiophen-2-yl)-benzothiazole (DTBT):
5ꢀ for Postdoctoral Research Funds(1402010B) and the Research Fund
Acenaphthenꢀ5ꢀylꢀthiopheneꢀ2ꢀ carbaldehyde(0.52 g, 2 mmol) and for Nanjing University of Posts and Telecommunications
ꢀaminoꢀbenzenethiol (0.25 g, 2 mmol) were dissolved in DMF (3 (NY213177).
2
o
mL). The mixture was stirred at 120 C for 24 h. The mixture was
poured into water. After removal of the solvent, the crude product Notes and references
was purified by column chromatography (silica gel, 50:1 petroleum
1
J. P. Desvergne, A. W. Czarnik, Kluwer: Dordrecht 1997; A.
W.Czarnik, Ed. American Chemical Society: Washington, DC
992; A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson,
A. J. M. Huxley, C. P. McCoy, J. T. Rademacher, T. E. Rice,
Chem. Rev. 1997, 97, 1515.
M. Nadal, M. Schuhmacher, J. L. Domingo, Sci. Total
Environ. 2004, 321, 59; W. F. Fitzgerald, C. H. Lamgorg, C.
R. Hammerschmidt, Chem. Rev. 2007, 107, 641; C. J.
Koester, Anal. Chem. 2005, 77, 3737; S. D. Richardson, T. A.
Ternes, Anal. Chem. 2005, 77, 3807.
ether/ ethyl acetate). Further recrystallization of the products was by
petroleum ether to obtain the desired compound as yellow powder in
1
o
1
5
2.3% (0.38 g) yield. m.p. 151ꢀ153 C. H NMR (400 MHz, CDCl
δ (ppm): 8.06 (dd, 2H, = 14.1, 8.3 Hz), 7.87 (d, 1H, = 8.0 Hz),
= 3.8 Hz), 7.65 (d, 1H, = 7.1 Hz), 7.55ꢀ7.47 (m, 2H),
.39ꢀ7.33 (m, 4H), 3.44 (t,4H, = 5.7 Hz). C NMR (100 MHz,
) δ (ppm) = 30.2, 30.6, 119.2, 119.9, 120.6, 121.5, 122.9,
3
)
J
J
2
7.73 (d, 1H,
J
J
1
3
7
J
CDCl
3
125.1, 126.4, 127.0, 127.2, 128.8, 129.1, 129.3, 129.5, 134.7, 136.4,
3
4
5
B. Valeur, I. Leray, Chem. Rev. 2000, 205, 3.
1
39.7, 146.5, 146.5, 147.5, 153.8, 161.4. GC MS (m/z=369). IR υ
ꢀ
1
E. M. Nolan, S. J. Lippard, Chem. Rev. 2008, 108, 3443.
E. Hrishikesan, C. Saravanan, P. Kannan, Ind. Eng. Chem.
Res. 2011, 50, 8225.
X. Zhang, Y. Shiraishi, T. Hirai, Tetrahedron Lett. 2007, 48,
5455; X. Chen, S. W. Nam, M. J. Jou, Y. Kim, S. J. Kim, S.
Park, J. Yoon, Org. Lett. 2008, 10, 5235; Y. Zhou, F. Wang,
Y. Kim, S. J. Kim, J. Yoon, Org. Lett. 2009, 11, 4442.
C. K. Song, J. S. Kim, S. M. Park, K. Chumg, S. Ahn, S.
Chang, Org. Lett. 2006, 8, 3413.
(
cm ): 3449, 3061, 3014, 2939, 1594, 1548, 1501, 1437, 1354,
316, 1252, 1233, 918, 825, 798, 751, 732. HRMS (ESI) calcd for
[M+H]+: 370.0613; found:370.0736.
(5-benzothiazol-2-yl-thiophen-2-yl)-2-exyl-benzo[de]
isoquinoline-1,3-dione (NTBT)
A solution of DTBT (0.43 g, 1.1
mmol) and K Cr (1.17 g, 4 mmol) in 10 mL of acetic acid was
1
23 2
C H15NS
6
6
:
2
o
2 7
O
7
8
stirred at 110 C for almost 30 min. Cooled to room temperature and
concentrated in vacuum. Washing the residue with acetic ester, the
organic layer was washed with water and dried by anhydrous
E. M. Nolan, M. E. Racine, S. J. Lippard, Inorg. Chem. 2006,
45, 2742; E. M. Nolan, S. J. Lippard, J. Mater. Chem. 2005,
1
5, 2778.
4
MgSO . After filtration, the solvent was removed under reduced
pressure to afford power. Then the power was dissolved in acetic
9
A. Misra, M. Shahid, J. Phys. Chem. C. 2010, 114, 16726; J.
B. Wang, X. H. Qian, J. N. Cui, J. Org. Chem. 2006, 71,
4
0 M. H. Yang, P. Thirupathi, K. H. Lee, Org. Lett. 2011, 13,
5028.
1 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, et., J. A.
GAUSSIAN 03 (Revision C. 02), Gaussian, Inc., Wallingford,
CT, 2004.
2 H. B. Sun, S. J. Liu, T. C. Ma, N. N. Song, Q. Zhao, W.
Huang, New J. Chem. 2011, 35, 1194; A. J. Zucchero, P. L.
McGrier, U. H. F. Bunz, Acc. Chem. Res. 2009, 42, 397.
3 E. M. Nolan, M. E. Racine, S. J. Lippard, Inorg. Chem. 2006,
45, 2742; W. Lin, L. Yuan, Z. Cao, Y. Feng, L. Long, Chem.
Eur. J. 2009, 15, 5096.
4 W. Lin, X. Cao, Y. Ding, L. Yuan, L. Long, Chem. Commun.
2010, 46, 3529.
5 R. G. Pearson, J. Am. Chem. Soc. 1963, 85, 3533.
6 Q. Zhao, S. J. Liu, F. Y. Li, T. Yi, C. H. Huang, Dalton
Trans. 2008, 29, 3836; Q. Zhao, T. Y. Cao, F. Y. Li, X. H. Li,
H. Jing, T. Yi, C. H. Huang, Organometallics. 2007, 26,
anhydride (10 mL), followed by the addition of hexylamine (0.22 g,
308.
o
2
2
.2 mmol), with the reaction mixture vigorously stirred at 70 C for
4 h. After cooling, the reaction solution was extracted with
1
1
dichloromethane and subsequently washed with water. The organic
phase was dried over magnesium sulfate. Further purification was
performed using flash silica gel column chromatography(silica gel,
5
0:1 petroleum ether/ ethyl acetate) to generate a yellow power (0.13
1
1
1
o
1
g, 22.5%). m.p. 155ꢀ156 C. H NMR (400 MHz, CDCl
3
) δ (ppm):
8
7
4
.71ꢀ8.63 (m, 3H), 8.07 (d, 1H,
.83ꢀ7.76 (m, 2H), 7.54ꢀ7.49 (m, 1H), 7.39 (d, 2H,
.18 (t, 2H, = 6.7 Hz), 2.17 (s, 4H), 1.74 (t, 3H,
J = 5.5 Hz), 7.90 (d, 2H, J = 9.0 Hz),
J
= 6.3 Hz), 4.22ꢀ
J
J = 10.5 Hz), 1.40
13
(s, 4H). C NMR (100 MHz, CDCl
3
) δ (ppm) = 206.8, 163.9, 163.6,
1
1
2
43.4, 139.1, 137.8, 134.9, 131.8, 131.3, 130.6, 129.8, 129.5, 128.9,
1
1
28.7, 127.4, 126.6, 125.5, 123.1, 122.9, 121.6, 121.4, 40.6, 31.9,
+
9.7, 29.4, 22.7, 14.0. MALDIꢀTOF mass (m/z): 497([M+H] ). IR υ
ꢀ
1
(cm ):3432, 2922, 2856, 1706, 1660 (ꢀNꢀC=O), 1594, 1455, 1362,
1
242, 779. HRMS (ESI) calcd for C29 [M+H]+: 497.1379;
24 2 2 2
H N O S
2
077.
found: 497.0730.
1
1
1
7 J. N. Weng, Q. B. Mei, Q. D. Ling, Q. L. Fan, W. Huang.
Tetrahedron. 2012, 68, 3129.
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Huang, B. H. Tong. New. J. Chem. 2012, 36, 1879.
9 M. J. Park, J. Lee, J. Kwak, I. H. Jung, J. H. Park, H. Kong,
Acknowledgements
The authors acknowledge financial support from the National Basic
Research Program of China (973 Program, 2012CB933301,
C. Lee, D. H. Hwang, H. K. Shim, Macromolecules. 2009,
2012CB723402), the Ministry of Education of China(IRT1148), the
4
2, 5551.
National Natural Science Foundation of China (21572001,
BZ2010043, 20974046, 20774043, 51173081, 50428303,
2
0 X. Zhang, Y. B. Wu, S. M. Ji, H. M. Guo, P. Song, K. Han,
W. T. Wu, W. H. Wu, T. D. James, J. Z. Zhao, J. Org. Chem.
61136003), the Priority Academic Program Development of Jiangsu
2
010, 75, 2578.
Higher Education Institutions (PAPD, YX03001), Jiangsu National
Synergistic Innovation Center for Advanced Materials (SICAM), the
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DOI: 10.1039/C5NJ02259B
COMMUNICATION
Journal Name
21 J. C. Li, H. Y. Lee, S. H. Lee, K. Zong, S. H. Jin, Y. S. Lee,
Synthetic Metals. 2009, 159, 201; J. C. Li, S. J. Kim, S. H.
Lee, Y. S. Lee, Macromolecular research, 2009, 17, 356.
1
0 | J. Name., 2013, 00, 1-3
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New Journal of Chemistry
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DOI: 10.1039/C5NJ02259B
A series of selective and sensitive fluorescent sensor based on
2+
thiophen-2-yl-benzothiazole unit for Hg
a
a
a
a
a
b
Qunbo Mei,* RuqiangTian, Yujie Shi, Qingfang Hua, Chen Chen, Bihai Tong, *
a
Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials(IAM),
Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing University of Posts &
Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
b
College of Metallurgy and Resources, Anhui University of Technology, Ma’anshan, Anhui 243002, P. R. China
∗
Corresponding author. e-mail: iamqbmei@njupt.edu.cn; tongbihai@ahut.edu.cn
2
+
Different types of fluorescent probes for Hg
based on the
5
-thiophen-2-yl-benzothiazole derivatives (TBT, CTBT, DTBT and NTBT) were
realized by changing the subsituents, including the fluorescence quenching probe, the
fluorescence enhancement probe and the ratiometric fluorescent probe.