A dual chemosensor for Cu2+and Fe3+based on π-extend tetrathiafulvalene derivative

Article abstract of DOI:10.1016/j.tet.2016.11.033

A new dual chemosensor (TTF-PBA) for Fe³⁺and Cu²⁺in different signal pathways was designed and synthesized. The absorption spectrum, fluorescence spectrum and cyclic voltammograms changed in the presence of Cu²⁺and Fe³⁺. The optical color changed within 5?s from yellow to orange upon the addition of Cu²⁺, and it changed to dark yellow when Fe³⁺existed. The cyclic voltammogram of Cu²⁺/TTF-PBA changed from E_ox?=?0.50?V, E_red?=?0.32?V to E_ox?=?0.64?V, E_red?=?0.80?V (vs Ag/AgCl) upon the addition of 2.0 equiv. Cu²⁺. As for Fe³⁺/TTF-PBA, its oxidation wave disappeared, and its reduction wave appeared at E_red?=??0.59?V (vs Ag/AgCl) upon the addition of 4.0 equv. Fe³⁺. The sensor displayed high selectivity for Cu²⁺and Fe³⁺over other ions including Pb²⁺, Zn²⁺, Ni²⁺, Ag⁺, Cr³⁺, Mn²⁺, Al³⁺, Co²⁺, Pd²⁺, Hg²⁺, Fe²⁺Cd²⁺, Ce³⁺, Bi³⁺and Au³⁺, the detection limits for Cu²⁺and Fe³⁺ion reached as low as 5.33?×?10^?7?mol/L and 5.34?×?10^?7?mol/L, respectively. Furthermore, when Fe³⁺existed, Cu²⁺can be detected sequentially by the sensor through the absorption spectrum and the color change observed by naked-eyes.

Full text of DOI:10.1016/j.tet.2016.11.033

Accepted Manuscript
2+
3+
A dual chemosensor for Cu and Fe based on π-extend tetrathiafulvalene
derivative
Yuwen Ma, Taohua Leng, Yarong Qu, Chengyun Wang, Yongjia Shen, Weihong Zhu
PII:
S0040-4020(16)31188-7
10.1016/j.tet.2016.11.033
TET 28247
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 29 September 2016
Revised Date: 8 November 2016
Accepted Date: 14 November 2016
Please cite this article as: Ma Y, Leng T, Qu Y, Wang C, Shen Y, Zhu W, A dual chemosensor for
2+
3+
Cu and Fe based on π-extend tetrathiafulvalene derivative, Tetrahedron (2016), doi: 10.1016/
j.tet.2016.11.033.
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ACCEPTED MANUSCRIPT
Graphical Abstract
A dual chemosensor for Cu2+ and Fe3+ based
An exTTF-based dual chemosensor for selective and sensitive
detection of copper (II) and iron (III) in different signal
pathways was prepared. Furthermore, when Fe3+ existed, Cu2+
can be detected sequentially by the sensor.
on π-extend tetrathiafulvalene derivative
Yuwen Maa, Taohua Lengb, Yarong Qua, Chengyun
Wanga, , Yongjia Shena, Weihong Zhu a,
a Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science &
Technology, Shanghai 200237, P. R. China.
b National Food Quality Supervision and Inspection Center (Shanghai) / Shanghai Institute of Quality
Inspection and Technical Research, Shanghai 200233, P. R. China.

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
A dual chemosensor for Cu2+ and Fe3+ based on π-extend tetrathiafulvalene derivative
Yuwen Maa, Taohua lengb, Yarong Qua, Chengyun Wang a*, Yongjia Shena, Weihong Zhua*
a Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, P. R. China.
b National Food Quality Supervision and Inspection Center (Shanghai) / Shanghai Institute of Quality Inspection and Technical Research, Shanghai 200233, P.
R. China.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A new dual chemosensor (TTF-PBA) for Fe3+ and Cu2+ in different signal pathways was
designed and synthesized. The absorption spectrum, fluorescence spectrum and cyclic
voltammograms changed in the presence of Cu2+ and Fe3+. The optical color changed within 5
seconds from yellow to orange upon the addition of Cu2+, and it changed to dark yellow when
Fe3+ existed. The cyclic voltammogram of Cu2+/TTF-PBA changed from Eox=0.50V, Ered=0.32V
to Eox=0.64V, Ered=0.80V (vs Ag/AgCl) upon the addition of 2.0 equiv. Cu2+. As for Fe3+/TTF-
PBA, its oxidation wave disappeared, and its reduction wave appeared at Ered=-0.59V (vs
Ag/AgCl) upon the addition of 4.0 equv. Fe3+. The sensor displayed high selectivity for Cu2+ and
Fe3+ over other ions including Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+，
Cd2+, Ce3+, Bi3+ and Au3+, the detection limits for Cu2+ and Fe3+ ion reached as low as 5.33×10−7
mol/L and 5.34×10−7 mol/L, respectively. Furthermore, when Fe3+ existed, Cu2+ can be detected
sequentially by the sensor through the absorption spectrum and the color change observed by
naked-eyes.
Available online
Keywords:
π-extend tetrathiafulvalene,
dual chemosensor,
copper (II),
iron (III)
2015 Elsevier Ltd. All rights reserved
.
Cu2+ were investigated, only a few of them can be used for
detection of both Fe3+ and Cu2+ in different signal pathways 13-16
1. Introduction
.
Recently, much attention has been paid to the design of
chemosensors for the selective detection of heavy metal ions due
to their potential applications in many fields including chemistry,
biology, medicine and environment 1-3. Iron (Fe3+) is one of the
most essential trace elements, it performs a major function in the
cells of all organisms systems and in various cellular bio-
chemical processes4. The iron deficiency can cause anemia,
hemochromatosis, liver damage, diabetes, Parkinson’s disease
Tetrathiafulvalene (TTF) and its derivatives play a leading
role in making redox sensors for metal ions based on its electron-
17
donating and electrochemical properties
. Usually, TTF
possesses a remarkable π-electron donor property and can result
in two sequential and reversible oxidation processes to generate
cation radical (TTF▪+) and dication (TTF2+) species. In particular,
TTF containing p-quinodimethane analogues (named π-extend
TTF) can be oxidized at lower potential due to its charge
delocalization and a decreased Coulombic repulsion in the
dicationic state 18-20. Based on these particular electronic and
geometrical features, the TTF containing p-quinodimethane
framework was used as redox-active sensor in previous
5
and cancer etc. . Nonetheless, iron excess in the blood and cells
can lead to an increased generation of reactive oxygen species via
Fenton chemistry, which causes undesirable reactions with
6
biomolecules contributing to induce cell death . Copper (Cu2+),
experiments 21
.
another heavy metal ion, is utilized as a catalytic co-factor for
various metalloenzymes, including superoxide dismutase,
cytochrome c oxidase, tyrosinase and nuclease 7,8. However,
excessive copper in cellular can cause serious neurodegenerative
diseases, such as Alzheimer’s, Menkes and Wilson’s diseases 9. It
may also cause infant liver damage 10,11 and childhood cirrhosis 12
when copper is accumulated excessively in the body. Due to the
above special properties of Fe3+ and Cu2+, it is very necessary to
develop methods for the detection of these two metal ions.
Although various colorimetric and fluorescent sensors for Fe3+ or
As reported before, two optical chemosensors were designed
by our group based on π-extend TTF, with di(pyridine-2-
ylmethyl)amine used as receptor. These two dyes show high
sensitivity and selectivity just for Cu2+ 22. In this work, we have
designed and synthesized a new dual chemosensor based on 2,2’-
(2-iodoanthracene-9,10-diylidene)bis(4,5-bis(methylthio)-1,3-
dithiole) (π-extend TTF), which can be used for detecting both
Fe3+ and Cu2+ in different signal pathways. In the new
chemosensor, π-extend TTF is used as electron donor and
picolinamide unit is used as electron acceptor. It is anticipated
———
* Corresponding author: Tel/fax: +086-21-64252967; E-mail address: cywang@ecust.edu.cn (C. -Y. Wang), whzhu@ecust.edu.cn (W.-H. Zhu)

2
Tetrahedron
that the chemosensor can exhibit high sensitivity and selectivity
TTF-PBA (The synthetic route shown in Scheme 1) was
ACCEPTED MANUSCRIPT
for Fe3+ and Cu2+.
synthesized in four steps and was easy to modify. The last step was
processed by Suzuki coupling reaction in 49.6% yield. The chemical
1
structure of TTF-PBA was confirmed by H-NMR, 13C-NMR and
mass spectroscopic data. (Fig.S1 - S6)
2. Results and discussion
2.1 Synthesis
S
S
S
S
O
S
I
S
S
S
S
S
S
S
2
i
S
S
O
S
S
S
O
1
NH
3
I
N
iv
S
S
H
N
H
N
O
O
O
H
O
O
O
B B
S
S
N
NH2
N
O
O
N
TTF-PBA
ii
iii
Br
Br
5
B
O
4
6
i) P(OEt)3/toluene, 100°C, overnight, 52.51%. (ii) DMF/CuI, 80°C, 24h, 62.79%. (iii) dioxane/KOAc/ Pd(dppf)Cl2,
100°C, overnight, 72.03%. (iv) toluene/H2O/K2CO3/ Pd(Pph3)4, reflux, 24h, 49.62%.
Scheme 1 The synthetic route of TTF-PBA.
2.2. The sensing responses for Cu2+ with TTF-PBA
plot, which was done by absorbance changes of consequent
titration (1/(A-A0)) against 1/[Cu2+], where A0 is the absorbance
of free TTF-PBA, A is the absorbance of TTF-PBA with Cu2+ in
different concentration (Fig.S7). The magnitude of Ka was
calculated from the ratio of intercept/slope of the straight line,
and estimated value is about 1.32×104 L/mol. With the addition
of more Cu2+ into the solution, the two new bands at 461nm and
419nm were almost not changed, while a new small one appeared
at 389 nm (Fig.1(a)). This phenomenon may be caused by the
oxidizing effect between Cu2+ and TTF-PBA. The spectrum did
not show any change until the Cu2+ amount achieved at 3.0 equiv.
The solution color began to change from light yellow to light
orange with the addition of 2.0 equiv. Cu2+, and with the more
amount of Cu2+, the color changed to orange. All the color
changes happened within 5 seconds. When the amount of Cu2+
reached at 3.0 equiv., the color did not change any more.
To evaluate the sensing behavior of the dye TTF-PBA
towards Cu2+, the absorption spectral titration of TTF-PBA with
Cu2+ in acetonitrile was carried out.
As shown in Fig.1(a), two absorption bands of TTF-PBA
were centered at 375 nm and 439 nm in acetonitrile. Upon
addition of Cu2+ into the solution, the absorption band at 439 nm
disappeared gradually. When the amount of Cu2+ achieved at 2.0
equiv., two new board bands appeared at 417 nm, 467 nm and the
band at 375 nm blue-shifted to 362 nm gradually. Through the
detection of Job’s Plot, the band at 467 nm experienced
dramatically increased and then decreased process. The
phenomenon can infer that picolinamide unit of the dye acts as a
ligand in complex with Cu2+ ion to form a four membered ring 23
,
in which, the two nitrogen atoms participate in coordination.
Furthermore, the ratio between Cu2+ and TTF-PBA was
confirmed by the Job’s Plot (Fig.2). The change of Job’s Plot
happened at [Cu2+]/([Cu2+]+[TTF-PBA])=0.5, which meant that
Fig. 1 (a) UV-vis spectra of TTF-PBA in acetonitrile (2×10-5mol/L)
upon addition of 0.2-3.2 equiv. CuCl2. (b) Color change of the addition
3.0 equiv. of CuCl2 into TTF-PBA solution (1×10-4 mol/L).
Fig. 2 Job’s Plot for the complex of Cu2+ with TTF-PBA determined by
UV-vis spectra.
Cu2+ and TTF-PBA formed a complex with a ratio of 1:1. The
binding constant (Ka) was estimated using Benesi-Hildebrand

3
The fluorescence titration studies of TTF-PBA for Cu2+ were
also carried out. The assessment of the selectivity of TTF-PBA
towards Cu2+ was studied by fluorescence spectroscopy, which
was given in Fig.3.
shifted from Eox=0.50V to Eox=1.12V (vs Ag/AgCl), and the
ACCEPTED MANUSCRIP
T
reduction wave shifted from Ered=0.32V to Ered=0.50V (vs
Ag/AgCl). These changes can be explained by the formation of
complex between Cu2+ and TTF-PBA 27, which was proved by
the Job’s Plot. When 2.0 equiv. Cu2+ was added into the solution,
a new oxidation wave appeared at Eox=0.64V (vs Ag/AgCl) and a
new reduction wave at Ered=0.80V (vs Ag/AgCl) appeared
gradually upon addition of Cu2+. With the addition of 4.0 equiv.
Cu2+ into the solution, the waves became much clearly. These
phenomena may be caused by the oxidation of TTF unit to cation
radical (TTF▪+). From the cyclic voltammograms, the new
oxidation and reduction waves may arise from the appearance of
cation radical TTF-PBA.
2.4. The sensing responses for Fe3+ with TTF-PBA
Fig. 3 Fluorescence emission spectra of TTF-PBA (2×10-5mol/L) in
acetonitrile upon addition of 0.2-3.2 equiv. of CuCl2.
As shown in Fig.3, the fluorescence emission wavelength of
TTF-PBA appeared at 522 nm when excited by 430 nm photon.
Then the fluorescence quenched gradually with the addition of
Cu2+ into the solution, and the fluorescence quenched mostly till
the Cu2+ amount achieved at 3.0 equiv., and the emission
wavelength blue-shifted to 496 nm. The ratio of the final
fluorescence intensity to the initial fluorescence intensity was
Fig. 5 (a) UV-vis spectra of TTF-PBA in acetonitrile (2×10-5mol/L)
upon addition of 0.5-4.5 equiv. FeCl3. (b) Color change of the addition
4.0 equiv. of FeCl3 into TTF-PBA solution (1×10-4 mol/L).
found to be 0.59. The quenching property of Cu2+ can be
24, 25
attributed to its paramagnetic nature with unfilled d-shell
.
The detection limit was calculated to be 5.33×10-7 M using 3σ/K
(Fig.S8).
2.3 Electrochemical sensing properties of TTF-PBA for Cu2+
Electrochemical sensing for Cu2+ by the dye TTF-PBA was
also investigated. The electrochemical property of TTF-PBA was
carried out on CHI620e electrochemistry workstation in
acetonitrile solution. As shown in Fig.4, TTF-PBA underwent an
oxidation wave at Eox=0.50V (vs Ag/AgCl) and a reduction wave
at Ered=0.32V (vs Ag/AgCl) for that TTF containing
anthraquinone exhibited a two-electron redox wave 26. This
meant that TTF-PBA underwent a reversible redox process.
Fig. 6 Fluorescence emission spectra of TTF-PBA (2×10-5mol/L) in
acetonitrile upon addition of 0.5-4.5 equiv. of FeCl3.
With further study, we found that the dye TTF-PBA can be
also used as chemosensor for detecting Fe3+ in acetonitrile. To
study the sensing property, the absorption titration of TTF-PBA
for Fe3+ was carried out. Unlike addition of Cu2+, with the
increasing of Fe3+, three new small bands appeared at 389 nm,
416 nm and 482 nm, and the two characteristic bands of TTF-
PBA at 375 nm and 439 nm were disappeared almost at the same
time (Fig.5(a)). These phenomena may result from the oxidation
of TTF unit to dication in the dye by Fe3+, for such π-extend TTF
can be oxidized at lower potential due to charge delocalization
and a decreased Coulombic repulsion in the dication state 28. The
different absorption spectra of TTF-PBA/Cu2+ and TTF-
PBA/Fe3+ indicated that the TTF-PBA exhibited
a high
selectivity for Cu2+ and Fe3+ with a different color change. As
shown in Fig.5(b), the solution color began to change upon
additional of 3.0 equiv. Fe3+, and the solution color changed from
light yellow to dark yellow when 4.0 equiv. Fe3+ existed. The
color did not change when more Fe3+ was added. All the color
changes happened within 5 seconds.
Fig. 4 Cyclic voltammogram of TTF-PBA (1×10-3mol/L) upon addition
of 0-4.0 equiv. CuCl2 (vs Ag/AgCl).
Upon gradual addition of Cu2+ into TTF-PBA solution, the
oxidation wave and reduction wave were changed (Fig.4). Upon
addition of 1.0 equiv. Cu2+, the oxidation wave of TTF-PBA

4
Tetrahedron
ACCEPTED MANUSCRIPT
As shown in fluorescence spectroscopy, Fe3+ quenched the
different ions were shown in Fig.9. It was found that upon
fluorescence (excited by 430 nm photon) with a little change in
the shape of the spectra as the same as the influence of Cu2+,
which was shown in Fig.6. The ratio of the final fluorescence
intensity to the initial fluorescence intensity was 0.59. As
reported, the fluorescence of oxidized TTF was increased 29, but
the fluorescence of the TTF-PBA solution with Fe3+ existed was
quenched. It may be attributed to that Fe3+ possesses the same
paramagnetic nature of Cu2+, and the paramagnetic nature plays a
leading role, as a result, the fluorescence is quenched. The
detection limit was calculated as 5.34×10-7 M using 3σ/K
(Fig.S9).
addition of various metal ions, the solution exhibited little change
in fluorescence intensity. However, Cu2+ and Fe3+ induced the
most pronounced fluorescence quenching respectively.
According to Stern-Volmer quenching constants (KSV) in Table
1, the constants of TTF-PBA/Cu2+ and TTF-PBA/Fe3+ are larger
than that of other ions, which means that TTF-PBA is easier to
combine with Cu2+ or Fe3+. Therefore, the results showed that
TTF-PBA possessed an excellent selectivity for Cu2+ and Fe3+
ions in fluorescence changes.
2.5 Electrochemical sensing properties of TTF-PBA for Fe3+
Fig. 7 Cyclic voltammogram of TTF-PBA (1×10-3mol/L) upon addition
of 0-4.0 equiv. FeCl3 (vs Ag/AgCl).
Fig. 8 (a) UV-vis spectra of TTF-PBA in acetonitrile (2×10-5mol/L)
upon addition of CuCl2, FeCl3, AgNO3, ZnCl2, MnCl2, NiCl2,
Hg(COOH)2, PbCl2, PdCl2, CoCl2, FeCl2, CdCl2, CrCl3, AlCl3, Ce2(SO4)3,
BiCl3, AuCl3. (b) Color changes of TTF-PBA solution (1×10-4 mol/L) in
presence of different metal ions (4.0 equiv.).
The cyclic voltammogram of TTF-PBA with Fe3+ was
different from that of Cu2+ (Fig.7). With the addition of 1.0
equiv. Fe3+, the oxidation wave shifted from Eox=0.50V to
Eox=0.06V (vs Ag/AgCl) and reduction wave shifted from Ered=-
0.32V to Ered=-0.48V (vs Ag/AgCl). With the amount of Fe3+
increased, the oxidation wave at 0.06V and the reduction wave at
-0.48V disappeared and a new one appeared at Ered=-0.59V (vs
Ag/AgCl). With the addition of 4.0 equiv. Fe3+ into the solution,
the waves did not change. From the change of cyclic
voltammogram, it can be inferred that the TTF unit of TTF-PBA
is oxidized to dication species (TTF2+) by Fe3+, as a result, the
oxidation wave is disappeared. The dication species (TTF2+)
changes to fully aromatic unit, and may conjugate with the
picolinamide unit, therefore, the structure is not easy to be
restored 28
.
2.6 The selectivity detection study for Cu2+ and Fe3+ with TTF-
PBA
High selectivity is one of the basic requirements for the
chemosensor to successfully recognize the target from various
metal ions. The ability of TTF-PBA recognizing Cu2+ or Fe3+ was
evaluated in acetonitrile by observing the changes in the
absorption spectra (Fig.8(a)). It showed no drastic absorbance
change with the additional metal ions (Pb2+, Zn2+, Ni2+, Ag+, Cr3+,
Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+ and Au3+) in
the solution. Therefore, the solution color only changed by Cu2+
and Fe3+.(Fig.8(b))
Fig. 9 Fluorescence emission spectra of TTF-PBA in acetonitrile (2×10-5
mol/L) upon addition of CuCl2, FeCl3, AgNO3, ZnCl2, MnCl2, NiCl2,
Hg(COOH)2, PbCl2, PdCl2, CoCl2, FeCl2, CdCl2, CrCl3, AlCl3, Ce2(SO4)3,
BiCl3, AuCl3.
Furthermore, as shown in Fig.10, when other ions such as
Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+,
Cd2+, Ce3+, Bi3+ and Au3+ existed in the solution of TTF-PBA,
Cu2+ and Fe3+ quenched the fluorescence respectively, illustrating
that other ions did not interfere with the detection of Cu2+ and
Fe3+, which meant that TTF-PBA exhibited high selectivity for
Cu2+ and Fe3+ over other metal ions.
To estimate the selectivity of TTF-PBA by fluorescence
intensity, other metal ions (Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+,
Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+ and Au3+) were used
for the fluorescence studies in acetonitrile. The changes of
fluorescence emission intensity of TTF-PBA in the presence of
Table 1 The Stern-Volmer quenching constants (KSV)

5
Ions
KSV
Ions
Ksv
Pb2+
380.3
Pd2+
Zn2+
Ni2+
Ag+
Cr3+
Mn2+
Al3+
Co2+
1309.6 1811.8 1621.4 1979.5 1758.7 3317.9 1432.4 3734.4
Hg2+ Fe2+ Ce3+ Bi3+ Au3+ Cu2+ Fe3+
Cd2+
ACCEPTED MANUSCRIPT
1766.6 2326.6 1998.9 2024.8 1841.9 2107.7 8686.4 8686.4
Fig. 10 (a) The selectivity of TTF-PBA in acetonitrile (2×10-5mol/L) for
Cu2+ in the presence of other metal ions (Pb2+, Zn2+, Ni2+, Ag+, Cr3+,
Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+, Au3+)
(wavelength:522nm). (b) The selectivity of TTF-PBA in acetonitrile
(2×10-5mol/L) for Fe3+ in the presence of other metal ions (Pb2+, Zn2+,
Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+,
Au3+) (wavelength:522nm).
2.7 The continues sensing property and selectivity for Cu2+ with
TTF-PBA/Fe3+
Fig. 12 Job’s Plot for the complex of Cu2+ with TTF-PBA/Fe3+
determined by UV-vis spectra.
Fig. 11 (a) UV-vis spectra of TTF-PBA/Fe3+ in acetonitrile (2×10-5
mol/L) upon addition of 0.2-3.0 equiv. CuCl2. (b) Color change of the
addition 3.0 equiv. of CuCl2 into TTF-PBA/Fe3+ solution (1×10-4
mol/L).
When Fe3+ was present in the solution, Cu2+ could also be
detected sequentially by the chemosensor. As shown in Fig.11,
with the addition of 4.0 equiv. Fe3+, the characteristic absorption
bands appeared at 389 nm, 416 nm and 482 nm. Then gradually
adding Cu2+ into the solution, a new band at 362 nm appeared
without changing of other two bands at 416nm and 482nm. The
band at 362nm stopped change upon addition of 3.0 equiv. Cu2+.
With additional of 3.0 equiv. Cu2+, the solution color changed
from orange to red. The ratio between Cu2+ and TTF-PBA/Fe3+
was proved by Job’s Plot, the change happened at
[Cu2+]/([Cu2+]+[TTF-PBA/Fe3+])=0.5 (Fig.12), which meant that
Cu2+ and TTF-PBA/Fe3+ formed a complex with a ratio of 1:1.
The binding constant (Ka) was estimated using Benesi-
Hildebrand plot to be 2.82×104 L/mol (Fig. S10). The reason of
the change can be explained that TTF-PBA is oxidized by Fe3+ at
first, then the Cu2+ is added and in complex with the picolinamide
unit of TTF-PBA. The absorption did not change obviously when
other metal ions (Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+,
Pd2+, Hg2+, Fe2+, Cd2+, Ce3+, Bi3+ and Au3+) were added into the
solution (Fig.13).
Fig. 13 UV-vis spectra of TTF-PBA/Fe3+ in acetonitrile (2×10-5mol/L)
upon addition of CuCl2, AgNO3, ZnCl2, MnCl2, NiCl2, Hg(COOH)2,
PbCl2, PdCl2, CoCl2, FeCl2, CdCl2, CrCl3, AlCl3, Ce2(SO4)3, BiCl3,
AuCl3.
3. Conclusions
In summary, a new dual chemosensor TTF-PBA for Fe3+ and
Cu2+ was designed and synthesized successfully, which can be
used to detect Fe3+ and Cu2+ in different signal pathways. In the
new
chemosensor,
2,2’-(2-iodoanthracene-9,10-
diylidene)bis(4,5-bis(methylthio)-1,3-dithiole) is used as electron
donor and picolinamide unit is used as electron acceptor. To
elongate the π-conjugation system, phenyl group is introduced.
The absorption spectrum, fluorescence spectrum and cyclic
voltammograms changed upon addition of Cu2+ and Fe3+. The
optical color changed within 5 seconds from yellow to orange
upon the addition of Cu2+, and it changed to dark yellow when
Fe3+ existed. The cyclic voltammogram of Cu2+/TTF-PBA
changed from Eox=0.50V, Ered=0.32V to Eox=0.64V, Ered=0.80V
(vs Ag/AgCl) upon the addition of 2.0 equiv. Cu2+. As for
Fe3+/TTF-PBA, its oxidation wave disappeared, and its reduction
wave appeared at Ered=-0.59V (vs Ag/AgCl) upon the addition of
4.0 equv. of Fe3+. The detection mechanism of Cu2+ is that Cu2+
complexed with picolinamide unit upon the addition of 1.0

6
Tetrahedron
equiv., and then the TTF unit was oxidized to cation radical
10 : 1) to get a white solid in 62.79% yield, m. p. 133.2 - 135.0
ACCEPTED MANUSCRIPT
(TTF▪+) upon the addition of more Cu2+. And the mechanism of
Fe3+ detection is that Fe3+ oxidized the TTF unit into dication
species (TTF2+). The fluorescence of the TTF-PBA solution was
quenched in the presence of Cu2+ or Fe3+, it may be attributed to
the paramagnetic nature of Cu2+ and Fe3+. The dye TTF-PBA
displayed high selectivity for Cu2+ and Fe3+ over other ions
including Pb2+, Zn2+, Ni2+, Ag+, Cr3+, Mn2+, Al3+, Co2+, Pd2+,
Hg2+, Fe2+, Cd2+, Ce3+, Bi3+, Au3+, and the detection limits for
Cu2+ and Fe3+ ion reached as low as 5.33×10−7 mol/L and
5.34×10−7 mol/L, respectively. Furthermore, when Fe3+ existed,
Cu2+ can be detected sequentially by the sensor through the
absorption spectrum and the color change observed by naked-
eyes.
°C. 1H-NMR (400 MHz, CDCl3) δ (ppm): 8.64 (s, 1 H) 8.37 (d, J
= 8.4 Hz, 1 H) 8.30 (d, J = 5.9 Hz, 1 H) 7.81 (d, J = 8.6 Hz, 2 H)
7.77 (dd, J1 = 8.4 Hz, J2 = 1.8 Hz, 1 H) 7.67 - 7.63(m, 2 H) 7.10 -
7.08 (m, 1 H).
N-(pyridin-2-yl)-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)benzamide (6)34
5 (200 mg, 0.72 mmol) and bis(pinacolato)diboron (367 mg,
1.44 mmol) were combined in anhydrous dioxane. Potassium
acetate (213 mg, 2.16 mmol) and Pd(dppf)Cl2 (53 mg, 0.07
mmol) were added to the mixture under argon atmosphere. The
mixture was stirred at 100 °C overnight. After evaporation of the
solvent, the residue was purified by silica column (eluent
petroleum ether : ethyl acetate = 5 : 1) to get a brown oil in
72.03% yield. 1H-NMR (400 MHz, CDCl3) δ (ppm): 8.82 (s, 1 H)
8.42 (d, J = 8.4 Hz, 1 H) 8.31 (d, J = 3.6 Hz, 1 H) 7.94 (s, 4 H)
7.78 (t, J = 8.8 Hz, 1 H) 7.09 (dd, J1 = 6.6 Hz, J2 = 5.0 Hz, 1 H)
1.37(s, 12 H).
4. Experimental Section
4.1 Materials and measurements
All chemical reagents and solvents were purchased from
commercial suppliers and were used without further purification
unless otherwise noted. Triethyl phosphite was distilled before
using. Dioxane was dried with metal sodium and distilled
immediately prior to use. All moisture-sensitive and air-sensitive
reactions were carried out under argon atmosphere.
1H-NMR and 13C-NMR spectra were measured on a Bruker
AM-400 spectrometer using d-chloroform as a solvent and
tetramethylsilane (TMS, δ = 0 ppm) as an internal standard. The
4-(9,10-bis(4,5-bis(methylthio)-1,3-dithiol-2-ylidene)-9,10-
dihydroanthracen-2-yl)-N-(pyridin-2-yl)benzamide (TTF-PBA)
3 (168 mg, 0.24 mmol), 6 (108 mg, 0.33 mmol) and K2CO3
(269 mg, 1.95 mmol) were dissolved in toluene (15 mL) and
water (5 mL). Then Pd(Pph3)4 (28 mg, 0.02 mmol) was added
under Argon atmosphere. The reaction mixture was heated to
reflux and stirred for 24 h. After completion of the reaction,
CH2Cl2 (20 mL) and water (30 mL) were added into the reaction
mixture. Then the organic layer was washed by water (10 mL ×
3) and dried over Na2SO4. After the solvent was removed, the
residue was purified by silica column (eluent CH2Cl2 : CH3OH =
20 : 1) to get a yellow solid in 49.62% yield, m. p. 210 - 212 °C.
1H-NMR(400 MHz, CDCl3) δ(ppm): 8.65 (s, 1 H) 8.42 (d, J = 8.4
Hz, 1 H) 8.05 (d, J = 8.4 Hz, 2 H) 7.81 (dd, J1 = 5.0 Hz, J2 = 11.5
Hz, 4 H) 7.68 (d, J = 8.1 Hz, 1 H) 7.60 - 7.56 (m, 2 H), 7.34 (dd,
J1 = 3.2 Hz, J2 = 5.6 Hz, 2 H) 7.13 - 7.05 (m, 2 H) 2.41 (s, 12 H).
13C-NMR(100 MHz, CDCl3) δ(ppm): 164.21, 150.60, 146.78,
143.12, 137.57, 136.46, 134.33, 134.13, 133.43, 131.88, 130.77,
130.61, 126.98, 126.28, 125.43, 125.31, 125.01, 124.77, 124.42,
124.29, 123.96, 123.04, 122.40, 122.03, 118.93, 113.29, 28.68.
ESI-MS [M + H+] Calcd. 761.0046 Found 761.0042.
UV-vis spectra were recorded on
a Varian CARY 100
spectrophotometer at room temperature. Fluorescence-emission
was detected on Varian Cary Eclipse spectrophotometer at room
temperature in acetonitrile. The cyclic voltammograms was
obtained from CHI620e electrochemistry workstation. The
supporting electrolyte was 0.1M TBAPF6 in acetonitrile. The
scan rate was 100 mV•s-1. The working electrode was glass
carbon, the counter electrode was platinum-wire coil, and the
reference electrode was Ag/AgCl.
4.2 Synthetic procedures
2-iodoanthracene-9,10-dione (1) and 4,5-bis(methylthio)-1,3-
dithiole-2- thione (2) were synthesized according to literatures 30,
31.
4.3 UV-vis and fluorescence titration
2,2’-(2-iodoanthracene-9,10-diylidene)-bis(4,5-bis(methylthio)-
1,3- dithiole) (3) 32
TTF-PBA (7.6 mg) was dissolved in 100 mL acetonitrile to
get a 1 × 10-4 mol/L solution. Then the solution was diluted to 2 ×
10-5 mol/L solution. CuCl2▪2H2O (51.0 mg) was dissolved in 10
mL acetonitrile to get 0.03 mol/L solution. A series of 3.0 mL 2 ×
10-5 mol/L TTF-PBA solutions were taken in cuvettes, then 0.4
ꢀL (0.2 equiv.), 0.8 ꢀL (0.4 equiv.), 1.2 ꢀL (0.6 equiv.), 1.6 ꢀL
(0.8 equiv.), 2.0 ꢀL (1.0 equiv.), 2.4 ꢀL (1.2 equiv.), 2.8 ꢀL (1.4
equiv.), 3.2 ꢀL (1.6 equiv.), 3.6 ꢀL (1.8 equiv.), 4.0 ꢀL (2.0
equiv.), 4.4 ꢀL (2.2 equiv.), 4.8 ꢀL (2.4 equiv.), 5.2 ꢀL (2.6
equiv.), 5.6 ꢀL (2.8 equiv.), 6.0 ꢀL (3.0 equiv.) and 6.4 ꢀL (3.2
equiv.) Cu2+ was added respectively. After mixing them for a few
seconds (in 5 seconds), UV-vis and fluorescence spectra tests
were taken at room temperature.
A mixture of 2-iodoanthracene-9,10-dione (1) (100 mg, 0.30
mmol), 4,5-bis(methylthio)-1,3-dithiole-2-thione (2) (68 mg, 0.30
mmol) in toluene (10 mL) and triethyl phosphite (5 mL) was
stirred at 100 °C under argon atmosphere for 1 h. Then 2 (68 mg,
0.30 mmol) was added to the reaction mixture. After the mixture
was stirred overnight, the solvent were removed and the residue
was purified by silica column (eluent Petroleum ether : CH2Cl2 =
5 : 1) to give a yellow solid in 52.51% yield, m. p. 198 - 200 °C.
1H-NMR (400 MHz, CDCl3) δ (ppm): 7.86 (d, J = 1.7 Hz, 1 H),
7.61 - 7.62 (dd, J1 = 8.2 Hz, J2 = 1.8 Hz, 1 H), 7.55 - 7.53 (m, 2
H), 7.33 - 7.30 (m, 2 H), 7.27 (d, J = 3.4 Hz, 1 H), 2.42 - 2.39 (m,
12 H).
The method of Fe3+ titration was as the same as Cu2+ titration.
FeCl3 (48.7 mg) was dissolved in 10 mL acetonitrile to get 0.03
mol/L solution.
4-bromo-N-(pyridin-2-yl)benzamide (5) 33
4-bromobenzaldehyde (200 mg, 1.09 mmol), pyridin-2-amine
(153 mg, 1.63 mmol) and CuI (21 mg, 0.11 mmol) were mixed in
5 mL DMF. The reaction mixture was stirred at 80 °C for 24 h.
Then the reactant was extracted with CH2Cl2 (3 × 10 mL) and
washed by water (3 × 10 mL). The organic layer was dried by
Na2SO4. After removing the solvent, the crude product was
purified by silica column (eluent petroleum ether : ethyl acetate =
4.4 UV-vis and fluorescence for selectivity
ZnCl2 (40.8 mg), PbCl2 (83.4 mg), AgNO3 (51.0 mg),
NiCl2▪6H2O (71.4 mg), CrCl3▪6H2O (79.8 mg), MnCl2▪4H2O
(59.4 mg), FeCl2▪4H2O (59.7 mg), Hg(COOH)2 (95.6 mg), CdCl2
(54.9 mg), CoCl2▪6H2O (71.4 mg), AlCl3 (39.9 mg), PdCl2 (53.1

7
mg), Ce2(SO4)3▪4H2O (121.3mg), BiCl3 (94.6mg), AuCl3
12 Liu, X.; Zhang, N.; Bing, T.; Shangguan, D.; Anal. Chem.,
2014, 4, 2289–2296.
ACCEPTED MANUSCRIPT
(123.6mg) were dissolved in 10 mL acetonitrile to get 0.03 mol/L
solution respectively. Then 6.0 ꢀL (3.0 equiv.) or 8.0 ꢀL (4.0
equiv.) ion solution was added into 3.0 mL 2 × 10-5 mol/L TTF-
PBA solution. After mixing them for a few seconds (in 5
seconds), UV-vis and fluorescence spectra tests were taken at
room temperature.
13 Wang, Y.; Wang, C.; Xue, S.; Liang, Q.; Li, Z.; Xu, S.; Rsc
Adv., 2016, 6, 6540-6550.
14 Yang, L.; Zhu, N. W.; Fang, M.; Zhang, Q.; Li, C.
Spectrochim. Acta, Part A, 2013, 109, 186-192.
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16 Fabian, J.; Nakazumi, H.; Matsuoka, M. Chem. Rev., 1992, 92,
1197-1226.
17 Canevet, D.; Sallé, M.; Zhang, G. X.; Zhang, D. Q.; Zhu, D.
B. Chem. Commun., 2009, 17, 2245-2269.
18 Yamashita, Y. ; Kobayashi, Y. ; Miyashi, T. Angew. Chem.
Int. Edit., 1989, 28, 1052-1053.
19 Bryce, M. R.; Moore, A. J.; Hasan, M.; Ashwell, G. J.; Fraser,
A. T.; Clegg, W.; Hursthouse, M. B.; Karaulov, A. I. Chem.
Int. Edit., 1990, 29, 1450-1452.
4.5. Job’s Plot measurements
600 ꢀL, 540 ꢀL, 480 ꢀL, 420 ꢀL, 360 ꢀL, 300 ꢀL, 240 ꢀL,
180 ꢀL, 120 ꢀL, 60 ꢀL and 0ꢀL 1×10-4 mol/L TTF-PBA solution
were taken and transferred to cuvette. 0 ꢀL, 0.2 ꢀL, 0.4 ꢀL, 0.6
ꢀL, 0.8 ꢀL, 1.0 ꢀL, 1.2 ꢀL, 1.4 ꢀL, 1.6 ꢀL, 1.8 ꢀL and 2.0 ꢀL
0.03 mol/L Cu2+ solution were added into each cuvette, then each
cuvette was dilute to 3.0 mL. After mixing for a few seconds (in
5 seconds), fluorescence spectra tests were taken at room
temperature.
20 Moore, A. J.; Bryce, M. R. J. Chem. Soc., Perkin Trans.
1,1991, 1, 157-168.
4.6 Calculation of detection limit
21 Lerouge, M. H.; Chesneau, B.; Allain, M.; Hudhomme, P.; J.
Org. Chem., 2012, 77, 2441-2445.
22 Ma, Y.; Lai, G.; Li, Z.; Wang, C.; Shen, Y. Tetrahedron, 2015,
71, 8717-8724.
23 Mandal, S. K.; Que, L.; Inorg. Chem., 1997, 36, 5424-5425.
24 Ding, H.; Liang, C. S.; Sun, K. B.; Wang, H. J.; Hiltunen, K.;
Chen, Z. J.; Shen, J. C. Biosens. Bioelectron, 2014, 59, 216-
220.
25 Gillissen, M. A. J.; Voets, I. K.; Meijer, E. W.; Palmans, A. R.
A. Polym. Chem., 2012, 3, 3166-3174.
The detection limit was determined from the fluorescence
titration data based on 3σ/K. Ten times of fluorescence intensity
of TTF-PBA were tested and σ can be calculated. According to
the result of fluorescence titrating experiment, the fluorescent
intensity data of TTF-PBA were normalized between the
minimum intensity and the maximum intensity respectively when
excited at 430 nm. The linear regression curve was then fitted to
these normalized fluorescent intensity data, and the slop K of line
could be calculated.
26 Chen, G.; Bouzan, S.; Zhao, Y. M. Tetrahedron Lett., 2010,
51, 6552-6556.
27 Gong, Z.; Zhong, Y.; Organometallics, 2013, 32, 7495-7502.
28 Guldi, D. M.; Sánchez, L.; Martin, N.; J. Phus. Chem. B, 2012,
105, 7139-7144.
Acknowledgements
This work is sponsored by Natural Science Foundation of
Shanghai (16ZR1408000), and the National Natural Science
Foundation of China (No. 21576087).
29 Huang, R.; Zuo, H.; Zhang, L.; Wang, C.; Shen, Y. Polym.
Bull., 2015, 72, 2527-2536.
30 Choi, W.; Harada, D.; Oyaizu, K.; Nishide, H. J. J. Am. Chem.
Soc., 2011, 133, 19839-19843.
31 Hasegawa, M.; Takeda, K.; Kuwatam, Y.; Yoshida, M.;
Matsuyama, Iyoda, H. M. J. Sulfur. Chem., 2009, 30, 301-308.
32 Chen, G.; Bouzan, S.; Zhao, Y. M.; Tetrahedron Lett., 2010,
51, 6552-6556.
33 Yang,S. Z.; Yan, H.; Ren, X. Y.; Shi, X. K.; Li, J.; Wang, Y.
L.; Huang, G. S. Tetrahedron, 2013, 69, 6431-6435.
34 Ma, Y.; Leng, T.; Lai, G.; Li, Z.; Xu, X.; Zou, J.; Shen, Y.;
Wang, C. Tetrahedron, 2016, 72, 2219-2225.
Supplementary data
1H-NMR, 13C-NMR, and MS of TTF-PBA are available.
Additional graphs for calculation of detection limit and binding
constant can be found in ESI.
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