A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion

Article abstract of DOI:10.1016/j.tet.2019.130675

A new tri-imidazolium salt, tris(4-(3-(2-((8-hydroxy-9,10-dioxo-9′,10′-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-3′-ium-1′-yl)phenyl)amine hexafluorophosphate was prepared and characterized. Particularly, the recognition performance of the tri-imidazo

Full text of DOI:10.1016/j.tet.2019.130675

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A new tridentate fluorescent-colorimetric chemosensor for copper(II)
ion
Zhi-Xiang Zhao 1, Ze-Liang Hu 1, Xian-Tao Zhang, Qing-Xiang Liu*
Tianjin Key Laboratory of Structure and Performance for Functional Molecules, MOE Key Laboratory of Inorganic-Organic Hybrid Functional Material
Chemistry, College of Chemistry, Tianjin Normal University, Tianjin 300387, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A
new tri-imidazolium salt, tris(4-(3-(2-((8-hydroxy-9,10-dioxo-90,100-dihydroanthracen-1-yl)oxy)
ethyl)-1H-imidazole-30-ium-10-yl)phenyl)amine hexafluorophosphate was prepared and characterized.
Particularly, the recognition performance of the tri-imidazolium salt for cations was investigated through
fluorescence and ultraviolet titrations, MS, IR spectra and 1H NMR titrations. The results indicated that
the tri-imidazolium salt can distinguish effectively copper(II) ion from other cations by the changes of
spectroscopy and colour (from yellow to orange under sunlight). Furthermore, the tri-imidazolium salt
was also used in detecting Cu2þ through employing smartphone with the computed detection limit
Received 4 May 2019
Received in revised form
6 September 2019
Accepted 1 October 2019
Available online xxx
Keywords:
down to 0.51 mM.
Tri-imidazolium
Copper(II) ion
Chemosensor
Colorimetric
Fluorescence
© 2019 Elsevier Ltd. All rights reserved.
1. Introduction
investigated through fluorescence and ultraviolet titrations, MS, IR
spectra and 1H NMR titrations.
Copper is a fundamental trace element in human body [1].
Excessive or lack of copper in the human body will lead to a series
of severe diseases, such as haematological manifestations, liver
damage, gastrointestinal disturbances, neurodegenerative diseases,
Wilson’s, Parkinson’s and Alzheimer’s disease [2e13]. In addition,
the excessive copper(II) ion of nature will destroy the ecosystem
[14]. Therefore, the accurate detection of Cu2þ is very important to
human and environment. Among the detection of Cu2þ, the fluo-
rescent method is one of significant tools. Particularly, fluorescent
chemosensors with colour change have attracted great attention of
researchers owing to their speediness and convenience for
providing qualitative information of analyte without any expensive
and sophisticated instrument [15,16]. Though lots of chemosensors
for Cu2þ have been reported [17e29], the design and synthesis of
new practical chemosensors are still desirable.
2. Results and discussion
2.1. Preparation and characterization of tri-imidazolium salt 1
Triphenylamine was treated with bromine to give tris(4-
bromophenyl)amine, which further reacted with imidazole to get
tris(4-(1H-imidazole-1-yl)phenyl)amine. Finally, tris(4-(1H-imid-
azole-1-yl)phenyl)amine was treated with 1-(2-bromoethoxy)-8-
hydroxy-9,10-anthraquinone to generate tris(4-(3-(2-((8-hydroxy-
9,10-dioxo-90,100-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-
30-ium-10-yl)phenyl)amine bromide, followed using NH4PF6 to
perform anion exchange in MeOH to afford tris(4-(3-(2-((8-
hydroxy-9,10-dioxo-90,100-dihydroanthracen-1-yl)oxy)ethyl)-1H-
imidazole-30-ium-10-yl)phenyl)amine hexafluorophosphate (1)
(Scheme 1). Compound 1 had good stability in the air, and it was
soluble in CH2Cl2, THF and DMSO, but nearly insoluble in petroleum
ether, ethyl acetate, diethyl ether and water. From the 1H NMR
spectra of 1 (Fig. S12), the signal of phenolic hydroxyl (ArOH) and
the signal of imidazolium proton (NCHN) were observed at
Herein, a new tri-imidazolium salt tris(4-(3-(2-((8-hydroxy-
9,10-dioxo-90,100-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-
30-ium-10-yl)phenyl)amine hexafluorophosphate (1) was designed
and synthesized. The recognition performance of 1 for cations was
d
¼ 12.44 ppm and 10.11 ppm, which are analogous to the signals of
* Corresponding author.
known 1-hydroxy-9,10-anthraquinone [30e32] and imidazolium
salts [33e40].
E-mail address: tjnulqx@163.com (Q.-X. Liu).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.tet.2019.130675
0040-4020/© 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

2
Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
Scheme 1. Preparation of compound 1.
2.2. Detection of Cu(II) employing 1 as a chemosensor
ascribed to the emission of anthraquinone (lex ¼ 415 nm, slit: 10
nm/10 nm, an equilibration time of 10 min). When 2.0 equivalent of
Several cations (Naþ, Liþ, NHþ4 , Agþ, Kþ, Ni2þ, Fe2þ, Fe3þ, Zn2þ
Cu2þ, Ca2þ, Mn2þ, Cr3þ, Cd2þ, Mg2þ, Co2þ, Pb2þ, Al3þ and Hg2þ
using nitrate salts of them) were selected as guests to research the
,
,
Naþ, Liþ, NH4þ, Agþ, Kþ, Ni2þ, Co2þ, Fe2þ, Fe3þ, Zn2þ, Ca2þ, Mn2þ
,
Cr3þ, Cd2þ, Mg2þ, Pb2þ, Al3þ and Hg2þ were added to the solutions
of 1, no obvious variations of fluorescent spectra and color were
observed. However, the fluorescence intensity decreased drastically
when the same amount of Cu2þ was added, and the color of solu-
tion altered from yellow to orange under sunlight within 1 min
cation detection capability of
spectroscopy.
1 via fluorescence and UV
As displayed in Fig.1(a), the emission peak of 1 at ca. 577 nm was
Fig. 1. (a) The fluorescent spectra of 1 (5 ꢀ 10ꢁ6 M) and adding 2.0 equivalent of different cations (NHþ4 , Naþ, Agþ, Kþ, Liþ, Ni2þ, Fe2þ, Fe3þ, Zn2þ, Cu2þ, Ca2þ, Mn2þ, Cr3þ, Cd2þ, Mg2þ
,
Hg2þ, Co2þ, Pb2þ and Al3þ, using nitrate salts of them) in DMSO/CH2Cl2 (v:v ¼ 1:49) at 25 ꢂC (lex ¼ 415 nm, slit: 10 nm/10 nm, lem ¼ 577 nm). (b) Visual colour variations of 1 with
various cations.
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
3
(Fig. 1(b)). The change of this fluorescent intensity should be
ascribed to the switched-on of the photoinduced electron transfer
(PET) process from the imidazole to anthraquinone [41e44].
Additionally,
the
absorption
peak
of
1
(ε ¼ 2.3 ꢀ 104 molꢁ1dm3cmꢁ1
)
at 415 nm did not exhibit any
remarkable response to the addition of these cations except Cu2þ
(Fig. S1). These results showed that 1 was able to effectively
distinguish Cu2þ from other cations.
After that, the fluorescence titration experiments were con-
ducted (Fig. 2). With the increasing C2Cþu , the fluorescent intensities
of 1 at ca. 577 nm reduced little by little. When the ratio of C2Cþu /C1
2þ
(C and C1 being the concentrations of Cu2þ and 1) was no more
Cu
than 2:1, the fluorescence intensity quickly decreased with
increasing C2Cþu . When the ratio was between 2:1 and 5:1, the
decreasing tendency of the fluorescence intensity slowed down.
2þ
Upon exceeding 5:1 of the ratio, higher C did not lead to further
Cu
emission decrease (the inset of Fig. 2). The reducing behavior of the
2þ
fluorescent intensity of 1 with the increasing C was discovered to
Cu
abide by a traditional Stern-Volmer equation (Eq. (1)) [45,46].
Fig. 3. The ultraviolet spectra of 1 (1 ꢀ 10ꢁ5 M) in DMSO/CH2Cl2 (v:v ¼ 1:49) at room
temperature. The concentrations of Cu2þ for curves 1e19 are 0, 0.04, 0.07, 0.11, 0.25,
0.43, 0.50, 0.57, 0.63, 0.85, 0.9, 1, 1.2, 1.4, 1.6, 2, 2.5, 3, 4 ꢀ 10ꢁ5 M. Inset: the Job’s plot of
1$Cu2þ complex at 415 nm in DMSO/CH2Cl2 (v:v ¼ 1:49).
.
F0 F ¼ 1 þ KSV C2Cþu
(1)
in which F0 represented the fluorescent intensity of free 1, and F
2þ
represented the fluorescent intensity of 1 with the addition of C
.
Cu
computed as 2.8 ꢀ 105 Mꢁ1 (R ¼ 0.997) [51,52] (Eq. (2), Fig. S4), and
it was analogous to the value of KSV (1 ꢀ 105 Mꢁ1) obtained by
fluorescent method.
The KSV defined the quenching efficiency of Cu2þ to 1.
The equation revealed that the value of F0/F increased along
2þ
with the increasing CC2þu . The C from 0 to 1 ꢀ 10ꢁ5 M displayed a
Cu
good linear relationship (R ¼ 0.998) to the value of F0/F, and the KSV
for 1$Cu2þ was calculated as 1 ꢀ 105 Mꢁ1 by using equation (1)
(Fig. S2). Also, the limit of detection (LOD) was determined to be
.
.
A0 ðA0 ꢁ AÞ ¼ ½εr = ðεr ꢁ εcÞꢃð1 KC2Cþu þ 1
(2)
0.049 mM according to the changes in fluorescence titrations
(Fig. S3) [47], and this value was similar to the minimum that of
reports [1,14,48,49] (the limits of detection for literatures were
where the absorption of free 1 was A0, and the discrepancy of ab-
sorption between free 1 and 1$Cu2þ was (A0-A). The molar
extinction coefficients of free 1 and 1$Cu2þ were εr and εc, respec-
tively. The ratio of intercept/slope was the stability constant K [53].
To measure the special selective capacity for Cu2þ, the compe-
tition experiments were carried out (Fig. S5). Firstly, 2.0 equivalent
from 0.023 mM to 2.16 mM).
In addition, the UV titration experiments and Job’s plot analysis
were also carried out. The absorption peak of 1 at 373e485 nm
2þ
of several cations (NHþ4 , Naþ, Agþ, Kþ, Liþ, Ni2þ, Fe2þ, Fe3þ, Zn2þ
,
reduced little by little with the enhancing C (Fig. 3). In the inset of
Cu
Cu2þ, Ca2þ, Mn2þ, Cr3þ, Cd2þ, Mg2þ, Co2þ, Pb2þ, Al3þ and Hg2þ) was
added to solution of 1, and then the same amount of Cu2þ was
added (5 ꢀ 10ꢁ6 moL/L). But no remarkable interference was
aroused by adding several cations, and the result displayed 1 had
good selectivity for Cu2þ [54].
Fig. 3, the cDA value approached the maximum value while molar
fraction (c) of 1 was equal to 0.5 [50], which displayed a stoichi-
ometry of 1:1 for 1$Cu2þ. Through the standard Benesi-Hildebrand
method, the value of K (stability constant) for 1$Cu2þ was
The anti-jamming capability to counteranions of 1 has also been
tested via using Cu(OAc)2, CuSO4, CuCO3 and CuCl2. After adding 2.0
equiv. of Cu(OAc)2, CuSO4, CuCO3 and CuCl2 to the solutions of 1
(5 ꢀ 10ꢁ6 moL/L), the decrease of fluorescence intensity and quick
colour change (from yellow to orange under sunlight) were
observed, which were similar to the case of only addition of
Cu(NO3)2. This test indicated that the recognition of 1 for Cu2þ had
high capacity of resisting disturbance to the anions (Fig. S6). Also,
we carried out reversible binding tests. From Fig. S7, the fluorescent
intensities of 1 at ca. 577 nm enhanced with adding EDTA, because
EDTA can capture Cu2þ from 1$Cu2þ to release free 1. After adding
Cu2þ again, 1$Cu2þ was regenerated and the fluorescent intensities
reduced again. This result showed that compound 1 exhibited good
regeneration ability.
2.3. Interactions of 1 with Cu2þ
The nitrogen atom of triphenylamine in compound 1 is sp3 hy-
bridization based on literatures [55e57], therefore, compound 1
should be a trigonal pyramidal molecular geometry as shown in
Scheme 2. According to the characteristics of 1, Cu2þ$$$N, Cu2þ$$$O
Fig. 2. The fluorescent titration spectra of 1 (5 ꢀ 10ꢁ6 M) with various C in DMSO/
2þ
Cu
2þ
CH2Cl2 (v:v ¼ 1:49) at 25 ꢂC (lex ¼ 415 nm, slit: 10 nm/10 nm, lem ¼ 577 nm). C for
Cu
curves 1e23 are 0, 0.3, 0.6, 0.9, 1.5, 2, 2.5, 3, 3.5, 4.0, 4.5, 5, 6, 7, 8, 9, 12, 15, 18, 21, 25, 30,
35 ꢀ 10ꢁ6 M. Inset: the fluorescence of 1 as a function of C /C1 at 577 nm.
and Cu2þ$$$
p interactions are the most likely binding mode. To get
2þ
Cu
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

4
Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
Scheme 2. The interactions of Cu2þ with 1.
relative information about the binding pattern for Cu2þ and 1, 1H
NMR titration tests were conducted in DMSO‑d6 (Fig. 4). As depic-
observed, and no widen signals was observed [58e60]. Therefore,
Cu2þ$$$
p interactions (p being from anthraquinone) was most
2þ
ted in Fig. 4, when C changed from 0 to 1 equivalent, the signals of
possible acting force between Cu2þ and 1, and this was corre-
Cu
Ha-Hg on anthraquinone moved little by little to upfield, whereas
other proton signals of 1 did not had remarkable shift. Thus,
Cu2þ$$$N interactions (N being from triphenylamine) can be
removed, otherwise, the proton signals on benzene rings of tri-
phenylamine should have obvious shift. In IR spectra (Fig. S9),
because of the carbonyl signal (O]C) having no remarkable
change, Cu2þ$$$O]C interactions should also be excluded. Besides,
Cu2þ$$$HO interactions were not likely binding mode, and the
reason was if there existed Cu2þ$$$HO interactions, the proton
signals on OH not only had remarkable shift but also widen due to
the paramagnetism effect of Cu2þ. But experimental results dis-
played that only upfield shift for proton signals on OH was
sponding above-mentioned the experimental results that the sig-
nals of Ha-Hg on anthraquinone had remarkable changes. Cu2þ$$$
p
interactions are also reasonable from the consideration of electron
cloud density, because anthraquinone has larger electron cloud
density in all
p
systems of 1, and it is easier to combine with the
interactions are not
positive charge of copper(II) ion. Cu2þ$$$
p
uncommon, and they have been reported in some literatures
[61e63]. Furthermore, through comparison of Fig. 4(v) and
Fig. 4(vi), the signals of Ha-Hg stayed the same upon adding more
Cu2þ, which displayed the formation of 1:1 complexation between
1 and Cu2þ. Additionally, the ESI-MS and cold ESI-MS of 1$Cu2þ
(Fig. S8 (a) and (b)) were measured with gas temperature at 300 ꢂC
and 220 ꢂC. Fig. S8(a) at 300 ꢂC displayed weak peaks in the range of
m/z ¼ 475e480. But the peak of [1e3(PFꢁ6 ) þ Cu(NO3)2]3þ/3 (m/z
477.1354) can be observed after Fig. S8(a) being enlarged as shown
in inset of Fig. S8(a). In Fig. S8(b) at 220 ꢂC, a distinct peak of
[1e3(PFꢁ6 ) þ Cu(NO3)2]3þ/3 (m/z 477.1354) was observed. This
further determined that a 1:1 complexation between 1 and Cu2þ
was generated. These results agreed with the survey of Job’s plot
experiment (Inset of Fig. 3). In IR spectra (Fig. S9), the absorption
peaks of phenolic hydroxyl group shifted from 3392 cmꢁ1 in free 1
to 3431 cmꢁ1 in 1$Cu2þ, CeO bending vibration peaks shifted from
1063 cmꢁ1 in free 1 to 1080 cmꢁ1 in 1$Cu2þ
Through the comprehensive analyses of above results, Cu2þ was
.
held by three anthraquinones through Cu2þ$$$
p interactions. It was
unfortunate that we failed to get the single crystal of 1$Cu2þ
.
2.4. Integration of 1 through RGB colour value
A smartphone APP of free downloads (RGB Colour Value; Red,
Green and Blue) was applied to detect the various analytes [64e66],
which can provide a method for the spot quantitative inspection of
Cu2þ
.
Herein, we integrated 1 with a APP of smartphone (RGB Colour
Value) to record the values of RGB when the yellow colour of free 1
changed to orange with increasing C2Cþu . The whole-number value
for each of the three colours (red, green and blue) from 0 to 255
represented the standard RGB scale. The variation in standard RGB
values (the number [0,0,0] was absolute black, whereas
[255,255,255] was true white) were recorded through applying the
back camera (using iPhone 6, we downloaded online the APP). The
RGB values of vials including 1 solution (5 ꢀ 10ꢁ6 M) with different
Fig. 4. The partial 1H NMR spectra. (i) Free 1; (ii) 0.25 equivalent of Cu2þ and 1; (iii) 0.5
equivalent of Cu2þ and 1; (iv) 0.75 equivalent of Cu2þ and 1; (v) 1 equivalent of Cu2þ
and 1; (vi) 1.5 equivalent of Cu2þ and 1.
2þ
C
(0, 2, 4, 8, 12, 16, 20, 24, 28, 32, 36 ꢀ 10ꢁ6 M) were obtained by
Cu
2þ
scanning these vials via the APP. In Fig. 5, the C
from 0 to
Cu
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
5
2þ
Fig. 5. The RGB colour values were caught through smartphone APP for confirming C in solvent.
Cu
36 ꢀ 10ꢁ6 M displayed a good linear relationship (R ¼ 0.98) to the
3.3. Preparation of tris[4-(1H-imidazole-1-yl)phenyl]amine
value of R/G. According to the calibration curve (R2 ¼ 0.98), the
linear equation (3) was obtained as
A DMF (50 mL) suspension of K2CO3 (1.27 g, 9.2 mmol), tris(4-
bromophenyl)amine (610 mg, 1.3 mmol), imidazole (920 mg,
13.5 mmol) and CuI (210 mg, 1.1 mmol) was stirred for 36 h at
130 ꢂC. After filtration, the mother solution was kept in ice bath for
0.5 h, and a white precipitate was formed. The precipitate was
separated by filtration. Then this solid was dissolved in ethanol
(100 mL), and the insoluble matter was removed through filtering.
The ethanol was removed by rotary evaporator to afford a white
powder of tris(4-(1H-imidazole-1-yl)phenyl)amine. Yield: 0.45 g
(80%). Mp: 243e245 ꢂC. Anal. Calcd for C27H21N7: C, 73.1; H, 4.7; N,
22.1%. Found: C, 73.05; H, 4.6; N, 22.35%. 1H NMR (400 MHz,
Y ¼ 0:02505X þ 1:05329
(3)
2þ
Cu
in which Y was R/G ratio and X was the C . Furthermore, the limit
of detection was calculated to be 0.51 mM.
3. Experimental section
3.1. General procedures
DMSO‑d6):
d
7.11 (s, 3H, ArH), 7.20 (d, J ¼ 8.8 Hz, 6H, ArH), 7.62 (d,
J ¼ 8.8 Hz, 6H, ArH), 7.69 (s, 3H, ArH), 8.20 (s, 3H, ArH).
1-(2-Bromoethoxy)-8-hydroxy-9,10-anthraquinone was pre-
pared according to the method reported in literature [30,31]. The
solvents and chemicals for experiment were analytical grade by
purchasing commercially. A RF-5301PC fluorescence spectropho-
tometer (Shimadzu) was used for the report of the fluorescence
spectra at room temperature (the emission and excitation slits were
10/10 nm). UVevis absorption spectra were recorded using JASCO-
V570 spectrometer at room temperature. 1H NMR and 13C NMR
spectra were collected using a Varian spectrometer. Perkin-Elmer
2400C Elemental Analyzer was applied in the test of elemental
analyses and the samples were prepared after crystallization.
Infrared spectra were reported applying a PerkinElmer spectro-
photometer. The Accurate-Mass Q-TOF LC/MS (Agilent) was applied
for recording ESI-MS spectra. A Boetius Block apparatus was
applied for measuring melting points.
3.4. Preparation of tris(4-(3-(2-((8-hydroxy-9,10-dioxo-90,100-
dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-30-ium-10-yl)
phenyl)amine hexafluorophosphate (1)
A DMF (100 mL) solution of tris(4-(1H-imidazole-1-yl)phenyl)
amine (150 mg, 0.3 mmol) and 1-(2-bromoethoxy)-8-hydroxy-
9,10-anthraquinone (350 mg, 1.0 mmol) was stirred for 48 h at
120 ꢂC. A yellow solid was precipitated after cooling to room tem-
perature. By filtration and washing with a small part of CH3CN, a
yellow powder of tris(4-(3-(2-((8-hydroxy-9,10-dioxo-90,100-dihy-
droanthracen-1-yl)oxy)ethyl)-1H-imidazole-30-ium-10-yl)phenyl)
amine bromide was obtained. And then this yellow powder was
dissolved in methanol (15 mL), following the methanol solution
(15 mL) of NH4PF6 (130 mg, 0.9 mmol) was added with stirring for
24 h at ambient temperature to form a yellow precipitate. A yellow
powder of tris(4-(3-(2-((8-hydroxy-9,10-dioxo-90,100-dihydroan-
thracen-1-yl)oxy)ethyl)-1H-imidazole-30-ium-10-yl)phenyl)amine
hexafluorophosphate (1) was gained by filtration. Yield: 0.35 g
3.2. Preparation of tris(4-bromophenyl)amine
A
chloroform solution (30 mL) of triphenylamine (5.50 g,
22.4 mmol) was stirred for 10 min at 0 ꢂC and then the bromine
(13.46 g, 84.2 mmol) was dropped slowly. The ethanol (100 mL) was
added when the solution color of the reaction turned green. The
mixture was continually stirred for 24 h at 40 ꢂC, and a large
amount of solid was formed. After filtration, the crude product was
washed with cold ethanol (20 mL) to obtain a white powder of
tris(4-bromophenyl)amine. Yield: 5.95 g (55%). Mp: 140e142 ꢂC.
Anal. Calcd for C18H12Br3N: C, 44.85; H, 2.5; N, 2.9%. Found: C, 44.6;
(71%). M.p: 259e260 ꢂC. HRMS (EI): m/z [(1 3PFꢁ6 )3þ
- /
3] ¼ 415.0414. Anal. Calcd for C75H54N7O12F18P3: C, 53.6; H, 3.2; N,
5.8%. Found: C, 53.7; H, 3.4; N, 6.0%. 1H NMR (400 MHz, DMSO‑d6):
d
4.68 (t, J ¼ 2.2 Hz, 6H, CH2), 4.84 (t, J ¼ 2.2 Hz, 6H, CH2), 7.25 (d,
J ¼ 8.4 Hz, 3H, ArH), 7.43 (d, J ¼ 8.8 Hz, 6H, ArH), 7.53 (d, J ¼ 7.6 Hz,
3H, ArH), 7.62 (t, J ¼ 8.0 Hz, 3H, ArH), 7.72 (d, J ¼ 8.8 Hz, 3H, ArH),
7.87 (t, J ¼ 3.8 Hz, 9H, ArH), 7.96 (t, J ¼ 4.0 Hz, 3H, ArH), 8.22 (s, 3H,
ArH), 8.37 (s, 3H, ArH), 10.11 (s, 3H, imiH), 12.40 (s, 3H, ArOH). 13
C
H, 2.3; N, 3.1%. 1H NMR (CDCl3, 400 MHz):
ArH), 7.36 (d, J ¼ 8.8 Hz, 6H, ArH).
d
6.93 (d, J ¼ 8.8 Hz, 6H,
NMR (100 MHz, DMSO‑d6):
d 48.7 (CH2), 67.0 (CH2), 116.6 (ArC),
118.4 (ArC), 120.0 (ArC), 120.2 (ArC), 120.9 (ArC), 123.2 (ArC), 124.3
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

6
Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
(ArC), 125.2 (ArC), 126.4 (ArC), 129.7 (ArC), 130.3 (ArC), 132.3 (ArC),
134.9 (ArC), 136.5 (ArC), 147.2 (ArC), 158.6 (ArC), 161.2 (ArC), 181.7
(CO), 188.1 (CO). IR (KBr, cmꢁ1): 3392s, 2938w, 2861w, 2403w,
2389w, 1653 m, 1574 m, 1435w, 1359w, 1289w, 1063vs, 1009 m,
937s, 761w, 741w, 517s.
Foundation of China (No. 21572159) and the Program for Innovative
Research Team in University of Tianjin (TD13-5074).
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2019.130675.
3.5. Fluorescent experiment
The stock solutions (1 ꢀ 10ꢁ4 M for 1 or 1 ꢀ 10ꢁ3 M for guests)
were prepared through dissolving 1 or the guests in DMSO/CH2Cl2
(v:v ¼ 1:49). In the screening experiments of cations, placed the
stock solutions (0.5 mL for 1 and 0.1 mL for guests) into a 10 mL
volumetric flask, which were diluted to 10 mL with DMSO/CH2Cl2
(v:v ¼ 1:49) to prepare test solutions (5 ꢀ 10ꢁ6 M for 1 and
10 ꢀ 10ꢁ6 M for guests). In fluorescence titrations, placed the stock
solutions (0.5 mL for 1 and 0e0.35 mL for guests) into a 10 mL
volumetric flask, which were diluted to 10 mL with DMSO/CH2Cl2
(v:v ¼ 1:49) to prepare test solutions (5 ꢀ 10ꢁ6 M for 1 and
0e35 ꢀ 10ꢁ6 M for guests). After adding Cu2þ, an equilibration time
of 10 min was allowed before the fluorescence spectra were
recorded, and the colour change was from yellow to orange under
sunlight within 1 min. A Shimadzu RF-5301PC fluorescence spec-
trophotometer was applied for reporting fluorescence spectra in
the range of 485e710 nm, and the excitation wavelength was
415 nm (slit: 10 nm/10 nm).
References
[1] Z.M. Bao, C.X. Qin, J.J. Wang, J. Sun, L.X. Dai, G.Q. Chen, F. Mei, Sens. Actuators,
B 265 (2018) 234e241.
[2] Q. Zou, X. Li, J. Zhang, J. Zhou, B. Sun, H. Tian, Chem. Commun. 48 (2012)
2095e2097.
[3] Z.Q. Guo, W.Q. Chen, M.X. Chen, Org. Lett. 12 (2010) 2202e2205.
[4] S. Dalapati, S. Jana, M.A. Alam, N. Guchhait, Sens. Actuators, B 160 (2011)
1106e1111.
[5] N. Shao, G.X. Pang, X.R. Wang, R.J. Wu, Y. Cheng, Tetrahedron 66 (2010)
7302e7308.
[6] M. Linder, A.M. Hazegh, Am. J. Clin. Nutr. 63 (1996) 797e811.
[7] R. Uauy, M. Olivares, M. Gonzalez, Am. J. Clin. Nutr. 67 (1998) 952e959.
[8] B. Zhang, Q. Diao, P. Ma, X. Liu, D. Song, X. Wang, Sens. Actuators, B 225 (2016)
579e585.
[9] D.J. Waggoner, T.B. Bartnikas, J.D. Gitlin, Neurobiol. Dis. 6 (1999) 221e230.
[10] G.J. Brewer, Curr. Opin. Chem. Biol. 7 (2003) 207e212.
[11] K.J. Barnham, A.I. Bush, Curr. Opin. Chem. Biol. 2 (2008) 222e228.
[12] P. Zatta, A. Frank, Brain Res. Rev. 54 (2007) 19e33.
[13] J. Emerit, A. Edeas, F. Bricaire, Biomed. Pharmacother. 1 (2004) 39e46.
[14] Z.F. Xu, P.H. Deng, J.H. Li, S.P. Tang, Sens. Actuators, B 255 (2018) 2095e2104.
[15] H.S. Jung, X. Chen, J.S. Kim, J. Yoon, Chem. Soc. Rev. 42 (2013) 6019e6031.
[16] X. Chen, F. Wang, J.Y. Hyun, T. Wei, J. Qiang, X. Ren, I. Shin, J. Yoon, Chem. Soc.
Rev. 45 (2016) 2976e3016.
3.6. UV titrations
[17] S.J. Ranee, G. Sivaraman, A.M. Pushpalatha, S. Muthusubramanian, Sens. Ac-
tuators, B 255 (2018) 630e637.
[18] L.N. Li, S.S. Shen, R.Y. Lin, Y. Bai, H.W. Liu, Chem. Commun. 53 (2017)
9986e9989.
[19] J. Wang, H.Y. Chen, F. Ru, Z. Zhang, X. Mao, D.L. Shan, J. Chen, X.Q. Lu, Chem.
Eur. J. 24 (2018) 3499e3505.
[20] Z.P. Li, Y.W. Zhang, H. Xia, Y. Mu, X.M. Liu, Chem. Commun. 52 (2016)
6613e6616.
[21] K.C. Ko, J.S. Wu, H.J. Kim, P.S. Kwon, J.W. Kim, R.A. Bartsch, J.Y. Lee, J.S. Kim,
Chem. Commun. 11 (2011) 3165e3167.
In UV titrations, we prepared the stock solutions using similar to
2þ
the methods of fluorescent titrations. The C1 and C
were
Cu
1 ꢀ 10ꢁ5 moL/L and 0e4 ꢀ 10ꢁ5 moL/L. A JASCO-V570 spectrometer
was used for recording absorption spectra in the range of
373e485 nm at room temperature.
[22] S.P. Wu, T.H. Wang, S.R. Liu, Tetrahedron 51 (2010) 9655e9658.
[23] R.L. Sheng, P.F. Wang, Y.H. Gao, Y. Wu, W.M. Liu, J.J. Ma, H.P. Li, S.K. Wu, Org.
Lett. 21 (2008) 5015e5018.
3.7. Job’s plot
[24] Y. Wang, H. Wu, W.N. Wu, S.J. Li, Z.H. Xu, Z.Q. Xu, Sens. Actuators, B 260 (2018)
106e115.
[25] J.L. Zhao, H. Tomiyasu, C. Wu, H. Cong, X. Zeng, S. Rahman, Tetrahedron 71
(2015) 8521e8527.
[26] Y. Wang, P.D. Mao, W.N. Wu, X.J. Mao, Y.C. Fan, X.L. Zhao, Sens. Actuators, B
255 (2018) 3085e3092.
[27] V.K. Gujuluva Gangatharan, K. Mookkandi Palsamy, S. Gandhi, A. Jamespandi,
A. Kandasamy, T. Arunachalam, Sens. Actuators, B 255 (2018) 3235e3247.
[28] J. Tang, S.G. Ma, D. Zhang, Y.Q. Liu, Y.F. Zhao, Y. Ye, Sens. Actuators, B 236
(2016) 109e115.
We prepared also the stock solutions using similar to the
methods of fluorescent tests. The total concentration maintained
2þ
10 ꢀ 10ꢁ6 M in the test solutions, and the molar ratios of C /C1
Cu
changed from 0:1 to 1:0. The absorption spectra were recorded on
according to the methods of UV titrations.
4. Conclusions
[29] S. Li, D. Zhang, X.Y. Xie, S.G. Ma, Y. Liu, Z.H. Xu, Y.F. Gao, Y. Ye, Sens. Actuators,
B 223 (2016) 661e667.
[30] Q.X. Liu, Z.L. Hu, Z.X. Zhao, Tetrahedron 74 (2018), 6710-6710.
[31] Q.X. Liu, Z.L. Hu, Z.X. Zhao, New J. Chem. 42 (2018) 20049e20055.
[32] M.G. Siskos, A.G. Tzakosa, I.P. Gerothanassis, Org. Biomol. Chem. 13 (2015)
8852e8868.
[33] F.E. Hahn, M.C. Jahnke, T. Pape, Organometallics 26 (2007) 150e154.
[34] P.L. Arnold, I.J. Casely, Chem. Rev. 109 (2009) 3599e3611.
[35] F.E. Hahn, M.C. Jahnke, Angew. Chem. Int. Ed. 47 (2008) 3122e3172.
[36] X.L. Liu, W.Z. Chen, Organometallics 31 (2013) 6614e6622.
[37] Q. Li, X. Li, J. Yang, H.B. Song, L.F. Tang, Polyhedron 59 (2013) 29e37.
[38] J.H. Chen, X.Q. Zhang, Q. Feng, M.M. Luo, J. Organomet. Chem. 691 (2006)
470e474.
[39] Z.X. Sun, Y. Cheng, Org. Biomol. Chem. 10 (2012) 4088e4094.
[40] B. Liu, Q. Xia, W.Z. Chen, Angew. Chem. Int. Ed. 48 (2009) 5513e5516.
[41] D. Escudero, Acc. Chem. Res. 49 (2016) 1816e1824.
[42] D. Aigner, S.A. Freunberger, M. Wilkening, R. Saf, S.M. Borisov, I. Klimant, Anal.
Chem. 86 (2014) 9293e9300.
In sum, a new compound tris(4-(3-(2-((8-hydroxy-9,10-dioxo-
90,100-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-30-ium-10-
yl)phenyl)amine hexafluorophosphate (1) was prepared and char-
acterized. The cation recognition performance of 1 was explored
through fluorescent and ultraviolet titrations, MS, 1H NMR titra-
tions and IR spectra. These results displayed that 1 was of good
selectivity for Cu2þ. After 1 was mixed with Cu2þ, a distinct and
quick colour change from yellow to orange under sunlight within
1 min was observed for naked eyes accompanying with obvious
fluorescent reducing. Even if the limit of detection was down to
0.049 m
M, the detection of 1 to Cu2þ was still sensitive. Further-
more, this chemosensor can be also used in the detecting Cu2þ
through applying smartphone with the computed detection limit
down to 0.51
mM. Therefore, compound 1 may have latent uses for
[43] S. Dalapati, S. Jana, N. Guchhait, Spectrochim. Acta Part A Mol. Biomol. Spectr.
129 (2014) 499e508.
[44] D. Collado, E.P. Inestrosa, R. Suaua, J.T.L. Navarrete, Tetrahedron 62 (2006)
2927e2935.
detection of Cu2þ
.
[45] F. Zhang, L. Luo, Y. Sun, F.J. Miao, J.H. Bi, S.L. Tan, D.M. Tian, H.B. Li, Tetrahedron
69 (2013) 9886e9889.
Acknowledgements
[46] H. Swaminathan, B. Karthikeyan, Sens. Actuators, B 264 (2018) 337e343.
[47] A. Caballero, R. Martinez, V. Lloveras, I. Ratera, J. Vidal-Gancedo, K. Wurst,
A. Tarraga, P. Molina, J. Veciana, J. Am. Chem. Soc. 127 (2005) 15666e15667.
Financial supports for this work were by Tianjin Natural Science
Foundation (No. 18JCZDJC99600), the National Natural Science
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675

Z.-X. Zhao et al. / Tetrahedron xxx (xxxx) xxx
7
[48] M.B. Gu, L.Y. Huang, Z.F. Xu, Z. Tan, M. Hua, Z.T. Yang, Y.X. Chen, C. Peng,
1992e2002.
W.P. Xiao, D.H. Yu, H.T. Li, Sens. Actuators, B 273 (2018) 118e125.
[49] X.H. Huang, L.J. Wang, X.J. Zhang, X.H. Yin, N. Bin, F.F. Zhong, Y.J. Liu, Q.Y. Cai,
Sens. Actuators, B 48 (2017) 1e8.
[57] P. Yin, M.C. Mala, H.C. Ma, Fine Chem. 36 (2019) 212e217.
[58] A. Mondal, A.R. Chowdhury, S. Bhuyan, S.K. Mukhopadhyay, P. Banerjee,
Dalton Trans. 48 (2019) 4375e4386.
[50] M.J. Cao, L.N. Jiang, F. Hu, Y.F. Zhang, W.C. Yang, S.H. Liu, J. Yin, RSC Adv. 5
(2015) 23666e23670.
[51] L. Wang, W.X. Li, W.J. Zhi, Y. Huang, J. Han, Y. Wang, Y.P. Ren, L. Ni, Sens.
Actuators, B 260 (2018) 243e254.
[52] X.L. Zhang, X.H. Guo, H.H. Yuan, X. Jia, B. Dai, Dyes Pigments 155 (2018)
100e106.
[53] J.S. Wang, S.G. Bodige, W.H. Watson, C.D. Gutsche, J. Org. Chem. 65 (2000)
8260e8263.
[54] B. Biswal, D. Mallick, M. Thirunavoukkarasu, R. Mohanty, B. Bag, Sens. Actu-
ators, B 232 (2016) 410e419.
[55] Y.Z. Lin, Y.F. Wang, J.Y. Wang, J.H. Hou, Y.F. Li, D.B. Zhu, X.W. Zhan, Adv. Mater.
26 (2014) 5137e5142.
[59] J.T. Yeh, W.C. Chen, S.R. Liu, S.P. Wu, 38 (2014) 4434-4439.
[60] T.M. Elmorsi, T.S. Aysha, O. Machalicky, M.B.I. Mohamed, A.H. Bedair, Sens.
Actuators, B 253 (2017) 437e450.
[61] Q.X. Liu, Z.Q. Yao, X.J. Zhao, Z.X. Zhao, X.G. Wang, Organometallics 32 (2013)
3493e3501.
[62] A.S. Mahadevi, G.N. Sastry, Chem. Rev. 113 (2013) 2100e2138.
[63] K. Ishihara, M. Fushimi, M. Akakura, Acc. Chem. Res. 40 (2007) 1049e1055.
[64] S. Sumriddetchkajorn, K. Chaitavon, Y. Intaravanne, Sens. Actuators, B 182
(2013) 592e597.
[65] Y. Upadhyay, S. Bothra, R. Kumar, S.K. Sahoo, Chemistry Select 3 (2018)
6892e6896.
[66] Y. Upadhyay, T. Anand, L.T. Babu, P. Paira, A.K. SK, R. Kumar, S.K. Sahoo,
J. Photochem. Photobiol., A 361 (2018) 34e40.
[56] R.V. Ambili, D. Sasikumar, P. Hridya, M. Hariharan, Chem. Eur. J. 25 (2019)
Please cite this article as: Z.-X. Zhao et al., A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion, Tetrahedron, https://
doi.org/10.1016/j.tet.2019.130675