Highly selective probes of copper(II) complexes for sulfide detection and cytotoxicity assay

Article abstract of DOI:10.1080/17415993.2018.1425410

Two probes based on novel Copper(II) complexes were developed in order to obtain H₂S molecular probes with higher selectivity. The molecular structures of the complexes were characterized by ¹H NMR, HRMS, IR and elemental analysis. The interaction of the compounds with biologically important anions and amino acids was determined by UV-vis and Fluorescence titration experiments. Results indicated that the compounds showed the highest binding ability for HS^? among studied anions (AcO^?, H₂PO₄ ^?, F^?, Cl^?, Br^? and I^?) and amino acids (GSH, HCys and Cys) accompanied by blue shift phenomenon in pure DMSO and aqueous solution. The possible mechanism of host–guest interaction may be that the Copper(II) ion of complex was captured by HS^? and free ligand released which showed a remarkable changes in UV-vis absorption. In addition, cytotoxicity of the synthesized compounds was studied on MCF-7 cells. Results indicated that the synthesized compounds had low cytotoxicity over a concentration range of 0–150 μg?mL^?1, which exhibited that the synthesized probes could be used to detect H₂S in vivo. The probes based on novel copper(II) complexes were synthesized and obtained by the reaction of substituent salicylaldehyde with amine derivatives, and then reacted with Cu(CH₃COO)₂·H₂O, respectively. Investigation on the interference from other species suggested that copper(II) complexes have high selectivity for HS^? over other anions (AcO^?, (Formula presented.), F^?, Cl^?, Br^? and I^?), followed by the release of the copper ion to give a remarkable increase in UV–VIS absorption in pure DMSO solution and aqueous solution.

Full text of DOI:10.1080/17415993.2018.1425410

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Highly selective probes of copper(II) complexes for
sulfide detection and cytotoxicity assay
Yanmei Chen, Xuefang Shang, Xing Zhao, Jie Li, Jianmei Yuan, Hongli Chen,
Jinlian Zhang & Tianyun Wang
To cite this article: Yanmei Chen, Xuefang Shang, Xing Zhao, Jie Li, Jianmei Yuan,
Hongli Chen, Jinlian Zhang & Tianyun Wang (2018): Highly selective probes of copper(II)
complexes for sulfide detection and cytotoxicity assay, Journal of Sulfur Chemistry, DOI:
10.1080/17415993.2018.1425410
To link to this article: https://doi.org/10.1080/17415993.2018.1425410
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JOURNAL OF SULFUR CHEMISTRY, 2018
https://doi.org/10.1080/17415993.2018.1425410
Highly selective probes of copper(II) complexes for sulfide
detection and cytotoxicity assay
Yanmei Chena, Xuefang Shanga, Xing Zhaob, Jie Lia, Jianmei Yuana, Hongli Chenc,
Jinlian Zhangd and Tianyun Wange
aKey Laboratory of Medical Molecular Probes, School of Basic Medical Sciences, Xinxiang Medical University,
Xinxiang, Henan, People’s Republic of China; bThe Third Affiliated Hospital of Xinxiang Medical University,
Xinxiang, Henan, People’s Republic of China; cSchool of Life Sciences and Technology, Xinxiang Medical
University, Xinxiang, Henan, People’s Republic of China; dSchool of Pharmacy, Xinxiang Medical University,
Xinxiang, Henan, People’s Republic of China; eDepartment of Biochemistry, Xinxiang Medical University,
Xinxiang, Henan, People’s Republic of China
ABSTRACT
ARTICLE HISTORY
Received 4 July 2017
Accepted 1 January 2018
Two probes based on novel Copper(II) complexes were developed
in order to obtain H2S molecular probes with higher selectivity.
The molecular structures of the complexes were characterized by
1H NMR, HRMS, IR and elemental analysis. The interaction of the
compounds with biologically important anions and amino acids
was determined by UV-vis and Fluorescence titration experiments.
Results indicated that the compounds showed the highest binding
ability for HS− among studied anions (AcO−, H2PO4−, F−, Cl−, Br−
and I−) and amino acids (GSH, HCys and Cys) accompanied by blue
shift phenomenon in pure DMSO and aqueous solution. The possi-
ble mechanism of host–guest interaction may be that the Copper(II)
ion of complex was captured by HS− and free ligand released which
showed a remarkable changes in UV-vis absorption. In addition, cyto-
toxicity of the synthesized compounds was studied on MCF-7 cells.
Results indicated that the synthesized compounds had low cytotoxi-
city over a concentration range of 0–150 µg · mL−1, which exhibited
that the synthesized probes could be used to detect H2S in vivo.
The probes based on novel copper(II) complexes were synthe-
sized and obtained by the reaction of substituent salicylaldehyde
with amine derivatives, and then reacted with Cu(CH3COO)2·H2O,
respectively. Investigation on the interference from other species
suggested that copper(II) complexes have high selectivity for HS−
over other anions (AcO−, H2PO4−, F−, Cl−, Br− and I−), followed by
the release of the copper ion to give a remarkable increase in UV–VIS
absorption in pure DMSO solution and aqueous solution.
KEYWORDS
Copper(II) complex;
hydrogen sulfide; UV–VIS
titration; fluorescence probe;
cytotoxicity
CONTACT Xuefang Shang
xuefangshang@126.com
Key Laboratory of Medical Molecular Probes, School of
Basic Medical Sciences, Xinxiang Medical University, Xinxiang, Henan 453003, People’s Republic of China
This article makes reference to supplementary material available on the publisher’s website at https://doi.org/10.1080/
17415993.2018.1425410
© 2018 Informa UK Limited, trading as Taylor & Francis Group

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Y. CHEN ET AL.
1. Introduction
Hydrogen sulfide, a foul-smelling gas and commonly being perceived as a toxic indus-
trial exhalation, is considered as the third signaling molecule in vivo as well as nitric oxide
[1–10] and carbon monoxide [11]. H2S can be produced by three typical pathways includ-
ing cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptropyruvate
sulfurtransferase (3-MPST) in different organs and tissues [3,12]. Studies have shown that
the H2S plays some important roles in various physiological processes in vivo, such as
vasodilation apoptosis, neurotransmission ischemia/reperfusion-induced injury, insulin
secretion and inflammation [4,13–18]. On the other hand, studies have established that the
abnormal level of H2S in cells may cause many types of disorders including Down’s syn-
drome, Alzheimer’s disease, liver cirrhosis and diabetes [1,8,19–23]. Therefore, it presents
a significant research value to develop efficient methods that can detect H2S in living bio-
logical systems. Traditional methods with complicated sample preparation and tissue or
cell destruction including colorimetry, gas chromatography, electrochemical analysis and
use of fluorescent have drawbacks for H2S detection [24]. Herein, we synthesized copper
complex for the detection of H2S which could be applied in the sample of environment,
pharmacy and so on with highly selective ability [25–28].
In the present work, bis(salicylaldehyde-o-nitroaniline) copper(II) and bis(5-nitro
alicylaldehyde-α-naphthylamine) copper(II) probes were synthesized to detect HS−
(Scheme 1). The results showed that the synthesized compounds especially bis(salicylal-
dehyde-o-nitroaniline) copper(II) have−high selectivity and good sensitivity to HS− among
the tested anions (HS−, AcO−, H2PO4 , F−, Cl−, Br− and I−) and amino acids (such as
GSH, HCys and Cys).
2. Results and discussion
2.1. UV–VIS titration
The binding properties of synthesized copper complexes (1 and 2) with various anions
(HS−, AcO−, H2PO−4 , F−, Cl−, Br− and I−) and amino acids (Cys, GSH and HCys)
were investigated through UV–VIS spectroscopy in DMSO at 298 K. The UV–VIS spectral
responses of copper complexes 1 during the titration with HS− in DMSO are shown in
Figure 1(a). In the absence of NaHS, compound 1 (4.0 × 10−5 mol L−1 in DMSO) revealed
a strong absorption band at about 375 nm. With the increase in the amount of HS−,
the intensity of absorption band decreased gradually. At the same time, a new absorp-
tion peak appeared centered at about 340 nm and the intensity increased gradually. In

JOURNAL OF SULFUR CHEMISTRY
3
Scheme 1. Synthesis route for copper(II) complex.
general, the absorption peak shifted to the short wavelength direction with the addition
of HS−. As a result, the blue shift phenomenon occurred after compound 1 interacted
with HS−. One clear isosbestic point appeared at 375 nm which indicated that the interac-
tion existed between compound 1 and HS−. In addition, there was a certain stoichiometric
ratio between the Cu(II) complex and HS−. Analogous investigations were carried out on
other normal anions (AcO−, H2PO−4 , F−, Cl−, Br− and I−) and amino acids (Cys, GSH
and HCys). The addition of H2PO−4 , Cys, GSH and HCys induced similar spectral changes
of Cu(II) complex compared with the addition of HS− (supplementary material, http://dx.
doi.org/10.1080/17415−993.2018.1425410). The above results indicated compound 1 also
interacted with H2PO4 , Cys, GSH and HCys. However, the addition of AcO−, F−, Cl−,
Br− and I− did not induce any spectral responses which indicated that complex 1 showed
almost no binding ability toward these anions or the binding abilities were very small and
could be ignored.
The spectral changes of compound 2 with HS− are also shown in Figure 1(b). We could
see that the absorbance intensity of compound 2 at 375 nm decreased with the increase in
HS− concentration. At the same time, a new absorption peak developed at about 450 nm
and the intensity increased gradually. In addition, one clear isosbestic point formed at
402 nm and the absorbance peak of compound 2 shifted to long wavelength direction
gradually. The addition of H2PO−4 , AcO−, Cys, GSH and HCys induced similar spectral
changes compared with HS− which showed H2PO−, AcO−, Cys, GSH and HCys inter-
acted with complex 2 (supplementary material, http4://dx.doi.org/10.1080/17415993.2018.
1425410). While, the additions of F−, Cl−, Br− and I− almost did not induce any spectral

4
Y. CHEN ET AL.
Figure 1. UV–VIS spectra of compounds (1 and 2) (4.0 × 10−5 mol L−1) with the addition of
HS− in DMSO solution. (a) Compound 1 (HS− (0–64.8) × 10−5 mol L−1) and (b) compound 2
(HS−(0–25.6) × 10−5 mol L−1). Arrows indicate the direction of increasing HS− concentration.

JOURNAL OF SULFUR CHEMISTRY
5
changes of compound 2 which indicated the binding abilities were very weak and could be
ignored.
Owing to complexes (1 and 2) having the strongest binding ability for HS− among
anions tested (HS−, AcO−, H2PO4−, F−, Cl−, Br− and I−) and in pure DMSO solvent, com-
plex 1 was tested in the DMSO–H2O (1:1, v/v) solution shown in supplementary material
(http://dx.doi.org/10.1080/17415993.2018.1425410). The addition of HS− induced simi-
lar spectral changes that were found in the DMSO–H2O (1:1, v/v) solution compared with
pure DMSO solvent. However, the response of UV–VIS spectra was weaker than that of
pure DMSO solvent which showed that the binding ability was weak to a certain degree.
The addition of H2PO−4 induced weak spectral changes at 381 nm compared with pure
DMSO solvent. However, the other anions (AcO−, F−, Cl−, Br− and I−) induced a murky
phenomenon. The above results exhibited that complex 1 could be used as a sensor for the
detection of HS− in aqueous solution.
Besides, the binding abilities of compound 1 and 2 with HS− (Figure 2(a,b)) were also
determined in HEPES buffer solution. Results indicated that the interaction existed in
host–guest. Similar spectral changes of complexes (1 and 2) with anions tested (AcO−,
H2PO−4 , F−, Cl−, Br− and I−) and amino acids (Cys, GSH and HCys) in pure DMSO
solvent compared with HS− were reported; and data are given in the supplementary
material (http://dx.doi.org/10.1080/17415993.2018.1425410). Results indicated that two
compounds showed different binding abilities for Cys, GSH and HCys which were weaker
than that of HS−. The reason may be that the copper(II) ion of the complex was cap-
tured by HS− and the free ligand was released after the copper complex interacted with
HS− [29,30]. UV–VIS spectral responses of compounds (1 and 2) (4.0 × 10−5 mol L−1
)
upon the addition of anions (AcO−, H2PO−4 , F−, Cl−, Br− and I−) and GSH are shown in
Figure 3 and (S-12), respectively. Results indicated that the high selectivity and sensitivity
of the copper(II) complex for HS− were not affected by the existence of other anions and
GSH.
Furthermore, the detection limit of compound 1 (4.0 × 10−5 mol L−1) was carried out
in pure DMSO solution through UV–VIS titration as shown in Figure 4. In the absence
of NaHS, the absorbance value of compound 1 (4.0 × 10−5 mol L−1) was 0.515 at 375 nm.
The absorption coefficient was calculated and the value was 10.4 mol cm. Compound 1
(4.0 × 10−5 mol L−1) and the concentration of HS− (0–5.6 × 10−5 mol L−1) have a good
linear relationship by UV–VIS intensity which indicated the quantitative detection of
HS− ranging from 0 to 5.6 × 10−5 mol L−1. The addition of HS− (3.2 × 10−5 mol L−1
)
to compound 1 leads to 1.3 times increase in the corresponding UV–VIS inten-
sity. The above results exhibited the detection limit of compound 1 for HS− was
3.2 × 10−5 mol L−1. Analogously, the detection limit of compound 1 (4.0 × 10−5 mol L−1
)
was also determined (supplementary material, http://dx.doi.org/10.1080/17415993.2018.
1425410). The value of the absorption coefficient for compound 2 (4.0 × 10−5 mol L−1
)
was 44.5 mol cm and the detection limit of compound 2 (4.0 × 10−5 mol L−1) for HS− was
4 × 10−6 mol L−1
.
2.2. Fluorescence response
The fluorescence properties of two compounds (1–2) after the addition of anions and
amino acids tested were also investigated in pure DMSO solution. Compound 1 exhibited

6
Y. CHEN ET AL.
Figure 2. UV–VIS spectra of compound (1 and 2) (4.0 × 10−5 mol L−1
)
toward HS−
((0–80) × 10−5 mol L−1) was recorded in DMSO–H2O (1:1, v/v 0.04 mol L−1 HEPES buffer at pH
7.38). (a) compound 1 (HS− (0–80) × 10−5 mol L−1) and (b) compound 2 (HS− (0–80) × 10−5 mol L−1).
Arrows indicate the direction of increasing HS− concentration.

JOURNAL OF SULFUR CHEMISTRY
7
Figure 3. UV–vis sp−ectral responses of compound 1 (4.0 × 10−5 mol L−1) upon the addition of 8 equiv
anions (AcO−, H2PO4 , F−, Cl−, Br− and I−) and 8 equiv GSH.
Figure 4. UV–VIS intensity of compound 1 in pour DMSO solution as a function of concentrations of
HS−.
an emission peak at about 340 nm. With the increasing concentration of HS−, the fluores-
cence emission was decreased obviously at about 343 nm (Figure 5(a)). The addition of Cys,
GSH and HCys induced similar fluorescence spectral changes of compound 1 compared
with the addition of HS− (supplementary material, http://dx.doi.org/10.1080/17415993.
2018.1425410). However, the additions of H2PO−, AcO−, F−, Cl−, Br− and I− produced
a nominal change in the fluorescence spectral of4the probe.
For compound 2, the fluorescence emission centered at 433 nm was gradually strength-
ened upon the addition of HS− (Figure 5(b)), which was because the addition of HS−
could c−oordinate with Cu2+ and release the free ligand. Upon the addition of other anions
(H2PO4 , AcO−) and amino acids (Cys, GSH and HCys) into the solution of compound

8
Y. CHEN ET AL.
Figure 5. Fluorescence response of compound (1 and 2) (4.0 × 10−5 mol L−1) up on the addition of
HS− in pure DMSO solution. (a) Fluorescence response (λex 289 nm, slit widths: 10 nm/10 nm) of com-
pound 1 up on the addition of HS− ((0–80) × 10−5 mol L−1) and (b) Fluorescence response (λex 327 nm,
slit widths: 2.5 nm/5 nm) of compound 2 up on the addition of HS− ((0–80) × 10−5 mol L−1). Arrows
indicate the direction of increasing HS− concentration.
2 induced similar fluorescence spectral changes of compound 2 compared with the addi-
tion of HS− (supplementary material, http://dx.doi.org/10.1080/17415993.2018.1425410).
There were no significant spectral changes observed upon the titration of compound 2 with
(Cl−, Br− and I−).
Then fluorescence spectral changes data of compounds (1–2) upon the addition of var-
ious anions (HS−, H2PO−4 , AcO−, F−, Cl−, Br− and I−) and amino acids (Cys, GSH and

JOURNAL OF SULFUR CHEMISTRY
9
Figure 6. Fluorescence spectral changes of compounds (1–2) upon the addition of various anions and
amino acids in pure DMSO solution. Fluorescence response (λex 289 nm, slit widths:10 nm/10 nm) of
compound 1 (4 × 10−5 mol L−1) upon the addition of various anions (HS−, AcO−, H2PO−4 , F−, Cl−, Br−
and I−) ((0–80) × 10−5 mol L−1) and amino acids (GSH, HCys and Cys) ((0–80) × 10−5 mol L−1). Fluo-
rescence response (λex, 327 nm, slit widths: 2.5 nm/5 nm) of compound 2 (4 × 10−5 mol L−1) up on the
addition of various various anions (HS−, AcO−, H2PO4−, F−, Cl−, Br− and I−) ((0–80) × 10−5 mol L−1
and amino acids (GSH, HCys and Cys) ((0–80) × 10−5 mol L−1).
)
HCys) were analyzed by using the bar graph in pure DMSO solution as shown in Figure 6.
The results also indicated th−at compounds (1–2) exhibited a different binding ability with
various anions (HS−, H2PO4 , AcO− and F−) and amino acids (Cys, GSH and HCys), and
complexes (1–2) showed a stronger binding ability for HS− than other anions (H2PO4−,
F−, AcO−, Cl−, Br− and I−) amino acids (Cys, GSH and HCys).
Besides, a comparison of spectra of compounds (1–2) measured in the presence of HS−
with the spectra of plain ligands is shown in Figure 7. And the spectra of compounds (1–2)
in the presence of HS− and plain ligands had the same emission. The result also indicated
the reason may be that the copper(II) ion of the complex was captured by HS− and free
ligand was released after the copper complex interacted with HS−.
2.3. Binding constants
Complexes 1 and 2 interacted with various anions as the ratio of 1:1 or 1:2 according
to the Job-plot curve (supplementary material, http://dx.doi.org/10.1080/17415993.2018.
1425410).
The binding constants of compounds with various anions and amino acids in DMSO
and DMSO/H2O solution were calculated using the method of non-linear least square
calculation [31–33]. The obtained binding constants are listed in the Table 1 and in the
supplementary material (http://dx.doi.org/10.1080/17415993.2018.1425410) according to

10
Y. CHEN ET AL.
Figure 7. A comparison of fluorescence spectra of compounds 2 (4.0 × 10−5 mol L−1) in the presence
of 0.8 equiv HS− with the spectra of plain ligand (4.0 × 10−5 mol L−1).
Table 1. Binding constants of Cu(II) complex with various anions.
Anion
Ks(1)(DMSO)
Ks(1)(DMSO:H2O (1:1v/v))
Ks(2)(DMSO)
HS−
(1.32 0.01) × 107a
(1.99 0.03) × 106a
(7.06 0.02) × 107a
(4.86 0.12) × 103b
(4.27 0.04) × 103b
ND
H2PO−
AcO−4
F−
(7.85 0.05) × 103b
(1.95 0.07) × 104ab
ND
ND
ND
ND
ND
ND
Cl− (Br− or I−)
ND
aThe binding ratio of host–guest is 1:2.
bThe binding ratio of host–guest is 1:1.
UV–VIS data. The binding ability trend of two complexes to anions and amino acids fol-
lowed the order of HS− > Cys, GSH and HCys > H2PO4− > AcO− ꢀ F−. In addition,
the binding constants of compounds with various anions and amino acids in HEPES solu-
tion were also calculated (supplementary material, http://dx.doi.org/10.1080/17415993.
2018.1425410). Results indicated that the binding ability trend was the same as the DMSO
solvent. In general, both the two complexes showed the strongest selectivity for HS− among
anions and amino acids tested. The reason may be that the copper(II) ion of the complex
was captured by HS− and the free ligand was released after the copper complex interacted
with HS−. These binding constants could provide a theoretical basis for the optimization
of sensor and so the calculation of binding constant was necessary.
2.4. Cytotoxicity assay
Scientific research suggests that glutathione peroxidase (GPx1) is an important
selenoprotein which is expressed in most tissues. However, GPx1 is not found in human
breast cancer cells (MCF-7). Therefore, we chose the MCF-7 cell, the special cell lines
[34,35]. Cytotoxicity of the compounds toward a cervical cancer cell line (MCF-7 cell)
was evaluated using a conventional MTT assay. No remarkable differences in the prolif-
eration of the cells were observed in the absence and presence of the fluorescence probe

JOURNAL OF SULFUR CHEMISTRY
11
Figure 8. Cellviabilityvalues(%)estimatedbyanMTTproliferationtestversusincubationconcentration
offluorescenceprobe.MCF-7cellswereculturedinthepresenceof0–150 μg mL−1 offluorescenceprobe
at 37°C for 24 h. Cell viability (expressed in%) was calculated considering 100% growth in the absence of
fluorescence probe.
(0–150 μg mL−1) (Figure 8). The cellular viability was estimated to be 80% after 24 h of
incubation with the fluorescence probe <150 μg mL−1. The anticipated cytotoxicity of the
fluorescence probe ( <150 μg mL−1) was expected to be low. In combination with binding
constants, compound 1 showed high binding ability and low cell cytotoxicity and may be
used to detect H2S in vivo.
3. Conclusion
In summary, we reported the development probes of copper complex for H2S detection
which were designed and synthesized based on an inorganic reaction. The probes, espe-
cially complex 1, exhibited highly sensitivity and selectivity to H2S among various relevant
anions and amino acids species in HEPES buffer solution. In addition, both two com-
pounds showed low cytotoxicity to MCF-7 cells. Therefore, these probes for hydrogen
sulfide could explain the function of this signaling molecular in the broader biological
environment and may assist to build up new diagnostic and therapeutic agents in neu-
rodegenerative and cardiovascular disease. Furthermore, the synthesized small molecular
compound can be used as an efficient probe to investigate functions that are related to H2S.
4. Material and methods
All reagents and solvents used were of analytical grade. Sodium hydrosulfide hydrate, all
anions in the form of tetrabutylammonium salts (such as (n-C4H9)4NCl, (n-C4H9)4NBr,
(n-C4H9)4NI, (n-C4H9)4NAcO and (n-C4H9)4NH2PO4), all amino acids (such as GSH,
HCys and Cys) and HEPES were purchased from Aladdin Chemistry Co. Ltd (Shanghai,
China). All anions and amino acids were stored in a desiccator under vacuum and used
without any further purification. Dimethyl sulfoxide (DMSO) was distilled in vacuum
after being dried with CaH2. 1H NMR spectra were recorded on a Unity Plus-400-MHz

12
Y. CHEN ET AL.
spectrometer. HRMS was performed with a Mariner apparatus. UV–VIS titration experi-
ments were made on a Shimadzu UV2550 Spectrophotometer (Shimadzu, Japan) at 298 K.
Fluorometric titration was performed on a Cary Eclipse Fluorescence Spectrophotometer
(Agilent, USA) at 298 K. IR was performed with a Shimadzu IRT racer-100 (Shimadzu,
Japan). The binding constant, Ks, was obtained by the non-linear least squares calculation
method for data fitting.
The cells at the logarithmic growth phase were seeded into a 96-well plate at a density
of 2.0 × 104 cells/well and cultured for 24 h. After that, the culture media were replaced
with 200 μL of RPMI 1640 medium containing different concentrations of the compound
and the cells were further incubated for 24 h. Next, the cells were washed with PBS three
times, and then 100 μL of the culture medium and 20 μL of MTT solution were, respec-
tively, added to each well. After additional incubation (4 h), the absorbance of each well
was detected at 490 nm using the microplate reader (Thermo Multiscan MK3, Thermo
Fisher Scientific, MA, USA) with the plain cell culture media as the control. The survival
curves were plotted and the IC50, defined as the compound concentrations required for
80% inhibition of cell growth, was calculated based on the survival curves.
4.1. Synthesis of Cu(II) complex
• Cu(II) complexes were synthesized according to the route shown in Scheme 1.
• Bis(salicylaldehyde-o-nitroaniline) copper(II) (compound 1).
Salicylaldehyde-o-nitroaniline was synthesized according to the literatures [36–38]. Sal-
icylaldehyde (1.22 g, 10 mmol) was dissolved in ethanol solution (25 mL) and the ethanol
solution (15 mL) containing nitroaniline (1.38 g, 10 mmol) was added slowly. Then, the
mixture was refluxed for 5 h and the red crude was obtained. The precipitate was recrys-
talled by ethanol, washed with water and dried under vacuum. Yield: 85%. m.p. 111–113°C.
1
−
H NMR (400 MHz, DMSO) δ 14.49 (s, 1H, minus;OH), 8.75 (s, 1H, –CH N–), 8.43
(s, 1H, ph-H), 8.30 (d, J = 7.5 Hz, 1H, ph-H), 7.50 (t, J = 7.3 Hz, 2H, ph-H), 7.38 (dd,
J = 15.0, 7.4 Hz, 3H, ph-H), 7.13 (d, J = 9.1 Hz, 1H, ph-H) (S-1). Elemental analysis: Calc.
for C13H10N2O3: C, 64.46; H, 4.16; N, 11.56; O, 19.82 Found: C, 64.35; H, 4.15; N, 11.54;
O, 19.80.
Then, bis(salicylaldehyde-o-nitroaniline) copper(II) was also synthesized according
to the above similar procedure. To a stirred solution of salicylaldehyde-o-nitroaniline
(242 mg, 1 mmol) in ethanol (15 mL), copper acetate hydrate (99 mg, 0.5 mmol) was added
slowly. Then, plenty of the red precipitate was produced at room temperature, sepa-
−
rated by filtration, washed with water and dried under vacuum. Yield: 82%. IR: C C
(Ph) 1445, 1591, 1601 and 1513 cm−1
;
CH: 749 cm−1; NO2:1514 and 1342 cm−1 (S-2).
−
Elemental analysis: Calc. for C26H18CuN4O6: C, 57.19; H, 3.32; Cu, 11.64; N, 10.26; O,
17.58 Found: C, 57.35; H, 3.32; Cu, 11.65; N, 10.24; O, 17.60. MS-HRMS (m/z): 568.0400
(M + Na)+ (S-3).
Bis(5-nitroalicylaldehyde-α-Naphthylamine) was synthesized according to the above
similar procedure. Yield: 75%. m.p. 174–176°C. 1H NMR (400 MHz, DMSO) δ 14.57 (s, 1H,
−
–OH), 8.82 (s, 1H, –CH N–), 8.48 (d, J = 2.7 Hz, 1H, ph-H), 8.34 (dd, J = 9.2, 2.7 Hz,
1H, ph-H), 8.26–8.18 (m, 1H, ph-H), 7.97–7.85 (m, 2H, ph-H), 7.65–7.52 (m, 3H, ph-
H), 7.26 (s, 1H, ph-H), 7.20 (d, J = 9.2 Hz, 1H, ph-H) (S-4). Elemental analysis: Calc. for

JOURNAL OF SULFUR CHEMISTRY
13
C17H12N2O3: C, 69.86; H, 4.14; N, 9.58; O, 16.42; Found: C, 70.01; H, 4.13; N, 9.60; O,
16.40.
Bis(5-nitroalicylaldehyde-α-Naphthylamine) copper(II) was also synthesized according
−1
−
to the above similar procedure. Yield: 78%. IR: C C (ph): 1468, 1492, 1573 and 1605 cm
;
CH: 773 and 795 cm−1; NO2: 1312 and 1492 cm−1 (S-5). Elemental analysis: Calc. for
−
C34H22CuN4O6: C, 63.20; H, 3.43; Cu, 9.84; N, 8.67; O, 14.86. Found: C, 63.25; H, 3.42;
Cu, 9.83; N, 8.66; O, 14.88. MS-HRMS (m/z): 668.0694 (M + Na)+ (S-6).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the Fund of Program for Science & Technology Innovation Talents in
Universities of Henan Province (15HASTIT039); Fund of Fluorescence Probe and Biomedical Detec-
tion Research Team of Xinxiang City (CXTD16001); and Fund of Key Scientific Research Projects
in Universities of Henan Province (15A610019).
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