Porous Cu(II)-organic framework for solvent-free cyanosilylation and anti-gastric cancer activity by inducing cell apoptosis

Article abstract of DOI:10.1007/s13738-020-01964-5

A novel metal–organic framework (MOF) containing Cu(II) ions with the chemical formula of {[Cu(L)₂(H₂O)₂](DMF)₃}_n (1) was successfully prepared by solvothermal reaction method using metal Cu²⁺

Full text of DOI:10.1007/s13738-020-01964-5

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-020-01964-5
ORIGINAL PAPER
Porous Cu(II)‑organic framework for solvent‑free cyanosilylation
and anti‑gastric cancer activity by inducing cell apoptosis
Shi‑Jie Fan · Ren Sun1,2 · Di Li · Yang Liu3
1
3
Received: 8 August 2019 / Accepted: 29 May 2020
©
Iranian Chemical Society 2020
Abstract
A novel metal–organic framework (MOF) containing Cu(II) ions with the chemical formula of {[Cu(L) (H O) ](DMF) }
2
2
2
3 n
2
+
(
1) was successfully prepared by solvothermal reaction method using metal Cu ions as nodes and bifunctional ligand
3
-(1H-tetrazol-5-yl)pyridine as organic linker. The activated MOF 1 (1a) could be utilized as catalyst for solvent-free het-
erogeneous catalytic cyanosilylation reaction because of its open Cu(II) metal positions, and its large amount of nitrogen
atoms could be applied as Lewis basic positions. Thus, its catalytic mechanism was also investigated in detail. The speciꢀc
mechanism was discussed, and its inhibition of the viability of MGC-803 gastric cancer cells was assessed. First, cell counting
kit-8 assay was performed to determine the anti-cancer eꢁect of compound 1a against the viability of MGC-803 cells. Then,
Annexin V-ꢂuorescein isothiocyanate/propidium iodide method was implemented to determine the percentage of apoptotic
MGC-803 cells. Finally, the accumulation of reactive oxygen species in MGC-803 cells treated with the compound was
determined via dichloro-dihydro-ꢂuorescein diacetate assay.
Keywords Cu(II)-MOF · Cyanosilylation · Solvent-free catalysis · Cell apoptosis
Introduction
occurs through speciꢀc pathways; these ꢀndings provide a
theoretical basis for the target and pathway of anti-tumor
drugs [3].
Malignant tumors (cancers) have become one of the major
public health issues that seriously threaten the health of the
Chinese population. Malignant tumors account for 23.91%
of the total causes of death [1]. Their incidence and mortal-
ity rates have been increasing in the past several decades.
The annual medical expenses for malignant tumors have
exceeded 220 billion; however, the situation of their preven-
tion and control remains worrisome [2]. Abnormal apoptosis
and tumorigenesis are closely related, and apoptosis is usu-
ally regulated by apoptosis-related signals and factors and
Organic polydentate ligands and metal ions can be used
to synthesize metal–organic frameworks (MOFs) under mild
conditions. These materials have distinct pore volume, large
speciꢀc surface area, pore shape and size, and their distri-
bution can be controlled by the selection of suitable metal
ion(s) and ligands [4–13]. MOFs are famous for their beau-
tiful and various architectures and advanced functions in
catalysis, separation, gas storage, luminescence, and sensing.
A few MOFs have been utilized as heterogeneous catalysts
[
14–16]. Organic groups can be designed to have functional
positions that are accessible to guests for applications in
heterogeneous catalysis. Reactants could bind to these posi-
tions by diꢁerent noncovalent interactions to activate these
organic groups. In addition, unstable solvent molecules
combined with metal ions could be removed by heating to
allow metal ions to become Lewis acid positions. Ligand
selection is also crucial for the construction of stable MOFs
that could be maintained after the removal of coordinated
and lattice solvents. Multiple N-donor ligands are a good
choice for obtaining MOFs with high framework robustness
*
Ren Sun
Sunren111@126.com
1
Laboratory of Cancer Prevention and Intervention, China
National Ministry of Education, The Second Aꢃliated
Hospital, Cancer Institute, Zhejiang University School
of Medicine, Hangzhou 310009, Zhejiang, China
2
3
Department of Molecular and Medical Pharmacology, David
Geꢁen School of Medicine, University of California at Los
Angeles, Los Angeles, CA 90095, USA
Department of Chemistry, Inner Mongolia University,
Tongliao, Inner Mongolia, China
[
17–19]. In the present research, a novel MOF containing
Vol.:(0
1
123456789)
3

Journal of the Iranian Chemical Society
Cu(II) ions with the chemical formula {[Cu(L) (H O) ]
Preparation and characterization of complex 1
2
2
2
(
DMF) } (1) was successfully prepared by solvothermal
3
n
reaction method using metal Cu ions as nodes and bifunc-
tional ligand 3-(1H-tetrazol-5-yl)pyridine as organic linker.
The synthesized complex 1 was characterized by powder
X-ray diffraction (PXRD), elemental analysis, Fourier
transform infrared (FT-IR) spectroscopy, thermogravimet-
ric analysis (TGA), and single-crystal X-ray diꢁraction
We mixed 0.043 mmol of 10 mg Cu(NO ) ·2.5H O,
3
2
2
−
1
0.031 mmol and 6 mg L , 1 mL of H O, and 4 mL of
2
dimethylformamide (DMF) to generate a mixture. We
then placed 20 mL of the mixture into a vessel with cap
and heated the mixture for 7 days at 80 °C. The prepared
1’s polyhedron blue crystals were harvested via ꢀltration
and dried in air, and its yield was 52% on the basis of the
L ligand. Elemental analysis showed that the calculated
composition of C H CuN O was 35.29% C, 2.94% H,
(
XRD). The activated MOF 1 could be utilized as catalyst
for solvent-free heterogeneous catalytic cyanation reaction
because of its open Cu(II) metal positions, and its numerous
nitrogen atoms could be applied as Lewis basic positions.
Thus, its catalytic mechanism was also investigated. The
inhibitory activity of compound 1a against the viability of
MGC-803 gastric cancer cells was measured. Cell count-
ing kit-8 (CCK-8) assay results revealed that the viability
of MGC-803 cells was remarkably reduced by compound
2
1
33
13
5
and 25.74% N, and its actual composition was 35.21% C,
2.98% H, and 25.79% N. The selected FT-IR result for
−
1
KBr pellet cm is as follows: 3410 (br), 3122 (s), 3054
(s), 1612 (s), 1545 (s), 1351 (s), 1205 (s), 1154 (s), 1111
(s), 1055 (s), 967 (s), 876 (s), 697 (s), and 642 (s).
The single-crystal XRD spectra of complex 1 at ambi-
ent temperature were acquired using the computer-con-
trolled diꢁractometer Oxford Xcalibu E, which utilizes
graphite monochromatic radiation Mo-Kα (λ = 0.71073
Å). SADABS was used for the correction of absorption.
SHELXS-2014 was used to solve this architecture, and
1
a. Annexin V-ꢂuorescein isothiocyanate (FITC)/propidium
iodide (PI) assay and the determination of reactive oxygen
species (ROS) were implemented to explore the mechanisms
of this compound. The obtained results reꢂected that the
outstanding anti-cancer eꢁect of compound 1a was because
the compound induced apoptosis and enhanced the accumu-
lation of ROS in cancer cells.
2
SHELXL-2014/6 on F was used for optimization using
the full-matrix least squares approach. All non-hydrogen
atoms were reꢀned anisotropically, and whole hydrogen
atoms were generated in the ideal sites. Guest DMF mol-
ecules are highly disordered in the skeleton of 1; thus,
these molecules could not be ꢀgured out in reꢀnement and
crystal structure solutions. Therefore, their electronic con-
tributions were removed through the PLATON SQUEEZE
operation, and the resulting HKL ꢀle formed by the PLA-
TON software without the DMF molecules’ structural fac-
tor was used. The ultimate chemical formula of complex
1 was detected through TGA and elemental analysis. The
crystallographic data, reꢀnement details, selection angle,
and bond distance of compound 1 are shown in Table 1.
Experimental
Chemicals and measurements
Synthetic reagents were purchased and applied as received
unless otherwise stated. Nitrogen, hydrogen, and carbon ele-
ments were analyzed by Vario EL elemental analyzer. TGA
was implemented using Mettler Toledo TGA/SDTA851 at
−
1
3
0–800 °C with heating rate of 10 °C min under nitro-
gen ꢂow. The infrared spectra of KBr pellets from 4000 to
−
1
4
00 cm were collected with a Nicolet iS10 FT-IR spec-
trometer. PXRD was performed using Bruker Advance D8
powder diꢁractometer at 40 mA, 40 kV, and Cu-Kα radiation
CCK‑8 assay
(
λ = 1.5406 Å) with a step size of 0.05° (2θ) and a scan-
−
1
ning speed of 0.2 s step . The sample was analyzed for
CCK-8 method was implemented to measure the inhibi-
tory activity of compound 1a against the viability of
MGC-803 gastric cancer cells. This experiment was per-
formed following the manufacturer’s instruction with
slight changes. In brief, MGC-803 cells in the phase of
logical growth were harvested and planted into 96-well
CO adsorption using Quantachrome NOVA 4200e at 77 K.
2
The progress of the reaction was monitored via gas chro-
matography (GC) using Agilent 7820 gas chromatograph
with cross-linked 95% dimethyl–5% diphenyl polysiloxane
column (HP-5, 30 m×0.32 mm×0.25 μm) with an injector
temperature of 250 °C and a ꢂame ionization detector tem-
perature of 300 °C. The oven temperature program was set
4
plates at a density of 1 × 10 cells per well. The cells were
incubated with 5% CO at 37 °C for 12 h before treat-
2
−
1
at 45 °C for 3 min, then increased to 280 °C at 20 °C min ,
and held at 280 °C for 2 min. The appraisal of all the cyano-
hydrin trimethylsilyl ether products was carried out through
the comparison of the retention times in mass spectrometry
and GC.
ment. Compound 1a was added into the wells at a series
of concentrations (1, 2, 4, 8, 10, 20, 40, and 80 μM) and
incubated for 1 day. The culture medium was replaced
with novel medium supplemented by 10% CCK-8 solution
1
3

Journal of the Iranian Chemical Society
Table 1 Crystallographic and reꢀnement parameters of complex 1
Dichloro‑dihydro‑ꢀuorescein diacetate (DCFH‑DA)
assay
Empirical formula
C H CuN O
12 12 10 2
Formula weight
Temperature/K
Crystal system
Space group
a/Å
b/Å
c/Å
α/°
391.86
293 (2)
Trigonal
R-3c
16.5216 (12)
16.5216 (12)
46.798 (4)
90
90
120
11062.6 (18)
18
1.059
ROS accumulation in MGC-803 gastric cancer cells after
treatment with compound 1a was measured by DCFH-DA
assay in accordance with the manufacturer’s protocols.
MGC-803 cells in the phase of logical growth were har-
5
vested and planted into 6-well plates at 1× 10 cells per
plate. Then, the cells were incubated with 5% CO at 37 °C
2
for 12 h and treated with compound 1a for 24 h. The treated
cells were labeled with DCFH-DA probe. Then, the ꢂuo-
rescence level of the cells in each group was measured at
β/°
γ/°
4
88/530 nm through ꢂow cytometry (BD VIA, New Jer-
Volume/Å3
sey, USA) and analyzed using the FlowJo 7.6 software. The
experiment was implemented at least thrice.
Z
3
ρcalcg/cm
μ/mm
−
1
1.447
Data/restraints/parameters
Goodness-of-ꢀt on F2
Final R indexes [I≥2σ (I)]
Final R indexes [all data]
Largest diꢁ. peak/hole/e Å−
CCDC
2450/30/115
1.102
Results and discussion
R =0.0854, ωR =0.2644
1
2
Molecular structures
R =0.0887, ωR =0.2683
1
2
3
1.28/−0.92
1999431
We acquired the blue crystals of complex 1 in moderate
yield via the reaction between Cu(NO ) ·3H O with HL
3
2
2
ligand in mixed DMF and water solvent. Its chemical for-
mula, {[Cu(L) (H O) ](DMF) } , was obtained by combin-
2
2
2
3 n
ing single-crystal XRD, elemental analysis, and TGA. The
structural solution and reꢀnement results of the crystal har-
vested at ambient temperature indicated that the acquired
2D MOF 1 was crystallized in trigonal system and its space
group was R-3c. Its structure revealed 3D supramolecular
skeleton and 1D hexagonal channels generated via 2D lay-
ered stacks. TGA and elemental analysis showed that the
MOF had a relevant asymmetric unit that consisted of 0.5
at.% Cu(II), an organic L ligand, a terminal coordinated mol-
(
Dojindo Laboratories, Kumamoto, Japan) for further
incubation. The absorbance of each plate was detected
with a microplate reader (ELX808; Bio Tek, Winooski,
VT, USA), and the viability of the cancer cells was drawn
in accordance with the absorbance results. The experi-
ment was implemented at least thrice, and the obtained
results were expressed as mean ± standard deviation.
ecule of H O, and two disordered lattice molecules of DMF.
2
As shown in Fig. 1a, the geometry of the octahedron coordi-
+
1
Annexin V‑FITC/PI assay
nation of Cu ion was completed by two pyridinyl nitrogen
atoms and two tetrazole nitrogen atoms in four L ligands,
and the other two binding positions were ꢀnished via two
coordination molecules of water. The bond lengths of Cu–N
ranged from 2.018(4) Å to 2.036(4) Å, and that of Cu–O was
2.426 Å. These values are within the normal ranges of the
bond distances of Cu–N and Cu–O in other Cu(II)-based
MOFs according to the multiple ligands of the nitrogen-
donor. The L ligand only possesses one coordination pattern,
that is, two Cu(II) ions unrelated to crystal were linked to a
tetrazole group atom by prying the nitrogen atom (Fig. 1b).
The tetrazole was not co-planar with the pyridinyl ring, and
its dihedral angle was 62.202°. Each copper ion was linked
to four neighboring copper ions by the L ligand, and each L
ligand uses two linked nodes. In this connection pattern, the
2D hierarchical network contained a large triangle window
with a size of 7.82 Å according to its van der Waals radius
Annexin V-FITC/PI staining (BD Biosciences, New Jer-
sey, USA) was performed to determine the percentage of
apoptotic MGC-803 cells after treatment with compound
1
a. The assay was accomplished according to the manu-
facturer’s instructions with slight modification. MGC-803
cells in the phase of logical growth were harvested and
6
planted into 6-well plates at 1 × 10 cells per well. The
cells were incubated with 5% CO and 37 °C for 12 h,
2
then treated with compound 1a for 24 h, and washed with
PBS. The cells were collected using 0.5% trypsin and
then suspended in 1 × binding buffer. Annexin V-FITC/
PI solution (5 μL) was added to the cell suspension in the
dark for 20 min. The absorbance at 525/625 and 488 nm
were detected by flow cytometry. The experiment was
repeated at least thrice.
1
3

Journal of the Iranian Chemical Society
Fig. 1 a Coordination environ-
2+
ment for Cu ion in complex
1
. b Coordination environment
for the L ligand. c 2D layered
network of complex 1. d 3D
packing pattern of complex 1
revealing the 1D channels
(
Fig. 1c). The superposition of the 2D layers of the c-axis
molecules, suggesting that the entire skeleton collapsed
because of the decomposition of the organic ligands. We
exchanged the DMF molecules in complex 1’s lattice with
methanol at high boiling point to activate complex 1 under
mild conditions and to obtain a solvent-free sample of
complex 1 (hereinafter referred to as 1a). In brief, 100 mg
of the newly prepared complex 1 sample was immersed in
20 mL of methanol for 72 h, during which novel methanol
was replaced every 12 h. The weight loss of the MeOH-
exchanged complex 1 at 50–150 °C was about 16% because
of the loss of two coordinated water molecules and guest
MeOH molecules. The MeOH-exchanged complex 1 was
activated at 423 K in vacuum (18 mTorr) overnight to
obtain 1a. The PXRD diagram of complex 1a was par-
allel to the PXRD pattern of complex 1, but their peak
intensities have some deviations, which might be caused
by the inexistence of coordinated and lattice guests in
the skeleton of complex 1a and the preferred orientation
of the crystal surface. Complex 1a had no weight loss at
50–300 °C. This ꢀnding indicated that complex 1a has no
coordinated water molecules and guest solvent and that
provided a 1D channel for the 3D supramolecular network,
and the size of this channel was 7.12 Å (Fig. 1d). Noticeably,
a large number of coordinated water molecules were directed
to the center of the channel. The removal of these coordina-
tion molecules could oꢁer the open sites of metal ions with
high density. Solvent 1’s free volume was 49.3%, and the
coordination molecules of water were not considered. The
results revealed that complex 1 could form numerous open
copper (II) positions and free N atoms as Lewis base posi-
tions after activation; hence, this complex possesses a great
application potential, especially in catalysis.
PXRD, TGA, and porosity analysis
PXRD was implemented to test the phase-purity of the
two complexes (Fig. 2a). The experimental and simulated
peak positions in the PXRD spectra were consistent and
exhibited that the crystal architectures genuinely represent
the crystal products with bulk shape. Their diꢁerence in
strength could be attributed to the preferred orientation of
the crystal samples. TGA was implemented at 25–800 °C
the skeletons are stable below 420 °C. N adsorption iso-
2
−
1
under nitrogen ꢂow and heating rate of 10 °C min to
study the thermal stability of complex 1. Its weight
loss of about 41.3% (the calculated value was 41.7%) at
therms at 1 atm and 77 K were detected to assess the pore
performance of complex 1a. The reversible adsorption iso-
therms of the type I N of complex 1a have a microporous
2
2
5–384 °C was attributed to the removal of three lattice
performance. Its Langmuir and Brunauer–Emmett–Teller
2
−1
DMF molecules and two coordinated water molecules. A
sharp weight loss was observed after the removal of these
surface areas were 380 and 307 m g , respectively. The
pore size distribution (PSD) curve determined via density
1
3

Journal of the Iranian Chemical Society
Fig. 2 a PXRD diagram, b TGA curve, c N sorption isotherm at 77 K, and d PSD of complex 1a
2
functional theory exhibits that the major pore size is 7.5
Å, which is equivalent to complex 1’s intersecting pore
system.
Catalytic activity
Complex 1 possesses water-held unsaturated metal cent-
ers and large pores; thus, complex 1 could be applied as
the latent Lewis acid catalyst for the cyanation of carbonyl
Table 2 The control study and optimization of catalyst 1a
Entry
Catalyst (mol%)
TMSCN
Temp. (°C)
Conversion (%)a
1
2
3
4
5
6
7
0
1
1
0.5
2 eq
1 eq
2 eq
2 eq
2 eq
2 eq
2 eq
40
40
r.t.
r.t.
r.t.
r.t.
r.t.
18.4
66.5
86.4
96.3
98.2
76.3
20.4
0.1
0.05
0.1 Complex 1
aTransformation detected via GC
1
3

Journal of the Iranian Chemical Society
compounds, and its catalytic performance was tested. Sol-
vent-free catalysis was performed using benzaldehyde as
standard molecule, and the model experiment was carried
out by altering the temperature and the amount of catalyst.
Table 2 shows that complex 1 had outstanding catalytic
activity. The conversion of benzaldehyde was 98% in 12 h
at ambient temperature and catalyst load of 0.1 mol% Cu,
which is only a ꢀfteenth of that of Cr-MIL-101 (Cr-active
position of 1.5 mol%), which possesses the highest cata-
lytic activity in cyanogenation reaction so far [20]. How-
ever, compound 1a, as catalyst, does not require the organic
solvent dichloromethane, which is required by the catalyst
Cr-MIL-101. The reaction was completely stopped after
48 h of reaction was only 83% of the cyanation conversion.
Complex 1 was then observed under identical reaction con-
ditions to study and explain the outstanding catalytic eꢁect
2
+
of its open Cu positions. Approximately 20.3% cyanation
conversion was acquired, and this value was similar to when
no catalyst was used. This ꢀnding could be attributed to the
2
+
saturated geometry of the octahedron of all the Cu ions in
complex 1. This ꢀnding also suggested that the coordina-
2
+
tion of unsaturated Cu positions in 1a have an essential
function during catalysis. The channel of cobalt MOFs is a
“microreactor” that oꢁers a good environment for cyanation.
2
+
Unsaturated Cu as Lewis acid positions could result in
the adsorption of aromatic substrates and thus improve the
reactivity of catalyst 1.
2
h via ꢀltration, and the total conversion oꢁered after 15 h
was only 45%. This result conꢀrmed that no homogeneous
catalyst species was present in the reaction solution and that
complex 1 is a heterogeneous catalyst. The total conversion
increased to 76.3% in 12 h at ambient temperature when the
amount of catalyst was reduced to 0.05 mol%. Therefore,
increasing the amount of catalyst from 0.5 to 1 mol% could
not increase the total conversion.
A rational reaction mechanism was suggested based
on previous studies [21–23] and the present experimental
results to discuss the catalytic cyanidation procedure of 1a.
The non-stable water molecules in the channel of compound
1a were removed by heating and exposing the unsaturated
metal position. Aldehydes were activated with the coordi-
nated unsaturated centers of copper (Scheme 1). The inter-
action between TMSNC (after TMSNC isomerization) and
the aldehydes was near the coordinated unsaturated center
of Cu. Aldehydes replaced the products, and the catalyst
that activated the aldehydes would continue to exist in the
following catalytic cycle.
Six carbonyl substrates containing cycloketones, aliphatic
aldehydes, and aromatics were cyanated under optimized
conditions (ambient temperature, 0.1 mol% catalyst, and 2
equivalent trimethylsilyl cyanide [TMSCN]). The acquired
results are summarized in Table 3, which exhibits that the
reaction possesses wide tolerance to diꢁerent substrates.
The equivalent products were acquired in outstanding yields
MOF-based catalysts could be recycled. The recycling
of catalysts is of great importance in the field of cataly-
sis, particularly in heterogeneous catalysis. Thus, catalyst
recovery was explored, and the recoverability of catalyst
1a in benzaldehyde cyanidation was discussed. Catalyst
1a was easily separated from the reaction liquid by GC
and mixed with methanol. Catalyst 1a was regenerated by
vacuum heating for 5 h at 100 °C and was directly utilized
in the following experimental cycle. The experimental
(
>90%) after 8–12 h under optimized conditions when the
aromatic aldehyde contains electronic eꢁect substituents of
electron-withdrawing NO and electron-donating CH , or the
2
3
various sites of the substituents were utilized. Nevertheless,
ketones and aliphatic aldehydes possess lower catalytic eꢃ-
ciency than aromatic aldehydes owing to their intrinsically
decreased reactivity. The conversion of cyclobutanone after
Table 3 Catalytic reaction of distinct substrates via 1a
a
Entry
R1
R2
Time (h)
Conversion (%)
1
2
3
4
5
6
Ph
H
H
H
H
H
12
12
12
8
30
48
98.2
94.3
93.7
99.6
68.3
54.1
2-CH C H
4-CH C H
4-NO C H
n-Propyl
3
6
4
3
6
4
2
6
4
(CH2)4
aConversion detected via GC
1
3

Journal of the Iranian Chemical Society
Compound 1a substantially inhibited the viability
of MGC‑803 cells
The inhibitory activity of compound 1a against the viability
of MGC-803 gastric cancer cells was determined by CCK-8
assay following the manufacturer’s instructions. The cyto-
toxicity of compound 1a against normal human cell line
HEK-293 was assessed as well. The results in Fig. 4a show
that compound 1a could obviously decrease the viability
of MGC-803 cells in a dose-dependent manner compared
with the control. The half maximal inhibitory concentra-
tion (IC ) of compound 1a against MGC-803 cells was
5
0
3
.11 ± 0.16 μM, which is much less than the IC of the
50
positive control (10.04± 0.23 μM). This result indicated that
compound 1a possesses much more outstanding anti-cancer
eꢁect than that of the control drug. Furthermore, compound
1
a had no inꢂuence on the viability of HEK-293 cells and
is remarkably diꢁerent with Cu(II). The cell viability curve
suggested that the prepared compound 1a has outstanding
anti-cancer eꢁect against MGC-803 cells and has low cyto-
toxicity on normal cells.
Scheme 1 Mechanism of the catalytic cyanidation of carbonyl com-
pounds via 1a
Compound 1a increased the percentage
of apoptotic MGC‑803 gastric cancer cells
results are revealed in Fig. 3a, which exhibits that cata-
lyst 1a can be reused at least four times under optimal
conditions without any remarkable decrease in activity in
cyanosilylation catalysis (TOF values were between 82.5
Most drugs exert anti-cancer eꢁect by inducing apopto-
sis. Apoptosis is very important for removing harmful and
unnecessary cells from the body and maintaining homeo-
stasis. Apoptosis has been used to inhibit the progression
of many diseases, such as cancer. Thus, in this research,
Annexin V-FITC/PI method was utilized to assess the apop-
totic levels after treatment with compound 1a. The results
in Fig. 5 exhibit that compound 1a had a good apoptosis-
inducing eꢁect. Compound 1a could reduce the levels of
apoptotic cells to 78.56% and 37.11% under 3× IC and
−
1
and 81.4 h ). In addition, the N adsorption isotherm
2
after four catalytic cycles shows that its N absorption
2
capacity did not decline substantially; thus, the catalyst
had a strong skeleton structure in the catalytic reaction
(
Fig. 3b).
5
0
1
×IC compound treatments, respectively.
50
Fig. 3 a Detection of the recovery of cyanoethylation catalyst 1a for benzaldehyde. b N sorption isotherms of 1a and 1a after catalysis at 77 K
2
1
3

Journal of the Iranian Chemical Society
Fig. 4 The viability of MGC-803 gastric cancer cells was remarkably
inhibited after treatment with compound 1a. a Viability of MGC-803
cells after treatment with a series of concentrations (1, 2, 4, 8, 10, 20,
method. The IC values of compound 1a were calculated by SPSS. b
5
0
Survival rate of HEK-293 cells after 1-day treatment with high-con-
centration complex
4
0, and 80 μg/mL) of compound 1a for 24 h as detected by CCK-8
Compound 1a promoted ROS accumulation
in MGC‑803 cells
Conclusion
We successfully produced a fresh MOF containing Cu(II)
by using metal Cu ions as nodes and bifunctional ligand
3-(1H-tetrazol-5-yl)pyridine as organic linker. The synthe-
sized complex 1 has been characterized by PXRD, elemen-
tal analysis, FT-IR spectrometry, TGA, and single-crystal
XRD. Furthermore, MOF 1a could be utilized as catalyst
for solvent-free heterogeneous catalytic cyanation reaction
because of its open Cu(II) metal positions, and its numerous
nitrogen atoms could be applied as Lewis basic positions.
Thus, its catalytic mechanism was also investigated. In this
research, the inhibitory activity of compound 1a against
MGC-803 gastric cancer cells was evaluated, and its anti-
cancer mechanism was explored as well. The results of the
CCK-8 assay revealed that compound 1a could decrease the
survival rate of MGC-803 cells in a dose-dependent manner.
Experimental results reꢂected that the inhibitory activity of
compound 1a against cancer cells was because of its abil-
ity to induce ROS production and apoptosis. In conclusion,
compound 1a has excellent inhibitory activity against MGC-
ROS has a substantial function in inducing apoptosis. The
over-accumulation of ROS in cells could trigger apoptosis.
We demonstrated compound 1a’s apoptosis-inducing eꢁect;
thus, we further conducted DCFH-DA assay to detect the
ROS levels in MGC-803 gastric cancer cells treated with
compound 1a. Figure 6 shows that the ROS level was
increased after treatment with compound 1a in a dose-
dependent matter. Compound 1a increased the ROS level to
7
5.66% and 0.21% at 1 ×IC and 0.1×IC , respectively.
50 50
This result revealed that compound 1a could inhibit the
viability of MGC-803 gastric cancer cells by inducing the
accumulation of ROS.
8
03 gastric cancer cells by inducing ROS accumulation and
apoptosis.
1
3

Journal of the Iranian Chemical Society
Fig. 5 Enhanced percentage of apoptotic MGC-803 gastric cancer cells after treatment with compound 1a. The percentage of apoptotic MGC-
8
03 cells was measured at 625 and 488/525 mm via ꢂow cytometry
1
3

Journal of the Iranian Chemical Society
Fig. 6 Promoted levels of ROS in MGC-803 gastric cancer cells after treatment with compound 1a. DCFH-DA was applied and ꢂow cytometry
was performed at 530/488 nm to measure the accumulation levels of ROS in MGC-803 cancer cells
Data Availability The data used to support the ꢀndings of this study
3. S.H. Yeo, K. Jung, M.I. Park, S.J. Kim, J.H. Kim, S.E. Kim, W.
are included within the article.**
Moon, S.J. Park, Korean J. Gastroenterol. 75, 212–215 (2020)
4
5
6
.
.
.
T.W. Lyons, M. Brookhart, Chem. - A Eur. J. 19, 10124–10127
(
2013)
Compliance with ethical standards
R. Wang, Z. Wang, Y. Xu, F. Dai, L. Zhang, D. Sun, Inorg. Chem.
5
3, 7086–7088 (2014)
Conflict of interest The author(s) declare(s) that there is no conꢂict of
J. Yang, X. Wang, F. Dai, L. Zhang, R. Wang, D. Sun, Inorg.
Chem. 53, 10649–10653 (2014)
interest regarding the publication of this paper.
7
8
.
.
D.M. Chen, X.J. Zhang, CrystEngComm 21, 4696–4700 (2019)
X. Feng, Y.Q. Feng, J.L. Chen, L.Y. Wang, Dalton Trans. 44,
8
04–816 (2015)
References
9. X. Feng, L.F. Ma, L. Liu, S.Y. Xie, L.Y. Wang, Cryst. Growth
Des. 13, 4469–4479 (2013)
1
0. X. Feng, J.G. Wang, B. Liu, L.Y. Wang, J.S. Zhao, S.W. Ng, Cryst.
Growth Des. 12, 927–938 (2012)
1
2
.
.
Y. Li, K. Dong, X. Fan, J. Xie, M. Wang, S. Fu, Q. Li, J. Cancer
1
1, 3717–3724 (2020)
1
1. X. Feng, N. Guo, H.P. Chen, H.L. Wang, L.Y. Yue, X. Chen, S.W.
Ng, X.F. Liu, L.F. Ma, L.Y. Wang, Dalton Trans. 46, 14192–
D. Maraghelli, F. Giusti, F. Marini, M.L. Brandi, Orphanet J. Rare
Dis. 15, 102 (2020)
1
4200 (2017)
1
3

Journal of the Iranian Chemical Society
1
1
2. W. Liu, H. Li, H. Zhu, P. Xu, Materials 13, 1180 (2020)
3. Z. Wang, X. Zhang, S. Jiang, Y. Qu, D. Ou, J. Wang, J. Alloys
Compd. 828, 154412 (2020)
19. J. Zhang, J. Wu, G. Tang, J. Feng, F. Luo, B. Xu, C. Zhang, Sens.
Actuators B Chem. 272, 166–174 (2018)
20. Z. Zhang, J. Chen, Z. Bao, G. Chang, H. Xing, Q. Ren, RSC Adv.
5, 79355–79360 (2015)
1
1
1
1
1
4. S. Zhang, L. Li, S. Zhao, Z. Sun, M. Hong, J. Luo, J. Mater. Chem.
A 30, 15764–15768 (2015)
21. L.J. Zhang, C.Y. Han, Q.Q. Dang, Y.H. Wang, X.M. Zhang, RSC
Adv. 5, 24293–24298 (2015)
5. R. Babu, A.C. Kathalikkattil, R. Roshan, J. Tharun, D.W. Kim,
D.W. Park, Green Chem. 18, 232–242 (2016)
22. A. Karmakar, G.M.D.M. Rúbio, A. Paul, M.F.C. Guedes da
Silva, K.T. Mahmudov, F.I. Guseinov, S.A.C. Carabineiro, A.J.L.
Pombeiro, Dalton Trans. 46, 8649–8657 (2017)
23. I.H. Choi, Y. Kim, D.N. Lee, S. Huh, Polyhedron 105, 96–103
(2016)
6. L. Liu, S.M. Wang, Z.B. Han, M. Ding, D.Q. Yuan, H.L. Jiang,
Inorg. Chem. 55, 3558–3565 (2016)
7. X.Z. Guo, S.S. Chen, W.D. Li, S.S. Han, F. Deng, R. Qiao, Y.
Zhao, ACS Omega 4, 11540–11553 (2019)
8. X.R. Wang, X.Z. Wang, Y. Li, K. Liu, S.X. Liu, J. Du, Z. Huang,
Y. Luo, J.Z. Huo, X.X. Wu, Y.Y. Liu, B. Ding, Ultrason. Sono-
chem. 44, 340–349 (2018)
1
3