Fe3O4@C@prNHSO3H: A novel magnetically recoverable heterogeneous catalyst in green synthesis of diverse triazoles

Article abstract of DOI:10.1002/jccs.202100239

The core–shell magnetic nano-catalyst of Fe₃O₄@C@PrNHSO₃H was proposed, synthesized, and fully described by transmission electron microscopy, field-emission scanning electron microscope, energy-dispersive X-ray, vibrating sample magnetometer, thermal gravimetric analysis, X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis. Nontoxic texture, magnetic recovery capability, high thermal stability as well as low-cost synthesis method were found as the unique features of the synthesized core–shell magnetic nano-catalyst. Fe₃O₄@C@PrNHSO₃H NPs were introduced as a modern magnetic heterogeneous catalyst in the solvent-free synthesis of triazole derivatives through one-pot, three-component condensation of aldehyde, ammonium acetate, and nicotinic hydrazide. The pleasant yield of products, straightforward work-up, mild reaction conditions, along with magnetically recoverable catalyst were enumerated as the most important advantages of the method. The Fe₃O₄@C@PrNHSO₃H could be easily separated from the reaction mixture by an external magnet and reused six times with the desired catalytic activity.

Full text of DOI:10.1002/jccs.202100239

Received: 14 June 2021
Revised: 3 August 2021
Accepted: 4 August 2021
DOI: 10.1002/jccs.202100239
A R T I C L E
Fe3O4@C@prNHSO3H: A novel magnetically recoverable
heterogeneous catalyst in green synthesis of diverse
triazoles
Niloufar Nasehi | Behrooz Mirza | Somayeh Soleimani-Amiri
Department of Chemistry, Karaj Branch,
Abstract
Islamic Azad University, Karaj, Iran
The core–shell magnetic nano-catalyst of Fe3O4@C@PrNHSO3H was pro-
posed, synthesized, and fully described by transmission electron microscopy,
Correspondence
Behrooz Mirza, Department of Chemistry,
field-emission scanning electron microscope, energy-dispersive X-ray, vibrat-
Karaj Branch, Islamic Azad University,
Karaj, Iran.
ing sample magnetometer, thermal gravimetric analysis, X-ray diffraction,
Email: b.mirza@kiau.ac.ir,
Fourier transform infrared, and X-ray photoelectron spectroscopy analysis.
b_mirza@azad.ac.ir
Nontoxic texture, magnetic recovery capability, high thermal stability as well
as low-cost synthesis method were found as the unique features of the synthe-
sized core–shell magnetic nano-catalyst. Fe3O4@C@PrNHSO3H NPs were
introduced as a modern magnetic heterogeneous catalyst in the solvent-free
synthesis of triazole derivatives through one-pot, three-component condensa-
tion of aldehyde, ammonium acetate, and nicotinic hydrazide. The pleasant
yield of products, straightforward work-up, mild reaction conditions, along
with magnetically recoverable catalyst were enumerated as the most important
advantages of the method. The Fe3O4@C@PrNHSO3H could be easily sepa-
rated from the reaction mixture by an external magnet and reused six times
with the desired catalytic activity.
K E Y W O R D S
core–shell nano-catalyst, green synthesis, heterogeneous catalyst, magnetic nanoparticles,
triazoles
1 | INTRODUCTION
batteries.[5–7] Heterogeneous catalysts have also been to
prominence in the field of heterocyclic synthesis because
of mild reaction conditions, cost-effectiveness, simple
work-up, atom economy, easy recyclability, and modifiable
surface properties.[8] Recently, nano-catalysts, with their
large surface area and high-density active sites, have
emerged as an alternative over various commercial cata-
lysts to develop the catalytic efficiency and application in
organic synthesis.[9–15] Among numerous species of nano-
catalysts, iron oxide nanoparticles (NPs) have achieved
much attention due to their idiosyncratic features such as
In recent years, the demand for designing and manufactur-
ing novel catalysts with excellent characteristics such as
recyclability, unique molecular architectures, and atom
economics to join green chemistry is growing. Heteroge-
neous catalysts such as metal–organic framework derived
catalysts could play a key role in the design of green cata-
lytic protocols due to their recoverability, reusability, and
stability in chemical processes.[1–4] Those are also widely
used in photovoltaic devices, decomposers, sensors, and
J Chin Chem Soc. 2021;1–14.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
1

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NASEHI ET AL.
ease of availability, chemical inertness, high surface area to
volume ratio, non-toxicity, excellent thermal stability, mag-
netic property,[16] and also the vast range of applicability in
catalysis,[17–21] protein separations,[22] magnetic resonance
imaging (MRI),[23] magnetic refrigeration,[24] drug
delivery,[25–27] and magnetic sensors.[28] The magnetic
nature of iron oxide NPs enables effortless separation from
the reaction mixture using an external magnet that not
only prevents the cumbersome filtration procedures but
also lessens energy consumption, catalyst waste, and saves
time in performing catalyst recovery.[29] Due to the strong
tendency of these magnetic NPs to agglomerate as a result
of self-interactions, much effort has been directed toward
imparting stability to them via immobilizing the nano-
catalysts onto the nano-carriers. To date, many nano-
carriers such as surfactant/polymer, silica, metal–organic
frameworks, clays, and carbon coating or embedding a
matrix/support have been utilized as protection strategies,
and the research along this field continues.[30,31] It is note-
worthy that the protective outer shells produced as a result
of coating not only stabilize the NPs but additionally provide
active sites for functionalization with other organic groups
suitable for desired applications.[32] Accordingly, the devel-
opment of a stable and magnetically retrievable core/shell
structured iron oxide nano-catalyst with reusability and
recyclability potentials is still challenging, and further, it
adds significant value to synthetic organic protocols such as
the multicomponent reactions (MCRs).[33–36]
In the past decades, MCRs have been considered as one
of the most effective and practical routes in organic synthe-
sis from an atom- and step-economical point of view for the
construction of heterocycles and natural products such as
triazole derivatives.[37] It is worthy to mention that among
the synthesized heterocyclic compounds, triazole core struc-
tures display a diverse array of biological activities in medici-
nal chemistry, and a large number of triazole-based
compounds as clinical drugs such as anticancer, antiviral,
anti-inflammatory, antiparasitic, and antimicrobial drugs
have been extensively used.[38–43] Therefore, developing new
approaches for the synthesis of the pharmacologically active
triazole derivatives remains to be attractive in contemporary
synthetic chemistry. We aim to improve the reaction condi-
tions and scale-up the multicomponent synthesis of triazole
building blocks, keeping in view the abovementioned bio-
logical activities of them.
2 | RESULT AND DISCUSSIONS
2.1 | Synthesis and characterization of
Fe3O4@C@PrNHSO3H
The core–shell magnetic nano-catalyst of Fe3O4@C@
PrNHSO3H was synthesized as outlined in Scheme 1. The
procedure consists of three steps: (1) Synthesis of core–
shell magnetic NPs of Fe3O4@C; (2) Optimal amination
of Fe3O4@C to Fe3O4@C@PrNH2; (3) Optimal sulfona-
tion of Fe3O4@C@PrNH2 to Fe3O4@C@PrNHSO3H.
The synthesized core–shell magnetic nano-catalyst of
Fe3O4@C@PrNHSO3H was characterized by spectral
techniques, containing Fourier transform infrared (FT-IR),
field-emission scanning electron microscope (FE-SEM),
energy-dispersive X-ray (EDX), elemental mapping, vibrat-
ing sample magnetometer (VSM), transmission electron
microscopy (TEM), thermal gravimetric analysis (TGA),
X-ray diffraction (XRD), and X-ray photoelectron spectros-
copy (XPS).
2.1.1 | FT-IR analysis
The FT-IR spectra of (a) Fe3O4@C, (b) Fe3O4@C@
PrNH2, (c) Fe3O4@C@PrNHSO3H NPs, aswell as
(d) recovered Fe3O4@C@PrNHSO3H, are observed in
Figure 1. As illustrated in FT-IR spectrum of Fe3O4@C NPs,
a broad band at about 3,430 cmÀ1 is related to the stretching
vibration mode of hydroxyl groups on the surface of NPs
(Figure 1a).[31,44–47] The bands at 1,614, and 1,404 cmÀ1 cor-
responded to C═C stretching vibrations related to carbon
shell. The observed signal at 1,110 cmÀ1 was assigned to the
C O stretching vibrations of Fe3O4@C. The last absorption
band at ꢀ594 cmÀ1 is related to the stretching vibration
mode of Fe O in the core of NPs. Moreover, the appear-
ance of a new absorption band at 2,924 cmÀ1 in
Fe3O4@C@PrNH2 can be attributed to the CH2 stretching
vibration (Figure 1b). Also, the strong bonds at ꢀ1,112 cmÀ1
were related to SO2 symmetric and asymmetric stretching
vibration for both Fe3O4@C@PrNHSO3H and recycled
Fe3O4@C@PrNHSO3H (Figure 1c,d).
2.1.2 | EDX analysis and elemental mapping
Following our studies on the development of
magnetic nano-catalysts and their applications in the
synthesis of organic compounds,[44–48] in this work,
Fe3O4@C@PrNHSO3H was synthesized for the first time
and applied in the one-pot synthesis of pharmaceutically
attractive diverse kinds of triazole derivatives via three-
component reactions to investigate the application scope of
the novel heterogeneous core–shell magnetic nano-catalyst.
The EDX spectrum of Fe3O4@C was displayed as Fe
(65.1%), O (30.1%), and C (4.8%); while Fe (60.2%), O
(30.7%), C (8.2%), Si (0.6%), N (0.4%) were detected for
Fe3O4@C@PrNH2 NPs (Figure 2). The presence of Fe
(42.9%), O (24.4%), C (13.6%), Si (12.7%), S (4.3%), and
N (2.0%) was clarified for Fe3O4@C@PrNHSO3H NPs by
EDX analysis (Figure 2). Moreover, the dispensation

NASEHI ET AL.
3
SCHEME 1 Synthesis
procedure of
Fe3O4@C@PrNHSO3H NPs
Wavelength (cm-1)
2800 2200
uniform distribution of all elements on the surface of
Fe3O4@C@PrNHSO3H NPs (Figure 2d).
4000
3400
1600
1000
400
(a)
(b)
2.1.3 | FE-SEM and TEM images
The morphology evaluation and average particle size of
Fe3O4@C, Fe3O4@C@PrNH2 and Fe3O4@C@PrNHSO3H
NPs were visualized by FE-SEM and TEM images. The
FE-SEM images of all three NPs displayed spherical mor-
phology and typical uniformity with a mean size ꢀ25,
ꢀ41, and ꢀ64 nm for Fe3O4@C, Fe3O4@C@PrNH2, and
Fe3O4@C@PrNHSO3H, respectively (Figure 3). The FE-
SEM images also showed some aggregations on the sur-
face of NPs. TEM images of Fe3O4@C@PrNHSO3H NPs
are shown in Figure 4. These images verified the spheri-
cal core–shell structure of these NPs, so that Fe3O4 black
cores were covered by gray shells.
(c)
(d)
2358
1404
2922
C=C
1614
C=C
3436
O-H
594
Fe-O
1108
1110
C-O
FIGURE 1 FT-IR spectra of (a) Fe3O4@C NPs;
(b) Fe3O4@C@PrNH2 NPs; (c) Fe3O4@C@PrNHSO3H NPs; and
(d) recycled Fe3O4@C@PrNHSO3H NPs after six runs
2.1.4 | XRD analysis
pattern of the detected structural elements in the
Fe3O4@C@PrNHSO3H NPs was well detected via
the images of elemental mapping, which confirmed the
A
comparison of the XRD analysis of Fe3O4@C,
Fe3O4@C@PrNH2, Fe3O4@C@PrNHSO3H, and recovered

4
NASEHI ET AL.
FIGURE 2 EDX spectra of (a) Fe3O4@C NPs; (b) Fe3O4@C@PrNH2 NPs; and (c) Fe3O4@C@PrNHSO3H NPs; along with (d) elemental
mapping of Fe3O4@C@PrNHSO3H NPs
Fe3O4@C@PrNHSO3H is shown in Figure 5. XRD pat-
terns of all the above NPs demonstrated high purity of
magnetite without any hematite phase or iron hydroxide
phase. Those identified as cubic magnetite crystalline
structure of Fe3O4 with six separate diffraction peaks
appeared at Bragg angles of 2θ—30.31ꢁ, 35.78ꢁ, 43.44ꢁ,
53.75ꢁ, 57.30ꢁ, and 62.97ꢁ corresponding to Miller indices
of (220), (311), (400), (422), (511), and (440), which was in
accordance with Fe3O4 reference code: 01-075-0449. Also,
the cubic crystalline structure with a space group of Fd-
3m, and space group number of 227 was detected for three
types of NPs at: 8.3200 Å, b: 8.3200 Å, c: 8.3200 Å, Alfa:
90.0000ꢁ, Beta: 90.0000ꢁ, Gamma: 90.0000ꢁ, with a calcu-
lated density of 5.34 g/cm3, volume cell of 575.93 Â 106
p.m.3, z: 8, RIR: 5.03, along with ICSD collection code of
029129. The broad bands in the range of 10ꢁ–25ꢁ were
appointed to amorphous carbon coating on the Fe3O4
NPs.[31,44–47] Although, according to the results, the Fe3O4
core structure has been preserved even with surface modi-
fications, in comparison with Fe3O4@C, there were dimin-
ished peak intensity due to the shielding effect of diverse
shells. Moreover, there were the same signals for the
recycled Fe3O4@C@PrNHSO3H NPs after six runs of the
model reaction of triazole synthesis.
the crystalline size of Fe3O4@C, Fe3O4@C@PrNH2, and
Fe3O4@C@PrNHSO3H was determined about 10.1, 10.8,
and 11.3 nm, which detect no significant change in
crystal size during modification processes.
2.1.5 | VSM analysis
The magnetic features of the produced Fe3O4@C,
Fe3O4@C@PrNH2, Fe3O4@C@PrNHSO3H, and recov-
ered Fe3O4@C@PrNHSO3H were measured by VSM
analysis at room temperature and air atmosphere
between À15 and 15 kOe (Figure 6). Magnetic hysteresis
loops displayed super-paramagnetic behavior for all
the mentioned NPs. The saturation magnetization of
Fe3O4@C, Fe3O4@C@PrNH2, Fe3O4@C@PrNHSO3H,
and recovered Fe3O4@C@PrNHSO3H was found about
65.77, 55.09, 34.27, and 48.42 emu/g, respectively. The
highest magnetic property of 65.77 emu/g was observed
for Fe3O4@C, while it decreased to 55.09 emu/g due to
modification with (3-Aminopropyl)trimethoxysilane. Sub-
sequently, the lowest saturation magnetization of
34.27 emu/g was detected for Fe3O4@C@PrNHSO3H
owing to a reaction with chlorosulfuric acid. Moreover,
48.42 emu/g magnetization was found for recycled
Fe3O4@C@PrNHSO3H, which could be due to the partial
Moreover, an estimation of the crystalline size was
derived from the Scherrer equation.[44–46] Accordingly,

NASEHI ET AL.
5
FIGURE 3 FE-SEM images of (a) Fe3O4@C NPs; (b) Fe3O4@C@PrNH2 NPs; and (c) Fe3O4@C@PrNHSO3H NPs
separation of the shell from the surface of NPs. Therefore,
all four types of applied NPs can be easily removed from
the reaction mixture due to their strong magnetization.
2.1.6 | TGA and derivative thermal
gravimetric
The thermal stability of Fe3O4@C@PrNHSO3H NPs was
investigated by TGA and derivative thermal gravimetric
(DTG) analyses in a range of 25–800ꢁC under the air atmo-
sphere (Figure 7). According to the TGA/DTG curves, the
first weight loss was observed at 1.94% at around 30–110ꢁC,
which was related to the endothermic loss of hydroxyl
groups and removal of water molecules in the surface of
Fe3O4@C@PrNHSO3H NPs.[31,45,46] The TGA/DTG dia-
gram presented 4.33% weight loss at ꢀ240–490ꢁC, which
was attributed to the decomposition of organic groups, sul-
fonamide, and sulfonic acid groups along with amorphous
FIGURE 4 TEM images of Fe3O4@C@PrNHSO3H NPs

6
NASEHI ET AL.
FIGURE 5 XRD patterns of (a) Fe3O4@C NPs; (b) Fe3O4@C@PrNH2 NPs; (c) Fe3O4@C@PrNHSO3H NPs; and (d) recycled
Fe3O4@C@PrNHSO3H after six runs
carbon shells of Fe3O4@C@PrNHSO3H NPs. Therefore,
87.28% residue weight was observed, which indicates the
high thermal stability of Fe3O4@C@PrNHSO3H NPs.
confirm that they correspond to Fe3O4 core. The XPS of
O 1s revealed two peaks at 530.2 and 532.1 eV. Also, two
peaks of 282.1 and 285 eV were assigned for C 1s.
2.1.7 | X-ray photoelectron spectroscopy
2.2 | Synthesis of triazole derivatives
using Fe3O4@C@PrNHSO3H
The elemental composition of Fe3O4@C@PrNHSO3H
NPs was investigated by the XPS spectrum (Figure 8).
The most critical photoelectron peaks of 285, 532,
The MCR of benzaldehyde (1), nicotinic hydrazide (2),
and ammonium acetate (3) was selected as the model
reaction and applied for optimization of the reaction
parameters under different conditions (Table 1). The
model reaction was examined with different amounts of
raw materials, various catalysts, altered catalyst loadings,
710, and 725 eV were assigned to C 1s, O 1s, Fe 2p2/3
,
and Fe 2p1/2, respectively.[49,50] The signals at 711.6 and
726.2 eV could be ascribed to Fe3+ species, while the
peaks at 710.5 and 725.9 eV were attributed to Fe+2 to

NASEHI ET AL.
7
66
FIGURE 6 VSM analysis of
(a) Fe3O4@C NPs; (b) Fe3O4@C@PrNH2
NPs; (c) Fe3O4@C@PrNHSO3H NPs; and
(d) recovered Fe3O4@C@PrNHSO3H NPs
after six runs
(a)
(b)
(d)
47
(c)
28
9
20000
15000
10000
5000
0
-5000
-10000
-15000
-20000
-10
-29
-48
-67
Applied Field (Oe)
FIGURE 7 TGA (dashed
line) and DTG (solid line)
diagrams of
Fe3O4@C@PrNHSO3H NPs
various temperatures, and in the presence of different sol-
vents as well as solvent-free conditions in order to
improve the reaction conditions. First, the model reaction
was carried out in the presence of Fe3O4@C@PrNHSO3H
NPs using H2O, EtOH, acetonitrile, toluene, and DMSO
as solvents under several temperatures (Table 1, entries
1–8). Low yields of products were found in the presence
of various solvents, which improved with increasing temper-
ature and the amount of catalyst used. The reaction was per-
formed under solvent-free conditions at 100ꢁC, using 0.06 g
catalyst loading of Fe3O4@C@PrNHSO3H NPs with high
efficiency of the product (Table 1, entry 9). The reaction
efficiency decreased following a reduction in the catalyst
consumption or the absence of the catalyst (Table 1, entries
10–11). The condensation of benzaldehyde (1; 1 mmo1),
nicotinic hydrazide (2; 1 mmol), and ammonium acetate (3;
2.5 mmol) using Fe3O4@C@PrNHSO3H NPs (0.06 g) at
100ꢁC under solvent-free conditions with 95% yield of
product was introduced as the optimized conditions
(Table 1, entry 12).
Next, Fe3O4@C@PrNHSO3H NPs were compared
with the other catalysts used in previous articles for
synthesis of 3-(3-phenyl-1H-1,2,4-triazol-5-yl)pyridine
derivatives (Table 2).[51,52] The significant supremacy
of Fe3O4@C@PrNHSO3H NPs was detected through
the results. Also, Fe3O4@C@PrNHSO3H NPs were
evaluated as an efficient catalyst due to magnetic
properties followed by convenient separation, produc-
tion of the high yields of product at a noticeable short
reaction time. Also, 3-(3-phenyl-1H-1,2,4-triazol-5-yl)

8
NASEHI ET AL.
FIGURE 8 XPS spectra of
Fe3O4@C@PrNHSO3H NPs:
(a) wide scan XPS spectra;
(b) C 1s; (c) O 1s; and (d) Fe 2P
spectra
(a)
(b) C 1s
2500
Fe 2p
O 1s
300
2000
1500
1000
500
0
C 1s
250
200
150
100
50
0
100 200 300 400 500 600 700 800
Binding energy (eV)
270
275
280
285
290
295
Binding energy (eV)
(c)
(d)
Fe 2p
O 1s
550
500
450
400
350
300
250
300
250
200
150
100
50
0
690 695 700 705 710 715 720 725 730 735
Binding energy (eV)
520
525
530
535
540
545
Binding energy (eV)
TABLE 1 The effect of different amounts of raw materials, solvents, temperatures, and catalyst loading in one-pot synthesis of triazole
1
2
3
T
(ꢁC)
Time
(min)
Catalyst
(g)
Yield
(%)
Entry (mmol) (mmol) (mmol) Solvent
Catalyst
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
Water
Water
R.T. 30
Fe3O4@C@PrNHSO3H 0.03
Fe3O4@C@PrNHSO3H 0.03
Fe3O4@C@PrNHSO3H 0.03
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.06
Fe3O4@C@PrNHSO3H 0.03
15
25
35
45
50
45
55
60
90
80
43
95
2
2
60
30
60
60
60
60
60
60
60
60
60
60
3
2
Water 100
Ethanol 100
4
2
5
2
Water 1:1 Ethanol 100
Acetonitrile 100
Toluene 100
6
2
7
2
8
2
DMSO 100
9
2
-
-
-
-
100
100
100
100
10
11
12
2
2
-
-
2.5
Fe3O4@C@PrNHSO3H 0.06

NASEHI ET AL.
9
TABLE 2 Screening of some
different catalysts in one-pot synthesis
of 3-(3-phenyl-1H-1,2,4-triazol-5-yl)
pyridine derivatives
Entry
Catalyst
T (ꢁC)
R.T.
R.T.
100
Time (min)
Yield (%)
1
2
3
4
5
Acetic acid[51]
24–28 hr
4–6 hr
60
68
90
95
60
64
Glacial acetic acid[52]
Fe3O4@C@PrNHSO3H
Fe3O4@C
100
60
Fe3O4@C@PrNH2
100
60
Note: The bold shows the optimized conditions that was used in the manuscript.
pyridine derivatives were synthesized using Fe3O4@
C@PrNHSO3H NPs under solvent-free conditions. As
evidenced, the destitute of organic solvents in the
reaction has been considered as an important privi-
lege in green chemistry. Moreover, a diminution in
reaction efficiency was recognized when Fe3O4@C
and Fe3O4@C@PrNH2 NPs were used instead of
Fe3O4@C@PrNHSO3H NPs (Table 2, entries 4–5).
The synthesis of diverse triazole derivatives was inves-
tigated to expand the scope of the method. Aromatic
aldehydes (1a–1j; 1 mmol) with varied groups (such as
electron-withdrawing and electron-donating and halogen
groups), nicotinic hydrazide (2; 1 mmol), ammonium
acetate (3; 2.5 mmol), and Fe3O4@C@PrNHSO3H NPs
(0.06 g) were mixed at 100ꢁC to produce different triazole
derivatives (4a–4j) in 60%–95% yields during 60–90 min
(Table 3). Accordingly, some novel products were found
in favorable yields and suitable reaction times.[51–53]
10ꢁ ≤ 2θ ≤ 80ꢁ with 0.5ꢁ/s scan rate. A field-emission
scanning microscope (FE-SEM) (ZEISS-Sigma VP model,
Germany), operating at a 15 kV, was used to visualize
the morphology and structure of the nanocrystalline
catalysts. The structural elements of each sample were
characterized using an energy-dispersive X-ray (EDS)
detector (Oxford instrument, England) under standard
conditions, attached to the FE-SEM, which is mentioned
above. The magnetic properties of the synthesized
nano-catalysts were measured using a vibrating sample
magnetometer (VSM) of LBKFB model from Meghnatis
Daghigh Kavir Company. The thermal gravimetric analy-
sis (TGA) and derivative thermogravimetry (DTG) were
found at 15–800ꢁC under air atmosphere using STA1500
model of Rheometric Scientific Co. X-ray photoelectron
spectroscopy (XPS) were carried out on an X-ray
8025-BesTec XPS system (Germany) with Mg Kα radia-
tion (hυ = 1,253.6 eV). The binding energy was calibrated
internally based on the C 1s line position.
3 | EXPERIMENTAL SECTION
3.1 | Material and equipment
3.2 | Synthesis procedure
of Fe3O4@C@PrNHSO3H NPs
All chemicals and solvents used for the experiment were
purchased from Merck and Sigma-Aldrich Companies.
The purity of products was observed by thin-layer chro-
matography (TLC) using silica gel SIL G/UV 254 plates.
Melting points were measured using an electro-thermal
9200 apparatus. The Fourier transform infrared (FT-IR)
spectra were recorded in the range of 400–4,000 cm1
using a PerkinElmer spectrophotometer (Spectrum Two
model, United States) by KBr pellets. Nuclear magnetic
resonance (1H NMR and 13C NMR) spectra were
recorded using Bruker DRX 500 in DMSO solvent. The
crystalline structure of the catalyst was examined by
X-ray diffraction (XRD) with a Bruker X-ray diffractome-
ter device (D8 Advanced Model, Germany) using Cu-Kα
radiation (λ = 0.154 nm, 40 kV, 30 mA) in the range of
The catalyst was prepared in three steps according to
Scheme 1. In the first step, the Fe3O4@C core–shell mag-
netic NPs were made of iron (III) chloride hexahydrate,
glucose, and urea in ethylene glycol solvent by the
solvothermal method. In this regard, the FeCl3.6H2O
(1.01 g) was dissolved in ethylene glycol until obtaining
an orange color of the mixture, and subsequently, urea
(2.25 g) and glucose (0.135 g) were added to the solution
under strong stirring. The clear mixture was transferred
to an autoclave and heated for 12 hr at 200ꢁC. The black
solid product (Fe3O4@C) was separated by an external
magnet and then washed with deionized water and
ethanol and dried at 60ꢁC for 6 hr.[44–47] In the second
step, 0.5 g of the synthesized Fe3O4@C catalyst was
mixed with dry toluene and placed in an ultrasonic bath

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NASEHI ET AL.
TABLE 3 One-pot syntheses of triazole derivatives using Fe3O4@C@PrNHSO3H NPsa
Entry
Ar
Product
M.P. (ꢁC) (literature)
Time (min)
Yieldb (%)
1
C6H5
133–134
60
95
(130–132)[51]
4a
4b
1a
4a
2
2-ClC6H4
137–140
60
60
(138–140)[51]
1b
4b
4c
3
4
3-ClC6H4
>240
60
60
80
70
4c
1c
4-ClC6H4
180–182
(181–183)[52]
4d
4e
4f
1d
4d
4e
4f
5
6
7
8
2,4-Cl2C6H3
233–235
90
60
60
60
90
83
95
60
(232–233)[53]
1e
3-BrC6H4
205
1f
3-NO2C6H4
>240
4g
1g
4g
4h
3-OHC6H4
188–190
4h
1h

NASEHI ET AL.
11
TABLE 3 (Continued)
Entry
Ar
Product
M.P. (ꢁC) (literature)
Time (min)
Yieldb (%)
9
3-MeC6H4
140–143
60
74
4i
1i
4i
10
C4H3S
>240
90
79
4j
1j
4j
aReaction conditions: Aromatic aldehydes (1 mmol), nicotinic hydrazide (1 mmol), ammonium acetate (2.5 mmol), and Fe3O4@C@PrNHSO3H NPs (0.06 g)
at 100ꢁC.
bIsolated yields of pure products.
at room temperature for 30 min. Then, 0.5 ml of
(3-Aminopropyl)trimethoxysilane (APTMS) was added
to it. Subsequently, the resulting solution was refluxed
at 100ꢁC for 48 hr. Finally, the resulting precipitate
(Fe3O4@C@PrNH2) was removed using a magnet and
washed several times with dry toluene, and placed in an
oven for hours to dry. In the third step, the resulting
Fe3O4@C@PrNH2 NPs were added to dichloromethane
(45 ml) in a three-neck flask. Then, chloro-sulfonic acid
(0.56 ml) was added to the mixture with stirring under atmo-
spheric N2 gas. After 15 min, when the HCl gas was
completely removed, the ultimate NPs (Fe3O4@C@
SCHEME 2 Reusability of Fe3O4@C@PrNHSO3H NPs during
PrNHSO3H NPs) were separated from the mixture utilizing
an external magnet. It was washed several times with dic-
hloromethane to remove excess chloro-sulfonic acid and
finally dried at room temperature.
the triazole synthesis
with ethanol/water (1:9) solution. Eventually, the prod-
uct was dried and purified by a rotary evaporator. All
synthesized triazole derivatives were identified by melt-
ing points (M.P.), FT-IR, 1H NMR, and 13C NMR
spectral data.
3.3 | General procedure for the synthesis
of triazole derivatives (4a–4j) in the
presence of Fe3O4@C@PrNHSO3H NPs
To synthesize the triazole derivatives, aromatic aldehydes
(1a–1j; 1 mmol), nicotinic hydrazide (2; 1 mmol), ammo-
nium acetate (3; 2.5 mmol), and Fe3O4@C@PrNHSO3H
NPs (0.06 g) were added to the reaction flask under stir-
ring at 100ꢁC. The reaction completion was monitored by
TLC. When the reaction was complete (60–90 min), the
produced sediments (4a–4j) were washed and filtered
3.4 | Investigation of
Fe3O4@C@PrNHSO3H NPs recyclability
The reusability of Fe3O4@C@PrNHSO3H NPs was inves-
tigated in the reaction of benzaldehydes (1a; 1 mmol),
nicotinic hydrazide (2; 1 mmol), ammonium acetate (3;

12
NASEHI ET AL.
2.5 mmol), and Fe3O4@C@PrNHSO3H NPs (0.06 g) at
100ꢁC as a model reaction (Scheme 2). After reaction
completion, Fe3O4@C@PrNHSO3H NPs were removed
with an external magnet, washed, and dried to prepare
for the next run. The Fe3O4@C@PrNHSO3H NPs could
be effectively recycled and reused for six runs without a
significant decrease in catalyst activity (Scheme 2).
Anal. Calculated for C13H9N5O2: C 58.43; H 3.39; N 26.21;
O 11.97%. Found: C 58.12; H 2.98; N 26.45; O 12.07%.
3.5.4 | 3-(5-(pyridin-3-yl)-1H-1,2,4-triazol-
3-yl)phenol (4h)
MP: 188–190ꢁC; IR (KBr) υ (cmÀ1): 3,776, 3,428, 3,212,
3,048, 2,928, 2,836, 2,716, 1,651, 1,574, 1,482, 1,407, 1,296,
1,140, 1,057, 967, 789, 681, 481; 1H-NMR (500 MHz,
DMSO-d6, Me4Si) δ (ppm): 7.51–7.53 (m, 3H), 7.77–7.82
(m, 3H), 8.45 (s, 1H), 8.77–8.78 (bs, 1H), 12.22 (s, 1H);
13C-NMR (500 MHz, DMSO-d6, Me4Si) δ (ppm): 162.11,
150.79, 150.01, 148.12, 140.81, 135.29, 133.42, 131.55,
129.43, 123.51, 121.97. MS Calculated for C13H10N4O
([M + H]+) 238.25 found 238. Anal. Calculated for
C13H10N4O: C 65.54; H 4.23; N 23.52; O 6.72%. Found: C
65.01; H 3.98; N 23.68; O 7.14%.
3.5 | The spectral data of some new
products
3.5.1 | 3-(3-(3-chlorophenyl)-1H-
1,2,4-triazol-5-yl)pyridine (4c)
MP: >240ꢁC; IR (KBr) υ (cmÀ1): 3,787, 3,448, 3,195,
3,016, 1,672, 1,553, 1,418, 1,270, 1,073, 957, 863, 679;
1H-NMR (500 MHz, DMSO-d6, Me4Si) δ (ppm): 7.52
(m, 2H), 7.72 (s, 1H), 7.82–7.84 (m, 2H), 8.46 (s, 1H), 8.79
(m, 2H), 12.22 (bs, 1H); 13C-NMR (500 MHz, DMSO-d6,
Me4Si) δ (ppm): 122.01, 126.41, 126.96, 130.48, 131.27,
134.16, 136.74, 140.75, 147.77, 150.82, 162.25. MS Calcu-
lated for C13H9ClN4 ([M + H]+) 256.05 found 256. Anal.
Calculated for C13H9ClN4: C 60.83; H 3.53; Cl 13.81;
N 21.83%. Found: C 61.03; H 3.12; Cl 13.93; N 21.85%.
3.5.5 | 3-(3-(m-tolyl)-1H-1,2,4-triazol-5-yl)
pyridine (4i)
MP: 140–143ꢁC; IR (KBr) υ (cmÀ1): 3,463, 3,197, 3,017,
1
1,667, 1,558, 1,404, 1,272, 1,063, 773, 680, 443; H-NMR
(500 MHz, DMSO-d6, Me4Si) δ (ppm): 2.37 (s, 3H), 7.17
(m, 2H), 7.50–7.57 (m, 2H), 8.15 (m, 1H), 8.45–8.70 (m,
2H), 8.35 (s, 1H), 12.27 (bs, 1H); 13C-NMR (500 MHz,
DMSO-d6, Me4Si) δ (ppm): 162.06, 150.78, 149.55, 140.95,
138.61, 134.46, 131.56, 129.24, 127.97, 125.16, 122.00. MS
Calculated for C14H12N4 ([M + H]+) 236.11 found 236.
Anal. Calculated for C14H12N4: C 71.17; H 5.12; N
23.71%. Found: C 70.97; H 5.45; N 23.86%.
3.5.2 | 3-(3-(3-bromophenyl)-1H-
1,2,4-triazol-5-yl)pyridine (4f )
MP: 205ꢁC decompose; IR (KBr) υ (cmÀ1): 3,787, 3,464,
3,194, 3,015, 1,674, 1,546, 1,413, 1,264, 1,136, 1,061,
1
947, 855, 667, 480; H-NMR (500 MHz, DMSO-d6, Me4Si)
δ (ppm): 7.44–7.96 (m, 5H), 8.44 (s, 1H), 8.80 (m, 2H),
12.21 (bs, 1H); 13C-NMR (500 MHz, DMSO-d6, Me4Si) δ
(ppm): 122.01, 122.67, 126.83, 129.80, 133.35, 140.74,
147.66, 150.81, 162.25. MS Calculated for C13H9BrN4 ([M
+ H]+) 300.00 found 300. Anal. Calculated for
C13H9BrN4: C 51.85; H 3.01; Br 26.53; N 18.60%. Found:
C 51.78; H 3.11; Br 26.42; N 18.58%.
3.5.6 | 3-(3-(thiophen-2-yl)-1H-1,2,4-triazol-
5-yl)pyridine (4j)
MP: >240ꢁC; IR (KBr) υ (cmÀ1): 3,936, 3,787, 3,410, 3,236,
2,836, 2,200, 1,687, 1,503, 1,409, 1,266, 1,144, 1,012, 799, 504;
1H-NMR (500 MHz, DMSO-d6, Me4Si) δ (ppm): 7.16 (s, 1H),
7.51–8.78 (m, 6H), 12.01 (bs, 1H); 13C-NMR (500 MHz,
DMSO-d6, Me4Si) δ (ppm): 121.92, 128.40, 129.90, 132.00,
136.74, 139.20, 140.88, 144.53, 149.85, 150.78, 161.88. MS
Calculated for C11H8N4S ([M + H]+) 228.27 found 228.
Anal. Calculated for C11H8N4S: C 57.88; H 3.53; N 24.54; S
14.04%. Found: C 58.05; H 3.72; N 24.37; S 13.84%.
3.5.3 | 3-(3-(3-nitrophenyl)-1H-1,2,4-triazol-
5-yl)pyridine (4g)
MP: >240ꢁC; IR (KBr) υ (cmÀ1): 3,421, 3,235, 3,064, 1,686,
1
1,529, 1,350, 1,266, 1,141, 1,063, 951, 820, 680; H-NMR
(500 MHz, DMSO-d6, Me4Si) δ (ppm): 7.42 (m, 2H), 7.84
(m, 2H), 8.01–8.03 (m, 1H), 8.68–8.78 (m, 2H), 8.87 (s,
1H), 12.22 (s, 1H); 13C-NMR (500 MHz, DMSO-d6, Me4Si)
δ (ppm): 121.97, 127.41, 128.03, 130.36, 131.75, 132.15,
133.87, 140.62, 145.35, 150.00, 150.78, 162.13, 168.43. MS
Calculated for C13H9N5O2 ([M + H]+) 267.08 found 267.1.
4 | CONCLUSIONS
In conclusion, Fe3O4@C@PrNHSO3H was synthesized
and introduced as a novel heterogeneous core–shell

NASEHI ET AL.
13
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magnetic nano-catalyst in the one-pot three-component
condensation reaction for the synthesis of triazole deriva-
tives. The beneficial features of the present protocol
include separability and reusability of the synthesized
nano-catalyst up to the six runs, short reaction time
period, excellent product yield, and operational simplic-
ity. Subsequently, the goal to design and prepare a new
and effective magnetic nano-catalyst for the green syn-
thesis of triazole derivatives with an increment in yield
and reduction in the waste footprint was achieved.
ꢀ
ꢀ
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How to cite this article: N. Nasehi, B. Mirza,
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