A novel water-dispersible and magnetically recyclable nickel nanoparticles for the one-pot reduction-Schiff base condensation of nitroarenes in pure water

Article abstract of DOI:10.1002/jccs.202100172

In this work, a heterogeneous nanocatalyst called Ni-Fe₃O₄@Pectin~PPA ~ Piconal was first synthesized, which was investigated as a bifunctional catalyst containing nickel functional groups. On the other hand, this Ni-Fe₃O₄@Pectin~PPA ~ Piconal catalyst in aqueous solvents shows a very effective performance at ambient temperature for the nitroarene reduction reaction with sodium borohydride, for which NaBH₄ is considered as a reducing agent. This is a novelty magnetic catalyst that was approved by various methods, including Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), Dynamic light scattering (DLS), Transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Inductively coupled plasma (ICP), Energy-dispersive X-ray spectroscopy (EDX), and Field emission scanning electron microscopy (FESEM) analyses. From the satisfactory results obtained from the reduction of nitrogen, this catalytic system is used for a one-pot protocol containing a reduction-Schiff base concentration of diverse nitroarenes. It was corroborated with the heterogeneous catalytic experiments on the one-pot tandem synthesis of imines from nitroarenes and aldehydes. Finally, the novel Ni-Fe₃O₄@Pectin~PPA ~ Piconal catalyst could function as a more economically desirable and environmentally amicable in the catalysis field. The favorable products are acquired in good to high performance in the attendance of Ni-Fe₃O₄@Pectin~PPA ~ Piconal as a bifunctional catalyst. This catalyst can be recycled up to six steps without losing a sharp drop.

Full text of DOI:10.1002/jccs.202100172

Received: 3 May 2021
Revised: 22 June 2021
Accepted: 24 June 2021
DOI: 10.1002/jccs.202100172
A R T I C L E
A novel water-dispersible and magnetically recyclable
nickel nanoparticles for the one-pot reduction-Schiff base
condensation of nitroarenes in pure water
Pouya Ghamari Kargar | Asiye Ravanjamjah | Ghodsieh Bagherzade
Department of Chemistry, College of
Abstract
Sciences, University of Birjand,
Birjand, Iran
In this work, a heterogeneous nanocatalyst called Ni-Fe3O4@Pectin~PPA ~ Piconal
was first synthesized, which was investigated as a bifunctional catalyst containing
nickel functional groups. On the other hand, this Ni-Fe3O4@Pectin~PPA ~ Piconal
catalyst in aqueous solvents shows a very effective performance at ambient tempera-
ture for the nitroarene reduction reaction with sodium borohydride, for which
NaBH4 is considered as a reducing agent. This is a novelty magnetic catalyst that
was approved by various methods, including Fourier-transform infrared spectros-
copy (FT-IR), X-ray powder diffraction (XRD), Dynamic light scattering (DLS),
Transmission electron microscopy (TEM), vibrating sample magnetometer (VSM),
Inductively coupled plasma (ICP), Energy-dispersive X-ray spectroscopy (EDX), and
Field emission scanning electron microscopy (FESEM) analyses. From the satisfac-
tory results obtained from the reduction of nitrogen, this catalytic system is used for
a one-pot protocol containing a reduction-Schiff base concentration of diverse
nitroarenes. It was corroborated with the heterogeneous catalytic experiments on
the one-pot tandem synthesis of imines from nitroarenes and aldehydes. Finally,
the novel Ni-Fe3O4@Pectin~PPA ~ Piconal catalyst could function as a more eco-
nomically desirable and environmentally amicable in the catalysis field. The favor-
able products are acquired in good to high performance in the attendance of Ni-
Fe3O4@Pectin~PPA ~ Piconal as a bifunctional catalyst. This catalyst can be
recycled up to six steps without losing a sharp drop.
Correspondence
Ghodsieh Bagherzade, Department of
Chemistry, College of Sciences, University
of Birjand, Birjand 97175-615, Iran.
Email: gbagherzade@gmail.com,
bagherzadeh@birjand.ac.ir
Funding information
University of Birjand
K E Y W O R D S
nanoparticles, nitroarene, pectin, reduction, Schiff base
1 | INTRODUCTION
The goal of green chemistry is to acquire new methods
and technologies and introduce them into the chemical
In the last two decades, the chemical industry has been
increasingly moving toward the availability and applica-
tion of safer chemical processes based on green chemis-
try.[1,2] According to the principles of green chemistry,
today we design chemical processes in such a way that
they have the least unpleasant effects on human health
and the environment, which is an inevitable necessity.[3,4]
production cycle to bring about a fundamental change in
chemical processes, and to eliminate the unfavorable envi-
ronmental effects caused by them as much as possible.[5]
In the design of chemical processes, raw materials with
the ability to reproduce, such as materials of plant and nat-
ural origin, should be used instead of materials such as
fossil fuels and mineral raw materials. The most important
J Chin Chem Soc. 2021;1–18.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
1

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GHAMARI KARGAR ET AL.
development in the field of green organic chemical reac-
tions is the use of green catalysts.[6] It is important to use
well-performing and recyclable catalysts and use safe sol-
vents such as water and ionic liquids.[7,8] Organic solvents
are sources of chemical pollutants due to their toxicity and
high use in the chemical industry, and their replacement
or removal helps the environment.[9] As mentioned, cata-
lysts are one of the most effective tools in green chemistry.
Increasing the selectivity of a reaction, reducing the
required temperature, reducing the reactions and by-prod-
ucts, and increasing the final products' efficiency are
advantages of using catalysts in chemical processes.
Among these catalysts, we can mention heterogeneous
catalysts, including heterogeneous magnetic catalysts,
which is an essential step in advancing green chemis-
try.[10,11] This ideal catalyst, while having high activity and
selectivity, allows it to be easily separated from the reac-
tion medium using only an exterior magnet. Magnetite
nanoparticles (Fe3O4) have recently been considered due
to their unique characteristics such as heat and mechani-
cal consistency, meager preparation price, and suitability
for production in larger sizes.[12,13] The surface of a
maghemite or magnetite nanoparticle magnetic is rela-
tively inert and does not usually allow strong covalent
bonds with functionalization molecules. However, the
reactivity of the magnetic nanoparticles can be improved
by coating a layer of silica, cellulose, pectin onto their sur-
face.[14–16] To prevent the accumulation and oxidation of
nanoparticles, suitable coatings are used to protect the
container are just a stable process that prevents product
separation during operation, minimizes the refining pro-
cess, and increases safety.[25] By imitating biological sys-
tems, some research groups have designed and
synthesized catalysts that include several sorts of active
centers to uplift domino reactions.[26] One of the most
available compounds in organic synthesis is nitro group
compounds. Today, toxic organic waste polluting the
environment has attracted widespread attention.
Nitroarene plays an important role in synthesizing
organic compounds, including reduction reaction and
aniline formation.[27,28]
In particular, 4-nitrophenol (4-NP) is a very harmful
organic pollutant due to its excellent solubility and stabil-
ity in water or agricultural or industrial wastewater. Cata-
lytic reduction of 4-nitrophenol to 4-aminophenol is
known as an effective method for the treatment of water
contaminated with 4-nitrophenol. Aromatic amines are
widely used as precursors and intermediates for the pro-
duction of herbicides, drugs, dyes, pigments, and other
agrochemicals.[29] Among the available methods, reducing
nitroarenes to arylamines using NaBH4 as a cost-effective
reducing agent performed by intermediates or other
catalysts is very important. Various catalysts have been
used in this field,[30] such as Ni2B,[31] Fe3O4@SiO2
@cellulose@poly-GMA@EDA@Cu2+ [32]
,
Pd
NPs/
RGO,[33] CuFe2O4,[34] Ag@VP/CTS,[35] Fe3O4/PVA-10%
Ag,[36] Ag/Fe3O4-IT,[37] and copper nanoparticles.[38]
Although the reported methods have their advantages, the
catalyst is environmentally friendly, its raw materials are
inexpensive, it is easy to manufacture, and it is highly
active. It can be easily separated from the reaction
medium. These catalysts are of great importance. One of
the derivatives of aniline is imines, which are various
mediators in organic synthesis and are generally prepared
by the reaction of amines and carbonyl compounds known
as azomethine. The azomethine group gives Schiff base
unique biological, medicinal, and antitumor properties.[39]
In addition, the Schiff base has applications in the
food industry. They are also used as pigments, intermedi-
ates in organic chemical reactions, catalysts in a variety
of reactions, including alcohol oxidation, polymer stabi-
lizers, and chemical sensors. Reports have been made
about the design of a method for the reduction of nitro
arenas in the presence of Au/TiO2/H2,[40] Fe/HCl,[41] Se/
NaOAc/CO,[42] Ni/SiO2/H2,[43] CoOx@NC-800/H2,[44] for
which the Schiff base intramolecular reaction is used and
introduced as a safe synthetic method. These protocols
start with nitroarene and require special equipment to
control high pressures, inflammable hydrogen gas, haz-
ardous carbon monoxide or highly acidic conditions, high
pressures, and high temperatures. These requirements
make the reported methods for synthetic chemistry on a
nanoparticles. The outer shells of iron oxides such as
[18]
polymers,[17] zeolites,
titanium dioxide,[19] and sil-
ica[20,21] are being studied. Recently, biopolymer-based
nanocomposites have been studied in all scientific fields.
On the other hand, these compounds have good applica-
tion and chemical properties.
These catalysts are offered due to their biocompatibil-
ity, catalytic degradability, thermal and chemical stabil-
ity, and some solid performance characteristics, which
include catalytic support. Pectin is a natural biopolymer
and a heterogeneous group of acidic structural polysac-
charides present in the skin cell walls of fruits and vege-
tables. It is one of the most numerous biodegradable
polymers due to its natural and nonhydrocarbon oil. Pec-
tin is also used as a drug carrier and release system for
cancer drugs.[22] Pectin nanoparticles can also be used as
a reliable carrier in gene transfer. Green nature and envi-
ronmental friendliness, high surface area, cheapness and
availability, good interaction, and consequent low metal
washing during catalytic cycles, and easy modification
have led to the use of pectin as catalytic support.[23]
Multifunctional catalysts that enable the multistage reac-
tion in a reaction vessel have great potential to increase
the reaction's performance.[24] Several reactions in a

GHAMARI KARGAR ET AL.
3
laboratory scale far from ideal. Since the synthesis of
environmentally safe catalysts is in line with our
research, we want to announce the synthesis of a new
dual-function heterogeneous nanocatalyst. After describ-
ing this catalyst, we used it for the reduction of nitroben-
zene to aniline. As well as sodium borohydride as a
reducing agent and water as a green solvent at ambient
temperature was used.
Herein, in accordance with green chemistry consid-
erations as well as an insight into the economic and
environmental factors, we developed an efficient proto-
col for the aniline reaction of nitroarenes with NaBH4
by introducing a new magnetically recoverable Ni-
F3O4@Pectin~PPA ~ Piconal nanocomposite in a highly
efficient and selective manner under mild conditions.
This catalyst greatly reduced this transformation cost,
and the resulted operation and work-up procedures
were greatly simplified. The advantages of using this cat-
alyst include simple recovery, green nature, good disper-
sion of its particles in a water solvent, low washing rate
of active species of nickel catalyst, and its high
reactivity. With promising results from nitroarene
reduction and to the extent of the versatility of the pre-
sent method, a one-pot Schiff base reduction cascade of
nitroarenes and benzaldehyde was performed by this
approach with high yields.
2 | RESULTS AND DISCUSSION
2.1 | Catalyst characterization
Scheme
1 shows the method of synthesis of Ni-
Fe3O4@Pectin~PPA ~ Piconal. At first, Fe3O4@pectin was
functionalized by 3-chlorotrimethoxypropylsilane and
reacted with Schiff base ligand PPA ~ Piconal. Finally, Ni-
Fe3O4@Pectin~PPA ~ Piconal was obtained from the reac-
tion of Fe3O4@Pectin~PPA ~ Piconal with Ni (OAc)2. Using
FT-IR spectroscopic technique, chemical structures of all the
synthesized compounds were authenticated FT-IR spectra of
the Schiff base ligand (a), Fe3O4 (b), Pectin (c), Fe3O4@Pectin
(d), Fe3O4@Pectin~Cl (e), Fe3O4@Pectin~ PPA ~ Piconal (f),
SCHEME 1 Synthesis of Ni-
Fe3O4@Pectin~PPA ~ Piconal
catalyst

4
GHAMARI KARGAR ET AL.
As shown in Figure 1a, the FT-IR spectrum of com-
pound PPA ~ Piconal indicates the Schiff base reaction
between p-phenyldiamine and 2-Picolinaldehyde, the
characteristic peaks at 1,232 cmÀ1 (C N stretching vibra-
tion), 1,470 and 1,580 cmÀ1 (C═C aromatic stretching
vibration), 1,661 cmÀ1 (C═N stretching vibration),
3,105 cmÀ1 (C H aromatic stretching vibration), and
3,295–3,380 cmÀ1 (NH2 stretching vibration) confirm the
structure of PPA ~ Piconal (Figure 1a). Figure 2b shows
the FT-IR spectrum of Fe3O4 spectrum (Figure 2b), and
the peaks appearing in the range of ~577, 1,625, and
3,420 cmÀ1 are attributed to the tensile vibration of
Fe O, the flexural vibration of the adsorbed water, as
well as the surface hydroxyl groups. The FT-IR spectrum
of pectin (Figure 2c) shows the stretching vibrations of
the O H group at 3,200–3,450 cmÀ1 and the stretching
vibrations of the C═O, C O group at around 1,710 and
1,120 cmÀ1
.
With the addition of pectin in the Fe3O4@Pectin
(d) spectrum, the stretching vibrations of the Fe O,
C═O, and O H at 577, 1,645, and 3,420 cmÀ1 confirmed
the formation of Fe3O4 nanoparticles. In addition, the
C O tensile vibration appeared at 1,044 cmÀ1 and C H
adsorptions of about 2,900–3,000 cmÀ1 have also
appeared. In the FT-IR spectrum of Fe3O4@Pectin~Cl
(Figure 1e), a new sharp peak at 1,155 cmÀ1 was assigned
to the stretching vibration of Si O. In the
Fe3O4@Pectin~PPA ~ Piconal spectrum (g), in addition
to the stretching vibration of Fe O, Si O, and C H ali-
phatic corresponding to the Fe3O4@Pectin~Cl, tensile
vibrations related to C N, C═C, C═N, and C H of the
Schiff base ligand are observed. These absorption bonds
confirm the successful preparation of the catalyst. Fur-
thermore, the complexation of nickel ions to nitrogen
causes the imine bond absorption 1,650 cmÀ1 to lower
wavenumbers 1,625 cmÀ1 by about 25 cmÀ1, and this
shift wavenumbers showed that azomethine nitrogen
participated in bonding with metal ion and affirming the
coordination of C═N stretch to the metal via a nitro-
gen atom.
FIGURE 1 FT-IR spectrum of Schiff base ligand PPA ~ Piconal
A vibrating sample magnetometer (VSM) device is
used to measure the magnetic properties of magnetic
materials. The VSM curve shows at ambient temperature
for nanoparticles (a) Fe3O4, (b) Fe3O4@Pectin, and
(c) Ni-Fe3O4@Pectin~PPA ~ Piconal. The magnetic satu-
ration values for these nanoparticles are 63.23, 53.08, and
43.23 emu/g, respectively, as shown in Figure 5. As it
turns out, Ni-Fe3O4@Pectin~PPA ~ Piconal has the least
amount of saturation, but the amount of magnetic for Ni-
Fe3O4@Pectin~PPA ~ Piconal is such that it can be easily
separated from the reaction medium using a magnet
(Figure 3).
FIGURE 2 FT-IR spectrum of (a) Fe3O4, (b) Pectin,
(c) Fe3O4@Pectin, (d) Fe3O4@Pectin~Cl, (e) PPA ~ Piconal (f)
Fe3O4@Pectin~PPA ~ Piconal (g) Ni-Fe3O4@Pectin~PPA ~ Piconal
and Ni-Fe3O4@Pectin~PPA ~ Piconal (g) catalysts respec-
tively shown in Figures 1 and 2.

GHAMARI KARGAR ET AL.
5
The X-ray diffraction pattern of the Fe3O4, Ni-
Fe3O4@Pectin~PPA ~ Piconal is shown in Figure 4.
Figure 2a shows the size of the magnetic NPs was
determined from X-ray line broadening using the
Debye–Scherrer formula (D = 0.9/ˇ cos, where D is the
average crystalline size. Several prominent Bragg reflec-
tions by their indices (220), (311), (400), (422), (511), and
(440) reveal that the resultant magnetic NPs were Fe3O4
and structure is that of an inverse spinel.[45] XRD pattern
in (Figure 4b) shows that peaks at 2θ = 35.87ꢀ, 43.97ꢀ,
62.92ꢀ, 71.72ꢀ, and 74.77ꢀ corresponding to the (111),
(200), (220), (311), and (222) crystallographic phases in
XRD pattern are related to Ni (II).[46] As a result, the high-
angle XRD pattern of Ni-Fe3O4@Pectin~PPA ~ Piconal
catalyst shown in Figure 4c in addition fracture peaks
corresponding to the standard Fe3O4 and Ni (II) indicate
that the surface modification of MNPs does not damage
the structure of Fe3O4 core. In contrast, two peaks at
2θ = 21ꢀ corresponding to the (101) XRD pattern confirm
in relation to pectin.[47]
FIGURE 3 VSM pattern (a) Fe3O4, (b) Fe3O4@Pectin and
(c) Ni-Fe3O4@Pectin~PPA ~ Piconal
We used field emission scanning electron microscopy
(FE-SEM) and TEM analyses to study the structure, distri-
bution, morphology, as well as average particle size. Fig-
ures 5 and 7 show the FE-SEM and TEM images of the Ni-
Fe3O4@Pectin~PPA ~ Piconal catalyst. As can be seen
from these two analyses, the catalyst has a spherical struc-
ture with a relatively uniform particle distribution. The
average particle size of Ni-Fe3O4@Pectin~PPA ~ Piconal
in the histogram is ~between 16 and 28 nm Figure 6. FE-
SEM and DLS analyses were employed to obtain a visual
image of the supported catalyst, find out the shape, mor-
phology, particle distribution, and also EDX analysis was
conducted to determine the elements in the prepared sam-
ples qualitatively.
FE-SEM and DLS analyses were employed to obtain a
visual image of the supported catalyst, find out the shape,
morphology, particle distribution, and also EDX analysis
FIGURE 4 XRD of (a) Fe3O4; (b) Ni (II); (c) Ni-
Fe3O4@Pectin~PPA ~ Piconal
FIGURE 5 TEM image of Fe3O4@NFC-ONSM-Ni (II)

6
GHAMARI KARGAR ET AL.
was conducted to determine the elements in the prepared
samples qualitatively (Figure 7).
The average diameters of particles are evaluated to be
about 18 nm for Fe3O4 (Figure 8a) and 28 nm for Ni-
Fe3O4@Pectin~PPA ~ Piconal (Figure 8b). Besides, the
best technique for verification of catalyst preparation is
inductively coupled plasma optical emission spectroscopy
(ICP-OES) analysis. Loading amount of Ni on the catalyst
was measured by inductively coupled plasma optical
emission spectroscopy (ICP-OES) instruments due to
more attainment. The experiment indicated that
1.2 mmol of Ni metal per gram of the catalyst (1.2 mmol
in 1 g) was loaded on the catalyst framework Ni-
Fe3O4@Pectin~PPA ~ Piconal. Also, the analyses give the
percentage of the elements as follows: 45.54%wt, 2.33%
wt, and 7.10%wt for Fe, Si, and Ni, respectively.
The thermo-gravimetric analysis (TGA) analysis was con-
ducted to determine the Ni-Fe3O4@Pectin~PPA ~ Piconal
nanocatalyst. The results are illustrated in Figure 9. TGA
spectrum of Ni-Fe3O4@Pectin ~PPA ~ Piconal shows little
weight loss, which is about 5% in the range of 25–800ꢀC. This
FIGURE 6 Particle size distribution histogram of
Ni-Fe3O4@Pectin~PPA ~ Piconal
FIGURE 7 FE-SEM image (left) and EDX (right) images of the magnetic nanoparticles: (a) Fe3O4, (b) Ni-Fe3O4@Pectin~PPA ~ Piconal

GHAMARI KARGAR ET AL.
7
FIGURE 8 DLS analysis of pure (a) Fe3O4, (b) Ni-Fe3O4@Pectin~PPA ~ Piconal
bifunctional heterogeneous catalyst for the one-pot analysis,
various efficiency levels were measured for the reduction of
nitroarenes. For this purpose, NaBH4 was used to produce
clean hydrogen. The catalytic performance of Ni-
Fe3O4@Pectin~PPA ~ Piconal was searched for nitroarene
reduction reaction (Scheme 3). For this purpose, the reduc-
tion of nitrobenzene at room temperature was chosen as a
model reaction to optimize the reaction conditions such as
solvent and the amount of the catalyst and NaBH4
(Table 1). As indicated in Table 1, aqueous media and
0.5 mol% of the catalyst are the best choices for these reac-
tions (Table 1, entry 3). It is worth mentioning that without
solvent and reducing agent using 0.5 mol% of the catalyst
after 24 hr, no product was obtained. In the presence of the
reducing agent, only a low conversion was obtained after a
reaction time of 24 hr (Table 1, entries 6 and 7). The exami-
nation of other organic solvents, both polar and non-polar,
showed that despite the high efficiency of other polar sol-
vents, water is the most suitable solvent for the nitroben-
zene reaction (Table 1, entry 1–5). This phenomenon could
be attributed to the property of greater activity of NaBH4 in
water. These reaction conditions have advantages such as
easy reactors, straightforward, and efficient work-up proce-
dures that are often more environmentally friendly and
safe. Increasing the amount of catalyst and sodium borohy-
dride (Table 1, entry 8–14) on improving the reaction effi-
ciency in aqueous solvent was investigated. Increasing the
amount of the catalyst to 0.6 mol% did not produce any
effect on the yield of the desired product (Table 1, entry 11).
The reaction proceeded smoothly in the absence of catalyst
and the presence of lower amounts of the catalyst (Table 1,
entries 8–10). The increase in the amount of sodium boro-
hydride of 1–2 mmol improved the efficiency from 75 to
90% (Table 1, entries 12 and 13). Finally, a further increase
in the amount of sodium borohydride does not positively
affect the reaction efficiency (Table 1, entries 14 and 15).
The nitroarene derivatives were obtained in satisfac-
tory yields and the results are summarized in Table 2.
However, the results of the nitroarene reactions depend
FIGURE 9 TGA curve for Ni-Fe3O4@Pectin~PPA ~ Piconal
might be due to the loss of residual water and organic com-
ponents in the Ni-Fe3O4@ Pectin~PPA ~ Piconal. The first
mass reduction phase occurred at 25–125ꢀC, caused by the
water's loss absorbed in the nanocatalyst surface. The second
phase occurred at 150–455ꢀC, which could have arisen due
to the breakdown of the bonds and destruction of the pectin
structure. Moreover, the weight loss of about 1% in the tem-
perature range between 650 and 800ꢀC may be due to the
decomposition of organic moieties on the surface of the
Fe3O4@Pectin core–shell nanoparticles.
2.2 | Catalytic performance of
Ni-Fe3O4@Pectin~PPA ~ Piconal
The adoption of ligand-functionalized core–shell nano cata-
lysts as a magnetic catalyst has been explored extensively in
recent years due to coordinatively unsaturated metal sites
and the microporous nature. It is believed that both the tun-
able pore structures and catalytically active sites of the cata-
lysts could be used at the same time to do the chemical
synthesis in a one-pot manner. Therefore, to evaluate the
catalytic activity of Ni-Fe3O4@Pectin~PPA ~ Piconal as a

8
GHAMARI KARGAR ET AL.
SCHEME 3 Model tandem
reduction-Schiff base
condensation catalyzed by Ni-
Fe3O4@Pectin~PPA ~ Piconal
TABLE 1 Optimization of nitrobenzene reduction reaction conditions by Ni-Fe3O4@Pectin~PPA ~ Piconal catalyst
Entry
Solvent
EtOH
MeOH
Water
CH3CN
DMF
Catalyst (mol%)
NaBH4 (mmol)
Temp. (ꢀC)
R.T.
Time (min)
Yielda (%)
1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
-
2.5
2.5
2.5
2.5
2.5
2.5
-
120
120
20
60
75
98
70
50
Trace
-
2
R.T.
3
R.T.
4
R.T.
60
5
R.T.
60
6
Neat
R.T.
24 hr
24 hr
180
60
7
Neat
R.T.
8
Water
Water
Water
Water
Water
Water
Water
Water
2.5
2.5
2.5
2.5
1
R.T.
30
85
93
98
75
90
96
92
9
0.1
0.3
0.6
0.5
0.5
0.5
0.5
R.T.
10
11
12
13
14
15
R.T.
45
R.T.
20
R.T.
60
2
R.T.
30
3
R.T.
20
4
R.T.
20
Note: Reaction conditions: Nitrobenzene (1.0 mmol), catalyst (0.5 mol%), sodium borohydride (2.5 mol%), and H2O (3 ml), room temperature.
aIsolated yield.
on the positions of the substitution groups on the aro-
matic ring, the effect of various electron-donating and
electron-withdrawing groups, and the catalyst activity.
The easiest heterogeneous process is chemisorption
followed by the Langmuir–Hinshelwood mechanism. The
most ordinary and known mechanism is the separation of
hydrogen atoms from sodium borohydride, which
takes place on the surface of the nickel in the
Ni ~ Fe3O4@Pectin~PPA ~ Piconal nanocatalyst (Scheme 2).
The single 1s electron of each hydrogen atom coordinates
with the d-orbitals of the nickel acetate, forming a pair of
chemisorption bonds (metal-hydride). Howbeit these new
bands are more permanent than the single covalent bond
they interchange (BH4À), the result hydrogen atoms are able
to transfer alongside the surface due to the successive scope
of the d-orbital conduction bond. Though the adsorbed
hydrogen atoms are not free radicals, they are nevertheless
highly reactive, so if a second, nitroarenes molecular species
adsorbs onto the same surface, an interchange of atoms may
be possible.[51] An acceptable mechanism for the catalytic
reduction of nitroarenes compounds was proposed based on
the Langmuir–Hinshelwood mechanism (Scheme 2).
According to the model, the decorated Ni(OAc)2 on the
Fe3O4@Pectin~PPA ~ Piconal surface acts as electron-
acceptors, reversibly adsorbing hydride onto the NPs from
NaBH4. The hydrogenated Ni-Fe3O4@Pectin~PPA ~ Piconal
catalyst adsorbs the substrate with the expulsion of hydro-
gen, followed by transferring four moles of surface-bound
hydride to the NO2 group of nitro compounds in the rate-
determining step of the reduction. Prompt desorption of the

GHAMARI KARGAR ET AL.
9
TABLE 2 Synthesis of nitrobenzene reduction reaction conditions by Ni-Fe3O4@Pectin~PPA ~ Piconal catalyst
Entry
Nitroarenes
Time (min)
Yielda (%)
M.P. (ꢀC) obtained reported
TON
—
TOF
—
Ref.
—
b
1
Nitrobenzene
20
30
20
15
20
15
20
15
20
20
45
20
20
20
30
98
97
80
98
96
96
95
98
98
97
93
93
96
97
85
—
2
4-nitobenzyl alcohol
1-Methyl-4 nitrobenzene
1-Chloro-4-nitrobenzene
1-Chloro-3-nitrobenzene
1-Bromo-4-nitrobenzene
1-Bromo-3-nitrobenzene
1-Methoxy-4-nitrobenzene
4-Nitroaniline
61–62
61–63
194
160
196
192
192
190
196
196
194
186
186
192
194
170
388
[48]
[48]
[48]
[49]
[48]
[49]
[48]
[48]
[49]
[49]
[50]
[50]
[48]
[50]
3
42–43
43–44
484.8
784
4
67–68
67–70
5
120–121
60–61
121–123
60–62
581.8
786
6
7
120–121
57–58
119–122
57
575.7
784
8
9
138–139
100–101
171–172
119–120
185–186
61–62
138–140
100–102
171–173
120–121
186–187
60–63
593.9
587.8
248
10
11
12
13
14
15
2-Nitroaniline
2-Nitrophenol
3-Nitrophenol
563.6
581.8
587.8
340
4-Nitrophenol
4-Nitrobenzaldehydec
5-Nitro-1H-indole
131–132
130
aIsolated yield.
bLiquid.
cProduct: 4-aminobenzyl alcohol.
(b)
(a)
(d)
(c)
SCHEME 2 The plausible mechanism for the Nitrobenzene reduction catalyzed by Ni-Fe3O4@Pectin~PPA ~ Piconal

10
GHAMARI KARGAR ET AL.
TABLE 3 Synergistic effects of the
present Ni-Fe3O4@Pectin~PPA ~
Piconal catalyst on the synthesis of
iminea
Entry
Catalyst
Time (hr)
Yieldb (%)
1
2
3
4
5
6
Fe3O4
24
24
24
3
0
Fe3O4@Pectin
0
PPA ~ Piconal
0
Fe3O4@Pectin-PPA ~ Piconal
Ni(OAc)2
Trace
30
95
3
Ni-Fe3O4@Pectin~PPA- ~ Piconal
1
aModel reaction conditions: Nitroarene (1 mmol), Benzaldehyde (1 mmol), NaBH4 (2.5 mol%), H2O, room
temperature.
bIsolated yields.
TABLE 4 Summary of the reduction-Schiff base condensation on substituted benzaldehyde derivatives and nitroarenes by Ni-
Fe3O4@Pectin~PPA ~ Piconal as a bifunctional heterogeneous catalysta
2a, 95%b, 60 min
2b, 85%b, 90 min
2c, 80%b, 90 min
TON: 190, TOF: 190
TON: 170, TOF: 113.3
TON: 160, TOF: 106.6
2d, 80%b, 60 min
2e, 92%b, 120 min
2f, 96%b, 75 min
TON: 160, TOF: 160
TON: 184, TOF: 368
TON: 192, TOF: 153.6
2g, 93%b, 90 min
2h, 86%b, 90 min
2i, 93%b, 90 min
TON: 186, TOF: 124
TON: 172, TOF: 103.6
TON: 186, TOF: 124
2j,85%b, 90 min
2k, 87%b, 90 min
2l, 85%b, 90 min
TON: 170, TOF: 113.3
TON: 174, TOF: 116
TON: 170, TOF: 113.3
2m, 90%b, 90 min
2n, 88%b, 90 min
2o, 80%b, 90 min
TON: 180, TOF: 120
TON: 176, TOF: 117.3
TON: 160, TOF: 106.6
aReaction conditions: Nitroarenes (1 mmol), Benzaldehyde derivatives (1 mmol), H2O, Ni-Fe3O4@Pectin~PPA ~ Piconal (0.5 mol%), room temperature.
bIsolated yields.
newly formed anilines then occurs, allowing the catalyst
surface to be regenerated for another reaction cycle. The
optimized reaction condition for nitroarenes reduction next
examined the one-pot synthesis of imines by reduction
of nitrobenzene followed by Schiff base formation
with benzaldehyde in aqueous media catalyzed by

GHAMARI KARGAR ET AL.
11
Ni-Fe3O4@Pectin~PPA ~ Piconal as a bifunctional hetero-
geneous catalyst (Scheme 3).
reduction-Schiff base condensation with aryl aldehydes,
yielding the corresponding imines. Fortunately, a good
result was achieved to produce the imine as a final prod-
uct in previous conditions in terms of temperature, cata-
lyst amount, and reaction medium (Table 4). The
substituted nitrobenzenes with halides ( Cl, Br) rev-
ealed excellent yields for the corresponding products
(respectively 2b, 2c). p-nitrobenzene gave the lowest yield
for the corresponding imine (2d) after only 60 min. Sali-
cylic aldehyde with nitrobenzene showed a high yield for
the corresponding product (2e). Second, p-anisidine and
benzaldehyde with the electron-withdrawing ( NO2)
and electron-donating ( OMe) functional groups as well
as displayed excellent yields (respectively 2j, 2k). The
reaction of p-anisidine and other substituted benzalde-
hyde ( OH, Cl, Br) gave good yields for their prod-
ucts (respectively 2g, 2h, 2i). Finally, the benzaldehyde
with different functional groups and p-bromoaniline as
the partner coupling produced the corresponding prod-
ucts with pleasant yields (2l-2o). It should be noted that
the reaction progress was evaluated in the absence of cat-
alyst, a negligible proceed was observed. The precursor
salt of Ni (OAc)2 showed negligible catalytic activity for
the reduction-Schiff base condensation.
For further research on the nature of the Ni-Fe3O4@
Pectin~PPA ~ Piconal and the important role of synthetic
components in the formation of this catalyst in the
reduction-Schiff base, condensation was investigated.
Before examining the imine derivatives, The model reac-
tion was carried out using Fe3O4, Fe3O4@Pectin,
PPA-Piconal, Fe3O4@Pectin-PPA-Piconal, Ni(OAc)2, and
Ni-Fe3O4@ Pectin-PPA-Piconal were separately studied
in the aniline reaction and then tandem imine reaction
(Table 3). As shown in Figure 8, no product was gained
by using Fe3O4, Fe3O4@Pectin and PPA-Piconal species.
However, when the reaction was carried out in the pres-
ence of Fe3O4@ Pectin-PPA-Piconal, the result was far
from satisfactory. Ni (OAc)2, as precursor salt of Ni-
Fe3O4@Pectin~PPA ~ Piconal, showed lower catalytic
activity than Ni-Fe3O4@ Pectin~PPA ~ Piconal, with a
conversion of 30% being obtained after 2 hr. These find-
ings indicated that the enhanced magnetic catalytic activ-
ity of Ni-Fe3O4@Pectin-PPA-Piconal could be attributed
to the synergistic effect of nickel metal and
Fe3O4@Pectin-PPA-Piconal toward the aniline and imine
reaction as a high-efficiency catalyst (see the magnetic
catalytic mechanism synthesis part for more details).
To show the versatility and the wide scope of this pro-
Our recent study on the reaction mechanism
between benzaldehyde and aniline is performed. The
imine reaction is two steps, which the mechanism of
tocol,
a variety of nitroarenes were subjected to
SCHEME 4 The plausible
mechanism for the imine catalyzed by
Ni-Fe3O4@Pectin~PPA ~ Piconal

12
GHAMARI KARGAR ET AL.
TABLE 5 Comparison of the reaction conditions and results for the synthesis of imine
Catalysts
Catalyst amount
25 mg
Conditions
Time (hr)
Yield (%)
Ref
RuO2/GO
Toluene/air/100ꢀC
H2O/O2/60ꢀC
3
12
2
63
94
91
65
92
99
92
92
97
95
[52]
Au6Ag1/PAAS
2 mol%
2 mol%
2 mol%
50 mg
[53]
Ru (OH)x/TiO2
Toluene/O2/100ꢀC
H2O/O2/40ꢀC
[54]
Au-Pd/resin
12
3
[55]
Cu0.9Fe0.1@RCAC
Pd-Au@Mn (II)-MOF
MnOx/TiO2@SBA-15
γ-Fe2O3
Toluene/air, LED/120ꢀC
Toluene/air/110ꢀC
Toluene/air/80ꢀC
Toluene/air/80ꢀC
Toluene/air/80ꢀC
H2O/air/R.T.
[56]
2 mg
30
24
12
2
[57]
100 mg
300 mg
50 mg
[58]
[59]
M-350 (amorphous manganese oxide)
Ni-Fe3O4@Pectin~PPA ~ Piconal
[60]
0.5 mol%
1
This work
the first step is similar to what is given in the previous
section (reduction of nitroarene to aniline in Scheme 2).
Concerning the catalysis of imine synthesis in the
basic, a plausible mechanism was proposed for the sec-
ond step (Scheme 4). Actually, the C-NH groups of
linkers could act as highly reactive base sites and a
Brønsted proton of aniline is absorbed by the nitrogen
of amine. The generated stable anion is subjected to
nucleophilic attack on the carbonyl carbon atom of the
2.3 | The recyclability tests of
Ni-Fe3O4@Pectin~PPA ~ Piconal
The separated catalyst was thoroughly washed with dis-
tilled water, then with ethanol, and then reused in
another cycle under the same conditions. The same
conditions were evaluated for the regenerative reduction-
Schiff base condensation. Residual activation was ana-
lyzed by ICP for measurement: the amount of nickel that
goes from the catalyst to the solution. Eventually, this
cycle was repeated six times. There was a slight decrease
in the yield of the obtained product, which can be attrib-
uted to the partial leaching of nickel from the substrate
surface. Figure 8 shows the catalyst stability diagram
with the efficiency of each cycle. Also, metal leaching of
the catalyst was measured in each cycle (Figure 10).
As shown in Figure 11, a few leaching was observed
for Ni-Fe3O4@Pectin~PPA ~ Piconal, whereas only 2.2%
for aniline reaction and 2.5% for reduction-Schiff base
condensation metal leaching was observed after the sixth
run. After being used for six cycles in successive reac-
tions, it still had high catalytic performance, as depicted
in Figure 10. Moreover, ICP analysis of the catalyst for
each element demonstrated an insignificant change in
their weight percentage than the corresponding fresh
values: Fe 45.58, Si 2.35, Ni 6.9 wt%. These results dem-
onstrated insignificant changes in the percentages of the
elements.
substituted
aromatic
aldehydes.
Finally,
Ni-
Fe3O4@Pectin-PPA-Piconal comes back to the initial
structure after two runs of protonation and
deprotonation, the product release from the surface of
the catalyst. According to the proposed mechanism,
the high catalytic activity of Ni-Fe3O4@Pectin-PPA-
Piconal in the imine reaction can be attributed to the
presence of the azomethine group in the linker.
These results indicated that the simultaneous
presence of the Fe3O4@Pectin-ligand and metal group in
the framework enhanced the catalytic activity.
To investigate the catalytic activity of Ni-
Fe3O4@Pectin~PPA ~ Piconal, we compared the results
of the reaction of imine (Table 5) with the previously
reported. Table 4 lists the approaches to the catalysts lit-
erature and each have their advantages, but some of
them suffer from various demerits such as the use of the
expensive catalyst, harsh reaction condition, toxic chemi-
cal, and longer reaction time. Catalysts in the literature
and results are given in Table 5. Overall, the obtained cat-
alyst showed better yield and values in a shorter reaction
time than other catalysts reported in the previous litera-
ture. Thus, the present protocol (Table 5, entry 10) has
several advantages from greener, economic, simple reac-
tion setup, and product isolation by simple magnet com-
pare with reported methods for the synthesis of imine
derivatives.
Furthermore, FT-IR spectrum, XRD, VSM, FE-SEM,
and EDX analyses of the recycled catalyst after six times
were examined (Figure 12).
Both the FT-IR spectrum of the recovered catalyst (red
and blue) has a complete match with the corresponding
fresh catalyst (Figure 2g), with the presence of the main
peaks for C═N, and Si O Si bonds at 1,700 and
1,120 cmÀ1. FT-IR analysis of the recovered catalyst

GHAMARI KARGAR ET AL.
13
FIGURE 10 Recycling potential of
Ni-Fe3O4@Pectin~PPA ~ Piconal
FIGURE 11 Leaching experiment of
Ni-Fe3O4@Pectin~PPA ~ Piconal for aniline
and reduction-Schiff base condensation
corroborated that the structure of the catalyst remained
completely intact during recycling (Figure 12a). The EDX
spectrum of the recovered catalyst revealed the presence of
the expected elements, thus confirming the catalyst's stabil-
ity during the reactions. An interesting point was that there
was an intensity of very small reduction in the Ni peak. This
was completely compatible with the Ni exchange and the
imine reaction, which reduces the peak intensity
(Figure 12d). The FE-SEM image, XRD, and VSM
(38.57 emu/g) analyses were obtained, and the results
showed that the catalyst after the six cycles did not show a
significant difference in the structure that this catalyst has
very high stability.
3 | EXPERIMENTAL
3.1 | Materials and instrumentation
Chemicals and solvents used by Merck Company have been
prepared. The products of the reactions were identified by
comparing the spectral data and their physical properties
with those reported in the sources. The progress of the reac-
tions was monitored using thin-layer chromatography with
60F-254 Al-Plates specification. FT-IR spectra were obtained
using a JASCO FT/IR 4600 spectrophotometer using KBr
pellet. Melting points were determined using an electrother-
mal C14500 apparatus. The content of Ni was analyzed by

14
GHAMARI KARGAR ET AL.
FIGURE 12 FE-SEM image, XRD, VSM, and EDX after reduction-Schiff base condensation and FT-IR spectra of Ni-
Fe3O4@Pectin~PPA ~ Piconal: (I) after Nitrobenzene reduction reaction; and (II) after reduction-Schiff base condensation
inductively coupled plasma optical emission spectrometry
(ICP-OES, 5300 DV, Perkin Elmer). The surface morphol-
ogy, size, and shape of the catalyst particles were
determined by field emission scanning electron microscopy
(FE-SEM) of Tescan MIRA3. EDX spectroscopy was per-
formed using a FE-SEM (JEOL 7600F). Thermo-gravimetric
analysis (TGA) was performed using a Shimadzu thermos-
gravimetric analyzer (TG-50). VSM analysis was performed

GHAMARI KARGAR ET AL.
15
using VSM (Lake Shore Cryotronics 7407). Powder X-ray
diffraction pattern was recorded on an XPert Pro MPD dif-
fractometer with radiation (λ = 0.15406 nm) and scanning
speed of 10/min from 2 to 50 at ambient temperature.
3.5 | Preparation of
Fe3O4@Pectin~PPA ~ Piconal (IV)
First,
PPA ~ Piconal
(1 mmol)
compound
and
Fe3O4@Pectin-Cl (1 g) were sonicated in dry toluene
(15 ml) for 30 min and added slowly to the mixture. Then,
the reaction was performed for 24 hr under N2 atmosphere
at reflux conditions. After completion of the reaction, the
obtained nanoparticles are separated with the external
magnet and washed several times with toluene and then
with dichloromethane and dried at 70ꢀC in a vacuum.
3.2 | Preparation of magnetic Pectin
(Fe3O4@Pectin) (I)
Synthesis of Fe3O4@Pectin was performed with a little mod-
ification. According to this, 0.5 g of pectin was dissolved in
50 ml of distilled water under stirring until a homogeneous
dispersion of pectin was obtained. FeCl3.6H2O (3 g) and
FeCl2.4H2O (1.6 g) were dissolved in 25 ml of distilled water
separately and then added. Then, slowly added them to the
mixture containing pectin, which resulted in a brown gel.
The reaction mixture was stirred under a gentle flow of N2
at 85ꢀC for 2 hr. After which an excess of ammonium
hydroxide (25 wt%) to the reaction mixture was added until
the pH reaches 11–12 and the mixture becomes black, indi-
cating the formation of magnetite and again the mixture
was under a gentle flow of N2 at 85ꢀC for 30 min. Finally,
the precipitate was separated by an external magnet and
washed with distilled water several times until the pH
dropped to ~7, then dried under a vacuum at 60ꢀC.
3.6 | Synthesis of Ni (OAc)2 of
Fe3O4@Pectin~PPA ~ Piconal (Ni-
Fe3O4@Pectin~PPA ~ Piconal) (V)
The synthesized Fe3O4@Pectin~PPA ~ Piconal (1 g) was
sonicated in EtOH (15 ml) for 30 min. In the next step,
Ni (OAc)2 (2 mmol) was dissolved in EtOH (5 ml) by stir-
ring at room temperature. Then, the Ni (OAc)2 was added
to the above solution under sonication. The mixture was
stirred for 12 hr at room temperature and then the solid
was filtered off, washed with EtOH, and finally with
diethyl ether and dried at 70ꢀC in the oven under a vac-
uum at 60ꢀC.
3.3 | Preparation of
Fe3O4@Pectin~Cl (II)
3.7 | General procedure for reduction of
nitroarenes using Ni-
Briefly, 1.0 g of Fe3O4@pectin nanoparticles were added
to 10 ml of dried toluene and dispersed by ultrasonic irra-
diation. Then, 2.5 ml of 3-chloropropyltrimethoxysilane
was added into the system and the mixture was stirred
for 15 min followed by further stirring under the reflux
for 24 hr. After washing with toluene and water, the
obtained magnetic nanoparticles were separated using an
external magnet and dried at room temperature to pre-
pare the (Fe3O4@Pectin~Cl) nanoparticles.
Fe3O4@Pectin~PPA ~ Piconal
Ni-Fe3O4@Pectin~PPA ~ Piconal (0.5 mol%) was added to
the stirring mixture of nitrobenzene (1 mmol) in H2O
(2 ml). NaBH4 (2.5 mmol) was added, and the resulting
mixture was continued to stir at room temperature for the
appropriate time (see Table 2). EtOAc (5 ml) was added to
the reaction mixture. Ni-Fe3O4@Pectin~PPA ~ Piconal was
separated by an external magnet and washed with EtOAc
(2 Â 5 ml) and H2O (2 Â 5 ml). The combined organic
layer was then dried over anhydrous MgSO4. Evaporation
of the solvent under reduced pressure gave the crude prod-
ucts. The pure products were isolated by chromatography
on silica gel eluting with n-hexane: EtOAc (ratio 5:1).
3.4 | Preparation of Schiff ligand
PPA ~ Piconal (III)
The Schiff base ligand was prepared by the condensation
of p-phenylenediamine (1 mmol) and 2-picolinaldehyde
(2 mmol) in CH2Cl2 (15 ml) at reflux temperature for 1 hr,
which was then used as a suitable organic linker for the
new catalyst (Scheme 1). After that, the product was sepa-
rated by using a centrifuge and thoroughly washed with
dry CH2Cl2 (3 Â 10 ml) to remove the unreacted sub-
strates. Finally, the product (PPA ~ Piconal) was dried
under vacuum at 50ꢀC temperature for 6 hr.
3.8 | General procedure for the one-pot
reduction-Schiff base formation from
nitroarenes
Ni-Fe3O4@Pectin~PPA ~ Piconal (0.5 mol%) was added
to the stirring mixture of nitrobenzene (1 mmol) in H2O
(2 ml). NaBH4 (2.5 mmol) was added, and the resulting

16
GHAMARI KARGAR ET AL.
mixture was continued to stir at room temperature for
30 min. Next, benzaldehyde (1 mmol) was subsequently
added to the above reaction mixture and stirred for an addi-
tional appropriate time at room temperature to afford the
corresponding products (See Table 3). After completion of
the reaction, the final product was purified by recrystalliza-
tion from absolute ethanol to yield pure secondary imine as
a yellowish solid. Also, Ni-Fe3O4@Pectin~ PPA ~ Piconal
was recovered by an external magnet, then washed several
times with H2O and EtOAc, dried, and reused for the next
run under the same reaction conditions.
3.9.6 | (E)-2-(((4-methoxyphenyl)imino)
methyl)phenol (2g)
1HNMR (DMSO-d6, 400 MHz): δ = 3.70 (s, 3H, O-Me),
6.79–6.89 (m, 3H), 7.09–7.16 (t, 1H, j = 8 Hz), 7.20–7.25
(t, 1H, j = 8 Hz), 7.36–7.41 (d, 2H, j = 8 Hz), 7.60–7.66
(d, 1H, j = 8 Hz), 9.07 (s, 1H, CH═N), 11.09 (s, 1H,
OH) ppm.
3.9.7 | (E)-1-(4-chlorophenyl)-N-
(4-methoxyphenyl)methanimine (2h)
3.9 | Spectral data
1HNMR (DMSO-d6, 400 MHz): δ = 3.96 (s, 3H, O-Me),
6.77–6.81 (d, 2H, j = 8 Hz), 7.39–7.49 (d,d, 4H, j = 8 Hz),
7.97–8.08 (d, 2H, j = 8 Hz), 8.50 (s, 1H, CH═N) ppm.
3.9.1 | (E)-N,1-diphenylmethanimine (2a)
1HNMR (DMSO-d6, 400 MHz): δ = 6.66–6.77 (t, 1H,
j = 8 Hz), 6.88–6.91 (t, 1H, j = 8 Hz), 7.00–7.23 (m, 6H),
7.59–7.63 (d, 2H, j = 8 Hz), 8.63 (s, 1H, CH═N) ppm.
3.9.8 | (E)-N-(4-methoxyphenyl)-
1-(4-nitrophenyl)methanimine (2j)
1HNMR (DMSO-d6, 400 MHz): δ = 3.77 (s, 3H, O-Me),
6.81–6.89 (d, 2H, j = 8 Hz), 7.41–7.49 (d,d, 4H, j = 8 Hz),
8.04–8.08 (d, 2H, j = 8 Hz), 8.22–8.24 (d, 2H, j = 8 Hz),
8.50 (s, 1H, CH═N) ppm.
3.9.2 | (E)-1-(4-chlorophenyl)-N-
phenylmethanimine (2b)
1HNMR (DMSO-d6, 400 MHz): δ = 6.91–6.96 (m, 1H),
6.99–7.43 (m, 4H), 7.63–7.68 (d, 1H, j = 8 Hz), 7.92–8.00
(s, 1H, CH═N) ppm.
3.9.9 | (E)-N,1-bis(4-methoxyphenyl)
methanimine (2k)
3.9.3 | (E)-1-(4-nitrophenyl)-N-
phenylmethanimine (2d)
1HNMR (DMSO-d6, 400 MHz): δ = 3.70 (s, 3H, O-Me),
3.80 (s, 3H, O-Me), 6.87–6.89 (d, 2H, j = 8 Hz), 7.04–7.06
(d, 2H, j = 8 Hz), 7.54–7.58 (d, 2H, j = 8 Hz), 7.81–7.89
(d, 2H, j = 8 Hz), 8.40 (s, 1H, CH═N) ppm.
1HNMR (DMSO-d6, 400 MHz): δ = 6.91–7.00 (m, 1H),
7.41 (s, 4H), 7.92–8.08 (d, 2H, j = 8 Hz), 8.37–8.42 (d, 2H,
j = 8 Hz), 8.77 (s, 1H, CH═N) ppm.
3.9.10 | (E)-N-(4-bromophenyl)-
1-phenylmethanimine (2l)
3.9.4 | (E)-2-([phenylimino]methyl)
phenol (2e)
1HNMR (DMSO-d6, 400 MHz): δ = 7.06–7.09 (d, 2H,
j = 8 Hz), 7.44–7.58 (m, 3H), 7.81–7.88 (d, 2H, j = 8 Hz),
8.35 (s, 1H, CH═N) ppm.
1HNMR (DMSO-d6, 400 MHz): δ = 6.73–6.80 (d, 1H,
j = 8 Hz), 6.92–7.11 (m, 3H), 7.41 (s, 3H), 7.63–7.69 (d, 1H,
j = 8 Hz), 9.03 (s, 1H, CH═N), 11.06 (s, 1H, OH) ppm.
3.9.11 | (E)-2-(((4-bromophenyl)imino)
methyl)phenol (2m)
3.9.5 | (E)-N-(4-methoxyphenyl)-
1-phenylmethanimine (2f )
1HNMR (DMSO-d6, 400 MHz): δ = 6.88–6.91 (d, 2H,
j = 8 Hz), 7.04–7.06 (d, 2H, j = 8 Hz), 7.17–7.22 (t,
1H, j = 8 Hz), 7.35–7.41 (t, 1H, j = 8 Hz), 7.71–7.77
(d, 2H, j = 8 Hz), 9.03 (s, 1H, CH═N), 10.79 (s, 1H,
OH) ppm.
1HNMR (DMSO-d6, 400 MHz): δ = 3.90 (s, 3H, O-Me),
6.75–6.81 (d, 2H, j = 8 Hz), 7.09–7.27 (m, 5H), 7.71–7.77
(d, 2H, j = 8 Hz), 8.64 (s, 1H, CH═N) ppm.

GHAMARI KARGAR ET AL.
17
3.9.12 | (E)-4-(((4-bromophenyl)imino)
methyl)phenol (2n)
ACKNOWLEDGMENTS
The authors are grateful to the University of Birjand for
financial support.
1HNMR (DMSO-d6, 400 MHz): δ = 6.68–6.73 (d, 2H,
j = 8 Hz), 7.09–7.13 (d, 2H, j = 8 Hz), 7.61–7.66 (d, 2H,
j = 16 Hz), 7.71–7.74 (d, 2H, j = 16 Hz), 8.36 (s, 1H,
CH═N), 9.30 (s, 1H, OH) ppm.
REFERENCES
[1] M. Poliakoff, Science (80-. ) 2002, 297, 807.
[2] P. Ghamari Kargar, S. Aryanejad, G. Bagherzade, Appl.
Organomet. Chem. 2020, 34, e5965.
[3] P. Ghamari Kargar, G. Bagherzade, H. Eshghi, RSC Adv 2021,
11, 4339.
[4] J. H. Clark, Green Chem. 1999, 1, 1.
[5] P. T. Anastas, M. M. Kirchhoff, Acc. Chem. Res. 2002, 35, 686.
[6] P. Ghamari Kargar, M. Bakherad, A. Keivanloo, A. H. Amin,
Iran. J. Catal 2018, 8, 179.
[7] S. Shylesh, V. Schünemann, W. R. Thiel, Angew. Chem. Int.
Ed. 2010, 49, 3428.
3.9.13 | (E)-N-(4-bromophenyl)-
1-(4-nitrophenyl)methanimine (2o)
1HNMR (DMSO-d6, 400 MHz): δ = 6.68–6.73 (d, 2H,
j = 8 Hz), 7.09–7.13 (d, 2H, j = 8 Hz), 8.14–8.17 (d, 2H,
j = 16 Hz), 8.24–8.28 (d, 2H, j = 16 Hz), 8.59 (s, 1H,
CH═N) ppm.
[8] Y. Zhu, L. P. Stubbs, F. Ho, R. Liu, C. P. Ship, J. A. Maguire,
N. S. Hosmane, ChemCatChem 2010, 2, 365.
[9] P. Ghamari Kargar, G. Bagherzade, H. Eshghi, RSC Adv 2020,
10, 32927.
[10] P. Ghamari Kargar, G. Bagherzade, H. Eshghi, RSC Adv. 2020,
10, 37086.
4 | CONCLUSIONS
We have demonstrated the successful synthesis of Ni-
Fe3O4@Pectin~PPA ~ Piconal as a bifunctional heteroge-
neous nanomagnetic catalyst. This newly synthesized cata-
lyst was characterized by different methods such as FT-IR,
XRD, FE-SEM, EDX, TEM, VSM, and ICP analyses. Ni-
Fe3O4@Pectin~PPA ~ Piconal was successfully used as a
new heterogeneous catalyst for reducing nitroarenes using
NaBH4 as a clean source of hydrogen generation in aque-
ous media at ambient temperature. The catalytic activity
of Ni-Fe3O4@Pectin~PPA ~ Piconal as a bifunctional het-
erogeneous catalyst was also evaluated in one-pot protocol
including reduction-Schiff base condensation of various
nitroarenes. In this reaction, amines were formed in situ,
using NaBH4 as a clean source of hydrogen generation, in
aqueous media at ambient temperature and further
reacted with aldehydes to yield imines. Using this proto-
col, a variety of imines were obtained in good to high
yields. The magnetic nature of the catalyst allows its facile
recovery using an external magnetic field. Bifunctional
catalysis of Ni-Fe3O4@Pectin~PPA ~ Piconal enabled
one-pot multistep reactions without requiring product
isolation in each step, using water as a green reaction
media and NaBH4 as a clean source of hydrogen genera-
tion, which is safer than hydrogen gas. True heteroge-
neous nature and simple and efficient recyclability of
the catalyst make the present methodology sustainable
and economic. This catalyst is a new and reusable cata-
lyst that has several advantages such as a shorter reac-
tion time, cleaner reaction, reusability of the catalyst,
and high reaction yield. Moreover, this innovative het-
erogeneous catalyst could be easily separated and reused
for at least six frequent cycles without a significant loss
in its catalytic activity.
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
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How to cite this article: P. Ghamari Kargar,
A. Ravanjamjah, G. Bagherzade, J Chin Chem Soc
2021, 1. https://doi.org/10.1002/jccs.202100172
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