Fe3O4?SiO2 nanoparticles–functionalized Cu(II) Schiff base complex with an imidazolium moiety as an efficient and eco-friendly bifunctional magnetically recoverable catalyst for the Strecker synthesis in aqueous media at room temperature

Article abstract of DOI:10.1002/aoc.5388

Cu(II) Schiff base complex supported on Fe₃O₄?SiO₂ nanoparticles was employed as a magnetic nanocatalyst (nanocomposite) with a phase transfer functionality for the one-pot preparation of α-aminonitriles (Strecker reaction). The desired α-aminonitriles were obtained from the reaction of aromatic or aliphatic aldehydes, aniline or benzyl amine, NaCN, and 1.6 mol% of the catalyst in water at room temperature and good to excellent yields were obtained for all substrates. The catalyst was characterized analytically and instrumentally including Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric, nuclear magnetic resonance, energy-dispersive X-ray spectroscopy, inductively coupled plasma spectroscopy, vibrating-sample magnetometry analysis, dynamic light scattering, Brunauer–Emmett–Teller surface area, field emission scanning electron microscopy, and transmission electron microscopy analyses. The reaction mechanism was investigated, in which the performance of the catalyst as a phase transition factor seems to be probable. The catalyst showed high activity, high turnover frequency (TOF)s, significant selectivity, and fast performance toward the Strecker synthesis. The nanocatalyst can be readily and quickly separated from the reaction mixture with an external magnet and can be reused for at least seven successive reaction cycles without significant reduction in efficiency.

Full text of DOI:10.1002/aoc.5388

Received: 19 December 2018
DOI: 10.1002/aoc.5388
Revised: 28 October 2019
Accepted: 2 November 2019
F U L L P A P E R
Fe3O4@SiO2 nanoparticles–functionalized Cu(II) Schiff base
complex with an imidazolium moiety as an efficient and
eco‐friendly bifunctional magnetically recoverable catalyst
for the Strecker synthesis in aqueous media at room
temperature
Milad Kazemnejadi1
Mohammad Ali Nasseri1
| Seyyedeh Ameneh Alavi G.1 | Zinat Rezazadeh1 |
| Ali Allahresani1 | Mohsen Esmaeilpour2
1 Department of Chemistry, Faculty of
Sciences, University of Birjand, Birjand
97175‐615, Iran
2 Department of Chemistry, College of
Science, Shiraz University, Shiraz
7194684795, Iran
Cu(II) Schiff base complex supported on Fe3O4@SiO2 nanoparticles was
employed as a magnetic nanocatalyst (nanocomposite) with a phase transfer
functionality for the one‐pot preparation of α‐aminonitriles (Strecker reaction).
The desired α‐aminonitriles were obtained from the reaction of aromatic or ali-
phatic aldehydes, aniline or benzyl amine, NaCN, and 1.6 mol% of the catalyst
in water at room temperature and good to excellent yields were obtained for all
substrates. The catalyst was characterized analytically and instrumentally
Correspondence
Milad Kazemnejadi, Department of
Chemistry, Faculty of Sciences, University
of Birjand, Birjand 97175‐615, Iran.
Email: miladkazemnejad@yahoo.com;
miladkazemnejadi@birjand.ac.ir
including Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermo-
gravimetric, nuclear magnetic resonance, energy‐dispersive X‐ray spectroscopy,
inductively coupled plasma spectroscopy, vibrating‐sample magnetometry
analysis, dynamic light scattering, Brunauer–Emmett–Teller surface area, field
emission scanning electron microscopy, and transmission electron microscopy
analyses. The reaction mechanism was investigated, in which the performance
of the catalyst as a phase transition factor seems to be probable. The catalyst
showed high activity, high turnover frequency (TOF)s, significant selectivity,
and fast performance toward the Strecker synthesis. The nanocatalyst can be
readily and quickly separated from the reaction mixture with an external mag-
net and can be reused for at least seven successive reaction cycles without sig-
nificant reduction in efficiency.
KEYWORDS
Cu(II) complex, eco‐friendly, magnetic catalyst, phase transfer catalyst, Strecker synthesis
1 | INTRODUCTION
the synthesis of synthetic α‐amino acids (Scheme 1) and
different nitrogen‐ or sulfur‐containing heterocycles such
The Strecker synthesis is one of the most applicable and
straightforward multicomponent reaction for the prepara-
tion of α‐aminonitriles (C–C bond formation).[1,2] Fur-
thermore, α‐aminonitriles are very useful precursors for
as thiadiazoles and imidazoles.[2] Various biological and
biochemical properties have been revealed for α‐
aminonitriles including enzyme inhibitors; antitumor,
anticarcinoma, and antiseminoma; fungicidal and
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© 2019 John Wiley & Sons, Ltd.
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Appl Organometal Chem. 2019;e5388.
https://doi.org/10.1002/aoc.5388

KAZEMNEJADI ET AL.
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SCHEME 1 Synthesis of α‐
aminonitriles and α‐amino acids
herbicidal activity; and gallium inhibitor.[3–6] Because of
the lack of any hydrolyzable moiety in an α‐amino nitrile,
it can be readily hydrolyzed to its corresponding α‐amino
acid in the presence of a concentrated acid (Scheme 1).
The traditional Strecker synthesis involves the
treatment of an aldehyde and/or ketone, amine, and
alkaline cyanide, in which the reaction proceeds by
nucleophilic addition of a cyanide ion to the imines cata-
lyzed by different homogeneous Lewis acids or bases.[7]
However, the concerns regarding using a homogeneous
medium (associated with difficulty in separation, tedious
work‐up, etc.)[8] as well as using toxic or expensive cyanide
sources, harsh reaction conditions, generation of wasteful
by‐products, etc. limited its use in organic synthesis. These
impediments have persuaded researchers to introduce
milder alternative conditions to modify this method.[9]
Subsequently, over the past decade, various catalytic
systems have been developed using a variety of cyanide
sources or heterogeneous recoverable catalysts. Heteroge-
neous catalysts cover most defects of homogeneous
catalysts and save cost and energy with easy separation
and recovery.[8] So far, various heterogeneous systems,
containing either transition metals or strong acids, have
been reported for the Strecker synthesis. For example, the
following were applied as heterogeneous catalysts in the
Strecker reaction: montmorillonite KSF clay,[10] molecular
sieves,[9,11] natural polymer sulfuric acid,[12,13] nanosize
materials,[14,15] sulfated tungstate,[16] metal–organic
framework,[17] supported complexes,[18,19] heteropoly
acids,[20] lithium tetrafluoroborate (LiBF4),[21] MCM‐
41,[22] CuFe2O4/chitosan,[23] Fe3O4@cellulose–OSO3H,[24]
and Fe3O4@PVA–SO3H.[25] Recently, Baghery et al.
applied Fe3O4@SiO2@urea and Fe3O4@SiO2@urethane
catalysts for the one‐pot Strecker synthesis of α‐
aminonitrile.[26] Various procedures have also been devel-
oped for the synthesis of α‐aminonitriles from aldehydes,
amines, and trimethylsilyl cyanide or tributyltin cyanide
using different Lewis acids such as lithium perchlorate,
polymeric scandium triflamide, vanadyl triflate, NiCl2,
BiCl3, zinc halides, RuCl3, ytterbium triflate, or montmo-
rillonite.[27] Furthermore, Gualtierotti et al. reported an
oxidative Strecker synthesis of aldehydes, amines, and
trimethylsilyl cyanide (TMSCN) in a biphasic solvent sys-
tem in the presence of Oxone, tetra‐n‐butylammonium
bromide, and sodium bicarbonate.[28]
tedious work‐up, and not being environmentally benign.
Besides, catalyst deactivation and/or decomposition in
the presence of water or amine is another drawback related
to the use of many of these catalysts.[10] By contrast, cya-
nide sources such as sodium or potassium cyanide are
more accessible, safer, and easier to handle than TMSCN,
CuCN, HCN, Zn(CN)2, K4Fe(CN)6, etc. Thus, given the
need to protect the environment, developing a new green,
simple, cost‐effective, and highly efficient method for the
synthesis α‐aminonitriles is warranted.
Because of their unique biological, physical, and
chemical properties, applications of nanoparticles (NPs)
have expanded in all fields of science.[29,30] In chemis-
try, owing to their high surface area, NPs are widely
used as a solid support and/or catalyst.[31] Nevertheless,
their high surface area causes them to stick together
and eventually agglomerate; therefore, they are usually
covered with compounds such as silica. This modifica-
tion allows for suitable functionalization of the NPs
with various compounds to achieve a specific goal.
However, problems related to their separation have lim-
ited their use as a catalyst in organic reactions. To over-
come this limitation, magnetic NPs (MNPs) are used as
a solid support, as it offers a smart methodology from a
green chemistry viewpoint. Application of MNPs in
organic synthesis is increasing every day because of
their unique properties such as superparamagnetic capa-
bility, low toxicity, low cost, and biocompatibility.[31]
Among MNPs, Fe3O4 NPs have attracted significant
attention in various chemical, medicinal, and industrial
applications because of their unique magnetic, biocom-
patibility, non‐toxic, and biodegradability proper-
ties.[32,33] Herein, we coated Fe3O4 NPs with silica
shell and functionalized them with a Schiff base Cu(II)
complex which was then networked using melamine.
The product thus obtained was evaluated as a heteroge-
neous magnetically recoverable catalyst for the Strecker
synthesis in the presence of an aqueous solution of
NaCN at room temperature. The present method sug-
gests that the catalytic activity of NP complex is affected
by its phase transfer nature resulting from the
imidazolium moiety. The presence of imidazolium
allows the catalyst to perform different roles in the reac-
tion while providing a synergistic effect.[34,35] Moreover,
to the best of our knowledge, it has not been reported
so far for the synthesis of α‐aminonitriles, in which
the cyanide ion takes part in the reaction by the phase
transfer nature of the catalyst.
However, most of these methods involve the use of
strong acidic or harsh conditions and expensive reagents,
while having unsatisfactory yield, long reaction times,

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KAZEMNEJADI ET AL.
Inductively coupled plasma (ICP) spectroscopy experi-
ments were accomplished using a Varian Vista‐PRO
CCD simultaneous ICP optical emission spectrometer
instrument. The surface area, pore volume, and pore
diameter of the obtained NPs were determined by N2
physisorption at −196 °C with a surface area and pore
size analyzer (Micromeritics ASAP 2000 instrument)
using the Brunauer–Emmett–Teller (BET) method.
2 | EXPERIMENTAL
2.1 | Materials and apparatus
All chemicals were obtained from Sigma (Darmstadt,
Germany) and Fluka (Rupert‐Mayer‐Str. 46, D‐81379
Munich) and used without further purification. All the
solvents were distilled and dried before use. All other
reagents were of analytical grade. Progress of reactions
was monitored by thin‐layer chromatography (TLC) on
silica gel or gas chromatography (GC) using
a
2.2 | Preparation of Cu(II) Schiff base
complex (3)
Shimadzu‐14B gas chromatography system equipped
with an HP‐1 capillary column and N2 carrier gas.
Anisole was used as internal standard. Fourier‐
transform infrared (FTIR) spectra were obtained with a
JASCO FT/IR 4600 spectrophotometer using KBr pellet.
First, 2‐hydroxy‐5‐chloromethyl benzaldehyde was syn-
thesized and purified according to a previously described
procedure[36] (purple solid, 98% yield). 2‐Hydroxy‐5‐
chloromethyl benzaldehyde (1; 2.0 mmol, 0.34 g) was dis-
solved in 20 mL of dry toluene and then imidazole
(10.0 mmol) was added to the mixture. The mixture
was refluxed with stirring for 48 hr under N2 atmo-
sphere. After refluxing, the reaction was stopped and
cooled to room temperature. The solvent was removed
under reduced pressure and product 2 was washed with
a dilute solution of NaOH and deionized water and then
dried in an oven at 50 °C (dark brown powder, 98%
yield). Transformation of 2‐hydroxy‐5‐imidazole benzal-
dehyde to 3 (pale yellow powder, 98% yield) was
achieved according to the procedure described else-
where.[23] 4‐([1H‐imidazole‐1‐yl]methyl)‐2‐([allylimino]
methyl)phenol (3, 1.0 mmol, 0.24 g) was complexed to
Cu(II) ions by dissolving it in 15 mL ethanol followed
addition of Cu(OAc)2·H2O (0.5 mmol, 0.145 g). The
resulting mixture was stirred for 12 hr at room tempera-
ture under a nitrogen atmosphere (Supporting informa-
tion, Scheme 2). Product 4 was filtered, washed with
cold ethanol and diethyl ether, and then dried at room
temperature and isolated as a light green powder
(Scheme 2).
1
The H nuclear magnetic resonance (NMR; 250 MHz)
and 13C NMR (62.9 MHz) spectra were recorded on a
Bruker Avance DPX‐250 spectrometer in CDCl3 with
dimethyl sulfoxide‐d6 (DMSO‐d6) as solvent and
tetramethylsilane as internal standard. Elemental analy-
ses were performed on a Perkin Elmer‐2004 instrument.
Field emission scanning electron microscopy (FE‐SEM)
images were obtained on a HITACHI S‐4160 micro-
scope. Transmission electron microscopy (TEM) was
performed on a Philips EM208 microscope operated at
100 kV. Energy‐dispersive X‐ray (EDX) spectroscopy
was performed using a field emission scanning electron
microscope (JEOL 7600F) equipped with an energy‐
dispersive X‐ray spectrometer (Oxford Instruments). Size
distribution of the NPs was measured by the dynamic
light scattering (DLS) analysis on a HORIBA LB‐550
instrument. Thermogravimetric analysis (TGA) and dif-
ferential scanning calorimetry (DSC) analyses of the
samples were performed on a NETZSCH STA 409
PC/PG in nitrogen atmosphere with a heating rate of
10 °C/min between 25 and 850 °C. The magnetic behav-
ior of the samples was evaluated on a Lake Shore
vibrating‐sample magnetometer at room temperature.
SCHEME 2 Preparation of the Cu(II)–Im Schiff base complex (4). RT, room temperature

KAZEMNEJADI ET AL.
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water and ethanol, and then dried in a vacuum oven
(6 hr, 60 °C). Scheme 3 shows the complete route for
the preparation of 8.
2.3 | Preparation of Fe3O4@SiO2 core–
shell NPs (6)
Core–shell Fe3O4@SiO2 nanospheres were prepared
according to
a
previously described procedure
2.5 | General procedure for the catalytic
preparation of α‐aminonitriles by
Fe3O4@SiO2@Im[CN]Cu(II) in water at
room temperature
(Scheme 3).[37]
2.4 | Preparation of Fe3O4@SiO2@Im[CN]
Cu(II) complex nanocomposite (8)
A mixture of amine (1.0 mmol), aldehyde (stoichiometric
amount), and NaCN (1.0 mmol) in water (3.0 mL) and
catalyst 8 (10 mg, 1.6 mol%) was stirred at room temper-
ature. Progress of the reaction was monitored by TLC
according to aldehyde consumption. After completion of
the reaction, the catalyst was separated with an external
magnetic field. Then, 10 mL of ethyl acetate was added
to the residual mixture. The organic layer was washed
with brine, dried over anhydrous MgSO4, and then con-
centrated under reduced pressure. The residue was puri-
fied by recrystallization from ethanol.
The Fe3O4@SiO2@Im[Cl]Cu(II) complex nanocomposite
was synthesized according to the following procedure:
Fe3O4@SiO2–Cl (1 g) was added to a solution of
Cu(II)–Im–Schiff base complex (3, 1.0 mmol, 0.54 g) in
20 mL p‐xylene and the resultant mixture was stirred
for 24 hr under N2 atmosphere and reflux conditions.
Then, the mixture was cooled to room temperature,
filtered using an external magnet, and the product
washed with p‐xylene to remove any unreacted species
and dried at 70 °C for 6 hr. The immobilized Cu(II)–
Im–Schiff base complex (7) along with a weighted
amount of melamine (molar ratio 6:1) was transferred
into a 25‐mL oven‐dried round‐bottomed flask equipped
2.6 | Reutilization of the catalyst
with
a
magnet and
a
condenser.
A
solution of
Reutilization of the Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite was examined by the oxidation of benzyl
alcohol to benzaldehyde, in which the catalyst was fil-
tered using a simple external magnet at the end of exper-
iment, washed with deionized water and ethanol, and
then reused in the next experiment without any pre‐
activation. The residue was analyzed by ICP to measure
the amount of Cu that leached from the catalyst to the
solution. Besides, the hot filtration test and mercury poi-
soning examinations were employed to investigate the
heterogeneous nature of the catalyst.
trimethylamine (4.0 mmol) in absolute MeOH (5.0 mL)
and AlCl3·2H2O (4.0 mmol) were added to the aforesaid
mixture. The mixture was refluxed in N2 atmosphere for
6 hr. The product, Fe3O4@SiO2@Im[Cl]Cu(II), was
collected using an external magnetic field, washed with
water (2 × 10 mL) and EtOH (2 × 10 mL), and then
re‐dispersed by sonication in 25 mL H2O followed by
the addition of 5 mmol NaCN. The mixture was shaken
for 2 hr at room temperature. The resultant product was
separated with an external magnetic field, washed with
SCHEME 3 Preparation of Fe3O4@Im[CN]Cu(II) (8)

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KAZEMNEJADI ET AL.
of 2 shows a series of peaks at 2490–2780 cm−1 related
to the imidazolium moiety, which are in agreement with
compounds containing imidazole moieties reported in the
literature (Figure 1b).[38] Moreover, the elimination of
C–Cl band at 725 cm−1 in 2 corroborates the imidazole
functionalization of 5‐chloromethylene salicylaldehyde.
The stretching vibration related to the N–H of the imidaz-
ole moiety appeared at 3413 cm−1. Imine formation of 3
was confirmed by the presence of C=N bond at
1611 cm−1 (Figure 1c).[39] This absorption, however,
shifted to 1563 cm−1 as a result of Cu complex formation.
This shift along with Cu–O and Cu–N stretching
vibrations at 617 and 650 cm−1, respectively, confirmed
the successful coordination of Cu ions through N and O
in 4 (Figure 1d).[8]] Fe3O4 NPs showed a single character-
istic peak at 570 cm−1 related to the Fe–O bond[40]
(Figure 1e). The presence of three main peaks at 578,
3 | RESULTS AND DISCUSSION
3.1 | Characterization of catalyst
Elemental analysis for the samples are tabulated in
Table 1. The results obtained were in good agreement
with the theoretical calculations and confirmed the prep-
aration of 1, 2, 3, and 4. Further, the results were in
accordance with the proposed structure sketched in
Scheme 2, which matches well with the previously
reported structure.[23]
Figure 1 shows the FTIR spectra of 1, 2, 3, 4, Fe3O4, 5,
6, 7, and 8 compounds. The FTIR absorption spectra of 1
show two characteristic peaks at 1481 and 725 cm−1
,
which correspond to the methylene (m substituted)
groups (–CH2–) and the stretching vibration of the C–Cl
group, respectively (Figure 1a).[13] The FTIR spectrum
TABLE 1 Elemental analysis results and colors of the compounds
Elemental analysis
Compound
Appearance
%C
%H
%N
2‐Hydroxy‐5‐chloromethyl benzaldehyde (1)
2‐Hydroxy‐5‐imidazole benzaldehyde (2)
4‐([1H‐imidazole‐1‐yl]methyl)‐2‐([allylimino]methyl)phenol (3)
Cu(II) Schiff base complex (4)
Purple powder
56.30 (56.82)a
65.74 (65.34)
69.47 (69.69)
62.65 (62.34)
4.14 (4.25)
5.09 (4.98)
6.22 (6.27)
5.18 (5.23)
—
Dark brown powder
Pale yellow powder
Light green powder
13.97 (13.85)
17.64 (17.41)
1580 (15.58)
aTheoretically calculated.
FIGURE 1 Fourier‐transform infrared spectra: (a) 1, (b) 2, (c) 3, (d) 4, (e) Fe3O4, (f) 5, (g) 6, (h) 7, and (i) 8

KAZEMNEJADI ET AL.
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779, and 1072 cm−1 correspond to stretching vibrations of
Fe–O, Si–O–Si (symmetrical), and Si–O–Si (asymmetri-
cal), respectively, which strongly confirm the coating of
Fe3O4 NPs by silica shells (Figure 1f).[40] Figure 1g
demonstrates the vibrations attributed to C–H stretching,
–CH2– bending, and C–Cl stretching at about 2920, 1458,
and 633 cm−1, respectively, which strongly confirmed the
preparation of Fe3O4@SiO2–Cl (Figure 1g). Incorporation
of complex 4 on Fe3O4@SiO2–Cl was proved by the
presence of C=N, Si–O–Si, Fe–O, and C=C bands that
correspond to the wavenumbers at 1567, 1017, 445, and
1401 cm−1
.
Figure 1i shows the spectrum of
Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite (8)
that clearly confirms the intercalation of melamine
between 8 and the nanocomposite prepared. More impor-
tantly, the sharp peak at 2350 cm−1 was related to the
cyanide ions, which strongly confirms and supports the
ion exchange of Cl− with CN−.
The X‐ray diffraction (XRD) spectra for the synthesized
NPs are shown in Figure 2. According to Figure 2a, Fe3O4
NPs have a highly crystalline cubic inverse spinel structure
that is in agreement with the standard Fe3O4 (cubic phase)
XRD spectrum (PDF# 88–0866). The characteristic diffrac-
tion peaks at 2θ = 30.1°, 35.4°, 43.1°, 53.4°, 57°, and 62.6°,
which were marked, respectively, by their indices (220),
(311), (400), (422), (511), and (440) demonstrated the
Fe3O4 structure (reference JCPDS card no. 19–629;
Figure 2).[37] These peaks can be observed for Fe3O4@SiO2
and Fe3O4@SiO2–Cl and indicate that the surface modifi-
cation of the Fe3O4 NPs does not lead to their phase change
or structural change. The XRD pattern of Fe3O4@SiO2 and
Fe3O4@SiO2–Cl shows an obvious diffraction peak at
2θ = 15–25°, which represents the coated amorphous silica
on Fe3O4 NPs (Figure 2b,c). The XRD pattern of the
Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite
contains peaks of both silica and Fe3O4 (shown by stars)
in the corresponding 2θ with an amorphous appearance.
The broadening of the peaks shows that Fe3O4@SiO2 NPs
were functionalized with an amorphous Cu(II) Schiff base
complex and revealed the successful preparation of the
nanocomposite. A comparison of diffraction patterns of
Fe3O4, Fe3O4@SiO2, Fe3O4@SiO2–Cl, and Fe3O4@SiO2@-
Im [CN]Cu(II) complex nanocomposite shows that the
intensity of peaks gradually decreases and the peaks
become amorphous. This behavior shows the loading of
different amorphous groups such as silica and copper com-
plex at each step in diffraction patterns of Fe3O4@SiO2–Cl
and Fe3O4@SiO2@Im[CN]Cu(II) complex nanocompos-
ite. In addition, by the formation of a network structure
resulting from the treatment of melamine with compound
7 and formation of nanocomposite 8, the peaks are
completely out of the crystalline state and have become
amorphous. The results also prove that more amorphous
FIGURE 2 X‐ray diffraction patterns: (a) Fe3O4, (b) Fe3O4@SiO2,
(c) Fe3O4@SiO2–Cl, and (d) Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite
structures at each step are exposed to the crystalline struc-
ture of Fe3O4, which reduces the effect of X‐rays on the
Fe3O4 crystals and subsequently reduces their peak inten-
sities. Besides, the presence of the new amorphous peak
at about 2θ = 12° indicates the synergistic effect of amor-
phous silica and copper complexes immobilized onto the
Fe3O4 crystalline NPs.[31] Besides other analyses, the size

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KAZEMNEJADI ET AL.
of NPs was calculated using the Scherrer equation: D = Kγ/
β cosθ, where K is a constant (K = 0.9 for Cu‐Kα), D is the
average diameter in Å, β is the broadening of the diffrac-
tion line measured at half of its maximum intensity in
radians, γ is the wavelength of the X‐rays, and θ is the
Bragg diffraction angle. Based on the calculations using
Scherrer equation, sizes of Fe3O4@SiO2, Fe3O4@SiO2–Cl,
and catalyst 8 were obtained as 10, 18, and 55 nm,
respectively.
The presence of elements in the catalyst was probed by
EDX (Figure 3a). The results confirm the successful
immobilization of Cu(II) Schiff base complex 4 on the
Fe3O4@SiO2–Cl NPs.
The vibrating‐sample magnetometry (VSM) analysis
results for Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@-
Im[CN]Cu(II) complex nanocomposites are shown in
Figure 3A. The NPs exhibited high permeability under
magnetization, which was sufficient to completely
separate it with an external magnetic field. The magne-
tization and demagnetization curves were coincident
and did not show any hysteresis phenomenon. As
shown in the figure, the remnant magnetization is
equal to zero for all NPs. Magnetic measurements
showed saturation magnetization values of 70.0, 39.8,
and 35.7 emu/g for Fe3O4, Fe3O4@SiO2, and
Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposites,
respectively (Figure 3B). These results demonstrate that
the magnetization of Fe3O4 decreased considerably
because of the presence of coated silica shell Schiff
base–Cu complex on its surface [Figure 3B; (b,c)].
Nevertheless, the Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite exhibited superparamagnetic characteris-
tics and high magnetization values, which allow it to be
readily separated from the mixture with a simple exter-
nal magnet.
The TGA curves of the samples were recorded
between 25 and 800 °C with a scan rate of 10 °C/min
(Figure 3C). The TGA curve of the melamine Schiff base
ligand presented only one weight loss step in the
temperature range of 98–345 °C [Figure3C; (a)]. The
TG spectrum of Cu(II) Schiff base complex 4 demon-
strated a main peak with a continuous weight loss. This
main weight loss may result from the decomposition of
Cu Schiff base ligand corresponding to approximately
62% weight loss. The weight loss continues with a mild
slope up to 720 °C, which may be a result of the
formation of copper oxide species.[41] The catalyst exhib-
ited high thermal stability [Figure 3C; (c)], with
the incorporation of melamine to 7 clearly revealing
the effect of melamine on the thermal behavior of the
FIGURE 3 (A) Energy‐dispersive X‐ray spectrum for the Fe3O4@SiO2@Im[CN]Cu(II) complex; (B) Magnetization curves at 300 K for (a)
Fe3O4, (b) Fe3O4@SiO2, and (c) Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite; (C) thermogravimetric analysis spectra for (a) Cu(II)
Schiff base complex 4, (b) Cu(II) Schiff base complex 7, and (c) catalyst 8; (D) differential scanning calorimetry analysis

KAZEMNEJADI ET AL.
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Fe3O4@SiO2@Im[Cl]Cu(II) complex nanocomposite.
diameter of the NPs is found to be about 65 nm
(Figure 4). As expected, as shown in the TEM image,
the NPs have a composite structure and thus not a
single particle is seen in the image but rather a set of
particles that are aligned due to the composite structure.
However, the spherical structure of the NPs with a
diameter of about 65 nm is evident in the image. As
shown in the sketched proposed structure in Scheme 3,
after the addition of melamine to structure 7, the com-
plex becomes cross‐linked and a nanocomposite is
formed.
Specific surface area and porosity of the samples were
investigated by N2 adsorption–desorption isotherm analy-
sis. The specific surface area values, the average pore
diameter (according to the Barrett–Joyner–Halenda
method), and total pore volume are tabulated in Table 2
. According to the BET isotherm, the active surface area
of the Fe3O4, Fe3O4@SiO2, Fe3O4@SiO2–Cl, and
Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposites
(catalyst 8) was determined as 480, 455, 400, and 370
m2/g, respectively (Table 2, entries 1–4).
Under
a nitrogen atmosphere, the nanocomposite
showed a 40% weight loss (compare with TG spectrum
of 7), which can be attributed to the decomposition of
water as well as organic moieties on the surface of
core–shell. First, a negligible weight loss (2.5%) was
observed in the region from 90 to 250 °C, which proves
the loss of hydrogen‐bonded water molecule present on
the surface of Fe3O4 core–shell. A second small weight
loss (3.5%) occurred between 280 and 480 °C that is
associated with the removal of water trapped in the lat-
tice.[41] The weight loss of about 35% in the temperature
range of 365–700 °C was assigned to the decomposition
of organic moieties on the surface of Fe3O4@SiO2 core–
shell NPs.
Furthermore, DSC analysis of the catalyst was also
carried out. The DSC thermogram represents variations
related to endothermic and exothermic reactions. Two
endothermic peaks at 250 and 450 °C were assigned to
the release and decomposition of adsorbed water in
the catalyst framework, respectively.[42,43]
A broad
exothermic peak was observed in the range of
500–1000 °C, which is attributed to the decomposition
of organic molecules present on the catalyst (thermos‐
oxidative degradation), which is confirmed by TGA
(Figure 3D).
The morphology and structure of the Fe3O4@Im[CN]
Cu(II) complex were also observed using TEM
(Figure 4). The TEM image reveals that the catalyst con-
tains well‐shaped spherical or ellipsoidal particles. The
According to FE‐SEM images, the synthesized Fe3O4
NPs and Fe3O4@SiO2 are nearly spherical in shape and
well dispersed, although in some areas bigger structures
with non‐spherical morphology are observed (Figure 5a,
b). The SEM images also confirm the spherical structure
of the NPs and show that the NPs have a homogeneous dis-
tribution and are uniform in size in accordance with the
TEM image. The SEM images show an increase in the size
of the NPs at each step, in accordance with the DLS results.
In addition, the resulting spherical morphology of
Fe3O4@SiO2 and catalyst 8 shows that the func-
tionalization of the NPs by the silica and copper complexes,
respectively, was performed uniformly and harmoniously,
with no deviation in shape or agglomeration in the
particles.
The Fe3O4 and Fe3O4@SiO2 particles have an average
diameter of 10–12 and 20–22 nm (Figure 5a,b), respec-
TABLE 2 Surface characteristics of Fe3O4, Fe3O4@SiO2,
Fe3O4@SiO2–Cl, and Fe3O4@SiO2@Im[Cl]Cu(II) complex nano-
composite (9)
Specific
surface
area
(m2/g)
Average
pore
volume radius
(cm3/g) (nm)
Pore
Entry Sample
1
2
3
4
Fe3O4
480
455
400
380
0.803
0.785
0.755
0.730
1.254
1.787
1.802
1.852
Fe3O4@SiO2
Fe3O4@SiO2–Cl
Fe3O4@SiO2–Cu–
complex 7
FIGURE 4 Transmission electron microscopy image of the
Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite
5
Catalyst 8
370
0.721
1.996

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KAZEMNEJADI ET AL.
FIGURE 5 Field emission‐scanning electron microscopy images and dynamic light scattering results of (a and d) Fe3O4, (b and e)
Fe3O4@SiO2, and (c and f) Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite
tively, consistent with their corresponding DLS analyses
(Figure 5d,e). Figure 5c shows an FE‐SEM image of
the core–shell Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite with near‐spherical morphology. After
coating successfully with the Cu–Schiff base complex,
this composite still maintains its spherical shape with
an average diameter of approximately 65 nm (Figure 5
d). The size distribution of these NPs was centered at
to this analysis, 1 g of the catalyst contains 11.0 mmol of
CN− ions.
3.2 | Optimization of reaction parameters
3.2.1 | Effect of solvent
a
value of 12, 20, and 68 nm for the Fe3O4,
The reaction of benzaldehyde, benzylamine, and NaCN
in the presence of catalyst 8 was utilized to investigate
the effect of solvent and catalyst amounts on the Strecker
reaction.
The role of solvent in the reaction efficiency was
screened by applying different solvents or their mixtures
to the model reaction (Figure 6). Water as a solvent
visibly showed higher efficiency compared with
all tested solvents with 98% isolated yield, as indicated
in Figure 6. To show the effect and vital role of water
in the reaction, some experiments were performed in
the aqueous mixture of organic solvents. According
Fe3O4@SiO2, and Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite, respectively (Figure 5d–f). Particle‐size
distributions of Fe3O4, Fe3O4@SiO2, and Fe3O4@-
SiO2@Im[CN]Cu(II) complex nanocomposite were
shown in Figure 5. The size distribution is centered at
a value of 12, 20, and 59 nm for Fe3O4, Fe3O4@SiO2,
and Fe3O4@SiO2@Im[CN]Cu(II) complex nanocompos-
ite, respectively, and is in agreement with the particle
sizes exhibited in SEM images.
The loading amount of Cu on the catalyst was mea-
sured by atomic absorption spectroscopy as well as by
ICP to ensure accuracy. Results of the two analyses were
close to each other with a minor difference (0.005). The
experiments indicated that 1.6 mmol of Cu metal per
gram of the catalyst (1.6 mmol g−1) was loaded onto the
catalyst framework 8.
to the obtained results, there was
a remarkable
enhancement in efficiency for organic solvents when
they are mixed with water. As will be discussed in the
next section, this behavior could be attributed to
the phase transfer nature of the catalyst, with the
presence of water aiding this behavior as well as the
separation of two phases. In addition, the ionization of
cyanide salt in water is completely accomplished, which
also aids the catalyst phase‐transfer effect. However,
Furthermore, the amount of cyanide ions present in
the catalyst (as imidazolium counter ion) was measured
based on the reaction of CN− ions with 2,2‐dihydroxy‐
1,3‐indandione, as proposed by Drochioiu.[44] According

KAZEMNEJADI ET AL.
10 of 17
FIGURE 6 Influence of solvent on the
synthesis of N‐benzylidenebenzylamine
catalyzed by the Fe3O4@SiO2@Im[CN]
Cu(II) complex nanocomposite. DEE,
diethyl ether; DMF, dimethylformamide;
DMSO, dimethyl sulfoxide; EA, ethyl
acetate
ethanol, being a protic‐polar solvent, provides a moder-
ate efficiency of 70% (Figure 6). The lowest efficiencies
α‐amino nitriles (Table 3). It is also important to note that
no cyanohydrin by‐product was found in any of the
experiments.
were
for
diethyl
ether
(DEE),
DMSO,
dimethylformamide, and ethyl acetate with 5, 7, 14,
and 20% efficiency, respectively.
To explore the scope of the present method, various
aldehydes were condensed and converted into the
desired α‐amino nitriles in high to excellent yield and
purity in the presence of Fe3O4@SiO2@Im[CN]Cu(II)
complex nanocomposite under optimized reaction
conditions summarized in Table 3. The results demon-
strated the versatility of the catalyst toward a variety
of aldehydes including acid‐sensitive aldehydes, such
as cinnamaldehyde (10 h, 10i), furfuraldehyde
(10j, 10 l), and thiophen‐2‐carbaldehyde (10 k, 10 m).
Besides, aliphatic aldehydes (10o, 10p, 10q) enabled
the conversion to the corresponding α‐amino nitrile in
acceptable yields; however, they had insignificant
lower conversions and higher reaction times than the
corresponding aromatic types. For example, condensa-
tion of butanal and aniline afforded 10o in 82%
yield for 95 min. Substituted benzaldehydes bearing
electron‐donating groups such as OMe– and Me–
3.2.2 | Effect of catalyst amount
Various amounts of the catalyst 8 were examined in the
model reaction to identify the sufficient amount of
catalyst to be used in the Strecker reaction (Figure 7).
As shown in Figure 7, by increasing the amount of the
catalyst to 1.6 mol%, the efficiency increases linearly
(Figure 7, yellow color), up to 98%. Increasing the
amount of catalyst, however, did not affect the efficiency.
3.3 | Catalytic activity
Finally, the premium conditions identified in the earlier
steps were utilized in the preparation of a variety of
FIGURE 7 Influence of catalyst
amount on the synthesis of N‐
benzylidenebenzylamine catalyzed by the
Fe3O4@SiO2@Im[CN]Cu(II) complex
nanocomposite

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KAZEMNEJADI ET AL.
TABLE 3 Synthesis of α‐aminonitriles catalyzed by the Fe3O4@SiO2@Im[CN]Cu(II) complex nanocomposite (see supporting
information for NMR spectra).
RT, room temperature; TOF, turnover frequency.
gave higher conversions with lower reaction times
(Table 3, entries 10f, 10 g) than those substituted with
electron‐withdrawing groups such as Cl (entries 10b,
10c, 10e). Benzylamine gave somewhat poorer efficien-
cies than aniline (e.g. see 10 h and 10i).
The efficiency of this method for the preparation of α‐
aminonitrile from ketones was also evaluated. Unfortu-
nately, the reaction did not lead to the production of
desired α‐aminonitriles for ketones. This could be
explained as follows: as shown in Scheme 4, the steric
SCHEME 4 Proposed mechanism for one‐pot preparation of α‐aminonitriles catalyzed by Fe3O4@Im[CN]Cu(II)

KAZEMNEJADI ET AL.
12 of 17
hindrance of ketones may prevent the CN− from
approaching the intermediate (b; route A); consequently,
the reaction proceeds via a path that produces only the
Schiff base compounds (Scheme 4, route B). Thus, no
aminonitrile product was found for ketones.
and nano SiO2, a catalytic synergistic effect of these moi-
eties on the catalyst can be considered.
3.4 | Reaction mechanism
Some separate control experiments were performed
under identical conditions to elucidate the effectiveness
and activity of catalyst 8. Table 4 presents the results,
where the synergistic effects of the imidazolium moiety,
copper active sites, SiO2, and network structure of cata-
lyst 8 were manifested. As shown in Table 4, the Fe3O4
and SiO2 NPs did not show any efficiency (Table 4,
entries 1 and 3). Fe3O4@SiO2 and Cu(OAc)2 provided
10% and 25% efficiency (Table 4, entries 2 and 4), respec-
tively. Complex 4 produced a moderate efficiency of 68%
(Table 4, entry 5). The most interesting results were
obtained using complex 7 as a catalyst, which afforded
90% isolated yield of the product (Table 4, entry 6). Treat-
ment of complex 7 with melamine provides a network‐
robust structure with an increased catalytic activity
(Table 4, entry 7). The results well confirm the effect of
the cyanide salt phase transition of the catalyst and con-
sequently the presence of the imidazole moiety on the
catalyst. In addition, given the high efficiency achieved
by catalyst 8 over other catalysts used, and owing to the
catalytic effect of complex 4, complex 7, Fe3O4@SiO2,
According to the previously reported mechanisms for the
one‐pot preparation of α‐aminonitriles, the reaction starts
with the nucleophilic addition of an amine to the
carbonyl group.[46,47] H bonding could be formed
between imidazole‐H‐2 and the oxygen of the carbonyl
group.[48–50] Therefore, imidazole‐H‐2 or coordinated
copper can activate the carbonyl group for this attack.
The aminohydrin intermediate (Scheme 4b) is placed in
a fixed position between copper and the imidazole‐H‐2
moiety, which can be responsible for the high efficacy
and selectivity of the products. In this step, the CN−
imidazolium counter ion can be readily added to the
intermediate (b) to obtain the desired α‐aminonitrile
product. Finally, the catalyst is reactivated by ion
exchange of OH− with CN− in the presence of cyanide
ions in the reaction mixture (Scheme 4c,d). The role of
water in this reaction could be explained by the proposed
mechanism, in which an ion exchange occurs in a
biphasic solution, with the OH– ion provided by the water
molecule.
The nanocomposite also functions as a phase transfer
catalyst, allowing for the transfer of the cyanide ion
between the aqueous and organic phases (Scheme 5). As
presented in Scheme 5, the imidazolium moiety could
continuously transfer the CN− anions into the organic
phase, in which the reaction between CN− and
aminohydrin occurs (Scheme 4). Finally, the catalyst is
regenerated for the next run as depicted in Schemes 4
and 5.
TABLE 4 Control experiments to show the activity of
Fe3O4@SiO2@Im [CN]Cu(II) complex in the reaction of
benzylamine with benzaldehyde in the presence of NaCN for the
preparation of 2‐(benzylamino)‐2‐phenylacetonitrilea,b
Entry
Catalyst
Time (min)
Yield (%)
1
2
3
4
5
6
7
Fe3O4
60
60
60
60
60
60
60
—
10
Fe3O4@SiO2
c
Nano SiO2
Trace
25
Cu(OAc)2·H2O
Complex 4
Complex 7d
Catalyst 8
3.5 | Recoverability of the nanocatalyst
68
The development of highly efficient and environmentally
friendly catalytic systems and materials is highly favor-
able in environmental science for green chemical synthe-
sis as well as for the remediation of polluted air, soil, and
wastewater. Therefore, unveiling the relationship
between material/chemical structure and functions in
heterogeneous catalysis offers valuable guidance for the
design of rational catalysts as well as for the challenges
of potential applications in environmental science. In
90
98
aReaction conditions: benzylamine (1.0 mmol), benzaldehyde (1.0 mmol),
NaCN (1.0 mmol), water (3.0 mL), catalyst (10 mg), room temperature.
bA constant amount of 1 mg was used for each catalyst.
cSiO2 nanoparticles were prepared according to
method.[45]
a previously reported
dComplex 7 was pre‐treated with 5.0 mmol NaCN in water at room temper-
ature (see section 2.4).
SCHEME 5 Phase transfer catalyst role
of the nanocatalyst. Q+, R–OH, and R–CN
represent the catalyst, aminohydrin
intermediate, and the α‐aminonitrile
product, respectively

13 of 17
KAZEMNEJADI ET AL.
light of these considerations, in this paper, the graphene
substrate was magnetized by magnetic Fe3O4 NPs and
found to be well recoverable and reusable using a simple
external magnet. Because of metal coordination, metal
leaching for nano‐based catalysts is unavoidable.
However, researchers’ efforts have always been to reduce
this and subsequently protect the environment.
Figure 8, after 4 hr of the reaction, addition of Hg(0)
almost suppressed further catalysis. However, the reac-
tion proceeded slowly compared with the filtration test,
with 58% conversion achieved after 4 hr post‐catalyst poi-
soning. This is in contrast to the filtration test results
which may be due to the fact that the reaction can pro-
ceed with the H‐2 in imidazole even in the absence of
metal (as shown in Scheme 4), although at a much slower
rate. The kinetic plot of the reaction in the absence of
Hg(0) is depicted in Figure 8. These results indicate the
vital role of coordinated Cu in catalysis of the reaction
as well as the heterogeneous nature of the catalyst, which
is consistent with the hot filtration test.
Next, the recyclability of the catalyst was studied by
separating it using an external magnetic field from the
reaction mixture of benzyl amine, benzaldehyde, and
NaCN in water at room temperature. The recovered cat-
alyst was then reused for at least seven consecutive
runs. As shown in Figure 9, limited loss was observed
in the catalytic activity of the catalyst after the seventh
cycle. Furthermore, analysis of the residue by ICP
revealed that the catalyst under the reaction conditions
has a very low leaching rate (4% after the seventh
cycle), which is very important for the environment.
The 5% reduction in catalyst efficiency over seven con-
secutive cycles reflects its stability. This reduction is
responsible for the slight decrease in efficiency observed
over successive cycles.
Before analyzing catalyst recoverability, first, to
manifest the heterogeneous nature of the catalyst, hot
filtration and mercury poisoning tests were performed
because some catalytic reaction would occur even if the
actual catalytic species is leached off from their
support.[51] In the hot filtration technique, the model
reaction was performed between benzaldehyde and
benzylamine in the presence of Fe3O4@Im[CN]Cu(II)
and NaCN in water at room temperature. The catalyst
was magnetically removed in situ after 30 min of reaction
time, with 45% conversion achieved (GC; Figure 8). The
reaction was allowed to proceed, and after 4 hr, only
47% of the efficiency was achieved. These results con-
firmed the heterogeneous performance of the catalyst in
the reaction and consequently negligible amounts of Cu
ions leached from the catalyst. To completely ensure the
heterogeneous act of the catalyst, mercury poisoning test
was also carried out. Mercury(0) was absorbed by the
metal catalyst (or by amalgamation) and significantly
deactivated by it[52] (active site). As a result, its catalyst
activity was suppressed. This test is a strong evidence of
the heterogeneity of catalysts having active centers such
as Co, Pd, and Cu.[52] The test was conducted based on
the aforementioned model reaction (optimized condi-
tions). After allowing to the contents to react for
30 min, 320 molar equivalents of mercury versus Cu cat-
alyst were added to the reaction mixture. The reaction
medium was stirred for over 4 hr, while the reaction con-
version was screened by TLC (Figure 8). As shown in
To ensure the structure of the recovered catalyst
remains stable after the seventh run, various instrumen-
tal analyses were performed. The FTIR spectrum of the
recovered catalyst presents a complete match with the
corresponding fresh catalyst with main peaks for cyanide
ion, imine, and Si–O–Si bonds observed at 2350, 1569,
and 1017 cm−1, respectively (Figure 10a). The EDX spec-
trum confirmed the structure of the recovered catalyst,
FIGURE 8 Plot of the preparation of 2‐
(benzylamino)‐2‐phenylacetonitrile (10a)
catalyzed by 8 versus time for the mercury
poisoning and hot filtration tests. GC, gas
chromatography

KAZEMNEJADI ET AL.
14 of 17
FIGURE 9 Recyclability and leaching studies of the Fe3O4@Im[CN]Cu(II) complex
FIGURE 10 (a) Fourier‐transform infrared, (b) energy‐dispersive X‐ray, (c) thermogravimetric analysis, and (d) X‐ray diffraction spectra,
and (e) vibrating‐sample magnetometry curves for the fresh (green) and the recovered catalyst 8 after the seventh run
demonstrating the presence of all elements in its frame-
work (Figure 10b). Furthermore, by comparing the TGA
spectra of the fresh and recovered catalysts, thermal sta-
bility of the catalyst was found to remain almost constant
during the recycling period (Figure 10c). The recovered
catalyst even after seven consecutive runs showed no
obvious change in its structure, as inferred by a compari-
son of the XRD spectra of the recovered catalyst with the
fresh catalyst (Figure 10d). To investigate the stability and
magnetic properties of the NPs, the VSM analysis of the
recovered catalyst after the seven run was performed
and compared with the freshly prepared catalyst. As
shown in Figure 10e, the catalyst retains its magnetic
behavior completely over successive cycles, with the
VSM curves of the freshly prepared and recovered cata-
lysts almost completely overlapping. The SEM image

15 of 17
KAZEMNEJADI ET AL.
FIGURE 11 (a) Field emission scanning electron microscopy and (b) transmission electron microscopy images of the recovered catalyst 8
after the seventh run
showed that the recovered catalyst retains its spherical
shape with a homogeneous distribution (Figure 11a). In
the TEM image, some agglomeration could be seen,
which seems reasonable due to the nature of the nano‐
sized catalyst (high aspect ratio) as well as several consec-
utive recycles and reuse of the catalyst (Figure 11b).
To indicate the effectiveness and efficiency of
Fe3O4@Im[CN]Cu(II), we present a comparison of some
catalysts reported in the literature for the preparation of
2‐phenyl‐2‐(phenylamino)acetonitrile Table 5. As shown
in Table 5, Fe3O4@Im[CN]Cu(II) as magnetic
a
nanocatalyst presents some advantages such as excellent
yield, short reaction time, and simple separation from
the reaction mixture. The catalyst produced the desired
product in much lower amounts of copper (based on
mol%). In addition, most reported methods use TMSCN
as a source of cyanide, which has disadvantages such as
high cost, toxicity, and hard storage and handling. In gen-
TABLE 5 Comparison of efficiency of Fe3O4@Im[CN]Cu(II) with the reported catalysts in the literature for the preparation of 2‐phenyl‐2‐
(phenylamino)acetonitrile
Cyanide
source
Solvent/T (° Time
Yield (%)a
Entry Catalyst
C)
(min)
Study
[52]
1
InCl3 (30.0 mol%)
KCN
THF/RT
Glycerol/RT
H2O/RT
–d/RT
360
189
60
75
98
98
96
95
79
99
92e
99
99
b
[53]
[47]
[14]
[54]
[55]
[56]
[4]
2
–
TMSCN
TMSCN
TMSCN
TMSCN
TMSCN
TMSCN
TMSCN
3
β‐Cyclodextrin
SBSANc (4.5 mol%)
4
300
20
5
Fe (Cp)2PF6 (5.0 mol%)
Pd (II) complex (3.0 mol%)
Sulfated polyborate (5 wt%)
IrCl (CO)[P(C6H5)3]2 (1 mol%)
–d/RT
6
DCM/RT
–d/RT
45
7
2
8
Toluene/RT
–d/RT
30
[57]
9
CdII ion‐based chiral metal–organic framework (10 wt%) TMSCN
240
50
10
Fe3O4@Im[CN]Cu(II) (1.6 mol%) NaCN
H2O/RT
Present work
aIsolated yield.
bCatalyst free.
cSilica boron sulfuric acid nanoparticles.
dSolvent free.
eFor 2‐(dimethylamino)‐2‐phenylacetonitrile.
DCM, dichloromethane; RT, room temperature; THF, tetrahydrofuran; TMSCN, trimethylsilyl cyanide.

KAZEMNEJADI ET AL.
16 of 17
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the presence of Fe3O4@Im[CN]Cu(II) as an efficient
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ACKNOWLEDGEMENT
Authors gratefully acknowledge the financial support for
this work by the Research Council of University of
Birjand.
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ORCID
[26] S. Baghery, M. A. Zolfigol, R. Schirhagl, M. Hasani, M. C.
Milad Kazemnejadi
https://orcid.org/0000-0002-5424-
Stuart, A. Nagl, Appl. Organomet. Chem. 2017, 31, e3883.
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SUPPORTING INFORMATION
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How to cite this article: Kazemnejadi M, Alavi
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functionalized Cu(II) Schiff base complex with an
imidazolium moiety as an efficient and eco‐friendly
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