Cu-Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efficient Catalyst for Domino One-Pot Preparation of Benzimidazole and Biginelli Reactions from Alcohols

Article abstract of DOI:10.1007/s10562-020-03371-0

An efficient magnetically recyclable bimetallic catalyst by anchoring copper and manganese complexes on the Fe₃O₄ NPs was prepared and named as Fe₃O₄@Cu-Mn. It was founded as a powerful catalyst for the domino one-pot oxidative benzimidazole and Biginelli reactions from benzyl alcohols as a green protocol in the presence of air, under solvent-free and mild conditions. Fe₃O₄@Cu-Mn NPs were well characterized by FT-IR, XRD, FE-SEM, TEM, VSM, TGA, EDX, DLS, and ICP analyses. The optimum range of parameters such as time, temperature, amount of catalyst, and solvent were investigated for the domino one-pot benzimidazole and Biginelli reactions to find the optimum reaction conditions. The catalyst was compatible with a variety of benzyl alcohols, which provides favorable products with good to high yields for all of derivatives. Hot filtration and Hg poisoning tests from the nanocatalyst revealed the stability, low metal leaching and heterogeneous nature of the catalyst. To prove the synergistic and cooperative effect of the catalytic system, the various homologues of the catalyst were prepared and then applied to a model reaction separately. Finally, the catalyst could be filtered from the reaction mixture simply, and reused for five consecutive cycles with a minimum loss in catalytic activity and performance. Graphic Abstract: A new magnetically recyclable Cu/Mn bimetallic catalyst has been developed for domino one-pot oxidation-condensation of benzimidazole and Biginelli reactions from alcohols. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-020-03371-0

Catalysis Letters
https://doi.org/10.1007/s10562-020-03371-0
Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs
as an Efcient Catalyst for Domino One‑Pot Preparation
of Benzimidazole and Biginelli Reactions from Alcohols
Mohammad Ali Nasseri1 · Zinat Rezazadeh1 · Milad Kazemnejadi1 · Ali Allahresani1
Received: 19 May 2020 / Accepted: 28 August 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
An efcient magnetically recyclable bimetallic catalyst by anchoring copper and manganese complexes on the Fe3O4 NPs
was prepared and named as Fe3O4@Cu-Mn. It was founded as a powerful catalyst for the domino one-pot oxidative benzi-
midazole and Biginelli reactions from benzyl alcohols as a green protocol in the presence of air, under solvent-free and mild
conditions. Fe3O4@Cu-Mn NPs were well characterized by FT-IR, XRD, FE-SEM, TEM, VSM, TGA, EDX, DLS, and ICP
analyses. The optimum range of parameters such as time, temperature, amount of catalyst, and solvent were investigated for
the domino one-pot benzimidazole and Biginelli reactions to fnd the optimum reaction conditions. The catalyst was compat-
ible with a variety of benzyl alcohols, which provides favorable products with good to high yields for all of derivatives. Hot
fltration and Hg poisoning tests from the nanocatalyst revealed the stability, low metal leaching and heterogeneous nature
of the catalyst. To prove the synergistic and cooperative efect of the catalytic system, the various homologues of the catalyst
were prepared and then applied to a model reaction separately. Finally, the catalyst could be fltered from the reaction mixture
simply, and reused for fve consecutive cycles with a minimum loss in catalytic activity and performance.
Graphic Abstract
A new magnetically recyclable Cu/Mn bimetallic catalyst has been developed for domino one-pot oxidation-condensation
of benzimidazole and Biginelli reactions from alcohols.
Keywords Bimetallic catalyst · Fe3O4@cu-mn · One-pot multicomponent reactions · Benzyl alcohols
Electronic supplementary material The online version of this
1 Introduction
article (https://doi.org/10.1007/s10562-020-03371-0) contains
supplementary material, which is available to authorized users.
Most sustainable intermediates have resulted from mul-
ticomponent reactions as a key synthetic method due to
obvious advantages including synthetic efficiency and
* Mohammad Ali Nasseri
manaseri@birjand.ac.ir
Extended author information available on the last page of the article
Vol.:(0123456789)
1 3

M. A. Nasseri et al.
molecular diversity. Among all these type of reactions,
Biginelli and benzimidazole reactions were highly regarded
due to the most robust biological and therapeutic activities
[1, 2]. Dihydropyrimidinones (DHPMs) and their deriva-
tives have been found to revolutionize situation in synthetic
methodologies that so-called Biginelli reaction. Biginelli
is a cyclo-condensation reaction which synthesized car-
bonyl components in the strong acidic medium [3–7]. On
the other hand, benzimidazoles are heterocyclic aromatic
compounds containing fused benzene and imidazole rings.
Benzimidazoles are efective bicyclic compounds for phar-
maceutical purposes such as anticancer, antifungal, and anti-
virus activities [7–12], that prepared from aldehydes and
o-phenylenediamines under vigorous conditions. These are
valuable techniques for the synthesis of simple to complicate
bicyclic compounds which have been found various potential
applications such as biological activity, optical properties,
thermos-stability, asymmetric synthesis, and combinatorial
chemistry [13–15]. Hence, the preparation of dihydropyrimi-
dinones and benzimidazoles are highlighted in the reports.
On the other hand, carbonyl scafolds play vital role because
of distinct features in diferent science aspects including
pharmacy, vitamin syntheses, perfuming industry, organic
synthesis, and tandem reactions. After polymerization
reactions, oxidations have been found the second circum-
stances in the chemical industries [16]. Selective oxidation
of alcohols to carbonyl are a category of chemical transfor-
mation under aerobic conditions as a non-toxic, cheap, and
safe oxidant. From the environmentally and atom economy
viewpoint, alcohols as the versatile, renewable, sustainable,
afordable, diverse, and abundant resources have received
great attention from engineers and scientists [16–20].
In spite of carbonyl compounds validity, considerable
reactions including Strecker, Hantzsch, Biginelli, Mannich,
Passerini, Ugi, N-heteroatom bicyclic, and etc. were handled
with these intermediates. Classical methods are based on
substrate interactions from elaboration carbonyl compounds
as more volatile, toxic, unstable, and more expensive. To
address this impediment, using alcohol derivatives is a
benign strategy in cascade reactions. Domino reactions are
facile, economic, and ecological rather than stepwise mod-
els. In this way, multicomponent reactions have been con-
sidered by the domino catalytic systems such as Biginelli,
Knoevenagel, benzimidazole, and pyridine rings synthesis
[21–25]. Thus, the replacement of the direct synthesis by
multi-step one, are manifold advantages for environmental
and industrial goals such as renewable materials, high atom
economy, and eco-friendly nature.
scale-up, and increasing chemoselectivity in aerobic con-
ditions. To overcome these problems, catalytic systems
based Cu, Rh, Pd, Fe, Au, Vo, Ir, and Mn introduced as
an emerging alternative method. Industrial point of view,
high selectivity, high efciency, mild conditions, afordable,
and energy saving were important goals to achieve with the
metal based catalytic systems in aerobic conditions [26–31].
Moreover, the design of bimetallic catalysts for aza-hete-
rocycle synthesis is clever mindful due to the specifc prop-
erties such as cooperativity efect, chemoselectivity, high
reaction rate, cost-efective, and two available active sites.
So pioneering bimetallic catalysts could be handle one-pot
reactions to obtain a target product with high yield, high
selectivity, low reaction time, and removal of purifcation/
separation step for the intermediates. Thus, energy saving
and the ultimate cost reduction of the product are advan-
tages of these catalysts in the cascade reactions, defnitely
[32–34]. In this regard, various bimetallic systems reported
for a variety of organic reactions such as multi component,
cross coupling, and domino one-pot reactions [35–39].
Wang et al. introduced a catalytic performance system as
name as PdxNiy@ZIF-8 for Sonogashira cross-coupling,
which synergistic efect studied between Pd and Ni in the
efciency and catalyst activity [40]. A novel Al-Ti bimetal
incorporated 3D mesoporous TUD-1 reported by Pasu-
phati et al. for Biginelli reaction under mild reactions. The
researchers suggested a plausible mechanism based on Al3+
and Ti4+ ions for the preparation of the 3,4-dihydropyrimi-
dones [41]. Kamjijo et al. illustrated the synthesis of vari-
ous triazoles from alkynes using Pd–Cu bimetallic catalyst
system [42]. Copper and manganese are two inexpensive
and nontoxic noble metals, with high abundance in nature.
The well-known Lewis acid activity of Cu and powerful
oxidation activity of Mn, make them as suitable metals for
the preparation of a bimetallic catalytic system for domino
oxidation-condensation reactions.
In this study, we synthesized a magnetically recycla-
ble Copper/Manganese bimetallic nanocatalyst (Fe3O4@
Cu-Mn) with high performance for domino oxidation-con-
densation reaction of Biginelli and benzimidazoles from
alcohols. Cooperatively and synergetic efects in Fe3O4@
Cu-Mn were investigated with various control experiments
(Scheme 1).
2 Experimental
2.1 Material and Instruments
Metal-based catalysts rather than traditional oxidants
founded special places in aerobic alcohol oxidations [26,
27]. Pivotal roles of metal-based catalysts in this feld are
removal of toxic Cr(VI) and Mn(VII), decreasing by-prod-
uct, high E-factor (mass of waste/mass of product), immense
All materials were purchased from Sigma and Fluka sup-
pliers and used without further treatment. The distilled
and dried solvents were used for all reactions. The analyti-
cal grade was selected for all other reagents. Thin layer
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
O
R1
O
OH
R2
NH
H2N
O
NH2
O
[Hmim]HSO4-NaNO3
80 o
Tetrahedron 51 (2010) 6436-6438
R1
C
Me
R2
Me
N
H
O
OH
R1
H2
H
N
Cat.
NH2
O
R1
Green Chemistry 12 (2015) 5172-5181
Cu-PMO
R2
R2
R1
Solvent, base
N
NH2
This work
OH
H
N
NH2
NH2
N
R
Benziimidazole reaction
high conversion up to 98%
R
Heterogeneous bimetallic Cu-Mn catalyst
4a-4k
Cu
Mn
Fe3O4
R
Mn
Cu
O
OH
O
Et
NH
Sustainable bimetalic catalyst
Domino catalytic system
Eco-friendly magnetic catalyst
High susbtrate diversity
H2N
O
NH2
Et
N
H
O
Et
Et
Aerobic oxidative conditions
Biginelli reaction
high conversion up to 97%
R
O
7a-7k
Scheme 1. The Chemical structure of Fe3O4@Cu-Mn bimetallic catalytic system for green one-pot Biginelli and benzimidazole reactions from
benzyl alcohols
chromatography (TLC) was performed for monitoring reac-
gas. Anisole was used as the internal standard. EDX analy-
ses were performed using a FESEM, JEOL 7600F appara-
tus equipped with a spectrometer of energy dispersion of
X-Ray from Oxford instruments. TEM microscopic images
were performed on a Philips EM208S microscope operated
at 100 kV. TGA analyses of the samples were performed
on a Q600 model from TA company made in U.S.A under
nitrogen atmosphere with a heating rate of 10 °C/min, and
in the temperature range of 25–1000 °C. VSM curve of the
samples was analyzed on a Lake Shore Cryotronics 7407 at
room temperature. ICP experiments were conducted using a
tion progress. FTIR spectra were obtained using a JASCO
1
FT/IR 4600 spectrophotometer using KBr pellet. The H
NMR (250 MHz) and 13CNMR (62.9 MHz) spectra were
recorded on a Bruker Avance DPX-250 spectrometer in
the deuterated solvents (CDCl3 and DMSO-d6) and TMS
as an internal standard. Field emission scanning electron
microscopy (FE-SEM) images were achieved on a SEM
FEI Quanta 200. Gas chromatography (GC) analyses were
performed using a Shimadzu-14B gas chromatograph
equipped with an HP-1 capillary column and N2 as a carrier
1 3

M. A. Nasseri et al.
VARIAN VISTA-PRO CCD simultaneous ICP-OES instru-
ment. XRD patterns were obtained on a Rigaku SmartLab
instrument. The size distribution of the nanoparticles was
measured using the dynamic light scattering (DLS) method
using a HORIBA-LB550 instrument.
and dried in a vacuum oven. Fe3O4@Mn-NH2 (compound
iii, Scheme 2) was characterized by FT-IR and EDX analyses
(Table 1).
To prepare the Cu–Mn bimetallic catalyst, a Schif base
moiety as a secondary ligand was designed in compound
(iii) structure through the mixing compound iii (0.5 g) and
5.0 mmol salicylaldehyde in ethanol at room temperature for
4 h. The obtained solid was separated and washed repeat-
edly (iv, Scheme 2). The Fe3O4@NH2-Mn-SB (compound
iv) was characterized by FT-IR and EDX analyses (Table 1).
2.2 Preparation of Fe3O4@Epoxide (i)
The Fe3O4 magnetic nanoparticles were synthesized accord-
ing to a previously reported procedure [43]. After dispersion
of Fe3O4 NPs (0.5 g) in 10 ml DMSO, 5.0 mmol trimethyl-
amine (Et3N) was added dropwise to the dispersed solution,
then epichlorohydrin (5.0 mmol) was added to the mixture at
90 °C in an oil bath. The mixture was stirred for 48 h under
N2 atmosphere. The Fe3O4@Epoxide product was separated
by a permanent magnetic feld and washed three times with
absolute ethanol. The resulted nanoparticles were dried
overnight, then characterized by FT-IR, and EDX analyses
(Table 1).
2.4 Preparation Route of Fe3O4@Cu‑Mn Catalyst (v)
Compound iv (0.5 g) and 0.1 g Cu(OAc)2.H2O was sus-
pended in 20 ml absolute ethanol then sonicated until it
became completely dispersed. Subsequently, the mixture
was stirred for 24 h at 60 °C under air atmosphere. The
resulting solid product (v) was separated and washed. The
product was characterized by FT-IR, and EDX analyses
(Table 1). Scheme 2 shows the general synthetic approach
for the preparation of i, ii, iii, iv, and v.
2.3 Preparation of Fe3O4@NH2 (ii)
In order to functionalize Fe3O4@Epioxide with NH2 groups,
a mixture of Fe3O4@Epoxide (0.5 g) and 5.0 mmol p-phe-
nylenediamine were stirred in 10 ml DMSO extremely in the
presence of Et3N (5.0 mmol) at 60 °C for 24 h. The desired
product ii (Scheme 2) was separated by an external magnet,
repeatedly washed with ethanol to remove unreacted materi-
als, then dried overnight. The product was characterized by
FT-IR and EDX analyses (Table 1).
2.5 General Procedure for Domino One‑Pot
Preparation of Benzimidazole and Biginelli
Derivatives Catalyzed by Fe3O4@Cu‑Mn
The one-pot synthesis of benzimidazole carried out in a
round-bottom fask with benzyl alcohol (1.2 mmol) and
ortho phenylenediamine (1.0 mmol) using Fe3O4@Cu-Mn
catalyst (0.008 g, 0.280 mol% Cu, 0.078 mol% Mn), under
solvent-free and aerobic conditions at 70 °C. The reac-
tion mixture was monitored with TLC. Upon reaction
completion, the catalyst was magnetically separated, then
the product was extracted to dichloromethane (3 × 5 mL).
The organic layers were combined, dried over Na2SO4 and
The coordination of Mn ions to the magnetic NPs (ii)
was performed via the mixing of Fe3O4@NH2 (0.5 g) with
1.0 mmol manganese(II) acetate in ethanol at 60 °C for 4 h.
Then, Fe3O4@epoxide-Mn complex was magnetically sepa-
rated, washed with deionized water and ethanol (3×12 mL),
Table 1 Representative data of the synthesized compounds
Compound FT-IR & EDX data
i
IR (KBr): υ (cm−1)=502 (Fe–O–Fe stretching), 635,733,1102 (asymmetric and symmetric stretching of epoxide ring), 3249 (OH
band). EDX analysis: Fe=40.32%wt, O=36.19%wt, C=23.48%wt (†ESI, Figure S1, S2)
ii
IR (KBr): υ (cm−1)=518 (Fe–O–Fe stretching), 1043 (C–O stretching), 1480 (Ph), 1596 (Ph), 2920 (CH-sp3), 2960 (CH-sp2),
3251,3303 (NH2 stretching), 3372 (OH band). EDX analysis: Fe=37.31%wt, O=34.40%wt, N=5.08%wt, C=23.21%wt (†ESI,
Figure S1, S3)
iii
iv
v
IR (KBr): υ (cm−1)=481 (Fe–O–Fe stretching), 635 (Mn–O stretching), 698 (Mn–N stretching), 1019 (C–O stretching), 1339
(Ph), 1590 (Ph), 2926 (CH-sp3), 2980 (CH-sp2), 3367 (OH band). EDX analysis: Fe=18.53%wt, O=50.26%wt, N=3.71%wt,
C=16.08%wt, Mn=11.42%wt (†ESI, Figure S1, S4)
IR (KBr): υ (cm−1)=505 (Fe–O–Fe stretching), 620 (Mn–O stretching), 631 (Mn–N stretching), 1016 (C–O stretching), 1150
(C–N stretching), 1370 (Ph), 1585 (Ph), 1650 (C=N stretching), 2852 (CH-sp3), 2922 (CH-sp2), 3370 (OH band). EDX analysis:
Fe=24.17%wt, O=41.17%wt, N=3.65%wt, C=23.71%wt, Mn=7.30%wt (†ESI, Figure S1, S5)
IR (KBr): υ (cm−1)=484 (Fe–O–Fe stretching), 560 (Cu–O stretching), 633 (Mn–O and Cu–N stretching), 676 (Mn–N stretching)
1032 (C–O stretching), 1132 (C–N stretching), 1339 (Ph), 1530 (Ph), 1620 (C=N stretching), 2928 (CH-sp3), 2980 (CH-sp2),
3367 (OH band). EDX analysis: Fe=24.58%wt, O=41.28%wt, N=10.10%wt, C=21.28%wt, Mn=0.54%wt, Cu=2.23%wt
(†ESI, Figure S1)
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
OH
OH
OH
OH
O
O
NH2
N
H
OH
4
e
4
Epichlorohydrin
p-Phenylenediamine
4
O
O
O
OH
O
3
3
OH
N
Et3
DMSO
h, Ref.
3
OH
Et3N
DMSO
48 h, Ref.
F e
F e
F e
24
OH
OH
OH
OH
OH
i
OH
ii
Mn(OAc)2.4H2O
OH
OH
N
OH
O
N
O
NH2
NH2
O
O
N
N
4
4
O
O
3
Mn
Salicylaldehyde
4 h, RT
OH
3
Mn
OH
F e
F e
O
N
N
OH
O
O
O
OH
iv
OH
iii
OH
N
N
O
O
N
O
O
4
Cu(OAc)2.H2O
Ethanol, 24 h
Cu
O
v
3
Mn
OH
F e
O
N
O
OH
Scheme 2 The general synthetic approach for preparation of the Fe3O4@Cu-Mn
purifed by silica-gel column chromatography (n-hexane:
EtOAc=10: 5).
3 Result and Discussion
For the Biginelli reaction, benzyl alcohol (1.2 mmol),
ethyl acetoacetate (1.2 mmol), and urea (1.0 mmol) were
reacted in the presence of Fe3O4@Cu-Mn catalyst (0.008 g,
0.280 mol% Cu, 0.078 mol% Mn) under solvent-free and
aerobic conditions at 70 °C. Repeatedly, the reaction per-
formance and product purifcation was as same as the ben-
zimidazole reaction. After the reaction completion, the mag-
netic catalyst was separated easily by an external magnet and
the product was extracted to dichloromethane (3 × 5 mL).
The organic layers were combined, dried over Na2SO4 and
purifed by silica-gel column chromatography (n-hexane:
EtOAc=12: 3). The products were characterized and iden-
tifed by comparing their melting point and NMR analyses
with those authentic samples.
The catalyst, Fe3O4@Cu-Mn, was characterized step by step
by FT-IR analysis to investigate its structure and formation
of the desired bands. The FT-IR spectra of the compounds
i, ii, iii, iv, and Fe3O4@Cu-Mn (v) was shown in Fig. 1.
As shown in Fig. 1, the characteristic peaks at 502 cm−1,
635 cm−1, 733 cm−1, 1102 cm−1, and 3249 cm−1 represent
the absorptions correspond to Fe–O-Fe (Stretching vibra-
tion), C–O–C asymmetric and symmetric stretching of
epoxide ring, and the broad O–H band (stretching vibration)
respectively, which confrms the structure of compound i
(Fig. 1) [44]. FT-IR spectrum of ii exhibited the absorption
bands at 518 cm−1 (Fe–O–Fe stretching), 1043 cm−1 (C–O
stretching), 1480 cm−1 (Ph), 1596 cm−1 (Ph), 2920 cm−1
(CH-sp3), 2960 cm−1 (CH-sp2), 3251, 3303 cm−1 (NH2
stretching), and 3372 cm−1 (OH band). These absorption
bands confrmed the successful preparation of ii with the
1 3

M. A. Nasseri et al.
amine groups. The presence of the bands at 635 cm−1
(Mn–O stretching), 698 cm−1 (Mn-N stretching) in the
FT-IR spectrum of iii, clearly represents the formation of
the manganese complex [45, 46]. Figure 1 shows the FTIR
spectrum iv with three characteristic peaks at 620, 631, and
1650 cm−1 related to Mn–O, Mn-N and C=N stretching
bands respectively, that approves the formation of Fe3O4@
NH2-Mn-SB nanoparticles [47]. The imine band absorption
(1650 cm−1) shifted to higher wavenumbers (1620 cm−1) in
the Cu-Mn bimetallic catalyst spectrum (compound v). Also,
three absorption bands at 560, 633, and 679 cm−1 could be
assigned to Cu–O, Cu–N, Mn–O, and Mn–N stretching
vibrations respectively [48].
a continuous weight loss with a mild slope up to~450 °C
(~6.49 weight loss), indicating the decomposition of Schif
base ligands [50]. Signifcant weight loss occurs at~708 °C
with a~16.43% weight loss (sharp slope), which is related
to the decomposition of diferent organic fragments on the
nanoparticles surface.
VSM analyses revealed the magnetic behavior of Fe3O4
and Fe3O4@Cu-Mn NPs (Fig. 4b). The saturation magneti-
zation for Fe3O4 and Fe3O4@Cu-Mn catalysts were deter-
mined as 74.28 and 56.80 emu/g respectively. Zero coerciv-
ity for the nanoparticles with no hysteresis loop indicates the
superparamagnetic properties of the NPs. The magnetization
decrease of 17.48 emu/g clearly illustrates the high immobi-
lization of Cu–Mn bimetal section on the Fe3O4 NPs with-
out signifcant change in the magnetic property, although
Cu–Mn complex operated as a distorted diamagnetic shell
[51]. Despite this reduction, the magnetite bimetallic nano-
particles were well and easily separated from the reaction
medium by a simple external magnetic feld which could be
a prerequisite for magnetic nature of a catalyst.
A quite uniform size with a spherical morphology vision
was proved by the FE-SEM image of Fe3O4@Cu-Mn nano-
particles (Fig. 2a). As shown in Fig. 2b, the TEM micro-
scopic image verifed the spherical morphology and charac-
teristic core–shell for the magnetic bimetallic catalyst with
an average size of 24 nm [49]. It is noted that the shape and
particle size of the catalyst did not change after functionali-
zation. The size distribution histogram was estimated a mean
diameter of 24–26 nm for Fe3O4@Cu-Mn nanoparticles,
which presented relatively narrow size distribution (Fig. 2c).
The catalyst was characterized step by step by EDX
analysis to investigate the structure and the presence of
the expected elements (Fig. 3 and †ESI, Fig. S1–S4). To
obtain more precise data about the amount of elements, the
EDX analyses were taken from the compound i, ii, iii, iv,
and v. EDX analysis was proved the removal of chloride
for Fe3O4@Epoxide (compound i) structure. The elements
including carbon, nitrogen, oxygen, iron, and manganese
confrmed the expected structures for compounds ii, iii,
as the manganese complexes, and also Schif base com-
plex (compound iv). The results confrmed all the expected
elements including Fe, O, C, Cu, Mn, and N with 24.58,
41.28, 21.28, 2.23, 0.54, 10.10 wt% values, respectively.
The expected elements such as copper and manganese with
specifed percentages confrmed the preparation of the bime-
tallic Cu-Mn system.
The six difraction peaks at 2θ=35.18°, 40.63°, 48.33°,
58.73°, 62.33°, and 67.83° related to respectively (220),
(311), (400), (422), (511), and (440) planes, were com-
pletely in agreement with the crystal structure of Fe3O4 NPs
characterized by XRD (JCPDS card no. 19-629) (Fig. 5)
[52]. Comparison of XRD patterns of Fe3O4 and the cata-
lyst, exhibited that the crystalline phase and peak location
related to magnetite crystal structure remained intact dur-
ing organic loading (functionalization), which confrmed
the chemical stability of the prepared Fe3O4 NPs. But, the
impressive decrease in peak intensity and peak broadening
indicated the loading of the amorphous functionality on the
magnetite nanoparticles. This occurrence can also be related
to the organic functional loading as an amorphous structure
on magnetite NPs, which is also a confrmation for the suc-
cessful functionalization of the Fe3O4 NPs. The crystallinity
peak intensity reduction after the functionalization process
was perfectly aligned with the VSM and TGA analyses (refer
to Fig. 4a, b). In addition, the size of the nanoparticles was
also investigated by XRD analysis. The crystallite size was
calculated by applying the Scherrer’s equation: D = Kλ/
βcosθ, where D is the average diameter, K is Sherrer’s con-
stant (0.94 for Cu-Kα), λ is ray wavelength, β is the peak
width of half-maximum, and θ is the Bragg difraction angle
[47]. According to the results, the size of Fe3O4@Cu-Mn
was found to be 42 nm.
Figure 4a shows the thermal behavior of the Fe3O4 and
Fe3O4@Cu-Mn NPs by TGA analysis. The Fe3O4 nanopar-
ticles showed only 4.89% weight loss which can be directly
related to the trapped water in the nanoparticles crystal
structure (25 °C–1000 °C). The TGA curve of Fe3O4@
Cu-Mn NPs illustrated about 40% weight loss between
25 °C and 1000 °C. In addition, removal of the adsorbed
water on the surface of the catalyst and trapped water in the
crystal structure occur at below 200 °C and 350 °C, respec-
tively. Another two weight losses revealed the removal of
Schif base ligands and diferent organic groups immobi-
lized on NPs, which proved the successful grafting of the
bimetallic complex onto the magnetite surface. The TGA
curve of the bimetallic Fe3O4@Cu-Mn nanoparticles shows
3.1 Optimization of Reaction Parameters
To study the multicomponent reactions parameters, time,
temperature, and amount of the bimetallic catalyst, as three
efective parameters were investigated in various condi-
tions over three model reactions of: (a) aerobic oxidation
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
oxidative multicomponent processes (Fig. 6b) [38, 53, 54].
Outstandingly, the medium to high efciencies were estab-
lished for solvent-free conditions at 70 °C.
In following with the obtained optimum conditions col-
lected in the preceding step, the catalytic activity of Fe3O4@
Cu-Mn was investigated in the oxidation of alcohols, one-
pot preparation of benzimidazole, and one-pot preparation
of Biginelli reactions. Efect of substituted benzylic alco-
hols for oxidation to aldehydes was investigated by Fe3O4@
Cu-Mn (0.178 mol% Cu, 0.049 mol% Mn) at room tempera-
ture in ethanol under aerobic conditions (Table 3, 2a–k).
Increasing reaction time was observed for benzyl alcohols
bearing electron-defcient and more steric hindrance sub-
stituent (Table 3, 2b, c and 2j–k). In general, there was no
signifcant diference in the efciency of alcohols bearing
electron-withdrawing and electron donating groups, and
good to excellent efciency was obtained for all derivatives
[55].
In following, the catalytic activity of Fe3O4@Cu-Mn was
investigated toward benzimidazole reaction (from alcohols)
in 80–98% overall yields (Table 4, 4a–4k). Various sub-
stituted benzyl alcohols with ortho phenylenediamine were
condensed in good to excellent yields under solvent-free and
aerobic conditions at 70 °C (Table 4). It should be noted
that the electron-withdrawing groups on benzyl alcohols
(Table 4, entry 4d–4j) reduced the efciency compared to
electron-donating groups (Table 4, 4b and c) [56, 57].
Biginelli reactions were conducted on a variety of benzyl
alcohols as well as ethyl acetoacetate with urea by Fe3O4@
Cu-Mn (0.280 mol% Cu, 0.078 mol% Mn) at 70 °C under
solvent-free conditions in 75–97% overall yields (Table 5,
7a–7k). Para substitution benzyl alcohols give satisfactory
yields than their corresponding ortho substitution, that may
be attributed to the steric hindrance efect (Tables 5, 7b, e
and c, l). The electron-donating groups on benzyl alcohols
(Table 5, entry 7d–7j) demonstrated more satisfactory yields
than the corresponding benzyl alcohol bearing electron-
withdrawing groups (Table 5, entry 7b, c) [4, 58].
Fig. 1 FT-IR spectra, (i) Fe3O4@Epoxide, (ii) Fe3O4@NH2, (iii)
Fe3O4@Epi- Mn-NH2, (iv) Fe3O4@Epi-NH2-Mn-SB, (v) Fe3O4@
Cu-Mn
of benzyl alcohol to aldehyde, (b) benzyl alcohol and ortho
phenylenediamine (as a benzimidazole reaction model), and
(c) benzyl alcohol as well as ethyl acetoacetate with urea as
a Biginelli reaction model. The selected premium conditions
achieved for the oxidation of benzyl alcohol to benzaldehyde
was as, 0.005 g amount of NPs at room temperature for 1.0 h
(Table 2, entry 2). Also, the one-pot benzimidazole reaction
give high possible efciency using 0.008 g of NPs, at 70 ºC
for 2 h (Table 2, entry 13); and the one-pot Biginelli reaction
was performed as same as the benzimidazole reaction condi-
tions (Table 2, entry 23). Table 2 shows various conditions
tested for the model reactions.
3.2 Mechanism Study
To elucidate the exact role of the copper and manganese
in the catalytic system for domino aerobic oxidative reac-
tions, some control experiments were designed and imple-
mented for the model one-pot Biginelli and benzimidazole
reactions under the same reaction conditions (Table 6, entry
1–8). Cu(OAc)2.H2O and Mn(OAc)2.4H2O didn’t give con-
siderable oxidation product (benzaldehyde) under open air
conditions, and subsequently a trace amount of benzimida-
zole and Biginelli was obtained for them (Table 6, entries
1, 2). No catalytic activity was observed for Fe3O4 NPs in
these conditions (Table 6, entry 3). Among the homologue
compounds, efciency of iii, vi, and vii was worthy and
Next, the infuence of solvent and oxidant type was evalu-
ated on the model reactions (Fig. 6a and b). The solvent-
free conditions had the best efect by providing 93% and
92% efciency at 70 °C for the one-pot benzimidazole and
Biginelli reactions, respectively. The screening results can
be justifed by the strong interaction of active sites with the
reactants in the solvent-free medium (Fig. 6a). Aerobic con-
ditions were provided high yield and then oxidants such as
H2O2 and O2 showed moderate to good efciencies, which
is in agreement with the literature for possible electron
transfer and contribution between Cu and Mn metals during
1 3

M. A. Nasseri et al.
Fig. 2 a FE-SEM, b TEM images, and c size distribution histogram of Fe3O4@Cu-Mn NPs
Fig. 3 EDX analysis of Fe3O4@Cu-Mn
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
Fig. 4 TGA and VSM curves of Fe3O4@Cu-Mn and Fe3O4
impressive (Scheme 3). Oxidation of benzyl alcohol to ben-
zaldehyde by iii and vi demonstrated a powerful efect of Mn
metal (55% yield) compared to Cu metal (35% yield) in the
domino oxidative process. As shown in Table 6, manganese
majorly performed the oxidation process with higher selec-
tivity (Table 6, entry 4, 5). Moreover, compounds v and vii,
as two bimetallic systems, have shown high selectivity in
the oxidation step, which proved the synergistic efect of Cu
and Mn centers in the catalyst for the green one-pot reactions
of Biginelli and benzimidazole. Finally, compound v didn’t
give any considerable oxidation product (benzaldehyde)
under N2 atmosphere, and a negligible amount of benzimi-
dazole and Biginelli was prepared subsequently (Table 6,
entries 8), which demonstrated the cooperative activity of
Cu–Mn bimetallic system for the aerobic (low dependence
to molecular oxygen) one-pot process under N2 atmosphere,
and the reaction could be processed somewhat in the absence
of any external oxidant. The results clearly manifested the
synergistic efect as well as cooperative activity between Mn
and Cu for domino oxidation-condensation reaction.
The heterogeneous nature of the catalyst was studied
by Hg(0)-poisoning and hot fltration tests over the model
one-pot oxidative benzimidazole reaction under optimized
conditions. In the fltration test, the catalyst was magneti-
cally recovered after one hour of the reaction. As shown in
Fig. 7, after 2 h, the efciency reached to 60% (GC analysis),
indicating the heterogeneous performance of the catalyst in
the reaction medium, which no metal leaching occur related
to the coordinated Cu or Mn metals in the reaction mixture
(Completely consistent with the results of the leaching stud-
ies). In addition, in the Hg(0)-poisoning test, mercury(0) was
added initially, and in a separate test, it was added after 1 h
of reaction time, which 4%, 55% conversion was obtained
respectively for the reactions (based on GC analysis). If the
catalyst is heterogeneous, the mercury deactivates its activ-
ity by poisoning the catalyst (blokes the Cu and Mn active
sites) [59] and subsequently the reaction stops. Mercury has
no efect on homogeneous catalysts. However, the proposed
mechanism is based on previous observations and reports
in Table 6 and Fig. 7, wherein the manganese centers were
proposed to conduct the reaction via oxidation benzyl alco-
hols as a Lewis acid and H-bond donor then Copper center
developed one-pot Biginelli and benzimidazole directions
(Scheme 4) [60–62].
Fig. 5 X-ray difraction pattern of Fe3O4@Cu-Mn and Fe3O4
1 3

M. A. Nasseri et al.
Table 2 Optimization results for maximum points in the oxidation of
(Scheme 4). Based on the control experiments, the bimetallic
compounds v, vii provided high selectivity and efciency
than single-metal components under air conditions. The
presence of the second metal could be acts as a co-oxidant
with a plausible electron exchange [66–68], and subse-
quently regeneration of the catalyst for the next cycle. In
this regard, the Cu and Mn active sites provide a synergistic
as well as cooperative performance, which air as a weak oxi-
dant gives a prominent activity. According to the literature,
for the preparation of dihydropyrimidone [63], the reaction
starts with the coordination of Cu active sites in the catalyst
to carbonyl of aldehyde (Intermediate II), then the nucleo-
philic addition of urea forms intermediate III (Scheme 4). In
the next step, the activated β-diketone attacks to the iminium
intermediate III and the resulting addition intermediate IV is
formed. A cyclization takes place through the nucleophilic
addition of amine to carbonyl group, which gives the desired
product after removal of a water molecule (Scheme 4). Ben-
zimidazole was also forms via the activation of carbonyl
of aldehyde by the catalyst, followed by the nucleophilic
addition of o-phenylenediamine (Intermediate VI). Finally,
a nucleophilic attack of another free amine group causes the
formation of benzimidazole ring. It worth noted, that the
oxidative activity of the catalyst helps the aromatization of
the fnal intermediate and promotes the efciency (Table 7).
Finally, the uniqueness of Fe3O4@Cu-Mn bimetallic
system in the one-pot synthesis of benzimidazole and dihy-
dropyrimidinone derivatives was compared with the recent
literatures. The Cu-Mn bimetallic catalyst with the advan-
tages/properties of magnetic, inexpensive, recoverable, and
eco-friendly can catalyze the one-pot Biginelli and benzi-
midazole reactions under open-air and mild conditions with
high efciency.
alcohols, Biginelli, and benzimidazole one-pot reactions
Entry Cu/Mn
catalyst
Time (h) Tem-
Yield (%)
perature
(g)
(°C)
Oxidation of
alcohol to
aldehydea
1
2
3
4
5
6
7
8
9
0.005
0.005
0.005
0.005
0.005
0.005
0.006
0.007
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.009
0.01
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.008
0.009
0.01
0.5
1
1.5
1
1
1
1
1
1
0.5
1
1.5
2
2.5
2
2
2
2
2
0.5
1
1.5
2
25
25
25
50
70
90
25
25
25
70
70
70
70
70
25
50
90
70
70
70
70
70
70
70
25
50
90
70
70
80
95
93
92
85
65
91
85
83
40
75
88
93
91
65
78
88
91
89
52
68
79
92
90
56
70
90
89
85
Benzimidazoleb 10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Biginellic
2.5
2
2
2
2
2
3.4 Recyclability Studies
aReaction conditions: Benzyl alcohol (1 mmol), Cat. (0.005 g,
0.175 mol% Cu, 0.049 mol% Mn), EtOH (2 mL), r.t, open air
In the heterogeneous catalysts feld, recovering and recycling
of the catalyst are prominent matters for environmental and
practical destinations [73]. In this way, the recyclability of
the catalyst was studied over the model benzimidazole reac-
tion (between benzyl alcohol and ortho phenylenediamine)
at 70 °C under open air and solvent-free conditions. As
shown in Fig. 8a, the catalyst could be recovered and reused
for at least fve consecutive times without any notable reduc-
tion in catalytic activity. Figure 8a also showed that every
recovery yields a very low-efciency drop, so that after the
ffth cycle the efciency reached to 88%, which is insignif-
cant. In addition, the residual solution after each cycle was
studied by ICP analysis to measure metal leaching including
Mn and Cu metals. To investigate the stability and structure
of the recovered catalyst (after 5th run), it was characterized
by FT-IR, FE-SEM, TEM, and TGA analyses (Fig. 8, 9). The
FE-SEM and FT-IR analyses of the recovered catalyst also
bReaction conditions: Benzyl alcohol (1.2 mmol) and ortho phenylen-
ediamine (1 mmol), Cat. (0.008 g, 0.280 mol% Cu, 0.078 mol% Mn),
solvent-free, 70 ˚C, open air
cReaction conditions: Benzyl alcohol (1.2 mmol), ethyl acetoace-
tate (1.2 mmol), and urea (1 mmol), Cat. (0.008 g, 0.280 mol% Cu,
0.078 mol% Mn), solvent-free, 70 °C, open airs
3.3 Proposed Mechanism
According to the proposed mechanism for Lewis acid
catalyzed preparation of dihydropyrimidone derivatives,
a plausible mechanism was suggested in agreements with
the observations and literature for domino one-pot prepara-
tion of benzimidazole as well as dihydropyrimidone com-
pounds [63–65]. Given that higher activity of Mn active
sites towards alcohol oxidation (Table 6), in frst, the alco-
hol oxidation was carried out with Mn active sites mainly
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
Fig. 6 The screening efect of the a solvent, and b oxidant on the
oxidation of alcohols, benzimidazole, and Biginelli reactions. Reac-
tion conditions: Biginelli: Benzyl alcohol (1.2 mmol), ethyl ace-
toacetate (1.2 mmol), and urea (1 mmol), Cat. (0.008 g, 0.280 mol%
Cu, 0.078 mol% Mn), solvent-free, 70 ˚C, open air. Benzimidazole:
Benzyl alcohol (1.2 mmol), ortho phenylenediamine (1 mmol), Cat.
(0.008 g, 0.280 mol% Cu, 0.078 mol% Mn), solvent-free, 70 ˚C, open
air. Oxidation of alcohols: Benzyl alcohol (1 mmol), Cat. (0.005 g,
0.175 mol% Cu, 0.049 mol% Mn), EtOH (2 mL), r.t, open air
Table 3 Oxidation of benzyl alcohols catalyzed by Fe3O4@Cu-Mn. Reaction conditions: Benzyl alcohol (1 mmol), Cat. (0.005 g, 0.175 mol%
Cu, 0.049 mol% Mn), EtOH (2 mL), r.t
2a, 95%, 1h
2d, 92%, 1.5 h 2e, 95%, 1 h 2f, 96%, 1 h
2b, 94%, 3 h
2c, 96%, 1 h
2j, 90%, 2.5 h 2k, 92%, 2h
2g, 94%, 1 h
2h, 90%, 2 h
2i, 93%, 2 h
1 3

M. A. Nasseri et al.
Table 4 Benzimidazole one-pot reaction of on benzyl alcohols with
ortho phenylenediamine catalyzed by Fe3O4@Cu-Mn. Reaction con-
ditions: Benzyl alcohol (1.2 mmol) and ortho phenylenediamine (1
mmol), Cat. (0.008 g, 0.280 mol% Cu, 0.078 mol% Mn), solvent free,
70 °C, under aerobic condition
4b, 80%, 4h
MP (ºC)= 204-206
4c, 85%, 4 h
MP (ºC)= 302-304
4a, 93%, 2h
MP (ºC)= 293-296
4d, 84%, 2 h
MP (ºC)= 300-302
4e, 80%, 2 h
MP (ºC)= 299-302
4f, 88%, 2 h
MP (ºC)= 297-299
4h, 98%, 2 h
MP (ºC)= 224-226
4i, 95%, 2 h
MP (ºC)= 265-268
4g, 88%, 2 h
MP (ºC)= 298-300
4j, 85%, 3 h
MP (ºC)= 241-243
4k, 80%, 3h
MP (ºC)= 232-235
proved the homogeneous and spherical morphology of the
nanoparticles as same as the fresh one. More importantly, no
signifcant agglomeration was seen in the images (Fig. 9a,
b). In addition, the TGA curve of the recovered catalyst was
quite similar to that of the fresh one (Fig. 9c), indicating
that the catalyst retained its structure after repeated recovery
and reuse.
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
Table 5 Biginelli one-pot reaction of on benzyl alcohols with ethyl
acetoacetate and urea catalyzed by Fe3O4@Cu-Mn. Reaction condi-
tions: Benzyl alcohol (1.2 mmol), ethyl acetoacetate (1.2 mmol), and
urea (1 mmol), Cat. (0.008 g, 0.280 mol% Cu, 0.078 mol% Mn), sol-
vent free, 70 ˚C, under aerobic condition
7d, 95%, 2 h
MP (ºC)= 225-227
7a, 92%, 2h
MP (ºC)= 200-202
7b, 75%, 3 h
MP (ºC)= 218-220
7c, 80%, 3 h
MP (ºC)= 207-208
7e, 94%, 2 h
MP (ºC)= 214-215
7f, 94%, 2 h
MP (ºC)= 212-214
7g, 92%, 2 h
MP (ºC)= 228-230
7h, 97%, 2 h
MP (ºC)= 206-208
7i, 94%, 2 h
MP (ºC)= 215-218
7j, 89%, 2 h
7k, 90%, 2h
MP (ºC)= 216-218
MP (ºC)= 228-229
1 3

M. A. Nasseri et al.
Table 6 Designed control
experiments for the oxidation
of alcohol, and the one-pot
preparation of benzimidazole,
and Biginelli reactions
Entry
Catalyst
Oxidation
Yield (%)
Biginelli
Yield(%)
Benzimida-
zole Yield
(%)
Selectivity (%)
1
2
3
4
5
6
7
8
Cu(OAc)2.H2O
Mn(OAc)2.4H2O
Fe3O4NPs
Compound (iii)
Compound (vi)
Compound (vii)
Compound (v)
Compound (v)a
15
25
–
55
35
80
95
20
55
45
–
80
75
97
99
99
Trace
Trace
–
30
40
80
93
10
Trace
Trace
–
30
35
85
92
10
aBenzimidazole model reaction under N2 atmosphere
preparation of benzimidazole and Biginelli derivatives from
alcohols as a green protocol under aerobic and mild con-
ditions. The catalyst plays the role of alcohol oxidation
as well as condensation/ multicomponent reactions at the
same time as a domino-type reaction. A wide variety of
4 Conclusion
In summary, a Cu-Mn bimetallic complex decorated on
magnetite Fe3O4 NPs was prepared and used as an environ-
mentally and economically catalyst for the one-pot oxidative
OH
OH
NH2
O
NH2
NH2
O
N
N
O
4
O
O
4
O
O
3
3
Mn
OH
e
Cu
OH
F e
F
O
NH2
N
N
O
O
OH
OH
iii
vi
OH
N
N
O
O
N
O
O
4
Mn
O
vii
3
Cu
OH
F e
O
N
O
OH
Scheme 3 Structure of iii, vi, and vii compounds as three homologue of the main catalyst (v)
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
dihydropyrimidinones and benzimidazoles derivatives have
been synthesized under optimum conditions with good to
high yields. Fe3O4@Cu-Mn catalyst was characterized using
diferent techniques such as FT-IR, XRD, TEM, FE-SEM,
VSM, EDX, and ICP, analyses. All mentioned analyses
emphasized the proposed structure, spherical morphology,
being nanoscale, magnetic nature, expected elements, and
metal loading respectively. Moreover, data of poisoning and
hot fltration experiments demonstrated the heterogeneity
nature of the bimetallic catalyst. The control experiments
proved that the catalytic activity of the catalyst is unique
for the oxidation of domino one-pot preparation of benzi-
midazole derivatives as well as Biginelli reaction. More
importantly, the bimetallic system controls the selectivity
of the oxidation and subsequently promotes the following
reactions. In this regard, a synergistic efect and coopera-
tive function could be considered for this system. Recycling
and recovering studies revealed that the catalyst could be
recycled for at least fve consecutive runs with reservation
of its stability, structure, morphology, and size distribution,
that was manifested by TGA, FT-IR, TEM, and FE-SEM
analyses over the recovered catalyst.
Fig. 7 The results of Hg poisoning and hot fltration tests in the one-
pot benzimidazole reaction of benzyl alcohol with ortho phenylenedi-
amine
Scheme 4 The plausible reac-
Mn
EtO
tion mechanism for the Biginelli
N
Et
HN
O
O
EtO
Mn
and benzimidazole reactions
catalyzed by Fe3O4@Cu-Mn
Ar
Cu
Et
O
Cu
catalyst
N
H
Ar
O
H
EtO
O
NH
H HN
Ar
V
NH
-H2
O
Et
- H2O
O
IV
H2N
H2N
Ar
NH2
N
H2N
NH
Mn
Cu
Et
H
O
Mn
O
Ar
Cu
Cu
VI
Mn
Ar
H
O
Mn
O
EtO
Ar
Cu
Ar
II
Ar
N
O
O
H2O
O
H
H
Cu
Cu
Mn
NH2
O2
in air
III
Mn
- H2O
I
H2N
H2N
O
1 3

M. A. Nasseri et al.
Table 7 Comparison of the
Fe3O4@Cu-Mn catalyst
activity in the Bigiinelli and
benzimidazole reactions with
other one-pot synthetization
methods
Entry Reaction
Catalystref
Benzimidazolea Fe3O4@Cu–Mn
Ru(II)-PNS(O) pincer H2O
Solvent
Solvent free 70
165
T (°C) Time (h) Yield (%) Ref
1
2–4
12
12
90–98
64–85
13.9–100 [39]
This work
[69]
2b
3
Cu-Pd/γ-Al2O3
Ru(II)-NNN pincer
Co complex
H2O
H2O
Toluene
Solvent free 70
180
165
150
4c
5d
5
12
24
2–3
2–6
3.5–4
60–97
28–99
75–97
50–97
78–95
[70]
[71]
This work
[25]
[72]
Biginellie
Fe3O4@Cu–Mn
6f
7g
[Hmim]HSO4-NaNO3 Solvent free 80
Oxone-KBr-TEMPO Solvent free r.t
aBenzimidazole reaction of benzyl alcohol and ortho phenylenediamine
bAdditive: NaBPh4 and Cs2CO3
cAdditive: NaBPh4 and 1,2-bis(diphenyl-phosphanyl)ethane
dAdditive: NaBEt3H
eBiginelli reaction of benzyl alcohol, ethyl acetoacetate, and urea
f[Hmim]HSO4: 1-methylimidazolium hydrogen sulphate
gMechanochemical (ball milling) condition
Fig. 8 a The recyclability studies of the catalyst for the model benzimidazole reaction (one-pot method from alcohol) under optimized condi-
tions. b FT-IR analysis of the recovered catalyst after 5th run
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
Fig. 9 a FE-SEM, b TEM, and (c) TGA analyses of the recovered catalyst after 5th run for the model benzimidazole reaction (one-pot method
from alcohol) under optimized conditions
1 3

M. A. Nasseri et al.
32. Sankar M, Dimitratos N, Miedziak PJ, Wells PP, Kiely CJ, Hutch-
ings GJ (2012) Chem Soc Rev 41:8099–8139
33. De S, Zhang J, Luque R, Yan N (2016) Energy Environ Sci
9:3314–3347
Acknowledgements The authors are grateful to the University of
Birjand for fnancial support.
34. Lorion MM, Maindan K, Kapdi AR, Ackermann L (2017) Chem
Soc Rev 46:7399–7420
References
35. Nemygina NA, Nikoshvili LZ, Tiamina IY, Bykov AV, Smirnov
IS, LaGrange T, Kaszkur Z, Matveeva VG, Sulman EM, Kiwi-
Minsker L (2018) Org Process Res Dev 22:1606–1613
36. Chen YZ, Zhou YX, Wang H, Lu J, Uchida T, Xu Q, Yu SH, Jiang
HL (2015) ACS Catal 5:2062–2069
1. Alvim HGO, Da Silva Júnior EN, Neto BAD (2014) RSC Adv
4:54282–54299
2. Slobbe P, Ruijter E, Orru RVA (2012) Medchemcomm
3:1189–1218
37. Katkar SV, Jayaram RV (2014) RSC Adv 4:47958–47964
38. Hou YL, Sun RWY, Zhou XP, Wang JH, Li D (2014) Chem Com-
mun 50:2295–2297
3. Patil RV, Chavan JU, Dalal DS, Shinde VS, Beldar AG, Comb
ACS (2019) Sci 21:105–148
4. Chen XH, Xu XY, Liu H, Cun LF, Gong LZ (2006) J Am Chem
Soc 128:14802–14803
39. Feng F, Ye J, Cheng Z, Xu X, Zhang Q, Ma L, Lu C, Li X (2016)
RSC Adv 6:72750–72755
5. Sheykhan M, Yahyazadeh A, Ramezani L (2017) Mol Catal
435:166–173
40. Wang Y, Zeng Y, Wu X, Mu M, Chen L (2018) Mater Lett
220:321–324
6. Ma Y, Qian C, Wang L, Yang M (2000) J Org Chem 65:3864–3868
7. Bin Bai Y, Zhang AL, Tang JJ, Gao JM (2013) J Agric Food Chem
61:2789–2795
41. Pasupathi M, Santhi N, Pachamuthu MP, Alamelu Mangai G,
Ragupathi C (2018) J Mol Struct 1160:161–166
42. Kamijo S, Jin T, Huo Z, Yamamoto Y (2003) J Am Chem Soc
125:7786–7787
8. Singh I, Luxami V, Paul K (2019) Eur J Med Chem 180:546–561
9. Huang ST, Hsei IJ, Chen C (2006) Bioorganic. Med Chem
14:6106–6119
43. Kang YS, Risbud S, Rabolt JF, Stroeve P (1996) Chem Mater
8:2209–2211
10. Tong Y, Bouska JJ, Ellis PA, Johnson EF, Leverson J, Liu X,
Marcotte PA, Olson AM, Osterling DJ, Przytulinska M, Rodriguez
LE, Shi Y, Soni N, Stavropoulos J, Thomas S, Donawho CK,
Frost DJ, Luo Y, Giranda VL, Penning TD (2009) J Med Chem
52:6803–6813
44. Jin FL, Yop Rhee K, Park SJ (2011) J Solid State Chem
184:3253–3256
45. Saremi SG, Keypour H, Noroozi M, Veisi H (2018) RSC Adv
8:3889–3898
46. Reddy AS, Mao J, Krishna LS, Badavath VN, Maji S (2019) J Mol
Struct 1196:338–347
11. Srestha N, Banerjee J, Srivastava S (2014) IOSR J Pharm
04:28–41
47. Kazemnejadi M, Alavi SA, Rezazadeh Z, Nasseri MA, Allahresani
A, Esmaeilpour M (2019) J Mol Struct 1186:230–249
48. Vieira AP, Wegermann CA, Da Costa Ferreira AM (2018) New J
Chem 42:13169–13179
12. Kanwal A, Saddique FA, Aslam S, Ahmad M, Zahoor AF, Mohsin
NUA (2018) Pharm Chem J 51:1068–1077
13. Guan Q, Sun Q, Wen L, Zha Z, Yang Y, Wang Z (2018) Org
Biomol Chem 16:2088–2096
49. Rajput S, Pittman CU, Mohan D (2016) J Colloid Interface Sci
468:334–346
14. Arnold EP, Mondal PK, Schmitt DC, Comb ACS (2020) Sci
22:1–5
50. Mungse HP, Verma S, Kumar N, Sain B, Khatri OP (2012) J
Mater Chem 22:5427–5433
15. Maiti B, Chanda K (2016) RSC Adv 6:50384–50413
16. Singla P, Luxami V, Paul K (2014) RSC Adv 4:12422–12440
17. Sharma AS, Kaur H, Shah D (2016) RSC Adv 6:28688–28727
18. Guo Z, Liu B, Zhang Q, Deng W, Wang Y, Yang Y (2014) Chem
Soc Rev 43:3480–3524
51. Kazemnejadi M, Alavi SAG, Rezazadeh Z, Nasseri MA, Allah-
resani A, Esmaeilpour M (2019) Green Chem 21:1718–1734
52. Xuan S, Wang YXJ, Yu JC, Leung KCF (1843) Langmuir
25(2009):11835–11841
19. Mobley JK, Crocker M (2015) RSC Adv 5:65780–65797
20. Katsina T, Clavier L, Gifard J-F, da Silva NMP, Fournier J,
Tamion R, Copin C, Arseniyadis S, Jean A (2020) Org Process
Res Dev
53. Feizpour F, Jafarpour M, Rezaeifard A (2018) Catal Letters
148:30–40
54. Erasmus E, Niemantsverdriet JW, Swarts JC (2012) Langmuir
28:16477–16484
21. Brioche J, Masson G, Zhu J (2010) Org Lett 12:1432–1435
22. Miao Z, Luan Y, Qi C, Ramella D (2016) Dalt Trans
45:13917–13924
55. Nasrollahzadeh M, Nezafat Z, Bidgoli NSS, Shafei N (2020) Mol
Catal 484:110775
56. Ghafuri H, Joorabchi N, Emami A, Esmaili Zand HR (2017) Ind
Eng Chem Res 56:6462–6467
23. Bala M, Verma PK, Sharma U, Kumar N, Singh B (2013) Green
Chem 15:1687–1693
57. Elhamifar D, Mofatehnia P, Faal M (2017) J Colloid Interface Sci
504:268–275
24. Hille T, Irrgang T, Kempe R (2014) Chem—A Eur J
20:5569–5572
58. Kappe CO (2000) Acc Chem Res 33:879–888
59. Forzatti P, Lietti L (1999) Catal Today 52:165–181
60. Saha S, Abd Hamid SB (2016) RSC Adv 6:96314–96326
61. Jeena V, Robinson RS (2015) Org Biomol Chem 13:8958–8977
62. Li G, Wang J, Yuan B, Zhang D, Lin Z, Li P, Huang H (2013)
Tetrahedron Lett 54:6934–6936
25. Garima P, Srivastava VP, Yadav LDS (2010) Tetrahedron Lett
51:6436–6438
26. Mei Q, Liu H, Yang Y, Liu H, Li S, Zhang P, Han B, Sustain ACS
(2018) Chem Eng 6:2362–2369
27. Rajabimoghadam K, Darwish Y, Bashir U, Pitman D, Eichelberger
S, Siegler MA, Swart M, Garcia-Bosch I (2018) J Am Chem Soc
140:16625–16634
63. Diarjani ES, Rajabi F, Yahyazadeh A, Puente-Santiago AR, Luque
R (2018) Materials (Basel) 11
28. Dhakshinamoorthy A, Alvaro M, Garcia H (2011) ACS Catal
1:48–53
64. Rezaei N, Ranjbar PR (2018) Tetrahedron Lett 59:4102–4106
65. Zeynizadeh B, Rahmani S, Eghbali E (2019) Polyhedron
168:57–66
29. Zhao X, Zhou Y, Huang K, Li C, Tao DJ, Sustain ACS (2019)
Chem Eng 7:1901–1908
66. Alshammari A, Kalevaru VN, Martin A (2016) Catalysts 6
67. Hamid S, Kumar MA, Lee W (2016) Appl Catal B Environ
187:37–46
30. Parmeggiani C, Cardona F (2012) Green Chem 14:547–564
31. Parmeggiani C, Matassini C, Cardona F (2017) Green Chem
19:2030–2050
1 3

Cu‑Mn Bimetallic Complex Immobilized on Magnetic NPs as an Efcient Catalyst for Domino One‑Pot…
68. Besenbacher F, Chorkendorff I, Clausen BS, Hammer B,
Molenbroek AM, Nørskov JK, Stensgaard I (1998) Science
279:1913–1915
71. Daw P, Ben-David Y, Milstein D (2017) ACS Catal 7:7456–7460
72. Sahoo PK, Bose A, Mal P (2015) Eur J Org Chem 2015:6994–6998
73. Sobhani S, Hosseini Moghadam H, Skibsted J, Sansano JM (2020)
Green Chem 22:1353–1365
69. Luo Q, Dai Z, Cong H, Li R, Peng T, Zhang J (2017) Dalt Trans
46:15012–15022
70. Li L, Luo Q, Cui H, Li R, Zhang J, Peng T (2018) ChemCatChem
10:1607–1613
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
Afliations
Mohammad Ali Nasseri1 · Zinat Rezazadeh1 · Milad Kazemnejadi1 · Ali Allahresani1
1
Department of Chemistry, Faculty of Sciences, University
of Birjand, Birjand 97175-615, Iran
1 3