Synthesis of Eu(III) fabricated spinel ferrite based surface modified hybrid nanocomposite: Study of catalytic activity towards the facile synthesis of tetrahydrobenzo[b]pyrans

Article abstract of DOI:10.1016/j.molstruc.2020.128598

The present work demonstrates a modified protocol for thesynthesis of Europium (Eu) anchored iminodiacetic acid functionalized silica modified core-shell CoFe₂O₄ magnetic nanoparticles.This is the first report of Eu immobilized nanoc

Full text of DOI:10.1016/j.molstruc.2020.128598

Journal Pre-proof
Synthesis of Eu(III) fabricated spinel ferrite based surface modified hybrid
nanocomposite: Study of catalytic activity towards the facile synthesis of
tetrahydrobenzo[b]pyrans
Taiebeh Tamoradi, Bikash Karmakar, Maryam Kamalzare, Mohammad Bayat,
Afsaneh Taheri Kal-Koshvndi, Ali Maleki
PII:
S0022-2860(20)30923-6
DOI:
https://doi.org/10.1016/j.molstruc.2020.128598
MOLSTR 128598
Reference:
To appear in: Journal of Molecular Structure
Received Date: 4 May 2020
Revised Date: 30 May 2020
Accepted Date: 2 June 2020
Please cite this article as: T. Tamoradi, B. Karmakar, M. Kamalzare, M. Bayat, A.T. Kal-Koshvndi, A.
Maleki, Synthesis of Eu(III) fabricated spinel ferrite based surface modified hybrid nanocomposite:
Study of catalytic activity towards the facile synthesis of tetrahydrobenzo[b]pyrans, Journal of Molecular
Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.128598.
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Credit author statement
Taiebeh Tamoradi: Conceptualization, Methodology. Bikash
Karmakar: Writing - Original Draft, Data Curation. Maryam
Kamalzare: Investigation. Mohammad Bayat: Resources. Afsaneh
Taheri Kal-Koshvndi: Methodology, Writing- Reviewing and
Editing, Supervision.

Synthesis of Eu(III) fabricated spinel ferrite based surface modified hybrid
nanocomposite : Study of catalytic activity towards the facile synthesis of
tetrahydrobenzo[b]pyrans
Taiebeh Tamoradi, Bikash Karmakar, Maryam Kamalzare, Mohammad Bayat, Afsaneh Taheri Kal-
Koshvndi,* Ali Maleki

1
Synthesis of Eu(III) fabricated spinel ferrite based surface modified hybrid nanocomposite
Study of catalytic activity towards the facile synthesis of tetrahydrobenzo[b]pyrans
:
b
c
a,d
d
Taiebeh Tamoradi, Bikash Karmakar, Maryam Kamalzare, Mohammad Bayat, Afsaneh Taheri Kal-
a,
a
Koshvndi, * Ali Maleki
a
Catalysts and Organic Synthesis Research Laboratory, Department of Chemistry, Iran University
of Science and Technology, Tehran, 16846-13114, Iran
b
Department of Chemistry, Islamic Azad University, Izeh, Iran
c
Department of Chemistry, Gobardanga Hindu College, India
d
Department of Chemistry, Faculty of Science, Imam Khomeini International University, Qazvin,
Iran
*
Corresponding author e-mail: afsaneh.taheri96@yahoo.com; Tel: +98-9904506849
Abstract
The present work demonstrates a modified protocol for thesynthesis of Europium (Eu) anchored
iminodiacetic acid functionalized silica modified core-shell CoFe
2
O
4
magnetic
nanoparticles.This is the first report of Eu immobilized nanocomposite in the synthesis of
biologically active organic compounds. The structural and physicochemical characteristics of the
material wereevaluated using different analytical techniques such asFourier transformed infrared
spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FESEM), Energy
Dispersive X-ray Spectroscopy (EDX), X-ray Elemental Mapping (WDX) and X-ray Diffraction
study (XRD). The Eu(III)/IDA/CPTS/CoFe O nanocomposite was catalytically investigated in
2
4
the multicomponent green synthesis of diverse substituted tetrahydrobenzo[b]pyrans by coupling
dimedone, malononitrile and a wide range of aromatic aldehydes. The magnetically retrievable
catalyst was stable enough to be reused up to six consecutive times in the reaction without
considerable loss in activity.
Keywords: Magnetic NP; Iminodiacetic acid; Eu(III) catalysis; Multicomponent reaction (MCR);
Tetrahydrobenzo[b]pyran; Reusablility.

2
1
. Introduction
In current material science the synthesis and applications of advanced functional nanomaterials
has garnered high attention due to their distinctive characteristics like site selective chemical
properties, tunable size and shape dependent physical properties, large surface to volume ratio,
1
-3
exceptional thermal and mechanical stability etc . In continuation to that trend, the use of
magnetic nanoparticles in heterogeneous green catalysis has become highly significant based on
their easy recovery from the reaction solutions and facile recycling by an external magnet, cost-
4
,5
effectiveness and bio-compatibility. In addition, they acquire high surface to volume ratio,
6
enhanced reactivity due to large number of active sites, high selectivity and thermal stability.
Due to such implications, magnetic nanoparticles (MNPs) have been greatly used in many
7
8,9
catalytic reactions such as, oxidation,
C-C and C-heteroatom coupling,
1
0
11
12
13
condensation, cycloaddition, photocatalysis, drug delivery and sensors .
Among the different magnetic nanomaterials, transition metal ferrites are of special priority due
5
to their uniqueelectronic, catalytic and magnetic behaviors. The spinel ferrites possess general
2
+
2+
2+
2+
2+
2+
formula MFe O (M = Mn , Fe , Co , Ni , Cu and Zn ),commonly known as multiferrites.
2
4
Owing to their special structural designs, they are more stable and bear higher paramagnetism
5
than bare Fe
3
O
4
. In particular, CoFe
2
O
4
acquires special attention due to its applications in
1
4
different fields like sensing, catalysis, electronics, magnetism and medicinal therapeutics.
Moreover, the large number of surface hydroxyl groups present in their peripheri facilitates them
1
5-16
towards surface modifications with suitable organic ligands.
These organic linkers can be
5
exploited to introduce a secondary layer of metal species as active constituent in catalysis. In
this article, we actually have adopted this very concept and introducediminodiacetic acid (IDA)

3
as the organic linker. IDA is a bis-glycine analog and a very good chelating ligand binding the
incoming metal in (1 : 2) ratio (Scheme 1).
4
H-pyran derivatives are important class of heterocyclic motifs having tremendous biological
1
7
applications. Specifically, tetrahydrobenzo[b]pyrans have been reported to have plethora of
1
8
19
pharmacological activities.
They are important antitumor,anti-cancer,
and
antiviral,
diuretic
antiallergenic,anti-ancaphylactic,anti-coagulant,antileishmanial,spasmolytic
2
0
21
22
compounds ,antioxidant, antibacterial, and antifungal compounds. They also have been
accounted for cognitive enhancers in the treatment of various neurodegenerative diseases,
including Alzheimer’s disease,Huntington’s disease, Down’s syndrome, AIDS-associated
2
3
24
25
dementia, Parkinson’s disease, and treatment of schizophrenia. Some of the significant
bioactive benzo[b]pyran derivatives have been shown in Fig 1.
Considering all these implications, synthesis of the scaffold has been of great interest and
2
6-28
thereby a number of synthetic methodologies have been explored by several groups.
Keeping
2
9,30
in view of sustainable chemistry, multicomponent reaction (MCR)
has been the most
promising protocol for the synthesis of such molecular hybrid. Thereby, the target molecule
could be built up by assembling dimedone, malononitrile and aldehydes. Different catalysts have
3
1
32
been reported for that procedure, like SiO NPs, Bi WO NPs, Ni0.5Zn0.5Fe O @HA-PRS
2
2
6
2
4
3
3
34
35
NPs, caffeine supported silica, ZnO-β zeolite, etc. Nonetheless, keeping in mind of their
own intrinsic worth, there is always scope of method development for the synthesis following the
pathway of sustainable green catalysis. Thereby, as part of our ongoing research based on the
3
6-39
multicomponent reaction,
acid (IDA) ligand functionalized CoFe
towards the multicomponent synthesis of 2-amino-3-cyano tetrahydrobenzo[b]pyrans for the
we would like to report the Eu (Europium) anchored iminodiacetic
2
O
4
nanoparticles as a magnetically isolable nanocatalyst

4
first time (Scheme 1 and 2). All the reactions were performed in ethanolic media at room
temperature and excellent yields were obtained in short reaction times.
OMe
OMe
MeO
Br
MeO
Br
CN
NH
CN
NH
Me
2
N
O
2
H
2
N
O
2
NH
2
O
O
O
HO
O
O
CN
NH
O
O
O
O
2
Fig.1. Examples of some bioactive molecules containing benzo[b]pyran scaffold
Scheme 1. Synthesis of Eu@MNPs nanocomposite

5
O
CHO
O
CN
CN
CN
Eu/IDA/CPTS@CoFe O4
2
+
+
O
O
NH2
Scheme 2. Eu nanocomposite catalyzed multicomponent synthesis of tetrahydrobenzo[b]pyrans
2
. Experimental
.1 Materials and instrumentations
The chemicals necessary for the synthesis of catalyst, such as, FeCl .6H O, CoCl .6H O, 3-
2
3
2
2
2
3 3
chloropropyl trimethoxysilane (CPTMS), iminodiacetic acid (IDA) and Eu(NO ) were purchased
from Sigma-Aldrich. The chemicals required for organic synthesis and the essential solvents
were purchased from Merck. All the reagents were used as such without further purification. FT-
IR analysis (KBr disc)was done using a VRTEX 70 model BRUKER FT-IR spectrophotometer.
The particle morphology, shape, size and atomic mapping of the material were studied using a
FESEM-TESCAN MIRA3 microscope equipped with EDX (TSCAN). In order to analyze the
crystallite nature powder XRD wasrecorded using Co Kα radiation (λ= 1.78897 Å) with an
operating voltage of 40 keV and a cathode current of 40 Ma in the scanning range of 2θ = 20 to
o
8
0 . Melting points were recorded in an Electrothermal 9100 apparatus.
2
2 4
.2 Synthesis of CoFe O nanoparticles
2
.63 g of FeCl .6H O and 1.19 g of CoCl .6H O were dissolved in 50 mL of deionized water
3
2
2
2
under vigorous stirring. 1: 1 aqueous ammonia solution was added to the mixture dropwise and

6
stirred at 80 ºC for 30 min. Immediately the NP formation started as indicated by blackening of
the solution. The products were isolated using a magnet and subsequently washed several times
º
with deionized water followed by ethanol. Finally they were dried at 60 C for overnight.
2
.3 Synthesis of CPTS functionalized CoFe O nanoparticles (CPTS@CoFe O )
2 4 2 4
For surface modification,1.0 g of the CoFe O NP was suspended in 30 mL anhydrous toluene
2
4
and 1.5 mmol of 3-CPTES was added dropwise. The resulting mixture was refluxed for 24 h
under stirring condition. After completion, the obtained grey product was separated using an
o
external magnet and washed with ethanol for several times. Finally it was dried in oven at 60 C.
2
.4 Synthesis of IDA/CPTS@CoFe O nanocomposite
2 4
For the ligand functionalization, 1.0 g of the CPTS@CoFe O composite was dispersed in 30 mL
2
4
anhydrous toluene and a 10 mL solution of iminodiacetic acid (IDA) (1.5 mmol) ligand in
toluene was added dropwise.The resulting mixture was then refluxed for 48 h to have
2 4
IDA/CPTS@CoFe O nanocomposite. It was again isolated and processed for the next step in
previous manner.
2
.5 Synthesis of Eu@MNPs nanocomposite
In this final step the IDA/CPTS@CoFe O nanocomposite (1.0 gm) andEu(NO ) (2.5 mmol)
2
4
3 3
were mixed in ethanol (30 ml). The mixture was refluxed for 16 h, filtered, washedthoroughly
with ethanol and dried in vacuum to have the Eu@MNPs nanocomposite.
2
.6Multicomponent synthesis of 2-amino-4-aryl-3-cyano tetrahydrobenzo[b]pyrans

7
In the typical procedure dimedone (1.0 mmol), malononitrile (1.1 mmol) and aryl aldehyde (1.0
mmol) were mixed together in 10 mL ethanolin presence of 0.03 gm catalyst and stirred at room
temperature for requisite time period. After completion (checked by TLC), a solid mass appears
in the reaction medium. The catalyst was isolated from the reaction flask by using a magnetic
stick. The corresponding product, 2-amino-4-aryl-3-cyanotetrahydrobenzo[b]pyran was filtered
and recrystallized from hot ethanol.
Spectral data of 2-amino-4-(2-chlorophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (4b)
1
H NMR (300 MHz, DMSO-d6): δ = 0.89 (3H, s, CH ), 0.99 (3H, s, CH ), 1.96 (2H, dd, CH ,
3
3
2
2
2
J=15.9 Hz), 2.16 (2H, dd, CH , J=16.2 Hz), 4.91 (1H, s, CH), 7.20 (2H, br s, NH ), 7.32 (1H,
2
2
3
3
13
d, Ar, J=9 Hz),7.41 (1H,t, Ar), 7.64 (1H, t, Ar), 7.78 (1H, d, Ar, J=9 Hz). C NMR (75 MHz,
DMSO-d6): δ = 27.13 (2CH ), 28.75 (C(CH )), 30.38 (CH), 32.30, 50, 56.80 (C(CN)), 112.78,
19.45, 124.18, 128.31, 130.74, 134.03, 139.44, 149.43, 159.66, 163.19 (C-NH ), 196.29 (C=O).
3
3
1
2
Spectral data of 2-amino-4-(3-methoxyphenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (4o)
1
3 3 2
H NMR (300 MHz, DMSO-d6): δ = 0.95 (3H, s, CH ), 1.02(3 H, s, CH ) 2.07 (2H, dd, CH ,
2
2
J=15 Hz), 2.22 (2H, dd, CH
2
, J=15 Hz), 3.69 (3H, s, OCH
3
), 4.12 ( 1H, s, CH), 6.63 ( 1H, s,
3
3
13
Ar), 6.67 (1H, d, Ar, J=9 Hz), 6.74 (1H, d, Ar, J=9 Hz), 7 (2H, br s, NH
2
), 7.19 (1H, t, Ar). C
NMR (75 MHz, DMSO-d6): 27.42 (2CH ), 28.79 (C(CH )), 32.39, 35.77 (CH), 50.79, 55.45
3
3
(
OCH ), 58.76 (C(CN)), 111.85, 113.19, 113.88, 120.16, 120.56, 130.20, 146.87, 159.28, 159.59
3
(
C-NH ), 163.27 (C-OMe), 196.27 (C=O).
2

8
3
. Results and Discussion
.1 Catalyst characterizations
3
We successfully synthesized the nanocomposite following post-functionalization approach. The
magnetic core NP provides the necessary arrangement for surface modification. The covalently
bonded organic molecule, IDA, is a tetradentate ligand and binds the incoming metal (Eu) in 1 :
2
fashion. The nanocomposite so prepared was systematically characterized using various
analytical techniques likeFourier Transformed Infrared Spectroscopy (FT-IR), Scanning Electron
Microscopy (SEM), Energy Dispersive X-ray Electron Spectroscopy (EDX), Wavelength
dispersive X-ray Electron Spectroscopy (WDX) and X-ray diffraction (XRD) studies.Fig. 2
represents
aone-plot
comparison
of
and Eu@MNPs composites.A sharp characteristic peak
(Fig. 2a). The
hydroxyl functionalities (O-H) over the spinel surface arerepresented by a broad peak at around
FT-IR
spectra
of
bare
2 4
CoFe O ,
CPTS@CoFe
2
O
4
,IDA/CPTS@CoFe O
2 4
-
1
2 4
appeared at around 590 cm is due to strong metal-oxygen absorption in CoFe O
-1
3
350-3400 cm .The typical C-H stretching vibrations, representing the chloropropyl
-1
functionalized MNP, appears at 2900 cm in Fig. 2b. IDA functionalization is justified by the
-1
-1
strong absorption peaks from COOH group at 1720 cm (C=O stretch) and 1400 cm (O-H
bend) respectively. O-H stretching frequency from COOH group overlaps with the
2 4 2 4
CoFe O surface hydroxyl groups. Spectrum of the two nanocomposites,IDA/CPTS@CoFe O
and Eu@MNPs (Fig 2c and 2d) looks alike, which implies that the basic skeletonsremained
intact even after metal grafting at final stage. However, the Eu attachment to the matrix is
exhibited in the widening of C=O stretching peak as shown in Fig 2d.

9
Fig. 2. FT-IR spectra of a) CoFe O , b) CPTS@CoFe O , c) IDA/CPTS@CoFe O and d)
2
4
2
4
2
4
Eu@MNPs
The particle morphology and external texture of the synthesized nanocomposite
Er/IDA/CPTS@CoFe O )was elucidated by SEM analysis. Fig. 3 represents the images at
(
2
4
different magnifications. The material is of fluffy cotton type which might be due to surface
modifications. Typically, a bilayer particulate nature is observed from the images.The small
grains of particles extended over the whole surface matrix signifiesthe surface modified active
molecules. Higher concentration during sampling is the reason for agglomeration of particles.

10
Fig. 3. SEM images of Eu@MNPs nanocomposite at different magnifications.
In order to evaluate the elemental composition and structural identity,theEnergy-Dispersive X-
ray spectroscopy (EDX) of the Eu@MNPs nanocompositewas carried out and the spectrum is
presented in Fig. 4.The proposed organic environment around the magnetic core also could be
assessed in this analysis. IDA and CPTS attachment are being confirmedby the presence of C, N,
O and Si species in the profile. It also exhibits Fe, Co and Eu atoms asmetallic constituantin the
nanocomposite.

11
Fig. 4.EDX spectrum of the Eu@MNPs nanocomposite
The X-ray atomic mapping or wavelength dispersive X-ray spectroscopy (WDX) is another
powerful device todemonstrate the atomic distribution over the catalyst surface with great
accuracy. A selected area of SEM image of the composite is scanned with X-ray in the analysis
and the result is displayed in Fig. 5. Interestingly, all atoms comprising the material are very well
dispersed throughout. It clearly reveals the higher concentration of Fe, Co and O atoms as
2 4
compared to C, N and Eu.This signifies that the concentrated inner core is made up of CoFe O
and a thin layer of organic functions being bonded to its surface including the Eu at its periphery.
The existence of C, N and O atoms additionally confirms the successful attachment of IDA over
CoFe O .
2
4

12
Fig. 5. The X-ray atomic mapping of Eu@MNPs nanocatalyst.
To conclude the catalytic characterizations, X-ray diffraction (XRD) study was carried out in
order to assess the phase purity and crystallinity of the nanocomposite.It displays a single
phase throughout the scanning zone without any phase separation. The diffraction pattern
bears a resemblance to that of polycrystalline CoFe O nanostructure as being authenticated
2
4
from standard JCPDS values.This evidently substantiates that the basic crystalline phases
remains unaltered even after the necessary surface engineering.The peaks appeared in the
XRD profile correspondto (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) crystal planes
respectively (Fig. 6).

13
Fig. 6. The X-ray diffraction pattern of Eu@MNPs nanocatalyst
3
.2 Analysis of reaction data
After completion of a rigorous chapter of catalyst synthesis and detailed characterizations,it was
the turn to explore the catalytic applications and hence we opted for thesynthesis of substituted
tetrahydrobenzo[b]pyransby multicomponent coupling over Eu@MNPs nanocatalyst.However,
at the outset, optimization of reaction conditions appeared important by selecting a probe
reaction between dimedone, malononitrile and 4-chlorobenzaldehyde and then different
conditions like solvent, catalyst load and temperaturewere imposed over it. The results are
documented in Table 1.
Table 1. Optimization of reaction conditions for the synthesis of 2-amino-4-(4’-chloroaryl)-3-
cyanotetrahydrobenzo[b]pyrans*

14
Entry
solvent
temperature
Amount of
catalyst(g)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
H O
r.t.
reflux
r.t.
60
60
60
60
60
25
25
25
25
Trace
30
2
H O
2
H
2
O
0.03
0.01
0.02
0.03
0.04
0.03
0.03
70
EtOH
EtOH
EtOH
EtOH
r.t.
70
r.t.
85
r.t.
96
r.t.
96
CHCl
3
r.t.
83
CH CN
r.t.
91
3
*Reaction conditions: Dimedone : malononitrile : aldehyde = 1: 1.1 : 1 (mmol), Eu@MNPs catalyst
Keeping in view of energy conservation, we preferred to carry out the reactions at room
temperature. While screening with different solvents like water, ethanol, chloroform and
acetonitrile, it was observed that the reaction afforded the best result in ethanol (entry 6-7, Table
1
). Only a trace of product was found in the absence of any catalyst (entry 1, Table 1). Even
under reflux in water at catalyst-free condition, the yield was not improved. Again, when the
reaction was tested with different amount of catalyst load, 0.03 g was found to be the optimum.
So, the best condition for the probe reaction was finally set to carry out in ethanol at room
temperature in the presence of 0.03 g of catalyst.Now, after having the standard conditions in
hand, it was the turn to establish the generality of the conditions and thereby a wide range of aryl
aldehydes were reacted with dimedone and malononitrile under the optimized conditions.
Different electron withdrawing (F, Cl, Br, NO ) and electron donating (OH, OCH , CH , NMe )
2
3
3
2
group substituted aryl aldehydes were well compatible under the reaction conditions and

15
produced excellent yields in short reaction times. The results with isolated yields have been
shown in Table 2.All the reactions were found to complete within 25-40 minutes. The products
were known and were authenticated by matching with their corresponding melting points.
Table 2. Synthesis of diverse substituted tetrahydrobenzo[b]pyrans*
Entry
Aldehyde
Product
Time Yields M.p. (Obs) M.P. (Lit)
(min)
(%)
(°C)
(°C)
O
1
25
96
216-219
217-219
(40)
2a
Cl
2
3
4
34
35
25
94
92
93
215-218
237-239
183-184
214-216
41)
(
234-236
42)
(
Cl
Cl
O
184-186
43
(
)
CN
O
NH2 4d

16
5
30
30
35
92
91
90
94
91
186-188
201-203
197-199
153-155
240-241
185-189
44
(
)
6
205-207
26)
(
7
8
199-201
45
(
)
2
7
157-159
46
(
)
9
30
236-238
41
(
)

17
1
1
1
1
1
0
1
2
3
4
30
35
40
40
40
92
88
94
85
84
218-221
229-232
198-200
213-215
210-212
218-219
47)
(
223-225
48)
(
201-203
49)
(
215-217
50)
(
213-215
48)
(

18
OH
O
O
1
1
1
5
6
7
CN
3
4
0
0
87
233-236
237-239
48)
(
O
NH2 4o
86
94
178-180
234-236
181-183
46)
(
35
238-240
28)
(
*Reaction conditions: Dimedone : malononitrile : aldehyde = 1: 1.1 : 1 (mmol), 0.03 g Eu@MNPs catalyst, EtOH,
room temperature stirring.
The plausible mechanistic pathway has been depcted in Fig. 7. Aryl aldehyde and malononitrile
being activated over the Eu@MNPs nanocomposite undergoes classical Knoevenagel
condensation to generate the intermediate I. Dimedone, the active methylene component then
undergoes Michael type addition to I to produce the intermediate II. Subsequently, cyclization
occures via the enolic oxygen affording III. This finally undergoes imine-enamine
tautomerisation to afford the final product IV.

19
NC
H
OH
H O
2
Ar
N
O
I
Ar
Eu
Eu
H
O
CN
NC
O
Ar
H
CoFe O
2
4
O
CPTMS
IDA
CN
CN
II
Eu
Eu
CN
H N
2
Ar
NC
O
H
HN
Ar
O
O
O
IV
III
Fig. 7. A practical mechanism towards the tetrahydrobenzo[b]pyranover Eu@MNPs core-shell
nanocomposite
3
.3 Study of reusability
The prime reason to use a magnetic nanocatalyst is the easy isolation from the reaction mixture
and its reusability. In view of current green perspectives, this is an important criterion too.
Thereby, after completion of a fresh batch of the probe reaction, the Eu@MNPs nanocomposite
was retrieved using an external bar magnet, washed with solvents and dried. The regenerated
catalyst was again used in the further batches of reactions to study its stability and efficiency.
Interestingly, it retained its activity for the successive six cycles. The result has been depicted in
Fig. 8.

20
1
00
9
9
8
8
5
0
5
0
1
2
3
4
5
6
Run
Fig. 8. Study of reusability with the Eu@MNPs nanocatalyst.
3
.4 Exclusivity of the catalytic results:
In order to show the the usefulness of Eu@MNPs catalyst, it was compared with other
potentially feasible reported heterogeneous catalysts towards the synthesis of a particular
tetrahydrobenzo[b]pyran derivative (2a) and the results have been documented in table 3.
Evidently, in terms of yield, reaction time and reaction conditions, our protocol is superior to the
shown catalytic results.
Table 3. Comparison of catalytic performance of Eu@MNPs catalyst with that other recently
studied catalysts
Sl no. Reaction conditions
Time (min) Yield
%
Ref.
51
1
2
3
Fe
3
O
4
@SiO
2
@5-SA, 0.02 g, H
2
O, 60 °C
100
92
96
95
TMDPS, ball mill, solvent free, 5 mol%, RT
Fe O @g-C N , 0.02 g, EtOH, 60 ºC
30
52
60
53
3
4
3
4

21
4
5
6
Fe
3
O
4
@THAM@PhSO
3
H, 0.01 g, EtOH/H
2
O, 100 ºC
15
90
90
90
54
55
56
[MPim][HSO ]@SBA15, 2 mol %, H O, 45 ºC
120
300
4
2
γ
-Fe O DMNP, 10 mol%, H O, RT
2
3
2
7
8
9
1
1
1
1
NH H PO /Al O , 0.03 g, EtOH, 78°C
15
25
12
3
92
90
98
97
94
91
96
57
58
59
60
61
62
4
2
4
2
3
Fe
3
O
4 2 2
@SiO /DABCO, 0.05 g,H O, 80 °C
MMWCNTs-D-(CH ) SO H, 0.04 g, EtOH, 78°C
2
4
3
0
1
2
3
GO-Si-NH -PMo, 0.02 g, solvent free, 90 °C
2
TiO
2
/H
2
SO
4
, EtOH, US, 40 °C
15
5
Fe O @D-NH -HPA, 0.02 g, EtOH, 78°C
3
4
2
Eu@MNPs, 0.03 g, EtOH, RT
25
This work
4
. Conclusion
In conclusion, we report herein the facile synthesis of the rare earth Eu(III) immobilized over a
tetradentate ligand iminodiacetic acid (IDA) functionalized silica modified magnetic
2 4
CoFe O nanocomposite for the first time. The catalyst was then exploredtowards the convenient
and mild synthesis of diverse range of tetrahydrobenzo[b]pyran derivatives under simply stirring
in ethanol at room temperature. The catalyst was so efficient that excellent yields were obtained
in short reaction times in all the reactions irrespective of nature of substitutions of the
substrates.Due to strong magnetic core, the catalyst was easily recovered and reused in six
consecutive cycles without a significant loss in catalytic activity.
Acknowledgements

22
The authors are deeply grateful to Iran National Science Foundation (INSF) for financial support
Code number 97009059) and Iran University of Science and Technology for partial support of
(
this research project. BK thanks Gobardanga Hindu College for affiliation.
References
1
2
3
4
.
.
.
.
D. Yadav, S. K. Awasthi, New J. Chem. 44 (2020) 1320-1325.
D. Yadav, S. K. Awasthi, Dalton Trans. 49 (2020) 179-186.
Subodh, K. Prakash, D. T. Masram, Dalton Trans. 49 (2020) 1007-1010.
T. Tamoradi, A. Ghorbani-Choghamarani, M. Ghadermazi, New J. Chem.41 (2017)
1
1714-11721.
T. Tamoradi, H. Veisi, B. Karmakar, J. Gholami, Mater. Sci. Eng. C, 107 (2020) 110260-
10270.
Subodh, N. K. Mogha, K. Chaudhary, G. Kumar, D. T. Masram, ACS Omega, 3 (2018)
6377-16385
5
6
7
.
.
.
1
1
F. Sadri, A. Ramazani, A. Massoudi, M. Khoobi, V. Azizkhani, R. Tarasi, L. Dolatyari,
B.-K. Min, B. Korean. Chem. Soc.35 (2014) 2029-2032.
8
9
1
1
.
S. J. Hoseini, V. Heidari, H. Nasrabadi, J. Mol. Catal. A Chem.396 (2015) 90-95.
K. Azizi, M. Karimi, A. Heydari, Tetrahedron Lett.56 (2015) 812-816.
P. Heidari, R. Cheraghali, H. Veisi, Appl. Organometal. Chem.30 (2016) 991-997.
D. Toulemon, B. P. Pichon, X. Cattoën, M. W. C. Man, S. Begin-Colin, Chem.
Commun.47 (2011) 11954-11956.
.
0.
1.
1
2.
M. Arruebo, R. Fernández-Pacheco, M. R. Ibarra, J. Santamaría, NanoToday 2(2007) 22-
3
2.
1
1
3.
4.
H. Teymourian, A. Salimi, S. Khezrian, BiosensBioelectron49 (2013) 1-8.
T. Tamoradi, A. Ghorbani-Choghamarani, M. Ghadermazi, Solid State Sci.88 (2019) 81-
9
4.
1
1
5.
X.-H. Huang, Z.-H. Chen, Scr. Mater.54 (2006) 169-173.
6. K. Chaudhary, Subodh, K. Prakash, N. K. Mogha, D. T. Masram, Arabian J. Chem. 13
2019) 4869-4881.
7. W. S. Shehab, A. A. Ghoneim, Arab. J. Chem.9 (2016) S966-S970.
(
1

23
1
1
2
8.
9.
0.
A. M. Dar, S. Uzzaman, Eur. Chem. Bull.4 (2015) 249-259.
B. Maleki, S. Sheikh, Org. Prep. Proced. Int.47 (2015) 368-378.
M. G. Dekamin, S. Z. Peyman, Z. Karimi, S. Javanshir, M. R. Naimi-Jamal, M. Barikani,
Int.J.Biol.Macromol.87 (2016) 172-179.
2
2
2
1.
2.
3.
A. R. Saundane, K. Vijaykumar, A. V. Vaijinath, Bioorg. Med.Chem.Lett.23 (2013)
1
978-1984.
A. Hasaninejad, N. Golzar, M. Shekouhy, A. Zare, Helv. Chim. Acta94 (2011) 2289-
294.
H. A. Oskooie, M. M. Heravi, N. Karimi, M. E. Zadeh, Synth. Commun.41 (2011) 436-
40.
2
4
2
2
2
4.
5.
6.
Z. Ye, R. Xu, X. Shao, X. Xu, Z. Li, Tetrahedron Lett.51 (2010) 4991-4994.
S. Tabassum, S. Govindaraju, M. A. Pasha, Ultrason.Sonochem.24 (2015) 1-7.
R. Mohammadi, S. Esmati, M. Gholamhosseini-Nazari, R. Teimuri-Mofrad, J. Mol.
Liq.275 (2019) 523-534.
2
2
2
7.
8.
M. G. Dekamin, M. Eslami, Green Chem.16 (2014) 4914-4921.
H. Sharma, S. Srivastava, RSC Adv.8 (2018) 38974-38979.
9. Subodh, K. Chaudhary, K. Prakash, D. T. Masram, Appl. Surf. Sci. 509 (2020) 144902-
44911
0. Subodh, K. Prakash, K. Chaudhary, D. T. Masram, Appl. Catal. A-General, 593 (2020)
17411-117417
1
3
1
3
3
1.
2.
P. Mohammadi, H. Sheibani, Mater. Chem. Phys.228 (2019) 140-146.
B. Paplal, S. Nagaraju, P. Veerabhadraiah, K. Sujatha, S. Kanvah, B. V. Kumar, D.
Kashinath, RSC Adv.4 (2014) 54168-54174.
3
3
3.
4.
A. Javid, F. Moeinpour, B. Chem. Soc. Ethiopia32 (2018) 501-511.
M. Bakherad, A. Keivanloo, E. Moradian, A. H. Amin, R. Doosti, M. Armaghan, J. Iran.
Chem. Soc.15 (2018) 2811-2819.
3
5.
S. S. Katkar, M. K. Lande, B. R. Arbad, S. T. Gaikwad, Chin. J. Chem.29 (2011) 199-
2
02.
3
3
6.
7.
E. Soleimani, M. M. Khodaei, A. T. K. Koshvandi, Chin. Chem. Lett.22 (2011) 927-930.
E. Soleimani, M. M. Khodaei, A. T. K. Koshvandi, Synth. Commun.42 (2012) 1367-
1
371.

24
3
3
8.
9.
E. Soleimani, M. M. Khodaei, A. T. K. Koshvandi, C. R. Chim. 15 (2012) 273-277.
A. T. Kal-Kashvandi, M. M. Heravi, S. Ahmadi, T. Hosseinnejad, J. Inorg. Organomet.
Polym. Mater.28 (2018) 1457-1467.
4
4
4
4
0.
1.
2.
3.
A. Maleki, R. Ghalavand, R. Firouzi Haji, Appl. Organometal. Chem.32 (2018) e3916.
R. Mozafari, F. Heidarizadeh, Polyhedron 162 (2019) 263-276.
M. Haghighat, F. Shirini, M. Golshekan, J.Nanosci.Nanotechno. 19 (2019) 3447-3458.
T. R. Garbe, M. Kobayashi, N. Shimizu, N. Takesue, M. Ozawa, H. Yukawa, J.Nat.Prod.
6
3 (2000) 596-598.
4
4
4.
5.
M. Hajjami, F. Gholamian, R. H. Hudson, A. M. Sanati, Catal. Lett.149 (2019) 228-247.
B. Maleki, M. Baghayeri, S. A. J. Abadi, R. Tayebee, A. Khojastehnezhad, RSC Adv.6
(2016) 96644-96661.
4
4
4
6.
7.
8.
M. A. Zolfigol, M. Safaiee, N. Bahrami-Nejad, New J. Chem. 40 (2016) 5071-5079.
D. Azarifar, Y. Abbasi, Synth. Commun.46 (2016) 745-758.
M. Wanzheng, A. G. Ebadi, R. Javahershenas, G. Jimenez, RSC Adv.9 (2019) 12801-
1
2812.
4
5
9.
0.
M. Esmaeilpour, J. Javidi, F. Dehghani, F. N. Dodeji, RSC Adv.5 (2015) 26625-26633.
H. Alinezhad, M. Tarahomi, B. Maleki, A. Amiri, Appl. Organometal. Chem.33 (2019)
e4661.
5
1.
F. Saboury, N. Azizi, Z. Mirjafari, M. M. Hashemi, J. Iran. Chem. Soc. (2020)
https://doi.org/10.1007/s13738-020-01948-5
5
5
5
2.N.G. Khaligh, T. Mihankhah, Mohd R. Johan, J. Mol. Liq. 277 (2019) 794–804
3.N. Azizi, T.S. Ahooie, M.M. Hashemi, I. Yavari, Synlett,29 (2018) 645-649
4. H. F. Niya, N. Hazeri, M. R. Kahkhaiye, M. T. Maghsoodlou, Res. Chem. Intermed. (2019)
https://doi.org/10.1007/s11164-019-04056-z
5
5.
S. Rostamnia, A. Hassankhani, H. Hossieni, H. Golchin, G. Behnam, H. Xin, J. Mol.
Catal. A Chem. 395 (2014) 463-469
5
6.
S. Rostamnia, A. Nuri, H. Xin, A. Pourjavadi, S.H. Hosseini, Tetrahedron Lett. 54 (2013)
3
344-3347
5
5
7.
8.
B. Maleki, S. S. Ashrafi, RSC Adv. 4 (2014) 42873–42891.
J. Davarpanah, A.R. Kiasat, S. Noorizadeh, M. Ghahremani, J. Mol. Catal. A-Chem. 376
(2013) 78-89

25
5
6
6
6
9.
0.
1.
2.
F. Adibian, A.R. Pourali, B. Maleki, M. Baghayeri, A. Amiri, Polyhedron 175 (2019)
14179-114200
1
F. Ataie, A. Davoodnia, A. Khojastehnezhad, Polycycl. Aromat. Compd. (2019)
https://doi.org/10.1080/10406638.2019.1622137
D. Azarifar, S. -M. Khatami, M. A. Zolfigol, R. Nejat-Yami, J. Iran. Chem. Soc. 11
(2013) 1223-1230
A. Jamshidi, B. Maleki, F. M. Zonoz, R. Tayebee, Mater. Chem. Phys. 209 (2018) 46-59

Highlights
•
Europium (Eu) anchored iminodiacetic acid functionalized silica
modified core-shell CoFe2O4 magnetic nanoparticles is produced.
•
For the first time, utilization of Europium (Eu) to the preparation of
hetereogeneous catalysts and the biologically and pharmaceutically
organic compounds is developed.
•
•
It was characterized by FT-IR, SEM, EDX, and XRD analyses.
It was successfully performed for the synthesis of diverse substituted
tetrahydrobenzo [b] prawns in green conditions.
•
It can be easily recovered by an external magnet and reused six
times.

Declaration of interests
☒
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
☒
The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests:
The authors declare that they have no conflict of interest