Fabrication and characterization of the immobilized Cu(II) and Ni(II) species on silica-coated copper ferrite: as novel magnetically reusable nanocatalysts toward synthesis of biscoumarins

Article abstract of DOI:10.1007/s13738-019-01750-y

In this study, we have synthesized magnetically nanoparticles (MNPs) of CuFe₂O₄@SiO₂@AAPTMS@Ni(II) and CuFe₂O₄@SiO₂@AAPTMS@Cu(II). The prepared nanocomposite systems were characterized usin

Full text of DOI:10.1007/s13738-019-01750-y

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-019-01750-y
ORIGINAL PAPER
Fabrication and characterization of the immobilized Cu(II) and Ni(II)
species on silica‑coated copper ferrite: as novel magnetically reusable
nanocatalysts toward synthesis of biscoumarins
Behzad Zeynizadeh1 · Maryam Sadeghbari · Nader Noroozi Pesyan
1
1
Received: 12 February 2019 / Accepted: 2 August 2019
©
Iranian Chemical Society 2019
Abstract
In this study, we have synthesized magnetically nanoparticles (MNPs) of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @
2
4
2
2
4
SiO @AAPTMS@Cu(II). The prepared nanocomposite systems were characterized using scanning electron microscopy,
2
Fourier-transform infrared spectroscopy, X-ray diꢀraction, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller
analysis, vibrating-sample magnetometer and inductively coupled plasma optical emission spectroscopy. Catalytic activity
of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@Cu(II) MNPs was also studied toward one-pot the
2
4
2
2
4
2
Knoevenagel–Michael reaction of aromatic aldehydes with 4-hydroxycoumarin. All reactions were carried using 40 mg of
the nanocatalysts in reꢁuxing H O within 12‒45 min to aꢀord biscoumarin materials in 84–96% yield. The obtained results
2
exhibited that catalytic activity of the Ni(II)-composite system was higher than the Cu(II)-analogue. Moreover, reusability
of the nanocatalysts was examined for ꢂve consecutive cycles without the signiꢂcant loss of the catalytic activity.
Keywords Cu(II) · CuFe O @SiO · 4-Hydroxycoumarin · Knoevenagel–Michael · Ni(II)
2
4
2
Introduction
attracted the attention of many scientists in academic and
pharmaceutical points of view [11–16]. Among coumarin
materials, biscoumarins also exhibited the signiꢂcant phar-
macological activities such as anti-HIV [17–19], antitumor
[20], antibacterial [21–23], antifungal [23], anti-inꢁamma-
tory [24], anticoagulant [25], cytotoxic, enzyme [23, 26, 27]
inhibitor, radical scavengers and chain-breaking antioxidants
[28]. In this area, some biscoumarin compounds also rep-
resented urease inhibitor activity [29]. Urease is an enzyme
Recently, the synthesis and application of reusable heteroge-
neous catalysts as well as anchored homogeneous catalysts
on nanomagnetic materials have attracted a great deal of
attention. Using heterogeneous nanocatalysts in chemical
reactions brings faster reaction rates, selectivity, high yields
and simple workup procedures. In this context, the recovery
of nanocatalysts is the most demanding subject which makes
a process as a green choice for practical applications. Conse-
quently, high surface area of the nanoparticles provides the
extreme contact area between the reactants and the utilized
nanocatalyst systems. As well due to insolubility of nanopar-
ticles in various solvents, the nanocatalyst systems become
heterogeneous, and therefore, they can be easily separated
from the reaction mixture [1–10].
which decomposes urea to ammonia and CO , and therefore,
2
it has an important role in the formation of renal stones. It
is notable that dicoumarol (3,3′-methylene-bis(4-hydroxy-
coumarin) is naturally produced in moldy clover [30], and
it was used as a signiꢂcant starting material for synthesis of
benzopyran and furanocoumarin compounds [31].
The literature review shows that synthesis of biscou-
marins, because of widespread biological activities, has
attracted the considerable interest of numerous scientists.
In this area, molecular iodine [32], ZnCl [33], Zn(Proline)
During the last decades, coumarins have been considered
as prominent biological active materials, and therefore, they
2
2
[
34], phosphotungstic acid [35], n-Bu NBr [36], sulfated
4
*
Behzad Zeynizadeh
titania [37], P4VPy-CuO NPs [38], silica sulfuric acid
NPs [39], silica-bonded N-propylpiperazine sodium n-pro-
pionate [40], silica-supported Preyssler NPs [41], silica-
supported sodium hydrogen sulfate and indion 190 resin
bzeynizadeh@gmail.com
1
Department of Chemistry, Faculty of Science, Urmia
University, Urmia 5756151818, Iran
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Fig. 1 Synthesis of biscoumarin materials catalyzed by Ni(II) and Cu(II)-nanocomposite systems
[
(
[
42], mesoporous FeTUD-1 [43], sodium dodecyl sulfate
SDS) [44], n-dodecylbenzene sulfonic acid (DBSA) [45],
Et NH][HSO ] [46], propane-1,2,3-triyl-tris(hydrogen sul-
Although most of the reported methods have the own
merits and shortcomings, however, development of environ-
mental friendly procedures is a subject of more interest and
demands new challenges toward synthesis of biscoumarin
materials. In line with the outlined strategies and continua-
tion of our research program directed to the immobilization
of Ni(II) and Cu(II) species on magnetic materials, herein,
we wish to introduce the fabrication and characterization of
magnetically nanoparticles of CuFe O @SiO @AAPTMS@
3
4
fate) [47], sulfonated rice husk ash (RHA-SO H) [48, 49],
3
graphene oxide nanosheets [50], nano Fe O @ZrO -H PO
3
4
2
3
4
[
51], task-speciꢂc ionic liquids [52], tetramethylguanid-
ium-based ionic liquids [53], [MIM(CH ) SO H][HSO ]
2
4
3
4
[
54], SO H-functionalized ionic liquids based on benzimi-
3
dazolium cation [PSebim][OTf] [55] and mesoporous acid-
activated montmorillonite K10 [56] are some of the catalyst
systems which have been successfully utilized for synthesis
of biscoumarin materials.
2
4
2
Ni(II) and CuFe O @SiO @AAPTMS@Cu(II). At the next,
2
4
2
catalytic activity of the prepared nanocomposites was fur-
ther investigated toward one-pot the Knoevenagel–Michael
Fig. 2 Synthesis of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@Cu(II) MNPs
2
4
2
2
4
2
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Journal of the Iranian Chemical Society
reaction of 4-hydroxycoumarin with aromatic aldehydes in
water as a green solvent (Fig. 1).
aꢀord CuFe O @SiO @AAPTMS@Ni(II) MNPs and the
2 4 2
Cu(II)-analogue.
Fourier‑transform infrared spectroscopy (FT‑IR)
Results and discussion
Figure 3 shows the FT-IR spectra of (a) CuFe O , (b)
2
4
Synthesis of magnetically nanoparticles
CuFe O @SiO , (c) CuFe O @SiO @AAPTMS, (d)
2 4 2 2 4 2
of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @
CuFe O @SiO @AAPTMS@Ni(II) and (e) CuFe O @
2 4 2 2 4
2
4
2
2
4
SiO @AAPTMS@Cu(II)
SiO @AAPTMS@Cu(II) MNPs. In the spectrum of
2
2
CuFe O (Fig. 3a), the absorption bands at 466 and
2
4
−
1
Synthesis of magnetically nanoparticles (MNPs) of
CuFe O @SiO @AAPTMS@Ni(II) and the Cu(II)-ana-
580 cm are attributed to stretching vibration of Cu–O
and Fe‒O bonds, respectively. As well, a small broadband
2
4
2
−
1
logue was carried out via a four-step procedure (Fig. 2): (i)
around 3400 cm is assigned to stretching vibration of sur-
face hydroxyl groups. Comparing the FT-IR spectrum of
CuFe O , CuFe O @SiO , CuFe O @SiO @AAPTMS,
preparation of CuFe O MNPs by chemical co-precipita-
2
4
tion of FeCl ·6H O and CuCl ·2H O in an aqueous solu-
3
2
2
2
2
4
2
4
2
2
4
2
tion of NaOH, (ii) layering of silica around the nanocores of
CuFe O @SiO @AAPTMS@Ni(II) MNPs and the Cu(II)-
2 4 2
−
1
CuFe O using tetraethyl orthosilicate (TEOS), (iii) surface-
analogue validates that a broadband at 1090 cm is cor-
responded to stretching vibration of Si–O bond. Based on
2
4
linking of CuFe O @SiO MNPs with 3-(2-aminoethyl-
2
4
2
−
1
amino)propyl trimethoxysilane (AAPTMS), and ꢂnally (iv)
the absorption at 1090 cm , therefore, the immobilization
of silica layer around the surface of copper ferrite nucleuses
was successfully demonstrated.
complexation of CuFe O @SiO @AAPTMS MNPs by an
2
4
2
aqueous solution of Ni(OAc) ·4H O or Cu(OAc) ·H O to
2
2
2
2
Fig. 3 FT-IR spectra of a
CuFe O , b CuFe O @SiO , c
2
4
2
4
2
CuFe O @SiO @AAPTMS, d
2
4
2
CuFe O @SiO @AAPTMS@
2
4
2
Ni(II) and e CuFe O @SiO @
2
4
2
AAPTMS@Cu(II) MNPs
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Journal of the Iranian Chemical Society
Fig. 4 SEM images of a CuFe O , b CuFe O @SiO @AAPTMS@Ni(II) and c CuFe O @SiO @AAPTMS@Cu(II) MNPs
2
4
2
4
2
2
4
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Journal of the Iranian Chemical Society
Scanning electron microscopy (SEM)
SiO @AAPTMS@Ni(II) and (c) CuFe O @SiO @
2 2 4 2
AAPTMS@Cu(II) MNPs. The graph analysis showed that
all the required elements existed in the structure of nano-
composites. Therefore, the successful anchoring of Ni(II)
and Cu(II) species on CuFe O @SiO @AAPTMS MNPs
The morphology and size distribution of the prepared nano-
composite systems were investigated by scanning electron
microscopy technique. SEM images of CuFe O , CuFe O @
2
4
2
4
2
4
2
SiO @AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@
was concluded.
2
2
4
2
Cu(II) MNPs (Fig. 4) show that all the composite systems
are constituted from uniform and granular segments. In addi-
tion, the size distribution of CuFe O , CuFe O @SiO @
X‑ray diꢀraction (XRD) analysis
2
4
2
4
2
AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@
X-ray diꢀraction as another tool was used for structural anal-
ysis of the prepared nanocomposite systems. Figure 6 shows
XRD diꢀractograms of (a) CuFe O , (b) CuFe O @SiO @
2
4
2
Cu(II) MNPs is located in the range of 15–66 nm (Fig. 4a),
2
0–38 nm (Fig. 4b), and 20–25 nm (Fig. 4c), respectively,
2
4
2
4
2
proving the mesoporous structure of all the composite
systems.
AAPTMS@Ni(II) and (c) CuFe O @SiO @AAPTMS@
2 4 2
Cu(II) MNPs. XRD pattern of CuFe O MNPs (Fig. 6a)
2
4
shows the signals at 2θ=19.01°, 30.2°, 35.8°, 43.3°, 54.3°,
Energy‑dispersive X‑ray spectroscopy (EDX)
57.9° and 62.6° corresponding to the reꢁection planes of
(
1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4
Energy-dispersive X-Ray (EDX) analysis is an eꢀective
technique to determine the elemental proꢂle of materials.
Figure 5 shows EDX spectra of (a) CuFe O , (b) CuFe O @
4 0), respectively. Comparison of the current pattern with
the standard one of CuFe O (JCPDS 77-0010) illustrated
2
4
that the prepared laboratory sample of copper ferrite has
2
4
2
4
high crystallinity in a cubic spinel structure and good phase
Fig. 5 EDX spectra of a CuFe O , b CuFe O @SiO @AAPTMS@Ni(II) and c CuFe O @SiO @AAPTMS@Cu(II) MNPs
2
4
2
4
2
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Journal of the Iranian Chemical Society
Fig. 6 XRD patterns of a
CuFe O , b CuFe O @SiO @
2
4
2
4
2
AAPTMS@Ni(II) and c
CuFe O @SiO @AAPTMS@
2
4
2
Cu(II) MNPs
purity of the nanoparticles. In addition, comparing the
XRD pattern of CuFe O @SiO @AAPTMS@Ni(II) and
nanocomposites are described in Table 1. The average pores
size clearly demonstrates that both of the nanocomposites
are located in the category of mesoporous materials.
2
4
2
CuFe O @SiO @AAPTMS@Cu(II) MNPs with the labo-
2
4
2
ratory sample of CuFe O exhibited that during the layering
2
4
of SiO @AAPTMS moiety as well as anchoring of Ni(II)
Vibrating‑sample magnetometer (VSM) analysis
2
and Cu(II) species, the cubic spinel structure of CuFe O
2
4
remained intact. Moreover, the crystallinity and phase purity
At the next, magnetic properties of CuFe O , CuFe O @
2
4
2
4
of the nanoparticles were remained in high degree.
SiO @AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@
2
2
4
2
Cu(II) MNPs were determined using vibrating-sample mag-
netometer (VSM) analysis. Figure 8 shows that the saturation
magnetization (Ms) values of CuFe O , CuFe O @SiO @
Brunauer–Emmett–Teller (BET) analysis
2
4
2
4
2
AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@Cu(II)
2
4
2
−
1
Further investigation toward pore volume and porosity
of the prepared CuFe O @SiO @AAPTMS@Ni(II) and
MNPs were determined as 5.1, 3.51 and 4.14 emu g ,
respectively. Comparing of the Ms values clearly shows
that during the layering of magnetic nucleuses with non-
magnetic species, the saturation magnetization of the ꢂnal
nanocomposites was notably decreased. Although the values
were decreased, however, they were enough for any mag-
netic separation.
2
4
2
CuFe O @SiO @AAPTMS@Cu(II) MNPs was also car-
2
4
2
ried out by examining the N adsorption–desorption analy-
2
sis. According to the illustrated isotherms (Fig. 7), BET and
BJH calculations, the results for speciꢂc surface area, pore
volume and average pores size distribution for both of the
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Journal of the Iranian Chemical Society
Fig. 7 The N adsorption–desorption analysis for a CuFe O @SiO @AAPTMS@Ni(II) and b CuFe O @SiO @AAPTMS@Cu(II) MNPs
2
2
4
2
2
4
2
Table 1 Surface characteristics
CuFe O @SiO @AAPTMS@Ni(II) MNPs
CuFe O @SiO @AAPTMS@Cu(II) MNPs
2 4 2
2
4
2
of CuFe O @SiO @
2
4
2
AAPTMS@Ni(II)/Cu(II) MNPs
2
−1
2 −1
Speciꢂc surface area (S )=28.945 m g
Speciꢂc surface area (SBET)=14.667 m g
BET
3
−1
3
−1
Pore volume=0.1195 cm g
Pores volume=0.074312 cm g
Average pores size=16.512 nm
Average pores size=20.267 nm
Inductively coupled plasma optical emission
spectroscopy (ICP‑OES)
systems was investigated at the programmable heating
(30–790 °C). The results of this investigation are docu-
mented in Table 2. Observation of the results represented
that through the raising of temperature, the overall mass los-
ing of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @
Elemental composition of the prepared nanocomposite sys-
tems was determined by inductively coupled plasma opti-
cal emission spectroscopy. Through the analysis, the exact
amount of Fe, Cu and Ni in CuFe O @SiO @AAPTMS@
2
4
2
2
4
SiO @AAPTMS@Cu(II) MNPs was 11.78% and 13.83%,
2
respectively. These data clearly represent that the prepared
nanocomposite systems had high thermal stability. As well,
thermal stability of Ni(II)-nanocomposite was higher than
the Cu(II)-analogue (11.78% vs. 13.83%).
2
4
2
Ni(II) MNPs was measured 29.67%, 18.04% and 21.11%,
respectively. As well, the exact amounts of Cu and Fe in
CuFe O @SiO @AAPTMS@Cu(II) MNPs were deter-
2
4
2
mined 31.69% and 19.01%, respectively.
The Knoevenagel–Michael reaction of aromatic
aldehydes with 4‑hydroxycoumarin
Thermogravimetric analysis (TGA)
After the successful synthesis and structural elucidation
of CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @
Thermogravimetric analyses of CuFe O @SiO @
2
4
2
2
4
2
2
4
AAPTMS@Ni(II) and CuFe O @SiO @AAPTMS@Cu(II)
SiO @AAPTMS@Cu(II) MNPs, catalytic activity of the
2
4
2
2
MNPs are illustrated in Fig. 9. In this context and via the
processing of dehydration, removing of organic moiety, frag-
mentation and calcination, mass losing of the nanocomposite
mesoporous materials in the Knoevenagel–Michael reac-
tion of aromatic aldehydes with 4-hydroxycoumarin was
further investigated. To optimize the reaction conditions,
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Journal of the Iranian Chemical Society
Fig. 8 Saturation magnetization graphs of a CuFe O , b CuFe O @SiO @AAPTMS@Ni(II) and c CuFe O @SiO @AAPTMS@Cu(II) MNPs
2
4
2
4
2
2
4
2
the condensation reaction of benzaldehyde (1 mmol) with
At the next and in order to clarify the role of anchored
Ni(II) species on silica-layered copper ferrite, the Knoev-
enagel–Michael reaction of benzaldehyde with 4-hydrox-
ycoumarin in the presence of CuFe O , CuFe O @SiO
4
-hydroxycoumarin (2 mmol) in the presence of CuFe O @
2 4
SiO @AAPTMS@Ni(II) MNPs as a model reaction was
2
studied. Consequently, the inꢁuence of temperature, reac-
tion solvent as well as the amounts of nanocatalyst on the
rate of reaction was thoroughly investigated (Table 3). Table
shows that the reaction in the absence of nanocatalyst did
not aꢀord a satisfactory yield. However, using the small
amounts of nanocatalyst dramatically promoted the conden-
sation reaction. By examining of the titled reaction in THF,
CH CN, MeOH, EtOH, H O–EtOH, H O–MeOH and H O
2
4
2
4
2
and CuFe O @SiO @AAPTMS MNPs was also investi-
2
4
2
gated and then compared with that of CuFe O @SiO @
2
4
2
AAPTMS@Ni(II) MNPs. The summarized results in Table 4
show that the three parent nanocatalysts exhibited the poor
eꢃciency within 12 min, however, the inꢁuence of Ni(II)-
composite was signiꢂcantly greater than the others (entry
4). In this area, catalyzing the model reaction by CuFe O @
3
2
2
2
2
4
with 20–40 mg of the nanocatalyst, it resulted that H O as
SiO @AAPTMS@Cu(II) MNPs at the optimized reaction
2
2
a green solvent was the best solvent of choice and 40 mg of
the nanocatalyst was the adequate amount to promote the
condensation reaction perfectly. Moreover, using reꢁux con-
ditions completed the condensation reaction within 12 min.
Therefore, the conditions mentioned in entry 5 (Table 3)
were selected as the requirements to carry out the reaction
of benzaldehyde with 4-hydroxycoumarin eꢃciently.
conditions was also eꢃcient and completed the condensation
reaction within 18 min. Comparing the results of entries 4
and 5 (Table 4) clearly represents that the catalytic activity
of CuFe O @SiO @AAPTMS@Ni(II) MNPs was higher
2
4
2
than the Cu(II)-analogue.
The usefulness and catalytic activity of CuFe O @SiO @
2
4
2
AAPTMS@Ni(II) MNPs and the Cu(II)-analogue were further
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Journal of the Iranian Chemical Society
Fig. 9 TGA analysis of
CuFe O @SiO @AAPTMS@
2
4
2
Ni(II) and CuFe O @SiO @
2
4
2
AAPTMS@Cu(II) MNPs
studied toward one-pot the Knoevenagel–Michael reaction of
structurally diverse aromatic aldehydes with 4-hydroxycou-
marin at the optimized reaction conditions (Table 5). Review-
ing of the results shows that all the condensation reactions
were carried out successfully within 12–45 min to aꢀord the
corresponding biscoumarin materials in high yields. Moreo-
ver, CuFe O @SiO @AAPTMS@Ni(II) MNPs in terms of
2
4
2
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Journal of the Iranian Chemical Society
Table 2 Results of thermogravimetric analysis for CuFe O @SiO @AAPTMS@Ni(II)/Cu(II) MNP
2
4
2
CuFe O @SiO @AAPTMS@Ni(II) MNPs
CuFe O @SiO @AAPTMS@Cu(II) MNPs
2 4 2
2
4
2
4
8
3
0–80 °C, dehydration (1.77%)
0–335 °C, removing of organic moiety (3.54%)
30–260 °C, dehydration (1.22%)
260–500 °C, removing of organic moiety (0.67%+3.34%)
35–775 °C, fragmentation, removing of silica layer and calcination
500–790 °C, fragmentation, removing of silica layer and
(
2.54%+2.06%+1.87%)
calcination (5.95%+2.65%)
Overall mass losing: 11.78%
Overall mass losing: 13.83%
Table 3 Optimization experiments for the Knoevenagel–Michael reaction of benzaldehyde with 4-hydroxycoumarin catalyzed by CuFe O @
2
4
SiO @AAPTMS@Ni(II) MNPs
2
Entry
CuFe O @SiO @AAPTMS@ Solvent (3 mL)
Condition (°C)
Time (min)
Conver-
2
4
2
Ni(II) (mg)
sion (%)a
1
2
3
4
5
6
7
8
9
–
H O
Reꢁux
r.t.
Reꢁux
70
Reꢁux
Reꢁux
Reꢁux
Reꢁux
Reꢁux
Reꢁux
Reꢁux
120
120
45
50
12
20
80
95
96
100
95
70
60
90
40
40
2
40
20
40
40
40
40
40
40
40
40
H O
2
H O
2
H O
2
H O
2
H O-EtOH (1:1)
90
2
EtOH
MeOH
120
120
120
120
120
H O-MeOH (1:1)
2
1
1
0
1
THF
CH CN
3
All reactions were carried out with 1 mmol of benzaldehyde and 2 mmol of 4-hydroxycoumarin
a
Conversions less than 100% were determined on the basis of recovered 4-hydroxycoumarin
the rate and yield of reactions exhibited higher eꢃciency than
the Cu(II)-analogue.
Accordingly, the Michael reaction of second molecule of
4-hydroxycoumarin with the prepared benzylidene-coumarin
intermediate aꢀords the ꢂnal biscoumarin material.
At the next, the suitability of this synthetic method was
highlighted by comparison of the obtained results for
CuFe O @SiO @AAPTMS@Ni(II)/Cu(II) MNPs with those
Reusability of CuFe O @SiO @AAPTMS@Ni(II)
2
4
2
2
4
2
of reported for other protocols. Table 6 shows that in terms of
the yield, reaction time and reusability of the nanocatalysts,
the present work exhibited a more or comparable eꢃciency
than the previous systems.
and CuFe O @SiO @AAPTMS@Cu(II) MNPs
2 4 2
The economic and green aspect of the Knoevenagel–Michael
reaction of benzaldehyde with 4-hydroxycoumarin in the pres-
ence of Ni(II) and Cu(II)-nanocomposite systems were further
studied by examining the reusability of the nanocomposites
at the optimized reaction conditions. In this context, once the
condensation reaction was completed, the nanocatalyst was
magnetically separated from the reaction mixture washed
with EtOAc and then dried under air atmosphere. The vessel
of reaction was again charged with the fresh benzaldehyde,
Although the exact mechanism of this synthetic protocol
is not clear, however, a depicted mechanism in Fig. 10 repre-
sents the role of CuFe O @SiO @AAPTMS@Ni(II)/Cu(II)
2
4
2
MNPs in catalysis of the Knoevenagel–Michael reaction of
aromatic aldehydes with 4-hydroxycoumarin. The Figure
shows that through the activation of aldehyde by nanocatalyst,
nucleophilic attack of 4-hydroxycoumarin was taken place.
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Journal of the Iranian Chemical Society
Table 4 Comparison of the reactivity of CuFe O -based nanocatalysts toward Knoevenagel–Michael reaction of benzaldehyde with 4-hydroxy-
2
4
coumarin
Entry
Catalyst
Solvent (3 mL)
Condition
Time (min)
Conver-
sion (%)a
1
2
3
4
5
6
CuFe O
H O
Reꢁux
Reꢁux
Reꢁux
Reꢁux
Reꢁux
Reꢁux
12
12
12
12
12
18
25
32
40
100
93
100
2
4
2
CuFe O @SiO
H O
2
4
2
2
CuFe O @SiO @AAPTMS
H O
2
4
2
2
CuFe O @SiO @AAPTMS@Ni(II)
H O
2
4
2
2
CuFe O @SiO @AAPTMS@Cu(II)
H O
2
4
2
2
CuFe O @SiO @AAPTMS@Cu(II)
H O
2
4
2
2
All reactions were carried out with 1 mmol of benzaldehyde and 2 mmol of 4-hydroxycoumarin in the presence of 40 mg of the nanocatalysts
a
Conversions less than 100% were determined on the basis of recovered 4-hydroxycoumarin
4
-hydroxycoumarin and the recycled nanocatalyst to run the
were measured by vibrating-sample magnetometer
(Meghnatis Daghigh, Iran) under magnetic ꢂelds up to
condensation reaction for a second time. Figure 11 shows
that CuFe O @SiO @AAPTMS@Ni(II)/Cu(II) MNPs can
20 KOe. N adsorption–desorption analysis was carried
2
4
2
2
be reused for ꢂve consecutive cycles without the signiꢂcant
loss of catalytic activity. Moreover, EDX analysis (Fig. 12)
and SEM image (Fig. 13) of ꢂrst recycling step of CuFe O @
on Belsorp-Max, Japan. Brunauer–Emmett–Teller (BET)
method was used to determine the speciꢂc surface area
of nanoparticles. The volume and size distribution of the
pores were measured using desorption isotherms accord-
ing to Barrett–Joyner–Halanda (BJH) method. Elemental
analysis of Fe, Cu and Ni was carried out by inductively
coupled plasma optical emission spectrometry (ICP-OES,
Varian 730-ES). The irradiation of ultrasound was carried
out on SOLTEC SONICA 2400MH S3 (305 W).
2
4
SiO @AAPTMS@Ni(II) MNPs represented that through the
2
progress of the reaction, the morphology and elemental com-
position of the nanocatalyst remained intact. The analysis also
showed that the size of recycled MNPs was distributed in the
range of 15–34 nm.
Experimental
Synthesis of CuFe O MNPs
2
4
General
Synthesis of CuFe O MNPs was carried out through
2
4
All materials and reagents were purchased from commer-
cial sources and they were used without further puriꢂca-
the reported chemical co-precipitation procedure [57].
Brieꢁy, FeCl ·6H O (2.216 g, 8.2 mmol) and CuCl ·2H O
3
2
2
2
1
tions. FT-IR, H NMR spectra were recorded on Thermo
(0.699 g, 4.1 mmol) were dissolved in deionized water
Nicolet Nexus 670 and Bruker Avance 300 MHz spec-
trometers, respectively. The obtained products were char-
acterized using physical and spectral data followed by a
comparison with authentic data. Purity of chemicals as
well as progress of the reactions was monitored by TLC
over silica gel 60 F aluminum sheet. X-ray diꢀractions
(75 mL) and stirred under N atmosphere at room temper-
2
ate for a few minutes. In a meanwhile of stirring, NaOH
(3 g in 15 mL H O) was added in drop-wise manner into
2
the solution within 10 min. Through the addition of NaOH,
the ꢂne brown–black particles of CuFe O were precipi-
2
4
tated. The mixture was heated on an oil bath (90 °C) for
5 h. After cooling to the room temperature, the obtained
precipitate was separated using an external magnetic ꢂeld
and washed with deionized water (30 mL) and ethanol
(20 mL). The precipitate was then dried in an oven at
2
54
were recorded by X’PertPro Panalytical diꢀractometer at
4
2
0 kV (30 mA, CuKα radiation source, λ = 1.5418 Å) in
θ = 10°‒80°. Size and morphology of the particles were
determined using SEM images by FESEM ZEISS-Sigma
VP instrument. Magnetic properties of the nanocatalysts
1
3

Journal of the Iranian Chemical Society
Table 5 Synthesis of
CuFe
2
O
4
@SiO
2
@
CuFe
2 4 2
O @SiO @
biscoumarin materials
AAPTMS@Ni(II)
AAPTMS@Cu(II)
o
catalyzed by CuFe O @SiO @
Entry
Substrate
Product
Mp ( C)
2
4
2
Time
Yield
(%)a
Time
(min)
Yield
(%)a
AAPTMS@Ni(II) and the
(
min)
Cu(II)-analogue
2
2
2
2
2
30‒232
34]
1
12
96
94
90
89
88
18
35
45
25
43
95
92
90
85
86
[
34‒236
49]
2
3
4
5
18
26
24
40
[
13‒215
34]
[
56‒257
49]
[
03‒205
49]
[
2
2
2
03‒206
35]
6
7
8
20
30
32
87
91
90
30
25
35
85
89
89
[
35‒238
29]
[
48‒250
49]
[
9
38
30
40
35
84
93
85
89
35
28
45
30
86
92
84
87
202‒204
242‒245
250‒252
1
1
1
0
1
2
2
68‒270
[54]
1
3

Journal of the Iranian Chemical Society
Table 5 (continued)
All reactions were carried out with 1 mmol of aromatic aldehydes and 2 mmol of 4-hydroxycoumarin in
the presence of 40 mg of the nanocatalysts in reꢁuxing H O (3 mL)
2
a
Yield refers to isolated pure product
Table 6 Comparison of the synthesis of dicumarol with CuFe O @SiO @AAPTMS@Ni(II)/Cu(II) MNPs and other reported systems
2
4
2
Entry
Catalyst
Time (min)
Yield (%)
Condition
Reusability
References
1
2
3
4
5
6
7
8
9
CuFe O @SiO @AAPTMS@Ni(II)
12
18
27
20
30
15
20
30
150
60
25
15
12
120
25
96
95
93
93
95
96
92
90
93
87
92
80
97
96
95
H O/reꢁux
5
5
–
5
–
5
–
3
5
–
–
4
4
2
6
*
*
2
4
2
2
CuFe O @SiO @AAPTMS@Cu(II)
H O/reꢁux
2
4
2
2
Molecular iodine
Phosphotungstic acid
H O/100 °C
[32]
[35]
[36]
[37]
[39]
[42]
[44]
[45]
[49]
[50]
[51]
[55]
[56]
2
H O/80 °C
2
n-Bu NBr
H O/100 °C
4
2
Sulfated titania
H O/80 °C
2
Silica sulfuric acid NPs
NaHSO /SiO
H O/reꢁux
2
Toluene/100 °C
4
2
Sodium dodecyl sulfate
n-Dodecylbenzene sulfonic acid
H O/60 °C
2
10
11
12
13
14
15
H O/40 °C
2
RHA-SO H
Solvent-free/80 °C
3
Graphene oxide nanosheets
Nano Fe O @ZrO -H PO
H O/reꢁux
2
H O/reꢁux
3
4
2
3
4
2
[PSebim][OTf] as IL (ionic liquid)
Acid-activated montmorillonite
IL/70 °C
H O/r.t.
2
*
Present work
8
0 °C for 12 h. The obtained CuFe O MNPs was calci-
Synthesis of CuFe O @SiO @AAPTMS MNPs
2 4 2
2
4
nated at 700 °C for 5 h.
Magnetically nanoparticles of CuFe O @SiO @AAPTMS
2
4
2
Synthesis of CuFe O @SiO MNPs
were prepared via the functionalization of hydroxyl groups
2
4
2
of CuFe O @SiO MNPs with 3-(2-aminoethylamino)pro-
2
4
2
CuFe O MNPs were coated with silica layer via the reported
pyl trimethoxysilane (AAPTMS). To do this, the fabricated
2
4
procedure [57]. A mixture of CuFe O (1.5 g) MNPs in dis-
CuFe O @SiO MNPs (2 g) were dispersed in absolute etha-
2
4
2
4
2
tilled water (20 mL) and 2-propanol (200 mL) was prepared.
nol (140 mL) by sonication under N atmosphere for 40 min.
2
The prepared mixture was homogenized by ultrasound for
Then, AAPTMS (4 mL) was added and the resulting mixture
was sonicated for 1 h. Next, stirring of the reaction mixture
was carried out vigorously for 20 h at 50 °C. The resulting
CuFe O @SiO @AATPMS MNPs were collected using an
3
0 min. To the prepared suspension of CuFe O , PEG–400
2 4
(
5.36 g), distilled water (20 mL), ammonia (25 wt%, 10 mL)
and tetraethyl orthosilicate (TEOS, 2 mL) were then added
and the resulting mixture was stirred vigorously at room
temperature for 28 h. Once the reaction was completed, the
product was collected using an external magnetic ꢂeld. The
separated nanoparticles were washed two times with ethanol
and distilled water and dried at room temperature for 24 h.
2
4
2
external magnetic ꢂeld and washed with acetone and deion-
ized water for several times. Finally, the nanoparticles were
dried in an oven (60 °C) for 24 h.
1
3

Journal of the Iranian Chemical Society
Fig. 10 Proposed mechanism for the Knoevenagel–Michael reaction of aromatic aldehydes with 4-hydroxycoumarin
Synthesis of CuFe O @SiO @AAPTMS@Ni(II)/Cu(II)
using an external magnetic ꢂeld and washed several times
with ethanol. Drying under air atmosphere aꢀorded magneti-
cally nanoparticles of CuFe O @SiO @AAPTMS@Ni(II)
2
4
2
MNPs
2
4
2
CuFe O @SiO @AAPTMS MNPs (1 g) were added into the
or the Cu(II)-analogue.
2
4
2
solution of Ni(OAc) ·4H O (0.5 g) or Cu(OAc) ·H O (0.5 g)
2
2
2
2
in ethanol (25 mL), and the mixture was stirred for 24 h
under reꢁux conditions. The resulting MNPs were collected
CuFe2O4@SiO2@AAPTMS@Ni(II)
CuFe2O4@SiO2@AAPTMS@Cu(II)
1
00
9
9
8
8
7
5
0
5
0
5
1
2
3
4
5
Run
Fig. 11 Reusability of CuFe O @SiO @AAPTMS@Ni(II) and
Fig. 12 EDX spectrum of the recovered CuFe O @SiO @
2 4 2
2
4
2
Cu(II) MNPs
AAPTMS@Ni(II) MNPs
1
3

Journal of the Iranian Chemical Society
Fig. 13 SEM image of the recovered CuFe O @SiO @AAPTMS@Ni(II) MNPs
2
4
2
Typical procedure for Knoevenagel–Michael
reaction of benzaldehyde with 4‑hydroxycoumarin
showed an excellent catalytic activity toward the Kno-
evenagel–Michael reaction of aromatic aldehydes with
4
-hydroxycoumarin in water as a green solvent. All reac-
A mixture of benzaldehyde (0.106 g, 1 mmol) and 4-hydrox-
ycoumarin (0.324 g, 2 mmol) in water (3 mL) was prepared.
CuFe O @SiO @AAPTMS@Ni(II) or the Cu(II)-analogue
tions were carried out within 12–45 min to aꢀord biscou-
marin materials in high yields. The present method pro-
vides several advantages in terms of the novel synthesis of
CuFe O @SiO @AAPTMS@Ni(II) and CuFe O @SiO @
2
4
2
(
40 mg) was then added and the mixture was stirred for
2
4
2
2
4
2
1
2–18 min under reꢁux conditions. Once the reaction was
AAPTMS@Cu(II) MNPs, the use of H O as a green sol-
2
completed (monitored by TLC, n-hexane/EtOAc: 4/2), the
mixture was cooled to the room temperature. The nanocata-
lyst was magnetically separated from the reaction mixture.
EtOAc (5 mL) was then added and the reaction mixture
was stirred for additional 10 min. The organic layer was
separated and then dried over anhydrous Na SO . Evapora-
vent, short reaction times, high yield of the products, simple
workup procedure and the perfect reusability of the fabri-
cated nanocatalysts.
Acknowledgements The authors gratefully acknowledged the ꢂnancial
support of this work by the research council of Urmia University.
2
4
tion of the solvent under reduced presssure aꢀords the pure
3
,3′-benzylidenebis(4-hydroxycoumarin) in 95–96% yield
−
1
(
Table 5, entry 1). FT-IR (KBr, υ Cm ) 3065, 2737, 1659,
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