Design and Synthesis of Novel Cage like CuFe2O4 Hollow Nanostructure as an Efficient Catalyst for Synthesis of 4,4″-(aryl methylene)bis(3-methyl-1H-pyrazol-5-ol)s

Article abstract of DOI:10.1007/s10562-019-02818-3

Abstract: Cage like CuFe₂O₄ hollow nanostructure has been synthesized successfully using hard template method under the hydrothermal condition. Cu(NO₃)₂·6H₂O, Fe(NO₃)₂·9H₂

Full text of DOI:10.1007/s10562-019-02818-3

Catalysis Letters
https://doi.org/10.1007/s10562-019-02818-3
Design and Synthesis of Novel Cage like CuFe2O4 Hollow
Nanostructure as an Efcient Catalyst for Synthesis of 4,4′‑(aryl
methylene)bis(3‑methyl‑1H‑pyrazol‑5‑ol)s
Reza Khalifeh1 · Roghayeh Shahimoridi1 · Maryam Rajabzadeh1
Received: 18 February 2019 / Accepted: 8 May 2019
© Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
Cage like CuFe2O4 hollow nanostructure has been synthesized successfully using hard template method under the hydro-
thermal condition. Cu(NO3)2·6H2O, Fe(NO3)2·9H2O and glucose were dissolved in water, and the mixture was heated to
180 °C in an autoclave. The removal of carbon was achieved by calcination at 800 °C and fnally, the cage like CuFe2O4 hol-
low structure was obtained. This cage like CuFe2O4 hollow structure was characterized by FE-SEM, EDS, TEM and XRD.
The catalytic performance of this hollow nanostructure was evaluated for the synthesis of bis pyrazol-5-ols. To this end, the
one pot condensation reactions of phenylhydrazine, ethyl acetoacetate and diferent aromatic aldehyde at 80 °C under the
solvent free condition were performed. The optimum amount of applied catalyst for this transformation was obtained to be
0.04 mol %. Noteworthy, catalyst was easily recoverable and was reused for 7 times with the remaining of its initial structure
as well as its catalytic activity.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s10562-019-02818-3) contains
supplementary material, which is available to authorized users.
* Reza Khalifeh
khalifeh@sutech.ac.ir
1
Department of Chemistry, Shiraz University of Technology,
71555-313 Shiraz, Iran
Vol.:(0123456789)
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R. Khalifeh et al.
Graphical Abstract
Cage like CuFe2O4 hollow nanostructure are stably and efciently attainable for conversion of precursors to 4,4′-(aryl meth-
ylene)bis(3-methyl-1H-pyrazol-5-ol)s
Keywords Hollow nanostructure · CuFe2O4 · Heterogeneous catalyst · One pot reaction · Bis pyrazole derivatives
The 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) com-
pounds are known as important chemicals because they
display extensive domain of approved biological activities
[16, 17], such as antipyretic [18], anti-infammatory agents
[19], antifungal [20], and antitumor [21]. Several methods
and catalysts have been studied for synthesis of these het-
erocyclic compounds. The most common method for the
synthesis of 4,4´-(arylmethylene)bis(1H-pyrazol-5-ol)s are
reaction of 2 equivalent 3-methyl-1-phenyl-5-pyrazolone
with aldehydes or the one‐pot condensation of phenylhy-
drazine, ethyl acetoacetate, and aldehydes. Compared to the
classical stepwise synthetic routes, the one‐pot condensation
is a promising approach owning to some advantages such as
fewer by-products, and lower costs, time, and energy [22].
Poly(ethylene glycol) bound sulfonic acid [23], acetic acid
or piperidine [24], ETBA [25], 1,3,5-tris(hydrogensulfato)
benzene [26], lithium hydroxide monohydrate [27], ceric
ammonium nitrate [28], N-(3-silicapropyl)-N-methyl imida-
zolium hydrogen sulfate [29], and silica-bonded S-sulfonic
acid [30] HAP@AEPH2-SO3H [31], Sulfonated Honeycomb
Coral [32], Fe3O4 Based Vanadic Acid [33], 2-Carbamoyl-
hydrazine-1-sulfonic acid and carbamoylsulfamic acid [34]
1 Introduction
Soft magnetic materials have concerned several attentions in
recent years due to their unique properties which make them
as one of the most promising multifunctional future materials
[1]. Among these magnetic materials, the cubic spinel struc-
tures (metal ferrites) have attracted more and more attention
in material science and catalysis for their mechanical, elec-
trical, chemical and magnetic properties [2–4]. The physi-
ochemical properties as well as the catalytic performance
of these materials are strongly infuenced by the shape and
morphology of these structures [5]. Therefore, the diferent
morphologies and shapes of spinel structures such as spheres,
wires, cubes and hollow structures in several applied felds
have been reported [6–9]. Especially, in comparison with
bulk materials, hollow nanostructures with low density and
large specifc surface area have been extensively studied due
to their unique properties and the important potential applica-
tions [10]. Among them, the hollow spherical materials are
shining because of their signifcant performance and wide-
spread applications in photosynthesis, sensors, solar cells,
optical devices and also in catalysis [11–15].
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Design and Synthesis of Novel Cage like CuFe2O4 Hollow Nanostructure as an Efcient…
have been used as catalysts for this transformation. Although
these procedures provide an improvement in the synthesis
of 4,4´-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol)s, but
using of these methods have some shortcomings and limita-
tions, such as harsh reaction conditions, long reaction times,
moderate yields, non-recoverability of the catalyst as well
as the use of toxic reagents and organic solvents. So, the
designation of new heterogeneous catalyst possessing the
recyclability and ease of separation for the clean chemical
synthesis of 4,4´-(arylmethylene)bis(3-methyl-1H-pyrazol-
5-ol)s is desirable. Despite the widespread application of hol-
low nanostructures in variety of felds, few articles have been
published about the uses of these structures as a catalyst for
synthesis of organic compounds [35–37]. So, it could be prof-
itable to study hollow spherical materials with porous shells
in the catalysis of the one‐pot condensation reactions. As a
part of our ongoing program in designing of novel heteroge-
neous catalysts and development of environmentally benign
methods in organic reaction [38–49], we try to develop a
facile synthetic protocol to construct cage like CuFe2O4 hol-
low nanostructure as efcient catalysts with high activity.
Eventually, the prepared hollow nanostructure showed an
acceptable and satisfactory catalytic activity for the synthe-
sis of 4,4´-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol)s.
dried at 100 °C. Finally, the hollow spheres were obtained
after calcination at 800 °C for 6 h.
2.3 General Procedure for Preparation
of 4,4′‑(phenylmethylene)bis(3‑methyl‑1
phenyl‑1H‑pyrazol‑5‑ol)
A mixture of aldehyde (1 mmol), ethyl acetoacetate
(2 mmol), phenylhydrazine/hydrazinhydrate (2 mmol), and
0.04 mol % of catalyst was stirred at 80 °C under solvent free
condition. The reaction progress was monitored by thin layer
chromatography (TLC), after the completion of the reaction,
hot ethanol (10 mL) was added to the reaction mixture and
the catalyst was separated with external magnet and washed
with ethanol. The mixture reaction was allowed to cool and
the resulting precipitates were recrystallized from EtOH/
H2O to obtain the pure compound. All the products were
1
confrmed by the spectroscopic method using H and 13C
NMR. (See supporting information, Spectral data).
3 Results and Discussion
The strategy for synthesis of cage like CuFe2O4 hollow
nanostructure is divided into two steps: 1) the simultane-
ous inclusion of metal ions into the carbon spheres during
their formation under the designed hydrothermal process
2) The carbon spheres containing metal-ions were calcined
in air to remove the carbon component, which result in the
formation of the hollow nanostructure of porous CuFe2O4
spheres (Scheme 1).
2 Experimental
2.1 Materials and Apparatus
The phase analysis of catalyst was studied using XRD with
a Bruker D8 ADVANCE difractometer. NMR spectra were
obtained applying Bruker AMX 300 MHz instruments.
FE-SEM images were recorded using a TESCAN, Model:
MIRA3 scanning electron microscope operating at an accel-
eration voltage of 30.0 kV. Elemental compositions were
determined with an SC7620 energy-dispersive X-ray analy-
sis (EDX) presenting a 133 eV resolution at 20 kV. Trans-
mission electron microscopy (TEM) was performed with a
Leo 912 AB (120 kV) microscope (Zeiss, Germany). All
compounds were obtained from Merck in analytical grade
and were used without any further purifcation.
Figure 1a shows the FE-SEM image of the uniformly
distributed carbon spheres prepared from glucose/water
solutions without any additives under the hydrothermal
condition at 180 °C. Obviously, carbon spheres have the
spherical morphology and their diameters are about 1 µm.
The carboxylic and hydroxyl groups on the surface of car-
bon spheres provide the active sites for metal ion adsorption
[50]. Cu(NO3)2·6H2O and Fe(NO3)2·6H2O were mixed in
a solution of glucose at room temperature then heated at
180 °C in the hydrothermal process to achieve the metal
ions-adsorbed carbon. Thus, during the hydrothermal for-
mation of carbon spheres, the accumulation of metal ions
into the hydrophilic shell of carbon could be expected. The
FE-SEM image in Fig. 1b shows a signifcant increase in
diameter of carbon spheres that confrms the presence of
metal ions on the surface. Finally, following the calcination
process, carbon sphere templates are thermally removed and
the formation of the spinel structure of CuFe2O4 from metal
atoms in the shell.
2.2 General Procedure for Preparation of Cage
like CuFe2O4 Hollow Nanostructure
20 mL of 1 M glucose solution, 2 mL of Fe(NO3)3·9H2O
solution (1 M), 1 mL of Cu(NO3)3·6H2O solution (1 M) were
dispersed in 17 mL distilled water. After being stirred for
about 20 min, the mixture was transferred into a Tefon-lined
stainless steel autoclave. The autoclave was maintained at
180 °C for 24 h and then naturally cooled to ambient temper-
ature. The precipitate was fltered, washed with water, and
FE-SEM micrographs in Fig. 2a display the hollow nano-
structure of the calcined sample, which obviously show the
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R. Khalifeh et al.
Scheme 1 Synthesis of cage like CuFe2O4 hollow nanostructure from hydrothermally treated glucose/metal salts mixtures
Fig. 1 FE-SEM of a carbon spheres produced without any additive under hydrothermal method, b carbon spheres containing metal ions that
formed by hydrothermal method
spherical porous particles with a diameter of about 700 nm.
Compared to carbon microspheres, the mean diameter of
the obtained structure is smaller, that confrms the forma-
tion of more compact structure during the calcination. The
hollow spaces inside the cavities in the structure could be
clearly observable. The formation of these cavities and hol-
low spaces are attributed to the release of CO2 gas during the
calcination. The EDS analysis also confrmed the removal of
carbon by calcination at 800 °C and the existence of Cu and
Fe elements in the fnal nanostructure (Fig. 2b).
a=8.396 Å, b=8.396 Å and c=8.396 Å. The difraction
peaks at 30.32, 35.56, 43.32, 53.72, 57.48 and 63.12 are
attributed to (220), (311), (400), (422), (511) and (440) lattice
planes of the cubic CuFe2O4, respectively (JCPDS: 77-0010).
In continuation of our recent studies of the application
of heterogeneous catalysts in organic reaction, the catalytic
performance of cage like CuFe2O4 hollow nanostructure
was investigated for the synthesis of 4,4´-(arylmethylene)
bis(3-methyl-1H-pyrazol-5-ol). To find a suitable reac-
tion condition for the synthesis of 4,4´-(arylmethylene)
bis(3-methyl-1H-pyrazol-5-ol)s, one‐pot condensation of
ethyl acetoacetate, phenylhydrazine and benzaldehyde as
the model reaction were evaluated under diverse reaction
conditions, such as, diferent solvents, diverse temperatures
and the various amounts of catalyst. The results are sum-
marized in Table 1. In the optimization of diferent solvents,
The transmission electron micrograph (TEM) was
brought in Fig. 3. It also confrmed that the CuFe2O4 spheres
have the hollow and porous structure which is in good agree-
ment with the results of FE-SEM.
The XRD pattern (Fig. 4) exposes that the product has the
cubic spinel structure of CuFe2O4 with the lattice constants:
1 3

Design and Synthesis of Novel Cage like CuFe2O4 Hollow Nanostructure as an Efcient…
Fig. 2 a FE-SEM image of the
cage like CuFe2O4 hollow struc-
ture b EDS spectrum of cage
like CuFe2O4 hollow structure
the highest yield of corresponding product was obtained in
the solvent free condition (Table 1, entry 5). In H2O, EtOH/
H2O, EtOH and CH3CN, only 73, 88, 70 and 43% of the
corresponding product was identifed, respectively (Table 1,
entries 1–4). So, we examined the diferent temperatures for
the one‐pot condensation of ethyl acetoacetate, phenylhy-
drazine and benzaldehyde catalyzed by cage like CuFe2O4
hollow nanostructure in the solvent-free condition. When
the model reaction was carried out at 80 °C, the desired
product was observed in 98% yields at 2 min (Table 1, entry
5). However, higher reaction times and lower yield of the
corresponding product were obtained, when the reaction
was performed at 60, 40 °C and room temperature. (Table 1,
entries 6-8) Also, the yield of product increases from 60%
to 98% with increase the amount of catalyst from 0.004 to
0.04 mol%. Higher amount of catalyst (0.06 mol %) has no
signifcant infuence on the yield of the product (Table 1,
entries 9–12). When the model reaction was carried out for
10 min, no further progress in reaction (over 98%) has been
observed (Table 1, entry 13).
1 3

R. Khalifeh et al.
were surveyed, and the results are summerized in Table 2.
As demonstrated in Table 2, diferent types of aromatic alde-
hydes bearing electron‐donating groups such as OH, OCH3
and CH3, were converted into the corresponding products
in the excellent yields under the optimal reaction conditions
(Table 2, entries 2–6). Also, we explored the synthesis of
bis-pyrazole-5-ols starting from the phenylhydrazine and
ethyl acetoacetate, by the one pot condensation reactions
with aromatic aldehydes bearing electron‐withdrawing
groups such as Cl, NO2 and obtained the corresponding
products in high yields (Table 2, entries 7-11). Pyridine car-
boxaldehyde also reacted without any problems to provide
the intended bis-pirazole-5-ols in high yields. (Table 2, entry
12) The use of furan‐2‐carbaldehyde aforded the bridged
bis-pirazole-5-ols in 90% yield (Table 2, entry 13). In pur-
pose to broaden the scope of our methodology, the feasi-
bility of performing the reaction with hydrazine instead of
phenylhydrazine was also studied. In this way, hydrazine
was reacted with ethyl acetoacetate and aromatic aldehydes
bearing both electron‐withdrawing and electron‐donating
groups in the presence of cage like CuFe2O4 hollow nano-
structure at 80 °C. This reaction resulted in the rapid forma-
tion of the corresponding products, in high yields (Table 2,
entries 14–20). Therefore, these investigation revealed that
cage like CuFe2O4 hollow structure catalyst system is also
efective for the one pot condensation of phenylhydrazine or
hydrazine, ethyl acetoacetate and aromatic aldehydes with
high yields and short reaction times under the solvent free
condition.
Fig. 3 TEM image of cage like CuFe2O4 hollow structure
Recyclability of the cage like CuFe2O4 hollow nanostruc-
ture catalyst was also studied under the described reaction
conditions. For this purpose, after completion of the reac-
tion, catalyst was carefully separated using external mag-
netic feld, washed and dried to be applied in the next syn-
thesis run. No signifcant loss of activity of the catalyst is
observed after seven reuse cycles (Fig. 5). In addition, TEM
Fig. 4 The XRD pattern of cage like CuFe2O4 hollow structure
Based on the optimized reaction conditions, with
0.04 mol % of nanocatalyst under the solvent free condition
at 80 °C, the efciency of this protocol for other substrates
Table 1 Optimization of
Entry
Solvent
Catalyst (Mol %)
Temperature (°C)
Time (min)
Yield (%)
reaction conditions for one
pot condensation reaction
of phenylhydrazine, ethyl
acetoacetate benzaldehyde
1
2
3
4
5
6
7
8
H2O
H2O/EtOH(1:1)
EtOH
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
–
0.004
0.02
0.06
0.04
80
80
Refux
Refux
80
60
40
r.t.
80
80
80
80
80
40
20
35
120
2
10
45
120
24 h
40
15
2
73
88
70
43
98
96
94
45
10
60
87
98
98
CH3CN
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
9
10
11
12
13
10
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Design and Synthesis of Novel Cage like CuFe2O4 Hollow Nanostructure as an Efcient…
Table 2 Synthesis of bis-pirazole-5-ols from various aldehyde, phenylhydrazine/hydrazinhydrate and ethyl acetoacetate in the presence of cage
like CuFe2O4 hollow nanostructure as catalyst
Entry
R1
R2
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
H
H
H
H
H
H
H
C6H5
2
3
6
10
5
6
15
8
98
98
90
89
98
93
89
96
90
92
89
94
90
98
98
95
96
90
93
98
4-OHC6H4
3-OHC6H4
2-OHC6H4
4-OMeC6H4
4-MeC6H4
2-ClC6H4
4-ClC6H4
2,4-(Cl)2C6H3
3-NO2C6H4
2-NO2C6H4
2-Pyridyl
9
5
10
11
12
13
14
15
16
17
18
19
20
10
12
15
25
8
20
7
8
10
5
2-Furyl
C6H5
4-ClC6H4
4-MeC6H4
3-OHC6H4
2-OHC6H4
3,5-(OMe)2C6H3
4-OMeC6H4
8
Fig. 5 One pot condensation reaction of phenylhydrazine, ethyl ace-
toacetate benzaldehyde for synthesis of bis pyrazol-5-ols in the pres-
ence of reused cage like CuFe2O4 hollow nanostructure
of the reused catalyst showed that there was no signifcant
change in its morphology after the seven times of recycles
(Fig. 6).
Fig. 6 TEM image of cage like CuFe2O4 hollow nanostructure after 7
times reuse
1 3

R. Khalifeh et al.
Table 3 Comparison of the efciencies of a number of diferent reported catalysts with cage like CuFe
of 4,4′-(phenyl methylene)bis(3-methyl-1H-pyrazol-5-ol)
2O4 hollow nanostructure in the synthesis
Entry
Reaction conditions
Yield (%)
Refer-
ences
1
2
3
4
5
6
Sodium dodecyl sulfate, H2O, Refux, 60 min
Ultrasonic irradiation, H2O/EtOH (1:1), r.t., 15 min
2-Hydroxy ethylammonium propionate, Solvent-free, 90 °C, 30 min
Silica sulfuric acid, EtOH/H2O, 60
Silica-bonded N-propylpiperazine sulfamic acid, Solvent-free, 80 °C, 45 min
Cage like CuFe2O4 hollow nanostructure, Solvent-free, 80 °C, 2 min
86.8
98
91
93
93
[51]
[52]
[53]
[54]
[55]
This work
98
5. Si C, Zhang Y, Zhang C, Gao H, Ma W, Lv L, Zhang Z (2017)
Electrochim Acta 245:829
The catalytic activity of cage like CuFe2O4 hollow nano-
structure was compared with various reported catalysts in
the literature [51–55] toward the synthesis of bis pyrazol-
5-ols. It was observed that cage like CuFe2O4 hollow nano-
structure promotes the yield of products and reaction time
efectively in comparison with other catalysts. So, cage like
CuFe2O4 hollow nanostructure can be considered as efcient
catalyst in the synthesis of bis pyrazol-5-ols compounds
(Table 3).
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In summary, a general process applicable to the synthesis
of cage like CuFe2O4 hollow nanostructure via hydrother-
mal method using Cu(NO3)2·6H2O, Fe(NO3)3·9H2O and
glucose solution as carbon source was reported. The study
results indicate that the cage like CuFe2O4 hollow nano-
structure shows a high catalytic activity in one pot con-
densation reaction of phenylhydrazine, ethyl acetoacetate
and aldehyde for synthesis of bis pyrazol-5-ols. The high
activity of this catalyst could be described by the presence
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