Design and synthesis of novel natural clinoptilolite-MnFe2O4 nanocomposites and their catalytic application in the facile and efficient synthesis of chalcone derivatives through Claisen-Schmidt reaction

Article abstract of DOI:10.1007/s11164-018-3366-4

A series of three novel nanocomposites were prepared by modifying the surface of natural clinoptilolite using various amounts of manganese ferrite (MnFe₂O₄) nanoparticles. These manganese ferrite-modified nanocomposites (MFO–NC) were fully characterized by XRD, FT-IR, EDX, VSM and TEM analyses. One of these novel nanocomposites with 40?wt% of manganese ferrite in clinoptilolite (MFO–NC-3) showed a strong catalytic behavior in the aldol-type Claisen–Schmidt reaction for the synthesis of chalcones. A strong catalytic synergy was observed between nano-MnFe₂O₄ particles and natural clinoptilolite in the structure of these nanocomposites. The products with a broad range of substituents on the reactants were efficiently obtained under room-temperature conditions within relatively short reaction times with good to excellent yields in the presence of one of the prepared MFO–NC nanocomposites. This nanocomposite also showed a strong stability and substantial reusability in the synthesis of chalcones.

Full text of DOI:10.1007/s11164-018-3366-4

Res Chem Intermed
https://doi.org/10.1007/s11164-018-3366-4
Design and synthesis of novel natural clinoptilolite-
MnFe2O4 nanocomposites and their catalytic
application in the facile and efficient synthesis
of chalcone derivatives through Claisen-Schmidt
reaction
Reza Aryan1
Noshin Mir1 Hamid Beyzaei1 Amin Kharade1
•
•
•
Received: 1 December 2017 / Accepted: 1 March 2018
Ó Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract A series of three novel nanocomposites were prepared by modifying the
surface of natural clinoptilolite using various amounts of manganese ferrite
(MnFe2O4) nanoparticles. These manganese ferrite-modified nanocomposites
(MFO–NC) were fully characterized by XRD, FT-IR, EDX, VSM and TEM anal-
yses. One of these novel nanocomposites with 40 wt% of manganese ferrite in
clinoptilolite (MFO–NC-3) showed a strong catalytic behavior in the aldol-type
Claisen–Schmidt reaction for the synthesis of chalcones. A strong catalytic synergy
was observed between nano-MnFe2O4 particles and natural clinoptilolite in the
structure of these nanocomposites. The products with a broad range of substituents
on the reactants were efficiently obtained under room-temperature conditions within
relatively short reaction times with good to excellent yields in the presence of one of
the prepared MFO–NC nanocomposites. This nanocomposite also showed a strong
stability and substantial reusability in the synthesis of chalcones.
Keywords Heterogeneous catalysis Á Manganese ferrite Á Natural clinoptilolite Á
Nanocomposite Á Chalcones Á Claisen–Schmidt reaction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11164-
018-3366-4) contains supplementary material, which is available to authorized users.
&
Reza Aryan
rezaaryanchemist@yahoo.com; rezaaryan@uoz.ac.ir
1
Department of Chemistry, Faculty of Science, University of Zabol,
P. O. Box: 9861335856, Zabol, Iran
123

R. Aryan et al.
Introduction
As iron-containing materials, MFe2O4 (M=Co, Mn, Ni, Cu, etc.), are very important
substances with magnetic properties which have been widely studied for numerous
applications [1, 2]. Among ferrites, MnFe2O4 nanopaticles have been widely used
for magnetic resonance imaging technology and other electronic applications [3–7].
Furthermore, this material with its complex system [8] can also be applied for
catalytic purposes as a heterogeneous catalyst [9–11] and for photodegradation of
dyes [12, 13]. In spite of the high surface areas and abundant Lewis acidic reaction
sites of ferrite nanoparticles [10], in order to decrease the manufacturing cost,
increase the reusability potential and also prevent the possible toxicity of the applied
nanocatalysts, there is a growing interest in using a natural porous substrate for
hosting the nanoparticles. Natural clinoptilolite has recently been the subject of
many studies as an abundant, cost-effective, and eco-friendly catalyst with a high
surface area [14–16].
So far, various materials have been embedded in clinoptilolite structures for
various applications. Depending on the employed material, the resulting composite
has different properties. Clinoptilolite functions as a porous substrate which hosts
the nanomaterial and improves its efficiency. Compared to other modified
clinoptilolites [17–19], MnFe2O4-clinoptilolite is a non-toxic and stable material
having good Lewis acid properties which make it an excellent candidate for
catalytic industrial applications. Moreover, it can be easily separated by an external
magnetic field. The synthetic procedure of this nanocatalyst, on the other hand,
should be precisely controlled to avoid unwanted possible impurities including iron
and manganese oxide materials.
Chalcone derivatives have played a very important role in organic chemistry as
important building blocks with a wide range of biological and medicinal properties.
Natural products having chalcone building blocks have been extracted showing
antifungal (Fig. 1, compound 1) [20], antiviral (Fig. 1, compound 2) [21],
antiprotozoal (Fig. 1, compound 3) [22] and antidiabetic activities (Fig. 1,
compound 4) [23].
The Claisen–Schmidt reaction is the most important route toward chalcone
derivatives through the C–C bond forming an aldol condensation between
acetophenone and benzaldehyde derivatives. A literature survey of very recently
published methods revealed a plethora of catalytic conditions which have been used
R1
R4
O
R8
R7
(1) : R1, R3, R6 = OH; R2 = prenyl;
R4, R5, R7, R8 =H;
R2
R3
(2) : R1, R3, R6 = OH; R2 = prenyl;
R4, R7, R8 =H; R5 =OMe
R5
R6
(3): R1, R2, R4, R5 = H; R3, R6 = OH;
R7 = Prenyl; R8 = OMe
(4): R1, R3, R6 = OH; R2 = geranyl,
R4, R5, R7, R8 = H
Fig. 1 Naturally occurring chalcone derivatives with valuable bioactivity effects
123

Design and synthesis of novel natural clinoptilolite-…
to promote this reaction, including the application of strong hydroxide bases and a
wide variety of metallic catalysts in the presence of various solvents at different
temperatures [24–36]. All these methods suffer from one or more serious drawbacks
such as stepwise reaction conditions, demanding inert atmosphere, high reaction
temperatures, long reaction times and limitations in the scope of the reactants.
Therefore, novel heterogeneous catalysts are required so as to overcome these
weaknesses.
According to the above-mentioned considerations and in continuation of our
recent attempts to provide novel green media and catalysts for organic synthesis
[37, 38], in the present study, MnFe2O4-modified natural clinoptilolite (MFO–NC)
was prepared and applied in the Claisen–Schmidt reaction for the synthesis of some
chalcone derivatives. Although various types of modified clinoptilolite have been
reported [39–43], to the best of our knowledge, this is the first time that manganese
ferrite-modified clinoptilolite has been synthesized and applied as an efficient
catalyst.
Experimental
Materials and characterization
The chemicals applied in this work were obtained from Fluka or Merck and used
without further purification. Melting points of the products were recorded on a
KRUSS type KSP1 N melting point meter apparatus and are uncorrected. FT-IR
spectra were recorded on a Bruker Tensor-27 FT-IR spectrometer in KBr pellets. 1H
and 13C NMR spectra were measured on a Bruker DRX-400 spectrometer, at 400
and 100 MHz, respectively, using TMS as an internal standard. Chemical shifts (d)
were reported relative to TMS, and coupling constants (J) were reported in Hertz
(Hz). Mass spectra were recorded on a Shimadzu QP 1100 EX mass spectrometer
with 70-eV ionization potential. Elemental analyses of the new compounds were
performed with a Vario EL III 0 serial no. 11024054 instrument. X-ray diffraction
(XRD) patterns were recorded by a Philips-X’PertPro X-ray diffractometer using
Ni-filtered Cu Ka radiation in a scan range of 10 \ 2h \ 80. Fourier transform
infrared (FT-IR) spectra were recorded on a Magna-IR, spectrometer 550 Nicolet
with 0.125–1 cm resolution in KBr pellets in the range of 400–4000 cm-1. TEM
images were taken on an EM208S Philips transmission electron microscope with an
accelerating voltage of 200 kV. Room-temperature magnetic properties were
investigated using a vibrating sample magnetometer (VSM) device, made by
Meghnatis Daghigh Kavir (Iran) in an applied magnetic field sweeping between
10000 Oe. Energy dispersive X-ray analysis (EDX) was performed by scanning
electron microscopy (LEO-1455VP).
Synthesis of MFO–NC
In order to prepare the homoionic Na?-exchanged form of the clinoptilolite, the
required amount of crude clinoptilolite was stirred in 2 M NaCl solution for about
123

R. Aryan et al.
24 h at 25 °C, and then the Na?-nanozeolite clinoptilolite was filtered off and
washed twice with distilled water (50 mL). The Na?-nanozeolite was dried in an
oven at 100 °C and then 5 g was poured into a 250-mL round-bottomed flask and
4 M sulfuric acid solution (100 mL) was added [44]. This mixture was heated at
80 °C for 1 h, allowed to cool, and then the activated nanozeolite precipitates were
filtered off. The precipitates were washed with distilled water until complete
neutralization and dried at 80 °C.
A homogeneous aqueous solution of 1 g CTAB in 100 ml distilled water was
prepared by stirring for 10 min at 50 °C. This solution was transferred into a round-
bottomed flask and 7 g activated nanozeolite was added to this solution. MnCl2
(3 mmol) was then added at 80 °C under N2 inert atmosphere and the mixture was
stirred for 15 min at this temperature. Next, Fe2(SO4)3.H2O (3 mmol) was added to
the reaction mixture under N2 atmosphere and the reaction was heated at 100 °C for
15 min. Ammonium hydroxide was then added to the solution to reach a pH range
of 13–14. The reaction mixture was stirred at 100 °C for another 2 h. Upon
completion of the reaction, the solution was transferred to a Teflon-lined autoclave
and heated at 250 °C for 4 h. After cooling, the obtained black precipitate was
washed with deionized water and then dried at 100 °C for 12 h. Three modified
nanozeolite catalysts with 10, 20, and 40 wt% of MnFe2O4 nanocrystals in
clinoptilolite, denoted as MFO–NC-1, MFO–NC-2, and MFO–NC-3, respectively,
were prepared. Pure MnFe2O4 was also prepared through similar methodology,
except that no nanozeolite was used in the reaction flask.
General experimental approach for the preparation of chalcone derivatives
catalyzed by MFO–NC-3
Acetophenone derivative (1 mmol), benzaldehyde derivative (1 mmol), MFO–NC-
3 (0.06 g) were poured into a reaction tube containing an EtOH:water (1:1) mixture
(2 ml) as solvent. The reactions were carried out at room temperature within
relatively short times. TLC analysis was applied to monitor the reactions’ progress
(various mixtures of ethyl acetate and n-hexane as eluent). After completion of the
reactions, the reaction mixture was vacuum-filtered off with a Bu¨chi funnel and the
catalyst was further washed with EtOH in order to complete the separation of the
organic products. The organic layer was then poured onto ice and the chalcone
precipitates were collected by vacuum filtration, dried at room temperature and
recrystallized from the EtOH:water mixture whenever necessary.
Spectroscopic data for selected chalcone derivatives prepared in the present study
(see Table 2 in ‘‘Results and discussion’’)
4-((E)-3-oxo-3-phenylprop-1-enyl)benzonitrile (Table 2, entry 1) IR (KBr): 3110,
2221, 1665, 1604 cm-1 1HNMR (400 MHz, CDCl3): d 7.52–7.64 (m, 4H),
.
7.72–7.81 (m, 5H), 8.02 (d, J = 6.8 Hz, 2H).
(E)-3-(3-nitrophenyl)-1-phenylprop-2-en-1-one (Table 2, entry 3) IR (KBr):
3069, 1666, 1604 cm-1 1HNMR (400 MHz, CDCl3): d 7.52–7.68 (m, 5H),
.
7.79–7.90 (m, 2H), 8.02–8.05 (m, 2H), 8.24 (d, J = 7.8 Hz, 1H), 8.49 (s, 1H).
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Design and synthesis of novel natural clinoptilolite-…
(E)-3-(2,4-dichlorophenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (Table 2,
1
entry 7) IR (KBr): 3078, 3005, 2958, 2934 cm-1. HNMR (400 MHz, CDCl3): d
3.95 (s, 6H), 6.90 (d, J = 10 Hz, 1H), 7.27 (d, J = 7.5 Hz, 1H), 7.43–7.49 (m, 2H),
7.59–7.65 (m, 3H), 8.06 (d, J = 15 Hz, 1H).
(E)-3-(4-(benzyloxy)phenyl)-1-(3,4-dimethoxyphenyl)prop-2-en-1-one (Table 2,
.
entry 9) IR (KBr): 3055, 2982, 2829, 2744, 1687, 1652, 1601 cm-1 1HNMR
(400 MHz, CDCl3): d 3.97 (s, 6H), 5.15 (s, 2H), 7.08 (d, J = 8.5 Hz, 2H), 7.37–7.42
(m, 6H), 7.84 (d, J = 8.5 Hz, 2H). 13CNMR (100 MHz, CDCl3): d 55.9, 69.5, 112.7,
114.4, 114.8, 120.6, 123.6, 127.2, 127.9, 128.0, 128.2, 130.1, 132.9, 136.3, 143.7,
151.1, 154.3, 159.2, 187.3 ppm. MS (m/z): 374 (M?). Elemental analysis C24H22O4
Calculated: C, 76.99; H, 5.92; O, 17.09. Found: C, 76.53; H, 6.22; O, 17.25.
N-(4-((E)-3-(3,4-dimethoxyphenyl)-3-oxoprop-1-enyl)phenyl)acetamide (Table 2,
entry 10) IR (KBr): 3350, 3091, 2987, 2936, 1691, 1642 cm-1. 1HNMR (400 MHz,
CDCl3): d 2.21 (s, 3H), 3.97 (s, 6H), 6.92 (d, J = Hz, 1H), 7.25 (s, 1H), 7.52–7.80
(m, 8H) ppm. 13CNMR (100 MHz, CDCl3): d 22.8, 57.6, 112.9, 114.0, 119.9, 120.6,
123.6, 129.5, 129.8, 132.4, 139.7, 145.1, 149.5, 155.6, 168.2, 188.1 ppm. MS (m/z):
325 (M?). Elemental analysis C19H19NO4 Calculated: C, 70.14; H, 5.89; N, 4.31; O,
19.67. Found: C, 69.72; H, 6.17; N, 4.75; O, 19.36.
(E)-3-(2,6-dichlorophenyl)-1-(4-nitrophenyl)prop-2-en-1-one (Table 2, entry 11)
IR (KBr): 3104, 3078, 1665, 1598 cm-1. 1HNMR (400 MHz, CDCl3): d 7.23–7.26
(m, 1H), 7.38–7.41 (m, 2H), 7.64 (d, J = 16 Hz, 1H), 7.90 (d, J = 16 Hz, 1H), 8.14
(d, J = 7.8 Hz, 2H), 8.34 (d, J = 7.8 Hz, 2H) ppm. 13CNMR (100 MHz, CDCl3): d
123.2, 124.9, 126.3, 128.8, 129.9, 132.2, 132.7, 135.1, 141.8, 152.5, 188.7 ppm. MS
(m/z): 321 (M?). Elemental analysis C15H9Cl2NO3 Calculated: C, 55.93; H, 2.82;
Cl, 22.01; N, 4.35; O, 14.90. Found: C, 55.61; H, 3.11; Cl, 21.74; N, 4.76; O, 14.78.
(E)-3-(2,6-dichlorophenyl)-1-(4-fluorophenyl)prop-2-en-1-one (Table 2, entry
16) (KBr): 3101, 3063, 1663, 1601 cm-1 1HNMR (400 MHz, CDCl3): d
.
7.28–7.31 (m, 1H), 7.38–7.46 (m, 2H), 7.63–7.67 (m, 3H), 7.86 (d, J = Hz, 2H),
8.10 (d, J = 7.8 Hz, 1H), ppm. 13CNMR (100 MHz, CDCl3): d 115.1, 115.4, 124.9,
126.2, 129.3, 130.8, 131.6, 131.9, 132.1, 134.4, 134.7, 135.0, 135.5, 161.8, 166.9,
189.2 ppm. MS (m/z): 295 (M?). Elemental analysis C15H9Cl2FO Calculated: C,
61.04; H, 3.07; Cl, 24.02; F, 6.44; O, 5.42. Found: C, 60.79; H, 3.36; Cl, 23.8‘; F,
6.12; O, 5.93.
Results and discussion
The prepared magnetic MnFe2O4-modified natural clinoptilolite nanocomposite was
first characterized by XRD, FT-IR, EDX, VSM and TEM analyses (see Electronic
Supporting Information, ESI). In order to characterize the phase and purity of the as-
prepared products, X-ray diffraction patterns were used (Fig S1, ESI file).
Figures S1a–S1c show the XRD pattern of three different samples after the one-
pot hydrothermal reaction including MFO–NC-1, MFO–NC-2, and MFO–NC-3,
respectively. It can be seen that a mixed phase of clinoptilolite and MnFe2O4 is
formed in all the samples. Moreover, some weak peaks representative of a-Fe2O3
impurity are also observed. The appearance of a-Fe2O3 sometimes occurs,
123

R. Aryan et al.
especially when MnFe2O4 is accompanied by other modifying agents. For instance,
Hu et al. [45] observed a-Fe2O3 and b-MnO2 when they tried to prepare modified
MnFe2O4. It occurs because the stoichiometry of the initial salts changes due to the
interactions of a part of the precursor with the host sample.
The diffraction peaks corresponding to MnFe2O4 are in agreement with the
mineral called Jacobsite with the JCPDS No. of 01-074-2403, a cubic crystal
system, and Fd-3 m space group. The related peaks of the embedded MnFe2O4
nanocrystals located at 2h = 29.5°, 34.1°, 42.5°, 45.9°, 52.0°, 55.1°, 61.5°, 64.0°,
65.5°, and 69.2° are related to (220), (311), (400), (331), (422), (333), (440), and
(620), respectively. The XRD pattern of clinoptilolite crystallites are assigned to the
JCPDS No. 39-1383 which is in agreement with the previous reports of the Iranian
clinoptilolite from the Semnan region [41]. By tracking the intensities of the
MnFe2O4 crystalline lines, it is obvious that, from Fig. S1a to S1c, the peaks are
getting sharper, while, on the other hand, the lines of a-Fe2O3 are getting weaker.
This shows that higher amounts of iron and manganese concentration result in better
crystallization of the MnFe2O4 phase in the clinoptilolite lattice.
For characterization of the surface chemistry and functional groups of the
sample, FT-IR spectra of tthe hree MFO–NC samples were recorded and atr shown
in Fig S2a-d for natural clinoptilolite, MFO–NC-1, MFO–NC-2, and MFO–NC-3
samples, respectively. In all cases, the wide band at 3430 cm-1 is due to the
vibration of the O–H….O hydrogen bond of Si–O(H)–Al. In addition, the bands
appearing at 1636 and 1091 cm-1 are attributed to the deformation vibration of the
absorbed water and the asymmetric valence vibrations in tetrahedral SiO4,
respectively [46]. The bands observed in the range of 705–660 cm-1 are assigned
to the vibrations of 4- and 6-membered rings in the zeolite structure [47]. It has been
shown that, by entering transition metal oxides into zeolitic frameworks, the
vibrations below 900 cm-1 may be shifted [41]. In Fig. S2a–d, it can be seen that
the vibration at 471 cm-1 in the FT-IR spectrum of pure natural clinoptilolite
(Fig. S2a) is shifted to higher wavenumbers after incorporation of MnFe2O4 into the
zeolite structure. However, such shifts are not obvious for the peaks at 611 and
796 cm-1. The peak at 471 cm-1 is related to the bending vibrations of Si–O or Al–
O and the observed slight shift in this peak shows a change in the bond strength due
to the incorporation of MnFe2O4 in the zeolite rings. The absorption bands of Mn–
O and Fe–O bonds generally appear at 404, 502, and 556 cm-1, respectively [48],
which have overlapped with clinoptilolite peaks and are not clearly observed in
these spectra.
TEM images of natural clinoptilolite and MFO–NC (sample MFO–NC-3) are
shown in Fig. S3a–S3b and S3c–S3d with different magnifications, respectively. In
Fig. S3a–S3b, only the clinoptilolite structure is detected and no nanoparticles are
observed in its structure. The similar contrast of the sample shows that the chemical
structure is the same. For MFO–NC (Fig. S3c–S3d), in both images, it is clear that
the MnFe2O4 nanoparticles with cubic and spherical shapes are embedded in the
clinoptilolite layers. The size range of the nanoparticles was found to be 90–130 nm
and they were not agglomerated. Different contrasts of nanoparticles and natural
clinoptilolite show different chemical structure of the materials.
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Design and synthesis of novel natural clinoptilolite-…
The elemental compositions of the samples were characterized by using EDX
spectroscopy. Fig. S4a–c shows the EDX spectra of the MFO–NC-1, MFO–NC-2,
and MFO–NC-3 samples, respectively. The presence of Si, Al, and O, which are
from clinoptilolite and Fe, Mn, and O, due to the incorporation of MnFe2O4
nanoparticles are confirmed by EDX. It can be observed that the Fe:Mn ratios for
the samples MFO–NC-1, MFO–NC-2 and MFO–NC-3 are 2.33, 2.26, and, 2.14,
respectively.
VSM analysis was carried out for MFO–NC-1, MFO–NC-2, and MFO–NC-3 at
room temperature and revealed ferromagnetic behavior of all the samples (Fig. S5,
left). The measured values of saturation magnetization (Ms) were 3.55, 3.05, and
0.23 emu.g-1 and the remnant magnetization (Mr) values were 0.05, 1.44, and 1.52
emu.g-1 for MFO–NC-1, MFO–NC-2, and MFO–NC-3, respectively. These values
are much lower than those of the reported bare MnFe2O4 particles (Ms * 35
emu.g-1 and Mr * 5 emu g-1) [49], which shows the effect of clinoptilolite in
decreasing the magnetization of the product. The coercivities of the samples were
100.3, 190.2, and 122.6 Oe for MFO–NC-1, MFO–NC-2, and MFO–NC-3,
respectively, which shows the resistance of the sample against demagnetization.
These results show that the MFO–NC-2, and MFO–NC-3 samples are easily
removed by an external magnetic field after the completion of the catalytic reaction.
This fact is shown in Fig. S5, right, which demonstrates that that MFO–NC-1 was
not removed by an external magnet even after 5 min. However, both MFO–NC-2,
and MFO–NC-3 samples were easily separated by the magnet under 1 min.
The catalytic efficiency of the as-prepared MFO–NC nanocomposites was
investigated in the Claisen–Schmidt reaction for the preparation of chalcone
derivatives. The model reaction was performed using acetophenone (1 mmol),
4-chlorobenzaldehyde (1 mmol) and various catalysts including pure natural
clinoptilolite, nano-MnFe2O4 and the three as-prepared MFO–NC nanocomposites
(0.06 g) (Table 1) in the presence of various solvents at room temperature.
(Scheme 1).
The model reaction did not proceed in the presence of MnFe2O4 and natural
clinoptilolite as individual catalysts. The reaction was also slow in the presence of
MnFe2O4 as the catalyst and a low yield of chalcone was obtained (Table 1, entry
1). The pure natural clinoptilolite showed less catalytic activity, and no sign of
chalcone was observed even after 10 h (Table 1, entry 2), although a strong
synergistic effect was established between the magnetic nano-MnFe2O4 and the
natural clinoptilolite as the building components of nanocomposite catalysts MFO–
NC-1 to MFO–NC-3 (Table 1, entries 3–9). For ferrites, the catalytic activity
depends upon a variety of factors, such as the particle size, morphology and redox
properties of metal ions and their distribution among the tetrahedral (A) sites and
octahedral (B) sites of the cubic spinel lattice. The metal ions present in the
octahedral sites play a crucial role in catalysis. This is because the octahedral sites
are exposed on the surface. Mn3? ions have a preference for the octahedral sites of
the ferrite sub-lattice. The synergistic effect between the Fe–Mn ions present in the
octahedral sites comes into play. [50] Therefore, the modification of the
clinoptilolite surface by manganese ferrite nanoparticles provides a good opportu-
nity for Mn3? and Fe3? ions to be better exposed to the reactants to use their Lewis
123

R. Aryan et al.
O
O
O
Catalyst
+
Solvent
r.t.
Cl
Cl
Scheme 1 Model Claisen–Schmidt reaction catalyzed by various novel clinoptilolite modified by
manganese ferrite
Table 1 Optimization of the model Claisen–Schmidt reaction catalyzed by novel nanozeolite-modified
manganese ferrite
Run
No.
Catalysta
Solventb
Time
(min.)
Yield
(%)c
Comments
1
2
MnFe2O4(MFO)
EtOH:H2O
(1:1)
300
600
42
–
Natural clinoptilolite
(NC)
EtOH:H2O
(1:1)
Mixture of reactants and
product
3
4
MFO–NC-3
MFO–NC-3
EtOH
Water
120
720
61
–
Mixture of reactants and
product
5
6
7
MFO–NC-3
MFO–NC-3
MFO–NC-1
DMF
300
330
60
67
54
90
No Solvent
EtOH:H2O
(1:1)
8
9
MFO–NC-2
MFO–NC-3
EtOH:H2O
(1:1)
45
15
93
96
EtOH:H2O
(1:1)
aCatalyst loading was 0.06 g per 1 mmol of benzaldehyde
bAmount of solvent used was 2 ml per 1 mmol of benzaldehyde
cIsolated yield
acidity and facilitate the formation of chalcone derivatives. Correspondingly, the
MFO–NC-3 with the highest weight percentage of manganese ferrite nanoparticles
is expected to show the best catalytic activity among these three nanocomposites
(Table 1, entries 3–6 and 9). Moreover, as can be inferred from the TEM images of
MFO–NC-3 as the most prosperous catalyst, modification of the natural clinoptilo-
lite surface by MnFe2O4 inhibited the aggregation of the magnetic nanoparticles.
This reasonably led to the maintaining of the high surface area of MnFe2O4
necessary for optimum catalytic activity and catalyst stability. The reaction times
were significantly decreased and yields were considerably increased in the presence
of these as-prepared catalysts. The reactions were also carried out in pure ethanol,
water, dimethylformamide (DMF) and under solvent-free conditions in the presence
of MFO–NC-3 catalyst. In the case of water as solvent, the reaction was not
completed even after 12 h and the TLC analysis showed a mixture of reactants and
123

Design and synthesis of novel natural clinoptilolite-…
product (Table 1, entry 4). Under solvent-free conditions and in DMF as solvent, the
model reaction proceeded slowly and moderate yields were obtained using MFO–
NC-3 as the catalyst (Table 1, entries 5 and 6). The reaction was rather faster in pure
ethanol as the solvent and using MFO–NC-3 as the catalyst, but the yield was still
moderate. Using an ethanol:water (1:1) mixture as the solvent resulted in shorter
reaction times and excellent yields (Table 1, entries 7–9). In these cases, the three
MFO–NC catalysts were satisfactorily applied in the model reaction but the MFO–
NC-3 showed a better catalytic activity by accomplishing the reaction within only
15 min and the best yield was obtained (Table 1, entry 9). Therefore, the MFO–NC-
3 and ethanol:water (1:1) mixture were chosen as the best reaction conditions for the
model reaction.
Next, catalyst loading was examined for the model reaction with various amounts
of MFO–NC-3 in ethanol:water (1:1) at room temperature (Fig. 2). As indicated in
Fig. 2, the higher amounts of MFO–NC-3 did not noticeably affect the reaction time
and yield, while lower catalyst loading led to a slower reaction rate with similar
yield. So, the amount of 0.06 g was chosen as the optimum amount of catalyst.
In order to examine the scope and generality of this novel catalytic protocol for
the preparation of chalcone derivatives, various acetophenone and benzaldehyde
derivatives possessing divergent electron demands were applied under the optimum
reaction conditions (Scheme 2; Table 2; Fig. 3).
The results in Table 2 show a high electronic tolerance of the optimum catalyst
for the present protocol. Electron-donating and electron-withdrawing substituents
on the two reactants did not affect the rate and the facility of the process, and in all
cases the products were prepared efficiently within short reaction times and good to
excellent yields. Also, the products were easily separated from the catalyst by
vacuum filtration using a Bu¨chi funnel, and in many cases no further purification
was needed.
A plausible mechanism has been proposed for the clarification of the role of the
MFO–NC-3 nanocomposite as the catalyst in the synthesis of chalcones according
to the above-mentioned considerations (Scheme 3). Both the acetophenone and
¨
benzaldehyde derivatives are activated by the dual Lewis acidic and Bronsted basic
96
89
95
98
81
100
50
60
30
15
0.06
15
0.08
15
0.1
0.02
1
0.04
2
0
3
4
5
Catalyst amount (g)
Time (min.)
Fig. 2 Effect of MFO–NC-3 catalyst loading on the Claisen–Schmidt reaction. All reactions were
performed using 1 mmol of the reactants in 2 ml of ethanol: water (1:1) at room temperature
123

R. Aryan et al.
O
O
O
MFO-NC-1
+
X
Y
Y
X
EtOH:H2O
(1:1), r.t.
2
3
1
X = H, 4-Br, 4-F, 4-NO2, 3,4-(OMe)2
Y = 4-Cl, 2,4-(Cl)2, 2,6-(Cl)2, 3-NO2,
4-NO2, 4-BnO, 4-AcNH, 4-Br, 2-Cl
Scheme 2 The scope and generality of MFO–NC-3-catalyzed synthesis of chalcone derivatives
Table 2 Synthesis of various chalcone derivatives using the MFO–NC-3 nanocomposite catalyst under
optimized reaction condoitions (Fig. 3)
Run no.
Product no.
Time (min.)
Yield (%)a
m.p. (°C)
Lit. m.p. (°C)
1
2
3
4
5
3a
3b
3c
3d
3e
3f
30
15
15
45
20
10
45
30
25
15
25
25
15
30
45
45
25
88
96
93
84
87
95
85
89
91
94
93
83
89
88
86
85
92
150–153
115–117
155–157
199–203
169–172
161–162
135–137
138–140
130–133
79–81
151–153 [51]
114–115 [52]
159–162 [52]
210–212 [52]
–
–
6
3g
3h
3i
110–112 [53]
132–135 [54]
128 [55]
–
7
8
9
3j
10
11
12
13
14
15
16
3k
3l
210–213
148–150
205–210
186–188
84–86
–
–
3m
3n
3o
3p
3q
202–205 [56]
183–185 [57]
88–91 [54]
102–103 [58]
–
85–86
112–115
aIsolated crude yields
features of nano-manganese ferrite supported on the surface of natural clinoptilolite.
The enolate of acetophenone is formed in the presence of O-2 anions of MnFe2O4 as
stronger nucleophilic species. Then, this enolate attacks the benzaldehyde derivative
coordinated to the Fe?3 and Mn?2 ions, leading to the formation of intermediate A,
which undergoes dehydration to provide the desired chalcone derivative.
Subsequently, the catalyst reusability was examined in the model reaction as a
significant factor in the application of novel heterogeneous catalysts. The
nanocomposite catalyst MFO–NC-3 was filtered off the reaction medium after
completion of the reaction, dried, and reapplied in the model reaction along with
4-chlorobenzaldehyde and acetophenone as reactants. The reaction was then carried
out for 15 min at room temperature and the results are shown in Fig. 4.
123

Design and synthesis of novel natural clinoptilolite-…
O
O
O
NO2
CN
Cl
O
3b
3a
3c
O
O
O
Cl
O
Ph
N
H
Cl
Cl
3e
3d
3f
O
O
Cl
O
3i
MeO
MeO
MeO
MeO
MeO
Cl MeO
Cl
3g
3h
3j
NO2
O
O
MeO
MeO
MeO
MeO
O
Ph
O
N
H
3k
O
Cl
O
O2N
Br
O2N
Cl
NO2
Cl
3m
3l
O
O
Br
Br
3o
O
3n
O
Cl
Cl
F
Br
Cl
Cl
3p
3q
Fig. 3 The scope of the MFO–NC-3 catalyzed Claisen–Schmidt reaction
As indicated, only a slight loss of catalytic activity was observed after 4 reaction
runs, which implies a good reusability of this novel catalytic system in catalysing
the Claisen–Schmidt reaction.
Conclusion
A novel heterogeneous natural clinoptilolite-based catalyst was introduced by
modifying the surface of natural clinoptilolite with various amounts of nano-
manganese ferrite. These catalysts were characterized by XRD, FT-IR, EDX, TEM
and VSM analyses. Then, the application of these catalysts was examined in the
Claisen–Schmidt reaction for the synthesis of chalcones as a very important class of
123

R. Aryan et al.
Ar2
Scheme 3 Proposed
H
mechanism for the MFO–NC
catalyzed Claisen–Schmidt
reaction synthesis of chalcone
derivatives
O
Ar2
HO
Ar1
O
Ar1
O
O
A
O
O
Ar1
-H2O
O
O
O
Ar1
Ar2
HO
OH
OH
HO
O
= Nano MnFe2O4
MnFe2O4 modified
Natural Clinoptilolite
Nanocatalyst Reusability
98
98
92
88
100
80
60
40
20
0
15
15
15
15
Yield (%)
Time (min)
1
2
3
4
Time (min)
Yield (%)
Fig. 4 Reusability of MFO–NC-3 catalyst in the model reaction for the synthesis of chalcones
organic building blocks with a wide range of applications. A strong synergistic
collaboration was observed between the magnetic nano-MnFe2O4 and natural
clinoptilolite as the building components of nanocomposite catalysts. Even though
the MnFe2O4 and natural clinoptilolite individually failed to effectively promote the
process, the reactions were successfully catalyzed by the as-prepared MFO–NC-3
nanocomposite having 40 wt% of MnFe2O4 relative to natural clinoptilolite at room
temperature under mild conditions, achieving the desired products within short
reaction times with good to excellent yields, and without any laborious purification
method. The catalyst was easily collected and separated from the reaction mixture
by an external magnet and vacuum filtration. The MFO–NC-3 catalyst also showed
123

Design and synthesis of novel natural clinoptilolite-…
valuable catalytic activities over a broad range of reactants with various electron
demands and the corresponding chalcones were obtained with good to excellent
yields. Moreover, the MFO–NC-3 showed a notable reusability and was repeatedly
used four times with an infinitesimal loss of catalytic activity.
Acknowledgements The corresponding author gratefully acknowledges helpful scientific consultations
from Dr. Masoomeh Nojavan. Partial financial support of this work by University of Zabol Research
Council and the Dean of the Faculty of Science are also appreciated.
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