Green Synthesis Using Tragacanth Gum and Characterization of Ni–Cu–Zn Ferrite Nanoparticles as a Magnetically Separable Catalyst for the Synthesis of Hexabenzylhexaazaisowurtzitane Under Ultrasonic Irradiation

Article abstract of DOI:10.1134/S0022476618070296

In this work, we report the synthesis, characterization, and catalytic evaluation of Ni–Cu–Zn ferrite using tragacanth gum as a biotemplate and metal nitrates as the metal source by the sol-gel method without using any organic chemicals. The sample is cha

Full text of DOI:10.1134/S0022476618070296

Journal of Structural Chemistry. Vol. 59, No. 7, pp. 1730-1736, 2018.
Original Russian Text © 2018 S. Taghavi Fardood, A. Ramazani, Z. Golfar, S. W. Joo.
GREEN SYNTHESIS USING TRAGACANTH GUM
AND CHARACTERIZATION OF Ni–Cu–Zn FERRITE
NANOPARTICLES AS A MAGNETICALLY SEPARABLE
CATALYST FOR THE SYNTHESIS
OF HEXABENZYLHEXAAZAISOWURTZITANE
UNDER ULTRASONIC IRRADIATION
1
S. Taghavi Fardood , A. Ramazani , Z. Golfar ,
1,2
1
3
and S. W. Joo
In this work, we report the synthesis, characterization, and catalytic evaluation of Ni–Cu–Zn ferrite using
tragacanth gum as a biotemplate and metal nitrates as the metal source by the sol-gel method without using
any organic chemicals. The sample is characterized by powder X-ray diffraction (XRD), Fourier transform
infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), scanning electron microscopy
(SEM), and energy dispersive X-ray analysis (EDX). The powder XRD analysis reveals the formation of
cubic-phase ferrite MNPs with an average particle size of 20 nm. The magnetic analysis reveals that the
Ni–Cu–Zn ferrite nanoparticles have ferromagnetic behavior at room temperature with a saturation
magnetization of 52.76 emu/g. The catalytic activity of Ni–Cu–Zn ferrite MNPs is evaluated for the
synthesis of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo [5.5.0.05,9.03,11]dodecane (HBIW)
under ultrasonic irradiation. Mild reaction conditions, short reaction times, the use of an economically
convenient catalyst, and excellent product yields are the advantageous features of this method. The catalyst
could be easily recycled and reused few times without a noticeable decrease in the catalytic activity.
DOI: 10.1134/S0022476618070296
Keywords: ferrite, tragacanth gum, natural gel, hexabenzylhexaazaisowurtzitane (HBIW), ultrasonic
irradiation.
INTRODUCTION
Soft ferrites have been extensively used for many kinds of magnetic devices such as transformers, inductors, and
magnetic heads for a high frequency because their electrical resistivity is higher than those of soft magnetic alloys. Various
substitutions have been incorporated to achieve the desired electrical and magnetic properties [1-4]. Therefore, the synthesis
of soft ferrites by a facile and green method is interesting. In general, ferrites belong to a large class of compounds having
1
2
Department of Chemistry, University of Zanjan, Zanjan, Iran; saeidt64@gmail.com. Research Institute of Modern
3
Biological Techniques, University of Zanjan, Zanjan, Iran; aliramazani@gmail.com. School of Mechanical Engineering,
Yeungnam University, Gyeongsan, Republic of Korea; swjoo@yu.ac.kr. The text was submitted by the authors in English.
Zhurnal Strukturnoi Khimii, Vol. 59, No. 7, pp. 1789-1795, September-October, 2018. Original article submitted November
9, 2017.
1730
0022-4766/18/5907-1730 © 2018 by Pleiades Publishing, Ltd.

a spinel structure. Their physical properties are related to the structure of solids. The spinel unit cell consists of a cubic array
3+ 2+
of 32 oxygen anions, 16 Fe ions, and 8 Fe ions. A total of 24 metal cations are partitioned between eight tetrahedral and
2+
16 octahedral interstices. In NiCuZn spinel ferrites, Zn ions are known to prefer the occupation of tetrahedral (A) sites [5, 6]
2+
2+
3+
while Ni and Cu ions prefer the occupation of octahedral (B) sites, and Fe ions partially occupy the A and B sites [5, 7].
Highly energetic compounds play an important role in the defense industry and other high-tech fields. In recent
years, cage crystal molecules containing nitro groups have received great attention and are widely used as energetic materials
[8, 9]. Hexanitrohexaazaisowurtzitane (HNIW or CL-20) with a wurtzitane ring system including nitramine, is the most
prominent and relatively new powerful explosive in this class [10-12]. Hexabenzylhexaazaisowurtzitane (HBIW) is used as
a precursor for the synthesis of HNIW. The condensation of glyoxal with benzylamine in the presence of formic acid as
a catalyst is the only available method for constructing the HBIW cage [13, 14]. This method is efficient, but the catalyst
could not be recovered and reused. Therefore, the introduction of efficient procedures with easily separable and reusable
catalysts for the HBIW preparation is needed. For this purpose the use of magnetic catalysts such as Ni–Cu–Zn ferrite has
received considerable attention. Its remarkable catalytic activity, easy synthesis, nontoxicity, reusability, economic viability,
ecofriendliness, and recoverability encouraged us to utilize it as a catalyst for the HBIW synthesis.
Tragacanth gum (TG) is an acidic polysaccharide obtained from the bark of Astragalus gummifer (Fabaceae family),
a native tree of Western Asia. Tragacanth gum is most commonly found in Iran [15, 16]. In the present study, we have
synthesized Ni–Cu–Zn ferrite nanoparticles by Tragacanth gel without any surfactant. The catalytic activity of Ni–Cu–Zn
ferrite nanoparticles has been evaluated for the HBIW synthesis with a facility and the appropriate method under eco-friendly
conditions, as shown in Scheme 1.
2 4
Scheme 1. HBIW synthesis in the presence of NiCuZnFe O MNPs.
EXPERIMENTAL
Materials and techniques. Tragacanth gum (TG) was obtained from a local health food store. All the chemicals
were purchased from Fluka AG, Merck, daijung (Darmstadt, Korea), Aldrich and were used without further purification. The
reactions were monitored by TLC. Sonication was performed in Bandelin (Berlin, Germany) SONOPULS ultrasonic
homogenizers with a 20 kHz processing frequency, a nominal power of 250 W, and uniform sonic waves. The melting point
was measured with an Electrothermal 9100 apparatus (LABEQUIP LTD., Markham, Ontario, Canada) and was uncorrected.
1
13
6 6
H (DMSO-d ) and C NMR (DMSO-d ) spectra were recorded on a Bruker DRX-250 Avance spectrometer at 250.13 MHz
and 62.90 MHz, respectively.
The synthesized nanoparticles were characterized by four methods. Diffraction patterns and crystal structures of NPs
were analyzed by XRD (X′Pert-PRO advanced diffractometer) at 40 kV with Cu(K
α
) radiation (40 mA current, wavelength:
1.5406 Å) at room temperature in the 2θ range from 20° to 70°; the powder form of NPs was kept in sample tubs with
double-sided tape to determine the structural morphology by SEM (Zeiss EVO 18) with an energy dispersive X-ray
spectrometer (EDX) installed. The IR spectra were measured on a Jasco 6300 FT-IR spectrometer (KBr disks); the magnetic
properties of sample were identified by vibrating sample magnetometer (VSM, Meghnatis Kavir Kashan Co., Kashan, Iran).
Methods. Preparation of Ni0.35Cu0.25Zn0.4Fe
0 ml of deionized water and stirred for 80 min at 70 °C to achieve a clear Tragacanth gel (TG) solution. Then, 0.35 mmol of
Ni(NO ⋅6H O, 0.25 mmol of Cu(NO ⋅6H O, 0.4 mmol of Zn(NO ⋅6H O, and 2 mmol of Fe(NO ⋅9H O were added to
2 4
O MNPs. Firstly, 0.2 g of Tragacanth gum (TG) was dissolved in
4
)
3 2
2
)
3 2
2
)
3 2
2
)
3 3
2
1731

the TG solution. The reaction was performed at 75 °C in a sand bath with continuous stirring until the formation of brown
resin. Finally, the powder was calcined at 700 °C for 4 h.
Typical procedure for the HBIW synthesis. Benzylamine (0.0085 mol, 0.937 ml), NiCuZnFe O MNPs (7% mol
2 4
with respect to glyoxal), acetonitrile (7.75 ml), and water (0.775 ml) were placed in a round-bottomed flask of 100 ml. The
reaction mixture was stirred at room temperature and glyoxal (40% aqueous solution; 0.00375 mol, 0.427 ml) was added
dropwise (15 min). Then the mixture was irradiated with ultrasound with a power of 150 W for 5 min. The HBIW formation
was monitored by TLC. After the completion of the reaction, the reaction mixture was washed with excess cold ethanol and
the catalyst was removed by a magnetic field. The precipitate was collected by simple paper filtration. For further purification
acetonitrile was used. The reaction yield was 95% based on the obtained recrystallized product.
Spectral data. White solid; m.p.: 155-157 °C. FT-IR (KBr): 3022, 2942, 2835, 1951, 1601, 1450, 1351, 1169, 1138,
1
89, 926, 836, 732, 699. HNMR (CDCl
9
3 H 2 2
) δ : 7.24-7.28 (m, 30H, phenyl CH), 4.16 (s, 4H, CH ), 409 (s, 8H, CH ), 4.04 (s,
13
H, CH), 3.57 (s, 2H, CH). CNMR (CDCl ): 56.21-56.88 (6C, CH -phenyl), 76.51-80.64 (6C, CH (skeletal), 126.62-140.74
4
3
2
(36C, phenyl).
RESULTS AND DISCUSSION
Catalyst characterization. The analysis of FT-IR spectra suggests two ranges of the absorption bands: in the range
–1 –1
00-1000 cm , a metal–oxygen absorption band, typical of the spinel structure of ferrite, was observed at 580 cm (Fig. 1).
4
This band strongly suggests the intrinsic stretching vibrations of metal (Fe ↔ O) at the tetrahedral site. The bands at
–
1
–1
404 cm and 1632 cm are attributed to the hydroxyl group (O–H) vibrations. The peaks at 1456 cm and 1017 cm
–1
–1
3
correspond to C–O and –C–O–C stretching modes [17].
The XRD pattern of as-synthesized NiCuZnFe
2
O
4
prepared through the sol-gel method is shown in Fig. 2. It is seen
from Fig. 2 that the XRD pattern consists of well-resolved peaks, which confirms the polycrystalline and monophasic nature
of the prepared material.
Fig. 1. FT-IR spectra of Ni0.35Cu0.25Zn Fe O MNPs.
0.4 2 4
Fig. 2. XRD pattern of Ni0.35Cu0.25Zn Fe O MNPs calcined in air at
0.4 2 4
700 °C for 4 h.
1732

The identical XRD pattern of the sample exhibiting diffraction peaks at 2θ of 29.93, 35.36, 37.11, 43.01, 53.65,
56.83, and 62.51 corresponding to the (220), (311), (222), (400), (422), (511), and (440) planes of the crystal lattice,
respectively, reveal their cubic structure, as found in the standard reference data (JCPDS Card no. 48-0489).
The average ferrite crystallite size can be calculated from the most intense (311) peak of the XRD pattern with the
aid of the Scherrer formula
D = 0.9λ/βcosθ,
α
where D is the crystallite size; λ is the incident X-ray wavelength (CuK = 1.54 Å); θ is the diffraction angle; β is the full
width at half maximum (FWHM) of the most intense (311) diffraction peak [18]. We calculated an average crystallite size of
0 nm for the sample.
The SEM image of green synthesized NiCuZnFe O MNPs is shown in Fig. 3. The morphology of synthesized
2
2
4
MNPs identified the average size of 30-50 nm. The particles were clearly identified by their spherical shapes.
In order to study the magnetic behavior of Ni0.35Cu0.25Zn0.4Fe –NPs, magnetization measurements recorded with
VSM were performed. The magnetization curve shows the ferromagnetic properties with magnetic remanence (M ) and
coercive force (H ) being 80.14 Oe and 4.03 emu/g, respectively. As can be observed in Fig. 4, the specific saturation
2 4
O
r
c
magnetization value was measured to be 52.76 emu/g for the sample.
EDX was performed to characterize the composition of the obtained nanoparticles. Fig. 5 demonstrates that
2 4
Ni0.35Cu0.25Zn0.4Fe O MNPs obtained contains Ni, Cu, Zn, Fe, and O.
The role of the prepared catalyst in the HBIW synthesis was investigated under ultrasonic irradiation. We optimized
the reaction conditions such as the catalyst amount, ultrasonic power, solvent type, and reaction times.
Fig. 3. SEM image of Ni0.35Cu0.25Zn0.4Fe O
2
4
MNPs.
Fig. 4. Magnetization curve of Ni0.35Cu0.25Zn0.4Fe
2 4
O
MNPs.
Fig. 5. EDX micrograph of Ni0.35Cu0.25Zn Fe O
0.4 2 4
MNPs.
1733

Effect of the catalyst amount on the product yield. In order to verify the catalyst effect on the product yield, the
reaction between benzylamine and glyoxal was carried out under different catalytic conditions. As shown in Table 1, when
2 4
the reaction was carried out in the presence of Ni–Cu–ZnFe O MNPs (7 mol% with respect to glyoxal), it led to the desired
product in a 95% yield (Table 1, entry 4). In the absence of a catalyst, the reaction yielded only 14% of the product within
min (Table 1, entry 1).
Effect of various solvents on the product yield. We have investigated the effect of various solvents such as
acetonitrile, chloroform, ethanol, methanol, and dichloromethane on the HBIW synthesis under ultrasound irradiation (5 min,
50 W). The results were summarized in Table 2. It is demonstrated that acetonitrile was the best choice for the model
reaction.
5
1
Effect of the reaction time on the product yield. In order to optimize the reaction time, different reaction times
selected for this study were 1 min, 3 min, 5 min, and 10 min. The effect of the reaction time on the HBIW performance was
examined and the results are reported in Table 3.
Effect of the ultrasound power on the product yield. The effect of ultrasonic power inputs from 50 W to 200 W
on the HBIW synthesis was evaluated (Table 4). The reaction yield increased with the ultrasonic power at 150 W in
comparison to 50 W and 100 W but decreased at 200 W.
2 4
The catalytic activity and the ability to recycle and reuse of Ni–Cu–ZnFe O MNPs were studied in this system.
After the magnetic separation of the catalyst from the reaction mixture, the catalyst was washed with ethanol and dried to
remove any remaining ethanol, and reused in the further reactions for several times. The average chemical yield for six
consecutive runs was 89%, which clearly demonstrates the practical recyclability of this catalyst (Fig. 6).
2 4
A comparison of the catalytic efficiency of Ni–Cu–ZnFe O MNPs with other catalysts for the HBIW synthesis is
listed in Table 5. The result displays that this catalyst is superior to some other catalysts in terms of the magnetic separation,
reusability, reaction time, and yield.
TABLE 1. Effect of the Catalyst in the HBIW Synthesis
Ultrasonic
power, W
a
Yield , %
Entry
Catalyst, mol%
Time, min
1
2
3
4
5
None
150
150
150
150
150
5
5
5
5
5
14
67
90
95
95
3
5
7
10
Reaction conditions: benzylamine (0.0085 mol, 0.937 mL), glyoxal (0.0037 mol, 0.427 mL), CH
O (0.775 mL), and Ni–Cu–ZnFe MNPs (mol% with respect to glyoxal).
a
3
CN (7.75 mL),
H
2
2 4
O
Isolated yields.
TABLE 2. Synthesis of HBIW in the Presence of Ni–Cu–ZnFe
2
O
4
MNPs in Different Solvents
a
Yield , %
Entry
Solvent
1
2
3
4
5
Acetonitrile
Chloroform
Ethanol
95
63
67
78
58
Methanol
Dichloromethane
Reaction conditions: benzylamine (0.0085 mol, 0.937 ml), glyoxal (0.0037 mol, 0.427 ml), solvent (7.75 ml), H
0.775 ml), and Ni–Cu–ZnFe MNPs (7 mol% with respect to glyoxal).
Yield of the product under ultrasound irradiation (5 min, 150 W).
2
O
(
2 4
O
a
1734

TABLE 3. Different Runs for Choosing the Optimum Duration
a
Yield , %
Entry
Tim, min
1
2
3
4
1
3
41
78
95
95
5
10
Reaction conditions: benzylamine (0.0085 mol, 0.937 ml), glyoxal (0.0037 mol, 0.427 ml), acetonitrile (7.75 ml),
O (0.775 ml), and Ni–Cu–ZnFe MNPs (7 mol% with respect to glyoxal).
Ultrasound irradiation (150 W).
H
2
2 4
O
a
TABLE 4. Effect of the Ultrasonic Irradiation Power on the HBIW Synthesis
a
Yield , %
Entry
Power, W
Time, min
1
2
3
4
50
5
5
5
5
62
86
95
93
100
150
200
Reaction conditions: benzylamine (0.0085 mol, 0.937 ml), glyoxal (0.0037 mol, 0.427 ml), acetonitrile (7.75 ml),
O (0.775 ml), and Ni–Cu–ZnFe MNPs (7 mol% with respect to glyoxal).
a
H
2
2 4
O
Yield of the product.
Fig. 6. Recyclability of Ni0.35Cu0.25Zn Fe O MNPs.
0.4 2 4
TABLE 5. Comparison of the Catalytic Activity of Ni–Cu–ZnFe
2
O
4
with Several Known Catalysts
a
Yield , %
Entry
Catalyst
Solvent
Conditions
Time, min
References
1
2
3
4
5
6
H
2
SO
Chloric(VII) acid
Citric acid
SiO NPs
CuFe MNPs
Ni–Cu–ZnFe MNPs
4
MeOH
60 °C
50 °C
US
540
360
5
67
68
89
89
89
95
[19]
[20]
Water/MeOH
Water/acetonitrile
Water/acetonitrile
Water/acetonitrile
Water/acetonitrile
[21]
2
US
5
[8]
2
O
4
US
16
5
[22]
2
O
4
US
[This work]
Reaction conditions: benzylamine (0.0085 mol, 0.937 ml), glyoxal (0.0037 mol, 0.427 ml), acetonitrile (7.75 ml),
O (0.775 ml), and Ni–Cu–ZnFe MNPs (7 mol% with respect to glyoxal).
Yield of the product under ultrasound irradiation (5 min, 150 W).
H
2
2 4
O
a
1735

CONCLUSIONS
2 4
In this study, we have reported the green synthesis of Ni0.35Cu0.25Zn0.4Fe O nanoparticles by the sol-gel method with
tragacanth gel (TG) as a biopolymeric template. A single phase with a cubic spinel structure was formed after heat treatment
at 700 °C for only 4 h. This method has many advantages such as nontoxicity, economic viability, easiness to scale up, less
time consuming and environmentally friendly approach for the synthesis of Ni–Cu–Zn ferrite nanoparticles without using any
organic chemicals. The catalytic activity of Ni–Cu–Zn ferrite nanoparticles has been evaluated for the HBIW synthesis under
ultrasonic irradiation. The catalyst is inexpensive and easily available. Moreover, mild reaction conditions, simple procedure,
short reaction times, easy workup, high yields of products, and easy separation and recyclability of the catalyst are the salient
features of the presented work.
This work is funded by grant NRF-2018R1A2B3001246 of the National Research Foundation of Korea.
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