Synthesis of Fe3O4@SiO2@DOPisatin-Ni(II) and Cu(II) nanoparticles: Highly efficient catalyst for the synthesis of sulfoxides and disulfides

Article abstract of DOI:10.1002/aoc.3844

The catalytic activity of two magnetic catalysts Fe₃O₄@SiO₂@DOPisatin-M(II) (M?=?Ni, Cu) was investigated in the environmentally green H₂O₂ oxidant-based oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides. By using these catalysts, various substrates were successfully converted into their corresponding product. These catalysts could also be reused multiple time without significant loss of activity. The physical and chemical properties of the catalysts were determined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), energy dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS).

Full text of DOI:10.1002/aoc.3844

Received: 26 October 2016
DOI: 10.1002/aoc.3844
Revised: 29 November 2016
Accepted: 18 March 2017
F U L L PA P E R
Synthesis of Fe3O4@SiO2@DOPisatin‐Ni(II) and Cu(II)
nanoparticles: Highly efficient catalyst for the synthesis of
sulfoxides and disulfides
Maryam Hajjami
| Fatemeh Sharifirad | Fatemeh Gholamian
Department of Chemistry, Faculty of
Science, Ilam University, PO Box:
69315516, Ilam, Iran
The catalytic activity of two magnetic catalysts Fe3O4@SiO2@DOPisatin‐M(II)
(M = Ni, Cu) was investigated in the environmentally green H2O2 oxidant‐
based oxidation of sulfides to sulfoxides and oxidative coupling of thiols to
disulfides. By using these catalysts, various substrates were successfully con-
verted into their corresponding product. These catalysts could also be reused
multiple time without significant loss of activity. The physical and chemical
properties of the catalysts were determined using scanning electron microscopy
(SEM), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction
(XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer
(VSM), energy dispersive X‐ray spectroscopy (EDX) and atomic absorption
spectroscopy (AAS).
Correspondence
Maryam Hajjami, Department of Chemistry,
Faculty of Science, Ilam University,
P.O. Box: 69315516, Ilam, Iran.
Email: mhajjami@yahoo.com;
m.hajjami@ilam.ac.ir
KEYWORDS
disulfides, Fe3O4@SiO2@DOPisatin‐M(II), oxidation, oxidative coupling, sulfoxides
1 | INTRODUCTION
Among the two main catalysts, homogeneous and
heterogeneous,[7] homogeneous catalysts, have various
Catalytic conversion oforganic sulfides to sulfoxides is a funda-
mental component of in several chemical areas,[1] biologically
significant molecules[2] and therapeutic areas such as drugs of
antiulcerative, antihypertensive, cardiotonic, psychotonics and
vasodilators.[3] Also, the oxidation of thiols is one of the most
important pathways to synthesize disulfides. This compound
plays an essential role in a wide variety of areas, such as pep-
tides, bioactive molecules, and oil sweetening processes,
sulfonylation of enolates and as vulcanizing agent for rubber.[4]
In this light, development of a new, mild and efficient protocol
for the synthesis of sulfoxides and disulfides is desirable.
Several oxidants that can effectively form sulfoxides of
disulfides currently exist. Among them, hydrogen peroxide
(H2O2) is a green oxidant because it is clean and environmen-
tally friendly, of moderate cost, readily available, can be
safely stored, and a main byproduct is water.[5,6]
benefits. But heterogeneous catalysts are widely applied
due to their easy recovery.[8] In recent years, nanostruc-
tured materials, especially magnetic nanoparticles (MNPs)
recognize as an excellent supports due to their high sur-
face area, easy preparation and functionalization, facile
and easy recovery by a magnetic field,[9] which lead
to optimize operational cost and enhance the product's
purity.[10]
In this light, herein, we report the synthesis, characteriza-
tion and catalytic properties of Fe3O4@SiO2@DOPisatin‐
Ni(II) and Fe3O4@SiO2@DOPisatin‐Cu(II) for oxidation of
sulfides to sulfoxides and oxidative coupling of thiols to
disulfides. Also, use of the environmentally green H2O2
oxidant and solvent free conditions, or the use of the green
solvent PEG, attracts much attention from environmental
and economic points of view.
Appl Organometal Chem. 2017;e3844.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
1 of 10
https://doi.org/10.1002/aoc.3844

2 of 10
HAJJAMI ET AL.
2 | EXPERIMENTAL
2.1.5 | Preparation of
Fe3O4@SiO2@DOPisatin‐Ni(II) and
2.1 | Preparation of catalyst
2.1.1 | Preparation of MNPs
Fe3O4@SiO2@DOPisatin‐Cu(II)
For the preparation of final catalyst as Fe3O4@SiO2@-
DOPisatin‐Ni(II), 0.3 g Fe3O4@SiO2@DOPisatin was dis-
persed in 25 ml absolute ethanol using an ultrasonic bath
for 30 min. Then, the reaction mixture was refluxed with
0.6 mmol Ni(NO3)2.6H2O for 24 h. The obtained catalyst
was separated using an external magnet and washed with eth-
anol and finally, dried at room temperature.
For the synthesis of second catalyst, (Fe3O4@SiO2@-
DOPisatin‐Cu(II)), the resulting Fe3O4@SiO2@DOPisatin
powder (0.3 g) was dispersed in 25 ml absolute ethanol using
an ultrasonic bath for 30 min. In the next step 0.9 mmol
Cu(NO3)2.3H2O was added to the solution and the resultant
mixture was under reflux for 24 h. Finally the obtained cata-
lyst was separated using an external magnet, washed with
ethanol and dried at room temperature.
Fe3O4 nanoparticles were obtained by chemical
co‐precipitation of Fe3+ and Fe2+ ions. In this direction, a
mixture of FeCl3·6H2O (21.66 mmol) and FeCl2·4H2O
(11.17 mmol) in 100 mL deionized water was stirred under
nitrogen atmosphere with rapid mechanical stirring until the
salts dissolved completely. Then, 10 ml of 30% NH4OH
was added for 30 min at 80°C. Finally formed black precipi-
tate was separated with an external magnet, washed with
deionized H2O and dried at room temperature.[11]
2.1.2 | Preparation of Fe3O4@SiO2
The resulting Fe3O4 NPs (1g) was dispersed in 10 ml
deionized water and 50 ml absolute ethanol using an
ultrasonic bath for 30 min. In the next step 5.39 g PEG,
10 ml NH3 and 2 ml tetraethylorthosilicate (TEOS) were
added to the reaction mixture and was stirred at room
temperature for 38 h. Finally the resultant particles were
isolated by magnetic decantation, and washed with deion-
ized water and ethanol several times and dried at room
temperature.
2.2 | General procedure for the oxidation of
sulfides
In a typical oxidative reaction, the sulfide (1 mmol) was
added to a mixture of 30% H2O2 (0.4 ml, 3.92 mmol) and
Fe3O4@SiO2@DOPisatin‐M (II) (M = Ni, 0.0022 mmol
and M = Cu, 0.0017 mmol), and the mixture was stirred
at room temperature for the time specified. The progress
of the reaction was observed using thin layer chromatogra-
phy (TLC). After reaction completion, the catalyst was sep-
arated from the reaction mixture by an external magnet.
Then water (5 ml) was added to the mixture and product
was extracted with CH2Cl2 (4 × 5 ml). The organic layer
was dried over anhydrous Na2SO4. Finally, organic solvents
were evaporated and sulfoxides produced in excellent
yields (90–96%).
2.1.3 | Preparation of Fe3O4@SiO2@DOP
The obtained Fe3O4@SiO2 (1g) was dispersed in 25 ml abso-
lute ethanol using an ultrasonic bath for 30 min. Then
9.8 mmol 4‐(2‐aminoethyl) benzene‐1,2‐diol (dopamine)
was added to the reaction mixture and stirred at room temper-
ature for 24 h. The dopamine‐functionalized magnetic Fe3O4
nanoparticles (Fe3O4@SiO2@DOP) were collected by an
external magnet and washed with ethanol to remove
unreacted species and dried at room temperature.
2.3 | General procedure for the oxidative
coupling of thiols
2.1.4 | Preparation of Fe3O4@SiO2@DOPisatin
Fe3O4@SiO2@DOPisatin‐M (II) (M = Ni, 0.0017 mmol
and M = Cu, 0.0012 mmol) were added to solution of thiol
(1 mmol) and H2O2 30% (0.4 ml, 3.92 mmol) in PEG
(3 ml). The reaction mixture was stirred at room tempera-
ture, and the progress of the reaction was monitored by
TLC. After completion of the reaction, the catalyst was
separated using an external magnet, and the product was
extracted with CH2Cl2. Anhydrous Na2SO4 was used to
dry the organic layer, filtered and solvent was removed
by simple evaporation to produce the corresponding pure
disulfides.
The amino group of the dopamine‐functionalized magnetic
Fe3O4 nanoparticles was reacted with active carbonyl group
of isatin to afford the Fe3O4@SiO2@DOPisatin. In this
light, the obtained Fe3O4@SiO2@DOP (0.6 g) was dis-
persed in 25 ml absolute ethanol using an ultrasonic bath
for 30 min. Then 3 mmol isatin and 2–3 drops of acetic
acid was added to the reaction mixture and was refluxed
at 80 °C for 24 h. Ultimately the product was separated
by an external magnet, washed several times with ethanol
and dried.

HAJJAMI ET AL.
3 of 10
2.4 | Spectral data of some representative
2.4.4 | 1,2‐diphenyldisulfane
1H NMR (400 MHz, CDCl3): δ = 7.55–7.52 (m, 2H), 7.39–7.32
(m, 2H), 7.29–7.24 (m, 1H) ppm. IR (KBr) cm_1: 3070, 2915,
2871, 1574, 1474, 1438, 1099, 1071, 1021, 737, 686, 472, 462.
sulfoxides and disulfides
2.4.1 | Sulfinylbis(methylene)dibenzene
1H NMR (400 MHz, CDCl3): δ = 7.46–7.38 (m, 3H),
7.37–7.29 (m, 2H,), 3.98–3.89 (m, 2H) ppm. IR (KBr) cm_1:
3082, 3062, 2957, 1603, 1455, 1412, 1075, 1032, 778, 700, 499.
3 | RESULT AND DISCUSSION
3.1 | Preparation of
2.4.2 | 1‐(methylsulfinyl)dodecane
Fe3O4@SiO2@DOPisatin‐Ni(II) and
1H NMR (400 MHz, CDCl3): δ = 3.05–3.01 (m, 1H), 2.93
(s, 1H,), 2.80–2.73 (m, 2H), 2.71–2.64 (m, 2H), 2.59 (m,
5H), 1.90–1.83 (m, 1H), 1.80–1.75 (m, 4H), 1.51–1.46
(m, 5H), 0.92–0.89 (m, 7H) ppm. IR (KBr) cm−1: 3000,
2954, 2916, 2849, 1473, 1267, 1142, 1079, 1036, 1020,
988, 952, 777, 729, 719, 539, 511, 494. MS: m/z = 232
(m+), 215, 149, 97, 81, 57, 43.
Fe3O4@SiO2@DOPisatin‐Cu(II)
The detailed synthesis procedure of Fe3O4@SiO2@DOPisatin‐
Ni(II) and Fe3O4@SiO2@DOPisatin‐Cu(II) is showed in
2.4.3 | 1,2‐Bis(4‐methylphenyl)disulfane
1H NMR (400 MHz, CDCl3): δ = 7.44–7.42 (d, 2H,
J = 8 Hz), 7.16–7.14(d, 2H, J = 8 Hz), 2.36 (s, 3H) ppm.
IR (KBr) cm_1: 3016, 2914, 2871, 1636, 1488, 1395, 1115,
1078, 1038, 833, 487.
SCHEME
synthesis of Fe3O4@SiO2@DOPisatin‐Cu(II)
1
Synthesis of Fe3O4@SiO2@DOPisatin‐Ni(II) and
FIGURE 1 SEM images of (a) Fe3O4@SiO2@DOPisatin‐Ni(II) (b)
Fe3O4@SiO2@DOPisatin‐Cu(II)

4 of 10
HAJJAMI ET AL.
Scheme 1. Initially the magnetic nano particles of Fe3O4
have been prepared by methods explained in literature.[11]
After coating the Fe3O4 nanoparticles with tetra-
ethylorthosilicate (TEOS), obtained product was added to
dopamine. Then Fe3O4@SiO2@DOP was modified with
isatin (Fe3O4@SiO2@DOPisatin). In the final step,
Ni(NO3)2. 6H2O was added to the mixture reaction, includ-
ing of Fe3O4@SiO2@DOPisatin, to afford the Fe3O4@-
SiO2@DOPisatin‐Ni(II). Also for preparation of Fe3O4@
SiO2@DOPisatin‐Cu(II), Cu(NO3)2.3H2O was added to
Fe3O4@SiO2@DOPisatin.
FESEM‐TESCAN MIRA3), Fourier transform infrared
(FT‐IR, Bruker, Germany) spectroscopy, X‐ray diffraction
(XRD, GBC‐Difftech MMA), thermogravimetric analysis
(TGA, PerkinElmer Pyris Diamond, UK), vibrating sample
magnetometer (VSM, MDKFD), energy dispersive X‐ray
(EDX, FESEM‐TESCAN MIRA3), and atomic absorption
spectroscopy (AAS, Analyticaljena novAA400p).
For investigation of the morphology and average particle
size, the scanning electron microscopy (SEM) analysis was
used. As shown in Figure 1‐a, the shape of the
Fe3O4@SiO2@DOPisatin‐Ni(II) is spherical with an average
diameter less than 84 nm. Also SEM image of
Fe3O4@SiO2@DOPisatin‐Cu(II) shows spherical morphology
of catalyst with an average size range of 35 nm (Figure 1‐b).
Figure 2 shows the FT‐IR spectra of Fe3O4@SiO2 (a),
Fe3O4@SiO2@DOP (b), Fe3O4@SiO2@DOPisatin (c) and
Fe3O4@SiO2@DOPisatin‐Ni(II) (d) Fe3O4@SiO2@DOPisatin‐
3.2 | Catalyst characterization
Reagents and solvents were purchased from Aldrich and
Merck chemical companies. The synthesized catalysts were
characterized by scanning electron microscopy (SEM,
FIGURE 2 FT‐IR spectra of Fe3O4@SiO2 (a), Fe3O4@SiO2@DOP (b), Fe3O4@SiO2@DOPisatin (c) and Fe3O4@SiO2@DOPisatin‐Ni(II) (d)
Fe3O4@SiO2@DOPisatin‐Cu(II) (e)

HAJJAMI ET AL.
5 of 10
Cu(II) (e). For confirmation that the silica has been success-
fully coated on the surface of MNPs, we show the spectrum
of Fe3O4@SiO2 (curve a). This spectrum shows peaks at
1094 cm−1 and 955 cm−1 is assigned to the asymmetric and
symmetric stretching vibration of Si‐O‐Si bond. Also the peak
that appears at 585 cm−1 is contributed to the Fe‐O vibration.
As shown in Figure 2 (b) the peaks contributed to stretching
vibration of Fe‐O, asymmetric stretching of Si‐O‐Si,
stretching vibration of C‐N and bending of NH appeared at
578 cm−1, 954–1091 cm−1, 1499 cm−1 and 1620 cm−1 respec-
tively. In this spectrum, it can be seen that there is a peak at
3403 cm−1 which belongs to N‐H stretching. In this spectrum,
it can be seen that there are the peaks at 2830 cm−1 and
2905 cm−1 which are belong to C‐H stretching of the ethyl
group. As shown in Figure 2 (c), the band that appears at
582 cm−1 assigned to the Fe‐O vibration. The peaks at
1092 cm−1 and 956 cm−1 are contributed to the asymmetric
and symmetric stretching vibration of Si‐O‐Si bond. Also
stretching of the C = N bond appeared at 1619 cm−1. There
are two peaks that include C O stretch of the amide group
FIGURE 3 XRD pattern of Fe3O4, Fe3O4@SiO2@DOPisatin‐Ni(II)
and Fe3O4@SiO2@DOPisatin‐Cu(II)
FIGURE 4 TGA diagram of Fe3O4, Fe3O4@SiO2@DOPisatin‐Ni
(II) and Fe3O4@SiO2@DOPisatin‐Cu(II)
FIGURE 5 VSM of MNPs of Fe3O4, Fe3O4@SiO2@DOPisatin‐Ni
(II) and Fe3O4@SiO2@DOPisatin‐Cu(II)
FIGURE 6 EDX spectrum for (a) Fe3O4@SiO2@DOPisatin‐Ni(II)
and (b) Fe3O4@SiO2@DOPisatin‐Cu(II)

6 of 10
HAJJAMI ET AL.
and O‐H stretching band at 1716 cm−1 and 3400 cm−1 respec-
tively. Figure 2 (d) shows the FT‐IR spectra of the
Fe3O4@SiO2@DOPisatin‐Ni(II). As it can be seen in
Figure 2‐d, the Fe‐O vibration and stretching of the C = N
bond appear at 585 cm−1 and 1624 cm−1, respectively. Also
the peaks at 1092 cm−1 and 956 cm−1 are contributed to the
asymmetric and symmetric stretching vibration of Si‐O‐Si
bond. The stretch of the amide group and O‐H stretching band
indicate at 1719 cm−1 and 3417 cm−1 respectively. Figure 2 (e)
indicates the FT‐IR spectra of the Fe3O4@SiO2@DOPisatin‐
Cu(II). The Fe3O4@SiO2@DOPisatin‐Cu(II) was confirmed
Functionalization of the Fe3O4 nanoparticles with
SiO2@DOPisatin‐M (II) (M = Ni or Cu) can be inferred from
the thermogravimetric analysis (TGA). The TGA curve of the
catalysts indicates the weight loss of the organic functional
group as it decomposes upon heating. The weight loss at tem-
peratures below 200 °C for the sample is apparently due to
loss of adsorbed water or the water that formed from the con-
densation of hydroxyl groups. As shown in Figure 4, for
Fe3O4@SiO2@DOPisatin‐Ni(II), there is a weight loss of
6% between 225 °C and 625 °C related to the breakdown
of the SiO2@DOPisatin‐Ni (II) moieties. Also, a weight loss
8.5% between 250 °C and 650 °C, observed for
Fe3O4@SiO2@DOPisatin‐Cu(II).
The magnetic property of MNPs and, Fe3O4@SiO2@-
DOPisatin‐Ni(II) and Fe3O4@SiO2@DOPisatin‐Cu(II) was
characterized by vibrating sampling magnetometry (VSM).
The room temperature magnetization curves of MNPs,
Fe3O4@SiO2@DOPisatin‐Ni(II) and Fe3O4@SiO2@DO-
Pisatin‐Cu(II) are shown in Figure 5. As expected, the bare
MNPs showed the higher magnetic value in comparison with
Fe3O4@SiO2@DOPisatin‐Ni(II) and Fe3O4@SiO2@DOP-
isatin‐Cu(II). It is due to the coating of silica and the attached
layer on the catalysts.
via FT‐IR by peaks at 587 cm−1, 1624 cm−1 and 1711 cm−1
,
which corresponds to the Fe‐O vibration, the bond of
stretching of C N and C O stretch of the amide group, respec-
tively. Additional peaks at 1094 cm−1 and 956 cm−1 are con-
tributed to the asymmetric and symmetric stretching
vibration of Si‐O‐Si bond.[12] As shown in Figures 2‐d and
2‐e, the bond of C N, shifts to 1624 cm−1 due to the coordina-
tion of the nitrogen with the metal.
X‐ray diffraction (XRD) is one of the analytical tech-
niques which used for phase recognition of a crystalline
material. The position of all peaks in the XRD pattern of
Fe3O4@SiO2@DOPisatin‐Ni(II) (2θ = 23.58, 40.02, 46.46,
55.58, 66.58, 72.3 and 79.26) and Fe3O4@-
SiO2@DOPisatin‐Cu(II) (2θ = 24.18, 39.9, 45.94, 55.34,
67.62, 72.3 and 79.06) are in accord with standard XRD pat-
tern of Fe3O4. This pattern indicated crystalline inverse cubic
spinel structure (Figure 3).
The energy dispersive X‐ray (EDX) spectrum indicates
the kinds of elements present in the synthesized catalysts.
As shown in Figure 6‐a the elements of C, N, O, Si, Fe and
Ni in the EDX spectrum of Fe3O4@SiO2@DOPisatin‐Ni(II)
are presented.
TABLE 1 Optimization of the solvent, Fe3O4@SiO2@DOPisatin‐M(II) (M = Ni, cu) and H2O2 for the synthesis of sulfoxidea
Cat(mmol)
M = Ni/cu
H2O2(mmol)
M = Ni/cu
Time (min)
M = Ni/cu
Yield%
M = Ni/cu
Entry
Solvent M = Ni/cu
1
2
3
4
5
6
7
8
9
10
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Solvent free
Ethanol
0.0011/0.0009
0.0022/0.0017
0.0032/0.0026
0.0043/0.0035
0.0065/ 0.0052
0.0022/0.0017
0.0022/0.0017
0.0022/0.0017
0.0022/0.0017
0.0022/0.0017
3.92
3.92
3.92
3.92
3.92
2.94
4.9
15/ 15
15/ 15
15/ 15
15/ 15
15/ 15
45/ 40
30/ 25
15/ 15
15/ 15
15/ 15
74/ 80
95/ 96
95/95
93/ 95
96/ 96
71/ 75
96/ 96
40/ 35
50/ 50
30/ 30
3.92
3.92
3.92
H2O
CH2Cl2
aMethyl phenyl sulfide (1 mmol), r.t, solvent (3 mL)

HAJJAMI ET AL.
7 of 10
Another EDX spectrum (Figure 6‐b) contributed to
Fe3O4@SiO2@DOPisatin‐Cu(II) indicated the presence of
C, N, O, Si, Fe and Cu in the catalyst.
To extend the scope of catalyst characterization, we have
determined amount of Ni and Cu in catalysts, by AAS tech-
nique. From this analysis, the amount of Ni and Cu in the cat-
alysts is found to be 0.217 and 0.173 mmol/g respectively.
Also to investigate leaching of the metal species, experiment
was carried out in oxidation of tetrahydrothiophene. In repre-
sentative test, the solid catalyst was filtered out and the
filtrate was analyzed Ni and Cu content using AAS. The
amounts of Ni and Cu obtained 0.202 and 0.132 mmol/g
respectively and a slight decrease of 1.5% and 4% were
observed.
3.3 | Catalytic study
After characterization of the prepared nanocatalysts, in the
present work we were also interested in finding a simple
and efficient method for oxidation of sulfides and oxidative
TABLE 2 Oxidation of sulfides to the corresponding sulfoxides using H2O2 (30%) and catalytic amounts of Fe3O4@SiO2@DOPisatin‐M(II)a
Time (min)
M = Ni/cu
Yield%
M = Ni/cu
M.P (°C)
M = Ni/Cu
Entry
Substrate
Ref.
[13]
1
2
3
4
5
6
7
8
9
Dibenzyl sulfide
20/15
15/15
5/5
96/96
95/96
90/91
95/95
90/92
92/92
91/91
90/90
91/94
128–130/129–130
29–32/29–32
Oil/oil
[14]
[15]
[13]
[16]
[17]
[14]
[16]
[14]
Methyl phenyl sulfide
Tetrahydrothiophene
Dimethyl sulfide
10/10
9/8
Oil/oil
2‐(Phenylthio)ethanol
Diallyl sulfide
Oil/oil
9/8
Oil/oil
Dipropyl sulfide
10/9
5/5
Oil/oil
2‐(Methylthio)ethanol
Dodecyl methyl sulfide
Oil/oil
135/120
50–58/51–60
aConditions: sulfide (1 mmol), H2O2 (0.4 ml, 3.92 mmol), Fe3O4@SiO2@DOPisatin‐Ni(II) (0.0022 mmol), Fe3O4@SiO2@DOPisatin‐Cu(II) (0.0017 mmol), solvent free, r.t.
TABLE 3 Optimization of the solvent and amount of catalyst for the synthesis of disulfidesa
Ni catalyst
(mmol)
Cu catalyst
(mmol)
H2O2
(mmol)
Time (min)
M = Ni/Cu
Yield%
M = Ni/Cu
Entry
Solvent
PEG
1
0
0
3.92
3.92
3.92
3.92
3.92
3.92
2.94
4.9
8/ 8
8/ 8
Trace/trace
73/ 75
95/ 96
91/ 91
93/ 95
96/ 96
75/ 80
96/ 97
50/ 55
95/ 95
70/ 60
30/ 35
2
PEG
0.0011
0.0017
0.0022
0.0043
0.0065
0.0017
0.0017
0.0017
0.0017
0.0017
0.0017
0.0009
0.0012
0.0017
0.0035
0.0052
0.0012
0.0012
0.0012
0.0012
0.0012
0.0012
3
PEG
8/ 8
4
PEG
8/ 8
5
PEG
8/ 8
6
PEG
8/ 8
7
PEG
8/ 8
8
PEG
8/ 8
9
Solvent free
Ethanol
H2O
3.92
3.92
3.92
3.92
20/ 20
60/ 60
240/ 210
300/ 330
10
11
12
CH2Cl2
a4‐methylthiophenol (1 mmol), room temperature and solvent (3 ml)

8 of 10
HAJJAMI ET AL.
TABLE 4 Oxidative coupling of thiols of to the corresponding disulfides using H2O2 (30%) and catalytic amounts of Fe3O4@SiO2@DOPisatin‐
M(II) in PEG at room temperaturea
Time (min)
M = Ni/Cu
Yield%
M = Ni/Cu
M.P (°C)
M = Ni/Cu
Entry
Substrate
Ref.
[16]
1
2
3
4
5
6
7
8
9
4‐Methylthiophenol
Thioglycolic acid
2‐Mercaptoethanol
2‐Mercaptobenzothiazole
Thiophenol
8/8
5/5
95/96
91/92
92/91
99/99
98/98
99/99
98/98
98/96
91/91
35–37/36–38
Oil/oil
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[16]
3/3
Oil/oil
10/9
3/3
175/174–175
54–57/54–58
133/131–133
84–89/85–90
277/277
2‐Naphtalenethiol
2‐Mercaptobenzoxazole
Thiosalicylic acid
2‐Aminothiophenol
50/45
10/10
9/9
15/15
80–84/80–84
aConditions: thiol (1 mmol), H2O2 30% (0.4 ml, 3.92 mmol) and Fe3O4@SiO2@DOPisatin‐M(II) (M = Ni 0.0017 mmol, M = Cu 0.0012 mmol), r.t, PEG (3 ml).
coupling of thiols by using these compounds as a new, active
and magnetically recoverable nanocatalyst. To illustrate the
catalytic activity of Fe3O4@SiO2@DOPisatin‐M(II)
(M = Ni, Cu), initially we were choose the oxidation of
methyl phenyl sulfide with H2O2 as a model reaction and
the effect of different parameters such as solvents, amount
of catalyst and amount of H2O2 were investigated (Table 1).
Initially the effect of catalysts amount on the oxidation of
methyl phenyl sulfide was investigated. Catalysts amount
were varied from 0.005 to 0.03 g. As shown in Table 1 entry
2, 0.01 gr catalysts were found to be the most effective. Then
effects of amount of H2O2 were investigated and 0.4 ml
(3.91 mmol) was obtained yield of 95% for
Fe3O4@SiO2@DOPisatin‐Ni(II) and yield of 96% for
Fe3O4@SiO2@DOPisatin‐Cu(II). Subsequently, the influ-
ence of different solvents was evaluated (Table 1, entries 2
and 8–10). Among the solvents examined for two catalysts,
the highest yield was achieved in solvent free condition
(Table 1, entry 2).
After the optimization of the reaction condition for oxida-
tion of sulfides with two catalyst, Fe3O4@SiO2@DOPisatin‐
M(II) (M = Ni, Cu), a wide range of aromatic and aliphatic
sulfides were successfully converted to the corresponding
sulfoxides. The results are presented in Table 2.
The next part of the study focused on the utility of these
catalysts for oxidative coupling of thiols into their
corresponding disulfides. First, to optimize the reaction con-
ditions for the synthesis of disulfide derivative, we
FIGURE 7 Recyclability of Fe3O4@SiO2@DOPisatin‐Ni(II) (green
column) and Fe3O4@SiO2@DOPisatin‐cu(II) (blue column) in
oxidation of tetrahydrothiophene
TABLE 5 Comparison results of Fe3O4@SiO2@DOPisatin‐M(II) (M = Ni, cu) with other catalysts for the oxidation of methyl phenyl sulfide by
using of H2O2
Entry
Condition
Time (min)
Yield%
Ref
[25]
1
2
3
4
5
6
7
MNPs‐PSA (5 mg, 0.95 mol%), solvent free, r.t
DSA@MNPs (0.02 g), EtOH, r.t
80
360
20
87
98
98
96
98
95
96
[8]
[22]
[26]
[27]
Boehmite‐Si‐DSA (0.03 g), solvent free, r.t
Cu‐SPATB/Fe3O4 (0.005 g), solvent free, r.t
TFE/SBA‐15 (0.02 g), r.t
130
35
Fe3O4@SiO2@DOPisatin‐Ni(II) (0.0022 mmol), solvent free, r.t
Fe3O4@SiO2@DOPisatin‐cu(II) (0.0017 mmol), solvent free, r.t
15
This work
This work
15

HAJJAMI ET AL.
9 of 10
investigated the reaction of 4‐methylthiophenol (1 mmol) and
Fe3O4@SiO2@DOPisatin‐M(II) (M = Ni, Cu) in various sol-
vents and various amount of H2O2. As shown in Table 3,
entries 1–6, 0.0017 mmol of Fe3O4@SiO2@DOPisatin‐
Ni(II) and 0.0012 mmol of Fe3O4@SiO2@DOPisatin‐Cu(II)
were found to be the most effective amounts and the product
was obtained in 95% yield and 96% yield respectively. The
effects of solvent free condition and different solvents such
as: PEG, Ethanol, H2O and CH2Cl2 on the oxidative coupling
of thiols with Fe3O4@SiO2@DOPisatin‐Ni(II) and
Fe3O4@SiO2@DOPisatin‐Cu(II) were also tested. The
results indicated that the highest product yield was obtained
in PEG as a green solvent (Table 3, entry 3).
ACKNOWLEDGEMENTS
Financial support for this work by the research affairs of Ilam
University, Ilam, Iran is gratefully acknowledged.
REFERENCES
[1] D. J. Thompson, J. E. Barker Paredes, L. Villalobos, M. Ciclosi,
R. J. Elsby, B. Liu, P. E. Fanwick, T. Ren, Inorg. Chim. Acta
2015, 424, 150.
[2] T. H. Chen, Z. Yuan, A. Carver, R. Zhang, Appl. Catal. A Gen.
2014, 478, 275.
[3] P. Gogoi, M. Kalita, T. Bhattacharjee, P. Barman, Tetrahedron Lett.
2014, 55, 1028.
Finally, the best conditions for the oxidative coupling
of thiols were obtained. The scope and generality of this
reaction have been explored by the reaction of a wide range
of aromatic and aliphatic thiols. As shown in Table 4,
thiols were successfully converted to the corresponding
disulfides.
[4] B. V. Tamhankar, Int. J. Res. Org. Chem. 2014, 4, 4.
[5] M. Kirihara, J. Yamamoto, T. Noguchi, Y. Hirai, Tetrahedron Lett.
2009, 50, 1180.
[6] A. Rostami, B. Atashkar, J. Mol. Catal. A: Chem. 2015, 398, 170.
[7] H. Veisi, J. Gholami, H. Ueda, P. Mohammadi, M. Noroozi, J. Mol.
Catal. A: Chem. 2015, 216, 396.
The possibility of recovery and recyclability of catalysts
were examined in the model reaction for the oxidation of
tetrahydrothiophene under the optimized conditions. Upon
completion of the reaction, the catalyst was separated with
an external magnet and mixture of reaction was extracted
with CH2Cl2. Then the separated catalyst was dried at room
temperature and reused for another same reaction. As shown
in Figure 7, the recycling ability of the catalysts was tested for
5 times.
[8] A. Ghorbani‐Choghamarani, H. Rabiei, B. Tahmasbi, B. Ghasemi,
F. Mardi, Res. Chem. Intermed. 2016, 42, 5723.
[9] A. Rostami, Y. Navasi, D. Moradi, A. Ghorbani‐Choghamarani,
Catal. Commun. 2014, 43, 16.
[10] Y. Jiang, C. Guo, H. Xia, I. Mahmood, C. Liu, H. Liu, J. Mol.
Catal. B: Enzym. 2009, 58, 103.
[11] A. Ghorbani‐Choghamarani, G. Azadi, RSC Adv. 2015, 5, 9752.
[12] M. Esmaeilpour, J. Javidi, F. Nowroozi Dodeji, M. Mokhtari
To demonstrate the merit of Fe3O4@SiO2@DOPisatin‐
Ni(II) and Fe3O4@SiO2@DOPisatin‐Cu(II), we compared
the results of the oxidation of methyl phenyl sulfide with
the previous reported in the literature. As shown in Table 5,
in comparison with other catalysts employed for the synthesis
of methyl phenyl sulfoxide, by using of H2O2,
Abarghoui, J. Mol. Catal. A: Chem. 2014, 393, 18.
[13] K. Bahrami, M. M. Khodaei, B. H. Yousefi, M. S. Arabi, Tetrahe-
dron Lett. 2010, 51, 6939.
[14] A. Ghorbani‐Choghamarani, Z. Darvishnejad, B. Tahmasbi, Inorg.
Chim. Acta 2015, 435, 223.
[15] M. Hajjami, Z. Yousofvand, Catal. Lett. 2015, 145, 1733.
Fe3O4@SiO2@DOPisatin‐Ni(II)
and
Fe3O4@SiO2@-
[16] A. Ghorbani‐Choghamarani, B. Tahmasbi, F. Arghand, S. Faryadi,
RSC Adv. 2015, 5, 92174.
DOPisatin‐Cu(II) indicated significant catalytic activity in
terms of the best reaction time and high yield.
[17] K. Bahrami, Tetrahedron Lett. 2006, 47, 2009.
[18] A. Ghorbani‐Choghamarani, M. Nikoorazm, H. Goudarziafshar, A.
Shokr, H. Almasi, J. Chem. Sci. 2011, 123, 453.
4 | CONCLUSION
[19] A. Ghorbani‐Choghamarani, M. Nikoorazm, G. Azadi, J. Serb.
Chem. Soc. 2012, 77, 1.
Fe3O4@SiO2@DOPisatin‐Ni(II) and Fe3O4@SiO2@DOPi-
satin‐Cu(II) show good catalytic activity for the oxidation
of sulfides to sulfoxides and oxidative coupling of thiols to
disulfides by H2O2, and give well to excellent yields under
solvent‐free conditions and PEG at room temperature. The
merits of this research are the first report of Fe3O4
@SiO2@DOPisatin‐Ni(II) and Fe3O4@SiO2@DOPisatin‐
Cu(II) synthesized and used as the catalyst for the synthesis
of sulfoxide and disulfide. Also these new catalysts have
several benefits such as: easy preparation and
functionalization, easy separation, superficial recovery,
low toxicity and price.
[20] S. Shoghpour Bayraq, A. Nikseresht, I. Khosravi, Phosphorus Sul-
fur 2013, 188, 1236.
[21] C. C. Silveira, S. R. Mendes, Tetrahedron Lett. 2007, 48, 7469.
[22] M. Hajjami, A. Ghorbani‐Choghamarani, R. Ghafouri‐Nejad, B.
Tahmasbi, New J. Chem. 2016, 40, 3066.
[23] A. Ghorbani‐Choghamarani, S. Sardari, J. Sulfur Chem. 2011, 32,
63.
[24] M. Soleiman‐Beigi, Z. Taherinia, Monatsh. Chem. 2014, 145,
1151.
[25] A. Rostami, B. Tahmasbia, F. Abedi, Z. Shokri, J. Mol. Catal. A:
Chem. 2013, 378, 200.

10 of 10
HAJJAMI ET AL.
[26] A. Ghorbani‐Choghamarani, B. Tahmasbi, P. Moradi, N. Havasi,
Appl. Organomet. Chem. 2016, https://doi.org/10.1002/aoc.3478.
How to cite this article: Hajjami M, Sharifirad F,
Gholamian F. Synthesis of Fe3O4@SiO2@DOPisatin‐
Ni(II) and Cu(II) nanoparticles: Highly efficient
catalyst for the synthesis of sulfoxides and disulfides.
Appl Organometal Chem. 2017;0:e3844. https://doi.
org/10.1002/aoc.3844
[27] S. Rostamnia, E. Doustkhah, K. Bahrami, S. Amini, J. Mol. Liq.
2015, 207, 334.
SUPPORTING INFORMATION
Additional Supporting Information may be found online in
the supporting information tab for this article.