Green, inexpensive, and fast conversion of sulfides to sulfoxides by multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe3O4 nanoparticles in solvent-free conditions

Article abstract of DOI:10.1016/j.crci.2017.07.004

In the present study, the macrocyclic-based Mo(VI) Schiff base complex was harbored on Fe₃O₄ nanoparticles and characterized by X-ray powder diffraction, scanning electron microscope, energy-dispersive X-ray spectroscopy, infrared spectroscopy, transmission electron microscopy, vibrating sample magnetometry, diffuse reflectance spectra, and atomic absorption spectroscopy. Separable nanocatalyst was tested under solvent-free conditions for the oxidation of methyl phenyl sulfide, diphenyl sulfide, benzyl phenyl sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl sulfide, bis (4-hydroxyphenyl) sulfide, diallyl sulfide, and benzothiophene using H₂O₂ (30% in water) as green oxidant. This catalyst is very efficient for thioanisole oxidation with 100% conversion in 3 min. We were able to separate the nanocatalyst magnetically using external magnetic field and to apply the catalyst at least six consecutive times without a significant decrease in conversion. Remarkable and excellent turnover frequency of the catalyst was obtained to oxidize the thioanisole (526,000 h^?1), dimethyl sulfide (526,000 h^?1), diallyl sulfide (526,000 h^?1), dibutyl sulfide (521,000 h^?1), and dipropyl sulfide (500,000 h^?1). The prepared nanocatalyst has been beneficial in catalytic activity, selectivity, reaction time, and reusability with easy separation.

Full text of DOI:10.1016/j.crci.2017.07.004

C. R. Chimie xxx (2017) 1e11
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Full paper/M eꢀ moire
Green, inexpensive, and fast conversion of sulfides to
sulfoxides by multiusable Mo(VI) macrocyclic Schiff base
complex supported on Fe O nanoparticles in solvent-free
3
4
conditions
*
Abolfazl Bezaatpour , Fatemeh Payami, Habibollah Eskandari
Department of Chemistry, Faculty of Basic Science, University of Mohaghegh Ardabili, 179, Ardabil, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present study, the macrocyclic-based Mo(VI) Schiff base complex was harbored on
Received 8 May 2017
Accepted 13 July 2017
Available online xxxx
3 4
Fe O nanoparticles and characterized by X-ray powder diffraction, scanning electron
microscope, energy-dispersive X-ray spectroscopy, infrared spectroscopy, transmission
electron microscopy, vibrating sample magnetometry, diffuse reflectance spectra, and
atomic absorption spectroscopy. Separable nanocatalyst was tested under solvent-free
conditions for the oxidation of methyl phenyl sulfide, diphenyl sulfide, benzyl phenyl
sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl sulfide, bis (4-hydroxyphenyl) sulfide,
Keywords:
Macrocyclic ligand
Oxidation
2 2
diallyl sulfide, and benzothiophene using H O (30% in water) as green oxidant. This
Nanocatalyst
catalyst is very efficient for thioanisole oxidation with 100% conversion in 3 min. We were
able to separate the nanocatalyst magnetically using external magnetic field and to apply
the catalyst at least six consecutive times without a significant decrease in conversion.
Remarkable and excellent turnover frequency of the catalyst was obtained to oxidize the
Molybdenum
Solvent-free conditions
ꢀ
1
ꢀ1
ꢀ1
thioanisole (526,000 h ), dimethyl sulfide (526,000 h ), diallyl sulfide (526,000 h ),
ꢀ
1
ꢀ1
dibutyl sulfide (521,000 h ), and dipropyl sulfide (500,000 h ). The prepared nano-
catalyst has been beneficial in catalytic activity, selectivity, reaction time, and reusability
with easy separation.
©
2017 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
complexes have been used intensively as catalysts for se-
lective oxidation of organic compounds [18e20]. There are
Over the past two decades, the oxidation of sulfides to
some key advantages for solvent-free reactions, such as
significant contributions to protect the environment,
health of people, high cost efficiency, and waste reduction
[21]. According to previous reports, aqueous solution of
hydrogen peroxide (30%) is one of the greenest oxidants,
because it is cheap, nontoxic, and environmentally benign
without waste products, so that water is the only residue
[22e24]. A homogeneous catalyst recovering from a reac-
tion mixture is often difficult and costs high, as well as is
associated with additional wastes. Furthermore, insuffi-
cient chemical and thermal stability, the active metal
leaching into the solvent, and catalyst recycling remain a
sulfoxides and sulfones gives beneficial starting chemical
materials [1e5]. Sulfoxides are the major chemical in-
termediates to synthesize valuable chemicals, including
medications [6,7] and antifungal agents [8,9], and also can
play a role in the activation of enzymes. Numerous recent
reports are available on the conversion of sulfides into
sulfoxides using transition metal complexes [10e13],
especially with Mo complexes [14e17]. The Mo(VI)
*
Corresponding author.
E-mail address: bezaatpour@uma.ac.ir (A. Bezaatpour).
http://dx.doi.org/10.1016/j.crci.2017.07.004
631-0748/© 2017 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes

2
A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
Scheme 1. Preparation of the heterogeneous nanocatalyst, (i) K
2
CO
3
/DMF, (ii) tetraethoxysilane/EtOH, (iii) APTMS/EtOH, (iv) 1,4-bis(2-carboxyaldehyde phenoxy)
ꢁ
butane þ stirring at 70 C for 48 h/EtOH, and (v) MoO
Cl (DMF) /EtOH.
2 2 2
basic research subject in the catalytic fields [18,27e29]. A
main idea for supporting of metal complexes is to anchor
the metal complex onto a large surface area of inorganic
materials, such as zeolite and metal oxide [30e36].
Nowadays, magnetite nanoparticles (NPs) have been
recruited because of their unique properties, including the
large surface area, low toxicity, separate-ability, and
biocompatibility [37e43]. Magnetic separation renders the
recycling of catalysts from the solution by external mag-
netic fields much easier than filtration and centrifugation.
Following our previous review on catalytic activity of Schiff
base complexes [19,27,30,44e46], herein we report the
anchoring of novel cis-dioxomolybdenum(VI) macrocyclic
Schiff base complex by
carboxyaldehyde phenoxy) butane, MoO
amino-modified magnetite NPs. The novel nanocatalyst
Fe @Si(CH ePBSB/MoO ) (PBSB: propylbromo Schiff
base) was characterized using infrared (IR) spectroscopy,
scanning electron microscope (SEM), transmission electron
microscopy, diffuse reflectance spectra (DRS), vibrating
sample magnetometry, energy-dispersive X-ray (EDX)
a
reaction of 1,4-bis(2-
Cl (DMF) and
2
2
Fig. 1. FT-IR spectrum of (a) Fe
Fe @SiO e(CH ePBSB, (d) Fe
3
O
O
4
NP, (b) Fe
@SiO e(CH
3
O
4
@SiO
2 2 3 2
e(CH ) eNH , (c)
2
3
O
4
2
2
)
3
3
4
2
2
)
3
ePBSB/MoO .
2
(
3
O
4
2
)
3
2
scientific challenge [25]. Replacement of a homogeneous
oxidation catalyst with environmental friendly heteroge-
neous catalyst may be promising address for such problems
[26]. Accordingly, metal complex supporting has been the
3 4 2 2 3 2
Fig. 2. Pattern of XRD, (a) magnetite NPs, (b) Fe O @ SiO e(CH ) ePBSB/MoO .
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
3 4
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe O nanoparticles in solvent-free conditions, Comptes
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A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
3
spectroscopy, and X-ray powder diffraction (XRD) tech-
niques and tested for methyl phenyl sulfide, diphenyl sul-
fide, benzyl phenyl sulfide, dipropyl sulfide, dibutyl sulfide,
dimethyl sulfide, bis(4-hydroxyphenyl) sulfide, diallyl sul-
2
N was used as a carrier gas at a flow rate of 20 mL/min. IR
spectra were obtained using a Fourier transform infrared
(FT-IR) spectrometer spectomrx 1 in KBr pellets over the
ꢀ1
range of 4000e400 cm . Vibrating sample magnetometer
(VSM) was recorded with MDKF-FORC/VSM (Megnatis-
Daghigh-Kashan Co.). DRS data were recorded by Scinco
4100 in the range 200e900 nm using barium sulfate as
reference. The powder small angle XRD studies were per-
fide, and benzothiophene with H
oxidant. The reusability of Fe @Si-APFSB-MoO
aminopropyl phenoxybutane Schiff base) was also studied
within the oxidation of methyl phenyl sulfide with H
30% aqueous) under solvent-free conditions for six times.
2
O
2
(30% aqueous) as
3
O
4
2
(APFSB:
2 2
O
(
formed using Philips X'Pert with Cu Ka radiation
(
k ¼ 1.54 Å). Surface morphology and distribution of NPs
were investigated using LEO 1430 VP scanning electron
microscopy.
2
. Experimental section
.1. Materials and instruments
Methyl phenyl sulfide, diphenyl sulfide, benzyl phenyl
2
3 4 2 2 3 2
2.2. Preparation of Fe O @SiO e(CH ) NH
sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl sulfide,
bis(4-hydroxyphenyl) sulfide, diallyl sulfide, benzothio-
phene, 1,4-dibromobutane, 2-hydroxybenzaldehyde, N,N -
Fe
chemical coprecipitation method given in the literature
[39,47,48]. To this end, 1.25 g of FeCl $4H O and 3.40 g of
3
O
4
NPs and Fe
3
O
4
@SiO
2
were prepared according to
0
2
2
dimethylformamide, ferrous chloride, ferric chloride, 3-
aminopropyltrimethoxysilane (APTMS), and ammonia
FeCl
3
$6H
2
O were dissolved in 100 mL deionized water
ꢁ
under nitrogen gas at 60 C, and then 6 mL of 25% ammonia
was added and stirred for 45 min. Next, the magnetite
precipitates were separated and washed with water and
(
25%[w/w]) were purchased from Merck Chemical Com-
pany. Proton nuclear magnetic resonance spectra were
recorded using a Bruker NMR 400 (400 MHz) spectropho-
tometer in a CDCl solvent. CHNS analyses were performed
3
ethanol several times. For preparation of Fe
0.145 g of magnetic NPs were dispersed under ultra-
sonification for 30 min in the presence of N atmosphere.
O (5 mL), ammonia (3 mL), and TEOS (0.4 mL) were
3 4 2
O @SiO ,
using an Elemental Analyzer CHNSO-A PE 2400 series II
system. Atomic absorption analysis was carried out on an
Analytik Jena atomic absorption spectrometry. Analysis of
the oxidation products was determined by gas chroma-
tography (GC) using Agilent 7890 A with a capillary column
and flame ionization detector. Column temperature was
2
H
2
added to the mixture and stirred for 5 h at room temper-
ature. Afterward, the obtained solid was separated and
washed several times with ethanol and water and dried
under vacuum at room temperature. To the suspension of
ꢁ
ꢁ
programmed between 180 and 200 C with 2 C/min rate.
Fe
3
O
4
@SiO
2
(0.5 g) in ethanol (50 mL) was added dropwise
ꢁ
Fig. 3. Magnetization response of (a) magnetite NPs and (b) Fe
3
O
4
@SiO
2
e(CH
2
)
3
ePBSB/MoO
2
at 25 C.
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes

4
A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
the APTMS (2.5 mL) dissolved in 50 mL ethanol. After
stirring the mixture at 70 C for 12 h, the aminated mag-
dimethylformamide and then was added dropwise to a
solution of 2-hydroxybenzaldehyde (1.22 g, 10 mmol) and
potassium carbonate (0.691 g, 5.0 mmol) in dime-
thylformamide (30 mL). The mixture was refluxed for 15 h
and cooled at room temperature. Next, 70 mL of distilled
ꢁ
netic NPs were collected with external magnetic field and
ꢀ1
washed with water three times, FT-IR (KBr, cm ): 3406
[
[
y
(OeH)], 2924 [
(FeeO)].
y(CeH) aliphatic], 998 [y(SieO)], 610
ꢁ
y
water was poured into the mixture and was kept at 0e4 C
for 2 h. The creamy precipitated solids were filtered and
washed with water and dried in air. The obtained powder
was crystallized from ethanol to characterize yield 1.19 g,
80% of 1,4-bis (2-carboxyaldehyde phenoxy)butane. Anal.
2
.3. Synthesis of 1,4-bis(2-carboxyaldehyde phenoxy)butane
1,4-Bis(2-carboxyaldehyde phenoxy)butane was syn-
thesized in accordance with Ilhan et al. [49]; thus, 1,4-
dibromobutane (1.08 g, 5 mmol) was dissolved in 5 mL of
Calcd for C18
H
18
O
4
: C, 72.47; H, 6.08; Found: C, 72.1; H,
ꢁ
ꢀ1
6.50; mp: 108 C, IR (KBr, cm ): 1678 [
y
(C]O)], 2956, 2862
): 10.52 (s, 2H,
CH]O), 7e7.80 (m, 8H, aromatic), 4.2 (t, 4H, aliphatic
OeCH eC), 2.1 (t, 4H, CeCH eC) (supporting information,
Fig. S1).
1
[y(aliphatic CeH)]. HNMR (400 MHz, CDCl
3
2
2
3 4 2 2 3
2.4. Preparation of Fe O @SiO e(CH ) ePBSB
A
solution of 1,4-bis(2-carboxyaldehyde phenoxy)
butane (1.49 g, 5 mol, in 60 mL of ethanol) was added to
Fe @SiO e(CH NH (1.0 g in 60 mL of ethanol) sus-
pension. The reaction mixture was refluxed by stirring for 2
days. After cooling the mixture, Fe @SiO e(CH ePBSB
was separated using the external magnet and washed
3
O
4
2
2
)
3
2
3
O
4
2
2 3
)
ꢀ
1
several times with water and ethanol, IR (KBr, cm ): 623
[
[
y
(FeeO)], 994 [
(aliphatic)CeH ], 3418 [
y
(SieO)], 1636 [
y(imine)C]N], 2925, 2849
y
y
(OeH)].
2
.5. Preparation of Fe
3
O
4
@SiO
2
2
e(CH )
3
ePBSB/MoO
2
345.2 g (1 mmol) of MoO
2
Cl (DMF)
2
2
(prepared by the
method given in the literature [50]) dissolved in 40 mL of
dichloromethane was added dropwise to the suspension
containing 1 g of Fe O @SiO e(CH ) ePBSB in 40 mL of
3 4 2 2 3
methanol, and the mixture was refluxed for a day. Then, the
solid was separated using the external magnetic field and
washed several times with water and ethanol to remove
ꢁ
the unreacted MoO
2
Cl
(FeeO)], 916, 946[
(SieOeSi)], 1652 [ (C]N)], 2938, 2860 [aliphatic, CeH],
410 [ (OeH)].
2
(DMF)
2
and dried at 40 C. IR (KBr,
ꢀ1
cm ): 588 [
y
y(cis, O]Mo]O)], 1024
[
y
y
3
y
2.6. Studies of catalytic activity
3 4 2
The catalytic activity of heterogeneous Fe O @SiO
e(CH ) ePBSB/MoO catalyst was evaluated by the oxida-
2 3 2
tion of various sulfides [methyl phenyl sulfide, diphenyl
sulfide, benzyl phenyl sulfide, dipropyl sulfide, dibutyl
sulfide, dimethyl sulfide, bis (4-hydroxyphenyl) sulfide,
diallyl sulfide, and benzothiophene]. For testing catalytic
ꢀ
4
oxidation activity, 0.0008 g (3.8 ꢂ 10 mol) of Fe
e(CH ePBSB/MoO , sulfides (10 mmol) and H
10 mmol) were added in a ratio of 1:1 to the catalytic
reactor. The catalytic system was mixed by stirring for
min, the catalyst was removed by the external magnetic
3
O
4
@SiO
2
2
)
3
2
O (30%)
2 2
(
3
Fig. 4. Scanning electron microscopy images of (a) magnetite NPs, (b)
field, and the oxidation products were monitored
through GC.
3
Fe O
4
@SiO
2
e(CH
2
)
3
ePBSB/MoO
@SiO e(CH
2
,
and transmission electron microscopy
ePBSB/MoO
images of (c) Fe
3
O
4
2
2
)
3
2
.
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
3 4
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe O nanoparticles in solvent-free conditions, Comptes
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004

A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
5
3 4 2 2 3 2
Fig. 5. EDX spectrum of Fe O @ SiO e(CH ) ePBSB/MoO .
ꢀ
1
3
. Results and discussion
.1. Synthesis and characterization
Heterogeneous Fe @SiO e(CH
two adjacent bands at 916 and 946 cm
presence of MoO
bands at about 2900 cm can be assigned to aliphatic
group (CH ) of APTMS. Considering all vibrations of IR
indicates the
2
group (Fig. 1d) [52]. The existence of
ꢀ
1
3
2
3
O
4
2
2
)
3
ePBSB/MoO
2
cata-
spectra confirms the supporting of Schiff base Mo(VI)
lyst was prepared according to procedures shown in
Scheme 1 using a reaction of 1,4-bis(2-carboxyaldehyde
complex on the magnetic NPs. Fig. 2 shows the XRD pattern
of Fe
The comparison of two patterns (Fig. 2a and b) and those of
standard Fe NPs (reference JCPDS card no. 87-2334)
demonstrated diffraction peaks for Fe NPs and
Fe @SiO e(CH ePBSB/MoO . The observed broad peak
(about @SiO e(CH NH and
¼ 22e29) of Fe
Fe @SiO e(CH ePBSB/MoO was assigned to the ex-
istence of amorphous silicon dioxide. Fig. 3 shows the
magnetization properties of synthesized Fe NPs and
3 4 3 4 2 2 3 2
O NP (a) and Fe O @SiO e(CH ) ePBSB/MoO (b).
phenoxy) butane, MoO
Fe @SiO NPs. Fig. 1 indicates the FT-IR vibration of Fe
NP (Fig. 1a), Fe @SiO e(CH NH (Fig. 1b), supporting
Schiff base ligand (Fig. 1c), and Fe @SiO e(CH ePBSB/
MoO (Fig. 1d). FeeO and SieO stretching bands appeared at
10 and 998 cm . As shown in Fig. 1c and d, the assigned
band to C]N stretching vibration of supporting Schiff base
2 2 2
Cl (DMF) , and amino-modified
3
O
4
2
3
O
4
3 4
O
3
O
4
2
2
)
3
2
3 4
O
3
O
4
2
2
)
3
3
O
4
2
2
)
3
2
2
2q
3
O
4
2
2
)
3
2
ꢀ
1
6
3
O
4
2
2
)
3
2
ꢀ
1
ꢀ1
ligand at 1636 cm has shifted to 1652 cm after coor-
3 4
O
dination with Mo6 center [51]. Hence, the appearance of
þ
Fe
)
3
ePBSB/MoO
. The magnetization plots
3
O
4
2
@SiO e(CH
2
2
(1 mmol) and catalyst (3.8 ꢂ 10ꢀ mmol)
4
Fig. 6. Oxidation of thioanisole (1 mmol) in various solvents (5 mL) and under solvent-free conditions with 30% H
during 3 min.
2 2
O
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes

6
A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
1
8
6
4
00
1
00
0
80
60
40
20
0
0
0
20
0
20
30
40
50
60
70
80
90
100
Temperature (°C)
(1 mmol), catalyst (3.8 ꢂ 10ꢀ mmol), solvent-free conditions, 3 min.
4
2 2
Fig. 7. Optimization of catalytic reaction temperature, thioanisole (1 mmol), 30% H O
1
00
100
80
60
40
20
0
80
60
40
20
0
0
1
2
3
4
5
6
[
H O ]/[Thioanisole]
2 2
ꢀ
4
Fig. 8. Effect of a [H
free conditions, 3 min, 50 C.
2
O
2
]/[thioanisole] ratio on sulfoxidation conversion (left axis) and sulfoxidation selectivity (right axis), catalyst (3.8 ꢂ 10 mmol), solvent-
ꢁ
1
20
00
Table 1
Results of catalytic oxidation of various sulfides with H
catalyzed by Fe
2
O
2
(30% aqueous)
1
00
a
95
94
3
O
4
2 2
@SiO e(CH )
3
ePBSB/MoO
2
.
1
9
1
8
4
Sulfides
Sulfide
%
TOF
(mmol) Conversionb
(h )c
ꢀ1
80
60
40
20
0
7
2
S
10
100
526,000
S
10
10
100
100
526,000
526,000
S
10
99<
<521,000
S
3
0
S
S
10
1
95
2
500,000
1052
0.0007 0.0008
0.001
0.003
0.005
0.007
Amount of catalyst (mg)
Fig. 9. Effect of
solvent-free conditions, thioanisole (10 mmol), H
reaction time ¼ 3 min.
a
catalyst amount on sulfoxidation conversion under
ꢁ
2
O
2
(10 mmol), T ¼ 50 C,
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
3 4
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe O nanoparticles in solvent-free conditions, Comptes
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004

A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
7
Table 1 (continued )
Sulfides
The thermal stability of the catalyst was studied using
thermogravimetric assay. Given the thermogravimetric
analysis in Fig. S2, the weight loss at 125 and 413 C for
Sulfide
%
TOF
b
(h )c
ꢀ1
ꢁ
(mmol) Conversion
3 4 2 2 3 2
Fe O @SiO e(CH ) ePBSB/MoO can be attributed to the
water removal and onset of molybdenum complex
decomposition.
S
1
12
6300
1
1
20
10,520
S
3.2. Catalytic oxidation of sulfides by Fe
ePBSB/MoO
3 4 2 2 3
O @SiO e(CH )
2
S
15
7890
The Fe
3
O
4
@SiO
2
e(CH
2
)
3
ePBSB/MoO
2
catalyst was used
to oxidize various sulfides using 30% H
2 2
O . In the beginning
O
H
OH
of the catalytic process, some parameters were optimized,
including the kind of solvent, amount of the catalyst,
temperature of the catalytic reactor, reaction time, and
substrate to oxidant molar ratio. After running the catalytic
process for thioanisole oxidation with 30% H O and
2 2
various solvents (5 mL), it has been found that solvent-free
conditions bring about the highest conversion (100%) in
a
Catalytic reaction condition: solvent free; [sulfides]/[H
2
O
2
]
(1:1),
ꢁ
catalyst ¼ 0.00038 mmol, reaction temperature ¼ 50 C, reaction time ¼
3
min.
b
Conversion were determined by GC-FID (flame ionization detector),
conversion ¼ [(mole of SO) þ (mole of SO )]/(mole of initial sulfide).
Calculated as (mmol of product)/(mmol of catalyst) ꢂ hours.
2
c
3
min (Fig. 6). Fig. 7 shows that the best conversion of
ꢁ
of Fe
no hysteresis loop and have the magnetic saturation at
7.67 and 13.63 emu/g, respectively. It seems that the silica
layer on magnetite NPs in Fe @SiO e(CH ePBSB/MoO
is the leading cause of decreased magnetic saturation.
However, the result suggests that the catalyst can be
separated from the solution using the external magnetic
3
O
4
NPs and Fe
3
O
4
@SiO
2
e(CH
2
)
3
ePBSB/MoO
2
reveal
thioanisole to oxidation products was obtained at 50 C.
The thioanisole was oxidized by several [H O ]/[thio-
anisole] ratios. For this purpose, the 0.5, 1, 1.5, 2 ratios were
set in the separate catalytic reactions. According to Fig. 8,
the best sulfoxidation result was obtained in the ratio of 1:0
[H O ]/[thioanisole]. Our results suggested that sulfone
2
2
5
3
O
4
2
2
)
3
2
2
2
product was increased by rising the [H O ]/[thioanisole]
2
2
field. Fig. 4a and b presents the SEM image of Fe
Fe @SiO e(CH ePBSB/MoO . The comparison of SEM
images showed no change in morphology. Fig. 4c shows
transmission electron microscopy images of the Fe @-
SiO e(CH ePBSB/MoO nanocatalyst, which is approxi-
mately 15e18 nm in size. As presented in Fig. 5, EDX of
Fe @SiO e(CH ePBSB/MoO provides the existence of
Mo, Si, C, Cl, and the other elements on the catalyst surface.
3
O
4
NPs and
ratio more than 1:0. The catalyst level was optimized for
thioanisole oxidation using 0.0, 0.0007, 0.0008, 0.001,
0.003, 0.005, 0.007 g of Fe O @SiO e(CH ) ePBSB/MoO .
3
O
4
2
2
)
3
2
3
4
2
2 3
2
3
O
4
As illustrated in Fig. 9, the optimal amount of the catalyst
was reported as 0.0008 g. It appears that by increasing the
catalyst amount more than 0.0008 g caused the decom-
position of H O . Finally, we selected the sulfides (10 mmol)
2
2
)
3
2
3
O
4
2
2
)
3
2
2
2
as substrate, 30% H O (10 mmol) as oxidant, and 0.0008 g
2
2
ꢁ
2 2
Fig. 10. Conversion and selectivity for oxidation of sulfides by the catalyst, solvent-free conditions, H O (30%), 50 C, 3 min.
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes

8
A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
(10 mmol), catalyst (3.8 ꢂ 10ꢀ mmol), 3 min, 50 C,
4
ꢁ
2 2
Fig. 11. Running of the catalyst several times, reaction conditions: solvent-free; thioanisole (10 mmol), H O
*
Hot filtration test: after 1 min, the catalyst was removed from the reaction mixture (83% conversion) and the conversion was calculated after next 6 min (85%
conversion).
of the catalyst (3.8 ꢂ 10ꢀ mmol determined by atomic
4
ꢁ
absorption spectroscopy) at 50 C by stirring under solvent-
free conditions for 3 min. The catalyst reactor monitoring
exhibited no color and Mo leaching (detected by atomic
absorption spectroscopy) in the final solution after the
catalytic procedure. The results of catalytic oxidation of
sulfides, methyl phenyl sulfide, diphenyl sulfide, benzyl
phenyl sulfide, dipropyl sulfide, dibutyl sulfide, dimethyl
sulfide, bis(4-hydroxyphenyl) sulfide, diallyl sulfide, and
benzothiophene, are summarized in Table 1. Our results
demonstrated 100% conversion for thioanisole, dimethyl
Fe3O4@Si(CH2)3-
PBSB/MoO2
sulfide, and diallyl sulfide, as well as <99% conversion for
dibutyl sulfide in 3 min. Therefore, excellent turnover fre-
quency of the catalyst was achieved to oxidize the thio-
ꢀ
1
ꢀ1
ꢀ1
anisole (526,000 h ), dimethyl sulfide (526,000 h ),
3500
2500
1500
500
ꢀ1
diallyl sulfide (526,000 h ), dibutyl sulfide (521,000 h ),
-1
Wavenumber (cm )
ꢀ1
and dipropyl sulfide (500,000 h ). Accordingly, the reason
for low oxidation conversion of bis(4-hydroxyphenyl) sul-
fide, diphenyl sulfide, benzyl phenyl sulfide, and
Fig. 12. FT-IR spectrum of Fe @ SiO e(CH
3
O
4
2
2
)
3
ePBSB/MoaO
2
before the
catalytic reaction (solid line) and after the sixth run (dashed line).
Fig. 13. DRS spectrum of Fe
3
O
4
@ SiO
2
e(CH
2
)
3
ePBSB/MoaO
2
before the catalytic process (solid line) and after the sixth run (dashed line).
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
3 4
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe O nanoparticles in solvent-free conditions, Comptes
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004

A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
9
Table 2
Comparison of literature reports on the oxidation of thioanisole under various conditions.
Catalyst
Oxidant
Solvent
Time
%Conversion
95
Ref.
SBA-15 þ ImCl þ MoO
5
H
H
H
H
H
H
H
H
H
H
H
H
H
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
2
2
2
2
2
2
2
2
2
2
2
2
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
(30%)
Methanol
60 min
[
[
[
[
[
[
[
[
[
[
[
[
14]
60]
64]
55]
56]
62]
63]
57]
58]
54]
59]
61]
TiO2/AA/MoO
2
Ethanol
30 min
10 min
180 min
120 min
15 min
15 min
120 min
120 min
90 min
85 min
5 min
100
98
[(n-C
4
H
9
)
4
N]
4
(
a
-Mo
8
O
26
)
Methanol
ML
2
(Cu, Co Zn, Pd)
Solvent-free
Solvent-free
Methanol
80
Ti-MCM-41
89
[
[
PO
4
{WO(O
2
)
2
}
4
]@PIILP
95
MRAMoO
2
(O
2
)]
Methanol
99
VO-2A3HP-MCM-41
Ti-IEZ-MWW
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
96
<99
97
Fe
p-TsOH
e3O @APTMS/fluorene-SBeMoO
Fe @Si-APFSB-MoO
3 4
O @chit-based Cu complex
90
4
2
99
3
O
4
2
3 min
100
This work
benzothiophene is related to the steric effect of sulfides and
the catalyst. The selectivity of oxidation reactions for sulf-
oxide production is in the acceptable ranges (Fig. 10). The
further investigations of catalyst leaching. For this purpose,
the catalyst was removed from the reaction mixture after
1 min and the conversion was calculated after the other
3 min. The conversion showed no significant increase.
Fig. 12 presents no change in the IR spectra for the catalyst
before oxidation and sixth run. Therefore, comparison be-
tween DRS spectra of the catalyst (Fig. 13) before and after
the oxidation process shows no change. Regarding the
conversion results and literature [53], the proposed
mechanism seems to be followed through a seven-
2 2
catalytic oxidation of the substrate with aqueous H O in
the blank run (without catalysts) occurs with 2% conver-
sion. The chemical and physical stabilities of the catalyst
result in recycling and reusing of the catalyst several times
(
six times). As shown in Fig. 11, the catalyst was separated
easily with the magnet and used several times for epoxi-
dation process. A hot filtration test was performed for
3 4 2 2 3 2 2 2
Scheme 2. Proposed catalytic cycle for oxidation of sulfides by Fe O @SiO e(CH ) ePBSB/MoO with H O .
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes

10
A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
coordinate intermediate (Scheme 2). In a catalytic cycle,
oxidation process starts with attacking of H to Mo
center and generation of oxoeperoxo Mo(VI) precursor. In
[7] A. Rostami, B. Tahmasbi, F. Abedi, Z. Shokri, J. Mol. Catal. A: Chem.
78 (2013) 200e205.
3
2 2
O
[
[
8] M. Madesclaire, Tetrahedron 42 (1986) 5459e5495.
9] A.R. Supale, G.S. Gokavi, Catal. Lett. 124 (2008) 284e287.
*
the following, sulfur electron pair attacks the
s
(OeO) of oxo
[10] M. Bagherzadeh, M. Zare, J. Sulfur Chem. 32 (2011) 335e343.
11] K. Krishnasamy, V. Venkateswaran, M. Shanmugam, J. Dharmaraja, J.
Sulfur Chem. 28 (2007) 365e369.
12] M. Rahimizadeh, M. Bakavoli, H. Hassani, M. Gholizadeh, J. Sulfur
Chem. 28 (2007) 265e268.
13] A. Basak, A.U. Barlan, H. Yamamoto, Tetrahedron: Asymmetry 17
[
[
[
[
eperoxo Mo(VI), and the catalyst is regenerated with pro-
duction of sulfoxide.
Table 2 shows the comparison between the novel pre-
sented catalyst and literature reports. The Fe
e(CH ePBSB/MoO indicated higher oxidation catalytic
activity of thioanisole with excellent TOF (TOF: turnover
3 4 2
O @SiO
(2006) 508e511.
2
)
3
2
14] C.J. Carrasco, F. Montilla, L. Bobadilla, S. Ivanova, J.A. Odriozola,
A. Galindo, Catal. Today 255 (2015) 102e108.
[15] M. Bagherzadeh, M.M. Haghdoost, A. Ghanbarpour, M. Amini,
H.R. Khavasi, E. Payab, A. Ellern, L.K. Woo, Inorg. Chim. Acta 411
ꢀ1
frequency) (<526,000 h ). Finally, by comparing the cat-
alytic reaction time of the reported works in the literature
(2014) 61e66.
(
6
Table 2), 90 min [54], 180 min [55], 120 min [56e58],
0 min [14], 85 min [59], 30 min [60,61], and 15 min [62,63]
with Fe @SiO e(CH ePBSB/MoO (3 min), it is found
[16] N. Gharah, S. Chakraborty, A.K. Mukherjee, R. Bhattacharyya, Inorg.
Chim. Acta 362 (2009) 1089e1100.
17] A. Fuerte, M. Iglesias, F. S ꢀa nchez, A. Corma, J. Mol. Catal. A: Chem.
[
3
O
4
2
2
)
3
2
211 (2004) 227e235.
that the presented catalyst is efficient, time saving, and
paramount.
[18] M. Bagherzadeh, M. Zare, J. Coord. Chem. 66 (2013) 2885e2900.
[19] A. Bezaatpour, S. Khatami, M. Amiri, RSC Adv. 6 (2016) 27452
e27459.
[
20] A.K. Sah, N. Baig, Catal. Lett. 145 (2015) 905e909.
4
. Conclusions
[21] M.A. Martins, C.P. Frizzo, D.N. Moreira, L. Buriol, P. Machado, Chem.
Rev. (Washington, DC, U. S.) 109 (2009) 4140e4182.
[
[
[
[
22] R. Noyori, M. Aoki, K. Sato, Chem. Commun. (Cambridge, U. K.)
In the present study, following our previous researches
(2003) 1977e1986.
on the catalytic activity, we found successful covalent
anchoring of a phenoxy butane-based Mo(VI) tetradentate
Schiff base complex on magnetite NPs. The novel para-
magnetic recoverable catalyst has been studied as nano-
catalyst for oxidation of methyl phenyl sulfide, diphenyl
sulfide, benzyl phenyl sulfide, dipropyl sulfide, dibutyl
sulfide, dimethyl sulfide, bis(4-hydroxyphenyl) sulfide,
diallyl sulfide, and benzothiophene. The catalyst was
recovered successfully using the magnet from the catalytic
reactor and reused as a catalyst for six times without
23] S. Caron, R.W. Dugger, S.G. Ruggeri, J.A. Ragan, D.H.B. Ripin, Chem.
Rev. (Washington, DC, U. S.) 106 (2006) 2943e2989.
24] A. Podgor ꢁs ek, M. Zupan, J. Iskra, Angew. Chem., Int. Ed. 48 (2009)
8424e8450.
25] R. Dileep, B. Rudresha, RSC Adv. 5 (2015) 65870e65873.
[26] A. Mavrogiorgou, M. Baikousi, V. Costas, E. Mouzourakis,
Y. Deligiannakis, M. Karakassides, M. Louloudi, J. Mol. Catal. A:
Chem. 413 (2016) 40e55.
[
27] A. Bezaatpour, M. Amiri, V. Jahed, J. Coord. Chem. 64 (2011) 1837
e1847.
[
[
28] L. Hamidipour, F. Farzaneh, C. R. Chimie 17 (2014) 927e933.
29] C. Baleiz a~ o, B. Gigante, D. Das, M. Alvaro, H. Garcia, A. Corma, J. Catal.
ꢀ
223 (2004) 106e113.
decrease in conversion and selectivity. Fe
e(CH ePBSB/MoO catalyst illustrated excellent cata-
lytic activity and remarkable short catalytic time (3 min)
than the other reported catalysts. The Fe @SiO e(CH
ePBSB/MoO catalyst indicated a remarkable high TOF
3
O
4
@SiO
2
[30] A. Bezaatpour, M. Behzad, V. Jahed, M. Amiri, Y. Mansoori,
Z. Rajabalizadeh, S. Sarvi, Reac. Kinet. Mech. Cat. 107 (2012) 367e381.
2
)
3
2
[31] M. Fadhli, I. Khedher, J.M. Fraile, J. Mol. Catal. A: Chem. 420 (2016)
282e289.
3
O
4
2
2
)
3
[32] S.P. Shylesh, M. Jia, A. Seifert, S. Adappa, S. Ernst, W.R. Thiel, New J.
Chem. 33 (2009) 717e719.
[33] A.M. Garcia, V. Moreno, S.X. Delgado, A.E. Ramírez, L.A. Vargas,
2
ꢀ
1
(
<526,000 h ).
ꢀ
M.A. Vicente, A. Gil, L.A. Galeano, J. Mol. Catal. A: Chem. 416 (2016)
10e19.
[
[
[
34] J. Zhang, P. Jiang, Y. Shen, W. Zhang, X. Li, Microporous Mesoporous
Mater. 206 (2015) 161e169.
35] P. Piaggio, P. McMorn, C. Langham, D. Bethell, P.C. Bulman-Page,
F.E. Hancock, G.J. Hutchings, New J. Chem. 22 (1998) 1167e1169.
36] T. Chattopadhyay, A. Chakraborty, S. Dasgupta, A. Dutta,
M.I. Men eꢀ ndez, E. Zangrando, Appl. Organomet. Chem. (2016),
Acknowledgments
The authors would like to thank and appreciate
Research Deputy of Mohaghegh-e-Ardabili University, Iran,
for financial support under the project (Grant number:
http://dx.doi.org/10.1002/aoc.3663.
2
81).
[37] P.B. Bhat, B.R. Bhat, New J. Chem. 39 (2015) 273e278.
[
[
[
[
[
[
38] A. Farokhi, H. Hosseini-Monfared, New J. Chem. 40 (2016) 5032
e5043.
39] J. Sun, G. Yu, L. Liu, Z. Li, Q. Kan, Q. Huo, J. Guan, Catal. Sci. Technol. 4
Appendix A. Supplementary data
(2014) 1246e1252.
40] M. Mohammadikish, M. Masteri-Farahani, S. Mahdavi, J. Magn.
Magn. Mater. 354 (2014) 317e323.
41] T. Li, C. Yang, X. Rao, F. Xiao, J. Wang, X. Su, Ceram. Int. 41 (2015)
Supplementary data related to this article can be found
at http://dx.doi.org/10.1016/j.crci.2017.07.004.
2214e2220.
42] C.I. Fernandes, M.D. Carvalho, L.P. Ferreira, C.D. Nunes, P.D. Vaz, J.
Organomet. Chem. 760 (2014) 2e10.
43] X. Zhang, G. Wang, M. Yang, Y. Luan, W. Dong, R. Dang, H. Gao, J. Yu,
Catal. Sci. Technol. 4 (2014) 3082e3089.
References
[
[
1] O.A. Wong, Y. Shi, Chem. Rev. 108 (2008) 3958e3987.
2] C.A. Gamelas, A.C. Gomes, S.M. Bruno, F.A. Almeida Paz, A.A. Valente,
[44] A. Bezaatpour, Reac. Kinet. Mech. Cat. 112 (2014) 453e465.
[45] D.M. Boghaei, A. Bezaatpour, M. Behzad, J. Mol. Catal. A: Chem. 245
(2006) 12e16.
[46] J. Rahchamani, M. Behzad, A. Bezaatpour, V. Jahed, G. Dutkiewicz,
M. Kubicki, M. Salehi, Polyhedron 30 (2011) 2611e2618.
[47] Z. Peng, K. Hidajat, M. Uddin, J. Colloid Interface Sci. 271 (2004) 277
e283.
M. Pillinger, C.C. Rom a~ o, I.S. Gonalves, Dalton Trans. 41 (2012) 3474
e3484.
[
[
[
[
3] F. Bigi, H.Q. Nimal Gunaratne, C. Quarantelli, K.R. Seddon, C. R.
Chimie 14 (2011) 685e687.
4] B.B. Loura, T.G. Alhazov, O. Fioletova, N.S. Amirgouliane, C. R. Chimie
7
(2004) 45e50.
5] S. Menati, H. Amiri Rudbari, B. Askari, M. Riahi Farsani, F. Jalilian,
G. Dini, C. R. Chimie 19 (2016) 346e355.
6] N. Baig, V.K. Madduluri, A.K. Sah, RSC Adv. 6 (2016) 28015e28022.
[48] X. Huang, W. Guo, G. Wang, M. Yang, Q. Wang, X. Zhang, Y. Feng,
Z. Shi, C. Li, Mater. Chem. Phys. 135 (2012) 985e990.
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
3 4
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe O nanoparticles in solvent-free conditions, Comptes
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004

A. Bezaatpour et al. / C. R. Chimie xxx (2017) 1e11
11
[
[
49] S. Ilhan, H. Temel, A. KIlIc, J. Coord. Chem. 61 (2008) 277e284.
50] F.J. Arnaiz, R. Aguado, J. Sanz-Aparicio, M. Martinez-Ripoll, Poly-
hedron 13 (1994) 2745e2749.
51] W. Hill, N. Atabay, C. McAuliffe, F. McCullough, S. Razzoki, Inorg.
Chim. Acta 35 (1979) 35e41.
52] J. Topich, Inorg. Chem. 20 (1981) 3704e3707.
[58] Y. Kon, T. Yokoi, M. Yoshioka, S. Tanaka, Y. Uesaka, T. Mochizuki,
K. Sato, T. Tatsumi, Tetrahedron 70 (2014) 7584e7592.
[59] A. Rostami, F. Hassanian, A. Ghorbani-Choghamarani, S. Saadati,
Phosphorus, Sulfur Silicon Relat. Elem. 188 (2013) 833e838.
[60] M. Jafarpour, A. Rezaeifard, M. Ghahramaninezhad, F. Feizpour,
Green Chem. 17 (2015) 442e452.
[
[
[
53] M. Bagherzadeh, M.M. Haghdoost, M. Amini, P.G. Derakhshandeh,
Catal. Commun. 23 (2012) 14e19.
[61] A. Bezaatpour, E. Askarizadeh, S. Akbarpour, M. Amiri, B. Babaei, J.
Mol. Catal. A: Chem. 436 (2017) 199e209.
[
[
54] A. Fakhri, A. Naghipour, Mater. Technol. 31 (2016) 846e853.
55] M. Khorshidifard, H.A. Rudbari, B. Askari, M. Sahihi, M.R. Farsani,
F. Jalilian, G. Bruno, Polyhedron 95 (2015) 1e13.
[62] S. Doherty, J.G. Knight, M.A. Carroll, J.R. Ellison, S.J. Hobson,
S. Stevens, C. Hardacre, P. Goodrich, Green Chem. 17 (2015) 1559
e1571.
[
56] Y. Kon, T. Yokoi, M. Yoshioka, Y. Uesaka, H. Kujira, K. Sato,
T. Tatsumi, Tetrahedron Lett. 54 (2013) 4918e4921.
57] M. Nikoorazm, A. Ghorbani-Choghamarani, M. Khanmoradi, Appl.
Organomet. Chem. 30 (2016) 236e241.
[63] J.J. Boruah, S.P. Das, S.R. Ankireddy, S.R. Gogoi, N.S. Islam, Green
Chem. 15 (2013) 2944e2959.
[64] C. Yang, Q. Jin, H. Zhang, J. Liao, J. Zhu, B. Yu, J. Deng, Green Chem. 11
(2009) 1401e1405.
[
Please cite this article in press as: A. Bezaatpour, et al., Green, inexpensive, and fast conversion of sulfides to sulfoxides by
multiusable Mo(VI) macrocyclic Schiff base complex supported on Fe
Rendus Chimie (2017), http://dx.doi.org/10.1016/j.crci.2017.07.004
3 4
O nanoparticles in solvent-free conditions, Comptes