Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction

Article abstract of DOI:10.1007/s10562-021-03755-w

A novel Pd-NHC functionalized magnetic Fe₃O₄@SBA-15@NHC-Pd was synthesized and used as an efficient heterogeneous catalyst in the Suzuki–Miyaura C–C bond formation reactions. The Fe₃O₄@SBA-15@NHC-Pd characterized by X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy?(TEM), Energy Dispersive X-ray analysis (EDX), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA). The Inductively Coupled Plasma-Optical emission spectroscopy (ICP-OES)?analysis was used to determine the exact amount of Pd (0.33?wt%) in Fe₃O₄@SBA-15@NHC-Pd. The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the catalyst's structure, while no reducing agent was used. The NHC moieties in the catalyst structure could be stabilize Pd(0) nanoparticles prevents agglomeration. The magnetic catalyst was effectively used in the Suzuki–Miyaura cross-coupling reaction of substituted phenylboronic acid derivatives with (hetero)aryl bromides in the presence of a K₂CO₃ at room temperature in aqueous media and magnetic catalyst could be simply extracted from the reaction mixture by an external magnet. Different aryl bromides were converted to coupled-products in excellent yields with spectacular TOFs values (up to 1,960,339?h^?1); in the presence of 1?mg of Fe₃O₄@SBA-15@NHC-Pd catalyst (contains 3.1 × 10^–6?mol% Pd) at room temperature in aqueous media. After reusability experiments, it is found that this catalyst was effectively used up to ten times in the reaction with almost consistent catalytic efficiency. A decrease in the activity of the 10th reused catalyst was found as 9%. Graphic Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-021-03755-w

Catalysis Letters
https://doi.org/10.1007/s10562-021-03755-w
Highly Active Fe3O4@SBA‑15@NHC‑Pd Catalyst for Suzuki–Miyaura
Cross‑Coupling Reaction
Mitat Akkoç1,2 · Nesrin Buğday2 · Serdar Altın3 · İsmail Özdemir2,4 · Sedat Yaşar2,4
Received: 16 March 2021 / Accepted: 22 July 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021
Abstract
A novel Pd-NHC functionalized magnetic Fe3O4@SBA-15@NHC-Pd was synthesized and used as an efcient heterogene-
ous catalyst in the Suzuki–Miyaura C–C bond formation reactions. The Fe3O4@SBA-15@NHC-Pd characterized by X-Ray
Difraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy, Scanning
Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray analysis (EDX), Ther-
mogravimetric Analysis (TGA), Diferential Thermal Analysis (DTA). The Inductively Coupled Plasma-Optical emission
spectroscopy (ICP-OES) analysis was used to determine the exact amount of Pd (0.33 wt%) in Fe3O4@SBA-15@NHC-Pd.
The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the catalyst’s structure,
while no reducing agent was used. The NHC moieties in the catalyst structure could be stabilize Pd(0) nanoparticles prevents
agglomeration. The magnetic catalyst was efectively used in the Suzuki–Miyaura cross-coupling reaction of substituted
phenylboronic acid derivatives with (hetero)aryl bromides in the presence of a K2CO3 at room temperature in aqueous media
and magnetic catalyst could be simply extracted from the reaction mixture by an external magnet. Diferent aryl bromides
were converted to coupled-products in excellent yields with spectacular TOFs values (up to 1,960,339 h−1); in the presence
of 1 mg of Fe3O4@SBA-15@NHC-Pd catalyst (contains 3.1×10–6 mol% Pd) at room temperature in aqueous media. After
reusability experiments, it is found that this catalyst was efectively used up to ten times in the reaction with almost consist-
ent catalytic efciency. A decrease in the activity of the 10th reused catalyst was found as 9%.
Graphic Abstract
Catalyst
Keywords Magnetic palladium catalyst · Pd(II)-N-heterocyclic carbene complex · Suzuki–Miyaura cross-coupling
reaction · SBA-15 · Magnetite
Extended author information available on the last page of the article
Vol.:(0123456789)
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M. Akkoç et al.
chemistry and catalysis during the last 30 years. NHC
ligands have been used as an alternative to phosphine
ligands in homogeneous and heterogeneous catalysis in
recent years due to their superior properties such as easy
synthesis, stability against air and moisture, non-toxicity,
strong σ-donor, and weak π-acceptor features [31, 32].
These features make an essential contribution to the sta-
bility of the catalyst in homogeneous and heterogeneous
catalysis systems. In catalysis, Pd-NHC complexes have
ofered similar or often better results than Pd-phosphine
complexes. For this reason, Pd-NHC complexes can be
considered as one of the best options as a catalyst for
Suzuki–Miyaura [32–41], Heck [42–44], Sonogashira [44,
45], and Hiyama [46] cross-coupling reactions [47]. Thus,
the immobilization of Pd-NHC species to support materi-
als that generate heterogeneous catalysts is being studied
intensively [47]. The core-shell structure of magnetite
nanoparticles-mesoporous Silica provides high surface
area and magnetic properties essential for heterogeneous
catalyst features. The immobilization of Pd-NHC with
MNPs coated silicates such as SiO2, MCM-41, SBA-15
have been reported and applied on C–C bond formation
reactions successfully [48–58]. Silica-coated magnetite
was frst used with diferent ligands for immobilizing Pd
metal. For example, Dong et al. synthesized a supported
Pd(II) complex on magnetite core–shell of Fe3O4@SiO2
for the Suzuki–Miyaura cross-coupling reaction [49].
They claimed that their catalyst’s reusability is high and
can catalyze the Suzuki reaction six times without sig-
nifcantly decreasing the catalyst performance at 80 °C
in EtOH. Khazaei et al. prepared nano-Fe3O4@SiO2 sup-
ported Pd(0) nanocatalyst and used as a catalyst on Suzuki
coupling reaction of aryl iodide and aryl bromide with
aryl boronic acid derivatives in the presence of CaO as
a base at 85 °C in aqueous media [51]. This catalyst can
also show high catalytic activity and reusability without
loss on catalytic activity after fve runs. Fafee et al. also
prepared Fe3O4@SiO2 supported Vitamin B1-Pd complex
and investigated its catalytic activity on Suzuki coupling
of aryl halides at 60 °C in EtOH [59]. They reported good
to high yields of coupled products of aryl halides with
substituted phenylboronic acid derivatives. Also, the cata-
lyst reported showed fve reusabilities with a slight loss of
its activity. Tai et al. prepared mesoporous Silica, which
functionalized sulfonic acid, coated magnetite-Pd catalyst,
and used as a catalyst for propionic acid’s esterifcation
reaction. They have achieved satisfactory results with fac-
ile separation and reuse [60]. Pd(II)-Schif base complex
supported to Fe3O4 nanoparticles synthesized by Keypour
et al., and they used this heterogeneous catalyst on the
Suzuki cross-coupling reactions of aryl halides (Cl, Br,
I) with phenylboronic acid and Heck coupling reactions
of aryl halides (Br, I) with styrene [61]. After that, recent
1 Introduction
Magnetic nanoparticles (MNPs) and mesoporous materials
take attention in recent years due to their outstanding prop-
erties in the context of green chemistry. The applications
of MNPs in the various felds are getting increase due to
the versatility of MNPs, such as low toxicity, biocompat-
ibility, and high magnetic susceptibility [1–4]. Last 3 dec-
ades, porous materials are prevalent because of the large
surface area combined with uniform pore size, well-defned
pores, enhanced accessibility, and their ability to anchor
diverse chemical functionalities on their surface. Santa Bar-
bara Amorphous (SBA), which is one of the most popular
a porous material, was considered a suitable candidate for
many applications such as catalysis, adsorption, immobi-
lization, drug delivery, and chromatographic techniques
thanks to their well-defned pore structure, large pore size,
inert matrix, thick pore layer, and high thermal and hydro-
thermal stability [5–8]. Diferent types of SBA materials
such as SBA-1 (Pm3n, cubic), SBA-15 (P6mm, hexago-
nal), and SBA-16 (Im3m, cubic) [9–11] were reported in
the literature. According to IUPAC nomenclature, SBA-15
is classifed as mesoporous materials [12–15] due to pore
size between 2 and 50 nm. For these reasons, it has been
considered for the simple functionalization inside for metal
removal [16], the release of large molecules [17], and as
support for catalysts [18].
Recently, scientists have studied the catalytic potential of
mesoporous materials. Kqnoevenagel condensation, biomass
transformations, selective oxidation reactions in the conver-
sion of hydrocarbons and hydrodesulfurization, and C–C
bond formation reactions have been performed using diverse
mesoporous MCM-41, MCM-48, MCM-50, SAB-15, SiO2,
SBA-16 as support materials [19–22]. Suzuki–Miyaura,
Negishi, Hiyama, Mizoroki–Heck, Sonogashira-Hagihara,
and Stille are the most efective palladium-catalyzed C–C
bonds formations reactions ever reported between two mol-
ecules to produce fne chemicals. The chemicals produced
by these catalytic systems are used in many industrial felds
such as polymers, agriculture, health, optics, and medicine
[23–27]. Therefore, it is crucial to develop catalytic systems
and catalysts to synthesize these valuable and essential prod-
ucts in green chemistry. However, the design and synthesis
of efective catalysts that can work in catalytic systems cre-
ated within green chemistry are still challenging. Immobi-
lization of homogeneous species to support materials with
a high surface area, easy functionalization capability, and
high thermal and chemical stability is a crucial method
frequently used to synthesize new types of heterogeneous
catalysts [28–30].
N-heterocyclic carbenes (NHCs) have become an indis-
pensable ligand for transition metals in organometallic
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
studies have been reported to make optimum use of the
superior physical and chemical properties of mesoporous
support materials such as SBA-15 and MCM-41 deriva-
tives [58, 62–64].
2.2 Suzuki–Miyaura Cross‑Coupling Reaction
Aryl halide (0.5 mmol), aryl boronic acid (0.6 mmol), potas-
sium carbonate (1 mmol), and 1 mg of Fe3O4@SBA-15@
NHC@Pd catalyst (contains 3,1 × 10–6 mol% Pd) were
placed in the reaction tube under air, and 3 ml of 2-propanol/
water mixture (1:2, v:v) was added and stirred at room tem-
perature. Fe3O4@SBA-15@NHC@Pd was separated from
the reaction mixture by an external magnet after the reaction.
Then, 3 ml of water and 3 ml of DCM were added to the
reaction mixture, and the organic phase was separated by
extraction and dried over MgSO4. All volatiles evaporated
to obtain the corresponding crude product.
To our knowledge, a few SBA-15 supported Pd-NHC
complex catalyzed Suzuki reactions have been reported
so far [62]. Thus, we reported the synthesis and charac-
terization of the Fe3O4@SBA-15@NHC@Pd catalyst and
investigation of catalytic activity on Suzuki–Miyaura cross-
coupling reaction for (hetero)aryl bromides with substituted
phenylboronic acids at room temperature in aqueous media.
SBA-15 was chosen as a support material due to its high
surface area, high thermal and chemical stability, and abun-
dant Si–OH bonds that facilitate NHC ligand over -OH
group connection. As a result, the Fe3O4@SBA-15@NHC-
Pd catalyst showed spectacular efciency and TOFs up to
1,960,339 h−1 in Suzuki–Miyaura reactions with a simple
reaction condition at room temperature in aqueous media.
2.3 Synthesis
2.3.1 Synthesis of NHC Precursor
2.3.1.1 (1‑(2,3,4,5,6‑pentamethylbenzyl)‑3‑(etanole)‑ben‑
2 Experimental
2.1 General Considerations
Otherwise stated, all manipulations were carried out in aero-
bic conditions. All chemicals and solvents were purchased
from Sigma Aldrich, Fluorochem, and BLDpharm chemi-
cal companies and used as obtained. A Bruker Avance III,
400 MHz NMR spectrometer was used to perform NMR
analysis. All catalytic reactions were monitored on a Shi-
madzu GC2010 Plus system by GC-FID with an HP-5 col-
umn. New catalytic products were characterized with difer-
ent spectroscopic techniques and presented in the Supporting
Information section. The GC–MS analysis of compounds
was performed on a Shimadzu GC–MS 2010 plus using a
TRX-5 column on positive ESI mode. The FTIR analysis
was performed with a PerkinElmer Spectrum 100 Gladi-
ATR FT/IR spectrometer. The crystal structure analysis of
the synthesized powder was performed by an X-ray difrac-
tometer labeled Rigaku Rint 2000, which powered by Cu
Kα radiation was used for characterization. The scan rate
was chosen as 20/min between 2° and 80°/min. The micro-
structural properties and the surface morphology of the syn-
thesized powders were investigated by Leo EVO-40 VPX
scanning electron microscope (SEM). For XPS analyse: XPS
instrument: PHI 5000 VersaProbe II, X rays: hn=1486,6 eV
monochromatic, spot 200 µm and Energy resolution (hi-res-
olution spectra): 0.8 eV were used. The TEM analyses were
performed by FEI TECNAI OSIRIS operating at 200 kV,
Morphological analysis with HAADF-STEM imaging mode,
Chemical analysis with the Super-X EDX detector system
(4 SDD detectors).
zimidazolium iodine)
The NHC precursor was synthesized according to the litera-
ture [65–67]. 2-iyodoethanole (1.8 g; 110 mmol) was added to
10 mL n-BuOH solution of 1-(2,3,4,5,6-pentamethylbenzyl)
benzimidazole (2.78 g; 100 mmol). Then, the reaction solution
was refuxed for 4 h. After the reaction cooled to room tem-
perature, yellow crystals were formed by themselves. Crystals
removed from the solution by fltration, washed diethyl ether
(5×5 mL), and dried under vacuum. Yellow crystals were
characterized by 1H and 13C NMR spectroscopy.
1
Yield: 75%, H NMR (400 MHz, DMSO-d6) δ = 8.97
(s, 1H, NCHN), 8.19 and 8.12 (d, J = 28 Hz, 4H, C6H4),
5.72 (s, 2H, CH2C6(CH3)5–2,3,4,5,6), 5.02 (s, 1H,
CH2CH2OH), 4.54 (t, j = 4.6 Hz, 2H, CH2CH2OH), 3.74
(m, 2H, CH2CH2OH), 2.27 (s, 3H, CH2C6(CH3)5–2,3,4,5,6),
2.24 (s, 6H, CH2C6(CH3)5–2,3,4,5,6), 2.21 (s, 6H,
CH2C6(CH3)5–2,3,4,5,6).13C NMR (100 MHz, DMSO-d6)
δ=141.8, 137.8, 134.4, 133.4, 132.1, 131.9, 127.1, 127.0,
125.9, 114.6, 114.3, 59.1, 49.8, 46.8, 17.5, 17.2, 16.9. Ele-
mental analysis for C21H27N2OI: %Calc. C: 56.01, H: 6.04,
N: 6.22; %found C: 56.12, H: 6.14, N: 6.38.
2.3.2 Catalyst Preparation
The synthesis of the Fe3O4@SBA-15@NHC@Pd catalyst
was presented in Scheme 1. First, the nano magnetite (Fe3O4)
1 3

M. Akkoç et al.
was synthesized via the co-precipitation method reported
with modifcations using FeCl3·6H2O and FeCl2·4H2O [68].
Next, synthesized Fe3O4 nanoparticles were coated with
Silica by tetraethylorthosilicate (TEOS) then doped in the
SBA-15 skeleton to produce Fe3O4@SBA-15 [62]. Then,
Fe3O4@SBA-15 was functionalized with the NHC ligand via
the hydroxyl group on the NHC. In the fnal step, Pd(OAc)2
was introduced to Fe3O4@SBA-15@NHC to aford Fe3O4@
SBA-15@NHC@Pd catalyst labeled as 3 (Scheme 1). These
Pd-doped nanoparticles were characterized by TEM, SEM,
FT-IR, XRD, XPS, DTA, TGA, and ICP-OES techniques.
As a result of the ICP-OES analysis, it was determined that
catalyst 3 contains 0.33 wt% Pd (3,1×10–6 mol% Pd).
3 Result and Discussions
3.1 Catalyst Characterization
The structural properties of Fe3O4@SBA-15@NHC-Pd were
investigated by XRD pattern, as shown in Fig. 1. Due to the
layer-by-layer production process, the XRD pattern should
exhibit several phases, including the starting materials in
the powders. We should indicate that the XRD pattern con-
sists of an amorphous structure and crystalline phases. It
is well known that SBA-15 gives a broad peak in the XRD
pattern [69], and a similar formation was also observed in
Scheme 1 Synthesis pathway of the Fe3O4@SBA-15@NHC@Pd catalyst
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
bands at 3352 (OH stretching), 1445, 1563 (C–N stretching)
and C–H stretching 2920, 2964, 1078, 765, 614, 415 cm−1
(Table 1) [70, 72]. After the connection of NHC to Fe3O4@
SBA-15 surface, the bands at 3352 cm−1 disappeared, and
these results indicate that it was successfully performed the
functionalization of Fe3O4@SBA-15 with NHC. The loss
of signal at 1563 cm−1 (CNC stretching of benzimidazole)
was attributed to the formation of the Pd–C bond (Pd-CNC
stretching of benzimidazole) after reaction with Pd(OAc)2.
The SEM image of Fe3O4@SBA-15@NHC-Pd is pre-
sented in Fig. 3a, and it is seen that the grain formation has
two diferent forms. We think that the large grain formation
may be due to the clustering of the small grains. The EDX
dot mapping analysis of Fe3O4@SBA-15@NHC-Pd was
presented in Fig. 3b–h, and it is seen that elements were
dispersed homogeneously on the surface.
Fig. 1 XRD pattern of Fe3O4@SBA-15@NHC-Pd
this study. The crystalline phase, which gives the Bragg
peaks in the pattern, was well matched by magnetite and Pd
phases. Furthermore, 2θ values at 30.47°, 35.82°, 43.63°,
53.61°, 57.31°, and 63.06° are assigned to the magnetite
phase (JCPDF number: 19-0629), the broad peaks below
2θ = 30° are matched by SBA-15 [69], and the peaks of
40.05°, 46.36° and 63.06° are assigned to Pd crystalline
phase (JCPDF number: 46-1043). According to the XRD
results, the Fe3O4@SBA-15@NHC-Pd catalyst was success-
fully synthesized, and the results are compatible with the
literature [62].
The HAADF-STEM analysis was used to determine the
elemental distribution in the particles (Fig. 4a). The ele-
mental distribution of the Fe3O4@SBA-15@NHC-Pd was
investigated by EDX analysis and revealed the presence of
the elemental distribution of C, Si, O, N, Fe, and Pd in the
Fe3O4@SBA-15@NHC@Pd catalyst. The particle size of Pd
was found below 100 nm (Fig. 4b). Figure 4c–g shows the
chemical analysis of the powders depending on the elements.
It is seen that Si, Fe, and O have a homogeneous distribution
in the structure which was also proven by EDX analysis.
At the same time, palladium particles have a homogeneous
distribution within the catalyst structure.
The bond structures of Fe3O4@SBA-15@NHC-Pd and
other chemical components were investigated by FTIR
spectroscopy (Fig. 2). The characteristic absorption peak
for Fe3O4 was observed at 442 cm−1 which belongs to Fe–O
bands, and the peak at 3352 cm−1 associated with the O–H
stretching vibration groups on the surface and physisorbed
H2O [70–73]. The absorption bands at 803 and 1056 cm−1
were attributed to Si–O–Si stretching vibrations [71, 72].
According to FT-IR analysis, Fe3O4 was coated with a
silica layer successfully. The FT-IR spectra of NHC give
The structural characterization of the catalyst was con-
tinued using the X-ray photoelectron spectroscopy (XPS)
analysis and detailed XPS spectra for each ion present in
Fig. 5a–h. The XPS spectrum should be investigated by the
aspect of all layers in the Fe3O4@SBA-15@NHC-Pd. The
large window XPS spectrum in Fig. 5a shows the spectrum
of existing elements in the material. The XPS peaks of SBA-
15 were given in Figs. 5b and c. The Si2s, Si2p, C1s, and
O1s electrons were observed at 153, 102, 282, and 531 eV,
respectively (Fig. 5b–e). The energy level of C1s in Fig. 5c
should be related to C–C/C=C bonds [74]. The N1s electron
Fe3O4@SBA-15@NHC-Pd
Fe3O4@SBA-15@NHC
Table 1 FTIR characteristic absorption of NHC, Fe3O4@SBA-15,
Fe3O4@SBA-15
Fe3O4@SBA-15@NHC and Fe3O4@SBA-15@NHC@Pd
Entry
Functional group
Absorption (cm−1
)
References
NHC
1
2
3
4
5
Fe–O streching
Si–O stretching
C–H bending
442
803, 1056
415, 614, 765, 1078
1186
1445, 1563
[70]
[71, 72]
[72]
[72]
[72]
C–O stretching
1000
2000
3000
4000
C–N stretching of
Wavenumber (cm-1)
benzimidazole
6
7
C–H stretching
O–H stretching
2920, 2964
3352
[70, 72]
[73]
Fig. 2 FTIR spectra of Fe3O4@SBA-15@NHC-Pd and other chemi-
cal components
1 3

M. Akkoç et al.
Fig. 3 SEM image of a Fe3O4@
SBA-15@NHC-Pd, b elemental
dot mapping analysis of the
sample at 1kx, and individual
mapping of c Si, d Pd, e Fe, f O,
g C, h N
Fig. 4 a and b TEM images of
Fe3O4@SBA-15@NHC-Pd, c
EDX-dot mapping and d, e, f
and g elemental distribution of
Pd, Fe, O, and Si, respectively
peak at 397 eV in Fig. 5f is due to the imidazolate-N atom
[75], and the peak reveals at 531 eV for O1s belongs to
the O atom in the NHC ligand [76]. It is well known that
Fe3p shows the existence of Fe ions and Fe2p split into two
energy level at ∼708 eV for 2p1/2 and ∼721 eV for 2p3/2
(Fig. 5g), and it can be explained by the formation of Fe2+
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
1400
Si 2s
1200
1000
800
600
400
200
164 162 160 158 156 154 152 150 148 146
Binding Energy (eV)
(b)
(a)
C 1s
1600
Si 2p
1600
1200
800
400
0
1200
800
400
112
108
104
100
96
296
292
288
284
280
Binding Energy (eV)
Binding Energy (eV)
(d)
(c)
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
O 1s
544
540
536
532
528
524
Binding Energy (eV)
(e)
(f)
(g)
(h)
Fig. 5 XPS spectra of a Fe3O4@SBA-15@NHC-Pd, b Si2s, c Si2p, d C1s, e O1s, f N1s, g Fe2p, and h Pd3d
1 3

M. Akkoç et al.
and Fe3+ in the structure which is an expected result for
magnetite [77]. Figure 5h exhibits the XPS spectra of the
Pd element in the structure and gives peaks at 333.22 eV,
338.43 eV, 334,89 eV, and 340,09 eV which correspond
to 3d5/2 and 3d3/2 orbitals of metallic state Pd0 and PdII,
respectively [6569]. As seen in the XPS analyzes, the syn-
thesized catalyst contains both Pd0 and Pd2+. Unlike the
literature [75–79], these results show that Pd+2 is reduced
to Pd0 due to the heat applied in the synthesis process. The
reduction of Pd(II) without any particular reduction reagent
is the desired situation for synthesizing Pd0 nanomaterials.
The net amount of palladium doped into the Fe3O4@
SBA-15@NHC was determined by ICP-OES analysis. 0.33
wt% Pd was measured in the structure of Fe3O4@SBA-15@
NHC-Pd.
3.2 Catalytic Studies
We performed a series of trial reactions to show the cata-
lyst’s activity on the Suzuki–Miyaura coupling reaction.
For this aim, a model reaction of bromoacetophenone and
PhB(OH)2 was chosen, and the results were presented in
Table 2. Initially, we settled on the reaction conditions in
our previous work [33–40], where 2-propanol/H2O used an
ad solvent system and K2CO3 as a base at room temperature.
After determining the solvent, these conditions were applied
to determine sufcient catalyst loading (Table 2, entries
1–4). When 1 mg of catalyst was used, the reaction was
completed simultaneously with the exact yield of 2 mg of the
catalyst used (Table 2, entries 1, 2). However, the catalyst
loading was reduced to 0.5 mg; a lower yield was obtained
(Table 2, entry 3). Thus, the sufcient amount of catalyst was
determined to be 1 mg (3.1×10–6 mol% Pd). Also, no prod-
uct formation was observed in our model reaction when no
catalyst was used (Table 2, entry 4). After defnition efcient
catalyst loading and reaction temperature, the suitability of
diferent types of bases was investigated on model reaction.
It is believed that carbonate-derived bases may be suitable
for this designed system due to their excellent solubility in
aqueous solutions (Table 2, entries 5, 6). The other standard
bases were also tried, and results showed that K2CO3 is an
appropriate base for this designed catalytic system (Table 2,
entries 7–9). After that, we used diferent solvents and aque-
ous solutions to choose solvents for our catalytic system.
2-propanol, EtOH, water, DMF, and dioxane did not give
good results due to insolubility or low solubility of 4-bro-
moacetophenone and PhB(OH)2 at the same time (Table 2,
entries 10–17). The aqueous solution of 2-propanol (1:2,
v/v) creates the best solvent environment to reveal the cata-
lyst’s activity. The aqueous solution of 2-propanol provides
optimum solubility of the substrate and boronic acid deriva-
tives together. 4-chloroacetophenone also tried to show the
efciency of catalyst on aryl chloride substrate. Unfortu-
nately, no product formed in the reaction of 4-chloroaceto-
phenone under the same reaction condition settled for aryl
bromides (Table 2, entry 19). However, an average yield
was obtained in the reaction performed at 80 °C for 12 h
Thermogravimetric analysis was used to determine the
presence of organic groups immobilized on the surface of
Fe3O4@SBA-15. Thermal gravimetric analysis (TGA) and
diferential thermal analysis (DTA) of the Fe3O4@SBA-15@
NHC-Pd are presented in Fig. 6. DTA and TG analysis show
three regions for both data related to endothermic activity in
the samples. The mass loss at a temperature below 166.4 °C
corresponds to the removed water and solvents from the
structure [43]. The second weight loss at 166.4 °C is related
to the calcination of the NHC ligand on the catalyst. The
other two reactions at 398.2 °C and 802.9 °C are related to a
thermal transformation of the crystal phase to the new stage,
losing some oxygen and nitrogen ions from the structure and
condensation of the silanol groups of SBA-15 [22, 75]. It
can be seen from these results that the catalyst has structural
stability at high temperatures and can be used for catalytic
reactions in this temperature range safely.
Fe3O4@SBA-15@NHC@Pd catalyst has a high mag-
netic response in the solvent. Figure 7 shows that when an
external magnetic feld is applied, the catalyst shows high
magnetization quickly.
Fig. 7 Magnetic response of the Fe3O4@SBA-15@NHC@Pd catalyst
in the i-PrOH
Fig. 6 DTA and TGA curve of the Fe3O4@SBA-15@NHC-Pd
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
Table 2 Optimization of the Suzuki-cross coupling reaction of phenylboronic acid and 4-bromoacetophenone catalyzed by Fe3O4@SBA-15@
NHC@Pd
Entrya
Catalyst loading
Base
Solvent
Temp/Time
Yield (%)
1
2
3
4
5
6
7
8
2 mg
1 mg
0.5 mg
–
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
1 mg
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
Cs2CO3
KtOBu
NaOH
KOH
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O
i-PrOH
EtOH
DMF
Dioxane
DMF/H2O
H2O/EtOH
H2O/Dioxane
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
H2O/i-PrOH
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 1 min
rt, 5 h
100
100
40
0
66
38
23
63
53
8
9
8
0
2
81
94
76
–
30
70
33
25
100
9
10
11
12
13
14
15
16
17
18b
19b
20b
21
22
23c
1 mg
1 mg
1 mg
3 mg
80 °C, 5 h
80 °C, 5 h
80 °C, 5 min
80 °C, 5 min
rt, 1 min
Pd(OAc)2, 0,0069 mg
PdCl2, 0.0055 mg
1 mg
aReaction conditions: 1 mg of Fe3O4@SBA-15@NHC@Pd (contains 3.1×10–6 mol% Pd), phenylboronic acid (0.6 mmol), 4-bromoacetophe-
none (0.5 mmol), Base (1.0 mmol), solvent 3 ml. GC yields determine according to 4-bromoacetophenone using (trifuoromethyl)benzene as an
internal standard
b4-Chloroacetophenone used as aryl halide
c4-Iodoanisole is used as aryl halide
(Table 2, entry 20). The developed catalytic system here is
more suitable for cross-coupling reactions of aryl bromides
than aryl chlorides from these results. Trials were carried out
with 4-chloroacetophenone to examine the efectiveness of
the catalyst in reactions with chlorinated aryl halides. Unfor-
tunately, no product formed in the reaction of 4-chloroace-
tophenone under the same reaction condition settled for aryl
bromides in 5 h (Table 2, entry 18). It was understood from
this experiment that the Suzuki cross-coupling reaction of
chlorinated aryl halides requires heat for product formation.
Thus, we applied heat to the reaction of 4-chloroacetophe-
none with PhB(OH)2, and an average yield was obtained in
the reaction performed at 80 °C for 12 h (Table 2, entry 19).
In order to see the efect of the catalyst loading on prod-
uct formation in the same reaction, a relatively better result
was obtained in our experiment by increasing the amount of
catalyst by three times (Table 2, entry 20). The developed
catalytic system here is more suitable for cross-coupling
reactions of aryl bromides than aryl chlorides from these
results. For comparison, diferent commercially available
palladium sources such as PdCl2 and Pd(OAc)2 were tested
at the same concentration in the catalytic system we created.
From the results we obtained, it was seen that the catalyst
we synthesized had much better activity than commercially
available palladium sources (Table 2, entries 20–22). The
reaction with 4-iodoanisole showed that the catalyst could
also have high activity in iodo aryl halides (Table 2, entries
23). After these optimization experiments, the optimum con-
ditions for the Suzuki–Miyaura coupling reactions of the
aryl bromides and substituted boronic acid derivatives are
as follows: 1 mg of catalyst (contains 3.1×10–6 mol% Pd),
1 3

M. Akkoç et al.
0.5 mmol ArBr, 0.6 mmol PhB(OH)2, 1 mmol K2CO3, and
2-propanol/H2O (1:2, v/v) at room temperature.
necessary for various applications such as biological and
doing more chemistry. 1,4-Dibromobenze was also used
on Suzuki cross-coupling reaction with diverse phenylbo-
ronic acid derivatives. Results show that both mono and di-
coupled products were formed simultaneously except in the
case of 3-formyl-4-methoxyboronic acid, where the mono-
coupled product formed selectively (Table 3, entry 22). In
other cases, the di-coupled products are formed proportion-
ally more selective than mono coupled products (Table 3,
entries 11, 33, 46). All these results show that the developed
catalytic system in this work works perfectly except for the
2-methylboronic acid case.
The optimization reaction condition on hand,
Suzuki–Miyaura cross-coupling reaction of wide-range
aryl bromides with diferent phenylboronic acid derivatives
were examined (Table 3). First, the cross-coupling reaction
of electron-withdraw p-substituted aryl bromides contains
CN, NO2, COCH3, CH3, and CF3 groups with phenylbo-
ronic acid, 4-tert-buthylboronic acid, 2-methoxyboronic
acid, and 3-formyl-4-methoxyboronic acid were studied.
With this catalytic system, approximately 2 million TOFs
values were obtained for the Suzuki coupling reaction of
electron-withdrawing substrates with 4-methoxy-3-formyl-
boronic acid and napthylboronic acis (Table 3, entries 34,
35, 36, 38, 39, 41). The results clearly showed that the reac-
tion could be completed in 0.5–5 min with excellent yields
for electron-withdrawing substituted aryl bromides and sub-
stituted phenylboronic acids. The reaction of 2-bromoben-
zonitrile with phenylboronic acid derivatives was also suc-
cessfully achieved in a short time with high yields (Table 3,
entries 7, 19, 29). While the reaction of 4-bromobenzonitrile
with the same phenylboronic acid derivatives is completed
in 1 min (Table 3, entries 8, 20, 30) 2-bromobenzonitrile is
completed in 5 min. It was seen from these results that steri-
cally compelling aryl bromides prolong the reaction time
at least fve times. The cross-coupling reaction of 2-meth-
ylboronic acid with aryl bromides needs at least 12 h to get
over 90% yields. However, reactions of 2-methoxyboronic
acid with aryl bromides resulted in high yields in a short
time. From these results, it is seen that the electronic efect
of substituents on the ortho position of phenylboronic acid
more critical rather than its steric efect. Here, it is thought
that the methoxy group’s mesomeric efect is more efec-
tive than its steric efect for high yields. The Suzuki cross-
coupling reaction of electron-donating aryl bromides with
substituted phenylboronic acids takes a longer time for
high yields (Table 3, entries 1–3, 13–15, 31–33, 43–45).
Although this is the case, the Suzuki reactions of electron-
donating substrates resulted in high yields in a maximum
of 30 min. The cross-coupling reaction of heteroaryl bro-
mides was also tested, and results were delighted with the
selectivity of mono or di-coupled products (Table 3, entries
10, 12, 22, 24, 49). The 2,6-dibomopyridine with phenylbo-
ronic acid and 4-tert-butylboronic acid resulted in the high
mono-coupled product, while napthylboronic acid gave a
di-coupled product. The reaction of 5-bromofuraldehyde
with phenylboronic acid and 4-tert-boronic acid formed
coupled products with high yields in minutes. The cross-
coupling reaction of heteroaryl compounds can be signif-
cant in the content of the obtained products, which may be
The catalyst’s reusability was investigated in the Suzuki
cross-coupling reaction of 4-bromoacetophenone with
PhB(OH)2 (Fig. 8). In repeated experiments, after the reac-
tion, the catalyst was separated from the reaction medium
with a magnet’s help. It was washed with a sufcient amount
of double distilled water and ethyl alcohol and dried in the
oven at 80 °C for hours to be used in the following reac-
tion. For each recent run, new substrates were used. Losses
amount of catalyst occurring in each separation was not con-
sidered. The results showed that the catalyst exhibit excellent
performance without signifcant loss in its catalytic activity
even on the 10th run.
In order to understand the leaching of Pd from the catalyst
structure, a fltration test was performed during the reaction.
For this purpose, we chose the Suzuki–Miyaura coupling
reaction of 4-methoxybenzene with PhB(OH)2. Five min-
utes after the reaction started, the reaction was stopped, and
the catalyst was removed from the reaction medium by an
external magnet, and the 0.1 mL of the reaction solution
was taken and analyzed by GC. Then, the solution without
catalyst was stirred at room temperature for an additional
5 min. After 5 min, another sample was taken for GC analy-
sis. After GC results, the 5th and 10th minutes yields were
found the same. In the light of these results, it can be consid-
ered that Pd metal is not leaching from the catalyst structure
under these reaction conditions. The amount of Pd in the ten
times used catalyst was determined by ICP-OES analysis
to validate the room temperature fltration test and found a
value very close to the initial amount (0.29 wt% Pd). This
result may shed light on the high catalytic activity of the
catalyst on reuse. However, the NHC ligand in the catalyst
structure may prevent the leaching of Pd metal. As is known,
NHCs are capable of forming strong covalent bonds with
transition metals. This strong covalent bond between Pd and
NHC contributes to the catalyst’s stability and saves the Pd
metal within the catalyst. The chemical stability of catalysts
is essential for both homogeneous and heterogeneous cata-
lytic systems under harsh conditions. Figure 9 shows the
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
Table 3 Suzuki–Miyaura cross-coupling of aryl bromides with substituted phenylboronic acids derivatives catalyzed by Fe3O4@SBA-15@
NHC@Pd
Entry
1
Ar-B(OH)2
Ar-Br
Pruduct
Time (min)
5
Yielda (%)
72
TON/TOF/(h−1
16,121/139287
)
2
3
4
5
5
1
69
64
16,215/134264
16,207/124472
16,202/972133
100
5
6
7
1
1
5
100
100
94
15,961/957696
16,336/980170
15,944/179849
8
9
1
1
100
100
15,944/956643
16,240/974438
10
11
3
1
95
16,213/308053
16,121/967273
62
38
35
12
13
20
10
16,053/16856
16,121/89956
93
14
15
16
10
10
1
90
86
16,215/87563
16,207/83630
16,202/972133
100
17
18
19
1
1
5
100
100
100
15,962/957695
16,336/980169
15,944/191328
20
21
1
1
100
100
15,944/956643
16,240/974437
22
23
2
1
96
16,213/466944
16,121/967273
58
42
1 3

M. Akkoç et al.
Table 3 (continued)
Entry
24
Ar-B(OH)2
Ar-Br
Pruduct
Time (min)
20
Yielda (%)
43
TON/TOF/(h−1
16,053/20709
)
25
26
27
28
20
20
20
1
82
80
16,121/39658
16,215/38917
16,207/35980
16,202/972133
74
100
29
30
1
1
94
20
65
15,944/899244
16,121/41109
31
32
33
30
30
30
91
95
89
16,121/29341
16,215/30809
16,207/28849
34
35
36
0.5
0.5
0.5
100
100
100
16,202/1944267
15,962/1915392
16,336/1960339
37
38
39
40
1
99
100
100
99
15,944/947076
15,944/1913287
16,240/1948875
16,394/973831
0.5
0.5
1
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
Table 3 (continued)
Entry
41
Ar-B(OH)2
Ar-Br
Pruduct
Time (min)
0.5
Yielda (%)
100
TON/TOF/(h−1
)
16,202/1944266
42
43
44
45
46
47
48
1
100
85
15,944/956643
16,121/54812
16,215/51890
16,207/49270
15,961/957696
16,336/980170
16,394/983667
15
15
15
1
80
76
100
100
62
1
1
38
49
50
20
55
5
16,325/29386
16,202/1256
12 h
93
51
52
53
54
12 h
12 h
12 h
12 h
87
85
82
89
16,121/1169
16,215/1149
16,207/1108
15,944/1183
1 3

M. Akkoç et al.
Table 3 (continued)
aReaction conditions: 1 mg of 3 (contains 3.1×10–6 mol% Pd), phenylboronic acid (0.6 mmol), aryl bromide (0.5 mmol), Base (1.0 mmol),
i-PrOH/water (1:2, 3 mL), room temperature (rt). GC yields determine according to aryl bromide using (trifuoromethyl)benzene as an internal
standard
Fig. 8 Recyclability of the
catalyst for the Suzuki–Miyaura
cross-coupling reaction
Recyclability
100
95
90
85
80
1
2
3
4
5
6
7
8
9
10
Run
3.2.2 Poisoning Test
O
O
O
O
Si
Si
O
Si
As it is known from the literature, the commercially avail-
able PVP and mercury are used for poisoning tests of cata-
lysts to determine the nature of catalysis [80–82]. According
to the XPS analysis, it is understood that the Pd metal is
bound to the NHC ligand by a covalent bond. If it is consid-
ered that some Pd leach from the structure of the catalyst and
passes into the solution, both heterogeneous (supported) and
homogeneous (leached) catalytic systems take palace. How-
ever, the activity of the homogeneous catalyst can be stopped
by adding PVP ligands to bind palladium. Herein, the PVP
ligand has been used to inhibit Pd metals in the solution. On
the other hand, the addition of water-insoluble PVP to the
reaction of 4-bromoastophenone with phenylboronic acid
does not afect the reaction yield. This result suggests that
the catalyst described here has only heterogeneous.
O
Si
O
Si
O
S i
O
S
i
O
Si
O
O
Ar-X
O
O
Ar-Ph
Fe3O4@SBA-15@NHC@Pd
Ar
X
Ph
Ar
Reductive
elimination
Oxidative
addition
O
O
Si
O
Si
O
Si
O
O
O
O
Si
O
O
S i
S
O
i
O
O
Si
O
Si
O
O
Si
O
Si
O
S i
S i
O
O
Transmetallation
Si
O
O
Si
O
O
S i
O
O
Si
O
O
K2CO3
PhB(OH)3
+ B(OH)3
X
PhB(OH)2
After many catalytic reactions, our Fe3O4@SBA-15@
NHC-Pd catalyst has shown high catalytic activity on
the Suzuki–Miyaura cross-coupling reaction for various
boronic acids and aryl bromides. Comparing the activities
of Fe3O4@SBA-15@NHC-Pd catalyst with similar types of
palladium catalysts on Suzuki–Miyaura coupling reactions
[83–85], it is seen that our catalyst has excellent catalytic
activity, spectacular TOFs values, and good recyclability
than many reported catalysts (Table 4) [48, 51, 79, 84–92].
Generally, most reported catalysts require high temperature
and high catalyst loading on Suzuki–Miyaura cross-coupling
reactions of aryl bromides with phenylboronic acid [48, 51,
79, 84–92]. In contrast, similar products were easily synthe-
sized at room temperature with high yields and spectacular
TOFs values via our catalyst. Another advantage of our cata-
lyst is the number of catalyst loadings. As seen in Table 4,
the reported works’ catalyst loadings are much higher than
Fig. 9 Proposed reaction mechanism of the Suzuki–Miyaura cross-
coupling reaction catalyzed by Fe3O4@SBA-15@NHC-Pd catalyst
possible mechanism of the Suzuki coupling reaction cata-
lyzed by Fe3O4@SBA-15@NHC-Pd catalyst schematically.
3.2.1 Characterization of the Recovered Catalyst
To see the changes in the used catalyst structure, the SEM
and EDX analyses were carried out. According to the SEM
and EDX analyses, there were small agglomerations without
severe catalyst structure changes (Fig. 10).
1 3

Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction
Fig. 10 SEM image and EDX spectrum of recycled catalyst
Table 4 Comparison of Fe3O4@SBA-15@NHC@Pd in the Suzuki–Miyaura reaction of 4-bromobenzonitrile with phenylboronic acid with
reported catalysts
Refs
Cat. (mol%), solvent, temperature
Time (min)
Yield (%)
[48]
[51]
[79]
[84]
[85]
[86]
[87]
SBA-15/CCPy/Pd(II) (0.3 mol%), EtOH/H2O (2:1), 50 °C, X=I, Xb =Cl
Fe3O4@SiO2-Pd(II)(0.03 mol%), EtOH, 85 °C, X=Br
60
98
65, 30a
20, 20a
120, 30a
180, 300b
120
85, 90a
98, 95a
92, 96a
94, 52b
99
Fe3O4@SiO2@VB1-Pd NPs (0.022 mol%), EtOH, 60 °C, X=Br
γ-Fe2O3-acetamidine-Pd, DMF, 100 °C, X=Br
CMC-NHC-Pd (0.8 mol%), EtOH/H2O (1:1), 60 °C, X=Br, Xb =Cl
Cell-NHC-Pd (0.75 mol%), DMF/H2O (1:1), 80 °C, X=Br
Pd/C-NHC-P(OR)3 (0.03 mol%), EtOH, 80 °C, X=Br
60
98
[88]
[89]
[49]
[90]
[91, 92]
This work
Pd-TEG, (0.005 mol%) H2O, 25 °C, X=Br
840
91
(PdII-NHC)n@SiO2 (0.27 mol%), DMF/H2O (2:1), 60 °C, X=Br
Fe3O4@SiO2@mSiO2-Pd(II)(0.5 mol%), EtOH, 80 °C, X=Br
Fe3O4@SiO2-NHC-Pd(II) (0.37 mol%), H2O, 60 °C, X=I
Fe3O4@MCM-41@NHC@Pd (0.01127 mmol%, i-PrOH/H2O (1:2), rt, X=Br
Fe3O4@SBA-15@NHC@Pd (3.1×10–8 mol Pd, i-PrOH/H2O (1:2), rt, X=Br
8a
95a
480a
95a
60, 90a
1, 15a
1, 5a
92, 93a
100, 100a
100,72a
aYield obtained for 4-bromobenzene substrate
bYield obtained for 4-chlorobenzene substrate
our catalytic system. However, our catalytic system does
not have the same efectiveness for aryl chlorides at room
temperature despite these superior features. For example,
although product formation is observed when the heat is
applied to the Suzuki reaction of 4-chloroacetophenone with
PhB(OH)2, the result is still unsatisfactory.
the amount of active catalyst, high reusability, high yields,
and a reasonably wide substrate tolerance, this catalytic
system seems to be more efective than the Pd catalyzed
Suzuki–Miyaura catalytic systems reported so far. Therefore,
we hope that this catalyst may have the potential for other
C–C bond formation reactions that require high temperatures
from these results.
Consequently, this catalyst showed extraordinary cata-
lytic activity on Suzuki–Miyaura reactions of very wide
aryl bromides and substituted PhB(OH)2. When considering
1 3

M. Akkoç et al.
12. Chen Y, Wang M, Zhang L, Liu Y, Han J (2017) RSC Adv
7:47104–47110. https://doi.org/10.1039/C7RA09947A
13. Nasrollahzadeh M, Issaabadi Z, Tohidi MM, Mohammad Sajadi S
(2018) Chem Rec 18:165–229. https://doi.org/10.1002/tcr.20170
0022
4 Conclusions
We could synthesize essential chemicals for many felds with
the catalytic system composed of a highly active and reus-
able magnetic Fe3O4@SBA-15 supported NHC-Pd catalyst
within the boundaries of green chemistry. In this catalytic
system we created, the catalyst reached very high TOF val-
ues. This novel catalyst showed spectacular catalytic activity
for an extensive range of aryl bromides in Suzuki–Miyaura
cross-coupling reactions with high reusability without
activity loss. The catalyst’s facilitating features, such as
the catalyst’s chemical stability, together with its moisture
and oxygen tolerance, high reusability, and strong magnetic
properties, make the catalyst very attractive. The appli-
cability of this catalyst in other palladium-catalyzed C–C
bond formation systems is under research. We expect that it
will provide high catalytic activity with reusability in other
reactions.
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Supplementary Information The online version contains supplemen-
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Acknowledgements XPS and TEM studies performed in France
(CEA LETI/DTSI/SCMC Grenoble Cedex 9 FRANCE and thanks
to N. GAMBACORTI for the organization of XPS and TEM analy-
sis) within the framework of the NFFA-Europe Transnational Access
Activity (NFFA Project ID: 723).
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M. Akkoç et al.
Authors and Afliations
Mitat Akkoç1,2 · Nesrin Buğday2 · Serdar Altın3 · İsmail Özdemir2,4 · Sedat Yaşar2,4
2
* Mitat Akkoç
mitat.akkoc@ozal.edu.tr
Catalysis Research and Application Center, İnönü University,
44280 Malatya, Turkey
3
4
* Sedat Yaşar
sedat.yasar@inonu.edu.tr
Faculty of Science and Arts, Department of Physics, İnönü
University, 44280 Malatya, Turkey
Faculty of Science and Arts, Department of Chemistry, İnönü
University, 44280 Malatya, Turkey
1
Hekimhan Vocational College, Department of Property
Protection and Security, Malatya Turgut Özal University,
Hekimhan, Malatya, Turkey
1 3