Synthesis, characterization, and catalytic activity in Suzuki coupling and catalase-like reactions of new chitosan supported Pd catalyst

Article abstract of DOI:10.1016/j.carbpol.2016.03.019

The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst and examination of its catalytic activity in: Suzuki coupling reactions by improving a simple, fast, and solvent-free microwave method.H₂O₂ decomposition reaction to find out its redox potential. Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR, TG/DTG, XRD, ¹H NMR, ¹³C NMR, SEM-EDAX, ICP-OES, Uv-vis spectroscopies, and magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst indicated high activity and long life time as well as excellent turnover number (TON) and turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst catalyzed H₂O₂ decomposition reaction with considerable high activity using comparatively small loading catalyst (10 mg). Redox potential of biomaterial supported Pd catalyst was still high without negligible loss (13% decrease) after 10 cycles in reusability tests. As a consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as high thermal stability, long life time, easy removal from reaction mixture and durability to air, moisture and high temperature.

Full text of DOI:10.1016/j.carbpol.2016.03.019

Accepted Manuscript
Title: Synthesis, Characterization, and Catalytic Activity in
Suzuki Coupling and Catalase-like Reactions of New Chitosan
Supported Pd Catalyst
Author: Talat Baran Tu¨lden Inanan Ayfer Mentes¸
PII:
S0144-8617(16)30226-0
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.carbpol.2016.03.019
CARP 10856
To appear in:
Received date:
Revised date:
Accepted date:
14-12-2015
23-2-2016
8-3-2016
Please cite this article as: Baran, Talat., Inanan, Tddotulden., & Mentes¸, Ayfer.,
Synthesis, Characterization, and Catalytic Activity in Suzuki Coupling and Catalase-
like Reactions of New Chitosan Supported Pd Catalyst.Carbohydrate Polymers
http://dx.doi.org/10.1016/j.carbpol.2016.03.019
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Synthesis, Characterization, and Catalytic Activity in Suzuki Coupling and Catalase-
like Reactions of New Chitosan Supported Pd Catalyst
Talat Baran*talatbaran_66@hotmail.com, Tülden Inanantkalburcu@gmail.com, Ayfer
Menteşayfermentes@yahoo.com
Department of Chemistry, Faculty of Science and Letters, Aksaray University, Aksaray,
Turkey

Corresponding author: Department of Chemistry, Faculty of Science and Letters, Aksaray
University, Aksaray, Turkey, 68100. Tel/fax: +903822882142

Highlights
ꢀ Catalase-like activity of biomaterial supported Pd catalyst decreased by only 12.9 % at
the end of 10 cycle.
ꢀ Synthesis of biarlys using free solvent at 4 min. under MW was succeeded.
ꢀ TON and TOF values for both applications determined high.
ꢀ Suzuki reaction exhibited high selectivity and no homo-coupling by-products.

Abstract:
The aim of this study is to analyze the synthesis of a new chitosan supported Pd catalyst
and examination of its catalytic activity in:
1) Suzuki coupling reactions by improving a simple, fast, and solvent-free microwave method
2) H2O2 decomposition reaction to find out its redox potential.
Pd catalyst was synthesized using chitosan as a biomaterial and characterized with FTIR,
1
13
TG/DTG, XRD, H-NMR, C-NMR, SEM-EDAX, ICP-OES, Uv-Vis spectroscopies, and
magnetic moment, along with molar conductivity analysis. Biomaterial supported Pd catalyst
indicated high activity and long life time as well as excellent turnover number (TON) and
turnover frequency (TOF) values in Suzuki reaction. Biomaterial supported Pd catalyst
catalyzed H2O2 decomposition reaction with considerable high activity using comparatively
small loading catalyst (10 mg). Redox potential of biomaterial supported Pd catalyst was still
high without negligible loss (13 % decrease) after 10 cycles in reusability tests. As a
consequence, eco-friendly biomaterial supported Pd catalyst has superior properties such as
high thermal stability, long life time, easy removal from reaction mixture and durability to air,
moisture and high temperature.
Keywords: Biomaterial supported Pd catalyst, Suzuki coupling reaction, redox potential,
microwave irradiation, solvent-free

1. Introduction
Green chemistry is one of the most attracted subjects nowadays (H. Clark, 1999). It is
concerned with catalysis, environmentally favorable solvents, supercritical fluids, and some
techniques such as microwave and real time analysis for pollution prevention (Fuji, 1993; H.
Clark, 1999; Li, 2005; Nuchter, Ondruschka, Bonrath & Gum, 2004). Catalysts are most
favored materials with superior properties such as ease of preparation, reusability, and
selectivity (Makha, Raston, Skelton & White, 2004). TON and TOF are significant
parameters due to their influence on both the commercial sustainability and the catalyst
potential for clean chemistry.
Biomaterial supported catalysts have attracted much attention in last 20 years due to their
eco-friendliness, non-toxicity, low-cost, bio-degradable features, and high metal adsorption
capacity (Sin, Yi & Lee, 2010; Yi, Lee, Sin & Lee, 2007). They have the advantages of being
economic and being used as eco-friendly reagents under mild reaction conditions (Calo et al.,
2004) Thus, solid supported biocatalysts, homogenous or heterogeneous, are operated in
Suzuki-coupling, Heck, decomposition, and aerobic oxidation reactions (Sin, Yi & Lee,
2010).
Chitin, chitosan, cellulose, silica, zeolite, and carbon are widely used biomaterial based
catalysts (Cui, Zhang & Li, 2005; Puthiaraj & Pitchumani, 2014; Zhu, Wang, Wang, Li &
Diao, 2013). Chitosan (CS) is one of the most important and majorly used biomaterials due to
its several applications in different areas such as waste water treatment, radioactive element
and textile waste removal, medicine, agriculture, biotechnology, and food and pharmaceutical
industries (Muzzarelli, 2011; Zeng, Zhang, Shao, Qi & Zhang, 2012).
The synthesis of biaryls in the presence of palladium catalysts are generally performed by
Suzuki coupling reactions (Miyaura & Suzuki, 1995). Suzuki coupling reactions require high

reaction temperature, long reaction time, large amounts of energy and solvents, and inert
atmosphere (Alonso & Najera, 2010; Das, Sarmah, Tairai & Bora, 2011). To improve these
drawbacks, microwave irradiation techniques are popularly utilized for Suzuki coupling
reactions (S. Varma, 1999; Singh, Kaval, Tomar, Van der Eycken & Parmar, 2008).
Advantages of microwave irradiation techniques can be sorted as ease of work-up, safety,
high reaction yield in short time, clean synthesis, and high selectivity, and good economic and
environmental conditions (Hajipour, Karami & Pirisedigh, 2011).
In addition, several metal ions supported biomaterial catalysts have redox potential (Gupta
& Abdulkadir, 2008). Thus, these chemically modified new catalysts find application areas
for decomposition reactions (Demetgul, 2012; Gupta & Abdulkadir, 2008). The catalytic
activities of metal supported catalysts are investigated by choosing catalase-like
decomposition reaction of H2O2 as a model reaction. It has been reported that complexation of
metal ions with different ligands affect the reactivity of metal complexes in decomposition of
H2O2.
In the current study, synthesis and characterization of a new biomaterial supported Pd
catalyst were aimed, and catalytic activity of the new catalyst was tested in two different
reactions:
a) Synthesis of biaryls by Suzuki coupling reactions that uses a new solvent-free
microwave irradiation technique in a short reaction time of 4 minutes.
b) Investigation of redox potential of biomaterial supported Pd catalyst in catalase-like
reaction of H2O2 and optimization of reaction conditions such as time, substrate
concentration, temperature, and amount of catalyst.
The newly synthesized biomaterial supported Pd catalyst was illuminated with fourier
transform infrared (FTIR), thermal gravimetric analysis (TG/DTG), X-Ray Diffraction
13
(XRD), proton and carbon nuclear magnetic resonance (1H-NMR and C-NMR), scanning

electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDAX), inductively
coupled plasma atomic emission spectroscopy (ICP-OES), ultraviolet visible (Uv-Vis)
spectroscopies and magnetic moment, and molar conductivity analysis. Catalytic activity
results ensure that biomaterial supported Pd catalyst shows high conversion yield and long
life time at small catalyst loading. TON and TOF values of biomaterial supported Pd catalyst
proved to be higher than the ones in the previous studies (Karthikeyan, Vanitha, Radhika,
Suresh & Sugumaran, 2013; Leonhardt et al., 2010; Liu, Li, Gao, Wang & Jin, 2015). As a
consequence, the catalyst can easily find potential uses in different industrial and
pharmaceutical applications.
2. Materials and Method
2.1 Materials
All chemicals used in the study were purchased from Sigma-Aldrich. The FTIR spectra of
the all compounds were analyzed on a Perkin Elmer Spectrum 100 FTIR spectrophotometer.
1
The H-NMR spectra of the biarlys were recorded on Agilent 600 MHz spectrometer using
Acetone-d6 solvents. The 13C-NMR spectra of Schiff base ligand (SBL) and O-carboxymethyl
chitosan Schiff base ([OCMCS-SBL]) were measured with Agilent 600 MHz spectrometer
using DMSO-d6 and D2O solvent, respectively. TG/DTG curves of CS, [OCMCS-SBL], and
biomaterial supported Pd catalyst were performed with an EXSTAR S11 7300 at a heating
rate of 10 ºC min-1. XRD spectra of CS, [OCMCS-SBL], and biomaterial supported Pd
catalyst were measured with a Rigaku Dmax 2000 system at 40 kV, 30 mA, and 2θ with a
scan angle from 5° to 50°. GC/MS spectra of biarlys were obtained with Agilent GC-7890 A-
MS 5975. Surface images were acquired using a QUANTA-FEG 250 ESEM. The EDAX
spectrum of the Pd catalyst was obtained with an EDAX-Metek. The metal content of
biomaterial supported Pd catalyst was studied with a Perkin Elmer Optima 2100 DV

Inductively Coupled Plasma (ICP) Optical Emission Spectrometer (OES). UV-Vis spectrum
of biomaterial supported Pd catalyst was recorded with a Genesys 10S UV-Vis
spectrophotometer. Magnetic susceptibility of biomaterial supported Pd catalyst was
measured with a Sherwood magnetic susceptibility balance at 25 °C. The molar conductivity
of biomaterial supported Pd catalyst was determined using a tabletop-digital conductivity-
meter CD-2005 at 25 °C. Domestic microwave oven was used in the synthesis of biarlys.
Crystallinity indexes of CS, [OCMCS-SBL], and biomaterial supported Pd catalyst were
calculated by using the equation below:
(1)Crystalline index(%) [(I110 - Iam )/ I110 ] 100
I110 is the maximum intensity at ~ 20°.
Iam is the intensity of amorphous diffraction at 16°.
2.2 Synthesis of mono-imine Schiff base ligand (SBL)
4-aminobenzenesulfonic acid (1 g, 5.77 mmol) and 2,6-diacetylpyridine (0.94 g, 5.77
mmol) were dissolved in methanol (40 mL) and refluxed for 72 hours. The reaction was
followed with FTIR and thin layer chromatography (TLC). At the end of the reaction time,
participated yellowish product was filtered and washed with cold methanol and ether (92 %
yield).
2.3 Synthesis of chitosan supported Pd catalyst
[OCMCS-SBL] was synthesized according to our previous study (Baran, Menteş &
Arslan, 2015) . Briefly, condensation of SBL with chitosan was refluxed and stirred for 48 h.
Then, monochloroacetic acid was added, the reaction mixture was stirred at 60°C. After 7
days, water soluble [OCMCS-SBL] derived from biomacromolecule was achieved (79 %

yield). 0.2 g [OCMCS-SBL] was dissolved in water (10 mL) and mixed with Na2PdCl4
solution (0.35 g in 10 mL water) at room temperature for 5 h. Yellow-green product was
filtered and rinsed with water to remove unreacted reactants, and biomaterial supported Pd
catalyst was successfully obtained (71 % yield) (Scheme 1).
…………………………………………Scheme 1……………………………………..…
2.4 Suzuki coupling Reaction
Base system, reaction time, and catalysts amount parameters must be optimized to obtain
C-C coupling reactions with high selectivity. Therefore, coupling reaction of 4-bromoanisol
with phenylboronic acid was selected as the model reaction, and optimum conditions were
determined for coupling reaction in the presence of biomaterial supported Pd catalyst.
To determine the optimum catalyst amount, biomaterial supported Pd catalyst was used at
different loading catalyst (2.5, 5.0, 10.0, 20.0) x 10-3 mol % under microwave irradiation at
400 W in solvent-free reaction mixture (50°C). Reaction time was investigated from 1 min to

5 min, and NaOH, K2CO3, KOH, and Cs2CO3 base systems were examined for optimum
coupling reaction condition.
Different aryl halides (1.12 mmol), K2CO3 (3.75 mmol), phenylboronic acid (1.87 mmol),
and biomaterial supported Pd catalyst (0.01 % mol) were mixed, and the reaction was allowed
under microwave irradiation at 400 W in solvent-free media for 4 min (Scheme 2). At the end
of the reaction period, the product was extracted with toluene:water (4:2, v:v). Organic phase
was separated, and MgSO4 was added to remove water. The chemical identifications of
synthesized biaryls were illuminated with 1H-NMR and gas chromatography-mass
spectroscopy (GC-MS) analyses.
…………………………………………Scheme 2……………………………………..…
At the end of the coupling reaction, biomaterial supported Pd catalyst was filtered and
washed with hot water and methanol to re-activate the biocatalyst. Then, the same biomaterial
supported Pd catalyst was used for recycling experiments for model reaction under optimum
reaction conditions for 10 times. Leaching test was applied to supernatant of all recycle
experiments to determine Pd ion in the solution.

2.5 Catalase-like activity of biomaterial supported Pd catalyst
Biomaterial supported Pd catalyst was applied for the catalase-like decomposition reaction
of H2O2. Concentration of H2O2 was followed by permanganate reaction in acidic media after
decomposition reaction, and reaction equation was given as follows:
-
2MnO4 + 5H2O2 + 6H+→ 2 Mn2+ + 5O2 + 8H2O
Decomposition or initial reaction solution (0.5 mL) was mixed with 0.1 M H2SO4 (5 mL)
and titrated with 0.01 M KMnO4 until the solution became colorless. Conversion ratio was
calculated using the initial and final concentrations of reaction media.
Decomposition reaction was investigated at different reaction periods (till 150 min.) to
optimize the reaction period. H2O2 concentrations ranged from 10 mM to 45 mM. The
reaction temperature was investigated between 5 °C to 60 °C to obtain maximum conversion
yield. Finally, biomaterial supported Pd catalyst was changed from 5 to 20 mg to optimize
catalyst amount. To determine the reusability of biomaterial supported Pd catalyst, catalase-
like reaction was repeated 10 times at optimum reaction conditions.
3. Results and Discussion
3.1 Characterization of biomaterial supported Pd catalyst
3.1.1. FTIR analysis
FTIR spectra of SBL, [OCMCS-SBL], and biomaterial supported Pd catalyst are
presented in Figure 1. In the FTIR spectrum of SBL, absence of NH2 stretching of 4-
aminobenzenesulfonic acid and new band at 1651 cm-1 attribute to imine groups showed the
condensation of 4-aminobenzenesulfonic acid with 2,6-diacetylpyridine. Stretching band at
1702 cm-1 of free carbonyl groups of 2,6-diacetylpyridine decreased after condensation of 2,6-
diacetylpyridine with 4-aminobenzenesulfonic acid. This change proved that the condensation

was achieved at 1:1 ratio. The characteristic peaks of chitosan can be examined in detail in
our previous study (Baran, Menteş & Arslan, 2015). As seen in the spectrum of [OCMCS-
SBL], NH2 stretching of CS disappeared, and the imine band was observed at 1635 cm-1. This
observation ensures the condensation of CS with SBL. The carbonyl stretching of
carboxymethyl at 1729 cm-1 indicated successful carboxymethylation of CS (Baran & Menteş,
2015; Baran, Menteş & Arslan, 2015). In addition, asymmetric and symmetric stretching of
these carbonyl groups are shown at 1599 and 1506 cm-1, respectively (Fig.1). Also, lack of
stretching belonging to primer hydroxyl groups at 1029 cm-1 of CS indicated that the
carboxymethylation occurred from the C6-O of CS (Kaya, Cakmak, Baran, Asan-Ozusaglam,
Mentes & Tozak, 2014; Liu, Zhao & Wang, 2013). In the spectrum of biomaterial supported
Pd catalyst, imine band shifted to the lower wavelength (1623 cm-1) according to [OCMCS-
SBL]. This alteration originated from the coordination of Pd ions to the nitrogen atoms of
imine groups (Demetgul, Karakaplan & Serin, 2008).

…………………………………………Figure 1……………………………………..…
3.1.2. 13C-NMR Spectrum
13
In the C-NMR spectrum of SBL, the signal of imine carbon atom seen at 167.18 ppm
demonstrated condensation between 4-aminobenzenesulfonic acid and 2,6-diacetylpyridine
(Fig. 2). Signal belonging to free carbonyl carbon at 199.29 ppm confirmed the formation of
condensation reaction at 1:1 ratio. Other signals in the spectrum are listed below:

13C NMR : 25.79 C(1); 199.29 C(2); 155.11 C(3); 122.83 C(4); 136.52 C(5); 125.06 C(6);
149.28 C(7); 167.18 C(8); 16.42 C(9); 144.27 C(10); 122.96 C(11); 127.09 C(12); 138.04
C(13).
The carbonyl signal of SBL at 199.29 ppm disappeared after the condensation of CS with
SBL. A new imine carbon signal at 168.43 ppm was also observed, and this change proved
the condensation of SBL with CS (Fig. 2). Furthermore, carbonyl signal of carboxymethyl at
173.40 ppm was the other proof of accomplished carboxymethylation (Yin, Chen, Yuan, Lin,
Ji & Liu, 2011). Important signals are presented as:
13C NMR : 97.48 C(1); 55.73 C(2); 69.99 C(3); 76.28 C(4); 74.70 C(5); 59.90 C(6); 42.46
C(7); 173.40 C(8); 168.43 C(9); 23.78 C(10); 154.44 C(11); 121.63 C(12); 131.69 C(13);
124.28 C(14); 149.90 C(15); 166.38 C(16); 13.40 C(17); 142.94 C(18); 122.08 C(19); 127.26
C(20); 138.47 C(21).

…………………………………………Figure 2……………………………………..…
3.1.3. TG/DTG and XRD Analysis

It was reported that chemical modifications of chitosan (Schiff base, carboxymethylation,
metal coordination, cyanoethylation, acylation, and sulfation) induce cleavage of hydrogen
bonds (Antony, Manickam, Saravanan, Karuppasamy & Balakumar, 2013; Trimukhe &
Varma, 2009). Thus, crystallinity value of CS decreases. All these alterations bring about a
drastic decline at main thermal degradation temperature (DTGmax) of CS. In the current study,
DTGmax of CS was determined as 302 °C while DTGmax values of [OCMCS-SBL] and Pd
biomaterial supported Pd catalyst were observed as 219 °C and 232 °C, respectively, after
chemical modifications (Fig.3). Biomaterial supported Pd catalyst was detected to be
thermally more stable than [OCMCS-SBL]. High thermal stability of the Pd catalyst ramps up
the usage potential in different catalytic studies that require high reaction temperature.
…………………………………………Figure 3……………………………………..…
Crystallinity indexes of CS, [OCMCS-SBL], and biomaterial supported Pd catalyst were
calculated (Zhang, Xue, Xue, Gao & Zhang, 2005) as 82, 55, and 15 %, respectively. As

expected, biomaterial supported Pd catalyst has a more amorphous nature with regard to CS
and [OCMCS-SBL].
3.1.4. SEM/EDAX
Surface morphology of CS was examined, and a smooth surface was detected. Surface
picture and particle size of [OCMCS-SBL] were altered due to the chemical modification of
CS. The drastic change on the surface morphology of biomaterial supported Pd catalyst in
comparison to CS and [OCMCS-SBL] demonstrated the coordination of Pd with [OCMCS-
SBL] (Antony, Manickam, Saravanan, Karuppasamy & Balakumar, 2013; Demetgul, 2012)
(Fig.4). EDAX spectrum of biomaterial supported Pd catalyst was recorded to determine the
existence of Pd ions. The coordination of Pd ions with [OCMCS-SBL] was proved with the
appearance of both Pd ions and metal coordinated chlorine ions (Fig.5).
…………………………………………Figure 4……………………………………..…

…………………………………………Figure 5……………………………………..…
3.1.5. Uv-Vis Spectroscopy and Magnetic Moment/Molar Conductivity Measurements
It is known that Uv-Vis spectrum of CS has no transition in the range of 200-800 nm
(Kumar, Nigam, Ghosh, Dutta, Yadav & Pandey, 2010). Two transitions were observed at
260 and 320 nm when Uv-Vis spectrum of [OCMCS-SBL] was recorded. These transitions
were attributed to aromatic ring π-π* and imine groups (C=N) n-π* (Antony, David,
Saravanan, Karuppasamy & Balakumar, 2013; Demetgul, 2012). They shifted to higher
wavelength compared to [OCMCS-SBL] in the spectrum of biomaterial supported Pd catalyst
due to the coordination of Pd ions with nitrogen atoms of imine groups (Antony, Manickam,
Saravanan, Karuppasamy & Balakumar, 2013). In addition, two weak d-d transitions which
were determined at 360 and 465 nm supported the square planar geometry of biomaterial
supported Pd catalyst (Anan, Hassan, Saad, Butler & Mostafa, 2011; Mostafa & Badria,
2008).
Magnetic moment and molar conductivity measurements were performed to promote
geometry the catalyst. Magnetic moment measurements showed that biomaterial supported Pd
catalyst had diamagnetic properties. Molar conductivity value of biomaterial supported Pd
catalyst at room temperature was measured as 58 Ω−1 cm2 mol-1. This value was compatible
with 1:1 electrolyte nature of biomaterial supported Pd catalyst (Al-Nahary, 2009).
Furthermore, both magnetic moment and molar conductivity values ensured the square planar
geometry of biomaterial supported Pd catalyst.
3.2 Suzuki Coupling Reaction
3.2.1. Optimization of Suzuki reaction conditions

In the current study, catalytic activity of biomaterial supported Pd catalyst was
investigated by developing a new technique under microwave irradiation using solvent-free
media for 4 min at 400 W to use energy more efficiently, to reduce waste products by
preventing formation of by-products and to have higher reaction yield in a shorter reaction
time. Amount of biomaterial supported Pd catalyst, base system, and reaction time parameters
must be optimized to achieve high conversation yield in C-C coupling reaction.
Preliminary experiments were applied with different loading mol percentages of
biomaterial supported Pd catalyst to determine the optimum biomaterial supported Pd catalyst
amount. As seen in Figure 6, the optimum Pd catalyst amount was chosen as 0.01 mol %.
…………………………………………Figure 6……………………………………..…
Base plays a significant role in transmethylation step thus; choice of base is a critical
parameter for coupling reactions. Thus, different base systems were tested in model reaction,
and the results are presented in Table 1. K2CO3 was selected as the suitable base system for
more selective coupling reaction.

Table 1. Base Optimization for Suzuki reaction
Base
NaOH
KOH
Yield (%)
59
55
88
Cs2CO3
K2CO3
>99
Reaction conditions: 1.12 mmol 4-bromoanisole, 1.87 mmol phenyl boronic acid, 3.75 mmol base, 0.01 mol % catalyst, 50
°C, 4 min under MW.
Reaction time was ranged from 1 to 5 min (Fig.7) under microwave irradiation, and
maximum reaction yield was achieved at 4 min.
…………………………………………Figure 7……………………………………..…
3.2.2. Investigation of catalytic activity of biomaterial supported Pd catalyst
TON and TOF values which were calculated for all C-C coupling reactions with several
halides are given in Table 2. These TON and TOF values which were achieved with notably
small biomaterial supported Pd catalyst loading were higher than those in literatures
(Karthikeyan, Vanitha, Radhika, Suresh & Sugumaran, 2013; Leonhardt et al., 2010; Liu, Li,
Gao, Wang &Jin, 2015).

Coupling reactions between different aryl halides with phenyl boronic acid were
conducted under optimum reaction conditions to determine the effect of several functional
groups of substrates on Suzuki coupling reactions, and the reaction yields of several halides
are given in Table 2. It was determined that coupling reactions with withdrawing bromides
occurred at considerably higher selectivity than electron-donor aryl bromides (entries 2-8).
Conversion yields of coupling reactions in the presence of aryl iodides were (entries 9-13)
determined to be higher than the one in the presence of aryl chlorides (entry14). As expected,
low conversion yields with aryl chlorides originated from the poor activity of aryl chlorides in
Suzuki reactions (Littke, Dai & Fu, 2000). It is thought that various conversion yields
obtained with several aryl halides was caused by the radii of halogens and bond dissociation
energy (Baran, Açıksöz & Menteş, 2015; Makhubela, Jardine& Smith, 2011). Finally, para-
substitue groups were the most effective while orto-substitue groups showed lower reaction
yield.
Coupling reaction between 4-bromoanisol and phenyl boronic acid was also carried out
with conventional heating method (100 °C, 48h). It is clearly understood from the conversion
yields in Table 2 that microwave heating method catalyzed coupling reaction with higher
conversion yield in a shorter reaction time compared to conventional heating method (entry
15).
Different commercial Pd compounds were investigated for model reaction at optimum
reaction conditions (0.01 mol % biomaterial supported Pd catalyst, K2CO3, under microwave
irradiation at 400 W, and 4 min), and results are given in Table 2 (entries 16-17).
The newly synthesized biomaterial supported Pd catalyst had excellent catalytic activity
compared to commercial Pd compounds. Furthermore, blank experiments (without the
catalyst) were performed under microwave irradiation, but no conversion was obtained. These

results indicate that biomaterial supported Pd catalyst ensures C-C coupling reaction
successfully with perfect conversion yield.

Table 2. The effects of biomaterial supported Pd catalyst on Suzuki cross-coupling reaction.
X
Y
Yield (%)
TON yield / per mol
of Pd
TOF TON/reaction
time
1
Br
Br
Br
Br
Br
Br
Br
Br
I
2‐OCH3
3‐OCH3
4‐OCH3
3‐CH3
93
96
>99
64
74
80
82
88
57
41
54
78
74
57
58
55
45
9300
9600
10000
6400
7400
8000
8200
8800
5700
4100
5400
7800
7400
5700
5800
5500
4500
140909
145454
151515
96967
112121
121212
124242
133333
86364
62121
81818
118182
112121
86364
121
2
3
4
5
4‐CH3
6
3‐NH2
4‐NH2
3‐NO2
2‐CH3
7
8
9
10
11
12
13
14
15*
16†
17#
I
3‐CH3
I
4‐CH3
I
4‐NH2
3‐NO2
3‐NO2
4‐OCH3
4‐OCH3
4‐OCH3
I
CI
Br
Br
Br
Reacti
on
conditi
ons:
83333
68182
1.12
mmol
aryl halide, 1.87 mmol phenyl boronic acid, 3.75 mmol K2CO3, 0.01 mol % catalyst, 50 °C, 4 min, under MW.
*Conventional Method: 1.12 mmol aryl halide, 1.87 mmol phenyl boronic acid, 3.75 mmol K2CO3, 0.01 mol %
catalyst, 100 °C, 48 h, 6 mL toluene.
†Commercial Pd catalyst; Reaction conditions: 1.12 mmol aryl halide, 1.87 mmol phenyl boronic acid, 3.75
mmol K2CO3, 0.01 mol % Na2PdCl4, 50 °C, 4 min, under MW.
#Commercial Pd catalyst; Reaction conditions: 1.12 mmol aryl halide, 1.87 mmol phenyl boronic acid, 3.75
mmol K2CO3, 0.01 mol % PdCl2, 50 °C, 4 min, under MW.

Characterization of all biaryls compounds which were synthesized by C-C coupling
reaction using various aryl halides were defined with 1H-NMR and GC-MS. It is observed on
the spectra of biarlys that coupling reaction exhibited high selectivity and generated no homo-
coupling by-products.
3.3 Catalase-like activity of biomaterial supported Pd catalyst
3.3.1. Optimization of decomposition reaction conditions
Reaction time, substrate concentration, temperature, and catalyst amount parameters were
tested for the optimization of catalase-like activity reaction. Conversion of H2O2 was followed
until 150 min using both 15 mM and 25 mM H2O2 solutions with 20 mg biomaterial
supported Pd catalyst (Fig.8). For both concentrations, conversion reaction reached a plateau
value at 120 min and did not change after then. Thus, all experiments were performed for 120
min.
A linear equation (y:-0.0005 x + 3.2136, R2:0.9915) which was obtained from the plot of
log (converted H2O2 concentration) with reaction time(s) demonstrated that catalase-like
decomposition obviously agreed with the first order kinetics (Gupta & Abdulkadir, 2008).
Using the equation given above, rate constant (k) for catalase-like reaction was calculated as
5x10-4 s-1.
Fig. 8.jpg
…………………………………………Figure 8……………………………………..…

Several substrate concentrations in the range of 10 mM to 45 mM H2O2 were investigated
and are given in Fig.9a. Non-significant difference at conversion yield was observed between
10 and 35 mM H2O2 although conversion yield decreased at 45 mM H2O2. Effect of
temperature, as seen in Fig. 9b, was tested using 25 mM H2O2 solution because maximum
conversion was observed at this concentration. The results showed that temperature positively
effected decomposition reaction. All of H2O2 (99%) was decomposed by 20 mg biomaterial
supported Pd catalyst at 40°C and 60°C. This result made us think that high conversion yields
could be achieved by using lower catalyst amounts at high reaction temperatures. Therefore,
decomposition reaction was investigated using 5 mg and 10 mg biomaterial supported Pd
catalyst both at 40°C and 60°C, and the results are seen in Fig. 9c. The decomposition of all
H2O2 (99%) was succeeded with 5 mg biomaterial supported Pd catalyst at 60°C. As a result,
optimum conditions were specified as 120 min, 25 mM H2O2 with 5 mg biomaterial
supported Pd catalyst at 60°C.
Fig. 9.jpg
…………………………………………Figure 9……………………………………..…
3.4. Reusability of biomaterial supported Pd catalyst
The reusability potential of biomaterial supported Pd catalyst was investigated on model
reaction at optimum reaction conditions and are given in Table 3. After 10 cycles, biomaterial
supported Pd catalyst still exhibited high conversion. Biomaterial supported Pd catalyst is
economical and proper for industrial applications due to its high conversion yields at small

amounts. In addition, leaching test was applied for all runs, and negligible amounts of Pd ions
(< 0.5 %) were determined by ICP-OES.
Reusability studies for decomposition reaction were performed by using 25 mM H2O2
with 5 mg biomaterial supported Pd catalyst at 60°C for 120 min. At the end of 10 cycles,
redox potential of the catalyst decreased by 12.9 %. This result demonstrated long life time of
biomaterial supported Pd catalyst for decomposition reaction. TON values for each cycle at
60°C (Table 3) are in accordance with the results of biomaterial supported Pd catalyst nature.
Table 3. Reusability of biomaterial supported Pd catalyst
*Suzuki C-C reaction
+Catalase like reaction
The number of cycle
Yield (%)
TON
10000
9700
9700
9700
9500
9200
8800
7900
7800
7800
Yield (%)
TON
1234
1203
1184
1131
1156
1106
1094
1116
1132
1074
1 st
2 nd
3 rd
4 th
5 th
6 th
7 th
8 th
9 th
10 th
>99
97
97
97
95
92
88
79
78
78
99
96
95
91
93
89
88
89
90
86
*Reaction conditions: 1.12 mmol 4-bromoanisole, 1.87 mmol phenyl boronic acid, 3.75 mmol base, 0.01 mol % catalyst, 50
°C, 4 min under MW
+
Reaction conditions: 25 mM H2O2, 0.08 mol % catalyst, 60 °C, 120 min.

4. Conclusion
In the current study, a new biomaterial supported Pd catalyst was synthesized and
1
13
characterized with FTIR, TG/DTG, XRD, H-NMR, C-NMR, SEM-EDAX, ICP-OES, Uv-
Vis spectroscopy, magnetic moment, and molar conductivity analysis. Catalytic activity of
environment friendly biomaterial supported Pd catalyst was evaluated in Suzuki coupling
under microwave irradiation without solvent in a short time. Furthermore, its redox potential
in H2O2 decomposition reaction was investigated, and effects of time, substrate concentration
and catalyst amount were optimized. TON and TOF values were higher than those in previous
studies for both Suzuki coupling and decomposition reactions. Reusability of biomaterial
supported Pd catalyst was tested for 10 cycles for catalytic studies. Biomaterial supported Pd
catalyst can be used economically for several applications since it catalyses without
significant loss in activity after 10 cycles. The new biomaterial supported Pd catalyst can also
find different applications in environmental technologies, textile, and pharmaceutical
industries owing to its superior features such as high catalytic activity at small loading
catalyst, simple work-up, short reaction time in solvent-free media, durability to air, moisture,
and high reaction temperature.
Acknowledgements
We would like to thank the Scientific and Technological Research Council of Turkey
(TUBITAK) (Project Number: 113Z296) for financial support.

References
Al-Nahary, T. T. (2009). Synthesis and characterization of metal complexes of Cr(III),
Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Ru(III), Rh(III) and Pd(II) with derivatives of
1,3,4-thiadiazole-2,5-dithiol as new ligands. Journal of Saudi Chemical Society, 13(3),
253-257.
Alonso, D. A., & Najera, C. (2010). Oxime-derived palladacycles as source of palladium
nanoparticles. Chemical Society Reviews, 39(8), 2891-2902.
Anan, N. A., Hassan, S. M., Saad, E. M., Butler, I. S., & Mostafa, S. I. (2011). Preparation,
characterization and pH-metric measurements of 4-hydroxysalicylidenechitosan
Schiff-base complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(III), Rh(III), Pd(II)
and Au(III). Carbohydrate Research, 346(6), 775-793.
Antony, R., David, S. T., Saravanan, K., Karuppasamy, K., & Balakumar, S. (2013).
Synthesis, spectrochemical characterisation and catalytic activity of transition metal
complexes derived from Schiff base modified chitosan. Spectrochimica Acta Part A-
Molecular and Biomolecular Spectroscopy, 103, 423-430.
Antony, R., Manickam, S. T. D., Saravanan, K., Karuppasamy, K., & Balakumar, S. (2013).
Synthesis, spectroscopic and catalytic studies of Cu(II), Co(II) and Ni(II) complexes
immobilized on Schiff base modified chitosan. Journal of Molecular Structure, 1050,
53-60.
Baran, T., Açıksöz, E., & Menteş, A. (2015). Carboxymethyl chitosan Schiff base supported
heterogeneous palladium(II) catalysts for Suzuki cross-coupling reaction. Journal of
Molecular Catalysis A: Chemical, 407, 47-52.