Pd-Co bimetallic nanoparticles supported on graphene as a highly active catalyst for Suzuki-Miyaura and Sonogashira cross-coupling reactions

Article abstract of DOI:10.1016/j.tet.2014.05.083

Graphene (G) supported Pd-Co bimetallic nanoparticles (NPs) as a highly active catalyst was prepared by a chemical reduction method and used for coupling reactions. With the characterization of X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectrum, the composition of resulting Pd-Co material was identified to be alloy structural. The Pd-Co (1:1)/G exhibited the highest catalytic activity for the Sonogashira-type coupling reactions and also exerted satisfied catalytic activity and recycle stability for Suzuki-Miyaura cross-coupling reactions. This Pd-Co/G material also possessed other advantages such as low-cost, easy recycled from reaction system by a magnet for their magnetic property, and easy experimental handling.

Full text of DOI:10.1016/j.tet.2014.05.083

Tetrahedron xxx (2014) 1e5
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
PdeCo bimetallic nanoparticles supported on graphene as a highly
active catalyst for SuzukieMiyaura and Sonogashira cross-coupling
reactions
Yi-Si Feng b, Xin-Yan Lin a b, Jian Hao a b, Hua-Jian Xu a
a
,
,
,
,b,
*
a
School of Chemistry and Chemical Engineering, School of Medical Engineering, Hefei University of Technology, Hefei 230009, PR China
Key Laboratory of Advanced Functional Materials and Devices, Anhui Province, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Graphene (G) supported PdeCo bimetallic nanoparticles (NPs) as a highly active catalyst was prepared by
a chemical reduction method and used for coupling reactions. With the characterization of X-ray dif-
fraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectrum, the
composition of resulting PdeCo material was identified to be alloy structural. The PdeCo (1:1)/G ex-
hibited the highest catalytic activity for the Sonogashira-type coupling reactions and also exerted sat-
isfied catalytic activity and recycle stability for SuzukieMiyaura cross-coupling reactions. This PdeCo/G
material also possessed other advantages such as low-cost, easy recycled from reaction system by
a magnet for their magnetic property, and easy experimental handling.
Received 26 February 2014
Received in revised form 17 May 2014
Accepted 22 May 2014
Available online xxx
Keywords:
PdeCo
Graphene
Graphene oxide
Coupling reaction
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
problem may be solved by using proper substrate for supported
bimetallic NPs.
During the past decades, homogeneous palladium(II) complexes
are one of the most popular catalysts used to catalyze carbon-
ecarbon coupling reactions such as Sonogashira-, Heck-, and
As one of the members of the carbon family, G is a single atomic
layer of sp carbon atoms, which has large specific surface area
and high adsorption capacity. Hence, G and its derivatives can be
2
12
1
e3
13,14
Suzuki-type reactions.
However, the homogeneous catalysis
used as the substrates to host metal nanoparticles.
In recent
15
owns numerous drawbacks, especially, high cost, and non-re-
studies, Zhang’s group successfully modified G with palladium
nanoparticles and demonstrated that the PdeG hybrids can act as
an efficient catalyst for the Suzuki reaction under aqueous and
aerobic conditions, indicating that the enhanced catalytic activity
due to the special nature of G. Therefore, G-supported PdeCo bi-
metallic nanoparticles may be acted as an efficient catalyst to car-
bonecarbon bond coupling.
4
usability. Pd nanoparticles (NPs) with high catalytic activity seem
to be one promising option to replace the homogeneous catalysis
5
for these reactions. To reduce the usage of noble material Pd, the
hybrid structure alloyed by Pd and non-noble (e.g., Fe, Co, Cu)
4
metals was designed and synthesized. In many cases, the syn-
thesized Pd/non-noblemetal catalysts not only show a combination
of the properties associated with two different metals but also has
Herein we disclosed that PdeCo bimetallic nanoparticles can be
dispersed on G with controllable size of nanomaterial by a facile
route. The catalytic performances are evaluated in Sonogashira-,
Suzuki-type reactions. Furthermore, this efficient catalyst could be
used repetitively by a magnet for five times, shows good potential
in future industrial applications.
6
an enhancement in specific properties due to synergistic effects.
Especially, if magnetic metals are alloyed into noble metals, such
as Co metals, the nano-catalyst would have a magnetic nature,
which could overcome the issue of catalyst separation and re-
usability.7 In a previous paper, Li, etc. successfully prepared
PdeCo bimetallic hollow nanospheres, which had been demon-
strated to be a good catalyst for the Sonogashira reaction in aque-
ous media. However, very tiny nanoparticles usually add problems
in catalyst separation1 and also induce agglomeration due to high
,8
9
2. Results and discussion
0
11
surface energy, leading to the decrease in catalytic efficiency. The
2.1. Structural characteristics
The crystalline structure of PdeCo (x:y)/G catalysts with differ-
*
Corresponding author. E-mail address: hjxu@hfut.edu.cn (H.-J. Xu).
ent Pd/Co nominal atomic ratios was characterized by XRD and
0
040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.05.083
Please cite this article in press as: Feng, Y.-S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.083

2
Y.-S. Feng et al. / Tetrahedron xxx (2014) 1e5
3
2
shown in Fig. 1. The XRD patterns of Pd/G and Co/G that included in
lamellae sp hybridized carbon atoms re-converted to sp hybrid-
2
the figure were used as a comparison. The first diffraction peak at
ized carbon atoms, but the average of sp carbon ribbons’ area
became smaller, making the D peak and G peak ratio increase.
These results indicated that GO had been reduced and subsequently
gave rise to the restoration of sp network with small and isolated
domains of aromatics within the sheets.
Fig. 3 shows the morphology and structure of PdeCo (1:1)/G
catalyst determined by TEM and HRTEM. It can be seen that
nanoparticles are well-dispersed on graphene. From Fig. 3b, it is
clearly that the size distribution of PdeCo (1:1)/G catalyst was
3e16 nm, with an average size of 8.96 ꢂ0.4 nm, which is con-
sistent with X-ray diffraction pattern. The elemental mapping
images (Fig. 3d, e) reveal that a single alloy nanoparticle was built
up by Pd (Fig. 3d) and Co (Fig. 3e). Furthermore, to confirm the
PdeCo alloy structure, the energy dispersive spectrometer (EDS)
was texted (as shown in Fig. 3f), which reveals the presence of C,
Pd, and Co on the surfaces of the G sheets (Si and Cu peaks from
the TEM grid).
ꢀ
about 26 in all the XRD patterns was originated from the G sup-
ꢀ ꢀ ꢀ ꢀ
port. The peaks at 2q values of 40.1 , 46.80 , 68.20 , and 82.16 are
2
due to the (111), (200), (220), and (311) diffraction peaks of face
centered cubic Pd (JCPD-46-1043). The XRD pattern of the pure Co
21
ꢀ
ꢀ
sample exhibited two diffraction peaks around 2
q
¼44.5 , 47.3 ,
which increased the lattice structure of the Co (JCPD-15-0806)
species. As the cobalt content increases, the diffraction peak posi-
tion was shifted to a higher angle. This confirms the alloy formation
between Pd and Co, and which indicates a lattice contraction,
which was caused by the incorporation of Co into the Pd face
centered cubic structure. But no significant diffraction peak
characteristic was found when the content of Co decreased, which
was likely due to their poor crystallinity.
16
Fig. 1. XRD patterns of PdeCo/G with different Pd/Co atomic ratios (a) Co/G; (b)
PdeCo (1:3)/G; (c) PdeCo(1:1)/G; (d) Pd eCo (3:1)/G; (e) Pd/G.
3 3
Fig. 3. (a, b) TEM image and the particle size distribution of PdeCo (1:1)/G catalyst, (c)
TEM image of a single PdeCo (1:1)/G nanoparticle, (d) Pd and (e) EDS mapping pro-
files, (f) EDS of PdeCo (1:1)/G catalyst.
Raman spectra of GO and PdeCo (1:1)/G were shown in Fig. 2.
ꢁ
1
The band at about w1355 cm
corresponded to the disorder-
induced D band may be due to disorder-induced features caused
by lattice defect.17 While the in-phase vibration of the G lattice (G
ꢁ
1
band) at about w1605 cm represented the first-order scattering
As shown in Fig. 4, the surface composition of GO and PdeCo/G
was further analyzed by X-ray photoelectron spectroscopy (XPS).
The binding energies obtained in the XPS analysis were corrected
18
of the E2g vibrational mode within aromatic carbon rings. The
GO
I(D)/I(G) intensity ratio of GO (I(D)/I(G) ¼0.92) was slightly lower
G
19,20
than that of PdeCo (1:1)/G (I(D)/I(G) ¼1.41).
Such an en-
for specimen charging by referencing the
C
1s signal to
2
5
hancement therefore suggested after restored large number of
284.70 eV. The survey spectra of GO and PdeCo/G were shown in
Fig. 4a. Compared to that of GO, the XPS spectrum of PdeCo/G not
only exhibits O 1s and C 1s but also exhibits two additional peaks,
which correspond to the Pd 3d and Co 2p states. The higher res-
olution XPS data of C 1s peaks of GO and PdeCo/G are shown in the
Fig 4b and c, respectively. From the C 1s XPS spectrum of GO
(
Fig. 4b), the most resolved peak, located at 284.7 eV, corresponds
17,25,27
to CeC bonds of the G such as CeC, C]C, CeH bonds.
The
weak peak centered at 285.08 eV was attributed to CeO, and the
other two peaks at 286.8 eV and 288.2 eV were attributed to epoxy
carbon and carbonyl carbon. The C 1s XPS spectrum of the PdeCo/
G also exhibits the same functionalities, and their peak intensities
are a litter smaller than those in GO, revealing that most of the
epoxide and hydroxy functional groups were successfully re-
moved. In addition, the O 1s XPS spectra of GO and PdeCo/G are
presented in Fig. 4d, which exhibit different peak shape. The O 1s
peak of GO at 532.38 eV is closely related to the significant hy-
droxyl groups on the surface of GO, whereas, the O 1s peak of
PdeCo/G is at around 530.5 eV. All these results further confirm
GO reduction to G, the successful integration between PdeCo
Fig. 2. The Raman spectra of (a) GO, (b) PdeCo (1:1)/G.
Please cite this article in press as: Feng, Y.-S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.083

Y.-S. Feng et al. / Tetrahedron xxx (2014) 1e5
3
was shown in Supplementary data. All the Pd-based catalysts
displayed nearly 100% selectivity to diphenylacetylene. From
Table 1, it could be clearly found that PdeCo (1:1)/G was more
active than other ratio of PdeCo/G samples. PdeCo/G exhibited
high selectivity, which may be related to the presence of Co spe-
cies. The enhanced reactivity was attributed to both the large
surface area of G and the promotional effect of Co-dopants, which
provided more Pd active sites for the reactants. The position of
substituted group of aryl iodide showed obvious effect on re-
activity (entries 2 and 3).
Table 1
a
PdeCo (x:y)/G catalyzed Sonogashira coupling reactions
Entry
X
R
1
Time/h
Conversion/%
Selectivity/%
1
2
3
4
5
6
I
I
I
I
Br
Br
I
I
I
H
12
12
12
12
12
12
12
12
12
12
98
Trace
99
90
37
56
84
87
80
100
100
100
100
100
100
100
100
100
d
2-NO
4-NO
4-Me
H
4-NO
H
H
H
H
2
2
2
b
7
8
c
d
9
1
0e
I
Trace
a
Reaction conditions: aryl halide (1.0 mmol), phenylacetylene (1.2 mmol),
3
a catalyst amount containing 0.02 mmol Pd (PdeCo(1:1)/G), PPh (0.020 mmol), CuI
(
0.0030 mmol), and Et
3
N (1.2 mmol), THF (1 mL), water (1 mL), T¼80 ꢀC.
b
3
Catalyst: PdeCo (1:3)/G.
Catalyst: Pd/G.
c
d
e
Catalyst: Pd
3
Co (3:1)/G.
Catalyst: Co/G.
Fig. 4. XPS of PdeCo/G and GO. (a) The survey XPS spectra of the GO and PdeCo/G; C1s
XPS spectra of GO (b) and PdeCo/G (c); O 1s XPS spectra of GO and PdeCo/G (d); XPS
spectra showing the (e) Pd3d and (f) Co 2p peaks.
To extend the scope of coupling reaction, we examined the
Suzuki reaction of phenylboronic acid with iodobenzene (Table 2).
All the Pd-based catalysts displayed nearly 100% selectivity to
diphenyl. As the similar result with Sonogashira reaction, the re-
sult meant that the reaction is relatively insensitive to the elec-
tronic characteristics of the substituent groups. PdeCo/G could be
easily separated from the reaction solution by a magnet and used
at least five times for the aqueous coupling reaction between
iodobenzene and boronic acid. The recyclability and reusability
showed its superiority over the homogeneous Pd catalyst (Fig. 5:
reaction conditions are listed in Table 2). No significant decrease in
the selectivity to diphenyl was observed in the catalyst recycling
study. This suggested that the nature of Pd active sites did not
change after five runs. Because the weight of catalyst decreased
bimetallic alloy and G.26 The Pd 3d XPS spectra (Fig 4e) show two
major peaks with binding energy at 335.6 eV and 340.91 eV, cor-
responding to Pd 3d5/2 and Pd 3d3/2, and the binding energy sep-
aration between them is 5.31 eV. The peak at 335.6 eV is
0
corresponding to the Pd state, which shifted by 0.9 eV
toward higher binding energy with respect to Pd/C,2
2e24
sug-
gesting that their alloy structure. The peak at 336.28 eV for PdeCo/
G can be owed to Pd2 states. The XPS for Co 2p core level region
þ
16
is shown in Fig 4f, there were two major peaks with binding en-
ergies at 780.59 and 796.22 eV, corresponding to Co 2p3/2 and Co
2
8
2
p
1/2
,
revealing that it is in good agreement with the literature
value for the PdeCo alloy, which also matches well with literature
reports for cobalt metallic.
16
Table 2
a
PdeCo/G catalyzed Suzuki coupling reactions
2
.2. Catalytic performances
The PdeCo bimetallic alloy supported on the G is very stable
Entry
R
X
Time/h
Conversion/%
Selectivity/%
and has little influence on the diffusion of reaction molecules in
liquid-phase reaction. More importantly, these nanospheres can
be readily dispersed in liquid-phase solution due to their low
density and cycling performance from reaction system by a mag-
net for their magnetic property. All these properties present the
opportunities for this material to be used as a highly efficient
catalyst in liquid-phase reaction. The synthesized PdeCo (x:y)/G
catalysts was subjected to Sonogashira-type coupling reactions
between aryl iodide and terminal alkyne in water and THF. The
general procedure for the Sonogashira cross-coupling reactions
1
2
3
4
5
6
7
8
Ph
I
I
I
I
2
2
2
2
2
4
4
4
96
97
95
94
84.5
76
82
90
100
100
100
100
100
100
100
100
4-NO eC H
4-MeeC
4-OMeeC
2-Pyridine
Phe
4-NO
2-NO eC H
2
6
4
6
H
4
6
H
4
I
Br
Br
I
2 6 4
eC H
2
6 4
a
Reaction conditions: boronic acid (0.55 mmol), aryl halide (0.5 mmol), a catalyst
amount containing 0.02 mmol Pd (PdeCo(1:1)/G), Na CO (2 mmol), ethanol (1 mL),
water (1 mL), T¼80 C.
2
3
ꢀ
Please cite this article in press as: Feng, Y.-S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.083

4
Y.-S. Feng et al. / Tetrahedron xxx (2014) 1e5
follows: first the solution was prepared by dissolving a given
amount of Co(OAc) $4H O and 0.02 M of deep-brown PdCl powder
2
2
2
in 10 mL deionized water, and then 0.3 g GO, which was already
sonicated for 4 h in 20 mL deionized water was dispersed in it. After
magnetic stirring for 60 min, a solution of 0.1 M N
NH $H O was added into the suspension. Under vigorous stirring at
0 C and reacted for 4 h, the nanoparticle product was isolated by
2 4
H with 0.2 M
3
ꢀ
2
8
centrifugation with deionized water until a pH w7, and then the
prepared nanoparticle was achieved and dried overnight. The ob-
ꢀ
tained dark powder was heated in a tube furnace at 300 C under
constant flow of a mixture of nitrogen and hydrogen (3:1 ratio) for
2
h, the subsequently cooled to room temperature under nitrogen.
ꢀ
Finally, the powder was annealed at 500 C under constant flow of
a mixture of nitrogen and hydrogen (3:1 ratio) for another 2 h, thus
forming a G-supported PdeCo bimetallic nanoparticles catalyst as
shown in Fig. 6.
Fig. 5. Recyling test of PdeCo/G catalyzed coupling reaction of iodobenzene and
phenylboronic acid.
slightly after five consecutive runs while no significant change in
the composition of PdeCo/G, we assumed that the loss of catalyst
during the separation process, rather than the leaching of Pd
species from PdeCo/G, was the main factor responsible for the
slightly decrease of the conversion of iodobenzene during the
recycling tests.
3
. Conclusions
The results in the present study supplied a facile way to syn-
Fig. 6. Illustration of the synthesis procedure for PdeCo(x:y)/G.
thesize a series of PdeCo nanoparticles with different compositions
on G sheets and characterized by XRD, Raman, TEM, and XPS
techniques. The catalytic efficiencies of these PdeCo/G were tested
in various Sonogashira-type reactions. Among these different kinds
of PdeCo/G NPs tested, the PdeCo (1:1) NPs were found to be the
most active catalyst for the coupling between phenylacetylene and
aryl halide in a tetrahydrofuran/water mixture by using triethyl-
amine as a base at 80 C. The as-prepared PdeCo/G had also sat-
isfied catalytic activity and recycle stability for SuzukieMiyaura
cross-coupling reactions due to their magnetic nature, providing
4
.2. Physical characterization
X-ray photoelectron spectroscopy (XPS) were recorded on
Thermo Fisher Scientific ESCALAB 250. X-ray source was Al KR at
2 kV and all the binding energies reported were corrected using
1
ꢀ
the signal for the carbon peak (C 1 s) at 284.5 eV. Transmission
electron microscopy (TEM) images, high-resolution transmission
electron microscopy (HRTEM) and energy dispersive spectrometer
8
6% conversion after five successive catalytic runs. The enhanced
(EDS) patterns were observed by JEOL JEM-2100F electron micro-
reactivity was attributed to both the large surface area of G and the
promotional effect of Co-dopants, which provided more Pd active
sites for the reactants. Combined both efficiency of a homogeneous
catalyst and the durability of a heterogeneous catalyst, the PdeCo/G
composites provide great potential for G to support other bimetallic
nanoparticles, which offer more opportunities for designing new
catalysts.
scope performed at an accelerating voltage of 120 kV. X-ray dif-
fraction (XRD) patterns were carried out on a D/MAX 2500 V
ꢀ
ꢀ
diffractometer using Cu K
a
radiation (
l
¼1.5406 A) between 10 and
ꢀ
90 . Raman spectra were collected at room temperature on
LABRAM-HR, using an Ar-ion laser operating at 514.5 nm. For the
structural determination of the Sonogashira and Suzuki reaction
1
13
products, H NMR and C NMR spectra were determined on
a BrukerAV 300with TMS as internal standard.
4
4
. Experimental section
4
.3. General procedure for the Sonogashira cross-coupling
.1. Preparation of catalyst lists
reactions
The chemicals used in this experiment were analytical grade
For the cross-coupling catalysis experiments, a typical experi-
and graphene oxide (GO) was prepared by the oxidation of graphite
powder (Aldrich) according to an improved Hummers’ method.
ment was carried out as follows. Aryl halide (1.0 mmol) and phe-
nylacetylene (1.2 mmol) were dissolved in a mixture of 2 mL of
2
9
The G-supported Pd-Co bimetallic nanoparticles catalysts in-
2
H O/THF (1:1), then the catalyst (containing 0.020 mmol Pd), PPh
3
volved two metal precursors, palladium(II) chloride and cobalt
(0.020 mmol), CuI (0.003 mmol), and Et N (1.2 mmol) were added
3
II
ꢀ
acetate anhydrous (Pd Cl
2
and Co(OAc)
2
$4H
2
O), with varying
into it. Under argon, the mixture was stirred in 80 C oil bath for the
appropriate time. After the reaction completed, the mixture was
extracted with ether, and then centrifuged. The product was ana-
lyzed by TLC.
atomic ratios of Pd to Co, 1:11:3 and 3:1, at the same time Pd/G and
Co/G were also prepared for compassion. The graphene supported
2
0 wt % PdeCo bimetallic nanoparticles catalysts were prepared as
Please cite this article in press as: Feng, Y.-S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.083

Y.-S. Feng et al. / Tetrahedron xxx (2014) 1e5
5
4
4
.3.1. Diphenylacetylene. 1H NMR (400 MHz, CDCl
3
)
)
d
7.56e7.50 (m,
131.60, 128.29
(m, 2H); 13C NMR (101 MHz, CDCl
131.98, 128.72, 128.26, 128.19, 127.91, 124.10, 77.38, 77.06, 76.74.
3
)
d
149.32, 137.40, 136.36, 132.31,
13
H), 7.40e7.29 (m, 6H); C NMR (101 MHz, CDCl
3
d
(
d, J¼8.9 Hz), 123.25, 89.36, 77.33, 77.02, 76.70.
Acknowledgements
4
.3.2. 1-Methyl-4-(phenylethynyl)benzene. 1
H
NMR (400 MHz,
CDCl 7.56e7.48 (m, 2H), 7.43 (d, J¼8.1 Hz, 2H), 7.33 (d, J¼7.3 Hz,
3
) d
We gratefully acknowledge financial assistance from the Na-
tional Natural Science Foundation of China (Nos. 21272050,
1371044) and the Program for New Century Excellent Talents in
University of the Chinese Ministry of Education (NCET-11-0627).
13
3
H), 7.15 (d, J¼7.9 Hz, 2H), 2.36 (s, 3H); C NMR (101 MHz, CDCl
138.42, 132.54, 131.56 (d, J¼4.9 Hz), 129.16, 128.36, 128.11, 123.50,
20.21, 89.60, 88.76, 77.38, 77.07, 76.75, 21.56.
3
)
d
2
1
4
d
.3.3. 1-Nitro-4-(phenylethynyl)benzene. 1H NMR (400 MHz, CDCl
)
3
Supplementary data
8.22 (d, J¼8.6 Hz, 2H), 7.67 (dd, J¼14.0, 8.7 Hz, 2H), 7.56 (dd, J¼7.3,
2
.2 Hz, 2H), 7.43e7.34 (m, 3H).
Copies of 1H and 13C NMR spectra for the products. Supple-
mentary data associated with this article can be found in the online
version, at http://dx.doi.org/10.1016/j.tet.2014.05.083. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
4
.4. General procedure for the SuzukieMiyaura cross-
coupling reactions
A typical experiment was carried out as follows: boronic acid
(
0.55 mmol) and aryl bromide (0.5 mmol) were dissolved in
References and notes
a mixture of 3 mL of ethanol (1 mL) and water (2 mL), then the
catalyst (containing 0.020 mmol Pd) and sodium carbonate
(
in 80 C oil bath for the appropriate time. After the reaction com-
pleted, the mixture was extracted with ether, and then centrifuged.
The product was analyzed by TLC.
1
2
. Rafael, C.; Carmen, N. Chem. Rev. 2007, 107, 874e922.
. Akira, S. J. Organomet. Chem. 1999, 576, 147e168.
3. Jwanro, H.; Marc, S.; Christel, G.; Emmanuelle, S.; Marc, L. Chem. Rev. 2002, 102,
359e1469.
2 mmol) were added into it. Under argon, the mixture was stirred
ꢀ
1
4
5
6
. Wang, D.; Li, Y. Adv. Mater. 2011, 23, 1044e1060.
. Angelica, B.; Cyril, G.; Carmen, C. Chem. Soc. Rev. 2011, 40, 4973e4985.
. Bao, J.; Chen, W.; Liu, T.; Zhu, Y.; Jin, P.; Wang, L.; Liu, J.; Wei, Y.; Li, Y. ACS Nano
4
(
.4.1. Biphenyl. 1H NMR (400 MHz, CDCl
dd, J¼10.3, 4.8 Hz, 4H), 7.38e7.30 (m, 2H); C NMR (101 MHz,
CDCl
141.21, 128.74, 127.19 (d, J¼8.3 Hz), 77.33, 77.01, 76.69.
3
) d 7.63e7.55 (m, 4H), 7.43
2
007, 1, 293e298.
7. Sankaranarayanapillai, S.; Volker, S.; Werner, R. T. Angew. Chem., Int. Ed. 2010,
9, 3428e3459.
8. Didier, A.; Lu, F.; Jaime, R. A. Angew. Chem., Int. Ed. 2005, 44, 7852e7872.
. Li, H.; Zhu, Z.; Liu, J.; Xie, S.; Li, H. J. Mater. Chem. 2010, 20, 4366e4370.
10. Zhang, H.; Zhu, Q.; Zhang, Y.; Wang, Y.; Zhao, L.; Yu, B. Adv. Funct. Mater. 2007,
7, 2766e2771.
13
4
3
) d
9
.4.2. 4-Nitrobiphenyl. 1H NMR (400 MHz, CDCl
8.26e8.18 (m,
4
3
) d
1
13
2
H), 7.70e7.63 (m, 2H), 7.59e7.52 (m, 2H), 7.48e7.34 (m, 3H);
C
11. Robert, S.; Sharifah, B. A. H. Angew. Chem., Int. Ed. 2004, 43, 1628e1637.
12. Luo, J.; Jaemyung, K.; Huang, J. Acc. Chem. Res. 2013, 46, 2225e2234.
3
NMR (101 MHz, CDCl ) d
147.63, 147.07, 138.77, 129.16, 128.92,
1
1
1
3. Bruno, F. M.; Philippe, S. Catal. Sci. Technol. 2012, 2, 54e75.
4. Bai, S.; Shen, X. RSC Adv. 2012, 2, 64e98.
5. Li, Y.; Fan, X.; Wang, L.; Qi, J.; Ji, J.; Wang, S.; Zhang, G.; Zhang, F. Nano Res. 2010,
3, 429e437.
127.80, 127.39, 124.11, 77.35, 77.03, 76.71.
4
.4.3. 4-Methoxybiphenyl. 1H NMR (400 MHz, CDCl
3
) d 7.53 (t,
16. Maheswari, S.; Karthikeyan, S.; Murugan, P.; Sridhar, P.; Pitchumani, S. Phys.
J¼8.4 Hz, 4H), 7.41 (t, J¼7.3 Hz, 2H), 7.29 (t, J¼7.0 Hz, 1H), 6.97 (d,
Chem. Chem. Phys. 2012, 14, 9683e9695.
1
3
J¼8.3 Hz, 2H), 3.83 (s, 3H); C NMR (101 MHz, CDCl
3
) d 159.17,
1
7. Yang, D.; Aruna, V.; G u€ lay, B.; Sungjin, P.; Meryl, S.; Richard, D. P.; Sasha, S.;
Inhwa, J.; Daniel, A. F.; Carl, A. V. J.; Rodney, S. R. Carbon 2009, 47, 145e152.
1
40.86, 133.80, 128.77, 128.20, 126.74 (d, J¼7.8 Hz), 114.23, 77.40,
18. Lin, Y.; Kent, A. W.; Michael, J. F.; Sayata, G.; Joseph, G. S.; Donavon, M. D.; Cao,
7
7.08, 76.76, 55.38.
W.; Roy, E. C.; John, W. C. ACS Nano 2009, 3, 871e884.
1
9. Kabeer, J.; Vikas, B. ACS Nano 2009, 3, 2358e2366.
4
.4.4. 4-Methylbiphenyl. 1H NMR (400 MHz, CDCl
3
)
d
7.57 (dd,
20. Tong, L.; Li, Z.; Zhu, T.; Xu, H.; Liu, Z. J. Phys. Chem. C 2008, 112, 7119e7123.
21. Konstantin, N. K.; Bulent, O.; Hannes, C. S.; Robert, K. P.; Ilhan, A. A.; Roberto, C.
J¼8.2, 1.2 Hz, 2H), 7.52e7.45 (m, 2H), 7.45e7.36 (m, 2H), 7.34e7.27
13
NanoLett 2008, 8, 36e41.
2. Weightman, P.; Andrews, P. T. J. Phys. C: Solid State Phys. 1980, 13, 815e819.
(
3
m, 1H), 7.26e7.19 (m, 2H), 2.39 (s, 3H); C NMR (101 MHz, CDCl )
2
d
141.21, 138.40, 137.07, 129.53, 128.77, 127.04 (d, J¼2.1 Hz), 77.40,
23. Brun, M.; Berthet, A.; Bertolini, J. C. J. Electron. Spectrosc. Relat.Phenom. 1999,
04, 55e60.
4. Andrzej, G.; Anna, M. T.; J oꢁ zef, J. Z.; Leszek, K.; J oꢁ zef, W.; W1odzimierz, T. J. Catal.
005, 229, 332e343.
1
7
7.08, 76.76, 21.16.
2
2
4
.4.5. 2-Phenylpyridine. 1H NMR (400 MHz, CDCl
3
)
d
8.78e8.62 (m,
25. Lu, Y.; Wang, X.; Mai, Y.; Xiang, J.; Zhang, H.; Li, L.; Gu, C.; Tu, J.; Mao, S. J. Phys.
1
H), 8.09e7.91 (m, 2H), 7.83e7.66 (m, 2H), 7.58e7.44 (m, 2H),
Chem. C 2012, 116, 22217e22225.
26. Shukla, A. K.; Neergat, M.; Parthasarathi, B.; Jayaram, V.; Hegde, M. S. J. Elec-
troanal. Chem. 2001, 504, 111e119.
7. Zhang, S.; Shao, Y.; Liao, H.; Mark, H. E.; Yin, G.; Lin, Y. ACS Nano 2001, 5,
1785e1791.
13
7
.44e7.37 (m, 1H), 7.22 (ddd, J¼6.1, 4.8, 2.4 Hz, 1H); C NMR
(
101 MHz, CDCl 157.48, 149.69, 139.41, 136.79, 128.98, 128.78,
3
) d
2
2
2
126.94, 122.13, 120.60, 77.40, 77.08, 76.76.
8. Yi, L.; Liu, L.; Liu, X.; Wang, X.; Yi, W.; He, P.; Wang, X. Int. J. Hydrogen Energy
2012, 37, 12650e12658.
4
.4.6. 2-Nitrobiphenyl. 1H NMR (400 MHz, CDCl
3
)
d
7.86 (dd, J¼8.1,
9. Daniela, C. M.; Dmitry, V. K.; Jacob, M. B.; Alexander, S.; Sun, Z.; Alexander, S.;
Lawrence, B. A.; Lu, W.; James, M. T. ACS Nano 2010, 4, 4806e4814.
1.2 Hz, 1H), 7.62 (td, J¼7.6, 1.3 Hz, 1H), 7.51e7.40 (m, 5H), 7.35e7.30
Please cite this article in press as: Feng, Y.-S.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.05.083