Electronic behavior of calcined material obtained from 2,2-diphenylphosphino-1,1-binaphthyldichloro palladium

Article abstract of DOI:10.1016/j.ssc.2008.09.016

The calcinations of 2,2-diphenylphosphino-1,1-binaphthyldichloro palladium under an argon atmosphere gave nano-sized Pd₅P₂/carbon cluster composite material. The ESR spectral examination of the material, and the reaction of either methylene blue or 2,3,5-trimethylhydroquinone in the presence of the material revealed that the calcined material has a visible light-responsive oxidation-reduction function through an electron transfer from the carbon clusters to the Pd₅P₂ particles.

Full text of DOI:10.1016/j.ssc.2008.09.016

Solid State Communications 148 (2008) 274–278
Contents lists available at ScienceDirect
Solid State Communications
journal homepage: www.elsevier.com/locate/ssc
Electronic behavior of calcined material obtained from
2
,2-diphenylphosphino-1,1-binaphthyldichloro palladium
S. Yamamoto , H. Matsui , T. Okajima , S. Karuppuchamy , M. Yoshiharab,c
a
b
b
c,∗
a
Taki Chemical Co. Ltd., 641, Nishiwaki, Befu-cho, Kakogawa, Hyogo, 675-0125, Japan
Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka, 577-8502, Japan
Molecular Engineering Institute, Kinki University, 11-6, Kayanomori, Iizuka, Fukuoka, 820-8555, Japan
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 March 2007
Received in revised form
The calcinations of 2,2-diphenylphosphino-1,1-binaphthyldichloro palladium under an argon atmo-
sphere gave nano-sized Pd5P2/carbon cluster composite material. The ESR spectral examination of the
material, and the reaction of either methylene blue or 2,3,5-trimethylhydroquinone in the presence
of the material revealed that the calcined material has a visible light-responsive oxidation–reduction
function through an electron transfer from the carbon clusters to the Pd5P2 particles.
1
5 May 2008
Accepted 6 September 2008 by J.F. Sadoc
Available online 11 September 2008
©
2008 Elsevier Ltd. All rights reserved.
PACS:
7
7
7
7
1.20.Rv
1.20.Nr
2.80.Tm
3.63.Rt
Keywords:
A. Nanostructures
A. Metals
A. Polymers
D. Electronic transport
1
. Introduction
by the calcination of common organometallic compounds. In the
present work, we describe the composition and electronic behavior
of material obtained by the calcination of 2,2-diphenylphosphino-
1,1-binaphthyldichloro palladium I (Scheme 1).
Construction of a charge-separated electron transfer with
photo-responsive function is important for obtaining novel
photocatalysts and many works on semiconductors have been
reported [1–7]. However, an electron transport under whole
visible light irradiation does not seem to have been established
yet. We assumed that such a transport will be obtained by
combining semiconductors and carbon clusters, since carbon
clusters are considered to act as a visible-light absorption and
electron transport sites, and semiconductors to act as an electron
excitation site. We have recently reported that the calcination
of metal-organic moiety hybrid copolymers under a reducing
atmosphere gave nano-sized inorganic metal compound/carbon
clusters composite materials and an electron transfer between the
metal compounds and the carbon clusters took place to exhibit
a visible light-responsive oxidation–reduction function [8–13].
Here, we consider that such composite materials will be obtained
2. Experimental
Commercially available chemicals, 2,2-diphenylphosphino-1,1-
binaphthyl (BINAP), bis (acetonitrile) dichloropalladium, anhy-
drous dichloromethane, anhydrous cyclohexane, anthraquinone,
pyrogallol, methylene blue, and 2,3,5-trimethylhydroquinone
were used.
A solution of 0.623 g (1 mmol) of BINAP in 10 ml of
anhydrous dichloromethane was added into a solution of 0.229 g
(
1 m mol) of bis(acetonitrile)dichloropalladium in 10 ml of
anhydrous dichloromethane, and the mixture was stirred at
room temperature for 24 h to obtain precipitates. The obtained
precipitates were recrystallized from cyclohexane by vapor
diffusion method to obtain orange-colored compound I (90%).
0
.1 g of compound I in a porcelain crucible was heated under an
◦
∗
argon atmosphere with a heating rate of 5 C/min using Denken
Corresponding author. Tel.: +81 948 22 5706; fax: +81 948 22 5706.
E-mail address: chamy@mol-eng.fuk.kindai.ac.jp (S. Karuppuchamy).
gas convertible electric furnace KDF-75 and kept for 1 h at 300,
0
038-1098/$ – see front matter © 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ssc.2008.09.016

S. Yamamoto et al. / Solid State Communications 148 (2008) 274–278
275
Scheme 1. Syntheses of compound I and calcined material Ic.
Scheme 2. Plausible electron transfer process.
Table 1
Elemental analyses of compound I and calcined materials
Materials
Found (%)
Cb
Color
H
Pd
P
Cl
Ia
65.83
59.18
53.44
55.10
45.52
48.77
4.17
3.52
3.14
2.81
1.77
1.44
12.99
15.10
17.46
17.84
20.73
8.53
8.06
7.68
8.69
9.79
7.36
4.88
8.36
0
Orange
Dark green
Black
Ic-300
Ic-400
Ic-500
Ic-600
Ic-700
0
0
Black
0
Black
Black
0
a
Calcd (%): C 66.06, H 4.03, Pd 13.30, P 7.74, Cl 8.86.
C value is within the range of +/−0.3% from the given value while repeating
b
the experiment.
◦
00, 500, 600 and 700 C to obtain calcined materials Ic-300, Ic-
4
4
00, Ic-500, Ic-600, and Ic-700, respectively.
The reduction and oxidation abilities of Ic-600 were examined
in the following way: A mixture of 50 mg of Ic-600 and 20
mL of 10 µM methylene blue aqueous solution or 10 µM
2
,3,5-trimethylhydroquinone acetonitrile solution was kept in the
dark overnight. The mixture was irradiated by visible light for
fixed time and then the absorbance of methylene blue or 2,3,5-
trimethylhydroquinone was determined by UV-VIS spectrometry.
Elemental analysis was performed for C and H using Yanaco MT-
Fig. 1. XRD patterns of calcined materials.
6
7
, for Cl using Yanaco YS-10, and for P and Pd using Shimadzu ICP-
500. FT/IR spectra were measured using Nihon Bunko FT/IR-470.
P-NMR spectra were taken using Jeol ECA500. X-ray diffraction
contents for the calcined materials were below 100%. A reason
is incomplete elemental analyses, since insoluble residues in
acidic solutions were yielded at the ICP analyses of the materials
and partly black-colored residues after the elemental analyses
operations were observed. Fig. 1 is the XRD patterns of the calcined
3
1
(
XRD) spectra were obtained using Rigaku Mini Flex. Transmission
electron microscopy (TEM) observations were carried out using
Jeol JEM-3010 spectrometer. UV-VIS spectra were measured
using Hitachi U-4000 spectrometer. Electron spin resonance (ESR)
spectra were taken using Jeol JES-TE200 spectrometer. Visible light
was generated using Hoya–Schott Megalight 100 halogen lamp.
◦
◦
◦
materials and peaks at 2Θ = 33 , 39 and 43 due to Pd P were
5 2
observed. It should be indicated that the XRD spectra showed a
◦
◦
peak at 2Θ = 22 due to a graphite and at 2Θ = 12 due
to a layered structure of graphite with the basal space of 8.23 Å.
The TEM images (Fig. 2) showed that the calcined materials have
ultrafine particles with the diameters of a few nm, possibly metal
compound Pd5P2, in the matrix of carbon clusters. These results
suggest that the material was composed of nano-sized Pd5P2 and
carbon clusters.
3. Results and discussion
Compound I was synthesized according to the procedure
reported by Sannicola [14] and the results of elemental analyses
of I are shown in Table 1. The observed values were nearly equal
to the calculated values. FT/IR spectra of I showed frequencies at
In order to examine further the electronic behavior of the
calcined materials, their ESR spectra were measured (Fig. 3). A
peak at 337 mT (g = 2.003) due to a free electron was detected
and the highest intensity was observed for Ic-600. Our opinion
is that an electron transfer between the metal compound and
the carbon clusters took place to form a free electron on the
carbon clusters. The peak intensity of Ic-600 at 337 mT slightly
decreases in response to 15 min visible light irradiation but almost
−
1
1
1
567 and 1512 cm due to the naphthyl and phenyl groups and at
−1
31
447 cm due to the P–C bond. The P-NMR spectra of I showed
a peak at 28.6 ppm due to the P atom. These results suggest the
formation of compound I.
The results of the elemental analyses of the calcined materials
are summarized in Table 1. The total amounts of the observed

2
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S. Yamamoto et al. / Solid State Communications 148 (2008) 274–278
Fig. 2. TEM images of calcined materials.
Fig. 4. ESR spectra of Ic-600 under visible light irradiation.
Fig. 3. ESR spectra of calcined materials.
between the concentrations of methylene blue and the irradiation
time either in the dark or under the visible light irradiation. The
Pd5P2 have high electron density compared to the methylene blue
and hence a slight electron movement may occur from Pd5P2
to methylene blue in the dark. So the reduction of methylene
blue could occur in the dark. However, the degree of decrease
of methylene blue under the light irradiation was higher than
that in the dark, indicating that Ic-600 had visible light-responsive
reduction ability. Fig. 8 shows the UV-VIS spectral change of 2,3,5-
trimethylhydroquinone in the presence of Ic-600 under the visible
light irradiation and the absorbance was found to decrease with
the increase of the irradiation time. Fig. 9 shows the relationships
between the 2,3,5-trimethylhydroquinone concentrations and
the irradiation time either in the dark or under the light
irradiation. The 2,3,5-trimethylhydroquinone have rather high
increased back to the initial intensity when kept it for 15 min
after the irradiation had stopped (Fig. 4), suggesting that Ic-600
had a visible-light responsive function. The peak intensity of Ic-
6
00 increases with the addition of an oxidant (anthraquinone) but
decreases with the addition of a reductant (pyrogallol) (Fig. 5),
indicating that the peak signal was due to a cation radical. These
results suggest that an electron transfer from the carbon clusters
to the Pd5P2 particles took place to form an oxidation site at
the carbon clusters and a reduction site at the Pd5P2 particles
(
Scheme 2).
The photoresponsive oxidation–reduction ability of Ic-600
was also examined. Fig. 6 shows the UV-VIS spectral change of
methylene blue in the presence of Ic-600 under visible light-
irradiation and the absorbance was found to decrease with the
increase of the irradiation time. Fig. 7 shows the relationships

S. Yamamoto et al. / Solid State Communications 148 (2008) 274–278
277
Fig. 5. ESR spectra of Ic-600 in the presence of oxidant or reductant.
Fig. 8. UV-VIS spectra of 2,3,5-trimethylhydroquinone in the presence of Ic-600
under visible light irradiation.
Fig. 9. Relationships between 2,3,5-trimethylhydroquinone concentration and
time in the presence of Ic-600 either in the dark or under visible light irradiation.
electron density and hence the electron transfer may occur from
2,3,5-trimethylhydroquinone to the positive charge containing
Carbon. Thus, the concentration of 2,3,5-trimethylhydroquinone
slightly decreases by the oxidation in the dark. However, here
again, the visible light effectively decreases the concentration of
Fig. 6. UV-VIS spectra of methylene blue in the presence of Ic-600 under visible
light irradiation.
2
,3,5-trimethylhydroquinone compared to the same in the dark,
indicating that Ic-600 had a visible light-responsive oxidation
function.
In conclusion, the calcinations of 2,2-diphenylphosphino-1,1-
binaphthyldichloropalladium I under an argon atmosphere gave
nano-sized Pd5P2/carbon clusters composite material. ESR spectral
examination of the material and the reaction of methylene blue
or 2,3,5-trimethylhydroquinone in the presence of the material
showed that the composite material have visible light-responsive
oxidation–reduction ability through an electron transfer from
the carbon clusters to the Pd5P2 particles. We believe that such
an electron transfer will be achieved by the combination of
carbon clusters and various semiconductors, and our findings will
contribute to the development of new photo-science, including
electronic and/or optical devices production, organic synthesis
catalysts, artificial photosynthesis catalysis, solar cells production,
and so on.
Fig. 7. Relationships between methylene blue concentration and time in the
presence of Ic-600 either in the dark or under visible light irradiation.

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S. Yamamoto et al. / Solid State Communications 148 (2008) 274–278
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