number 138

Contribution

Environmental-friendly Catalysts Learned from Vitamin B12-Dependent Enzymes

Hisashi Shimakoshi and Yoshio Hisaeda

Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University,

Fukuoka 819-0395, Japan

1. Introduction +1 to +3; Co(I) imparts a gray-green color, Co(II) imparts

a yellow-to-orange color, and Co(III), which is the most
It is widely known that vitamin B12 derivatives are unique common form, imparts a red color to the B12 derivatives,
coenzymes that possess cobalt–carbon (Co–C) bonds and is known as the “red vitamin.” Methylcobalamin and
in vivo and are involved in a variety of catalytic functions adenosylcobalamin as the coenzyme forms are parts
in combination with various apoproteins.1 Vitamin B12 is of in vivo enzymes that catalyze the biosynthesis of
a metal complex in which cobalt ions are coordinated to methionine and the isomerizations with carbon-skeleton
4 ring nitrogen atoms in a corrin ring (Figure 1). It was rearrangements, respectively.3 Recent studies revealed
originally developed as a magic bullet for the treatment that the complex of such corrin ring structures acts on the
of pernicious anemia, and its unique structure was active center of the dechlorination reaction in anaerobic
elucidated by Hodgkin et al. by X-ray crystallography.2 bacteria; this suggests a new function for the B 12 -
The oxidation state of the central cobalt ions range from dependent enzymes (Scheme 1).4

H2NOC CONH2
CH3
H CH3
H2NOC CONH2
A L B
H3C N N H
H 3C
Co H
H OH OH
H N N CH3
D C
H2NOC N
CH3 L = CH O N Adenosylcobalamin
2
H N N
CH3 CH3 NH2
CONH2
CH3 L = CH3 Methylcobalamin
O C N
NH L = CN Cyanocobalamin
N CH3
H3C H
HO
H O
HO
O- P H
O
O H CH2OH

Figure 1. Structure of vitamin B12 derivatives.

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Isomerization
O
H H O H CoA
HOOC CoA HOOC

Succinyl-CoA Methylmalonyl-CoA

Methylation
NH3+ NH3+

H S CO2- H3C S CO2-

Homocysteine Methionine

Dehalogenation

Cl Cl Cl H
C C C C
Cl Cl Cl Cl
Tetrachloroethylene Trichloroethylene

Scheme 1.

The most remarkable feature of the B 12-dependent the organic halide and produces organic radical species
enzyme reaction is the formation of a unique during cleavage of the Co–C bond (Scheme 2). By
organometallic structure with a metal-carbon bond. This focusing on the above-mentioned features of the Co–C
structure is mainly produced by the reactions of Co(I) bond, we developed a molecular transformation utilizing
with an organic halide and Co(III) with Grignard reagents, the formation and cleavage of the Co–C bond with a B12
and it readily undergoes homolytic cleavage under mild model complex that stimulates the active center of the
exogenous stimuli such as visible light, heat, and redox B12 enzymes.5 In this article, we present our results on
treatment. Especially, when the former reaction occurs, the synthesis of a vitamin B12 derivative and its catalytic
formation of the Co–C bond involves dehalogenation of application.

CoI + RCl CoIII

Supernucleophile Alkylated complex

Cl-

Dechlorination

R + CoII
Photolysis
Thermolysis
Electrolysis Radical type organic synthesis

Scheme 2.

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2. Modeling of vitamin B12 chain substituents from cyanocobalamin for synthesizing

the hydrophobic vitamin B12 (heptametyl cobyrinate) by
Vitamin B 12 is obtained on a large scale from chemical modification of all the peripheral side-chains
cyanocobalamin-producing organisms for use as dietary into ester groups (Figure 2, Type A).6 About 80% of
supplements or livestock feed. Thus far, no problems the hydrophobic vitamin B 12 can be obtained using a
have occurred with regards to the safety or economics of single synthesis process by heating cyanocobalamin in
using natural vitamin B12 as a catalyst resource. However, alcohol in the presence of an acid catalyst, even when
natural vitamin B12 supplied from bacteria contains many cyanocobalamin is used as the raw material, which is
vitamin B12-related substances, suggesting that it may abundantly produced by microorganisms as mentioned
have a poor chemical stability. This is not because of above. Using the hydrophobic vitamin B12 as a starting
the instability of the corrin ring structure, but because of material, it is possible to synthesize various B12 catalysts
the deterioration of the side-chain substituents. As will that can have wide applications (Figure 2, Type B-D).
be described later, the corrin ring structure has a high The corrin rings present in natural B 12 are retained in
stability. To use the vitamin B12 derivative as a catalyst, the above-mentioned complexes, and hence, the redox
the following conditions should be satisfied: (1) the corrin potential and electronic property of the central cobalt ion of
ring structure should be retained, (2) the central cobalt the synthetic B12 derivative are similar to those of natural
atoms should be intact, and (3) the modifiable side-chains B12, suggesting that the synthetic B12 derivative will show
should be maintained. In light of these 3 conditions, we a high reactivity during molecular transformations like
temporarily removed the physiologically essential side- original enzymes.6

(A) (B)
CO2R CO2R
CO2Me O C NH R
H Me
Me
RO2C CO2R H Me
Me
Me H
N N MeO2C CO2Me
Me Me H
Co N N
H N N Me
Co R = -(CH2)3Si(OMe)3,
RO2C Me H N N
H NH2
Me Me MeO2C Me
Me H H -(CH2)3NH
Me Me
CO2R CO2R Me H
NH
CO2Me CO2Me
R = CH3~C8H17
(C) (D)

CO2Me CO2Me
COOH COOH
H Me
H Me Me
Me
MeO2C CO2Me
HOOC COOH H
H Me N N
Me N N Me
Me Co X
Co H X = Cl, Br, NO2, NH2,
H N N
N N MeO2C
HOOC Me
Me H
H O O
Me Me
Me Me Me H
Me H N
O O
CO2Me CO2Me C O O
COOH COOH

Figure 2. Modification of vitamin B12 derivatives.

3. Electroorganic reaction using B12 complex was used for generating Co(I) species of the B12 complex,
in which the B 12 complex works as a mediator for the
As described above, nucleophilic Co(I) species of the electroorganic reaction (Figure 3).7
B12 derivative reacts with organic halides, which results in We developed various molecular transformations by
dehalogenation followed by the simultaneous production controlled-potential electrolyses at the potentials of –1.4 or
of an alkylated complex. Therefore, it may be important –1.5 V vs. Ag/AgCl using the hydrophobic vitamin B12 as
to develop a method to produce reactive Co(I) species to a mediator (Scheme 3). For example, when bromoalkyl
form the alkylated complex, which is a key intermediate of acrylate was used as a substrate, large-membered
the B12-dependent enzyme reaction. The synthesized B12 ring lactones were synthesized by intramolecular
complex can be reduced by chemical reductants, such as cyclization of organic radical species generated by the
sodium borohydride, metallic zinc, and sodium amalgam, homolytic cleavage of the alkylated complex (Scheme
thus the mass use of these chemical reagents is not 3, eq. 1).8 The formation of the alkylated complex as
desirable in terms of synthetic as well as recent green the intermediate was directly observed by monitoring
chemistry. Consequently, an electrochemical technique the electrolysis solution using electrospray ionization

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Cathode Vitamin B12 complex

CoII or CoIII

e- or 2e-
Turnover
CoI

Substrate : RBr
Products
-
e- Br
R

CoIII Alkylated complex

e- or 2e-

Figure 3. Electroorganic reactions mediated by vitamin B12 model complex.

mass spectrometry (ESI-MS) and UV-vis spectra. The reaction (Scheme 2). Furthermore, the B12 catalyst was
hydrophobic vitamin B 12 can also effectively act as a not degraded after the reactions. Its high durability was
dechlorination catalyst of environmental pollutants, such confirmed by UV-vis and mass spectrum analyses after
as dichlorodiphenyltrichloroethane (DDT) (Scheme 3, the reaction. When other cobalt complexes, such as the
eq. 2). 9 It is noteworthy that the B12 catalytic system porphyrin complex, were used under the same conditions,
does not generate toxic secondary pollutants such as the complexes were severely degraded during the
chlorine gas and phosgene, because the chlorine atoms electrolysis.
are dechlorinated to harmless chloride ions during the

O
B12
Br-(CH2)n O O (1)
O -1.5 V vs. Ag/AgCl (CH2)n

n = 2, 6,12

Cl H Cl Cl
Cl Cl B12 Cl Cl
(2)
+
-1.4 V vs. Ag/AgCl
Cl Cl Cl Cl Cl Cl
DDT

CO2C2H5 CO2C2H5 CO2C2H5

B12
H2C C CH3 H3C C CH3 + H2C CH CH3 (3)
-1.5 V vs. Ag/AgCl
Br CO2C2H5 (AcOH) CO2C2H5 CO2C2H5

O O
B12 O
Br CH3
+ (4)
CO2C2H5 -1.5 V vs. Ag/AgCl CO2C2H5
n n n CO2C2H5
n = 1~4

CO2Et B12 CO2Et Ph CO2Et

H2C C Ph Me C Ph + H 2C CH
-1.5 V vs. Ag/AgCl
Br CO2Et CO2Et (5)
CO2Et

Scheme 3.

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number 138

Si(OMe)3
O
CO2Me NH
C O
H Me O Si CoII
Me
MeO2C CO2Me MeO e- CH2
Me H
Me N N Pt oxide O CH2 Br
Co e- O Si Co I
H N N Immobilization
MeO2C Me MeO
H
Me Me H Me + Br-
Pt cathode
CO2Me CO2Me
-1.4 V vs. Ag/AgCl Turnover number
6,000 / h
= CoII Si(OMe)3

Figure 4. B12 modified electrode for electroorganic reaction.

To utilize repeatedly such a robust B12 catalyst, the B12 When the electrolysis of DDT was carried out in an
complex was immobilized on the electrodes or dissolved in ionic liquid by using the B12 complex as a catalyst, the
an ionic liquid for recovering or recycling after the reaction. reaction proceeded effectively in the same manner as
In the former case, the B12 complex could be immobilized the dechlorination reaction in the polar organic solvent
on the platinum electrode surface at a coverage rate containing supporting electrolytes. Furthermore, during
of approximately 1.6 × 10 –10 mol/cm 2 by introducing the extraction process after the reaction, the product and
a trimethoxysilyl group into the side-chain (Figure 2, B12 complex could be separated in the organic solvent
Type B). The reactivity was evaluated using phenethyl layer and the ionic liquid layer, respectively. The B 12
bromide as the model substrate, which demonstrated complex dissolved in an ionic liquid can be recycled
a high catalytic activity with 6,000 turnover number per for the reaction (Figure 5). 15 More interestingly, the
hour (Figure 4).10 After the reaction, the product and the reactivity of the B12 complex improved in the ionic liquid;
B12 catalyst could be easily separated as the B12 catalyst i.e., the conversion efficiency of the substrate increased
was immobilized on the electrode. Other examples of approximately 4-times that of the reaction performed in
the B 12-modified electrodes were also reported, such dimethylformamide (DMF). This enhanced reactivity in
as a polymer-covered electrode, interface-polymerized the ionic liquid over that in DMF could be explained by
electrode, and sol-gel film doped electrode.11-13 the application of the Hughes–Ingold predictions 16 of
On the other hand, when an ionic liquid was used as solvent polarity effects on reaction rates. The reaction
the reaction solvent, the B12 complex was supported in an of electrochemically generated Co(I) with DDT is a
ionic liquid and showed the following various benefits. In ‘‘Menschutkin type of reaction’’ in which two neutral
general, an electroorganic reaction was carried out in a reactants, Co(I) and DDT, react to form charged products
polar organic solvent containing supporting electrolytes. via a charge-separated activated complex in the polar
However, such a reaction using organic solvents ionic liquid, which ultimately decreases the activation
containing many of the supporting electrolytes may not energy, resulting in an increase in the reaction rate. A
be desirable with regard to the recent regulated use of similar accelerating effect of the reaction in an ionic liquid
chemical reagents, even though this procedure is used has been closely examined by the reaction of methyl
to degrade chlorinated organic compounds. Recently, p-nitrobenzenesulfonate with tri-n-butylamine.17 Actually,
electroorganic reactions in an ionic liquid have been the ETN value18 of the ionic liquid has been determined as
increasingly studied in order to address such issues. The a polarity index. For example, the value of 1-n-butyl-3-
ionic liquid is a room temperature liquid salt under ordinary methylimidazolium tetrafluoroborate is 0.673, indicating it
pressure, which is characterized by its nonvolatility, fire is highly polar compared to a polar organic solvent, such
retardance, and excellent electrical conductivity and is as DMF (ETN = 0.386).19
a superior solvent for the electroorganic reactions. 14

Cl H Cl
Cl Cl H H H H
Electrolysis
+
Cl Cl -1.5 V vs. Ag/AgCl Cl ClH Cl Cl
DDT DDO DDMS etc...

Run Conversion
Et2O Product of DDT (%)

1st 75
H2O
2nd 82
N N 3rd 73
Co
BF4-
Vitamin B12 complex
Ionic liquid

Recycle use

Figure 5. Reaction of vitamin B12 complex in ionic liquid.

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4. Photosensitized reaction of B12 complex by electron transfer from the ruthenium photosensitizer.
Based on this strategy as shown in Figure 6, the
We attempted to design a light-driven catalyzing dechlororination of DDT was carried out using the B 12
system that could be used for the development of a complex in the presence of the ruthenium photosensitizer
clean molecular transformation using the B12 complex. and sacrificial electron donor. Consequently, most of
Light is one of the abundant and cleanest energies on the DDT was converted to DDD, a mono-dechlorination
the earth and has been used in organic syntheses for product, within 3 hours. The reaction was hardly
a long time. Thus, we focused on a ruthenium(II) tris facilitated in the absence of the B12 complex or in the dark.
bipyridine complex ([Ru II (bpy) 3 ]Cl 2 ), which has been Therefore, it is suggested that Co(I), which is produced by
widely used as a photosensitizer, and constructed the a photo-induced electron transfer reaction, might act as an
catalyzing system using a photo-induced electron transfer active species to initiate the reaction. The ESR spectral
reaction for producing Co(I) species.20 The [RuII(bpy)3]Cl2 change confirmed that the electron transfer reaction of
complex was excited under visible light irradiation and the the ruthenium photosensitizer reduces the B12 complex to
[Ru(bpy)3]+ complex with high reduction potential (–1.35 V Co(I) species. Characteristic ESR signals were detected
vs. Ag/AgCl) was produced due to reductive quenching for the paramagnetic Co(II) of B12, while the corresponding
by a sacrificial electron donor such as triethanolamine.21 ESR signals for diamagnetic Co(I) were absent in the
Therefore, it is possible to generate the catalytically photoreaction (Figure 7).
active B12 complex (E1/2(CoII/CoI) = – 0.6 V vs. Ag/AgCl)

CO2R
RO2C

RO2C CO2R
N N Products
CoII
1.3 V vs. Ag/AgCl RO2C N N Visible light
Triethanol [Ru(bpy)3]+
amine Cl Cl
[Ru(II)(bpy)3]2+ * e CO2R CO2R
Cl Cl + Cl
N N
CoI CoIII
II
N Ru N
Visible light
N N E1/2 (CoII/CoI) =
Cl
0.5 V ~ 0.6 V vs. Ag/AgCl Cl Cl
[Ru(II)(bpy)3]2+
Cl Cl
DDT
Figure 6. Sterategy for photosensitized system for B12 catalysis.

(c)
(a) g1 = 2.53 CoII
g2 = 2.32 CoII
g3 = 2.00

A3Co = 139 G 500 G

(b)
g = 2.00 CoI
(a) Before irradiation with visible light.
(b) After irradiation with visible light.
(c) After open to air (autooxidation).

Figure 7. ESR sepectral change of vitamin B12 derivative in

the presence of [Ru(bpy)3]Cl2 and triethanolamine.

5. B12-TiO2 hybrid catalyst effects of metal complexes and semiconductors. Thus,

we focused on titanium oxide, 24 which is an n-type
Recently, hybrid catalysts composed of a metal complex semiconductor, to develop a light energy driven B 12 -
and various semiconductors with photosensitizing ability TiO2 hybrid catalyst. The reduction power of the excited
have been reported.22,23 According to this technique, it electrons in the titanium oxide (TiO 2)-conduction band
is possible to develop a hybrid catalyst with concerted (–0.5 V vs. normal hydrogen electrode (NHE))25 enabled

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O
COOH Cl Cl CCl4
Br
COOH
CO2Et CHCl3
HOOC Cl Cl
COOH
N N Cl O
Co Cl Cl Br Ph OEt
N N C
HOOC H2 C OEt
Cl Cl O
DDT Br
HOOC COOH

Vitamin B12 complex Products

e-
= CoII
CoII CoI
Conduction band
Super-
UV O Nucleophilicity
O O
O
HO Ti O Ti OH
O
Ti O
O Ti
Valance band O O
TiO2

Figure 8. Molecular transformations catalyzed by B12-TiO2 hybrid catalyst.

the reduction of the B12 complex to the catalytically active of TiO2. Furthermore, both the B12 complex and TiO2
Co(I) species, and this indicated that a light energy-driven are non-toxic, thus the B12-TiO2 hybrid catalyst may be
hybrid catalyst can be developed by immobilizing the B12 an environmental/human friendly catalyst. In addition,
complex on TiO2. In this case, TiO2 not only played a we investigated the use of the hybrid catalyst in radical
role as a scaffold for the B12 complex, but also served as reactions for organic synthesis. This result indicated that
an electron source for the reduction of the B12 complex this hybrid catalyst could be applied to various molecular
(Figure 8). Here, the B12 complex was immobilized on transformations, including the above-mentioned ring
TiO2 by multiple interactions of the carboxyl groups of B12 expansion reactions (Scheme 3, eq. 4) and 1,2-migration
(Figure 2, Type C) and surface hydroxyl groups of TiO2. of the functional group (Scheme 3, eq. 5). Thus, the
Approximately 3–4 × 10 –5 mol (40–50 mg) of the B 12 hybrid catalyst can be used as an alternative for the
complex (cobyrinic acid) was found to immobilize on 1 g conventional radical organic synthetic reagent that uses a
of TiO2 and 70–80% of the TiO2 surface was covered with tin compound (Bu3SnH/AIBN system).
the B12 complex. The resulting B12 complex was firmly TiO2 can also be immobilized on carriers, such as glass
immobilized on the TiO2 surface, and the immobilization substrates and beads, when it is converted to slurry
remained stable for more than 1 year even after being sol solutions. Thin films of TiO 2 (with a thickness of a
dispersed in various organic solvents, such as an alcohol, few hundred nanometers), which are prepared on glass
and was not separated by ultrasonic treatment. substrates by dip-coating, can be hybridized with the B12
When a degradation reaction of a chlorinated organic complex by only dipping into the B 12 complex solution
compound, such as DDT, is performed using this containing carboxyl groups. Thus the prepared B12-TiO2
hybrid catalyst, only a few milligrams of the catalyst can hybrid catalyst on a glass plate also catalyzed the above-
dechlorinate 100 times that of DDT in approximately mentioned reactions (Figure 9). The immobilization of the
1 day. 26 The hybrid catalyst was activated by light B12-TiO2 hybrid catalyst on a glass plate can simplify the
energy so that neither chemical reagents nor expensive reaction process, and furthermore, facilitate the separation
reactors are required. Ultraviolet irradiation provided by procedure of the product from the reaction mixture.
black light (365 nm) is sufficient for the photoexcitation

Dechlorination of various organic chloride catalyzed

by B12-TiO2 coated glass plate.a

Substrate Conversion Substrate Conversion

Cl
B12-TiO2 layer Cl Cl Cl
Cl Cl
99 % 99 %
Cl Cl Cl
Cl
Glass plate Cl Cl Cl Cl
300 nm 98 % ~100 %
Cl Cl Cl Cl
Cl
a
Under irradiation with 365 nm black light.

Figure 9. Immobilization of B12-TiO2 hybrid catalyst onto glass plate.

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6. Vitamin B12-hyperbranched polymer hybrid molecules. 29 Considering the nanospace provided by

catalyst the hyperbranched polymers as a new catalyst reaction
field, the B12-hyperbranched polymer hybrid catalyst was
A hyperbranched polymer is one of the dendric polymers synthesized (Scheme 4).30 The amount of B12 complex
that are synthesized via a one-step polymerization used can be adjusted to somewhere between a few % and
reaction in an inexpensive and easy way, and it has 70% per terminal functional groups of the hyperbranched
various advantages when compared to dendrimers, which polymers, and the density of the B 12 complex can be
are synthesized via multiple-step polymerizations. 27 readily controlled. When the B 12 complex is densely
Furthermore, as the polymer has a higher solubility and immobilized, a cooperative effect of the adjacent
lower solution viscosity compared to linear polymers, complex facilitates the dimerization reaction of phenethyl
it is expected to be used in a homogeneous solution.28 bromide.31 It is expected that the variable size and main
In fact, the hyperbranched polymers that have many chain polymer of the hyperbranched polymer will be able
terminal functional groups due to their highly branched to produce various reaction characteristics.
structure are appropriate for carrying functionalized

HO2C
DC CO2R
OH
OH HO DC RO2C
DC CO2R
DC OH NX N
DC + Co
HO OH OH N XN = CO2H
Co
DC DC
OH HO DC RO2C

CO2R CO2R
DC = S NEt2
S X=CN

Mw=12600, Mw/Mn=2.6
O
Co Co
DC O
O HO DC
EDC O
DC DC
in dry CH2Cl2 DC O
O O
Co OH Co
O DC DCO DC
Co
O

Modified yield : 72 %

Scheme 4.

7. Conclusions development of this bio-inspired chemistry introduced

by us will play an important role in the next generation’s
We have outlined the development of molecular science and technology.
transformations learned from the B12-dependent enzymes.
The hybrid catalyst composed of synthesizing metal
complexes, which are similar to the active center of the Acknowledgments - This work was partially supported
B12 enzyme, enabled various molecular transformations by a Grant-in-Aid for Scientific Research on Priority
including environmatally-friendly organic synthesis Areas (452 and 460) and Global COE Program “Science
reactions and degradation reactions of organic halides for Future Molecular Systems” from the Ministry of
pollutants by an electroorganic reaction or a photochemical Education, Culture, Sports, Science and Technology
reaction. Combining the benefits of natural enzymes and (MEXT) of Japan, and an Industrial Technology Research
engineering methods will allow the development of a new Grant Program in 2005 from New Energy and Industrial
catalyst system that will exceed biological reactions. The Technology Development Organization (NEDO) of Japan.

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References 15. M. Jabbar, H. Shimakoshi, Y. Hisaeda, Chem.

Commun. 2007, 1653-1654.
1. (a) Vitamin B12 and B12-Proteins ed. by B. Kräutler, 16. K. A. Cooper, M. L. Dhar, E. D. Hughes, C. K. Ingold,
D. Arigoni, B. T. Golding, Wiley-VCH 1998; (b) B. J. MacNulty, L. I. Woolf, J. Chem. Soc. 1948,
Chemistry and Biochemistry of B 12 ed. by R. 2043-2046.
Banerjee, Wiley-Interscience 1999. 17. L. Crowhurst, N. L. Lancaster, J. M. P. Arlandis, T.
2. (a) D. C. Hodgkin, J. Pickworth, J. H. Robertson, Welton, J. Am. Chem. Soc. 2004, 126, 11549-11555.
K. N. Trueblood, R. J. Prosen, J. G. White, Nature 18. C. Reichardt, Solvent and Solvent Effects in Organic
1955, 176, 325-328; (b) D. C. Hodgkin, J. Kamper, M. Chemistry, VCH (UK) Ltd., Cambridge, UK, 2nd edn,
Mackay, J. Pickworth, K. N. Trueblood, J. G. White, 1998.
Nature 1956, 178, 64-66; (c) P. G. Lenhert and D. C. 19. (a) S. N. V. K. Aki, J. F. Brennecke, A. Samanta,
Hodgkin, Nature 1961, 192, 937-938. Chem. Commun. 2001, 413-414; (b) M. J. Muldoon,
3. (a) R. Banerjee and S. W. Ragsdale, Annu. Rev. C. M. Gordon, I. R. Dunkin, J. Chem. Soc., Perkin
Biochem. 2003, 72, 209-247; (b) T. Toraya, Chem. Trans. 2, 2001, 433-435.
Rev. 2003, 103, 2095-2127; (c) B. Kräutler, Biochem. 20. (a) H. Shimakoshi, M. Tokunaga, T. Baba, Y.
Soc. Trans. 2005, 33, 806-810. Hisaeda, Chem. Commun. 2004, 1806-1807; (b) H.
4. (a) G. Glod, U. Brodmann, W. Angst, C. Holliger, R. Shimakoshi, S. Kudo, Y. Hisaeda, Chem. Lett. 2005,
P. Schwarzenbach, Environ. Sci. Technol. 1997, 31, 34, 1806-1807.
3154-3160; (b) C. Holliger, G. Wohlfarth, G. Diekert, 21. A. Juris, V. Balzani, F. Barigelletti, S. Campagna, P.
FEMS Microbiol. Rev. 1999, 22, 383-398; (c) B. Belser, A. V. Zelewsky, Coord. Chem. Rev. 1988, 84,
Kräutler, W. Fieber, S. Ostermann, M. Fasching, 85-277.
K. –H. Ongania, K. Gruber, C. Kratky, C. Mikl, A. 22. (a) S. O. Obare, T. Ito, G. J. Meyer, Environ. Sci.
Siebert, G. Diekert, Helv. Chim. Acta 2003, 86, Technol. 2005, 39, 6266-6272; (b) Y. Astuti, E.
3698-3716; (d) S. Ruppe, A. Neumann, G. Diekert, Palomarse, S. A. Haque, J. R. Durrant, J. Am. Chem.
W. Vetter, Environ. Sci. Technol. 2004, 38, 3063- Soc. 2005, 127, 15120-15126; (c) S. O. Obare, T. Ito,
3067; (e) K. M. McCauley, D. A. Pratt, S. R. Wilson, G. J. Meyer, J. Am. Chem. Soc. 2006, 128, 712-713;
J. Shey, T. J. Burkey, W. A. van der Donk, J. Am. (d) B. I. Ipe and C. M. Niemeyer, Angew. Chem. Int.
Chem. Soc. 2005, 127, 1126-1136; (f) J. E. Argüello, Ed. Engl. 2006, 45, 504-507.
C. Costentin, S. Griveau, J. –M. Sáveant, J. Am. 23. R. J. Kuhler, G. A. Santo, T. R. Caudill, E. A.
Chem. Soc. 2005, 127, 5049-5055. Betterton, R. G. Arnold, Environ. Sci. Technol. 1993,
5. Reviews: (a) Y. Hisaeda, T. Nishioka, Y. Inoue, K. 27, 2104-2111.
Asada, T. Hayashi, Coord. Chem. Rev. 2000, 198, 24. (a) M. A. Fox, Acc. Chem. Res. 1983, 16, 314-321;
21-25; (b) K. L. Brown, Chem. Rev. 2005, 105, 2075- (b) M. D. Ward, J. R. White, A. J. Bard, J. Am. Chem.
2150. Soc. 1983, 105, 27-31; (c) M. A. Fox and M. T. Dulay,
6. (a) Y. Murakami, Y. Hisaeda, A. Kajihara, Bull. Chem. Chem. Rev. 1993, 93, 341-357; (d) M. R. Hoffmann,
Soc. Jpn. 1983, 56, 3642-3646; (b) Y. Murakami, Y. S. T. Martin, W. Choi, D. W. Bahnemann, Chem.
Hisaeda, A. Kajihara, T. Ohno, Bull. Chem. Soc. Jpn. Rev. 1995, 95, 69-96.
1984, 57, 405-411. 25. A. Fujishima, T. N. Rao, D. A. Tryk, J. Photochem.
7. R. Scheffold, G. Rytz, L. Walder, Modern Synthetic Photobiol. C: Photochem. Rev. 2000, 1, 1-21.
Methods, Vol. 3, ed. By R. Scheffold, John Wiley & 26. H. Shimakoshi, E. Sakumori, K. Kaneko, Y. Hisaeda,
Sons, 1983, 355-440. Chem. Lett. 2009, 38, 468-469.
8. H. Shimakoshi, A. Nakazato, T. Hayashi, Y. Tachi, Y. 27. M. Jikei and M. Kakimoto, Prog. Polym. Sci. 2001,
Naruta, Y. Hisaeda, J. Electroanal. Chem. 2001, 507, 26, 1233-1285.
170-176. 28. P. H. Toy and K. D. Janda, Acc. Chem. Res. 2000,
9. (a) H. Shimakoshi, M. Tokunaga, Y. Hisaeda, 33, 546-554.
Dalton Trans. 2004, 878-882; (b) H. Shimakoshi, 29. (a) K. Ishizu and A. Mori, Polym. Int. 2001, 50, 906-
Y. Maeyama, T. Kaieda, T. Matsuo, E. Matsui, Y. 910; (b) K. Ishizu, T. Shibuya, A. Mori, Polym. Int.
Naruta, Y. Hisaeda, Bull. Chem. Soc. Jpn. 2005, 78, 2002, 51, 424-428; (c) K. Ishizu, T. Shibuya, J. Park,
859-863. S. Uchida, Polym. Int. 2004, 53, 259-265.
10. H. Shimakoshi, M. Tokunaga, K. Kuroiwa, K. 30. K. Tahara, H. Shimakoshi, A. Tanaka, Y. Hisaeda,
Kimizuka, Y. Hisaeda, Chem. Commun. 2004, 50-51. Tetrahedron Lett. 2007, 48, 5065-5068.
11. (a) A Ruhe, L. Walder, R. Scheffold, Helv. Chim. Acta 31. K. Tahara, H. Shimakoshi, A. Tanaka, Y. Hisaeda,
1985, 68, 1301-1311; (b) Y. Murakami, Y. Hisaeda, T. unpublished result.
Ozaki, Y. Matsuda, J. Chem. Soc., Chem. Commun.
1989, 1094-1096; (c) D.-L. Zhou, C. K. Njue, J. F.
Rusling, J. Am. Chem. Soc. 1999, 121, 2909-2914; (d) (Received Jul. 2009)
C. K. Njue and J. F. Rusling, Electrochem. Commun.
2002, 4, 340-343.
12. R. Fraga, J. P. Correia, R. Keese, L. M. Abrantes,
Electrochim. Acta 2005, 50, 1653-1655.
13. H. Shimakoshi, A. Nakazato, M. Tokunaga, K.
Katagiri, K. Ariga, J. Kikuchi, Y. Hisaeda, Dalton
Trans. 2003, 2308-2312.
14. T. Welton, Chem. Rev. 1999, 99, 2071-2083.

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Introduction of the authors

Hisashi Shimakoshi
Assistant Professor, Graduate School of Engineering, Kyushu University

Education:
B. S. and M. S., Doshisha University
Ph. D., Kyushu University
Professional Experiences:
1996-present Assistant Professor, Kyushu University
Honors:
2002 Synthetic Organic Chemistry Award for Young Scientists in Kyushu-Yamaguchi
2004 Electroorganic Chemistry Award for Young Scientists
Expertise and Speciality:
Coordination chemistry, Bioinorganic chemistry

Yoshio Hisaeda
Professor, Graduate School of Engineering, Kyushu University

Education:
B. S., M. S., and Ph. D., Kyushu University
Professional Experiences:
1981-1988 Research Associate, Kyushu University
1988-1995 Associate Professor, Kyushu University
1993-1994 Visiting Professor, The University of Texas at Austin
1995-present Professor, Kyushu University
Honors:
1991 The Chemical Society of Japan Award for Young Chemists (The 40th Shinpo-sho)
2008 BCSJ Award Article
Expertise and Speciality:
Biofunctional chemistry, Coordination chemistry, and Electroorganic chemistry

TCI Related Compound

H2NOC CONH2
CH3
H CH3
H2NOC CONH2
A L B
H3C N N H
H3C
Co H
H
H N N CH3
D C
H2NOC
Cyanocobalmin (vitamin B12) CH3
100mg, 1g [C0449] H
CH3 CH3
CONH2
O C N CH3
NH
N CH3
H 3C H
HO
H O
HO
O - P H
O
O H CH2OH

11