The improvement of formic acid production from CO2 with visible-light energy and formate dehydrogenase by the function of the viologen derivative with carbamoylmethyl group as an electron carrier

Article abstract of DOI:10.1016/j.jphotochem.2017.09.044

Formate dehydrogenase (FDH) is an attractive biocatalyst for converting CO₂ to formic acid in ambient conditions. FDH is applied to the catalyst for the visible-light induced CO₂ – formic acid conversion system consisting of an electron donor, a photosensitizaer and an electron carrier. For improvement of the formic acid production efficiency with this system, the enhancement of electron relay processes among a photosensitizer, an electron carrier and FDH has been needed. We aimed to solve this problem by developing novel electron carrier based on the viologen derivative instead of methylviologen (MV), widely used as an electron carreir. In this study, viologen derivatives with carbamoyl group, 1,1′-dicarbamoylmethyl-4,4′-bipyridinium diiodide (CV) and 1-carbamoylmethyl-1′-methyl-4,4′-bipyridinium diiodide (CMV) were synthesized and applied to the electron carrier for photoinduced CO₂-formic acid conversion system consisting of triethanolamine, water-soluble zinc porphyrin and FDH. By using CV and CMV, the effective formic acid production in the system of water-soluble zinc porphyrin and FDH was improved compared with that of MV.

Full text of DOI:10.1016/j.jphotochem.2017.09.044

Accepted Manuscript
Title: The improvement of formic acid production from CO2
with visible-light energy and formate dehydrogenase by the
function of the viologen derivative with carbamoylmethyl
group as an electron carrier
Authors: Shusaku Ikeyama, Takayuki Katagiri, Yutaka Amao
PII:
S1010-6030(17)30949-8
DOI:
Reference:
https://doi.org/10.1016/j.jphotochem.2017.09.044
JPC 10891
To appear in:
Journal of Photochemistry and Photobiology A: Chemistry
Received date:
Revised date:
Accepted date:
5-7-2017
7-9-2017
20-9-2017
Please cite this article as: Shusaku Ikeyama, Takayuki Katagiri, Yutaka Amao, The
improvement of formic acid production from CO2 with visible-light energy and
formatedehydrogenase bythe functionoftheviologenderivativewithcarbamoylmethyl
group as an electron carrier, Journal of Photochemistry and Photobiology A:
Chemistry https://doi.org/10.1016/j.jphotochem.2017.09.044
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The improvement of formic acid production from CO2 with visible-light
energy and formate dehydrogenase by the function of the viologen
derivative with carbamoylmethyl group as an electron carrier
Shusaku Ikeyamaa, Takayuki Katagirib, Yutaka Amaoa,b,c*
a Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka
City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan.
b Graduate School of Science, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku,
Osaka 558-8585, Japan.
c Research Center for Artificial Photosynthesis (ReCAP), Osaka City University,
Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan.
Corresponding Author: Y. Amao
Fax: +81 6 6605 3726; Tel: +81 6 6605 3726; E-mail: amao@ocarina.osaka-cu.ac.jp
1

Graphical Abstract
Highlights·
 Viologen derivative (BP) with carbamoyl group was developed and applied as
an electron carrier in the visible-light induced CO2 to formic acid conversion
system consisting of the Zn porphyrin and formate dehydrogenase (FDH) for
improvement of the formic acid production efficiency.
 The photoreduction efficiency of BP depends on the redox potential and
effective photoreduction was observed using 1,1′-dicarbamoylmethyl-4,4′-
bipyridinium diiodide with the lowest redox potential among BP’s.
2

 ・The effective formic acid production was observed by using 1-
carbamoylmethyl-1’-methyl-4,4′-bipyridinium diiodide, compared with the other
BP’s.
Abstract
Formate dehydrogenase (FDH) is an attractive biocatalyst for converting CO2 to formic
acid in ambient conditions. FDH is applied to the catalyst for the visible-light induced
CO2 - formic acid conversion system consisting of an electron donor, a photosensitizaer
and an electron carrier. For improvement of the formic acid production efficiency with
this system, the enhancement of electron relay processes among a photosensitizer, an
electron carrier and FDH has been needed. We aimed to solve this problem by
developing novel electron carrier based on the viologen derivative instead of
methylviologen (MV), widely used as an electron carreir. In this study, viologen
derivatives with carbamoyl group, 1,1’-dicarbamoylmethyl-4,4’-bipyridinium diiodide
(CV) and 1-carbamoylmethyl-1’-methyl-4,4’-bipyridinium diiodide (CMV) were
synthesized and applied to the electron carrier for photoinduced CO2-formic acid
conversion system consisting of triethanolamine, water-soluble zinc porphyrin and
FDH. By using CV and CMV, the effective formic acid production in the system of
water-soluble zinc porphyrin and FDH was improved compared with that of MV.
3

Keywords: Artificial photosynthesis; CO2 reduction; biocatalyst; formate
dehydrogenase; viologen derivative; electron carrier
1. Introduction
The CO2 based material conversion system with visible light energy has been
much paid attention as an artificial photosynthesis, a chemical process that replicates of
the natural photosynthesis. To construct the system, the development of the catalyst for
CO2 conversion is important factor. Until now, many catalysts have been reported to
apply the photoinduced CO2 based material conversion system [1-11]. These catalysts
are classified into a photocatalyst, molecule catalyst and a biocatalyst. Among various
types of catalysts, biocatalyst is an attractive catalyst for CO2 based material conversion,
because it has high selectivity for substrate and product in aqueous solutions at room
temperature and ordinary pressure. The photoinduced CO2 based material conversion
system has also been developed in the presence of various biocatalysts such as formate
(FDH), aldehyde (AldDH), alcohol dehydrogenase (ADH) and malic enzyme (ME) for
the chemical conversion of valuable organic compounds such as formic acid, ethanol,
malic acid etc [12-20]. Scheme 1 shows the photoinduced CO2 based material
conversion consisting of an electron donor (D), a photosensitizer (P), an electron carrier
(C) and biocatalyst. Among various biocatalysts, FDH from Candida boidinii with the
4

CO2 reduction catalytic activity has been used for the visible-light induced CO2 - formic
acid conversion system. In the system, the electron transfer among a photosensitizer, an
electron carrier and FDH is an important process to improve the CO2 - formic acid
conversion. Therefore, the choice of the electron carrier is important for the
improvement of the formic acid production efficiency with the system as shown in
Scheme 1 .
NAD+ acts as a natural co-enzyme involving electron transfer for FDH. Therefore,
NAD+ was used as an electron carrier for FDH with the combination of NAD+
photoreduction scheme [21]. However, the one electron reduced NAD+ with a
photosensitizer such as tris(bipyridine)ruthenium(II), Ru(bpy)32+ forms a NAD dimer,
(NAD)2, and (NAD)2 is an inactive co-enzyme for FDH [22]. From this reason, it is
difficult to combine NAD+ photoreduction into the CO2 - formic acid conversion system
with FDH. To solve this problem, viologen derivative (BP) has been used as an electron
carrier instead of NAD+ [23]. BP is easily reduced to produce the reduced form of BP
with organic dye molecule like chlorophyll, porphyrin and so on, so that BP is used as
an electron carrier in the visible-light induced CO2 - formic acid conversion system with
FDH. We reported the visible-light induced formic acid production from CO2 with FDH
system consisted of zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) as a
5

photosensitizer, BP as an electron carrier and FDH [24,25]. BP has the role of the
electron acceptor from the excited state of photosensitizer and forms one electron
reduced from. In addition, the one electron reduced form of BP acts as electron donor
for FDH in CO2 - formic acid conversion. Thus, the design of the chemical structure of
BP is needed for a suitable electron donor for FDH to use the CO2 reduction catalytic
activity efficiently. Until now, various BPs as electron carriers were applied to the
improvement of formic acid production efficiency from CO2 with FDH in the system
[26]. But the interaction between the reduced form of BP and FDH was not reported. So
we focused on the effect of BP on the catalytic activity of FDH. Through our previous
study, the effect of various BP’s on the formic acid oxidation catalytic activity and CO2
reduction catalytic activity of FDH were revealed by enzyme kinetic analysis [27].
Oxidized form of BP doesn’t act as an electron acceptor in formic acid - CO2
conversion. On the contrary, one electron reduced form of BP acts as an electron donor
for FDH in CO2 - formic acid conversion. In addition, we previously reported that the
“steric effect” and “ionic effect” of BP affected the function of BP as an electron donor
for FDH in CO2-formic acid conversion [28-30]. The detail mechanism of the
interaction between the reduced form of BP and FDH is still unclear. But previous result
of enzyme kinetic analysis implies that the reduced form of BP acts as an electron donor
6

in molecular recognition field for FDH as a possibility. In the field, NAD+ has high
affinity for FDH. Hence we aimed to the enhanced the function of the reduced form of
BP as an electron donor for FDH in the CO2 - formic acid conversion with FDH.
In this study, BP’s with carbamoyl group, NAD analogue, shown in Figure 1 were
synthesized and applied to the visible-light induced CO2 - formic acid conversion
system consisting of TEOA as an electron donor, ZnTPPS as a photosensitizer and
FDH. We assessed those function of novel BP as an electron carrier, as an electron
acceptor from ZnTPPS and as an electron donor for FDH in visible-light induced formic
acid production from CO2 system.
2. Experimental
2.1. Materials
FDH from Candida boidinii was purchased from Roche Diagnostics K.K.. The
molecular weight of FDH from Candida boidinii was estimated to be 74 kDa [31].
Methylviologen (MV, C12H14Cl2N2), iodomethane, and 4,4’-bipyrdyl were purchased
from Tokyo Kasei Co. Ltd. Iodoacetamide and sodium pyrophosphate were obtained
from Wako Co. Ltd. The other chemical regents were analytical grade or highest grade
available.
7

Zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS) was synthesized according to
previous report [32]. The absorption spectrum of ZnTPPS exhibits an intense Soret band
at 421 nm and Q bands at 555 and 594 nm in neutral aqueous solution [33].
2.2. Synthesis of BP with carbamoyl group
1-Methyl-4,4’-bipyridinium iodide was synthesized using following method. 4,4’-
Bipyridine and iodomethane was stirred at the molar ratio of 1:1 in 200 ml acetone at
room temperature. The residue was dried under vacuum overnight.
1-Carbamoylmethyl-1’-methyl-4,4’-bipyridinium diiodide (CMV, C13H15I2N3O)
was synthesized by refluxing 1-methyl-4,4’-bipyridinium iodide with the molar
equivalent of iodoacetamide in 200 ml acetonitrile at 90 °C for 48 h.
1,1’-Dicarbamoylmethyl-4,4’-bipyridinium diiodide (CV, C14H16I2N4O2) was
synthesized by refluxing 4,4’-bipyridine and iodoactamide in 200 ml acetonitrile at 90
°C for 48 h according to the previous report [34].
Reduction potential of BP was measured using cyclic voltammetry (HOKUTO
HZ-3000) with a carbon electrode as a working, platinum electrode as a counter; Ag /
AgCl electrode as a reference in 50 mM sodium pyrophosphate buffer (pH 7.4). The
sample solution consisted of BP (2.0 mM).
8

The dihedral angle between the pyridine rings of BP was calculated by molecular
orbital method (AM-1method).
2.3. Formic acid - CO2 conversion with FDH and BP with carbamoyl group
The formic acid - CO2 conversion was carried out as following procedure. The
sample solution was consisted of sodium formate (5 mM), FDH (7.5 μM) and BP (0.2
mM) in 50 mM sodium pyrophosphate buffer (pH 7.4) saturated flushed with nitrogen
gas. The absorption of the reduced form of BP was detected using UV-visible
absorption spectroscopy (SHIMADZU, MaltiSpec-1500).
2.4. Photoreduction of BP with carbamoyl group by photosensitization of ZnTPPS
Photoreduction of BP with ZnTPPS was carried out as follows. The sample
solution was consisted of TEOA (0.3 M), ZnTPPS (10 µM), BP (0.1 mM) in 1.0 mM
sodium pyrophosphate buffer (pH 7.4). The sample solution was deaerated by freeze-
pump-thaw cycles repeated 5 times. The absorption of reduced form of BP was detected
by using UV-visible absorption spectroscopy (SHIMADZU, MaltiSpec-1500). The
molecular extinction coefficients (ε) of CV, CMV and MV are 7,800 (λmax=595 nm),
12,700 (λmax=600 nm) and 12,000 M·cm-1 (λmax=605 nm), respectively. 250 W halogen
lamp (TOSHIBA, JD110V85WNP-EHTB) was used as a visible light source.
9

Fluorescence emission spectrum of ZnTPPS in the presence of BP was measured
using fluorescence spectrophotometer (SHIMADZU RF5300PC). The excitation
wavelength was 422 nm due to the Soret band of ZnTPPS. In these experiments the
absorbance at 422 nm was kept constant to be 0.34 for all the sample solutions.
2.5. Photoinduced formic acid production from CO2 with ZnTPPS, BP and FDH
Photoinduced formic acid production from CO2 system with ZnTPPS, BP and
FDH was carried out under the following method. The sample solution was consisted of
TEOA (0.3 M), ZnTPPS (10 µM), BP (0.1 mM) and FDH (6.4 µM) in CO2 saturated
sodium pyrophosphate buffer (pH 7.4), the sample solution was deaerated by freeze-
pump-thaw cycles repeated 5 times and flushed with CO2 gas. The amount of formic
acid was detected by an ion chromatography system (Thermo ICS-1100).
3. Results and discussion
3.1. Characterization of BP with carbamoyl group
Table 1 shows the reduction potentials (vs Ag / AgCl) and dihedral angles of BPs.
First and second potentials of CV were estimated to be – 0.50 (Ered1) and – 0.91 V
(Ered2), respectively. First and second potentials of CMV were estimated to be – 0.59
(Ered1) and – 0.93 V (Ered2), respectively. Reduction potential of BP depended on the
10

number of carbamoyl groups. Carbamoyl group is an electron withdrawing substituent,
leading these difference of reduction potentials among BPs.
Dihedral angles of CV, CMV and MV were estimated to be 43.9, 43.4 and 43.4 º
respectively. There are little differences of dihedral angles between pyridine rings of
CV, CMV and MV, indicating that there is little steric effect by introducing carbamoyl
group to BP.
3.2. Formic acid - CO2 conversion with FDH and BP with carbamoyl group
FDH mainly catalyzes formic acid to CO2 in the presence of NAD+. Thus the
investigation of the function of BP as an co-enzyme in formic acid - CO2 conversion
with FDH is important factor. If the oxidized form of BP acted as a co-enzyme, one
electron reduced form of BP was produced with proceeding the formic acid oxidation.
In all case, no reduced form of BPs were produced. This result shows that BPs with
carbamoyl group do not act as a co-enzyme for FDH in formic acid - CO2 conversion.
3.3. Photoreduction of BP with carbamoyl group by photosensitization of ZnTPPS
Figure 2 shows the relationship between the photoirradiation time and the
concentration of the reduced form of BP produced. The reduced form of CV and CMV
were produced with photosensitization of ZnTPPS. The first and second potentials of
11

BP affect the behavior of the reduced form of BP. Bird and Kuhn reported that
‘dispropportionation’ and ‘conpropportionation’ reaction (equations 1 and 2) occur in
solution exist of the reduced form of BP [35].
These equation shows that two one electron reduced form of BPs (BP·+) react and
divide into oxidize form of (BP2+) and two electron reduced form of BP (BP0) in the
sample solution for the reduction of BP with photosensitization of ZnTPPS. The two
one-electron reduced forms of BP used in this study act as a co-enzyme for FDH,
however, two electron reduced form of BPs are nearly insoluble in aqueous solution and
assumed not to act as co-enzyme of FDH in CO2 - formic acid conversion. Therefore,
the one electron reduced form of BP remain is essentially to proceed the photoinduced
formic acid production from CO2. The conproportionation constant (kconp) for BP has
been obtained from those potentials by using equation 3 [36] and the ratio of one
electron reduced form of BP in the sample solution can be determined by equation 4,
which was expressed by Hunig and Sauer [37].
푘
√
푐표푛푝
% one electron reduced form =
+2 ×100 (4)
푘
√
푐표푛푝
The obtained kconp values for BPs and the ratio of one electron reduced form of
BP (%) were listed in Table 2. In all case, the reduced form of BP with
12

photosensitization of ZnTPPS are assumed to exist at least 99.5 % as one electron
reduced form of BP and little disproportionation of the one electron reduced form of BP
occurs.
The concentration of the reduced form of CV, CMV and MV after 180 min
irradiation were estimated to be 96, 52 and 46 μM, respectively. CV was the easiest
likely to be reduced in other BPs.
To investigate the cause of the difference of the amount of reduced form of BP
production, the interaction between ZnTPPS and BP was estimated by measurement of
the fluorescence of ZnTPPS in the presence of BP. Figure 3 shows the fluorescence
spectra changes of ZnTPPS in the presence of BP. The shape of the fluorescence
spectrum of ZnTPPS in the presence of BP was the same as that of ZnTPPS without BP,
but the fluorescence intensity of ZnTPPS in the presence of BP was lower than that of
ZnTPPS without BP, indicating that the fluorescence of the ZnTPPS was quenched by
BP.
Figure 4 shows the Stern-Volmer plot for the quenching of fluorescence from the
ZnTPPS in the presence of BP.
13

The ratio of fluorescence intensities of ZnTPPS in the absence of BP and in the
presence of BP (I0/I) increased linearly, indicating that the fluorescence of ZnTPPS was
quenched with BP obeyed by Stern-Volmer relationship. Table 3 shows the value of
quenching constant (Ksv) of ZnTPPS in the presence of each BP. The Ksv values of MV,
CMV and CV were 0.195, 0.141 and 0.115 μM-1, respectively. The Ksv value of MV is
the largest in other BPs and the Ksv value is lowered with the number of carbamoyl
group in BP. This result shows that the interaction between ZnTPPS and BP depends on
the chemical structure of BP. By introducing carbamoyl group to BP, the affinity with
ZnTPPS is lowered compared with that of MV with methyl group in the molecule.
In this study, CMV and CV with iodide as a counter ion were used as an electron
carrier and the counter ion affects the fluorescence quenching of ZnTPPS. Counter ion
of CMV and CV was exchanged iodide for chloride according to the previous report
[30] and fluorescence emission spectrum of ZnTPPS in the presence of CMV and CV
with chloride ion were measured for investigation of the effect of counter ion of BP on
the fluorescence emission of ZnTPPS. The Ksv values in the presence of CMV and CV
with chloride ion were 0.272 and 0.213 µM-1, respectively. The Ksv values of CMV and
CV with chloride ion are larger than that of CMV and CV with iodide ions, indicating
that counter ion of BP affects the fluorescence emission of ZnTPPS. However, BP is not
14

reduced by the electron transfer from the singlet excited sate of ZnTPPS, but by the
electron transfer from the triplet excited state of ZnTPPS [38].
The Gibbs free energy change of the photoreduction of BP with photosensitization
of ZnTPPS was calculated from the redox potential of BP and ZnTPPS. In the
photoreduction of BP, photoinduced electron transfer from the photoexcited triplet state
of ZnTPPS (3ZnTPPS*) to BP proceeded. The redox potential of the excited triplet state
of ZnTPPS, E (ZnTPPS+ / 3ZnTPPS*) and E (3ZnTPPS* / ZnTPPS-) were reported to be
-0.75 and 0.45 V, respectively [33]. The Gibbs free energy change of photoreduction of
CV, CMV and MV were estimated to be -24.1, -15.4 and -7.7 kJ·mol-1, respectively.
The Gibbs free energy change shifted to negative in the number of carboxyl group in the
BP, indicating that the CV and CMV are easy to be reduced than that of MV. Actually,
the amount of the concentration of the reduced form of CV was largest, followed in
order by CMV and MV after 180 min irradiation. This result shows that the reduced
form of BP production depends on that the reduction potential of BP. The reduction
potential of CV was the lowest in other BPs, leading the amount of reduced form of CV
was the largest in other BPs.
3.4. Photoinduced formic acid production from CO2 with ZnTPPS, BP and FDH
15

Figure 5 shows the relationship between the photoirradiation time and formic acid
production. The amount of photoinduced formic acid production after 180 min
irradiation with MV, CV and CMV were estimated to be 105, 149 and 172 μM,
respectively. The formic acid production after 180 min irradiation was increased by
using CMV and CV with carbamoyl group than that using MV. By using CMV as an
electron carrier, especially, the efficiency of visible-light induced CO2 - formic acid
conversion system with the system consisting of ZnTPPS and FDH in the presence of
TEOA was improved approximately 60 % than that using MV. From these results,
carbamoyl group in BP affected the electron transfer, leading the improvement of
formic acid production with FDH. To explain the cause of result, the detail analysis of
mechanism of converting CO2 - formic acid via FDH and the reduced form of BP is
needed. Unfortunately, the CO2 reduction catalytic mechanism of FDH with the reduced
form of BP is still unclear. However, we previously reported the effect of functional
group in the reduced form of BP on the CO2 reduction catalytic activity of FDH. The
functional group may have affected the affinity for FDH [28-30]. Molecular recognition
of FDH from Candida boidinii is consisted of Asp 96, Tyr 194, Asp 195, Tyr 196, Gln
197 and His 232 [39]. Especially, Asp 195 plays an important role in providing specific
to co-enzymes such as NAD+. NAD+ has high affinity with FDH, indicating that
16

nicotinamide with a role of electron transfer in NAD+ has little steric hindrance and
electrostatic repulsion with Asp 195 in the molecule recognition field. Carbamoyl group
in CV or CMV affects the interaction between Asp 195, leading that CV or CMV makes
closer contact to Asp 195 via electrostatic effect than that of MV which has only methyl
group. From the reason, the reduced form of CV and CMV acted as an electron donor
for FDH more efficiency compared with MV. Compared with the ratio of the reduced
form of BP production with photosensitization of ZnTPPS, the abundance of reduced
form of CV was the largest in other BPs, but the amount of formic acid production with
CV was lower than that of CMV. One possible reason of this result, the reduced form of
CV may have the higher affinity for FDH than that of CMV. This leads the stabilization
of FDH - CV complex and lowering the CO2 - formic acid conversion reaction rate or
the inhibitory effect of CV for FDH in the course of the reaction.
In the photoinduced CO2 - formic acid production system consisting of ZnTPPS,
BP and FDH, the reduced form of CMV acted as the most effective co-enzyme for FDH
in other BPs.
4. Conclusion
17

In this work, BPs with carbamoyl group were developed and the function as an
electron transfer was investigated in the visible-light induced conversion of CO2 to
formic acid with the system consisting of ZnTPPS and FDH in the presence of TEOA as
an electron donor molecule. In the photoreduction of BP with the photosensitization of
ZnTPPS, the reduction efficiency of BP depends on the redox potential of BP and
effective photoreduction was observed using CV with two carbamoyl groups. In the
photoinduced formic acid production, the amount of formic acid production was
improved by using CMV as an electron carrier than that using MV, indicating that
carbamoyl group affected the interaction between BP and FDH. By using CV and
CMV, the formic acid production was improved compared with that of MV.
Acknowledgement
This work was partially supported by Grant-in-Aid for Challenging Exploratory
Research (Japan Society for the Promotion of Science) (15K14239), and Grant-in-Aid
for Scientific Research on Innovative Areas “Artificial Photosynthesis (2406)”.
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21

Captions to Figures
Figure 1. Chemical structures of BPs.
Figure 2. The relationship between the photoirradiation time and the amount of the
reduced form of CV (◇), CMV (△) and MV (●). The sample solution was consisted of
TEOA (0.3 M), ZnTPPS (10 µM), BP (0.1 mM) in 1.0 mM sodium pyrophosphate
buffer (pH 7.4).
Figure 3. Change of fluorescence intensity of ZnTPPS in the presence of CV (a), CMV
(b) or MV (c). The sample solution was consisted of ZnTPPS (0.5 μM) and BP in pH
7.4 sodium pyrophosphate buffer (1.0 mM). The concentration of BP was changed
between 0 to 3.0 µM.
Figure 4. Stern-Volmer plots for the quenching of the fluorescence of ZnTPPS in the
presence of CV (◇), CMV (△) or MV (●).
Figure 5. The relationship between the photoirradiation time and the formic acid
production with CMV (△), CV (◇) and MV (●). The sample solution was consisted of
TEOA (0.3 M), ZnTPPS (10 µM), BP (0.1 mM) and FDH (6.4 μM) in CO2 saturated
1.0 mM sodium pyrophosphate buffer (pH 7.4).
22

Scheme 1 Photoinduced material conversion system with biocatalyst consisting of an
electron donor (D), a photosensitizer (P), an electron carrier (C2+).
Fig. 1
Fig. 2
23

24

Fig. 3
Fig. 4
25

Fig. 5
Scheme 1
Table 1. Reduction potential and dihedral angle of BP.
BP
Reduction potential
/ V
Dihedral angle
/ º
Ered1
Ered2
CV
CMV
MV
- 0.50
- 0.91
43.9
43.4
43.4
- 0.59
- 0.67
-0.93
-0.98
26

Table 2. Conproportion constant and abundance ratio of one electron reduced form of
BP.
BP
Conproportion
constant
% one electron reduced form
CV
CMV
MV
8.7×106
99.9
99.7
99.5
5.7×105
1.8×105
Table 3. Stern-Volmer Quenching constant Ksv of ZnTPPS in the presence of BP.
BP
CV
Ksv / μM-1
0.115
CMV
MV
0.141
0.195
27