Improvement of TiO2/dye/electrolyte interface conditions by positional change of alkyl chains in modified panchromatic Ru complex dyes

Article abstract of DOI:10.1002/chem.201202709

A series of panchromatic ruthenium sensitizers (MJ sensitizers) with attached thiophene and phenyl units bearing alkyl chains was synthesized. A new synthetic route was used to examine all possible positions for the alkyl chains. The absorption spectra showed the sum of a ruthenium complex and peripheral organic chromophore units. The hypochromic effect and blueshift of the metal-to-ligand charge-transfer band observed in the modified ruthenium sensitizers were suppressed by changing the positions of the alkyl chains on the attached thiophene ring. Changing only one alkyl chain also influenced the performance of dye-sensitized solar cells. Ruthenium sensitizer MJ-10 with bulky substituent harvests visible and near-infrared light, and solar cells sensitized by MJ-10 exhibit an efficiency of 9.1 % under 1sun irradiation. An unsymmetric terpyridine ligand having a bromo group as a connection point for the introduction of various substituents by Suzuki coupling reactions with boronic acids was used to explore the effect of substituents on the energy-conversion efficiency of dye-sensitized solar cells (DSSCs). Introduction of a peripheral bulky substituent improved the DSSC performance, and MJ-10 (see figure) harvests visible and near-infrared light, whereas solar cells sensitized by MJ-10 exhibit an efficiency of 9.1 % under 1sun irradiation. Copyright

Full text of DOI:10.1002/chem.201202709

DOI: 10.1002/chem.201202709
Improvement of TiO2/Dye/Electrolyte Interface Conditions by Positional
Change of Alkyl Chains in Modified Panchromatic Ru Complex Dyes
Mutsumi Kimura,*[a] Junya Masuo,[a] Yuki Tohata,[a] Kazumichi Obuchi,[a]
Naruhiko Masaki,[a] Takurou N. Murakami,[b] Nagatoshi Koumura,[b] Kojiro Hara,[b]
Atsushi Fukui,[c] Ryohsuke Yamanaka,[c] and Shogo Mori*[a]
Abstract: A series of panchromatic
ruthenium sensitizers (MJ sensitizers)
with attached thiophene and phenyl
units bearing alkyl chains was synthe-
sized. A new synthetic route was used
to examine all possible positions for
the alkyl chains. The absorption spectra
showed the sum of a ruthenium com-
plex and peripheral organic chromo-
phore units. The hypochromic effect
and blueshift of the metal-to-ligand
charge-transfer band observed in the
modified ruthenium sensitizers were
suppressed by changing the positions of
the alkyl chains on the attached thio-
phene ring. Changing only one alkyl
chain also influenced the performance
of dye-sensitized solar cells. Ruthenium
sensitizer MJ-10 with bulky substituent
harvests visible and near-infrared light,
and solar cells sensitized by MJ-10 ex-
hibit an efficiency of 9.1% under 1 sun
irradiation.
Keywords: dyes/pigments · energy
conversion · ruthenium · solar cells ·
tridentate ligands
Introduction
on the TiO2 surface and L’ is a bipyridine ligand with alkyl,
alkoxyl, thiophene, carbazole, or other substituents.
Since the report in 1991 by OꢀRegan and Grꢁtzel,[1] dye-sen-
sitized solar cells (DSSCs) have attracted a special attention
owing to their possibility of high power conversion efficien-
cies through low-cost production processes.[2] In recent
years, considerable developments have been made in the en-
gineering of new sensitizers to enhance the performance of
DSSCs.[3] In particular, ruthenium(II) polypyridine com-
plexes have been extensively investigated as highly efficient
sensitizers due to their wide absorption band.[4] Progress in
developing ruthenium-based sensitizers for DSSCs has fo-
cused on enhancing light-harvesting properties, redshifting
the metal-to-ligand charge transfer (MLCT), tuning HOMO
and LUMO levels, and enhancing long-term stability by the
introduction of substituent groups into the polypyridine li-
gands.[3,4] Such developments have mostly been based on the
The highest conversion efficiency in DSSCs has been
achieved with panchromatic [RuLACTHNUTRGNENUG(SCN)3], which is known
as the black dye N749.[5,6] The black dye is composed of one
tridentate terpyridine ligand having three carboxyl groups,
three thiocyanato ligands, and one ruthenium ion. While its
absorption range extends close to 900 nm, the absorption co-
efficients of the black dye are lower than those of the red
dye. Major efforts have focused on replacement of thio-
AHCTUNGTREGcNNNU yanato with other ligands to enhance the absorptivity of
black dyes.[7–13] On the other hand, the functionalization of
terpyridine ligands in the black dye has been barely ex-
plored. Recently, Yang et al. synthesized functionalized
black dyes with a terpyridine ligand having two carboxyl
groups and one p-electron-donating moiety.[14,15] While sev-
eral functional units were attached to the terpyridine ligand,
the variation was limited by their synthetic route to the ter-
pyridine ligand. Here we report on a synthesis of a dicarbox-
yterpyridine ligand which opens a new synthetic route to
attach various functional groups to ligands, and on tuning of
black dyes by varying the position of alkyl chains. We found
that changing the position of only one alkyl chain improved
both short-circuit current and open circuit voltage.
cis-[RuLL’ACHTUNGTRENNUNG(SCN)2] family (red dye), where L is a bipyridine
ligand having two carboxyl groups as anchors for adsorption
[a] Prof. Dr. M. Kimura, J. Masuo, Y. Tohata, K. Obuchi, N. Masaki,
Prof. Dr. S. Mori
Faculty of Textile Science and Technology
Shinshu University, Ueda 386-8567 (Japan)
Fax : (+81)268-21-5499
E-mail: mkimura@shinshu-u.ac.jp
shogmori@shinshu-u.ac.jp
Results and Discussion
[b] T. N. Murakami, N. Koumura, K. Hara
National Institute of Advanced Industrial Science
and Technology (AIST)
Synthesis of ruthenium sensitizers: We synthesized novel un-
symmetric terpyridine ligand 1 (Scheme 1), in which the
bromo group is a connection point for functional substitu-
ents through metal-catalyzed coupling reactions. Ligand 1
offers a versatile platform for the design of functionalized
1-1-1 Higashi, Tsukuba 305-8564 (Japan)
[c] A. Fukui, R. Yamanaka
Sharp Corporation, Katsuragi 639-2198 (Japan)
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FULL PAPER
cal structure as PRT-12,[14] was synthesized by the coupling
reaction of 1 with 5-hexyl-2-thiopheneboronic acid pinacol
ester.
The dyes MJ-4, MJ-6, MJ-7, and MJ-2 have almost the
same structure with one alkyl chain but differ in the position
of the alkyl chain. The absorption spectra of MJ-6 and MJ-2
in ethanol are shown in Figure 1, and photophysical and
electrochemical data of all compounds and reference N749
are collected in Table 1. The ligands of the new dyes exhibit-
Figure 1. Absorption spectra of MJ-6 (solid line), 2 (dotted line), and
N749 (dashed line) in EtOH.
Scheme 1. i) NH4OAc in refluxing MeOH; ii) KMnO4; iii) H2SO4 in
À
EtOH; iv) RB(OH)2 or RB
G
G
Table 1. Photophysical and electrochemical data of all compounds and
reference N749.
black dyes. The targeted terpyridine ligand 1 was synthe-
sized according the Krçhnke method.[16] The ligand having a
furan moiety was obtained by the reaction of pyridinium ion
with the enone derived from 2-acetyl-5-bromopyridine and
2-furaldehyde in the presence of ammonium acetate in 40%
yield. The furan moiety was oxidized with KMnO4, followed
by esterification in ethanol with H2SO4.[17] Ligand 1 is a ver-
satile molecular platform for preparation of designed black
dyes by introduction of various functional units in cross-cou-
pling reactions. The functionalized ligands were used to pre-
pare ruthenium(II) sensitizer dyes, coded MJ, according to
the method reported by Yang et al. (Scheme 2).[14] Sensitizer
2 having a 5-hexylthiophene unit, which has the same chemi-
Dye
lmax [nm] (e mÀ1 cmÀ1
)
Eox[a] [V]
ELUMO[b] [V]
2
594 (6230), 368 (37300)
594 (6840), 347 (32600)
608 (7150), 365 (36600)
603 (6490), 362 (27900)
608 (7420)
0.87
0.87
0.86
0.86
0.89
À0.76
À0.76
À0.82
À0.81
À0.77
MJ-4
MJ-6
MJ-7
N749
[a] The oxidation potential (vs. NHE) was measured in dry DMF with
0.1m TBAPF6. [b] ELUMO =EoxÀE0–0. E0–0 was determined from the cross-
point of the normalized absorbance and fluorescence spectra.
ed an intense absorption band in the range of 350–400 nm,
which was assigned to p–p* transitions of phenyl and thio-
phene units, in addition to a broad band at around 600 nm,
which was assigned to the
MLCT transition feature of
panchromatic
[RuLACHTUNGTRENNUNG(SCN)3]
complexes having carboxyl
groups.[5] The onsets of the ab-
sorption spectra are all close to
870 nm. While 2 (e at 595 nm:
6220mÀ1 cmÀ1)
and
MJ-7
showed shifting of the MLCT
band, the MLCT band of the
structural isomer MJ-6 was
almost the same as that of
N749.[18] This indicates that the
position of the alkyl chain in
the thiophene ring affects the
electronic state of ruthenium
complexes.
The first oxidation potential
Eox, determined by differential
pulse voltammetry in dry DMF
Scheme 2. i) RuCl3 in refluxing MeOH; ii) TBASCN, DMF, 1408C; iii) TBAOH in refluxing acetone, acidifica-
tion.
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M. Kimura, S. Mori et al.
containing 0.1m tetrabutylammonium hexafluorophosphate
(TBAPF6) as supporting electrolyte, of all MJ dyes appeared
at about +0.86 V versus NHE. It was assigned as the oxida-
tion process of the Ru2+/3+ redox couple.[5] The HOMO
À
levels are more positive than the potential of the IÀ/I3
redox couple at +0.42 V versus NHE, so that sufficient driv-
À
ing force for regeneration of the Ru3+ complex by IÀ/I3 in
DSSCs is available.[17] The Eox values of MJ dyes were
slightly lower than that of N749 (+0.89 V vs. NHE), due to
the direct connection of electron-donating thiophene with
the terpyridine ligand of [RuLACHTNUGRTENUNG(SCN)3] complexes. This elec-
trochemical behavior agrees with the results previously re-
ported by Yang et al. on PRT dyes.[14] The zero–zero excita-
tion energies E0–0 of MJ dyes were determined to be 1.62–
1.68 eV from the absorption and emission peak in terms of
energy in DMF. The LUMO energy levels of MJ dyes, esti-
mated from the difference between the HOMO energy level
and E0À0, were in the range À0.76 to À0.82 V versus NHE.
The LUMO levels were also more negative than the conduc-
tion band (CB) edge of the TiO2 electrode (ca. À0.50 V vs.
NHE).[19]
Figure 2. a) Photocurrent–voltage curves obtained with DSSCs based on
MJ-6 (dashed line), MJ-10 (solid line), and N749 (dotted line) with anti-
reflection films under standard global AM1.5 solar conditions. b) Inci-
dent photon-to-current conversion efficiency spectra for DSSCs based on
MJ-6 (dashed line), MJ-10 (solid line), and N749 (dotted line).
Table 2. Photovoltaic performance of DSSCs based on MJ dyes and 2
compared to N749.
Photovoltaic performance of MJ-4, MJ-6, and MJ-7 cells:
The DSSC performance of MJ sensitizers was examined by
using triple-layered TiO2 electrodes composed of a 14 mm-
thick transparent layer of 20 nm TiO2 nanoparticles, a 7 mm-
thick scattering layer, and a 7 mm-thick reflection layer ap-
plied to transparent conducting glass substrates by the
screen printing technique. The TiO2 electrodes were im-
mersed in 0.2 mm dye solutions containing 20.0 mm cheno-
deoxycholic acid (CDCA) for 48 h at 258C and rinsed with
acetonitrile to remove unadsorbed dye. The co-adsorption
of CDCA suppresses undesired dye aggregation/interaction
on the TiO2 surface and results in enhanced photovoltaic
performance. Broadening of the absorption spectra of MJ
sensitizers adsorbed on TiO2 electrodes compared to those
in solutions suggested the electronic interaction with the
TiO2 surface. Figure 2 shows the photocurrent density–volt-
age curves and incident photon-to-current conversion effi-
ciency (IPCE) spectra of DSSCs using MJ-6- and N749-
loaded TiO2 electrodes. The short-circuit photocurrent den-
sity Jsc, open-circuit voltage Voc, fill factors (FF), and overall
cell efficiencies (PCE) for all DSSCs are summarized in
Table 2. The performance of a cell containing N749-loaded
TiO2 electrode is provided as a benchmark. The PCE values
strongly depend on the substituents in the ruthenium com-
plexes (Table 2). Dye MJ-4 with a 4-hexylphenyl group
showed a markedly lower PCE value than MJ-6 with a 4-
hexylthiophene moiety. Dyes MJ-6 and MJ-7, which are
structural isomers of 2, gave Jsc =18.1 mAcmÀ2, Voc =
680 mV, and FF=0.71, corresponding to an overall conver-
sion efficiency of PCE=8.7%, and Jsc =16.6 mAcmÀ2, Voc =
620 mV, and FF=0.72, corresponding to PCE=7.4%, re-
spectively; thus, the position of one alkyl chain can change
the efficiency drastically. Interestingly, the PCE and IPCE
values in the entire visible-light region of the MJ-6 cell are
higher than those of 2 and MJ-7 cells. Since we employed
Dye
Voc [mV]
Jsc [mAcmÀ2
]
FF
PCE [%]
MJ-4
MJ-6
MJ-7
2
MJ-10
MJ-11
MJ-12
N749
540
680
620
620
690
670
650
690
10.9
18.1
16.6
15.1
18.3
18.7
18.1
19.0
0.72
0.71
0.72
0.72
0.72
0.70
0.71
0.70
4.2
8.7
7.4
6.7
9.1
8.7
8.4
9.2
thick TiO2 electrodes, if the difference were due to the dif-
ference in extinction coefficient, at least similar IPCE values
would be expected at the peak wavelength of the MLCT
band. Alternatively, the results imply that the charge-injec-
tion efficiency could be altered by changing the position of
the alkyl chain.
Effect of bulky substituents in Ru complex dyes on photo-
voltaic performance: On the basis of the results for MJ-6,
we further examined the effect of alkyl chains, as one would
expect that one alkyl chain would not be sufficient. Other
functional groups can be introduced at the 5-position of the
thiophene ring in MJ-6. Sun and Hagfeldt investigated the
effect of bulky alkoxyl donor substituents in organic sensitiz-
ers.[20] They found that the introduction of a bulky 2,4-butox-
yphenyl unit suppressed recombination in DSSCs by using
À
IÀ/I3 or cobalt electrolytes. Han et al. also reported an en-
hanced PCE value of an N749 cell by using donor–acceptor-
type co-adsorbents having 2,4-butoxyphenyl groups.[21] The
strong absorption peaks of the organic co-adsorbent allowed
the IPCE dip of N749 around 380 nm due to competitive
À
light absorption of I3 to be offset. Hence, we examined ad-
dition of a bulky dihexyloxyphenyl unit on the thiophene
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Modified Panchromatic Ru Complex Dyes
FULL PAPER
ring of MJ-6 and the effect of the positions of two additional
alkyl chains (Scheme 2).
The absorption spectrum of MJ-10 is shown in Figure 3,
and photophysical and electrochemical data of MJ-10, MJ-
11, and MJ-12 are listed in Table 3. The absorption spectrum
Figure 3. Absorption spectrum of MJ-10 in DMF.
Table 3. Photophysical and electrochemical data of MJ-10, MJ-11, and
MJ-12.
Figure 4. Photocurrent–voltage curves for DSSCs based on MJ-10 (solid
line), MJ-11 (dashed line), and MJ-12 (gray line) under standard global
AM1.5 solar conditions (a) and in the dark (b).
Dye
lmax [nm] (e [mÀ1 cmÀ1
]
Eox[a] [V]
MJ-10
MJ-11
MJ-12
630 (6450), 393 (35100)
630 (6500), 383 (32800)
631 (6430), 384 (37900)
0.82
0.83
0.82
dark current, the onset voltage increases in the order MJ-
12<MJ-11<MJ-10 (Figure 4). This order coincides with the
trend in Voc values. Various groups have reported improve-
ment of PCE values of DSSCs by introduction of hydropho-
bic alkyl chains into the dye structure.[23,24] The dye layers
[a] The oxidation potential (vs. NHE) was measured in dry DMF with
0.1m TBAPF6.
À
of MJ-10 exhibits an intense absorption peak at 393 nm,
work as a blocking layer for approach of I3 or cations to
which was attributed to intra
li
E
the TiO2 surface. In our case, the molecular monolayer on
the TiO2 surface is composed of ruthenium sensitizers and
CDCA, and the adsorption density of MJ-10 on the TiO2
surface (3.7ꢃ10À11 molcmÀ2) is low. Thus, the contribution
of the alkyl chains to the enhancement of blocking effect for
shift of this absorption position compared to MJ-6 indicated
expansion of p conjugation. The position and absorption in-
tensity of the MLCT band of MJ-10 agreed with those of
MJ-6. When the terpyridine ligand of MJ-10 was excited at
393 nm, the ligand emitted strong fluorescence at 480 nm.
This fluorescence was completely quenched in ruthenium
complex MJ-10, and this suggested highly efficient intramo-
lecular energy transfer. The onset of the IPCE spectrum of
the MJ-10 cell is close to 900 nm, and the IPCE value in the
visible-light region is greater than 70% (Figure 2). The MJ-
10 cell had Jsc =18.3 mAcmÀ2, Voc =690 mV, and FF=0.72,
corresponding to an overall conversion efficiency of PCE=
9.1%. This PCE of MJ-10 is almost the same as that of the
N749 cell (PCE=9.2%)[22] obtained by the same cell-fabri-
cation and efficiency-measuring procedures. Attachment of
a bulky 2,4-hexyloxyphenyl unit into the thiophene-linked
terpyridine ligand increased Voc and Jsc compared to the
DSSC performance of the parent MJ-6 cell. While the IPCE
of the MJ-6 cell from 550 to 370 nm gradually decreased to
55%, the MJ-10 cell remained above 70% IPCE in this
wavelength range.
À
I3 would be slight. The recombination lifetime can be facili-
tated by the interaction between dye and acceptor species[25]
and thus, the higher Voc of MJ-10 obtained by appropriate
position of the alkyl chains would reduce the effect of the
dispersion force between molecules. The MJ-10 cell without
CDCA exhibited significantly worse DSSC performance
(Jsc =12.4 mAcmÀ2, Voc =604 mV, FF=0.60, PCE=4.5%),
that is, prevention of molecular aggregation of ruthenium
complexes within the dye monolayer on the TiO2 surface is
essential to obtain a high conversion efficiency in DSSCs.
À
Recently, replacement of the I3 /IÀ redox system by
cobalt polypyridine complexes has attracted attention be-
cause of their tunable redox potentials and low visible-light
absorption.[26,27] Whereas the N749 cell with CDCA exhibit-
ed a low PCE (Jsc =2.3 mAcmÀ2, Voc =510 mV, FF=0.51,
PCE=0.6%) when [CoACTHNUTRGNEUNG
(bpy)3]2+/3+ electrolyte was used
under one-sun conditions, the MJ-10 cell showed higher
PCE performance (Jsc =5.0 mAcmÀ2, Voc =674 mV, FF=
0.65, PCE=2.2%) under the same conditions (Figure 5).
Modification of the terpyridine ligand was also effective for
the alternative Co2+/3+ redox shuttle.[28] Investigations are
underway to optimize the structure of panchromatic rutheni-
um sensitizers for the Co2+/3+ redox shuttle.
The PCEs of structural isomers MJ-11 and MJ-12 having
2,5- and 2,3-hexyloxyphenyl groups were lower than that of
MJ-10 (Table 2). The IPCE spectra of MJ-11 and MJ-12
cells were in fair agreement with that of the MJ-10 cell, and
indicate the same light-harvesting properties of the three
ruthenium complexes. The lower PCEs of MJ-11 and MJ-12
cells are mainly due to the lower Voc values. In view of the
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M. Kimura, S. Mori et al.
0.1m methanolic sodium hydroxide solution (394 mL). The reaction mix-
ture was stirred for 4 h at 08C, after which the mixture was filtered and
the solvent removed. Water was added and the mixture extracted with
CH2Cl2 three times. The organic layers were combined and washed with
water and brine, dried over MgSO4, and evaporated. The residue was pu-
rified by column chromatography (silica gel, hexane:AcOEt 20:1 to 10:1
v/v) to give
a
yellowish solid (8.2 g, 75%). 1H NMR (CDCl3,
400.13 MHz): d=8.78 (d, J=4.0 Hz, 1H, ArH), 8.07 (d, J=6.4 Hz, 1H,
ArH), 8.04 (m, 1H, ArH), 7.99 (d, J=12.6 Hz, 1H, ArH), 7.69 (d, J=
16.0 Hz, 1H, ArH), 7.55 (m, 1H, ArH), 6.78 (d, J=4.4 Hz, 1H, COCH=
CH), 6.52 ppm (d, J=7.2 Hz, 1H, COCH=CH); 13C NMR (CDCl3,
100.61 MHz): d=188.3, 152.9, 152.0, 150.0, 145.3, 139.6, 131.0, 124.9,
124.0, 118.2, 116.6, 112.7 ppm.
Figure 5. Photocurrent–voltage curves for DSSCs based on MJ-10 (solid
line) and N749 (dashed line) with [Co
(bpy)3]2+/3+ electrolyte (0.22m
[Co(bpy)3][B(CN)4]2, 0.02m [Co(bpy)3][B(CN)4]3, 0.2m LiClO4, and 0.6m
tert-butylpyridine in acetonitrile) under standard global AM1.5 solar con-
ditions. The onsets of the dark-current densities of the cells are also
shown.
AHCTUNGTRENNUNG
Synthesis of 1: A mixture of 4 (2.31 g, 5.8 mmol), 5 (1.08 g, 3.9 mmol),
and ammonium acetate (0.6 g, 7.7 mmol) in 40 mL of methanol was re-
fluxed for 17 h. After evaporation of the solvent, the residue was purified
by column chromatography (activated alumina, CH2Cl2) to give 3 (0.74 g,
AHCTUNGTRENNUNG
1
43%). H NMR (CDCl3, 400.13 MHz): d=9.09 (s, 1H, ArH), 8.87 (d, J=
5.2 Hz, 1H, ArH), 8.77 (s, 1H, ArH), 8.71 (d, J=8.4 Hz, 2H, ArH), 8.57
(d, J=8.4 Hz, 1H, ArH), 8.00 (d, J=8.4 Hz, 1H, ArH), 7.89 (d, J=
4.8 Hz, 1H, ArH), 7.60 (s, 1H, ArH), 7.11 (d, J=3.4 Hz, 1H, ArH), 6.57
(d, J=3.4 Hz, 1H, ArH), 4.49 (q, J=7.2 Hz, 2H, COOCH2CH3),
1.47 ppm (t, J=7.2 Hz, 3H, COOCH2CH3); 13C NMR (CDCl3,
100.61 MHz): d=165.2, 156.8, 155.0, 154.9, 154.1, 151.6, 149.9, 149.7,
143.7, 139.4, 139.3, 138.5, 122.7, 122.4, 121.2, 120.4, 115.3, 115.1, 112.1,
Conclusion
We have synthesized novel unsymmetric terpyridine ligand 1
having a bromo group as a connection point to introduce
various substituents through metal-catalyzed cross-coupling
reactions. Six terpyridine ligands were synthesized by Suzuki
coupling reaction between 1 and boronic acids to explore
the effect of substituents on the energy-conversion efficiency
of DSSCs. Structural modification of the terpyridine ligand
induced a hypochromic effect and blueshift of the MLCT
band. This unfavorable change of the MLCT band was sup-
pressed by changing the position of the alkyl chain in the at-
tached thiophene ring. Moreover, introduction of a periph-
eral bulky substituent improved the DSSC performance.
MJ-10 showed a comparable efficiency to N749 when used
as a light-harvesting dye on a TiO2 electrode under one-sun
conditions. The PCE values of cells were in order of MJ-4<
2<MJ-7<MJ-11<MJ-6=MJ-12<MJ-10. To elucidate the
origin of performance differences, studies are now in prog-
ress to examine the charge-injection efficiency and charge-
recombination lifetime in these DSSCs.
109.3, 61.8, 14.2 ppm; FTIR (ATR): n=1728 cmÀ1 (COOCH2CH3).
~
KMnO4 (0.87 g, 5.5 mmol) was added to a solution of 3 (0.5 g, 1.1 mmol)
in pyridine (12 mL) and H2O (6 mL). The reaction was monitored by
TLC (eluent: CH2Cl2) and the reaction mixture was stirred until the spot
of starting material 2 disappeared. The remaining KMnO4 was reduced
by addition of Na2S2O3 and the solution was made basic by adding aque-
ous NaOH solution. The formed MnO2 precipitate was removed by filtra-
tion and the filtrate evaporated. The remaining solid was dissolved in
0.01m aqueous NaOH solution. After filtration, the filtrate was adjusted
to pH 4 with HCl. The white precipitate was collected by filtration,
washed with water, and dried under vacuum to yield a white solid, which
was used without further purification. A suspension of crude product in
ethanol (50 mL) and H2SO4 (0.2 mL) was heated to reflux for 16 h, water
was added, and the mixture extracted with CH2Cl2 three times. The or-
ganic layers were combined and washed with water and brine, dried over
MgSO4, and evaporated. The residue was purified by column chromatog-
raphy (activated alumina, CH2Cl2) to give white solid 1 (0.24 g, 49% for
1
two steps). H NMR (CDCl3, 400.13 MHz): d=9.05 (s, 1H, ArH), 8.99 (s,
1H, ArH), 8.97 (s, 1H, ArH), 8.87 (d, J=4.8 Hz, 1H, ArH), 8.77 (s, 1H,
ArH), 8.54 (d, J=8.4 Hz, 1H, ArH), 8.01 (d, J=8.4 Hz, 1H, ArH), 7.90
(d, J=5.2 Hz, 1H, ArH), 4.49 (m, 4H, COOCH2CH3), 1.47 ppm (t, J=
7.0 Hz, 6H, COOCH2CH3); 13C NMR (CDCl3, 100.61 MHz): d=165.1,
164.9, 156.2, 155.6, 155.5, 153.5, 150.2, 149.9, 140.1, 139.4, 138.7, 123.0,
122.5, 121.6, 120.7, 120.5, 120.4, 61.9, 61.8 14.3, 14.2 ppm; FTIR (ATR):
Experimental Section
General: NMR spectra were recorded on a Bruker AVANCE 400 FT
NMR spectrometer at 399.65 and 100.62 MHz for 1H and 13C in CDCl3
solution. Chemical shifts are reported in parts per million (ppm) relative
to internal TMS. IR spectra were obtained on a Shimadzu IR Prestige-21
with DuraSample IR II. UV/Vis spectra were measured on a JASCO V-
650. MALDI-TOF mass spectra were obtained on a Bruker Autoflex
with dithranol as matrix.
n=1724 cmÀ1 (COOCH2CH3).
~
Synthesis of 6: Bromo-terminated terpyridine 1 (0.37 g, 810 mmol) and 4-
hexyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene
(0.35 g,
1.18 mmol) were dissolved in a mixture of toluene (0.87 mL), THF
(1.3 mL), and 2.0m aqueous K2CO3 solution (0.67 mL). After degassing
by nitrogen gas, [PdACHTNUTRGNE(UNG PPh3)4] (30.3 mg, 26 mmol) was added to the solu-
Materials: All chemicals were purchased from commercial suppliers and
tion. The reaction mixture was stirred at 708C for 48 h under nitrogen at-
mosphere, after which it was diluted with CH2Cl2 (50 mL) and washed
with water. The organic layer was dried over MgSO4 and concentrated
under vacuum. The residue was purified by column chromatography (ac-
tivated alumina, CH2Cl2) and recycling preparative HPLC to give 6 as a
white solid (0.26 g, 58%). 1H NMR (CDCl3, 400.13 MHz): d=9.07 (s,
1H, ArH), 8.99 (s, 1H, ArH), 8.96 (s, 2H, ArH), 8.87 (d, J=5.6 Hz, 1H,
ArH), 8.61 (d, J=8.0 Hz, 1H, ArH), 8.01 (d, J=8.4 Hz, 1H, ArH), 7.89
(d, J=5.2 Hz, 1H, ArH), 7.28 (s, 1H, ArH), 6.98 (s, 1H, ArH), 4.50 (m,
4H, COOCH2CH3), 2.64 (t, J=8.1 Hz, 2H, ArCH2), 1.67 (m, 2H,
ArCH2CH2), 1.47 (m, 6H, COOCH2CH3), 1.31 (m, 6H, CH2), 0.90 ppm
(t, J=7.0 Hz, 3H, CH3); 13C NMR (CDCl3, 100.61 MHz): d=165.3, 165.2,
156.6, 156.5, 155.7, 153.7, 150.0, 146.1, 144.8, 140.1, 139.9, 138.8, 133.4,
used without purification. Ethyl 2-acetylisonicotinic acid, 2-acethyl-5-bro-
mopyridine,
iodide 3, [Co
N-{2-oxo-2-[2-(4-ethoxycarbonylpyridyl)]ethyl}pyridinium
(bpy)3][B(CN)4]2 and [Co(bpy)3][B(CN)4]3 (bpy=2,2’-bipyri-
N
ACHTUNGTRENNUNG
dine) were synthesized according to literature methods.[1—3,29] Column
chromatography was performed with activated alumina (Wako, 200
mesh) or Wakogel C-200. Recycling preparative gel-permeation chroma-
tography was carried with by a JAI recycling preparative HPLC with
CHCl3 as eluent. Analytical TLC was performed with commercial Merck
plates coated with silica gel 60 F254 or aluminum oxide 60 F254
.
Syntheses of asymmetric terpyridine ligands[30–32]
Synthesis of 5: 2-Acetyl-5-bromopyridine (7.8 g, 39.4 mmol) and 2-fural-
dehyde (3.8 g, 3.3 mL, 39.4 mmol) in 40 mL of methanol were added to a
1032
www.chemeurj.org
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 1028 – 1034

Modified Panchromatic Ru Complex Dyes
FULL PAPER
131.0, 125.8, 123.0, 121.3, 121.0, 120.6, 120.5, 120.4, 61.9, 61.8, 31.7, 30.5,
ArH), 4.50 (q, J=6.8 Hz, 4H, COOCH2CH3), 4.03 (t, J=6.8 Hz, 4H,
OCH2), 3.83 (t, J=6.8 Hz, 2H, OCH2), 2.58 (t, J=7.8 Hz, 2H, ArCH2),
1.81–1.89 (m, 2H, ArCH2CH2), 1.51–1.64 (m, 4H, ArOCH2CH2), 1.48 (t,
J=6.8 Hz, 6H, COOCH2CH3), 1.14–1.39 (m, 18H, CH2), 0.92 (t, J=
7.2 Hz, 3H, CH3), 0.85 (t, J=6.8 Hz, 3H, CH3), 0.79 ppm (t, J=7.0 Hz,
3H, CH3); 13C NMR (CDCl3, 100.61 MHz): d=165.3, 156.7, 156.5, 155.8,
153.5, 152.9, 150.0, 146.9, 146.0, 142.0, 140.2, 138.9, 138.3, 134.9, 133.1,
131.2, 128.6, 125.9, 123.7, 123.5, 123.1, 121.3, 120.6, 120.4, 113.4, 73.5,
À1
~
30.4, 29.0, 22.6, 14.3, 14.3, 14.1 ppm; FTIR (ATR): n=1724 cm
(COOCH2CH3); MALDI-TOF MS: m/z 544 ([M+H]+, 100%).
Synthesis of 7: Ligand 7 was synthesized from 1 and 4-hexylphenylboron-
ic acid by the same procedure as 6. Yield 53%. 1H NMR (CDCl3,
400.13 MHz): d=9.10 (s, 1H, ArH), 9.03 (s, 1H, ArH), 8.97 (s, 2H,
ArH), 8.87 (d, J=5.2 Hz, 1H, ArH), 8.67 (d, J=8.0 Hz, 1H, ArH), 8.05
(d, J=8.2 Hz, 1H, ArH), 7.89 (d, J=5.2 Hz, 1H, ArH), 7.59 (d, J=
8.0 Hz, 2H, ArH), 7.31 (d, J=8.0 Hz, 2H, ArH), 4.49 (m, 4H,
COOCH2CH3), 2.67 (t, J=8.0 Hz, 2H, ArCH2), 1.66 (m, 2H,
ArCH2CH2), 1.46 (m, 6H, COOCH2CH3), 1.32 (m, 6H, CH2), 0.90 ppm
(t, J=7.0 Hz, 3H, CH3); 13C NMR (CDCl3, 100.61 MHz): d=165.3, 165.2,
156.6, 156.5, 155.7, 153.7, 150.0, 147.5, 143.3, 140.1, 138.8, 136.9, 134.9,
68.8, 61.9, 61.8, 31.7, 31.6, 30.6, 30.2, 29.4, 29.2, 25.8, 25.6, 22.7, 22.6, 14.4,
À1
~
14.3, 14.1, 14.0 ppm; FTIR (ATR): n=1728 cm
(COOCH2CH3);
MALDI-TOF MS: m/z 820 ([M+H]+, 100%).
Synthesis of ruthenium(II) complexes MJ-4, MJ-6, MJ-7, MJ-10, MJ-11,
and MJ-12
129.2, 126.9, 123.0, 121.3, 120.7, 120.6, 120.4, 61.9, 61.8, 35.6, 31.7, 31.4,
Synthesis of MJ-6: A solution of 6 (200 mg, 367 mmol) in CH2Cl2 (5 mL)
was added to a solution of RuCl3·3H2O (115 mg, 441 mmol) in ethanol
(8 mL) and the mixture stirred for 2 h at 808C under nitrogen atmos-
phere. After 4 h, the solvent was removed by evaporation and the re-
maining product was washed with cooled ethanol and diethyl ether to
remove unconverted RuCl3. The resulting dried powder and tetrabuty-
lammonium thiocyanate (540 mg, 1.83 mmol) were dissolved in dry DMF
and heated at 1508C for 4 h. After evaporation, the crude product was
purified by column chromatography (silica gel, CH2Cl2/AcOEt 10:1) to
give esterified MJ-6 as a white solid (140 mg, 35%). 1H NMR (CDCl3,
400.13 MHz): d=9.12–9.14 (m, 2H, ArH), 8.63 (s, 1H, ArH), 8.55 (s, 1H,
ArH), 8.39 (s, 1H, ArH), 8.02–8.07 (m, 2H, ArH), 7.91 (d, J=6.4 Hz,
1H, ArH), 7.46 (s, 1H, ArH), 7.06 (s, 1H, ArH), 4.52–4.56 (m, 4H,
COOCH2CH3), 3.22–3.24 (m, 8H, -CH2-), 2.62 (t, J=8.1 Hz, 2H,
ArCH2), 1.75–1.79 (m, 8H, CH2), 1.67 (m, 2H, ArCH2CH2), 1.51–1.53
À1
~
29.0, 22.6, 14.3, 14.2, 14.1 ppm; FTIR (ATR): n=1728 cm
(COOCH2CH3); MALDI-TOF MS: m/z 538 ([M+H]+, 100%).
Synthesis of 8: Ligand 8 was synthesized from 1 and 3-hexyl-2-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)thiophene by the same procedure as
1
6. Yield 67%. H NMR (CDCl3, 400.13 MHz): d=9.13 (s, 1H, ArH), 9.04
(s, 1H, ArH), 9.00 (s, 1H, ArH), 8.88 (d, J=4.8 Hz, 1H, ArH), 8.83 (s,
1H, ArH), 8.69 (d, J=8.0 Hz, 1H, ArH), 7.94 (d, J=5.2 Hz, 1H, ArH),
7.89 (d, J=4.8 Hz, 1H, ArH), 7.34 (d, J=5.2 Hz, 1H, ArH), 7.04 (d, J=
5.2 Hz, 2H, ArH), 4.50 (m, 4H, COOCH2CH3), 2.72 (t, J=8.0 Hz, 2H,
ArCH2-), 1.65 (m, 2H, ArCH2CH2), 1.46 (m, 6H, COOCH2CH3), 1.26–
1.32 (m, 6H, -CH2-), 0.87 ppm (t, J=7.0 Hz, 3H, CH3); 13C NMR
(CDCl3, 100.61 MHz): d=165.3, 165.2, 156.6, 156.4, 155.8, 153.7, 150.0,
149.2, 140.4, 140.2, 138.8, 137.3, 137.3, 133.6, 131.5, 129.9, 123.1, 121.1,
120.7, 120.6, 120.5, 61.9, 61.8, 31.7, 31.1, 29.2, 28.9, 22.6, 14.3, 14.2,
À1
(m, 6H, COOCH2CH3), 1.30–1.37 (m, 14H, CH2), 0.84–0.90 ppm (m,
~
14.1 ppm; FTIR (ATR): n=1728 cm (COOCH2CH3); MALDI-TOF
À1
MS: m/z 544 ([M+H]+, 100%).
~
15H, CH3); FTIR (ATR): n=2096 (SCN), 1725 cm (COOCH2CH3);
MALDI-TOF MS: m/z 1090 ([M+H]+).
Synthesis of 9: Ligand 9 was synthesized by the same procedure as 6.
Yield 67%. 1H NMR (CDCl3, 400.13 MHz): d=9.12 (s, 1H, ArH), 9.03
(s, 1H, ArH), 8.99 (s, 1H, ArH), 8.98 (s, 1H, ArH), 8.88 (d, J=5.0 Hz,
1H, ArH), 8.64 (d, J=8.4 Hz, 1H, ArH), 8.04 (d, J=8.4 Hz, 1H, ArH),
7.91 (d, J=5.2 Hz, 1H, ArH), 7.34 (s, 1H, ArH), 7.21 (d, J=8.0 Hz, 1H,
ArH), 6.52–6.55 (m, 2H, ArH), 4.50 (q, J=7.2 Hz, 4H, COOCH2CH3),
3.92–4.04 (m, 4H, OCH2), 3.90 (t, J=7.0 Hz, 2H, OCH2), 2.51 (t, J=
7.8 Hz, 2H, ArCH2), 1.77–1.84 (m, 2H, ArCH2CH2), 1.70–1.77 (m, 2H,
ArOCH2CH2), 1.56–1.63 (m, 2H, ArOCH2CH2), 1.47 (t, J=7.2 Hz, 6H,
COOCH2-CH3), 1.22–1.41 (m, 18H, CH2), 0.92 (t, J=7.0 Hz, 3H, CH3),
0.83–0.86 ppm (m, 6H, CH3); 13C NMR (CDCl3, 100.61 MHz): d=165.3,
160.6, 157.9, 156.7, 156.6, 155.8, 153.3, 150.0, 145.9, 141.5, 140.2, 138.9,
137.6, 135.5, 133.0, 132.7, 131.3, 125.9, 123.0, 121.3, 120.6, 120.3, 115.5,
Esterified MJ-6 (100 mg, 91 mmol) was dissolved in acetone, and a 1m
methanolic solution of tetrabutylammonium hydroxide (0.5 mL,
490 mmol) was added to this solution. The solution was heated at 608C
for 2 h, after which the solvent was removed by evaporation and remain-
ing solid dissolved in water (3 mL). The aqueous solution was acidified
by addition of 1m HNO3 and the resulting precipitate collected by centri-
fugation and washed with water and diethyl ether to give MJ-6 as a black
powder (77 mg, 85%). 1H NMR (MeOD, 400.13 MHz): d=9.22 (s, 1H,
ArH), 9.16 (d, J=6.0 Hz, 1H, ArH), 8.87 (s, 1H, ArH), 8.75 (s, 1H,
ArH), 8.54 (s, 1H, ArH), 8.23 (d, J=8.4 Hz, 1H, ArH), 8.18 (d, J=
5.6 Hz, 1H, ArH), 8.03 (d, J=7.2 Hz, 1H, ArH), 7.60 (s, 1H, ArH), 7.18
(s, 1H, ArH), 3.19–3.23 (m, 8H, CH2), 2.61–2.66 (m, 2H, ArCH2), 1.61–
1.65 (m, 8H, CH2), 1.33–1.38 (m, 14H, CH2, ArCH2ACHTUNGTRENUNG(CH2)4CH3) 0.94 ppm
104.9, 100.3, 68.6, 68.2, 61.9, 61.8, 31.6, 31.4, 30.6, 29.3, 29.2, 29.0, 25.8,
(t, J=7.2 Hz, 15H, CH3); FTIR (ATR): n=2096 (SCN), 1711 cmÀ1
(COOH); elemental analysis (%) calcd for C46H61N7O4S4Ru: C 54.94, H
6.12, N 9.75; found: C 54.6, H 6.3, N 9.4.
À1
~
~
25.7, 22.6, 14.4, 14.1, 14.0 ppm; FTIR (ATR): n=1728 cm
(COOCH2CH3); MALDI-TOF-MS: m/z 820 ([M+H]+, 100%).
Synthesis of 10: Ligand 10 was synthesized by the same procedure as 6.
Yield 67%. 1H NMR (CDCl3, 400.13 MHz): d=9.12 (s, 1H, ArH), 9.03
(s, 1H, ArH), 9.00 (s, 1H, ArH), 8.98 (s, 1H, ArH), 8.88 (d, J=5.2 Hz,
1H, ArH), 8.65 (d, J=8.2 Hz, 1H, ArH), 8.06 (d, J=8.2 Hz, 1H, ArH),
7.91 (d, J=5.2 Hz, 1H, ArH), 7.35 (s, 1H, ArH), 6.86–6.93 (m, 3H,
ArH), 4.50 (q, J=7.2 Hz, 4H, COOCH2CH3), 3.94 (t, J=7.0 Hz, 2H,
OCH2), 3.90 (t, J=7.0 Hz, 4H, OCH2), 2.56 (t, J=7.8 Hz, 2H, ArCH2),
1.76–1.81 (m, 2H, ArCH2CH2), 1.67–1.72 (m, 2H, Ar-O-CH2-CH2-),
1.57–1.65 (m, 4H, ArOCH2CH2), 1.48 (t, J=7.2 Hz, 6H, COOCH2CH3),
1.22–1.37 (m, 18H, CH2), 0.91 (t, J=7.0 Hz, 3H, CH3), 0.86 (t, J=7.0 Hz,
3H, CH3), 0.84 ppm (t, J=7.0 Hz, 3H, CH3); 13C NMR (CDCl3,
100.61 MHz): d=165.3, 156.7, 156.5, 155.8, 153.5, 152.9, 151.0, 146.0,
141.8, 140.2, 138.8, 138.2, 135.2, 133.1, 131.2, 125.9, 124.1, 123.1, 121.3,
120.7, 120.4, 118.2, 115.4, 114.4, 69.7, 68.7, 61.9, 31.7, 31.6, 31.5, 30.6, 29.4,
MJ-4, MJ-7, MJ-10, MJ-11, and MJ-12 were prepared by the same proce-
dure as MJ-6.
1
MJ-4: Yield 30%. H NMR (MeOD, 400.13 MHz); d=9.12–9.22 (m, 2H,
ArH), 8.64–8.88 (m, 3H, ArH), 8.36–8.50 (m, 1H, ArH), 8.18–8.20 (m,
2H, ArH), 7.70–7.76 (m, 2H, ArH), 7.34–7.38 (m, 4H, ArH), 3.16–3.21
(m, 8H, CH2), 2.70 (t, J=7.8 Hz, 2H, ArCH2), 1.60–1.71 (m, 8H, CH2),
1.27–1.37 (m, 14H, CH2, ArCH2ACHTUNGTRENUNG(CH2)4CH3) 0.94 ppm (t, J=7.2 Hz, 15H,
À1
~
CH3); FTIR (ATR): n=2096 (SCN) and 1710 cm (COOH); elemental
analysis (%) calcd for C48H63N7O4S3Ru: C 57.69, H 6.35, N 9.81; found:
C 57.1, H 6.6, N 9.6.
1
MJ-7: Yield 34%. H NMR (MeOD, 400.13 MHz); d=9.21 (d, J=8.4 Hz,
1H, ArH), 9.16 (d, J=5.6 Hz, 1H, ArH), 9.08 (s, 1H, ArH), 8.71–8.87
(m, 3H, ArH), 8.66 (s, 1H, ArH), 8.44–8.48 (m, 1H, ArH), 8.15–8.18 (m,
1H, ArH), 8.00–8.03 (m, 1H, ArH), 7.58–7.63 (s, 1H, ArH), 7.15–7.18
(m, 1H, ArH), 3.20–3.23 (m, 8H, CH2), 2.70–2.78 (m, 2H, ArCH2), 1.61–
~
29.3, 29.2, 25.8, 25.7, 22.6, 14.4, 14.3, 14.1, 14.0 ppm; FTIR (ATR): n=
1728 cmÀ1 (COOCH2CH3); MALDI-TOF MS: m/z 820 ([M+H]+,
100%).
1.66 (m, 8H, CH2), 1.33–1.38 (m, 14H, CH2, ArCH2ACHTUNGTRENUNG(CH2)4CH3) 0.88–
0.98 ppm (m, 15H, CH3); FTIR (ATR): n=2095 (SCN), 1712 cmÀ1
(COOH); elemental analysis (%) calcd for C46H61N7O4S4Ru: C 54.94, H
6.12, N 9.75; found: C 54.3, H 6.4, N 9.3.
~
Synthesis of 11: Ligand 11 was synthesized by the same procedure as 6.
Yield 67%. 1H NMR (CDCl3, 400.13 MHz): d=9.12 (s, 1H, ArH), 9.04
(s, 1H, ArH), 9.01 (s, 1H, ArH), 8.99 (s, 1H, ArH), 8.88 (d, J=4.8 Hz,
1H, ArH), 8.66 (d, J=8.0 Hz, 1H, ArH), 8.06 (d, J=8.2 Hz, 1H, ArH),
7.91 (d, J=4.8 Hz, 1H, ArH), 7.36 (s, 1H, ArH), 6.93–7.08 (m, 3H,
MJ-10: Yield 25%. 1H NMR (MeOD, 400.13 MHz); d=9.14–9.18 (m,
2H, ArH), 8.63 (s, 1H, ArH), 8.57 (s, 1H, ArH), 8.45 (s, 1H, ArH), 7.95–
Chem. Eur. J. 2013, 19, 1028 – 1034
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1033

M. Kimura, S. Mori et al.
8.09 (m, 3H, ArH), 7.54 (s, 1H, ArH), 7.22 (d, J=8.8 Hz, 1H, ArH),
6.52–6.55 (m, 2H, ArH), 3.96–4.03 (m, 4H, OCH2), 3.20–3.41 (m, 8H,
CH2), 2.50–2.54 (m, 2H, CH2), 1.55–1.75 (m, 12H, CH2), 1.26–1.38 (m,
[4] N. Robertson, Angew. Chem. 2006, 118, 2398; Angew. Chem. Int.
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[5] M. K. Nazeeruddin, P. Pꢄchy, T. Renouard, S. M. Zakeeruddin, R.
Humphry-Baker, P. Comte, P. Liska, L. Cevey, E. Costa, V. Shklov-
er, L. Spiccia, G. B. Deacon, C. A. Bignozzi, M. Grꢁtzel, J. Am.
Chem. Soc. 2001, 123, 1613.
[6] Y. Chiba, A. Islam, Y. Watanabe, R. Komiya, N. Koide, L. Han, Jpn.
J. Appl. Phys. 2006, 45, L638.
[7] A. Islam, F. A. Chowdhury, Y. Chiba, R. Komiya, N. Fuke, N. Ikeda,
K. Nozaki, L. Han, Chem. Mater. 2006, 18, 5178.
[8] T. Funaki, M. Yanagida, N. Onozawa-Komatsuzaki, K. Kasuga, Y.
Kawanishi, M. Kurashige, K. Sayama, H. Sugighara, Inorg. Chem.
Commun. 2009, 12, 842.
[9] B.-S. Chen, K. Chen, Y.-H. Hong, W.-H. Liu, T.-H. Li, C.-H. Lai, P.-
T. Chou, Y. Chi, G.-H. Lee, Chem. Commun. 2009, 5844.
[10] K. Chen, Y. H. Hong, W.-H. Liu, B. S. Chen, P. T. Chou, J. Mater.
Chem. 2009, 19, 5329.
[11] C.-C. Chou, K.-L. Wu, Y. Chi, W.-P. Hu, S. J. Yu, G.-H. C.-L. Lin, P.-
T. Chou, Angew. Chem. 2011, 123, 2102; Angew. Chem. Int. Ed.
2011, 50, 2054.
[12] J.-J. Kim, H. Choi, S. Paek, C. Kim, K. Lim, M. J. Ju, M. H. S. Kang,
M. S. Kang, J. Ko, Inorg. Chem. 2011, 50, 11340.
28H, CH2, ArCH2ACHTUNGTRENNUNG(CH2)4CH3) 0.86–0.93 ppm (m, 21H, CH3); FTIR
À1
~
(ATR): n=2094 (SCN), 1713 cm (COOH); elemental analysis (%)
calcd for C64H89N7O6S4Ru: C 59.97, H 7.00, N 7.65; found: C 60.1, H 7.1,
N 6.9.
MJ-11: Yield 30%. 1H NMR (MeOD, 400.13 MHz); d=9.18 (s, 1H,
ArH), 9.15 (d, J=6.0 Hz, 1H, ArH), 8.63 (s, 1H, ArH), 8.57 (s, 1H,
ArH), 8.47 (s, 1H, ArH), 8.10 (d, J=8.4 Hz, ArH), 7.95–8.02 (m, 2H,
ArH), 7.55 (s, 1H, ArH), 6.90–6.92 (m, 3H, ArH), 3.88–3.97 (m, 4H,
OCH2), 3.21–3.42 (m, 8H, CH2), 2.57 (t, J=7.6 Hz, 2H, CH2), 1.54–1.78
(m, 12H, CH2), 1.25–1.40 (m, 28H, CH2, ArCH2ACHTUNGTRENUNG(CH2)4CH3) 0.86–
0.93 ppm (m, 21H, CH3); FTIR (ATR): n=2094 (SCN), 1713 cmÀ1
(COOH); elemental analysis (%) calcd for C64H89N7O6S4Ru: C 59.97, H
7.00, N 7.65; found: C 60.0, H 7.1, N 7.4.
~
MJ-12: Yield 34%. 1H NMR (MeOD, 400.13 MHz); d=9.19 (s, 1H,
ArH), 9.15 (d, J=6.1 Hz, 1H, ArH), 8.63 (s, 1H, ArH), 8.58 (s, 1H,
ArH), 8.47 (s, 1H, ArH), 8.10 (d, J=8.4 Hz, ArH), 7.63–8.02 (m, 2H,
ArH), 7.57 (s, 1H, ArH), 6.92–7.09 (m, 3H, ArH), 4.04 (t, J=6.4 Hz, 2H,
OCH2), 3.82 (t, J=6.4 Hz, 4H, OCH2), 3.21–3.42 (m, 8H, CH2), 2.60 (t,
J=7.7 Hz, 2H, CH2), 1.58–1.85 (m, 12H, CH2), 1.21–1.40 (m, 28H, CH2,
[13] K. Hu, K. C. D. Robson, P. G. Johansson, C. P. Berlinguette, G. J.
Meyer, J. Am. Chem. Soc. 2012, 134, 8352.
~
ArCH2ACHTUNGTRENNUNG(CH2)4CH3) 0.84–0.90 ppm (m, 21H, CH3); FTIR (ATR): n=2094
(SCN), 1713 cmÀ1 (COOH); elemental analysis (%) calcd for
C64H89N7O6S4Ru: C 59.97, H 7.00, N 7.65; found: C 59.0, H 7.5, N 7.3.
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pastes of TiO2 nanoparticles having diameters of 15–20 and 400 nm onto
transparent conducting glass substrates (SnO2:F on 1.8 mm thick glass
substrate, Asahi Glass) by the screen-printing technique. The DSSC per-
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formance with [CoACHTUNGTRENNUNG
(bpy)3]2+/3+ electrolyte was examined with 6 mm-thick
layer of TiO2 nanoparticles (Solaronix Ti-Nanooxide D37/SP) on the
transparent conducting glass. The electrodes were sintered at 5508C for
30 min in air. TiCl4 treatment was applied to obtain high efficiency. The
apparent surface area of the TiO2 electrode was 0.25 cm2 (0.5ꢃ0.5 cm). A
black mask (0.16 cm2) was applied on the cell to reduce diffusive light.
The ruthenium dyes were attached to nanocrystalline TiO2 films of the
preformed metal oxide electrodes in 0.2 mm toluene solutions of the dyes
containing 20 mm chenodeoxycholic acid (CDCA) for 48 h at 258C. The
dye-loaded TiO2 electrodes were washed with toluene to completely
remove the physically adsorbed dye before measurements. Working and
Pt counterelectrodes were separated by a 50 mm thick film (Surlyn,
DuPont) and sealed by heating. Redox electrolytes (0.1m LiI, 0.6m 1,2-di-
methyl-3-propylimidazolium iodide, 0.5m 4-tert-butylpyridine, and 0.05m
I2 in dehydrated acetonitrile or 0.22m [CoACHTNUGTRNE(UGN bpy)3][B(CN)4]2, 0.02m
[Co(bpy)3]3+[B(CN)4]3, 0.2m LiClO4, and 0.6m tert-butylpyridine in dehy-
drated acetonitrile) were introduced into the space between the dye-
loaded TiO2 electrode and the counterelectrode, and then the photovolta-
ic performance was measured under 1 sun conditions (AM1.5,
100 mWcmÀ2) by using a solar simulator (YSS-100, Yamashita Denso)
after applying an antireflection film.
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Acknowledgements
We acknowledge financial support from the New Energy and Industrial
Technology Development Organization (NEDO) of Japan. We thank Mr.
Katusmi Kobayashi of Fujifilm Corporation for valuable discussions on
the molecular design of MJ dyes. We also thank Mr. Shingo Takano of
Sumitomo Osaka Cement Co., Ltd for the supply of TiO2 pastes.
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Received: July 28, 2012
Revised: October 17, 2012
Published online: November 29, 2012
1034
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Chem. Eur. J. 2013, 19, 1028 – 1034