Molecular engineering of organic sensitizers containing indole moiety for dye-sensitized solar cells

Article abstract of DOI:10.1016/j.tet.2008.08.045

Three organic dyes, JK-77, JK-78, and JK-79 containing indole unit are designed and synthesized. Nanocrystalline TiO₂ dye-sensitized solar cells were fabricated using these dyes. Under standard global AM 1.5 solar condition, the JK-79 sensitize

Full text of DOI:10.1016/j.tet.2008.08.045

Tetrahedron 64 (2008) 10417–10424
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Molecular engineering of organic sensitizers containing indole moiety
for dye-sensitized solar cells
,
a,
*
Duckhyun Kim a, Moon-Sung Kang b, Kihyung Song c, Sang Ook Kang a , Jaejung Ko
*
a Department of Advanced Material Chemistry, Korea University, Jochiwon, Chungnam 339-700, Republic of Korea
b Energy & Environment Laboratory, Samsung Advanced Institute of Technology (SAIT), Yongin 446-712, Republic of Korea
c Department of Chemical Education, Korea National University of Education, Cheongwon, Chungbuk 363-791, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 July 2008
Received in revised form 11 August 2008
Accepted 14 August 2008
Available online 19 August 2008
Three organic dyes, JK-77, JK-78, and JK-79 containing indole unit are designed and synthesized.
Nanocrystalline TiO2 dye-sensitized solar cells were fabricated using these dyes. Under standard global
AM 1.5 solar condition, the JK-79 sensitized solar cell gave a short circuit photocurrent density of
13.62 mA cmꢀ2, open-circuit voltage of 0.705 V, and a fill factor of 0.74, corresponding to an overall
conversion efficiency
h of 7.18%. We found that the h of JK-79 was higher than those of other two cells
due to the higher Voc. The improved Voc value is attributed to the suppression of dark current owing to
the blocking effect of a long alkyl chain.
Keywords:
Indole
Organic dye
Dye-sensitized solar cell
DSSCs
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
replacement of the above units with an indole group included ad-
vantage of expanded
p-conjugation as well as electron donor
Global warming and depletion of fossil fuels urge the de-
velopment of efficient solar energy conversion technology that
fulfills the green energy demands. Dye-sensitized nanocrystalline
TiO2 solar cells (DSSCs) based on Ru complex photosensitizers have
been intensively studied as an alternative to the conventional solar
cells because of their low-cost production and high performance.1
Organic dyes have been also utilized as photosensitizers in DSSCs.
Recently, the solar cell performance of DSSCs based on organic dyes
has been remarkably improved. Impressive photovoltaic perfor-
mance has been obtained with some organic coumarin,2 oligoene,3
merocyanine,4 hemicyanine,5 and indoline dyes6 having efficien-
cies in the range of 6–9%. An important approach on the design of
organic sensitizers has been the structural variation of the
compounds in order to obtain sensitizers showing high power
conversion efficiency and long-term stability. Modification of the
dye is one of the strategies to improve the performance of DSSCs.
Recently, we have reported efficient and stable organic sensitizers
containing bis-dimethylfluorenyl amino unit. In the previous
studies, we adapted the (9,9-dimethylfluoren-2-yl)aminophenyl,7
benzo[b]furan,8 benzo[b]thiophene,9 and N-aryl carbazole units10
as the donor moieties. In order to improve the photovoltaic per-
ability. Even such structural changes of dyes result in significant
changes in redox energies, absorption spectra, and the energy gaps
between the highest occupied molecular orbital and lowest un-
occupied molecular orbital of the dyes, affecting dramatically the
performance of DSSCs.
In this article, as part of our efforts to develop more efficient
organic dyes, we report three new organic sensitizers containing an
indole unit as electron donor and a cyanoacrylic acid as electron
acceptor bridged by thiophene unit (Fig. 1).
2. Results and discussion
The three dyes JK-77, JK-78, and JK-79 were synthesized by the
stepwise synthetic protocol (Scheme 1). Bromination of 2-phenyl-
indole was performed using NBS to give 1. The X-ray structure
analysis of 1 confirmed the bromo substituted structure at C10 (see
Supplementary data). Disappearance of H10 resonance at
6.90 ppm was evident in the 1H NMR spectrum. Suzuki coupling
reaction of 1 with 4,4,5,5-tetramethyl-2-(5-(5-(5,5-dimethyl-1,3-
dioxan-2-yl)thiophen-2-yl)thiophen-2-yl)-1,3,2-dioxaborolane 211
in the presence of Pd(PPh3)4 led to 3. N-Phenylation of 3 was carried
out under Ullmann coupling reaction.12 Subsequent cleavage of 1,3-
dioxalane protecting group in aqueous acid produced the aldehyde
5-(5-(1-(9,9-dimethylfluoren-7-yl)-2-phenylindol-3-yl)thio-phen-
2-yl)thiophene-2-carbaldehyde 5. The aldehyde reacted with
formance of DSSCs,
a successful approach would be the
* Corresponding authors. Tel.: þ82 41 860 1337; fax: þ82 41 867 5396.
E-mail address: jko@korea.ac.kr (J. Ko).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.08.045

10418
D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
NC
NC
COOH
COOH
NC
COOH
S
S
S
S
S
N
N
S
N
JK-77
JK-78
JK-79
Figure 1. Structure of JK-77, JK-78, and JK-79.
cyanoacetic acid in the presence of a catalytic amount of piperidine
in acetonitrile to give the JK-77. Fischer indole synthesis13 of
acetonitrile and bromophenylhydrazine led to 5-bromo-2-phenyl-
indole. Suzuki coupling reaction of 6 with 2, followed by N-phe-
nylation of 7 gave 8. The thiophene derivative was converted into
its corresponding thiophene aldehyde 9 by dedioxanylation with
trifluoroacetic acid (TFA), which yielded the dye JK-78 on treatment
of cyanoacetic acid. We have also designed to introduce the long
alkyl group on JK-78 in order to prevent the recombination re-
action. The synthetic methodology of JK-79 is essentially same as
that of JK-78.
To gain insight into the geometrical configuration and charac-
teristic features of the electronic structure, molecular orbital cal-
culations of three dyes were performed with the TD-DFT on B3LYP/
3-21G
*
. The calculation indicates that the HOMO of JK-77 is delo-
calized over the
p-conjugated system through the phenylamino
group and the thienyl unit next to the phenyl group (Fig. 3). On the
other hand, the HOMO of JK-78 and JK-79 is delocalized over the
conduit channel through an entire bridging unit.
The LUMO of the three dyes is delocalized over the cyanoacrylic
unit through thiophene. Examination of the HOMO and LUMO of
these dyes indicates that HOMO–LUMO excitation moves the
electron distribution from the phenylamino unit to the cyanoacrylic
acid moiety. The change in electron distribution induced by pho-
toexcitation results in an efficient charge separation.
The UV–vis and emission spectra of JK-77 and JK-79 in ethanol
are shown in Figure 2 and listed in Table 1, together with the UV–vis
spectra of the corresponding dyes absorbed on TiO2 film. The ab-
sorption spectra of JK-78 and JK-79 exhibit visible band at 429 and
For the preparation of DSSC, a washed FTO (Pilkington, 8
glass plate was immersed in 40 mM TiCl4 aqueous solution as
reported by the Gra¨tzel group.15 The first TiO2 layer of 12
thickness was prepared by screen printing TiO2 paste (13 nm ana-
tase), and the second layer of 4 m thickness (400 nm) was coated.
U )
s qꢀ1
431 nm, respectively, which is due to the
p
–
p transition of the
*
conjugated molecule. On the other hand, the absorption spectrum
of JK-77 caused a slightly red shift to 433 nm relative to the JK-78
and JK-79 due to a relatively weak electron donating ability of the
indole moiety in JK-77, indicating that a ring structure in the indole
framework is important for a red shift in the absorption spectrum.
Adsorption of dyes JK-77–JK-79 onto a TiO2 electrode was observed
to broaden the absorption spectrum and to red shift the absorption
threshold up to 650 nm. Similar broadening and red shifts have
been reported in other organic dyes on TiO2 electrodes.2b,14 Such
wide absorption and red shift of absorption maximum in the visible
region is desirable for harvesting the solar spectrum and leads to
a large photocurrent. We also observed that the dyes JK-77–JK-79
exhibited strong luminescence maxima at 566–603 nm when they
mm
m
The TiO2 electrodes were immersed into the dyes solution in the
presence of 10 mM 3a,7a-dihydroxy-5b-cholic acid solution in
ethanol and kept at room temperature for 18 h. Cholic acid de-
rivative has been employed as co-adsorbates in DSSCs to suppress
dye aggregation on the TiO2 surface. Counter electrodes were
prepared by coating with a drop of H2PtCl6 solution (2 mg Pt in
1 mL ethanol) on a FTO plate. The electrolyte was then introduced
into the cell, which was composed of 0.6 M 3-hexyl-1,2-dimethyl-
imidazolium iodide, 0.05 M iodide, 0.1 M LiI, and 0.5 M tert-bu-
tylpyridine in acetonitrile. The active area was 0.25 cm2 with
employing a mask.
are excited within their
p–
*
p bands in EtOH at 298 K. The fluo-
rescence emission peaks in the visible region disappear when the
dyes are adsorbed onto a nanocrystalline TiO2 film, demonstrating
that the electron injection from an excited state to TiO2 occurs
efficiently.
Figure 4 shows action spectra of monochromatic incident-to-
current conversion efficiencies (IPCEs) for DSSCs based on JK-77–
JK-79. The onset of IPCE spectra for DSSCs based on JK-78 and JK-79
was 680 nm. IPCE values higher than 80% were observed in the
range from 420 to 545 nm with a maximum value of 82% at 463 and
492 nm for the DSSC based on JK-78 and JK-79, respectively. The
IPCE spectrum of JK-77 sensitizer is red shifted by about 25 nm
compared to those of JK-78 and JK-79 as a result of positive shift in
the reduction potential of JK-77. However, the maximum IPCE value
of JK-77 is much lower than those of both dyes. A plausible reason
for this is that electron transfer from the excited dye to TiO2 would
be suppressed due to a small energy gap between the LUMO of the
dye and the conduction band edge of TiO2. The J–V curve for the
cells based on the JK-77, JK-78, and JK-79 is presented in Figure 4.
Under standard global AM 1.5 solar condition, the JK-77 cell gave
To thermodynamically evaluate the possibility of electron
transfer from the excited state of the dye to the conduction band of
TiO2 electrode and the photophysical property of the dyes, cyclic
voltammogram was carried out to determine the redox potential
(Table 1). The redox potentials of three dyes JK-77–JK-79 were
measured in CH3CN with 0.1 M tetrabutylammonium hexa-
fluorophosphate. TiO2 films coated with the sensitizers were used
as working electrodes. Redox potential of the dyes was quite sen-
sitive to the substitution of the functional groups. The JK-77 and JK-
78 absorbed on TiO2 film show a quasi-reversible couple at 1.42 and
1.40 V versus NHE with a separation of 0.20 and 0.18 V, which is
assigned to the oxidation of the 1-(9,9-dimethylfluoren-7-yl)-2-
phenylindole. The reduction potentials of three dyes calculated
from the oxidation potentials and the E0–0 determined from the
intersection of absorption and emission spectra are listed in Table 1.
the short circuit photocurrent density (Jsc) of 12.89 mA cmꢀ2
,
open-circuit voltage (Voc) of 0.679 V, and a fill factor of 0.73, cor-
responding to an overall conversion efficiency of 6.43%. In the same
condition, the JK-79 sensitized cell gave Jsc of 13.62 mA cmꢀ2, Voc of
The excited state oxidation potentials (Eox
*
) of the dyes (JK-77:
0.705 V, and ff of 0.74, corresponding to
sults (Table 1), we have observed that the
than those of other cells. Of particular importance is the 10–25 mV
increase in Voc of JK-79 cell under illumination. This improved Voc
value is attributed to suppression of dark current owing to the
h
of 7.18%. From these re-
of JK-79 was higher
ꢀ0.85 V; JK-78: ꢀ0.96 V; JK-79: ꢀ0.93 V vs NHE) are much
negative than the conduction band of TiO2 at ꢀ0.5 V vs NHE,
allowing the electron injection from the LUMO of dye to the con-
duction band of TiO2.
h

D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
10419
O
O
S
S
O
Br
B
O
2
NBS
+
Pd(PPh3)4, K2CO3
THF, H2O
N
H
N
H
1
O
O
I
O
HN
S
S
S
N
S
Cu, K2CO3
18-crown-6
O
4
3
NC
COOH
NC COOH
CHO
TFA
THF, H2O
S
S
S
S
piperidine, CH3CN
N
N
5
JK-77
Fischer indole
synthesis
Br
2, Pd(PPh3)4, K2CO3
THF, H2O
Br
HN
H2N
+
O
N
H
6
O
O
O
I
TFA
THF, H2O
O
S
S
S
S
N
HN
Cu, K2CO3
18-crown-6
8
7
O
NC
COOH
S
S
NC COOH
N
S
S
N
piperidine, CH3CN
9
JK-78
Fischer indole
synthesis
Br
2, Pd(PPh3)4, K2CO3
THF, H2O
Br
HN
H2N
+
O
N
H
10
O
O
O
S
S
S
TFA
S
HN
O
N
I
THF, H2O
11
Cu, K2CO3
18-crown-6
12
NC
O
COOH
S
S
NC COOH
piperidine, CH3CN
N
S
S
N
13
JK-79
Scheme 1. Schematic diagram for the synthesis of organic dyes JK-77, JK-78, and JK-79.

10420
D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
Figure 5 shows the electron diffusion coefficient (De) and life-
time ( e) of the DSSCs employing different dyes (i.e., JK-77, JK-78,
s
and JK-79) as a function of the Jsc and the Voc, respectively. The De
and se values were determined by the photocurrent and photo-
voltage transients induced by a stepwise change in the laser light
intensity controlled with a function generator.16–18 The De value
was obtained by a time constant (
of the photocurrent transient with exp(ꢀt/
thickness (
) using the equation, De¼
2/(2.77
was also determined by fitting a decay of photovoltage transient
e).16 The De values of the photoanodes adsorbing the
s
c) determined by fitting a decay
c) and the TiO2 film
c).16 The se value
s
u
u
s
with exp(ꢀt/
s
organic dyes are shown to be similar to each other at the identical
short circuit current condition, showing the similar trend to those
of coumarin dyes.19 Meanwhile, the difference in the
se values was
clearly observed among the cells employing different dyes. The
increasing order of the se values was JK-77<JK-78<JK-79 at
the identical open-circuit voltage condition, demonstrating that
the electron recombination process was effectively controllable
by the modification of dye molecular structure (such as the in-
troduction of hydrophobic alkyl chain in JK-79). The results of the
electron lifetime are also well consistent with those of the Voc
shown in Table 1.
Figure 2. Absorption and emission spectra of JK-77 (black solid line) and JK-78 (gray
solid line) in EtOH and absorption spectra of JK-77 (black dashed line) and JK-78 (gray
dashed line) adsorbed on a TiO2 film. The emission spectra were obtained using the
same solution by exciting at 430 nm at 298 K.
Table 1
Optical, redox, and DSSC performance parameters of dyes
The ac impedances of the cells were measured at the dark and
illumination conditions. Figure 6 shows the ac impedance spectra
of the DSSCs measured in dark and illumination (inset) conditions.
In the dark under forward bias (ꢀ0.67 V), the semicircle in in-
termediate frequency regime demonstrates the dark reaction im-
pedance caused by the electron transport from the conduction
band of TiO2 to Iꢀ3 ions in electrolyte.20 The increased radius of the
semicircle in intermediate frequency regime means the reduced
electron recombination rate at the dyed TiO2/electrolyte interface.
In dark, the radius of the intermediate frequency semicircle showed
Dye
labsa/nm
/Mꢀ1 cmꢀ1
Eoxb/V E0–0c/V ELUMOd/V Jsc
(mA cmꢀ2
)
Voc (V) ff
h (%)
(
3
)
JK-77 433 (20,369) 1.42
JK-78 429 (28,075) 1.40
JK-79 431 (29,370) 1.46
2.27
2.36
2.39
ꢀ0.85
ꢀ0.96
ꢀ0.93
12.89
13.68
13.62
0.679 0.73 6.43
0.694 0.73 6.96
0.705 0.74 7.18
a
Absorption spectra were measured in ethanol.
Redox potential of dyes on TiO2 were measured in CH3CN with 0.1 M
b
(n-C4H9)4NPF6 with a scan rate of 50 mV sꢀ1 (vs Fc/Fcþ).
c
E0–0 was determined from intersection of absorption and emission spectra in ethanol.
d
ELUMO was calculated by EoxꢀE0–0
.
the increasing order of JK-77 (70.9 U)<JK-78 (71.7 U)<JK-79
blocking effect of a long alkyl chain. Minimization of interfacial
charge recombination losses in the device is also evident from the
dark current data for the cells.
(96.2 U), in accord with the trends of the Voc and se values.
Under the illumination (100 mW cmꢀ2, open-circuit voltage
(OCV) condition), the radius of the intermediate frequency
Figure 3. Isodensity surface plots of the HOMO and LUMO of (a) JK-77, (b) JK-78, and (c) JK-79.

D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
10421
15
10
5
were synthesized using a modified procedure of previous refer-
ences. 1H and 13C NMR spectra were recorded on a Varian Mercury
300 spectrometer. Elemental analyses were performed with a Carlo
Elba Instruments CHNS-O EA 1108 analyzer. Mass spectra were
recorded on a JEOL JMS-SX102A instrument. The absorption and
photoluminescence spectra were recorded on a Perkin–Elmer
Lambda 2S UV–visible spectrometer and a Perkin LS fluorescence
spectrometer, respectively.
JK-77
JK-78
JK-79
80
60
40
20
0
JK-77
JK-78
JK-79
3.2. Cyclovoltagram
Cyclic voltammetry was carried out with a BAS 100B (Bio-
analytical Systems, Inc.). A three-electrode system was used and
consisted of a gold disk, working electrode and a platinum wire
electrode. Redox potential of dyes on TiO2 were measured in CH3CN
400
500
Wavelength (nm)
600
700
800
0
0.0
0.2
0.4
Voltage (V)
0.6
0.8
with 0.1 M (n-C4H9)4N–PF6 with a scan rate of 50 mV sꢀ1
.
Figure 4. J–V curve and IPCE spectra of JK-77 (dashed dot line), JK-78 (dashed line),
and JK-79 (solid line).
3.3. Characterization of DSSC
semicircle in the Nyquist plot decreased in the order of JK-77
(85.2 U)>JK-78 (54.6 U)>JK-79 (49.8 U), indicating the improved
electron generation and transport. This result also well corresponds
to that of the overall efficiency.
In conclusion, we have designed and synthesized three novel
organic dyes (JK-77, JK-78, and JK-79). We obtained a maximum
The cells were measured using 1000 W xenon light source,
whose power of an AM 1.5 Oriel solar simulator was calibrated by
using KG5 filtered Si reference solar cell. The incident photon-to-
current conversion efficiency (IPCE) spectra for the cells were
measured on an IPCE measuring system (PV measurements).
solar energy to electricity conversion efficiency (h) of 7.18% under
AM 1.5 irradiation with a DSSC based on JK-79. The power con-
version efficiency was shown to be sensitive to the structural
modifications. A large increase in Voc of JK-79 with a long alkyl
chain results in a lengthening of the lifetime by preventing the
approach of acceptors to the TiO2 surface. The improved Voc value
is attributed to suppression of dark current. Our results suggest
that the development of highly efficient organic sensitizers can
be possible through the more sophisticated structural
modifications.
3.4. Electron transport measurements
Electron diffusion coefficients and lifetimes were measured by
the stepped light-induced transient measurements of photocur-
rent and voltages (SLIM-PCV).16–18 The transients were induced
by a stepwise change in the laser intensity. A diode laser
(l¼635 nm) as a light source was modulated using a function
generator (UDP-303, PNCYS Co. Ltd., Korea). The initial laser in-
tensity was a constant 90 mW cmꢀ2 and was attenuated up to
approximately 10 mW cmꢀ2 using a ND filter, which was posi-
tioned at the front side of the fabricated samples (0.04 cm2). The
laser was operated at the voltage of 3.0 V and stepped down to
2.9 V for 5 s. Then the single shot of the time-profiles of the
photocurrent and photovoltage was obtained from an oscilloscope
3. Experimental
3.1. General methods
All reactions were carried out under an argon atmosphere.
Solvents were distilled from appropriate reagents. All reagents
were purchased from Sigma–Aldrich. 2-Iodo-9,9-dimethyl-
fluorene21 and 4,4,5,5-tetramethyl-2-(5-(5-(5,5-dimethyl-1,3-di-
oxan-2-yl)thiophen-2-yl)thiophen-2-yl)-1,3,2-dioxaborolane (2)11
(TDS 3052B, Tektronix) through a current amplifier (SR570,
Stanford Research Systems) and a voltage amplifier (5307, NF
electronic Instruments), respectively. For the measurement of
SLIM-PCV, the TiO2 thickness of the photoelectrode was con-
trolled as approximately 10 mm.
(a)
(b)
1E-3
JK-77
JK-78
JK-79
JK-77
JK-78
JK-79
1E-4
1E-5
1E-6
10
0.1
1
Short-circuit current (mA cm-2)
10
0.5
0.52
0.54
Open-circuit voltage (V)
0.56
0.58
0.6
0.62
Figure 5. Electron diffusion coefficients (a) and lifetimes (b) in the photoelectrodes adsorbing different dyes (i.e., JK-77, JK-78, and JK-79).

10422
D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
100
80
60
40
20
0
129.5,129.4,129.0,127.7,126.6,124.9,123.4,123.1,121.2,120.0,112.3,
107.8, 98.7, 77.7, 30.6, 23.1, 21.8. MS: m/z 471 [Mþ]. Anal. Calcd for
23H25NO2S2: C, 71.31; H, 5.34. Found: C, 71.21; H, 5.27.
60
40
20
0
@ dark/ 0.67V
@ 1sun/ OCV
JK-77
JK-78
JK-79
C
JK-77
JK-78
JK-79
3.8. 3-(5-(5-(5,5-Dimethyl-1,3-dioxan-2-yl)thiophen-2-
yl)thiophen-2-yl)-1-(9,9-dimethylfluoren-7-yl)-2-
phenylindole (4)
0
20
40
60
Z' (Ω)
80
100 120
A stirred mixture of 3 (0.64 g, 1.35 mmol), 2-iodo-9,9-dime-
thylfluorene (0.44 g, 1.35 mmol), powdered anhydrous potassium
carbonate (0.37 g, 2.70 mmol), copper bronze (0.074 g, 0.41 mmol),
and 18-crown-6 (0.054 g, 0.20 mmol) in 1,2-dichlorobenzene
(40 mL) was refluxed for 36 h. After cooling, the insoluble inorganic
material was filtered off and washed with dichloromethane
(3ꢂ30 mL). The combined filtrate and organic phase were washed
with dilute aqueous ammonia and water and dried with magne-
sium sulfate. The solvent was removed under reduced pressure. The
pure product 3 was obtained by silica gel chromatography using
a mixture of methylene chloride and n-hexane (1:3) as an eluent
0
40
80
Z' (Ω)
120
160
Figure 6. Electrochemical impedance spectra measured in the dark and under the
illumination (1 sun, inset) for the cells employing different dyes (i.e., JK-77, JK-78, and
JK-79).
(yield 86%). Mp: 133 ꢁC. 1H NMR (CDCl3):
d
8.04 (d, 1H, J¼8.1 Hz),
7.73 (d, 1H, J¼8.1 Hz), 7.71 (d, 1H, J¼8.1 Hz), 7.45–7.18 (m, 12H), 7.07
(d, 1H, J¼3.9 Hz), 7.05 (s, 1H), 6.99 (d, 1H, J¼3.9 Hz), 6.98 (t, 1H,
J¼6.9 Hz), 6.87 (d, 1H, J¼3.9 Hz), 5.61 (s, 1H), 3.70 (m, 4H), 1.29 (s,
3.5. The ac impedance measurements
3H), 0.80 (s, 3H). 13C{1H} NMR (CDCl3):
d 154.6, 153.9, 139.5, 138.4,
The ac impedance measurements were carried out under illu-
mination (1 sun) and dark conditions using an impedance analyzer
(1260A, Solartron, UK).
138.3, 138.1, 137.6, 136.5, 136.3, 135.6, 131.4, 128.2, 128.1, 127.6, 127.2,
127.1, 126.7, 126.6, 126.4, 125.8, 124.0, 123.1, 123.0, 122.8, 122.5,
121.3, 120.3, 120.2, 120.0, 111.0, 109.6, 98.3, 77.6, 46.9, 30.3, 26.8,
23.1, 21.9. MS: m/z 663 [Mþ]. Anal. Calcd for C43H37NO2S2: C, 77.79;
H, 5.62. Found: C, 77.64; H, 5.54.
3.6. 3-Bromo-2-phenylindole (1)
To a solution of 2-phenylindole (1.0 g, 5.17 mmol) in CHCl3
(120 mL) at 0 ꢁC was added N-bromosuccinimide (0.92 g,
5.17 mmol) over 5 min as a small potion. The mixture was stirred at
same temperature for 3 h. After evaporating the solvent, the resi-
due was extracted by dichloromethane and washed by H2O. The
organic layer was separated and dried in MgSO4. The solvent was
removed in vacuo. The pure product 1 was obtained by silica gel
chromatography using a mixture of methylene chloride and
n-hexane (1:3) as an eluent (yield 91%). Mp: 108 ꢁC.1H NMR (CDCl3):
3.9. 5-(5-(1-(9,9-Dimethylfluoren-7-yl)-2-phenylindol-3-
yl)thiophen-2-yl)thiophene-2-carbaldehyde (5)
THF (30 mL) and water (30 mL) were added to a flask containing
acetal 4 (0.77 g, 1.16 mmol). Then, TFA (0.1 mL) was added to the
solution. The resulting reaction mixture was stirred for 3 h at room
temperature, quenched with saturated aqueous sodium bi-
carbonate, and extracted with dichloromethane. The combined
organic phases were washed with aqueous sodium bicarbonate (2%
w/v), dried (Na2SO4), and evaporated in vacuo. The pure product 5
was obtained by silica gel chromatography using a mixture of
methylene chloride and n-hexane (1:1) as an eluent (yield 95%).
d
8.29 (s, 1H), 7.82 (d, 2H, J¼7.5 Hz), 7.63 (d, 1H, J¼7.5 Hz), 7.51 (t, 2H,
J¼7.5 Hz), 7.42 (t, 1H, J¼7.5 Hz), 7.38 (d, 1H, J¼6.9 Hz), 7.27 (t, 1H,
J¼7.5 Hz), 7.23 (t, 1H, J¼6.9 Hz). 13C{1H} NMR (CD3COCD3):
d 135.2,
Mp: 171 ꢁC. 1H NMR (CDCl3):
d
9.84 (s, 1H), 8.03 (d, 1H, J¼8.2 Hz),
129.5, 129.3, 129.0, 128.8, 128.6, 128.4, 123.9, 121.2, 119.5, 112.5, 88.9.
MS: m/z 271 [Mþ]. Anal. Calcd for C14H10BrN: C, 61.79; H, 3.70.
Found: C, 61.66; H, 3.64.
7.73 (d, 1H, J¼8.1 Hz), 7.71 (d, 1H, J¼8.1 Hz), 7.64 (d, 1H, J¼3.9 Hz),
7.45–7.21 (m, 13H), 7.17 (d, 1H, J¼3.9 Hz), 7.05 (s, 1H), 6.93 (d, 1H,
J¼3.6 Hz), 1.28 (s, 6H). 13C{1H} NMR (CDCl3):
d 182.6, 154.6, 153.8,
3.7. 3-(5-(5-(5,5-Dimethyl-1,3-dioxan-2-yl)thiophen-2-
yl)thiophen-2-yl)-2-phenylindole (3)
148.0, 140.9, 139.6, 138.7, 138.4, 138.3, 138.0, 137.8, 137.7, 136.2,
134.0, 131.4, 131.2, 128.4, 128.3, 127.7, 127.2, 126.8, 126.7, 126.6,
123.5, 123.3, 122.9, 122.8, 121.6, 120.4, 120.2, 119.8, 111.2, 109.2, 46.9,
26.8. MS: m/z 577 [Mþ]. Anal. Calcd for C38H27NOS2: C, 79.00; H,
4.71. Found: C, 78.89; H, 4.68.
To a stirred solution of 1 (0.59 g, 2.19 mmol) and Pd(PPh3)4
(0.13 g, 0.11 mmol) in tetrahydrofuran (15 mL) were added 4,4,5,5-
tetramethyl-2-(5-(5-(5,5-dimethyl-1,3-dioxan-2-yl)thiophen-2-yl)-
thiophen-2-yl)-1,3,2-dioxaborolane (2) (0.89 g, 2.19 mmol), potas-
sium carbonate (2.76 g, 20 mmol) in THF (15 mL), and H2O (10 mL).
The mixture was refluxed for 18 h. After cooling the solution, H2O
(30 mL) was added to the solution and extracted by dichloro-
methane (30 mLꢂ3). The organic layer was separated and dried in
MgSO4. The solvent was removed in vacuo. The pure product 3 was
obtained by silica gel chromatography using a mixture of methylene
chloride and n-hexane (1:1) as an eluent (yield 81%). Mp: 137 ꢁC. 1H
3.10. 2-Cyano-3-(5-(5-(1-(9,9-dimethylfluoren-7-yl)-2-
phenylindol-3-yl)thiophen-2-yl)thiophen-2-yl)-
acrylic acid (JK-77)
In a vacuum-dried flask cyanoacetic acid (0.051 g, 0.060 mmol)
and 5 (0.26 g, 0.40 mmol) were placed under argon. Then aceto-
nitrile (30 mL) and piperidine (0.04 mL) were added. The solution
was refluxed for 6 h. After cooling the solution, the organic layer
was removed in vacuo. The pure product was obtained by silica gel
chromatography using a mixture of methylene chloride and
methanol (10:1) as an eluent (yield 91%). Mp: 254 ꢁC. 1H NMR
NMR (CD3COCD3):
d
10.83 (s, 1H), 7.77 (d, 1H, J¼8.1 Hz), 7.65 (d, 2H,
J¼8.1 Hz), 7.48 (t, 1H, J¼8.1 Hz), 7.42 (d, 1H, J¼7.2 Hz), 7.41 (t, 2H,
J¼8.1 Hz), 7.26 (d, 1H, J¼3.9 Hz), 7.22 (t, 1H, J¼8.1 Hz), 7.15 (t, 1H,
J¼7.2 Hz), 7.09 (d, 1H, J¼3.9 Hz), 7.03 (d, 1H, J¼3.9 Hz), 6.98 (d, 1H,
J¼3.9 Hz), 5.67 (s, 1H), 3.69 (m, 4H), 1.23 (s, 3H), 0.79 (s, 3H). 13C{1H}
(DMSO-d6):
d
8.08 (s, 1H), 7.98 (d, 1H, J¼8.1 Hz), 7.87 (d, 1H,
J¼8.1 Hz), 7.84 (d, 1H, J¼8.1 Hz), 7.62 (d, 1H, J¼3.9 Hz), 7.51 (d, 1H,
J¼7.8 Hz), 7.40 (d, 1H, J¼3.9 Hz), 7.39–7.28 (m, 13H), 6.99 (d, 1H,
NMR (CD3COCD3):
d 141.6, 138.2, 137.4, 137.2, 136.7, 136.6, 133.2,

D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
10423
J¼3.6 Hz), 1.26 (s, 6H). 13C{1H} NMR (DMSO-d6):
d
164.7, 163.5,
J¼3.9 Hz), 7.51–7.15 (m, 15H), 6.86 (s, 1H), 1.36 (s, 6H). 13C{1H} NMR
154.2, 153.5, 141.4, 140.2, 138.5, 137.8, 137.6, 137.4, 137.2, 136.2, 135.7,
135.3, 133.6, 131.3, 130.8, 128.6, 128.2, 127.7, 127.2, 126.7, 126.5,
125.9,123.9,123.4,123.1,122.8,121.6,120.7,120.5,119.3,118.8,110.9,
109.1, 108.4, 46.4, 26.4. MS: m/z 644 [Mþ]. Anal. Calcd for
(CDCl3): d 182.6, 154.9, 153.9, 147.6, 145.8, 142.0, 141.4, 139.5, 138.5,
138.3, 137.7, 136.9,135.0, 132.2, 129.2, 129.1, 128.3, 127.7, 127.3, 127.0,
126.6, 126.0, 125.9, 125.6, 124.0, 123.7, 122.8, 122.6, 120.7, 120.4,
120.3, 111.2, 102.9, 46.9, 26.9. MS: m/z 577 [Mþ]. Anal. Calcd for
C
41H23N2O2S2: C, 76.37; H, 4.38. Found: C, 76.30; H, 4.29.
C38H27NOS2: C, 79.00; H, 4.71. Found: C, 78.91; H, 4.66.
3.11. 5-Bromo-2-phenylindole (6)
3.15. 2-Cyano-3-(5-(5-(1-(9,9-dimethylfluoren-2-yl)-2-
phenylindol-5-yl)thiophen-2-yl)thiophen-2-yl)-
acrylic acid (JK-78)
To a suspension of acetophenone (1.03 g, 5.0 mmol) and 4-
bromophenylhydrazine hydrochloride (1.12 g, 5.0 mmol) in ethanol
(5 mL) was added a few drops of glacial acetic acid. The reaction
was stirred at 80 ꢁC for 2 h. Solvent was evaporated to yield the
phenylhydrazone intermediate, which was added to poly-
phosphoric acid (20 g). The reaction mixture was stirred at 120 ꢁC
for 2 h. The mixture was poured into crashed ice and then neu-
tralized with 1 M NaOH and extracted with CH2Cl2. The combined
organic extracts were washed with water, dried over anhydrous
Na2SO4, and evaporated to give the desired 5-bromo-2-phenyl-
indole (6) (0.92 g, 68%) as a pale yellow solid. Mp: 132 ꢁC. 1H NMR
The product was synthesized according to the procedure as
described above for synthesis of JK-77, giving a red solid of the
product JK-78 in 91% yield. Mp: 264 ꢁC. 1H NMR (DMSO-d6):
d 8.08
(s, 1H), 8.01 (s, 1H), 7.93 (d, 1H, J¼7.2 Hz), 7.85 (d, 1H, J¼7.2 Hz),
7.70–7.63 (m, 2H), 7.58–7.43 (m, 4H), 7.39–7.22 (m, 10H), 6.94 (s,
1H), 1.30 (s, 6H). 13C{1H} NMR (DMSO-d6):
d 163.3, 154.6, 153.6,
145.6, 143.3, 141.6, 141.3, 141.0, 140.0, 139.3, 137.9, 137.8, 137.7, 136.5,
136.2, 135.9, 135.6, 134.7, 131.6, 128.9, 128.7, 128.4, 128.3, 127.8,
127.2, 126.6,125.2,124.6,122.9,121.0,120.5,119.7,119.4,110.8,109.7,
102.6, 46.5, 26.4. MS: m/z 644 [Mþ]. Anal. Calcd for C41H28N2O2S2:
C, 76.37; H, 4.38. Found: C, 76.24; H, 4.33.
(CD3COCD3):
d
10.89 (br s, 1H), 7.86 (d, 2H, J¼7.8 Hz), 7.73 (s, 1H),
7.46 (t, 2H, J¼7.8 Hz), 7.38 (d, 1H, J¼9.0 Hz), 7.35 (t, 1H, J¼7.8 Hz),
7.21 (d, 1H, J¼9.0 Hz), 6.90 (s, 1H). 13C{1H} NMR (CD3COCD3):
d
133.3, 129.8, 125.8, 124.8, 122.7, 121.6, 118.9, 118.0, 116.2, 106.7,
3.16. 5-Bromo-2-(4-hexylphenyl)indole (10)
106.1, 92.3. MS: m/z 271 [Mþ]. Anal. Calcd for C14H10BrN: C, 61.79; H,
3.70. Found: C, 61.68; H, 3.67.
The product was synthesized according to the procedure as
described above for synthesis of 6, giving a white solid of the
3.12. 5-(5-(5-(5,5-Dimethyl-1,3-dioxan-2-yl)thiophen-2-
yl)thiophen-2-yl)-2-phenylindole (7)
product 10 in 70% yield. Mp: 131 ꢁC. 1H NMR (CD3COCD3):
d 10.83 (s,
1H), 7,76 (d, 2H, J¼8.4 Hz), 7.71 (s, 1H), 7.36 (d, 1H, J¼8.4 Hz), 7.29
(d, 2H, J¼8.4 Hz), 7.19 (d, 1H, J¼8.4 Hz), 6.83 (s, 1H), 2.64 (t, 2H,
J¼7.8 Hz), 1.62 (m, 2H), 1.32 (m, 6H), 0.88 (m, 3H). 13C{1H} NMR
The product was synthesized according to the procedure as
described above for synthesis of 2, giving a yellow solid of the
(CD3COCD3): d 143.6, 140.6, 136.8, 132.0, 130.4, 129.8, 126.0, 124.9,
product 7 in 73% yield. Mp: 131 ꢁC. 1H NMR (CD3COCD3):
d
10.97 (br
123.2, 113.6, 113.1, 98,8, 36.2, 32.4, 32.1, 29.6, 23.2, 14.3. MS: m/z 355
[Mþ]. Anal. Calcd for C20H22BrN: C, 67.42; H, 6.22. Found: C, 67.29;
H, 6.18.
s, 1H), 7.95 (d, 2H, J¼7.5 Hz), 7.57 (d, 1H, J¼3.9 Hz), 7.48 (t, 2H,
J¼7.5 Hz), 7.46 (s, 1H), 7.41 (d, 1H, J¼7.5 Hz), 7.35 (d, 1H, J¼3.6 Hz),
7.34 (d, 1H, J¼7.5 Hz), 7.22 (d, 1H, J¼3.6 Hz), 7.19 (t, 1H, J¼7.5 Hz),
7.08 (d, 1H, J¼3.9 Hz), 5.69 (s, 1H), 3.71 (m, 4H), 1.25 (s, 3H), 0.80 (s,
3.17. 2-(4-Hexylphenyl)-5-(5-(5-(5,5-dimethyl-1,3-dioxan-2-
yl)thiophen-2-yl)thiophen-2-yl)indole (11)
3H). 13C{1H} NMR (CD3COCD3):
d 143.9, 141.9, 139.8, 139.1, 138.1,
136.7, 133.2, 129.8, 128.6, 127.0, 126.8, 126.4, 126.1, 125.4, 123.5,
122.9,119.5,112.0, 99.5, 98.7, 77.7, 30.6, 23.1, 21.8. MS: m/z 471 [Mþ].
Anal. Calcd for C23H25NO2S2: C, 71.31; H, 5.34. Found: C, 71.16; H,
5.31.
The product was synthesized according to the procedure as
described above for synthesis of 2, giving a white solid of the
product 11 in 75% yield. Mp: 105 ꢁC. 1H NMR (CD3COCD3):
d 10.79
(s, 1H), 7.68 (s, 1H), 7.79 (d, 2H, J¼8.1 Hz), 7.45 (m, 2H), 7.33 (d, 1H,
J¼3.9 Hz), 7.31 (d, 2H, J¼8.1 Hz), 7.25 (d, 1H, J¼3.9 Hz), 7.15 (d, 1H,
J¼3.9 Hz), 7.06 (d, 1H, J¼3.9 Hz), 6.91 (s, 1H), 5.68 (s, 1H), 3.71 (m,
4H), 2.65 (t, 2H, J¼7.8 Hz), 1.65 (m, 2H), 1.33 (m, 6H), 1.24 (s, 3H),
3.13. 5-(5-(5-(5,5-Dimethyl-1,3-dioxan-2-yl)thiophen-2-
yl)thiophen-2-yl)-1-(9,9-dimethylfluoren-2-yl)-2-
phenylindole (8)
0.88 (m, 3H), 0.80 (s, 3H). 13C{1H} NMR (CD3COCD3):
d 143.4, 141.9,
The product was synthesized according to the procedure as
140.9, 138.5, 138.2, 135.7, 130.7, 129.8, 128.1, 126.7, 125.9, 125.7,
125.6, 123.4, 123.2, 120.8, 117.9, 112.8, 112.5, 98.7, 77.7, 36.2, 32.4,
32.2, 30.6, 29.6, 23.2, 23.1, 21.8, 14.3. MS: m/z 555 [Mþ]. Anal. Calcd
for C34H37NO2S2: C, 73.47; H, 6.71. Found: C, 73.45; H, 6.59.
described above for synthesis of 3, giving a yellow solid of the
product 8 in 89% yield. Mp: 153 ꢁC. 1H NMR (CDCl3):
d 7.93 (s, 1H),
7.79 (d, 1H, J¼8.1 Hz), 7.76 (d, 1H, J¼8.1 Hz), 7.47–7.04 (m, 16H), 6.85
(s, 1H), 5.64 (s, 1H), 3.72 (m, 4H), 1.35 (s, 3H), 1.31 (s, 6H), 0.82 (s,
3H). 13C{1H} NMR (CDCl3):
d
154.9, 153.9, 142.9, 141.6, 140.1, 139.5,
3.18. 2-(4-Hexylphenyl)-5-(5-(5-(5,5-dimethyl-1,3-dioxan-2-
yl)thiophen-2-yl)thiophen-2-yl)-1-(9,9-dimethylfluoren-2-
yl)indole (12)
138.4,138.3,138.0,137.1,136.6,132.4,129.2,129.1,128.2,127.6,127.5,
127.2, 126.6, 125.9, 125.7, 125.6, 124.5, 122.9, 122.8, 122.6, 120.6,
120.2, 120.1, 110.5, 103.2, 98.3, 77.5, 46.9, 30.3, 26.9, 23.1, 21.9. MS:
m/z 663 [Mþ]. Anal. Calcd for C43H37NO2S2: C, 77.79; H, 5.62. Found:
C, 77.63; H, 5.57.
The product was synthesized according to the procedure as
described above for synthesis of 3, giving a yellow solid of the
product 12 in 80% yield. Mp: 125 ꢁC. 1H NMR (CDCl3):
d 7.91 (s, 1H),
3.14. 5-(5-(1-(9,9-Dimethylfluoren-2-yl)-2-phenylindol-5-
yl)thiophen-2-yl)thiophene-2-carbaldehyde (9)
7.79 (d,1H, J¼8.1 Hz), 7.75 (d,1H, J¼8.1 Hz), 7.48–7.35 (m, 6H), 7.23–
7.14 (m, 5H), 7.11 (s, 1H), 7.05 (d, 2H, J¼8.1 Hz), 7.03 (d, 2H,
J¼8.1 Hz), 6.81 (s, 1H), 5.63 (s, 1H), 3.71 (m, 4H), 2.53 (t, 2H,
J¼7.8 Hz), 1.53 (m, 2H), 1.34 (s, 6H), 1.30 (s, 3H), 1.26 (m, 6H), 0.86
The product was synthesized according to the procedure as
described above for synthesis of 4, giving an orange solid of the
(m, 3H), 0.81 (s, 3H). 13C{1H} NMR (CDCl3):
d 165.8, 154.8, 153.9,
product 9 in 94% yield. Mp: 184 ꢁC. 1H NMR (CDCl3):
d
9.87 (s, 1H),
145.3,142.5,142.1,139.7,138.9,138.5,138.4,138.1,137.2,135.5,129.7,
129.0, 128.9, 128.3, 127.6, 127.3, 127.1, 126.3, 125.9, 124.8, 122.8,
7.96 (s, 1H), 7.79 (d, 1H, J¼8.1 Hz), 7.76 (d, 1H, J¼8.1 Hz), 7.69 (d, 1H,

10424
D. Kim et al. / Tetrahedron 64 (2008) 10417–10424
120.8, 120.6, 120.2, 117.7, 111.1, 104.3, 103.3, 98.3, 77.5, 46.9, 35.7,
31.8, 31.4, 30.3, 29.0, 26.9, 23.1, 22.7, 21.9, 14.2. MS: m/z 747 [Mþ].
Anal. Calcd for C49H49NO2S2: C, 78.67; H, 6.60. Found: C, 78.61; H,
6.52.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2008.08.045.
3.19. 5-(5-(2-(4-Hexylphenyl)-1-(9,9-dimethylfluoren-2-
yl)indol-5-yl)thiophen-2-yl)thiophene-2-carbaldehyde (13)
References and notes
1. (a) O’Regan, B.; Gra¨tzel, M. Nature 1991, 353, 737; (b) Gra¨tzel, M. Nature 2001,
414, 338; (c) Yanagida, M.; Yamaguchi, T.; Kurashige, M.; Hara, K.; Katoh, R.;
Sugihara, H.; Arakawa, H. Inorg. Chem. 2003, 42, 7921; (d) Wang, P.; Klein, C.;
Humphry-Baker, R.; Zakeeruddin, S. M.; Gra¨tzel, M. J. Am. Chem. Soc. 2005,
127, 808.
2. (a) Hara, K.; Sato, T.; Katoh, R.; Furube, A.; Ohga, Y.; Shinpo, A.; Suga, S.; Sayama,
K.; Sugihara, H.; Arakawa, H. J. Phys. Chem. B 2003, 107, 509; (b) Hara, K.;
Kurashige, M.; Dan-oh, Y.; Kasada, C.; Shinpo, A.; Suga, S.; Sayama, K.; Arakawa,
H. New J. Chem. 2003, 27, 783; (c) Hara, K.; Sayama, K.; Ohga, Y.; Shinpo, A.;
Suga, S.; Arakawa, H. Chem. Commun. 2001, 569.
3. (a) Hara, K.; Kurashige, M.; Ito, S.; Shinpo, A.; Suga, S.; Sayama, K.; Arakawa, H.
Chem. Commun. 2003, 252; (b) Kitamura, T.; Ikeda, M.; Shigaki, K.; Inoue, T.;
Anderson, N. A.; Ai, X.; Lian, T.; Yanagida, S. Chem. Mater. 2004, 16, 1806; (c)
Hara, K.; Sato, T.; Katoh, R.; Furube, A.; Yoshihara, T.; Murai, M.; Kurashige, M.;
Ito, S.; Shinpo, A.; Suga, S.; Arakawa, H. Adv. Funct. Mater. 2005, 15, 246.
4. (a) Sayama, K.; Tsukagoshi, S.; Hara, K.; Ohga, Y.; Shinpo, A.; Abe, Y.; Suga, S.;
Arakawa, H. J. Phys. Chem. B 2002, 106, 1363; (b) Sayama, K.; Hara, K.; Mori, N.;
Satsuki, M.; Suga, S.; Tsukagoshi, S.; Abe, Y.; Sugihara, H.; Arakawa, H. Chem.
Commun. 2000, 2063.
The product was synthesized according to the procedure as
described above for synthesis of 4, giving an orange solid of the
product 13 in 95% yield. Mp: 161 ꢁC. 1H NMR (CDCl3):
d 9.86 (s, 1H),
7.94 (s, 1H), 7.79 (d, 1H, J¼7.5 Hz), 7.75 (d, 1H, J¼7.5 Hz), 7.68 (d, 1H,
J¼3.9 Hz), 7.49–7.31 (m, 6H), 7.28–7.24 (m, 3H), 7.18 (d, 2H,
J¼8.1 Hz), 7.11 (s, 1H), 7.04 (d, 2H, J¼8.1 Hz), 6.83 (s, 1H), 2.53 (t, 2H,
J¼7.5 Hz), 1.55 (m, 2H), 1.34 (s. 6H), 1.26 (m, 6H), 0.87 (m, 3H).
13C{1H} NMR (CDCl3):
d
182.6, 154.8, 153.9, 148.3, 147.9, 142.7, 142.4,
141.1, 138.7, 138.4, 138.3, 137.7, 137.1, 133.9, 129.5, 129.0, 128.9, 128.3,
127.7, 127.4, 127.3, 126.4, 126.3, 123.7, 123.2, 122.8, 122.7, 120.7,
120.6, 120.3, 118.0, 111.3, 103.4, 47.0, 35.7, 31.8, 31.4, 29.0, 26.9, 22.7,
14.2. MS: m/z 661 [Mþ]. Anal. Calcd for C44H39NOS2: C, 79.84; H,
5.94. Found: C, 79.75; H, 5.88.
5. (a) Yao, Q.-H.; Shan, L.; Li, F.-Y.; Tin, D.-D.; Huang, C.-H. New J. Chem. 2003, 27,
1277; (b) Wang, J.-S.; Li, F.-Y.; Huang, C. H. Chem. Commun. 2000, 2063.
6. (a) Horiuchi, T.; Miura, H.; Uchida, S. Chem. Commun. 2003, 3036; (b) Horiuchi,
T.; Miura, H.; Sumioka, K.; Uchida, S. J. Am. Chem. Soc. 2004, 126, 12218; (c)
Schmidt-Mende, L.; Bach, U.; Humphry-Baker, R.; Horiuchi, T.; Miura, H.; Ito, S.;
Uchida, S.; Gra¨tzel, M. Adv. Mater. 2005, 17, 813; (d) Ito, S.; Zakeeruddin, S. M.;
Humphry-Baker, R.; Liska, P.; Charvet, R.; Comte, P.; Nazeeruddin, M. K.; Pe´chy,
P.; Takada, M.; Miura, H.; Uchida, S.; Gra¨tzel, M. Adv. Mater. 2006, 18, 1202.
7. (a) Kim, S.; Lee, J. K.; Kang, S. O.; Ko, J.; Jum, J.-H.; Fantacci, S.; DeAngelis, F.; Di
Censo, D.; Nazeeruddin, M. K.; Gra¨tzel, M. J. Am. Chem. Soc. 2006, 128, 16701; (b)
Choi, H.; Baik, C.; Kang, S. O.; Ko, J.; Kang, M.-S.; Nazeeruddin, M. K.; Gra¨tzel, M.
Angew. Chem., Int. Ed. 2008, 47, 327; (c) Kim, S.; Choi, H.; Kim, D.; Song, K.; Kang,
S. O.; Ko, J. Tetrahedron 2007, 63, 9206; (d) Kim, S.; Choi, H.; Baik, C.; Song, K.;
Kang, S. O.; Ko, J. Tetrahedron 2007, 63, 11436.
3.20. 2-Cyano-3-(5-(5-(2-(4-hexylphenyl)-1-(9,9-dimethyl-
fluoren-2-yl)indol-5-yl)thiophen-2-yl)thiophen-2-yl)acrylic
acid (JK-79)
The product was synthesized according to the procedure as
described above for synthesis of JK-77, giving a red solid of the
product JK-79 in 85% yield. Mp: 260 ꢁC. 1H NMR (DMSO-d6):
d 8.05
(s, 1H), 8.01 (s, 1H), 7.95 (d, 1H, J¼7.2 Hz), 7.87 (d, 1H, J¼7.2 Hz), 7.65
(d, 1H, J¼3.9 Hz), 7.53–7.45 (m, 3H), 7.48 (d, 1H, J¼3.9 Hz), 7.42 (d,
1H, J¼3.9 Hz), 7.40–7.25 (m, 5H), 7.17 (d, 2H, J¼7.8 Hz), 7.07 (d, 2H,
J¼7.8 Hz), 6.90 (s, 1H), 2.47 (m, 2H), 1.46 (m, 2H), 1.29 (s, 6H), 1.19
8. Jung, I.; Lee, J. K.; Song, K. H.; Song, K.; Kang, S. O.; Ko, J. J. Org. Chem. 2007, 72,
3652.
(m, 6H), 0.80 (m, 3H). 13C{1H} NMR (DMSO-d6):
d 162.9,154.4,153.5,
145.5, 142.0, 141.7, 141.1, 139.6, 138.1, 137.7, 136.5, 135.9, 135.6, 133.5,
129.0, 128.7, 128.5, 128.4, 128.3, 128.1, 127.6, 127.2, 126.7, 126.2,
125.9, 123.9, 123.7, 122.8, 122.6, 120.9, 120.4, 119.5, 117.2, 111.1, 110.0,
103.2, 46.4, 34.7, 31.0, 30.7, 28.1, 26.3, 22.0, 13.9. MS: m/z 728 [Mþ].
Anal. Calcd for C47H40N2O2S2: C, 77.44; H, 5.53. Found: C, 77.28; H,
5.50.
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Acknowledgements
We are grateful to the Korea Science and Engineering Founda-
tion (KOSEF) through the National Research Lab. Program funded
by the Ministry of Science and Technology (No. R0A-2005-000-
10034-0) and BK-21 (2006). We also appreciate Jeonju University
for a financial support.