Novel conjugated organic dyes containing bis-dimethylfluorenyl amino phenyl thiophene for efficient solar cell

Article abstract of DOI:10.1016/j.tet.2007.06.061

Two novel organic dyes (JK-5 and JK-6) containing bis-dimethylfluorenyl amino phenyl thiophene and additional methine unit are synthesized. Nanocrystalline TiO₂ dye-sensitized solar cell was fabricated using these dyes. A solar-to-electric conv

Full text of DOI:10.1016/j.tet.2007.06.061

Tetrahedron 63 (2007) 9206–9212
Novel conjugated organic dyes containing bis-dimethylfluorenyl
amino phenyl thiophene for efficient solar cell
Sanghoon Kim,a Hyunbong Choi,a Duckhyun Kim,a Kihyung Song,b
a,
Sang Ook Kanga, and Jaejung Ko
*
*
aDepartment of Chemistry, Korea University, Jochiwon, Seochang 208, Chungnam 339-700, Republic of Korea
bDepartment of Chemistry, Korea National University of Education, Chongwon, Chungbuk 363-791, Republic of Korea
Received 23 April 2007; revised 14 June 2007; accepted 18 June 2007
Available online 23 June 2007
Abstract—Two novel organic dyes (JK-5 and JK-6) containing bis-dimethylfluorenyl amino phenyl thiophene and additional methine unit
are synthesized. Nanocrystalline TiO2 dye-sensitized solar cell was fabricated using these dyes. A solar-to-electric conversion efficiency of
5.12% and 4.78% is achieved with JK-5 and JK-6, respectively.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
the DSSCs is due to the sharp and narrow absorption band
of organic dyes. Therefore, the absorption spectra of organic
dyes must be broadened and red-shifted for efficient solar-
cell performance. One of the approaches to improve perfor-
mance of organic dyes would be to increase p-conjugation
by extending the methine unit into the framework of organic
dyes. Arakawa and co-workers11 reported that the introduc-
tion of methine unit into the coumarin framework (NKX-
2388) expanded the p-conjugation in the dye and resulted
in wide absorption in the visible region. These novel dyes
performed as efficient photosensitizers for DSSCs. Recently,
we12 reported the highly efficient and stable organic dyes
(JK-1 and JK-2) having bis-dimethylfluorenyl amino phenyl
donor unit with an overall conversion efficiency of 8.01%.
Dye-sensitized solar cells (DSSCs) present an important al-
ternative to current solar technology.1–4 These cells employ
mostly ruthenium polypyridyl complexes as charge-transfer
sensitizers. Until now only three polypyridyl ruthenium
complexes have achieved power conversion efficiencies
over 10% in standard air mass 1.5 sunlight.5 Some organic
dyes with rich photophysical properties are shown to be
promising sensitizers for nanocrystalline solar cells. Re-
cently, the solar-cell performance of DSSCs based on organic
dye photosensitizers has been remarkably improved, and
an impressive photovoltaic performance has been obtained
with some organic coumarin,6 indoline,7 oligoene,8 mero-
cyanine,9 and hemicyanine10 dyes having efficiencies in the
range of 5–9%. Nevertheless, many organic dyes have still
presented the low conversion efficiency. The major factor
for the low conversion efficiency of many organic dyes in
In order to improve the efficiency of such dyes, a wide
absorption range in the visible region for the sensitizers is
required. Accordingly, we envisioned that if we could
CN
N
N
S
S
S
COOH
CN
HOOC
JK-1
JK-2
Keywords: Organic dye; Dimethylfluorenyl amino unit; Methine unit; Solar cell.
* Corresponding authors. Tel.: +82 41 860 1337; fax: +82 41 867 5396; e-mail: jko@korea.ac.kr
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.06.061

S. Kim et al. / Tetrahedron 63 (2007) 9206–9212
9207
CN
N
N
S
S
S
COOH
CN
HOOC
JK-5
JK-6
Figure 1. Structure of the dyes JK-5 and JK-6.
introduce the –CH]CH– unit into the JK-1 and JK-2 frame-
work, the sensitizers would expand the conjugation in the
dyes resulting in a wide absorption in the visible region.
Here we report two new organic dyes (JK-5 and JK-6) con-
taining [bis(9,9-dimethylfluorene-2-yl)amino]benzene as
electron donor and cyano acrylic acid as electron acceptor
bridged by thiophene-vinylene units. The photovoltaic prop-
erties, electronic and optical properties of the two sensitizers
JK-5 and JK-6 are described (Fig. 1).
with methyltriphenylphosphonium iodide under Horner–
Emmons–Wittig reaction15 using potassium tert-butoxide in
THF led to intermediates 5 and 6. Subsequent Vilsmeier–
Haack reaction of 5 and 6 produced the aldehydes
3-{5-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-thiophene-
2-yl}acrylaldehyde 7 and 3-{50-[N,N-bis(9,9-dimethylfluor-
ene-2-yl)phenyl]-2,20-bisthiophene-5-yl}acrylaldehyde 8. The
aldehydes 7 and 8, on reaction with cyanoacetic acid in
the presence of a catalytic amount of piperidine in acetoni-
trile, produced the JK-5 and JK-6 dyes.
2. Results and discussion
Figure2showstheabsorptionandemissionspectraoftheJK-5
andJK-6sensitizersmeasuredinethanolandthedataarelisted
in Table 1. The absorption spectrum of JK-5 displays two
The novel organic dyes JK-5 and JK-6 were prepared by the
stepwise synthetic protocol illustrated in Scheme 1. New
dyes are readily synthesized in four steps according to mod-
ified procedures reported in the literature.13 Carbaldehydes 3
and 4 were prepared from 1 and 2 by a Vilsmeier–Haack
reaction.14 Coupling reaction of carbaldehydes 3 and 4
absorption maxima at 438 nm (3¼38,000 dm3 molꢀ1 cmꢀ1
)
and 362 (3¼84,000 dm3 molꢀ1 cmꢀ1), which are due to the
p–p* transitions of the conjugated molecule. Under similar
conditions the JK-6 sensitizer that contains two thiophene
units exhibits absorption peaks at 459 nm (3¼38,000 dm3
MePh3PI
POCl3
N
N
N
t
DMF
THF, KO Bu
S
S
S
n
COH
n
n
3 : n = 1
4 : n = 2
1 : n = 1
2 : n = 2
5 : n = 1
6 : n = 2
POCl3
DMF
NC
COOH
CN
COOH
N
N
MeCN, piperidine
S
S
COH
n
n
JK-5 : n = 1
JK-6 : n = 2
7 : n = 1
8 : n = 2
Scheme 1. Schematic diagram for the synthesis of organic dyes JK-5 and JK-6.

9208
3.0
S. Kim et al. / Tetrahedron 63 (2007) 9206–9212
3.0
2.5
2.0
1.5
1.0
0.5
0.0
that the red shift in the absorption owing to the introduction
of the methine unit can be attributed to positive shifts in the
reduction potentials of JK-5 and JK-6 rather than negative
shifts in the oxidation potentials.
2.5
2.0
1.5
1.0
0.5
0.0
In order to obtain the geometrical configuration and charac-
teristic features of the electronic structure, molecular orbital
calculations of JK-5 and JK-6 were performed with the TD-
DFT on B3LYP/3-21G*. The HOMO is delocalized over the
p-conjugated system via the amino phenyl unit, and LUMO
is delocalized over the cyanoacrylic unit through methine
units (Fig. 3). Examination of the HOMO and LUMO of
JK-5 and JK-6 indicates that HOMO–LUMO excitation
moved the electron distribution from the bis-dimethylfluor-
enyl amino phenyl unit to the vinylene cyanoacrylic acid
group. The change in electron distribution induced by photo-
excitation results in an efficient charge separation.
300
400
500
600
700
800
Wavelength (nm)
Figure 2. Absorption and emission spectra of JK-5 (solid line) and JK-6
(dotted line) in ethanol and absorption spectra of JK-5 (dashed line) and
JK-6 (dot-dashed line) absorbed on TiO2 film.
Figure 4 shows the incident monochromatic photon-to-cur-
rent conversion efficiency (IPCE) obtained with a sandwich
cell using 0.6 M 3-hexyl-1,2-dimethyl imidazolium iodide,
0.04 M iodine, 0.025 M LiI, 0.05 M guanidinium thiocya-
nate, and 0.28 M tert-butylpyridine in acetonitirle. The IPCE
for JK-5 reached about 70% at 480 nm, and JK-6 reached
about 58% at 450 nm. The IPCE spectrum of JK-6 is red-
shifted by about 20 nm compared to the JK-6 as a result
of extended p-conjugation, which is consistent with the ab-
sorption spectrum of JK-6. Photovoltaic performance of the
JK-5 and JK-6 sensitized cells is summarized in Table 1.
Under standard global AM 1.5 solar condition, an overall
conversion efficiency (h) of 5.12% for JK-5 and 4.78% for
JK-6 sensitized cells (for JK-5: short-circuit photocurrent
density, Jsc¼10.47 mA cmꢀ2; open-circuit voltage, Voc¼
molꢀ1 cmꢀ1) and 367 nm (3¼46,000 dm3 molꢀ1 cmꢀ1) that
are red-shifted relative to the absorptions of JK-5. The sensi-
tizers JK-5 and JK-6 induced bathochromatic shifts of the
absorption spectra compared to the peaks of JK-1 and JK-
2 due to the introduction of methine unit conjugated with
thiophene group. The absorption spectrum of JK-6 on TiO2
film is relatively broadened. Such broadening has been re-
ported in several organic dyes on TiO2 electrodes.16 When
the JK-5 sensitizer was absorbed on TiO2 electrode, a slight
blue shift from 438 nm to 432 nm was observed probably due
to the H-aggregation.17 We observedthat thesensitizers JK-5
and JK-6 exhibited strong luminescence maxima at 605 nm
and 631 nm, respectively, when they are excited within their
p–p* bands in an air-equilibrated solution at 298 K.
0.69 V; fill factor, ff¼0.71. For JK-6: Jsc¼10.52 mA cmꢀ2
;
Voc¼0.64 V; ff¼0.70) was obtained (Fig. 5). In the same
condition, the N719 sensitized cell gave a Jsc of
16.79 mA cmꢀ2, Voc of 0.75 V, and a fill factor of 0.63 cor-
responding to h of 7.98%. A slightly higher Voc of JK-5
compared to JK-6 suggests that the Voc and different dark
currents are caused by changing the band gap between the
conduction band of TiO2 electrode and redox couple of
Iꢀ/Iꢀ3 , resulting in reduced dark current. Of particular note
is that the efficiencies of JK-5 and JK-6 with more conjuga-
tion system are lower than those of JK-1 and JK-2. One of
the reasons for that is the photoisomerization, which is one
of the major decay pathways for methine dyes available
for the excited singlet in solvent such as acetonitrile. An-
other reason is that because the more conjugated organic
dyes with additional methine unit are more flexible on
TiO2 surface than that of rigid conjugated dyes, the flexible
The cyclic voltammogram of JK-5 on TiO2 film measured
in acetonitile containing 0.1 M tetrabutylammonium hexa-
fluorophosphate shows a quasi-reversible couple at 1.01 V
versus NHE, which is assigned to the oxidation of the
3-{5-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]. The sepa-
ration between the cathodic and anodic wave is 0.18 V.
Under identical experimental conditions JK-6 shows
a quasi-reversible wave at 0.99 V versus NHE with a separa-
tion of 0.20 V. The ELUMO of JK-5 and JK-6 calculated
from the redox potential and the energy at the intersection
point of absorption and emission spectra observed in solu-
tion are ꢀ1.04 V and ꢀ0.98 V. The positive shift of the re-
duction potential in JK-6 compared to that of JK-5 is
attributable to the extention of the p-conjugation. The
LUMO values of JK-5 and JK-6 are much positively shifted
compared to those of JK-1 and JK-2. This result suggests
Table 1. Optical, redox, and DSSC performance data of JK-5 and JK-6
b
,
d
,
Dye
labs,a nm (3, Mꢀ1 cmꢀ1
)
lem,a nm
Eox
V (DEp)
E0ꢀ0,c V
ELUMO
V
Jsc, mA cmꢀ2
Voc,
V
ff
h,e %
JK-5
JK-6
N719
438 (38,000); 362 (84,000)
459 (38,000); 367 (46,000)
605
631
1.01 (0.18)
0.99 (0.20)
2.05
1.97
ꢀ1.04
ꢀ0.98
10.47
10.52
16.79
0.69
0.64
0.75
0.71
0.70
0.63
5.12
4.78
7.98
3: absorption coefficient; Eox: oxidation potential; E0ꢀ0: voltage of intersection point between absorption and emission spectra.
Jsc: short-circuit photocurrent density; Voc: open-circuit photovoltage; ff: fill factor; h: total power conversion efficiency.
Absorption spectra were measured in ethanol solution.
a
Oxidation potential of dyes on TiO2 were measured in CH3CN with 0.1 M (n-C4H9)4NPF6 with a scan rate of 50 mV sꢀ1 (vs NHE).
E0ꢀ0 was determined from intersection of absorption and emission spectra in ethanol.
b
c
d
e
ELUMO was calculated by EoxꢀE0ꢀ0
.
Performances of DSSCs were measured with 0.18 cm2 working area.

S. Kim et al. / Tetrahedron 63 (2007) 9206–9212
9209
Figure 3. Isodensity surface plots of the HOMO and LUMO of (a) JK-5 and (b) JK-6.
conjugated organic dyes can lie on the neighboring TiO2 sur-
face and can affect the electronic state of band potential of
TiO2 conduction band, and these effects can reduce the elec-
tron injection efficiency from the excited state to TiO2 by fil-
tering effect. Thus Jsc and Voc of JK-5 and JK-6 may be
lower than those of JK-1 and JK-2 because of these reasons.
compared to those of JK-1 and JK-2 may be attributable
to the photoisomerization and dye aggregation. We believe
that the development of highly efficient organic dyes over
8% power conversion efficiency can be possible through
the more sophisticated structural modifications, and these
works are now in progress.
In summary, we have designed and synthesized two novel
organic dyes (JK-5 and JK-6) containing bis-dimethylfluor-
enyl amino phenyl thiophene moiety with methine unit in
order to understand the role of more conjugated system. The
power conversion efficiency of the DSSCs based on JK-5
and JK-6 sensitizers reaches 5.12% and 4.78%, respectively.
The lower power conversion efficiency of JK-5 and JK-6
3. Experimental section
3.1. General methods
All experiments were performed under a nitrogen atmo-
sphere in a Vacuum Atmospheres drybox or by standard
20
15
10
5
100
90
80
70
60
50
40
30
20
10
0
0
400
500
600
Wavelength (nm)
700
800
0.0
0.1
0.2
0.3
0.4 0.5
Voltage (V)
0.6
0.7
0.8
0.9
Figure 4. Spectra of monochromatic incident photon-to-current conversion
efficiencies (IPCEs) for DSSC based on spectra of JK-5 (dashed line), JK-6
(dotted line), and N719 (solid line).
Figure 5. A photocurrent voltage curve obtained with a DSSC based on
JK-5 (dashed line), JK-6 (dotted line), and N719 (solid line) under AM
1.5 radiation (100 mW cmꢀ2).

9210
S. Kim et al. / Tetrahedron 63 (2007) 9206–9212
Schlenk techniques. THF and toluene were distilled from so-
dium benzophenone. N,N-Dimethylformamide (DMF) and
acetonitrile were dried and distilled from CaH2. The
1H and 13C NMR spectra were recorded on a Varian Gemini
300 spectrometer operating at 300.00 MHz and 75.44 MHz,
respectively. The IR spectra were recorded on a Biorad FTS-
165 spectrometer. Mass spectra were recorded on a JEOL
JMS-SX102A instrument. Elemental analyses were per-
formed with a Carlo Erba Instruments CHNS-O EA 1108
analyzer. The absorption and photoluminescence spectra
were recorded on a Perkin–Elmer Lambda 2S UV–visible
spectrometer and a Perkin LS fluorescence spectrometer,
respectively. 2-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
thiophene,18 and 5-[N,N-bis(9,9-dimethylfluorene-2-yl)-
phenyl]-2,20-bithiophene18 were synthesized according to
procedures reported in the literature.
chromatography using a mixture of ethyl acetate and n-hex-
ane (1:10) as an eluent (yield 81%). 1H NMR (CDCl3,
300 MHz): d 9.87 (s, 1H), 7.72 (d, 1H), 7.67 (d, 2H), 7.64
(d, 2H), 7.57 (d, 2H), 7.41 (d, 2H), 7.36–7.33 (m, 3H),
7.31 (t, 2H), 7.28 (d, 1H), 7.25 (s, 1H), 7.20 (d, 2H), 7.15
(d, 2H), 1.43 (s, 12H). 13C{1H} NMR (CDCl3,
75.44 MHz): d 182.5, 155.4, 153.7, 149.4, 146.6, 141.3,
138.9, 137.9, 135.2, 134.7, 127.4, 127.2, 126.9, 123.9,
123.0, 122.9, 122.7, 120.9, 120.8, 119.7, 119.4, 47.0, 27.2.
MS: m/z 587.16 [M+]. Anal. Calcd for C41H33NOS: C,
83.78; H, 5.66. Found: C, 83.65; H, 5.52.
3.3.2. 50-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
2,20-bithiophene-5-carbaldehyde (4). The product was
synthesized according to the procedure as described above
1
for the synthesis of 3, giving product 4 in 82% yield. H
NMR (CDCl3, 300 MHz): d 9.86 (s, 1H), 7.67 (d, 1H),
7.66 (d, 1H), 7.62 (d, 2H), 7.50 (d, 2H), 7.40 (d, 2H),
7.34–7.33 (m, 3H), 7.30 (t, 2H), 7.29 (d, 1H), 7.25 (d, 2H),
7.22–7.18 (m, 4H), 7.13 (d, 2H), 1.36 (s, 12H). 13C{1H}
NMR (CDCl3, 75.44 MHz): d 182.6, 155.3, 153.7, 148.3,
147.6, 146.9, 146.4, 141.3, 138.9, 137.7, 134.8, 134.2, 127.4,
127.3, 127.2, 126.8, 126.7, 123.9, 123.6, 123.5, 123.3, 122.7,
120.8, 119.6, 119.1, 46.9, 27.1. MS: m/z 669.13 [M+]. Anal.
Calcd for C45H35NOS2: C, 80.68; H, 5.27. Found: C, 80.59;
H, 5.15.
3.2. Cyclovoltagram
Cyclic voltammetry was carried out with a BAS 100B (Bio-
analytical System, Inc.). A three-electrode system was used
and consisted of a gold disk, working electrode, and a plati-
num wire electrode. Redox potential of the dyes on TiO2 was
measured in CH3CN with 0.1 M (n-C4H9)4N–PF6 with
a scan rate of 50 mV sꢀ1
.
3.3. Fabrication and characterization of DSSC
3.3.3. 3-{5-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
thiophene-2-yl}acrylaldehyde (7). A mixture of 3
For the preparation of DSSC, a washed FTO (Pilkington,
8 U sqꢀ1) glass plate was immerged in 40 mM TiCl4 (aque-
ous) at 70 ꢁC for 30 min and washed with water and ethanol.
The first TiO2 layer of 13 mm thickness was prepared by
screen printing TiO2 paste (Solaronix, 13 nm anatase), and
the second scattering layer containing 400 nm sized anatase
particles (Catalysis & Chemicals Ind. Co. Ltd.) was depos-
ited by twice screen printing. The TiO2 electrodes were im-
mersed into JK-5 and JK-6 solutions (0.3 mM in ethanol
containing 3a,7a-dihydroxy-5b-cholic acid (10 mM) and
kept at room temperature for 18 h. Counter electrodes were
prepared by coating with a drop of H2PtCl6 solution (2 mg
of Pt in 1 mL of ethanol) on a FTO plate. The dye-absorbed
TiO2 electrode and Pt-counter electrode were assembled into
a sealed sandwich-type cell. A drop of electrolyte was then
introduced into the cell, which was composed of 0.6 M
3-hexyl-1,2-dimethyl imidazolium iodide, 0.04 M iodine,
0.025 M LiI, 0.05 M guanidinium thiocyanate, and 0.28 M
tert-butylpyridine in acetonitrile. The cells were measured
using 1000 W xenon light source, whose power of an
AM 1.5 Oirel 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 measure-
ments).
(0.41 g, 0.7 mmol), methyltriphenylphosphonium iodide
(0.35 g, 0.84 mmol), and potassium tert-butoxide (0.17 g,
0.84 mmol) in THF (20 mL) was stirred at 60 ꢁC for 2 h. Af-
ter extraction with methylene chloride (15 mL) and evapora-
tion of the solvent, 0.5 g of oily product 5 was obtained. To
the resulting 0.5 g of 5 in N,N-dimethylformamide (DMF)
was added phosphorous oxychloride (0.5 g, 0.12 mmol) at
0 ꢁC. The solution was warmed to room temperature and
stirred for additional 2 h. After removal of DMF in vacuo,
the reaction mixture was neutralized with sodium acetate
and extracted with methylene chloride. The crude product
was purified by column chromatography using a mixture
of ethyl acetate and n-hexane (1:10) as an eluent (yield
1
72%). H NMR (CDCl3, 300 MHz): d 9.63 (d, 1H), 7.67
(d, 2H), 7.63 (d, 2H), 7.54 (d, 1H), 7.52 (d, 2H), 7.41 (d,
2H), 7.32 (d, 2H), 7.30 (d, 2H), 7.28 (m, 3H), 7.19 (d, 2H),
7.14 (d, 2H), 6.50 (dd, 1H), 1.43 (s, 12H). 13C{1H} NMR
(CDCl3, 75.44 MHz): d 192.8, 155.4, 153.7, 149.3, 148.8,
146. 8, 138.9, 137.4, 135.1, 134.0, 127.2, 127.0, 126.8,
126.5, 124.1, 123.8, 126.5, 124.1, 123.8, 123.4, 122.6,
120.9, 119.3, 47.0, 27.2. MS: m/z 613.17 [M+]. Anal. Calcd
for C43H35NOS: C, 84.14; H, 5.75. Found: C, 84.11; H, 5.69.
3.3.4. 3-{50-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
2,20-bisthiophene-5-yl}acrylaldehyde (8). The product
was synthesized according to the procedure as described
above for the synthesis of 7, giving product 8 in 69% yield.
1H NMR (CDCl3, 300 MHz): d 9.62 (d, 1H), 7.66 (d, 2H),
7.62 (d, 2H), 7.53 (d, 1H), 7.50 (d, 2H), 7.39 (d, 2H), 7.31
(d, 2H), 7.29 (d, 2H), 7.27–7.24 (m, 4H), 7.19 (d, 2H), 7.18
(d, 2H), 7.12 (d, 2H), 6.47 (dd, 1H), 1.42 (s, 12H). 13C{1H}
NMR (CDCl3, 75.44 MHz): d 192.8, 155.4, 153.7, 149.9,
148.9, 146.8, 144.6, 141.9, 138.9, 137.5, 135.1, 133.9, 130.2,
127.2, 127.1, 126.9, 126.5, 124.2, 123.9, 123.4, 123.2, 122.7,
3.3.1. 5-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
thiophene-2-carbaldehyde (3). To 2-[N-,N-bis(9,9-dime-
thylfluorene-2-yl)phenyl]-thiophene (0.85 g, 1.52 mmol) in
N,N-dimethyl-formamide (DMF) was added phosphorous
oxychloride (0.17 mL, 1.82 mmol) at 0 ꢁC. The solution was
warmed to room temperature and stirred for additional 2 h.
After removal of DMF in vacuo, the reaction mixture was
neutralized with sodium acetate and extracted with methyl-
ene chloride. The crude product was purified by column

S. Kim et al. / Tetrahedron 63 (2007) 9206–9212
9211
€
Klein, C.; Humphry-Baker, R.; Zakeeruddin, S. M.; Gratzel,
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122.4, 120.9, 119.7, 119.3, 119.1, 47.0, 27.1. MS: m/z
695.19 [M+]. Anal. Calcd for C47H37NOS2: C, 81.11; H,
5.36. Found: C, 81.01; H, 5.29.
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3.3.5. 5-{5-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
thiophene-2-yl}-2-cyanopenta-2,4-dienoic acid (JK-5).
The resulting acrylaldehyde thiophene (0.25 g, 0.41 mmol)
and cyanoacetic acid (0.05 g, 0.61 mmol) were allowed to
react in acetonitrile in the presence of piperidine (0.02 mL,
0.21 mmol). The solution was refluxed for 6 h. After removal
of acetonitrile in vacuo, the crude product was extracted with
methylene chloride and water. The crude product was puri-
fied by column chromarography using methanol as an eluent
to give a red solid product 5-{5-[N,N-bis(9,9-dimethylfluor-
ene-2-yl)phenyl]-thiophene-2-yl}-2-cyanopenta-2,4-dienoic
acid (0.19 g, 0.28 mmol, yield 68%). Mp: 203 ꢁC. 1H NMR
(CD3OD-d4, 300 MHz): d 8.15 (s, 1H), 7.76 (d, 1H), 7.69 (d,
2H), 7.66 (d, 2H), 7.59 (d, 2H), 7.42 (d, 2H), 7.32 (d, 2H),
7.30 (d, 2H), 7.16 (d, 2H), 7.11–7.07 (m, 2H), 6.99 (d, 1H),
1.39 (s, 12H). 13C{1H} NMR (CD3OD-d4, 75.44 MHz): d
164.1, 154.9, 153.3, 148.5, 147.6, 146.3, 145.7, 139.0, 138.2,
136.8, 135.4, 134.4, 134.3, 132.5, 127.2, 126.9, 126.5, 124.1,
123.5, 122.8, 122.5, 121.3, 119.7, 119.5, 118.9, 118.2, 46.5,
26.7. MS: m/z 680.94 [M+]. Anal. Calcd for C46H36N2O2S:
C, 81.15; H, 5.33. Found: C, 80.88; H, 5.07.
4. Jang, S.-R.; Lee, C.; Choi, H.; Ko, J.; Lee, J.; Vittal, R.; Kim,
K.-J. Chem. Mater. 2006, 18, 5604.
5. (a) Nazeeruddin, M. K.; De Angelis, F.; Fantacci, S.; Selloni,
€
A.; Viscardi, G.; Liska, P.; Ito, S.; Takeru, B.; Gratzel, M.
J. Am. Chem. Soc. 2005, 127, 16835; (b) Nazeeruddin, M. K.;
ꢀ
Pechy, P.; Renouard, T.; Zakeeruddin, S. M.; Humphry-Baker,
R.; Comte, P.; Liska, P.; Cevey, L.; Costa, E.; Shklover, V.;
€
Spiccia, L.; Deacon, G. B.; Bignozzi, C. A.; Gratzel, M.
J. Am. Chem. Soc. 2001, 123, 1613.
6. (a) Hara, K.; Sayama, K.; Ohga, Y.; Shinpo, A.; Suga, S.;
Arakawa, H. Chem. Commun. 2001, 569; (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.; Miyamoto, K.; Abe, Y.; Yanagida, M. J. Phys.
Chem. B 2005, 109, 23776.
7. (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,
3.3.6. 5-{50-[N,N-Bis(9,9-dimethylfluorene-2-yl)phenyl]-
2,20-bisthiophene-5-yl}-2-cyanopenta-2,4-dienoic acid
(JK-6). The resulting acrylaldehyde bithiophene (0.26 g,
0.38 mmol) and cyanoacetic acid (0.05 g, 0.56 mmol) were
allowed to react in acetonitrile in the presence of piperidine
(0.02 mL, 0.19 mmol). The solution was refluxed for 6 h.
After removal of acetonitrile in vacuo, the crude product
was extracted with methylene chloride and water. The crude
product was purified by column chromarography using meth-
anol as an eluent to give a deep red solid product 5-{50-[N,
N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,20-bisthiophene-
5-yl}-2-cyanopenta-2,4-dienoic acid (0.16 g, 0.21 mmol,
€
S.; Uchida, S.; Gratzel, M. Adv. Mater. 2005, 17, 813; (d) Ito,
S.; Zakeeruddin, S. M.; Humphry-Baker, R.; Liska, P.;
ꢀ
Charvet, R.; Comte, P.; Nazeeruddin, M. K.; Pechy, P.;
Takada, M.; Miura, H.; Uchida, S.; Gratzel, M. Adv. Mater.
1
yield 55%). Mp: 207 ꢁC. H NMR (DMSO-d6, 300 MHz):
€
2006, 18, 1202.
d 8.09 (s, 1H), 7.76 (d, 2H), 7.74 (d, 2H), 7.67 (d, 2H), 7.62 (d,
2H), 7.49 (d, 2H), 7.46 (d, 2H), 7.33–7.29 (m, 3H), 7.27–7.24
(m, 4H), 7.09 (d, 2H), 7.05 (d, 2H), 6.74 (dd, 1H), 1.36 (s,
12H). 13C{1H} NMR (DMSO-d6, 75.44 MHz): d 163.7,
154.9, 153.2, 149.5, 147.3, 146.4, 145.1, 143.5, 139.2, 138.3,
135.9, 134.2, 134.1, 132.6, 130.4, 130.2, 127.2, 126.9, 126.8,
126.5, 125.0, 124.2, 123.3, 123.1, 122.8, 121.3, 119.7, 118.7,
117.7, 116.3, 46.5, 26.7. MS: m/z 762.63[M+]. Anal. Calcd for
C50H38N2O2S2: C, 78.71; H, 5.02. Found: C, 78.38; H, 4.91.
8. (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.
9. (a) Sayama, K.; Tsukagoshi, S.; Hara, K.; Ohga, Y.; Shinpou,
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, 1173.
Acknowledgements
10. (a) Yao, Q.-H.; Shan, L.; Li, F.-Y.; Yin, D.-D.; Huang, C.-H.
New J. Chem. 2003, 27, 1277; (b) Wang, Z.-S.; Li, F.-Y.;
Huang, C. H. Chem. Commun. 2000, 2063.
We are grateful to the KOSEF through National Research
Laboratory (No. M10500000034-06J0000-03410) program
and BK21 (2006).
11. 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, 597.
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