2D-π-A type organic dyes based on N,N-dimethylaryl amine and rhodamine-3-acetic acid for dye-sensitized solar cells

Article abstract of DOI:10.1002/cjoc.201190066

Three organic dyes XS17-19 based on N,N-dimethylaryl amine and rhodamine-3-acetic acid moieties are designed and synthesized. These dyes were applied into nanocrystalline TiO₂ dye-sensitized solar cells through standard operations, showing stro

Full text of DOI:10.1002/cjoc.201190066

FULL PAPER
2D-π-A Type Organic Dyes Based on N,N-Dimethylaryl Amine
and Rhodamine-3-acetic Acid for Dye-sensitized Solar Cells
Tang, Kaia(唐恺)
Liang, Maob(梁茂)
Liu, Yongkanga(刘永康)
Sun, Zheb(孙

)
Xue, Song*,b(薛松)
a Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, China
b Department of Applied Chemistry, Tianjin University of Technology, Tianjin 300384, China
Three organic dyes XS17— 19 based on N,N-dimethylaryl amine and rhodamine-3-acetic acid moieties are de-
signed and synthesized. These dyes were applied into nanocrystalline TiO2 dye-sensitized solar cells through stan-
dard operations, showing strong absorption bands at around 320— 650 nm, and exhibiting broad IPCE responses.
Cell based on XS17 gave a Jsc of 3.7 mA/cm2, an open circuit voltage of 550 mV, and a fill factor of 0.68, corre-
sponding to an overall conversion efficiency of 1.4%. The low overall conversion efficiency is due to the modest
IPCE and Voc values, which mainly stem from the acceptor of rhodanine-3-acetic acid.
Keywords dye-sensitized solar cell, photovoltaic, N,N-dimethylaryl amine, organic dyes
Introduction
Based on the above consideration, we have designed
and synthesized three new organic sensitizers XS17—
19 (Scheme 1), which consist of double N,N-dimethyl-
aryl amine moieties as electron-donating groups, as well
as diphenylvinyl moieties, which is a possible alterna-
tive to induce a red shift of the absorption spectrum and
to retain efficient light-induced charge separation.
Meanwhile, the thiophene and phenyl units act as
π-bridge to adjust the molecular energy levels of the
dyes, and rhodamine-3-acetic acid acts as electron ac-
ceptor. Here, we wish to report the synthesis, charac-
terization, and photovoltaic properties of these new or-
ganic dyes.
Dye-sensitized solar cells (DSSCs), which emerged
as a new generation photovoltaic device, have received
considerable attention in recent years because of their
high efficiency and low-cost since 1991.1 In these com-
ponents, dye is one of the key components for high
power conversion efficiencies. Until now, two kinds of
sensitizer, metal-organic complexes2,3 and metal-free
organic dyes,4-19 were developed for light harvesting. It
is of great interest to design and synthesize metal-free
organic dyes, owing to their high molar absorption co-
efficient, simple synthesis procedure and high efficiency,
although Ru complexes have achieved power conver-
sion efficiencies over 11% under AM 1.5 irradiation.20
Recently, organic dyes used for the DSSCs were devel-
oped rapidly, which indicated the promising perspective
of organic dyes for cells. Great effort has been made on
the design of new organic dyes in order to obtain excel-
lent sensitizers with high power conversion efficiency
and long-term stability.
Most organic sensitizers are constituted by donor,
conjugate bridge, and acceptor moieties, thereby form-
ing a D-π-A structure. Recently, organic dyes with
2D-π-A structure are reported by several groups.21-23
Their studies suggested that good performance of or-
ganic dyes based on 2D-π-A structure over the simple
D-π-A configuration could be achieved by molecular
design. The double donor moieties afforded organic
sensitizers with high electron-density of donor, which
resulted in enhanced molar extinction coefficient and
high overall power conversion efficiency.24
Results and discussion
The synthetic routes of the organic dyes XS17— 19
are shown in Scheme 2. Treatment of compound 1 with
n-BuLi and DMF gave an aldehyde 2. The target dye
XS17 was obtained via Knoevenagel condensation reac-
tion of the aldehyde 2 with rhodamine-3-acetic acid in
the presence of a catalytic amount of piperidine. The
aldehyde 4 was prepared from boronic acid 3 and
4-bromobenzaldehyde via Suzuki coupling reaction.
Treatment of phosphonate 5 with thiophene-2-carbal-
dehyde in the presence of t-BuOK gave intermediate 6.
Aldehyde 7 was prepared from 6 via bromonation reac-
tion with NBS and Suzuki reaction with 4-formylphen-
ylboronic acid. Subsequently, the Knoevenagel conden-
sation reactions of aldehydes 4 and 7 with rhoda-
mine-3-acetic acid gave the target dyes XS18 and XS19,
respectively.
*
E-mail: xuesong@ustc.edu.cn
Received June 29, 2010; revised August 31, 2010; accepted September 24, 2010.
Project supported by the National 863 Program (No. 2009AA05Z421) and the Tianjin Natural Science Foundation (No. 09JCZDJC24400).
Chin. J. Chem. 2011, 29, 89— 96
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FULL PAPER
Scheme 1 Structure of dyes XS17— 19
Scheme 2 Synthesis of organic dyes XS17— 19
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2D-π-A Type Organic Dyes for Dye-sensitized Solar Cells
The UV-vis and emission spectra of organic dyes in
chloroform solution are listed in Table 1. As shown in
Figure 1, the three dyes XS17— 19 show strong absorp-
tion bands at around 320—650 nm, and display two
visible bands, appearing at 374/500 nm, 388/444 nm
and 394/496 nm, respectively. The first absorption
bands for three dyes are similar, which are attributed to
the π-π* electron transition of the conjugated mole-
cule.25 However, the second absorption bands for three
dyes are obviously different from each other. To gain
insight into this optical properties, time-dependent DFT
(TDDFT) calculations of the excited states were per-
formed on the optimized model at the B3LYP/6-31G(d)
level in vacuo. The lowest 10 singlet-singlet electronic
transitions are calculated and the electronic states with
the largest oscillator strength (f) for the XS17—19 dyes
are HOMO→LUMO (f＝0.78, 2.22 eV), HOMO－2→
LUMO (f＝1.35, 2.98 eV) and HOMO→LUMO (f＝
0.94, 1.99 eV), respectively. The isodensity surface
plots of them are presented in Figure 2. For the XS17
and XS19, the HOMO is delocalized on the di-
phenylethene and phenyl; the LUMO is, on the other
hand, delocalized across the phenyl and rhodamine
group, with sizable contributions from the latter. The
second absorption band for XS17 and XS19 can be con-
sidered as an intramolecular charge transfer (ICT) tran-
sition excitation from HOMO to LUMO.26 In contrast,
the second absorption band for XS18 is significantly
blue-shifted compared to the XS17 and XS19. It can be
seen from the electronic states mentioned above as well.
The HOMO－2 of XS18 is delocalized throughout the
entire molecule, with maximum components on the two
phenyl rings that lies between rhodamine and di-
phenylethene; the LUMO is a single π* orbital delocal-
ized across the phenyl and rhodamine group, with simi-
lar contribution from the latter. The second absorption
band for XS18 might stem from the π→π* transition
from HOMO－2→LUMO. This excited energy of π→
π* transition is higher than that of ICT transition for
Figure 1 Absorption and emission spectra of dyes XS17— 19 in
chloroform (5× 10－ 5 mol/L).
Figure 2 Isodensity surface plots of the HOMO and LUMO of
XS17— 19.
XS17 and XS19, consequently, resulting in the blue
shift of the second absorption band for XS18. Interest-
ingly, according to the experimental absorption of XS17
—19, the ICT transition process are in the order of
XS17＞XS19＞XS18. Theoretical calculation suggests
that the ICT transition of XS17—19 is dependent on the
molecular geometry. The spacer in XS17 is shorter than
that of XS18—19, leading to an effective ICT transition
from the diphenylethene to rhodamine ring. In contrast,
the spacer for XS18—19 is too large for an effective
ICT transition. The only difference for XS18—19 is π
spacer, the former contains two phenyl units, the latter
contains a thiophene unit and a phenyl unit. The dihe-
dral angles of them are 43.4° and 22.0°, respectively.
Therefore, XS19 gave a more planar conjugating system
compared to XS18 because of the smaller torsion an-
gle,27 and favored the ICT transition.
Table 1 Optical properties and electrochemical properties of
the three dyes
Eredf/V
vs.
d
λmaxa/nm
λmaxb/ λintc/ E0-0
/
Eoxe/V
Dye
[ε/(L• mol－ 1• cm－ 1)] nm nm eV vs. NHE
NHE
374 (23875),
XS17
XS18
XS19
655 583 2.12
565 514 2.41
621 551 2.25
0.88
0.84
0.82
－
－
－
1.24
1.57
1.43
500 (37408)
388 (52852),
444 (37004)
394 (32224),
496 (21104)
It is found that the molar extinction coefficients (ε)
Absorption spectra, b emission spectron. c The intersect of the
normalized absorption and the emission spectra. E0-0 values
a
－
－
－
1
1
1
of three dyes (21104 L•mol •cm to 37408 L•mol •
d
－
1
cm ) are much higher than that of ruthenium com-
plexes, (N719 dye, 14100 L•mol－ •cm ), indicating
good ability for light harvesting. Figure 3 shows the
absorption spectra of XS17—19 anchored on transpar-
ent mesoporous TiO2 films (2 µm). The maximum
－
1
1
were calculated from intersect of the normalized absorption and
e
the emission spectra (λint): E0-0
＝
1240/λint. The oxidation poten-
tials (vs. NHE) of dyes were measured in CH3CN with tetrabu-
tylammonium perchlorate (TBAP, 0.1 mol/L) as supporting elec-
trolyte. f Ered was calculated from Eox－ E0-0
.
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Figure 3 Absorption spectra of dyes XS17— 19 on TiO2 film.
Figure 5 IPCE spectra for DSSCs based on XS17— 19.
absorption peaks are similar to the spectra of these dyes
in dichloromethane, but exhibit a slightly blue-shifted
and broad absorption compared to that in solution,
which may be ascribed to the formation of dye
H-aggregates on the TiO2 surface and/or the interaction
between the dyes and TiO2.28 When the dyes were ex-
cited within respective π-π* bands in an air-equilibrated
chloroform solution at 298 K, they exhibited strong lu-
minescence maximum of 450—750 nm.
provide sufficient driving forces for electron injection.
On the other hand, the HOMO levels for these dyes
(0.82 to 0.88 eV) are more positive than the iodine re-
dox potential (0.4 V vs. NHE).29 Thus, these oxidized
dyes can be regenerated from the reduced species in the
electrolyte to give an efficient charge separation.
The incident photon-to-current conversion efficiency
(IPCE) of DSSCs based on XS17—19 is measured in
the visible region (400—800 nm), as shown in Figure 5.
To prevent dye aggregation, 3 mmol/L chenodeoxy-
cholic acid (CDCA) was employed as a co-adsorbate.
The onsets of the IPCE spectra for the dye-based de-
vices are significantly broadened and red-shifted com-
pared to the absorption spectrum of the dyes absorbed
on TiO2.9,30 XS17 gives a higher IPCE value between
400 nm and 800 nm than the other two dyes in this se-
ries, with a highest value of 55% at 400 nm. The IPCE
values of XS19 based DSSCs with CDCA as coadsor-
bent showed improvement than that without CDCA,
implying the dye aggregation on the surface of TiO2
film. Unfortunately, the IPCE values for the three dyes
were modest, and resulted in low short-circuit photo-
current density.
Figure 6 shows the I-V curves for DSSCs based on
XS17 —19. The light-to-electricity conversion effi-
ciency (η) of the DSSCs under white-light irradiation
can be calculated from the shortcircuit photocurrent
density (Jsc), the open-circuit photovoltage (Voc), the fill
factor of the cell (ff): η＝Jsc×Voc×ff.6c The main
photovolataic parameters are listed in Table 2. The
DSSCs based on XS17 with 3 mmol/L CDCA as coad-
sorbent gave a Jsc of 3.7 mA/cm2, an open circuit volt-
age of 550 mV, and a fill factor of 0.68, corresponding
to an overall conversion efficiency of 1.4%. Under the
same conditions, the XS19 sensitized cell yields a η of
1.3%. The photovoltaic performance of XS17 is supe-
rior to that of XS18−19, which suggests that dye aggre-
gations aroused by the increasing number of π bridges
in turn decreased the photocurrent.
The oxidation potential (Eox) of as-synthesized dyes
was determined from square-wave voltammograms un-
der Ar atmosphere. The Eox corresponds to the highest
occupied molecular orbital (HOMO). The reduction
potential (Ered), which corresponds to the lowest unoc-
cupied molecular orbital (LUMO), can be calculated
from Eox－E0-0 (E0-0 values were calculated from λint:
E0-0＝1240/λint).13 As depicted in Figure 4, extension of
the conjugation length by adding thiophene unit or
phenyl unit adjusts the HOMO and the LUMO level of
these dyes. Negative shifts of the HOMO level (0.04 V)
and the LUMO level (0.33 V) can be observed for XS18
vs XS17, which broads the HOMO and LUMO gaps.
Also, this tendency holds for XS19 vs. XS17 due to the
extension of conjugation system by introduction of
thiophene unit. The LUMO levels for these dyes
(－1.23 to －1.57 eV) are more negative than the con-
duction band of TiO2 (－0.5 V vs. NHE), which will
Possible reasons for the low IPCE and Voc obtained
for DSSCs based on XS17—19 dyes are discussed as
follows. From the Figure 2, it can be found that the
electron density on the TiO2-binding oxygen in the
Figure 4 Schematic energy levels of XS17— 19 based on ab-
sorption and electrochemical data.
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Chin. J. Chem. 2011, 29, 89— 96

2D-π-A Type Organic Dyes for Dye-sensitized Solar Cells
iting. Therefore, I3− ions in electrolyte can easily pene-
trate the adsorbed dye layer, leading to fast electron re-
combination, and thus low photovoltages.32 In addition,
the dye aggregation on the TiO2 surface leading to
self-quenching can be ignored for low conversion effi-
ciency.7a
Conclusion
A new class of 2D-π-A type organic dyes based on
N,N-dimethylaryl amine for dye-sensitized solar cells is
designed. The three dyes XS17—19 show strong ab-
sorption bands at around 320—650 nm, and exhibit
broad IPCE responses, suggesting that the
N,N-dimethylaryl amine and diphenylvinyl moieties are
effective unit for constructing photosensitizer. Unfortu-
nately, devices based on XS17—19 dyes gave low
overall conversion efficiencies with modest IPCE and
Voc values, which mainly stem from the acceptor of rho-
danine-3-acetic acid. Cell based on XS17 gave a Jsc of
3.7 mA/cm2, an open circuit voltage of 550 mV, and a
fill factor of 0.68, corresponding to an overall conver-
sion efficiency of 1.4%. Further optimization of chemi-
cal structure of N,N-dimethylaryl amine will be done in
our next work.
Figure 6 Current-potential (I-V) curves for the DSSCs based on
XS17— 19 under AM 1.5 irradiation (100 mW•cm－ 2).
Table 2 Photovoltaic performance of DSSCs sensitized with
the four dyes a
Dye
Jsc/(mA•cm－
)
Voc/mV
550
FF
η/%
1.4
0.9
1.3
1.0
6.2
2
XS17
XS18
XS19
XS19b
3.7
2.5
3.3
2.5
12.3
0.68
0.67
0.69
0.73
0.68
539
559
535
N719b
711
a
Experimental
Photovoltaic performances of DSSCs were measured under
irradiation of AM 1.5 G simulated solar light (100 mW•cm－ 2) at
room temperature with a 0.16 cm2 working area. The thickness of
The FTO conducting glass (fluorine doped SnO2,
sheet resistance 10 Ω/square, transmission＞90% in the
visible) was obtained from Nippon Sheet Glass, Hyogo,
Japan, and cleaned by a standard procedure. All reac-
tions were conducted under nitrogen atmosphere in
oven-dried glassware with magnetic stirring. Dichloro-
methane was dried and freshly distilled from calcium
hydride under nitrogen atmosphere. Chromatographic
purification was performed on silica gel (100—200
mesh) and analytical thin layer chromatography (TLC)
on silica gel 60-F254, which was detected by fluores-
b
the TiO2 film was 9 µm. Chenodeoxycholic acid (3 mmol/L)
was not employed as co-adsorbate.
1
cence. H NMR (400 MHz) and 13C NMR (100 MHz)
spectra were measured with a Bruker AC 400 spec-
trometer using TMS as an internal standard. High reso-
lution mass spectra were obtained with a Micromass
GCT-TOF mass spectrometer. IR spectra were recorded
as thin films or as solids in KBr pellets on a
Perkin-Elmer FT210 spectrophotometer.
The absorption spectra of the dyes either in solution
or on the adsorbed TiO2 films were measured by HI-
TACHI U-3310 spectrophotometer. Adsorption of the
dye on the TiO2 surface was done by soaking the TiO2
electrode in a dry chlorof－orm solution of the dye (stan-
dard concentration 3×10 4 mol/L) at room temperature
for 24 h. Fluorescence measurement was carried with a
HITACHI F-4500 fluorescence spectrophotometer.
FT-IR spectra were obtained with a Bio-Rad FTS 135
FT-IR instrument.
Figure 7 Graphical illustration of the geometries of the ad-
sorbed dyes.
LUMO of XS17—19 is negligible. This could result in
lower electronic coupling between the dye and the
semiconductor and, thereby, slower electron injection
and also decrease the IPCE.31 On the other hand, the
value of Voc is dependent on the adsorption behavior of
these dyes. As shown in Figure 7, the three dyes exhibit
lying orientations on the TiO2 surface. This adsorption
geometry on TiO2 leaves the π-conjugated system open
to the electrolyte though bulky blocking moieties exhib-
Electrochemical measurements were performed at
room temperature under Ar atmosphere on a Voltam-
metric Analyzer (Metrohm, µAutolab III) with polymer
Chin. J. Chem. 2011, 29, 89— 96
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Tang et al.
FULL PAPER
coated ITO glass as the working electrode, and platinum
(Pt) plate as the counter electrode, using Ag/Ag ＋
(nonaqueous) electrode as reference electrode with a
scan rate of 50 mV/s. Tetrabutylammonium perchlorate
(TBAP, 0.1 mol/L) and acetonitrile were used as sup-
porting electrolyte and solvent, respectively. The meas-
urements were calibrated using ferrocene as standard.
The redox potential of ferrocene internal reference was
taken as 0.63 V vs. NHE.13 The solutions were purged
with argon and stirred for 15 min before the measure-
ments.
The photocurrent-voltage (I-V) characteristics of so-
lar cells were carried out using a Keithley 2400 digital
source meter controlled by a computer and a standard
AM1.5 solar simulator-Oriel 91160—1000 (300 W)
SOLAR SIMULATOR 2×2 BEAM. The active elec-
trode area was 0.16 cm2. The action spectra of mono-
chromatic incident photon-to-current conversion effi-
ciency (IPCE) for solar cells were performed by using a
commercial setup (QTest Station 2000 IPCE Measure-
ment System, CROWNTECH, USA).
this solution n-BuLi (0.42 mL, 2.7 mol/L in hexane,
1.134 mmol) was added dropwise through a dropping
funnel. The mixture was stirred at this temperature for 2
h before DMF (0.32 mL, 4.0 mmol) dissolved in 10 mL
of dry THF was added in a dropwise manner. The solu-
tion was allowed to warm to room temperature and
stirred for 12 h. The reaction was quenched with satu-
rated NH4Cl, extracted with chloroform and dried over
MgSO4. After filtration and removal of the solvent un-
der vacuum, the product was purified by a silica gel
column [V(petroleum)∶V(ethyl acetate)＝3∶1 as elu-
ent] to give a yellow product (260 mg, 70% yield). m.p.:
1
178—180 ℃; H NMR (CDCl3, 300 MHz) δ: 9.81 (s,
1H), 7.57 (d, J＝8.4 Hz, 2H), 7.21 (d, J＝8.7 Hz, 2H),
7.13 (d, J＝8.4 Hz, 2H), 7.01 (d, J＝8.7 Hz, 2H), 6.70
(s, 1H), 6.62 (d, J＝8.7 Hz, 2H), 6.61 (d, J＝8.7 Hz,
2H), 2.94 (s, 6H), 2.93 (s, 6H); 13C NMR (75 MHz,
CDCl3) δ: 191.8, 150.6, 150.2, 146.8, 145.7, 133.6,
131.6, 129.7, 129.6, 129.3, 127.8, 122.4, 112.3, 111.9,
40.5; IR (－KBr) ν: 3430, 3041, 2802, 2728, 1691, 1608,
1582 cm 1; HRMS(EI) calcd for C25H26N2O (M)＋
370.2045, found 370.2049.
TiO2 colloid was prepared according to the litera-
ture,33 which was used for the preparation of the
nanocrystalline films. The TiO2 paste consisting of 18
wt% TiO2, 9 wt% ethyl cellulose and 73 wt% terpineol
was firstly prepared, which was printed on a conducting
glass using a screen printing technique. The thickness of
the TiO2 film was controlled by selection of screen
mesh size and repetition of printing. The film was dried
in air at 120 ℃ for 30 min and calcined at 500 ℃ for
30 min under flowing oxygen before cooling to room
temperature. The heated electrodes were impregnated
with a 0.05 mol/L titanium tetrachloride solution in a
water-saturated desiccator at 70 ℃ for 30 min and then
recalcined at 500 ℃ for 30 min. The as-prepared TiO2
electrode was stained by immersing it into a dye solu-
tion containing 300 µmol/L dye sensitizers and 3
mmol/L chenodeoxycholic acid (CDCA) in a mixture of
chloroform and methanol (volume ratio 10/1) for 24 h.
The CDCA was employed as a coadsorbate to prevent
dye aggregations on the TiO2 surface. Pt catalyst was
deposited on the FTO glass by coating with a drop of
H2PtCl6 solution (40 mmol/L in ethanol) with the heat
treatment at 395 ℃ for 15 min to give photoanode.
The photocathode (the dye-deposited TiO2 film) was
placed on top of the counter electrode and was tightly
clipped together to form a cell. Electrolyte was then
injected into the seam between two electrodes. The
electrolyte employed was a solution of 0.6 mol/L
1,2-dimethyl-3-n-propylimidazolium iodide (DMPImI),
0.1 mol/L LiI, 0.05 mol/L I2, and 0.5 mol/L tertbu-
tylpyridine in acetonitrile.
(5-(1-(4-(2,2-Bis-(4-dimethylamino-phenyl)-
vinyl)-phenyl)-meth-ylidene)-4-oxo-2-thioxo-thiazo-
lidin-3-yl) acetic acid (XS17) To a solution of com-
pound 2 (279 mg, 0.75 mmol) and rhodamine-3-acetic
acid (150 mg, 0.78 mmmol) in absolute ethanol (15 mL)
was added piperidine (50 µL). The solution was re-
fluxed for 24 h. After cooling the solution, the solvent
was removed in vacuo. The pure product was obtained
by silica gel chromatography [V(CHCl3)∶V(MeOH)＝
10∶1 as eluent] as a wine powder (363 mg, 89% yield).
1
m.p.: 153—154 ℃; H NMR (DMSO-d6, 300 MHz) δ:
7.68 (s, 1H), 7.38 (d, J＝8.4 Hz, 2H), 7.18—7.13 (m,
4H), 6.95 (d, J＝8.7 Hz, 2H), 6.79 (s, 1H), 6.74—6.66
(m, 4H), 4.46 (s, 2H), 2.95 (s, 6H), 2.92 (s, 6H); 13C
NMR (DMSO-d6, 75 MHz) δ: 193.6, 167.7, 167.4,
150.9, 150.5, 146.1, 142.1, 133.2, 131.4, 131.2, 130.8,
130.3, 129.2, 127.5, 122.2, 121.6, 112.9, 112.4, 47.8,
44.－2; IR (KBr) ν: 3750, 3648, 2358, 2342, 1608, 151＋9
1
cm ; HRMS (ESI) calcd for C30H29N3O3S2 (M＋H)
544.1723, found 544.1731.
4'-(2,2-Bis-(4-dimethylamino-phenyl)-vinyl)-bi-
phenyl-4-carbaldehyde (4) A mixture of
4-bromobenzaldehyde (162 mg, 0.84 mmol), 4-(2,2-
bis(4-(dimethylamino)phenyl)vinyl)phenylboronic acid
(3) (216 mg, 0.56 mmol), Pd(PPh3)4 (50 mg, 0.042
mmol), aqueous 1 mol/L Na2CO3 (3 mL), and 10 mL
DME was refluxed for 18 h under Ar. Ethyl acetate was
added before cooling down to room temperature. The
organic layer was separated and washed 3 times with
water, dried over anhydrous MgSO4, and filtered. After
removing the solvent, the resulting solid was purified by
column chromatography on silica gel (petroleum∶ethyl
acetate＝10∶1 as eluent) as a yellow powder (332 mg,
The detailed experimental procedures and
characterization data
1
4-(2,2-Bis(4-(dimethylamino)phenyl)vinyl)benz-
aldehyde (2) A solution of compound 1 (421 mg, 1.0
mmol) in dry THF (10 mL) was cooled to －78 ℃. To
62 % yield). m.p.: 114—116 ℃; H NMR (CDCl3, 400
MHz) δ: 10.03 (s, 1H), 7.72 (d, J＝8.4 Hz, 2H), 7.44 (d,
J＝8.4 Hz, 2H), 7.27 (d, J＝8.4 Hz, 2H), 7.18 (d, J＝
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2D-π-A Type Organic Dyes for Dye-sensitized Solar Cells
8.4 Hz, 2H), 7.12—7.10 (m, 4H), 6.78 (s, 1H), 6.70 (d,
J＝8.4 Hz, 2H), 6.68 (d, J＝8.4 Hz, 2H), 3.00 (s, 6H),
2.98 (s, 6H); 13C NMR (CDCl3, 100 MHz) δ: 191.9,
150.3, 149.9, 147.1, 144.1, 139.4, 136.4, 134.9, 132.2,
131.5, 130.3, 129.9, 128.9, 128.4, 127.2, 126.8, 122.9,
112.4, 112.0, 40.6; IR (KBr) ν: 3449, 3072, 3027, 2952,
4-formylphenyl-boronic acid according to the procedure
for compound 4, giving an orange powder of the prod-
1
uct (289 mg, 32% yield). m.p.: 103—104 ℃; H NMR
(CDCl3, 400 MHz) δ: 9.96 (s, 1H), 7.81 (d, J＝8.4 Hz,
2H), 7.58 (d, J＝8,4 Hz, 2H), 7.29—7.25 (m, 3H), 7.17
(d, J＝8.4 Hz, 2H), 7.09 (s, 1H), 6.90—6.85 (m, 3H),
6.69 (d, J＝8.8 Hz, 2H), 3.07 (s, 6H), 2.99(s, 6H); 13C
NMR (CDCl3, 100 MHz) δ: 40.4, 40.6, 112.0, 113.0,
116.6, 124.6, 125.4, 128.6, 130.3, 130.7, 131.1, 134.5,
140.5, 140.6, 142.4, 145.1, 150.1, 150.6, 191.3; IR (KBr)
ν: 3764, 3648, 2358, 1700, 1597, 1520, 1336, 1201, 81＋7
－1
2801, 1698, 1607, 1590 cm ; HRMS (EI) calcd for
C31H30N2O (M＋) 446.2358, found 446.2361.
(5-(1-(4-(2,2-Bis-(4-dimethylamino-phenyl)vinyl)-
phenyl)-methylidene)-4-oxo-2-thioxo-thiazolidin-3-yl)
acetic acid (XS18) The product was synthesized ac-
cording to the procedure for synthesis of XS17, giving a
wine powder of the product in 65% yield. m.p.: 165—
168 ℃; 1H NMR (DMSO-d6, 300 MHz) δ: 7.90 (s, 1H),
7.85 (d, J＝8.4 Hz, 2H), 7.69 (d, J＝8.7 Hz, 2H), 7.56
(d, J＝8.4 Hz, 2H), 7.18—7.14 (m, 4H), 6.96 (d, J＝8.4
Hz, 2H), 6.80—6.66 (m, 5H), 4.71 (s, 2H), 2.94 (s, 6H),
2.91 (m, 6H); 13C NMR (DMSO-d6, 75 MHz) δ: 193.7
167.9, 167.1, 150.7, 150.3, 143.9, 142.6, 139.3, 136.1,
134.2, 134.1, 132.2, 132.1, 131.6, 131.3, 130.2, 128.9,
128.0, 122.7, 121.9, 112.9, 112.5, 45.8, －40.6; IR (KBr) ν:
－1
cm ; HRMS (ESI) calcd for C29H28N2OS (M＋H)
453.1995, found 453.1990.
(5-(1-(4-(5-(2,2-Bis-(4-dimethylamino-phenyl)-
vinyl)-thiophen-2-yl)-phenyl)-methylidene)-4-oxo-2-
thioxo-thiazolidin-3-yl)-acetic acid (XS19) The
product was synthesized according to the procedure for
synthesis of XS17, giving a wine powder of the product
1
in 81% yield. m.p.: 168—170 ℃; H NMR (DMSO-d6,
400 MHz) δ: 7.70—7.30 (m, 6H), 7.16—7.13 (m, 4H),
7.01—6.99 (m, 3H), 6.85 (d, J＝8.4 Hz, 2H), 6.66 (d,
J＝8.4 Hz, 2H), 4.43 (s, 2H), 2.99 (s, 6H), 2.91 (s, 6H);
13C NMR (DMSO-d6, 100 MHz) δ: 193.4, 169.1, 167.3,
150.8, 150.4, 144.3, 141.9, 140.5, 136.5, 134.7, 131.9,
131.1, 130.0, 129.9, 128.2, 128.0, 126.7, 125.8, 122.2,
121.2, 113.3, 112.4, 46.6, 44－.0; IR (KBr) ν: 3734, 3648,
1
3674, 3545, 2358, 2342, 1558, 1507＋cm ; HRMS (ESI)
calcd for C36H33N3O3S2 (M＋H) 620.2036, found
620.2031.
4-(1-(4-(dimethylamino)phenyl)-2-(thiophen-2-
yl)vinyl)-N,N-dimethylbenzenamine (6) To a sus-
pension of diethyl bis(4-(dimethylamino) phenyl)
methylphosphonate (5) (1.5g, 3.6 mmol) in 20 mL dry
THF at 0 ℃ under Ar, t-BuOK (600 mg, 5.4 mmol) was
added and the mixture turned yellow. The mixture was
stirred at this temperature for 1 h before thiophene-2-
carbaldehyde (336 mg, 3 mmol) dissolved in 10 mL dry
THF was added dropwise. The mixture was stirred at 0
℃ for 1 h and moved into room temperature for another
12 h. Saturated NH4Cl was added and the resulting
mixture was extracted with EtOAc (20 mL×3). The
combined extracts were washed with water and dried
over MgSO4. After filtration and removal of the solvent
under vacuum, the crude product was purified by col-
umn chromatography to give a yellow product in 44%
yield. m.p.: 147—149 ℃; 1H NMR (CDCl3, 300 MHz)
δ: 7.26—7.23 (m, 2H), 7.13—7.10 (m, 3H), 6.96—6.95
(m, 1H), 6.90—6.89 (m, 1H), 6.86—6.79 (m, 3H), 6.65
(d, J＝5.1 Hz, 2H), 3.02 (s, 6H), 2.94 (s, 6H); 13C NMR
(CDCl3, 75 MHz) δ: 150.5, 150.1, 143.1, 140.7, 131.5,
131.2, 128.1, 127.7, 126.2, 125.0, 117.4, 113.1, 112.3,
40.8; IR (KBr) ν: 3800, 3566, 2359, 1610, 1521, 135＋2
1
2358, 2342, 1608, 1558 cm ; HRMS (ESI) calcd for
C34H31N3O3S3 (M－H)＋ 624.1580, found 624.1589.
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Chin. J. Chem. 2011, 29, 89— 96