Synthesis and characterization of D-D-π-A-Type organic dyes bearing carbazole-carbazole as a donor moiety (D-D) for efficient dye-sensitized solar cells

Article abstract of DOI:10.1002/ejoc.201300373

A series of new D-D-π-A-type organic dyes - CCTnA (n = 1-3), CCT3N and CCT2PA, bearing the 3-(3′,6′-di-tert-butylcarbazol-N′-yl)-N- dodecylcarbazol-6-yl system as an electron donor moiety (D-D) - were synthesized by convenient methods and successfully uti

Full text of DOI:10.1002/ejoc.201300373

Job/Unit: O30373
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Pages: 14
FULL PAPER
D–D–π–A Type Organic Dyes
New organic dyes based on the carbazole–
carbazole system as a donor moiety show
great abilities as sensitizers in dye-sensi-
tized solar cells, with overall conversion ef-
ficiencies reaching Ͼ96% of that of the ref-
erence N719-based device.
T. Sudyoadsuk, S. Pansay, S. Morada,
R. Rattanawan, S. Namuangruk,
T. Kaewin, S. Jungsuttiwong,
V. Promarak* .................................. 1–14
Synthesis and Characterization of D–D–π–
A-Type Organic Dyes Bearing Carbazole–
Carbazole as a Donor Moiety (D–D) for
Efficient Dye-Sensitized Solar Cells
Keywords: Dyes / Dye-sensitized solar cell /
Sensitizers / Photochemistry / Energy con-
version / Oligothiophenes
0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Job/Unit: O30373
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V. Promarak et al.
FULL PAPER
DOI: 10.1002/ejoc.201300373
Synthesis and Characterization of D–D–π–A-Type Organic Dyes Bearing
Carbazole–Carbazole as a Donor Moiety (D–D) for Efficient Dye-Sensitized
Solar Cells
[
a]
[a]
[a]
Taweesak Sudyoadsuk, Sakravee Pansay, Somphob Morada,
[
a]
[b]
[a]
Rattanawalee Rattanawan, Supawadee Namuangruk, Tinnagon Kaewin,
[a]
[c]
Siriporn Jungsuttiwong, and Vinich Promarak*
Keywords: Dyes / Dye-sensitized solar cell / Sensitizers / Photochemistry / Energy conversion / Oligothiophenes
A series of new D–D–π–A-type organic dyes – CCTnA (n =
–3), CCT3N and CCT2PA, bearing the 3-(3Ј,6Ј-di-tert-butyl-
timal incident photon-to-current conversion efficiencies
(IPCEs) exceeding 80%. The devices containing oligothio-
1
carbazol-NЈ-yl)-N-dodecylcarbazol-6-yl system as an elec- phene bridging groups performed better than those with
tron donor moiety (D–D) – were synthesized by convenient
methods and successfully utilized as dye sensitizers for dye-
oligothiophene-phenylene bridging groups. Of solar cells
based on these dyes, the CCT3A-based one gave a maximum
sensitized solar cells (DSSCs). The central π-conjugated brid- IPCE value of 84%, a short-circuit photocurrent density (Jsc
)
–
2
ges were made of oligothiophene and oligothiophene-phen-
ylene units, whereas the acceptor groups were either cyano-
acrylic acid or cyanoacrylamide. Detailed investigation into
the relationship between the structures, spectral and electro-
chemical properties, and performances of the DSSCs is de-
scribed. The DSSC devices performed remarkably well, with
typical overall conversion efficiencies of 3.60–5.69%, and op-
of 11.31 mAcm , an open-circuit voltage (Voc) of 0.71 V and
a fill factor (FF) of 0.71, corresponding to an overall conver-
sion efficiency (η) of 5.69% (Ͼ96% of that of the reference
N719-based cell, η = 5.92%). This work suggests that the or-
ganic dyes based on donor moieties or donor molecular
architectures of this type are promising candidates for im-
provement of the performances of DSSCs.
sorption intensity.[2,4] Enormous effort is also being dedi-
cated to the development of new and efficient dyes featuring
Introduction
Dye-sensitized solar cells (DSSCs) have attracted con- modest cost, ease of synthesis and modification, large mo-
[
5]
siderable, sustained attention because they offer the pos- lar extinction coefficients, and long-term stability.
sibility of low-cost conversion of photoenergy.[1] To date,
Ru-free organic dyes meet all of these criteria. Although
remarkable progress has been made in the use of organic
dyes as sensitizers for DSSCs, with efficiencies exceeding
DSSCs with validated efficiency records of Ͼ11% have
[2]
been obtained with Ru complex dyes. More recently, a
2
[
6]
17 cm DSSC submodule consisting of eight parallel cells
1
1% having been achieved, the optimization and simplifi-
and displaying a conversion efficiency of Ͼ9.9% was fabri-
cation of their chemical structures for further improvements
in performance is still needed. In terms of electronic struc-
ture, the LUMO energy level of a dye has to be higher than
[
3]
cated by Sony. Although there is still room for efficiency
improvement in Ru-based DSSCs, Ru dyes are costly, diffi-
cult to produce and normally display only moderate ab-
the energy of the conductive band (CB) of a TiO electrode
2
for efficient electron injection, whereas the LUMO energy
–
level of the dye has to be lower than the iodide/triiodide (I /
[
a] Department of Chemistry and Center of Excellence for
Innovation in Chemistry, Faculty of Science, Ubon Ratchathani
University,
–
I ) redox potential for oxidation and regeneration of dye,
3
respectively. Additionally, a high absorption coefficient over
a wide range of visible light wavelength is required for light-
harvesting efficiency.
Ubon Ratchathani, 34190 Thailand
[
[
b] National Nanotechnology Center (NANOTEC),
1
30 Thailand Science Park, Klong Luang, Pathumthani 12120
Thailand
In terms of molecular structure, avoidance of unfavour-
in Chemistry, Institute of Science, Suranaree University of able aggregation of dyes is also necessary to achieve high
c] School of Chemistry and Center of Excellence for Innovation
Technology,
efficiency. π–π Aggregation can lead not only to self-
quenching and reduction of electron injection into TiO ,
2
but also to instability of the organic dye, due to the forma-
tion of excited triplet states and unstable radicals under
light irradiation conditions. Stability of the dye in its ex-
Nakhon Ratchasima, 30000 Thailand
Fax: +66-44224648
E-mail: pvinich@sut.ac.th
pvinich@gmail.com
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201300373.
[
7]
2
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Organic Dyes for Efficient Dye-Sensitized Solar Cells
Figure 1. Molecular structures of the designed dyes.
cited and ionized states is important for efficiency and du- transport capabilities and have become classic hole-trans-
[
13]
rability. These requirements occasionally seem to conflict porting materials. Moreover, the bulky, nonplanar struc-
with one another other; great flexibility in molecular design ture of this carbazole–carbazole (D–D) moiety might prove
is therefore essentially important. Organic dyes constructed valuable for solving the intractable problem of the close π–
out of donor (D), π-conjugation and acceptor (A) moieties π aggregation of the dye molecules. Both the 3,6-di-tert-
offer such design flexibility, and broad ranges of conversion butyl and the N-dodecyl substituents can not only provide
efficiencies have been achieved by using D–π–A struc- the solubility of the dye, but can also form a hydrophobic
[
6,8]
tures.
Most of the organic dyes used for highly efficient blocking layer on the TiO surface to suppress the approach
2
–
–
DSSCs have long π-conjugated spacers between D and A; of I /I3 in the electrolyte to the TiO , consequently leading
2
however, introduction of long π-conjugation segments re- to improvement of the short-circuit photocurrent density
[
14]
sults in prolonged, rod-like molecules, which can facilitate (J ).
The use of either cyanoacrylic acid or cyanoacryl-
sc
–
the recombination of the electrons with I and magnify amide as electron-accepting and anchoring groups (A) was
3
aggregation between molecules.[
7,9]
investigated, as well as the use of either oligothiophene or
Because of such findings, organic dyes with 2D–π–A oligothiophene-phenylene systems as π-spacers (π) linking
structures, in which two D moieties are connected to a π- the two functional moieties. Here we report in detail the
spacer, have recently been reported.[ These studies sug- synthesis and physical and photophysical properties of
gested that organic dyes with 2D–π–A structures might these carbazole–carbazole-based dyes. In addition, their
achieve better performances than those with the simple D– properties as dye sensitizers in DSSCs in comparison with
π–A structures. We have recently reported on a set of new, dyes N719 and CCTT3A, which contains bis(3,6-di-tert-
simple 2D–D–π–A-type organic dyes (CCTT3A) containing butylcarbazol-9-ylphenyl)aniline as donor moiety (2D–D),
10]
a
bis(3,6-di-tert-butylcarbazol-9-ylphenyl)aniline donor are also reported.
[
11]
moiety (2D–D). These dyes showed significant bathoch-
romic shifts (50–79 nm) in their ICT peaks, relative to a
simple D–π–A-type organic dye, together with increases in
the ε values (1.45–1.48 fold). Their DSSC devices exhibited
Results and Discussion
larger short-circuit photocurrent densities (J ) and higher
overall conversion efficiencies (η) than a solar cell based on
a D–π–A dye. However, the efficiencies of these DSSCs
sc
Synthesis and Characterization
The dye molecules were synthesized as outlined in
were somewhat lower than that of the reference N3-based Scheme 1. Firstly, the key intermediate 6-bromo-3-(3Ј,6Ј-di-
device. tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazole (3) was syn-
In this work we therefore report on our further structural thesized by Ullmann coupling between 3,6-di-tert-butyl-
[
15]
modification of 2D–D–π–A-type organic dyes in the form carbazole (1)
and 3,6-dibromo-N-dodecylcarbazole
of D–D–π–A-type organic dyes (Figure 1). In our design, (2), themselves obtained by alkylation of carbazole with
the 3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarb- tert-butyl chloride and by direct bromination of N-dodecyl-
azol-6-yl system is employed as an electron donor moiety carbazole with NBS/THF, respectively. A stoichiometric re-
D–D). Many groups have recently reported that DSSCs action between 2 (4 equiv.) and 1 (1 equiv.) in the presence
[
16]
(
based on carbazole-based dyes have shown η values of up of a catalytic system involving CuI as catalyst, (Ϯ)-trans-
to 9.1%, indicating the importance of their further investi- 1,2-diaminocyclohexane as co-catalyst and K PO as base
3
4
[
12]
gation in DSSCs. In addition, carbazole derivatives have in toluene afforded intermediate 3 in a moderate yield of
stimulated great interest because of their excellent hole- 77%.
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Scheme 1. Synthesis of the designed organic dyes.
From 3, the intermediates 6-(5-bromothiophen-2-yl)-3- phenylboronic acid yielded the benzaldehyde 11 in a 91%
3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazole (5) yield.
(
and 6-(5Ј-bromo-2,2Ј-bithiophen-5-yl)-3-(3Ј,6Ј-di-tert-but-
Final Knoevenagel condensation of these aldehydes with
ylcarbazol-NЈ-yl)-N-dodecylcarbazole (7) were synthesized 2-cyanoacetic acid in the presence of a catalytic amount of
in an iterative manner by combinations of Suzuki cross- piperidine in CHCl at reflux for 18 h (Scheme 1) gave the
3
coupling and bromination reactions. Suzuki cross-coupling desired cyanoacrylic acid dyes (E)-3-{2-[3-(3Ј,6Ј-di-tert-but-
with thiophene-2-boronic acid catalysed by Pd(PPh ) / ylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]thiophen-5-yl}-2-
3
4
Na CO (2 m, aq.) in THF was employed to achieve in- cyanoacrylic acid (CCT1A), (E)-3-{5Ј-[3-(3Ј,6Ј-di-tert-but-
2
3
creased numbers of thiophene units in the molecule, ylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-2,2Ј-bithiophen-
whereas bromination with NBS in THF selectively intro- 5-yl}-2-cyanoacrylic acid (CCT2A), (E)-3-{5ЈЈ-[3-(3Ј,6Ј-di-
duced a bromo function at the α-position of the terminal tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-
thiophene ring, allowing further Suzuki cross-coupling to 2,2Ј:5Ј,2ЈЈ-terthiophen-5-yl}-2-cyanoacrylic acid (CCT3A)
be performed. Suzuki coupling of 3 and 5 with thiophene- and (E)-3-(4-{5Ј-[3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-
2-boronic acid afforded the thiophene compounds 4 and 6 dodecylcarbazol-6-yl]-2,2Ј-bithiophen-5-yl}phenyl)-2-cyano-
in good yields of 86% and 80%, respectively, whereas acrylic acid (CCT2PA), in yields of 57%, 60%, 67% and
bromination of 4 and 6 with NBS gave the brominated in- 96%, respectively. On the other hand, condensation of the
termediates 5 and 7 in 91% and 79% yields, respectively. aldehyde 10 with 2-cyanoacetamide, catalysed by NH OAc/
4
Subsequent coupling of bromo compounds 3, 5 and 7 with AcOH in a THF/CH CN mixture at reflux, afforded (E)-3-
3
5
-formylthiophene-2-boronic acid under the same Suzuki {5ЈЈ-[3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarb-
coupling conditions provided the corresponding aldehydes azol-6-yl]-2,2Ј:5Ј,2ЈЈ-terthiophen-5-yl}-2-cyanoacrylamide
, 9 and 10 in yields of 57%, 63% and 66%, respectively, (CCT3N) in a 70% yield. The colours of the solid products
whereas coupling of the bromo compound 7 with p-formyl- deepened as the number of thiophene units in the molecules
8
4
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Organic Dyes for Efficient Dye-Sensitized Solar Cells
increased, from orange for CCT1A, to red for CCT2A, and
finally to dark red for CCT3A, CCT2PA and CCT3N. Their
chemical structures were characterized unambiguously by
1
13
FTIR, H NMR and C NMR spectroscopy, as well as by
HRMS. These compounds show good solubility in most
organic solvents, probably as a result of their bulkiness and
the tert-butyl and dodecyl substituents on the carbazole
rings of the donor moiety.
Photophysical and Thermal Properties
UV/Vis absorption spectra of the dyes, measured in
CH Cl , are shown in Figure 2 (a) and the characteristic
2
2
data are summarized in Table 1. The spectra of the dyes
each displayed two characteristic absorption bands. The ab-
sorption band at ca. 297 nm corresponded to a localized π–
π* transition in the carbazole donor, whereas the bands at
longer wavelengths (ca. 500–550 nm) were attributed to in-
tramolecular charge transfer (ICT) transitions from the
carbazole–carbazole donor moiety to the cyanoacrylic acid
or cyanoacrylamide acceptors. This was confirmed by a
negative solvatochromic shift [i.e., hypsochromic shift of
maximum wavelengths (λmax) of the ICT peaks in more po-
lar solvents], whereas the positions of the π–π* transition
peaks were almost independent of solvent polarity (Fig-
ure 2, b).
2 2
Figure 2. (a) UV/Vis absorption spectra of dyes in CH Cl . (b) UV/
Vis absorption spectra of CCT1A in different solvents.
The molar extinction coefficient (ε) values of the ICT
bands of the synthesized dyes were moderate to high, rang-
–
1
–1
ing from 21010 to 28890 m cm . As the number of thio- larger (17–19°). Use of cyanoacrylamide as an acceptor in
phene units in the molecules increased from one unit in CCT3N resulted in a red shift in the ICT band relative to
CCT1A, two units in CCT2A to three units in CCT3A, ba- that of CCT3A. However, CCT3N showed a significantly
thochromic shifts and increased molar extinction coeffi- lower ε value. Direct comparison between the optical prop-
cients (ε) of the ICT peaks were observed. CCT3A, with a erties of CCT3A and those of CCTT3A, with bis(3,6-di-
terthiophene moiety as a π-linkage, exhibited a larger ba- tert-butylcarbazol-9-ylphenyl)aniline as a donor moiety
thochromic shift of the ICT band than CCT2PA, contain- (2D–D), revealed that CCT3A had a narrower absorption
ing a bithiophene-phenylene as π-linkage, but CCT2PA had spectrum and a lower ε value than CCTT3A (abs
=
max
–1
–1 [11]
a higher ε value.
464 nm, ε = 33926 m cm ).
However, the ε values of these synthesized dyes at their
The optimized geometries of these last two dyes revealed
that the π-linkage of CCT3A adopted a more planar con- ICT bands were considerably larger than that of the stan-
–1
–1 [17]
formation than that of CCT2PA, as illustrated in Figure 3. dard Ru dye N719 at 535 nm (ε = 14400 m cm ), indi-
The dihedral angle between adjacent thiophene rings (T2– cating good light-harvesting capabilities. The greater maxi-
T ) was near zero in the oligothiophene-type linkage, but mum absorption coefficients of the organic dyes allow cor-
3
the angle between the thiophene (T ) and phenylene (P) in respondingly thinner nanocrystalline films, thus avoiding
2
the bithiophene-phenylene-type linkage was considerably reductions in the mechanical strengths of the films. This
Table 1. Optical, thermal and electrochemical and electronic properties of the dyes.
Absmax[a]
ε
Abs.[b]
[nm]
E
1/2(ox)[c]
[V]
E
1/2(red)[c]
[V]
T
[d]
E
g
[e]
HOMO[f]
[V]
LUMO[f]
[V]
Dye
5d
[m–1 cm ]
–1
[°C]
[eV]
[nm]
CCT1A
CCT2A
CCT3A
CCT2PA
CCT3N
N719
433
457
443
416
487
535
21952
23492
27938
28874
21037
14400
413
433
442
421
447
–
0.99, 1.40
0.95, 1.11, 1.25
0.85, 1.19, 1.40
0.88, 1.17, 1.41
0.88, 1.08, 1.17, 1.39
–
–1.64
–1.58
–1.54
–1.66
–1.15
–
357
379
342
339
335
–
2.41
2.22
2.15
2.36
2.17
1.80
–5.36
–5.27
–5.21
–5.20
–5.28
–5.05
–2.95
–3.05
–3.06
–2.84
–3.11
–3.25
[
a] Measured in CH
2
Cl
2
solution. [b] Measured as dyes adsorbed on TiO
2
film. [c] Measured by CV with a glassy carbon working
NPF as supporting electrolyte in CH Cl . [d] Measured
. [e] Estimated from the optical onset: E = 1240/λonset. [f] Calculated from the first
oxidation potential: HOMO = –(Eonset + 4.44); LUMO = HOMO + E
+
electrode, Pt counter electrode and Ag/Ag reference electrode and 0.1 m nBu
by TGA at heating rate of 10 °Cmin under N
4
6
2
2
–1
2
g
ox
g
.
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V. Promarak et al.
FULL PAPER
(
Figure 2, d). Such high thermal stability of the dye is im-
[
20]
portant for the lifetimes of solar cells.
Electrochemical Properties
The cyclic voltammetry (CV) and differential pulse vol-
tammetry (DPV) curves of each dye exhibited multiple qua-
sireversible oxidations and one irreversible reduction (Fig-
ure 4). The reduction was attributed to the reduction of the
acceptor moiety. The first oxidation wave was consistent
with the removal of electrons from the peripheral carbazole
unit in the donor moiety to give a radical cation, and the
rest corresponded to the oxidation of the remaining donor
and oligothiophene moieties. The first oxidation potentials
decreased from 0.99 to 0.95 to 0.85 V as the lengths of the
Figure 3. Schematic views of the ground-state structures for
CCT3A (top) and CCT2PA (bottom).
π-conjugated bridges increased, as also observed in other
also benefits the electrolyte diffusion in the film and reduces
the likelihood of recombination of light-induced charges
during transportation.[
[21]
oligothiophenes.
Multiple CV scans revealed identical
CV curves, with no additional peak at lower potential on
18]
the cathodic scan (E ) being observed, suggesting that
pc
The absorption spectra of the synthesized dyes adsorbed
these dyes were, as expected, electrochemically stable mole-
cules. Electrochemical coupling reactions of this type can
be detected in some carbazole derivatives with unsubsti-
on TiO films were slightly blue-shifted relative to their
2
solution spectra (Figure 4, a). Such a phenomenon is com-
monly observed in the spectral response of other organic
dyes, and may be ascribed to H-aggregation of the dye mo-
[22]
tuted 3,6-positions and might occur upon charge separa-
tion, which hampers the dye regeneration. It is therefore
important that the dyes are electrochemically stable mole-
cules.
lecules on the TiO surface and/or interaction between the
2
[
19]
anchoring groups of the dyes and the surface of TiO2.
Of these dyes, the absorption spectrum of CCT3A is the
broadest, which is an advantageous spectral property for
light harvesting over the solar spectrum.
The highest occupied molecular orbitals (HOMOs) of
the dyes, calculated from the onset oxidation potentials in
the CV curves, range from –5.20 eV to –5.36 eV. This is
–
–
lower than the redox potential of the I /I3 couple
–5.16 V), so dye regeneration should be thermodynami-
(
cally favourable and could compete efficiently with recap-
ture of the injected electrons by the dye radical cations. The
lowest unoccupied molecular orbitals (LUMOs) of the dyes
were estimated from the HOMOs and the energy gaps (Eg)
obtained from the optical onset. The LUMOs (–2.84 to
–3.11 eV) were less negative than the CB-edge energy level
of the TiO electrode (–4.00 vs. vacuum), ensuring efficient
2
charge injection from excited dyes to TiO . These values
2
were also less negative that the potential of N719 dye
[
23]
(
–3.25 eV). Consequently, all dyes possess sufficient driv-
ing force for electron injection from the excited dyes to the
conduction band of TiO . As a result, all dyes have enough
2
energetic driving force for efficient DSSCs with use of a
–
–
TiO photocatalyst and the I /I redox couple. Moreover,
2
3
with their high LUMO potentials these dyes become very
attractive for other metal oxide semiconductors with con-
duction bands more negative than the conduction band of
[24]
TiO , such as ZnO, Nb O , SrTiO and their composites,
2
2
3
3
to achieve high open-circuit voltage (V ), resulting in much
oc
improved cell efficiency.
Figure 4. (a) UV/Vis absorption spectra of dyes adsorbed on a TiO
2
film. (b) CV curves measured in CH
supporting electrolyte.
2 2 4 6
Cl containing nBu NPF as
Quantum Chemical Calculation
The thermal properties of these dyes were investigated by
thermogravimetric analysis (TGA). Those results suggested
The calculated ground-state molecular structures of the
that the synthesized dyes were thermally stable materials dyes are shown in Figure 3. A major factor behind low con-
with temperatures at 5% weight loss (T ) well over 335 °C version efficiencies of many organic dyes in DSSCs is dye
5
d
6
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Organic Dyes for Efficient Dye-Sensitized Solar Cells
aggregation at the semiconductor surface.[25] We therefore Table 2. Natural charges (e) of different units in the molecules cal-
culated at the B3LYP/6-31G(d,p) level of theory.
designed the bulky donor moiety based on 3,6-di-tert-bu-
tylcarbarzole connected to the N-dodecylcarbazole unit to
C–C[a]
Dye
T
1
T
2
T
3
P
A
provide steric hindrance in this part of the molecule. The
CCT1A
CCT2A
CCT3A
CCT2PA
0.08
0.06
0.04
0.04
–
–
0.02
0.02
–
0.11
0.10
0.10
–
–
–
–
–0.20
–0.20
–0.20
–0.14
dihedral angles formed between carbazole (D ) and carb-
1
0.05
0.04
0.04
azole (D ) planes in all molecules were as large as ca. 58°,
2
0.06
resulting in bulky structures that might help to prevent
close π–π aggregation between the dye molecules. Nonco- [a] C stands for carbazole, T for thiophene, P for phenylene and A
for acceptor.
planar geometry can also reduce contact between molecules
and enhance their thermal stability.[ The aromatic rings
26]
of the π-conjugated spacers adopted more planar confor- drogen bonding between an oxygen atom on the TiO sur-
2
mations. This suggested that π electrons from the donor face and a hydrogen atom of the dye) or through chemi-
moiety can delocalize effectively to the acceptor moiety, and sorption (the H atom of the carboxylic acid dissociates and
subsequently transfer to the conduction band of TiO2.
a bond is formed between the carboxylic oxygen atoms and
The ICT behaviour was analysed in terms of the frontier the surface titanium atoms of TiO ; this can be of mono-
2
molecular orbital (FMO) contribution. As shown in Fig- dentate ester, bidentate chelating or bidentate bridging
[
27]
ure 5, the results showed the electronic clouds correspond- type). Many experimental studies (FTIR) have indicated,
ing to the HOMO delocalized over the carbazole–carbazole however, that carboxylic acids usually adsorb onto a TiO
2
[
28]
donor moiety in each dye, whereas the LUMO showed elec- surface through bidentate-type bridging.
Only bidentate
tron distribution delocalized over the π-spacer and acceptor bridging adsorption of the synthesized dyes is presented in
moieties (cyanoacrylic acid anchoring group). The HOMO– this study. The adsorption complex was first fully optimized
LUMO transition thus corresponded to intramolecular by use of the Perdew–Burke–Ernzerhof (PBE) functional in
charge transfer behaviour. Natural Bond Orbital (NBO) conjunction with the Double-Numerical with polarization
3
analysis was employed to provide further insight into the performed in the DMol program. Optimized structures of
effects of ICT in CCT2PA and CCT3A. Table 2 shows the dye-(TiO2)38 adsorption complexes are shown in Figure 6
natural charges of the cyanoacrylic acid, phenylene, thio- (a). The bond lengths between 5c-Ti and O atom of dyes
phene and carbazole moieties in the dye molecules. The were calculated to be in the 2.08–2.16 Å range. The adsorp-
positive NBO values in the carbazole moiety correspond to tion energies (Eads) of CCTnA (n = 1–3) and CCT2PA were
the carbazole being an effective double-electron-donor unit. calculated to be –17.24, –21.19, –23.09 and
In contrast, the negative NBO charge in the cyanoacrylic
acid components revealed that all five dyes trap the elec-
trons in their acceptor units. After computation, it was also
found that the natural charge of the cyanoacrylic acid com-
ponent in the CCT3A dye was –0.20 e, which decreased to
–0.14 e on replacement of the thiophene with the phenylene
unit in CCT2PA. These results indicated that the insertion
of the phenylene ring significantly affected the electron-ac-
cepting capability of the acceptor.
Figure 5. The HOMO (bottom) and LUMO (top) orbitals of
CCT3A and CCT2PA calculated with the B3LYP/6–31G(d,p) set
Figure 6. (a) Optimized bidentate bridging modes of CCT1A and
CCT3A on the (TiO 38 cluster calculated by PBE/DNP with the
DMol program. (b) The adsorption data for the dyes onto TiO
films measured over a period of 50 h at room temperature (line
a carboxylic acid group can be either by physisorption (hy- represents the numerical regression fit).
(isovalue = 0.02).
2
)
3
2
In dye-TiO adsorption, the adsorption of a dye through
2
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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V. Promarak et al.
FULL PAPER
Table 3. Performance parameters of DSSCs constructed with the dyes.[a]
Dye uptake[b]
ϫ1015 molecule cm ) (mAcm ) (V)
J
sc
V
oc
FF IPCEmax
(%)
η
(%)
Relative η compared with the reference N719
Cal. Jsc
[c]
Dye
–2
–2
–2
(
(η/ηN719
)
(mAcm )
CCT1A
CCT2A
CCT3A
CCT2PA
CCTT3A
N719
66.80Ϯ2.62
76.42Ϯ2.23
84.04Ϯ2.87
84.61Ϯ2.81
53.90Ϯ0.50
56.11Ϯ1.00
7.35
9.70
11.31
9.94
9.98
11.63
0.74 0.67
82
81
84
81
76
81
3.64
4.80
5.69
4.82
4.62
5.92
68.2%
89.9%
96.1%
90.3%
78.0%
100%
7.13
9.64
11.12
9.81
9.91
11.50
0.73 0.68
0.71 0.71
0.70 0.69
0.70 0.67
0.71 0.72
2
[
a] Experiments were conducted under identical conditions with TiO
2
photoanodes of approximately 11 μm thickness and 0.25 cm work-
–1
ing area on the FTO (8 ohmsq ) substrates. [b] Obtained from measurement of dye adsorption. [c] Obtained from integration of the
corresponding IPCE spectra.
–
1
–
20.43 kcalmol , respectively, indicating strong interac- corresponding current density/voltage (J/V) characteristics
tions between the dyes and the TiO surface. and the incident monochromatic photon-to-current conver-
2
The performance of the DSSC is based not only on the sion efficiency (IPCE) plots are shown in Figure 7, and the
absorption of the harvesting dye but also on the total resulting photovoltaic parameters (average values) are sum-
amount of dye present. Dye uptakes were therefore deter- marized in Table 3. The IPCE spectra of CCTnA and
mined by the reported method.[29] It was found that the CCT2PA as sensitizers became broadened and red-shifted
maximum uptake of each dye at equilibrium was as the number of thiophene units in the molecule increased,
1
5
15
15
15
6
6.80ϫ10 , 76.42ϫ10 , 84.04ϫ10 and 84.61ϫ10
consistently with the results of the absorption spectra. The
–
2
moleculescm for CCT1A, CCT2A, CCT3A and CCT2PA, maximum IPCE values of all devices were as high as 76–
respectively (Figure 6, b, and Table 3). Unfortunately, the 84%, higher than those of the reference N719-based cell,
CCT3N dye was poorly adsorbed on TiO , suggesting an due to the larger molar extinction coefficients of the synthe-
2
ineffective dye sensitizer for DSSC. The lower dye uptake sized dyes, but the N719-based cell showed a broader IPCE
of CCT1A on the TiO film relative to the others can prob- spectrum, consistently with its wide absorption spectrum.
2
ably be explained in terms of steric hindrance of the donor This suggests that the structure modification of these dyes
moiety around the carboxylic acid anchoring group, re- by use of carbazole–carbazole as donor strongly influences
sulting from the considerably shorter π-spacer of CCT1A the collection efficiencies, in turn having a significant effect
as shown in Figure 6 (a). As a result, the dyes CCT3A and on the IPCEs and overall conversion efficiencies (η) of the
CCT2PA, with longer π-conjugated spacers, were found to devices.
be more spacious for accommodation of the donor moiety,
allowing better dye uptake. The chemisorption of all dyes
onto the surfaces of TiO films was confirmed by FTIR
2
spectroscopy, which showed absorption peaks both of the
dyes and of TiO at 2965 (C–H), 2207 (CϵN), 1611 (C=O),
2
–1
1
508 (C=C), 1365 (C=O), 1317, 1292 and 1226 cm . The
characteristic carboxylate group vibration modes, symmet-
–
1
–1
ric (1365 cm ) and asymmetric (1611 cm ), were identical
for all the dyes and similar to those reported for other dyes,
independent of molecular volume.[ This indicates that all
30]
such dyes bind to the TiO in the same way, so observed
2
differences in performance can be directly related to the ef-
fect of molecular volume and the amount of dye absorbed.
Photovoltaic Properties
These newly synthesized dyes were used as sensitizers for
dye-sensitized TiO solar cells (DSSCs). Cells with effective
2
2
areas of 0.25 cm (0.5 cmϫ0.5 cm) were fabricated with
TiO2 working electrode, platinum (Pt) counter electrode
and an electrolyte composed of 0.03 m I /0.6 m LiI/0.1 m
2
guanidinium thiocyanate/0.5 m tert-butylpyridine in a 15:85
(v/v) benzonitrile/acetonitrile solution. A reference cell with
the same structure but based on N719 dye as the sensitizer
was also made for purposes of comparison. For the mea-
surement of the photovoltaic performance, five cells were
Figure 7. (a) IPCE plots and (b) J/V curves for the DSSCs based
prepared and measured under the standard conditions. The on the synthesized dyes and on the reference N719 dye.
8
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Organic Dyes for Efficient Dye-Sensitized Solar Cells
Under standard AM 1.5G 100 mWcm–2 illumination exhibited high absorptivity in the blue/green region of solar
conditions, the CCT3A-sensitized cell showed the highest light. DSSC devices fabricated by use of these materials as
overall efficiency of the three dyes and gave a short-circuit dye sensitizers displayed medium to high overall conversion
–
2
photocurrent density (J ) of 11.31 mAcm , an open-cir- efficiencies (η) ranging from 3.6% to 5.69%. The optimal
sc
cuit voltage (V ) of 0.71 V and a fill factor (FF) of 0.71, IPCE value reached beyond 84%.
oc
corresponding to an overall conversion efficiency (η) of
The structures of the bridges are also influential. The
5
.69%. The Jsc and η values for the DSSCs were in the presence of thiophene units in a bridge improves coplanar-
–
2
order CCT3A (11.31 mAcm , 5.69%)
Ͼ
–2
CCT2PA ity, thus promoting better resonance delocalization, whereas
–
2
(9.94 mAcm , 4.82%) Ͼ CCT2A (9.70 mAcm , 4.80%) Ͼ the phenylene group is twisted with a large dihedral angle.
–
2
CCT1A (7.35 mAcm , 3.64%). The measured J values The performance of the oligothiophene-bridged dye was
sc
for these solar cells were also cross-checked with the Jsc better than that of the oligothiophene-phenylene type.
values calculated by integration of their corresponding
The dye containing cyanoacrylamide as an acceptor,
IPCE spectra (cal. J ), partly verifying the reported effi- however, could not be used as a sensitizer in DSSC, due to
sc
ciencies and the results found in agreement to within 5% its poor adsorption on TiO . Out of these dyes, the best
2
(Table 3). The better solar cell performance (highest η and performance was found with CCT3A, which exhibited a
Jsc values) of the CCT3A-based cell in relation to CCT2PA maximum IPCE value of 84%, Jsc value of
a
–2
and the other dyes in this series could be explained by the 11.31 mAcm , a V value of 0.71 and a FF value of 0.71,
oc
red-shift of the absorption spectrum of CCT3A, which re- corresponding to an η value of 5.59% (Ͼ96% of the refer-
sulted in a better light-harvesting efficiency of CCT3A. The ence N719-based cell). This device performs better than
lower efficiency of the CCT1A-based cell relative to CCT2A that with CCTT3A as sensitizer.
and CCT3A could be attributed both to the poorer spectral
The bulkiness of the carbazole–carbazole moiety (D–D)
properties and to the lower dye content adsorbed on TiO2 might effectively hinder self-aggregation of the dyes on
film. It should be noted that the Voc values of the CCTnA- TiO surfaces, whereas the hydrophobic properties of the
2
based DSSCs were as high as 0.74 V. This might be attribut- tert-butyl and the long dodecyl substituents should also
able to suppression of dark current owing to the hydro- minimize the losses due to charge recombination in the de-
phobic blocking effect of the tert-butyl and the long dode- vice.
cyl substituents on the carbazole donors shielding the TiO
Our results suggest that alternative highly efficient or-
2
–
–
surface from I /I in the electrolyte, thus reducing the ganic dyes comparable in performance to Ru complexes
3
charge recombination or dark reaction. The larger size of could potentially be developed through the use of the 3-(3Ј,6Ј-
the carbazole–carbazole group might also effectively hinder di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl system
self-aggregation of the dyes on a TiO surface. The minimi- as a donor. Development of this dye, based on further
2
zation of interfacial charge recombination losses in the de- broadening of its absorption spectrum to enhance its light
vice is also evident from the dark current data for the cells. harvesting ability through extension of its π-conjugation
For the same reason, the performance of the CCT3A-based system, is in progress.
DSSC in terms of Jsc value, FF value and η is superior
to that of the CCTT3A-based DSSC (Table 1). The results
suggest that the use of the 3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ- Experimental Section
yl)-N-dodecylcarbazol-6-yl moiety (D–D) as a donor has a
Materials and Instruments: All reagents were purchased from Ald-
significant effect on the device performance. The efficiency
rich, Acros or Fluka and were used without further purification.
of the CCT3A-based device reached Ͼ96% of that of the
reference N719-based cell (η = 5.92%). The slightly better
efficiency of the N719-based device in relation to its
All solvents were supplied by Thai companies and used without
further distillation. THF was heated at reflux with sodium and
benzophenone and distilled prior to use. CH Cl for electrochemi-
2
2
CCT3A counterpart originates from its slightly larger Jsc cal measurements was washed with conc. H SO and distilled twice
2
4
value; N719 has a broader IPCE spectrum, which is consis- from calcium hydride.
tent with its wide absorption spectrum.
1H and 13C NMR spectra were recorded with a Bruker AVANCE
00 MHz spectrometer with TMS as the internal reference in
CDCl or CDCl /[D ]DMSO as solvents. Infrared (IR) spectra
3
3
3
6
were measured with a Perkin–Elmer FT-IR spectrum RXI spec-
trometer as potassium bromide (KBr) discs. UV/Vis spectra were
recorded with dilute solutions in spectroscopic grade dichlorometh-
ane with a Perkin–Elmer UV Lambda 25 spectrometer. Diffuse re-
Conclusions
In summary, we have synthesized new organic dyes –
CCTnA, CCT3N and CCT2PA – containing 3-(3Ј,6Ј-di-tert-
butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl units as their
donor moieties. In their structures, either oligothiophene or
oligothiophene-phenylene systems, together with cyano-
acrylic acid or cyanoacrylamide units, were used as π-conju-
gated linkages and as acceptors, respectively. These dyes dis-
2
flectance spectra of dye-sensitized TiO samples were measured at
room temperature with a Shimadzu UV-3101 spectrophotometer.
Barium sulfate was used as a standard. The measured reflectance
spectra were then converted into absorption spectra by the Kub-
elka–Munk method. Thermal gravimetric analyses (TGA) were
performed with a Rigaku TG-DTA 8120 thermal analyser and a
–
1
played high thermal and electrochemical stability, which heating rate of 10 °Cmin under nitrogen. Cyclic and differential
can enhance the stability of a solar cell. These compounds pulse voltammetry (CV and DPV) measurements were carried out
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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9

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V. Promarak et al.
FULL PAPER
with an Autolab potentiostat PGSTAT 12 and a three-electrode
system (platinum counter electrode, glassy carbon working elec-
trode, and Ag/Ag+ reference electrode) at a scan rate of 50 mVs–1
forward and backward scans with bias steps and delay times of
10 mV and 40 ms, respectively, by the method of Koidea and
Han. Simulated sunlight was provided by a Newport sun simula-
[32]
in CH
nBu NPF
trations of analytical materials and electrolyte were 1ϫ10 m and
.1 m, respectively. Melting points were measured with an Electro-
thermal IA 9100 series digital melting point instrument and are
uncorrected. HRMS was performed by the Mass Spectrometry
Unit, Mahidol University, Thailand.
2
Cl
2
with tetrabutylammonium hexafluorophosphate
tor 96000 with an AM 1.5G filter. To minimize error of measure-
–
2
(
4
6
) as a supporting electrolyte under argon. The concen- ment, the irradiation intensity of 100 mWcm was approximated
–
3
with a calibrated BS-520 Si photodiode (Bunnkoukeiki Co., Ltd.,
Japan), the spectral response of which was very similar to that of
the DSSCs. The spectral output of the lamp was also matched to
the standard AM 1.5G solar spectrum in the 350–750 nm region
0
with the aid of a KG-5 filter with spectral mismatch of less than
33]
2
% as reported by Yanagida et al.[ Incident photon-to-electron
Dye Adsorption Measurements: The absorption spectra of the initial
conversion efficiencies (IPCEs) of the devices under short-circuit
conditions were determined with the aid off an Oriel 150-W Xe
lamp fitted with a CornerstoneTM 130 1/8 m monochromator as a
monochromatic light source, a Newport 818-UV silicon photodi-
ode as power density calibration and a Keithley 6485 picoammeter.
All measurements were performed with use of a black plastic mask
dye solutions (2.6–2.7ϫ10–5 m) in CH
Shimazu MultiSpec-1501 spectrophotometer. The TiO
Cl
were measured with a
substrates
2
2
2
with active areas of 0.25 cm2 (0.5 cmϫ0.5 cm), prepared in the
same manner as the substrates used for fabrication of DSSCs, were
baked at 450 °C for 30 min and allowed to cool to 70–80 °C before
immersion into the dye solution in a screw cap quartz cuvette
2
with an aperture area of 0.180 cm and no mismatch correction for
(
1 cmϫ1 cm). The absorption changes were monitored hourly for
h and then every 2 h for 50 h. The amount of dye uptake was
calculated from the calibration plot of known dye concentration.
The chemisorption of all dyes onto TiO film was characterized
the efficiency conversion data.
6
Quantum Chemical Calculations: Ground-state geometries were
fully optimized by use of a DFT level with the B3LYP hybrid func-
tional. All optimizations were calculated without any symmetry
constraints with use of the 6-31G(d,p) basis set and the
2
with a Perkin–Elmer FT-IR spectrum RXI spectrometer.
Fabrication and Characterisation of DSSCs
[34]
Gaussian 09 software package. The natural bond orbital analysis
NBO) was obtained with B3LYP/6–31G(d,p). The adsorption of
dyes on the (TiO 38 cluster was performed by means of DFT calcu-
lations and the DMol program in Materials Studio version 5.5.
The structure of (TiO 38 was composed of 38 TiO units that mod-
elled a TiO nanoparticle, as in the researchers’ previous report.
Device Fabrication: The photoanodes composed of nanocrystalline
(
[
31]
TiO
ine-doped SnO
2
were prepared by a previously reported procedure. Fluor-
2
)
–1
(FTO) conducting glasses (8 ohmsq , TCO30–8,
3
2
Solaronix) were used for transparent conducting electrodes. The
double nanostructure thick film (≈11 μm thickness) consisting of a
transparent (Ti-Nanoxide 20T/SP, Solaronix) and a scattering (Ti-
2
)
2
[35]
2
6
(
-Bromo-3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazole
3): A mixture of 2 (31.44 g, 63.48 mmol), 1 (4.43 g, 15.87 mmol),
CuI (1.51 g, 7.94 mmol), K PO (8.42 g, 39.68 mmol) and (Ϯ)-
Nanoxide R/SP, Solaronix) TiO
TiCl -treated FTO. The thickness of the TiO
by selection of screen mesh size and repetition of printing. Prior to
dye sensitization, the TiO electrode with cell geometry of
.5ϫ0.5 cm were treated with an aqueous solution of TiCl
4ϫ10–2 m) at 70 °C in a water saturation atmosphere, heated to
50 °C for 30 min and then allowed to cool to 80 °C. The TiO
2
layer were screen-printed on
4
2
film was controlled
3
4
trans-1,2-diaminocyclohexane (0.90 g, 7.94 mmol) in toluene
2
2
(200 mL) was stirred at reflux under N for 48 h. Water (50 mL)
0
4
2
was added, and the mixture was extracted with CH Cl2 (50 mL
2
(
ϫ2). The combined organic phase was washed with water (50 mL
4
2
–4
ϫ2) and brine (100 mL), dried with anh. Na SO and filtered, and
electrodes were immersed in the dye solution (3ϫ10 m N719 in
2
4
ethanol, and 5ϫ10–4 m organic dyes in CH
the solvents were removed. Purification by column chromatography
over silica gel with elution with a mixture of CH Cl and hexane
1:5) followed by recrystallization with a mixture of CH Cl and
methanol afforded the product (8.43 g, 77%) as a white solid (m.p.
2
Cl ) in the dark at
room temperature for 30 h to stain the dye onto the TiO surfaces.
Excess dye was removed by rinsing with the appropriate solvent.
To ensure maximum dye adsorption on the TiO film, dye concen-
2
2
2
2
(
2
2
2
1
1
3
76 °C). H NMR (300 MHz, CDCl ): δ = 8.18–8.15 (m, 4 H),
trations higher (Ͼ10-fold) than those used for dye adsorption ex-
periments were used. The Pt counter electrode was prepared on a
predrilled TCO30–8 FTO glass (Solaronix) by thermal decomposi-
7.57–7.45 (m, 3 H), 7.44 (d, J = 1.13 Hz, 2 H), 7.32–7.27 (m, 3 H),
4
.38 (t, J = 7.20 Hz, 2 H), 1.96 (t, J = 6.90 Hz, 2 H), 1.65–1.25 (m,
1
3
2 6
PtCl
(7ϫ10–3 m) in propan-2-ol solution at 385 °C. The
36 H), 0.93 (t, J = 6.30 Hz, 3 H) ppm.
C NMR (75 MHz, CDCl3):
tion of H
dye-adsorbed TiO
δ = 139.29, 129.54, 128.42, 123.45, 123.42, 123.24, 111.95, 111.89,
2
photoanode and Pt counter electrode were as-
1
2
11.31, 111.19, 111.10, 110.60, 109.54, 43.36, 31.93, 30.70, 29.95,
9.58, 29.35, 28.84, 28.28, 28.01, 12.74, 27.22, 22.71, 14.82 ppm.
sembled into a sealed cell by heating a gasket Meltonix 1170–25
film (25 μm thickness, Solaronix) as a spacer between the elec-
trodes. An electrolyte solution of I (0.05 m)/LiI (0.1 m)/tetraprop-
2
–
1
FTIR (KBr): ν˜ = 3053, 2957, 1490, 1362, 1289, 1261, 800 cm .
HRMS: m/z calcd. for C44 55BrN 690.3549; found 692.3601 [M
+
H
2
ylammonium iodide (0.4 m)/tert-butylpyridine (0.4 m) in a valeroni-
trile/acetonitrile 15:85 (v/v) mixture was filled through the pre-
drilled hole by a vacuum backfilling method. The hole was capped
by use of hot-melt sealing film (Meltonix 1170–25, 25 μm thickness,
Solaronix) and a thin glass cover. Finally, Scotch 3M conducting
tape and silver paint (SPI supplies) were coated onto the electrodes
to enhance the electric contact. For each dye, five devices were fab-
ricated and measured for consistency; averaged cell data are re-
ported. Reference cells with the same device configuration based
on N719 dye as the sensitizer were also fabricated for comparison.
+
2H] .
6
-(Thiophen-2-yl)-3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-dodecyl-
carbazole (4): A mixture of 3 (1.00 g, 1.44 mmol), thiophene-2-bor-
onic acid (0.09 g, 1.21 mmol), Pd(PPh (0.02 g, 0.02 mmol) and
Na CO solution (2 m, 15 mL) in THF (20 mL) was degassed with
for 3 min. The mixture was heated at reflux under N for 48 h.
After the mixture had cooled, water (50 mL) was added, and the
mixture was extracted with CH Cl (50 mL ϫ2). The combined
organic phase was washed with water (50 mL ϫ 2) and brine
(50 mL), dried with anh. Na SO and filtered, and the solvents
were removed to dryness. Purification by column chromatography
over silica gel with elution with a mixture of CH Cl and hexane
3 4
)
2
3
N
2
2
2
2
Device Characterization: The current density/voltage characteristics
of the DSCs were measured with a Keithley 2400 source meter unit
in a 4-terminal sense configuration. The data were averaged from
2
4
2
2
10
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/KAP1
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Organic Dyes for Efficient Dye-Sensitized Solar Cells
1:6) gave the product (0.85 g, 86%) as a pearl-white solid (m.p.
(
125.45, 124.95, 124.50, 123.59, 123.50, 123.30, 123.08, 122.69,
1
1
32 °C). H NMR (300 MHz, CDCl
H), 8.20 (s, 2 H), 7.79 (d, J = 8.40 Hz, 1 H), 7.59 (q, 2 H), 7.48
m, 3 H), 7.35 (m, 3 H), 7.24 (s, 2 H), 7.10 (t, J = 4.50 Hz, 1 H), 22.70, 14.12 ppm. FTIR (KBr): ν˜ = 3041, 2956, 1493, 1363, 1295,
3
): δ = 8.28 (d, J = 4.80 Hz, 2 119.34, 117.79, 116.21, 110.48, 109.85, 109.45, 109.17, 43.55, 34.75,
32.08, 31.92, 30.92, 29.63, 29.60, 29.54, 29.43, 29.35, 29.11, 27.36,
(
–
1
4
3
2 2
.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.56–1.27 (m, 1263, 811 cm . HRMS: m/z calcd. for C52H59BrN S 854.3303;
6 H), 0.87 (t, J = 6.90 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl
):
found 855.3364 [M + H] .
+
3
δ = 145.51, 142.44, 140.61, 140.31, 139.81, 129.64, 128.01, 126.09,
5
-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-
1
1
3
25.35, 124.88, 123.80, 123.68, 123.50, 123.07, 122.97, 122.14,
19.37, 118.05, 116.20, 109.77, 109.34, 109.19, 43.53, 34.76, 32.09,
1.93, 29.64, 29.55, 29.45, 29.36, 29.13, 27.37, 22.70, 14.13 ppm.
thiophene-2-carbaldehyde (8): A mixture of 3 (1.20 g, 1.73 mmol),
-formylthiophene-2-boronic acid (0.26 g, 1.73 mmol), Pd(PPh
(0.05 g, 0.04 mmol) and Na CO solution ( 2 m, 20 mL) in THF
30 mL) was degassed with N for 3 min. The mixture was heated
for 48 h. After the mixture had cooled, water
Cl
5
3 4
)
–
1
2
3
FTIR (KBr): ν˜ = 3047, 2952, 1490, 1362, 1292, 1233, 797 cm .
(
2
HRMS: m/z calcd. for C48
H] .
H
58
N
2
S 694.4321; found 695.4405 [M +
+
at reflux under N
2
(
50 mL) was added, and the mixture was extracted with CH
2
2
6-(5-Bromothiophen-2-yl)-3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-do- (50 mL ϫ2). The combined organic phase was washed with water
decylcarbazole (5): NBS (0.87 g, 4.98 mmol) was added in small
portions to a stirred solution of 4 (3.30 g, 4.75 mmol) in THF
2 4
(50 mL ϫ2) and brine (50 mL), dried with anh. Na SO and fil-
tered, and the solvents were removed to dryness. The crude product
was purified by silica gel column chromatography with a mixture
(
70 mL). The mixture was stirred at room temperature for 3 h.
Water (20 mL) was added, and the mixture was extracted with
CH Cl (50 mL ϫ3). The combined organic phase was washed
with water (50 mL) and brine (50 mL), dried with anh. Na SO
of CH
zation with a mixture of CH
uct (0.71 g, 57 %) as a yellow solid (m.p. 230 °C). H NMR
(300 MHz, CDCl ): δ = 9.87 (s, 1 H), 8.37 (s, 1 H), 8.27 (s, 1 H),
2
Cl
2
and hexane (1:3) as an eluent followed by recrystalli-
2
2
2
Cl and methanol afforded the prod-
2
1
2
4
and filtered, and the solvents were removed to dryness. Purification
by column chromatography over silica gel with elution with a mix-
3
8.19 (s, 2 H), 7.83 (d, J = 8.70 Hz, 1 H), 7.75 (d, J = 3.90 Hz, 1
H), 7.67–7.58 (q, 2 H), 7.51–7.43 (m, 4 H), 7.35 (d, J = 8.70 Hz, 2
ture of CH
a mixture of CH
1%) as a green solid (m.p. 174 °C). H NMR (300 MHz, CDCl
δ = 8.26 (s, 2 H), 8.21 (s, 2 H), 7.69 (d, J = 8.40 Hz, 3 H), 7.61 (d, CDCl
J = 6.90 Hz, 3 H), 7.50–7.46 (m, 3 H), 7.35 (d, J = 8.70 Hz, 2 H), 137.76, 130.19, 125.78, 125.05, 124.52, 123.54, 123.14, 123.00,
2
Cl
2
and hexane (1:3) followed by recrystallization with
2
Cl
2
and methanol afforded the product (3.33 g, H), 4.40 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.57–1.27
1
13
9
3
): (m, 36 H), 0.87 (t, J = 6.90 Hz, 3 H) ppm. C NMR (75 MHz,
): δ = 182.54, 155.91, 142.58, 141.66, 141.44, 140.22, 139.88,
3
7
2
.08–7.04 (q, 2 H), 4.40 (t, J = 7.20 Hz, 2 H), 1.98 (t, J = 6.90 Hz,
119.39, 118.69, 116.24, 110.05, 109.68, 109.12, 43.63, 34.75, 32.07,
31.91, 30.91, 29.71, 29.62, 29.58, 29.52, 29.41, 29.34, 29.09, 27.34,
22.68, 14.10 ppm. FTIR (KBr): ν˜ = 2952, 1647(C=O), 1495, 1435,
1
3
H), 1.57–1.27 (m, 36 H), 0.89 (t, J = 6.90 Hz, 3 H) ppm.
C
NMR (75 MHz, CDCl
3
): δ = 147.02, 142.48, 140.76, 140.26,
–
1
1
1
1
2
3
39.81, 130.82, 129.79, 125.50, 125.30, 124.49, 123.54, 123.50, 1361, 1295, 1240, 1060, 807 cm . HRMS: m/z calcd. for
+
23.08, 123.00, 122.23, 119.34, 117.80, 116.21, 110.03, 109.85,
09.47, 109.15, 43.55, 34.75, 32.08, 31.92, 29.63, 29.60, 29.53,
9.43, 29.35, 29.10, 27.35, 22.69, 14.12 ppm. FTIR (KBr): ν˜ =
C
49
H
58
N
2
OS 722.4270; found 723.4365 [M + H] .
5
Ј-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-
–1
2,2Ј-terthiophene-2-carbaldehyde (9): Compound 9 (0.32 g, 63%)
047, 2952, 1490, 1359, 1297, 1230, 808 cm . HRMS: m/z calcd.
+
was synthesized from 5 in similar manner to 8 and obtained as an
2
for C48H57BrN S 772.3426; found 773.3482 [M + H] .
1
orange solid (m.p. Ͼ 250 °C). H NMR (300 MHz, CDCl
3
): δ =
6
-(2,2Ј-Bithiophen-5-yl)-3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-yl)-N-do- 9.85 (s, 1 H), 8.27 (s, 2 H), 8.20 (s, 2 H), 7.78 (d, J = 7.20 Hz, 1
decylcarbazole (6): Compound 6 (1.35 g, 80 %) was synthesized H), 7.66 (d, J = 3.90 Hz, 1 H), 7.63–7.57 (q, 2 H), 7.50–7.47 (m, 3
from 5 in similar manner to 4 and obtained as a pale yellow solid H), 7.37–7.35 (m, 3 H), 7.29 (d, J = 3.90 Hz, 1 H), 7.24 (d, J =
): δ = 8.27 (s, 2 H), 8.20 3.90 Hz, 1 H), 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2
1
(
(
m.p. 142 °C). H NMR (300 MHz, CDCl
s, 2 H), 7.78 (d, J = 8.40 Hz, 1 H), 7.60 (q, 2 H), 7.49–7.46 (m, 3
3
1
3
H), 1.58–1.27 (m, 36 H), 0.88 (t, J = 6.90 Hz, 3 H) ppm. C NMR
(75 MHz, CDCl ): δ = 182.40, 147.59, 147.57, 142.53, 141.17,
.9 Hz, 1 H), 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 141.01, 140.25, 139.83, 137.49, 133.95, 129.92, 127.32, 125.58,
H), 7.36 (d, J = 8.4 Hz, 2 H), 7.27–7.16 (m, 3 H), 7.03 (t, J =
3
1
3
1
3
.50–1.27 (m, 36 H), 0.89 (t, J = 6.90 Hz, 3 H) ppm. C NMR 125.02, 124.55, 123.65, 123.56, 123.52, 123.15, 123.11, 123.08,
): δ = 144.35, 142.46, 140.68, 140.28, 139.81, 119.35, 118.00, 116.24, 109.94, 109.56, 109.15, 43.58, 34.76, 32.09,
(
75 MHz, CDCl
3
1
1
1
2
37.73, 135.62, 129.74, 127.81, 125.71, 125.39, 124.68, 124.50, 31.93, 29.64, 29.60, 29.54, 29.43, 29.36, 29.12, 27.36, 22.70, 14.13,
24.02, 123.64, 123.50, 123.29, 123.08, 123.03, 122.66, 119.34, 140.91, 140.50, 140.26, 139.82, 134.79, 130.51, 129.86, 126.21,
17.73, 116.19, 109.81, 109.41, 109.19, 43.55, 34.75, 32.08, 31.92, 125.51, 125.44, 124.54, 1223.61, 123.53, 123.37, 123.11, 123.06,
9.63, 29.60, 29.54, 29.43, 29.35, 29.12, 27.36, 22.69, 14.12 ppm.
119.33, 117.93, 116.24, 109.91, 109.50, 109.17, 43.57, 34.77, 32.10,
31.93, 29.64, 29.61, 29.55, 29.44, 29.37, 29.13, 27.37, 22.71,
14.14 ppm. FTIR (KBr): ν˜ = 3055, 2956, 1647 (C=O), 1493, 1452,
–
1
FTIR (KBr): ν˜ = 3047, 2946, 1490, 1365, 1292, 1233, 791 cm .
HRMS: m/z calcd. for C52 776.4198; found 777.4290 [M
+
60 2 2
H N S
+
–1
H] .
1363, 1295, 1223, 1047, 807 cm . HRMS: m/z calcd. for
+
C
53
H
60
N
2
OS
2
804.4147; found 805.4189 [M H] .
6
-(5Ј-Bromo-2,2Ј-bithiophen-5-yl)-3-(3Ј,6Ј-di-tert-butylcarbazol-NЈ-
yl)-N-dodecylcarbazole (7): Compound 7 (0.98 g, 79%) was synthe-
sized from 6 in similar manner to 5 and obtained as a green solid
5ЈЈ-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-
2,2Ј:5Ј,2ЈЈ-terthiophene-2-carbaldehyde (10): Compound 10 (0.66 g,
1
(
(
=
1
m.p. 234 °C). H NMR (300 MHz, CDCl
3
): δ = 8.24 (s, 2 H), 8.17 66%) was synthesized from 7 in similar manner to 9 and obtained
1
s, 2 H), 7.74 (d, J = 5.58 Hz, 1 H), 7.59–7.57 (m, 2 H), 7.47 (d, J
as a red orange solid (m.p. Ͼ 250 °C). H NMR (300 MHz,
8.60 Hz, 3 H), 7.33 (d, J = 8.60 Hz, 3 H), 7.21 (d, J = 3.72 Hz, CDCl ): δ = 9.85 (s, 1 H), 8.27 (s, 2 H), 8.21 (s, 2 H), 7.77 (d, J =
H), 7.10 (d, J = 3.72 Hz, 1 H), 6.97–6.90 (q, 2 H), 4.37 (t, J =
3
8.40 Hz, 1 H), 7.65–7.56 (m, 3 H), 7.50–7.45 (m, 3 H), 7.36 (d, J
= 8.40 Hz, 2 H), 7.26–7.20 (m, 4 H), 7.12 (d, J = 3.30 Hz, 1 H),
4.38 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.57–1.27 (m,
7
.20 Hz, 2 H), 1.98 (t, J = 6.90 Hz, 2 H), 1.57–1.27 (m, 36 H), 0.85
13
3
(t, J = 6.90 Hz, 3 H) ppm. C NMR (75 MHz, CDCl ): δ = 144.90,
1
3
1
42.48, 140.75, 140.26, 139.81, 139.22, 134.50, 130.64, 129.78, 36 H), 0.88 (t, J = 6.90 Hz, 3 H) ppm. C NMR (75 MHz, CDCl
3
):
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
11

Job/Unit: O30373
/KAP1
Date: 01-07-13 09:43:10
Pages: 14
V. Promarak et al.
FULL PAPER
δ = 182.35, 146.97, 145.60, 142.52, 141.45, 140.82, 140.26, 139.81, m/z calcd. for C56
H
61
N
3
O
2
S
2
871.4205; found 872.4288 [M + H]+.
1
1
1
3
1
1
39.57, 137.37, 134.46, 134.01, 129.84, 129.84, 127.02, 125.51,
25.34, 124.47, 124.12, 123.90, 123.59, 123.52, 123.11, 123.06,
22.88, 119.32, 117.82, 116.23, 109.88, 109.49, 109.17, 43.56, 34.76,
2.09, 31.93, 29.63, 29.61, 29.54, 29.43, 29.35, 29.12, 27.36, 22.70,
4.13 ppm. FTIR (KBr): ν˜ = 3055, 2953, 1651 (C=O), 1491, 1453,
(
6
E)-3-{5ЈЈ-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-
-yl]-2,2Ј:5Ј,2ЈЈ-terthiophen-5-yl}-2-cyanoacrylic Acid (CCT3A):
Compound CCT3A (0.19 g, 67%) was synthesized from 10 in sim-
ilar manner to CCT1A and obtained as a dark red solid (m.p.
Ͼ 250 °C). H NMR (300 MHz, [D
H), 8.47 (s, 1 H), 8.22 (s, 3 H), 7.98–7.79 (m, 4 H) 7.67–7.58 (m, 3
H), 7.45–7.27 (m, 7 H), 4.48–4.45 (m, 2 H), 2.06–1.83 (m, 2 H),
1
–
1
6
]DMSO/CDCl
3
): δ = 8.56 (s, 1
362, 1295, 1231, 1047, 807 cm . HRMS: m/z calcd. for
+
57 62 2 3
C H N OS , 886.4024; found 887.4091 [M + H] .
1
3
4
2
-{5Ј-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-yl]-
,2Ј-bithiophen-5-yl}benzaldehyde (11): Compound 11 (0.89 g, 91%)
1.40–1.15 (m, 36 H), 0.77 (s, 3 H) ppm. C NMR (75 MHz, [D6]-
DMSO/CDCl ): δ = 162.89, 142.59, 140.93, 139.96, 137.63, 136.48,
3
was synthesized from 7 and 4-formylphenylboronic acid in similar
manner to 9 and obtained as a yellow solid (m.p. Ͼ 250 °C). H
134.05, 129.41, 126.97, 126.28, 125.13, 124.80, 124.02, 123.90,
123.53, 122.96, 119.76, 116.81, 111.13, 110.66, 109.54, 43.19, 36.30,
1
NMR (300 MHz, CDCl
3
): δ = 9.99 (s, 1 H), 8.27 (s, 2 H), 8.21 (s, 34.90, 32.31, 31.71, 31.28, 29.40, 29.26, 29.10, 28.96, 27.57, 26.84,
2
2
3
1
H), 7.88 (d, J = 8.10 Hz, 2 H), 7.79–7.72 (m, 3 H), 7.65–7.56 (q,
22.50, 14.32 ppm. FTIR (KBr): ν˜ = 3417 (O–H), 2937, 2213
–
1
H), 7.50–7.46 (m, 3 H), 7.38–7.35 (m, 3 H), 7.21 (d, J = 3.60 Hz, (CϵN), 1610 (C=O), 1490, 1365, 1295, 1262, 808 cm . HRMS:
+
H), 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.57–
m/z calcd. for C H N O S 953.4082; found 953.4265 [M] .
6
0
63
3
2 3
.27 (m, 36 H), 0.88 (t, J = 6.90 Hz, 3 H) ppm. 13C NMR (75 MHz,
(
E)-3-(4-{5Ј-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarb-
azol-6-yl]-2,2Ј-bithiophen-5-yl}phenyl)-2-cyanoacrylic Acid
CCT2PA): Compound CCT2PA was synthesized from 11 in sim-
ilar manner to CCT1A and obtained as a red solid (0.15 g, 96%),
CDCl
3
): δ = 191.30, 145.25, 142.51, 140.79, 140.66, 140.27, 139.82,
1
1
1
2
39.35, 134.98, 130.49, 129.83, 125.92, 125.56, 125.46, 125.24,
(
24.48, 124.38, 123.61, 123.51, 123.11, 123.06, 122.85, 119.33,
17.81, 116.22, 109.87, 109.48, 109.18, 43.56, 34.76, 32.08, 31.92,
9.63, 29.60, 29.54, 29.43, 29.35, 29.12, 27.36, 22.69, 14.11 ppm.
1
m.p. Ͼ 250 °C. H NMR (300 MHz, [D
6 3
]DMSO/CDCl ): δ = 8.72
(
s, 2 H), 8.45 (s, 2 H), 8.27 (s, 3 H), 8.17 (s, 2 H), 7.79–7.56 (m, 8
FTIR (KBr): ν˜ = 3064, 2952, 1692 (C=O), 1602, 1490, 1454, 1359,
–
1
H), 7.41 (d, J = 8.40 Hz, 2 H), 7.25 (d, J = 8.40 Hz, 2 H), 4.42 (t,
J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.57–1.27 (m, 36 H),
1
8
261, 1211, 791 cm . HRMS: m/z calcd. for C59
H
64
N
2
OS
2
+
80.4460; found 881.3466 [M + H] .
1
3
0
.87 (t, J = 6.90 Hz, 3 H) ppm. C NMR (75 MHz, [D
6
]DMSO/
(
E)-3-{2-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-6-
yl]thiophen-5-yl}-2-cyanoacrylic Acid (CCT1A): Piperidine
0.14 mL) was added to a mixture of 8 (0.41 g, 0.55 mmol) and 2-
cyanoacetic acid (0.09 g, 1.12 mmol) in CHCl (20 mL). The solu-
CDCl ): δ = 166.30, 142.43, 139.97, 139.86, 134.70, 130.61, 129.44,
3
1
1
2
25.22, 124.36, 123.73, 1223.84, 123.73, 1223.48, 122.88, 119.16,
17.64, 116.21, 110.37, 109.38, 43.28, 34.74, 32.17, 31.80, 30.95,
9.51, 29.45, 29.28, 29.22, 22.58, 14.24 ppm. FTIR (KBr): ν˜ = 3416
(
3
tion was heated at reflux overnight. The solvent was removed to
dryness. Purification by column chromatography over silica gel
with elution with a mixture of CH
by recrystallization with a mixture of CH
forded the product (0.25 g, 57 %) as a red-orange solid (m.p.
(
1
O–H), 3047, 2924, 2214 (CϵN), 1598 (C=O), 1491, 1363, 1293,
–1
65 3 2 2
148, 792 cm . HRMS: m/z calcd. for C62H N O S 947.4518;
Cl
2
and hexane (4:1) followed
+
2
found 947.4775 [M] .
2
2
Cl and methanol af-
(E)-3-{5ЈЈ-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-
1
176 °C). H NMR (300 MHz, [D
6
]DMSO/CDCl
3
): δ = 8.40 (s, 1 6-yl]-2,2Ј:5Ј,2ЈЈ-terthiophen-5-yl}-2-cyanoacrylamide (CCT3N): A
H), 8.30 (d, J = 7.45 Hz, 2 H), 8.20 (s, 2 H), 7.90 (d, J = 8.59 Hz,
mixture of 10 (0.30 g, 0.34 mmol), 2-cyanoacetamide (0.04 g,
H), 7.80 (d, J = 8.61 Hz, 1 H), 7.60 (q, 2 H) 7.50 (q, 4 H), 7.40
0.51 mmol) and NH OAc (0.13 g, 1.69 mmol) was dissolved in
d, 2 H) 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J = 6.90 Hz, 2 H), 1.57– AcOH (25 mL), CH CN (20 mL) and THF (20 mL). The solution
.27 (m, 36 H), 0.87 (t, J = 6.90 Hz, 3 H) ppm. 13C NMR (75 MHz,
was heated at reflux overnight. After the mixture had cooled, water
]DMSO/CDCl ): δ = 164.18, 151.97, 142.55, 141.50, 139.90,
(50 mL) was added, and the mixture was extracted with CH Cl
38.03, 135.10, 131.94, 129.61, 129.08, 125.41, 125.08, 124.61, (50 mL ϫ2). The combined organic phase was washed with water
23.99, 123.58, 123.01, 119.80, 119.21, 119.04, 116.90, 111.22, (50 mL ϫ2) and brine (100 mL), dried with anh. Na SO and fil-
tered, and the solvents were removed to dryness. Purification by
column chromatography over silica gel with elution with CH Cl
followed by recrystallization with a mixture of CH Cl and meth-
anol afforded the product (0.22 g, 70%) as a red solid (m.p.
1
(
1
4
3
[
D
6
3
2
2
1
1
1
2
2
4
10.81, 109.52, 105.73, 43.15, 34.91, 34.17, 32.31, 31.71, 29.42,
9.29, 29.12, 28.99, 26.84, 24.96, 22.50, 14.32 ppm. FTIR (KBr): ν˜
2
2
=
3413 (O–H), 3047, 2923, 2211 (CϵN), 1604 (C=O), 1490, 1363,
2
2
–
1
1
7
294, 1262, 801 cm . HRMS: m/z calcd. for C52
H
59
N
3
O
2
S
+
1
89.4328; found 789.4462 [M] .
Ͼ 250 °C). H NMR (300 MHz,CDCl
3
): δ = 8.31 (s, 1 H), 8.26 (s,
2
7
6
6
H), 8.19 (s, 2 H), 7.75 (d, J = 7.80 Hz, 1 H), 7.61–7.55 (q, 3 H),
(
6
E)-3-{5Ј-[3-(3Ј,6Ј-Di-tert-butylcarbazol-NЈ-yl)-N-dodecylcarbazol-
-yl]-2,2Ј-bithiophen-5-yl}-2-cyanoacrylic Acid (CCT2A): Com-
.49–7.47 (m, 3 H), 7.35 (d, J = 8.40 Hz, 2 H), 7.26–7.12 (m, 5 H),
.20 (s, 1 H), 5.75 (s, 1 H), 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t, J =
.90 Hz, 2 H), 1.71–1.28 (m, 36 H), 0.89 (t, J = 6.90 Hz, 3 H) ppm.
pound CCT2A (0.27 g, 60 %) was synthesized from 9 in similar
manner to CCT1A and obtained as a red solid (m.p. 250 °C). H
NMR (300 MHz, [D ]DMSO/CDCl ): δ = 8.50 (s, 1 H), 8.40 (s, 1
6 3
1
13
3
C NMR (75 MHz, CDCl ): δ = 162.36, 146.72, 145.76, 145.14,
1
1
1
1
3
1
1
42.52, 140.85, 140.27, 139.90, 139.82, 138.91, 134.44, 134.27,
33.75, 129.88, 127.28, 125.61, 125.49, 125.33, 124.48, 124.25,
24.12, 123.61, 123.50, 123.11, 123.03, 122.93, 119.32, 117.83,
17.42, 116.20, 109.87, 109.48, 109.17, 43.56, 34.74, 32.06, 31.90,
0.86, 29.60, 29.57, 29.51, 29.40, 29.32, 29.09, 27.34, 22.66,
4.07 ppm. FTIR (KBr): ν˜ = 3442 (N–H), 3053, 2924, 2218 (CϵN),
H), 8.15 (s, 2 H), 8.10 (s, 2 H), 7.75 (t, 2 H), 7.60 (q, 3 H), 7.40 (d,
J = 5.40 Hz, 4 H), 7.3 (t, 2 H) 4.39 (t, J = 7.20 Hz, 2 H), 1.97 (t,
J = 6.90 Hz, 2 H), 1.57–1.27 (m, 36 H), 0.87 (t, J = 6.90 Hz, 3
H) ppm. 13C NMR (75 MHz, [D
]DMSO/CDCl
6
3
): δ = 163.47,
1
1
1
1
2
45.98, 142.56, 141.85, 140.99, 140.24, 139.92, 139.84, 136.36,
35.93, 133.92, 129.44, 127.09, 125.21, 124.91, 124.50, 124.16,
23.96, 119.74, 119.60, 118.45, 116.75, 111.04, 110.61, 110.05,
09.53, 43.16, 34.87, 32.29, 31.71, 29.40, 29.27, 29.11, 28.96, 26.84,
2.50, 14.30 ppm. FTIR (KBr): ν˜ = 3417 (O–H), 3047, 2925, 2211
–1
596 (C=O), 1491, 1363, 1294, 1187, 794 cm . HRMS: m/z calcd.
+
for C60
H
64
N
4
OS
3
952.4242; found 953.4238 [M + H] .
Supporting Information (see footnote on the first page of this arti-
CϵN), 1609 (C=O), 1490, 1363, 1295, 1152, 801 cm . HRMS: cle): PL spectra, TGA and DPV curves, more quantum chemical
–1
(
12
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O30373
/KAP1
Date: 01-07-13 09:43:10
Pages: 14
Organic Dyes for Efficient Dye-Sensitized Solar Cells
results, FTIR spectra of dyes adsorbed on TiO
NMR spectra of the dyes and intermediates.
2
, and H and 13C
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This work was supported by the Thailand Research Fund (grant
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13

Job/Unit: O30373
/KAP1
Date: 01-07-13 09:43:10
Pages: 14
V. Promarak et al.
FULL PAPER
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Received: March 19, 2013
Published Online: ᭿
14
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0