Isotruxene-derived cone-shaped organic dyes for dye-sensitized solar cells

Article abstract of DOI:10.1021/jo101831p

The synthesis, electronic properties, and performance in dye-sensitized solar cells (DSSCs) of four cone-shaped organic dyes (ITD, ITD-Th, ITD-Hx, and ITD-OM) containing the isotruxene π-scaffold are reported. Selective substitution of the unsymmetrical i

Full text of DOI:10.1021/jo101831p

pubs.acs.org/joc
Isotruxene-Derived Cone-Shaped Organic Dyes for Dye-Sensitized
Solar Cells
Shih-Hsun Lin,† Ying-Chan Hsu,‡ Jiann T. Lin,*,‡ Cheng-Kai Lin,† and
Jye-Shane Yang*,†
†Department of Chemistry, National Taiwan University, Taipei, 10617 Taiwan, and ‡Institute of Chemistry,
Academia Sinica, Taipei, 11529, Taiwan
jsyang@ntu.edu.tw; jtlin@chem.sinica.edu.tw
Received September 16, 2010
The synthesis, electronic properties, and performance in dye-sensitized solar cells (DSSCs) of four
cone-shaped organic dyes (ITD, ITD-Th, ITD-Hx, and ITD-OM) containing the isotruxene π-scaffold
are reported. Selective substitution of the unsymmetrical isotruxene core with two diarylamino donors
and one cyanocarboxylic acid acceptor was achieved by using a prefunctionalized dibromoisotruxene
building block. The ortho-para-branched isotruxene core allows strong electronic couplings among the
donors and the acceptor, leading to red-shifted absorption profiles with significant charge-transfer
character. All four isotruxene dyes display reversible anodic waves in cyclic voltammagrams with both
HOMO and LUMO potentials suitable for application in DSSCs. The DSSCs fabricated with these cone-
shaped organic dyes exhibited high open-circuit voltages (0.67-0.76 V) and fill factors (0.67-0.72) with a
power conversion efficiency (η) up to 5.45%, which is 80% of the ruthenium dye N719-based standard
cell fabricated and measured under the same conditions.
Introduction
performance of DSSCs and to understand the structure-prop-
erty relationship. Because of the advantages of low cost, easy
Dye-sensitized solar cells (DSSCs) have emerged as one
of the most attractive photovoltaic devices. To date, a variety
of transition-metal complexes1-4 and metal-free organic
sensitizers5-10 have been explored in order to improve the
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DOI: 10.1021/jo101831p
r
Published on Web 10/25/2010
J. Org. Chem. 2010, 75, 7877–7886 7877
2010 American Chemical Society

Lin et al.
JOCArticle
purification, and structural diversity, metal-free organic dyes
are particularly attractive. While recent progress in power
conversion efficiency (η) has reached a new record of η =
10.3% for organic dyes,10 this still falls behind the performance
of Ru dyes such as N719 (η=11.18%)3 and CYC-B11 (η =
11.5%)4 and the challenging 15% efficiency. Strategies toward
high-performance organic dyes include (i) increasing the light-
harvesting efficiency, (ii) decreasing the tendency of dye aggre-
Results and Discussion
Synthesis. We have recently developed facile synthetic
methods toward construction of the unsymmetrical isotruxene
scaffold.13 Subsequent derivatizations of the parent iso-
truxene toward star-shaped π-conjugated systems have also
been demonstrated.12 However, selective substitution of the
parent isotruxene with donor and acceptor groups as in ITDs is
unknown and more likely to be very difficult. Thus, we have
adopted one of our synthetic protocols for isotruxene to
prepare prefunctionalized isotruxenes. Scheme 1 shows the
synthesis of the isotruxene dibromides 6 and 7 from 3-penta-
none and 4,40-dibromobenzil through intermediates 1-5. The
facts of lower solubility and reagent compatibility caused by the
bromo substituents force us to modify some of the reaction
conditions. For example, the solubility of dibromoisotruxe-
none 5 is too low to be characterized with NMR spectroscopy.
Consequently, the carbonyl reduction was achieved by directly
reacting with boron trifluoride etherate (catalyst) and triethyl-
silane (hydride source) in the absence of solvents rather than
by the Wulff-Kishner reaction.14 In addition, to avoid metal-
halide exchange, the previously used12 base n-BuLi was
replaced by t-BuOK for the alkylation of 6. On the other hand,
the presence of bromo substituents in the substrates is not
always detrimental to the synthesis. For example, the intramo-
lecular Friedel-Crafts acylation in 2 f 3 proceeds excellently
with sulfuric acid. However, sulfuric acid led to water-soluble
unknown compounds in the case of the bromo-free analogue,
and a resolution of this problem by using polyphosphoric acid
requires higher temperature (140 vs 70 °C) and longer reaction
time (48 h vs 30 min).13
gations, and (iii) reducing the chance of charge recombination
-
of the injected electrons in the TiO2 with the triiodide ions (I3
)
in the electrolyte. It has recently been shown that cone-shaped
organic dyes7-9 derived from branched π-conjugated spacers
are promising in the latter two issues.8,9 One particular example
is provided by truxene dyes (TDs),9 which exhibited higher
open-circuit voltages (Voc = 0.69-0.75 V) and fill factors
(ff =0.70-0.74) than N719 for devices fabricated under the
same condition. However, the relatively low short-circuit cur-
rents (Jsc = 6.86-7.89 mA/cm2) preclude high η values (3.61-
4.27%). In this context, isotruxene dyes (ITDs) are intriguing,
because the ortho-para-substituted isotruxene core possesses a
broader absorption profile toward visible light harvesting than
the meta-meta substituted truxene isomer.11,12 We report
herein the synthesis and DSSC performance of four ITDs:
ITD, ITD-Hx, ITD-Th, and ITD-OM. Our results show that
the dye ITD retains the merits of high Voc and ff values of the
TDs and reaches a η value of 5.45%.
The alkylated isotruxene dibromides 7a and 7b are free of
the solubility problem, and thus their subsequent derivatiza-
tion is straightforward. Scheme 2 shows the synthesis of ITD,
ITD-Hx, and ITD-OM. Formylation of 7a and 7b at the
desired position was achieved by titanium tetrachloride and
dichloromethyl methyl ether.15 The palladium-catalyzed
C-N coupling of the resulting 8a or 8b with diphenylamine
or 4,40-dimethoxyphenylamine afforded compounds 9a, 9b,
and 9c, which were finally converted to ITD, ITD-Hx, and
ITD-OM, respectively, through the Knoevenagel condensa-
tion reaction with 2-cyanoacetic acid.
(8) (a) Thomas, K. R. J.; Hsu, Y.-C.; Lin, J. T.; Lee, K.-M.; Ho, K.-C.;
Lai, C.-H.; Cheng, Y.-M.; Chou, P.-T. Chem. Mater. 2008, 20, 1830–1840.
(b) Ning, Z.; Zhang, Q.; Wu, W.; Pei, H.; Liu, B.; Tian, H. J. Org. Chem.
2008, 73, 3791–3797. (c) Hagberg, D. P.; Yum, J.-H.; Lee, H.; De Angelis, F.;
Marinado, T.; Karlsson, K. M.; Humphry-Baker, R.; Sun, L.; Hagfeldt, A.;
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Gratzel, M.; Nazeeruddin, M. K. J. Am. Chem. Soc. 2008, 130, 6259–6266.
(d) Jiang, X.; Marinado, T.; Gabrielsson, E.; Hagberg, D. P.; Sun, L.;
Hagfeldt, A. J. Phys. Chem. C 2010, 114, 2799–2805. (e) Chen, H.; Huang,
H.; Huang, X.; Clifford, J. N.; Forneli, A.; Palomares, E.; Zheng, X.; Zheng,
L.; Wang, X.; Shen, P.; Zhao, B.; Tan, S. J. Phys. Chem. C 2010, 114, 3280–
3286.
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J. Phys. Chem. C 2009, 113, 10307–10313.
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Pan, C.; Wang, P. Chem. Mater. 2010, 22, 1915–1925.
(11) Lang, K. F.; Zander, M.; Theiling, E. A. Chem. Ber. 1960, 93,
321–325.
(12) (a) Yang, J.-S.; Lee, Y.-R.; Yan, J.-L.; Lu, M.-C. Org. Lett. 2006, 8,
5813–5816. (b) Yang, J.-S.; Huang, H.-H.; Ho, J.-H. J. Phys. Chem. B 2008,
112, 8871–8878. (c) Yang, J.-S.; Huang, H.-H.; Liu, Y.-H.; Peng, S.-M. Org.
Lett. 2009, 11, 4942–4945.
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50, 3121–3124.
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SCHEME 1
SCHEME 2
For ITD-Th, compound 7a was iodinized to form 10 so
that a thiophene group could be selectively introduced to the
desired position via Suzuki-Miyaura coupling (Scheme 3).
Subsequent amination of the resulting 11 removed the bromo
substituents, and thus formylation of the intermediate 12 could
proceed with the commonly used reagents n-BuLi and DMF.
Again, the synthesis was accomplished by Knoevenagel reac-
tion of the precursor 13 with 2-cyanoacetic acid.
Photophysical and Electrochemical Properties. The photo-
physical properties of the ITDs in THF are summarized in
Table 1. The absorption profiles (Figure 1) display several
vibration peaks in the region 250-400 nm and a broad
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SCHEME 3. Synthesis of ITD-Th
TABLE 1. Photophysical and Electrochemical Data for ITDs
a
c
e
f
g
λabs
(nm)
λfl
log εb (nm) Φfl
E0-0
(eV)
Eox
(V)
Eox*
(V)
d
dye
ITD
383 (380) 4.71 529 0.28 2.37 (2.32) 0.88, 1.08 -1.49
ITD-Hx 383 (382) 4.71 525 0.27 2.35 (2.30) 0.88, 1.08 -1.47
ITD-Th
398 (395) 4.70 576 0.05 2.28 (2.23) 0.85, 1.06 -1.43
ITD-OM 388 (388) 4.72 577 0.29 2.32 (2.19) 0.68, 0.82 -1.64
aMaximum of the absorption band in THF. The maximum of the
absorption band on 2 μm TiO2 films is shown in parentheses. bExtinction
coefficient of the absorption band in THF. Maximum of the fluores-
c
cence spectra in THF. dFluorescence quantum yield in THF. eEstimated
from the onset of the absorption spectra in THF. Values in parentheses
are from the onset of the spectra on the surface of TiO2. Oxidation
f
potentials measured vs Fcþ/Fc in DCM were converted to normal
hydrogen electrode (NHE) by addition of þ0.63 V. gEnergy of the
FIGURE 1. The absorption spectra of ITD, ITD-Hx, ITD-Th, and
ITD-OM in THF.
LUMO of dyes estimated by Eox - E0-0
.
shoulder with a maximum at ca. 480 nm. On the basis of our
previous studies on isotruxene systems,12 the former can be
attributed to localized excitation and the latter to delocalized
transition with a significant intramolecular charge-transfer
character. More evidence for an intramolecular charge-transfer
lowest singlet excited state for these ITDs include (a) structure-
less fluorescence spectra in THF (Figure 2), (b) the presence
of vibrational structure in the delocalized absorption band for
the donor-only intermeidate 12 but not for the donor-acceptor
systems 13 and ITD-Th (Figure S1 in the Supporting Informa-
tion), and (c) the distinct distribution of electron density in
HOMO and LUMO, which are donor-localized and acceptor-
localized, respectively (Figures 3). Compared to ITD, the addi-
tional thiophene and methoxy groups in ITD-Th and ITD-OM,
respectively, result in a red shift of the absorption and fluores-
cence profiles (Figures 1 and 2) and a decrease of the 0-0
excitation energy (E0-0) estimated from the absorption onset.
In contrast, an elongation of the alkyl chains as in ITD-Hx is,
as expected, of little influence in the molecular electronic
FIGURE 2. The fluorescence spectra of ITD, ITD-Hx, ITD-Th,
and ITD-OM in THF.
properties. It should be noted that the 450-nm shoulder in the
fluorescence profile of ITD-Th is due to contamination of a
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FIGURE 3. AM1-derived frontier molecular orbitals for ITD, ITD-Th,
and ITD-OM.
trace amount of 12 (0.1%), which is strongly fluorescent
(Figure S2 in the Supporting Information) with a fluorescence
quantum yield (Φfl) of 0.79. The relatively lower Φfl value for
ITD-Th as compared to the other ITDs might be attributed to
thiophene-enhanced intersystem crossing toward the triplet
excited states.16
FIGURE 4. Comparison of the absorption spectra of ITD, ITD-
Hx, ITD-Th, and ITD-OM in THF (black curve) and on 2 μm TiO2
films (red curve).
Figure 4 compares the absorption spectra of the ITDs in
dilute THF solutions and on the surface of TiO2. The absorp-
tion maxima of the ITDs are nearly unchanged on going
from dilute solutions to the thin solid films (Table 1).
Regarding the absorption onset, it is red-shifted in a similar
size (ΔE0-0 = 0.05 eV) for ITD, ITD-Hx, and ITD-Th but
relatively larger for ITD-OM (ΔE0-0 = 0.13 eV). The small
shift in the former compounds indicates that these unsym-
metrical cone-shaped molecules are inapt to π-stacking and
aggregations. A larger change in the absorption profile
and thus a larger degree of intermolecular interactions for
ITD-OM adsorbed on TiO2 might be detrimental to its cell
performance (vide infra).
The oxidation potentials (Eox) of the ITDs were deter-
mined with cyclic voltammetry (CV) and differential pulse
voltammetry (DPV) (Figure S3 in the Supporting Informa-
tion), and the data with respect to normal hydrogen electrode
(NHE) are shown in Table 1. Two reversible anodic curves
are present for all four ITD dyes, which could be attributed
to sequential oxidation of the two amino groups. This is
in part based on the facts that oxidation of the parent iso-
truxene is much more difficult (Eox=1.42 V vs NHE) and
that the Eox value of π-extended isotruxene hydrocarbons
is saturated at ca. 1.0 V (vs NHE).12 The first oxidation
potentials of ITD, ITD-Hx, and ITD-Th are similar
(0.85-0.88 V), but it shifts negatively by ca. 200 mV for
ITD-OM. In addition, the separation of the two oxidation
peaks is smaller for ITD-OM (0.14 eV) than the other ITDs
(0.20-0.21 eV). Both phenomena can be attributed to the
electron-donating methoxy groups that raise the HOMO
potential and reduce the Coulombic repulsion between the
two charges. Nevertheless, the HOMO potentials of all four
TABLE 2. DSSCs Performance Parameters of Dyesa
dye
rel loadingb VOC (V) JSC (mA/cm2) η (%) ff
τR (ms)
ITD
1.00
0.73
1.03
0.96
0.87
0.75
0.76
0.69
0.67
0.70
10.13
7.31
9.71
5.53
14.02
5.45 0.72 0.73
3.64 0.66 0.72
4.62 0.69 0.68
2.48 0.67 0.58
6.81 0.69 0.58
ITD-Hx
ITD-Th
ITD-OM
N719
aExperiments were conducted with TiO2 photoelectrodes with
approximately 10 μm thickness and 0.16 cm2 working area on the
FTO (7 Ω/sq.) substrates. bThe dye adsorption on TiO2 relative to
the dye ITD, which is 1.82 ꢀ 10-7 mol/cm2.
-
ITDs (0.68-0.88 V) are more positive than that of the I-/I3
redox couple (0.42 V vs NHE),17 and thus regeneration of the
oxidized dyes is thermodynamically feasible. The LUMO or
excited-state oxidation potentials (Eox* = Eox - E0-0) of the
ITDs (Eox*) are more negative than the conduction-band-
edge energy level of the TiO2 electrode (-0.5 V vs NHE),17
which assures that the electron injection process is energeti-
cally favorable.
Photovoltaic Performance. Table 2 shows the performance
statistics of DSSCs fabricated with the ITDs on nanocrystal-
line anatase TiO2 particles and with liquid electrolyte of
0.05 M I2, 0.1 M LiI, 0.5 M 1-methyl-3-propylimidazolium
iodide, and 0.5 M tert-butylpyridine in acetonitrile. The cells
have an effective area of 0.16 cm2 and their performance was
evaluated under AM 1.5 G illumination (100 mW cm-2). The
corresponding photocurrent-voltage (J-V) curves and the
J-V plot in the dark are shown in Figure 5, and the incident
photocurrent conversion efficiencies (IPCE) are shown in
Figure 6.
Among the four ITDs, the ITD cell exhibits the best power
conversion efficiency (η = 5.45%), which reaches 80% of a
N719-based DSSC fabricated and measured under similar
(16) (a) Becher, R. S.; de Melo, J. S.; Mac-anita, A. L.; Elisei, F. J. Phys.
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FIGURE 5. J-V curves (solid curves) and dark current plots
(dashed curves) of DSSCs based on the ITDs and N719 dyes.
FIGURE 7. Transient photovoltage plots of DSSCs based on the
ITDs and N719 dyes.
close to the TiO2 surface. This might result from the presence
of more void space near the surface of TiO2 and/or larger
pores between neighboring dye molecules, as schematically
depicted in Figure 8. Other factors such as (a) a smaller
driving force for regeneration of the oxidized dyes due to
a higher HOMO potential and (b) a greater chance of self-
quenching of the excited dyes due to dye aggregation
(Figure 4) might also account for the relatively poor perfor-
mance of the ITD-OM cell.
The relative cell performance of truxene- and isotruxene-
based dyes might deserve a comment. For this purpose, the
pair of ITD-Th and the truxene counterpart (TD-Th) are
compared,9 because they have the same donor, acceptor,
and alkyl groups and differ only in the branched cores. To
account for the difference in DSSC fabrication, the perfor-
mance is better discussed relative to the corresponding
reference cells of N719. The relative values of Voc, Jsc, ff,
and η are 95%, 66%, 111%, and 69% for TD-Th vs N719
and 99%, 69%, 100%, and 68% for ITD-Th vs N719. Both
dyes have Voc and ff comparable or superior to N719, but
their Jsc are unsatisfactory. Overall, the η for TD-Th and
ITD-Th is lower than that for N719. Although the light
harvesting in the region of 550-600 nm for ITD-Th
(ca. 40%) is more efficient than that for TD-Th (ca. 10%)
in terms of the IPCE profiles, which might account for
the slightly larger Voc and Jsc, it is offset by the lower ff for
ITD-Th vs TD-Th and thus results in a similar η value for
both dyes.
FIGURE 6. IPCE plots of DSSCs based on the ITDs and N719
dyes.
conditions (Table 2). Such a performance stems from high Voc
(0.75 V), ff (0.72), and IPCE (>80% in the range 390-510 nm
with a maximum of 88% at 400 nm) values. The observation of
high Voc for the DSSCs suggests that the processes of charge
recombination between the injected electrons in TiO2 and
triiodide (I3-) in electrolyte are miminized.18 This in turn
indicates that the adsorbed dyes can effectively block the
approach of electrolyte to the TiO2 surface. While a high Voc
(0.76 V) is also displayed by the ITD-Hx cell, the cell is less
efficient in ff and η, attributable to the lower Jsc value. In view
of the parallel reduction (27-28%) in Jsc and the amount of dye
adsorption on TiO2 (Table 2) on going from ITD to ITD-Hx,
the poorer cell performance for the latter can be attributed to
less dye loading and thus less efficient light harvesting. In
contrast, both the ITD-Th and ITD-OM cells have lower Voc
and enhanced dark current than the ITD cell, indicating that
the TiO2 f electrolyte charge recombination route becomes
more significant. Further verification of this argument is
provided by the measurement of transient photovoltage at
open circuit (Figure 7). The resulting recombination lifetimes
(τR) of the photoinjected electron with the redox couples for
ITD, ITD-Hx, and ITD-Th are indeed higher than that for
ITD-OM and N719 (Table 2). With a similar amount of dye
loading for ITD, ITD-Th, and ITD-OM, it appears that an
elongation of either the cone length (ITD-Th) or the cone radius
(ITD-OM) would increase the chance of the electrolyte being
Conclusions
We have synthesized a new class of cone-shaped organic
sensitizers for DSSCs. The rigid, planar, and para-ortho-
branched isotruxene spacer is critical for effective conjuga-
tion and light harvesting. The DSSC devices with the dye
ITD have reached a power conversion efficiency of 5.45%,
which is 80% of the Ru dye N719 fabricated under the same
conditions. Further studies are required to understand the
structure-property relationship in these unsymmetrical cone-
shaped dyes in terms of the cone dimensions (length vs radius)
and the relative positions of the donor and acceptor groups.
Experimental Section
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General Methods. All the spectral and electrochemical data
were collected at room temperature (23 ( 1 °C). The cyclic
voltammetry (CV) and differential pulse voltammetry (DPV)
were recorded on a CHI 612B electrochemical analyzer, and a
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FIGURE 8. Schematic representation of the relationship of the molecular shape of (a) ITD, (b) ITD-Th, and (c) ITD-OM and the amount of
electrolyte molecules near the surface of TiO2.
glassy carbon served as the working electrode. The substrates
are dissolved 1 mM in CH2Cl2 solution containing 0.1 M
Bu4NPF6 as a supporting electrolyte. UV-visible spectra were
measured on a Cary300 double beam spectrophotometer. Fluor-
escence spectra were recorded on an Edinburgh FLS920 spectrom-
eter and corrected for the response of the detector. Fluorescence
quantum yield was determined with an integrating sphere (150 mm
diameter, BaSO4 coating) for N2-bubbled THF solution of the
ITDs. The optical density of all solutions was about 0.1 at the
wavelength of excitation, and an error of (10% is estimated for
the fluorescence quantum yields. The frontier molecular orbitals
(FMOs) were derived by semiempirical (AM1)19 level calculation.
The optimized geometry results from a step-growth strategy:
namely, structural optimization starts with the isotruxene segment
and then optimized again for each time of adding one more
segment like diphenylamine and thiophene until the full structure
is reached. The ethyl or hexyl groups were replaced by methyl
groups in order to expedite the calculations. The preparation of
TiO2 precursor and the electrode fabrication were carried out
based on a previous report20 with an autoclaved temperature of
240 °C. The film thickness measured by a profilometer (Dektak3,
Veeco/Sloan Instruments Inc., USA) was about 10 μm. The TiO2
electrode with a 0.16 cm2 geometric area was immersed in a
acetonitrile/tert-butanol mixture (volume ratio 1:1) containing
3ꢀ 10-4 Mcis-di(thiocyanato)bis(2,20-bipyridyl-4,40-dicarboxylato)-
ruthenium(II) bis(tetrabutylammonium) (N719, Solaronix S. A.,
Switzerland) or in EtOH solutions containing 3 ꢀ 10-4 M organic
sensitizers for overnight. A platinized FTO was used as a counter
electrode and was controlled to have an active area of 0.36 cm2 by
adhered polyester tape with a thickness of 60 μm. After rinsing with
EtOH, the photoanode was placed on top of the counter electrode
and tightly clipped together to form a cell. A 0.5 ꢀ 0.5 cm2
cardboard mask was clipped onto the device to constrain the
illumination area. The photoelectrochemical characterizations on
the solar cells were carried out by using an Oriel Class A solar
simulator (Oriel 91195A, Newport Corp.). Photocurrent-voltage
characteristics of the DSSCs were recorded with a potentiostat/
galvanostat (CHI650B, CH Instruments, Inc., USA) at a light
intensity of 1.0 sun calibrated by an Oriel reference solar cell (Oriel
91150, Newport Corp.). The monochromatic quantum efficiency
was recorded through a monochromator (Oriel 74100) at short
circuit condition. The intensity of each wavelength was in the range
of 1-3mW/cm2. The photovoltage transients of assembled devices
were recorded with a digital oscilloscope (LeCroy, WaveSurfer
24Xs). Pulsed laser excitation was applied by a Q-switched Nd:
YAG laser (Continuum, model Minilite II) with 1 Hz repetition
rate at 532 nm and a 5 ns pulse width at half-height. The beam size
was slightly larger than 0.5 ꢀ 0.5 cm2 to cover the area of the device.
The photovoltage of each device was adjusted by incident pulse
energy to be 40 mV. The average electron lifetime can be estimated
approximately by fitting a decay of the open circuit voltage
transient with exp(-t/τR), where t is time and τR is an average
time constant before recombination.
Materials. The synthesis of 1 was previously reported21,22 and
our melting points and 1H NMR spectrum conform to the
literature data.
Synthesis of 2. To a stirred solution of compound 1 (10.00 g,
24.0 mmol) and ethyl phenylpropiolate (4.36 g, 25.0 mmol) in
toluene (15 mL) was heated to reflux for 24 h. The toluene was
removed under reduced pressure, and the residue was recrys-
tallized from MeOH to afford the white solid of 2 with a yield of
91%: mp 207-209 °C; 1H NMR (400 MHz, CDCl3) δ 0.93
(t, J = 7.2 Hz, 3H), 1.75 (s, 3H), 2.02 (s, 3H), 3.94 (q, J = 7.2 Hz,
2H), 6.78-6.48 (m, 4H), 7.27-7.40 (m, 9H); 13C NMR (100
MHz, CDCl3) δ 14.1, 18.4, 19.2, 61.3, 120 (ꢀ2), 127.5, 128.2,
129.6, 129.7, 131.2 (ꢀ2), 131.5, 131.7, 132.4, 135.1, 138.9, 139.0,
139.4, 139.5, 139.9, 141.6, 169.7; IR (KBr) 3053, 3024, 2978,
2933, 2872, 1722, 1592, 1493 cm-1; EI-HRMS calcd for
C29H24Br2O2 562.0143, found 562.0133.
Synthesis of 3. The mixture of compound 2 (10.00 g, 17.7
mmol) and 17.7 M H2SO4 (100 mL) was heated at 70 °C for
30 min. After cooling to room temperature, the mixture was
poured into H2O. The precipitate was collected on a filter,
washed with H2O, and dried under vacuum to afford the yellow
solid of 3 with a yield of 95%: mp 202-204 °C; 1H NMR (400
MHz, CDCl3) δ 2.27 (s, 3H), 2.35 (s, 3H), 6.76-6.82 (m, 4H),
7.28-7.34 (m, 5H), 7.49 (t, J = 7.6 Hz, 1H), 7.68-7.71 (m, 2H);
13C NMR (100 MHz, CDCl3) δ 15.6, 18.1, 120.7, 120.9, 123.6,
123.9, 128.4, 129.7, 130.5, 130.9, 131.0, 131.1, 131.5, 134.3,
135.0, 135.4, 138.0, 138.5, 142.3, 144.0, 146.7; IR (KBr) 3047,
2922, 2868, 1699, 1605 cm-1; EI-HRMS calcd for C27H18Br2O
515.9724, found 515.9724.
Synthesis of 4. The mixture of compound 3 (5.00 g, 9.7 mmol)
in pyridine (55 mL) and KMnO4 (5.00 g, 31.6 mmol) in H2O
(2 mL) was heated at reflux for 2.5 h. Additional batches of 2 mL
of H2O and 5.00 g of KMnO4 were added every 30 min for five
times. The reaction mixture was further refluxed for 48 h. The
hot solution (ca. 80 °C) was filtered to remove the MnO2 solid
and the solid was washed with MeOH. The filtrate was con-
centrated and the acid was recovered by addition of 1 M HCl.
The precipitate was filtered and washed by H2O and dried under
vacuum to afford the yellow solid of 4 with a yield of 86%:
mp >300 °C; 1H NMR (400 MHz, MeOH-d4) δ7.02(d, J=6.4Hz
2H), 7.06 (d, J = 6.4 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 7.37 (d,
J = 8.0 Hz, 2H), 7.45 (t, J=7.6 Hz,1H), 7.59 (t, J = 7.6 Hz,
1H), 7.71 (d, J = 7.6 Hz, 1H), 7.74 (d, J = 7.6 Hz, 1H); 13C
NMR (100 MHz, MeOH-d4) δ 123.0, 123.1, 123.6, 125.4, 130.0,
131.3, 131.9, 131.9, 132.9, 133.1, 133.2, 134.4, 135.2, 136.5,
136.7, 137.3, 139.3, 140.0, 142.8, 144.9, 169.6, 170.4, 191.6; IR
(KBr) 3424, 2918, 2562, 1717, 1698, 1604, 1440, 1306, 1222
cm-1; EI-HRMS calcd for C27H14Br2O5 575.9208, found
575.9216.
Synthesis of 5. The mixture of powdered compound 4 (3.00 g,
5.2 mmol) and 17.7 M H2SO4 (90 mL) were added in a 250 mL
round-bottomed flask and heated to 130 °C under stirring for
1 h. After cooling to room temperature, the solution was poured
into ice. The precipitate was collected by filtration, washed with
(19) Dewar, M. J. S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J. J. P.
J. Am. Chem. Soc. 1985, 107, 3902–3909.
(20) Huang, C.-Y.; Hsu, Y.-C.; Chen, J.-G.; Suryanarayanan, V.; Lee,
K.-M.; Ho, K.-C. Sol. Energy Mater. Sol. Cells 2006, 90, 2391–2397.
(21) Goodson, F. E.; Novak, B. M. Macromolecules 1997, 30, 6047–6055.
(22) Mackay, D.; Pilger, C. W.; Wong, L. L. J. Org. Chem. 1973, 38, 2043–
2049.
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Lin et al.
JOCArticle
5% NaOH(aq) (3 ꢀ 30 mL) and then acetone, and dried under
vacuum to afford the dark red solid of 5 with a yield of 70%. Due
to its very poor solubility, the corresponding 1H and 13C NMR
spectra were not determined: mp >300 °C; IR (KBr) 3098, 3065,
1731, 1716, 1595, 1578 cm-1; FAB-HRMS calcd for C27H10-
Br2O3 539.8997, found 539.8997.
column chromatography (silica gel, ethyl acetate/hexanes: 1/20)
to provide 8a with a yield of 73%: mp 113-115 °C; H NMR
1
(400 MHz, CDCl3) δ 0.08-0.32 (m, 18H), 2.03-2.13 (m, 6H),
2.61-2.68 (m, 4H), 2.85-2.95 (m, 2H), 7.45-7.48 (m, 3H), 7.56
(s, 1H), 7.85 (s, 1H), 7.87 (d, J = 8.0 Hz, 1H), 8.20 (d, J =
8.0 Hz, 1H), 8.23 (d, J = 8.0 Hz, 1H), 8.23 (d, J = 8.0 Hz, 1H),
8.37 (d, J = 8.0 Hz, 1H), 10.08 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 8.8, 8.9, 9.0, 29.7, 32.9, 32.9, 58.2, 58.5, 59.9, 121.2,
121.5, 121.5, 123.3, 124.0, 124.3, 125.0, 125.6, 129.0, 129.1,
129.3, 134.5, 136.7, 138.1, 139.2, 139.4, 144.9, 145.1, 146.3,
146.6, 152.0, 153.7, 154.2, 191.8; IR (KBr) 2965, 2931, 2873,
1962, 1603, 1461 cm-1; FAB-HRMS calcd for C40H40Br2O
694.1446, found 694.1442.
Synthesis of 6. The mixture of compound 5 (1.5 g, 2.77 mmol)
in triethylsilane (50 mL) and boron trifluoride etherate (3 mL)
was heated at reflux for 2 h. Additional batches of 3 mL of boron
trifluoride etherate were added every 2 h for two times. The
reaction mixture was further refluxed for 24 h. The precipitate
was collected by filtration, washed with MeOH, and dried under
vacuum to afford the white solid of 6 with a yield of 80%. Due to
the very poor solubility of 6, the corresponding 13C NMR
spectrum was not determined: mp 281-283 °C; 1H NMR (400
MHz, CDCl3) δ 3.95 (s, 1H), 4.20 (s, 1H), 7.36 (t, J = 7.2 Hz,
1H), 7.46 (t, J = 7.2 Hz, 1H), 7.56 (d, J = 7.2 Hz, 1H), 7.58
(d, J = 7.2 Hz, 1H), 7.61 (d, J = 7.2 Hz, 1H), 7.73 (s, 1H), 7.78
(s, 1H), 7.86 (d, J = 8.4 Hz, 1H), 8.26 (d, J = 8.4 Hz, 1H), 8.28
Synthesis of 8b. The procedure is similar to that of 8a with a
yield of 66%: mp 52-54 °C; 1H NMR (400 MHz, CDCl3)
δ 0.50-1.09 (m, 66H), 1.93-2.10 (m, 6H), 2.41-2.50 (m, 4H),
2.77-2.84 (m, 2H), 7.43-7.50 (m, 3H), 7.55 (s, 1H), 7.82 (s, 1H),
7.87 (d, J = 8.0 Hz, 1H), 8.18 (d, J = 8.0 Hz, 1H), 8.21 (d, J =
8.0 Hz, 1H), 8.38 (d, J = 8.0 Hz, 2H), 10.08 (s, 1H); 13C NMR
(100 MHz, CDCl3) δ 14.3, 14.4, 14.4, 22.7, 23.0, 23.1, 24.2, 24.3,
24.4, 29.6, 29.7, 29.8, 31.6, 32.0, 32.1, 37.2, 40.8, 40.9, 57.1, 57.3,
58.7, 109.2, 120.9, 121.1, 121.2, 123.2, 124.0, 124.1, 124.6, 125.3,
128.6, 128.7, 128.9, 134.2, 136.0, 137.3, 173.4, 138.6, 138.8,
145.2, 145.4, 145.6, 146.7, 152.7, 154.2, 154.7, 191.4; IR (KBr)
2955, 2926, 2857, 1697, 1604, 1466, 1375 cm-1; FAB-HRMS
calcd for C64H88Br2O 1030.5205, found 1030.5189.
(d, J = 8.4 Hz, 1H); IR (KBr) 1457, 1414, 1367, 1083, cm-1
;
FAB-HRMS calcd for C27H16Br2 497.9619, found 497.9618.
Synthesis of 7a. To a solution of compound 6 (2.00 g,
4.00 mmol) and potassium tert-butoxide (5 g, 45 mmol) in dry
THF (80 mL) was added 18-crown-6 (cat. amount) at 0 °C. The
solution was stirred for 30 min at room temperature, and then
bromoethane (6.2 mL, 7.1 mmol) was added slowly. The solu-
tion was stirred further for another 120 min at 40 °C. The solu-
tion was cooled to 0 °C and an additional 6.2 mL of bromo-
ethane was added. The solution was then stirred at 40 °C for
20 h. The solvent was removed and the residue was extracted
with dichloromethane/water. The organic layer was dried with
MgSO4, filtered, and concentrated by rotary evaporation. The
residue was purified by using column chromatography (silica
gel, elution with hexane) to provide 7 with a yield of 52%:
Synthesis of 9a. Compound 8a (0.22 g, 0.3 mmol), diphenyl-
amine (0.12 g, 0.7 mmol), Pd2(dba)3 (18 mg, 0.02 mmol), and
sodium tert-butoxide (79.20 mg, 0.9 mmol) were mixed in a
Schlenk tube. Under N2, P(t-Bu)3 (0.59 mL, 0.05 M in toluene,
0.03 mmol) and toulene (0.5 mL) were added. The mixture was
heated to reflux with stirring for 24 h. The reaction mixture was
then cooled to room temperature, diluted with H2O, and
extracted with ethyl acetate. The combined organic solution
was washed with brine and dried over MgSO4. The solution was
concentrated under reduced pressure, and the residue was puri-
fied with column chromatography (silica gel, ethyl acetate/
hexanes: 1/10) to provide 9a with a yield of 45%: mp 112-114 °C;
1H NMR (400 MHz, CD2Cl2) δ 0.24-0.38 (m, 18H), 1.90-1.94
(m, 3H), 2.00-2.07 (m, 3H), 2.11-2.17 (m, 3H), 2.56-2.60 (m,
3H), 2.63-2.68 (m, 3H), 2.82-2.88 (m, 3H), 6.96-7.29 (m, 24H),
7.83 (s, 1H), 7.83 (d, J= 8.4 Hz, 1H), 8.28 (d, J= 8.4 Hz, 1H), 8.31
1
mp 208-210 °C; H NMR (400 MHz, CD2Cl2) δ 0.09-0.31
(m, 18H), 2.04-2.19 (m, 6H), 2.58-2.70 (m, 4H), 2.92-3.00
(m, 2H), 7.35-7.38 (m, 3H), 7.46-7.50 (m, 3H), 7.60 (s, 1H),
8.21-8.28 (m, 3H); 13C NMR (100 MHz, CDCl3) δ 9.2, 9.2,
9.4, 29.7, 33.2, 33.4, 58.1, 58.5, 59.9, 120.6, 121.3, 123.0, 123.6,
124.0, 124.7, 125.3, 125.8, 126.5, 128.5, 128.6, 136.0, 136.2,
139.4, 139.4, 139.6, 139.7, 143.1, 144.5, 144.9, 150.8, 153.1,
154.1; IR (KBr) 2967, 2930, 2873, 1456 cm-1; EI-HRMS calcd
for C39H40Br2 666.1497, found 666.1484.
(d, J = 8.4 Hz, 1H), 8.36 (d, J = 8.4 Hz, 1H), 10.05 (s, 1H); 13
C
Synthesis of 7b. The procedure is similar to that of 7a and
an oil-like product was obtained with a yield of 37%; 1H NMR
(400 MHz, CD2Cl2) δ 0.48-1.11 (m, 66H), 1.98-2.10 (m, 6H),
2.46-2.54 (m, 4H), 2.87-2.90 (m, 2H), 7.29-7.36 (m, 3H),
7.44-7.50 (m, 3H), 7.60 (s, 1H), 8.21 (d, J = 8.4 Hz, 1H), 8.26
(d, J = 8.4 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 14.4, 14.4,
22.7, 23.0, 23.1, 24.2, 24.2, 24.4, 29.7, 29.8, 29.9, 31.6, 32.1, 32.1,
37.1, 40.9, 41.2, 56.9, 57.2, 58.6, 120.6, 121.0, 123.1, 123.7, 124.0,
124.5, 125.2, 125.6, 126.5, 128.4, 128.5, 135.6, 135.7, 138.9,
139.1, 139.2, 139.2, 143.9, 144.9, 145.3, 151.7, 154.0, 155.0; IR
(KBr) 2955, 2926, 2856, 1466 cm-1; FAB-HRMS calcd for
C63H88Br2 1002.5253, found 1002.5214.
Synthesis of 8a. Under nitrogen atmosphere, 7a (0.45 g,
0.67 mmol) was dissolved in dried CH2Cl2 (10 mL) at 0 °C.
A batch of 1 M TiCl4 in CH2Cl2 (8.3 mL) was added dropwise in
30 min with sufficient stirring. The purple reaction mixture was
stirred for another 1 h at 0 °C, and then a solution of CH3O-
CHCl2 (0.18 mL, 2.01 mmol) in 10 mL of CH2Cl2 was added
dropwise over 10 min at 0 °C. The mixture was allowed to warm
slowly and stirred for 1 h at room temperature. The purple mix-
ture was poured into crushed ice. The organic layer was sepa-
rated, and the aqueous layer was extracted with ethyl acetate.
The combined organic fractions were washed with water and
brine and finally dried over MgSO4. The solution was concen-
trated under reduced pressure, and the residue was purified with
NMR (100 MHz, CD2Cl2) δ 9.2, 9.4, 30.2, 30.3, 30.6, 33.4, 33.5,
58.3, 58.8, 60.0, 117.6, 112.4, 122.0, 122.3, 122.4, 123.1, 123.1,
123.4, 124.2, 124.4, 124.5, 124.8, 129.3, 129.6, 134.9, 136.4, 145.6,
147.4, 147.8, 148.2, 152.6, 153.4, 153.6, 192.1; IR (KBr) 2965, 2929,
2873, 1964, 1594, 1492, 1484 1375, 1330, 1278 cm-1; FAB-HRMS
calcd for C64H60N2O1 872. 4706, found 872.4705.
Synthesis of 9b. The procedure is similar to that of 9a with a
yield of 45%: mp 244-246 °C; 1H NMR (400 MHz, CD2Cl2) δ
0.44-1.15 (m, 66H), 1.84-2.09 (m, 6H), 2.43-2.54 (m, 4H),
2.76-2.78 (m, 2H), 6.95-7.28 (m, 24H), 7.82 (s, 1H), 7.83 (d,
J = 8.4 Hz, 1H), 8.28 (d, J=8.4 Hz, 1H), 8.31 (d, J = 8.4 Hz,
1H), 8.38 (d, J = 8.4 Hz, 1H), 10.05 (s, 1H); 13C NMR
(100 MHz, CD2Cl2) δ 14.6, 14.8, 23.2, 23.5, 24.8, 24.9, 30.1,
30.3, 32.1, 32.6, 32.6, 37.6, 41.2, 41.4, 57.21, 57.5, 58.6, 117.5,
118.3, 121.6, 122.1, 122.7, 122.7, 123.1, 124.0, 124.0, 124.5,
128.7, 129.2, 134.4, 135.7, 136.6, 145.5, 146.0, 146.5, 146.8,
147.1, 147.8, 153.0, 154.0, 154.3, 191.6; IR (KBr) 2954, 2926,
2856, 1696, 1595, 1494, 1375, 1331, 1278 cm-1; FAB-HRMS
calcd for C88H108N2O 1208.8462, found 1208.8429.
Synthesis of 9c. The procedure is similar to that of 9a with a
yield of 52%: mp 136-138 °C; 1H NMR (400 MHz, CD2Cl2) δ
0.22-0.35 (m, 18H), 1.85-1.91 (m, 3H), 1.97-2.02 (m, 3H),
2.09-2.14 (m, 3H), 2.51-2.56 (m, 3H), 2.61-2.66 (m, 3H),
2.79-2.84 (m, 3H), 6.84-7.10 (m, 20H), 7.81 (s, 1H), 7.82 (d,
J = 8.0 Hz, 1H), 8.18 (d, J = 8.4 Hz, 1H), 8.21 (d, J = 8.4 Hz,
7884 J. Org. Chem. Vol. 75, No. 22, 2010

Lin et al.
JOCArticle
1H), 8.33 (d, J = 8.0 Hz, 1H), 10.04 (s, 1H); 13C NMR (100
MHz, CD2Cl2) δ 9.2, 9.2, 9.4, 30.2, 30.3, 33.4, 33.5, 56.0, 58.2,
58.7, 59.8, 114.3, 115.0, 115.2, 119.2, 119.3, 122.0, 123.0, 123.9,
124.7, 126.6, 126.6, 129.3, 134.6, 134.7, 137.0, 137.3, 139.1,
141.5, 141.6, 145.1, 145.3, 147.6, 148.4, 148.7, 152.5, 153.2,
153.6, 156.1, 156.2, 192.2; IR (KBr) 2964, 2929, 2873, 1692,
1601, 1506, 1240 cm-1; FAB-HRMS calcd for C68H69N2O5
992.5128, found 992.5133.
Synthesis of 10. A mixture of compound 7a (1.00 g, 1.5 mmol)
and 14 mL of mixed solvents (CH3COOH:H2SO4:H2O:CHCl3 =
100:5:20:8) was heated to 40 °C with stirring. The reagents HIO3
(0.13 g, 0.8 mmol) and I2 (0.38 g, 1.5 mmol) were then added.
The solution was heated to 80 °C and stirred for 24 h. The solution
was cooled to room temperature and extracted with CH2Cl2.
The organic layer was washed with Na2S2O3 and concentrated
under reduced pressure, and the residue was purified with column
chromatography (silica gel, hexanes) to provide 10 with a yield of
95%: mp 208-210 °C; 1H NMR (400 MHz, CDCl3) δ 0.23-0.30
(m, 18H), 1.97-2.13 (m, 6H), 2.54-2.63 (m, 4H), 2.80-2.85
(m, 2H), 7.42-7.46 (m, 3H), 7.53 (s, 1H), 7.62 (s, 1H), 7.65
(d, J = 8.4 Hz, 1H), 7.93 (d, J = 8.4 Hz, 1H), 8.16 (d, J =
8.4 Hz, 1H), 8.21 (d, J = 8.4 Hz, 1H); 13C NMR (100 MHz,
CDCl3) δ 9.2, 9.3, 29.7, 33.2, 33.2, 58.1, 28.7, 59.9, 92.6, 120.8,
120.9, 123.1, 123.6, 124.7, 125.3, 125.6, 128.6, 128.8, 130.4, 134.8,
136.1, 136.7, 138.3, 139.2, 139.3, 143.4, 144.3, 144.5, 153.1, 153.4,
153.9; IR (KBr) 2965, 2928, 2871, 1457, 1366 cm-1; FAB-HRMS
calcd for C39H39Br2I 792.0463, found 792.0460.
Synthesis of 11. A mixture of compound 10 (0.30 g, 0.4 mmol),
2-thienylboronic acid (53 mg, 0.4 mmol), and Pd(PPh3)4 (44 mg,
0.04 mmol) was mixed in a Schlenk tube. Under N2, P(t-Bu)3
(0.63 mL, 0.05 M in toluene, 0.04 mmol), THF (2 mL), and
K3PO4 (0.3 mL, 2 M in H2O, 0.6 mmol) were added into the
tube. The solution was stirred for 48 h at room temperature. The
reaction mixture was diluted with H2O and extracted with
CH2Cl2. The combined organic solution was washed with brine,
dried over MgSO4, and concentrated under reduced pressure.
The residue was washed with methanol and collected by filtra-
tion to provide 11 with a yield of 84%: mp >300 °C; 1H NMR
(400 MHz, CDCl3) δ 0.23-0.32 (m, 18H), 2.02-2.16 (m,
6H), 2.60-2.65 (m, 4H), 2.89-2.95 (m, 2H), 7.10 (t, J = 4.4
Hz, 1H), 7.30 (d, J = 6 Hz, 1H), 7.41 (d, J = 4.4 Hz, 1H), 7.2
(s, 1H), 7.44-7.46 (m, 3H), 7.52 (s, 1H), 7.55 (s 1H), 7.61(d, J =
8.0 Hz, 1H), 8.16-8.24 (m, 3H); 13C NMR (100 MHz, CDCl3) δ
8.9, 9.0, 9.0, 29.6, 33.0, 33.2, 58.0, 58.6, 59.8, 118.6, 120.9, 122.9,
123.3, 123.8, 124.1, 124.6, 124.9, 125.6, 128.0, 128.8, 129.0,
132.8, 136.4, 136.7, 139.2, 139.5, 139.7, 139.9, 143.5, 144.5,
144.9, 145.4, 152.1, 153.5, 154.5; IR (KBr) 1966, 2929, 2872,
1459, 1367, 809.8 cm-1; FAB-HRMS calcd for C43H42Br2S
748.1374, found 748.1375.
132.8, 136.7, 136.8, 137.1, 137.6, 138.5, 140.7, 144.2, 144.7,
145.1, 145.4, 147.2, 147.3, 148.3, 152.7, 153.1, 154.0; IR (KBr)
2966, 2930, 2873, 1593, 1492, 1280 cm-1; FAB-HRMS calcd for
C67H62N2S 926.4634, found 926.4636.
Synthesis of 13. To a solution of compound 12 (0.20 g,
0.2 mmol) in THF (15 mL) at -20 °C was added a solution of
1.6 M n-butyl lithium (0.15 mL, 0.2 mmol) over 20 min. Dry
DMF (0.1 mL) was added at -40 °C with stirring for 10 min.
The solution was warmed to room temperature over 10 min
before being quenched (1 M NH4Cl, 10 mL) and extracted with
ethyl acetate. The combined organic solution was washed with
brine, dried over MgSO4, and then concentrated under reduced
pressure. The residue was purified with column chromatog-
raphy (silica gel, CH2Cl2/hexanes: 1/2) to provide 13 with a yield
of 78%: mp 171-173 °C; 1H NMR (400 MHz, CD2Cl2) δ
0.32-0.41 (m, 18H), 1.92-1.95 (m, 2H), 2.00-2.22 (m, 4H),
2.53-2.67 (m, 4H), 2.83-2.87 (m, 2H), 7.01-7.28 (m, 24H),
7.52 (d, J = 4 Hz, 1H), 7.63 (s, 1H), 7.69 (d, J = 8.0 Hz, 1H),
7.77 (d, J = 4 Hz, 1H), 8.26-8.33 (m, 3H), 9.87 (s, 1H); 13C
NMR (100 MHz, CD2Cl2) δ 9.5, 9.5, 9.6, 30.2, 33.5, 33.7, 58.1,
59.9, 109.6, 117.5, 118.2, 122.1, 122.7, 123.0, 123.9, 129.2, 137.6,
142.0, 145.0, 146.7, 152.7, 153.4, 182.2; IR (KBr) 2967, 2929,
2872, 1669, 1592, 1494, 1443, 1279 cm-1; FAB-HRMS calcd for
C68H62N2OS 954.4583, found 954.4597.
Synthesis of ITD. A mixture of 9a (140 mg, 0.16 mmol),
cyanoacetic acid (50 mg, 0.6 mmol), ammonium acetate (50 mg,
0.7 mmol), and acetic acid (5 mL) was heated at 130 °C for 5 h.
After cooling to room temperature, it was precipitated by
pouring into water. The resulting solid was filtered, washed
thoroughly with water and methanol, and reprecipitated from
dichloromethane by pouring into methanol to provide ITD with
a yield of 80%. For DSSC fabrication, the compound was further
purified by column chromatography (eluent EA/MeOH = 1/5):
1
mp 282-284 °C; H NMR (400 MHz, CD2Cl2) δ 0.26-0.38
(m, 18H), 1.90-1.96 (m, 2H), 2.01-2.14 (m, 4H), 2.54-2.63
(m, 2H), 2.64-2.68 (m, 2H), 2.82-2.85 (m, 2H), 6.96-7.29
(m, 24H), 7.98 (s, 1H), 8.04 (d, J = 8.8 Hz, 1H), 8.28 (d, J =
8.8 Hz, 1H), 8.31 (d, J = 8.8 Hz, 1H), 8.35 (d, J = 8.8 Hz, 1H),
8.36 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ 9.4, 9.4, 9.6,
29.6, 57.9, 58.6, 59.6, 117.3, 118.1, 122.6, 123.6, 123.7, 124.3,
124.4, 124.8, 124.9, 130.1, 135.4, 135.7, 136.9, 137.4, 138.5,
145.2, 145.3, 147.3, 147.7, 147.8, 152.2, 153.1, 153.6, 154.6,
164.0; IR (KBr) 3441, 2967, 2931, 2874, 1592, 1491, 1482,
1376, 1331, 1280 cm-1; FAB-HRMS calcd for C67H61N3O2
939.4764, found 939.4775
Synthesis of ITD-Hx. The procedure is similar to that of ITD
1
with a yield of 55%: mp 256-258 °C; H NMR (400 MHz,
CD2Cl2) δ 0.64-1.10 (m, 66H), 1.83-2.13 (m, 6H), 2.45-2.55
(m, 4H), 2.79 (m, 2H), 6.94-7.27 (m, 24H), 8.01 (s, 1H), 8.08
(m, 1H), 8.27-8.34 (m, 3H), 8.50 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ 13.9, 14.0, 14.1, 22.4, 22.7, 24.0, 24.1, 29.4, 29.5, 29.7,
31.4, 31.8, 31.9, 31.9, 36.9, 40.6, 40.8, 56.6, 57.0, 58.0, 117.1,
118.1, 122.1, 122.6, 122.7, 123.3, 124.0, 124.0, 129.2, 129.8,
135.3, 135.6, 136.4, 136.8, 138.6, 145.6, 146.4, 147.0, 147.3,
147.8, 147.9, 153.3, 154.1, 154.4; IR (KBr) 3446, 2954, 2926,
2856, 1594, 1494, 1376, 1332, 1277 cm-1; FAB-HRMS calcd for
C91H109N3O2 1275.8520, found 1275.8517.
Synthesis of 12. Compound 11 (0.40 g, 0.5 mmol), diphenyl-
amine (0.19 g, 1.7 mmol), Pd2(dba)3 (50 mg, 0.05 mmol), and
sodium tert-butoxide (184 mg, 1.9 mmol) were mixed in a
Schlenk tube. Under N2, P(t-Bu)3 (1.33 mL, 0.05 M in toluene,
0.07 mmol) and toulene (1 mL) were added into the tube. The
tube was heated to reflux with stirring for 24 h. The reaction
mixture was then cooled to room temperature, diluted with
H2O, and extracted with ethyl acetate. The combined organic
solution was washed with brine, dried over MgSO4, and con-
centrated under reduced pressure. The residue was purified with
column chromatography (silica gel, CH2Cl2/hexanes: 1/6)
Synthesis of ITD-OM. The procedure is similar to that of ITD
1
with a yield of 80%: mp 276-278 °C; H NMR (400 MHz,
DMSO-d6) δ 0.16-0.27 (m, 18H), 1.82-2.07 (m, 6H), 2.5 (m,
4H), 2.73-2.78 (m, 2H), 3.75 (s, 12H), 6.73 (d, J = 9.6 Hz, 1H),
6.75 (d, J = 9.6 Hz, 1H), 6.86 (s, 1H), 6.92 (d, J = 7.2 Hz, 8H),
6.96 (s, 1H), 7.05 (d, J = 7.2 Hz, 8H), 7.88 (d, J = 8.0 Hz, 1H),
7.95 (s, 1H), 8.00 (s, 1H), 8.10 (d, J = 8.4 Hz, 1H), 8.14 (d, J =
8.4 Hz, 1H), 8.18 (d, J = 8.4 Hz, 1H); 13C NMR (200 MHz,
DMSO-d6) δ 8.5, 8.5, 8.7, 28.9, 32.1, 32.2, 55.2, 56.9, 57.6, 58.6,
112.7, 113.4, 114.9, 117.0, 118.2, 122.5, 123.4, 123.9, 124.1,
126.3, 129.2, 129.6, 132.8, 133.0, 136.1, 136.3, 137.9, 140.2,
1
to provide 12 with a yield of 57%: mp 168-170 °C; H NMR
(400 MHz, CD2Cl2) δ 0.28-0.39 (m, 18H), 1.90-2.12 (m, 6H),
2.55-2.67 (m, 4H), 2.85-2.90 (m, 2H), 6.96-7.32 (m, 26H),
7.32 (d, J = 3.2 Hz, 1H), 7.55 (s, 1H), 7.62 (d, J = 9.6 Hz, 1H),
8.20 (d, J = 8.0 Hz, 1H), 8.27 (d, J = 8.0 Hz, 1H), 8.33 (d, J =
8.0 Hz, 1H); 13C NMR (100 MHz, CD2Cl2) δ 9.3, 9.3, 9.4, 30.1,
33.4, 33.7, 58.1, 58.9, 59.9, 118.0, 118.6, 119.0, 122.5, 122.6,
123.0, 123.3, 123.3, 123.9, 124.4, 124.9, 125.1, 128.5, 129.6,
J. Org. Chem. Vol. 75, No. 22, 2010 7885

Lin et al.
JOCArticle
140.3, 144.1, 144.2, 144.6, 147.8, 148.1, 151.5, 152.2, 152.8,
153.3, 155.6, 155.6, 163.5; IR (KBr) 3446, 2965, 2931, 2873,
2932, 1602, 1506, 1240 cm-1; FAB-HRMS calcd for C71H69-
N3O6 1059.5186, found 1059.5192.
144.6, 145.0, 146.9, 147.1, 147.8, 152.6, 152.7, 153.4, 156.3,
167.2; IR (KBr) 3445, 2966, 2930, 2872, 1717, 1586, 1482,
1278, cm-1; FAB-HRMS calcd for C71H63N3O2S 1021.4641,
found 1021.4637.
Synthesis of ITD-Th. The procedure is similar to that of ITD
1
with a yield of 80%: mp 234-236 °C; H NMR (400 MHz,
Acknowledgment. We thank the National Science Council
of Taiwan, ROC, for financial support.
CD2Cl2) δ 0.29-0.40 (m, 18H), 1.91-2.17 (m, 6H), 2.56-2.70
(m, 4H), 2.83-2.88 (m, 2H), 6.97-7.30 (m, 24H), 7.59 (d, J =
4 Hz, 1H), 7.67 (s, 1H), 7.75 (d, J=8.0 Hz, 1H), 7.87 (d, J =
4 Hz, 1H), 8.29 (d, J = 8.0 Hz, 2H), 8.33 (d, J = 8.0 Hz, 1H),
8.42 (s, 1H); 13C NMR (100 MHz, CD2Cl2) δ 9.5, 9.5, 9.6,
30.2, 33.5, 33.7, 58.1, 59.0, 59.9, 115.9, 117.5, 118.1, 119.3,
122.1, 122.7, 123.0, 123.7, 124.0, 124.5, 124.9, 124.9, 129.2,
130.5, 134.4, 136.1, 136.8, 137.5, 138.0, 140.5, 142.8, 144.3,
Supporting Information Available: Absorption and fluo-
rescence spectra of 12 and 13, cyclic and differential pulse
1
voltammograms for the ITDs, and H and 13C NMR spectra
of new compounds. This material is available free of charge via
the Internet at http://pubs.acs.org.
7886 J. Org. Chem. Vol. 75, No. 22, 2010