Synthesis and photovoltaic properties of novel solution-processable triphenylamine-based dendrimers with sulfonyldibenzene cores

Article abstract of DOI:10.1039/b9nj00236g

Three conjugated dendrimers containing electron-accepting sulfonyldibenzene (SDB) cores and electron-donating triphenylamine dendrons have been synthesized through a convergent synthetic strategy without any protection/deprotection chemistry. The dendrimers were highly soluble in common organic solvents, and could form good quality optical films by spin coating. Their thermal, optical and electrical properties are manipulated by attaching different peripheral dendrons. Using these dendrimers as donors and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as acceptor, the bulk heterojunction solar cells with a structure of ITO-PEDOT-dendrimers:PCBM-LiF-Al were fabricated. The cell based on dendrimer G0 shows a relatively high power-conversion efficiency (PCE) of 0.34% under AM 1.5 illumination of 100 mW cm^-2.

Full text of DOI:10.1039/b9nj00236g

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Synthesis and photovoltaic properties of novel solution-processable
triphenylamine-based dendrimers with sulfonyldibenzene coresw
Kunpeng Li, Jiali Qu, Bin Xu, Yinhua Zhou, Leijing Liu, Ping Peng
and Wenjing Tian*
Received (in Montpellier, France) 5th June 2009, Accepted 15th July 2009
First published as an Advance Article on the web 10th August 2009
DOI: 10.1039/b9nj00236g
Three conjugated dendrimers containing electron-accepting sulfonyldibenzene (SDB) cores and
electron-donating triphenylamine dendrons have been synthesized through a convergent synthetic
strategy without any protection/deprotection chemistry. The dendrimers were highly soluble in
common organic solvents, and could form good quality optical films by spin coating.
Their thermal, optical and electrical properties are manipulated by attaching different
peripheral dendrons. Using these dendrimers as donors and [6,6]-phenyl C61-butyric acid
methyl ester (PCBM) as acceptor, the bulk heterojunction solar cells with a structure of
ITO–PEDOT–dendrimers:PCBM–LiF–Al were fabricated. The cell based on dendrimer
G0 shows a relatively high power-conversion efficiency (PCE) of 0.34% under AM 1.5
À2
illumination of 100 mW cm
.
donating ability, and isotropic optical and charge-transport
10,11
properties as well as a three-dimensional propeller structure.
Introduction
In the past decade, organic solar cells (OSCs) have been
extensively investigated because of their advantages of
On the other hand, molecules with D–p–A structure have
many advantages, such as lower bandgap due to the intra-
molecular charge transfer (ICT) between the donor and
acceptor and easily controlled energy levels by introducing
acceptor and donor moieties with different pull–push electron
1
–7
low-cost, light weight, and easy fabrication.
%-efficient thin-film OSCs based on a single donor–acceptor
Since the
1
8
D–A) heterojunction was reported by Tang, the power-
(
conversion efficiency (PCE) of OSCs has steadily improved
through the design and synthesis of new materials and the
optimization of the cell structures. Among the new active
materials, small-molecules have advantages such as well-
defined molecule structure, relatively simple and reproducible
synthesis and purification, its monodisperse nature, ability to
be vacuum deposited in multi-layer stacks, and so on. For the
purpose of practical applications, nevertheless, small molecules
have to be processed by expensive techniques, for example,
vacuum sublimation and vapor deposition, which are not well
suited to the manufacture of large size devices. Polymers are
generally of lower purity than small molecules but can achieve
larger size films at much lower costs using solution-based
deposition techniques such as spin coating, inkjet, and
roll-to-roll printing. Thus, the ideal materials should have
advantages of both small molecules and polymers.
12
abilities into the molecules. So considerable research efforts
have led to much progress in the synthesis of new molecules
which mainly consist of a TPA moiety linked to different
acceptor moieties, including dicyanovinyl, perylene, benzo-
13,14
thiadiazole, or 2-pyran-4-ylidenemalononitrile.
Therefore, dendrimers containing triphenylamine dendrons
and the D–p–A structure could be expected to be one of the
ideal active molecules for the application of thin-film OSCs.
In this paper, we designed and synthesized three novel
dendrimers with symmetrical donor–p-bridge–acceptor–
p-bridge–donor (D–p–A–p–D) structure with sulfonyl-
dibenzene as the core and triphenylamines as dendrons. These
conjugated dendrimers have good solubility in common
organic solvents, such as chloroform, dichloromethane,
1
,2-dichloroethane, and THF etc. They also exhibit good film
forming properties which is of great importance for their
application in photovoltaic devices. We investigated the
photovoltaic properties of the three dendrimers by fabricating
the bulk heterojunction solar cells with a structure of
ITO–PEDOT–dendrimers:PCBM–LiF–Al, and the PCEs of
the solar cells based on the three dendrimers are 0.34%, 0.19%
and 0.06%, respectively.
Dendrimers with molecular weights in the favorable
À1
range between 1000–10 000 g mol
can be purified to a
high degree using chromatographic techniques, and deposited
into a thin film from solution by a simple spin-coating
9
process.
Meanwhile, triphenylamine (TPA) derivatives have shown
excellent thermal and electrochemical stability, electron
Results and discussion
State Key Laboratory of Supramolecular Structure and Materials,
Jilin University, Changchun 130012, China.
E-mail: wjtian@jlu.edu.cn; Fax: +86 431 85193421;
Tel: +86 431 85166368
w Electronic supplementary information (ESI) available: Supplementary
figures, tables and spectra. See DOI: 10.1039/b9nj00236g
Synthesis of materials
The synthetic routes to the core and dendrons as well as the
dendrimer are shown in Scheme 1 and Scheme 2. Compound 1
2
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Scheme 1 Synthesis of the sulfonyldibenzene core and TPA-based dendrons.
was synthesized by a Friedel–Crafts acylation from 4-methyl-
benzene-1-sulfonyl chloride and toluene with a yield of 68%.
The bromination of compound 1 by employing N-bromo-
succinimide (NBS) in benzene successfully afforded the desired
compound 2. Compound 3 can be easily prepared from
compound 2 through the reaction with the triethyl phosphate
potassium tert-butoxide as base in a yield of 78%. The second
and third generation G1 and G2 were obtained through the
same synthetic method in yields of 61% and 45%, respectively.
1
Dendrons and dendrimers were characterized by H NMR,
1
C NMR, FT-IR, elemental analysis and MALDI-TOF mass
3
spectroscopy. G0, G1 and G2 exhibit an IR absorption band
À1
under the protection of N
2
. The strategy as reported by our
around 960 cm arising from the wagging vibration of the
21,22
1
5
group for the synthesis of the aldehyde-focused dendron
is illustrated in Scheme 1. Firstly, 4-(diphenylamino)-
benzaldehyde, which is the first generation aldehyde-focused
trans-double bond.
Additional definitive evidence for the
molecular structures of the dendrimers was obtained from
MALDI-TOF mass spectra. And the deviation between the
calculated and experimentally measured m/z values was no
more than one mass unit.
1
6,17
dendron G0–CHO,
through a Vilsmeier reaction in a yield of 90%. Then, iodination
of G0–CHO with KI–KIO in AcOH at 85 1C provided
compound 4 with a good yield of 95%, and the compound
was prepared in a 76% yield from the reaction of G0–CHO
was readily obtained from TPA
3
1
8
Thermal properties
5
The differential scanning calorimetry (DSC) second heating
with methyltriphenylphosphonium bromide. After that, the
second generation aldehyde-focused dendron G1–CHO was
prepared in a 55% yield via the coupling of compound 4
thermograms of G0, G1 and G2 recorded at a scanning rate of
À1
1
0 1C min under nitrogen protection indicated that the
Tg of G0, G1 and G2 (81 1C, 138 1C and 175 1C) increases
gradually, due to the reduced segmental motions and
enhanced intermolecular dipolar interaction to a certain extent
1
9
and compound 5 through the Heck reaction. The third
generation aldehyde-focused dendron G2–CHO can be
obtained from compound 4 and compound 6 through the
Heck reaction, while compound 6 can be synthesized by
(
see Fig. S1, ESIw).
2
0
the Wittig reaction
of G1–CHO and methyltriphenyl-
Absorption
phosphonium bromide. The first-generation of dendrimer G0
was synthesized via a typical Wittig–Horner reaction between
aldehyde G0-CHO and compound 3 in dry THF, using
Fig. 1 shows the UV-vis absorption spectra of the dendrimers
in films coated on quartz substrate. G0 displays two
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Scheme 2 Synthesis of the sulfonyldibenzene-based dendrimers.
This explains that the increase of TPA units with the increasing
generations of dendrimers results in the extension of the
conjugated length and a stronger electron-donating ability of
the donor parts in G1 and G2. It also indicates that the
conjugated length in the dendrimers could be increased by
2
3
the introduction of TPA units, but the increasing degree
might be saturated when the conjugated chain was enlarged to
a certain extent by such large size and non-coplanar TPA
dendrons.
It is noted that the Y-axis in Fig. 1 represents the extinction
coefficient (a) of the three dendrimer films with the same
thickness. The decrease of the extinction coefficient from G0
to G2 films is due to the large size of TPA dendrons which
occupy a large space in the dendrimer films. When the thick-
ness of the films of G0, G1 and G2 is the same (70 nm), the
molecule number of G2 in the film is less than those of G0 and
G1, resulting in less ICT transition and ultimately the decrease
of the absorption from G0 to G2 films. The UV and PL spectra
of G0, G1 and G2 in solution can be seen in the ESI.w
Fig. 1 UV-vis absorption-coefficient (a) spectra of G0, G1 and G2 in
the films. All films were measured on a glass–ITO–PEDOT:PSS
substrate and corrected for substrate absorption.
absorption peaks at 304 nm and 410 nm, which are ascribed to
the absorption of the n–p* transition of the SDB moiety and
the intramolecular charge transfer between the TPA donor
and the SDB acceptor, respectively. It was also observed that
G1 displayed two absorption peaks at 307 nm and 416 nm, and
G2 at 311 nm and 419 nm. Comparing with G0, the ICT
transitions of G1 and G2 red-shift 6 nm and 9 nm, respectively.
Electrochemistry
Fig. 2 shows the cyclic voltammetry (CV) diagrams of the
three dendrimers in CH Cl in the presence of TBAPF as the
2
2
6
supporting electrolyte with platinum button working electrodes,
a platinum wire counter electrode and an Ag/AgNO reference
3
2
122 | New J. Chem., 2009, 33, 2120–2127
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2 2
Fig. 2 CV diagrams of the three dendrimers in CH Cl .
2
electrode under an N atmosphere. The redox potential of
+
Fig. 3 The HOMO (top) and LUMO (bottom) orbitals in the
optimized ground-state structure of G0.
Fc/Fc , which has an absolute energy level of À4.8 eV relative
to the vacuum level for calibration, is located at 0.20 V
in TBAPF
6
À1
(0.1 M)–CH
2
Cl
2
solution at a scan rate of
Quantum-chemical calculations
1
00 mV S . The CV curve of G0 shows a pair of reversible
redox peaks in the negative region because of the high
electrical activity of the SDB core, but there are no redox
peaks in the negative region for G1 and G2 due to the
surrounding effect of TPA flock. In the positive region, the
oxidation peaks of G0, G1 and G2 can be attributed to TPA
In order to investigate the electron distribution of the LUMO
and HOMO energy levels of the dendrimers, quantum-chemical
calculations were carried out through the Gaussian 03
27
program at the B3LYP/6-31G* level. Fig. 3 shows the
electron distribution of the LUMO and HOMO in the
optimized ground-state structure of G0. Comparison of the
electron distribution in the frontier on the molecular orbitals
reveals that the HOMO is localized on the triphenylamine
donor moiety, while the LUMO is localized on the sulfonyl-
dibenzene acceptor moiety, which is generally an indication
of a HOMO - LUMO absorption transition bearing a
onset
donating groups. The onset oxidation potentials (EOx ) are
observed at +0.67 V, +0.63 to +0.45 V for G0, G1 and G2.
The evaluation of the highest occupied molecular orbital
(
HOMO) and the lowest unoccupied molecular orbital
LUMO) energy levels can be done according to the following
(
2
4
equations:
2
8,29
significant charge-transfer character.
onset
HOMO (eV) = À(eEOx + 4.60 eV)
onset
LUMO (eV) = À(eERed + 4.60 eV)
(1)
(2)
Photovoltaic properties
In order to investigate the photovoltaic properties of the three
dendrimers, bulk heterojunction solar cells (cell 1, cell 2 and
cell 3) with G0, G1 and G2 as donors and PCBM as an
acceptor were fabricated. Devices based on compound–PCBM
blend films with varied ratios (2 : 1, 1 : 1, 1 : 2, 1 : 3, 1 : 4) were
prepared, and the active layer thickness was optimized. We
found that when the blend ratio reaches 1 : 2, the device
performance is the best and 65–70 nm is the best active layer
thickness for all kinds of devices. Detailed information is listed
in Table S1 ESI.w The monochromatic incident photon-to-
electron conversion efficiency (IPCE) spectra of the three cells
under monochromatic irradiation are shown in Fig. 4, which
coincide well with the absorption spectra of the three active
onset
onset
where EOx and ERed are the onset redox potentials relative
+
25
to Ag/Ag . The electrochemical properties as well as the
energy levels of G0, G1 and G2 are summarized in Table 1.
The HOMO energy levels of G0, G1 and G2 is À5.27 eV,
À5.23 eV and À5.05 eV, respectively, which means that with
the increase of the number of TPAs in the external group, the
electron-donating ability of the external groupis enhanced.
The LUMO energy level of G0 is obtained from eqn (2), while
those of G1 and G2 were estimated from the HOMO energy
opt 26
level and the optical band gap (Eg ). The LUMO energy
levels of the three dendrimers are similar due to their
containing the same acceptor group SDB.
Table 1 The electrochemical properties and energy levels of G0, G1 and G2
onset
Ox /V
onset
Red /V
opta
Eg /eV
elc
Eg /V
Dendrimer
E
E
HOMO/eV
LUMO/eV
G0
G1
G2
0.67
0.63
0.45
À1.8
—
—
À5.27
À5.23
À5.05
À2.8
2.59
2.45
2.30
2.47
—
—
b
À2.78
b
À2.75
a
opt
b
opt
The Eg
el
Eg = band gap from electrochemistry.
was obtained from the absorption edge. LUMO of G1 and G2 is calculated by the equation |LUMO| = |HOMO| À Eg
.
c
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so despite the equal Voc and higher FF (0.32), the PCE is
about half of that of cell 1. For cell 3, the Voc decreases slightly
to 0.77, with an FF equal to 0.28, and a PCE of 0.06%. The
photovoltaic parameters of the solar cells are summarized in
Table 2. It can be seen that the drop of PCE from G0 to G2
mainly results from the drop of I . As we know, I is firstly
sc
sc
determined by the absorption of the active layer. Comparing
the absorptions of G0, G1 and G2 in Fig. 1, G1 and G2 absorb
larger-wavelength photons, which is beneficial to Isc. But the
extinction coefficients of G1 and G2 are lower than that of G0,
which means G0 absorbs more photons than G1 and G2 in a
film with the same thickness. Meanwhile, the low Isc of G2 is
caused by the aggregated configuration in a G2–PCBM blend
film. The AFM images of blend films of G0–PCBM and
G2–PCBM, as shown in Fig. S2 (ESIw), reveal a roughness
with root mean square (RMS) 0.45 nm and 2.23 nm, respectively,
which reveals that G0 has better film-forming properties
compared with G2. The poor solubility due to the huge
molecular weight of G2 may lead to the bad film-forming
ability. The better photovoltaic behavior obtained with G0 as
a donor should be ascribed to the synergistic effects of its
enhanced absorption of incident light, high quality uniform
spin-cast film.
Fig. 4 Photocurrent action spectra of bulk heterojunctions of G0–2
and PCBM (1 : 2, w/w) under monochromatic irradiation.
Conclusion
In conclusion, we have synthesized three conjugated dendrimers
bearing electron-accepting sulfonyldibenzene groups as the
cores, and TPA moieties as electron-donating dendrons, through
a convergent synthetic strategy without any protection/
deprotection chemistry. The dendrimers are highly soluble in
common organic solvents, and could form excellent-quality
optical films by spin coating. Their thermal, optical and
electrical properties are manipulated by attaching different
peripheral dendrons. Quantum-chemical calculations of
electronic structure show that the HOMO and LUMO of G0
are highly localized on the donor and acceptor moieties,
respectively. Using G0, G1 and G2 as donors and PCBM as
an acceptor, bulk heterojunction solar cells with a structure of
ITO–PEDOT–dendrimers:PCBM–LiF–Al were fabricated.
The cell based on G0 shows a relatively high PCE of 0.34%.
Fig. 5 Current–voltage curves of cells prepared from the active layers
of dendrimers : PCBM (1 : 2, w/w) under AM 1.5 G irradiation with an
À2
intensity of 100 mW cm
.
layers. The photoresponse in the range of 300–360 nm is from
the absorption of n–p* and PCBM and that in the visible
region 370–550 nm is mainly from the absorption of ICT from
the donor to the acceptor. The different IPCEs of the three
cells originated from the different PCEs.
Fig. 5 shows the current density–voltage (I–V) characteristics
of the solar cells with the thickness of an active layer of 70 nm
Experimental
under AM 1.5 (AM: air mass) illumination with an intensity of
À2
1
00 mW cm . Cell 1 has the best PCE of 0.34% compared
General
with cell 2 and cell 3, with a relatively high short circuit current
À2
All chemicals, reagents, and solvents were used as received
from commercial sources without further purification.
Tetrahydrofuran (THF) was refluxed with sodium and benzo-
(
I
sc) of 1.6 mA cm , an open circuit voltage (Voc) of 0.79 V
and a fill factor (FF) of 0.28, which is relatively lower than the
PCE of solar cells based on donor–acceptor molecules reported
1
13
phenone, and distilled. H NMR and C NMR spectra were
recorded on an AVANCE 500 spectrometer and a Varian
Mercury-300 NMR, with tetramethylsilane (TMS) as the
standard. The FT-IR spectra were recorded via the KBr pellet
method by using a Nicolet Impact 410 FT-IR spectro-
photometer. The mass spectra were recorded on a Kratos
MALDI-TOF mass spectrometer, and the spectra were
recorded in the reflection mode with anthracene-1,8,9-triol as
the matrix. The synthetic routes to the core and dendrons as
well as the dendrimer are shown in Scheme 1 and Scheme 2.
1
4,30
À2
in other papers.
Cell 2 reveals Isc of 0.74 mA cm ,
Table 2 Summary of cell performance for ITO–PEDOT–dendrimers:
PCBM–LiF–Al based solar cells
Dendrimer : PCBM
(w/w ratio)
À2
V
oc/V
Isc/mA cm
FF
Z (%)
G0
G1
G2
1 : 2
1 : 2
1 : 2
0.79
0.79
0.77
1.6
0.74
0.28
0.28
0.32
0.28
0.34
0.19
0.06
2
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1
Dendrons and dendrimers were characterized by H NMR,
(500 MHz, CDCl
3
) d 9.81 (s, 1H, CHO), 7.67 (d, J = 9.0 Hz,
1
3
C NMR, FT-IR, elemental analysis and MALDI-TOF mass
2H, Ar), 7.34 (m, 4H, Ar), 7.17 (m, 6H, Ar), 7.01 (d, J =
spectroscopies. UV-vis absorption spectra were measured
using a Shimadzu UV-3100 spectrophotometer. Film thickness
was recorded on a Veeco Dektak 150 Surface Profiler. AFM
images were obtained using a Nanoscope IIIa Dimension
8.5 Hz, 2H, Ar). MALDI-TOF MS: Calcd for C H NO
1
9
15
273.1, Found: 273.6. Anal. Calcd for C H NO: C, 83.49; H,
15
1
9
5.53; N, 5.12%. Found: C, 83.90; H, 6.01; N, 5.07%.
Compound 4. 4-(N,N-Diphenylamino)benzaldehyde (14.00 g,
3
100. The OSCs were fabricated in the configuration of the
5
1.28 mmol), potassium iodide (11.43 g, 68.85 mmol) and
traditional sandwich structure with an indium tin oxide (ITO)
anode and metal cathode. A thin layer of poly(3,4-ethylene-
dioxythiophene)–poly(styrene sulfonate) (PEDOT:PSS) (Baytron,
PVP 4083, Germany) was spin-coated onto the ITO glass and
dried in a vacuum oven at 120 1C for 20 min. Subsequently,
the active layer was prepared by spin coating the composite
chloroform solution of dendrimer : PCBM (1 : 2, w/w) on the
top of the PEDOT:PSS layer. The cathode, a bilayer of a thin
acetic acid (210 mL) was heated to 85 1C and the solution was
allowed to cool. Then the potassium iodate (10.97 g,
5
8
1.26 mmol) was added and the reaction was heated at
5 1C for 5 h. The solution was cooled to room temperature
and poured into ice–water under stirring. The yellow precipi-
tated solid was collected by filtration, and the collected solid
was poured into 5% NaHSO
3 2
(100 ml) to eliminate I and
KIO . The final filtrated yellow solid was pure compound 4.
3
(
1 nm) LiF layer covered with 100 nm Al, was thermally
À4
1
H NMR (500 MHz, CDCl ) d 9.85 (s, 1H, CHO), 7.71 (d, J =
3
evaporated through a mask at a pressure of 5 Â 10 Pa. The
2
active area of the cell was 5 mm . Cell characterization was
8.5 Hz, 2H, Ar), 7.63 (d, J = 8.5 Hz, 4H, Ar), 7.05 (d, J =
8
.5 Hz, 2H, Ar), 6.89 (d, J = 8.5 Hz, 4H, Ar).
performed under AM 1.5 G irradiation with an intensity of
À2
1
00 mW cm on an Oriel Xenon solar simulator. Current–
Compound 5. Methyltriphenylphosphonium bromide (4.28 g,
2 mmol) and G0–CHO (2.73 g, 10 mmol) were dissolved
voltage characteristics were recorded with a Keithley 2400.
1
Synthesis
in 100 ml of dry THF, and the resulting solution was added
dropwise slowly to t-BuOK (1.68 g, 15 mmol) in 30 ml
of dry THF. The mixture was stirred for 8 h, and was
then filtrated and evaporated to give the powder. The
powder was purified using column chromatography
Compound 1. A mixture of 4-methylbenzene-1-sulfonyl
chloride (7.6 g, 40 mmol), toluene (17.0 mL, 160 mmol), and
3
AlCl (5.33 g, 40 mmol), was stirred at room temperature for
over 1.5 h. Then it was poured into amount of water.
The system was extracted with ether and concentrated to
(
petroleum ether : CH Cl = 4 : 1) to give 2.06 g (76%) of
2 2
1
product 5 as a white solid. H NMR (500 MHz, CDCl
3
) d 7.28
d, J = 8.5 Hz, 2H, Ar), 7.23–7.26 (m, 4H, Ar), 7.09
d, J = 8.0 Hz, 4H, Ar), 6.98–7.03 (m, 4H, Ar), 6.63–6.69
m, 1H, CH), 6.63 (d, J = 16.5 Hz, 1H, CHQCH ), 5.15
d, J = 8.5 Hz, 1H, CHQCH ).
recrystallize from ethanol to afford 6.70 g (68%) of product
1
as white pure powder. H NMR (500 MHz, CDCl
(
(
(
(
1
3
) d 7.81
(
d, J = 8.5 Hz, 4H, Ar), 7.28 (d, J = 8.5 Hz, 4H, Ar), 2.39
2
(
s, 6H, CH3).
2
Compound 2. A mixture of p-tolyl sulfone (10 g, 41 mmol)
Compound G1–CHO. Compound 4 (5.25 g, 10 mmol),
compound 5 (7.0 g, 26 mmol) and K PO (6.5 g, 30 mmol)
were mixed in dimethylacetamide (DMAc) (50 mL) with 10 mg
Pd(OAc) as catalyst; the mixture was heated at 110 1C and
stirred under an N atmosphere for 24 h. After being cooled to
and N-bromosuccinimide (NBS) (22 g, 123 mmol) dissolved in
00 mL of benzene was refluxed in the presence of benzoyl
3
4
5
peroxide (0.1 g, 0.41 mmol). After refluxing overnight, the
reaction mixture was cooled and filtered. The transparent
yellow filtrate was washed with distilled water and dried with
2
2
room temperature, the reaction mixture was poured into water
4
anhydrous MgSO . The solvent was removed under reduced
and extracted with CH Cl (3 Â 50 mL). The combined
2
2
pressure to give a pale yellow solid, which was purified by flash
column chromatography (petroleum ether : CH Cl = 2 : 1) to
organic extracts were washed with brine, dried (MgSO ),
4
2
2
1
afford 9.11 g (55%) of product 2 as a white solid. H NMR
and concentrated to dryness under vacuum. The crude
product was purified by flash column chromatography
(
500 MHz, CDCl ) d 7.91 (d, J = 8.5 Hz, 4H, Ar), 7.53 (d, J =
3
(
petroleum ether : CH
product G1–CHO as a yellow solid. H NMR (500 MHz,
CDCl ) d 9.83 (s, 1H, CHO), 7.71 (d, J = 8.5 Hz, 2H, Ar), 7.45
2 2
Cl = 2 : 1) to give 4.47 g (55%) of
8
2
.5 Hz, 4H, Ar), 4.46 (s, 4H, CH ).
1
Compound 3. A mixture of compound 2 (4.04 g, 10 mmol)
and P(OC (6.9 mL, 40 mmol) was refluxed for over
4 h under N . After distilling the liquid, the powder was
3
5
H )
3
(d, J = 8.5 Hz, 4H, Ar), 7.38 (d, J = 8.5 Hz, 4H, Ar),
7.25–7.28 (m, 12H, Ar), 7.10–7.15 (m, 12H, Ar), 7.00–7.06
(m, 8H, Ar), 6.96 (d, J = 16.5 Hz, 2H, Ar), MALDI-TOF
2
2
2
recrystallized from n-hexane to give 3.27 g (63%) of product 3
1
as a white solid. H NMR (500 MHz, CDCl ) d 7.87
MS: Calcd for C59
45 3
H N O 812.0, Found: 812.9. Anal. Calcd
3
(
d, J = 8.5 Hz, 4H, Ar), 7.43 (d, J = 8.5 Hz, 4H, Ar), 4.01
45 3
for C59H N O: C, 87.27; H, 5.59; N, 5.17%. Found: C, 87.15;
(
s, 8H, CH ), 3.18 (d, 4H, CH ), 1.22 (s, 12H, CH ).
2
2
3
H, 5.70; N, 5.09%.
Compound G0–CHO. A mixture of TPA (10.0 g, 40 mmol)
and POCl (29.4 mL, 315 mmol) in DMF (30.0 mL, 388 mmol)
Compound 6. G1–CHO (2.02 g, 2.5 mmol) and methyl-
triphenylphosphonium bromide (1.1 g, 3 mmol) were dissolved
in 50 mL of dry THF. 0.45 mg (4 mmol) of t-BuOK in 10 mL
of dry THF was added dropwise slowly to the resulting
solution at 0 1C then the reaction mixture was warmed to
3
was heated to 45 1C for 2.5 h, which was then poured into
water and filtrated to obtained solid. The solid was purified
through column chromatography using silica gel with chloro-
1
form as eluent to afford 10.0 g (90%) of G0-CHO. H NMR
room temperature and stirred under N for 12 h. The reaction
2
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1
Compound G2: H NMR (500 MHz, CDCl
mixture was poured into water and extracted with CH
Cl
2 2
3
) d 7.90 (d, J =
(
3 Â 50 mL). The combined organic extracts were washed with
8.0 Hz, 4H), 7.58 (d, J = 8.0 Hz, 4H), 7.36–7.41 (m, 52H, Ar),
1
7.24–7.27 (m, 28H, Ar), 6.96–7.17 (m, 140H, Ar). C NMR
3
brine, dried (MgSO ), and concentrated to dryness under
4
vacuum. The crude product was purified by flash column
(125 MHz, CDCl ) 147.54, 147.11, 146.59, 146.373, 146.155,
3
chromatography (petroleum ether : CH Cl = 4 : 1) to give
2
142.532, 139.614, 132.809, 132.470, 132.144, 131.734, 130.894,
130.624, 130.072, 129.265, 129.016, 128.043, 127.904, 127.118,
127.031, 126.879, 126.773, 126.545, 126.402, 125.725, 124.893,
124.627, 124.422, 124.280, 124.177, 123.655, 123.525, 122.965.
2
1
1
.36 g (67%) of product 6 as a yellow solid. H NMR
500 MHz, CDCl ) d 7.31–7.39 (m, 12H, Ar), 7.10–7.27
m, 12H, Ar), 7.01–7.09 (m, 20H, Ar), 6.65–6.71 (m, 1H,
), 5.18 (d, J =
), MALDI-TOF MS: Calcd for
809.4, Found: 811.4. Anal. Calcd for C60
(
(
3
CH), 6.70 (d, J = 17.5 Hz, 1H, CHQCH
1.0 Hz, 1H, CHQCH
2
MALDI-TOF MS: falcd for C292
3990.2. Anal. Calcd for C292
H
220
N
14
O
2
S 3989.0, found:
1
2
H
220
N
14
O
2
S: C, 87.92; H, 5.66; N,
C
60
H
47
N
3
H
47
N
3
:
4.92%. Found: C, 87.75; H, 5.78; N, 5.58%.
C, 88.96; H, 5.85; N, 5.19%. Found: C, 88.85; H, 6.01;
N, 5.07%.
Acknowledgements
Compound G2–CHO. The synthesis of G2–CHO was similar
1
to G1–CHO and characterized by H NMR spectroscopy.
This work was supported by the State Key Development
Program for Basic Research of China (Grant No.2009CB623605),
the National Natural Science Foundation of China
1
H NMR (500 MHz, CDCl ) d 9.83 (s, 1H, CHO), 7.71 (d, J =
3
8.5 Hz, 2H, Ar), 7.36–7.41 (m, 20H, Ar), 7.24–7.27 (m, 12H, Ar),
7.14 (d, J = 8.5 Hz, 2H, Ar), 7.08–7.12 (m, 30H, Ar),
6.96–7.05 (m, 32H, Ar). MALDI-TOF MS: calcd for
(
Grant No. 50673035), Program for New Century Excellent
Talents in Universities of China Ministry of Education, the
11 Project (Grant No. B06009), the Research Project of Jilin
1
C
C
139
139
H
H
105
105
N
N
7
O
1887.9, found: 1889.2. Anal. Calcd for
Province (Grant No.20080305) and the Graduated Innovation
Fund of Jilin University (No.20080109).
7
O: C, 88.36; H, 5.60; N, 5.19%. Found: C, 88.25;
H, 5.73; N, 5.08%.
Compound G0. Compound 3 (155.6 mg, 0.3 mmol) and
G0–CHO (213.2 mg, 0.78 mmol) were dissolved in 20 mL of
dry THF and the resulting solution was added dropwise slowly
to t-BuOK (107.7 mg, 0.96 mmol) in 10 mL of dry THF
at 0 1C, then the reaction mixture was warmed to room
Notes and references
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6
7
8
2
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dried over MgSO . After removing the solvent, the
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(
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1
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1
3
7
.05 (d, J = 8.5 Hz, 8H), 6.94 (d, J = 8.5 Hz, 4H). C NMR
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(
75 MHz CDCl
3
1
1
5
`
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H N O
2
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1
1
Compound G1 and compound G2. The synthesis of G1 and
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1
from H NMR and C NMR spectra.
13
1
Compound G1: H NMR (500 MHz, CDCl ) d 7.90 (d, J =
3
2
000, 39, 517.
8
.5 Hz, 4H), 7.58 (d, J = 8.5 Hz, 4H), 7.40 (d, J = 8.5 Hz,
1
1
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1
3
(
d, J = 7.5 Hz, 4H), 6.97–7.17 (m, 64 H). C NMR (125 MHz,
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31.613, 130.558, 129.262, 129.023, 128.021, 127.883, 127.256,
1
2
9 Q. Yao, E. P. Kinney and Z. Yang, J. Org. Chem., 2003, 68, 7528.
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3
1
1
1
27.182, 126.755, 126.271, 124.847, 124.615, 124.435, 123.971,
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2
6
2
C132H100N O S: C, 86.43; H, 5.49; N, 4.58%. Found: C, 86.31;
6
2
H, 5.43; N, 4.62%.
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