Thiophene-substituted fulleropyrrolidine derivatives as acceptor molecules in a thin film organic solar cell

Article abstract of DOI:10.1016/j.tet.2012.02.080

A study of the design of thiophene-substituted fulleropyrrolidine derivatives as the acceptor in photovoltaic cells has been carried out using poly(3-hexylthiophene) (P3HT) as the model donor polymer. It was found that five types of thiophene-substituted fulleropyrrolidine worked as a good acceptor partner with P3HT, and the highest power conversion efficiency (PCE) was obtained for 1-(2-(2-methoxyethoxy)ethyl)-2-(2-thiophen-2-yl)fulleropyrrolidine (2.99%); this is superior to that of the P3HT polymer including methyl [C60]-PCBM under the same experimental conditions.

Full text of DOI:10.1016/j.tet.2012.02.080

Tetrahedron 68 (2012) 3605e3610
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Tetrahedron
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Thiophene-substituted fulleropyrrolidine derivatives as acceptor molecules
in a thin film organic solar cell
,
Ken Yoshimura a b, Kei Matsumoto a, Yasunori Uetani b, Shigeki Sakumichi a, Shuichi Hayase a, Motoi
,
Kawatsura a, Toshiyuki Itoh a
*
a Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan
b Sumitomo Chemical Co., Ltd. 6 Kitahara, Tsukuba 300-3294, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A study of the design of thiophene-substituted fulleropyrrolidine derivatives as the acceptor in photo-
voltaic cells has been carried out using poly(3-hexylthiophene) (P3HT) as the model donor polymer. It
was found that five types of thiophene-substituted fulleropyrrolidine worked as a good acceptor partner
with P3HT, and the highest power conversion efficiency (PCE) was obtained for 1-(2-(2-methoxyethoxy)
ethyl)-2-(2-thiophen-2-yl)fulleropyrrolidine (2.99%); this is superior to that of the P3HT polymer in-
cluding methyl [C60]-PCBM under the same experimental conditions.
Received 18 January 2012
Received in revised form 27 February 2012
Accepted 29 February 2012
Available online 7 March 2012
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
On the other hand, several examples have also been reported
concerning the use of fulleropyrrolidines as the acceptor source of
Use of photovoltaic technology is now well recognized as one of
the most important ways to prevent the exhaustion of fossil fuels.
Organic photovoltaics (OPV) have been attracting much attention
as a next-generation photovoltaic system, because of their light
weight and shape flexibility, as well as the potential to achieve low
cost production.1
polymer solar cells. Reported PCE values of the solar cells derived
from fulleropyrrolidine, however, have remained insufficient.18e25
We were fascinated by the fulleropyrrolidines from the stand-
point of their stable nature under atmospheric conditions and the
ease of producing various types of analogues,26 and conducted
a systematic study of the design as an acceptor partner in polymer
solar cells.27
We found that OPV devices using several fulleropyrrolidine
derivatives, in particular 1-(2-(2-methoxyethoxy)ethyl)-2-(2-
methoxyphenyl) fulleropyrrolidine, showed higher PCE compared
to devices using [C60]-PCBM. Further, we established that the
open-circuit voltage (Voc) of devices using fulleropyrrolidine de-
rivatives strongly depends on the substituent groups on the pyr-
rolidine ring.27
Fullerene and its derivatives are widely used as n-type materials
in the active layer of OPVs due to their high electron mobility and
adequate LUMO level.2,3 Fullerene-based OPV can be fabricated via
vapor deposition; however, considering the expected demand for
enhancing cost performance by mass production in the near future,
application of roll-to-roll processing (i.e., the solvent casting
method) appears highly desirable. Therefore, development of stable
fullerene derivatives that show both a high power conversion effi-
ciency (PCE) and a sufficient solubility against organic solvents is
strongly desired.1e3 Various types of fullerene derivatives for use as
OPV n-type materials have thus been developed. Methyl [6,6]-
phenyl-C61-butylate ([C60]-PCBM)4 is known to be the best blend-
ing material among these derivatives as an acceptor with poly-
thiophene, which is a donor partner in polymer solar cells.5e15
Troshin and co-workers also synthesized various types of meth-
anofullerene derivatives as acceptors for P3HT.15 Recently Matsuo
and co-workers reported OPV devices using silylmethylfullerene
Heeger and co-workers reported that the Voc of an OPV device is
determined by the difference between the HOMO level of the p-
type semiconductor and the LUMO level of the n-type conductor.8
Therefore, it might be expected that appropriate modification of
the pyrrolidine ring could enhance the LUMO level, possibly im-
proving the Voc. We hypothesized that introduction of a
p-conju-
gated moiety to the fulleropyrrolidine might affect the
HOMOeLUMO level as well as the charge separation process, which
could cause significant change in OPV properties. We herein report
the synthesis of thiophene-substituted fulleropyrrolidine de-
rivatives 1e6 (Fig. 1) and results of their evaluation as acceptor
materials with P3HT in solar cells. Thus, we have established that
the introduction of a thiophene moiety on the pyrrolidine ring of
fulleropyrrolidines has a favorable effect on the PCE of a solar cell.
(SIMEF) that showed PCE superior to devices using [C60]-PCBM16,17
.
* Corresponding author. E-mail address: titoh@chem.tottori-u.ac.jp (T. Itoh).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.02.080

3606
K. Yoshimura et al. / Tetrahedron 68 (2012) 3605e3610
silica-gel flash column chromatography or silica-gel thin layer
chromatography; the desired mono adducts were thus obtained in
acceptable yields from 40% to 78%. We further synthesized bridged
type fulleropyrrolidine 6 by the reaction of [2,20:50,200-terthio-
phene]-5,500-dicarbaldehyde and N-methoxyethoxy glycine in the
presence of [C60]-fullerene. To our delight, the desired bridged type
compound 6 was obtained as a single isomer.
Using these fulleropyrrolidine derivatives, we prepared solar
cells and evaluated their efficiency as follows: fulleropyrrolidines
were mixed with poly(3-hexylthiophene) (1/1 (wt/wt)) in o-di-
chlorobenzene, and the resulting solution was spin-coated onto ITO
or ITO with poly(3,4-ethylenedioxythiophene)/poly(styrenesulfo
nate) (PEDOT:PSS)29 as a positive electrode to make an active layer
of organic photovoltaic cells. LiF and aluminum were used as
a negative electrode. The PCE values were measured using a solar
simulator (AM1.5G, 100 mW/cm2). The results are summarized in
Table 1.
Table 1
Photovoltaic performances of the P3HT-based organic photovoltaic devices with
various types of fulleropyrrolidine derivativesa
Entry
Fullerene
derivative
PCE %
Jsc mA/cm2
Voc Volt
FF
1b
2
3
4
5
1
2
3
4
5
6
3.0
2.9
2.8
2.8
2.4
0.61
2.5
7.5
7.7
7.9
6.8
6.4
3.1
6.9
0.61
0.62
0.61
0.64
0.65
0.65
0.58
0.66
0.61
0.57
0.64
0.56
0.31
0.63
6
7
[C60]-PCBM
a
Under the illumination of AM 1.5G, 100 mW/cm2.
Ref. 27.
b
The characteristic currentevoltage parameters of polymer solar
cells composed of six isomers, 1e6 (entries 1e6) were investigated;
the PCE of isomers 1e4 was higher than that of [C60]-PCBM (entry
7). The PCE of 1 was highest among three mono-thiophene de-
rivatives (entries 1e3) due to its having the highest fill factor (FF),
while it showed the lowest open-circuit voltage (Voc) and short-
circuit current (Jsc) (entry 1). The Voc of these thiophene-
substituted fulleropyrrolidine devices was higher than that of
[C60]-PCBM, which was assumed to be due to their electron-
donating property of thiophene. The Jsc and FF of terthiophene
substituted derivative 5 were lower than devices 1e4, as a result of
its reduced solubility compared to mono-thiophene and bithio-
phene derivatives. The distinctive feature of 5 is among the high Voc
(0.65 V) when compared to 1e4 and [C60]-PCBM; the reason for
that will be discussed below using cyclic voltammograms.
Fig. 1. Thiophene-substituted fulleropyrrolidine derivatives and [C60]-PCBM.
We previously reported that PCE significantly depended on the
position of functional group on the benzene ring of the related
fulleropyrrolidine derivatives, and high PCE was recorded for
compounds, which have a methoxy or methyl group at the ortho-
position of the phenyl group.27 Because the alkyl group is believed
to be a moderate electron-donating group, we next incorporated an
alkyl group to the thiophene ring. As expected, PCE of 2 and 3 were,
in fact, higher than that of [C60]-PCBM, though it was found that
introduction of methyl or ethyl group at 5-position of the thiophene
ring had no significant influence on the PCE (entries 2 and 3).
Rather, introduction of ethyl group at the 5-position caused a slight
drop of PCE due to reduced FF by the steric effect (entry 3).
Bis-[C60]-PCBM was reported to show higher Voc than [C60]-
PCBM, because bis-[C60]-PCBM possesses a higher LUMO level
due to a break in the conjugated bond.4 Although the bridged type
fulleropyrrolidine 6 showed higher Voc than that of [C60]-PCBM,
poor PCE was obtained due to its low Jsc and FF (entry 6).
2. Results and discussion
Thiophene is well known as an electron-releasing substituent
group, therefore, it is expected that the thiophene group becomes
a
p-conjugated moiety and thus influences both the light-
absorbing behavior and charge separation process of fullerene
molecules. We hypothesized that thiophene-substituted full-
eropyrrolidine might become a good candidate as acceptor in
polymer solar cells. Synthesis of a thiophene derivative full-
eropyrrolidine (1) was reported earlier in our previous literature.27
Resulting fulleropyrrolidine derivatives (2e6) were also prepared
by a similar method,26,27 which was originally developed by Prato
and co-workers.1a N-Methoxyethoxyethyl glycine28 was treated
with the [C60]-fullerene in the presence of a thiophene-substituted
aldehyde in chlorobenzene and the mixture was heated at 130 ꢀC
for 3 h. Purification of the desired compounds was accomplished by
Recently, an ITO electrode coated with poly(3,4-ethylene
dioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS)29 has been

K. Yoshimura et al. / Tetrahedron 68 (2012) 3605e3610
3607
widely used as the hole transport layer for a solar cell. This is
explained by the layer working as anantistatic agent and prevent-
ing electrostatic discharges during the film production. However,
we prepared solar cells using a simple ITO electrode, which lacked
the PEDOT:PSS layer, because we were concerned that protonation
of the nitrogen atom on the pyrrolidine ring by PSS might inhibit
the electron transfer pathway between fullerene molecules and
P3HT. Although investigation on modification of redox properties
of fulleropyrrolidine derivatives induced by protonation has been
carried out, no detailed report on the photovoltaic performances
has been reported.30 To investigate this, we prepared three types of
solar cells using ITO electrodes: those that lacked PEDOT:PSS, those
having PEDOT:PSS, and those having neutral PEDOT, and evaluated
their efficiency using bithiophene-substituted fulleropyrrolidine 4
as acceptor partner with P3HT (Table 2).
Fig. 2. UVevisible spectra of fulleropyrrolidine 4 in the presence and absence of TFA or
p-TsOH in CS2 (4/Acid¼1:20 (mol/mol). Concentration of 4 in CS2 is approximately
0.02 mM).
Table 2
Photovoltaic performances of the P3HT-based organic photovoltaic devices with
bithiophene-substituted fulleropyrrolidine 4 using three ITO electrodes
Entry Acceptor
PCE (%) Jsc (mA/cm2) Voc(V) FF
Antistatic agent
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
1/P3HT
1
2
3
4
5
6
7c
8
[C60]-PCBM 2.5
[C60]-PCBM 2.6
[C60]-PCBM 2.5
4
4
4
7
7
6.7
7.0
7.2
6.8
0.71
5.9
7.6
6.5
0.56
0.56
0.55
0.64
0.48
0.54
0.64
0.52
0.66 No
5/P3HT
[C60]-PCBM/P3HT
0.67 PEDOT:PSSa
0.64 Neutral PEDOTb
0.64 No
2.8
0.10
1.8
3.0
0.51
0.29 PEDOT:PSS
0.57 Neutral PEDOT
0.63 No
0.15 PEDOT:PSS
a
PEDOT:PSS (AI4083 (pH¼1.8)): baked at 120 ꢀC for 10 min under air, 44 nm.
0.05
b
Neutral PEDOT: 0.4 wt % diethanolamine, 2,4,7,9-tetramethyldec-5-yne-4,7-diol
0
300
(surfactant) 100 ppm (pH7.5), baked at 120 ꢀC for 10 min under air, 45 nm.
400
500
600
700
800
c
Ref. 27.
Wavelength (nm)
Fig. 3. UVevisible spectra of 1/P3HT, 5/P3HT,, and [C60]-PCBM/P3HT.
As shown in Table 2, the PCE of [C60]-PCBM solar cells was in-
dependent of the use of electrode (entries 1e3). On the contrary, as
anticipated, using acidic PSS in the electrode with isomer 4 caused
a significant drop of PCE, mainly due to reduced Jsc (entry 5). In fact,
a slight improvement of PCE was obtained when the cell was pre-
pared by neutral PEDOT (entry 6), but PCE was still lower than the
devices made using a simple ITO electrode that lacked PEDOT:PSS
(entry 4). It was thus found that it was essential to obtain good PCE
for thiophene-substituted fulleropyrrolidine based solar cells in
order to use an electrode lacking PEDOT:PSS. In addition, a similar
significant reduction of photovoltaic performance was recorded
when 1-(2-(2-methoxyethoxy)ethyl)-2-([1,10-biphenyl]-2-yl)full-
eropyrrolidine (7)27 was used as an acceptor (entry 8).
0.6
0.5
0.4
0.3
0.2
0.1
0
5/P3HT
[C60]-PCBM/P3HT
300
400
500
600
700
800
It is reported that the protonation of the fulleropyrrolidine by
trifluoroacetic acid caused a blue shift on the UVevisible spec-
trum.30 Fig. 2 shows UVevisible spectra of fulleropyrrolidine 4 with
and without acids, when trifluoroacetic acid (TFA) and p-toluene-
sulfonic acid (p-TsOH) were used as acid. As can be seen, blue shift
of the fulleropyrrolidine was observed in the presence of both TFA
and p-TsOH. Since p-TsOH is thought to be a model compound of
PSS, it is likely that protonation of the fulleropyrrolidine indeed
formed when PEDOT:PSS was used as hole transport layer.
Wavelength (nm)
Fig. 4. External quantum efficiency of terthiophene derivative 5/P3HT and [C60]-
PCBM/P3HT.
the EQE between 350 and 400 nm reached around 0.5, thus re-
vealing that the terthiophene moiety of 5 not only absorbed the
light but also contributed to produce exciton within the range of
350e400 nm.
Fig. 3 shows the UVevisible spectra of the P3HT/1, P3HT/5, and
P3HT/[C60]-PCBM. All films showed a broad pep* absorption from
Fulleropyrrolidine 6 has a terthiophene bridge, which should
have a similarabsorption spectrumto compound 5. However, thePCE
of the device using P3HT/6 was unexpectedly low as mentioned
above, which indicated that bridged-terthiophene moiety showed
poor PCE (entry 6 inTable 1). The bridged-terthiophene moiety might
be too close to the fullerene ring, preventing charge separation.
The highest Voc was found when mono-thiophene 5 was used as
an electron acceptor component in the active layer. To learn the
reason for the high Voc of 5 compared to [C60]-PCBM, the electro-
chemical properties of terthiophene 5 and [C60]-PCBM were
studied by cyclic voltammetry. The cyclic voltammograms of the
fullerene derivatives in the potential range of 1.0 to ꢁ2.0 V versus
400 to 700 nm and the lmax of the three films was around 500 nm,
which was attributable to the P3HT. The P3HT/5 blend has distinc-
tive broad absorption between 350 and 400 nm, which was assumed
to be caused by terthiophene moiety on the fulleropyrrolidine
molecule.
External quantum efficiency (EQE) of the P3HT/5 and P3HT/
[C60]-PCBM are shown in Fig. 4. Since there is less absorption in
the range of 350e400 nm in the UVevisible spectrum of P3HT/
[C60]-PCBM film, the EQE of the film in this range stayed low
(EQE¼0.3e0.4). On the other hand, as can be seen on the P3HT/5,

3608
K. Yoshimura et al. / Tetrahedron 68 (2012) 3605e3610
4. Experimental section
[C60]-PCBM
5
4.1. General procedures
Photovoltaic devices were prepared by spin-coating the
fulleropyrrolidine-polymer blends from chlorobenzene onto an
indium tin oxide (ITO) glass electrode as follows: to a P3HT
(1.0 wt %) solution of chlorobenzene were added fulleropyrrolidine
1 (equal weight vs P3HT) and silica gel (1.0 wt % vs P3HT solution),
then the mixture was stirred for 12 h at ambient temperature. It
was then filtered through a Teflon (0.2 mm) filter. The resulting
solution was applied to the surface of an ITO plate by the spin-
coating method at a thickness of ca. 100 nm, and the surface was
washed with acetone and irradiated under UV light and ozone gas
for 20 min to decompose the impurities. After drying under vac-
uum for 20 min, the resulting plate was placed in a vacuum
chamber and the surface was coated with the electrode layers of
lithium fluoride (LiF) (4 nm) and aluminum (100 nm) by evapora-
tion at 10ꢁ4 Pa at rt. We placed the glass plate on the resulting film
and the plate was firmly fixed using a bonding agent under an ar-
gon atmosphere to produce the solar cell. The PCE values were
obtained using the solar simulator OTENTO-SUN II (AM1.5G,
100 mW/cm2). Cyclic voltammograms were obtained in acetonitrile
with 0.1 mM tetrabutylammonium hexafluorophosphate (n-
Bu4NPF6) as a supporting electrolyte using a glassy carbon (1 mm
diameter) as a working electrode, a Pt counter electrode and Ag/
AgCl reference electrode. UVevisible spectra were obtained using
the spectrophotometer JASCO V-670.
0.5
-2.5
-2
-1.5
-1
-
0
0.5
1
1.5
potential (V)
Fig. 5. Cyclic voltammograms of [C60]-PCBM and 5 in CH3CN (0.1 mM) with 0.1 M n-
Bu4NPF6 at a scan rate of 10 mV/s.
ferrocene (Fc)/Fþc are shown in Fig. 5. In the negative potential
range, it can be seen that these derivatives showed three apparent
reversible reduction waves, respectively, in the potential range
from ꢁ0.8 to ꢁ1.8 V. The half-wave potentials of which are defined
as E0¼[EcþEa]/2 (wherein Ec and Ea are the potential of cathodic
peak and anodic peak, respectively) of the reduction process are
summarized in Table 3. The first (E01), second (E20), and third (E30)
reduction potentials of 5 were shifted negatively when compared
to [C60]-PCBM.
Table 3
Estimated half-wave potentials and LUMO of the fullerene derivativesa
Entry
E10
V
E02 V
E03 V
LUMO eV
4.2. Materials
1
2
[C60]-PCBM
5
ꢁ1.09
ꢁ1.15
ꢁ1.49
ꢁ1.53
ꢁ2.00
ꢁ2.08
ꢁ3.71
ꢁ3.65
The [C60]-fullerene was purchased from Frontier Carbon (nanom
purple ST-A) and P3HT from Aldrich. The silica gel was purchased
from Wako Pure Chemical Industry, Ltd. (Wakogel C-300,
45e75 mm).
a
The potential values in this table versus Fc/Fcþ.
The LUMO energy levels of the fullerene derivatives were esti-
mated from their first half-wave potentials (E01) indicated in the
cyclic voltammograms. The E01 of terthiophene 5 and [C60]-PCBM
were ꢁ1.09 and ꢁ1.15 V versus Fc/Fcþ, respectively. The LUMO
energy levels of the fullerene derivatives from the onset reduction
potentials were calculated by use of the following equation: LUMO
(eV)¼ꢁ(E01þ4.80). The LUMO energy levels of [C60]-PCBM and 5
calculated by this method are ꢁ3.71 and ꢁ3.65 eV, respectively, and
are summarized in Table 3. The LUMO level of 5 is raised by 0.06 eV
in comparison with that of [C60]-PCBM. The higher LUMO level of 5
is desirable for its application as acceptor in the active layer to
4.2.1. 1-(2-(2-Methoxyethoxy)ethyl)-2-(2-thiophen-2-yl) fulleropyrroli
dine (1).27 A solution of [C60]-fullerene (500 mg, 0.69 mmol), [2-(2-
methoxyethoxy)ethylamino]acetic acid26,28 (177 mg, 1.0 mmol), and
thiophene-2-carbaldehyde (188 mg, 1.38 mmol) in chlorobenzene
(100 mL) was stirred for 3 h at 130 ꢀC under argon. The solvent was
evaporated under reduced pressure and the residue was purified by
flash chromatography (toluene, then CS2/ethyl acetate¼10/1)
affording the product 1 (351 mg, 0.36 mmol) as a dark brown solid in
52% yield, and the unreacted fullerene (174 mg) was recovered in 35%
yield. Fulleropyrrolidines showed no clear melting point and only
caused decomposition. Decomposition point was shown as ‘dp’.
Rf 0.61 (toluene/methanol¼2/1); dp >300 ꢀC; 1H NMR
obtain Voc
.
(400 MHz, CDCl3, J¼Hz)
d 2.87e2.93 (1H, m), 3.39 (3H, s), 3.49e3.57
(3H, m), 3.60e3.62 (2H, m), 3.92e3.97 (1H, m), 4.00e4.05 (1H, m),
4.26 (1H, d, J¼9.8 Hz), 5.19 (1H, d, J¼9.8 Hz), 5.47 (1H, s), 6.99 (1H, t,
J¼4.9 Hz), 7.31 (1H, d, J¼5.9 Hz), 7.34 (1H, d, J¼4.0 Hz); 13C NMR
3. Conclusions
In summary, we have carried out the rational design of
thiophene-substituted fulleropyrrolidine derivatives (1e5) as the
acceptor partner with poly-3-hexylthiophene and established that
these fulleropyrrolidines worked as good acceptor partners with
P3HT. A high power conversion efficiency was obtained, superior to
that of the P3HT-based devices including [C60]-PCBM under the
same experimental conditions. It was also found that using an
electrode that lacked PEDOT:PSS was essential to obtain good PCE
for fulleropyrrolidine based solar cells.
We expect to be able to develop efficient donor polymers, which
are appropriate for our fulleropyrrolidine derivatives. Further in-
vestigation into the development of novel donor polymers as
a partner of our fulleropyrrolidine will allow the creation of even
more efficient solar cells in the near future.
(100 MHz, CDCl3) d 52.25, 58.77, 67.60, 68.56, 70.41, 70.51, 71.87,
75.82, 77.68, 126.37, 126.44, 127.83, 127.99, 128.6, 135.27, 135.60,
136.33, 136.74, 139.28, 139.60, 139.84, 139.89, 140.72, 141.28, 141.36,
141.56, 141.66, 141.71, 141.73, 141.81, 141.83, 141.85, 141.92, 141.94,
142.27, 142.37, 142.68, 142.83, 144.03, 144.06, 144.32, 144.40, 144.81,
144.89, 144.91, 144.95,145.01, 145.05, 145.11, 145.17, 145.24, 145.29,
145.45,145.61,145.75, 145.78,145.84,145.88,145.96,146.00,146.02,
146.55, 146.96, 152.82, 152.96, 153.77, 155.82; IR (KBr, cmꢁ1) 2864,
2812, 1462, 1427, 1180, 1107, 839, 768, 700, 527; MALDI-TOF-MS
(matrix: SA) found 947.0978 (calculated for C71H17NO2S, exact
mass: 947.0981).
Reaction of 5-methylthiophene-2-carbaldehyde or 5-
ethylthiophene-2-carbaldehyde with C60-fullerene gave full-
eropyrrolidine 2 or 3 in similar yield in the reaction of 1.

K. Yoshimura et al. / Tetrahedron 68 (2012) 3605e3610
3609
4.2.2. 1-(2-(2-Methoxyethoxy)ethyl)-2-(5-methylthiophen-2-yl)full-
0.84 mmol, 83%) and [2,20:50,200-terthiophene]-5,500-dicarbaldehyde
eropyrrolidine (2). Dp >300 ꢀC; 1H NMR (500 MHz, CDCl3, J¼Hz)
(9)33 (68.0 mg, 0.22 mmol, 22%), respectively.
d
2.47 (3H, s), 2.89e2.95 (1H, m), 3.44 (3H, s), 3.57e3.59 (1H, m),
(2) A solution of C60 (250 mg, 0.35 mmol), [2-(2-
3.61e3.70 (2H, m), 3.77e3.84 (2H, m), 3.98e4.02 (1H, m),
4.04e4.08 (1H,m), 4.25 (1H, d, J¼9.7 Hz), 5.16 (1H, s), 5.39 (1H, s),
6.06 (1H, dd, J¼3.5, 1.1 Hz), 7.16 (1H, d, J¼3.5 Hz); 13C NMR
methoxyethoxy)ethylamino]acetic acid (92 mg, 0.52 mmol),
and [2,20:50,200-terthiophene]-5-carbaldehyde (8) (192 mg,
0.69 mmol) in chlorobenzene (50 mL) was stirred for 3 h at 130 ꢀC
under argon. The resulting mixture was separated by silica-gel flash
chromatography to give 3 (157 mg, 0.14 mol) in 41% yield, and the
unreacted fullerene (118 mg) was recovered in 47% yield.
(100 MHz, CDCl3)
d 15.63, 52.16, 59.14, 67.66, 68.91, 70.50, 70.54,
72.00, 76.15, 78.25, 124.57, 128.36, 135.54, 135.77, 136.60, 138.30,
139.58, 139.84, 140.06, 140.08, 141.25, 141.53, 141.62, 141.90, 141.93,
141.98, 142.08, 142.12, 142.19, 142.51, 142.52, 142.62, 142.91, 143.09,
144.32, 144.59, 144.68, 145.17, 145.21, 145.26, 145.30, 145.45, 145.49,
145.73, 145.87, 145.89, 146.01, 146.05, 146.10, 146.15, 146.24, 146.34,
146.45, 147.25, 153.39, 153.60, 154.24, 156.27; IR (KBr, cmꢁ1) 2853,
1684, 1458, 1425, 1107, 795; MALDI-TOF-MS (matrix: SA) found
961.1138 (calculated for C72H19NO2S, exact mass: 961.1138).
Dp >300 ꢀC; 1H NMR (500 MHz, CDCl3, J¼Hz)
d 2.87e2.93 (1H, m),
3.39(3H, s), 3.49e3.57 (4H, m), 3.60e3.62(2H, m), 3.92e3.97 (1H, m),
4.00e4.05 (1H, m), 4.26 (1H, d, J¼9.8 Hz), 5.19 (1H, d, J¼9.8 Hz), 6.96
(1H, dd, J¼5.1, 3.6 Hz), 7.00 (2H, dd, J¼9.2, 3.6 Hz), 7.03 (d, 1H,
J¼3.6 Hz), 7.09 (1H, dd, J¼3.4,1.0 Hz), 7.15 (1H, dd, J¼5.0, 0.9 Hz), 7.26
(1H, d, J¼3.7 Hz); 13C NMR (125 MHz, CDCl3)
d 52.40, 58.81, 67.68,
68.67, 70.49, 71.93, 75.83, 77.94,122.71, 123.61, 124.17, 124.27, 124.44,
127.69, 128.74, 135.27, 135.65, 135.92, 136.35, 136.84, 136.94, 138.21,
139.54, 139.74, 139.93, 140.03, 141.37, 141.43, 141.62, 141.70, 141.79,
141.88, 141.98, 142.01, 142.33, 142.45, 142.74, 142.90, 144.12, 144.40,
144.46, 144.89, 144.97, 145.03, 145.13, 145.18, 145.21, 145.29, 145.39,
145.50, 145.67, 145.81, 145.87, 145.94, 146.01, 146.08, 146.54, 147.03,
152.71, 152.81, 153.77, 155.79; IR (KBr, cmꢁ1) 2864, 2812, 1462, 1427,
1180, 1107, 839, 768, 700, 527; MALDI-TOF-MS (matrix: SA) found
1111.0753 (calculated for C79H21NO2S3, exact mass: 1111.0736).
4.2.3. 1-(2-(2-Methoxyethoxy)ethyl)-2-(5-ethylthiophen-2-yl)full-
eropyrrolidine (3). Dp 290 ꢀC; 1H NMR (500 MHz, CDCl3, J¼Hz)
d
1.28 (3H, t, J¼7.5 Hz), 2.82 (2H, q, J¼7.5 Hz), 2.90e2.95 (1H, m),
2.88 (3H, s), 3.58e3.62 (1H, m), 3.63e3.70 (2H, m), 3.78e3.84 (2H,
m), 3.99e4.04 (1H, m), 4.06e4.09 (1H, m), 4.26 (1H, d, J¼9.7 Hz),
5.16 (1H, d, J¼9.8 Hz), 5.40 (1H, s), 6.68 (1H, d, J¼3.5 Hz), 7.18 (1H, d,
J¼3.5 Hz); 13C NMR (125 MHz, CDCl3)
d 15.70, 23.60, 52.18, 59.14,
67.66, 68.90, 70.49, 70.54, 72.00, 76.20, 78.31, 122.57, 128.13, 135.55,
136.61, 136.93, 137.80, 139.52, 139.82, 140.05, 141.86, 141.93, 141.98,
142.09, 142.12, 142.19, 142.24, 142.51, 142.62, 142.91, 143.10, 144.32,
144.59, 144.67, 145.07, 145.18, 145.23, 145.29, 145.45, 145.48, 145.73,
145.87, 146.01, 146.04, 146.10, 146.15, 146.23, 146.26, 146.35, 146.44,
146.95, 147.25, 148.89, 153.39, 153.64, 154.25; IR (KBr, cmꢁ1) 2866,
1670, 1508, 1458, 1425, 1107, 802; MALDI-TOF-MS (matrix: SA)
found 975.1292 (calculated for C73H21NO2S, exact mass: 975.1294).
4.3. Bridge type terthiophene fullerobipyrrolidine (6)
A solution of [C60]-fullerene (630 mg, 0.88 mmol), [2-(2-
methoxyethoxy)ethylamino]acetic acid (142 mg, 0.80 mmol), and
[2,20:50,200-terthiophene]-5,500-dicarbaldehyde
(9)
(43
mg,
0.14 mmol) in chlorobenzene (60 mL) was stirred for 3 h at 130 ꢀC
under argon. The solvent was evaporated under reduced pressure
and the residue was purified by flash chromatography (toluene,
then CS2/ethyl acetate¼10/1) affording the product 6 (196 mg,
0.16 mmol) as a dark brown solid in 76% yield, and the unreacted
fullerene (174 mg) was recovered in 35% yield. Rf 0.61 (toluene/
methanol¼2/1): dp >300 ꢀC; 1H NMR (500 MHz, ppm, CDCl3, J¼Hz)
4.2.4. 1-(2-(2-Methoxyethoxy)ethyl)-2-([2,20-bithiophen]-5-yl)full-
eropyrrolidine (4). A solutionof [C60]-fullerene(500 mg, 0.69 mmol),
[2-(2-methoxyethoxy)ethylamino]acetic
acid26,28
(177
mg,
1.0 mmol), and 5-(thiophen-2-yl)thiophene-2-carbaldehyde31
(268 mg, 1.40 mmol) in chlorobenzene (100 mL) was stirred for 3 h
at 130 ꢀC under argon. The resulting mixture was separated by silica-
gel flash chromatography to give 2 (298 mg, 0.29 mol) in 42% yield,
and the unreacted fullerene (275 mg) was recovered in 55% yield.
d
2.91e2.95 (2H, m), 3.39 (6H, s), 3.56e3.65 (6H, m), 3.72e3.79 (4H,
m), 3.94e3.98 (2H, m), 4.01e4.07 (2H, m), 4.25 (2H, d, J¼10.0 Hz),
Dp >300 ꢀC; 1H NMR (500 MHz, CDCl3, J¼Hz)
d 2.93e3.01 (1H,
5.18 (2H, d, J¼10.0 Hz), 5.41 (2H, s), 7.00 (2H, s), 7.03 (2H, d,
m), 3.15 (3H, s), 3.60e3.70 (3H, m), 3.75e3.85 (2H, m), 3.98e4.04
(1H, m), 4.05e4.10 (1H, m), 4.28 (1H, d, J¼9.7 Hz), 5.23 (1H, d,
J¼9.6 Hz), 5.44 (1H, s), 6.98 (1H, dd, J¼5.5, 3.7 Hz), 7.07 (1H, d,
J¼3.7 Hz), 7.15 (1H, dd, J¼3.7,1.0 Hz), 7.18 (1H, dd, J¼5.7,1.0 Hz), 7.28
J¼3.7 Hz), 7.25 (2H, d, J¼4.0 Hz); 13C NMR (125 MHz, CDCl3)
d 52.37,
58.86, 67.66, 68.67, 70.49, 70.58, 71.92, 75.85, 77.92, 122.83, 124.35,
128.78, 135.28, 135.68, 136.23, 136.37, 136.94, 138.12, 139.54, 139.84,
139.94, 140.18, 141.38, 141.43, 141.62, 141.72, 141.80, 141.90, 141.99,
142.03, 142.34, 142.46, 142.75, 142.90, 144.11, 144.40, 144.48, 144.90,
144.98, 145.04, 145.11, 145.15, 145.19, 145.31, 145.39, 145.50, 145.68,
145.82, 145.87, 145.95, 146.02, 146.09, 146.53, 147.04, 152.72, 152.79,
153.78, 155.78; IR (KBr, cmꢁ1) 2866, 1460, 1425, 1105, 727; MALDI-
TOF-MS (matrix: SA) found 1255.40 (calculated for C86H35N2O4S3
(MHþ), exact mass: 1255.1765).
(1H, d, J¼3.7 Hz); 13C NMR (125 MHz, CDCl3)
d 52.35, 59.04, 67.74,
68.87, 70.52, 70.55, 71.99, 76.03, 78.01. 122.89, 123.78, 124.50,
127.77, 128.90, 135.82, 136.53, 137.08, 137.31, 139.66, 139.87, 139.94,
140.07, 140.52, 141.59, 141.80, 141.87, 141.95, 142.04, 142.07, 142.14,
142.20, 142.49, 142.60, 142.89, 143.06, 144.29, 144.54, 144.63,
145.06, 145.15, 145.20, 145.24, 145.35, 145.40, 145.43, 145.52, 145.67,
145.84, 145.98, 146.03, 146.08, 146.10, 146.22, 146.73, 147.22, 153.05,
154.01, 156.02; IR (KBr, cmꢁ1) 2864, 1638, 1107, 795; MALDI-TOF-
MS (matrix: SA) found 1029.0873 (calculated for C75H19NO2S2, ex-
act mass: 1029.0859).
Acknowledgements
The present work was supported by a Grant-in-Aid for Scientific
Research of the New Energy and Industrial Technology De-
velopment Organization (NEDO), from the Ministry of Economy,
Trade and Industry of Japan.
4.2.5. 1-(2-(2-Methoxyethoxy)ethyl)-2-([2,20:50,200-terthiophen]-5-
yl)fulleropyrrolidine (5). (1) To a solution of terthiophene (250 mg,
1.01 mmol) in dichloromethane (CH2Cl2)(5.0 mL) was added N,N-
dimethylformaldehyde (DMF) (162 mg, 2.21 mmol) under argon,
then 0.21 mL of POCl3 (2.21 mmol) was added at 0 ꢀC and the
resulting mixture was stirred at 50 ꢀC for 2 h. The reaction was
quenched by addition of 1 M sodium acetate (NaOAc) aqueous
solution then extracted with CH2Cl2. After evaporation, silica-gel
flash column chromatography (CH2Cl2/ethyl acetate¼1/0 to 10/1) to
afford [2,20:50,200-terthiophene]-5-carbaldehyde (8)32 (231 mg,
Supplementary data
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2012.02.080. These data includes MOL files and
InChiKeys of the most important compounds described in this article.

3610
K. Yoshimura et al. / Tetrahedron 68 (2012) 3605e3610
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