Synthesis of a π-conjugated oligomer-fullerene dyad through a versatile [6,6]diphenylmethanofullerene carboxylic acid

Article abstract of DOI:10.1016/j.tet.2008.10.077

In this article we describe the synthesis of an electron donor-acceptor dyad containing a [6,6]diphenylmethanofullerene moiety as the electron acceptor and a dialkylamino-substituted oligo-p-phenylenevinylene as the electron donor. The synthesis of this m

Full text of DOI:10.1016/j.tet.2008.10.077

Tetrahedron 65 (2009) 540–546
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Synthesis of a
p
-conjugated oligomer–fullerene dyad through a versatile
[6,6]diphenylmethanofullerene carboxylic acid
*
*
´
´
Rafael Gomez , Jose L. Segura
´
´
Departamento de Qu´ımica Organica, Facultad de Quımica, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 July 2008
Received in revised form 16 October 2008
Accepted 23 October 2008
Available online 26 October 2008
In this article we describe the synthesis of an electron donor–acceptor dyad containing a [6,6]diphe-
nylmethanofullerene moiety as the electron acceptor and a dialkylamino-substituted oligo-p-phenyl-
enevinylene as the electron donor. The synthesis of this material has been successfully accomplished by
an esterification reaction between a [6,6]diphenylmethanofullerene functionalized with a carboxylic acid
and the corresponding oligomer substituted with a benzyl alcohol. Cyclic voltammetry and absorption
spectroscopy show that both electroactive units preserve their nature in the ground state, whereas
preliminary photophysical investigations show a strong fluorescence quenching.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
be used as model compounds for the study of a variety of photo-
physical processes and as active materials in devices. The exploi-
The exploration of organic semiconductors as active elements in
electronic devices, such as light emitting diodes,1 thin film tran-
sistors,2 solid-state lasers3 or organic solar cells4 has experienced
much progress in recent years. This progress has been possible due
to the unique features that organic semiconductors offer, such as
the tuning of the electronic properties, easy structural modifica-
tions, possibility of self-assembly or mechanical flexibility. All this
enables the exploitation of organic semiconductors as materials for
large-area and low-cost disposable electronic products. Since the
discovery of ultrafast and efficient photoinduced electron transfer
tation of these properties in dyads based on p-conjugated
oligomers covalently linked to [60]fullerene has given rise to the
synthesis of a large number of derivatives.5a,7 Thus, we have pre-
pared linear,8 and branched9 oligo-p-phenylenevinylenes co-
valently linked to [60]fullerene and carrying different electron
donor groups. In this respect, we and others have shown that the
properties of these dyads can be appropriately tailored by struc-
tural modifications and that the presence of dibutylamino groups
greatly favours photoinduced electron transfer, disregarding the
limited conjugation length of most conjugated backbones reported
so far.9,10
between
p-conjugated oligomers (electron donors) and [60]fuller-
ene derivatives (electron acceptors),5 considerable interest for bulk
heterojunction solar cells based on interpenetrating networks of
conjugated systems and [60]fullerene derivatives has been gener-
ated.6 However, the tendency of [60]fullerene to phase separate
from the oligomer and crystallize is one of the prime limitations, as
Methanofullerenes are one of the most extensively studied
[60]fullerene derivatives, because of their easiness in handling,
synthetic availability, and striking resemblance to [60]fullerene in
physical properties.11 For the preparation of methanofullerenes,
several methods have been developed to date, such as the Bingel
reaction, the addition-thermal decomposition of diazo compounds
or silylated nucleophiles, or the addition–elimination of stabilized
onium ylides, among others.12 However, most of these methods
employ strongly basic conditions, which diminish their function-
ality tolerance. Taking this fact into account, a more general strat-
egy has been followed: first, a soluble methano[60]fullerene
possessing a protected functional group (9) has been prepared as
a precursor, which has been converted into a reacting carboxylic
acid group (10) later. Fulleroalkanoic acid 10 emerges as an in-
teresting and versatile synthon in fullerene chemistry: simple
monofunctionalized structure, synthetic accessibility and potential
reactivity. The presence of alkyl chains provides synthon 10 a good
solubility, making unnecessary to introduce the [60]fullerene
it imposes severe requisites for solubility in
p-conjugated oligo-
meric matrices. A synthetic approach investigated during the last
years to reduce clustering formation consists in the covalent link-
age between the
p-conjugated donor and the [60]fullerene. Con-
jugated oligomers are well defined in length, constitution and
shape. They are also readily synthesized and processable from so-
lution for film-formation. These properties have turned
p-conju-
gated oligomers into one exciting class of electroactive materials, to
* Corresponding authors. Tel.: þ34 91 394 5142; fax: þ34 91 394 4103.
E-mail addresses: rafaelgomez@quim.ucm.es (R. Go´mez), segura@quim.ucm.es
(J.L. Segura).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.10.077

R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
541
moiety in the last synthetic step, as it is usually preferred to cir-
CN
cumvent the inherent weak solubility of [60]fullerene.8–10 In this
respect, Nierengarten et al. have recently reported an interesting
methanofullerene carboxylic acid prepared by a Bingel reaction
from a soluble malonate.13 On the other hand, it has been shown
that particularly diphenylmethanofullerenes, structurally similar to
the paradigmatic [6,6]-phenyl-C61 butyric acid methyl ester
(PCBM), show remarkable photophysical properties14 and good
performance as acceptors in organic solar cells.15 Therefore, we
have developed a synthetic route for the synthesis of soluble
diphenylmethanofullerenes endowed with a carboxylic acid, which
will enable its further reactivity.
CHO
CN
t-BuOK
+
THF
O
P
H3CO
OCH3
3
N
H9C4
C4H9
2
In this article we report the synthesis of an electron donor–ac-
ceptor dyad containing a [6,6]diphenylmethanofullerene moiety as
the electron acceptor unit and a dialkylamino-substituted oligo-p-
phenylenevinylene as the electron donor.
N
1
OH
H9C4
C4H9
OHC
2. Synthesis
DIBAL-H
CH2Cl2
The synthesis of dyad 14 (Scheme 4) has been carried out by an
esterification reaction between a [6,6]diphenylmethanofullerene
derivative bearing a carboxylic acid group and the corresponding
conjugated oligomer functionalized with a benzyl alcohol.
NaBH4
THF
5
4
N
H9C4
C4H9
2.1. Synthesis of functionalized oligo-p-phenylenevinylenes
N
H9C4
C4H9
The halogen-lithium exchange followed by quenching of the
lithiated intermediate with N,N-dimethylformamide has been often
claimed as an straight procedure leading to oligo-p-phenyl-
enevinylene functionalized with aldehyde groups.16 The presence
of aldehyde groups is necessary for the elongation/functionaliza-
tion of conjugated oligomers in conjunction with the Wittig–
Horner protocol, one of the choice procedures in the chemistry of
this type of systems as it usually yields exclusively E isomers.17
However, in our hands it is much more convenient to introduce
the aldehyde group masked as a nitrile, which can be further
reduced.8,9,17 Thus, Wittig–Horner reaction between 4-[20-(400-
dibutylaminophenyl)vinyl]benzaldehyde (1)18 and dimethyl 4-
cyanobenzylphosphonate (2)19 in tetrahydrofuran and using
potassium tert-butoxyde as the base affords the corresponding
cyano-substituted derivative 3 (Scheme 1). Further selective re-
duction of the cyano groups with diisobutylaluminium hydride
affords aldehyde 4. This procedure allows the convenient and
straightforward obtention of 4 in a higher overall yield than the
four-step procedure described in a short communication by Le
Bozec et al. (21% vs. 65%).20
Scheme 1. Synthesis of benzyl alcohol functionalized oligo-p-phenylenevinylene 5.
unnecessary to introduce the [60]fullerene moiety in the last syn-
thetic step, as it is usually preferred considering the reduction of
solubility induced by this bulky unit.
Thus, Williamson etherification reaction between 6 and ethyl
bromoacetate
affords
the
unsymmetrically
substituted
H C12
O
25
O
H25C12
O
O
BrCH2COOCH2CH3
K2CO3 / DMF / NaI
6
O
7
OH
O
CH3
OCH2CH3
O
O
H3CH2CO
S
O
Finally, reduction of the aldehyde group in 4 with sodium bo-
rohydride in dichloromethane afforded the target hydroxymethyl-
functionalized oligomer 5 in excellent yield.
O
HN
H25C12
O
N
1. MeONa / Pyr.
9
2. C60
p-TosNH-NH2
o-DCB / Δ
2.2. Synthesis of functionalized diphenylmethanofullerenes
Toluene / EtOH
p-TosH
OC12H25
O
Among the above-mentioned synthetic approaches to meth-
anofullerenes, the 1,3-dipolar cycloaddition reaction of the diazo
compounds generated in situ by a Bamford–Stevens reaction be-
tween p-tosylhydrazones and sodium methoxide is one of the most
versatile. The synthesis of the target p-tosylhydrazone bearing
one solubilizing alkoxy chain in one of the phenyl rings and
a carboxylic acid on the other was designed starting from 4-hex-
yloxy-40-hydroxybenzophenone (6),21 readily prepared from the
commercially available 4,40-dihydroxybenzophenone by selective
alkylation. Obviously, as the Bamford–Stevens reaction is carried
out in a strong basic medium, the desired carboxylic acid group
must be protected, advantageously as an ethyl ester. On the other
hand, the presence of a long alkyl chain provides these diphe-
8
OCH2CH3
O
HCl / AcOH
H2O
OH
O
H25C12
O
O
10
nylmethanofullerene derivatives
a
good solubility, making
Scheme 2. Synthesis of functionalized diphenylmethanofullerenes.

542
R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
benzophenone 7 in good yield. Further condensation of 7 with p-
tosylhydrazide in mixture of toluene and ethanol affords
OH
+
a
p-tosylhydrazone 8, which after sequential treatment with sodium
methoxide in pyridine first and then with [60]fullerene in refluxing
o-dichlorobenzene (o-DCB) affords 9 in 26% yield, comparable to
similar reactions.15,22 No methyl ester could be detected during this
reaction, thus excluding ethyl–methyl interchange by an addition–
elimination mechanism, in spite of the presence of methanolate. By
following a similar synthetic procedure, the corresponding [6,6]-
bis-(4-hexyloxyphenyl)-methanofullerene (13), used as a refer-
ence, was synthesized from 4,40-dihexyloxybenzophenone (11)
(Scheme 3). Although both [6,6]-closed and [5,6]-open isomers
could be expected from the cycloaddition reaction, the high tem-
perature at which the reaction proceeds allows the obtention of the
thermodynamically more stable [6,6]-closed isomer solely. Thus,
the 13C NMR data for the series of diphenylmethanofullerenes 9, 10
and 13 shows well resolved 22–28 resonances, which is in good
agreement with the high symmetry of the proposed structure. In
addition, the peaks assignable to the cyclopropane carbons (ca.
57 ppm for C60-sp3 and 79 ppm for CDPM bridgehead) can be also
clearly observed.
OH
O
H25C12
O
O
10
H9C4
N
C4H9
DCC / DMAP Toluene
O
H25C12
O
O
O
Eventually, the acid promoted hydrolysis of the ethyl ester group
in 9 yields the target diphenylmethanofullerene carboxylic acid 10
(Scheme 2).
2.3. Synthesis of dyad 14
N(C4H9)2
14
As it has been mentioned, the synthesis of dyad 14 was ac-
complished by a condensation reaction between 10 and benzyl
alcohol 5. The treatment of diphenylmethanofullerene carboxylic
acid 10 with 5 in the presence of N,N-dicyclohexylcarbodiimide
(DCC) and 4-(dimethylamino)-pyridine (DMAP) affords dyad 14 as
the main reaction product in a 64% yield (Scheme 4).
Dyad 14, as well as all the synthetic intermediates, was char-
acterized by the common analytical and spectroscopic techniques,
all data being in good agreement with the proposed structures.
Thus, the 1H NMR spectra of dyad 14 show the correct ratio of al-
iphatic and aromatic protons, and most characteristic signals in the
1H NMR spectra could be assigned. As in its precursors, dyad 14
Scheme 4. Synthesis of dyad 14.
shows in the aromatic region a series of AB doublets arising from
the diphenylmethane and phenylene moieties, the protons located
at the sp2 carbons in alpha position respect to the dibutylamino
substituents appearing at around 6.5 ppm, and at lower fields the
three types of methylene groups directly linked to the oxygen (5.26,
4.71 and 3.99 ppm, for the Ar–CH2–O, O–CH2–CO and Alkyl–CH2–O,
respectively) and nitrogen (3.31 ppm) atoms. Besides, the rest of
the signals corresponding to the alkyl chains can be observed at
higher fields (1.50–0.89 ppm). Vinylenic protons are displayed at
3
7.07 and 6.88 ppm, with the characteristic Jtrans coupling of ca.
CH3
16 Hz and showing a clear AB pattern.
13C NMR spectra show multiple peaks in the range 115–
145 ppm, mostly arising from the methanofullerene moiety. As it
was previously mentioned, resonances at ca. 57 for the C60-sp3 and
79 for the CDPM bridgehead ensure the permanence of the
[6,6]closed isomer. In the FTIR spectra of 14 the strong hydroxy
bands around 3500 cmꢀ1 of the precursor 5 disappear, and the
most diagnostic bands are the one corresponding to the ester car-
bonyl group at 1763, the wagging vibration of the trans-configured
double bonds, which is located at 959 cmꢀ1, and the typical band
corresponding to the [60]fullerene moiety at 526 cmꢀ1. Finally,
evidence concerning the purity of 14, as in the case of all the in-
termediates used in their synthesis, is given by elemental analysis,
that is in accordance with the expected values.
O
S
O
HN
H13C6O
H13C6O
O
N
p-TosNH-NH2
Toluene / EtOH
11
p-TosH
OC6H13
OC6H13
12
1. MeONa / Pyr.
2. C60 / o-DCB / Δ
3. Electrochemistry
The electrochemical behaviour of dyad 14, along with references
5 and 13, has been investigated by cyclic voltammetry in o-di-
chlorobenzene/acetonitrile (4:1) mixtures. These experiments
were carried out using tetrabutylammonium perchlorate as the
supporting electrolyte, platinum as the working electrode and
counter electrode, and Ag/Agþ as a quasi-reference electrode. The
potentials were then referred to the ferrocene–ferrocenium couple.
The cyclic voltammogram of 14 (Fig. 1) shows the amphoteric
behaviour of this material. Thus, at negative values the first three
OC6H13
H13C6O
13
Scheme 3. Synthesis of reference diphenylmethanofullerene 13.

R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
543
5
14
5
14
13
13
420 425 430 435 440
300
400
Wavelength (nm)
500
600
-2.5
-2.0
-1.5
-1.0
E (V)
-0.5
0.0
0.5
1.0
Figure 2. UV–vis spectra of dyad 14 along with references [6,6]-bis-(4-hexyloxy-
phenyl)methanofullerene (13) and 5.
Figure 1. Cyclic voltammogram of dyad 14 along with references [6,6]-bis-(4-hexy-
loxyphenyl)methanofullerene (13) and 5 (10ꢀ2 M, Pt as working and counter electrode,
TBAClO4 (0.1 M) as supporting electrolyte and a scan rate of 200 mV sꢀ1 at room
temperature. Ag/Agþ was used as quasi-reference electrode, values vs. Fc/Fcþ).
Fluorescence emission spectra of diphenylmethanofullerene-
conjugated oligomer dyad 14 and oligobenzyl alcohol 5 were
measured in diluted dichloromethane solutions at fixed optical
density using an excitation wavelength of 405 nm. The fluorescence
properties of the fluorescent chromophore in dyad 14, i.e. the
one-electron reduction waves arising from the stepwise reduction
of the [6,6]methanofullerene moiety are clearly visible around
Ered ¼ꢀ1.07, ꢀ1.48 and ꢀ2.00 V. These redox potentials are fully
1/2
comparable to those of the reference [6,6]-bis-(4-hexyloxyphenyl)-
dibutylamino-substituted
p-conjugated system, are greatly af-
methanofullerene (13) (Ered ¼ꢀ1.07, ꢀ1.47 and ꢀ1.98 V) under
1/2
fected by the presence of the diphenylmethanofullerene moiety.
Thus, a quantitative quenching (ca. 99%) of the oligomer fluorescent
emission was observed in dyad 14 in comparison with the fluo-
rescence spectrum of oligobenzyl alcohol reference (Fig. 3).
To explain this strong fluorescence quenching, energy transfer
can be ruled out as the p-conjugated fragment has a smaller optical
bandgap than the diphenylmethanofullerene moiety, i.e. there is
little spectral overlap between the absorption spectrum of the
the same experimental conditions and are similar to those reported
for other diphenylmethanofullerene derivatives showing very high
values of open circuit voltages in photovoltaic devices.15,23
The positive scanning displays a reversible wave arising from the
oxydation of the conjugated dibutylamino-substituted oligo-p-phe-
nylenevinylene fragment at Eox ¼þ0.10 V. Compound 5, used as
1/2
a reference shows a similar peak at Eox ¼þ0.08 V. These values are
1/2
in full agreement with the electrochemical data reported for other
dialkylamino-substituted conjugated systems17 and, although no
coulombimetric experiments have been yet carried out, the com-
parison between the intensity of this wave and those arising from the
monoelectronic reduction waves of the methanofullerene fragment
suggests the also one-electron nature of this oxydation wave.
Furthermore, the similarity of oxydation and reduction poten-
tials between dyad 14 and their respective references 5 and 13
suggests that no significant interaction takes place between both
electroactive moieties in the ground state.
p
-conjugated system and the fluorescence spectrum of the
diphenylmethanofullerene fragment. Quenching by the diphe-
nylmethanofullerene/ -conjugated system energy transfer pro-
cess due to the Fo¨rster mechanism will be prohibited, according to
the energy level of both units (2.75 eV24 for the
-conjugated
oligomer and 1.76 eV for diphenylmethanofullerene9b).
p
p
Thus, we ascribe the complete fluorescence intensity quenching
in dyad 14 to photoinduced electron transfer (PET) processes be-
tween the dibutylamino-substituted
p
-conjugated system and the
4. Optical properties
14
5
1000
800
600
400
200
0
The UV–vis absorption spectra of the donor–acceptor dyad 14
together with that of references [6,6]-bis-(4-hexyloxy-
phenyl)methanofullerene (13) and benzyl alcohol 5 in diluted (ca.
5$10ꢀ6 M) dichloromethane solution are depicted in Figure 2.
The absorption spectrum of dyad 14 consists on the approxi-
mate superposition of the absorption features of its constitutive
units. This confirms the minimal interaction between the chro-
mophores in the ground state, and is in agreement with the elec-
trochemical behaviour. No new intramolecular charge-transfer
bands above 600 nm were detected in dyad 14. The absorption
spectrum of dyad 14 shows the characteristic bands arising from
the fullerene units between 230 and 260 nm and at around 330 nm,
the latter overlapping with a band arising from the conjugated
fragment. Besides, it is worth mentioning that also the diagnostic
weak band for dihydrofullerenes at around 430 nm (see inset in
450
500
550
wavelength (nm)
600
650
700
Fig. 2) is obscured by the HOMO–LUMO transition of the
gated system.
p-conju-
Figure 3. Fluorescence spectrum of dyad 14 along with oligobenzyl alcohol reference 5.

544
R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
diphenylmethanofullerene units. Indeed, a PET process is ener-
added. The resulting precipitate is filtered, thoroughly washed with
methanol and dried under vacuum to yield 4-(20-{400-[2%-(4&-dibu-
tylaminophenyl)ethenyl]phenyl}ethenyl)benzonitrile (3) as a bright
orange solid in 90% yield. Mp: 117 ꢁC (methanol); 1H NMR (CDCl3,
getically favourable as the corresponding free energy
DGPET was
estimated to be ꢀ2.54 eV using the Weller equation.25 However,
time-resolved absorption spectral studies (PIA) will be needed to
provide further evidence for the above assumption.
200 MHz)
d
¼7.71 (d, 2H, J¼8.70 Hz), 7.64 (d, 2H, J¼8.70 Hz), 7.45 (d, 2H,
J¼8.80 Hz), 7.33–7.24 (m, 4H), 7.15 (d, 1H, Jtrans¼16.23 Hz, –CH]CH–),
7.13 (d, 1H, Jtrans¼16.23 Hz, –CH]CH–), 6.93 (d, 2H, Jtrans¼16.23 Hz,
–CH]CH–), 6.69 (d, 2H, J¼8.90 Hz), 3.36 (t, 4H, J¼7.26 Hz, –N–CH2–),
1.69–1.58 (m, 4H, –CH2–), 1.52–1.34 (m, 4H, –CH2–), 0.93 (t, 6H,
5. Conclusions
In conclusion, we have described the synthesis of the electron
donor–acceptor dyad 14, which contains a diphenylmethanofuller-
ene moiety as the electron acceptor fragment and a dialkylamino-
substituted oligo-p-phenylenevinylene as the electron donor. Cyclic
voltammetry and absorption spectroscopy show that both elec-
troactive units preserve their nature in the ground state, whereas
photoluminescence investigations show a strong fluorescence
quenching, which makes this material a good candidate for the
further investigation of the photophysical processes taking place
after irradiation.
J¼7.12 Hz, –CH3); 13C NMR (CDCl3, 50 MHz)
¼148.15, 142.21, 139.09,
d
134.50, 132.59, 132.37, 129.78, 128.03, 127.36, 126.85, 126.41, 125.83,
124.34, 122.95, 111.75, 50.90 (–N–CH2–), 29.61, 20.47, 14.12; FTIR (KBr,
cmꢀ1
)
n
¼2960, 2923, 2852, 2226,1687,1605,1586,1523,1176, 967, 834;
MS (FAB): 434 (Mþ). Anal. Calcd for C31H34N2: C: 85.67%; H: 7.88%; N:
6.44%. Found: C: 85.74%; H: 7.66%; N: 6.36%.
6.3. 4-(20-{400-[2%-(4&-Dibutylaminophenyl)ethenyl]phenyl}-
ethenyl)benzaldehyde (4)
6. Experimental
6.1. General
To a refluxing solution of 4-(20-{400-[2%-(4&-dibutylaminophe-
nyl)ethenyl]phenyl}ethenyl)benzonitrile (3) (1.50 g, 3.60 mmol) in
50 of dry dichloromethane,
a diisobutylaluminium hydride
dichloromethane solution (1 M, 4.20 ml, 4.20 mmol) is added
dropwise during a period of 1 h under argon atmosphere. The so-
lution is allowed to react at reflux for 24 h and cooled to room
temperature. Methanol is then carefully added until the reaction
crude becomes a thick suspension. After water is added, the reaction
crude is treated with concentrated hydrochloric acid until complete
solution and extracted with chloroform. The combined organic ex-
tracts are then washed with water and dried over anhydrous mag-
nesium sulfate. After vacuum evaporation of the solvent, the
remaining residue is purified by column chromatography (silica gel,
hexane/dichloromethane 3:7) to afford 4-(20-{400-[2%-(4&-dibuty-
laminophenyl)ethenyl]phenyl}ethenyl)benzaldehyde (4) as an or-
ange solid in 72% yield. Mp: 98 ꢁC (hexane/dichloromethane); 1H
Materials. Compounds 1,18 2,19 621 and 11 were prepared by
following previously reported synthetic procedures. All other
chemicals were purchased from Aldrich and used as received
without further purification. Column chromatography was per-
formed on Merck Kieselgel 60 silica gel (230–240 mesh). Thin layer
chromatography was carried out on Merck silica gel F254 flexible
TLC plates. Solvents and reagents were dried by usual methods
prior to use and typically used under inert gas atmosphere.
Characterization. Melting points were measured with an Electro-
thermal melting point apparatus and are uncorrected. FTIR spectra were
recorded as KBr pellets in a Shimadzu FTIR 8300 spectrometer. NMR
were recorded on a Bruker AC-200, Avance 300 or AMX-400 apparatus
as noted, and the chemical shifts were reported relative to tetrame-
NMR (CDCl3, 200 MHz)
d
¼9.92 (s,1H, –CHO), 7.80 (d, 2H, J¼8.30 Hz),
thylsilane (TMS) at 0.0 ppm (for 1HNMR) and CDCl3 at 77.16 ppm (for 13
C
7.58 (d, 2H, J¼8.30 Hz), 7.44 (d, 2H, J¼9.35 Hz), 7.40 (d, 2H,
J¼9.35 Hz), 7.32 (d, 2H, J¼8.80 Hz), 7.20 (d, 1H, Jtrans¼16.31 Hz,
–CH]CH–), 7.05 (d, 1H, Jtrans¼16.31 Hz, –CH]CH–), 7.02 (d, 1H,
Jtrans¼16.31 Hz, –CH]CH–), 6.80 (d,1H, Jtrans¼16.31 Hz, –CH]CH–),
6.58 (d, 2H, J¼8.86 Hz), 3.22 (t, 4H, J¼7.25 Hz, –N–CH2–), 1.59–1.49
(m, 4H, –CH2–), 1.38–1.18 (m, 4H, –CH2–), 0.89 (t, 6H, J¼7.12 Hz,
NMR). The splitting patterns are designated as follows: s (singlet),
d (doublet), m (multiplet) and q (quadruplet). Mass spectra were
recorded with a Varian Saturn 2000 GC–MS and with a MALDI-TOF MS
Bruker Reflex 2 (dithranol as matrix). Elemental analyses were per-
formed on a Perkin–Elmer EA 2400.
Electrochemistry. Cyclic voltammetry experiments were per-
formed with a computer controlled EG & G PAR 273 potentiostat in
a three-electrode single-compartment cell (5 ml). The platinum
working electrode consisted of a platinum wire sealed in a soft glass
tube with a surface of A¼0.785 mm2, which was polished down to
–CH3); 13C NMR (CDCl3, 50 MHz)
d¼191.56 (C]O), 147.98, 143.67,
138.81, 135.12, 134.64, 132.04, 130.23, 129.54, 127.88, 127.21, 126.76,
126.27, 124.25, 122.84, 111.61, 50.76 (–N–CH2–), 29.47, 20.33, 13.98;
FTIR (KBr, cmꢀ1
)
n
¼2964, 2918, 2846,1696,1615,1516,1172, 834; MS
(FABI): 437 (Mþ). Anal. Calcd for C31H35NO: C: 85.08%; H: 8.06%; N:
3.20%. Found: C: 84.76%; H: 8.32%; N: 3.00%.
0.5 mm with Buehler polishing paste prior to use in order to obtain
reproducible surfaces. The counter electrode consisted of a platinum
wire and the reference electrode was a Ag/AgCl secondary electrode.
All potentials were internally referenced to the ferrocene–ferroce-
nium couple. Forthemeasurements, concentrationsof5.10ꢀ3 mol lꢀ1
of the electroactive species were used in freshly distilled and dea-
erated dichloromethane (Lichrosolv, Merck) and 0.1 M tetrabuty-
lammonium perchlorate (TBAClO4, Fluka), which was twice
recrystallized from ethanol and dried under vacuum prior to use.
6.4. 4-(20-{400-[2%-(4&-Dibutylaminophenyl)ethenyl]phenyl}-
ethenyl)benzyl alcohol (5)
To a well-stirred suspension of 4-(20-{400-[2%-(4&-dibutyl-
aminophenyl)ethenyl]phenyl}ethenyl)benzaldehyde (4) (450 mg,
1.03 mmol) in 50 ml of anhydrous tetrahydrofurane, sodium boro-
hydride(39 mg,1.03 mmol)isaddedportionwiseatreflux andunder
argon atmosphere. The reaction crude is allowed to react for 3 h and
cooled down to room temperature. The resulting solution is treated
with methanol and water and extracted with dichloromethane. The
combined organic extracts are dried over magnesium sulfate and the
solvent evaporated under vacuum. The remaining residue is purified
by column chromatography (silica gel, dichloromethane) to afford
benzyl alcohol 5 as a bright yellow solid in 92% yield. Mp: 164 ꢁC
6.2. 4-(20-{400-[2%-(4&-Dibutylaminophenyl)ethenyl]phenyl}-
ethenyl)benzonitrile (3)
To a refluxing and well-stirred suspension of 4-[20-(400-dibutylami-
nophenyl)ethenyl]benzaldehyde (1) (1.24 g, 3.70 mmol) and dimethyl
4-cyanobenzylphosphonate (2) (1.17 g, 5.20 mmol) in 60 ml of anhy-
drous tetrahydrofuran, potassium tert-butoxide (582 mg, 5.20 mmol) is
added portionwise under argon atmosphere. After 24 h, the reaction
crude is allowed to cool down to room temperature and methanol is
(dichloromethane); 1H NMR (CDCl3, 200 MHz)
7.55 (d, 2H, J¼8.01 Hz), 7.57 (d, 2H, J¼8.66 Hz), 7.37 (d, 3H,
Jtrans¼16.26 Hz, –CH]CH–), 6.80 (d,1H, Jtrans¼16.26 Hz, –CH]CH–),
d
¼7.73–7.65 (m, 6H),

R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
545
6.81 (d, 2H, J¼8.81 Hz), 4.90 (s,1H, –CH2–OH), 4.87 (s,1H, –CH2–OH),
3.48 (t, 4H, J¼7.31 Hz, –N–CH2–),1.83–1.75 (m, 4H, –CH2–),1.60–1.49
(m, 4H, –CH2–), 1.14 (t, 6H, J¼7.19 Hz, –CH3); 13C NMR (CDCl3,
0.43 mmol) in 35 ml of o-dichlorobenzene is added at once and
the resulting crude is heated at 180 ꢁC for 18 h. After cooling to
room temperature, the solvent is stripped away in a rotary
evaporator and the remaining solid is purified by column chro-
matography (silica gel, toluene/dichloromethane 7:3) to yield 9 as
a black solid in 26% yield after washing with methanol and
50 MHz)
d¼147.99, 140.17, 138.01, 137.12, 135.56, 129.07, 128.71,
127.91, 127.48, 126.89, 126.71, 126.32, 124.57, 123.29, 111.77, 65.27
(–CH2–OH), 50.89 (–N–CH2–), 29.59, 20.45, 14.10; FTIR (KBr, cmꢀ1
)
n
¼3575, 2957, 2931, 2871,1606,1590,1520,1369,1220, 966, 827; MS
diethyl ether. 1H NMR (CDCl3, 200 MHz)
d¼7.94 (d, 2H,
(FAB): 439 (Mþ). Anal. Calcd for C31H37NO: C: 84.69%; H: 8.48%; N:
3.19%. Found: C: 84.91%; H: 8.32 %; N: 3.26%.
J¼8.72 Hz), 7.89 (d, 2H, J¼8.72 Hz), 6.95–6.89 (m, 4H), 4.58 (s, 2H,
–O–CH2–COOR), 4.23 (q, 2H, J¼7.15 Hz, –O–CH2–CH3), 3.91 (t, 2H,
J¼6.48 Hz, –O–CH2–), 1.72 (m, 2H, –CH2–), 1.48–1.19 (m, 18H,
–CH2–), 0.80 (t, 6H, J¼6.68 Hz, –CH3); 13C NMR (CDCl3, 75 MHz)
6.5. Unsymmetrically substituted benzophenone 7
d
¼169.20 (C]O), 159.20 (CAr–O), 157.81 (CAr–O), 148.87, 148.83,
To a solution of 4-dodecyloxy-40-hydroxybenzophenone (6)
(2.00 g, 5.23 mmol) in 40 ml of anhydrous N,N-dimethylforma-
mide, potassium carbonate (1.44 g, 10.5 mmol), ethyl bromoacetate
(1.16 ml, 10.5 mmol) and a catalytic amount of sodium iodide were
added under argon atmosphere. The mixture was heated at reflux
for 72 h. The crude was allowed to reach the room temperature and
treated with an 1 M HCl aqueous solution. The resulting mixture
was extracted with dichloromethane and the combined organic
fractions dried over MgSO4 and evaporated under vacuum. The
remaining residue was purified by column chromatography (silica
gel, hexane/dichloromethane 1:1) to give 7 as a white solid in 76%
yield. Mp: 77 ꢁC (hexane/dichloromethane); 1H NMR (CDCl3,
145.76, 145.58, 145.49, 145.11, 145.02, 144.64, 144.25, 143.39,
143.32, 142.72, 142.69, 142.52, 141.23, 138.63, 138.56, 133.15,
132.40, 132.28, 131.44, 115.33, 115.06, 79.88 (CDPM), 68.48 (C–O),
65.98 (C–O), 61.85 (C–O), 57.53 (C60-sp3), 32.33, 30.08, 30.05,
30.02, 30.00, 29.83, 29.76, 29.72, 26.52, 23.10, 14.62, 14.53; FTIR
(KBr, cmꢀ1
)
n
¼2957, 2920, 1766, 1627, 1323, 1250, 1217, 1174, 764,
526; MS (FAB): 1172 (Mþ), 720 (C60). Anal. calcd for C89H40O4: C:
91.11%; H: 3.44%. Found: C: 92.00%; H: 3.42%.
6.8. [6,6]Diphenylmethanofullerene carboxylic acid 10
To a well-stirred solution of the [6,6]diphenylmethanofullerene
derivative 9 (194 mg, 0.17 mmol) in 120 ml of toluene, concentrated
hydrochloric acid (4 ml) and acetic acid (10 ml) are added and the
mixture is heated at reflux for 48 h. The reaction crude is allowed to
cool down to room temperature and vacuum evaporated. The
remaining solid is then washed with methanol and diethyl ether, to
afford carboxylic acid 10 in 92% yield as a brown solid. 1H NMR
200 MHz)
d
¼7.69 (d, 2H, J¼8.87 Hz), 7.68 (d, 2H, J¼8.87 Hz), 6.91–
6.76 (m, 4H), 4.61 (s, 2H, –O–CH2–COOR), 4.22 (q, 2H, J¼7.15 Hz,
–O–CH2–CH3), 3.94 (t, 2H, J¼6.48 Hz, –O–CH2–), 1.72 (m, 2H, –CH2–
), 1.36–1.17 (m, 18H, –CH2–), 0.78 (t, 6H, J¼6.74 Hz, –CH3); 13C NMR
(CDCl3, 50 MHz)
d¼168.27 (C]O), 162.54 (CAr–O), 160.72 (CAr–O),
132.18, 132.05, 131.79, 114.00, 113.89, 68.20 (C–O), 65.21 (C–O),
61.48 (C–O), 31.82, 29.54, 29.49, 29.25, 29.04, 25.91, 22.59, 14.07,
(CDCl3, 200 MHz)
d
¼7.82 (d, 2H, J¼8.68 Hz), 7.76 (d, 2H, J¼8.68 Hz),
14.01; FTIR (KBr, cmꢀ1
)
n
¼2957, 2920, 2852, 1765, 1638, 1604, 1309,
6.84 (d, 2H, J¼8.75 Hz), 6.78 (d, 2H, J¼8.75 Hz), 4.53 (s, 2H, -O–CH2–
COOH), 3.80 (t, 2H, J¼6.39 Hz, –O–CH2–), 1.63 (m, 2H, –CH2–), 1.13–
1.08 (m, 18H, –CH2–), 0.72 (t, 3H, J¼6.67 Hz, –CH3); 13C NMR (CDCl3,
1295, 1255, 1209, 1174, 765; MS (FAB): 468 (Mþ). Anal. Calcd for
C29H40O5: C: 74.32%; H: 8.60%. Found: C: 74.72%; H: 8.64%.
75 MHz)
d
¼162.68 (CAr–O), 160.66 (CAr–O), 148.69, 148.65, 145.77,
6.6. Substituted benzophenone p-tosylhydrazone 8
145.74, 145.64, 145.56, 145.15, 145.11, 145.07, 144.99, 144.74, 144.29,
143.45, 143.40, 143.36, 143.35, 142.70, 142.67, 142.67, 142.56, 141.32,
138.74, 138.64, 133.65, 132.56, 132.31, 131.24, 115.37, 115.14, 79.74
(CDPM), 68.52 (C–O), 65.31 (C–O), 57.39 (C60-sp3), 32.58, 30.35,
30.32, 30.30, 30.29, 30.11, 30.04, 29.97, 26.78, 23.43, 14.79; FTIR
Under argon atmosphere, a solution of 7 (700 mg,1.5 mmol) and
p-tosylhydrazide (556 mg, 3.0 mmol) in 60 ml of toluene and 8 ml of
ethanol is refluxed for 72 h in the presence of a catalytic amount of
p-toluensulphonic acid. After cooling to room temperature, the
crude is concentrated under vacuum, cooled in an ice bath and the
precipitate is collected by filtration, washed with cold toluene and
diethyl ether to yield p-tosylhydrazone 8 in 53% yield as an off-white
(KBr, cmꢀ1
)
n
¼2920, 2850, 1741, 1703, 1611, 1234, 526; MS (FAB):
1144 (Mþ), 720 (C60). Anal. Calcd for C87H36O4: C: 91.24%; H: 3.17%.
Found: C: 90.00%; H: 3.32%.
solid. Mp: 154 ꢁC (diethyl ether); 1H NMR (CDCl3, 200 MHz)
d
¼7.85
(d, 2H, J¼8.32 Hz), 7.53 (s, 1H), 7.42–7.32 (m, 3H), 7.05 (d, 2H,
J¼9.16 Hz), 6.99 (d, 2H, J¼9.16 Hz), 6.81 (d, 1H, J¼6.91 Hz), 6.81 (d,
1H, J¼6.91 Hz), 4.62 (s, 2H, –O–CH2–COOR), 4.32–4.11 (m, 2H, –O–
CH2–), 4.02 (t, 2H, J¼6.46 Hz, –O–CH2–), 2.44 (s, 3H, –CH3), 2.05 (s,
1H, –NH–), 1.83 (m, 2H, –CH2–), 1.58–1.23 (m, 18H, –CH2–), 0.89 (t,
6.9. 4,40-Dihexyloxybenzophenone-p-tosylhydrazone (12)
Under argon atmosphere,
a
solution of 4,40-dihexyloxy-
benzophenone (11) (382 mg, 1.0 mmol) and p-tosylhydrazide (186 mg,
1.0 mmol) in 25 ml of toluene is refluxed for 20 h in the presence of
a catalytic amount of p-toluensulphonic acid. After cooling to room
temperature, thecrudeisvacuumevaporatedandtheresidueispurified
bycolumn chromatography (silica gel, hexane/ethyl acetate 9:1) toyield
4,40-dihexyloxybenzophenone-p-tosylhydrazone (12) in 70% yield as
6H, J¼6.74 Hz, –CH3); 13C NMR (CDCl3, 50 MHz)
¼160.34 (C]O),
d
158.96 (CAr–O),154.08 (CAr–O),143.83,135.48,130.47,129.71,129.45,
129.13,127.74,122.48,115.39,114.05, 68.08 (C–O), 65.13 (C–O), 61.29
(C–O), 31.74, 29.42, 29.18, 28.99, 25.87, 22.51, 21.43,13.93; FTIR (KBr,
cmꢀ1
)
n
¼2924, 2853, 1758, 1606, 1509, 1200, 1162, 813; MS (EI, %I):
a yellowish oil. 1H NMR (CDCl3, 200 MHz)
d
¼7.85 (d, 2H, J¼8.32 Hz),
636 (Mþ, 3), 481 (MþꢀTos, 66), 454 (MþꢀTos–NH–N, 68), 286 (51),
199 (58), 91 (100). Anal. Calcd for C36H48N2SO6: C: 67.89%; H: 7.60%;
N: 4.40%; S: 5.03%. Found: C: 67.62%; H: 7.42%; N: 4.67%; S: 5.34%.
7.53 (s, 1H), 7.42–7.32 (m, 3H), 7.05 (d, 2H, J¼9.16 Hz), 6.99 (d, 2H,
J¼9.16 Hz), 6.81 (d,1H, J¼6.91 Hz), 6.81 (d,1H, J¼6.91 Hz), 4.32–4.11 (m,
2H, –O–CH2–), 4.02 (t, 2H, J¼6.46 Hz, –O–CH2–), 2.44 (s, 3H, –CH3), 2.05
(s,1H, –NH–),1.83 (m, 2H, –CH2–),1.58–1.23 (m,14H, –CH2–), 0.89 (t, 6H,
6.7. [6,6]Diphenylmethanofullerene ethoxycarbonyl
derivative 9
J¼6.74 Hz, –CH3); 13C NMR (CDCl3, 50 MHz)
¼160.57, 160.22, 154.54
d
(CAr–O), 143.87, 135.62, 129.85, 129.53, 129.26, 129.19, 127.86, 122.79,
115.45,114.00, 68.16 (C–O), 68.03 (C–O), 31.48, 29.07, 25.65, 25.60, 22.52,
To a solution of p-tosylhydrazone 8 (346 mg, 0.54 mmol) in
10 ml of anhydrous pyridine, sodium methoxyde (30 mg,
0.54 mmol) is added under argon atmosphere. After stirring at
room temperature for 15 min, a solution of [60]fullerene (311 mg,
21.55,13.95; FTIR (KBr, cmꢀ1
)
n
¼2931, 2859,1607,1510,1248,1171,1161,
881, 664; MS (EI, %I): 550 (Mþ, 8), 395 (MþꢀTos, 100), 366 (MþꢀTos–
NH–N, 39), 311 (23),197 (25). Anal. Calcd for C32H42N2SO4: C: 69.78%; H:
7.69%; N: 5.09%; S: 5.82%. Found: C: 69.42%; H: 5.13%; S: 5.47%.

546
R. Go´mez, J.L. Segura / Tetrahedron 65 (2009) 540–546
6.10. [6,6]-Bis-(4-hexyloxyphenyl)methanofullerene (13)
2126, Group no. 910759) for financial support. R.G. is indebted to
´
the ‘Programa Ramon y Cajal’.
To a solution of 4,40-dihexyloxybenzophenone-p-tosylhydrazone
(12) (200 mg, 0.36 mmol) in 8 ml of anhydrous pyridine, sodium
methoxyde (19 mg, 0.36 mmol) is added under argon atmosphere.
After stirring at room temperature for 15 min, a solution of [60]ful-
lerene (276 mg, 0.36 mmol) in 30 ml of o-dichlorobenzene is added
at once and the resulting crude is heated at 180 ꢁC for 24 h. After
cooling to room temperature, the solvent is stripped away in a rotary
evaporator and the remaining solid is purified by column chroma-
tography (silica gel, toluene/dichloromethane 1:1) to yield [6,6]-bis-
(4-hexyloxyphenyl)methanofullerene (13) as a black solid in 32%
yield after washing with methanol and diethyl ether.1H NMR (CDCl3,
References and notes
1. (a) Organic Light-Emitting Devices; Mu¨llen, K., Scherf, U., Eds.; Wiley-VCH:
Weinheim, 2006; (b) Organic Electroluminescence; Kafafi, Z. H., Ed.; Taylor &
Francis: Boca Raton, 2005; (c) Organic Light-Emitting Devices; Shinar, J., Ed.;
Springer: New York, NY, 2003.
2. Murphy, A. R.; Frechet, J. M. J. Chem. Rev. 2007, 107, 1066–1096.
3. (a) Samuel, I. D. W.; Turnbull, G. A. Chem. Rev. 2007, 107, 1272–1295; (b) Cal-
`
zado, E. M.; Villalvilla, J. M.; Boj, P. G.; Quintana, A.; Go´mez, R.; Segura, J. L.;
´
´
Dıaz-Garcıa, M. A. J. Phys. Chem. C. 2007, 111, 13595–13605.
4. Go´mez, R.; Segura, J. L. Handbook of Organic Electronics and Photonics; American
Scientific: Los Angeles, 2007; Vol. 3.
5. For reviews, see: (a) Segura, J. L.; Martı´n, N.; Guldi, D. M. Chem. Soc. Rev. 2005,
34, 31–47; (b) Imahori, H.; Mori, Y.; Matano, Y. J. Photochem. Photobiol., C:
Photochem. Rev. 2003, 4, 51–83; (c) Gorgues, A.; Hudhomme, P.; Salle´, M. Chem.
Rev. 2004, 104, 5151–5184.
200 MHz)
d
¼7.97 (d, 4H, J¼8.80 Hz), 6.98 (d, 4H, J¼8.80 Hz), 3.98 (t,
4H, J¼6.62 Hz, –O–CH2–), 1.79 (m, 4H, –CH2–), 1.50–1.26 (m, 12H,
–CH2–), 0.91 (t, 6H, J¼6.68 Hz, –CH3); 13C NMR (CDCl3, 50 MHz)
6. Gu¨ nes, S.; Neugebauer, H.; Sariciftci, N. S. Chem. Rev. 2007, 107, 1324–1338.
7. Roncali, J. Chem. Soc. Rev. 2005, 34, 483–495.
d
¼158.70 (CAr–O), 148.59, 145.40, 145.15, 145.06, 144.68, 144.57,
144.19, 143.83, 142.97, 142.90, 142.31, 142.09, 140.78, 138.18, 131.80,
´
´
8. (a) Segura, J. L.; Gomez, R.; Martın, N.; Luo, C.; Guldi, D. M. Chem. Commun. 2002,
701–702; (b) Segura, J. L.; Go´mez, R.; Martı´n, N.; Guldi, D. M. Synth. Met. 2001, 119,
65–66; (c) Guldi, D. M.; Luo, C.; Swartz, A.; Go´mez, R.; Segura, J. L.; Martı´n, N.;
Brabec, C.; Sariciftci, N. S. J. Org. Chem. 2002, 67,1141–1152; (d) Guldi, D. M.; Luo, C.;
Swartz, A.; Go´mez, R.; Segura, J. L.; Martı´n, N. J. Phys. Chem. A 2004, 108, 455–467.
9. (a) Segura, J. L.; Gomez, R.; Martın, N.; Luo, C.; Swartz, A.; Guldi, D. M. Chem.
Commun. 2001, 707–708; (b) Guldi, D. M.; Swartz, A.; Luo, C.; Go´mez, R.; Segura,
J. L.; Martı´n, N. J. Am. Chem. Soc. 2002, 124, 10875–10886.
131.32, 114.63, 79.66 (CDPM), 68.05 (C–O), 57.38 (C60-sp3), 31.58,
29.27, 25.76, 22.59,14.02; FTIR (KBr, cmꢀ1
)
n
¼2922, 2851,1608,1508,
1484,1246,1182, 526; MS (FAB): 1086 (Mþ), 720 (C60). Anal. Calcd for
C85H34O2: C: 91.22%; H: 3.06%. Found: C: 91.04%; H: 3.72%.
´
´
10. (a) Liu, S. G.; Rivera, J.; Liu, H.; Raimundo, J. M.; Roncali, J.; Gorgues, A.; Eche-
goyen, L. J. Org. Chem. 1999, 64, 4884–4886; (b) Martineau, C.; Blanchard, P.;
Rondeau, D.; Delaunay, J.; Roncali, J. Adv. Mater. 2002, 14, 283–287; (c) Gu, T.;
Tsamouras, D.; Melzer, C.; Kranikov, V.; Gisselbrecht, J.-P.; Gross, M.; Had-
zioannou, G.; Nierengarten, J.-F. Chem. Phys. Chem. 2002, 1, 124–127.
11. (a) Diederich, F.; Isaacs, L.; Philp, D. Chem. Soc. Rev. 1994, 23, 243–256; (b) Wudl,
F. Acc. Chem. Res. 1992, 25, 157–161; (c) Keshavarz, K. M.; Knight, B.; Haddon, R.
C.; Wudl, F. Tetrahedron 1996, 52, 5149–5159; (d) Nierengarten, J.-F.; Habicher,
T.; Kessinger, R.; Cardullo, F.; Diederich, F. Helv. Chim. Acta 1997, 80, 2238–2276.
12. Hirsch, A.; Brettreich, M. Fullerenes: Chemistry and Reactions; Wiley-VCH:
Weinheim, 2004.
13. Ge´gout, A.; Holler, M.; Figueira-Duarte, T. M.; Nierengarten, J.-F. Eur. J. Org.
Chem. 2008, 3627–3634.
14. Bensasson, R. V.; Bienvenu¨e, E.; Fabre, C.; Janot, J.-M.; Land, E. J.; Leboulaire, V.;
Rassat, A.; Roux, S.; Seta, P. Chem.dEur. J. 1998, 4, 270–278; (b) Bonifazi, D.;
Salomon, A.; Enger, O.; Diederich, F.; Cahen, D. Adv. Mater. 2002, 14, 802–805.
6.11. [6,6]Diphenylmethanofullerene-conjugated oligomer
dyad 14
To a solution of [6,6]diphenylmethanofullerene carboxylic acid
10 (70 mg, 0.06 mmol), N,N-dicyclohexylcarbodiimide (25 mg,
0.12 mmol) and 4-(dimethylamino)-pyridine (15 mg, 0.12 mmol) in
40 ml of anhydrous toluene and under argon atmosphere, a solu-
tion of benzyl alcohol 5 (80 mg, 0.18 mmol) in 10 ml of anhydrous
toluene is added. After 3 days, the reaction crude is vacuum
evaporated and the remaining residue purified by column chro-
matography (silica gel, dichloromethane) and washed with meth-
anol and diethyl ether to yield 14 in 66% yield as a black solid. 1H
NMR (CDCl3, 500 MHz)
d
¼8.00 (d, 2H, J¼8.48 Hz), 7.98 (d, 2H,
15. Riedel, I.; Hauff, E.; Parisi, J.; Martı
´n, N.; Giacalone, F.; Dyakonov, V. Adv. Funct.
Mater. 2005, 15, 1979–1987.
16. (a) Stalmach, U.; Kolshorn, H.; Meier, H. Liebigs Ann. Chem. 1996, 1449–1456; (b)
Kim, S.; Sens, P.; Meier, H. J. Org. Chem. 2004, 1761–1764.
J¼8.48 Hz), 7.50–7.41 (m, 6H), 7.39 (d, 2H, J¼8.74 Hz), 7.33 (d,
2H, J¼8.74 Hz), 7.07 (d, 2H, Jtrans¼16.00 Hz, –CH]CH–), 7.00 (d, 2H,
J¼8.70 Hz), 6.98 (d, 2H, J¼8.70 Hz), 6.88 (d, 2H, Jtrans¼16.00 Hz,
–CH]CH–), 6.64 (d, 2H, J¼8.70 Hz), 5.26 (s, 2H, Ar–CH2–O–), 4.71
(s, 2H, –O–CH2–CO), 3.99 (t, 2H, J¼6.42 Hz, –O–CH2–), 3.31 (t, 4H,
J¼7.54 Hz, –CH2–N–), 1.82 (q, 2H, J¼6.93 Hz, –CH2–), 1.46–1.27 (m,
26H, –CH2–), 0.98 (t, 6H, J¼7.20 Hz, –CH3), 0.89 (t, 3H, J¼6.60 Hz,
17. (a) Segura, J. L.; Go´ mez, R.; Martı´n, N.; Guldi, D. M. Org. Lett. 2001, 3, 2645–
´
´
2648; (b) Gomez, R.; Segura, J. L.; Martın, N. Org. Lett. 2000, 2, 1585–1587; (c)
Dı´ez-Barra, E.; Garcı´a-Martı´nez, J. C.; Rodrı´guez-Lo´ pez, J.; Go´mez, R.; Segura, J.
L.; Martı´n, N. Org. Lett. 2000, 2, 3651–3653; (d) Go´ mez, R.; Segura, J. L.; Martı´n,
´
´
N. J. Org. Chem. 2000, 65, 7566–7574; (e) Gomez, R.; Segura, J. L.; Martın, N. J.
Org. Chem. 2000, 65, 7501–7511; (f) Go´ mez, R.; Veldman, D.; Langeveld, B. M.
W.; Segura, J. L.; Janssen, R. A. J. J. Mater. Chem. 2007, 17, 4274–4288.
18. Ashwell, G. J.; Maxwell, A. A.; Green, A. J. Mater. Chem. 2002, 12, 2192–2196.
19. Frampton, M. J.; Magennis, S. W.; Pillow, J. N. J.; Burn, P. L.; Samuel, I. D. W. J.
Mater. Chem. 2003, 13, 235–242.
–CH3); 13C NMR (CDCl3, 125 MHz)
d
¼169.20 (C]O), 159.18 (CAr–O),
157.69 (CAr–O),148.84,148.80, 148.28,145.77,145.75,145.57,145.48,
145.10,145.04,145.00,144.63,144.23,143.38,143.32,142.68,142.50,
141.22, 138.61, 138.55, 138.51, 135.63, 134.44, 133.18, 132.39, 132.29,
131.44, 129.67, 129.50, 129.41, 128.24, 127.43, 127.28, 127.01, 126.64,
124.76, 123.47, 115.29, 115.03, 112.00, 79.86 (CDPM), 68.48 (C–O),
67.37 (C–O), 65.91 (C–O), 57.49 (C60-sp3), 51.20 (C–N), 32.34, 30.09,
30.06, 30.03, 29.89, 29.84, 29.77, 29.72, 26.52, 23.11, 20.77, 14.56,
20. Viau, L.; Maury, O.; Le Bozec, H. Tetrahedron Lett. 2003, 45, 125–128.
21. Kunitake, T.; Okahata, Y.; Shimomura, M.; Yasunami, S.; Takarabe, K. J. Am.
Chem. Soc. 1981, 103, 5401–5413.
´
´
22. Gomez, R.; Segura, J. L.; Martın, N. Org. Lett. 2005, 7, 717–720.
23. Riedel, I.; Martı´n, N.; Giacalone, F.; Segura, J. L.; Chirvase, D.; Parisi, J.; Dyako-
nov, V. Thin Solid Films 2004, 451, 43–47.
24. Value corresponding to the band onset featured in the emission spectra.
14.44; FTIR (KBr, cmꢀ1
)
n
¼2952, 2923, 2852, 1763, 1607, 1591, 1519,
25. Weller, A. Z. Phys. Chem. (Muenchen, Ger.) 1982, 133, 93–98
D
GPET¼e[Eox
(oligomer)ꢀEred(DPM)]ꢀE(S1)ꢀe2/4p303sRccꢀe2/8p30(1/rþþ1/rꢀ)(1/3refꢀ1/3s). In
1509, 1285,1174, 959, 821, 742, 526; MS (FAB): 1565 (Mþ), 720 (C60).
Anal. Calcd for C118H71NO4: C: 90.45%; H: 4.57%; N: 0.89%. Found: C:
90.89%; H: 4.42%; N: 0.63%.
this equation, Eox(oligomer) and Ered(DPM) are the oxidation and reduction
potentials of the donor and acceptor in a solvent with relative permittivity 3ref
;
E(S1) the energy of the excited state from which electron transfer occurs; Rcc
the center-to-center distance of the positive and negative charges in the charge
separated state; rþ and rꢀ are the radii of the positive and negative ions; 3s is
the relative permittivity of the solvent; and e and 30 are the electron charge and
the vacuum permittivity, respectively. The radius of the DPM unit (4.4 Å), the
oligomeric system (9.5 Å) and Rcc (12.8 Å) was estimated by semiempirical PM3
calculations, assuming a conformation with both electroactive units as sepa-
rated as possible.
Acknowledgements
We thank the MCyT (Ref. CTQ2007-60459) and a Comunidad de
Madrid-Universidad Complutense joint project (CCG07-UCM-PPQ-