Fullerene derivatives functionalized with diethylamino-substituted conjugated oligomers: Synthesis and photoinduced electron transfer

Article abstract of DOI:10.1002/chem.200901216

Diethylamino-substituted oligophenylenevinylene (OPV) building blocks have been prepared and used for the synthesis of two [60]fullereneOPV dyads, F-Dl and F-D2, which exhibit different conjugation length of the OPV fragments. The electrochemical properti

Full text of DOI:10.1002/chem.200901216

FULL PAPER
DOI: 10.1002/chem.200901216
Fullerene Derivatives Functionalized with Diethylamino-Substituted
Conjugated Oligomers: Synthesis and Photoinduced Electron Transfer
Aline Gꢀgout,[a, b] Jean-FranÅois Nierengarten,*[a] Bꢀatrice Delavaux-Nicot,*[b]
Carine Duhayon,[b] Alix Saquet,[b] Andrea Listorti,[c] Abdelhalim Belbakra,[c]
Claudio Chiorboli,[d] and Nicola Armaroli*[c]
In memory of Jean-Marie Nierengarten
Abstract: Diethylamino-substituted oli-
gophenylenevinylene (OPV) building
blocks have been prepared and used
for the synthesis of two [60]fullerene–
OPV dyads, F-D1 and F-D2, which ex-
hibit different conjugation length of
the OPV fragments. The electrochemi-
cal properties of these acceptor–donor
dyads have been studied by cyclic vol-
tammetry. The first reduction is always
assigned to the fullerene moiety and
the first oxidation centered on the di-
ethylaniline groups of the OPV rods,
thus making these systems suitable can-
didates for photoinduced electron
transfer. Both the OPV and the fuller-
ene-centered fluorescence bands are
quenched in toluene and benzonitrile,
which suggests the occurrence of pho-
toinduced electron transfer from the
amino-substituted OPVs to the carbon
sphere in the dyads in both solvents.
By means of bimolecular quenching ex-
periments, transient absorption spectral
fingerprints of the radical cationic spe-
cies are detected in the visible
(670 nm) and near-IR (1300–1500 nm)
regions, along with the much weaker
fullerene anion band at lmax =1030 nm.
Definitive evidence for photoinduced
electron transfer in F-D1 and F-D2
comes from transient absorption meas-
urements. A charge-separated state is
formed within 100 ps and decays in less
than 5 ns.
Keywords: electrochemistry ·
electron transfer · fullerenes · oligo-
AHCTUNGTRENGNpUN henylenevinylene · photophysics
Introduction
[a] Dr. A. Gꢀgout, Prof. Dr. J.-F. Nierengarten
Laboratoire de Chimie des Matꢀriaux Molꢀculaires
Universitꢀ de Strasbourg et CNRS (UMR 7509)
Ecole Europꢀenne de Chimie, Polymꢁres et Matꢀriaux (ECPM)
25 rue Becquerel, 67087 Strasbourg Cedex 2 (France)
Fax : (+33)3-90-242-774
Owing to their potential for photovoltaic applications,[1]
hybrid compounds combining fullerene with p-conjugated
oligomers have generated intense research activities in the
past few years.[2] In addition, C60–(p-conjugated oligomer)
hybrid systems also offer interesting perspectives for optical
limiting or photodynamic therapy applications.[3] The pecu-
liar electronic properties of C60–(p-conjugated oligomer)
dyads led to the development of dendritic systems with in-
teresting light-harvesting properties[4] or used for evidencing
original dendritic effects.[5] As part of this research, we have
designed numerous C60–oligophenylenevinylene (C60–OPV)
dyads and studied systematically their electronic proper-
ties.[6] As far as their photophysical properties are con-
cerned, a characteristic feature in all these systems is an ul-
trafast energy transfer from the lowest singlet excited state
of the OPV-conjugated system to populate the fullerene sin-
glet.[6] This first event can be followed by an electron trans-
fer, depending on the donating ability of the OPV oligomer,
on structural factors, and on the solvent polarity.[6,7] Actual-
E-mail: nierengarten@chimie.u-strasbg.fr
[b] Dr. A. Gꢀgout, Dr. B. Delavaux-Nicot, Dr. C. Duhayon,
Dr. A. Saquet
Laboratoire de Chimie de Coordination du CNRS
205 route de Narbonne, 31077 Toulouse Cedex 4 (France)
Fax : (+33)5-61-55-30-03
E-mail: beatrice.delavaux-nicot@lcc-toulouse.fr
[c] Dr. A. Listorti, A. Belbakra, Dr. N. Armaroli
Molecular Photoscience Group
Istituto per la Sintesi Organica e la Fotoreattivitꢂ
Consiglio Nazionale delle Ricerche
via Gobetti 101, 40129 Bologna (Italy)
Fax : (+39)051-6399844
E-mail: nicola.armaroli@isof.cnr.it
[d] Dr. C. Chiorboli
Istituto per la Sintesi Organica e la Fotoreattivitꢂ
Consiglio Nazionale delle Ricerche, Sezione di Ferrara
via Borsari 46, 44100 Ferrara (Italy)
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ly, for C60–OPV conjugates combining the fullerene-accept-
ing unit with relatively short OPV oligomers, the charge-sep-
arated state is higher in energy than the first fullerene sin-
glet excited state, no matter what the conditions.[6] In this
case, the light energy absorbed by the conjugated system is
promptly conveyed to the fullerene lowest singlet excited
state by means of energy transfer and no longer yields
charge separation. By increasing the length of the OPV-con-
jugated backbone and thus its donating ability, dramatic ef-
fects of the solvent polarity have been observed upon photo-
excitation of the OPV moiety.[6,7] In apolar solvents, the
charge-separated state is still higher in energy than the first
fullerene singlet excited state and no charge separation
could be evidenced. In contrast, the situation is completely
different in more polar solvents. Effectively, since the
energy of the charge-separated state drops below that of the
first fullerene singlet excited state, electron transfer is ob-
served upon the initial singlet energy-transfer event. Similar
findings have been reported by Martin, Guldi, and co-work-
ers[8] for a series of oligonaphthylenevinylene–fullerene
dyads. In this paper, we now report the synthesis and the
electronic properties of two new C60–OPV dyads. Owing to
the presence of diethylamino substituents on the OPV frag-
ments, their donating ability has been improved. In this way,
the energy level of the charge-separated state is significantly
lower in energy. As a result, the thermodynamic driving
force is more favorable and electron transfer occurs whatev-
er the solvent.
Scheme 1. Reagents and conditions: a) LiAlH4, THF, 08C (99%); b) I2,
(OEt)3, 08C to RT (45%); c) tBuOK, THF, 08C to RT (42%);
d) TBAF, THF, 08C (80%); e) DCC, DMAP, CH2Cl2, 08C to RT (70%).
PACHTUNGTRENNUNG
PACHTNUTRGENNG(U OEt)3, phosphonate 3 was directly obtained from alcohol
2 in 45% yield. Reaction of 3 with dialdehyde 4[11] in the
presence of tBuOK in THF afforded the OPV model com-
pound D1 in 42% yield. All the spectroscopic studies and
elemental analysis results were consistent with the structure
of D1. In particular, coupling constants of approximately
16 Hz for the AB systems corresponding to the signals of
Results and Discussion
1
the vinylic protons in the H NMR spectrum were in good
Synthesis: The synthesis of the C60–OPV conjugates is based
on the esterification reaction of a fullerene carboxylic acid
building block with OPV oligomers bearing one hydroxy
group. To this end, we have first prepared alcohols 5 and 10
(Schemes 1 and 2). The synthetic approach to preparing the
conjugated backbone of both building blocks relies upon re-
action of phosphonate 3 and a bis-aldehyde derivative.
Indeed, the Wadsworth–Emmons reaction has proven to be
a powerful tool for the synthesis of OPV derivatives as the
trans olefines are selectively produced from benzylic phos-
phonates.[9]
Phosphonate 3 was obtained in two steps from commer-
cially available aldehyde 1 (Scheme 1). Reduction of 1 with
lithium aluminum hydride (LiAlH4) in THF gave alcohol 2
in 99% yield. The preparation of phosphonate 3 was then
achieved from benzylic alcohol 2 under the reaction condi-
tions developed by Marder and co-workers.[10] Actually, ben-
zylic phosphonate is usually prepared by halogenation of
agreement with the E stereochemistry of all the double
bonds in D1. This was further confirmed by the X-ray crys-
tal-structure analysis of compound D1 (Figure 1). Interest-
ingly, the conjugated backbone of D1 adopts a twisted con-
formation in the solid state, with an angle of approximately
708 being observed between the planes of the two terminal
aromatic rings (A and C). The peculiar twist of the OPV
core can be easily explained by close inspection of the pack-
ing. Observation of the crystal lattice down the crystallo-
graphic axis a reveals a layered structure in which the mole-
cules aligned with axis b are arranged alternatively up and
down along axis c. As shown in Figure 1, the twisting of the
conjugated system results from the presence of the bulky
triisopropylsilyl (TIPS) groups of the neighboring molecules.
Furthermore, this twist allows the establishment of an at-
ꢀ
tractive intermolecular CH–p interaction between one C H
of phenyl unit C and the aromatic ring A of its neighboring
molecule (not shown).
the benzylic alcohol followed by treatment with P
(OEt)3
Treatment of D1 with tetra-n-butylammonium fluoride
(TBAF) in THF at 08C afforded alcohol 5. Finally, N,N’-di-
cyclohexylcarbodiimide (DCC)-mediated esterification of 5
with carboxylic acid 6[12] yielded dyad F-D1. The structure
under Arbuzov conditions. This route, however, is not ap-
propriate when starting from electron-rich benzylic alcohol
derivatives such as 2 owing to the instability of the corre-
sponding benzylic halide. The choice of the appropriate con-
ditions for the preparation of phosphonate 3 was indeed the
key to this synthesis. Under Marder conditions using I2 and
1
and purity of compound F-D1 were confirmed by H and
13C NMR spectroscopy, mass spectrometry, and elemental
analysis.
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Fullerene Derivatives
FULL PAPER
Figure 1. Top: ORTEP plot of the structure of D1 (thermal ellipsoids are
drawn at the 50% probability level). Bottom: stacking within the D1 lat-
tice (view down the crystallographic axis a).
Scheme 2. Reagents and conditions: a) 4, tBuOK, THF, 08C to RT
(73%); b) CF3CO2H, CH2Cl2, H2O, RT (76%); c) 3, tBuOK, THF, 08C
to RT (33%); d) TBAF, THF, 08C (70%); e) 6, DCC, DMAP, CH2Cl2,
08C to RT (60%).
The preparation of the second dyad with an OPV pen-
tameric subunit is depicted in Scheme 2. Reaction of dialde-
hyde 4 with phosphonate 7 gave OPV trimer 8 in 73%
yield. Subsequent treatment with CF3CO2H in CH2Cl2/H2O
afforded dialdehyde 9 in 76% yield. The TIPS-protected
OPV pentamer D2 was then prepared under Wadsworth–
Emmons conditions from dialdehyde 9 and phosphonate 3.
The moderate yield for this step (33%) is mainly associated
with difficulties encountered during the purification of D2.
Alcohol 10 was obtained in 70% yield by treatment with
TBAF in THF at 08C. Reaction of 10 with carboxylic acid 6
under esterification conditions using DCC and 4-dimethyla-
minopyridine (DMAP) afforded compound F-D2 in 60%
yield. Owing to the presence of the alkyloxy groups, com-
pound F-D2 is highly soluble in common organic solvents
(CH2Cl2, CHCl3, benzene, toluene, THF) and was thus
as supporting electrolyte, with a Pt wire as the working elec-
trode and a saturated calomel electrode (SCE) as a refer-
ence. Potential data for all of the compounds are collected
in Table 1. As a typical example, the cyclic voltammogram
obtained from F-D2 is shown in Figure 2.
1
easily characterized by FTIR, H NMR, and 13C NMR spec-
Table 1. Electrochemical data of F, D1, D2, F-D1, and F-D2 determined
by CV on a Pt working electrode in CH2Cl2/0.1m nBu4NBF4 at room tem-
perature.
troscopies. The structure of F-D2 was also confirmed by its
MALDI-TOF mass spectrum showing the expected molecu-
lar ion peak at m/z 2493.0 ([M]+; m/z calcd for
Oxidation
E1
Reduction
[a]
[a]
[b]
[b]
[b]
E1
E2
E3
E4
C
175H170N2O12: 2493.28).
F
D1
F-D1
D2
F-D2
–
ꢀ0.51
–
ꢀ0.89
–
ꢀ1.11
–
ꢀ1.36
–
+0.59[c]
+0.62[c]
+0.59[c]
+0.61[c]
Electrochemistry: The electrochemical properties of hybrid
compounds F-D1 and F-D2 were investigated by cyclic vol-
tammetry (CV). For the sake of comparison, electrochemi-
cal measurements were also carried out with model com-
pounds D1, D2, and F. All the experiments were performed
at room temperature on solutions of the samples in CH2Cl2
containing tetra-n-butylammonium tetrafluoroborate (0.1m)
ꢀ0.53
ꢀ0.90
ꢀ1.12
ꢀ1.37
–
–
–
–
ꢀ0.51
ꢀ0.88
ꢀ1.12
ꢀ1.37
[a] Values for (Epa+Epc)/2, in which Epa and Epc are the oxidation and re-
duction peak values, respectively, in V versus SCE at a scan rate of
0.1 Vsꢀ1. [b] Peak potential value at a scan rate of 0.1 Vsꢀ1, irreversible
process. [c] Bielectronic process.
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J.-F. Nierengarten, B. Delavaux-Nicot, N. Armaroli et al.
consequence of small electronic interactions between the
OPV core and the C60 units, resulting in a more difficult oxi-
dation for the OPV subunit. However, for both F-D1 and F-
D2, the different subunits are separated by rather long
spacers and the photophysical studies revealed no particular
ground-state electronic interactions (vide infra). Therefore,
it appears more reasonable to ascribe the observed potential
shift to solvation effects resulting from the presence of the
surrounding apolar fullerene groups as already reported to
explain slight potential changes of related C60–OPV conju-
gates.[6,11]
Ground-state absorption and luminescence properties: The
electronic absorption spectra of dyads F-D1 and F-D2 in tol-
uene are reported in Figure 3a. Peaks at l<350 nm are at-
Figure 2. Cyclic voltammogram of compound F-D2 on a Pt electrode at
v=0.1 Vsꢀ1 in CH2Cl2/0.1m nBu4NBF4 (* indicates the reduction of an
electrogenerated species, see text).
In the cathodic region, compound F shows the classical
behavior observed for methanofullerene derivatives.[13]
Whereas the first reduction observed at ꢀ0.59 V versus SCE
is always reversible, the second is irreversible at low scan
rates but becomes reversible upon increasing the scan rate.
The third wave gradually disappears when the second one
becomes reversible, so that it likely implies reduction of the
product formed after the second reduction.[13,14] Indeed, a
bond breaking in the cyclopropane ring upon the second re-
duction may explain this peculiar behavior, as already re-
ported for several methanofullerene derivatives.[15] Finally,
the reduction observed at ꢀ1.36 V versus SCE corresponds
to the redox couple C603ꢀ/C602ꢀ. In the anodic region, model
compound F presents an irreversible peak at +1.66 V versus
SCE, which can be likely attributed to the oxidation of the
dialkyloxyphenyl unit.[16] In the anodic region, both oligo-
mers D1 and D2 exhibit a reversible two-electron transfer
process at +0.59 V versus SCE centered on the diethylani-
line subunits.[17] Indeed, in both cases, the two terminal di-
ethylaniline subunits are oxidized at the same potential. Ir-
reversible reduction processes were also observed at ꢀ1.82
and ꢀ2.18 V versus SCE for D2 and D1, respectively. The
cyclic voltammograms recorded for hybrid compounds F-D1
and F-D2 shows the characteristic electrochemical features
of both constitutive units (i.e., methanofullerene and OPV).
Figure 3. a) Absorption spectra of F-D1 (gray) and F-D2 (black) in tolu-
ene at 298 K. b) Normalized fluorescence spectra of D1 (gray) and D2
(black) in toluene at lexc =400 nm. c) Absorption spectra of F-D1 (gray)
and its constituents D1 (black) and F (dotted black); the dashed lines
represent the OPV-centered fluorescence bands of F-D1 (gray) and D1
(black) in toluene at lexc =400 nm. d) Fullerene-centered fluorescence
spectra: F (dotted black) and F-D1 (gray) in toluene at lexc =550 nm.
tributable to the fullerene moiety, whereas the lowest
energy absorption band is due to the OPV fragment, red-
shifted in the case of the pentamer (F-D2), which is charac-
terized by a more extensive conjugation.[18] The absorption
spectra of both dyads exhibit minor differences when com-
pared with the sum of the spectra of the related reference
compounds, indicating negligible ground-state electronic in-
teractions.
As typically observed for OPV-type molecules, D1 and
D2 exhibit intense and short-lived emission (Table 2, Fig-
ure 3b), attributable to deactivation of the lowest singlet
1
The comparison of the E = potentials of F-D1 and F-D2 with
2
the corresponding model compounds clearly shows that, for
both hybrid compounds, the four first reduction waves cor-
respond to fullerene-centered processes, whereas the oxida-
tion process is centered on the conjugated OPV backbone.
Comparison of the redox potentials of F-D1 and F-D2 with
those of the corresponding model compounds D1 and D2
reveals that the oxidation potential of both moieties are
slightly shifted to more positive values. This shift could be a
Table 2. Fluorescence data of solutions of the compounds in toluene.
298 K
t [ns]
77 K
lmax [nm]
lmax [nm]
f
D1
D2
F-D1
F-D2
461
521
471
527
0.9
1.0
<0.5
<0.5
0.43
0.49
0.003
0.03
470
534
473
545
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Fullerene Derivatives
FULL PAPER
electronic level.[7,19] This fluorescence signal is substantially
quenched in all dyads, suggesting the occurrence of OPV–
C60 excited-state interactions (Table 2, Figure 3c). As exten-
sively discussed in the past for similar OPV–C60 structures,
in oxygen-free benzonitrile (BN). The broad absorption
band with a peak of 700 nm and appearing immediately
after the ns-laser pulse is attributed to the fullerene triplet
(3F*);[21] for comparison, see the typical long-lived triplet ab-
sorption features of F alone in benzonitrile (Figure 4b). The
early triplet spectral trace of F (700 ns) then disappears and
a new spectral profile appears with two broad bands in the
visible and near-IR regions at lmax =640 and 1300 nm. Such
bands are assigned to the radical cation of D2[22] and their
rise occurs within about 15 ms after excitation (Figure 4a,
inset). By adding oxygen to the solution, in which an inter-
1
the quenching mechanism is ultrafast 1OPV! C60 singlet
energy transfer.[5,6,20] Importantly, sensitization of the carbon
sphere through the OPV moiety (lexc =450 nm) or direct ex-
citation of the fullerene singlet level (lexc =550 nm) does not
result in any fullerene fluorescence even in apolar toluene
(see Figure 3d as an example). Moreover, no singlet oxygen-
sensitized emission is detected in the near-IR at 1270 nm,
also ruling out the population of the fullerene triplet level
for both F-D1 and F-D2. These results can be rationalized
by assuming that the electronic excited states centered on
the two moieties are quenched due to the presence of a low-
lying charge-separated state indicated as Fꢀ–D+, with the
positive charge being located on the terminal amine residue
of the OPV moiety. This is also in line with findings report-
ed by Martin, Guldi, and co-workers on a series of fullerene
derivatives substituted with conjugated dendritic wedges
functionalized with peripheral dibutylaniline subunits.[4f]
3
molecular energy transfer from C60* to oxygen takes
place,[23,24] the electron-transfer event is suppressed and the
novel spectral traces are no longer detected, confirming the
occurrence of electron transfer from the fullerene triplet
level. Despite several efforts, a detailed Stern–Volmer kinet-
ic analysis of the bimolecular quenching process with deter-
mination of the electron-transfer yield (Fet) and rate
(ket),[22,24,25] was not possible due to the substantial overlap-
ping of the fullerene triplet spectral features with the in-
tense radical cation bands, which prevents a reliable evalua-
tion of the pseudo-first-order decay-rate constant of 3F*.
The strong intensity of the radical cation band of D2 also
masks the weak radical anion feature of methanofullerene
above 1000 nm[26] (Figure 4a). However, in an attempt to ob-
serve this band, which can serve as final evidence for elec-
tron transfer, bimolecular quenching experiments were also
carried out with D1. In this case, the near-IR cationic peak
in the near-IR region is shifted to 1500 nm and the finger-
print of the fullerene radical anion was unambiguously ob-
served at 1020 nm (Figure 4c).
Transient absorption spectroscopy: To get evidence for the
occurrence of photoinduced electron transfer, transient ab-
sorption investigations were first accomplished by means of
bimolecular quenching experiments, with the aim of reveal-
ing the spectral features of the involved cationic and anionic
species. Experiments were carried out both in toluene and
in more polar benzonitrile and the results obtained are vir-
tually identical. Figure 4a depicts the transient absorption
spectra in the nano- and microsecond timescale obtained
with a solution of F (0.1 mm) in the presence of D2 (0.1 mm)
Transient absorption spectra were then recorded for both
F-D1 and F-D2 in deaerated benzonitrile and toluene on
the ns–ms timescale. However, no transient absorption spec-
tral traces of any sort (including fullerene triplet) can be de-
tected in either solvent with nanosecond resolution. This
suggests that the forward- and back-electron transfer pro-
cesses occur on a shorter timescale. The fast charge-recom-
bination process is ascribable to the short distance (both
through bond and through space) between the donor and
acceptor moieties in both F-D1 and F-D2 dyads.
To get a clearer picture of the photoinduced processes oc-
curring in both F-D1 and F-D2, transient absorption investi-
gations were carried out on samples in toluene using a fem-
tosecond laser apparatus. The two dyads excited at 550 nm
show, immediately after the excitation pulse, an intense and
broad absorption feature with a maximum at 740 nm and a
lifetime of 36 and 60 ps for F-D1 and F-D2, respectively
(Figure 5). A broad band is then detected at longer times
with a maximum around 700 nm, which does not decay in
the time window of the ultrafast spectrometer (1 ns). This
latter band looks quite similar to that observed in bimolecu-
lar experiments on the nanosecond timescale (Figure 4a and
c) and is assigned to the cation of the OPV donor moiety. In
summary, a forward photoinduced electron-transfer process
is observed within 60 ps and the related charge-separated
state exists more than 1 ns. Moreover, the aforementioned
Figure 4. Transient absorption spectra of oxygen-free benzonitrile con-
taining a) F and D2 and c) F and D1, at 1ꢄ10ꢀ4 m. Depicted spectral
traces are at 1, 2, 11, 70, 170, and 350 ms (from bigger to smaller circles)
after the laser pulse. Insets: absorbance decay at 710 (black), 600 (gray),
and 1020 nm (light gray). lexc =532 nm. Energy: 0.5 mJ per pulse. b) Ref-
erence transient absorption spectra of oxygen-free benzonitrile contain-
ing F. Depicted spectral traces are taken between 1 and 80 ms (from
bigger to smaller circles). Inset: absorbance decay at 700 nm. lexc
=
532 nm; energy: 0.5 mJ per pulse.
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J.-F. Nierengarten, B. Delavaux-Nicot, N. Armaroli et al.
glet state no intermediates are clearly identified. This could
be due to a strong difference in the absorption coefficient
values and a partial superimposition of the radical-ion ab-
sorption features compared with the singlet OPV ones. Ac-
cordingly, in principle, population of either singlet and trip-
let fullerene excited states cannot be excluded. Indeed, pho-
toinduced electron transfer from the fullerene triplet level
may lead to the formation of the charge-separated state as
demonstrated with bimolecular quenching experiments.
However, the rate of formation of the OPV cation in these
dyads (36 and 60 ps) indicates a fast electron-transfer pro-
cess, which rules out the involvement of the fullerene triplet
level that is formed on the nanosecond timescale.
Figure 5. Ultrafast transient absorption spectra of a) F-D1 and b) F-D2 in
toluene (1ꢄ10ꢀ4 m); lexc =550 nm. Energy: 20 mJ per pulse. Inset: Decay
kinetics recorded at 740 nm.
Conclusion
We have developed novel diethylamino-substituted OPV de-
rivatives bearing an alcohol group, which allows their fur-
ther functionalization with a fullerene subunit. The electro-
chemical properties of the resulting C60–OPV dyads have
been investigated. Whereas the first reduction of both C60–
OPV conjugates is centered on the C60 unit, the first oxida-
tion is assigned to the terminal diethylaniline residues of the
OPV rods. Importantly, both OPV derivatives D1 and D2
possess excellent donating abilities and appear to be an
ideal electron donor for the fullerene acceptor in photoin-
duced electron transfer. This process has been first unambig-
uously evidenced by means of bimolecular quenching ex-
periments monitored by transient absorption spectroscopy.
Intermolecular photoinduced electron transfer originates
from triplet quenching of the reference fullerene molecule
(F) by D1 and D2. These experiments allow also for the de-
termination of the spectral fingerprints of radical-ion transi-
ent species in the visible/near-IR region, which are formed
within 15 ms after the laser pulse. An intramolecular photo-
induced electron-transfer process has also been evidenced in
both dyads by the lack of the typical OPV- and fullerene-
centered fluorescence. Photoinduced electron transfer
occurs in 36 and 60 ps for F-D1 and F-D2, respectively, and
the charge-separated state is evaluated to exist between 1
and 5 ns. In conclusion, the functionalization of the conju-
gated oligomers with dialkylamino groups is an efficient
strategy to promote electron transfer in C60–OPV conju-
gates. This is an important design principle for the engineer-
ing of new molecular photovoltaic materials. The short life-
time of the intramolecular charge-separated state in solution
is actually not an obstacle for their photovoltaic applica-
tions. Indeed, long-lived charge-separated states are usually
evidenced in thin films (millisecond time domain) in strong
contrast with the short lifetimes determined in solutions.[7a]
This is attributed to the migration of opposite charges to dif-
ferent molecules in the solid state.
lack of signals attributable to radical-ion species in nanosec-
ond transient absorption experiments, throughout the visi-
ble/near-IR region, suggests that the back-electron transfer
process occurs at time shorter than 5 ns (nanosecond appa-
ratus time resolution). Accordingly, the charge-separated
state is estimated to exist between 1 and 5 ns in toluene so-
lution.
To find out the excited levels involved in the formation of
the charge-separated state, we also investigated the transient
absorption behavior of F, D1, and F-D1 upon ultrafast exci-
tation (Figure 6). This allowed us to unambiguously assign
Figure 6. Transient absorption spectra of F (dark gray), D1 (light gray),
and F-D1 (black) recorded immediately after the laser pulse (lexc
550 nm). Energy: 20 mJ per pulse.
=
the absorption band shown by the dyads (Figure 5) at
740 nm to the singlet excited state of the OPV moieties. For
D1 and D2, transient absorption traces decrease on a much
longer time scale (ns); this is in agreement with the ob-
served fluorescence decays.
The precise pathway of excited-state deactivation follow-
ing light excitation of F-D1 and F-D2 cannot be completely
disclosed. Indeed, after the fast formation of the OPV sin-
8830
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ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 8825 – 8833

Fullerene Derivatives
FULL PAPER
was filtered and evaporated. Column chromatography (silica gel, CH2Cl2/
hexane 1:1) followed by gel permeation chromatography (Biorad, Bio-
beads SX1, CH2Cl2) gave F-D1 (409 mg, 70%) as a dark brown glassy
product. 1H NMR (CDCl3, 300 MHz): d=7.60 (d, J=8 Hz, 1H), 7.39 (m,
6H), 7.09 (d, J=16 Hz, 1H), 7.05 (d, J=16 Hz, 1H), 6.97 (d, J=16 Hz,
1H), 6.88 (s, 1H), 6.64 (brd, J=8 Hz, 4H), 6.56 (d, J=2 Hz, 2H), 6.37 (t,
J=2 Hz, 1H), 5.43 (s, 2H), 5.34 (s, 2H), 5.03 (s, 2H), 3.85 (t, J=7 Hz,
4H), 3.37 (m, 8H), 1.71 (m, 4H), 1.25 (m, 36H), 1.16 (2t, J=7 Hz, 12H),
0.88 ppm (t, J=7 Hz, 6H); 13C NMR (CDCl3, 75 MHz): d=166.5, 163.0,
160.4, 147.6, 147.4, 145.2, 145.15, 145.1, 145.0, 144.9, 144.7, 144.6, 144.5,
144.4, 143.8, 143.8, 143.0, 142.95, 142.9, 142.8, 142.2, 142.1, 141.85, 141.8,
140.9, 140.7, 139.8, 138.4, 136.9, 136.7, 136.1, 131.3, 131.27, 128.9, 128.2,
127.9, 126.4, 125.7, 122.9, 119.2, 111.7, 107.3, 101.7, 71.2, 69.0, 68.1, 66.1,
62.7, 44.4, 31.9, 29.7, 29.65, 29.5, 29.4, 29.3, 26.1, 22.7, 14.1, 12.7 ppm; IR
(neat): n˜ =1747 cmꢀ1 (C=O); MALDI-TOF MS: m/z: calcd for
C127H95N2O8: 1775.71; found: 1775.4 [M+H]+; elemental analysis calcd
(%) for C127H94N2O8 (1776.15): C 85.88, H 5.33, N 1.58; found: C 85.95,
H 5.27, N 1.50.
Experimental Section
General: Reagents and solvents were purchased as reagent grade and
used without further purification. Compounds 4,[11] 6,[12] 7,[27] and F[12]
were prepared according to the literature. THF was distilled over sodium
benzophenone ketyl. All reactions were performed in standard glassware
under an inert argon atmosphere. Evaporation and concentration were
done at water aspirator pressure and drying in vacuo at 10ꢀ2 torr.
Column chromatography: silica gel 60 (230–400 mesh, 0.040–0.063 mm)
was purchased from E. Merck and treated with Et3N (1% in CH2Cl2) for
the purification of compounds bearing NEt2 groups. Thin-layer chroma-
tography (TLC) was performed on glass sheets coated with silica gel 60
F254 purchased from E. Merck, visualization by UV light. IR spectra
(cmꢀ1) were measured using an ATI Mattson Genesis Series FTIR instru-
ment. NMR spectra were recorded on a Bruker AC 300 with solvent
peaks as reference. MALDI-TOF MS were obtained using a Bruker BI-
FLEXTM mass spectrometer. Elemental analyses were performed by the
analytical service at the Institut Charles Sadron, Strasbourg.
Compound 8: As described for D1, with 4 (400 mg, 1.25 mmol), 7 (1.60 g,
2.75 mmol), and tBuOK (340 mg, 3.00 mmol). Column chromatography
on silica gel (CH2Cl2/hexane 3:2) yielded 8 (1.10 g, 73%) as an orange
glassy product. C76H124O9Si (Mr =1209.90); 1H NMR (CDCl3, 300 MHz):
d=7.68 (d, J=8 Hz, 1H), 7.67 (s, 1H), 7.57 (d, J=16 Hz, 1H), 7.48 (m,
2H), 7.41 (d, J=16 Hz, 1H), 7.34 (s, 1H), 7.33 (s, 1H), 7.27 (d, J=
16.5 Hz, 1H), 7.18 (s, 1H), 7.17 (s, 1H), 5.74 (s, 2H), 4.94 (s, 2H), 4.03 (t,
J=7 Hz, 4H), 3.98 (t, J=7 Hz, 4H), 3.72 (AB, J=11 Hz, 8H), 1.83 (m,
8H), 1.34 (m, 40H), 1.10 (m, 21H), 0.88 (m, 18H), 0.80 ppm (s, 6H).
Compound 2: A 1m solution of LiAlH4 in THF (7 mL) was added to a
stirred solution of 1 (1.00 g, 5.64 mmol) in dry THF (120 mL) at 08C.
After 4 h, MeOH was added, then water. The resulting mixture was fil-
tered over Celite and evaporated. Column chromatography (silica gel,
CH2Cl2/hexane 1:1) yielded
2 (1.01 g, 99%) as a pale bluish oil.
C11H17NO (Mr =179.26); 1H NMR (CDCl3, 300 MHz): d=7.24 (d, J=
7 Hz, 2H), 6.62 (d, J=7 Hz, 2H), 4.55 (s, 2H), 3.35 (q, J=7 Hz, 4H),
1.17 ppm (t, J=7 Hz, 6H).
Compound 3: I2 (1.62 g, 6.39 mmol) was added to a solution of 2 (1.15 g,
6.39 mmol) in PACHTUNGTRENNUNG(OEt)3 (11 mL) at 08C. After 10 min, the mixture was al-
Compound 9:
A mixture of 8 (1.00 g, 0.83 mmol), CH2Cl2 (5 mL),
CF3CO2H (4 mL), and H2O (5 mL) was vigorously stirred at room tem-
perature for 2 h. The organic layer was then washed with H2O, dried
(MgSO4), and evaporated. A rapid filtration on silica gel (CH2Cl2/hexane
1:1) yielded 9 (650 mg, 76%) as an orange-red glassy product. 1H NMR
(CDCl3, 300 MHz): d=10.48 (s, 2H), 7.68 (d, J=8 Hz, 1H), 7.67 (s, 1H),
7.57 (d, J=16 Hz, 1H), 7.48 (m, 2H), 7.41 (d, J=16 Hz, 1H), 7.34 (s,
1H), 7.33 (s, 1H), 7.27 (d, J=16,5 Hz, 1H), 7.18 (s, 1H), 7.17 (s, 1H),
4.97 (s, 2H), 4.08 (m, 8H), 1.85 (m, 8H), 1.30 (m, 40H), 1.10 (m, 21H),
0.88 ppm (m, 12H); 13C NMR (CDCl3, 75 MHz): d=189.2, 156.2, 150.85,
150.8, 139.2, 136.9, 135.4, 134.4, 134.3, 132.1, 128.7, 126.2, 126.0, 125.9,
124.8, 124.4, 124.3, 123.1, 110.8, 110.7, 110.2, 110.1, 69.3, 69.2, 69.1, 63.8,
31.8, 29.35, 29.3, 26.1, 22.7, 18.1, 14.1, 12.1 ppm; IR (neat): n˜ =1692 cmꢀ1
(C=O); elemental analysis calcd (%) for C66H104O7Si (1037.63): C 76.40,
H 10.10; found: C 76.33, H 9.86.
lowed to slowly warm to room temperature (within 1 h), then stirred for
2 h, and evaporated. The residue was taken up with Et2O, washed with a
saturated aqueous NH4Cl solution, dried (MgSO4), filtered, and evapo-
rated. Column chromatography (silica gel, CH2Cl2/AcOEt 4:1) yielded 3
(861 mg, 45%) as a pale bluish oil. C15H26NO3P (Mr =299.35); 1H NMR
(CDCl3, 300 MHz): d=7.12 (m, 2H), 6.62 (d, J=7 Hz, 2H), 4.00 (m,
4H), 3.32 (m, 4H), 3.04 (d, J=21 Hz, 2H), 1.25 (t, J=7 Hz, 6H),
1.13 ppm (t, J=7 Hz, 6H).
Compound D1: tBuOK (83 mg, 0.74 mmol) was added to a stirred solu-
tion of 3 (210 mg, 0.69 mmol) and 4 (100 mg, 0.31 mmol) in THF (15 mL)
at 08C. After 1 h, the mixture was allowed to slowly warm to room tem-
perature (within 1 h), then stirred for 2 h, filtered, and evaporated.
Column chromatography (silica gel, hexane/CH2Cl2 4:1) followed by re-
crystallization in EtOH/CHCl3 yielded D1 (81 mg, 42%) as yellow crys-
Compound D2: As described for D1, with 3 (240 mg, 0.72 mmol), 9
(340 mg, 0.33 mmol), and tBuOK (89 mg, 0.80 mmol). The mixture was
subjected to column chromatography on silica gel three times (CH2Cl2/
hexane 1:4) to yield D2 (150 mg, 33%) as an orange-red glassy product.
1H NMR (CDCl3, 300 MHz): d=7.67 (d, J=8 Hz, 1H), 7.64 (s, 1H), 7.49
(d, J=16.5 Hz, 2H), 7.42 (d, J=8 Hz, 4H), 7.39 (m, 3H), 7.26 (d, J=
16.5 Hz, 2H), 7.16 (d, J=16.5 Hz, 2H), 1.08 (s, 2H), 7.05 (d, J=16.5 Hz,
2H), 6.68 (d, J=8 Hz, 4H), 4.97 (s, 2H), 4.05 (m, 8H), 3.39 (q, J=7 Hz,
8H), 1.86 (m, 8H), 1.31 (m, 40H), 1.19 (t, J=7 Hz, 12H), 1.13 (m, 21H),
0.89 ppm (m, 12H); 13C NMR (CDCl3, 75 MHz): d=151.3, 150.7, 147.3,
138.5, 137.0, 135.2, 129.0, 128.3, 128.1, 127.9, 126.1, 125.9, 125.6, 125.5,
125.45, 125.4, 125.3, 124.9, 124.7, 123.2, 118.55, 118.5, 118.45, 111.7, 111.1,
111.05, 110.0, 69.8, 69.6, 63.8, 44.4, 31.8, 29.6, 29.55, 29.53, 29.45, 29.4,
29.35, 29.3, 26.35, 26.3, 26.2, 22.7, 22.65, 18.2, 14.1, 12.7, 12.1 ppm; ele-
mental analysis calcd (%) for C88H134N2O5Si (1328.13): C 79.58, H 10.17,
N 2.11; found: C 79.26, H 10.57, N 1.90.
1
tals. H NMR (CDCl3, 300 MHz): d=7.65 (s, 1H), 7.56 (d, J=8 Hz, 1H),
7.39 (d, J=8 Hz, 4H), 7.35 (d, J=16 Hz, 1H), 7.06 (d, J=16 Hz, 1H),
7.05 (d, J=16 Hz, 1H), 6.97 (s, 1H), 6.89 (d, J=16 Hz, 1H), 6.67 (d, J=
8 Hz, 4H), 4.96 (s, 2H), 3.39 (m, 8H), 1.19 (t, J=7 Hz, 12H), 1.13 ppm
(m, 21H); 13C NMR (CDCl3, 75 MHz): d=128.15, 128.1, 127.9, 127.8,
127.7, 125.0, 124.6, 124.3, 120.2, 120.1, 111.8, 111.7, 63.5, 44.4, 18.2, 12.6,
12.1 ppm; elemental analysis calcd (%) for C40H58N2OSi (611.00): C
78.63, H 9.57, N 4.58; found: C 78.66, H 10.11, N 4.60.
Compound 5: A 1m solution of TBAF in THF (0.4 mL) was added to a
stirred solution of D1 (170 mg, 0.27 mmol) in dry THF (5 mL) at 08C
under argon. After 2 h, H2O (10 mL) was added. The THF was evaporat-
ed and CH2Cl2 was added. The organic layer was washed with water,
dried (MgSO4), and evaporated. Column chromatography (silica gel,
CH2Cl2/hexane 2:1) yielded 5 (98 mg, 80%) as an orange glassy product.
C31H38N2O (Mr =454.66); 1H NMR (CDCl3, 300 MHz): d=7.63 (s, 1H),
7.60 (s, 1H), 7.39 (d, J=7 Hz, 4H), 7.36 (d, J=16 Hz, 1H), 7.19 (d, J=
16 Hz, 1H), 7.06 (d, J=16 Hz, 1H), 6.97 (s, 1H), 6.88 (d, J=16 Hz, 1H),
6.67 (d, J=8 Hz, 4H), 4.84 (d, J=6 Hz, 2H), 3.39 (m, 8H), 1.19 ppm (t,
J=7 Hz, 12H); 13C NMR (CDCl3, 75 MHz): d=130.6, 128.5, 128.1, 127.8,
126.1, 125.75, 125.7, 125.6, 125.6, 124.9, 123.3, 119.9, 111.7, 63.9, 44.4,
17.7, 12.6, 12.3 ppm.
Compound 10: As described for 5, with D2 (100 mg, 0.08 mmol) and
TBAF (0.10 mmol). Column chromatography on silica gel (CH2Cl2/
hexane 2:1) yielded 10 (65 mg, 70%) as an orange-red glassy product.
1H NMR (CDCl3, 300 MHz): d=7.67 (d, J=8 Hz, 1H), 7.64 (s, 1H), 7.49
(d, J=16.5 Hz, 2H), 7.42 (d, J=8 Hz, 4H), 7.39 (m, 3H), 7.26 (d, J=
16.5 Hz, 2H), 7.16 (d, J=16.5 Hz, 2H), 7.08 (s, 2H), 7.05 (d, J=16.5 Hz,
2H), 6.68 (d, J=8 Hz, 4H), 4.88 (d, J=5 Hz, 2H), 4.05 (m, 8H), 3.39 (q,
J=7 Hz, 8H), 1.86 (m, 8H), 1.31 (m, 40H), 1.19 (t, J=7 Hz, 12H),
0.89 ppm (m, 12H); 13C NMR (CDCl3, 75 MHz): d=151.5, 151.3, 150.7,
147,3, 137.9, 137.3, 135.8, 129.15, 129.1, 128.5, 128.3, 127.9, 127.7, 126.8,
Compound F-D1: DCC (162 mg, 0.79 mmol) and DMAP (8 mg,
0.07 mmol) were added to a solution of 5 (150 mg, 0.33 mmol) and 6
(486 mg, 0.36 mmol) in CH2Cl2 (40 mL) at 08C. After 1 h, the mixture
was allowed to slowly warm to room temperature. After 2 h, the mixture
Chem. Eur. J. 2009, 15, 8825 – 8833
ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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8831

J.-F. Nierengarten, B. Delavaux-Nicot, N. Armaroli et al.
126.1, 126.0, 125.9, 125.7, 125.5, 125.4, 124.4, 123.6, 118.5, 111.7, 111.5,
110.9, 110.1, 109.8, 69.9, 69.8, 69.6, 69.5, 63.8, 44.4, 31.8, 29.7, 29.6, 29.6,
29.5, 29.4, 29.3, 22.7, 14.15, 12.7 ppm; elemental analysis calcd (%) for
C79H114N2O5 (1171.78): C 80.98, H 9.81, N 2.39; found: C 80.47, H 9.87, N
2.04.
spectrophotometer. Emission spectra were obtained using an Edinburgh
FLS920 spectrometer (continuous 450 W Xenon lamp), equipped with a
Peltier-cooled Hamamatsu R928 photomultiplier tube (185–850 nm) or a
Hamamatsu R5509-72 supercooled photomultiplier tube (193 K, 800–
1700 nm range). Emission quantum yields were determined according to
the approach described by Demas and Crosby[31] using quinine sulfate in
1n H2SO4 (F=0.546)[32] as standard. Emission lifetimes were determined
with the time-correlated single-photon counting technique using an Edin-
burgh FLS920 spectrometer equipped with a laser diode head as excita-
tion source (1 MHz repetition rate, lexc =407 or 635 nm, 200 ps time reso-
lution upon deconvolution) and an Hamamatsu R928 PMT as detector.
Transient absorption spectra in the nanosecond/microsecond time
domain were obtained by using the nanosecond flash photolysis appara-
tus described previously.[33] Experimental uncertainties are estimated to
be 8% for lifetime determinations, 20% for emission quantum yields,
10% for relative emission intensities in the near-IR, and 1 and 5 nm for
absorption and emission peaks, respectively.
Compound F-D2: As described for F-D1, with 6 (74 mg, 0.06 mmol), 10
(60 mg, 0.05 mmol), DCC (25 mg, 0.12 mmol), and DMAP (1.2 mg,
0.01 mmol). Column chromatography on silica gel (CH2Cl2/hexane 1:3)
yielded F-D2 (75 mg, 60%) as a dark brown glassy product. 1H NMR
(CDCl3, 300 MHz): d=7.67 (d, J=8 Hz, 1H), 7.54–7.34 (m, 10H), 7.28
(d, J=16.5 Hz, 2H), 7.16 (d, J=16.5 Hz, 2H), 7.09 (s, 2H), 7.05 (d, J=
16.5 Hz, 2H), 6.68 (brd, J=7 Hz, 4H), 6.54 (d, J=2 Hz, 2H), 6.36 (t, J=
2 Hz, 1H), 5.46 (s, 2H), 5.34 (s, 2H), 5.00 (s, 2H), 4.02 (m, 8H), 3.84 (t,
J=7 Hz, 4H), 3.39 (q, J=7 Hz, 8H), 1.86 (m, 8H), 1.70 (m, 4H), 1.30
(m, 76H), 1.19 (t, J=7 Hz, 12H), 0.89 ppm (m, 18H); 13C NMR (CDCl3,
75 MHz): d=166.5, 163.0, 162.9, 160.4, 151.4, 151.3, 150.7, 147.3, 145.15,
145.1, 145.0, 144.95, 144.9, 144.8, 144.6, 144.5, 144.4, 144.2, 143.8, 143.75,
143.0, 142.95, 142.9, 142.85, 142.8, 142.7, 142.2, 142.1, 141.8, 141.7, 140.8,
140.7, 139.8, 138.3, 137.4, 136.6, 131.9, 129.2, 129.1, 128.8, 128.6, 128.4,
127.95, 127.9, 127.3, 126.6, 126.4, 126.3, 126.25, 126.2, 125.6, 125.45, 125.4,
124.1, 123.6, 118.5, 111.7, 111.1, 110.95, 110.9, 110.0, 109.9, 107.2, 101.7,
71.1, 69.7, 69.5, 69.4, 69.0, 68.1, 65.8, 62.7, 62.5, 44.4, 31.9, 31.8, 29.7, 29.6,
29.55, 29.5, 29.45, 29.4, 29.35, 29.3, 29.25, 26.5, 26.4, 26.3, 26.2, 22.75, 22.7,
14.1, 12.7 ppm; IR (neat): n˜ =1747 cmꢀ1 (C=O); MALDI-TOF MS: m/z:
calcd for C175H170N2O12: 2493.28; found 2493.0 [M]+; elemental analysis
calcd (%) for C175H170N2O12 (2493.28): C 84.30, H 6.87, N 1.12; found: C
84.43, H 6.71, N 1.05.
Femtosecond time-resolved experiments were performed using a pump-
probe setup based on the Spectra-Physics Hurricane Ti:sapphire laser
source and the Ultrafast Systems Helios spectrometer.[34] The 550 nm
pump pulses were generated with a Spectra Physics 800 OPA. Probe
pulses were obtained by continuum generation on a sapphire plate. The
effective time resolution was approximately 300 fs, the temporal chirp
over the white-light 450–750 nm range was approximately 200 fs, and the
temporal window of the optical delay stage was 0–1000 ps. The time-re-
solved spectral data were analyzed using the Ultrafast Systems Surface
Explorer Pro software.[35]
Electrochemistry: The cyclic voltammetric measurements were carried
out using a potentiostat Autolab PGSTAT100. Experiments were per-
formed at room temperature in a homemade airtight three-electrode cell
connected to a vacuum/argon line. The reference electrode consisted of a
saturated calomel electrode (SCE) separated from the solution by a
bridge compartment. The counter electrode was a platinum wire of ap-
proximately 1 cm2 apparent surface. The working electrode was a Pt mi-
Acknowledgements
This research was supported by the Centre National de la Recherche Sci-
entifique (UMR 7509), the Agence Nationale de la Recherche (Solaire
Photovoltaꢆque—Nanorgysol), the CNR (Commessa PM.P04.010,
MACOL) and the EC through the Marie-Curie RTN PRAIRIES
(MRTN-CT-2006-035810) and ITN FINELUMEN (PITN-GA-2008-
215399). A.G. thanks the Agence de l’Environnement et de la Maꢇtrise
de l’Energie—Rꢀgion Alsace for her fellowship.
crodisc (0.5 mm diameter). The supporting electrolyte [nBu4N]ACTHNUTRGENUG[N BF4]
(Fluka, 99% electrochemical grade) was used as received and simply de-
gassed under argon. Dichloromethane was freshly distilled over CaH2
prior to use. The solutions used during the electrochemical studies were
typically 10ꢀ3 m for the compound and 0.1m for the supporting electrolyte.
Before each measurement, the solutions were degassed by bubbling
argon, and the working electrode was polished using a polishing machine
(Presi P230). Under these experimental conditions, Fc+/Fc was observed
at (+0.54ꢁ0.01) V versus SCE.
[1] D. M. Guldi, Chem. Soc. Rev. 2002, 31, 22–36; H. Imahori, J. Phys.
Chem. B 2004, 108, 6130–6143; J.-F. Nierengarten, Sol. Energy
Mater. Sol. Cells 2004, 83, 187–199; J.-F. Nierengarten, New J.
Chem. 2004, 28, 1177–1191.
[2] J. L. Segura, N. Martin and D. M. Guldi, Chem. Soc. Rev. 2005, 34,
31–47; T. M. Figueira-Duarte, A. Gꢀgout, J.-F. Nierengarten, Chem.
Commun. 2007, 109–119.
[3] T. M. Figueira-Duarte, J. Clifford, V. Amendola, A. Gꢀgout, J. Olivi-
er, F. Cardinali, M. Meneghetti, N. Armaroli, J.-F. Nierengarten,
Chem. Commun. 2006, 2054–2056.
[4] a) A. G. Avent, P. R. Birkett, F. Paolucci, S. Roffia, R. Taylor, N. K.
Wachter, J. Chem. Soc. Faraday Trans. 2 2000, 1409–1414; b) J. L.
Segura, R. Gomez, N. Martin, C. P. Luo, A. Swartz, D. M. Guldi,
Chem. Commun. 2001, 707–708; c) M. Schwell, N. K. Wachter, J. H.
Rice, J. P. Galaup, S. Leach, R. Taylor, R. V. Bensasson, Chem. Phys.
Lett. 2001, 339, 29–35; d) F. Langa, M. J. Gomez-Escalonilla, E.
Diez-Barra, J. C. Garcia-Martinez, A. de La Hoz, J. Rodriguez-
Lopez, A. Gonzalez-Cortes, V. Lopez-Arza, Tetrahedron Lett. 2001,
42, 3435–3438; e) G. Accorsi, N. Armaroli, J.-F. Eckert, J.-F. Nieren-
garten, Tetrahedron Lett. 2002, 43, 65–68; f) D. M. Guldi, A. Swartz,
C. P. Luo, R. Gomez, J. L. Segura, N. Martin, J. Am. Chem. Soc.
2002, 124, 10875–10886; g) J.-F. Nierengarten, N. Armaroli, G. Ac-
corsi, Y. Rio, J.-F. Eckert, Chem. Eur. J. 2003, 9, 36–41; h) N. Ar-
maroli, G. Accorsi, J. N. Clifford, J.-F. Eckert, J.-F. Nierengarten,
Chem. Asian J. 2006, 1, 564–574; i) J. N. Clifford, A. Gꢀgout, S.
Zhang, R. Pereira de Freitas, M. Urbani, M. Holler, P. Ceroni, J.-F.
Nierengarten, N. Armaroli, Eur. J. Org. Chem. 2007, 5899–5908.
X-ray crystal structure of D1: Crystals suitable for X-ray crystal-structure
analysis were obtained by slow diffusion of EtOH into a solution of D1
in CHCl3. Data were collected at 180 K using a Xcalibur Oxford Diffrac-
tion diffractometer with graphite-monochromated MoKa radiation (l=
0.71073 ꢅ) and equipped with an Oxford Cryosystems Cryostream
Cooler device. The structures were solved by direct methods using
SIR92[28] and refined by means of least-squares procedures on F using
the programs of the PC version of CRYSTALS.[29] Atomic scattering fac-
tors were taken from the International Tables for X-ray Crystallogra-
phy.[30] The non-hydrogen atoms were anisotropically refined. Hydrogen
atoms were located in a difference map, but those attached to carbon
atoms were repositioned geometrically. All hydrogen atoms were refined
using a riding model. C40H58N2OSi (Mr =611.00); yellow block crystal;
crystal size 0.10ꢄ0.20ꢄ0.40 mm; triclinic; space group P1; a=9.913(1),
b=12.583(1), c=15.767(2) ꢅ; a=76.006(9), b=76.869(9), g=76.070(8)8;
ACTHNUTRGNEUNG
V=1822.2(3) ꢅ3; Z=2; m(MoKa)=0.096 mmꢀ1; 17130 reflections mea-
sured; 9643 unique reflections (Rint =0.04) and a total of 397 parameters
were used. The final agreement factors were R=0.070, wR=0.074 for
the 3993 reflections having I>3s. CCDC-728646 contains the supplemen-
tary crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Photophysical measurements: The photophysical investigations were car-
ried out in benzonitrile and toluene (Carlo Erba, spectrofluorimetric
grade). Absorption spectra were recorded using a Perkin–Elmer l40
8832
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ꢃ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 8825 – 8833

Fullerene Derivatives
FULL PAPER
[5] M. Gutierrez-Nava, G. Accorsi, P. Masson, N. Armaroli, J.-F. Nier-
engarten, Chem. Eur. J. 2004, 10, 5076–5086.
Beulen, L. Echegoyen, J. A. Rivera, M. A. Herranz, A. Martin-Do-
menech, N. Martin, Chem. Commun. 2000, 917–918.
[16] T. Gu, P. Ceroni, G. Marconi, N. Armaroli, J.-F. Nierengarten, J.
Org. Chem. 2001, 66, 6432–6439.
[17] T. Gu, D. Tsamouras, C. Melzer, V. Krasnikov, J.-P. Gisselbrecht, M.
Gross, G. Hadziioannou, J.-F. Nierengarten, ChemPhysChem 2002,
3, 124–127.
[18] N. Armaroli, G. Accorsi, Y. Rio, J. F. Nierengarten, J. F. Eckert,
M. J. Gomez-Escalonilla, F. Langa, Synth. Met. 2004, 147, 19–28.
[19] J.-F. Nierengarten, S. Zhang, A. Gꢀgout, M. Urbani, N. Armaroli, G.
Marconi, Y. Rio, J. Org. Chem. 2005, 70, 7550–7557.
[20] N. Clifford, T. Gu, J. F. Nierengarten, N. Armaroli, Photochem. Pho-
tobiol. Sci. 2006, 5, 1165–1172.
[21] D. M. Guldi, M. Prato, Acc. Chem. Res. 2000, 33, 695–703.
[22] H. Onodera, Y. Araki, M. Fujitsuka, S. Onodera, O. Ito, F. Bai, M.
Zheng, J. L. Yang, J. Phys. Chem. A 2001, 105, 7341–7349.
[23] N. Armaroli in Fullerenes: From Synthesis to Optoelectronic Proper-
ties (Eds.: D. M. Guldi, N. Martin), Kluwer Academic, Dordrecht,
2002, pp. 137–162.
[24] M. El-Khouly, M. Fujitsuka, O. Ito, M. El-Kemary, J. Photochem.
Photobiol. A 2001, 141, 1–7.
[25] T. Nojiri, A. Watanabe, O. Ito, J. Phys. Chem. A 1998, 102, 5215–
5219.
[26] T. Konishi, A. Ikeda, T. Kishida, B. S. Rasmussen, M. Fujitsuka, O.
Ito, S. Shinkai, J. Phys. Chem. A 2002, 106, 10254–10260.
[27] M. J. Gomez-Escalonilla, F. Langa, J.-M. Rueff, L. Oswald, J.-F.
Nierengarten, Tetrahedron Lett. 2002, 43, 7507–7511.
[28] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, J. Appl.
Crystallogr. 1993, 26, 343–350.
[6] J.-F. Eckert, J.-F. Nicoud, J.-F. Nierengarten, S.-G. Liu, L. Echegoy-
en, F. Barigelletti, N. Armaroli, L. Ouali, V. Krasnikov, G. Had-
ziioannou, J. Am. Chem. Soc. 2000, 122, 7467–7479; N. Armaroli, F.
Barigelletti, P. Ceroni, J.-F. Eckert, J.-F. Nicoud, J.-F. Nierengarten,
Chem. Commun. 2000, 599–600; F. Langa, M. J. Gomez-Escalonilla,
J.-M. Rueff, T. M. Figueira Duarte, J.-F. Nierengarten, V. Palermo, P.
Samorꢈ, Y. Rio, G. Accorsi, N. Armaroli, Chem. Eur. J. 2005, 11,
4405–4415.
[7] a) E. Peeters, P. A. van Hal, J. Knol, C. J. Brabec, N. S. Sariciftci,
J. C. Hummelen, R. A. J. Janssen, J. Phys. Chem. B 2000, 104,
10174–10190; b) D. M. Guldi, C. Luo, A. Swartz, R. Gomez, J. L.
Segura, N. Martin, C. Brabec, N. S. Sariciftci, J. Org. Chem. 2002, 67,
1141–1152; c) D. M. Guldi, C. Luo, A. Swartz, R. Gomez, J. L.
Segura, N. Martin, J. Phys. Chem. A 2004, 108, 455–467; d) A. M.
Ramos, S. C. J. Meskers, P. A. van Hal, J. Knol, J. C. Hummelen,
R. A. J. Janssen, J. Phys. Chem. A 2003, 107, 9269–9283.
[8] J. L. Segura, R. Gomez, N. Martin, C. Luo, D. M. Guldi, Chem.
Commun. 2000, 701–702.
[9] K. Mꢉllen, G. Wegner, Electronic Materials: the Oligomer Approach,
Wiley-VCH, Weinheim, 1998.
[10] S. Zheng, S. Barlow, T. C. Parker, S. R. Marder, Tetrahedron Lett.
2003, 44, 7989–7992.
[11] A. Gꢀgout, M. Holler, T. M. Figueira-Duarte, J.-F. Nierengarten,
Eur. J. Org. Chem. 2008, 3627–3634.
[12] U. Hahn, K. Hosomizu, H. Imahori, J.-F. Nierengarten, Eur. J. Org.
Chem. 2006, 85–91.
[13] F. Cardullo, P. Seiler, L. Isaacs, J.-F. Nierengarten, R. F. Haldimann,
F. Diederich, T. Mordasini-Denti, W. Thiel, C. Boudon, J.-P. Gissel-
brecht, M. Gross, Helv. Chim. Acta 1997, 80, 343–371; D. Felder, H.
Nierengarten, J.-P. Gisselbrecht, C. Boudon, E. Leize, J.-F. Nicoud,
M. Gross, A. Van Dorsselaer, J.-F. Nierengarten, New J. Chem. 2000,
24, 687–695; R. Pereira de Freitas, J. Iehl, B. Delavaux-Nicot, J.-F.
Nierengarten, Tetrahedron 2008, 64, 11409–11419.
[14] U. Hahn, E. Maisonhaute, C. Amatore, J.-F. Nierengarten, Angew.
Chem. 2007, 119, 969–972; Angew. Chem. Int. Ed. 2007, 46, 951–
954.
[29] P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout, D. J.
Watkin, J. Appl. Crystallogr. 2003, 36, 1487.
[30] International Tables for X-ray Crystallography, Vol. IV, Kynoch
Press, Birmingham, 1974.
[31] J. N. Demas, G. A. Crosby, J. Phys. Chem. 1971, 75, 991–1024.
[32] S. R. Meech, D. Phillips, J. Photochem. 1983, 23, 193–217.
[33] L. Flamigni, J. Phys. Chem. 1992, 96, 3331–3337.
[34] C. Chiorboli, M. A. J. Rodgers, F. Scandola, J. Am. Chem. Soc. 2003,
125, 483–491.
[15] B. Knight, N. Martꢊn, T. Ohno, E. Ortꢊ, C. Rovira, J. Veciana, J.
Vidal-Gancedo, P. Viruela, R. Viruela, F. Wudl, J. Am. Chem. Soc.
1997, 119, 9871–9882; R. Kessinger, J. Crassous, A. Herrmann, M.
Rꢉttimann, L. Echegoyen, F. Diederich, Angew. Chem. 1998, 110,
2022–2025; Angew. Chem. Int. Ed. 1998, 37, 1919–1922; M. W. J.
[35] Surface Xplorer, analysis software for transient absorption data,
Ultrafast Systems LLC, http://www.ultrafastsystems.com/surface_
xplorer.htm
Received: May 7, 2009
Published online: July 27, 2009
Chem. Eur. J. 2009, 15, 8825 – 8833
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