Fullerene derivatives substituted with differently branched phenyleneethynylene dendrons: Synthesis, electronic and excited state properties

Article abstract of DOI:10.1002/ejoc.200700689

Fullerene derivatives functionalized with isomeric phenyleneethynylene- based dendrons possessing either 1,3,5-triethynylbenzene or 1,2,4- triethynylbenzene branching units have been prepared. The electrochemical properties of these compounds are not stro

Full text of DOI:10.1002/ejoc.200700689

FULL PAPER
DOI: 10.1002/ejoc.200700689
Fullerene Derivatives Substituted with Differently Branched
Phenyleneethynylene Dendrons: Synthesis, Electronic and Excited State
Properties
John N. Clifford,[a] Aline Gégout,[b] Sheng Zhang,[b] Rossimiriam Pereira de Freitas,[b,c]
Maxence Urbani,[b] Michel Holler,[d] Paola Ceroni,*[e] Jean-François Nierengarten,*[b] and
Nicola Armaroli*[a]
Keywords: Conjugated systems / Dendrimers / Electrochemistry / Energy transfer / Fullerene / Photophysical properties
Fullerene derivatives functionalized with isomeric phen-
yleneethynylene-based dendrons possessing either 1,3,5-tri-
ethynylbenzene or 1,2,4-triethynylbenzene branching units
have been prepared. The electrochemical properties of these
compounds are not strongly dependent on the branching pat-
terns since the corresponding redox processes are localized
either on the C60 cage (acceptor unit) or on the dialkyloxy-
benzene moieties (donor units) at the dendron periphery. The
hybrid systems. Importantly, the different π-conjugation pat-
terns in the two series have a dramatic effect on their elec-
tronic properties as attested by the differences observed in
their absorption and emission spectra. The lower lying ab-
sorption onset and the wider spectral profile of the dyads
with 1,2,4-triethynylbenzene branching units when com-
pared to their 1,3,5-triethynylbenzene analogues clearly
points out an improved light harvesting capability.
photophysical investigations performed in CH2Cl2 have re- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
vealed an ultrafast dendronǞC60 energy transfer in all these
Germany, 2007)
preparation of new sensors or photochemical molecular de-
vices.[6] In particular, their absorption properties have been
widely exploited for the design of light harvesting sys-
tems[7–9] in which the π-conjugated dendritic chromophore
is able to transfer the collected light energy to the central
core of the dendrimer.[10] Photophysical studies of such
multicomponent molecular devices are not only important
for the fundamental understanding of photoinduced pro-
cesses, but appears of great interest for the design of new
photovoltaic materials with optimized absorption proper-
ties,[11] or even organic light-emitting diodes.[12] Among the
various terminal energy acceptors used in such light har-
vesting systems, [60]fullerene (C60) has proven to be particu-
larly interesting.[8,9] Effectively, its first singlet and triplet
excited-states are relatively low in energy and photoinduced
energy-transfer events have been evidenced in numerous ful-
lerene-based dyads.[13] In this paper, we report the synthesis
and the electronic properties of fullerene derivatives func-
tionalized with isomeric phenyleneethynylene-based den-
drons possessing 1,3,5-triethynylbenzene or 1,2,4-triethynyl-
benzene branching units (Figure 1). Whereas the π-conjuga-
tion of the dendritic antenna in C60-G1 and C60-G2 is
rather limited due to the all-meta-branching scheme, the
dendritic scaffold of C60-Y1 and C60-Y2 exhibits an increase
of the conjugation length when going from the first to the
second generation compound. The different conjugation
length does not strongly affect the electrochemical processes
since reduction is localized on the fullerene cage and oxi-
Introduction
The past several years have seen a growing interest in the
synthesis and the study of dendrimers with a π-conjugated
backbone.[1] Interestingly, their electronic properties can be
easily tailored by either introducing various substituents,[2]
changing the conjugation lengths of the different fragments
within the dendritic shell,[3] or modulating the substitution
pattern of the branching aromatic units.[4,5] The characteris-
tic features of these compounds, such as large molar extinc-
tion coefficients and sometimes high fluorescence efficienc-
ies, make them attractive photoactive components for the
[a] Molecular Photoscience Group, Istituto per la Sintesi Organica
e la Fotoreattività, Consiglio Nazionale della Ricerche,
Via Gobetti 101, 40129 Bologna, Italy
E-mail: armaroli@isof.cnr.it
[b] Groupe de Chimie des Fullerènes et des Systèmes Conjugués,
Laboratoire de Chimie de Coordination du CNRS,
205 route de Narbonne, 31077 Toulouse Cedex 4, France
E-mail: jfnierengarten@lcc-toulouse.fr
[c] Universidade Federal de Minas Gerais, Departamento de
Química,
Av. Antônio Carlos 6627, 31270901 Belo Horizonte, MG, Brazil
E-mail: rossipdf@yahoo.com.br
[d] Laboratoire de Physico-Chimie Bioinorganique, Université
Louis Pasteur et CNRS, Ecole Européenne de Chimie,
Polymères et Matériaux (ECPM),
25 rue Becquerel, 67087 Strasbourg Cedex 2, France
E-mail: mholler@chimie.u-strasbg.fr
[e] Dipartimento di Chimica “G. Ciamician”, Università di
Bologna,
Via Selmi 2, 40126 Bologna, Italy
E-mail: paola.ceroni@unibo.it
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P. Ceroni, J.-F. Nierengarten, N. Armaroli et al.
FULL PAPER
dation on the dialkyloxybenzene peripheral units. On the
other hand, the photophysical properties of the two families
are significantly different. Indeed, the absorption of the an-
tenna unit in C60-Y2 is significantly red-shifted when com-
pared to the one in C60-G2, thus the light harvesting capa-
bilities of the system have been improved when going from
C60-G2 to C60-Y2.
Scheme 1. Reagents and conditions: (a) Pd(PPh3)2Cl2, CuI, PPh3,
Et3N, THF, 65 °C (4: 86%,5: 82%); (b) C60, N-methylglycine, tolu-
ene, ∆ (C60-G1: 61%, C60-Y1: 46%).
1
The H NMR spectra of the pyrrolidinofullerene deriva-
tives C60-G1 and C60-Y1 are in full agreement with the C1
symmetry resulting from the presence of a stereogenic cen-
ter in the pyrrolidine ring. At room temperature, the spectra
exhibit the expected features with the characteristic signals
arising from the 3,4-didodecyloxyphenyl units, a singlet for
the methyl group, an AB quartet and a singlet for the pyr-
rolidine protons. For both C60-G1 and C60-Y1, the signals
corresponding to the protons of the phenyl group directly
attached to the pyrrolidine ring are broad at room tempera-
ture. A variable-temperature NMR study showed clear co-
alescence, and the reversible narrowing of all these peaks
reveals a dynamic effect. This indicates restricted rotation
of the phenyl substituent on the pyrrolidine ring.[16] The 1H
NMR spectrum of compound C60-G1 recorded at 110 °C
in C2D2Cl4 is shown in Figure 2. At high temperatures, an
AX2 system is seen for the aromatic protons of the 3,5-
diethynylphenyl unit. Indeed, the exchange between H1 and
H1Ј is fast on the NMR timescale under these conditions,
and protons H1 and H1Ј appear equivalent in the 1H NMR
spectrum. In contrast, by cooling the solution to –50 °C,
this exchange resulting from the rotation of the phenyl unit
Figure 1. Compounds C60-G1, C60-G2, C60-Y1, and C60-Y2.
Results and Discussion
Synthesis
The preparation of the first generation derivatives C60- around the phenyl-pyrrolidine bond becomes slow on the
G1 and C60-Y1 is depicted in Scheme 1. Reaction of alkyne NMR timescale, as attested by the three sets of signals ob-
1 with 3,5-dibromobenzaldehyde (2) and 3,4-dibromobenz- served for the aromatic protons H1, H1Ј, and H2. In con-
aldehyde (3) under Sonogashira[14] conditions gave the first trast, the effect observed for C60-Y1 is resulting from a dy-
generation dendrons 4 and 5, respectively. The functionali- namic exchange between two atropisomers (A and B, Fig-
zation of C60 was based on the 1,3-dipolar cycloaddition of ure 2).[16] When the 1H-NMR spectrum of C60-Y1 is re-
the azomethine ylide[15] generated in situ from aldehydes 4 corded in C2D2Cl4 at 100 °C (Figure 2), the dynamic ex-
and 5. The reaction of C60 with 4 in the presence of an change between the two atropisomers is fast on the NMR
excess of N-methylglycine in refluxing toluene gave com- timescale, leading to a well resolved average spectrum under
pound C60-G1 in 61% yield. Compound C60-Y1 was ob- these conditions. By decreasing the temperature, a nar-
1
tained in 46% yield from 5, C60 and N-methylglycine under rowing of all the peaks is also observed but the H NMR
similar conditions.
spectrum becomes more complex. By –50 °C, the dynamic
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Phenyleneethynylene-Based Dendrons
1
Figure 2. (top left) H NMR spectra (400 MHz) of C60-G1 recorded in C2D2Cl4 at 110 and 50 °C, and in CDCl3 at room temperature
(* solvent peak); (top right) 1H NMR spectra (400 MHz) of C60-Y1 recorded in C2D2Cl4 at 100, 50, 40 and 27 °C (* solvent peak);
(bottom) 1H NMR spectra (400 MHz) of C60-Y1 recorded in CDCl3 at 10, 0, and –50 °C (* solvent peak; for the numbering, see Figure 2
top right).
exchange between the two atropisomers is slow on the action with 1 to yield dendron 8. Subsequent treatment with
NMR timescale and the spectra of both conformers are K2CO3 in THF/MeOH gave terminal alkyne 9 in 91% yield.
clearly observed.
The second generation dendron 10 was then obtained in
The synthesis of C60-G2 is depicted in Scheme 2. Treat- 96% yield by Pd-catalyzed cross-coupling between 9 and
ment of 2 with CBr4/PPh3/Zn under the conditions de- 3,5-dibromobenzaldehyde (2). Finally, reaction of 10 with
scribed by Corey–Fuchs[17] yielded dibromo olefin 6 in 95% C60 and N-methylglycine in refluxing toluene gave C60-G2
yield. Elimination of HBr and halogen–metal exchange was in 52% yield.
best achieved with an excess of LDA in THF at –78 °C and
the resulting anion was quenched with triethylsilyl chloride aldehyde (3) by following
Compound C60-Y2 was prepared from 3,4-dibromobenz-
similar synthetic route
a
(TESCl) to give protected alkyne 7 in 70% yield. Com- (Scheme 3). Dibromoolefination according to Corey–Fuchs
pound 7 was subjected to a Pd-catalyzed cross-coupling re- provided 11 which after treatment with an excess of LDA
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Scheme 3. Reagents and conditions: (a) CBr4, PPh3, Zn, CH2Cl2,
0 °C to room temp. (95%); (b) LDA, THF, –78 °C, then TESCl,
THF, –78 °C (63%); (c) 1, Pd(PPh3)2Cl2, CuI, PPh3, Et3N, THF,
65 °C (99%); (d) TBAF, THF, 0 °C (92%); (e) 3, Pd(PPh3)2Cl2,
CuI, PPh3, Et3N, THF, 65 °C (84%); (f) C60, N-methylglycine, tolu-
ene, ∆ (50%).
Scheme 2. Reagents and conditions: (a) CBr4, PPh3, Zn, CH2Cl2,
0 °C to room temp. (95%); (b) LDA, THF, –78 °C, then TESCl,
THF, –78 °C (70%); (c) 1, Pd(PPh3)2Cl2, CuI, PPh3, Et3N, THF,
65 °C (99%); (d) K2CO3, THF, MeOH, room temp. (91%); (e) 2,
Pd(PPh3)2Cl2, CuI, PPh3, Et3N, THF, 65 °C (96%); (f) C60, N-
methylglycine, toluene, ∆ (52%).
in THF at –78 °C and quenching with TESCl afforded pro-
tected alkyne 12. Compound 12 was subjected to a Pd-cata-
lyzed cross-coupling reaction with 1 to yield the second gen-
eration dendron 13. Treatment with tetra-n-butyl ammo-
nium fluoride (TBAF) and subsequent reaction of the re-
sulting 14 with 3 under Sonogashira conditions afforded
dendron 15. Treatment of 15 with C60 and N-methylglycine
finally gave C60-Y2 in 50% yield.
Compounds C60-G2 and C60-Y2 are well soluble in com-
mon organic solvents such as CH2Cl2, CHCl3, or THF and
complete spectroscopic characterization was easily
1
achieved. Both H and 13C-NMR spectra are in full agree-
ment with their C1 symmetry resulting from the presence of
a stereogenic center in the pyrrolidine ring. Variable-tem-
1
perature H NMR studies were also carried out with com-
pounds C60-G2 and C60-Y2. In both cases, a dynamic effect
was evidenced and the results are closely similar to that
discussed in detail for compounds C60-G1 and C60-Y1. Fi-
nally, the structure of C60-G2 and C60-Y2 was confirmed
by mass spectrometry. In both cases, the expected molecular
ion peak was clearly observed.
Figure 3. Model compounds G1, G2, Y1, and Y2.
Electrochemistry
In addition, compounds G1, G2, Y1 and Y2 (Figure 3)
which were used as reference compounds, were prepared by
The cyclic voltammetric patterns of all the hybrid sys-
diisobutylaluminum hydrid (DIBAL-H) reduction of benz- tems studied in CH2Cl2 show three reversible one-electron
aldehydes 4, 10, 5 and 15, respectively. transfer processes in the cathodic region and two chemically
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Phenyleneethynylene-Based Dendrons
irreversible electron-transfer processes corresponding to ill- CH2Cl2 solutions at 298 K are shown in Figure 5. As ex-
defined peaks in the anodic region (Table 1). Comparison pected, the increase in the size of the conjugated network
with the (N-methylpyrrolidino)fullerene reference com- for G2 relative to G1 results in a higher molar extinction
pound MeF (Figure 4) allows us to assign the three ob- coefficient. The absorption maxima as well as the end-ab-
served reductions to the fullerene core. The C60-based elec- sorptions are found similar for both G1 and G2. This trend
tron-transfer processes are almost unaffected by the pres- shows that the all-meta ramification does not promote ef-
ence of the phenyleneethynylene-based dendrons: only a ficient π-electronic conjugation within the branched den-
very small positive shift of the half-wave potentials is ob- dritic structure, as already observed for related phenylenevi-
served.
nylene-based dendrimers.[5,8] In contrast, when going from
Y1 to Y2, an absorption onset at lower energy and a wider
spectral profile are observed. This is due the presence of
Table 1. Half-wave potentials (in V vs. SCE) of C60-G1, C60-G2,
C60-Y1, C60-Y2 and the corresponding reference compounds re-
corded in CH2Cl2 + 0.1  nBu4NPF6 at room temperature using a two π-conjugated moieties made of 3 para-phenylacetylene
glassy carbon working electrode.
units in Y2. As a result, the larger delocalization in Y2 leads
[a]
[a]
to a 70 nm red-shift of the absorption onset relative to Y1.
The absorption spectrum of MeF (Figure 6) shows the well-
known features of pyrrolidinofullerenes.[19]
Red3
Red2
Red1
Ox1
Ox2
MeF
C60-Y1
Y1
C60-G1
G1
C60-Y2
Y2
C60-G2
G2
–1.54
–1.49
–1.01
–0.97
–0.62
–0.59
+1.41
+1.35
+1.40
+1.37
+1.41
+1.41
+1.40
+1.41
+1.52
+1.50
+1.54
+1.48
–1.50
–1.49
–1.48
–0.97
–0.97
–0.96
–0.60
–0.60
–0.59
[a] Chemically irreversible electron-transfer process; Epa value at
0.2 V/s.
Figure 5. Absorption and normalized fluorescence spectra (inset)
of (a) Y1 (black), G1 (grey); (b) Y2 (black), G2 (grey); CH2Cl2,
298 K. Emission spectra were recorded upon excitation at the ab-
sorption maximum (O.D. = 0.1).
Figure 4. Model compound MeF.
In the cathodic region, the observed processes are as-
signed to the peripheral dialkyloxyphenyl units, as expected
on the basis of the electrochemical properties of 1,2-di-
methoxybenzene.[18] The oxidation process observed for the
dendrons is very close to the first of the corresponding hy-
brid systems (Epa values reported in Table 1), except for a
slight negative shift in the case of Y1 and G1. Moreover,
the potential values corresponding to the first and second
oxidation processes of all the C60-based compounds are
very similar without any significant difference between the
Y and G series, thus suggesting that the electron transfers
are mainly localized on the dialkyloxybenzene units. Sur-
prisingly, in the case of C60-G1, C60-G2, C60-Y1, and C60-
Y2 two oxidation processes are observed, while for the cor-
responding dendrons only one process is present in the
same potential window (Table 1). Although the evaluation
of the number of electrons exchanged is precluded by the
chemical irreversibility of the oxidation processes, these re-
sults suggest that the dialkyloxyphenyl units are no longer
equivalent from the electrochemical point of view when the
C60 unit is present.
Figure 6. Absorption spectra of dyad compounds: (a) fulleropyrrol-
idine reference MeF (dashed), C60Y1 (black), C60G1 (grey); (b) full-
eropyrrolidine reference MeF (dashed), C60Y2 (black), C60G2
(grey); CH2Cl2, 298 K. Beyond 400 nm, spectra are increased by a
factor of 10 for display purposes.
Hybrid systems. The absorption spectra of the hybrid sys-
tems C60-G1, C60-G2, C60-Y1, and C60-Y2 recorded in
Electronic Absorption Spectra
Reference compounds. The electronic absorption spectra CH2Cl2 solutions are shown in Figure 6. In all cases the
of reference compounds G1, G2, Y1 and Y2 recorded in contributions from the fullerene and antenna components
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P. Ceroni, J.-F. Nierengarten, N. Armaroli et al.
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are clearly visible and distinguishable. Comparison of the
Hybrid systems. Following excitation at 310 nm, negligi-
absorption spectra of these hybrid systems with spectra re- ble fluorescence of the dendritic subunits is observed for
sulting from the linear superimposition of the individual C60-G1, C60-G2, C60-Y1, and C60-Y2. Indeed, when com-
components (i.e. C60 and antenna) show no significant dif- pared to the fluorescence intensity observed for reference
ferences. This indicates that there are minimal ground state compounds G1, G2, Y1 and Y2 under the same conditions,
interactions between the fullerene and the conjugated den- it appears that fluorescence is quenched by about two or-
dritic subunits within these systems which would agree with ders of magnitude (Table 2). Additionally, we observe a
the electrochemical data (vide supra).
fluorescence band at approximately 710 mn which is almost
Fully selective excitation of the dendritic unit in all hy- identical in all cases to fluorescence observed for the fuller-
brid systems is not possible due to overlap of their absorp- ene reference compound MeF. Indeed the intensity of the
tion profiles with that of the C60 unit. For C60-G1 and C60- bands observed for all hybrids is nearly equal to that of
Y1, excitation at 310 nm corresponds to an average of 50% the fullerene reference MeF under the same experimental
light absorption by the conjugated dendritic antenna. How- conditions (same absorbance at the excitation wavelength).
ever, greater selectivity is possible for C60-G2 and C60-Y2 These results suggest that efficient intramolecular singlet–
owing to the increased intensity of the absorption for the singlet energy transfer takes place, as seen previously for
dendritic subunit of these compounds (selectivity as high as analogous systems.[8] This process, clearly, must be on a ti-
86% is possible at 310 nm). Completely selective excitation mescale faster than that of the fluorescence of the conju-
of the C60 unit is possible for all hybrids at wavelengths gated dendritic units (≈ 1 ns). Excitation spectra taken in
Ͼ 460 nm.
the range 300–450 nm at λem = 730 nm (fullerene fluores-
cence) show that sensitization of the C60 moiety occurs for
C60-G1, C60-G2, C60-Y1, and C60-Y2 giving strong support
to a dendronǞC60 singlet-singlet energy-transfer process.
In previous studies involving similar hybrid systems, namely
C60 derivatives bearing linear π-conjugated fragments, the
initial energy-transfer event populates the lowest fullerene
singlet excited state which is capable of promoting electron
transfer from the oligomer to the C60 unit.[21] Actually, this
can take place only when the charge separated state is lower
in energy than the fullerene singlet. This is not the case here
where the fulleropyrrolidine lowest singlet excited state is
placed at 1.7 eV[8] above the ground state, i.e. substantially
lower lying than the charge separated level which is located
at about 2.9 eV for C60-G1, C60-G2, C60-Y1, and C60-Y2, as
derived from the electrochemical data in CH2Cl2 (Table 1).
Experimental evidence for a 100% efficient dendronǞC60
energy transfer is also obtained in benzonitrile from fluo-
rescence data. Thus, for the present dyads, the large differ-
ence in energy between the fullerene singlet and the charge
separated state does not enable charge separation even in
polar media, thus preventing tuning of photoinduced pro-
cesses by solvent polarity as observed previously for a
number of C60 multicomponent systems.[13]
Luminescence Properties and Photoinduced Processes
Reference compounds. G1, G2, Y1 and Y2 exhibit fluores-
cence bands in CH2Cl2 solution (Figure 5, Table 2). The
singlet excited state lifetimes determined at room tempera-
ture are in the nanosecond range for all the compounds as
typically observed for oligophenyleneethynylene systems.[20]
The fluorescence spectra of G1 and G2 have practically the
same shape, but the emission maximum of G2 is slightly
red-shifted (18 nm). The fluorescence quantum yield and
the singlet excited state lifetime of G1 are nearly identical
to those of G2. When going from Y1 to Y2, a larger red-
shift of the emission maximum (40 nm) is observed.
Furthermore, the emission quantum yields of Y1 and Y2
are much larger when compared to G1 and G2. The latter
observations point out the differences in π-delocalization in
the two families of branched systems already deduced from
their absorption features (see above).
Table 2. Luminescence properties in CH2Cl2 at 298 K.
C60
λmax
[nm]
Dendron
λmax
[nm]
[a]
[b]
[a]
[b]
Φem
(ϫ104) [ns]
τ[c]
Φem
τ[d]
[ns]
MeF
Y1
C60-Y1
G1
C60-G1
Y2
C60-Y2
G2
C60-G2
714
5.50
5.56
4.74
4.80
5.69
1.19
1.27
1.22
1.31
1.32
400
478
382
438
440
498
400
422
0.440 1.30
0.002
0.110 1.25
0.001
Conclusions
714
712
714
714
Two series of isomeric dyads with differently branched
phenyleneethynylene-based moieties and a pyrrolidinoful-
lerene core have been prepared. The photophysical proper-
ties revealed an ultrafast and very efficient dendronǞC60
energy transfer in all these hybrid systems. Importantly, the
different π-conjugation patterns in Y1–2 relative to G1–2
have a dramatic effect on their electronic properties as at-
tested by the differences observed in their absorption and
emission spectra. The lower lying absorption onset and the
0.55
1.23
0.006
0.17
1.24
0.002
[a] Emission maxima from corrected spectra. [b] Emission quantum
yields obtained in aerated samples. [c] Excited state lifetimes ob-
tained in aerated samples; λex = 337 nm. [d] Excited state lifetimes
obtained in aerated samples; λex = 465 nm.
Pyrrolidinofullerene MeF exhibit singlet excited state pa- wider spectral profile of C60-Y2 when compared to C60-G2
rameters (Table 2) identical to those of very similar systems clearly points out an improved light harvesting capability
reported previously.[19]
for the former compound. On the other hand, the electro-
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Phenyleneethynylene-Based Dendrons
General Procedure for the Preparation of Compounds 7 and 12: A
solution of LDA in THF was slowly added to a solution of the
appropriate dibromo olefine in THF at –78 °C under argon. After
2 h, a solution of triethylsilyl chloride was added at the same tem-
perature. After 2 h a saturated aqueous NH4Cl solution was added.
The reaction mixture was diluted with hexane, washed with water,
dried with MgSO4 and the solvents evaporated. The product was
then purified as outlined in the following text.
chemical properties of the two series of compounds are not
strongly different since reduction and oxidation processes
are mainly localized on the C60 core and the dialkoxyben-
zene peripheral units, respectively.
Experimental Section
General: Reagents and solvents were purchased as reagent grade
and used without further purification. THF was distilled from so-
dium benzophenone ketyl. All reactions were performed in stan-
dard glassware under an inert Ar atmosphere. Evaporation and
concentration were done at water aspirator pressure and drying in
vacuo at 10–2 Torr. Column chromatography: silica gel 60 (230–
400 mesh, 0.040–0.063 mm) was purchased from E. Merck. Thin-
layer chromatography (TLC) was performed on glass sheets coated
with silica gel 60 F254 purchased from E. Merck, visualization by
UV light. IR spectra (cm–1) were measured on an ATI Mattson
Genesis Series FTIR instrument. NMR spectra were recorded on
a Bruker AC 300 with solvent peaks as reference. FAB-mass spectra
(m/z; % relative intensity) were taken on a ZA HF instrument with
4-nitrobenzyl alcohol as matrix. MALDI-TOF-mass spectra
(m/z;% relative intensity) were carried out on a Bruker BIFLEXTM
matrix-assisted laser desorption time-of-flight mass spectrometer
equipped with SCOUTTM High Resolution Optics, an X-Y multi-
sample probe and a gridless reflector. Ionization is accomplished
with the 337 nm beam from a nitrogen laser with a repetition rate
of 3 Hz. All data were acquired at a maximum accelerating poten-
tial of 20 kV in the linear positive ion mode. The output signal
from the detector was digitized at a sampling rate of 1 GHz. A
saturated solution of 1,8,9-trihydroxyanthracene (dithranol
ALDRICH EC: 214-538-0) in CH2Cl2 was used as a matrix. Typi-
cally, a 1/1 mixture of the sample solution in CH2Cl2 was mixed
with the matrix solution and 0.5 µL of the resulting mixture was
deposited on the probe tip. Elemental analyses were performed by
the analytical service at the Institut Charles Sadron, Strasbourg.
Compound 7: This compound was prepared from 6 (4.00 g,
9.53 mmol), LDA (38.12 mmol) and TESCl (10.48 mmol) in THF
(250 mL) and column chromatography (SiO2, hexane) yielded 7
(2.50 g, 70%). Colorless oil. IR (CH Cl ): ν = 2164 (CϵC) cm–1.
˜
2
2
1H NMR (CDCl3, 300 MHz): δ = 7.61 (t, J = 2 Hz, 1 H), 7.54 (d,
J = 2 Hz, 2 H), 1.04 (m, 9 H), 0.68 (m, 6 H) ppm. 13C NMR
(CDCl3, 75 MHz): δ = 134.0, 133.4, 126.7, 122.5, 102.9, 95.2, 7.4,
4.3 ppm. C14H18Br2Si (374.19): calcd. C 44.94, H 4.85; found C
44.85, H 4.91.
Compound 12: This compound was prepared from 11 (1.59 g,
3.79 mmol), LDA (15.16 mmol) and TESCl (4.17 mmol) in THF
(100 mL) and column chromatography (SiO2, hexane) yielded 10
(0.89 g, 63%). Colorless solid (m.p. 155 °C). IR (KBr): ν = 2162
˜
1
(CϵC) cm–1. H NMR (300 MHz, CDCl3): δ = 7.72 (d, J = 2 Hz,
1 H), 7.55 (d, J = 8 Hz, 1 H), 7.25 (dd, J = 8 and 2 Hz, 1 H), 1.05
(m, 9 H), 0.7 (m, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
136.7, 133.3, 131.7, 125.0, 124.5, 124.0, 103.5, 94.6, 7.5, 4.3 ppm.
C14H18Br2Si (374.19): calcd. C 44.94, H 4.85; found C 44.99, H
4.84.
Compound 9: K2CO3 (50 mg, 0.36 mmol) was added to a solution
of 8 (1.55 g, 1.99 mmol) in a mixture of THF (10 mL) and MeOH
(100 mL). After 3 h, the reaction mixture was filtered through a
celite pad and the solvent evaporated. The crude product was di-
luted with dichloromethane. The resulting solution was washed
with water, dried with MgSO4 and the solvents evaporated. Column
chromatography (SiO2, hexane) yielded 9 (1.20 g, 91%). Pale yellow
glassy product. IR (KBr): ν = 3304 (CϵC–H), 2152 (CϵC) cm–1.
˜
1H NMR (300 MHz, CDCl3): δ = 7.66 (t, J = 2 Hz, 1 H), 7.60 (d,
J = 2 Hz, 2 H), 5.30 (s, 8 H), 3.12 (s, 1 H), 1.14 (s, 42 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 134.7, 134.6, 132.4, 132.3, 132.0,
131.5, 131.1, 123.9, 123.8, 123.0, 122.5, 106.5, 93.1, 90.4, 89.3, 81.9,
78.5, 18.7, 11.3 ppm. C46H54Si2·H2O (681.11): calcd. C 81.13, H
8.30; found C 81.15, H 8.28.
General Procedure for the Preparation of Compounds 6 and 11: A
mixture of CBr4, PPh3 and Zn dust in dry CH2Cl2 was stirred at
room temperature for 24 h. The suspension was then cooled to 0 °C
and the appropriate aldehyde dissolved in CH2Cl2 was added at
once. The resulting mixture was slowly warmed to room tempera-
ture and stirred overnight. The resulting thick suspension was fil-
tered and the solvents evaporated. The residue was dissolved in
a minimum of CH2Cl2, then hexane was added to precipitate the
remaining P-containing by-products. The resulting mixture was fil-
tered and the solvents evaporated. The product was then purified
as outlined in the following text.
Compound 14: A 1  solution of TBAF in THF (2.60 mL,
2.60 mmol) was added to a solution of 13 (3.00 g, 2.60 mmol) in
THF (150 mL) at 0 °C under argon. After 2 h, water was added.
The reaction mixture was diluted with dichloromethane, washed
with water, dried with MgSO4 and the solvent was evaporated. Col-
umn chromatography (SiO2, hexane/CH2Cl2, 7:3) yielded 14
Compound 6: This compound was prepared from 2 (3.00 g,
11.37 mmol), CBr4 (18.85 g, 56.85 mmol), PPh3 (14.91 g,
56.85 mmol) and Zn dust (3.72 g, 56.85 mmol) in CH2Cl2 (300 mL)
and column chromatography (SiO2, hexane) yielded 6 (4.55 g,
(2.45 g, 92%). Pale yellow glassy product. IR (KBr): ν = 3290
˜
(CϵC–H), 2155 (CϵC) cm–1. 1H NMR (300 MHz, CDCl3): δ =
7.66 (d, J = 2 Hz, 1 H), 7.47 (d, J = 8 Hz, 1 H), 7.36 (dd, J = 2
and 8 Hz, 1 H), 7.13 (2 dd, J = 2 and 8 Hz, 2 H), 7.05 (d, J = 2 Hz,
2 H), 6.81 (d, J = 8 Hz, 2 H), 4.00 (2t, J = 7 Hz, 4 H), 3.89 (2t, J
= 7 Hz, 4 H), 3.17 (s, 1 H), 1.81 (m, 8 H), 1.27–1.76 (m, 72 H),
0.89 (t, J = 7 Hz, 12 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
150.0, 149.9, 148.8, 134.8, 131.2, 131.0, 126.4, 126.3, 125.0, 124.9,
121.4, 116.5, 115.1, 113.0, 96.0, 94.6, 86.6, 86.0, 82.6, 79.0, 69.0,
32.0, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 26.1, 26.0, 22.7, 14.1 ppm.
C72H110O4 (1039.64): calcd. C 83.18, H 10.66; found C 83.37, H
10.69.
1
95%). Colorless solid. H NMR (CDCl3, 300 MHz): δ = 7.65 (t, J
= 2 Hz, 1 H), 7.61 (2d, J = 2 Hz, 2 H), 7.37 (s, 1 H) ppm. 13C
NMR (CDCl3, 75 MHz): δ = 138.3, 133.9, 133.8, 129.8, 122.8, 93.1
ppm.
Compound 11: This compound was prepared from 3 (1.00 g,
3.79 mmol), CBr4 (6.28 g, 18.95 mmol), PPh3 (4.97 g, 18.95 mmol)
and Zn dust (1.24 g, 18.95 mmol) in CH2Cl2 (100 mL) and column
chromatography (SiO2, hexane) yielded 11 (1.51 g, 95%). Pale yel-
1
low solid. H NMR (300 MHz, CDCl3): δ = 7.80 (d, J = 2 Hz, 1
H), 7.62 (d, J = 8 Hz, 1 H), 7.38 (s, 1 H), 7.34 (dd, J = 8 and 2 Hz,
1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 135.8, 134.4, 133.5,
133.2, 128.2, 124.9, 124.8, 92.0 ppm.
General Procedure for the Preparation of Compounds 4, 5, 8, 10, 13
and 15: To an oven-dried glass screw capped tube were added all
solids including the halide, alkyne, CuI, PPh3 and palladium cata-
Eur. J. Org. Chem. 2007, 5899–5908
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5905

P. Ceroni, J.-F. Nierengarten, N. Armaroli et al.
FULL PAPER
lyst. The atmosphere was removed via vacuum and replaced with
dry argon (3ϫ). THF and triethylamine were added by syringe and
the reaction was heated at 65 °C in an oil bath while stirring. Upon
cooling the reaction mixture was filtered via gravity filtration to
remove solids and diluted with dichloromethane. The reaction mix-
ture was extracted with an aqueous NH4Cl solution. The organic
layer was dried with MgSO4 and the solvent was evaporated. The
product was then purified as outlined in the following text.
4.03 (t, J = 7 Hz, 16 H), 1.83 (m, 16 H), 1.28–1.57 (m, 144 H), 0.91
(m, 24 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 150.1, 148.8,
139.5, 136.7, 134.4, 133.6, 132.3, 125.1, 124.6, 124.5, 123.0, 116.7,
114.7, 113.2, 91.2, 90.2, 87.9, 86.2, 69.3, 69.1, 32.0, 29.7, 29.6, 29.5,
29.4, 29.3, 29.2, 29.1, 26.1, 26.0, 22.7, 14.1 ppm. C151H222O9
(2181.41): calcd. C 83.14, H 10.26; found C 83.24, H 10.27.
Compound 13: This compound was prepared from 1 (1.13 g,
2.40 mmol), 12 (0.30 g, 0.80 mmol), Pd(PPh3)2Cl2 (68 mg,
0.10 mmol), CuI (7.5 mg, 0.04 mmol) and PPh3 (32 mg, 0.12 mmol)
in THF/Et3N, 4:1 (10 mL). Column chromatography (SiO2, hexane/
Compound 4: This compound was prepared from 2 (0.40 g,
1.52 mmol),
1
(2.14 g, 4.55 mmol), Pd(PPh3)2Cl2 (128 mg,
0.18 mmol), CuI (14.5 mg, 0.08 mmol) and PPh3 (60 mg,
0.23 mmol) in THF/Et3N, 4:1 (10 mL). Column chromatography
CH2Cl2, 9:1) yielded 13 (0.92 g, 99%). Glassy product. IR (KBr):
1
ν = 2154 (CϵC) cm–1. H NMR (300 MHz, CDCl ): δ = 7.65 (d,
˜
3
(SiO2, hexane/CH2Cl2, 9:1) yielded 4 (1.36 g, 86%). Yellow glassy
J = 2 Hz, 1 H), 7.45 (d, J = 8 Hz, 1 H), 7.36 (dd, J = 8 and 2 Hz,
1 H), 7.13 (2 dd, J = 8 and 2 Hz, 2 H), 7.05 (d, J = 2 Hz, 2 H),
6.80 (d, J = 8 Hz, 2 H), 3.97 (2t, J = 7 Hz, 4 H), 3.88 (2t, J = 7 Hz,
4 H), 1.80 (m, 8 H), 1.19–1.56 (m, 72 H), 1.06 (t, J = 8 Hz, 9 H),
0.89 (t, J = 7 Hz, 12 H), 0.69 (q, J = 8 Hz, 6 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 150.4, 150.0, 149.9, 148.7, 148.6, 134.7,
131.0, 130.8, 126.2, 126.0, 125.9, 124.9, 122.6, 117.0, 116.5, 115.2,
113.9, 113.0, 105.3, 95.8, 94.4, 93.8, 86.8, 86.1, 69.1, 69.0, 32.0,
29.8, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 26.1, 26.0, 25.9, 22.7, 14.0,
7.4, 4.3 ppm. C78H124O4Si (1153.90): calcd. C 81.19, H 10.83;
found C 81.14, H 10.88.
1
product. IR (KBr): ν = 2151 (CϵC), 1704 (C=O) cm–1. H NMR
˜
(300 MHz, CDCl3): δ = 10.00 (s, 1 H), 7.93 (d, J = 2 Hz, 2 H), 7.88
(t, J = 2 Hz, 1 H), 7.12 (dd, J = 8 and 2 Hz, 2 H), 7.05 (d, J =
2 Hz, 2 H), 6.86 (d, J = 8 Hz, 2 H), 4.03 (2 t, J = 7 Hz, 8 H), 1.83
(m, 8 H), 1.28–1.49 (m, 72 H), 0.89 (m, 12 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 191.0, 150.2, 149.8, 139.2, 136.6, 131.4,
125.2, 116.7, 114.4, 113.2, 91.9, 85.8, 69.3, 69.2, 31.9, 29.7, 29.6,
29.4, 29.3, 29.2, 29.1, 26.0, 22.7, 14.1 ppm. C71H110O5 (1043.63):
calcd. C 81.71, H 10.62; found C 81.55, H 10.76.
Compound 5: This compound was prepared from 1 (2.01 g,
4.26 mmol),
3 (0.38 g, 1.42 mmol), Pd(PPh3)2Cl2 (120.00 mg,
Compound 15: This compound was prepared from 3 (169 mg,
0.64 mmol), 14 (2.00 g, 1.92 mmol), Pd(PPh3)2Cl2 (54 mg,
0.08 mmol), CuI (6 mg, 0.03 mmol) and PPh3 (25 mg, 0.10 mmol)
in THF/Et3N, 4:1 (7 mL). Column chromatography (SiO2, hexane/
0.17 mmol), CuI (13.5 mg, 0.07 mmol) and PPh3 (56 mg,
0.21 mmol) in THF/Et3N, 4:1 (10 mL). Column chromatography
(SiO2, hexane/CH2Cl2, 4:1) yielded C (1.21 g, 82%). Glassy prod-
uct. IR (KBr): ν = 2151 (CϵC), 1702 (C=O) cm–1. 1H NMR
˜
CH2Cl2, 7:3) yielded 15 (1.17 g, 84%). Glassy product. IR (KBr):
(300 MHz, CDCl3): δ = 10.00 (s, 1 H), 8.02 (d, J = 2 Hz, 1 H), 7.79
(dd, J = 8 and 2 Hz, 1 H), 7.67 (d, J = 8 Hz, 1 H), 7.17 (2 dd, J =
8 and 2 Hz, 2 H), 7.07 (2 d, J = 2 Hz, 2 H), 6.83 (2 d, J = 8 Hz, 2
H), 4.01 (2 t, J = 7 Hz, 4 H), 3.90 (2 t, J = 7 Hz, 4 H), 1.83 (m, 8
H), 1.27–1.56 (m, 72 H), 0.89 (m, 12 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 190.8, 150.4, 150.1, 148.8, 134.9, 132.9, 131.8, 131.7,
127.7, 126.9, 125.3, 125.0, 116.6, 116.5, 114.8, 114.6, 113.1, 113.0,
98.3, 95.4, 86.7, 85.8, 69.1, 31.1, 29.8, 29.7, 29.6, 29.5, 29.4, 29.3,
29.2, 26.1, 26.0, 22.7, 14.1 ppm. C71H110O5·0.5H2O (1052.64):
calcd. C 81.01, H 10.63; found C 81.06, H 10.64.
1
ν = 2150 (CϵC), 1702 (C=O) cm–1. H NMR (300 MHz, CDCl ):
˜
3
δ = 10.04 (s, 1 H), 8.07 (broad s, 1 H), 7.85 (broad d, J = 8 Hz, 1
H), 7.79 (m, 2 H), 7.72 (d, J = 8 Hz, 1 H), 7.52 (m, 4 H), 7.14 (m,
4 H), 7.05 (m, 2 H), 7.02 (m, 2 H), 6.77 (2d, J = 8 Hz, 4 H), 4.00
(t, J = 7 Hz, 4 H), 3.87 (m, 12 H), 1.81 (m, 16 H), 1.27–1.56 (m,
144 H), 0.89 (t, J = 7 Hz, 24 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 150.2, 150.1, 150.0, 149.9, 148.8, 148.7, 135.4, 134.6, 134.5,
133.1, 132.3, 131.5, 131.2, 130.6, 130.5, 129.3, 126.7, 126.4, 125.2,
125.1, 122.0, 121.8, 116.6, 116.5, 115.1, 115.0, 114.9, 114.8, 113.1,
96.9, 96.5, 96.3, 95.0, 94.9, 94.4, 86.6, 89.0, 86.9, 86.0, 85.9, 69.1,
69.0, 68.9, 32.0, 29.7, 29.5, 29.4, 29.3, 29.2, 26.1, 26.0, 23.0, 14.1
ppm. C151H222O9 (2181.37): calcd. C 83.14, H 10.26; found C
83.17, H 10.28.
Compound 8: This compound was prepared from 7 (500 mg,
1.34 mmol),
0.16 mmol), CuI (13 mg, 0.07 mmol) and PPh3 (53 mg, 0.20 mmol)
in THF/Et3N, 4:1 (10 mL). Column chromatography (SiO2, hexane/
1
(1.89 g, 4.01 mmol), Pd(PPh3)2Cl2 (113 mg,
General Procedure for the Preparation of G1, G2, Y1, and Y2: A
1  DIBAL-H solution in hexane was slowly added to a solution
of the appropriate benzaldehyde in THF at 0 °C under argon. After
3 h, methanol then water were added. The reaction mixture was
filtered through a celite pad, dried with MgSO4 and the solvent
was evaporated. The product was then purified as outlined in the
following text.
CH Cl , 8:2) yielded 8 (1.54 g, 99%). Glassy product. IR (KBr): ν
˜
2
2
= 2151 (CϵC) cm–1. H NMR (300 MHz, CDCl3): δ = 7.59 (t, J
= 2 Hz, 1 H), 7.55 (d, J = 2 Hz, 2 H), 7.09 (2 dd, J = 8 and 2 Hz,
2 H), 7.03 (d, J = 2 Hz, 2 H), 6.84 (d, J = 8 Hz, 2 H), 4.02 (t, J =
7 Hz, 8 H), 1.84 (m, 8 H), 1.27–1.56 (m, 72 H), 1.06 (t, J = 8 Hz,
9 H), 0.89 (t, J = 7 Hz, 12 H), 0.69 (q, J = 8 Hz, 6 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 150.0, 148.8, 134.0, 133.9, 125.1,
124.2, 124.0, 116.7, 114.9, 113.3, 104.8, 92.9, 90.8, 86.3, 69.3, 69.2,
53.4, 31.9, 29.8, 29.7, 29.6, 29.4, 29.3, 29.2, 29.1, 26.1, 26.0, 22.7,
14.1, 7.5, 4.4 ppm. C78H124O4Si (1153.90): calcd. C 81.19, H 10.83;
found C 81.15, H 10.80.
1
Compound G1: This compound was prepared from 4 (200 mg,
0.19 mmol), DIBAL-H (0.50 mL), in THF (7 mL). Column
chromatography (SiO2, hexane/CH2Cl2, 7:3) yielded G1
(158.00 mg, 79%). Yellow glassy product. IR (KBr): ν = 3212
˜
1
Compound 10: This compound was prepared from 2 (169 mg,
(–OH), 2151 (CϵC) cm–1. H NMR (300 MHz, CDCl3): δ = 7.60
0.64 mmol),
9
(2.00 g, 1.92 mmol), Pd(PPh3)2Cl2 (54 mg, (t, J = 2 Hz, 1 H), 7.44 (d, J = 2 Hz, 2 H), 7.10 (dd, J = 8 and
0.08 mmol), CuI (6 mg, 0.03 mmol) and PPh3 (25 mg, 0.10 mmol)
in THF/Et3N, 4:1 (5 mL). Column chromatography (SiO2, hexane/
2 Hz, 2 H), 7.04 (d, J = 2 Hz, 2 H), 6.83 (d, J = 8 Hz, 2 H), 4.68
(s, 2 H), 4.01 (t, J = 7 Hz, 8 H), 1.84 (m, 8 H), 1.28–1.49 (m, 72
CH2Cl2, 7:3) yielded 10 (1.34 g, 96%). Glassy product. IR (KBr): H), 0.90 (m, 12 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 149.7,
1
ν = 2150 (CϵC), 1702 (C=O) cm–1. H NMR (300 MHz, CDCl ): 148.6, 141.4, 133.2, 129.0, 125.0, 124.0, 116.6, 115.0, 113.1, 90.3,
˜
3
δ = 10.04 (s, 1 H), 8.00 (d, J = 2 Hz, 2 H), 7.91 (t, J = 2 Hz, 1 H), 86.9, 69.2, 69.1, 64.4, 31.9, 29.7, 29.65, 29.6, 29.4, 29.35, 29.2,
7.66 (t, J = 2 Hz, 2 H), 7.63 (d, J = 2 Hz, 4 H), 7.12 (dd, J = 2
and 8 Hz, 4 H), 7.05 (d, J = 2 Hz, 4 H), 6.85 (d, J = 8 Hz, 4 H),
29.15, 25.9, 22.7, 14.0 ppm. C71H112O5 (1045.65): calcd. C 81.54,
H 10.80; found C 81.03, H 10.83.
5906
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 5899–5908

Phenyleneethynylene-Based Dendrons
Compound G2: This compound was prepared from 10 (200 mg,
0.09 mmol), DIBAL-H (0.23 mL), in THF (14 mL). Column
chromatography (SiO2, hexane/CH2Cl2, 7:3) yielded G2 (160 mg,
29.4, 29.3, 29.2, 29.15, 26.0, 25.95, 22.7, 14.1 ppm. FAB-MS:
1791.6 (60%, [M]+, calcd. for C133H115O4N 1791.4), 1070.9 (100%,
[M – C60]+, calcd. for C73H115O4N 1070.7). C133H115O4N (1791.34):
calcd. C 89.17, H 6.47, N 0.78; found C 88.78, H 6.55, N 0.45.
80%). Yellow glassy product. IR (KBr): ν = 3200 (–OH), 2152
˜
(CϵC) cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.61–7.64 (m, 6 H),
7.51 (s, 3 H), 7.12 (dd, J = 2 and 8 Hz, 4 H), 7.05 (d, J = 2 Hz, 4
H), 6.84 (d, J = 8 Hz, 4 H), 4.72 (s, 2 H), 4.03 (t, J = 7 Hz, 16 H),
1.83 (m, 16 H), 1.29–1.49 (m, 144 H), 0.89 (m, 24 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 149.9, 148.7, 141.7, 133.9, 133.6,
133.5, 129.9, 125.1, 124.4, 123.5, 123.4, 116.7, 114.8, 113.2, 90.9,
89.2, 88.7, 86.3, 69.3, 69.2, 64.3, 31.9, 29.7, 29.65, 29.6, 29.4, 29.35,
29.2, 29.15, 26.0, 22.7, 22.4, 14.1 ppm. C151H224O9 (2183.39): calcd.
C 83.05, H 10.35; found C 83.03, H 10.54.
Compound C60-G2: This compound was prepared from 10 (500 mg,
0.23 mmol), C60 (182 mg, 0.25 mmol), N-methylglycine (165 mg,
1.86 mmol) in toluene (180 mL). Column chromatography (SiO2,
hexane/CH2Cl2, 7:3) yielded C60-G2 (352 mg, 52%). Brown glassy
product. IR (KBr): ν = 2152 (CϵC) cm–1. 1H NMR (400 MHz,
˜
CDCl3, –10 °C): δ = 8.18 (s, 1 H), 7.67 (t, J = 2 Hz, 1 H), 7.63 (s,
7 H), 7.09 (dd, J = 2 and 6 Hz, 4 H), 7.03 (d, J = 2 Hz, 4 H), 6.83
(d, J = 8 Hz, 4 H), 5.02 (d, J = 10 Hz, 1 H), 4.93 (s, 1 H), 4.25 (d,
J = 10 Hz, 1 H), 4.01 (2t, J = 7 Hz, 16 H), 2.85 (s, 3 H), 1.88 (m,
16 H), 1.48 (m, 144 H), 0.89 (2t, J = 7 Hz, 24 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 145.2, 145.15, 145.1, 145.05, 144.6, 144.5,
144.3, 143.0, 142.9, 142.6, 142.5, 142.2, 142.1, 142.0, 141.9, 141.85,
141.6, 141.5, 140.1, 139.6, 138.2, 137.1, 136.5, 135.9, 135.6, 135.0,
134.0, 133.7, 125.1, 124.4, 123.4, 116.6, 114.8, 113.2, 91.2, 89.3,
86.4, 82.6, 69.8, 69.2, 69.1, 68.9, 40.0, 31.9, 31.7, 29.7, 29.6, 29.4,
29.35, 29.2, 29.15, 26.1, 26.0, 22.7, 22.4, 14.1 ppm. MALDI-TOF-
MS: 2930.3 (9%, [M]+, calcd. for C213H228O8N: 2930.2), 2208.6
(100%, [M – C60]+, calcd. for C153H227O8N 2208.5), 720.0 (100%,
[C60]+, calcd. for C60 720.0). C213H227O8N (2929.08): calcd. C
87.34, H 7.81, N 0.48; found C 86.61, H 7.85, N 0.61.
Compound Y1: This compound was prepared from 5 (200 mg,
0.19 mmol), DIBAL-H (0.50 mL), in THF (7 mL). Column
chromatography (SiO2, hexane/CH2Cl2, 7:3) yielded Y1
(163.00 mg, 81%). Yellow glassy product. IR (KBr): ν = 3678
˜
1
(–OH), 2220 (CϵC) cm–1. H NMR (300 MHz, CDCl3): δ = 7.53
(m, 2 H), 7.27 (s, 1 H), 7.14 (2dd, J = 8 and 2 Hz, 2 H), 7.06 (2d,
J = 2 Hz, 2 H), 6.81 (d, J = 8 Hz, 2 H), 4.71 (d, J = 5 Hz, 2 H),
4.00 (2t, J = 7 Hz, 4 H), 3.89 (2t, J = 7 Hz, 4 H), 1.80 (m, 8 H),
1.27–1.58 (m, 72 H), 0.89 (m, 12 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 149.8, 149.75, 148.7, 140.5, 131.5, 129.5, 126.2, 126.0,
125.1, 124.9, 116.6, 115.4, 115.3, 113.1, 94.0, 93.9, 86.8, 86.8, 69.15,
69.1, 64.6, 31.9, 29.7, 29.65, 29.6, 29.5, 29.4, 29.35, 29.2, 26.1, 26.0,
22.7, 14.1 ppm. C71H112O5·0.5H2O (1054.66): calcd. C 80.86, H
10.80; found C 80.87, H 11.02.
Compound C60-Y1: This compound was prepared from 5 (350 mg,
0.34 mmol), C60 (266 mg, 0.37 mmol), N-methylglycine (242 mg,
2.71 mmol) in toluene (200 mL). Column chromatography (SiO2,
hexane/CH2Cl2, 7:3) yielded C60-Y1 (275 mg, 46%). Brown glassy
Compound Y2: This compound was prepared from 15 (200 mg,
0.09 mmol), DIBAL-H (0.23 mL), in THF (14 mL). Column
chromatography (SiO2, hexane/CH2Cl2, 7:3) yielded Y2 (86.00 mg,
product. IR (KBr): ν = 2157 (CϵC) cm–1. 1H NMR (400 MHz,
˜
C2D2Cl2, 90 °C): δ = 8.02 (d, J = 2 Hz, 1 H), 7.82 (dd, J = 2 and
8 Hz, 1 H), 7.62 (d, J = 8 Hz, 1 H), 7.13 (2dd, J = 2 and 8 Hz, 2
H), 7.08 (d, J = 2 Hz, 1 H), 7.03 (d, J = 2 Hz, 1 H), 6.80 (2d, J =
8 Hz, 2 H), 5.00 (d, J = 10 Hz, 1 H), 4.92 (s, 1 H), 4.28 (d, J =
10 Hz, 1 H), 3.99 (2t, J = 7 Hz, 4 H), 3.87 (2t, J = 7 Hz, 4 H), 2.83
(s, 3 H), 1.79 (m, 8 H), 1.26–1.44 (m, 72 H), 0.89 (m, 12 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 142.1, 142.05, 142.0, 141.95,
141.9, 141.8, 141.6, 141.5, 140.0, 139.9, 139.6, 136.9, 136.85, 136.4,
135.9, 135.6, 131.7, 128.5, 126.2, 124.9, 124.8, 116.4, 115.2, 113.0,
94.9, 94.7, 87.1, 86.9, 82.9, 69.9, 69.0, 68.9, 68.8, 40.0, 32.1, 31.9,
31.7, 29.7, 29.65, 29.6, 29.5, 29.45, 29.4, 29.35, 29.3, 29.2, 26.1,
26.05, 26.0, 22.9, 22.7, 22.4, 14.1 ppm. FAB-MS: 1791 (19%,
[M]+, calcd. for C133H115O4N: 1791.4), 1070.6 (100%, [M – C60]+,
calcd. for C73H115O4N 1070.7). C133H115O4N (1791.34): calcd. C
89.17, H 6.47, N 0.78; found C 88.78, H 6.55, N 0.45.
43%). Orange glassy product. IR (KBr): ν = 3212 (–OH), 2151
˜
(CϵC) cm–1. 1H NMR (300 MHz, CDCl3): δ = 7.77 (s, 2 H), 7.49–
7.58 (m, 7 H), 7.13 (d, J = 7 Hz, 4 H), 7.04 (dd, J = 7 and 2 Hz, 4
H), 6.80 (d, J = 8 Hz, 2 H), 6.74 (d, J = 8 Hz, 2 H), 4.74 (s, 2 H),
4.00 (t, J = 7 Hz, 4 H), 3.87 (m, 12 H), 1.78 (m, 16 H), 1.28–1.57
(m, 144 H), 0.89 (m, 24 H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 149.9, 149.8, 148.8, 148.687 141.3, 134.4, 131.9, 131.5, 130.7,
130.4, 129.9, 126.7, 126.5, 125.95, 125.9, 125.8, 125.1, 125.0, 124.8,
122.6, 122.5, 116.5, 116.45, 115.2, 115.1, 113.0, 95.9, 94.7, 93.1,
92.9, 90.2, 86.9, 86.1, 69.1, 69.0, 68.9, 64.5, 31.9, 31.6, 29.7, 29.5,
29.45, 29.4, 29.3, 26.1, 26.1, 22.7, 14.1, 13.9 ppm. C151H224O9
(2183.39): calcd. C 83.05, H 10.35; found C 83.07, H 10.33.
General Procedure for the Preparation of C60-G1, C60-G2, C60-Y1,
and C60-Y2: A solution of the appropriate benzaldehyde, C60, and
N-methylglycine in toluene was refluxed under argon for 24 h. Af-
ter cooling, the resulting solution was evaporated to dryness. The
product was then purified as outlined in the following text.
Compound C60-Y2: This compound was prepared from 15 (500 mg,
0.23 mmol), C60 (182 mg, 0.25 mmol), N-methylglycine (165 mg,
1.86 mmol) in toluene (180 mL). Column chromatography (SiO2,
hexane/CH2Cl2, 7:3) yielded C60-Y2 (337 mg, 50%). Brown glassy
Compound C60-G1: This compound was prepared from 4 (50 mg,
0.48 mmol), C60 (380 mg, 0.53 mmol), N-methylglycine (346 mg, product. IR (KBr): ν = 2151 (CϵC) cm–1. 1H NMR (400 MHz,
˜
0.53 mmol) in toluene (225 mL). Column chromatography (SiO2,
C2D2Cl2, 110 °C): δ = 8.10 (s, 1 H), 7.91 (d, J = 8 Hz, 1 H), 7.82
(d, J = 2 Hz, 1 H), 7.79 (d, J = 2 Hz, 1 H), 7.70 (d, J = 8 Hz, 1
H), 7.53 (m, 2 H), 7.49 (dd, J = 2 and 8 Hz, 2 H), 7.17 (dd, J = 2
hexane/CH2Cl2, 7:3) yielded C60-G1 (522 mg, 61%). Brown glassy
product. IR (KBr): ν = 2157 (CϵC) cm–1. 1H NMR (400 MHz,
˜
C2D2Cl2, 110 °C): δ = 7.98 (d, J = 1 Hz, 2 H), 7.66 (t, J = 2 Hz, 1 and 8 Hz, 4 H), 7.12 (dd, J = 2 and 5 Hz, 4 H), 6.87 (d, J = 8 Hz,
H), 7.11 (dd, J = 2 and 8 Hz, 2 H), 7.06 (d, J = 2 Hz, 2 H), 6.83
(d, J = 8 Hz, 2 H), 5.00 (d, J = 10 Hz, 1 H), 4.90 (s, 1 H), 4.27 (d,
2 H), 6.83 (d, J = 8 Hz, 2 H), 5.00 (d, J = 10 Hz, 1 H), 4.93 (s, 1
H), 4.25 (d, J = 10 Hz, 1 H), 3.99 (t, J = 7 Hz, 8 H), 3.86 (m, 8
J = 10 Hz, 1 H), 4.01 (t, J = 7 Hz, 8 H), 2.83 (s, 3 H), 1.83 (2t, J H), 2.81 (s, 3 H), 1.76 (m, 16 H), 1.27 (m, 144 H), 0.89 (2t, J =
= 7 Hz, 8 H), 1.27–1.47 (m, 72 H), 0.89 (m, 12 H) ppm. 13C NMR 7 Hz, 24 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 145.3, 145.25,
(75 MHz, CDCl3): δ = 146.0, 145.95, 145.9, 145.7, 145.6, 145.5, 145.2, 145.1, 144.7, 144.6, 144.4, 143.1, 142.9, 142.7, 142.5, 142.2,
145.35, 145.3, 145.2, 145.1, 144.6, 144.5, 144.3, 143.0, 142.9, 142.7, 142.1, 142.0, 141.9, 141.65, 141.6, 140.2, 139.7, 137.8, 137.0, 136.4,
142.5, 142.25, 142.2, 142.1, 142.0, 141.95, 141.9, 141.6, 140.1, 135.9, 135.6, 134.5, 134.4, 131.5, 130.4, 126.5, 126.0, 125.7, 125.1,
139.6, 137.7, 137.0, 136.5, 135.9, 135.6, 134.5, 125.1, 116.6, 114.9, 125.0, 122.4, 116.5, 115.2, 115.1, 113.0, 96.1, 94.8, 93.7, 93.6, 90.1,
113.2, 90.9, 87.1, 82.9, 69.9, 69.2, 69.1, 69.0, 40.1, 31.9, 29.7, 29.6, 86.9, 86.1, 82.9, 76.6, 69.9, 69.1, 69.0, 68.9, 40.0, 31.9, 29.7, 29.5,
Eur. J. Org. Chem. 2007, 5899–5908
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5907

P. Ceroni, J.-F. Nierengarten, N. Armaroli et al.
FULL PAPER
[3]
J. S. Moore, Z. Xu, Macromolecules 1991, 24, 5893–5894; J. S.
Moore, Z. Xu, J. Am. Chem. Soc. 1994, 116, 4537–4550; J. S.
Moore, Z. Xu, Angew. Chem. Int. Ed. Engl. 1993, 32, 246–248.
Z. Peng, Y. Pan, B. Xu, J. Zhang, J. Am. Chem. Soc. 2000, 122,
6619–6623.
J.-F. Nierengarten, S. Zhang, A. Gégout, M. Urbani, N. Arma-
roli, G. Marconi, Y. Rio, J. Org. Chem. 2005, 70, 7550–7557.
J. S. Moore, Acc. Chem. Res. 1997, 30, 402–413.
C. Devadoss, P. Bharathi, J. S. Moore, J. Am. Chem. Soc. 1996,
118, 9635–9644; Y. Pan, M. Lu, Z. Peng, J. S. Melinger, J. Org.
Chem. 2003, 68, 6952–6958.
N. Armaroli, F. Barigelletti, P. Ceroni, J.-F. Eckert, J.-F. Nic-
oud, J.-F. Nierengarten, Chem. Commun. 2000, 599–600; G.
Accorsi, N. Armaroli, J.-F. Eckert, J.-F. Nierengarten, Tetrahe-
dron Lett. 2002, 43, 65–68; J.-F. Nierengarten, N. Armaroli, G.
Accorsi, Y. Rio, J.-F. Eckert, Chem. Eur. J. 2003, 9, 36–41; N.
Armaroli, G. Accorsi, J. N. Clifford, J.-F. Eckert, J.-F. Nieren-
garten, Chem. Asian J. 2006, 1, 564–574.
F. Langa, M. J. Gomez-Escalonilla, E. Diez-Barra, J. C. Gar-
cia-Martinez, A. de la Hoz, J. Rodriguez-Lopez, A. Gonzalez-
Cortes, V. Lopez-Arza, Tetrahedron Lett. 2001, 42, 3435–3438;
J. L. Segura, R. Gomez, N. Martin, C. P. Luo, A. Swartz,
D. M. Guldi, Chem. Commun. 2001, 707–708; 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; L. Pérez,
J. C. Garcia-Martinez, E. Diez-Barra, P. Atienzar, H. Garcia,
J. Rodriguez-Lopez, F. Langa, Chem. Eur. J. 2006, 12, 5149–
5157.
V. Balzani, S. Campagna, G. Denti, A. Juris, S. Serroni, M.
Venturi, Acc. Chem. Res. 1998, 31, 26–34; V. Balzani, P. Ceroni,
A. Juris, M. Venturi, S. Campagna, F. Puntoriero, S. Serroni,
Coord. Chem. Rev. 2001, 219, 545–572; A. Adronov, J. M. J.
Frechet, Chem. Commun. 2000, 1701–1710; M. Fischer, F.
Vögtle, Angew. Chem. Int. Ed. 1999, 38, 885–905.
29.45, 29.4, 29.3, 26.1, 26.0, 22.7, 14.1 ppm. MALDI-TOF-MS:
2229.6 (7%, [M]+, calcd. for C213H227O8N: 2229.2), 2208.7 (100%,
[M
(2929.08): calcd. C 87.34, H 7.81, N 0.48; found C 87.45, H 7.92,
N 0.07.
–
C60]+, calcd. for C153H227O8N 2208.5). C213H227O8N
[4]
[5]
Electrochemistry: The electrochemical experiments were carried out
in argon-purged CH2Cl2 solutions at 298 K with an EcoChemie
Autolab 30 multipurpose instrument interfaced to a personal com-
puter. In the cyclic voltammetry (CV) the working electrode was a
glassy carbon electrode (0.08 cm2, Amel) or a Pt disk ultramicro-
electrode (r = 25 µm). In all cases, the counter electrode was a Pt
spiral, separated from the bulk solution with a fine glass frit, and
a silver wire was employed as a quasi-reference electrode (AgQRE).
The potentials reported are referred to SCE by measuring the
AgQRE potential with respect to ferrocene. The concentration of
the compounds examined was of the order of 5ϫ10–4 ; 0.05 
tetrabutylammonium hexafluoro-phosphate (TBAPF6) was added
as supporting electrolytes. Cyclic voltammograms were obtained
with scan rates in the range 0.05–20 Vs–1.
[6]
[7]
[8]
[9]
Photophysics: The photophysical investigations were carried out in
CH2Cl2 (Carlo–Erba, spectrofluorimetric grade). The samples were
placed in fluorimetric 1-cm path cuvettes. Absorption spectra were
recorded with a Perkin–Elmer λ40 spectrophotometer. Uncorrected
emission spectra were obtained with a Spex Fluorolog II spectro-
fluorimeter (continuous 150-W Xe lamp), equipped with a Hama-
matsu R-928 photomultiplier tube. The corrected spectra were ob-
tained via a calibration curve. Fluorescence quantum yields ob-
tained from spectra on an energy scale [cm–1] were measured with
the method described by Demas and Crosby[22] using as standards
[10]
[11]
air equilibrated solutions of quinine sulfate in 1  H2SO4 (Φem
=
0.546).[23] Emission lifetimes on the nanosecond time scale were
determined with an IBH single-photon counting spectrometer
equipped with a thyratron gated nitrogen lamp working in the
range 2–40 kHz (λexc = 337 nm, 0.5 ns time resolution); the detector
was a red-sensitive (185–850 nm) Hamamatsu R-3237-01 photo-
multiplier tube. Experimental uncertainties are estimated to be 8%
for lifetime determinations, 20% for emission quantum yields, and
1 nm and 5 nm for absorption and emission peaks respectively.
J. Baffreau, L. Perrin, S. Leroy-Lhez, P. Hudhomme, Tetrahe-
dron Lett. 2005, 46, 4599–4603; J.-F. Nierengarten, New J.
Chem. 2004, 28, 1177–1191; J.-F. Nierengarten, Sol. Energy
Mater. and Sol. Cells 2004, 83, 187–199.
P. L. Burn, S.-C. Lo, I. D. W. Samuel, Adv. Mater. 2007, 19,
1675–1688.
N. Armaroli, in Fullerenes: from synthesis to optoelectronic
properties (Eds.: D. M. Guldi, N. Martin), Kluwer Academic
Publishers, Dordrecht, 2002, pp. 137–162.
[12]
[13]
[14] Metal-catalyzed Cross-coupling Reactions (Eds.: F. Diederich,
P. J. Stang), Wiley-VCH, Weinheim, 1998.
[15] M. Prato, M. Maggini, Acc. Chem. Res. 1998, 31, 519–526.
[16] F. Ajamaa, T. M. Figueira Duarte, C. Bourgogne, M. Holler,
P. W. Fowler, J.-F. Nierengarten, Eur. J. Org. Chem. 2005, 3766–
3774.
[17] E. J. Corey, P. L. Fuchs, Tetrahedron Lett. 1972, 13, 3769–3772.
[18] M. Goez, G. Eckert, J. Phys. Chem. 1991, 95, 1179.
[19] J.-F. Eckert, J.-F. Nicoud, J.-F. Nierengarten, S.-G. Liu, L. Ech-
egoyen, F. Barigelletti, N. Armaroli, L. Ouali, V. Krasnikov, G.
Hadziioannou, J. Am. Chem. Soc. 2000, 122, 7467–7479; N.
Armaroli, G. Accorsi, J.-P. Gisselbrecht, M. Gross, V. Krasni-
kov, D. Tsamouras, G. Hadziioannou, M. J. Gomez-Escalon-
illa, F. Langa, J.-F. Eckert, J.-F. Nierengarten, J. Mater. Chem.
2002, 12, 2077–2087.
Acknowledgments
This research was supported by the Consiglio Nazionale delle
Ricerche (CNR) (Commessa PM.P04.010, MACOL), the Centre
National de la Recherche Scientifique (CNRS) (UPR 8241), Minis-
tero dell’Università e della Ricerca (PRIN, “Sistemi supramolecol-
ari per la conversione dell’energia luminosa”) and the European
Union (HPRN-CT-2002-00171, FAMOUS). S. Z. thanks the Di-
rection de la Recherche of the French Ministry of Research, A. G.
the Agence de l’Environnement et de la Maîtrise de l’Energie –
Région Alsace for their fellowships and R. P. F the Conselho Na-
cional de Desenvolvimento Científico e Tecnológico (Brazil). We
further thank L. Oswald and R. Cortesi for technical help and J.-
M. Strub for MS measurements.
[20] J. N. Clifford, T. Gu, J.-F. Nierengarten, N. Armaroli, Pho-
tochem. Photobiol. Sci. 2006, 5, 1165–1172.
[21] T. M. Figueira-Duarte, A. Gégout, J.-F. Nierengarten, Chem.
Commun. 2007, 109–119.
[22] J. N. Demas, G. A. Crosby, J. Phys. Chem. 1971, 75, 991.
[23] S. R. Meech, D. Phillips, J. Photochem. 1983, 23, 193–217.
Received: July 25, 2007
[1] G. R. Newkome, C. N. Moorefield, F. Vögtle, Dendrimers and
Dendrons: Concepts, Syntheses, Applications, VCH, Weinheim,
2001.
[2] D. M. Guldi, A. Swartz, C. P. Luo, R. Gomez, J. L. Segura, N.
Martin, J. Am. Chem. Soc. 2002, 124, 10875–10886.
Published Online: October 8, 2007
5908
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 5899–5908