Amphiphilic Diblock Dendrimers with a Fullerene Core

Article abstract of DOI:10.1021/jo035040a

Amphiphilic dendrimers with a C₆₀ core have been obtained by cyclization of dendritic 1,3-phenylenebis(methylene)-tethered bis-malonate derivatives at the carbon sphere. The relative position of the two cyclopropane rings in the resulting bis-m

Full text of DOI:10.1021/jo035040a

Am p h ip h ilic Diblock Den d r im er s w ith a F u ller en e Cor e
Sheng Zhang,†,§ Yannick Rio,†,§ Franc¸ois Cardinali,†,§ Cyril Bourgogne,†
J ean-Louis Gallani,† and J ean-Franc¸ois Nierengarten*,†,§
Groupe des Mate´riaux Organiques, Institut de Physique et Chimie des Mate´riaux de Strasbourg,
Universite´ Louis Pasteur et CNRS, UMR 7504, 23 rue du Loess, B.P. 43, 67034 Strasbourg Cedex 2,
France, and Groupe de Chimie des Fullere`nes et des Syste`mes Conjugue´s, Ecole Europe´enne de Chimie,
Polyme`res et Mate´riaux (ECPM), Universite´ Louis Pasteur et CNRS, UMR 7504 (IPCMS),
25 rue Becquerel, 67087 Strasbourg Cedex 2, France
jfnierengarten@chimie.u-strasbg.fr
Received J uly 18, 2003
Amphiphilic dendrimers with a C60 core have been obtained by cyclization of dendritic 1,3-
phenylenebis(methylene)-tethered bis-malonate derivatives at the carbon sphere. The relative
position of the two cyclopropane rings in the resulting bis-methanofullerene derivatives has been
1
determined based on the molecular symmetry (Cs) deduced from the H and 13C NMR spectra. The
hydrophobic-hydrophilic balance of these dendrimers has been systematically modified by changing
the size of the polar headgroup in order to investigate the role of the amphiphilicity both at the
air-water interface and during deposition onto solid substrates. Langmuir studies have revealed
a conformational change in the dendritic structure with the size of the polar headgroup. Because
of a better anchoring onto the water surface, the compounds with the largest polar headgroup
adopt a more compact structure and the dendritic branches are forced to wrap the fullerene core.
This model is nicely confirmed by the amount of fullerene-fullerene interactions within the
Langmuir-Blodgett films as deduced from their absorption spectra.
In tr od u ction
studies reported by Meijer and co-workers with poly-
(propylene imine) dendrimers modified with peripheral
long hydrophobic chains are of particular interest.3 They
have shown that these compounds are able to arrange
themselves in monolayers in which the dendritic poly-
(propylene imine) part acts as a polar headgroup and the
alkyl chains packed together form a hydrophobic moiety,
thus revealing the high flexibility of such dendrimers.
Langmuir films have also been obtained with several
amphiphilic dendritic molecules with a small polar head-
group at the focal point.4 Even though this has been a
convenient technique to directly determine the size of
such compounds, the stability of the films appears to be
a problem because of the difference in size between the
hydrophobic and hydrophilic groups. As a result, their
transfer onto solid substrates for the preparation of
Langmuir-Blodgett films is rather difficult.4 As part of
this research, we have recently shown that the peripheral
substitution of a diblock globular dendrimer with hydro-
phobic chains on one hemisphere and hydrophilic groups
on the other one provides a perfect hydrophobic-hydro-
philic balance allowing the formation of stable Langmuir
films.5 Furthermore, transfer experiments of the result-
ing monolayers onto solid substrates have been carried
out, and the deposition occurs regularly with a transfer
ratio of 1. In this paper, we report the synthesis of the
new amphiphilic diblock dendrimers depicted in Figure
1.
The past several years have seen a considerable
interest in the use of dendrimers at surfaces and inter-
faces.1 In particular, the preparation of Langmuir films
from amphiphilic dendrimers has been investigated by
several research groups.2-5 Studies of the behavior of
dendrimers at the air-water interface have yielded
important information about their size, shape, compress-
ibility, and flexibility.2-5 In this respect, the Langmuir
* To whom correspondence should be addressed. Phone: + 33 390
242645. Fax: + 33 390 242706.
† Institut de Physique et Chimie des Mate´riaux de Strasbourg.
§ Ecole Europe´enne de Chimie, Polyme`res et Mate´riaux (ECPM).
(1) (a) Tully, D. C.; Fre´chet, J . M. J . Chem. Commun. 2001, 1229.
(b) Bosman, A. W.; J anssen, H. M.; Meijer, E. W. Chem. Rev. 1999,
99, 1665.
(2) (a) Cardullo, F.; Diederich, F.; Echegoyen, L.; Habicher, T.;
J ayaraman, N.; Leblanc, R. M.; Stoddart, J . F.; Wang, S. Langmuir
1998, 14, 1955. (b) Maierhofer, A. P.; Brettreich, M.; Burghardt, S.;
Vostrwsky, O.; Hirsch, A.; Langridge, S.; Bayerl, T. M. Langmuir 2000,
16, 8884. (c) Bo, Z.; Rabe, J . P.; Schlu¨ter, A. D. Angew. Chem., Int. Ed.
1999, 38, 2370.
(3) (a) Schenning, A. P. H. J .; Elissen-Roman, C.; Weener, J .-W.;
Baars, M. W. P. L.; van der Gaast, S. J .; Meijer, E. W. J . Am. Chem.
Soc. 1998, 120, 8199. (b) Weener, J .-W.; Meijer, E. W. Adv. Mater. 2000,
12, 741.
(4) (a) Saville, P. M.; White, J . W.; Hawker, C. J .; Woley, K. L.;
Fre´chet, J . M. J . J . Phys. Chem. 1993, 97, 293. (b) Mulders, S. J . E.;
Brouwer, A. J .; Kimkes, P.; Sudho¨lter, E. J . R.; Liskamp, R. M. J . J .
Chem. Soc., Perkin Trans. 2 1998, 1535. (c) Kampf, J . P.; Frank, C.
W.; Malmstro¨m, E. E.; Hawker, C. J . Langmuir 1999, 15, 227. (d)
Felder, D.; Gallani, J .-L.; Guillon, D.; Heinrich, B.; Nicoud, J .-F.;
Nierengarten, J .-F. Angew. Chem., Int. Ed. 2000, 39, 201.
(5) Nierengarten, J .-F.; Eckert, J .-F.; Rio, Y.; Carreon, M. P.; Gallani,
J .-L.; Guillon, D. J . Am. Chem. Soc. 2001, 123, 9743.
10.1021/jo035040a CCC: $25.00 © 2003 American Chemical Society
Published on Web 11/15/2003
J . Org. Chem. 2003, 68, 9787-9797
9787

Zhang et al.
F IGURE 1. Fullerodendrimers 1-5.
The hydrophobic-hydrophilic balance has been sys-
tematically modified by changing the size of the polar
headgroup in order to investigate the role of the am-
phiphilicity both at the air-water interface and during
deposition onto solid substrates. In the design of these
compounds, it was also decided to use a fullerene sphere
as a photoactive core unit in order to gain more insight
into structural factors. Effectively, changes in the na-
noenvironment of the C60 chromophore dramatically
affect its electronic properties making it a sensitive probe
to demonstrate shielding effects resulting from the pres-
ence of the surrounding dendritic shell.6
Diederich and co-workers,7 which led to macrocyclic bis-
adducts of C60 by a cyclization reaction at the C sphere
with bis-malonate derivatives in a double Bingel8 cyclo-
propanation. The cyclic fullerene bis-adduct 1 with no
polar headgroup was obtained in two steps from 69 and
77b (Scheme 1). Treatment of diacid 7 with alcohol 6 and
N,N′-dicyclohexylcarbodiimide (DCC) in the presence of
4-(dimethylamino)pyridine (DMAP) and 1-hydroxyben-
zotriazole (HOBt) gave bis-malonate 8 in 76% yield.
Subsequent reaction with C60, I2, and 1,8-diazabicyclo-
[5.4.0]undec-7-ene (DBU) in toluene at room temperature
afforded the desired cyclization product 1 in 44% yield.
The preparation of the amphiphilic fullerene derivative
2 bearing an ethylene glycol chain as the polar headgroup
was achieved following a similar route. Reaction of bis-
malonic acid 910 with alcohol 6 under esterification
conditions (DCC, DMAP, HOBt) yielded bis-malonate 10.
Resu lts a n d Discu ssion
Syn th esis. All of the fullerene derivatives reported in
the present paper have been prepared by taking advan-
tage of the versatile regioselective reaction developed by
(7) (a) Nierengarten, J .-F.; Gramlich, V.; Cardullo, F.; Diederich, F.
Angew. Chem., Int. Ed. Engl. 1996, 35, 2101. (b) Nierengarten, J .-F.;
Habicher, T.; Kessinger, R.; Cardullo, F.; Diederich, F.; Gramlich, V.;
Gisselbrecht, J .-P.; Boudon, C.; Gross, M. Helv. Chim. Acta 1997, 80,
2238.
(6) (a) Rio, Y.; Accorsi, G.; Nierengarten, H.; Rehspringer, J .-L.;
Ho¨nerlage, B.; Kopitkovas, G.; Chugreev, A.; Van Dorsselaer, A.;
Armaroli, N.; Nierengarten, J .-F. New J . Chem. 2002, 26, 1146. (b)
Rio, Y.; Accorsi, G.; Nierengarten, H.; Bourgogne, C.; Strub, J .-M.; Van
Dorsselaer, A.; Armaroli, N.; Nierengarten, J .-F. Tetrahedron (Sym-
posium-in-Print on Recent Developments in Dendrimer Chemistry)
2003, 59, 3833. (c) Nierengarten, J .-F.; Armaroli, N.; Accorsi, G.; Rio,
Y.; Eckert, J .-F. Chem.sEur. J . 2003, 9, 36.
(8) Bingel, C. Chem. Ber. 1993, 126, 1957.
(9) Forier, B.; Dechaen, W. Tetrahedron 1999, 32, 9829.
(10) Felder, D.; Carreon, M. P.; Gallani, J .-L.; Guillon, D.; Nieren-
garten, J .-F.; Chuard, T.; Deschenaux, R. Helv. Chim. Acta 2001, 84,
1119.
9788 J . Org. Chem., Vol. 68, No. 25, 2003

Amphiphilic Diblock Dendrimers
SCHEME 1. P r ep a r a tion of F u ller od en d r im er s 1 a n d 2a
aReagents and conditions: (i) DCC, DMAP, HOBt, CH2Cl2, 0 °C to room temperature, 24 h (76%); (ii) DCC, DMAP, HOBt, CH2Cl2, 0
°C to room temperature, 24 h (70%); (iii) C60, I2, DBU, toluene, rt, 24 h (44%); (iv) C60, I2, DBU, toluene, rt, 24 h (42%).
Fullerodendrimer 2 was then obtained in 42% yield by
reaction of 10 with C60, I2, and DBU in toluene at room
temperature.
Treatment of 19 and 24 with 6 under DCC-mediated
esterification conditions afforded the corresponding bis-
malonates 20 and 25 in moderate yields. Actually, the
yields were limited by abnormally high proportions of
N-acyldicyclohexylurea byproducts resulting from the
rearrangement of the activated acid intermediates.13 This
is a clear indication that the reaction of the alcohol with
the activated acid is slow. The latter observation results
certainly from the reduced accessibility of the reactive
groups located at the focal point of dendritic moieties for
both reactants. Finally, treatment of C60 with 20 and 25
in the presence of I2 and DBU in toluene gave the
targeted bis-adducts 4 and 5, respectively.
The preparation of the fullerene derivative bearing two
triethylene glycol chains is depicted in Scheme 2. Treat-
ment of bromide 1111 with dimethyl 5-hydroxyisophtha-
late in the presence of K2CO3 in DMF at 70 °C afforded
12 in 82% yield. Lithium aluminum hydride (LAH)
reduction then gave diol 13, and subsequent treatment
with Meldrum’s acid12 (2,2-dimethyl-1,3-dioxane-4,6-di-
one) afforded diacid 14 in 98% yield. Reaction of alcohol
6 with diacid 14 under esterification conditions using
DCC, DMAP, and HOBt in CH2Cl2 gave bis-malonate 15
in 43% yield. Finally, reaction of 15 with C60, I2, and DBU
in toluene at room temperature afforded the bis-adduct
3 in 33% yield.
Fullerodendrimers 1-5 have been characterized by 1H
and 13C NMR, UV-vis spectroscopy, and IR spectroscopy.
In addition, the structures of 1-5 have also been con-
firmed by MALDI-TOF mass spectrometry. The relative
position of the two cyclopropane rings in 1-5 on the C60
core has been determined based on the molecular sym-
Fullerodendrimers 4 and 5 were obtained from 1611
and 21,11 respectively, by following a synthetic route
similar to the one used for the preparation of compound
3 (Schemes 3 and 4). Diacids 19 and 24 were prepared
by alkylation of dimethyl 5-hydroxyisophthalate with the
corresponding bromide followed by LAH reduction and
subsequent reaction with Meldrum’s acid.
1
metry (Cs) deduced from the H and 13C NMR spectra. It
is also well established that the 1,3-phenylenebis(meth-
ylene)-tethered bis-malonates produce regioselectively
the Cs symmetrical cis-2 addition pattern at C60.7,14 As
(11) (a) Rio, Y.; Nicoud, J .-F.; Rehspringer, J .-L.; Nierengarten, J .-
F. Tetrahedron Lett. 2000, 41, 10207. (b) Hannon, M. J .; Mayers, P.
C.; Taylor, P. C. J . Chem. Soc., Perkin Trans. 1 2000, 1881.
(12) Chen, B.-C. Heterocycles 1991, 32, 529.
(13) Kurzer, F.; Douraghi-Zadeh, K. Chem. Rev. 1967, 67, 107.
(14) (a) Nierengarten, J .-F.; Schall, C.; Nicoud, J .-F. Angew. Chem.,
Int. Ed. 1998, 37, 1934. (b) Woods, C. R.; Bourgeois, J .-P.; Seiler, P.;
Diederich, F. Angew. Chem., Int. Ed. 2000, 39, 3813.
J . Org. Chem, Vol. 68, No. 25, 2003 9789

Zhang et al.
SCHEME 2. P r ep a r a tion of F u ller od en d r im er 3a
a
Reagents and conditions: (i) dimethyl 5-hydroxyisophthalate, K2CO3, 18-crown-6, acetone, ∆, 48 h (82%); (ii) LAH, THF, 0 °C, 6 h
(88%); (iii) Meldrum’s acid, 120 °C, 4 h (quantitative); (iv) 6, DCC, DMAP, HOBt, CH2Cl2, 0 °C to room temperature, 24 h (53%); (v) C60
,
I2, DBU, toluene, rt, 24 h (33%).
typical examples, the 13C NMR spectra of compounds 1
and 5 recorded in CDCl3 are shown in Figures 2 and 3.
The colors and, accordingly, the absorption spectra of
C60 bis-adducts are highly dependent on the addition
pattern and are characteristic for each of the regioiso-
mers.14 The orange color and the UV-vis spectra of 1-5
are indeed fully consistent with those of previously
reported analogous cis-2 bis-adducts.7,15 As a typical
example, the UV-vis spectrum of fullerodendrimer 1 in
CH2Cl2 is shown in Figure 4. The absorption spectrum
is much less resolved than that of plain C60. In the UV
only one distinct band is present (λmax ) 263 nm) with
two shoulders above 300 nm, compared with the two well-
distinct bands observed for the parent C60 in the same
region.16 In the visible spectral region, the spectrum is
very broad and the band corresponding to the lowest-
allowed singlet transition, which is very sharp and well
distinguishable for C60, is barely detectable at about 437
nm.
La n gm u ir F ilm s. Compound 1 with no polar head-
group does not form any Langmuir film, even when
compressed down to unrealistic molecular areas. In
contrast, Langmuir films have been obtained with den-
drimers 2-5. Regardless of its size, the polar headgroup
of these compounds is responsible for an attractive
interaction with the aqueous subphase thus forcing the
The spectrum of 1 is in full accordance with the
proposed molecular structure. The 32 expected fullerene
resonances are clearly observed: two at δ ) 66.77 and
70.57 for the two different sp3 C atoms and 30 between
δ ) 134 and 146 for the 30 different sp2 C atoms. It is
worth noting that four of the resonances seen in the sp2
region show half-intensity signals. Actually, the latter
observation is an unambiguous proof for the Cs symmetry
of compound 1. Effectively, for such a C60 derivative, there
are 26 pairs of equivalent sp2 fullerene C atoms and four
unique ones. The 35 expected non-fullerenic signals are
also observed for Cs symmetrical 1. Interestingly, the
aromatic C atoms of the dendritic wedges appear as four
groups of three signals having a 4:2:1 relative intensity
in perfect agreement with their branched structure. The
13C NMR spectrum of fullerodendrimer 5 shows the same
characteristic features as 1 with additional signals aris-
ing from the additional dendritic unit. It can be noted
that the patterns seen for the fullerene C atoms in the
sp2 region are nearly identical for both 1 and 5. Actually,
the same pattern is also observed in the 13C NMR spectra
of 2-4, thus showing that the relative position of the two
cyclopropane rings on the C60 core is the same for the
five compounds.
(15) Hirsch, A.; Lamparth, I. S.; Karfunkel, H. R. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 437.
9790 J . Org. Chem., Vol. 68, No. 25, 2003

Amphiphilic Diblock Dendrimers
SCHEME 3. P r ep a r a tion of F u ller od en d r im er 4a
a
Reagents and conditions: (i) dimethyl 5-hydroxyisophthalate, K2CO3, 18-crown-6, acetone, ∆, 48 h (87%); (ii) LAH, THF, 0 °C, 6 h
(89%); (iii) Meldrum’s acid, 120 °C, 4 h (quantitative); (iv) 6, DCC, DMAP, HOBt, CH2Cl2, 0 °C to room temperature, 24 h (41%); (v) C60
,
I2, DBU, toluene, rt, 24 h (30%).
molecules toward the water surface in a two-dimensional
arrangement. The pressure/area (Π/A) isotherms of ful-
lerodendrimers 2-5 are depicted in Figure 5.
be more effective in the case of 4 and 5, and as a result,
the molecules adopt a more compact structure. In other
words, the two C12H25-terminated dendritic branches are
forced to wrap the fullerene core. In contrast, for com-
pounds 2 and 3 the dendritic structure may be less
densely packed around the central fullerene core because
of the weaker anchoring on the water surface. This model
is further supported by observations done on the Lang-
muir-Blodgett films prepared from the Langmuir films
of compounds 2-5 (discussed later). The larger molecular
area observed for compound 3 compared to 2 seems,
however, to be in contradiction with the proposed model.
Actually, it must be noted that the unique ethylene glycol
subunit in 2 is directly connected to the bridging phenyl
ring, whereas the two polar chains in 3 are separated
from the core unit by an additional benzylic moiety.
Therefore, even if the anchoring on the water is weaker
for 2 compared to 3, the two dodecyloxy-functionalized
dendrons are closer to the aqueous surface in the case of
2. As a result, the repulsion of the dendritic branches
from the water surface must be slightly more effective
for 2. Therefore, this compound adopts a more compact
structure and its molecular area is smaller.
The four compounds exhibit a similar behavior: the
surface pressure Π increases smoothly at molecular areas
between 400 and 500 Å2 before taking a sharper rise
between 250 and 350 Å2, depending on the compound.
The general shape of the isotherms indicates that the
films are at first in a liquid-condensed phase. The rather
big molecular areas at which the molecules start to
physically interact are not surprising given the size of
these molecules and the fact that alkyl chains and C60
will initially tend to segregate, pushing the alkyl chains
away from the core. The molecules have, therefore, a
rather large radius on the water surface before being
forced to adopt a more compact conformation because of
the compression. Such behavior has already been ob-
served.5 Final molecular areas, A0, extrapolated at zero
surface pressure are 307 ( 3 (2), 320 ( 3 (3), 295 ( 3
(4), and 280 ( 3 Å2 (5) which are in good agreement with
the value which can be estimated by molecular modeling.
Interestingly, the A0 values are smaller for the two
compounds with the largest polar headgroup (4 and 5).
The latter observation could be ascribed to a conforma-
tional change in the dendritic structure when the anchor-
ing on the water surface is stronger. The repulsion of the
C12H25-terminated dendrons from the water surface must
Upon further compression all films reach a final
collapse pressure Πc which strongly depends on the size
of the polar headgroup. Let us mention here that the
isotherms of 2-5 showed excellent reversibility (no
J . Org. Chem, Vol. 68, No. 25, 2003 9791

Zhang et al.
SCHEME 4. P r ep a r a tion of F u ller od en d r im er 5a
a
Reagents and conditions: (i) dimethyl 5-hydroxyisophthalate, K2CO3, 18-crown-6, acetone, ∆, 48 h (85%); (ii) LAH, THF, 0 °C, 6 h
(91%); (iii) Meldrum’s acid, 120 °C, 4 h (quantitative); (iv) 6, DCC, DMAP, HOBt, CH2Cl2, 0 °C to room temperature, 24 h (25: 35%); (v)
C
60, I2, DBU, toluene, rt, 24 h (36%).
F IGURE 2. 13C NMR spectrum (CDCl3, 50 MHz) of fullerodendrimer 1 (/ indicates the four sp2 fullerene C atoms showing
half-intensity signals).
hysteresis) as long as the collapse pressure was not
exceeded. The following Πc values have been taken at the
point where the compressibility of the film starts to
decrease: 10.5 ( 1.0 (2), 30.5 ( 1.0 (3), 41 ( 1.0 (4), and
42.5 ( 1.0 mN‚m-1 (5). For a given compound, the Πc
values obtained from different films did not vary signifi-
cantly. Changes in the collapse pressure with the number
of ethylene glycol subunits show how critically the
strength of the polar headgroup needs to match that of
the hydrophobic part. Put in an Orwellian style: no head,
no film; small head, weak films. The only films able to
withstand a significant compression before collapsing are
9792 J . Org. Chem., Vol. 68, No. 25, 2003

Amphiphilic Diblock Dendrimers
F IGURE 3. 13C NMR spectrum (CDCl3, 50 MHz) of fullerodendrimer 5.
F IGUR E 4. Absorption spectrum of fullerodendrimer
1
recorded in CH2Cl2 solution.
F IGURE 6. Brewster angle microscopy images for Langmuir
films: (a) 2 at A ) 840 Å2; (b) 3 at A ) 900 Å2; (c) 5 at A ) 530
Å2; (d) 5 at A ) 211 Å2. The dark areas are the water subphase,
the fringes are caused by the laser light.
compound 4 with four ethylene glycol chains to compound
5 with eight chains. This is because even perfectly
anchored films will start buckling because of their limited
rigidity.
Microscopy at the Brewster angle (BAM) allows for
visual observation of film formation at a microscopic level.
Except for 1, observations reveal a very similar behavior
for the different compounds. At large molecular areas,
the films are in the liquid-expanded state, with the
molecules assembled in smooth-edged domains sur-
rounded by water (Figure 6a). These domains are not
solid, and lots of “holes” remain through which water can
be seen (Figure 6b). Upon further compression, being
liquid, all of these domains gently merge together (Figure
6c) and the final film exhibits no defects (Figure 6d). It
must be emphasized that just before the final collapse,
films from all compounds were identical to the one
pictured in Figure 6d.
F IGURE 5. Pressure/area isotherms of compounds 2-5 taken
on pure water at 20 °C. The collapse pressure increases with
the size of the polar headgroup.
those for which the hydrophilic force anchoring the
molecules on the water balances the hydrophobic forces.
It is interesting to note that there is no significant
improvement of the collapse pressure when going from
J . Org. Chem, Vol. 68, No. 25, 2003 9793

Zhang et al.
F IGURE 7. Absorption spectra of LB films of 2 and 5.
La n gm u ir -Blod gett F ilm s. When the Langmuir-
Blodgett (LB) technique is used, it has been possible to
transfer the Langmuir films made from 2-5 and to
obtain multilayers on solid substrates. In accordance with
previous observations,5 transfer is more efficient upon
increasing the size of the polar headgroup. The excellent
quality of the LB films prepared from these amphiphilic
dendrimers is deduced from the plot of their UV-vis
absorbance as a function of the layer number which
results in straight lines, indicating an efficient stacking
of the layers.17 The UV-vis spectra of the LB films
obtained from 2 and 5 are shown in Figure 7.
F IGURE 8. Snapshot of the theoretical structure of fullero-
dendrimer 5 at 300 K obtained from a molecular dynamics
calculation.19
studies.19 As shown in Figure 8, the calculated structure
of fullerodendrimer 5 reveals that the dendritic shell is
effectively able to completely cover the fullerene core (the
calculations have been performed in the absence of
solvent, our aim being only to estimate the possible
degree of isolation).
The main feature of the UV-vis spectrum of the LB
film of 2 is the broadening of the absorption in the film
compared to that of the solution. The latter observation
is indicative of fullerene-fullerene interactions within
the LB films.18 Because of the presence of the dendritic
subunits around the C60 core within a layer, we believe
that these fullerene-fullerene interactions may be the
result of the contact of carbon spheres from neighboring
layers rather than from within the layers. The absorption
spectra of LB films prepared from compound 3 (not
shown) are also broad. Remarkably, a clear evolution can
be seen by going from 2 to 5: the broadening of the
absorption spectrum seen for 2 is almost vanished for 4
and 5. Actually, the UV-vis spectra of LB films of 4 and
5 are close to the ones recorded in CH2Cl2 solutions
suggesting limited fullerene-fullerene interactions with-
in the LB film. This observation is in full agreement
with the more compact structures proposed for 4 and 5
at the air-water interface compared to 2 and 3. The
latter hypothesis was also confirmed by computational
Con clu sion
Amphiphilic diblock dendrimers with a C60 core have
been obtained by cyclization of dendritic bis-malonate
derivatives at the carbon sphere. All of the amphiphilic
derivatives show good spreading characteristics and a
reversible behavior upon successive compression-expan-
sion cycles. The Langmuir studies have revealed a
conformational change in the dendritic structure with the
size of the polar headgroup. Because of a better anchoring
onto the water surface, the compounds with the largest
polar headgroup adopt a more compact structure and the
dendritic branches are forced to wrap the fullerene core.
This model is nicely confirmed by the amount of fullerene-
fullerene interactions within the LB films as deduced
from their absorption spectra. On the one hand, the
results obtained in this systematic study show some of
the fundamental architectural requirements for obtaining
stable Langmuir films with amphiphilic dendrimers. On
the other hand, it is worth noting that the fullerene
chromophores are almost isolated from external contacts
by the dendritic structure thus paving the way toward
ordered thin films of isolated functional molecular units.
This appears to be an important finding for future
nanotechnological applications, in particular, for data
storage at a molecular level.
(16) Armaroli, N.; Boudon, C.; Felder, D.; Gisselbrecht, J .-P.; Gross,
M.; Marconi, G.; Nicoud, J .-F.; Nierengarten, J .-F.; Vicinelli, V. Angew.
Chem., Int. Ed. 1999, 38, 3730.
(17) The structural quality of the LB films was also probed by
preliminary grazing incidence X-ray diffraction measurements. In all
of the spectra, many Kiessig fringes can be seen, which is evidence
that the film roughness is quite low (typically R ≈ 5.5 Å). Further
experiments are still in progress and will be reported in due time.
(18) (a) Guldi, D. M.; Hungerbu¨hler, H.; Asmus, K.-D. J . Phys. Chem.
1995, 99, 13487. (b) J onas, U.; Cardullo, F.; Belik, P.; Diederich, F.;
Gu¨gel, A.; Harth, E.; Herrmann, A.; Isaacs, L.; Mu¨llen, K.; Ringsdorf,
H.; Thielgen, C.; Uhlmann, P.; Vasella, A.; Waldraff, C. A. A.; Walter,
M. Chem.sEur. J . 1995, 1, 243. (c) Guldi, D. M. J . Phys. Chem. A 1997,
101, 3895. (d) Guldi, D. M.; Hungerbu¨hler, H.; Asmus, K.-D. J . Phys.
Chem. A 1997, 101, 1783. (e) Felder, D.; Guillon, D.; Le´vy, R.; Mathis,
A.; Nicoud, J .-F.; Nierengarten, J .-F.; Rehspringer, J .-L.; Schell, J . J .
Mater. Chem. 2000, 10, 887. (f) Felder, D.; Gutie´rrez Nava, M.;
Carreon, M. P.; Eckert, J .-F.; Luccisano, M.; Schall, C.; Masson, P.;
Gallani, J .-L.; Heinrich, B.; Guillon, D.; Nierengarten, J .-F. Helv. Chim.
Acta 2002, 85, 288.
(19) The molecular dynamics (MD) studies have been performed on
SGI Origin 200 and Octane workstations using the Discover 3 software
from Accelrys (www.accelrys.com) with the pcff force field. The
previously minimized structures were allowed to equilibrate for 500
ps at a 300 K isotherm by the MD simulation (in the NVT ensemble
with a time step of 1 fs).
9794 J . Org. Chem., Vol. 68, No. 25, 2003

Amphiphilic Diblock Dendrimers
(s, 12 H). 13C NMR (CDCl3, 50 MHz, δ): 159.7, 159.6, 158.5,
142.8, 139.2, 138.8, 117.2, 111.6, 105.7, 105.6, 101.2, 100.7,
71.5, 70.4, 70.2, 70.1, 69.5, 69.3, 67.1, 64.2, 62.0, 58.6. Anal.
Calcd for C57H84O21: C, 61.94; H, 7.66. Found: C, 61.61; H,
7.83.
Exp er im en ta l Section
Gen er a l. Reagents and solvents were purchased as reagent
grade and used without further purification. THF was distilled
over sodium benzophenone ketyl. Compounds 6,9 7,7b 9,10 11,11
16,11 and 2111 were prepared as previously reported.
Gen er a l P r oced u r e for th e Syn th esis of Diester s 12,
17, a n d 22. A mixture of dimethyl 5-hydroxyisophthalate (1
equiv), the appropriate bromide (1 equiv), K2CO3 (5 equiv), and
18-crown-6 (0.5 equiv) in acetone was refluxed for 48 h. The
resulting mixture was diluted with CH2Cl2, filtered, and
evaporated. The crude product was then purified as outlined
in the following text.
Diol 23. This compound was prepared from 22 and purified
by column chromatography (SiO2, acetone/CH2Cl2 7:3) to give
1
23 (91%) as a colorless glassy product. H NMR (CDCl3, 200
MHz, δ): 6.95 (s, 1 H), 6.88 (s, 2 H), 6.65 (broad s, 4 H), 6.57
(broad s, 13 H), 6.44 (broad s, 4 H), 4.97 (s, 14 H), 4.63 (d, 4
H), 4.10 (m, 16 H), 3.83 (m, 16 H), 3.75-3.50 (m, 64 H), 3.37
(s, 24 H). 13C NMR (CDCl3, 50 MHz, δ): 159.4, 159.3, 158.3,
142.7, 139.0, 138.7, 138.5, 116.9, 111.1, 105.7, 105.3, 100.9,
100.4, 71.2, 70.9, 70.1, 69.9, 69.8, 69.2, 69.0, 66.8, 63.7, 58.3.
Anal. Calcd for C113H164O41‚H2O: C, 61.79; H, 7.62. Found: C,
61.52; H, 7.89.
Diester 12. This compound was prepared from 11 and
purified by column chromatography (SiO2, acetone/CH2Cl2 4:1)
to give 12 (82%) as a colorless glassy product. IR (CH2Cl2,
1
cm-1): 1725. H NMR (CDCl3, 200 MHz, δ): 8.30 (t, J ) 1.5
Gen er a l P r oced u r e for th e Syn th esis of Dia cid s 14, 19,
a n d 24. A mixture of Meldrum’s acid (2 equiv) and the
appropriate diol (1 equiv) was heated at 120 °C for 4 h. Cooling
and drying afforded the corresponding diacid which was used
in the next step as received. Compounds 14, 19, and 24 have
been characterized by 1H NMR spectroscopy; the spectra being
typically broad, they are not described here.
Hz, 1 H), 7.82 (d, J ) 1.5 Hz, 2 H), 6.60 (d, J ) 2 Hz, 2 H),
6.46 (t, J ) 2 Hz, 1 H), 5.07 (s, 2 H), 4.12 (m, 4 H), 3.95 (s, 6
H), 3.85 (m, 4 H), 3.75-3.50 (m, 16 H), 3.38 (s, 6H). 13C NMR
(CDCl3, 50 MHz, δ): 165.22, 159.57, 158.02, 137.79, 131.15,
122.48, 119.39, 105.34, 100.63, 71.32, 70.19, 70.03, 69.93,
69.53, 69.02, 66.91, 58.33, 51.77. Anal. Calcd for C31H44O13
C, 59.60; H, 7.10. Found: C, 59.62; H, 7.26.
:
Diester 17. This compound was prepared from 16 and
purified by column chromatography (SiO2, acetone/CH2Cl2 3:7)
to give 17 (1.07 g, 87%) as a colorless glassy product. IR (CH2-
Gen er a l P r oced u r e for th e Syn th esis of Bis-Ma lon a tes
8, 10, 15, 20, a n d 25. DCC (2.2 equiv) was added to a stirred
solution of 6 (2 equiv), the appropriate diacid (1 equiv), HOBt
(0.1 equiv), and DMAP (0.5 equiv) in CH2Cl2 at 0 °C. After 1
h, the mixture was allowed to slowly warm to room temper-
ature (within 1 h), then stirred for 24 h, filtered, and
evaporated. The crude product was then purified as outlined
in the following text.
1
Cl2, cm-1): 1725 (CdO). H NMR (CDCl3, 200 MHz, δ): 8.30
(t, J ) 1.5 Hz, 1 H), 7.82 (d, J ) 1.5 Hz, 2 H), 6.66 (d, J ) 1.5
Hz, 2 H), 6.59 (d, J ) 1.5 Hz, 4 H), 6.56 (t, J ) 1.5 Hz, 1 H),
6.45 (t, J ) 1.5 Hz, 2 H), 5.08 (s, 2 H), 4.96 (s, 4 H), 4.12 (m,
8 H), 3.95 (s, 6 H), 3.82 (m, 8 H), 3.75-3.50 (m, 32 H), 3.38 (s,
12 H). 13C NMR (CDCl3, 50 MHz, δ): 164.9, 159.3, 159.3, 157.8,
138.4, 137.8, 130.9, 122.2, 119.1, 105.5, 105.1, 100.9, 100.8,
71.1, 70.0, 69.8, 69.7, 69.3, 69.2, 68.8, 66.7, 58.1, 51.6. Anal.
Calcd for C59H84O23: C, 61.02; H, 7.29. Found: C, 61.13; H,
7.56.
Bis-Ma lon a te 8. This compound was prepared from 7 and
purified by column chromatography (SiO2, CH2Cl2/hexane 2:1)
to give 8 (76%) as a colorless glassy compound. IR (CH2Cl2,
cm-1): 1748 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 7.29 (m, 4
H), 6.66 (broad s, 8 H), 6.55 (broad s, 26 H), 6.40 (broad s, 8
H), 5.16 (s, 4 H), 5.10 (s, 4 H), 4.95 (broad s, 24 H), 3.93 (t, J
) 6.5 Hz, 32 H), 3.47 (s, 4 H), 1.77-1.73 (m, 32 H), 1.50-1.20
(m, 288 H), 0.90-0.87 (t, J ) 6.5 Hz, 48 H). Anal. Calcd for
Diester 22. This compound was prepared from 21 and
purified by column chromatography (SiO2, acetone/CH2Cl2 1:1)
to give 27 (85%) as a colorless glassy product. IR (CH2Cl2,
cm-1): 1725 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 8.30 (broad
s, 1 H), 7.82 (broad s, 2 H), 6.68 (broad s, 4 H), 6.60 (broad s,
13 H), 6.45 (broad s, 4 H), 5.03 (s, 2 H), 4.96 (s, 12 H), 4.11
(m, 16 H), 3.95 (s, 6 H), 3.82 (m, 16 H), 3.75-3.50 (m, 64 H),
3.38 (s, 24 H). 13C NMR (CDCl3, 50 MHz, δ): 165.1, 159.4,
159.4, 158.0, 138.6, 138.5, 137.9, 122.4, 119.3, 105.6, 105.3,
100.8, 100.3, 71.2, 70.1, 69.9, 69.8, 69.4, 69.2, 68.9, 66.8, 50.7.
Anal. Calcd for C115H164O43: C, 61.81; H, 7.40. Found: C, 61.83;
H, 7.69.
Gen er a l P r oced u r e for th e P r ep a r a tion of Diols 13,
18, a n d 23. A 1 M LiAlH4 solution in THF (2 equiv) was added
to a stirred solution of the appropriate diester (1 equiv) in THF
at 0 °C. The resulting mixture was stirred for 6 h at 0 °C, and
then MeOH was carefully added. The reaction mixture was
filtered and evaporated. The crude product was then purified
as outlined in the following text.
C
304H478O36: C, 77.47; H, 10.31. Found: C, 77.51; H, 10.60.
Bis-Ma lon a te 10. This compound was prepared from 9 and
purified by column chromatography (SiO2, acetone/CH2Cl2 3:2)
to give 10 (70%) as a colorless glassy compound. IR (CH2Cl2,
cm-1): 1749 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 6.86 (broad
s, 3 H), 6.66 (broad s, 8 H), 6.54 (broad s, 26 H), 6.39 (broad s,
8 H), 5.11 (broad s, 8 H), 4.93 (broad s, 24 H), 4.11 (m, 2 H),
3.91 (t, 32 H, J ) 6.5 Hz), 3.85 (m, 2 H), 3.60-3.40 (m, 8 H),
3.37 (s, 3 H), 3.34 (s, 4 H), 1.75 (m, 32 H), 1.50-1.20 (m, 288
H), 0.88 (t, J ) 6.5 Hz, 48 H). Anal. Calcd for C311H496O40: C,
76.62; H, 10.25. Found: C, 76.18; H, 10.51.
Bis-Ma lon a te 15. This compound was prepared from 14
and purified by column chromatography (SiO2, CH2Cl2/acetone
97:3) to give 15 (53%) as a colorless glassy product. IR (CH2-
1
Cl2, cm-1): 1748 (CdO). H NMR (CDCl3, 200 MHz, δ): 6.90
Diol 13. This compound was prepared from 12 and purified
by column chromatography (SiO2, CH2Cl2/MeOH 9:1) to give
(broad s, 3 H), 6.66 (broad s, 8 H), 6.54 (broad s, 28 H), 6.40
(broad s, 9 H), 5.11 (broad s, 8 H), 4.93 (broad s, 26 H), 4.11
(m, 4 H), 3.92 (t, J ) 6.5 Hz, 32 H), 3.78 (m, 4 H), 3.75-3.50
(m, 16 H), 3.38 (s, 6 H), 3.32 (s, 4 H), 1.76 (m, 32 H), 1.50-
1.20 (m, 288 H), 0.88 (t, J ) 6.5 Hz, 48 H). Anal. Calcd for
1
13 (88%) as a colorless glassy product. H NMR (CDCl3, 200
MHz, δ): 6.94 (t, J ) 1.5 Hz, 1 H), 6.91 (d, J ) 1.5 Hz, 2 H),
6.59 (d, J ) 2 Hz, 1 H), 6.43 (t, J ) 2 Hz, 2 H), 5.02 (s, 2 H),
4.66 (d, J ) 5.5 Hz, 2 H), 4.11 (m, 4 H), 3.83 (m, 4 H), 3.50-
3.75 (m, 16 H), 3.38 (s, 6H). 13C NMR (CDCl3, 50 MHz, δ):
159.5, 158.3, 142.7, 139.0, 117.1, 111.1, 105.5, 100.4, 71.3, 70.2,
70.1, 70.0, 69.1, 66.9, 63.9, 58.5. Anal. Calcd for C29H44O11: C,
61.25; H, 7.80. Found: C, 61.01; H, 7.99.
C
325H516O45: C, 75.89; H, 10.11. Found: C, 75.68; H, 10.39.
Bis-Ma lon a te 20. This compound was prepared from 19
and purified by column chromatography (SiO2, CH2Cl2/acetone
5:1) to give 20 (41%) as a colorless glassy product. IR (CH2-
1
Cl2, cm-1): 1748 (CdO). H NMR (CDCl3, 200 MHz, δ): 6.90
Diol 18. This compound was prepared from 17 and purified
by column chromatography (SiO2, acetone/CH2Cl2 7:3) to give
(broad s, 3 H), 6.66 (broad s, 8 H), 6.54 (broad s, 34 H), 6.39
(broad s, 9 H), 5.11 (broad s, 8 H), 4.93 (broad s, 30 H), 4.10
(m, 8 H), 3.92 (t, J ) 6.5 Hz, 32 H), 3.80 (m, 8 H), 3.75-3.50
(m, 32 H), 3.36 (s, 12 H), 3.32 (s, 4 H), 1.76 (m, 32 H), 1.50-
1.20 (m, 288 H), 0.88 (t, J ) 6.5 Hz, 48 H). Anal. Calcd for
1
18 (89%) as a colorless glassy product. H NMR (CDCl3, 200
MHz, δ): 6.95 (broad s, 1 H), 6.82 (broad s, 2 H), 6.59 (broad
s, 2 H), 6.55 (d, J ) 1.5 Hz, 4 H), 6.54 (broad s, 1 H), 6.43 (t,
J ) 1.5 Hz, 2 H), 5.03 (s, 2 H), 4.97 (s, 4 H), 4.64 (d, J ) 6 Hz,
2 H), 4.13 (m, 8 H), 3.82 (m, 8 H), 3.75-3.50 (m, 32 H), 3.38
C
353H552O55: C, 74.70; H, 9.80. Found: C, 74.58; H, 10.05.
J . Org. Chem, Vol. 68, No. 25, 2003 9795

Zhang et al.
Bis-Ma lon a te 25. This compound was prepared from 24
and purified by column chromatography (SiO2, CH2Cl2/acetone
5:1) to give 25 (35%) as a colorless glassy product. IR (CH2-
J ) 14 Hz, 4 H), 5.05 (d, J ) 14 Hz, 2 H), 4.90 (broad s, 26 H),
4.12 (m, 4 H), 3.91 (t, J ) 6.5 Hz, 32 H), 3.85-3.50 (m, 20 H),
3.38 (s, 6 H), 1.75 (m, 32 H), 1.50-1.20 (m, 288 H), 0.88 (t, J
) 6.5 Hz, 48 H). 13C NMR (CDCl3, 50 MHz, δ): 162.5, 160.4,
160.1, 160.0, 158.8, 148.6, 147.3, 146.0, 145.7, 145.5, 145.3,
145.1, 144.8, 144.5, 144.2, 144.1, 143.9, 143.7, 143.5, 143.1,
142.6, 141.1, 140.9, 140.0, 138.8, 138.6, 138.1, 137.9, 136.9,
135.6, 112.7, 107.7, 106.6, 106.5, 105.8, 102.4, 101.7, 100.8,
77.2, 71.9, 70.8, 70.6, 70.5, 70.1, 69.6, 68.0, 67.5, 66.8, 59.0,
49.2, 31.9, 31.6, 29.4, 29.3, 26.1, 21.8, 14.1. MALDI-TOF-MS
(m/z): [M + H]+ calcd for C385H512O45, 5861.3; found, 5862.
Anal. Calcd for C385H512O45: C, 78.91; H, 8.81. Found: C, 78.32;
H, 8.51.
1
Cl2, cm-1): 1748 (CdO). H NMR (CDCl3, 200 MHz, δ): 6.90
(broad s, 3 H), 6.66-6.38 (m, 63 H), 5.14 (broad s, 8 H), 4.91
(broad s, 38 H), 4.09 (m, 16 H), 3.92 (t, J ) 6.5 Hz, 32 H), 3.81
(m, 16 H), 3.75-3.50 (m, 64 H), 3.36 (s, 24 H), 3.32 (s, 4 H),
1.75 (m, 32 H), 1.50-1.20 (m, 288 H), 0.87 (t, J ) 6.5 Hz, 48
H). Anal. Calcd for C353H552O55: C, 72.74; H, 9.49. Found: C,
72.40; H, 9.78.
Gen er a l P r oced u r e for th e Syn th esis of F u ller od en -
d r im er s 1-5. DBU (4 equiv) was added to a stirred solution
of C60 (1 equiv), I2 (3 equiv), and the appropriate bis-malonate
(1 equiv) in toluene (2 mL/mg of C60). The resulting solution
was stirred for 24 h, then filtered through a short plug of SiO2,
and eluted first with toluene (to remove unreacted C60) and
then with CH2Cl2/8% MeOH. The crude product was then
purified as outlined in the following text.
F u ller od en d r im er 4. This compound was prepared from
15 and purified by column chromatography (SiO2, CH2Cl2/
acetone 9:1) followed by gel permeation chromatography
(Biorad, Biobeads SX-1, CH2Cl2) to give 4 (30%) as an orange
glassy compound. UV-vis (CH2Cl2) λmax, nm (ꢀ): 437 (2950),
380 (sh, 9750), 327 (sh, 27 450), 263 (91 500). IR (CH2Cl2,
cm-1): 1749 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 7.10 (broad
s, 1 H), 6.79 (broad s, 2 H), 6.63 (broad s, 8 H), 6.54 (broad s,
34 H), 6.39 (broad s, 9 H), 5.74 (d, J ) 14 Hz, 2 H), 5.24 (AB,
J ) 14 Hz, 4 H), 5.03 (d, J ) 14 Hz, 2 H), 4.90 (broad s, 30 H),
4.11 (m, 8 H), 3.91 (t, J ) 6.5 Hz, 32 H), 3.85-3.50 (m, 40 H),
3.37 (s, 12 H), 1.75 (m, 32 H), 1.50-1.20 (m, 288 H), 0.88 (t, J
) 6.5 Hz, 48 H). 13C NMR (CDCl3, 50 MHz, δ): 162.6, 160.5,
160.1, 160.0, 159.9, 158.8, 148.6, 147.3, 147.2, 146.0, 145.9,
145.7, 145.5, 145.2, 145.1, 144.9, 144.8, 144.5, 144.2, 144.1,
144.0, 143.9, 143.7, 143.5, 143.1, 142.6, 142.3, 141.1, 140.9,
140.0, 139.0, 138.8, 138.2, 137.9, 136.9, 135.8, 135.5, 134.3,
112.5, 107.7, 106.5, 106.1, 105.8, 102.4, 101.7, 101.1, 100.8,
77.2, 75.2, 71.9, 70.8, 70.6, 70.5, 70.1, 69.9, 69.7, 68.0, 67.5,
66.8, 59.0, 49.1, 31.9, 29.7, 29.6, 29.4, 29.3, 29.2, 26.1, 23.0,
F u ller od en d r im er 1. This compound was prepared from
8 and purified by column chromatography (SiO2, toluene/
hexane 2:1) followed by gel permeation chromatography (Bio-
rad, Biobeads SX-1, CH2Cl2) to give 1 (44%) as a dark-orange
glassy product. UV-vis (CH2Cl2) λmax, nm (ꢀ): 437 (2000), 382
(sh, 8200), 323 (sh, 23 600), 263 (85 600). IR (CH2Cl2, cm-1):
1751 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 7.40 (m, 4 H),
6.69 (broad s, 8 H), 6.52 (broad s, 26 H), 6.41 (broad s, 8 H),
5.84 (d, J ) 14 Hz, 2 H), 5.20 (AB, J ) 14 Hz, 4 H), 5.06 (d, J
) 14 Hz, 2 H), 4.93-4.86 (m, 24 H), 3.92 (t, J ) 6.5 Hz, 32 H),
1.76 (m, 32 H), 1.50-1.22 (m, 288 H), 0.88 (t, J ) 6.5 Hz, 48
H). 13C NMR (CDCl3, 50 MHz, δ): 162.6, 162.0, 160.4, 160.1,
159.9, 145.9, 145.8, 145.6, 145.5, 145.4, 145.1, 145.0, 144.9,
144.7, 144.6, 144.4, 144.1, 144.0, 143.9, 143.8, 143.6, 143.4,
143.0, 142.5, 142.2, 141.0, 140.8, 139.9, 138.8, 138.7, 137.8,
136.8, 136.5, 135.8, 135.5, 134.26, 128.8, 126.7, 123.6, 107.6,
106.4, 105.6, 102.3, 101.6, 100.7, 70.6, 70.1, 70.0, 68.4, 67.9,
67.3, 66.8, 49.1, 31.8, 29.6, 29.6, 29.55, 29.5, 29.4, 29.3, 29.2,
26.0, 22.6, 14.0. MALDI-TOF-MS (m/z): [M + H]+ calcd for
14.1. MALDI-TOF-MS (m/z): [M + H]+ calcd for C413H553O55
,
6397.9; found, 6399. Anal. Calcd for C413H552O55: C, 77.55; H,
8.70. Found: C, 77.46; H, 8.49.
F u ller od en d r im er 5. This compound was prepared from
24 and purified by column chromatography (SiO2, CH2Cl2/
acetone 8:2) followed by gel permeation chromatography
(Biorad, Biobeads SX-1, CH2Cl2) to give 5 (36%) as an orange
glassy compound. UV-vis (CH2Cl2) λmax, nm (ꢀ): 438 (3000),
382 (sh, 9800), 327 (sh, 28 100), 263 (92 500). IR (CH2Cl2,
cm-1): 1748 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 7.15 (broad
s, 1 H), 6.76 (broad s, 2 H), 6.70-6.35 (m, 63 H), 5.73 (d, J )
14 Hz, 2H), 5.22 (AB, J ) 14 Hz, 4 H), 5.02 (d, J ) 14 Hz,
2H), 4.90 (m, 38 H), 4.10 (m, 16 H), 3.89 (t, J ) 6.5 Hz, 32 H),
3.83 (m, 16 H), 3.75-3.50 (m, 64 H), 3.36 (s, 24 H), 1.74 (m,
32 H), 1.50-1.20 (m, 288 H), 0.87 (t, J ) 6.5 Hz, 48 H). 13C
NMR (CDCl3, 50 MHz, δ): 162.6, 162.5, 160.4, 160.0, 159.9,
158.8, 148.6, 147.3, 145.9, 145.8, 145.6, 145.5, 145.4, 145.2,
145.0, 144.9, 144.7, 144.4, 144.2, 144.1, 144.0, 143.9, 143.6,
143.4, 143.0, 142.7, 142.5, 142.2, 142.0, 141.7, 141.0, 140.9,
140.0, 139.0, 138.9, 138.8, 138.2, 137.8, 136.8, 135.7, 135.4,
134.2, 112.4, 107.7, 106.5, 106.0, 105.7, 102.4, 101.6, 101.1,
100.7, 77.2, 71.8, 70.7, 70.6, 70.5, 70.0, 69.6, 68.0, 67.4, 66.7,
58.9, 49.2, 31.8, 31.5, 29.6, 29.5, 29.4, 29.3, 29.2, 26.0, 22.6,
C
364H479O36,5430.8;found,5430.5.Anal.Calcd for C364H478O36‚CH2-
Cl2: C, 79.50; H, 8.77. Found: C, 79.35; H, 8.80.
F u ller od en d r im er 2. This compound was prepared from
10 and purified by column chromatography (SiO2, CH2Cl2)
followed by gel permeation chromatography (Biorad, Biobeads
SX-1, CH2Cl2) to give 2 (42%) as a dark-orange glassy product.
UV-vis (CH2Cl2) λmax, nm (ꢀ): 438 (2560), 381 (sh, 8750), 326
(sh, 24 100), 262 (87 200). IR (CH2Cl2, cm-1): 1751 (CdO). 1H
NMR (CDCl3, 200 MHz, δ): 7.10 (broad s, 1 H), 6.77 (broad s,
2 H), 6.63 (broad s, 8 H), 6.54 (broad s, 26 H), 6.39 (broad s, 8
H), 5.75 (d, J ) 14 Hz, 2 H), 5.25 (AB, J ) 14 Hz, 4 H), 5.04
(d, J ) 14 Hz, 2 H), 4.91 (broad s, 24 H), 4.09 (m, 2 H), 3.91 (t,
32 H, J ) 6.5 Hz), 3.80 (m, 2 H), 3.70-3.40 (m, 8 H), 3.37 (s,
3 H), 1.75 (m, 32 H), 1.50-1.20 (m, 288 H), 0.88 (t, J ) 6.5
Hz, 48 H). 13C NMR (CDCl3, 50 MHz, δ): 162.6, 162.5, 160.5,
160.1, 160.0, 158.8, 148.6, 147.3, 147.3, 147.2, 146.0, 145.9,
145.7, 145.6, 145.5, 145.2, 145.1, 145.0, 144.8, 144.4, 144.2,
144.1, 143.9, 143.7, 143.5, 143.1, 142.6, 142.3, 141.1, 140.9,
140.0, 138.8, 138.1, 137.1, 136.9, 135.9, 135.5, 134.1, 115.1,
112.5, 107.7, 106.5, 105.7, 102.4, 101.7, 100.8, 71.9, 70.8, 70.6,
70.5, 70.2, 70.1, 69.6, 68.5, 68.0, 67.5, 67.3, 66.8, 59.0, 49.1,
31.9, 29.7, 29.6, 29.5, 29.4, 29.3, 26.1, 22.7, 14.1. MALDI-TOF-
MS (m/z): [M + H]+ calcd for C371H493O40, 5593.0; found, 5593.
Anal. Calcd for C371H492O40‚CH2Cl2: C, 78.71; H, 8.77. Found:
C, 78.83; H, 8.65.
14.0. MALDI-TOF-MS (m/z): [M + H]+ calcd for C469H633O75
,
7471.1; found, 7471. Anal. Calcd for C469H632O75: C, 75.41; H,
8.53. Found: C, 75.57; H, 8.52.
La n gm u ir a n d La n gm u ir -Blod gett F ilm s. The setup for
the Langmuir and LB experiments is described in ref 5.
Solutions at ≈1 mg‚mL-1 concentration were prepared using
chloroform (Analysis Grade). Usually, 50 µL of these solutions
was spread on the water surface using a microsyringe. Films
were left to equilibrate for 15 min before any measurement
was started. The monolayers were compressed at typical
F u ller od en d r im er 3. This compound was prepared from
15 and purified by column chromatography (SiO2, CH2Cl2/
acetone 97:3) followed by gel permeation chromatography
(Biorad, Biobeads SX-1, CH2Cl2) to give 3 (33%) as an orange
glassy compound. UV-vis (CH2Cl2) λmax, nm (ꢀ): 439 (2850),
380 (sh, 9430), 327 (sh, 25 650), 261 (89 200). IR (CH2Cl2,
cm-1): 1748 (CdO). 1H NMR (CDCl3, 200 MHz, δ): 7.15 (broad
s, 1 H), 6.77 (broad s, 2 H), 6.63 (broad s, 8 H), 6.54 (broad s,
28 H), 6.39 (broad s, 9 H), 5.74 (d, J ) 14 Hz, 2 H), 5.25 (AB,
speeds of 40 Å2‚molecule-1‚min-1
.
LB films were obtained by transfer on hydrophilic silicon
wafers (111) at surface pressures of 9, 25, 35, and 35 mN‚m-1
for 2, 3, 4, and 5, respectively. Transfers started from below
the surface, with a typical emersion speed of 1 mm/min. The
9796 J . Org. Chem., Vol. 68, No. 25, 2003

Amphiphilic Diblock Dendrimers
silicon wafers were rendered hydrophilic by treatment with
an oxidizing mixture of H2SO4/H2O2 (1:1 v/v), followed by
several rinses in water. All treatments were done in an
ultrasonic bath.
J eunes Chercheurs). S.Z. and Y.R. thank the Direction
de la Recherche of the French Ministry of Research and
F.C. thanks the Re´gion Alsace for their fellowships. We
further thank L. Oswald for technical help and J .-M.
Strub for the MALDI-TOF-MS measurements.
Ack n ow led gm en t. This research was supported by
the CNRS and the French Ministry of Research (ACI
J O035040A
J . Org. Chem, Vol. 68, No. 25, 2003 9797