Ferrocenyl dendrimers with ionic tethers and dendrons

Article abstract of DOI:10.1021/om400650s

Whereas covalently constructed dendrimers are very numerous, there are only a few examples of dendrimers based on ionic bonds with tethers or dendrons. Here such constructions were designed in order to examine their physicochemical consequences: in partic

Full text of DOI:10.1021/om400650s

Article
pubs.acs.org/Organometallics
Ferrocenyl Dendrimers with Ionic Tethers and Dendrons
Amalia Rapakousiou, Yanlan Wang, Frida Nzulu, Rodrigue Djeda, Noel Pinaud, Jaime Ruiz,
̈
and Didier Astruc*
ISM, UMR CNRS No. 5255, University of Bordeaux, 33405 Talence Cedex, France
S
* Supporting Information
ABSTRACT: Whereas covalently constructed dendrimers are very
numerous, there are only a few examples of dendrimers based on ionic
bonds with tethers or dendrons. Here such constructions were
designed in order to examine their physicochemical consequences: in
particular, the electrochemical and redox properties. Two series of
secondary polyamine dendrimers containing ferrocenyl and octame-
thylferrocenyl were synthesized by condensation of polyamine
dendrimers, obtained by reduction of the polyazide dendrimers by
LiAlH4 or NaBH4 with ferrocenyl aldehyde or octamethylferrocenyl
aldehyde, followed by reduction of the resulting polyimine dendrimers.
Primary and secondary ferrocenyl polyammonium dendrimer salts
have been synthesized by quaternization of the dendritic amines
including ferrocenyl secondary polyamines by reaction with a
triferrocenyl dendron containing a carboxylic acid as the focal point. Cyclic voltammetry data show the electrostatic effect of
the intradendritic secondary ammonium groups and the distinction between intradendritic and peripheral ferrocenyl groups.
the dendritic zeroth-generation nonaamine core 3 that is
protonated using aqueous HPF6 to give the nonaammonium
salt 4 (Scheme 1). The following generation is obtained upon
Williamson reaction of the nonachloro core 1 with the phenol
triallyl dendron 9 according to a known procedure followed by
substitution of the terminal chloride by the azido group11 that is
subsequently reduced to the primary amine.12 This gives the
first-generation dendrimer 5 containing 27 NH2 termini, and
the 27-ammonium species 8 is obtained upon protonation of 5
with aqueous HPF6 or aqueous HCl12 (Scheme 2). These 9-
NH2- and 27-NH2-terminated dendrimers are used to
introduce the ferrocenyl groups upon reaction with either
ferrocenyl aldehyde or octamethylferrocenyl aldehyde, although
5 slowly polymerizes in the condensed phase and should be
used as freshly prepared. Both ferrocenyl13 and octamethylfer-
rocenyl14 derivatives have already been condensed with
polyimine DAB dendrimers by the groups of Jutzi and Casado,
respectively, and have also been successfully used here to
synthesize new ferrocenyl-terminated dendrimers. The imino-
ferrocenyl dendrimers obtained using these reactions are
reduced to the secondary aminomethylferrocenyl dendrimers
6 and 7 (Scheme 1). The new ferrocenyl-functionalized
secondary polyamine dendrimer 6 (Scheme 1) is soluble in
toluene, diethyl ether, dichloromethane, and tetrahydrofuran.
This amino metallocene was insoluble in acetonitrile, but the
ferrocenyl alcohol derived from the reduction of the excess of
INTRODUCTION
■
Dendrimers now constitute a well-developed field1 that has
applications in biomedicine,2 materials science,3 and catalysis.4
Most dendrimers are constructed covalently, but ionic bonding
has recently attracted attention for enhanced drug encapsula-
tion and specific physicochemical properties, including
mesogens and energy-related aspects.5,6 Here we report
arene-centered polyamine dendrimers with ferrocenyl termini
and a triferrocenyl dendron with a carboxylic group at the focal
point and their ionic assemblies, i.e. dendrimers containing
ammonium carboxylate linkers, some of which contain two
kinds of functional ferrocenyl termini. The goal was to
investigate the possibility of ionic linkages as a viable method
for the design of redox sensors and energy-related materials.
Among redox-active dendrimers, ferrocenyl derivatives7 are the
most practical ones, given the richness and applications of
ferrocene chemistry8 that is well illustrated inter alia in this
issue and the robustness of the ferrocenyl derivatives.
RESULTS AND DISCUSSION
■
Synthesis of New Ferrocenyl Dendrimers Containing
Secondary Amine Groups. We begin with the synthesis of
arene-centered dendrimers according to our classic CpFe+-
induced nonaallylation of mesitylene in [FeCp(η6-1,3,5-
C6H3(CH3)3)][PF6]9 according to a 1→3 connectivity10
providing the nonaallyl core11 followed by hydrosilylation
with chloromethyldimethylsilane, substitution of the terminal
chloro group in 1 by reaction with sodium azide to give the
nonaazide 2,11 and reduction of the azido groups in 2 to
primary amine termini.12 This sequence of reactions provides
Special Issue: Ferrocene - Beauty and Function
Received: July 2, 2013
© XXXX American Chemical Society
A
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 1
ferrocenyl aldehyde in the reaction solution is soluble in
acetonitrile. We acted on this solubility difference to purify the
products by precipitation of the crude reaction from acetonitrile
with a small amount of dichloromethane. For the synthesis of
the octamethylferrocenyl-functionalized dendrimer 7, instead of
ferrocenyl aldehyde, octamethylferrocenyl aldehyde15 was used
with the same route as the synthesis of the dendrimer
ferrocenyl moieties, except for the process of reduction from
imine to amine, which was achieved in this case by using
NaBH4 in a MeOH/THF mixture as solvent. The function-
alized secondary polyamine dendrimer 7 with attached
octamethylferrocenyl termini is soluble in toluene, diethyl
ether, dichloromethane, and tetrahydrofuran. The polyamine
ferrocenyl dendrimer is more aerobically stable than those
containing octamethylferrocenyl termini in solution, because
the eight methyl ferrocene substituents facilitate oxidation to
ferrocenium derivatives by oxygen. These two secondary
polyamine dendrimers 6 and 7 were characterized by 1H
NMR and 13C NMR, IR, DOSY NMR, cyclic voltammetry, and
elemental analyses.
Synthesis of the New Triferrocenyl Dendrons. A
triferrocenyl dendron containing a carboxylic acid group at
the focal point, 13, used for the quaternization reaction, was
synthesized according to Scheme 3. The synthesis of this
dendron starts by the known CpFe+-induced triallylation and
exocyclic C−O cleavage in p-methylethoxytoluene obtained by
B
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 2
reaction of ethanol and sodium carbonate with [FeCp(η6-p-
CH3C6H4Cl)][PF6]. The phenol triallyl dendron 9 obtained in
this way was hydrosilylated with dimethylsilylferrocene to give
the known complex 10.9c Then an SN2 reaction of
BrCH2COOMe with the phenol derivative 10 in the presence
of K2CO3 provided the new ester 11. Saponification15 of the
ester group was conducted with NaOH in H2O/dioxane. The
sodium carboxylate dendron product was obtained as a red oil
in 90% yield, and acidification was carried out upon addition of
aqueous HCl to give the ether-soluble carboxylic acid dendron
13 (Scheme 3). These new triferrocenyl dendrons were
characterized by 1H NMR and 13C NMR, IR, mass
spectrometry, cyclic voltammetry, and elemental analyses.
Synthesis of the Primary Polyammonium Den-
drimers. The nonaammonium hexafluorophosphate den-
drimer 4 was synthesized from the primary polyamine nona
dendrimer 3 in dichloromethane by dropwise addition of
aqueous HPF6. The turbid solution was stirred for an additional
30 min. The same procedure was used for the synthesis of the
ionic dendrimer 8 from the polyamine precursor 5 with
aqueous HCl. These dendrimers were soluble only in very polar
solvents such as water, DMF, and DMSO. In 1H NMR and 13
C
C
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 3
Chart 1
D
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chart 2
NMR in D2O, all of the characteristic peaks of the dendrimers
are observed. Products 4 and 8 were also analyzed by IR and
elemental analysis.
were soluble in dichloromethane, toluene, and THF. The
dendron 13 with carboxylic acid at the focal point was ether
soluble, as well as the secondary polyamine ferrocenyl and
octamethylferrocenyl dendrimers 6 and 7. On the other hand,
the sodium carboxylate dendron 12 was insoluble in ether. The
same phenomenon is noticed in the polyammonium carbox-
ylate dendrimers that are not ether soluble. Finally, as the
ammonium carboxylate functions are located at the interior of
the dendrimers, the ionic groups are shielded, and they cause
these ionic dendrimers to be insoluble in polar solvents such as
water, acetone, and acetonitrile. Products 14−17 were
Synthesis of the Supramolecular Ionic Ferrocenyl
Dendrimers. The construction of higher generations of
ferrocenyl dendrimers, generations 1 (products 14, 16, and
17) and 2 (product 15), were achieved in a facile and clean
acid−base reaction (Charts 1−3). One equivalent of the
primary and secondary polyamine dendrimer precursors,
generations 0 and 1, were mixed with 9 and 27 equiv of the
dendron 13 in dichloromethane at room temperature, yielding
orange sticky oils. The solubility of the final supramolecular
products is influenced as expected by the periphery of the
dendrimers that contains 27 (products 14, 16, and 17) and 81
(product 15) ferrocenyl moieties, and these final dendrimers
1
characterized by H NMR and 13C NMR, IR, DOSY NMR,
cyclic voltammetry, and elemental analyses.
NMR Spectroscopy. NMR spectroscopy proved to be a
key tool for this study, confirming the proposed structures.
E
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chart 3
1
Table 1. H NMR, 13C NMR, and IR Data of Dendrons 11−13 and Dendrimers 3−8 and 14−17
1
1
compd
CH2COOR H/13C (ppm)
SiCH2NHx 1H/13C (ppm)
HxNCH2Cp H/13C (ppm)
IR KBr (cm−1
)
a
dend-COOMe 11
4.66/65.10
4.29/64.00
4.56/66.29
1765; 1607
1633
a
dend-COONa 12
a
dend-COOH 13
1722; 1607
3365; 1570
3350; 1581
3431; 830
3425
a
G0-NH2 3
2.04/29.90
2.06/30.00
2.34/27.76
2.43/27.86
2.27/25.58
2.30/27.96
2.10/29.70
2.04/29.72
2.20/30.00
2.22/29.70
a
G1-NH2 5
b
G0-NH3PF6 4
b
G1-NH3Cl 8
a
G1-NH3-Fc27 14
4.38/67.98
4.41/66.51
3445; 1636
3452; 1643
3448; 1592
3456; 1593
3452; 1641
3461; 1630
a
G2-NH3-Fc81 15
a
G0-NH-Fc 6
3.54/53.15
3.48/50.20
3.89/50.38
3.97/51.19
a
G0-NH-Fc# 7
a
G1-NH2-Fc36 16
4.42/65.99
4.42/67.85
a
G1-NH2-Fc# Fc27 17
9
a
b
NMR in CDCl3 at 25 °C. NMR in D2O at 25 °C.
Table 1 shows the comparative NMR (and IR) data for the
dendronic carboxylic acid 13, the corresponding carboxylate
sodium salt 12, the dendritic primary and secondary poly-
amines (3 and 5−7), and the dendritic primary and secondary
polyammonium carboxylates (4, 8, and 14−17). For the
dendron 11, the 1H NMR signals at 4.66 ppm of the
CH2COOMe group and the methyl group at 3.86 ppm
appeared, integrating for two and three protons, respectively.
After the saponification reaction, the dendron 12 showed the
CH2COONa signal at lower field as expected around 4.29 ppm,
whereas the signal of the methyl group disappeared. The
acidification reaction that turned the focal point into a
F
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
carboxylic acid group was checked by the downfield shift of the
CH2COOH signal at 4.56 ppm. 13C NMR spectroscopy also
confirms the above structures (see the Supporting Informa-
tion). The syntheses of the dendrimers 6 and 7 were also
monitored by 1H NMR. The resulting imine dendrimers
resulting from the condensation reactions between 3 and the
ferrocenyl and octamethylferrocenyl aldehydes showed the
appearance of the −NCH− signal at 8.1−8.2 ppm. After
reduction to the corresponding secondary amines, this signal
completely disappeared, and the −NHCH2−Cp signal
appeared at 3.54 and 3.48 ppm, respectively. The correspond-
ing signals of the ferrocene and octamethylferrocene moieties
also confirmed the structures of the dendrimers 6 and 7. The
ionic dendrimers 4 and 8 were dissolved in D2O, but their
solubility in CDCl3 (for the sake of comparison) was not
For the primary polyamines 3 and 5 two broad bands were
observed in the region 3400−3300 cm−1 (−NH2 stretching),
whereas for the secondary polyamines 6 and 7 one broad band
was observed in this region (−NH− stretching). For the
primary and secondary polyammonium dendrimers (products
5, 8, and 14−17), one broad absorption was observed in the
+
region 3420−3460 cm−1 due to −NH3+ or −NH2 − stretching
(see Table 1).
DOSY NMR. DOSY (diffusion-ordered spectroscopy)
experiments were conducted for the dendrimers 6, 7, 14, 16,
and 17. The main goal of these experiments was to measure the
diffusion coefficient D and determine the size of the dendrimer
in solution. The latter also reflects the purity of the products.
The D value allows calculation of the hydrodynamic diameter
of a molecule. Dendrimers are regarded as spherical molecular
objects and characterized by an apparent diffusion coefficient.
The Stokes−Einstein law, D = kBT/6πηrH, gives an estimate for
the diameter of the molecule, where D is the diffusion
coefficient, kB the Boltzmann constant, T the absolute
temperature, η the solvent viscosity, and rH the hydrodynamic
radius of the species (Table 2). The diameter values that are
+
determined. Nevertheless, the −CH2NH3 signals showed an
important downfield shift. In the case of the primary
polyammonium ferrocenyl dendrimers 14 and 15, by
comparison with the primary polyamine precursors 3 and 5
+
and dendron 13, the −CH2NH3 proton signal was deshielded
by about 0.25 ppm due to the presence of a nearby positive
charge, and the signal of the −CH2COO− protons was found to
be shielded by about 0.17 ppm due to the presence of a nearby
negative charge. These shifts in comparison to the neutral
termini are in agreement with the formation of the ionic
ammonium carboxylate linker. In the case of the secondary
polyammonium dendrimers 16 and 17, in comparison to the
precursors 6 and 7 and dendron 13, the differences are slightly
Table 2. Calculated Diffusion Coefficients and
Hydrodynamic Radii Obtained by DOSY NMR
a
b
compd
D
( 0.1), 10−10 m2/s
rH ( 0.1), nm
G0-NH-Fc 6
1.947
1.768
1.044
1.261
1.216
2.08
2.29
3.87
3.21
G0-NH-Fc# 7
G1-NH3-Fc27 14
G1-NH2-Fc36 16
+
smaller, as −CH2NH2 protons are deshielded by about 0.10
and 0.18 ppm, respectively and the −CH2COO− protons are
shielded by 0.14 ppm. This decrease of the charge effect is
taken into account by the fact that the secondary ammonium
groups are larger than the primary groups, resulting in a
dilution of the positive charge and weaker (longer) ionic bond
G1-NH2-Fc# Fc27 17
3.33
9
a
b
D is the diffusion coefficient, measured in CDCl3 at 25 °C, rH is the
hydrodynamic radius, calculated using the Stokes−Einstein equation.
obtained include peripheral solvation of the products by solvent
molecules in solution. This method was very useful for a clear
comparison between the generations of the dendrimers and
provided evidence for the formation of distinct ionic
assemblies. For the nonionic dendrimers 6 and 7 (generation
0), the calculated rH values are 2.08 and 2.29 nm, respectively,
which shows the effect of the presence of methyl groups in 7
and provides a hydrodynamic radius that is 0.21 nm larger
herewith. When the latter products were allowed to react with
the dendron 13, giving the next generation (generation 1)
dendrimers 16 and 17, it was found that the sizes of the
obtained dendritic ionic assemblies represented by rH are 3.21
and 3.33 nm, respectively. This finding that 17 has a larger rH
value than 16 is in agreement with the relative sizes of their
precursors, respectively 6 and 7. Finally, DOSY NMR, apart
from providing valuable data such as the diffusion coefficients
of the new dendrimers, also gives clear evidence of the size
progression upon an increase of the dendrimer generation. It
also allows comparing the sizes of the dendrimers (ionic and
nonionic) that contain different metallocenes and distinguish-
ing between the assemblies of primary and secondary
polyammonium dendrimers of the same generation.
+
with the carboxylate. On the other hand, the −NH2 CH2−Cp
signal of the secondary polyammonium dendrimers 16 and 17
are much more shifted (0.3 and 0.5 ppm) toward lower field
than the signals of the other protons. Interestingly, the 13C
+
NMR spectra show the opposite effect for the −CH2NH3
(shielded compared to −CH2NH2) and −CH2COO− carbons
(deshielded in comparison to −CH2COOH) in comparison to
proton signals in dendrimers 14 and 15 (see Table 1). Finally,
for the ionic dendrimers, the corresponding proton signals of
the carboxylates are found at an intermediate region between
those of the dendronic acid 13 and those of the dendronic
sodium carboxylate salt 12, probably because of the hydrogen
bonding between the primary or secondary ammonium group
with the carboxylate group.
Infrared Spectroscopy. The infrared spectra also provided
valuable information on the new series of dendrons and
dendrimers. Dendron 11 has the characteristic absorption of
the ester group at 1765 cm−1, and in dendron 13 the presence
of a focal point consisting of the carboxylic acid was checked by
the frequencies related to the carbonyl group at 1722 and 1607
cm−1 (and a broad band due to the O−H stretching at 3400
cm−1). For the dendron 12 the single carbonyl band was shifted
to the region between the two, at 1633 cm−1 due to the
carboxylate absorption (both resonance forms equally contrib-
ute to the ground state of the molecule). Similarly, for the
dendritic polyammonium carboxylates 14−17, a strong band
due to −COO− stretching was found in the region 1630−1643
cm−1.
Cyclic Voltammetry.16 The new dendron 13 and the series
of polyamine and polyammonium ferrocenyl dendrimers were
studied by cyclic voltammetry using decamethylferrocene
(FeCp*2) as the internal reference,17 although ferrocene was
used in the cases of the octamethylferrocenyl dendrimers 7 and
17. The cyclic voltammograms were recorded in dichloro-
methane, and the E1/2 data (measured vs FeCp*2) are gathered
G
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Table 3. Redox Potentials and Chemical (ia/ic) and Electrochemical (Epa − Epc = ΔE) Reversibilities for Compounds 6, 7, and
α
13−17
FeIII/II dendron
ΔE, V
FeIII/II dendrimer
Fe#III/II dendrimer
compd
E
1/2, V
ia/ic
E1/2, V
ΔE, V
ia/ic
E1/2, V
ΔE, V
ia/ic
13
6
0.54
0.068
0.76
0.55
0.065
1
7
0.10
0.040
1
14
15
16
17
0.52
0.53
0.54
0.52
0.015
0.012
0.065
0.025
0.57
0.42
1
0.62
0.060
1
1
0.27
0.030
0.9
α
Conditions: supporting electrolyte, [n-Bu4N][PF6] 0.1 M; solvent, CH2Cl2; reference electrode, Ag; working and counter electrodes, Pt; scan rate,
0.2 V/s; internal reference, FeCp*2.
in Table 3. For all of the dendrons and dendrimers, a single
oxidation wave is observed for all the ferrocenyl groups, which
appear seemingly equivalent, due to the weakness of the
electrostatic factor between the redox sites of the dendron and
metallodendrimers, as their redox sites are far away from one
another, being separated by several bonds.18 This single wave
for all these three products is chemically and electrochemically
reversible, although this reversibility is sometimes more or less
perturbed by adsorption of these macromolecules onto the
electrode. The electrochemical reversibility involving all the
redox groups and signifying fast heterogeneous electron
transfer is due to two factors that probably simultaneously
occur: (i) fast rotation of the metallodendrimer within the
electrochemical time scale, whereby all redox groups come in
turn close to the electrode,19 and (ii) electron hopping among
the redox sites borne by flexible tethers, allowing hopping at an
optimal distance and mutual orientation.20 For dendron 13 and
dendrimer 6, the FeIII/II oxidation potentials of the ferrocenyl
redox centers are about 0.54 V, whereas for dendrimer 7 this
potential is 0.1 V. This cathodic shift is accounted for by both
the electron-releasing property of the eight methyl substituents
of the ferrocenyl groups that facilitate oxidation to ferrocenium.
For primary polyammonium dendrimers 14 and 15, the
oxidation potentials are about the same as that of the dendron
(only 20 mV less positive). The ferrocenyl centers at the
periphery of the dendrimers are not influenced by the
ammonium carboxylate linkages that are located in the
dendritic interior. In the case of secondary polyammonium
dendrimers with two kinds of ferrocenyl centers (product 16)
and the mixed ferrocenyl−octamethylferrocenyl dendrimer 17,
two waves are observed corresponding to each type of
ferrocenyl redox center. For products 16 and 17, oxidation of
the peripheral ferrocenes also is recorded at 0.54 V, because
they are not influenced by the remote interior ammonium
carboxylate linkages. Oxidation of the interior ferrocenyl groups
that are close to the ammonium groups now takes place at
much more positive potentials, which is due to the interaction
with and proximity of the ammonium cation. This trend is
more marked for 17, because the ammonium cation stabilizes
the electron-rich octamethylferrocenyl group, which is oxidized
at a potential 170 mV more positive (Figure 1).
Figure 1. CV of 17 in CH2Cl2 solution. Conditions: reference
electrode, Ag; working and counter electrodes, Pt; scan rate, 0.2 V/s;
supporting electrolyte, [n-Bu4N][PF6].
the oxidation potentials of the peripheral ferrocenyl groups,
which confirms the formation of ionic generation-1 and -2
dendrimers and the existence of electrostatic forces. For the
ionic compounds 16 and 17 adsorption is also highly marked.
On the other hand, the dendron 13 and dendrimers 6 and 7 do
not adsorb and cannot modify the Pt electrodes. This is not the
case for dendrimers 14 and 16, which deposit onto the
electrode surfaces upon scanning toward potentials that are
positive to ferrocenyl oxidation. Modification of electrodes with
films of dendrimers containing reversible redox systems has
been successful, resulting in detectable electroactive material.
This electrochemical behavior of modified electrodes was
studied in dichloromethane containing only the supporting
electrolyte (Figures 2 and 3). A well-defined, symmetrical redox
wave is observed, which is characteristic of a surface-confined
redox couple, with the expected linear relationship of peak
current with potential sweep rate v.21 Repeated scanning does
not change the voltammograms, demonstrating that the
modified electrodes are stable to electrochemical recycling.
However, splitting between oxidation and reduction peaks is
observed (ΔE = 40 mV), which suggests that a structural
reorganization takes place within the electrochemical redox
process within these ionic dendritic assemblies. Values of the
full width at half-maximum for compounds 14 and 16 were
The adsorption phenomenon during cyclic voltammetry of
cationic dendrimers is much more marked for ionic dendritic
assemblies than for neutral species. Indeed, for the dendron 13
and the generation-0 dendrimers 6 and 7, adsorption is not
observed, but in the case of the ionic compounds 14−17
adsorption is strong. Especially for compounds 14 and 15
adsorption onto the electrode is observed by scanning around
measured at a scan rate of 100 mV/s and found to be ΔEfwhm
=
150 and 140 mV, respectively, suggesting the existence of
H
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
peripheral ferrocenyl layers such as those synthesized here.
The effect of the intradendritic positive charges of the
ammonium groups clearly appears on the NMR chemical shifts
and electrochemical potentials (E1/2 values) of the inner
ferrocenylmethyl groups. Interestingly, this electrostatic effect is
more pronounced on the octamethylferrocenyl layer than on
the parent ferrocenyl layer, probably because of the electron-
rich methyl substituents in comparison to parent ferrocenyl
sites. The E1/2 value of the inner ferrocenyl layer is sufficiently
shifted anodically to show a CV wave (shoulder) that is slightly
distinct from that of the outer ferrocenyl layer. When the
ferrocenyl substituents are different (H vs CH3), the two
separate CV waves clearly appear with relative intensities
corresponding to their ratio (3/1). Finally, a characteristic of all
the ionic ferrocenyl dendrimers is their strong ability to adsorb
on electrodes and form derivatized electrodes that is
considerably more marked than that of their neutral
constituents. Potential applications are, for instance, the
dendritic encapsulation of ionic or polar biomedical molecules
in hydrophobic media and recyclable redox sensors.
Figure 2. Cyclic voltammograms of 14 in CH2Cl2 solution containing
0.1 M [n-Bu4N][PF6]: (a) in solution; (b) intensity as a function of
scan rate (linearity shows the expected behavior of an absorbed
dendrimer); (c) modified Pt electrode at various scan rates in a
CH2Cl2 solution (containing only the supporting electrolyte).
EXPERIMENTAL SECTION
■
General Data. For general data including solvents, apparatuses,
compounds, reactions, spectroscopy, and CV, see the Supporting
Information . Gn indicates the generation number n.
G0-9-dend-NHCH2-Fc (6). To a solution of ferrocenyl aldehyde
(0.077 g, 0.358 mmol, 1.02 equiv/branch) in 30 mL of dry toluene was
added dropwise at 70 °C a solution of polyamine dendrimer 3 (0.050
g, 0.033 mmol) in 20 mL of dry toluene under nitrogen. The reaction
mixture was heated at 75 °C for 12 h. The red solution was then
evaporated to dryness under reduced pressure, the resulting reddish
solid containing Gn-3n+2-dend-NCH-Fc was dissolved in 20 mL of
THF, and a suspension of LiAlH4 (2 equiv/branch) in 20 mL of THF
was added slowly at 0 °C. After the addition, the mixture was stirred
for 16 h at 50 °C under nitrogen. To the reaction solution at 0 °C was
added dropwise H2O (6 equiv/branch), and the mixture was stirred
for 20 min. After drying under vacuum, the crude product was washed
with acetonitrile in order to remove the excess of ferrocene aldehyde/
methanol. Further purification was achieved from precipitation in
acetonitrile, and the product was obtained as an orange sticky oil.
Yield: 70%.
1H NMR (CDCl3, 300 MHz): δ (ppm) 7.01 (3H, CH core), 4.22
(18H, Cp sub), 4.15 (45H, Cp free), 4.15 (18H, Cp sub), 3.54 (18H,
CpCH2NH), 2.10 (18H, SiCH2NH), 1.63 (18H, CqCH2CH2CH2Si),
1.11 (18H, CqCH2CH2CH2Si) 0.54 (18H, CqCH2CH2CH2Si), 0.03 (s,
54H, Si(CH3)2). 13C NMR (CDCl3, 75 MHz): δ (ppm) 145.7 (Cq of
arom core), 128.7 (CH of arom core), 86.3, 68.6, 68.4, 67.7 (Cp-C),
53.2 (CH2-Cp), 43.1 (CqCH2CH2CH2Si), 42.1 (CqH2CH2CH2Si),
29.7 (Si(CH3)2CH2NH), 17.7 (CqCH2CH2CH2Si), 15.1
(CqCH2CH2CH2Si), −3.8 (Si(CH3)2). Anal. Calcd for
C162H237Si9N9Fe9: C, 63.46; H, 7.79.. Found: C, 63.33; H, 7.80.
G0-9-dend-NHCH2-Fc# (7). To a solution of octamethylferrocene
(54.8 mg, 0.16 mmol, 1.2 equiv/branch) in 30 mL of dry toluene was
added dropwise at 70 °C a solution of nonaamine dendrimer (19.2 mg,
0.015 mmol) in 20 mL of dry toluene under nitrogen. The reaction
mixture was heated to 75 °C for 16 h. The red solution was then
evaporated to dryness under reduced pressure, and the resulting
reddish solid containing G0-dend-NCH-Fc# was washed with 20 mL
of CH3CN three times to remove the excess octamethylferrocene
aldehyde/methanol. The resulting reddish solid was dried under
reduced pressure and dissolved in a mixture of THF (10 mL) and
CH3OH (10 mL), and then NaBH4 (3 equiv/branch) was slowly
added at 0 °C. After the addition, the mixture was stirred for 30 min at
0 °C under nitrogen. The solvent was removed under reduced
pressure. To the remaining solid was added dropwise H2O (30 mL),
and the compound was extracted three times with distilled diethyl
ether. The combined organic phase was dried under anhydrous
Figure 3. Cyclic voltammograms of 16 in CH2Cl2 solution containing
0.1 M [n-Bu4N][PF6]: (a) in solution; (b) intensity as a function of
scan rate (linearity shows the expected behavior of an absorbed
dendrimer); (c) modified Pt electrode at various scan rates in CH2Cl2
(solution containing only the supporting electrolyte).
repulsive forces between the ferrocenyl sites attached onto the
electrode surface.22 These Pt electrodes that are modified with
dendrimers 14 and 16 are durable and reproducible, as no loss
of electroactivity is observed after scanning several times or
after standing in air for several days. The surface coverages of
the electroactive ferrocenyl sites of the modified electrodes of
metallodendrimers 14 and 16 are Γ = 1 × 10−11 and 1.7 ×
10−11 mol cm−2, respectively.
Concluding Remarks. The assembly of ionic dendrons and
dendrimers represents a convenient way to synthesize large
dendrimers with defect-free periphery insofar as the dendrimer
purity solely depends on the purities of the dendrons and
dendritic cores. The ionic linkers at the dendritic interiors are
shielded so that the properties of these dendrimers essentially
depend on the periphery. Of specific interest are ionic
ferrocenyl dendrimers containing both intradendritic and
I
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Na2SO4. After evaporation, the compound was obtained as a yellow
solid without further purification. Yield: 77%.
17.87 (CqCH2CH2CH2Si), 17.39 (CqCH2CH2CH2Si), −2.08 (Si-
(CH3)). MS (m/z): calcd for C55H72O3Si3Fe3 1032.2832, found
1032.7785.
1H NMR (CDCl3, 300 MHz): δ (ppm) 6.92 (3H, CH core), 3.48
(18H, NHCH2C5(CH3)4), 3.28 (9H, C5(CH3)4H), 2.04 (18H,
SiCH2NH), 1.83, 1.79, 1.77, 1.71 (216H, C5(CH3)4), 1.58 (18H,
CqCH2CH2CH2Si), 1.04 (18H, CqCH2CH2CH2Si), 0.47 (18H,
CqCH2CH2CH2Si), 0.05 (54H, Si(CH3)2). 13C NMR (CDCl3, 75
MHz): δ (ppm) 145.7 (Cq of arom core), 128.7 (CH of arom core),
80.5, 80.0, 79.8, 79.7, 79.4, and 70.5 (Cp-C), 50.2 (Cp-CH2NH), 43.8
(CqCH2CH2CH2Si), 42.0 (CqCH2CH2CH2Si), 29.7 (Si-
(CH3)2CH2NH), 17.8 (CqCH2CH2CH2Si), 15.1 (CqCH2CH2CH2Si),
11.0, 10.0, 9.9, 9.4 (C5(CH3)4), −4.0 (Si(CH3)). Anal. Calcd for
C234H381Si9+Fe9N9: C, 68.95; H, 9.43. Found: C, 68.71; H, 9.14.
G0-NH3 PF6− (4). To a stirred solution of 3 (100 mg, 0.078 mmol)
in 20 mL of distilled dichloromethane was added dropwise aqueous
HPF6 (1.1 equiv/branch) diluted in 3 mL of dichloromethane. Then a
white precipitate started to form, but the product was stirred for an
additional 30 min. The solution was evaporated, and the white solid
was washed with acetone. The water-soluble white product 4 was
obtained quantitatively.
1
Dendron 12. H NMR (CDCl3, 300 MHz): δ (ppm) 7.15, 6.81
(4H, arom), 4.34 (6H, Cp sub), 4.29 (2H, CH2COONa), 4.12 (15H,
Cp free), 4.08 (6H, Cp sub), 3.86 (3H, CH2COO−CH3), 1.62 (6H,
CqCH2CH2CH2Si), 1.12 (6H, CqCH2CH2CH2Si), 0.64 (6H,
CqCH2CH2CH2Si), 0.19 (18H, Si(CH3)2). 13C NMR (CDCl3, 75
MHz): δ (ppm) 167.16 (COONa), 154.07 (OCq arom), 140.17 (Cq
arom), 127.61, 113.71 (CH arom), 73.00, 70.72 (CH of Cp sub),
70.98 (Cq of Cp sub), 68.17 (Cp free), 64.00 (CH2COONa), 42.89
(Cq CH2 CH2 CH2 Si), 41.82 (Cq CH2 CH2 CH2 Si), 17.76
(CqCH2CH2CH2Si), 17.23 (CqCH2CH2CH2Si), −1.79 (Si(CH3)).
1
Dendron 13. H NMR (CDCl3, 300 MHz): δ (ppm) 7.22, 6.90
(4H, arom), 4.56 (2H, CH2COOH), 4.35 (6H, Cp sub), 4.13 (15H,
Cp free), 4.06 (6H, Cp sub), 1.65 (6H, CqCH2CH2CH2Si), 1.17 (6H,
CqCH2CH2CH2Si), 0.65 (6H, CqCH2CH2CH2Si), 0.21 (18H, Si-
(CH3)2). 13C NMR (CDCl3, 75 MHz): δ (ppm) 174.41 (COOH),
155.11 (OCq arom), 141.32 (Cq arom), 127.63, 114.42 (CH arom),
73.19, 70.90 (CH of Cp sub), 71.51 (Cq of Cp sub), 68.43 (Cp free),
66.29 (CH2 COOH), 43.33 (Cq CH2 CH2 CH2 Si), 42.04
(Cq CH2 CH2 CH2 Si), 18.26 (Cq CH2 CH2 CH2 Si), 17.74
(CqCH2CH2CH2Si), −1.87 (Si(CH3)2). MS (m/z): calcd for
C54H70O3Si3Fe3 1018.2681, found 1018.2715. Anal. Calcd for
C54H70O3Si3Fe3: C, 63.65; H, 6.92. Found: C, 63.32; H, 7.07.
General Synthesis of Ionic Polyammonium Carboxylate
Dendrimers. To a stirred solution of secondary or primary polyamine
dendrimer in 10 mL of distilled dichloromethane was added dropwise
a solution of triferrocenyl carboxylic acid (1 equiv/branch) in 10 mL
of dichloromethane, and the mixture was stirred for 20 min. The
solvent was removed under vacuum, and the compound was obtained
as an orange-yellow sticky oil in quantitative yield.
1H NMR (D2O, 300 MHz): δ (ppm) 6.92 (3H, CH core), 2.26
+
(18H, SiCH2NH3 ), 1.55 (18H, CqCH2CH2CH2Si), 0.99 (18H,
CqCH2CH2CH2Si) 0.50 (18H, CqCH2CH2CH2Si), 0.03 (s, 54H,
Si(CH3)2). 13C NMR (D2O, 75 MHz): δ (ppm) 145.72 (Cq arom),
121.65 (CH arom), 43.66 (Cq CH2 CH2 CH2 Si), 41.11
(CqCH2CH2CH2Si), 27.76 (Si(CH3)2CH2NH2+), 17.41
(CqCH2CH2CH2Si), 13.60 (CqCH2CH2CH2Si), −4.95 (Si(CH3)).
Anal. Calcd for C63H156Si9N9P9F54·2H2O: C, 28.73; H, 6.13. Found: C,
28.82; H, 6.17.
+
G1-NH3 Cl− (8). To a stirred solution of 5 (50 mg, 0.009 mmol) in
20 mL of distilled dichloromethane was added dropwise aqueous HCl
(1.2 equiv/branch) diluted in 5 mL of dichloromethane. Then a white
precipitate started to form, but the product was stirred for an
additional 30 min. The solution was evaporated, and the white solid
was washed with acetone. The water-soluble white waxy product 8 was
obtained quantitatively.
Dendrimer 14. The ionic dendrimer 14 was synthesized from 3 (10
mg, 0.008 mmol, 1 equiv) and 13 (71.5 mg, 0.070 mmol, 9 equiv)
using the general synthesis of ionic polyammonium carboxylate
dendrimers.
1H NMR (D2O, 300 MHz): δ (ppm) 7.15, 6.72 (39H, CH core),
1H NMR (CDCl3, 300 MHz): δ (ppm) 7.17 (18H, arom), 7.02
(3H, arom core), 6.86 (18H, arom), 4.38 (18H, CH2COO−), 4.33
(54H, Cp sub), 4.12 (135H, Cp free), 4.05 (54H, Cp sub), 2.27 (18H,
SiCH2NH3+), 1.63 (72H, CqCH2CH2CH2Si), 1.15 (72H,
CqCH2CH2CH2Si), 0.64 (72H, CqCH2CH2CH2Si), 0.20, 0.10
(216H, Si(CH3)2). 13C NMR (CDCl3, 75 MHz): δ (ppm) 174.88
(COO−), 155.62 (OCq arom of dendron), 140.46 (Cq arom), 127.48,
114.35 (CH arom), 72.91, 71.29, 70.75, 68.25 (Cp−C), 67.98
(CH2COO−), 43.24 (CqCH2CH2CH2Si), 42.19 (CqCH2CH2CH2Si),
+
3.73 (18H, CH2OAr), 2.43 (54H, SiCH2NH3 ), 1.88 (72H,
CqCH2CH2CH2Si), 1.16 (72H, CqCH2CH2CH2Si), 0.63 (72H,
CqCH2CH2CH2Si), 0.13 (216H, Si(CH3)2). 13C NMR (D2O, 75
MHz): δ (ppm) 158.72 (OCq arom of dendron), 139.56 (Cq arom),
127.23, 113.77 (CH arom), 43.16 (CqCH2CH2CH2Si), 41.69
(CqCH2CH2CH2Si), 27.86 (Si(CH3)2CH2NH3+), 17.60
(CqCH2CH2CH2Si), 14.56 (CqCH2CH2CH2Si), −4.19 (Si(CH3)2).
Anal. Calcd for C288H624Si36N27O9Cl27·5H2O: C, 51.88; H, 9.59.
Found: C, 51.60; H, 9.57.
+
25.58 (Si(CH3)2CH2NH3 ), 18.14 (CqCH2CH2CH2Si), 17.66
Triferrocenyl Carboxylic Acid (13). To a solution of 10 (0.351 g,
0.365 mmol) in 40 mL of acetonitrile were added K2CO3 (0.101 g,
0.731 mmol) and methyl bromoethanoate (0.084 g, 0.548 mmol), and
the resulting solution was heated at 90 °C for 16 h under a nitrogen
atmosphere. After the solvent and excess methyl bromethanoate were
removed, the crude product was dissolved in 100 mL of dichloro-
methane and the solution filtered through Celite. The solvent was
removed under vacuum, and the product was obtained as an orange
oil. Then product 11 (0.360 g, 0.35 mmol) was dissolved in 18 mL of
dioxane, and a solution of NaOH (56 mg, 1.39 mmol) in 5 mL of H2O
was added dropwise. The solution was stirred for 16h at room
temperature. Then, the solution was evaporated, and the product was
washed in water and extracted from dichloromethane. Acidification of
12 in dichloromethane/water with aqueous HCl gave product 13 as an
orange shiny oil. Yield: 90%.
(CqCH2CH2CH2Si), −1.85, −3.99 (Si(CH3)2). Anal. Calcd for
C540H777Si36Fe27N9O27: C, 62.69; H, 7.58. Found: C, 63.02; H, 7.73.
Dendrimer 15. The ionic dendrimer 15 was synthesized from 5 (10
mg, 0.002 mmol, 1 equiv) and 13 (49.5 mg, 0.049 mmol, 27 equiv)
using the general synthesis of ionic polyammonium carboxylate
dendrimers.
1H NMR (CDCl3, 300 MHz): δ (ppm) 7.17 (72H, arom), 6.95
(3H, arom core), 6.85 (72H, arom), 4.41 (54H, CH2COO−), 4.33
(162H, Cp sub), 4.12 (405H, Cp free), 4.05 (162H, Cp sub), 3.55
+
(CH2OAr), 2.30 (54H, SiCH2NH3 ), 1.64 (234H, CqCH2CH2CH2Si),
1.13 (234H, CqCH2CH2CH2Si), 0.65 (72H, CqCH2CH2CH2Si), 0.21,
0.05 (216H, Si(CH3)2). 13C NMR (CDCl3, 75 MHz): δ (ppm) 174.10
(COO−), 154.87 (OCq arom of dendron), 141.22 (Cq arom), 127.54,
114.34 (CH arom), 72.92, 71.28, 70.62, 68.09 (Cp-C), 66.51
(CH2COO−), 43.27 (CqCH2CH2CH2Si), 42.09 (CqCH2CH2CH2Si),
1
Dendron 11. H NMR (CDCl3, 300 MHz): δ (ppm) 7.20, 6.90
+
27.96 (Si(CH3)2CH2NH3 ), 18.07 (CqCH2CH2CH2Si), 17.60
(4H, arom), 4.66 (2H, CH2COOMe), 4.35 (6H, Cp sub) 4.13 (15H,
Cp free), 4.06 (6H, Cp sub), 3.86 (3H, CH2COO−CH3), 1.65 (6H,
CqCH2CH2CH2Si), 1.15 (6H, CqCH2CH2CH2Si), 0.65 (6H,
CqCH2CH2CH2Si), 0.21 (18H, Si(CH3)2). 13C NMR (CDCl3, 75
MHz): δ (ppm) 168.48 (COOMe), 155.08 (OCq arom), 141.20 (Cq
arom), 127.32, 113.91 (CH arom), 72.75, 70.36 (CH of Cp sub),
71.16 (Cq of Cp sub), 67.81 (Cp free), 65.10 (CH2COOMe), 52.17
(COOCH3), 43.24 (CqCH2CH2CH2Si), 41.80 (CqCH2CH2CH2Si),
(CqCH2CH2CH2Si), −1.91, −3.40 (Si(CH3)2). Anal. Calcd for
C1719H2487Si117Fe81N27O90·2CH2Cl2: C, 62.74; H, 7.63. Found: C,
62.64; H, 7.89.
Dendrimer 16. The ionic dendrimer 16 was synthesized from 6 (10
mg, 0.003 mmol, 1 equiv) and 13 (29.9 mg, 0.029 mmol, 9 equiv)
using the general synthesis of ionic polyammonium carboxylate
dendrimers.
J
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1H NMR (CDCl3, 300 MHz): δ (ppm) 7.21, 6.89 (39H, arom),
4.41 (18H, CH2COO−), 4.35, 4.14, 4.07 (324H, Cp), 3.89 (18H,
+ NH2 CH2 Cp), 2.20 (18H, SiCH2 NH2 + ), 1.65 (72H,
CqCH2CH2CH2Si), 1.17 (72H, CqCH2CH2CH2Si) 0.66 (72H,
CqCH2CH2CH2Si), 0.22, 0.07 (216H, Si(CH3)2). 13C NMR (CDCl3,
75 MHz): δ (ppm) 174.18 (COO−), 155.70 (OCq arom of dendron),
140.79 (Cq arom), 127.67, 114.56 (CH arom), 73.10, 71.50, 71.19,
Biomedical Use; Wiley: Chichester, U.K., 2011. (f) Designing
Dendrimers; Campagna, S., Ceroni, P., Puntoriero, F., Eds.; Wiley:
Hoboken, NJ, 2012.
(2) (a) Svenson, S.; Tomalia, D. A. Adv. Drug. Deliv. Rev. 2005, 57,
2106−2129. (b) Boas, U.; Heegard, P. M. H. Chem. Soc. Rev. 2004, 33,
43−63. (c) Gillies, E. R.; Frechet, J. M. J. Drug Deliv. Today 2005, 10,
́
35−43. (d) Wolinsky, J. B.; Grinstaff, M. W. Adv. Drug. Deliv. Rev.
2008, 60, 1037−1055. (e) Tekade, R.; Kumar, P. V.; Jain, N. K. Chem.
Rev. 2009, 109, 49−87. (f) Sevenson, S.; Tomalia, D. A. Adv. Drug
Delivery Rev. 2012, 64, 102−115.
(3) (a) Moore, J. S. Acc. Chem. Res. 1997, 30, 402−413.
(b) Newkome, G. R. Pure Appl. Chem. 1998, 70, 2337−2343.
(c) Adronov, A.; Frechet, J. M. J. Chem. Commun. 2000, 1701−1710.
́
+
70.81, 69.31, 68.99, 68.28 (Cp-C), 65.99 (CH2NH2 CH2Cp), 50.38
(CH2 NH2 + CH2 Cp), 43.42 (Cq CH2 CH2 CH2 Si), 42.32
(CqCH2CH2CH2Si), 30.00 (Si(CH3)2CH2NH2+), 18.26
(CqCH2CH2CH2Si), 17.76 (CqCH2CH2CH2Si), −1.73, −3.40 (Si-
(CH3)). Anal. Calcd for C639H867Si36Fe36N9O27: C, 63.28; H, 7.21.
Found: C, 62.95; H, 7.12.
Dendrimer 17. The ionic dendrimer 17 was synthesized from 7 (10
mg, 0.002 mmol, 1 equiv) and 13 (22.5 mg, 0.022 mmol, 9 equiv)
using the general synthesis of ionic polyammonium carboxylate
dendrimers.
(d) Nirengarten, J.-F. Top. Curr. Chem. 2003, 228, 87−110. (e) Scott,
R.W. J.; Wilson, O. M.; Crooks, R. M. J. Phys. Chem. B 2005, 109,
692−704. (f) Lo, S.-C.; Burn, P.-L. Chem. Rev. 2007, 107, 1097−1116.
(g) Balzani, V.; Bergamini, G.; Ceroni, P.; Vogtle, F. Coord. Chem. Rev.
̈
1H NMR (CDCl3, 300 MHz): δ (ppm) 7.16, 6.95, 6.82 (39H,
arom), 4.42 (18H, CH2COO−), 4.34, 4.13, 4.06 (324H, Cp of Fc),
2007, 251, 525−535. (h) Astruc, D. Nat. Chem. 2012, 4, 255−267.
(4) (a) Newkome, G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999,
99, 1689−1746. (b) Oosterom, G. E.; Reek, J. N. H.; Kamer, P. C. J.;
van Leeuwen, P.W. N. M. Angew. Chem., Int. Ed. 2001, 40, 1828−1849.
(c) Astruc, D.; Chardac, F. Chem. Rev. 2001, 101, 2991−3024.
(d) Kreiter, R.; Kleij, A. W.; Gebbink, R. J. M. K.; van Koten, G.
Dendrimers IV: Metal Coordination, Self Assembly, Catalysis. In
+
3.93 (18H, NH2CH2Cp of Fc#), 3.28 (9H, C5(CH3)4H of Fc#), 2.23
+
(18H, SiCH2NH2 ), 1.83−1.68 (216H, C5(CH3)4), 1.66 (72H,
CqCH2CH2CH2Si), 1.22 (72H, CqCH2CH2CH2Si), 0.65 (72H,
CqCH2CH2CH2Si), 0.21, 0.07 (216H, Si(CH3)2). 13C NMR (CDCl3,
75 MHz): δ (ppm) 174.18 (COO−), 155.70 (OCq arom of dendron),
140.79 (Cq arom), 127.55, 114.53 (CH arom), 86.31, 83.14, 81.88,
72.94, 71.19, 70.63, 68.11 (Cp-C), 67.85 (CH2COO−), 51.19
(CH2 NH2 + CH2 Cp), 43.27 (Cq CH2 CH2 CH2 Si), 42.15
(CqCH2CH2CH2Si), 29.70 (Si(CH3)2CH2NH2+), 18.09
(CqCH2CH2CH2Si), 17.76 (CqCH2CH2CH2Si), −1.02, −3.20 (Si-
(CH3)2). Anal. Calcd for C711H1002Si36Fe36N9O27·2CH2Cl2: C, 64.39;
H, 7.63. Found: C, 64.22; H, 7.85.
Topics in Current Chemistry; Vogtle, F., Schalley, C. A., Eds.; Springer-
̈
Verlag: Berlin, 2001; Vol. 217, pp 163−199. (e) van Heerbeeck, R.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Reek, J. N. H. Chem. Rev.
2002, 102, 3717−3756. (f) Heuze, K.; Mer
́
y, D.; Gauss, D.; Blais, J.-C.;
het,
Astruc, D. Chem. Eur. J. 2004, 10, 3936−3944. (g) Liang, C.; Frec
́
J. M. J. Prog. Polym. Sci. 2005, 30, 385−402. (h) de Jesus, E.; Flores, J.
C. Ind. Eng. Chem. Res. 2008, 47, 7968−7981. (i) Astruc, D.
Tetrahedron: Asymmetry 2010, 21, 1041−1054. (j) Zaera, F. Chem.
Soc. Rev. 2013, 42, 2746−2762.
ASSOCIATED CONTENT
* Supporting Information
■
S
(5) (a) Gonzales, L.; Skov, A. L.; Hvilstead, S. J. Polym. Sci. Part A,
Polym. Chem. 2013, 51, 1359−1371. (b) Tanaka, K.; Chujo, Y. Polym.
J. 2013, 45, 247−254. (c) Eleftheriou, E.; Karatass, K. J. Chem. Phys.
2012, 137 (14), N°144905. (d) Pavan, G. M.; Monteagudo, S.;
Guerra, J.; Carrion, B.; Ocana, V.; Rodriguez-Lopez, J.; Danani, A.;
Perez-Martinez, F. C.; Cena, V. Curr. Med. Chem. 2012, 19, 4929−
4941. (e) Prevette, L. E.; Nikoleva, E. N.; Al-Hashimi, H. M.; Holl, M.
M. B. Mol. Pharm. 2012, 9, 2743−2749. (f) Das, S.; Sresh, B. R.;
Jataraman, N.; Bhattacharyya, A. J. J. Polym. Res. 2012, 19 (8), N°
9924. (g) Jeong, Y. H.; Yoon, H. J.; Jang, W. D. Polym. J. 2012, 44,
512−521. (h) Garzoni, M.; Cheval, N.; Fahmi, A.; Danani, A.; Pavan,
G. M. J. Am. Chem. Soc. 2012, 134, 3349−3357. (i) Vergara, J.;
Gimeno, N.; Cano, M.; Barbera, J.; Romero, P.; Serrano, J. L.; Ros, M.
B. Chem. Mater. 2011, 23, 4931−4940. (j) Cgu, F. Q.; Lin, B. C.; Yan,
F.; Qiu, L. H.; Lu, J. M. J. Power Sources 2011, 196, 7979−7984.
(k) Choi, J. W.; Cho, B.-K. Soft Matter 2011, 7, 4045−4049.
(l) Willerich, I.; Li, Y.; Franziska, G. J. Phys. Chem. B 2010, 114,
15466−15476.
Text and figures giving general data, spectroscopic data for
compounds, NMR and mass spectra, IR and DOSY NMR
spectra, and cyclic voltammograms. This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail for D.A.: d.astruc@ism.u-bordeaux1.fr.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Helpful assistance and discussion with Christophe Deraedt
(synthesis), Claire Mouche (mass spectrometry), and Jean-
Michel Lanier (NMR) from the CESAMO, Universite
́
Bordeaux 1, and financial support from the Universite
1, the Centre National de la Recherche Scientifique (CNRS),
the Agence Nationale de la Recherche (ANR), the Ministere de
l’Enseignement Superieur et de la Recherche Scientifique de
Cote d’Ivoire (Ph.D. grant to R.D.), and the China Scholarship
́
Bordeaux
(6) Reviews: (a) Tang, M. X.; Szka, F. C. Gene Ther. 1997, 4, 823−
832. (b) Kojima, C.; Kono, K.; Maruyama, K.; Takagishi, T.
Bioconjugate Chem. 2000, 11, 910−917. (c) Kohlhe, P.; Misra, E.;
Kannan, R. M. Int. J. Pharm. 2003, 259, 143−160. (d) Gupta, U.;
Agashe, H. B.; Asthana, A.; Jain, N. K. Biomacromolecules 2006, 7,
649−658.
̀
́
̂
Council (Ph.D. grant to Y.W.) is gratefully acknowledged.
(7) (a) Casado, C. M.; Cuadrado, I.; Moran, M.; Alonso, B.; Garcia,
B.; Gonzales, B.; Losada, J. Coord. Chem. Rev. 1999, 185−186, 53−79.
(b) Hwang, S. H.; Shreiner, C. D.; Moorefield, C. N.; Newkome, G. R.
New J. Chem. 2007, 31, 1192−1217. (c) Astruc, D.; Liang, L.;
Rapakousiou, A.; Ruiz, J. Acc. Chem. Res. 2012, 45, 630−640.
(d) Casado, C. M.; Alonso, B.; Losada, J.; Garcia-Armada, M. P. In
Designing Dendrimers; Campagna, S., Ceroni, P., Puntoriero, F., Eds.;
Wiley: Hoboken, NJ, 2012; pp 219−262.
REFERENCES
■
(1) (a) Newkome, G. R.; Moorefield, C. N.; Vogtle, F. Dendrons and
Dendrimers. Concepts, Synthesis and Applications; Wiley-VCH: Wein-
heim, Germany, 2001. (b) Dendrimers and other Dendritic Polymers;
̈
Tomalia, D., Frec
́
het, J. M. J., Eds.; Wiley-VCH: New York, 2002.
(c) Vogtle, F.; Richardt, G.; Werner, N. Dendrimer Chemistry. Concepts,
̈
Syntheses, Properties, Applications; Wiley-VCH: Weinheim, Germany,
2009. (d) Astruc, D.; Boisselier, E.; Ornelas, C. Chem. Rev. 2010, 110,
1857−1959. (e) Caminade, A.-M.; Turin, C.-O.; Laurent, R.; Ouali, A.;
Delavaux-Nicot, B. Dendrimers. Towards Catalytic, Material and
(8) (a) Togni, A.; Hayashi, T. Ferrocenes; Wiley-VCH: Weinheim,
Germany, 1995. (b) Adams, R. D. J. Organomet. Chem. 2001, 1, 637−
639. (c) Ferrocenes; Stepnicka, P., Ed.; Wiley: Weinheim, Germany,
K
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
2008. (d) For a recent overview of ferrocenes in nanomedicine, see:
Ornelas, C. New J. Chem. 2011, 35, 1973−1985.
́
(9) (a) Valerio, C.; Fillaut, J. L.; Ruiz, J.; Guittard, J.; Blais, J. C.;
Astruc, D. J. Am. Chem. Soc. 1997, 119, 2588−2589. (b) Sartor, V.;
Djakovitch, L.; Fillaut, J. L.; Moulines, F.; Neveu, F.; Marvaud, V.;
Guittard, J.; Blais, J. C.; Astruc, D. J. Am. Chem. Soc. 1999, 121, 2929−
2930. (c) Astruc, D.; Ruiz, J. Tetrahedron 2010, 66, 1769−1785.
(10) (a) Newkome, G. R.; Yao, Z.; Baker, G. R.; Gupta, V. K. J. Org.
Chem. 1985, 50, 2003−2004. (b) Newkome, G. R.; Shreiner, C. Chem.
Rev. 2010, 110, 6338−6442.
(11) (a) Ruiz, J.; Lafuentes, G.; Marcen, S.; Ornelas, C.; Lazare, S.;
Cloutet, E.; Blais, J.-C.; Astruc, D. J. Am. Chem. Soc. 2003, 125, 7250−
7257. (b) Ornelas, C.; Ruiz, J.; Belin, C.; Astruc, D. J. Am. Chem. Soc.
2009, 131, 590−601. (c) Boisselier, E.; Diallo, A. K.; Salmon, L.;
Ornelas, C.; Ruiz, J.; Astruc, D. J. Am. Chem. Soc. 2010, 132, 2729−
2742.
(12) Djeda, R.; Ornelas, C.; Ruiz, J.; Astruc, D. Inorg. Chem. 2010, 49,
6085−6101.
(13) Salmon, A.; Jutzi, P. J. Organomet. Chem. 2001, 637−639, 595−
608.
(14) Zamora, M.; Herrero, S.; Losada, J.; Cuadrado, I.; Casado, C.
M.; Alonso, B. Organometallics 2007, 26, 2688−2693.
(15) (a) Tezuka, Y.; Tanaka, S.; Imai, K. Polymer 1986, 27, 123−128.
(b) Anderluh, M.; Cesar, J.; Stefanic, P.; Kikelj, D.; Janes, D.; Murn, J.;
Nadrah, K.; Tominc, M.; Addicks, E.; Giannis, A.; Stegnar, M.; Dolenc,
M. Eur. J. Med. Chem. 2005, 40, 25−49.
(16) (a) Geiger, W. E. J. Am. Chem. Soc. 1974, 96, 2632−2634.
(b) Connelly, N. G.; Geiger, W. E. Adv. Organomet. Chem. 1984, 23,
1−93. (c) Geiger, W. E.; Connelly, N. G. Adv. Organomet. Chem. 1985,
24, 87−130. (d) Geiger, W. E. J. Organomet. Chem. Libr. 1990, 23,
142−172. (e) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96,
877−910. (f) For a historical review, see: Geiger, W. E.
Organometallics 2007, 26, 5738−5765. (g) For a perspective review,
see: Geiger, W. E. Organometallics 2011, 30, 28−31.
(17) Ruiz, J.; Astruc, D. C. R. Acad. Sci., Ser. IIc: Chim. 1998, 1, 21−
27.
(18) (a) Flanagan, J. B.; Margel, S.; Bard, A. J. Am. Chem. Soc. 1978,
100, 4248−4253. (b) Sutton, J. E.; Sutton, P. M.; Taube, H. Inorg.
Chem. 1979, 18, 1017−1024. (c) Richardson, D. E.; Taube, H. Coord.
Chem. Rev. 1984, 60, 107−129. (d) Barrier
̀
e, F.; Geiger, W. E. Acc.
Chem. Res. 2010, 43, 1030−1039.
(19) Gorman, C. B.; Smith, B. L.; Parkhurst, H.; Sierputowska-Gracz,
H.; Haney, C. A. J. Am. Chem. Soc. 1999, 121, 9958−9966.
(20) Amatore, C.; Bouret, Y.; Maisonhaute, E.; Goldsmith, J. I.;
Abruna, H. D. Chem. Eur. J. 2001, 7, 2206−2226.
̃
(21) (a) Abruna, H. D. In Electroresponsive Molecular and Polymeric
̃
Systems; Skotheim, T. A., Ed.; Dekker: New York, 1988; Vol. 1, p 97.
(b) Murray, R. W. In Molecular Design of Electrode Surfaces; Murray, R.
W., Ed.; Wiley: New York, 1992; Techniques of Chemistry XXII, p 1.
(22) (a) Peerce, P. J.; Bard, A. J. J. Electroanal. Chem. 1980, 114, 89−
111. (b) Lenhard, J. R.; Murray, R. W. J. Am. Chem. Soc. 1978, 100,
7870−7875. (c) Brown, A. P.; Anson, F. C. Anal. Chem. 1977, 49,
1589−1595. (d) Laviron, E. J. Electroanal. Chem. 1981, 122, 37−44.
L
dx.doi.org/10.1021/om400650s | Organometallics XXXX, XXX, XXX−XXX