Investigation of a molecular morphology effect on polyphenylazomethine dendrimers; physical properties and metal-assembling processes

Article abstract of DOI:10.1002/chem.200600511

A series of novel dendritic polyphenylazomethines (DPA) with asymmetric morphologies was synthesized. Their physical properties, such as encapsulating effect, molecular dynamics, and metal assembly, are strongly dependent on the entire conformation of the

Full text of DOI:10.1002/chem.200600511

DOI: 10.1002/chem.200600511
Investigation of a Molecular Morphology Effect on Polyphenylazomethine
Dendrimers; Physical Properties and Metal-Assembling Processes
Takane Imaoka, Reiko Tanaka, and Kimihisa Yamamoto*[a]
Abstract: A series of novel dendritic
polyphenylazomethines (DPA) with
asymmetric morphologies was synthe-
sized. Their physical properties, such as
encapsulating effect, molecular dynam-
ics, and metal assembly, are strongly
dependent on the entire conformation
of the molecules. The most important
property is layer-by-layer metal assem-
bly in the dendrimer structure from the
core to the outside. Bis- and tris-substi-
tuted DPAs of the fourth generation
also act as frameworks for stepwise as-
sembly of a metal component (SnCl2),
like the fully substituted symmetric
DPA. However, extensive investigation
of metal assembly in specific DPAs re-
vealed that they do not follow the step-
wise process. The molecular density
calculated from the experimental hy-
drodynamic volume indicated that bis-
and tris-substituted DPAs with asym-
metric morphology still retain a free
space similar to that of fully substituted
symmetric DPA. The monosubstituted
nals of the porphyrin core. It was dem-
onstrated that the conformation is not
fixed at room temperature in solvated
DPAs, especially in monosubstituted
DPA. A similar observation was for
the smaller DPAs (third generations)
with asymmetric morphologies. These
dendrimers do not follow the stepwise
complexation process. The structures of
bis- and tris-substituted dendrimers
which accurately follow the stepwise
process are fixed. These observations
provide a new insight into the finely
controlled metal-assembly chemistry of
dendritic macromolecules, and a rigid
and fixed conformation is one of im-
portant factors for their unique proper-
ties.
DPA, however, displayed
a slightly
higher density (smaller space) than the
other DPAs. The experimental results
suggest a bent conformation of the
dendrimer in which the core moiety is
folded into the dendron structure. In
addition, the molecular dynamics were
1
probed by means of the H NMR sig-
Keywords: dendrimers · molecular
dynamics · N ligands · porphyri-
noids · UV/Vis spectroscopy
Introduction
the cationic metal ion and entropy relaxation should pre-
dominate. This would lead to a system with a polydisperse-
metal-assembled structure in a monodisperse macromolecu-
lar ligand.[16]
Metal-assembling macromolecular ligands of low polydisper-
sity are key materials for size-controlled synthesis of metal
nanoparticles in the solution phase.[1–3] Dendritic architec-
ture is suitable for this concept because it may allow multi-
ple metal ions to be bound.[4–8] The spherical topology and
uniform molecular weight[9–15] would greatly contribute to
templated nanoparticle synthesis. However, most dendrimer
ligands, such as poly(amidoamine) (PAMAM), randomly as-
semble metal ions in spite of their unimolecular structure. In
the metal-assembling process, electronic repulsion between
Since the discovery of stepwise radial complexation in a
dendritic polyphenylazomethine (DPA),[17] variations of this
molecule were synthesized.[18–25] The DPA family of macro-
molecular ligands has a unique metal-assembling process in
which metal ions bind to the branching monomer units in
perfect order from the core to the outside termini. One of
the principal driving forces for stepwise assembly may be a
steep basicity gradient through the dendritic cascade struc-
ture, based on the strong electron-donating effect of the
phenylazomethine building blocks stacked on the outer con-
nections.[16]
In addition, it is likely that the rigid p-conjugated struc-
ture is indispensable for the unique metal-assembling prop-
erty. Dendrimers with a flexible backbone tend to exhibit
many conformations including backfolding of the terminal
monomers into the core even at room temperature.[26–32]
[a] Dr. T. Imaoka, R. Tanaka, Prof. Dr. K. Yamamoto
Department of Chemistry, Keio University
223–8522 Yokohama (Japan)
Fax : (+81)45-566-1718
E-mail: yamamoto@chem.keio.ac.jp
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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FULL PAPER
Therefore, the exact position of each monomer unit in the
flexible dendrimer cannot be defined. In contrast, the con-
formational variations of dendrimers composed of rigid
backbones are far fewer, and backfolding is avoided.[33–35]
Fine control of the coordination process is feasible for this
type of dendrimer. The DPAs belong to the group of rigid
dendrimers, as shown by their experimental hydrodynamic
and solid-state properties.[19,24,36] A three-dimensional (3D)
model obtained from MO calculations also indicates a stiff
structure which prevents the folding of the termini. As a
result, the DPA has enough space for full complexation of
metal ions until every coordination site is filled.
the same token, the morphology should affect the coordina-
tion properties in dependence on the dynamics of the DPAs.
The goal of this work was to determine the requirements for
finely controlled metal assembly in dendritic macromole-
cules from the aspects of morphology and dynamics. The
molecular form was investigated on the basis of the hydro-
dynamic parameters obtained from the intrinsic viscosity.
1
The H NMR signals predict the timescales of configuration-
al changes in the dendrimer structure. These properties are
related to SnCl2 assembly, as was determined by titration
with UV/Vis absorption spectroscopy.
It is important to elucidate how precise assembly is con-
trolled in DPAs. The mechanism would help new molecular
designs for advanced hybridized materials with macromolec-
ular and metallic elements. Herein we report on metal coor-
dination by zinc–porphyrin-cored DPAs in various molecu-
lar morphologies. Jiang and Aida reported that the number
of dendrimer substituent at the porphyrin meso positions
strongly affects their photo-energy-funneling properties
through morphology-controlled molecular dynamics.[37] By
Results
Synthesis and characterization of dendritic phenylazome-
thines (DPA) with different numbers of dendrons: Mono-,
di-, and tridendronized zinc–porphyrins (Scheme 1: ZnP-
[Dn]m, n=1–4, m=1–3) were prepared from zinc–meso-tet-
raphenylporphyrins with one, two, or three amino groups at
the para positions of their meso-phenyl rings (ZnP-[NH2]m).
Scheme 1. Synthesis and structures of DPAs with a zinc–porphyrin core.
Chem. Eur. J. 2006, 12, 7328 – 7336
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K. Yamamoto et al.
The aminoporphyrins were prepared by nitration of tetra-
phenylporphine (H2TPP) followed by reduction to the
amino group by using the literature method (see Supporting
and ZnP-[D4]3. Similarly, two singlets and two doublets
would be observed for ZnP-[D4]2. This is actually observed
in the experimental spectra for ZnP-[D4]2 and ZnP-[D4]3.
However, ZnP-[D4]1 displayed a broad peak in which the
signals are not separately identifiable. This indicates free ro-
tation of the dendron groups on the NMR timescale. For
the third-generation dendrimers ZnP-[D3]m, no peak split-
ting was observed even in the bis- and tris-substituted com-
pounds (m=2 and 3). In fact, all the conformations of these
high-generation (n=4) compounds with m=2–4dendrons
are fixed due to the rigid p-conjugated backbone and large
steric effect. The factor controlled by these numbers (m, n)
is important for their molecular dynamics in the solution
phase.
Information).[38] The product with cis
(syn) configuration of
G
the bis-substituted porphyrin (H2P-[NH2]2: aminophenyl
groups at the 5- and 10-positions of the porphyrin ring) was
isolated by column chromatography on silica gel. The Zn
complexes of these precursors were connected to the corre-
sponding phenylazomethine dendrons (Dn: n=1–4) by
using TiCl4 as dehydrating reagent. Dendrons of various
generations were synthesized by the established proce-
dure.[39] These products were isolated and purified by
column chromatography on silica gel and preparative HPLC
on size-exclusion chromatography (SEC) columns. The fully
dendronized zinc–porphyrins (ZnP-[Dn]4) were also pre-
pared by the reported method.
Hydrodynamic properties of the dendrimers: The hydrody-
namic properties of the fully substituted DPAs with a por-
phyrin core were determined on the basis of experimental
data (Table 1). The partially substituted DPAs (m=1–3)
were also studied on the basis of experimentally obtained
intrinsic viscosity [h]. The fully (m=4) and partially (m=2,
3) substituted dendrimers have [h] values that parallel each
other. For example, the bis-substituted DPA with four gener-
ations of dendrons ZnP-[D4]2 and the fully substituted DPA
with three generations ZnP-[D3]4 have similar [h] values,
which indicate similar hydrodynamic properties (radius,
volume, or molecular density). An exception is the mono-
substituted DPA, the [h] value of which is smaller. This
means that the density of the monosubstituted DPA mole-
cule is higher than those of the others because the [h] value
is proportional to Vh/Mw, in which Vh is the hydrodynamic
volume.[41] In other words, the free space (volume) inside
the monosubstituted dendrimer is smaller.
All compounds were characterized by MADLI-TOF MS
and 1H NMR and 13C NMR spectroscopy. The MS results
clearly show the monodisperse molecular weight of these
compounds in accordance with the theoretical masses (Sup-
porting Information). In the 1H NMR spectra, each signal
for the dendrons and the porphyrin core (b protons on the
pyrrole moieties) were identified at different chemical shifts.
The b-proton signal (d=8.7 ppm) indicates structural sym-
metry around the porphyrin core. For example, ZnP-[D4]4
showed a singlet at d=8.77 ppm that indicates a symmetric
conformation around the porphyrin core. The slight peak
broadening relative to standard zinc–porphyrin compounds
is due to the short spin–spin relaxation time T2 resulting
from the large encapsulating effect.[40] The b-proton signals
of the mono-, bis-, and tris-substituted compounds ZnP-
[D4]m (m=1–3) were split into multiple peaks, because the
symmetry of the molecular topology was lost (Figure 1). In
principle, four doublets would be observed for ZnP-[D4]1
Free volumes Vfree were estimated by subtraction of van
der Waals volumes VVW from Vh. The calculated fractions of
free space in the entire hydrodynamic volume (Vfree/Vh)
clearly demonstrated the differences between the monosub-
stituted dendrimer (m=1) and the others. The Vfree/Vh of
ZnP-[D4]1 was estimated to be 72%, while those of ZnP-
[D4]2, ZnP-[D4]3 and ZnP-[D4]4 were both 78%. Accord-
ing to NMR measurements, ZnP-[D4]1 could be in a bent
conformation with free rotation of the dendron group. The
smaller free space in ZnP-[D4]1 is consistent with the NMR
result. In contrast, the multisubstituted DPAs (m=2–4) pre-
vent backfolding and fix the dendron unit with retention of
the nanospace around the core. In both cases, the DPAs
have a relatively stiff backbone, as was shown by the larger
free volumes. The DPAs with a zinc–porphyrin core retain a
much larger free space than aryl ether dendrimers with the
same core unit and number of branching generations. For
example, the fully substituted aryl ether dendrimer with
four generations of dendrons retains 45% free volume per
unit hydrodynamic volume,[42] much smaller than that in the
DPA architecture (78%). The difference between these den-
drimers indicates effective restriction of backfolding in the
DPA due to its rigid backbone. This also means that the
layer-by-layer cascade topology of the dendrimer is main-
Figure 1. 1H NMR spectra of DPAs in CDCl3 focusing on b-protons at
the porphyrin core.
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Polyphenylazomethine Dendrimers
FULL PAPER
Table 1. Physical properties of the DPAs with a zinc–porphyrin core. The data of fully-substituted dendrimers
two effects of the dendrons:
the direct electron-donating
effect through covalent bond-
ing, and the local-domain
effect created by the encapsu-
lating character of the den-
drons. Increasing the genera-
tion number resulted in a con-
tinuous shift of E1/2 for the
multiply substituted DPAs.
However, the E1/2 of the mono-
substituted DPAs (m=1) did
not change while the genera-
tion number increased from
n=2 to 4. These results sug-
gesting absence of encapsulat-
ing character are consistent
with the 3D model of ZnP-
[D4]1, which shows an open-
shell configuration (Supporting
Information).
(m=4) are from a previous paper.[24]
Compound
m[a]
n[b]
[h][c] [dLgÀ1
]
Vh[d] [Š3]
Vfree[e] [Š3]
Vfree/Vh [%]
NMR[f]
N (n)[g]
ZnP-[D1]1
-[D2]1
1
1
1
1
1
2
3
4
0.0350
0.0401
0.0467
0.0473
1990
3230
5990
1280
2200
4330
7670
64.4
68.2
72.2
72.3
br
br
br
br
1 (1)
1 (2)
– (3)
– (4)
-[D3]1
-[D4]1
10600
ZnP-[D1]2
-[D2]2
2
2
2
2
1
2
3
0.0377
0.0458
0.0555
2590
5320
11700
1720
3820
8920
66.5
71.7
76.3
br
br
br
1 (1)
1 (2)
– (3)
4 (4)
-[D3]2
-[D4]2
40.0601
20024
18900
78.0
s, s, d, d
ZnP-[D1]3
-[D2]3
3
3
3
3
1
2
3
0.0419
0.0528
0.0598
3380
8020
17600
2350
6040
13700
69.6
75.3
77.9
br
br
br
1 (1)
1 (2)
– (3)
4 (4)
-[D3]3
-[D4]3
40.0603
35000
27300
78.0
d, d, d, d
ZnP-[D1]4
-[D2]4
41 05 0.04
3750
10000
0.0592
0.0591
2570
7580
22400
44900
68.4
75.5
17400
34800
s
1 (1)
42
4
0.0534
3
4
s
1 (2)
s
-[D3]4
-[D4]4
77.7
77.5
3 (3)
4 (4)
4
s
[a] Number of dendrons. [b] Number of generations. [c] Intrinsic viscosity. [d] Hydrodynamic volume. [e] Free
volume within the molecular hydrodynamic radius (Vfree =VhÀVVW). [f] 1H NMR signals of the b-protons on
the porphyrin ring. [g] Number of isosbestic points observed during UV/Vis titration with SnCl2 (numbers in
the parentheses are the ideal numbers for the complete stepwise processes), and bold face indicates cases in
which ideal stepwise complexation was observed.
It is known that dendritic
encapsulation of the core indu-
ces a significant change in the
redox potential.[46] This arises
tained in the real conformational structure of the DPA,
even in the solution phase. This structural character could
be one of the important factors allowing stepwise layer-by-
layer radial complexation without any distortion of the
metal assembly.
from noncovalent interaction between the redox center and
the dendrons (or external environment). Fine-tuning of the
nanospace inside the dendrimer could provide substrate spe-
cificity for molecular sensing.[47]
These experimental results support the molecular models
(Supporting Information) provided by optimizing calcula-
tions on these DPAs. The model of the fully substituted den-
drimer ZnP-[D4]4 in particular predicts effective isolation of
the porphyrin core from the external environment.[24] It was
also shown that the dendrimer contains a large free volume
in its dendritic shell. All models of the DPAs were generat-
ed by the same calculation procedure and adequately sup-
port all the obtained experimental data. Especially the
asymmetric dendrimers with two or three dendrons retain
their nanospace around the core in spite of their missing
arms. However, monosubstituted ZnP-[D4]1 no longer re-
tains the nanospace, and the porphyrin core is protrudes
from the molecular cage. These structural characteristics are
also supported by experimental data of their electrochemical
behavior on an electrode surface. The standard electron-
transfer kinetic constants k8 of the DPA series were deter-
mined by analyzing their cyclic voltammograms in THF. As
shown in Figure 2, the porphyrin core in higher substituted
dendrimers has a smaller k8 value. Although the kinetics on
an electrode surface involve many factors, such as the elec-
tron transfer distance, adsorption equilibria, and environ-
ment around the redox center, it was definitely observed
that the kinetics are attenuated by large substitution and
generation numbers.[43–45] The half-wave redox potential E1/2
of the zinc–porphyrin core also changed with generation
number n and substitution number m. It is influenced by
Figure 2. A) Standard redox potentials of the ZnP/ZnP+ redox couple
obtained from cyclic voltammograms of the DPAs. B) Standard rate con-
stants of these redox reactions on a glassy carbon electrode in THF con-
taining 0.1 molLÀ1 Bu4NPF6 as supporting electrolyte. Data for the fully
substituted DPA (m=4) were reported previously.[24]
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K. Yamamoto et al.
Metal assembly in asymmetric DPAs: DPAs can generally
[17]
assemble metallic compounds, such as SnCl2 or FeCl3.[24,48]
All of the imino groups in each layer of the dendrimer are
coordinating centers for these metal components. When 1:1
coordinating metals are selected, the number of coordina-
tion centers and assembled metal atoms would be identical.
Previously, we confirmed stepwise radial complexation from
the core to the outside layer in a fully substituted porphyrin-
cored DPA (Scheme 2) by a spectroscopic investigation.
Scheme 2. Schematic representation of stepwise complexation in fully
substituted phenylazomethine dendrimers with a zinc–porphyrin core.
Similarly, stepwise complexation in asymmetric DPAs is also
expected, because this is mainly based on the electronic
character of the dendrons. The complexation process of
SnCl2 to these dendrimers was determined by using the UV/
Vis absorption spectra.
Figure 3. UV/Vis spectra for stepwise addition of SnCl2 to a solution of
A) ZnP-[D4]1, B) ZnP-[D4]2, and C) ZnP-[D4]3 in C6H6/CH3CN (1:1).
Complexation of SnCl2 with the imino nitrogen atom of a
phenylazomethine unit brings about changes in UV/Vis ab-
sorption, accompanied by an isosbestic point around
360 nm. If coordination were a random process with no in-
terchromophore interaction, the isosbestic point should
appear at only one wavelength. However, the isosbestic
point is not necessarily fixed in the case of a nonuniformly
coordinating system in which complexation to a specific
center is preferred relative to the other centers. The DPAs
have multiple coordinating centers in a cascade topology. A
pair of centers in the same cascade layer is located in the
same chemical environment, but the another center in a dif-
ferent layer is in a different environment. In particular, the
DPAs have a highly graduated basicity of the coordinating
center across these layers. As a result, stepwise complexa-
tion successively proceeds during the addition of small
amounts of SnCl2 until full complexation. This is a stoichio-
metric process due to the 1:1 complexation between the
imine nitrogen atoms and SnCl2. In this case, the isosbestic
point should shift only when coordination switches to the
next layer during titration.
ters (imino groups) in the first, second, and third layers
from the core of ZnP-[D4]3. Bis-substituted ZnP-[D4]2 also
displayed a stepwise shift, which suggests possible metal as-
sembly in a stepwise fashion even in asymmetric DPAs.
However, the monosubstituted porphyrin ZnP-[D4]1 has
disordered metal-assembling behavior (Scheme 3). During
the titration of ZnP-[D4]1 by SnCl2, more than four isosbes-
tic points were observed. The DPAs with three generations
(ZnP-[D3]m) were also studied (Supporting Information).
Although complexation to give a fully substituted ZnP-
[D3]4 is a three-step process from the core to the outside,
the asymmetric series ZnP-[D3]m (m=1–3) did not show a
definite isosbestic point. It gradually shifted toward a short-
er wavelength on titration.
Discussion
The relationship between structural character of the DPA
and metal-assembling behavior was reconsidered. In summa-
ry, the backbone conformations of the multiply substituted
dendrimers with four generations ZnP-[D4]m (m=2–4) are
rigid and fixed due to their self-fixation, while those of mon-
osubstituted ZnP-[D4]1 and the DPAs with three genera-
Such observations were also confirmed during the titra-
tion of ZnP-[D4]3 and ZnP-[D4]2 (Figure 3). For example,
the isosbestic point shifted when 3, 9, and 21 molar equiva-
lents of SnCl2 versus ZnP-[D4]3 were added. These quanti-
ties are in agreement with the number of coordination cen-
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Polyphenylazomethine Dendrimers
FULL PAPER
Many dendritic multiligands are known, such as PAMAM
and polypropyleneamine dendrimers. Although they can col-
lect multiple metal ions in their vacant space, the detailed
metal-assembling process could never be defined and recog-
nized. It should be a random process because of their indefi-
nite conformation and roughly even distribution of electron-
ic density. These dendrimers have relatively flexible back-
bones. In contrast, DPAs have a rigid p-conjugated frame-
work in which the electron-donating property of the imine
units enhances electron density nearer the core. Not only
the basicity factor, but also the fixed conformation due to
stiff chemical bonding is a key property for finely controlled
metal assembly in DPAs. This provides us with information
about the molecular design strategy for novel metal-assem-
bling materials.
Conclusion
Scheme 3. Schematic representation of stepwise complexation in partially
substituted phenylazomethine dendrimers with a zinc–porphyrin core.
An asymmetric series of dendritic phenylazomethines
(DPAs) with a porphyrin core was synthesized to reveal the
structural requirements for stepwise radial complexation.
All the DPAs prepared in this study are macromolecular li-
gands capable of stoichiometric assembly of metal com-
pounds. However, the stepwise reaction from the core to the
outside proceeded successfully only in the multidendronized
DPAs with four generations. This can be related to the static
or dynamic conformation of the DPAs in solution. Dendrim-
ers ZnP-[D4]m (m=2–4) with finely controlled metal assem-
bly have fixed conformations, at least on the NMR time-
scale. These dendrimers retain the nanospace created in the
molecule without backfolding of the dendron termini. In
contrast, the conformations of the distorted metal-assem-
bling dendrimers (ZnP-[D4]1 and ZnP-[D3]m: m=1–3) are
not fixed. In these molecules, a topological layer-by-layer
structure is not necessarily retained in the actual geometric
space. Because identical coordinating environments in the
same layer would be distorted, the ideal stepwise reaction is
no longer feasible. This observation provides new insight
into design strategy for finely controlled metal-assembling
materials. The primary requirement is an intrinsic basicity
gradient along the molecular cascades, which could be gen-
erated by amplification of the electron-donating/withdraw-
ing property of the dendritic building blocks. The next re-
quirement is conformational stability of the molecules in
order to retain the unique layer-by-layer architecture.
tions (ZnP-[D3]m: m=1–4) are not. There is a mutual rela-
tion between structural character and metal complexation.
The group ZnP-[D4]m (m=2–4), in which the conformation
is fixed, is capable of finely controlled metal assembly from
the core to the outside. In contrast, the other group (ZnP-
[D3]m: m=1–3) could not precisely control complexation.
In our previous study, a DPA with a monosubstituted
phenyl group as core also exhibited similar stepwise com-
plexation starting from the core.[16] It is likely that stepwise
complexation is a characteristic property of the dendritic
phenylazomethine block. Distortion of the inherent property
gradient based on the electron density or donor strength
should be due to the bent conformation toward the vacant
space around the core unit. This could be confirmed by
quantitative analysis of the free space inside the dendrimer
structure. The smaller space in ZnP-[D4]1 (Vfree/Vh =72%)
than in ZnP-[D4]m (Vfree/Vh =78%) is direct evidence of the
bent structure shown by the molecular models. The lost free
volume in the DPA molecule should be equivalent to the
nanospace around the porphyrin center. On the experimen-
tal side, six distinguishable isosbestic points were deter-
mined by careful observation in the UV/Vis spectra on the
titration of ZnP-[D4]1. A possible reason for the unusual ti-
tration behavior is loss of the structural symmetry due to
the bent bridges and rotation of the core–dendron connec-
tion. Similar considerations are also applicable for the parti-
ally substituted asymmetric dendrimers with three genera-
tions (ZnP-[D3]m: m=1–3). The 1H NMR spectroscopic
data indicate that the molecular conformations of these den-
drimers are not fixed in solution at room temperature. The
molecular dynamics strongly influence the finely controlled
metal-assembling property of the DPA blocks. This idea is
also supported by the indistinct isosbestic point during the
titration of ZnP-[D3]m (m=1–3).
Experimental Section
General methods: The NMR spectra were recorded on an FT-NMR spec-
trometer (JEOL, JNM-GX 400) operating at 400 MHz (1H) or 100 MHz
(13C) at room temperature (258C). The 1H NMR chemical shifts were ref-
erenced to the residual proton signal of CDCl3 (d=7.26 ppm) and TMS
(d=0 ppm) as internal standards. The 13C NMR chemical shifts were ref-
1
erenced to CDCl3 (d=77.0 ppm). The H NMR pulse relaxation times T1
were measured in the saturation–recovery data-processing mode. The
MALDI-TOF mass spectra were obtained on
a
Shimadzu/Kratos
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K. Yamamoto et al.
AXIMA CFR plus mass spectrometer in positive mode with dithranol
(1,8-dihydroxy-9[10H]-anthracenone) as the matrix. Dendrimers were pu-
rified by preparative recycling HPLC (Japan Analytical Industry: LC908)
with chloroform or THF as eluent at a flow rate of 3.5 mLminÀ1
Materials: Titanium(IV) chloride (TiCl4), 1,4-diazabicyclo[2.2.2]octane
(DABCO), benzophenone, chlorobenzene, and all solvents used for the
purifications were purchased from Kantoh Kagaku Co. All other solvents
for the measurements were of dehydrated grade for organic synthesis
from Kantoh Kagaku Co. The partially substituted aminophenyl porphy-
Synthesis of ZnP-[D4]1: Porphyrin H2P-[NH2Ph]1 (40 mg, 0.058 mmol),
G4dendron (100 mg, 0.037 mmol), DABCO (251 mg, 2.2 mmol), and
TiCl4 (30 mL, 0.27 mmol) were used for the synthesis. An 80 mg (75%)
amount of product was isolated after purification. 1H NMR (400 MHz,
CDCl3, 258C, TMS): d=8.85 (br, 8H; pyrrole), 8.13 (br, 6H), 7.87–
6.57 ppm (m, 149H); 13C NMR (100 MHz, CDCl3, 258C): d=169.05,
168.82, 168.56, 168.35, 168.20, 168.08, 153.82, 152.01, 150.03, 142.87,
139.33, 135.85, 135.65, 134.50, 133.46, 132.41, 131.77, 130.97, 130.47,
130.16, 130.06, 129.44, 128.86, 128.24, 128.06, 127.88, 126.46, 122.24,
120.91, 120.56, 120.35, 119.48, 118.11 ppm; MALDI-TOF-MS (dithranol):
m/z calcd: 3367.38 [M+H]+, found: 3367.42; UV/Vis (CHCl3/CH3CN 1/
1): lmax (lge)=291 (5.191), 427 (5.637), 558 (4.293), 600 nm (3.950).
ACHTREUNG
.
AHCTREUNG
rins as precursors of the dendrimer core were synthesized by a modified
literature method (see Supporting Information). All DPA dendrons (G2–
G4) were synthesized as previously described.[39] All fully substituted
DPAs with a zinc–porphyrin core (ZnP-[Dn]4: n=1–4) were prepared by
a previously reported method.[24]
Synthesis of ZnP-[D1]2: Porphyrin H2P-[NH2Ph]2 (75 mg, 0.11 mmol),
benzophenone (G1, 58 mg, 0.32 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 73 mg (73%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.91–8.83 (br, 8H; pyrrole), 8.81 (br,
4H), 7.96–6.98 ppm (m, 34H); 13C NMR (100 MHz, CDCl3, 258C): d=
169.14, 150.91, 150.00, 143.01, 142.77, 139.42, 137.54, 136.38, 135.65,
134.28, 131.65, 130.90, 129.81, 129.43, 128.88, 128.28, 128.16, 127.96,
127.31, 126.40, 125.45, 120.77, 119.00 ppm; MALDI-TOF-MS (dithranol):
m/z calcd: 1037.55 [M+H]+, found: 1037.48; UV/Vis (CHCl3/CH3CN 1/
1): lmax (lge)=313 (4.345), 429 (5.606), 559 (4.298), 601 nm (4.017).
General synthetic procedure for partially dendronized porphyrin (ZnP-
[Dn]m): Aminophenylporphyrin H2P-[NH2Ph]m was treated with an
excess of anhydrous ZnCl2 in refluxing THF under an N2 atmosphere for
3 h. The resulting mixture was concentrated, and the product precipitated
with distilled water and collected by filtration to obtain ZnP-[NH2Ph]m
as a purple solid. The crude product was used for the next reaction after
washing with water. ZnP-[NH2Ph]m, DABCO, and the corresponding
DPA dendron (generation number n) were dissolved in chlorobenzene
(15 mL). TiCl4 (dehydrating reagent) was added through a dropping
funnel as a 1:4solution in chlorobenzene. The reaction mixture was
heated at 1258C for 2 h. It was then filtered, and the solution concentrat-
ed to dryness. The dendrimer products ZnP-[Dn]m were isolated by chro-
matography on a silica-gel column with hexane/chloroform/ethyl acetate
as eluent in the presence of 0.5% triethylamine and purified by prepara-
tive recycling HPLC with THF as eluent.
Synthesis of ZnP-[D2]2: Porphyrin H2P-[NH2Ph]2 (60 mg, 0.085 mmol),
G2 dendron (138 mg, 0.26 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. An 88 mg (64%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.91 (br, 8H; pyrrole), 8.21 (br, 4H),
7.93 (br, 4H), 7.81–6.75 (m, 64H), 6.57 ppm (br, 2H); 13C NMR
(100 MHz, CDCl3, 258C): d=168.88, 168.44, 153.63, 152.03, 150.96,
150.23, 149.91, 142.77, 139.32, 139.05, 137.21, 135.85, 135.60, 134.71,
134.47, 134.33, 131.87, 131.75, 130.89, 130.61, 130.16, 129.97, 129.46,
129.39, 129.30, 129.24, 128.85, 128.39, 128.18, 128.16, 128.05, 127.59,
127.32, 126.42, 120.57, 120.22, 119.49 ppm; MALDI-TOF-MS (dithranol):
m/z calcd: 1754.42 [M+H]+, found: 1753.81; UV/Vis (CHCl3/CH3CN 1/
1): lmax (lge)=286 (4.920), 428 (5.699), 559 (4.327), 601 nm (4.064).
Synthesis of ZnP-[D1]1: Porphyrin H2P-[NH2Ph]1 (50 mg, 0.072 mmol),
benzophenone (G1, 53 mg, 0.29 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 25 mg (54%)
amount of product was isolated after purification. 1H NMR (400 MHz,
CDCl3, 258C, TMS): d=8.94–8.86 (br, 8H; pyrrole), 8.20 (br, 6H), 7.94–
7.38 (m, 21H), 7.07 ppm (d, J=7.8 Hz, 2H); 13C NMR (100 MHz, CDCl3,
258C): d=169.15, 150.93, 150.21, 150.03, 142.75, 139.40, 137.49, 136.35,
134.31, 131.82, 130.89, 129.80, 129.43, 128.89, 128.27, 127.94, 127.37,
126.44, 120.92, 119.04 ppm; MALDI-TOF-MS (dithranol): m/z calcd:
856.24[ M+H]+, found: 856.39; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=
315 (4.287), 425 (5.747), 557 (4.297), 599 nm (3.922).
Synthesis of ZnP-[D3]2: Porphyrin H2P-[NH2Ph]2 (45 mg, 0.064 mmol),
G3 dendron (240 mg, 0.19 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 107 mg (58%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.96–8.89 (br, 8H; pyrrole), 8.18 (br,
4H), 7.96 (br, 4H), 7.78–6.70 (m, 122H), 6.62 (d, J=8.0 Hz, 8H), 6.49 (d,
J=5.6 Hz, 4H), 6.31 ppm (d, J=8.4Hz, 4H); 13C NMR (100 MHz,
CDCl3, 258C): d=168.94, 168.56, 168.45, 168.32, 168.13, 168.06, 154.08,
153.72, 153.66, 152.45, 151.91, 151.56, 150.96, 150.14, 149.80, 142.83,
139.26, 139.07, 137.35, 135.79, 135.75, 135.59, 135.32, 134.47, 134.38,
134.28, 134.19, 131.88, 131.59, 130.87, 130.59, 130.43, 130.35, 130.18,
130.11, 129.41, 129.38, 128.91, 128.84, 128.39, 128.17, 128.02, 127.92,
127.53, 127.31, 126.40, 120.90, 120.71, 120.52, 120.31, 120.00, 119.59 ppm;
MALDI-TOF-MS (dithranol): m/z calcd: 3188.16 [M+H]+, found:
3186.84; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=292 (5.187), 429
(5.691), 559 (4.325), 601 nm (4.054).
Synthesis of ZnP-[D2]1: Porphyrin H2P-[NH2Ph]1 (50 mg, 0.072 mmol),
G2 dendron (157 mg, 0.29 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 33 mg (50%)
amount of product was isolated after purification. 1H NMR (400 MHz,
CDCl3, 258C, TMS): d=8.93 (br, 8H; pyrrole), 8.20 (br, 6H), 7.92 (br,
2H), 7.80–6.59 ppm (m, 39H); 13C NMR (100 MHz, CDCl3, 258C): d=
168.2, 168.44, 168.36, 153.65, 152.04, 151.00, 150.24, 150.02, 142.74, 142.72,
139.31, 139.11, 137.18, 135.85, 135.61, 134.68, 134.44, 134.32, 131.80,
130.90, 130.65, 130.16, 129.45, 129.38, 129.31, 129.25, 128.84, 128.42,
128.19, 128.16, 128.06, 127.62, 127.36, 126.44, 120.60, 120.23, 119.46 ppm;
MALDI-TOF-MS (dithranol): m/z calcd: 1216.77 [M+H]+, found:
1216.67; UV/Vis (CHCl3/CH3CN 1/1) lmax (lge)=287 (4.683), 422 (5.694),
558 (4.301), 599 nm (3.950).
Synthesis of ZnP-[D4]2: Porphyrin H2P-[NH2Ph]2 (30 mg, 0.043 mmol),
G4dendron (360 mg, 0.13 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 160 mg (68%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.91 (s, 2H; pyrrole), 8.80 (d, J=
4.4 Hz, 2H; pyrrole), 8.78 (s, 2H; pyrrole), 8.71 (d, J=4.4 Hz, 2H; pyr-
role), 8.04(d, J=7.2 Hz, 4H), 7.82–6.54 (m, 266H), 6.36 (d, J=6.8 Hz,
4H), 6.24 (d, J=7.2 Hz, 4H), 6.05 (d, J=7.6 Hz, 4H), 6.01 (d, J=8.0 Hz,
4H), 5.74ppm (d, J=6.8 Hz, 4H); 13C NMR (100 MHz, CDCl3, 258C):
d=168.88, 168.40, 168.34, 168.17, 167.99, 167.85, 167.78, 153.91, 153.70,
153.29, 151.91, 151.40, 151.16, 150.16, 149.88, 139.23, 139.15, 138.94,
138.87, 135.78, 135.54, 135.18, 134.43, 134.24, 131.93, 130.89, 130.61,
130.38, 130.09, 129.87, 129.71, 129.40, 129.06, 128.82, 128.17, 127.99,
127.88, 127.76, 126.27, 121.26, 120.71, 120.48, 120.26, 120.06, 119.44 ppm;
MALDI-TOF-MS (dithranol): m/z calcd: 6055.64[ M+H]+, found:
Synthesis of ZnP-[D3]1: Porphyrin H2P-[NH2Ph]1 (50 mg, 0.072 mmol),
G3 dendron (364mg, 0.29 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 52 mg (48%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.93 (br, 8H; pyrrole), 8.21 (br, 6H),
7.97 (d, J=7.8 Hz, 2H), 7.78–6.61 (m, 71H), 6.50 (d, J=7.6 Hz, 2H),
6.29 ppm (d, J=8.4Hz, 2H); 13C NMR (100 MHz, CDCl3, 258C): d=
168.95, 168.58, 168.45, 168.37, 168.18, 168.11, 154.12, 153.73, 153.66,
152.45, 151.90, 151.53, 151.29, 150.02, 149.93, 142.79, 142.73, 139.26,
139.07, 137.98, 137.26, 135.78, 135.60, 135.32, 134.39, 134.24, 134.19,
131.79, 130.89, 130.61, 130.46, 130.35, 130.11, 129.41, 128.91, 128.82,
128.40, 128.18, 128.02, 127.91, 127.54, 127.35, 126.45, 121.22, 120.91,
120.67, 120.52, 120.32, 120.01, 119.55 ppm; MALDI-TOF-MS (dithranol):
m/z calcd: 1933.64[ M+H]+, found: 1932.88; UV/Vis (CHCl3/CH3CN 1/
1): lmax (lge)=291 (4.927), 423 (5.710), 558 (4.279), 599 nm (3.919).
7334
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 7328 – 7336

Polyphenylazomethine Dendrimers
FULL PAPER
6055.77; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=289 (5.468), 432
(5.679), 560 (4.294), 602 nm (4.046).
[1] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. 2005, 117, 8062–
8083; Angew. Chem. Int. Ed. 2005, 44, 7852–7872.
[2] R. Shenhar, T. B. Norsten, V. M. Rotello, Adv. Mater. 2005, 17, 657–
669.
[3] B. L. Cushing, V. L. Kolesnichenko, C. J. OꢁConnor, Chem. Rev.
2004, 104, 3893–3964.
Synthesis of ZnP-[D1]3: Porphyrin H2P-[NH2Ph]3 (50 mg, 0.069 mmol),
benzophenone (G1, 63 mg, 0.35 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 15 mg (19%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.90–8.82 (br, 8H; pyrrole), 8.20 (br,
2H), 7.97–7.42 (m, 37H), 7.08 ppm (br, 8H); 13C NMR (100 MHz,
CDCl3, 258C): d=168.88, 168.40, 168.34, 168.17, 167.99, 167.85, 167.78,
153.91, 153.70, 153.29, 151.91, 151.40, 151.16, 150.16, 149.88, 139.23,
139.15, 138.94, 138.87, 135.78, 135.54, 135.18, 134.43, 134.24, 131.93,
130.89, 130.61, 130.38, 130.09, 129.87, 129.71, 129.40, 129.06, 128.82,
128.17, 127.99, 127.88, 127.76, 126.27, 121.26, 120.71, 120.48, 120.26,
120.06, 119.44 ppm; MALDI-TOF-MS (dithranol): m/z calcd: 6055.64
[M+H]+, found: 6055.77; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=312
(4.437), 429 (5.763), 559 (4.351), 601 nm (4.111).
[4] V. Vicinelli, P. Ceroni, M. Maestri, V. Balzani, M. Gorka, F. Vçgtle,
J. Am. Chem. Soc. 2002, 124, 6461–6468.
[5] F. L. Derf, E. Levillain, G. TrippØ, A. Gorgues, M. SallØ, R.-M. Se-
bastían, A.-M. Caminade, J.-P. Majoral, Angew. Chem. 2001, 113,
230–233; Angew. Chem. Int. Ed. 2001, 40, 224–227.
[6] M. Tominaga, J. Hosogi, K. Konishi, T. Aida, Chem. Commun. 2000,
719–720.
[7] F. Vçgtle, S. Gestermann, C. Kauffmann, P. Ceroni, V. Vicinelli, V.
Balzani, J. Am. Chem. Soc. 2000, 122, 10398–10404.
[8] M. F. Ottaviani, F. Montalti, N. J. Turro, D. A. Tomalia, J. Phys.
Chem. B 1997, 101, 158–166.
[9] R. M. Crooks, M. Zhao, L. Sun, V. Chechik, L. K. Yeung, Acc.
Chem. Res. 2001, 34, 181–190.
[10] S. KØki, J. Tçrçk, G. Deµk, L. Daróczi, M. Zsuga, J. Colloid Inter-
face Sci. 2000, 229, 550–553.
[11] Y. Nakanishi, T. Imae, J. Colloid Interface Sci. 2005, 285, 158–162.
[12] X. Sun, S. Dong, E. Wang, Macromolecules 2004, 37, 7105–7108.
[13] H. Ye, R. M. Crooks, J. Am. Chem. Soc. 2005, 127, 4930–4934.
[14] M. Zhao, R. M. Crooks, Adv. Mater. 1999, 11, 217–220.
[15] M. Zhao, R. M. Crooks, Angew. Chem. 1999, 111, 375–377; Angew.
Chem. Int. Ed. 1999, 38, 364–366.
[16] K. Yamamoto, T. Imaoka, Bull. Chem. Soc. Jpn. 2006, 79, 511–526.
[17] K. Yamamoto, M. Higuchi, S. Shiki, M. Tsuruta, H. Chiba, Nature
2002, 415, 509–511.
[18] T. Imaoka, H. Horiguchi, K. Yamamoto, J. Am. Chem. Soc. 2003,
125, 340–341.
[19] N. Satoh, J.-S. Cho, M. Higuchi, K. Yamamoto, J. Am. Chem. Soc.
2003, 125, 8104–8105.
Synthesis of ZnP-[D2]3: Porphyrin H2P-[NH2Ph]3 (40 mg, 0.056 mmol),
G2 dendron (150 mg, 0.28 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 72 mg (67%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.56 (br, 8H; pyrrole), 7.82–6.72 (m,
97H), 6.47 ppm (m, 4H); 13C NMR (100 MHz, CDCl3, 258C): d=168.83,
168.78, 168.40, 168.23, 153.57, 152.00, 150.72, 149.74, 149.68, 149.44,
142.87, 139.35, 139.01, 137.38, 135.85, 135.60, 134.74, 134.32, 131.32,
130.88, 130.54, 130.14, 129.47, 129.39, 129.29, 129.19, 128.87, 128.17,
128.06, 127.53, 127.08, 126.18, 120.57, 120.26, 120.16, 119.23 ppm;
MALDI-TOF-MS (dithranol): m/z calcd: 2292.07 [M+H]+, found:
2292.87; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=285 (5.056), 432
(5.716), 560 (4.338), 602 nm (4.142).
Synthesis of ZnP-[D3]3: Porphyrin H2P-[NH2Ph]3 (30 mg, 0.042 mmol),
G3 dendron (261 mg, 0.48 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (60 mL, 0.55 mmol) were used for the synthesis. A 97 mg (62%)
amount of the product was isolated after purification. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=8.91–8.84(br, 8H; pyrrole), 8.15 (br,
2H), 7.95 (br, 6H), 7.78–6.51 (m, 193H), 6.31 ppm (d, J=7.2 Hz, 8H);
13C NMR (100 MHz, CDCl3, 258C): d=168.92, 168.54, 168.44, 168.31,
168.10, 168.01, 154.05, 153.70, 153.66, 152.42, 151.89, 151.57, 150.90,
150.01, 139.26, 139.06, 137.48, 135.79, 135.73, 135.58, 135.32, 134.51,
134.39, 134.29, 134.19, 134.10, 131.63, 130.85, 130.61, 130.44, 130.34,
130.10, 129.40, 129.36, 128.92, 128.83, 128.40, 128.16, 128.02, 128.92,
128.54, 128.39, 120.88, 120.72, 120.50, 120.30, 120.00, 119.59 ppm;
MALDI-TOF-MS (dithranol): m/z calcd: 4442.68 [M+H]+, found:
4440.21; UV/Vis (CHCl3/CH3CN 1/1): lmax (lge)=291 (5.344), 433
(5.701), 560 (4.333), 603 nm (4.124).
[20] M. Higuchi, M. Tsuruta, H. Chiba, S. Shiki, K. Yamamoto, J. Am.
Chem. Soc. 2003, 125, 9988–9997.
[21] O. Enoki, T. Imaoka, K. Yamamoto, Org. Lett. 2003, 5, 2547–2549.
[22] A. Kimoto, K. Masachika, J.-S. Cho, M. Higuchi, K. Yamamoto,
Org. Lett. 2004, 6, 1179–1182.
[23] N. Satoh, T. Nakashima, K. Yamamoto, J. Am. Chem. Soc. 2005,
127, 13030–13038.
[24] T. Imaoka, R. Tanaka, S. Arimoto, M. Sakai, M. Fujii, K. Yamamo-
to, J. Am. Chem. Soc. 2005, 127, 13896–13905.
Synthesis of ZnP-[D4]3: Porphyrin H2P-[NH2Ph]3 (50 mg, 0.069 mmol),
the G4dendron (1.00 g, 0.37 mmol), DABCO (250 mg, 2.2 mmol), and
TiCl4 (100 mL, 0.91 mmol) were used for the synthesis. A 242 mg (43%)
amount of product was isolated after purification. 1H NMR (400 MHz,
CDCl3, 258C, TMS): d=8.87 (d, J=4.0 Hz, 2H; pyrrole), 8.81 (d, J=
4.0 Hz, 2H; pyrrole), 8.75 (d, J=4.4 Hz, 2H; pyrrole), 8.66 (d, J=4.0 Hz,
2H; pyrrole), 7.97–6.06 (m, 423H), 5.83 (d, J=8.0 Hz, 2H); 13C NMR
(100 MHz, CDCl3, 258C): d=169.11, 168.87, 168.36, 168.13, 167.84,
153.69, 151.90, 139.27, 135.76, 135.56, 130.88, 130.60, 130.37, 130.09,
129.36, 129.09, 128.80, 128.18, 128.00, 127.88, 127.82, 127.53, 121.10,
120.90, 120.49, 120.24, 120.05 ppm; MALDI-TOF-MS (dithranol): m/z
calcd: 8743.90 [M+H]+, found: 8743.00; UV/Vis (CHCl3/CH3CN 1/1):
lmax (lge)=290 (5.643), 434 (5.687), 560 (4.315), 602 nm (4.108).
[25] O. Enoki, H. Katoh, K. Yamamoto, Org. Lett. 2006, 8, 569–571.
[26] W. Oriz, A. E. Roitberg, J. L. Krause, J. Phys. Chem. B 2004, 108,
8218–8225.
[27] M. Han, P. Chen, X. Yang, Polymer 2005, 46, 3481–3488.
ˇ
[28] P. K. Maiti, T. C¸ agin, G. Wang, W. A. Goddard III, Macromolecules
2004, 37, 6236–6254.
[29] D. Boris, M. Rubinstein, Macromolecules 1996, 29, 7251–7260.
[30] M. Chai, Y. Niu, W. J. Youngs, P. L. Rinaldi, J. Am. Chem. Soc.
2001, 123, 4670–4678.
[31] D. Pçtschke, M. Ballauff, P. Lindner, M. Fischer, F. Vçgtle, Macro-
molecules 1999, 32, 4079–4087.
[32] M. Ballauff, Top. Curr. Chem. 2001, 212, 177–194.
[33] M. Ballauff, C. N. Likos, Angew. Chem. 2004, 116, 3060–3082;
Angew. Chem. Int. Ed. 2004, 43, 2998–3020.
[34] S. Rosenfeldt, N. Dingenouts, D. Pçtschke, M. Ballauff, A. J. Berre-
sheim, K. Müllen, P. Lindner, Angew. Chem. 2004, 116, 111–114;
Angew. Chem. Int. Ed. 2004, 43, 109–112.
[35] M. Wind, K. Saalwächter, U.-M. Wiesler, K. Müllen, H. W. Spiess,
Macromolecules 2002, 35, 10071–10086.
Acknowledgements
[36] M. Higuchi, S. Shiki, K. Ariga, K. Yamamoto, J. Am. Chem. Soc.
2001, 123, 4414–4420.
[37] D.-L. Jiang, T. Aida, J. Am. Chem. Soc. 1998, 120, 10895–10901.
[38] W. J. Kruper, T. A. Chamberlin, Jr., M. Kochanny, J. Org. Chem.
1989, 54, 2753–2756.
This work was supported in part by the Core Research for Evolutional
Science and Technology (CREST) program of the Japan Science and
Technology (JST) Agency, and by a Scientific Research Program for the
21st Century Center of Excellence (COE) (Keio-LCC) of the Ministry of
Education, Culture, Sports, Science and Technology (MEXT) of Japan.
Chem. Eur. J. 2006, 12, 7328 – 7336
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7335

K. Yamamoto et al.
[39] K. Takanashi, H. Chiba, M. Higuchi, K. Yamamoto, Org. Lett. 2004,
6, 1709–1712.
[40] D. D. Traficante in Encyclopedia of Nuclear Magnetic Resonance,
Vol. 6 (Eds.: D. M. Grant, R. K. Harris), Wiley, New York, 1996,
p. 3988.
[41] T. H. Mourey, S. R. Turner, M. Rubinstein, J. M. J. FrØchet, C. J.
Hawker, K. L. Wooley, Macromolecules 1992, 25, 2401–2406.
[42] M. S. Matos, J. Hofkens, W. Verheijen, F. C. de Schryver, S. Hecht,
K. W. Pollak, J. M. J. FrØchet, B. Forier, W. Dehaen, Macromolecules
2000, 33, 2967–2973.
[44] C. B. Gorman, J. S. Smith, Acc. Chem. Res. 2001, 34, 60–71.
[45] C. B. Gorman, J. C. Smith, M. W. Hager, B. L. Parkhurst, H. Sierzpu-
towska-Gracz, C. A. Haney, J. Am. Chem. Soc. 1999, 121, 9958–
9966.
[46] C. M. Cardona, S. Mendoza, A. E. Kaifer, Chem. Soc. Rev. 2000, 29,
37–42.
[47] D. Astruc, M.-C. Daniel, J. Ruiz, Chem. Commun. 2004, 2637–2649.
[48] R. Nakajima, M. Tsuruta, M. Higuchi, K. Yamamoto, J. Am. Chem.
Soc. 2004, 126, 1630–1631.
[43] T. L. Chasse, R. Sachdeva, Q. Li, Z. Li, R. J. Petrie, C. B. Gorman, J.
Am. Chem. Soc. 2003, 125, 8250–8254.
Received: April 11, 2006
Published online: August 3, 2006
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