Supramolecular nanofiber formation of macrocyclic dendrimer

Article abstract of DOI:10.1021/ma0492364

Novel macrocyclic dendrimers (Scheme 2), having two czs-1,3,5- cyclohexanetricarboxamide (1) or 1,3,5-benzenetricarboxamide units (3) in their core, were synthesized, and their self-assembly behaviors were evaluated in solution. Infrared spectroscopy of c

Full text of DOI:10.1021/ma0492364

Macromolecules 2004, 37, 7325-7330
7325
Supramolecular Nanofiber Formation of Macrocyclic Dendrimer
Woo-Don g J a n g* a n d Ta k u zo Aid a
Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo,
7
-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, J apan
Received April 20, 2004; Revised Manuscript Received J une 18, 2004
ABSTRACT: Novel macrocyclic dendrimers (Scheme 2), having two cis-1,3,5-cyclohexanetricarboxamide
(
1) or 1,3,5-benzenetricarboxamide units (3) in their core, were synthesized, and their self-assembly
behaviors were evaluated in solution. Infrared spectroscopy of cis-1,3,5-cyclohexanetricarboxamide cored
dendrimer (1) in CHCl indicated that formation of strong hydrogen-bonding interactions is taking place
among the core units. The H NMR spectrum of 1 in CDCl
were sharpened by adding one drop of CF CO H. GPC analysis showed the formation of self-assembled
3
1
3
showed broadenings of all the peaks, which
3
2
particles having ultrahigh molecular weight, whose average diameter was evaluated as about 140 nm by
DLS measurement. AFM observation of the cast on mica film showed that 1 forms a fibrous assembly of
uniform thickness with a diameter of 6 nm. In sharp contrast to 1, 1,3,5-benzenetricarboxamide units
cored dendrimer (3) did not form a fibrous assembly under identical conditions because of the twisted
arrangement of the core units.
In tr od u ction
Sch em e 1. Hyd r ogen -Bon d in g-Med ia ted
Self-Assem bly Str u ctu r es of
cis-1,3,5-Cycloh exa n etr ica r boxa m id e (Righ t) a n d
Secondary and tertiary structures of natural macro-
molecules such as polypeptides, polynucleotides, and
polysaccharides are mostly controlled by noncovalent
interactions. These interactions are very important in
macromolecular chemistry where hydrogen bonding and
other weak reversible interactions can make a major
contribution to designing new polymeric architectures.
In recent years, a number of concepts have been
proposed that use noncovalent interactions for the
1,3,5-Ben zen etr ica r boxa m id e (Left)
1
construction of a supramolecular polymeric assembly.
To obtain a linear type supramolecular polymeric as-
2
sembly, it is desirable to have interactions sufficiently
strong, directional, and sufficiently reversible to alter-
nate covalent bonds. cis-1,3,5-Cyclohexanetricarbox-
amide and 1,3,5-benzenetricarboxamide4 units are
potential scaffolds for the construction of supramolecu-
lar polymeric assembly systems. Both of them exhibit
a discotic supramolecular assembly via intermolecular
hydrogen bonding (Scheme 1). cis-1,3,5-Cyclohexane-
tricarboxamide has three unidirectional amide units in
which the cis-1,3,5-cyclohexanetricarboxamide deriva-
tives form a physical gel or viscoelastic fluid depending
3
3
on the solvents. 1,3,5-Benzenetricarboxamide deriva-
macrocycle with a significantly high molecular weight
attributable to intermolecular hydrogen bonding in
solution.
tives also form unidirectional hydrogen bonds with a
typical helical arrangement within the supramolecular
assembly structure.4
On the other hand, dendrimers are nanometer-sized
hyperbranched macromolecules with well-predictable
three-dimensional shapes and potential building blocks
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter istic. A series of poly-
benzyl ether) dendrimers (Scheme 2) having macro-
(
5
,6
for the construction of organized functional materials.
cyclic cores, which contain two cis-1,3,5-cyclohexane-
tricarboxamide or 1,3,5-benzenetricarboxamide units,
were synthesized and characterized by H NMR and
MALDI-TOF-MS spectroscopy. Details of the syn-
thetic methodology for the macrocyclic dendrimers are
shown in Scheme 3. First, phthalimide was introduced
to 3,5-di-tert-butyldiphenylsilyloxybenzyl alcohol (4) ac-
Since dendrimers have unique three-dimensional shapes,
solution properties are predominantly dependent on the
peripheral functionalities, and core structures are pos-
1
7
sibly insulated from the outer environment. From this
point of view, three-dimensional warping of the su-
pramolecular assembly system using dendrimer frame-
works has potentials for providing a very interesting
aspect. In this paper, we demonstrate a novel fibrous
supramolecular assembly8 formation of a dendritic
9
cording to the Mitsunobu’s coupling reaction. Then, 5
thus obtained was reacted with Frechet’s dendron
1
0
bromide (6) to get phthalimide cored dendron (7),
which was changed to amine core dendrimer (8) using
hydrazine. Tris-p-nitrophenyl-cis-1,3,5-cyclohexane tri-
*
Corresponding author. E-mail: jang@bmw.t.u-tokyo.ac.jp.
1
0.1021/ma0492364 CCC: $27.50 © 2004 American Chemical Society
Published on Web 08/25/2004

7
326 J ang and Aida
Macromolecules, Vol. 37, No. 19, 2004
Sch em e 2. Ma cr ocyclic Den d r im er s
exhibited patterns quite different from that of 1, where
the N-H stretching vibration band was exhibited at
carboxylate (10) prepared by dicyclohexyl carbodiimide
mediated condensation of p-nitrophenol and cis-1,3,5-
cyclohexanetricarboxylic acid (9). Tris-p-nitrophenyl-
benzene tricarboxylate (13) was prepared by condensa-
tion reaction of trimesoyl chloride (10) and p-nitrophenol.
And then, 8 was reacted with 10 or 13 to get precursors
for the macrocycle 11 or 14, respectively. 11 or 14 thus
obtained was reacted with 4,4′-biphenyldiaminomethyl
to get the corresponding macrocyclic dendrimers 1 and
-
1
3
390 cm and stretching vibrations of amide I and II
-
1
were exhibited at 1660 and 1518 cm , respectively
(
Figure 1), indicating no hydrogen bonding.
On the other hand, the H NMR spectrum of 1 in
1
CDCl3 (1 mM) displayed significantly broad bands of all
1
the characteristic peaks (Figure 2a), whereas the H
NMR spectrum of 3 in CHCl3 displayed simple sharp
peaks. These observations again indicate possible for-
mation of molecular assembly via hydrogen bonding,
3
, respectively. 1 has two different isomeric structures
because of the orientation of amide bonds of core
cyclohexyl units. However, all the evaluation of 1 was
performed as a mixture of the two isomers because the
two isomers were not distinguishable or separable by
the conventional analytic methods. The N-methylated
derivative macrocyclic dendrimer (2) was prepared from
1
which leads to the broadening of H NMR signals of 1
because of the restriction of conformational change in
CDCl3. It is interesting that all the peaks of 1 in CDCl3
were changed to simple sharp peaks to be identified by
the addition of a drop of CF3CO2H, a strong hydrogen-
bonding acceptor (Figure 2b). These changes indicate
that the CF3CO2H molecules dissociated the assembled
dendrimers.
Dyn a m ic Ligh t Sca tter in g (DLS) a n d Gel P er -
m ea tion Ch r om a togr a p h y (GP C). Figure 3 shows
the histogram profile of DLS result of 1 (0.06 mM) in
1
by alkali mediated coupling reaction with MeI. All the
macrocyclic dendrimers were highly soluble to the
halogenated solvents or polar aprotic solvents, such as
CHCl3, CH2Cl2, CH2ClCH2Cl, DMF, DMSO, etc.
Sp ectr oscop ic Stu d ies of Ma cr ocyclic Den d r im -
er s. The infrared spectrum (IR) of CHCl3 solution of 1
CHCl , which indicates the formation of quite a large
3
(
5.0 mM) displayed relatively broad absorption bands
particles. The average diameter of the particles was
-1
-1
at 3290 cm , with sharp bands at 1640 and 1550 cm
,
evaluated as 142 ( 48 nm. However, 3 has insufficient
light scattering intensity in the DLS measurement to
be detected as particles. Therefore, the average molec-
ular weight of particles was examined by GPC. The
result showed that 1 exhibited a peak at extremely high
molecular weight region (Figure 4a), eluting at the time
of the exclusion limit of a column (TSKgel GMHXL
which are characteristics of stretching vibrations of
N-H, amide I, and amide II, respectively.1 These
spectral characteristics indicate that the amide groups
of 1 are hydrogen bonded to each other despite diluted
concentration in solution. Very interestingly, however,
the IR spectrum of CHCl3 solution of 3 (5.0 mM)
1

Macromolecules, Vol. 37, No. 19, 2004
Sch em e 3. Syn th esis of Ma cr ocyclic Den d r im er sa
Macrocyclic Dendrimers 7327
a
Reagents and reaction conditions: (i) DEAD, PPh
3
, phthalimide, in THF at 0 °C for 1 h and 25 °C for 11 h; (ii) KF, 18-crown-6
ether, 6, in acetone reflux 3 h; (iii) DCC, p-nitrophenol, in DMF at 0 °C for 1 h and 25 °C for 12 h; (iv) in DMF at 60 °C for 36 h;
v) in DMF at 60 °C for 72 h; (vi) H NNH ‚H O in THF/EtOH (1/1) reflux 12 h; (vii) p-nitrophenol, 1,3,5-collidine, in DMF at 0 °C
h and 25 °C 12 h.
(
2
2
2
1
3
F igu r e 1. FT-IR spectra of 1 (solid) and 3 (dotted) in CHCl .
F igu r e 2. 1H NMR spectra of 1 in CHCl
included CHCl (b).
(a) and in TFA
3
exclusion limit: 4 × 108, eluent: CHCl3). Interestingly,
when the solution containing a small amount of CF3-
CO2H was eluted, the retention time was significantly
increased (Figure 4b). This observation agrees with the
3
1
ever, IR and H NMR spectra revealed that it was hard
for 3 to form hydrogen bonds. GPC analysis of 3 also
exhibited a single sharp peak with the same retention
time as 2, indicating that 3 does not associate under
the GPC condition (Figure 4d).
1
H NMR result. As a non-hydrogen-bonding model
compound, the N-methylated derivative (2) was newly
1
synthesized and unambiguously characterized by
H
NMR and MALDI-TOF-MS spectroscopy. The GPC
profile of 2 exhibited a single sharp peak with the same
retention time as the solution of 1 containing CF3CO2H,
indicating that the addition of CF3CO2H dissociated the
assembled macrocyclic dendrimers (Figure 4c). Consid-
ering the number of hydrogen-bonding sites, 3 also has
a possibility to form a supramolecular assembly. How-
Atom ic F or ce Micr oscop ic (AF M) Obser va tion of
Ma cr ocyclic Den d r im er . To find the morphology of
the dendrimer assembly, the CHCl3 solution of macro-
cyclic dendrimers was spin-coated on a mica film and
then subjected to AFM. Clearly 1 formed as entangled
fibrous structures (Figure 5a). With sufficient dilution

7
328 J ang and Aida
Macromolecules, Vol. 37, No. 19, 2004
Th er m a l Sta bility of Assem bly. Variable-temper-
1
ature H NMR measurement was performed to check
the thermal stability of hydrogen bond of self-assembled
dendrimers (Figure 6). At room temperature, the 1
H
NMR spectrum of 1 in o-dichlorobenzene-d4 displayed
broad bands of all the peaks, similar to that in CDCl3.
On raising the temperature, these broad bands re-
mained up to 150 °C. At 150 °C, all the peaks sharpened
enough to be identified. For comparison with the
behavior in solution, the thermal behavior of the dried
samples (1 and 2) was studied by differential scanning
calorimetry (DSC). Each sample was prepared by evapo-
ration from its CHCl3 solution. Upon heating at a rate
F igu r e 3. Histogram analysis of DLS measurement of 1 in
CHCl (0.06 mM).
-
1
of 10 °C min from 0 °C, both samples exhibited a
single endothermic thermal transition, but the temper-
ature was significantly different. 1 exhibited an endo-
3
-
1
thermic transition at 144 °C (∆H ) -39.7 kJ mol ), a
much higher temperature than that of 2, which ap-
-
1
peared at 60 °C (∆H ) -26.6 kJ mol ). The high
transition temperature of 1 might be a result of the
hydrogen-bonding interaction of amide units. Notably,
the transition temperature of 1 was very close to the
1
sharpening temperature of the H NMR spectrum,
revealing a very interesting aspect that the self-as-
sembly of 1 remarkably stables even in solution.
Syn th esis of Low Molecu la r Weigh t Mod el Com -
p ou n d . In our attempt to prepare macrocyclic com-
pound without dendritic substitution, benzylamine,
instead of 8, was reacted with 10 to prepare a precursor
for the macrocycle (Scheme 4). Benzylamine-substituted
cyclohexane derivative (15) thus obtained was reacted
with 4,4′-diphenyldiaminomethyl in the identical condi-
tion to that for 1. Unlike the case of 1, the reaction
mixture formed an insoluble mass. By the MALDI-
TOF-MS analysis of this mass, the existence of a
dimeric macrocycle was definitely confirmed. However,
purification of macrocyclic compound was impossible
because of the disordered network formed by hydrogen
bonding. This means that the dendritic substitution is
important for the formation of a soluble assembly and
might control the ordered interaction among the core
amide groups. Therefore, the supramolecular assembly
formation of large dendrimer possibly occurred by the
three-dimensional warping of core groups by the den-
dritic wedges, which may prevent a disordered network
formation and possibly stabilize hydrogen-bonding in-
teractions because of the hydrophobic characteristics of
the dendritic wedge in addition to possible van der
Waals interaction.
F igu r e 4. GPC profiles of 1 (a, b: including TFA), 2 (c), and
(d).
3
of the solution, we could get a single filament of the
assembly (Figure 5b,c). This fibrous structure has a
homogeneous thickness of 6 nm, which agrees with the
computer-aided calculated diameter of the dendrimer,
indicating a linear supramolecular assembly formation.
In contrast to the result of 1, the AFM results of 2 or 3
showed a clearly different feature. Under identical
conditions, 2 or 3 exhibited only an agglomerated mass.
Even though both core units of 1 or 3 have six amide
bonds, with a potential to form a self-assembled su-
pramolecular structure, only 1 formed the supramo-
lecular polymeric assembly. It is assumed that 1,3,5-
benzenetricarboxamide derivatives are twisted into a
helical arrangement in the most stable hydrogen-
bonding mode; thus, the two 1,3,5-benzenetricarbox-
amide units in the core of 3 cannot form hydrogen bonds
simultaneously among the core units to form a linear
type supramolecular polymeric assembly. In sharp
contrast, the two cis-1,3,5-cyclohexanetricarboxamide
units in the core of 1 can form the hydrogen bonds
simultaneously to reinforce each other, so that 1 exhibits
an ultrahigh molecular weight and a fibrous assembly
formation even in solution.
Exp er im en ta l Section
P r ep a r a tion of Den d r im er s: Ch em ica ls. Chemicals
were used as received from commercial sources (Aldrich, TCI).
Solvents were freshly distilled according to literature methods.
F igu r e 5. AFM image of fibrous assembly of 1.

Macromolecules, Vol. 37, No. 19, 2004
Macrocyclic Dendrimers 7329
washed with cold ethanol and recrystallized twice in hot
ethanol to get 10 as a white crystalline solid in 32% yield.
+
MALDI-TOF-MS for C27
H
3
21
N
3
O
12 m/z: calcd: 579 [M ];
1
found: 579. H NMR (CDCl
cyclohexyl), 2.69 (m, 3H; axial H of CH
m, 3H; CH in cyclohexyl), 4.27 and 8.28 (m, 12H; H in
nitrophenyl).
1. A DMF solution (10 mL) of a mixture of 10 (0.43 mmol)
): δ 1.90 (q, 3H; equatorial H of
2
in cyclohexyl), 2.91
(
1
and 8 (0.14 mmol) was vigorously stirred under Ar at 60 °C
for 36 h. The reaction mixture was poured into water and
extracted with ethyl acetate. The combined extracts were
washed three times with an aqueous solution of 1 M NaOH
and evaporated to dryness. The resulting mixture was then
subjected to recyclable preparative GPC, where the first
fraction was collected and freeze-dried from benzene to give
1
1 as a white solid in 72% yield. MALDI-TOF-MS for
+
1
C
142
H
141
N
3
O
39 m/z: calcd: 2514 [M + H ]; found: 2514.
): δ 1.56-2.51 (m, 9H; cyclohexyl), 3.67 (s, 48H;
OMe), 4.23 (d, 2H; CH -N), 4.84 (s, 28H; -CH -), 5.86 (t,
H; N-H), 6.28-6.56 (m, 45H; o, p-H in C ), 7.08 and 8.06
m, 8H; C in p-nitrophenyl).
3. To a DMF solution (30 mL) of 12 (13.8 mmol) was added
H
NMR (CDCl
3
F igu r e 6. 1H NMR spectra of 1 in o-dichlorobenzene at
different temperatures.
-
1
(
2
2
6 3
H
6 4
H
5
. To a tetrahydrofuran (THF) solution (60 mL) of a mixture
1
of 4 (9.0 mmol), phthalimide (10.8 mmol), and triphenylphos-
phine (10.8 mmol) was added 40% toluene solution of diethyl-
azodicarboxylic acid (DEAD; 10.8 mmol), and the resulting
mixture was stirred under Ar at 0 °C for 1 h and 25 °C for 11
h. The reaction mixture was then evaporated to dryness, and
p-nitrophenol (48.3 mmol), and the reaction mixture was
vigorously stirred at 0 °C for 1 h and 25 °C for 12 h. The
reaction mixture evaporated to dryness and washed with cold
ethanol and then recrystallized twice in hot ethanol to get 13
as a white crystalline solid in 12% yield. MALDI-TOF-MS
the residue was chromatographed on silica gel with CH
2
Cl
2
+
1
for C27
H
15
N
3
O
12 m/z: calcd: 573 [M ]; found: 573. H NMR
): δ 7.71 and 8.38 (d, 12H; H in p-nitrophenyl), 8.91
).
4. A DMF solution of a mixture of 13 (0.09 mmol) and 8
0.75 mmol) was vigorously stirred under Ar at 60 °C for 36
as eluent, where the second fraction was collected and evapo-
(
(
DMSO-d
s, 3H; C
6
rated to give 5 as transparent oil in 87% yield. MALDI-TOF-
6
H
3
+
1
MS for C48
48 4 2
H O Si m/z: calcd: 745 [M ]; found: 745. H NMR
1
(
CDCl
3
): δ 0.94 (s, 18H; tert-Bu), 4.47 (s, 2H; -CH
), 6.30 (d, 2H; o-H in C ), 6.03-7.48 (m,
), 7.69 and 7.76 (m, 4H, C in phthalimide).
. A acetone solution (20 mL) of a mixture of 5 (0.8 mmol),
(1.6 mmol), and 18-crown-6 (0.2 mmol), containing KF (1.9
2
-), 6.04
(
(t, 1H; p-H in C
6
H
3
6 3
H
h. The reaction mixture was treated in a manner similar to
that for the preparation of 11 to give 14 as a white solid in
2
0H; -C
7
6
H
5
6 4
H
5
2
4
6
2% yield. MALDI-TOF-MS for C142
H
135
N
3
O
39 m/z: calcd:
529 [M + Na ]; found: 2531. H NMR (CDCl ): δ 3.73 (s,
8H; -OMe), 4.50 (d, 2H; CH -N), 4.89 (m, 30H; -CH -),
.34-6.58 (m, 45H; o, p-H in C of dendritic wedge), 7.36
in p-nitrophenyl), 8.76 and 8.95 (m, 3H;
6
+
1
3
mmol), was refluxed under Ar for 3 h. The reaction mixture
was poured into water (50 mL) and extracted three times with
ethyl acetate (50 mL). The combined extracts were dried over
2
2
6
H
3
and 8.21 (d, 8H; C
in core).
5. A DMF solution of a mixture of 10 (0.69 mmol) and
6 4
H
anhydrous MgSO
CH Cl as eluent, where the third fraction was collected and
freeze-dried from benzene to give 7 as a white solid in 90%
yield. MALDI-TOF-MS for C129 127NO32 m/z: calcd: 2241
M + K ]; found: 2243. H NMR (CDCl ): δ 3.74 (s, 48H;
- N), 4.93 (s, 28H; -CH -), 6.35-
), 7.62 and 7.77 (m, 4H; C in
4
and chromatographed on silica gel with
6 3
C H
2
2
1
benzylamine (0.35 mmol) was vigorously stirred under Ar at
60 °C for 3 h. The reaction mixture was treated in a manner
similar to that for the preparation of 11 to give 15 as white
H
+
1
[
3
-
OMe), 4.73 (s, 2H; -CH
.65 (m, 45H; o, p-H in C
phthalimide).
. To a THF/EtOH (1:1) solution (20 mL) of 7 (0.72 mmol)
2
2
solid in 75% yield. MALDI-TOF-MS for C28
H
25
N
3
O
9
m/z:
): δ 1.84-2.76
-N), 5.82 (t, 1H; N-H),
), 7.26 and 8.06 (d, 8H; C in
6
6
H
3
6 4
H
+
1
calcd: 547 [M ]; found: 547. H NMR (CDCl
m, 9H; cyclohexyl), 4.45 (d, 2H; CH
.24-7.34 (m, 5H; C
p-nitrophenyl).
3
(
2
8
7
6
H
5
6 4
H
was added hydrous hydrazine (10 mL), and the resulting
mixture was refluxed for 12 h. Then, insoluble fractions were
filtered off from the reaction mixture, and the filtrate was
poured into water (100 mL) and extracted three times with
ethyl acetate (50 mL). The combined extracts were dried over
1. A DMF solution of a mixture of 11 (0.2 mmol) and 4,4′-
biphenyldiaminomethyl (0.2 mmol) was vigorously stirred
under Ar at 60 °C for 72 h. The reaction mixture was poured
into water and extracted with ethyl acetate. The combined
extracts were washed three times with aqueous solution of 1
M NaOH and evaporated to dryness. The resulting mixture
was then subjected to recyclable preparative GPC, where the
first fraction, which is exceeded in the exclusion limit of the
column, was collected and freeze-dried from benzene to give
11 as a white solid in 42% yield. MALDI-TOF-MS for
anhydrous MgSO
dried from benzene to give 8 as a white solid in quantitative
yield. MALDI-TOF-MS for C121 125NO30 m/z: calcd: 2073
): δ 3.71 (s, 48H; -OMe),
4
and evaporated to dryness and then freeze-
H
+
1
[
M ]; found: 2075. H NMR (CDCl
3
4
4
.78 (m, 28H, -CH
2
-), 4.95 (s, 2H; -CH
).
2
-N), 6.31-6.63 (m,
8H; o, p-H in C
6
H
3
1
0. To a DMF solution (10 mL) of 9 (4.6 mmol) and
p-nitrophenol (16.1 mmol) was added dicyclohexylcarbodiimide
DCC; 16.1 mmol), and the reaction mixture was vigorously
+
1
C
288
H
294
N
6
O
66 m/z: calcd: 4918 [M + Na ]; found: 4919. H
NMR (TFA included CDCl ): δ 1.65-2.37 (m, 18H, H in
cyclohexyl) 3.75 (s, 90H, -OMe), 4.26 (m, 12H, CH -N), 4.94
(d, 60H; -CH -), 6.40-6.65 (m, 90H; o, p-H in C ), 7.16-
7.40 (m, 8H; C ).
(
3
stirred at 0 °C for 1 h and 25 °C for 12 h. Insoluble fractions
were filtered off from the reaction mixture, and the filtrate
was evaporated to dryness. Then, the resulting mixture was
2
2
6 3
H
6
H
4
Sch em e 4. Syn th esis of Low Molecu la r Non d en d r itic Mod el

7
330 J ang and Aida
Macromolecules, Vol. 37, No. 19, 2004
2
. To a THF solution of a mixture of 1 (4 µmol) and NaH
assembly structure of dendritic macrocycle also have
tubular internal space. A novel ultrahigh molecular
weight supramolecular polymeric assembly which is
composed of macrocyclic units was designed, and its
solubility was controlled by introducing of a dendritic
architecture.
(
12 µmol) was added MeI (12 µmol) and vigorously stirred
under Ar at 25 °C for 12 h. Insoluble fractions were filtered
off from the reaction mixture, and filtrate was evaporated to
dryness. Then, the resulting mixture was subjected to re-
cyclable preparative GPC, where the first fraction was collected
and freeze-dried from benzene to give 2 as a white solid in
quantitative yield. MALDI-TOF-MS for C294
H
306
N
6
O
66 m/z:
calcd: 5002 [M + Na ]; found: 5002. H NMR (CDCl ): δ
.62-2.32 (m, 18H, H in cyclohexyl) 2.89 (s, 18H; N-Me), 3.74
+
1
Refer en ces a n d Notes
3
1
(
1) Sherrington, D. C.; Taskinen, K. A. Chem. Soc. Rev. 2001,
0, 83 and references therein.
(
-
8
s, 90H, -OMe), 4.46-4.50 (m, 12H, CH
2
-N), 4.93 (d, 60H;
), 7.36-7.46 (m,
3
CH
2
-), 6.36-6.64 (m, 90H; o, p-H in C
).
. A DMF solution of a mixture of 14 (0.03 mmol) and 4,4′-
6
H
3
(
2) Brunsveld, L.; Folmer, B. J . B.; Meijer, E. W.; Sijbesma, R.
6 4
H; C H
P. Chem. Rev. 2001, 101, 4071 and references therein.
3
(3) Hanabusa, K.; Kawakami, A.; Kimura, M.; Shirai, H. Chem.
biphenyldiaminomethyl (0.03 mmol) was vigorously stirred
under Ar at 60 °C for 72 h. The reaction mixture was treated
in a manner similar to that for the preparation of 11 to give 1
Lett. 1997, 191.
(4) (a) Yasuda, Y.; Iishi, E.; Inada, H.; Shirai, Y. Chem. Lett.
1996, 575. (b) Hanabusa, K.; Koto, C.; Kimura, M.; Shirai,
H.; Kakehi, A. Chem. Lett. 1997, 429. (c) Lightfoot, M. P.;
Mair, F. S.; Pritchard, R. G.; Warren, J . E. Chem. Commun.
as a white solid in 55% yield. MALDI-TOF-MS for C288
282
H -
+
1
N
6
O
66 m/z: calcd: 4906 [M + Na ]; found: 4908. H NMR
CDCl ): 3.70 (s, 90H, -OMe), 4.42 (m, 12H, CH -N), 4.87
d, 60H; -CH -), 6.32-6.59 (m, 90H; o, p-H in C of
), 8.00 and 8.31 (m,
1
999, 1945.
(
(
3
2
(
5) (a) Frechet, J . M. J . Science 1994, 263, 1710. (b) Tomalia, D.
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2
6 3
H
dendritic wedge), 7.17-7.30 (m, 8H; C
H, C in core).
Mea su r em en t: In str u m en ts. H NMR spectra were mea-
sured in CDCl or DMSO-d at 21 °C on a J EOL GSX-270
spectrometer operating at 270 MHz, where the chemical shifts
were determined with respect to CHCl (δ 7.28 ppm) and CH
SOCD H (δ 7.28 ppm). Matrix-assisted laser desorption ioniza-
6 4
H
6
6 3
H
1
3
6
3
3
-
1
996, 271, 1095. (c) Lorenz, K.; Holter, D.; Stuhn, B.;
2
M u¨ lhaupt, R.; Frey, H. A. Adv. Mater. 1996, 8, 414. (d)
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tion time-of-flight mass spectrometry (MALDI-TOF-MS) was
performed on a Bruker model Protein TOF mass spectrometer
using 9-nitroanthracene (9NA) or indole acetic acid (IAA) as
a matrix. FT-IR spectra were recorded on a J ASCO model FT/
IR 610. Dynamic light scattering (DLS) measurements were
carried out using by an Otsuka model DLS-700 instrument at
2
5 °C.
GP C Mea su r em en ts. Analytical GPC was carried out on
a TOSOH model HLC-8020 equipped with TSKgel GMHXL
column as eluent of CHCl at 25 °C. Recyclable preparative
GPC was carried out on a J AI model LC-908 equipped with
J AIGEL 2H and J AIGEL 3H column as eluent of CHCl at 25
C.
Atom ic F or ce Micr oscop y (AF M). AFM was carried out
on a J EOL model J SPM 4200. One drop of dilute solution of 1
0.2 mM) in CHCl was placed on a freshly cleaved mica
1
998, 391, 161. (j) Yamaguchi, N.; Hamilton, L. M.; Gibson,
3
H. W. Angew. Chem., Int. Ed. 1998, 37, 3275. (k) Schenning,
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P. L.; van der Gaast, S. J .; Meijer, E. W. J . Am. Chem. Soc.
1998, 120, 8199. (l) Tomioka, N.; Takasu, D.; Takahashi, T.;
Aida, T. Angew. Chem., Int. Ed. 1998, 37, 1531. (m) J ang,
W.-D.; J iang, D.-L.; Aida, T. J . Am. Chem. Soc. 2000, 122,
3
°
3
8
232. (n) J ang, W.-D.; Aida, T. Macromolecules 2003, 36,
461.
(
3
surface and spin-cast for AFM observation.
(
7) Sato, T.; J iang, D.-L.; Aida, T. J . Am. Chem. Soc. 1999, 121,
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0658.
Con clu sion
(
8) (a) Yamaguchi, T.; Ishii, N.; Tashiro, K.; Aida, T. J . Am.
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In our demonstration of the self-assembly of dendritic
macrocycle, spectroscopic studies revealed that the
hydrogen bonding among core amide groups is the
driving force for the supramolecular assembly. Ultra-
high molecular weight assembly formation of the mac-
rocyclic dendrimer 1 was observed by GPC and DLS
analysis, whereas 3 cannot form a high molecular
weight supramolecular assembly, presumably because
of the twist arrangement of hydrogen bonds between
core 1,3,5-benzenetricarboxamide units. The linear stack-
(9) Hawker, C. J .; Fr e´ chet, J . M. J . J . Am. Chem. Soc. 1990, 112,
7
638.
(
(
10) Mitsunobu, O. Synthesis 1981, 1, 1.
11) Bellamy, L. J . The Infrared Spectra of Complex Molecules,
3
rd ed.; Chapman and Hall: New York.
(
12) (a) Shimizu, L. S.; Smith, M. D.; Hughes, A. D.; Shimizu, K.
D. Chem. Commun. 2001, 1592. (b) Bong, D. T.; Clark, T. D.;
Granja, J . R.; Ghadiri, M. R. Angew. Chem., Int. Ed. 2001,
1
2
ing of macrocycle may provide a tubular structure.
1
4
0, 988. (c) Gong, B. Chem.sEur. J . 2001, 7, 4337.
exhibited a fibrous supramolecular assembly structure
by AFM. It is possible that the fibrous supramolecular
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