Self-assembly and dynamics of [2]- and [3]rotaxanes with a dinuclear macrocycle containing reversible Os-N coordinate bonds

Article abstract of DOI:10.1002/1521-3765(20010618)7:12<2687::AID-CHEM26870>3.0.CO;2-A

With a dinuclear macrocycle 2 that contains weak reversible Os^VI-N coordinate bonds, self-assembly and equilibrium dynamics of [2]- and [3]rotaxanes have been investigated. When the macrocycle 2 was mixed together with threads 4a-e, which all contain an adipamide station but different sizes of end groups, [2]pseudorotaxane- and rotaxane-like complexes were immediately formed with large association constants > of 7 × 10³M^-1 in CDCl₃ at 298 K. Exchange dynamics, explored by 2D-EXSY experiments, suggest that assembly and disassembly of complexes occur through two distinct pathways, slipping or clipping, and this depends on the size of the end groups. The slipping pathway is predominant with smaller end groups that give pseudorotaxane-like complexes, while the clipping pathway is observed with larger end groups that yield rotaxane-like complexes. Under the same conditions, exchange barriers (ΔG^≠) were 14.3 kcal mol^-1 for 4a and 16.7 kcal mol^-1 for 4d, and indicate that the slipping process is at least one order of magnitude faster than the clipping process. Using threads 13a and 13b that contain two adipamide groups, more complicated systems have been investigated in which [2]rotaxane, [3]rotaxane, and free components are in equilibrium. Concentration- and temperature-dependent ¹H NMR spectroscopic studies allowed the identification of all possible elements and the determination of their relative distributions in solution. For example, the relative distribution of the free components, [2]rotaxane, and [3]rotaxane are 30, 45, and 25%, respectively, in a mixture of 2 (2mM) and 13a (2mM) in CDCl₃, at 10°C. However, [3]rotaxane exists nearly quantitatively in a mixture of 2 (4mM) and 13a (2mM) in CDCl₃ at a low temperature - 10°C.

Full text of DOI:10.1002/1521-3765(20010618)7:12<2687::AID-CHEM26870>3.0.CO;2-A

FULL PAPER
Self-Assembly and Dynamics of [2]- and [3]Rotaxanes with a Dinuclear
Macrocycle Containing Reversible Os N Coordinate Bonds
Sung-Youn Chang, JeungSoon Choi, and Kyu-Sung Jeong*[a]
Abstract: With a dinuclear macrocycle
2 that contains weak reversible OsVI
of the end groups. The slipping pathway
is predominant with smaller end groups
that give pseudorotaxane-like com-
plexes, while the clipping pathway is
observed with larger end groups that
yield rotaxane-like complexes. Under
the same conditions, exchange barriers
contain two adipamide groups, more
complicated systems have been investi-
gated in which [2]rotaxane, [3]rotaxane,
and free components are in equilibrium.
Concentration- and temperature-de-
N
coordinate bonds, self-assembly and
equilibrium dynamics of [2]- and [3]ro-
taxanes have been investigated. When
the macrocycle 2 was mixed together
with threads 4a ± e, which all contain an
adipamide station but different sizes of
end groups, [2]pseudorotaxane- and ro-
taxane-like complexes were immediate-
ly formed with large association con-
stants of >7 Â 103 m 1 in CDCl3 at 298 K.
Exchange dynamics, explored by 2D-
EXSY experiments, suggest that assem-
bly and disassembly of complexes occur
through two distinct pathways, slipping
or clipping, and this depends on the size
1
pendent H NMR spectroscopic studies
allowed the identification of all possible
elements and the determination of their
relative distributions in solution. For
example, the relative distribution of the
free components, [2]rotaxane, and [3]ro-
taxane are 30, 45, and 25%, respectively,
in a mixture of 2 (2mm) and 13a (2mm)
in CDCl3 at 108C. However, [3]rotaxane
exists nearly quantitatively in a mixture
of 2 (4mm) and 13a (2mm) in CDCl3 at a
low temperature 108C.
1
(DG=) were 14.3 kcalmol for 4a and
1
16.7 kcalmol for 4d, and indicate that
the slipping process is at least one order
of magnitude faster than the clipping
process. Using threads 13a and 13b that
Keywords: coordination modes
´
macrocycles ´ rotaxanes ´ self-as-
sembly ´ supramolecular chemistry
of these pseudorotaxane features into the rotaxanes may
eventually yield more sophisticated and versatile, but readily
accessible, supramolecular machines. One way to accomplish
this goal would be to replace one or more of the covalent
bonds in either the macrocycle or linear molecules with
reversibly controllable, weak bonds.[5] Among possible weak
bonds, the coordinate bond may be the most suitable because
both the bond strength and geometry are tunable with the
selection of the right combination of metal and ligands.
A number of coordinate-bond-based rotaxanes have been
described thus far, but in all cases the bond between the
transition metal and ligand was used for either attaching
stoppers to the thread or connecting one thread with
another.[6] Although a variety of macrocycles that possess
reversible coordinate bonds have been prepared by self-
assembly over the last decade,[7] none has been used for the
construction of rotaxanes. We recently described the rotaxane
complex 1 ´ 4d derived from the macrocycle 1 which contains
two reversible OsVI N coordination bonds at one corner.[8]
Herein we report our continued efforts to devise rotaxanes
that reversibly assemble from and disassemble into their
components under thermodynamic conditions. Instead of
using the mononuclear macrocycle 1 as a bead component the
Introduction
Rotaxanes and pseudorotaxanes are chemical entities com-
prising macrocycles (beads) and linear molecules (threads),
they contain mutual recognition sites and consequently
assemble in a threading mode.[1, 2] In rotaxanes, bulky stoppers
at the ends of the thread prevent dissociation into the
individual components. In contrast, pseudorotaxanes have
small end groups, and can be reversibly converted into the
free components. Both supermolecules have unique proper-
ties and are at the frontier in the construction of molecular-
level machines.[3, 4] The intrinsic high kinetic stability of the
rotaxanes makes it easy to control and define their motion and
function. The synthesis of the pseudorotaxanes, on the other
hand, is much simpler in that they self-assemble from a
mixture of individual components. In addition, the pseudo-
rotaxanes display more diverse motional modes associated
with their reversible assembly and disassembly. Incorporation
[a] Prof. K.-S. Jeong, S.-Y. Chang, J.S. Choi
Department of Chemistry
Yonsei University, Seoul 120-749 (South Korea)
Fax : (‡2)364-7050
E-mail: ksjeong@yonsei.ac.kr
Chem. Eur. J. 2001, 7, No. 12
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K.-S. Jeong et al.
FULL PAPER
Me
Me
Bu
O
Os O
O
N
Me
O
Bu
Bu
Bu
O
O
O
O
Me
Os
O
O
N
N
N
N
H
N
H
N
N
N
H
O
O
N
H
H
O(CH2)6
O
N
(CH2)4
N(CH2)6O
H
N
N
O
O
H
O
N
O
H
H
N
N
H
N
O
N
O Os
N
Bu
Bu
O
O
O
Bu
Bu
2
1 4d
+
1or 2
dinuclear macrocycle 2 was used (Figure 1) because it was
found to have several advantages for this study. First, the
symmetrical nature of macrocycle 2 makes it much easier to
synthesize than 1. Second, 2 shows at least an order of
magnitude higher affinity toward the threads than 1, and
consequently the relative population of the resulting rotaxane
is dramatically increased in solution. This high affinity
between thread and bead molecules is a critical factor
required for the efficient construction of [n]rotaxanes with
multiple beads.[9] The thread molecules studied here contain
one or two adipamide station(s), as well as different sizes of
end groups. The dynamics of the exchange processes, studied
1or 2
1
by H NMR spectroscopy, suggest that pseudorotaxanes and
O
H
N
rotaxanes are reversibly formed by two distinct pathways,
slipping and clipping. Furthermore, with the two-station
threads we also describe more intricate systems wherein
[2]rotaxane, [3]rotaxane, and free components exist in equi-
librium. The relative distribution of these components in
solution can be tuned by simply adjusting the ratio of bead
and thread components.
N
H
O
Figure 1. Schematic representation for the reversible formation of rotax-
anes studied here.
Results and Discussion
Design and synthesis: The macrocycle 2 was spontaneously
assembled from a mixture of osmium tetraoxide, 5,6-dibutyl-
5-decene, and bispyridyl ligand as described previously.[10]
Here, a symmetrical tetra-substituted olefin, 5,6-dibutyl-5-
decene,[11] was chosen in order to 1) increase the solubility of 2
in organic solvents, 2) increase the stability of 2 upon contact
with air and protic solvents, and 3) avoid the production of a
diastereomeric mixture of 2. The macrocycle 2 contains a well-
defined square cavity in which four hydrogen donors (NHs)
are inwardly directed by virtue of internal N (central
pyridine) ´´´ H N (amide) hydrogen bonds.[12] During the
course of extensive binding studies, adipamide derivatives
were found to bind strongly and selectively to the cavity of
2.[10] This functionality was therefore employed in all threads
as the station for 2. To minimize possible steric repulsion and
thus maximize the association between 2 and threads, the
adipamide station was separated from the bulky stoppers by
inserting either a hexyl or a tri(ethylene glycol) chain between
them. The threads thus prepared could be categorized into
three different types on the basis of the number of stations
inside and the similarity of the end groups.
Symmetrical one-station threads 4a ± e: Syntheses of threads
4b ± e were straightforward and are outlined in Scheme 1.
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[2]- and [3]Rotaxanes
2687±2697
O
Pd/C). The compounds 8a and 8b, obtained from 1,4-
dihydroxybenzene and 1,5-dihydroxynaphthalene, were con-
verted into the corresponding amines 9a and 9b. Finally,
coupling reactions of 7 with 9a or 9b in the presence of 2,2-
dimethylpropionyl chloride gave the threads 10a and 10b,
respectively.
a-d
Y
HO
N
OH
3b–e
O
H
N
O
e,f
Y
Y
N
H
O
4a–e
Two-station threads 13a and 13b: As outlined in Scheme 3,
threads 13a and 13b were prepared by similar reaction
sequences used for 10a and 10b.
C(CH3)3
a Y =H
b Y =
e Y =
d Y =
O
O
O
C(CH3)3
C(CH3)3
C(CH3)3
O
d
H2N
Ar
NH2
a,b,c
HO
Ar
OH
O
c Y =
O
2
O
O
2
2
2
12a, b
11a, b
C(CH3)3
Scheme 1. Synthesis of threads 4b ± e. Reagents and conditions: a) toluene-
p-sulfonyl chloride, Et3N, THF, 08C 1 h, 37%; b) phenols (H ´ b ± e),
K2CO3, DMF or acetonitrile, 60 ± 708C, 5 ± 16 h, 76 ± 82%; c) toluene-p-
sulfonyl chloride, Et3N, CH2Cl2, 08C to RT, 5 ± 19 h, 77 ± 84%;
d) phthalimide, K2CO3, DMF, 60 ± 708C; 9 ± 17 h, 72 ± 94%; e) H2NNH2 ´
H2O, EtOH, reflux, 4 h; f) adipoyl chloride or bis(pentafluorophenyl)
adipate, Et3N, CH2Cl2, 08C to RT, 2 ± 4 h, 40 ± 76%.
O
O
H
N
H
N
R
R
Ar
N
H
N
H
O
13a, b
O
O
3
3
2
2
O
O
Ph
a Ar =
b Ar =
O
O
R =
O
Ph
Ph
O
Stepwise tosylations followed by sequential displacements of
hexane-1,6-diol with phenols and phthalimide under basic
conditions gave the amine precursors 3b ± e. After treatment
with hydrazine, the resulting amines were coupled with
adipoyl chloride or pentafluorophenyl diester to give the
threads 4b ± e. In addition, the thread of hexanedioic acid bis-
hexylamide (4a) was prepared in 67% yield by coupling
adipic acid with 1-aminohexane.
Scheme 3. Synthesis of threads 13a and 13b. Reagents and conditions:
a) toluene-p-sulfonyl chloride, Et3N, CH2Cl2, RT, ca. 24 h, 82 ± 94%;
b) phthalimide, K2CO3, DMF, 60 ± 708C; ~30 h, 73%; c) H2NNH2 ´ H2O,
EtOH/CH2Cl2, reflux, 8 h; d) 7, 2,2-dimethylpropionyl chloride, Et3N,
CH2Cl2, 08C to RT, 1 h, then 12a ± b, RT, 1 h, 38% ± 63%.
Association constants between macrocycle 2 and threads
4a ± e: When macrocycle 2 and each of threads 4c, 4d, and 4e
were mixed together in CDCl3, a new set of 1H NMR signals
corresponding to the complexes could immediately be seen at
room temperature (Figure 2d). On the basis of 1H NMR
integration of five different stock solutions ranging in the
concentration from 5.0 to 0.2mm in CDCl3, the average
association constants (Ka Æ 20%) of 2 with 4c, 4d, and 4e
Unsymmetrical one-station threads 10a and 10b: Adipamide
monoacid 7 was obtained by the coupling of amine 5 with acid
6
in the presence of 2,2-dimethylpropionyl chloride
(Scheme 2), followed by catalytic debenzylation (H2, 5%
O
Ph
Ph
Ph
1
+
OCH2Ph
were calculated to be 8900, 8400, and 7200m , respectively
O
NH2
HO
5
(Table 1). With threads 4a and 4b, in which there are small
end groups, association constants could not be accurately
determined because the free and complex components gave
considerably broadened and weight-averaged 1H NMR spec-
tra at room temperature (Figure 2b). Therefore, the associ-
ation constants for 4a and 4b were estimated by dilution
experiments. When a 5mm CDCl3 solution of each component
was diluted to 0.5mm, changes in the chemical shifts were
negligible (that is, the NH proton of 2, Dd < 0.1 ppm relative
O
6
O
Ph
Ph
Ph
a,b
OH
O
N
H
O
7
f
c,d,e
NH2
Ar
OH
Ar
O
O
2
2
9a, b
8a, b
O
H
N
1
to Ddmax ˆ 1.5 ppm), and this suggests Ka > 1  104 m for
Ph
Ph
Ph
Ar
O
N
H
O
threads 4a and 4b.
2
O
Two trends observed in the binding affinities are worthy of
note. First, the magnitudes of the association constants
depend slightly on the size of the end groups on the threads.
As the stopper size increases the association constant
decreases, possibly owing to a weak steric repulsion between
the macrocycle and end groups. Second, the association
constants for 2 and the threads are much higher than the
constants obtained with mononuclear macrocycle 1 under the
same conditions, as seen in the Table 1. The enhanced affinity
of the dinuclear macrocycle 2 is probably a result of the
10a, b
a Ar =
b Ar =
O
O
OCH2CH2OCH3
OCH2CH2OCH3
Scheme 2. Synthesis of threads 10a and 10b. Reagents and conditions:
a) 2,2-dimethylpropionyl chloride, Et3N, CH2Cl2, 73%; b) 5% H2/Pd-C,
MeOH/EtOAc, 88%; c) toluene-p-sulfonyl chloride, Et3N, CH2Cl2, RT, ca.
20 h, 69 ± 79%; d) phthalimide, K2CO3, DMF, 60 ± 708C; 6 h, 70 ± 76%;
e) H2NNH2 ´ H2O, EtOH, reflux, 4 h; f) 2,2-dimethylpropionyl chloride,
Et3N, CH2Cl2, 08C to RT, 1 h, then 7, RT, 1 h, 51 ± 54%.
Chem. Eur. J. 2001, 7, No. 12
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K.-S. Jeong et al.
FULL PAPER
Figure 3. 2D-EXSY spectrum obtained with 2 (10mm) and 4d (15mm) at
258C in CDCl3 using mixing time (tm) of 50 ms, indicating that the exchange
occurs between complex 2 ´ 4d and its free components.
Figure 2. 1H NMR (500 MHz) spectra in CDCl3 at 258C of a) 4b, b) 4b
(2mm) ‡ 2 (2mm), c) 2, d) 4d (2mm) ‡ 2 (2mm), and e) 4d.
Table 1. Association constants (Ka Æ 20%, m 1) of macrocycles 1 and 2
with one-station threads 4a ± e in CDCl3 at 25 8C.
0.5, respectively, compared with d ˆ 2.2 and 1.7 for the free 4.
These spectroscopic changes are nearly identical to those
observed on the formation of a pseudorotaxane complex
between mononuclear macrocycle 1 and thread 4a, the
structure of the complex 1 ´ 4 was previously confirmed by
X-ray crystal analysis.[8] Further information on the structure
of complexes 2 ´ 4 was obtained from kinetic exchange studies
1
Thread
Ka (m
)
Macrocycle 1
Macrocycle 2
4a
4b
4c
4d
4e
1300
900
520
520
> 1 Â 104
> 1 Â 104
8900
8400
7200
not determined
Bu
Bu
Bu
O
O
O
Bu
Os
O
N
N
O
H
N
N
H
O
coordination of all four lutidines to the osmium centers, which
in turn leads to an increased hydrogen bonding donor ability
of the amide NHs inside the cavity of 2.
O
N
(CH2)6
Y
H
N
(CH2)4
N(CH2)6
Y
H
N
N
O
O
H
O
N
O
H
N
O
N
O
Os
O
Bu
Bu
Bu
Bu
Spectroscopic evidence for formation of pseudorotaxanes and
rotaxanes 2 ´ 4: As shown in Figure 2, the 1H NMR spectra of
complexes 2 ´ 4 are clearly different from their free compo-
nents. The NH signal of 2 was significantly shifted downfield
(Dd ˆꢀ 1.5 ppm) as a result of strong hydrogen bond for-
mation. In addition, the signal for CH hydrogens (see H4 and
H5 in Figure 3) a and b to the carbonyls in the adipamide
station of 4 appeared at the far-upfield region of d ˆ 1.1 and
2 4
between complexes 2 ´ 4 and their free components (discussed
later). The 2D-EXSY experiments[13] suggest that the ex-
change rates are faster in the cases of pseudorotaxane-like
complexes, but are slower for rotaxane-like complexes. In
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[2]- and [3]Rotaxanes
2687±2697
other words, the kinetic stability of the complex increases as
the size of the end group increases, as expected for pseudo-
rotaxane or rotaxane formation.[14, 15] As mentioned in the
binding studies, the opposite is true in the thermodynamic
stability of the complexes. All of the observations described
thus far are consistent with a proposed structure of complexes
2 ´ 4 in which the macrocycle 2 encircles the adipamide station
of the threads, and consequently forms pseudorotaxanes or
rotaxanes.[16]
2. To obtain quantitative data on the dynamics of the
exchange between the complexes and their components, we
performed coalescence temperature[17] and 2D-EXSY experi-
ments (Table 2).[13] With threads 4a and 4b, the values are in
the range of 13.1 ± 13.6 kcalmol 1 at 286 ± 302 K based on the
coalescence temperature method. However, based on the
EXSY experiments, the values with threads 4c, 4d, and 4e
Table 2. Activation barriers [DG=] of exchange between complexes and
their free components 2 and one-station threads 4a ± e, 10a, and 10b.
Dynamics of exchange between complexes 2 ´ 4 and their
components: Two possible pathways may be considered for
the reversible formation of pseudorotaxane or rotaxane
complexes (Figure 4). One is a slipping process where threads
1
[b]
Entry
Thread
Method[a]
Temp. [8C]
DG=[kcalmol
]
1
2
3
4
5
6
7
8
9
4a
coalescence
EXSY
coalescence
EXSY
EXSY
EXSY
EXSY
EXSY
EXSY
13 ± 27
10
16 ± 29
25
25
10
25
10
25
13.1 ± 13.5
14.3
13.2 ± 13.6
15.3
15.5
16.7
15.5
14.9
15.2
4b
4c
4d
+
4e
10a
10b
[a] For 2D-EXSY experiments, the concentration of each macrocycle and
thread is 10 ± 20mm in CDCl3 with the molar ratio of 0.7 or 1.5, and the
mixing time (tm) is 50 ms except entry 6 (300 ms) and entry 9 (80 ms).
1
[b] Errors are within Æ0.2 kcalmol
.
slipping
clipping
1
suddenly increase to ꢀ15.5 kcalmol at 298 K. This value
remains constant despite an increase in the steric bulkiness of
the end groups from 4d to 4e. The activation energy (DG=) for
the exchange depends on the temperature. Therefore, we
determined and compared the activation barriers at the same
temperature 283 K, at which the free components and
complex gave well-resolved separate 1H NMR signals regard-
less of the end group size on the threads 4. The threads 4a and
4d were chosen as representative examples of small and large
end groups, respectively. The exchange energies (DG=) at
283 K, determined by EXSY experiments, were
Figure 4. Schematic representation of two possible pathways, slipping and
clipping, for assembly and disassembly of pseudorotaxane or rotaxane
complexes.
4 slide in and out though the cavity of macrocycle 2. This
pathway is only possible when the size of the end group is
smaller than the size of the cavity. Another is a clipping
process that requires the dissociation of the OsVI N coordi-
nate bond in 2, followed by the formation of intermediate
complexes, and finally the reconstruction of the coordinate
bond. The two pathways, slipping and clipping, are expected
to have different activation barriers, the latter process
depends more on the strength of the coordinate bond in the
macrocycle, rather than on the size of the end groups in the
thread.
1
1
14.3 kcalmol for 4a and 16.7 kcalmol for 4d, and these
1
values correspond to exchange rates (k) of ꢀ50 and 0.8 s ,
respectively. Both slipping and clipping pathways are possible
with 4a, but only a clipping pathway is possible with 4d,
therefore, it is clear that the slipping process is at least an
order of magnitude faster than the clipping process under the
same conditions.
As mentioned earlier, broad and weight-averaged 1H NMR
signals were observed at room temperature when the macro-
cycle 2 was mixed with threads 4a and 4b, while sharp and
separated signals were seen with threads 4c, 4d, and 4e. This
spectral difference must be closely related to the exchange
rate between complexes and their free components. Qualita-
tively, the exchange rates are relatively fast on the NMR time
scale in threads 4a and 4b with smaller end groups, but slow in
threads 4c, 4d, and 4e with bulkier end groups. Corey ±
Pauling ± Koltun (CPK) models show that the threads 4a
and 4b can penetrate into the cavity of 2, but the end groups in
the threads 4c, 4d, and 4e are too bulky to pass through the
cavity without breaking at least one of the coordinate bonds in
Complex formation between macrocycle 2 and unsymmetrical
threads 10a and 10b: The unsymmetrical one-station threads
10a and 10b were prepared as a reference for two-station
threads 13a and 13b. When 10a and 10b were added to a
1
CDCl3 solution of the macrocycle 2, the observed H NMR
spectral changes were consistent with the formation of
complexes by hydrogen bonding as described earlier with
the symmetrical threads 4a ± e. However, owing to the
unsymmetrical nature of threads 10a and 10b, some
1H NMR signals of the macrocycle 2 become further split at
lower temperatures when complexed. For example, the four
amide NH protons of 2 split into two singlets at 08C, otherwise
all protons appear at the same resonance (Figure 5).
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2
+
13a or 13b
2
clipping
clipping
shuttling
[2]rotaxane
clipping
[2]rotaxane
+
clipping
1
[3]rotaxane
Figure 5. Partial H NMR (500 MHz) spectra of the amide NH signals of
macrocycle 2, which split into two singlets when complexed with unsym-
metrical threads 10a (left) and 10b (right) in CDCl3 at a low temperature
(08C).
= 4-tritylphenyl
=adipamide
= phenylene, or
naphthalene
Figure 7. Possible equilibria and processes between [2]rotaxane, [3]rotax-
ane, and their free components, macrocycle 2 and two-station threads 13a
and 13b.
1
The H NMR spectra also depend on the size of the aryl
groups at one end, phenyl versus naphthyl, as seen in Figure 6.
With the thread 10a (2mm in CDCl3) with the smaller phenyl
group, a broad and poorly resolved H NMR spectrum was
of threads 13a and 13b prevent the slipping in and out, but
allow the clipping on and off of the macrocycle 2.
1
When two-station threads 13a and 13b and the macrocycle
2 were mixed together in CDCl3, the 1H NMR spectral
behavior was similar to that observed for the one-station
threads and the reference threads described above. Therefore,
[2]rotaxane, [3]rotaxane, and their free components could be
1
clearly identified by H NMR spectroscopy. The two most
diagnostic signals are the amide NH protons of both macro-
cycle 2 and thread 13a or 13b. The NH signal of the
complexed 2 was split into four singlets at 108C; two singlets
each for the [2]- and [3]rotaxane (Figure 8). As the concen-
1
Figure 6. Partial H NMR (500 MHz) spectra in the region of the thread
NH signals; a) 10a (2mm) ‡ 2 (1mm), b) 10a (2mm), c) 10b (2mm) ‡ 2
(1mm), and d) 10b (2mm) in CDCl3 at 258C.
obtained at room temperature when approximately 0.5 equiv-
alents of the macrocycle 2 were added. On the other hand,
sharp and well-resolved signals of both complex and the free
components were observed in the case of the naphthyl-ended
thread 10b. The activation energies (DG=) for assembly and
disassembly were determined by 2D-EXSY experiments and
1
found to be 14.9 kcalmol at 283 K for 2 and 10a, and
1
15.2 kcalmol at 298 K for 2 and 10b. These values suggest
that the slipping process dominates in the small phenyl-ended
thread 10a, while the clipping process is preferred in the large
naphthyl-ended thread 10b.
Equilibrium between [2]rotaxane and [3]rotaxane derived
from two-station threads 13a and 13b: Possible equilibria and
processes between macrocycle 2 and two station threads 13a
and 13b are schematically summarized in Figure 7. As
discussed earlier, bulky tritylphenyl groups at both termini
1
Figure 8. Partial H NMR (500 MHz) spectra of the amide NH signals of
macrocycle 2 when complexed with two-station threads 13a (left) and 13b
(right) in CDCl3 at 108C; a) macrocycle (1mm) and thread (2mm),
b) macrocycle (2mm) and thread (2mm), and c) macrocycle (4mm) and
thread (2 mm).
2692
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Chem. Eur. J. 2001, 7, No. 12

[2]- and [3]Rotaxanes
2687±2697
Table 3. Relative distributions [%][a] of the free, [2]rotaxane and [3]rotax-
ane in a mixture of macrocycle 2 and two-station threads 13a and 13b in
CDCl3 at 10 8C.
tration of 2 increased from 1 to 4mm, a set of two singlets was
initially dominant, then nearly equal to, and eventually
replaced by another set of singlets. It is therefore clear that
[2]rotaxane corresponds to the initial set, and [3]rotaxane to
the later set of signals. Additional information for each
component in solution can be obtained from the thread NH
Entry Thread (2mm) Concentration of 2 Free [2]Rotaxane [3]Rotaxne
1
2
3[b]
4
5
6[b]
13a
13a
13a
13b
13b
13b
1mm
2mm
4mm
1mm
2mm
4mm
58 34
30 45
ꢀ 0 16
58 37
32 49
ꢀ 0 16
8
25
84
5
19
84
1
signals in the region between d ˆ 5 and 7 in the H NMR
spectra (Figure 9). In the [2]rotaxane, one station of the thread
[a] Relative distributions were estimated by the 1H NMR integration of the
thread NH signals, and errors in the integration are within 15%. [b] Upon
cooling the solution down to 108C, [3]rotaxane could only be seen and
1
other components are negligible in the H NMR spectrum.
relative populations of [2]- and [3]rotaxane become 16 and
84%, respectively, by increasing the concentration of 2 to
4mm (1 equivalent based on the number of adipamide
stations) under the same conditions, and eventually [3]rotax-
ane exists nearly quantitatively upon cooling the solution
down 108C. This clearly shows that the relative population
of the components in solution could be varied by adjusting
molar ratios, concentrations, and/or temperature.
The phenylene and naphthalene groups in the middle of
13a and 13b are inserted in order to control a possible
shuttling process of [2]rotaxane,[18] an assembly of 13a (or
13b) with one macrocycle 2. It was difficult, however, to
notice the difference in 1H NMR spectra between threads 13a
and 13b at various conditions when mixed together with 2,
except the thread 13b gives better-resolved signals under the
same conditions. Attempts to sort out exchange dynamics
between [2]rotaxane, [3]rotaxane, and the free components
were not successful because the peak separation between
components was too small to give satisfactory 2D-EXSY
results. The studies with the reference threads 10a and 10b
provide, at this moment, indirect evidence for the possibility
of the shuttling process of the [2]rotaxane; the macrocycle 2
may shuttle back and forth across the smaller phenylene, but
not the larger naphthalene group.
1
Figure 9. Partial H NMR (500 MHz) spectra of a mixture of 2 ‡ 13b in
CDCl3 at 108C; a) 13b (2 mm), b) 13b (2mm) and 2 (1mm), c) 13b (2mm)
and 2 (2mm), and d) 13b (2mm) and 2 (4mm).
is occupied by the macrocycle 2, but the other is unoccupied.
Fortunately, the NH signals for the occupied station of
[2]rotaxane appear at the different position from those of
[3]rotaxane. Likewise, the unoccupied station of [2]rotaxane
and the free thread 13a or 13b give separate signals for the
amide NH protons in 1H NMR spectroscopy. For the example
of 2 and 13b (2mm of each in CDCl3) at 108C, two NH signals
for the occupied station of [2]rotaxane appear at d ˆ 6.80 and
5.37, and signals for the unoccupied one appear d ˆ 6.16 and
5.87. On the other hand, two NH signals of [3]rotaxane appear
at d ˆ 6.85 and 5.31, and the signals of free thread 13b appear
at d ˆ 6.23 and 5.90 under the same conditions. This spectral
behavior makes it possible to analyze the relative distribution
of [2]rotaxane, [3]rotaxane, and the free component (Table 3).
For example, distributions of the free, [2]rotaxane, and
[3]rotaxane are 32, 49, and 19%, respectively, in a mixture
of 2 (2mm) and 13b (2mm) in CDCl3 at 108C. In addition, the
Conclusion
Reversibility and self-assembly are two main features in
natural systems. Recently, much effort has been carried out in
the area of supramolecular chemistry to incorporate these
important characteristics into artificial counterparts. In this
context, we herein describe the self-assembly of rotaxane
complexes in solution at ambient conditions. The reversibility
stems from the weak OsVI N coordinate bonds of macrocycle
2, a bead molecule that was also spontaneously assembled
from its constituents. The macrocycle 2 strongly binds (Ka >
7 Â 103 m 1 in CDCl3 at 298 K) in a threading mode to threads
4a ± e that all contain an adipamide station but different sizes
of end groups. Exchange dynamics, studied by 2D-EXSY
experiments, clearly show that the processes of complexation
and decomplexation switch from slipping to clipping when the
end groups of 4a ± e are bulkier than the cavity size of the
Chem. Eur. J. 2001, 7, No. 12
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2693

K.-S. Jeong et al.
FULL PAPER
solution, saturated NaHCO3 solution, and brine, and dried over anhydrous
MgSO4. The product was purified by column chromatography (EtOAc/n-
hexane 1:1) to give toluene-4-sulfonic acid 6-hydroxyhexyl ester (26 g, 37%
macrocycle 2. Finally, two-station threads 13a and 13b give us
an opportunity to study a more complicated equilibrium
system of [2]rotaxane, [3]rotaxane, and free components. All
of these possible components could be clearly identified in
CDCl3, and their distributions were therefore estimated by
1H NMR spectroscopy. At a low ratio of 2 to 13a (or 13b),
[2]rotaxane was a major component, while [3]rotaxane was
predominant at a higher ratio, as expected. The reversibility in
our system inevitably results in a decrease in the kinetic
stability of individual components. We are currently pursuing
systems that balance these contradictory properties for the
self-assembly of molecular machines, for example, shuttles
that respond to outside stimuli.
l
yield) as a colorless liquid. H NMR (250 MHz, CDCl3, 258C): d ˆ 7.80 (d,
3J(H,H) ˆ 8.2 Hz, 2H; Ar-H), 7.35 (d, 3J(H,H) ˆ 8.0 Hz, 2H; Ar-H), 4.02 (t,
3J(H,H) ˆ 6.4 Hz, 2H; ArOCH2), 3.60 (t, 3J(H,H) ˆ 6.4 Hz, 2H; CH2O),
2.45 (s, 3H; Ar-CH3), 1.66 (m, 2H), 1.52 (m, 2H), 1.35 ± 1.31 (m, 4H);
elemental analysis calcd (%) for C13H20O4S (272.36): C 57.33, H 7.40; found:
C 57.35, H 7.42.
A
solution of toluene-4-sulfonic acid 6-hydroxyhexyl ester (5.0 g,
18.4 mmol), phenol (3.2 mL, 36.8 mmol, 2 equiv), and K2CO3 (7.6 g,
55 mmol, 3 equiv) in dry DMF (50 mL) was heated at 60 ± 708C for 5 h
under argon, and then the solution was filtered. The filtrate was
concentrated, then taken up in ethyl acetate, and washed with H2O, and
brine and the residue was dried over anhydrous MgSO4 and concentrated.
The residue was purified by column chromatography (EtOAc/n-hexane
1:1) to give 6-phenoxyhexane-1-ol (2.7 g, 76% yield) as a colorless liquid.
lH NMR (250 MHz, CDCl3, 258C): d ˆ 7.30 ± 7.24 (m, 2H; Ar-H), 6.95 ± 6.87
(m, 3H; Ar-H), 3.96 (t, J ˆ 6.4 Hz, 2H; ArOCH2), 3.67 (m, 2H; CH2O),
1.80 (m, 2H), 1.61 ± 1.53 (m, 2H), 1.48 ± 1.41 (m, 4H); 13C NMR (63 MHz,
CDCl3): d ˆ 159.2, 129.5, 120.6, 114.6, 67.8, 63.0, 32.8, 29.4, 26.0, 25.7;
elemental analysis calcd (%) for C12H18O2 (194.27): C 74.19, H 9.34; found:
C 74.17, H 9.34.
Experimental Section
General methods: All reagents were, unless otherwise noted, used as
received. Chloroform, dichloromethane, and acetonitrile were distilled
under nitrogen from calcium hydride (CaH2), diethyl ether, and tetrahy-
drofuran from Na/benzophenone, and triethylamine from KOH. Dime-
thylformamide (DMF) was distilled under reduced pressure after drying
with anhydrous magnesium sulfate (MgSO4). Melting points were deter-
mined by using a Mel-Temp II capillary melting point apparatus and were
uncorrected. Infrared spectra were obtained on a Nicolet impact 410 FT-IR
spectrometer. All NMR spectra were recorded on a Bruker DPX-250 or
DRX-500 spectrometer and chemical shifts were reported in ppm down-
field relative to the residual protonated solvent peaks (CHCl3: 7.26 ppm for
1H NMR spectra, 77 ppm for 13C NMR spectra). Mass spectra were
obtained with a JMS-HS 110/110A mass spectrometer (JEOL inc., Japan)
and nitrobenzyl alcohol was used as a matrix in CHCl3 as solvent.
To a solution of 6-phenoxyhexan-1-ol (2.3 g, 11.8 mmol) in CH2Cl2 (40 mL)
was added toluene-p-sulfonyl chloride (4.5 g, 23.6 mmol, 2 equiv) and Et3N
(4.9 mL, 2 equiv) at 08C under nitrogen. The mixture was stirred at room
temperature under nitrogen for 6 h, then washed with HCl (1n) solution,
saturated NaHCO3, and brine then dried over anhydrous MgSO4, and
concentrated. The residue was purified by column chromatography
(EtOAc/n-hexane 1:4) to give toluene-4-sulfonic acid 6-phenoxyhexyl
ester (3.3 g, 80%) as a colorless oil: lH NMR (250 MHz, CDCl3, 258C): d ˆ
7.80 (d, 3J(H,H) ˆ 8.3 Hz, 2H; Ar-H), 7.35 (d, 3J(H,H) ˆ 8.3 Hz, 2H; Ar-H),
7.27 ± 7.24 (m, 2H; Ar-H), 6.95 ± 6.85 (m, 3H; Ar-H), 4.04 (t, 3J(H,H) ˆ
6.5 Hz, 2H; ArOCH2), 3.91 (t, 3J(H,H) ˆ 6.4 Hz, 2H; ArOCH2), 2.44 (s,
3H; Ar-CH3), 1.76 ± 1.62 (m, 4H), 1.41 ± 1.38 (m, 4H); 13C NMR (63 MHz,
CDCl3): d ˆ 159.1, 144.8, 133.3, 129.9, 129.5, 128.0, 120.7, 114.5, 70.6, 67.6,
29.1, 28.9, 25.6, 25.3, 21.7; elemental analysis calcd (%) for
C19H24O4S(348.46): C 65.49, H 6.94; found: C 65.44, H 6.98.
Macrocycle 2: The macrocycle was prepared by following the procedure
described previously.[10b] M.p. > 2008C (decomp); 1H NMR (250 MHz,
CDCl3, 258C): d ˆ 9.19 (s, 4H; NH), 8.59 (d, 3J(H,H) ˆ 7.8 Hz, 4H; Ar-H),
8.55 (s, 8H; Ar-H), 8.28 (t, 3J(H,H) ˆ 7.8 Hz, 2H; Ar-H), 2.28 (s, 24H;
CH3), 2.08 ± 1.98 (m, 8H; CH2), 1.87 ± 1.75 (m, 8H; CH2), 1.52 ± 1.29 (m,
32H; CH2), 0.96 (t, 3J(H,H) ˆ 6.6 Hz, 24H; CH3); 13C NMR (63 MHz,
A
solution of toluene-4-sulfonic acid 6-phenoxyhexyl ester (1.70 g,
4.88 mmol), phthalimide (2.15 g, 14.6 mmol, 3 equiv), and K2CO3 (3.03 g,
21.9 mmol, 4.5 equiv) in DMF (30 mL) was heated at 60 ± 708C for 9 h. The
mixture was concentrated under reduced pressure and the residue was
taken up in CH2Cl2. The organic solution was washed with HCl (1n)
solution, saturated NaHCO3, and brine, dried over anhydrous MgSO4, and
concentrated. The residue was purified by column chromatography
(EtOAc/n-hexane/CH2Cl2 1:4:1) to give 2-(6-phenoxyhexyl)isoindole-1,3-
dione (3b; 1.48 g, 94%) as a white solid. M.p. 62 ± 648C; lH NMR
(250 MHz, CDCl3, 258C): d ˆ 7.85 ± 7.82 (m, 2H; Ar-H), 7.71 ± 7.68 (m, 2H;
Ar-H), 7.29 ± 7.23 (m, 2H; Ar-H), 6.93 ± 6.85 (m, 3H; Ar-H), 3.94 (t,
3J(H,H) ˆ 6.4 Hz, 2H; ArOCH2), 3.69 (t, 3J(H,H) ˆ 7.2 Hz, 2H; NCH2),
1.83 ± 1.66 (m, 4H; CH2), 1.57 ± 1.37 (m, 4H; CH2); 13C NMR (63 MHz,
CDCl3): d ˆ 168.6, 159.2, 134.0, 132.3, 129.5, 123.3, 120.6, 114.6, 67.8, 38.1,
CDCl3): d ˆ 160.8, 149.5, 148.6, 145.7, 131.5, 127.3, 94.4, 34.7, 27.5, 24.6,
1
ˆ
ˆ
16.9, 15.1; IR (KBr): nÄ ˆ 3307 (NH), 1691 (C O), 829 (Os O) cm
;
‡
FAB-MS: m/z (%): 1480 (0.017) [M (OC(C4H9)2)2] , 1194 (0.034)
‡
[M 2(OC(C4H9)2)2] ;
elemental
analysis
calcd(%)
for
C78H114N10O12Os2(1764.3): C 53.10, H 6.51, N 7.94; found: C 53.15, H 6.57,
N 7.98.
Hexane-1,6-dioic acid bis(hexylamide) 4a: A suspension of adipic acid
(0.50 g, 3.42 mmol) in thionyl chloride (2.0 mL) containing a catalytic
amount of DMF was heated at reflux for 2 h, and excess thionyl chloride
was removed. The residue was dissolved in CHCl3 (15 mL) and to this
solution, 1-aminohexane (0.95 mL, 7.3 mmol, 2.1 equiv) and Et3N (1.0 mL,
7.2 mmol, 2.1 equiv) were added at 08C (ice-water bath) under argon. The
solution was stirred for 1 h at room temperature, then washed with
saturated NaHCO3 solution, brine, dried over anhydrous MgSO4, and
concentrated. The residue was purified by column chromatography
(MeOH/CH2Cl2 1:10) to give 4a (0.72 g, 67%) as a white solid. M.p.
29.3, 28.7, 26.8, 25.8; IR (KBr): nÄ ˆ 1702 (C O) cm 1; elemental analysis
ˆ
calcd (%) for C20H21NO3 (323.4): C 74.28, H 6.55, N 4.33; found: C 73.81, H
7.06, N 4.36.
A solution of 3b (1.40 g, 4.33 mmol) and hydrazine hydrate (55% N2H4,
1.5 mL, excess) in ethanol (50 mL) was heated at reflux for 18 h, then
cooled to room temperature, and filtered. The filtrate was concentrated,
then taken up in CH2Cl2 (50 mL), washed with H2O and brine, and dried
over anhydrous MgSO4, and concentrated. The resulting yellowish liquid of
6-phenoxyhexylamine was used in the next step without further purifica-
tion (0.90 g). A solution of hexane-1,6-dioic acid bis(pentafluorophenyl)
ester (0.59 g, 1.23 mmol) in dry CH2Cl2 (5 mL) was added under argon at
l
1608C; H NMR (250 MHz, CDCl3, 258C): d ˆ 5.66 (s, 2H; NH), 3.23 (m,
3
ˆ
4H; NCH2), 2.19 (t, J(H,H) ˆ 5.8 Hz, 4H; C( O)CH2), 1.65 (m, 4H; CH2),
1.49 (m, 4H; CH2), 1.33 ± 1.29 (m, 12H; CH2), 0.88 (m, 6H; CH3); 13C NMR
(63 MHz, CDCl3): d ˆ 172.8, 39.7, 36.4, 31.6, 29.7, 26.7, 25.2, 22.7, 14.1; IR
(KBr): nÄ ˆ 3313 (NH), 1632 (C O) cm 1; elemental analysis calcd(%) for
ˆ
C18H36N2O2 (312.49): C 69.18, H 11.61, N 8.96; found: C 69.21, H 11.60, N
8.96.
08C (ice-water bath) to
a solution of 6-phenoxyhexylamine (0.60 g,
General procedure of 4b ± e: Compounds 4b, 4c, 4d, and 4e were prepared
in similar yields from hexane-1,6-diol in six steps. As a representative
example the synthesis of 4b is described below. To a solution of hexane-1,6-
diol (30 g, 0.25 mol) in dry THF (70 mL) were added Et3N (70 mL, 0.5 mol,
2 equiv) and toluene-p-sulfonyl chloride (48 g, 0.25 mol, 1 equiv) at 08C
(ice-water bath) under argon. After stirring for 1 h at 08C, the solution was
concentrated, the residue was taken up in CH2Cl2, washed with 1n HCl
3.10 mmol, 2.5 equiv), Et3N (0.69 mL, 4.95 mmol, 4 equiv), and 4-dimethy-
laminopyridine (DMAP) (0.15 g, 1.23 mmol, 1 equiv) in CH2Cl2 (10 mL).
After stirring at room temperature for 4 h, the mixture was washed with
HCl solution (1n), saturated NaHCO3 solution, and brine, and then the
mixture was dried over anhydrous MgSO4. The product was purified by
column chromatography (MeOH/CH2Cl2 1:10) to give hexane-1,6-dioic
acid bis[(6-phenoxyhexyl)amide] 4b (0.40 g, 65%) as a white solid. M.p.
2694
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Chem. Eur. J. 2001, 7, No. 12

[2]- and [3]Rotaxanes
2687±2697
132 ± 1338C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ 7.30 ± 7.23 (m, 4H; Ar-
H), 6.95 ± 6.86 (m, 6H; Ar-H), 5.66 (s, 2H; NH), 3.94 (t, 3J(H,H) ˆ 6.4 Hz,
(t, 3J(H,H) ˆ 6.3 Hz, 2H; ArOCH2), 3.25 (m, 2H; NCH2), 2.38 (t,
3
J(H,H) ˆ 6.3 Hz, 2H; C( O)CH2), 2.19 (t, 3J(H,H) ˆ 6.7 Hz, 2H; CH2),
ˆ
ˆ
4H; OCH2), 3.25 (m, 4H; NCH2), 2.17 (brs, 4H; C( O)CH2), 1.77 (m, 4H;
1.76 ± 1.67 (m, 6H; CH2), 1.53 ± 1.27 (m, 6H; CH2); 13C NMR (63 MHz,
CDCl3, 258C): d ˆ 178.3, 173.1, 157.1, 147.1, 138.9, 132.3, 131.2, 127.5, 125.9,
113.3, 67.7, 63.4, 39.7, 36.3, 33.8, 29.6, 29.3, 26.8, 25.9, 25.1, 24.3; IR (KBr):
CH2), 1.65 (brs, 4H; CH2), 1.56 ± 1.34 (m, 12H; CH2); 13C NMR (63 MHz,
CDCl3) d ˆ 172.8, 159.2, 129.6, 120.7, 114.6, 67.8, 39.6, 36.3, 29.7, 29.3, 26.8,
25.9, 25.1; IR (KBr): nÄ ˆ 3297 (NH), 1636 (C O) cm 1; elemental analysis
nÄ ˆ 3432 (COOH), 1707 (C O), 1623 (C O) cm 1; elemental analysis calcd
(%) for C37H41NO4 (563.7): C 78.83, H 7.33, N 2.48; found: C 78.86, H 7.46,
N 2.50.
ˆ
ˆ
ˆ
calcd (%) for C30H44N2O4 (496.7): C 72.55, H 8.93, N, 5.64; found: C 72.57,
H 8.92, N 5.61.
Hexane-1,6-dioic acid bis{[6-(3,5-di-tert-butylphenoxy)hexyl]amide} (4c):
The compound 4c was prepared by following the same procedures
described for 4b except 3,5-di-tert-butylphenol was used instead of phenol.
M.p. 1398C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ 7.01 (t, 4J(H,H) ˆ
1.5 Hz, 2H; Ar-H), 6.75 (t, 4J(H,H) ˆ 1.5 Hz, 4H; Ar-H), 5.62 (brs, 2H;
2-(2-{2-[4-(2-Methoxyethoxy)phenoxy]ethoxy}ethoxy)ethanol (8a): Com-
pound 8a was prepared by sequential coupling reactions of p-hydroquinone
with approximately one equivalent of each toluene-4-sulfonic acid
2-methoxyethyl ester and tri(ethylene glycol) mono-p-tosylate. Reactions
were heated at reflux in CH3CN for 5 ± 7 h in the presence of K2CO3
(3 equiv), and yields were 34% and 56% for the first and second steps,
respectively. M.p. 35 ± 378C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ 6.79 (s,
4H; Ar-H), 4.04 ± 3.98 (m, 4H; OCH2CH2O), 3.78 (m, 2H; OCH2CH2O),
3.68 ± 3.61 (m, 8H; OCH2CH2O), 3.55 (m, 2H; OCH2CH2O), 3.38 (s, 3H;
OCH3); 13C NMR (63 MHz, CDCl3, 258C): d ˆ 153.1, 153.0, 115.5, 72.5,
71.1, 70.7, 70.3, 69.8, 67.9, 67.8, 61.6, 59.1; IR (KBr): nÄ ˆ 3367 (OH), 2876
(CH2-O-CH2) cm 1; elemental analysis calcd (%) for C15H24O6 (300.4): C
59.98, H 8.05; found: C 59.91, H 8.01.
3
NH), 3.95 (t, J(H,H) ˆ 6.4 Hz, 4H; ArOCH2), 3.26 (m, 4H; NCH2), 2.19
ˆ
(brs, 4H; C( O)CH2), 1.76 (m, 4H; CH2), 1.66 (brs, 4H; CH2), 1.56 ± 1.48
(m, 8H; CH2), 1.41 (m, 4H; CH2), 1.30 (s, 18H; C(CH3)3); 13C NMR
(63 MHz, CDCl3): d ˆ 172.8, 158.8, 152.3, 115.0, 108.9, 67.7, 39.6, 36.4, 35.1,
1
ˆ
31.6, 29.8, 29.6, 26.9, 26.0, 25.1; IR (KBr): nÄ ˆ 3302 (NH), 1638 (C O) cm
;
elemental analysis calcd (%) for C46H76N2O4 (721.1): C 76.62, H 10.62, N
3.88; found: C 76.59, H 10.68, N 3.91.
Hexane-1,6-dioic acid bis{[6-(4-tritylphenoxy)hexyl]amide} (4d): The
compound 4d was prepared by following the same procedures described
for 4b but 4-tritylphenol and adipoyl chloride were used instead of phenol
and hexane-1,6-dioic acid bis(pentafluorophenyl) ester, respectively. M.p.
158 ± 1598C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ 7.24 ± 7.14 (m, 30H;
Ar-H), 7.08 (d, 3J(H,H) ˆ 8.9 Hz, 4H; Ar-H), 6.75 (d, 3J(H,H) ˆ 8.9 Hz,
2-(2-{2-[5-(2-Methoxyethoxy)naphthalen-1-yloxy]ethoxy}ethoxy)ethanol
(8b): Compound 8b was prepared from 1,5-dihydroxynaphthalene with
approximately one equivalent each of toluene-4-sulfonic acid 2-methoxy-
ethyl ester and tri(ethylene glycol) mono-p-tosylate. The mixture was
heated at reflux in CH3CN overnight (ꢀ16 h) in the presence of K2CO3
(3 equiv), and yields were 37% and 83% for the first and second steps,
3
4H; Ar-H), 5.68 (s, 2H; NH), 3.91 (t, J(H,H) ˆ 6.3 Hz, 4H; OCH2), 3.24
1
ˆ
(m, 4H; NCH2), 2.17 (brs, 4H; C( O)CH2), 1.74 (m, 4H; CH2), 1.63 (m,
respectively. M.p. 29 ± 318C; H NMR (250 MHz, CDCl3, 258C): d ˆ 7.91 ±
4H; CH2), 1.57 ± 1.36 (m, 12H; CH2); 13C NMR (63 MHz, CDCl3): d ˆ
7.85 (m, 2H; Ar-H), 7.39 ± 7.32 (m, 2H; Ar-H), 6.85 (m, 2H; Ar-H), 4.32 ±
4.27 (m, 4H; OCH2CH2O), 4.00 (m, 2H; OCH2CH2O), 3.89 (m, 2H;
OCH2CH2O), 3.82 (m, 2H; OCH2CH2O), 3.79 ± 3.69 (m, 4H; OCH2-
CH2O), 3.62 (m, 2H; OCH2CH2O), 3.51 (s, 3H; OCH3); 13C NMR
(63 MHz, CDCl3, 258C): d ˆ 154.5, 154.4, 126.9, 126.8, 125.2, 114.8, 114.7,
105.8, 72.6, 71.2, 71.1, 70.6, 69.9, 68.0, 67.9, 61.9, 59.4; IR (KBr): nÄ ˆ 3455
(OH) cm 1; elemental analysis calcd(%) for C19H26O6 (350.4): C 65.13, H
7.48; found: C 65.15, H 7.51.
172.8, 157.1, 147.1, 138.9, 132.3, 131.2, 127.5, 126.0, 113.3, 67.7, 64.4, 39.6, 36.3,
1
ˆ
29.7, 29.4, 26.8, 26.0, 25.1; IR (KBr): nÄ ˆ 3295 (NH), 1644 (C O) cm
;
elemental analysis calcd (%) for C68H72N2O4 (981.3): C 83.23, H 7.40, N
2.85; found: C 83.20, H 7.45, N, 2.87.
Hexane-1,6-dioic acid bis[(6-{4-[tris(4-tert-butylphenyl)methyl]phenoxy}-
hexyl)amide] (4e): The compound 4e was prepared by following the same
procedures described for 4b except 4-[tris(4-tert-butylphenyl)methylphe-
l
nol was used instead of phenol. M.p. 2168C; H NMR (250 MHz, CDCl3,
Hexane-1,6-dioic acid [2-(2-{2-[4-(2-methoxyethoxy)phenoxy]ethoxy}-
ethoxy)ethyl]amide [6-(4-tritylphenoxy)hexyl]amide (10a): Amines 9a
and 9b were prepared from the precursor alcohols 8a and 8b, according to
the same procedures described for the conversion of hexane-1,6-diol into
6-phenoxyhexylamine. To a solution of carboxylic acid 7 (0.20 g, 0.35 mmol,
1.2 equiv) in dry CH2Cl2 (20 mL), trimethylacetyl chloride (0.034 mL,
0.28 mmol, 0.9 equiv), and Et3N (0.10 mL, 0.72mmol, 2.4 equiv) were
added. The solution was stirred under argon for 1 h at room temperature,
and then amine 9a (0.089 g, 0.30 mmol) was added. After stirring for 2 h at
room temperature, the mixture was washed with saturated NaHCO3 and
brine, dried over anhydrous MgSO4, and concentrated. The residue was
purified by column chromatography (MeOH/CH2Cl2 1:15) to give 10a
(0.13 g, 51%) as a white solid. M.p. 99 ± 1018C; 1H NMR (250 MHz,
CDCl3, 258C): d ˆ 7.23 ± 7.17 (m, 15H; Ar-H), 7.08 (d, 3J(H,H) ˆ 8.9 Hz,
2H; Ar-H), 6.84 (s, 4H; Ar-H), 6.75 (d, 3J(H,H) ˆ 8.9 Hz, 2H; Ar-H), 6.21
(brs, 1H; NH), 5.81 (brs, 1H; NH), 4.10 ± 4.04 (m, 4H; OCH2), 3.91 (t,
3J(H,H) ˆ 6.3 Hz, 2H; ArOCH2), 3.82 (t, 3J(H,H) ˆ 4.6 Hz, 2H; OCH2-
CH2O), 3.74 ± 3.69 (m, 4H; OCH2CH2O), 3.65 (m, 2H; OCH2CH2O), 3.56
(t, 3J (H,H) ˆ 4.9 Hz, 2H; NCH2CH2O), 3.44 (brs, 5H; NCH2, OCH3), 3.24
258C): d ˆ 7.24 ± 7.20 (m, 12H; Ar-H), 7.09 ± 7.05 (m, 16H; Ar-H), 6.73 (d,
3
3J(H,H) ˆ 8.8 Hz, 4H; Ar-H), 5.64 (s, 2H; NH), 3.91 (t, J(H,H) ˆ 6.3 Hz,
ˆ
4H; ArOCH2), 3.24 (m, 4H; NCH2), 2.17 (brs, 4H; (C O)CH2), 1.78 ± 1.37
(m, 20H; CH2), 1.29 (s, 54H; C(CH3)3); 13C NMR (63 MHz, CDCl3): d ˆ
172.8, 157.0, 148.4, 144.3, 139.6, 132.4, 130.9, 124.2, 113.1, 67.7, 63.2, 39.6,
36.3, 34.4, 31.6, 29.8, 29.4, 26.9, 26.0, 25.1; IR (KBr): nÄ ˆ 3421 (NH), 1648
(C O) cm 1; elemental analysis calcd (%) for C92H120N2O4 (1318.0): C
ˆ
83.84, H 9.18, N 2.13; found: C 83.84, H 9.30, N 2.17.
5-[6-(4-Tritylphenoxy)hexylcarbamoyl]pentanoic acid (7): A solution of
benzyl alcohol (8.3 g, 77 mmol, 0.5 equiv) and Et3N (15 mL, 110 mmol,
0.8 equiv) in dry CH2Cl2 (100 mL) was slowly added to a solution of adipoyl
chloride (26 g, 142 mmol) in dry CH2Cl2 (50 mL) over 20 min at 08C (ice-
water bath) under argon. After stirring for 2 h at room temperature, the
mixture was washed with H2O, and dried over anhydrous MgSO4. The
residue was purified with short silica column chromatography (CH2Cl2) to
give 6 (6.6 g) which was contaminated by some impurities (ꢀ5%), but used
without further purification. 1H NMR (250 MHz, CDCl3, 258C): d ˆ 7.35 (s,
ˆ
5H; Ar-H), 5.12 (s, 2H; ArCH2O), 2.42 ± 2.35 (m, 4H; C( O)CH2), 1.71 ±
ˆ
(m, 2H; NCH2), 2.14 (brs, 4H; C( O)CH2), 1.76 (m, 2H; CH2), 1.61 (brs,
1.68 (m, 4H; CH2). To a solution of 6 (2.2 g, 9.2 mmol, 2 equiv) and Et3N
(1.9 mL, 13.8 mmol, 3 equiv) in CH2Cl2 (15 mL) was added 2,2-dimethyl-
propionyl chloride (1.1 mL, 9.2 mmol, 2 equiv) at 08C. The mixture was
stirred at room temperature for 1 h under argon, and 6-(4-tritylphenoxy)-
hexylamine 5 (2.0 g, 4.6 mmol) was added to the solution. After stirring for
an additional 1 h at room temperature, the mixture was washed with
saturated NaHCO3 and brine, and then dried over anhydrous MgSO4, and
concentrated. The residue was purified by column chromatography
(MeOH/CH2Cl2 1:30) to give the desired amide (2.20 g, 73%) as a white
solid, which was dissolved in EtOAc (50 mL) and MeOH (50 mL). A
catalytic amount (ꢀ0.3 g) of 5% Pd/C was added and the solution was
stirred under a H2 balloon for 1 h. The solution was then filtered through
Celite and concentrated under reduced pressure to give 7 (1.67 g, 88%) as a
white solid. M.p. 136 ± 1388C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ 9.93
(br, 1H; COOH), 7.23 ± 7.15 (m, 15H; Ar-H), 7.09 (d, 3J(H,H) ˆ 8.8 Hz,
2H; Ar-H), 6.76 (d, 3J(H,H) ˆ 8.8 Hz, 2H; Ar-H), 5.74 (brs, 1H; NH), 3.92
4H; CH2), 1.55 ± 1.37 (m, 6H; CH2); 13C NMR (125 MHz , CDCl3): d ˆ
173.0, 172.8, 157.1, 153.4, 153.1, 147.2, 138.9, 132.3, 131.2, 127.5, 125.9, 115.7,
113.3, 71.3, 70.8, 70.3, 70.0, 69.9, 68.3, 68.0, 67.8, 64.4, 59.3, 40.0, 39.3, 36.4,
36.1, 29.7, 29.4, 26.8, 26.0, 25.3, 25.0; IR (KBr): nÄ ˆ 3300 (NH), 1640
(C O) cm 1; elemental analysis calcd (%) for C52H64N2O8 (845.1): C 73.91,
ˆ
H 7.63, N 3.31; found: C 73.95, H 7.60, N 3.36.
Hexane-1,6-dioic acid [2-(2-{2-[5-(2-methoxyethoxy)naphthalen-1-yloxy]-
ethoxy}ethoxy)ethyl]amide [6-(4-tritylphenoxy)hexyl]amide (10b): The
compound 10b was prepared in 54% yield by following the same procedure
described for 10a. M.p. 88 ± 908C; 1H NMR (250 MHz, CDCl3, 258C): d ˆ
7.87 (t, 3J(H,H) ˆ 8.6 Hz, 2H; Ar-H), 7.34 (t, 3J(H,H) ˆ 8.0 Hz, 2H; Ar-H),
3
7.24 ± 7.17 (m, 15H; Ar-H), 7.08 (d, J(H,H) ˆ 8.9 Hz, 2H; Ar-H), 6.84 (d,
3J(H,H) ˆ 7.6 Hz, 2H; Ar-H), 6.75 (d, 3J(H,H) ˆ 8.9 Hz, 2H; Ar-H), 6.08
(brs, 1H; NH), 5.73 (brs, 1H; NH), 4.32 ± 4.26 (m, 4H; ArOCH2), 3.99 (t,
3J(H,H) ˆ 4.6 Hz, 2H; OCH2CH2O), 3.93 ± 3.86 (m, 4H; ArOCH2), 3.79
Chem. Eur. J. 2001, 7, No. 12
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0712-2695 $ 17.50+.50/0
2695

K.-S. Jeong et al.
FULL PAPER
(m, 2H; OCH2CH2O), 3.67 (m, 2H; OCH2CH2O), 3.56 (t, 3J(H,H) ˆ
sine bell in F1 and 608 shifted in F2 domain. The data file was zero-filled,
affording a spectrum of 2 Â 256 K real data points. The rate constants (k)
were calculated employing Equations (1) ± (5) shown below, where IAB and
IBA are cross peak intensities, IAA and IBB are diagonal peak intensities, and
XA, XB are molar fractions of the free and complex which was determined
4.9 Hz, 2H; NCH2CH2O), 3.50 (s, 3H; OCH3), 3.43 (m, 2H; NCH2), 3.22
ˆ
(m, 2H; NCH2), 2.06 ± 2.03 (m, 4H; C( O)CH2), 1.73 (m, 2H; CH2), 1.50 ±
1.34 (m, 10H; CH2); 13C NMR (125 MHz, CDCl3): d ˆ 172.9, 172.8, 157.1,
154.6, 154.4, 147.2, 138.9, 132.3, 131.2, 127.5, 127.0, 126.9, 126.0, 125.3, 125.2,
115.0, 114.6, 113.3, 106.0, 105.9, 71.3, 71.0, 70.5, 70.0, 69.9, 68.1, 68.0, 67.8,
1
by H NMR integration.
64.4, 59.4, 39.5, 39.3, 36.3, 36.0, 29.7, 29.4, 26.8, 26.0, 25.2, 24.9; IR (KBr):
k1
1
A„B
(1)
(2)
(3)
ˆ
nÄ ˆ 3292 (NH), 1638 (C O) cm
; elemental analysis calcd (%) for
C56H66N2O8 (895.1): C 75.14, H 7.43, N 3.13; found: C 75.08, H 7.53, N 3.18.
k
1
k ˆ k1‡k
1
Hexane-1,6-dioic acid [6-(4-tritylphenoxy)hexyl]amide (2-{2-[2-(4-{2-[2-(2-
{5-[6-(4-tritylphenoxy)hexylcarbamoyl]pentanoylamino}ethoxy)ethoxy]-
ethoxy}phenoxy)ethoxy]ethoxy}ethyl)amide (13a): Diamines 12a and 12b
were prepared according to the same procedures that were described
earlier for the preparation of monoamines 9a and 9b from p-hydroquinone
and 1,5-dihydroxynaphthalene, respectively. To a solution of carboxylic
acid 7 (0.30 g, 0.53 mmol, 3 equiv) in CH2Cl2 (20mL) was added 2,2-
dimethylpropionyl chloride (0.065 mL, 0.53 mmol, 2.9 equiv) and Et3N
(0.10 mL, 0.72 mmol, 4 equiv). The mixture was stirred for 1 h under argon
and diamine 12a (0.066 g, 0.18 mmol) was added. After stirring for 1 h at
room temperature, the mixture was washed with saturated NaHCO3 and
brine, dried over anhydrous MgSO4, and concentrated. The residue was
purified with column chromatography (MeOH/CH2Cl2 1:10) to give 13a
(0.10 g, 38%) as a white solid. M.p. 98 ± 1008C; 1H NMR (250 MHz,
CDCl3, 258C): d ˆ 7.24 ± 7.16 (m, 30H; Ar-H), 7.08 (d, 3J(H,H) ˆ 9.0 Hz,
4H; Ar-H), 6.83 (s, 4H; Ar-H), 6.75 (d, 3J(H,H) ˆ 9.0 Hz, 4H; Ar-H), 6.23
(brs, 2H; NH), 5.86 (brs, 2H; NH), 4.08 (m, 4H; ArOCH2), 3.91 (t,
3J(H,H) ˆ 6.3 Hz, 4H; ArOCH2), 3.82 (m, 4H; OCH2CH2O), 3.70 (m, 4H;
OCH2CH2O), 3.64 (m, 4H; OCH2CH2O), 3.55 (t, 3J(H,H) ˆ 4.9 Hz, 4H;
OCH2CH2O), 3.44 (m, 4H; NCH2), 3.22 (m, 4H; NCH2), 2.14 (brs, 8H;
CH2), 1.74 (m, 4H; CH2), 1.61 (m, 8H; CH2), 1.52 ± 1.33 (m, 12H; CH2);
13C NMR (63 MHz, CDCl3, 258C): d ˆ 173.0, 172.8, 157.2, 153.2, 147.2,
138.9, 132.3, 131.3, 127.5, 126.0, 115.8, 113.3, 70.9, 70.4, 70.0, 69.9, 68.3, 67.8,
64.4, 39.6, 39.3, 36.4, 36.1, 29.7, 29.4, 26.9, 26.0, 25.3, 25.0; IR (KBr): nÄ ˆ 3299
1
r ‡ 1
k ˆ  In
tm
r
1
ꢁIAA ‡ IBB
ꢁIAB ‡ IBA
†
†
rˆ 4XaXb
(XA XB)2
(4)
(5)
kh
DG=ˆ RTIn
kbT
(Rˆ 1.9872 cal K 1 mol 1, kB ˆ 3.2995 10 24 calK 1, h ˆ 1.5836 10 34 cals)
Acknowledgements
This work was supported by Korea Research Foundation (KRF-2000-041-
D00190). We thank Professor Weontae Lee (Yonsei University) for help in
2D-EXSY experiments, and D. Hill and N. Zimmerman (University of
Illinois, Urbana-Champaign) for the proofreading of the manuscript. We
also thank referees of this paper for valuable suggestions and comments.
[1] For reviews on pseudorotaxanes and rotaxanes, see: a) D. B. Amabi-
lino, J. F. Stoddart, Chem. Rev. 1995, 95, 2725 ± 2828; b) R. Jäger, F.
Vögtle, Angew. Chem. 1997, 109, 966 ± 980; Angew. Chem. Int. Ed.
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J. 1998, 4, 1362 ± 1366; d) J.-P. Sauvage, Acc. Chem. Res. 1998, 31, 611 ±
619; e) S. A. Nepogodiev, J. F. Stoddart, Chem. Rev. 1998, 98, 1959 ±
1
ˆ
(NH), 1640 (C O) cm
;
elemental analysis calcd (%) for
C92H110N4O12(1463.9): C 75.48, H 7.57, N 3.83; found: C 75.43, H 7.52, N
3.83.
Hexane-1,6-dioic acid [6-(4-tritylphenoxy)hexyl]amide (2-{2-[2-(5-{2-[2-(2-
{5-[6-(4-tritylphenoxy)hexylcarbamoyl]pentanoylamino}ethoxy)ethoxy]-
ethoxy}naphthalen-1-yloxy)ethoxy]ethoxy}ethyl)amide (13b): The com-
pound 13b was prepared in 63% yield by following the same procedure
described for 10a. M.p. 108 ± 1108C; 1H NMR (250 MHz, CDCl3, 258C):
d ˆ 7.86 (d, 3J(H,H) ˆ 8.5 Hz, 2H; Ar-H), 7.34 (t, 3J(H,H) ˆ 8.0 Hz, 2H; Ar-
H), 7.26 ± 7.13 (m, 30H; Ar-H), 7.08 (d, 3J(H,H) ˆ 8.8 Hz; 4H; Ar-H), 6.85
(d, 3J (H,H) ˆ 7.5 Hz, 2H; Ar-H), 6.76 (d, 3J(H,H) ˆ 8.8 Hz, 4H; Ar-H),
6.09 (brs, 2H; NH), 5.80 (brs, 2H; NH), 4.30 (t, 3J(H,H) ˆ 4.7 Hz, 4H;
Â
1976; f) M.-J. Blanco, M. C. Jimenez, J.-C. Chambron, V. Heitz, M.
Linke, J.-P. Sauvage, Chem. Soc. Rev. 1999, 28, 293 ± 295; g) F. M.
Raymo, J. F. Stoddart, Chem. Rev. 1999, 99, 1643 ± 1663; h) G. A.
Breault, C. A. Hunter, P. C. Mayers, Tetrahedron 1999, 55, 5265 ± 5293.
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Lett. 2000, 2, 593 ± 595; b) J. E. H. Buston, J. R. Young, H. L.
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A. Sobanski, F. Vögtle, Chem. Eur. J. 2000, 6, 1674 ± 1682; d) T.
Fujimoto, Y. Sakata, T. Kaneda, Chem. Commun. 2000, 2143 ± 2144;
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3456; h) J. O. Jeppesen, J. Perkins, J. Becher, J. F. Stoddart, Org. Lett.
2000, 2, 3547 ± 3550; i) A. M. Parham, B. Windisch, F. Vögtle. Eur. J.
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Cantrill, P. T. Glink, R. L. Garrell, J. F. Stoddart, Org. Lett. 2000, 2,
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Encinas, F. Barigelletti, L. Flamigni, J. Am. Chem. Soc. 2000, 122,
11834 ± 11844.
3
3
ArOCH2), 4.00 (t, J(H,H) ˆ 4.6 Hz, 4H; OCH2CH2O), 3.90 (t, J(H,H) ˆ
6.4 Hz, 4H; ArOCH2), 3.78 (m, 4H; OCH2CH2O), 3.66 (m, 4H;
OCH2CH2O), 3.55 (t, 3J(H,H) ˆ 5.0 Hz, 4H; OCH2CH2O), 3.41 (m, 4H;
OCH2CH2O), 3.21 (m, 4H; NCH2), 2.07 ± 2.04 (m, 8H; CH2), 1.80 ± 1.72 (m,
4H; CH2), 1.57 ± 1.36 (m, 20H; CH2); 13C NMR (63 MHz, CDCl3, 258C):
d ˆ 172.9, 172.8, 157.2, 154.5, 147.2, 138.9, 132.3, 131.3, 127.5, 126.9, 126.0,
125.4, 114.8, 113.3, 106.0, 71.1, 70.5, 70.0, 69.9, 68.2, 67.8, 64.4, 39.6, 39.3,
36.4, 36.1, 29.7, 29.4, 26.9, 26.0, 25.2, 24.9; IR (KBr): nÄ ˆ 3296 (NH), 1641
(C O) cm 1; elemental analysis calcd (%) for C96H112N4O12 (1513.9): C
ˆ
76.16, H 7.46, N 3.70; found: C 76.16, H 7.48, N.3.71
Determination of binding constant (Ka, m 1): Chloroform was stored over
4 Š molecular sieves, and filtered through basic alumina (Al2O3) prior to
use. The CDCl3 solutions of a 1:1 molar mixture of macrocycle 2 and
threads 4c ± e were separately prepared in five NMR tubes, concentrations
of which were 5.0, 2.0, 1.0, 0.5, and 0.2mm. The 1H NMR (500 MHz)
spectrum of each solution was recorded at 258C, and the integration of
well-separated amide NH peaks of both 2 and 4c ± e gave the ratios of the
free components and the complex. The association constants reported were
an average of ten values obtained for each combination of the macrocycle
and the thread, and errors were within 20%.
2D-EXSY experiments:[16] The EXSY spectrum was recorded on a DRX-
500 spectrometer at a given temperature. The concentration of each
macrocycle and thread is 10 ± 20mm in CDCl3 and molar ratios of two
components are in the range of 0.7 ± 1.5. The mixing time was 50 ± 300 ms,
and each of 128F1 increments was the accumulation of 32 scans. Prior to
Fourier transformation, the FIDs were multiplied by a 908 shifted square
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Â
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2696
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0712-2696 $ 17.50+.50/0
Chem. Eur. J. 2001, 7, No. 12

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2687±2697
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V. Balzani, M. Bìlohradsky, M. T. Gandolfi, O. Kocian, L. Prodi, F. M.
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Received: December 27, 2000 [F2968]
Chem. Eur. J. 2001, 7, No. 12
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