A Mechanically Interlocked Bundle

Article abstract of DOI:10.1002/chem.200305687

The prototype of an artificial molecular machine consisting of a trisammonium tricationic component interlocked with a tris(crown ether) component to form a molecular bundle with averaged C_3ν symmetry has been designed and synthesized. The system is based on noncovalent interactions, which include 1) N⁺-H...O hydrogen bonds; 2) C-H...O interactions between the CH₂NH₂ ⁺CH₂ protons on three dibenzylammonium-ion-containing arms, which are attached symmetrically to a benzenoid core, and three dibenzo[24]crown-8 macrorings fused onto a triphenylene core; and 3) π...π stacking interactions between the aromatic cores. The template-directed synthesis of the mechanically interlocked, triply threaded bundle involves post-assembly covalent modification, that is, the efficient conversion of three azide functions at the ends of the arms of the bound and threaded trication into bulky triazole stoppers, after 1,3-dipolar cycloaddition with di-tert-butylacetylenedicarboxylate to the extremely strong 1:1 adduct that is formed in dichloromethane/acetonitrile (3:2), on account of a cluster effect associated with the paucivalent adduct. Evidence for the averaged C_3ν symmetry of the molecular bundle comes from absorption and luminescence data, as well as from electrochemical experiments, ¹H NMR spectroscopy, and mass spectrometry. The photophysical properties of the mechanically interlocked bundle are very similar to those of the super-bundle that precedes the formation of the bundle in the process of supra-molecular assistance to covalent synthesis. Although weak non-nucleophilic bases (e.g., nBu₃N and iPr₂NEt) fail to deprotonate the bundle, the strong tBuOK does, as indicated by both luminescence and ¹H NMR spectroscopy. While deprotonation undoubtedly loosens up the interlocked structure of the molecular bundle by replacing relatively strong N⁺-H...O hydrogen bonds by much weaker N-H...O ones, the π...π stacking interactions ensure that any structural changes are inconsequential, particularly when the temperature of the solution of the neutral molecular bundle in dichloromethane is cooled down to considerably below room temperature.

Full text of DOI:10.1002/chem.200305687

FULL PAPER
A Mechanically Interlocked Bundle
Jovica D. Badjic¬,[a] Vincenzo Balzani,[b] Alberto Credi,*[b] James N. Lowe,[a]
Serena Silvi,[b] and J. Fraser Stoddart*[a]
Abstract: The prototype of an artificial
molecular machine consisting of a tris-
ammonium tricationic component in-
terlocked with a tris(crown ether) com-
ponent to form a molecular bundle
with averaged C3v symmetry has been
designed and synthesized.The system
is based on noncovalent interactions,
functions at the ends of the arms of the
bound and threaded trication into
bulky triazole stoppers, after 1,3-dipo-
lar cycloaddition with di-tert-butylacet-
ylenedicarboxylate to the extremely
strong 1:1 adduct that is formed in di-
chloromethane/acetonitrile (3:2), on
account of a cluster effect associated
with the paucivalent adduct.Evidence
for the averaged C3v symmetry of the
molecular bundle comes from absorp-
tion and luminescence data, as well as
from electrochemical experiments,
1H NMR spectroscopy, and mass spec-
trometry.The photophysical properties
of the mechanically interlocked bundle
are very similar to those of the super-
bundle that precedes the formation of
the bundle in the process of supra-
molecular assistance to covalent syn-
thesis.Although weak non-nucleophilic
bases (e.g., nBu3N and iPr2NEt) fail to
deprotonate the bundle, the strong
tBuOK does, as indicated by both lumi-
nescence and 1H NMR spectroscopy.
While deprotonation undoubtedly loos-
ens up the interlocked structure of the
molecular bundle by replacing relative-
which include 1) N+ H¥¥¥O hydrogen
À
À
bonds; 2) C H¥¥¥O interactions be-
tween the CH2NH2+CH2 protons on
three dibenzylammonium-ion-contain-
ing arms, which are attached symmetri-
cally to a benzenoid core, and three di-
benzo[24]crown-8 macrorings fused
onto a triphenylene core; and 3) p¥¥¥p
stacking interactions between the aro-
matic cores.The template-directed syn-
thesis of the mechanically interlocked,
triply threaded bundle involves post-
assembly covalent modification, that is,
the efficient conversion of three azide
ly strong N+ H¥¥¥O hydrogen bonds by
À
À
much weaker N H¥¥¥O ones, the p¥¥¥p
stacking interactions ensure that any
structural changes are inconsequential,
particularly when the temperature of
the solution of the neutral molecular
bundle in dichloromethane is cooled
down to considerably below room tem-
perature.
Keywords: hydrogen
bonds
¥
luminescence ¥ molecular recognition ¥
multivalency ¥ self-assembly
Introduction
with a remarkable degree of architectural control and preci-
[3]
sion.The discovery
in the mid-90s that suitably sized
Nowadays, there seems to be an almost inexhaustible collec-
tion of complex supramolecular assemblies known[1] that uti-
lize hydrogen bonding as their main source of noncovalent
interactions to hold together, often in highly cooperative
ways, a number of molecular building blocks or tectons[2]
crown ether macrocycles will thread spontaneously onto sec-
ondary dialkylammonium ions, forming interpenetrating
complexes called pseudorotaxanes,[4] primarily as a result of
[5]
N+ H¥¥¥O hydrogen bonds and C H¥¥¥O interactions, has
evolved[6] from these early beginnings, where only one
monotopic crown ether macrocycle was threaded onto one
dialkylammonium ion center, to the construction of much
more elaborate multiply threaded superstructures.This very
simple recognition motif, in which the sources of the nonco-
valent interactions are primarily hydrogen bonds, is aug-
mented, not only by multivalency,[8] but also by the fact that
one molecular structure (the cationic component) interpene-
trates the other molecular structure.[9] In the limit, of course,
post-assembly covalent modification can be employed to
transport the multivalent supramolecular assembly into a
mechanically interlocked molecular domain.It is this limit
that will be addressed in this paper.
À
À
¬
[a] Dr.J.D.Badjic , Dr.J.N.Lowe, Prof.J.F.Stoddart
Department of Chemistry and Biochemistry
University of California, Los Angeles
405 Hilgard Avenue, Los Angeles, CA 90095-1569 (USA)
Fax : (+1)310-206-1843
E-mail: stoddart@chem.ucla.edu
[b] Prof.V.Balzani, Dr.A.Credi, S.Silvi
Dipartimento di Chimica ™G.Ciamician∫
Universit‡ di Bologna
Via Selmi 2, 40126 Bologna (Italy)
Fax : (+39)051-209-9456
E-mail: alberto.credi@unibo.it
1926
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DOI: 10.1002/chem.200305687
Chem. Eur. J. 2004, 10, 1926 1935

1926 1935
We have described quite recently an example[10] of multi-
valency at work in which a tritopic crown ether, in which
three benzo[24]crown-8 rings are fused onto a triphenylene
core, forms an extremely stable (Ka >107 molLÀ1 in CH2Cl2)
triply threaded, two-component superbundle with a trifur-
cated trication, wherein three dibenzylammonium ions are
linked to a central benzenoid core.The assembly and dis-
assembly of this superbundle can be reversibly and quantita-
tively controlled by an acid base input.[10] As such, it lends
itself conceptually to the construction of molecular ma-
chines[12,13] of nanometer-scale dimensions, as well as to the
self-assembly of supramolecular polymers[14] of considerable
size and stability with rigid architectures, but whose super-
structures could be sensitive to pH and solvent polarity.
Against this background, we report here 1) the template-di-
rected synthesis[15] of a mechanically interlocked, triply
threaded tricationic bundle [3-H3]3+ with averaged C3v sym-
metry by treating the trifurcated trisammonium ion [2-H3]3+
, which carries azide functions on the para-positions of its
three benzyl groups, with di-tert-butylacetylenedicarboxylate
in the presence of the tritopic crown ether 1 (Scheme 1) and
2) the full characterization of the [3-H3]3+ species by
1H NMR spectroscopy and mass spectrometry.Inspired by
the rapidly growing interest[16] in the construction of redox-
controllable molecular electronic devices for possible appli-
cations to nanoelectronics,[17] we have also investigated 3)
the photophysical and electrochemical properties of the me-
chanically interlocked bundle and 4) the reversible co-con-
formational changes[18] undergone by the superbundle upon
acid base treatment using (variable temperature) H NMR
1
spectroscopy as the probe.
Results and Discussion
Template-directed synthesis of the mechanically interlocked
bundle: The syntheses of 1,3,5-tris(p-formylphenyl)benzene
(4) and the tris(crown ether) have already been reported in
an earlier paper.[10b] The preparation of the trifurcated tris-
ammonium salt [2-H3][PF6]3 is outlined in Scheme 2.1,3,5-
Tris(p-formylphenyl)benzene (4) was condensed with 4-
(aminoethyl)benzyl alcohol[19] to give the trisimine 5, which
was reduced (NaBH4/MeOH) to the trisamine 6.Trisamine
6 was then Boc-protected to afford the triol 7, which was
converted subsequently (NCS/Ph3P/THF) to the trischloride
8 and then (NaN3/18C6/MeCOEt) to the trisazide 9.Follow-
ing TFA deprotection of 9 in CHCl3 and counterion ex-
change (NH4PF6/MeOH/H2O), the trifurcated trisammoni-
um salt [2-H3][PF6]3 was obtained.The mechanically inter-
locked bundle [3-H3][PF6]3 was obtained by using a tem-
plate-directed threading approach, followed by post-assem-
bly covalent modification whereby
a
1,3-dipolar
cycloaddition[20] is repeated three times over within the 1:1
adduct formed between the tris(crown ether) 1 and the tris-
ammonium ion [2-H3]3+.The
1:1 triply threaded superbundle
was assembled initially in
CH2Cl2/MeCN (3:2) containing
1 and [2-H3][PF6]3 (Scheme 1).
The azidomethyl groups on the
three para-positions of the
three terminal benzyl groups of
the [2-H3]3+ ion, each threaded
through one of the three mac-
rocyclic rings associated with
the tris(crown ether) 1, were
then treated[21] with di-tert-
butylacetylenedicarboxylate, af-
fording [3-H3][PF6]3 in 40%
yield.[22] The fact that the prod-
uct survived the purification by
column chromatography pro-
vides circumstantial evidence
that it is mechanically inter-
locked, and also that the tri-
azole stoppers are large enough
to ensure that the molecular
components cannot dissoci-
ate.[20]
Spectrometric and NMR spec-
troscopic characterization of
the bundle: Fast atom bom-
bardment (FAB) mass spec-
trometry of [3-H3][PF6]3 strong-
ly supports the structural as-
Scheme 1.The template-directed synthesis of the mechanically interlocked bundle [ 3-H3][PF6]3 by means of ki-
netically controlled, [1,3]-dipolar cycloadditions to trap the superbundle formed in CH2Cl2/MeCN (3:2) at
408C between the tritopic tris(crown ether) 1 and the trifurcated trisammonium salt [2-H3][PF6]3.The labeled
protons on the two structural components of the bundle are referred to in a range of 1H NMR spectra, illus-
trated in Figures 2 4.
1927
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J.F.Stoddart, A.Credi, et al.
FULL PAPER
signment of the mechanically
interlocked bundle made in
Scheme 1.The FAB mass spec-
trum revealed peaks at m/z=
3283, 3140, 2993, 2850, and
1497 corresponding to the
[M]+, [MÀPF6]+, [MÀ2PF6]+,
[MÀ3PF6]+, and [MÀ2PF6]2+
ions, respectively.Furthermore,
high-resolution electron spray
(HR-ESI) mass spectrometry of
[3-H3][PF6]3 revealed (Figure 1)
that the most intense peak in
the spectrum occurred at m/z=
1496.6814 with an isotope distri-
bution corresponding to the
[MÀ2PF6]+ ion.
1
The H NMR spectrum of [3-
H3][PF6]3 recorded in CD2Cl2
reveals a complex array of well-
defined resonances (Figure 2a).
The peak assignments (see
Scheme 1 for proton labels) to
these resonances produced by
the bundle [3-H3]3+ were made
with the aid of 1H 1H COSY
Scheme 2.The synthesis of the trisammonium salt [ 2-H3][PF6]3 carrying three azide functions for reaction
(Scheme 1) with di-tert-butylacetylenedicarboxylate to form bulky triazole stoppers.
Figure 1.a) Low-resolution fast atom bombardment (FAB) mass spectrum of [ 3-H3][PF6]3 with peaks at m/z 3283, 3140, 2993, 2850, and 1497 correspond-
ing to the [M]+, [MÀPF6]+, [MÀ2PF6]+, [MÀ3PF6]+, and [MÀ2PF6]2+ ions, respectively.b) High-resolution electrospray ionization (HR-ESI) mass
spectrum of [3-H3][PF6]3 with a major peak at m/z 1496.6814 corresponding to the [MÀ2PF6]2+ ion.Experimental (c) and calculated (d) isotope distribu-
tions for the peak at m/z 1496.6814 in the HR-ESI mass spectrum.
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Chem. Eur. J. 2004, 10, 1926 1935

A Mechanically Interlocked Bundle
1926 1935
Figure 2.The 1H NMR spectra (500 MHz, CD2Cl2, 9. 8mm, 298 K) of a) [3-H3][PF6]3, b) the deprotonated mechanically interlocked bundle, namely 3,
after addition of slightly more than three equivalents of solid tBuOK to [3-H3][PF6]3, and c) the reprotonated bundle, that is, [3-H3]3+, after the subse-
quent addition of a slight excess (>3 equiv) of trifluoroacetic acid (TFA).
(Figure 3a and b) and TROESY (Figure 4) two-dimensional
1H NMR experiments.They are completely in accordance
with molecules that have averaged C3v symmetry.The meth-
ylene protons, He and Hd, adjacent to the secondary dialkyl-
+
À
À
ammonium ( NH2 ) centers resonate (Figure 2a) at d=
4.91 and 4.72 ppm, respectively; chemical shifts that are not
Figure 4.Selected regions of the 1H 1H TROESY NMR spectrum
(500 MHz, CD2Cl2, 9. 8mm, 298 K) of the mechanically interlocked super-
bundle [3-H3][PF6]3.
all that dissimilar from those (d=4.87 and 4.80 ppm, respec-
tively) for the analogous methylene protons in the kinetical-
ly-stable,
triply
threaded
interwoven
superbundle
(Scheme 3) lacking the triazole stoppers.[10] Relative to [10-
H3]3+, in which the CH2NH2+CH2 protons resonate at d=
4.29 and 4.25 ppm, the downfield shifts and multiplicities ex-
hibited by He and Hd in [3-H3]3+ are diagnostic[3] of the
threading of dibenzylammonium ions through dibenzo[24]-
crown-8 (DB24C8) rings.They demonstrate the interlocked
nature of the two components in the mechanically inter-
locked bundle [3-H3]3+.The resonances for aromatic core
protons (Ha and Hi at d=7.60 and 7.40 ppm, respectively) of
the two components are shifted upfield significantly relative
to the chemical shifts (d=7.97 and 7.83 ppm, respectively)
of the analogous protons in the separate components–
namely, 1 and [10-H3]3+ of the superbundle [1ꢀ10-H3]3+
shown in Scheme 3–indicating p¥¥¥p stacking of the central
aromatic cores of the components with respect to one anoth-
er.Inspection of the region between d=3.6 and 4.4 ppm in
Figure 3.Selected regions (a and b) of the 1H 1H COSY NMR spectrum
(500 MHz, CD2Cl2, 9. 8mm, 298 K) of [3-H3][PF6]3.
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J.F.Stoddart, A.Credi, et al.
FULL PAPER
Scheme 3.The equilibrium between the tris(crown ether) 1 and the trisammonium ion [10-H3]3+, which lies very much to the right in favor of the super-
bundle in solvents such as acetonitrile and dichloromethane.The graphical representation of the superbundle portrays the good surface-to-surfac e match
+
+
3+
À
À
À
between the two interpenetrating components.The dots indicate the N
H¥¥¥O hydrogen bonds between the NH2
centers of [10-H3] and the fused
DB24C8 rings in 1, and the horizontal dashes indicate the p¥¥¥p stacking interactions between the central aromatic cores.The superbundle can be dis-
assembled by addition of base (e.g., nBu3N) and reassembled by addition of acid (e.g., CF3CO2H).
1
the H NMR spectrum (Figure 2a) reveals that all the pairs
of O-methylene protons are anisochronous in the tris(crown
ether) component of [3-H3]3+, since these protons are dia-
stereotopic on account of the fact that the plane of symme-
try in the plane of the −free× tris(crown ether) 1 is no longer
present in the mechanically interlocked bundle.Thus, all the
1H NMR spectroscopic evidence supports the mechanically
interlocked, triply threaded structure proposed in Scheme 1
for the tricationic bundle [3-H3]3+
.
Absorption, luminescence, and electrochemical properties
of the bundle: Absorption and luminescence data, obtained
in air-equilibrated MeCN at room temperature, for the me-
chanically interlocked bundle [3-H3]3+ and the tris(crown
ether) 1 are gathered together in Table 1, along with the
Figure 5.Absorption (full line) and luminescence (dashed line: lex
=
280 nm) spectra recorded at room temperature of [3-H3]3+ in an air-
equilibrated MeCN.
Table 1.Spectroscopic and electrochemical data obtained in MeCN at room
temperature
Absorption
Luminescence Electrochemistry
of 1 (lmax =383 nm) and from 1,3,5-triphenylbenzene unit of
[10-H3]3+ (lmax =359 nm) are no longer present in the me-
chanically interlocked bundle; however, the interlocked
bundle shows a weaker and broad luminescence band with
lmax =408 nm and t=4.6 ns. This new fluorescence band
most likely originates from a lower lying excited state that
arises from the p¥¥¥p stacking of the aromatic cores of the
two components.Interestingly, this band exhibits a structure
somewhat reminiscent of that observed for 1.The excitation
spectrum of [3-H3]3+, recorded at lem =408 nm, matches ex-
actly its absorption spectrum, showing that light irradiation
leads to the fluorescence excited state of the mechanically
interlocked bundle, irrespective of which component is ex-
cited.In summary, the photophysical properties of [ 3-H3]3+
are very similar to those[10b] of the triply threaded, two-com-
ponent superbundle [1ꢀ10-H3]3+, illustrated in Scheme 3.
lmax [nm] e [mÀ1 cmÀ1
]
lmax [nm] t [ns] Ep [V vs SCE][a]
1
276
260
100000
66000
383
9.6
17.0
11.6
4.6
+1.00, +1.23, +1.38
[10-H3]3+
359
[1ꢀ10-H3]3+ 267[b]
130000[b]
121000
410[b]
408
+1.08[c], +1.43[c]
+1.07, +1.43
[3-H3]3+
267
[a] Irreversible processes; potential values estimated from DPV peaks.[b] Ob-
tained on a 2î10À5 molLÀ1 1:1 mixture of 1 and [10-H3]3+ in which about 80%
of the components are associated to give the superbundle after subtraction of
the bands arising from the uncomplexed components.[c] Obtained on 5î
10À4 molLÀ1 1:1 mixture of 1 and [10-H3]3+ in which >95% of the components
are associated to give the superbundle.
data for the trisammonium ion [10-H3]3+, which can be re-
garded as a model for the dumbbell component of the
bundle, and its 1:1 adduct [1ꢀ10-H3]3+ with 1.The absorp-
tion and luminescence spectra of [3-H3]3+ are shown in
Figure 5.
The absorption spectrum of the mechanically interlocked
bundle does not differ significantly from that expected on
the basis of the spectra obtained for its components.The in-
tense luminescence bands arising from the triphenylene unit
In contrast to what happens with [1ꢀ10-H3]3+, deprotona-
+
À
À
tion of the three NH2
centers of the mechanically inter-
locked bundle cannot possibly lead to the disassembly of its
two components, since they are mechanically interlocked on
account of the bulky stoppers located at the three extremi-
ties of the trisammonium ion component.Therefore, this
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Chem. Eur. J. 2004, 10, 1926 1935

A Mechanically Interlocked Bundle
1926 1935
bundle offers the interesting possibility of disabling the tem-
plate employed for its preparation.It has been observed
three processes, it would be inappropriate to enter into any
further speculation.
[23]
that removal of the CuI template in transition-metal-assem-
bled catenates leads to a substantial rearrangement of the
mechanically interlocked structure for the derived catenane.
The triply threaded architecture of the [3-H3]3+ bundle, to-
gether with the size and shape of its two components, sug-
gests that disruption of the hydrogen-bonding interaction
between them should not lead to substantial structural rear-
rangements.
Deprotonation/reprotonation of the mechanically inter-
locked bundle: One of the reasons for assembling mechani-
cally interlocked molecular compounds like [3-H3]3+ is to
develop machines on the nanoscale level which can be pH-
driven.Since the bundle [ 3-H3]3+ can be looked upon as a
prototype of a new class of artificial molecular machines, we
were motivated to subject it to deprotonation and subse-
quent reprotonation, that is, to demonstrate a reversible
cycle.
Non-nucleophilic tertiary amines, such as nBu3N or
e,24]
iPr2NEt, have been employed[13c
routinely to deproton-
+
À
À
ate NH2
centers.Indeed, in MeCN, the trisammonium
Addition of slightly more than a threefold excess of
tBuOK to a CD2Cl2 solution of [3-H3][PF6]3 results in a dra-
ion [10-H3]3+ is fully deprotonated[10b] on addition of three
equivalents of nBu3N.Addition of nBu3N (up to a large
excess) to a solution of [3-H3]3+ in MeCN did not result in
any appreciable changes in the absorption and luminescence
spectra, suggesting that deprotonation does not take place.
The result could be related to the large stabilization of the
protonated form of the mechanically interlocked bundle as
a consequence of multiple hydrogen-bonding interactions.[25]
1
matic change in its H NMR spectrum (Figure 2b).The reso-
nances for the methylene protons Hd and He in [3-H3]3+ are
shifted upfield from d=4.72 and 4.91 ppm, respectively, to
d=4.12 ppm in 3, indicating complete deprotonation of all
+
À
À
three NH2
centers.The resonance for the central aro-
matic core protons (Ha) in the trisammonium ion compo-
nent is shifted upfield from d=7.60 ppm in [3-H3]3+ to d=
7.19 ppm in 3, implying either some conformational change
in the component itself or a relative movement with respect
to the hexaoxytriphenylene core of the trisammonium ion
Deprotonation, however, does take place in the case of the
[10b]
superbundle [1ꢀ10-H3]3+
.
The different behavior be-
tween the mechanically interlocked and supramolecular
bundles can be attributed[26] to entropic factors related to
the possibility for [1ꢀ10-H3]3+ to disassemble into its molec-
ular components–a possibility which is precluded to [3-
H3]3+.Such a disassembly process implies a substantial in-
crease in entropy, because 1) the number of species increas-
es and 2) the ™disassembled∫ molecular components are
characterized by much larger conformational freedom.
Upon addition of three equivalents of tBuOK–a very
much stronger proton acceptor compared to tertiary
amines–to [3-H3]3+, changes were observed in the absorp-
tion and emission spectra.In particular, the shape of the lu-
minescence band with lmax =408 nm is slightly modified and
its intensity diminishes to ca.40% of its initial value.Such a
quenching phenomenon could be supported by the appear-
ance of lower lying n p* excited states, arising from the
presence of amino groups.[27] It is important to note that
these spectroscopic changes are reversed after addition of
an acid in an amount equivalent to that of the previously
added base.
component.While the resonance for the nearby H protons
b
in the trisammonium ion component experiences an equally
dramatic shift from d=7.70 ppm in [3-H3]3+ to d=7.10 ppm
in 3, the adjacent Hc protons on the same phenylene rings
change very little chemical shiftwise.The same is true for
the protons Hf, Hg, and Hh in the trisammonium ion compo-
nent in the vicinity of the three triazole stoppers.In the
tris(crown ether), the O-methylene protons retain their dia-
stereotopicities, indicating that the two components are still
interacting intimately with each other.This conclusion is fur-
ther vindicated by the fact that the resonances for the aro-
matic protons Hi on the central hexaoxytriphenylene core of
the tris(crown ether) component undergo no change in their
chemical shifts whatsoever.We are drawn to the conclusion
that there is no substantial change in the relative geometries
of the two components in the bundle in going from the
tricationic to the neutral form.It is not unlikely that a com-
bination of strong N+ H¥¥¥O hydrogen bonds and weak
À
3+
À
C H¥¥¥O interactions in [3-H3] are replaced in 3 by weak
The electrochemical data for the bundle [3-H3]3+, tris-
(crown ether) 1, the trisammonium ion [10-H3]3+, and the
1:1 adduct [1ꢀ10-H3]3+ in MeCN (Scheme 3) are reported
in Table 1.In the potential window examined (from +2 to
À1.2 V vs SCE), [10-H3]3+ is not electroactive, and 1 and [3-
H3]3+ exhibit only oxidation processes.The tris(crown
ether) 1 shows three irreversible oxidation peaks at poten-
tials (obtained from DPV measurements) of +1.00, +1.23,
and +1.38 V. The bundle undergoes only two irreversible
oxidation processes at +1.07 and +1.43 V, a behavior quite
similar to that of [1ꢀ10-H3]3+.On the basis of the results
of a previous investigation,[10b] the first oxidation peak
(+ 1.07 V) can be assigned to the hexaoxytriphenylene core,
and the second one (+1.43 V) to oxidation of the three pe-
ripheral catechol units.Given the irreversible nature of the
N H¥¥¥O hydrogen bonds and even weaker C H¥¥¥O interac-
tions, with the p¥¥¥p stacking interactions remaining essen-
tially intact, albeit that the relative geometry between the
two aromatic cores has most likely altered somewhat.This
interpretation of the structural changes undergone in going
from [3-H3]3+ to 3 has some precedence[28] in a model [2]ro-
taxane, for which the X-ray crystal structures are available
(Figure 6) for both the charged and neutral forms.They
reveal that the macrorings encircle and interact with the het-
eroatomic centers in the dumbbell components, whether
they are charged or neutral.
À
À
1
Variable temperature H NMR spectra were recorded for
both [3-H3]3+ and 3 in CD2Cl2.In the case of the tricationic
bundle [3-H3]3+, as the solution was cooled down from 298
to 208 K, no significant changes in chemical shifts were ob-
served, indicating that the two components are tightly inter-
1931
Chem. Eur. J. 2004, 10, 1926 1935
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¹ 2004 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim

J.F.Stoddart, A.Credi, et al.
FULL PAPER
Figure 7.A series of 1H NMR spectra (500 MHz, CD2Cl2, 9. 8mm) of the
deprotonated mechanically interlocked bundle, namely 3, recorded at
various temperatures: a) 298 K, b) 278 K, c) 268 K, d) 248 K, e) 228 K,
f) 208 K.
Figure 6.Ball-and-stick representations of the solid-state structures of
A) a charged [2]rotaxane stabilized by two N+-H¥¥¥N hydrogen bonds
À
(a and b) and two C H¥¥¥p interactions (c and d), and B) a neutral [2]ro-
À
À
taxane stabilized by one N H¥¥¥O (a) and one N H¥¥¥N (b) hydrogen
+
bond and a p¥¥¥p stacking interaction (c).
À
À
Our observation that the three trigonally disposed NH2
centers, encircled by three trigonally oriented DB24C8
rings, can all be deprotonated and reprotonated lends au-
thority to our belief that artificial molecular machines,[12,13]
whereby chemical input induces mechanical output, can be
constructed with a view to making them run in a cyclical
manner.This goal is one which is now being pursued jointly
with some gusto in our two different laboratories.
locked with little freedom to undergo co-conformational
changes.By contrast, when a solution of 3 was cooled down,
there were notable changes in chemical shifts (Figure 7), in-
dicative of alterations in co-conformations within the neutral
bundle commensurate with its containing much weaker non-
covalent bonds between its two components.We have also
noted that the resonances for protons Hc, Hf, and Hg in 3 un-
dergo a pattern of chemical shifts changes that leave them,
at low temperatures, with d values reminiscent of those for
the same protons in [3-H3]3+.This phenomenon supports
the contention that deprotonation/reprotonation of [3-H3]3+/3
is associated by only relatively small differences in the over-
all structure of the mechanically interlocked bundle, wheth-
er it be tricationic or neutral.
Experimental Section
General: All chemicals were purchased from Aldrich and were used
without further purification.Column chromatography was performed on
silica gel 60 (Merck 40 60 nm, 230 400 mesh).Melting points were deter-
mined on an Electrothermal 9200 apparatus and reported uncorrected.
1H and 13C NMR spectra were recorded on Bruker Avance-500 at 500
and 125 MHz spectrometers, respectively.The chemical shift values are
expressed as d values and the coupling constants values (J) are in Hertz
(Hz).The following abbreviations were used for signal multiplicities: s,
singlet; d, doublet; t, triplet; and m, multiplet.Fast atom bombardment
mass spectrometry (FABMS) was performed on a VG ZAB-SE mass
spectrometer, equipped with a krypton primary atom beam and with a 3-
nitrobenzyl alcohol matrix.Both high-resolution matrix-assisted laser de-
sorption ionization spectra (HR-MALDI) and electron-spray mass spec-
tra (HR-ESI) were measured on an IonSpec Fourier transform mass
spectrometer.The experimental setup for the photophysical and electro-
chemical experiments was described in detail in ref.[10b].
Conclusion
The fact that we have been able to harness the cluster
effect, associated with paucivalency, to assemble a supra-
molecular bundle and then convert it into its triply locked
counterpart in a kinetically fast and efficient manner has
demonstrated that the realm of interlocked molecules can
be extended beyond merely simple catenanes and rotaxanes.
Compound 6:
A mixture of 4-(aminomethyl)benzylalcohol (3.2 g,
23.3 mmol) and 4[10b] (3.0 g, 7.7 mmol) was heated in PhMe (100 mL)
1932
¹ 2004 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
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Chem. Eur. J. 2004, 10, 1926 1935

A Mechanically Interlocked Bundle
1926 1935
under reflux overnight, while H2O was removed through a Dean Stark
trap.The reaction mixture was cooled down in a freezer to À108C and
the resulting suspension filtered to give the trisimine 5 as a white solid
(4.02 g, 74%). M.p. 166 1688C; 1H NMR (500 MHz, CD3SOCD3, 258C):
d=4.50 (d, J=4.5 Hz, 6H), 4.81 (s, 6H), 5.17 (br, 3H), 7.32 (m, 12H),
7.92 (d, J=8.0 Hz, 6H), 8.01 (m, 9H), 8.58 ppm (s, 3H); 13C NMR
(125 MHz, CDCl3, 258C): d=64.7, 65.0, 125.4, 127.1, 127.4, 128.1, 128.8,
135.4, 138.6, 139.6, 141.7, 143.0, 161.5 ppm; HRMS (MALDI): m/z calcd
for C51H46N3O3: 748.3534 [M+H]+ ; found: 748.3578.
6H), 7.60 (d, J=8 Hz, 6H), 7.91 (d, J=8 Hz, 6H), 7.97 ppm (s, 3H);
13C NMR (125 MHz, CDCl3, 258C): d=51.0, 51.1, 53.5, 125.2, 127.8,
128.8, 129.8, 130.1, 130.6, 130.7, 137.6, 141.3, 141.5 ppm; HRMS(MAL-
+
DI): m/z calcd for C51H49N12
829.4231.
:
829.4198 [MÀ2HPF6ÀPF6]+
; found:
Salt [3-H3][PF6]3: The trisammonium salt [2-H3][PF]6 (0.06 g,
0.005 mmol) and the tris(crown ether) 1 (0.06 g, 0.005 mmol) were dis-
solved in CH2Cl2/MeCN (2.5 mL, 3:2). Di-tert-butylacetylenedicarboxy-
late (0.27 g, 1.194 mmol) was then added to the reaction mixture, which
was subsequently heated at 408C under an argon atmosphere for 24 h.
The solution was cooled down to room temperature, evaporated in
vacuo, and the residue purified by column chromatography (SiO2:
CHCl3/MeCN, 8:2) to yield [3-H3][PF6]3 (0.06 g, 40%) as a white solid.
M.p. 1898C; 1H NMR (500 MHz, CD3CN, 258C): d=1.43 (s, 27H), 1.53
(s, 27H), 3.60 4.20 (m, 60H), 4.22 4.30 (m, 6H), 4.50 4.54 (m, 6H),
4.79 4.82 (m, 6H), 4.86 4.90 (m, 6H), 5.72 (s, 6H), 6.84 6.92 (m, 12H),
7.23 (d, J=8 Hz, 6H), 7.35 (s, 6H), 7.42 (s, 3H), 7.54 (br, 6H), 7.56 7.62
(m, 18H); 13C NMR (125 MHz, CD3CN, 258C): d=26.9, 27.2, 51.1, 52.1,
52.8, 67.3, 67.4, 70.4, 70.5, 71.8, 82.7, 85.0, 104.5, 112.2, 121.0, 122.7, 125.7,
127.9, 129.2, 129.6, 129.9, 130.4, 131.0, 132.9, 135.9, 137.2, 138.1, 141.0,
146.2, 147.6, 157.2, 159.4 ppm; HRMS(ESI): m/z calcd for
C159H195O36N12F6P: 1496.6714 [MÀ2PF6]2+ ; found: 1496.6814.
NaBH4 (1.02 g, 26.8 mmol) was added portionwise to a solution of 5
(white solid) in dry MeOH (100 mL) and dry THF (100 mL).After the
reaction had been left to stir overnight the solvent was removed in
vacuo.The resulting solid was partitioned between THF (150 mL) and
brine (100 mL).The aqueous phase was washed with THF (100 mL).The
organic phases were combined and dried (MgSO4), and the solvent was
removed in vacuo to give 6 as a yellow liquid (3.6 g, 90%). 1H NMR
(500 MHz, CDCl3, 258C): d=3.74 (s, 6H), 3.77 (s, 6H), 4.50 (s, 6H), 7.22
(d, J=8 Hz, 6H), 7.43 (d, J=8 Hz, 6H), 7.67 (d, J=8 Hz, 6H), 7.80 ppm
(s, 3H); 13C NMR (125 MHz, CDCl3, 258C): d=50.7, 50.9, 61.9, 123.3,
124.2, 124.9, 125.7, 126.5, 129.1, 137.6, 138.6, 139.4, 140.2 ppm;
HRMS(MALDI): m/z calcd for C51H52N3O3: 754.4003 [M+H]+ ; found:
754.3147.
Compound 7: The trisamine 6 (2.7 g, 3.6 mmol) was dissolved in CHCl3
(450 mL) and then di-tert-butyl dicarbonate (7.9 g, 36.1 mmol) was
added.The reaction mixture was left to stir for 24 h, before being washed
with 2m HCl aqueous solution (2î200 mL) and H2O (200 mL).The or-
ganic phase was dried (MgSO4) and evaporated under reduced pressure
to yield the crude product, which was subsequently purified by column
chromatography (SiO2: CH2Cl2/MeOH, 95:5) to yield 7 (2.3 g, 60%).
Acknowledgement
This work was supported by the National Science Foundation under
CHE-9910199 and CHE-9974928 research grants and under CHE-
9974928 and CHE-0092036 equipment grants in the United States, and
MIUR (Supramolecular Devices Project), FIRB (Manipolazione moleco-
lare per macchine nanometriche) and the University of Bologna (Funds
for selected research topics) in Italy.Support from the European Union
through the Molecular-level devices and machines Network (HPRN-CT-
2000 00029) is also acknowledged.
1
M.p. 68 708C; H NMR (500 MHz, CDCl3, 258C): d=1.52 (s, 27H), 4.45
(br, 12H), 4.71 (s, 6H), 7.20 7.34 (m, 6H), 7.35 (d, J=8 Hz, 6H), 7.66 (d,
J=8 Hz, 6H), 7.77 ppm (s, 3H); 13C NMR (125 MHz, CDCl3, 258C): d=
28.4, 48.7, 48.9, 65.0, 80.2, 124.8, 127.2, 127.4, 127.6, 127.9, 128.2, 128.4,
137.2, 139.9, 141.9, 155.9 ppm; HRMS(MALDI): m/z calcd for
C66H75N3O9Na+ : 1076.5401 [M+Na]+ ; found: 1076.5425.
Compound 8: Triphenylphosphine (4.1 g, 15.8 mmol) in THF (100 mL)
was added to N-chlorosuccinimide (2.4 g, 18.1 mmol) in THF (100 mL)
under an argon atmosphere, to form a white suspension.The triol
7
[1] For some recent examples, see: a) C.-Y. Su, Y.-P. Cai, C.-L. Chen, F.
Lissner, B.-S. Kang, W. Kaim, Angew. Chem. 2002, 114, 3519 3523;
Angew. Chem. Int. Ed. 2002, 41, 3371 3375; b) O.Hayashida, A.
(2.0 g, 1.9 mmol), dissolved in THF (40 mL), was then slowly added and
the reaction mixture was left to stir overnight.The solvent was evaporat-
ed and the product purified by column chromatography (SiO2: hexanes/
EtOAc, 7:3).The product 8 was obtained as an off-white solid (2.0 g,
Shivanyuk, J.Rebek, Jr,.
Angew. Chem. Int. Ed. 2002, 41, 2423 2426; c) P.A.Gale, K.Nava-
khun, S.Camiolo, M.E.Light, M.B.Hursthouse, J. Am. Chem. Soc.
Angew. Chem. 2002, 114, 3573 3576;
95%).Mp..62 64
8C; 1H NMR (500 MHz, CDCl3, 258C): d=1.57 (s,
27H), 4.45 (s, 6H), 4.52 (s, 6H), 4.65 (s, 6H), 7.22 7.40 (m, 12H), 7.42
(d, J=8 Hz, 6H), 7.71 (d, J=8 Hz, 6H), 7.82 ppm (s, 3H); 13C NMR
(125 MHz, CDCl3, 258C): d=28.5, 46.0, 48.9, 49.2, 80.3, 125.0, 127.5,
127.8, 128.5, 128.9, 136.6, 137.4, 138.4, 140.1, 142.0, 156.0 ppm;
2002, 124, 1128 1129; d) M.Kercher, B.Kˆnig, H.Zieg, L.
De Cola, J. Am. Chem. Soc. 2002, 124, 11541 11551; e) A.Marquis,
J-.P.Kintzinger, R.Graff, P.N.N.Baxter, J-.M.Lehn,
Angew. Chem.
HRMS(MALDI): m/z calcd for C66H72N3O6Cl3Na+ : 1130.4384 [M+Na]+
;
2002, 114, 2884 2888; Angew. Chem. Int. Ed. 2002, 41, 2760 2764;
f) V.Paraschiv, M.Crego-Calama, T.Ishii, C.J.Padberg, P.Timmer-
man, D.N. Reinhoudt, J. Am. Chem. Soc. 2002, 124, 7638 7639;
g) M.Aoyagi, S.Tashiro, M.Toominaga, K.Biradha, M.Fujita,
Chem. Commun. 2002, 2036 2037; h) C.A. Schalley, T. Muller, P.
found: 1130.4398.
Compound 9: Sodium azide (1.1 g, 18.1 mmol) was added to the trischlor-
ide 8 (1.0 g, 0.9 mmol) in 2-butanone (80 mL), followed by a few crystals
of [18]crown-6, and the suspension was heated under reflux for 18 h.
Evaporation of the solvent, followed by filtration through a thin silica
pad (SiO2, hexanes/EtOAc, 7:3) yielded 9 (0.93 g, 91%) as a white solid.
Linnartz, M.Witt, M.Sch‰fer, A.L¸tzen,
Chem. Eur. J. 2002, 8,
3538 3551; i) G.R.Newkome, T.J.Cho, C.N.Moorefield, R.Cush,
PS. .Russo, L.A.GordÌnez, M.J.Saunders, P.Mohaparta,
Chem.
1
M.p. 50 528C; H NMR (500 MHz, CDCl3, 258C): d=1.57 (s, 27H), 4.39
Eur. J. 2002, 8, 2946 2954; j) V.Percec, T.K.Bera, M.Glodde, Q.
(s, 6H), 4.46 (s, 6H), 4.55 (s, 6H), 7.34 (m, 18H), 7.12 (d, J=8 Hz , 6H),
7.83 ppm (s, 3H); 13C NMR (125 MHz, CDCl3, 258C): d=28.4, 48.9, 49.2,
54.4, 80.2, 124.9, 127.4, 127.8, 127.8, 128.4, 134.3, 137.3, 138.2, 140.0,
Fu, V.S.K.Balagurusamy, P.A.Heiney,
935; k) E.Mertz, S.C.Zimmerman,
Chem. Eur. J. 2003, 9, 921
J. Am. Chem. Soc. 2003, 125,
3424 3425; j) T.Ishi-i, M.A.Mateos-Timoneda, P.Timmerman, M.
Crego-Calama, DN. .Reinhoudt, S.Shinkai, Angew. Chem. 2003,
115, 2402 2407; Angew. Chem. Int. Ed. 2003, 42, 2300 2305; k) A.
Wu, L.Isaacs, J. Am. Chem. Soc. 2003, 125, 4831 4835; l) W.S.
142.0, 155.9 ppm; HRMS(MALDI) m/z calcd for C66H72N12O6Na+
1151.5595 [M+Na]+ ; found: 1151.5684.
:
Salt [2-H3][PF6]3: Trifluoroacetic acid (ca.20 mL) was added to the tBoc-
protected trisamine 9 (0.9 g, 0.8 mmol) in CHCl3 (120 mL), and the reac-
tion mixture was stirred at room temperature for 16 h.The solvent was
evaporated, and the residue dissolved in MeOH (15 mL).A saturated
solution of NH4PF6 in H2O was added dropwise, followed by H2O
Horne, D.C. Stout, M.R. Ghadiri,
J. Am. Chem. Soc. 2003, 125,
9372 9376; m) P.Zhu, H.Kang, A.Facchetti, G.Evmenenko, P.
Dutta, T.J.Marks, J. Am. Chem. Soc. 2003, 125, 11496 11497.
[2] a) M.Simard, S.Du, JD. .Wuest,
J. Am. Chem. Soc. 1991, 113,
J. Am. Chem. Soc.
(50 mL).The aqueous phase was extracted with CH Cl2/MeNO2 (100 mL,
4696 4698; b) X.Wang, M.Simard, J.D.Wuest,
2
5:2), and the organic phase washed with water (3î100 mL), dried
1994, 116, 12119 12120; c) P.Brunet, M.Simard, JD. .Wuest,
Am. Chem. Soc. 1997, 119, 2737 2738; d) J-H.Fournier, T.Maris,
J.
(Na2SO4), and evaporated to yield [2-H3][PF6]3 (0.75 g, 74%) as a yellow
solid.Mp..156 158
6H), 4.33 (s, 6H), 4.46 (s, 6H), 7.46 (d, J=8 Hz, 6H), 7.53 (d, J=8 Hz,
8C; 1H NMR (500 MHz, CD3CN, 258C): d=4.31 (s,
J.D.Wuest, W.Guo, E.Galoppini,
1002 1006.
J. Am. Chem. Soc. 2003, 125,
1933
Chem. Eur. J. 2004, 10, 1926 1935
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¹ 2004 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim

J.F.Stoddart, A.Credi, et al.
FULL PAPER
[3] a) AG. .Kolchinski, DH. .Busch, NW. .Alcock,
J. Chem. Soc.
Lowe, D.A.Fulton, S-.H.Chiu, A.M.Elizarov, S.J.Cantrill, S.J.
Chem. Commun. 1995, 1289 1291; b) P.R. Ashton, P.J. Campbell,
Rowan, J.F. Stoddart, J. Org. Chem. 2004, 69, in press; p) J.D.
¬
E.J.T.Chrystal, P.T.Glink, S.Menzer, D.Philp, N.Spencer, J.F.
Badjic, S.J.Cantrill, J.F.Stoddart,
J. Am. Chem. Soc. 2004, 126, in
Stoddart, P.A. Tasker, D.J. Williams,
Angew. Chem. 1995, 107,
press.
1997 2001; Angew. Chem. Int. Ed. Engl. 1995, 34, 1865 1869;
[9] a) P.R.Ashton, I.Baxter, S.J.Cantrill, M.C.T.Fyfe, P.T.Glink,
c) P.R.Ashton, E.J.T.Chrystal, P.T.Glink, S.Menzer, C.Schiavo,
J.F.Stoddart, A.J.P.White, D.J.Williams,
Angew. Chem. 1998, 110,
J.F.Stoddart, P.A.Tasker, D.J.Williams,
Angew. Chem. 1995, 107,
1344 1347; Angew. Chem. Int. Ed. 1998, 37, 4295 4307; b) S.J.Can-
2001 2004; Angew. Chem. Int. Ed. Engl. 1995, 34, 1869 1871;
d) P.R.Ashton, E.J.T.Chrystal, P.T.Glink, S.Menzer, C.Schiavo,
N.Spencer, J.F.Stoddart, P.A.Tasker, A.J.P.White, D.J.Williams,
Chem. Eur. J. 1996, 2, 709 728.
trill, G.J.Youn, J.F.Stoddart, D.J.Williams,
6857 6872; S-H. .Chiu, SJ..Rowan, SJ..Cantrill, JF. .Stoddart,
A.J.P.White, D.J.Williams, Chem. Commun. 2002, 2948 2949.
[10] a) M.C.T.Fyfe, J.N.Lowe, J.F.Stoddart, D.J.Williams, Org. Lett.
2000, 2, 1221 1224; b) V.Balzani, M.Clemente-Leon, A.Credi,
J. Org. Chem. 2001, 66,
[4] Pseudorotaxanes are complexes (supermolecules) that resemble ro-
taxanes by virtue of being comprised of wheel- and axlelike compo-
nents, but their components are free to dissociate from each other.
¬
J.N.Lowe, J.D.Badjic , J.F.Stoddart, D.J.Williams,
Chem. Eur. J.
2003, 9, 5348 5360.
See: P.R.Ashton, D.Philp, N.Spencer, J.F.Stoddart,
Chem. Commun. 1991, 1677 1679.
[5] F.M. Raymo, M.D. Bartberger, K.N. Houk, J.F. Stoddart,
Chem. Soc., 2001, 123, 9246 9267.
J. Chem. Soc.
[11] It has been noted that another trivalent system, namely tris(vanco-
mycin carboxamide) binds a trivalent ligand derived from d-Ala-d-
Ala with much higher affinity than avidin binds biotin.See: J.Rao,
J. Am.
J.Lahiri, L.Isaacs, R.M.Weis, G.M.Whitesides,
Science 1998, 280,
[6] a) PT..Glink, C.Schiavo, JF..Stoddart, DJ..Williams,
Commun. 1996, 1483 1490; b) M.C.T.Fyfe, J.F.Stoddart,
Chem.
Adv. Su-
708 711.In the abstract to this article the authors state ™High affin-
ity trivalent binding and monovalent binding are fundamentally dif-
ferent.In trivalent (and more generally, polyvalent) binding, dissoci-
ation occurs in stages, and its rate can be accelerated by monovalent
ligands at sufficiently high concentrations.In monovalent binding,
dissociation is determined solely by the rate constant for dissocia-
tion and cannot be accelerated by added monomer.∫
pramol. Chem. 1999, 5, 1 53; c) T.J.Hubin, A.G.Kolchinski, A.L.
Vance, D.H.Busch, Adv. Supramol. Chem. 1999, 5, 237 357; d) T.J.
Hubin, D.H. Busch, Coord. Chem. Rev. 2000, 200 202,
5 52;
e) M.C.T.Fyfe, J.F.Stoddart, D.J.Williams, Struct. Chem. 1999, 10,
243 259; f) S.J. Cantrill, A.R. Pease, J.F. Stoddart,
J. Chem. Soc.
Dalton Trans. 2000, 3715 3734.
[12] a) V.Balzani, A.Credi, F.M.Raymo, J.F.Stoddart,
2000, 112, 3484 3530; Angew. Chem. Int. Ed. 2000, 39, 3348 3391;
b) V.Balzani, A.Credi, M.Venturi, Molecular Devices andMa-
Angew. Chem.
[7] a) P.R.Ashton, A.N.Collins, M.C.T.Fyfe, P.T.Glink, S.Menzer,
J.F. Stoddart, D.J. Williams, Angew. Chem. 1997, 109, 1991 1994;
Angew. Chem. Int. Ed. Engl. 1997, 36, 59 62; b) P.R.Ashton, A.N.
Collins, MC.T. .Fyfe, S.Menzer, JF..Stoddart, DJ..Williams,
chines–A Journey into the Nano World, Wiley-VCH, Weinheim,
2003.
Angew. Chem. 1997, 109, 760 763; Angew. Chem. Int. Ed. Engl.
1997, 36, 735 739; c) M.C.Feiters, M.C.T.Fyfe, M-.V.MartÌnez-
DÌaz, S.Menzer, R.J.M.Nolte, J.F.Stoddart, P.J.M.van Kan, D.J.
Williams, J. Am. Chem. Soc. 1997, 119, 8119 8120; d) P.R.Ashton,
M.C.T.Fyfe, P.T.Glink, S.Menzer, J.F.Stoddart, A.J.P.White,
[13] For an example of working supramolecular machines in the form of
[2]pseudorotaxanes trapped in glass and mounted on the surface of
silica films, see: a) S.Chia, J.Cao, J.F.Stoddart, J.I.Zink,
Angew.
Chem. 2001, 113, 2513 2517; Angew. Chem. Int. Ed. 2001, 40,
2447 2451; for a recent example where a [2]pseudorotaxane, as a
self-assembled monolayer on gold, has been shown to undergo re-
versible dethreading and rethreading of its ring, and to exhibit ion
gating behavior, see: b) K. Kim, W.S. Jeon, J-.K. Kang, J.W. Lee,
D.J. Williams, J. Am. Chem. Soc. 1997, 119, 12514 12524; e) P.R.
Ashton, M.C.T. Fyfe, S.K. Hickingbottom, S. Menzer, J.F. Stod-
dart, A.J.P. White, D.J. Williams,
Chem. Eur. J. 1998, 4, 577 589;
f) P.R. Ashton, M.C.T. Fyfe, M.-V. MartÌnez-DÌaz, S. Menzer, C.
SY. .Jon, T.Kim, K.Kim,
Angew. Chem. 2003, 115, 2395 2398;
Schiavo, J.F. Stoddart, A.J.P. White, D.J. Williams,
1998, 4, 1523 1534; g) M.C.T. Fyfe, J.F. Stoddart,
Chem. Eur. J.
Coord. Chem.
Angew. Chem. Int. Ed. 2003, 42, 2293 2296; for examples of acid
base switchable [2]rotaxanes which have been demonstrated to
switch in solution, see: c) MV. .MartÌnez-DÌaz, N.Spencer, JF. .
Stoddart, Angew. Chem. 1997, 109, 1991 1994; Angew. Chem. Int.
Ed. Engl. 1997, 36, 1904 1907; d) P.R. Ashton, R. Ballardini, V.
Balzani, I. Baxter, A. Credi, M.C.T. Fyfe, M.T. Gandolfi, M.
GÛmez-LÛpez, M.V. MartÌnez-DÌaz, A. Piersanti, N. Spencer, J.F.
Rev. 1999, 183, 139 155; h) J-.C Meillon, N.Voyer, E.Biron, F.San-
schagrin, J.F. Stoddart, Angew. Chem. 2000, 112, 147 149; Angew.
Chem. Int. Ed. 2000, 39, 143 145; i) M.V.MartÌnez-DÌaz, M.S.Ro-
driguez-Morgade, M.C.Feiters, P.J.M.van Kan, R.J.M.Nolte, J.F.
Stoddart, T.Torres, Org. Lett. 2000, 2, 1057 1060; j) T.Chang,
A.M. Heiss, S.J. Cantrill, M.C.T. Fyfe, A.R. Pease, S.J. Rowan,
J.F.Stoddart, D.J.Williams, Org. Lett. 2000, 2, 2943 2946; k) S.-H.
Chiu, A.R. Pease, J.F. Stoddart, A.J.P. White, D.J. Williams,
Angew. Chem. 2002, 114, 280 284; Angew. Chem. Int. Ed. 2002, 41,
270 274.
Stoddart, M.Venturi, A.J.P.White, D.J.Williams,
J. Am. Chem.
Soc. 1998, 120, 11932 11942; e) A.M. Elizarov, S-.H. Chiu, J.F.
Stoddart, J. Org. Chem. 2002, 67, 9175 9181.
[14] Supramolecular Polymers (Ed.: A. Ciferri), Marcel Deker, New
York, 2000.
[8] a) M.Mammen, S-.K.Choi, G.M.Whitesides,
Angew. Chem. 1998,
[15] a) D.H. Busch, N.A. Stephensen,
Coord. Chem. Rev. 1990, 100,
Acc.
110, 2908 2953; Angew. Chem. Int. Ed. 1998, 37, 2754 2794;
b) R.T. Lee, Y.C. Lee, Glyconjugate J. 2000, 17, 543 551; c) P.I.
Kitov, J.M.Sadawska, G.Mulvey, G.D.Armstrong, H.Ling, N.S.
Pannu, R.J.Read, D.R.Bundle, Nature 2000, 403, 669 672; d) M.
Mourez, R.S.Kane, J.Mogridge, S.Metallo, P.Deschatelets, B.R.
Sellman, G.M.Whitesides, R.J.Collier, Nature Biotechnology 2001,
19, 958 961; e) C.W. Cairo, J.E. Gestwicki, M. Kanai, L.L. Kies-
sling, J. Am. Chem. Soc. 2002, 124, 1615 1619; f) J.E. Gestwicki,
119 154; b) S.Anderson, HL. .Anderson, JK. M. .Sanders,
Chem. Res. 1993, 26, 469 475; c) R.Cacciapaglia, L.Mandolini,
Chem. Soc. Rev. 1993, 22, 221 231; d) R.Hoss, F.Vˆgtle, Angew.
Chem. 1994, 106, 389 398; Angew. Chem. Int. Ed. Engl. 1994, 33,
375 384; e) TemplatedOrganic Synthesis (Eds.: F. Diederich, P. J.
Stang), Wiley-VCH, Weinheim, 2000; f) J.F.Stoddart, H-.R.Tseng,
Proc. Natl. Acad. Sci. USA 2002, 99, 4797 4800.
[16] a) R.F.Service, Science 2001, 291, 426 427; b) R.F.Service, Science
2001, 294, 2442 2443; c) A.R.Pease, J.O.Jeppesen, J.F.Stoddart,
C.W. Cairo, L.E. Strong, K.A. Oetjen, L.L. Kiessling,
J. Am.
Chem. Soc. 2002, 124, 14922 14933; g) J.J.Lundquist, E.J.Toone,
Chem. Rev. 2002, 102, 555 578; h) T.Christensen, D.M.Gooden,
J.E. Kung, E.J. Toone, J. Am. Chem. Soc. 2003, 125, 7357 7366;
i) E.Arranz-Plaza, AS. .Tracy, A.Siriwardena, JM. .Pierce, G-.J.
Boons, J. Am. Chem. Soc. 2002, 124, 13035 13046; j) E.K.Woller,
Y.Luo, C.P.Collier, J.R.Heath,
Acc. Chem. Res. 2001, 34, 433
434; d) A.R. Pease, J.F. Stoddart, Struct. Bonding 2001, 99, 189
236; e) J.R.Heath, M.A.Ratner, Phys. Today 2003, 56, 43 49.
[17] a) CP..Collier, EW. .Wong, M.Belohradsky, FM. .Raymo, JF. .
Stoddart, P.J.Kuekes, R.S.Williams, J.R.Heath,
391 394; b) E.W. Wong, C.P. Collier, M. Belohradsky, F.M.
Raymo, J.F. Stoddart, J.R. Heath, J. Am. Chem. Soc. 2000, 122,
5831 5840; c) C.P.Collier, G.Mattersteig, E.W.Wong, Y.Luo, K.
Beverly, J.Sampaio, F.M.Raymo, J.F.Stoddart, J.F.Heath,
2000, 289, 1172 1175; d) C.P. Collier, J.O. Jeppensen, Y. Luo, J.
Science 1999, 285,
ED. .Walter, JR. .Morgan, DJ..Singel, MJ..Cloninger,
J. Am.
Chem. Soc. 2003, 125, 8820 8826; k) S.L. Tobey, E.V. Anslyn, J.
Am. Chem. Soc. 2003, 125, 10963 10970; l) P.I. Kitov, D.R.
Bundle, J. Am. Chem. Soc. 2003, 125, 16271 16284; m) G.Ercolani,
J. Am. Chem. Soc. 2003, 125, 16097 16103; n) D.A. Fulton, S.J.
Cantrill, J.F. Stoddart, J. Org. Chem. 2002, 67, 7968 7981; o) J.N.
Science
Perkins, E.W.Wong, J.R.Heath, J.F.Stoddart,
J. Am. Chem. Soc.
1934
¹ 2004 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 1926 1935

A Mechanically Interlocked Bundle
1926 1935
2001, 123, 12632 12641; e) Y.Luo, CP. .Collier, JO. .Jeppesen,
K.A.Nielsen, E.DeIonno, G.Ho, J.Perkins, H-.R.Tseng, T.Yama-
moto, J.F.Stoddart, J.R.Heath, ChemPhysChem 2002, 3, 519 525;
f) M.R. Diehl, D.W. Steuerman, H-.R. Tseng, S.A. Vignon, A.
that one major product is formed with complete conversion of the
starting material.
[23] a) C.O.Dietrich-Buchecker, J-.P.Sauvage, J.M.Kern,
J. Am. Chem.
Soc. 1984, 106, 3043 3045; b) D.B. Amabilino, C.O. Dietrich-Bu-
checker, A.Livoreil, L.Perÿz-GarcÌa, J-.P.Sauvage, J.F.Stoddart,
Am. Chem. Soc. 1996, 118, 3905 3913; c) D.J.Cardenas, A. Livor-
J.
Star, PC. .Celestre, JF..Stoddart, JR. .Heath,
ChemPhysChem
2003, 4, 1335 1339; g) H.Yu, Y.Luo, K.Beverly, H-.R.Tseng, J.F.
Stoddart, J.R.Heath, Angew. Chem. 2003, 115, 5884 5889; Angew.
Chem. Int. Ed. 2003, 42, 5706 5711; h) H.-R. Tseng, D. Wu, N. X.
Fang, X.Zhang, J.F.Stoddart, ChemPhysChem 2004, 5, 111 116.
[18] We have introduced and used the term co-conformation to designate
the three-dimensional spatial arrangements of 1) the constituent
parts of supramolecular systems and 2) the components of inter-
eil, J.-P. Sauvage, J. Am. Chem. Soc. 1996, 118, 11980 11981; d) L.
Raehm, J.-M. Kern, J.-P. Sauvage, Chem. Eur. J. 1999, 5, 3310 3317;
e) CO. .Dietrich-Buchecker, B.Colasson, M.Fujita, A.Hori, N.
Geum, S.Sakamoto, K.Yamaguchi, J-.P.Sauvage, J. Am. Chem. Soc.
2003, 125, 5717 5725.
[24] M.Montalti, R.Ballardini, L.Prodi, V.Balzani,
Chem. Commun.
1996, 2011 2012; b) PR. .Ashton, R.Ballardini, V.Balzani, M.
GÛmez-LÛpez, S.E. Lawrence, M.-V. MartÌnez-DÌaz, M. Montalti,
locked molecular systems.See: MC. T. .Fyfe, JF. .Stoddart,
Acc.
Chem. Res. 1997, 30, 393 401.
A. Piersanti, J.F. Stoddart, D.J. Williams,
J. Am. Chem. Soc. 1997,
[19] G.A.Julia, M.A.Garcia, A.J.Benesi, T.E.Mallouk,
J. Org. Chem.
119, 10641 10651; c) PR. .Ashton, R.Ballardini, V.Balzani,
M.C.T.Fyfe, M.T.Gandolfi, M-.V.MartÌnez-DÌaz, M.Morosini, C.
Schiavo, K.Shibata, JF. .Stoddart, AJ.P. .White, DJ..Williams,
Chem. Eur. J. 1998, 4, 2332 2341; E.Ishow, A.Credi, V.Balzani,
H.D.A. Hoffman, M-.V. MartÌnez-DÌaz, F.M. Raymo, J.F. Stod-
dart, M.Venturi, Chem. Eur. J. 2001, 7, 3482 3493.
1998, 63, 7663 7669.
[20] [1,3]-Dipolar cycloadditions have already been used successfully in
the template-directed synthesis of [2]-rotaxanes, using a threading-
followed-by-stoppering approach. See: a) P.R. Ashton, P.T. Glink,
J.F.Stoddart, P.A.Tasker, A.J.P.White, D.J.Williams,
Chem. Eur.
J. 1996, 2, 729 736; b) J.Cao, M.C.T.Fyfe, J.F.Stoddart, G.R.L.
Cousins, P.T.Glink, J. Org. Chem. 2000, 65, 1937 1946.[1,3]-Dipo-
lar cycloadditions are among a group of highly efficient reactions
which have earned them the status of so-called ™click chemistry∫ re-
[25] The stability constant for the formation of the [2]pseudorotaxane
[1ꢀ10-H3]3+ in MeCN at 298 K is about 1î106 mÀ1, corresponding to
a DG8 value of 8.3 kcalmolÀ1.See references [10] and [11].
[26] H.-J. Schneider, A. Yatsimirsky, Principles andMethods in Supra-
molecular Chemistry, Wiley, Chichester, 2000.
actions.See: H.C.Kolb, M.G.Finn, K.B.Sharpless,
Angew. Chem.
2001, 113, 2056 2075; Angew. Chem. Int. Ed. 2001, 40, 2004 2021.
[27] R.A. Bissell, A.P. de Silva, H.Q.N. Gunaratne, P.L.M. Lynch,
[21] S.T.Abu-Orabi, M.A.Atfah, I.Jibril, F.M.Mari×i, A.A.S.Ali,
J.
G.E.M.Maguire, C.P.McCoy, K.R.A.S.Sandanayaka,
Chem. 1993, 168, 223 264.
Top. Curr.
Heterocycl. Chem. 1989, 26, 1461 1468.
[22] We consider this yield of 40% to be a lot lower than it might have
been because of the loss of a substantial amount of the product on
the silica gel chromatography column used to isolate it.When the
[28] P.T.Glink, A.J.Oliva, J.F.Stoddart, A.J.P.White, D.J.Williams,
Angew. Chem. 2001, 113, 1922 1927; Angew. Chem. Int. Ed. 2001,
40, 1870 1875.
1
reaction is followed by H NMR spectroscopy, all the indications are
Received: November 5, 2003 [F5687]
1935
Chem. Eur. J. 2004, 10, 1926 1935
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim