The effect of incorporating fre dendrons into rotaxanes and molecular shuttles contaning the 1,2-bis(pyridinium)ethane?[24]crown-8 templating motif

Article abstract of DOI:10.1002/chem.200903174

Frechet-type dendrons (G0G3) were added as both axle stoppering units and cyclic wheel appendages in a series of [2]rotaxanes, [3]rotaxanes, and molecular shuttles that employ 1,2bis(pyridinium)ethane axles and 24membered crown ethers wheels. The addition of dendrimer wedges as stoppering units dramatically increased the solubility of simple [2]rotaxanes in nonpolar solvents. The X-ray structure of a G1-stoppered [2]rotaxane shows how the dendritic units affect the structure of the interlocked components. Increased solubility allows observation of how the interaction of dendritic units on separate components in interlocked molecules influences switching properties and molecular size. In a series of [2]rotaxane molecular shuttles incorporating two recognition sites, it was demonstrated that an increase in generation on either the stoppering unit or cyclic wheel could influence both the rate of shuttling and the site preference of the wheel on the axle.

Full text of DOI:10.1002/chem.200903174

DOI: 10.1002/chem.200903174
The Effect of Incorporating Frꢀchet Dendrons into Rotaxanes and
Molecular Shuttles Containing the 1,2-Bis(pyridinium)ethaneꢀ[24]Crown-8
Templating Motif
David A. Tramontozzi, Natalie D. Suhan, S. Holger Eichhorn, and Stephen J. Loeb*[a]
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Chem. Eur. J. 2010, 16, 4466 – 4476

FULL PAPER
Abstract: Frꢁchet-type dendrons (G0–
G3) were added as both axle stopper-
ing units and cyclic wheel appendages
in a series of [2]rotaxanes, [3]rotaxanes,
and molecular shuttles that employ 1,2-
bis(pyridinium)ethane axles and 24-
membered crown ethers wheels. The
addition of dendrimer wedges as stop-
pering units dramatically increased the
solubility of simple [2]rotaxanes in
nonpolar solvents. The X-ray structure
of a G1-stoppered [2]rotaxane shows
how the dendritic units affect the struc-
ture of the interlocked components. In-
creased solubility allows observation of
how the interaction of dendritic units
on separate components in interlocked
molecules influences switching proper-
ties and molecular size. In a series of
[2]rotaxane molecular shuttles incorpo-
rating two recognition sites, it was
demonstrated that an increase in gener-
ation on either the stoppering unit or
cyclic wheel could influence both the
rate of shuttling and the site preference
of the wheel on the axle.
Keywords: dendrimers · molecular
machines
rotaxanes
· molecular shuttles ·
Introduction
A fundamental understanding of the dynamic nature of me-
chanically interlocked molecules has led to the design and
construction of a number of chemical systems that display
basic machine-like properties at the molecular level.[1] To
transform interlocked molecules such as [2]rotaxanes or
[2]catenanes into molecular machines, these systems must
be capable of accessing two or more distinct molecular ar-
rangements (coconformations) and undergoing a simple pro-
cess that allows switching between the two states.[2] Al-
though there are a number of well-defined and understood
examples that operate in solution,[1] the incorporation of
molecular machinery into modern materials requires com-
bining the properties of these two relatively disparate chem-
ical worlds and understanding this interface.[3] Strategies
that lead to the fabrication of solid-state nanoscale devices
from interlocked molecules have been investigated,[1a] but
there still remains a great deal to learn before we can pro-
duce functional materials driven by molecular machinery.[4]
As a first step towards incorporating interlocked mole-
cules based on the 1,2-bis(pyridinium)ethaneꢀ[24]crown-8
template[5] (Scheme 1) into materials, we have focused on
elaborating this small-molecule chemistry for the generation
of liquid crystalline and polymeric materials. Herein, we
report the results of incorporating Frꢁchet-type dendrons[6]
into [2]rotaxanes and [2]rotaxane molecular shuttles. In par-
ticular, the attachment of dendritic units to both the linear
and cyclic components of a molecular shuttle results in a
large difference in size between the two coconformations.
The effect of these changes on molecular shuttling and co-
conformational distribution is described.[7]
Scheme 1. A linear 1,2-bis(4,4’-bipyridinium)ethane dication and a diben-
zo[24]crown-8 (DB24C8) macrocycle act as axle and wheel to form the
interpenetrated [2]pseudorotaxane, 12+ (top). This can be converted into
a fully interlocked [2]rotaxane, 24+, by alkylation with bulky capping
groups, such as tBu-benzyl (bottom). Anions are not shown but are PF6
throughout unless otherwise noted.
Results and Discussion
[2]Rotaxanes containing a DB24C8 wheel and Frꢀchet-type
dendrimer stoppers: The first step in incorporating Frꢁchet-
type polyaryl ether units into 1,2-bis(pyridinium)eth-
A
ous generations (Scheme 2) to stopper [2]rotaxanes contain-
ing a simple DB24C8 wheel.[8] This provided a baseline for
gauging the changes in basic physical properties, primarily
solubility. A series of [2]rotaxanes were prepared that were
identical to compound 2 (Scheme 1), except that different
generations (G1, G2, G3) of dendrimeric wedges were used
in place of tert-butylbenzyl and that groups (G0 and G1)
1
[a] Dr. D. A. Tramontozzi, Dr. N. D. Suhan, Prof. S. H. Eichhorn,
Prof. S. J. Loeb
were also appended to the crown ether. H NMR spectros-
copy and ESIMS verified the purity and identity of each
[2]rotaxane. These are designated by the generations used in
their construction in the order first axle stopper, wheel ap-
pendage, second axle stopper; for example, [2]rotaxane [G3-
Department of Chemistry and Biochemistry
University of Windsor, Windsor, ON, N9B 3P4 (Canada)
Fax : (+1)519-973-7098
E-mail: loeb@uwindsor.ca
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S. J. Loeb et al.
Scheme 2. The various Frꢁchet-type dendritic wedges (G0, G1, G2, G3) used in this study as stoppers for the pyridinium axles and appendages on the
crown ether wheels. When there is no appendage on the crown ether, that is, for DB24C8, the code used is “H”).
G1-G3]4+ has G3 stoppering units on each end of the axle
with a G1 appendage on the crown ether wheel.
The single-crystal X-ray structure of the [2]rotaxane [G1-
H-G1]4+ is shown in Figure 1. The two stoppering units are
oriented on opposite sides of the central linear portion,
which adopts the same basic conformation previously ob-
served when tert-butylbenzyl stoppering units were used.[9]
The presence of these larger stoppering units has no signifi-
cant structural effect on the interactions between the pyridi-
nium axle and the crown ether wheel.[10] Even the addition
of larger generations (G2 and G3) showed no changes to
1
the H NMR spectra (other than increased intensity for the
aryl ether resonances) and it was concluded that the stop-
pering wedges extend away from the core and therefore
exert little effect on the interlocked core of the structure.
The addition of dendrimer stoppering groups did however
have significant effect on the solubility of the [2]rotaxanes
and the material properties of the solid. The original rotax-
ane 2 and [G1-H-G1]4+ are soluble in most polar organic
solvents, such as DMSO, DMF, MeOH, CH3NO2, and
MeCN, but not in less polar ones. Addition of larger den-
drimers allowed dissolution of the rotaxane structure in less
polar solvents to the extent that [G1-G1-G1]
in acetone, [G2-G1-G2][PF6]4 in CH2Cl2 and CHCl3, and
[G3-G1-G3][PF6]4 in THF and even benzene and toluene
ACHTUGNTREN[UNNG PF6]4 is soluble
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
(see Figure 2).
The fact that a tetracationic species can be manipulated
to the point that it becomes soluble in toluene shows the
extent to which addition of dendrimer stoppers can change
the physical properties of these molecules without apparent-
ly altering significantly the structure of the interlocked core.
Figure 1. X-ray structure of the [2]rotaxane [G1-H-G1]4+. Top: A ball-
and-stick representation with the numbering scheme depicted. Bottom:
A space-filling view: pyridinium axle=blue, crown ether wheel=red, G1
dendrimeric stoppering unit=green. There is a crystallographically im-
posed center of symmetry.
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Incorporating Frꢁchet Dendrons into Rotaxanes and Molecular Shuttles
FULL PAPER
Figure 3. A molecular mechanics derived space-filling model of the [G3-
H-G3]4+ rotaxane.
Figure 2. 1H NMR spectra of [G3-G1-G3]4+ in [D8]toluene at 303 (top)
and 343 K (bottom) showing the four pyridinium resonances on the axle.
Materials properties of rotaxanes with dendritic stoppers:
The addition of Frꢁchet dendrons had a significant effect on
the solution behavior of these rotaxanes and since the intro-
duction of these bulky groups has the potential to impart
mesomorphic properties to the solid state, we also decided
to undertake a preliminary investigation of their basic mate-
A clue to how this occurs comes from changes in the
1H NMR spectra in a single solvent, MeCN, as the complexi-
ty of the rotaxane is varied from [G1-H-G1]4+ to [G3-G1-
G3]4+. The pyridinium proton closest to the dendrimer stop-
per is exposed to surrounding solvent to the greatest extent.
As the generation size is increased, this hydrogen atom is
rials properties. The mesomorphism of [G1-H-G1]
ACHTUNGTRENNUNG[PF6]4,
shielded more from the polar solvent by the organic groups
of the dendrimer and systematically shifts upfield as a
result; d=8.92 ppm for [G1-H-G1]4+ to d=8.78 ppm for
[G3-G1-G3]4+. One can imagine with G3 stoppers and a G1
appendage on the crown that the dendrimer wedges of [G3-
G1-G3]4+ completely encapsulate the charged core. This
probably limits the direct interaction of the pyridinium ni-
trogen atoms with solvent molecules and, along with re-
duced charge density and weakened cohesion in the solid
state, leads to in an increase in solubility in nonpolar media,
such as toluene or benzene.
[G2-H-G2][PF6]4, and [G3-H-G3][PF6]4 were studied by po-
G
ACHTUNGTRENNUNG
larized optical microscopy (POM), thermogravimetric analy-
sis (TGA), differential scanning calorimetry (DSC), and X-
ray diffraction (XRD).
ACHNUTRETG[NGNNU G1-H-G1]CAHUTTGNREN[NGU PF6]4, [G2-H-G2]AHCTUNGERTGN[NNU PF6]4, and [G3-H-G3]ACHTUNGTRENNUNG[PF6]4
are thermally stable to ꢁ1908C under inert gas based on
the onset temperature of weight loss determined by thermal
gravimetric analysis at a heating rate of 28Cminꢂ1. Since it
is the bond between the pyridinium unit of the thread and
the benzylic methylene group of the stopper that is thermal-
ly most labile, it is not surprising that [G1-H-G1]
ACHTUGNERTN[NUNG PF6]4, [G2-
1
Interestingly, the H NMR spectrum of [G3-G1-G3]4+ in
H-G2][PF6]4, and [G3-H-G3][PF6]4 all decompose at about
A
ACHTUNGTRENNUNG
[D8]toluene at room temperature (303 K) is extremely
broad, whereas raising the temperature to 343 K yields a
spectrum essentially identical to that seen in more polar sol-
vents (Figure 2). As described above, it is likely that upon
dissolution in this very nonpolar solvent the peripheral den-
drimer units fold back around the polar core resulting in a
more globular-shaped molecule, which causes the relative
motion of the rotaxane components to be hindered. When
interconversion between the available conformations is
close to the NMR timescale, very broad signals are observed
as shown in Figure 2 (top) for [G3-G1-G3]4+ at 303 K in
[D8]toluene. At high temperature (343 K), the rate of inter-
conversion between the available conformations is fast on
the NMR timescale and only sharp averaged signals are ob-
served.
the same temperature, as confirmed by POM. It should be
noted that this decomposition temperature is ꢁ308C higher
than the values reported for derivatives of N,N-dibenzyl-
substituted 4,4’-bipyridine (viologen). This stabilizing effect
could be attributed to protection of the viologen unit by the
attached crown ether, but since there is no difference in sta-
bility between [G1-H-G1]
H-G3][PF6]4 this effect cannot be related to the incorpora-
tion of the different dendrons.
ACHTUNTGRENGU[N PF6]4, [G2-H-G2]ACHTUNGTRNEN[UGN PF6]4, and [G3-
AHCTUNGTRENNUNG
All three rotaxanes showed second-order phase transi-
tions between 80–1008C in the DSC graphs that coincide
with softening temperatures of mechanically sheared sam-
ples observed by POM. Transitions from the birefringent to
the isotropic state occur over wide temperature ranges of
173–1818C for [G1-H-G1]
ACHTUNGTRENNUNG
Figure 3 shows a molecular mechanics[11] derived model of
the [G3-H-G3]4+ rotaxane in space-filling mode. Even in
this relatively idealized conformation, it is fairly clear that
the very large G3 stoppering units almost completely encap-
sulate the core.
N
ACHTUNGTRENNUNG
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S. J. Loeb et al.
cosity is also the reason why the birefringence requires sev-
eral days to develop upon cooling from the isotropic state.
Two broad reflections dominate the XRD patterns of all
three compounds and are indicative of nematic mesophases
and the observed schlieren-type defect textures agree with
this assignment (see Figure 4), however, texture analysis is
Figure 4. XRD patterns of [G1-H-G1]
ACHTUNTGRENNGU[PF6]4 (black), [G2-H-G2]CAHUTNGTREN[NUGN PF6]4
(blue), and [G3-H-G3][PF6]4 (orange) in their nematic glass phases at
ACHTUNGTRENNUNG
228C. Inserted is a POM image of the texture of [G2-H-G2]
1058C.
ACHTUGNRTNE[NUNG PF6]4 at
complicated by the high viscosity of these compounds. The
maxima of the small-angle reflections between 21 and 24 ꢂ
agree with the approximate lengths of the rotaxanes and the
wide-angle reflections between 4 and 5 ꢂ represent the typi-
cal packing distances of aliphatic and aromatic groups. All
small-angle peaks show shoulders between 11 and 16 ꢂ that
agree with the estimated lateral packing distance of the mol-
ecules. Amorphous Frꢁchet dendrons have been shown to
give a broad reflection at 5 ꢂ, whereas the packing distances
of aromatic units in the core is expected at around 4 ꢂ.
Scheme 3. A [2]rotaxane molecular shuttle can be created in which the
cyclic wheel (shown here as DB24C8) can shuttle rapidly between two
different 1,2-bis(pyridinium)ethane recognition sites on the same axle.
During the synthesis of these [2]rotaxanes, a corresponding [3]rotaxane is
also produced that contains two of the crown ethers utilized in the prepa-
ration (shown here as DB24C8).
(VT)-NMR spectral data, it was determined that the barrier
to shuttling was 54 kJmolꢂ1 and the ratio of site occupancy
was determined to be 65:35 in favor of the 1,2-bis(4,4’-bipyr-
idinium)ethane site over the site terminated in a 4-tert-butyl-
pyridinium group;[13] see Scheme 3 for designations of major
and minor translational isomers.
Molecular shuttles containing Frꢀchet-type dendrimer units
on both the DB24C8 wheel and stoppering unit: The most
widely studied type of molecular switch based on inter-
locked molecules is the [2]rotaxane molecular shuttle pio-
neered by Stoddart et al.[12] In a molecular shuttle, two dif-
ferent recognition sites are present on the axle for the bind-
ing of a single macrocyclic wheel. The two coconformations
are translational isomers related by the relative positioning
of the two interlocked components.
To study the effect of dendrimer incorporation on molec-
ular shuttling, we synthesized a series of [2]rotaxanes that
contain G1 or G2 stoppers on one end of the axle and as
the cyclic component a DB24C8 derivative, that is, [G1-H]5+
[G1-G0]5+, [G1-G1]5+, [G1-G2]5+, [G2-H]5+, [G2-G0]5+
,
,
In an earlier study, we showed that by extending our 1,2-
bis(pyridinium)ethaneꢀ[24]crown-8 template so that the
axle contained two recognition sites, both [3]- and [2]ro-
taxane molecular shuttles could be prepared. Scheme 3
shows a [2]rotaxane molecular shuttle with two different
bis(pyridinium)ethane binding sites and a single molecule of
[G2-G1]5+, and [G2-G2]5+. As outlined in Scheme 3, an un-
intentional but inevitable byproduct in each of these prepa-
rations was the corresponding [3]rotaxane,[14] that is, [G1-H/
H]5+, [G1-G0/G0]5+, [G1-G1/G1]5+, [G1-G2/G2]5+, [G2-H/
H]5+, [G2-G0/G0]5+, [G2-G1/G1]5+, and [G2-G2/G2]5+. The
[3]rotaxanes were isolated by column chromatography and
characterized by NMR spectroscopy and mass spectrometry
(see the Experimental Section), but due to the small
amounts produced no further details are reported herein.
1
DB24C8.[14] Since only one set of H NMR resonances was
observed for the axles at room temperature, it was conclud-
ed that the DB24C8 molecule was undergoing fast exchange
between the two binding sites. From variable-temperature
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Incorporating Frꢁchet Dendrons into Rotaxanes and Molecular Shuttles
FULL PAPER
Previously reported studies incorporating dendritic units
into molecular shuttles focused exclusively on systems in
which the dendrimers were part of the stoppering groups.[7a]
As a result, fundamental characteristics of a molecular shut-
tle, such as coconformational preference and shuttling rate
for the macrocycle, were really no different than in analo-
gous systems with conventional stoppers. In contrast, the
molecular shuttles presented in this study contain a signifi-
cant increase in structural complexity. Since the dendritic
units are attached to both the axle and wheel components,
the two possible coconformations have dramatically differ-
ent sizes and shapes and for the first time coconformational
preference and shuttling rate can be correlated to the size of
the molecular units involved. The ability to significantly re-
organize the shape of a macromolecular species by switching
the components of an interlocked core at the molecular
level may find interesting applications in polymer chemis-
try[15] and may also provide insight into the fundamental
nature of biological macromolecules, which are known to
rely heavily on changes in shape for their function.[16]
the more compact “short” version of the molecule, which
has the crown ether wheel situated on the 1,2-bis(4,4’-bipyri-
dinium)ethane recognition site (Scheme 4).
Scheme 4. The incorporation of dendrons onto both the axle and the
wheel of a [2]rotaxane molecular shuttle dramatically influences the size
of the two possible coconformations.
The eight new molecular shuttles were isolated and char-
acterized by 1H NMR spectroscopy and ESIMS (see the
Supporting Information). Each was then investigated by VT
1H NMR spectroscopy and the experimental data simulat-
ed[17] to determine rates of exchange between the two recog-
nition sites. The tBu peaks were used for analysis because
these were easily identified singlets in a noncrowded portion
of the spectrum. In each case, at room temperature a single
peak was observed. This broadened as the temperature was
lowered, eventually coalescing and then splitting into two
separate resonances at the lowest temperatures. Direct inte-
gration of the low-temperature limiting resonances allowed
measurement of a site occupancy ratio. The results are sum-
marized in Table 1.
For the barrier to translational motion to increase, there
must be an extra energy cost associated with shuttling. As
the dendritic wedge size increases, there is likely to be more
shielding of the rotaxane core by the large organic frag-
ments. This could create a microenvironment at the recogni-
tion site that would be more favorable for the noncovalent
interactions between axle and wheel. This would be akin to
reducing the polarity of the solvent, which is already known
to have a dramatic effect on shuttling rates. However, an-
other factor that must be taken into account is the observa-
tion that there is a preference for the “short” coconforma-
tion. It may be that there are positive forces stabilizing this
coconformation. As estimated by molecular mechanics cal-
culations, there is a difference of >1 nm in length between
the long and short versions of the molecule (ꢁ42 versus
ꢁ54 ꢂ) equal to the distance between the two recognition
sites.[19] From a thermodynamic point of view, the more com-
pact molecule might be favorable, since it simply requires
less solvation, but another factor that could contribute to
stabilizing the smaller isomer is the formation of an arrange-
ment of axle and wheel, as shown in Figure 5. As the den-
dritic wedges increase in size, there would be an increased
likelihood of interdigitation of the aromatic rings which
would add to the noncovalent interactions to be overcome
to facilitate shuttling.
Table 1. Results of VT 1H NMR spectroscopy studies on dendritic mole-
cule shuttles.[a]
Stoppering
unit
Crown appendage
Barrier to shuttling
[kJmolꢂ1
Site occupancy
ratio[b]
N
]
H
H
H
54
58
64
69
72
68
70
71
84
67:33[c]
78:22
83:17
85:15
88:12
79:21
83:17
87:13
88:12
G1
G1
G1
G1
G2
G2
G2
G2
G0
G1
G2
H
G0
G1
G2
[a] NMR spectra were recorded in [D3]MeCN. Energy barriers and rates
were obtained from simulations using the program gNMR.[17] [b] Occu-
pancy ratios were determined from direct integration of tBu resonances.
The ratio refers to major/minor as pictured in Scheme 4. [c] Data from
reference [13].
Conclusion
There are two clear trends: 1) as the size of the dendritic
wedges increase on either the stopper or the wheel, the bar-
rier to shuttling increases, thus decreasing the rate of shut-
tling, and 2) there is a concomitant increasing preference for
We have shown that adding Frꢁchet-style dendrons to the
stoppering groups of [2]rotaxanes will allow their dissolution
in very nonpolar solvents such as toluene. This may have
utility for depositing these compounds on substrates, for ex-
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S. J. Loeb et al.
tion mass spectrometry (HRMS) experiments were performed on a Mi-
cromass-LCT electrospray (ES) time-of-flight (TOF) mass spectrometer.
Solutions of 50–100 ngmLꢂ1 were prepared in 1:1 MeCN/H2O (unless oth-
erwise indicated), and injected for analysis at a rate of 5 mLminꢂ1 using a
syringe pump. Aryl ether dendrons,[18] 3-hydroxymethyldibenzo[24]-
[20]
crown-8 ether,[19] and axles 1,2-bis(4,4’-bipyridinium)ethane
ACTHNUGTRNEGNU[PF6]2 and
[21]
3ACTHNURGTNEG[UN PF6]4 were synthesized as previously reported in the literature.
Synthesis of G0-DB24C8: 3-Hydroxymethyldibenzo[24]crown-8 ether
(0.461 g, 0.963 mmol) and benzylbromide (0.267 g, 1.56 mmol) were
added to a suspension of sodium hydride (0.253 g, 10.5 mmol) in dry
THF (50 mL) and the mixture was heated at reflux for 3 d under a nitro-
gen atmosphere. Water (30 mL) was slowly added to quench the reaction
and the product was extracted into CH2Cl2 (3ꢄ20 mL). The organic
layers were combined, dried (anhydrous MgSO4), filtered, and concen-
trated. The residue was subjected to column chromatography; SiO2,
CH2Cl2 and then methanol was added to elute the last compound. Like
fractions were combined and then concentrated to yield a yellow oil,
which was subsequently dissolved in CHCl3 (3 mL). Hexanes were added
to precipitate G0-DB24C8 as a white solid (0.471 g, 86%). 1H NMR
(CDCl3): d=7.33–7.14 (m, 5H), 6.89–6.81 (m, 7H), 4.51 (s, 2H), 4.45 (s,
2H), 4.15–4.13 (m, 8H), 3.91–3.89 (m, 8H), 3.82 ppm (s, 8H); HRMS
(ESI): m/z calcd for [G0-DB24C8+Na]+: 591.2570; found: 591.2592.
Figure 5. A molecular mechanics (MM3) derived space-filling model
showing how interdigitation of the dendrons on the axle and wheel could
act as a stabilizing interaction to favor this more compact [2]rotaxane co-
conformation.
Synthesis of G1-DB24C8: The same procedure as that used for G0-
DB24C8 was used with bromomethyl-G1 in place of benzylbromide to
1
yield G1-DB24C8 as a white solid (0.748 g, 90%). H NMR (CDCl3): d=
7.42–7.31 (m, 10H), 6.90–6.83 (m, 7H), 6.62 (d, , 4J=1.3 Hz 2H), 6.56 (t,
4J=1.3 Hz, 1H), 5.03 (s, 4H), 4.46 (s, 2H), 4.44 (s, 2H), 4.16–4.13 (m,
8H), 3.92–3.89 (m, 8H), 3.83–3.82 ppm (m, 8H); HRMS (ESI): m/z calcd
for [G1-DB24C8+Na]+: 803.3407; found: 803.3372.
ample, in the production of thin films. We also reported that
the addition of these large organic groups leads to materials
that are soft and show simple alignment in the solid state.
Most importantly, we have demonstrated that incorporating
large dendritic fragments into the components of a molecu-
lar shuttle increases the barrier to shuttling and skews the
distribution of coconformations in favor of a single recogni-
tion site. Since the shuttling event causes a dramatic change
in the shape of the molecule, this also demonstrates the po-
tential of using interlocked components to manipulate the
shape of macromolecules. One can envisage using a bistable
molecular shuttle as the core machinery to open and close
large capsules or perhaps even initiate a macroscopic phase
change under the right circumstances.
Synthesis of G2-DB24C8: The same procedure as that used for G0-
DB24C8 was used with bromomethyl-G2 in place of benzylbromide to
yield G2-DB24C8 as a yellow oil (1.007 g, 96%). 1H NMR (CDCl3): d=
7.45–7.33 (m, 20H), 6.91–6.83 (m, 7H), 6.70 (d, 4J=2.2 Hz, 4H), 6.59 (t,
4J=2.2 Hz, 2H), 6.62 (d, 4J=2.2 Hz, 2H), 6.53 (t, 4J=2.2 Hz, 1H), 5.05
(s, 8H), 4.99 (s, 4H), 4.47 (s, 2H), 4.45 (s, 2H), 4.18–4.12 (m, 8H), 3.94–
3.89 (m, 8H), 3.84–3.83 ppm (m, 8H); HRMS (ESI): m/z calcd for [G2-
DB24C8+Na]+: 1227.5082; found: 1227.5071.
Synthesis of rotaxane [G1-H-G1]
ACHTUNGTRENNUNG
ethane[PF6]2 (0.070 g, 0.111 mmol),
AHCTUNGTRENNUNG
0.461 mmol), DB24C8 (0.102 g, 0.227 mmol), and a catalytic amount of
TBAI (15 mg) were dissolved in MeNO2 (10 mL). Water (10 mL) and a
saturated aqueous solution of NH4PF6 (2 mL) were added and the two-
layer reaction was stirred at room temperature for 21 d (at 7 and 14 d the
aqueous layer was replaced with fresh distilled water). The organic layer
was separated, dried (anhydrous MgSO4), concentrated (2 mL), and pre-
cipitated with diethyl ether. The precipitate was filtered through Celite
and washed into a clean flask with MeCN. The solvent was evaporated
and the red/orange residue was subjected to column chromatography
(SiO2; methanol/MeNO2/2m NH4Cl (aq), 7:1:2). Like fractions were com-
bined, anion exchanged (NH4PF6), and evaporated to yield [G1-H-G1]-
Experimental Section
General: [18]Crown-6, benzyl bromide, carbon tetrabromide, 3,5-dihy-
droxybenzyl alcohol, sodium hydride, tetrabutyl ammonium iodide
(TBAI), triphenyphosphine, ammonium chloride, ammonium hexafluoro-
phosphate, catechol, cesium carbonate, 2-[2-(2-chloroethoxy)ethoxy]etha-
nol, 1,2-dibromoethane, 3,4-dihydroxybenzaldehyde, 4,4’-dipyridyl, mag-
nesium sulfate, 4-methylpyridine, 4-phenylpyridine, potassium carbonate,
pyridine, sodium borohydride, thionyl chloride, p-toluenesulfonyl chlo-
ride, and 4-trifluoromethylpyridine were purchased from Aldrich and
used as received. All [2]rotaxanes were prepared as the hexafluorophos-
phate (PF6ꢂ) salts unless otherwise noted. Deuterated solvents were ob-
tained from Cambridge Isotope Laboratories and used as received. Sol-
vents were dried by using an Innovative Technologies Solvent Purifica-
tion System. TLC was performed by using Merck Silica gel 60 F254 plates
and viewed under UV light. Column chromatography was performed by
using Silicycle Ultra Pure Silica Gel (230–400 mesh). 1H NMR experi-
ments were performed on a Brꢃker Avance 500 instrument operating at
500.1 MHz. The deuterated solvent was used as the lock and the residual
solvent or TMS as the internal reference. Conventional 2D NMR experi-
ments (1H–1H COSY and NOESY) were used to assign all peaks. Dia-
grams and tables showing the assignments for all 1H NMR resonances
are provided in the accompanying Supporting Information. High-resolu-
AHCTUNGTRENNUNG
[PF6]4 as a red/orange glassy solid (0.103 g, 47%, Rf =0.49). 1H NMR
(CD3CN): d=9.33 (d, 3J=6.9 Hz, 4H), 8.91 (d, 3J=6.9 Hz, 4H), 8.15 (d,
3J=6.9 Hz, 4H), 8.07, (d, 3J=6.9 Hz, 4H), 7.46–7.35 (m, 20H), 6.77 (t,
4J=2.2 Hz, 2H), 6.74 (d, 4J=2.2 Hz, 4H), 6.65–6.64 (m, 4H), 6.47–6.45
(m, 4H), 5.73 (s, 4H), 5.62 (s, 4H), 5.13 (s, 8H), 4.05–4.01 ppm (m,
24H); HRMS (ESI): m/z calcd for [(G1-H-G1)
found: 1829.5514; m/z calcd for [(G1-H-G1)
(PF6)2]2+: 842.2920; found:
842.2927; ; m/z calcd for [(G1-H-G1)]4+: 348.6639; found: 348.6633.
Synthesis of rotaxane [G1-H-G1][BF4]4: 1,2-Bis(4,4’-
bipyridinium)ethane[BF4]2 (0.103 g, 0.200 mmol), bromomethyl-G1
(PF6)3]+: 1829.5481;
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
(0.311 g, 0.814 mmol), DB24C8 (0.182 g, 0.406 mmol), and a catalytic
amount of TBAI (15 mg) were dissolved in MeCN (20 mL) and the reac-
tion was stirred at room temperature for 7 d. The mixture was filtered
and the filtrate was concentrated (3 mL) and precipitated with diethyl
ether. The red/orange precipitate was filtered through Celite and washed
into a clean flask with MeCN. The solvent was evaporated and the red/
orange residue was subjected to column chromatography (SiO2; metha-
nol/MeNO2/2m NH4Cl (aq), 3:1:1). Like fractions were combined, anion
4472
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 4466 – 4476

Incorporating Frꢁchet Dendrons into Rotaxanes and Molecular Shuttles
FULL PAPER
exchanged (NaBF4), and evaporated to yield G1-H-G1 (tetrafluoroborate
salt) as a red/orange glassy solid (0.113 g, 33%, Rf =0.45). X-ray quality
crystals were grown by slow diffusion of diethyl ether into a concentrated
4H), 5.03 (s, 8H), 5.00 (s, 32H), 4.94 (s, 16H), 3.96–3.90 ppm (m, 24H);
HRMS (ESI): m/z calcd for [(G3-H-G3)ACTHNGUTERNNUG
(PF6)3]+: 2114.7943; found:
(PF6)2]2+
2114.7844; m/z calcd for [(G3-H-G3)CAHTUNGTERNNUNG : 1266.4594; found:
solution of [G1-H-G1]
H-G1)
(BF4)3]+: 1655.6643; found: 1655.6611; m/z calcd for [(G1-H-G1)-
(BF4)2]2+: 784.3307; found: 784.3337.
X-ray diffraction analysis of rotaxane [G1-H-G1]
of [G1-H-G1][BF4]4 was frozen in paratone oil inside a cryoloop. Reflec-
G
1266.4589.
ACHTUNGTRENNUNG
Synthesis rotaxane
bipyridinium)ethaneACHTUNGTERNN[UNG PF6]2 (0.043 g, 0.0682 mmol) and G1-DB24C8
of
[G1-G1-G1]
N
1,2-Bis(4,4’-
ACHTUNGTRENNUNG
(0.106 g, 0.136 mmol) were dissolved in MeNO2 (25 mL) and stirred for
10 min. At this point, TBAI (10 mg) and bromomethyl-G1 (0.115 g,
0.300 mmol) were added along with water (10 mL) and a saturated aque-
ous solution of NH4PF6 (1 mL) and the two-layer reaction was then
stirred at room temperature for 12 d (at 7 d the aqueous layer was re-
placed with fresh distilled water). The organic layer was separated, dried
(anhydrous MgSO4), concentrated (5 mL), and precipitated with diethyl
ether. The red/orange precipitate was filtered through Celite and washed
into a clean flask with MeCN. The solvent was evaporated and the red/
orange residue was subjected to column chromatography (SiO2; metha-
nol/MeNO2/2m NH4Cl(aq), 7:1:2). Like fractions were combined, anion
exchanged (NH4PF6), concentrated (2 mL), and precipitated from the
concentrated MeNO2 solution by slow diffusion of isopropyl ether to
ACHTUNGTRENNUNG
tion data were integrated from frame data obtained from hemisphere
scans on a Bruker APEX diffractometer with a CCD detector. Decay
was monitored by 50 standard data frames measured at the beginning
and end of data collection. Diffraction data and unit-cell parameters
were consistent with assigned space groups. Lorentzian polarization cor-
rections and empirical absorption corrections, based on redundant data
at varying effective azimuthal angles, were applied to the data sets. The
structures were solved by direct methods, completed by subsequent Four-
ier syntheses and refined by using full-matrix least-squares methods
against jF2 j data. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were treated as idealized contributions. Scattering fac-
tors and anomalous dispersion coefficients are contained in the
SHELXTL 5.03 program library (G. M. Sheldrick, Madison, WI).[22,23]
Crystal data: C94H99N7O12B2F16Cl2, Mr =1915.3, orange blocks (0.22ꢄ
yield [G1-G1-G1]ACHTUNGTRNEG[UN PF6]4 as a red/orange oil (0.090 g, 57%, Rf =0.42).
1H NMR (CD3CN): d=9.32 (d, 3J=6.8 Hz, 4H), 8.82 (d, 3J=6.8 Hz,
4H), 8.14 (d, 3J=6.8 Hz, 4H), 8.03, (d, 3J=6.8 Hz, 4H), 7.44–7.31 (m,
30H), 6.74–6.45 (m, 16H), 5.62 (s, 4H), 5.60 (s, 4H), 5.10 (s, 8H), 5.03 (s,
4H), 4.28 (s, 2H), 4.05–3.99 ppm (m, 26H); HRMS (ESI): m/z calcd for
¯
0.16ꢄ0.10 mm), triclinic, P1, a=10.731(2), b=15.949(4), c=16.299(3) ꢂ,
a=108.506(3)8, b=101.889(2)8, g=100.471(4)8, U=2495.0(9) ꢂ3, Z=1,
1calcd =1.275 gcmꢂ3
,
m=0.155 mmꢂ1
,
min trans.=0.4847, max trans.=
0.7457, 2qmax =50.08, MoKa, l=0.71073 ꢂ, T=173.0(2) K, 16796 total re-
flections (R(int)=0.0444), R1=0.1385, wR2=0.3659 [I>2sI], R1=
[(G1-G1-G1)
G1-G1)
(PF6)2]2+: 1008.3626; found: 1008.3625; m/z calcd for [(G1-G1-
G1)
(PF6)]3+: 623.9203; found: 623.9235; m/z calcd for [(G1-G1-G1)]4+
431.6992; found: 431.7012.
Synthesis of rotaxane
bipyridinium)ethane
(PF6)3]+: 2162.6893; found: 2162.6340; m/z calcd for [(G1-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
G
R
:
0.1703, wR2=0.3897 (all data), GoF(F2)=1.165, data/variables/re-
straints=8514/640/6. CCDC-744117 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
[G2-G1-G2]
1,2-Bis(4,4’-
AHCTUNGTREN[GUNN PF6]2 (0.044 g, 0.0698 mmol) and G1-DB24C8
(0.107 g, 0.137 mmol) were dissolved in MeNO2 (20 mL) and CHCl3
(5 mL) and stirred for 10 min. At this point, TBAI (10 mg) and bromo-
methyl-G2 (0.230 g, 0.285 mmol) were added along with water (10 mL)
and a saturated aqueous solution of NH4PF6 (1 mL) and the two-layer re-
action was stirred at room temperature for 14 d (at 7 d the aqueous layer
was replaced with fresh distilled water). The organic layer was separated,
dried (anhydrous MgSO4), concentrated (5 mL), and precipitated with di-
ethyl ether. The red/orange precipitate was filtered through Celite and
washed into a clean flask with MeCN. The solvent was evaporated and
the red/orange residue was heated in toluene three times, the toluene
was decanted, and the solid was allowed to dry. The red/orange solid was
subjected to column chromatography (SiO2; CH2Cl2/EtOH, 95:5). Like
fractions were combined, anion exchanged (NH4PF6), concentrated
(2 mL), and precipitated from the concentrated solution in MeNO2 by
Synthesis rotaxane
of
[G2-H-G2]
G
1,2-Bis(4,4’-
bipyridinium)ethaneACHTUNGTRENNUNG[PF6]2 (0.047 g, 0.0738 mmol), bromomethyl-G2
(0.258 g, 0.319 mmol), DB24C8 (0.076 g, 0.168 mmol), and a catalytic
amount of TBAI (15 mg) were dissolved in MeNO2 (10 mL) and CHCl3
(10 mL). Water (10 mL) and a saturated aqueous solution of NH4PF6
(2 mL) were added and the two-layer reaction was stirred at room tem-
perature for 21 d (at 7 and 14 d the aqueous layer was replaced with
fresh distilled water). The organic layer was separated, dried (anhydrous
MgSO4), concentrated (2 mL), and precipitated with diethyl ether. The
precipitate was filtered through Celite and washed into a clean flask with
MeCN. The solvent was evaporated and the red/orange residue was sub-
jected to column chromatography (SiO2; methanol/MeNO2/2m NH4Cl
(aq), 3:1:1). Like fractions were combined, anion exchanged (NH4PF6),
slow diffusion of isopropyl ether to yield [G2-G1-G2]ACHTNUGTRNEG[UN PF6]4 as a red/
and evaporated to yield [G2-H-G2]
N
orange solid (0.049 g, 22%, Rf =0.49). 1H NMR (CD3CN): d=9.29 (d,
3J=6.7 Hz, 4H), 8.83 (d, 3J=6.7 Hz, 4H), 8.12 (d, 3J=6.7 Hz, 4H), 8.03,
(d, 3J=6.7 Hz, 4H), 7.40–7.31 (m, 50H), 6.71–6.53 (m, 28H), 5.63 (s,
4H), 5.58 (s, 4H), 5.03 (s, 16H), 5.02 (s, 8H), 4.96 (s, 4H), 4.22 (s, 2H),
4.04–3.95 ppm (m, 26H); HRMS (ESI): m/z calcd for [(G2-G1-G2)2-
(0.081 g, 39%, Rf =0.43). 1H NMR (CD3CN): d=9.31 (d, 4H, 3J=
6.9 Hz), 8.92 (d, 4H, 3J=6.9 Hz), 8.13 (d, 4H, 3J=6.9 Hz), 8.08, (d, 4H,
3J=6.9 Hz), 7.42–7.33 (m, 40H), 6.73–6.72 (m, 6H), 6.69 (d, 8H, 4J=
2.2 Hz), 6.63–6.61 (m, 4H), 6.58 (t, 4H, 4J=2.2 Hz), 6.47–6.45 (m, 4H),
5.73 (s, 4H), 5.60 (s, 4H), 5.06 (s, 8H), 5.05 (s, 16H), 4.05–3.99 ppm (m,
A
:
:
1432.5300; found: 1432.5309; m/z calcd for [(G2-G1-G2)-
24H); HRMS (ESI): m/z calcd for [(G2-H-G2)
R
906.6986; found: 906.6961; m/z calcd for [(G2-G1-G2)]4+
:
found: 1266.4589.
643.7829; found: 643.7830.
Synthesis of rotaxane
dipyridinium)ethaneACTHNUTRGNEUNG[PF6]2 (0.054 g, 0.0857 mmol) and G3-DB24C8
Synthesis of rotaxane [G3-H-G3]
G
[G3-G1-G3]
E
1,2-Bis(4,4’-
ethane
N
0.362 mmol), DB24C8 (0.076 g, 0.168 mmol), and a catalytic amount of
TBAI (15 mg) were dissolved in MeNO2 (10 mL) and CHCl3 (10 mL).
Water (10 mL) and a saturated aqueous solution of NH4PF6 (2 mL) were
added and the two-layer reaction was stirred at room temperature for
21 d (at 3 d the aqueous layer was replaced with fresh distilled water).
The organic layer was separated, dried (anhydrous MgSO4), and concen-
trated. The red/orange residue was subjected to column chromatography
(SiO2; CH2Cl2 to EtOH in CH2Cl2 (5%)). Like fractions were combined,
(0.136 g, 0.174 mmol) were dissolved in MeNO2 (20 mL) and stirred for
10 min. TBAI (10 mg) and bromomethyl-G1 (0.592 g, 0.357 mmol), dis-
solved in CH2Cl2 (10 mL), were added along with water (10 mL) and a
saturated aqueous solution of NH4PF6 (1 mL) and the two-layer reaction
was stirred at room temperature for 21 d (at 3 d the aqueous layer was
replaced with fresh distilled water). The organic layer was separated,
dried (anhydrous MgSO4), concentrated (2 mL), and precipitated with di-
ethyl ether. The red/orange precipitate was filtered through Celite and
washed into a clean flask with MeCN. The solvent was evaporated and
the residue was subjected to column chromatography (SiO2; CH2Cl2/
EtOH, 95:5). Like fractions were combined, anion exchanged (NH4PF6),
concentrated (2 mL), and precipitated from the concentrated solution in
anion exchanged (NH4PF6), and evaporated to yield [G3-H-G3]
ACHTUGNRTNE[NUNG PF6]4 as
a red/orange glassy solid (0.085 g, 22%, Rf =0.41). 1H NMR (CD3CN):
3
3
3
d=9.22 (d, J=6.4 Hz, 4H), 8.86 (d, J=6.4 Hz, 4H), 8.07 (d, J=6.4 Hz,
4H), 8.01, (d, 3J=6.4 Hz, 4H), 7.38–7.27 (m, 80H), 6.71 (brs, 2H), 6.68
(brs, 4H,), 6.62–6.51 (m, 40H), 6.42–6.40 (m, 4H), 5.67 (s, 4H), 5.52 (s,
MeNO2 by slow diffusion of isopropyl ether to yield [G3-G1-G3]ACHTUNGTRENNUNG[PF6]4 as
Chem. Eur. J. 2010, 16, 4466 – 4476
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4473

S. J. Loeb et al.
1
a red/orange oil (0.103 g, 25%, Rf =0.51). H NMR (CD3CN): d=9.23 (d,
G
R
:
3J=6.6 Hz, 4H), 8.78 (d, 3J=6.6 Hz, 4H), 8.07 (d, 3J=6.6 Hz, 4H), 7.98,
(d, 3J=6.6 Hz, 4H), 7.37–7.25 (m, 90H), 6.70–6.48 (m, 52H), 5.62–5.55
(m, 4H), 5.51 (s, 4H), 4.99–4.88 (m, 60H), 4.17 (s, 2H), 3.98–3.85 ppm
(m, 26H); HRMS (ESI): m/z calcd for [(G3-G1-G3)ACTHNUTRGNEUNG
(2PF6)]2+: 2280.8649;
3
found: 2280.8748.
Synthesis of [2]rotaxane [G1-H]
ACHTUNTGRENNG[U PF6]5 and [3]rotaxane [G1-H/H]ACHTUNGTREN[NUGN PF6]5:
Compound 3[PF6]4 (0.099 g, 0.116 mmol), DB24C8 (0.107 g, 0.239 mmol),
ACHTUNGTRENNUNG
bromomethyl-G1 (0.108 g, 0.282 mmol), and a catalytic amount of TBAI
(10 mg) were dissolved in MeNO2 (10 mL). Water (10 mL) and a saturat-
ed aqueous solution of NH4PF6 (1 mL) were added and the two-layer re-
action was stirred at room temperature for 14 d (at 7 d, the aqueous layer
was replaced with fresh distilled water). The organic layer was separated,
dried (anhydrous MgSO4), concentrated, and precipitated from solution
by the addition of diethyl ether (40 mL). The red/orange precipitate was
collected through Celite and subjected to column chromatography (SiO2;
methanol/MeNO2/2m NH4Cl(aq), 7:1:2). Like fractions were collected
and anion exchanged (NH4PF6) to yield [G1-H]
ACHTUNGTRENNUNG
G
(0.049 g, 26%, Rf =0.48). 1H NMR (CD3CN): d=9.23 (brs, 4H), 8.99
(brs, 2H), 8.92 (d, 3J=6.6 Hz, 2H), 8.71 (brs, 2H), 8.22 (brs, 2H), 8.16–
8.13 (m, 6H), 8.03 (brs, 2H), 7.44–7.33 (m, 10H), 6.76 (t, 4J=2.2 Hz,
1H), 6.72 (d, 4J=2.2 Hz, 2H), 6.68–6.65 (m, 4H), 6.55 (brs, 4H), 5.73 (s,
2H), 5.52 (brs, 4H), 5.28 (brs, 2H), 5.19 (brs, 2H), 5.12 (s, 4H), 4.07–
3.99 (m, 24H), 1.38 ppm (brs, 9H); HRMS (ESI): m/z calcd for [(G1-H)-
ACHTUNGTRENNUNG ACHUTNGTREN[NUNG PF6]5 (0.075 g, 49%, Rf =
(3PF6)]2+: 844.7728; found: 844.7759. [G1-H/H]
0.22); 1H NMR (CD3CN): d=9.33–9.29 (m, 6H), 8.95 (d, 3J=6.8 Hz,
2H), 8.95 (d, 3J=6.8 Hz, 2H), 8.90 (d, 3J=6.8 Hz, 2H), 8.08 (d, 3J=
6.8 Hz, 2H), 8.02 (d, 3J=6.8 Hz, 2H), 7.86 (d, 3J=6.7 Hz, 2H), 7.83 (d,
3J=6.7 Hz, 2H), 7.76 (d, 3J=6.8 Hz, 2H), 7.46–7.39 (m, 10H), 6.75–6.74
(m, 11H), 6.70–6.68 (m, 4H), 6.56–6.53 (m, 4H), 5.73 (s, 2H), 5.64–5.61
(m, 6H), 5.47–5.44 (m, 2H), 5.13 (s, 4H), 4.10–3.98 (m, 48H), 1.19 ppm
(s, 9H); HRMS (ESI): m/z calcd for [(G1-H/H)
found: 2282.7285; m/z calcd for [(G1-H/H)
(3PF6)]2+: 1068.8777; found:
1068.8715; m/z calcd for [(G1-H/H)
(2PF6)]3+: 664.2637; found: 664.2667;
m/z calcd for [(G1-H/H)
(PF6)]4+: 461.9568; found: 461.9517; m/z calcd
for [(G1-H/H)]5+: 340.5726; found: 340.5720.
Synthesis of [2]rotaxane [G1-G0][PF6]5 and [3]rotaxane [G1-G0/G0]-
[PF6]5: The procedure for [G1-H][PF6]5 was used with G0-DB24C8 em-
ployed instead of DB24C8. [G1-G0][PF6]5 and [G1-G0/G0][PF6]5 were
[PF6]5
(4PF6)]+: 2282.7196;
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
isolated as red/orange glassy products in 9% overall yield. [G1-G0]ACHTGNUTRENNUNG
(0.0107 g, 5%, Rf =0.42); 1H NMR (CD3CN): d=9.24 (brs, 4H), 8.93
(brs, 2H), 8.82 (brs, 2H), 8.66 (brs, 2H), 8.18–8.04 (brm, 10H), 7.43–
7.30 (m, 15H), 6.75–6.60 (m, 8H), 6.53 (brs, 2H), 5.64 (s, 2H), 5.51 (brs,
4H), 5.18–5.11 (brs, 4H), 5.10 (s, 4H), 4.40 (s, 2H), 4.14–3.96 (m, 26H),
:
1.37 ppm (brs, 9H); HRMS (ESI): m/z calcd for [(G1-G0)
904.8016; found: 904.8058; m/z calcd for [(G1-G0)
(2PF6)]3+: 554.8797;
379.9187; found:
(3PF6)]2+
ACHTUNGTERNNUNG :
AHCTUNGTRENNUNG
(PF6)]4+
found: 554.8765; m/z calcd for [(G1-G0)ACTHUNGTERNUNGN :
379.9184; m/z calcd for [(G1-G0)]5+: 274.9421; found: 274.9547. [G1-G0/
1
G0]
[PF6]5 (0.0071 g, 4%, Rf =0.53); H NMR (CD3CN): d=9.33–9.28 (m,
6H), 8.91 (d, 3J=6.8 Hz, 2H), 8.76 (d, 3J=6.5 Hz, 2H), 8.00 (d, 3J=
5.7 Hz, 2H), 7.96–7.91 (m, 6H), 7.72 (d, 3J=6.8 Hz, 2H), 7.44–7.30 (m,
20H), 6.77–6.51 (m, 17H), 5.63–5.60 (m, 8H), 5.46–5.42 (m, 2H), 5.11 (s,
4H), 4.50 (d, J=2.7 Hz, 2H), 4.37 (dd, J=2.7, 4.2 Hz, 2H), 4.34 (s, 2H),
4.13–3.93 (m, 50H), 1.14 ppm (brs, 9H); HRMS (ESI): m/z calcd for
[(G1-G0/G0)
G0)ACHTUNGTRENNUNG ACHTUNTGRENNUGN :
(2PF6)]3+: 744.3021; found: 744.3076; m/z calcd for [(G1-G0)(PF6)]4+
ACHTUNGTRENNUNG
(3PF6)]2+: 1188.9352; found: 1188.9347; m/z calcd for [(G1-
521.9855; found: 521.9852; m/z calcd for [(G1-G0)]5+: 388.5956; found:
388.5957.
Synthesis of [2]rotaxane [G1-G1]
[PF6]5: The procedure for [G1-H][PF6]5 was used with G1-DB24C8 em-
ployed instead of DB24C8. [G1-G1][PF6]5 and [G1-G1/G1][PF6]5 were
isolated as red/orange glassy products in 18% overall yield. [G1-G1]-
ACHTUNGTRENNUNG
[PF6]5 (0.0203 g, 10%, Rf =0.42); 1H NMR (CD3CN): d=9.24 (brs, 4H),
ACHTUGNTERN[NUNG PF6]5 and [3]rotaxane [G1-G1/G1]-
orange glassy solids in 18% overall yield. [G2-H]AHCTUNGTRENNUNG
1
N
ACHTUNGTRENNUNG
Rf =0.51); H NMR (CD3CN): d=9.22 (brs, 4H), 8.98 (brs, 2H), 8.91 (d,
3J=6.7 Hz, 2H), 8.70 (brs, 2H), 8.18–8.04 (brm, 10H), 7.41–7.31 (m,
20H), 6.70 (s, 3H), 6.67 (d, 3J=2.2 Hz, 4H), 6.66–6.64 (m, 4H), 6.57 (t,
3J=2.2 Hz, 2H), 6.53 (brs, 4H), 5.72 (s, 2H), 5.51 (brs, 4H), 5.19 (brs,
4H), 5.04 (s, 12H), 4.06–3.95 (m, 24H), 1.37 ppm (s, 9H); HRMS (ESI):
A
ACHTUNGTRENNUNG
8.98 (brs, 2H), 8.83 (d, 3J=5.4 Hz, 2H), 8.69 (brs, 2H), 8.22–8.03 (brm,
10H), 7.42–7.32 (m, 20H), 6.74–6.53 (m, 13H), 5.62 (s, 2H), 5.53 (brs,
4H), 5.20 (brm, 4H), 5.09 (s, 4H), 5.04 (s, 4H), 4.34 (s, 2H), 4.13–3.92
(m, 26H), 1.36 ppm (brs, 9H); HRMS (ESI): m/z calcd for [(G1-G1)-
m/z calcd for [(G2-H)
for [(G2-H)
(2PF6)]3+: 656.2497; found: 656.2512; m/z calcd for [(G2-H)-
(PF6)]4+: 455.9462; found: 455.9470; m/z calcd for [(G2-H)]5+: 335.7641;
(3PF6)]2+: 1056.8566; found: 1056.8572; m/z calcd
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
4474
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 4466 – 4476

Incorporating Frꢁchet Dendrons into Rotaxanes and Molecular Shuttles
FULL PAPER
found: 335.7646. [G2-H/H]
N
5 min. Bromomethyl-G2 (0.094 g, 0.116 mmol), dissolved in CH2Cl2
(3 mL), a catalytic amount of TBAI (5 mg), water (10 mL), and a saturat-
ed aqueous solution of NH4PF6 (1 mL) were added and the two-layer re-
action stirred at room temperature for 21 d. The organic layer was sepa-
rated, washed with water (3ꢄ50 mL), dried (anhydrous MgSO4), and
concentrated. The orange residue was dissolved in a minimum amount of
MeCN/toluene (5 mL) and diethyl ether was added to precipitate an
orange solid, which was collected through Celite and stirred in methanol
(20 mL). The methanol was decanted and the residue was air dried
before being subjected to column chromatography (SiO2; 0.025m NH4PF6
in MeCN/CH2Cl2, 3:2). Like fractions (as determined by NMR spectros-
copy) were collected, anion exchanged (NH4PF6), and precipitated from
(CD3CN): d=9.32–9.27 (m, 6H), 8.92 (d, 3J=6.8 Hz, 2H), 8.89 (d, 3J=
6.7 Hz, 2H), 8.03 (d, 3J=6.7 Hz, 2H), 7.99 (d, 3J=6.7 Hz, 2H), 7.85 (d,
3J=6.7 Hz, 2H), 7.82 (d, 3J=6.7 Hz, 2H), 7.75 (d, 3J=6.8 Hz, 2H), 7.42–
7.32 (m, 20H), 6.73 (s, 8H), 6.71 (s, 3H), 6.68 (d, J=2.3 Hz, 4H), 6.67–
6.65 (m, 4H), 6.57 (t, J=2.3 Hz, 2H), 6.54–6.51 (m, 4H), 5.72 (s, 2H),
5.63–5.59 (m, 6H), 5.46–5.42 (m, 2H), 5.05 (s, 4H), 5.04 (s, 8H), 4.08–
3.97 (m, 48H), 1.17 ppm (s, 9H); HRMS (ESI): m/z calcd for [(G2-H/H)
(3PF6)]2+: 1280.9614; found: 1280.9652; m/z calcd for [(G2-H/H)
: 805.6529; found: 805.6569; m/z calcd for [(G2-H/H)
(PF6)]4+: 567.9986;
found: 567.9973; m/z calcd for [(G2-H/H)]5+: 425.4061; found: 425.4064.
Synthesis of [2]rotaxane [G2-G0][PF6]5 and [3]rotaxane [G2-G0/G0]-
[PF6]5: The same procedure as that used for [G2-H][PF6]5 and [G2-H/H]-
[PF6]5 was used with G0-DB24C8 instead of DB24C8. [G2-G0][PF6]5 and
[PF6]5 were isolated as red/orange glassy solids in 12% over-
MeCN by slow diffusion of isopropyl ether to yield [G2-G2]
[G2-G2/G2][PF6]5 as red/orange glassy products in 17% overall yield.
[G2-G2]
[PF6]5 (0.0201 g, 11% Rf =0.39); 1H NMR (CD3CN): d=9.30–
ACHTUNGTRENNUNG[PF6]5 and
T
AHCTUNGTRENNUNG
T
AHCTUNGTRENNUNG
[G2-G0/G0]ACHTUNGTRENNUNG
9.21 (m, 4H), 8.91 (brs, 2H), 8.72 (brs, 2H), 8.62 (brs, 2H), 8.25–8.22
(m, 4H), 8.07–7.89 (m, 6H), 7.40–7.29 (m, 40H), 6.66–6.51 (m, 25H),
5.55–5.52 (m, 6H), 5.19–5.11 (m, 4H), 5.03–4.90 (m, 24H), 4.24 (s, 2H),
4.07–3.94 (m, 26H), 1.39 ppm (brs, 9H); HRMS (ESI): m/z calcd for
all yield. [G2-G0]ACHTUNGTRENNUNG[PF6]5 (0.0088 g, 6%, Rf =0.50); H NMR (CD3CN): d=
9.20 (brs, 4H), 8.91 (brs, 2H), 8.80 (m, 2H), 8.62 (brs, 2H), 8.23–7.98
(m, 10H), 7.37–7.29 (m, 25H), 6.70–6.47 (m, 16H), 5.59 (s, 2H), 5.52
(brs, 4H), 5.22–5.15 (m, 4H), 5.02–4.99 (m, 12H), 4.28 (s, 2H), 4.10–3.85
(m, 26H), 1.38 ppm (brs, 9H); HRMS (ESI): m/z calcd for [(G2-G0)-
[(G2-G2)
(PF6)]4+: 645.0234; found: 645.0221; m/z calcd for [(G2-G2)]5+: 487.0259;
found: 487.0271. [G2-G2/G2]
[PF6]5 (0.0147 g, 6% Rf =0.57); 1H NMR
(PF6)2]3+: 908.3526; found: 908.3544; m/z calcd for [(G2-G2)-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
AHCTUNGTRENNUNG
696.2683; found: 696.2710; m/z calcd for [(G2-G0)CAHTUNGTRENNUNG
(CD3CN): d=9.29 (d, 3J=6.5 Hz, 2H), 9.25 (d, 3J=6.3 Hz, 2H), 9.22 (d,
3J=6.5 Hz, 2H), 8.90 (d, 3J=6.7 Hz, 2H), 8.70 (d, 3J=6.4 Hz, 2H), 7.91–
7.87 (m, 6H), 7.81 (d, 3J=6.4 Hz, 2H), 7.72 (d, 3J=6.7 Hz, 2H), 7.38–
7.28 (m, 60H), 6.71–6.48 (m, 41H), 5.57–5.52 (m, 8H), 5.40–5.38 (m,
2H), 5.01–4.86 (m, 36H), 4.41 (brs, 2H), 4.27 (d, J=5.4 Hz, 2H), 4.21 (d,
J=2.8 Hz, 2H), 4.02–3.90 (m, 50H), 1.15 ppm (s, 9H); HRMS (ESI): m/z
ACHTUNGTRENNUNG
(d, 3J=6.6 Hz, 2H), 9.28 (d, 3J=6.6 Hz, 2H), 9.27 (d, 3J=6.6 Hz, 2H),
8.93 (d, 3J=6.6 Hz, 2H), 8.76 (d, 3J=6.6 Hz, 2H), 7.94–7.90 (m, 4H),
7.89–7.85 (m, 4H), 7.72 (d, 3J=6.6 Hz, 2H), 7.40–7.30 (m, 30H), 6.72–
6.43 (m, 23H), 5.61–5.56 (m, 8H), 5.44–5.40 (m, 2H), 5.00 (s, 8H), 4.96
(s, 4H), 4.43 (d, J=2.2 Hz, 2H), 4.29 (d, J=5.5 Hz, 2H), 4.25 (s, 2H),
4.04–3.94 (m, 50H), 1.13 ppm (s, 9H); HRMS (ESI): m/z calcd for [(G2-
calcd for [(G2-G2/G2)
for [(G2-G2/G2)
(PF6)]4+: 946.1529; found: 946.1552; [(G2-G2/G2)]5+
727.9295; found: 727.9299.
(PF6)2]3+: 1309.8587; found: 1309.8571; m/z calcd
ACHTUNGTRENNUNG
N
:
G0/G0)
G0)
(PF6)2]3+: 995.6907; found: 995.6914; m/z calcd for [(G2-G0/G0)-
(PF6)]4+: 628.0268; found: 628.0270.
Synthesis of [2]rotaxane [G2-G1][PF6]5 and [3]rotaxane [G2-G1/G1]-
[PF6]5: Compound [PF6]4 (0.061 g, 0.072 mmol) and G1-DB24C8
ACHTUNGTRENNUNG
(PF6)3]2+: 1401.0184; found: 1401.0177; m/z calcd for [(G2-G0/
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Acknowledgements
A
3ACHTUNGTRENNUNG
(0.121 g, 0.155 mmol) were dissolved in MeNO2 (20 mL) and stirred for
5 min. Bromomethyl-G2 (0.127 g, 0.157 mmol), a catalytic amount of
TBAI (10 mg), water (15 mL), CH2Cl2 (2 mL), and NH4PF6 (aq) (1 mL)
were added and the two-layer reaction stirred at room temperature for
21 d. The organic layer was separated, washed with water (2ꢄ50 mL),
dried (anhydrous MgSO4), concentrated (2 mL), and precipitated from
solution with diethyl ether (3ꢄ40 mL). The red/orange precipitate was
collected through Celite and subjected to column chromatography (SiO2;
0.025m NH4PF6 in MeCN/CH2Cl2, 7:3 to 3:2). Like fractions (as deter-
mined by NMR) were collected, anion exchanged (NH4PF6), and precipi-
tated from MeNO2 by slow diffusion of isopropyl ether to yield [G2-G1]-
S.J.L. is grateful to the NSERC of Canada for awarding of a Discovery
Grant in support of this research.
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A
ACHTUNGTRENNUNG[PF6]5 as red/orange glassy solids in 10% overall
ACHTUNGTRENNUNG
9.21 (brs, 4H), 8.92 (brs, 2H), 8.80 (m, 2H), 8.64 (brs, 2H), 8.22–7.99
(m, 10H), 7.38–7.30 (m, 30H), 6.69–6.47 (m, 19H), 5.59 (s, 2H), 5.52
(brs, 4H), 5.21–5.13 (m, 4H), 5.03–4.99 (m, 16H), 4.28 (s, 2H), 4.11–3.87
(m, 26H), 1.37 ppm (brs, 9H); HRMS (ESI): m/z calcd for [(G2-G1)-
A
N
:
766.9634; found: 766.9647; m/z calcd for [(G2-G1)CAHTUNGTRENNUNG
ACHTUNGTRENNUNG
(d, 3J=6.5 Hz, 2H), 9.28 (d, 3J=6.7 Hz, 2H), 9.26 (d, 3J=6.7 Hz, 2H),
8.91 (d, 3J=6.7 Hz, 2H), 8.75 (d, 3J=6.4 Hz, 2H), 7.94–7.92 (m, 4H),
7.90–7.86 (m, 4H), 7.72 (d, 3J=6.7 Hz, 2H), 7.40–7.29 (m, 40H), 6.74–
6.44 (m, 29H), 5.61–5.56 (m, 8H), 5.44–5.40 (m, 2H), 5.02 (s, 4H), 5.01
(s, 4H), 5.00 (s, 8H), 4.96 (s, 4H), 4.43 (d, J=2.0 Hz, 2H), 4.29 (d, J=
5.9 Hz, 2H), 4.25 (s, 2H), 4.06–3.93 (m, 50H), 1.14 ppm (s, 9H); HRMS
(ESI): m/z calcd for [(G2-G1/G1)
m/z calcd for [(G2-G1/G1)
(PF6)2]3+: 1027.0804; found: 1027.0823; m/z
calcd for [(G2-G1/G1)
(PF6)]4+: 734.0692; found: 734.0714.
Synthesis of [2]rotaxane [G2-G2][PF6]5 and [3]rotaxane [G2-G2/G2]-
[PF6]5: Compound [PF6]4 (0.049 g, 0.058 mmol) and G2-DB24C8
(0.137 g, 0.114 mmol) were dissolved in MeNO2 (20 mL) and stirred for
(PF6)3]2+: 1613.1027; found: 1613.0958;
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
3ACHTUNGTRENNUNG
Chem. Eur. J. 2010, 16, 4466 – 4476
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4475

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Received: November 18, 2009
Published online: March 29, 2010
4476
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 4466 – 4476