Versatile formation of [2]catenane and [2]pseudorotaxane structures; threading and noncovalent stoppering by a self-assembled macrocycle

Article abstract of DOI:10.1021/ol036127l

(Equation presented) A self-assembled dimeric macrocycle between 4,4′-bis(4-pyridylmethoxy)biphenyl (L) and (en)Pd(NO₃) ₂ was constructed, and its interactions with cyclodextrins of different cavity size resulted in the formation of [2]catenane and [2]pseudorotaxane systems, respectively. The structures were identified by 1D and 2D NMR spectroscopy and cold spray ionization mass (CSI-MS) spectrometry.

Full text of DOI:10.1021/ol036127l

ORGANIC
LETTERS
2004
Vol. 6, No. 7
1079-1082
Versatile Formation of [2]Catenane and
[2]Pseudorotaxane Structures;
Threading and Noncovalent Stoppering
by a Self-Assembled Macrocycle
,†,§
Choon Woo Lim,† Shigeru Sakamoto,‡ Kentaro Yamaguchi,‡ and Jong-In Hong*
Department of Chemistry, College of Natural Sciences, Seoul National UniVersity,
Seoul 151-747, Korea, Chemical Analysis Center, Chiba UniVersity,
Inageku, Chiba 263-8522, Japan, and Center for Molecular Design and Synthesis,
KAIST, Daejon 305-701, Korea
jihong@plaza.snu.ac.kr
Received October 31, 2003
ABSTRACT
A self-assembled dimeric macrocycle between 4,4′-bis(4-pyridylmethoxy)biphenyl (L) and (en)Pd(NO ) was constructed, and its interactions
3 2
with cyclodextrins of different cavity size resulted in the formation of [2]catenane and [2]pseudorotaxane systems, respectively. The structures
were identified by 1D and 2D NMR spectroscopy and cold spray ionization mass (CSI-MS) spectrometry.
Recently, linear motors such as myosin and kinesin and
rotary motors such as bacterial flagellum and F1-ATPase have
come to be recognized as distinctive examples of molecular
motors found in biological systems.1 Supramolecular chem-
istry has been extensively applied to mimic molecular devices
in biological systems by aiding the creation of interlocked
molecules with precise structures in high yields. Interlocked
molecules2 such as catenanes,3 rotaxanes,4 and knots5 have
been studied as potential candidates for molecular devices,
and there have been extensive synthetic approaches directed
toward the development of molecular devices. Herein we
report on new controllable systems that are composed of â-
(2) (a) Schill, G. Catenanes, Rotaxanes, and Knots; Academic: New
York, 1971. (b) Cram, D. J.; Cram, J. M. In Container Molecules and their
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G.; Vance, A. L.; Busch, D. H. AdV. Supramol. Chem. 1999, 5, 237. (e)
Molecular Catenanes, Rotaxanes and Knots; Sauvage, J.-P., Dietrich-
Buchecker, C., Eds.; VCH-Wiley: Weinheim, 1999.
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120, 2297. (b) Brouwer, A. M.; Frochot, C.; Gatti, F. G.; Leigh, D. A.;
Mottier, L.; Paolucci, F.; Roffia, S.; Wurpel, G. W. H. Science 2001, 291,
2124. (c) Kawaguchi, Y.; Harada, A. J. Am. Chem. Soc. 2000, 122, 3797.
† Seoul National University.
‡ Chiba University.
§ KAIST.
(1) (a) Special Issues-Movement: Molecular to Robotic. Science 2000,
288, 79. (b) Howard, J. Nature 1997, 389, 561. (c) Mooseker, M. S.; Cheney,
R. E. Annu. ReV. Cell DeV. Biol. 1995, 11, 633. (d) Barton, N. R.; Goldstein,
L. S. B. Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 1735. (e) Rayment, I.;
Holden, H. M.; Whittaker, M.; Yohn, C.; Lorenz, M.; Holmes, K. C.;
Milligan, R. A. Science 1993, 261, 58. (f) Noji, H.; Yasuda, R.; Yoshida,
M.; Kinosita, K., Jr. Nature 1997, 386, 299. (e) Allison, W. S. Acc. Chem.
Res. 1998, 31, 819.
10.1021/ol036127l CCC: $27.50 © 2004 American Chemical Society
Published on Web 03/04/2004

or γ-cyclodextrin (CD) and a macrocyclic complex (M) self-
assembled by L and Pd(en) moieties. Depending on the
cavity size of the CDs, this controllable system produces
either rotaxane or catenane structures. Whereas the combina-
tion of â-CD and M leads to the formation of a [2]catenane
structure, the combination of γ-CD and M results in a novel
pseudorotaxane structure. As one component of the system,
M was prepared by treating L with (en)Pd(NO3)2 as shown
in Scheme 1.6
Scheme 1 a
1
Figure 1. Concentration-dependent H NMR spectra (500 MHz)
of M in D2O: (a) 4, (b) 2, (c) 1, (d) 0.3, and (e) 0.1 mM. See
Scheme 1 for proton labeling.
trometry (CSI-MS). The CSI-MS spectrum shows fragments
of the dinuclear Pd complex M (Figure 2).8
a (a) 60% NaH, DMF; (b) 4-(chloromethyl)pyridine hydrochlo-
ride, DMF; (c) (en)Pd(NO3)2, MeOH/H2O.
Because several self-assembled systems constructed by Pd-
(II) ions and ligand molecules having pyridine moieties in
D2O have shown guest-induced or concentration-dependent
1
reorganization behavior,7 we performed H NMR measure-
ments at various concentrations in D2O to investigate the
structure of M as a function of the concentration. Self-
assembly of L and (en)Pd(NO3)2 showed concentration-
1
dependent behavior as expected. H NMR spectra (Figure
1a) revealed the self-assembled structures of oligomers or
multicomponents at relatively high concentrations (>2 mM).
Lowering the concentration gradually led to single sets of
Figure 2. CSI-MS spectrum of the dinuclear Pd(II) complex M.
1
signals in H NMR spectra, which are presumably derived
from a dimeric structure (M). At concentrations lower than
1 mM, 1H NMR spectra (Figure 1d,e) revealed the formation
of a self-assembled dimeric structure as a dominant species,
which was confirmed by cold spray ionization mass spec-
It has been known for many years that the cavity of γ-CD
is sufficiently large to contain two aromatic residues
simultaneously.9 Therefore, we expected that the formation
of a [2]pseudorotaxane would be possible upon addition of
γ-CD to M (Scheme 2). Subsequently, the quantitative
formation of a rotaxane-like structure between M and γ-CD
was observed in the H NMR spectra (Figure 3). The H
NMR spectrum clearly shows one set of newly emerging
signals for the rotaxane-like structure (Figure 3b-e), which
indicates that the equilibrium kinetics between pseudoro-
(5) (a) Rapenne, G.; Dietrich-Buchecker, C. O.; Sauvage, J.-P. J. Am.
Chem. Soc. 1999, 121, 994. (b) Ashton, P. R.; Matthews, O. A.; Menzer,
S.; Raymo, F. M.; Spencer, N.; Stoddart, J. F.; Williams, D. J. Liebigs Ann.
Chem. 1997, 2485. (c) Meyer, M.; Albrecht-Gary, A. M.; Dietrich-
Buchecker, C. O.; Sauvage, J.-P. J. Am. Chem. Soc. 1997, 119, 4599.
(6) The macrocyclic Pd(II) complexes were prepared by mixing the
complex (en)Pd(NO3)2 in H2O and equimolar amounts of L in MeOH,
followed by the removal of solvents.
(7) (a) Fujita, M.; Sasaki, O.; Mitsuhashi, T.; Fujita, T.; Yazaki, J.;
Yamaguichi, K.; Ogura, K. Chem. Commun. 1996, 1635. (b) Lee, S. B.;
Hwang, S.; Chung, D. S.; Yun, H.; Hong, J.-I. Tetrahedron Lett. 1998, 39,
873. (c) Ma, G.; Jung, Y. S.; Chung, D. S.; Hong, J.-I. Tetrahedron Lett.
1999, 40, 531.
1
1
(8) M is dissolved in aqueous DMF solution.
(9) Kobayashi, N.; Ueno, A.; Osa, T. J. Chem. Soc., Chem. Commun.
1981, 340.
1080
Org. Lett., Vol. 6, No. 7, 2004

diaminocyclohexane) was used instead of ethylenediamine
(en) on the Pd center to prevent the circumrotation of γ-CD.
If the spectrum due to 2:2:1 assembly of (1,2-diamino-
cyclohexane)Pd(NO3)2, L, and γ-CD is different from that
of 2:2:1 assembly of (en)Pd(NO3)2, L, and γ-CD, the self-
assembled structure between M and γ-CD would be a
catenane. However, if both spectra remain the same, the self-
assembled structure would be a rotaxane. We observed
Scheme 2
1
exactly the same H NMR spectrum as in the case of the
formation of an interlocked molecule by use of a Pd(en)
moiety.10 This indicates that the self-assembly of M and
γ-CD should generate a rotaxane as shown in Scheme 2.
Analysis of 2D ROESY spectra of the self-assembled
structure10 also clearly shows that the biphenyl groups of M
are included in the cavity of γ-CD, in which the cross-peaks
arise from intercomponent through-space correlations be-
tween the biphenyl protons (Ha and Hb) and the inner cavity
protons of γ-CD (H-3 and H-5). The stoichiometry of the
rotaxane-like structure is shown to be 1:1, from the relative
integration ratio of the protons of M to those of γ-CD (H-
1). The formation of this rotaxane-like structure was also
supported by the CSI-MS spectrum.8 The isotope patterns
correspond to the related molecular ions (Figure 5b).10
However, excimer emission peaks expected from the two
biphenyl moieties inside the γ-CD cavity cannot be clearly
located because of the spectral overlap with the Pd(II)
emission peak in the same region. It is known that most
rotaxanes have been constructed by the combination of a
single rod and macrocycles. We believe that this is the first
example of a dual rod-threaded [2]pseudorotaxane (similar
to a ring-in-ring complex)11a-d formed by the self-assembly
of the macrocyclic complex M and γ-CD in D2O in which
the dual rod12 derives from M and Pd(en) moieties. Although
the Pd(II) complexes prepared at 2 mM concentrations exist
not as a single dimeric species (M) but as oligomers or
multicomponents, addition of γ-CD to the 1:1 mixture of L
and (en)Pd(NO3)2 at 2 mM concentration led to the spon-
taneous and quantitative formation of a rotaxane-like
structure.11e-g As the amount of γ-CD increases, the newly
1
taxane and free ring M are slow, at 500 MHz, on the H
NMR time scale.
Figure 3. 1H NMR spectra (500 MHz) showing the formation of
a pseudorotaxane (V) by the addition of γ-CD to M (b, 0.3 mM) in
D2O, according to the equivalents of γ-CD added: (a) 0, (b) 0.6,
(c) 1.2, (d) 1.8, and (e) 2.8 equiv.
1
In the H NMR spectra, the signals corresponding to the
new components appear upfield under the influence of the
chiral γ-CD ring, indicating that both biphenyl moieties are
accommodated in the cavity of γ-CD and interact with each
other. However, since the large cavity of γ-CD might enable
γ-CD to circumrotate along the macrocycle ring M without
interfering with a Pd(en) moiety, the formation of catenanes
could also be expected as in the case of â-CD (Scheme 2).
To examine the possibility of a catenane formation in the
self-assembly of M and γ-CD, a bulky ancillary ligand (1,2-
Figure 4. 1H NMR spectra (500 MHz) showing the formation of
[2]catenane structure by the addition of â-CD to M (V, 0.5 mM) in
D2O, according to the equivalents of â-CD added: (a) 2, (b) 8,
and (c) 20 equiv.
Org. Lett., Vol. 6, No. 7, 2004
1081

0.3 mM concentrations (Figure 3), indicating the specific
formation of a γ-CD-based [2]pseudorotaxane.10
The cavity of â-CD is structured to accommodate only
one biphenyl group. Therefore, the formation of a catenane
structure was observed, as shown in Scheme 2. When 2 equiv
of â-CD was added to a solution of M in D2O (0.5 mM)
(Figure 4a), signals of a new component, which was expected
1
to be the [2]catenane structure, began to appear in the H
NMR spectrum. With an increase of the molar concentration
of â-CD, complicated signals of a new component were
observed. Because the (en)Pd moiety region of a macrocycle
prevents the circumrotation of â-CD along the macrocycle
ring M, the signals of M in the inside cavity of â-CD become
magnetically nonequivalent to the signals in the outside
cavity upon the formation of a catenane structure, which
1
results in four different sets of signals in the H NMR
spectrum of a catenated macrocycle.
The structure of [2]catenane in solution was confirmed
from HH COSY and NOE studies.10 The formation of the
[2]catenane structure was also supported by the CSI-MS
spectrum.8 The isotope patterns correspond to the related
molecular ions (Figure 5a).10
In both [2]pseudorotaxane and [2]catenane structures, the
movement of CDs around the Pd(II) center seems to have a
high energy barrier due to electrostatic and steric criteria.
In summary, we have demonstrated that the self-assembly
of the macrocyclic ring M and γ-CD or â-CD in D2O results
in the formation of [2]pseudorotaxane and [2]catenane
structures, respectively, depending on the cavity size of CDs.
Extension of this work toward the development of poly-
rotaxanes and switching devices using the rotaxane structure
as new scaffolds is underway.
Figure 5. CSI-MS spectrum of (a) [2]catenane and (b) [2]-
pseudorotaxane by the self-assembly of M and â-CD or γ-CD,
respectively.
Acknowledgment. Financial support from the MOST
(Grant M10213030002-03B1503-00210) is gratefully ac-
knowledged. C.W.L. thanks the Ministry of Education for
the award of a BK 21 fellowship.
manifested signals of the 1H NMR spectra correspond to the
same signals as those of the H NMR spectra observed at
1
(10) Spectral data can be found in Supporting Information.
(11) (a) Chiu, S.-H.; Pease, A. P.; Stoddart, J. F.; White, A. J. P.;
Williams, D. J. Angew. Chem., Int. Ed. 2002, 41, 270. (b) Schmittel, M.;
Ganz, A.; Fenske, D. Org. Lett. 2002, 4, 2289. (c) Kim, S.-Y.; Jung, L.-S.;
Lee, E.; Kim, J.; Sakamoto, S.; Yamaguchi, K.; Kim, K. Angew. Chem.,
Int. Ed. 2002, 41, 270. (d) Jeppesen, J. O.; Vignon, S. A.; Stoddart, J. F.
Chem. Eur. J. 2003, 9, 4611. (e) Ballardini, R.; Balzani, V.; Di Fabio, A.;
Gandolfi, M. T.; Becher, J.; Lau, J.; Nielson, M. B.; Stoddart, J. F. New J.
Chem. 2001, 25, 293. (f) McArdle, C. P.; Vittal, J. J.; Puddephatt, R. J.
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Supporting Information Available: Selected spectral
data (1H NMR, HH COSY, 2D ROESY, 2D NOESY, 1D
NOE, and CSI-MS spectra) for compounds M, [2]catenane,
and [2]pseudorotaxane structures, and 1H NMR spectra upon
addition of γ-CD to the 1:1 mixture of L and (en)Pd(NO3)2
or (1,2-diaminocyclohexane)Pd(NO3)2 at 2 and 0.1 mM
concentrations, respectively. This material is available free
of charge via the Internet at http://pubs.acs.org.
(12) (a) Harada, A.; Li, J.; Kamachi, M. Nature 1994, 370, 126. (b)
Wylie, R. S.; Macartney, D. H. J. Am. Chem. Soc. 1992, 114, 3136. (c)
Rao, T. V.; Lawrence, D. S. J. Am. Chem. Soc. 1990, 112. 2440.
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