Separated and Aligned Molecular Fibres in Solid State Self-Assemblies of Cyclodextrin [2]Rotaxanes

Article abstract of DOI:10.1002/chem.200305279

The conformations of two [2]rotaxanes, each comprising α -cyclodextrin as the rotor, a stilbene as the axle and 2,4,6-trinitrophenyl substituents as the capping groups, have been examined in solution and in the solid state, using ¹H NMR spectroscopy and X-ray crystallography, respectively. In solution, introducing substituents onto the stilbene prevents the cyclodextrin from being localized over one end of the axle. Instead the cyclodextrin moves back and forth along the substituted stilbene. In the solid state, the axles of the rotaxanes form extended molecular fibres that are separated from each other and aligned along a single axis. The molecular fibres are strikingly similar to those formed by the axle component of one of the rotaxanes in the absence of the cyclodextrin, but in the latter case they are neither separated nor all aligned.

Full text of DOI:10.1002/chem.200305279

C. J. Easton et al.
5971
Chem. Eur. J. 2003, 9, 5971 5977
DOI: 10.1002/chem.200305279
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

FULL PAPER
Separated and Aligned Molecular Fibres in Solid State Self-Assemblies of
Cyclodextrin [2]Rotaxanes
Hideki Onagi,[a] Benedetta Carrozzini,[b] Giovanni L. Cascarano,[b]
[c]
Christopher J. Easton,*[a] Alison J. Edwards,[a] Stephen F. Lincoln, and A. David Rae[a]
Abstract: The conformations of two
[2]rotaxanes, eachcomprising a-cyclo-
dextrin as the rotor, a stilbene as the
axle and 2,4,6-trinitrophenyl substitu-
ents as the capping groups, have been
examined in solution and in the solid
from being localized over one end of
the axle. Instead the cyclodextrin
moves back and forthalong the substi-
tuted stilbene. In the solid state, the
axles of the rotaxanes form extended
molecular fibres that are separated
from eachother and aligned along a
single axis. The molecular fibres are
strikingly similar to those formed by
the axle component of one of the ro-
taxanes in the absence of the cyclodex-
trin, but in the latter case they are nei-
ther separated nor all aligned.
Keywords: cyclodextrins
¥
¥
1
state, using H NMR spectroscopy and
nanostructures
self-assembly
chemistry
¥
rotaxanes
X-ray crystallography, respectively. In
solution, introducing substituents onto
the stilbene prevents the cyclodextrin
¥
supramolecular
Introduction
phy has been used to examine the structures of several cate-
18]
26]
nanes,[8,14
rotaxanes,[8,19
pseudorotaxanes and pseudo-
31]
Supramolecular chemistry is a key aspect of the growing in-
terest in nanotechnology, and the associated development of
nanomaterials, molecular machines and microelectronic de-
polyrotaxanes.[18,27
Cyclodextrins are particularly versatile building blocks
for supramolecular chemistry, since they occur naturally in a
vices.[1 It provides access to novel and complex structures,
range of sizes and are readily modified.[32,33] Many cyclodex-
7]
38]
and allows for the prefabrication of molecular entities. In
this regard, rotaxanes and catenanes are of particular inter-
est since they comprise multiple species that are physically
trin-based rotaxanes have been synthesized,[34
and a
number of crystal structures of cyclodextrin inclusion com-
plexes have been reported,[39] but to the best of our knowl-
edge there have been only two reports of crystal structures
of cyclodextrin pseudopolyrotaxanes[40,41] and one of a cyclo-
dextrin [2]rotaxane.[42] Previously we reported the synthesis
of the rotaxane 1a and an analysis of its conformation in
solution.[43] In order to manipulate the conformation, we
have now modified the stilbene moiety and synthesized the
dimethoxystilbene derivative 1b. We have also examined
the solid-state structures of both the rotaxanes 1a and 1b,
as well as that of the dumbbell component 2a of the former,
in order to explore the effects of cyclodextrin complexation
and guest modification on self-assembly.
inter-locked and unable to dissociate.[8 For the full poten-
12]
tial of suchsupramolecular species to be realised, it will be
necessary to understand and be able to control their self-as-
sembly in the solid state.[13] To this end, X-ray crystallogra-
[a] Prof. C. J. Easton, Dr. H. Onagi, Dr. A. J. Edwards, Prof. A. D. Rae
Research School of Chemistry, Institute of Advanced Studies
Australian National University
Canberra ACT 0200 (Australia)
Fax : (+61)2-6125-8114
E-mail: easton@rsc.anu.edu.au
[b] Dr. B. Carrozzini, Dr. G. L. Cascarano
ICCNR, c/o Dipartimento Geomineralogico, Universit‡ di Bari
Campus Universitario
Results and Discussion
Via Orabona 4, 70125 Bari (Italy)
[c] Prof. S. F. Lincoln
In our previous report, the yield of the rotaxane 1a was
given as 10%.[43] This has now been increased to 79%,
mainly by improving the isolation procedure. The conforma-
Department of Chemistry, University of Adelaide
Adelaide, SA 5005 (Australia)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
1
tion of 1a was determined using a variety of H NMR ex-
5972
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/chem.200305279
Chem. Eur. J. 2003, 9, 5971 5977

5971 5977
material revealed a single component, showing the charac-
teristic ultraviolet absorbance of the dumbbell, and pink col-
ouration of a cyclodextrin on exposure to acidic naphtha-
lene-1,3-diol. The deprotonated molecular ion of the prod-
uct was found at m/z 1663 by ESI-MS operated in the nega-
tive ion mode. These data clearly show that the isolated ma-
terial is the mechanically interlocked molecule 1b.
The conformation of the rotaxane 1b was determined by
employing 2D DQF-COSY and ROESY experiments, as
outlined previously for the rotaxane 1a.[43] As found for 1a,
with 1b the simplicity of the resonances of the cyclodextrin
protons in the 1D NMR spectrum shows that the cyclodex-
trin is freely rotating around the stilbene moiety. Figure 1b
is a portion of the ROESY spectrum, which shows that,
unlike the case with the rotaxane 1a, the cyclodextrin of the
dimethoxy-substituted rotaxane 1b is not localized over one
periments, and is illustrated in
Figure 1a together with a por-
tion of the key ROESY NMR
spectrum. Withtihs rotaxane,
the cyclodextrin is freely rotat-
ing around, but localized over,
one end of the stilbene moiety.
The free rotation is evident
from the simplicity of the reso-
nances of the cyclodextrin pro-
tons, and the localization is ap-
parent through the observation
of NOEs between the cyclodex-
trin protons and protons H(1)
H(5) of the stilbene, and the
absence of any NOE between
stilbene protons H(6) and the
cyclodextrin protons.
It was considered that incor-
poration of
a substituent in
place of a stilbene H(1) proton
would alter the conformation,
due to buttressing between the
substituent and the rim of sec-
ondary hydroxy groups of the
cyclodextrin. To examine this,
the rotaxane 1b was prepared
as outlined in Scheme 1. A mix-
ture of the stilbene 6 and a-cy-
clodextrin, in aqueous buffer at
room temperature and pH 10,
was allowed to equilibrate for
2 h. 2,4,6-Trinitrobenzene-1-sul-
fonate (7) was then added and
the mixture was stirred for a
further 10 h. The crude product
mixture was subjected to
a
Diaion HP-20 column to isolate
the rotaxane 1b, which was ob-
tained in 27% yield as an
Figure 1. Resonance assignments and portions of the 500 MHz ROESY NMR spectra recorded in [D4]-metha-
orange powder. TLC of this nol witha mixing time of 250 ms for a) the rotaxane 1a and b) the rotaxane 1b.
5973
Chem. Eur. J. 2003, 9, 5971 5977 www.chemeurj.org ¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

C. J. Easton et al.
FULL PAPER
rotaxane 1b appear to affect its conformation in solution, in-
creasing the mobility of the cyclodextrin along the stilbene
axle.
The solid-state structures of the rotaxanes 1a and b were
also examined, through X-ray crystallographic analysis. For
comparison, the solid-state structure of the stilbene deriva-
tive 2a was also determined. The dumbbell 2a had been
prepared, in 85% yield, through reaction of 4,4’-diaminostil-
bene with2,4,6-trinitrobenzene-1-sulfonate ( 7).[43] In a simi-
lar manner, the dimethoxy-substituted dumbbell 2b was ob-
tained from the dimethoxystilbene 6. However, repeated at-
tempts to obtain crystals of the dumbbell 2b suitable for
analysis were not successful. Crystals of the analogue 2a
were obtained from N,N-dimethylformamide. Crystals of
eachof the rotaxanes 1a and b were also prepared, by slow
diffusion of methanol into saturated aqueous solutions, in
sealed containers.
The crystallographic analysis of compounds 1a, 1b and
2a was not straightforward and the procedures that were
used are described in the Supporting Information. The struc-
tures thus determined are illustrated in Figure 2. Across all
three structures there is a remarkable similarity in the mode
of packing of the substituted stilbenes. This packing is domi-
nated by a chain-like motif as shown in Figure 3. Each of
the chains is inherently centrosymmetric. In the case of the
dumbbell 2a, eachmolecule is located about a crystallo-
graphic centre of inversion and adjacent molecules are like-
wise crystallographically related. In the rotaxanes 1a and
1b, the presence of the cyclodextrin precludes the occur-
rence of crystallographic centres of inversion. Nevertheless,
the centrosymmetric relationship within the chains holds lo-
cally and is strictly followed.
Scheme 1.
The chains in the dumbbell 2a are formed by molecules
1
3
end of the stilbene. Instead, the NOE cross-peaks indicate
that the cyclodextrin is moving on the NMR time-scale,
back-and-forth on the axle, from one end of the stilbene to
the other. This accounts for the observation of: i) NOE
cross-peaks between eachof teh stilbene protons and at
least one type of the interior cyclodextrin-C3, C5 and C6
protons; ii) interactions of many of the stilbene protons with
more than one type of cyclodextrin proton; and iii) NOEs
between the cyclodextrin C6-HA protons and H(4) H(6) of
the stilbene. The latter and their similar intensities in partic-
ular show that the cyclodextrin must be mobile, otherwise
the H(4) H(6) stilbene protons are too far apart to show
NOEs withone type of cyclodextrin proton, given the in-
verse-dependence of NOE intensity on the sixth power of
the distance between interacting protons.[44] This argument
is based on the assumption that the axis delineated by the 4-
and 4’-carbons of the stilbene is close to parallel to the C6
axis of symmetry of the cyclodextrin. In principle, the NOEs
observed, including those between the cyclodextrin C6-HA
protons and H(4) H(6) of the stilbene, could be explained if
these axes were substantially out of alignment. Then the stil-
bene H(4), H(5) and H(6) protons could eachrotate in a
circle at a similar distance from the cyclodextrin C6-HA pro-
tons. However, sucha deviation of the axes from parallel is
very unlikely considering the sizes and shapes of the cyclo-
dextrin and stilbene. Thus the methoxy substituents of the
related by the translation = +x, = +y, z, and these chains
2 2
then pack alongside equivalent chains to form layers lying
parallel to the ab plane of the unit cell. Alternate layers are
rotated about the crystallographic two-fold axis so that
chains in adjacent layers are not parallel. By contrast, the
chains formed from the rotaxanes 1a and 1b are separated
from each other and all aligned parallel, along the crystallo-
graphic b axis. In the case of the rotaxane 1a, the two crys-
tallographically independent but quite similar conformations
of the dumbbell component found in the asymmetric unit al-
ternate along each chain. The cyclodextrins form head-to-
head/tail-to-tail and head-to-tail/tail-to-head hydrogen-
bonded columnar networks in the rotaxanes 1a and 1b, re-
spectively. Eachaccommodates the chains of aligned and
separated dumbbell components.
In summary, comparison with the structure of the stil-
bene derivative 2a indicates that in the solid state the cyclo-
dextrins of the rotaxanes 1a and 1b align and separate the
chains formed by the dumbbell components. They do so
without substantially altering the conformations of the
dumbbell components or their intermolecular interactions
along the chains. The result is self-assembled structures that
resemble co-axial cables, withthe cyclodextrins insulating
but not otherwise affecting molecular fibres formed by the
axles. Although the properties of the rotaxanes 1a and 1b
as electrical conductors have not yet been examined, in
5974
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 5971 5977

Molecular Fibres
5971 5977
analogous systems, Cacialli and co-workers[45] have recently
demonstrated the insulating properties of the cyclodextrins
of b-cyclodextrin-poly(p-phenylene) polyrotaxanes, to pre-
serve the semiconducting properties of the p-phenylene pol-
ymer in the solid state. This supports speculation that such
species might one day find applications in new-generation
microelectronics.
Experimental Section
General: 1H NMR spectra were recorded at 500 MHz using a Varian
Inova 500 spectrometer or at 300 MHz using a Varian Mercury 300 spec-
trometer, and 13C NMR spectra were recorded at 75.5 MHz using a
1
Varian Inova 300 spectrometer. Rotating frame H,1H nuclear overhauser
effect spectroscopy (ROESY) was performed witha mixing time of
250 ms. [D4]Methanol with an isotopic purity of 99.8% and [D6]DMSO
withan isotopic purity of 99.9% were purchased from Cambridge Iso-
1
tope Laboratories Inc., MA., and were referenced to d=3.31 for H and
49.15 for 13C (CD3OD) and d=2.50 for 1H ([D6]DMSO) withrespect to
the resonance of Me4Si. Electrospray ionization (ESI) mass spectrometry
was carried out witha Micromass VG Quattro II mass spectrometer.
Thin-layer chromatography (TLC) was performed on Kieselgel 60 F254
coated plates (Merck). Developed plates were visualized by UV light
and/or dipping the plate into a solution of 0.1% naphthalene-1,3-diol in
ethanol/water/H2SO4 200:157:43, followed by heating with a heat-gun. El-
emental analyses were performed by the Australian National University
Microanalytical Service. Melting points were performed on a Reichert
hot-stage apparatus and are uncorrected.
a-Cyclodextrin was the generous gift of Nihon Shokuhin Kako Co.,
Japan. It was recrystallized from water and dried in vacuo over P2O5 to
constant weight before use. 2,4,6-Trinitrobenzene-1-sulfonic acid sodium
salt dihydrate (TNBS) (7) was purchased from Tokyo Kasei. 5-Methyl-2-
nitrophenol (3) was purchased from Aldrich Chemical Company. Diaion
HP-20 resin was purchased from Supelco, PA, USA.
[(E)-4,4’-Bis(2,4,6-trinitrophenylamino)stilbene]-[a-cyclodextrin]-[rotax-
ane] (1a): The [2]rotaxane 1a was prepared as reported previously[43]
except that the crude product was dissolved in water and the solution
was loaded onto a Diaion HP-20 column (310î25 mm). The column was
flushed with water until no more unreacted a-cyclodextrin was detected
Figure 2. Solid-state structures of a) the dumbbell 2a, and b) and c) the
rotaxanes 1a and 1b, respectively, where the trinitrophenylamino-substi-
tuted stilbenes are represented by spheres and the cyclodextrins by lines.
Figure 3. The chain-like motif formed by the trinitrophenylamino-substituted stilbenes in the solid state structures of a) the dumbbell 2a, and b) and
c) the rotaxanes 1a and 1b, respectively.
5975
Chem. Eur. J. 2003, 9, 5971 5977
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

C. J. Easton et al.
FULL PAPER
in the eluent by TLC (ca. 2.5 dm3). The column was then eluted with a
water/methanol gradient. The rotaxane 1a was obtained when the
column was eluted with 50 70% methanol. The fractions containing this
material were concentrated under reduced pressure and the residue was
lyophilized to give a red powder in 79% yield, with physical and spectro-
nances), 61.8, 57.5, 57.4; MS (ESI, Àve): m/z: 1663 [MÀH+]; elemental
analysis calcd (%): for C64H80N8O44¥5H2O: C 44.24, H 5.11, N 6.45, found
C 44.29, H 5.24, N 6.42.
Crystallographic analysis of the rotaxanes 1a and 1b, and the dumbbell
2a: Crystals of the rotaxanes 1a and 1b suitable for single crystal X-ray
diffraction studies were grown by slow diffusion of methanol into saturat-
ed aqueous solutions. Those of the dimethoxystilbene derivative 1b were
of a remarkably uniform tetrahedral morphology and size. Crystals of the
dumbbell 2a[43] were obtained from N,N-dimethylformamide. None of
the crystals was strongly diffracting. At the 3s level, 1a had less than
50% of reflections to 2V=458 observable, 1b had 70% observable to
2V=488 and 2a had 80% to 2V=468. Data were collected by means of
CCD images on a Nonius KappaCCD single crystal diffractometer,[48]
[43]
scopic properties consistent withthose reported previously.
3-Methoxy-4-nitrotoluene (4): Dimethyl sulfate (80 g, 0.63 mol) was
added to
a stirred mixture of 5-methyl-2-nitrophenol (3) (25.0 g,
0.16 mol) and potassium carbonate (36 g) in xylenes (100 mL) which was
heated under reflux. After 20 h at reflux, additional dimethyl sulfate
(25 g, 0.20 mol) was added. After a further 4 h at reflux, the mixture was
cooled and aqueous sodium hydroxide (0.75 molLÀ1, 1.0 L) was added.
The solvent was then removed by distillation. Water (100 mL) was added
to the residue and the solution was extracted with diethyl ether. The
ether extracts were dried over MgSO4 and concentrated under reduced
pressure to yield the toluene 4 as a tan solid (37.7 g, 72%). M.p. 58 618C
[lit.:[46] 618C]; 1H NMR (300 MHz, [D6]DMSO): d=7.76 (d, J = 8.2 Hz,
1H; ArH), 6.86 (s, 1H; ArH), 6.79 (d, J = 8.2 Hz, 1H; ArH), 3.92 (s,
3H; OMe), 2.39 (s, 3H; Me); MS (EI): m/z (%): 167 (100) [M +], 137
(22), 120 (72), 91 (37), 78 (15).
withMo
radiation (l=0.71073 ä), and extracted using routine meth-
Ka
ods,[49] before being corrected for absorption.[50] The principal crystallo-
graphic data are shown in Table 1. Procedures used to solve[51,52] and
refine[53] the structures are described in Supporting Information.
Table 1. Principal crystallographic data for the rotaxanes 1a and 1b and
the dumbbell 2a.
(E)-3,3’-Dimethoxy-4,4’-dinitrostilbene (5): A solution of the toluene 4
(3.0 g, 0.018 mol) in acetone (4.5 mL) was added to a stirred solution of
KOH (50 g) in methanol (150 mL) maintained at 108C. Oxygen was bub-
bled through the mixture while it was stirred at 108C for 2 h, then the
mixture was poured into water (500 mL). The resultant precipitate was
collected by filtration, and washed with water, then methanol and then
dichloromethane. The solid residue was recrystallized from chloroben-
zene to yield the stilbene 5 as a tan solid (1.5 g, 50%). M.p. 215 2408C
[lit.:[47] 190 2408C]; 1H NMR (300 MHz, [D6]DMSO): d=7.94 (d, J =
8.5 Hz, 2H; ArH), 7.59 (s, 2H), 7.58 (d, J = 1.5 Hz, 2H; ArH), 7.37 (dd,
J = 1.5 and 8.5 Hz, 2H; ArH), 3.99 (s, 6H; OMe); MS (EI): m/z (%):
330 (100) [M +], 300 (7), 175 (11), 165 (17), 152(7).
1a
1b
2a
formula
Mr
crystal system
space group
a [ä]
C62H76N8O42
1605.30
monoclinic
P21
13.4291(2)
17.6940(3)
35.7701(7)
95.0575(7)
8466.4(3)
4
C64H80N8O44
1665.36
monoclinic
P21
13.4266(5)
17.8128(8)
18.4482(7)
107.410(3)
4210.0(3)
2
C26H16N8O12¥2C3H7NO
778.66
monoclinic
C2/c
29.2792(6)
6.8221(2)
18.7367(6)
114.7760(11)
3398.1(3)
4
b [ä]
c [ä]
b [8]
V [ä3]
Z
(E)-4,4’-Diamino-3,3’-dimethoxystilbene (6): A mixture of the dinitrostil-
bene 5 (1.5 g, 9.0 mmol) and SnCl2 (7 g, 7.2 mmol) in conc. HCl (7 mL)
and acetic acid (6 mL) was heated at reflux for 4 h, then it was cooled,
and poured into ice-cold water (150 mL). The resultant precipitate was
collected by filtration. Recrystallization from ethanol yielded the stilbene
T [K]
200
125
200
CCDC-213579 (1a), -213578 (1b) and -213580 (2a) contain the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44)1223-336033; or deposit@ccdc.cam.uk).
1
6 as tan flakes (180 mg, 7.4%). M.p. 1578C [lit.:[47] 148 1508C]; H NMR
(300 MHz, [D6]DMSO): d=6.97 (d, J = 1.6 Hz, 2H; ArH), 6.81 (dd, J
= 1.6 and 8.2 Hz, 2H; ArH), 6.79 (s, 2H), 6.56 (d, J = 8.2 Hz, 2H;
ArH), 4.80 (s, 4H; NH2), 3.79 (s, 6H; OMe); MS (EI): m/z (%): 270
(100) [M +], 238 (6), 223 (8), 210 (7), 195 (8), 135 (7).
[(E)-4,4’-Bis(2,4,6-trinitrophenylamino)-3,3’-dimethoxystilbene]-[a-cyclo-
dextrin]-[rotaxane] (1b): A mixture of a-cyclodextrin (1.8 g, 1.85 mmol)
and the diaminostilbene
6 (100 mg, 0.37 mmol) in carbonate buffer
Acknowledgements
(0.2 molLÀ1, pH 10, 25 mL) was stirred at room temperature for 2 h.
TNBS 7 (260 mg, 0.74 mmol) was then added and the mixture was stirred
at room temperature for 10 h. The resulting dark red solution was
washed with ethyl acetate (5î25 mL), then it was concentrated under re-
duced pressure. The residue was dissolved in water (50 mL) and the solu-
tion was applied to a Diaion HP-20 column (310î25 mm). The column
was flushed with water until no more unreacted a-cyclodextrin was de-
tected in the eluent by TLC (ca. 2.5 L). The column was then eluted with
a water methanol gradient. The rotaxane 1b was obtained when the
column was eluted with 50 70% methanol. The fractions containing this
material were concentrated under reduced pressure and the residue was
lyophilized to give a red powder (165 mg, 27%), TLC (n-butanol/etha-
nol/H2O 5:4:3): Rf =0.65 (relative to the solvent front); 1H NMR
(500 MHz, CD3OD): d=9.09 (s, 2H; trinitrophenyl), 8.99 (s, 2H; trinitro-
phenyl), 7.85 (d, J = 8.5 Hz, 1H; stilbene), 7.44 (d, J = 8.5 Hz, 1H; stil-
bene), 7.28 (d, J = 8.5 Hz, 1H; stilbene), 7.24 (d, Jtrans = 16.0 Hz, 1H;
stilbene), 7.21 (d, J = 8.5 Hz, 1H; stilbene), 7.17 (s, 1H; stilbene), 7.08
This research was made possible through the generous support of the
Australian ResearchCouncil.
[1] J.-M. Lehn, Angew. Chem. 1988, 100, 91; Angew. Chem. Int. Ed.
Engl. 1988, 27, 89.
[2] J.-M. Lehn, Supramolecular Chemistry: Concepts and Perspectives,
VCH, Weinheim, Germany, 1995.
[3] M. C. T. Fyfe, J. F. Stoddart, Acc. Chem. Res. 1997, 30, 393.
[4] V. Balzani, A. Credi, F. M. Raymo, J. F. Stoddart, Angew. Chem.
2000, 112, 3484; Angew. Chem. Int. Ed. 2000, 39, 3348.
[5] V. Balzani, A. Credi, Chem. Rec. 2001, 1, 422.
[6] R. Ballardini, V. Balzani, A. Credi, M. T. Gandolfi, M. Venturi, Acc.
Chem. Res. 2001, 34, 445.
[7] J.-M. Lehn, Proc. Natl. Acad. Sci. USA 2002, 99, 4763.
[8] P. L. Anelli, P. R. Ashton, R. Ballardini, V. Balzani, M. Delgado,
M. T. Gandolfi, T. T. Goodnow, A. E. Kaifer, D. Philp, M. Pietrasz-
kiewicz, L. Prodi, M. V. Reddington, A. M. Z. Slawin, N. Spencer,
J. F. Stoddart, C. Vicent, D. J. Williams, J. Am. Chem. Soc. 1992, 114,
193.
[9] C. O. Dietrich-Buchecker, J. P. Sauvage, Chem. Rev. 1987, 87, 795.
[10] D. B. Amabilino, J. F. Stoddart, Chem. Rev. 1995, 95, 2725.
[11] J. P. Sauvage, Acc. Chem. Res. 1998, 31, 611.
(d, Jtrans = 16.0 Hz, 1H; stilbene), 6.72 (s, 1H; stilbene), 4.92 (d, J1,2
=
3.5 Hz, 6H; cyclodextrin-C1-H), 3.91 (apparent t, J = 9.5 Hz, 6H; cyclo-
dextrin-C3-H), 3.87 3.84 (m, 6H; cyclodextrin-C5-H), 3.87 (s, 3H;
OMe), 3.85 (s, 3H; OMe), 3.73 (m, 6H; cyclodextrin-C6-H), 3.61 (m,
6H; cyclodextrin-C6-H’), 3.58 (apparent t, J = 8.5 Hz, 6H; cyclodextrin-
C4-H), 3.44 (dd, J = 3.5 and 9.5 Hz, 6H; cyclodextrin-C2-H); 13C NMR
(75.5 MHz, CD3OD): d=153.9, 153.7 140.2, 140.0, 139.8, 139.6, 137.9,
137.1, 136.7, 136.6, 131.0, 129.5, 128.0, 127.5, 127.4, 127.2, 126.1, 124.3,
120.0, 117.9, 113.6, 113.5, 104.2, 83.3, 75.2, 74.0, 74.0 (two coincident reso-
[12] F. M. Raymo, J. F. Stoddart, Chem. Rev. 1999, 99, 1643.
5976
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 5971 5977

Molecular Fibres
5971 5977
[13] D. D. MacNicol, F. Toda, R. Bishop in Comprehensive Supramolec-
ular Chemistry, Vol. 6 (Series Eds.: J. L. Atwood, J. E. D. Davies,
D. D. MacNicol, F. Vˆgtle, J.-M. Lehn), Pergamon, Oxford, 1996.
[14] P. R. Ashton, C. L. Brown, E. J. T. Chrystal, T. T. Goodnow, A. E.
Kaifer, K. P. Parry, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, D. J.
Williams, Angew. Chem. 1991, 103, 1055; Angew. Chem. Int. Ed.
Engl. 1991, 30, 1039.
[15] P. R. Ashton, C. L. Brown, E. J. T. Chrystal, T. T. Goodnow, A. E.
Kaifer, K. P. Parry, D. Philp, A. M. Z. Slawin, N. Spencer, J. F. Stod-
dart, D. J. Williams, J. Chem. Soc. Chem. Commun. 1991, 634.
[16] F. Vˆgtle, W. M. M¸ller, U. M¸ller, M. Bauer, K. Rissanen, Angew.
Chem. 1993, 105, 1356; Angew. Chem. Int. Ed. Engl. 1993, 32, 1295.
[17] D. B. Amabilino, P. R. Ashton, M. S. Tolley, J. F. Stoddart, D. J. Wil-
liams, Angew. Chem. 1993, 105, 1358; Angew. Chem. Int. Ed. Engl.
1993, 32, 1297.
[18] M. Asakawa, P. R. Ashton, C. L. Brown, M. C. T. Fyfe, S. Menzer,
D. Pasini, C. Scheuer, N. Spencer, J. F. Stoddart, A. J. P. White, D. J.
Williams, Chem. Eur. J. 1997, 3, 1136.
[19] P. R. Ashton, M. Grognuz, A. M. Z. Slawin, J. F. Stoddart, D. J. Wil-
liams, Tetrahedron Lett. 1991, 32, 6235.
[20] A. C. Benniston, A. Harriman, V. M. Lynch, J. Am. Chem. Soc.
1995, 117, 5275.
[21] M. Asakawa, P. R. Ashton, S. Iqbal, A. Quick, J. F. Stoddart, N. D.
Tinker, A. J. P. White, D. J. Wiliams, Isr. J. Chem. 1996, 36, 329.
[22] G. J. E. Davidson, S. J. Loeb, N. A. Parekh, J. A. Wisner, J. Chem.
Soc. Dalton Trans. 2001, 3135.
[31] J. Tiburcio, G. J. E. Davidson, S. J. Loeb, Chem. Commun. 2002,
1282.
[32] J. Szejtli, T. Osa, in Comprehensive Supramolecular Chemistry,
Vol. 3 (Series Eds.: J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F.
Vˆgtle, J.-M. Lehn), Pergamon, Oxford, 1996.
[33] C. J. Easton, S. F. Lincoln, Modified Cyclodextrins. Scaffolds and
Templates for Supramolecular Chemistry, Imperial College Press,
London, 1999.
[34] H. Ogino, J. Am. Chem. Soc. 1981, 103, 1303.
[35] G. Wenz, E. von der Bey, L. Schmidt, Angew. Chem. 1992, 104, 758;
Angew. Chem. Int. Ed. Engl. 1992, 31, 783.
[36] S. Anderson, T. D. W. Claridge, H. L. Anderson, Angew. Chem.
1997, 109, 1367; Angew. Chem. Int. Ed. Engl. 1997, 36, 1310.
[37] A. Harada, J. Li, M. Kamachi, Chem. Commun. 1997, 1413.
[38] S. A. Nepogodiev, J. F. Stoddart, Chem. Rev. 1998, 98, 1959.
[39] W. Saenger, J. Inclusion Phenom. 1984, 2, 231.
[40] S. Kamitori, O. Matsuzaka, S. Kondo, S. Muraoka, K. Okuyama, K.
Noguchi, M. Okada, A. Harada, Macromolecules 2000, 33, 1500.
[41] K. A. Udachin, L. D. Wilson, J. A. Ripmeester, J. Am. Chem. Soc.
2000, 122, 12375.
[42] C. A. Stanier, M. J. O’Connell, W. Clegg, H. L. Anderson, Chem.
Commun. 2001, 493.
[43] C. J. Easton, S. F. Lincoln, A. G. Meyer, H. Onagi, J. Chem. Soc.
Perkin Trans. 1 1999, 2501.
[44] S. L. Gordon, K. W¸thrich, J. Am. Chem. Soc. 1978, 100, 7094.
[45] F. Cacialli, J. S. Wilson, J. J. Michels, C. Daniel, C. Silva, R. H.
Friend, N. Severin, P. SamorÏ, J. P. Rabe, M. J. O×Connell, P. N.
Taylor, H. L. Anderson, Nat. Mater. 2002, 1, 160.
[46] D. W. Hein, E. S. Pierce, J. Am. Chem. Soc. 1955, 77, 4107.
[47] E. Khotinsky, W. Jacopson-Jacopmann, Ber. Dtsch. Chem. Ges. 1909,
42, 3097.
[48] COLLECT data collection software, B. V. Nonius, 1998.
[49] DENZO-SMN, Z. Otwinowski, W. Minor, ™Processing of X-ray Dif-
fraction Data Collected in Oscillation Mode∫ in Methods in Enzy-
mology, Macromolecular Crystallography, Part A, Vol. 276 (Eds.:
C. W. Carter Jr., R. M. Sweet), Academic Press, New York, 1997,
pp. 307 326.
[23] M. J. MacLachlan, A. Rose, T. M. Swager, J. Am. Chem. Soc. 2001,
123, 9180.
[24] P. T. Glink, A. I. Oliva, J. F. Stoddart, A. J. P. White, D. J. Williams,
Angew. Chem. 2001, 113, 1922; Angew. Chem. Int. Ed. 2001, 40,
1870.
[25] G. Brancato, F. Coutrot, D. A. Leigh, A. Murphy, J. K. Y. Wong, F.
Zerbetto, Proc. Natl. Acad. Sci. USA 2002, 99, 4967.
[26] M. Asakawa, G. Brancato, M. Fanti, D. A. Leigh, T. Shimizu,
A. M. Z. Slawin, J. K. Y. Wong, F. Zerbetto, S. Zhang, J. Am. Chem.
Soc. 2002, 124, 2939.
[27] P. R. Ashton, T. T. Goodnow, A. E. Kaifer, M. V. Reddington, K. P.
Parry, A. M. Z. Slawin, N. Spencer, J. F. Stoddart, C. Vicent, D. J.
Williams, Angew. Chem. 1989, 101, 1404; Angew. Chem. Int. Ed.
Engl. 1989, 28, 1396.
[28] P. L. Anelli, P. R. Ashton, N. Spencer, A. M. Z. Slawin, J. F. Stod-
dart, D. J. Williams, Angew. Chem. 1991, 103, 1052; Angew. Chem.
Int. Ed. Engl. 1991, 30, 1036.
[29] P. R. Ashton, D. Philp, M. V. Reddington, A. M. Z. Slawin, N.
Spencer, J. F. Stoddart, D. J. Williams, J. Chem. Soc. Chem.
Commun. 1991, 1680.
[30] P. R. Ashton, D. Philp, N. Spencer, J. F. Stoddart, D. J. Williams, J.
Chem. Soc. Chem. Commun. 1994, 181.
[50] P. Coppens in Crystallographic Computing (Eds.: F. R. Ahmed, S. R.
Hall, C. P. Huber), Copenhagen, Munksgaard, 1970, pp. 255 270.
[51] SIR2002: M. C. Burla, M. Camalli, B. Carrozzini, G. L. Cascarano,
C. Giacovazzo, G. Polidori, R. Spagna, J. Appl. Crystallogr. 2003, 36,
1103
[52] SIR97: A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115.
[53] D. J. Watkin, C. K. Prout, J. R. Carruthers, P. W. Betteridge, R. I.
Cooper, CRYSTALS Issue 11, Chemical Crystallography Laborato-
ry, Oxford (UK), 2001.
Received: June 26, 2003 [F5279]
5977
Chem. Eur. J. 2003, 9, 5971 5977
www.chemeurj.org
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim