Dual emission of a bis(pyrene)-functionalized, perbenzylated β-cyclodextrin

Article abstract of DOI:10.1039/b803144d

A bis(pyrene)-functionalized β-cyclodextrin (1) has been prepared in two steps from perbenzylated β-cyclodextrin. This compound shows dual emission properties, which arise from the pyrenyl chromophores. Upon excitation of 1 at 355 nm, monomer blue fluorescence (386, 407 and 428 nm) is observed in DMSO solution, whereas excimer green fluorescence (477 nm) is seen upon addition of ≥20 vol% water in DMSO. This suggests that modified β-cyclodextrin 1 changes its shape in response to the environment. The sensing properties of 1 towards carboxylic acids and alcohols were investigated in H₂O-DMSO (80: 20 v/v). Monomer fluorescence is restored selectively by medium length normal carboxylic acids, such as enanthic acid (C₇) found in rancid oils and capric acid (C₁₀), while both monomer and excimer emissions are enhanced by homologous alcohols, such as 1-heptanol, used in cosmetics and 1-decanol. Remarkably, bulkier substrates, such as tert-butyl alcohol or 1-adamantylcarboxylic acid are not detected. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b803144d

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Dual emission of a bis(pyrene)-functionalized, perbenzylated
b-cyclodextrinw
Cheng Huo, Jean-Claude Chambron* and Michel Meyer
Received (in Montpellier, France) 29th February 2008, Accepted 18th April 2008
First published as an Advance Article on the web 4th June 2008
DOI: 10.1039/b803144d
A bis(pyrene)-functionalized b-cyclodextrin (1) has been prepared in two steps from perbenzylated
b-cyclodextrin. This compound shows dual emission properties, which arise from the pyrenyl
chromophores. Upon excitation of 1 at 355 nm, monomer blue fluorescence (386, 407 and
4
28 nm) is observed in DMSO solution, whereas excimer green fluorescence (477 nm) is seen
upon addition of Z 20 vol% water in DMSO. This suggests that modified b-cyclodextrin 1
changes its shape in response to the environment. The sensing properties of 1 towards carboxylic
2
acids and alcohols were investigated in H O–DMSO (80 : 20 v/v). Monomer fluorescence is
restored selectively by medium length normal carboxylic acids, such as enanthic acid (C ) found
7
in rancid oils and capric acid (C ), while both monomer and excimer emissions are enhanced by
1
0
homologous alcohols, such as 1-heptanol, used in cosmetics and 1-decanol. Remarkably, bulkier
substrates, such as tert-butyl alcohol or 1-adamantylcarboxylic acid are not detected.
6
b,c,e
Introduction
b-CD.
The construction of bichromophoric CDs usually
involves ditosylation of the primary (at glucose 6-C) hydroxyl
groups of the narrow rim as first step. Applied to b-CD, this
reaction leads to three positional isomers noted 6A6B, 6A6C
and 6A6D,y which can be separated by column chromatogra-
phy. Elegant alternatives are regiospecific disulfonate cap-
13
ping, and, as reported recently, regioselective deprotection of
14
perbenzylated CDs, using an excess of DIBAL-H. In the
Cyclodextrins (CDs) are naturally-occurring, cone-shaped
hollow molecules made from six (a-CD), seven (b-CD), and
eight (g-CD) a-1,4-connected D-(+)-glucopyranosyl subunits,
which can include various hydrophobic organic molecules
inside their cavity, in aqueous medium or water–solvent
12
1
mixtures. b- and g-cyclodextrins modified with fluorophores
tethered on the narrow rim have been shown to act as
luminescent sensors for compounds of biological and environ-
mental interest, such as steroids, terpenes, (chloro)phenols and
latter conditions, perbenzylated b-CD leads to the 6A6D diol
exclusively, which can be further functionalized and depro-
14b,c
tected by catalytic hydrogenolysis.
2
other aromatic molecules. In several instances, the signalling
event relies on the dual emission of reporter groups able to
The work reported here uses this latter strategy to prepare a
bis(pyrene)-functionalized, perbenzylated b-CD, whose dual
emission properties in water–DMSO mixtures in the absence
and presence of various substrates are described.
3
form excimers, such as those based on naphthyl, dansyl,
4
5
6
and pyrenyl fluorophores, the latter being of particular
relevance to the present work.
Pyrene itself can show excimer fluorescence in the presence of
7
8
g-CD, but not b-CD, an observation that has been analyzed in
terms of different stoichiometries of the pyreneCCD inclusion
complexes: in the case of g-CD, while excimer fluorescence
Results and discussion
Synthesis
9
a,c
originates from the 2 : 2 complex,
monomer emission is due
The three-step preparation of 1 from b-CD is shown in
Scheme 1. At first, b-cyclodextrin was reacted with benzyl
chloride at room temperature in DMSO in the presence of
9b
to the 1 : 1 adduct; in the case of smaller b-CD, monomer
9b,10b
emission is mainly due to the 1 : 2 complex,
but partial
1
inclusion of pyrene in 1 : 1 complexes has been also observed.
0
14b,c,15
excess NaH to give perbenzylated b-cyclodextrin 2.
Subsequent regiospecific debenzylation with DIBAL-H in
Pyrene excimer fluorescence can also be shown by cyclodex-
trins equipped with two pyrene luminophores.z Bis(pyrenyl)/
14a,b
toluene at 30 1C, as reported, afforded diol 3.
reaction of an excess of 1-hydroxypyrene with diol 3 in
Finally,
6
a,d
CD conjugates reported so far are built either on g-CD
or
16
1
7
Mitsunobu reaction conditions (DIAD, PPh , THF, 0 1C
3
Institut de Chimie Mole´culaire de l’Universite´ de Bourgogne (ICMUB,
UMR CNRS no 5260), 9 avenue Alain Savary, BP 47870, 21078
Dijon Cedex, France. E-mail: jean-claude.chambron@u-bourgogne.fr;
to RT) afforded target modified b-cyclodextrin 1 in 90% yield
after chromatography. Two sets of peaks were observed by
Fax: (+33) (0)3 8039 6117; Tel: (+33) (0)3 8039 61161
z Remarkably, g-CD with a single tethered pyrenyl group can form
association dimers, while self-inclusion complexes, in which both
dangling pyrenyl arms reside inside the CD cavity, can be observed
in the case of doubly functionalized systems. These complexes are
usually detected by excimer fluorescence.
y The seven sugar subunits of b-CD are labelled A–G, see Scheme 2.
w Electronic supplementary information (ESI) available: H NMR of
1
1
1
13
1
(details of assignment, H/ H COSY, TOCSY and ROESY), H/
correlations (HSQC and HMBC), electronic absorption spectra of 1 in
O–DMSO mixtures, fluorescence spectra of 1 in the presence of
C
H
2
4
a,11
different analytes, photographs showing the color of luminescence of 1
in various conditions. See DOI: 10.1039/b803144d
1
536 | New J. Chem., 2008, 32, 1536–1525
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Scheme 1 Synthesis of 1. The benzyl groups are distributed on both sides of the CD ring (5 upper, 14 lower).
MALDI-TOF mass spectrometry. They correspond to the
+ +
Na (m/z = 3269.48) and K (m/z = 3285.46) adducts,
assigned within the pairs (A, D), (B, F) and (C, G), and the
isolated subunit E. The other (38) belong to the 19 benzylic
diastereotopic proton pairs, as the one giving rise to the AB
signal centered at 4.32 ppm (JAB = 12.3 Hz, Dn = 12.7 Hz).
Assignment of the aliphatic protons is initiated with a ROESY
experiment (Fig. 2 and S3, ESIw). The detailed map of Fig. 2
respectively.
1
H NMR Spectroscopy
1
The solution structure of 1 was investigated by H (600 MHz)
00
1
3
shows through space correlations between 10 A,D-H (respec-
0
and C (151 MHz) NMR spectroscopy using a combination
of 2D techniques (COSY, TOCSY, ROESY, HSQC and
0
tively, 2 A,D-H) of the pyrenyl subunits and 4A,D-H (respec-
0
1
8
tively 6A,D-H and 6 A,D-H) of the sugars A and D, which
HMBC, see Fig. S1–S8, ESIw). The structural formula of 1
is represented in Scheme 2, with proton labelling and selected
NOE correlations indicated. The assigned proton spectrum in
provides starting points for the b-CD framework. Correlations
between two consecutive sugar subunits involve protons 1-H
1
8b
6
d -acetone, which is better resolved than in CDCl
and 4-H, respectively. They are also shown in Fig. 2, with
the exception of the correlations 1 -H/4 -H and 1 -H/4 -H,
3
, CD
2
Cl
2
6
A
B
D
E
and particularly, d -DMSO solutions (Fig. S9, ESIw),
is represented in Fig. 1 and S10 (ESIw). Comparison with
the spectrum of precursor diol 3 (Fig. S11, ESIw) illustrates the
scattering effect of the anisotropic pyrenyl substituents on the
which are very weak (Fig. S3, ESIw). The corresponding
through-bond correlations involving 1-C (resp. 4-C) and 4-H
(
(
resp. 1-H) are also clearly seen in the HMBC spectrum
Fig. S6 and S8, ESIw). Noteworthy, in addition to the NOE
7
sugar b-CD protons. Due to the C symmetry of the parent
correlation 4
F E F
-H/1 -H, sugar F shows the correlation 3 -H/
b cyclodextrin, the two pyrenyl moieties, which are placed in
the A and D positions, are not equivalent, however they could
not be differentiated from each other. Of the pyrenyl protons,
1
E
-H. As expected from earlier studies, the doublets attributed
1
4b
to 1-H are observed in the downfield region (5.5–5.1 ppm).
The dd signals of 2-H, which are coupled to 1-H and 3-H, and
00
00
only 2 A,D-H and 10 A,D-H, which are the closest to the
oxygen atoms connecting the chromophores to the 6A,D-C of
the b-CD platform show significant shifts by comparison with
0
the broad doublets of 6 -H are observed in the upfield part of
the aliphatic region (3.35–3.85 ppm). All the other sugar
protons resonate between 4.30 and 3.85 ppm, with the excep-
0
1
-hydroxypyrene (ꢁ0.18 and 0.12 ppm, respectively) (Fig. S11,
tion of 4A,D-H, 5A,D-H, and diastereotopic 6A,D-H and 6 A,D
-
ESIw).
1
H of the sugars A and D bearing the pyrenyl chromophores,
The H NMR spectrum of 1 in the high-field region is very
intricate due to the asymmetry of the molecule. Of the 87
different aliphatic protons, all the sugar protons (49) could be
which resonate at lower fields. This deshielding (which is
0
41 ppm for 6 A,D-H) is due to the fact that these protons
are located near the edge of the pyrenyl aromatic rings, an
observation consistent with the ROESY studies.
Conformational analysis of wide-rim perbenzylated CDs is
1
9
well documented. In particular, compounds that carry 6-C
substituents commensurate with the internal cavity do not
display exclusively the conical shape of the native CDs. For
example, whereas perbenzylated b-CD itself is conical
7
(C symmetry), its analogue that bears naphthoyl groups on
the narrow rim instead exists as a 1 : 1 equilibrium mixture of
C symmetrical and unsymmetrical (C ) conformers in CDCl
3
7
1
at room temperature. The C conformer results from internal
1
rotation of one glucopyranose ring around its 1,4 axis, leading
to inclusion of the corresponding naphthoyl substituent inside
the cyclodextrin cavity. In the case of native b-CD, sugar 3-H
and 5-H are located internally, whereas 1-H, 2-H and
4
-H point outside. The fact that all through space NOE
Scheme 2 Structural formula of 1 (R = Bn) viewed from the lower
rim with sugar nomenclature and atom numbering detailed for the
pyrenyl substituents and sugar B. The double ended arrows show key
NOE correlations.
correlations between 1-H and 4-H of consecutive sugars are
observed in 1 shows that this modified cyclodextrin has nearly
the ideal b-CD torus shape, the additional NOE correlation
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1
6
Fig. 1 H NMR spectrum (d -acetone, 600 MHz) of 1. The aromatic region is detailed in Fig. S10 (ESIw).
3
F
-H/1
E
-H suggesting a small distortion of the torus at
molar absorption coefficients are consistent with the double
0
2
the hinge between sugar
correlations 10
E
-H (resp. 10
and sugar F. The NOE
functionalization of b-CD with the pyrenyl chromophore.
When excited at the maximum of pyrene absorption
0
0
00
00
A
-H/4
00
A
D
-H/4
0
D
D
-H), 2
A
-H/6
A
-H
00
0
00
ꢁ6
ꢁ3
(
2
D
-H/6
D
-H) and 2
A
-H/6
A
-H (2
D
-H/6
-H) observed be-
(355 nm), dilute (10 mol dm ) solutions of 1 in DMSO
show the strong fluorescence of the pyrenyl luminophores,
with emission maxima at 386, 407 and 428 nm. However, upon
addition of increasing amounts of water, this emission de-
creases at the expense of the characteristic excimer emission of
pyrene at 477 nm (Fig. 3). As shown in the inset at four
different wavelengths, the monomer (386, 407 and 428 nm)
and excimer (477 nm) emission intensities are approximately
constant for concentrations of water in DMSO below 17%.
Then, between 18 and 20%, the monomer emission intensity
decreases abruptly. Finally, above E22% of water, the mono-
mer and excimer emissions are no longer significantly changed.
The water-tuned emission of 1 in DMSO–water mixtures is
illustrated by the photograph of Fig. S13 (ESIw) taken under
UV-lamp irradiation at 365 nm, which shows that increasing
the amount of water changes the color of the emitted light
from blue to green. As can be anticipated from Fig. 3,
blue–green emission is observed for solutions containing
E18% of water.
tween the pyrenyl and sugars A (resp. D) subunits show that
the luminophores point outside the b-CD cavity and are
positioned equatorially with respect to the b-CD torus, the
0
6
,6 -H proton pair pointing upwards. Therefore, the pyrenyl
chromophores are efficiently separated from each other by the
b-CD platform in the moderately polar solvent acetone.
UV-visible absorption and luminescence spectroscopy
The UV-Vis absorption spectrum of 1 in DMSO (Fig. S12, ESIw)
is characterized by the sharp absorption of the benzyl sub-
3
ꢁ1
ꢁ1
stituents at 281 nm (e = 95 500 dm mol cm ) and the broad,
albeit structured, manifold of the pyrenyl subunits in the near
3
ꢁ1
ꢁ1
UV, with maxima at 348 (e = 52 000 dm mol cm ) and
55 nm (e = 51 700 dm mol cm ). Sharp satellite absorp-
tions are observed at 365 (e = 35 500 dm mol cm ) and
84 nm (e = 21500 dm mol cm ). The magnitudes of the
3
ꢁ1
ꢁ1
3
3
ꢁ1
ꢁ1
3
ꢁ1
ꢁ1
3
Absorption changes at various selected water concentra-
tions are shown in Fig. S14 (ESIw). Unexpectedly, the spectra
obtained for pure DMSO and water–DMSO (80 : 20 v/v)
ꢁ6
ꢁ3
Fig. 3 Fluorescence spectra of 1 (1.0 ꢂ 10 mol dm , 25 1C) at
various concentrations of water in DMSO solution. The inset shows
intensities changes at 386, 407, 428 and 477 nm.
1
6
Fig. 2 Portions of the ROESY H NMR spectrum of 1 (d -acetone,
00 MHz, mixing time: 300 ms).
6
1
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solutions are very similar with each other, which indicates that
the pyrenyl residues do not show electronic interaction in the
ground state. However, in the transition region of fluorescence
(1-heptanol and 1-decanol) produced brighter luminescence.
These
compounds were selected for detailed spectroscopic studies.
As shown in Fig. 4, upon addition of increasing amounts of
1-heptanoic acid in acidic (0.04% HCl) water–DMSO
regime (18–20% H O), the absorption spectra are obscured by
2
a background residual absorption, which gradually disappears
as the concentration of water is increased, becoming negligible
ꢁ6
ꢁ3
(80 : 20 v/v) mixture to 10 mol dm solutions of 1, the
monomer emission gradually develops at the expense of the
excimer emission, which nearly completely vanishes. Visuali-
zation of the phenomenon under the UV lamp is shown in Fig.
S15 (ESIw). Similar results were obtained with 1-decanoic acid
and 6-chloro-1-hexanol (Fig. S16 and S17, ESIw). However, in
the case of 1-heptanol and 1-decanol both monomer fluores-
cence and excimer emission intensities increase concomitantly.
In addition, the excimer band undergoes a slight red shift
(E8 nm). This is illustrated in Fig. 5 for 1-heptanol and
Fig. S18 (ESIw) for 1-decanol. The fluorescence spectra of
above 40% H O. The largest changes are observed at E19.5%
2
of water, where the absorption band of the benzyl substituents
is broadened and blue-shifted by 2 nm. In fact, careful
examination of the corresponding solutions shows the
presence of turbidity, which is detected to the naked eye by
light scattering.
Switching of the monomer/excimer dual emission of the
pyrenyl fluorophores can, in principle, be rationalized in terms
of hydrophobic effects. In pure DMSO solution, as demon-
6
strated in d -acetone, 1 is likely to have an open form too, in
ꢁ ꢁ3
6
which the pyrenyl luminophores are distant form each other,
and therefore display the monomer-type emission.z This
situation does not change until the proportion of water in
DMSO reaches E17%. At 80% of water, the hydrophobic
pyrenyl moieties of 1 reduce their exposure to the solvent most
likely by folding at the upper rim of the cyclodextrin platform,
the resulting pyrenyl ‘‘dimer’’ being too bulky to penetrate the
hydrophobic b-cyclodextrin cavity. Moreover, it is reasonable
to assume that the five upper-rim benzyl substituents fold
around the pyrene dimer, and the fourteen lower-rim benzyl
substituents curl up at the lower opening of the cyclodextrin
cavity to further reduce the availability of these aromatic
surfaces for interaction with the wet solvent. Unfortunately,
10 mol dm solutions of 1 in the presence of the other
ꢁ
3
compounds of Chart S1 at 0.1 mol dm
(1,4-benzenedimethanol, 1-adamantylcarboxylic acid and
concentrations
ꢁ
2
myristic acid excepted, which were employed at 5.0 ꢂ 10 ,
mol dm , respectively) are
ꢁ3
ꢁ4
ꢁ3
2.0 ꢂ 10 , and 5.0 ꢂ 10
collected in Fig. S19 (ESIw). Cyclohexanol produces very
similar features as 1-heptanol, but without luminescence en-
hancement, and malonic acid has practically no effect. The
other compounds simply quench the emission intensity of 1 to
various extents. Among these are short chain linear 1-butanoic
acid and 1-butanol, compounds with a bulkier, ball-like shape
such as benzoic and 1-adamantylcarboxylic acids, tert-butanol
and phenol. These observations suggest that the dual fluores-
cence changes of b-CD 1 are governed by host–guest effects.
Unfortunately, the numerical analysis of the fluorescence
spectra by using realistic binding models, such as that invol-
ving a 1 : 1 ratio between host and guest, did not give
reasonable results for the association constants. This would
suggest that aggregates involving substrate and receptor
1
2
was not soluble enough in Z 20 vol% H O in DMSO to
1
verify these hypotheses by H NMR spectroscopy. Between
these extremes, the situation is more complex, especially in the
17–22% concentration range, where the formation of aggre-
gates is likely to occur.
In summary, modified b-cyclodextrin 1 is a dual light
emitter controlled by water concentration in DMSO. Remark-
ably, the transition between the two emission modes occurs in
quite a narrow water concentration range (17–20%), making
this compound a genuine on/off switch. Interestingly, the
fluorescence properties of b-cyclodextrin 1 in water–DMSO
mixtures nicely complement those of a reported bis(pyrene)-
modified b-cyclodextrin dimer, which shows maximum
6e
excimer emission in DMSO–water (90 : 10 v/v).
Sensing properties of 1 by luminescence
The possibility to recover the monomer fluorescence by addi-
tion of potential guest species to solutions of modified b-CD
host 1 showing excimer fluorescence, was next investigated.
The solvent mixture water–DMSO (80 : 20 v/v) was selected,
as it favors hydrophobic interactions while still allowing to
solubilize 1 in the micromolar concentration range. A variety
of organic compounds (Chart S1, ESIw) were screened
ꢁ
6
ꢁ3
qualitatively, by observation of 2 ꢂ 10 mol dm solutions
of 1 under the UV lamp at 365 nm. In particular,
ꢁ
6
ꢁ3
mol dm ) upon
6
1
-chloro-1-hexanol, and the linear aliphatic 1-heptanoic and
-decanoic carboxylic acids changed the color of fluorescence
Fig. 4 Fluorescence spectra of 1 (1.0 ꢂ 10
addition of 1-heptanoic acid ((1) 0, (2) 5.0 ꢂ 10 , (3) 1.0 ꢂ 10
ꢁ
3
ꢁ2
,
ꢁ2
ꢁ2
ꢁ2
ꢁ2
of 1 from green to blue, whereas the corresponding alcohols
(4) 1.5 ꢂ 10 , (5) 2.0 ꢂ 10 , (6) 2.5 ꢂ 10 , (7) 3.0 ꢂ 10 , (8) 3.5 ꢂ
ꢁ2 ꢁ3
1
0
mol dm ) in acidic (0.04% HCl) H
2
O–DMSO (80 : 20 v/v),
z 1 shows blue, monomer-like fluorescence in acetone.
25 1C. The inset shows the excimer emission.
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ꢁ
6
ꢁ3
Fig. 6 Sensitivity parameters of host 1 (1.0 ꢂ 10 mol dm ) with
guests G1–G5 at 386 (black bars), 407 (gray bars) and 477 (white bars) nm
ꢁ
6
ꢁ3
ꢁ2
Fig. 5 Fluorescence spectra of 1 (1.0 ꢂ 10
mol dm ) upon
ꢁ2
ꢁ3
in H
2
O–DMSO (80 : 20 v/v) at 25 1C. (i) 3.5 ꢂ 10 mol dm
ꢁ3
addition of 1-heptanol ((1) 0, (2) 5.0 ꢂ 10 , (3) 1.0 ꢂ 10 , (4) 1.5
ꢁ3 ꢁ3
1
-heptanoic acid, G1–0.04% HCl; (ii) 1.2 ꢂ 10 mol dm 1-decanoic
ꢁ2
ꢁ2
ꢁ2
ꢁ2
ꢁ2
,
ꢂ 10 , (5) 2.0 ꢂ 10 , (6) 2.5 ꢂ 10 , (7) 3.0 ꢂ 10 , (8) 3.5 ꢂ 10
ꢁ2
ꢁ3
acid, G2–0.04% HCl; (iii) 4.0 ꢂ 10 mol dm 1-heptanol, G3; (iv) 1.4 ꢂ
ꢁ2
ꢁ3
(
9) 4.0 ꢂ 10 mol dm ) in H
2
O–DMSO (80 : 20 v/v) at 25 1C.
ꢁ3
ꢁ3
ꢁ2
ꢁ3
10
mol dm 1-decanol, G4 and (v) 3.0 ꢂ 10 mol dm 6-chloro-
1-hexanol, G5.
molecules are formed. In addition, 1 being a perbenzylated b-
CD, its binding properties in water-rich environment may
differ significantly from those of native CDs, especially in
view of the expected steric crowding of its openings (see the
previous section). This observation is supported by the fact
that
1
-heptanoic (enanthic) acid, a contributor to the odour of
2
2
some rancid oils, while 1-butanoic acid, found in rancid
butter, is not detected.
Conclusion
1
-adamantylcarboxylic acid, which shows the highest binding
1
An interesting feature of bis(pyrene)-functionalized perbenzy-
lated b-CD 1 is the quasi-direct anchoring of the pyrenyl
luminophores to the cyclodextrin backbone. This results in
effective transduction of conformational changes that are
triggered by the environment (e.g. solvent polarity or presence
of analytes) into switching of luminescence regime. However,
the phenomena that come into play are not as straightforward
as it may appear from this picture and most probably involve
complex molecular assemblies. Future work in this context
will entail light scattering studies and comparison with un-
protected cyclodextrins, since the inclusion properties of these
systems in aqueous solutions are well established.
c
constant with b-cyclodextrin, has practically no influence on
the dual fluorescence of 1.
The different effects of 1-heptanoic and 1-decanoic acids,
and 6-chloro-1-hexanol on the one hand (enhancement of
monomer emission and depletion of excimer emission),
1
-heptanol and 1-decanol on the other hand (enhancement
of monomer and excimer emission accompanied by a red shift
of the latter), can both result from interaction of these two
groups of guests with the b-CD host 1, but in different
manners. As a matter of fact, the direct anchoring of the
pyrenyl substituents to the small rim of 1 makes their emission
behavior very sensitive to the nature (shape and flexibility) of
the substrate that binds to b-CD 1: excimer formation can be
suppressed by distortion of the cyclodextrin backbone, while
enhancement of emission can be brought about by rigidifica-
tion of the complex by comparison with the free host. Indeed,
enhancement of pyrene fluorescence has been noted for tern-
Experimental
General
b-Cyclodextrin was dried under vacuum over P O prior to
2
5
2
1a
ary complexes between b-CD, pyrene, and alcohols
amino acids.
or
use. All other reagents were used without further purification.
1
2
1b
4b,c,15
14 16
and 3, and 1-hydroxypyrene were
Modified b-CDs 2
prepared according to literature methods. Solvents used in the
In order to quantify the sensing ability of 1, DI/I ratios (DI
0
=
I ꢁ I , where I and I represent the emission intensities of 1
0
0
syntheses were dried and distilled under standard conditions.
1
All reactions were performed under a nitrogen atmosphere. H
with and without added analyte, respectively) were measured
at three different wavelengths (386 and 407 nm for the mono-
mer emission, and 477 nm for the excimer emission), and were
1
3
and C NMR spectra were recorded on a Bruker AVANCE
00 instrument. Chemical shifts are referenced downfield from
Me Si and coupling constants are given in Hz. Mass spectra
6
4
a
used as sensitivity parameters for the acids and alcohols
mentioned above (Fig. 6). This shows that 1-heptanoic and 1-
decanoic acids are detected by b-CD 1 with higher sensitivity
than the corresponding alcohols. In summary, modified
cyclodextrin b-CD 1 is quite a selective fluorescent sensor for
4
were recorded on a Bruker ProFLEX III spectrometer (MAL-
DI/TOF) using dithranol as the matrix. Elemental analyses
were performed on a Fisons EA 1108 CHNS instrument.
UV-visible spectra were recorded on either a Varian Cary 5
1
540 | New J. Chem., 2008, 32, 1536–1525
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or a Cary 50 spectrophotometer and photoluminescence spec-
tra were collected on a Fluorolog-III Horiba-Jobin-Yvon
spectrofluorimeter.
128.71, 128.76, 128.77, 128.87, 128.91, 129.08 (Ar-CH), 139.46,
139.50, 139.55, 139.62, 139.65, 139.66, 139.70, 139.72, 139.75,
140.32, 140.38, 140.40, 140.49, 140.56, 140.59 (Ar quaternary C).
1
-Hydroxypyrene
A
D
,6 -Dipyrenyl-2
AꢁG AꢁG
B
C
E
F
G
,6 ,6 ,6 ,6 ,6 -nonadecakis-O-
6
,3
6
(600 MHz; d -acetone; Me
d
H
4
Si) 7.62 (1 H, d, J 8.4, 2-H), 7.92
benzyl-b-cyclodextrin (1)
(
1 H, d, J 9.0, 5-H), 7.98 (1 H, t, J 7.8, 7-H), 8.02 (1 H, d, J 9.0,
-H), 8.06 (1 H, d, J 9.3, 9-H), 8.11 (1 H, d, J 8.4, 3-H), 8.14 (1
H, br d, J 7.8, 6-H or 8-H), 8.15 (1 H, br d, J 7.8, 6-H or 8-H),
.43 (1 H, d, J 9.0, 10-H) and 9.44 (1 H, br m, OH); d (151
A solution of 3 (1.0 g, 0.35 mmol) and 1-hydroxypyrene
0.380 g, 1.76 mmol) in THF (5 mL) was added dropwise to
4
(
a stirred solution of DIAD (225 mL, 1.07 mmol) and triphenyl-
phosphine (0.276 g, 1.05 mmol) in THF (5 mL) at 0 1C. The
resulting mixture was stirred for 3 h at 0 1C and then allowed to
warm to room temperature. After 2 days stirring, the solvent
was removed with a rotary evaporator. Column chromatogra-
phy on silica gel (1 : 4 EtOAc–heptane) afforded 1 (1.04 g, 90%
yield) as a colorless solid (Found: C, 75.72; H, 6.28.
8
C
6
MHz; d -acetone; Me
4
Si) 113.9 (2-C), 119.5 (10a-C), 122.2
(
10-C), 124.6 (6-C or 8-C), 124.9 (6-C or 8-C), 125.1 (5-C),
25.5 (10c-C), 125.9 (3a-C), 126.6 (9-C), 126.8 (3-C), 126.9
1
(
10b-C), 127.0 (7-C), 128.3 (4-C), 132.8 (d, 5a-C and 8a-C) and
52.7 (1-C).
1
B
C
E
F
G
6
Heptakis(2,3-di-O-benzyl)-6 ,6 ,6 ,6 ,6 -penta-O-benzyl-b-
cyclodextrin (3)
C207H200O35 requires C, 76.55; H, 6.21%); dH (600 MHz; d -
acetone; Me Si) 3.41 (1 H, dd, J 9.3 and 3.3, 2 -H or 2 -H),
4
C
G
6
(600 MHz; d -acetone; Me
C G
3.42 (1 H, dd, J 9.6 and 3.6, 2 -H or 2 -H), 3.45 (1 H, dd, J 9.3
d
3
2
H
4
Si) 3.43–3.49 (4 H, m, 2-H),
.44 (1 H, dd, J 9.0 and 3.0, 2-H), 3.52 (1 H, dd, J 9.3 and 3.3,
-H), 3.54 (1 H, dd, J 9.0 and 3.6, 2-H), 3.57 (0.3 H, dd, J 12.6
0
0
and 3.3, 2
F
-H), 3.47 (1 H, br dd, J 10.2, 6
C
-H or 6
G
-H), 3.48
(
1 H, dd, J 9.3 and 3.9, 2
B
-H), 3.53 (1 H, dd, J 9.3 and 3.3, 2 -
E
0
0
H), 3.55 (1 H, br dd, J 10.2, 6
C
-H or 6
G
-H), 3.59 (1 H, br dd, J
and 4.8, 6-H),8 3.58 (0.3 H, dd, J 12.6 and 4.8, 6-H),8 3.68 (1
H, dd, J 11.4 and 1.2, 6 -H), 3.71 (1 H, dd, J 11.4 and 1.2, 6 -
0
0
0
0
0
9.6, 6
F
), 3.60 (1 H, br dd, J 10.2, 6
-H or 2
-H), 3.81 (1 H, dd, J 10.2 and 0.6, 6
3.88 (1 H, overlapped dd, 6 -H or 6 -H), 3.88 (1 H, br t, J 9.0,
-H or 4 -H), 3.89 (1 H, br t, J 9.0, 4 -H or 4 -H), 3.94 (1 H,
dd, J 11.2 and 3.9, 6 -H or 6 -H), 4.00 (1 H, dd, J 9.0 and 8.4,
-H), 4.03–4.25 (21 H, m, 5 ꢂ PhCH, 3 -H, 3 -H, 3 -H, 3
H, 3 -H, 3 -H, 3 -H, 4 -H, 4 -H, 5 -H, 5 -H, 5 -H, 5 -H,
-H, 6 -H or 6 -H, 6 -H), 4.25 (1 H, dd, J 11.4 and 3.6, 6
or 6 -H), 4.33 (2 H, AB, JAB 12.3, Dn 12.7, PhCH
s, PhCH
), 4.40–4.71 (21 H, m, 15 ꢂ PhCH, 4
-H, 6 -H), 4.78 (1 H, d, J 10.8, PhCH), 4.79 (1 H, d, J
1.4, PhCH), 4.80 (1 H, d, J 10.2, PhCH), 4.80 (1 H, d, J 11.4,
B
-H or 6
E
-H), 3.73 (1 H,
0
dd, J 6.6 and 3.6, 2
-H or 2
A
-H), 3.74 (1 H, dd, J 6.6 and 3.6,
D
H), 3.72 (1 H, dd, J 10.2 and 1.2, 6 -H), 3.73 (1 H, dd, J 11.4
0
0
0
-H),
E
0
2
A
D
-H or 6
B
and 1.2, 6 -H), 3.74 (1 H, dd, J 10.8 and 1.2, 6 -H), 3.82–3.87
0
C
G
(
2 H, m, 6 A/D-H), 3.91–4.01 (2 H, m, 5-H; 2 H, m, 6-H; 7 H,
4
C
G
C
G
m, 4-H), 4.01–4.11 (5 H, m, 5-H; 7 H, m, 3-H), 4.11–4.18 (5 H,
m, 6-H), 4.42–4.62 (22 H, m, PhCH), 4.66 (1 H, d, J 12.6,
C
G
4
F
A
B
C
D
-
2
-PhCH), 4.68 (1 H, d, J 12.6, 2-PhCH), 4.74 (1 H, d, J 10.8,
E
F
G
B
E
B
C
E
F
PhCH), 4.75 (1 H, d, J 11.4, PhCH), 4.75 (1 H, d, J 10.8,
PhCH), 4.76 (1 H, d, J 10.2, PhCH), 4.79 (2 H, d, J
5
G
B
E
F
B
-H
E
2
), 4.38 (2 H,
1
1
0.8, PhCH), 4.80 (1 H, d, J 10.8, PhCH), 4.98 (1 H, d, J
0.8, PhCH), 5.05 (1 H, d, J 11.4, PhCH), 5.12 (1 H, d, J 10.2,
2
A D A
-H, 4 -H, 5 -H,
5
1
D
-H, 6
A
D
PhCH), 5.14 (1 H, d, J 10.2, PhCH), 5.16 (1 H, d, J 10.8,
PhCH), 5.16 (1 H, d, J 10.8, PhCH), 5.17 (1 H, d, J
PhCH), 4.83 (1 H, d, J 10.8, PhCH), 4.85 (1 H, d, J 10.2,
PhCH), 4.86 (1 H, d, J 10.8, PhCH), 4.92 (1 H, dd, J 10.2 and
10.8, PhCH), 5.23 (3 H, d, J 3.6, 1-H), 5.24 (1 H, d, J 3.6, 1-
H), 5.30 (1 H, d, J 3.6, 1-H), 5.40 (1 H, d, J 3.0, 1-H), 5.47 (1
0
0
0
6
3.0, 6
A
-H or 6
D
-H), 4.94 (1 H, dd, J 10.8 and 3.0, 6 -H or
A
H, d, J 3.6, 1-H), 7.05–7.40 (95 H, m, C
acetone; Me Si) 62.21 (1 C, 6A,D-C), 62.29 (1 C, 6A,D-C), 70.27
1 C, 6-C), 70.30 (1 C, 6-C), 70.35 (2 C, 6-C), 70.39 (1 C, 6-C),
H
6 5
C
); d (151 MHz; d -
0
6
5
D
-H), 5.10 (1 H, d, J 10.8, PhCH), 5.12–5.19 (4 H, m, PhCH),
-H), 5.17 (1 H, d, J 3.0, 1 -H), 5.21 (1 H,
4
.15 (1 H, d, J 3.0, 1
F
B
(
d, J 11.4, PhCH), 5.23 (1 H, d, J 11.4, PhCH), 5.33 (1 H, d, J
7
2.51 (2 C, 5-C), 72.60 (1 C, 5-C), 72.63 (2 C, 5-C), 73.13
PhCH), 73.18 (PhCH), 73.23 (PhCH), 73.30 (PhCH), 73.38 (1
3
.6, 1
.6, 1
E
-H), 5.37 (1 H, d, J 3.6, 1
C
-H or 1
G
-H), 5.39 (1 H, d, J
-H or 1 -H), 5.48 (1
-H), 6.98–7.38 (95 H, m, C
(
C, 5-C), 73.44 (1 C, 5-C), 73.70 (PhCH), 73.72 (PhCH), 73.77
3
C
-H or 1 -H), 5.47 (1 H, d, J 3.0, 1
G
A
D
H, d, J 3.0, 1
A
-H or 1
D
00
6
00
H
5
), 7.41 (1
(
PhCH), 73.78 (PhCH), 75.67 (PhCH), 75.79 (PhCH), 75.85
PhCH), 76.01 (PhCH), 76.04 (PhCH), 76.22 (PhCH),
0
0
00
H, d, J 8.4, 2
A
-H or 2
D
-H), 7.47 (1 H, d, J 8.4, 2
0
A
-H or 2
D
-
(
0
00
H), 7.92 (1 H, d, J 9.0, 5 A-H or 5 D-H), 7.95 (1 H, d, J 9.0,
0
7
4
6.26 (PhCH), 77.36 (1 C, 4-C), 78.05 (1 C, 4-C), 79.33 (1 C,
-C), 79.71 (1 C, 2-C or 4-C), 79.76 (1 C, 2-C or 4-C), 79.80 (1
0
00 00 00
4
H, d, J 9.0, 5 A-H or 5 D-H), 7.98 (1 H, t, J 7.8, 7 A-H or 7 D-
A-H or 4 D-H), 7.96 (1 H, t, J 7.8, 7 A-H or 7 D-H), 7.96 (1
00
0
0
00
00
C, 2-C or 4-C), 79.93 (1 C, 2-C or 4-C), 79.98 (1 C, 2-C or 4-C),
0.18 (2 C, 2-C or 4-C), 80.22 (1 C, 2-C or 4-C), 80.29 (2 C, 2-C
0
0
00
H), 7.99 (1 H, d, J 9.0, 5 A-H or 5 D-H), 8.01 (1 H, d, J 8.4,
0
8
0
00
00
00
3
H, d, J 8.4, 3
A
-H or 3
D
-H), 8.05 (1 H, d, J 9.0, 9
00
A
-H or 9
D
-H), 8.06 (1
00
or 4-C), 80.38 (1 C, 2-C or 4-C), 81.45 (2 C, 3-C), 81.77 (1 C, 3-
C), 81.81 (1 C, 3-C), 81.89 (1 C, 3-C), 81.95 (1 C, 3-C), 82.08 (1
C, 3-C), 98.17 (1 C, 1-C), 98.37 (1 C, 1-C), 98.81 (2 C, 1-C),
0
0
00
A
-H or 3
D
-H), 8.08 (1 H, d, J 9.0, 9
0
A
-H or 9
D
-
0
00
H), 8.10 (1 H, d, J 7.8, 8
0
A
-H or 8
D
-H), 8.13 (1 H, dd, J 7.8
00
0
00
and 0.6, 8
0
A
-H or 8
D
-H), 8.15 (1 H, dd, J 7.8 and 0.6, 6
00
A
-H
9
1
1
1
8.84 (1 C, 1-C), 98.94 (1 C, 1-C), 99.03 (1 C, 1-C), 127.61,
27.63, 127.67, 127.69, 127.71, 128.06, 128.07, 128.10, 128.12,
28.15, 128.16, 128.18, 128.20, 128.23, 128.26, 128.33, 128.38,
28.40, 128.41, 128.53, 128.56, 128.57, 128.59, 128.66, 128.67,
0
00
or 6
D
-H), 8.17 (1 H, dd, J 7.8 and 0.6, 6
0
A
-H or 6
D
-H), 8.54
00
0
00
(1 H, d, J 9.0, 10
0
or 10
A
-H or 10
D
-H), 8.56 (1 H, d, J 9.0, 10
A
-H
0
6
(151 MHz; d -acetone; Me
D
-H); d
C
4
Si) 69.69, 69.71
(2 C, 6A,D-C), 70.22, 70.31 (2 C, 6C,G-C), 70.41, 70.47 (2 C,
6B,E-C), 70.54 (1 C, 6 -C), 71.76, 71.85 (2 C, 5A,D-C), 72.54,
6
In d -acetone, protons 6A,D show exchange signals with the two dd
8
at 3.57 and 3.58 ppm.
F
72.68, 72.81, 72.88 (5 C, 5 -, 5 -, 5 -, 5 - and 5 -C), 73.30,
G
B
C
E
F
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7
3.32, 73.46, 73.84, 73.85, 73.96, 75.95, 76.01, 76.05, 76.19
PhCH), 78.74, 79.04 (2 C, 4B,E-C), 79.57 (1 C, 4 -C), 79.78,
9.84, 79.96 (5 C, 2 -, 2 -, 4 -, 4 - and 4 -C), 80.14, 80.25,
2 (a) A. Ueno, I. Suzuki and T. Osa, Anal. Chem., 1990, 62,
2
461–2466; (b) K. Hamasaki, H. Ikeda, A. Nakamura, A. Ueno,
F. Toda, I. Suzuki and T. Osa, J. Am. Chem. Soc., 1993, 115,
035–5040; (c) H. Ikeda, M. Nakamura, N. Ise, N. Oguma, A.
(
F
7
8
8
9
1
1
1
1
1
1
1
1
1
1
1
1
1
3
C
G
A/D
C
G
5
0.30, 81.65 (6 C, 2 -, 2 -, 2 -, 2 -, 2 - and 4A/D-C), 81.80,
F
A
B
D
E
Nakamura, T. Ikeda, F. Toda and A. Ueno, J. Am. Chem. Soc.,
1996, 118, 10980–10988; (d) M. Narita, E. Tashiro and F. Hamada,
Anal. Sci., 2001, 17, 1453–1455; (e) M. Narita and F. Hamada, J.
Chem. Soc., Perkin Trans. 2, 2000, 823–832; (f) Y. Liu, J. Shi and
D.-S. Guo, J. Org. Chem., 2007, 72, 8227–8234.
1.95, 82.00, 82.05 (7 C, 3
9.42 (7 C, 1
-C), 98.88, 99.06, 99.16, 99.36,
00
AꢁG
-C), 110.86, 110.88 (2 C, 2 A,D-C), 121.22,
AꢁG
00
00
21.27 (2 C, 10a A,D-C), 122.07, 122.12 (2 C, 10 A,D-C),
0
0
00
25.15, 125.19, 125.30, 125.34 (4 C, 6 A,D-C and 8 A,D-C),
3
F. M. Winnik, Chem. Rev., 1993, 93, 587–614.
0
0
00
25.67, 125.70 (2 C, 10c A,D-C), 125.91, 125.96 (2 C, 5 A,D-C),
4 (a) A. Ueno, S. Minato and T. Osa, Anal. Chem., 1992, 64,
2562–2565; (b) F. Hamada, S. Minato, T. Osa and A. Ueno, Bull.
Chem. Soc. Jpn., 1997, 70, 1339–1346.
0
0
26.29, 126.33 (2 C, 3a A,D-C), 126.54, 126.59, 126.66 (Ar-CH),
0
0
00
27.15, 127.19 (2 C, 7 A,D-C), 127.47 (2 C, 9 A,D-C), 127.70,
27.73, 127.80, 127.83, 128.05, 128.09, 128.13, 128.17, 128.19,
28.24, 128.30, 128.34, 128.39, 128.48, 128.46, 128.50, 128.55,
28.58, 128.60, 128.73, 128.74, 128.78, 128.80, 128.81, 128.88,
28.91, 128.93, 128.95, 128.97, 129.06, 129.08, 129.11 (Ar-CH),
32.53, 132.55, 132.66, 132.69 (4 C, 5aA,D-C and 8aA,D-C),
39.37, 139.48, 139.51, 139.55, 139.59, 139.60, 140.34, 140.38,
40.39, 140.41, 140.45 (Ar quaternary C), 153.78, 153.83 (2 C,
5
M. Sato, M. Narita, N. Ogawa and F. Hamada, Anal. Sci., 1999,
5, 1199–1205.
6 (a) I. Suzuki, M. Ohkubo, A. Ueno and T. Osa, Chem. Lett., 1992,
1
2
8
69–272; (b) A. Ueno, T. Suzuki and H. Ikeda, Proceedings of the
th International Symposium on Cyclodextrins, Budapest, 1996;
(
c) A. Ueno, M. Takahashi, Y. Nagano, H. Shibano, T. Aoyagi
and H. Ikeda, Macromol. Rapid Commun., 1998, 19, 315–317; (d)
M. Narita, S. Mima, N. Ogawa and F. Hamada, Anal. Sci., 2001,
17, 379–385; (e) M. Toda, N. Ogawa, H. Itoh and F. Hamada,
Anal. Chim. Acta, 2005, 548, 1–10.
+
A,D-C); m/z (MALDI/TOF): 3285.46 (M + K , 100%),
+
269.48 (M + Na , 33%).
7
(a) K. Kano, I. Takenoshita and T. Ogawa, Chem. Lett., 1982,
321–324; (b) T. Yorozu, M. Hoshino and M. Imamura, J. Phys.
Chem., 1982, 86, 4426–4429.
Fluorescence measurements
8 H. E. Edwards and J. K. Thomas, Carbohydr. Res., 1978, 65,
73–182.
(a) S. Hamai, J. Phys. Chem., 1989, 93, 6527–6529; (b) A. Mun
de la Pena, T. Ndou, J. B. Zung and I. M. Warner, J. Phys. Chem.,
991, 95, 3330–3334; (c) A. S. M. Dyck, U. Kisiel and C. Bohne, J.
Phys. Chem. B, 2003, 107, 11652–11659.
1
ꢁ
6
ꢁ3
1
0
mol dm solutions of 1 in water–DMSO mixtures of
n : (10 ꢁ n) v/v compositions were prepared by filling 10 mL
ꢁ3
volumetric flasks sequentially with 1 mL of a 10 mol dm
9
˜
oz
˜
ꢁ
5
1
stock solution of 1 in DMSO, (9 ꢁ n) mL of DMSO and n mL
of water. The flasks were completed with the required amount
of water–DMSO n : (10 ꢁ n) v/v in order to compensate the
default volume due to the non-ideal behavior of the solvent
1
0 (a) K. Kano, H. Matsumoto, Y. Yoshimura and S. Hashimoto,
J. Am. Chem. Soc., 1988, 110, 204–209; (b) W. Xu, J. N. Demas,
B. A. DeGraff and M. Whaley, J. Phys. Chem., 1993, 97,
6
546–6554.
11 A. Ueno, I. Suzuki and T. Osa, J. Chem. Soc., Chem. Commun.,
988, 1373–1374.
ꢁ
6
ꢁ3
mixture. Acidic (0.04% HCl) 10 mol dm solutions of 1 in
water–DMSO 80 : 20 v/v containing various amounts of
carboxylic acid substrates were prepared by filling 10 mL
1
1
2 K. Fujita, A. Matsunaga and T. Imoto, Tetrahedron Lett., 1984,
25, 5533–5536.
ꢁ
5
ꢁ3
13 (a) I. Tabushi, Y. Kuroda, K. Yokota and L. C. Yuan, J. Am.
Chem. Soc., 1981, 103, 711–712; (b) I. Tabushi, K. Yamamura and
T. Nabeshima, J. Am. Chem. Soc., 1984, 106, 5267–5270.
volumetric flasks sequentially with 1 mL of a 10 mol dm
ꢁ
3
stock solution of 1 in DMSO, (1 ꢁ n) mL of a 0.5 mol dm
solution of guest in DMSO, n mL of DMSO, 0.08 mL of 5%
aqueous HCl, and 7.92 mL of water. In the case of the alcohol
substrates, the latter were replaced by 8 mL of water. The
flasks were completed with the required amount of
water–DMSO (80 : 20 v/v).
14 (a) A. J. Pearce and P. Sinay, Angew. Chem., Int. Ed., 2000, 39,
¨
3610–3612; (b) T. Lecourt, A. Herault, A. J. Pearce, M. Sollogoub
and P. Sinay
H. Fenger, L. G. Marinescu and M. Bols, Eur. J. Org. Chem., 2007,
04–710.
¨
, Chem.–Eur. J., 2004, 10, 2960–2971; (c) J. Bjerre, T.
7
15 T. Sato, H. Nakamura, Y. Ohno and T. Endo, Carbohydr. Res.,
1990, 199, 31–35.
1
0 mm quartz cells were used throughout. Absorbances of
1
6 R. K. Sehgal and S. Kumar, Org. Prep. Proced. Int., 1989, 21,
23–225.
7 O. Mitsunobu, Synthesis, 1981, 1, 1–28.
diger and H. Ikeda, Chem.
Rev., 1998, 98, 1755–1785; (b) O. Bistri, P. Sinay, J. Jimenez
Barbero and M. Sollogoub, Chem.–Eur. J., 2007, 13
757–9774.
the solutions were o0.1. Excitation wavelength was 355 nm.
Excitation and emission slits were set to 1 nm. Spectra were
collected on fresh solutions.
2
1
18 (a) H.-J. Schneider, F. Hacket, V. Ru
¨
¨
´
Acknowledgements
9
1
9 (a) L. Jullien, J. Canceill, L. Lacombe and J.-M. Lehn, J. Chem.
Soc., Perkin Trans. 2, 1994, 989–1002; (b) L. Catoire, V. Michon,
L. Monville, A. Hocquet, L. Jullien, J. Canceill, J.-M. Lehn, M.
´
We thank the Conseil Regional de Bourgogne for a post-doctoral
´
fellowship to C. H. and are grateful to Marie-Jose Penouilh for
´
Piotto and C. Herve du Penhoat, Carbohydr. Res., 1997, 303,
379–393.
0 P. Babu, N. M. Sangeetha, P. Vijaykumar, U. Maitra, K. Rissanen
help with the NMR, Evelyne Pousson for performing the ele-
mental analysis, and Prof. Gerhard Wenz for helpful discussions.
2
and A. R. Raju, Chem.–Eur. J., 2003, 9, 1922–1932.
˜ ˜
1 (a) A. Munoz de la Pena, T. T. Ndou, J. B. Zung, K. L. Greene, D.
H. Live and I. M. Warner, J. Am. Chem. Soc., 1991, 113,
1572–1577; (b) H. Yang and C. Bohne, J. Phys. Chem., 1996,
100, 14533–14539.
2
References
1
(a) A. Harada, in Large Ring Molecules, ed. J. A. Semlyen, John
Wiley and Sons, Chichester, 1996, ch. 11, pp. 407–432; (b) J. Szejtli,
Chem. Rev., 1998, 98, 1743–1753; (c) M. V. Rekharsky and Y.
Inoue, Chem. Rev., 1998, 98, 1875–1917.
22 M. Timm-Heinrich, X. Xu, N. S. Nielsen and C. Jacobsen, Eur. J.
Lipid Sci. Technol., 2003, 105, 436–448.
1
542 | New J. Chem., 2008, 32, 1536–1542
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