Anion templated assembly of an indolocarbazole containing pseudorotaxane on beads and silica nanoparticles

Article abstract of DOI:10.1039/b818854h

The surface covalent attachment of fluorescent axles of indolocarbazole enables anion templation to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral isophthalamide macrocycles. In utilising the surface of polystyrene

Full text of DOI:10.1039/b818854h

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Anion templated assembly of an indolocarbazole containing
pseudorotaxane on beads and silica nanoparticlesw
Liyun Zhao, Kathleen M. Mullen, Micha$ J. Chmielewski, Asha Brown,
Nick Bampos, Paul D. Beer* and Jason J. Davis*
Received (in Durham, UK) 24th October 2008, Accepted 2nd December 2008
First published as an Advance Article on the web 14th January 2009
DOI: 10.1039/b818854h
The surface covalent attachment of fluorescent axles of indolocarbazole enables anion templation
to be exploited in the formation of pseudorotaxane assemblies via the threading of neutral
isophthalamide macrocycles. In utilising the surface of polystyrene beads this threading process
can be followed by both magnetic resonance methods and changes in the axle fluorescent emission
spectrum. The analogous surface assembly and anion templated threading can be achieved, with
fluoride and sulfate, on silica nanoparticles where anion recognition and macrocycle threading are
associated with equivalent and specific optical change.
Gale.27–42 With the aim of using anions to template the
Introduction
formation of interpenetrated and interlocked structures,43
indolo[2,3-a]carbazoles are attractive anion receptors due to
both their rod-like shape and their preorganised hydrogen
bond donating pyrrole groups which have been shown to bind
anions strongly.29,30,32,37 We have recently reported the
unprecedented anion templation of a neutral pseudorotaxane
assembly using an indolocarbazole threading component.27
Indeed threading of the indolocarbazole component through
the annulus of an isophthalamide containing macrocycle is
only observed upon the addition of either the doubly charged
sulfate anion, or fluoride. Furthermore we have demonstrated
analogous anion templated pseudorotaxane assembly on gold
surfaces as monitored by SPR.27
The prospect of utilising triggered molecular motion in sensing,
data storage or machine-type applications has stimulated a
great deal of interest in the synthesis and characterisation
of interpenetrated and interlocked structures such as
pseudorotaxanes, rotaxanes and catenanes. Though solution
phase analyses have resolved cation, pH, redox and light
triggered molecular motion,1–11 it is the controlled interfacing
of these molecules with solid electroactive or optically
transparent surfaces that will lie central to many proposed
applications. From a host–guest sensing perspective the
advantages of tethering to a transducing interface, such as
that presented by an electrode or optically transparent surface,
are also considerable. In addition to the possibility of generating
a robust and renewable host surface capable of operation in a
variety of fluid media (static or flowing) there exists considerable
evidence that the thermodynamics of host–guest association
are favoured at such interfaces.12,13 Although there have been
several reported examples of the covalent attachment of
interlocked molecular systems to solid surfaces,14–24 in
comparatively few instances has surface assembly been
well-defined. One of the most highly investigated classes of
supramolecular systems is the rotaxanes and pseudorotaxanes.
While the surface assembly of these has been achieved using
intermolecular forces between neutral species20 or cationic
species,19,25 employing anions to template the formation of
surface confined interpenetrated structures has only recently
been investigated.26,27
Towards the ultimate goal of fabricating fluorescent anion
responsive interlocked host functionalised receptors we report
herein the TentaGel polystyrene bead and silica nanoparticle
surface immobilisation of indolocarbazole axles together with
anion association and templated pseudorotaxane formation
with a charge neutral isophthalamide macrocycle (see Fig. 1).
Though surface spectroscopic (and electroanalytical) methods
can be powerfully applied to the characterisation of surface
The incorporation of the indole motif into anion receptors is
a recent development in the field of anion recognition. The
strong binding affinities and high anion selectivity of the
indole- and biindole motif has, in particular, been used by
the groups of Beer, Jeong, Pfeffer, Jurczak, Sessler and
Chemistry Research Laboratory, University of Oxford, Mansfield
Road, Oxford, UK OX1 3TA. E-mail: paul.beer@chem.ox.ac.uk.
E-mail: jason.davis@chem.ox.ac.uk
Fig. 1 Structure of isophthalamide macrocycle 1, model indolo-
carbazole compound 2, silica nanoparticle tethered indolocarbazole 3,
and polystyrene bead tethered indolocarbazole 4.
w Electronic supplementary information (ESI) available: FTIR of 3,
1H NMR titration spectra of 4 and 13. See DOI: 10.1039/b818854h
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confined molecules, they are not, generally, capable of providing
information as ‘‘chemically-refined’’ as that offered by magnetic
resonance (the latter having now been extensively applied to
the analysis of structural and dynamic characteristics of
interlocked systems in solution). To bridge this gap and
confirm the presence of anion templated and particle surface
confined pseudorotaxanes we have used herein high resolution
magic angle spinning (HR MAS) 1H NMR on molecules
tethered to swollen polymer resin beads (facilitating access
to data gathered routinely in solution).44–51 For both particle
types anion association and templated threading is additionally
monitored through perturbations in the indolocarbazole axle
fluorescence emission spectrum.52
(the emission spectrum of the particle solution bearing the
indolocarbazole fingerprint and the formation of Si–O–Si
bonds on the particle surface being detectable by FTIR—see
Fig. S1, ESIw). Model compound 2 was also synthesised
according to literature procedures for comparative solution
phase titration experiments.37
Carboxyl-terminated indolocarbazole derivatives suitable
for tethering to polystyrene bead surfaces were prepared using
the synthetic pathway shown in Scheme 2. Unsymmetrically
functionalised indolocarbazole 9 was synthesised from a
one-pot Fisher indolisation of cyclohexane-1,2-dione with
4-hydrazinylbenzoic acid and p-tolylhydrazine. Ester hydrolysis
afforded indolocarbazole 10. Microwave irradiation of 10,
2-(2-(2-chloroethoxy)ethoxy)ethanol, and Cs2CO3 in dry
DMF, gave the polyethylene glycol substituted indolocarbazole
11. This was converted to the acid derivative 12 via reaction
with succinic anhydride and attached to TentaGel HL-OH
polystyrene beads using literature procedures (with a 20 fold
excess of the calculated maximum possible bead loading
reported to be 0.40 mmol gꢁ1 by the manufacturer).53,54
Although a variety of similar polystyrene resins with various
functionality are now commercially available, TentaGel-OH
beads, with terminal alcohol groups, were selected to tether the
indolocarbazole thread as these have been previously used
successfully in HR MAS NMR experiments.53 The loading of
the indolocarbazole tethered beads 4 was calculated by
elemental analysis to be 0.21 mmol gꢁ1, which is approximately
Results and discussion
Synthesis
The indolocarbazole silica nanoparticles 3 and indolocarbazole
functionalised polystyrene beads 4 as shown in Fig. 1, were
synthesised according to Scheme 1 and 2. Triethoxysilyl-
terminated indolocarbazole derivatives suitable for tethering
to silica nanoparticle surfaces were prepared as shown in
Scheme 1. Methyl ether functionalised indolocarbazole 6 was
prepared according to literature procedures via stepwise Fisher
indolisation of cyclohexane-1,2-dione with p-tolylhydrazine
followed by reaction with 4-methoxyphenylhydrazine
hydrochloride.27 Demethylation of 6 was achieved using
BBr3 to give mono-hydroxy indolocarbazole derivative 7.
Reaction of 7 with 3-(triethoxysilyl)propyl isocyanate in
THF afforded the triethoxylsilane tethered indolocarbazole 8
in quantitative yield. Confinement of 8 on silica nanoparticles
was obtained by refluxing commercially available silica
nanoparticles with freshly prepared 8 in THF (in an amount
designed to provide a well-dispersed particle coverage—see
53% of the estimated functional group loading (0.40 mmol gꢁ1
)
reported by the manufacturer. This surface coverage has been
shown to be sufficient in order to obtain good quality 1H
spectra using HR MAS NMR.54 12 was also converted to its
methyl ester 13 to provide a model compound for comparative
solution NMR experiments.
below). Functionalised nanoparticles 3 were repeatedly
washed and centrifuged with THF, the covalent attachment
of 8 being confirmed by FTIR and fluorescence spectroscopy
NMR investigations
We have previously reported the anion templated pseudo-
rotaxane assembly between an isophthalamide macrocycle 1 and
indolocarbazole in d3-acetonitrile solution.27 In the absence of
sulfate (or fluoride) no evidence of pseudorotaxane assembly is
observed by 1H NMR. However when TBA sulfate is added to
a 1 : 1 solution of macrocycle 1 and indolocarbazole the
macrocycle hydroquinone protons are observed to shift
significantly upfield, which is indicative of interpenetration.
In extending this work to surfaces one would normally not
retain access to structural and dynamic information available
in solution. The use of high resolution magic angle spinning
(HR MAS) NMR on systems covalently attached to swollen
polymer resin beads (such as TentaGel-OH), however, allows
the possibility of obtaining NMR spectra comparable to
solution state spectra.44,45,48–51 Hence direct comparison can
be made between solution and solid-tethered self-assembly and
dynamics of complex supramolecular systems. Thus in an
effort to bridge this gap HR MAS 1H NMR studies of
polystyrene tethered indolocarbazole beads 4 were performed.
The HR MAS 1H NMR spectrum in d3-acetonitrile of
the indolocarbazole tethered beads 4 indicated successful
attachment of the thread to the polystyrene beads with
resonances for the indolocarbazole NH protons evident at
Scheme 1 Synthesis of indolo[2,3-a]carbazole silica nanoparticles 3;
(i) H2SO4, EtOH, reflux, 16 h, 39%; (ii) 4-methoxyphenylhydrazine
hydrochloride, H2SO4, n-BuOH, 90 1C, 24 h, 48%; (iii) BBr3, CH2Cl2,
ꢁ78 1C 1 h, to r.t. 16 h, 85%; (iv) 3-(triethoxysilyl)propyl isocyanate,
Et3N, THF, reflux, 48 h, 98%; (v) silica nanoparticles, THF, reflux, 24 h.
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Scheme 2 Synthesis of polystyrene bead tethered indolo[2,3-a]carbazole 4; (i) H2SO4, BuOH, 90 1C, 4 h; (ii) p-tolylhydrazine, 90 1C, 24 h;
(iii) Pd/C, DMF, reflux, 24 h, 68%; (iv) KOH, i-PrOH–H2O, reflux, 36 h, 72%; (v) 2-(2-(2-chloroethoxy)ethoxy)ethanol, K2CO3, 140 1C, 1 h, 41%;
(vi) succinic anhydride, DMAP, Et3N, r.t, 18 h, 74%; (vii) tentagel-OH beads, EDAC, HOBt, Et3N, THF–CH2Cl2, r.t, 10 days; (viii) EDAC,
DMAP, MeOH–CH2Cl2, r.t, 18 h, 93%.
Fig. 2 Direct NMR comparison between solution phase and solid
bound indolocarbazole threads: top spectrum – HR MAS 1H NMR
spectrum of TentaGelt-OH bound indolocarbazole 4 in CD3CN;
bottom spectrum
(3 mM) in CD3CN.
–
1H NMR spectrum of indolocarbazole 13
Fig. 3 (a) 1H NMR spectrum of a 1 : 1 : 1 mixture of indolocarbazole
13, macrocycle 1 and (TBA)2SO4 in CD3CN, (b) HR MAS NMR
spectrum of TentaGelt-OH bound indolocarbazole 4 in the presence
of excess macrocycle 1 and (TBA)2SO4 in CD3CN, (c) 1H NMR
spectrum of a 1 : 1 mixture of macrocycle 1 and (TBA)2SO4
(both 3 mM) in CD3CN.
10.48 and 9.99 ppm with additional indolocarbazole proton
peaks at 8.85, 8.07, 7.90, 7.66, 7.49, 7.20 ppm (Fig. 2). Slight
downfield shifts in the NH protons for the bead tethered system
when compared directly to the 1H NMR spectrum of the
solution analogue 13 were observed. Addition of an excess of
(TBA)2SO4 to the Tentagel-bound indolocarbazole in CD3CN
produced large (B4 ppm) downfield shifts in the indolo-
carbazole NH proton resonances due to strong hydrogen
bonding with the sulfate anion. Though accurately quantified
binding constants cannot be generated, the extent of this NH
proton shift is both consistent with that seen in analogous
solution studies, and indicative of non-compromised anion
binding at the solid surface (see Fig. S2, ESIw). Under similar
concentration conditions, an equimolar solution of macrocycle
1 and TBA sulfate was then added to the indolocarbazole
tethered beads. The NH peaks again were observed to have
shifted significantly downfield (to 14.29 and 13.61 ppm,
respectively), though to a slightly lesser extent than that
observed for systems containing only TBA sulfate in the
absence of macrocycle (Fig. 3). Similar shifts are observed in
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analogous solution studies (see Fig. S3, ESIw) and attributed to
a weakening of the anion–indolocarbazole hydrogen bonds due
to macrocycle binding i.e., are indicative of pseudorotaxane
formation. More conclusive evidence of pseudorotaxane
formation arises from the fact that two distinct sets of macro-
cycle proton resonances were evident (Fig. 3b). The more
downfield (green) set of protons displayed an NH peak at
10.20, and hydroquinone peaks at 6.90 and 6.77 ppm. Direct
comparison with the analogous solution studies suggests that
this species corresponds to a 1 : 1 macrocycle–(TBA)2SO4
complex (Fig. 3c). The other (more upfield) set of macrocycle
protons (blue) has a NH peak at 10.03, and hydroquinone peaks
at 6.47 and 6.25 ppm. In solution studies we have shown that
upfield shifts in the macrocycle hydroquinone protons are
indicative of the formation of interpenetrated structures.27
Furthermore direct comparison with analogous solution studies
indicate that the chemical shifts of these protons are consistent
with a pseudorotaxane 1 : 1 : 1 macrocycle–indolocarbazole–
(TBA)2SO4 structure (Fig. 3b), thus confirming that anion
induced threading of solid surfaces is possible.
Contrary to solution experiments, these results suggest that
the pseudorotaxane formation on the bead surface is in slow
exchange on the chemical shift timescale. Given the diffusive
restrictions present at even a highly curved interface, this is not
surprising. However, it is possible that the downfield set of
macrocycle resonances (green) originates from molecules
physically ‘entangled’ in the bead core (and thus unable to
access the indolocarbazole thread) as has been observed in
other systems.53 Though further elucidation of this would
require detailed variable temperature analyses, results herein
confirm that sulfate templated pseudorotaxane formation on
the surface of the polystyrene beads is occurring, regardless of
whether the dynamics are in fast or slow exchange.
Fluorescence investigations
Previous work has demonstrated the indolocarbazole hydrogen
bonding association with anions can be followed by fluorescence
modulation of the host.52 Consistent with this, the addition of
TBA sulfate to an acetonitrile solution of 2 was observed to
lead to a loss of emission at 370 and 387 nm and an increase
at 405 nm. The subsequent addition of a molar equivalent
of macrocycle 1 to 2 and TBA sulfate leads to further
perturbation of the emission spectrum (Fig. 4). These changes,
which are not observed on the addition of macrocycle to 2 in
the absence of anion, are ascribed to macrocycle threading
over the indolocarbazole axle hydrogen bonded to the
templating anion. These observations are, additionally, anion
specific; analogous threading induced emission changes are
observed with fluoride but not with chloride or hydrogen
sulfate, fully consistent with the reduced hydrogen bonding
1
affinity of these anions as evidenced from H NMR titrations
(Fig. 5).27
Silica nanoparticles are diffusively mobile, non-quenching,
optically transparent and lend themselves to solution phase
optical switching or optical detection applications that
Fig. 5 Fluorescence titration plots (scattered) and associated fitting
curves (solid) of emission changes in axle 2 on the addition of
macrocycle 1 in the presence of different anions. Significant emission
intensity changes are observed with sulfate but not with chloride
(titrations in acetonitrile, 4.2 ꢂ 10ꢁ5 mol Lꢁ1 in 2). Excitation
330 nm; emission 387 nm.
Fig. 4 (a) Sequential fluorescence titration spectra showing the effects
of adding a molar equivalent of sulfate followed by macrocycle 1 into
an acetonitrile solution of compound 2 (4.2 ꢂ 10ꢁ5 mol Lꢁ1) and
(b) plotted emission changes at 371, 387 and 405 nm (as arrow indicated).
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silica nanoparticles as reactant, respectively. The derived value
of 26–30 nm2 (indicative of a low packing density; this is both
consistent with the axle emission spectrum being the same as
that observed in solution and facilitates threading) can be used
to estimate the relative concentrations of axle and anion in
solution phase titrations. The titration curves shown in Fig. 6
show the macrocycle induced axle emission change in the
presence of different anions. Significant changes are observed
with sulfate and fluoride but not chloride or hydrogen sulfate
consistent with the ability of only the former to template
threading. Though anion and macrocycle are present in a
1 : 1 molar equivalence to each other, spectral changes in
surface confined 2 continue to be observed at several molar
equivalents to the axle (presumably reflecting a kinetic barrier
associated with accessing the surface constrained axle). The fact
that the same anion selectivity for these changes is maintained
as observed for 2 in solution or bead mounted 4 (in that
macrocycle induced axle emission changes are observed only
in the presence of fluoride and sulfate, Fig. 6) strongly supports
the occurrence of template threading at the nanoparticle
surface.
Fig. 6 Fluorescence titration curves (scattered) and associated fitting
curves (solid) of macrocycle 1 addition to acetonitrile solutions of
indolocarbazole modified silicate nanoparticles 3 in the presence of
different anions. Significant emission intensity decreases are observed
for SO4 and Fꢁ but not for Clꢁ or HSO4ꢁ. Excitation: 330 nm;
2ꢁ
emission: 387 nm.
Though spectral quality was limited by particle scattering,
axle derivatised beads 4 (suspended in solution) exhibited
optical responses to sulfate and macrocycle 1 consistent with
that observed in solution with the free axle. A comparison of
sequential titration results of systems 2, 3, and 4 in acetonitrile
is displayed in Fig. 7. In all cases, the initial hydrogen bonding
association of sulfate leads to emission intensity decrease and a
5–6 nm bathochromic shift. Subsequent addition of macrocycle
1 leads to further emission decrease with no associated spectral
shift. It is noteworthy that these observations are not made
unless both sulfate and macrocycle are present in solution.
encompass the advantages of receptor surface immobilisation.
This transparency facilitates an equivalent optical analysis of
anion association with surface confined indolocarbazole
moieties and their subsequent templated threading (Fig. 6
and 7). The addition of sulfate to functionalised nanoparticle
solutions leads to fluorescence intensity decrease and 6 nm
bathochromic shift in the two resolved emission maxima.
Subsequent addition of 1 leads to further decrease in emission
with no further spectral shift. In assuming that the surface
hydroxyl group density is not limiting in the silane condensation
efficacy and that the reaction goes to completion, the footprint
MIꢂASꢂWS
Conclusion
of the axle can be estimated from Fp ¼
where AS is
WIꢂNA
the surface area of silica nanoparticles (manufacturers value
590–690 m2 ꢁ1), MI is the molecular weight of 8, NA is
Avogadro’s number, and WI and WS are the mass of 8 and
Despite the highly tuneable optical and electrical character-
istics potentially offered, there have been only a few published
studies in which a synthesised interlocked structure has been
g
Fig. 7 Fluorescence spectra of (a) 2 (solid curve) in acetonitrile (4.2 ꢂ 10ꢁ5 mol Lꢁ1) and on the sequential addition of 1 molar equivalence of
sulfate (dotted curve) and macrocycle 1 (dashed curve); (b) silica nanoparticle surface confined indolocarbazole 3 (solid curve) in acetonitrile
(0.05 wt%) and the results of sequential addition of sulfate (dotted curve) and macrocycle 1 (dashed curve), respectively; and (c) polystyrene beads
confined indolocarbazole 4 (solid curve) and its sequential addition of sulfate (dotted curve) and macrocycle 1 (dashed curve), respectively. Initial
peak shape and wavelength differences for 2, 3 and 4 in the absence of anions and macrocycles are attributed to the combined effects of different
conformational freedom/aggregation states of the emitter.
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assembled on a nanoparticle surface. In the first example,
Fitzmaurice and co-workers described the assembly of a
hetero[2]pseudorotaxane and an electrochemically addressable
and switchable hetero[2]rotaxane on titanium dioxide nano-
particles through the attachment of a tripodal phosphonate
unit.21,55 Stoddart and co-workers have subsequently reported
the establishment of a series of ‘‘nanovalves’’ on silica nano-
particles from redox or pH driven motion in assembled bistable
[2]pseudorotaxanes. These units are demonstrably capable of
functioning as gatekeepers for the controlled release of dye
molecules from the underlying porous silica nanoparticle.23,24,56
Silica nanoparticles are readily prepared by the controlled
polymerisation of silane precursors under a variety of solution
phase conditions. Highly monodisperse preparations are now
accessible and can be doped with a variety of imaging
agents.57–60 In most preparations the surface of these particles
remain accessible to subsequent robust modification with
dyes, biomolecules or host–guest receptors.61–66 We have
demonstrated here the nanoparticle surface assembly of
hydrogen bonding indolocarbazole axles. The subsequent
specific anion templated threading of an appropriate charge
neutral macrocycle over these can be monitored spectroscopically.
These fluorescence observations mirror those made on swollen
polymer beads where HR MAS NMR analysis has further
confirmed pseudorotaxane formation. The nature of the
anion dictates whether surface pseudorotaxane assembly is
successful, where fluoride and sulfate are effective whilst
chloride and hydrogen sulfate are not, paralleling observations
made in solution.
using a Biotage Initiator 2.0 microwave. Melting points were
recorded on a Gallenkamp capillary melting point apparatus
and are uncorrected. 6-Methyl-2,3,4,9-tetrahydro-1H-carbazol-
1-one 5,27 3-methoxy-8-methyl-11,12-dihydroindolo[2,3-a]-
carbazole 6,27 8-methyl-11,12-dihydroindolo[2,3-a]carbazol-3-ol
7,27 3,8-dimethyl-11,12-dihydroindolo[2,3-a]carbazole 2,52 and
isophthalamide macrocycle 1 were prepared as described
previously.67 FTIR spectra were recorded using a Varian
Digilab FTS 7000 series FTIR spectrometer, with
a
DurasamplIR II diamond attenuated total reflectance
(ATR) accessory. Fluorescence spectra were recorded on a
Hitachi F-4500 Fluorescence Spectrometer (excitation
wavelength set at 330 nm). Solution phase sequential
titration protocol: (1) sulfate added until 1 molar equivalence
into acetonitrile solution of 2 (4.2 ꢂ 10ꢁ5 mol Lꢁ1);
(2) macrocycle added until
1
molar equivalence into
1
: 1 molar equivalence of indolocarbazole–sulfate in
acetonitrile. Particle confined systems titration protocols
are as follows: (1) sulfate added to acetonitrile suspension
of particle confined indolocarbazole until emission
stabilises; (2) macrocycle added until 1 molar equivalence to
total sulfate into particle confined indolocarbazole–sulfate
suspension.
8-Methyl-11,12-dihydroindolo[2,3-a]carbazol-3-yl
3-(triethoxysilyl)propylcarbamate 8
3-Hydroxy-8-methyl-11,12-dihydroindolo[2,3-a]carbazole
7
(65 mg, 0.23 mmol) and 3-(triethoxysilyl)propyl isocyanate
(60 mL, 0.23 mmol) were suspended in dry THF (10 ml)
under N2. Et3N (60 mL) was then added and the mixture
was refluxed under N2 for 48 h. After this time, solvent
and excess Et3N were removed by rotary evaporation
and the product was dried under high vacuum to give
an off-white solid in quantitative yield which was used
immediately without further purification; dH (300 MHz,
DMSO-d6) 11.01 (1 H, s, NH), 10.92 (1 H, s, NH), 7.91
(1 H, s, ArH), 7.82 (1 H, d, J 0.1, ArH), 7.82 (1 H, s, ArH),
7.81 (1 H, d, J 5.5, ArH), 7.71 (1 H, t, J 5.1, NH), 7.61 (1 H, d,
J 8.7, ArH), 7.54 (1 H, d, J 8.4, ArH), 7.18 (1 H, d, J 8.0, ArH),
7.05 (1 H, dd, J 8.7 and 2.0, ArH), 3.71 (6 H, q, J 6.1, CH2),
2.90 (2 H, m, CH2), 2.48 (3 H, s, CH3, coincident with
DMSO), 1.37 (2 H, m, CH2), 1.12 (9 H, t, J 7.9, CH3), 0.47
(2 H, t, J 7.9, CH2); m/z (EI) 533.2 (M+, C29H35N3O5Si
requires 533.2).
Experimental
General considerations
Dry solvents were obtained by purging with nitrogen and then
passing through an MBraun MPSP-800 column. H2O was
de-ionised and microfiltered using
machine. Tetrabutylammonium sulfate was purchased from
a
Milli-Qs Millipore
Sigma-Aldrich as
concentrated on
a
50% aqueous solution, which was
rotary evaporator and subsequently
a
dehydrated by azeotroping with tetrahydrofuran and then dried
over phosphorus pentoxide in a vacuum desiccator. All
tetrabutylammonium salts were stored in a vacuum desiccator
over phosphorus pentoxide prior to use. All other solvents
and commercial grade reagents were used without further
purification.
Solution 1H and 13C NMR spectra were recorded on a
Varian Mercury-VX 300, a Varian Unity Plus 500 or a Bruker
AVII500 with cryoprobe at 293 K. HR MAS NMR spectra
Synthesis of indolo[2,3]carbazole-functionalised silica
nanoparticles 3
were acquired on
a
Bruker DRX400 spectrometer at
1 g of pre-dried silica nanoparticles (Aldrich, silica nano-
powder, 10 nm, BET surface area 590–690 m2 gꢁ1
)
room temperature using a Bruker HR MAS probe. Rotors
containing a suspension of the beads in CDCN3 were spun at
4 kHz. One-dimensional HR MAS spectra were obtained with
64 scans. CPMG pulse sequence contained 32 or 2000 p-pulses
with a repetition time of 30 ms. Chemical shifts (d) are
reported in parts per million relative to residual solvent.
J values are given in Hz. Mass spectra were obtained using a
Micromass GCT (EI) instrument or a Micromass LCT
(ESMS) instrument. Microwave reactions were carried out
were suspended in 50 ml dry THF under N2. Freshly
prepared 8-methyl-11,12-dihydroindolo[2,3-a]carbazol-3-yl
3-(triethoxysilyl)propylcarbamate (20 mg, 0.07 mmol)
8
was added and the mixture was refluxed for 24 h. The
obtained functionalised nanoparticles were repeatedly washed
and centrifuged with THF until there was no fluorescence
signal in the supernatant. The nanoparticles were then dried
under high vacuum and stored in a glove box.
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Butyl 8-methyl-11,12-dihydroindolo[2,3-a]carbazole-3-
2-(2-(2-Hydroxyethoxy)ethoxy)ethyl 8-methyl-11,12-
carboxylate 9
dihydroindolo[2,3-a]carbazole-3-carboxylate 11
p-Hydrazinebenzoic acid (0.76 g, 5.0 mmol) and 1,2-cyclo-
hexanedione (0.56 g, 5.0 mmol) were dissolved in n-butanol
(20 mL). Concentrated H2SO4 (1 mL) was then added
dropwise via syringe. The solution was heated to 90 1C for
4 h, after which time p-tolylhydrazine (0.95 g, 6.0 mmol) was
added as a solid. After being heated to 90 1C for a further 24 h,
the reaction mixture was cooled to room temperature and then
allowed to stand at 4 1C for 16 h. The resulting precipitate was
collected by filtration and washed with H2O (100 mL), MeOH
(3 ꢂ 10 mL) and CH2Cl2 (2 ꢂ 10 mL). The pale yellow solid
was then dissolved in DMF (20 mL) and 10% Pd/C (0.125 g,
B10% by weight) was added. The reaction mixture was
refluxed under N2 for 24 h. After this time the solution
was filtered to remove the catalyst, which was washed with
hot DMF (5 mL). The filtrate and DMF washings were
combined and diluted with H2O (100 mL), upon which a
white precipitate formed. This was collected by filtration,
Dry, de-gassed DMF (10 mL) was added to a mixture of
8-methyl-11,12-dihydroindolo[2,3-a]carbazole-3-carboxylic acid
10 (0.20 g, 0.64 mmol) and K2CO3 (0.22 g, 0.64 mmol) in a
microwave vial. The vial was sealed and 2-(2-(2-chloroethoxy)-
ethoxy)ethanol (0.18 mL, 1.2 mmol) was added via syringe.
The mixture was purged with N2 for 10 minutes before being
heated to 140 1C for 60 minutes using microwave irradiation.
After cooling to room temperature the mixture was filtered
and the precipitate was washed with DMF (2 ꢂ 10 mL). The
combined filtrate and DMF washings were concentrated
in vacuo to yield a viscous yellow oil. Addition of H2O
(100 mL) caused the product to precipitate as an oily white
solid. This was collected by filtration through a plug of celite
and the celite was washed with H2O (4 ꢂ 20 mL). The product
was then eluted from the celite by washing with CH2Cl2–MeOH
1 : 1 (B200 mL) until the filtrate contained no UV active
material. The CH2Cl2–MeOH washings were concentrated
in vacuo and the residual pale yellow oily solid was purified
by column chromatography (SiO2; 2% MeOH–CH2Cl2) to
give the title compound (0.12 g, 41%) as a waxy white solid;
mp 228–230 1C; dH (300 MHz, DMSO-d6) 11.54 (s, 1 H, NH),
11.01 (s, 1 H, NH), 8.80 (1 H, d, J 1.3, ArH), 8.02 (1 H, dd,
J 8.2, and 1.3, ArH), 7.99 (1 H, d, J 8.2, ArH), 7.98 (1 H, br s,
ArH), 7.94 (1 H, d, J 8.2, ArH), 7.77 (1 H, d, J 8.2, ArH), 7.59
(1 H, d, J 8.2, ArH), 7.23 (1 H, dd, J 8.21 and J 1.2) ArH), 4.59
(1 H, t, J 5.6, OH), 4.44 (2 H, m, CH2), 3.81 (2 H, m, CH2),
3.67–3.63 (2 H, m, CH2), 3.59–3.56 (3 H, m, CH2), 3.49–3.44
(3 H, m, CH2); dC (75 MHz, DMSO-d6) 166.6, 141.8, 137.4,
127.7, 126.3, 126.2, 125.8, 125.6, 123.7, 123.6, 121.8, 120.7,
120.2, 119.9, 119.6, 112.6, 111.4, 72.4, 70.0, 69.8, 68.6, 63.7,
60.2, 21.2; m/z (ES) 469.1734 ([M + Na]+, C26H26N2NaO5
requires 469.1734).
washed with H2O (8
ꢂ
30 mL) followed by MeOH
(3 ꢂ 10 mL) and dried under high vacuum to afford the
product (1.261 g, 68%) as a white solid; mp 275 1C (decomp.);
dH (300 MHz; DMSO-d6) 11.53 (1 H, s, NH), 11.01
(1 H, s, NH), 8.80 (1 H, d, J 1.5, ArH), 8.01 (1 H, dd, J 8.7
and 1.5, ArH), 8.0 (1 H, d, J 8.2, ArH), 7.97 (1 H, br s, ArH),
7.94 (1 H, d, J 8.2, ArH), 7.77 (1 H, d, J 8.7, ArH), 7.59
(1 H, d, J 8.2, ArH), 7.23 (1 H, dd, J 8.2 and 1.5, ArH), 4.33
(2 H, t, J 6.5, CO2CH2), 2.50 (3 H, CH3 coincident with
DMSO), 1.76 (2 H, m, CH2), 1.49 (2 H, m, CH2), 0.98
(2 H, t, J 7.3, CH3); dC (125 MHz; DMSO-d6) 166.6,
141.7, 137.4, 127.7, 126.3, 126.2, 125.8, 125.5, 123.8, 123.6,
121.7, 120.6, 120.5, 119.9, 119.6, 112.5, 111.5, 111.4, 64.0,
30.5, 21.2, 18.9, 13.7; m/z (EI) 370.19 (M+, C24H22N2O2
requires 370.17).
8-Methyl-11,12-dihydroindolo[2,3-a]carbazole-3-carboxylic
1-(8-Methyl-11,12-dihydroindolo[2,3-a]carbazol-3-yl)-1,12-
acid 10
dioxo-2,5,8,11-tetraoxapentadecan-15-oic acid 12
Butyl 8-methyl-11,12-dihydroindolo[2,3-a]carbazole-3-carboxylate
9 (0.62 g, 1.7 mmol) was suspended in propan-2-ol (24 mL)
and a solution of potassium hydroxide (6.0 g, 106 mmol) in
H2O (40 mL) was added. The mixture was heated to
2-(2-(2-Hydroxyethoxy)ethoxy)ethyl 8-methyl-11,12-dihydro-
indolo[2,3-a]carbazole-3-carboxylate 11 (0.10 g, 0.22 mmol),
succinic anhydride (0.067 g, 0.67 mmol) and 4-(dimethylamino)-
pyridine (0.003 g, 0.025 mmol) were dissolved in dry DMF
(3 mL). Distilled Et3N (0.16 mL, 1.2 mmol) was added and the
solution was stirred at room temperature under N2 for 18 h.
The reaction mixture was then diluted with CH2Cl2 (100 mL)
and washed with 1 M HCl(aq) (3 ꢂ 50 mL), H2O (2 ꢂ 75 mL)
and brine (75 mL). The organic layer was evaporated to
dryness. The residual yellow solid was dissolved in MeOH,
dry-loaded onto silica and purified by column chromatography
(SiO2; 5% MeOH–EtOAc) to yield the product (0.091 g, 74%)
as a pale yellow solid; mp 190 1C (decomp.); dH (300 MHz,
DMSO-d6) 12.23 (1 H, br s, CO2H), 11.71 (1 H, s, NH), 11.15
(1 H, s, NH), 8.80 (1 H, d, J 1.8, ArH), 8.03–8.00 (1 H, dd,
J 8.5 and 1.8 , ArH), 8.00–7.97 (1 H, d, J 8.2, ArH), 7.97
(1 H, s, ArH), 7.95–7.92 (1 H, d, J 8.2, ArH), 7.78–7.74
(1 H, d, J 8.5, ArH), 7.60–7.57 (1H, d, J 8.2, ArH),
7.24–7.21 (1 H, dd, J 8.2 and 1.2, ArH), 2.48 (1 H, s, CH3);
dC (125 MHz, DMSO-d6) 178.4, 172.2, 166.5, 141.8, 137.4,
127.7, 126.3, 126.2, 125.8, 125.6, 123.7, 123.6, 121.8, 120.6,
reflux under N2 for 36
h until the starting material
had dissolved. The reaction mixture was cooled to room
temperature and acidified with 1 M HCl(aq). The resulting
yellow precipitate was collected by filtration and washed
thoroughly with H2O (8 ꢂ 25 mL) followed by MeOH
(2 ꢂ 15 mL) and CH2Cl2 (2 ꢂ 15 mL). After drying under
high vacuum, the title compound was obtained as a white solid
(0.40 g, 75%); mp 4 300 1C; dH (300 MHz, DMSO-d6) 12.56
(1 H, br s, CO2H), 11.47 (1 H, s, NH), 10.98 (1 H, s, NH), 8.80
(1 H, s, ArH), 8.05–8.02 (1 H, dd, J 8.5 and 1.2, ArH),
7.99–7.90 (2H, m, ArH), 7.75–7.73 (1 H, d, J 8.50, ArH),
7.60–7.58 (1 H, d, J 8.5, ArH), 7.24–7.22 (1 H, d, J 7.9,
ArH), 2.50 (1 H, CH3, coincident with DMSO-d6); dC
(75 MHz; DMSO-d6) 168.3, 141.6, 137.4, 127.7, 126.3, 126.2,
125.9, 125.8, 123.8, 123.6, 122.0, 121.4, 120.6, 120.0, 119.6,
112.5, 111.5, 111.4, 111.3, 21.2; m/z (EI) 314.1059
(M+, C20H14N2O2 requires 314.1055).
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120.2, 119.9, 119.6, 112.6, 111.5, 111.4, 69.9, 69.8, 68.6,
68.3, 63.7, 63.4, 28.7, 28.6, 21.2; m/z (ES) 569.1876
(M + Na+, C30H30N2NaO8 requires 569.1894).
References
1 A. R. Pease, J. O. Jeppesen, J. F. Stoddart, Y. Luo, C. P. Collier
and J. R. Heath, Acc. Chem. Res., 2001, 34, 433–444.
2 A. N. Shipway and I. Willner, Acc. Chem. Res., 2001, 34,
421–432.
Methyl 2-(2-(2-(8-methyl-11,12-dihydroindolo[2,3-a]carbazole-
3 J. Collin, C. Dietrich-Buchecker, P. Gavin, M. C. Jimenez-Molero
and J. Sauvage, Acc. Chem. Res., 2001, 34, 477–487.
4 J. D. Badjic, V. Balzani, A. Credi, S. Silvi and J. F. Stoddart,
Science, 2004, 303, 1845–1849.
5 J. D. Badjic, C. M. Ronconi, J. F. Stoddart, V. Balzani, S. Silvi and
A. Credi, J. Am. Chem. Soc., 2005, 128, 1489–1499.
6 D. S. Marlin, D. G. Cabrera, D. A. Leigh and A. M. Z. Slawin,
Angew. Chem., Int. Ed., 2006, 45, 77–83.
7 D. S. Marlin, D. G. Cabrera, D. A. Leigh and A. M. Z. Slawin,
Angew. Chem., Int. Ed., 2006, 45, 1385–1390.
8 V. Balzani, A. Credi, S. Silvi and M. Venturi, Chem. Soc. Rev.,
2006, 35, 1135–1149.
9 H. Tian and Q.-C. Wang, Chem. Soc. Rev., 2006, 35, 361–374.
10 D. Tuncel, O. Ozsar, H. B. Tiftik and B. Salih, Chem. Commun.,
2007, 1369–1371.
11 E. R. Kay, D. A. Leigh and F. Zerbetto, Angew. Chem., Int. Ed.,
2007, 46, 72–191.
12 P. D. Beer, J. J. Davis, D. A. Drillsma-Milgrom and F. Szemes,
Chem. Commun., 2002, 1716–1717.
13 J. J. Davis and P. D. Beer, The Encyclopedia of Nanoscience and
Nanotechnology, Marcel Dekker, New York, 2004, pp. 2477–2492.
14 S. Chia, J. Cao, J. F. Stoddart and J. I. Zink, Angew. Chem., Int.
Ed., 2001, 40, 2447–2451.
15 F. Cecchet, P. Rudolf, S. Rapino, M. Margotti, F. Paolucci,
J. Baggerman, A. M. Brouwer, E. R. Kay, J. K. Y. Wong and
D. A. Leigh, J. Phys. Chem. B, 2004, 108, 15192–15199.
16 I. Willner, V. Pardo-Yissar, E. Katz and K. T. Ranjit,
J. Electroanal. Chem., 2001, 497, 172–177.
17 L. Raehm, J.-M. Kern, J.-P. Sauvage, C. Hamann, S. Palacin and
J.-P. Bourgoin, Chem.–Eur. J., 2002, 8, 2153–2162.
18 N. Weber, C. Hamann, J. Kern and J. Sauvage, Inorg. Chem.,
2003, 42, 6780–6792.
19 K. Kim, W. S. Jeon, J.-K. Kang, J. W. Lee, S. Y. Jon, T. Kim and
K. Kim, Angew. Chem., Int. Ed., 2003, 42, 2293–2296.
20 E. Katz, O. Lioubashevsky and I. Willner, J. Am. Chem. Soc.,
2004, 126, 15520–15532.
21 B. Long, K. Nikitin and D. Fitzmaurice, J. Am. Chem. Soc., 2003,
125, 15490–15498.
3-carbonyloxy)ethoxy)ethoxy)ethyl succinate 13
1-(8-Methyl-11,12-dihydroindolo[2,3-a]carbazol-3-yl)-1,12-di-
oxo-2,5,8,11-tetraoxapentadecan-15-oic acid 12 (0.060 g, 0.11 mmol)
and 4-(dimethylamino)pyridine (0.0030 g, 0.025 mmol) were
dissolved in a 1 : 1 v/v mixture of CH2Cl2 and MeOH
(10 mL) and N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide
hydrochloride (0.084 g, 0.44 mmol) was added. After stirring
at room temperature under N2 for 18 h, the solvent was
removed in vacuo and the residual yellow solid was purified
by column chromatography (SiO2; 2% MeOH–CH2Cl2) to
give the product (0.057 g, 93%) as an off-white solid; mp
164–165 1C; dH (500 MHz, DMSO-d6) 11.51 (1 H, s, NH),
10.98 (1 H, s, NH), 8.80 (1 H. d, J 1.5, ArH), 8.02 (1 H, dd,
J 8.8 and 1.5, ArH), 7.99 (1 H, d, J 8.5, ArH), 7.97 (1 H, br s,
ArH), 7.93 (1 H, d, J 8.5, ArH), 7.77 (1 H, d, J 8.5, ArH), 7.59
(1 H, d, J 8.2, ArH), 7.23 (1 H, dd, J 8.2 and 1.2, ArH), 4.45
(2 H, t, J 4.7, CH2), 4.11 (2 H, t, J 4.7, CH2), 3.82 (2 H, t, J .7,
CH2), 3.67–3.57 (10 H, m, CH2), 3.56 (3 H, s, CH3); dC
(125 MHz, DMSO-d6) 172.3, 171.9, 166.6, 141.8, 137.4,
127.7, 126.4, 126.2, 125.8, 125.6, 123.8, 123.6, 121.8, 120.7,
120.2, 119.9, 119.6, 112.6, 111.5, 111.4, 69.9, 69.8, 68.6, 68.3,
63.7, 63.5, 51.4, 28.5, 28.4, 21.2; m/z (ES) 583.2029
(M + Na+, C31H31N2NaO8 requires 583.2051).
TentaGelt-OH bound indolocarbazole 4
1-(8-Methyl-11,12-dihydroindolo[2,3-a]carbazol-3-yl)-1,12-di-
oxo-2,5,8,11-tetraoxapentadecan-15-oic acid 12 (0.148 g,
0.27 mmol), N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide
hydrochloride (0.078 g, 0.41 mmol) and 1-hydroxybenzotriazole
hydrate (0.055 g, 0.41 mmol) were dissolved in dry THF
(1 mL) and dry CH2Cl2 (4 mL). Et3N (0.042 mL, 0.30 mmol)
and TentaGel-OHt beads (0.030 g, TentaGelt-HL-OH,
Sigma Aldrich) were then added and the mixture was allowed
to stand at room temperature under N2 for 10 days without
stirring. The beads were then filtered and washed successively
with CH2Cl2 (5 mL), CH2Cl2–MeOH 1 : 1 (5 mL), THF
(5 mL), CH2Cl2 (5 mL), acetone (5 mL), H2O (5 mL),
1 M HCl(aq) (5 mL), H2O (5 mL), sat. NaHCO3(aq) (5 mL),
H2O (5 mL), acetone (5 mL), hexane (2 mL), CH2Cl2
(2 mL), hexane (2 mL), CH2Cl2 (2 mL), MeOH (4 mL) and
diethyl ether (2 mL). The resulting pale yellow beads
22 H. Yu, Y. Luo, K. Beverly, J. F. Stoddart, H.-R. Tseng and
J. R. Heath, Angew. Chem., Int. Ed., 2003, 42, 5706–5711.
23 T. D. Nguyen, K. C.-F. Leung, M. Liong, C. D. Pentecost,
J. F. Stoddart and J. I. Zink, Org. Lett., 2006, 8, 3363–3366.
24 T. D. Nguyen, Y. Liu, S. Saha, K. C. F. Leung, J. F. Stoddart and
J. I. Zink, J. Am. Chem. Soc., 2007, 129, 626–634.
25 M. Clemente-Leon, A. Credi, M.-V. Martınez-Dıaz, C. Mingotaud
´ ´ ´
and J. F. Stoddart, Adv. Mater., 2006, 18, 1291–1296.
26 S. R. Bayley, T. M. Gray, M. J. Chmielewski, P. D. Beer and
J. J. Davis, Chem. Commun., 2007, 2234–2236.
27 M. J. Chmielewski, L. Zhao, A. Brown, D. Curiel,
M. R. Sambrook, A. L. Thompson, S. M. Santos, V. Felix,
J. J. Davis and P. D. Beer, Chem. Commun., 2008, 3154–3156.
28 K. J. Chang, D. Moon, M. S. Lah and K. S. Jeong, Angew. Chem.,
Int. Ed., 2005, 44, 7926–7929.
29 T. H. Kwon and K. S. Jeong, Tetrahedron Lett., 2006, 47,
8539–8541.
were dried under high vacuum. Found
C 64.36, H
7.88, N 0.58, from which the loading is calculated to be
0.21 mmol gꢁ1; dH (400 MHz, CD3CN) 10.47 (1 H, s, NH),
9.98 (1 H, s, NH), 8.85 (1 H, s, ArH), 8.07 (1 H, s, ArH), 7.90
(3 H, s, ArH), 7.65 (1 H, d, ArH), 7.49 (1 H, d, ArH), 7.19
(1 H, d, ArH), 4.44 (2 H, br s, CH2), 4.09 (2 H, m, CH2),
3.64–3.58 (10 H, m, CH2).
30 K. J. Chang, M. K. Chae, C. Lee, J. Y. Lee and K. S. Jeong,
Tetrahedron Lett., 2006, 47, 6385–6388.
31 J. Y. Lee, M. H. Lee and K. S. Jeong, Supramol. Chem., 2007, 19,
257–263.
32 K. J. Chang, B. N. Kang, M. H. Lee and K. S. Jeong, J. Am. Chem.
Soc., 2005, 127, 12214–12215.
33 F. M. Pfeffer, K. F. Lim and K. J. Sedgwick, Org. Biomol. Chem.,
2007, 5, 1795–1799.
34 J. L. Sessler, D. G. Cho and V. Lynch, J. Am. Chem. Soc., 2006,
128, 16518–16519.
Acknowledgements
35 G. W. Bates, P. A. Gale and M. E. Light, Chem. Commun., 2007,
2121–2123.
We thank the EPSRC for postdoctoral fellowships (LZ, MJC,
KMM), and DTA funding (AB).
36 G. W. Bates, Triyanti, M. E. Light, M. Albrecht and P. A. Gale,
J. Org. Chem., 2007, 72, 8921–8927.
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View Article Online
37 D. Curiel, A. Cowley and P. D. Beer, Chem. Commun., 2005,
236–238.
38 P. Piatek, V. M. Lynch and J. L. Sessler, J. Am. Chem. Soc., 2004,
126, 16073–16076.
54 K. D. Johnstone, Self-Assembling Porphyrin Supramolecules, PhD
Thesis, University of New England, Armidale, 2004.
55 K. Nikitin, B. Long and D. Fitzmaurice, J. Am. Chem. Soc., 2003,
125, 15490–15498.
39 M. J. Chmielewski, M. Charon and J. Jurczak, Org. Lett., 2004, 6,
3501–3504.
56 T. D. Nguyen, H.-R. Tseng, P. C. Celestre, A. H. Flood, Y. Liu,
J. F. Stoddart and J. I. Zink, Proc. Natl. Acad. Sci. U. S. A., 2005,
102, 10029–10034.
57 S. Santra, H. Yang, D. Dutta, J. T. Stanley, P. H. Holloway,
W. Tan, B. M. Moudgil and R. A. Mericle, Chem. Commun., 2004,
2810–2812.
40 P. A. Gale, Chem. Commun., 2008, 4525–4540.
41 C. Caltagirone, J. R. Hiscock, M. B. Hursthouse, M. E. Light and
P. A. Gale, Chem.–Eur. J., 2008, 14, 10236–10243.
42 C. Caltagirone, P. A. Gale, J. R. Hiscock, S. J. Brooks,
M. B. Hursthouse and M. E. Light, Chem. Commun., 2008,
3007–3009.
58 M. Nakamura, M. Shono and K. Ishimura, Anal. Chem., 2007, 79,
6507–6514.
43 M. D. Lankshear and P. D. Beer, Acc. Chem. Res., 2007, 40,
657–668.
44 B. J. Egner and M. Bradley, Drug Discovery Today, 1997, 2,
102–109.
45 G. Lippens, M. Bourdonneau, C. Dhalluin, R. Warrass,
T. Richert, C. Seetharaman, C. Boutillon and M. Piotto, Curr.
Org. Chem., 1999, 3, 147–169.
59 E. Rampazzo, S. Bonacchi, M. Montalti, L. Prodi and
N. Zaccheroni, J. Am. Chem. Soc., 2007, 129, 14251–14256.
60 E. Rampazzo, E. Brasola, S. Marcuz, F. Mancin, P. Tecilla and
U. Tonellato, J. Mater. Chem., 2005, 15, 2697–2706.
61 G. Farruggia, S. Iotti, L. Prodi, M. Montalti, N. Zaccheroni,
P. B. Savage, V. Trapani, P. Sale and F. I. Wolf, J. Am. Chem.
Soc., 2006, 128, 344–350.
46 K. D. Johnstone, N. Bampos, J. K. M. Sanders and M. J. Gunter,
Chem. Commun., 2003, 1396–1397.
62 M. Arduini, F. Mancin, P. Tecilla and U. Tonellato, Langmuir,
2007, 23, 8632–8636.
47 K. D. Johnstone, N. Bampos, J. K. M. Sanders and M. J. Gunter,
New J. Chem., 2006, 30, 861–867.
63 X. Y. Ling, D. N. Reinhoudt and J. Huskens, Langmuir, 2006, 22,
8777–8783.
48 M. J. Shapiro and J. R. Wareing, Curr. Opin. Chem. Biol., 1998, 2,
372–375.
49 D. Huster, K. Kuhn, D. Kadereit, H. Waldmann and K. Arnold,
Angew. Chem., Int. Ed., 2001, 40, 1056–1058.
50 M. A. Gallop and W. L. Fitch, Curr. Opin. Chem. Biol., 1997, 1,
94–100.
64 G. Barbillon, A. C. Faure, N. ElKork, P. Moretti, S. Roux,
O. Tillement, M. G. Ou, A. Descamps, P. Perriat, A. Vial,
J.-L. Bijeon, C. A. Marquette and B. Jacquier, Nanotechnology,
2008, 19, 035705.
65 N. Baker, G. M. Greenway, R. A. Wheatley and C. Wiles, Analyst,
2007, 132, 104–106.
51 E. Brule, K. K. M. Hii and Y. R. de Miguel, Org. Biomol. Chem.,
2005, 3, 1971–1976.
52 D. Curiel, A. Cowley and P. D. Beer, Chem. Commun., 2005,
236–238.
53 K. M. Mullen, K. D. Johnstone, M. Webb, N. Bampos, J. K.
M. Sanders and M. Gunter, Org. Biomol. Chem., 2008, 6, 278–286.
66 K. Patel, S. Angelos, W. R. Dichtel, A. Coskun, Y.-W. Yang,
J. I. Zink and J. F. Stoddart, J. Am. Chem. Soc., 2008, 130,
2382–2383.
67 M. R. Sambrook, P. D. Beer, J. A. Wisner, R. L. Paul,
A. R. Cowley, F. Szemes and M. G. B. Drew, J. Am. Chem.
Soc., 2005, 127, 2292–2302.
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768 | New J. Chem., 2009, 33, 760–768