A rotaxane host system containing integrated triazole C-H hydrogen bond donors for anion recognition

Article abstract of DOI:10.1039/c2ob27229f

Two rotaxanes incorporating a 3,5-bis(triazole)-pyridinium axle component have been prepared using either an anion templated amide condensation or ring closing metathesis (RCM) clipping strategy. The respective yields of interlocked receptor were found to be significantly higher when the RCM clipping synthetic route was used. Proton NMR titration experiments in competitive 1:1 CDCl ₃-CD₃OD solvent media reveal that the rotaxane prepared by the clipping procedure is selective for halide anions over larger, more basic oxoanions. Interestingly, the interlocked host displays an unusual preference for bromide over other halide anions.

Full text of DOI:10.1039/c2ob27229f

Organic &
Biomolecular Chemistry
View Article Online
View Journal | View Issue
PAPER
A rotaxane host system containing integrated triazole
C–H hydrogen bond donors for anion recognition†
Cite this: Org. Biomol. Chem., 2013, 11,
1326
Nicholas G. White and Paul D. Beer*
Two rotaxanes incorporating a 3,5-bis(triazole)-pyridinium axle component have been prepared using
either an anion templated amide condensation or ring closing metathesis (RCM) clipping strategy. The
respective yields of interlocked receptor were found to be significantly higher when the RCM clipping
synthetic route was used. Proton NMR titration experiments in competitive 1 : 1 CDCl3–CD3OD solvent
media reveal that the rotaxane prepared by the clipping procedure is selective for halide anions over
larger, more basic oxoanions. Interestingly, the interlocked host displays an unusual preference for
bromide over other halide anions.
Received 16th November 2012,
Accepted 18th December 2012
DOI: 10.1039/c2ob27229f
www.rsc.org/obc
Introduction
Since independent reports in 2008 demonstrated that synthetic
host systems containing 1,2,3-triazole groups can interact with
anions in organic solvents solely through C–H⋯anion hydro-
gen bonds,1–3 numerous receptors incorporating these hetero-
cycles have been described.4–28 These triazole groups can be
readily prepared using copper(I)-catalyzed azide–alkyne cyclo-
addition (CuAAC) reactions,29,30 and indeed this reaction has
frequently been used to construct mechanically interlocked
architectures.31–35 Surprisingly, however, to the best of our
knowledge, only two36 triazole containing interlocked host
systems have been reported where the triazole group is used as
an anion recognition motif.37,38
Li and co-workers’ triazole axle containing rotaxane acts as
a dual response molecular switch, with translocation of the
macrocyclic component occurring in response to acid/base
stimulus, and chloride anion addition causing subsequent
rotation of the macrocycle.37 Furthermore, the non-protonated
form of the rotaxane was reported to display modest associ-
ation with halide anions in CD3CN.
Fig. 1 Halide anion selective bis-triazole pyridinium catenane 1·PF6.38
is an order of magnitude more pronounced for the tria-
zole containing host than for the analogous 3,5-bis(amide)-
pyridinium catenane receptor.
Previous rotaxane receptor systems have displayed stronger
and more selective anion recognition when compared to cate-
nane analogues. This was attributed to their more rigid struc-
ture, and the introduction of aryl–axle substituents to the
amide donor groups, increasing the acidity of these hydrogen
bond donors.39 Herein, we describe the integration of the bis-
triazole pyridinium motif into the axle component of a rotax-
ane structural framework and investigate the anion recognition
properties of the resulting interlocked host.
We recently reported a catenane containing a 3,5-bis-
(triazole)-pyridinium motif (Fig. 1), which selectively binds
halide anions over dihydrogenphosphate in competitive 1 : 1
CDCl3–CD3OD solvent mixtures.38 Importantly, this selectivity
Results and discussion
Chemistry Research Laboratory, Department of Chemistry, University of Oxford,
12 Mansfield Road, Oxford, OX1 3TA, UK. E-mail: paul.beer@chem.ox.ac.uk;
Two chloride anion templated synthetic procedures were
undertaken to prepare the target triazole containing rotaxane
host structure, an acid chloride/amine condensation reaction40
and a RCM clipping protocol.41 Both synthetic routes required
the initial preparation of a new 3,5-bis(triazole)-pyridinium
axle component.
Fax: +44 (0) 1865 272690; Tel: +44 (0) 1865 285142
†Electronic supplementary information (ESI) available: 1H and 13C NMR spectra
of new compounds, ROESY NMR spectrum of 9·PF6, details of instrumentation,
titration protocols and full crystallographic data in CIF format. CCDC 911205
and 911206. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c2ob27229f
1326 | Org. Biomol. Chem., 2013, 11, 1326–1333
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
Scheme 1 Synthesis of axle component 5·PF6.
Synthesis of bis-triazole pyridinium axle component
macrocycle amide group. Surprisingly no aromatic donor–
acceptor interactions are observed between the pyridinium
ring of the axle and the macrocycle’s hydroquinone groups
(closest centroid⋯centroid distance = 3.99 Å).
The azide-appended stopper group 2 was prepared from
amine 342 using sodium nitrite and sodium azide in 9 : 1
ethanol–conc. HCl(aq) (Scheme 1). CuAAC reaction of two
equivalents of 2 and 3,5-diethynyl pyridine43 gave the bis-
triazole axle component 4 in 83% yield. Selective alkylation of
the pyridine group was achieved using excess methyl iodide in
dichloromethane at room temperature to give 5·I. It was found
that halide salts of 5+ exhibited very poor solubility in
common organic solvents, and as a consequence 5·I was anion
exchanged using Amberlite® resin to give 5·PF6 in an overall
yield of 63% from 4.
Synthesis of rotaxane via clipping
Given the small amounts of rotaxane isolated using an amide
condensation route, a clipping strategy41 was instead investi-
gated for the preparation of the target triazole containing
rotaxane (Scheme 3). The addition of Grubbs’ II catalyst to an
1 : 1 : 1.5 stoichiometric mixture of 5·PF6, TBA·Cl (TBA = tetra-
butylammonium) and bis-vinyl-appended macrocycle precur-
sor 847 in dry dichloromethane gave the target rotaxane 9+,
with integration of the crude 1H NMR spectrum indicating a
yield of formation of approximately 65%.
Purification by preparative TLC, anion exchange by washing
with NH4PF6(aq) and recrystallisation afforded 9·PF6 in 44%
overall isolated yield. The new rotaxane was characterized by
1H, 13C, 19F and 31P NMR, as well as by high resolution ESI
mass spectrometry. The interlocked nature of the rotaxane was
also confirmed by 2D ROESY NMR spectroscopy (Fig. S10†).
The synthesis of analogous rotaxanes containing a bis-
amide pyridinium axle component proceeded in similar yields
via RCM clipping (43–57%)41,47 or amide condensation
(55–60%) strategies.40 By contrast, with the bis-triazole pyridi-
nium axle component 5·PF6, the crude and isolated yields of
rotaxane are significantly higher for clipping than conden-
sation (65 and 20% crude yields, and 44 and 11% isolated
yields for clipping and condensation, respectively).
Synthesis of rotaxane via amide condensation strategy
Rotaxane formation was initially attempted via condensation
of a bis-amine and bis-acid chloride in the presence of axle
component 5+, as this synthetic procedure has proven to be an
effective method for preparing rotaxanes containing a bis-
amide pyridinium axle component.40,44 An equimolar mixture
of axle 5·PF6,45 bis-amine 646 and isophthaloyl dichloride were
stirred in dry dichloromethane containing excess triethylamine
1
(Scheme 2). Integration of the H NMR spectrum of the crude
reaction mixture indicated that the rotaxane had formed in
approximately 20% yield. After purification by preparative TLC
and anion exchange by washing the product with aqueous
NH4PF6, the target rotaxane 7·PF6 was isolated in 11% yield,
1
and characterized by H and 19F NMR spectroscopy, as well as
high resolution ESI mass spectrometry. Twinned crystals of
7·PF6 suitable for X-ray diffraction structural analysis were
obtained, enabling solid state characterization and confir-
Anion recognition properties of 9·PF6
mation of the interlocked nature of the product (Fig. 2). Three
−
weak rotaxane⋯PF6 hydrogen bonds are observed, two The anion recognition properties of 9·PF6 were investigated
from the axle component’s triazole donors and one from a using 1H NMR titration experiments in the competitive solvent
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 1326–1333 | 1327

View Article Online
Paper
Organic & Biomolecular Chemistry
Scheme 2 Synthesis of rotaxane 7·PF6.
mixture 1 : 1 CDCl3–CD3OD. Addition of halide anions to 9·PF6 stoichiometric association constants (Table 1), which are com-
causes downfield shifts in the rotaxane’s cavity resonances a–c pared with association constant values obtained for the bis-tria-
and 1–3 (Fig. 3), consistent with hydrogen bonding between zole pyridinium catenane 1·PF6.38 The rotaxane host displays
these protons and the anion. Interestingly, the addition of an unusual preference for bromide anion, with this halide
chloride and bromide anions to 9·PF6 causes significantly being bound significantly more strongly than iodide, which is
smaller shifts in the cavity protons than was observed for the itself complexed more strongly than chloride. This may be a
analogous bis-triazole pyridinium catenane 1·PF6.38 Given its result of the complementary size of the axle’s 3,5-bis(triazole)-
lower basicity compared to chloride and bromide, it is note- pyridinium binding cleft, which is two atoms larger than in the
worthy that iodide causes the largest magnitude perturbations analogous 3,5-bis(amide) pyridinium containing rotaxane. The
(Fig. 4).
rotaxane displays a strong preference for the halide anions over
WINEQNMR248 analysis of the titration data, monitoring the larger, more basic oxoanions, although this is not as pro-
the axle component’s triazole resonance determined 1 : 1 nounced as was observed with the catenane analogue 1·PF6.38
1328 | Org. Biomol. Chem., 2013, 11, 1326–1333
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
This is perhaps unexpected, as amide based rotaxane host
systems have typically exhibited a much higher degree of selec-
tivity for halides over oxoanions than analogous catenanes,
attributed to their more rigid nature.39 Importantly, enhanced
selectivity is however observed for the new triazole containing
38
rotaxane host over catenane analogue 1·PF6
in discrimi-
nation between the halide anions. A tentative explanation for
this can be postulated by considering the differing binding
modes of the various anions: the halides bind inside the inter-
locked hosts’ three-dimensional cavities39 allowing the more
rigid rotaxane to exhibit a degree of selectivity that is absent in
the catenane. Conversely, the larger basic oxoanions associate
on the exterior of the host,40 and so are affected more by the
strongest donor groups in the host, in this case the charged
bis-triazole pyridinium motif, and less by the three-dimen-
sional cavity. The aryl-substituted bis-triazole pyridinium
Fig. 2 Solid state structure of 7·PF6. Solvent molecules, and most hydrogen
atoms are omitted for clarity.
Scheme 3 Synthesis of rotaxane 9·PF6.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 1326–1333 | 1329

View Article Online
Paper
Organic & Biomolecular Chemistry
t
Fig. 3 Truncated 1H NMR spectrum of 9·PF6 upon addition of one equivalent
of chloride anion (293 K, 1 : 1 CDCl3–CD3OD, 500 MHz).
Fig. 5 Solid state structure of 9·Cl. Minor position of butyl disorder, and most
hydrogen atoms omitted for clarity.
the axle component’s para-pyridinium proton and the macro-
cycle’s interior phenylene proton. Receptor⋯anion hydrogen
bonds are significantly shorter in this structure than in
the crystal structure of catenane 1·Cl, although no pyridi-
nium⋯hydroquinone aromatic donor–acceptor interactions
are present in the solid state structure of the rotaxane, which
were observed in the catenane crystal structure.
Conclusions
Two novel rotaxanes incorporating the bis-triazole pyridinium
motif have been prepared. It was found that an amide conden-
sation route gave relatively low yields of the interlocked
product (20% crude yield, 11% isolated yield), while a chloride
anion templated ring-closing metathesis strategy was signifi-
cantly more successful (65% crude yield, 44% isolated yield). It
is noteworthy that rotaxane 9·PF6 displays an unusual prefer-
ence for bromide over the other halide anions, and all halides
are bound significantly more strongly than the larger more
basic oxoanions. The selectivity preferences for the rotaxane
are markedly different from the bis-triazole containing cate-
nane 1·PF6,38 which displays little preference between the
halide anions, but a more pronounced selectivity for the
halides over oxoanions.
Fig. 4 Experimental titration data (points) and fitted binding isotherms (lines)
for addition of anions to 9·PF6 (293 K, 1 : 1 CDCl3–CD3OD, 500 MHz).
Table 1 Association constants, Ka (M−1) for anions and pyridinium bis-triazole
interlocked host systemsa
38
Anion
Rotaxane 9·PF6
Catenane 1·PF6
Cl−
411(18)
936(40)
640(29)
186(9)
679(20)
632(45)
509(10)
49(4)
Br−
I−
H2PO4
OAc−
−
b
137(3)
—
a Anions added as TBA salts, estimated standard errors are given in
parentheses. Association constants calculated using WINEQNMR248
(1 : 1 CDCl3–CD3OD, 293 K). b Movement of peaks too small to infer a
binding event.
Experimental
General remarks
TBTA,49 tetraphenyl amine 3,42 bis-amine 6,46 and macrocycle
precursor 847 were prepared as previously described.
3,5-Diethynyl pyridine was prepared by deprotecting bis-
(trimethylsilylethynyl)pyridine50 using KOH in methanol.51
Other chemicals are available commercially, and used as
received. Where solvents are specified as “dry”, they were
purged with nitrogen and passed through an MBraun
MPSP-800 column. NEt3 was distilled from, and stored over
KOH pellets. Water was deionised and microfiltered using a
motif in the rotaxane is a more potent anion complexant than
the alkyl-substituted motif in the catenane, and so stronger
recognition of the oxoanions, and concomitant reduced selec-
tivity results.
Small single crystals of 9·Cl suitable for synchrotron X-ray
structural analysis were obtained from the 1H NMR titration
experiment (Fig. 5). The chloride anion is bound within the
rotaxane’s host cavity with significant hydrogen bonds
observed from both amide and both triazole groups, as well as
1330 | Org. Biomol. Chem., 2013, 11, 1326–1333
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
Milli-Q Millipore machine. TBA salts, TBTA and [Cu(CH3CN)4]- exchange beads. The suspension was separated from the beads
(PF6) were stored in a vacuum dessicator. Chromatography was by decanting, and the acetone removed under reduced
performed on silica gel (particle size: 40–63 μm) or preparative pressure. The remaining aqueous suspension was extracted
TLC plates (20 × 20 cm, silica thickness: 1 mm). Details of with CH2Cl2 (4 × 50 mL) and the combined organic fractions
instrumentation, copies of NMR spectra, and details of titra- washed with NH4 PF6(aq) (2 × 75 mL) and H2O (2 × 75 mL), and
tion protocols are given in the ESI.†
then dried (MgSO4) to give 5·PF6 as an off-white powder. Yield:
0.211 g (63%).
Azide-appended stopper 2
4
4
1H NMR (CDCl3): 9.21 (t, J = 1.2 Hz, 1H, Hpy), 9.18 (d, J =
Aniline stopper 3, (1.01 g, 2.00 mmol) was suspended in 9 : 1 1.2 Hz, 2H, Hpy), 8.83 (s, 2H, Htrz), 7.63–7.68 (m, 4H, HAr),
ethanol–conc. HCl(aq) (500 mL), and the mixture gently 7.39–7.44 (m, 4H, HAr), 7.23–7.29 (m, 12H, HAr), 7.10–7.15
warmed, causing all material to dissolve. It was cooled to 0 °C (m, 12H, HAr), 4.48 (s, 3H, HCH3), 1.30 (s, 54H, HtBu). 13C NMR
and sodium nitrite (0.276 g, 4.00 mmol) was added, followed (d6-DMSO): 148.5, 148.1, 143.3, 141.3, 135.3, 134.3, 133.8,
by sodium azide (0.260 g, 4.00 mmol). The reaction was stirred 131.9, 130.6, 129.9, 124.7, 122.8, 119.8, 63.3, 48.7, 34.1, 31.1.
under a nitrogen atmosphere for an hour at 0 °C, before being 19F NMR (d6-DMSO): −71.2 (d, JP,F = 711 Hz). 31P NMR
allowed to warm to room temperature overnight. The reaction (d6-DMSO): −144.3 (septet, JP,F = 711 Hz). HRESI-MS (pos.):
was diluted with water (200 mL), and extracted with diethyl 1200.7586, calc. for [C84H94N7]+ = 1200.7565.
ether (2 × 200 mL). The combined organic fractions were
Amide condensation rotaxane 7·PF6
washed with saturated aqueous sodium carbonate (2
×
150 mL) and brine (150 mL), dried (MgSO4) and taken to The axle component 5·PF6 (0.040 g, 0.030 mmol) was dissolved
dryness under reduced pressure. The resulting white powder in dry CH2Cl2 (50 mL). NEt3 (0.010 mL, 0.0076 g, 0.075 mmol)
was taken up in 1 : 1 petrol–dichloromethane and filtered was added, followed by bis-amine 6 (0.014 g, 0.030 mmol) and
through a short pad of silica, washing through with further isophthaloyl dichloride (0.0061 g, 0.030 mmol) in dry CH2Cl2
1 : 1 petrol–dichloromethane. Evaporation of the solvent gave (2 mL). The reaction was stirred at room temperature under a
pure 2 as a white powder. Yield: 0.876 g (83%).
nitrogen atmosphere for 2 hours, washed with HCl(aq) (10%,
1H NMR (CDCl3): 7.24 (d, J = 8.6 Hz, 6H, HAr), 7.17 (d, J = 2 × 30 mL), brine (30 mL), dried (MgSO4), and taken to dryness
8.8 Hz, 2H, HAr), 7.07 (d, 3J = 8.6 Hz, 6H, HAr), 6.90 (d, 3J = under reduced pressure. Integration of the crude 1H NMR
8.8 Hz, 2H, HAr), 1.30 (s, 54H, HtBu). 13C NMR (CDCl3): 148.7, spectrum suggested the rotaxane was formed in approximately
144.5, 143.8, 137.4, 132.7, 130.8, 124.3, 117.9, 63.4, 34.5, 31.5. 20% yield. The crude solid was purified by preparative TLC
3
3
HRMS (EI/FI): 529.3448, calc. for [C37H43N3]+ = 529.3457.
(3% CH3OH in CH2Cl2), then taken up in CH2Cl2 (20 mL) and
washed with NH4PF6(aq) (0.1 M, 6 × 20 mL) and H2O (2 ×
Pyridine bis-triazole axle 4
20 mL). Drying thoroughly in vacuo gave 7·PF6 as a white
1
The azide 2 (0.233 g, 0.440 mmol) and 3,5-diethynylpyridine powder, which was shown by H NMR spectroscopy to contain
(0.025 g, 0.20 mmol) were dissolved in CH2Cl2 (25 mL). DIPEA small amounts of impurities. Yield: 0.0062 g (11%). A pure
(0.090 mL, 0.065 g, 0.50 mmol), TBTA (0.021 g, 0.040 mmol), sample was obtained by recrystallization from CH3OH–CHCl3
and [Cu(CH3CN)4](PF6) (0.015 g, 0.040 mmol) were added and (4 : 1).
the resulting yellow solution stirred at room temperature
under a nitrogen atmosphere for 5 days. The reaction mixture
1H NMR (1 : 1 CDCl3–CD3OD): 9.03 (s, 2H, Hpy), 8.93 (s, 2H,
trz), 8.68 (s, 1H, Hpy), 8.51 (s, 1H, Hint. macro. Ar CH), 8.01–8.06
H
was taken to dryness under reduced pressure and purified by (m, 3H, Hext. macro. Ar CH), 7.68 (d, J = 8.8 Hz, 4H, HAr), 7.43
column chromatography (3% CH3OH in CHCl3) to give 4 as a (d, J = 8.8 Hz, 4H, HAr), 7.31–7.34 (m, 12H, HAr), 7.12–7.15
white powder. Yield: 0.197 g (83%).
(m, 12H, HAr), 6.36 (d, J = 9.1 Hz, 4H, Hhydroquinone), 6.17 (d, J =
4
4
1H NMR (CDCl3): 9.13 (d, J = 1.9 Hz, 2H, Hpy), 8.76 (t, J = 9.1 Hz, 4H, Hhydroquinone), 4.43 (s, 3H, HCH3), 3.88 (t, J = 4.8 Hz,
1.9 Hz, 1H, Hpy) 8.34 (s, 2H, Htrz), 7.66–7.69 (m, 4H, HAr), 4H, HCH2), 3.82–3.84 (m, 4H, HCH2), 3.73–3.75 (m, 4H, HCH2),
7.42–7.45 (m, 4H, HAr), 7.25–7.29 (m, 12H, HAr), 7.11–7.14 3.64–3.71 (m, 8H, HCH2), 3.51–3.53 (m, 4H, HCH2), 1.30
(m, 12H, HAr), 1.32 (s, 54H, HtBu). 13C NMR (CDCl3): 149.1, (s, 54H, HtBu). 19F NMR (CDCl3): −73.4 (d, JP,F = 711 Hz).
148.9, 146.8, 145.1, 143.4, 134.5, 132.8, 130.8, 130.1, 126.7, HRESI-MS (pos.): 1911.0968, calc. for [C122H144N9O11
+
]
=
124.5, 119.6, 118.6, 63.8, 34.5, 31.5. HRESI-MS (pos.): 1911.0980.
1208.7231, calc. for [C83H91N7Na]+ = 1208.7228.
Clipping rotaxane 9·PF6
Pyridinium bis-triazole axle 5·PF6
The pyridinium bis-triazole axle component 5·PF6 (0.034 g,
The neutral axle component 4 (0.297 g, 2.50 mmol) was dis- 0.025 mmol) was dissolved in dry CH2Cl2 (70 mL), and the solu-
solved in dry CH2Cl2 (20 mL) in a vial. CH3I (0.37 mL, 0.85 g, tion reduced in volume to 20 mL under reduced pressure.
6.0 mmol) was added, and the vial sealed. It was stirred at The macrocycle precursor 8 (0.024 g, 0.038 mmol), TBA·Cl
room temperature for 7 days and then purified by column (0.0069 g, 0.025 mmol) and Grubbs’ II catalyst (0.0024 g, 10%
chromatography (2% CH3OH in CHCl3) to give the product as by weight) were added, and the mixture stirred at room temp-
its iodide salt. It was suspended in 7 : 3 acetone–H2O (100 mL) erature under a nitrogen atmosphere for 3 days. It was taken
and stirred for 16 hours with PF6−-loaded Amberlite® anion to dryness and purified by preparative TLC (2% CH3OH
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 1326–1333 | 1331

View Article Online
Paper
Organic & Biomolecular Chemistry
in CH2Cl2) to give a crude product containing a mixture of
rotaxane and ring-closed macrocycle (accounting for the pres-
Acknowledgements
ence of macrocycle impurity, the yield at this point was esti- We thank Diamond Lightsource for an award of beamtime on
mated to be 65% on the basis of 1H NMR analysis). This Beamline I19. NGW thanks the Clarendon Fund, Trinity
material was taken up in CH2Cl2 (20 mL), washed with NH4PF6(aq) College Oxford, and the Vice-Chancellors’ Fund for financial
(0.1 M, 7 × 20 mL), and H2O (3 × 20 mL) and taken to support.
dryness. Recrystallization from CH3OH–CHCl3 (5 mL,
∼4 : 1) gave pure 9·PF6 as a pale yellow powder. Yield: 0.022 g
(44%).
Notes and references
1H NMR (1 : 1 CDCl3–CD3OD): 9.15 (s, 1H, Hpy), 9.03 (s, 2H,
Hpy), 8.84–8.87 (m, 3H, Hint. macro.Ar CH, 2 × Htrz), 8.78 (s, 2H,
ext. macro. Ar CH), 8.53 (br. s, 2H, Hamide), 7.70 (d, J = 8.8 Hz,
4H, HAr), 7.45 (d, J = 8.8 Hz, 4H, HAr), 7.28 (d, J = 8.6 Hz,
12H, HAr), 7.12 (d, J = 8.6 Hz, 12H, HAr), 6.14–6.27 (m, 8H,
1 H. Juwarker, J. M. Lenhardt, D. M. Pham and S. L. Craig,
Angew. Chem., Int. Ed., 2008, 47, 3740–3743.
2 Y. Li and A. H. Flood, Angew. Chem., Int. Ed., 2008, 47,
2649–2652.
H
H
hydroquinone), 5.99 (br. s, 2H, Halkene), 4.39 (s, 3H, HCH3),
3 R. M. Meudtner and S. Hecht, Angew. Chem., Int. Ed., 2008,
47, 4926–4930.
4 Y. Li, M. Pink, J. A. Karty and A. H. Flood, J. Am. Chem. Soc.,
2008, 130, 17293–17295.
5 Y. Li and A. H. Flood, J. Am. Chem. Soc., 2008, 130,
12111–12122.
6 Y. Hua and A. H. Flood, J. Am. Chem. Soc., 2010, 132,
12838–12840.
4.03–4.06 (m, 4H, HCH2), 3.65–3.86 (m, 16H, HCH2), 1.30
(s, 54H, HtBu). 13C NMR (1 : 1 CDCl3–CD3OD): 166.7, 153.5,
153.3, 150.2, 149.5, 149.3, 144.1, 141.7, 140.2, 137.0, 135.4,
134.6, 133.3, 132.5, 132.1, 131.3, 130.5, 126.1, 125.1, 122.4,
119.7, 115.5, 115.1, 78.5, 71.5, 69.9, 68.4, 67.3, 64.4, 40.8, 34.9,
31.7. 19F NMR (1 : 1 CDCl3–CD3OD): −72.6 (d, JP,F = 712 Hz).
31P NMR (1 : 1 CDCl3–CD3OD): −144.3 (septet, JP,F = 712 Hz).
HRESI-MS (pos.): 1821.9881, calc. for [C116H129N10O10]+
1821.9888.
=
7 S. Lee, Y. Hua and H. P. A. H. Flood, Org. Lett., 2010, 12,
2100–2102.
8 Y. Hua, R. O. Ramabhadran, E. O. Uduehi, J. A. Karty,
K. Raghavachari and A. H. Flood, Chem.–Eur. J., 2011, 17,
312–321.
9 R. O. Ramabhadran, Y. Hua, Y. Li, A. H. Flood and
K. Raghavachari, Chem.–Eur. J., 2011, 17, 9123–9129.
X-ray crystallography
Crystals of 7·PF6 and 9·Cl were very small and weakly-diffract-
ing. Therefore, single crystal X-ray diffraction data were col- 10 K. McDonald, R. O. Ramabhadran, S. Lee, K. Raghavachari
lected on Beamline I19 of Diamond Lightsource52 using
and A. H. Flood, Org. Lett., 2011, 13, 6260–6263.
synchrotron radiation (λ = 0.6889 and 1.1949 Å for 7·PF6 and 11 Y. Hua, R. O. Ramabhadran, J. A. Karty, K. Raghavachari
9·Cl, respectively). A Cryostream N253 open-flow cooling device
and A. H. Flood, Chem. Commun., 2011, 47, 5979–5981.
was used to cool the samples to 100 K. Series of scans were 12 H. Juwarker, J. M. Lenhardt, J. C. Castillo, E. Zhao,
performed in such a way as to collect a complete set of unique
S. Krishnamurthy, R. M. Jamiolkowski, K.-H. Kim and
reflections to a maximum of 0.80 Å for 7·PF6 and approxi-
S. L. Craig, J. Org. Chem., 2009, 74, 8924–8934.
mately 1.0 Å for 9·Cl. Raw frame data (including data 13 Y. Wang, F. Bie and H. Jiang, Org. Lett., 2010, 12,
reduction, inter-frame scaling, unit cell refinement and 3630–3633.
absorption corrections) were processed using CrysAlisPro.54 14 Y. Wang, J. Xiang and H. Jiang, Chem.–Eur. J., 2011, 17,
The structures were solved by charge-flipping methods using 613–619.
SUPERFLIP55 and refined using full-matrix least-squares on 15 V. Haridas, S. Sahu and P. Venugopalan, Tetrahedron, 2011,
F2 within the CRYSTALS suite.56 All non-hydrogen atoms were
67, 727–733.
refined with anisotropic displacement parameters. Hydrogen 16 M. R. Krause, R. Goddard and S. Kubik, J. Org. Chem.,
atoms were generally visible in the difference map and were 2011, 76, 7084–7095.
initially refined with restraints on bond lengths and angles, 17 C.-H. Lee, S. Lee, H. Yoon and W.-D. Jang, Chem.–Eur. J.,
after which the positions were used as the basis for a riding 2011, 17, 13898–13903.
model.57 Crystals of 7·PF6 were found to be twinned: an appro- 18 Q.-Y. Cao, T. Pradhan, S. Kim and J. S. Kim, Org. Lett.,
priate twin law was determined using the ROTAX package,58
2011, 13, 4386–4389.
within the CRYSTALS suite.56 The relative fraction of each twin 19 Y.-H. Lau, P. J. Rutledge, M. Watkinson and M. H. Todd,
component was refined. An area of diffuse electron density Chem. Soc. Rev., 2011, 40, 2848–2866.
was present in the structure of 9·Cl, believed to be a result of 20 F. García, M. R. Torres, E. Matesanz and L. Sánchez, Chem.
disordered solvent molecules. This could not be sensibly mod- Commun., 2011, 47, 5016–5018.
elled, and so PLATON-SQUEEZE59,60 was used to include this 21 L. C. Gilday, N. G. White and P. D. Beer, Dalton Trans.,
electron density in the refinement. Crystallographic data for 2012, 41, 7092–7097.
the structures have been deposited with the Cambridge Crys- 22 G. Yu, Z. Zhang, C. Han, M. Xue, Q. Zhou and F. Huang,
tallographic Data Centre. CCDC: 911205 and 911206.†
Chem. Commun., 2012, 48, 2958–2960.
1332 | Org. Biomol. Chem., 2013, 11, 1326–1333
This journal is © The Royal Society of Chemistry 2013

View Article Online
Organic & Biomolecular Chemistry
Paper
23 N. G. White and P. D. Beer, Supramol. Chem., 2012, 24, 41 J. A. Wisner, P. D. Beer, M. G. B. Drew and M. R. Sambrook,
473–480. J. Am. Chem. Soc., 2002, 124, 12469–12476.
24 S. C. Picot, B. R. Mullaney and P. D. Beer, Chem.–Eur. J., 42 H. W. Gibson, S.-H. Lee, P. T. Engen, P. Lecavalier, J. Sze,
2012, 18, 3620–3626.
Y. X. Shen and M. Bheda, J. Org. Chem., 1993, 58,
3748–3756.
43 E. Bosch and C. L. Barnes, Organometallics, 2000, 19,
5522–5524.
25 Y.-J. Li, L. Xu, W.-L. Yang, H.-B. Liu, S.-W. Lai, C.-M. Che
and Y.-L. Li, Chem.–Eur. J., 2012, 18, 4782–4790.
26 L. Xu, Y. Li, Y. Yu, T. Liu, S. Cheng, H. Liu and Y. Li, Org.
Biomol. Chem., 2012, 10, 4375–4380.
44 L. M. Hancock and P. D. Beer, Chem.–Eur. J., 2009, 15, 42–44.
27 Q.-Y. Cao, T. Pradhan, M. H. Lee, D. H. Choi and J. S. Kim, 45 The hexafluorophosphate salt of the axle component was
Tetrahedron Lett., 2012, 53, 4917–4920.
28 M. Caricato, A. Olmo, C. Gargiulli, G. Gattuso and
D. Pasini, Tetrahedron, 2012, 68, 7861–7866.
used due to the very low solubility of 5·Cl in organic sol-
vents. This is expected to have only a very minor effect on
rotaxane formation as chloride anion is produced during
amide condensation.
29 V. V. Rostovtsev, L. G. Green, V. V. Fokin and
K. B. Sharpless, Angew. Chem., Int. Ed., 2002, 41, 2596–2599. 46 K.-Y. Ng, V. Félix, S. M. Santos, N. H. Rees and P. D. Beer,
30 C. W. Tornøe, C. Christensen and M. Meldal, J. Org. Chem.,
2002, 67, 3057–3064.
31 A. Fahrenbach and J. F. Stoddart, Chem.–Asian J., 2011, 6,
2660–2669.
Chem. Commun., 2008, 1281–1283.
47 M. R. Sambrook, P. D. Beer, M. D. Lankshear, R. F. Ludlow
and J. A. Wisner, Org. Biomol. Chem., 2006, 4, 1529–1538.
48 M. J. Hynes, J. Chem. Soc., Dalton Trans., 1993, 311–312.
32 K. D. Hänni and D. A. Leigh, Chem. Soc. Rev., 2010, 39, 49 B.-Y. Lee, S. R. Park, H. B. Jeon and K. S. Kim, Tetrahedron
1240–1251. Lett., 2006, 47, 5105–5109.
33 A. Joosten, Y. Trolez, J.-P. Collin, V. Heitz and J.-P. Sauvage, 50 H. Goto, J. M. Heemstra, D. J. Hill and J. S. Moore, Org.
J. Am. Chem. Soc., 2012, 134, 1802–1809. Lett., 2004, 6, 889–892.
34 H. Lahlali, K. Jobe, M. Watkinson and S. M. Goldup, 51 T. X. Neenan and G. M. Whitesides, J. Org. Chem., 1988, 53,
Angew. Chem., Int. Ed., 2011, 50, 4151–4155. 2489–2496.
35 Y. Yamada, M. Okamoto, K. Furukawa, T. Kato and 52 H. Nowell, S. A. Barnett, K. E. Christensen, S. J. Teat and
K. Tanaka, Angew. Chem., Int. Ed., 2012, 51, 709–713. D. R. Allan, J. Synchrotron Radiat., 2012, 19, 435–441.
36 An anion binding indolocarbazole catenane that contains 53 J. Cosier and A. M. Glazer, J. Appl. Crystallogr., 1986, 19,
triazole groups has also been reported, although the key 105.
anion recognition motif appears to be the indolocarbazole 54 CrysAlisPro, Oxford Diffraction, 2011.
unit (Y. Zhao, Y. Li, Y. Li, H. Zheng, X. Yin and H. Liu, 55 L. Palatinus and G. Chapuis, J. Appl. Crystallogr., 2007, 40,
Chem. Commun., 2010, 46, 5698–5700).
37 H. Zheng, W. Zhou, J. Lv, X. Yin, Y. Li, H. Liu and Y. Li, 56 P. W. Betteridge, J. R. Carruthers, R. I. Cooper, K. Prout
Chem.–Eur. J., 2009, 15, 13253–13262. and D. J. Watkin, J. Appl. Crystallogr., 2003, 36, 1487.
38 N. G. White and P. D. Beer, Chem. Commun., 2012, 48, 57 R. I. Cooper, A. L. Thompson and D. J. Watkin, J. Appl. Crys-
8499–8501. tallogr., 2010, 43, 1100.
39 M. D. Lankshear and P. D. Beer, Acc. Chem. Res., 2007, 40, 58 R. I. Cooper, R. O. Gould, S. Parsons and D. J. Watkin,
657–668. J. Appl. Crystallogr., 2002, 35, 168–174.
786.
40 L. M. Hancock, L. C. Gilday, S. Carvalho, P. J. Costa, 59 A. Spek, J. Appl. Crystallogr., 2003, 36, 7–13.
V. Félix, C. J. Serpell, N. L. Kilah and P. D. Beer, Chem.–Eur. 60 P. S. van der Sluis and A. L. Spek, Acta Crystallogr., Sect. A:
J., 2010, 16, 13082–13094.
Fundam. Crystallogr., 1990, 46, 194–201.
This journal is © The Royal Society of Chemistry 2013
Org. Biomol. Chem., 2013, 11, 1326–1333 | 1333