An All-Halogen Bonding Rotaxane for Selective Sensing of Halides in Aqueous Media

Article abstract of DOI:10.1002/anie.201403659

The synthesis and anion binding properties of the first rotaxane host system to bind and sense anions purely through halogen bonding, is described. Through a combination of polarized iodotriazole and iodotriazolium halogen bond donors, a three-dimensional cavity is created for anion binding. This rotaxane incorporates a luminescent rhenium(I) bipyridyl metal sensor motif within the macrocycle component, thus enabling optical study of the anion binding properties. The rotaxane topology was confirmed by single-crystal X-ray structural analysis, demonstrating halogen bonding between the electrophilic iodine atoms and chloride anions. In 50 % H₂O/CH₃CN solvent mixtures the rotaxane host exhibits strong binding affinity and selectivity for chloride, bromide, and iodide over a range of oxoanions. Sense and selectability: The first anion-templated rotaxane, assembled purely through halogen bonding, is described. A photoactive rhenium(I) bipyridyl bis(iodotriazole) macrocycle is combined with a bis(iodotriazolium)-functionalized carbazole axle to produce a rotaxane host system, which is capable of selectively sensing Cl^-, Br^-, and I^- over a range of oxoanions in up to 50 % H₂O/CH₃CN solvent mixtures.

Full text of DOI:10.1002/anie.201403659

.
Angewandte
Communications
DOI: 10.1002/anie.201403659
Halogen Bonding
An All-Halogen Bonding Rotaxane for Selective Sensing of Halides in
Aqueous Media**
Benjamin R. Mullaney, Amber L. Thompson, and Paul D. Beer*
Abstract: The synthesis and anion binding properties of the
first rotaxane host system to bind and sense anions purely
through halogen bonding, is described. Through a combination
of polarized iodotriazole and iodotriazolium halogen bond
donors, a three-dimensional cavity is created for anion binding.
This rotaxane incorporates a luminescent rhenium(I) bipyridyl
metal sensor motif within the macrocycle component, thus
enabling optical study of the anion binding properties. The
rotaxane topology was confirmed by single-crystal X-ray
structural analysis, demonstrating halogen bonding between
the electrophilic iodine atoms and chloride anions. In 50%
H O/CH CN solvent mixtures the rotaxane host exhibits strong
architectures with unique three-dimensional anion-binding
[12]
cavities.
Through electrostatics, convergent hydrogen
bonding, and cavity size, these systems have demonstrated
high degrees of selectivity between different anionic species.
We recently reported the first XB rotaxane, containing an
iodotriazolium axle, which selectively bound iodide in aque-
ous media through a combination of halogen and hydrogen
[13]
bonding.
In addition, an XB catenane was shown to
selectively bind chloride and bromide through cooperative
[
14]
halogen bond bromoimidazolium donor groups.
Herein we describe the anion-templated synthesis of the
first all-halogen bonding rotaxane, which cooperatively uses
two iodotriazole and two iodotriazolium XB donors to
selectively recognize chloride, bromide, and iodide. Through
the incorporation of a photoactive rhenium(I) bipyridyl
center within the rotaxaneꢀs macrocycle component, we
demonstrate, by using luminescence spectroscopy, the rotax-
aneꢀs ability to optically sense these halide anions in aqueous
solvent mixtures containing up to 50% water.
Figure 1 illustrates schematically the synthetic strategy
undertaken for the construction of the target XB rotaxane.
Halogen bond donor iodotriazole and iodotriazolium motifs,
integrated into the rhenium(I) bipyridyl macrocycle precursor
and carbazole axle components, respectively, form an anion-
templated orthogonal assembly which upon cyclization by
ring-closing metathesis (RCM) affords an all-halogen bond-
ing rotaxane.
2
3
binding affinity and selectivity for chloride, bromide, and
iodide over a range of oxoanions.
H
alogen bonding (XB) is the intermolecular interaction
between a polarized, electron-deficient halogen atom, and
[
1]
a Lewis base. As a highly directional analogue to hydrogen
bonding, XB has been used extensively in the solid-state
crystal engineering of liquid-crystalline, magnetic, and
conducting materials, and more recently in the design of
[2]
[3]
[4]
[5]
[6]
catalysts and potential pharmaceuticals.
The undeniable importance of anions in a range of
biological, environmental, medical, and chemical processes
has provoked a considerable effort to develop synthetic anion
[
7]
receptors.
Many efficient anion receptors have been
reported and exploit a variety of supramolecular synthons
[
8]
including electrostatic, hydrogen bonding, Lewis acid–base,
[
9]
and anion–p interactions. Nevertheless, the challenge of
developing synthetic receptors that rival the recognition
properties of biotic systems thus far remains unfulfilled. By
virtue of their comparable strength to hydrogen bonds and
more strict linear geometry preference, a promising avenue
to raise the bar of anion-binding affinity and selectivity of
anion host systems is to integrate XB motifs into their
[
10]
[
11]
structural frameworks.
Taking inspiration from natureꢀs selective anion-binding
proteins, we have used anion templation to form interlocked
[*] B. R. Mullaney, Dr. A. L. Thompson, Prof. P. D. Beer
Chemistry Research Laboratory
Department of Chemistry, University of Oxford
Mansfield Road, Oxford, OX1 3TA (UK)
E-mail: paul.beer@chem.ox.ac.uk
Figure 1. Anion-templated assembly to be used for the synthesis of the
[
**] We thank the Diamond Light Source for an award of beamtime on
I19 (MT7768), and the instrument scientists for their generous help
and support. We are grateful for synthetic assistance from Thomas
Mole, and B.R.M. thanks Wolfson College for partial financial
support.
target all-halogen bonding rotaxane.
The rhenium(I) bipyridyl macrocycle precursor 5 was
prepared using the stepwise procedure shown in Scheme 1.
The allyl-appended amine 1 was converted into the azide
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201403659.
[
15]
1
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Angew. Chem. Int. Ed. 2014, 53, 11458 –11462

Angewandte
Chemie
Scheme 2. Synthesis of the axle component 8·2BF . Reagents and
4
conditions: a) NaI, Cu(ClO ) ·6H O, TBTA, DBU, THF, RT, 16 h
4
2
2
(
76%); b) Me OBF , CH Cl , 16 h (82%).
3 4 2 2
Scheme 1. Synthesis of the acyclic precursor 5. Reagents and condi-
tions: a) imidazole sulfonylazide hydrogensulfate, K CO ,
2
3
CuSO ·5H O, methanol, RT, 3 d (77%); b) NaI, Cu(ClO ) ·6H O,
4
2
4
2
2
TBTA, DBU, THF, RT, 16 h (80%); c) [Re(CO) Cl], CHCl , reflux, 3 d
5
3
(
75%). DBU=1,8-diazabicyclo[5.4.0]undec-7-ene, TBTA=tris(benzyl-
triazolylmethyl)amine, THF=tetrahydrofuran.
derivative 2 using the hydrogensulfate salt of imidazole
sulfonylazide in the presence of K CO and a catalytic amount
2
3
[16]
of CuSO ·5H O in 77% yield. Reaction of two equivalents
4
2
of 2 with 4,4’-diethynyl-2,2’-bipyridine (3) in the presence of
[
17]
Cu(ClO ) ·6H O, NaI, DBU, and TBTA,
gave bis(iodo-
4
2
2
triazole) bipyridyl compound 4 in 80% yield. Complexation
with [Re(CO) Cl] afforded the macrocycle precursor 5 in
5
a yield of 75%.
The axle 8 was synthesized as shown in Scheme 2. The
bis(azido)carbazole 6 was reacted with two equivalents of the
[17]
alkyne–appended stopper 7 in a one-pot reaction to form
the neutral bis(iodotriazole) axle precursor in 76% yield,
which was methylated to form 8·2BF in a yield of 82%.
4
Scheme 3. Synthesis of the rotaxane 9·2PF . Reagents and conditions:
6
The rotaxane 9·Cl·BF4 was synthesized by Stewart–
Grubbsꢀ-catalyzed RCM reaction of an equimolar mixture
a) Stewart–Grubbs’ catalyst (10 wt%), TBACl, CH Cl , 3 d (7%);
2
2
À
achieved by repeated washing with
6
b) anion exchange for PF
aqueous NH PF (0.1m). TBACl=tetra-n-butylammonium chloride.
of 5 and 8·2BF , in dry dichloromethane in the presence of
4
6
4
one equivalent of the TBACl template (Scheme 3). After
purification by preparative silica TLC, the rotaxane was anion
exchanged with aqueous NH PF , to give the rotaxane 9·2PF
in 7% overall yield upon isolation. The rotaxane synthesis
was undertaken in the absence of chloride and although
evidence of rotaxane formation was observed by electrospray
mass spectrometry, no interlocked product could be isolated,
which suggests the rotaxane is only formed in negligible yield
in the absence of a chloride anion template. The rotaxane
slow evaporation of a 45:45:10 CDCl /CD OD/D O mixed
4
6
6
3
3
2
[
18]
solvent solution of the rotaxane with excess TBACl. The
structure clearly shows convergent halogen bonding between
À
the iodotriazoles and iodotriazoliums, and the two Cl
À
counterions (Figure 3). One of the Cl anions is bound by
three halogen bond donors within the rotaxane cavity, two
from the macrocycle and one from the minor component of
the disordered axle, while the other halide counterion forms
1
13
9
·2PF was characterized by H and C NMR spectroscopy,
6
1
1
high-resolution mass spectrometry, and H- H ROESY NMR
spectroscopy (see the Supporting Information).
The interlocked nature of the rotaxane 9 was confirmed
by single-crystal X-ray diffraction analysis (Figure 2).
a halogen bond to the remaining axle iodotriazolium [dI···Cl =
2.98–3.13(6) ꢁ]. The halogen bond distances are all signifi-
2
+
[20]
cantly lower than the sum of the van der Waals radii, with
[19]
%vdWI,Cl = 79–85%, thus confirming the strength of these
2
+
[21]
Single crystals of the chloride salt of 9 were obtained by
halogen bonding interactions.
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Angewandte
Communications
Figure 2. Single-crystal structure of rotaxane 9·2Cl, displaying the
interlocked topology and halogen bonds. Green chloride, purple iodine.
Solvent molecules, hydrogen atoms and disorder have been omitted
for clarity.
1
Figure 4. H NMR spectral changes observed in 9·2PF in 45:45:10
6
CDCl /CD OD/D O after addition of up to 10 equivalents of chloride
3
3
2
ions. Only macrocycle peaks are visible in the spectral range shown.
4
À1
K > 10 m , thus indicating strong selective binding of the
a
[
23]
larger halide anion.
Luminescence spectroscopy was used to investigate the
anion sensing potential and to determine anion binding
[23]
affinities of 9·2PF in H O/CH CN solvent mixtures
by
6
2
3
monitoring the intensity of MLCT emission band of the
rotaxaneꢀs rhenium(I) bipyridyl macrocycle upon the addition
of a variety of anions. Upon excitation at l = 400 nm the
ex
emission spectrum of the rotaxane exhibited the expected
MLCT emission band of the rhenium(I) bipyridyl center at
À5
lem = 583 nm (c = 1 ꢂ 10 m in 10% H O/CH CN). In 10%
2
3
À
H O/CH CN, the addition of up to 20 equivalents of Cl
2
3
resulted in an initial increase in the intensity of the rotaxaneꢀs
MLCT emission band, followed by a subsequent decrease in
the intensity (see Figure S7 in the Supporting Information).
À
Analogous behavior was observed upon addition of Br .
À
Addition of I gave the most notable optical response,
producing significant fluorescence quenching of the rotax-
[
24]
À
À
ane. In contrast, the oxoanions AcO and H PO did not
2
4
Figure 3. Close-up of the receptor portions of the single-crystal struc-
ture of 9·2Cl. Thermal ellipsoids are displayed at 30% probability.
2
+
noticeably affect the emission properties of 9 , suggesting no
[
25]
binding. The data were modelled using Specfit to determine
:1 and 1:2 stoichiometric association constants (Table 1)
which reveal strong binding of the halides with a selectivity
1
1
À
À
À
Preliminary H NMR anion-binding studies of 9·2PF6
preference of I > Br @ Cl .
were first undertaken with TBACl in 45:45:10 CDCl3/
CD OD/D O (Figure 4). Importantly, significant perturba-
Considering the strong halide anion binding affinities
exhibited by 9·2PF6 in the 10% water/solvent mixture,
analogous titrations were undertaken with a wider range of
anions in aqueous media containing a higher water content
(20% and 50%). Similar luminescence sensing behavior was
observed upon addition of the halides (Figure 5). Importantly,
Table 1 shows that despite the increased water content, the
3
2
tions were observed in the chemical shifts of the rotaxaneꢀs
3
5
macrocycle component protons H and H , which are
proximal to the XB donor iodotriazole groups, which suggests
the halide anion is being bound within the interlocked cavity.
Downfield shifts in the external carbazole protons of the axle
were also noted (see the Supporting Information). The
À
À
À
association constants for Cl , Br , and I remain substantial
in magnitude, especially for the heavier halides. Furthermore,
it is noteworthy that the halides are bound preferentially over
5
changes in the chemical shift of the proton H were
monitored, and a 1:1 stoichiometric association constant of
À1
À
2À
1
030(30)m was determined using the WinEQNMR2 soft-
all the oxoanions and fluoride. Indeed, only HCO3 and SO4
[
22]
1
ware.
An analogous H NMR titration experiment with
demonstrated any evidence of binding, which was much
weaker than the aforementioned halides. These data indicate
TBAI determined an association constant for iodide of
1460 www.angewandte.org
1
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Angew. Chem. Int. Ed. 2014, 53, 11458 –11462

Angewandte
Chemie
Table 1: Anion association constants for 9·2PF in H O/CH CN solvent
mixtures at 298 K.
bipyridyl bis(iodotriazole) macrocycle is combined with
6
2
3
a bis(iodotriazolium)-functionalized carbazole axle compo-
nent to produce a rotaxane host system, which is capable of
[
a]
1
0% H O
20% H O
50% H O
log(K11)
2
2
2
[
b]
[c]
[c]
[c]
[c]
[c,d]
À
À
À
Anion
log(K )
log(K12)
log(K11)
log(K12)
selectively sensing the halide anions Cl , Br , and I over
a range of oxoanions in up to 50% H O/CH CN solvent
1
1
À
2
3
F
–
n.b.
3.49
4.49
4.95
n.b.
n.b.
–
À
mixtures, as determined by luminescence spectroscopy. These
observations together with solid-state structural evidence
imply that the rotaxaneꢀs unique preorganized halogen bond
donor host binding cavity complements spherical halide guest
species. Indeed, this halogen bonding rotaxane is the most
potent interlocked host system for halide recognition
Cl
4.04
5.02
5.14
n.b.
n.b.
–
–
–
–
2.81
3.42
3.74
2.63
2.87
3.61
2.71
3.76
4.38
–
–
–
–
–
–
À
Br
À
I
À
AcO
À
H PO4
2
À
[e]
HCO3
NO3
ClO4
SO4
<2.0
À
n.b.
n.b.
[
12a]
À
reported to date.
The integration of various halogen
2
À
[e]
<1.0
bond donor groups into interlocked host structural frame-
works for sensing is ongoing in our laboratories.
[
a] Excitation wavelength: l =400 nm for 10% and 20% H O;
e
x
2
l =390 nm for 50% H O. [b] Anions were added as their tetrabutyl-
ammonium salts, except HCO3 , which was added as the tetraethyl-
ex
2
À
Received: March 24, 2014
Revised: May 27, 2014
Published online: July 7, 2014
À
ammonium salt. [c] Errors <10%. [d] No evidence of 1:2 binding for Cl
À
À
or Br . K12 values were not calculated for I because of precipitation
À
problems at greater than 16 equivalents of I . [e] The binding strength
was too low to accurately determine an association constant. n.b.=no
evidence of binding.
Keywords: anions · halogen bonding ·
.
noncovalent interactions · rotaxanes · supramolecular chemistry
[
1] a) P. Metrangolo, F. Meyer, T. Pilati, G. Resnati, G. Terraneo,
Angew. Chem. 2008, 120, 6206 – 6220; Angew. Chem. Int. Ed.
2008, 47, 6114 – 6127; b) T. M. Beale, M. G. Chudzinski, M. G.
Sarwar, M. S. Taylor, Chem. Soc. Rev. 2013, 42, 1667 – 1680;
c) G. R. Desiraju, P. S. Ho, L. Kloo, A. C. Legon, R. Marquardt,
P. Metrangolo, P. A. Politzer, G. Resnati, K. Rissanen, Pure
Appl. Chem. 2013, 85, 1711 – 1713.
[
2] a) G. Resnati, P. Metrangolo, Science 2008, 321, 918 – 919;
b) C. B. Aakerçy, M. Fasulo, N. Schultheiss, J. Desper, C.
Moore, J. Am. Chem. Soc. 2007, 129, 13772 – 13773.
[
[
3] K. Rissanen, CrystEngComm 2008, 10, 1107 – 1113.
4] a) M. Fourmiguꢃ, P. Batail, Chem. Rev. 2004, 104, 5379 – 5418;
b) F. Zordan, L. Brammer, P. Sherwood, J. Am. Chem. Soc. 2005,
1
27, 5979 – 5989; c) P. Metrangolo, C. Prasang, G. Resnati, R.
Liantonio, A. C. Whitwood, D. W. Bruce, Chem. Commun. 2006,
290 – 3292; d) J. Xu, X. Liu, J. K.-P. Ng, T. Lin, C. He, J. Mater.
3
Chem. 2006, 16, 3540 – 3545; e) R. Liantonio, P. Metrangolo, F.
Meyer, T. Pilati, W. Navarrini, G. Resnati, Chem. Commun.
2006, 1819 – 1821; f) P. Metrangolo, F. Meyer, T. Pilati, D. M.
Proserpio, G. Resnati, Cryst. Growth Des. 2007, 8, 654 – 659;
g) D. Cin cˇ i c´ , T. Fri sˇ cˇ i c´ , W. Jones, Chem. Eur. J. 2008, 14, 747 –
7
53; h) D. W. Bruce, P. Metrangolo, F. Meyer, C. Prasang, G.
Resnati, G. Terraneo, A. C. Whitwood, New J. Chem. 2008, 32,
77 – 482; i) C. Prꢄsang, H. L. Nguyen, P. N. Horton, A. C.
4
Whitwood, D. W. Bruce, Chem. Commun. 2008, 6164 – 6166;
j) D. Bruce in Halogen Bonding, Vol. 126 (Eds.: P. Metrangolo,
G. Resnati), Springer, Berlin, 2008, pp. 161 – 180; k) S. K. Maity,
S. Bera, A. Paikar, A. Pramanik, D. Haldar, Chem. Commun.
À5
Figure 5. a) Changes in the emission spectra of 9·2PF (1ꢀ10 m in
2
6
0% H O/CH CN) upon addition of iodide. b) Change in the emission
2 3
intensity at l=590 nm upon addition of iodide. Points denote data
2
013, 49, 9051 – 9053; l) J. Lieffrig, O. Jeannin, A. Fr a˛ ckowiak, I.
´
Olejniczak, R. Swietlik, S. Dahaoui, E. Aubert, E. Espinosa, P.
and the line corresponds to the binding model.
Auban-Senzier, M. Fourmiguꢃ, Chem. Eur. J. 2013, 19, 14804 –
14813.
[
[
5] a) A. Bruckmann, M. A. Pena, C. Bolm, Synlett 2008, 900 – 902;
b) D. A. Kraut, M. J. Churchill, P. E. Dawson, D. Herschlag, ACS
Chem. Biol. 2009, 4, 269 – 273; c) S. M. Walter, F. Kniep, E.
Herdtweck, S. M. Huber, Angew. Chem. Int. Ed. 2011, 50, 7187 –
that the halogen bond donor cavity of the rotaxane is of
complementary shape and size for the spherical halide guests,
whereas oxoanions are too large and are of the wrong
geometry to penetrate the interlocked hostꢀs binding
7
191; Angew. Chem. 2011, 123, 7325 – 7329; d) S. Dordonne, B.
Crousse, D. Bonnet-Delpon, J. Legros, Chem. Commun. 2011,
7, 5855 – 5857.
[
26]
domain.
4
In summary, the first anion-templated all-halogen bond-
ing rotaxane has been prepared. A photoactive rhenium(I)
6] a) Y. Lu, T. Shi, Y. Wang, H. Yang, X. Yan, X. Luo, H. Jiang, W.
Zhu, J. Med. Chem. 2009, 52, 2854 – 2862; b) L. A. Hardegger, B.
Angew. Chem. Int. Ed. 2014, 53, 11458 –11462
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 11461

.
Angewandte
Communications
Kuhn, B. Spinnler, L. Anselm, R. Ecabert, M. Stihle, B. Gsell, R.
Thoma, J. Diez, J. Benz, J.-M. Plancher, G. Hartmann, D. W.
Banner, W. Haap, F. Diederich, Angew. Chem. Int. Ed. 2011, 50,
[15] N. G. White, P. J. Costa, S. Carvalho, V. Fꢃlix, P. D. Beer, Chem.
Eur. J. 2013, 19, 17751 – 17765.
[16] E. D. Goddard-Borger, R. V. Stick, Org. Lett. 2007, 9, 3797 –
3800.
314 – 318; Angew. Chem. 2011, 123, 329 – 334.
[
7] a) J. L. Sessler, P. Gale, W.-S. Cho, Anion Receptor Chemistry,
RSC, Cambridge, 2006; b) P. D. Beer, P. A. Gale, Angew. Chem.
Int. Ed. 2001, 40, 486 – 516; Angew. Chem. 2001, 113, 502 – 532;
c) J. M. Llinares, D. Powell, K. Bowman-James, Coord. Chem.
Rev. 2003, 240, 57 – 75; d) E. J. OꢀNeil, B. D. Smith, Coord.
Chem. Rev. 2006, 250, 3068 – 3080; e) R. Martꢅnez-MꢆÇez, F.
Sancenꢇn, Coord. Chem. Rev. 2006, 250, 3081 – 3093; f) T.
Gunnlaugsson, M. Glynn, G. M. Tocci, P. E. Kruger, F. M.
Pfeffer, Coord. Chem. Rev. 2006, 250, 3094 – 3117; g) C. R.
Rice, Coord. Chem. Rev. 2006, 250, 3190 – 3199; h) P. A. Gale,
S. E. Garcia-Garrido, J. Garric, Chem. Soc. Rev. 2008, 37, 151 –
[17] W. S. Brotherton, R. J. Clark, L. Zhu, J. Org. Chem. 2012, 77,
6443 – 6455.
[18] Significant quantities of the ring-closed macrocycle product
were also isolated. No significant improvement in the yield of
isolated rotaxane was observed using iodide (added as TBAI)
instead of chloride.
[19] Single-crystal diffraction data for were collected at low temper-
ature with synchrotron radiation (l = 0.68890 ꢁ) using beamline
I19 (EH1) at the Diamond Light Source (H. Nowell et al., J.
Synch. Rad. 2012, 19, 435 – 441). The data were collected using
CrystalClear (Rigaku) and reduced using CrysAlisPro (Oxford
Diffraction/Agilent Technologies). The structure was solved
with SuperFlip [L. Palatinus, G. Chapuis, J. Appl. Crystallogr.
2007, 40, 786 – 790] and refined using full-matrix least-squares
within CRYSTALS. (P. W. Betteridge et al., J. Appl. Crystallogr.
2003, 36, 1487; R. I. Cooper, A. L. Thompson, D. J. Watkin, J.
Appl. Crystallogr. 2010, 43, 1100 – 1107; P. van der Sluis, A. L.
Spek, Acta Crystallogr. Sect. A 1990, 46, 194 – 201; A. L. Spek, J.
Appl. Crystallogr. 2003, 36, 7 – 13) as per the Supporting
Information (CIF). The macrocycle was modelled as being
disordered over two positions with near-equal occupancy.
Furthermore, one of the axle triazolium units is disordered
over two positions antiparallel to one another, pointing either
190; i) J. Pꢃrez, L. Riera, Chem. Soc. Rev. 2008, 37, 2658 – 2667;
j) J. W. Steed, Chem. Soc. Rev. 2009, 38, 506 – 519; k) S. Kubik,
Chem. Soc. Rev. 2009, 38, 585 – 605; l) Y. Hua, A. H. Flood,
Chem. Soc. Rev. 2010, 39, 1262 – 1271; m) P. A. Gale, R. Pꢃrez-
Tomꢆs, R. Quesada, Acc. Chem. Res. 2013, 46, 2801 – 2813.
8] T. W. Hudnall, C.-W. Chiu, F. P. Gabbaꢈ, Acc. Chem. Res. 2009,
[
[
42, 388 – 397.
9] a) P. Gamez, T. J. Mooibroek, S. J. Teat, J. Reedijk, Acc. Chem.
Res. 2007, 40, 435 – 444; b) B. P. Hay, V. S. Bryantsev, Chem.
Commun. 2008, 2417 – 2428; c) B. L. Schottel, H. T. Chifotides,
K. R. Dunbar, Chem. Soc. Rev. 2008, 37, 68 – 83; d) Y. S.
Rosokha, S. V. Lindeman, S. V. Rosokha, J. K. Kochi, Angew.
Chem. Int. Ed. 2004, 43, 4650 – 4652; Angew. Chem. 2004, 116,
À
toward, or away from the cavity-bound Cl (see Supporting
4
750 – 4752; e) O. B. Berryman, F. Hof, M. J. Hynes, D. W.
Information for further details). CCDC 993328 contains the
supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[20] A. Bondi, J. Phys. Chem. 1964, 68, 441 – 451.
Johnson, Chem. Commun. 2006, 506 – 508; f) M. M. Watt, L. N.
Zakharov, M. M. Haley, D. W. Johnson, Angew. Chem. Int. Ed.
2
013, 52, 10275 – 10280; Angew. Chem. 2013, 125, 10465 – 10470.
10] P. Politzer, J. S. Murray, T. Clark, Phys. Chem. Chem. Phys. 2010,
2, 7748 – 7757.
[
[
1
[21] It is noteworthy that the solid-state structure also provides
evidence of a weak CÀH···Cl interaction from the methyl group
11] a) A. Mele, P. Metrangolo, H. Neukirch, T. Pilati, G. Resnati, J.
Am. Chem. Soc. 2005, 127, 14972 – 14973; b) M. G. Sarwar, B.
Dragisic, L. J. Salsberg, C. Gouliaras, M. S. Taylor, J. Am. Chem.
Soc. 2010, 132, 1646 – 1653; c) M. G. Sarwar, B. Dragisic, S.
Sagoo, M. S. Taylor, Angew. Chem. Int. Ed. 2010, 49, 1674 – 1677;
Angew. Chem. 2010, 122, 1718 – 1721; d) E. Dimitrijevi c´ , O.
Kvak, M. S. Taylor, Chem. Commun. 2010, 46, 9025 – 9027;
e) M. G. Chudzinski, C. A. McClary, M. S. Taylor, J. Am. Chem.
Soc. 2011, 133, 10559 – 10567; f) N. L. Kilah, M. D. Wise, P. D.
Beer, Cryst. Growth Des. 2011, 11, 4565 – 4571; g) F. Zapata, A.
Caballero, N. G. White, T. D. W. Claridge, P. J. Costa, V. Felix,
P. D. Beer, J. Am. Chem. Soc. 2012, 134, 11533 – 11541.
of the disordered axle iodotriazolium group, with a C···Cl
distance of 3.7638(2) ꢁ, and an angle of 166.528.
[22] M. J. Hynes, J. Chem. Soc. Dalton Trans. 1993, 311 – 312.
1
[23] Unfortunately it was not possible to conduct further H NMR
titration experiments in the same water/acetonitrile solvent
mixtures as used for the luminescence titration experiments
because of solubility limitations of the rotaxane at the concen-
1
trations required for H NMR analysis.
[24] A qualitative study was conducted on a neutral XB 4,4’-
bis(iodotriazole)-2,2’-bipyridyl rhenium(I) acyclic model recep-
tor in 10% water/acetonitrile, which demonstrated no change in
the MLCT emission behavior upon addition of iodide, thus
implying that there was no binding. This confirms that the
quenching behavior observed with the rotaxane is a consequence
of iodide binding within the interlocked hostꢀs cavity.
[
12] a) L. M. Hancock, L. C. Gilday, S. Carvalho, P. J. Costa, V. Fꢃlix,
C. J. Serpell, N. L. Kilah, P. D. Beer, Chem. Eur. J. 2010, 16,
13082 – 13094; b) K. M. Mullen, J. Mercurio, C. J. Serpell, P. D.
Beer, Angew. Chem. Int. Ed. 2009, 48, 4781 – 4784; Angew.
Chem. 2009, 121, 4875 – 4878; c) N. G. White, P. D. Beer, Chem.
Commun. 2012, 48, 8499 – 8501; d) G. T. Spence, P. D. Beer, Acc.
Chem. Res. 2013, 46, 571 – 586.
[25] Specfit v. 2.02 ed., Spectrum Software Associates Chapel Hill,
NC, USA, 1997.
[26] The anion association constants obtained for the rotaxane are
significantly higher than those determined for acyclic systems
based on the bis(iodotriazolium)carbazole axle motif, which
[
13] N. L. Kilah, M. D. Wise, C. J. Serpell, A. L. Thompson, N. G.
White, K. E. Christensen, P. D. Beer, J. Am. Chem. Soc. 2010,
À
À
À
132, 11893 – 11895.
displayed the selectivity trend Cl > Br > I . These results will
[
14] a) A. Caballero, F. Zapata, N. G. White, P. J. Costa, V. Felix, P. D.
Beer, Angew. Chem. Int. Ed. 2012, 51, 1876 – 1880; Angew.
Chem. 2012, 124, 1912 – 1916.
be published as part of a future manuscript.
1
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