A Triphasic Sorting System: Coordination Cages in Ionic Liquids

Article abstract of DOI:10.1002/anie.201505774

Host-guest chemistry is usually carried out in either water or organic solvents. To investigate the utility of alternative solvents, three different coordination cages were dissolved in neat ionic liquids. By using ¹⁹F NMR spectroscopy to monitor the presence of free and bound guest molecules, all three cages were demonstrated to be stable and capable of encapsulating guests in ionic solution. Different cages were found to preferentially dissolve in different phases, allowing for the design of a triphasic sorting system. Within this system, three coordination cages, namely Fe₄L₆ 2, Fe₈L₁₂ 3, and Fe₄L₄ 4, each segregated into a distinct layer. Upon the addition of a mixture of three different guests, each cage (in each separate layer) selectively bound its preferred guest.

Full text of DOI:10.1002/anie.201505774

.
Angewandte
Communications
International Edition: DOI: 10.1002/anie.201505774
German Edition: DOI: 10.1002/ange.201505774
Host–Guest Systems
A Triphasic Sorting System: Coordination Cages in Ionic Liquids
Angela B. Grommet, Jeanne L. Bolliger, Colm Browne, and Jonathan R. Nitschke*
Abstract: Host–guest chemistry is usually carried out in either
water or organic solvents. To investigate the utility of alter-
native solvents, three different coordination cages were
selectively encapsulates the guest to which it binds most
favorably, influencing the composition of each layer.
Nondeuterated ILs were used in this study, precluding the
19
1
dissolved in neat ionic liquids. By using F NMR spectroscopy
to monitor the presence of free and bound guest molecules, all
three cages were demonstrated to be stable and capable of
encapsulating guests in ionic solution. Different cages were
found to preferentially dissolve in different phases, allowing for
the design of a triphasic sorting system. Within this system,
three coordination cages, namely Fe L 2, Fe L 3, and Fe L4
use of H NMR techniques. ESI-MS also did not give
meaningful results because high-intensity peaks from the
charged solvent obscure solute peaks (see Section S2 in the
19
Supporting Information). The use of F NMR spectroscopy,
however, proved to be a fruitful method for the character-
ization of host–guest complexes of cages in IL solutions, with
fluorinated guests reporting the presence of the cage.
4
6
8
12
4
4
, each segregated into a distinct layer. Upon the addition of
When a fluorinated prospective guest molecule was
dissolved in an IL, its characteristic spectrum was recorded
a mixture of three different guests, each cage (in each separate
layer) selectively bound its preferred guest.
19
using F NMR spectroscopy. If this spectrum remained
unchanged after the addition of a cage, we inferred that no
complexation had occurred. In this case, the cage might not be
stable in the IL. Alternatively the cage could be intact, but
there may be no driving force for encapsulation: for example,
the prospective guest might be too large.
D
esigning new functionality into supramolecular cage
systems can be accomplished via two different routes: by
[
1]
[2]
building a cage with a cavity of specific size, shape, or
chemical functionality; or by changing the environmental
conditions that govern guest binding. The first method may
[
3]
[4]
A significant change in the chemical shifts of the
[
5]
19
require considerable synthetic effort, whereas the second
requires only variation of the reaction temperature or solvent.
Guest binding is enhanced, for example, in a solvent in which
the guest is poorly solvated. Although extensive solution-
based host–guest investigations have been carried out either
in water or in organic solvents, far fewer studies have
involved a third class of solvents—ionic liquids (ILs). These
salts, which are molten below 1008C, are good solvents for the
encapsulation of guests into organic capsules, such as
resonance signals in the F NMR spectrum of the guest,
however, would be consistent with guest encapsulation in fast
exchange on the NMR timescale, allowing us to conclude that
[
6]
[13]
the cage is intact and functional.
The detection of an
19
additional set of F NMR resonance signals for a guest
molecule would indicate the presence of both free and
encapsulated guests in slow exchange, also confirming guest
[
7]
[8]
[14]
binding within a stable cage.
To probe the stability of coordination cages in ionic
[
9]
[10]
[15]
cucurbiturils and calixarenes.
Similarly, Daguenet and
liquids, a solution of cage 1 (3.3 mm) in 1-ethyl-3-methyl-
Dyson have demonstrated that a Ni metallacage binds
chloride in a range of ionic liquids.
imidazolium ethylsulfate ([emim][EtOSO ]) was prepared
(Scheme 1a). After 1,3,5-trifluorobenzene (guest A; 5 equiv)
3
[
11]
Here we introduce the concept of using different coordi-
nation cages in multiple IL phases simultaneously. Three
cages are shown to be stable and capable of encapsulating
guests in imidazolium and phosphonium ILs, allowing us to
selectively dissolve cages in specific phases and bind specific
guests within hosts. We present a triphasic system (consisting
of water and two mutually immiscible, hydrophobic ILs) in
which each of three different cages is soluble in only one
layer. Upon the addition of three different guests, each cage
was added to a solution of 1 in [emim][EtOSO ] and the
3
mixture stirred for one week at 296 K (Scheme 1b), three
19
resonances were observed by F NMR spectroscopy (Fig-
ure S8b in the Supporting Information). Signals correspond-
À
ing to trifluoromethanesulfonate (triflate or TfO , the
counterion for cage 1) and free 1,3,5-trifluorobenzene were
detected at the same chemical shift values in the presence and
absence of the cage. We attribute the new signal to 1,3,5-
trifluorobenzene within 1, in slow exchange with free 1,3,5-
trifluorobenzene on the NMR timescale.
[12]
As previously reported, iron(II) tetrahedral cages can be
“unlocked” by adding p-toluenesulfonic acid, resulting in
[
*] A. B. Grommet, Dr. J. L. Bolliger, Dr. C. Browne, Prof. J. R. Nitschke
Department of Chemistry, University of Cambridge
Lensfield Road, Cambridge, CB2 1EW (UK)
E-mail: jrn34@cam.ac.uk
[16]
guest release.
We inferred that cage 1 should also be
unlockable in an IL. Since a cage must first be locked in order
to be unlocked, success would further confirm that the cage
remains intact and functional in the IL (Scheme 1c). p-
Toluenesulfonic acid (10 equiv) was thus added to a solution
Homepage: http://www-jrn.ch.cam.ac.uk
Dr. C. Browne
Current Address: School of Chemistry, University of Manchester
Oxford Road, Manchester, M13 9PL (UK)
of 1,3,5-trifluorobenzeneꢀ1 in [emim][EtOSO ]. After stir-
3
ring at room temperature overnight, the purple solution was
Supporting information and ORCID(s) from the author(s) for this
article are available on the WWW under http://dx.doi.org/10.1002/
anie.201505774.
19
observed to turn brown, and the F NMR resonance signal
assigned to encapsulated 1,3,5-trifluorobenzene disappeared
1
5100
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 15100 –15104

Angewandte
Chemie
19
Scheme 1. a) Cage 1 dissolved in the IL [emim][EtOSO ]. b) F NMR spectroscopy was used to show that guest A was bound within 1. c) Guest A
3
was released from “unlocked” 1 following the addition of p-toluenesulfonic acid.
(
Figure S8c). The signals from triflate and free 1,3,5-trifluoro-
was replaced by signals attributable to free and encapsulated
A (Figure S12b), indicating that A had replaced bound
triflate. Following the addition of 1-fluoroadamantane B
(5 equiv), the signal for encapsulated A diminished in
intensity and signals assigned to free and encapsulated B
appeared (Figure S12c). Using the free triflate signal as
a reference, the proportion of cage 1 binding 1,3,5-tri-
fluorobenzene was determined to be 58% before and 20%
after the addition of 1-fluoroadamantane (see Section S6 for
further discussion). The decrease in the proportion of cage-
bound 1,3,5-trifluorobenzene indicated that B displaced the
more weakly binding A, as anticipated based upon their
binding constants.
benzene, however, remained unchanged. The disappearance
of the F resonance signal at d = À105.85 ppm suggested that
cage 1 had indeed unlocked to release encapsulated 1,3,5-
1
9
1
trifluorobenzene. The H NMR spectrum of the sample after
the color change confirmed that the IL had not decomposed.
In water and acetonitrile, strongly binding guests have
been shown to displace weakly binding guests within
coordination cages. Competition experiments carried out
using a cage in IL solution were undertaken to further probe
whether guest encapsulation proceeds similarly in ILs as in
water and organic solvents. Two fluorinated guests, 1,3,5-
trifluorobenzene (A) and 1-fluoroadamantane (B), were
[17]
added to separate solutions of cage
1
dissolved in
The properties of ILs, such as their polarity and hydro-
phobicity, can be tuned through the choice of the cation and
anion, each of which contribute different characteristics to the
bulk liquid. ILs can thus be designed to dissolve different
solutes selectively and be rendered mutually miscible or
immiscible. In combination with coordination cages, complex
[
emim][EtOSO ]. After one week, the binding constants
3
(
K ) of the two guests were determined by integrating the
a
1
9
[12]
F resonance signals from the free and encapsulated species
Section S6 in the Supporting Information). 1-Fluoro-
(
À1
adamantane (K = 150m ) was found to bind more strongly
than 1,3,5-trifluorobenzene (K = 80m ), which in turn
a
À1
phase-sorting behavior may thus be engineered, as shown in
a
À1
À
bound more strongly than triflate (K = 4.4m ), the counter-
Scheme 3. The triflimide anions (NTf ) of [P
][NTf ] and
6,6,6,14 2
a
2
19
ion for 1. No significant change to the F NMR spectrum was
detected after an additional week, indicating that equilibrium
had been attained (see Section S6 for a short discussion on
the kinetics and thermodynamics of this system).
[emim][NTf ] render these ILs hydrophobic. The large,
2
+ +
lipophilic [P6,6,6,14] ion and small, more polar [emim] ions
do not associate strongly with each other, making the two ILs
mutually immiscible. Together with water, these two ILs form
a triphasic system.
Based on these differences in guest-binding affinity, we
designed a sequence of guest exchanges involving 1 dissolved
[16]
Cage 2
(Scheme 3) bears twelve sulfonate groups,
19
in [emim][EtOSO ] (Scheme 2). Initially, F NMR signals
rendering this cage highly soluble in water and insoluble in
3
[18]
for both free and encapsulated triflate were detected
the two hydrophobic IL layers. Cage 3
(Scheme 3) is
(
(
Figure S12a). After the addition of 1,3,5-trifluorobenzene
5 equiv), the signal for encapsulated triflate disappeared and
decorated with 24 decyl chains, making it lipophilic and
insoluble in water. Although [emim][NTf ] is hydrophobic, it
2
is also highly polar: a combination of properties unique
[19]
to ILs.
Therefore, only [P6,6,6,14][NTf ] offers a suitably
2
lipophilic solvent for cage 3.
Selecting a cage that dissolves readily in [emim][NTf2]
required a nuanced approach. Cage 1 is only sparingly soluble
in [emim][NTf ], despite having good solubility in the similar
2
IL, [emim][EtOSO ]. Since the only difference between these
3
two ILs is their anion, we hypothesized that the more fluorous
environment in [emim][NTf ] contributed to the poor solu-
2
bility of cage 1. We therefore incorporated twelve fluorine
atoms into the periphery of cage 4 by employing 5-fluoro-2-
Scheme 2. Selective guest exchange within 1 dissolved in in the IL
emim][EtOSO ], based upon differences in guest-binding affinity.
[
3
Angew. Chem. Int. Ed. 2015, 54, 15100 –15104
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 15101

.
Angewandte
Communications
Scheme 3. Within a triphasic system, cages 2, 3, and 4 were observed to partition selectively into H O, [P6,6,6,14][NTf ], and [emim][NTf ], and to
2
2
2
bind selectively 1-fluorobenzene, 9-trifluoroacetylanthracene, and 1-fluoroadamantane, respectively.
formylpyridine as a subcomponent instead of the parent 2-
formylpyridine used in the preparation of 1 (Section S3). This
change resulted in a marked increase in the solubility of 4 in
[
emim][NTf ], and cage 4 was therefore used in the sorting
2
system of Scheme 3. As seen in Figure 1, the affinity of each
cage (2–4) for its designated layer was visually conspicuous.
Each of three vials were filled with 0.5 mL of each phase
(
water (top layer), [P6,6,6,14][NTf2] (middle layer), and
[
emim][NTf ] (bottom layer)). Solid samples of cage 2,
2
cage 3, and cage 4 were added to the first, second, and third
vials, respectively. After the addition of the cage, all vials were
shaken vigorously and the phases were allowed to settle.
Cage 2 was thus observed to be soluble only in water
(
(
Figure 1a), whereas cage 3 dissolved only in [P6,6,6,14][NTf2]
Figure 1b), and cage 4 only in [emim][NTf ] (Figure 1c).
2
Figure 1. Equal volumes (0.5 mL) of water (top layer), [P6,6,6,14][NTf2]
middle layer), and [emim][NTf ] (bottom layer) were added to each
By considering the partially overlapping guest-binding
(
2
preferences of the three cages in Scheme 3, we were able to
bring about a situation in which each host bound a single guest
selectively in its respective phase. Many of the guests bound
by cage 2 can also be encapsulated by cage 4. In water,
benzene binds strongly to 2 and weakly to the fluorine-free
vial. A solid sample of cage 2 was added to the first vial, 3 to the
second vial, and 4 to the third vial, respectively. Each vial was shaken
vigorously for 10 seconds and allowed to settle before the photo was
taken. a) Cage 2 is soluble only in water. b) Cage 3 is soluble only in
[
P6,6,6,14][NTf ]. c) Cage 4 is soluble only in [emim][NTf ].
2
2
1
5102 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 15100 –15104

Angewandte
Chemie
[
15,20]
analogue of 4 (cage 1).
We therefore selected 1-fluoro-
How to cite: Angew. Chem. Int. Ed. 2015, 54, 15100–15104
Angew. Chem. 2015, 127, 15315–15319
benzene as a guest for 2. Cage 3 has been previously shown to
encapsulate 9-acetylanthracene in cyclohexane.
[18]
Since a
fluorinated guest is required for this study, 9-trifluoro-
acetylanthracene was chosen as a guest for cage 3. This
guest is too large to bind inside 2 or 4 and therefore can only
be encapsulated by 3. Cage 1 has been previously shown to
encapsulate adamantane with high affinity in acetonitrile.
Therefore, 1-fluoroadamantane was selected as a guest for
cage 4.
[1] a) Y. Fang, T. Murase, S. Sato, M. Fujita, J. Am. Chem. Soc. 2013,
135, 613 – 615; b) C. A. Schalley, A. Lutzen, M. Albrecht, Chem.
Eur. J. 2004, 10, 1072 – 1080; c) Q. Zhang, K. Tiefenbacher, Nat.
Chem. 2015, 7, 197 – 202.
[15]
[
2] a) S. Turega, W. Cullen, M. Whitehead, C. A. Hunter, M. D.
Ward, J. Am. Chem. Soc. 2014, 136, 8475 – 8483; b) M. W.
Schneider, I. M. Oppel, A. Griffin, M. Mastalerz, Angew. Chem.
Int. Ed. 2013, 52, 3611 – 3615; Angew. Chem. 2013, 125, 3699 –
3703.
To a triphasic mixture of 2 in water (5.0 mm), 3 in
[
P6,6,6,14][NTf ] (1.5 mm), and 4 in [emim][NTf ] (1.5 mm),
2
2
3
9
0 equivalents each (relative to 2, 3, or 4) of 1-fluorobenzene,
-trifluoroacetylanthracene, and 1-fluoroadamantane were
[3] a) C. García-Simón, R. Gramage-Doria, S. Raoufmoghaddam,
T. Parella, M. Costas, X. Ribas, J. N. H. Reek, J. Am. Chem. Soc.
2
015, 137, 2680 – 2687; b) M. Han, R. Michel, B. He, Y.-S. Chen,
D. Stalke, M. John, G. H. Clever, Angew. Chem. Int. Ed. 2013, 52,
319 – 1323; Angew. Chem. 2013, 125, 1358 – 1362.
added. The mixture was stirred for two weeks at room
temperature. A control experiment, in which identical
amounts of the three phases and guests were present, but
no cages, was set up and stirred in parallel. The layers were
then allowed to separate and each layer was isolated for
1
[
4] a) J. S. Mugridge, A. Zahl, R. van Eldik, R. G. Bergman, K. N.
Raymond, J. Am. Chem. Soc. 2013, 135, 4299 – 4306; b) A.
Stephenson, S. P. Argent, T. Riis-Johannessen, I. S. Tidmarsh,
M. D. Ward, J. Am. Chem. Soc. 2011, 133, 858 – 870; c) K.
Tiefenbacher, K.-d. Zhang, D. Ajami, J. Rebek, J. Phys. Org.
Chem. 2015, 28, 187 – 190; d) M. Whitehead, S. Turega, A.
Stephenson, C. A. Hunter, M. D. Ward, Chem. Sci. 2013, 4,
1
9
analysis by F NMR spectroscopy.
19
In the top layer (2 in H O), a F NMR signal was detected
2
for encapsulated 1-fluorobenzene (Figure S15). No signals
were detected for any free guests in water because all three
guests were preferentially soluble in the IL layers. In the
2
744 – 2751; e) O. Dumele, N. Trapp, F. Diederich, Angew. Chem.
Int. Ed. 2015, 54, 12339 – 14344; Angew. Chem. 2015, 127, 12516 –
12521.
19
middle layer (3 in [P6,6,6,14][NTf ]), F NMR signals were
2
evident for encapsulated 9-trifluoroacetylanthracene, free 9-
trifluoroacetylanthracene, free triflimide, free 1-fluoro-
benzene, and free 1-fluoroadamantane (Figure S16). In the
[5] a) P. A. Gale, Acc. Chem. Res. 2006, 39, 465 – 475; b) B. P. Hay,
T. K. Firman, B. A. Moyer, J. Am. Chem. Soc. 2005, 127, 1810 –
1
819; c) J. J. Lavigne, E. V. Anslyn, Angew. Chem. Int. Ed. 2001,
19
40, 3118 – 3130; Angew. Chem. 2001, 113, 3212 – 3225.
bottom layer (4 in [emim][NTf ]), F NMR signals were
2
[
6] D. H. Leung, R. G. Bergman, K. N. Raymond, J. Am. Chem. Soc.
detected for encapsulated 1-fluoroadamantane, free 9-tri-
fluoroacetylanthracene, free triflimide, free 1-fluorobenzene,
and free 1-fluoroadamantane (Figure S17). The cage in each
layer thus encapsulated only the guest that it was observed to
bind most strongly. Crucially, this system allowed guests to be
partitioned into phases that they would have avoided in the
absence of the hosts.
2
008, 130, 2798 – 2805.
[
7] a) B. A. Moyer, R. Custelcean, B. P. Hay, J. L. Sessler, K.
Bowman-James, V. W. Day, S.-O. Kang, Inorg. Chem. 2013, 52,
3473 – 3490; b) Y. Ruan, E. DalkiliÅ, P. W. Peterson, A. Pandit,
A. Dastan, J. D. Brown, S. M. Polen, C. M. Hadad, J. D. Badji c´ ,
Chem. Eur. J. 2014, 20, 4251 – 4256; c) S. T. J. Ryan, J. Del Barrio,
I. Ghosh, F. Biedermann, A. I. Lazar, Y. Lan, R. J. Coulston,
W. M. Nau, O. A. Scherman, J. Am. Chem. Soc. 2014, 136, 9053 –
This study establishes the use of guest-binding coordina-
tion cages in IL phases, which have become an increasingly
9
2
060; d) T. Sawada, H. Hisada, M. Fujita, J. Am. Chem. Soc.
014, 136, 4449 – 4451; e) T. Sawada, M. Yoshizawa, S. Sato, M.
[
21]
used alternative to traditional organic solvents,
with
Fujita, Nat. Chem. 2009, 1, 53 – 56; f) P. R. Symmers, M. J. Burke,
D. P. August, P. I. T. Thomson, G. S. Nichol, M. R. Warren, C. J.
Campbell, P. J. Lusby, Chem. Sci. 2015, 6, 756 – 760.
[
22]
potential applications in fields as diverse as catalysis,
[23]
[24]
cellulose processing,
tion.
CO2 sequestration,
and extrac-
[
25]
[8] a) C. J. Bruns, D. Fujita, M. Hoshino, S. Sato, J. F. Stoddart, M.
Fujita, J. Am. Chem. Soc. 2014, 136, 12027 – 12034; b) A. Galµn,
G. Gil-Ramírez, P. Ballester, Org. Lett. 2013, 15, 4976 – 4979;
c) T. Liu, Y. Liu, W. Xuan, Y. Cui, Angew. Chem. Int. Ed. 2010,
49, 4121 – 4124; Angew. Chem. 2010, 122, 4215 – 4218.
This work adds to the toolbox of complex self-
[
26]
assembled systems by extending the preparation of such
systems into new solvents. The triphasic system described
herein appears extensible, for example, to fluorous phases.
Given the selective guest binding detected, new applications
are envisaged in chemical separations or in phase-transfer
catalysis.
[9] a) P. Montes-Navajas, A. Corma, H. Garcia, J. Mol. Catal. A
2
008, 279, 165 – 169; b) L. Wang, X. Wang, M. Qi, R. Fu, J.
Chromatogr. A 2014, 1334, 112 – 117.
[
10] a) P. K. Mohapatra, A. Sengupta, M. Iqbal, J. Huskens, W.
Verboom, Inorg. Chem. 2013, 52, 2533 – 2541; b) J.-h. Shi, Q.-q.
Jia, S.-x. Xu, Chromatographia 2012, 75, 779 – 787; c) M.
Matsumoto, N. Oku, K. Kondo, Solvent Extr. Res. Dev. Jpn.
Acknowledgements
2
013, 20, 219 – 224.
This work was supported by the European Research Council
[11] C. Daguenet, P. J. Dyson, Inorg. Chem. 2007, 46, 403 – 408.
[
[
12] A. Arce, M. J. Earle, S. P. Katdare, H. Rodriguez, K. R. Seddon,
Chem. Commun. 2006, 2548 – 2550.
13] B. R. Hall, L. E. Manck, I. S. Tidmarsh, A. Stephenson, B. F.
Taylor, E. J. Blaikie, D. A. V. Griend, M. D. Ward, Dalton Trans.
(
259352). We also thank the Cambridge Chemistry NMR
service for experimental assistance.
Keywords: coordination cages · encapsulation · host–
guest systems · ionic liquid · supramolecular chemistry
2
011, 40, 12132 – 12145.
14] K. D. Shimizu, J. Rebek, Proc. Natl. Acad. Sci. USA 1995, 92,
2403 – 12407.
[
1
Angew. Chem. Int. Ed. 2015, 54, 15100 –15104
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 15103

.
Angewandte
Communications
[
[
15] J. L. Bolliger, T. K. Ronson, M. Ogawa, J. R. Nitschke, J. Am.
Chem. Soc. 2014, 136, 14545 – 14553.
16] P. Mal, D. Schultz, K. Beyeh, K. Rissanen, J. R. Nitschke, Angew.
Chem. Int. Ed. 2008, 47, 8297 – 8301; Angew. Chem. 2008, 120,
2013, 52, 12350 – 12353; Angew. Chem. 2013, 125, 12576 – 12579;
c) A. George, A. Brandt, K. Tran, S. M. S. N. S. Zahari, D. Klein-
Marcuschamer, N. Sun, N. Sathitsuksanoh, J. Shi, V. Stavila, R.
Parthasarathi, S. Singh, B. M. Holmes, T. Welton, B. A. Simmons,
J. P. Hallett, Green Chem. 2015, 17, 1728 – 1734.
8
421 – 8425.
[
[
17] a) S. C. Ma, M. M. J. Smulders, Y. R. Hristova, J. K. Clegg, T. K.
[24] J. E. Brennecke, B. E. Gurkan, J. Phys. Chem. Lett. 2010, 1,
3459 – 3464.
Ronson, S. Zarra, J. R. Nitschke, J. Am. Chem. Soc. 2013, 135,
5
2
678 – 5684; b) M. M. J. Smulders, J. R. Nitschke, Chem. Sci.
012, 3, 785 – 788.
[25] X. Q. Sun, H. M. Luo, S. Dai, Chem. Rev. 2012, 112, 2100 – 2128.
[26] a) J. E. Beves, B. A. Blight, C. J. Campbell, D. A. Leigh, R. T.
McBurney, Angew. Chem. Int. Ed. 2011, 50, 9260 – 9327; Angew.
Chem. 2011, 123, 9428 – 9499; b) H. T. Chifotides, K. R. Dunbar,
Acc. Chem. Res. 2013, 46, 894 – 906; c) S. Dhers, H. L. C.
Feltham, S. Brooker, Coord. Chem. Rev. 2015, 296, 24 – 44;
d) Z. Huang, L. Yang, Y. Liu, Z. Wang, O. A. Scherman, X.
Zhang, Angew. Chem. Int. Ed. 2014, 53, 5351 – 5355; Angew.
Chem. 2014, 126, 5455 – 5459; e) H. Weissman, B. Rybtchinski,
Curr. Opin. Colloid Interface Sci. 2012, 17, 330 – 342; f) K. M. C.
Wong, M. M. Y. Chan, V. W. W. Yam, Adv. Mater. 2014, 26,
5558 – 5568; g) Z. Zhang, D. S. Kim, C.-Y. Lin, H. Zhang, A. D.
18] C. Browne, S. Brenet, J. K. Clegg, J. R. Nitschke, Angew. Chem.
Int. Ed. 2013, 52, 1944 – 1948; Angew. Chem. 2013, 125, 1998 –
2
002.
19] Y. Fukaya, H. Ohno, Phys. Chem. Chem. Phys. 2013, 15, 4066 –
072.
20] M. M. J. Smulders, S. Zarra, J. R. Nitschke, J. Am. Chem. Soc.
013, 135, 7039 – 7046.
[
[
4
2
[
[
21] K. R. Seddon, Nat. Mater. 2003, 2, 363 – 365.
22] a) R. Kumar, Saima, A. Shard, N. H. Andhare, Richa, A. K.
Sinha, Angew. Chem. Int. Ed. 2015, 54, 828 – 832; Angew. Chem.
ˇ
2
015, 127, 842 – 846; b) H.-P. Steinrück, P. Wasserscheid, Catal.
Lammer, V. M. Lynch, I. Popov, O. S. Miljani c´ , E. V. Anslyn, J. L.
Lett. 2015, 145, 380 – 397; c) P. Wasserscheid, W. Keim, Angew.
Chem. Int. Ed. 2000, 39, 3772 – 3789; Angew. Chem. 2000, 112,
Sessler, J. Am. Chem. Soc. 2015, 137, 7769 – 7774.
3
926 – 3945.
23] a) J. L. Song, H. L. Fan, J. Ma, B. X. Han, Green Chem. 2013, 15,
619 – 2635; b) P. S. Barber, C. S. Griggs, G. Gurau, Z. Liu, S. Li,
Z. Li, X. Lu, S. Zhang, R. D. Rogers, Angew. Chem. Int. Ed.
[
Received: June 23, 2015
Revised: September 4, 2015
Published online: October 23, 2015
2
1
5104 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 15100 –15104