Chemical signals turn on guest binding through structural reconfiguration of triangular helicates

Article abstract of DOI:10.1002/anie.201305245

Be my guest: The function of a system based on self-assembled Zn ^II complexes can be controlled by external chemical stimuli. The complexes are based on a C₃-symmetric ligand that forms a unique triangular triple helicate structure 1

Full text of DOI:10.1002/anie.201305245

Angewandte
Chemie
DOI: 10.1002/anie.201305245
Systems Chemistry
Chemical Signals Turn On Guest Binding through Structural
Reconfiguration of Triangular Helicates**
Anne Sørensen, Ana M. Castilla, Tanya K. Ronson, Michael Pittelkow, and
Jonathan R. Nitschke*
Biological processes are controlled through highly complex
networks of assembling and disassembling functional enti-
ties,[1,2] for example, cascades of enzymes.[1] Abiological
chemical networks provide a means to study the fundamental
phenomena that underpin the functioning of biochemical
networks.[3] Understanding these phenomena also enables the
design of increasingly intricate synthetic chemical systems
with new functions.[4]
Chemical self-assembly has been employed to create
architectures with increasingly intricate geometries,[5] with
great strides having been made in recent years on the creation
of complex three-dimensional architectures.[6] The dynamic
nature of the linkages between these assembliesꢀ building
blocks opens the possibility of including these structures
as parts of self-sorting multi-component systems[7] or explor-
ing functions related to adaptation in response to chemical
or physical stimuli.[8] The subcomponent self-assembly
method,[9] by which complex architectures are built through
simultaneous formation of metal–ligand coordinative and
dynamic-covalent imine bonds,[10] enables the creation of
structures that are robust, yet capable of dynamic exchange
involving both kinds of labile bonds.[11] This technique has
afforded a range of discrete metal–organic complexes[12] that
can rearrange by taking advantage of enthalpic and entropic
driving forces.[13]
Herein we describe a system based on self-assembled ZnII
complexes, wherein the expression of function can be
controlled by chemical stimuli. The complexes are based on
a C3-symmetric ligand that forms a unique triangular triple
helicate structure. This structure, upon addition of a subcom-
ponent, is able to transform into a double helicate structure
that selectively encapsulates flat, aromatic guests.
The reaction of subcomponent A (3 equiv), 4-methoxy-
aniline (B, 9 equiv), and zinc(II) triflimide (Zn(NTf2)2,
[*] A. Sørensen, Dr. A. M. Castilla, Dr. T. K. Ronson, Dr. J. R. Nitschke
University of Cambridge, Department of Chemistry
Lensfield Road, Cambridge, CB2 1EW (UK)
E-mail: jrn34@cam.ac.uk
Homepage: http://www-jrn.ch.cam.ac.uk
A. Sørensen, Dr. M. Pittelkow
University of Copenhagen, Department of Chemistry
Universitetsparken 5, 2100 Copenhagen Ø (Denmark)
[**] This work was supported by the Lundbeck Foundation and the
European Research Council. We thank Diamond Light Source (UK)
for synchrotron beamtime on I19 (MT7984) and Christopher S.
Wood for developing the synthetic procedure of the boronic acid
intermediate.
Figure 1. a) Synthesis and schematic representation of triangular triple
helicate 1. Conditions: CH3CN, 343 K, 16 h, yield 94%. b) Front and
side view of the crystal structure of 1(NTf2)6.[15] For clarity, hydrogen
atoms and anions are omitted, and each strand is a different color.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201305245.
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3 equiv) resulted in the selective formation of
triangular triple helicate (Figure 1a). The
1
1H NMR spectrum of 1 is complex, with 30 signals
in the aromatic region and three signals in the
aliphatic region (Supporting Information, Fig-
ure S2). This crowded spectrum reflects a non-
symmetrical arrangement of the three ligands in
the assembly, as a symmetrical disposition would
only show 11 signals in total. Two-dimensional
NMR spectroscopy allowed the assignment of the
peaks to three distinct ligand environments. Dif-
fusion ordered 1H NMR spectroscopy (DOSY)
was consistent with the presence of a single species
in solution (Figure S3). The [Zn3L3] (where L = A
+ 3B À 3H2O) stoichiometry of the assembly was
further confirmed by electrospray ionization mass
spectrometry (ESI-MS; Figure S4).
The structure of 1 inferred by ESI-MS and
NMR spectroscopy measurements, was further
confirmed in the solid-state by single-crystal X-ray
analysis (Figure 1b).[14] The crystal structure
revealed a metallosupramolecular [Zn3L3]6+ trian-
gular triple helicate, which crystallizes with C3
point symmetry, such that only one-third of it lies
in the asymmetric unit and all ZnII centers are
crystallographically equivalent. Three facially-
coordinated ZnII centers are bridged by three
tris-bidentate ligands with Zn–Zn distances of
14.73 ꢁ. Each ZnII center adopts a flattened and
distorted octahedral coordination geometry, and
Figure 2. a) Synthesis and schematic representation of triangular double helicate 2.
Conditions: CH3CN, 343 K, 18 h, yield 95%. b) and c) Front and side view of the
MM2-optimized structures of 2 and pyreneꢀ2. For clarity, hydrogen atoms are not
shown, and each strand is a different color.
all the ZnII stereocenters within one helicate share the same D
or L stereochemistry. Both enantiomers are present in the
crystal. Each ligand thus adopts a C3-symmetric propeller-like
helical arrangement within 1.
triangular double helicate 2, where the use of two tris-
tridentate ligands instead of the three tris-bidentate ligands of
1 was envisaged to enable the inclusion of a planar guest in
place of the third ligand in 1. Host 2 (Figure 2a) was prepared
through the reaction of subcomponent A (2 equiv) with
quinolin-8-amine (C, 6 equiv) and Zn(NTf2)2 (3 equiv) as
confirmed by ESI-MS and NMR measurements (Figures S6–
The three ligands are stacked on top of each other; the
centroid-centroid distances of 3.7 ꢁ between the phenyl rings
of two of the adjacent ligands are consistent with p–p
stacking, leaving no void space within the structure. Two of
the ligands (red and green, Figure 1) wrap around each other
in a helical manner while the third ligand (blue, Figure 1) caps
the top of the assembly. The central triazine rings of each
ligand are vertically stacked on top of each other along the C3
axis with centroid-centroid separations of 3.4 and 3.6 ꢁ
between adjacent ligands. Complex 1 is a new structure type;
to our knowledge this is the first time a threefold-symmetric
ligand has been used to build a triangular triple helicate.
The asymmetrical conformation of 1 persisted in solution
upon heating to 338 K, as indicated by variable temperature
NMR spectroscopy (Figure S9). Heating 1 to 363 K for
10 days also did not result in its degradation or transformation
into another structure, suggesting considerable thermody-
namic stability.
We explored the possibility of intercalating guests into
1,[16] or of inducing 1 to rearrange into a suitable host through
guest addition.[17] However, of the 20 guests examined (Fig-
ure S10), none led to an observable change in the H NMR
spectra, even after heating to 343 K for 15 h.
The conformation adopted by the ligands in 1 inspired the
design of the [Zn3L’2] (where L’ = A + 3C À 3H2O)
1
S8). The symmetry of 2 is reflected in its simple H NMR
spectrum, displaying only one set of ligand resonance signals
and two-dimensional NMR spectroscopy allowed the assign-
Table 1: Guests explored for the triangular double helicate 2.
Guest
Encapsulation[a]
anthracene
pyrene
perylene
coronene
yes
yes
yes
yes
yes
yes
yes
1,3,5-trimethoxybenzene
naphthalene-1,5-diol
2,2’-(((naphthalene-1,5-diylbis(oxy))bis(ethane-2,1-
diyl))bis(oxy))diethanol
fluorescein
triphenylene-2,3,6,7,10,11-hexaol
2,4,6-tri(pyridin-2-yl)-s-triazine
triptycene
yes
yes
yes
no
no
no
no
1
C60
cyclohexane
cyclodecane
[a] Monitored by 1H NMR spectroscopy and ESI-MS.
2
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ment of all the signals of triangular double helicate 2. The
presence of only a single species in solution was further
confirmed by DOSY NMR spectroscopy (Figure S7).
Figure 2b shows the MM2 optimized structure of helicate
2. The two ligands are twisted around each other giving rise to
a D3-symmetric structure, consistent with the simple 1H NMR
spectrum of 2.[18]
acetonitrile afforded helicate 2. This transformation is driven
by the displacement of 4-methoxyaniline (B) for quinolin-8-
amine (C), in analogous fashion to previously reported
transformations, where differences in the electronic and
steric properties of various amines, together with the chelate
effect, were utilized as driving forces for imine exchange.[13]
Based on this behavior we have built a simple chemical
network, where chemical signals trigger a functional response.
As shown in Figure 3, the action of chemical stimuli (C and
The distance between the centroids of the two outer
triazine rings in the crystal structure of 1 was measured to be
7.0 ꢁ. It was therefore hypothesized that the space
between the ligands in 2 could provide a cavity
with enough space to accommodate planar aro-
matic guest molecules.[16] Table 1 lists all of the
prospective guest molecules tested. In all cases
where host–guest complexation was inferred to
1
occur, shifts in signals of the H NMR spectra of
both host and guest were observed (Figures S15–
S24), consistent with fast guest exchange on the
1H NMR time scale. ESI-MS spectra showed ions
corresponding to guestꢀ2 complexes (Fig-
ures S33–S39) indicating that the structure of 2
remains intact upon encapsulation of the guest
molecules. Conversely, none of the molecules
inferred not to bind to 2 (Table 1), were observed
to form adducts detectable by ESI-MS or 1H NMR
spectroscopy. Both electron-rich and electron-
deficient polycyclic aromatic guests were observed
to bind to 2, whereas non-planar (triptycene and
C60) and non-aromatic (cyclohexane and cyclo-
decane) molecules showed no evidence of inter-
action.
Figure 3. Schematic representation of the dynamic system of transformations linking
To rule out the possibility of the guests the triangular triple helicate 1 to the host–guest complex pyreneꢀ2.
interacting with the exterior of the triangular
double helicate 2 by p–p stacking instead of being
incorporated within the cavity, we further explored the
behavior of the complex pyreneꢀ2. A Job plot verified the
1:1 binding stoichiometry (Figure S40) and the binding
constant was determined to be 1240 Æ 80mÀ1 in acetonitrile
by means of 1H NMR titration, with data fitting well to a one-
to-one binding model (Figure S41). Increasing the polarity of
the solvent through addition of methanol did not change the
1H NMR spectrum of pyreneꢀ2 (Figure S42). These results
are consistent with the formation of a pyreneꢀ2 inclusion
complex; further evidence for 1:1 guest binding is presented
in the Supporting Information (sections 3.2 and 4.7).
The structures of the guestꢀ2 complexes were investi-
gated using molecular modeling (Figure S49). As an example,
pyreneꢀ2 is shown in Figure 2c. The MM2 optimized
structure of pyreneꢀ2 allows us to infer that 2 is indeed
able to accommodate aromatic guest molecules such as
pyrene. The dynamic nature of the coordinative bonds
together with the flexibility of subcomponent A enable 2 to
adopt a conformation containing a void space able to adapt to
accommodate a guest molecule.[16]
ZnII) resulted in the transformation of 1 into 2, which is able
to adapt its cavity in the presence of an aromatic guest to
effect guest intercalation. The conversion from 1 into guestꢀ2
(where pyrene was used as a representative guest, Figure 3)
can be achieved along three pathways: 1) a direct trans-
formation from triple helicate 1 to guestꢀ2 triggered by the
addition of C, additional ZnII, and guest at once; 2) a two-step
transformation where 2 is formed as the intermediate upon
addition of C and ZnII to 1. The subsequent addition of guest,
as a second stimulus, brought about encapsulation. Finally,
3) a two-step transformation in which a mixture of 1 and
pyrene is considered the first stage. Only after addition of C
and ZnII, was pyrene encapsulated in a pyreneꢀ2 complex.
This third pathway illustrates the chemical orthogonality of
the systemꢀs processes of imine exchange and guest binding.
Each step in the dynamic system was monitored by 1H NMR
spectroscopy and inferred to have reached equilibrium after
24 h at 298 K (Figures S51–S53).
In summary, a triangular triple helicate 1, representing
a new structure type, has been prepared from ZnII and
Building on prior work on imine exchange,[13,19] we
envisaged that double helicate 2 could also be formed by
subcomponent substitution, starting from triple helicate 1.
The addition of stoichiometric amounts of quinolin-8-amine
(C, 9 equiv) and Zn(NTf2)2 (1.5 equiv) to a solution of 1 in
a threefold-symmetric trialdehyde subcomponent. The
dynamic nature of the linkages holding 1 together has allowed
the creation of a simple system of assembled structures whose
function is controlled by external stimuli. Through subcom-
ponent substitution, triple helicate 1 transformed into double
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[7] a) B. H. Northrop, Y.-R. Zheng, K.-W. Chi, P. J. Stang, Acc.
Chem. Res. 2009, 42, 1554 – 1563; b) M. M. Safont-Sempere, G.
Fernꢂndez, F. Wꢃrthner, Chem. Rev. 2011, 111, 5784 – 5814.
[8] a) P. Mukhopadhyay, A. Wu, L. Isaacs, J. Org. Chem. 2004, 69,
6157 – 6164; b) S. Liu, P. Y. Zavalij, Y.-F. Lam, L. Isaacs, J. Am.
Chem. Soc. 2007, 129, 11232 – 11241; c) P. J. Lusby, P. Mꢃller, S. J.
Pike, A. M. Z. Slawin, J. Am. Chem. Soc. 2009, 131, 16398 –
16400; d) S. M. Landge, I. Aprahamian, J. Am. Chem. Soc.
2009, 131, 18269 – 18271; e) T. Yasuda, K. Tanabe, T. Tsuji, K. K.
Coti, I. Aprahamian, J. F. Stoddart, T. Kato, Chem. Commun.
2010, 46, 1224 – 1226; f) M. Han, R. Michel, B. He, Y.-S. Chen, D.
Stalke, M. John, G. H. Clever, Angew. Chem. 2013, 125, 1358 –
1362; Angew. Chem. Int. Ed. 2013, 52, 1319 – 1323.
helicate 2, which has the ability to adapt its conformation in
the presence of planar aromatic guest molecules. It was found
that 2 forms 1:1 complexes with a range of aromatic guest
molecules which have been characterized by 1H NMR
spectroscopy and ESI-MS. Current efforts are focused upon
the use of such triggered guest binding phenomena as parts of
more complex and functional chemical networks, in particular
where such transformations might be undertaken reversibly.
Received: June 18, 2013
Revised: July 26, 2013
Published online: && &&, &&&&
[9] a) V. E. Campbell, J. R. Nitschke, Synlett 2008, 3077 – 3090; b) J.
Dçmer, J. C. Slootweg, F. Hupka, K. Lammertsma, F. E. Hahn,
Angew. Chem. 2010, 122, 6575 – 6578; Angew. Chem. Int. Ed.
2010, 49, 6430 – 6433; c) X.-P. Zhou, J. Liu, S.-Z. Zhan, J.-R.
Yang, D. Li, K.-M. Ng, R. W.-Y. Sun, C.-M. Che, J. Am. Chem.
Soc. 2012, 134, 8042 – 8045; d) S. Yi, V. Brega, B. Captain, A. E.
Kaifer, Chem. Commun. 2012, 48, 10295 – 10297; e) K.-C. Sham,
S.-M. Yiu, H.-L. Kwong, Inorg. Chem. 2013, 52, 5648 – 5650; f) Y.
Wu, X.-P. Zhou, J.-R. Yang, D. Li, Chem. Commun. 2013, 49,
3413 – 3415.
Keywords: host–guest systems · metal–organic complexes ·
self-assembly · systems chemistry · zinc
.
[1] J. Ricard in Emergent Collective Properties, Networks and
Information in Biology (Ed.: G. Bernardi), Elsevier Science,
Amsterdam, 2006.
[10] J. Hamblin, L. J. Childs, N. W. Alcock, M. J. Hannon, J. Chem.
Soc. Dalton Trans. 2002, 164 – 169.
[2] a) M. B. Elowitz, S. Leibler, Nature 2000, 403, 335 – 338; b) A.
Aderem, Cell 2005, 121, 511 – 513.
[11] C. D. Meyer, C. S. Joiner, J. F. Stoddart, Chem. Soc. Rev. 2007,
36, 1705 – 1723.
[3] a) P. B. Glover, P. R. Ashton, L. J. Childs, A. Rodger, M.
Kercher, R. M. Williams, L. De Cola, Z. Pikramenou, J. Am.
Chem. Soc. 2003, 125, 9918 – 9919; b) R. F. Ludlow, S. Otto,
Chem. Soc. Rev. 2008, 37, 101 – 108; c) M. Lista, E. Orentas, J.
Areephong, P. Charbonnaz, A. Wilson, Y. Zhao, A. Bolag, G.
Sforazzini, R. Turdean, H. Hayashi, Y. Domoto, A. Sobczuk, N.
Sakai, S. Matile, Org. Biomol. Chem. 2013, 11, 1754 – 1765.
[4] a) L. M. Greig, D. Philp, Chem. Soc. Rev. 2001, 30, 287 – 302;
b) E. Opsitnick, D. Lee, Chem. Eur. J. 2007, 13, 7040 – 7049; c) K.
[12] a) R. A. Bilbeisi, J. K. Clegg, N. Elgrishi, X. de Hatten, M.
Devillard, B. Breiner, P. Mal, J. R. Nitschke, J. Am. Chem. Soc.
2012, 134, 5110 – 5119; b) I. A. Riddell, M. M. J. Smulders, J. K.
Clegg, Y. R. Hristova, B. Breiner, J. D. Thoburn, J. R. Nitschke,
Nat. Chem. 2012, 4, 751 – 756; c) C. Browne, S. Brenet, J. K.
Clegg, J. R. Nitschke, Angew. Chem. 2013, 125, 1998 – 2002;
Angew. Chem. Int. Ed. 2013, 52, 1944 – 1948; d) I. A. Riddell,
Y. R. Hristova, J. K. Clegg, C. S. Wood, B. Breiner, J. R.
Nitschke, J. Am. Chem. Soc. 2013, 135, 2723 – 2733.
[13] a) D. Schultz, J. R. Nitschke, J. Am. Chem. Soc. 2006, 128, 9887 –
9892; b) V. E. Campbell, X. de Hatten, N. Delsuc, B. Kauffmann,
I. Huc, J. R. Nitschke, Nat. Chem. 2010, 2, 684 – 687; c) Y. R.
Hristova, M. M. J. Smulders, J. K. Clegg, B. Breiner, J. R.
Nitschke, Chem. Sci. 2011, 2, 638 – 641; d) W. Meng, T. K.
Ronson, J. K. Clegg, J. R. Nitschke, Angew. Chem. 2013, 125,
1051 – 1055; Angew. Chem. Int. Ed. 2013, 52, 1017 – 1021.
[14] X-ray diffraction was done using synchrotron radiation at
Diamond Light Source, see H. Nowell, S. A. Barnett, K. E.
Christensen, S. J. Teat, D. R. Allan, J. Synchrotron Radiat. 2012,
19, 435 – 441.
[15] CCDC 934781 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
[16] a) S. Mirtschin, A. Slabon-Turski, R. Scopelliti, A. H. Velders, K.
Severin, J. Am. Chem. Soc. 2010, 132, 14004 – 14005; b) Y.-F.
Han, G.-X. Jin, Chem. Asian J. 2011, 6, 1348 – 1352.
[17] For previous reports on this strategy see: a) ref. 12a; b) M.
Scherer, D. L. Caulder, D. W. Johnson, K. N. Raymond, Angew.
Chem. 1999, 111, 1689 – 1694; Angew. Chem. Int. Ed. 1999, 38,
1587 – 1592; c) S. Hiraoka, T. Yi, M. Shiro, M. Shionoya, J. Am.
Chem. Soc. 2002, 124, 14510 – 14511; d) S. Hiraoka, K. Harano,
M. Shiro, M. Shionoya, Angew. Chem. 2005, 117, 2787 – 2791;
Angew. Chem. Int. Ed. 2005, 44, 2727 – 2731; e) X. Zhang, X.-P.
Zhou, D. Li, Cryst. Growth Des. 2006, 6, 1440 – 1444; f) K.
Harano, S. Hiraoka, M. Shionoya, J. Am. Chem. Soc. 2007, 129,
5300 – 5301; g) M. Han, J. Hey, W. Kawamura, D. Stalke, M.
Shionoya, G. H. Clever, Inorg. Chem. 2012, 51, 9574 – 9576; h) R.
Custelcean, P. V. Bonnesen, N. C. Duncan, X. Zhang, L. A.
ˇ
´
Osowska, O. S. Miljanic, Angew. Chem. 2011, 123, 8495 – 8499;
Angew. Chem. Int. Ed. 2011, 50, 8345 – 8349; d) E. Krieg, B.
Rybtchinski, Chem. Eur. J. 2011, 17, 9016 – 9026; e) Z. Qi, P.
Malo de Molina, W. Jiang, Q. Wang, K. Nowosinski, A. Schulz,
M. Gradzielski, C. A. Schalley, Chem. Sci. 2012, 3, 2073 – 2082;
f) C. J. Kloxin, C. N. Bowman, Chem. Soc. Rev. 2013, 42, 7161 –
7173.
[5] a) P. T. Corbett, J. Leclaire, L. Vial, K. R. West, J.-L. Wietor,
J. K. M. Sanders, S. Otto, Chem. Rev. 2006, 106, 3652 – 3711;
b) M. Yoshizawa, J. K. Klosterman, M. Fujita, Angew. Chem.
2009, 121, 3470 – 3490; Angew. Chem. Int. Ed. 2009, 48, 3418 –
3438; c) R. Chakrabarty, P. S. Mukherjee, P. J. Stang, Chem. Rev.
2011, 111, 6810 – 6918; d) E. Moulin, G. Cormos, N. Giuseppone,
Chem. Soc. Rev. 2012, 41, 1031 – 1049; e) T. K. Ronson, S. Zarra,
S. P. Black, J. R. Nitschke, Chem. Commun. 2013, 49, 2476 –
2490; f) M. Mastalerz, Synlett 2013, 781 – 786.
[6] a) B. Hasenknopf, J.-M. Lehn, B. O. Kneisel, G. Baum, D.
Fenske, Angew. Chem. 1996, 108, 1987 – 1990; Angew. Chem. Int.
Ed. Engl. 1996, 35, 1838 – 1840; b) K. S. Chichak, S. J. Cantrill,
A. R. Pease, S.-H. Chiu, G. W. V. Cave, J. L. Atwood, J. F.
Stoddart, Science 2004, 304, 1308 – 1312; c) S. Bonnet, J.-P.
Collin, M. Koizumi, P. Mobian, J.-P. Sauvage, Adv. Mater. 2006,
18, 1239 – 1250; d) Q.-F. Sun, J. Iwasa, D. Ogawa, Y. Ishido, S.
Sato, T. Ozeki, Y. Sei, K. Yamaguchi, M. Fujita, Science 2010,
328, 1144 – 1147; e) A. Stephenson, S. P. Argent, T. Riis-Johan-
nessen, I. S. Tidmarsh, M. D. Ward, J. Am. Chem. Soc. 2011, 133,
858 – 870; f) Z. Zhao, Y.-R. Zheng, M. Wang, J. B. Pollock, P. J.
Stang, Inorg. Chem. 2010, 49, 8653 – 8655; g) F. Li, J. K. Clegg,
L. F. Lindoy, R. B. Macquart, G. V. Meehan, Nat. Commun.
2011, 2, 205 – 207; h) N. Ponnuswamy, F. B. L. Cougnon, J. M.
Clough, G. D. Pantos¸, J. K. M. Sanders, Science 2012, 338, 783 –
785; i) J.-F. Ayme, J. E. Beves, D. A. Leigh, R. T. McBurney, K.
Rissanen, D. Schultz, Nat. Chem. 2012, 4, 15 – 20.
4
www.angewandte.org
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Chemie
Watson, G. Van Berkel, W. B. Parson, B. P. Hay, J. Am. Chem.
Soc. 2012, 134, 8525 – 8534.
[18] B. Conerney, P. Jensen, P. E. Kruger, C. MacGloinn, Chem.
Commun. 2003, 1274 – 1275.
[19] a) M. M. J. Smulders, A. Jimꢄnez, J. R. Nitschke, Angew. Chem.
2012, 124, 6785 – 6789; Angew. Chem. Int. Ed. 2012, 51, 6681 –
6685; b) N. Ousaka, J. K. Clegg, J. R. Nitschke, Angew. Chem.
2012, 124, 1493 – 1497; Angew. Chem. Int. Ed. 2012, 51, 1464 –
1468.
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Communications
Systems Chemistry
A. Sørensen, A. M. Castilla, T. K. Ronson,
M. Pittelkow,
J. R. Nitschke*
&&&& — &&&&
Chemical Signals Turn On Guest Binding
through Structural Reconfiguration of
Triangular Helicates
Be my guest: The function of a system
based on self-assembled ZnII complexes
can be controlled by external chemical
stimuli. The complexes are based on a C3-
symmetric ligand that forms a unique
triangular triple helicate structure 1.
Upon subcomponent substitution, 1 is
able to transform into a triangular double
helicate 2 which, unlike 1, can encapsu-
late guests.
6
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