Liquid-Crystalline Mesogens Based on Cyclo[6]aramides: Distinctive Phase Transitions in Response to Macrocyclic Host–Guest Interactions

Article abstract of DOI:10.1002/anie.201505278

Producing macrocyclic mesogens that are responsive to guest encapsulation presents a significant challenge. Cyclo[6]aramides, a type of macrocycle with a hydrogen-bond-constrained backbone, exhibit thermotropic lamellar, discotic nematic, hexagonal, and r

Full text of DOI:10.1002/anie.201505278

Angewandte
Chemie
International Edition: DOI: 10.1002/anie.201505278
German Edition: DOI: 10.1002/ange.201505278
Liquid Crystals
Liquid-Crystalline Mesogens Based on Cyclo[6]aramides: Distinctive
Phase Transitions in Response to Macrocyclic Host–Guest Interactions
Xiaowei Li, Bao Li, Long Chen, Jinchuan Hu, Chengdanyang Wen, Qingdong Zheng, Lixin Wu,
Huaqiang Zeng, Bing Gong,* and Lihua Yuan*
Abstract: Producing macrocyclic mesogens that are respon-
sive to guest encapsulation presents a significant challenge.
Cyclo[6]aramides, a type of macrocycle with a hydrogen-
bond-constrained backbone, exhibit thermotropic lamellar,
discotic nematic, hexagonal, and rectangular columnar meso-
phases over a considerably wide temperature range, including
at room temperature. Additionally, cyclo[6]aramides show
unusual mesophase transitions from lamellar to hexagonal
columnar phase mediated by macrocyclic host–guest (H–G)
interactions between the macrocycles and alkylammonium
salts. The phase transition, triggered by an organic guest
engaging in H–G interactions with a macrocyclic cavity,
provides a novel strategy for manipulating the properties of
liquid-crystalline materials. The crystal structure of a homolo-
gous cyclo[6]aramide reveals a disk-shaped, near-planar
molecular backbone that facilitates intermolecular p–p stack-
ing and leads to columnar assembly.
cycles,[4] porphyrins,[5] phthalocyanines,[6] cyclopeptides,[7]
cyclo[8]pyrroles,[8] pillar[5]arenes,[9] calixarenes,[10] and other
cyclic species.[11] In many cases, the observations of LC
properties rely heavily on the presence of an additional
mesogenic handler.[7,9,12] Furthermore, producing macrocyclic
mesogens with rich mesomorphic phases over wide temper-
ature ranges is still a formidable task. Recently, host–guest
(H–G) interactions involving macrocyclic molecules have
been intensely investigated to construct various supramolec-
ular architectures.[13] Surprisingly, despite their inner cavities,
none of the currently known macrocycles have been explored
to effect the phase transition of LC materials by taking
advantage of H–G interactions. We report herein that, with
appropriate peripheral structural modifications, cyclo-
[6]aramides 1a–1e (Figure 1), derived from hydrogen-
U
ncovering new macrocyclic mesogens often leads to the
discovery of functional materials endowed with unique liquid-
crystal behavior.[1] Early work on macrocyclic mesogens
included reports on conformationally flexible mesogens
composed of macrocyclic oligoethers or paracyclophane.[2]
Among macrocycles that could serve as the constituents of
mesophases, those with a more or less rigid core bearing
peripheral flexible side groups are recognized as successful
discotic liquid-crystalline (LC) materials, as typically demon-
strated by phenylacetylene macrocycles,[3] Schiff-base macro-
[*] X. W. Li, L. Chen, J. C. Hu, C. D. Y. Wen, Prof. L. H. Yuan
College of Chemistry, Key Laboratory for Radiation Physics and
Technology of Ministry of Education
Figure 1. Molecular structures and schematic representation of cyclo-
[6]aramides 1–4 and alkylammonium chlorides.
Sichuan University, Chengdu 610064 (China)
E-mail: lhyuan@scu.edu.cn
Dr. B. Li, Prof. L. X. Wu
State Key Laboratory of Supramolecular Structure and Materials
Jilin University, Changchun 130012 (China)
bonded (H-bonded) aromatic amide foldamer precursors,[14]
could serve as a new class of mesogens to form rich
mesophases. These mesophases, including thermotropic
lamellar, discotic nematic, hexagonal, and rectangular col-
umnar mesophases, form over a very wide temperature range
including at room temperature. This constitutes the first
observation of tunable LC phases of mesogens based on
a highly effective shape-persistent macrocyclic backbone.
More importantly and significantly, in the case of 1c a distinct
phase transition from a lamellar to a hexagonal mesophase
could be induced through macrocyclic H–G interactions upon
the addition of cationic guests, such as triethylammonium
chloride, which offers a new strategy for tuning mesophase
Dr. H. Q. Zeng
Institute of Bioengineering and Nanotechnology
31 Biopolis Way, The Nanos, Singapore 138669 (Singapore)
Prof. Q. D. Zheng
State Key Laboratory of Structural Chemistry Fujian Institute of
Research on the Structure of Matter Chinese Academy of Sciences
Fuzhou, Fujian 350002 (China)
Prof. B. Gong
Department of Chemistry, The State University of New York
Buffalo, NY 14260 (USA)
E-mail: bgong@buffalo.edu
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201505278.
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transitions. A single crystal of macrocycle 4[15] was obtained to
help elucidate a possible self-assembly mechanism to explain
the occurrence of liquid crystallinity.
In recent years, H-bonded aromatic amide macrocycles,[16]
featuring amide linkages and a persistent molecular shape,
have received increasing attention because of their interesting
H–G chemistry and the ability to form channels through self-
assembly.[16c,17] In particular, macrocycles with amide oxygen
atoms inwardly oriented are intriguing in their ability to form
H–G complexes. Nevertheless, mesomorphism for these
macrocycles has never been reported since their discovery
a decade ago.[18] Given the backbone conformation of these
macrocycles, that is, with a near-planar disc-shaped large
p surface,[19] we speculate that the smallest member of the
macrocycle family, denoted cyclo[6]aramide,[20] may exhibit
interesting mesophases.
Results based on acyclic analogues of cyclo[6]aramides
show that a balanced core dimension and flexible periphery
could impart the designed oligoamide with mesomorphism.[21]
Unexpectedly, compounds 2 and 3 with alkyl side chains
failed to show any LC properties. This prompted us to prepare
a series of compounds 1a–1e bearing oligoether side chains or
a combination of polar and alkyl chains attached to the
periphery of the macrocycle.[3f, 4b] The resultant macrocycles
were unambiguously characterized by NMR and MALDI-
TOF mass-spectral analyses (see Figures S1–13 in the Sup-
porting Information). Thermogravimetric analysis of 1–3
revealed no mass loss up to circa 3008C, indicating the great
thermal stability of these macrocycles (Figure S14–21,
Table S1). Furthermore, intramolecular H-bonding was
found to remain essentially unchanged as inferred from the
lack of an N H stretching frequency shift around 3380 cmÀ1 in
À
variable-temperature FTIR spectra (Figure S22–26). These
results suggest the persistence of a macrocyclic backbone at
high temperatures.
Figure 2. Polarized optical micrograph of a) Colh of 1a at 1208C,
b) Colr of 1b at 2178C, c) ND of 1c at 2108C, d) Lcol of 1c at 1008C,
e) Colsqu of 1d at 2008C, and f) rectangular columnar mesophase of
1e at 1008C upon cooling from the isotropic melt. Scale bar in (a–
f)=50 mm. g) Phase diagrams of the macrocycles 1a–1e traced during
Indeed, replacing all the alkyl chains of 2 with polar
triethylene glycol (TEG) chains led to compound 1a. This
compound exhibits a dendritic texture in polarized optical
microscopy (POM) images over a temperature range from
1708C to 668C that is characteristic of classical textures of
hexagonal columnar phases (Colh; Figure 2a,g). A phase-
transition behavior for 1a was identified by differential
scanning calorimetry (DSC) analysis (Figure S34). Consistent
with the microscopic data, variable-temperature X-ray dif-
fractions showed patterns characteristic of a Colh phase
(Figure S44,45). Typically, the XRD pattern at 1608C (Fig-
ure 3a) for the oriented sample reveal five reflections at
23.25, 13.51, 11.78, 8.84, and 7.76 Š in the low-angle regime
the second heating cycle in DSC with a heating rate of 108CminÀ1
.
Phase notations: Cr=crystal; Colh =hexagonal columnar mesophase;
Colr =rectangular columnar mesophase; Lcol =columnar lamellar
mesophase; ND =discotic nematic mesophase; Colsqu =tetragonal
columnar mesophase; Iso=isotropic liquid.
liquid) on the second heating, suggesting the significant
influence of polarity and side-chain length on the LC
properties. In contrast to 1b, the DSC trace of 1c shows two
enantiotropic phase transitions at 68.95 and 225.418C with
a wide temperature range of 156.468C. Interestingly, the
POM images of 1c reveal spherical textures with a black cross
in the center from the isotropic temperature up to 1908C in
the first cooling. However, the texture disappears at 1908C
into a mosaic texture. This clearly indicates the presence of
two different mesophases for 1c, which is corroborated by
variable-temperature XRD experiments (Figure S50). The
XRD pattern at 1808C in the low-angle regime reveals
diffraction peaks with the reciprocal spacing ratio of 1:1/2:1/
3:1/4:1/5, confirming the presence of a layered phase with
a periodicity of 23.21 Š. In contrast, the XRD pattern at
pffiffiffi
pffiffiffi
pffiffi
with the reciprocal spacing ratio of 1: 1= 3: 1/2: 1= 7: 1= 9.
They are assigned as the (100), (110), (200), (210), and (300)
reflections, respectively, which are indicative of a hexagonal
phase with a periodicity of 26.85 Š (Table S6). Additionally,
the d spacing of 3.88 Š agrees well with typical aromatic p–p
stacking distance.
Elongation of peripheral groups afforded macrocycles 1b
and 1c. As expected, both compounds also exhibit columnar
liquid crystallinity (Figure 2b,c, and g). However, they both
show enhanced clearing temperatures over 2258C (the
temperature over which the compound exists as an isotropic
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The growth of single crystals of cyclo[6]aramide[23] has
proved to be highly challenging since their first report in
2004.[18] Fortunately, slowly evaporation of a solution of 4 in
chloroform and ethanol (1:1, v/v) led to the formation of
single crystals of this macrocycle,[15] that shares exactly the
same backbone as 1a but has shorter peripheral groups. This
is one of the first crystal structures of these H-bonded
aromatic oligoamide macrocycles with backbones enforced
by three-center hydrogen bonds.[14d,22b] The diameter of the
cavity measures 8.17 Š (Figure 4a), which is large enough to
accommodate different guest molecules or ions. Interestingly,
the macrocycle has a nearly flat backbone (Figure 4b), rather
than the shallow bowl conformation previously predicted by
computational studies.[19] The very small dihedral angle of
1.568 suggests almost perfect face-to-face p–p stacking
between the macrocyclic aromatic backbones. The interpla-
nar distance between two adjacent macrocycles is found to be
3.89 Š (Figure 4c), which is in good agreement with the
intermolecular p–p stacking distance of 3.88 Š revealed by
the XRD data of 1a, and further suggests similar columnar
stacking in the liquid-crystalline phases.
Figure 3. X-ray diffraction patterns of a) 1a at 1608C and b) 1d at
2308C on cooling from the isotropic phase at a cooling rate 28CminÀ1
Inset in (a) and (b): possible 2D packing models for a) 1a in its
hexagonal columnar mesophase at 1608C and b) 1d in its rectangular
columnar mesophase at 2308C.
.
2008C shows no obvious reflection peaks in the low-angle
regime. This observation is significant as it is extremely rare
for a cavity-containing macrocycle to display such a distinct
mesophase transition.[4b]
Given that peripheral substitution with linear alkyl chains
greatly promotes the intermolecular aggregation that is
necessary for columnar stacking[22] and that the introduction
of polar ether chains tends to result in mesomorphism,[4b,21c]
the amalgamation of both traits is expected to provide an
alternative means to fine-tune LC properties. This led to the
design of amphiphilic cyclo[6]aramides 1d and 1e. Indeed,
both compounds exhibit columnar liquid crystallinity (Fig-
ure 2d, e, and g) with rectangular (Figure 3b) and square
phases. The higher clearing points and the much wider
temperature ranges (> 2208C) for 1d and 1e, compared with
1a–1c, are especially noteworthy. This is most likely because
of the enhanced p–p stacking interaction associated with
a nanoscale phase separation caused by the two types of
incompatible side chains of 1d and 1e.[5b] It should be noted
that most of the previously reported macrocycles exhibited
mesophases at relatively high temperatures and with narrow
temperature ranges. Except for the metal complexes of some
macrocycles,[5c,d] we are not aware of any other examples of
macrocyclic mesogens having such a wide temperature range
for liquid crystallinity.
Figure 4. X-ray crystal structure of cyclo[6]aramide 4. a) Top view,
b) side view in the CPK model, illustrating a near-planar macrocyclic
backbone, and c) molecular packing viewed along the a axis with the
dashed green lines drawn passing through the cavities of the macro-
cycles. The dashed green lines in (a) indicate hydrogen bonds.
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Inspired by our recent work on the strong binding of
dialkylammonium salts by cyclo[6]aramides,[24] we probed the
possibility of exploiting macrocyclic H–G interactions to
additionally influence the LC process. First, the binding
affinities of 1a·DEA-HCl, 1a·TEA-HCl, 1c·DEA-HCl, and
1c·TEA-HCl
(DEA-HCl = diethylammonium
chloride,
TEA-HCl = triethylammonium chloride) were determined
1
by H NMR titration experiments and found to range from
(2.71 Æ 0.55) ” 103 mÀ1 to (9.10 Æ 2.08) ” 103 mÀ1 in CDCl3
(Table 1). These data show sufficiently strong binding abilities
Table 1: 1H NMR titration data of the complexes at 298 K and XRD data
of host–guest complexes (host:guest=1:1).
System
Molar ratio[a]
10À3 ”Ka
[mÀ1 [b]
Range Phase/T a [Š]
]
[8C][c]
[8C][d]
1a
–
–
52
69
63
156
161
140
Colh/160 26.85
Colh/100 26.43
Colh/180 26.57
1a·DEA-HCl
1a·TEA-HCl
1c
1c·DEA-HCl
1c·TEA-HCl
1:1
1:1
–
1:1
1:1
2.71Æ0.55
4.55Æ0.79
–
Lcol/180
23.21
4.15Æ0.69
Colh/100 27.14
Colh/100 25.90
9.10Æ2.08
[a] The 1:1 stoichiometry of the complexes was established by the molar
ratio method in CDCl3. [b] The association constants Ka values were
obtained by 1H NMR titrations at 298 K in CDCl3. [c] The temperature
ranges of the mesophases were determined by DSC or POM based on
the second heating cycle. [d] XRD measurement temperature.
Figure 5. Polarized optical micrographs showing mesophases of
a) 1a·DEA-HCl at 1008C (Colh), b) 1a·TEA-HCl at 1508C (Colh),
c) 1c·DEA-HCl at 1008C (Colh), and d) 1c·TEA-HCl at 1708C (Colh)
upon cooling from the isotropic melt. e) Phase diagrams of the
complexes (host: guest=1:1) traced during the heating cycle by POM
with a heating rate of 28CminÀ1 by the addition of 1 molar equivalent
of DEA-HCl or TEA-HCl. Scale bar in (a–d)=50 mm.
of these macrocycles towards cationic guests. Accordingly
DEA-HCl or TEA-HCl are added to a solution of 1a or 1c in
chloroform, which is followed by solvent evaporation to
afford the 1:1 complexes. Results from two-dimensional
NOESY experiments suggest that alkylammonium ions are
bound inside the cavity instead of locating around the
periphery of 1a or 1c (Figure S59–83). Next, the H–G
complexes were subjected to POM imaging. On cooling
from the isotropic melt, clear dendritic (Figure 5a,b) or
pseudo focal conic textures (Figure 5c,d) are observed,
suggesting formation of columnar LC assemblies. For 1a,
forming a complex with organic salts only imparts a very
limited effect upon the LC textures and phase diagrams
(Figure 5e). Nevertheless and to our delight, a mesogenic
were also investigated (Figure S94–98, Tables S11 and 12), but
the results failed to show any discernable change in meso-
phase transitions. Moreover, addition of a second component
results in temperature ranges for 1a and 1c–1e that vary only
within a narrow window of 10–178C (Table S13). This is
partially rationalized by the fact that the guest is only trapped
inside the cavity, thus producing a negligible effect upon the
packing surroundings of macrocyclic molecules in a LC phase.
In conclusion, we have demonstrated the ability of
cyclo[6]aramides 1a–1e to serve as a new class of H-bonded
macrocyclic mesogens that produce stable lamellar, discotic
nematic, hexagonal, and rectangular mesophases over a very
wide temperature range. The rich mesophases are readily
achieved by incorporating side chains of different polarities
and lengths. The organic-guest-triggered phase transition
based on supramolecular H–G interactions involving the
macrocyclic cavity offers a hitherto unexplored strategy for
manipulating the properties of LC materials. Further struc-
tural variations around the exterior of these mesogenic
macrocycles are expected to create new LC materials with
novel thermal and chemical responsiveness.
transition occurs from the lamellar columnar phase (Lcol
)
observed for 1c to a more densely and well-organized
hexagonal columnar phase (Colh) for 1c·TEA-HCl. A similar
trend follows when DEA-HCl is used as the guest salt
(Table 1). The XRD patterns of H–G complexes recorded at
measurement temperatures (Figures S92, S93) also point to
a transition from the Lcol mesophase for uncomplexed 1c to
the Colh mesophase for both H–G complexes 1c·DEA-HCl
and 1c·TEA-HCl. Meanwhile, the Colh mesophases of the
complexes remain intact at varying molar ratios of host and
guest as indicated by POM and DSC data (Figure S89–91).
These unprecedented macrocyclic discotic LC phase transi-
tions from a lamellar to hexagonal phase may arise from the
electrostatic interaction and steric exclusion between adja-
cent macrocyclic cores containing bulky alkylammonium ions
in the H–G complexes. The other two complexes 1d·TEA-
HCl and 1e·TEA-HCl based on amphiphilic cyclo[6]aramides
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B. Mu, Q. Li, X.-Y. Hu, C. Lin, D. Chen, L. Y. Wang, Adv. Funct.
Mater. 2015, 25, 3571.
Acknowledgements
[10] a) B. Xu, T. M. Swager, J. Am. Chem. Soc. 1993, 115, 1159; b) S.-
X. Fa, X.-F. Chen, S. Yang, D.-X. Wang, L. Zhao, E.-Q. Chen, M.-
X. Wang, Chem. Commun. 2015, 51, 5112.
This work is supported by the National Natural Science
Foundation of China (21172158), the Doctoral Program of the
Ministry of Education of China (20130181110023), the
National Science Foundation for Fostering Talents in Basic
Research of the National Natural Science Foundation of
China (J1210004 and J1103315), the Open Project of the State
Key Laboratory of Supramolecular Structure and Materials
(SKLSSM2015026), the Open Project of the State Key
Laboratory of Structural Chemistry (20140013), and the US
National Science Foundation (CHE-1445742 and CBET-
1512164). The Comprehensive Training Platform of the
Specialized Laboratory, College of Chemistry, Sichuan Uni-
versity, is acknowledged for NMR and FTIR analyses.
[11] a) A. Liebmann, C. Mertesdorf, T. Plesnivy, H. Ringsdorf, J. H.
Wendorff, Angew. Chem. Int. Ed. Engl. 1991, 30, 1375; Angew.
Chem. 1991, 103, 1358; b) G. Lattermann, S. Schmidt, R.
Kleppinger, J. H. Wendorff, Adv. Mater. 1992, 4, 30; c) M.
Ricco, E. Dalcanale, J. Phys. Chem. 1994, 98, 9002; d) T.
Hegmann, B. Neumann, J. Kain, S. Diele, C. Tschierske, J.
Mater. Chem. 2000, 10, 2244; e) B. Neumann, T. Hegmann, C.
Wagner, P. R. Ashton, R. Wolf, C. Tschierske, J. Mater. Chem.
2003, 13, 778; f) J. L. Sessler, W. Callaway, S. P. Dudek, R. W.
Date, V. Lynch, D. W. Bruce, Chem. Commun. 2003, 2422; g) W.
Pisula, M. Kastler, C. Yang, V. Enkelmann, K. Müllen, Chem.
Asian J. 2007, 2, 51; h) H. Norouzi-Arasi, W. Pisula, A.
Mavrinskiy, X. Feng, K. Müllen, Chem. Asian J. 2011, 6, 367;
i) Y. Norikane, Y. Hirai, M. Yoshida, Chem. Commun. 2011, 47,
1770.
Keywords: host–guest systems · liquid crystals · macrocycles ·
mesogens · mesophase transitions
[12] a) G.-T. Wang, X. Zhao, Z.-T. Li, Tetrahedron 2011, 67, 48;
b) F. F. Yang, Y. M. Zhang, H. Y. Guo, New J. Chem. 2013, 37,
2275.
How to cite: Angew. Chem. Int. Ed. 2015, 54, 11147–11152
Angew. Chem. 2015, 127, 11299–11304
[13] For reviews, see: a) D.-W. Zhang, X. Zhao, Z.-T. Li, Acc. Chem.
Res. 2014, 47, 1961; b) S. Y. Dong, B. Zheng, F. Wang, F. H.
Huang, Acc. Chem. Res. 2014, 47, 1982; c) Z. Qi, C. A. Schalley,
Acc. Chem. Res. 2014, 47, 2222; d) N. Song, Y.-W. Yang, Chem.
Soc. Rev. 2015, 44, 3474; e) K. C. Jie, Y. J. Zhou, Y. Yao, F. H.
Huang, Chem. Soc. Rev. 2015, 44, 3568; f) H. C. Zhang, R. Q.
Zou, Y. L. Zhao, Coord. Chem. Rev. 2015, 294, 74; g) G. C. Yu,
K. C. Jie, F. H. Huang, Chem. Rev. 2015, DOI: 10.1021/
cr5005315; h) X. Ma, Y. L. Zhao, Chem. Rev. 2015, DOI:
10.1021/cr500392w.
[14] a) Y. Hamuro, S. J. Geib, A. D. Hamilton, Angew. Chem. Int. Ed.
Engl. 1994, 33, 446; Angew. Chem. 1994, 106, 465; b) S. H.
Gellman, Acc. Chem. Res. 1998, 31, 173; c) S. Hecht, I. Huc,
Foldamers: Structure, Properties, and Applications, Wiley-VCH,
Weinheim, 2007; d) B. Gong, Acc. Chem. Res. 2008, 41, 1376;
e) Z.-T. Li, J.-L. Hou, C. Li, Acc. Chem. Res. 2008, 41, 1343; f) Q.
Gan, Y. Ferrand, C. Y. Bao, B. Kauffmann, A. GrØlard, H. Jiang,
I. Huc, Science 2011, 331, 1172; g) N. Chandramouli, Y. Ferrand,
G. Lautrette, B. Kauffmann, C. D. Mackereth, M. Laguerre, D.
Dubreuil, I. Huc, Nat. Chem. 2015, 7, 334.
[15] CCDC 1400074 (4) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre.
[16] For reviews, see: a) D.-W. Zhang, X. Zhao, J.-L. Hou, Z.-T. Li,
Chem. Rev. 2012, 112, 5271; b) K. Yamato, M. Kline, B. Gong,
Chem. Commun. 2012, 48, 12142; c) B. Gong, Z. F. Shao, Acc.
Chem. Res. 2013, 46, 2856; d) H. L. Fu, Y. Liu, H. Q. Zeng,
Chem. Commun. 2013, 49, 4127; e) W. Ong, H. Q. Zeng, J.
Inclusion Phenom. Macrocyclic Chem. 2013, 76, 1.
[1] a) S. Kumar, Chem. Soc. Rev. 2006, 35, 83; b) S. Laschat, A. Baro,
N. Steinke, F. Giesselmann, C. Hagele, G. Scalia, R. Judele, E.
Kapatsina, S. Sauer, A. Schreivogel, M. Tosoni, Angew. Chem.
Int. Ed. 2007, 46, 4832; Angew. Chem. 2007, 119, 4916; c) C.
Tschierske, Angew. Chem. Int. Ed. 2013, 52, 8828; Angew. Chem.
2013, 125, 8992.
[2] a) P. R. Ashton, D. Joachimi, N. Spencer, J. F. Stoddart, C.
Tschierske, A. J. P. White, D. J. Williams, K. Zab, Angew. Chem.
Int. Ed. Engl. 1994, 33, 1503; Angew. Chem. 1994, 106, 1563;
b) V. Percec, A. D. Asandei, M. Zhao, Chem. Mater. 1996, 8, 301.
[3] a) J. Zhang, J. S. Moore, J. Am. Chem. Soc. 1994, 116, 2655;
b) O. Y. Mindyuk, M. R. Stetzer, P. A. Heiney, J. C. Nelson, J. S.
Moore, Adv. Mater. 1998, 10, 1363; c) S. Hçger, V. Enkelmann,
K. Bonrad, C. Tschierske, Angew. Chem. Int. Ed. 2000, 39, 2267;
Angew. Chem. 2000, 112, 2355; d) S. Hçger, Chem. Eur. J. 2004,
10, 4352; e) M. Fischer, G. Lieser, A. Rapp, I. Schnell, W.
Mamdouh, S. De Feyter, F. C. De Schryver, S. Hçger, J. Am.
Chem. Soc. 2004, 126, 214; f) S. H. Seo, T. V. Jones, H. Seyler,
J. O. Peters, T. H. Kim, J. Y. Chang, G. N. Tew, J. Am. Chem. Soc.
2006, 128, 9264.
[4] a) J. K. H. Hui, J. Jiang, M. J. MacLachlan, Can. J. Chem. 2012,
90, 1056; b) S.-i. Kawano, Y. Ishida, K. Tanaka, J. Am. Chem.
Soc. 2015, 137, 2295.
´
[5] a) M. Ste˛pien, B. Donnio, J. L. Sessler, Chem. Eur. J. 2007, 13,
6853; b) H. Masunaga, K. Osaka, M. Takata, T. Aida, J. Am.
Chem. Soc. 2008, 130, 13812; c) T. Sakurai, K. Tashiro, Y.
Honsho, A. Saeki, S. Seki, A. Osuka, A. Muranaka, M.
Uchiyama, J. Kim, S. Ha, K. Kato, M. Takata, T. Aida, J. Am.
Chem. Soc. 2011, 133, 6537; d) K. Ban, K. Nishizawa, K. Ohta, H.
Shirai, J. Mater. Chem. 2000, 10, 1083.
[17] a) A. J. Helsel, A. L. Brown, K. Yamato, W. Feng, L. Yuan, A. J.
Clements, S. V. Harding, G. Szabo, Z. Shao, B. Gong, J. Am.
Chem. Soc. 2008, 130, 15784; b) X. B. Zhou, G. D. Liu, K.
Yamato, Y. Shen, R. X. Cheng, X. X. Wei, W. L. Bai, Y. Gao, H.
Li, Y. Liu, F. T. Liu, D. M. Czajkowsky, J. F. Wang, M. J. Dabney,
Z. H. Cai, J. Hu, F. V. Bright, L. He, X. C. Zeng, Z. F. Shao, B.
Gong, Nat. Commun. 2012, 3, 949; c) Y. Zhao, H. Cho, L.
Widanapathirana, S. Y. Zhang, Acc. Chem. Res. 2013, 46, 2763;
d) W. Si, P. Y. Xin, Z.-T. Li, J.-L. Hou, Acc. Chem. Res. 2015, 48,
1612.
[6] a) C. Piechocki, J. Simon, A. Skoulios, D. Guillon, P. Weber, J.
Am. Chem. Soc. 1982, 104, 5245; b) C. F. van Nostrum, S. J.
Picken, A.-J. Schouten, R. J. M. Nolte, J. Am. Chem. Soc. 1995,
117, 9957; c) B. Cabezón, M. Nicolau, J. Barberµ, T. Torres,
Chem. Mater. 2000, 12, 776.
[7] a) K. Sato, Y. Itoh, T. Aida, J. Am. Chem. Soc. 2011, 133, 13767;
b) M. Amorín, A. Perez, J. Barbera, H. L. Ozores, J. L. Serrano,
J. R. Granja, T. Sierra, Chem. Commun. 2014, 50, 688.
[18] L. H. Yuan, W. Feng, K. Yamato, A. R. Sanford, D. G. Xu, H.
Guo, B. Gong, J. Am. Chem. Soc. 2004, 126, 11120.
´
[8] M. Ste˛pien, B. Donnio, J. L. Sessler, Angew. Chem. Int. Ed. 2007,
[19] L. Q. Yang, L. J. Zhong, K. Yamato, X. H. Zhang, W. Feng, P. C.
Deng, L. H. Yuan, X. C. Zeng, B. Gong, New J. Chem. 2009, 33,
729.
46, 1431; Angew. Chem. 2007, 119, 1453.
[9] a) I. Nierengarten, S. Guerra, M. Holler, J. F. Nierengarten, R.
Deschenaux, Chem. Commun. 2012, 48, 8072; b) S. Pan, M. F. Ni,
Angew. Chem. Int. Ed. 2015, 54, 11147 –11152
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
11151

.
Angewandte
Communications
[20] a) L. J. Zhong, L. Chen, W. Feng, S. L. Zou, Y. Y. Yang, N. Liu,
L. H. Yuan, J. Inclusion Phenom. Macrocyclic Chem. 2012, 63,
4079; b) Y. Z. He, M. Xu, R. Z. Gao, X. W. Li, F. X. Li, X. D. Wu,
D. G. Xu, H. Q. Zeng, L. H. Yuan, Angew. Chem. Int. Ed. 2014,
53, 11834; Angew. Chem. 2014, 126, 12028.
[21] a) P. J. Stals, M. M. Smulders, R. Martin-Rapun, A. R. Palmans,
E. W. Meijer, Chem. Eur. J. 2009, 15, 2071; b) P. J. Stals, J. C.
Everts, R. de Bruijn, I. A. Filot, M. M. Smulders, R. Martin-
Rapun, E. A. Pidko, T. F. de Greef, A. R. Palmans, E. W. Meijer,
Chem. Eur. J. 2010, 16, 810; c) S. L. Zou, L. T. He, J. Zhang, Y. Z.
He, L. H. Yuan, L. X. Wu, J. Luo, Y. H. Wang, W. Feng, Org.
Lett. 2012, 14, 3584.
G. X. Liang, L. Shen, S. F. Ma, D. K. Sukumaran, T. Szyperski,
W. H. Fang, L. He, X. Chen, B. Gong, J. Am. Chem. Soc. 2015,
137, 5879.
[23] W. Feng, K. Yamato, L. Q. Yang, J. S. Ferguson, L. J. Zhong, S. L.
Zou, L. H. Yuan, X. C. Zeng, B. Gong, J. Am. Chem. Soc. 2009,
131, 2629.
[24] a) J. C. Hu, L. Chen, Y. Ren, P. C. Deng, X. W. Li, Y. J. Wang,
Y. M. Jia, J. Luo, X. S. Yang, W. Feng, L. H. Yuan, Org. Lett.
2013, 15, 4670; b) J. C. Hu, L. Chen, J. Shen, J. Luo, P. C. Deng, Y.
Ren, H. Q. Zeng, W. Feng, L. H. Yuan, Chem. Commun. 2014,
50, 8024.
[22] a) Y. A. Yang, W. Feng, J. C. Hu, S. L. Zou, R. Z. Gao, K.
Yamato, M. Kline, Z. H. Cai, Y. Gao, Y. B. Wang, Y. B. Li, Y. L.
Yang, L. H. Yuan, X. C. Zeng, B. Gong, J. Am. Chem. Soc. 2011,
133, 18590; b) X. X. Wu, R. Liu, B. Sathyamoorthy, K. Yamato,
Received: June 9, 2015
Published online: August 11, 2015
11152 www.angewandte.org
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Angew. Chem. Int. Ed. 2015, 54, 11147 –11152