DOI: 10.1002/chem.201301022
Supramolecular Polymers Based on Efficient Pillar[5]arene—Neutral Guest
Motifs
Chunju Li,*[a, b] Kang Han,[a] Jian Li,[a] Yanyan Zhang,[c] Wei Chen,[a] Yihua Yu,[c] and
Xueshun Jia*[a]
Supramolecular polymers, a combination of the advantag-
es of supramolecular chemistry and polymeric materials,
have attracted considerable attention in recent years.[1] The
reversible and tunable characteristics of noncovalent inter-
actions endow supramolecular polymers with some novel
properties, including responsiveness to environmental stimu-
li, recycling, self-healing, adaptivity and degradability. Fur-
thermore, noncovalent preparation based on molecular rec-
ognition/assembly can be employed to achieve facile fabrica-
tion of complex architectures. Although a single noncova-
lent bond is weak, multiple and cooperative noncovalent in-
teractions,[2] such as host–guest complexation and multiple
hydrogen bonds, are strong enough and have been employed
to create a variety of functional polymeric materials.[3] The
design and development of novel building blocks with
strong binding interactions is always an important topic in
this area. Therein, host–guest recognition motifs based on
crown ethers, cyclodextrins, calixarenes and cucurbiturils un-
doubtedly occupy a special position.
guests.[13–15] Scheme 1 shows a series of efficient neutral mo-
lecular recognition motifs based on pillar[5]arenes (P5As),
as previously demonstrated by our group.[12] Building on
Pillararenes are a new family of macrocyclic host mole-
cules, made up of hydroquinone units linked by methylene
bridges at 2,5-positions. They have shown desirable and in-
triguing applications in the construction of molecular
switches/machines,[4] metal–organic frameworks,[5] pH-re-
sponsive vesicles,[6] as well as artificial transmembrane chan-
nels,[7] and have aroused remarkable interest and advanced
significantly in the past five years.[8–12] Compared with other
macrocyclic hosts, the most peculiar host–guest properties of
pillararenes are their strong affinities towards neutral guests
in organic media,[12] since crown ethers, calixarenes and re-
sorcarenes generally interact strongly with cationic
Scheme 1. Some efficient neutral molecular recognition motifs based on
P5As[12] and the redesign of asymmetric guest 1.
these studies, we want to explore whether neutral supramo-
lecular polymers can be created utilizing these guest moiet-
ies, and whether a star pillararene-based motif for supramo-
lecular polymerization/assembly could be provided that is
comparable with some typical host–guest pairs, such as 24-
crown-8 and secondary ammonium salt, b-cyclodextrin and
adamantane, calixarene and organic cation, as well as the
1:1:1 ternary complex between cucurbit[8]uril with an elec-
tron–acceptor guest and an electron–donor guest. However,
it is difficult or impracticable to synthesize P5A derivatives
modified by these disubstituted butane units to afford self-
complementary heteroditopic (AB-type) monomers, or to
link these units to get ditopic/tritopic (B2/B3-type) guests.
On the other hand, monosubstituted butane guests usually
exhibit very weak binding affinities with P5As, giving Ka
values in the vicinity of 10~102 mÀ1.[12a–c]
[a] Prof. Dr. C. Li, K. Han, Dr. J. Li, W. Chen, Prof. Dr. X. Jia
Department of Chemistry, Shanghai University
Shanghai, 200444 (P.R. China)
[b] Prof. Dr. C. Li
Beijing National Laboratory for Molecular Sciences (BNLMS)
Beijing, 100190 (P.R. China)
[c] Y. Zhang, Prof. Dr. Y. Yu
Shanghai Key Laboratory of Magnetic Resonance
Department of Physics, East China Normal
University, Shanghai, 200062 (P.R. China)
Thus, we designed an asymmetric guest 1 possessing a
cyano site and a triazole site at its ends (Scheme 1 and
Supporting information for this article is available on the WWW
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