atoms of the guests, and the multiple π–π stacking interaction and CÀH•••π interactions between triptycene subunits and the aromatic rings of the guests, along with the
squaraine dyes inside of the channels. However, the similar honeycombed superstructures could not be found in the free macrocycles; it suggested that the non-covalent
interactions between the host and the guest as well as the solvent interactions played
important roles in the arrangement of extended channels. Moreover, it was further
found that the [2]rotaxane with nonsymmetrical macrocycles could self-assemble into
an oriented nonsymmetrical channel-like structure (Fig. 20) [35].
6.3
Helicarenes: New Chiral Macrocyclic Arenes
During the past decades, chiral synthetic hosts based on the macrocyclic arenes have
attracted much attention for their wide applications in chiral recognition and selfassembly. Generally, chiral macrocyclic arenes could be obtained by introducing
chiral auxiliary into the macrocyclic skeleton [38]. Introducing inherent chirality is
another strategy to build chiral macrocyclic arenes [39, 40], but their fussy synthesis
and the difficulty in utilizing the macrocyclic cavities limit their practical applications to some extent. Recently, Ogoshi and coworkers [41] reported a new type of
planar chiral macrocyclic arenes based on pillararenes. Undoubtedly, chiral building
62
H
N
HN
N
H
NH
N
NC
CN
N
CN
NC
(a)
(b)
A
B
(c)
Fig. 19 (a) Molecular structure of 62, (b) crystal structure with the asymmetric unit of 62, and
(c) space-filling representation of a 62-based nanotube
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Y. Han and C.-F. Chen
squaraine dyes inside of the channels. However, the similar honeycombed superstructures could not be found in the free macrocycles; it suggested that the non-covalent
interactions between the host and the guest as well as the solvent interactions played
important roles in the arrangement of extended channels. Moreover, it was further
found that the [2]rotaxane with nonsymmetrical macrocycles could self-assemble into
an oriented nonsymmetrical channel-like structure (Fig. 20) [35].
6.3
Helicarenes: New Chiral Macrocyclic Arenes
During the past decades, chiral synthetic hosts based on the macrocyclic arenes have
attracted much attention for their wide applications in chiral recognition and selfassembly. Generally, chiral macrocyclic arenes could be obtained by introducing
chiral auxiliary into the macrocyclic skeleton [38]. Introducing inherent chirality is
another strategy to build chiral macrocyclic arenes [39, 40], but their fussy synthesis
and the difficulty in utilizing the macrocyclic cavities limit their practical applications to some extent. Recently, Ogoshi and coworkers [41] reported a new type of
planar chiral macrocyclic arenes based on pillararenes. Undoubtedly, chiral building
62
H
N
HN
N
H
NH
N
NC
CN
N
CN
NC
(a)
(b)
A
B
(c)
Fig. 19 (a) Molecular structure of 62, (b) crystal structure with the asymmetric unit of 62, and
(c) space-filling representation of a 62-based nanotube
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Y. Han and C.-F. Chen