specific features including lower steric hindrance between neighboring units,
straightforward and facile synthesis, and no self-occupied cavity (Fig. 8b). Definitely, the single crystal analyses in conjunction with the
1 H NMR, 2D NMR
experiments demonstrated four representative conformations that are interconvertible in 48. In other words, the conformation changed predictably due to the structural
difference of certain guests being applied (Fig. 8c). Similarly, oxatub[5,6]arenes
(49, 50) with larger cavity size and more interconvertible conformations were
reported by the same group in 2017 (Fig. 8a) [65]. Due to the larger cavity size,
50 exhibited a nice binding affinity toward both C 60 and C 70 (216 M
À1 for C 60 and
548 M
À1 for C 70 ). Thus, the diversiform and flexibility of oxatub[n]arenes indicate
its wide application in different host-guest systems.
7.3.6 [m]Biphenyl-Extended Pillar[n]arenes
Macrocyclic arenes with large cavity size are always obtained in poor synthetic
yields [22, 24]. In order to conquer this challenge, [m]biphenyl-extended pillar
[n]arenes ([m]Bp-ExPns) were successfully designed and prepared by our
group in 2016 [66]. [m]Bp-ExPns with rigid backbone and large cavity size
were facilely synthesized by a two-step strategy. Firstly, pre-connection of the
Fig. 7 (a) Synthetic route to campestarenes (41–45) [60, 61]; (b) different modes of single crystal
structure of 45 [61]; (c) general chemical structures and single crystal structures of 46 and 47 [63]
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D. Dai et al.
straightforward and facile synthesis, and no self-occupied cavity (Fig. 8b). Definitely, the single crystal analyses in conjunction with the
1 H NMR, 2D NMR
experiments demonstrated four representative conformations that are interconvertible in 48. In other words, the conformation changed predictably due to the structural
difference of certain guests being applied (Fig. 8c). Similarly, oxatub[5,6]arenes
(49, 50) with larger cavity size and more interconvertible conformations were
reported by the same group in 2017 (Fig. 8a) [65]. Due to the larger cavity size,
50 exhibited a nice binding affinity toward both C 60 and C 70 (216 M
À1 for C 60 and
548 M
À1 for C 70 ). Thus, the diversiform and flexibility of oxatub[n]arenes indicate
its wide application in different host-guest systems.
7.3.6 [m]Biphenyl-Extended Pillar[n]arenes
Macrocyclic arenes with large cavity size are always obtained in poor synthetic
yields [22, 24]. In order to conquer this challenge, [m]biphenyl-extended pillar
[n]arenes ([m]Bp-ExPns) were successfully designed and prepared by our
group in 2016 [66]. [m]Bp-ExPns with rigid backbone and large cavity size
were facilely synthesized by a two-step strategy. Firstly, pre-connection of the
Fig. 7 (a) Synthetic route to campestarenes (41–45) [60, 61]; (b) different modes of single crystal
structure of 45 [61]; (c) general chemical structures and single crystal structures of 46 and 47 [63]
192
D. Dai et al.