As shown in Fig. 22, Stoddart and Sauvage et al. [44] used a simple [2]rotaxane
(cyclophane as macrocycle and naphthyl-based oligomethylene glycol as axle)
as substrate and constructed a molecular 8 architecture conveniently in high
yield via “click” chemistry in 2011. The electron-deficient tetracationic cyclophane
as acceptor and the electron-rich naphthalene-containing polyether chain as donor
together formed a donor-acceptor molecular 8. It’s very important to identify
both structure and dynamics of a higher-order topological structure, so they
separated a pair of trans- and cis-constitutional isomers of molecular 8 later
in 2012 [45]. And in this work, with the knowledge of the solid-state structure (the
stereochemistry of the major product) of molecular 8 in mind, they realized that they
achieved incorrect results from ab initio calculations before.
4.5
Pretzelane
If we further connect the mechanically interlocked molecules [n]cantenane with
covalent bonds, the original two or more separated covalent components will be
covalently linked, resulting with a more complicated structure. Vogtle et al. [14] had
been focused on the construction and investigation of the mechanically interlocked
architectures over a long term since the year of 1996, during which for the first time
they constructed a mechanically interlocked structure through covalently connected
two cyclic amide-based macrocycles in a [2]catenane system, as shown in Fig. 23b.
Because of its topological similarity to the pretzel (Fig. 23a) favored by western
Europeans, this kind of structure was given the name “pretzelane.”
Stoddart et al. [46, 47] also reported some beautiful pretzelane structures. In 2005,
they covalently connected the crown ether and the cyclophane in a [2]catenane using
Fig. 22 Construction of molecular figures-of-eight based on cyclophane using “click” chemistry
[44]
4 Mechanically Self-Locked Molecules
101
(cyclophane as macrocycle and naphthyl-based oligomethylene glycol as axle)
as substrate and constructed a molecular 8 architecture conveniently in high
yield via “click” chemistry in 2011. The electron-deficient tetracationic cyclophane
as acceptor and the electron-rich naphthalene-containing polyether chain as donor
together formed a donor-acceptor molecular 8. It’s very important to identify
both structure and dynamics of a higher-order topological structure, so they
separated a pair of trans- and cis-constitutional isomers of molecular 8 later
in 2012 [45]. And in this work, with the knowledge of the solid-state structure (the
stereochemistry of the major product) of molecular 8 in mind, they realized that they
achieved incorrect results from ab initio calculations before.
4.5
Pretzelane
If we further connect the mechanically interlocked molecules [n]cantenane with
covalent bonds, the original two or more separated covalent components will be
covalently linked, resulting with a more complicated structure. Vogtle et al. [14] had
been focused on the construction and investigation of the mechanically interlocked
architectures over a long term since the year of 1996, during which for the first time
they constructed a mechanically interlocked structure through covalently connected
two cyclic amide-based macrocycles in a [2]catenane system, as shown in Fig. 23b.
Because of its topological similarity to the pretzel (Fig. 23a) favored by western
Europeans, this kind of structure was given the name “pretzelane.”
Stoddart et al. [46, 47] also reported some beautiful pretzelane structures. In 2005,
they covalently connected the crown ether and the cyclophane in a [2]catenane using
Fig. 22 Construction of molecular figures-of-eight based on cyclophane using “click” chemistry
[44]
4 Mechanically Self-Locked Molecules
101