stereospecific synthesis and obtained a pretzelane as shown in Fig. 24a. Then they
investigated the chiral and electrochemical properties of the pretzelane systematically. Due to the introduction of the stereogenic center and the pretzelane’s helical
chirality, one conformational diastereoisomer was much preferred over the other
one. In 2009, they reported a bistable pretzelane composing of a crown ether
containing TTF and 1,5-dihydroxynaphthalene and a covalently tethered cyclophane
ring (Fig. 24b). When this pretzelane was oxidized or reduced, it could exhibit
unidirectional motion forwards or backwards.
Because of the fascinating topological features and potential functions as
components of molecular devices, our group [48] also reported a pretzelane
Fig. 23 (a) Photo of pretzel and (b) schematic illustration of pretzelane constructed from [2]
catenane
Fig. 24 (a) Structure of crown ether- and cyclophane-based pretzelane [46]; (b) bistable pretzelane
containing a crown ether-containing TTF, 1,5-dihydroxynaphthalene, and a covalently tethered
cyclophane ring [47]
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S.-H. Li et al.