title: Construction of hetero[n]rotaxanes by use of polyfunctional rotaxane frameworks.
abstract: Heterorotaxanes, one class of topological organic structures, have attracted increasing interesting during the past two decades. In general, two types of heterorotaxane structures exist, one in which two or more different macrocycles are threaded onto one dumbbell-shaped molecule and the other where one macrocycle is threaded onto two or more different dumbbell-shaped molecules. In comparison to these traditional types, another family of topologically interesting heterorotaxanes can be envisaged as arising from polyfunctional molecules that possess both host (crown ether) and guest (ammonium templates). In the present investigation, we have explored the construction of selected members of this new heterorotaxane family, which possess crown ether moieties that are wrapped around a dumbbell-shaped molecule. These structures are prepared by routes in which "stitching" processes, involving template-directed clipping reaction or olefin metathesis reactions, are used to install crown ether ring systems encircling ammonium cation centers. This is then followed by implementation of a threading-followed-by-stoppering sequence to install a second encircling crown ether ring. The results show that the polyfunctional building blocks assemble with high efficiencies. Finally, this investigation provides a foundation for future studies aimed at constructing more complicated heterorotaxane architectures, such as switchable systems, self-assembling polymers, and functional molecular machines.
authors.affiliation: Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University , Wuhan 430079, People's Republic of China.
authors.forename: Ziyong
authors.initials: Z
authors.lastname: Li
authors.forename: Guoxing
authors.initials: G
authors.lastname: Liu
authors.forename: Wen
authors.initials: W
authors.lastname: Xue
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Ying-Wei
authors.initials: YW
authors.lastname: Yang
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu
authors.forename: Sheng Hua
authors.initials: SH
authors.lastname: Liu
authors.forename: Juyoung
authors.initials: J
authors.lastname: Yoon
authors.forename: Jun
authors.initials: J
authors.lastname: Yin