title: Insights into the Difference Between Rotaxane and Pseudorotaxane.
abstract: Rotaxane and pseudorotaxane are two types of mechanically interlocked molecular architectures, and there is a clear topological difference and boundary between them. In this work, a "suggested [2]rotaxane 1⊂α-CD" was constructed based on axle molecule 1 bearing two terminal ferrocene groups and a wheel component α-cyclodextrin (α-CD), but the result obtained indicated that the ferrocene group cannot prevent α-CD dethreading under UV irradiation. That is, 1⊂α-CD is just a pseudo[2]rotaxane. Furthermore, the two ferrocene groups in 1⊂α-CD were encapsulated by two cucurbit[7]uril (CB[7]) units to obtain a heteropseudo[4]rotaxane 1⊂α-CD⋅2CB[7]. This heteropseudo[4]rotaxane displayed high stability towards harsh temperatures and the isomerization of azobenzene in 1, so it can be regarded as a [2]rotaxane. In this [2]rotaxane, the stoppers are not the bulky groups covalently bonded to the axle, but the cyclic CB[7] units connected through noncovalent interactions.
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: He-Lue
authors.initials: HL
authors.lastname: Sun
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.|Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Heng-Yi
authors.initials: HY
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Dai
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Xu
authors.initials: X
authors.lastname: Han
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.|Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D003505:Cyclodextrins / Q000737:chemistry; D043862:Rotaxanes / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D003505:Cyclodextrins; D043862:Rotaxanes; C009850:azobenzene
keywords: cyclodextrins; isomerization; pseudorotaxanes; rotaxanes; supramolecular chemistry