title: A musclelike [2](2)rotaxane: synthesis, performance, and molecular dynamics simulations.
abstract: A novel bistable symmetric [2](2)rotaxane was prepared by a threading-followed-by-stoppering strategy and characterized with (1)H, (13)C, and 2D ROESY NMR spectroscopy and HR-ESI spectrometry. The symmetric [2](2)rotaxane system consists of an anthracene-based bis(crown ether) as macrocycles, and each of the two dibenzo[24]crown-8 (DB24C8) rings is threaded by the pendant substituents of a symmetrically substituted central rotatable ferrocene subunit that possesses two distinguishable recognition sites for the DB24C8 ring: namely, a dibenzylammonium site and an N-methyltriazolium site. The uniform shuttling motion of the thread relative to the two DB24C8 rings in [2](2)rotaxane can be driven by external acid-base stimuli, which was evidenced by (1)H and 2D ROESY NMR spectroscopy. Furthermore, molecular dynamics simulations of the [2](2)rotaxane were carried out both in protonated (stretched) and in neutral (contracted) forms. The calculated percentage change in molecular length of the [2](2)rotaxane between the two end-capping bis(methoxyl)phenyl groups is about 48% in the two different states (in acetone), which is much larger than the percentage change (∼27%) in human muscle. Moreover, in the two states, the C*-Cp-Cp-C* dihedral angles are computed as -177° in the stretched state and -112° in the contracted state, indicating a correlation between the translational and rotational motions of the [2](2)rotaxane.
authors.affiliation: Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology , Shanghai 200237, People's Republic of China.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Hans
authors.initials: H
authors.lastname: Agren
authors.forename: Da-Hui
authors.initials: DH
authors.lastname: Qu
mesh_terms: D043844:Crown Ethers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D043862:Rotaxanes / Q000138:chemical synthesis* / Q000737:chemistry*; D014230:Triazoles / Q000737:chemistry*
chemical_list: D043844:Crown Ethers; D000644:Quaternary Ammonium Compounds; D043862:Rotaxanes; D014230:Triazoles; C007316:dibenzyldimethylammonium