Synthesis and Dynamics of Nanosized Phenylene–Ethynylene–Butadiynylene Rotaxanes and the Role of Shape Persistence. Issue 10 (2nd February 2016)

• Record Type: Journal Article
• Authors: Schweez, Christopher; Shushkov, Philip; Grimme, Stefan; Höger, Sigurd
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 10(2016)
• Page Start: 3328
• Page End: 3333
• Publication Date: 2016-02-02
• Subjects: density functional calculations -- interlocked systems -- molecular modeling -- rotaxanes -- template synthesis; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201509702
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Phenylacetylene‐based [2]rotaxanes were synthesized by a covalent‐template approach by aminolysis of the corresponding prerotaxanes. The wheel and the bulky stoppers are made of phenylene–ethynylene–butadiynylene macrocycles of the same size. The stoppers are large enough to enable the synthesis and purification of the rotaxane. However, the wheel unthreads from the axle at elevated temperatures. The deslipping kinetics and the activation parameters were determined. We described theoretically the unthreading by state‐of‐the‐art DFT‐based molecular‐mechanics models and a string method for the simulation of rare events. This approach enabled us to characterize in detail the unthreading mechanism, which involves the folding of the stopper during its passage through the wheel opening, a process that defies intuitive geometrical considerations. The conformational and energetic features of the transition allowed us to infer the molecular residues controlling the disassembly timescale. Abstract : Escape artist extraordinaire : How shape‐persistent is "shape‐persistent"? Novel phenylene–ethynylene–butadiynylene rotaxanes synthesized by a covalent‐template approach were found to undergo unthreading of the wheel from the axis (see picture). The detailed unthreading mechanism was investigated theoretically by state‐of‐the‐art DFT‐based molecular mechanics and a string method for the simulation of rare events.