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Rational Design for Rotaxane Synthesis through Intramolecular Slippage: Control of Activation Energy by Rigid Axle Length
Author(s) -
Masai Hiroshi,
Terao Jun,
Fujihara Tetsuaki,
Tsuji Yasushi
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201600429
Subject(s) - rotaxane , intramolecular force , chemistry , steric effects , slippage , covalent bond , molecule , axle , stereochemistry , supramolecular chemistry , materials science , organic chemistry , mechanical engineering , engineering , composite material
We describe a new concept for rotaxane synthesis through intramolecular slippage using π‐conjugated molecules as rigid axles linked with organic soluble and flexible permethylated α‐cyclodextrins (PM α‐CDs) as macrocycles. Through hydrophilic–hydrophobic interactions and flipping of PM α‐CDs, successful quantitative conversion into rotaxanes was achieved without covalent bond formation. The rotaxanes had high activation barrier for their de‐threading, so that they were kinetically isolated and derivatized even under conditions unfavorable for maintaining the rotaxane structures. 1 H NMR spectroscopy experiments clearly revealed that the restricted motion of the linked macrocycle with the rigid axle made it possible to control the kinetic stability by adjusting the length of the rigid axle in the precursor structure rather than the steric bulkiness of the stopper unit.