Deslipping of Rotaxanes with Axle Center Pieces of Different Lengths

P. Linnartz, C. A. Schalley— 2004

A series of rotaxanes equipped with tetralactam wheels and di-t-butyl stopper groups, which differ only with respect to the length of the alkyl chain serving as the axle center piece, are examined with respect to their deslipping behavior at elevated temperatures. 1H NMR experiments are used to follow the deslipping reactions kinetically, and it is found that the axle length does not have a significant influence on the rate of deslipping. In accordance with expectation, this result confirms that the rate-determining step of the reaction is the passage of the wheel over the stopper group. It also sheds new light on earlier results on rotaxanes bearing ester groups in the axle center piece. The deslipping reaction rate for these rotaxanes was extremely dependent on the choice of solvent and the orientation of the ester groups. The rotaxanes presented here do not contain functional groups in their center pieces and no such effects are observed. For these rotaxanes, the simple model of a thin thread inside a macrocycle mechanically trapped by bulky stopper groups is valid.

Deslipping of Rotaxanes with Axle Center Pieces of Different Lengths
AuthorP. Linnartz, C. A. Schalley
IdentifierDOI 10.1080/1061027042000204010
CitationSupramol. Chem. 2004, 16, 263-267