Switching from <i>altro</i>-α-Cyclodextrin Dimer to <i>pseudo</i>[1]Rotaxane Dimer through Tumbling

Abstract

An alkyl altro-alpha-CD dimer was converted to the pseudo[1]rotaxane dimer through tumbling of the altropyranose unit of altro-alpha-CD in D(2)O. The tumbling of the altropyranose unit was found to be a rotational vibration with 1.18 x 10(-3) s(-1) at 293 K. The activation free energy (DeltaG(double dagger)(288K)) for the conformational change from an alkyl altro-alpha-CD dimer to pseudo[1]rotaxane dimer was 88.0 kJ mol(-1), which corresponds to the breakage of the hydrogen bond network for the tumbling of an altropyranose unit.