Modulating the shuttling motion of [2]rotaxanes built of p -xylylenediamine units through permethylation at the benzylic positions of the ring.

In this study, we show the effect of the gem -dimethyl substitution at the four benzylic carbons of the ring on the internal dynamics of two-station [2]rotaxanes. Such structural modification of the polyamide macrocycles promotes a drastic change of the internal dynamics as shown by variable-temperature (VT) 1 H NMR experiments. We determined that the shuttling rates of the octamethylated macrocycle along a series of symmetrical threads were significantly faster compared to the non-substituted ring. This effect was particularly pronounced in the fumaramide-based system, in which the rate was 27 times faster than that of the model system.