Three series of rotaxanes have been synthesized variously by slipping synthesis, in which axis and wheel are melted in admixture, by recognition of amide groups inside the macrocyclic wheel, or by an anionic template method, in which the stoppering phenolates are hydrogen bonded to the wheel and then joined by reaction with a semi‐axle. The 3,5‐di‐tert‐butylphenyl stopper used for most of these rotaxanes is large enough to permit their isolation, but still allows the wheel to deslip from the axle under appropriate conditions. The deslipping activation parameters for all rotaxanes are derived from 1H NMR kinetic measurements and have been evaluated from the Arrhenius equation as well as according to Eyring theory. Small structural variations give rise to surprising effects on the activation parameters. Firstly, in some examples, the axle length affects the deslipping barrier, although the size complementarity of stopper and wheel remain unchanged. Secondly, stopper flexibility has an important influence on the deslipping rate. Thirdly, exchange of a carbonamide for a sulfonamide in the wheel significantly reduces the entropic costs of the deslipping, resulting in a pronounced deslipping rate enhancement. Fourthly, intramolecular hydrogen bonding within the wheel decelerates deslipping by a factor of more than 104.

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The “dynamic spatial demand” of Fréchet‐type dendrons is compared with that of “conventional” building blocks by evaluation of the deslipping behavior of dendritic rotaxanes (see picture). This method leads to a ranking list of the size of voluminous building blocks, which will be useful for the rating of steric effects and the design and synthesis of new rotaxanes or less‐stable pseudorotaxanes.

A mechanically linked molecule, consisting of an axle and two equivalent wheels, shows an analogous stereochemistry to the classical example tartaric acid. Though the components are not chiral themselves, a (cyclo)diastereomeric species is obtained, the enantiomers (shown schematically) and the meso form of which were completely separated and chiroptically characterized.