In this work, the first example of a pair of radial hetero[5]catenanes displaying isomeric sequences of the interlocked macrocycles is reported. Encoding specific sequence of mechanically interlocked macrocycles in catenanes and other mechanically bonded molecules is of great interest to both the fundamental stereochemistry of mechanical bond and the realization of new generation of information-embedded molecular machines. Yet, the synthesis of [_n_]catenane with multiple numbers of interlocked macrocycles of more than two types is extremely challenging due to the difficulty in the precise control in the macrocycle interlocking process.  

In this work, cucurbit[6]uril-mediated azide-alkyne cycloaddition (CBAAC) was used for the efficient catenane formation from strategically designed building blocks. A pair of [5]catenane isomers featuring different cyclic sequences of the
interlocked cucurbit[6]uril (CB[6]) and β-cyclodextrin (β-CD) was obtained in high yields (>80%). Due to the different binding strengths of the macrocycles and the difference in the sequence of the peripheral macrocycles, very different dynamics of the interlocked β-CD and fragmentation behavior were observed on the [5]catenanes in variable temperature NMR and tandem MS experiments respectively.  

Isomeric [5]Catenanes with Different Sequences of Mechanically Bonded Peripheral Macrocycles

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