(Organic Chemistry) Oral Abstract Title: Isomerism due to Mechanical Bonding: Radial [5]catenanes of Isomeric Sequences of Peripheral Interlocked Macrocycles

Similar to encoding genetic information by sequences of nucleotides in DNA, arranging macrocycles in specific sequences by mechanical bond is important to the realization of new generation information-embedded molecular machines. Synthesis of hetero[n]catenane with multiple numbers and types of interlocked macrocycles is however very challenging due to the difficulty in the precise control of macrocycle interlocking process.1 In this presentation, the first example of a pair of hetero[5]catenane having specific isomeric sequences of interlocked β-cyclodextrin (β-CD) and cucurbit[6]uril (CB[6]) is reported.2 Cucurbit[6]uril-mediated azide-alkyne cycloaddition (CBAAC) was employed to synthesize the isomers from strategically-designed building blocks with good efficiency. A pair of [5]catenane isomers with either a cyclic ‒ABAB‒ or ‒AABB‒ sequences of the interlocked β-CD and CB[6] was obtained in high yields (>80%). Due to the different binding strength of the macrocycles, sequence-dependent dynamics and fragmentation behaviour of the [5]catenane isomers were observed from variable-temperature NMR and tandem mass spectrometry. By enhancing or weakening the solution ionic strength, the translocation kinetics of the β-CD in the ‒ABAB‒ [5]catenane isomer could be tuned accordingly. This work deepens our understanding on the macrocycle dynamics and implicates the potential of mechanically-interlocked molecules (MIMs) in information-embedded functional materials. References 1. H. Y. Au-Yeung, C.-C. Yee, A. W. H. Ng, K. Hu, Inorg. Chem., 2018, 57, 3475. 2. A. W. H. Ng, C.-C. Yee, H. Y. Au-Yeung, Angew. Chem. Int. Ed., 2019, 58, 17375. O N N N O