For achieving the on-off operation of the superstructure formation of hermaphrodite cyclodextrin derivatives, we synthesized azobenzene-modified permethylated α-cyclodextrins, 1 and 2. These compounds formed Janus pseudorotaxanes in CD3OD-D2O mixtures. The E-Z photoisomerization of 1 by UV light irradiation resulted in the dissociation of the superstructure, but, by boiling the solution, the superstructure was recovered through the thermal isomerization of (Z)-1 to (E)-1. These processes could be repeated many times without any side reactions. This is the first example of the dynamic control of the pseudorotaxane formation of modified cyclodextrins by external stimuli.
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