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Pyridyl-Acyl Hydrazone Rotaxanes and Molecular Shuttles

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journal contribution
posted on 04.05.2017, 00:00 by David A. Leigh, Vanesa Marcos, Tugrul Nalbantoglu, Iñigo J. Vitorica-Yrezabal, F. Tuba Yasar, Xiaokang Zhu
We report on rotaxanes featuring a pyridyl-acyl hydrazone moiety on the axle as a photo/thermal-switchable macrocycle binding site. The pyridyl-acyl E-hydrazone acts as a hydrogen bonding template that directs the assembly of a benzylic amide macrocycle around the axle to form [2]­rotaxanes in up to 85% yield; the corresponding Z-hydrazone thread affords no rotaxane under similar conditions. However, the E-rotaxane can be smoothly converted into the Z-rotaxane in 98% yield under UV irradiation. The X-ray crystal structures of the E- and Z-rotaxanes show different intercomponent hydrogen bonding patterns. In molecular shuttles containing pyridyl-acyl hydrazone and succinic amide ester binding sites, the change of position of the macrocycle on the thread can be achieved through a series of light irradiation and heating cycles with excellent positional integrity (>95%) and switching fidelity (98%) in each state.