Construction and single crystal structures of pseudo[1]rotaxanes based on pillar[5]arene mono-pyridylimine derivatives

A series of functionalized pillar[5]arenes mono-pyridylimine derivatives with different lengths of diaminoalkylene units as the side chains on the pillar[5]arene's rim were conveniently synthesized. The investigation of 1H NMR spectra and single crystal structures indicated that the formation of free forms or pseudo[1]rotaxanes turned out to be controlled by both the axle lengths of diaminoalkylene chains and the solvent effect. The pillar[5]arene mono-pyridylimines with short hydrazinyl and diaminoethylene chains exist in free form. On the other hand, pillar[5]arene mono-pyridylimines with longer than diaminopropylene chains formed stable pseudo[1]rotaxanes both in solution and in the crystal state.

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