Convenient construction of unique bis-[1]rotaxanes based on azobenzene-bridged dipillar[5]arenes

A series of azobenzene-bridged dipillar[5]arenes were conveniently synthesized by coupling reaction of aminoalkyl-functionalized pillar[5]arenes with azobenzene-4,4’-dioxyacetic acid or azobenzene-4,4’-dioxybutanoic acid in dry chloroform under the combinatorial catalysis of HOBt/EDCl. 1H NMR, 2D NOESY spectra and single crystal structure clearly indicated that the unique bis-[1]rotaxanes could be formed by threading two diaminoalkylene units into the two cavities of pillar[5]arenes depending on the length of the diaminoalkylene chains. Under light irradiation at 365 nm, the trans-azobenzene unit transferred to cis-configuration, while the basic bis-[1]rotaxane structure was kept unchanged.