Synthesis, characterisation and photoswitchability of a new [2]rotaxane of α-cyclodextrin with a diazobenzene containing π-conjugated molecular dumbbell

In this work, a new [2]rotaxane consisted of a diazobenzene containing p-conjugated linear compartment, including the 4,4'-bipyridyl moiety and alpha-cyclodextrin (alpha-CD) as the macrocyclic compartment, was synthesised with yields of nearly 57% and fully characterised. alpha-CD easily assembled with the linear compartment and suitable bulky ends (stoppers) in water to give a new [2] rotaxane. The characterisation of this supramolecular compound was accomplished using several spectroscopic techniques such as H-1 NMR, C-13 NMR and 2D NMR spectroscopy, powder X-ray diffraction, fourier transform infrared spectroscopy, induced circular dichroism and UV-vis spectrophotometry, as well as scanning electron microscopy and Energy Dispersive X-ray. Furthermore, the reversible E-Z photoisomerisation of both [2] rotaxane and its molecular dumbbell was investigated by irradiation with UV light.