Synthesis and photoisomerization of an azobenzene derivative bearing two β-cyclodextrin units at both ends

An azobenzene derivative with two beta-cyclodextrin units was synthesized as a novel photo-switchable host. It undergoes trans-to-cis photoisomerization in aqueous solution with 65.8% cis at the photostationary state and returns to the original trans form with half life of 54,8 h at 25 degrees C. It exhibits circular dichroism bands in the pi-pi* and n-pi* absorption regions of azobenzene in spite of the fact that the azobenzene unit cannot be included in the cyclodextrin cavity, and their absolute dichroism intensities of the cia form become much larger than those of trans one.