Synthesis of Bis Dansyl-Modified β-Cyclodextrin Dimer Linked with Azobenzene and Its Fluorescent Molecular Recognition

Flexible dimeric host, 4,4'-azobenzenediamido-bis-{6-(2-dansyl-aminoethyl)6-deoxy-β-cyclodextrin}(beta;-1), has been synthesized in order to investigate itsfluorescent molecular sensory system transforming photoisomerization. Photoisomerizationof β-1 was performed with photoirradiation by a 500W-Xelamp using a Corning 7-37 filter. Host beta;-1 showed puremonomer fluorescence, exhibiting a decrease in fluorescence intensity on accommodationof the guest, and the extent of fluorescence variation with a guest was employed to displaythe sensing ability of β-1, in which the sensing parameter(Δ I/I0)was used to describe the sensing ability. Host β-1could detect chenodeoxycholic acid, ursodeoxycholic acid and hyodeoxycholic acid withhigh selectively. The behaviors of the appended moieties of β-1during host-guest complexation were studied by induced circular dichroism (ICD) andfluorescence spectra and MM2 energy-minimized structure. The ICD and fluorescenceintensities of β-1 decreased on the addition of a guest.The guest-induced variations in the ICD and fluorescence spectra, and MM2 energy-minimized structure suggested that the dansyl moieties of β-1 worked as a hydrophobic cap when a host-guest complexation occurred.