Analytical Sciences

Guest-Responsive FluorescenceVariations of gamma-Cyclodextrins Labeled with Hetero-Functionalized Pyreneand Tosyl Moieties

Akira MAKABE, Kentaro KINOSHITA, MiyukiNARITA, and Fumio HAMADA 

Department of Materials-processEngineering and Applied Chemistry for Environments, Faculty of Engineeringand Resource Science, Akita University, Tegata, Akita 010-8502,Japan

Regioselectively hetero-labeled hosts,6^A-pyrenebutylate-6^X-tosyl-modifiedgamma-cyclodextrins (X = B or H, C or G, D or F, and E for gamma-1,gamma-2, gamma-3, and gamma-4, respectively), weresynthesized in order to investigate their chemo-sensor properties forapplications to organic compounds, such as bile acids and terpenes. Thehosts (gamma-1, gamma-2, gamma-3, and gamma-4)exhibit pure monomer fluorescence. The guest-induced fluorescenceemissions of these hosts were suppressed in the presence of guests. Theextent of fluorescence variations of these hosts with guests was recognizedas a manifestation of the sensing ability of the hosts. A sensingparameter (deltaI/I⁰, where I andI⁰ are the fluorescence intensities in the presence andabsence of a guest and deltaI = I⁰ - I) wasused to describe the sensing ability of these hosts. Host gamma-analogswere able to detect progesterone, ursodeoxycholic acid, chenodeoxycholicacid, and (-)-borneol with high sensitivity. The behaviors of the appendedmoieties of these hosts during the formation of host-guest complexes werestudied using induced circular dichroism (ICD) spectra, fluorescencespectra and the MM2-energy-minimized structure. The host gamma-analogsexhibited different ICD spectra patterns before and after the addition ofursodeoxycholic acid. The guest-induced variations of ICD and thefluorescence spectra and MM2-minimized structures suggest that the pyreneand tosyl moieties move by altering the spatial relationship between them,in which the pyrene moiety works as a hydrophobic cap and the tosyl moietyis speculated to act as a spacer.

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