Analytical Sciences

Fluorescence Response Mechanism of D-Glucose Selectivity for Supramolecular Probes Composed of Phenylboronic-acid-modified β-Cyclodextrin and Styrylpyridinium Dyes

Iwao SUZUKI,* Akiyo YAMAUCHI,* Yoshiko SAKASHITA,* Kazuaki HIROSE,* Takashi MIURA,* and Takashi HAYASHITA**

*Graduate School of Pharmaceutical Sciences, Tohoku University, Aramaki, Aoba, Sendai 980-8578, Japan
**Department of Chemistry, Faculty of Science and Engineering, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo 102-8554, Japan

Supramolecular complex formation of phenylboronic-acid-modified β-cyclodextrin (1) with 1-methyl-4-(4-dimethylaminostyryl)pyridinium (C1SP) in aqueous solutions containing saccharides was fully clarified to gain an insight into the observed D-glucose (D-glc) selectivity of a supramolecular fluorescent probe composed of 1 and the 1-heptyl analogue of C1SP (Chem. Commun., 2006, 4319). At pH 9.6, where 1 was in its anionic form, both the stability and the fluorescence of the 1/C1SP complex were reduced by the formation of boronate esters of 1 with saccharides. Among the saccharides, D-glc had the smallest effect on destabilization of the 1/C1SP complex, almost completely retaining the fluorescence of the 1/C1SP complex that was reduced by other saccharides by approximately 2/3. Under neutral conditions, D-glc enhanced the fluorescence of the 1/C1SP complex by increasing the fraction of anionic 1 while minimally decreasing the stability and fluorescence of the 1/C1SP complex. Although other saccharides also increased the fraction of the anionic 1, their relatively large effects on the destabilization and reduction of fluorescence of the 1/C1SP complex limited the enhancement of the fluorescence of the 1-C1SP system under neutral conditions.

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