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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