Illumination of the Effect of Urea on the Microenvironment of ^β-Cyclodextrin Cavity with Fluorescence Probe

Pyrene was used as a fluorescent probe to illuminate the effect of urea on the microenvironment of ^β-cycldextrin cavity. Addition of urea to the solution of ^β-cyclodextrin increased the polarity of ^β-cyclodextrin cavity and decreased the formation constant of pyrene-^β-cyclodextrin inclusion complex, proving that "hydrophobic interaction" was one of the binding forces of cyclodextrin inclusion complex. The results in other inclusion complex systems strengthened the conclusions. Connected with the results of fluorescence quantum yield and lifetime estimations, a particular interaction of urea with ^β-cyclodextrin,other than changing the physical properties of the solvent, mainly hydrogen-bonding interaction, was proposed.