No abstract

The a-, Pand y-cyclodextrins (CyDs) are cyclic, water-soluble receptor molecules with characteristic bucket-shaped cavities. They form inclusion complexes with compounds of size and geometry compatible with the dimensions of these cavities. Van der Waals interactions, hydrogen bonding, release of strain energy in the CyD ring and release of high-energy water molecules from the cavity are involved in complex formation. Various chemical effects of CyD inclusion complexes on guest molecules have been reported, including the sheltering of the concealed parts of and enhanced reactivity of the exposed parts of a guest molecule, and strong interactions between a pair of guest molecules. Many spectroscopic properties of the complexed molecules may also be affected, fluorescence enhancement phenomena being particularly common.o-Phthalaldehyde (OPA) forms rather unstable fluorescent isoindoles with amino acids in the presence of thiols.'*2 We have used flow injection analysis (FIA) to study the host-guest complex formation and the effects of CyDs on the stabilities and fluorescence intensities of these products.