Probing Nanocavities with Proton-Transfer Fluorescence

Abstract

The ability of cyciodextrins (CD) to encapsulate functional compounds such as emitting dyes has led to intensive studies of their inclusion complexes.[1-7] In these species proton transfer,[ [8,9] energy transfer,[4,5] and bond rotation"[10] can give rise to new molecular forms of the sequestered dye with different physicochemical properties. Here we describe the light-induced tautomerism of a fluorophore encapsulated by α-,β-, or у CD, for which both proton transfer and conformational changes cause spectral shifts that are directly related to the size of the CD cavity. The color change of the fluorescence provides a simple way of exploring and quantifying subtle details of the induced fit and cavity diameter.