Taming fluorescent dyes with cucurbituril

摘要

The potential of the supramolecular host molecule cucurbit[7]uril to serve as a stabilizing additiveand enhancement agent was investigated for the following dyes in aqueous solution: rhodamine 6G,rhodamine 123, tetramethylrhodamine, cresyl violet, fluorescein, coumarin 102, pyronin B, pyronin Y, twocyanine 5 and one cyanine 3 derivative, and IR140 as well as IR144. For most cationic dyes photostabilizationwas established, and a pronounced thermal stabilization due to deaggregation and solubilizationwas observed for the xanthene dyes. The advantageous effects are attributed to the formation of inclusioncomplexes with different photophysical and photochemical properties. The complexation is accompanied byspectral shifts characteristic for the inclusion in a less polar environment, while the fluorescence quantumyields as well as the brightness show an increase, with few exceptions. As a consequence of the low polarizabilityinside the cucurbituril cavity, the fluorescence lifetimes of the included dyes increase substantiallyand systematically. Applications of the new photostabilizing additive for dye lasers, for prolonged storageof dye solutions, in scanning confocal microscopy, and fluorescence correlation spectroscopy are discussed.