Fluorescence quenching inhibition of substituted indoles by neutral and ionized cyclodextrins nanocavities

The effect of cyclodextrins (CDs) in the excited state proton transfer process of indole compounds has been studied by fluorescence quenching, in acid and alkaline media. The quenching efficiency decreases in the presence of CDs in both media indicating a remarkable protection mediated by CD against external quenchers. An interesting non-linear behaviour for the Stern–Volmer plots was observed in basic media. This was interpreted as total inhibition of the quenching process by ionized cyclodextrin. Induced circular dichroism has been used to determine the indole position into the cyclodextrin cavities.