Excited state proton transfer of pyranine in a γ-cyclodextrin cavity

Excited state proton transfer of pyranine (8-hydroxypyrene-1,3,6-trisulfonate, HPTS) in γ-cyclodextrin (γ-CD) is studied using picosecond and femtosecond fluorescence spectroscopy. It is shown that confinement of pyranine in γ-CD cavity accelerates recombination of the geminate ion pair and slows down the initial proton transfer step and the dissociation of the geminate ion pair. This results in enhanced emission from the protonated species.