Ultrafast relaxation of electronically-excited states of a styryl dye in the cavity of cucurbit[n]urils (n = 6, 7)

Abstract The ultrafast relaxation of an electronically-excited styryl dye and its complexes with cucurbit[ n ]urils was studied by the fluorescence up-conversion technique at various fluorescence wavelengths. The relaxation is faster at a blue side of the fluorescence band than at a red one where a fluorescence rise was observed. Addition of either cucurbiturils significantly increases the longest decay time from about 50 ps to that in the range of 100–200 ps. Such features are attributed to displacements of the electronically-excited styryl dye deep into the cavity, increasing the potential barrier between the intramolecular charge transfer state and the conical intersection region.