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

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. (C) 2016 Elsevier B.V. All rights reserved.