Intramolecular photo-induced electron transfer between pyrene and a xanthene dye

The bi-exponential fluorescence decay of a rhodamine substituted with two 4 -(1-pyrenyl)-butyl moieties is attributed to a reversible intramolecular ph oto-induced electron transfer. The additional decay channel is confirmed by a decrease of the fluorescence quantum yield. Global compartmental analysi s of fluorescence decays obtained at different scales allowed the determina tion of the different rate constants of the excited state equilibrium. Tran sient absorption indicates that the decay of the charge transfer state popu lates the locally excited triplet state of the rhodamine. (C) 2000 Elsevier Science B.V. All rights reserved.