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 photo-induced electron transfer. The additional decay channel is confirmed by a decrease of the fluorescence quantum yield. Global compartmental analysis of fluorescence decays obtained at different scales allowed the determination of the different rate constants of the excited state equilibrium. Transient absorption indicates that the decay of the charge transfer state populates the locally excited triplet state of the rhodamine.