Photoinduced intramolecular electron transfer of fluorescein and violgen, carbazole

A series of polyads consisting of covalently —(CH2)4— linked fluorescein with carbazole and violgen have been synthesized and characterized. The studies of absorption, emission spectra and fluorescence lifetime quenching indicated that the intramolecular fluorescence quenching of fluorescein by violgen is mainly a static process through the formation of non-emission complex (fluorescence quenching efficiency ϕq= 0. 97, lifetime quenching efficiency ϕET = 0, quenching efficiency of formation of non-emission complex ϕc = 0.97); while the quenching by carbazole is mainly a dynamic electron transfer process (ϕQ = 0. 63, ϕET = 0.63, ϕc = 0). In the violgen-fluorescein-carbazole triads, ϕQ = 0.97, ϕET = 0.65, ϕc = 0.32, which suggests that the photoinduced interaction of fluorescein-carbazole pair and that of violgen-fluorescein pair are in a competitive process, the dynamic electron transfer from carbazole to fluorecein is dominant in the process. The free energy change of the photoinduced electron transfer and the back reactions in our polyads are also estimated.