Photoinduced intramolecular electron transfer in an anthraquinone-fluorescein-carbazole model

A triad molecule consisting of fluorescein covalently linked to carbazole at site 2' and anthraquinone at site 6 was synthesized and investigated by comparison of its photophysical properties with those of the model dyads. The absorption and emission spectra and fluorescence quenching results indicate that the intramolecular ground state interaction between donor and acceptor is negligible and photoinduced intramolecular electron transfer is mainly a dynamic process. In the triad molecule, there is competing electron transfer between the fluorescein-carbazole and anthraquinone-fluorescein pairs. The electron transfer between fluorescein and carbazole dominates the initiated process with Phi(et) = 0.94 and K-ET = 1.8 X 10(9) s(-1), which are in good agreement with other work. We have also estimated the free energy change of the other electron transfer and the back reaction in our triad molecule.