Azafullerene C59N-Phthalocyanine Dyad: Synthesis, Characterisation and Photoinduced Electron Transfer

The synthesis of a new azafullerene C59Nphthalocyanine (Pc) dyad is described. The key step for the synthesis of the C59NPc dyad was the formation of the C59N-based carboxylic acid, which was smoothly condensed with hydroxy-modified Pc. The structure of the C59NPc dyad was verified by 1H and 13C NMR spectroscopy, IR spectroscopy, UV/Vis spectroscopy and MS measurements. The photophysical and electrochemical properties of the C59NPc dyad were investigated in both polar and non-polar solvents by steady state and time-resolved photoluminescence and absorption spectroscopy, as well as by cyclic voltammetry. Different relaxation pathways for the photoexcited C59NPc dyad, as a result of changing the solvent polarity, were found, thus giving rise to energy-transfer phenomena in non-polar toluene and charge-transfer processes in polar benzonitrile. Finally, the detailed quenching mechanisms were evaluated and compared with that of a C60Pc dyad, which revealed that the different excited-state energies and reduction potentials of the two fullerene spheres (i.e. C59N vs. C60) strongly diverged in the deactivation pathways of the excited states of the corresponding phthalocyanine dyads.