Synthesis and electrochemistry of ferrocenylphthalocyanines

A series of phthalocyanines containing 4, 8, and 16 2-ferrocenylethoxy moieties on the periphery have been prepared and spectroscopically characterized. The UV-vis spectrum of the tetraferrocenyl phthalocyanine 4 shows an unusual long-wavelength band at ca. 760 nm in nonpolar solvents. When the spectral changes of this compound and its analogue [1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato]zinc(II) (12) are studied in different solvents and at various concentrations, along with their fluorescence spectra, it can be concluded that this band is not likely due to a slipped cofacial dimer as reported previously. Compound 4 is-not emissive, which can be explained by the efficient quenching due to electron transfer from ferrocene to the excited phthalocyanine. The value of Delta G degrees for this photoinduced electron transfer has been estimated to be -0.48 eV. Electrochemical studies of these phthalocyanine-ferrocene conjugates by cyclic voltammetry have revealed that all the ferrocenyl redox centers attached to the macrocyclic core are electrochemically independent and undergo an oxidation at the same potential.