Solvent Effects on Electronic States of Phthalocyanines

Article abstract of DOI:10.1246/bcsj.66.1016

The absorption spectra of a ?-?^* transition (the Q band) of titanium(IV) oxide phthalocyaninate (TiOpc) and phthalocyanine (H2pc) were measured in various organic solvents.It has been shown that the wavelength of the ?-?^* transition is dependent on 1) the permanent dipole moment of the solvent, 2) the coordination of the solvent, and 3) the dispersion force and induced dipole moment of the solvent.A single ?-?^* peak and its significant red-shift in the absorption spectrum of H2pc in trifluoroacetic acid (TFA) suggested a protonation of the inner nitrogen atoms, leading to H4pc²⁺.TiOpc in TFA was cleaved, followed by the release of H2pc.The overall reaction was proposed to be as follows; TiOpc + 4CF3COOH <*> Ti(CF3COO)4 + H2O + H2pc.