SOLVENT EFFECTS ON ELECTRONIC STATES OF PHTHALOCYANINES

The absorption spectra of a pi-pi* 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 pi-pi* 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 pi-pi* 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 half arrow right over half arrow left Ti(CF3COO)4+H2O+H2PC.