Photophysical properties of gallium hydroxyl tetratolylporphyrin and 132-demethoxycarbonyl-(gallium hydroxyl)–methyl-pheophorbide a

Two metal tetrapyrroles containing gallium, gallium hydroxyl tetratolylporphyrin and 132-demethoxycarbonyl-(gallium hydroxyl)–methyl pheophorbide a (Ga-(OH)-chlorin), were synthesized from their respective free bases using Ga(III)-acetylacetonate in a phenol melt. Their photophysical properties were investigated and the quantum yields of different monomolecular deactivation processes were determined. For Ga-(OH)-porphyrin S2-fluorescence was observed and quantified. In contrast, for Ga-(OH)-chlorin no S2-fluorescence was observed. Both compounds should be useful as efficient photosensitizers in photodynamic therapy.