Abstract: Some phthalocyanines have been synthesized and their fluorescence spectra studied. The fluorescence quantum yields have been measured, the value of which are 0.7, 0.3, 0.025 for magnesium, zinc and cobalt, respectively.Study of photosensitized reduction reaction together with the fluorescence quenching, the quenching rate constant k_q (1 × 10¹⁰ sec^-1) has been calculated. The result shows that the rate of the first step of photosensitized reduction, i.e. electron transfer reaction, is diffusion-controlled. Since EDTA can not quench the fluorescence of phthalocyanine, the following scheme for the reduction of RV²⁺ is proposed:

The photosensitization activities of phthalocyanines are in the order of Mg > Zn> Co, while the activity of butyl viologen is higher than that of methyl viologen.