[Suppression of singlet oxygen luminescence by porphyrins and metalloporphyrins]

The luminescene of 1O2 (1270 nm) has been observed upon illumination of air saturated solutions of different porphyrins and their complexes with Zn in CCl4. In solutions of Co-, Cu-, Ni- and Fe-porphyrins this luminescence has not been revealed. All the porphyrins studied have shown to quench 1O2, the rate constants of the "physical" and "chemical" quenching being measured. The physical way of quenching is found to be much more effective. The quenching activity of the pigments depends greatly on the presence and nature of the central metall atom incorporated into porphyrin (H2 less than Cu less than Zn less than Co approximately Ni approximately Fe) increases with hydrogenation of the semiisolated double bonds (porphyrins are less active than chlorins and bacteriochlorins).