Observations of the Triplet State in Phthalocyanines

The triplet‐state lifetime of metal‐free phthalocyanine has been found to vary from 10−6 sec at room temperature to 150×10−6 sec at 77°K. Decay from the first excited state proceeds via the triplet state. Excitation by a giant‐pulse ruby laser completely empties the ground state. Luminescence is quenched in metallic phthalocyanines by the extremely rapid intersystem crossing.