Photoperoxidation of a Diamino Zinc Porphyrazine to the seco-Zinc Porphyrazine:  Suicide or Murder?

We report on the efficient photooxidation of hexapropyl bis(dimethylamino) zinc porphyrazine. The process is shown to be autocatalytic. The triplet state of the seco-ZnPz sensitizes the formation of excited-state singlet oxygen with a quantum yield of 0.54 and subsequent cleavage of the pyrrole double bond occurs to give the product, seco-zinc porphyrazine. The photophysics of the two porphyrazines is examined using absorption, emission, and transient absorption spectroscopy. The efficiency of production of singlet oxygen is monitored using the phosphorescence emission signature at 1270 nm.