Photochemistry of doubly N-confused porphyrin bonded to non-conventional high oxidation state Ag(III) and Cu(III) ions

The photophysical properties of the free base, silver(III) and copper(III) doubly N-confused porphyrin complexes were examined. The free base species exhibits a low fluorescence quantum yield of 9.1×10−3, which is completely suppressed in the M(III) complexes. However, high singlet oxygen quantum yields were found for the Ag(III) (φΔ=0.92) and Cu(III) (φΔ=0.66) complexes. These results were ascribed to the enhanced intersystem crossing rates, induced by heavy atom effect, rather than to a redox quenching involving the metal ions in unusually high oxidation state. The confused porphyrins are photochemically stable in oxygen-free solution but are bleached more or less rapidly by the photogenerated singlet oxygen, in the absence of other quenchers.