Singlet oxygen quantum yields and photostability of planar binuclear phthalocyanines

The singlet oxygen (O-1(2)) quantum yield of the near-infrared absorbing (lambda(max) = 839 nm) planar pi-conjugated binuclear zinc phthalocyanine (ZnPc) was measured and compared to the O-1(2) quantum yields of the mononuclear and the planar binuclear phthalocyanine without pi-conjugation between Pc rings. In addition, the photooxidative stability of the pi-conjugated binuclear Pc was determined and compared to the stabilities of the mononuclear ZnPc and the known near-infrared photosensitizer, zinc tetra-tert-butylnaphthalocyanine (lambda(max) = 761 nm). The results are explained by DFT calculations and cyclic voltammetry.