The photophysical properties of five novel phthalocyanine analogues, dihydroxy phosphorus(v) triazatetrabenzocorrole (PTBC) substituted with –NO₂, –SO₃H, OⁱPr, and –NH₂, respectively, were studied by a combination of absorption, steady-state emission, time-resolved fluorescence, and laser flash photolysis. All substituents, even for the strong electron-donating –NH₂, cause only a slight red shift of their absorption and emission maxima. These complexes are generally monomeric in organic solution, whereas the sulfonated derivative, PTBC(SO₃H)₄, slightly aggregates in aqueous buffer. Distinct from phthalocyanines, PTBCs substituted with –NO₂ or –NH₂ still show high photo activities. The electron-withdrawing –NO₂ and –SO₃H decrease the fluorescence quantum yield but increase the triplet formation yield to 0.76 and 0.82, respectively. All PTBCs have long triplet lifetimes and hence generate singlet oxygen efficiently with a quantum yield from 0.43 to 0.75. Together with the ground-state absorption properties, the results suggest that these PTBCs may be used as excellent photosensitizers for photodynamic therapy.