pH-Response Optimization of Amino-Substituted Tetraphenylporphyrin Derivatives as pH-Activatable Photosensitizers.

Amino-substituted tetraphenylporphyrin derivatives have been designed as pH-activatable photosensitizers for photodynamic cancer therapy. The photophysical processes of the monoamino-substituted derivative N1 and nonsubstituted derivative N0 have been studied. The quantum yields of the fluorescence and photosensitization of singlet oxygen by N1 were very low in the neutral condition (OFF state), but these quantum yields were recovered by adding acid (ON state).