Types I and Ii Sensitized Photooxidation of Aminoacid by Phthalocyanines: A Flash Photochemical Study

In connection with the use of red light‐photosensitizers for photodynamic therapy, the redox reactivity of excited metallophthalocyanines (M = Al, Ga) was investigated by flash photolysis in order to establish whether photooxidations proceed by Foote's mechanisms I or II. Aminoacids (tryptophan, tyrosine) were seen to function as electron transfer quenchers of the excited phthalocyanines with rate constants 10 7 k 10 4 M ‐1 s ‐1 . This was not the case of purines or ATP. The ability of the excited phthalocyanines to sensitize photooxidations by mechanisms I and II is discussed in terms of evaluated rate constants.