11. A mono-exponential curve was obtained for 1, 4 and 5. The presence of uridine (conjugate 4) increased the triplet quantum yield and lifetime of ZnMCPPc, 1 (Table 1). Increases in triplet quantum yields have also been observed on linking of mono substituted phthalocyanines to pyrene and folic SNG-1153  and . Thus, uridine increases both the triplet yields and lifetimes, showing its importance when linked to photosensitizers for PDT.