A simple and efficient synthetic route for making purpurin-18-N-aminoimides is described. The purpurin-18-Naminoimides are obtained by treatment of purpurin-18 methyl ester with various amines. These new compounds have long wavelength absorptions in the range of 706 - 711 nm. In preliminary screening, the purpurin-18-N-aminoimides have shown promising photosensitizing activity for the cancer cell by in vitro study in photodynamic therapy.