Photodynamic Cancer Therapy A Study of the Photochemical Properties of meso-T ties of meso-Tetra (2,3,4-trifluor a (2,3,4-trifluorophenyl) P ophenyl) Porphyrin and orphyrin and meso-Tetra (2,3,5,6-tetr a (2,3,5,6-tetrafluorophenyl) P ophenyl) Porphyrin orphyrin