Synthesis, circular dichroism, DNA cleavage and singlet oxygen photogeneration of 4-amidinophenyl porphyrins

5,10,15,20-tetrakis(4-amidinophenyl) porphyrin (Por 1), its Zn complex (Por 2) and its conjugate with a tetraphenylporphyrin to form a bisporphyrin (Por 3) were prepared. The monomeric Por 1 and Por 2 showed both intercalative and external binding with DNA whereas only external DNA binding was seen in the bisporphyrin, Por 3 by circular dichroism and UV-vis. The DNA photocleavage activities of these porphyrins followed the order: Por 1 similar to Por 2 > Por 3, which did not correlate with their measured O-1(2) production rates. It suggests 4-amidinophenylporphyrins are promising new photodynamic therapeutic agents.