Tuning the mechanism of DNA cleavage photosensitized by ruthenium dipyridophenazine complexes by varying the structure of the two non intercalating ligands.

The influence of the nature of ligands on the efficiency of ruthenium complexes for photosensitizing DNA cleavage was investigated. Ru(bipy)2dppz2+ and Ru(bpz)2dppz2+ were selected as DNA breakers on the basis of their high affinity for DNA due to the presence of a dppz ligand which can partially intercalate in the major groove of DNA. Their photosensitizing properties were compared to those of Ru(bipy)3(2+), a complex which binds to DNA with a far lower constant.

DNA cleavage photoinduced by new water-soluble zinc porphyrins linked to 9-methoxyellipticine.

Two hybrid molecules based on a water-soluble zinc porphyrin covalently linked to 9-methoxyellipticine, 1 and 2, were studied as photoactivable DNA cleavers. The behaviour and efficiency of these photosensitizers were compared with the constitutive units of the hybrid molecules: meso-tetrakis(4-N-methylpyridiniumyl)porphyrinato-zinc(II) tetraacetate (ZnTMPyP, 3) and 9-methoxy-N2methylellipticinium acetate (9-OMe-NME, 4). On irradiation at 436 nm, the efficiency of these hybrids is similar to that of ZnTMPyP and 50-fold greater than that of haematoporphyrin derivative (HPD).