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This article describes the synthesis of a polypyridyl ligand, namely 2-(2, 5-dimethoxyphenyl)-1H-imidazo-[4,5-f]1,10-phenanthroline (DMPIP) and its Ru(II) complexes, namely [Ru(bipy) 2 DMPIP] 2? (1), [Ru(dmb) 2 DMPIP] 2? (2) and [Ru(phen) 2 DMPIP] 2? (3) ((bipy = 2,2 0 -bipyridine, dmb = 4,4 0 -dimethyl-2,2 0 -bipyridine, phen = 1,10-phenanthroline). The complexes were characterized by elemental analysis, plus IR, 1 H-NMR and 13 C [ 1 H]-NMR spectra. The interactions of the complexes with calf thymus DNA were investigated. The results indicate that the three complexes can intercalate into DNA. Under irradiation at 365 nm, all three complexes promote the photocleavage of plasmid pBR 322 DNA. Inhibitor studies suggest that singlet oxygen plays a significant role in the cleavage mechanism for the complexes.

The polypyridyl ligand 7-Nitro dipyrido[3,2-a:2'-3'-c]phenazine (7-Nitro-dppz) and its complexes [Co(bpy)(2)(7-NO(2)-dppz)](3+)(1) (bpy = 2,2'-bipyridine), [Co(dmb)(2)(7-NO(2)-dppz)](3+)(2), (dmb = 4,4'-dimethyl-2,2'-bipyridine), and [Co(phen)(2)(7-NO(2)-dppz)](3+)(3) (phen = 1,10-phenanthroline) were synthesized and characterized by UV/VIS, IR, elemental analysis, (1)H and (13)C-NMR, and mass spectra. The binding properties of the three complexes to CT-DNA were investigated by different spectroscopic methods and viscosity measurements and DNA cleavage assay. The experimental results suggest that these complexes bind to CT-DNA through an intercalative mode. Also, the three complexes promote the photocleavage of plasmid pBR-322 DNA under irradiation. Toxicological effects of the selected complexes were estimated with different microorganisms.

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