Synthesis, characterization, DNA-binding, and DNA-photocleavage properties of [Co(bpy)2(7-NO2-dppz)]3+, [Co(dmb)2(7-NO2-dppz)]3+, and [Co(phen)2(7-NO2-dppz)]3+ complexes: (7-nitro-dppz = 7-nitro dipyrido[3,2-a:2'-3'-c]phenazine; bpy = 2,2'-bipyridine; dmb = 4,4'-dimethyl-2,2'-bipyridine; phen = 1,10-phenanthroline) and their toxicity on different microorganisms.

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)(1) (bpy = 2,2'-bipyridine), Co(dmb)(2)(7-NO(2)-dppz)(2), (dmb = 4,4'-dimethyl-2,2'-bipyridine), and Co(phen)(2)(7-NO(2)-dppz)(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.