A new polypyridyl ligand 2-benzo[b]thiophen-3-yl- 1H-1,3,7,8-tetraazacyclopenta[l]phenanthrene (BTCP) and its Ru II complexes [Ru(bpy) 2 (BTCP)] 2+ (1) (bpy = 2,2 -bipyridine), [Ru(phen) 2 (BTCP)] 2+ (2) (phen = 1,10-phenanthroline), and [Ru(dmb) 2 (BTCP)] 2+ (3) (dmb = 4,4 -dimethyl-2,2 -bipyridine), have been synthesized and characterized. The DNAbinding properties of the three complexes were investigated by spectroscopic methods and viscosity measurements. The results indicate that complexes 1, 2, and 3 bind to DNA by an intercalative mode and the ancillary ligands have a significant effect on the binding strengths of Ru II complexes to DNA. When irradiated at 365 nm, complex 2 was found to be a more effective DNA-cleaving agent than complexes 1 and 3. Results and Discussion Synthesis and CharacterizationAn outline of the synthesis of the Ru II complexes 1, 2, and 3 with the new BTCP ligand is presented in Scheme 1. The ligand was prepared through condensation of 1,10-phenanthroline-5,6dione (4) with benzo[b]thiophene-3-carboxaidehyde (5) according to literature methods. [36] The complexes 1, 2, and 3 were then prepared in yields of 39, 53, and 44%, respectively, by

A novel polypyridyl ligand phenyl- (4,5,9,14-tetraaza-benzo[b]triphenylen-1,1-yl)-methanone (PTBM) and its complexes [Ru(phen) 2 (PTBM)] 2+ (1) (phen = 1,10-phenanthroline) and [Ru(bpy) 2 (PTBM)] 2+ (2) (bpy = 2,2′-bipyridine) have been synthesized and characterized by elemental analysis, mass spectroscopy, and 1 H NMR. The DNA-binding properties of the two complexes were investigated by spectroscopic and viscosity measurements. The results indicate that both complexes bind to DNA via an intercalative mode and the DNA-binding affinity of complex 1 is greater than that of complex 2. When irradiated at 365 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.