Synthesis and spectroscopic DNA binding studies of [Ru(phen)2(tbtc)]2+ and [Ru(2,9-dmp)2(tbtc)]2+

A new polypyridyl ligand tbtc {tbtc = 4,5,9,14-tetraaza-benzo[b]triphenylene-11-carboxylic acid methyl ester} and its complexes [Ru(phen)2(tbtc)]2+ (1) (phen = 1,10-phenanthroline) and [Ru(2,9-dmp)2(tbtc)]2+ (2) (2,9-dmp = 2,9-dimethyl-1,10-phenanthroline) were synthesized and characterized by element analysis, MS, and 1H NMR. The DNA binding properties of both complexes to calf thymus DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode, and the DNA binding affinity of complex 1 is much greater than that of complex 2. This difference in binding affinity probably was caused by the different ancillary ligands. Also, when irradiated at 365 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.