Synthesis, characterization and interaction with DNA of ruthenium(II) mixed-ligand complexes containing pyridino[3,2-f] [1,7]phenanthroline

A series of new complexes [RuL2(pdphen)]2+, where pdphen is the planar ligand pyridino[3,2-f] [1,7]phenanthroline and L = 2,2′-bipyridine, phenanthroline, 2,9-dimethylphenanthroline or 5-nitrophenanthroline, were prepared and characterized. The binding of [RuL2-(pdphen)] 2+ to calf thymus DNA was investigated using absorption, fluorescence and circular dichroism (c.d.) spectroscopies. All of the complexes show absorption hypochromicity associated with binding to calf thymus DNA. [Ru(bipy)2pdphen]2+ and [Ru(phen)2pdphen]2+ also show fluorescence intensities and excited state life-time increases. The c.d. spectra of dialyzates from solutions of racemic complexes versus calf thymus DNA indicate enantioselectivity associated with binding to DNA.