A series of bimetallic (Ru^II, Pt^{II</sup) complexes were synthesized with the general formula (tpy)RuCl(BL)PtCl₂ (tpy = 2,2':6',2"-terpyridine and BL = bridging ligand) and their spectroscopic, electrochemical, and DNA binding properties studied. The bridging ligands used in these complexes were 2,3-bis(2'-pyridyl)pyrazine (dpp), 2,3-bis(2'-pyridyl)quinoxaline (dpq) and 2,3-bis(2'-pyridyl)benzoquinoxaline (dpb). These complexes combine light-absorbing RuII-polypyridyl chromophores and a cis-PtCl₂ structural motif known to bind DNA. The Ru-bound chloride may be substituted, enabling further modification of the spectroscopic properties. The synthesis of (tpy)RuCl(BL)PtCl₂ utilizes a building block approach that allows modifications to the series of complexes within the general synthetic scheme. This illustrates the applicability of this scheme to the development of new series of complexes.}

The lowest-energy absorption for the three complexes is assigned to a Ru(dπ) → BL(π*) charge transfer transition. This transition shifts to lower energy as the ligand is varied from dpp to dpq to dpb. The first and second reductions are BL^0/- and BL^-/2- based and shift to more positive potentials from dpp to dpq to dpb. The Ru^II/III redox couple remains at a nearly constant potential for the series. All three compounds show DNA binding when incubated with linearized plasmid DNA. Adduct formation was assessed by agarose gel electrophoresis as a retardation of band migration.