A series of mixed-metal complexes coupling ruthenium light absorbers to platinum reacti
ve metal sites throughpolyazine bridging ligands ha
ve been prepared of the form [(tpy)RuCl(BL)PtCl
2](PF
6) (BL = 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq), 2,3-bis(2-pyridyl)benzoquinoxaline (dpb); tpy = 2,2':6',2' '-terpyridine). These systems possess electron-rich Ru metal centers bound to fi
ve polyazine nitrogens and onechloride ligand. This leads to complexes with low-energy Ru
BL charge-transfer bands that are tunable with BL
variation occurring at 544, 632, and 682 nm for dpp, dpq, and dpb, respecti
vely. This tuning of the charge-transferenergy results from a stabilization of the BL(
*) orbitals in this series as e
videnced by the cathodic shift in the firstreduction of these complexes occurring at -0.50, -0.32, and -0.20 V
vs Ag/AgCl, for dpp, dpq, and dpb, respecti
vely.The chlorides bound to the Pt
II center are substitutionally labile gi
ving these complexes the ability to co
valentlybind to DNA. All three title bimetallics, [(tpy)RuCl(BL)PtCl
2](PF
6), a
vidly bind double-stranded DNA with
t1/2 = 1-2min, substantially reducing the migration of DNA through an agarose gel. Details of the synthetic methods, FABMS data, spectroscopic and electrochemical properties, and DNA binding studies are presented.