title: Synthesis, characterization, and DNA binding properties of a series of Ru, Pt mixed-metal complexes.
abstract: A series of mixed-metal complexes coupling ruthenium light absorbers to platinum reactive metal sites through polyazine bridging ligands have 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 five polyazine nitrogens and one chloride 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, respectively. This tuning of the charge-transfer energy results from a stabilization of the BL(pi) orbitals in this series as evidenced by the cathodic shift in the first reduction of these complexes occurring at -0.50, -0.32, and -0.20 V vs Ag/AgCl, for dpp, dpq, and dpb, respectively. The chlorides bound to the Pt(II) center are substitutionally labile giving these complexes the ability to covalently bind to DNA. All three title bimetallics, [(tpy)RuCl(BL)PtCl(2)](PF(6)), avidly bind double-stranded DNA with t(1/2) = 1-2 min, substantially reducing the migration of DNA through an agarose gel. Details of the synthetic methods, FAB MS data, spectroscopic and electrochemical properties, and DNA binding studies are presented.
authors.affiliation: Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
authors.forename: R Lee
authors.initials: RL
authors.lastname: Williams
authors.forename: H Nathaniel
authors.initials: HN
authors.lastname: Toft
authors.forename: Brenda
authors.initials: B
authors.lastname: Winkel
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Brewer
mesh_terms: D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D004563:Electrochemistry; D004587:Electrophoresis, Agar Gel; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D009944:Organoplatinum Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D017671:Platinum Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D011810:Quinoxalines / Q000737:chemistry*; D017975:Ruthenium Compounds / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: C482207:((2,2'-6',2''-terpyridine)ruthenium(chloro)(2,3-bis(2-pyridyl)pyrazine)(dichloroplatinum)); C482208:2,3-bis(2-pyridyl)benzoquinoxaline; D008024:Ligands; D009944:Organoplatinum Compounds; D017671:Platinum Compounds; D011725:Pyridines; D011810:Quinoxalines; D017975:Ruthenium Compounds; D004247:DNA; D009584:Nitrogen