title: The effects of grafting of 2-pyridyl to [Ru(bpy)(2)(Hpip)](2+) on acid-base and DNA-binding properties: experimental and DFT studies.
abstract: A new Ru(II) complex of [Ru(bpy)(2)(Hpip)](2+) {bpy = 2,2'bipyridine; Hppip = 2-(4-(pyridin-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} has been synthesized by grafting of 2-pyridyl to parent complex [Ru(bpy)(2)(Hpip)](2+) {Hppip = 2-(4-phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline}. The acid-base properties of [Ru(bpy)(2)(Hpip)](2+) studied by UV-visible and luminescence spectrophotometric pH titrations, revealed off-on-off luminescence switching of [Ru(bpy)(2)(Hpip)](2+) that was driven by the protonation/deprotonation of the imidazolyl and the pyridyl moieties. The complex was demonstrated to be a DNA intercalator with an intrinsic DNA binding constant of (5.56 ± 0.2) x 10(5) M-1 in buffered 50 mM NaCl, as evidenced by UV-visible and luminescence titrations, reverse salt effect, DNA competitive binding with ethidium bromide, steady-state emission quenching by [Fe(CN)6]4-, DNA melting experiments and viscosity measurements. The density functional theory method was also used to calculate geometric/electronic structures of the complex in an effort to understand the DNA binding properties. All the studies indicated that the introduction of 2-pyridyl onto Hpip ligand is more favorable for extension of conjugate plane of the main ligand than that of phenyl, and for greatly enhanced ct-DNA binding affinity accordingly.
authors.affiliation: College of Chemistry, Beijing Normal University, Beijing 100875, China.
authors.forename: An-Guo
authors.initials: AG
authors.lastname: Zhang
authors.forename: Huai-Xia
authors.initials: HX
authors.lastname: Yang
authors.forename: Ke-Zhi
authors.initials: KZ
authors.lastname: Yang
mesh_terms: D004247:DNA / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007364:Intercalating Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D015394:Molecular Structure; D009691:Nucleic Acid Denaturation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D010618:Phenanthrolines / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D012428:Ruthenium / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013816:Thermodynamics
chemical_list: D007364:Intercalating Agents; D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; C560355:ruthenium(2-(4-(pyridin-2-yl)phenyl)-1H-imidazo(4,5-f)(1,10)phenanthroline); D012428:Ruthenium; D004247:DNA