title: Off-on-off pH luminescence switching and DNA binding properties of a free terpyridine-appended ruthenium complex.
abstract: A ruthenium(II) complex [Ru(bpy)2(HL(1))](ClO4)2·3H2O {bpy=2,2'-bipyridine and HL(1)=2-(2,6-di(pyridin-2-yl)pyridin-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline}, denoted as RuHL(1), was synthesized and characterized by elemental analysis, proton nuclear magnetic resonance spectroscopy, and mass spectrometry. The pH effects on the UV-visible (UV-vis) absorption and emission spectra and the luminescence lifetimes of RuHL(1) have been studied, and their ground- and excited-state acid ionization constants were derived. The complex was found to exhibit pH-induced "off-on-off" luminescence switching properties via protonation/deprotonation of the grafted imidazole and terpyridyl groups. A pH-induced emission on-off intensity ratio of 166 was observed as pH was increased from 2.00 to 5.44, which is one of the largest values observed among imidazole-containing Ru(II) complex-based acidic-pH-induced pH luminescence switches. RuHL(1) also strongly binds to calf thymus DNA in mixed binding modes involving classic intercalation and partial intercalation, as determined by UV-vis absorption and emission spectrophotometric DNA titration, ethidium bromide displacement, DNA denaturation and DNA viscosity measurements.
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Ze-Bao
authors.initials: ZB
authors.lastname: Zheng
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Si-Yuan
authors.initials: SY
authors.lastname: Kang
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Xun
authors.initials: X
authors.lastname: Yi
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China. Electronic address: kzwang@bnu.edu.cn.
authors.forename: Ke-Zhi
authors.initials: KZ
authors.lastname: Wang
mesh_terms: D000818:Animals; D002417:Cattle; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004996:Ethidium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007364:Intercalating Agents / Q000138:chemical synthesis / Q000737:chemistry*; D049449:Luminescence; D009691:Nucleic Acid Denaturation; D010618:Phenanthrolines / Q000737:chemistry; D011522:Protons; D011725:Pyridines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014783:Viscosity
chemical_list: D056831:Coordination Complexes; D007364:Intercalating Agents; D010618:Phenanthrolines; D011522:Protons; D011725:Pyridines; D012428:Ruthenium; D004247:DNA; C427203:calf thymus DNA; D004996:Ethidium
keywords: DNA; Luminescence spectroscopy; Ruthenium; UV–visible spectroscopy; pH