title: Ruthenium(II) and osmium(II) mixed chelates based on pyrenyl-pyridylimidazole and 2,2'-bipyridine ligands as efficient DNA intercalators and anion sensors.
abstract: We report herein the synthesis and characterization of two monometallic ruthenium(II) and osmium(II) complexes of composition [(bpy)2M(HImzPPy)] (ClO4)2 derived from pyrenylimidazole-10-pyridin-2-yl-9H-9,11-diazacyclopenta[e]pyrene (HImzPPy) and 2,2'-bipyridine (bpy) ligands. X-ray crystallographic study shows that both crystals belong to the triclinic system having space group P1̅. The photophysical properties of 1 and 2 in acetonitrile indicate that the metal-to-ligand charge-transfer excited state is mainly centered in the [M(bpy)2](2+) moiety of the complexes and slightly affected by the extended conjugation of the pyrenylimidazole moiety. Both complexes display one-electron reversible metal-centered oxidative processes and a number of quasi-reversible reductive processes. The binding affinities of the complexes toward calf-thymus DNA (CT-DNA) were thoroughly studied through different methods such as absorption, emission, excited-state lifetime, circular dichroism, and thermal denaturation of DNA and a relative DNA binding study using ethidium bromide. All of these experiments account for the intercalative nature of both 1 and 2 toward CT-DNA as well as their light-switch behavior. The anion recognition study through different spectroscopic techniques reveals that both complexes act as "turn-on" luminescence sensors for H2PO4(-) and "turn-off" sensors toward F(-) and AcO(-). The imidazole N-H proton of the receptors gets deprotonated with the excessive addition of F(-) and AcO(-), while it interacts with H2PO4(-) through hydrogen-bonding interaction. Theoretical calculations (DFT and TD-DFT) were also performed to understand the photophysical properties of the metalloreceptors.
authors.affiliation: Department of Chemistry, Inorganic Chemistry Section, Jadavpur University , Kolkata 700032, India.
authors.forename: Sourav
authors.initials: S
authors.lastname: Mardanya
authors.forename: Srikanta
authors.initials: S
authors.lastname: Karmakar
authors.forename: Dinesh
authors.initials: D
authors.lastname: Maity
authors.forename: Sujoy
authors.initials: S
authors.lastname: Baitalik
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D000818:Animals; D000838:Anions / Q000032:analysis; D002417:Cattle; D002614:Chelating Agents / Q000737:chemistry; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004563:Electrochemistry; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009992:Osmium / Q000737:chemistry*; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D013696:Temperature
chemical_list: D000838:Anions; D002614:Chelating Agents; D007093:Imidazoles; D007364:Intercalating Agents; D008024:Ligands; D009992:Osmium; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D004247:DNA; C427203:calf thymus DNA