Showing papers on "Ruthenium published in 1989"

Homoleptic Complexes of 2,2′-Bipyridine

Abstract: Publisher Summary This chapter offers information on homoleptic complexes of 2,2'-bipyridine (bpy). The chapter focuses on the class of complexes that contain only bpy ligands bonded to the metal. The unique metal-binding properties of bpy were recognized from the outset. The third renaissance in bpy chemistry can be traced to the commercial availability of the ligand in the 1950s, when large amounts were required for the preparation of Diquat insecticides. The current interest in complexes of bpy is associated with the extremely interesting electrochemical, photophysical, and photoelectrochemical properties that they exhibit. 2,2'-Bipyridine is a strong field ligand that forms relatively stable complexes, with the inherent M–N bond strength enhanced by the chelate effect. Complexes with main group metal ions, and with lanthanides and actinides, can be prepared in water or organic solvents. The bis complexes are known for a range of metals and oxidation states though they tend to be more common for lower formal oxidation states. The bpy ligand is remarkable for the wide range of formal oxidation states with which it is associated. The chapter discusses the general trends in the reactivity of specific complexes under the appropriate elements. Iron, ruthenium, and osmium have played a crucial role in the development of the chemistry of 2,2'-bipyridine.

Energy level tailoring in ruthenium(II) polyazine complexes based on calculated and experimental ligand properties

Abstract: The effects of experimental and calculated ligand properties on the electronic structure of ruthenium(II) polyazines have been rationalized in the complexes (L 3 Ru) 2+ , [(L)Ru(bpy) 2 ] 2+ , and {(η 4 ,μ-L)[Ru(bpy) 2 ] 2 } 4+ , where L denotes the four isomeric bidiazines 3,3'-bipyridazine, 2,2'-bipyrazine, and 4,4'-bipyrimidine and η 2 -azo-2,2'-bipyridine and where η 4 ,μ-L denotes the symmetrically bridging ligands 2,2'-bipyrimidine, 2,5-bis(2-pyridyl)pyrazine, 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, and azo-2,2'-bipyridine. Crucial factors determining the redox potentials and metal-to-ligand charge-transfer (MLCT, d →π*) absorption energies are the ground-state basicities, the π* orbital energies, and electron densities at the coordinating atoms of the ligands. Mono- and binuclear complexes with unusually long wavelength MLCT absorptions have been obtained by applying the described strategies in the design and selection of ligands

A study of some polypyridylruthenium(II) complexes as DNA binders and photocleavage reagents.

Abstract: The nature of the binding of several ruthenium polypyridyl complexes containing 2, 2`-bipyridine (bipy), 4, 4`-dimethyl-2, 2`-bipyridine (DMB), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline(DPP), 2, 2`, 2`-terpyridine (terpy), 2, 2`-biquinoline (biq), 1,4,5,8-tetraazaphen-anthrene (TAP) and 1,4,5,8,9,12-hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A-T)] and poly[d(G-C)] were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+ and Ru(phen)32+, which bind by partial intercalation, also show a strong preference for poly[d(A-T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)32+ which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G-C)] or CT-DNA, due to photoredox interaction with guanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)32+ is the most efficient sensitiser while uncharged complexes and complexes with very short-lived excited states do not cleave DNA.

Organometallic Chemistry of Arene Ruthenium and Osmium Complexes

Abstract: Publisher Summary This chapter focuses on the organometallic chemistry and new aspects of arene ruthenium and osmium complexes. It explores that arene ruthenium and osmium complexes play an increasingly important role in organometallic chemistry. They appear to be good starting materials for access to reactive arene metal hydrides or 16-electron metal (0) intermediates that have been used recently for carbon-hydrogen bond activation. Various methods of access to cyclopentadienyl, borane, and carborane arene ruthenium and osmium complexes have been reported. Recently, from classic organometallic arene ruthenium and osmium chemistry has grown an area making significant contributions to the chemistry of cyclophanes. These compounds are potential precursors of organometallic polymers, which show interesting electrical properties and conductivity. The possibility of coordination of a two-electron ligand, in addition to arene, to the ruthenium or osmium atom provides a route to mixed metal or cluster compounds. Cocondensation of arene with ruthenium or osmium vapors has recently allowed access to new types of arene metal complexes and clusters. It reviews that arene ruthenium and osmium appear to be useful and specific catalyst precursors, apart from classic hydrogenation, for carbon–hydrogen bond activation and activation of alkynes; such compounds may become valuable reagents for organic syntheses.

New Ruthenium Complexes for the Treatment of Cancer

Abstract: The aim of developing new tumor-inhibiting ruthenium complexes, in particular compounds which act against tumors that have been chemoresistant up to now, has led us to the synthesis of different classes of ruthenium complexes. These were selected for further evaluation on the basis of increase in survival time in the P388 tumor model and water-solubility. The water-soluble ruthenium complexes coordinated with heterocycle ligands intrans-position, HB(RuB2Cl4), and the corresponding pentachloro derivatives, (HB)2(RuBCl5), were identified as being the most active ones. Their chemical properties were investigated by means of x-ray analyses, Mossbauer spectra, NMR spectra, and other methods. Their galenic formulation was relatively easy to establish owing to their solubility in water or in physiological saline. Stability of the complexes turned out to be sufficient for infusion therapy. Antitumor activity of such compounds was confirmed not only in the P388 tumor model but also in the Walker 256 carcinosarcoma, the Stockholm Ascitic tumor, the subcutaneously growing B 16 melanoma, the intramusculary growing sarcoma 180 and the AMMN-induced colorectal tumors of the rat.

Oxidation chemistry of ruthenium-salen complexes

Abstract: The synthesis of [Ru III (salen)(X)(Y)] n [n=1, (X)(Y)=(CN) 2 ; n=0, (X)(Y)=(PPh 3 )(PBu 3 ), (PPh 3 )(py); n=1, (X)(Y)=(PPh 3 )(N 3 ), (PPh 3 )(TsO) (TsO=tosylate anion) from [Ru III (salen)(PPh 3 )(Cl)] is described. These ruthenium(III) complexes are dark green air-stable solids. Their cyclic voltammograms display reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples. At room temperature, they catalyze oxidation of alkenes by PhIO. With norbornene and cyclooctene, epoides are formed. The mechanism of the catalytic oxidation is discussed

Acid-base behavior in the ground and excited states of ruthenium(II) complexes containing tetraimines or dicarboxybipyridines as protonatable ligands

Abstract: Reference LPI-ARTICLE-1989-024doi:10.1021/ic00322a015View record in Web of Science Record created on 2006-02-21, modified on 2016-08-08

Photoinduced electron-transfer kinetics of singly labeled ruthenium bis(bipyridine) dicarboxybipyridine cytochrome c derivatives

Abstract: Cytochrome c derivatives labeled at specific lysine amino groups with ruthenium bis(bipyridine) dicarboxybipyridine [RuII(bpy)2(dcbpy)] were prepared by using the procedure described previously [Pan, L. P., Durham, B., Wolinska, J., & Millett, F. (1988) Biochemistry 27, 7180-7184]. Four additional singly labeled derivatives were purified, bringing the total number to 10. These derivatives have a strong luminescence emission centered at 662 nm arising from the excited state, RuII*. Transient absorption spectroscopy was used to directly measure the rate constants for the photoinduced electron-transfer reaction from RuII* to the ferric heme group (k1) and for the thermal back-reaction from the ferrous heme group to RuIII (k2). The rate constants were found to be k1 = 14 X 10(6) s-1 and k2 = 24 X 10(6) s-1 for the derivative modified at lysine 72, which has a distance of 8-16 A between the ruthenium and heme groups. Similar rate constants were found for the derivatives modified at lysines 13 and 27, which have distances of 6-12 A separating the ruthenium and heme groups. The rate constants were significantly slower for the derivatives modified at lysine 25 (k1 = 1 X 10(6) s-1, k2 = 1.5 X 10(6) s-1) and lysine 7 (k1 = 0.3 X 10(6) s-1, k2 = 0.5 X 10(6) s-1), which have distances of 9-16 A. Transients due to photoinduced electron transfer could not be detected for the remaining derivatives, which have larger distances between the ruthenium and heme groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A ruthenium heteropolyanion as catalyst for alkane and alkene oxidation

Abstract: A ruthenium heteropolyanion, SiRu(H2O)W11O395–, has been synthesized which catalyses the liquid phase oxidation of alkanes and alkenes with various primary oxidants including potassium persulphate, sodium periodate, t-butyl hydroperoxide, and iodosylbenzene; the activity and selectivity vary with the oxidant used

Synthesis of a highly reactive (benzyne)ruthenium complex: C-C, C-H, N-H, and O-H activation reactions

Abstract: The authors report here the synthesis and chemistry of an exceptionally reactive ruthenium benzyne complex, (PMe{sub 3}){sub 4}Ru({eta}{sup 2}-C{sub 6}H{sub 4}) (1). The ruthenium-carbon bond in this molecule reacts with a wide range of organic substrates that are typically inert toward late transition-metal-carbon bonds, including those in benzyne complexes. For example, complex 1 reacts cleanly with arylamine N-H bonds, water O-H bonds, and benzyl and aryl C-H bonds. It reacts with acetophenone to yield an O-bound enolate complex, inserts benzaldehyde cleanly, and cleaves the C-C bond of acetone.

Synthesis and characterization of mononuclear and dinuclear bis(2,2'-bipyridine)ruthenium(II) complexes containing sulfur-donor ligands

Abstract: Preparation d'une serie de complexes du ruthenium(II). Etude radiocristallographique, spectrometrie UV visible, RPE et voltammetrie cyclique

A novel photo-sensitized polymerization of pyrrole

Abstract: A novel photo-sensitized polymerization of pyrrole by the use of tris(2,2′-bipyridine)ruthenium(II) as a photo-sensitizer has been investigated in aqueous solution and in polymer matrix for the fabrication of fine conducting polymer patterns.

Photosubstitution reactions of terpyridine complexes of ruthenium(II)

Abstract: Photosubstitution de Ru [trpy] L 3 2+ et Ru [trpy] L 2 Cl + par l'acetonitrile, les ions chlorures, la pyridine, la picoline-4 et le propiononitrile. Les ligands L sont la triphenylphosphine et la pyridine (trpy=terpyridine-2,2':6',2″)

Novel ruthenium-oxo complexes of saturated macrocycles with nitrogen and oxygen donors and X-ray crystal structure of trans-[RuIV(L)O(H2O)][ClO4]2

Abstract: We describe the generation of a new class of highly oxidizing ruthenium-oxo complexes, which effect chemical and electrochemical oxidation of organic substrates with a macrocyclic ligand L (1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane). The structure of the novel trans-Ru IV (L)O-(H 2 O)] 2+ complex, a prototype example of trans-oxoaquoruthenium (IV) system, has been established by X-ray crystallography

Electrochemical assembly of metallopolymeric films via reduction of coordinated 5-chlorophenanthroline

Abstract: Electrochemical reduction of iron, osmium, and ruthenium complexes containing the ligand 5-chlorophenanthroline leads to the controlled growth of metallopolymers as electrode coatings. The coatings are electroactive and display a reversible electrochromic effect upon metal oxidation. Auger electron spectroscopy studies show that the polymerization mechanism involves carbon-chlorine bond cleavage and the generation of exchangeable chloride ions. The proposed linkage mechanisms involve direct carbon-carbon coupling of phenanthroline ligands. The possible utility of these new polymers in redox conductivity studies and in microstructure fabrication is noted

Redox regulation in ruthenium(II) complexes of 2,6-bis(N-pyrazolyl)pyridine ligands: synthetically versatile analogs of 2,2':6',2''-terpyridine

Abstract: We report here the synthesis of a new family of planar tridentate ligands based on 2,6-bis(N-pyrazolyl)pyridine

Metal oxide electrodes

Abstract: An electrode for measuring the activity of ionic species. The electrode comprises a material which is chemically sensitive to at least one ionic species. The material comprises an insulating component and a conductive component of lower resistivity than the insulating component. The insulating component has a density of proton binding sites sufficiently large to be sensitive to the ionic species. The conductive component comprises particles, the size of which are sufficiently small to modify the bulk conductive properties such that the susceptibility of the particles to redox interference in the operation of the electrode is decreased, while maintaining sufficient conductivity to operate in Faradaic electrode configurations. Illustratively, the insulating component is tantalum oxide, zirconium oxide or aluminum oxide and the conductive component is iridium, platinum, ruthenium, palladium, rhodium or osmium oxide.