Interaction Of Ru Research Articles

Halogen Bonded Supramolecular Assemblies of [Ru(bipy)(CN)4]2− Anions and N-Methyl-Halopyridinium Cations in the Solid State and in Solution

The interactions between the [Ru(bipy)(CN)(4)](2-) anion and N-methyl-halopyridinium cations have been examined in both the solid state and in solution. In the solid state, crystal structures of [Ru(bipy)(CN)(4)](2-) salts containing iodinated cations (N-methyl-3-iodopyridinium and N-methyl-3,5-diiodopyridinium) show clear C-I...NC(Ru) halogen bonds between the externally directed cyanide lone pairs of the anion and the iodine atoms of the cation which dominates the structures. In contrast the analogous brominated cations (N-methyl-3-bromopyridinium and N-methyl-3,5-dibromopyridinium) do not exhibit C-Br...NC(Ru) interactions in the solid state, with the cyanide groups instead involved in hydrogen bonding, principally to lattice water molecules. The charge-assisted C-I...NC(Ru) interactions are therefore clearly of value as synthons in crystal engineering applications. In CH(2)Cl(2) solution, spectroscopic titrations between [Ru(4,4'-(t)Bu(2)-bipy)(CN)(4)](2-) and both N-methyl-3-iodopyridinium and N-methyl-3-bromopyridinium cations show clear evidence for formation of distinct 1:1, 3:2, and then 2:1 cation/anion adducts with high association constants (>10(7) M(-1) for the first 1:1 association constant). However the presence of identical results using the non-halogenated cation N-methyl-pyridinium indicates that this strong cation/anion association in CH(2)Cl(2) is dominated by electrostatic effects: either C-H...NC(Ru) hydrogen bonds or C-X...NC(Ru) halogen bonds could be involved in the ion pairs but it is the charge-assistance that makes the association strong. This is confirmed by a titration between [Ru(4,4'-(t)Bu(2)-bipy)(CN)(4)](2-) and the neutral halogen-bond acceptor C(6)F(5)I for which the first association constant is very low (ca. 6 M(-1)). The formation of adducts between [Ru(4,4'-(t)Bu(2)-bipy)(CN)(4)](2-) and the various N-methyl-pyridinium cations in solution results in a clear blue-shift of the (1)MLCT absorption maxima associated with the Ru(II) unit, a characteristic consequence of interaction of the cyanide lone pairs with a Lewis-acidic site on the cation. The (3)MLCT luminescence from the [Ru(4,4'-(t)Bu(2)-bipy)(CN)(4)](2-) center, however, does not show the usual associated increase in intensity associated with this blue shift in the (1)MLCT absorptions, most likely because of electron-transfer quenching by the N-methyl-pyridinium cations in the assemblies.

DNA interactions of dinuclear Ru II arene antitumor complexes in cell-free media

We recently synthesized and characterized water-soluble dinuclear Ru II arene complexes, in which two {( η 6-p-isopropyltoluene)RuCl[3-(oxo-κO)-2-methyl-4-pyridinonato-κO 4]} units were linked by flexible chains of different length [(CH 2) n ( n = 4, 6, 8, 12)]. These new dinuclear ruthenium drugs were found to exert promising cytotoxic effects in human cancer cells. In the present work DNA modifications by these new dinuclear Ru II arene compounds, which differed in the length of the linker between the two Ru II centers, were examined by biochemical and biophysical methods. The complexes bind DNA forming intrastrand and interstrand cross-links in one DNA molecule in the absence of proteins. An intriguing aspect of the DNA-binding mode of these dinuclear Ru II compounds is that they can cross-link two DNA duplexes and also proteins to DNA—a feature not observed for other antitumor ruthenium complexes. Thus, the concept for the design of interhelical and DNA–protein cross-linking agents based on dinuclear Ru II arene complexes with sufficiently long linkers between two Ru centers may result in new compounds which exhibit a variety of biological effects and can be also useful in nucleic acids research.

Enhanced electrochemical activity for ethanol oxidation on the carbon-supported Pt3Te nanocatalysts by addition of Ru

Ternary Pt–Te–Ru catalysts with different atomic ratios were synthesized by reducing the precursor with formic acid. The physical and electrochemical characterization of the Pt3TeRu0.25/C catalyst was performed by transmission electron microscopy (TEM), X-ray diffraction, energy-dispersive X-ray spectroscopy equipped with TEM (TEM-EDX), X-ray photoelectron spectrometer, ethanol oxidation, and CO stripping. In TEM images, the Pt3TeRu0.25/C nanoparticles with an average particle size of around 2.9 nm were well dispersed on the carbon support. The Pt3TeRu0.25/C catalyst was superior to the Pt3Te/C catalyst in respect of catalytic activity, durability, and CO tolerance. The positive effect of the Ru presence in the Pt3TeRu0.25/C catalyst was ascribed to the interactions of Ru or Ru oxides.

DNA Binding, Photocleavage, and Topoisomerase Inhibition of Functionalized Ruthenium(II)‐Polypyridine Complexes

The interaction of ruthenium(II)-polypyridyl complexes with DNA has attracted considerable interests during the past two decades. This paper presents some recent progresses in our laboratory on the interaction of Ru(II)-polypyridyl complexes with DNA. The first part describes the effect of modulating the intercalative ligand on the DNA-binding behaviors of the complexes, such as DNA-binding affinity, DNA-binding enantioselectivity, DNA molecular 'light switch' effect, and DNA sequence selectivity. The second part focuses on the DNA photocleavage by the complexes and its mechanism. In the final part, we discuss the topoisomerase inhibition and its mechanism, as well as the antitumor activity of the Ru(II)-polypyridyl complexes.

A Kinetic Study of the Ru(III)-Catalysed Oxidation of Glutathione by Methylene Blue in Acidic Medium

Glutathione (GSH, RSH) and Methylene Blue (MB) interact in a mole ratio of 2:1 in acidic medium forming the corresponding disulfide and the leuco base. The reaction shows zero-order kinetics in MB and first-order kinetics in GSH, i.e. the rate is not affected on varying [MB]. The rate shows a fractional dependence on [H+] while there is no influence of variation of ionic strength on the rate of reaction. The rate constant increases linearly on increasing [Ru(III)]. The zero-order rate constant remains unaffected on varying the time of equilibration of the catalyst with the ingredients of the reaction system. The rate is not affected on addition of the disulfide, but addition of the leuco base slightly retards the rate. Activation parameters have been evaluated and a plausible reaction scheme has been proposed by presuming the interaction of transient Ru(II) with protonated MB as the rate limiting step. The kinetic results indicate that the glutamyl tripeptide moiety of GSH inhibits the reactivity of cysteine–SH towards MB in the presence of Ru(III).

Interatomic versus intraatomic Ru interactions in perovskites

The competition between interatomic Ru–O–Ru interactions responsible for itinerant-electron ferromagnetism in SrRuO 3 and intraatomic spin–orbit coupling that suppresses some Ru–O–Ru magnetic interactions in CaRuO 3 so as to prevent long-range magnetic order has been further tested by investigating the double perovskites La 2RuZnO 6, La 2RuCoO 6, La 2TiCoO 6, and the solid solution Ca 2−2 x La 2 x Ru 2− x Co x O 6 (0.0⩽ x⩽1.0). The paramagnetic state of the low-spin, localized Ru 4+:t 4e 0 configuration of LaRuZnO 6 undergoes a progressive transition on lowering the temperature to a non-magnetic state ( J=0) as a result of spin–orbit coupling, λ L· S. Comparison of the susceptibilities of La 2RuCoO 6 and La 2TiCoO 6 shows a similar behavior with long-range antiferromagnetic cobalt ordering via non-magnetic RuO 6/2 and TiO 6/2 bridges. Comparison is also made of the effect of substituting Ga for Ru in CaRuO 3 with the effect of other dopants M in CaRu 1− x M x O 3. The evolution of transport properties in Ca 2−2 x La 2 x Ru 2− x Co x O 6 is also presented.

Stopped-flow kinetic fluorimetric studies of the interaction of Ru(II) complex with DNA and its analytical application

A simple, rapid, and sensitive stopped-flow kinetic fluorometric approach was established for the assay of DNA in synthetic samples and real samples by using the measures of initial reaction rate. The increased initial reaction rate is in proportion to the concentration of DNA in the range of 2.0 × 10 −8 M to 2.1 × 10 −6 M. The optimum conditions for various parameters on which the binding of Ru(phen) 2(dppz) 2+ to DNA depends, were investigated. The influence of various surfactants on the interaction was discussed. Furthermore, stopped-flow techniques were employed to determine kinetic parameters of Ru(phen) 2(dppz) 2+ binding to DNA under pseudo-first-order conditions. It was found that the interaction of Ru(phen) 2(dppz) 2+ with DNA was very fast. A two-step reaction mechanism, a fast phase followed by a slow phase, was proposed.

Introduction

The Theoretical Biophysics Symposium series started in March 2003 in the beautiful city of Donostia (San Sebastian) in the southern Basque Country, just at the west end of the Pyrenees mountains. The second symposium of the series was hosted by the University of the historical city of Örebro in Sweden, from June 28 to July 1, 2005. From June 16 to June 20, 2007, the third Symposium of the series was arranged at the picturesque city of Cetraro in southern Italy. Continuing with the tradition established by the previous editions, the aim of the symposium was not only to present explicit results from recent modeling studies, but also to allow for presentations of novel methodologies, and to do so in a setting that allowed for plentiful discussions and exchange of knowledge and ideas. To this end, it was decided to restrict the number of participants to allow for a more intimate setting. The symposium thus brought together 80 participants, ranging from senior researchers to first year PhD students, representing a total of 43 universities from 13 countries. Methodology-oriented papers presented advances in the applications of pure density functional methods to model systems large enough as to be realistic models of the biological phenomena sought and still amenable as to handle computationally. Also, recent developments of new QM/MM hybrid methods and molecular mechanics force fields for molecular dynamics modeling were discussed. Additionally, advances in time-dependent DFT for excited state properties and dynamics, topological approaches to the chemical bonding of biological systems, new quantum molecular simulations techniques, and new approaches to radiation damage mechanisms in biological systems were covered. Several of the presentations in the more applied areas were devoted to enzyme catalysis, such as radical enzymes, Zinc metalloenzymes, ribozyme catalytic reactions, the catalytic mechanism of VanX, peptide bond cleavage, phosphate ester hydrolysis, etc. We also had several contributions on computer-aided rational drug design. Finally, just to mention a few, the role of aluminosilicate surfaces as promoters of peptide bond formation, peptide misfolding and aggregation triggered by metal cations, the effect of carboxylate binding mode on metalloproteins, and the interaction of aqueous Ru(II) complexes with DNA, were some of the topics covered in the presentations. The meeting generated much discussion, as well as a splendour of social activities; in all a most successful event, providing valuable new insights in an informal setting. It is our hope that the articles presented in these symposium proceedings is able to give a flavor of some of the excellent science being conducted in the area of theoretical biophysics. For the organizing committee,

The TiO 2/Ru(dcbpyH 2) 2(NCS) 2/Au Schottky junction

Ru(dcbpyH 2) 2(NCS) 2 molecules have specific binding sites for TiO 2 and Au surfaces and a large dipole moment what makes them attractive for engineering of Schottky junctions. The rectification of the junction conditioned with a monolayer of Ru(dcbpyH 2) 2(NCS) 2 molecules increased by several orders of magnitude in comparison to the bare TiO 2/Au junction. The influence of (i) trap-assisted tunneling, of (ii) specific interaction of Ru(dcbpyH 2) 2(NCS) 2 molecules with oxygen vacancies at the TiO 2 surface and of (iii) the dipole moment of the Ru(dcbpyH 2) 2(NCS) 2 molecules on the activation energy of the diode saturation current was demonstrated. The estimated projected dipole moment of one Ru(dcbpyH 2) 2(NCS) 2 molecule amounted to about 5 D.

MgO-supported cluster catalysts with Pt–Ru interactions prepared from Pt3Ru6(CO)21(μ3-H)(μ-H)3

Bimetallic MgO-supported catalysts were prepared by adsorption of Pt3Ru6(CO)21(μ3-H)(μ-H)3 on porous MgO. Characterization of the supported clusters by infrared (IR) spectroscopy showed that the adsorbed species were still in the form of metal carbonyls. The supported clusters were decarbonylated by treatment in flowing helium at 300 °C, as shown by IR and extended X-ray absorption fine structure (EXAFS) data, and the resulting supported PtRu clusters were shown by EXAFS spectroscopy to have metal frames that retained Pt–Ru bonds but were slightly restructured relative to those of the precursor; the average cluster size was almost unchanged as a result of the decarbonylation. These are among the smallest reported bimetallic clusters of group-8 metals. The decarbonylated sample catalyzed ethylene hydrogenation with an activity similar to that reported previously for γ-Al2O3-supported clusters prepared in nearly the same way and having nearly the same structure. Both samples were also active for n-butane hydrogenolysis, with the MgO-supported catalyst being more active than the γ-Al2O3-supported catalyst.

One‐Step Synthesis of Ru(2,2′‐Bipyridine)3Cl2‐Immobilized Silica Nanoparticles for Use in Electrogenerated Chemiluminescence Detection

AbstractOne‐step synthesis of Ru(bpy)3Cl2‐immobilized (bpy = 2,2′‐bipyridine) silica nanoparticles (Ru–silica nanoparticles) for use in electrogenerated‐chemiluminescence (ECL) detection is reported. Ru–silica nanoparticles are prepared by using the Stöber method. Compared with free Ru(bpy)3Cl2, Ru–silica nanoparticles are seen to exhibit a red‐shift of the UV‐vis absorbance peak and a longer fluorescence lifetime, which are attributed to the electrostatic interaction of Ru(bpy)32+ and silica. Because silica nanoparticles are used as immobilization matrices, the surfaces of Ru–silica nanoparticles are easily modified or functionalized via the assembly of other nanoparticles, such as Au. For ECL detection, Au‐colloid‐modified Ru–silica nanoparticles are immobilized on a 3‐mercaptopropyl‐trimethoxysilane‐modified indium tin oxide electrode surface by Au–S interaction; the surface concentration of electroactive Ru(bpy)3Cl2 is obviously higher than that in silica films. The modified electrode exhibits excellent ECL signals and gives a good linear range over 5 × 10–7–1.4 × 10–3 M with a detection limit of 50 nM towards the tripropylamine (TPA) detection. Moreover, the electrode has better reproducibility and long‐term stability for the determination of TPA than electrodes modified with pure Nafion, Nafion–silica, Nafion–TiO2, or sol‐gel films containing Ru(bpy)3Cl2. Immobilization of Ru(bpy)3Cl2 on the electrode surface by this method is simple and easy, so it shows potential applications in the field of ECL analysis and detection.

Investigation of thin filament near‐neighbour regulatory unit interactions during force development in skinned cardiac and skeletal muscle

Ca(2+)-dependent activation of striated muscle involves cooperative interactions of cross-bridges and thin filament regulatory proteins. We investigated how interactions between individual structural regulatory units (RUs; 1 tropomyosin, 1 troponin, 7 actins) influence the level and rate of demembranated (skinned) cardiac muscle force development by exchanging native cardiac troponin (cTn) with different ratio mixtures of wild-type (WT) cTn and cTn containing WT cardiac troponin T/I + cardiac troponin C (cTnC) D65A (a site II inactive cTnC mutant). Maximal Ca(2+)-activated force (F(max)) increased in less than a linear manner with WT cTn. This contrasts with results we obtained previously in skeletal fibres (using sTnC D28A, D65A) where F(max) increased in a greater than linear manner with WT sTnC, and suggests that Ca(2+) binding to each functional Tn activates < 7 actins of a structural regulatory unit in cardiac muscle and > 7 actins in skeletal muscle. The Ca(2+) sensitivity of force and rate of force redevelopment (k(tr)) was leftward shifted by 0.1-0.2 -log [Ca(2+)] (pCa) units as WT cTn content was increased, but the slope of the force-pCa relation and maximal k(tr) were unaffected by loss of near-neighbour RU interactions. Cross-bridge inhibition (with butanedione monoxime) or augmentation (with 2 deoxy-ATP) had no greater effect in cardiac muscle with disruption of near-neighbour RU interactions, in contrast to skeletal muscle fibres where the effect was enhanced. The rate of Ca(2+) dissociation was found to be > 2-fold faster from whole cardiac Tn compared with skeletal Tn. Together the data suggest that in cardiac (as opposed to skeletal) muscle, Ca(2+) binding to individual Tn complexes is insufficient to completely activate their corresponding RUs, making thin filament activation level more dependent on concomitant Ca(2+) binding at neighbouring Tn sites and/or crossbridge feedback effects on Ca(2+) binding affinity.

Chemical routes to ultra thin films for copper barriers and liners

Triruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. Films as thin as 7 nm were grown. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼ 15 at.% P had a resistivity of 210 μΩ cm. Ion scattering studies reveal that ∼ 0.4 nm Cu films completely wet amorphous Ru–P alloy films. First-principles density-functional calculations are presented revealing the interaction of Ru with P, and predicting that the amorphous structure should be most stable above 20 at.% P.

Thermoelectric properties of the AA′3B4O12-type ordered perovskite oxides

Abstract The perovskite transition-metal oxide ABO3 has been extensively studied in various areas in solids. While the B ion determines the electronic properties, e.g., ferroelectricity, ferromagnetism, and superconductivity, the A site has been regarded as a “back-seat player” to change the doping level or the bandwidth. However, in the ordered perovskite oxide AA′3B4O12, the A site order is closely related to the peculiar electronic states. In CaMn3Mn4O12, the unusually small bandwidth justifies to extrapolate the transport data to the high-temperature limit, and in CaCu3Ru4O12, a novel heavy-fermion state is realized through the Cu–O–Ru interaction.

Chemical Routes to Ultra Thin Films for Copper Barriers and Liners

ABSTRACTTriruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.

Impact of rare earth magnetic moment on ordering of Ru in Sr 2RuREO 6 (RE=Gd and Eu)

We report the synthesis and magnetization of Sr 2RuREO 6 (RE/Ru-211O 6) with RE=Gd and Eu. Both Gd and Eu/Ru-211O 6 are formed in distorted perovskite-type single phase with monoclinic P2 1/n space group. Magnetization ( M/ T) measurements exhibited antiferromagnetic ordering of Ru moments for both Gd and Eu compounds at a T N of around 30 K due to super-exchange Ru–O–O–Ru interaction. Interestingly enough, detailed M/ H plots of Gd/Ru-211O 6 exhibited the development of a ferromagnetic (FM) component at 20 K. Furthermore, below 10 K, the FM component disappears, and rather spin freezing field ( H SF) of around 1000 Oe is seen at 5 K. In case of Eu/Ru-211O 6, the basic antiferromagnetic ordering of Ru moments remains invariantly down to 5 K, and the appearance of the FM component is not seen. It seems that the high magnetic moment of 8 μ B for Gd 3+ influences the anti ferromagnetic (AFM) ordering of Ru in case of Gd/Ru-211O 6.

Quantum chemistry studies on the Ru–M interactions and the 31P NMR in [Ru(CO) 3(Ph 2Ppy) 2(MCl 2)] (M = Zn, Cd, Hg)

To study the Ru–M interactions and their effects on 31P NMR, complexes [Ru(CO) 3(Ph 2Ppy) 2] (py = pyridine) ( 1) and [Ru(CO) 3(Ph 2Ppy) 2MCl 2] (M = Zn, 2; Cd, 3; Hg, 4) were calculated by density functional theory (DFT) PBE0 method. Moreover, the PBE0-GIAO method was employed to calculate the 31P chemical shifts in complexes. The calculated 31P chemical shifts in 1– 3 follow 2 > 3 > 1 which are consistent to experimental results, proving that PBE0-GIAO method adopted in this study is reasonable. This method is employed to predict the 31P chemical shift in designed complex 4. Compared with 1, the 31P chemical shifts in 2– 4 vary resulting from adjacent Ru–M interactions. The Ru → M or Ru ← M charge-transfer interactions in 2– 4 are revealed by second-order perturbation theory. The strength order of Ru → M interactions is the same as that of the P–Ru → M delocalization with Zn > Cd > Hg, which coincides with the order of 31P NMR chemical shifts. The interaction of Ru → M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M 2+, results in the delocalization of P–Ru → M, which decreases the electron density of P nucleus and causes the downfield 31P chemical shifts. Except 2, the back-donation effect of Ru ← M, arising from the delocalization from s valence orbital of M 2+ to the valence orbital of Ru, is against the P–Ru → M delocalization and results in the upfield 31P chemical shifts in 4. Meanwhile, the binding energies indicate that complex 4 is stable and can be synthesized experimentally. However, as complex [Ru(CO) 3(Ph 2Ppy) 2HgCl] + 5 is more stable than 4, the reaction of 1 with HgCl 2 only gave 5 experimentally.

Electronic Interaction of Acetonitrile and Ru(N3)-dye on Nano-Crystalline TiO2 Investigated by Means of Synchrotron Induced Photoelectron Spectroscopy

not Available.

Influence of DMSO on the electroreductive Ru(bpy)(CO)2Cl2 (bpy=2,2′-bipyridine) polymer film formation

Abstract The electroreductive film formation process for trans (Cl)-Ru(bpy)(CO) 2 Cl 2 in DMSO is disturbed at low polarisation by decoordination of chloride ligands as a result of strong DMSO–Ru(I) interaction. Unusually high chloride concentrations were measured at potentials positive of the actual film deposition step, and the chloride oxidation response in bulk electrolysis and hydrodynamic ring-disc experiments was used to probe the reaction mechanisms. Soluble intermediates were found, of which one was identified as a cationic dimer, which absorption peak at 450 nm coincides with that of reversibly dissociating pure dimer. Initial film deposition is assigned to reduction and coupling of soluble, possibly dissociated cationic, tetramer units. At full activation the two electron reduction and Ru(0) polymer formation was confirmed.

Redox-Dependent Isomerization of Organometallic RuII/RuIIICompounds Containing the Hydrotris(methimazolyl)borate Ligand: An Electrochemical Square Scheme Mechanism

[Cp*RuIII{HB(mt)3}]X (1A(X); X = Cl, PF6) and [Cp*RuII{HB(mt)3}] (2A) (Cp* = η5-C5Me5, mt = N-methyl-2-mercaptoimidazol-1-yl) were synthesized by the reactions of K[HB(mt)3] with [Cp*RuIIICl2]2 and [Cp*RuII(OMe)]2, respectively. 1A and 2A exist in the solid state in κ3-S,S‘,S‘‘ coordination, so that the sulfur atom in each mt group coordinates to the central Ru ion, producing the normal tripodal geometry of the [HB(mt)3] ligand. However, both compounds undergo an isomerization reaction in solution, where the sulfur on one mt group is displaced in favor of coordination to the hydrogen bonded to the boron (an agostic B−H−Ru interaction), resulting in κ3-H,S,S‘ coordination about the Ru (κ3-H,S,S‘ forms of [Cp*RuIII{HB(mt)3}] and [Cp*RuII{HB(mt)3}] are designated 1B and 2B, respectively). The rate and equilibrium constants associated with the reactions 1A ⇌ 2A ⇌ 2B ⇌ 1B ⇌ 1A have been determined by theoretical digital simulation comparisons of experimental 1H NMR spectroscopic and cyclic voltammetric data over a range of temperatures.