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We report the synthesis, characterization, and antiproliferative activity of organo-osmium(II) and organo-ruthenium(II) half-sandwich complexes [(η6-p-cym)Os(L)Cl]Cl (1 and 2) and [(η6-p-cym)Ru(L)Cl]Cl (3 and 4), where L = N-(2-hydroxy)-3-methoxybenzylidenethiosemicarbazide (L1) or N-(2,3-dihydroxybenzylidene)-3-phenylthiosemicarbazide (L2), respectively. X-ray crystallography showed that all four complexes possess half-sandwich pseudo-octahedral "three-legged piano-stool" structures, with a neutral N,S-chelating thiosemicarbazone ligand and a terminal chloride occupying three coordination positions. In methanol, E/Z isomerization of the coordinated thiosemicarbazone ligand was observed, while in an aprotic solvent like acetone, partial dissociation of the ligand occurs, reaching complete displacement in a more coordinating solvent like DMSO. In general, the complexes exhibited good activity toward A2780 ovarian, A2780Cis cisplatin-resistant ovarian, A549 lung, HCT116 colon, and PC3 prostate cancer cells. In particular, ruthenium complex 3 does not present cross-resistance with the clinical drug cisplatin in the A2780 human ovarian cancer cell line. The complexes were more active than the free thiosemicarbazone ligands, especially in A549 and HCT116 cells with potency improvements of up to 20-fold between organic ligand L1 and ruthenium complex 1. [ABSTRACT FROM AUTHOR]

We demonstrate here the synthesis of a novel class of metallo-supramolecular polymers with shackled structure, via the coordination of cyclic di(bisterpyridine-triphenyl ether ester) ligands with ruthenium-(II) ions. The constraint from the ring topology via the shackling of ligands provides novel properties to these metallo-supramolecular polymers, including the formation of dendritic crystals, red-shift of absorption bands in the UV--vis spectra from interchain charge-transfer transitions, and a typical flash-type memory behavior. [ABSTRACT FROM AUTHOR]

We describe the development of a mechanochemical approach for Ru-catalyzed olefin metathesis, including cross-metathesis and ring-closing metathesis. The method uses commercially available catalysts to achieve high-yielding, rapid, room-temperature metathesis of solid or liquid olefins on a multigram scale using either no or only a catalytic amount of a liquid. [ABSTRACT FROM AUTHOR]

The role of electronic friction and,more generally, of nonadiabaticeffects during dynamical processes at the gas/metal surface interfaceis still a matter of discussion. In particular, it is not clear ifelectronic nonadiabaticity has an effect under “mild”conditions, when molecules in low rovibrational states interact witha metal surface. In this paper, we investigate the role of electronicfriction on the dissociative sticking and (inelastic) scattering ofvibrationally and rotationally cold H2molecules at a Ru(0001)surface theoretically. For this purpose, classical molecular dynamicswith electronic friction (MDEF) calculations are performed and comparedto MD simulations without friction. The two H atoms move on a six-dimensionalpotential energy surface generated from gradient-corrected densityfunctional theory (DFT), that is, all molecular degrees of freedomare accounted for. Electronic friction is included via atomic frictioncoefficients obtained from an embedded atom, free electron gas (FEG)model, with embedding densities taken from gradient-corrected DFT.We find that within this model, dissociative sticking probabilitiesas a function of impact kinetic energies and impact angles are hardlyaffected by nonadiabatic effects. If one accounts for a possibly enhancedelectronic friction near the dissociation barrier, on the other hand,reduced sticking probabilities are observed, in particular, at highimpact energies. Further, there is always an influence on inelasticscattering, in particular, as far as the translational and internalenergy distribution of the reflected molecules is concerned. Additionally,our results shed light on the role played by the velocity distributionof the incident molecular beam for adsorption probabilities, where,in particular, at higher impact energies, large effects are found. [ABSTRACT FROM AUTHOR]

Photophysics of the MLCT excited-state of [Ru(bpy)(tpy)(OH2)]2+ (1) and [Ru(bpy)(tpy)(OD2)]2+ (2) (bpy = 2,2'-bipyridine and tpy = 2,2':6',2'-terpyridine) have been investigated in room-temperature H2O and D2O using ultrafast transient pump-probe spectroscopy. An inverse isotope effect is observed in the ground-state recovery for the two complexes. These data indicate control of excited-state lifetime via a pre-equilibrium between the ³MLCT state that initiates H-bond dynamics with the solvent and the ³MC state that serves as the principal pathway for nonradiative decay. [ABSTRACT FROM AUTHOR]

A series of hetero- and homoleptic tridentate ruthenium(II) and osmium(II) complexes of compositions [(tpy-PhCH3)Ru(tpy-HImzphen)](ClO4)2 (1), [(H2pbbzim)Ru(tpy-HImzphen)](ClO4)2 (2), and [M(tpy-HImzphen)2](ClO4)2 [M = RuII (3) and OsII (4)], where tpy-PhCH3 = 4′-(4-methylphenyl)-2,2′:6′,2″-terpyridine, H2pbbzim = 2,6-bis(benzimidazole-2-yl)pyridine and tpy-HImzphen = 2-(4-[2,2′:6′,2″]terpyridine-4′-yl-phenyl)-1H-phenanthro[9,10-d]imidazole, have been synthesized and characterized by using standard analytical and spectroscopic techniques. X-ray crystal structures of three complexes 2, 3, and 4 have been determined. The absorption spectra, redox behavior, and luminescence properties of the complexes have been thoroughly investigated. All of the complexes display moderately strong luminescence at room temperature with lifetimes in the range of 10-55 ns. The effect of solvents on the absorption and emission spectral behavior of the complexes has also been studied in detail. The anion sensing properties of all the complexes have been studied in solution using absorption, emission, and 1H NMR spectral studies and by cyclic voltammetric (CV) measurements. It has been observed that the complexes 1, 3, and 4 act as sensors for F-only, whereas 2 acts as sensor for F-, AcO-, and to some extent for H2PO4-. It is evident that in the presence of excess of anions deprotonation of the imidazole N-H fragment(s) occurs in all cases, an event which is signaled by the development of vivid colors visible with the naked eye. The receptor-anion binding/equilibrium constants have been evaluated. [ABSTRACT FROM AUTHOR]

Ruthenium(II) polypyridyl complexes pro- mote the efficient radical cation Diels-Alder cycloaddition of electron-rich dienophiles upon irradiation with visible light. These reactions enable facile [4 + 2] cycloadditions that would be electronically mismatched under thermal conditions. Key to the success of this methodology is the availability of ligand-modified ruthenium complexes that enable rational tuning of the electrochemical properties of the catalyst without significantly perturbing the overall photophysical properties of the system. [ABSTRACT FROM AUTHOR]

Laser-ablated ruthenium atoms undergo reaction with acetylene during condensation in excess neon and argon matrices to form a metallacycle complex, insertion into the C-H bond, and rearrangement to the vinylidene complex. The subject molecules were identified by 13C2H2 and C2D2, isotopic substitutions and density functional theory (DFT) frequency calculations. The HRuCCH molecule is described by Ru-H, CH, and CC stretching modes and CCH deformation modes. A very strong CC double bond stretching, weak CH stretching, and CCH deformation frequencies were observed for the Ru=C=CH2 complex. The metallacycle Ru-η²-(C2H2) is characterized through CC double bond stretching, CH stretching and CCH deformation modes. The reaction mechanism for formation of the Ru=C=CH2 complex was investigated by B3LYP internal reaction coordinate calculations, and the hydrido-alkyny complex is the rate-determining step. The delocalized three-center-four-electron π bond using the Ru 4dxz electron pair contributes to the C-C π* orbital and provides stabilization energy (ΔE(²), second-order perturbation) for the vinylidene Ru=C=CH2 complex. [ABSTRACT FROM AUTHOR]

We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H2ase) by CO. We present a model study, using a NiRu H2ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the RuII center rather than taking an axial position on the NiII center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H2ase by complexing to the FeII center. [ABSTRACT FROM AUTHOR]

Among the many mechanisms for the oxidation of guanine derivatives (G) assisted by transition metals, RuIII and PtIV metal ions share basically the same principle. Both RuIII- and PtIV-bound G have highly positively polarized C8--H's that are susceptible to deprotonation by OH-, and both undergo two-electron redox reactions. The main difference is that, unlike PtIV, RuIII is thought to require O2 to undergo such a reaction. In this study, however, we report that [RuIII(NH3)5(dGuo)] (dGuo = deoxyguanosine) yields cyclic-5'-O-C8-dGuo (a two-electron G oxidized product, cyclic-dGuo) without O2. In the presence of O2, 8-oxo-dGuo and cyclic-dGuo were observed. Both [RuII(NH3)5(dGuo)] and cyclic-dGuo were produced from [RuIII(NH3)5(dGuo)] accelerated by [OH-]. We propose that [RuIII(NH3)5(dGuo)] disproportionates to [RuII(NH3)5(dGuo)] and [RuIV(NH3)4(NH2-)(dGuo)], followed by a 5'-OH attack on C8 in [RuIV(NH3)4(NH2-)(dGuo)] to initiate an intramolecular two-electron transfer from dGuo to RuIV, generating cyclic-dGuo and RuII without involving O2. [ABSTRACT FROM AUTHOR]

An electrospun poly(acrylonitrile-co-actylic acid) nanofiber mat (PAN-co-PAAnfm) was successfully collected on the surface of a glassy carbon electrode (GCE). Scanning electron microscope (SEM) images showed that the porous electrospun mat was composed of -160 nm diameter of uniform knitted nanofibers. The cationic luminescence probe, tris(2,2'-bipyridyl)ruthenium(Ii) complex ([Ru(bpy)3]2+), was innovatively and first incorporated into the negatively charged PAN-coPAA,-modified GCE via electrostatic interaction. Compared with the [Ru(bpy)3]2+ immobilized on normal PAN-co-PAA deposited coating, [Ru(bpy)3]2+/ PAN-co-PAAnfm exhibited dramatically enhanced electrochemical and electrochemiluminescence (ECL) performances, namely, more than 100 times higher ECL intensity could be feasibly obtained via the elecfrospinning technique. [ABSTRACT FROM AUTHOR]

Dynamic kinetic asymmetric transformation (DYKAT) of 1 ,5-diols via combined lipase and ruthenium catalysis provides enantiomerically pure diacetates in high diastereoselectivity, which can serve as intermediates in natural product synthesis. This is demonstrated by the synthesis of (+)-Solenopsin A. [ABSTRACT FROM AUTHOR]

Films containing [Os(bpy)2(PVP)10Cl]+ and [Ru(bpy)2- (PVP)10Cl]+ metallopolymers were assembled layer by layer on pyrolytic graphite electrodes to make sensors that selectively detect oxidized DNA. These films showed reversible, independent electrochemistry for electroactive Os3+/Os2+ and Ru3+/Ru2+ centers, with formal potentials of 0.34 and 0.76 V vs SCE, respectively. The combination of ruthenium and osmium metallopolymers in the films provided a catalytic Os square wave voltammetry (SWV) peak that is mainly selective for 8-oxoguanine and the detection of other oxidized nucleobases from the Ru peak. The method is applicable to measurements on DNA in solution or DNA incorporated into films. Using the Os SWV peak, 1 oxidized nucleobase in 6000 was detected. The sensor is simple and inexpensive, and the approach may be useful for the detection of oxidized DNA as a clinical biomarker for oxidative stress. [ABSTRACT FROM AUTHOR]

Examines the large kinetic isotope effects for proton-coupled electron transfer in ruthenium polypyridyl complexes. Importance of nuclear quantum effects; Mechanisms of the electron and proton transfer reactions; Elements of the gas-phase valence bond matrix.

Compares the hole-transfer superexchange in dinuclear mixed-valence ruthenium complexes. Mechanism of hole-transfer; Reagents and methodology used in the study; Isolation of triammine complexes.

Reports on resonance Raman (RR) and time-resolved resonance Raman (TR3) spectra of ruthenium (II) complexes containing inherently assymetric 2-(2-pyridyl)pyraxzine(pypz) and its selectively deuteriated analogue. Preparation of compounds; Differentiation of `radical' and `neutral ligand' modes; Analysis of `radical' features; Structural interpretation of the TR3 spectrum.

Studies methods for ruthenium isotope measurement by both positive and negative ion thermal ionization mass spectrometry. Mass fractionation and Ru isotope ratios; Isotope abundance and atomic weight of Ru.

Focuses on the accurate measurement of ruthenium isotopes by a form of mass spectrometry. Experimental section; Results and discussion.

The treatment of [Ru(LOEt)(N)Cl2] (1; LOEt- = [Co(η5-C5H5){P(O)(OEt)2}3]-) with Et3SiH affords [Ru(LOEt)Cl2(NH3)] (2), whereas that with [Ru(LOEt)(H)(CO)(PPh3)] (3) gives the dinuclear imido complex [(LOEt)Cl2Ru(μ-NH)Ru(CO)(PPh3)(LOEt)] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) Å. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10-5 M-1 s-1. [ABSTRACT FROM AUTHOR]

The cationic complex [(pymox-Me2)RuCl2]+BF4−was found to be a highly effective catalyst for the C−H bond oxidation reaction of arylalkanes in water. For example, the treatment of ethylbenzene (1.0 mmol) with t-BuOOH (3.0 mmol) and 1.0 mol % of the Ru catalyst in water (3 mL) cleanly produced PhCOCH3at room temperature. Both a large kinetic isotope effect (kH/kD= 14) and a relatively large Hammett value (ρ = −1.1) suggest a solvent-caged oxygen rebounding mechanism via a Ru(IV)-oxo intermediate species. [ABSTRACT FROM AUTHOR]

The article offers a description of a ruthenium/chiral diimino-diphosphine (PNNP)-catalyzed asymmetric Diels-Alder reaction. It notes that the PNNP complexes promote the enantioselective Diels-Alder reaction of α-methylene &#03B2;-keto esters to give tetrahydro-1-indanones. It explains that the diene attacks the open re enantioface of metal-bound dienophile in highly enantioselective fashion.

The article reports the first experimental evidence that nuclear isotopic substitution of molecular sensitizers can indeed be used to control excited-state interfacial electron injection yields. The synthesis of the ruthenium ammine compounds is very similar to reported procedures for closely related compounds. The extent of the reaction was monitored by infrared spectroscopy, wherein the N-H stretching modes decreased with a concomitant increase of the N-D stretching intensity. It was found that the N-H stretching bands were essentially gone after four consecutive exchanges in MeOD.

Reports on the coupling of propargyl alcohols through allenylidene-alkynyl or vinylvinylidene-alkynyl combination on a thiolate-bridged diruthenium center. Syntheses and crystal structures of diruthenacyclopentanone and diruthenacyclopentenone complexes; Interaction of organic and organometallic propargyl derivatives with transition metals.