Search

Promising and highly novel catalysts based on ruthenium (Ru) supported on reduced graphene oxide were synthesized, characterized and tested for COx-free hydrogen generation by catalytic ammonia decomposition. Metal loading and amount of a pre-reducing agent clearly affect the catalytic properties of the final catalysts. A Ru loading higher than 2.5 wt% resulted in Ru particles of size higher than 5 nm, which were agglomerated, thus decreasing the amount of the most active sites (B5 type-sites) and therefore the ammonia conversion. Additionally, a graphene oxide (GO) hydrothermal pre-reduction with 2-chloroethylamine hydrochloride, led materials with a more ordered structure which is associated with a good electronic conductivity and, higher basicity. Optimal catalytic activity is achieved using a reducing agent/GO ratio of 5/3 (wt/wt) and a Ru loading of 2.5 wt%. Thus, 2.5Ru/10C-rGO catalyst resulted in excellent hydrogen (H2) production from ammonia decomposition, with an ammonia conversion close to 96% and hydrogen production rate of 9.1 mmolH2 gcat−1 min−1 at 400 °C. Reduced graphene oxide proved to be a suitable support in the development of nanosized Ru catalysts being the optimal one highly active in COx-free hydrogen generation during more than 60 h of reaction, providing virtuous stability., Catalizadores prometedores y altamente novedosos basados ​​en rutenio (Ru) soportado en óxido de grafeno reducido fueron sintetizados, caracterizados y probados para CO x-generación de hidrógeno libre por descomposición catalítica de amoníaco. La carga de metal y la cantidad de un agente prerreductor afectan claramente las propiedades catalíticas de los catalizadores finales. Una carga de Ru superior al 2,5% en peso resultó en partículas de Ru de tamaño superior a 5 nm, que se aglomeraron, disminuyendo así la cantidad de los sitios más activos (sitios tipo B5) y por lo tanto la conversión de amoníaco. Además, una prerreducción hidrotermal de óxido de grafeno (GO) con clorhidrato de 2-cloroetilamina, llevó a materiales con una estructura más ordenada que se asocia con una buena conductividad electrónica y una mayor basicidad. La actividad catalítica óptima se logra utilizando una relación de agente reductor/GO de 5/3 (p/p) y una carga de Ru de 2,5 % en peso. Por lo tanto, el catalizador 2.5Ru/10C-rGO resultó en un excelente hidrógeno (H 2) producción a partir de la descomposición del amoníaco, con una conversión de amoníaco cercana al 96% y una tasa de producción de hidrógeno de 9,1 mmolH 2 g cat −1 min −1 a 400 °C. El óxido de grafeno reducido demostró ser un soporte adecuado en el desarrollo de catalizadores de Ru nanométricos siendo el óptimo altamente activo en la generación de hidrógeno libre de CO x durante más de 60 h de reacción, proporcionando una estabilidad virtuosa.

A versatile Ru(II) complex bearing an anthracene moiety was synthesized in our search for suitable compounds towards efficient molecular devices. The new engineered dye, cis‑[Ru(dcbH2)(NCS)2(mbpy‑anth)] (dcbH2 = 2,2′‑bipyridyl‑4,4′‑dicarboxylic acid, mbpy‑anth = 4‑[N‑(2‑anthryl)carbamoyl]‑4′‑methyl‑2,2′‑bipyridine), exhibits a blueish emission in a vibronically structured spectrum ascribed to the fluorescence of a 1LCAnth (ligand centered) excited state in the anthracene and has a potential to be exploited in the fields of smart lighting and displays. This complex was also employed in dye-sensitized solar cells with fairly efficient solar energy conversion with the use of self-assembled TiO2 compact layers beneath the TiO2 mesoporous film to prevent meso‑TiO2/dye back reactions. Further photoelectrochemical investigations through incident photon-to-current efficiency and electrochemical impedance spectra showed that the all-nano-TiO2 compact layer acts as contact layers that increase the electron harvesting in the external circuit, enhancing efficiencies up to 50%.

The influence of addition of a series of non noble and noble metals to a manganese oxide octahedral molecular sieve (OMS) with a cryptomelane structure (K-OMS-2) has been studied for NO oxidation in view of fast selective catalytic reduction applications. Fe, Cu, Zn, Pt, Pd, Ru and Ag were selected as dopant metals with a metal loading around 2 wt.%. The catalysts were characterized in detail by ICP-OES, N2 adsorption/desorption at 77 K, XRD, H2-TPR and HR-TEM. The highest NO conversion was obtained for a K-OMS-2 catalyst modified with ruthenium, showing a reaction rate up to 5.3 μmol g−1 s−1 at 584 K. A markedly higher catalyst reducibility upon incorporation of ruthenium can be proposed as an underlying reason for the enhanced catalytic performance., Se ha estudiado la influencia de la adición de una serie de metales nobles y no nobles a un tamiz molecular octaédrico (OMS) de óxido de manganeso con estructura de criptomelano (K-OMS-2) para la oxidación de NO con vistas a aplicaciones de reducción catalítica selectiva rápida. Se seleccionaron Fe, Cu, Zn, Pt, Pd, Ru y Ag como metales dopantes con una carga de metal de alrededor del 2 % en peso. Los catalizadores se caracterizaron en detalle por ICP-OES, adsorción/desorción de N 2 a 77 K, XRD, H 2 -TPR y HR-TEM. La mayor conversión de NO se obtuvo para un catalizador K-OMS-2 modificado con rutenio , mostrando una velocidad de reacción de hasta 5,3 μmol g - 1 s - 1 a 584 K. Se puede proponer una reducibilidad del catalizador marcadamente más alta tras la incorporación de rutenio como una razón subyacente para el rendimiento catalítico mejorado.

The concept of negatively charged electrostatic blocking barrier is demonstrated using benzotriazole (btzH) as ancillary ligands in a new ruthenium-dicarboxybipyridine photosensitizer, [Ru(dcbpyH)2(btzH)2], which was deprotonated in a stepwise manner generating the (Bu4N)2[Ru(dcbpy)2(btzH)2], (Bu4N)3[Ru(dcbpy)2(btzH)(btz)] and (Bu4N)4[Ru(dcbpy)2(btz)2] acid-base conjugates. All compounds were isolated as solids and used for the preparation of DSSCs with structurally similar TiO2/dye interface but distinct electric charge properties. The results revealed that the negative charges at the TiO2 surface, generated by deprotonation of the dcbpyH ligands, are less effective than those generated by deprotonation of the ancillary ligands located much farther from the surface. This peripheral electrostatic field probably is more effective in inhibiting the approach of the negatively charged hole transporter I3−, and consequently the electron recombination, thus enhancing the overall cell performance. This hypothesis was confirmed by measuring the interfacial resistance and capacitance of running cells, and simulating the respective impedance spectroscopy data using the transmission line model.

Made available in DSpace on 2018-11-26T15:37:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-02-24 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Prope The catalytic activity of the five-coordinated [RuCl2(PPh3)(S-dmso)(2)] complex was investigated for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and for atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). Syntheses via ROMP of polyNBE were dependent on the ethyl diazoacetate (EDA) amount, used as starting carbene source, monomer concentration, temperature, and reaction time. The best polyNBE yields were obtained at 50 degrees C for 120 min with [NBE]/[Ru] = 5000 in presence of 5 mu L of EDA. MMA polymerization via ATRP was conducted as a function of time with different ethyl 2-bromoisobutyrate initiator and monomer concentrations. The kinetic data for ATRP show linear increase between MMA conversion and molecular weight. Kinetic studies with the six-coordinated [RuCl2(S-dmso)(3)(O-dmso)] complex also showed an increase in the molecular weight with conversion, but with a marked deviation from theoretical molecular weights. This is consistent with the better control in the polymerization supported by electronic and steric properties of the PPh3 ligand in the title complex (C) 2016 Elsevier B.V. All rights reserved. Univ Estadual Paulista, Fac Ciencias & Tecnol, BR-19060900 Presidente Prudente, SP, Brazil Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, Fac Ciencias & Tecnol, BR-19060900 Presidente Prudente, SP, Brazil FAPESP: 2013/10002-0 Prope: 2180/002/14-PROPe/CDC

FAPESP (Brazil) CNPq (Brazil) CAPES (Brazil) nBioNet (Brazil) We report on the interaction between mer-[RuCl3(dppb)(VPy)] (dppb = 1,4-bis(diphenylphosphine)-butane and VPy=4-vinylpyridine) (RuVPy) and dipalmitoyl phosphatidyl serine (DPPS), in Langmuir and Langmuir-Blodgett (LB) films. Interaction of RuVPy with DPPS, which predominates in cancer cell membranes, should be weaker than for other phospholipids since RuVPy is less toxic to cancer cells than to healthy cells. Incorporation of RuVPy induced smaller changes in electrochemical properties of LB films of DPPS than for other phospholipids, but the same did not apply to surface pressure isotherms. This calls for caution in establishing correlations between effects from a single property and phenomena on cell membranes. (C) 2014 Elsevier B.V. All rights reserved. Univ Estadual Ponta Grossa, Appl Chem Program, BR-84035900 Ponta Grossa, PR, Brazil Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP, Brazil Univ Fed Sao Paulo, Dept Exact Sci, BR-09972270 Diadema, SP, Brazil Univ Fed Sao Paulo, Dept Exact Sci, BR-09972270 Diadema, SP, Brazil Web of Science

This investigation combines theoretical results and experimental data to elucidate the main kinetic and mechanism for the ring opening metathesis polymerization of norbornene by means of the [RuCl2(PPh3)2(piperidine)] complex as catalyst initiator. Structural species were defined and a kinetic profile of the entire reaction is depicted. The determined mechanism showed an associative reaction between the [RuCl2(PPh3)2(piperidine)] complex initiator and ethyl diazoacetate as the first step, resulting in a metal-carbene species. This species loses one triphenylphosphine molecule (PPh3) and the global rate-determining step is associated with a removal of the second PPh3 molecule due to an electronic trans-synergism between piperidine and this PPh3 molecule. Entropic factors are crucial to the spontaneity observed for the dissociation of both PPh3 ligands. The step following the rate-determining one is associated with the binding of a norbornene molecule and a similar trans-synergism between this monomer and piperidine activates the catalysis. This electronic effect maintains the system in a very important conformation along the catalytic chain.

The complex [Ru(η 2 -O 2 CCH 2 CH 3 )(dppe) 2 ]PF 6 (dppe = 1,2-bis(diphenylphosphino)ethane) was prepared and characterized by elemental analysis, spectroscopic techniques, X-ray crystallography, HRESIMS and HRESIMS/MS. The characterization data are consistent with a cis arrangement for the dppe ligands and a bidentate coordination of the propionate ligand through carboxylate oxygens. Cytotoxicity assays were carried out on human and murine cancer and normal cell lines. In general, the [Ru(η 2 -O 2 CCH 2 CH 3 )(dppe) 2 ]PF 6 complex was more cytotoxic than both its precursor cis –[RuCl 2 (dppe) 2 ] and the reference metallodrug cisplatin. The best results against the HepG2 human tumour cell line and S180 murine tumour cell line were found with IC 50 values of 6.5 ± 0.2 and 0.18 ± 0.03 μM, respectively.

The electrocatalytic reduction of Fe(III) was investigated using a carbon fibre microelectrode modified with a ruthenium oxide hexacyanoferrate film (RuOHCF/CFM). At surfaces containing this chemical modifier, Fe(III) is electrocatalytically reduced at 0.0 V without interference from Fe(II), hence allowing the speciation of Fe(III). A linear relationship between the cathodic current and concentration of Fe(III) was obtained by amperometry in the range 10–210 μmol L−1 with detection and quantification limits of 0.22 (S/N = 3) and 0.74 (S/N = 10) μmol L−1, respectively. The described amperometric method was successfully applied for the determination of Fe(III) in different wine samples.

Changes in the reactivity of phosphorus(III) esters, which are promoted by coordination to the ruthenium(II) metal centre, were the focus of this study. Nuclear magnetic resonance data, which were acquired as a function of time, suggest that the phosphite coordination to the ruthenium(II) centre stabilises these molecules in terms of hydrolysis. This stabilisation is greater when the coordination occurs to the trans -[Ru(H 2 O)(NH 3 ) 4 ] 2+ rather than to the trans -[Ru(NO)(NH 3 ) 4 ] 3+ fragment, and these results are interpreted considering the 4dπ(Ru II ) → 3dπ(P(III)) back-bonding interactions. The correlation between the data on alkyl phosphite hydrolysis constants in trans -[Ru(NO)(NH 3 ) 4 P(III)] n + (P(III) = P(OEt) 3 , P(O)(OEt) 2 , P(O i Pr) 3 and P(OBu) 3 ) complexes and the δ 13C data show that the hydrolysis of phosphites that are coordinated to Ru(II) preferably occurs via the Michaelis–Arbuzov mechanism. Only the nitrosyl complex, where P(III) = P(OMe) 3 , did not exhibit this correlation, which suggests that the hydrolysis likely occurs via the Aksnes mechanism in this case.

Made available in DSpace on 2022-04-28T18:59:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-01 [RuCl2(S-DMSO)2(X-py)2] type complexes, with X = H (1), 4-CONH2 (2), or 3-CONH2 (3), exhibited trans,cis,cis conformational isomer (species A), with additional cis,cis,cis isomer type (species B) for 1. Electronic spectra with bands in the wavelength range of 270-450 nm were unchanged for 120 min at 25 °C in CH3CN. Irradiation at 350 nm provided replacement of DMSO ligands by CH3CN solvent molecules. Cyclic voltammetry studies in CH3CN revealed an electrochemical-chemical process with a Ru-(S-DMSO) to Ru-(O-DMSO) linkage isomerization for species B from 1. The complexes were inactive for the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) for 60 min at 25°C. However, polyNBE was produced by aging the complex solutions for 90-200 min at 25°C, raising the temperature to 50°C, irradiating the solutions at 350 nm for 5-10 min or when the complexes were in the presence of NBu4ClO4. © 2014 Elsevier B.V. All rights reserved. Instituto de Química de São Carlos Universidade de São Paulo, P.O. Box 780, 13560-970 São Carlos, SP Faculdade de Ciencias e Tecnologia Universidade Estadual Paulista, 19060-900 Presidente Prudente, SP Faculdade de Ciencias e Tecnologia Universidade Estadual Paulista, 19060-900 Presidente Prudente, SP

Electrochemical, SERS and SPR results indicated that the SAM of [Ru(NH3)4(CNpy)(pyS)]2+ complex was successfully formed on gold. At first, the modification procedure was achieved by the self-assembling of the sulphate starting complex, [Ru(SO4)(NH3)4(pyS)]+. Then, a potential of −0.4 V vs. Ag/AgCl was applied in order to reduce the metal center and induce the substitution reaction of (SO4)2− by H2O which, in turn, was replaced by CNpy. The surface pKa of the SAM formed with [Ru(NH3)4(CNpy)(pyS)]2+ was calculated as 3.05 indicating an increasing in the π-back–bonding interaction upon adsorption since a value of 2.66 is observed for the complex in solution. This behavior was reinforced by the observation of the shift of the ν(C≡N) mode to lower frequency (2190 cm−1) in the SERS spectrum in comparison to the spectrum in the solid state (2201 cm−1). The enhancement of the back–bonding interaction upon adsorption is consistent with the existence of gold adatoms in 1+ oxidation state that is assumed to act as a withdrawing group attached to the pyS moiety. The mass of the adsorbed complexes per unit area, calculated by SPR, indicated an excess of CNpy which is consistent with the SERS results where it was observed the frequency assigned to the C≡N mode of CNpy free of coordination.

A terpyridine ligand encompassing a terminal 4-carboxyphenyl group (cptpy), was employed in a new Ru(II) black dye, in the presence of 8-quinolinolate (Q) and SCN − as ancillary ligands. Such compound, here referred as [Ru(cptpy) (Q) (NCS)], was designed aiming its inclusion into carboxymethyl-beta-cyclodextrin, anchored on TiO 2 . This host–guest strategy was employed to prevent the formation of aggregates and protect the photoinjecting moiety against parallel deactivation events. Such expectation has indeed been fulfilled by the system. On the other hand, 8-quinolinolate as a strong electron donor ligand, effectively enhanced the light harvesting behavior of the dye, shifting and spreading the IPCE peaks over the entire visible region. Unfortunately, the red shift of visible charge-transfer bands was compensated by a decrease of the Ru(III)/(II) potentials, slowing down the electron transfer kinetics with the I 3 /I − redox mediator. Therefore, the observed counterbalance between charge transfer energies and redox potentials imposes a critical limit in the design of better mononuclear ruthenium-polypyridine dyes.

The reduction of trans- [Ru(NO)(NH 3 ) 4 (P(OEt) 3 )] 3+ ion was investigated in aqueous medium. Due to the phosphite ligand trans -effect and trans -influence, this complex selectively releases NO or HNO after one or two electrons reduction centered at the nitrosonium ligand (NO + ). These reactions were carried out through electrochemical reduction and using Eu 2+ and zinc amalgam, and the products were identified using electrochemical and spectroscopic techniques. Only the reduction of the nitrosonium ligand to nitric oxide is observed when europium is used as reductant. When the reaction is carried out with Zn(Hg), nitric oxide formation was not observed and N 2 O, an indirect marker of HNO, is detected in solution.