RESUMO
The redox reactions of a pyrazine-bridged binuclear [(edta)RuIIIpzRuIII(edta)]2- (edta4- = ethylenediaminetetraacetate; pz = pyrazine) have been investigated spectrochemically and spectroelectrochemically for the first time. The kinetics of the reduction of [(edta)RuIIIpzRuIII(edta)]2- (RuIII-RuIII) with the ascorbic acid anion (HA-) was studied as a function of ascorbic concentration and temperature at a fixed pH 6.0. The overall reaction of RuIII-RuIII was found to consist of two-steps involving the initial formation of the mixed-valence [(edta)RuIIpzRuIII(edta)]3- (RuII-RuIII) intermediate complex (λmax = 462 nm, εmax = 10 000 M-1 cm-1), which undergoes further reduction by ascorbic acid to produce the [(edta)RuIIpzRuII(edta)]4-(RuII-RuII) ultimate product complex (λmax = 540 nm, εmax = 20 700 M-1 cm-1). Our studies further revealed that the RuII-RuIII and RuII-RuII species are formed in the electrochemical reduction of the RuIII-RuIII complex at 0.0 and -0.4 V (vs. SHE), respectively. Formation of RuII-RuIII and RuII-RuII was further corroborated by magnetic moment measurements and DFT calculations. Kinetic data and activation parameters are interpreted in terms of a mechanism involving rate-determining outer-sphere electron transfer between Ru(III) and the ascorbate monoanion (HA-) at pH 6.0. A detailed reaction mechanism in agreement with the spectral, spectro-electrochemical and kinetic data is presented. The results of the spectral and kinetic studies of the reaction of the RuII-RuII complex with molecular oxygen (O2) reveal the ability of the RuII-RuII species to effect the oxygen reduction reaction (ORR) leading to the formation of H2O2, a partial reduction product of dioxygen (O2).
RESUMO
The presented Review is focused on the latest research in the field of inorganic chemistry performed by the van Eldik group and his collaborators. The first part of the manuscript concentrates on the interaction of nitric oxide and its derivatives with biologically important compounds. We summarized mechanistic information on the interaction between model porphyrin systems (microperoxidase) and NO as well as the recent studies on the formation of nitrosylcobalamin (CblNO). The following sections cover the characterization of the Ru(II)/Ru(III) mixed-valence ion-pair complexes, including Ru(II)/Ru(III)(edta) complexes. The last part concerns the latest mechanistic information on the DFT techniques applications. Each section presents the most important results with the mechanistic interpretations.
RESUMO
The reaction of hydrogen sulfide (H2S) and nitric oxide (NO) is of great physiological significance in human organisms. Our present studies show that Ru(III)(edta) (edta(4-) = ethylenediaminetetraacetate) mediates the S-nitrosylation of bisulfide ion (HS(-)) using NO to form [Ru(III)(edta)(SNO)](2-), the first-ever example of a ruthenium complex containing thionitrite (SNO(-)) in aqueous solution. The reaction product [Ru(III)(edta)(SNO)](2-) was characterized by IR, electron paramagnetic resonance, and electrospray ionization mass spectroscopy. Our studies further show that formation of the putative thionitrous acid coordinated to Ru(III)(edta) does not occur via the reaction of [Ru(III)(edta)NO](-) with HS(-).
RESUMO
The presence of transition-metal single-atom catalysts effectively enhances the interaction between the substrate and reactant molecules, thus exhibiting extraordinary catalytic performance. In this work, we for the first time report a facile synthetic procedure for placing highly dispersed Ru single atoms on stable CNF(ZnO) nanocages. We unravel the atomistic nature of the Ru single atoms in CNF(ZnO)/Ru systems using advanced HAADF-STEM, HRTEM, and XANES analytical methods. Density functional theory calculations further support the presence of ruthenium single-atom sites in the CNF(ZnO)/Ru system. Our work further demonstrates the excellent photocatalytic ability of the CNF(ZnO)/Ru system with respect to H2 production (5.8 mmol g-1 h-1) and reduction of CO2 to CH3OH [249 µmol (g of catalyst)-1] with apparent quantum efficiencies of 3.8% and 1.4% for H2 and CH3OH generation, respectively. Our studies unambiguously demonstrate the presence of atomically dispersed ruthenium sites in CNF(ZnO)/Ru catalysts, which greatly enhance charge transfer, thus facilitating the aforementioned photocatalytic redox reactions.
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The reduction of molecular oxygen (O2) and hydrogen peroxide (H2O2) by [RuII(edta)(pz)]2- (edta4- = ethylenediaminetetraacetate; pz = pyrazine) has been studied spectrophotometrically and kinetically in aqueous solution. Exposure of the aqua-analogue [RuII(edta)(H2O)]2- to O2 and H2O2 resulted in the formation of [RuIII(edta)(H2O)]- species, with subsequent formation of the corresponding RuV[double bond, length as m-dash]O complex. A working mechanism for the O2 and H2O2 reduction reactions mediated by the RuII(edta) complexes is proposed. The role of the coordinated water molecule (by its absence or presence in the primary coordination sphere) in controlling the mechanistic pathways, outer-sphere or inner-sphere, is discussed.
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The advancement of Ru(edta) complexes (edta4- = ethylenediamineteraacetate) mediated reactions, including NO generation and its utilization, has not been systematically reviewed to date. This review aims to report the research progress that has been made in exploring the application of Ru(edta) complexes in trapping and generation of NO. Furthermore, utilization of the potential of Ru(edta) complexes to mimic NO synthase and nitrite reductase activity, including thermodynamics and kinetics of NO binding to Ru(edta) complexes, their NO scavenging (in vitro), and antitumor activity will be discussed. Also, the role of [Ru(edta)(NO)] in mediating electrochemical reduction of nitrite, S-nitrosylation of biological thiols, and cross-talk between NO and H2S, will be covered. Reports on the NO-related chemistry of Fe(edta) complexes showing similar behavior are contextualized in this review for comparison purposes. The research contributions compiled herein will provide in-depth mechanistic knowledge for understanding the diverse routes pertaining to the formation of the [Ru(edta)(NO)] species, and its role in effecting the aforementioned reactions of biochemical significance.
Assuntos
Complexos de Coordenação/química , Sequestradores de Radicais Livres/química , Óxido Nítrico/química , Arginina/química , Azidas/química , Catálise , Ferro/química , Óxido Nítrico/síntese química , Nitritos/química , Oxirredução , Rutênio/química , S-Nitrosotióis/síntese químicaRESUMO
This review covers highlights of the work performed in the van Eldik group on inorganic reaction mechanisms over the past two decades in the form of a personal journey. Topics that are covered include, from NO to HNO chemistry, peroxide activation in model porphyrin and enzymatic systems, the wonder-world of RuIII(edta) chemistry, redox chemistry of Ru(iii) complexes, Ru(ii) polypyridyl complexes and their application, relevant physicochemical properties and reaction mechanisms in ionic liquids, and mechanistic insight from computational chemistry. In each of these sections, typical examples of mechanistic studies are presented in reference to related work reported in the literature.
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[RuIII(edta)(OH2/OH)]1-/2- (edta = ethylenediaminetetraacetate) inhibits protein tyrosine phosphatase (PTP) at physiological pH values in a mechanism that involves binding of the Cys residue of the catalytic domain of the enzyme and similar interactions may be important in the anti-cancer properties of the active forms of many Ru pro-drugs.
Assuntos
Ácido Edético/química , Ácido Edético/farmacologia , Proteínas Tirosina Fosfatases/antagonistas & inibidores , Compostos de Rutênio/química , Compostos de Rutênio/farmacologia , Estrutura Molecular , Proteínas Tirosina Fosfatases/metabolismo , Espectrofotometria , Yersinia enterocolitica/efeitos dos fármacos , Yersinia enterocolitica/enzimologiaRESUMO
Photocatalytic decoloration kinetics of triazine (Reactive Red 11, Reactive Red 2, and Reactive Orange 84) and vinylsulfone type (Reactive Orange 16 and Reactive Black 5) of reactive dyes have been studied spectrophotometrically by following the decrease in dye concentration with time. At ambient conditions, over 90-95% decoloration of above dyes have been observed upon prolonged illumination (15 h) of the reacting system with a 150 W xenon lamp. It was found that the decoloration reaction followed first-order kinetics. The values of observed rate constants were found to be dependent of the structure of dyes at low dye concentration, but independent at higher concentration. It also reports for the first time the decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst. Rate of decoloration of two different dyes together in a binary dye mixture using visible light-irradiated TiO(2) photocatalyst is governed by the adsorptivity of the particular dye onto the surface of the TiO(2) photocatalyst.
Assuntos
Cor , Corantes/química , Semicondutores , Titânio/química , Adsorção , Catálise , Cinética , FotoquímicaRESUMO
Pleomorphic rhabdomyosarcoma of the diaphragm represents fewer than 0.0001% of all cancers. One case is reported, and a total of eight cases to date are reviewed. It is an adult disease of both sexes, the lowest reported age being 14 years. The tumor presents at a late stage, and the average symptom-death interval is only a few months. Early diagnosis and wide excision are essential along with radiotherapy and chemotherapy before any survival--much less worthwhile survival--can be hoped for. There is evidence of host immune response against rhabdomyosarcomas. Immunotherapy, therefore, should be considered. For assessment of the biological behavior of the tumor and the treatment, standardization of staging and grading are essential, although there is some evidence that the prognosis of primary and recurrent tumors treated radically are similar.
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Diafragma , Neoplasias Musculares , Rabdomiossarcoma , Adulto , Humanos , Masculino , Neoplasias Musculares/diagnóstico , Neoplasias Musculares/cirurgia , Rabdomiossarcoma/diagnóstico , Rabdomiossarcoma/cirurgiaRESUMO
An effective procedure for selective reduction of O2 to H2O2 exploring the use of hydrogen sulfide, an obnoxious industrial pollutant as reductant is reported herein. The reduction of [Ru(III)(EDTA)pz](-) (EDTA(4-) = ethylenediaminetetraacetate; pz = pyrazine) by hydrogen sulfide resulting in the formation of a red [Ru(II)(EDTA)pz](2-) complex (λmax = 462 nm) has been studied spectrophotometrically and kinetically using both rapid scan and stopped-flow techniques. The time course of the reaction was followed as a function of [HS(-)]i, pH (5.5-8.5), and temperature. Alkali metal ions were found to have a positive influence (K(+) > Na(+) > Li(+)) on the reaction rate. Kinetic data and activation parameters are interpreted in terms of a mechanism (admittedly speculative) involving outer-sphere electron transfer between the reaction partners. Reaction of the red [Ru(II)(EDTA)pz](2-) complex with molecular oxygen regenerates the [Ru(III)(EDTA)pz](-) species in the reacting system along with the formation of H2O2, a partially reduced product of dioxygen (O2) reduction. A detailed reaction mechanism in agreement with the spectral and kinetic data is presented.
Assuntos
Complexos de Coordenação/química , Ácido Edético/química , Sulfeto de Hidrogênio/química , Oxigênio/química , Rutênio/química , Catálise , Concentração de Íons de Hidrogênio , Cinética , Oxirredução , TemperaturaRESUMO
Reported is the first example of a ruthenium(III)-complex, Ru(III)(EDTA) (EDTA(4-) = ethylenediaminetetraacetate), that mediates O-atom transfer from nitrite to the biological thiols cysteine and glutathione, leading to the formation of [Ru(III)(EDTA)(NO(+))](0). However, at pH below 5.0, the coordinated nitrite ion in the [Ru(III)(EDTA)(NO2)](2-) complex undergoes proton-assisted decomposition, resulting in the formation of a [Ru(III)(EDTA)(NO(+))](0) species.
Assuntos
Complexos de Coordenação/química , Ácido Edético/química , Nitritos/química , Rutênio/química , Catálise , Concentração de Íons de Hidrogênio , Conformação Molecular , Oxirredução , Espectrofotometria InfravermelhoRESUMO
The [Ru(III)(edta)(H2O)](-) (edta(4-) = ethylenediaminetetraacetate) complex catalyzes the oxidation of azide (N3(-)) with H2O2, mimicking the action of metallo-enzymes such as catalase and peroxidase in biochemistry. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid-scan spectrophotometry as a function of [Ru(III)(edta)], [H2O2], [N3(-)] and pH. The catalytic activity of the different oxidizing species produced in the reaction of [Ru(III)(edta)(H2O)](-) with H2O2 for the oxidation of azide was compared to the oxidation of coordinated azide in [Ru(III)(edta)N3](2-) by H2O2. Detailed reaction mechanisms in agreement with the spectroscopic and kinetic data are presented for both reaction paths.
Assuntos
Azidas/química , Complexos de Coordenação/química , Ácido Edético/química , Peróxido de Hidrogênio/química , Rutênio/química , Catálise , Concentração de Íons de Hidrogênio , Cinética , OxirreduçãoRESUMO
Reported here is the first example of a ruthenium(iii) complex [Ru(III)(EDTA)(H2O)](-) (EDTA(4-) = ethylenediaminetetraacetate) that mediates S-nitrosylation of cysteine in the presence of nitrite at pH 4.5 (acetate buffer) and results in the formation of [Ru(III)(EDTA)(SNOCy)](-). The kinetics of the reaction was studied by stopped-flow and rapid-scan spectrophotometry as a function of [Cysteine], [NO2(-)] and pH (3.5-8.5). Formation of [Ru(III)(EDTA)(SNOCy)](-), the product of the S-nitrosylation reaction, was identified by ESI-MS experiments. A working mechanism in agreement with the spectroscopic and kinetic data is presented.
Assuntos
Complexos de Coordenação/química , Cisteína/química , Ácido Edético/química , Nitritos/química , Rutênio/química , Concentração de Íons de Hidrogênio , Cinética , EspectrofotometriaRESUMO
Reported is the first example of a ruthenium(III) complex, Ru(III)(edta) (edta(4-) = ethylenediaminetetraacetate), that catalyzes the disproportion of H2O2 to O2 and water in resemblance to catalase activity, and shedding light on the possible mechanism of action of the [Ru(V)(edta)(O)](-) formed in the reacting system.
Assuntos
Catalase/metabolismo , Compostos Organometálicos/metabolismo , Rutênio/metabolismo , Materiais Biomiméticos/química , Materiais Biomiméticos/metabolismo , Catálise , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/metabolismo , Estrutura Molecular , Compostos Organometálicos/química , Oxigênio/química , Oxigênio/metabolismo , Rutênio/química , Água/química , Água/metabolismoRESUMO
Reported here is the first example of a ruthenium complex, [Ru(III)(edta)(H(2)O)](-) (edta(4-) = ethylenediaminetetraacetate), that catalyzes the oxidation of thiourea (TU) in the presence of H(2)O(2). The kinetics and mechanism of this reaction were investigated in detail by using rapid-scan spectrophotometry as a function of both the hydrogen peroxide and thiourea concentrations at pH 4.9 and 25 °C. Spectral analyses and kinetic data clearly support a catalytic process in which hydrogen peroxide reacts directly with thiourea coordinated to the Ru(III)(edta) complex. HPLC product analyses revealed the formation of formamidine disulfide (TU(2)) as a major product at the end of the catalytic process, however, formation of other products like thiourea dioxide (TUO(2)), thiourea dioxide (TUO(3)) and sulfate was also observed after longer reaction times. Catalytic intermediates such as [Ru(III)(edta)(OOH)](2-) and [Ru(V)(edta)(O)](-) were evidently found to be non-reactive in catalyzing the oxidation of thiourea by H(2)O(2) under the specified conditions.
Assuntos
Complexos de Coordenação/química , Ácido Edético/química , Peróxido de Hidrogênio/química , Rutênio/química , Tioureia/análogos & derivados , Catálise , Concentração de Íons de Hidrogênio , Cinética , Oxirredução , Espectrofotometria Ultravioleta , Tioureia/químicaRESUMO
The [Ru(III)(edta)(H2O)](-) (edta(4-) = ethylenediaminetetraacetate) complex is shown to catalyze the oxidation of thiocyanate (SCN(-)) with H2O2 mimicking the action of peroxidases. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid scan spectrophotometry as a function of [Ru(III)(edta)], [H2O2], [SCN(-)], pH (3.2-9.1) and temperature (15-30 °C). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which hydrogen peroxide reacts directly with thiocyanate coordinated to the Ru(III)(edta) complex. Catalytic intermediates such as [Ru(III)(edta)(OOH)](2-) and [Ru(V)(edta)(O)](-) were found to be non-reactive in the oxidation process under the specified conditions. Formation of SO4(2-) and OCN(-) was identified as oxidation products in ESI-MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented.
Assuntos
Ácido Edético/química , Peróxido de Hidrogênio/química , Compostos Organometálicos/química , Rutênio/química , Tiocianatos/química , Água/química , Catálise , Cianatos/síntese química , Cianatos/química , Concentração de Íons de Hidrogênio , Conformação Molecular , Compostos Organometálicos/síntese química , Oxirredução , Sulfatos/síntese química , Sulfatos/química , TemperaturaRESUMO
The oxidation of [Ru(II)(tpy)(pic)H(2)O](+) (tpy = 2,2',6',2''-terpyridine; pic(-) = picolinate) by peroxidisulfate (S(2)O(8)(2-)) as precursor oxidant has been investigated kinetically by UV-VIS, IR and EPR spectroscopy. The overall oxidation of Ru(II)- to Ru(IV)-species takes place in a consecutive manner involving oxidation of [Ru(II)(tpy)(pic)H(2)O](+) to [Ru(III)(tpy)(pic)(OH)](+), and its further oxidation of to the ultimate product [Ru(IV)(tpy)(pic)(O)](+) complex. The time course of the reaction was followed as a function of [S(2)O(8)(2-)], ionic strength (I) and temperature. Kinetic data and activation parameters are interpreted in terms of an outer-sphere electron transfer mechanism. Anti-microbial activity of Ru(II)(tpy)(pic)H(2)O](+) complex by inhibiting the growth of Escherichia coli DH5α in presence of peroxydisulfate has been explored, and the results of the biological studies have been discussed in terms of the [Ru(IV)(tpy)(pic)(O)](+) mediated cleavage of chromosomal DNA of the bacteria.
Assuntos
Anti-Infecciosos/química , Compostos Organometálicos/química , Peróxidos/química , Rutênio/química , Sulfatos/química , Anti-Infecciosos/farmacologia , Carga Bacteriana , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Cinética , Compostos Organometálicos/farmacologia , Concentração Osmolar , Oxirredução , Ácidos Picolínicos/química , Ácidos Picolínicos/farmacologia , Piridinas/química , Piridinas/farmacologia , Rutênio/farmacologiaRESUMO
The kinetics of the Ru(III)-(edta) (edta(4-) = ethylenediaminetetraacetate) catalyzed oxidation of l-arginine by H(2)O(2) mimicking the action of nitric oxide synthases (NOSs) has been studied spectrophotometrically. The time course of the reaction of [Ru(V)(edta)O](-) with l-arginine was followed at 390 nm under catalytic turn-over conditions. Formation of NO in the reacting system has been confirmed with an isolated nitric oxide free radical analyzer. A detailed reaction mechanism in agreement with the spectral and kinetic data is presented.
Assuntos
Arginina/química , Complexos de Coordenação/química , Ácido Edético/química , Peróxido de Hidrogênio/química , Óxido Nítrico/química , Rutênio/química , Catálise , Cinética , Óxido Nítrico Sintase/metabolismo , Oxirredução , Espectrofotometria UltravioletaRESUMO
The kinetics of reduction of [Ru(III)(edta)pz]â» (edta4â» = ethylenediaminetetraacetate; pz = pyrazine) by thioamino acids (RSH = cysteine, glutathione) resulting in the formation of a red [Ru(II)(edta)pz]²â» species (λ(max) = 462 nm) has been studied spectrophotometrically using both conventional mixing and stopped-flow techniques. The time course of the reaction was followed as a function of [RSH], pH, temperature and pressure. Alkali metal ions were found to have a positive influence (K(+) > Na(+) > Li(+)) on the reaction rate. Kinetic data and activation parameters are interpreted in terms of a mechanism involving outer-sphere electron transfer between the reaction partners. A detailed reaction mechanism in agreement with the spectral and kinetic data is presented.