• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 54
  • 40
  • 13
  • 8
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 147
  • 28
  • 26
  • 25
  • 18
  • 17
  • 17
  • 16
  • 10
  • 9
  • 9
  • 9
  • 9
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Jacob Ruff's Adam und Heva (1550) : a critical edition with introduction and notes

Whitelaw, Janice Kay January 1998 (has links)
Jacob Ruff's Adam und Heva, written in 1550 by the Zurich town surgeon with the dual purpose of entertaining and instructing Zurich's citizens in the new Protestant faith, is important for the way in which Ruff, a follower of the Swiss reformer, Zwingli, was intent on using images from the Old Testament to dramatise the Reformation tenets of sola scriptura, sola fide and sola gratia on the open-air stage of the Miinsterhof in Zurich. The original Froschauer print of 1550, of which there are four copies still extant in libraries in Zurich, St. Gallen, Munich and Berlin, has, until more recent years, been neglected by scholarship, and the last major study of the drama, which takes place over two days and involves a cast of one hundred and six, was the 1848 edition by the German literary historian, Hermann Marcus Kottinger. In the present study, I provide a critical edition which seeks to make the Adam und Heva more accessible to the modern reader, and also a commentary, in which I undertake a detailed analysis of the way in which Ruff pursues a more medieval syncretism by fusing various dramatic elements of the Middle Ages with what is nevertheless a Reformation theology, thereby incoporporating medieval and contemporary thought in a medieval and modern framework, and creating some of the most innovative scenes in the long tradition of medieval creation literature. In addition, by comparing the Adam una Heva to the works of contemporaries of Ruff, namely the Swiss Reformation dramatists Hans von Rote and Jos Murer, and the Germans, Valten Voith and Hans Sachs, I study how elements of the drama of the Middle Ages could exist alongside the external and contemporary influences of the Swiss and German literary traditions, and how Swiss drama, largely neglected by the literary historian, may be placed firmly within the German evangelical dramatic tradition.
12

ENHANCING GAS PHASE FISCHER-TROPSCH SYNTHESIS CATALYST DESIGN

Dasgupta, Debalina 01 January 2008 (has links)
This dissertation research resulted in the development of a Fe based catalyst with Co as a co catalyst, and Ru and ZnO as promoters. The role of Cu and K as promoters and the effect of SiO2 as an alternate support to gamma- Al2O3 were also investigated. A series of Fe-based catalysts for Fischer-Tropsch (F-T) synthesis were prepared. The different promoters were incorporated into the catalyst by impregnation The catalysts were characterized by several methods. The catalytic performance of these materials for F-T synthesis were investigated in a newly designed fixed bed reactor system in the gas phase. It should be noted that the three phase slurry bubble reactors systems are commercially preferred. The reaction conditions were varied for benchmarking the Fe-Zn-K/ gamma- Al2O3 catalyst and for the bimetallic Fe-Co-Zn/ gamma- Al2O3 catalyst and to identify optimal process parameters for further catalyst designs. The H2:CO ratio used in this study was 2. The newly designed catalysts showed significantly high activity towards CO conversion (>70 %), along with low selectivity towards CO2 (5 -15 %) and methane (ND - 3 %). The data show that varying the process conditions, it is possible to achieve narrow distribution of the liquid products. The results employing Fe-Zn-K catalysts showed that an increase in pressure increased the mean carbon chain length. In contrast, an increase in temperature resulted in a decline in the average carbon chain length. Increasing the feed flow rate, or in other words decreasing the residence time of the reactants and the intermediates, resulted in a decrease in the average carbon number in the product hydrocarbons. The evaluation of the effect of process conditions on the performance of Fe-Co-Zn catalysts revealed that the effect of pressure on the carbon chain length was reversed. Increasing the pressure from 250 to 350 psig decreased the carbon chain length. The increase in temperature, however, resulted in a decrease in the carbon chain length as observed in the Fe-Zn-K catalysts. Fe catalysts groups containing different proportions of Co were prepared. It was determined that an Fe:Co ratio of 4:1 is sufficient to obtain high CO conversions with a high selectivity towards liquid hydrocarbons. The hydrocarbon distribution on the other hand remained almost unchanged due to a change in the Co content. The use of silica, as opposed to alumina as the catalyst support, enhanced the CO conversion and the selectivity of the process towards liquid hydrocarbons. The methane and CO2 selectivities on both the supports remained unchanged. However, a significant difference in the liquid hydrocarbon distribution was observed. Addition of K to the catalyst resulted in a change in the liquid hydrocarbon distribution in that a slight increase in the heavier hydrocarbons was observed. A series of Fe4Co1Zn0.04 based catalysts for Fischer-Tropsch (F-T) synthesis, in which the different amounts of Ru are incorporated by the impregnation were also studied. The results showed the incorporation of Ru suppressed the CH4 formation at the cost of increasing the CO2 selectivity.
13

ENSAIO ELETROMAGN?TICO BASEADO NO RU?DO DE BARKHAUSEN PARA ACOMPANHAMENTO DE FORMA??O DE FASE

Carvalho Filho, Jos? Adeilton 27 April 2018 (has links)
Submitted by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-06-05T13:53:31Z No. of bitstreams: 1 50- Jos? Adeilton de Carvalho Filho - ENSAIO ELETROMAGN?TICO BASEADO NO RU?DO DE BARKHAUSEN PARA ACOMPANHAMENTO DE TRANSFORMA??ES MICROESTRUTURAIS.pdf: 2334721 bytes, checksum: cac8178284a5f34e1858292feb29e043 (MD5) / Approved for entry into archive by Programa de P?s-Gradua??o Engenharia El?trica (ppgee@ifpb.edu.br) on 2018-06-05T13:59:49Z (GMT) No. of bitstreams: 1 50- Jos? Adeilton de Carvalho Filho - ENSAIO ELETROMAGN?TICO BASEADO NO RU?DO DE BARKHAUSEN PARA ACOMPANHAMENTO DE TRANSFORMA??ES MICROESTRUTURAIS.pdf: 2334721 bytes, checksum: cac8178284a5f34e1858292feb29e043 (MD5) / Made available in DSpace on 2018-06-05T13:59:49Z (GMT). No. of bitstreams: 1 50- Jos? Adeilton de Carvalho Filho - ENSAIO ELETROMAGN?TICO BASEADO NO RU?DO DE BARKHAUSEN PARA ACOMPANHAMENTO DE TRANSFORMA??ES MICROESTRUTURAIS.pdf: 2334721 bytes, checksum: cac8178284a5f34e1858292feb29e043 (MD5) Previous issue date: 2018-04-27 / O ru?do de Barkhausen ? utilizado em ensaios eletromagn?ticos para acompanhamento de fases em materiais ferromagn?ticos. Esse ru?do ? gerado da intera??o de uma onda emitida por uma bobina e uma induzida em outra posicionada no material. As caracter?sticas da onda emitida como frequ?ncia e amplitude e da bobina receptora variam nesses experimentos e dificultam a padroniza??o. No presente trabalho ? realizado um estudo para determina??o da frequ?ncia e amplitude ideais da onda emissora capaz de gerar o ru?do Barkhausen, ao passar numa microestrutura formada de precipitados finamente distribu?dos dentro do material. Esta onda ideal ? em seguida utilizada para acompanhar o endurecimento e capacidade de absorver energia por impacto de um a?o inoxid?vel duplex, na temperatura de fragiliza??o de 475 ?C, por tempos de tratamentos at? 100 horas. Ondas emissoras com frequ?ncia de 5, 25, 75 e 100 Hz e amplitudes de 1, 3, 5, 7 e 9 V foram utilizadas. Medidas de raiz m?dia quadr?tica foram utilizadas como par?metro de medi??o do ru?do de Barkhausen. Os sinais obtidos na bobina leitora foram passados para o dom?nio da frequ?ncia e utilizados por diferentes filtros passa alta. Os resultados foram correlacionados com medidas de dureza Rockwell C e energia absorvida por impacto. A configura??o utilizada mostrou ser capaz de registrar o ru?do de Barkhausen e uma onda emissora de frequ?ncia de 5 Hz e amplitude de 3 V foi determinada entre as estudadas como ideal. Esta onda, ao ser aplicada para acompanhamento do endurecimento do a?o inoxid?vel mostrou ter valores de RMS crescentes no primeiro estagio de endurecimento, maior taxa, e descrever no segundo de menor taxa, refletindo que o efeito paramagn?tico da fase formada reduz os efeitos de RMS no segundo estagio. Al?m disso, foi capaz de acompanhar a redu??o da energia absorvida por impacto das amostras estudadas. Tudo isso mostrando que os valores de medida de RMS podem ser utilizados como par?metro para acompanhamento de precipitados finos dentro do material estudado.
14

Metal Nanoparticles Over Active Ionic-Conductive Supports for the Reverse Water Gas Shift Reaction

Einakchi, Raha January 2016 (has links)
Increase in carbon dioxide emissions due to economic activity induce global warming. The strong increase in energy demand, mainly based on oil and coal, induces a rapid increase in CO2 in the atmosphere. Within Canada, the amount of human-produced carbon dioxide is considerable because a large portion of energy is supplied by burning of fossil fuels. The Reverse Water Gas Shift (RWGS) reaction is a promising catalytic process for the utilization and subsequent activation of carbon dioxide to carbon monoxide, which can be further converted into fuels such as gasoline. The current thesis studies the development of nano-catalytic systems for the RWGS reaction. Mono- and bi-metallic nanoparticles based on Cu, Fe, Ru and Pt were prepared using a polyol synthesis method. The catalytic performance of three different types of metal oxides (ionically conductive, mixed ionic-electronic conductive and non-conductive) was investigated for the RWGS reaction. Conductive metal oxides including samarium-doped ceria (SDC), ceria (CeO2), yttria-stabilized zirconia (YSZ) and iron III oxide (Fe2O3) were further used as the catalyst supports and the nanoparticles of Cu, Fe, CuxFe1-x (x = 50 and 95 at.%), Ru, Pt, Ru50Pt50 and RuxFe1-x (x = 80 and 90 at.%) were subsequently deposited on them. A stoichiometric mixture of H2 and CO2, i.e. H2/CO2 = 1, was used under atmospheric pressure in the temperature range of 300 - 600°C in order to evaluate the catalyst performance in terms of activity, stability and selectivity. Nanoparticles deposited on ceria-based supports (CeO2 and SDC) showed superior catalytic performance compared to other metal oxides. Among all the catalyst tested, 5 wt.% Ru50Pt50/CeO2 showed the highest CO yield and satisfactory stability for RWGS reaction. The second best catalytic systems were based on Ru90Fe10/CeO2 and Ru80Fe20/CeO2, which are more attractive from the practical point of view.
15

Low Power Photoluminescence and Photochemical Upconversion

Islangulov, Radiy Rashitovich 02 November 2006 (has links)
No description available.
16

The effectiveness of flowers as a change element in the office environment on the attitudes of employees

Thompson, Janet Leigh January 1983 (has links)
No description available.
17

Modèles fonctionnels d’hydrogénases [NiFe]

Pieri, Cyril 09 November 2012 (has links)
Les sources d'approvisionnement en énergie proviennent essentiellement des matières fossiles, qui se raréfient et dont la combustion relargue dans l'atmosphère des polluants et gaz à effet de serre.Un vecteur d'énergie apparaît comme l'avenir pour subvenir aux besoins énergétiques de la planète : l'hydrogène ; cependant, son coût de production reste très élevé.Dans la nature, des enzymes, les hydrogénases, sont capables de produire et d'oxyder l'hydrogène de manière très efficace. Les scientifiques se sont alors inspirés de ces enzymes afin de concevoir des complexes qui seraient des catalyseurs bien plus robustes pour produire de l'hydrogène.Au cours de cette thèse, nous avons pris comme source d'inspiration les hydrogénases [NiFe], dont le site actif est composé d'un coeur bimétallique Ni-Fe coordiné par quatres ligands thiolates.Nous avons synthétisé divers ligands en vue d'obtenir des complexes polymétalliques de Ni, Fe ou Ru, rassemblant ce qui semble être quelques unes des propriétés clés de l'activité des hydrogénases [NiFe] : ligands thiolate sur le nickel, dont deux pontants avec le second métal, géométrie tétraédrique du nickel. Pour cela, de nouvelles familles de ligands polythiolates ont été conçues et préparées.Les complexes ainsi préparés ont été caractérisés et leur activité évaluée par différentes techniques, dont la voltammétrie cyclique et l'électrolyse couplé à une GC, qui nous ont permis d'évaluer l'activité de nos catalyseurs (TON, TOF, surtension). Un des catalyseurs actifs a été utilisé comme support pour des simulations en DFT qui nous ont aidés à mieux comprendre le mécanisme catalytique de production d'hydrogène. / The energy supply sources are mainly based on fossil materials which are growing scarce and release pollutants and greenhouse gases.In this context, an energy vector appears as the future to feed the energetic needs of the planet: the Hydrogen; but its current production costs remain very high.Nature has deviced enzymes, hydrogenases, able to produce and oxidize hydrogen very efficiently. Nevertheless, the manipulation of these organisms is not easy, notably because of their susceptibility (oxygen inhibition, organic solvents, high temperatures), and their production costs are high.So, scientists have taken this inspiration source in order to design biomimetic and bioinspired models, which would much more robust and cheap catalysts to produce hydrogen.During this thesis, we have drawn our inspiration from [NiFe] hydrogenases, where the active site is a Ni-Fe core coordinated by four thiolate ligands. Our goal has been to design new polythiolate ligands, that gather some of the key hydrogenases [NiFe] properties responsible for their activity: thiolate ligands on the nickel, among them two brinding with the second metal, nickel tetraedric geometry.The synthesised complexes have been characterized and their activity tested (TON, TOF, overvoltage) by different techniques, among them cyclic voltammetry and electrolysis coupled to a GC.Finally, the bests have been tested further, thank to bulk electrolysis, which, coupled to a GC system, has enabled us to qualify and quantify the hydrogen production.One of our most active catalysts has been used as a support for DFT calculations, helping us to better undersand the catalytic hydrogen evolving mechanism.
18

Comportamento em solução de P(OH)(OEt)2 e P(OH)3 coordenados a tetraaminas de Ru(II) / Behavior in solution of P(OH)(OEt)2 and P(OH)3 coordinated to ruthenium(II) tetraammines

Truzzi, Daniela Ramos 19 February 2010 (has links)
A estabilidade do ligante dietil fosfito foi analisada por 1H RMN em solução pH 1,0 e 3,0 a 25°C na presença e na ausência do íon [RuII(H2O)(NH3)5]2+. A hidrólise do dietil fosfito livre não foi observada em pH 3,0, enquanto na presença do íon [RuII(H2O)(NH3)5]2+, neste mesmo pH, esta reação foi observada (kobs=1,0.10-4 s-1). Em solução pH 1,0 a hidrólise ocorre tanto na presença do centro metálico (kobs=6,2.10-4 s-1) quanto na ausência (kobs=1,8.10-4 s-1). O complexo trans-[RuII(NO+)(NH3)4P(OH)3](Cl)3 foi sintetizado e caracterizado por técnicas espectroscópicas e espectrofotométricas. O espectro vibracional no estado sólido indicou que a νNO+ ocorre em duas frequências diferentes (1903 e 1867 cm-1) devido à presença do ligante P(OH)3 na forma protonada e desprotonada. O ENO+/NO0 foi determinado por Voltametria Cíclica em -0,52 V vs. ECS (0,5 mol L-1 CF3COOH, 25°C). O espectro eletrônico deste complexo apresentou três bandas nas regiões de 241nm (ε=1385 mol-1 L cm-1), 319 nm (ε=773 mol-1 L cm-1) e 500 nm (ε=20 mol-1 L cm-1). O valor de pKa para o ácido fosforoso no íon complexo trans-[RuII(NO+)(NH3)4P(OH)3]3+ foi determinado por meio de Espectroscopia Vibracional em solução (pKa=0,74 ±0,05). Como confirmado por Uv-vis, Voltametria Cíclica e Espectroscopia Vibracional, o íon trans-[RuII(NO+)(NH3)4P(OH)3]3+ sofre reação de aquação, dando origem ao ácido fosforoso livre e ao íon complexo trans-[RuII(NO+)(NH3)4(H2O)]3+ (λ=322 nm - ε=297 mol-1 L cm-1; ENO+/NO0=-0,40 vs. ESC; νNO+= 1849 cm-1). Dados de 31P RMN e Espectroscopia Vibracional sugerem que, anterior à dissociação do ligante P(OH)3, ocorre a formação de isômeros em que o ácido fosforoso pode estar coordenado ao centro metálico também pelo átomo de oxigênio. Os dados de experimentos cinéticos indicam que a dissociação do P(OH)3 é dependente da concentração hidrogeniônica do meio. / The stability of the ligand diethyl phosphite was analyzed by 1H NMR in solution at pH 1.0 and 3.0 and 25°C in the presence and in the absence of the ion [RuII(H2O)(NH3)5]2+. The hydrolysis of the free diethyl phosphite in solution at pH 3.0 was not observed, while in the presence of the ion [RuII(H2O)(NH3)5]2+, at this same pH, the reaction took place with kobs=1.0 10-4 s-1. In solution at pH 1.0 the hydrolysis reaction took place in the presence (kobs=6.2 10-4 s-1) and in the absence (kobs=1.8 10-4 s-1) of the metal center. The complex trans-[RuII(NO+)(NH3)4P(OH)3](Cl)3 was synthesized and characterized by spectroscopic and spectrophotometric techniques. Vibrational spectra showed a νNO+ in the solid state at two differents frequencies (1903 and 1867 cm-1) due to the presence of the ligand P(OH)3 in the protonated and deprotonated forms. The ENO+/NO0 was determined by Cyclic Voltammetry at -0.52 V vs. SCE (0.5 mol L-1 CF3COOH, 25°C). The electronic spectrum of this complex exhibited three bands at 241nm (ε=1385 L mol-1 cm-1), 319 nm (ε=773 L mol-1 cm-1) and 500nm (ε=20 mol L-1 cm-1). The pKa value for the phosphorous acid in the complex íon trans-[RuII(NO+)(NH3)4P(OH)3]3+ was determined by Vibrational Spectroscopy in solution (pKa=0.74 ± 0.05). As judged from UV-vis, Cyclic Voltammetry and Vibrational Spectroscopy the ion trans-[RuII(NO+)(NH3)4P(OH)3]3+ suffer aquation reaction yelding free phosphorous acid and the ion complex trans-[RuII(NO+)(NH3)4(H20)]3+ (λ=322 nm - ε=297 L mol-1 cm-1; ENO+/NO0=-0.40 vs. SCE; νNO+= 1893 cm-1). 31P NMR and Vibrational Spectroscopy data suggest that, before the dissociation of the P(OH)3 ligand, occurs the formation of linkage isomers in which the phosphorous acid can be coordinated to the metal center also by the oxygen atom. The data obtained by kinetics experiments suggest that the P(OH)3 dissociation is dependent of the hydrogen ionic concentration of the medium.
19

Sínteses de monômeros derivatizados com 3-aminopiridina contendo complexos polipiridínicos de Ru(II) do tipo cis-[RuCl2(α-diimina)] onde α-diimina: 2,2᾿-bipiridina e 1,10-fenantrolina e 5-Cl-1,10-fenantrolina / Synthesis of monomers derivatized with 3-aminopyridine containing complexes of ruthenium(II) of type cis-[RuCl2(α-diimine)]where α-diimine: 2,2᾿-bipyridine and 1,10-phenantroline and 5-Cl-1,10-phenantroline

Santos, Evania Danieli Andrade 13 March 2009 (has links)
Os monômeros ligantes 3amdpy2oxaNBE (1), 3imdpyoxaNBE (2) e ácido âmico (3) foram sintetizados e caracterizado por analise elementar (CHN), infravermelho e RMN 1H e 13C. A partir do monômero 1 sintetizou-se compostos partindo de complexos do tipo [RuCl2(LL)], onde foi LL=bpy 37 (complexo 4), phen (complexo 6) ou 5-Cl-phen (complexo 7), e foram realizados estudos de fotoquímica e fotofísica. Os complexos 6 e 7 apresentaram uma eficiente fotofísica e não apresentaram fotoquímica, enquanto os complexos semelhante [Ru(bpy)2(3amnpy)2](PF6)2 (5) e [Ru(phen)2(3amnpy)2](PF6)2 (8) que possui a aminopiridina no lugar do monômero 1, apresentaram fotoquímica. Observou-se que as diferenças na rigidez dos ligantes phen e bpy podem causar diferentes propriedades fotoquímicas e fotofísicasem sistemas do tipo cis-[RuCl2(?-diimina)]. Todos os complexos exibiram absorções na região de 350 nm e entre 420 a 500 nm. Sendo que 5 e 8 apresentaram fotoquímica e os complexos 6 e 7 apresentaram fotofisica. Estes foram estudados em diferentes solventes (DMF, CH3CN, CH2Cl2, THF) e em diferentes comprimentos de onda de irradiação (340, 440 e 500 nm). A emissão dos complexos 6 (580 nm) e 7 (582 nm) em acetonitrila é atribuída a uma MLCT (Ru_phen). Sendo observada a independência do _irr, mas existe dependência da emissão quando a temperatura é abaixada. Além disso, suas propriedades fotocatalíticas são demonstradas pela supressão oxidativa através de íons receptores do metilviologenio. Ainda deve-se levar em conta que, o anel quelante do monômero ligante 1 contribui ainda mais para a estabilização destes complexos, ao contrario, 5 e 8 possuem uma fotolabilização . / The monomer ligands 3amdpy2oxaNBE (1), 3imdpyoxaNBE (2) and amic acid (3) were synthesized and characterized by elementar analysis (CHN), infrared and 1H e 13C NMR. Since monomer 1, it was synthesized complexes of type [RuCl2(LL)], where LL=bpy 37 (complex 4), phen (complex 6) or 5-Cl-phen (complexo 7), with which photophysics and photochemical studies were performed. The complexes 6 and 7 presented efficient photophysics and they do not presented photochemistry, while the similar complexes [Ru(bpy)2(3amnpy)2](PF6)2 (5) and [Ru(phen)2(3amnpy)2](PF6)2 (8), which possess the aminopyridine in place of monomer 1, presented photochemistry. It was observed that the difference in the rigidity of the ligands phen and bpy may cause different photochemical and photophysical properties in systems of type cis-[RuCl2(?- diimine)]. All complexes exhibited absorptions in region of 350 nm and between 420 and 500 nm, where 5 and 8 presented photochemistry and the complexes 6 and 7 presented photophysics. They were studied in different solvents (DMF, CH3CN, CH2Cl2, THF) and in different irradiation wavelength (340, 440 e 500 nm). The emission of the complexes 6 (580 nm) and 7 (582 nm) in acetonitrile is attributed to an MLCT (Ru_phen). It was observed independence of _irr, however there is dependence of emission when the temperature is lowered. Furthermore, their photocatalytic properties are demonstrated by oxidative quenching using methylviologen ion. One should consider that the chelating ring of monomer ligand 1 contributes even more to the stabilization of these complexes, unlike, 5 and 8 that possess photolabilization.
20

Comportamento em solução de P(OH)(OEt)2 e P(OH)3 coordenados a tetraaminas de Ru(II) / Behavior in solution of P(OH)(OEt)2 and P(OH)3 coordinated to ruthenium(II) tetraammines

Daniela Ramos Truzzi 19 February 2010 (has links)
A estabilidade do ligante dietil fosfito foi analisada por 1H RMN em solução pH 1,0 e 3,0 a 25°C na presença e na ausência do íon [RuII(H2O)(NH3)5]2+. A hidrólise do dietil fosfito livre não foi observada em pH 3,0, enquanto na presença do íon [RuII(H2O)(NH3)5]2+, neste mesmo pH, esta reação foi observada (kobs=1,0.10-4 s-1). Em solução pH 1,0 a hidrólise ocorre tanto na presença do centro metálico (kobs=6,2.10-4 s-1) quanto na ausência (kobs=1,8.10-4 s-1). O complexo trans-[RuII(NO+)(NH3)4P(OH)3](Cl)3 foi sintetizado e caracterizado por técnicas espectroscópicas e espectrofotométricas. O espectro vibracional no estado sólido indicou que a νNO+ ocorre em duas frequências diferentes (1903 e 1867 cm-1) devido à presença do ligante P(OH)3 na forma protonada e desprotonada. O ENO+/NO0 foi determinado por Voltametria Cíclica em -0,52 V vs. ECS (0,5 mol L-1 CF3COOH, 25°C). O espectro eletrônico deste complexo apresentou três bandas nas regiões de 241nm (ε=1385 mol-1 L cm-1), 319 nm (ε=773 mol-1 L cm-1) e 500 nm (ε=20 mol-1 L cm-1). O valor de pKa para o ácido fosforoso no íon complexo trans-[RuII(NO+)(NH3)4P(OH)3]3+ foi determinado por meio de Espectroscopia Vibracional em solução (pKa=0,74 ±0,05). Como confirmado por Uv-vis, Voltametria Cíclica e Espectroscopia Vibracional, o íon trans-[RuII(NO+)(NH3)4P(OH)3]3+ sofre reação de aquação, dando origem ao ácido fosforoso livre e ao íon complexo trans-[RuII(NO+)(NH3)4(H2O)]3+ (λ=322 nm - ε=297 mol-1 L cm-1; ENO+/NO0=-0,40 vs. ESC; νNO+= 1849 cm-1). Dados de 31P RMN e Espectroscopia Vibracional sugerem que, anterior à dissociação do ligante P(OH)3, ocorre a formação de isômeros em que o ácido fosforoso pode estar coordenado ao centro metálico também pelo átomo de oxigênio. Os dados de experimentos cinéticos indicam que a dissociação do P(OH)3 é dependente da concentração hidrogeniônica do meio. / The stability of the ligand diethyl phosphite was analyzed by 1H NMR in solution at pH 1.0 and 3.0 and 25°C in the presence and in the absence of the ion [RuII(H2O)(NH3)5]2+. The hydrolysis of the free diethyl phosphite in solution at pH 3.0 was not observed, while in the presence of the ion [RuII(H2O)(NH3)5]2+, at this same pH, the reaction took place with kobs=1.0 10-4 s-1. In solution at pH 1.0 the hydrolysis reaction took place in the presence (kobs=6.2 10-4 s-1) and in the absence (kobs=1.8 10-4 s-1) of the metal center. The complex trans-[RuII(NO+)(NH3)4P(OH)3](Cl)3 was synthesized and characterized by spectroscopic and spectrophotometric techniques. Vibrational spectra showed a νNO+ in the solid state at two differents frequencies (1903 and 1867 cm-1) due to the presence of the ligand P(OH)3 in the protonated and deprotonated forms. The ENO+/NO0 was determined by Cyclic Voltammetry at -0.52 V vs. SCE (0.5 mol L-1 CF3COOH, 25°C). The electronic spectrum of this complex exhibited three bands at 241nm (ε=1385 L mol-1 cm-1), 319 nm (ε=773 L mol-1 cm-1) and 500nm (ε=20 mol L-1 cm-1). The pKa value for the phosphorous acid in the complex íon trans-[RuII(NO+)(NH3)4P(OH)3]3+ was determined by Vibrational Spectroscopy in solution (pKa=0.74 ± 0.05). As judged from UV-vis, Cyclic Voltammetry and Vibrational Spectroscopy the ion trans-[RuII(NO+)(NH3)4P(OH)3]3+ suffer aquation reaction yelding free phosphorous acid and the ion complex trans-[RuII(NO+)(NH3)4(H20)]3+ (λ=322 nm - ε=297 L mol-1 cm-1; ENO+/NO0=-0.40 vs. SCE; νNO+= 1893 cm-1). 31P NMR and Vibrational Spectroscopy data suggest that, before the dissociation of the P(OH)3 ligand, occurs the formation of linkage isomers in which the phosphorous acid can be coordinated to the metal center also by the oxygen atom. The data obtained by kinetics experiments suggest that the P(OH)3 dissociation is dependent of the hydrogen ionic concentration of the medium.

Page generated in 0.0343 seconds