Dissertations / Theses on the topic 'Nitro compounds. Reduction (Chemistry)'

NRs are enzymes that catalyze the reduction of nitroaromatics to their corresponding nitroso, hydroxylamine, and, in limited cases, amine They have gathered interest in many scientific communities, and are currently actively researched bioremediation and prodrug activation. Here we attempt to utilize them for the purpose of synthesizing substituted aromatic amines that are found in a number of active pharmaceutical ingredients (APIs). As NRs described in the literature have varying product distribution ranges (from those that produce hydroxylamine to others that yield amine) several similar and different NRs were studied for their selectivity. Additionally, a quantitative structure-activity relationship (QSAR) was determined to characterize the substrate specificity of NRs. To employ the use of flavoenzymes in synthesis, multiple reaction- and protein-engineering approaches were devised. One scheme was to establish an enzymo-chemical synthesis where NRs were paired with reducing agents for a chemical reduction. Another method was to create a monomeric NR through directed evolution from ER scaffolds for future immobilization applications. Protein engineering techniques were also utilized on NADH oxidases which we characterized and developed for nicotinamide cofactor regeneration. As a whole, this dissertation expands our current understanding on NRs and demonstrates the possibility of using several flavoenzymes in the synthesis of organic molecules.

The work described in this thesis is a study of iron-sulphur-nitrosyls and related compounds. Chapter One is an introduction to the work presented. Chapter one is introduction to the work presented. Chapter Two is concerned with the analogous Fe2(SR)2(CO)6 and its conversion to Fe2(SR)2(NO)4. Chapter Three is concerned with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 and [Fe4X3(NO)7] (X=S, Se). Chapter four is concerned with an e.p.r. examination with an n.m.r. study of Fe2(SR)2(NO)4, Fe2X4(NO)4 [Fe4X3(NO)7] (X=S,Se). Chapter four is concerned with an e.p.r. examination of Fe2(SR)2(NO)4 and bridging ligand exchange reactions. Chapter Five is concerned with a similar examination of Fe2I2(NO)4.Chapter six is concerned with an examination of ligand exchange processes in Fe4S4(NO)4 and [Fe4S4(NO)4]. Chapter Seven is concerned with an investigation of iron-sulphur protein models and their conversion to iron-nitrosyls.

A polymer bound catalyst is a relatively new type of catalyst. The basis of polymer bound catalysis lies in the chemical attachment of a homogeneous catalyst to a solid support, in our case, polystyrene. Applications of polymer bound catalysts started in the late 1960’s, and have been used in several types of reactions. In some cases such a catalyst offers a series of advantages over the classical models of catalysis, homogeneous and heterogeneous. The hydrogenation of various aromatic and aliphatic nitro compounds, such as nitro-benzene and 2-nitropropane, were performed successfully. The hydrogenation activity in most cases was high, and in some reactions the catalyst was able to hydrogenate molecules that the analogous homogeneous catalyst could not. Different metals; specifically palladium, platinum, nickel, and rhodium, were attached to the polymer and the effects of varying the metal on the activity were studied. Palladium supported catalysts with anthranilic acid as a polymer supported ligand were found to be more active and selective than palladium catalysts with a bipyridyl ligand. Substitution on the aromatic ring of the substrate alters the reaction rate. Steric effects have a large influence over the catalytic activity. Electron withdrawing groups do not alter reaction rates greatly, while resonance effects can increase the rate of reaction. Finally the effect of the reaction conditions (temperature, pressure and time) on the catalyst activity were analyzed.

Some reactions of aromatic nitro-compounds with carbon nucleophiles have been investigated. The techniques used include NMR spectroscopy, UV-visible spectroscopy and stopped-flow spectrophotometry. The initial rapid reactions of carbanions derived from ring-substituted phenylacetonitriles with 1,3,5-trinitrobenzene yield σ-adducts. Carbanions were generated from the phenylacetonitriles by reaction with sodium methoxide in methanol. Values of the equilibrium constants for the deprotonation reaction were determined spectrophotometrically. Rate constants for the σ-adduct forming reactions were measured in methanol using the stopped-flow method. With increasing carbanion reactivity rate constants for the C-C bond forming reaction increase to a limit of circa 10(^9) dm(^3) mol(^-1) s(^-1) close to the diffusion limit. Data were also obtained for reaction of the carbanions with 4-nitrobenzofuroxan and with 4-nitrobenzofurazan.An interesting slower reaction was observed in the reaction of carbanions with 1,3,5- TNB, 4-nitrobenzofuroxan and 4-nitrobenzofurazan. This yields coloured products and the nature of the process has been investigated. Attempts have been made to isolate the σ-adducts formed from carbanions. The adduct formed from 1,3,5-trinitrobenzene and phenylacetonitrile in the presence of triethylamine has been produced in crystalline form. NMR measurements in situ have indicated the formation of adducts from 4-nitrobenzofuroxan and from 4-nitrobenzofiirazan with deuterated nitromethane in the presence of triethylamine.

The central topic of this dissertation is to seek the answer to the question: Is the single transition state model appropriate for (1) the proton transfer reactions of nitroalkanes and (2) the aromatic nucleophilic reactions of trinitroarenes? If not, what are the real mechanisms? This objective has been accomplished by careful kinetic and mechanistic studies which take advantage of modern digital acquisition of absorbance - time data, combined with extensive new data analysis of results from pseudo-first-order kinetic measurements. Several new analysis procedures for pseudo-first-order kinetics that are capable of distinguishing between single-step and multi-step mechanisms have been introduced and intensively confirmed during the application in the kinetic study of the target reactions. The procedures include (1) half-life dependence of apparent rate constant, (2) sequential linear pseudo-first-order correlation, (3) approximate instantaneous rate constant analysis, and (4) time-dependent apparent kinetic isotope effects. Various conventional and nonconventional pseudo-first-order kinetic analyses of the reactions of nitroalkanes in aqueous solutions revealed that the reactions are complex and involve kinetically significant intermediates. The spectral evidence for the formation of reactive intermediates was obtained by carrying out the kinetic experiments at the isosbestic points where changes in reactant and product absorbance cancel. The apparent deuterium kinetic isotope effects studies indicated that the deuterium kinetic isotope effects are not associated with the formation of the intermediates. The observations of anomalous Brønsted exponents previously found for this reaction series could be rationalized well with the complex mechanisms proposed in this work, which indicate that the nitroalkane anomaly does not exist, but arises from an interpretation based upon the incorrect assumption that the reactions follow a simple one-step mechanism. Simulations revealed that the generally accepted competitive mechanism was not appropriate to describe the Meisenheimer complex formation during the reaction of 2,4,6-trinitroanisole with methoxide ion in methanol. This conclusion is supported by the conventional pseudo-first-order kinetic analysis. A reversible consecutive mechanism that accounts for the kinetic behavior has been proposed, which involves an intermediate dianion complex that is formed reversibly from the initial 1,3-σ-complex, and then eliminates methoxide ion to form the 1,1-σ-complex product.

The reactions of cyanide ions with some benzene derivatives activated with electron-withdrawing groups have been studied in methanol, and in DMSO, and in mixtures of these solvents. The studies have involved spectroscopic measurements of reactants, intermediates and products together with kinetic measurements and the isolation of reaction products. The techniques used include uv/visible spectrophotometry, proton N.M.R. spectroscopy, e.s.r. spectroscopy, polarography and H.P.L.C. There is evidence from the reaction of 1,3,5-trinitrobenzene with excess cyanide in methanol that methanolysis of the cyanide ion produces a significant concentration of methoxide ions, which may also attack the substrate. A methanolysis constant of approximately 4xl0(^-4)moldm(^-3) has been calculated, which leads to a value of 13.52 for the pK(_a) of hydrogen cyanide in methanol. The reaction of a slight excess of potassium cyanide with meta-dinitrobenzene in methanol has been previously reported to yield 2-methoxy-6-nitrobenzonitrile. The author has confirmed that this is the major product, although isomeric methoxy- nitrobenzonitriles are also produced in small quantities. The reactions of the possible intermediates, 2,4- and 2,6-dinitrobenzonitrile, with methoxide in methanol have been studied. There is evidence for initial partitioning of the parent between reversible production of solvate, via attack of the methoxide at the cyano group, and irreversible substitution of a nitro group by methoxide. In a second slower stage the solvate is converted, via parent, to substitution products. With the same reagents in DMSO there is evidence for the reversible formation of sigma-adducts by attack at unsubstituted ring positions, followed by the irreversible substitution of niffo groups. There is evidence for common intermediates and products in the reactions oimeta- dinitrobenzene, 2,4-dinitrobenzonitrile and l-fluoro-2,4-dinitrobenzene with cyanide in media rich in DMSO. Under such conditions mera-dinitrobenzene and l-fluoro-2,4- dinitrobenzene undergo reaction to produce 2,4-dinitrobenzonitrile, which then reacts further with excess cyanide to produce two isomeric nitro-dicyanophenols. The natures of these reactions, which involve substitution of a ring hydrogen by a cyano group, are discussed. With a large excess of cyanide in media rich in DMSO l-chloro-, 1-bromo- and l-iodo-2,4-dinitrobenzene yield a product with a uv/vis spectrum similar to 2,4-dinitro- phenoxide. With small excesses of cyanide there is NMR evidence for the production of 5-cyano-2,4-dinitrophenol. Tentative suggestions are made for the possible mechanisms for the production of these species, and comparisons drawn with the reactions of l-fluoro-2,4-dinitrobenzene under similar conditions. A common feature of these reactions is the unusual ability of the cyanide ion to replace a ring hydrogen atom. It is suggested that initial attack of cyanide at unsubstituted ring positions yields anionic adducts which may transfer an electron to yield radicals. The presence of the electron-withdrawing cyano group makes these radicals sufficiently acidic to lose a proton, yielding aromatic radical anions containing cyano substituents. The latter species give rise to the observed products. Evidence is presented for the observation of dicyano-diniffobenzene radical anions.

Kinetic and equilibrium studies of the reactions between three trinitroaromatic species, 1,3,5-trinitrobenzene, ethyl 2,4,6-trmitrophenyl ether and phenyl 2,4,6- trinitrophenyl ether and the ahphatic amines n-butylamine, pyrrolidine and piperidine, in acetonitrile were undertaken. It was found that the reactions between 1,3,5-trinitrobenzene and each amine were too fast to measure. However kinetic information was gamed from the decomposition of the c-adducts formed from1.3.5- trinitrobenzene and both pyrrolidine and piperidme. Both the 3-adduct and the 1-adduct are observed as intermediates m the reaction of the ethyl ether with each amine, though formation of the 3-adduct was too fast to measure by stopped flow spectrometry. Formation of the picramides is subject to general acid catalysis due to the poor leaving group ability of the ethoxide ion. Only the 3-adduct intermediate was observed in the formation of each picramide from the phenyl ether. The fact that the 1-adduct is not seen is attributed to the phenoxide ion being a weaker base and hence a much superior leaving group to the ethoxide ion. The equilibrium constants K(_c,3)º and K(_c,1)º are a factor of ca. 10(^4) smaller in acetonitrile than dimethyl sulphoxide. This is due to acetonitrile being inferior to dimethyl sulphoxide in its ability to solvate charged species. The value of k(AM) for reaction at an unsubstituted position approaches the diffusion controlled Unit of acetonitrile. The reactions of propanal, 2-chloroethanal, 2,2-dichloroethanal and 2,2,2- trichloroethanal (chloral) with ammonia and several primary amines were studied. Only the reactions of ammonia with propanal and 2-chloroethanal produced the corresponding 2,4,6-trisubstituted-l,3,5-hexahydrotriazme.Reactions of the aldehydes with primary ammes yield propylidene imines as relatively stable species. Trimerisation was not observed however the imine may undergo dimerisation together with elimination of amine. Kinetic and equilibrium studies are reported on the formation in acetonitrile of2.4.6- triethyl-l,3,5-hexahydrotriazine, (TEHT), from propanal and ammonia, and also the corresponding decomposition reaction. The equilibrium constant was found to decrease with increasing water content in the acetonitrile which can be attributed to stabilisation of ammonia by the water. Good correlation was achieved for values of the equilibrium constant calculated directly from absorbance measurements and from combination of rate constants obtained from the formation and decomposition reactions.

Anthropogenic volatile organic compounds (VOCs) and semi-volatile organic (SVOCs) compounds are atmospheric pollutants contributing to the photochemical formation of tropospheric ozone. We combined adsorption and UV photolysis techniques for the removal and degradation of selected VOCs and SVOCs. For adsorption, we synthesized magnetite nanoparticles, a naturally occurring material, to avoid unknown detrimental impacts associated with new materials, as was the case with chlorofluorcarbons. The removal efficiency with magnetite was up to 98 % for aromatics, and 30% for light alkanes. Magnetite nanoparticles were regenerated, characterized (TEM, XRD, BET), and reused with no decrease in reported removal efficiencies. Photolysis alone removed up to 30% of aromatics, and less than 20% of light alkanes. The combination of adsorption, and photolysis did not improve the removal efficiency. Adsorption was attributed to London dispersion interactions for light alkanes, and to acid-base properties for aromatics. Reductions by photolysis were attributed to reactive radicals.
Les composés volatiles et semi-volatiles organiques de sources anthropogéniques sont des polluants atmosphériques participant à la formation d'ozone troposphérique. Nous avons associé l'adsorption et la photolyse par rayons ultraviolets, pour enlever et détruire ces composés. Nous avons synthétisé des nanoparticules de magnétite, un matériel abondant dans la nature, afin d'éviter la création d'un autre problème de pollution comme il est parvenu avec l'utilisation des fluorocarbure chlorés. L'efficacité d'enlèvement par adsorption atteint un maximum de 98 % pour les composés aromatiques et un maximum de 30% pour les alcanes légers. Les particules ont été regénérées, caractérisées (MET, XRD, BET), et réutilisées; aucune baisse en efficacité d'enlèvement n'est notée. Les expériences de photolyse atteignent une réduction maximale de 30% pour les composés aromatiques et de 20% pour les alcanes légers. Sous nos conditions expérimentales, aucune amélioration n'est notée par l'association des deux processus (adsorption et photolyse). La réduction par adsorption est attribuée aux forces d'attraction London pour les alcanes et aux propriétés acides et basiques pour les aromatiques. La réduction par photolyse s'explique par la formation de radicaux réactifs.

The electrochemical reduction of a series of quaternary phenacyclammonium and tertiary phenacylsulphonium salts in aqueous solution at a mercury cathode has been investigated using polarography, coulometry, titrimetry and product analysis methods.

The reactions of diagonal and lateral Cp'Re(CO)2Br2 (where Cp' = n5-C5H5, n5-C5Me5) and (n5-CgH7)Re(CO)3 with reducing agents have been examined. Hydride reduction at -78 °C is observed to occur at the Cp ring in both CpRe(CO)2Br2 isomers, affording a thermally unstable [(n4 -C5Hg)Re(CO)2Br2]- complex. The product of hydride ring attack has been characterized by low-temperature IR and 1H NMR measurements in addition to 13C NOE and heteronuclear 2D NMR measurements. Reaction of lateral CpRe(CO)2Br2 with either MeLi or PhLi affords both Cp-ring attack and metalhalogen exchange, [CpRe(CO)2Br]- (1) while t-BuLi reacts exclusively via metal-halogen exchange. diag-CpRe(CO)2Br2 reacts with the above lithium reagents to yield the same metal-halogen exchange anion. Analogous reactions using diag- and lat-Cp*Re(CO)2Br2 (where Cp* = n5-CgMe5) afford only the corresponding rhenium metal-halogen exchange anion, [Cp*Re(CO)2Br] (2). The molecular structures of 1-[Li/15-Crown-5] and 2-PPP were established by X-ray crystallography. 1-[Li/15-Crown-5] crystallizes in the monoclinic space group P21 with a = 10.860(4) A, b = 13.116(5) A, c = 7.417(3) A, B = 105.26(3)0, V = 1018.7(3) A3 , and Z = 2. 2-PPP crystallizes in the orthorhombic space group Pbca with a = 20.646(5) A, b = 17.690(5) A, c = 17.553(3) A, and z = 8. Solution FT-IR studies of 2 in THF reveal the presence of only solvent-separated ion pairs when the gegencation is Li+, K+, or PPP+ from -70 °C to room temperature. 2-Na at room temperature displays a 39:61 mixture of carbonyl oxygen-sodium and solvent-separated ion pairs, respectively. These ion pairs reveals a reversible temperature-dependent equilibrium. The equilibrium constant has been determined by IR band shape analysis over the temperature range -70 °C to room temperature and values of AH and AS are reported. The reaction of the ring-attacked complex, diag-[(n4-C5H6)Re(CO)2Br2]- with PPh3, P(OPh)3, or Me3CNC leads to the formation of the CpRe(CO)2L. Treatment of [Cp'Re(CO)2Br]- with methyltriflate, TFA, and magic ethyl yields the corresponding diag-Cp'Re(CO)2Br(R) (R = CH3, H, C2H5) complexes based on in situ IR analysis. All of these functionalized complexes decomposed in solution over a period of days to give Cp'Re(CO)3 as the only isolable product (20-30 %). The reaction of the [Cp,Re(C0)2Br]- with Bu3SnH at 60 °C leads to the formation of diag-Cp'Re(CO)2(SnBu3)2, which was also synthesized independently by the deprotonation of diag-Cp'Re(CO)2H2 with Et3N in the presence of Bu3SnBr at room temperature. The reaction of Cp'Re(CO)2Br2 with Bu3SnH at room temperature was discovered to afford the dihydride in excellent yield and, thus represents an improved synthetic route for the synthesis of diag-Cp'Re(CO)2H2. The hydride reduction of (n5-CgH7)Re(CO)3 at room temperature leads to the immediate formation of [(n5-CgH7)Re(CO)2H]- complex, which has been characterized by IR analysis and 1H and 13C NMR spectroscopy.

This work investigates polyols – glycerol and sucrose – as an alternative ligand for electroless copper plating systems with reducer formaldehyde. Natural polyols are environmentally friendly, easily bio-degradable materials, but has not been studied enough for suitability for copper plating systems. In order to increase of the efficiency, the electroless copper plating was investigated in ultrasonic milieu to observe how ultrasound impacts the copper plating rate and properties of the obtained coatings. Studies have shown that sucrose and glycerol can be used as ligands in solutions for electroless copper plating. A plating rate of copper under optimum conditions can reach 2.2 m h-1 (sucrose) and 3.4 m h-1 (glycerol) and copper surface roughness factors ranging 8.5 - 25.3 (sucrose) and 2,3 - 4.3 (glycerol). Correlations between dependences on pH observed for copper plating speeds, overpotentials, surface roughness factors, anodic oxidation currents of formaldehyde. A use of ultrasound for electroless copper plating systems change speeds. Depending on the choice of copper plating system and ultrasonic frequency, plating rate can decrease or may increase up to 5 times and can reach high values (10.87 m h-1). The copper surface formed in ultrasound environment more compact, smoother.
Šiame darbe tiriami polihidroksiliai alkoholiai sacharozė bei glicerolis, kaip ligandų alternatyvos cheminio variavimo sistemoms su reduktoriumi formaldehidu. Tai yra ekologiškos, biologiškai lengvai suyrančios medžiagos. Šiame darbe atlikti šių medžiagų kompleksų pusiausvyros skaičiavimai, eksperimentai parodantys sacharozės bei glicerolio praktinį pritaikomumą cheminio variavimo sistemose. Ultragarso poveikio cheminėms sistemoms dėsningumai dar nėra vienareikšmiškai ištirti ir suprasti. Siekiant padaryti cheminį metalų nusodinimą efektyvesniu pastaruoju metu cheminio metalizavimo procesams bandoma taikyti ultragarsą. Atlikti tyrimai parodė, kad naudojant sacharozę ir glicerolį ligandais cheminio variavimo tirpaluose vario nusėdimo greitis optimaliomis sąlygomis siekia atitinkamai 2,2 ir 3,4 m/h, o chemiškai nusodinto vario paviršiaus šiurkštumo faktoriai varijuoja 8,5-25,3 ir 2,3-4,3 ribose. Analizuojant gautus duomenis stebimos koreliacijos tarp vario nusėdimo greičio, viršįtampio, paviršiaus šiurkštumo faktoriaus, formaldehido anodinės oksidacijos srovių maksimumų priklausomybių nuo pH. Ultragarso panaudojimas cheminio variavimo sistemose keičia vario nusėdimo greičius. Priklausomai nuo pasirinktos cheminio variavimo sistemos, ultragarso dažnio ar jo skleidimo būdo vario nusėdimo greitis sumažėja iki visiško proceso sustabdymo arba gali padidėti 2-5 kartus ir pasiekti dideles vertes (10,87 μm/h). Ultragarso aplinkoje dažniausiai susiformuoja kompaktiškesnės, lygesnės... [toliau žr. visą tekstą]

This thesis concerns the development of metal-free applications using diaryliodonium salts. The first project describes an arylation protocol of allylic and benzylic alcohols in aqueous media. The method proceeds under mild conditions and the ether products were obtained in moderate to good yields. The methodology was also expanded to include arylation of phenols, giving diaryl ethers in good to excellent yields. In the second project, an arylation method that included a wider range of aliphatic alcohols was developed. The scope of accessible alkyl aryl ethers was studied and included a comparative study of phenylation and nitrophenylation of various alcohols. Finally, a formal metal-free synthesis of butoxycain was performed, illustrating the applicability of the developed method. The third project focused on the limitations and side reactions occurring in Chapter 2 and 3. First, an approach to access symmetric diaryl ethers via arylation of hydroxide was presented. This reaction gave rise to a number of side products, which we hypothesized to originate from aryne-type intermediates. A mechanism for the formation of these side products was suggested, supported by trapping and deuterium labeling experiments. Oxidation of the alcohol to the corresponding ketone was also observed and the mechanism of this interesting side reaction was investigated. The latter was suggested to proceed via an intramolecular oxidation without the involvement of radicals or arynes. The fourth project covers a method to synthesize highly sterically congested alkyl aryl ethers via arylation of tertiary alcohols using diaryliodonium salts. The method displayed a broad scope of tertiary alcohols and was also suitable for fluorinated alcohols. The final project detailed in this thesis deals with C-arylation with diaryliodonium salts, showcasing nitroalkanes as well as a nitro ester as suitable nucleophiles for metal-free arylation.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.

Title from PDF of title page (University of Missouri--Columbia, viewed on March 2, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Kent S. Gates, Dissertation Supervisor. Vita. Includes bibliographical references.

The enzymatic reduction of a high-valence form of metals to a low-valence reduced form has been proposed as a strategy to treat water contaminated with a range of metals and radionuclides. Metal reduction by sulphate reducing bacteria (SRB) is carried out either chemically (involving reduction by hydrogen sulphide) or enzymatically (involving redox enzymes such as the hydrogenases). While reduction of metal ions by hydrogen sulphide is well known, the enzymatic mechanism for metal reduction is poorly understood. The aims of this study were to investigate the role of SRB in facilitating platinum removal, and to investigate the role of a hydrogenase in platinum reduction in vitro. In order to avoid precipitation of platinum as platinum sulphide, a resting (non-growing) mixed SRB culture was used. The maximum initial concentration of platinum (IV), which SRB can effectively remove from solution was shown to be 50 mg.l⁻¹. Electron donor studies showed high platinum (IV) uptake in the presence of hydrogen, suggesting that platinum (IV) uptake from solution by SRB requires careful optimization with respect to the correct electron donor. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis indicated that platinum was being precipitated in the periplasm, a major area of hydrogenase activity in SRB. Purification of the hydrogenase by ammonium sulphate precipitation (65%), Toyopearl-Super Q 650S ion exchange and Sephacry 1 S-100 size exclusion chromatography revealed that the hydrogenase was monomeric with a molecular weight of 58 KDa, when analyzed by 12% SDS-PAGE. The purified hydrogenase showed optimal temperature and pH at 35°C and 7.5 respectively, and a poor thermal stability. In vitro investigation of platinum reduction by purified hydrogenase from mixed SRB culture showed that hydrogenase reduces platinum only in the presence of hydrogen. Major platinum (IV) reduction was observed when hydrogenase was incubated with cytochrome C₃ (physiological electron carrier in vivo) under hydrogen. The same observations were also noted with industrial effluent. Collectively these findings suggest that in vitro platinum reduction is mediated by hydrogenase with a concerted action of cytochrome C₃ required to shuttle the electron from hydrogenase.

Ce travail porte sur la synthèse, la caractérisation et l’évaluation en catalyse de réduction des protons en dihydrogène, de nouveaux complexes de Ni(II), Co(III), Cu(II) et Pd(II) basés sur des ligands de type thiosemicarbazone. La nature de l’espèce catalytique active a été étudiée par voltampérométrie cyclique et des propositions de mécanisme ont été formulés sur la base de calcul quantique de type DFT.Le premier chapitre introduit le contexte scientifique. Le second chapitre concerne la synthèse et la caractérisation des ligands de type N2S2 et des complexes mononucléaires associés de Ni, Cu et Pd. Le troisième chapitre présente la synthèse et la caractérisation de complexes binucléaires de Co et trinucléaire de Ni.Les études électrochimiques de ces complexes dans le DMF en présence d’une source de protons, nous a permis d’évaluer leur efficacité catalytique. Nos résultats montrent que les complexes du Cu et du Pd présentent une vague irréversible spécifique pour la réduction des protons, mais une décomposition est observée durant l’électrolyse. Par contre, les complexes de Ni et de Co ont montré une stabilité électrochimique ainsi que de bonnes performances catalytiques. En particulier, le nouveau complexe mononucléaire de Ni présente des propriétés catalytiques remarquables qui le classent parmi les meilleurs catalyseurs de la réduction des protons décrits dans la littérature. L’ensemble de ce travail fourni une description complète du comportement électrochimique des ligands de type N2S2 complexés à des métaux de transition. Il permet d’envisager des développements futurs dans l’amélioration des propriétés catalytiques de ces complexes
This work focuses on the synthesis, the characterization and the catalytic evaluation in the reduction of protons into dihydrogen, of new complexes of Ni(II), Co(III), Cu(II) and Pd(II) based ligands Type thiosemicarbazone. The catalytically active species during the process of the proton reduction was studied by cyclic voltammetry and mechanisms were formulated on the basis quantum chemical calculation.The first chapter introduces the scientific context, the goals and the main objectives of this work. The second chapter concerns the synthesis and the characterization of the N2S2 ligands and their associated mononuclear complexes, Ni, Cu and Pd. The third chapter presents the synthesis and the characterization of binuclear Co and trinuclear Ni based on N2S2 ligand.Electrochemical studies of these complexes in DMF in the presence of a proton source (trifluoroacetic acid), allowed us to evaluate their catalytic efficiency. Our results show that Cu and Pd complexes have a specific irreversible wave for the reduction of protons, but decomposition is observed during electrolysis, which makes these uninteresting complexes for the reduction of protons.On the contrary, Ni and Co complexes showed an electrochemical stability and good catalytic performances. In particular, the new mononuclear Ni complex exhibits remarkable catalytic properties that rank it among the best catalysts for the reduction of protons reported in the literature. All this work provided a complete description of the electrochemical behavior of N2S2 thiosemicarbazone ligands complexed to transition metals. It allows considering future developments in improving the catalytic properties of these complexes

Air pollutants pose a high risk for humans, and the environment, and this pollution is one of the major environmental problems facing modern society. Active air sampling is the technique that has been traditionally used to monitor nonpolar aromatic air pollutants. However, active high volume samplers (HiVols) require a power supply, maintenance and specialist operators, and the equipment is often expensive. Thus, there is a need to develop new, less complicated sampling techniques that can increase the monitoring frequency, the geographical distribution of the measurements, and the number of sites used in air monitoring programs. In the work underlying this thesis, the use of semipermeable membrane devices (SPMDs) as tools for monitoring gas phase concentrations of nonpolar aromatic compound was evaluated using the compound classes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs) and nitrated PAHs (nitro-PAHs) as test compounds.

High wind-speeds increased the uptake and release in SPMDs of PAHs and PCBs with log K_OA values > 7.9, demonstrating that the uptake of most nonpolar aromatic compounds is controlled by the boundary layer at the membrane-air interface. The use of a metal umbrella to shelter the SPMDs decreased the uptake of PAHs and PCBs by 38 and 55 percent, respectively, at high wind/turbulence, and thus reduced the wind effect. Further, the use of performance reference compounds (PRCs) to assess the site effect of wind on the uptake in SPMDs reduced the between-site differences to less than 50 percent from as much as three times differences in uptake of PCBs and PAHs. However, analytical interferences reduced the precision of some PRCs, showing the importance of using robust analytical quality control.

SPMDs were shown to be efficient samplers of gas phase nonpolar aromatic compounds, and were able to determine local, continental and indoor spatial distributions of PAHs, alkyl- PAHs and nitro-PAHs. In addition, the use of the SPMDs, which do not require electricity, made sampling possible at remote/rural areas where the infrastructure was limited. SPMDs were also used to determine the source of PAH pollution, and different approaches were discussed. Finally, SPMDs were used to estimate the importance of the gas phase exposure route to the uptake of PAHs in plants. The results demonstrate that SPMDs have several advantages compared with HiVols, including integrative capacity over long times, reduced costs, and no need of special operators, maintenance or power supply for sampling. However, calibration data of SPMDs in air are limited, and spatial differences are often only semi-quantitatively determined by comparing amounts and profiles in the SPMDs, which have limited their use in air monitoring programs. In future work, it is therefore important that SPMDs are properly sheltered, PRCs are used in the sampling protocols, and that calibrated sampling rate data, or the SPMD-air partition data, of specific compounds are further developed to make determination of time weighted average (TWA) concentrations possible.

Redukuojant vandeniliu Ni ir W oksidus 1000-1100˚C temperatūrų intervale, nepriklausomai nuo mišinio sudėties, susidaro tik intermetalinis junginys Ni4W. Rentgeno struktūrinės analizės pagalba buvo nustatyta kietafazių reakcijų produktų sudėtis. Nikelio ir volframo oksidų mišiniuose vykstant redukcijai susidarantis nikelis yra volframo oksidų redukcijos katalizatorius. Nikeliui sudarius intermetalinį junginį Ni4W, volframo oksidai redukuojasi sunkiau. Mišiniai, kuriuose Ni:W=4:1, redukuojasi žemesnėje temperatūroje ir esant mažesnei vandenilio dujų koncentracijai.
During the reduction of nickel and tungsten in a temperature range from1000- 1100˚C independent of composition mixtures form only Ni4W intermetallic compuond. Their formation was analyzed be of the X-ray diffraction techniques composition the products of the solid-state reactions was determined. Nickel wich is formed during the rediction is catalyst of tungsten oxide. When nickel is formed intermetallic compound Ni4W, tungsten oxide reducible heavily. Reduction of mixture (Ni:W = 4:1) lesses of the temperature and hydrogen concentration.

[ES] La presente tesis doctoral se enmarca en el ámbito de la Química Sostenible, en el cual se identifica la catálisis como una de las herramientas más importantes para su aplicación. En este sentido, en esta tesis doctoral, se han desarrollado catalizadores de cobalto para llevar a cabo reacciones de interés industrial o relacionadas con las tecnologías energéticas emergentes a través de la activación de moléculas pequeñas. Estas reacciones se llevan a cabo a nivel industrial con catalizadores basados en metales nobles o en condiciones de reacción severas. El objetivo es reemplazar estos catalizadores por otros basados en metales más abundantes en la corteza terrestre, en este caso el cobalto, o llevar a cabo las reacciones en condiciones de reacción más suaves, respectivamente, estudiando en todo caso la relación entre la estructura y la actividad del catalizador. Los resultados de esta tesis doctoral se presentan en cuatro capítulos. En el capítulo cuatro, se presentan los resultados del desarrollo de catalizadores de cobalto estables al aire y a la humedad basados en compuestos de coordinación para llevar a cabo la hidrosililación de alquenos sin aditivos y evitando el uso de atmósfera inerte durante la reacción. Además, se ha estudiado la actividad de estos catalizadores usando un amplio rango tanto de alquenos como de silanos para comprobar la generalidad de la reacción. Finalmente, se ha estudiado el mecanismo de reacción usando Raman in-situ, lo cual ha permitido identificar la especie de cobalto activa como intermedio de reacción. En el capítulo cinco, uno de los compuestos de coordinación estudiados para el proceso de hidrosililación de alquenos, se ha heterogeneizado usando como soporte un carbón activo de alta área superficial. La presencia de 6 nitrógenos coordinados al cobalto en el precursor inicial ha sido clave en la formación del material final, que es altamente activo y selectivo en la reacción de hidrogenación de nitroarenos y en la síntesis de aminas secundarias y de isoindolinonas en reacciones tándem en condiciones de reacción más suaves que las reportadas en bibliografía y usando agua como medio de reacción. Además, este catalizador puede ser reusado en varios ciclos de reacción sin una pérdida apreciable de actividad, demostrando que es un material heterogéneo y robusto. La estructura del catalizador se ha estudiado por varias técnicas de caracterización avanzadas, con el fin de correlacionar su estructura con la actividad en estas reacciones catalíticas. En el sexto capítulo se resumen los resultados obtenidos para el desarrollo de una familia de compuestos tetranucleares de cobalto, cuya densidad electrónica puede ser modulada haciendo uso de diferentes ligandos. Esta densidad electrónica está correlacionada con su actividad catalítica en reacciones de oxidación, como la oxidación de ciclohexano a ciclohexanol y ciclohexanona. En este sentido, se ha llevado a cabo un amplio estudio de la actividad catalítica de esta familia de catalizadores, que han demostrado ser activos y selectivos en esta reacción, en condiciones netas y usando aire empobrecido como oxidante, y del mecanismo de reacción a través de EPR y Raman, que ha permitido correlacionar la estructura de cada catalizador con su papel en cada proceso individual del mecanismo global de esta reacción. Finalmente, en el capítulo siete, uno de los compuestos tetranucleares de cobalto se ha utilizado como precursor en la síntesis de MOFs con ligandos ampliamente utilizados en la síntesis de estos materiales, como son el H3BTC y el H2bda, obteniéndose dos MOFs nuevos, el primero de ellos (Co2-MOF) basado en dos SBUs de cobalto dinucleares en la que una de ellas presenta tres posiciones de coordinación libres, con las ventajas que esto conlleva y, el segundo de ellos (2D-Co-MOF), basado en nanoláminas dobles apiladas por interacciones π-π stacking entre los ligandos piridina axiales. La dispersión de estos MOFs en Nafion da como resultado los correspondientes composites, que presentan una buena adherencia a los electrodos de grafito, una alta estabilidad a largo plazo y, además, un elevado rendimiento electrocatalítico para la reacción de oxidación del agua en medio neutro, mejorando los resultados reportados en bibliografía para materiales similares. Además, se ha estudiado el mecanismo de reacción, que sigue sin conocerse a ciencia cierta hoy en día, para el 2D-Co-MOF, basándonos en su topología particular y en estudios espectroscópicos y electroquímicos.
[CA] La present tesi doctoral s'emmarca en l'àmbit de la Química Sostenible, en el qual s'identifica la catàlisi com una de les eines més importants per a la seua aplicació. En aquest sentit, en aquesta tesi doctoral, s'han desenvolupat catalitzadors de cobalt per a dur a terme reaccions d'interés industrial o relacionades amb les tecnologies energètiques emergents a través de l'activació de molècules xicotetes. Aquestes reaccions es duen a terme a nivell industrial amb catalitzadors basats en metalls nobles o en condicions de reacció severes. L'objectiu és reemplaçar aquests catalitzadors per altres basats en metalls més abundants en l'escorça terrestre, en aquest cas el cobalt, o dur a terme les reaccions en condicions de reacció més suaus, respectivament, estudiant en tot cas la relació entre l'estructura i l'activitat del catalitzador. Els resultats d'aquesta tesi doctoral es presenten en quatre capítols. En el quart capítol, es presenten els resultats del desenvolupament de catalitzadors de cobalt estables a l'aire i a la humitat basats en compostos de coordinació per a dur a terme la hidrosililació d'alquens sense additius i evitant l'ús d'atmosfera inerta durant la reacció. A més, s'ha estudiat l'activitat d'aquests catalitzadors usant un ampli rang tant d'alquens com de silanes per a comprovar la generalitat de la reacció. Finalment, s'ha estudiat el mecanisme de reacció usant Raman in-situ, la qual cosa ha permés identificar l'espècie de cobalt activa com a intermedi de reacció. En el quint capítol, un dels compostos de coordinació estudiats per al procés de hidrosililació d'alquens, s'ha heterogeneït usant com a suport un carbó actiu d'alta àrea. La presència de 6 nitrògens coordinats al cobalt en el precursor inicial ha sigut clau en la formació del material final, que és altament actiu i selectiu en la reacció d'hidrogenació de nitroarenos i en la síntesi d'amines secundàries i de isoindolinons en reaccions tàndem en condicions de reacció més suaus que les reportades en bibliografia i usant aigua com a mitjà de reacció. A més, aquest catalitzador pot ser reusat en diversos cicles de reacció sense una pèrdua apreciable d'activitat, demostrant que és un material heterogeni i robust. L'estructura del catalitzador s'ha estudiat per diverses tècniques de caracterització avançades, amb la finalitat de correlacionar la seua estructura amb l'activitat en aquestes reaccions catalítiques. En el capítol sis es resumeixen els resultats obtinguts per al desenvolupament d'una família de compostos tetranuclears de cobalt, la densitat electrònica del qual pot ser modulada fent ús de diferents lligands. Aquesta densitat electrònica està correlacionada amb la seua activitat catalítica en reaccions d'oxidació, com l'oxidació de ciclohexà a ciclohexanol i ciclohexanona. En aquest sentit, s'ha dut a terme un ampli estudi de l'activitat catalítica d'aquesta família de catalitzadors, que han demostrat ser actius i selectius en aquesta reacció, en condicions netes i usant aire empobrit com a oxidant, i del mecanisme de reacció a través de EPR i Raman, que ha permés correlacionar l'estructura de cada catalitzador amb el seu paper en cada procés individual del mecanisme global d'aquesta reacció. Finalment, en el sèptim capítol, un dels compostos tetranuclears de cobalt s'ha utilitzat com a precursor en la síntesi de MOFs amb lligands àmpliament utilitzats en la síntesi d'aquests materials, com són l'H3BTC i el H2bda, obtenint-se dos MOFs nous. El primer d'ells (Co2-MOF) basat en dos SBUs de cobalt dinuclears en la qual una d'elles presenta tres posicions de coordinació lliures, amb els avantatges que això comporta. El segon (2D-Co-MOF), basat en nanolámines per interaccions π-π stacking entre els lligands piridina axials. La dispersió d'aquests MOFs en Nafion dona com a resultat els corresponents composites, que presenten una bona adherència als elèctrodes de grafit, una alta estabilitat a llarg termini i, a més, un elevat rendiment electrocatalític per a la reacció d'oxidació de l'aigua al mig neutre, millorant els resultats reportats en bibliografia per a materials similars. A més, s'ha estudiat el mecanisme de reacció, que segueix sense conéixer-se amb certesa hui dia, per al 2D-Co-MOF, basant-nos en la seua topologia particular i en estudis espectroscòpics i electroquímics.
[EN] This thesis is focused on the field of Green Chemistry, in which catalysis is identified as one of the most important tools for its application. In this sense, in this thesis, cobalt catalysts were developed to carry out reactions of industrial interest or related to emerging energy technologies, through the activation of small molecules. These reactions are usually performed at industrial scale with catalysts based on noble metals or under severe reaction conditions. The main objective of this thesis is to replace these catalysts by others based on more abundant metals in the earth's crust, in this case cobalt, or to carry out the reactions in milder reaction conditions, respectively, studying in each case the relationship between the structure and the activity of the catalyst. The results of this thesis are presented in four chapters. In the first chapter, the results for the catalytic hydrosilylation of alkenes under aerobic conditions and without dry solvents or additives are presented, where the development of air-stable cobalt-aquo complexes is pivotal. In fact, this is the first case where these reactions are performed under aerobic conditions with first-row transition metal complexes. In addition, the activity of these catalysts has been studied using a wide range of both alkenes and silanes to check the scope of the reaction. Finally, the reaction mechanism has been studied using in-situ Raman, which has allowed the identification of the active cobalt species as a reaction intermediate. In the second chapter, one of the coordination compounds studied for the alkene hydrosilylation process has been heterogenized using an activated carbon with high area as support. The employment of a suitable molecular complex consisting of six bounds N-Co as initial precursor has been key in the formation of the final material. This catalyst has demonstrated to be highly active and selective in the hydrogenation of nitroarenes and in the synthesis of secondary amines and isoindolinones in tandem reactions under milder reaction conditions than those reported in the literature and using water as reaction medium. Moreover, this catalyst can be reused in several reaction cycles without an appreciable loss of activity. The structure of the catalyst has been studied by several advanced characterization techniques in order to correlate its structure with the activity in these catalytic reactions. In the third chapter, the results obtained for the development of a family of tetranuclear cobalt compounds, whose electron density is modulated by using different ligands, are summarized. This electron density is correlated with their catalytic activity in the oxidation of cyclohexane to cyclohexanol and cyclohexanone. In this sense, an extensive study of the catalytic activity of this family of catalysts, which have been shown to be active and selective in this reaction, has been carried out under neat conditions and using depleted air as oxidant. Moreover, the reaction mechanism has been studied through EPR and Raman, which has allowed to correlate the structure of each catalyst with its role in each individual step of the global mechanism of this reaction. Finally, in the fourth chapter, one of the tetranuclear cobalt compounds has been used as precursor in the synthesis of MOFs with ligands widely used in the synthesis of these materials, such as H3BTC and H2bda, obtaining two new MOFs. The first one (Co2-MOF) based on two dinuclear cobalt SBUs in which one of them presents three free coordination positions, with the advantages that this entails and, the second one (2D-Co-MOF), based on double nanolayers stacked by π-π stacking interactions between the axial pyridine ligands. The dispersion of these MOFs in Nafion results in the corresponding composites, which exhibit good adherence to graphite electrodes, high long-term stability and, in addition, high electrocatalytic performance for the water oxidation reaction (OER) in neutral media, improving the results reported in literature for similar materials. Furthermore, the reaction mechanism, which is still unresolved, has been studied for 2D-Co-MOF, based on its particular topology and on spectroscopic and electrochemical studies.
Gutiérrez Tarriño, S. (2021). Desarrollo de catalizadores de cobalto polinucleares y multifuncionales para la activación de moléculas pequeñas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172324
TESIS

Les amines aromatiques sont largement considérées comme des intermédiaires réactionnels prometteurs pour la production de colorants, d'antioxydants, de produits pharmaceutiques et de produits chimiques agricoles. La méthode la plus utilisée pour la préparation des amines aromatiques est l’hydrogénation catalytique en général. Les procédés d'hydrogénation catalytique des composés nitroaromatiques utilisent des métaux de transition, tels que (Pt, Ni, Pd,..), de solvants organiques et source d’hydrogène comme H2. Cependant, l'utilisation de catalyseurs métalliques présente certains inconvénients tels que le coût élevé, le recyclage du système, ainsi que certaines préoccupations environnementales. Les solvants organiques ont également été utilisés au cours de ces processus, ce qui a nécessité une consommation d'énergie élevée pour la récupération des amines aromatiques. Enfin, l’utilisation de H2 peut entraîner également des risques liés à la sécurité. Dans le présent travail, des procédés « verts » et sûrs pour la réduction des composés nitroaromatiques en amines aromatiques en présence de matériaux carbonés ou de biomasse lignocellulosique dans des conditions subcritiques ont été développés. Dans un premier temps notre intérêt dans ce travail s'est porté sur l'utilisation directe du carbone qui présente comme avantages, son faible coût et sa disponibilité, cela a donné lieux à un nouveau procédé plus « vert » et plus sécuritaire. Le mécanisme réactionnel de ce dernier a été étudié en utilisant le logiciel CIRCE qui est un logiciel de thermodynamique basé sur la méthode de Monte Carlo. Ce procédé a été ensuite appliqué à différents composés nitrés aromatiques substitués par une fonction organique en particulier pour la préparation du 3-aminobenzoique à partir du 3-nitrobenzaldehyde. Par la suite les matériaux carbonés ont été remplacés par de la biomasse lignocellulosique qui est la sciure de bois imprégné par une base dans l’eau à l’état subcritique. En effet l'eau connue comme solvant vert pourraient impliquer de nouveaux procédés « verts » en conditions critiques et engendrer H2 permet d’apporter le dihydrogène nécessaire pour la faisabilité de la réaction
Aromatic amines are widely regarded as promising reaction intermediates for the production of dyes, antioxidants, pharmaceuticals and agricultural chemicals. The most widely used method for the preparation of aromatic amines is catalytic hydrogenation in general. The catalytic hydrogenation processes of nitroaromatic compounds use transition metals, such as (Pt, Ni, Pd, ..), organic solvents and hydrogen source like H2. However, the use of metal catalysts has certain disadvantages such as the high cost, recycling of the system, as well as certain environmental concerns. Organic solvents were also used during these processes, which required high energy consumption for the recovery of aromatic amines. Finally, the use of H2 can also lead to safety risks. In the present work, “green” and safe processes for the reduction of nitroaromatic compounds into aromatic amines in the presence of carbonaceous materials or lignocellulosic biomass under subcritical conditions have been developed. Initially, our interest in this work focused on the direct use of carbon which has the advantages, its low cost and its availability, this gave rise to a new process that is "greener" and safer. The reaction mechanism of the latter was studied using CIRCE software which is thermodynamic software based on the Monte Carlo method. This process was then applied to various aromatic nitro compounds substituted by an organic function in particular for the preparation of 3-aminobenzoic starting from 3-nitrobenzaldehyde. Subsequently carbonaceous materials were replaced by lignocellulosic biomass which is sawdust impregnated with a base in water in the subcritical state. Indeed, water known as a green solvent could involve new "green" processes in critical conditions and generate H2 makes it possible to supply the dihydrogen necessary for the feasibility of the reaction

Dans une première partie, synthèse d'alkyl-4 dihydro-1,4 benzyl-1 et -phényl-1p éthyl-1 (diméthyl-4,4 oxazoline-2yl-2)-3 pyridines et étude de leur activité réductrice vis-a-vis de p-nitrobenzaldéhyde et de benzenéglyoxylate de méthyle en présence de mg**(2+) ; dans la seconde partie, étude de modèles plus énantiosélectifs : méthyl-1 dihydro-1,4 n-(hydroxyméthyl-1 propyl) nicotinamide (=méthyl-1 a), o-, m- et p- xylylene-1, 1' bis-a, dihydro-1,4 methyl-1 nicotinate de (dihydro-1,4 methyl-1 nicotinoylamino)-2 butyle et le cyclophane correspondant à ce dernier composé (pont xylylene entre les azotes des pyridines) ; interaction entre les noyaux pyridines

Ces bronzes de titane de type hollandite sont des composes a vfalence mixte de formule generale a::(x)tio::(2), avec a=k, rb, cs et 0,125