No description available.

The preparation of a number of 2-substituted homophthalimides through the condensation of homophthalic anhydride with different arylalkyl arnines is reported. The prepared compounds were alkylated at the 4-position to generate 4-mono-, 4,4-disubstituted and 4-spirocyclic homphthalimides, the analogues of which were reported to have interesting biological activity. Regioselective reduction of the 4-substituted derivatives generated the corresponding carbinolamides. Treating the carbinolamides with mineral or Lewis acids generated N-acyliminiurn ions, which were trapped in situ by one of the following: ( 1) aromatic neucleophiles to generate analogues of the natural product berberine, (2) alkyl chain migration to generate tetrahydrophenanthridones and functionalised isoquinolones, (3) cyclopropane ring-opening to generate 4-alkylisoquinolones, (4) addition to double bond to generate cyclopentaisoquinolones and (5) benzyl or allyl elimination. The oxidation of 4-monosubstituted homophthalimides with triplet dioxygen in alkaline media was investigated, and it generated 4-hydroxyhomophthalimides and isobenzofurancarboxamides. Treating isobenzofurancarboxamides with POCI3 provided a concise route to analogues of the neuroactive naturally-occurring phthalideisoquinolines.

The main objective of this research was to develop a protocol in which pyridoxal phosphate (PLP) would act as a tag to identify PLP-dependent enzymes from complex mixtures or cell lysates. Following the purification of a PLP-dependent enzyme (CysM), a method was developed to reduce the PLP-lysine Schiff base to form a chemically stable bond between the PLP and the protein. The reduced protein was enzymatically digested resulting in multiple peptide fragments with one or more containing PLP (bound to the active site lysine). These fragments were analyzed by monitoring the absorbance or fluorescence using High Performance Liquid Chromatography. Immobilized Metal Ion Affinity Chromatography (IMAC) was then used to enrich the PLP-peptide(s) from the peptide mixture. The PLP-bound peptide(s) was then analyzed using Liquid Chromatography-Mass Spectrometry (LC-MS). More specifically, sodium borohydride (NaBH4) was used to reduce the Lysine-PLP bond in CysM. This reaction was monitored by either UV-vis spectroscopy or mass spectrometry. Trypsin was used to enzymatically digest the reduced CysM before it was enriched with IMAC and analyzed with LC-MS. Since the objective of this project was to develop a method which could be applied to a cell lysate, IMAC was used as an enrichment method to separate the PLP-peptide(s) from other peptides within the mixture. The PLP-peptide(s) was then located in the peptide mixture by monitoring the absorbance at 325 nm. The LC-MS results of the full reaction before IMAC treatment versus the final column, when monitoring the mass spectrum, showed that the treatment using the IMAC column separated the PLP-peptides from all other peptides within the sample. Using IMAC to enrich specifically the PLP-peptides, followed by analysis with LC-MS, may be a useful method for studying PLP-dependent enzymes within the proteome or the "PLP-ome."

L’hydrogène en tant que vecteur énergétique reste tributaire, pour un développement à grande échelle, de son stockage et de la facilité de dégagement du combustible stocké. Pour les applications embarquées, portables et stationnaires, aucune technologie de stockage (H2 comprimé, H2 liquide, hydrures métalliques ou chimiques) ne répond aujourd’hui au cahier des charges d’un système de stockage. De nombreuses études se penchent donc à la fois sur l'optimisation des composants et le développement de sources d'énergie miniatures. Dans cette optique, la production d'hydrogène par l'hydrolyse des borohydrures est une technologie prometteuse pour les piles à combustible portables. En particulier, le borohydrure de sodium (NaBH4) présente de multiples avantages. Par exemple, les solutions aqueuses de NaBH4 sont non inflammables assurant ainsi la sécurité des procédés, le taux de génération d’hydrogène est facilement contrôlé par un catalyseur, les produits de réaction sont respectueux de l'environnement et peuvent être recyclés. La réaction d’hydrolyse du borohydrure alcalin peut être décrite de la façon suivante : MBH4 + (2+x) H2O → 4 H2 + MBO2.xH2O L’optimisation de la réaction d’hydrolyse et plus globalement l’optimisation du fonctionnement de la cartouche et de ces performances nécessite d’améliorer les connaissances sur les propriétés physico-chimiques du borohydrure et des métaborates en milieu aqueux plus ou moins complexe. L’un des principaux défis consiste à augmenter la concentration en NaBH4 de la solution de la cartouche, tout en évitant les inconvénients induits par la cristallisation des sous-produits (NaBO2.xH2O). Mais il est alors nécessaire de contrôler la stabillité de cette solution, par ajout d'hydroxyde de sodium qui limitera l'auto–décomposition NaBH4. Ce travail montre les deux aspects de l'analyse de la durée de vie de la cartouche génératrice d’hydrogène : – La cinétique d'hydrolyse spontanée des solutions alcalines aqueuses NaBH4 en fonction de la concentration de NaOH (élément stabilisant) et de la plage de température de fonctionnement de la cartouche,– La compréhension sans équivoque de l'opération de cristallisation NaBO2 et plus particulièrement la délimitation du domaine de la phase liquide homogène dans le système quaternaire NaBH4–NaBO2–NaOH–H2O, qui représente l’évolution du mélange lors du fonctionnement de la cartouche d'hydrogène / Numerous investigations are addressing both component optimization and development of miniature energy sources. The rise of portable eletronic devices, brings to the fore the crucial issues of power supply. The foresceable evolution in functionalities and utilizations, as regards portable eletronic devices, together with the introduction of novel electronic components, entail considerable changes in requirements, in terms of power consumption and autonomy. Hydrogen generation by means of the hydrolysis of borohydrides is a promising technology for portable fuel cells. Particularly, sodium borohydride (NaBH4) presents many advantages for that purpose. For example, NaBH4 solutions are non–flammable thus yielding safe processes; the rate of H2 generation is easily controlled by a catalyst; reaction products are environmentally benign and finally the reaction by–product can be recycled. The hydrolysis of NaBH4 in water to produce H2 gives by–products, NaBO2.yH2O, hydrated sodium borate according to MBH4 + (2+x) H2O → 4 H2 + MBO2.xH2O The interesting point of this work is to increase the amount of produced H2 in order to improve the energy density of the H2 generator system. For this, one of the main challenges is to increase the NaBH4 concentration of the cartridge solution thus avoiding the drawbacks induced by NaBO2 crystallization, but also to control the stabillity of this solution, it means add sodium hydroxyde to limit the NaBH4 self–decomposition, thus stabilizing the system. This work shows the two aspects of the analysis of the cartridge timelife : – The kinetic of spontaneous hydrolysis of alkaline aqueous NaBH4 solutions as function of NaOH concentration and the operation temperature range of the cartridge, – An unequivocal understanding of the NaBO2 crystallization process and more specifically the delimitation of the homogeneous liquid phase domain in the quaternary system NaBH4– NaBO2–NaOH–H2O, which represents the mixture present during the hydrogen cartridge operation

No description available.

Sodium borohydride reduces alkyl halides and their related tosylate derivatives in the order primary > secondary > tertiary, while the relative order of leaving-group ability is Ts⁻ ≥ I⁻ > Br⁻ > > Cl⁻. The yields obtained ranged from 90-100% for most simple, primary and secondary iodides, bromides, and tosylates, to 1-2% for the tertiary compounds. As in the case of the more reactive lithium aluminum hydride, the. reduction is believed to occur by an S_N2 displacement on carbon. The reduction of a series of para-substituted benzyl chlorides revealed that the electronic effects of groups ranging from p-methoxy to p-nitro had a rather small effect on the rate of reduction. Aryl halides arc reduced by sodium borohydride in yields dependent upon the particular halogen involved, the presence of other ortho and para electron-withdrawing substituents, and the reaction temperature, among other factors. The same relative order of dehalogenation displayed by the alkyl halides was found. Polyhalomethanes such as carbon tetrachloride react with sodium borohydride to give the monohydro and dihydro compounds as the major products, the former predominating. The exact mechanism of the reduction is as yet undetermined, as water apparently catalyzes the reaction in some unknown manner. / Master of Science

PtBi/C e PdBi/C foram preparados em diferentes razões atômicas (100:0, 90:10, 80:20, 70:30, 60:40 e 50:50) pelo método de redução via borohidreto de sódio (com adição total da solução de borohidreto em uma única etapa) utilizando H2PtCl6.6H2O, Pd(NO3)2, (BiNO3)3.5H2O como fonte de metais, Vulcan® (XC72-Cabot) como suporte de carbono e com uma carga metálica correspondente a 20% em massa. Os eletrocatalisadores obtidos foram caracterizados por difração de raios-X (DRX), microscopia eletrônica de transmissão (MET) e voltametria cíclica (VC). A atividade dos diferentes materiais preparados para a oxidação eletroquímica do ácido fórmico foi realizada em eletrólito ácido e alcalino utilizando-se as técnicas de voltametria cíclica, e cronoamperometria. Para estes estudos foi utilizado a técnica do eletrodo de camada fina porosa. A caracterização eletroquímica permitiu comparar o desempenho eletroquímico da platina e paládio, além de avaliar o benefício da presença do bismuto nas razões atômicas propostas. Os difratogramas de raio-X (DRX) confirmaram para todos os compostos de PtBi/C e PdBi/C a formação da estrutura cúbica de face centrada (cfc) característicos da rede cristalina da platina e do Paládio respectivamente. Outros picos encontrados foram associados a presença de fases de óxido de bismuto em ambos os compostos, PtBi/C e PdBi/C. A microscopia eletrônica de transmissão (MET) indicou que a presença de maiores teores de bismuto não acarretaram em aumento do tamanho médio da partícula. Os resultados eletroquímicos em meio alcalino indicaram que ainda é necessário uma otimização da concentração de ácido fórmico para que possamos observar melhores resultados quanto à adição de bismuto na platina ou paládio, no entanto os estudos em meio ácido mostraram o efeito benéfico da adição de bismuto tanto para platina quanto para o paládio. / PtBi/C and PdBi/C were prepared with different atomic ratios (100:0, 90:10, 80:20, 70:30, 60:40 and 50:50) by sodium borohydride reduction method (with total addition of the borohydride solution in just one step) using H2PtCl6.6H2O, Pd(NO3)2, (BiNO3)3.5H2O as source of metals, Vulcan® (XC72-Cabot) as carbon support and a metallic charge correspondent to 20% mass. The obtained electrocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). The activity of the different materials used for the formic acid electrochemical oxidation was performed in acid and alkaline electrolyte through cyclic voltammetry and chronoamperometry, using the porous thin-film electrode technique. The electrochemical characterization allowed for the comparison between the platinum and palladium electrochemical performance, as well as the evaluation of the benefit of having bismuth in the proposed atomic ratios. The X-ray diffraction (XRD) diffractograms confirmed, for every PtBi/C and PdBi/C compounds, the formation of the face-centered cubic structure (fcc) distinctive to platinum and palladiums crystalline net, respectively. Other peaks were found associated to the presence of bismuth oxide phases in both compounds, PtBi/C and PdBi/C. The transmission electron microscopy (TEM) indicated that a higher bismuth presence did not result in a larger particle size. The electrochemical results in alkaline medium indicated that an optimization on formic acid concentration is still necessary so that better results concerning bismuth addition to platinum or palladium could be observed, although the studies done in acid medium presented the beneficial effect of bismuth addition to both platinum and palladium.

The use of microporous materials with ordered porous structures as the hosts to stabilize metal nanoclusters has attracted particular interest in the catalysis because the pore size restriction could confine the growth of nanoclusters and lead to an increase in the percentage of catalytically active surface atoms. In this dissertation we report the preparation, characterization and the investigation of the catalytic performance of zeolite framework stabilized ruthenium(0) nanoclusters in the hydrolysis of sodium borohydride and the hydrogenation of aromatics. The zeolite framework stabilized ruthenium(0) nanoclusters were prepared by borohydride reduction of ruthenium(III)-exchanged zeolite-Y in aqueous solution at room temperature and isolated as black powders. Their characterization by using ICP-OES, XRD, TEM, ZC-TEM, HR-TEM, TEM-EDX, SEM, XPS, DR-UV-vis, far-IR, mid-IR, Raman spectroscopy, N2 adsorption-desorption technique and (P(C6H11)3)/(PC6H11O3) poisoning experiments reveal the formation of ruthenium(0) nanoclusters within the zeolite cages as well as on the external surface of zeolite without causing alteration in the framework lattice or loss in the crystallinity. The catalytic performance of zeolite framework stabilized ruthenium(0) nanoclusters depending on the various parameters was tested in the hydrolysis of sodium borohydride and the hydrogenation of aromatics. The important results obtained from these experiments can be listed as follows: (i) the zeolite framework stabilized ruthenium(0) nanoclusters provide a record total turnover number (103200 mol H2/mol Ru) and turnover frequency (33000 mol H2/mol Ru&bull / h) in the hydrolysis of sodium borohydride at room temperature, (ii) they also catalyze the same reaction in the basic medium (in 5 wt % NaOH solution) at room temperature with the unprecedented catalytic activity (4000 mol H2/mol Ru&bull / h) and lifetime (27200 mol H2/mol Ru), (iii) the isolated and vacuum dried samples of zeolite framework stabilized ruthenium(0) nanoclusters are active catalysts in the hydrogenation of cyclohexene, benzene, toluene and o-xylene in cyclohexane, they provide TOF values of 6150, 5660, 3200, and 1550 mol H2/mol Ru&bull / h, respectively under mild conditions (at 22.0 &plusmn / 0.1 &deg / C, and 40 &plusmn / 1 psig of initial H2 pressure), (iv) more importantly, the zeolite framework stabilized ruthenium(0) nanoclusters are the lowest temperature, most active, most selective (100 % selectivity with complete conversion) and longest lifetime catalyst hitherto known for the hydrogenation of benzene to cyclohexane in the solvent-free system (TTON of 2420 and TOF of 1040 mol benzene/mol Ru&bull / h) under mild conditions (at 22.0 &plusmn / 0.1 &deg / C, and 40 &plusmn / 1 psig of initial H2 pressure), (v) moreover, the resultant ruthenium(0) nanoclusters exhibit high durability throughout their catalytic use against agglomeration and leaching. This significant property makes them reusable catalyst without appreciable loss of their inherent activity.

Recent study has shown that ruthenium(III) acetylacetonate acts as a homogeneous catalyst in the hydrolysis of sodium borohydride. When two equivalents of trimethylphosphite per ruthenium is added to the reaction solution containing sodium borohydride and ruthenium(III) acetylacetonate in the mixture of water and tetrahydrofuran, the rate of hydrogen generation is practically stopped (or reduced to the level of self hydrolysis). However, the catalytic hydrogen evolution of sodium borohydride restarts at an unexpectedly high rate in a certain period of time (induction time) after addition of trimethylphosphite. Consequently, trimethylphosphite known to be a poison in the hydrolysis, is involved in the formation of a new active catalyst (ruthenium species containing trimethylphosphite ligands) which has much higher catalytic activity in comparison with sole ruthenium(III) acetylacetonate. The same rate enhancement is observed by addition of two equivalents of triphenylphosphite per ruthenium into the medium. Varying the phosphorus compound affects not only the life time of catalyst but also the kinetic and activation parameters of the hydrolysis of sodium borohydride. However, varying the mole ratio of phosphorus compound to ruthenium does not affect the rate of hydrolysis or in other words, the rate of hydrogen generation is independent of phosphite concentration. Trans- and cis-[Ru(acac)2{P(OMe)3}2] complexes do not show significant catalytic activity in hydrogen generation of sodium borohydride. However, catalytic activity of cis-isomer is highly increased in the presence of two equivalents of trimethylphosphite, showing that the active catalyst formed during hydrolysis of sodium borohydride starting with Ru(acac)3 or cis-[Ru(acac)2{P(OMe)3}2], has more than two phosphine ligands. For the first time, a ruthenium(I) complex was isolated from aqueous solution after finishing the catalytic hydrolysis of sodium borohydride starting with ruthenium(III) acetylacetonate and trimethylphosphite. Hydridotetrakis(trimethylphosphite)ruthenium(I), [Ru{P(OMe)3}4H] was isolated and characterized by single crystal X-ray diffraction, Mass, UV-visible, FTIR, 1H, 13C and 31PNMR spectroscopy. Following the catalytic reaction by UV-Visible spectroscopy shows in-situ formation of a Ru(II) species which is mostly converted back to ruthenium(III) acetylacetonate after hydrolysis reaction along with formation of [Ru{P(OMe)3}4H] complex as a minor product. Although Ru(II) species could not be isolated, adding 1 equivalent of 2,2&#039 / -bipyridine yielded [Ru(acac)(bipy){P(OMe)3}H] complex which could be isolated and characterized by Mass, UV-Visible, FTIR, 1H, 13C and 31PNMR spectroscopy. In-situ generated Ru(II) species has much higher catalytic activity in comparison with its stabilized form [Ru(acac)(bipy){P(OMe)3}H] or [Ru{P(OMe)3}4H] complex. Conclusively, the fac-[Ru(acac){P(OMe)3}3H] complex is believed to be the in-situ generated Ru(II) species and the active catalyst in the hydrolysis of sodium borohydride.

Because of the growing concerns over the depletion of fossil fuel supplies, environmental pollution and global warming caused by a steep increase in carbon dioxide and other greenhouse gases in the atmosphere, much attention has been given to the development of renewable energy sources that are the only long-term solution to the energy requirements of the world&rsquo / s population, on the way towards a sustainable energy future. Hydrogen has been considered as a clean and environmentally benign new energy carrier for heating, transportation, mechanical power and electricity generation. However, the lack of effective, safe, and low-cost hydrogen storage materials for mobile, portable, and stationary applications is one of the major hurdles to be overcome for the implementation of hydrogen economy. Among various solid state hydrogen storage materials, chemical hydrogen storage materials such as sodium borohydride (NaBH4) and ammonia borane (H3NBH3) have received much attention as promising candidates for fuel cell applications under ambient conditions due to their high gravimetric and volumetric hydrogen storage capacities. Both sodium borohydride and ammonia borane generate hydrogen upon hydrolysis in the presence of suitable metal catalysts. Transition metal nanoclusters can be used as active catalysts to catalyze the hydrolysis reactions of sodium borohydride and ammonia borane for hydrogen generation since they exhibit unique properties that differ from their bulk counterparts. Although the catalytic activity of metal nanoclusters increases with decreasing particle size, they are unstable with respect to agglomeration into the bulk metal leading to a significant decrease in activity in their catalytic applications. Therefore, the exploitation of microporous and mesoporous materials with ordered porous structures as hosts to encapsulate metal nanoclusters has attracted great interest since the pore size restriction of these host materials could limit the growth of nanoclusters leading to an increase in the percentage of the catalytically active surface atoms. In this dissertation, we report the preparation, characterization and the investigation of the catalytic activities of zeolite confined cobalt(0) nanoclusters in the hydrolysis of sodium borohydride and ammonia borane. The zeolite confined cobalt(0) nanoclusters were prepared by the reduction of cobalt(II)-exchanged zeolite-Y by sodium borohydride in aqueous solution at room temperature with no alteration in the framework lattice or loss in the crystallinity. The characterization of zeolite confined cobalt(0) nanoclusters were done by using inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-visible spectroscopy (DR-UV-Vis), infrared spectroscopy (IR), Raman spectroscopy, and N2 adsorption-desorption technique. The catalytic activity of zeolite confined cobalt(0) nanoclusters and the kinetics of hydrogen generation from the hydrolysis of sodium borohydride and ammonia borane were studied depending on catalyst concentration, substrate concentration and temperature. The rate laws and the activation parameters (Arrhenius activation energy, Ea / activation enthalpy, &Delta / H# / and activation entropy, &Delta / S#) for both catalytic hydrolysis reactions were calculated from the obtained kinetic data.