It was the purpose of this investigation to study the hyperfine structure of the β-unstable isotopes of samarium using the atomic beam magnetic resonance technique. A brief review is given of the nuclear and atomic theory necessary for the interpretation of the experiments. The hyperfine interaction constants (Mc/sec) for Sm153, and the nuclear moments inferred from them, are summarized below: A1 = - 2.100(5) B1 = 289.042(4) A2 = - 2.573(6) B2 = 306.521(21) C2 = - 0.0003(9) A3 = - 3.115(4) B3 = 165.824(20) C3 = - 0.0087(12) μI = - 0.021(1) n.m. Q = 1.1(3) barns From the quadrupole moment it follows that the nuclear deformation δ = 0.25(5). The magnetic moment disagrees with the predictions of the Nilsson model for either spin 3/2 state with which the Sm153 ground state might be associated. Also determined was the spin of Sm155. The result, I = 3/2, confirms the assignment from the less direct evidence available from radioactive decay studies. The more extensive measurements necessary to determine the moments were not attempted. / Thesis / Doctor of Philosophy (PhD)

Two-neutron pick up reactions have been performed on targets of 149Sm and radioactive 151Sm using 18 MeV protons. The outgoing tritons from the 151Sm target were analyzed with a magnetic spectrograph at 16 angles between 6 degrees and 8 degrees. Unlike the two-neutron transfer data on neighbouring even-even targets, the angular distributions indicated l=o transitions to many levels in the final nucleus. Partial angular distributions for the 149Sm (p, t) 147Sm reaction were obtained, but showed only one strong l=o transition populating the 147Sm ground state. In addition, spectra from the 152Sm (p, t) reaction were measured at several angles in order to provide normalization to previous results. / Thesis / Master of Science (MSc)

La réduction du CO₂ est considérée comme une des approches les plus intéressantes pour convertir ce gaz en produits chimique d’intérêt tels que les acides carboxyliques. Le marché de ces composés devrait augmenter considérablement au cours des prochaines années, d'où la nécessité de trouver des méthodes de production durables et respectueuses de l'environnement. Les complexes de samarium divalents sont reconnus pour leur fort pouvoir réducteur monoélectronique, ce qui en fait des réactifs de choix pour la réduction de certains groupes fonctionnels difficiles à réduire tels que le CO₂. Cependant, dans la littérature, bien que ce réactif ait été utilisé en association avec le CO₂, prouvant ainsi que la réduction du CO₂ est possible, mais jamais à notre connaissance pour des applications synthétiques. Nous rapportons ici l'activation du CO₂ initiée par le samarium bivalent électrogénéré. Grâce à notre méthode, récemment mise au point, pour la production électrochimique in situ d’espèces divalentes de samarium, la synthèse de dérivés de l’acide benzoïque a été réalisée avec succès. De plus, les conditions d'activation électrocatalytique du CO₂ ont été établies dans ce travail et appliquées non seulement à la préparation des acides phénylacétiques à partir de dérivés du chlorure de benzyle, mais également à l'hydrocarboxylation régiosélective des analogues du styrène et du phénylacétylène. Ce protocole à base de Sm (II) électrogénéré offre la prochaine génération de systèmes durables pour la transformation du CO₂ en molécules de haute valeur sous des conditions douces et sans l'ajout de co-réducteurs. / CO₂ activation is considered one of the most attractive tools to convert this cheap, abundant and non-toxic gas into valuable chemical feedstocks such as carboxylic acids. The market value of these compounds is expecting a significant increase in the next few years, thus the urgent need for sustainable and eco-friendly production pathways. Divalent samarium complexes are known for their strong monoelectronic reductive power that made them the perfect choice for the reduction of some challenging functional groups. Indeed, in the literature, this reagent has been used in combination with CO₂ but only to achieve the reductive disproportionation of CO₂ while no example reported C-C bond formation via CO₂ activation using the Sm(II) complexes. Herein, we report the CO₂ activation initiated by electrogenerated divalent samarium. Taking advantage of our recently developed method for the in situ generation of Sm(II) species, the synthesis of benzoic acid derivatives was successfully achieved. Furthermore, electrocatalytic CO₂ activation conditions were established in this work and applied not only for the preparation of phenylacetic acids from benzyl chloride derivatives but also for the regioselective hydrocarboxylation of styrene and phenylacetylene analogs. This electrochemical Sm(II)-based protocol offers the next generation of sustainable system to transform CO₂ into highly valued molecules under mild conditions and without the addition of co-reductants.

The research in permanent magnet thin films focuses on the search of new materials and methods to increase the prevalent data storage limit. In the recent past the work towards the application of these films to micro systems have also gained momentum. Materials like samarium cobalt with better magnetic properties and temperature stability are considered to be suitable in this regard. The essential requirement in miniaturization of these films is to deposit them on silicon substrates that can alleviate the micro fabrication process. In this work, an effort has been made to deposit SmCo films with better magnetic properties on silicon substrates. In the deposition of SmCo, the composition of the deposited films and the structural evolution are found to play an important role in determining the magnetic properties. Proper control over these parameters is essential in controlling the magnetic properties of the deposited films. SmCo being a two component material the composition of the films is dependent on the nature of the source and the transport of the material species from source to substrate. On the other hand, structural evolution is dependent on the energetical considerations between the SmCo lattice and substrate lattice. This most often is dominated by the lattice match between the condensing lattice and the substrate lattice. As such Si does not provide good lattice match to SmCo lattice. Hence suitable underlayers are essential in the deposition of these films. Materials like W, Cu, Mo and Cr were used as underlayers. Out of all these Cr is found to provide good lattice match and adhesion to SmCo lattice. Sputtering being the common deposition tool, SmCo could be sputtered either from the elemental targets of Sm and Co or from the compound target of SmCo5. Sputtering of elemental targets of Sm and Co provides the flexibility of varying the composition whereas sputtering from the SmCo alloy target provides to flexibility of controlling the structural evolution by different process parameters. In this work two different techniques namely Facing Target Sputtering (FTS) and Ion Beam Sputter Deposition (IBSD) were followed in depositing SmCo films. In FTS technique, SmCo films were directly deposited on silicon substrates by simultaneous sputtering of samarium and cobalt targets facing each other. This sputtering geometry enabled to achieve films with a wide composition range of 55 – 95 at. % of cobalt in single deposition. The resulting composition variation and material property variation were investigated in terms of process parameters like pressure, temperature, SubstrateTarget Distance (STD) and InterTarget Distance (ITD). The composition distribution of the films was found to be dependent on the thermalisation distances and the mean free path available during the transport. To explain the process and the composition variation, a simulation model based on Monte Carlo method has been employed. The simulated composition variation trends were in good agreement with that of the experimental observations. IBSD, known for its controlled deposition, was employed to deposit both Cr (as an underlayer) and SmCo films. Cr with close epitaxial match with SmCo induces structural evolution in deposited films. The initial growth conditions were found to play a dominant role in the structural evolution of these Cr films. Hence, initial growth conditions were modified by means of oblique incidence and preferential orientation of (200) plane was obtained. With three different angles of incidence, three different surface orientations of Cr films were achieved. These films were then used as structural templates in the deposition of SmCo films. The influence of parameters like composition, impurities, film thickness, beam energy, ion flux, annealing, angles of incidence and underlayer properties on the structural and magnetic properties of SmCo was studied. The structural evolution of SmCo has been found to depend on the structural orientation of Cr underlayers. This followed the structural relation of SmCo(100)||Cr(110)||Si(100) and SmCo(110)||Cr(100)||Si(100). A mixed surface plane orientation was observed in the case of mixed orientation Cr template. The magnetic coercivities were found to increase from 50 Oe to 5000 Oe with the change in the structure of the deposited films.

Le couplage croisé entre les esters allyliques et les composés carbonylés promu par le diiodure de samarium est une méthode efficace pour la formation de liaisons carbone-carbone. Une approche « umpolung » de réaction entre un composé carbonylé électrophile et un allylsamarien nucléophile, obtenu sans la réduction préalable d’espèces de type π-allylmétal de transition intermédiaires, fournirait une nouvelle voie plus simple pour la construction de cette liaison dans des conditions douces.Les esters allyliques de type dihydropyranyle se sont montrés d’excellents substrats dans les réactions d'allylation, d’aldéhydes ou de cétones, induites par le diiodure de samarium évitant ainsi l'utilisation de catalyseurs au palladium ou d’un autre additif. En série glycal, la nature et la configuration du substituant en position C-4 jouent un rôle très important à la fois sur le rendement et sur la structure des produits modifiés. Les couplages réducteurs directs ont lieu régiosélectivement en C-3 avec une stéréochimie relative 3,4-trans. La même stratégie appliquée aux dérivés Neu5Ac2en de l’acide sialique a permis d’obtenir par réactions à basse température, les produits de couplage en C-2 avec des rendements quantitatifs et une parfaite régio- et stéréosélectivité. Cette transformation donne un nouvel accès facile, rapide et très efficace aux α-C-sialosides. / The cross-coupling of allylic esters and carbonyl compounds promoted by samarium diiodide is an efficient method for the formation of carbon-carbon bonds. An umpolung approach, reaction between a carbonyl electrophile and an allyl samarium nucleophile, without the prior reduction of the intermediate π-allyl transition metal complexes, would provide a simple route for this bond construction under mild conditions.Dihydropyranyl allylic esters have been found to be excellent substrates for carbonyl allylation reactions mediated by samarium diiodide – without the use of palladium catalysts or any other additive. In glycal series, the nature and the configuration of the substituent at the C-4 position play crucial roles both on yields and structures of the modified products. The direct reductive couplings take place regioselectively at C-3 with a 3,4-trans relationship. Applied to Neu5Ac2en derivatives of sialic acid, the same strategy furnished the coupling products at the anomeric position in quantitative yields and with a perfect regio- and stereoselectivity. This transformation provides an easy, rapid and efficent access to α-C-sialosides.

Les acides ulosoniques constituent une famille de monosaccharides complexes dont les glycoconjugués présentent des propriétés biologiques importantes. L’acide sialique ou acide N-acétylneuraminique (Neu5Ac), membre le plus couramment rencontré de cette famille joue notamment un rôle dans l’infection par le virus Influenza. La liaison α-O-glycosylée des résidus naturels de Neu5Ac est cependant sensible à l’hydrolyse chimique et enzymatique. La synthèse d’analogues C-glycosylés qui présentent l’avantage d’être non-hydroysables, constituent alors un axe de recherche de grand intérêt. Les dérivés C-sialylés peuvent être préparés de manière rapide et efficace selon une méthode de couplage de type Reformatsky promue par le diiodure de samarium. Le travail réalisé au cours de cette thèse propose de nouvelles méthodes impliquant l’utilisation de ce métal divalent et permettant un accès rapide à des structures C-sialylées originales. Les réactions de samariation réductice réalisées sur des substrats sialylés fonctionnalisés par un groupement amide ont sélectivement conduit, après réduction d’un acétate anomère à l’obtention d’α-C-sialosides. Ces réactions sont réalisées dans les conditions de Barbier et d’excellents rendements ont été obtenus lorsque des cétones cycliques sont utilisées comme partenaire électrophile. Nous avons également montré qu’il était possible d’appliquer la samariation réductrice à la formation d’α-C-sialylspirolactones. La cyclisation est assurée par réaction de l’intermédiaire réactionnel sur un piège anionique de type cétone introduit sur le sucre grâce à la fonction acide carboxylique en position 2. Cette réaction peut être effectuée au départ de précurseurs porteurs de groupements réductibles acétate ou 2-thiopyridyle. Finalement, un travail méthodologique nous a permis de développer pour la première fois une synthèse sélective de β-C-sialosides. Sous l’action du samarium divalent en présence d’électrophile, la structure figée ⁵C₂ du dérivé lactonique bicylique de l’acide sialique identifié par Ogura en 1988, conduit sélectivement à des produits de couplage de configuration β. Les résultats obtenus par réduction d’un groupement anomère de type tosylate sont les plus encourageants. / Ulosonic acids are a complex monosaccharide family whose glycoconjugates present important biological properties. Sialic acid or N-acetylneuraminic acid (Neu5Ac), the most widespread member of this family, plays a crucial role in the infection with the virus Influenza. As the α-O-glycosidic bond of Neu5Ac conjugates is sensitive towards chemical and enzymatic hydrolysis, the synthesis of carbonated analogs that are not hydrolysable represents an important subject of research. The aim of our project was to develop new synthetic methods using samarium diiodide in order to obtain original C-sialylated structures. These derivatives can be easily prepared using Reformatsky coupling reactions promoted by this very efficient reductive reagent. Reductive samariation conditions applied to sialylated substrates functionalized by an amide group, selectively led to α-C-sialosides, via the reduction of the anomeric acetate group. These reactions were performed at room temperature under Barbier conditions and excellent yields of coupling products were obtained using ketones as electrophilic partner. We have also demonstrated that reductive samariation could be applied to the synthesis of α-C-sialylspirolactones. The Sm(II) mediated cyclizations were enable by reactions of the anomeric organometallic intermediates with keto anionic traps linked to the sugar via esterification of the carboxylic acid function of sialic acid derivatives. These reactions were conducted starting from sugar derivatives either with acetate or 2-thiopyridyle reductible groups in anomeric position. Finally, we have developed a new and selective synthesis of β-C-sialosides. Submitted to samarium diiodide in presence of electrophile, the conformationaly restricted ⁵C₂ bicyclic lactonic silalyl derivative described by Ogura in 1988, selectively led to β-coupling products. Our last results obtained from reductions of the anomeric tosylale group were the most promising.

Les nitrones peuvent être réduites par le diiodure de samarium et réagir selon une additionconjuguée avec des acrylates-silylés, silylés ou ,disilylés. Ce couplage réducteur,développé avec des aldonitrones simples, a conduit à des dérivés silylés de g-Nhydroxyaminoacides.Ces derniers ont pu être réduits puis cyclisés en g-lactames substituéspar un groupement silylé, dont la position et la configuration dépendent de l’acrylate dedépart. L’oxydation de Tamao-Fleming a ensuite permis la conversion des composés silylésen leurs correspondants hydroxylés avec rétention de configuration. Cet enchaînementréactionnel a alors été appliquée à une nitrone cyclique polyalkoxylée dérivée du L-xylose, cequi a permis les synthèses de la 7-desoxy Uniflorine A et de la (+)-Australine, deuxpyrrolizidines polyhydroxylées inhibiteurs de glucosidases. / Nitrones are reduced by samarium diiodide and react through a conjugated addition with silylacrylates. This cross coupling, developed with simple aldonitrones, allowed the preparation ofsilyl g-N-hydroxyaminoacids derivatives. The latter were reduced and cyclised in g-lactams inwhich the position and the configuration of the silyl group depend of the starting acrylate.Tamao-Fleming oxidation was used for the conversion of silyl group to hydroxyl group withretention of configuration. Then, the reaction was applied to a cyclic polyalkoxy nitronederived from L-xylose and it allowed the synthesis of 7-deoxy Uniflorine A and (+)-Australine, polyhydroxylated pyrrolizidines exhibiting glucosidases inhibition.

Made available in DSpace on 2014-10-09T12:36:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:21Z (GMT). No. of bitstreams: 1 03764.pdf: 1726774 bytes, checksum: 796db2a57899dea32f57ba34e954e2c2 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:36:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:21Z (GMT). No. of bitstreams: 1 03764.pdf: 1726774 bytes, checksum: 796db2a57899dea32f57ba34e954e2c2 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The physical properties of single crystals of samarium monosulfide exhibit a first order semiconductor-to-metal transition near 6.5 kbar. However, thin films of SmS show only a gradual change in their properties on applying pressure and this renders the technical utilization of the material difficult. Several mechanisms have been proposed as the cause of the smoothing of the transition. They include intrinsic stress, impurities, grain size, improper stoichiometry, and porosity, all of which can be traced to the physical vapor deposition techniques employed in preparing the films. In contrast, chemical vapor deposition was employed in this study because previous work had shown that it could minimize these detrimental modifications in thin films. A new CVD system was tested using a volatile organometallic as the samarium source and reacting it with H₂S. The deposited films contained considerable amounts of oxygen as evidenced by structure analysis, and the origin was traced to the samarium organometallic. The reaction of oxygen-free samarium tricyclopentadienyl with H₂S as well as chemical transport are suggested for deposition of stress-free SmS thin films in future work.