Medium-sized organic ring synthesis poses a seemingly insurmountable challenge, and because of this it is a field under immense investigation. Heterocyclic containing medium-sized rings are common structural motifs in nature, which has caused researchers to investigate their potential biological activity and properties as materials. This research focused on the grand challenge of medium-sized heterocyclic ring synthesis, providing the synthesis community with new tools to generate these highly evasive products, while elucidating energetic and geometric properties of one of Nature's least understood organic ring systems. Cobalt(II)-Amidoporphyrins, [Co(D2-Por)], are an emerging class of metalloradical catalysts (MRC) which can facilitate a wide range of atom and group transfer reactions. A strategy was employed using [Co(D2-Por)] to carry out an intramolecular C-H amination reaction using sulfamoyl azides as the radical nitrene source to aminate the highly reactive aldehydic C-H bond. This newfound reaction allowed for the generation of previously unobtainable medium-sized heterocycles, which surprisingly provided a racemic mixture of chiral medium-sized rings. A wide array of chiral amidoporphyrins including meso-heteroatom containing porphyrins were synthesized as well during the course of research to probe their potential as new chiral ligands for the emerging field of cobalt(II)-amidoporphyrin catalyzed MRC system. A practical synthetic scheme was discovered employing the highly selective Zn(II)-bromoporphyrin synthon to generate a new library of chiral amidoporphyrin ligands for the MRC system through well-established cross-coupling methodologies.

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The oxidation of 4-t-butyltoluene in glacial acetic acid by hydrogen peroxid in a process catalysed by cobalt(II) acetate tetrahydrate and sodium bromide has been studied with the aim of increasing the selectivity towards 4-t-butylbenzaldehyde.

Graduation date: 1997

Ce travail de doctorat s’inscrit dans le cadre de la recherche fondamentale inhérente à la réaction catalytique d’hydrogénation du CO, qui permet de produire du pétrole de synthèse à partir des autres ressources fossiles disponibles à l’état naturel (gaz naturel et charbon). Les objectifs de ce travail s’articulent autour de deux méthodes originales, respectivement de préparation et de caractérisation des catalyseurs. La première permet la formation in situ de catalyseurs par voie oxalique, alors que la seconde est une méthode de cinétique transitoire chimique appliquée à la réaction CO + H2. Dans un premier temps, la préparation de catalyseurs « modèles » de cobalt et de nickel a été réalisée en faisant intervenir un oxalate comme précurseur à la formation in situ du catalyseur. L’étude de cette méthode de préparation par « voie oxalique » nous a tout d’abord permis de discuter du mécanisme de formation de l’oxalate, que nous envisageons comme une polymérisation faisant intervenir des ligands oxalate tétradentates établissant des ponts entre les atomes métalliques. La décomposition thermique de l’oxalate de cobalt a été étudiée dans un second temps. Nous nous somme penchés en particulier sur l’influence de l’atmosphère de la décomposition sur la nature du catalyseur obtenu in fine. Utiliser l’hydrogène comme gaz réducteur permet d’obtenir des catalyseurs purement métalliques développant une surface spécifique intéressante. Ces catalyseurs ont été utilisés pour les études cinétiques transitoires chimiques de la réaction CO + H2. Les phénomènes transitoires observés ont permis de corréler les hypothèses formulées pour l’élaboration d’un mécanisme original initialement proposé par A. Frennet. En particulier, la dépendance des vitesses réactionnelles aux pressions partielles de CO et d’hydrogène permet d’envisager un mécanisme d’allongement de chaîne basé sur la réactivité d’un intermédiaire réactionnel avec les réactifs en phase gazeuse. Au vu des recouvrements de surface sous conditions réactionnelles ainsi que des phénomènes transitoires observés, cet intermédiaire est constitué de plusieurs atomes (carbone, oxygène et hydrogène), et est à l’origine de la formation des produits de la réaction (CH4 et alcanes à plus longues chaînes), dont la désorption en phase gazeuse suit un processus en deux étapes lors duquel l’influence de l’hydrogène est primordiale.

Thermoelectric materials are solid state devices having the capability to convert heat to electrical energy and vice versa. These materials are simple, have no moving parts and use no greenhouse gases. But the major drawback of these materials is their low conversion efficiency. Hence enhancement of thermoelectric efficiency is required to make the use of these devices widespread. Thermoelectric efficiency is related to a parameter termed figure of merit, ZT which is associated with the inter-related transport properties such as Seebeck coefficient, electrical and thermal conductivity. Efficient thermoelectric material should possess high Seebeck coefficient (S), high electrical conductivity () and low thermal conductivity (). The present investigation revolves around improvement of ZT of CoSb3 either by chemical doping or through microstructural modifications. These materials possess structural voids, which can be filled with foreign atoms. The rattling motion of these filler atoms reduces the thermal conductivity of these materials, thereby increasing the thermoelectric efficiency. The rattler atoms chosen for the present study are Mn and Yb. Both coarse and fine-grained MnxCo4Sb12 (x = 0. 0.2, 0.4, 0.8, 1.2 and 1.6) and Yb0.19Co4Sb12 have been synthesized and subjected to various structural and functional property characterizations. The structural study based on Rietveld Analysis and the corresponding difference Fourier maps confirms the void occupancy by Mn and Yb in MnxCo4Sb12 (x 0.2, 0.4 and 0.8) and Yb0.19Co4Sb12. In higher Mn content, x=1.2 and 1.6, Mn was found to partially substitute Co site and partially fill the voids and the remaining precipitated out as free particles. A comparative study of coarse and fine-grained CoSb3 has thrown light in to the grain size effect on the thermoelectric properties. Lowering of grain size helped in enhancement of ZT in CoSb3. Seebeck coefficient (thermoelectric power), electrical and thermal conductivity have been measured for different concentrations of the filler Mn atoms between 300K and 673K. A change in sign of the Seebeck coefficient from negative to positive occurs, when Mn concentration exceeds x=0.8. Electrical resistivity values was found to decrease initially with Mn filling with the minimum value at Mn content, x=0.4 and then gradually increase as Mn content increases. The thermal conductivity value decreases with Mn content in the CoSb3 indicating their rattling property which helps in the enhancement of the overall thermoelectric efficiency. There is a reduction in the value of ktotal in Mn filled CoSb3 than that of the unfilled counterpart. This decrease in the ktotal is a clear indication of the rattling motion of the filler Mn atom in the structural void of CoSb3. Highest ZT of 0.36 is achieved by Mn0.4Co4Sb12 at 373K. Higher concentration of Mn (with x= 1.2 and 1.6) proved to be detrimental in terms of improvement of the value of ZT. Grain size reduction helped in improvement of ZT in Mn0.2Co4Sb12. Maximal ZT of 0.06 at 523K is achieved in hot pressed Mn0.2Co4Sb12. The corresponding coarse-grained material is found to possess ZT of 0.01 at the said temperature. The enhancement can be attributed to high / ratio and high density. Similarly, fine grained Yb0.19Co4Sb12 shows higher ZT compared to the coarse-grained sample because high / and high S.

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This research project is part of a larger Canadian endeavour to evaluate feasibility of using new nanocatalyst formulations for Fischer-Tropsch synthesis (FTS) to convert fossil-derived or renewable gaseous fuels into green diesel. The green diesel is a clean fuel (with no aromatics and sulfur compounds) suitable for the commonly used transportation system. The catalyst investigated is cobalt metal supported on carbon nanotubes (CNTs). The physical properties of CNTs have improved the common cobalt catalyst currently used in industry. Carbon nanotubes have high surface area, a very stable for FTS activity and, contrary to other common supports, do not interact with the catalyst active phase to produce undesirable compounds. Moreover, CNTs differ from graphite in their purity and by their cylindrical form, which increases the metal dispersion and allows confinement of the particles inside the tubes. Thus, carbon nanotubes as a new type of carbon material have shown interesting properties, favoring catalytic activity for FTS cobalt catalyst. Their surface area can be modified from 170 to 214 m^2/g through acid treatment. The CNT support lowers the amount of Ru promoter needed to increase the catalyst activity up to 80 % CO conversion and potassium promoter increases the selectivity for á-olefins. The olefin to paraffin (O/P) ratio for Co/CNT and CoK/CNT are 0.76 and 0.90, respectively. Moreover, the Co-Fe bimetallic catalysts supported on CNT have proved to be much more attractive in terms of alcohol formation, up to 26.3 % for the Co10Fe4/CNT. The structural characteristics of CNTs have shown to be suitable for use as catalytic support materials for FTS using microemulsion preparation method as applied to produce nanoparticle catalysts. Microemulsion technique results show uniform nanoparticle that are easy to reduce. In addition, the confinement of the particles inside the CNT has improved the lifetime of the catalyst by decreasing the rate of sintering. The deactivation rate at high FTS activity is linear (XCO = -0.13 t(hr) + 75) and at low FTS activity is related to a power law expression of order 11.4 for the cobalt particles outside the tubes and 30.2 for the cobalt particles inside the tube. The optimized catalyst studied was the CoRuK/CNT catalyst. The best kinetic model to describe the CoRuK/CNT catalyst is: 18.5 x 10 ^-5 PH2^0.39/ (1 + 7.2 10 ^-2 PCO^0.72 PH2^0.1)^2.

El cobalt Procedent de kobold, goblin o esperit maligne, com era anomenat antigament. El seu descobriment s'atribueix el 1735 al químic suec Georg Brandt (1694-1768). Químicament, el cobalt, de configuració electrònica [Ar] 4s2 3d7, es troba en els estats d'oxidació +1 (d8), +2 (d7) i +3 (d6), sent el més estable el Co(II). D'altra banda, aquests cations existeixen en diferents estats d'espín i electrònics, fruit de la diferent ocupació dels orbitals 3d i del 4s (ocupació fonamental en la interacció Colligand). Així, el catió Co(I) es pot trobar en els estats 3F, 1G (procedents d'una ocupació 3d8) i 5F (procedent d'una ocupació 4s1 3d7). Anàlogament, per al Co(II) es poden trobar els estats 4F i 2G (derivats de la configuració 3d7).La glicina Glicina, Gly o G. Un dels aminoàcids que formen les proteïnes, de fórmula NH2CH2COOH, on la cadena lateral correspon a un àtom d'H. Per aquest motiu, és el més senzill i l'únic no quiral. La lisina Lisina, L-lisina, Lys, K. De fórmula NH2CH[(CH2)4NH2]COOH, és un dels aminoàcids bàsics, degut al NH2 terminal de la cadena lateral (-(CH2)4NH2). Forma part del grup d'aminoàcids essencials, no podent ser sintetitzat pels humans. La basicitat de la seua cadena lateral el fa susceptible d'interaccionar amb els cations metàl·lics. Homopèptids També anomenats oligopèptids, polipèptids. Cadenes formades per la unió d'aminoàcids del mateix tipus, NH2CHR(CONHCHR)nCOOH (n=1- ...; R = cadena lateral). Cada polímer conté n+1 residus del mateix aminoàcid i n enllaços peptídics. La presència (lisina) o absència de cadena lateral (glicina) determina la interacció dels cations metàl·lics amb aquests lligands. El DFT Acrònim per a Teoria del Funcional de la Densitat. Formulació alternativa de la mecànica quàntica que permet obtindre informació sobre l'energia i l'estructura de sistemes amb múltiples partícules a partir de la densitat electrònica d'aquests. Densitat calculada mitjançant eines computacionals. L'espectrometria de masses Eina d'anàlisi consolidada en diversos camps, com la proteòmica, on s'empra en la seqüenciació de pèptids. L'objectiu: buscar patrons de fragmentació d'un pèptid per determinar-ne la seqüència d'aminoàcids, fragmentacions que s'aconsegueixen mitjançant tècniques d'ionització. Aquests blocs anteriors conflueixen en el treball d'aquesta memòria. Així, s'ha realitzat un estudi de la interacció dels cations Co(I) i Co(II), en diferents estats d'espín, amb els aminoàcids glicina i lisina i amb homopèptids derivats d'ells, emprant eines computacionals i d'espectrometria de masses. / Cobalt From kobold, goblin, the way it was called in ancient times. Its discovery, in 1735, is attributed to the Swedish chemist Georg Brandt (1694-1768). Chemically, Cobalt has an electronic configuration [Ar] 4s2 3d7 and it can be found in the following oxidation states: +1 (d8), +2 (d7) and +3 (d6), being the Co(II) the most stable. On the other hand, these cations can exist in different spin and electronic states, arising from a different occupation of the 3d and 4s orbitals (such occupation is crucial in the Co-ligand interaction). Thus, Co(I) can be found in the 3F, 1G (both arising from a 3d8 occupation) and 5F (coming from a 4s1 3d7 occupation) states. In the same way, for Co(II) we can find the 4F and 2G states, arising from a 3d7 occupation. Glycine Glycine, Gly or G. One of the amino acids found in proteins, which has the formula NH2CH2COOH, where the side chain is an H atom. For this reason, it is the simplest amino acid and the only that is not chiral. Lysine Lysine, L-lysine, Lys, K. Having a formula NH2CH[(CH2)4NH2]COOH, it is one of the basic amino acids, due to the terminal NH2 group of the side chain (-(CH2)4NH2). It is one of the essential amino acids, for what it cannot be synthesized by humans. Its side chain basicity makes it capable of interacting with metal cations. Homopeptides Also known as oligopeptides and polypeptides. Polymeric chains formed by the union of amino acids of the same type, NH2CHR(CONHCHR)nCOOH (n=1- ...; R = side chain). Each polymer contains n+1 residues of the same amino acid and n peptide bonds. The presence (lysine) or absence (glycine) of the side chain determines the interaction of metal cations with these ligands. DFT Acronym that stands for Density Functional Theory. Alternative formulation of the quantum mechanics that allows obtaining information about the energy and the structure of many body systems, from their electronic density. Density calculated by means of computational techniques.Mass spectrometry Analysis tool consolidated in different areas, such as proteomics, where it is used in peptide sequencing. The goal: to look for peptide's fragmentation patterns in order to determine the amino acid sequence. These fragmentations are achieved by means of ionization techniques. These blocks converge in the work presented in this manuscript. Thus, a study about the interaction of Co(I) and Co(II) cations, in different spin states, with the amino acids glycine and lysine and with their homopeptides, has been made, using both computational and mass spectrometry techniques.