No description available.

No description available.

No description available.

ABSTRACT Solventless reactions of substituted cyclopentadienyl metal carbonyls of iron and ruthenium with electron donor ligands have been carried out. The reactions between CpFe(CO)2I and a range of phosphine ligands occurred in melt phase and yielded two typical compounds : salt product, [CpFe(CO)2PR3]I, and non-salt product, CpFe(CO)PR3I with the salt product being predominant. The complex [CpFe(CO)2]2 was used to catalyze these reactions. The progress of the reactions was followed by 1H NMR spectroscopy. The characterization of products correlates well with the products obtained when working in solution medium. The presence of a Me substituent on the Cp ring was found to favour the salt product formation but generally led to lower rates of reaction. Solventless reactions between RCpRu(CO)2I (R = H, Me) and solid phosphine ligands were also carried out. It has been observed that the ruthenium complexes were less reactive compared with their iron analogues but led to the same types of products namely salt and non-salt. The phosphite ligands were found to be less reactive than their phosphine analogues. In fact, the solventless reactions between RCpM(CO)2I (R = H, Me; M = Fe, Ru) were very slow even in the presence of [CpFe(CO)2]2 as a catalyst. However, when Me3NO.2H2O was added to the reaction mixture in solventless conditions, the non-salt product was obtained in a short period of time at 80oC. A range of cyclopentadienyl based metal complexes e.g [CpMo(CO)3]2, [MeCpRu(CO)2]2 etc. and palladium based compounds such as PdO, Pd/CaCO3 5% etc. were found to be good catalysts for the solventless reactions between CpFe(CO)2I and PPh3. Solventless migratory-insertion reactions have been successfully conducted between CpFe(CO)2CH3 and a range of solid phosphine ligands. Only the acetyl products, CpFe(CO)[PR3]COCH3 were obtained. SO2 insertion into RCpFe(CO)2R’ (R = H, CH3; R’ = CH3, CH2Ph) occurred quite easily at room temperature. However, when R was a carboxylic acid group, CO2H, no reaction took place. CO insertion into the same systems did not happen in solventless conditions.

A series of aluminia and titania promoted, silica- supported chromium (III) acetate catalysts were characterized using X-ray photoelectron spectroscopy (XPS) prior to, and after, activation in oxygen at 780 C. The results indicated that Cr (VI) was formed in each case as a result of the activation process. Increased promoter metal binding energies implied an interaction between the promoter and silica support. It is proposed that there is insertion of aluminium and titanium atoms into the silica network, which leads to formation of surface silicates. A qualitative measure of the metal dispersions has been made using the XPS results. In general, the chromium dispersion fell on activation, but the greatest decline was seen with the lowest chromium loading (0.5% Cr), Promoter metal dispersion was unchanged on activation, except in the case of the highest titanium loading (4.35% Ti), where small titania clusters are formed. Mass spectral analysis of the gases evolved during thermal decomposition in argon led to a mechanism being proposed for the decomposition of the acetate precursor. The first step is dehydration of the silica support, which is followed by decompositon of acetate ligands to form an intermediate, which was thought to be a carbonate, and the final stage is the decomposition of this intermediate to chromium (III) oxide for the unpromoted catalysts. Where a promoter is present a structural and electronic interaction between the chromium complex and the promoter is proposed, which leads to formation of mixed surface oxides of perovskite (M(^II)Ti(^IV)0(_3)) or spinel (M(^II)Al(_2)(^III)0(_4)) structure, where M = Cr. For activation under oxygen the pattern of decomposition was much simpler. Studies of the promoted catalysts showed the oxidation to occur—in two stages. It was not clear which chromium species were present after the first step, but the second step led to the formation of chromium (VI) oxide for all catalysts. Modelling of the adsorption sites on metal surfaces has also been undertaken with a series of triosmium carbonyl complexes containing ligands derived from aniline, phenol, pyrrole, furan, thiophene and benzene. These complexes have been characterized using Fourier Transform Infra Red spectroscopy and their vibrational spectra assigned in full. The usefulness of these complexes as models, and in the assignment of vibrational spectra of adsorbates on metal surfaces, is discussed.

Student Number : 0009404H - PhD thesis - School of Chemistry - Faculty of Science / Six-coordinate ruthenium complexes of the type ttt-RuX2(RNC)2(PPh3)2 (X = Cl ; R = tBu, 2,6-xylyl, benzyl, 2-OMe-4-Clphenyl and iPr; X = Br; R = = tBu, 2,6-xylyl, benzyl, iPr ) were synthesized and fully characterised by IR, NMR spectroscopy and elemental analysis. These complexes were all found to undergo solid-state isomerisation from the ttt-isomer to the cct-isomer. It was found that solid state isomerisation occurred before melting i.e. in the solid state for all the ttt-RuX2(RNC)2(PPh3)2 complexes investigated . The thermal solid state isomerisation process was monitored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomicroscopy and X-ray powder diffraction techniques. The results revealed that the isomerisation process occurred exothermally with darkening of the crystal. A mechanism which involved rotation of small ligands was proposed to explain the solid-state isomerisation process. Kinetic studies of the solid-state isomerisation of some of the ttt-RuCl2(RNC)2(PPh3)2 complexes were carried out and monitored by NMR spectroscopy and compared with kinetic studies performed by XRD methods. The results are similar and also suggest that the isomerisation reaction follows first order kinetics. The crystal and molecular structure of ttt-RuCl2(2,6-xylylNC)2(PPh3)2 was determined by X-ray single crystal diffraction techniques and its structure was compared with related ttt- RuX2(RNC)2(PPh3)2 complexes. Inter-molecular and intra-molecular interactions in these molecules in the solid state were analysed and used to rationalise the solid-state isomerisation results. The results obtained for the ruthenium complexes suggested that other six-coordinate complexes could undergo solid state isomerisation reactions and this study was extended to molybdenum complexes of the type cis-Mo(CO)4L2. These complexes undergo cis to trans isomerisation in solution. The solid state reactivity of these complexes was investigated for the first time. The complexes with L = PPh2Me and PPh2Et isomerised in the melt whist complexes with L = PPh3 amd P(m-tolyl)3 were indeed found to undergo solid state isomerisation reactions. Structural studies and thermomicroscopic investigations were done on cis- Mo(CO)4(PPh3)2 and Mo(CO)4{P(m-tolyl)3)2 and the results were used to rationalize the solid state reactivity of these complexes.

This dissertation can be divided into two parts project goals. The first one is the synthesis of rhenium (Re) complexes which are potential reverse saturable absorber (RSA) materials. The second one is the polymerization of ruthenium (Ru) polypyridyl monomers to have an oligomer ensemble for solar light harvesting purposes. THE FIRST part starts with an introduction to optical limiting materials (OLM) (chapter 1). The main discussion in chapter 4 is about the photophysical properties and energy-transfer reactions for three series of facial Re(I) tri-carbonyl complexes. The complexes are of the general type fac-[Re(CO)3(N-N)Cl], where Cl is the chloride and N-N are novel mono functionalized aryl-oligo(p-phenylene-vinylene) bipyridine (bpy) ligands. These series is as a result of changing the aryl group of the ligands to either anthracene or pyrene, and di-alkoxy attachments of phenyl ring in anthracene bipyridine ligands. The synthesis of the bpy ligands involved attaching various aryls by utilizing successive multi-step Wittig-Horner reactions (chapter 2). The ligands were later reacted with Re pentacarbonyl chloride to obtain the complexes. Chromium complexes synthesis is also included (chapter 3). The characterization involved 1H NMR, ESI-MS and elemental analysis. There is also another set of ligands where the aryl group is di-methylaminophenyl where the solvatochromic emission properties of the ligands were studied but were not coordinated to metals. The excited-state properties using both the nanosecond (ns) and picosecond (ps) time resolved transient absorption (TA) of Re(I) complexes shows strong positive excited-state absorption signals in 500-800 nm range. From the TA (ps) and time-resolved infrared of the carbonyl region, the excited state forms instantaneously after excitation. Their observed lifetimes are relatively long (2 μs-40 μs range) and they increase as the phenylene-vinylene linker increases. The excited state triplet energies values for the complexes were obtained experimentally using energy transfer method from the simple Sandros relation. They decreases as the π-conjugated phenylene-vinylene linker decreases, this is because the extended backbone bridge serves to lower the energy of the triplet excited state. Lastly, the Re(I) complexes triplet-triplet molar extinction coefficients(δex) were measured by energy transfer to a standard method and their ratios to the ground state molar absorptivity(δg ) are all (δex/δg ≥40) at 530nm which make them potential candidates for RSA. THE SECOND part involves RAFT polymerization of two new acrylamide functionalized Ru(II) polypyridyl monomers. Photoinduced electron transfer reactions for the obtained Ru oligomers and complexes were done using 10-methylphenothiazine (MPT) quencher (chapter 8). The synthesized acrylamide functionalized bipyridine ligand (chapter 6) was reacted with complex precursors cis-[Ru(L)2Cl2] where the ligand (L) is either 2,2’- bipyridine or biquinoline (chapter 7). The obtained Ru(II) photosensitizers acts as energy donating and accepting respectively. The attachment of these Ru complexes to oligomer backbone as side chains is by a C11 alkyl linker. 1H NMR, UV-Vis spectroscopy, and differential pulse voltammetry (DPV) were used to characterize the ligand, monomers and oligomers. The excited state REDOX potentials were determined using the cyclic voltammetry (CV) values and steady state emission values converted to electron volt (eV). Lastly, the TAs (ns) obtained in the presence of MPT electron donating quencher was in agreement with the ones calculated/ predicted from spectroelectrochemistry. These efforts are toward the goal of making a panchromatic solar light collector in the visible region (chapter 5). / acase@tulane.edu

Die vorliegende Arbeit beschreibt die Synthese Ferrocenyl-funktionalisierter Phosphole und deren elektrochemische sowie spektroelektrochemische Charakterisierung zur Bestimmung der Stärke der Metall-Metall-Wechselwirkungen. Aufgrund der mangelnden Aromatizität stehen das freie Elektronenpaar am Phosphoratom und das dienische System für weitere Reaktionen zur Verfügung. Somit konnten gezielt Modifikationen am heterozyklischen Grundgerüst vorgenommen werden, um dessen elektronische Eigenschaften zu beeinflussen. Ein Schwerpunkt der Arbeit lag im Aufbau eines Phospholsystems mit Ferrocenyl-substituenten in 2- und 5-Position des Heterozyklus. Weiterhin wurden die Auswirkungen auf die elektronischen Eigenschaften des Moleküls nach chemischer Oxidation des Phosphoratoms von PIII zu PV mit Schwefel und Selen untersucht. Ein weiterer Schwerpunkt lag in der Synthese von Übergangsmetallkomplexen des 2,5-Diferrocenyl-1-phenyl-1H-phosphols, um den Einfluss des Phosphoratoms und des dienischen Systems auf die elektronische Wechselwirkung der Ferrocenylgruppen genauer zu untersuchen und die elektronischen Eigenschaften gezielt zu beeinflussen. In weiteren Arbeiten wurden räumlich anspruchsvolle Substituenten am Phosphoratom zur Veränderung der Geometrie der pyramidalen Phosphorumgebung und somit zur Erhöhung der Delokalisierung im Heterozyklus eingeführt. Die Phosphole mit räumlich anspruchsvollen Gruppen zeigten die größte Metall-Metall-Wechselwirkung der Fc/Fc+-Gruppen über den Phospholring.

Made available in DSpace on 2016-06-02T20:34:56Z (GMT). No. of bitstreams: 1 6264.pdf: 6241491 bytes, checksum: c10b9312872f17d86e9c24ccd25b2508 (MD5) Previous issue date: 2014-10-09 / Universidade Federal de Minas Gerais / Due to its versatile chemistry and ability to stabilize metals with low oxidation states, carbonyl compounds of transition metals play an important role in various fields of organometallic chemistry. In our research group, we have studied carbonyl compounds of manganese (I) over time and investigated their photochemical and spectroscopic properties. We carried out studies in photochemistry, electrochemistry (cyclic voltammetry and spectroelectrochemistry accompanied by UV-Vis and IR) and photoinduced intermolecular electron transfer (ET) reactions (with the electron acceptor MV2+, methylviologen) for the compound fac- [Mn(phen)(CO)3(4MeImH)](SO3CF3) (fac-1) where phen = 1,10-phenanthroline, 4MeImH = 4-methyl-imidazol and SO3CF3 = triflate ion, compound already synthesized and processed by the group. fac-1 shows electronic absorption bands in the UV-Vis at 380 (MLCT) and 270 nm (LLCT) in CH3CN and intense bands in IR between 2200 and 1800 cm-1, consistent with the facial arrangement of the three CO ligands in the sphere of coordination of the metal. The complex is stable in solid state and is a mixture of two isomers while in solution, the adjacent (A) and remote (R) isomers relative to the nitrogen atom (N) of the 4MeImH ligand which coordinates to the metal Mn. Encouraged by the results obtained by the group before, in which the compound fac-1 under irradiation of light in aqueous solution and in the absence of oxidizing agents in the reaction medium was able to cleave a molecule of water to produce molecular oxygen (O2) detected by a Clark electrode, we investigated the reduction and conversion of carbon dioxide molecules (CO2) to CO using this compound of Mn in organic solution, by photochemical and electrochemical means in N2 and CO2 atmosphere. Through the development of chemical processes, the petrochemical industry has made great contributions to mankind but at the same time the release of large amounts of CO2 in the atmosphere has harmed the environment. Capturing this gas emitted into the atmosphere primarily by the burning fossil fuels is a necessary strategy to minimize the greenhouse effect. In our photochemical studies, the complex was able to reduce CO2 to CO, product detected by 13C NMR (185 ppm), and the mechanisms of photochemical and electrochemical reactions of fac-1 in the presence of CO2 were checked. We carried out DFT calculations to corroborate experimental data and the results show the agreement of the UV-Vis and IR spectrum for the proposed product. A comparison of results shows the importance of ligand 4MeImH in the multiple photoinduced electron transfer reactions assisted by protons and the great potential of the fac-1 compound to participate in photocatalytic processes of interest, such as the reduction and conversion of CO2 to products of interest to the chemical industry. / Devido a sua química versátil e habilidade em estabilizar metais com baixos estados de oxidação, os complexos carbonílicos de metais de transição desempenham um papel importante em vários campos da química organometálica. No nosso grupo de pesquisa complexos carbonílicos de manganês (I) vêm sendo estudados ao longo do tempo e suas propriedades espectroscópicas e fotoquímicas investigadas. Neste trabalho estudos fotoquímicos, eletroquímicos (voltametria cíclica e espectroeletroquímica acompanhada por UV-Vis e IV) e de reações de transferência de elétrons (TE) intermoleculares fotoinduzidas (com o receptor de elétrons MV2+, metilviologênio) foram realizados para o complexo fac- [Mn(phen)(CO)3(4MeImH)](SO3CF3) (fac-1) em que phen = 1,10-fenantrolina, 4MeImH = 4-metil-imidazol e SO3CF3 = íon triflato, complexo já sintetizado e caracterizado pelo grupo. fac-1 apresenta bandas de absorção eletrônica no UV-Vis em 380 (MLCT) e 270 nm (LLCT) em CH3CN e bandas intensas no IV entre 2200 e 1800 cm-1, consistentes com o arranjo facial dos três ligantes CO na esfera de coordenação do metal. O complexo é estável no estado sólido e em solução e se apresenta como uma mistura de dois isômeros, o adjacente (A) e o remoto (R) em relação ao átomo de nitrogênio (N) do ligante 4MeImH que se coordena ao metal Mn. Estimulados pelos resultados anteriormente obtidos pelo grupo em que o complexo fac-1 sob irradiação de luz em solução aquosa e na ausência de agentes oxidantes no meio reacional foi capaz de clivar a molécula de água produzindo oxigênio molecular (O2) detectado por eletrodo de Clark, nesta etapa do nosso trabalho investigamos a redução da molécula de gás carbônico (CO2) a CO usando o complexo de Mn em solução orgânica, por via fotoquímica e eletroquímica em atmosfera de N2 e CO2. Através do desenvolvimento de processos químicos, a indústria petroquímica tem realizado grandes contribuições para a humanidade, mas ao mesmo tempo, a liberação de grandes quantidades de CO2 na atmosfera tem prejudicado o ambiente. A captura deste gás, emitido principalmente pela queima de combustíveis fósseis, é uma estratégia necessária para minimizar o efeito estufa. Nos nossos estudos fotoquímicos, o complexo foi capaz de reduzir CO2 a CO, produto detectado por RMN 13C em 185 ppm, e os mecanismos das reações fotoquímicas e eletroquímicas na presença de CO2 foram averiguados. Cálculos computacionais do tipo DFT foram realizados para corroborar os dados experimentais e os resultados mostram a concordância nos espectros de UV-Vis e IV para os produtos propostos. A comparação dos resultados mostra a importância do ligante 4MeImH nas reações fotoinduzidas de transferência de elétrons múltiplas assistidas por prótons e o grande potencial do complexo fac-1 em participar de processos fotocatalíticos de interesse, como a conversão do CO2 a produtos de interesse da indústria química.

Die vorliegende Arbeit beschreibt die Synthese Ferrocenyl-funktionalisierter Phosphole und deren elektrochemische sowie spektroelektrochemische Charakterisierung zur Bestimmung der Stärke der Metall-Metall-Wechselwirkungen. Aufgrund der mangelnden Aromatizität stehen das freie Elektronenpaar am Phosphoratom und das dienische System für weitere Reaktionen zur Verfügung. Somit konnten gezielt Modifikationen am heterozyklischen Grundgerüst vorgenommen werden, um dessen elektronische Eigenschaften zu beeinflussen. Ein Schwerpunkt der Arbeit lag im Aufbau eines Phospholsystems mit Ferrocenyl-substituenten in 2- und 5-Position des Heterozyklus. Weiterhin wurden die Auswirkungen auf die elektronischen Eigenschaften des Moleküls nach chemischer Oxidation des Phosphoratoms von PIII zu PV mit Schwefel und Selen untersucht. Ein weiterer Schwerpunkt lag in der Synthese von Übergangsmetallkomplexen des 2,5-Diferrocenyl-1-phenyl-1H-phosphols, um den Einfluss des Phosphoratoms und des dienischen Systems auf die elektronische Wechselwirkung der Ferrocenylgruppen genauer zu untersuchen und die elektronischen Eigenschaften gezielt zu beeinflussen. In weiteren Arbeiten wurden räumlich anspruchsvolle Substituenten am Phosphoratom zur Veränderung der Geometrie der pyramidalen Phosphorumgebung und somit zur Erhöhung der Delokalisierung im Heterozyklus eingeführt. Die Phosphole mit räumlich anspruchsvollen Gruppen zeigten die größte Metall-Metall-Wechselwirkung der Fc/Fc+-Gruppen über den Phospholring.