This thesis is principally concerned with the interaction of cobalt porphyrin complexes with halocarbons. There have been no previous studies of these, despite the afct that the ability to readily introduce substituents into the porphyrin ligand makes it ideal for inducing subtle electronic and steric changes into the complexes. The reactions of various substituted cobalt tetraphenylporphyrins with halocazbons was studied. Three series of experiments were performed involving activation by heat, visible light and ultraviolet light. Products were characterized by electronic, nmr and mass spectrometry. The five coordinate complexes, [CoX (Por)] , obtained from thermally activated reactions and those performed with uv irradiation under nitrogen, proved particularly difficult to characterize since they are subject to disproportionation giving paramagnetic products. This aspect is discussed in detail and the results obtained allow clarification of conflicting reports in the literature. A qualitative investigation of relative reaction rates has led to the tentative suggestion that thermal reactions proceed by an electron transfer mechanism, whereas an atom abstraction mechanism applies to reactions involving activation by ultraviolet light. No reaction took place between cobalt porphyrins and the substrates in the presence of visible light. Aerobic ultraviolet radiation results in the formation of cobalt porphyrin [pi]-cation radicals with either a1u or azU. ground states, depending on the substituent pattern of the porphyrin. The cobalt porphyrins were all shown to possess catalytic activity for halocarbon-alkene addition reactions. Furthermore, studies in this area suggest that the catalytic activity could be correlated wíth the substituent pattern on the porphyrin ligand and, thus, complements the studies described above. A related rhodium complex was also synthesized and examined but was shown to have a disappointingly low catalytic activity. Products of [RuC1[sub]2z(PPh[sub]3)[sub]3] -catalysed additions of halocarbons to cyclohexa-1,3-diene were investigated by chromatographic and spectroscopic analyses to ascertain the stereochemistry of the products. The ratio of the two isomeric products was found to depend on steric effects of the addend groups, CX[sub]3 (X = Cl, Br) and X (X = Cl, Br).

The thesis is presented in two parts, part one concerns the synthesis and biodistribution of technetium–porphyrin complexes. A series of compounds with the general formula TcO(Porhyrin)OAc and TcO(Phthalocyanine)OPh have been synthesised via a novel route. The starting material comprised NH4TcO4 with acetic acid for the porphyrin and phenol for the phthalocyanine. The compounds have been characterised both qualitatively and quantitatively by infra-red, ultra-violet and mass spectrometry. Thin Layer Chromatography (TLC) and electrophoresis have also been employed to further analyse the complexes. Preliminary biodistribution studies have been performed in a model of inflamed tissue. The results suggest that the labelled porphyrins are capable of imaging such tissue. One of the complexes was tested for an ability to accumulate in, and image tumours, however this proved unsuccessful.

The development of an efficient, catalytically active, biomimetic model for cytochrome P-450 enzymes has been an area of intense research activity. Ruthenium porphyrin complexes have been the center of this research and have successfully been utilized, as catalysts, in major oxidation reactions such as the hydroxylation of alkanes, the epoxidation of alkenes and aromatic rings, and the N-oxidation of amines, among others. In this project, the kinetics of two-electron sulfoxidation of para-substituted phenyl methyl sulfides to the corresponding sulfoxides with well-characterized trans-dioxoruthenium(VI) porphyrin complexes were studied by rapid stopped-flow spectroscopy. The substituent effect in sulfides and in dioxoruthenium(VI) complexes were also kinetically investigated. The low-reactive trans-dioxoruthenium(VI) porphyrin complexes (3a-b) were synthesized from the oxidation of their carbonylruthenium(II) porphyrin precursors with m-chloroperoxybenzoic acid (m-CPBA) and characterized spectroscopically by 1H-NMR, IR, and UV-vis. The low-reactivity of these complexes makes them suitable for kinetic studies. The sulfoxidation with the trans-dioxoruthenium(VI) species followed a pseudo-first order kinetic decay from RuVI to RuIV species with no accumulation of intermediates. The reactivity order in the series of dioxoruthenium(VI) complexes follows 3b > 3a >3c, which is consistent with expectations based on the electrophilic nature of high-valent metal-oxo species. Steric effect of the substituents on the complexes also affected the reactivity order. The kinetic results revealed that the sulfoxidation reaction with these well-characterized dioxoruthenium(VI) complexes is 3 – 4 orders of magnitude faster than the epoxidation reaction with the same complexes under similar conditions.

Durante o desenvolvimento deste projeto, foram obtidos diversos resultados relativos à construção de distintos sensores eletroquímicos para a determinação de oxigênio em meio aquoso em amostras biológicas e ambientais. Para a construção destes sensores foram usadas diferentes superfícies eletródicas, preparadas pela incorporação de porfirinas de cobalto sintetizadas e caracterizadas no laboratório do Prof. Dr. Koiti Araki, tais como a 5,10,15,20-meso-tetrafenilporfirina de cobalto (CoTPP) e a [tetrakis-bisdimetil-bipiridina cloro rutênio(II)]-5,10,15,20-Tetrapiridinaporfirina de cobalto (II) (CoTRP). Eletrodos de ouro modificados com nanoestruturas de ouro também foram empregados para a detecção de oxigênio. Em alguns casos, óxido de grafeno (GO) foi imobilizado nas superfícies eletródicas para melhorar o transporte de elétrons. Porfirinas de CoTPP foram imobilizadas em eletrodo de carbono vítreo (GCE) e o comportamento eletroquímico desse eletrodo modificado para a redução de oxigênio em solução aquosa de KNO3 0,1 mol L-1 foi comparado com o do GCE, observando-se diminuição do sobrepotencial. A utilidade do sensor foi demonstrada pelo monitoramento amperométrico contínuo do consumo de oxigênio mitocondrial e os resultados foram concordantes com aqueles obtidos em medições paralelas realizadas usando um eletrodo comercial (\"eletrodo de Clark\"). GO foi misturado com a porfirina de CoTRP para a preparação de compósitos, os quais foram posteriormente imobilizados em superfícies eletródicas. Verificou-se que as moléculas de CoTRP ficavam em forma horizontal na superfície do GO, gerando nanoestruturas mais dispersas em meios aquosos dependendo da quantidade relativa de CoTRP e GO. Esta característica foi usada para modular a atividade eletrocatalítica dos compostos na reação de redução de oxigênio (ORR) em meio neutro. O material foi caracterizado por microscopia eletrônica de transmissão, Raman, espectroscopia UV-vis e microscopia de força atômica (AFM), e os resultados confirmaram que a porfirina CoTRP é fortemente ancorada no GO por meio de interações eletrostáticas. A ORR no eletrodo modificado CoTRP/GO foi avaliada por técnicas eletroquímicas e baixo sobrepotencial (0,05 V) foi notado no processo de quatro elétrons envolvendo a redução do oxigênio. Esse valor é dramaticamente deslocado para potenciais menos negativos (0,88V em relação ao GCE), e o excelente desempenho do eletrodo permite sua utilização como sensor efetivo para o monitoramento contínuo de oxigênio dissolvido em meio aquoso. Filmes nanoporosos de ouro (NPGF) foram preparados em superfície de ouro pela aplicação de potencial de 2,0 V por 60 minutos em solução de H2SO4 0,5 mol L-1. A presença de nanoestruturas de ouro foi confirmada por microscopia eletrônica de varredura (MEV) e o eletrodo NPGF mostrou atividade eletrocatalítica superior para a ORR em comparação com a superfície polida de ouro Superfícies de ouro mais ativas eletrocataliticamente também foram preparadas por redução eletroquímica de Au3+ em eletrodos de carbono vítreo. Com um tempo de deposição ótimo de 90 s, superfícies rugosas foram obtidas e caracterizadas por MEV e difração de raios X (XRD). Esses eletrodos modificados foram empregados com sucesso para o monitoramento de oxigênio dissolvido em amostras de água e o desempenho analítico foi avaliado com base em parâmetros como sensibilidade, seletividade, reprodutibilidade, estabilidade e limite de detecção (LOD). / During the development of this project, several results were obtained concerning the construction of different electrochemical sensors for the determination of oxygen in aqueous media in biological and environmental samples. Different electrode surfaces were used for the construction of these sensors, which were prepared by the incorporation of cobalt porphyrins synthesized and characterized in the laboratory of Prof. Koiti Araki, such as cobalt 5,10,15,20-meso- tetraphenylporphyrin (CoTPP) and [tetrakis-bisdimethyl-bipyridine chlorine (II)] - 5,10,15,20-Cobalt tetrahydrin (II) (CoTRP). Gold electrodes modified with gold nanostructures were also employed for the detection of oxygen. In some cases, graphene oxide (GO) was immobilized on the electrode surfaces to improve the electron transport. CoTPP porphyrins were immobilized on a vitreous carbon electrode (GCE) and the electrochemical behavior of this modified electrode for the reduction of oxygen in 0.1 mol L-1 KNO3 aqueous solution was compared with that of a GCE, a reduction of the overpotential being observed. The utility of the sensor was demonstrated by the continuous amperometric monitoring of the mitochondrial oxygen consumption and the results were in agreement with those obtained in parallel measurements performed by using a commercial electrode (\"Clark electrode\"). GO was mixed with the CoTRP porphyrin for the preparation of composites, which were subsequently immobilized on electrode surfaces. The CoTRP molecules were found to be horizontal in the GO surface, generating more dispersed nanostructures in aqueous media depending on the relative amount of CoTRP and GO. This characteristic was used to modulate the electrocatalytic activity of the compounds in the oxygen reduction reaction (ORR) in neutral medium. The material was characterized by transmission electron microscopy, Raman, UV-vis spectroscopy and atomic force microscopy (AFM), and the results confirmed that CoTRP porphyrin is strongly anchored in the GO by means of electrostatic interactions. The ORR in the modified CoTRP / GO electrode was evaluated by electrochemical techniques and a low overpotential (0.05 V) was observed in the four-electrons process involving the reduction of oxygen. This value is dramatically shifted to less negative potentials (0.88V compared to GCE), and the excellent electrode performance allows its use as an effective sensor for the continuous monitoring of oxygen dissolved in aqueous medium. Gold nanoporous films (NPGF) were prepared on a gold surface by application of 2.0 V for 60 minutes in 0.5 mol L-1 H2SO4 solution. The presence of gold nanostructures was confirmed by scanning electron microscopy (SEM) and the NPGF electrode showed superior electrocatalytic activity for the ORR compared to the gold polished surface. More electrocatalytically active gold surfaces were also prepared by electrochemical reduction of Au3+ on glassy carbon electrodes. With an optimum deposition time of 90 s, rough surfaces were obtained and characterized by SEM and XRD. These modified electrodes were successfully used for the monitoring of dissolved oxygen in water samples and the analytical performance was evaluated based on parameters such as sensitivity, selectivity, reproducibility, stability and limit of detection (LOD).

Durante o desenvolvimento deste projeto, foram obtidos diversos resultados relativos à construção de distintos sensores eletroquímicos para a determinação de oxigênio em meio aquoso em amostras biológicas e ambientais. Para a construção destes sensores foram usadas diferentes superfícies eletródicas, preparadas pela incorporação de porfirinas de cobalto sintetizadas e caracterizadas no laboratório do Prof. Dr. Koiti Araki, tais como a 5,10,15,20-meso-tetrafenilporfirina de cobalto (CoTPP) e a [tetrakis-bisdimetil-bipiridina cloro rutênio(II)]-5,10,15,20-Tetrapiridinaporfirina de cobalto (II) (CoTRP). Eletrodos de ouro modificados com nanoestruturas de ouro também foram empregados para a detecção de oxigênio. Em alguns casos, óxido de grafeno (GO) foi imobilizado nas superfícies eletródicas para melhorar o transporte de elétrons. Porfirinas de CoTPP foram imobilizadas em eletrodo de carbono vítreo (GCE) e o comportamento eletroquímico desse eletrodo modificado para a redução de oxigênio em solução aquosa de KNO3 0,1 mol L-1 foi comparado com o do GCE, observando-se diminuição do sobrepotencial. A utilidade do sensor foi demonstrada pelo monitoramento amperométrico contínuo do consumo de oxigênio mitocondrial e os resultados foram concordantes com aqueles obtidos em medições paralelas realizadas usando um eletrodo comercial (\"eletrodo de Clark\"). GO foi misturado com a porfirina de CoTRP para a preparação de compósitos, os quais foram posteriormente imobilizados em superfícies eletródicas. Verificou-se que as moléculas de CoTRP ficavam em forma horizontal na superfície do GO, gerando nanoestruturas mais dispersas em meios aquosos dependendo da quantidade relativa de CoTRP e GO. Esta característica foi usada para modular a atividade eletrocatalítica dos compostos na reação de redução de oxigênio (ORR) em meio neutro. O material foi caracterizado por microscopia eletrônica de transmissão, Raman, espectroscopia UV-vis e microscopia de força atômica (AFM), e os resultados confirmaram que a porfirina CoTRP é fortemente ancorada no GO por meio de interações eletrostáticas. A ORR no eletrodo modificado CoTRP/GO foi avaliada por técnicas eletroquímicas e baixo sobrepotencial (0,05 V) foi notado no processo de quatro elétrons envolvendo a redução do oxigênio. Esse valor é dramaticamente deslocado para potenciais menos negativos (0,88V em relação ao GCE), e o excelente desempenho do eletrodo permite sua utilização como sensor efetivo para o monitoramento contínuo de oxigênio dissolvido em meio aquoso. Filmes nanoporosos de ouro (NPGF) foram preparados em superfície de ouro pela aplicação de potencial de 2,0 V por 60 minutos em solução de H2SO4 0,5 mol L-1. A presença de nanoestruturas de ouro foi confirmada por microscopia eletrônica de varredura (MEV) e o eletrodo NPGF mostrou atividade eletrocatalítica superior para a ORR em comparação com a superfície polida de ouro Superfícies de ouro mais ativas eletrocataliticamente também foram preparadas por redução eletroquímica de Au3+ em eletrodos de carbono vítreo. Com um tempo de deposição ótimo de 90 s, superfícies rugosas foram obtidas e caracterizadas por MEV e difração de raios X (XRD). Esses eletrodos modificados foram empregados com sucesso para o monitoramento de oxigênio dissolvido em amostras de água e o desempenho analítico foi avaliado com base em parâmetros como sensibilidade, seletividade, reprodutibilidade, estabilidade e limite de detecção (LOD). / During the development of this project, several results were obtained concerning the construction of different electrochemical sensors for the determination of oxygen in aqueous media in biological and environmental samples. Different electrode surfaces were used for the construction of these sensors, which were prepared by the incorporation of cobalt porphyrins synthesized and characterized in the laboratory of Prof. Koiti Araki, such as cobalt 5,10,15,20-meso- tetraphenylporphyrin (CoTPP) and [tetrakis-bisdimethyl-bipyridine chlorine (II)] - 5,10,15,20-Cobalt tetrahydrin (II) (CoTRP). Gold electrodes modified with gold nanostructures were also employed for the detection of oxygen. In some cases, graphene oxide (GO) was immobilized on the electrode surfaces to improve the electron transport. CoTPP porphyrins were immobilized on a vitreous carbon electrode (GCE) and the electrochemical behavior of this modified electrode for the reduction of oxygen in 0.1 mol L-1 KNO3 aqueous solution was compared with that of a GCE, a reduction of the overpotential being observed. The utility of the sensor was demonstrated by the continuous amperometric monitoring of the mitochondrial oxygen consumption and the results were in agreement with those obtained in parallel measurements performed by using a commercial electrode (\"Clark electrode\"). GO was mixed with the CoTRP porphyrin for the preparation of composites, which were subsequently immobilized on electrode surfaces. The CoTRP molecules were found to be horizontal in the GO surface, generating more dispersed nanostructures in aqueous media depending on the relative amount of CoTRP and GO. This characteristic was used to modulate the electrocatalytic activity of the compounds in the oxygen reduction reaction (ORR) in neutral medium. The material was characterized by transmission electron microscopy, Raman, UV-vis spectroscopy and atomic force microscopy (AFM), and the results confirmed that CoTRP porphyrin is strongly anchored in the GO by means of electrostatic interactions. The ORR in the modified CoTRP / GO electrode was evaluated by electrochemical techniques and a low overpotential (0.05 V) was observed in the four-electrons process involving the reduction of oxygen. This value is dramatically shifted to less negative potentials (0.88V compared to GCE), and the excellent electrode performance allows its use as an effective sensor for the continuous monitoring of oxygen dissolved in aqueous medium. Gold nanoporous films (NPGF) were prepared on a gold surface by application of 2.0 V for 60 minutes in 0.5 mol L-1 H2SO4 solution. The presence of gold nanostructures was confirmed by scanning electron microscopy (SEM) and the NPGF electrode showed superior electrocatalytic activity for the ORR compared to the gold polished surface. More electrocatalytically active gold surfaces were also prepared by electrochemical reduction of Au3+ on glassy carbon electrodes. With an optimum deposition time of 90 s, rough surfaces were obtained and characterized by SEM and XRD. These modified electrodes were successfully used for the monitoring of dissolved oxygen in water samples and the analytical performance was evaluated based on parameters such as sensitivity, selectivity, reproducibility, stability and limit of detection (LOD).

High-valent iron-oxo intermediates play central roles as active oxidants in enzymatic and synthetic catalytic oxidations. Many transition metal catalysts are designed for biomimetic studies of the predominant oxidation catalysts in Nature, the cytochrome P450 enzymes. In this work, a new photochemical method to generate high-valent iron-oxo porphyrin models was discovered. As controlled by the electronic nature of porphyrin ligands, iron(IV)-oxo porphyrin radical cations (Compound I model) and iron(IV)-oxo porphyrin derivatives (Compound II model) were produced. These observations indicate that the photochemical reactions involve a heterolytic cleavage of O-Br in precursors to give a putative iron(V)-oxo intermediate, which might relax to Compound I through electron transfer from porphyrin to the iron or undergo rapid comproportionation reaction with residual iron(III) to afford the Compound II derivative. Furthermore, visible light photolysis of bis-porphyrins-dimanganese(III)-μ-oxo complexes, [MnIII(Por)]2O, was studied in three porphyrin systems. Direct conversion of manganese(III)-μ-oxo dimers to manganese(IV)-oxo porphyrins [MnIV(Por)(O)] and manganese(III) products was observed in benzene solution upon light irradiation. The spectral signature of [MnIV(Por)(O)] was further confirmed by production of the same species in the reported reaction of the [MnIII(Por)Cl] with PhI(OAc)2. Continuous irradiation of bis-porphyrins-dimanganese(III)-μ-oxo complexes in the presence of pyridine or triphenylphospine gave rise to the formation of [MnII(Por)(Py)] or [MnII(Por)(PPh3)], which are stable to be detected. A photo-disproportionation mechanism similar to that for bis-porphyrins-diiron(III)-μ-oxo complex was proposed to explain above photochemical behaviors of bis-porphyrins-dimanganese(III)-μ-oxo complexes. With iodobenzene diacetate [PhI(OAc)2] as the oxygen source, manganese(III) porphyrin complexes exhibit remarkable catalytic activity towards the selective oxidation of alkenes and activated hydrocarbons. Conspicuous is the fact that the readily soluble PhI(OAc)2 in the presence of a small amount of water is more efficient oxygen source than the commonly used PhIO under same conditions. High selectivity for epoxides and excellent catalytic efficiency with up to 10,000 Turnovers (TONs) were achieved in alkene epoxidations. A manganese(IV)-oxo porphyrin was observed in the oxidation of the manganese(III) porphyrin and PhI(OAc)2. However, catalytic competition and Hammett studies suggested that the more reactive manganese(V)-oxo intermediate was favored as the premier active oxidant, even it is too short-lived to be detected in the catalytic reaction.

No description available.