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In the society of today the need for alternative energy sources is increasing. The construction of artificial devices for the conversion of sunlight into electricity or fuel seems very attractive from an environmental point of view, since these devices are based on processes that does not necessarily generate any harmful biproducts. In the oxygen evolving photosynthetic process highly efficient energy and electron transfer reactions are responsible for the conversion of the sunlight into chemically stored energy and if the same principles can be used in an artificial device, the only electron supply required, is water. This thesis describes energy and electron transfer reactions in supramolecular complexes where the reactions are intended to mimic the basic steps in the photosynthetic process. All complexes are based on ruthenium(II)-trisbipyridine as photosensitizer, that is covalently linked to electron donors or electron or energy acceptors. The photochemical reactions were studied with time resolved transient absorption and emission measurements. In the complexes that mimic the donor side of Photosystem II, where a manganese cluster together with tyrosine catalyses the oxidation of water, intramolecular electron transfer was found to occur from Mn(II) or tyrosine to photo-oxidized Ru(III). Studies of a series of Ru(II)-Mn(II) complexes gave information of the quenching of the Ru(II) excited state by the coordinated Mn(II), which is important for the development of multi-nuclear Ru(II)-Mn complexes. In the supramolecular triad, PTZ-Ru2+-Q, the charge separated state, PTZ+●-Ru2+-Q-●, was rapidly formed, and further development where a second electron acceptor is linked to quinone is planned. Ultra fast energy transfer τ<200 fs), was obtained between ruthenium(II) and osmium(II) in a small artificial antenna fragment. Fast and efficient energy transfer is important in larger antennas or photonic wires where a rapid energy transfer is desired over a large distance.

LiMn2O4 is ideal as a high-capacity Li-ion battery cathode material by virtue of its low toxicity, low cost, and the high natural abundance of Mn. Surface related reactions and bulk kinetics have been the major focus of this work. The main techniques exploited have been: electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy and thermal analysis. Interface formation between the LiMn2O4 cathode and carbonate-based electrolytes has been followed under different pre-treatment conditions. The variables have been: number of charge/discharge cycles, storage time, potential, electrolyte salt and temperature. The formation of the surface layer was found not to be governed by electrochemical cycling. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, LixPFy (or LixBFy, depending on the electrolyte salt used), LixPOyFz (or LixBOyFz) and poly(oxyethylene). Additional compounds were found at elevated temperatures: phosphorous oxides (or boron oxides) and polycarbonates. A model has been presented for the formation of these surface species at elevated temperatures. The cathode surface structure was found to change towards a lithium-rich and Mn3+-rich compound under self-discharge. The reduction of LiMn2O4, in addition to the high operating potential, induces oxidation of the electrolyte at the cathode surface. A novel in situ electrochemical/structural set-up has facilitated a study of the kinetics in the LiMn2O4 electrode. The results eliminate solid-phase diffusion as the rate-limiting factor in electrochemical cycling. The electrode preparation method used results in good utilisation of the electrode, even at high discharge rates.

In today’s society there is an increasing need for energy, an increase which for the most part is supplied by the use of fossil fuels. Fossil fuel resources are limited and their use has harmful effects on the environment, therefore the development of technologies that produce clean energy sources is very appealing. Natural photosynthesis is capable of converting solar energy into chemical energy through a series of efficient energy and electron transfer reactions with water as the only electron source. Thus, constructing an artificial system that uses the same principles to convert sunlight into electricity or storable fuels like hydrogen is one of the major forces driving artificial photosynthesis research. This thesis describes supramolecular complexes with the intention of mimicking the electron transfer reactions of the donor side in Photosystem II, where a manganese cluster together with a tyrosine catalyses the oxidation of water. All complexes are based on Ru(II)-trisbipyridine as a photosensitizer that is covalently linked to electron donors like tyrosine or manganese. Photochemical reactions are studied with time-resolved transient absorption and emission measurements. Electrochemical techniques are used to study the electrochemical behavior, and different photoelectrochemical techniques are used to investigate the complexes adsorbed onto titanium dioxide surfaces. In all complexes, intramolecular electron transfer occurs from the linked donor to photo-oxidized Ru(III). It is also observed that coordinated Mn(II) quenches the excited state of Ru(II), a reaction that is found to be distance dependent. However, by modifying one of the complexes, its excited state properties can be tuned in a way that decreases the quenching and keeps the electron transfer properties. The obtained results are of significance for the development of multinuclear Ru-Mn complexes that are capable of multi-electron transfer.

Ny kunnskap om billeddannelse av hjertet ved magnetisk resonans (MR) fremkommer i sivilingeniør Wibeke Nordhøys doktoravhandling ved Norges teknisk-naturvitenskapelige universitet (NTNU). Denne kunnskapen vil ha stor betydning for hvordan man kan finne fram til noninvasive undersøkelser, dvs. uten fysiske inngrep, av hjertemuskelens levedyktighet hos pasienter med tilstopninger i kransarterier (iskemisk hjertesykdom). Mangan som kontrastmiddel og markør for levedyktighet (viabilitet) Arbeidet har gitt ny kunnskap om mangan som intracellulær kontrastgiver og om vannutveksling i hjertemuskelen. Manganforbindelser har et stort potensial som kontrastmidler for MR av hjertet. I dyreforsøk har Nordhøy vist hvordan det magnetiske sporstoffet mangan tas opp i hjerteceller via fysiologiske ionekanaler, og hvordan det øker kontrasten i MR-bilder ved å «lyse opp hjertecellene innenfra». Hun har også gitt viktige bidrag til forståelsen av hvordan man med MR kan skille mellom vann inne i og utenfor hjertecellene. I sum betyr dette at man har kommet et skritt videre mot at MR av hjertet vil gi gradert informasjon om nettopp hjertecellenes tilstand. Avhandlingen representerer derfor et viktig norsk bidrag til den internasjonale forskning innen molekylær billeddannelse. Avhandlingen Avhandlingen har tittelen «Manganese and the heart: Intracellular MR relaxation and water exchange across the cardiac cell membrane / Mangan og hjertet: Intracellulær MR relaksasjon og vannutveksling over cellemembranen i hjertet.» Avhandlingen er blitt til innenfor et tverrfaglig samarbeid mellom biofysiker, fysiologer og kjemikere med professor Per Jynge, Institutt for sirkulasjon og bildediagnostikk, NTNU, som hovedveileder og professor Jostein Krane, Kjemisk institutt, NTNU, som medveileder. Arbeidet har vært initiert via Norges forskningsråds strategiske universitetsprogram for medisinsk teknologi (SUP-I) i Trondheim. Det er finansiert av Norges forskningsråd, Det medisinske fakultet (NTNU) og Amersham Health.

Possibly the most fascinating biochemical mechanism remaining to be solved is the formation of oxygen from water in photosystem II. This is a critical part of the photosynthetic reaction that makes solar energy accessible to living organisms. The present thesis uses quantum chemistry, more specifically the density functional B3LYP, to investigate a mechanism where an oxyl radical bound to manganese is the active species in O-O bond formation. Benchmark calculations on manganese systems confirm that B3LYP can be expected to give accurate results. The effect of the self-interaction error is shown to be limited. Studies of synthetic manganese complexes support the idea of a radical mechanism. A manganese complex with an oxyl radical is active in oxygen formation while manganese-oxo complexes remain inactive. Formation of the O-O bond requires a spin transition but there should be no effect on the rate. Spin transitions are also required in many short-range electron-transfer reactions. Investigations of the superproficient enzyme orotidine decarboxylase support a mechanism that involves an invariant network of charged amino acids, acting together with at least two mobile water molecules.

This study was conducted to investigate the urban geochemistry of the city of Windsor (Ontario) and to provide added source apportionment information to work being carried out by the Canadian government. The goal of this study was to investigate the distribution, spatial variation and sources of manganese in urban Windsor soil. The literature indicates that human exposure to high levels of manganese, via inhalation, can cause respiratory and/or neurological effects. At the outset of the present study it was first hypothesized that vehicular traffic was the dominant source of anthropogenic manganese. An alternative hypothesis was that there were multiple anthropogenic sources of manganese in Windsor. The sample collection scheme was designed to determine (1) the current and background soil concentrations of manganese in Windsor, (2) the spatial distribution of manganese in order to reveal sources of manganese, and (3) the manganese content of moss-sequestered airborne particles, which can potentially deposit onto the soil surface, using low-technology biomonitoring. The first phase of the study consisted of a preliminary soil survey which identified elevated areas of soil manganese concentrations. During this survey, the field efficiency of a field portable X-ray fluorescence (FPXRF) instrument, as well as sample preparation methods were evaluated. Efficiency of the FPXRF was determined by comparison to ICP-MS, a traditional trace element analysis method. The preliminary soil survey identified several areas of elevated (ranging from 884 to 2390 ppm) soil manganese which were further investigated during the second, more complete, soil survey. The moss biomonitoring technique of using moss bags was used to collect airborne particles for semi-quantitative analysis. Analysis of soil samples included total manganese and other trace elements, pH, moisture and carbon content, and manganese speciation. Urban Windsor soil manganese distribution revealed both natural and anthropogenic sources of soil manganese and three distinct soil sample types, transect, baseline and natural. In general, manganese in Windsor had a west-to-east trend of decreasing levels in soil and moss-sequestered airborne particles. The latter showed a modern-day elemental signature while the former (collocated soil) a legacy elemental signature. It was concluded that both the FPXRF instrument and the moss biomonitoring technique can be useful screening tools in studies of urban environments.

This study was conducted to investigate the urban geochemistry of the city of Windsor (Ontario) and to provide added source apportionment information to work being carried out by the Canadian government. The goal of this study was to investigate the distribution, spatial variation and sources of manganese in urban Windsor soil. The literature indicates that human exposure to high levels of manganese, via inhalation, can cause respiratory and/or neurological effects. At the outset of the present study it was first hypothesized that vehicular traffic was the dominant source of anthropogenic manganese. An alternative hypothesis was that there were multiple anthropogenic sources of manganese in Windsor. The sample collection scheme was designed to determine (1) the current and background soil concentrations of manganese in Windsor, (2) the spatial distribution of manganese in order to reveal sources of manganese, and (3) the manganese content of moss-sequestered airborne particles, which can potentially deposit onto the soil surface, using low-technology biomonitoring. The first phase of the study consisted of a preliminary soil survey which identified elevated areas of soil manganese concentrations. During this survey, the field efficiency of a field portable X-ray fluorescence (FPXRF) instrument, as well as sample preparation methods were evaluated. Efficiency of the FPXRF was determined by comparison to ICP-MS, a traditional trace element analysis method. The preliminary soil survey identified several areas of elevated (ranging from 884 to 2390 ppm) soil manganese which were further investigated during the second, more complete, soil survey. The moss biomonitoring technique of using moss bags was used to collect airborne particles for semi-quantitative analysis. Analysis of soil samples included total manganese and other trace elements, pH, moisture and carbon content, and manganese speciation. Urban Windsor soil manganese distribution revealed both natural and anthropogenic sources of soil manganese and three distinct soil sample types, transect, baseline and natural. In general, manganese in Windsor had a west-to-east trend of decreasing levels in soil and moss-sequestered airborne particles. The latter showed a modern-day elemental signature while the former (collocated soil) a legacy elemental signature. It was concluded that both the FPXRF instrument and the moss biomonitoring technique can be useful screening tools in studies of urban environments.

Diamond cuboid-, rhombohedron- and hexagon-shaped nanocrystals as well as branched rods of the solid solution Co1-xMnxO have been synthesized via a solvothermal synthetic route from manganese formate and cobalt acetate at elevated temperature. Rhombohedra and hexagons have dimensions no larger than 50 nm on the longest axis, rods have branches up to 150 nm long and cuboids grow up to 250 nm on a side. X-ray and electron diffraction and transmission electron microscopy analyses show that these nanoparticles are single crystals of wurtzite-type and rock salt-type Co1-xMnxO. Varying the surfactant, water and precursor ratios allows control of particle size, morphology and stoichiometry. Extending growth time at high temperatures (>370°C) leads to the disappearance of the wurtzite phase due to Ostwald ripening. Longer reaction times at temperatures between 345-365°C lead to more crystalline wurtzite-lattice particles. These results show that nanoparticle morphologies and crystal lattices arise from crystal growth and Ostwald ripening at different rates selecting for either small, smooth-surfaced wurtzite lattice particles or large, dendritically-grown rock salt lattice particles.

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