<p>This thesis deals with the synthesis and characterisation of a series of dinuclear manganese complexes. Their ability to donate electrons to photo-generated ruthenium(III) has been investigated in flash photolysis experiments followed by EPR-spectroscopy. These experiment shows several consecutive one-electron transfer steps from the manganese moiety to ruthenium(III), that mimics the electron transfer from the oxygen evolving centre in photosystem II.</p><p>The redox properties of these complexes have been investigated with electro chemical methods and the structure of the complexes has been investigated with different X-ray techniques. Structural aspects and the effect of water on the redox properties have been shown.</p><p>One of the manganese complexes has been covalently linked in a triad donor-photosensitizer-acceptor (D–P–A) system. The kinetics of this triad has been investigated in detail after photo excitation with both optical and EPR spectroscopy. The formed charge separated state (D^––P–A⁺) showed an unusual long lifetime for triad based on ruthenium photosensitizers.</p><p>The thesis also includes a study of manganese-salen epoxidation reactions that we believe can give an insight in the oxygen transfer mechanism in the water oxidising complex in photosystem II.</p>

This thesis deals with the synthesis and characterisation of a series of dinuclear manganese complexes. Their ability to donate electrons to photo-generated ruthenium(III) has been investigated in flash photolysis experiments followed by EPR-spectroscopy. These experiment shows several consecutive one-electron transfer steps from the manganese moiety to ruthenium(III), that mimics the electron transfer from the oxygen evolving centre in photosystem II. The redox properties of these complexes have been investigated with electro chemical methods and the structure of the complexes has been investigated with different X-ray techniques. Structural aspects and the effect of water on the redox properties have been shown. One of the manganese complexes has been covalently linked in a triad donor-photosensitizer-acceptor (D–P–A) system. The kinetics of this triad has been investigated in detail after photo excitation with both optical and EPR spectroscopy. The formed charge separated state (D––P–A+) showed an unusual long lifetime for triad based on ruthenium photosensitizers. The thesis also includes a study of manganese-salen epoxidation reactions that we believe can give an insight in the oxygen transfer mechanism in the water oxidising complex in photosystem II.

This thesis deals mainly with two oxidation reactions: water oxidation and aerobic oxidation, both of which have been applied in a biomimetic fashion. In the former reaction molecular oxygen is generated whereas in the latter it was used as terminal oxidant in oxidation reactions. The first part of this thesis describes the synthesis of different ruthenium and manganese complexes that could potentially act as catalysts for water oxidation. This part includes a discussion of the stability and reactivity of a new manganese(III) amide-type complex, that has been used as a catalyst for both epoxidation of stilbene and alcohol oxidation. The second part of this thesis discusses the synthesis of two new hybrid catalysts consisting of hydroquinone linked cobalt(II) salophen and cobalt(II) salmdpt, which have been used as oxygen-activating catalysts in aerobic oxidation reactions. The former catalyst was applied to the Pd-catalyzed reactions such as 1,4-diacetoxylation of cyclohexadiene whereas the latter was applied to the Ru-catalyzed oxidation of secondary alcohols to ketones. Moreover, these two hybrid catalysts could be used in the Pd-catalyzed carbocyclization of enallenes. In all cases molecular oxygen was used as the stoichiometric oxidant.

<p> The distribution of manganese in blood serum and erythrocytes has been investigated using a combination of radioactive tracer method with both gel chromatography and disc gel electrophoresis. </p> <p> In serum, there are two manganese-binding proteins. The first is a(beta)1 globulin with a molecular weight of 70,000. This forms a relatively labile manganese complex both in vitro and in vivo, and is remarkably similar in both its chromatographic and electrophoretic behaviour to the iron-binding protein, transferrin. The second protein is a higher molecular weight (beta) globulin. It is found to incorporate radiomanganese in vivo only, thereupon forming a very stable entity. </p> <p> In erythrocytes, manganese occurs predominantly in a porphyrin bound to apoglobin, giving rise to a species similar to hemoglobin . </p> / Thesis / Doctor of Philosophy (PhD)