The synthesis of high value acrylic monomers is currently done industrially via cyanohydrin hydration using concentrated acids, resulting in large quantities of useless byproducts. This current process is energy intensive and lacks atom economy; therefore, alternative cyanohydrin hydration strategies are under investigation. Ideally, cyanohydrin hydration would be done using organometallic nitrile hydration catalysts. Cyanohydrin hydration with these catalysts is challenging, because it needs to be done at low temperatures and under acidic conditions to reduce cyanohydrin degradation and catalyst poisoning with cyanide. This dissertation describes the reactivity of [Ru(#951; / 10000-01-01

In this study, we used different ways to synthetize four-coordinate zinc(II) and nickel(II) complexes with optically active Schiff base offering N2S2 coordination, i.e. N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cycholhexyl- enediaminatozinc(II) (1) and N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cychol- hexylenediaminatonickel(II) (2). We obtained the crystal structure of 2 and the pyridine adduct of 1, N,N'-Bis(2-thiobenzylidene)-l,2-(R,R)cycholhexylenediaminopyridylzinc(II) (1¡DPy). Coordination geometry around Zn atom in 1¡DPy is a distorted trigonal bipyramid. These structures were compared with the N2O2 stuctural analogues reported in the literature. We hope these chiral complexes can make contribution to the enzyme model studies in the future.

The work presented in this Thesis describes the design, synthesis and reactivity of a symmetric and various asymmetric Schiff-base macrocycles that are capable of forming a wedge-shaped “Pacman” conformation upon metal binding. Chapter One introduces catalysts for small molecule transformation as well as transition metal complexes of pyrrole-containing macrocycles. Further to this, Pacman systems, including previous work from Love and co-workers, and complexes capable of secondary coordination-sphere control will be discussed. Chapter Two details the design and synthesis of two asymmetric macrocycles that both contain one neutral and one N₄-donor imine-pyrrole binding pocket, H₂LP and H₂LNMe. The synthesis and characterisation of the series of complexes [M(LP)] and [M(LNMe)] (M = Pd, K₂, Co, VCl, TiCl, Mg, Fe and Mn) and their characteristics highlighted, including the formation of a supramolecular cyclic hexamer. Chapter Three presents the modification of the above ligands at the meso-group, the N-substituent and the non-pyrrolic binding pocket to give H2LFP and H₂LFNMe, H₂LNMes and H₂L(NH)NMe respectively. Palladium and cobalt complexes of these macrocycles were prepared and characterised. Chapter Four describes the design and synthesis of the ligand H₄LEt as well as the synthesis and characterisation of tin-alkyl and mononuclear calcium complexes of LEt, as well as the heterobimetallic complexes [SnMe₂(M)(THF)(LEt)] (M = Zn or Fe). The homobimetallic complexes [M₂(LEt)] (M = Co, Mg and NbCl) are also presented along with a magnesium-cubane structure of LEt in which the cubane is encapsulated by two, bowl-shaped macrocycles. Chapter Five provides a summary of the work presented in this thesis. Chapter Six describes the full experimental details and analytical data for all compounds synthesised in this work.

Biomimetic catalysis is an important research field, as a better understanding of nature´s powerful toolbox for the conversion of molecules can lead to technological progress. [FeFe]-hydrogenases are very efficient catalysts for hydrogen production. These enzymes play a crucial role in the metabolism of green algae and certain cyanobacteria. Their active site consists of a diiron complex that is embedded in an interactive protein matrix. In this thesis, two pathways for mimicking the outer coordination sphere effects resulting from the protein matrix are explored. The first is the construction of model complexes containing phosphine ligands that are coordinated to the iron center as well as covalently linked to the bridging ligand of the complex. The effect of such linkers is an increased energy barrier for the rotation of the Fe(CO2)(PL3)-subunit, which potentially could stabilize a terminal hydride that is an important intermediate in the proton reduction cycle. The second pathway follows the incorporation of [FeFe]-hydrogenase active site model complexes into metal-organic frameworks (MOFs). Resulting MOF-catalysts exhibit increased photocatalytic activity compared to homogenous references due to a stabilizing effect on catalytic intermediates by the surrounding framework. Catalyst accessibility within the MOF and the influence of the framework on chemical reactivity are examined in the work presented. Furthermore, an initial step towards application of MOF-catalysts in a device was made by interfacing them with electrodes. The work of this thesis highlights strategies for the improvement of biomimetic model catalysts and the knowledge gained can be transferred to other systems mimicking the function of enzymes.

La synthèse de l'hydrogène est une alternative viable à l'utilisation du pétrole. Les méthodes telles que l’électrocatalyse font appel à une source d’énergie primaire, ce qui favorise les déchets générés par ces méthodes, de même que le gaspillage d’énergie. Bien qu’ayant de très faibles rendements, les systèmes photocatalytiques permettent la synthèse d’un hydrogène propre et quasi sans déchets. Une perspective permettant d’améliorer encore leur potentiel serait d’éliminer les solvants organiques tels que le DMF, qui sont nocif pour l’environnement et la santé des êtres vivants. Étant donné que le solvant doit être changé, il faut prendre garde à modifier le donneur d’électron sacrificiel et le photosensibilisateur en conséquence. La production de tels solvants est également source de pollution, ce qui atténue le potentiel environnemental de ces méthodes. L’objectif de ce travail est de développer et de tester de nouveaux catalyseurs hydro-solubles variés permettant une amélioration des performances photo-catalytiques actuelles ainsi qu’une performance acceptable dans l’eau. L’étude des propriétés catalytiques est réalisée par l’étude de systèmes homogènes conjugués principalement avec le [Ru(bpy)3]2+ en tant que photosensibilisateur et avec le triethanolamine (dans le DMF) et l’acide ascorbique (dans l’eau) en tant que donneur d’électron sacrificiel. Les catalyseurs présentés lors de ce travail sont des catalyseurs à base de polypyridyl, de cobaloximes et de N-imidoylamidine. Les catalyseurs à base de poly-pyridyl ont d’abord été étudiés puisqu’ils sont réputés pour leur performance en milieux aqueux. La seconde approche consistait à produire des catalyseurs à base de cobaloxime qui aient une performance relativement constante tout d’abord dans les solvants organiques, puis d’adapter ces performances en milieu aqueux. La troisième approche a été de tester des catalyseurs à base de N-imidoylamidine, ce type de catalyseurs n’ayant jamais été testé pour la production d’hydrogène, puis d’en étudier les performances dans l’objectif de paver la voie pour de futures recherches sur le sujet. / The synthesis of hydrogen is a viable alternative to the use of petroleum. Methods such as electrocatalysis use a primary energy source, which reduces the waste generated by these methods, as well as the waste of energy. Although having very low yields, photocatalytic systems allow the synthesis of clean hydrogen with virtually no waste. One prospect to further improve their potential would be to eliminate organic solvents such as DMF, which are harmful to the environment and the health of living beings. Giving the fact that we change the solvent, we need to change the electron sacrificial donor and the photosensitizer as well. The production of such solvents is also a source of pollution, which reduces the environmental potential of these methods. The objective of this work is to develop and test various new water-soluble catalysts allowing an improvement of the current photo-catalytic performances as well as an acceptable performance in water. The study of the catalytic properties is carried out by the study of homogeneous conjugated systems mainly with [Ru(bpy)3]2+ as photosensitizer and with triethanolamine (in DMF) and ascorbic acid (in water) as a sacrificial electron donor. The catalysts presented during this work are catalysts based on polypyridyl, cobaloximes, and N-imidoylamidine. Poly-pyridyl-based catalysts were first studied because they are known for their performance in aqueous media. The second approach was to produce cobaloxime-based catalysts that had relatively constant performance first in organic solvents and then to match this performance in aqueous media. The third approach was to test catalysts based on N-imidoylamidine, as this type of catalyst have never been tested to produce hydrogen, then to study their performance to pave the way for future research on the subject.