The aim of the research is to design and synthesise advanced nickel-iron dinuclear compounds as structural models for the active site of nickel containing hydrogenases. Ultimately, these nickel-iron complexes will be used to yield insight in the mechanism of action of the hydrogenases. The experimental work consists of the design and synthesis of new thiolate containing ligands, and the subsequent synthesis of mononuclear nickel compounds of these ligands. The complexes are studied using various spectroscopic techniques, and whenever possible, the X-ray structures will be solved. The redox properties of the compounds will be studied in combination with EPR spectroscopy, for comparison with the natural systems.
Nature provides examples for such systems with the active sites of hemocyanin and tyrosinase.
Both enzymes are capable of binding, transporting, and releasing molecular dioxygen, while the latter enzyme also functions as an oxidation catalyst. The active sites of these metalloproteins contain two copper ions in close proximity. Dioxygen is bonded as a bridging ligand between the two copper ions, which are further coordinated by imidazole groups of histidine residues of the protein backbone. Sofar only a few model systems are reported which are capable of binding dioxygen, but only at very low temperature. The really big challenge is now to design a ligand system, which will hold two copper ions in close proximity, capable of not only binding but also capable of releasing molecular dioxygen.