Copper model complexes of lytic polysaccharide monooxygenases

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The LPMOs are a new class of copper-containing enzymes which are capable of oxidising C-H of around 100 kcal/mol. The copper active site of these enzymes contains the copper coordinated by a 'histidine brace' where the amino terminus of the protein is used to coordinate to the copper ion. Such coordination is extremely rare in bioinorganic chemistry and many questions are posed as to what the role of this group is in allowing the copper complex to generate highly oxidising species.This PhD will concentrate on preparing and studying two types of small molecule complexes and examining their spectroscopic and structural properties in the context of LPMOs. The first class of complexes will contain either an NH2 or and NH group as part of the copper's coordination set to examine whether the hydrogen atoms are important in the chemistry of the copper ion. The second class will contain deprotonated amide/amine in the coordination set to examine whether such a similar species could exist in LPMOs. In both cases the complexes will be studied spectroscopically and structurally. The reactivity of the Cu(I) forms of these complexes will also be studied, with a view to understanding more about the analogous reactivity in LPMOs.The principal spectroscopic techniques will be multi-frequency EPR, visible absorption spectroscopy and magnetic circular dichroism. These techniques will be augmented with a theoretical approach to interpreting the related spin-Hamiltonian parameters and the orbital energetics. The latter will be determined using density functional calculations. It is anticipated that new theoretical methods may need to be deployed in the interpretation of EPR data of Cu complexes. As such, new approaches which use DFT energetics alongside sum-over-states perturbative calculations will be examined.