Oxidase enzymes reliably perform oxidation reactions in very high yields and are regularly employed in organic chemistry as selective catalysts (eg. horseradish peroxidase). The utilization of enzymes, however, requires that the reaction be performed under nearly physiological conditions (aqueous solution, 37oC, pH 7). Providing a chemically more versatile and robust alternative to oxidase enzymes would be a valuable resource for synthetic chemists and is the aim of this research. In recent years, molecularly imprinted polymers (MIPs) containing transition metal catalysts have emerged as a promising new alternative to metalloenzymes.
This project aims to develop a methodology for the synthesis of iron and copper containing MIP catalysts, which imitate non-heme metallaoxidases. In order to generate polymers with oxidase-analogue metal binding sites (eg. a His-His-Carboxylate facial triad), we will employ "dummy metal complexes" having multidentate N/O-chelate ligands with polymerisable vinyl side-chains. After polymerisation under the conditions of molecular imprinting, the dummy metal ions will be cleaved off, thereby generating a rigid polymer with site-isolated binding sites, which will subsequently be occupied by the biologically relevant metal ion (e g. Fe2+). This approach circumvents some of the main problems that are frequently encountered when metallaoxidases are modelled in homogeneous solution (low solubility in water, aggregation etc.). The resulting MIPs will be stable, robust, and recyclable solids, which act as functional analogues of the respective oxidases.
A further advantage of our methodology is the possibility to modulate the microenvironment of the catalytically active metal centre using appropriate dummy complexes. This allows fine-tuning of the substrate- and regio-selectivity of the artificial oxidase. Catalytically active polymers of this kind may find applications as versatile tools in organic synthesis.
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