Synthesis and Investigation of Copper(I) Complexes with Polydentate N-Donor Ligands as Model Systems for Copper-Containing Monooxygenases
Copper-containing enzymes are responsible for important reactions such as oxygen activation and electron transfer processes. For example, the enzyme tyrosinase is responsible for the monooxygenation of phenols and by this mediates the first step of melanin biogenesis. The investigation of factors influencing the reactivity of enzymes and their reaction mechanisms is of key importance. This thesis describes the development and investigation of new mono- and dinuclear tyrosinase model systems and their reactivity toward monophenols. The first part describes the study of dinuclear model systems supported by the bis-tridentate ligand (Tw1) and bis-bidentate ligands (Tw2/3). The influence of ligand denticity and type of N-donor groups present was evaluated by studying the reactivity of the prepared new Cu(I) complexes toward phenolic substrates and dioxygen. In contrast to the first part, the second and third part comprise studies of mononuclear model systems. Novel iminotriazole ligands Ltrz1 and Ltrz2 were synthesized and the corresponding Cu(I) complexes were prepared with PF6- and Al(pftb)4- as two different anions. With these complexes, higher yields of quinone were obtained compared to previous systems. In particular, for the complex with Al(pftb)4- the highest catalytic activity so far was obtained. Moreover, a mononuclear reaction pathway for the conversion of phenols could be verified for these systems. Furthermore, due to similarities found in the mononuclear pathways of the CuAAC reaction and phenol monooxygenation as well as the employed ligands, six Cu(I) complexes supported by aminotriazole ligands were prepared and investigated. The ability of the prepared complexes to mediate the CuAAC reaction and phenol monooxygenation was investigated. An opposite reactivity was observed.
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