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TY - THES AU - Laurini, Larissa Daniela TI - Biomimetic copper-guanidine complexes for multi-phase reactions PB - RWTH Aachen University VL - Dissertation CY - Aachen M1 - RWTH-2025-05322 SP - 1 Online-Ressource : Illustrationen PY - 2024 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2025 N1 - Dissertation, RWTH Aachen University, 2024 AB - Many synthesis pathways of basic chemicals used in industrial processes are oxidation reactions utilizing simple, gaseous oxidants like molecular oxygen or air. Continuous flow reactors or semi-batch reactors are most commonly used in which the gaseous oxidant is bubbled through the liquid phase containing further reactants dissolved in the reaction mixture. To create an accessible oxidizing agent, cost-intensive and/or hazardous transition metal catalysts are needed for oxygen activation. In nature, oxygen activation is mediated by metalloenzymes like tyrosinase. The enzyme consists of a catalytically active Cu2O2 peroxido center stabilized by six histidine N-donor ligands. While most enzymes are working substrate-specific, tyrosinase converts phenols as well as ortho-dihydroxybenzenes to the related ortho-quinones. New inexpensive, environmentally-friendly oxidation catalysts for industrial applications are needed mimicking the natural catalytic activity of tyrosinase. In this study, the catalytically active Cu2O2 peroxido center of tyrosinase is mimicked by synthetic peroxido as well as isoelectronic oxido complexes. Therein, the Cu2O2 center is stabilized by bisguanidine, hybrid guanidine or diamino ligands. The intermediate species present during the catalytic hydroxylation and subsequent oxidation of phenols mediated by tyrosinase is still under debate. Therefore, a synthetic model of the intermediate is generated using a hybrid guanidine ligand and investigated via X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) spectroscopy. A bisguanidine ligand is used to synthesize an oxido complex able to convert a broad spectrum of non-natural substrates like naphthols, quinolinols and indolols. The resulting ortho-quinone products are unstable under ambient conditions and are transformed into stable phenazine products in a following condensation reaction with 1,2-phenylenediamine. As naturally occurring phenazine derivatives function as anti-microbial agents, the antibacterial behavior of synthesized phenazine products is tested evaluating their potential as antibiotics. Industrial oxidation processes are focusing on maximizing yield and selectivity of the desired product with minimal use of reactants. A significant influencing factor is the mass transfer of the gaseous oxidizing agent into the liquid phase where the reaction takes place. Formation and decay of Cu2O2 species as well as catalytic conversion of phenolic substrates are involving the reaction of molecular oxygen with a liquid reaction mixture. These consecutive and competitive consecutive reactions are investigated herein to get deeper insights in the influencing factors of mass transfer. Therefore, several types of (confined) reaction set-ups are used: Small Taylor flows (V = 0.03 l) with bubble movements limited to one direction over Hele-Shaw cells allowing movements in two directions (V = 0.08 l) to unconfined bubble columns near to industrial conditions (V = 2 l). Thereby, the independence of mass transfer from the chemical system used is studied. Additionally, the influence of bubble / reactor parameters on the selectivity of a competitive consecutive reaction is investigated. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2025-05322 UR - https://publications.rwth-aachen.de/record/1013074 ER -