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@PHDTHESIS{Laurini:1013074,
author = {Laurini, Larissa Daniela},
othercontributors = {Herres-Pawlis, Sonja and Liauw, Marcellus},
title = {{B}iomimetic copper-guanidine complexes for multi-phase
reactions},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-05322},
pages = {1 Online-Ressource : Illustrationen},
year = {2024},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2025; Dissertation, RWTH Aachen University, 2024},
abstract = {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.},
cin = {151210 / 150000},
ddc = {540},
cid = {$I:(DE-82)151210_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-05322},
url = {https://publications.rwth-aachen.de/record/1013074},
}
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