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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},
}