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dc.contributor.advisor Meyer, Franc Prof. Dr. Brinkmeier, Alexander 2018-01-26T09:04:07Z 2019-01-08T23:50:04Z 2018-01-26
dc.language.iso eng de
dc.publisher Niedersächsische Staats- und Universitätsbibliothek Göttingen de
dc.subject.ddc 540 de
dc.title Bimetallic Copper Complexes for Bioinspired Dioxygen Activation and Catalytic Water Oxidation de
dc.type doctoralThesis de
dc.contributor.referee Meyer, Franc Prof. Dr. 2018-01-08
dc.description.abstracteng In this thesis a pyrazolate based dicopper(I) complex featuring a constrained substrate binding pocket was reacted with dioxygen to form a dicopper(II) peroxo complex which shows the peroxide anion in an unusual cis-µ-η1:η1 binding mode (CP). Such O2-binding is assumed to be relevant during initial stages on the trajectory of O2 reduction in type III copper active sites.1,2 This abnormally bound peroxide was found to interact with alkali metal ions that affect the Cu-O-O-Cu torsion angle of this CP species, causing a significant change of the electronic structure of the Cu2/O2 core. The peroxide thereby functions as a Lewis base, which interacts with the different Lewis acidic alkali metal ions. This host-guest complex formation was studied in detail by means of UV/vis absorption spectroscopy for which binding constants could be derived, showing that the strength of adduct formation is a function of Lewis acidity of the coordinating alkali metal ion. The influence of redox-inactive metal ions on the electronic structure of metal oxo and peroxo intermediates is receiving great attention because it may play a key role in natural or chemical systems for the modulation of redox potential and reactivity.3 While previously seen in iron(III) peroxo chemistry3, such interaction has been unprecedented in copper peroxo systems. This thesis thus furthermore focused on the electrochemical properties of the dicopper(II) peroxo intermediate and its alkali adducts. Detailed electrochemical studies revealed the reversible formation of a dicopper(II) superoxo complex of which a solid state structure could be determined. Following studies of the corresponding alkali metal adducts showed that this superoxo species can also be generated electrochemically from these species. The redox potential of the corresponding oxidation was thereby observed to increase upon alkali metal binding, whereas the total shift in redox potential is a function of Lewis acidity of the coordinating alkali metal ion. This work thus provides first spectroscopic evidence for modulation of redox potential of a dicopper(II) peroxo core by interaction with redox inert metal ions. Kinetic studies with the superoxo compound were performed upon which a dicopper(II) hydroperoxo complex is formed via H-atom transfer from the substrate TEMPO-H. This hydroperoxo compound can also be directly generated from the dicopper(II) peroxo intermediate by protonation with e.g. 2,6-luthidinium triflate. Detailed UV/vis titration experiments allowed the determination of the pKa value for the hydroperoxo species for which a Bond Dissociation Free Energy could be calculated. No matter which of the above discussed Cu2/O2 complexes is considered, all are forming the same decomposition product over time, where the two CuII ions are bridged by a hydroxide and an additional water molecule (denoted as H3O2 bridge). Until to date this species has been discarded when formed which is rather unsatisfactory, since the corresponding ligand is generated in a multi-step synthesis under a high consumption of resources. With respect to “green chemistry” the “recycling” of this decomposition product via e.g. generating the dicopper(I) complex which again can be selectively reacted into the corresponding dioxygen complexes, was studied. This thesis shows that the decomposition product can be selectively transformed into all above mentioned Cu2/O2 complexes. Furthermore the H3O2 bridged compound was studied towards electrocatalytic water oxidation. First results show the formation of molecular dioxygen whereas the potential water oxidation catalyst stays intact during catalysis. (1) Dalle, K. E.; Gruene, T.; Dechert, S.; Demeshko, S.; Meyer, F. J. Am. Chem. Soc. 2014, 136, 7428. (2) Kindermann, N.; Bill, E.; Dechert, S.; Demeshko, S.; Reijerse, E. J.; Meyer, F. Angew. Chem. Int. Ed. 2015, 54, 1738. (3) Bang, S.; Lee, Y.-M.; Hong, S.; Cho, K.-B.; Nishida, Y.; Seo, M. S.; Sarangi, R.; Fukuzumi, S.; Nam, W. Nat. Chem. 2014, 6, 934. de
dc.contributor.coReferee Schneider, Sven Prof. Dr.
dc.subject.eng Copper Complexes de
dc.subject.eng Dioxygen Activation de
dc.subject.eng Electronic Absorption Spectroscopy de
dc.subject.eng Resonance Raman Spectroscopy de
dc.subject.eng SQUID Magnetometry de
dc.subject.eng Kinetics de
dc.subject.eng Water Oxidation de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-002E-E335-6-5 Fakultät für Chemie de
dc.subject.gokfull Chemie  (PPN62138352X) de
dc.description.embargoed 2019-01-08
dc.identifier.ppn 1011714507

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