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  • 1
    UID:
    b3kat_BV002485008
    Format: 124 S. , graph. Darst.
    Note: Marburg, Univ., Diss.
    Language: German
    Keywords: Hochschulschrift
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  • 2
    UID:
    edochu_18452_19292
    Format: 1 Online-Ressource (7 Seiten)
    ISSN: 1477-9234 , 1477-9234
    Content: Two new heterobimetallic [LNiO2Cu(RPY2)]+ (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the mononuclear side-on LNiII superoxo precursor bearing a β-diketiminate ligand (L = [HC-(CMeNC6H3(iPr)2)2]) with the Cu(I) complexes. In contrast to the oxo groups in known high-valent [M2(μ-O)2]n+ (M = Fe, Co, Ni, Cu) cores that display electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions. However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously reported [LNiO2Cu(MeAN)]+ complex containing a more basic (nucleophilic) N,N,N′,N′,N′-pentamethyl-dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands affect the electron density of the oxygen atoms of the heterodinuclear {Ni(μ-O)2} core and 3a/3b undergo slower nucleophilic and faster electrophilic reactions than the previously reported [LNiO2Cu(MeAN)]+ intermediate. The present study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic [Ni(μ-O)2Cu]2+ cores by controlling the electron donation from the ancillary ligands, and underlines the significance of subtle electronic changes in the physical and chemical properties of the biologically relevant heterobimetallic metal–dioxygen intermediates.
    Content: Peer Reviewed
    Note: Available open access thanks to the RSC Gold for Gold initiative. Shared according to the terms set out in the CC licence.
    In: Dalton Transactions, : The Royal Society of Chemistry, 45,2016,40, Seiten 15994-16000, 1477-9234
    Language: English
    URL: Volltext  (kostenfrei)
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  • 3
    UID:
    b3kat_BV024558747
    Format: 31, [17] S. , 17 graph. Darst.
    Note: Aachen, Techn. Hochschule, Fak. f. Bergbau u. Huettenwesen, Diss., 1964
    Language: Undetermined
    Keywords: Hochschulschrift
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  • 4
    UID:
    gbv_429752288
    Format: 26,31 S., mehr. Bl. Abb., Anh. 8"
    Note: Aachen, T. H., F. f. Bergbau u. Hüttenw., Diss. v. 16. Sept. 1965
    Language: Undetermined
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  • 5
    UID:
    b3kat_BV024608443
    Format: 1 Online-Ressource
    Note: Berlin, Techn. Univ., Diss., 2005
    Language: English
    Keywords: Hochschulschrift
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  • 6
    UID:
    b3kat_BV024607541
    Format: VI, 92 S. , graph. Darst.
    Note: Berlin, Techn. Univ., Diss., 2005
    Language: English
    Keywords: Hochschulschrift
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  • 7
    UID:
    edochu_18452_27183
    Format: 1 Online-Ressource (8 Seiten)
    Content: In vielen Metallenzymen sind Schwefel-enthaltende Liganden an Elektronen-Transfer-Reaktionen beteiligt. In dem hier diskutierten biomimetischen Ansatz wird der Einfluss einer Schwefelkoordination auf eine Kobalt-katalysierte Sauerstoff-Reduktionsreaktion (ORR) demonstriert. Ein Vergleich des ORR-Vermögens eines vierfach Stickstoff-koordinierten [Co(Cyclam]2+-Komplexes (1; Cyclam=1,5,8,11-Tetraaza-cyclotetradecan) und dessen Schwefel-Analogons [Co(S2N2-Cyclam)]2+ (2; S2N2-Cyclam=1,8-Dithia-5,11-diazacyclotetradecan) zeigt verbesserte katalytische Eigenschaften mit dem in die Ligandensphäre am Kobalt eingeführten Chalkogen. Isolierung und Charakterisierung der Intermediate, die sich im Zuge der Sauerstoffaktivierung an den Kobalt(II)-Zentren von 1 und 2 bilden, identifizieren eine Beteiligung des Schwefels am O2-Reduktionsprozess als entscheidenden Faktor für die verbesserten Eigenschaften von 2 bei der katalytischen ORR.
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 135,6
    Language: German
    URL: Volltext  (kostenfrei)
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  • 8
    UID:
    edochu_18452_23755
    Format: 1 Online-Ressource (5 Seiten)
    ISSN: 1433-7851 , 1433-7851
    Content: S=2 oxoiron(IV) species act as reactive intermediates in the catalytic cycle of nonheme iron oxygenases. The few available synthetic S=2 FeIV=O complexes known to date are often limited to trigonal bipyramidal and very rarely to octahedral geometries. Herein we describe the generation and characterization of an S=2 pseudotetrahedral FeIV=O complex 2 supported by the sterically demanding 1,4,7-tri-tert-butyl-1,4,7-triazacyclononane ligand. Complex 2 is a very potent oxidant in hydrogen atom abstraction (HAA) reactions with large non-classical deuterium kinetic isotope effects, suggesting hydrogen tunneling contributions. For sterically encumbered substrates, direct HAA is impeded and an alternative oxidative asynchronous proton-coupled electron transfer mechanism prevails, which is unique within the nonheme oxoiron community. The high reactivity and the similar spectroscopic parameters make 2 one of the best electronic and functional models for a biological oxoiron(IV) intermediate of taurine dioxygenase (TauD-J).
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 60,12, Seiten 6752-6756, 1433-7851
    Language: English
    URL: Volltext  (kostenfrei)
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  • 9
    UID:
    edochu_18452_27192
    Format: 1 Online-Ressource (7 Seiten)
    Content: In Class Ib Ribonukleotidreduktasen (RNRs) aktiviert ein Dimangan(II)-Cluster Superoxid (O2⋅−) anstelle von molekularem Sauerstoff (O2), um eine hochvalente MnIII-O2-MnIV-Spezies zu bilden, die für die Oxidation von Tyrosin zum Tyrosyl-Radikal verantwortlich ist. Im vorliegenden biomimetischen Ansatz wird ein Thiolat-gebundener Dimangan-Komplex [MnII2(BPMT)(OAc)2](ClO)4 (BPMT=(2,6-Bis{[bis(2-pyridylmethyl)amino]methyl}-4-methylthiophenolat) (1) synthetisiert und dessen Reaktion mit O2⋅− zur Bildung des [(BPMT)MnO2Mn]2+-Komplexes 2 gezeigt. Resonanz-Raman-Untersuchungen zeigen das Vorliegen einer O-O-Bindung in 2, während die ESR-Analyse ein Signal bei g=2 mit 16 Linien für St=urn:x-wiley:00448249:media:ange202217076:ange202217076-math-0001 aufzeigt, das typischerweise mit einem MnIIIMnIV-Kern assoziiert wird, wie es auch in Class Ib RNR detektiert wurde. Anders als zuvor publizierte Mn-O2-Mn-Komplexe, die durch O2⋅−-Aktivierung an Mn2-Zentren gebildet wurden, ist 2 ein geeignetes elektrophiles Oxidationsmittel für Aldehyd-Deformylierungsreaktionen und Phenol-Oxidationsreaktionen, sodass es eines der besten strukturellen und funktionalen Modelle der Class Ib RNRs darstellt.
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 135,12
    Language: German
    URL: Volltext  (kostenfrei)
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  • 10
    UID:
    edochu_18452_27839
    Format: 1 Online-Ressource (7 Seiten)
    Content: In many metalloenzymes, sulfur-containing ligands participate in catalytic processes, mainly via the involvement in electron transfer reactions. In a biomimetic approach, we now demonstrate the implication of S-ligation in cobalt mediated oxygen reduction reactions (ORR). A comparative study between the catalytic ORR capabilities of the four-nitrogen bound [Co(cyclam)]2+ (1; cyclam=1,5,8,11-tetraaza-cyclotetradecane) and the S-containing analog [Co(S2N2-cyclam)]2+ (2; S2N2-cyclam=1,8-dithia-5,11-diaza-cyclotetradecane) reveals improved catalytic performance once the chalcogen is introduced in the Co coordination sphere. Trapping and characterization of the intermediates formed upon dioxygen activation at the CoII centers in 1 and 2 point to the involvement of sulfur in the O2 reduction process as the key for the improved catalytic ORR capabilities of 2.
    Content: Peer Reviewed
    In: Weinheim : Wiley-VCH, 62,6
    Language: English
    URL: Volltext  (kostenfrei)
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