Reaction behavior of iron and copper complexes towards dioxygen

To provide a better understanding of the reactions of iron and copper proteins with dioxygen, the corresponding reactions of small molecule model complexes with dioxygen were analysed using spectroscopic and kinetic methods. Special attention focused upon the binding and activation of dioxygen by iron proteins such as hemerythrin (Hr) and protocatechuat-3,4-dioxygenase (3,4-PCD) and by copper proteins like hemocyanin (Hc) and tyrosinase. Iron complexes of the ligand tmpa (tmpa = tris[(2-pyridyl)methyl]amine, also known as tpa in literature) were synthesised and modifications of the tmpa ligand were made. Increasing as well as decreasing chelate ring sizes in the highly active complex [Fe(tmpa)(dbc)]B(C6H5)4 (dbc = 3,5-di-tert-butylcatecholate dianion), only resulted in decreased reactivity of the investigated compounds. A detailed low-temperature stopped-flow investigation of the reaction of dioxygen with [Fe(tmpa)(dbc)]B(C6H5)4 was performed and activation parameters of Delta H# = 23 +- 1 kJ mol-1 and Delta S# = -199 +- 4 J mol-1 K-1 were obtained. Crystal structures of bromo-(tetrachlorocatecholato-O,O\u27)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N\u27,N\u27\u27)-iron(III) (2), (mu-oxo)-bis(bromo)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N\u27,N\u27\u27,N\u27\u27\u27)-diiron(III) (3), dichloro-((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N\u27,N\u27\u27,N\u27\u27\u27)-iron(III) (4) and (tetrabromocatecholato-O,O\u27)((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N\u27,N\u27\u27,N\u27\u27\u27)-iron(III) (5) are reported (Chapter 2). Besides altering the chelate ring size the influence of the donor atoms of the ligand on catechol dioxygenase reactivity was investigated. Two derivatives of the tmpa ligand (uns-penp and acetyl-uns-penp) were synthesised, where one aromatic nitrogen donor was replaced by an aliphatic nitrogen donor. The iron(III) complexes of the tripodal ligands N\u27,N\u27-bis[(2-pyridyl)methyl]ethylenediamine (uns-penp), [Fe(uns-penp)Cl2]ClO4 x CH3CN, [{Fe(uns-penp)Cl}2O](ClO4)2 x 2CH3CN and the amide derivative N-Acetyl-N\u27,N\u27-bis[(2-pyridyl)methyl]ethylenediamine (acetyl-uns-penp), [Fe2(acetyl-uns-penp)2O](ClO4)2 x H2O, [Fe(acetyl-uns-penp)(tcc)Br] x (C2H5)2O and [{Fe(acetyl-uns-penp)(tcc)}2O] x (C2H5)2O x CH3OH were synthesised and characterised. Catechol dioxygenase reactivity of in situ prepared complex solutions only showed slower reactions in comparison with the iron tmpa system (Chapter 3). Corresponding ligand system variations in the small molecule model complexes of copper proteins were made and analysed with respect to dioxygen reactivity. Intramolecular ligand hydroxylation was observed during the reactions of dioxygen with the dicopper(I) complexes of the ligands L3 (L3 = alpha,alpha\u27-bis[(2-pyridylethyl)amino]-m-xylene) and L5 (L5 = alpha,alpha\u27-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)-amino]-m-xylene). The dinuclear copper(I) complex [Cu2L5](ClO4)2 and the dicopper(II) complex [Cu2(L3-O)(OH)(ClO4)]ClO4 were characterised by single-crystal X-ray structure analysis. Furthermore, phenolate-bridged complexes were synthesised with the ligand L4-OH and Me-L5-OH (structurally characterised: [Cu2(L4-O)Cl3] with L4 = alpha,alpha\u27-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylene and [Cu2(Me-L5-O)(mu-X)](ClO4)2 x nH2O with Me-L5-OH = 2,6-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-4-methylphenol and X = C3H3N2- (prz), MeCO2- and N3-). Temperature-dependent magnetic studies revealed the antiferromagnetic coupling of the copper ions of these complexes (Chapter 4). The reactions of dioxygen with copper(I) complexes of the tridentate ligands 1,1,4,7,7-pentamethyldiethylethylenetriamine (Me5dien), 1,1,4,7,7-pentaethyldiethylethylenetriamine (Et5dien), N-methyl-[bis(2-pyridyl)methyl]amine (Me-bpa) and N-methyl-[(2-pyridyl)ethyl(2-pyridyl)methyl]amine (MeL) have been investigated using low-temperature stopped-flow techniques. The formation of a bis(mu-oxo) copper complex as a reactive intermediate could only be detected spectroscopically at low temperatures for [Cu(Me5dien)(CH3CN)]ClO4 and allowed a quantitative kinetic analysis to be performed. Crystal structures of the copper(II) complexes [(Me-bpa)Cu(Cl)2], [{(Me-bpa)Cu(Cl)(ClO4)}2], [{(MeL)Cu(Cl)(ClO4)}2] and [(MeL)Cu(NCS)2] are reported. (Chapter 5)Zum besseren Verständnis der Reaktionen von Eisen- und Kupferproteinen mit elementarem Sauerstoff wurden im Rahmen dieser Arbeit für Eisen- und Kupferproteine Modellkomplexe mit geringer Molekularmasse mit spektroskopischen oder kinetischen Methoden untersucht. Besondere Aufmerksamkeit wurde hierbei der Bindung und der Aktivierung von elementarem Sauerstoff durch die Eisenproteine, wie z. B. Hämerythrin (Hr) und Protocatechuat-3,4-dioxygenase (3,4-PCD), und die Kupferproteine, wie z. B. Hämocyanin (Hc) und Tyrosinase, gewidmet. Bezüglich der Modelle für Eisenenzyme wurde der Ligand tmpa (tmpa = tris[(2-pyridyl)methyl]amin; in der Literatur auch mit tpa abgekürzt) untersucht und systematisch variiert. Die Vergrößerung und Verkleinerung der Chelatringgröße im hochreaktiven Komplex [Fe(tmpa)(dbc)]B(C6H5)4 (dbc = 3,5-Di-tert-butylcatecholat Dianion) führte nur zu einer verringerten Reaktivität der untersuchten Verbindungen. Die Reaktion von elementaren Sauerstoff mit [Fe(tmpa)(dbc)]B(C6H5)4 wurde mittels der Tieftemperatur-\u27stopped-flow\u27-Technik untersucht und ergab die Aktivierungsparameter Delta H# = 23 +- 1 kJ mol-1 und Delta S# = -199 +- 4 J mol-1 K-1. Weiterhin wurden die Kristallstrukturanalysen der Verbindungen bromo-(tetra-chlorocatecholato-O,O\u27)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N\u27,N\u27\u27)-eisen(III) (2), (mü-oxo)-bis(bromo)(bis((2-pyridyl)methyl)-2-pyridylamine-N,N\u27,N\u27\u27,N\u27\u27\u27)-dieisen (III) (3), dichloro-((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl)amine-N,N\u27,N\u27\u27,N\u27\u27\u27)-eisen (III) (4) und (tetrabromocatecholato-O,O\u27)((2-(2-pyridyl)ethyl)bis((2-pyridyl)methyl) amine-N,N\u27,N\u27\u27,N\u27\u27\u27)-eisen (III) (5) beschrieben (Kapitel 2). Neben der Änderung der Chelatringgröße wurde auch der Einfluss der Donoratome des Liganden untersucht. Dazu wurden abgeleitet vom tmpa zwei Liganden (uns-penp und acteyl-uns-penp) synthetisiert, bei denen ein aromatischer Stickstoff durch einen aliphatischen Stickstoff ersetzt wurde. Die Eisen(III)-Komplexe mit den tripodalen Liganden N\u27,N\u27-bis[(2-pyridyl)methyl]ethylenediamin (uns-penp), [Fe(uns-penp)Cl2]ClO4 x CH3CN, [{Fe(uns-penp)Cl}2O](ClO4)2 x 2CH3CN und dem Amidderivat N-Acetyl-N\u27,N\u27-bis[(2-pyridyl)methyl]ethylenediamin (acetyl-uns-penp), [Fe2(acetyl-uns-penp)2O](ClO4)2 x H2O, [Fe(acetyl-uns-penp)(tcc)Br] x (C2H5)2O und [{Fe(acetyl-uns-penp)(tcc)}2O] x (C2H5)2O x CH3OH wurden synthetisiert und charakterisiert. Untersuchungen zur Catecholdioxygenasereaktivität der in situ dargestellten Komplexlösungen zeigten nur langsamere Reaktionen im Vergleich zu dem Eisen-tmpa-System (Kapitel 3) Die Ligandensysteme für Modelle von Kupferproteinen wurden nach denselben Gesichtspunkten verändert wie bei den Modellen für die Eisenproteine. Intramolekulare Hydroxylierung des Liganden war bei der Reaktion von elementaren Sauerstoff mit Dikupfer(I)-Komplexen der Liganden L3 (L3 = alpha,alpha\u27-bis[(2-pyridylethyl)amino]-m-xylol) und L5 (L5 = alpha,alpha\u27-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)-amino]-m-xylol) zu beobachten. Der dinukleare Kupfer(I)-Komplex [Cu2L5](ClO4)2 und der Dikupfer(II)-Komplex [Cu2(L3-O)(OH)(ClO4)]ClO4 konnten durch Einkristallröntgenstrukturanalyse charakterisiert werden. Zusätzlich wurden Phenolatverbrückte Komplexe mit den Liganden L4-OH und Me-L5-OH synthetisiert (Strukturlösungen für [Cu2(L4-O)Cl3] mit L4 = alpha,alpha\u27-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylol und [Cu2(Me-L5-O)(mü-X)](ClO4)2 x nH2O (Me-L5-OH = 2,6-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-4-methylphenol und X = C3H3N2- (prz), MeCO2- und N3-). Temperaturabhängige magnetische Untersuchungen zeigten antiferromagnetische Kopplung der Kupferionen in diesen Komplexen (Kapitel 4). Die Reaktionen von elementaren Sauerstoff mit Kupfer(I)-Komplexen der dreizähnigen Liganden 1,1,4,7,7-pentamethyldiethylethylenetriamin (Me5dien), 1,1,4,7,7-pentaethyldiethylethylenetriamin (Et5dien), N-methyl-[bis(2-pyridyl) methyl]amin (Me-bpa) und N-methyl-[(2-pyridyl)ethyl(2-pyridyl)methyl]amin (MeL) mit Hilfe der Tieftemperatur-\u27stopped-flow\u27-Technik untersucht. Die Bildung eines bis(mü-oxo)-Kupferkomplexes konnte dabei bei tiefen Temperaturen nur für den Komplex [Cu(Me5dien)(CH3CN)]ClO4 spektroskopisch beobachtet und quantitativ kinetisch analysiert werden. Die Komplexe [(Me-bpa)Cu(Cl)2], [{(Me-bpa)Cu(Cl)(ClO4)}2], [{(MeL)Cu(Cl)(ClO4)}2] und [(MeL)Cu(NCS)2] konnten kristallographisch charakterisiert werden. (Kapitel 5

Nonequilibrium Zeeman-splitting in quantum transport through nanoscale junctions

We calculate the nonequilibrium differential conductance $G(V)$ through a quantum dot as function of bias voltage $V$ and applied magnetic field $H$. We use a Keldysh conserving approximation for weakly correlated and the scattering states numerical renormalization group for the intermediate and strongly correlated regime out of equilibrium. In the weakly correlated regime, the Zeeman splitting observable in $G(V)$ strongly depends on the asymmetry of the coupling to the two leads, as well as on particle-hole asymmetry of the quantum dot. In contrast, in the strongly correlated regime, where Kondo-correlations dominate, the position $\Delta_K$ of the Zeeman-split zero-bias anomaly is independent of such asymmetries and always found to be of the order of the Zeeman energy $\Delta_0$. We find a crossover from the purely spin-fluctuation driven Kondo regime at small magnetic fields with $\Delta_K<\Delta_0$ to a regime at large fields where the contribution of charge fluctuations induces larger splittings with $\Delta_K>\Delta_0$ as it was observed in recent experiments.Comment: 3 figure

Data Enabled Failure Management Process (DEFMP) across the Product Value Chain

The continuously increasing amount of production data and the advancing development of digitization solutions promote advanced data analytics as a promising approach for failure management. Beyond the consideration of single units, examining the end-to-end value chain, including development, production, and usage, offers potential for failure in management-related investigations. Nonetheless, challenges regarding data integration from different entities along the value creation process, data volume and formats handling, effective analytics, and decision support arise. The CRISP-DM approach has become a widely established reference as a conceptual framework for data-driven solutions. However, the linkage between existing failure management procedures and the subsequent development of data-driven solutions needs to be specified. Accordingly, this paper presents a cross-value chain Data Enabled Failure Management Process (DEFMP). The central element is a process model to implement a cross-value chain data-enabled failure management, considering established quality management and data analytics approaches. Based on available failure, product, and process knowledge along the value chain, a path towards developing a comprehensive decision support system is shown. DEFMP combines a reactive failure process with a data-driven approach to incorporate data analytics for proactive improvements. Using DEFMP, the failure management process of a commercial vehicle manufacturer is adapted. With this, partial automation of failure management is made possible. In addition, the potential for improvements is identified and prioritized

Dynamic susceptibilities of the single impurity Anderson model within an enhanced non-crossing approximation

The single impurity Anderson model (SIAM) is studied within an enhanced non-crossing approximation (ENCA). This method is extended to the calculation of susceptibilities and thoroughly tested, also in order to prepare applications as a building block for the calculation of susceptibilities and phase transitions in correlated lattice systems. A wide range of model parameters, such as impurity occupancy, temperature, local Coulomb repulsion and hybridization strength, are studied. Results for the spin and charge susceptibilities are presented. By comparing the static quantities to exact Bethe ansatz results, it is shown that the description of the magnetic excitations of the impurity within the ENCA is excellent, even in situations with large valence fluctuations or vanishing Coulomb repulsion. The description of the charge susceptibility is quite accurate in situations where the singly occupied ionic configuration is the unperturbed ground state; however, it seems to overestimate charge fluctuations in the asymmetric model at too low temperatures. The dynamic spin excitation spectra is dominated by the Kondo-screening of the impurity spin through the conduction band, i.e. the formation of the local Kondo-singlet. A finite local Coulomb interaction U leads to a drastic reduction of the charge response via processes involving the doubly occupied impurity state. In the asymmetric model, the charge susceptibility is enhanced for excitation energies smaller than the Kondo scale T_K due to the influence of valence fluctuations.Comment: 16 pages, 13 figure

Reducing Wastage In Manufacturing Through Digitalization: An Adaptive Solution Approach For Process Efficiency

The transformation to digital manufacturing has become increasingly critical for companies to remain competitive and achieve efficient manufacturing processes. However, manufacturing operations are often plagued by suboptimal allocation of resources, which can lead to higher costs and lower productivity. Digitalization has the potential to address these challenges by enabling real-time data monitoring, reducing quality costs, and improving product quality. Previous studies have shown that digital manufacturing can improve the efficiency of manufacturing processes and lead to productivity increases in organizations. However, despite these advantages, many digital innovation projects in manufacturing fall short of their initial ambitions, often resulting in incremental improvements to an existing manufacturing system. This is partly due to the challenges faced by manufacturing companies in quantifying the added value versus the costs of digitization technologies. Therefore, the objective of this paper is to propose an adaptive solution approach that addresses the need of aiding the decision process in selecting and assessing digital technologies to reduce wastage in manufacturing processes. The approach combines the 'Makigami' methodology, an 'Activity Diagram' (AD) modelling methodology, and a simplified 'Flow Chart', representing an aggregated view of the more detailed AD via a custom modelling schema, into one coherent framework. We further introduce the 'Methods-Misallocation-Measure' (3M-Graph) framework, which maps methods onto elements of wastage and misallocation, and subsequently assigns potential countermeasures. This tripartite mapping facilitates the identification of wastage during process analysis, the allocation of digital optimization measures and eases the assessment of cost effectiveness. The proposed approach aims to improve process efficiency and reduce wastage in manufacturing through digitalization. We conduct a case study of the approach and its application to an industrial assembly station, comparing the initial and then optimized processes. Future work includes the identification of further improvements and extending the framework by methodologies for estimating cost effectiveness more concisely

Kinks in the electronic dispersion of the Hubbard model away from half filling

We study kinks in the electronic dispersion of a generic strongly correlated system by dynamic mean-field theory (DMFT). The focus is on doped systems away from particle-hole symmetry where valence fluctuations matter potentially. Three different algorithms are compared to asses their strengths and weaknesses, as well as to clearly distinguish physical features from algorithmic artifacts. Our findings extend a view previously established for half-filled systems where kinks reflect the coupling of the fermionic quasiparticles to emergent collective modes, which are identified here as spin fluctuations. Kinks are observed when strong spin fluctuations are present and, additionally, a separation of energy scales for spin and charge excitations exists. Both criteria are met by strongly correlated systems close to a Mott-insulator transition. The energies of the kinks and their doping dependence fit well to the kinks in the cuprates, which is surprising in view of the spatial correlations neglected by DMFT.Comment: 13 pages, 15 figure

Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin–phonon interactions

Antiferromagnetic materials have been proposed as new types of narrowband THz spintronic devices owing to their ultrafast spin dynamics. Manipulating coherently their spin dynamics, however, remains a key challenge that is envisioned to be accomplished by spin-orbit torques or direct optical excitations. Here, we demonstrate the combined generation of broadband THz (incoherent) magnons and narrowband (coherent) magnons at 1 THz in low damping thin films of NiO/Pt. We evidence, experimentally and through modeling, two excitation processes of spin dynamics in NiO: an off-resonant instantaneous optical spin torque in (111) oriented films and a strain-wave-induced THz torque induced by ultrafast Pt excitation in (001) oriented films. Both phenomena lead to the emission of a THz signal through the inverse spin Hall effect in the adjacent heavy metal layer. We unravel the characteristic timescales of the two excitation processes found to be 300 fs, respectively, and thus open new routes towards the development of fast opto-spintronic devices based on antiferromagnetic materials

Interplay between superconductivity and magnetism in K-doped EuFe2As2

Superconductivity is found in 50% K-doped EuFe2As2 sample below 33 K. Our results of electrical resistivity, magnetic susceptibility and 57Fe and 151Eu Mossbauer spectroscopy provide clear evidence that the ordering of the Fe moments observed at 190 K in undoped EuFe2As2 is completely suppressed in our 50% K doped sample, thus there is no coexistence between the Fe magnetic order and the superconducting state. However, short range ordering of the Eu moments is coexisting with the superconducting state below 15 K. A bump in the susceptibility well below Tc as well as a slight broadening of the Fe Mossbauer line below 15 K evidence an interplay between the Eu magnetism and the superconducting state.Comment: 7 pages, 6 figure