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Bernt Krebs

Bio: Bernt Krebs is an academic researcher from University of Münster. The author has contributed to research in topics: Crystal structure & Ligand. The author has an hindex of 56, co-authored 729 publications receiving 16336 citations. Previous affiliations of Bernt Krebs include Leiden University & Clariant.


Papers
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Journal ArticleDOI
TL;DR: In this article, a tetranuclear Cu(II) complex was reported, which exhibits an unusual [(CuCl)4(μ-Cl)2] binding mode with a Cu··· Cu distance of 6.856(3) A.

5 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis, single crystal X-ray crystallographic, magnetic and electrochemical characterization of eight representative symmetric and unsymmetric complexes as structural model compounds for active sites in PAPs is reported.
Abstract: The synthesis, single crystal X-ray crystallographic, magnetic and electrochemical characterization of eight representative symmetric and unsymmetric complexes as structural model compounds for active sites in PAPs is reported. A mixed valent diiron as well as an iron(III)–zinc(II) complex as models for the active, reduced form of mammalian and plant PAPs, respectively, were synthesized and characterized. Five diiron(III) compounds as structural models for the oxidized uteroferrin-phosphato and -arsenato complex and a model for the oxidized form of PAP from beef spleen are reported. In addition to the structural relevance the catalase and peroxidase activity of one of these model complexes is introduced. Further we summarize our recent research concerning synergistic investigations on catechol oxidase and on synthetic copper coordination complexes. The catechol oxidase is an important type 3 copper protein for the activation of dioxygen. The development of low-molecular weight catalysts should facilitate the oxidation of organic substances by O2. In particular the reported copper(II) complexes may serve as structural and functional bioinorganic model compounds for the active sites of dioxygen binding and dioxygen activating copper proteins, respectively. These investigations provided a new X-ray crystallographically characterized type of peroxo copper(II) complexes with a μ4-(η1)4 coordination mode.

5 citations

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TL;DR: In this paper, an improved technique for the preparation of solid specimens suitable for X-ray absorption measurements is described which is especially useful for air or water sensitive materials, and the finely powdered materials are enclosed in a polymer matrix.
Abstract: An improved technique for the preparation of solid specimens suitable for X-ray absorption measurements is described which is especially useful for air or water sensitive materials. The finely powdered materials are enclosed in a polymer matrix. Homogeneous, stable, and uniformly thick films can be obtained by this method. The capabilities of the technique have been tested within a series of iron and cobalt compounds.

5 citations

Journal ArticleDOI
TL;DR: In this article, a single crystal structure analysis of the phenyl derivative 5b, the Fe-Fe distance was found to be 2.508 Å, where the two C atoms are bridging the Fe2 group in a somewhat distorted manner, whereas the bridging keto oxygen is symmetrically bound to both Fe (1.927 and 2.004 Å).
Abstract: Abstract Cyclohexylamino(keto)carbene complexes of group VI B metals which contain a terminally bound carbene ligand, on reaction with Fe2(C0)9 give binuclear oxallyl iron complexes 5, in which the carbene carbon and the keto function form a bridge consisting of three atoms bound to two iron atoms. From a single crystal structure analysis of the phenyl derivative 5b, the Fe-Fe distance was found to be 2.508 Å. The two C atoms are bridging the Fe2 group in a somewhat distorted manner (C(l)-Fe(l) 2.461, C(l)-Fe(2) 1.912, C(2)-Fe(l) 2.024, C(2)-Fe(2) 2.478 Å), whereas the bridging keto oxygen is symmetrically bound to both Fe (1.927 and 2.004 Å). Alkylamino(phenyl)carbene complexes like 11 react with Fe2(C0)9 to give a four atom bridging ligand by migration of a hydrogen atom from nitrogen and an ortho hydrogen from the phenyl group to the carbene carbon. Free or complexed alkylimines may be intermediates in this reaction.

5 citations

Journal ArticleDOI
TL;DR: The configurations of the mitosane derivatives described in the previous communications1) were established by spectroscopic investigations and X-ray analysis of rac-1e as discussed by the authors, and they were used in the synthesis of Mitomycins.

5 citations


Cited by
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TL;DR: This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material.
Abstract: The chemistry of graphene oxide is discussed in this critical review Particular emphasis is directed toward the synthesis of graphene oxide, as well as its structure Graphene oxide as a substrate for a variety of chemical transformations, including its reduction to graphene-like materials, is also discussed This review will be of value to synthetic chemists interested in this emerging field of materials science, as well as those investigating applications of graphene who would find a more thorough treatment of the chemistry of graphene oxide useful in understanding the scope and limitations of current approaches which utilize this material (91 references)

10,126 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
TL;DR: The hydrogen bond is the most important of all directional intermolecular interactions, operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological.
Abstract: The hydrogen bond is the most important of all directional intermolecular interactions. It is operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological. Research into hydrogen bonds experienced a stagnant period in the 1980s, but re-opened around 1990, and has been in rapid development since then. In terms of modern concepts, the hydrogen bond is understood as a very broad phenomenon, and it is accepted that there are open borders to other effects. There are dozens of different types of X-H.A hydrogen bonds that occur commonly in the condensed phases, and in addition there are innumerable less common ones. Dissociation energies span more than two orders of magnitude (about 0.2-40 kcal mol(-1)). Within this range, the nature of the interaction is not constant, but its electrostatic, covalent, and dispersion contributions vary in their relative weights. The hydrogen bond has broad transition regions that merge continuously with the covalent bond, the van der Waals interaction, the ionic interaction, and also the cation-pi interaction. All hydrogen bonds can be considered as incipient proton transfer reactions, and for strong hydrogen bonds, this reaction can be in a very advanced state. In this review, a coherent survey is given on all these matters.

5,153 citations

Journal ArticleDOI
TL;DR: The transition metal dichalcogenides are about 60 in number as discussed by the authors, and two-thirds of these assume layer structures and can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions.
Abstract: The transition metal dichalcogenides are about 60 in number. Two-thirds of these assume layer structures. Crystals of such materials can be cleaved down to less than 1000 A and are then transparent in the region of direct band-to-band transitions. The transmission spectra of the family have been correlated group by group with the wide range of electrical and structural data available to yield useful working band models that are in accord with a molecular orbital approach. Several special topics have arisen; these include exciton screening, d-band formation, and the metal/insulator transition; also magnetism and superconductivity in such compounds. High pressure work seems to offer the possibility for testing the recent theory of excitonic insulators.

3,313 citations

Journal ArticleDOI
TL;DR: Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers.
Abstract: Copper is an essential trace element in living systems, present in the parts per million concentration range. It is a key cofactor in a diverse array of biological oxidation-reduction reactions. These involve either outer-sphere electron transfer, as in the blue copper proteins and the Cu{sub A} site of cytochrome oxidase and nitrous oxide redutase, or inner-sphere electron transfer in the binding, activation, and reduction of dioxygen, superoxide, nitrite, and nitrous oxide. Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. 428 refs.

3,241 citations