Author
Bernt Krebs
Other affiliations: Leiden University, Clariant, Darmstadt University of Applied Sciences ...read more
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 published on a yearly basis
Papers
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TL;DR: In this article, Farblose et al. present a sample of the composition Tl2S · 2 B2S3, which is isotypic with RbBS3.
Abstract: Farblose, plattchenformige Kristalle von RbBS3 (P21/c, a=7,082(2) A, b=11,863(4) A, c=5,794(2) A, β=106,54(2)°) entstehen aus einem stochiometrischen Ansatz von Rubidiumsulfid, Bor und Schwefel bei 600°C und anschliesendem Tempern. Die zu RbBS3 isotype Phase TlBS3 (P21/c, a=6,874(3) A, b=11,739(3) A, c=5,775(2) A, β=113,08(2)°) erhalt man aus dem Ansatz Tl2S · 2 B2S3. Das nach 7 h bei 850°C erhaltene glasige Produkt wird in einem Zweizonenofen 400 h bei 400350°C ausgelagert. Gelbe Kristalle der Verbindung bilden sich in der warmeren Ofenzone. Das ebenfalls gelbe Tl3B3S10 (P1, a=6,828(2) A, b=7,713(2) A, c=13,769(5) A, α=104,32(2)°, β=94,03(3)β, γ=94,69(2)°) bildet sich aus stochiometrischen Mengen von Thalliumsulfid, Bor und Schwefel bei 850°C und anschliesendem Tempern.
Die ausschlieslich tetraedrisch koordiniertes Bor enthaltenden Verbindungen bilden polymere Kettenstrukturen, die sich im Fall des RbBS3 und TlBS3 aus spirocyclisch uber die Boratome verknupften, nichtplanaren Trithiadiborolan-Ringen aufbauen. Ersetzt man in diesen Anionenketten jeden dritten B2S3-Funfring durch einen B(S2)2B-Sechsring, so erhalt man die Anionenstruktur des Tl3B3S10.
The Perthioborates RbBS3, TIBS3, and Tl3B3S10.
RbBS3 (P21/c, a=7.082(2) A, b=11.863(4) A, c=5.794(2) A, β=106.54(2)°) was prepared as colourless, plate-shaped crystals by reaction of stoichiometric amounts of rubidium sulfide, boron, and sulfur at 600°C and subsequent annealing. TlBS3 (P21/c, a=6.874(3) A, b=11.739(3) A, c=5.775(2) A, β=113.08(2)°) which is isotypic with RbBS3 was synthesized from a sample of the composition Tl2S · 2 B2S3. The glassy product which was obtained after 7 h at 850°C was annealed in a two zone furnace for 400 h at 400350°C. Yellow crystals of TlBS3 formed at the warmer side of the furnace.
Tl3B3S10 (P1, a=6.828(2) A, b=7.713(2) A, c=13.769(5) A, α=104.32(2)°, β=94.03(3)°, γ=94.69(2)°) was prepared as yellow plates from stoichiometric amounts of thallium sulfide, boron, and sulfur at 850°C and subsequent annealing.
All compounds contain tetrahedrally coordinated boron. The crystal structures consist of polymeric anion chains. In the case of RbBS3 and TlBS3 nonplanar five-membered B2S3 rings are spirocyclically connected via the boron atoms. To obtain the anionic structure of Tl3B3S10 every third B2S3 ring of the polymeric chains of MBS3 is to be substituted by a six-membered B(S2)2B ring.
27 citations
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TL;DR: A highly selective method for the determination of porcine liver esterase by means of enzyme amplified lanthanide luminescence (EALL) was developed and may be carried out at neutral pH and without further additives.
Abstract: Screening of a small library of tripod ligands resulted in the discovery of bis(2-pyridylmethyl)-(2-hydroxybenzyl)amine (HL1) as a new sensitiser, which is able to transfer its excitation energy to terbium(III). After synthesis of the acetic acid ester of HL1, a highly selective method for the determination of porcine liver esterase by means of enzyme amplified lanthanide luminescence (EALL) was developed. Enzyme-catalysed cleavage of the ester results in the formation of HL1. After excitation at 297 nm, the characteristic emission of Tb(III) at 545 nm is observed and used to determine the esterase concentration. In contrast to existing EALL methods, this method may be carried out at neutral pH and without further additives. Limit of detection for porcine liver esterase is 10−9 mol l−1 and limit of quantification is 3 × 10−9 mol l−1. A linear calibration range of two decades starting at the limit of quantification is observed.
27 citations
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TL;DR: Etude RX du sel [Ph 4 P] 4 [Cu 12 S 8 ]: cristallisation dans P2 1 /n avec Z=2; affinement jusqu'a R=0,037
Abstract: Etude RX du sel [Ph 4 P] 4 [Cu 12 S 8 ]: cristallisation dans P2 1 /n avec Z=2; affinement jusqu'a R=0,037
27 citations
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21 Aug 1996TL;DR: BleBleach composition comprising one or more bleaching agents and polyoxometallates of the formula: (Q)q(A a X x M m O y Z z(H2O)b).cndot.
Abstract: Bleach composition comprising one or more bleaching agents and one or more polyoxometallates of the formula: (Q)q(A a X x M m O y Z z(H2O)b).cndot.cH2O as bleaching catalyst, the symbols Q, A, X, M, Z, q, a, x, m, y, z, b and c being as defined in the description. These polyoxometallates increase the bleaching activity, especially at lower washing temperatures.
27 citations
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TL;DR: In this paper, temperature dependent magnetic susceptibility measurements of the reduced and of the oxidized diiron forms of purple acid phosphatase from kidney bean (KBP) and from bovine spleen (BSP) have been carried out in the temperature range 4.2-220 K in order to detect the strength of the exchange coupling between the two metal centers in the active site.
27 citations
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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
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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
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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
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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
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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