Search

Synthesis and characterization of [OsH(PNP)(bipy)]+ (PNP=N(CHCHPtBu2)2) are reported, as the second osmium(III) hydrido complex next to [OsH(en)2(py)]2+. While the osmium(II) precursor, [OsH(PNP)(bipy)], exhibits two reversible oxidations in the cyclic voltammogram, the product from 2‐electron oxidation could not be isolated due to rapid decay. Thermochemical examinations attribute the stability of the osmium(III) hydride to both thermodynamic and kinetic reasons. In contrast, the high estimated acidity of [OsH(PNP)(bipy)]2+ presumably leads to rapid decay. [ABSTRACT FROM AUTHOR]

The introduction of enhanced functionalization is a key aspect in the current design of cage chemistry. At the moment, several approaches are intensively investigated. The synthesis of cage compounds that display endohedral functionalization plays a key role among them. Here, the studies of reactions that occur in endohedral‐functionalized cage compounds is reviewed. After an introduction in current trends in cage‐chemistry the discussion of reactions in endohedral‐cage compounds is divided into three sections. These are: 1) Endohedral groups that are by themselves functional, 2) endohedral groups that can bind to a transition‐metal complex and 3) endohedral groups that can bind by themselves to a metal. The article closes with an outlook on additional current developments in the field of endohedral‐functionalized cage‐compounds, which may contribute in the future towards reactivity in cage compounds. [ABSTRACT FROM AUTHOR]

On a Wendelstein 7-X (W7-X), an alkali metal beam (AMB) diagnostic system was installed in order to measure the plasma edge electron density profiles and turbulence transport. A sodium beam was injected in the plasma, and the light emission was observed by an optical system. During the last operation phase, OP1.2b campaign trial spectral measurements were performed with a dedicated optical branch. The results showed the emergence of potential CX lines in the light spectra during sodium injection. The lines were identified as Carbon III, which were the dominant lines observed by other diagnostics at the edge plasma. Based on these results, an additional dedicated optical system was developed and installed in 2021 for the upcoming operational phase, OP2. The optics were designed for multiple purposes: spectral measurements for the AMB system and for a He/Ne gas jet. The system was designed to allow implementation of further diagnostics on this port later (e.g., coherence imaging system). The details of the implementation of the design requirements and the main challenges of the manufacturing process and installation are discussed in this paper. [ABSTRACT FROM AUTHOR]

The active site of particulate methane monooxygenase (pMMO) and its mechanism of action are not known. Recently, the CuC site emerged as a potential active site, but to date it lacks any study on biomimetic resemblance of the coordination environment provided by the enzyme. Here, the synthesis of a cage ligand providing such an environment is reported. Copper is incorporated, and coordination occurs by the two imidazole and one carboxylate group offered by the ligand. Depending on the oxidation state, it can adopt different coordination modes, as evidenced by the solid‐state structures and computational investigation. The copper(I) state readily reacts with dioxygen and thereby undergoes CH activation. Moreover, the catalytic aerobic oxidation of hydroquinones as ubiquinol mimics is shown. Clean one‐electron oxidation occurs under mild conditions and EPR analysis of the copper(II) state in the presence of water reveals striking similarities to the data obtained from pMMO. [ABSTRACT FROM AUTHOR]

C−H amination and amidation by catalytic nitrene transfer are well‐established and typically proceed via electrophilic attack of nitrenoid intermediates. In contrast, the insertion of (formal) terminal nitride ligands into C−H bonds is much less developed and catalytic nitrogen atom transfer remains unknown. We here report the synthesis of a formal terminal nitride complex of palladium. Photocrystallographic, magnetic, and computational characterization support the assignment as an authentic metallonitrene (Pd−N) with a diradical nitrogen ligand that is singly bonded to PdII. Despite the subvalent nitrene character, selective C−H insertion with aldehydes follows nucleophilic selectivity. Transamidation of the benzamide product is enabled by reaction with N3SiMe3. Based on these results, a photocatalytic protocol for aldehyde C−H trimethylsilylamidation was developed that exhibits inverted, nucleophilic selectivity as compared to typical nitrene transfer catalysis. This first example of catalytic C−H nitrogen atom transfer offers facile access to primary amides after deprotection. [ABSTRACT FROM AUTHOR]

A conceptual approach for the synthesis of quasi‐heteroleptic complexes with properly endo‐functionalized cages as ligands is presented. The cage ligand reported here is of a covalent organic nature, it has been synthesized via a dynamic combinatorial chemistry approach, making use of a masked amine. Inspired by enzymatic active sites, the described system bears one carboxylate and two imidazole moieties as independent ligating units through which it is able to coordinate to transition metals. Analysis of the iron(II) complex in solution and the solid state validates the structure and shows that no undesired but commonly observed dimerization process takes place. The solid‐state structure shows a five‐coordinate metal center with the carboxylate bidentately bound to iron, which makes Fe@2 an unprecedentedly detailed structural model complex for this kind of non‐heme iron oxygenases. As, as confirmed by the crystal structure, sufficient space for other organic ligands is available, the biologically relevant ligand α‐ketoglutarate is implemented. We observe biomimetic reaction behavior towards dioxygen that opens studies investigating Fe@2 as a functional model complex. [ABSTRACT FROM AUTHOR]

Ein konzeptioneller Ansatz für die Synthese von quasi‐heteroleptischen Komplexen auf der Basis von endo‐funktionalisierten organischen Käfigen wird vorgestellt. Die Synthese des Liganden erfolgt über einen dynamisch kombinatorischen Ansatz und bedient sich eines maskierten Amins. Inspiriert von der facialen Triade in den aktiven Zentren diverser Enzyme besitzt dieser eine Carboxylat‐ und zwei Imidazolfunktionen als koordinierende Einheiten. Untersuchungen der FeII‐ und ZnII‐Komplexe bestätigen die angestrebte Struktur und insbesondere auch, dass keine unerwünschte, jedoch bei klassischen biomimetischen Komplexen oft beobachtete Dimerisierung stattfindet. Die Kristallstruktur des Eisen‐Triethylamin‐Komplexes zeigt ein fünffach koordiniertes Metallzentrum mit zweizähniger Anbindung des Carboxylatliganden, wodurch Fe@2 eine beispiellos genaue strukturelle Nachbildung von dieser Art von nicht‐Häm‐Eisenoxygenasen darstellt. Da, wie in der Kristallstruktur zu sehen, innerhalb der Kavität genug Platz für die Koordination externer Liganden möglich ist, wird der in diesem Kontext biologisch relevante Ligand α‐Ketoglutarat eingeführt, was in biomimetischer Reaktivität gegenüber Sauerstoff resultiert. [ABSTRACT FROM AUTHOR]

The operational regimes in the first divertor campaign of W7-X were limited by unexpectedly high heat loads on certain baffle tiles. In the high-mirror configuration, a permanent hotspot on the baffle plate was detected by the thermographic system, which was further confirmed during the post-campaign inspections of the plasma-facing components. The maximum heat load on three baffle tiles reached about 4.5 MW m−2, which was almost an order of magnitude above its designed value of 0.5 MW m−2. The paper presents a detailed analysis to understand how the baffle plate, which is originally designed to screen the recycling neutrals and is therefore hidden from the hot plasma, can receive such a high heat load - a level that is expected for target plates. Three main causes have been identified: 1) the three baffle tiles are radially only about 5 mm away from a main heat channel towards a target, which is much shorter than the radial power decay length of several centimeters derived from the thermographic measurements in this region; 2) the three baffle tiles are intersected with field-lines of about 30 m length, which are long enough to collect considerable amount of heat via cross-field transport; 3) the baffle tiles have locally large grazing angles. In addition, the analysis method shown in this paper is of general use to estimate the heat flows in shadow areas of targets and thus to evaluate heat loads on the potentially critical components occurring in these areas, especially required for the design of complex 3D divertors like the one in W7-X. [ABSTRACT FROM AUTHOR]

The mechanisms involved in the catalytic enantio- and stereoselective radical cyclization process facilitated by a regiodivergent epoxide opening are discussed. The significance of the catalysts in controlling the process is also demonstrated.

An imidazole-functionalised cage is synthesised that can coordinate to Cu(i). X-ray analysis reveals a T-shaped coordination of copper by the imidazole ligands reminiscent of the coordination geometry found in enzymatic active sites. This cage complex can catalyse the oxidation of benzylic alcohols to benzaldehydes utilizing oxygen as the terminal oxidant. [ABSTRACT FROM AUTHOR]

Trioxo‐rhenium complexes are well known catalysts for the deoxydehydration (DODH) of vicinal diols (glycols). In this work, we report on the DODH of diols and biomass‐derived polyols using CpttReO3 as a new catalyst (Cptt=1,3‐di‐tert‐butylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of CpttReO3 and 3‐octanol as both reductant and solvent. The CpttReO3 catalyst exhibits an excellent activity for biomass‐derived polyols. Specifically, glycerol is almost quantitatively converted to allyl alcohol and mucic acid gives 75 % of muconates at 91 % conversion. In addition, the loading of CpttReO3 can be reduced to 0.1 mol % to achieve a turn‐over number as high as 900 per Re when using glycerol as substrate. Examination of DODH reaction profiles by NMR spectroscopy indicates that catalysis is related to Cp‐ligand release, which raises questions on the nature of the actual catalyst. Less is more! Diols and biomass‐derived polyols, sustainable starting materials, were efficiency converted to very useful industrial olefin building blocks by using CpttReO3 as catalyst and a secondary alcohol as reductant. Remarkably, the loading of CpttReO3 can be reduced to 0.1 mol % to achieve a turn‐over number as high as 900 per Re when using glycerol as substrate. [ABSTRACT FROM AUTHOR]

Keywords: bioinorganic chemistry; confined space; organocatalysis; self-assembly; size-selective catalysis EN bioinorganic chemistry confined space organocatalysis self-assembly size-selective catalysis 1 1 1 05/11/23 20230508 NES 230508 B The Front Cover b illustrates the self-assembly of a cartoon parachute group conducting experiments. Bioinorganic chemistry, confined space, organocatalysis, self-assembly, size-selective catalysis Front Cover: Reactions in Endohedral Functionalized Cages (Eur. J. Org. [Extracted from the article]

A method for the regioselective transformation of dienes to carbonyl compounds has been developed. Electron-rich olefins react selectively to yield valuable aldehydes and ketones. The method is based on the catalyst [Fe(OTf)2(mix-BPBP)] with an oxidant combination of H2O2 (1.0 equiv.) and NaIO4 (1.5 equiv.); it uses mild conditions and short reaction times, and it outperforms other olefin cleavage methodologies. [ABSTRACT FROM AUTHOR]

A cobalt-porphyrin catalyst encapsulated in a cubic M8L6 cage allows cyclopropanation reactions in aqueous media. The caged-catalyst shows enhanced activities in acetone/water as compared to pure acetone. Interestingly, the M8L6 encapsulated catalyst reveals size-selectivity. Smaller substrates more easily penetrate through the pores of the 'molecular ship-in-a-bottle catalysts' and are hence converted faster than bigger substrates. In addition, N-tosylhydrazone sodium salts are easy to handle reagents for cyclopropanation reactions under these conditions. [ABSTRACT FROM AUTHOR]

Assembly of the superconducting stellarator Wendelstein 7-X is well advanced, and commissioning of the device is being prepared. A first draft of the commissioning tasks has been developed and will be discussed in this paper. [ABSTRACT FROM PUBLISHER]

The synthesis of a new, cubic M8L6 cage is described. This new assembly was characterised by using NMR spectroscopy, DOSY, TGA, MS, and molecular modelling techniques. Interestingly, the enlarged cavity size of this new supramolecular assembly allows the selective encapsulation of tetra(4-pyridyl)metalloporphyrins (MII(TPyP), M=Zn, Co). The obtained encapsulated cobalt-porphyrin embedded in the cubic zinc-porphyrin assembly is the first example of a catalytically active encapsulated transition-metal complex in a cubic M8L6 cage. The substrate accessibility of this system was demonstrated through radical-trapping experiments, and its catalytic activity was demonstrated in two different radical-type transformations. The reactivity of the encapsulated CoII(TPyP) complex is significantly increased compared to free CoII(TPyP) and other cobalt-porphyrin complexes. The reactions catalysed by this system are the first examples of cobalt-porphyrin-catalysed radical-type transformations involving diazo compounds which occur inside a supramolecular cage. [ABSTRACT FROM AUTHOR]

The magnetic confinement of plasmas in fusion experiments can significantly degrade due to perturbations of the magnetic field. A precise analysis of the magnetic field in a stellarator-type experiment utilizes electrons as test particles following the magnetic field line. The usual fluorescent detector for this electron beam limits the provided information to two-dimensional cut views at certain toroidal positions. However, the technique described in this article allows measuring the three-dimensional structure of the magnetic field by means of close-range photogrammetry. After testing and optimizing the main diagnostic components, measurements of the magnetic field lines were accomplished with a spatial resolution of 5 mm. The results agree with numeric calculations, qualifying this technique as an additional tool to investigate magnetic field configurations in a stellarator. For a possible future application, ways are indicated on how to reduce experimental error sources. [ABSTRACT FROM AUTHOR]

Focuses on a study which developed a three-dimensional elastic registration algorithm. Use of trilinear Bezier-splines to find a veridical transformation that maps activation patterns from functional magnetic resonance imaging experiments; Discussion on the registration of functional and anatomical image data; Preprocessing; Global affine alignment; Correction of spatial distortions.

Contrast agent-enhanced magnetic resonance (MR) mammography is a highly sensitive method in breast cancer detection. The inflow of contrast agent is tracked to classify tissue as malignant or benign. In this article, we introduce approaches to overcome two of the most prominent problems in MR mammography: (a) variability in contrast agent dynamics, and (b) motion of the patient during data acquisition. The variability of contrast agent dynamics is considered using data-driven analysis based on self-organizing maps. Motion during data acquisition is handled by means of a fast local elastic matching algorithm. © 1999 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 10, 199–206, 1999 [ABSTRACT FROM AUTHOR]

The software animation system PASTIS (Program Animation System with Interactive Solutions) for program animation with emphasis on the visualization of the dynamic behaviour of algorithms and data structures is presented. Its main properties are unmodified source code of the visualized program, concurrent multiple views on algorithms and data structures, and interactive alterations of views during run time. PASTIS is distinguished by high modularity and strict separation of its components. This makes it particularly suitable for distributed computing environments. The interface between program and animation is a relational data model. Animations are directed by a single tuple, or sets of tuples, called relations, or sets of relations, called networks. Animations can be nested hierarchically. A prototype of PASTIS was implemented under Unix using the GNU source level debugger gdb and the X-window system. [ABSTRACT FROM AUTHOR]

Review: 154 refs. [ABSTRACT FROM AUTHOR]

A system for coupling catalytic radical cyclization and Ir-catalyzed hydrogen atom transfer (HAT) is described. It is essential that the HAT catalyst activates H2 quickly and is not a hydrogenation catalyst. Vaska's complex was found to fulfill both purposes efficiently. [ABSTRACT FROM AUTHOR]

The front cover of the March 2016 issue of the "European Journal of Inorganic Chemistry" is presented.

A supramolecular cage catalyst, generated by encapsulation of Co(tetra(4-pyridyl)porphyrin) into a Nitschke-type M8L6 cubic cage is utilized in these reactions. [ABSTRACT FROM AUTHOR]