A General and Practical Route to Functionalized Bicyclo[1.1.1]Pentane-Heteroaryls Enabled by Photocatalytic Multicomponent Heteroarylation of [1.1.1]Propellane

1-Aryl-substituted bicyclo[1.1.1]pentanes (BCPs) are an important class of BCP derivatives with widespread application in drug development. Most syntheses of these materials require multiple chemical steps via BCP electrophiles or nucleophiles derived from [1.1.1]propellane. Although one-step, multicomponent radical cross-coupling reactions could provide a more sustainable and rapid route to access diverse heteroarylated BCPs, current approaches are limited to tertiary alkyl radicals, leading to a decrease in their practical value. In this study, a conceptually different approach enabled by a radical multicomponent heteroarylation of [1.1.1]propellane to access functionalized heteroarylated BCPs is described. Importantly, this protocol is compatible with primary-, secondary-, and tertiary aliphatic radicals, as well as various fluoroalkyl radical sources, thus enabling rapid library generation of sought-after BCP derivatives for drug development.     

Tuning the Electronic Properties of Platinum in Hybrid-Nanoparticle Assemblies for use in Hydrogen Evolution Reaction

Platinum is the best electrocatalyst for the hydrogen evolution reaction (HER). Here, we demonstrate that by contact electrification of Pt nanoparticle satellites on a gold or silver core, the Fermi level of Pt can be tuned. The electronic properties of Pt in such hybrid nanocatalysts were experimentally characterized by X-ray photoelectron spectroscopy (XPS) and surface-enhanced Raman scattering (SERS) with the probe molecule 2,6-dimethyl phenyl isocyanide (2,6-DMPI). Our experimental findings are corroborated by a hybridization model and density functional theory (DFT) calculations. Finally, we demonstrate that tuning of the Fermi level of Pt results in reduced or increased overpotentials in water splitting.     

Quantum chemical study of trivalent group 12 fluorides

In view of the recent experimental observation of the existence of tetravalent Hg (IV) in HgF 4, a quantum chemical study of various trivalent group 12 M(III) fluoride complexes has been carried out. The M-F bonds in neutral MF 3 are relatively weak, making these species unlikely targets. Some additional stability can be obtained by dimerizing HgF3 to Hg2F6, which has a doubly fluorine-bridged triplet ground state. Anionic [MF4]- and [MF5]2- species are found to be more stable toward F2 elimination and M-F bond breaking than neutral MF 3.     

Structures, physical properties, and chemistry of layered oxychalcogenides and oxypnictides

A series of layered oxychalcogenide and oxypnictide solids is described that contain oxide layers separated by distinct layers, which contain the softer chalcogenide (S, Se, Te) or pnictide (P, As, Sb, Bi) anions. The relationships between the crystal structures adopted by these compounds are described, and the physical and chemical properties of these materials are related to the structures and the properties of the elements. The properties exhibited by the oxychalcogenide materials include semiconductor properties, for example, in LaOCuCh (Ch = chalcogenide) and derivatives, unusual magnetic properties exhibited by the class Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni), and redox properties exhibited by the materials Sr 2MnO 2Cu 2 m-0.5 S m+1 ( m = 1-3) and Sr 4Mn 3O 7.5Cu 2Ch 2 (Ch = S, Se). Recent results in the oxychalcogenide area are reviewed, and some new results on the intriguing series of compounds Sr 2MO 2Cu 2-deltaS 2 (M = Mn, Co, Ni) are reported. Oxypnictides have received less recent attention, but this is changing: a new frenzy of research is underway following the discovery of high-temperature superconductivity (>40 K) in derivatives of the layered oxyarsenide LaOFeAs. The early results in this exciting new area will be reviewed.     

Diastereoselective synthesis of carbapenams via Kinugasa reaction

A facile approach to carbapenams via Kinugasa reaction between terminal copper acetylides and nonracemic cyclic nitrones derived from malic and tartaric acid is reported. The stereochemical preferences observed in these reactions are explained. The reaction provides an entry to the carbapenams basic skeleton.     

On Korn's first inequality for tangential or normal boundary conditions with explicit constants

We will prove that for piecewise C²‐concave domains in Korn's first inequality holds for vector fields satisfying homogeneous normal or tangential boundary conditions with explicit Korn constant . Copyright © 2016 John Wiley & Sons, Ltd.     

Thermo‐visco‐elasticity for Norton‐Hoff‐type models with Cosserat effects

We consider the quasi‐static evolution of thermo‐visco‐elastic material. The main goal of this paper is to present how taking into account the additional effects may improve the result of solutions' existence. We added a micropolarity effect to thermo‐visco‐elastic model regarding Norton‐Hoff‐type constitutive function. This additional phenomenon improves the regularity of solution. Copyright © 2016 John Wiley & Sons, Ltd.     

Notes on simplicial rook graphs

The simplicial rook graph \(\mathrm{SR}(m,n)\) is the graph of which the vertices are the sequences of nonnegative integers of length m summing to n, where two such sequences are adjacent when they differ in precisely two places. We show that \(\mathrm{SR}(m,n)\) has integral eigenvalues, and smallest eigenvalue \(s = \max \left( -n, -{m \atopwithdelims ()2}\right) \), and that this graph has a large part of its spectrum in common with the Johnson graph \(J(m+n-1,n)\). We determine the automorphism group and several other properties.     

Virtual boundaries of Hadamard spaces with admissible actions of higher rank

In this paper, we prove that every conformal minimal immersion of an open Riemann surface into \({\mathbb {R}}^n\) for \(n\ge 5\) can be approximated uniformly on compacts by conformal minimal embeddings (see Theorem 1.1). Furthermore, we show that every open Riemann surface carries a proper conformal minimal embedding into \({\mathbb {R}}^5\) (see Theorem 1.2). One of our main tools is a Mergelyan approximation theorem for conformal minimal immersions to \({\mathbb {R}}^n\) for any \(n\ge 3\) which is also proved in the paper (see Theorem 5.3).