Comment on gas phase infrared spectrum and ab initio calculations of phosphorus(III) thiocyanide, SPCN

We show that two of the three bands assigned to SPCN are assignable to cyanogen and that the bands assigned to SPCl are done so in error, with the 712 cm(-1) band in the spectrum of Allaf and Odeh assignable to HCN. There is no evidence for either ClPS or SPCN in the spectra shown. Finally low resolution IR spectroscopy by itself, whilst useful in assisting in the identification of pyrolysis products does not provide unambiguous identification and requires support by rigorous computation, band modelling and correct use of the literature. None of these are evidenced in the present paper of Allaf and Odeh nor indeed in the work that was the subject of our previous criticism and re-analysis.     

A posteriori error analysis of a cell-centered finite volume method for semilinear elliptic problems

In this paper, we conduct a goal-oriented a posteriori analysis for the error in a quantity of interest computed from a cell-centered finite volume scheme for a semilinear elliptic problem. The a posteriori error analysis is based on variational analysis, residual errors and the adjoint problem. To carry out the analysis, we use an equivalence between the cell-centered finite volume scheme and a mixed finite element method with special choice of quadrature.     

Perfluoropentaphenylborole: A New Approach to Lewis Acidic,Electron‐Deficient Compounds

Zirconocene is the key : A new synthetic method, which utilizes zirconocene‐mediated coupling of alkynes, has been developed for the preparation of a new class of highly Lewis acidic boroles (see scheme). Such compounds hold potential for applications in catalysis and the field of electron‐deficient organic materials.

     

K3(Sc0.875Nb0.125)Nb2O9H1.75: a new scandium niobate with a unique cage structure

Potassium scandium niobate hydroxide, K₃(Sc_0.875Nb_0.125)Nb₂O₉H_1.75, is a new scandium niobate with a unique cage structure. The structure contains two non‐equivalent K⁺ sites (3m and m2 site symmetry), one disordered Sc³⁺/Nb⁵⁺ site (m site symmetry), one Nb⁵⁺ site (3m site symmetry), two O²⁻ sites (m and mm2 site symmetry) and one H⁺ site (m site symmetry). Both scandium and niobium have octahedral environments, which combine to form cages around potassium. One K atom lies in a cube‐like cage built of seven octahedra, while the other K atom is encapsulated by an eight‐membered trigonal face‐bicapped prism. The cages form sheets that extend along the ab plane.     

A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole cycloadditions

The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels–Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations via the marriage of two powerful cycloaddition strategies. First, a formal Cp₂Zr-mediated [2 + 2 + 1] cycloaddition is used to generate a stannole-annulated PAH. Secondly, the stannoles are employed as diene components in a [4 + 2] cycloaddition/aromatization cascade with an aryne, enabling π-extension to afford a larger PAH. This discovery of stannoles as highly reactive – yet stable for handling – diene equivalents, and the development of a modular strategy for their synthesis, should significantly extend the structural scope of PAHs accessible by a [4 + 2] cycloaddition approach.

Stannoles are introduced as a new, spontaneously aromatizing diene for [4 + 2] cycloadditions that can be easily introduced into diverse conjugated systems, facilitating the efficient synthesis of complex PAHs and their π-extension.     

Tangent Fermions: Dirac or Majorana Fermions on a Lattice Without Fermion Doubling

Methods to discretize the Hamiltonian of a topological insulator or topological superconductor, without giving up on the topological protection of the massless excitations (respectively, Dirac fermions or Majorana fermions) are reviewed. The method of tangent fermions, pioneered by Richard Stacey, is singled out as being uniquely suited for this purpose. Tangent fermions propagate on a $2+1$ dimensional space-time lattice with a tangent dispersion: ${\tan }^2(\mathit{\epsilon }/2)={\tan }^2(k_x/2)+{\tan }^2(k_y/2)$ in dimensionless units. They avoid the fermion doubling lattice artefact that will spoil the topological protection, while preserving the fundamental symmetries of the Dirac Hamiltonian. Although the discretized Hamiltonian is nonlocal, as required by the fermion-doubling no-go theorem, it is possible to transform the wave equation into a generalized eigenproblem that is local in space and time. Applications that are discussed include Klein tunneling of Dirac fermions through a potential barrier, the absence of localization by disorder, the anomalous quantum Hall effect in a magnetic field, and the thermal metal of Majorana fermions.     

Tetracopper σ-Bound μ-Acetylide and -Diyne Units Stabilized by a Naphthyridine-based Dinucleating Ligand

Reactions of a dicopper(I) tert-butoxide complex with alkynes possessing boryl or silyl capping groups resulted in formation of unprecedented tetracopper(I) μ-acetylide/diyne complexes that were characterized by NMR and UV/Vis spectroscopy, mass spectrometry and single-crystal X-ray diffraction. These compounds possess an unusual μ₄-η¹:η¹:η¹:η¹ coordination mode for the bridging organic fragment, enforced by the rigid and dinucleating nature of the ligand utilized. Thus, the central π system remains unperturbed and accessible for subsequent reactivity and modification. This has been corroborated by addition of a fifth copper atom, giving rise to a pentacopper acetylide complex. This work may provide a new approach by which metal-metal cooperativity can be exploited in the transformation of acetylide and diyne groups to a variety of substrates, or as a starting point for the controlled synthesis of copper(I) alkyne-containing clusters.     

Effects of poloxamer on the gelation of silk fibroin

The influence of the concentration of poloxamer 407, the pH and the temperature on the gelation of silk fibroin (SF) were studied. It was found that the gelation of SF occurred in the presence of poloxamer at pH value of 7.0 while gelation of SF itself did not occur. The gelation time of SF was shortened with increasing the poloxamer concentration and the temperature. The sol‐gel transition of SF became reversible with an addition of poloxamer. From infrared (IR) and circular‐dichroism (CD) spectroscopy measurements, it was found that a conformational change of the SF in the SF/poloxamer system from random coil to β‐structure was accelerated after forming a polymer complex with the poloxamer. The crystallinity of the poloxamer was reduced by SF from X‐ray diffraction measurements.