Electrode polarization and interface effects in liquid crystal systems with mobile ions: development of a model of bipolar diffusion

The influence of mobile ions on the results of impedance spectroscopy (dielectric spectroscopy) measurements performed on a liquid crystal cell using the new mathematical model recently described was investigated. This mathematical model reformulates the fundamental equation system of continuity for mobile charge carriers and the Poisson equation using new variables. One makes the following assumptions: ions have different mobilities and diffusion coefficients, there is no generation-recombination process, the equilibrium carrier concentrations are uniform and equal each other, the electrodes are either completely blocking or blocked with adsorption-desorption processes. The final result is the analytical expression of the equivalent admittance for the system, allowing to have a clearer picture of the mobile ions and of the processes that occur at the electrode interface influencing the dielectric behavior.     

Fractal aspects of calcium binding protein structures

The structures of EF-hand calcium binding proteins may be classified into two distinct groups: extended and compact structures. In this paper we studied 20 different structures of calcium binding proteins using the fractal analysis. Nine structures show extended shapes, one is semi-compact and the other 10 have compact shapes. Our study reveals different fractal characteristics for protein backbones belonging to different structural classes and these observations may be correlated to the physicochemical forces governing the protein folding.     

La3Br3Ni: Jahn–Teller Distortion in the Reduced Rare Earth Metal Halide

A ternary lanthanum bromide La₃Br₃Ni was synthesized from lanthanum, LaBr₃ and nickel under argon at 800 °C. It crystallizes in the tetragonal space group I4₁22 (No. 98) with lattice constants a = 12.1758(9) Å and c = 11.744(2) Å. The structure is derived from the cubic Gd₃I₃C type of space group I4₁32 through a tetragonal distortion resulting in a squeezed nickel‐centered La₆ octahedron. Electronic structure and bonding of the compound have been investigated.     

Conformational Analysis of Acyclic α-Fluoro Sulfur Motifs

Bioactive small molecules containing α-fluoro sulfur motifs [RS(O)_nCH₂F] are appearing with increasing frequency in the pharmaceutical and agrochemical sectors. Prominent examples include the anti-asthma drug Flovent^® and the phenylpyrazole insecticide pyrafluprole. Given the popularity of these structural units in bioactive small molecule design, together with the varying oxidation states of sulfur, a conformational analysis of α-fluoro sulfides, sulfoxides, and sulfones, would be instructive in order to delineate the non-covalent interactions that manifest themselves in structure. A combined crystallographic and computational analysis demonstrates the importance of hyperconjugative donor-acceptor interactions in achieving acyclic conformational control. The conformational disparity in the syn- and anti-diastereoisomers of α-fluorosulfoxides is particularly noteworthy.     

A Novel Approach for the Synthesis of 5‐Pyridylindolizine Derivatives via 2‐(2‐Pyridyl)pyridinium Ylides

New indolizine derivatives were synthesized by an efficient one‐pot three‐component procedure starting from commercially available materials such as 2,2′‐dipyridyl, substituted bromoacetophenones, and electron‐poor alkynes in 1,2‐epoxybutane as reaction solvent and acid scavenger.     

A simple method for desymmetrizing 1,1′-ferrocenedicarboxaldehyde

A simple chromatography-free method for desymmetrizing ferrocene is described starting from the readily available dialdehyde. Oxidation of 1,1′-ferrocenedicarboxaldehyde in a water/acetonitrile mixture with KMnO₄ produced 1′-formyl-ferrocenecarboxylic acid. The same reaction carried out in a water/acetone mixture produced 1′-[(E)-3-oxo-but-1-enyl]-ferrocenecarboxylic acid.