Chiral Discrimination in Dimers of Diphosphines PH2PH2 and PH2PHF

A theoretical study of the conformational profile of two diphosphines, PH₂?PH₂ and PH₂?PHF, is carried using second‐order Møller–Plesset perturbation theory (MP2) computational methods. The chiral minima found are used to build homo‐ and heterochiral dimers. Six minima are found for the (PH₂?PH₂)₂ dimers and 27 for the (PH₂?PHF)₂ dimers. Pnicogen and hydrogen bonds, the non‐covalent forces that stabilize the complexes, are characterized by Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) methodologies. Those with several pnicogen bonds are more stable than those with hydrogen bonds. The chirodiastaltic energies amount to a total of 1.77 kJ mol^?1 for the R_a:R_a versus R_a:S_a (PH₂?PH₂)₂ dimers, 0.81 kJ mol^?1 for the RS_a:RS_a versus RS_a:SR_a (PH₂?PHF)₂ dimers, and 2.93 kJ mol^?1 for the RR_a:RR_a versus RR_a:SS_a (PH₂?PHF)₂ dimers. In the first and second cases, the heterochiral complex is favored whereas in the third case, the homochiral complex is favored.     

Electronic and Structural Properties of Highly Aluminum Ion Doped TiO2 Nanoparticles: A Combined Experimental and Theoretical Study

This study presents the experimental and theoretical study of highly internally Al‐doped TiO₂ nanoparticles. Two synthesis methods were used and detailed characterization was performed. There were differences in the doping and the crystallinity, but the nanoparticles synthesized with the different methods share common features. Anatase to rutile transformation occurred at higher temperatures with Al doping. X‐ray photoelectron spectroscopy showed the generation of oxygen vacancies, which is an interesting feature in photocatalysis. In turn, the band‐gap energy and the valence band did not change appreciably. Periodic density functional calculations were performed to model the experimentally doped structures, the formation of the oxygen vacancies, and the band gap. Calculation of the density of states confirmed the experimental band‐gap energies. The theoretical results confirmed the presence of Ti⁴⁺ and Al³⁺. The charge density study and electron localization function analysis indicated that the inclusion of Al in the anatase structure resulted in a strengthening of the Ti?O bonds around the vacancy.     

Ab Initio Study on the Stability of NgnBe2N2, NgnBe3N2 and NgBeSiN2 Clusters

The global minima of Be₂N₂, Be₃N₂ and BeSiN₂ clusters are identified using a modified stochastic kick methodology. The structure, stability and bonding nature of these clusters bound to noble gas (Ng) atoms are studied at the MP2/def2‐QZVPPD level of theory. Positive Be?Ng bond dissociation energy, which gradually increases down Group 18 from He to Rn, indicates the bound nature of Ng atoms. All of the Ng‐binding processes are exothermic in nature. The Xe and Rn binding to Be₂N₂ and Be₃N₂ clusters and Ar?Rn binding to BeSiN₂ are exergonic processes at room temperature; however, for the lighter Ng atoms, lower temperatures are needed. Natural population analysis, Wiberg bond index computations, electron density analysis, and energy decomposition analysis are performed to better understand the nature of Be?Ng bonds.     

Isolation and Immobilization of Influenza Virus-Specific N-SA-α-2,3-Gal Receptors Using Magnetic Nanoparticles Coated with Chitosan and Maackia amurensis Lectin

Avian influenza viruses preferentially bind to sialic acid alpha-2,3-galactose (N-SA-α-2,3-Gal) receptors on epithelial cells. Herein, we describe a procedure we have developed for isolation of N-SA-α-2,3-Gal receptors from porcine trachea using magnetic nanoparticles (NPs) coated with chitosan (NP-Ch) and functionalized with Maackia amurensis lectin (NP-lectin). Magnetic nanoparticles were coated with chitosan in a one-step co-precipitation, and then M. amurensis lectin was immobilized covalently using glutaraldehyde. Lectin coated nanoparticles were incubated with sialic acid enriched fraction of tracheal homogenate, and N-SA-α-2,3-Gal receptor was extracted under magnetic field in two cycles. The presence of 66.4 kDa protein was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The interaction of immobilized receptor (NP-Ch-R) with M. amurensis lectin (NP-Ch-R-L) was demonstrated by Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA).     

Identification of Novel Rab27a/Melanophilin Blockers by Pharmacophore-Based Virtual Screening

Melanocytes are unique cells that produce specific melanin-containing intracellular organelles called melanosomes. Melanosomes are transported from the perinuclear area of melanocytes toward the plasma membrane as they become more melanized in order to increase skin pigmentation. In this vesicular trafficking of melanosomes, Rab27a, melanophilin, and myosin Va play crucial roles in linking melanosomes to actin-based motors. To identify novel compounds to inhibit binding interface between Rab27a and melanophilin, a pharmacophore model was built based on a modeled 3D structure of the protein complex that describes the essential binding residues in the intermolecular interaction. A pharmacophore model was employed to screen a chemical library database. Finally, 25 virtual hits were selected for biological evaluations. The biological activities of 11 analogues were evaluated in a second assay. Two compounds were identified as having concentration-dependent inhibitory activity. By analyzing structure–activity relationships of derivatives of BMD-20, two hydroxyl functional groups were found to be critical for blocking the intermolecular binding between Rab27a and melanophilin.     

The Hellmann–Feynman theorem for statistical averages

We discuss the Hellmann–Feynman theorem for degenerate states and its application to the calculation of the derivatives of statistical averages with respect to external parameters.     

Synthesis of polypyrrole nanoparticles by batch and semicontinuous heterophase polymerizations

Nanoparticles of semiconducting polypyrrole (PPy) were synthesized by batch heterophase (BHP) and semicontinuous heterophase polymerization (SHP) using ferric chloride (FeCl₃), potassium persulfate (KPS), or ammonium persulfate (APS) as the oxidizing agent, sodium dodecyl sulfate (SDS) as surfactant, and ethanol (EtOH) or iso-pentyl alcohol (iC₅OH) as co-surfactants. In all cases, the molar ratios of monomer/oxidizing agent were 1/1. Pyrrol polymerization by BHP and SHP allowed using much lower percentages of surfactant than those employed in microemulsion polymerization of this monomer. The effects of temperature, oxidizing agent, and co-surfactant on conductivity were studied. The polymers were analyzed by transmission electron microscopy (TEM), UV/Visible and Fourier transform infrared (FTIR) spectroscopies, and cyclic voltammetry. Higher PPy conductivities were obtained by polymerizing at 0 °C with FeCl₃ as the oxidizing agent, in the presence of iC₅OH as co-surfactant. When the reaction was carried out by SHP with low reaction times, smaller particles with similar conductivities were obtained compared to those obtained by BHP; the conductivity of PPy decreases with increasing polymerization time, which can be explained by PPy overoxidation.     

Switchable dielectric permittivity with temperature and Dc-bias in a semifluorinated azobenzene derivative

The thermodynamic, optical, structural, and dynamic properties of the semifluorinated (E)-1-(4-octylphenyl)-2-(4-(perfluorooctyl)phenyl)diazene (4) and the corresponding (E)-1,2-bis(4-octylphenyl)diazene (5) have been studied with differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and dielectric spectroscopy. 4 combines the azobenzene properties with the fluorophobic effect and gives rise to a responsive material with a temperature and dc-bias-driven switchable dielectric permittivity within the narrower nematic phase. This is caused by the nematic potential that inevitably brings some fluorocarbon chains in proximity to the hydrocarbon chains from adjacent molecules. Frustration is alleviated by reducing the nematic-to-isotropic transition temperature and by increasing the crystalline-to-nematic transition temperature, thus limiting the stability of the nematic phase. Unlike the normal isotropic phase of compound 5, the isotropic phase of compound 4 contains dipoles with short-range orientation correlations. Optimizing the type of interactions may result in materials with applications as molecular switches and electrooptic devices.     

Electro-Mechanochemical Atom Transfer Radical Cyclizations using Piezoelectric BaTiO3

The formation and regeneration of active Cu^I species is a fundamental mechanistic step in copper-catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active Cu^I species in the reaction mixture is secured by using high Cu^I catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO₃) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a Cu^II precatalyst into the active Cu^I species in copper-catalyzed mechanochemical solvent-free ATRC reactions.