Insights on the Lewis Superacid Al(OTeF5)3: Solvent Adducts,Characterization and Properties**

Preparation and characterization of the dimeric Lewis superacid [Al(OTeF₅)₃]₂ and various solvent adducts is presented. The latter range from thermally stable adducts to highly reactive, weakly bound species. DFT calculations on the ligand affinity of these Lewis acids were performed in order to rank their remaining Lewis acidity. An experimental proof of the Lewis acidity is provided by the reaction of solvent-adducts of Al(OTeF₅)₃ with [PPh₄][SbF₆] and OPEt₃, respectively. Furthermore, their reactivity towards chloride and pentafluoroorthotellurate salts as well as (CH₃)₃SiCl and (CH₃)₃SiF is shown. This includes the formation of the dianion [Al(OTeF₅)₅]²⁻.     

Palladium(II) saccharinate complexes trans-[Pd(sac)2(LH)2] with amino- and acetylamino-pyridine co-ligands: molecular structures of trans-[PdCl2(2-ampyH)2].2dmf (2-ampyH = 2-amino-3-methylpyridine) and trans-[Pd(κ2-2-acmpy)2] (2-acmpyH = 2-acetylamino-3-methylpyridine)

Reaction of Na₂[PdCl₄] with two equivalents of amino- or acetylamino-pyridines (LH) affords trans-[PdCl₂-(LH)₂] {LH = 2-amino-3-methylpyridine (2-ampyH), 3-aminopyridine (3-apyH), 2-acetylamino-3-methylpyridine (2-acmpyH), 3-acetylamino-pyridine (3-acpyH)}. An X-ray crystal structure of trans-[PdCl₂(2-ampyH)₂] shows that the 2-ampy-H ligands are coordinated in a monodentate fashion via the nitrogen atoms of the pyridine rings. Treatment of trans-[PdCl₂(2-acmpyH)₂] with NEt₃ affords the cyclometalated complex, trans-[Pd(κ²-2-acmpy)₂], the X-ray structure of which shows that the 2-acmpy ligand is coordinated to palladium in a bidentate fashion via the nitrogen atom of the pyridine ring and oxygen. Reaction of trans-[PdCl₂(LH)₂] with two equivalents of sodium saccharinate affords the bis(saccharinate) complexes, trans-[Pd(sac)₂(LH)₂], in which the saccharinate anions are coordinated via the amide nitrogen atom.     

Synthesis of 1-O-R-5-deoxy-β-D-ribofuranosides with (CH3)2As and (CH3)2AsO as substituents at the 5-position and a methyl or 2′,3′-dihydroxypropyl group as the aglycone in the 1-position

Six arsenic-containing β-D -ribofuranosides, including the naturally occurring (2′R)-dimethyl[1-O-(2′,3′-dihydroxypropyl)-5-deoxy-β-D -ribofuranos-5-yl]arsine oxide, were prepared in multi-step reactions from D -ribose and tetramethyldiarsine. The synthetic procedure uses the early substitution of the hydroxy group with bromine at C5, subsequent attachment of a chiral three-carbon aglycone at C1, and final delivery of arsenic at C5. The synthesis provides a viable route for the preparation of multigram quantities of the natural product.     

On the equation of state for thermal polymer solutions and melts with attractive interaction

We perform Monte Carlo simulations of a lattice model for polymer melts, i. e., the bond fluctuation model in three dimensions. By using an energy parameter that prefers relatively long bonds, the model exhibits a glass transition at low temperatures, in close qualitative similarity to experiment. We modify this model by adding an attractive interaction of variable strength. We demonstrate that a small interaction strength has only a very small effect on the static properties of the melt. For a fixed strength of the potential, the chemical potential is measured by a modified particle-insertion method over a large range of temperatures and densities. The osmotic pressure is obtained by thermodynamic integration. In contrast to the original version our extended model exhibits a positive thermal expansion.     

Brownian dynamics simulation of grafted polymer brushes

We present results of computer simulations by the method of Brownian dynamics of polymeric brushes attached to impenetrable planes. For testing both model and method we have used one polymer brush attached to a repulsive plane and compare some results with Monte Carlo results of Lai and Binder on the bond fluctuation model. We have also studied two polymeric brushes attached to two parallel planes at different distances between planes, and investigate the interplay between the interpenetration of the brushes and the configurational properties of the grafted chains.     

Quantum Fourier Transform-Based Arithmetic Logic Unit on a Quantum Processor

This study proposes and construct a primitive quantum arithmetic logic unit (qALU) based on the quantum Fourier transform (QFT). The qALU is capable of performing arithmetic ADD (addition) and logic NAND gate operations. It designs a scalable quantum circuit and presents the circuits for driving ADD and NAND operations on two-input and four-input quantum channels, respectively. By comparing the required number of quantum gates for serial and parallel architectures in executing arithmetic addition, it evaluates the performance. It also execute the proposed quantum Fourier transform-based qALU design on real quantum processor hardware provided by IBM. The results demonstrate that the proposed circuit can perform arithmetic and logic operations with a high success rate. Furthermore, it discusses in detail the potential implementations of the qALU circuit in the field of computer science, highlighting the possibility of constructing a soft-core processor on a quantum processing unit.     

Quark condensation, induced symmetry breaking and color superconductivity at high density

The phase structure of hadronic matter at high density relevant to the physics of compact stars and relativistic heavy-ion collisions is studied in a low-energy effective quark theory. The relevant phases that figure are (1) chiral condensation, (2) diquark color condensation (color superconductivity) and (3) induced Lorentz-symmetry breaking (“ISB”). For a reasonable strength for the effective four-Fermi current–current interaction implied by the low-energy effective quark theory for systems with a Fermi surface we find that the “ISB” phase sets in together with chiral symmetry restoration (with the vanishing quark condensate) at a moderate density while color superconductivity associated with scalar diquark condensation is pushed up to an asymptotic density. Consequently, color superconductivity seems rather unlikely in heavy-ion collisions although it may play a role in compact stars. Lack of confinement in the model makes the result of this analysis only qualitative but the hierarchy of the transitions we find seems to be quite robust.     

Determination of the Absolute Configuration of Super-Carbon-Chain Compounds by a Combined Chemical,Spectroscopic, and Computational Approach: Gibbosols A and B

Marine dinoflagellates produce remarkable organic molecules, particularly those with polyoxygenated long-carbon-chain backbones, namely super-carbon-chain compounds (SCCCs), characterized by the presence of numerous stereogenic carbon centers on acyclic polyol carbon chains. Even today, it is a challenge to determine the absolute configurations of these compounds. In this work, the planar structures and absolute configurations of two highly flexible SCCCs, featuring either a C₆₉- or C₇₁-linear carbon backbone, gibbosols A and B, respectively, each containing thirty-seven stereogenic carbon centers, were unambiguously established by a combined chemical, spectroscopic, and computational approach. The discovery of gibbosols A and B with two hydrophilic acyclic polyol chains represents an unprecedented class of SCCCs. A reasonable convergent strategy for the biosynthesis of these SCCCs was proposed.