The Crystal and Molecular Structure of a Trifluoroacetylacetonate Complex of Scandium, Sc(CH\u3csub\u3e3\u3c/sub\u3eCOCHCOCF\u3csub\u3e3\u3c/sub\u3e)\u3csub\u3e3\u3c/sub\u3e

The crystal and molecular structure of Sc(CH3COCHCOCF3)3 has been determined by X-ray diffraction. The compound crystallizes as pure mer-isomer in the orthorhombic space group Pbca with lattice parameters a=15.166(8) Å, b=13.560(7) Å, c=19.327(10) Å, α=β=γ=90°, V=3974(4) Å3, Z=8. The complex at 100 K is partially disordered in the crystal structure in an approximate 5:1 ratio with 83% fluorine population at C-11 and 17% at C-15. NMR data is compared to that previously reported

Polytropic Behavior of Solar Wind Protons Observed by Parker Solar Probe

A polytropic process describes the transition of a fluid from one state to another through a specific relationship between the fluid density and temperature. The value of the polytropic index that governs this relationship determines the heat transfer and the effective degrees of freedom during the process. In this study, we analyze solar wind proton plasma measurements, obtained by the Faraday cup instrument on-board Parker Solar Probe. We examine the large-scale variations of the proton plasma density and temperature within the inner heliosphere explored by the spacecraft. We also address a polytropic behavior in the density and temperature fluctuations in short-time intervals, which we analyze in order to derive the effective polytropic index of small time-scale processes. The large-scale variations of the solar wind proton density and temperature which are associated with the plasma expansion through the heliosphere, follow a polytropic model with a polytropic index ~5/3. On the other hand, the short time-scale fluctuations which may be associated with turbulence, follow a model with a larger polytropic index. We investigate possible correlations between the polytropic index of short time-scale fluctuations and the plasma speed, plasma beta, and the magnetic field direction. We discuss the scenario of mechanisms including energy transfer or mechanisms that restrict the particle effective degrees of freedom.Comment: 20 pages, 9 figure

Crystal and molecular structure of bis(8-phenylmenthyl) 2-(2-methyl-5-oxo-3-cyclohexen-1-yl)propandioate, C\u3csub\u3e42\u3c/sub\u3eH\u3csub\u3e54\u3c/sub\u3eO\u3csub\u3e5\u3c/sub\u3e• CH\u3csub\u3e3\u3c/sub\u3eCN

The X-ray crystal structure of the title compound, as crystallized from acetonitrile-water was determined. The relative stereochemistry of the cyclohexenone ring with respect to the 8-phenylmenthyl esters was determined. The title compound crystallizes in the noncentrosymmetric space group P21, with a=8.9850(10) Å, b=15.575(3) Å, c=14.478(2) Å, β=94.61(2)°, and D calc=1.118 g cm−3 for Z=2

Preparation, Characterization and Reactivity of (3-Methylpentadienyl)iron(1+) Cations

The title cations (9 and 12) were prepared by dehydration of (3-methyl-2,4-pentadien-1-ol)Fe(CO)2L+ complexes. The structure of the (CO)2PPh3-ligated 12 was determined by single-crystal X-ray analysis. Reaction of carbon and heteroatom nucleophiles to (3-methylpentadienyl)Fe(CO)3+ cations 9 and 12 proceeds either via attack at the dienyl terminus to give (3-methyl-1,3Z-diene)iron complexes or via attack at the internal carbon, followed by carbon monoxide insertion and reductive elimination to afford 3-methyl-4-substituted cyclohexenones. Cyclohexenone formation was found to be prevalent for addition of stabilized nucleophiles with strongly dissociated counterions to cation 9 (L = CO). Reaction of cation 9 with sodium bis[(−)-8-phenylmenthyl] malonate gave a single diastereomeric cyclohexenone

Synthesis and reactivity of tricarbonyl(1-methoxycarbonyl-5-phenylpentadienyl)iron(1+) cation

Tricarbonyl(1-methoxycarbonyl-5-phenylpentadienyl)iron(1+) hexafluorophosphate (7) was prepared in two steps from tricarbonyl(methyl 6-oxo-2,4-hexadienoate)iron. While addition of carbon and heteroatom nucleophiles to 7 generally occurs at the phenyl-substituted dienyl carbon to afford (2,4-dienoate)iron products, the addition of phthalimide proceeded at C2 to afford a (pentenediyl)iron product (18). Complex 18 was structurally characterized by X-ray diffraction analysis. The reaction of the title cation with carbon and heteroatom nucleophiles was examined. In general, the products arise from nucleophilic attack at C5 to give E,E- or E,Z-dienoate iron complexes. Addition of phthalimide anion proceeds at C2 of the cation to afford a (pentenediyl)iron complex, whose structure was confirmed by X-ray diffraction analysis

Parallel-propagating Fluctuations at Proton-kinetic Scales in the Solar Wind are Dominated by Kinetic Instabilities

We use magnetic helicity to characterise solar wind fluctuations at proton-kinetic scales from Wind observations. For the first time, we separate the contributions to helicity from fluctuations propagating at angles quasi-parallel and oblique to the local mean magnetic field, $\mathbf{B}_0$. We find that the helicity of quasi-parallel fluctuations is consistent with Alfv\'en-ion cyclotron and fast magnetosonic-whistler modes driven by proton temperature anisotropy instabilities and the presence of a relative drift between $\alpha$-particles and protons. We also find that the helicity of oblique fluctuations has little dependence on proton temperature anisotropy and is consistent with fluctuations from the anisotropic turbulent cascade. Our results show that parallel-propagating fluctuations at proton-kinetic scales in the solar wind are dominated by proton temperature anisotropy instabilities and not the turbulent cascade. We also provide evidence that the behaviour of fluctuations at these scales is independent of the origin and macroscopic properties of the solar wind.Comment: Accepted for publication in ApJL. 6 Pages, 3 figures, 1 tabl

Perfect Quantum Privacy Implies Nonlocality

Private states are those quantum states from which a perfectly secure cryptographic key can be extracted. They represent the basic unit of quantum privacy. In this work we show that all states belonging to this class violate a Bell inequality. This result establishes a connection between perfect privacy and nonlocality in the quantum domain.Comment: 4 pages, published versio

Twisted bilayer graphene revisited: minimal two-band model for low-energy bands

An accurate description of the low-energy electronic bands in twisted bilayer graphene (tBLG) is of great interest due to their relation to correlated electron phases, such as superconductivity and Mott-insulator behavior at half-filling. The paradigmatic model of Bistritzer and MacDonald [PNAS 108, 12233 (2011)], based on the moir\'e pattern formed by tBLG, predicts the existence of "magic angles" at which the Fermi velocity of the low-energy bands goes to zero, and the bands themselves become dispersionless. Here, we reexamine the low-energy bands of tBLG from the ab initio electronic structure perspective, motivated by features related to the atomic relaxation in the moir\'e pattern, namely circular regions of AA stacking, triangular regions of AB/BA stacking and domain walls separating the latter. We find that the bands are never perfectly flat and the Fermi velocity never vanishes, but rather a "magic range" exists where the lower band becomes extremely flat and the Fermi velocity attains a non-zero minimum value. We propose a simple $(2+2)$-band model, comprised of two different pairs of orbitals, both on a honeycomb lattice: the first pair represents the low-energy bands with high localization at the AA sites, while the second pair represents highly dispersive bands associated with domain-wall states. This model gives an accurate description of the low-energy bands with few (13) parameters which are physically motivated and vary smoothly in the magic range. In addition, we derive an effective two-band hamiltonian which also gives an accurate description of the low-energy bands. This minimal two-band model affords a connection to a Hubbard-like description of the occupancy of sub-bands and can be used a basis for exploring correlated states

P–C and C–H Bond Cleavages of dppm in the Thermal Reaction of [Ru\u3csub\u3e3\u3c/sub\u3e(CO)\u3csub\u3e10\u3c/sub\u3e(μ-dppm)] with Benzothiophene: X-ray structures of [Ru\u3csub\u3e6\u3c/sub\u3e(μ-CO)(CO)\u3csub\u3e13\u3c/sub\u3e{μ\u3csub\u3e4\u3c/sub\u3e-PhP(C\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)PPh}(μ\u3csub\u3e6\u3c/sub\u3e-C)] and [Ru\u3csub\u3e4\u3c/sub\u3e(CO)\u3csub\u3e9\u3c/sub\u3e(μ\u3csub\u3e3\u3c/sub\u3e-η\u3csup\u3e2\u3c/sup\u3e-PhPCH\u3csub\u3e2\u3c/sub\u3ePPh\u3csub\u3e2\u3c/sub\u3e)(μ\u3csub\u3e4\u3c/sub\u3e-η\u3csup\u3e6\u3c/sup\u3e:η\u3csup\u3e1\u3c/sup\u3e:η\u3csup\u3e1\u3c/sup\u3e-C\u3csub\u3e6\u3c/sub\u3eH\u3csub\u3e4\u3c/sub\u3e)(μ-H)]

The thermal reaction of [Ru3(CO)10(μ-dppm)] (1) with benzothiophene in refluxing toluene gives a complex mixture of products. These include the known compounds [Ru2(CO)6{μ-CH2PPh(C6H4)PPh}] (2), [Ru2(CO)6{μ-C6H4PPh(CH2)PPh}] (3), [Ru3(CO)9{μ3-η3-(Ph)PCH2P(Ph)C6H4}] (4) and [Ru3(CO)10{μ-η2-PPh(CH2)(C6H4)PPh}] (6), as well as the new clusters [Ru6(μ-CO)(CO)13{μ3-η2-PhP(C6H4)PPh}(μ6-C)] (5) and [Ru4(CO)9(μ3-η2-PhPCH2PPh2)(μ4-η6:η1:η1-C6H4)(μ-H)] (7). The solid-state molecular structures of 5 and 7 were confirmed by single crystal X-ray analyses. Compound 5 consists of interesting example of a hexaruthenium interstitial carbido cluster having a tetradentate diphosphine ligand derived from the activation of P–C and C–H bonds of the dppm ligand in 1. The tetranuclear compound 7 consists of a unique example of a non-planar spiked triangular metal fragment of ruthenium [Ru(1), Ru(2) and Ru(3)] unit with Ru(4) being bonded to Ru(1). The μ4-η1:η6:η1-benzyne ligand in this compound represents a previously uncharacterized bonding mode for benzyne. Compounds 5 and 7 do not contain any benzothiophene-derived ligand. The reaction of 4 with benzothiophene gives 2, 3, 5 and 6. Thermolysis of 1 in refluxing toluene gives 2, 3 and 4; none of 5 and 7 is detected in reaction mixture