Phase transitions and vibrational study of Rb2SeO4·Te(OH)6 and Rb1.12(NH4)0.88SO4·Te(OH)6

Calorimetry, conductivity, IR and Raman studies of the two ionic-protonic conductors Rb₂SeO₄·Te(OH)₆ (RbSeTe) and Rb_1.12(NH₄)_0.88SO₄·Te(OH)₆ (RNST) have been recorded and analyzed. These compounds crystallize in the monoclinic system, the space groups being, respectively, P2₁/c and P2₁/a for (RbSeTe) and (RNST) with four formula units in their unit cells.

The main feature of these atomic arrangements is the coexistence of two independent and different types of anions in the unit cell, connected by hydrogen bonds, which insure the cohesion of the crystalline edifice. Differential scanning calorimetry traces show three peaks for both the materials, corresponding to three phase transitions, at 430, 470 and 493 K for RbSeTe and at 418, 458 and 483?K for RNST.

A sudden surge in the temperature dependence of conductivity confirms the presence of the third transition, which is characterized by a high conductivity. The Raman spectra of these two materials were investigated in the range 295–600?K and IR spectra achieved at room temperature between 10 and 4000?cm^?1, confirm the presence of the phase transitions and show that anionic groups coexist independently in the same crystal.     

Vibrational properties of polyatomic molecules by quantum chemical methods

Force constants and dipole moment derivatives have been computed for the molecules CH₃ X(X=F, Cl, Br, I) using MO wavefunctions with pseudo-potentials for the interaction between the inner shell and valence electrons. The values obtained at the SCF approximation level from a set of gaussian valence orbitals contracted in double-zeta form and enriched with polarization functions compare well with experimental assignments of force and interaction constants, as well as integrated intensities from infrared data. The transferability of atomic force fields and polar tensors (second derivatives of total energies and first derivatives of dipole moments with respect to atomic displacements in cartesian coordinates) is discussed.     

Synthesis, crystal structure, and spectroscopic study of K0.92(2) Zn0.08(2) H1.92(2) (PO4) (Zn-KDP)

The structure of K0.92₍₂₎ Zn_0.08(2) H_1.92(2) (PO₄) was determined using single-crystal X-ray diffraction. The crystal structure of the Zn-KDP belonged to the tetragonal space group $ \mathrm{I}\overline{4}2\mathrm{d} $ , with cell parameters of a?=?b?=?7.4487(5)?Å and c?=?6.9703(5)?Å, 386.73(5) Å3, Z?=?4, and R?=?0.023. Zn²⁺ ions were used as substitutes for K⁺ ions with hydrogen vacancy. The Zn-KDP single crystals were submitted to further Raman, infrared, and ¹H NMR studies to investigate chemical group functionalisation, possible bonding between the organic and inorganic materials, and partial substitution of K⁺ by Zn²⁺. The latter partial substitution was confirmed by the deviation of IR frequencies for O–H stretching, the variation of IR and Raman frequencies for stretching and bending vibrations ν(PO₄) of H₂PO₄, and the appearance of additional Raman (147, 386 and 481 cm^?1) vibrational bands. Electrical conductivity measurements were performed on polycrystalline pellets of Zn-KDP and pure KDP at room temperatures (RT) of up to 473K. In both cases, a conductivity jump close to 453K was observed, and a stronger increase of conductivity was measured.     

X-ray structure refinement and ionic conductivity of Na6.69Ca3.355(SO4)6Cl0.77F0.63

The structure of Na_6.69Ca_3.355(SO₄)₆Cl_0.77F_0.63, isostructural with fluorapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed a space group P6₃/m with lattice parameters of a?=?9.477 (2) Å, c?=?6.865 (5) Å. Final refinement led to R _F?=?1.83 % and R _B?=?7.64 %. The location of Na⁺ ions in the M (2) sites surrounding the channels was related particularly to the high polarizability of the Ca²⁺. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at σ _500 °C?=?1.03?×?10^?5?S?cm^?1 and E_a?=?0.70 eV.     

Nonconvex Differential Variational Inequality and State-Dependent Sweeping Process

We prove the existence of solutions of a differential variational inequality involving a prox-regular set in an infinite dimensional Hilbert space via a new existence result of a non-convex state-dependent sweeping process.     

Integrated 3D-QSAR,molecular docking,and molecular dynamics simulation studies on 1,2,3-triazole based derivatives for designing new acetylcholinesterase inhibitors

Alzheimer’s disease (AD) is a multifactorial and polygenic disease. It is the most prevalent reason for dementia in the aging population. A dataset of twenty-six 1,2,3-triazole-based derivatives previously synthetized and evaluated for acetylcholinesterase inhibitory activity were subjected to the three-dimensional quantitative structure-activity relationship (3D-QSAR) study. Good predictability was achieved for comparative molecular field analysis (CoMFA) (Q² = 0.604, R² = 0.863, r_ext² = 0.701) and comparative molecular similarity indices analysis (CoMSIA) (Q² = 0.606, R² = 0.854, r_ext² = 0.647). The molecular features characteristics provided by the 3D-QSAR contour plots were quite useful for designing and improving the activity of acetylcholinesterase of this class. Based on these findings, a new series of 1,2,3-triazole based derivatives were designed, among which compound A1 with the highest predictive activity was subjected to detailed molecular docking and compared to the most active compound. The selected compounds were further subjected to 20 ns molecular dynamics (MD) simulations to study the comparative conformation dynamics of the protein after ligand binding, revealing promising results for the designed molecule. Therefore, this study could provide worthy guidance for further experimental analysis of highly effective acetylcholinesterase inhibitors.     

Enantioselective Rhodium-Catalyzed Synthesis of α-Chloromethylene-γ-Butyrolactams from N-Allylic Alkynamides

The first enantioselective cycloisomerization with intramolecular halogen migration of various 1,6-enynes promoted by a cationic Rh-Synphos catalyst is reported. This method provides an efficient route to enantiomerically enriched γ-butyrolactam derivatives, which are important core scaffolds found in numerous natural products and biologically active molecules. Good yields and enantiomeric excesses up to 96% are achieved.     

Temperature impact on the turbulence generated by the interaction of twin inline inclined jets in crossflow

Consideration is given to the interaction of twin tandem jets with an oncoming uniform crossflow. A variable temperature is assumed for the emitted jets while the crossflow is maintained constant, equivalent to the ambient temperature. Both jet nozzles are elliptic, as initially inclined with an angle of 60°, placed three diameters apart in line with the crossflow and discharge a nonreactive fume. The handled configuration is numerically simulated in the present work, by means of the finite volume method together with a non uniform grid system. The model is first validated with reference to available experimental data, in the simple isothermal case of air jets in air crossflow. It is then upgraded by considering a nonreactive fume discharged at a variable temperature. The upgraded model turbulence is described by means of the Reynolds Stress Model second order turbulent closure model. The present work is to our knowledge pioneering in the introduction of this particular model is such a configuration and its introduction proved to be highly valuable since is described satisfyingly the turbulent behavior of the resulting flowfield. This behavior is, precisely, specified in terms of shear stress components whose evolutions, explored along the different directions of the domain, showed a more pronounced vertical mixing, and gave rise to more significant vortices in most characterizing zones: near the injection plane as well as within the discharging nozzles.     

Synthesis,structural characterisation and thermal decomposition of a new organic–inorganic hybrid material (C5H14N2)[Cu(SO4)2(H2O)4] · H2O

The crystal structure of copper sulfate templated by 2-methylpiperazine, (C₅H₁₄N₂)[Cu(SO₄)₂(H₂O)₄] · H₂O, was investigated using single crystal X-ray diffraction data. At room temperature, it crystallises in the monoclinic P2₁/n space group with the following unit-cell parameters: a = 6.9153(1), b = 23.1295(3), c = 10.4472(1) Å, β = 104.227(1)°, V = 1619.75(4) Å³ and Z = 4. The Cu^II cation adopts a slightly distorted octahedral geometry, arising from four water molecules and two sulfate tetrahedra leading to the formation of [Cu(SO₄)₂(H₂O)₄] units. The structure consists of isolated [Cu(SO₄)₂(H₂O)₄]²⁻ anions, 2-methylpiperazinediium cations (C₅H₁₄N₂)²⁺ and water molecules connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the copper oxide.