Phase transitions in solid Kr–CH₄ solutions and rotational excitations in phase II

The heat capacity CP of solid Kr–n CH₄ solutions with the CH₄ concentrations n = 0.82, 0.86, 0.90 as well as solutions with n = 0.90, 0.95 doped with 0.002 O₂ impurity has been investigated under equilibrium vapor pressure over the interval 1–24 K. The (T,n)-phase diagram was refined and the region of two-phase states was determined for Kr–n CH₄ solid solutions. The contribution of the rotational subsystem, Crot, to the heat capacity of the solutions has been separated. Analysis of Crot(T) at T < 3 K made it possible to estimate the effective conversion times τ and the energy gaps E₁ and E₂ between the tunnel levels of the A-, T- and A-, E-nuclear-spin species of CH₄ molecules in the orientationally ordered subsystem, and to determine the effective energy gaps E₁ between the lowest levels of the A- and T- species. The relations τ(n) and E₁(n) stem from changes of the effective potential field caused as the replacement of CH₄ molecules by Kr atoms at sites of the ordered sublattices. The effective gaps EL between a group of tunnel levels of the ground-state libration state and the nearest group of excited levels of the libration state of the ordered CH₄ molecules in the solutions with n = 0.90 (EL = 52 K) and 0.95 (EL = 55 K) has been estimated

Heat capacity of methane-krypton solid solutions. Conversion effect

The heat capacity of Kr-nCH₄ solid solutions with the concentrations n= 1; 5; 10% and of the solid solution Kr-1%CH₄-0.2%O₂ has been studied at 0.7-8 K. The contributions of Crot to the heat capacity of the solutions caused by the rotation of the CH₄ molecules are estimated. The deviations of the measured Crot from the values corresponding to the equilibrium distribution of the nuclear spin CH₄ modifications are dependent on the correlation between the characteristic times of conversion and of the calorimetric experiment. The effects of temperature, O₂ impurities, and CH₄ clusters upon the conversion rate are studied. It is shown that the hybrid mechanism of conversion proposed by Berlinsky and Nijman, which takes into account both intramolecular and intermolecular interactions of the proton spins, is predominant

Cu(II), Ni(II), and Co(II) Complexes of Tetradentate Azomethine Ligands: Chemical and Electrochemical Syntheses, Crystal Structures, and Magnetic Properties

Abstract: Complexes CuL1 ⋅ MeOH (Ia), NiL1 ⋅ MeOH (Ib), CоL1 ⋅ MeOH (Ic), CuL2 (IIa), NiL2 (IIb), and CоL2 (IIc) of the tetradentate azomethine compounds, namely, 4-methyl-N-[2-[(E)-2-[2-[2-[(E)-[2-(p-toluenesulfamino)phenyl]methyleneamino]ethoxy]ethyliminomethyl]phenyl]benzenesulfamide (H2L1) and 4-methyl-N-[2-[(E)-3-[4-[3-[(E)-[2-(p-toluenesulfamino)phenyl]methyleneamino]propoxy]butoxy]-propyliminomethyl]phenyl]benzenesulfamide (H2L2), which are the condensation products of 2-(N-tosylamino)benzaldehyde with 3,4-dioxa-1,8-octanediamine and 4,9-dioxa-1,12-dodecanediamine, are synthesized using the chemical and electrochemical methods. The structures, compositions, and properties of the synthesized metal complexes are studied by the methods of elemental analysis, IR spectroscopy, X-ray absorption spectroscopy, magnetochemistry, and X-ray diffraction analysis (СIF files CCDC nos. 1910746 (Ia), 1910747 (Ib), and 1910748 (Ic)). In the molecules of compounds Ia–Ic, the L1 macrocyclic ligand coordinates the metal atom by four nitrogen atoms via the tetradentate chelate mode to form the polyhedron as a distorted tetrahedron. © 2019, Pleiades Publishing, Ltd