Thermochemical properties of new N,O-chelate Sc, Eu, and Tb complexes for OLED-devices

A new class of Sc, Eu, and Tb complexes with N,O-chelate ligands was synthesized for the first time. The mass spectra, thermogravimetric analysis, differential scanning calorimetry data, as well as the data on the saturated vapor pressure of the compounds were obtained. The main thermochemical parameters of the compounds were calculated.     

Inhomogeneous state of the electron system in BaPb1 − x Sb x O3 superconducting perovskites: The 207Pb NMR study

Comprehensive measurements of the ²⁰⁷Pb NMR spectra, Knight shifts ²⁰⁷ K _s , spin-lattice relaxation rate ²⁰⁷ T ₁ ^?1 , and the Pb spin echo decay ²⁰⁷ E(2t) in BaPb_{1 ? x} Sb _x O₃ superconducting oxides (x ≤ 0.33) have been performed. A considerable increase in the shift distribution width when Sb is substituted for Pb indicates the formation of the inhomogeneous state of the electron system in the oxide conduction band. The shift magnitude proportional to the density of states near the Fermi energy, ²⁰⁷ K s ∝ N(E _F ), reaches its maximum in the compounds with x = 0.18–0.25 with the maximum temperatures T _c of the superconducting transition. In the BaPb_{1 ? x} Sb _x O₃ compounds, the Korringa relation is met, indicating that all of the samples are in the metal phase. The data on the Pb spin echo decay and the relevant estimates of the indirect coupling constants of the nuclei of the nearest neighbor Pb atoms clearly demonstrate the development of the electron system state in the oxide metal phase, which is microscopically inhomogeneous over the crystal.     

Studying the volatility of pyrazolone complexes of rare-earth elements by means of Knudsen effusion

The temperature dependences of the pressure of saturated vapor of pyrazolone complexes of rare-earth elements Ln(PMIP)₃ (where Ln = Y, Ho, Er, Tm, Lu; PMIP = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone) are studied via Knudsen effusion, and the enthalpy of their sublimation is determined. Mass spectra and differential scanning calorimetry data are obtained.     

Lignin conversion to hydrogen-containing gas under the action of microwave radiation

The paper describes the carbon dioxide reforming of lignin in the presence of Ni-, Fe, and Ni/Fe-containing active components formed directly on the surface under microwave irradiation. The deposition of 0.1 wt % iron acetylacetonate on the lignin surface results in a sharp increase in the microwave absorption capacity at a 0.5 kW power and induces lignin conversion to hydrogen-containing gas with a degree of hydrogen recovery reaching 90 %. The maximum lignin conversion (65%) is attained in 10 min under microwave irradiation. It was shown for the first time that deposition of metals (Fe and Ni) on lignin can provide for targeted change of the selectivity of reforming to synthesis gas and the process can thus be classified as a plasma catalytic one. Using the obtained results, it is possible to minimize the amount of catalyst and to propose an efficient route for hydrogen and synthesis gas production from lignin waste.     

The Thermodynamic Properties of (α,α′-Dipyridyl)bis(4-methoxy-3,6-di-tert-butyl-o-benzosemiquinone)cobalt over the Temperature Range from T → 0 to 320 K

The heat capacity of (g?,g?′-dipyridyl)bis(4-methoxy-3,6-di-tert-butyl-o-benzosemiquinone)cobalt over the temperature range 7–320 K was studied by precision adiabatic vacuum calorimetry. A physical transformation observed at 134–222 K accompanied the reversible transition of the semiquinone-catecholate complex of low-spin cobalt into the bis-semiquinone adduct of high-spin cobalt. The enthalpy and entropy of this redox-isomeric transition were determined. The data obtained were used to calculate the standard thermodynamic functions of the complex, C _p ^o (T), H^o(T)-H^o(0), S^o(T), and G ^o (T)-H ^o (0), over the temperature range from T → 0 to 320 K. The low-temperature heat capacity of the complex was analyzed using the Debye theory of the heat capacity of solids and its multifractal generalization. The conclusion was drawn that the complex had a predominantly chain structure.     

Low-Frequency Dynamics of Charge Carriers in CuAlO2 Semiconductor According to NMR Data

Journal of Experimental and Theoretical Physics - The 63Cu and 27Al NMR spectra have been obtained on a polycrystalline CuAlO2 sample in external magnetic field H0 = 92.8 kOe in temperature range...     

Vibrational spectroscopy studies of structural changes in lignin under microwave irradiation

Structural changes that occur in lignin surface-modified with nickel nanoparticles during microwave- assisted dry reforming (DR) are studied via vibrational spectroscopy. IR spectroscopy reveals that the nickel deposition has a considerable effect on the structural characteristics of lignin. It is found that nickel deposition from an acetate salt substantially reduces the intensity of absorption bands at 1700 cm^?1. This finding suggests that Ni(2+) interacts mostly with formate groups, which are subsequently oxidized to carboxylate groups. It is shown that with the deposition of metallic nickel particles from a colloidal nickel solution in toluene prepared via metal vapor synthesis, the nickel particles do not interact with the surface functional groups of the lignin. Deep conversion of an organic mass of lignin by DR to form synthesis gas reduces the intensity of the absorption bands of the identified functional groups and raises the intensity of the absorption bands of the aromatic rings. Raman spectroscopy shows that during lignin conversion, the aromatic rings condense partially to form amorphized graphite. In operando studies reveal that the DR of nickel-modified lignin heated to 200–400°C results in the isolation of vanillic oxygenates that are probably intermediate products of reforming.     

Exchange of halogens in the 3a,6a-diaza-1,4-diphosphapentalene derivatives: Crystal structures of iodides

1,4-Dichloro-3a,6a-diaza-1,4-diphosphapentalene (II) easily exchanges halogen with methyl iodide to form the corresponding 1,4-diiodo derivative (V) in a quantitative yield. The reaction of compound II with diiodine (1 equiv) affords compound III, the crystal structure of which contains 55% II and 45% V. Under the conditions of iodine excess (1 : 3), a ionic compound (IV) is formed, the crystal of which contains alternating layers consisting of planar networks [I₂I₃]? and heterocyclic cations [DDP–Cl]⁺. For the crystallographic information for compounds III–V, see CIF files CCDC no. 1560 410 (V), 1560 411 (III), and 1560 412 (IV).     

Investigation of cobalt (1,10-phenanthroline)-bis-(3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzosemiquinolate) by X-ray diffraction,IR and ESR spectroscopy,magnetochemistry, and precision calorimetry

The bistable cobalt complex containing two symmetrical 3,6-di-tert-butyl-o-benzoquinone and one 1,10-phenanthroline moieties as ligands (1) was synthesized. Complex 1 was isolated in the individual state and characterized by IR and ESR spectroscopy, X-ray diffraction, magnetochemical studies, and precision calorimetry. A change in temperature causes the reversible metal-ligand electron transfer and spin crossover (redox isomerism) in complex 1 in the crystalline state. The redox-isomeric transformation at ∼250 K is accompanied by the phase transition. The structural study at two temperatures confirmed the changes in the molecular and crystal structure associated with the redox-isomeric transformation.