Investigation of level crossing in the tetragonal paramagnet YbPO4 in ultrahigh magnetic fields up to 400 T

The crossing of the energy levels of Yb³⁺ ions in paramagnetic YbPO₄ in ultrahigh magnetic fields of up to 400 T, produced by an explosive method, is investigated experimentally and theoretically. A wide maximum is found in the differential susceptibility dM/dH in a field H _c ≈280 T. This maximum is due to the crossing of the energy levels of the magnetic ions in the field. The magnetocalorimetric effect is calculated under the assumption that the magnetization process in the pulsed fields is adiabatic. The effect is nonmonotonic as a function of the field and is accompanied by a substantial cooling of the crystal near H _c . Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 691–694 (10 May 1997)     

Study of ESR spectra of Ce<Superscript>3+</Superscript> ions in polycrystalline Sr<Subscript>2</Subscript>B<Subscript>5</Subscript>O<Subscript>9</Subscript>Br

ESR spectra of Ce³⁺ ions in polycrystalline Sr₂B₅O₉Br were studied, and the two crystallographic positions of the Ce³⁺ ion in this compound were identified on the basis of the data obtained. The ESR spectrum of Ce³⁺ ions with local charge compensation contains a broad line indicating the existence of several types of charge compensation. ESR spectra of Ce³⁺ ions in samples activated additionally by K⁺ ions are similar to those of the regular Ce³⁺ centers, which indicates that the effect of the univalent cation on Ce³⁺ is negligible.     

4-Hydroxy-2-quinolones. 111. Simple synthesis of 1-substituted 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acids

A preparative method of obtaining 1-substituted 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acids is proposed. Features of their spatial structure have been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 69–74, January, 2007.     

4-Hydroxy-2-quinolones. 44. Synthesis of 2-R-3-oxomorpholino[5,6-c]-6-R'-Quinolin-5-ones

Treatment of 1-R-2-oxo-4-hydroxyquinolin-3-ylamides of -halogen-substituted carboxylic acids with sodium methoxide leads to the formation of 2-R-3-oxomorpholino-[5,6-c]-6-R-quinolin-5-ones. The antituberculosis activity of the compounds synthesized was studied.For Communication 43, see [1].National Pharmaceutical Academy of Ukraine, Kharkov 310002; e-mail: igor@uiv.kharkov.ua. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1080–1083, August, 2000.     

4-hydroxy-2-quinolones. 34. Structure of photocondensation products of 3-amino-1R-2-oxo-4-hydroxyquinolines

3-Amino-2-oxo-4-hydroxyquinolines when exposed to light are quantitatively converted to di(1R-2-oxo-4-hydroxyquinolin-3-yl)amines. We have carried out an x-ray diffraction study of one such compound.For Communication 33, see [1].Ukrainian Pharmaceutical Academy, Kharkov 310002. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–940, July, 1997.     

Guanidines based on tryptamine and histamine in reactions with electrophiles

Reactions of 4,6-dimethylpyrimidin-2-ylcyanamide with tryptamines and histamine gave the corresponding disubstituted guanidines. The molecular parameters of the products were calculated using GAUSSIAN 03 software package. The direction of electrophilic attack on these compounds was predicted on the basis of the geometric shape of their highest occupied molecular orbital (HOMO) and molecular electrostatic potential (MEP) maps. Acyl, carbamoyl, and cyclic derivatives were obtained, whose structure was consistent with the results of quantum-chemical calculations.     

4-Hydroxy-2-quinolones. 90. Synthesis and antitubercular activity of 4-methyl-2-thiazolylamides of halo-substituted 4-hydroxy-2-oxo-1,2-dihydro-3-quinolinecarboxylic acids

Several variants were studied for the synthesis of esters of halogen derivatives of 4-hydroxy-2-oxo-1,2-dihydro-3-quinolinecarboxylic acids, whose reaction with 2-amino-4-methylthiazole gives the corresponding hetarylamides. Results are given for a study of the antitubercular activity of these products. Communication 89, see ref. [1]. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 71–76, January, 2006.     

Stimuli-responsive mixed grafted polymer films with gradually changing properties: direct determination of chemical composition

Infrared spectroscopic ellipsometry (IRSE) and visible monochromatic ellipsometry (VISE) approaches were applied to investigate the chemical structure and thickness of ultrathin polymer films. Mixed polystyrene-poly(2-vinylpyridine) and polystyrene-poly(tert-butyl acrylate) polymer grafted films (mixed brushes) with gradually changing composition (1D gradient mixed brush) along the sample were prepared on a temperature gradient stage via two subsequent "grafting to" reactions. The films were characterized by high-precision mapping VISE at a single wavelength (632.8 nm) and IRSE. The set of 1D IRSE spectra of the polymer brush films obtained by mapping the 1D gradient brush were used to estimate the thickness and the local composition of the film and to construct the 1D map of the film in terms of the chemical composition of the brush. The results were compared with the data obtained using monochromatic ellipsometry where the brush composition was estimated from the results of two subsequent measurements followed each grafting step. The measurements of the brush thickness and composition with both methods were found to be in gratifying agreement. The results demonstrate the high potential of IRSE methods for the one-step characterization (by thickness and chemical composition) of ultrathin polymer films of complex composition.     

4-Hydroxy-2-quinolones. 56. 4-(Adamant-1-yl)thiazolyl-2-amides of 1-R-4-Hydroxy-2-oxoquinoline-3-carboxylic Acids as Potential Antitubercular Agents

The synthesis, antitubercular, anti-HIV, and antitumor activity of the 4-(adamant-1-yl)thiazolyl-2-amides of 1-R-4-hydroxy-2-oxoquinoline-3-carboxylic acids have been studied. An efficient method for purifying the 4-hydroxy-2-oxoquinoline derivatives from their metal salts is proposed.