Supramolecular triangular and linear arrays of metal-radical solids using pyrazolato-silver(I) motifs

New chelating radical ligands pzNNH, pzINH, and pzbisINH (3-pyrazolyl nitronyl nitroxide, 3-pyrazolyl imino nitroxide, and pyrazole-3,5-diyl bis(imino nitroxide), respectively) were prepared. Complexation of these ligands with Ag+ gave [Ag(pzNN)]n, [Ag(pzIN)]6, and [Ag(pzbisIN)]n containing the corresponding anionic forms of the ligands. From the X-ray crystal structure analysis, [Ag(pzIN)]6 was characterized as a dimer of almost planar triangular moieties where the pyrazolate worked as a bridge, and metal-metal bonds brought about dimerization of triangles. [Ag(pzbisIN)]n was characterized as a uniform zigzag chain consisting of pyrazolate bridges and Ag ions with a cis-Npz-Ag-Npz coordination structure. Antiferromagnetic interactions observed could be analyzed based on the structures determined for both compounds. Ferromagnetic coupling was observed in [Ag(pzNN)]n, and a polymeric structure was assumed although the crystal structure could not be determined. Novel supramolecular architectures using pyrazolate-substituted imino nitroxides have been developed, using the unique coordinative versatility of the pyrazolate derivatives     

Improvement of chemical analysis of antibiotics. X. Determination of eight tetracyclines using thin-layer and high-performance liquid chromatography

Analytical methods for eight tetracyclines (TCs) were established using silica gel high-performance thin-layer chromatography (HPTLC), reversed-phase thin-layer chromatography (RP-TLC) and high-performance liquid chromatography (HPLC). Good separations of eight TCs were obtained using chloroform-methanol-5% disodium ethylenediaminetetraacetate solution (65:20:5) (lower layer) and methanol acetonitrile 0.5 M oxalic acid solution (1:1:4) (pH 3.0) on silica gel HPTLC and C8 TLC plates, respectively. A combination of HPTLC and RP-TLC made possible the identification of the eight TCs. Each calibration graph was linear between 0.1 and 1.0 microgram using UV densitometry except for rolitetracycline. For detection reagents, the diazonium salts including Fast Violet B gave variously coloured spots with the eight TCs and good sensitivities were obtained except with minocycline. In HPLC, the simultaneous analysis of the eight TCs on a C8 column was possible using methanol-acetonitrile-0.01 M oxalic acid solution (1:1.5:7) adjusted to pH 3.0 as the mobile phase. A linear relationship was obtained between 1.0 and 10 ng using the usual sample preparation except for rolitetracycline. The direct determination of rolitetracycline was possible using tetrahydrofuran, dimethyl sulphoxide and the mobile phase as solvents for preparation of the sample. For the determination of residual rolitetracycline, it was effective to measure the amount of rolitetracycline as tetracycline by HPLC, HPTLC and RP-TLC after conversion of rolitetracycline to tetracycline by incubating for 5 min in methanol at 50 degrees C.     

Aryloxyacetic acid diuretics with uricosuric activity. II. Substituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids and the related compounds.

Di- and tri-substituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids, and 4-oxo-3-phenyl-4H-furo[2,3-h]-[1]benzopyran-8-carboxylic acid were synthesized and tested for natriuretic and uricosuric activities. Among the compounds tested, 3,5-disubstituted [(4-oxo-4H-1-benzopyran-7-yl)oxy]acetic acids (6c-f, h, n and x) showed potent natriuretic and uricosuric activities, whereas 4-oxo-3-phenyl-4H-furo[2,3-h][1]benzopyran-8-carboxylic acid (6dd) possessed only potent natriuretic activity. The structure-activity relationships are also discussed.     

Suppressive effect of the SOS-inducing activity of chemical mutagen by citric acid esters from Prunus mume Sieb. Et Zucc. using the Salmonella typhimurium TA1535/pSK1002 umu test

A methanol extract from Prunus mume Sieb. Et Zucc. showed a suppressive effect of the SOS-inducing activity on the mutagen 3-amino-1,4-dimethyl-SH-pyrido[4,3-b]indole(Trp-P-1) in the Salmonella typhimurium TA1535/pSK1002 umu test. The methanol extract was re-extracted with hexane, dichloromethane, ethyl acetate, butanol and water. The dichloromethane and ethyl acetate fractions showed suppressive effect. Suppressive compounds were isolated by silica gel column chromatography and identified as trimethyl citrate (1) and dimethyl citrate (2) by GC-MS, IR and 1H and 13C-NMR spectroscopy. Compounds 1 and 2 suppressed 51 and 39% of the SOS-inducing activity at a concentration of 2.0 micromol/mL.     

Assembled catalyst of palladium and non-cross-linked amphiphilic polymer ligand for the efficient heterogeneous Heck reaction

The efficient heterogeneous Heck reaction was achieved by a new networked and supramolecular catalyst PdAS-V (1b). Employing of PdAS-V in 5.0×10⁻⁵ mol equiv. efficiently progressed the heterogeneous Heck reaction of a series of aryl iodides with acrylates, styrenes and acrylic acid. PdAS-V was successfully recycled five times without any decrease in its activity, and showed good stability in toluene and water, and hence the Heck reaction was efficiently performed in both reaction media. The use of 8.0×10⁻⁷ mol equiv. of PdAS-V resulted in the coupling product in 92% yield with the turnover number (TON) and the turnover frequency (TOF) of PdAS-V reached up to 1,150,000 and 12,000, respectively. The efficient synthesis of resveratrol was achieved via the PdAS-V-promoted Heck reaction.     

Ca0.8Y2.4Sn0.8O6, a quaternary oxide with mixed occupations of Ca/Y and Y/Sn

A new quaternary oxide, calcium yttrium stannate, Ca_0.8Y_2.4Sn_0.8O₆, is isostructural with Mg₃TeO₆ (trigonal, R). The empirical formula can be expressed as (Ca_0.2667Y_0.7333)₆(Y_0.4Sn_0.6)SnO₁₂. The Ca/Y site has a distorted coordination octa­hedron of O atoms, with Ca/Y—O distances ranging from 2.227 (3) to 2.350 (3) Å, while the octa­hedra of O atoms that coordinate to the Sn and Y/Sn sites are nearly regular, with an Sn—O distance of 2.066 (2) Å and a Y/Sn—O distance of 2.147 (3) Å.     

A stereochemical investigation of 2-methyl- and 2,5-dimethyl-3-phenyl-1,3-oxazolidines using NMR

The stereochemical properties of two 2-methyl-3-phenyl-1,3-oxazolidines and two of its 5-methyl substituted and four of its 2,5-dimethyl substituted derivatives have been investigated by pmr and cmr methods. The compounds of 2,5-dimethyl-3-phenyl-1,3-oxazolidines exist in isomeric cis and trans forms at the two methyl groups on the heterocyclic ring.     

Identification of beta-decay of150La

The -decay of¹⁵⁰La, the heaviest isotope of lanthanum, has been identified by observing -rays from mass separated activities obtained at KUR-ISOL. From the decay curves of 97.0 and 208.7 keV -rays in¹⁵⁰Ce and of Ce-K X-ray, the half-life of¹⁵⁰La has been determined as 0.51(3) s. This value is in agreement with theoretical predictions from microscopic theory.     

Spin dynamics and spin correlations in the spinS=1 two-dimensional square-lattice Heisenberg antiferromagnet La2NiO4

The static and dynamic spin fluctuations in the spinS=1, two-dimensional (2D) square-lattice antiferromagnet La₂NiO₄ have been studied over a wide temperature range using neutron scattering techniques. The spin correlations in La₂NiO₄ exhibit a crossover from two- to three-dimensional (3D) behavior as the Néel temperature is approached from above. Critical slowing down of the low-energy spin fluctuations is also observed just aboveT _N . The correlation length, (T), and the static structure factor,S(0), have been measured and are compared with recent theoretical calculations for the quantum 2D Heisenberg antiferromagnet using microscopic parameters determined from previous spin-wave measurements. Good agreement for (T) is found with the exact low-temperature result of Hasenfratz and Niedermeyer provided that 2 p _s is renormalized by 20% from the spin-wave value.