Spin-frustrated (VO)36+-triangle-sandwiching octadecatungstates as a new class of molecular magnets

Spin-frustrated polyoxometalates, K(11)H[(VO)(3)(SbW(9)O(33))(2)].27H(2)O (1) and K(12)[(VO)(3)(BiW(9)O(33))(2)].29H(2)O (2), containing approximately equilateral and isosceles (VO)(3)(6+)-triangles (V(IV)...V(IV) separation of 5.4-5.5 A) sandwiched by two diamagnetic alpha-B nonatungstate ligands ([SbW(9)O(33)](9)(-) and [BiW(9)O(33)](9)(-)) with approximate D(3)(h) symmetry, are found to show magnetization jumps with distinct hysteresis for the S = (1)/(2) <--> S = (3)/(2) level crossing under fast sweeping pulsed magnetic fields (approximately 10(3) T/s) at T < or = 0.5 K. This unusual phenomenon is attributed to the theoretical prediction of half step magnetization, which is expected for an antiferromagnetic spin triangle with antisymmetrical Dzyaloshinky-Moriya interaction. The degeneracy of the S = (1)/(2) states for 1 is removed by slightly lower symmetry effects of triangular structure for 2. The calorimetry of 1 and 2 shows the heat capacity anomaly at 2 < or = T < or = 20 K which is associated with a thermal excitation from the S = (1)/(2) ground states to the S = (3)/(2) state at zero field. Zero-field splitting energies (5-7 K) between S = (1)/(2) and S = (3)/(2) states for 1 and 2, readily estimated by the level-crossing field for the magnetization, allow us to measure the hyperfine-structural 22 lines due to three equivalent I = (7)/(2) (51)V nuclei, the fine-structural triplet line of the S = (3)/(2) excited state, and the g anisotropy on the high-frequency ESR spectra. The spin-frustrated (VO)(3)(6+)-triangle for 1 and 2 is a good model of the magnetization between pure quantum states S = (1)/(2) and (3)/(2) and provides a new class of single-molecule magnets.     

Determination of sugar alcohols in confectioneries by high-performance liquid chromatography after nitrobenzoylation

A method was developed for the determination of sugar alcohols, meso-erythritol, xylitol, D-glucitol, D-mannitol, maltitol and parachinit by high-performance liquid chromatography (HPLC). The sugar alcohols were converted into strong ultraviolet (UV)-absorbing derivatives with p-nitrobenzoyl chloride. HPLC was performed on a phenyl column, using acetonitrile-water (67:33) as mobile phase and UV detection (260 nm). The calibration curves for all sugar alcohols tested were linear in the 10-250 microg/ml range. The average recoveries of the sugar alcohols from four sugarless confectioneries spiked at 5 and 10% levels of six sugar alcohol standards ranged from 73.2 to 109.0% with relative standard deviations ranging from 0.7 to 9.0%. The detection limit of the developed method was 0.1% for the above sugar alcohols contained in the samples.     

Liquid chromatographic determination of sugar alcohols in beverages and foods after nitrobenzoylation

Use of p-nitrobenzoyl chloride (PNBC) to form an ultraviolet-absorbing derivative was attempted to determine the sugar alcohols meso-erythritol, xylitol, D-sorbitol, and D-mannitol by liquid chromatography (LC). LC determination of derivatives was performed on an ODS column with acetonitrile-water (65 + 35) as mobile phase. Calibration curves were linear in the concentration range 0.01-100 micrograms/mL. Method sensitivity is 10 to 1000 times higher than that of LC with refractive index detection and gas chromatography with flame ionization detection. Recoveries of sugars added to various foods at 0.1 and 1% ranged from 91 to 102% for meso-erythritol, 75 to 115% for xylitol, 81 to 105% for D-sorbitol, and 81 to 108% for D-mannitol.     

Hyperfine interactions of interstitial12B in Fe,V and Ta studied by use of the asymmetric β decay

Magnetic hyperfine fields and spin-lattice relaxation times of interstitial and substitutional¹²B nuclei in Fe are studied in a temperature range, 100 K<T<1200 K, by use of the asymmetric decay from the spin polarized nuclei and NMR detection. In order to infer information regarding the location of¹²B nuclei and expansion in the nearest Fe surrounding following recoil implantation, hyperfine interactions of¹²B in non-magnetic bcc V and Ta crystals are studied.     

The use of trifluoroacetaldehyde ethyl hemiacetal or hydrate in a simple and practical regioselective synthesis of beta-hydroxy-beta-trifluoromethyl ketones from enamines and imines

The reaction of trifluoroacetaldehyde ethyl hemiacetal or hydrate with an equimolar amount of enamines, derived from various methyl ketones, smoothly proceeded to give the corresponding beta-hydroxy-beta-trifluoromethyl ketones in high yields. An equimolar amount of imines derived from various methyl ketones with aliphatic, aromatic, and heteroaromatic substituents also readily reacted with trifluoroacetaldehyde ethyl hemiacetal or hydrate to afford the corresponding beta-hydroxy-beta-trifluoromethyl ketones in good to excellent yields. Difluoroacetaldehyde ethyl hemiacetal as well as pentafluoropropionaldehyde also participated in the reaction, affording good yields of the corresponding beta-hydroxy-beta-difluoromethyl or beta-pentafluoropropyl ketones.     

Creation of the nuclear alignment and theG-parity conservation law in weak nucleon currents

-ray angular distributions from nuclear spin aligned¹²B and¹²N were detected and the correlation coefficients were determined. From the comparison of these with the experimental weak magnetism term, it was concluded that the parity of the weak nucleon currents in the iso-spin space was strictly conserved.     

Precise measurement of quadrupole moment of8B by use of a modified β-NMR

The nuclear quadrupole moment of⁸B(I =2⁺,T _1/2=769 ms) has been determined by use of a modified -NMR detection as |Q(⁸B)|=68.3±2.1 mb. A field gradient was obtained in a single crystal Mg at room temperature.     

Hyperfine interactions of12B in BN (hexagonal)

Hyperfine interactions of¹²B(I =1⁺,T _1/2=21 ms) implanted in the substitutional site of B in BN (hexagonal) was studied by detecting -NMR. In order to measure the quadrupole coupling constant efficiently, we employed a newly developed quadrupole resonance technique (NNQR). The quadrupole moment of¹²B was determined to be |Q(¹²B)|=13.21±0.26 mb.