Antimony-121 mössbauer spectra of antimony (III) compounds with a stereochemically active lone pair

The Sb-121 Mössbauer parameters at 20 K for 23 antimony(III) compounds were obtained and the data are discussed in terms of known crystal structures. The isomer shifts and quadrupole coupling constants depend strongly on the type of configuration around the Sb(III) atoms with stereochemically active lone pair electrons.     

Flash photolysis study for reactions of NO3· with sulfur compounds in acetonitrile solution

The rate constants for the reaction of NO₃· with sulfur compounds in acetonitrile have been determined by the flash photolysis method. The rate constant for dimethyl sulfone (2.7 × 10⁴ M^?1s^?1 at ?10°C) is larger than that of the deuterium derivative, indicating that NO₃· abstracts the hydrogen atom from dimethyl sulfone. In the case of dimethyl sulfide, the rate constant was evaluated to be 1.5 × 10⁹ M^?1 s^?1 at ?10°C; the transient absorption band attributable to the cation radical was observed after the decay of NO₃·, suggesting the electron transfer reaction from the sulfide to NO₃·. For diphenyl sulfide and dimethyl disulfide, the electron transfer reactions were also confirmed. For dimethyl sulfoxide, the reaction rate constant of 1.2 × 10⁹ M^?1 s^?1 (at ?10°C) was not practically affected by the deuterium substitution, suggesting that NO₃· adds to sulfur atom forming (CH₃)₂?(O)-ONO₂. On the other hand, for diphenyl sulfoxide, the electron transfer reaction occurs. By the comparison of these rate constants in acetonitrile solution with the reported rate constants in the gas phase, the change of the reaction paths was revealed.     

High-quality two-dimensional electron gas at large scale GaN/AlGaN wafer interface prepared by mass production MOCVD systems

Basic electronic properties of two-dimensional electron gas (2DEG) formed at GaN/AlGaN hetero-interface in large-scale (100 mm) wafer made by metal organic chemical vapour deposition (MOCVD) have been reported and discussed. From conventional Hall measurements, highest electron mobility was found to be μ_e∼1680 and 9000 cm²/V s at room temperature and at ∼5 K, respectively, for sheet electron density of n_s∼8×10¹² cm⁻². In magneto-resistance (MR) measurements carried out at 1.5 K in Hall bar sample defined by photolithography and ion implantation, very clear Schubnikov de-Haas oscillations and integer quantum Hall effect were observed in diagonal (R_xx) and off-diagonal (R_xy) resistances, respectively. In addition, a good insulating nature of GaN layer is confirmed by capacitance-voltage (C-V) measurement. These results suggest the high-qualitiness of our 100 mm GaN/AlGaN high electron mobility transistor (HEMT) wafers comparable to those so far reported.     

An electron microscopic study of the archaeal feast/famine regulatory protein: 6. The cylindrical assembly form

Using a microcrystal of the feast/famine regulatory protein (FFRP) pot0434017 (FL11), a cryo-electron micrograph was taken, showing a projection of cylinder-like assemblies packed parallel to each other. This electron micrograph was processed in the Fourier space by selecting spots reflecting the packing and, in addition, those reflecting stacking of units inside the cylinders. Twenty seven subimages were selected, each containing three cylinders of 24 discs each, running nearly parallel to each other. By averaging these images and in combination with another average showing a different view [Ishijima, S. A., Clowney, L., and Suzuki, M. (2004) Proc. Jpn. Acad., Ser. B 80, 183–188], some details of the 3D structure of the cylindrical assembly form are discussed.     

Accuracy of Phase-Doppler Anemometry in the Presence of Flames

The objectives of the present study were to clarify the influence of flames on phase-Doppler anemometry (PDA) and to consider quantitatively the accuracy of measured sizes and velocities using a known-size polystyrene particle and a Bunsen burner placed in the optical path in PDA simulating the variation of refractive index in a combusting field. It was found that fluctuations of a flame had some influence on the measurement, especially on size, while the velocities obtained in these experiments showed little influence of the flame. Furthermore, a compensation procedure for the error was discussed by comparing the scattered data in size measurement with the displacement of incident laser beams. As a result, it was found that the displacement of the laser beams can be related to the degree of errors caused by the influence of a flame on the optical path in PDA.     

Concentration of metal chelate on a membrane filter using surfactant

The most sensitive metal reagents, water-soluble porphyrins with anionic side-chain, and cationic side-chain and their metal complexes were found to be associated by the surfactants with opposite charges and to be collected on membrane filters quantitatively. The ion-associates were dissolved in a few ml of H₂SO₄/DMF together with the filter paper, and the absorbance of the solution was readily measured. Concentration of 1/200 to 1/1000 of original volume was possible. Determination of 50 to 500 ng/1 level of copper ion will be presented.     

Reaction of diazoindenothiophenes with mono- and dibenzoylacetylenes

Reaction of diazoindenothiophenes ( 1 and 2 ) with benzoyl acetylene ( 4 ) afforded the rearrangement products ( 6a and b ) of the initial adducts. The major product of the reaction of diazo indenothiophene ( 3 ) with 4 was butadiene derivative 8a . Reaction of 1 with dibenzoylacetylene ( 5a ) gave the rearranged pyrazole ( 12 ), while the reaction of 2 and 3 , afforded the butadiene derivatives ( 8b-d ).     

Hydrophilic polymer-immobilized lipoamides-iron(II) system as a new reducing catalyst for the reduction of O-benzylhydroxylamine by sodium borohydride

Based on a redox function of 1,2-dithiolane ? 1,3-dithiol, lipoamide immobilized on hydrophilic polymers such as polyacrylamide, polyethyleneimine, and chitosan was found to work as polymeric reducing catalysts for the reduction of O-benzylhydroxylamine to benzyl alcohol and ammonia with sodium borohydride in the presence of ferrous ion. These polymers were easily separable and maintained high reactivities even after repeated uses.     

Transition metal complexes coordinated by an NAD(P)H model compound and their enhanced hydride-donating abilities in the presence of a base

The ruthenium(II) and rhenium(I) complexes containing an NAD(P)H model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH), as ligand, [Ru(tpy)(bpy)(BNAH)]2+ (1 a) and [Re(bpy)(CO)3(BNAH)]+ (1 b), were quantitatively produced by the reaction of the corresponding metal hydrido complexes with BNA(+) (1-benzylnicotinamidium cation). In the presence of base with pK(a) = 8.9, 1 a and 1 b have much greater reducing power than "free" BNAH. The oxidation potentials of 1 a in the absence and the presence of triethylamine were 0.55 V and -0.04 V, respectively, versus Ag/AgNO(3), whereas that of "free" BNAH was 0.30 V. Spectroscopic results clearly showed that the base extracts a proton from the carbamoyl group on 1 a and 1 b to give the deprotonated BNAH coordinating to the transition-metal complexes [Ru(tpy)(bpy)(BNAH-H+)]+ (3 a) and [Re(bpy)(CO)3(BNAH-H+)] (3 b); this deprotonation underlies the enhancement in reducing ability. The deprotonated forms 3 a and 3 b can efficiently reduce other NAD(P) models to give the corresponding 1,4-dihydro form, resulting in the deprotonated BNA+ being coordinated to the metal complexes [Ru(tpy)(bpy)(BNA(+)-H+)]2+ (2 a) and [Re(bpy)(CO)3(BNA+-H+)]+ (2 b); "free" BNAH and the protonated adducts 1 a and 1 b cannot act in this way. X-ray crystallography was performed on the PF6- salt of 2 a, and showed that the deprotonated nitrogen atom on the carbamoyl group coordinates to the ruthenium(II) metal center with a bond length of 2.086(3) Angstroms. Infrared spectral data suggested that the deprotonated carbamoyl group on the reduced forms 3 a and 3 b is converted to the imido group, and that the oxygen atom coordinates to the metal center.