Intramolecular Hydrogen Bonding in Calix[4]arene-Based Nitroxide Monoradical and Biradical as Studied by CW-ESR and Pulse-ESR HYSCORE Spectroscopy

A calix[4]arene-based biradical with two tert-butyl nitroxide radicals and a monoradical derived from the biradical have been studied by continuous-wave electron spin resonance (CW-ESR) and pulse-ESR-based hyperfine sublevel correlation (HYSCORE) spectroscopy. The two nitroxide radical sites antiferromagnetically interact with each other, generating a thermally accessible triplet state located 4?cm^?1 above the singlet ground state. The present fine-structure and hyperfine spectral simulation for the spin Hamiltonian parameters of the biradical is sensitive to the local molecular structure at the spin-bearing site, illustrating a salient electronic structure of the radical sites with the ??-orbitals on the nitrogen (and oxygen) atoms cross-facing each other. The derived structure contrasts with the molecular structure determined by an X-ray crystal analysis for the hydroxylamine precursor of the biradical. The distance between the two midpoints of the nitrogen?Coxygen bonds at the radical sites is by 0.234?nm longer than the one (=0.314?nm) of the two hydroxyl groups of the precursor determined by the X-ray analysis. The lack of intramolecular hydrogen bonds between the nitrogen and hydrogen of the hydroxyl groups, caused by the oxidation of the hydroxyamino precursor, gives rise to such a sizable increase in the distance between the radical sites. The HYSCORE experiments gave a direct evidence of the local molecular structure of the radical site of the partially oxidized monoradical. The experimentally derived molecular structures of both the bi-, monoradicals and the precursor are in good agreement with those obtained by density functional theory calculations.     

Quasisteady high-confinement reversed shear plasma with large bootstrap current fraction under full noninductive current drive condition in JT-60U

A quasisteady reversed shear plasma with a large bootstrap current fraction ( approximately 80%) has been obtained for the first time in the JT-60U tokamak. The shrinkage of reversed shear region was suppressed by the bootstrap current peaked at the internal transport barrier (ITB) layer and the ITBs at a large radius were sustained, which, by combination with an H-mode edge pedestal, resulted in a high confinement or 2.2 times the H-mode scaling for 6 times energy confinement time or 2.7 s. Furthermore, a full noninductive current drive was obtained by the bootstrap current and the beam driven current.     

Determination of 3-nitrobenzanthrone in surface soil by normal-phase high-performance liquid chromatography with fluorescence detection

A sensitive method for determining 3-nitrobenzanthrone in surface soil was developed. 3-Nitrobenzanthrone was reduced to 3-aminobenzanthrone by refluxing at 60 degrees C with hydrazine and Raney nickel for 20 min, and 3-aminobenzanthrone was determined by normal-phase high-performance liquid chromatography (HPLC) with fluorescence detection. We used a cyanopropyl stationary phase and an n-hexane-ethyl acetate (3:1, v/v) mobile phase, since 3-aminobenzanthrone exhibits fluorescence in a low-polarity solvent such as n-hexane or ethyl acetate, but not in a polar solvent such as water or methanol. The calibration graph showed good linearity (r2>0.9999) in the range of 0.002-2 ng, and the detection limit was 0.002 ng (S/N=3). 3-Nitrobenzanthrone in extracts from surface soil collected in the Chubu area (central area) of Japan was determined after clean-up using silica gel chromatography and high-performance liquid chromatography on a pyrenylethyl stationary phase. The concentration of 3-nitrobenzanthrone in surface soil was determined in the range of 1.2-1020 pg/g soil.     

Synthesis of micron-sized, monodisperse polymer particles of disc-like and polyhedral shapes by seeded dispersion polymerization

Micron-sized, monodisperse polymer particles having unique disc-like and polyhedral shapes were produced by seeded dispersion polymerization of various methacrylates with 1.57 m-sized polystyrene seed particles in the presence of saturated hydrocarbon droplets in methanol/water. Such nonspherical shapes were controllable by the polymerization conditions.Part CCLX of the series Studies on Suspension and Emulsion     

Production of (2R,3S)-3-(4-methoxyphenyl)glycidic acid methyl ester using an emulsion bioreactor containing lipase fromSerratia marcescens

An emulsion bioreactor for production of (2R,3S)-3-(4-methoxyphenyl) glycidic acid methyl ester ([-]MPGM) from a racemic mixture ([±]MPGM) using the lipase fromSerratia marcescens has been proposed. Kinetics of hydrolyzing reaction and purification of (-)MPGM from the reaction mixture were investigated to provide a basis for industrial application of this bioreactor. The hydrolyzing reaction in the bioreactor proceeded at a rate that was first order in substrate concentration. The reaction rate was affected by a stirring speed and the ratio of the aqueous phase containing lipase to the toluene phase containing substrate. Phase separation after the enzymatic reaction was accomplished by addition of surfactant to the reaction mixture, and crystalline (-)MPGM with a chemical purity of 100% and optical purity of 100% enantiomeric excess was obtained in a high yield of 40–43% by concentration of the toluene solution.     

62Cu-labeling of human serum albumin-dithiosemicarbazone (HSA-DTS) conjugate for regional plasma volume measurement: application of new 62Zn/62Cu generator system

62Cu-Labeling of human serum albumin-dithiosemicarbazone (HSA-DTS) conjugate was performed using a newly developed 62Zn/62Cu generator system. HSA-DTS was easily labeled with 62Cu, by simple mixing with 62Cu-generator eluate. In vivo blood clearance of 62Cu-HSA-DTS was similar to 131I-HSA, indicating the high applicability of 62Cu-HSA-DTS as a method for plasma volume measurement. In a positron emission tomography study of a dog, a clear plasma pool image of the head region was obtained.     

Preparation and magnetic properties of Mn(hfac)(2)-complexes of 2-(5-pyrimidinyl)- and 2-(3-pyridyl)-substituted nitronyl nitroxides

Mn(hfac)(2) complexes of [2-(5-pyrimidinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H- imidazoline-1-oxyl 3-oxide] (1) and its 2-(3-pyridyl) analogue (2) were prepared. Both complexes formed similar dimer structures. However, their packing patterns were considerably different. The pyrimidine dimers were aligned to form a linear chain structure, and each dimer was weakly bound by two sets of O6-C2 short contacts. In the pyridine dimer complex, two structurally similar but independent dimers were alternatively arranged, and two dimer-dimer contacts, O6-C2 (3.13 A) and O6-C3 (3.30 A), were observed. The pyrimidine complex showed strong antiferromagnetic behavior in the high temperature region (150-300 K) and weak ferromagnetic behavior below 100 K. Two models were used to analyze these magnetic properties. One is a quintet-septet thermal equilibrium model with mean-field approximation, which can reproduce the round minimum observed at about 150 K in chi(p)T plots (J(1)/k(B) = -148 +/- 2 K with theta = +2.5 +/- 0.1 K). The other is a ferromagnetic S = 2 chain model to fit the chi(p)T values in the lower temperature region (J(S=2)/k(B) = +0.31 +/- 0.01 K). The pyridine complex showed antiferromagnetic interactions both in the high and low temperature regions. The magnetic behavior was similarly analyzed with the following parameters: J(1)/k(B) = -140 +/- 2 K with theta = -0.55 +/- 0.05 K, and J(S=2)/k(B) = -0.075 +/- 0.003 K. The ligand-ligand interactions for both of the complexes were theoretically analyzed. The calculated results agreed well with the experiments. The stronger antiferromagnetic behavior observed in both the complexes at high temperatures was attributed to the magnetic interaction between the Mn(II) and the coordinating nitroxide oxygen atom. The weaker ferromagnetic interaction, J(S=2)/k(B) = +0.31 +/- 0.01 K, in the pyrimidine complex was attributed to the coulombic O6-C2 contact. Antiferromagnetic interaction J(S=2)/k(B) = -0.075 +/- 0.003 K in the pyridine complex was attributed to the O6-C3 contact.