Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate]: a new chiral Rh(II) catalyst for enantioselective amidation of C---H bonds

Dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], characterized by substitution of chlorine atoms for four hydrogen atoms on the phthalimido group in the parent dirhodium(II) complex has been found to be well suited for enantioselective amidation of benzylic C---H bonds with [(4-nitrophenyl)sulfonylimino]phenyliodinane. The observed enantioselectivity of up to 84% ee is the highest reported to date for dirhodium(II) complex-catalyzed C---H amidations.     

Kohn anomaly in MgB2 by inelastic X-ray scattering

We study phonons in MgB2 using inelastic x-ray scattering (1.6 and 6 meV resolution). We clearly observe the softening and broadening of the crucial E(2g) mode through the Kohn anomaly along GammaM, in excellent agreement with ab initio calculations. Low temperature measurements (just above and below T(c)) show negligible changes for the momentum transfers investigated and no change in the E(2g) mode at A between room temperature and 16 K. We report the presence of a longitudinal mode along GammaA near in energy to the E(2g) mode that is not predicted by theory.     

Duality, phase structures, and dilemmas in symmetric quantum games

Symmetric quantum games for 2-player, 2-qubit strategies are analyzed in detail by using a scheme in which all pure states in the 2-qubit Hilbert space are utilized for strategies. We consider two different types of symmetric games exemplified by the familiar games, the Battle of the Sexes (BoS) and the Prisoners’ Dilemma (PD). These two types of symmetric games are shown to be related by a duality map, which ensures that they share common phase structures with respect to the equilibria of the strategies. We find eight distinct phase structures possible for the symmetric games, which are determined by the classical payoff matrices from which the quantum games are defined. We also discuss the possibility of resolving the dilemmas in the classical BoS, PD, and the Stag Hunt (SH) game based on the phase structures obtained in the quantum games. It is observed that quantization cannot resolve the dilemma fully for the BoS, while it generically can for the PD and SH if appropriate correlations for the strategies of the players are provided.     

Sigma-Pi Rearrangements of Organotransition Metal Compounds

σ-Bonded organic groups in transition-metal complexes can rearrange to π-bonding ligands and vice versa: the classic example is the formation of π-arenechromium complexes from σ-arylchromium compounds. Rearrangements of this kind can be induced, inter alia, by reactions of the metal or of the ligand, as well as by migration or insertion of a ligand. Rearrangements play a role in many industrial processes, including the polymerization and isomerization of olefins and the hydroformylation of olefins.     

Structure and redox properties of electropolymerized film obtained from iron meso‐tetrakis(3‐thienyl)porphyrin

Oxidative polymerization of bromoiron(III) meso‐tetrakis(3‐thienyl)porphyrin gave a novel polymeric porphyrin complex randomly crosslinked at the 2,5‐positions of the peripheral thienyl groups. The electrical semiconductivity of ca. 10^?5 S/cm after I₂ doping indicated that the polymer had a π‐conjugated structure with a moderate delocalization of π electrons over the thienylporphyrin units. PM3 calculations for free‐base models revealed that HOCO (the highest occupied crystal orbital) band width was reduced by introduction of the porphyrin moieties into the thienylene backbone and yet low HOCO‐LUCO (the lowest unoccupied crystal orbital) gap was maintained, which accounted for the relatively low electrical conductivity of the porphyrin polymer. The modified electrode prepared by electropolymerization was redox‐active due to the presence of iron(II/III) couple and the semiconductivity of the film, which served as a novel non‐enzymatic electrochemical sensor for superoxide anion radical based on the facile electrocatalytic oxidation of the superoxide. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrochemical sensor for superoxide anion radical using polymeric iron porphyrin complexes containing axial 1‐methylimidazole ligand as cytochrome c mimics

A needle‐type electrochemical sensor for the facile detection of superoxide anion radical (O) was devised using an electrodeposited film of a polymeric porphyrin complex attached to a carbon microelectrode which was placed in a stainless steel 18G needle tube as an auxiliary electrode. The sensing element was prepared by means of electropolymerization of bromoiron(III) meso‐ tetra(3‐thienyl)porphyrin in the presence of 1‐methylimidazole in CH₂Cl₂ containing 100 mM tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte, which gave a smooth film of the corresponding polymer. The film was electrochemically active to give a redox response near −0.05 V versus Ag/AgCl due to the iron(II/III) couple. The microsensor was applied to detect O produced by xanthine oxidation catalyzed by xanthine oxidase. The amperometric response for O was monitored at an electrode potential of 0.5 V versus the auxiliary electrode in a 10 mM phosphate buffer. The microsensor displayed a high catalytic activity for the oxidation of O and showed a linear relationship between the current and the O concentration. Axial coordination of an imidazole ligand to the iron porphyrin center enhanced selectivity for O by impeding the undesired coordination of H₂O₂ that resulted from the dismutation of O. Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation of source and sealed absorber holder for237Np and238U Mössbauer measurements

Preparation of source and sample holder is described for the Mössbauer studies of²³⁷Np and²³⁸U. For the Mössbauer measurement of²³⁷Np, a source assembly with small sources of²⁴¹Am metal was developed taking account of the transport regulations for radioactive substances. The source assembly of²⁴¹Am showed a sufficient activity enough to measure the Mössbauer spectra of²³⁷Np. In order to handle²³⁷Np compounds safely, trebly sealed holders were designed which could encapsulate²³⁷Np samples without the seepage of liquid helium. A source for²³⁸U Mössbauer measurement was also developed from a highly pure²⁴²PuO₂.     

High-density speed optical near-field recording reading with a pyramidal silicon probe on a contact slider

We demonstrate high-density-speed phase-change recording-reading by use of a pyramidal silicon structure. The contact slider, which has a pyramidal silicon probe array with height dispersion of less than 10 nm, is fabricated by use of a silicon-on-insulator wafer. By illumination with a laser beam (lambda = 830 nm) of one element of the probe array, we find the shortest phase-change mark length and the carrier-to-noise ratio to be 110 nm and 10 dB, respectively, corresponding to a data transmission rate of 2.0 MHz. This rate can be increased to 200 MHz by use of all elements of the probe array.