Catalytic asymmetric ring-opening of meso-aziridines with malonates under heterodinuclear rare earth metal Schiff base catalysis

Catalytic asymmetric ring-opening of meso-aziridines with malonates is described. The combined use of two rare earth metal sources with different properties promoted the desired ring-opening reaction. A 1:1:1 mixture of a heterobimetallic La(O-iPr)(3)/Yb(OTf)(3)/Schiff base 1a (0.25-10 mol %) efficiently promoted the reaction of five-, six-, and seven-membered ring cyclic meso-aziridines as well as acyclic meso-aziridines with dimethyl, diethyl, and dibenzyl malonates, giving chiral cyclic and acyclic γ-amino esters in 99-63% yield and >99.5-97% ee.     

Adsorption of CO and O2 on W2C(0001)

CO, O(2), and H(2) adsorption on a clean W(2)C(0001)√13×√13 R ± 13.9° reconstructed surface at room temperature (RT) were investigated using high-resolution electron energy loss spectroscopy (HREELS). The W(2)C(0001) adsorbs CO molecularly and adsorbs O(2) dissociatively, but does not adsorb H(2) at RT. In the CO adsorption system, two C-O stretching (antisymmetric CCO stretching) modes were found at 242.3 meV (1954 cm(-1)) and at 253.0 meV (2041 cm(-1)). The low-frequency site is occupied at first with subsequent conversion to the high-frequency site with increasing coverage. Additionally, a small peak was apparent at 104.5 meV (843 cm(-1)), and a middle peak at 50-51 meV (400-410 cm(-1)), which are assignable to a symmetric stretching mode and a hindered translational mode, respectively, of a CCO (ketenylidene) species. These observations are consistent with the CO adsorption model on top of the surface carbon. For oxygen adsorption, two adsorption states were found at 65.2-68.1 meV (526-549 cm(-1)) and 73.6 meV (594 cm(-1)): typical frequencies to oxygen adsorption on metal surfaces. Results suggest that atomic oxygen adsorption occurred on a threefold hollow site of the second W layer.     

Infrared diode-laser spectrum of the CH3CN ν2 band: Analysis of local resonances with ν6±1 + 2ν8±2, ν4 + ν7±1 + ν8±1, ν4 + ν6±1, ν4 + ν7±1, and 2ν70 + ν8±1 states

Fifty-one sections of infrared diode-laser spectra of acetonitrile have been measured in the region from 2283.5 to 2235.7 cm^?1. About 450 transitions belonging to the ν₂ band have been assigned for K ≦ 7 and J ≦ 44. Anomalies found in the rotational structure have been proven to be due to five local resonances. Observed transition frequencies have been fitted by a least-squares method to a model which includes Fermi-type resonances (Δk = 0, Δ? = ± 3n) with ν₆^±1 + 2ν₈^±2 and ν₄ + ν₇^±1 + ν₈^±1 states, x, y-type Coriolis resonances (Δk = ±1, Δ? = ?3n ± 1) with ν₄ + ν₆^±1 and ν₄ + ν₇^±1 + ν₈^±1 states, and a centrifugal-distortion-type resonance (Δk = ±2, Δ? = ?3n ± 2) with a 2ν₇⁰ + ν₈^±1 state. The 11 × 11 dimensional energy matrix has been diagonalized in order to obtain the perturbed energy levels. The standard deviation for the fit is 1.075 × 10^?3 cm^?1. The molecular constants determined are also listed.     

Regulated Incorporation of Two Different Metal Ions into Programmed Sites in a Duplex by DNA Polymerase Catalyzed Primer Extension

Metal‐mediated base pairs formed by the coordination of metal ions to natural or artificial bases impart unique chemical and physical properties to nucleic acids and have attracted considerable interest in the field of nanodevices. Ag^I ions were found to mediate DNA polymerase catalyzed primer extension through the formation of a C–Ag^I–T base pair, as well as the previously reported C–Ag^I–A base pair. The comparative susceptibility of dNTPs to Ag^I‐mediated enzymatic incorporation into the site opposite cytosine in the template was shown to be dATP>dTTP?dCTP. Furthermore, two kinds of metal ions, Ag^I and Hg^II, selectively mediate the incorporation of thymidine 5′‐triphosphate into sites opposite cytosine and thymine in the template, respectively. In other words, the regulated incorporation of different metal ions into programmed sites in the duplex by DNA polymerase was successfully achieved.     

Effect of Quantum Well Width Reduction for GaInNAs/GaAs Lasers

We investigated the function of the quantum well (QW) width for laser characteristics especially for reduction of the well width. We pointed out that such reduction has almost no influence on the optical gain or the carrier overflow for a large conduction band offset system, such as GaInNAs QWs. A thin QW is advantageous for suppression of the carrier overflow to the higher quantized energy levels which results in good temperature and gain characteristics. Thin GaInNAs QWs is a good candidate for an active layer structure of the lasers utilized in the next optical communication systems.     

Time-resolved Fourier transform infrared spectroscopy: Application to pulsed discharges

Time-resolved Fourier transform spectroscopy (TR-FTS) is reviewed, with emphasis on synchronous FTS using continuously scanning interferometers. By using a high-resolution Bruker IFS 120 HR, a TR-FTS method has been developed with the help of a microcontroller SX, where a maximum of 64 time-resolved data are recorded with a preset time interval in a single scan of the interferometer. The time resolution is 1 μs, limited by the response time of the detector system used. This method has been applied to a pulsed discharge in an Ar and H₂ mixture to observe time profiles of ArH⁺ and ArH emission spectra. Electronic transitions of He₂ have been observed in the infrared region with this method, and from the time profiles, He₂ in Rydberg states with higher energy than the b³Π state is found to be produced efficiently in afterglow plasma. Fifteen bands in the 2300-8000 cm⁻¹ region have been assigned by using previously reported data from the optical region. A new band from the 5f state has been assigned for the first time through the 5f-4d band in the 2600 cm⁻¹ region.     

Possible generation of electric multipole radiation from solid state quantum rings

The self-organized crystal growth of semiconductor quantum rings has opened a new possibility to study and exploit optical transitions between ring-shaped quantum states. In such states, orbital angular momenta of particle envelope functions are well-defined. We investigate theoretically the intraband interlevel transitions between such states and examine the possibility of electrical multipole radiations (EMRs). Selections rules due to envelope function quantum numbers are deduced. To enhance the EMR efficiency, we propose a novel coupled dot–ring structure, by which the lowest allowed EMR can be selected and manipulated, allowing the efficient radiation of multipole photons.     

Reversed-phase high-performance liquid chromatography of several metal-8-quinolinethiol complexes.

The reversed-phase high-performance liquid chromatography of 8-quinolinethiol (Hqt) complexes of Fe, Co, Ni, Cu, Zn, Hg and Pb on an octadecyl-bonded silica gel stationary phase was examined. The Pb complex dissociated in the column. The retention and separation of other complexes depended on the composition of the mobile phase. EDTA as an additive displaced the Zn complex and eliminated its peak. All the other metal complexes and also Hqt and its disulphide were separated in 23 min by using methanol-water (82:18, v/v) as the mobile phase. The complexes formed by the reaction of Co(II) and Hqt gave three peaks, which were assigned as fac(S)-CoIII(qt)3, mer(S)-CoIII(qt)3 and CoII(qt)2, respectively. This method is applicable to the simultaneous determination of Fe, Co, Ni, Cu and Hg.