Size-dependent reactivity of cobalt cluster ions with nitrogen monoxide: Competition between chemisorption and decomposition of NO

Reactions of NO molecules on cobalt cluster ions were studied in a beam-gas geometry by using a tandem mass spectrometer. Single-particle collision reactions of Co_mNO⁺ (m = 3–10) with NO were found to proceed in such a manner that NO decomposition dominates at m = 4–6 with the maximum reaction cross section at m = 5 and chemisorption dominates in m ≥ 7. On the other hand, in two-particle collision reactions of Co_n⁺ (n = 2–10) with NO, NO decomposition at n ≥ 5 and chemisorption of two NO molecules with Co atoms loss at n ≥ 8 were found to proceed. These results indicate that the size-dependency of the multiple collision reactions originates from secondary attacking of an NO molecule to primary products of the initial single collision reactions. The DFT calculation supports the scheme that both the decomposition and chemisorption of two-particle collision reactions proceed via a common intermediate, Co_mN₂O₂⁺, in which the two NO molecules are dissociatively chemisorbed on the cobalt cluster ion, and the size-dependency of the two-particle collision reactions is explained in terms of the structure of this reaction intermediate.     

Energetics of the manganese oxide cluster cations Mn(N)O+ (N = 2-5): role of oxygen in the binding of manganese atoms

The photodissociation of manganese oxide cluster cations Mn(N)O+ (N = 2-5), into Mn(N-1)O+ (one-atom loss) and Mn(N-2)O+ (two-atom), was investigated in the photon-energy range of 1.08-2.76 eV. The bond-dissociation energies D0(Mn(N-1)O+...Mn) for N = 3, 4, and 5 were determined to be 1.84+/-0.03, 0.99+/-0.05, and 1.25+/-0.14 eV, respectively, from the threshold energies for the one- and two-atom losses. As Mn2O+ did not dissociate even at the highest photon energy used, the bond dissociation energy of Mn2O+, D0(Mn+...MnO), was obtained from a density-functional-theory calculation to be 3.04 eV. The present findings imply that the core ion Mn2O+ is bound weakly with the rest of the manganese atoms in Mn(N)O+.     

Rhodiolosides A-E, monoterpene glycosides from Rhodiola rosea

Five new monoterpene glycosides, rhodiolosides A-E (1-5), were isolated from the roots of Rhodiola rosea (Crassulaceae). Their structures were elucidated as (2E,6E,4R)-4,8-dihydroxy-3,7-dimethyl-2,6-octadienyl beta-D-glucopyranoside (1), (2E,4R)-4-hydroxy-3,7-dimethyl-2,6-octadienyl alpha-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (2), (2E,4R)-4-hydroxy-3,7-dimethyl-2,6-octadienyl beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranoside (3), (2E,4R)-4,7-dihydroxy-3,7-dimethyl-2-octenyl beta-D-glucopyranoside (4), and (2E)-7-hydroxy-3,7-dimethyl-2-octenyl alpha-L-arabinopyranosyl(1-->6)-beta-D-glucopyranoside (5), on the basis of various spectroscopic analyses and chemical degradation.     

Measurements of electron beam damage for organic crystals in a high voltage electron microscope with image plates

The critical dose for extinction of the diffraction pattern from behenic acid monolayer crystals increased with increasing accelerating voltages. The mean values at 114, 500 and 1000kV were 0.6, 1.8 and 2.2 electrons/A(2), respectively. The critical dose at 500-1000kV is three or more times as large as that at 114kV. Considering this with the recent measured value of the detective quantum efficiency of the image plate, 0.5 at 500kV and 0.4 at 1000kV, 1.5 times as much information can be collected from a crystal at 500-1000kV as at 114kV. Therefore, the combined use of high voltage electron microscopy and image plate detectors offers a significant improvement over conventional electron microscopy approaches for the study of radiation sensitive organic molecule crystals.     

Raman-Nath diffraction by microparticles in water

In Raman-Nath diffraction by water, the intensities of even order light beams are selectively enhanced by suspension of microparticles. The diffracted beams remain for several seconds even after the ultrasonic oscillation stops. These phenomena are elucidated by assuming the laminar arrangement of micropaticles due to the ultrasonic wave.     

Specific detection of nicotinamide coenzymes by liquid chromatography and amperometric detection with immobilized glucose-6-phosphate dehydrogenase

A liquid chromatographic system for the specific and simultaneous detection of nicotinamide coenzymes is constructed by combining an immobilized glucose-6-phosphate dehydrogenase reactor with an amperometric system based on a phenazine methosulphate-mediated reaction, after separation on a reversed-phase column. The calibration graphs are linear from 0.05 to 20 nmol for all four coenzymes. The detection limits are 3.2, 5.2, 7.9 and 9.4 pmol for NADP⁺, NADPH, NAD⁺ and NADH, respectively. The enzyme reactor retains most of its original activity after repeated use for 2 months.     

Single-electron transport through an individual InAs SAQD embedded in a graded-dope semiconductor nano-pillar

By using the semiconductor nano-pillar with a graded-dope configuration, we implemented the measurement for a single-electron transport through an individual InAs self-assembled quantum dot (SAQD). An atomic-force microscope observation showed that the SAQD had a disk-like shape with a diameter of 30 nm. We succeeded in observing a significant diamagnetic shift of the Coulomb oscillation peak under the magnetic field applied perpendicular to the disk plane. The measurement gave us a lateral confinement energy of 14 meV and an electron effective mass of 0.039, which provided us with quantitative evidence that the constituent material of the observed quantum dot originates from the InAs SAQD.     

Total synthesis of (±)-dicranenones,novel cyclopentenonyl fatty acids

Dicranenones 1 and 2 have been synthesized from the intermediate 12, which was either derived from methyl jasmonate 7 or prepared by the intramolecular ring formation of diazo compound 14.     

Selective preparation of pyridines, pyridones, and iminopyridines from two different alkynes via azazirconacycles

Selective preparation of pyridine derivatives from two different alkynes and a nitrile was achieved by a novel procedure in which an alkyne and a nitrile couple first to give an azazirconacyclopentadiene followed by reaction with the second alkyne in the presence of 1 equiv of NiCl(2)(PPh(3))(2). This procedure gives only single products of pyridine derivatives from two different symmetrical alkynes and a nitrile. Our novel procedure can be used even with two similar alkyl-substituted alkynes such as 3-hexyne and 4-octyne. Two possible pyridine isomers from 3-hexyne, 4-octyne, and acetonitrile could be completely and independently prepared as single products by this method. The origin of the selectivity comes from the addition order of two different alkynes. This method was applied for the formation of pyridones and iminopyridines using isocyanate and carbodiimide derivatives instead of nitriles, respectively. Reaction of an alkyne with Cp(2)ZrEt(2) and an isocyanate or a carbodiimide gives an azazirconacycle. Treatment of the azazirconacycle with the second alkyne in the presence of 1 equiv of NiCl(2)(PPh(3))(2) gave a pyridone or an iminopyridine derivative. The use of two different unsymmetrical alkynes afforded the pyridine with five different substituents when the first alkyne has a trialkylsilyl group and the second alkyne has a phenyl group as functional groups. On the other hand, azazirconacyclopentadienes reacted with propargyl bromide in the presence of CuCl with excellent regioselectivity to give tetrasubstituted pyridine derivatives as single products. With the assistance of the trialkylsilyl groups, pyridines with all different substituents including H were also prepared.