Bulk-sensitive spectroscopic studies on noncentrosymmetric superconducting system of Mg–Ir–B

We present the data from ultrahigh-resolution laser-excited photoemission spectroscopy on a newly discovered noncentrosymmetric superconductor Mg₁₀Ir₁₉B₁₆. We observed the evidences for the opening of superconducting gap where numerical fittings show that isotropic s-wave model can satisfactorily explain the behavior of spectra near the Fermi level. We also present the valence band photoemission spectrum and B K fluorescence spectrum to discuss the basic electronic structure of Mg₁₀Ir₁₉B₁₆.     

Tuning of Electronic Properties of Single‐Walled Carbon Nanotubes under Homogenous Conditions

Reversible and non‐bonding interaction between SWNTs and ODCB is observed from the analyses of visible near‐infrared absorption data and Raman spectroscopies (see spectra). The solvent effect on SWNTs effectively controls the electronic structure of SWNTs under homogeneous conditions.

     

Study of the acute cardiovascular effects of several antihypertensive agents with the measurement of plasma catecholamines in mice

A highly sensitive determination method was established for catecholamines (norepinephrine (NE), epinephrine, and dopamine) with high-performance liquid chromatography-peroxyoxalate chemiluminescence reaction detection. In this study, the method was applied to mouse plasma, and it was determined that only 10 μl of mouse plasma was necessary for the selective and reproducible determination of catecholamines. Studies were then conducted in acute cardiovascular effects of sodium nitroprusside, nicardipine, captopril (angiotensin-converting enzyme (ACE) inhibitor), candesartan, and olmesartan (type 1 angiotensin receptor antagonists (AT₁ antagonists)) by this method. Sodium nitroprusside and nicardipine elevated plasma NE concentrations significantly, whereas the ACE inhibitor and the AT₁ antagonists did not change plasma NE concentrations in anesthetized mice. These results suggested that angiotensin II-induced augmentation may be mainly carried through the central baroreflex pathway.     

A surface hopping method for chemical reaction dynamics in solution described by diabatic representation: an analysis of tunneling and thermal activation

We present a surface hopping method for chemical reaction in solution based on diabatic representation, where quantum mechanical time evolution of the vibrational state of the reacting nuclei as well as the reaction-related electronic state of the system are traced simultaneously together with the classical motion of the solvent. The method is effective in describing the system where decoherence between reactant and product states is rapid. The diabatic representation can also give a clear picture for the reaction mechanism, e.g., thermal activation mechanism and a tunneling one. An idea of molecular orbital theory has been applied to evaluate the solvent contribution to the electronic coupling which determines the rate of reactive transition between the reactant and product potential surfaces. We applied the method to a model system which can describe complex chemical reaction of the real system. Two numerical examples are presented in order to demonstrate the applicability of the present method, where the first example traces a chemical reaction proceeded by thermal activation mechanism and the second examines tunneling mechanism mimicking a proton transfer reaction.     

Photosensitized reduction of water to hydrogen using human serum albumin complexed with zinc-protoporphyrin IX

We present the photophysical properties of complexes of recombinant human serum albumin (rHSA) with Zn(II)-protoporphyrin IX (ZnPP) and their activities in the photosensitized reduction of water to hydrogen (H2) using methyl viologen (MV2+) as an electron relay. The ZnPP is bound in subdomain IB of wild-type rHSA [rHSA(wt] by an axial coordination of Tyr-161 and, in the rHSA(I142H/Y161L) mutant [rHSA(His], by a His-142 coordination. Both the rHSA(wt)-ZnPP and rHSA(His)-ZnPP complexes showed a long-lived photoexcited triplet state with lifetimes (tauT) of 11 and 2.5 ms, respectively. The accommodation of ZnPP into the protein matrix efficiently eliminated the collisional triplet self-quenching process. The addition of a water-soluble electron acceptor, MV2+, resulted in a significant decrease in the triplet lifetime. The transition absorption spectrum revealed the oxidative quenching of rHSA-3ZnPP* by MV2+. The quenching rate constant (kq) and backward electron transfer rate constant (kb) were determined to be 1.4 x 10(7) and 4.7 x 10(8) M(-1) s(-1) for rHSA(wt)-ZnPP. In the presence of the colloidal PVA-Pt as a catalyst and triethanolamine (TEOA) as a sacrificial electron donor, the photosensitized reduction of water to H2 takes place. The efficiency of the photoproduction of H2 was greater than that of the system using the well-known organic chromophore, tetrakis(1-methylpyridinium-4-yl)porphinatozinc(II) (ZnTMPyP4+), under the same conditions.     

Selective synthesis of 2-pyridones and pyrimidine-2,4-diones by neutral rhodium(I) complex-catalyzed cyclocotrimerization of alkynes and isocyanates

A neutral rhodium(I) complex, ‘RhCl(PPh₃)₂’ generated by the combination of [RhCl(C₂H₄)₂]₂ with a fourfold amount of PPh₃, effectively catalyzed the cyclocotrimerization of alkynes (1) and isocyanates (2) to give 2-pyridones (3) and/or pyrimidine-2,4-diones (4), selectively, by controlling the molar ratio of alkynes (1) and isocyanates (2).     

Efficient method for the deprotection of tert-butyldimethylsilyl ethers with TiCl4-Lewis base complexes: application to the synthesis of 1beta-methylcarbapenems

TiCl4-Lewis base (AcOEt, CH3NO2) complexes smoothly deprotected tert-butyldimethylsilyl (TBDMS) ethers. The reaction velocity with these complexes, which seemed less reactive due to the influence of Lewis bases, was considerably greater than that with TiCl4 alone. Selective desilylations between aliphatic and aromatic TBDMS ethers (1 and 5), between 1 and benzyl, allyl, tosyl, methoxyphenyl, and chloroacetyl ethers (13, 14, 15, 16, and 17), and between TBDMS and TBDPS ethers (18 and 19) were successfully performed. Desilylation of TBDMS-aldol, acyloin, and beta-lactam analogues 9-12 proceeded smoothly due to anchimeric assistance by the neighboring carbonyl groups. The present method was successfully applied to the practical synthesis of 1beta-methylcarbapenems 20a'-f'.     

DFT calculations for Au adsorption onto a reduced TiO2 (110) surface with the coexistence of Cl

Residual chlorines, which originate from HAuCl₄, enhance the aggregation of gold (Au) nanoparticles and clusters, preventing the generation of highly active supported Au catalysts. However, the detailed mechanism of residual-chlorine-promoted aggregation of Au is unknown. Herein to investigate this mechanism, density functional theory (DFT) calculations of Au and Cl adsorption onto a reduced rutile TiO₂ (110) surface were performed using a generalised gradient approximation Perdew, Burke, and Ernzerhof formula (GGA–PBE) functional and plane-wave basis. Although both Au and Cl atoms prefer to mono-absorb onto oxygen defect sites, Cl atoms have a stronger absorption onto a reduced TiO₂ (110) surface, abbreviated as rTiO₂ (110) in the following, than Au atoms. Additionally, co-adsorption of a Cl atom and a Au atom or Au nanorod onto a rTiO₂ surface was investigated; Cl adsorption onto an oxygen defect site weakens the interaction between a Au atom or Au nanorod and rTiO₂ (110) surface. The calculation results suggest that the depletion of interaction between Au and rTiO₂ surface is due to strong interaction between Cl atoms at oxygen defect sites and neighbouring bridging oxygen (O^B) atoms.     

Effect of laser annealing using high repetition rate pulsed laser on optical properties of phosphorus-ion-implanted ZnO nanorods

The effect of high repetition rate pulsed laser annealing with a KrF excimer laser on the optical properties of phosphorus-ion-implanted zinc oxide nanorods has been investigated. The recovery levels of phosphorus-ion-implanted zinc oxide nanorods have been measured by photoluminescence spectra and cathode luminescence images. Cathode luminescence disappeared over 300 nm below the surface due to the damage caused by ion implantation with an acceleration voltage of 25 kV. When the annealing was performed at a low repetition rate of the KrF excimer laser, cathode luminescence was recovered only in a shallow area below the surface. The depth of the annealed area was increased along with the repetition rate of the annealing laser. By optimizing the annealing conditions such as the repetition rate, the irradiation fluence and so on, we have succeeded in annealing the whole damaged area of over 300 nm in depth and in observing cathode luminescence. Thus, the effectiveness of high repetition rate pulsed laser annealing on phosphorus-ion-implanted zinc oxide nanorods was demonstrated.     

Additive-free nucleophilic addition of imidazolines and imidazoles to haloacetylenes

Nucleophilic addition of imidazolines to 1-halo-1-alkynes takes place by simple heating in DMF without any additives to give (Z)-N-(1-halo-1-alken-2-yl)imidazolines in good yield and in a highly regio- and stereoselective manner. These reaction conditions are also valid for the similar addition of imidazoles.