Dynamical valence fluctuation at the charge-density-wave phase boundary in iodide-bridged Pt compound [Pt(chxn)2I]I2

We synthesized a novel iodo-bridged linear chain platinum compound, having the quasi-two-dimensional charge-density-wave (CDW) ground state and the smallest band gap. In this compound, we discovered an anomalous valence state in the boundary region at which the CDW phase alternates in the crystal by means of ESR, X-ray diffuse scattering, STM, and electrical resistivity. This anomalous state can be explained by the fast fluctuation between Pt(IV)-I...Pt(II) and Pt(II)...I-Pt(IV) in the double well potential. This is the first observation of the dynamical fluctuation of the CDW phase among the quasi one-dimensional halogen-bridged complexes.     

Highly enantioselective construction of a chiral spirocyclic structure by the [2 + 2 + 2] cycloaddition of diynes and exo-methylene cyclic compounds

The enantioselective [2 + 2 + 2] cycloaddition of 1,6-diynes with alpha-methylene lactones and cyclic ketones gave various chiral spirocyclic compounds. The reaction proceeded with high enantioselectivity when the rhodium-xylylBINAP complex was used as a chiral catalyst. Not only exo-methylene cyclic compounds but also exo-methylene acyclic compounds could be used as coupling partners for diynes. The present protocol provides access to a new chiral library possessing a quaternary carbon center, including a spirocyclic system.     

Rh(I)-catalyzed silylation of aryl and alkenyl cyanides involving the cleavage of C-C and Si-Si bonds

The Rh(I)-catalyzed silylation of nitriles with disilanes is described. The cleavage of inert carbon-cyano and silicon-silicon bonds occurs in this catalysis.     

Palladium-catalyzed intramolecular cyanoamidation of alkynyl and alkenyl cyanoformamides

[reaction: see text] The five- to seven-membered alpha-alkylidene lactams were prepared in 45-99% yield by the palladium-catalyzed cyanoamidation of alkynyl cyanoformamides. The reaction proceeded exclusively in a 5-exo mode, giving the corresponding (Z)-alkenes as major products. The reaction was also applied to 1,1-disubstituted alkenes to afford oxindoles bearing a quaternary carbon center.     

Direct-type catalytic three-component mannich reactions leading to an efficient synthesis of alpha,beta-diamino acid derivatives

[reaction: see text] The first example of the Lewis acid-catalyzed three-component direct-type Mannich reaction of simple aromatic and enolizable aliphatic aldehydes, secondary amines, and glycine derivatives is described. The procedure is highly atom economical and can be performed in a simple one-pot operation under mild conditions to afford a wide variety of synthetically important anti-alpha,beta-diamino ester derivatives in high yields with high diastereoselectivities.     

In situ observation of Ni–Mo–S phase formed on NiMo/Al2O3 catalyst sulfided at high pressure by means of Ni and Mo K‐edge EXAFS spectroscopy

To obtain direct evidence of the formation of the Ni–Mo–S phase on NiMo/Al₂O₃ catalysts under high‐pressure hydrodesulfurization conditions, a high‐pressure EXAFS chamber has been constructed and used to investigate the coordination structure of Ni and Mo species on the catalysts sulfided at high pressure. The high‐pressure chamber was designed to have a low dead volume and was equipped with polybenzimidazole X‐ray windows. Ni K‐edge k³χ(k) spectra with high signal‐to‐noise ratio were obtained using this high‐pressure chamber for the NiMo/Al₂O₃ catalyst sulfided at 613 K and 1.1 MPa over a wide k range (39.5–146 nm^?1). The formation of Ni–Mo and Mo–Ni coordination shells was successfully proved by Ni and Mo K‐edge EXAFS measurement using this chamber. Interatomic distances of these coordination shells were almost identical to those calculated from Ni K‐edge EXAFS of NiMo/C catalysts sulfided at atmospheric pressure. These results support the hypothesis that the Ni–Mo–S phase is formed on the Al₂O₃‐supported NiMo catalyst sulfided under high‐pressure hydrodesulfurization conditions.     

Direct writing of conductive silver micropatterns on flexible polyimide film by laser-induced pyrolysis of silver nanoparticle-dispersed film

This article describes fabrication of Ag micropatterns on a flexible polyimide (PI) film by laser direct writing using an Ag nanoparticle-dispersed film as a precursor. Ag micropatterns are characterized by optical microscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), surface profilometry, and resistivity measurements. The line width of Ag micropatterns can be effectively controlled by altering the experimental parameters of laser direct writing especially laser intensity, objective lens, and laser beam scanning speed etc. Using an objective lens of 100× and laser intensity of 170.50 kW/cm², Ag micropatterns with a line width of about 6 μm have been achieved. The Ag micropatterns show strong adhesion to polyimide surface as evaluated by Scotch-tape test. The resistivity of the Ag micropatterns is determined to be 4.1 × 10⁻⁶ Ω cm using two-point probe method. This value is comparable with the resistivity of bulk Ag (1.6 × 10⁻⁶ Ω cm).     

Van Vleck paramagnetism of the trivalent Eu ions

Magnetic susceptibilities of Eu₂O₃, EuF₃ and EuBO₃ have been measured over the wide temperature range 5-650 K. The Van Vleck paramagnetism, with the ground state of ⁷F₀ (S=3, L=3), has been investigated comprehensively. The temperature independent paramagnetism emerges manifestly below approximately 100 K. The variation of the susceptibility with temperature for EuBO₃ is in satisfactory agreement with the coupling constant , where the spin-orbit interaction is λL·S for the Russell-Saunders coupling on the basis of Van Vleck theory with one parameter λ. The value of can fit the susceptibility data of EuF₃. The deviation from the theory arises in Eu₂O₃. This discrepancy originates mainly from the influence of the crystalline field. Susceptibility of Gd₂O₃, having the ground state of ⁸S_7/2 (S=7/2, L=0), is also presented as a magnetic standard compound in comparison with these results.     

Effect of intergranular interactions on recording characteristics

The dependence of intergranular exchange interaction on medium SNR was investigated by micromagnetic simulation. It was found that the medium SNR at a high recording density takes its maximum value at the point where the magnitude of the maximum intergranular exchange field is about same as that of the maximum demagnetization field.