A compact permanent‐magnet system for measuring magnetic circular dichroism in resonant inelastic soft X‐ray scattering

A compact and portable magnet system for measuring magnetic dichroism in resonant inelastic soft X‐ray scattering (SX‐RIXS) has been developed at the beamline BL07LSU in SPring‐8. A magnetic circuit composed of Nd–Fe–B permanent magnets, which realised ～0.25 T at the center of an 11 mm gap, was rotatable around the axis perpendicular to the X‐ray scattering plane. Using the system, a SX‐RIXS spectrum was obtained under the application of the magnetic field at an angle parallel, nearly 45° or perpendicular to the incident X‐rays. A dedicated sample stage was also designed to be as compact as possible, making it possible to perform SX‐RIXS measurements at arbitrary incident angles by rotating the sample stage in the gap between the magnetic poles. This system enables facile studies of magnetic dichroism in SX‐RIXS for various experimental geometries of the sample and the magnetic field. A brief demonstration of the application is presented.     

Modification by H-termination in growth process of titanium silicide on Si(0 0 1)-2 × 1 observed with scanning tunneling microscopy

Formation processes of titanium silicide on hydrogen-terminated H/Si(0 0 1)-2 × 1 surface are studied at the atomic scale with a scanning tunneling microscopy (STM). Square-shaped nanoislands were observed on the Ti/H/Si(0 0 1) surface after annealed at 873-1073 K. These are the epitaxial nanoislands moderately grown due to the local orientation relationship between C49-TiSi₂ and Si(0 0 1), because passivation by surface hydrogen on Si(0 0 1) suppresses active and complex bond formation of Ti-Si.     

Preparation of organic acid anion-modified magnesium hydroxides by coprecipitation: A novel material for the uptake of heavy metal ions from aqueous solutions

New layered magnesium hydroxides whose brucite layers had been bridged with malate²⁻ and tartrate²⁻ were prepared by dropwise addition of Mg(NO₃)₂ to malate and tartrate solutions at a constant pH of 10.5. Malate²⁻ and tartrate²⁻ may have been also absorbed on the surfaces of hydroxides. In the case of using citrate solution, Mg(OH)₂ absorbed with citrate³⁻ was produced. These materials were found to take up Cu²⁺ rapidly from an aqueous solution at pH 5.0. Copper uptake by precipitates is attributed to the formation of chelate complexes of Cu²⁺ with citrate³⁻, malate²⁻, and tartrate²⁻.     

Silver-catalyzed cross-coupling reactions of alkyl bromides with alkyl or aryl Grignard reagents

Treatment of secondary or tertiary alkyl bromides with alkyl Grignard reagents in the presence of catalytic amounts of silver bromide and potassium fluoride in CH₂Cl₂ afforded the corresponding cross-coupling products in reasonable yields. Moreover, silver showed catalytic activity for the cross-coupling reactions of alkyl bromides with aryl Grignard reagents.     

Improvement of Ni/SDC anode by alkaline earth metal oxide addition for direct methane–solid oxide fuel cells

The anodic performances of Ni/CeO₂–Sm₂O₃(Ni/SDC) modified by the addition of alkaline earth metal oxides (MgO, CaO, and SrO) were investigated for direct oxidation of CH₄ in solid oxide fuel cells (SOFCs). Although the initial power density of cell with Ni/SDC anode modified by the addition of CaO was slightly lower than that of cell with Ni/SDC, the former anode exhibited an excellent stability compared to the latter one. Such a high stability of Ni–CaO/SDC anode may come from the inhibition of carbon deposition in addition to the retained ionic conductivity of anode.     

Photocatalytic decomposition of an alkylammonium cation in a Langmuir-Blodgett film of a titania nanosheet

The formation of inorganic-organic hybrid films of a titania nanosheet and an amphiphilic alkylammonium cation has been investigated, and the photocatalytic decomposition of the alkylammonium cation in the film has been pursued. When a solution of the amphiphilic alkylammonium salt (octadecylammonium chloride: ODAH+ Cl-) was spread on an interface between the air and a titania nanosheet suspension, the negatively charged nanosheets were adsorbed onto the floating monolayer of ODAH+ to form a hybrid monolayer. The hybridization was confirmed by pi-A isotherm measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. Multilayered films were fabricated in a layer-by-layer way by transferring the hybrid monolayers onto glass plates. Areas per ODAH+ cation in the films were estimated from the infrared (IR) spectra of the films, but these areas were smaller than those estimated from the pi-A isotherm curves. The orientation of the alkyl chain of ODAH+ in the hybrid film was determined by means of polarized IR spectroscopy. The alkyl chains were tilted 41 +/- 1 degrees and 47 +/- 1 degrees from the surface normal for the films prepared from the 8 and 20 ppm (ppm = mg dm(-3)) suspensions, respectively. Together with X-ray diffraction data of the films, the structure of the hybrid film was discussed. When the films were illuminated with a UV light, the absorption intensities due to the alkyl chain of ODAH+ decreased exponentially, indicating the photocatalytic decomposition of ODAH+ by the titania nanosheets in the films. Deviation from the exponential trend in the decomposition rate was observed in the initial period for the hybrid films prepared from the suspensions at low concentrations. Interestingly, the layered structure of the hybrid film was disturbed significantly after the ODAH+ cations were decomposed.     

Synthesis and characterization of phosphorous-bridged bisphenoxy titanium complexes and their application to ethylene polymerization

Phosphorous-bridged bisphenoxy titanium complexes were synthesized and their ethylene polymerization behavior was investigated. Bis[3-tert-butyl-5-methyl-2-phenoxy](phenyl)phosphine tetrahydrofuran titanium dichloride (4a) was obtained by treatment of 3 equiv of n-BuLi with bis[3-tert-butyl-2-hydroxy-5-methylphenyl](phenyl)phosphine hydrochloride salt (3a) followed by TiCl₄(THF)₂ in THF. THF-free complexes 5a-5d were synthesized more conveniently by the direct reaction of MOM-protected ligands (2a-2d) with TiCl₄ in toluene. X-ray analysis of 4a revealed that the ligand is bonded to the octahedral titanium (IV) center in a facial fashion and two chlorine atoms possess cis-geometry. Complexes 4a and 5a-5d were utilized as catalyst precursors for ethylene polymerization. Complex 5c gave high molecular weight polyethylene (M_w = 1,170,000, M_w/M_n = 2.0) upon activation with Al(ⁱBu)₃/[Ph₃C][B(C₆F₅)₄] (TB). Ethylene polymerization activity of 5d activated with Al(ⁱBu)₃/TB reached 49.0 × 10⁶ g mol (cat) ⁻¹ h⁻¹.     

Study on the base-catalyzed reverse vinylogous aldol reaction of (4abeta,5beta)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one under Robinson annulation conditions

[reaction: see text] We have proposed a pathway for the base-catalyzed reverse vinylogous aldol reaction of (-)-(4abeta,5beta)-4,4a,5,6,7,8-hexahydro-5-hydroxy-1,4a-dimethylnaphthalen-2(3H)-one [(-)-8] under Robinson annulation conditions. For confirmation, 4-(2,6-dimethyl-3-oxocyclohex-1-enyl)butanal (11) and 4-(2,6-dimethyl-5-oxocyclohex-1-enyl)butanal (12), both of which potentially produce enolate I, were synthesized regioselectively. Unexpectedly, 11 gave a complex mixture, including only a trace amount of (+/-)-8 (less than 5% yield), under these basic conditions. To the contrary, 12 cleanly afforded (+/-)-8 in 66% yield. This result provides evidence for our proposed mechanism of the above reaction.     

Efficient construction of the hexacyclic ring core of palau'amine: the pKa concept for proceeding with unfavorable equilibrium reactions

Palau''amine has received a great deal of attention as an attractive synthetic target due to its intriguing molecular architecture and significant immunosuppressive activity, and we achieved its total synthesis in 2015. However, the synthesized palau''amine has not been readily applicable to the mechanistic study of immunosuppressive activity, because it requires 45 longest linear steps from a commercially available compound. Here, we report the short-step construction of the ABCDEF hexacyclic ring core of palau''amine. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with unfavorable equilibrium reactions, and a palau''amine analog without the aminomethyl and chloride groups is synthesized in 20 longest linear steps from the same starting material. The palau''amine analog is confirmed to retain the immunosuppressive activity. The present synthetic approach for a palau''amine analog has the potential for use in the development of palau''amine probes for mechanistic elucidation.

A palau''amine analog (2) was synthesized from 2-cyclopentenone in 20 steps. The construction of the CDE tricyclic ring core in a single step is achieved by our pK_a concept for proceeding with the unfavorable equilibrium reactions.