Local-moment formation and metal-nonmetal transition in Ca1−x Y x VO3 and Ca1−x Y x TiO3

Electron-doped metallic states of Ca_1−x Y _x VO₃ and Ca_1−x Y _x TiO₃ change into non-metallic states around x∼0.4 and 0.6, respectively. The residual resistivity in the metallic states increases with increasing effective magnetic moment or coefficient of T ² term of resistivity. The effective moment reaches ∼ 0.5 μ_B/molecule in Ca_1−x Y _x VO₃ and also in Ca_1−x Y _x TiO₃ near the metal-nonmetal phase boundary. In these metallic states. ∼ 10% of 3d atoms seem to have large localized magnetic moments. In electron-doped metallic sample of Ca_1−x Y _x VO₃, the temperature dependence of resistance shows no resistance-minimum. However, weak negative magneto-resistance is observed for the sample with x=0.2 up to 50 Tesla at 4.2 K.     

Determination of pressure effect on thermocouple electromotive force using multi-anvil apparatus

We developed a method to determine the absolute pressure effect on thermocouple electromotive force (EMF), based on a single wire method using Kawai-type multi-anvil apparatus. In this method, pressure conditions along the wires were evaluated based on in situ X-ray diffraction using synchrotron X-ray radiation. The pressure effect of the Seebeck coefficients of chromel and alumel was determined up to 7?GPa and 600°C by the analyses of single wire EMFs and pressure-temperature profiles along the wires. The temperature correction for the type K thermocouple was calculated to be from 0°C to –3°C in the studied conditions. Since the multi-anvil apparatus is capable of achieving much higher pressure and temperature, the method presented in this study promises to reveal absolute temperature correction for thermocouples over a wide range of pressure and temperature conditions.     

Pd-P(t-Bu)(3)-catalyzed consecutive cross-coupling of p-phenylenedizinc compound with two different electrophiles leading to unsymmetrically 1,4-disubstituted benzenes

Pd-P(t-Bu)3 was found to be a chemoselective catalyst for the reaction of p-phenylenedizinc compound with equimolar amounts of carbon electrophiles to afford the single cross-coupling products in good yields, effectively suppressing the formation of double cross-coupling products. The subsequent additions of other electrophiles to the resulting solutions caused the second cross-coupling of the incipient products to take place, achieving a novel and efficient one-pot synthesis of unsymmetrically 1,4-disubstituted benzenes. The origin of the observed high chemoselectivity was speculated.     

Direct and selective arylation of tertiary silanes with rhodium catalyst

We have developed a convenient and efficient approach to the arylation of tertiary silanes under mild conditions. A variety of arylsilanes were synthesized in a one-step process with good to excellent yields in the presence of a rhodium catalyst with a base. The reaction was highly solvent dependent, and amides were the most effective of the various solvents used. This common catalyst system is highly tolerant of the various sensitive functional groups on the substrates, which might be difficult to extract by other methods. The rhodium-promoted silylation of aryl halides with electron-donating groups occurred more efficiently than the silylation of aryl halides substituted with electron-withdrawing groups. Heteroaromatic halides were also found to be readily silylated with tertiary silanes. The successful application of this reaction to the synthesis of a TAC-101 analogue, which is a trialkylsilyl-containing synthetic retinoid benzoic acid derivative with selective binding affinity for retinoic acid receptor-alpha, is also described.     

Anti-estrogenic activity of mansorins and mansonones from the heartwood of Mansonia gagei DRUMM

Through an anti-estrogenic bioassay-guided fractionation of the methanol extract of Mansonia gagei, three new coumarins, called mansorins I (1), II (2) and III (3) and a new naphthoquinone, mansonone I (4), were isolated. Their structures were determined based on their NMR data and CD spectroscopy. The anti-estrogenic activity of the fractions and the isolated compounds were investigated using a yeast two-hybrid assay method expressing estrogen receptors alpha (ERalpha) and beta (ERbeta). In addition, an ERalpha competitor screening system (ligand binding screen) was used to verify the binding affinities of the isolated compounds to the estrogen receptor. 1,2-Naphthoquinones (mansonones) showed more binding affinities to ER in both assay systems. All the tested compounds showed higher binding affinities to ERbeta than to ERalpha in the yeast two-hybrid assay. Mansonones F and S showed the most potent estrogen binding and estrogen antagonistic effects.     

Testing the anomaly mediation at the LHC

We consider a supersymmetric model in which gaugino masses are generated by the anomaly-mediation mechanism while scalar masses are from tree-level supergravity interaction. In such a model, scalar fermions as well as Higgsinos become as heavy as O(10–100 TeV)$\mathrm{O}(10\text{–}100\text{TeV})$ and hence only the gauginos are superparticles kinematically accessible to the LHC. We study how and how well the properties of gauginos can be studied. We also discuss the strategy to test the anomaly-mediation model at the LHC.     

Efficient preparation of monohydrosilanes using palladium-catalyzed Si-C bond formation

The arylation of dihydrosilanes with aryl iodides or heteroaryl iodides in the presence of a palladium catalyst provides the corresponding monohydrosilanes in good to high yield. Moderate to good yields are obtained even in the presence of a variety of reactive functional groups, such as -NH2, -OH, or -CN, without their protection.     

Tri- and Tetranuclear Metal-String Complexes with Metallophilic d10–d10 Interactions

The reaction of 2,6-F₂C₆H₃SiMe₃ with Ph₂PLi provided 2,6-(Ph₂P)₂C₆H₃SiMe₃ ( 1 ), which can be regarded as precursor for the novel anionic tridentate ligand [2,6-(Ph₂P)₂C₆H₃]⁻ (PCP)⁻. The reaction of 1 with [AuCl(tht)] (tht=tetrahydrothiophene) afforded 2,6-(Ph₂PAuCl)₂C₆H₃SiMe₃ ( 2 ). The subsequent reaction of 2 with CsF proceeded with elimination of Me₃SiF and yielded the neutral tetranuclear complex linear-[Au₄Cl₂(PCP)₂] ( 3 ) comprising a string-like arrangement of four Au atoms. Upon chloride abstraction from 3 with NaBAr^F₄ (Ar^F=3,5-(CF₃)₂C₆H₃) in the presence of tht, the formation of the dicationic tetranuclear complex linear-[Au₄(PCP)₂(tht)₂](BAr^F₄)₂ ( 4 ) was observed, in which the string-like structural motif is retained. Irradiation of 4 with UV light triggered a facile rearrangement in solution giving rise to the dicationic tetranuclear complex cyclo-[Au₄(PCP)₂(tht)₂](BAr^F₄) ( 5 ), which comprises a rhomboidal motif of four Au atoms. In 3 – 5 , the Au atoms are associated by a number of significant aurophilic interactions. The atom-economic and selective reaction of 3 with HgCl₂ yielded the neutral trinuclear bimetallic complex [HgAu₂Cl₃(PCP)] ( 6 ) comprising significant metallophilic interactions between the Au and Hg atoms. Therefore, 6 may be also regarded as a metallopincer complex [ClHg(AuCAu)] between Hg^II and the anionic tridentate ligand [2,6-(Ph₂PAuCl)₂C₆H₃]⁻ (AuCAu)⁻ containing a central carbanionic binding site and two “gold-arms” contributing pincer-type chelation trough metallophilic interactions. Compounds 1 – 6 were characterized experimentally by multinuclear NMR spectroscopy and X-ray crystallography and computationally using a set of real-space bond indicators (RSBIs) derived from electron density (ED) methods including Atoms In Molecules (AIM), the Electron Localizability Indicator (ELI-D) as well as the Non-Covalent Interaction (NCI) Index.