Amorphous metal-hydrogen alloys prepared by mechano-chemical reaction

The mechano-chemical formation of crystalline and amorphous hydrides is described. Niobium transformed into β-Nb hydride by milling with liquid normal-heptane. Chromium and manganese were transformed into amorphous hydrides. The hydrocarbon served as the source of hydrogen atoms through a dehydrogenation reaction.     

Photoinversion of cisoid/transoid binaphthyls

Axially chiral binaphthyl-azobenzene cyclic dyads in which the two moieties are connected by two linkers of different lengths were synthesized. In the case of benzylated-binaphthyl analogue 2b, photoirradiation resulted in a dramatic change of the CD spectrum and optical rotation. Experimental and theoretical analyses indicated that the dihedral angle of the two naphthalene rings is strongly coupled to the azobenzene photoisomerization; cis-azobenzene induces a transoid-binaphthyl structure, while trans-azobenzene induces a cisoid-binaphthyl structure.     

Crystal structure and characterization of pyrroloquinoline quinone disodium trihydrate

ABSTRACT: BACKGROUND: Pyrroloquinoline quinone (PQQ), a tricarboxylic acid, has attracted attention as a growthfactor, and its application to supplements and cosmetics is underway. The product used forthese purposes is a water-soluble salt of PQQ disodium. Although in the past, PQQdisodiumpentahydrates with a high water concentration were used, currently, low hydrationcrystals of PQQ disodiumpentahydrates are preferred. RESULTS: We prepared a crystal of PQQ disodium trihydrate in a solution of ethanol and water, studiedits structure, and analyzed its properties. In the prepared crystal, the sodium atom interactedwith the oxygen atom of two carboxylic acids as well as two quinones of the PQQ disodiumtrihydrate. In addition, the hydration water of the prepared crystal was less than that of theconventional PQQ disodium crystal. From the results of this study, it was found that the colorand the near-infrared (NIR) spectrum of the prepared crystal changed depending on the watercontent in the dried samples. CONCLUSIONS: The water content in the dried samples was restored to that in the trihydrate crystal by placingthe samples in a humid environment. In addition, the results of X-ray diffraction (XRD) andX-ray diffraction-differential calorimetry (XRD-DSC) analyses show that the phase of thetrihydrate crystal changed when the crystallization water was eliminated. The dried crystalhas two crystalline forms that are restored to the original trihydrate crystals in 20% relativehumidity (RH). This crystalline (PQQ disodium trihydrate) is stable under normalenvironment.     

Synthetic approach toward antibiotic tunicamycins — VI total synthesis of tunicamycins

Tunicamycins and their eight analogs have been synthesized by condensation of a N-acetyl-D-glucosamine derivative and an anomeric chloride of tunicaminyl uracil, followed by deprotections and N-acylation.     

Enantioselective synthesis of α-methylene-γ-butyrolactones using chiral Pd(II)-SPRIX catalyst

Combination of Pd(OCOCF₃)₂ and (M,S,S)-iPr-SPRIX ligand promoted the intramolecular cyclization of 2-alkynoates very effectively to form α-methylene-γ-butyrolactones in good yields with up to 92% ee.     

Recent developments on chiral ionic liquids: design, synthesis, and applications

The recent progress in chiral ionic liquids with respect to their syntheses and applications in enantioselective reactions and chiral recognition is described. In addition to the conventional chiral ionic liquids derived from chiral natural products, a library of novel chiral spiro compounds, including spiro bis(pyridinium) and spiro bis(imidazolium) salt, is also described.     

Microdroplet anodic stripping voltammetry at the in situ preparing antimony-modified rotating disk electrode for determination of Cd(II) and Pb(II)

A simple electroanalytical method for Cd(II) and Pb(II) detection based on differential pulse anodic stripping voltammetry (DPSV) with in situ prepared antimony-modified glassy carbon rotating disk electrode (in situ Sb-GC-RDE) was developed. The electrochemical detection was performed in a microdroplet (50 μL) of 0.01 M hydrochloric acid that is placed between the electrode surface (top) and a Parafilm®-covered glass slide to maintain a hydrophobic surface (bottom). This method includes a preconcentration process using a membrane filter (MF). The target metal ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) as a chelating agent, which was accumulated on the MF via filtration. The RDE microdroplet anodic stripping voltammetry was suitable for the elution and determination of metal ions accumulated on the MF. The in situ preparation of antimony-modified electrode allows the use of common GC electrode with high performance. The detection limits for Cd(II) and Pb(II) were 1.4 and 1.1 μg/L, respectively. The proposed method was successfully used in natural water samples for the simultaneous determination of Cd(II) and Pb(II).     

Charge-Segregated Stacking Structure with Anisotropic Electric Conductivity in NIR-Absorbing and Emitting Positively Charged π-Electronic Systems

Squarylium-based π-electronic cation with an augmented dipole was synthesized by methylation of zwitterionic squarylium. The cation formed various ion pairs in combination with anions, and the ion pairs exhibited distinct photophysical properties in the dispersed state, ascribed to the formation of J- and H-aggregates. The ion pairs provided solid-state assemblies based on cation stacking. It is noteworthy that complete segregation of cations and anions was observed in a pseudo-polymorph of the ion pair with pentacyanocyclopentadienide as a π-electronic anion. In the crystalline state, the ion pairs exhibited photophysical properties and electric conductivity derived from cation stacking. In particular, the charge-segregated ion-pairing assembly induces an electric conductive pathway along the stacking axis. The charge-segregated mode and fascinating properties were derived from the reduced electrostatic repulsion between adjacent π-electronic cations via dipole–dipole interactions.     

First catalytic asymmetric hydrophosphonylation of cyclic imines: Highly efficient enantioselective approach to a 4-thiazolidinylphosphonate via chiral titanium and lanthanoid catalysts

The catalytic and enantioselective hydrophosphonylation of a cyclic imine, namely the 3-thiazoline 1, is described. We have discovered a highly efficient enantioselective de novo approach to the pharmaceutically interesting 4-thiazolidinylphosphonate 2 using either titanium or lanthanoid chiral catalysts, which gives excellent enantiomeric purities (up to 98 %ee) and high chemical yields.