Direct Introduction of a Dimesitylboryl Group Using Base‐Mediated Substitution of Aryl Halides with Silyldimesitylborane

The first dimesitylboryl substitution of aryl halides with a silylborane bearing a dimesitylboryl group in the presence of alkali‐metal alkoxides is described. The reactions of aryl bromides or iodides with Ph₂MeSi?BMes₂ and Na(OtBu) afforded the desired aryl dimesitylboranes in good to high yields and with high borylation/silylation ratios. Selective reaction of the sterically less‐hindered C?Br bond of dibromoarenes provided monoborylated products. This reaction was used to rapidly construct a D‐π‐A aryl dimesityl borane with a non‐symmetrical biphenyl spacer.     

Nuclear field shift effect in isotope fractionation of thallium

Environmental transport of Tl is affected by redox reaction between Tl(I) and Tl(III) and ligand exchange reactions of them. In order to deepen the knowledge of Tl chemistry, we investigated fractionation of Tl stable isotopes (²⁰³Tl and ²⁰⁵Tl) in a chemical exchange system. Tl isotopes were fractionated in a liquid–liquid extraction system, in which aqueous and organic phases are hydrochloric acid solution and dichloroethane including a crown ether, respectively. After purification by ion-exchange chemistry, the isotope ratio of ²⁰⁵Tl/²⁰³Tl in equilibrated aqueous phase was measured precisely by multiple-collector–inductively-coupled-plasma–mass-spectrometry. A large isotope fractionation >1 ‰ was found. Electronic structures of possible Tl species (hydrated Tl⁺, Tl³⁺, and Tl chlorides) were calculated by ab initio methods, and the isotope fractionation factor was theoretically obtained. The isotope fractionation via intramolecular vibrations was calculated to be much smaller than the experimental result. The isotope fractionation via isotopic change in nuclear volume, named the nuclear field shift effect, was calculated to be >1 ‰ in Tl(I)–Tl(III) redox systems and/or ligand exchange systems of Tl(III). The nuclear field shift effect was found to be the major origin of Tl isotope fractionation.     

The novel approach to indole alkaloids by using Pd(II)-catalyzed cyclization

The synthesis of indole skeleton by using Pd(II)-catalyzed cyclization of the urethane has been achieved. The urethanes with allylic alcohol were converted into vinyl indolines in good yield. The vinyl indoline was transformed into some intermediates of indole alkaloids.     

Time-series observations of 210Po and 210Pb radioactivity in the western North Pacific

We carried out time-series observations of ²¹⁰Po and ²¹⁰Pb radioactivity in the western North Pacific Ocean. The sinking fluxes of particulate organic carbon (POC) in the mesopelagic zone were estimated from ²¹⁰Po radioactivity during several seasons in the subarctic and subtropical regions of the western North Pacific. The seasonal changes of POC fluxes at a depth of 400 m were larger in the subarctic region than in the subtropical region. The annual mean POC flux at a depth of 400 m was larger in the subarctic region (57 mgC m^?2 day^?1) than in the subtropical region (36 mgC m^?2 day^?1). The annual mean of the e-ratio (the ratio of POC flux to primary productivity) in the subarctic region (18 %) was about twice the e-ratio in the subtropical region (10 %). These results imply that the efficiency of the biological pump is larger in the subarctic region than in the subtropical region of the western North Pacific.     

Accurate intensity calibration for low wavenumber (−150 to 150 cm−1) Raman spectroscopy using the pure rotational spectrum of N2

We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N₂. The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N₂ pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10⁻⁴) in the wavenumber region of −150 to 150 cm⁻¹. We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands

A new H-bonded crystal [Ru^III(Him)₃(Im)₃] with three imidazole (Him) and three imidazolate (Im⁻) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the Ru^III complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10⁻⁵ S cm⁻¹ at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [Ru^III(Him)₃(Im)₃] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state ²H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered.     

Coordination and Redox Isomerization in the Reduction of a Uranium(III) Monoarene Complex

Synthetic studies on the redox chemistry of trivalent uranium monoarene complexes were undertaken with a complex derived from the chelating tris(aryloxide)arene ligand (^Ad,MeArO)₃mes^3?. Cyclic voltammetry of [{(^Ad,MeArO)₃mes}U^III] ( 1 ) revealed a nearly reversible and chemically accessible reduction at ?2.495 V vs. Fc/Fc⁺—the first electrochemical evidence for a formally divalent uranium complex. Chemical reduction of 1 indicates that reduction induces coordination and redox isomerization to form a uranium(IV) hydride, and addition of a crown ether results in hydride insertion into the coordinated arene to afford uranium(IV) complexes. This stoichiometric reaction sequence provides structural insight into the mechanism of arene functionalization at diuranium inverted sandwich complexes.     

Temperature dependence of methanol and ethanol vapor sorption in polyhedral oligomeric silsesquioxane (POSS) containing methacrylate membranes

This study aimed to determine the solubility and temperature dependence of methanol and ethanol vapor caused by the difference in the substituents of polyhedral oligomeric silsesquioxane (POSS)-containing polymethacrylate membranes and the spacer length between the backbone and POSS backbone. Vapor sorption of methanol and ethanol was measured at 25°C, 35°C, and 45°C for three kinds of POSS-containing polymer membranes, namely, poly(methacryl isobutyl POSS), poly(methacrylate isobutyl POSS), and poly(methacryl phenyl POSS). The primary structures of the three POSS-containing polymer chains were columnar. The solubility of alcohol vapor on the POSS-containing polymer membranes followed the mechanism of solid adsorption and not the general dissolution diffusion. The sorption amount at all three temperatures was related to the surface area of the cylindrical primary structure and the solid adsorption property of the alcohol molecule of the POSS substituent. The sorption amount increased because of the large surface area and adsorption property of alcohol molecules. Although a typical glassy polymer shows exothermic mixing and a rubbery polymer displays endothermic mixing, the sample with the POSS substituent of isobutyl group exhibited an unusual behavior of endothermic mixing despite being a glassy polymer.