Nondestructive neutron activation analysis of rare earth elements in hot spring water samples in Kusatsu-shirane area,Japan

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however, some pretreatment of the samples will be necessary.     

Synthesis of biodegradable amphiphilic AB‐type diblock copolymers of lactide and depsipeptide with pendant reactive groups

The syntheses of amphiphilic AB‐type diblock copolymers composed of hydrophobic polylactide segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups were performed. The protected cyclodepsipeptides cyclo[Glc‐Lys(Z)] and cyclo[Glc‐Asp(OBzl)] (where Glc is glycolic acid, Lys is lysine, Asp is aspartic acid, Z is benzyloxycarbonyl, and OBzl is benzyl) were first polymerized in tetrahydrofuran (THF) with potassium ethoxide as an initiator to obtain the corresponding protected polydepsipeptides. After the terminal hydroxyl groups of the protected polydepsipeptides were converted into the potassium alcoholates with K/naphthalene, L ‐lactide was polymerized in the presence of the corresponding polymeric alcoholates as macroinitiators in THF to obtain poly[Glc‐Lys(Z)]‐block‐poly(L ‐lactide) and poly[Glc‐Asp(OBzl)]‐block‐poly(L ‐lactide). Subsequent deprotection of Z and OBzl groups gave the objective amphiphiles poly(Glc‐Lys)‐block‐poly(L ‐lactide) and poly(Glc‐Asp)‐block‐poly(L ‐lactide), respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1218–1225, 2002     

Photoinduced magnetization in a two-dimensional cobalt octacyanotungstate

A new type of cyano-bridged Co-W bimetallic assembly, CsI[{CoII(3-cyanopyridine)2}{WV(CN)8}].H2O was synthesized. This compound exhibited a temperature-induced phase transition and a photoinduced magnetization. Irradiating with light induced a spontaneous magnetization with a magnetic phase transition temperature at 30 K. This photoinduced magnetization is due to the phase transition from CoIII(LS; S = 0)-WIV(S = 0) to CoII(HS; S = 3/2)-WV(S = 1/2) phases by the irradiation.     

Two‐Dimensional Perovskite Oxynitride K2LaTa2O6N with an H+/K+ Exchangeability in Aqueous Solution Forming a Stable Photocatalyst for Visible‐Light H2 Evolution

Undoped layered oxynitrides have not been considered as promising H₂‐evolution photocatalysts because of the low chemical stability of oxynitrides in aqueous solution. Here, we demonstrate the synthesis of a new layered perovskite oxynitride, K₂LaTa₂O₆N, as an exceptional example of a water‐tolerant photocatalyst for H₂ evolution under visible light. The material underwent in‐situ H⁺/K⁺ exchange in aqueous solution while keeping its visible‐light‐absorption capability. Protonated K₂LaTa₂O₆N, modified with an Ir cocatalyst, exhibited excellent catalytic activity toward H₂ evolution in the presence of I^? as an electron donor and under visible light; the activity was six times higher than Pt/ZrO₂/TaON, one of the best‐performing oxynitride photocatalysts for H₂ evolution. Overall water splitting was also achieved using the Ir‐loaded, protonated K₂LaTa₂O₆N in combination with Cs‐modified Pt/WO₃ as an O₂ evolution photocatalyst in the presence of an I₃^?/I^? shuttle redox couple.     

Tailoring of Deep‐Red Luminescence in Ca2SiO4:Eu2+

We report a new dicalcium silicate phosphor, Ca_2?xEu_xSiO₄, which emits red light in response to blue‐light excitation. When excited at 450 nm, deep‐red emission at 650 nm was clearly observed in Ca_1.2Eu_0.8SiO₄, the external and internal quantum efficiencies of which were 44 % and 50 %, respectively. The red emission from Ca_2?xEu_xSiO₄ was strongly related to the peculiar coordination environments of Eu²⁺ in two types of Ca sites. The red‐emitting Ca₂SiO₄:Eu²⁺ phosphors are promising materials for next‐generation, white‐light‐emitting diode applications.     

DFT study on chemical N2 fixation by using a cubane-type RuIr3S4 cluster: energy profile for binding and reduction of N2 to ammonia via Ru-N-NHx (x = 1-3) intermediates with unique structures

The N-N bond activation of the dinitrogen ligand in the cubane-type mixed-metal sulfido cluster, [(Cp*Ir) 3{Ru(tmeda)(N 2)}(mu 3-S) 4] (tmeda = Me 2NCH 2CH 2NMe 2), is investigated by using DFT calculations at the B3LYP level of theory. The elongated N-N bond distance, red-shifted N-N stretching, and negatively charged N 2 ligand indicate that the dinitrogen is reductively activated by complexation. The degree of the N-N bond activation is classified into the "moderately activated" category, [ Studt, F. ; Tuczek, F. J. Comput. Chem. 2006, 27, 1278 ] as in the Mo-triamidoamine complex that can catalyze N 2 reduction [ Yandulov, D. V. ; Schrock, R. R. Science 2003, 301, 76 ]. Availability of the RuIr 3S 4 cluster as a catalyst for N 2 reduction is discussed by optimizing possible intermediates in a catalytic cycle analogous to that proposed by Yandulov and Schrock. A calculated energy profile of the catalytic cycle demonstrates that the RuIr 3S 4 cluster can transform dinitrogen into ammonia in the presence of lutidinium cation and Cp* 2Co as proton and electron sources, respectively. The RuIr 3S 4 clusters with an NNH x ( x = 1-3) ligand, which are intermediates in the catalytic cycle, have a significantly bent Ru-N-N linkage, although precedent NNH x complexes generally adopt a linear M-N-N array. The unique structures of the nitrogenous ligands in these intermediates are interpreted in terms of the bonding interaction between the hydrogen atom bonded to the N 2 ligand and the adjacent iridium atom in the cuboidal RuIr 3S 4 framework.     

Separation of Isotopes of Lithium and Uranium by Electromigration Using Cation-Exchange Membranes

Isotope separation by chromatographic electromigration has been studied for lithium (⁶Li and ⁷Li) and uranium (²³⁵U and ²³⁸U), using cation-exchange membranes as migration media. The membranes were pulled back against the direction of the movement of isotopic cations in a countercurrent manner. In both cases of the elements the lighter isotope, ⁶Li or ²³⁵U, was concentrated at the frontal part of a migration zone; at the extreme front the ⁶Li atom % increased to 16.8% from the original value of 7.5% after 386 cm migration, and the ²³⁵ U atom % rose to 0.743% from the original value of 0.723% after 200 cm migration. Isotope separation coefficients were experimentally determined: ε = (3.7 ± 0.4) μ 10^?3 for lithium isotopes, and two slightly different values ε = (4.9 ± 1.0) μ 10^?5 and (5.4 ± 1.1) μ 10^?5 for uranium isotopes. The steep isotope accumulation was observed in a narrow boundary region. A mathematical expression for the isotope accumulation curve was derived, and the slope of the curve was assessed for each experimental result.     

Pseudo helix-sense-selective polymerisation of achiral substituted acetylenes

Pseudo helix-sense-selective polymerisation of a wide range of achiral substituted acetylenes having dynamic covalent bonds has been realised to yield static one-handed helical polymers without any other chiral moieties.     

Morphology-controlled synthesis of W18O49 nanostructures and their near-infrared absorption properties

The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W(18)O(49) were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W(18)O(49), such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl(6), W(EtO)(6), and WO(3) solids as the tungsten source. W(18)O(49) nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W(18)O(49) nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.     

ChemInform Abstract: DFT Analysis of Cubane‐Type FeIr3S4 Clusters. Dinitrogen Binding and Activation at the Tetrahedral Fe Site.

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