Ferromagnetic anomaly associated with the antiferromagnetic transitions in (donor)[Ni(mnt)2]-type charge-transfer salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.     

Preparation of Titania from Tetrakis(diethylamino)titanium via Hydrolysis

The conversion of tetrakis(diethylamino)titanium (Ti(NEt₂)₄) into titania via either a combination of hydrolysis (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : x, x = 2, 4, 10) at ambient conditions and calcination (method A) or hydrolysis in a water-tetrahydrofuran (THF) mixture (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : 100) at reflux (method B) was investigated. Titanium tertiary butoxide (Ti(O ^t Bu)₄) was also used as a substitute for Ti(NEt₂)₄. The hydrolysis via method A resulted in the formation of amorphous solids containing organics. Thermal analyses showed that the hydrolysis products showed mass losses up to 500°C probably due to the presence of diethylamine (Et₂NH) formed via the hydrolysis of Ti(NEt₂)₄ in the hydrolysis products, while a mass loss of the hydrolysis product from Ti(O ^t Bu)₄ was completed up to about 200°C. After calcination at 600°C, anatase or a mixture of anatase and rutile was obtained. The crystallization behavior of the hydrolysis products from Ti(NEt₂)₄ was different from that of the hydrolysis product from Ti(O ^t Bu)₄. The hydrolysis via method B gave only an amorphous material from Ti(NEt₂)₄, while a crystalline titania (anatase and brookite) formed from Ti(O ^t Bu)₄.     

Stereoregular control of poly(4‐vinyl pyridine) on free radical polymerization by using the inclusion complex with randomly methylated β‐cyclodextrin

Highly heterotactic poly(4‐vinyl pyridine)s (P4VPs) with the fraction of mr content (f_mr) > 0.81 were synthesized by free radical polymerization of 4‐vinyl pyridine (4VP) with randomly methylated β‐cyclodextrin (β‐RMCD) in acidic aqueous media of HNO₃ and CF₃COOH at 40 °C. The heterotacticity of P4VP strongly depended on the neutralization of 4VP. The complete neutralization of 4VP with HNO₃ or CF₃COOH increased the heterotacticity of P4VP, whereas atactic P4VP was obtained in water. The partial decomposition of β‐RMCD by HCl reduced the heterotacticity of P4VP (f_mr ≈ 0.74). The structures of inclusion complexed monomers were determined by Job's plot, 2D NMR with nuclear Overhauser enhancement spectroscopy analyses, and simulation by MM2. The 1:2 complex with [β‐RMCD]:[4VP] with meso placement of 4VPs in β‐RMCD was formed when 4VP was completely neutralized with acid, whereas the 1:1 complex was formed in water. The mechanism of heterospecific control by using β‐RMCD was proposed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Practical Synthesis of 2-Iodosobenzoic Acid (IBA) without Contamination by Hazardous 2-Iodoxybenzoic Acid (IBX) under Mild Conditions

We report a convenient and practical method for the preparation of nonexplosive cyclic hypervalent iodine(III) oxidants as efficient organocatalysts and reagents for various reactions using Oxone^® in aqueous solution under mild conditions at room temperature. The thus obtained 2-iodosobenzoic acids (IBAs) could be used as precursors of other cyclic organoiodine(III) derivatives by the solvolytic derivatization of the hydroxy group under mild conditions of 80 °C or lower temperature. These sequential procedures are highly reliable to selectively afford cyclic hypervalent iodine compounds in excellent yields without contamination by hazardous pentavalent iodine(III) compound.     

Presence of β-Turn Structure in Recombinant Spider Silk Dissolved in Formic Acid Revealed with NMR

Spider dragline silk is a biopolymer with excellent mechanical properties. The development of recombinant spider silk protein (RSP)-based materials with these properties is desirable. Formic acid (FA) is a spinning solvent for regenerated Bombyx mori silk fiber with excellent mechanical properties. To use FA as a spinning solvent for RSP with the sequence of major ampullate spider silk protein from Araneus diadematus, we determined the conformation of RSP in FA using solution NMR to determine the role of FA as a spinning solvent. We assigned ¹H, ¹³C, and ¹⁵N chemical shifts to 32-residue repetitive sequences, including polyAla and Gly-rich regions of RSP. Chemical shift evaluation revealed that RSP is in mainly random coil conformation with partially type II β-turn structure in the Gly-Pro-Gly-X motifs of the Gly-rich region in FA, which was confirmed by the ¹⁵N NOE data. In addition, formylation at the Ser OH groups occurred in FA. Furthermore, we evaluated the conformation of the as-cast film of RSP dissolved in FA using solid-state NMR and found that β-sheet structure was predominantly formed.     

Recent progress in multi-wafer CBE systems

We describe the recent progress of multi-wafer CBE systems demonstrating their potential capability of producing III–V semiconductor device structures with excellent uniformity and state-of-the-art performance. Up to three 4 inch wafers can be grown simultaneously with excellent uniformity and extremely small wafer-to-wafer variation (x in Al_xGa_1−x As: 0.2136 ± 0.0014). A specifically designed high-conductance metalorganic gas cell with a tilted aperture without any diffuser gives a high uniformity together with a fast switching at the heterointerfaces. An intrinsic difficulty for obtaining good compositional uniformity of ternary alloys containing indium is overcome by improvement in the design of an In-free substrate holder showing a uniform temperature profile within ± 0.9°C across a whole wafer. To extend the capability of CBE, an in situ cleaning method which combines hydrogen radical cleaning and As-free cleaning was investigated. The n-type GaAs epilayers showed a reduced depletion of electrons at the air-exposed regrown interface. From SIMS analysis, hydrogen radical and As-free cleaning show stronger effects on gettering carbon, and oxygen, respectively. Some C contamination during the 2nd As-free cleaning procedure is expected to be eliminated by decreasing the treatment temperature from the separately optimized one. The successful cleaning of InP substrates using trisdimethylaminophosphorous (TDMAP) would also extend the capability of CBE for the reproducible growth of large area (> 3 × 3 inch) InP-based materials.     

Synthesis and Structural Characterization of Isomers of Ru-Substituted Keggin-Type Germanotungstate with dmso Ligand

We found that three isomers of mono-Ru substituted Keggin-type germanotungstate with a dmso ligand, [GeW₁₁O₃₉Ru^II(dmso)]^6?, could be formed by a reaction of α-Keggin-type mono-lacunary germanotungstate, [α-GeW₁₁O₃₉]^8?, with Ru(dmso)₄Cl₂. The main isomer is an α-isomer, and the others are β₂-isomer and β₃-isomer, which were confirmed by ¹H NMR, cyclic voltammetry, IR, and single crystal X-ray structure analysis.     

Coherent-State Path Integrals and Brownian Motions

A stochastic approach to the rigorous foundation of the coherent-state (phase-space) path integral is given. Stochastic integrals and some generalizations of the Feynman–Kac theorem are used for this purpose. In this approach, quantum mechanics is described in terms of the Fock–Bargmann representation; a classical Hamiltonian is related to the corresponding quantum Hamiltonian on the Fock–Bargmann space, seen as a Hilbert subspace of L²(R²)L^{2}({\bf R}^{2}). The coherent-state path integral is realized as a conditional expectation of a stochastic process defined by the exponential of the Fisk–Stratonovich integral of the fundamental 1-form along a path of Brownian motion on the phase space R²{\bf R}^{2}.     

Production mechanism of active species on the oxidative bromination following perhydrolase activity

Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br^?. Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br^? and the strong brominating power with some tolerance against H₂O₂. Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis. Copyright © 2015 John Wiley & Sons, Ltd.