Coexistence of Spin–Lattice Relaxation and Phonon-Bottleneck Processes in GdIII–Phthlocyaninato Triple-Decker Complexes under Highly Diluted Conditions

Gd³⁺ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd³⁺ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd³⁺ complexes, we have investigated the magnetic properties and heat capacities of two Gd³⁺-phthalocyaninato triple-decker complexes, one of which has intramolecular Gd³⁺–Gd³⁺ interactions and the other does not. It was found that the Gd³⁺–Gd³⁺ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd³⁺ complexes into a large amount of diamagnetic Y³⁺ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin–lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes.     

Evaluation of measurement uncertainty in the elemental analysis of sintered silicon carbide using laser ablation in liquid—inductively coupled plasma mass spectrometry with external calibration and isotope dilution

Accreditation and Quality Assurance - The goal of this study was to evaluate the uncertainty of elemental analytical methods that use laser ablation in liquid (LAL) as a pretreatment. After LAL...     

Directing Aluminum Atoms into Energetically Favorable Tetrahedral Sites in a Zeolite Framework by Using Organic Structure‐Directing Agents

The Al location in zeolites can have massive influences on the zeolite properties because it directly correlates with the cationic active sites. Herein, the synthesis of IFR zeolites with controlled Al distribution at different tetrahedral sites (T sites) is reported. The computational calculations suggest that organic structure‐directing agents (OSDAs) used for zeolite synthesis can alter the energetically favorable T sites for Al. Zeolite products synthesized under identical conditions but with different OSDAs are found to have altered fractions of Al at different T sites in accordance with the energies derived from the zeolite–OSDA complexes. Our finding thus provides evidence for the ability of OSDAs to direct Al into more energetically favorable T sites, thereby offering rational synthetic guidelines for the selective placement of Al into specific crystallographic sites.     

Quantitative comparison of a corona-charged aerosol detector and an evaporative light-scattering detector for the analysis of a synthetic polymer by supercritical fluid chromatography

A corona-charged aerosol detector (CAD) was developed to improve the sensitivity, reproducibility and quantitativeness of detection as compared to evaporative light-scattering detector (ELSD) for liquid chromatography. Our laboratory used the corona CAD as a detector for supercritical fluid chromatography (SFC) and evaluated its performance compared to the ELSD by using a certified reference material of poly(ethylene glycol) (PEG) and a well-defined equimass mixture of uniform PEG oligomers. The corona CAD was able to detect a 10 times more dilute solution of uniform oligomers compared to the ELSD. Although the original data of molecular mass by ELSD was 4.6% smaller than the certified value of PEG 1000, molecular mass distribution obtained by corona CAD was virtually almost the same as the certified value without any calibrations.     

A novel electrosynthetic system for anodic substitution reactions by using parallel laminar flow in a microflow reactor

We have developed a novel electrosynthetic system for anodic substitution reactions by using parallel laminar flow in a microflow reactor. This system enables nucleophilic reactions to overcome the restraint, such as the oxidation potential of nucleophiles and the stability of cationic intermediates, by the combined use of ionic liquids as reaction media and the parallel laminar flow in the microflow reactor. By using this novel electrosynthetic system, the anodic substitution reaction of carbamates, especially of cyclic carbamates, with allyltrimethylsilane were carried out to provide the corresponding products in moderate to good conversion yields in a single flow-through operation at ambient temperature (without the need for low-temperature conditions).     

The promiscuity of beta-strand pairing allows for rational design of beta-sheet face inversion

Recent studies suggest the dominant role of main-chain H-bond formation in specifying beta-sheet topology. Its essentially sequence-independent nature implies a large degree of freedom in designing beta-sheet-based nanomaterials. Here we show rational design of beta-sheet face inversions by incremental deletions of beta-strands from the single-layer beta-sheet of Borrelia outer surface protein A. We show that a beta-sheet structure can be maintained when a large number of native contacts are removed and that one can design large-scale conformational transitions of a beta-sheet such as face inversion by exploiting the promiscuity of strand-strand interactions. High-resolution X-ray crystal structures confirmed the success of the design and supported the importance of main-chain H-bonds in determining beta-sheet topology. This work suggests a simple but effective strategy for designing and controlling nanomaterials based on beta-rich peptide self-assemblies.     

A new homostilbene and two new homoisoflavones from the bulbs of Scilla scilloides

A new homostilbene, named scillabene A (2), and two new homoisoflavones, named scillavones A (3) and B (4), were isolated from the bulbs of Scilla scilloides DRUCE (Liliaceae) along with 13 known compounds comprising a homostilbene, seven homoisoflavones, a xanthone, a lignan, and three nortriterpenes. The structures of 2-4 were characterized as 3,5,4'-trihydroxy-3'-methoxy-4-methyl-trans-stilbene, (3R)-5,7,2'-trihydroxy-3',4'-dimethoxyspiro{2H-1-benzopyran-7'-bicyclo[4,2,0]octa[1,3,5]-trien}-4-one and (3S)-3-(3,4-dihydroxybenzyl)-5-hydroxy-6,7-dimethoxychroman-4-one, respectively, on the basis of spectroscopic data and X-ray crystallographic analysis.     

Modification of Wide‐Band‐Gap Oxide Semiconductors with Cobalt Hydroxide Nanoclusters for Visible‐Light Water Oxidation

Cobalt‐based compounds, such as cobalt(II) hydroxide, are known to be good catalysts for water oxidation. Herein, we report that such cobalt species can also activate wide‐band‐gap semiconductors towards visible‐light water oxidation. Rutile TiO₂ powder, a well‐known wide‐band‐gap semiconductor, was capable of harvesting visible light with wavelengths of up to 850 nm, and thus catalyzed water oxidation to produce molecular oxygen, when decorated with cobalt(II) hydroxide nanoclusters. To the best of our knowledge, this system constitutes the first example that a particulate photocatalytic material that is capable of water oxidation upon excitation by visible light can also operate at such long wavelengths, even when it is based on earth‐abundant elements only.     

Miscibility of Polyoxymethylene Blends as Revealed by High-resolution Solid-state 13C-NMR Spectroscopy

The miscibility of polyvinylphenol (PVPh) or terpenephenol (TPh) with polyoxymethylene (POM) was examined by high-resolution solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy. It was found that the driving force for the mixing of POM and PVPh is the hydrogen-bonding interaction between the phenolic OH group of PVPh and the ether oxygen of POM, and that the mixing is preferentially induced in the noncrystalline phase. ¹H relaxation time experiments indicated that POM/PVPh blends were homogeneous on a scale of 20–30 nm but heterogeneous on a scale of 2–3 nm. On the other hand, Fourier transform infrared and cross-polarization/magic-angle-spinning ¹³C-NMR (nuclear magnetic resonance) spectra revealed that POM and TPh are also mixed in the noncrystalline phase through the intermolecular hydrogen-bonding interaction, while some fraction of POM is still crystallizable. Moreover, the domain size of the micro-phase separation was estimated to be about 1 nm by the direct ¹H spin-diffusion measurements, suggesting almost homogeneous mixing on a molecular level in the noncrystalline phase. © 1997 John Wiley & Sons, Ltd.