Reusable montmorillonite-entrapped organocatalyst for asymmetric Diels-Alder reaction

A chiral organocatalyst was successfully entrapped by montmorillonite clay using the cation-exchange method. The mont-entrapped organocatalyst acted as a highly efficient and reusable heterogeneous catalyst for the asymmetric Diels-Alder reaction, without loss of its initial activity.     

Theoretical design of an aromatic hydrocarbon rotor driven by a circularly polarized electric field

An aromatic hydrocarbon rotor without functional groups is theoretically designed. Such a molecular rotor is free from long-range electrostatic interactions. Induced dipole interactions are the rotor-driving forces under a nonresonant excitation condition. As an example, a molecular rotor with a condensed aromatic ring, a pentacene moiety mounted on a phenyl-acetylene axle that is driven by a circularly polarized electric field is considered. Results of simulations of the quantum dynamics of a rotor that take into account short-range rotor-bath interactions are presented by numerically solving the density matrix equations of the rotational motions.     

Revisiting Perkin's dye(s): the spectroscopy and photophysics of two new mauveine compounds (B2 and C)

Two new components have been identified in an early sample prepared according to the original recipe of Perkin, and perhaps even by Perkin himself around 1860--a new isomer of Perkin's mauveine B (designated as mauveine B2) together with a new mauveine compound (mauveine C)--and these compounds were synthesized again using starting materials chosen to reproduce Perkin's original synthesis and isolated by HPLC-DAD, identified by (1)H NMR, MS and their spectroscopic (UV/Vis and emission) and photophysical behaviour investigated.     

Metabolic profiling of β-cryptoxanthin and its fatty acid esters by supercritical fluid chromatography coupled with triple quadrupole mass spectrometry

In this study, a high-throughput and high-sensitivity profiling system for β-cryptoxanthin (βCX) and β-cryptoxanthin fatty acid ester (βCXFA) was constructed by supercritical fluid chromatography (SFC) coupled with triple quadrupole mass spectrometry (QqQMS). βCX and nine βCXFAs were successfully separated within 20 min using a column packed with octadecylsilyl-bonded silica particles. The limit of detection was 540 fmol for the free form and 32-130 fmol for the esterified forms. These results demonstrate that both the throughput and the sensitivity of this SFC-QqQMS system are considerably higher than those of conventional methods. When this system was applied for the analysis of Citrus unshiu, βCX and five βCXFAs were directly detected with much simpler sample pre-preparation. The analysis of other citrus fruits indicated that the βCXFA profiles varied with their breed variety. Furthermore, gas chromatography-mass spectrometry was used to analyze total fatty acid profiles in C. unshiu, and the results revealed that the profiles of fatty acids located in βCXFA were distinct. This is the first report on the analysis of βCX and its fatty acid derivatives by SFC-QqQMS. The profiling system developed in this study will be a powerful tool for investigating xanthophyll fatty acid esters.     

Unique catalysis of gold nanoparticles in the chemoselective hydrogenolysis with H2: cooperative effect between small gold nanoparticles and a basic support

Gold nanoparticles on hydrotalcite act as a heterogeneous catalyst for the chemoselective hydrogenolysis of various allylic carbonates to the corresponding terminal alkenes using H(2) as a clean reductant. The combination of gold nanoparticles and basic supports elicited significantly unique and selective catalysis in the hydrogenolysis.     

A newly investigated approach for the control of tunnel resistance of nanogaps using field-emission-induced electromigration

We report a newly investigated approach for the control of the tunnel resistance of nanogaps using field-emission-induced electromigration (“activation”), in order to decrease the power consumption during the process. The method is demonstrated by applying a bias current to initial nanogaps using a current source. As a result, a wide range control of the tunnel resistance of the nanogaps was achieved by performing the current-source-based activation. Furthermore, the average power could be successfully suppressed in comparison with that of the voltage-source-based activation. These results indicate that the current-source-based activation is suitable for the tuning of the tunnel resistance of nanogaps.     

System for coincidence measurements of the ions desorbed and projectiles scattered from noble gas solid surfaces by slow multiply charged ion impacts

We have developed a new experimental apparatus for performing coincidence measurements of the ions desorbed and projectiles scattered from the surfaces of noble gas solids by slow multiply charged ion impacts at grazing incidence angles. This simultaneously measures the desorbed ions' flight times and the scattered projectiles' charge states. We also conduct experiments on 6 keV Ar⁶⁺ impacts onto a solid Ne surface using the device.     

Synthesis of glycol diesters through the depolymerization of polyethylene glycols with carboxylic acids using a proton-exchanged montmorillonite catalyst

A convenient and sustainable method for the synthesis of glycol diesters was developed through the depolymerization of polyethylene glycols (PEGs) with carboxylic acids using proton-exchanged montmorillonite as an efficient solid acid catalyst. Several functionalized glycol diesters were obtained in good yields from PEGs and readily available carboxylic acids. Upon reaction completion, the catalyst could be easily separated by filtration and reused with its activity remaining unchanged.     

Ni2P Nanoalloy as an Air-Stable and Versatile Hydrogenation Catalyst in Water: P-Alloying Strategy for Designing Smart Catalysts

Non-noble metal-based hydrogenation catalysts have limited practical applications because they exhibit low activity, require harsh reaction conditions, and are unstable in air. To overcome these limitations, herein we propose the alloying of non-noble metal nanoparticles with phosphorus as a promising strategy for developing smart catalysts that exhibit both excellent activity and air stability. We synthesized a novel nickel phosphide nanoalloy (nano-Ni₂P) with coordinatively unsaturated Ni active sites. Unlike conventional air-unstable non-noble metal catalysts, nano-Ni₂P retained its metallic nature in air, and exhibited a high activity for the hydrogenation of various substrates with polar functional groups, such as aldehydes, ketones, nitriles, and nitroarenes to the desired products in excellent yields in water. Furthermore, the used nano-Ni₂P catalyst was easy to handle in air and could be reused without pretreatment, providing a simple and clean catalyst system for general hydrogenation reactions.