Selective Hydroperoxygenation of Olefins Realized by a Coinage Multimetallic 1-Nanometer Catalyst

The science of particles on a sub-nanometer (ca. 1 nm) scale has attracted worldwide attention. However, it has remained unexplored because of the technical difficulty in the precise synthesis of sub-nanoparticles (SNPs). We recently developed the “atom-hybridization method (AHM)” for the precise synthesis of SNPs by using a suitably designed macromolecule as a template. We have now investigated the chemical reactivity of alloy SNPs obtained by the AHM. Focusing on the coinage metal elements, we systematically evaluated the oxidation reaction of an olefin catalyzed by these SNPs. The SNPs showed high catalytic performance even under milder conditions than those used with conventional catalysts. Additionally, the hybridization of multiple elements enhanced the turnover frequency and the selectivity for the formation of the hydroperoxide derivative. We discuss the unique quantum-sized catalysts providing generally unstable hydroperoxides from the viewpoint of the miniaturization and hybridization of materials.     

Narrowband solid state vuv coherent source for laser cooling of antihydrogen

We describe the design and performance of a solid-state pulsed source of narrowband (< 100 MHz) Lyman-α radiation designed for the purpose of laser cooling magnetically trapped antihydrogen. Our source utilizes an injection seeded Ti:Sapphire amplifier cavity to generate intense radiation at 729.4 nm, which is then sent through a frequency doubling stage and a frequency tripling stage to generate 121.56 nm light. Although the pulse energy at 121.56 nm is currently limited to 12 nJ with a repetition rate of 10 Hz, we expect to obtain greater than 0.1 μJ per pulse at 10 Hz by further optimizing the alignment of the pulse amplifier and the efficiency of the frequency tripling stage. Such a power will be sufficient for cooling a trapped antihydrogen atom from 500 mK to 20mK.     

Growth of epitaxial TmFeCuO4 thin films by pulsed laser deposition

Epitaxial thin films of TmFeCuO₄ with a two-dimensional triangular lattice structure were successfully grown on yttria-stabilized-zirconia substrates by pulsed laser deposition and ex situ annealing in air. The films as-deposited below 500 °C showed no TmFeCuO₄ phase and the subsequent annealing resulted in the decomposition of film components. On the other hand, as-grown films deposited at 800 °C showed an amorphous nature. Thermal annealing converted the amorphous films into highly (0 0 1)-oriented epitaxial films. The results of scanning electron microscopic analysis suggest that the crystal growth process during thermal annealing is dominated by the regrowth of non-uniformly shaped islands to the distinct uniform islands of hexagonal base.     

Encapsulation of anilinonaphthalenesulfonates in carboxylate-terminated PAMAM dendrimer at the polarized water|1,2-dichloroethane interface

Molecular encapsulation of water-soluble anionic fluorescent dye molecules, 8-anilino-1-naphthalenesulfonic acid (ANS), and its bimolecular derivative (bis-ANS), in the generation 3.5 polyamidoamine (G3.5 PAMAM) dendrimer was investigated in the bulk aqueous phase and at the polarized water|1,2-dichloroethane interface. ANS(-) was electrostatically incorporated in the dendrimer, and the fluorescence enhancement with a blue shift of the emission maximum was observed at pH values <6, where the interior of the dendrimer was positively charged. The fluorescence enhancement of ANS was maximized around pH 3 and then decreased under more acidic conditions. The potential dependences of the molecular encapsulation and the interfacial mechanism were studied in detail by means of potential modulated fluorescence (PMF) spectroscopy. Under acidic conditions, the dendrimer incorporated ANS(-) at the positively polarized interface as well as in the aqueous phase. ANS(-) was released from the dendrimer at the intrinsic transfer potential and independently transferred across the interface. Bis-ANS exhibited relatively strong interaction with the dendrimer over a wide pH range (1 < pH < 8), and a negative shift of the transfer potential was observed under the corresponding pH condition. The PMF analysis clearly demonstrated that the interfacial mechanism of the dendrimer involves transfer and adsorption processes depending on the pH condition and the Galvani potential difference.     

Disturbance-free laser diode Sagnac interferometer using direct phase modulation

We exploited the wavelength tunability of the laser diode of a phase-shifting Sagnac interferometer to realize disturbance-free measurements. The Sagnac interferometer is robust against mechanical disturbances because it has a common path configuration and requires no special references. An unbalanced optical path was introduced between p- and s-polarized beams to enable easy phase shifting by direct current modulation. The experimental results indicate that the proposed system is effective for performing precise disturbance-free measurements.     

Anisotropic polymerization of a long-chain diacetylene derivative Langmuir-Blodgett film on a step-bunched SiO2/Si surface

Alternating facet/terrace nanostructures were fabricated on a SiO2 surface by step-bunching and thermal oxidation of a vicinal Si(111) substrate, and their influence upon the polymerization direction of a long-chain diacetylene derivative monolayer film was investigated by angle-dependent polarized near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. It was found that the peak intensity of the C 1s-pi transition was stronger when the electric vector plane of the incident X-ray was parallel to the direction of the periodic facet/terrace structures rather than perpendicular to them. On the contrary, a polymer film fabricated on a flat SiO2 surface showed no in-plane anisotropy of the peak intensity. These results indicate that the diacetylene groups in the diacetylene derivative monolayer are preferentially photopolymerized in the direction not across but along the periodic one-dimensional structures on the step-bunched and thermally oxidized SiO2/Si(111) surface.     

Channel-switching crystal with guest stress drive

By the addition of a "leverage" mechanism in a host component of a metal-organic crystal, a channel-switching property was developed in a porous single-crystal adsorbent driven by incorporated guest gas stress, which may provide new single-crystal devices with the active controllability of anisotropic guest diffusivity.     

A total synthesis of verbenachalcone, a bioactive diaryl ether from Verbena littoralis

Verbenachalcone 1, isolated from the aerial part of Verbena littoralis H. B. K. (Verbenaceae), has successfully been synthesized by employing anodic oxidation of the phenol derivative 3, as the key step. The bromine and chlorine substituents of 3 effected regioselective introduction of a methoxy group, as well as modulating the oxidation reaction. A flow-cell type apparatus of anodic oxidation provided the desired diaryl ether 4 in good yield.     

Enzymatic cyclizations of squalene analogs with threo- and erythro-diols at the 6,7- or 10,11-positions by recombinant squalene cyclase. Trapping of carbocation intermediates and mechanistic insights into the product and substrate specificities

In order to trap the carbocation intermediates formed during the squalene cyclization cascade, squalene analogs with threo- and erythro-diols at the 6,7- and 10,11-positions were incubated with the recombinant squalene cyclase from Alicyclobacillus acidocaldarius, leading to the construction of the triterpenes with tetrahydropyran, octahydrochromene, decahydronaphthalene with a carbonyl group, dodecahydrobenzo[f]chromene, tetradecahydronaphtho[2,1-b]oxepine and malabaricane skeletons, almost of which are novel compounds. These products indicate that 6-membered monocyclic, 6/6-fused bicyclic and 6/6/5-fused tricyclic cations were involved in the cyclization reaction in addition to acyclic cation. All the trapped cations were the stable tertiary cation, but not the secondary one, indicating that the polycyclization reaction proceeds with a Markovnikov closure. The product profiles revealed that the cyclization reactions proceeded with the product and substrate specificities in addition to enantioselectivity. Mechanistic insight into the observed stereochemical specificities indicated that the pre-organized chair-conformation of squalene-diols is tightly constricted by the cyclase and a free motion or a conformational change is not allowed in the reaction cavity, thus, the substrate and product specificities are dominantly directed by the least motion of the nucleophilic hydroxyl group toward the intermediary carbocation; a small rotation of the hydroxyl group afforded the cyclization products in a good yield, but a large rotation of the hydroxyl group gave a marginal or no detectable amount of products.     

Vinyl polymerization. 364. Polymerization of methyl methacrylate initiated with benzaldehyde

Benzaldehyde (PhCHO) is found to be able to initiate the radical polymerization of methyl methacrylate (MMA). The rate of polymerization is expressed by the following equation: R_p = const[PhCHO]^0.5[MMA]^1.5. The overall activation energy is estimated to be 56.3 kJ mole^?1. The mechanism of polymerization is discussed.