Catalysis by porous heteropoly compounds

This paper attempts to review recent works on catalysis of porous heteropoly compounds. The salts of heteropolyacids having Keggin structure with large cations like Cs⁺ are porous materials. For Cs hydrogen salts, the pore width can be controlled by the Cs content. Cs_2.5H_0.5PW₁₂O₄₀ has the largest amount of protons on the surface among the acidic Cs salts and possesses pores with bimodal distribution in the micro and meso region. Efficient performances were demonstrated for acid-catalyzed reactions such as skeletal isomerization of -butane in solid-gas system, alkylation and acylation in solid-liquid system, and hydrolysis and hydration in solid-water system. A microporous salt, Cs_2.2H_0.8PW₁₂O₄₀, exhibited reactant shape selectivity towards direct decomposition of esters. Furthermore, an ultramicroporous bifunctional catalyst, Pt–Cs_2.1H_0.9PW₁₂O₄₀ of which the pore width is around 5 Å, exhibits reactant shape selectivity for hydrogenation of alkenes and oxidation of hydrocarbons, and product shape selectivity for skeletal isomerization of -butane.     

Neutrino oscillations induced by two-loop radiative mechanism

Two-loop radiative mechanism, when combined with an U(1)_L′ symmetry generated by L_e − L_μ − L_τ (=L′), is shown to provide an estimate of Δm²/Δm²_atm εm_e/m_τ, where ε measures the U(1)_L′-breaking. Since Δm²_atm 3.5×10⁻³ eV², we find that Δm² ε10⁻⁶ eV², which will fall into the allowed region of the LOW solution to the solar neutrino problem for ε 0.1.     

Ruthenium-catalyzed intramolecular oxidative amination of aminoalkenes enables rapid synthesis of cyclic imines.

[RuCl2(CO)3]2/dppp is shown to be a highly effective catalyst system for the first intramolecular oxidative amination of a variety of aminoalkenes when it is used concomitantly with K2CO3 and allyl acetate in N-methylpiperidine, to give the corresponding cyclic imines and indoles in excellent yields. For example, the reaction of 2,2-diphenyl-4-pentenyl-1-amine performed in the presence of 2 mol % of [RuCl2(CO)3]2, 4 mol % of dppp, K2CO3, and allyl acetate in N-methylpiperidine at 140 degrees C for 8 h gives 4,4-diphenyl-2-methyl-1-pyrroline in quantitative (>99%) yield.     

Optical cavitation probe using light scattering from bubble clouds

To understand the behaviour of systems containing clouds of bubbles (multibubble system) in real sonochemical reactors, a new diagnosis method, i.e., optical cavitation probe (OCP), has been proposed. When a laser beam is introduced into the cavitation bubble cloud, the scattered light intensity changes by the collective oscillation of cavitation bubbles. The frequency domain spectrum of the scattered light contains rich information on the cavitation bubble clouds, comparable with the acoustic emission spectra detected by a hydrophone. The significant merits of OCP, such as capability for spatially resolved, non-invasive measurement of the cavitation bubble clouds, robustness even in a violent cavitation field have been experimentally demonstrated.     

Behavior of polymer chains grafted from latex particles at soft interfaces

We have studied the behaviors of a poly(methyl methacrylate) (PMMA) chains anchored to polystyrene particles at air/water and oil/water interfaces to recognize the roles of oil molecules in the PMMA property at the interfaces. Through the comparison of π-A isotherms we found two aspects of unique structural and rheological characteristics observed in PMMA-grafted polystyrene latex (PSL-PMMA) monolayer system in common. (1) The π-A isotherms showed surface pressure increase at larger occupied area compared to the PSL-PMMA size in solution at three different types of interfaces in most cases. (2) Compressional modulus, C _s ^?1, obtained by π-A isotherm analysis for PSL-PMMA at interfaces, showed the tendency to decrease with molecular weight of PMMA. This is opposite to that of PMMA homopolymer at interfaces. The effect of oil molecules on PSL-PMMA system at interfaces are found both in the difference of occupied area and C _s ^?1. The occupied areas were larger for the isotherms at the oil/water interfaces than those at the air/water interface in most cases, which suggested the reduced attractive interactions between anchored polymers by oil molecules. On the other hand, C _s ^?1 of PMMA monolayers is strongly dependent on the constituents of the interface and the order of C _s ^?1 is air/water?>?decane/water?>?dibutyl ether/water interfaces. The difference between oil species was not explained only by PMMA/oil interaction in bulk, but we suggested that interfacial tension of oil/water interface affects the miscibility of oil molecules with PMMA to cause higher miscibility between PMMA and dibutyl ether at the oil/water interfaces.     

Virus trap in human serum albumin nanotube

Infectious hepatitis B virus (HBV), namely Dane particles (DPs), consists of a core nucleocapsid including genome DNA covered with an envelope of hepatitis B surface antigen (HBsAg). We report the synthesis, structure, and HBV-trapping capability of multilayered protein nanotubes having an anti-HBsAg antibody (HBsAb) layer as an internal wall. The nanotubes were prepared using an alternating layer-by-layer assembly of human serum albumin (HSA) and oppositely charged poly-L-arginine (PLA) into a nanoporous polycarbonate (PC) membrane (pore size, 400 nm), followed by depositions of poly-L-glutamic acid (PLG) and HBsAb. Subsequent dissolution of the PC template yielded (PLA/HSA)(2)PLA/PLG/HBsAb nanotubes (AbNTs). The SEM measurements revealed the formation of uniform hollow cylinders with a 414 ± 16 nm outer diameter and 59 ± 4 nm wall thickness. In an aqueous medium, the swelled nanotubes captured noninfectious spherical small particles of HBsAg (SPs); the binding constant was 3.5 × 10(7) M(-1). Surprisingly, the amount of genome DNA in the HBV solution (HBsAg-positive plasma or DP-rich solution) decreased dramatically after incubation with the AbNTs (-3.9?log order), which implies that the infectious DPs were completely entrapped into the one-dimensional pore space of the AbNTs.     

Ruthenium-catalyzed [2 + 2 + 1] cocyclization of isocyanates, alkynes, and CO enables the rapid synthesis of polysubstituted maleimides

Intermolecular [2 + 2 + 1] cocyclization of isocyanates, alkynes, and CO (1 atm) proceeded smoothly in the presence of a catalytic amount of Ru3(CO)12 (3.3 mol %) in mesitylene at 130 degrees C for 3 approximately 42 h to give a variety of polysubstituted maleimides in excellent yields with high selectivity. The reaction may involve an azaruthenacyclopentenone intermediate derived from oxidative cyclization of an isocyanate and an alkyne on an active ruthenium species.     

Synthesis and functional evaluation of chiral dendrimer-triamine-coordinated Gd complexes as highly sensitive MRI contrast agents

Novel chiral dendrimer-triamine-coordinated Gd complexes were synthesized and shown to have longitudinal relaxivity (r1) 3 times higher than that of clinically used Gd-DTPA. The pharmacokinetic differences between optical isomers were estimated from the affinity of 2-(R) and 2-(S) with bovine serum albumin (BSA), respectively, by a quartz crystal microbalance (QCM) measurement. As a result, the association constant K_a of 2-(S) was about 4 times higher than that of 2-(R), which means that 2-(S) is retained in the vascular retention for a longer time after administration. This result was also supported by T1-weighted MR images of mice before and after the intravenous injection of 2-(R) and 2-(S), as well as the time-course of the signal intensities (SI) at the blood vessels and quantification of Gd³⁺ concentration in the blood and urine.     

Bubble population phenomena in sonochemical reactor: II. Estimation of bubble size distribution and its number density by simple coalescence model calculation

A simple bubble population model, with emphasis on the bubble–bubble coalescence, is proposed. In this model, the bubble size distribution is simulated through the iteration of fundamental bubble population process: generation, dissolution, and coalescence. With this simple modelling, the bubble size distribution experimentally observed by the pulsed laser diffraction method and the void rate obtained by the capillary system at 443 kHz were successfully simulated. The experimental results on the bubble population growth by the repetitive pulsed sonication and the effect of pulse width on the bubble population were recreated by the numerical simulation in a semi-quantitative manner. The importance of coalescence of bubbles especially for the effect of addition of surfactant is demonstrated. By decreasing the coalescence frequency by one order of magnitude in the simulation, both the drastic decrease in the total bubble volume as well as the depression of bubble size distribution centring from a few tens of microns in water to a few microns in a dilute surfactant solution can be simultaneously derived.     

Bubble population phenomena in sonochemical reactor: I Estimation of bubble size distribution and its number density with pulsed sonication – Laser diffraction method

To characterize the bubble populations (size and its number distribution) in a sonochemical reactor, a simple but powerful technique based on the Fraunhofer laser diffraction (LD) has been proposed. In this method, the acoustic wave disturbance to the laser probe in the sonochemical reaction field was eliminated by the temporal separation using pulsed sonication (pulsed LD). With this relatively simple strategy, the temporal development of the bubble size distribution could be evaluated by pulsed LD. A number density of bubbles was estimated by using a calibration data obtained with monosized standard particles. In addition, the effect of pulse length and a surfactant on the bubble population phenomena in a multibubble system are discussed.