Atom Hamasaki

Nanoscale Heterogeneous Structure of Ionic Liquid as Revealed by Magnetic Field Effects

Large magnetic field effects (MFEs) observed for photoinduced hydrogen abstraction reaction between benzophenone and thiophenol in an ionic liquid (N,N,N,-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide, TMPA TFSA) are analyzed by using the stochastic Liouville equation for the first time. The sphere cage model can well reproduce the observed MFEs and the nanoscale heterogeneous structure with a cage radius of 1.8 +/- 0.3 nm, and an effective viscosity in the cage of 1-2 cP is found to be formed in TMPA TFSA.

Anomalous magnetic field effects on photochemical reactions in ionic liquid under ultrahigh fields of up to 28 T.

The magnetic field effects (MFEs) on photoinduced hydrogen abstraction reactions between benzophenone and thiophenol in an ionic liquid, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (TMPA TFSI), were studied by a nanosecond laser flash photolysis technique under ultrahigh fields of up to 28 T. Extremely large and anomalous stepwise MFEs were observed for the first time. The escape yield of benzophenone ketyl radical decreased with increasing magnetic field strength (B) at 0 T<B<or=2 T. The decrease was almost saturated at 2 T<B<or=10 T. At much higher fields (10 T<B<or=28 T), the yield decreased again with increasing B, producing a 25% decrease at 28 T.

Magnetic field effect on a radical pair reaction as a probe of microviscosity.

The magnetic field effects (MFEs), caused by the Delta g mechanism, on the photoinduced hydrogen abstraction reaction of benzopheneone with thiophenol were investigated in alcoholic solutions of varying viscosities (eta = 0.55 to 59.2 cP) by a nanosecond laser flash photolysis technique. The escape yield of benzophenone ketyl radicals ( Y) gradually decreased with increasing magnetic field strength ( B) from 0 to 1.6 T. The relative yield observed at 1.6 T, R(1.6 T) = Y(1.6 T)/ Y(0 T), decreased with increasing eta in the range of 0.55 cP < or = eta < or = 5 cP, and then increased with increasing eta in the range of 5 cP < eta < or = 55.3 cP. When eta was higher than 55.3 cP, the R(1.6 T) value became 1.0, and MFEs were completely quenched. The observed eta dependence of the MFEs was analyzed by the stochastic Liouville equation (SLE), in which the effects of spin-orbit coupling by a heavy atom such as sulfur were taken into account. The observed MFEs were reproduced fairly well by the SLE analysis. The diffusion coefficients of the radicals obtained by the SLE were about three times smaller than those expected from the macroscopic solvent viscosities. One can probe the microviscosity in the vicinity of the radical pairs by observing MFEs on the present photochemical reaction system.

Construction of a Pulsed-Magnetic System for On-Site Use: Application to Liposomes for Biological Membrane Modeling

We constructed a pulsed-magnetic system to be able to apply high magnetic fields for experimental studies in chemistry and biology. Operated by a pulsed current derived from a small-sized capacitor bank to a coil-bore wound copper wire, the maximum pulsed fields of more than 20 T and the pulsewidth of ~3 ms are generated from a charging energy of 2.4 kJ (700 V and 10 mF). With a large room-temperature bore of 8 mm, we are able to examine from the dynamic light scattering changes in liposome of dipalmitoylphosphocholine employed as a biological membrane model, which are distorted by applied pulsed fields over a 5 min interval and divide through the induced magnetic orientation. These changes were confirmed by comparing the results of pulsed fields against those of zero fields. This result agrees with the studies involving static fields that have been used to explain the division induced by magnetic orientation. Despite the pulse field having an extremely short duration, this system yields the changes effective in liposome necessary for modeling the biological behavior under strong magnetic fields.

Magnetic Orientational Properties of Monosodium Urate Crystals

Monosodium urate (MSU) crystals, which cause gout, preferentially develop in joints with a low body temperature and cause joint inflammation and severe pain.

Micropore Formation of [Zn2(Oxac) (Taz)2]·(H2O)2.5 via CO2 Adsorption

As-synthesized [Zn2(Oxac) (Taz)2]·(H2O)2.5, referred to as ZOTW2.5, was prepared from aqueous methanol solutions of Zn5(CO3)2(OH)6 and two kinds of ligands of 1,2,4-triazole (Taz) and oxalic acid (Oxac) at 453 K for 12 h. The crystal structure was determined by the Rietveld method. As-synthesized ZOTW2.5 was pretreated at 383 K and 1 mPa for tpt h, ZOTWx(tpth). ZOTWx(≥3h) showed a type I adsorption isotherm for N2 at 77 K having a saturation amount (Vs) of 180 mg/g, but that pretreated shortly showed only 1/10 in Vs. CO2 was adsorbed at 303 K in sigmoid on nonporous ZOTWx(≤2h) and in Langmuir-type on ZOTWx(≥3h) to reach the adsorption amount of 120 mg/g at 700 Torr. N2 adsorption on ZOTWx(≤2h)deCO2, degassed after CO2 adsorption on ZOTWx(≤2h), was promoted 5-fold from 180 mg/g on ZOTWx(tpth) and ZOTWx(≥3h)deCO2 up to ca. 1000 mg/g. The interaction of CO2 and H2O molecules in micropores may lead to a new route for micropore formation.

Obtaining Microscopic Images Under a High 20-T Pulse Magnetic Field Using an Optimized Coil

We optimized the coil of a pulsed electromagnet to be able to obtain dynamically microscopic images of crystals in a pulsed magnetic field of a maximum intensity of 20 T and pulsewidth of 3 ms. The pulsed field induces an eddy current that influences the nearby apparatus and objective lens made up of a conducting non-magnetic material. Developing a much shorter length of coil was required, because the working distance of the objective lens was incapable of preventing eddy currents. We calculated the maximum field and pulsed width; as a result, a coil wound with wire of 1-mm diameter in ten layers gives an ideal shape of the magnetic field when using a 10-mF capacitor bank with charge voltage of 700 V. Wound to the prescribed coil parameter values, the coil performed as expected. We demonstrate its performance with microscopic images taken using the optimized coil of the dynamic orientational behavior of diamagnetic monosodium urate crystals suspended in aqueous solution. The lying down of the acicular crystals through magnetic orientation just after application of the pulse field was observed dynamically.