Pressure effects on the electron spin relaxation of several radicals in solution

The pressure effect on the decay rate of chemically induced dynamic electron spin polarization (CIDEP) was investigated on several free-radical intermediates in photolysis, and the spin-lattice relaxation times for these radicals were estimated from the decay rates of CIDEP signals at various pressures. The spin-lattice relaxation rates were retarded by increasing external pressure. From the pressure dependence of the spin-lattice relaxation rates the activation volume was estimated. The activation volumes of these radicals divide into two groups; ≈30 cm³ mol⁻¹ for negative ions and ≈10 cm³ mol⁻¹ for neutral radicals.     

Electrodeposition of manganese and molybdenum mixed oxide thin films and their charge storage properties

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO(4)2-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO(4)2- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film.     

Cp/mas 13c nmr and Electron Diffraction Study of Bacterial Cellulose Structure Affected by Cell Wall Polysaccharides

Acetobacter xylinum was cultured in Schramm–Hestrin medium containing pectin (pectin medium), xylan (xylan medium), or glucomannan (mannan medium). X-ray diffractometry revealed that xylan and glucomannan affected the size of the cellulose crystals and their d-spacing values. Solid-state cross polarization magic angle spinning carbon-13 nuclear magnetic resonance spectroscopy indicated that the ratio of cellulose I was reduced by the addition of polysaccharides. These effects were more remarkable on the cellulose in the mannan medium than that in the xylan medium, and were scarcely observed in the pectin medium. Electron diffraction analysis revealed that these effects on hemicelluloses along cellulose microfibrils are continuous in the mannan medium and discontinuous in the xylan medium. These findings suggest that the uronic acid in the polysaccharides prevents interactions with cellulose leading to alterations of the structure of the cellulose crystal.     

Structure,stability, and electronic and NMR properties of various oxo- and nitrido-derivatives of [L(Salen)Mn(III)]+, where L = none and imidazole. A density functional study

Structure, stability, and electronic and NMR properties of [(Salen)Mn(III)](+)-derived intermediates/reactants in the epoxidation/amination of unfunctionalized olefins, namely [(Salen)Mn(V)O](+) (1-oxo), [(Salen)Mn(IV)O] (2-oxo), and [(Salen)Mn(V)N] (3), have been studied with the B3LYP density functional method. It has been shown that the (1)A, (3)A, and (5)A states of cationic 1-oxo species are virtually degenerate, while for the neutral 2-oxo species the ground (4)A state lies 6.4 kcal/mol lower than (2)A. In the nitrido species 3, the (1)A state has been shown to be the ground state in agreement with experiment. We have investigated isomerization of 1-oxo and 2-oxo species into unusual [(OSalen)Mn(III)](+) (1-N-oxo and 1-peroxo) and [(OSalen)Mn(II)] (2-N-oxo and 2-peroxo) species, respectively. For cationic species 1, the 1-N-oxo isomers are more stable (by 10-12 kcal/mol) than the 1-oxo isomer and are separated from the latter by 21-22 kcal/mol barriers. On the other hand, 1-peroxo isomers are calculated to be 14-16 kcal/mol higher than the 1-oxo isomer. For neutral species 2, however, both 2-N-oxo and 2-peroxo isomers lie significantly higher in energy than the 2-oxo isomer. It has been shown that coordination of axial imidazole ligand alters relative energies of spin states for 1- and 2-oxo species, destabilizing low-spin states. For singlet states of H(2)Salen, 1-oxo, and 3, we have calculated (1)H, (13)C, (15)N, and (17)O NMR chemical shifts using the gauge-independent-atomic orbital (GIAO) approach.     

A new synthetic route to 2-substituted naphtho[2,3-b]furan-4,9-dione2-Substituted Naphtho[2,3-b]furan-4,9-dione

4,9-Dimethoxynaphtho[2,3-b]furan 9 was obtained in 91% yield via the reductive methylation of naphtho[2,3-b]furan-4,9-dione 2 . After treatment of 9 with butyllithium, the mixture was allowed to react with N,N-dimethylacetamide, followed by oxidization with cerium(IV) diammonium nitrate to give 2-acetylnaphtho[2,3-b]furan-4,9-dione 1 . 2-Formylnaphtho[2,3-b]furan-4,9-dione 13 and 2-trimethylsilyl-naphtho[2,3-b]furan-4,9-dione 14 were also obtained from 9 by a similar method. The halodesilylations of 14 easily gave 2-iodonaphtho[2,3-b]furan-4,9-dione 16 , 2-bromonaphtho[2,3-b]furan-4,9-dione 17 , and 2-chloronaphtho[2,3-b]furan-4,9-dione 18 in 82%, and 93% and 83% yield, respectively. Furthermore, the nitrodesilylation of 14 gave 2-nitronaphtho[2,3-b]furan-4,9-dione 3 in 77% yield.     

Polydimethylsiloxane connection for quartz microchips in a high-pressure system.

An interconnecting technique, the "PDMS connection method", for quartz microchips in a high-pressure system is presented. The connection between quartz microchips is an essential technology for modular microfluidic devices, such as microchip-HPLC. PDMS was applied to the seal material, being spread on the seal side of the chips, and set into the metal housing. The characteristics of the PDMS connection method concerning pressure resistance and the extension of the peak were examined. The experimental results showed a good seal at 5 MPa, which seem to be sufficient for realizing microchip-HPLC utilizing a monolithic silica capillary column as a separation medium. The influence of the extra column effect on chromatographic separation was almost the same as in the case using a commercial union fitting. In addition, the PDMS connection enabled the detachability of chip-based modules with user-friendliness. Our experimental findings suggest that the novel PDMS connection method can possibly be applied as a generic technology in high-pressure microTAS.     

New odorless method for the Corey-Kim and Swern oxidations utilizing dodecyl methyl sulfide (Dod-S-Me)

Development of the odorless dodecyl methyl sulfide (Dod-S-Me, 1) as an alternative for dimethyl sulfide (DMS) and new odorless methods for the Corey-Kim and Swern oxidations are described. These reactions have been developed with a view toward green chemistry, utilizing Dod-S-Me (1) and common solvents instead of dichloromethane.