Quantum Chemical Calculations on the Structure and Adsorption Properties of NO and N2O on Ag+ and Cu+ Ion-Exchanged Zeolites

Ab initio cluster quantum chemical calculations at the Hartree–Fock (HF/Lanl2dz) and correlated second-order Moller–Plesset perturbation theory (MP2/Lanl2dz) levels were performed for NO and N₂O interactions with Ag⁺ and Cu⁺ ion-exchanged zeolites. The interaction energies were estimated in a conventional way and also corrected for basis set superposition errors. It was shown that the highly dispersed Ag⁺ counterions establish twofold coordination to the lattice oxygens on the zeolite surface, similar to the case of Cu⁺ ions. However, both NO and N₂O bind relatively strongly to the Cu active sites of Cu⁺ ion-exchanged zeolites than those of the Ag⁺ site of the Ag⁺ ion-exchanged zeolites. Based on the results of these calculations, the two different forms of adsorption for these molecules on the catalyst surface, the nature of their binding and characteristics of the adsorption properties have been discussed. Finally, some comparisons with the results obtained by a variety of density functional theory calculations on target systems have been presented.     

Novel fluorous prolinol as a pre-catalyst for catalytic asymmetric borane reduction of various ketones

Novel prolinol carrying two perfluorohexylethyl groups at the α-position was prepared from l-proline as a starting chiral substrate. Catalytic asymmetric reduction of various ketones, including mono-, di-, and trifluoromethylated acetophenones, using fluorous oxazaborolidines derived from fluorous prolinol afforded the corresponding alcohols in good to excellent yields and with high enantioselectivities (up to 93.2% ee). The fluorous prolinol was recovered without any fluorous solvents or silica gel by simply cooling the organic phase and filtration.     

Determination of molybdenum(VI) in natural water and rock by ion-exchange absorptiometry combined with flow analysis

Ion-exchange absorptiometry combined with flow analysis has been applied to the determination of trace amounts of molybdenum(VI) in natural water and rock. By using a pretreatment column packed with Sephadex G-25 gel, molybdenum(VI) in a sample solution can be sorbed selectively on the gel at pH 3.5. The molybdenum(VI) in the column was desorbed with EDTA as the molybdenum(VI)-EDTA complex, and the solution was introduced into a Tiron solution stream. The yellow complex formed between molybdenum(VI) and Tiron in the flow system was then concentrated on a QAE-Sephadex A-25 anion exchanger packed in a flow-through silica micro-cell. The attenuation of incident light by the molybdenum(VI)-Tiron complex on the anion exchanger in the cell was continuously recorded with a spectrophotometer at 410 nm. The complex on the anion exchanger was easily desorbed with sodium nitrate, so the flow-through cell could be used repeatedly. The minimum amount that could be detected corresponded to 15 ng of molybdenum(VI). Molybdenum(VI) in three or four sample solutions could be determined within 1 h.     

Long-time tails of the velocity autocorrelation functions for the triangular periodic Lorentz gas

We present numrical results on the velocity autocorrelation function (VACF)C(t)=<ν(t)·ν(0)> for the periodic Lorentz gas on a two-dimensional triangular lattice as a function of the radiusR of the hard disk scatterers on the lattice. Our results for the unbounded horizon case confirm 1/t decay of the VACF for long times (out to 100 times the mean free time between collisions) and provide strong support for the conjecture by Friedman and Martin that the 1/t decay is due to long free paths along which a moving particle does not scatter up to timet. Even after new sets of long free paths become available forR<1/4, we continue to find good agreement between numerical results and an analytically estimated 1/t decay. For the bounded horizon case , our numerical VACFs decay exponentially, although it is difficult to discriminate among pure exponential decay, exponential decay with prefactor, and stretched exponential decay.     

Coulomb excitation of154Sm

The deformed nucleus¹⁵⁴Sm was studied by Coulomb excitation with NORDBALL by using a⁵⁸Ni beam. The ground-state band, the beta band, the gamma band and the octupole band (K=0-) were excited up to the 16+ state, the 6+ state, the 6+ state and the 13-state, respectively. A new band was established from 6+ to 14+ on the basis of the gamma-gamma coincidence spectra. The excitation probability of the new band is larger than that of the beta band.We would like to thank Dr. G. Sletten, Mr. J. Westergaard and the members of TAL, Niels Bohr Institute for their kind support. A part of this research is supported by Monbusho International Scientific Research Program (Joint Research No.01044037).