Theoretical study on vibrational circular dichroism spectra of tris(acetylacetonato)metal(III) complexes: anharmonic effects and low-lying excited states

The open-shell density functional theory calculations with M06 exchange-correlation functional and all-electron Douglas-Kroll second order scalar relativistic correction were performed to interpret the vibrational circular dichroism (VCD) spectra of four kinds of tris(acetylacetonato)metal(III), [M(III)(acac)(3)] (acac = acetylacetonato, M = Ru, Cr, Co, and Rh). It was deduced that the experimental spectra were well reproduced by the calculation with harmonic approximation in case of [Co(III)(acac)(3)] (d(6); S = 0), [Rh(III)(acac)(3)] (d(6); S = 0), and [Ru(III)(acac)(3)] (d(5); S = 1/2). In case of [Cr(III)(acac)(3)] (d(3); S = 3/2), anharmonic effects should be taken into account to predict the accurate vibrational frequencies of closely located modes. Time-dependent density functional theory calculations were performed to estimate the contribution of excited states in the VCD spectra. As a consequence, the presence of the low-lying excited states was predicted for [Ru(III)(acac)(3)] alone, which agreed with the experimental observation.     

Preparation and Thermal Decomposition of Cyclic Azoamidinium Salts as Water-Soluble Radical Initiators for Polymerization over A Wide Temperature Range

Abstract

A series of cyclic azoamidinium chlorides as water-soluble initiators were prepared by reactions of the iminoether derived from 2,2′-azobisisobutyronitrile with substituted alkylene diamines. The first-order rate constants for the decomposition of the azoamidinium salts varied from 0.59 × 10^?5 to 14.1 × 10^?5 s^?1 with the ring size and the alkyl substitution of the ring. Decomposition of 2,2′-azobis[2-(imidazoline-2-yl)propane] dihydrochloride was found to be accelerated by alkyl substitution on the imidazolinium ring. However, the azoamidinium compounds having larger rings, 2,2′-azobis[2-(3,4,5-trihydropyrimi-dine-2-yl)propane] dihydrochloride and 2,2′-azobis[2-(4,5,6,7-tetra-hydro-1H-1,3-diazepine-2-yl)propane] dihydrochloride, decomposed at a slower rate than the unsubstituted azobis[2-(imidazoline-2-yl)-propane] dihydrochloride. These new initiators were found to be capable of initiating radical polymerizations of acrylamide and vinyl acetate.     

Development of determination method of trace nickel in natural water by ID-oxygen added nitrogen-MIP-MS with direct measurement of liquid–liquid extracted organic phase

This work introduces the development of a novel determination method of trace nickel (ng l^–1 level) in natural water samples. Nickel in the water samples is liquid–liquid extracted into methyl isobutyl ketone (MIBK) as nickel-diethyldithiocarbamate (DDTC) complex, and isotope dilution-oxygen added nitrogen-microwave induced plasma mass spectrometry (ID-oxygen added nitrogen-MIP-MS) is conducted by direct measurement of the liquid–liquid extracted organic MIBK phase. The accuracy of the proposed method was confirmed by analysing certified reference materials (NRC NASS-5 seawater, NRC SLRS-3 riverine water and NRC SLRS-4 river water), and the analytical results obtained were in good agreement with the certified values. The detection limit for nickel is 1.3?ng?l^?1 when the water sample is 50 times concentrated. The precision as RSD is <4%. The proposed method was applied to clarify the concentration-depth vertical profiles of nickel in Lake Mashu, Japan, as the Baseline Station of the United Nations GEMS/Water (Global Environment Monitoring System/Water) Programme.     

Studies on the drift properties and spatial resolution using a microMEGAS-equipped time projection chamber

R&D studies on the performance as well as on the gas properties of the microMEGAS-based time projection chamber with standard readout were carried out in June 2005 using 4 GeV/c pion beam in a magnetic field from 0 to 1 T at the proton synchrotron beam line at KEK, Japan. Analysis of the electron drift velocity, diffusion constant and point resolution of padrow measurement for MicroMEGAS TPC filled with 95% argon and 5% isobutane gas are presented. The underlying physical mechanism which determines the optimal TPC performance are briefly discussed. Preliminary measurements of gas properties and spatial resolution in close agreement with the analytical calculation and MAGBOLTZ simulation are summarized and presented in this paper.      

Quantitative determination of phosphatidylcholine hydroperoxides during copper oxidation of LDL and HDL by liquid chromatography/mass spectrometry

1-Palmitoyl-2-linoleoylphosphatidylcholine monohydroperoxide (PC 16:0/18:2-OOH) and 1-stearoyl-2-linoleoylphosphatidylcholine monohydroperoxide (PC 18:0/18:2-OOH) were measured by liquid chromatography/mass spectrometry (LC/MS) using nonendogenous 1-palmitoyl-2-heptadecenoylphosphatidylcholine monohydroperoxide as an internal standard. The calibration curves for synthetic PC 16:0/18:2-OOH and PC 18:0/18:2-OOH, which were obtained by direct injection of the internal standard into the LC/MS system, were linear throughout the calibration range (0.8-12.8 pmol). Within-day and between-day coefficients of variation were less than 10%, and the recoveries were between 86% and 105%. The limit of detection (LOD) and the limit of quantification (LOQ) were determined using synthetic standards. The LOD (signal-to-noise ratio 3:1) was 0.01 pmol, and the LOQ (signal-to-noise ratio 6:1) was 0.08 pmol for both PC 16:0/18:2-OOH and PC 18:0/18:2-OOH. With use of this method, the concentrations of PC 16:0/18:2-OOH and PC 18:0/18:2-OOH in the lipoprotein fractions during copper-mediated oxidation were determined. We prepared oxLDL and oxHDL by incubating native LDL and native HDL from human plasma (n = 10) with CuSO(4) for up to 4 h. The time course of the PC 16:0/18:2-OOH and PC 18:0/18:2-OOH levels during oxidation consisted of three phases. For oxidized LDL, both compounds exhibited a slow lag phase and a subsequent rapidly increasing propagation phase, followed by a gradually decreasing degradation phase. In contrast, for oxidized HDL, both compounds initially exhibited a prompt propagation phase with a subsequent plateau phase, followed by a rapid degradation phase. The analytical LC/MS method for phosphatidylcholine hydroperoxides might be useful for the analysis of biological samples.     

Direct and practical synthesis of 2-arylbenzoxazoles promoted by activated carbon

[reaction: see text] 2-Arylbenzoxazoles were directly synthesized from substituted 2-aminophenols and aldehydes in the presence of activated carbon (Darco KB) in xylene under an oxygen atmosphere.     

Valence-delocalization of the mixed-valence oxo-centered trinuclear iron propionates [Fe 2 III FeIIO(C2H5CO2)6(py)3]npy;n=0, 1.5

Mixed-valence trinuclear iron propionates [Fe ₂ ^III Fe^IIO(C₂H₅CO₂)₆(py)₃]npy, wheren=0, 1.5, were synthesized and the structure of the pyridine-solvated complex was determined by single-crystal X-ray diffraction. Mössbauer spectra of the solvated propionate complex showed a temperature-dependent mixed-valence state related to phase transitions, reaching an almost delocalized valence state at room temperature. On the other hand, the non-solvated propionate showed a remarkable change of the spectral shape related to a phase transition, remaining in a localized valence state at higher temperatures up to room temperature.