Configurational stabilization of mixed-valence states in the star-burst tetranuclear ruthenium complex bridged with acetylene links

A new tetranuclear ruthenium complex in which a metal was bridged radially to three identical metals with acetylene links showed a mixed-valence state in cyclic voltammograms. The peak potential difference for the mixed-valence state was twice the potential difference for a mixed-valence state of the corresponding binuclear complex. This fact suggests stabilization of the mixed-valence state twice by configurational modification of redox centers. However, this is inconsistent with the prediction from the additive pair model of the redox interaction. A quantum chemical model of the redox interaction was presented, in which the potential difference was expressed by the overlap integral S and the nearest neighbor interaction energy between the reduced center and the oxidized one. Application of the theory gave a negative value of S, which demonstrated reasonably the stabilization of the mixed-valence state from a quantum chemical viewpoint.     

Stoichiometry and conformation of the azacrown moiety in sodium complexes of azacrown ethers. A Raman/IR spectroscopic study. Part I: Complexes of 4,13-Diaza-18-crown-6

Three sodium complexes (bromide, iodide and thiocyanate) of 4,13-diaza-18-crown-6 were studied using Raman and IR spectroscopy and normal coordinate calculations to probe the stoichiometry of the complexes and the variation in the conformation of azacrown moiety on complex formation. complex formation is accompanied by characteristic shifts of the bands, especially of those in the 800–900 cm^–1 region. Complexes of both 11 and 21 stoichiometry were observed. Normal coordinate calculations showed the reduction of symmetry of azacrown moiety toC _i , in contrast to theC _2h symmetry known for the parent azacrown and potassium thiocyanate complex.     

Efficient photocleavage of DNA utilising water-soluble lipid membrane-incorporated [60]fullerenes prepared using a [60]fullerene exchange method

Various types of lipid membrane-incorporated C60 with high C60 concentrations can be prepared easily in several hours using the C60 exchange method and the photocleaving activity of cationic lipid membrane-incorporated C60 was appreciably higher than that of the C60.gamma-CDx complex.     

Photodissociation spectrum of cyanobenzene dimer cation. Absence of intermolecular resonance interaction

Electronic spectra of a homo-molecular dimer cation, (C₆H₅CN)₂ ⁺, are measured by photodissociation spectroscopy in the gas phase. Broad features appeared in the 450–650 nm region are characteristic of π₃ → π_CN transitions of the C₆H₅CN⁺ chromophore. No intense band is observed in the 650–1300 nm region, where other aromatic dimer cations usually show charge resonance bands. Two component molecules of (C₆H₅CN)₂ ⁺ cannot take a parallel sandwich configuration suitable for the resonance interaction, because of geometrical constraints due to other stronger interactions.     

Effect of omega-hydrogenation on the adsorption of fluorononanols at the hexane/water interface: Temperature effect on the adsorption of fluorononanols

The interfacial tensions (gamma) of the hexane solutions of 1H,1H-perfluorononanol (FDFC9OH) and its omega-hydrogenated analogue 1H,1H,9H-perfluorononanol (HDFC9OH) against water were measured as a function of temperature and concentration under atmospheric pressure in order to know the effect of omega-dipoles on the adsorption behavior of fluorononanols. The interfacial pressure (pi) versus mean area per adsorbed molecule (A) curves consist of two discontinuous changes among three different states: the gaseous, expanded, and condensed states. The A values at given pi in the gaseous and expanded states are larger for HDFC9OH than for FDFC9OH. The changes in partial molar entropy (s1(H) - s1(O)) and energy (u1(H) - u1(O)) of adsorption were evaluated. Their values are negative, and therefore, the alcohols have a smaller entropy and energy at the interface than in the bulk solution. Furthermore, the u1(H) - u1(O) value is more negative for HDFC9OH than for FDFC9OH in the expanded state and also in the condensed film just above the expanded-condensed phase transition point. This seems to be due to the following: (1) HDFC9OH may tilt from interface normal for omega-dipoles to interact effectively with water molecules in the interfacial region and to reduce their own repulsive interaction between neighbors arranging parallel in the adsorbed film. This leads to a lower value for HDFC9OH than for FDFC9OH. (2) The contact of omega-dipoles with hexane molecules in the bulk solution is energetically unfavorable, and thus, the u1(O) value of HDFC9OH is expected to be larger than that of FDFC9OH.     

A method to circumvent the lot number of activated carbon affecting the performance of activated carbon silica gel columns used for cleanup of blood samples for analysis of 29 hazardous organochlorine compounds

We have previously described the use of a tandem simplified multilayer silica gel-activated carbon dispersed silica gel (TS-ML-AC) column for the cleanup of blood samples for the analysis of 29 hazardous organochlorine compounds (OCs)--the 17 major polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) and 4 non-ortho- and 8 mono-ortho-polychlorinated biphenyls (PCBs). We noted that the performance of the activated carbon-silica gel (ACS) column (lower column) varied with the lot number of the ACS. In this study, we compared the elution profiles of OCs eluted on 5 ACS columns, each with a different ACS lot number, and found that only mono-ortho-PCBs #114 and #123 were affected by lot number. The problem was that the 50 ml of n-hexane required to elute all the OCs from the simplified multilayer silica gel (MLS) column (upper column) into the AC column (lower column) also eluted varying amounts of PCBs #114 and #123 from the ACS column by ACS lot number. Although we could prevent PCBs #114 and #123 from being eluted from the ACS column by reducing the n-hexane volume to 10 ml, this volume was not sufficient to elute all the OCs from the MLS column. We solved this by separating the two columns; the sample solution was eluted with 50 ml of n-hexane from the MLS column, this eluate was concentrated to about 0.3 ml using a rotary evaporator, and then the concentrated solution was cleaned up on the ACS column. The recovery rates of #114 and #123 from blood samples were above 70% and the relative standard deviations of their concentration were below 10%, irrespective of the lot number, compared with recovery rates of 45-79% for #114 and 59-89% for #123, and relative standard deviations of their concentration above 15% when 50 ml of n-hexane was run through the tandem column. Our modified method affords reliable and reproducible cleanup of blood samples for analysis of 29 OCs, irrespective of the ACS lot number.     

Synthesis of phenyl arsenic analytical standards related to contaminated well water in Kamisu,Ibaraki, Japan

To facilitate, by the provision of internal standards, the liquid chromatographic and mass spectrometric analysis of diphenylarsinic acid in well water and other samples related to an incident of environmental contamination in Kamisu, Ibaraki, Japan, syntheses of the analogous perdeuterated and mono‐meta‐ and di‐meta‐methylated acids were undertaken. The acids were synthesized by cleavage of the triarylarsines by sodium in liquid ammonia. The triarylarsines were made from the reaction of arsenous chloride and sodium with the appropriate aryl‐bromo compound. Properties of the compounds are given. Copyright © 2005 John Wiley & Sons, Ltd.     

Quantification of ultrasonic intensity based on the decomposition reaction of porphyrin

A simple method is proposed for quantification of the effective ultrasonic intensity in the reaction vessel based on the decomposition reaction of 5,10,15,20-tetrakis(4-sulfotophenyl) porphyrin (H₂TPPS⁴⁻). The change of concentration of porphyrin in solution irradiated by the ultrasound wave depends on the irradiation time and the output power of ultrasound generator. The decomposition ratio of porphyrin is defined as the ratio of the concentration of porphyrin after ultrasonic irradiation to that before ultrasonic irradiation. A linear relationship between the decomposition ratio of porphyrin and the concentration Fe³⁺ in the Fricke solution under sonication was obtained. The decomposition ratio was related to the absorption dose in radiation chemistry.