Extended Open-Chain Polyenides as Versatile Delocalized Anion Ligands for Metal Chain Clusters

Although small cyclic- and open-chain unsaturated hydrocarbon anions such as cyclopentadienide and open-chain pentadienide are used as the strongly electron-donating auxiliary ligands for metal complexes, more extended π-conjugated unsaturated hydrocarbon anions have rarely been used in coordination chemistry, despite their potential ability to serve as the multiply bridging π-ligands for metal clusters. This work reports isolation of metal chain clusters bearing the multi-dentate, open-chain extended unsaturated hydrocarbon anion ligands. The extended open-chain π-conjugated polyenyl ligands could effectively stabilize oxidized palladium chains, including an unprecedented [Pd₄]⁴⁺ chain.     

Charge density study under high pressure

The experimental and analytical method of the high-pressure powder experiment at BL10XU, SPring-8, is described. There is no doubt that BL10XU must be one of the most appropriate beam lines for high pressure X-ray diffraction experiment taking advantage of third generation synchrotron source. As an example of the advanced charge density study under high pressure, the structural change of Cs₂Au₂Br₆ by applying pressure is studied by Rietveld/MEM analysis. It reveals that the structural change of Cs₂Au₂Br₆ by applying pressure occurs basically at electron level, such as valence state change and chemical bonding, which may be called the electronic phase transition.     

Preparation and Properties of Anti-Reflection/Anti-Static Thin Films for Cathode Ray Tubes Prepared by Sol-Gel Method Using Photoirradiation

A new technique for preparing anti-reflection/anti-static thin films for CRTs at low temperature has been developed. Double-layered films of SiO₂/SnO₂ were formed on a CRT panel surface by the sol-gel method using photoirradiation. The new method makes it possible to reduce heat treatment temperature (°C) by almost 50% and treatment time to approximately 33% of the conventional levels.     

ALFALFA SEEDLINGS GROWN OUTDOORS ARE MORE RESISTANT TO UV-INDUCED DNA DAMAGE THAN PLANTS GROWN IN A UV-FREE ENVIRONMENTAL CHAMBER

Abstract The relative UV sensitivities of alfalfa seedlings grown outdoors versus plants grown in a growth chamber under UV-filtered cool white fluorescent bulbs have been determined using three criteria: (1) level of endogenous DNA damage as sites for the UV endonuclease from Micrococcus luteus . (2) susceptibility to pyrimidine dimer induction by a UV challenge exposure and (3) ability to repair UV-induced damage. We find that outdoor-grown plants contain approximately equal frequencies of endogenous DNA damages, are less susceptible to dimer induction by a challenge exposure of broad-spectrum UV and photorepair dimers more rapidly than plants grown in an environmental chamber under cool white fluorescent lamps plus a filter that removes most UV radiation. These data suggest that plants grown in a natural environment would be less sensitive to UVB-induced damage than would be predicted on the basis of studies on plants grown under minimum UV.     

Dehydrogenation of ethylbenzene with CO2 over Cr-MCM-41 catalyst

M-MCM-41 catalysts (M: V, Cr, Fe, and Ga) prepared by direct hydrothermal synthesis (DHT) have been tested for dehydrogenation of ethylbenzene with CO₂. The synthesized materials were characterized by X-ray diffraction (XRD), N₂ adsorption (77 K), and diffuse reflectance UV–vis spectroscopic measurements. Cr-MCM-41 showed the highest activity among M-MCM-41 catalysts tested, resulting in the production of styrene with the conversion of 65% and the selectivity above 90%. The rate of styrene formation increased with increasing Cr loading up to 1.7 wt.%. It is suggested that Cr(VI)O₄ in tetrahedral coordination is formed as an active monochromate species and reduced to Cr(III)O₆ in octahedral coordination as a less active polychromate species during the reaction. Deactivated catalyst was regenerated by a treatment with gaseous oxygen or CO₂, during which redistribution as well as reoxidation of polymeric Cr(III)O₆ octahedra to monomeric Cr(VI)O₄ tetrahedra was observed. The rate of CO formation increased together with that of styrene formation, while the rate of H₂ formation decreased, with increasing partial pressure of CO₂. It was confirmed that reverse water-gas shift reaction took place over Cr-MCM-41 by a separate experiment. The rate of CO formation during the dehydrogenation of ethylbenzene with CO₂ over Cr-MCM-41 was well accounted for by assuming parallel occurrence of two reactions, i.e., direct oxidative dehydrogenation of ethylbenzene with CO₂ and simple dehydrogenation of ethylbenzene thermodynamically assisted by reverse water-gas shift reaction.     

DNA topology on an increase in positive writhing number of DNA: conformation changes in the time course of cis-diamminedichloroplatinum(II)-DNA adducts

We show that the topological significance of the gel mobility of cis-diamminedichloroplatinum(II) (DDP)-closed circular DNA (ccDNA) adducts decreases with reaction time, until a point at which it joins relaxed DNA, and that the mobility of the adducts increases again. There is no relationship between the relative length of the adducts and the gel mobility. Although the significance of the decrease of gel mobility is due to the unwinding of cis-DDP-DNA (or trans-DDP-DNA) adducts, the conformational significance of the subsequent increase in mobility is unclear. To elucidate the conformational significance for unwinding of the adducts, we measured the writhing number (Wk) of the adducts using electron microscopy and analyzed the topological states of cis-DDP (or trans-DDP) adducts based on the White rule, Lk=Wk+Tk. Where, Lk and Tk represent the linking and twisting number in the ring, respectively. From the data, we found that the Wk of cis-DDP-ccDNA adducts in comparison with trans-DDP-ccDNA adducts increases from a negative to a positive number with time. This suggests that cis-DDP plays a role in the change of the topological state of ccDNA. In the abstraction of platinum from the adducts with CN- ion, the differences in both topological states may explain why Pt in trans-DDP is abstracted more easily than in cis-DDP. To explain the abstraction of Pt ion, we also discuss the findings based on the thermodynamic cycle in a intermolecular crosslink model Pt(NH3)2(guanine)2(2+)-->Pt(CN)4(2-) using the Pt parametrized PM3 method.