An abrupt spin transition based on short S...S contacts in a novel Fe(II) complex whose ligand contains a 1,3-dithiole ring

The first preparation of an Fe(II) spin-crossover complex including a 1,3-dithiole ligand is reported. Crystal analyses of both the low- and the high-temperature phases reveal that short S...S contacts play a key role in an abrupt spin transition.     

Psoralen-conjugated oligonucleotide with hairpin structure as a novel photo-sensitive antisense molecule

Hairpin type psoralen-cojugated oligonucleotides cross-linked with RNA when they hybridized with a perfectly complementary RNA.     

Luminescence study of tetravalent uranium in aqueous solution

The luminescence spectrum of U4+ in aqueous solution was observed in the UV-Vis region with the lifetime < 20 ns at room temperature by excitation light corresponding to the 5f-5f electronic transition. All the luminescence peaks were assigned to individual electronic transitions.     

Polarographic study on poly alpha-L-glutamic acid-Cd2+,Co2+ complexes in the helix-coil pH region

Interactions between poly alpha- L-glutamic acid (PGA) and metal ions Cd(2+), Co(2+) were studied by direct current polarography. The diffusion currents of these ions decreased sharply in the presence of PGA in the pH region from 5.0 through neutral. A corresponding increase in the helix content of the PGA-metal ion complex was revealed by CD measurements on the same solutions. Helix contents determined by polarography were in good agreement with those by CD in the neutral pH region. On the contrary, the decrease of current in lower acidic pH regions was independent of helix formation and suggested that metal ions coordinate to sporadically-dissociated carboxylate groups to cause aggregation of the intra and/or inter polymer chains. The diffusion current of the ions, therefore, is a parameter sensitive to the conformational changes of PGA from acidic through neutral pH region.     

Variety of Special Linear Systems on k-Sheeted Coverings

Irreducibility of W¹ _d (X) for d g - (k - 2) [(h + 3)/2] - h+ 1, where X is a curve of genus g which admits an odd prime degree k map onto a general curve C of genus h > 0 is proved. Also, the existence of a component of W¹ _d(X) with expected dimension on a general k-sheeted covering X over a curve C is shown.     

An improvement of the Ivanov bound

Let be a distance-regular graph of diameterd, valencyk andr=max{i|(c _i ,b _i )=(c ₁,b ₁)}. In this paper, we prove that

Muon radiolysis in alkali halides

In order to shed new light on the initial loss of muon spin polarization, or socalled missing fraction, which is commonly observed in non-metallic solids, we have studied muon-induced excitation in various alkali halides by measuring the luminescences associated with the radiative decay of the self-trapped excitons (STE). The result strongly suggests that the spin-exchange interaction between muonium and muon radiolysis products including STE's causes fast muon depolarization in those materials.     

2-Alkoxy-3-substituted-4-quinolinols from the thermal reactions of N-phenylketenimines bearing ester groups

Several ketenimines bearing ester groups were prepared and their thermal reactions gave 2-alkoxy-3-substituted-4-quinolinols VIa-e via presumed iminoketene intermediates. Subsequent oxidation of 2-alkoxy-3-(3-methylbut-2-enyl)-4-quinolinols VIc and VId provided pyranoquinolines VIIIa and VIIIb.     

Preparation of 3-bromo-2-methylfuran and 4-bromo-2-methylfuran

4-endo-5-exo-Dibromo-3-methyl-3,6-endo-oxyperhydrophthalic anhydride 3b and 4-exo-5-endo-dibro-mo-3-methyl-3,6-endo-oxyperhydrophtbalic anhydride 3c were isolated from the bromo-adducts of 3-methyl-3,6-endo-oxy-1,2,3,6-tetrahydrophthalic anhydride 2. When 3b or 3c was heated in quinoline, only 3-bromo-2-methylfuran 4 was obtained from 3b and only 4-bromo-2-methylfuran 5 from 3c.     

The palladium-catalyzed “head-to-tail” cross-coupling reaction of 1-alkenylboranes with phenyl or 1-alkenyl iodides. A novel synthesis of 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes via organoboranes

The reaction of phenyl or 1-alkenyl iodides with 1-alkenyl-1,3,2-benzodioxaboroles readily obtainable via the hydroboration of 1-alkynes, gives the corresponding “head-to-tail” cross-coupling products, 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes, in good yields. The reaction is effectively catalyzed by catalytic amounts of palladium compounds in the presence of triethylamine.