Electrophilic behavior of the pi delocalized azepinium ion: Friedel-Crafts reactions with benzenes and five-membered aromatic heterocycles

[reaction: see text] Although the reactivity of tropylium ion with aromatic substrates is low, the reaction of azepinium ion with aromatic substrates such as benzene, phenol, furan, and thiophene resulted in the formation of 2-aryl-2H-azepine as a major product. An exceptional result in the formation of ring-contracted product was observed in the reaction with pyrrole.     

Synthesis and reactivity of a (mu-1,1-hydroperoxo)(mu-hydroxo)dicopper(II) complex: ligand hydroxylation by a bridging hydroperoxo ligand

A new tetradentate tripodal ligand (L3) containing sterically bulky imidazolyl groups was synthesized, where L3 is tris(1-methyl-2-phenyl-4-imidazolylmethyl)amine. Reaction of a bis(mu-hydroxo)dicopper(II) complex, [Cu2(L3)2(OH)2]2+ (1), with H2O2 in acetonitrile at -40 degrees C generated a (mu-1,1-hydroperoxo)dicopper(II) complex [Cu2(L3)2(OOH)(OH)]2+ (2), which was characterized by various physicochemical measurements including X-ray crystallography. The crystal structure of 2 revealed that the complex cation has a Cu2(mu-1,1-OOH)(mu-OH) core and each copper has a square pyramidal structure having an N3O2 donor set with a weak ligation of a tertiary amine nitrogen in the apex. Consequently, one pendant arm of L3 in 2 is free from coordination, which produces a hydrophobic cavity around the Cu2(mu-1,1-OOH)(mu-OH) core. The hydrophobic cavity is preserved by hydrogen bondings between the hydroperoxide and the imidazole nitrogen of an uncoordinated pendant arm in one side and the hydroxide and the imidazole nitrogen of an uncoordinated pendant arm in the other side. The hydrophobic cavity significantly suppresses the H/D and 16O/18O exchange reactions in 2 compared to that in 1 and stabilizes the Cu2(mu-1,1-OOH)(mu-OH) core against decomposition. Decomposition of 2 in acetonitrile at 0 degrees C proceeded mainly via disproportionation of the hydroperoxo ligand and reduction of 2 to [Cu(L3)]+ by hydroperoxo ligand. In contrast, decomposition of a solid sample of 2 at 60 degrees C gave a complex having a hydroxylated ligand [Cu2(L3)(L3-OH)(OH)2]2+ (2-(L3-OH)) as a main product, where L3-OH is an oxidized ligand in which one of the methylene groups of the pendant arms is hydroxylated. ESI-TOF/MS measurement showed that complex 2-(L3-OH) is stable in acetonitrile at -40 degrees C, whereas warming 2-(L3-OH) at room temperature resulted in the N-dealkylation from L3-OH to give an N-dealkylated ligand, bis(1-methyl-2-phenyl-4-imidazolylmethyl)amine (L2) in approximately 80% yield based on 2, and 1-methyl-2-phenyl-4-formylimidazole (Phim-CHO). Isotope labeling experiments confirmed that the oxygen atom in both L3-OH and Phim-CHO come from OOH. This aliphatic hydroxylation performed by 2 is in marked contrast to the arene hydroxylation reported for some (mu-1,1-hydroperoxo)dicopper(II) complexes with a xylyl linker.     

Synthesis and evaluation of novel pyrimido-acridone, -phenoxadine, and -carbazole as topoisomerase II inhibitors

As part of a series of studies to discover new topoisomerase II inhibitors, novel pyrimidoacridones, pyrimidophenoxadines, and pyrimidocarbazoles were synthesized, and in vitro and in vivo antitumor activities and DNA-protein and/or DNA-topoisomerase II cross-linking activity as an indicator of topoisomerase II-DNA cleavable complex formation were evaluated. The pyrimidocarbazoles possessed high in vitro and in vivo potencies. Compound 26 (ER-37326), 8-acetyl-2-[2-(dimethylamino)ethyl]-1H-pyrimido[5,6,1-jk]carbazole-1,3(2H)-dione, showed in vitro growth inhibitory activity with respective IC(50) values of 0.049 microM and 0.35 microM against mouse leukemia P388 and human oral cancer KB. In vivo, this compound inhibited the tumor growth of mouse sarcoma M5076 implanted into mice with T/C values of 42% and 13% at 3.13 and 6.25 mg/kg/d respectively without significantly affecting the body weight. In addition, compound 26 (ER-37326) increased the formation of DNA-topoisomerase II cross-linking in P388 cells.     

The enthalpy relaxation of amorphous Fe---Co alloys with metal-metalloid and metal-metal compositions

The enthalpy relaxation behaviour of metal-metalloid type (Fe_0.5Co_50.5)₈₃P₁₇ and metal-metal type (Fe_0.5Co_0.5) _90-Zr10 amorphous alloys was investigated with a DSC measurement. The annealing temperature (T_a) dependence of the annealing-induced reversible enthalpy relaxation evaluated with an endothermic showed the maximum at thesame T_a for the two alloys, but the magnitude of the relaxation was considerably smaller for the (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy. Moreover, it was found that the amorphous (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy has a larger atomic packing density and a higher activation energy of the enthalpy relaxation than the amorphous (Fe_0.5Co_0.5)₈₃P₁₇ alloy. Rhe small enthalpy relaxation and high activation energy for the amorphous (Fe_0.5Co_0.5)₉₀Zr₁₀ alloy were ascribed to the highly packed structure of the metal-metal type amorphous alloy.     

Photon activation analysis of iodine, thallium and uranium in environmental materials

Iodine, thallium and uranium were determined by photon activation analysis. Two electron linear accelerators were used for the analysis of several kinds of environmental, biological and geochemical reference materials under different irradiation conditions. Both analytical results for iodine were in good agreement with each other but not with literature values in the case of environmental samples. The results of thallium and uranium agreed well with their reference values. The detectable concentration levels of iodine, thallium and uranium were almost 0.3μg/g.     

Giant forced volume magnetostriction of Fe-rich iron-cobalt-zirconium amorphous alloys

The forced volume magnetostriction has been measured as a function of composition and temperature in amorphous (Fe_1?xCo_x)₉₀Zr₁₀ alloys. The maximum value of $\text{δω}\text{δH}$ (T = 0 K), equal to 285 × 10^-10 Oe^-1, has been observed for Fe₉₀Zr₁₀ alloys. The effect of pressure on the magnetization σ₀ at T = 0 K was calculated from $\text{δω}\text{δH}$ data. The pressure dependence of the Curie temperature T_c and σ₀ behaves in a similar way as those observed for crystalline NiPd and NiRh alloys.     

Selective coincidence spectrometry in the nondestructive determination of nickel in geological materials with high-energy photon activation

The combined use of photon activation and γ-γ coincidence spectrometry is described for the useful and selective nondestructive determination of nickel in geological materials. This method is characterized by the utilization of the nuclide emitting β⁺ particles in its decay and γ-γ coincidence counting with two gates: one for the annihilation photopeak region and the other for the higher Compton plateau region. The practical detection limits by this method for nickel, arsenic, rubidium, sodium and scandium in silicate matrices could be set at 2.0, 1.2, 9.0, 110 and 1.4 μg, respectively.     

Structure of amorphous Fe80-P13-C7 alloy by X-ray diffraction

In the frame of a semiclassical picture a systematic approximation scheme for the hopping-conductivity is derived which provides a classification in terms of the length of correlated hopping-chains. With the aid of an integral equation for the propagation probability of carriers and a decoupling procedure for configuration averages, conductivity is expressed by the zeroth and second moments of independently averaged contributions of paths containing less than a fixed number of hops. A sum rule allows to carry out the static limit explicitly. The lowest order conductivity reduces to a simple form which is presented for later evaluations.     

Highly Asymmetrical Porphyrins with Enhanced Push–Pull Character for Dye‐Sensitized Solar Cells

A porphyrin π‐system has been modulated by enhancing the push–pull character with highly asymmetrical substitution for dye‐sensitized solar cells for the first time. Namely, both two diarylamino moieties as a strong electron‐donating group and one carboxyphenylethynyl moiety as a strong electron‐withdrawing, anchoring group were introduced into the meso‐positions of the porphyrin core in a lower symmetrical manner. As a result of the improved light‐harvesting property as well as high electron distribution in the anchoring group of LUMO, a push–pull‐enhanced, porphyrin‐sensitized solar cell exhibited more than 10 % power conversion efficiency, which exceeded that of a representative highly efficient porphyrin (i.e., YD2)‐sensitized solar cell under optimized conditions. The rational molecular design concept based on highly asymmetric, push–pull substitution will open the possibilities of further improving cell performance in organic solar cells.