Methoxide of an Anderson-type polyoxometalate and its conversion to a new type of species, [IMo9O32(OH)(OH2)3]4-

A totally new type of polyoxometalate, [IMo(9)O(32)(OH)(OH(2))(3)](4)(-), has been synthesized by reacting [IMo(6)O(22)(OMe)(2)](3)(-) with water. The [IMo(9)O(32)(OH)(OH(2))(3)](4)(-) anion further transforms into [(IMo(7)O(26))(2)](6)(-), a molecular oxide that has a rutile core, in dry acetonitrile, while it stays intact for several hours in wet acetonitrile.     

Ring transformation of 4-amino-1H-1,5-benzodiazepine-3-carbonitrile and ethyl 4-amino-1H-1,5-benzodiazepine-3-carboxylate into benzimidazole derivatives with amines

The ring contraction of 4-ammo-1H-1,5-benzodiazepine-3-carbonitrile hydrochloride 1 and ethyl 4-amino-1H-1,5-benzodiazepine-3-carboxylate hydrochloride 2 with aromatic primary amines into benzimidazole derivatives 3 and 4 was readily accomplished by heating in methanol. Benzodiazepine 1 also reacted with methylamine and ethylamine at about 40° to give ring-opened amine adducts 7 which were recyclized to 1 with hydrochloric acid.     

Self‐Assembly and Host–Guest Chemistry of a 3.5‐nm Coordination Nanotube

Upon complexation with Pd^II ions, precisely designed strandlike ligands with two tris(3,5‐pyridine) units at both terminals were assembled, with the aid of a linear template molecule, into a discrete tubular complex with a length of 3.5 nm. The high stability and the well‐defined structure of the coordination nanotube were revealed by NMR spectroscopy, cold‐spray ionization MS, and single‐crystal X‐ray analysis. Guest lengths were discriminated by the tube: When the association of strandlike guest molecules, in which two biphenylene units are linked with an (OCH₂CH₂)_n linker, were compared, the tube selectively recognized an appropriate guest whose length was comparable to that of the tube. Tetrathiafulvalene (TTF)‐terminated linear guests were directly oxidized to TTF²⁺ in the tube, but reduced stepwise via TTF^+? outside the tube.     

Enhancement of initial permeability due to Mn substitution in polycrystalline Ni0.50−xMnxZn0.50Fe2O4

The structural and magnetic properties of Mn substituted Ni_0.50−xMn_xZn_0.50Fe₂O₄ (where x=0.00, 0.10 and 0.20) sintered at various temperatures have been investigated thoroughly. The lattice parameter, average grain size and initial permeability increase with Mn substitution. Both bulk density and initial permeability increase with increasing sintering temperature from 1250 to 1300 °C and above 1300 °C they decrease. The Ni_0.30Mn_0.20Zn_0.50Fe₂O₄ sintered at 1300 °C shows the highest relative quality factor and highest initial permeability among the studied samples. The initial permeability strongly depends on average grain size and intragranular porosity. From the magnetization as a function of applied magnetic field, M(H), it is clear that at room temperature all samples are in ferrimagnetic state. The number of Bohr magneton, n(μ_B), and Neel temperature, T_N, decrease with increasing Mn substitution. It is found that Mn substitution in Ni_0.50−xMn_xZn_0.50Fe₂O₄ (where x=0.20) decreases the Neel temperature by 25% but increases the initial permeability by 76%. Possible explanation for the observed characteristics of microstructure, initial permeability, DC magnetization and Neel temperature of the studied samples are discussed.     

(IMo(7)O(26))(2)](6)(-): A missing link between molecular and solid oxides

A new molecular oxide, [(IMo(7)O(26))(2)](6)(-), that has a self-contained structure has been synthesized. Its structural relevance both to the rutile structure and several molecular oxides that had been classified as "strange ones with odd structures" has given some insights as to why those species assume such structures. The novel yet self-contained nature of the structure suggests the existence of a new class of molecular oxides of related structures.     

A 3.5-nm coordination nanotube

A 3.5-nm coordination nanotube was self-assembled from 12 Pd(II) ions and four tape-shaped ligands with the aid of a 3.0-nm template. This tubular structure was unambiguously determined by the single-crystal X-ray analysis. Being cooperatively sustained by 24 Pd(II)-pyridine interactions, the framework was kinetically stable even when the template was removed. The empty tube was, of course, capable of binding other molecules in the cavity.     

Scanning tunneling microscopy and molecular orbital calculation of pentacene molecules adsorbed on the Si(100)2×1 surface

Adsorption of the organic molecule pentacene on Si(100)2×1 surfaces was imaged using scanning tunneling microscopy (STM). The molecular images exhibit distinct shapes corresponding to the expected shapes for adsorption configurations. Semi-empirical molecular orbital (MO) calculations reveal a local surface density of states for the adsorbed pentacene on the Si surface. In the cases where the pentacene molecule is adsorbed on an Si dimer row, the calculated MOs are in good agreement with the molecular images observed in STM. In the case of pentacene adsorbed on two or three Si-dimer rows, however, the MOs of the pentacene do not correlate directly with the observed STM images. It is thus considered that the STM images are produced by a combination of Si dimer states and MO.     

Electrical detection of single methylcytosines in a DNA oligomer

We report label-free electrical detections of chemically modified nucleobases in a DNA using a nucleotide-sized electrode gap. We found that methyl substitution contributes to increase the tunneling conductance of deoxycytidines, which was attributed to a shift of the highest occupied molecular orbital level closer to the electrode Fermi level by methylation. We also demonstrate statistical identifications of methylcytosines in an oligonucleotide by tunneling current. This result suggests a possible use of the transverse electron-transport method for a methylation level analysis.     

CHEMISTRY OF 1,3-OXAZINE-6-THIONES. RING TRANSFORMATION

Abstract

Two 1,3-oxazine-6-thione derivatives obtained by “S,N-Double Rearrangement²” reacted with several nucleophiles to produce 1,3-diazin-6-ones, 6-imino-1,3-oxazines, 1,3,4-triazoles, 1,2,4-oxadiazoles, and 1,3-thiazol-6-ones. Their ring transformations are discussed.     

Effect of the heterointerface on transport properties of in situ formed MgO/titanate heterostructured nanowires

Heterostructured transition metal oxide nanowires are potential candidates to incorporate rich functionalities into nanowire-based devices. Although the oxide heterointerface plays a crucial role in determining the physical properties, the effects of the heterointerface on the oxide nanowire's properties have not been clarified. Here we investigate for the first time the significant role of the heterointerface in determining the transport properties of well-defined MgO/titanate heterostructured nanowires by combining a technique for in situ formation of a oxide heterointerface and microwave conductivity measurement. Variation of the heterointerface strongly affects the nanowire's transport properties due to the crystallinity and the atomic interdiffusion at the oxide heterointerface. Thus, the precise in situ formation of a well-defined heterointerface is crucial to create oxide heterostructured nanowires with the desired transport properties.