Nonstoichiometry and defects in V2O3

The structural mechanism which accommodates nonstoichiometry in V₂O₃ was investigated by transmission electron microscopy. The existence of distinct diffuse scattering was observed as the boundary of the homogeneity range was approached. The analysis of the diffuse scattering indicates the formation of one-dimensional microdomains in the c direction having a structure similar to VO₂. Orientation relations between V₂O₃ and V₃O₅ (which is formed from V₂O₃ by heat treatment in an oxidizing atmosphere) show that V₃O₅ is formed by redistribution of vanadium ions among the octahedral interstitial sites of common close-packed sublattice consisting of oxygen ions. Possible relations between the present observations and physical properties in nonstoichiometric V₂O_3+x are discussed.     

Synthesis of 23,23-difluoro-25-hydroxyvitamin D3

23,23-Difluoro-25-hydroxyvitamin D₃ was synthesized from 6β-methoxy-3α,5-cyclo-23,24-dinor-5α-cholan-22-ol.     

Reactive fiber. V. Preparation and polymerization of p-styrenesulfonyl (β-chloroethyl)amide

p-Styrenesulfonyl(β-chloroethyl)amide (III) was prepared and copolymerized with styrene (M₁). The monomer reactivity ratios were determined (r₁ = 0.25 = 0.1, r₂ = 1.25 ± 0.25), and Q and e values were calculated (1.69 and 0.28, respectively). The polymer reacts with nucleophilic reagents such as amines and phenols in the presence of pyridine to the extent of 15–98%. Fibers from copolymers of acrylonitrile and III react with Congo Red in the presence of pyridine.     

The effects of Lewis acid on the 1,3-dipolar cycloaddition reaction of C-arylaldonitrones with alkenes

The regio- and stereoselectivity of the 1,3-dipolar cycloaddition reactions of C-aryl-N-alkylaldonitrones (1a-e) with some alkenes were found to be affected significantly by the addition of Lewis acid. The rate of the reaction was also affected by adding the Lewis acid. In the reactions using allyl alcohol as a dipolarophile an addition of Lewis acid caused a remarkable acceleration of the reaction and a great change in the stereoselectivity. In the reactions using ethyl acrylate as a dipolarophile the regioselectivity was reversed whether the reaction was performed in the presence or the absence of Lewis acid; i.e. isoxazolidine-5-carboxylates were obtained mainly in the absence of Lewis acid although isoxazolidine-4-carboxylates were obtained mainly in the presence of Lewis acid. When the reaction of C,N-diarylaldonitrones (1k, 1m, 1n) with ethyl acrylate was carried out in the presence of Lewis acid, the cleavage of the N-O bond of the cycloadducts giving gamma-aminoalcohols was also observed besides a reverse phenomenon of regioselectivity.     

Surface/interface electronic structure in C(60) anchored aminothiolate self-assembled monolayer: an approach to molecular electronics

Electronic structure in self-assembled monolayers (SAMs) of C(60) anchored 11-amino-1-undecane thiol (C(60)-11-AUT) on Au(111) was studied by means of ultraviolet photoelectron spectroscopy and hybrid density functional theory calculations. Valence band features of the molecular conformation revealed the interface electronic structure to be dominated by sigma(S-Au), localized at the thiolate anchor to Au. Formation of a localized covalent bond as a result of hybridization between N P(z) orbital of -NH(2) group of the thiolate SAM and the pi level of C(60) resulted in a symmetry change from I(h) in C(60) to C1 in C(60)-11-AUT SAM. Appearance of low, but finite amplitude surface electronic states of bonded C(60), much beyond the Fermi level, ruled out Au-C(60) end group contact. The band gap E(g) of the SAM, determined to be 2.7 eV, was drastically reduced from the insulating alkanethiol SAMs ( approximately 8.0 eV) and fell intermediate between the C(60) ground state (N electrons, 1.6 eV) and C(60) solid (N+/-1 electrons, 3.7 eV).     

New colorimetric detection of glucose by means of electron-accepting indicators: ligand substitution of [Fe(acac)3-n(phen)n]n+ complexes triggered by electron transfer from glucose oxidase

A new colorimetric detection technique for glucose, based on electron transfer from glucose oxidase (GODred) to iron(III) acetylacetonate(acac)/phenanthroline(phen) mixed complexes, is developed. When GOD is added to an aqueous mixture that contains tris(acetylacetonato)iron(III) complex (FeIII-(acac)3), 1,10-phenanthroline (phen), and glucose, the color immediately changes from pale yellow to red. The red color originates from formation of tris(1,10-phenanthroline)iron(II) complex ([FeII(phen)3]2+). Differential pulse voltammetry indicates that cationic, mixed-ligand complexes of [Fe(acac)3-n-(phen)n]n+ are formed upon mixing the labile FeIII(acac)3 complex and phenanthroline. The cationic mixed-ligand complexes electrostatically bind to GOD (pI 4.2), and are easily reduced by electron transfer from GODred. This electron transfer is not affected by the presence of oxygen. The reduced complex [FeII(acac)3-n(phen)n](n-1)+ then undergoes rapid ligand exchange to FeII (phen)3. Formation of the colored FeII complex is repressed when the salt concentration in the mixture is increased, or when anionic bathophenanthroline disulfonate (BPS) is employed in place of phenanthroline. The use of labile metal complexes as electron acceptors would be widely applicable to the design of new biochromic detection systems.     

Electrochemical quartz crystal microbalance study of copper ad-atoms on gold and platinum electrodes Part I. Adsorption of anions in sulfuric acid

The deposition and dissolution processes of copper ad-atoms on a gold or a platinum electrode in sulfuric acid electrolyte solution were investigated by using the electrochemical quartz crystal microbalance. It was found that the weight loss in the removal of the Cu-adlayer from the Au substrate was considerably larger than that expected from Faraday's law whereas the deviation for the Pt substrate was very small. The adsorption of bisulfate or sulfate anions both on Cu ad-atoms and on the electrode substrates was discussed quantitatively. It was demonstrated that higher coverage with Cu ad-atoms and lower adsorbability with bisulfate or sulfate anions were obtained on the Pt electrode than on the Au, and these effects could be ascribed to the difference in electronegativity between Pt and Au substrates.     

Rapid selection system of strains with higher avicel degrading ability in a cellulolytic fungus,Trichoderma

We have attempted to develop an active selection system for strains that have a higher potential for Avicel degradation using haploidized conidia from colchicine-treated Trichoderma reesei Rut C-30 as a model strain. Avicel, absorbent cotton, and wood powder were used as substrates for selection. It appeared that the strains that degrade Avicel actively could be effectively selected when the solid medium containing the selection substrate and the liquid medium containing Avicel were used.     

TEM observation of the high-temperature metal-insulator transition in Cr-doped V2O3

The high-temperature metal-insulator transition in Cr-doped V₂O₃, (V_1?xCr_x)₂O₃, was investigated by TEM at a composition x = 0.006. Boundaries between the metallic phase and the insulator phase were observed between room temperature and 150°C by both heating and cooling and their crystallographic features were investigated. Boundaries are low-index planes and their orientations are such that the change of dimension by the transition in the direction parallel to the specimen surface is zero. This indicates that the orientation of the boundary is determined by the condition of minimum strain energy. Misfit dislocations parallel to the specimen surface were found to exist under this condition. The motion of the boundaries is fast, but the boundaries can be trapped by defects or at those places where the area of boundaries becomes minimum. The observation is consistent with the existence of the temperature hysteresis of the transition and the discontinuous change of the resistivity-temperature curve of this transition.     

Conjugate addition of alkyl groups to α,β-unsaturated sulfoxides via Michael addition of nitroparaffins and subsequent denitration with tributyltin hydride

Michael addition of nitroparaffins to α,β-unsaturated sulfoxides is well effected in the presence of DBU. The nitro group in the adduct is replaced by hydrogen with Bu₃SnH without influence to the sulfinyl function. The overall reations provide an efficient method for the conjugate addition of alkyl groups to α,β-unsaturated sulfoxides.