Effects of X-rays on the electrical conductivity of liquid organic photoconductors

X-rays (wavelength 1.5 Å) alter the conductivity of methyl and phenyl halides (alone or in solution in diethyl ether) provided that the mixture contains some benzene rings. The effect is compared with the photoconductivity in these systems, and it is concluded that the metastable trapping sites for the electrons may be molecules of either halide or of the ether. A scheme is proposed to explain the trend in the photoconductivity; a kinetic equation is shown to fit the data.These tests were done to establish the mode of metastable electron attachment responsible for photoconductivity in liquid organic semiconductors based on diethyl ether containing methyl and phenyl halides. The trends in the positive and negative photoconductivities and other features indicate that electron processes predominate [1–6]. A model has been developed, and an equation in good agreement with experiment has been compiled. The detailed site of metastable attachment of the electron has been deduced on the basis that the halogen atoms act as acceptors, the electron being released from a R-H -bond and thereby increasing the concentrations of metastable electrons and holes, the latter being one-electron R-H bonds, or rather an electron deficit distributed evenly between identical bonds (as in It is considered that tunneling from one radical to another provides the hole conduction, if the large molecular ions are less mobile than the holes. The observed linear recombination is explained via universal combination of an electron with a hole after detachment from its site of metastable attachment. The formal model is in complete agreement with the observations, but there is no experimental evidence for the site of attachment of the electrons. X-rays have been used to elucidate this.     

Native and modified glucose oxidase in reversed micelles

The enzymatic activity of the native and modified glucose oxidase (GOx) from Aspergillus niger in the system of reversed micelles of Aerosol OT in octane was investigated. Two forms of the modified enzyme were studied: a hydrophobized form obtained by the attachment of palmitic chains to lysine amino groups by the reaction with palmitic acid ester of N-hydroxysuccinimide and a glycosylated (hydrophilized) form obtained by the attachment of the cellobiose moieties. The native glucose oxidase and its derivatives, while incorporated into micelles in a surfactant concentration range from 0.05 to 0.3 M, display an enzymatic activity, which is comparable with the activity in aqueous solution. The dependence of the enzymatic activity on hydration degree of surfactant (the molar ratio of water to surfactant, W₀) does not indicate the formation of qualitatively new associated forms of the enzyme subunits inside the micelles. The apparent size of Aerosol OT micelles obtained by dynamic light scattering gradually increases from 10±3 nm at low W₀ up to 25±5 nm at high W₀. Incorporation of the native and hydrophobized glucose oxidase into micelles does not affect their mean size. Kinetic analysis shows that the enzyme specificity is about an order of magnitude greater in the system of reversed micelles as compared with aqueous solution.     

The dehydrogenation of isopropanol on a nickel-manganese catalyst subjected to treatment in glow-discharge oxygen,argon, and hydrogen plasmas

The dependence of the activity of the (Ni 20 wt %-Mn 4 wt %)/SiO₂ catalyst on the treatment of its surface in glow-discharge oxygen, argon, and hydrogen plasmas was studied. Catalytic experiments were performed in a flow reactor and under static conditions in a vacuum. The highest activity was observed after catalyst treatment in an argon plasma. Glow-discharge plasma treatment changed the structure and number of active centers, which resulted in a change in the reaction mechanism. Ab initio quantum-chemical calculations were performed using the Hartree-Fock (UHF) method for the Ni₅ cluster. The results substantiated the suggested that the active center contained the hydrogen atom.     

Synthesis of 2-amino-4H-3,1-benzoxazines and 2-amino-4H-3,1-benzothiazines by the rearrangement of <Emphasis Type="Italic">o</Emphasis>-cyclopropylphenylureas and <Emphasis Type="Italic">o</Emphasis>-cyclopropylphenylthioureas

Syntheses are reported for 2-cyclopropylphenylureas and 2-cyclopropylphenylthioureas and the behavior of these compounds was studied under conditions for the acid-catalyzed opening of the cyclopropyl ring. Upon the action of concentrated sulfuric acid or trifluoroacetic acid, these ureas and thioureas can undergo rearrangement to the corresponding 3,1-benzoxazines and 3,1-benzothiazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 115–126, January, 2008.     

Molecular structure of 1-methyl-1-fluoroquasisilatrane (2-methyl-2-fluoro-1,3-dioxa-6-aza-2-silacyclooctane)

The molecular structure of 1-methyl-1-fluoroquasisilatrane (2-methyl-2-fluoro-1,3-dioxa-6-aza-2-silacyclooctane) MeFSi(OCH₂CH₂)₂NH (I) is determined by single crystal X-ray diffraction at 100 K. The coordination polyhedron of the silicon atom in this molecule is a slightly distorted trigonal bipyramid with an NH group and a strongly electron-withdrawing fluorine atom in the axial positions, and two endocyclic oxygen atoms and a CH₃ group in three vertices of the equatorial plane. The axial angle N→SiF is 171°. The length of the transannular donor-acceptor bond N→Si (2.058 Å) is as small as in 1-fluorosilatrane. The axial bond F-Si (1.660 Å) is longer than that in 1-fluorosilatrane and tetrahedral silicon compounds.     

Isomerization of 3-unsubstituted 4,5-dihydroisoxazoles over alumina. A new synthesis of β-hydroxy nitriles

3-Unsubstituted 4,5-dihydroisoxazoles obtained by nitrosation of arylcyclopropanes are capable of undergoing efficient isomerization into 3-aryl-3-hydroxypropanenitriles during chromatography on alumina.     

Heteroleptic LaIII Anilate/Dicarboxylate Based Neutral 3D-Coordination Polymers

Three new 3D metal–organic frameworks of lanthanum based on mixed anionic ligands, [(La₂(pQ)₂(BDC)₄)·4DMF]_n, [(La₂(pQ)₂(DHBDC)₄)·4DMF]_n, [(La₂(CA)₂(BDC)₄)·4DMF]_n (pQ—dianion of 2,5-dihydroxy-3,6-di-tert-butyl-para-quinone, CA—dianion of chloranilic acid, BDC-1,4-benzenedicarboxylate, DHBDC-2,5-dihydroxy-1,4-benzenedicarboxylate and DMF-N,N′-dimethylformamide), were synthesized using solvothermal methodology. Coordination polymers demonstrate the rare xah or 4,6T187 topology of a 3D framework. The homoleptic 2D-coordination polymer [(La₂(pQ)₃)·4DMF]_n was obtained as a by-product in the course of synthetic procedure optimization. The thermal stability, spectral characteristics and porosity of coordination polymers were investigated.     

69mZn-containing radiopharmaceuticals: a novel approach to molecular design

^69mZn was produced and separated for medical applications. Possibilities and perspectives for production of radiopharmaceuticals based on ^69mZn containing derivatives of thiazine, thiazoline and thiourea are considered. Each one of the latters is a zinc chelator and a nitric oxide synthase (NOS) effector at the same time. Cytotoxic effect of NOS activator and NOS inhibitors are shown in experiments with HL-60, K-562 and MOLT-4 cell lines and in bone marrow cells of the acute B-lymphoblastic leukemia patients. Some of those compounds are worthy to get selected for further application as radiopharmaceuticals including their antitumor speciements.

     

Kinetics and mechanism of the photolysis of CF<Subscript>2</Subscript>ClBr exposed to light with a wavelength of 253.7 nm

CF₂ClBr mixed with oxygen was photolyzed using a low pressure mercury lamp, and the kinetics of photolysis was studied. The absorption spectra of the starting material and products of photolysis were recorded in the wavelength range from 200 to 900 nm on an Agilent 8453 spectrophotometer. The concentrations of the main photolysis products at different irradiation times were calculated by the mathematical processing of the absorption spectra. The scheme of CF₂ClBr photolysis was suggested, the model calculations according to this scheme were performed, and the results of simulation were compared with experimental data.