Investigation of the electronic structure of the TCNQ-TTF system. I. TCNQ and TTF monomers and dimers in the all-valence-electron approximation

Closed-shell and DODS CNDO/2 calculations have been performed for neutral and charged TCNQ and TTF monomers and different dimers. For the sake of comparison the calculation have also performed for the corresponding TCNE molecules.The most important result obtained indicates a large splitting of the lowest unfilled level of TCNQ in going from the monomer to the stacked (TCNQ)₂ dimer. The same holds true for the HOMO level of the (TTF)₂ dimer. This indicates that one should expect a broad conduction band for the neutral poly (TCNQ) chain and a broad valence band for the neutral poly (TTF) chain. In order to test the quality of the CNDO/2 approximation scheme a comparison is attempted with existing experimental findings as well as with some MINDO results and available theoretical predictions within different approximation schemes.     

Mass spectrometric study of 4-azafluorenes

The dissociative ionization of 4-azafluorene and its methyl and phenyl derivatives was investigated. The relative intensity of the [M — CH₃]⁺ ion peak depends on the position of the CH₃ group in the 4-azafluorene ring. It was established that the loss of an RCN particle (R=H, CH₃, and C₆H₅) for unsubstituted 4-azafluorene takes place from the M⁺ and [M — H]⁺ ion, exclusively from the [M — H]⁺ ion for the methyl-substituted compounds, and from the [M — H]⁺ and [H — 2H]⁺ fragments for the phenyl-substituted derivatives. Randomization of the deuterium ions in the 9,9-d₂-4-azafluorene molecular ion was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–250, February, 1978.     

Spectres de Masse de Derives de l'Atractyloside. Determination du Nombre de Substituants par Combinaison d'Acetylation et de Silylation

Different transformations of the functions fixed on a heterocyclic molecule were made. It is thus possible to quickly determine the number of functions of each type present in the molecule: e.g. (i) all the functions are silylated and (ii) the alcohols are acetylated whilst the sulfates and acids are silylated. Mass spectra of atractylate, apoatractylate and gummiferine have been studied and the substituents are counted and enumerated.     

2-Benzopyrylium salts

The acylation of esters of 3,4-dimethoxyphenylpyruvic acid with anhydrides of aliphatic acids in the presence of 70% HClO₄ leads to the formation of 3-alkoxycarbonyl-1-alkyl-6,7-dimethoxy-2-benzopyrylium salts which, on being boiled with sodium acetate inglacial acetic acid, are converted into 3-alkoxycarbonyl-1-alkyl-6,7-dimethoxyisoquinolines.For Communication XIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1458–1460, November, 1973.     

Luminescence in some tantalate host lattices

The luminescence of the following systems are reported: ScTa_1−xNb_xO₄, Li₃Ta_1−xNb_xO₄, CaTa_2−2xNb_2xO₆ and Mg₄Ta_2−2xNb_2xO₉. The dependence of the luminescence properties on x becomes more pronounced if the distance between the pentavalent ions becomes shorter. In these systems the NbO₆ group gives an efficient blue emission at 300°K. The compound Mg₄Ta₂O₉ gives an efficient ultraviolet emission at 300°K. At 77°K both Mg₄Nb₂O₉ and Mg₄Ta₂O₉ show in addition a weaker emission peaking at wavelengths longer than the wavelength of the room temperature emission. This low-temperature emission can be excited by radiation with wavelengths longer than that of the absorption edge. The Mn²⁺ ion in Mg₄Ta₂O₉Mn acts as an efficient activator with a deep-red emission.     

Steroid Total Synthesis,Part II; (−)-17β-Hydroxy-des-A-androst-9-en-5-one

Based on the results obtained in the racemic series (part I), (—)-17β-hydroxy-des-A-androst-9-en-5-one has been synthesized, starting with (S)-(—)-5-heptanolide. The key step, viz. the condensation of (S)-(—)-7-hydroxy-1-nonen-3-one (or its amine adduct) with 2-methyl-cyclopentane-1, 3-dione involves an asymmetric induction. Model experiments with (R)-(+)-5-decanolide leading to the enantiomeric homolog of the BCD-tricyclic compound are also described.     

2-Benzopyrylium salts

The properties of 1,3-dimethyl-6,7-dialkoxy-2-benzopyrylium salts were studied. The heterocyclic oxygen atom is readily replaced by nitrogen by reaction of the 2-benzopyrylium salts with primary amines, hydrazine, phenylhydrazine, glycine ethyl ester, and hydroxylamine; reaction with secondary amines leads to naphthalene derivatives. The activities of the methyl groups in the 1 and 3 positions of the heterocyclic ring are compared.For Communication IX, see [6].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1308–1312, October, 1970.     

Carbohydrate-protein interactions at interfaces: comparison of the binding of Ricinus communis lectin to two series of synthetic glycolipids using surface plasmon resonance studies

Two C-lactosyl lipids and the related C-galactosyl lipids have been synthesised and their binding to RCA120 plant lectin was compared with a second series of thiolactosylethoxyalkanes. The interactions were measured quantitatively in real time by surface plasmon resonance (BIAcore) at a range of concentrations and temperatures from 5 to 30 degrees C. The C-galactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) bound much more weakly with a K(A) = 8.86 x 10(5) than the corresponding C-lactosyl lipid (1,3-dimethyl-5-[beta-D-galactopyranosyl-(1 --> 4)-beta-D-glucopyranosyl]-5-(4-octadecyloxybenzyl)pyrimidine-2,4,6-trione) (K(A) = 2.31 x 10(7)). The influence of the linker region of the two different series of lactosyl lipids was clearly demonstrated by the differences in the binding to RCA120 lectin. The changes in kinetic values and in the enthalpic and entropic contribution to the free energy of binding reflected the importance of the linker and the hydrocarbon anchor holding the synthetic glycolipids in the neomembrane.     

Relationship between hydration energy of zeolites and cation distribution in their crystals

A method is proposed for calculating the heat of immersion of zeolites in water from data on the composition and density of the zeolite framework. The phenomenon of localization of some of the zeolite cations in the unhydrated crystallographic positions is explained. For ferrisilicates with the ZSM-5 structure, the fraction of iron atoms in the framework has been estimated from data on the energy of hydration.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 2, pp. 174–179, March–April, 1993.     

Physicochemical aspects of the development of new functional materials based on heterosubstituted titanates of rare-earth elements with the Perovskite structure

In the example of titanates of rare-earth elements with the perovskite structure, relationships have been established for the influence of heterovalent substitution in the cation sublattices, through which the electrophysical properties within a single structural type can be controlled over a broad range, from microwave dielectrics to cationic conductors and semiconductors. V. I. Vernadskii Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine, 32/34 Akademika Palladina Prospekt, Kiev-142 252680, Ukraine. Translated from Teoretischeskaya i éksperimental'naya Khimiya, Vol. 34, No. 6, pp. 331–346, November–December, 1998.