CNDO/S-CI calculation of Hubbard parameters for doubly charged TCNQ tetramer

Using the CNDO/S-CI method the energies of the low-lying singlets and triplets of a doubly charged tetramer of TCNQ in the eclipsed geometry were calculated. The exact solution of the nearest-neighbour-version of the EHH for the case of two electrons and four sites was found. Fitting the EHH energy levels on the CNDO/S-CI spectra, the Hubbard parameters were estimated:U ₀=2.50 eV,V ₁=0.71 eV, ¦t¦=0.32 eV. The effect of strong correlation of the unpaired electrons on the electronic distribution in the ground and optically excited states of the tetramer is discussed.Dedicated to Professor Miroslav Trlifaj on the occasion of his sixtieth birthday.     

Elastic constants of the alloys Cd1−x Zn x (x<0.3%) and their temperature dependence

The temperature dependence of elastic constants of Cd_1–x Zn _x alloys, havingx=0.021, 0·042 and 0·233 at.%, has been measured in the temperature range from 4·2 to 300 K by the pulse-echo-overlap ultrasonic method. The adiabatic compressibilities and the Debye temperatures have been calculated. All elastic constants with the exception ofc ₄₄ increase slightly with the growing concentration of Zn.The summary of this paper was presented on the 7^th Conference on Ultrasonic Methods in ilina, September 11^th–13^th, 1980.     

Investigation of the products of the oxidation of gossypol structure of gossindan

A new compound, which we have called gossindan, has been isolated from the products of the oxidation of gossypol by oxygen in an alkaline medium. The structure of gossindan has been established on the basis of a study of IR, mass, PMR, and¹³C NMR spectra and x-ray structural analysis as 6,6-di-(2,7-dihydroxy-3-isopropyl-5-methylindan-1-one).A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 50–58, January–February, 1994.     

Processes in a Nickel-Zinc Battery with a Negative Electrode Containing a Calcium Hydroxide Additive

The influence exerted by a calcium hydroxide additive introduced into the negative electrode on the serviceability of a sealed nickel-zinc battery with a nickel oxide electrode fabricated from spherical nickel hydroxide on a foamed-nickel support was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 428–432.Original Russian Text Copyright © 2005 by Arkhangel’skaya, Krasnobryzhii, Kas’yan, Loginova, Vinogradova.     

Reaction of γ-nitroketones and methyl 4-nitrobutanoates with formaldehyde and primary amines

5-Nitropentan-2-one reacts with methylamine and formaldehyde according to the Mannich reaction pattern to give 5-hexahydropyrimidinylcarbonyl-substituted 1-nitro-3,7-diazabicyclo[3.3.1]nonane in one experimental stage. When methyl 3-R-4-nitrobutanoates are used, the reaction stops after the formation of substituted 5-nitrohexahydropyrimidines in 40–98% yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1687–1693, July, 2005.     

Flotation-spectrophotometric method for determining palladium by means of the ion-association complex of pentabromopalladate(II) with Rhodamine 6G

The conditions for the formation of a suitable coloured palladium ion-association complex with a basic dye have been examined, and a spectrophotometric method developed for the determination of palladium with bromide and Rhodamine 6G (R6G). Benzene is used for flotation and dimethylformamide for dissolution of the ion-association complex. The molar absorptivity is 3.0 x 10(5) l. mole(-1).cm(-1) at 53Onm. Beer's law is obeyed up to a palladium concentration of 0.3 mug/ml. The composition of the complex is [R6G(+)](3)[PdBr(3-)(5)]. Platinum interferes severely but other platinum metals interfere to a lesser degree. The method has been applied to the determination of traces of palladium in metallic platinum after a preliminary separation with nickel dimethylglyoximate as collector.     

π-facial interactions between Cl and [S4N3]. X-ray crystal structure of [S4N3]Cl

The X-ray structure of [S₄N₃]Cl reveals three independent molecules, which all display π-facial interactions between the Cl⁻ and the pseudo-aromatic [S₄N₃]⁺ rings to produce a structure containing “inverse sandwich” systems.     

Simultaneous analysis of tea catechins, caffeine, gallic acid, theanine and ascorbic acid by micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatography (MEKC) method for the simultaneous analysis of five tea catechins, theanine, caffeine, gallic acid and ascorbic acid has been developed. The catechins are (-)-epicatechin, (+)-catechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate. p-Nitrophenol serves as both reference and internal standard. All the components are separated within 13 min with a 57 cm uncoated fused-silica column. On-column detection was carried out at 200 nm. This method has been used to measure these compounds in fresh tea leaves and tea liquor. The limit of detection for all analytes ranged from 1 to 20 microg/ml.     

Capillary electrophoresis separation of vinpocetine and related compounds: prediction of electrophoretic mobilities in partly aqueous media

Offord's equation, a relationship between electrophoretic mobility and charge, size and shape of peptides, has been extended to quantitate the electrophoretic mobility of vinca alkaloids. Partly aqueous protonation constants and the derived theoretical mobilities have been proven to be able to predict experimental electrophoretic mobilities. In practice, seven vincamine derivatives of very low water-solubility were separated by capillary electrophoresis. Buffer total concentration, apparent pH and methanol content, the three most important parameters of the running buffer, were used in triangular resolution mapping to characterize separation. Even though electrophoresis is well known to slow down in partly aqueous media, under our optimized circumstances a baseline separation was achieved within 8 min in each case.     

Anti-oxidant and pro-oxidant reactivities of copper(II), manganese(II) and iron(III) 3,5-di-<Emphasis Type="Italic">i</Emphasis>-propylsalicylate chelates during peroxidation of alkylbenzenes

Bioactive copper(II), iron(III), and manganese(II) 3,5-di-i-propylsalicylate (3,5-DIPS) chelates were investigated in order to determine their ability to inhibit the free radical initiated chain reactions leading to the peroxidation of isopropylbenzene (i-PrPh) and ethylbenzene (EtPh). Quantitative kinetic studies of these chelates established the following order of anti-oxidant reactivities: manganese(II)-(3,5-DIPS)₂>iron(III)(3,5-DIPS)₃>copper(II)₂(3,5-DIPS)₄> > 3,5-DIPS acid. The mechanism of anti-oxidant reactivity of these three chelates is established as being due, in part, to their chain-breaking capacity resulting from the chemical reduction of the generated peroxyl radical to yield alkybenzenelhydroperoxides via reaction of the 3,5-DIPS ligand with the peroxyl radical. In the case of manganese(II)3,5-di-i-propylsalicylate, the central metalloelement also interacts with the peroxyl radical. The manganese(II)-(3,5-DIPS)₂ and copper(II)₂(3,5-DIPS)₄ chelates were also found to exhibit alkylhydroperoxide pro-oxidative reactivity leading to the formation of the alkylbenzeneperoxyl radical. In addition, the manganese(II) atom underwent oxidation to manganese(III) with the formation of the alkylbenzenehydroperoxide or superoxide with air oxygen oxidation. Amyl acetate and dipropylamine (n-Pr₂NH) were added to the reaction mixture to model the biochemical presence of ester or amine cellular components. Addition of amyl acetate to the reaction mixture increased the anti-oxidant reactivity of manganese(II)-(3,5-DIPS)₂ while decreasing its pro-oxidant reactivity. The weaker anti-oxidant reactivites of iron(III)(3,5-DIPS)₃ and copper(II)₂(3,5-DIPS)₄ were less affected by the addition of amyl acetate and the pro-oxidant reactivity of copper(II)₂(3,5-DIPS)₄ was not changed by the addition of amyl acetate, while the pro-oxidant property of iron(III)(3,5-DIPS)₃ was eliminated. In contrast to 2,6-di-t-butyl-4-methylphenol, butylated hydroxy toluene (BHT), anti-oxidant reactivities of copper(II), iron(III), and manganese(II) 3,5-DIPS chelates were dramatically enhanced by the addition of n-Pr₂NH to the reaction mixture. It is concluded that all three metalloelement chelates react with and remove alkylbenzeneperoxyl radicals and the hydroperoxyl radical. The manganese(II)-(3,5-DIPS)₂ and copper(II)₂(3,5-DIPS)₄ chelates may also be useful in removing hydroperoxides in vivo. These reactivities, in addition to their established superoxide dismutase (SOD)-mimetic and catalase-mimetic reactivities, are suggested to possibly permit anti-oxidant and pro-oxidant reactivities in aqueous and organic cellular compartments.