High-pressure phase behaviour of the binary system {CO2 + cis-decalin} from (292.75 to 373.75) K

The phase behaviour of the {CO₂ (1) + cis-decalin (2)} binary system has been experimentally studied at temperatures ranging from (292.75 to 373.75) K. Saturation pressures, ranging from (15.9 to 490.5) bar, were obtained using a variable volume high-pressure cell by visual observation of phase transitions at constant overall composition. For this system, no literature data are available and the results obtained in this study reveal the occurrence of vapor–liquid, liquid–liquid, and vapor–liquid–liquid phase transitions in the investigated temperature range. A total of 133 experimental points are reported including bubble points, dew points, liquid–liquid phase equilibria, and coordinates of the three-phase line. The experimental data can be reasonably predicted by the PPR78 model in which the temperature-dependent binary interaction parameter is calculated by a group contribution method.     

Holmium porphyrin compound liquid crystals: Synthesis and properties

5,10,15,20-Tetra-[(p-alkoxy-m-ethyloxy)phenyl]porphyrin and [5-(p-alkoxy)phenyl-10,15,20-tri-phenyl]porphyrin and their holmium(III) complexes are reported. They display a hexagonal columnar discotic columnar (Col_h) liquid crystal phase and were studied by cyclic voltammetry, surface photovoltage spectroscopy (SPS), electric-field-induced surface photovoltage spectroscopy (EFISPS) and luminescence spectroscopy. Within the accessible potential window, all these compounds exhibit two one-electron reversible redox reactions. Quantum yields of Q band are in the region 0.0045–0.21 at room temperature. The SPS and EFISPS reveal that all the compounds are p-type semiconductors and exhibit photovoltaic response due to π–π^* electron transitions.     

Europium(III) Compounds with Cyprofloxacine and Norfloxacine: Spectral and Luminescent Properties and Antibacterial Activity

Luminescence spectra of Eu(III) compounds with norfloxacine and cyprofloxacine are studied. The Stark components of the spectra of ⁵ D ₀–⁷ F _{0, 1, 2} transitions are analyzed. The results of the electron density transfer in ligands from substituent in position N(1) to the oxygen atoms of carboxyl and carbonyl groups are discussed. Antibacterial activity of the title compounds is studied.     

Luminescence of dihydro derivatives of benzo[f]quinoline

The spectral luminescence properties of 3-aryl-3,4-dihydrobenzo[f]quinolines containing alicycles and ester groups in the 1 and 2 positions were investigated. It is shown that compounds of this type have intense luminescence (52–76%). The quenching effect of an ester group in the heterocyclic ring was established. The spectral luminescence characteristics of compounds with an ester group in the alicycle are determined by the proton-acceptor properties of the carbonyl function of this group. The effect of the solvent on the spectral luminescence characteristics of the investigated compounds is discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–813, June, 1977.     

Reactions of lycoctonine alkaloids containing a 7,8-methylenedioxy group with Na in liquid ammonia

The reactions of 6-dehydroeldelidine and 6-dehydrodelcorine with sodium in liquid ammonia have been studied. Structures have been put forward for the compounds obtained. Features of the fragmentation of these compounds under electron impact are discussed.Abu Ali Ibn Sina [Avicenna] Tadzhik State Medical Institute, Dushanbe. Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 527–532, July–August, 1989.     

Characterization of the luminescence from low energy He/Xe and He/Kr reactions

The luminescence spectra produced by the reactions of 100 eV helium ions with xenon and krypton gas are reported and analyzed. In this paper spectral classifications have been made for the XeII and KrII transitions which produce radiation in the wavelength interval, 50–130 nm, and emission cross sections have been determined. Radiative transitions in the 130–890 nm interval have been treated similarly, and the results are available upon request. An important feature of the present work is that the experimental configuration utilized permits the excited products to radiate in the absence of significant perturbation from collisions or from electric or magnetic fields.     

Characteristic and spectroscopic properties of the Schiff-base model compounds

Two series of conjugated aromatic imines (Schiff-base model compounds) with different central groups and various side-group substitutions have been synthesized and characterized by elemental analysis, differential scanning calorimetry (DSC) technique, hydrogen nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and ultra-violet and visible light (UV–vis) spectroscopy measurements. The UV–vis absorption of solutions of these compounds in dimethylacetamid (DMA), chloroform and methanol was investigated in the optical range from 240 to 450 nm, where two distinct absorption bands: at 250–280 and 315–360 nm with the different level of absorption have been observed. The influence of compound molecular structure and polarity of solvent on the absorption spectra and the possible optical transitions have been discussed. Structure of diamines in the azomethine models fundamentally affected their spectroscopic properties and conjugation of π-electrons.     

Nature of the excited states of dialkylamino derivatives of aromatic and heteroaromatic compounds with an annelated oxazole ring

On the basis of analysis of the electron density redistribution upon excitation, drawing on charge transfer numbers, we have considered the nature of the electronic transitions in the absorption spectra of analogs of 2,5-diphenyloxazole, in which the carbon atom at position 4 of the oxazole ring is bonded to the ortho position of the 5-phenyl fragment of the vinylene, azomethine, amide, and ester groups. We have shown that the differences in the electronic transitions of the basal molecule and the studied structural analogs are determined by the electron-donor effect of the bridging group and the degree of its conjugation with the extended -electron system of the original molecule. The dialkylamino derivatives of the studied compounds, on the other hand, display a high degree of similarity in the electronic structure of the excited states, and the characteristics of their long-wavelength transitions, such as in the case of substitution of the 2-phenyl fragment, do not depend on the nature of the bridging group of atoms. We give a theoretical explanation of the experimentally observed increase in the intensity of the long-wavelength transitions and the efficiency of luminescence upon introduction of dialkylamino groups into the 2- and 5-phenyl fragments.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 6, pp. 644–650, November–December, 1990.     

Condensation of ethyl esters of 6-phenyl-and 6-(p-methoxyphenyl)-2,4-dioxocyclo-hexane-1-carboxylic acids with N-benzylidene-2-naphthylamines

A number of ethyl esters of 2,5-diaryl-4-hydroxy-1,2,5,6-tetrahydrobenzo[a]phenanthridine-3-carboxylic acid were obtained by condensation of ethyl esters of 6-phenyl- and 6-(p-methoxyphenyl)-2, 4-dioxocyclohexane-1-carboxylic acids with N-benzylidene-2-naphthyla-mines, and their spectral characteristics were studied. It was established that the luminescence properties of these compounds and the character of their reaction with the solvent are determined by the proton-acceptor properties of the carbonyl and hydroxy groups.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 976–979, July, 1980.     

Spectral characteristics and acid-base equilibria of 4,9-dihydroxy-5,10-dioxo-4,5,9,10-tetrahydro-4,9-diazapyrene and its 2,7-derivatives

The IR and electronic spectra of 2,7-disubstituted 4,9-dihydroxy-5,10-dioxo-4,5,9,10-tetrahydro-4,9-diazapyrene (R = H, I, NH₂, NO₂, OH) are studied. Analysis of the IR bands shows that, in crystalline form and in neutral and basic solutions, the compounds exist predominantly in the hydroxamic form. It is established that in sulfuric acid solutions the oxygen atoms of the C=O groups are protonated. The spectral characteristics of the neutral and ionized forms of the compounds are determined. The acid ionization constants are measured by potentiometric titration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–99, January, 1993.     

The coumarin composition ofSeseli tortuosum

The results are given of the identification of the known pyranocoumarin campestrinol (I), and the structures of four new coumarin derivatives have been studied — tortuosin (II), tortuosinin (III), tortuosinol (IV), and tortuosidin (V). On the basis of their spectral characteristics and chemical transformations, the corresponding structures have been established for compounds (II)-(V).Leningrad Sanitary-Hygienic Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 704–709, November–December, 1983.     

Two new compounds from <Emphasis Type="Italic">Phyllanthus niruri</Emphasis>

Three compounds were isolated from Phyllanthus niruri Linn. One effective method, improved dry column liquid chromatography for isolating these compounds, was applied on a silica gel column. It is a combination of conventional dry column chromatographic and flash chromatographic techniques. Structures of those obtained compounds were elucidated by means of spectral techniques including IR, MS, and 1D NMR and 2D NMR. Compound 1 was elucidated as 2,3,5,6-tetrahydroxybenzyl acetate. Compound 2 , 2,4,5-trihydroxy-3-(4,6,7-trihydroxy-3-oxo-1,3-dihydroisobenzofuran-5-yl)-benzoic acid methyl ester, was given the name phyllangin, and compound 3 was named corilagin. Compounds 1 and 2 are new compounds.Published in Khimiya Prirodnykh Soedinenii, No. 5, pp. 380–382, September–October, 2004.     

Quantum-chemical study of the electronic structures and spectral properties of oxazole analogs of 1,4-distyrylbenzene and the isomeric distyrylnaphthalenes

The electronic structures and spectral properties of a number of oxazole analogs of 1,4-distyrylbenzene and the isomeric 2,6-, 1,5-, and 2,7-distyrylnaphthalenes were studied within the framework of the Pariser-Parr-Pople method. The long-wave band of the electronic spectra of these compounds is formed by the S_o S₁ lower electron transition, which has general molecular character and is accompanied by intramolecular charge transfer. Intense electron transitions from fluorescent level S₁ to higher electron-excitation levels are absent over the range of the absorption and fluorescence bands.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 609–615 May, 1980     

Classification of IR spectra of organic compounds by the methods of multidimensional statistics

In order to clarify the possibilities of classifying the IR spectra of organic compounds by methods of multidimensional statistics, with the object of casting further light on the relationship between the structure of a compound and noncharacteristic spectral criteria, an experiment was carried out, in which methods of factor analysis were applied to the entire set of spectra. A clusterization was obtained of the original spectra conforming with the chemical classification of the compounds studied and universal vectors for transition into a low-dimensionality space, where the spectra studied are described by 11 factors instead of the initial 65. The concept of spatial identification of the spectra is discussed.K. A. Timiryazev Agricultural Academy. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 1, pp. 94–100, January–February, 1993.     

Fully automated multianalyte determination of different classes of pesticides,at picogram per litre levels in water,by on-line solid-phase extraction–liquid chromatography–electrospray–tandem mass spectrometry

This paper reports the development of a fully automated method for the multianalyte determination of twenty pesticides belonging to different classes (triazines, phenylureas, organophosphates, anilines, acidic, propanil, and molinate) in natural and treated waters. The method, based on on-line solid-phase extraction–liquid chromatography–electrospray–tandem mass spectrometry, is highly sensitive (limits of detection between 0.004 and 2.8 ng L^–1), precise (relative standard deviations between 2.0 and 12.1%), reliable (two selected reaction-monitoring transitions are monitored per compound), rapid (45 min per sample), and simple. The application of this method to the monitoring of the target compounds in a waterworks revealed the presence of the pesticides investigated at concentrations up to 516 and 82 ng L^–1 (total pesticide concentration) in river water and ground water, respectively, used as sources, and their gradual removal through the purification process.Dedicated to the memory of Wilhelm Fresenius     

Synthesis of polychlorinated 2,5-dihydro-2-furanones from maleic anhydride

The reaction of maleic anhydride with phosphorus pentachloride, which leads to polychlorinated 2,5-dihydro-2-furanones, was studied. The structures of the compounds obtained were proved by means of spectral methods.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 600–601, May, 1991.     

The Change in Coordination Mode of Malonodialdehyde Ligands in Be and Mg β-Diketonate Complexes

The process of torsion disclosure of the chelate ring in Be and Mg malonodialdehynates in the ground and excited states is studied with the aim to investigate photo- and thermodestruction of metal β-diketonates and the nature of the electron transitions in ab initio and density functional theory approximation. The change in the electronic structure parameters of the complexes under consideration with the changing coordination mode of a ligand is analyzed. The nature of the electron excited states and their role in stability of the studied compounds are established. The results of calculations obtained by different quantum-chemical methods are compared.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 6, 2005, pp. 415–422.Original Russian Text Copyright © 2005 by Lushchenko, L’vov, Vovna.     

Reactions of diterpenoids on solid supports. I. Oxidation of methyl abietate on the sorbents Al2O3 and SiO2 containing potassium permanganate

The oxidation of methyl abietate on the sorbents Al₂O₃ and SiO₂ containing potassium permanganate has been studied. It has been shown that the following are formed under the conditions selected: compounds of the dehydroabietane series, stereoisomeric mono- and diepoxides of methyl abietate, and the products of their transformation on the sorbents. The structures and stereochemistries of the compounds isolated have been established with the aid of spectral methods and XSA.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–378, May–June, 1994.     

Cyclovoltammetric and spectroscopic characterization of optically active cobalt(II) and copper(II) complexes with the Schiff base derived from (N,N′)-(1R,2R)-(−)-cyclohexylenediamine and 2-hydroxyacetophenone

The Schiff base prepared by reacting (–)-(1R,2R)-1,2-cyclohexanediamine with 2-hydroxyacetophenone was used as a ligand for Co^II and Cu^II. The coordination compounds were studied by u.v.–vis. absorption and by circular dichroism (c.d.) spectroscopy in solution. The complexes are four-coordinated in a slightly distorted square planar symmetry. The distortion from planarity is a main factor influencing the chiral surroundings of the metal ion. The d–d and c.t. transitions are consistent with the observed distortion, which arises from intramolecular interactions between the methyl groups attached to the Schiff base imine carbon and hydrogen atoms of the cyclohexane ring. The electrochemical properties of the Co^II and Cu^II complexes were observed in MeCN but investigations revealed weaker oxygen activation than of Co^II analogue with salicylaldehyde. The Cu^II complex is reduced in H₂O to Cu^I which disproportionates to Cu^II and Cu⁰.     

Theoretical study of structural and optical properties of regioregular head-to-tail oligo (3-n-octylthiophene) and related star molecules

The quantum chemical calculations of selected nonsubstituted or regioregular head-to-tail oligo (3-n-octylthiophene) and model thiophene–based star molecules using Density Functional Theory (DFT) are presented. The influence of the alkyl-substitution on the optimal geometries and relevant optical properties was analyzed. In the case of model star compounds, the presence of alkyl groups has a leading influence on structure as well as optical transitions. The Time Dependent DFT calculations of the vertically excited states show that the presence of alkyl group at the inner β-positions with respect to the phenylene central core is responsible for the generation of the low energy optical transitions with dominant oscillator strengths (over 0.25). The molecular orbital analysis of the lowest energy transition of the largest studied model star molecule (1,3,5-tris-(sexithienyl)-phenylene) also shows that the meta-conjugation in this zero-order dendrimer allows certain interactions among arms altogether.