Analogs of styryl dyes and the simplest AZO dyes from 2-dimethylaminothiophene

The condensation of 2-dimethylaminothiophene with the appropriate derivatives of quaternary benzothiazole salts has give the vinylene-homologous series of dyes with the structure (I). By coupling with benzenediazonium salts, the simplest azo dyes of structure (III) have been synthesized. The influence on the absorption spectra of the replacement of a dimethylaniline nucleus in polymethine and azo dyes by a 2-dimethylaminothiophene nucleus has been investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 923–925, July, 1973.     

Quantum-chemical investigation of the distribution of the electron density in asymmetric polymethine dyes

It has been shown with the use of the HMO, PPP, and CNDO/2 approximations that the distribution of the electron density in asymmetric polymethine dyes at the ends of the polymethine chain is determined mainly by the electron-donor ability of the nearby terminal groups, whereas in the middle their influence becomes weaker as the chain becomes longer. The asymmetry of the dyes causes a decrease in the alternation of the charges on the atoms and an increase in the alternation of the bond populations. These phenomena are most clearly displayed in the SCF approximations, which always emphasize alternation. The closer are the electron-donor properties of the terminal groups and the longer is the polymethine chain, the smaller is the difference in the distribution of the electron density near the terminal residues in asymmetric and symmetric dyes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 347–351, May–June, 1986.     

Fluorescent aggregates of cation-anionic polymethine dyes with simple structures

The absorption, fluorescence, and excitation spectra of two cation-anionic dyes with simple structures, which have the identical anions and variable cations, were studied in weakly polar and nonpolar solvents as well as in binary mixtures of solvents with different polarity. Under these conditions heterogeneous fluorescent aggregates were found at 20 °C. The structure of the cation has a significant influence on the formation and properties of the aggregates of cation-anionic polymethine dyes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 476–480, March, 1995.     

Interaction of chromophores in cationic/anionic dyes

The spectral properties of dyes containing colored organic cations and anions have been investigated in solvents differing in polarity. It has been established that the color of cationic/anionic dyes in low-polarity solvents is governed by the properties of the ion pairs that are formed. The chromophores in the ion pairs of cationic/anionic dyes interact, and this moves the absorption bands away from each other and redistributes their intensities.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 1, pp. 47–53, January–February, 1989.     

“Guest-Host” effect in polymer-dispersed nematic liquid crystals

In this paper we report on a new optoelectronic material representing a polymer-dispersed liquid crystal (PDLC) film. This material exhibits optical response to the applied electrical field and is useful for displays and light gates. The effect of azo and anthraquinone dyes on the optical density of PDLC films has been studied. The proportion of the dye dissolved in an LC cell and the molar absorption coefficients were determined, and the influence of the dyes on the scattering efficiency of PDLC films was calculated.Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 114–117, November–December, 1993.Translated by L. Smolina     

Some products of the coupling of gossypol with diazotized amines

Summary A series of products of the coupling of gossypol with diazotized amines has been obtained. It has been established that they are monoadducts. The possibility of using them as dyes for cotton fabric has been shown.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–609, September–October, 1976.     

Spectral-luminescent and generation properties of rhodamine dyes in thin polymer films under optical excitation

A study was made of the absorption, fluorescence, and emission spectra of organic dyes Rhodamine 6Zh and Rhodamine C in thin (0.6–1.0 µm) layers based on methyl methacrylate-methacrylic acid copolymers formed by centrifugation on optically transparent glasses. The influence of a terbium salt on the properties of laser dyes in acrylic films was elucidated.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1340–1345.Original Russian Text Copyright © 2004 by Vaitulevich, Eremina, Kopylova, Mokrousov, Samsonova, Svetlichnyi.     

Energy structures and electronic-transition wavelengths for trinuclear polymethine dyes

A study has been made on the energy structures and long-wave electronic transitions for linear trinuclear polymethine dyes by the method of additive generating functions. The necessary and sufficient conditions have been established for the occurrence of local levels related to the central nucleus. It is found that the bisvinylene shift is dependent on the structure of the central nucleus in this class of dyes. The relationship fits the available measurements, and it is predicted that there is a positive bridge effect, namely an increase in the bisvinylene shift in trinuclear dyes by comparison with binuclear ones.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 10–21, January–February, 1987.     

Principles of molecular design of binuclear polymethine systems

The electronic nature of reaction centers of reactants in the formation of polymethine compounds has been analyzed, and it has been established that the polymethine structures, depending on the combination of parity of the external polymethine chain and the signs of the electron-donor strength of the terminal heterocyclic nuclei, can be divided into two classes: classical polymethine dyes and generalized Hünig systems. In the generalized Hünig systems, the dependence of the charge distribution and bond orders in the polymethine chain on the difference in basicities of the terminal nuclei should be the opposite of the known relationships in a number of classical polymethine dyes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 307–314, May–June, 1990.     

Choice of the best region for channel-by-channel summation of estimating the intensity of single photopeaks

The influence of partial peak width integration on the statistical error has been investigated. It has been shown that integration of the central photopeak part —±(0.55–0.64) FWHM for narrow peaks and ±(0.50–0.53) FWHM for wide peaks-allows to decrease the statistical error 1.5–2.0 times in comparision with the TPA method. The results obtained are valid both for real photopeaks and for smoothed spectra. The theoretical results have been confirmed by experimental data.     

Anthocyans of some plants of Uzbekistan and the creation of food dyes from them

The chemical composition of anthocyan pigmentary substances of some plants of Uzbekistan have been studied. From the plant species investigated various flavonoids and glycosides of cyanidin and delphinidin have been isolated. A method has been developed for obtaining food dyes and this has been used to organize their production.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 382–385, May–June, 1995. Original article submitted November 7, 1994.     

Optimization of an analytical procedure for the determination of banned azo dyes in leather

The possibility of improving an existing method, based on supercritical-fluid extraction (SFE) and microwave-assisted extraction (MAE), for the determination of banned azo dyes in leather has been studied. Thus, optimization of experimental conditions in different steps (degreasing, reduction, and extraction) of the analytical procedure was performed. The influence of different variables (reaction time, temperature, and concentration of reducing agent) on the reduction process was evaluated by use of a factorial design. It was found that the concentration of the reducing agent and the interaction between time and temperature were the most influential variables. Consequently, by applying a higher temperature, the reaction time could be halved. The use of acidified water as extraction solvent in MAE was also investigated. Usually 1 mol L^–1 HCl was superior to methanol and buffer in terms of extraction efficiency. In conclusion, the present method gave significantly higher recoveries in comparison with the original method. All dyes were determined indirectly by measuring their corresponding harmful amines, formed after reduction by use of sodium dithionite.     

The homonuclear Overhauser effect and stereochemistry of a cyanine dye containing an orthophenylene bridge in the chromophore

Differential NMR spectroscopy has been used to derive the homonuclear Overhauser effect for protons in cyanine dyes, where the chromophore in each case contains an orthophenylene bridge. The data serve to define the polymethine chain conformation. A substituent in the meso position in the polymethine chain can alter the conformation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 4, pp. 505–507, July–August, 1988.     

UV–vis photodegradation of dyes in the presence of colloidal Q-CdS

The interaction of the dyes Safranin-O (SO) and Orange II (OII) with aqueous colloidal Q-CdS clusters, which emit single fluorescence bands with maximum wavelengths at 481 nm (excitonic band) or 559 nm (trapped band), has been studied. This was carried out by monitoring both the photodegradation of the dye in the presence of the clusters and the quenching of the clusters fluorescence by the dyes. The photolysis experiments were carried out by excitation either at 520 nm (the wavelength at which the dyes, but not the clusters absorb light) or at 350 nm (the wavelength at which the clusters strongly absorb light, and the dyes have absorbance minima). At 520 nm, photodegradation of SO could be observed, which follows a first-order kinetics (for trapped-band clusters) and a second-order kinetics (for excitonic-band clusters). For the excitation wavelength of 350 nm, photodegradation of either of the dyes could not be observed. The Stern–Volmer plots for the quenching of the excitonic band-clusters fluorescence by SO show an upward curvature, pointing to the occurrence of more than one species acting as the fluorescence quencher, whereas the Stern–Volmer plots for the quenching of the trapped band-clusters fluorescence by SO are linear, indicating that only one species acts as a fluorescence quencher. Lambert–Beer type plots (absorbance vs. concentration) are linear for SO in water and in trapped band-clusters solutions, but a similar study of SO in excitonic band-clusters solution show the occurrence of a new band, which can be assigned to a ground-state dimer of the dye. The latter can be used to explain both the upward curvature of the Stern–Volmer plots and the second-order kinetics observed for SO photodegradation in the SO-excitonic band-clusters system. The Stern–Volmer plots for the quenching of both fluorescence bands by OII are linear.     

Criteria of asymmetry of the electron density distribution of polymethine dyes with several chromophores

The absorption and fluorescence spectra of 6-B-thia- and 6-B-imidathiadimethinemerocyaninocyanines were investigated. It was established that the transition from absorption spectra to fluorescence spectra leads to an underestimation of the deviations. The influence of resonance interaction of the chromophores on the value of the deviations of the long-wave absorption and fluorescence bands of dyes with two chromophores is discussed. It was shown that resonance interaction leads to a decrease in the contribution to the deviation from alternation of the bonds in the polymethine chromophore and an increase in the topologic component of the deviation. A new criterion of asymmetry of the electron density distribution in dyes with several chromophores is proposed.Translated from Teoreticheskaya i Éksperimental'naya, Khimiya, Vol. 21, No. 6, pp. 641–650, November–December, 1985.     

Contribution of singlet oxygen to the accelerated decolorizing of dye mixtures

Binary mixtures of dispersed dyes, which during irradiation with polychromatic light give an effect of accelerated decolorization, were studied. Quantum yields of the formation of singlet oxygen by individual dyes were estimated during irradiation of solutions in ethyl acetate with light of 435 and 546 nm as well as quantum yields of the reaction of dyes with singlet oxygen. It was found that the contribution of the reaction of dyes with singlet oxygen to the effects of accelerated decolorization were vanishingly small. The quantum yield of the photodestruction of dyes in a mixture was 10^–3-10^–5 and the quantum yield of reaction with singlet oxygen was less than 10^–6. It was concluded that accelerated decolorization of the systems studied is not determined by reaction with singlet oxygen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2014–2017, September, 1991.     

Influence of the adsorption on the oxidation of oxalic acid on a gold electrode in acid media

Summary The influence of an adsorption process on the oxidation of oxalic acid on a gold electrode has been analysed. To disclose this influence, different supporting electrolytes have been used with different adsorption of the anion (SO ₄ ^2– , NO ₃ ^– and ClO ₄ ^– ). Moreover, it has been studied the modifications produced in the oxidation process by the presence of some species in solution with a strong adsorption (halides), but at low concentration levels.

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Der Einfluß der Adsorption auf die Oxidation von Oxalsäure an der Goldelektrode in saurem Medium

Zusammenfassung Um den Einfluß der Adsorption auf die Oxidation von Oxalsäure an der Goldelektrode in saurem Medium zu untersuchen, wurden Support-Elektrolyten mit verschiedener Anionenadsorption verwendet (SO ₄ ^2– , NO ₃ ^– und ClO ₄ ^– ). Außerdem wurden Modifikationen des Oxidationsprozesses in der Gegenwart von stark adsorbierten Spezies, diese allerdings in geringen Konzentrationen, untersucht (Halogenide).

     

Conformational Mobility of 4,4′-Bisdimethyl-Aminobenzophenone in the Excited State

Quantum-chemical calculations on various conformational states of the molecule of Michler’s ketone have been carried out by semi-empirical and non-empirical methods (HyperChem 7.0 suite of programs and Gaussian 98). The influence of solvation on the relative levels of different orbital types and on the spin states of the molecule has been examined. The possibility of the TICT process occurring in polar media, which may have an important effect on the spectral characteristics of Michler’s ketone, has been investigated.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 3, pp. 185–189, May–June, 2005.     

First electronic transitions in compounds with the perimeter π-system

In the Pariser-Parr-Pople approximation, an analysis has been made of the first -electron transitions in neutral and charged [N]annulenes with a closed shell. The influence of the ratio of numbers of -electrons and atoms in the annulene on the spectrum of the annulene has been examined critically. A similarity of the spectra of [N]annulenes and polymethine dyes has been noted.Deceased.Institute of Organic Chemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 493–499, July–August, 1991. Original article submitted February 8, 1988.     

Selectivity of the membrane action of a cytotoxin from the venom of the Central Asian cobra

It has been shown that the selectivity of the direct hemolytic effect of the cytotoxin on different erythrocytes correlates with its influence on the ionic permeability of the membranes of these erythrocytes. It has been established on bilayer phospholipid membranes that the influence of the cytotoxin on their ionic permeability depends on the amount of cholesterol in them. It is assumed that the resistance of the cells to the cytotoxin is determined by the stability of the phospholipid backbone of their membranes.Institute of Biochemistry of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 813–817, November–December, 1980.