Reaction of diisopropyl benzeneboronate with free radicals

Summary When diisopropyl benzeneboronate is treated with free radicals the initially formed diisopropyl benzeneboronate radical undergoes decomposition, which is reflected in the structure of the obtained polymer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 367–368, February, 1965     

Acid-catalyzed formation of free radicals in the reaction of hydroperoxides with ketones

The kinetics of formation of free radicals in the cyclohexanone (CH)-tert-butylhydroperoxide (TBHP)-para-toluenesulfonic acid (PTSA) system in acetonitrile was studied. The stoichiometry of the reaction corresponds to the consumption of two TBHP molecules per ketone molecule, whereas the yield of free radicals is -20 % based on the TBHP reacted.     

Reaction of free radicals with unsymmetrical organomercury compounds

Russian Chemical Bulletin -     

Mass spectrometry of polymethine dyes

The mass spectra of some unsubstituted (in the heteroresidues and polymethine chain) thiacarbo- and polycarbocyanines were investigated. It was ascertained that the first act of disintegration of the dye molecules is splitting out of an alkyl halide ion to give an anhydro base ion. Some regularities between the structure of the dyes and the fragmentation of the anhydro ions obtained from them are exposed. The peculiarities of the dissociative ionization of the dye molecules as the polymethine chain is lengthened are shown.     

Photochemistry of anionic polymethine dyes

Spectral and kinetic properties of photoisomers and triplet molecules of a number of anionic polymethine dyes, namely, differential absorption spectra, rate constants (k _i ) and activation parameters of reversecis-trans-isomerization, and triplet-state-decay rate constantsk _T are studied by flash photolysis. CINDP/2 calculations of electron density in anionic dyes show thatk _i andk _T in polar solvents are determined primarily by the electronic effect of the substituents in themeso-position of the polymethine chain of a dye. The increase ink _i due to the formation of ion pairs consisting of a dye with a counterion is observed in nonpolar solvents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 713–718, April, 1993.     

Imidazopyridine derivatives as polymethine dyes

Several new carbo- and dicarbocyanine, merocyanine, and merocyaninocyanine dyes with residues of the quaternary salt of 1-phenyl-1H-imidazo[4,5-c]pyridine were synthesized. The colors of the dyes were studied.See [1] for communication I.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 693–697, May, 1971.     

Cis-trans-isomerization of cationic-anionic polymethine dyes

The effect of solvent polarity and ion pair formation oncis-trans-isomerization of cationic-anionic polymethine dyes and of related simple cationic and anionic dyes is studied by flash photolysis. The change in the rate constant for reversecis-trans- isomerization of photoisomers due to the interaction of a cation with an anion in an ion pair is observed in nonpolar solvents. A drop in the yield of the photoisomers to zero is observed for a number of cationic-anionic dyes in weakly polar and nonpolar solvents which is possibly due to steric hindrances in the photoisomerization process in ion pairs.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 719–724, April, 1993.     

Photoisomerization of sterically hindered polymethine dyes

Conclusions In sterically hindered polymethine dyes the photoisomerization process, with the formation of sterically hindered trans and di-cis forms, successfully competes with the nonradiative degradation of the energy on the higher vibrational sublevels of the ground state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1926–1930, August, 1977.     

Imidazopyeidine derivatives as polymethine dyes

Several new polymethine dyes of the cyanine and merocyanine series with 1-methyl-1H-imidazo [4,5-b]pyridine residues were synthesized, and their colors were studied. Replacement of the benzimidazole residue in the cyanine dyes by a l-methyl-1H-imidazo[4,5-b]-pyridine residue leads to deepening of the dye color.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1561–1565, November, 1971.     

Fluorescent properties of cationic-anionic polymethine dyes

The fluorescence spectra were studied and the quantum yields of the fluorescence of a number of cationic-anionic polymethine dyes were measured in polar, low-polarity, and nonpolar solvents. It was shown that the fluorescence spectra of cationic-anionic dyes in polar solvents, like the absorption spectra, represent the sum of the fluorescence spectra of the corresponding cationic and anionic dyes. For dyes in which the absorption bands of the anion and cation are close and a new short-wave band arises in the ion pairs, excitation into this band virtually does not lead to fluorescence, which is a consequence of the forbidden nature of the long-wave transition that arises as a result of the interaction of the chromophores. For a number of cationic-anionic dyes in ion pairs an energy transfer is observed: When an ion possessing short-wave absorption is excited, an ion with long-wave absorption fluoresces.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2532–2539, November, 1992.     

[1.1.1]Propellane: Reaction with free radicals

[1.1.1]Propellane is more reactive towards free radicals than bicyclo[1.1.0]butane, and much more reactive than bicyclo[2.1.0]pentane. Therefore, the reactivity is not determined by strain energy relief or the HOMO energy. The addition of acetaldehyde is unique in that a 1:2 adduct is formed. A number of other additions are described, and provide convenient routes to 1,3-disubstituted bicyclo[1.1.1]pentanes.     

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.     

Polymethine-polyene transition parameter in polymethine dyes

Within the framework of the HMO approximation and an equal bond model, quantitative characteristics are proposed for the alternation of electron density on the atoms and bonds of an unsubstituted chain of polymethine dyes with arbitrary end-groups. These characteristics can be used, depending on the type of electron distribution, to classify a compound as a polymethine or polyene. A structural parameter determined by the nature of the end-groups has been found, this parameter being responsible for realization of one type of electron density distribution or the other in the polymethine chain.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 129–138, March–April, 1988.     

Study of fluorescent aggregates of polymethine dyes

Absorption, fluorescence, and fluorescence excitation spectra have been studied for a number of anionic, cationic, and cationic-anionic polymethine dyes in low-polar and nonpolar solvents, as well as in binary mixtures of solvents differing in polarity. For most of the dyes studied, fluorescent aggregates have been found to form. Their broad fluorescence bands are located in the long-wave region with respect to those of the initial dyes. The quantum yield of the aggregate fluorescence is normally higher than that of the initial dyes. Fluorescence excitation spectra of some cationic-anionic dyes in nonpolar solvents disagree with their absorption spectra because of contact and solvent-separated ion pairs simultaneously present in the solution.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 69–75, January, 1993.     

Photoprocesses in dimers and dimeric complexes of polymethine dyes with cucurbiturils

Russian Chemical Bulletin - The review is devoted to the structure and photoprocesses in dimers of polymethine dyes and their complexes as objects of supramolecular photochemistry. The results of...