A. S. Tatikolov

Fluorescent Properties of Some Thia- and Oxacarbocyanine Dyes in the Presence of DNA

Spectral and fluorescent properties of some thia- and oxacarbocyanine dyes were studied in the presence of DNA. Interaction of the dyes with DNA led to complex formation. A significant increase in the fluorescence quantum yield of the dyes in the presence of DNA was observed. The influence of a heteroatom and a substituent in the meso-position of the polymethine chain on the fluorescence growth was investigated. The stoichiometry of the strongly fluorescent dye–DNA complex was determined.

Quenching of the triplet state of meso-substituted thiacarbocyanine dyes by nitroxyl radicals, iodide ions, and oxygen in solutions and in complexes with DNA

Using the flash photolysis method, the spectral and kinetic characteristics of triplet states of a number of meso-substituted thiacarbocyanine dyes (3,3′-diethyl-9-methoxythiacarbocyanine iodide, 3,3′,9-triethylthiacarbocyanine iodide, 3,3′-diethyl-9-methylthiacarbocyanine iodide, and 3,3′-diethyl-9-thiomethylthiacarbocyanine iodide) were studied, and the rate constants of triplet quenching by a stable nitroxyl radical, iodide ion, and oxygen were determined in solutions and in complexes with DNA. The results obtained show the formation of two types of dye-DNA complexes: formed by binding of the dye in the groove of a DNA molecule and by intercalation of the dye between base pairs. The complexation creates steric hindrances upon quenching of the triplet states of the ligands and causes great differences between the rate constants of the quenching processes.

Photochemical properties of meso-substituted thiacarbocyanine dyes in solutions and in complexes with DNA

AbstractThe processes of cis-trans photoisomerization and thermal back isomerization as well as the effect of DNA on the spectral and kinetic characteristics of the triplet state of a number of meso-substituted thiacarbocyanine dyes: 3,3’-diethyl-9-methoxythiacarbocyanine iodide (K1), 3,3’,9-triethylthiacarbocyanine iodide (K2), 3,3’-diethyl-9-methylthiacarbocyanine iodide (K3), and 3,3’-diethyl-9-chlorothiacarbocyanine perchlorate (K4), were studied by the flash photolysis method. Upon flash photoexcitation, the processes of trans-cis and cis-trans photoisomerization were observed for dye K1; the data on the structure of the absorption bands of the photoisomers were obtained. Complexation with DNA leads to an increase in the quantum yield of the triplet state of the dyes, which is explained by growing rigidity of the bound molecules. In the presence of DNA, triplet state deactivation follows the two-exponential law, thus showing that the dyes form complexes of two different types. The processes of quenching of the dye triplet state by oxygen were studied in solutions and in complexes with DNA. The rate constants for oxygen quenching of the triplet state of the dyes in complexes with DNA were found to be much lower than the values expected for the diffusion-controlled reactions (with allowance for the spin statistical factor,

SYNTHESIS AND PHOTONICS OF KETOCYANINE DYES, 2,6-BIS(4-DIMETHYLAMINOALKA-1,3-DIENYL)-4H-PYRAN-4-ONES AND ETHOXYTRIDECAMETHINE SALTS BASED ON THEM

k_{qO_2 } < 1/9k_{dif}

Spectral and fluorescent properties of cross-conjugated polyene ketones with terminalN-methylpyrrole residues

), which is explained by the steric factor of the complexation.

Spectral and fluorescent properties and prototropic equilibrium of (bis-θ,θ′-dimethylaminopolyenyl)diketones

Methods for the synthesis of various types of polyfunctional conjugated polyenes based on aminals of unsaturated ω-amino aldehydes are surveyed. The influence of the interaction of chromophores on the photophysical properties of polyene bis(amino)-substituted ketones and polymethine salts based on them as well as on the properties of absorption and fluorescence spectra of the cation-anionic polymethine dyes are considered.

Synthesis of bis-and tetrakis-(ω-dimethylamino)-substituted cross-conjugated polyene α-diketones of the thiophene series

The reactions of β-dimethylaminoacrolein aminals with 2,6-dimethyl-γ-pyrone lead to 2,6-bis(4-dimethylaminoalka-1,3-dienyl)-4H-pyran-4-ones, whose alkylation affords ethoxytridecamethine salts. The spectral and fluorescence properties of the synthesized compounds were studied. Their absorption spectra are unusual; along with the long-wavelength band in the visible spectral region, they contain a much more intense short-wavelength band in the near UV region. This pattern of the absorption spectra is explained in terms of the model of chromophore interaction, assuming an acute angle between the chromophore “halves” of the polyene chain of the dye molecule. The central pyran ring in the ethoxytridecamethine salts can hamper conjugation in the polymethine chain. Thermochromism of 2,6-bis(4-dimethylaminoalka-1,3-dienyl)-4H-pyran-4-ones (the long-wavelength shift of the absorption spectra on cooling of the solutions) is observed; only the long-wavelength absorption band undergoes a pronounced thermochromic shift. The introduction of methyl or phenyl substituents into the polyene chains of substituted 4H-pyranones decreases the fluorescence quantum yield.

Kinetics of the interaction of ketyl and semiquinone radicals with dioxygen. Concerted electron and proton transfer involving ketyl and semiquinone radicals

The reactions of substituted 4H-pyrones and N-methyl-2,6-dimethylpyridone with dimethylformamide acetal and aminal acetals of conjugated ω-dimethylaminoaldehydes were studied. Cross-conjugated ketones and meso-ethoxy(dialkylamino)tridecamethine salts containing the pyran or pyridone fragment were synthesized and their spectroscopic properties were investigated. The replacement of the bridging O atom by the NMe group precludes an interaction between chromophores in cross-conjugated ketone and the related tridecamethine salt. In addition, the insertion of a meso-amino substituent into the polymethine chain of the salts containing the central pyrylium fragment leads to a sharp weakening of the chromophore interaction. In spite of the dramatic differences in the UV spectra of ketocyanines containing the bridging O or NMe fragments, these dyes have similar 13C NMR spectra.