Zh. A. Krasnaya

Dienone ⇆ 2H-pyran valence isomerization. (Review)

The researches of the author and her colleagues on the synthesis of α α-dicarbonyl-containing dienes with various structures and study of their valence isomerization to 2H-pyrans1H by an13C NMR, UV, and IR spectroscopy and flash photolysis are reviewed.

Fluorescence Spectra of Some Cross-Conjugate Ketones: Experiment and Calculations Based on the Model of Two-Well Adiabatic Potentials

Fluorescent properties of some cross-conjugate ketones were studied at 4.2, 77, and 300 K. Anomalies were observed in the fluorescence and fluorescence-excitation spectra of one of the studied compounds; these anomalies consisted in a pronounced upset of mirror symmetry of the spectra and a large Stokes shift. The experimental spectra and the spectra calculated theoretically using the theory of two-well adiabatic potentials were subjected to a comparative analysis.

Synthesis of ?-cyclohexyl- and ?,?-alkylene-?,?-dicarbonyl-substituted dienes and study of their valence isomerization

Abstractβ-Cyclohexylacrolein, β-cyclohexylmethacrolein, or α-cycloalkylidenalkanals were condensed with methyl acetoacetate or dimethyl malonate to give the δ-cyclohexyl- and δ,δ-alkylene-substituted α,α-dicarbonyl-containing α,β∶γ,δ-dienes. The structures of the reaction products were studied using1H NMR,13C NMR, and UV spectroscopy. The diene keto esters bearing no substituents at the γ-position were shown to be in fact three-component equilibrium mixtures comprised ofE- andZ-isomers of the diene (at the α,β bond) and a corresponding 2H-pyran. On the other hand, for keto esters with a Me group at the γ-position the equilibrium is shifted entirely to the 2H-pyrans. In contrast with the keto esters, dienic diesters exist only in the open form.

Manifestation of intramolecular vibronic interactions in the fine-structure fluorescence and fluorescence-excitation spectra of polyene δ -dimethylaminoketones

A vibrational analysis of the fluorescence and fluorescence-excitation spectra obtained by the Shpol’skiĭ method at 4.2 K has been carried out. The parameters of the intramolecular interactions of two δ-dimethylaminoketones have been calculated. To determine the overall intensities of the vibronic bands in spectra with fine structure on an intense continuous background, the spectra have been modelled by representing the band of each of the vibronic transitions by a zero-phonon line and a phonon wing with definite parameters (the half-widths and the Debye–Waller factor). It is shown that the breakdown of mirror symmetry in the conjugate fluorescence and fluorescence-excitation spectra of these two compounds can be explained by the interference of the Franck–Condon and the Herzberg–Teller interactions.

Synthesis and photonics of polyfunctional conjugated polyenes

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.

Photoinduced electron transfer in ion pairs of cation-anion polymethine dyes

Photoinduced electron transfer in ion pairs of cation-anion polymethine dyes was studied by flash photolysis. The formation of radicals, which are the products of photoinduced transfer of an electron from an anion to a cation in the ion pairs, was observed during photoexcitation of a number of cation-anion dyes in nonpolar and some weakly polar solvents (in particular, in toluene and chloroform). Photoinduced electron transfer is also observed during triplet sensitization of ion pairs of the cation-anion dyes. The redox potentials of the cations and anions constituting the dyes were measured; the radical yields were compared with the free energies of photoinduced electron transfer. Photoinduced electron transfer in the systems under study was compared with similar process in cyanineborate ion pairs.

Reactions of β-dimethylaminoacrolein aminal and 3-dimethylamino-1,1,3-trimethoxypropane with 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane

Reactions of 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane with β-dimethylaminoacrolein aminal, 3-dimethylamino-1,1,3-trimethoxypropane, DMF acetal, and ethyl orthoformate were studied. The reaction of 3-(dicyanomethylidene)indan-1-one with 3-dimethylamino-1,1,3-trimethoxypropane gave the 1,3-bis(1-dicyanomethylidene-3-oxoindane)trimethineoxanine salt in high yield, which was used to obtain a number of novel cation-anionic polymethine dyes.

Synthesis of δ-hetaryl-α,α-dicarbonylalkadienes and a study of their isomerization

The reaction of β-hetarylacrolein and β-hetaryl-α-methylacroleins with esters of acetoacetic and malonic acids was studied. The structures of the products obtained were established using1H and13C NMR and UV spectroscopy. (E) and (Z) isomers of α,α-dicarbonylalkadienes, their mixtures with the corresponding 2H-pyrans or exclusively 2H-pyrans are formed depending on the substitution in the starting aldehyde and the ester used. 6-Methyl- and 3,6-dimethyl-5-carbalkoxy-2-(2-pyridyl)pyrans are converted upon heating to substituted 2-(pyrilidene)pyrans.

Comparative study of the solvent effect on the spectral properties of aminopolyenic molecules with different acceptor substituents

The spectral and fluorescent properties of a number of ωω′-bis(aminopolyenyl)ketones (ketocyanines) and ωω′-bis(3-dimethylaminopropen-2-yliden)-alkylidenmalononitriles (dinitriles), being analogues of usual ketocyanines, but containing the dicyanomethylene fragment instead of the carbonyl group, were studied. Specific and nonspecific solvation of dinitriles and corresponding ketocyanines was studied on the basis of the solvatochromic shifts of the absorption spectra. The photophysical data obtained for the different molecular structures were correlated with different empirical parameters, which characterize solvation by organic solvents: the Dimroth-Reichardt ET(30) parameter of the solvating power, the acceptor number AN, the donor number DN, and the constant π* characterizing the solvent polarity and polarizability. A linear dependence of the maximums in the absorption spectra on the acceptor number AN, which characterizes specific solvation, was found for the ketocyanines under study. This indicates that the electrophilic solvation plays a key role in ketocyanine solutions. For dinitriles, the linear dependence of the maximums of the absorption spectra was obtained as f(π*, AN, DN). In the latter case, along with the electrophilic solvation, there is a substantial contribution of nonspecific and nucleophilic solvation.

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

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.