Yu. V. Smirnova

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.

Six-day modulation of the quiescent radio emission of SS 433

Two daily sets of monitoring data of the Galactic X-ray binary SS 433 (V1343 Aql) obtained on the RATAN-600 radio telescope (117 days in 1997 and 120 days in 1999) show variations in its quiescent radio emission with a period of 6.05±0.1 days at six frequencies from 0.96 to 22 GHz. This 10–15% modulation in the quiescent radio light curves differs significantly from the well-known 6.28-day periodicity in the emission of moving spectral features and in optical photometric data, which are related to nodding motions of the jets and accretion-disk wobble. This period coincides almost exactly with the theoretical value for the harmonic f=2(Io+Ip), related to the orbital (To=13.08 days) and precessional (Tp=162.4 days) periods for slaved accretion-disk models. The 6.06-day period corresponds to the combined frequency. It is proved that the modulation of the radio flux of SS 433 may be associated with relativistic boosting of the jet emission due to periodic variation of the orientation of the jets, which are nodding with a period of six days. The synchrotron emission of the two jets contributes to the quiescent radio flux of SS 433, and the six-day harmonic has the same radio spectrum as the quiescent radio flux: Sv∼v−0.6.

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.

Surface/interfacial tension dynamics of vesicle-forming surfactants

In the present work the dynamics of surface (at the aqueous solution/air interface) and interfacial (at the aqueous solution/n-decane interface) tensions were studied for diluted aqueous solutions of dialkyldimethylammonium bromides with alkyl chain lengths of 10 and 12 carbon atoms. These amphiphiles form different kinds of bilayer aggregates in aqueous systems, such as small unilamellar vesicles, multilamellar liposomes and random lamellar L3 phases, depending on the surfactant concentration. Dynamic tension measurements were performed by drop weight and drop volume methods. It was found that the rate and the character of surface tension equilibration is strongly dependent on surfactant concentration. The data obtained were analysed on the basis of modern theoretical conceptions and the diffusion coefficient values were estimated using the approach developed by Fainerman et al. (Colloids Surfaces A: Physicochem. Eng. Aspects, 87 (1994) 61).

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.

The interaction of dimethylaminomethylenemalonaldehyde aminal-acetal with indandione

The reaction of dimethylaminomethylenemalonaldehyde aminal-acetal with indandione leads to 2-(3-dimethylamino-2-formylpropenylidene)indan-1,3-dione, 1,3-bis(1,3-dioxo-indanylidene)-2-(dimethylaminomethylene)propane, or oxanine salt depending on the reagent ratio. The cationic-anionic polymethine dyes were obtained from the oxanine salt.

Synthesis and spectroscopic properties of cross-conjugated ketones and meso-substituted tridecamethine salts containing the pyran or pyridone fragment

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.

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

The spectral and fluorescent properties of a number of cross-conjugated ketones with one or two terminalN-methylpyrrole residues and those of polyene bis-ω, ω′-dimethylamino ketones with methyl substituents in the polyene chain and of some related compounds were studied. The photophysical properties of cross-conjugated ketones with terminalN-methylpyrrole residues are similar to those of the corresponding polyene bis-ω, ω′-dimethylamino ketones studied in detail previously. In both series of compounds, the absorption and fluorescence spectra undergo a bathochromic shift following an increase in the length of the polyene chains or introduction of α,α′-trimethylene or α,α′-dimethylene bridges into these chains; the same trend is observed on passing from less polar solvents to more polar solvents (positive solvatochromism). Thermochromism (long-wavelength shift of the absorption spectra upon cooling the solutions) is observed in both series of compounds. The introduction of methyl substituents into the polyene chains of bis-ω,ω′-dimethylamino ketones results in a decrease in the fluorescence quantum yield.

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

Bis-and tetrakis(ω-dimethylamino)-substituted cross-conjugated polyene α-diketones, containing two thiophene rings, were synthesized from α-diketones of the thiophene series and β-dimethylaminoacrolein aminals and also 2-aza-3-dimethylaminoacrolein acetal.