scholarly journals Nature of Lowest Electron Transitions in Anionic Polymethine Dyes With Keto-Containing Terminal Groups

2021 ◽  
Author(s):  
A. P. Naumenko ◽  
V. I. Borisyuk ◽  
Olexiy Kachkovsky ◽  
Yu. L. Slominskii ◽  
N. V. Obernikhina
Keyword(s):  
Absorption Spectra ◽  
Energy Gap ◽  
Dipole Moments ◽  
Spectral Band ◽  
Electron Transition ◽  
Polymethine Dyes ◽  
Polymethine Chain ◽  
Local Electron ◽  
Fluorescence Excitation ◽  
Electron Transitions

Abstract The complex quantum-chemical and spectral study of the anionic polymethine dyes with the simplest symmetrical terminal groups and with different length polymethine chain is performed. It was shown that these dyes produce the specific molecular orbitals positioned nearly the energy gap and located only within the terminal groups. By investigation of the absorption spectra, it was established that the typical highly intensive longwawelength spectral band is observed which are bathochromically shifted upon lengthening of the open conjugated chain; this polymethine band is connected with the electron transition between the frontier levels of the opposite symmetry. In the contrast, the local MOs take part in so-called quasi-local electron transitions involved also one the frontier orbital. The local transitions have small dipole moments and hence they do practically not appear in the absorption spectra, however, the local transitions cause the appearance of the non-deep minima in the spectra of the fluorescence excitation anisotropy.

scholarly journals Aggregation of cation-anionic and related polymethine dyes

2000 ◽  
Vol 2 (1) ◽  
pp. 17-21 ◽  
Author(s):  
A. S. Tatikolov ◽  
G. Ponterini ◽  
Zh. A. Krasnaya
Keyword(s):  
Absorption Spectra ◽  
Ion Pairs ◽  
Wavelength Region ◽  
Polymethine Dyes ◽  
Gradual Transition ◽  
Solvent Mixtures ◽  
Anionic Dyes ◽  
Excitation Spectra ◽  
Absorption Bands ◽  
Fluorescence Excitation

Absorption, fluorescence, and fluorescence excitation spectra were studied for a number of cation-anionic and related anionic polymethine dyes in weakly polarand nonpolarsolvents, as well as in binary mixtures of solvents of different polarity. For some dyes, aggregation is observed in toluene or acetonitrile-toluene mixtures with low amounts of acetonitrile, which is revealed as appearance of new absorption bands and/or broadening of the initial bands of a monomeric dye. Solvent mixtures butyronitrilehexane with low butyronitrile content were found to greatly stimulate the formation of dye aggregates for most of the dyes studied. The absorption spectra of the aggregates are often blue-shifted with respect to the corresponding absorption spectra of parent monomeric dyes and/or represent broad continuums located both in the blue and red regions. For one of the cation-anionic dyes studied, which consists of3,3′-diethylthiamonomethinecyanine cation and trimethinebenzoxanine anion, fluorescent aggregates were observed; their broad fluorescence band is located in the long-wavelength region. For this dye, gradual transition from nonfluorescent aggregates to fluorescent ones and then to monomeric ion pairs and dissociated ions was observed in butyronitrile-hexane mixtures with growing butyronitrile content.

scholarly journals Effects of chromophore interaction in photophysics and photochemistry of cyanine dyes

2000 ◽  
Vol 2 (1) ◽  
pp. 23-30 ◽  
Author(s):  
A. S. Tatikolov ◽  
Zh. A. Krasnaya ◽  
L. A. Shvedova ◽  
V. A. Kuzmin
Keyword(s):  
Absorption Spectra ◽  
Short Wavelength ◽  
Ion Pairs ◽  
Polymethine Dyes ◽  
Wavelength Band ◽  
Fluorescent Properties ◽  
Anionic Dyes ◽  
Short Wavelength Band ◽  
Fluorescence Excitation ◽  
Chromophore Interaction

Spectral and fluorescent properties of ketocyanine dyes (polyenic bis-ω,ω′-aminoketones) and cation-anionic polymethine dyes of various structures were studied. The symmetric ketocyanines were shown to have a long-wavelength absorption band bathochromically shifted in comparison with that of the asymmetric ketocyanines with the same total length of the polyenic chain. The nonlinear ketocyanines exhibit the additional short-wavelength band in their absorption spectra, which can be more intense than the longwavelength band. The absorption spectra of ion pairs of cation-anionic dyes with overlapping cation and anion bands contain a new intense short-wavelength band inactive in fluorescence excitation. These spectral peculiarities are explained on the basis of chromophore interaction model. It has also been shown that theT1levels of ketocyanine chromophores do not essentially interact with each other in a ketocyanine molecule in nonpolar solvents; in polar solvents this interaction becomes appreciable due to lowering the potential barrier for conjugation.

ULTRAVIOLET ABSORPTION SPECTRA AND ACIDITIES OF ISOMERIC THIATRIAZOLE AND TETRAZOLE DERIVATIVES

1959 ◽  
Vol 37 (3) ◽  
pp. 563-574 ◽  
Author(s):  
Eugene Lieber ◽  
J. Ramachandran ◽  
C. N. R. Rao ◽  
C. N. Pillai
Keyword(s):  
Absorption Spectra ◽  
Absorption Maximum ◽  
Dipole Moments ◽  
Ring System ◽  
Ultraviolet Absorption ◽  
Characteristic Absorption ◽  
Tetrazole Derivatives

The ultraviolet absorption spectra of 5-(substituted)amino-1,2,3,4-thiatriazoles and the corresponding isomeric 1-substituted-tetrazoline-5-thiones have been studied. The spectra and the dipole moments of the 5-(substituted)amino-1,2,3,4-thiatriazoles eliminate the possibility of meso-ionic structures for these compounds. The dipole moments of 5-amino-, 5-methylamino-, and 5-dimethylamino-1,2,3,4-thiatriazole were all high but approximately of the same value (5.77 to 5.84 D). This suggests that the amino thiatriazoles are best represented by conventional covalent structures with significant ionic resonance contributions. The thiatriazole ring system exhibits a characteristic absorption maximum at 250–255 mμ and an electron-withdrawing effect approximately equal to the tetrazolyl ring system. The tetrazolinethionolyl ring system is similarly electron-withdrawing. The relative acidities of the 1-substituted-tetrazoline-5-thiones and the 5-alkylmercaptotetrazoles have also been studied and the results support the observations made on the basis of their ultraviolet absorption spectra.

Furan and Thiophene Analogs of Phenanthrene A Theoretical Study of the Absorption Spectra of Benzodifurans, Benzodithiophenes and Thienobenzofurans

1971 ◽  
Vol 26 (12) ◽  
pp. 1235-1240 ◽  
Author(s):  
L. Klasinc ◽  
J. V. Knop
Keyword(s):  
Absorption Spectra ◽  
Theoretical Study ◽  
Oscillator Strengths ◽  
Electron Transitions ◽  
Good Agreement ◽  
Lcao Mo

The LCAO -MO -SCF -CI method was applied to benzo(1,2-b : 4,3-b′) -difuran and -dithiophene, benzo (2,1-b : 3,4-b′) -difuran and -dithiophene, benzo (1,2-b : 3,4-b′) -difuran and -dithiophene, thieno (2,3-e) benzofuran, thieno (3,2-e) benzofuran, thieno (3,2-g) benzofuran, thieno (2,3-g) benzofuran, benzofuran, benzothiophene and phenanthrene. The calculated π-electron transitions and their oscillator strengths are in good agreement with known absorption spectra. The resemblance of these spectra to the absorption spectra of phenanthrene and phenanthrolines is discussed.

scholarly journals Permittivity spectra and structure of d-bands of germanium telluride, tin telluride and lead telluride

2020 ◽  
pp. 44-49
Author(s):  
D.A. Perevoshchikov ◽  
◽  
V.Val. Sobolev ◽  
A.I. Kalugin ◽  
E.A. Antonov ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Lead Telluride ◽  
Germanium Telluride ◽  
General Behavior ◽  
Electron Transitions ◽  
Tin Telluride ◽  
Experimental Absorption ◽  
Exciton Transitions

Based on the experimental absorption spectra, the permittivity spectra of GeTe, SnTe, and PbTe crystals were obtained in the region of electron transitions from core d -bands of cations. Their specific features and general behavior are revealed. The permittivity spectra of each crystal were decomposed into six elementary components and their main parameters were determined by using of combined Argand diagrams method. Based on the theory of interband and exciton transitions, the nature of the formation of these oscillators was proposed.

scholarly journals Spectrophotometric Study of ?-Irradiated PM-355

2009 ◽  
Vol 6 (3) ◽  
pp. 584-589
Author(s):  
Baghdad Science Journal
Keyword(s):  
Absorption Spectra ◽  
Calibration Curve ◽  
Linear Relation ◽  
Response Curve ◽  
Energy Gap ◽  
Linear Part ◽  
Absorbed Dose ◽  
Spectrophotometric Study ◽  
High Dose ◽  
Radiation Induced

The aim of the present work is concerned with the effect of ?-irradiation on PM-355 with absorbed dose of (30-160Mrad) range. This polymer is evaluated spectrophotometrically for use as high dose dosimeters. The absorption spectra of irradiated samples showed radiation induced absorption changes. There is an increment in absorption proportional with absorbed dose. This increment is attributed to interfaces traps which, are formed by irradiation. Calibration curve was drawn .The linear relation was found in calibration curve, and dosimeter range was determined from the linear part. The linearity in response curve suggested that PM-355 could be used as dosimeter within (30-160Mrad) rang. Energy gap shift was used as a second tool to determine the dosimeter range. It was found that PM-355 energy gap systematically decreasing with absorbed dose, and it could be used as a second tool to determine the dosimeter range.

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