scholarly journals Nanoarchitecture of Aggregates of Polymethine Dyes

2019 ◽  
Vol 14 (2) ◽  
pp. 5-14
Author(s):  
B. I. Shapiro
Keyword(s):  
Alkyl Substituent ◽  
Structural Features ◽  
Short Wave ◽  
Polymethine Dyes ◽  
Polymethine Chain ◽  
Anionic Dyes ◽  
Long Wavelength ◽  
Optical And Electronic Properties ◽  
Meso Position ◽  
Cis And Trans

In recent years, the class of polymethine (cyanine) dyes has attracted increasing attention of researchers in the field of nanotechnology due to the structural features of their chromophore system and their tendency to form polymolecular states – dye aggregates. The processes of the formation of aggregates with new optical and electronic properties in aqueous solutions were studied as exemplified by anionic thyatrimethinecyanine dyes. It was shown that the aggregates are formed by a “block” mechanism from dimers. The nanoarchitecture of the aggregates is determined by the type of the alkyl substituent in the meso position of the polymethine chain of the dye. The C2H5 group promotes the formation of long-wavelength J-aggregates with the “brickwork” packing of molecules. The CH3 group promotes the formation of short-wave H-units with the “stepladder” packing of molecules. The formation of spatial isomers – J- and H-aggregates from cis and trans conformations of dye molecules – was established. Inorganic and organic cations, which stabilize highly organized aggregate structures, have a significant effect on the formation of aggregated forms of anionic dyes. Thus, the work presents the author's ideas about a new scientific direction – the nanoarchitecture of aggregates of polymethine dyes.

scholarly journals Preparation and Characterization of Cationized Cellulose for the Removal of Anionic Dyes

2001 ◽  
Vol 19 (3) ◽  
pp. 197-210 ◽  
Author(s):  
A. Hashem ◽  
Reda M. El-Shishtawy
Keyword(s):  
Adsorption Capacity ◽  
Freundlich Isotherm ◽  
Structural Features ◽  
Isotherm Models ◽  
Acid Orange 7 ◽  
Anionic Dyes ◽  
Adsorption Parameters ◽  
Direct Blue ◽  
Equilibrium Data

The factors influencing the cationization of microcrystalline cellulose with 3-chloro-2-hydroxypropyl triethylammonium chloride in the presence of NaOH were investigated. The course of the reaction was followed by estimating the nitrogen content of the cationized product while its structural features were confirmed by IR analysis. The ability of cationized cellulose to adsorb anionic dyes, viz. Acid Orange 7, Direct Blue 75 and Direct Violet 31, was investigated at 25°C and 50°C. The equilibrium data obtained were fitted by the Langmuir and Freundlich isotherm models, allowing the corresponding adsorption parameters to be determined. The results showed that the adsorption capacity was dependent on the adsorbent, temperature, the nature of the dye and (to some extent) on van der Waals and hydrogen bonding. Cationized cellulose exhibited a much better adsorption capacity towards anionic dyes than cellulose.

scholarly journals Электронное строение и спектрально-флуоресцентные свойства лазерных красителей тиопирило-4-трикарбоцианинов

2021 ◽  
Vol 129 (7) ◽  
pp. 862
Author(s):  
А.А. Ищенко ◽  
И.В. Курдюкова ◽  
М.В. Богданович ◽  
С.Л. Бондарев ◽  
А.А. Романенко ◽  
...  
Keyword(s):  
Radiative Transition ◽  
Polymethine Chain ◽  
Long Wavelength ◽  
Vibronic Interactions ◽  
Wide Range ◽  
Wavelength Absorption ◽  
Fluorescent State ◽  
Long Wavelength Absorption Band ◽  
Angle Of Rotation ◽  
Ab Initio Dft

It was found that the long-wavelength absorption band of the laser dye IR 1061 and its analogue with an unsubstituted polymethine chain is strongly broadened and decreases in intensity in polar solvents, while the fluorescence band remains narrow and practically does not change in a wide range of solvent polarities. Based on the quantum-chemical calculations of these dyes by the ab initio DFT/B3LYP/6-31G (d,p) and TDDFT methods, taking into account the polarity of the medium by the PCM method, it is shown that the reason for this difference is the weakening of solvation in the fluorescent state as compared to the ground state due to the greater equalization of the charge in the first than in the latter. An increase in the alternation of bond orders in the polymethine chain in the fluorescent state was found, which causes an increase of vibronic interactions in the radiative transition as compared to the absorptive one. Spectral effects caused by a change in the angle of rotation of phenyl groups in the thiopyrylium cycle upon excitation have been analyzed.

scholarly journals Method of obtaining and studying the optical properties of carbon quantum dots.

2019 ◽  
Vol 19 (3) ◽  
pp. 226-229
Author(s):  
S.D. Bardasevska ◽  
I.M. Budzulyak ◽  
S.I. Budzulyak ◽  
B.I. Rachiy ◽  
R.V. Ilnytskyi ◽  
...  
Keyword(s):  
Raw Materials ◽  
Wavelength Region ◽  
Short Wave ◽  
Carbon Quantum Dots ◽  
Long Wavelength ◽  
Plant Raw Materials ◽  
Wave Region ◽  
Exciton Mechanism ◽  
Short Wave Region ◽  
Kinetics Of

The proposed method of synthesis of CQDs on the basis of nanoporous carbon obtained from plant raw materials. It is established that in the short-wave region a band is registered, which is due to the exciton mechanism of recombination, whereas in the long-wavelength region it is related to the state of defects. The kinetics of PL extinction is not strictly exponential, which most likely indicates the distributed nature of fading from individual emitters.

ChemInform Abstract: POLYMETHINE DYES WITH HYDROCARBON BRIDGES. ANIONIC DYES FROM MALONONITRILE

1985 ◽  
Vol 16 (44) ◽  
Author(s):  
YU. L. SLOMINSKII ◽  
S. V. POPOV ◽  
A. YA. IL'CHENKO ◽  
A. I. TOLMACHEV
Keyword(s):  
Polymethine Dyes ◽  
Anionic Dyes

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 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.

ChemInform Abstract: Polymethine Dyes with Hydrocarbon Bridges. Anionic Dyes with an o-Phenylene Group in the Chromophore.

1986 ◽  
Vol 17 (4) ◽  
Author(s):  
YU. L. SLOMINSKII ◽  
S. V. POPOV ◽  
G. G. DYADYUSHA ◽  
A. D. KACHKOVSKII ◽  
A. I. TOLMACHEV
Keyword(s):  
Polymethine Dyes ◽  
Anionic Dyes ◽  
Phenylene Group

Long-wavelength absorbing fluorescent polymethine dyes derived from the 6-( N , N -diethylamino)-1,2,3,4-tetrahydroxanthylium system

2017 ◽  
Vol 347 ◽  
pp. 218-226
Author(s):  
D.S. Conceição ◽  
D.P. Ferreira ◽  
Y. Prostota ◽  
O.D. Kachkovsky ◽  
L.F.Vieira Ferreira ◽  
...  
Keyword(s):  
Polymethine Dyes ◽  
Long Wavelength

scholarly journals A Biocatalytic Platform for Synthesis of Chiral α-Trifluoromethylated Organoborons

2018 ◽  
Author(s):  
xiongyi Huang ◽  
Marc Garcia-Borràs ◽  
Kun Miao ◽  
S. B. Jennifer Kan ◽  
Arjun Zutshi ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Active Site ◽  
Alkyl Substituent ◽  
Structural Features ◽  
Diazo Compounds ◽  
Important Class ◽  
Rhodothermus Marinus ◽  
Stereogenic Centers

<p></p><p>There are few biocatalytic transformations that produce fluorine-containing molecules prevalent in modern pharmaceuticals. To expand the scope of biocatalysis for organofluorine synthesis, we have developed an enzymatic platform for highly enantioselective carbene B–H bond insertion to yield versatile <i>α-</i>trifluoromethylated (<i>α</i>-CF<sub>3</sub>) organoborons, an important class of organofluorine molecules that contain stereogenic centers bearing both CF<sub>3</sub> and boron groups. In contrast to current ‘carbene transferase’ enzymes that use a limited set of simple diazo compounds as carbene precursors, this system based on <i>Rhodothermus marinus</i> cytochrome <i>c</i> (<i>Rma</i> cyt <i>c</i>) can accept a broad range of trifluorodiazo alkanes and deliver versatile chiral <i>α</i>-CF<sub>3</sub> organoborons with total turnovers up to 2870 and enantiomeric ratios up to 98.5:1.5. Computational modeling reveals that this broad diazo scope is enabled by an active site environment that directs the alkyl substituent on the heme CF<sub>3</sub>-carbene intermediate towards the solvent-exposed face, thereby allowing the protein to accommodate diazo compounds with diverse structural features.</p><br><p></p>

scholarly journals High-efficiency polymethine dyes for passive Q-switch and mode locking of neodymium lasers

2021 ◽  
pp. 39-52
Author(s):  
Alexander A. Ishchenko ◽  
◽  
Yurii L. Slominskii ◽  
Illia P. Sharanov ◽  
◽  
...  
Keyword(s):  
Excited State ◽  
Cross Section ◽  
High Efficiency ◽  
Relaxation Times ◽  
Mode Locking ◽  
Membered Ring ◽  
Polymethine Dyes ◽  
Polymethine Chain ◽  
Neodymium Lasers ◽  
Low Sensitivity

New polymethine dyes (PD) based on benzene [c, d] indole were synthesized. Their spectral and nonlinear optical characteristics in liquid and polymer media have been studied. It was found that the relaxation times τ of the excited state of the new PDs are approximately the same as those of the dye 3274y, which is widely used as a passive Q-switch of neodymium lasers with a generation lengthwave of 1.06 μm. The low sensitivity of τ to changes in the chemical structure of such PDs indicates that the main contribution to the deactivation of the excited state is made by the benzene [c, d] indole heterocycle. High values ​​of the cross section in the range of 1.05-1.08 μm at low relaxation times allow the studied PD to be easily bleached in lasers at low intensities (about 10 MW/cm2). It is established that the photostability of the new PD significantly exceeds that for the dye 3274y. This is because they contain a saturated six-membered ring in the polymethine chain, which is much less reactive than the corresponding five-membered ring of dye 3274u with respect to the photoinitiator of free radicals of UV irradiation. It is shown that the efficiency of Q-switching and mode locking of new passive laser shutters is higher than their analogues based on the dye 3274y.

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