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.

Laser-induced fluorescence excitation spectroscopy of N2 + produced by VUV photoionization of N2 and N2O

1998 ◽  
Vol 5 (3) ◽  
pp. 1069-1071 ◽  
Author(s):  
Masakazu Mizutani ◽  
Hiromichi Niikura ◽  
Atsunari Hiraya ◽  
Koichiro Mitsuke
Keyword(s):  
Second Harmonic ◽  
Rotational Temperature ◽  
Wavelength Region ◽  
Grazing Incidence ◽  
Spectral Width ◽  
Laser Induced Fluorescence ◽  
Laser Wavelength ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Vuv Photoionization

Synchrotron radiation emitted from the UVSOR storage ring is monochromated by a grazing-incidence monochromator and introduced coaxially with the second harmonic of a mode-locked Ti:sapphire laser. Sample gases, N2 and N2O, are photoionized into vibronically ground N2 + with the fundamental light of the undulator radiation at 18.0 and 18.6 eV, respectively. Laser-induced fluorescence (LIF) excitation spectra of N2 + from N2 and N2O are measured in the laser wavelength region of the (B 2Σ u +, v′ = 0) ← (X 2Σg +, v′′ = 0) transition at 389–392 nm. The LIF excitation spectra of N2 + exhibit two maxima due to the P and R branches in which rotational bands are heavily overlapped. The rotational temperature is determined by simulating an LIF excitation spectrum by using the theoretical intensity distribution of rotation bands convoluted with the spectral width of the laser.

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 Influence of Surplus Negative Charge on Absorption and Fluorescence Excitation Spectra of Asymmetric Polymethine Dyes

2015 ◽  
Vol 60 (7) ◽  
pp. 593-600-593-600
Author(s):  
V.І. Borysyuk ◽  
◽  
V.M. Yashchuk ◽  
A.P. Naumenko ◽  
А.V. Stanova ◽  
...  
Keyword(s):  
Negative Charge ◽  
Polymethine Dyes ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Fluorescence Excitation Spectra

scholarly journals Asymmetry in the Qy Fluorescence and Absorption Spectra of Chlorophyll a Pertaining to Exciton Dynamics

2020 ◽  
Vol 8 ◽  
Author(s):  
Jeffrey R. Reimers ◽  
Margus Rätsep ◽  
Arvi Freiberg
Keyword(s):  
High Resolution ◽  
Chlorophyll A ◽  
Absorption Spectra ◽  
Magnetic Circular Dichroism ◽  
Photochemical Reactions ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Transport Dynamics ◽  
Exciton Transport ◽  
Fluorescence Excitation Spectra

Significant asymmetry found between the high-resolution Qy emission and absorption spectra of chlorophyll-a is herein explained, providing basic information needed to understand photosynthetic exciton transport and photochemical reactions. The Qy spectral asymmetry in chlorophyll has previously been masked by interference in absorption from the nearby Qx transition, but this effect has recently been removed using extensive quantum spectral simulations or else by analytical inversion of absorption and magnetic circular dichroism data, allowing high-resolution absorption information to be accurately determined from fluorescence-excitation spectra. To compliment this, here, we measure and thoroughly analyze the high-resolution differential fluorescence line narrowing spectra of chlorophyll-a in trimethylamine and in 1-propanol. The results show that vibrational frequencies often change little between absorption and emission, yet large changes in line intensities are found, this effect also being strongly solvent dependent. Among other effects, the analysis in terms of four basic patterns of Duschinsky-rotation matrix elements, obtained using CAM-B3LYP calculations, predicts that a chlorophyll-a molecule excited into a specific vibrational level, may, without phase loss or energy relaxation, reemit the light over a spectral bandwidth exceeding 1,000 cm−1 (0.13 eV) to influence exciton-transport dynamics.

A Novel Debromination of Tetrabromobisphenol A (TBBPA) by Hydrothermal Treatment with Reactive Minerals

2015 ◽  
Vol 768 ◽  
pp. 612-621 ◽  
Author(s):  
Zhi Tong Yao ◽  
Wen Yi Yuan ◽  
Zheng Miao Xie ◽  
Jun Hong Tang
Keyword(s):  
Iron Powder ◽  
Hydrothermal Treatment ◽  
Absorption Spectra ◽  
Flame Retardants ◽  
Wavelength Region ◽  
Tetrabromobisphenol A ◽  
Control Group ◽  
Absorption Bands ◽  
Before And After ◽  
Increasing Temperature

Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and relatively persistent in the environment. There has been increasing interest in the developing alternative approach for its degradation and debromination. In this study, we explored the debromination of TBBPA by alkaline hydrothermal treatment with reactive minerals, namely iron powder, layered double hydroxide (LDH) and gibbsite. The effects of hydrothermal temperatures and time, the initial TBBPA concentrations, and additive amounts of reactive minerals on debromination were investigated. As a comparison, the conventional hydrothermal treatment with no additive as the control group was included. The UV-vis absorption spectra of TBBPA before and after debromination were studied as well. The results showed that increasing temperature was helpful for the improvement of debromination. It significantly increased by 223.5, 54.3 and 78.1% with increasing temperature from 140 to 160 °C for the control, iron power and LDH groups, respectively. When the hydrothermal time was shorter than a critical value, the debromination rate increased with time rising. A maximum rate of 79.9% was achieved for iron powder group after reaction for 8 h. The preferred initial TBBPA concentration was determined as 60 ppm for all groups. The optimum amounts of reactive minerals were not consistent and determined as 0.08 g for iron powder, 0.32 g for LDH and 0.16 g for gibbsite, respectively. The maximum absorption bands of TBBPA increased as the pH was raised. They were located at 209 and 308 nm for neutral TBBPA and increased to 211 and 311 nm for TBBPA-Na2CO3. New absorption bands in the wavelength region of 225-275 and 300-350 nm were observed, when TBBPA was subjected to hydrothermal treatment. Keywords: Brominated flame retardants (BFRs); tetrabromobisphenol A (TBBPA); debromination; hydrothermal treatment; UV-vis absorption spectra

scholarly journals Luminescent determination of residues of trazodon hydrochloride and melatonin after cleaning pharmaceutical equipment

2019 ◽  
pp. 73-81
Author(s):  
O. D. Voitiuk ◽  
A. V. Yegorova ◽  
Yu. V. Scrypynets ◽  
S. N. Kashutskуy ◽  
V. P. Antonovich
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Xenon Lamp ◽  
Excitation Spectra ◽  
Absorption Bands ◽  
Limit Of Quantitation ◽  
Trazodone Hydrochloride

A prerequisite for ensuring the quality of medicines is their production in accordance with the rules of GMP (Good Manufacturing Practice for Medicinal Products), one of the most important requirements of which is equipment cleaning. In many cases, the same equipment is used in the production of various preparations. Therefore, to prevent contamination of each of the following drugs, the previous one, it is very important to carry out an effective equipment cleaning procedure with a mandatory assessment of its purity. The purpose of this study was to develop simple, express, selective methods for luminescent determination of residual quantities of APIs of trazodone hydrochloride (TG) and melatonin (MT) in washes to control the completeness of their removal when cleaning process equipment. The excitation and luminescence spectra were recorded using a Cary Eclipse "Varian" spectrofluorimeter (Australia) with a xenon lamp 150 W. Electronic absorption spectra were recorded on a UV-2401 PC spectrophotometer «Shimadzu» (Japan). The electronic absorption spectra of TG and MT have absorption bands in the UV spectral region. It was established experimentally that the excitation spectra of TG and MT are similar to their absorption spectra (λex = 318 nm (TG) and λem = 274 nm (MT)). The effect on the luminescence intensity of TG and MT of methanol, ethanol, acetonitrile, dimethylformamide, dimethylsulfoxide, propanol (50 v/v) was studied. It is established that the maximum luminescence is observed in water. The methods were validated according to the following parameters: specificity, linearity, accuracy, limit of quantitation. The degree of extraction of trazodone hydrochloride and melatonin from applicators and surfaces of pharmaceutical equipment is more than 90%. The developed methods can be recommended for determining the residual amounts of trazodone hydrochloride and melatonin while monitoring the quality of the cleaning of pharmaceutical equipment.

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