The nature of the long-wavelength absorption bands of simple unsaturated chromophores

1965 ◽  
pp. 540
Author(s):  
S. F. Mason ◽  
G. W. Vane
Keyword(s):  
Absorption Bands ◽  
Long Wavelength ◽  
Wavelength Absorption

Photocytotoxicity of Anthracyclines upon Laser Excitation in Their Long-Wavelength Absorption Bands

1991 ◽  
Vol 127 (1) ◽  
pp. 24 ◽  
Author(s):  
Alessandra Andreoni ◽  
Alberto Colasanti ◽  
Vincenzo Malatesta ◽  
Giuseppe Roberti
Keyword(s):  
Laser Excitation ◽  
Absorption Bands ◽  
Long Wavelength ◽  
Wavelength Absorption

Synthesis and spectroscopic properties of benzo- and naphthofuryl-3-hydroxychromones

2001 ◽  
Vol 79 (4) ◽  
pp. 358-363 ◽  
Author(s):  
Andrey S Klymchenko ◽  
Turan Ozturk ◽  
Vasyl G Pivovarenko ◽  
Alexander P Demchenko
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Spectroscopic Properties ◽  
Molecular Probe ◽  
Absorption Bands ◽  
Methyl Group ◽  
Long Wavelength ◽  
Excited State Proton Transfer ◽  
Wavelength Absorption ◽  
Long Wavelength Absorption Band

With the focus of designing new fluorescent probes, four new 3-hydroxy-chromone derivatives bearing benzofuran and naphthofuran groups were synthesized. They show bathochromic absorption shifts relative to 3-hydroxyflavone with the ability of retention to display the excited-state proton transfer. Disruption of the planarity by the methyl group in the furan ring leads to a decrease of both the extinction coefficient and the contribution of long wavelength absorption band, while molecules without a methyl group showed two distinct absorption bands. Shifts to longer wavelengths are also observed in fluorescent spectra, and the absence of the methyl group results in a dramatic increase of fluorescence quantum yield and lifetime. Of the extended 3-hydroxychromone derivatives, 3-hydroxy-2-naphtho[2,1-b]furan-2-yl-chromone has shown comparable, and in some cases better, absorption and fluorescence properties than the 3-hydroxychromones synthesized so far, which make it a highly promising candidate as molecular probe for analytical chemistry, biophysics, and cellular biology.Key words: benzo- and naphthofuryl-3-hydroxyflavone, synthesis, electronic spectra, fluorescence, excited state proton transfer.

Conjugated Compounds. II. Simple Potential Energy Functions, Absorption Spectra, and Ionization in Linear Polyenes

1950 ◽  
Vol 3 (1) ◽  
pp. 109 ◽  
Author(s):  
NS Bayliss
Keyword(s):  
Potential Energy ◽  
Absorption Bands ◽  
Energy Functions ◽  
Potential Energy Functions ◽  
Long Wavelength ◽  
Linear Polyenes ◽  
Wavelength Absorption ◽  
Two Parameters ◽  
Simple Potential ◽  
Conjugated Compounds

The π-electrons of a linear conjugated system are considered in terms of two simple models for the potential energy, (A) a rectangular well and (B) a " cosine-squared " well. In each case it is possible to account quantitatively for the positions of long wavelength absorption bands, their intensities, and the ionization energies in ethylene, butadiene, hexatriene, and octatetraene with the use of two parameters, the breadth and depth of the well. By comparing the models with actual periodic potential energies calculated along the long axes of polyene molecules, it is shown that an effective nuclear charge of carbon of Z?≈1 is appropriate for the models under consideration. The assumptions involved in the application of simple one-dimensional potential energy functions to linear conjugated systems are considered in detail.

Butyryl Coenzyme A Dehydrogenase: Studies on the Specificity of the Formation of Acyl Coenzyme A Complexes with Long-Wavelength Absorption

1972 ◽  
Vol 27 (9) ◽  
pp. 1080-1081 ◽  
Author(s):  
P. C. Engel
Keyword(s):  
Dissociation Constant ◽  
Coenzyme A ◽  
Wavelength Band ◽  
Straight Chain ◽  
Absorption Bands ◽  
Acid Stability ◽  
Long Wavelength ◽  
Green Form ◽  
Wavelength Absorption ◽  
Acyl Coenzyme A

Further studies of butyryl CoA dehydrogenase show that the enzyme forms tight complexes with long-wavelength absorption bands upon addition of α, β-unsaturated alicyclic carboxylic acyl CoA compounds. As in the straight chain series, the size of the acyl moiety is critical. The thiol portion by contrast determines neither whether a long-wavelength band is formed nor the wavelength of maximum absorption if such a band is present. It does however markedly affect the dissociation constant. Unusual features of the acid stability of the acyl CoA found on the native green form of the enzyme are also reported.

Optical properties of antimony tri-iodide

1963 ◽  
Vol 276 (1364) ◽  
pp. 136-148 ◽  
Keyword(s):  
Single Crystals ◽  
Absorption Edge ◽  
Room Temperature ◽  
Thermal Dissociation ◽  
Optic Axis ◽  
Refractive Indices ◽  
Absorption Bands ◽  
Long Wavelength ◽  
Wavelength Absorption ◽  
Experimental Values

Single crystals of pure antimony tri-iodide in which the optic axis is normal to the crystal plate have been prepared. The ordinary refractive index of antimony tri-iodide has been determined at wavelengths in the absorption edge and out to a wavelength of 2.5 pm. Crystals of the com pound have been shown to be uniaxial negative and the dispersion of the birefringence has been measured. The ordinary and extraordinary refractive indices calculated from the ionic refractivity of iodine agree with the experimental values. Antimony tri-iodide has a long-wavelength absorption edge at about 5000 Å, the variation of absorption coefficient with photon energy being in agreement with Urbach’s equation. Measurements of the light transmitted through an evaporated film 0.1 pm thick at 125 °K have shown that the absorption spectrum consists of a series of absorption bands having absorption coefficients of about 105 cm -1 . These absorption bands have been attributed to two hydrogenlike series of absorption levels, the first members of each series (separation 0.46 eV) being the halogen doublet due to (3/2, 1/2) splitting. The oscillator strength of the first member of the long-wavelength series is 0.65 x 10 -4 per atom at 125 °K. Reflexion measurements from a single crystal at 173 °K have shown that two reflectivity maxima occur in positions corresponding to the absorption bands of the halogen doublet. Photoconductivity has been observed in single crystals at room temperature. The temperature and light intensity dependence of the photocurrent suggests that the photocurrent arises from the thermal dissociation of the exciton states of the halogen doublet.

scholarly journals Spectral Properties of Dyes with Interfragmental Charge Transfer: Solvatochromism and Solvatofluorochromism of 2-(3-Coumaroyl)-benzopyrylium Perchlorates

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Edward V. Sanin ◽  
Alexander I. Novikov ◽  
Alexander D. Roshal
Keyword(s):  
Charge Transfer ◽  
Spectral Properties ◽  
Spectral Characteristics ◽  
Quantum Yields ◽  
Absorption Bands ◽  
Long Wavelength ◽  
Solvent Parameters ◽  
Wavelength Absorption ◽  
Solvent Molecules ◽  
The Stability

The paper deals with the spectral properties of dyes with interfragmental charge transfer, in particular, derivatives of 2-(3-coumaroyl)benzopyrylium (CBP) perchlorates. The positions of long-wavelength absorption and emission bands, quantum yields, and lifetimes of fluorescence were measured, mostly in aprotic solvents. Regression analysis of the relationship between the spectral characteristics of CBP and the main solvent parameters (polarity, polarisability, nucleophilicity, and electrophilicity) was carried out. It was found that the characteristics of CBP depend mainly on two solvent parameters—polarity and/or nucleophilicity. An increase in these parameters results in a hypsochromic shift of absorption bands and a decrease of lifetimes and fluorescence intensity. The positions of the emission bands can demonstrate either hypsochromism or bathochromism, depending on the nature of the substituents. The solvatofluorochromic effects are not as strong as the solvatochromic ones. We believe that the spectral behaviour of CBP can be explained by cation depolarisation and by a decrease in the stability of nucleophilic complexes with solvent molecules that is associated with interfragmental charge transfer following excitation, relaxation, and radiative deactivation of the excited state.

scholarly journals Electronic Spectra and Photochemistry of Tin(II), Lead(II), Antimony(III), and Bismuth(III) Bromide Complexes in Solution

1993 ◽  
Vol 48 (11) ◽  
pp. 1519-1523 ◽  
Author(s):  
Karin Oldenburg ◽  
Arnd Vogler
Keyword(s):  
Excited States ◽  
Electronic Spectra ◽  
Electronic Configuration ◽  
Low Energy ◽  
Absorption Bands ◽  
Chloro Complexes ◽  
Long Wavelength ◽  
Main Group Metal ◽  
Wavelength Absorption ◽  
Metal Charge Transfer

The electronic spectra of bromo complexes of main group metal ions with an s2 electronic configuration (SnBr3-, PbBr3-, PbBr42-, SbBr4-, SbBr63-, BiBr4-, BiBr63-) in acetonitrile show long-wavelength absorption bands which are assigned to metal-centered sp transitions. Compared to the corresponding chloro complexes the sp bands of the bromo complexes appear at longer wavelength due to sp/LMCT mixing (LMCT = ligand-to-metal charge transfer). As a result of this mixing the luminescence which originates from low-energy sp excited states is much weaker than that of the chloro complexes. Moreover, some of the bromo complexes (e.g. BiBr4-) undergo a photochemical redox decomposition induced by LMCT excitation.

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.

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