Vibronic Origin of the Qy Absorption Tail of Bacteriochlorophyll a Verified by Fluorescence Excitation Spectroscopy and Quantum Chemical Simulations

2017 ◽  
Vol 8 (17) ◽  
pp. 4231-4235 ◽  
Author(s):  
Kristjan Leiger ◽  
Juha Matti Linnanto ◽  
Arvi Freiberg
Keyword(s):  
Quantum Chemical ◽  
Bacteriochlorophyll A ◽  
Fluorescence Excitation ◽  
Absorption Tail

scholarly journals Establishment of the Qy Absorption Spectrum of Chlorophyll a Extending to Near-Infrared

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3796 ◽  
Author(s):  
Kristjan Leiger ◽  
Juha Matti Linnanto ◽  
Arvi Freiberg
Keyword(s):  
Chlorophyll A ◽  
Quantum Chemical ◽  
Near Infrared ◽  
Vibrational Modes ◽  
Fluorescence Excitation ◽  
Weak Absorption ◽  
Thermally Activated ◽  
Combination Modes ◽  
Anti Stokes ◽  
Absorption Tail

A weak absorption tail related to the Qy singlet electronic transition of solvated chlorophyll a is discovered using sensitive anti-Stokes fluorescence excitation spectroscopy. The quasi-exponentially decreasing tail was, at ambient temperature, readily observable as far as −2400 cm−1 from the absorption peak and at relative intensity of 10−7. The tail also weakened rapidly upon cooling the sample, implying its basic thermally activated nature. The shape of the spectrum as well as its temperature dependence were qualitatively well reproduced by quantum chemical calculations involving the pigment intramolecular vibrational modes, their overtones, and pairwise combination modes, but no intermolecular/solvent modes. A similar tail was observed earlier in the case of bacteriochlorophyll a, suggesting generality of this phenomenon. Long vibronic red tails are, thus, expected to exist in all pigments of light-harvesting relevance at physiological temperatures.

scholarly journals Спектрально-люминесцентные свойства некоторых производных бензальдегида

2019 ◽  
Vol 127 (8) ◽  
pp. 242
Author(s):  
О.К. Базыль ◽  
В.Я. Артюхов ◽  
Г.В. Майер ◽  
П.П. Першукевич ◽  
М.В. Бельков ◽  
...  
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Theoretical Data ◽  
Luminescent Properties ◽  
Fluorescence Excitation ◽  
Carcinogenic Activity ◽  
Long Wavelength ◽  
Yield Values ◽  
Low Toxicity ◽  
Substituted Benzaldehydes

Substituted benzaldehydes widely distributed in nature exhibit antibacterial, anti-inflammatory, antiviral, anti-carcinogenic activity with low toxicity, which make their promising in medicine. The results of an experimental and theoretical study of the spectral-luminescent properties of four neutral forms of hydroxy- and methoxy-substituted benzaldehydes are presented. The absorption spectra of the studied compounds were obtained in hexane and ethanol. Measurements of fluorescence spectra and fluorescence excitation of solutions were carried out in ethanol. Based on quantum chemical calculations, the orbital nature of electronic transitions, the features of the electron density distribution upon excitation and changes in the structure of the compound are determined and the rate constants of photophysical processes are estimated. According to calculations, for all compounds studied, the S1 state is formed by the nπ-type transition, and the intensity of the long-wavelength bands in these compounds is formed by one or two ππ-transitions. The fluorescence quantum yield values are estimated from experimental and theoretical data. As a result of the analysis and comparison of experimental data and the results of quantum chemical calculations it was concluded that the neutral forms of the studied substituted benzaldehydes are not responsible for the observed fluorescence in experiments with ethanol solutions.

Electronic absorption spectrum and π-electronic structure of cryptocyanine

1980 ◽  
Vol 45 (2) ◽  
pp. 307-320 ◽  
Author(s):  
Miloš Titz ◽  
Antonín Novák ◽  
Viktor Řehák
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Dipole Moment ◽  
Excited State ◽  
Absorption Band ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Fluorescence Excitation ◽  
Real Geometry ◽  
Optimum Model

Absorption, fluorescence excitation and APF spectra of cryptocyanine have been measured. Dipole moment of the respective S1 excited state has been estimated from shifts of the marked maximum of the first absorption band in various solvents. On the basis of quantum-chemical calculations carried out by the PPP method in the approximation of quasi-real geometry we have received the optimum model of π-electronic structure of the cryptocyanine molecule and therefrom the theoretical electronic singlet spectrum inclusive character of the S0 - S1 transition.

scholarly journals Probing of Higher Excited States of Merocyanine Derivatives of Azaazulene and Indandione by Fluorescence Excitation Anisotropy Spectra

2020 ◽  
Vol 65 (4) ◽  
pp. 321
Author(s):  
A. P. Naumenko ◽  
V. I. Borysuk ◽  
M. S. Iakhnenko ◽  
V. O. Gubanov ◽  
Y. L. Slominskii ◽  
...  
Keyword(s):  
Excited States ◽  
Electronic Transition ◽  
Quantum Chemical ◽  
Bathochromic Shift ◽  
Polymethine Dyes ◽  
Fluorescence Excitation ◽  
Chemical Studies ◽  
Anisotropy Spectra ◽  
Derivatives Of ◽  
Higher Excited States

This paper is dedicated to the spectral and quantum-chemical studies of higher excited states of merocyanine derivatives of azaazulene and indandione. A particular attention is paid to the analysis of fluorescence excitation anisotropy spectra of the mentioned compounds. The long-wave shift by ≈ 50 nm of a deep clear minimum in the fluorescence excitation anisotropy spectrum due to an elongation of the polymethine dye chromophore is established. Such shift is close in a value to the bathochromic shift of the first minimum in the anisotropy spectrum of symmetric ionic polymethine dyes, in which this minimum corresponds to the second electronic transition. The parallel spectral study and quantum-chemical calculations allowed us to correctly interpret the fluorescence excitation anisotropy spectra of merocyanines and relate the first clear minimum with the seventh electronic transition. The last resembles the second electronic transition between delocalized molecular orbitals (MO) in polymethine dyes.

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