scholarly journals Understanding/unravelling carotenoid excited singlet states

2018 ◽  
Vol 15 (141) ◽  
pp. 20180026 ◽  
Author(s):  
Hideki Hashimoto ◽  
Chiasa Uragami ◽  
Nao Yukihira ◽  
Alastair T. Gardiner ◽  
Richard J. Cogdell
Keyword(s):  
Functional Groups ◽  
Excited States ◽  
Excitation Energy Transfer ◽  
Solar Spectrum ◽  
Excited Singlet ◽  
Absorbed Energy ◽  
Singlet States ◽  
Excited Singlet States ◽  
Overall Efficiency ◽  
Natural Photosynthesis

Carotenoids are essential light-harvesting pigments in natural photosynthesis. They absorb in the blue–green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and thus expand the wavelength range of light that is able to drive photosynthesis. This process is an example of singlet–singlet excitation energy transfer, and carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. The photochemistry and photophysics of carotenoids have often been interpreted by referring to those of simple polyene molecules that do not possess any functional groups. However, this may not always be wise because carotenoids usually have a number of functional groups that induce the variety of photochemical behaviours in them. These differences can also make the interpretation of the singlet excited states of carotenoids very complicated. In this article, we review the properties of the singlet excited states of carotenoids with the aim of producing as coherent a picture as possible of what is currently known and what needs to be learned.

Ein Zusammenhang zwischen Anregungszuständen von Molekülen und biologischer Wirkung, wie Strahlensensibilisierung und Kanzerogenität / A Correlation between the Properties of Excited States of Molecules and Biological Activity, as Radiosensibilization and Carcinogenic Activity

1973 ◽  
Vol 28 (9-10) ◽  
pp. 517-522
Author(s):  
Fritz A. Popp
Keyword(s):  
Electronic Structure ◽  
Biological Activity ◽  
Excited States ◽  
Energy Transport ◽  
Transport Processes ◽  
Excited Singlet ◽  
Carcinogenic Activity ◽  
Uracil Derivatives ◽  
Singlet States ◽  
Excited Singlet States

Abstract From the differences in electronic structure of 5-halogenated uracil derivatives and thymine there is discussed the connection with different radiosensibilization. At the same time the calculated energy change of the second and third excited singlet states for the particularly sensibilizating substances 5-bromo-uracil and 5-iodo-uracil compared with the remaining uracil derivatives is remarkable. In connection with different charge distribution this difference in principle may cause different energy transport processes. The very phenomenon is to be mentioned which has been discussed in previous papers dealing with the different carcinogenic molecules 3,4-benzpyrene and 1,2-benzpyrene.

scholarly journals Elektronendelokalisierung im Grundzustand und in angeregten Zustanden / Electron Derealization in the Ground State and in Excited States

1977 ◽  
Vol 32 (2) ◽  
pp. 178-181 ◽  
Author(s):  
F. Fratev ◽  
W. Monev ◽  
O. E. Polansky ◽  
S. Stojanov ◽  
N. Tyutyulkov
Keyword(s):  
Excited States ◽  
Ground State ◽  
Excited Singlet ◽  
Singlet States ◽  
Excited Singlet States

The dependence of the fluorescence ability on the derealization of electrons in excited singlet states is discussed. It is shown that mainly those states fluoresce in which the electrons are most delocalized. The derealization can be described by Julg's Parameter A

An exciplex mechanism for the quenching of singlet excited states of aliphatic ketones by carbon tetrachloride

1976 ◽  
Vol 54 (5) ◽  
pp. 760-764 ◽  
Author(s):  
Rafik O. Loutfy ◽  
Allan C. Somersall
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Carbon Tetrachloride ◽  
Excited States ◽  
Excited Singlet ◽  
Decomposition Products ◽  
Classical Energy ◽  
Aliphatic Ketones ◽  
Singlet States ◽  
Excited Singlet States

Non-classical energy transfer from the excited singlet states of aliphatic ketones to carbon tetrachloride leads to sensitized decomposition products and fluorescence quenching. The correlation of the ionization potentials for a wide variety of such ketones with the corresponding quenching constants from fluorescence data has been rationalized by an exciplex mechanism. The correlation implies that charge transfer from the excited ketone to the carbon tetrachloride is a major contribution to the exciplex state for which two possible structures are tentatively proposed.

Haloalkane-Aromatic Complexes in the Ground and Excited States Molecular Orbital Calculation

1980 ◽  
Vol 35 (4) ◽  
pp. 418-422 ◽  
Author(s):  
I. M. Brinn
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Ground State ◽  
Substituent Effect ◽  
Molecular Orbital Calculation ◽  
Complex Stability ◽  
Excited Singlet ◽  
Singlet States ◽  
Aromatic Complexes ◽  
Excited Singlet States

Abstract CNDO/2 calculations have been carried out on a series of haloalkane-aromatic 1: 1 complexes in the ground and first excited singlet states and one 2 : 1 complex in the ground state. Calculated stabilities agree very well with reported experimental results for the ground state. Our calculations indicate that the substituent effect on complex stability in excited states will be the opposite of that found for the ground state.

Quasiparticle Excitations in Polyenes and Polyacetylene

1987 ◽  
Vol 109 ◽  
Author(s):  
Paul Tavan ◽  
Klaus Schulten
Keyword(s):  
Dispersion Relations ◽  
Excited Singlet ◽  
Quasi Particle ◽  
Double Excitation ◽  
Singlet States ◽  
Excited Singlet States ◽  
Electron Excitations ◽  
Quasiparticle Excitations

ABSTRACTWe apply the Pariser-Parr-Pople Hamiltonian to study many-electron excitations in polyenes and polyacetylene. The excited singlet states of polyenes, calculated by a multireference double excitation expansion, are classified as quasi-particle excitations, namely as triplet-triplet magnons and particle-hole excitons. From finite polyene spectra we derive approximate dispersion relations for these quasi-particles in the infinite polyene, i.e. polyacetylene.

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