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Spectroscopic and dynamic properties of the peridinin lowest singlet excited states

Zigmantas, Donatas LU ; Polivka, Tomas LU ; Hiller, Roger G.; Yartsev, Arkady LU and Sundström, Villy LU (2001) In The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 105(45). p.10296-10306
Abstract
Spectroscopic properties as well as excited state dynamics of the carotenoid peridinin in several solvents of different polarities were investigated by time-resolved fluorescence and transient absorption techniques. A strong dependence of the peridinin lowest excited states dynamics on solvent polarity was observed after excitation into the strongly allowed S-2 state. Peridinin relaxes to the ground state within 10 ps in the strongly polar solvent methanol, while in the nonpolar solvent n-hexane a 160 ps lifetime was observed, thus confirming the previous observations revealed by transient absorption spectroscopy in the visible region (Bautista, J. A.; et al. J. Phys. Chem. B 1999, 103, 8751). In addition, the solvent dependence in the... (More)
Spectroscopic properties as well as excited state dynamics of the carotenoid peridinin in several solvents of different polarities were investigated by time-resolved fluorescence and transient absorption techniques. A strong dependence of the peridinin lowest excited states dynamics on solvent polarity was observed after excitation into the strongly allowed S-2 state. Peridinin relaxes to the ground state within 10 ps in the strongly polar solvent methanol, while in the nonpolar solvent n-hexane a 160 ps lifetime was observed, thus confirming the previous observations revealed by transient absorption spectroscopy in the visible region (Bautista, J. A.; et al. J. Phys. Chem. B 1999, 103, 8751). In addition, the solvent dependence in the near-IR region is demonstrated by a strong negative feature in the transient absorption spectrum of peridinin in methanol, which is not present in n-hexane. This band, characterized by a 1 ps rise time, is ascribed to stimulated emission from an intramolecular charge-transfer (ICT) state. Time-resolved fluorescence data support assignment of this band to the emissive singlet state, whose dynamic characteristics depend strongly on the dielectric strength of the medium. On the basis of all our time-resolved measurements combined with simulations of the observed kinetics, we propose the following model: the initially populated S-2 state decays to the S-1 state within less than 100 fs for both solvents. Then, the population is transferred from the S-1 state to the S-0 and ICT states. The S1 --> ICT transfer is controlled by a solvent polarity dependent barrier. In n-hexane the barrier is high enough to prevent the S-1 --> ICT transfer and only S-1 --> S-0 relaxation characterized by a time constant of 160 ps is observed. An increase of solvent polarity leads to a significant decrease of the barrier, enabling a direct quenching of the S-1 state by means of the S-1 --> ICT transfer, which is characterized by a time constant of 148 ps for tetrahydrofuran, 81 ps for 2-propanol, and 11 ps for the most polar solvent methanol. The ICT state is then rapidly depopulated to the ground state. This relaxation also exhibits solvent dependence, having a time constant of 1 ps in methanol, 2.5 ps in 2-propanol, and 3.5 ps in tetrahydrofuran. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
energy-transfer, chlorophyll-protein complexes, amphidinium-carterae, internal-conversion, solvent dependence, beta-carotene, a protein, s-1 state, bacteriochlorophyll, photosynthesis
in
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
volume
105
issue
45
pages
10296 - 10306
publisher
The American Chemical Society
external identifiers
  • scopus:0035892221
ISSN
1520-5215
DOI
10.1021/jp010022n
language
English
LU publication?
yes
id
86e23d02-bad7-484c-a3e5-06e51bc4be45 (old id 1433113)
date added to LUP
2009-07-01 11:19:27
date last changed
2018-08-12 04:04:45
@article{86e23d02-bad7-484c-a3e5-06e51bc4be45,
  abstract     = {Spectroscopic properties as well as excited state dynamics of the carotenoid peridinin in several solvents of different polarities were investigated by time-resolved fluorescence and transient absorption techniques. A strong dependence of the peridinin lowest excited states dynamics on solvent polarity was observed after excitation into the strongly allowed S-2 state. Peridinin relaxes to the ground state within 10 ps in the strongly polar solvent methanol, while in the nonpolar solvent n-hexane a 160 ps lifetime was observed, thus confirming the previous observations revealed by transient absorption spectroscopy in the visible region (Bautista, J. A.; et al. J. Phys. Chem. B 1999, 103, 8751). In addition, the solvent dependence in the near-IR region is demonstrated by a strong negative feature in the transient absorption spectrum of peridinin in methanol, which is not present in n-hexane. This band, characterized by a 1 ps rise time, is ascribed to stimulated emission from an intramolecular charge-transfer (ICT) state. Time-resolved fluorescence data support assignment of this band to the emissive singlet state, whose dynamic characteristics depend strongly on the dielectric strength of the medium. On the basis of all our time-resolved measurements combined with simulations of the observed kinetics, we propose the following model: the initially populated S-2 state decays to the S-1 state within less than 100 fs for both solvents. Then, the population is transferred from the S-1 state to the S-0 and ICT states. The S1 --> ICT transfer is controlled by a solvent polarity dependent barrier. In n-hexane the barrier is high enough to prevent the S-1 --> ICT transfer and only S-1 --> S-0 relaxation characterized by a time constant of 160 ps is observed. An increase of solvent polarity leads to a significant decrease of the barrier, enabling a direct quenching of the S-1 state by means of the S-1 --> ICT transfer, which is characterized by a time constant of 148 ps for tetrahydrofuran, 81 ps for 2-propanol, and 11 ps for the most polar solvent methanol. The ICT state is then rapidly depopulated to the ground state. This relaxation also exhibits solvent dependence, having a time constant of 1 ps in methanol, 2.5 ps in 2-propanol, and 3.5 ps in tetrahydrofuran.},
  author       = {Zigmantas, Donatas and Polivka, Tomas and Hiller, Roger G. and Yartsev, Arkady and Sundström, Villy},
  issn         = {1520-5215},
  keyword      = {energy-transfer,chlorophyll-protein complexes,amphidinium-carterae,internal-conversion,solvent dependence,beta-carotene,a protein,s-1 state,bacteriochlorophyll,photosynthesis},
  language     = {eng},
  number       = {45},
  pages        = {10296--10306},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory},
  title        = {Spectroscopic and dynamic properties of the peridinin lowest singlet excited states},
  url          = {http://dx.doi.org/10.1021/jp010022n},
  volume       = {105},
  year         = {2001},
}