Photophysical properties of hydroxy-substituted flavothiones

Fausto Elisei, João C. Lima, Fausto Ortica, Gian G. Aloisi, Manuela Costa, Emília Leitão, Isabel Abreu, António Dias, Vasco Bonifácio, Jorge Medeiros, António L. Maçanita, Ralph S. Becker

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Flavothione and a number of synthesized hydroxy- (mono- and di-) substituted flavothiones have been thoroughly examined, particularly regarding their absorption, emission, photophysical (triplet yields and lifetimes), and oxygen-photosensitizing characteristics. These were all studied as a function of the nature of the solvent (four), which was particularly critical in terms of aiding in determining the energy and configurational nature of the lowest triplet state as well as the mechanism of intersystem crossing. Theoretical calculations were also performed. Both the location and number of hydroxyl groups have a substantial impact on the nature of the lowest excited triplet state as well as on the relative location of the two lowest excited singlet and triplet states. These in turn affect the magnitude and even the existence of triplet-state occupation as well as the ability to sensitize oxygen (to singlet oxygen). Three groups of compounds exist as characterized by the configurational nature of the triplet and the mechanism of intersystem crossing, or the essential absence of intersystem crossing altogether. The quantum yield of singlet oxygen formation is high for one group where the T(π, π*) state is lowest and generally high in another group where the T(n, π*) state is lowest, except in ethanol where competitive H-atom abstraction occurs. The potential of all hydroxy compounds as photosensitizers is evaluated.

Original languageEnglish
Pages (from-to)6095-6102
Number of pages8
JournalJournal of Physical Chemistry A
Volume104
Issue number25
DOIs
Publication statusPublished - 29 Jul 2000

Fingerprint

Singlet Oxygen
atomic energy levels
Oxygen
Photosensitizing Agents
Quantum yield
oxygen
Excited states
Hydroxyl Radical
Ethanol
Atoms
occupation
ethyl alcohol
life (durability)
excitation
atoms
energy

Keywords

  • Corn
  • Zea mays
  • Stalk rot

Cite this

Elisei, F., Lima, J. C., Ortica, F., Aloisi, G. G., Costa, M., Leitão, E., ... Becker, R. S. (2000). Photophysical properties of hydroxy-substituted flavothiones. Journal of Physical Chemistry A, 104(25), 6095-6102. https://doi.org/10.1021/jp000084y
Elisei, Fausto ; Lima, João C. ; Ortica, Fausto ; Aloisi, Gian G. ; Costa, Manuela ; Leitão, Emília ; Abreu, Isabel ; Dias, António ; Bonifácio, Vasco ; Medeiros, Jorge ; Maçanita, António L. ; Becker, Ralph S. / Photophysical properties of hydroxy-substituted flavothiones. In: Journal of Physical Chemistry A. 2000 ; Vol. 104, No. 25. pp. 6095-6102.
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Elisei, F, Lima, JC, Ortica, F, Aloisi, GG, Costa, M, Leitão, E, Abreu, I, Dias, A, Bonifácio, V, Medeiros, J, Maçanita, AL & Becker, RS 2000, 'Photophysical properties of hydroxy-substituted flavothiones', Journal of Physical Chemistry A, vol. 104, no. 25, pp. 6095-6102. https://doi.org/10.1021/jp000084y

Photophysical properties of hydroxy-substituted flavothiones. / Elisei, Fausto; Lima, João C.; Ortica, Fausto; Aloisi, Gian G.; Costa, Manuela; Leitão, Emília; Abreu, Isabel; Dias, António; Bonifácio, Vasco; Medeiros, Jorge; Maçanita, António L.; Becker, Ralph S.

In: Journal of Physical Chemistry A, Vol. 104, No. 25, 29.07.2000, p. 6095-6102.

Research output: Contribution to journalArticle

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T1 - Photophysical properties of hydroxy-substituted flavothiones

AU - Elisei, Fausto

AU - Lima, João C.

AU - Ortica, Fausto

AU - Aloisi, Gian G.

AU - Costa, Manuela

AU - Leitão, Emília

AU - Abreu, Isabel

AU - Dias, António

AU - Bonifácio, Vasco

AU - Medeiros, Jorge

AU - Maçanita, António L.

AU - Becker, Ralph S.

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Y1 - 2000/7/29

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AB - Flavothione and a number of synthesized hydroxy- (mono- and di-) substituted flavothiones have been thoroughly examined, particularly regarding their absorption, emission, photophysical (triplet yields and lifetimes), and oxygen-photosensitizing characteristics. These were all studied as a function of the nature of the solvent (four), which was particularly critical in terms of aiding in determining the energy and configurational nature of the lowest triplet state as well as the mechanism of intersystem crossing. Theoretical calculations were also performed. Both the location and number of hydroxyl groups have a substantial impact on the nature of the lowest excited triplet state as well as on the relative location of the two lowest excited singlet and triplet states. These in turn affect the magnitude and even the existence of triplet-state occupation as well as the ability to sensitize oxygen (to singlet oxygen). Three groups of compounds exist as characterized by the configurational nature of the triplet and the mechanism of intersystem crossing, or the essential absence of intersystem crossing altogether. The quantum yield of singlet oxygen formation is high for one group where the T(π, π*) state is lowest and generally high in another group where the T(n, π*) state is lowest, except in ethanol where competitive H-atom abstraction occurs. The potential of all hydroxy compounds as photosensitizers is evaluated.

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KW - Zea mays

KW - Stalk rot

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U2 - 10.1021/jp000084y

DO - 10.1021/jp000084y

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JF - Journal Of Physical Chemistry A

SN - 1089-5639

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Elisei F, Lima JC, Ortica F, Aloisi GG, Costa M, Leitão E et al. Photophysical properties of hydroxy-substituted flavothiones. Journal of Physical Chemistry A. 2000 Jul 29;104(25):6095-6102. https://doi.org/10.1021/jp000084y