Solvent effect on the quenching of singlet oxygen by 3-methylindole

Else Lemp, Nancy Pizarro, María Victoria Encinas, Antonio L. Zanocco

Resultado de la investigación: Article

12 Citas (Scopus)

Resumen

Detection of O2(1Δg) emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure total, kT, and chemical, kR, reaction rate constants for the reaction between 3-methylindole and singlet oxygen in several solvents. Values of kT range from 0.12 ± 0.008 × 107 M-1s-1 in n-heptane to 32.0 ± 1.12 × 107 M-1s-1 in D2O at pD = 7.4. Analysis of the solvent effect on kT by using the semiempirical and theoretical linear solvent free-energy relationship (LSER and TLSER) solvatochromic equations indicates that singlet oxygen deactivation by 3-methylindole is accelerated by solvents with large π* values. This result supports the participation of an exciplex intermediate with partial charge transfer character, leading to either chemical reaction or physical quenching. The contribution of chemical reaction to total quenching depends significantly on the solvent. Chemical reaction can be neglected in non-polar solvents, whereas in hydrogen-bond donor solvents, such as methanol or D2O, chemical reaction is near to 30-40%. Solvents with larger π* and α values increase the contribution of chemical reaction relative to that of physical quenching.

Idioma originalEnglish
Páginas (desde-hasta)5222-5225
Número de páginas4
PublicaciónPhysical Chemistry Chemical Physics
Volumen3
N.º23
DOI
EstadoPublished - 1 ene 2001

Huella dactilar

Skatole
Singlet Oxygen
Quenching
quenching
Chemical reactions
chemical reactions
oxygen
Laser excitation
heptanes
deactivation
Free energy
Reaction rates
Methanol
Charge transfer
Rate constants
Hydrogen bonds
reaction kinetics
methyl alcohol
free energy
charge transfer

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Citar esto

Lemp, Else ; Pizarro, Nancy ; Encinas, María Victoria ; Zanocco, Antonio L. / Solvent effect on the quenching of singlet oxygen by 3-methylindole. En: Physical Chemistry Chemical Physics. 2001 ; Vol. 3, N.º 23. pp. 5222-5225.
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Solvent effect on the quenching of singlet oxygen by 3-methylindole. / Lemp, Else; Pizarro, Nancy; Encinas, María Victoria; Zanocco, Antonio L.

En: Physical Chemistry Chemical Physics, Vol. 3, N.º 23, 01.01.2001, p. 5222-5225.

Resultado de la investigación: Article

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T1 - Solvent effect on the quenching of singlet oxygen by 3-methylindole

AU - Lemp, Else

AU - Pizarro, Nancy

AU - Encinas, María Victoria

AU - Zanocco, Antonio L.

PY - 2001/1/1

Y1 - 2001/1/1

N2 - Detection of O2(1Δg) emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure total, kT, and chemical, kR, reaction rate constants for the reaction between 3-methylindole and singlet oxygen in several solvents. Values of kT range from 0.12 ± 0.008 × 107 M-1s-1 in n-heptane to 32.0 ± 1.12 × 107 M-1s-1 in D2O at pD = 7.4. Analysis of the solvent effect on kT by using the semiempirical and theoretical linear solvent free-energy relationship (LSER and TLSER) solvatochromic equations indicates that singlet oxygen deactivation by 3-methylindole is accelerated by solvents with large π* values. This result supports the participation of an exciplex intermediate with partial charge transfer character, leading to either chemical reaction or physical quenching. The contribution of chemical reaction to total quenching depends significantly on the solvent. Chemical reaction can be neglected in non-polar solvents, whereas in hydrogen-bond donor solvents, such as methanol or D2O, chemical reaction is near to 30-40%. Solvents with larger π* and α values increase the contribution of chemical reaction relative to that of physical quenching.

AB - Detection of O2(1Δg) emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure total, kT, and chemical, kR, reaction rate constants for the reaction between 3-methylindole and singlet oxygen in several solvents. Values of kT range from 0.12 ± 0.008 × 107 M-1s-1 in n-heptane to 32.0 ± 1.12 × 107 M-1s-1 in D2O at pD = 7.4. Analysis of the solvent effect on kT by using the semiempirical and theoretical linear solvent free-energy relationship (LSER and TLSER) solvatochromic equations indicates that singlet oxygen deactivation by 3-methylindole is accelerated by solvents with large π* values. This result supports the participation of an exciplex intermediate with partial charge transfer character, leading to either chemical reaction or physical quenching. The contribution of chemical reaction to total quenching depends significantly on the solvent. Chemical reaction can be neglected in non-polar solvents, whereas in hydrogen-bond donor solvents, such as methanol or D2O, chemical reaction is near to 30-40%. Solvents with larger π* and α values increase the contribution of chemical reaction relative to that of physical quenching.

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