Excited state acidity of bifunctional compounds

Part 8. Competitive kinetics between solvent reorientation and proton transfer during ESIPT of 2-hydroxyphenyl-lapazole in protic solvents

Carlos E M Carvalho, Alexsandra S. Silva, Ira M. Brinn, Antonio V. Pinto, Maria C F R Pinto, Su Lin, Thomas A Moore, John Devens Gust, Marcel Maeder

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

2-Hydroxyphenyl-lapazole (HPL) is shown to undergo excited state intramolecular proton transfer (ESIPT) in the protic solvents methanol, propan-2-ol and octan-1-ol at room temperature. Investigation of the kinetics of this process, using time-resolved single photon counting and transient absorption spectroscopy, indicates the presence of three different excited-state species. These results are very different from that already reported for HPL in non-protic solvents, where it was found that the ESIPT process attains equilibrium during the lifetime of the excited state. Factor analysis of the steady state spectra supports the conclusions drawn from the kinetic results. The difference in behavior as a function of solvent is attributed to two factors that depend on the stronger solute-solvent interactions in the case of the protic solvents. (1) The slight slowing down of the process of proton transfer, which prevents equilibrium from being established during the lifetime of the excited singlet state. (2) The weakening of the intramolecular hydrogen bond, which allows rotation of the hydroxyphenyl moiety.

Original languageEnglish
Pages (from-to)3383-3389
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume4
Issue number14
DOIs
Publication statusPublished - 2002

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Proton transfer
Excited states
Acidity
acidity
retraining
Kinetics
protons
kinetics
excitation
life (durability)
factor analysis
Factor analysis
Absorption spectroscopy
Methanol
Hydrogen bonds
counting
absorption spectroscopy
solutes
Photons
methyl alcohol

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics

Cite this

Excited state acidity of bifunctional compounds : Part 8. Competitive kinetics between solvent reorientation and proton transfer during ESIPT of 2-hydroxyphenyl-lapazole in protic solvents. / Carvalho, Carlos E M; Silva, Alexsandra S.; Brinn, Ira M.; Pinto, Antonio V.; Pinto, Maria C F R; Lin, Su; Moore, Thomas A; Gust, John Devens; Maeder, Marcel.

In: Physical Chemistry Chemical Physics, Vol. 4, No. 14, 2002, p. 3383-3389.

Research output: Contribution to journalArticle

Carvalho, Carlos E M ; Silva, Alexsandra S. ; Brinn, Ira M. ; Pinto, Antonio V. ; Pinto, Maria C F R ; Lin, Su ; Moore, Thomas A ; Gust, John Devens ; Maeder, Marcel. / Excited state acidity of bifunctional compounds : Part 8. Competitive kinetics between solvent reorientation and proton transfer during ESIPT of 2-hydroxyphenyl-lapazole in protic solvents. In: Physical Chemistry Chemical Physics. 2002 ; Vol. 4, No. 14. pp. 3383-3389.
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AB - 2-Hydroxyphenyl-lapazole (HPL) is shown to undergo excited state intramolecular proton transfer (ESIPT) in the protic solvents methanol, propan-2-ol and octan-1-ol at room temperature. Investigation of the kinetics of this process, using time-resolved single photon counting and transient absorption spectroscopy, indicates the presence of three different excited-state species. These results are very different from that already reported for HPL in non-protic solvents, where it was found that the ESIPT process attains equilibrium during the lifetime of the excited state. Factor analysis of the steady state spectra supports the conclusions drawn from the kinetic results. The difference in behavior as a function of solvent is attributed to two factors that depend on the stronger solute-solvent interactions in the case of the protic solvents. (1) The slight slowing down of the process of proton transfer, which prevents equilibrium from being established during the lifetime of the excited singlet state. (2) The weakening of the intramolecular hydrogen bond, which allows rotation of the hydroxyphenyl moiety.

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