Vibrational photochemistry of porphine imbedded in a n-hexane-d14 shpol'skii matrix

Thomas J. Butenhoff, Roy S. Chuck, Hans Heinrich Limbach, C. Bradley Moore

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

The near-infrared-induced tautomerization of free-base porphine incorporated in a n-hexane-d14 matrix is reported. Porphine occupies two sites in a n-hexane-d14 matrix as opposed to one site in a n-hexane matrix. Two spectroscopically distinct tautomers, differing by a 90° rotation of the NH bond axes within the molecular plane, exist for each site. Nernst glower irradiation on the NH stretch fundamental does not induce tautomerization, but irradiation in the regions 4000 < v < 5100 cm-1 and 5630 < v < 7700 cm-1 does induce tautomerization. Narrow-band (8 cm-1 fwhm) laser irradiation studies in the NH symmetric plus antisymmetric stretch combination band region (6300 < v < 6600 cm-1) show that the near-infrared-induced tautomerization occurs at select wavelengths. Tautomer conversion in absence of site conversion is strong evidence that the observed photochemistry is due to absorption of light by porphine and not by hexane. The estimated quantum yield is roughly 5 × 10-4 for 6530-cm-1 irradiation; this is 1-3 orders of magnitude larger than the quantum yield expected from RRKM theory.

Original languageEnglish (US)
Pages (from-to)7847-7851
Number of pages5
JournalJournal of Physical Chemistry
Volume94
Issue number20
StatePublished - 1990
Externally publishedYes

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Photochemical reactions
Hexane
photochemical reactions
Irradiation
Quantum yield
irradiation
tautomers
matrices
Infrared radiation
Hexanes
Laser beam effects
narrowband
Wavelength
porphine
n-hexane
wavelengths
lasers

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Vibrational photochemistry of porphine imbedded in a n-hexane-d14 shpol'skii matrix. / Butenhoff, Thomas J.; Chuck, Roy S.; Limbach, Hans Heinrich; Moore, C. Bradley.

In: Journal of Physical Chemistry, Vol. 94, No. 20, 1990, p. 7847-7851.

Research output: Contribution to journalArticle

Butenhoff, TJ, Chuck, RS, Limbach, HH & Moore, CB 1990, 'Vibrational photochemistry of porphine imbedded in a n-hexane-d14 shpol'skii matrix', Journal of Physical Chemistry, vol. 94, no. 20, pp. 7847-7851.
Butenhoff, Thomas J. ; Chuck, Roy S. ; Limbach, Hans Heinrich ; Moore, C. Bradley. / Vibrational photochemistry of porphine imbedded in a n-hexane-d14 shpol'skii matrix. In: Journal of Physical Chemistry. 1990 ; Vol. 94, No. 20. pp. 7847-7851.
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N2 - The near-infrared-induced tautomerization of free-base porphine incorporated in a n-hexane-d14 matrix is reported. Porphine occupies two sites in a n-hexane-d14 matrix as opposed to one site in a n-hexane matrix. Two spectroscopically distinct tautomers, differing by a 90° rotation of the NH bond axes within the molecular plane, exist for each site. Nernst glower irradiation on the NH stretch fundamental does not induce tautomerization, but irradiation in the regions 4000 < v < 5100 cm-1 and 5630 < v < 7700 cm-1 does induce tautomerization. Narrow-band (8 cm-1 fwhm) laser irradiation studies in the NH symmetric plus antisymmetric stretch combination band region (6300 < v < 6600 cm-1) show that the near-infrared-induced tautomerization occurs at select wavelengths. Tautomer conversion in absence of site conversion is strong evidence that the observed photochemistry is due to absorption of light by porphine and not by hexane. The estimated quantum yield is roughly 5 × 10-4 for 6530-cm-1 irradiation; this is 1-3 orders of magnitude larger than the quantum yield expected from RRKM theory.

AB - The near-infrared-induced tautomerization of free-base porphine incorporated in a n-hexane-d14 matrix is reported. Porphine occupies two sites in a n-hexane-d14 matrix as opposed to one site in a n-hexane matrix. Two spectroscopically distinct tautomers, differing by a 90° rotation of the NH bond axes within the molecular plane, exist for each site. Nernst glower irradiation on the NH stretch fundamental does not induce tautomerization, but irradiation in the regions 4000 < v < 5100 cm-1 and 5630 < v < 7700 cm-1 does induce tautomerization. Narrow-band (8 cm-1 fwhm) laser irradiation studies in the NH symmetric plus antisymmetric stretch combination band region (6300 < v < 6600 cm-1) show that the near-infrared-induced tautomerization occurs at select wavelengths. Tautomer conversion in absence of site conversion is strong evidence that the observed photochemistry is due to absorption of light by porphine and not by hexane. The estimated quantum yield is roughly 5 × 10-4 for 6530-cm-1 irradiation; this is 1-3 orders of magnitude larger than the quantum yield expected from RRKM theory.

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