Journal of Photoscience

Korean Society of Photoscience (한국광과학회)
권호 표지

QUENCHING OF TYPE II PHOTOSENSITIZER IN THEIR TRIPLET STATES BY $\alpha$-TOCOPHEROL VIA AN ELECTRON TRANSFER REACTION

  • Boo, Yong-Chool (Department of Agricultural Chemistry , Seoul National University) ;
  • Lee, Keum-Pyo (Department of Agricultural Chemistry , Seoul National University) ;
  • Jung, Jin (Department of Agricultural Chemistry , Seoul National University)
  • Published : 1998.10.01
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Abstract

Occurrence of an electron (or H atom equivalent to one electron plus H+) transfer from $\alpha$- tocopherol $\alpha$(TOH) to a number of photosensitizers in theri triplet states were investigated by monitoring the ESR signal of $\alpha$-chromaoxyl radical ($\alpha$(TO.) in ethanolic solutions of $\alpha$TOH and the sensitizers under continuous illumination. Every sensitizer molecule examined, such as protocholorophyllide (Pchl), hematoporphyrin and rose bengal which are generally regarded as efficient type II photosensitizers and thus have long-lived triplet states, was found to actively participate in an electro transfer reaction with $\alpha$TOH even under air-saturation conditions, generating $\alpha$TOH complex as an intermediate in a fashion of Michaelis-Menten type of reaction. For the reaction of $\alpha$TOH with triplet Pchl, the rate law was derived by applying the steady approximation for the binary complex, triplet Pchl-$\alpha$TOH , which turned out to be well consistent with the kinetic data.

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