Photooxidation of alcohols by a porphyrin/quinone/TEMPO system

Takayuki Nagasawa, Suleyman Allakhverdiev, Yoshifumi Kimura, Toshi Nagata

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Photooxidation of alcohols to the corresponding aldehydes with a porphyrin/quinone/TEMPO (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyloxy free radical) system is described. This photoreaction is a combination of a photoinduced electron transfer from the porphyrin to the quinone and a TEMPO-catalyzed oxidation of alcohols triggered by one electron oxidation. The rates of oxidation were in the order of benzylic ≈ allylic > primary ≫ secondary, which is consistent with the intermediacy of the oxoammonium cation derived from TEMPO. Examination of the initial rates suggested that the reaction proceeded via the triplet excited state of the zinc porphyrin. The dependence of initial rates on the oxidation potentials of the porphyrin showed a characteristic bell shape, which is caused by two competitive factors, the efficiency of photoinduced electron transfer and the equilibrium of electron exchange between the porphyrin cation radical and TEMPO. The potential significance of this reaction in photosynthetic model chemistry is briefly discussed.

Original languageEnglish
Pages (from-to)174-180
Number of pages7
JournalPhotochemical and Photobiological Sciences
Volume8
Issue number2
DOIs
Publication statusPublished - Feb 11 2009
Externally publishedYes

Fingerprint

Photooxidation
photooxidation
Porphyrins
quinones
porphyrins
alcohols
Alcohols
Oxidation
Electrons
oxidation
Cations
electron transfer
cations
Excited states
Aldehydes
Free Radicals
aldehydes
bells
free radicals
electrons

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Photooxidation of alcohols by a porphyrin/quinone/TEMPO system. / Nagasawa, Takayuki; Allakhverdiev, Suleyman; Kimura, Yoshifumi; Nagata, Toshi.

In: Photochemical and Photobiological Sciences, Vol. 8, No. 2, 11.02.2009, p. 174-180.

Research output: Contribution to journalArticle

Nagasawa, T, Allakhverdiev, S, Kimura, Y & Nagata, T 2009, 'Photooxidation of alcohols by a porphyrin/quinone/TEMPO system', Photochemical and Photobiological Sciences, vol. 8, no. 2, pp. 174-180. https://doi.org/10.1039/b815101f
Nagasawa, Takayuki ; Allakhverdiev, Suleyman ; Kimura, Yoshifumi ; Nagata, Toshi. / Photooxidation of alcohols by a porphyrin/quinone/TEMPO system. In: Photochemical and Photobiological Sciences. 2009 ; Vol. 8, No. 2. pp. 174-180.
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