Photochemical magnetic-field effects of isoquinoline N-oxide in various alcohols.

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概要

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• A pronounced solvent dependence of the magnetic-field effect due to the HFI-J mechanism was found for the first time in the case of a photochemical isomerization of isoquinoline <I>N</I>-oxide into lactam (1-isoquinolone). The chemical yield of the lactam showed a minimum at a higher magnetic field as one changes the reaction medium from <I>t</I>-butyl alcohol to 2-propanol (or ethanol) and then to methanol, which was the same order as the p<I>K</I><SUB>a</SUB> value (<I>t</I>-butyl alcohol>2-propanole≈ethanol>methanol). Such a solvent dependence provides corroborating evidence that the photoisomerization proceeds via the S<SUB>1</SUB>-born singlet radical-ion-pair intermediate, which is linked by a hydrogen bond between the N→O group in the cation radical of <I>N</I>-oxide and the OH group in the anion radical of alcohol. Another interesting finding was that, in the case of the photochemical isomerization in <I>t</I>-butyl alcohol, the chemical yield of the lactam showed distinct maxima at approximately 0.9T and 1.35T in addition to a minimum at about 0.72T. The anomalous magnetic-field effect in a high field region (>0.8T) could reasonably be explained in terms of an HFI-J mechanism by assuming the T<SUB>1</SUB>-born triplet hydrogen-bonded radical-ion pair to have an electron-exchange interaction larger than that in the S<SUB>1</SUB>-born singlet hydrogen-bonded radical-ion pair.

• 公益社団法人 日本化学会の論文

著者

• Hata Norisuke

  Deparment of Chemistry, College of Science and Engineering, Aoyama Gakuin University

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• Photochemical magnetic-field effects of isoquinoline N-oxide in various alcohols.

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