| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
Development of synthetic reactions that utilize visible light energy efficiently depends on the creation of new dye redox couples that absorb visible light and undergo photo-induced electron transfer. This work demonstrates that chromophores of indigo and porphyrin are applied to this challenging project.
While N, N'-diacetylindigo which exists as a trans form undergoes one-electron transfer from tertiary amine to its singlet excited state followed by the rapid second one-electron transfer to give a leuco form, a cis-fixed indigo undergoes one-electron transfer to its triplet excited state due to efficient intersystem crossing. Because a triplet radical pair generated in the latter case tends to be separated, a one-electron reduced form (semiquinone radical) is accumulated in some cases. N, N'-Oxalyl-6, 6'-di-tert-butylindigo was photo-reduced with a high quantum efficiency (0.72) in the presence of 1000-fold molar excess of triethylamine to the semiquinone radical which in tern was aut
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ooxidized rapidly to regenerate the starting indigo. Thus, dealkylation of tributylamine was catalyzed photochemically by this indigo (2 mol-%) to lead to 50% conversion of tributylamine and 44% yield of dibutylamine by irradiation with a tungsten lamp for 3 hr under aerobic conditions.
We have found that introduction of a N, N'-bridging group into porphyrin chromophore causes strain at the 5-meso position surrounded by the N(21), N(22)-bridge and makes the 5H-phlorin structure in which -conjugation of porphyrin ring is interrupted at the 5-meso position accessible easily. N, N'-ethenooctaethylporphyrin hydroperchlorates were smoothly reduced by sodium borohydride to the N, N'-etheno-5H-phlorins which were airoxidized in 20 hr in ethanol containing acetic acid to regenerate the starting porphyrin. Whereas the 5H-phlorin failed to reduce benzyl under the same conditions as above, visible light irradiation with a tungsten lamp in acetonitrile containing trifluoroacetic acid resulted in the completion of redox reaction in 30 min. Less
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