Dual Emission of a Free-Base 5-Oxaporphyrinium Cation from its cis- and trans-NH Tautomers

Asahi Takiguchi, Seongsoo Kang, Norihito Fukui, Dongho Kim, Hiroshi Shinokubo

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Replacement of the meso methine carbon atoms of porphyrins with heteroatoms is a powerful strategy for tuning their optical and electronic properties. In particular, 5-oxaporphyrin is an attractive target due to its importance as an intermediate in heme catabolism. In this work, we describe the synthesis and properties of a free-base 5-oxaporphyrinium cation, which was prepared by the ring-closure of a bilindione with trifluoromethanesulfonic anhydride. This free-base 5-oxaporphyrinium cation exhibits dual fluorescence originating from its unique NH tautomerism. In contrast to normal porphyrins, the cis form of the 5-oxaporphyrinium cation is more stable than the trans form due to the effective delocalization of its positive charge. We thus demonstrate here that meso-modified heteroporphyrins enable the manipulation of NH tautomerism in porphyrinic macrocycles.

Original languageEnglish
Pages (from-to)2915-2919
Number of pages5
JournalAngewandte Chemie - International Edition
Issue number6
Publication statusPublished - 2021 Feb 8

Bibliographical note

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry


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