Fast self-exchange electron transfer and delocalization of unpaired electron between zinc porphyrin radical cations and zinc porphyrins

Shunichi Fukuzumi, Taku Hasobe, Yoshito Endo, Kei Ohkubo, Hiroshi Imahori

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Self-exchange electron transfer rates between π-radical cations of zinc porphyrins and the neutral metalloporphyrins have been determined from the line-width broadening in the ESR spectra in different solvents at various temperatures. Fine tuning of the substituent on the porphyrin ring and the proper choice of the solvent have enabled us to observe negative activation enthalpies for the self-exchange electron transfer reactions. The observation of negative activation enthalpies indicates that the self-exchange electron transfer occurs via the charge-transfer π-complexes formed between zinc porphyrin radical cations and the neutral zinc porphyrins. The complete delocalization of the unpaired electron over two porphyrin moieties is observed in the radical cation of a zinc porphyrin dimer, 5,5′ -bis(10,20-bis(3,5-di-tert-butylphenyl)porphyrinatozinc(II)). This is regarded as the extreme limit of the rapid self-exchange electron transfer between zinc porphyrin radical cation and the neutral form.

Original languageEnglish
Pages (from-to)328-336
Number of pages9
JournalJournal of Porphyrins and Phthalocyanines
Volume7
Issue number4-5
Publication statusPublished - 2003
Externally publishedYes

Fingerprint

Cations
Electrons
Porphyrins
Enthalpy
Ion exchange
Chemical activation
Metalloporphyrins
Linewidth
Dimers
Paramagnetic resonance
Charge transfer
Tuning
zinc hematoporphyrin
Temperature

Keywords

  • ESR
  • Self-exchange electron transfer
  • Zinc porphyrin
  • Zinc porphyrin dimer

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Fast self-exchange electron transfer and delocalization of unpaired electron between zinc porphyrin radical cations and zinc porphyrins. / Fukuzumi, Shunichi; Hasobe, Taku; Endo, Yoshito; Ohkubo, Kei; Imahori, Hiroshi.

In: Journal of Porphyrins and Phthalocyanines, Vol. 7, No. 4-5, 2003, p. 328-336.

Research output: Contribution to journalArticle

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AU - Fukuzumi, Shunichi

AU - Hasobe, Taku

AU - Endo, Yoshito

AU - Ohkubo, Kei

AU - Imahori, Hiroshi

PY - 2003

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N2 - Self-exchange electron transfer rates between π-radical cations of zinc porphyrins and the neutral metalloporphyrins have been determined from the line-width broadening in the ESR spectra in different solvents at various temperatures. Fine tuning of the substituent on the porphyrin ring and the proper choice of the solvent have enabled us to observe negative activation enthalpies for the self-exchange electron transfer reactions. The observation of negative activation enthalpies indicates that the self-exchange electron transfer occurs via the charge-transfer π-complexes formed between zinc porphyrin radical cations and the neutral zinc porphyrins. The complete delocalization of the unpaired electron over two porphyrin moieties is observed in the radical cation of a zinc porphyrin dimer, 5,5′ -bis(10,20-bis(3,5-di-tert-butylphenyl)porphyrinatozinc(II)). This is regarded as the extreme limit of the rapid self-exchange electron transfer between zinc porphyrin radical cation and the neutral form.

AB - Self-exchange electron transfer rates between π-radical cations of zinc porphyrins and the neutral metalloporphyrins have been determined from the line-width broadening in the ESR spectra in different solvents at various temperatures. Fine tuning of the substituent on the porphyrin ring and the proper choice of the solvent have enabled us to observe negative activation enthalpies for the self-exchange electron transfer reactions. The observation of negative activation enthalpies indicates that the self-exchange electron transfer occurs via the charge-transfer π-complexes formed between zinc porphyrin radical cations and the neutral zinc porphyrins. The complete delocalization of the unpaired electron over two porphyrin moieties is observed in the radical cation of a zinc porphyrin dimer, 5,5′ -bis(10,20-bis(3,5-di-tert-butylphenyl)porphyrinatozinc(II)). This is regarded as the extreme limit of the rapid self-exchange electron transfer between zinc porphyrin radical cation and the neutral form.

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