Efficient photoreduction process of [Ru33-O) (μ-CH3CO2)6L3]+ by electron-mediation via the viologen dication by excitation of a zinc porphyrin

Midoriko Otake, Mitsunari Itou, Yasuyuki Araki, Osamu Ito, Hiroaki Kido

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Photoinduced electron-transfer and electron-mediation processes from the excited triplet state of zinc tetraphenylporphyrin (3ZnTPP*) to the hexyl viologen dication (HV2+) in the presence of oxo-acetato-bridged triruthenium clusters, [Ru33-O) (μ-CH3CO2)6L3]+, have been revealed by the transient absorption spectra in the visible and near-IR regions. By the nanosecond laser-flash photolysis of ZnTPP in the presence of HV2+ and [Ru33-O)-(μ-CH 3CO2)6L3]+, the transient absorption bands of the radical cation of ZnTPP (ZnTPP•+) and the reduced viologen (HV•+) were initially observed with the concomitant decay of 3ZnTPP*, after which an extra electron of HV•+ mediates to [Ru33-O)(μ- CH3CO2)6L3]+, efficiently generating [Ru33-O)(μ-CH3CO 2)6L3]0 with high potential. Although back-electron transfer took place between ZnTPP•+ and [Ru33-O)(μ-CH3CO2) 6L3]0 in the diffusion-controlled limit, [Ru33-O)(μ-CH3CO2) 6L3]0 accumulates at a steady concentration upon further addition of 1-benzyl-1,4-dihydronicotinamide (BNAH) as a sacrificial donor to re-produce ZnTPP from ZnTPP•+. Therefore, we established a novel system to accumulate [Ru33-O) (μ-CH3CO2)6L3]0 as an electron pool by the excitation of ZnTPP as photosensitizing electron donor in the presence of HV2+ and BNAH as an electron-mediating reagent and sacrificial donor, respectively. With the increase in the electron-withdrawing abilities of the ligands, the final yields of [Ru33- O)(μ-CH3CO2)6L3]0 increased.

Original languageEnglish
Pages (from-to)8581-8586
Number of pages6
JournalInorganic chemistry
Volume44
Issue number23
DOIs
Publication statusPublished - 2005 Nov 14

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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