Photosensitized reduction of methyl viologen using eosin-Y in presence of a sacrificial electron donor in water-alcohol mixture

Shafiqul D.M. Islam, Toshifumi Konishi, Mamoru Fujitsuka, Osamu Ito, Yuko Nakamura, Yoshiharu Usui

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Photoreduction of methyl viologen (MV2+) by eosin-Y (EY2-) in the presence of triethanolamine (TEOA) has been investigated in water-methanol mixture by means of steady-state photolysis and laser-flash photolysis in the visible/near-infrared regions. The complete conversion to the persistent methyl viologen radical cation (MV-+) was observed in the presence of lower concentrations of EY2- and excess TEOA. By laser-flash photolysis measurements, electron transfer was confirmed to occur from the triplet state of EY2- [3(EY2-)*] to MV2+ in the rate constants of ca 2.0 x 1010 M-1 s-1. The rates and efficiencies of production of MV-+ were found to be dependent on solvent compositions and concentrations of MV2+, ionic salt and TEOA. The back electron transfer reaction from MV-+ to EY- was retarded in the presence of TEOA, which supports that EY2- is reproduced by accepting an electron from TEOA. In the presence of excess TEOA, the indirect formation of MV-+ from EY-3-, which was produced by accepting an electron from TEOA, was confirmed. The contributions of both the oxidative and reductive routes of 3(EY2-)* for the MV-+ formation have been confirmed.

Original languageEnglish
Pages (from-to)675-680
Number of pages6
JournalPhotochemistry and Photobiology
Issue number6
Publication statusPublished - 2000 Jun 1


ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

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