Photo-hydrogen-evolving molecular catalysts consisting of polypyridyl ruthenium(II) photosensitizers and platinum(II) catalysts: Insights into the reaction mechanism

Hironobu Ozawa, Masayuki Kobayashi, Bijitha Balan, Shigeyuki Masaoka, Ken Sakai

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The mechanism of photoinduced hydrogen evolution from water driven by the first photo-hydrogenevolving molecular catalyst (1), given by a coupling of [Ru(bpy)2(5-aminophen)]2+ and [PtCl2(4,4'- dicarboxybpy)] (bpy=2,2'-bipyridine, phen=1,10-phenanthroline), was investigated in detail. The H2 evolution rate was found to obey Michaelis-Menten enzymatic kinetics with regard to the concentration of EDTA (ethylenediamine tetra-acetic acid disodium salt, sacrificial electron donor), which indicates that an ion-pair formation between the dicationic 1 and the dianionic form of EDTA (pH 5) is a key step leading to H2 formation. A 2:1 coupling product of 1 and ethylenediamine (i.e., a {RuII2Pt II2} complex 2) was found to show significantly higher photo-hydrogen-evolving (PHE) activity than 1, which revealed the validity of the bimolecular activation proposed in our previous study. The PHE activity of 2 was also observed to be linear to the concentration of 2, which indicates that H2 formation through the intermolecular path competes with the intramolecular path. Molecular orbital diagrams, conformational features, and Pt···H(water or acetic acid) hydrogen bonds were characterized by DFT calculations.

Original languageEnglish
Pages (from-to)1860-1869
Number of pages10
JournalChemistry - An Asian Journal
Volume5
Issue number8
DOIs
Publication statusPublished - Aug 2 2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Organic Chemistry

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