Premium
Photo‐Hydrogen‐Evolving Molecular Catalysts Consisting of Polypyridyl Ruthenium(II) Photosensitizers and Platinum(II) Catalysts: Insights into the Reaction Mechanism
Author(s) -
Ozawa Hironobu,
Kobayashi Masayuki,
Balan Bijitha,
Masaoka Shigeyuki,
Sakai Ken
Publication year - 2010
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201000083
Subject(s) - chemistry , ethylenediamine , ruthenium , catalysis , hydrogen bond , intramolecular force , platinum , photochemistry , bipyridine , phenanthroline , medicinal chemistry , inorganic chemistry , molecule , stereochemistry , crystallography , organic chemistry , crystal structure
The mechanism of photoinduced hydrogen evolution from water driven by the first photo‐hydrogen‐evolving molecular catalyst ( 1 ), given by a coupling of [Ru(bpy) 2 (5‐amino‐phen)] 2+ and [PtCl 2 (4,4′‐dicarboxy‐bpy)] (bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline), was investigated in detail. The H 2 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 H 2 formation. A 2:1 coupling product of 1 and ethylenediamine (i.e., a {Ru II 2 Pt II 2 } 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 H 2 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.